[PATCH bpf-next v4 00/24] Local kptrs, BPF linked lists

[PATCH bpf-next v4 00/24] Local kptrs, BPF linked lists

[Kumar Kartikeya Dwivedi]

This series introduces user defined BPF objects, by introducing the idea
of local kptrs. These are kptrs (strongly typed pointers) that refer to
objects of a user defined type, hence called "local" kptrs. This allows
BPF programs to allocate their own objects, build their own object
hierarchies, and use the basic building blocks provided by BPF runtime
to build their own data structures flexibly.

Then, we introduce the support for single ownership BPF linked lists,
which can be put inside BPF maps, or local kptrs, and hold such
allocated local kptrs as elements. It works as an instrusive collection,
which is done to allow making local kptrs part of multiple data
structures at the same time in the future.

The eventual goal of this and future patches is to allow one to do some
limited form of kernel style programming in BPF C, and allow programmers
to build their own complex data structures flexibly out of basic
building blocks.

The key difference will be that such programs are verified to be safe,
preserve runtime integrity of the system, and are proven to be bug free
as far as the invariants of BPF specific APIs are concerned.

One immediate use case that will be using the entire infrastructure this
series is introducing will be managing percpu NMI safe linked lists
inside BPF programs.

The other use case this will serve in the near future will be linking
kernel structures like XDP frame and sk_buff directly into user data
structures (rbtree, pifomap, etc.) for packet queueing. This will follow
single ownership concept included in this series.

The user has complete control of the internal locking, and hence also
the batching of operations for each critical section.

The features are:
- Local kptrs - User defined kernel objects.
- bpf_obj_new, bpf_obj_drop to allocate and free them.
- Single ownership BPF linked lists.
  - Support for them in BPF maps.
  - Support for them in local kptrs.
- Global spin locks.
- Spin locks inside local kptrs.

Some other notable things:
- Completely static verification of locking.
- Kfunc argument handling has been completely reworked.
- Argument rewriting support for kfuncs.
- Search pruning now understands non-size precise registers.
- A new bpf_experimental.h header as a dumping ground for these APIs.

Any functionality exposed in this series is NOT part of UAPI. It is only
available through use of kfuncs, and structs that can be added to map value may
also change their size or name in the future. Hence, every feature in this
series must be considered experimental.

Follow-ups:
-----------
 * Support for kptrs (local and kernel) in local storage and percpu maps + kptr tests
 * Fixes for helper access checks rebasing on top of this series

Next steps:
-----------
 * NMI safe percpu single ownership linked lists (using local_t protection).
 * Lockless linked lists.
 * Allow RCU protected local kptrs. This then allows RCU protected list lookups,
   since spinlock protection for readers does not scale.
 * Introduce explicit RCU read sections (using kfuncs).
 * Introduce bpf_refcount for local kptrs, shared ownership.
 * Introduce shared ownership linked lists.
 * Documentation.

Changelog:
----------
 v3 -> v4
 v3: https://lore.kernel.org/bpf/20221102202658.963008-1-memxor@gmail.com

  * Fix compiler error for !CONFIG_BPF_SYSCALL (Kernel Test Robot)
  * Fix error due to BUILD_BUG_ON on 32-bit platforms (Kernel Test Robot)

 v2 -> v3
 v2: https://lore.kernel.org/bpf/20221013062303.896469-1-memxor@gmail.com

  * Add ack from Dave for patch 5
  * Rename btf_type_fields -> btf_record, btf_type_fields_off ->
    btf_field_offs, rename functions similarly (Alexei)
  * Remove 'kind' component from contains declaration tag (Alexei)
  * Move bpf_list_head, bpf_list_node definitions to UAPI bpf.h (Alexei)
  * Add note in commit log about modifying btf_struct_access API (Dave)
  * Downgrade WARN_ON_ONCE to verbose(env, "...") and return -EFAULT (Dave)
  * Add type_is_local_kptr wrapper to avoid noisy checks (Dave)
  * Remove unused flags parameter from bpf_kptr_new (Alexei)
  * Rename bpf_kptr_new -> bpf_obj_new, bpf_kptr_drop -> bpf_obj_drop (Alexei)
  * Reword comment in ref_obj_id_set_release_on_unlock (Dave)
  * Fix return type of ref_obj_id_set_release_on_unlock (Dave)
  * Introduce is_bpf_list_api_kfunc to dedup checks (Dave)
  * Disallow BPF_WRITE to untrusted local kptrs
  * Add details about soundness of check_reg_allocation_locked logic
  * List untrusted local kptrs for PROBE_MEM handling

 v1 -> v2
 v1: https://lore.kernel.org/bpf/20221011012240.3149-1-memxor@gmail.com

  * Rebase on bpf-next to resolve merge conflict in DENYLIST.s390x
  * Fix a couple of mental lapses in bpf_list_head_free

 RFC v1 -> v1
 RFC v1: https://lore.kernel.org/bpf/20220904204145.3089-1-memxor@gmail.com

  * Mostly a complete rewrite of BTF parsing, refactor existing code (Kartikeya)
  * Rebase kfunc rewrite for bpf-next, add support for more changes
  * Cache type metadata in BTF to avoid recomputation inside verifier (Kartikeya)
  * Remove __kernel tag, make things similar to map values, reserve bpf_ prefix
  * bpf_kptr_new, bpf_kptr_drop
  * Rename precision state enum values (Alexei)
  * Drop explicit constructor/destructor support (Alexei)
  * Rewrite code for constructing/destructing objects and offload to runtime
  * Minimize duplication in bpf_map_value_off_desc handling (Alexei)
  * Expose global memory allocator (Alexei)
  * Address other nits from Alexei
  * Split out local kptrs in maps, more kptrs in maps support into a follow up

Links:
------
 * Dave's BPF RB-Tree RFC series
   v1 (Discussion thread)
     https://lore.kernel.org/bpf/20220722183438.3319790-1-davemarchevsky@fb.com
   v2 (With support for static locks)
     https://lore.kernel.org/bpf/20220830172759.4069786-1-davemarchevsky@fb.com
 * BPF Linked Lists Discussion
   https://lore.kernel.org/bpf/CAP01T74U30+yeBHEgmgzTJ-XYxZ0zj71kqCDJtTH9YQNfTK+Xw@mail.gmail.com
 * BPF Memory Allocator from Alexei
   https://lore.kernel.org/bpf/20220902211058.60789-1-alexei.starovoitov@gmail.com
 * BPF Memory Allocator UAPI Discussion
   https://lore.kernel.org/bpf/d3f76b27f4e55ec9e400ae8dcaecbb702a4932e8.camel@fb.com

Kumar Kartikeya Dwivedi (24):
  bpf: Document UAPI details for special BPF types
  bpf: Allow specifying volatile type modifier for kptrs
  bpf: Clobber stack slot when writing over spilled PTR_TO_BTF_ID
  bpf: Fix slot type check in check_stack_write_var_off
  bpf: Drop reg_type_may_be_refcounted_or_null
  bpf: Refactor kptr_off_tab into btf_record
  bpf: Consolidate spin_lock, timer management into btf_record
  bpf: Refactor map->off_arr handling
  bpf: Support bpf_list_head in map values
  bpf: Introduce local kptrs
  bpf: Recognize bpf_{spin_lock,list_head,list_node} in local kptrs
  bpf: Verify ownership relationships for user BTF types
  bpf: Support locking bpf_spin_lock in local kptr
  bpf: Allow locking bpf_spin_lock global variables
  bpf: Rewrite kfunc argument handling
  bpf: Drop kfunc bits from btf_check_func_arg_match
  bpf: Support constant scalar arguments for kfuncs
  bpf: Teach verifier about non-size constant arguments
  bpf: Introduce bpf_obj_new
  bpf: Introduce bpf_obj_drop
  bpf: Permit NULL checking pointer with non-zero fixed offset
  bpf: Introduce single ownership BPF linked list API
  selftests/bpf: Add __contains macro to bpf_experimental.h
  selftests/bpf: Add BPF linked list API tests

 Documentation/bpf/bpf_design_QA.rst           |   44 +
 Documentation/bpf/kfuncs.rst                  |   30 +
 include/linux/bpf.h                           |  256 ++-
 include/linux/bpf_verifier.h                  |   22 +-
 include/linux/btf.h                           |   77 +-
 include/linux/filter.h                        |    8 +-
 include/uapi/linux/bpf.h                      |   10 +
 kernel/bpf/arraymap.c                         |   30 +-
 kernel/bpf/bpf_local_storage.c                |    2 +-
 kernel/bpf/btf.c                              | 1205 +++++++------
 kernel/bpf/core.c                             |   16 +
 kernel/bpf/hashtab.c                          |   38 +-
 kernel/bpf/helpers.c                          |  141 +-
 kernel/bpf/local_storage.c                    |    2 +-
 kernel/bpf/map_in_map.c                       |   19 +-
 kernel/bpf/syscall.c                          |  401 +++--
 kernel/bpf/verifier.c                         | 1504 ++++++++++++++---
 net/bpf/bpf_dummy_struct_ops.c                |   14 +-
 net/core/bpf_sk_storage.c                     |    4 +-
 net/core/filter.c                             |   34 +-
 net/ipv4/bpf_tcp_ca.c                         |   13 +-
 net/netfilter/nf_conntrack_bpf.c              |   17 +-
 tools/include/uapi/linux/bpf.h                |   10 +
 tools/testing/selftests/bpf/DENYLIST.s390x    |    1 +
 .../testing/selftests/bpf/bpf_experimental.h  |   63 +
 .../bpf/prog_tests/kfunc_dynptr_param.c       |    2 +-
 .../selftests/bpf/prog_tests/linked_list.c    |   79 +
 .../testing/selftests/bpf/progs/linked_list.c |  330 ++++
 tools/testing/selftests/bpf/verifier/calls.c  |    4 +-
 .../selftests/bpf/verifier/ref_tracking.c     |    4 +-
 30 files changed, 3190 insertions(+), 1190 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/bpf_experimental.h
 create mode 100644 tools/testing/selftests/bpf/prog_tests/linked_list.c
 create mode 100644 tools/testing/selftests/bpf/progs/linked_list.c


base-commit: d9095f92950bd16745b9ec24ebebc12d14b3a3e8
-- 
2.38.1

[PATCH bpf-next v4 01/24] bpf: Document UAPI details for special BPF types

[Kumar Kartikeya Dwivedi]

The kernel recognizes some special BPF types in map values or local
kptrs. Document that only bpf_spin_lock and bpf_timer will preserve
backwards compatibility, and kptr will preserve backwards compatibility
for the operations on the pointer, not the types supported for such
kptrs.

For local kptrs, document that there are no stability guarantees at all.

Finally, document that 'bpf_' namespace is reserved for adding future
special fields, hence BPF programs must not declare types with such
names in their programs and still expect backwards compatibility.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 Documentation/bpf/bpf_design_QA.rst | 44 +++++++++++++++++++++++++++++
 1 file changed, 44 insertions(+)

diff --git a/Documentation/bpf/bpf_design_QA.rst b/Documentation/bpf/bpf_design_QA.rst
index a210b8a4df00..b5273148497c 100644
--- a/Documentation/bpf/bpf_design_QA.rst
+++ b/Documentation/bpf/bpf_design_QA.rst
@@ -298,3 +298,47 @@ A: NO.
 
 The BTF_ID macro does not cause a function to become part of the ABI
 any more than does the EXPORT_SYMBOL_GPL macro.
+
+Q: What is the compatibility story for special BPF types in map values?
+-----------------------------------------------------------------------
+Q: Users are allowed to embed bpf_spin_lock, bpf_timer fields in their BPF map
+values (when using BTF support for BPF maps). This allows to use helpers for
+such objects on these fields inside map values. Users are also allowed to embed
+pointers to some kernel types (with __kptr and __kptr_ref BTF tags). Will the
+kernel preserve backwards compatibility for these features?
+
+A: It depends. For bpf_spin_lock, bpf_timer: YES, for kptr and everything else:
+NO, but see below.
+
+For struct types that have been added already, like bpf_spin_lock and bpf_timer,
+the kernel will preserve backwards compatibility, as they are part of UAPI.
+
+For kptrs, they are also part of UAPI, but only with respect to the kptr
+mechanism. The types that you can use with a __kptr and __kptr_ref tagged
+pointer in your struct is NOT part of the UAPI contract. The supported types can
+and will change across kernel releases. However, operations like accessing kptr
+fields and bpf_kptr_xchg() helper will continue to be supported across kernel
+releases for the supported types.
+
+For any other supported struct type, unless explicitly stated in this document
+and added to bpf.h UAPI header, such types can and will arbitrarily change their
+size, type, and alignment, or any other user visible API or ABI detail across
+kernel releases. The users must adapt their BPF programs to the new changes and
+update them to make sure their programs continue to work correctly.
+
+NOTE: BPF subsystem specially reserves the 'bpf_' prefix for type names, in
+order to introduce more special fields in the future. Hence, user programs must
+avoid defining types with 'bpf_' prefix to not be broken in future releases. In
+other words, no backwards compatibility is guaranteed if one using a type in BTF
+with 'bpf_' prefix.
+
+Q: What is the compatibility story for special BPF types in local kptrs?
+------------------------------------------------------------------------
+Q: Same as above, but for local kptrs (i.e. pointers to objects allocated using
+bpf_obj_new for user defined structures). Will the kernel preserve backwards
+compatibility for these features?
+
+A: NO.
+
+Unlike map value types, there are no stability guarantees for this case. The
+whole local kptr API itself is unstable (since it is exposed through kfuncs).
-- 
2.38.1

[PATCH bpf-next v4 02/24] bpf: Allow specifying volatile type modifier for kptrs

[Kumar Kartikeya Dwivedi]

This is useful in particular to mark the pointer as volatile, so that
compiler treats each load and store to the field as a volatile access.
The alternative is having to define and use READ_ONCE and WRITE_ONCE in
the BPF program.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 include/linux/btf.h | 5 +++++
 kernel/bpf/btf.c    | 3 +++
 2 files changed, 8 insertions(+)

diff --git a/include/linux/btf.h b/include/linux/btf.h
index f9aababc5d78..86aad9b2ce02 100644
--- a/include/linux/btf.h
+++ b/include/linux/btf.h
@@ -288,6 +288,11 @@ static inline bool btf_type_is_typedef(const struct btf_type *t)
 	return BTF_INFO_KIND(t->info) == BTF_KIND_TYPEDEF;
 }
 
+static inline bool btf_type_is_volatile(const struct btf_type *t)
+{
+	return BTF_INFO_KIND(t->info) == BTF_KIND_VOLATILE;
+}
+
 static inline bool btf_type_is_func(const struct btf_type *t)
 {
 	return BTF_INFO_KIND(t->info) == BTF_KIND_FUNC;
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 35c07afac924..f4d21eef6ebd 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -3225,6 +3225,9 @@ static int btf_find_kptr(const struct btf *btf, const struct btf_type *t,
 	enum bpf_kptr_type type;
 	u32 res_id;
 
+	/* Permit modifiers on the pointer itself */
+	if (btf_type_is_volatile(t))
+		t = btf_type_by_id(btf, t->type);
 	/* For PTR, sz is always == 8 */
 	if (!btf_type_is_ptr(t))
 		return BTF_FIELD_IGNORE;
-- 
2.38.1

[PATCH bpf-next v4 03/24] bpf: Clobber stack slot when writing over spilled PTR_TO_BTF_ID

[Kumar Kartikeya Dwivedi]

When support was added for spilled PTR_TO_BTF_ID to be accessed by
helper memory access, the stack slot was not overwritten to STACK_MISC
(and that too is only safe when env->allow_ptr_leaks is true).

This means that helpers who take ARG_PTR_TO_MEM and write to it may
essentially overwrite the value while the verifier continues to track
the slot for spilled register.

This can cause issues when PTR_TO_BTF_ID is spilled to stack, and then
overwritten by helper write access, which can then be passed to BPF
helpers or kfuncs.

Handle this by falling back to the case introduced in a later commit,
which will also handle PTR_TO_BTF_ID along with other pointer types,
i.e. cd17d38f8b28 ("bpf: Permits pointers on stack for helper calls").

Finally, include a comment on why REG_LIVE_WRITTEN is not being set when
clobber is set to true. In short, the reason is that while when clobber
is unset, we know that we won't be writing, when it is true, we *may*
write to any of the stack slots in that range. It may be a partial or
complete write, to just one or many stack slots.

We cannot be sure, hence to be conservative, we leave things as is and
never set REG_LIVE_WRITTEN for any stack slot. However, clobber still
needs to reset them to STACK_MISC assuming writes happened. However read
marks still need to be propagated upwards from liveness point of view,
as parent stack slot's contents may still continue to matter to child
states.

Cc: Yonghong Song <yhs@meta.com>
Fixes: 1d68f22b3d53 ("bpf: Handle spilled PTR_TO_BTF_ID properly when checking stack_boundary")
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 kernel/bpf/verifier.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 82c07fe0bfb1..7bf12c492201 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -5154,10 +5154,6 @@ static int check_stack_range_initialized(
 			goto mark;
 		}
 
-		if (is_spilled_reg(&state->stack[spi]) &&
-		    base_type(state->stack[spi].spilled_ptr.type) == PTR_TO_BTF_ID)
-			goto mark;
-
 		if (is_spilled_reg(&state->stack[spi]) &&
 		    (state->stack[spi].spilled_ptr.type == SCALAR_VALUE ||
 		     env->allow_ptr_leaks)) {
@@ -5188,6 +5184,11 @@ static int check_stack_range_initialized(
 		mark_reg_read(env, &state->stack[spi].spilled_ptr,
 			      state->stack[spi].spilled_ptr.parent,
 			      REG_LIVE_READ64);
+		/* We do not set REG_LIVE_WRITTEN for stack slot, as we can not
+		 * be sure that whether stack slot is written to or not. Hence,
+		 * we must still conservatively propagate reads upwards even if
+		 * helper may write to the entire memory range.
+		 */
 	}
 	return update_stack_depth(env, state, min_off);
 }
-- 
2.38.1

[PATCH bpf-next v4 04/24] bpf: Fix slot type check in check_stack_write_var_off

[Kumar Kartikeya Dwivedi]

For the case where allow_ptr_leaks is false, code is checking whether
slot type is STACK_INVALID and STACK_SPILL and rejecting other cases.
This is a consequence of incorrectly checking for register type instead
of the slot type (NOT_INIT and SCALAR_VALUE respectively). Fix the
check.

Fixes: 01f810ace9ed ("bpf: Allow variable-offset stack access")
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 kernel/bpf/verifier.c | 19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 7bf12c492201..eb111a8034e7 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -3181,14 +3181,17 @@ static int check_stack_write_var_off(struct bpf_verifier_env *env,
 		stype = &state->stack[spi].slot_type[slot % BPF_REG_SIZE];
 		mark_stack_slot_scratched(env, spi);
 
-		if (!env->allow_ptr_leaks
-				&& *stype != NOT_INIT
-				&& *stype != SCALAR_VALUE) {
-			/* Reject the write if there's are spilled pointers in
-			 * range. If we didn't reject here, the ptr status
-			 * would be erased below (even though not all slots are
-			 * actually overwritten), possibly opening the door to
-			 * leaks.
+		if (!env->allow_ptr_leaks && *stype != STACK_MISC && *stype != STACK_ZERO) {
+			/* Reject the write if range we may write to has not
+			 * been initialized beforehand. If we didn't reject
+			 * here, the ptr status would be erased below (even
+			 * though not all slots are actually overwritten),
+			 * possibly opening the door to leaks.
+			 *
+			 * We do however catch STACK_INVALID case below, and
+			 * only allow reading possibly uninitialized memory
+			 * later for CAP_PERFMON, as the write may not happen to
+			 * that slot.
 			 */
 			verbose(env, "spilled ptr in range of var-offset stack write; insn %d, ptr off: %d",
 				insn_idx, i);
-- 
2.38.1

[PATCH bpf-next v4 05/24] bpf: Drop reg_type_may_be_refcounted_or_null

[Kumar Kartikeya Dwivedi]

It is not scalable to maintain a list of types that can have non-zero
ref_obj_id. It is never set for scalars anyway, so just remove the
conditional on register types and print it whenever it is non-zero.

Acked-by: Dave Marchevsky <davemarchevsky@fb.com>
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 kernel/bpf/verifier.c | 9 +--------
 1 file changed, 1 insertion(+), 8 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index eb111a8034e7..14d350a25d5d 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -457,13 +457,6 @@ static bool reg_may_point_to_spin_lock(const struct bpf_reg_state *reg)
 		map_value_has_spin_lock(reg->map_ptr);
 }
 
-static bool reg_type_may_be_refcounted_or_null(enum bpf_reg_type type)
-{
-	type = base_type(type);
-	return type == PTR_TO_SOCKET || type == PTR_TO_TCP_SOCK ||
-		type == PTR_TO_MEM || type == PTR_TO_BTF_ID;
-}
-
 static bool type_is_rdonly_mem(u32 type)
 {
 	return type & MEM_RDONLY;
@@ -875,7 +868,7 @@ static void print_verifier_state(struct bpf_verifier_env *env,
 
 			if (reg->id)
 				verbose_a("id=%d", reg->id);
-			if (reg_type_may_be_refcounted_or_null(t) && reg->ref_obj_id)
+			if (reg->ref_obj_id)
 				verbose_a("ref_obj_id=%d", reg->ref_obj_id);
 			if (t != SCALAR_VALUE)
 				verbose_a("off=%d", reg->off);
-- 
2.38.1

[PATCH bpf-next v4 06/24] bpf: Refactor kptr_off_tab into btf_record

[Kumar Kartikeya Dwivedi]

To prepare the BPF verifier to handle special fields in both map values
and program allocated types coming from program BTF, we need to refactor
the kptr_off_tab handling code into something more generic and reusable
across both cases to avoid code duplication.

Later patches also require passing this data to helpers at runtime, so
that they can work on user defined types, initialize them, destruct
them, etc.

The main observation is that both map values and such allocated types
point to a type in program BTF, hence they can be handled similarly. We
can prepare a field metadata table for both cases and store them in
struct bpf_map or struct btf depending on the use case.

Hence, refactor the code into generic btf_record and btf_field member
structs. The btf_record represents the fields of a specific btf_type in
user BTF. The cnt indicates the number of special fields we successfully
recognized, and field_mask is a bitmask of fields that were found, to
enable quick determination of availability of a certain field.

Subsequently, refactor the rest of the code to work with these generic
types, remove assumptions about kptr and kptr_off_tab, rename variables
to more meaningful names, etc.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 include/linux/bpf.h     | 125 ++++++++++++-------
 include/linux/btf.h     |   3 +-
 kernel/bpf/arraymap.c   |  13 +-
 kernel/bpf/btf.c        |  67 +++++-----
 kernel/bpf/hashtab.c    |  14 +--
 kernel/bpf/map_in_map.c |  14 ++-
 kernel/bpf/syscall.c    | 263 +++++++++++++++++++++++-----------------
 kernel/bpf/verifier.c   |  96 +++++++--------
 8 files changed, 332 insertions(+), 263 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 8d948bfcb984..1440e7c3c510 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -165,35 +165,41 @@ struct bpf_map_ops {
 };
 
 enum {
-	/* Support at most 8 pointers in a BPF map value */
-	BPF_MAP_VALUE_OFF_MAX = 8,
-	BPF_MAP_OFF_ARR_MAX   = BPF_MAP_VALUE_OFF_MAX +
+	/* Support at most 8 pointers in a BTF type */
+	BTF_FIELDS_MAX	      = 8,
+	BPF_MAP_OFF_ARR_MAX   = BTF_FIELDS_MAX +
 				1 + /* for bpf_spin_lock */
 				1,  /* for bpf_timer */
 };
 
-enum bpf_kptr_type {
-	BPF_KPTR_UNREF,
-	BPF_KPTR_REF,
+enum btf_field_type {
+	BPF_KPTR_UNREF = (1 << 2),
+	BPF_KPTR_REF   = (1 << 3),
+	BPF_KPTR       = BPF_KPTR_UNREF | BPF_KPTR_REF,
 };
 
-struct bpf_map_value_off_desc {
+struct btf_field_kptr {
+	struct btf *btf;
+	struct module *module;
+	btf_dtor_kfunc_t dtor;
+	u32 btf_id;
+};
+
+struct btf_field {
 	u32 offset;
-	enum bpf_kptr_type type;
-	struct {
-		struct btf *btf;
-		struct module *module;
-		btf_dtor_kfunc_t dtor;
-		u32 btf_id;
-	} kptr;
+	enum btf_field_type type;
+	union {
+		struct btf_field_kptr kptr;
+	};
 };
 
-struct bpf_map_value_off {
-	u32 nr_off;
-	struct bpf_map_value_off_desc off[];
+struct btf_record {
+	u32 cnt;
+	u32 field_mask;
+	struct btf_field fields[];
 };
 
-struct bpf_map_off_arr {
+struct btf_field_offs {
 	u32 cnt;
 	u32 field_off[BPF_MAP_OFF_ARR_MAX];
 	u8 field_sz[BPF_MAP_OFF_ARR_MAX];
@@ -215,7 +221,7 @@ struct bpf_map {
 	u64 map_extra; /* any per-map-type extra fields */
 	u32 map_flags;
 	int spin_lock_off; /* >=0 valid offset, <0 error */
-	struct bpf_map_value_off *kptr_off_tab;
+	struct btf_record *record;
 	int timer_off; /* >=0 valid offset, <0 error */
 	u32 id;
 	int numa_node;
@@ -227,7 +233,7 @@ struct bpf_map {
 	struct obj_cgroup *objcg;
 #endif
 	char name[BPF_OBJ_NAME_LEN];
-	struct bpf_map_off_arr *off_arr;
+	struct btf_field_offs *field_offs;
 	/* The 3rd and 4th cacheline with misc members to avoid false sharing
 	 * particularly with refcounting.
 	 */
@@ -251,6 +257,37 @@ struct bpf_map {
 	bool frozen; /* write-once; write-protected by freeze_mutex */
 };
 
+static inline u32 btf_field_type_size(enum btf_field_type type)
+{
+	switch (type) {
+	case BPF_KPTR_UNREF:
+	case BPF_KPTR_REF:
+		return sizeof(u64);
+	default:
+		WARN_ON_ONCE(1);
+		return 0;
+	}
+}
+
+static inline u32 btf_field_type_align(enum btf_field_type type)
+{
+	switch (type) {
+	case BPF_KPTR_UNREF:
+	case BPF_KPTR_REF:
+		return __alignof__(u64);
+	default:
+		WARN_ON_ONCE(1);
+		return 0;
+	}
+}
+
+static inline bool btf_record_has_field(const struct btf_record *rec, enum btf_field_type type)
+{
+	if (IS_ERR_OR_NULL(rec))
+		return false;
+	return rec->field_mask & type;
+}
+
 static inline bool map_value_has_spin_lock(const struct bpf_map *map)
 {
 	return map->spin_lock_off >= 0;
@@ -261,23 +298,19 @@ static inline bool map_value_has_timer(const struct bpf_map *map)
 	return map->timer_off >= 0;
 }
 
-static inline bool map_value_has_kptrs(const struct bpf_map *map)
-{
-	return !IS_ERR_OR_NULL(map->kptr_off_tab);
-}
-
 static inline void check_and_init_map_value(struct bpf_map *map, void *dst)
 {
 	if (unlikely(map_value_has_spin_lock(map)))
 		memset(dst + map->spin_lock_off, 0, sizeof(struct bpf_spin_lock));
 	if (unlikely(map_value_has_timer(map)))
 		memset(dst + map->timer_off, 0, sizeof(struct bpf_timer));
-	if (unlikely(map_value_has_kptrs(map))) {
-		struct bpf_map_value_off *tab = map->kptr_off_tab;
+	if (!IS_ERR_OR_NULL(map->record)) {
+		struct btf_field *fields = map->record->fields;
+		u32 cnt = map->record->cnt;
 		int i;
 
-		for (i = 0; i < tab->nr_off; i++)
-			*(u64 *)(dst + tab->off[i].offset) = 0;
+		for (i = 0; i < cnt; i++)
+			memset(dst + fields[i].offset, 0, btf_field_type_size(fields[i].type));
 	}
 }
 
@@ -303,7 +336,7 @@ static inline void __copy_map_value(struct bpf_map *map, void *dst, void *src, b
 	u32 curr_off = 0;
 	int i;
 
-	if (likely(!map->off_arr)) {
+	if (likely(!map->field_offs)) {
 		if (long_memcpy)
 			bpf_long_memcpy(dst, src, round_up(map->value_size, 8));
 		else
@@ -311,11 +344,12 @@ static inline void __copy_map_value(struct bpf_map *map, void *dst, void *src, b
 		return;
 	}
 
-	for (i = 0; i < map->off_arr->cnt; i++) {
-		u32 next_off = map->off_arr->field_off[i];
+	for (i = 0; i < map->field_offs->cnt; i++) {
+		u32 next_off = map->field_offs->field_off[i];
+		u32 sz = next_off - curr_off;
 
-		memcpy(dst + curr_off, src + curr_off, next_off - curr_off);
-		curr_off += map->off_arr->field_sz[i];
+		memcpy(dst + curr_off, src + curr_off, sz);
+		curr_off += map->field_offs->field_sz[i] + sz;
 	}
 	memcpy(dst + curr_off, src + curr_off, map->value_size - curr_off);
 }
@@ -335,16 +369,17 @@ static inline void zero_map_value(struct bpf_map *map, void *dst)
 	u32 curr_off = 0;
 	int i;
 
-	if (likely(!map->off_arr)) {
+	if (likely(!map->field_offs)) {
 		memset(dst, 0, map->value_size);
 		return;
 	}
 
-	for (i = 0; i < map->off_arr->cnt; i++) {
-		u32 next_off = map->off_arr->field_off[i];
+	for (i = 0; i < map->field_offs->cnt; i++) {
+		u32 next_off = map->field_offs->field_off[i];
+		u32 sz = next_off - curr_off;
 
-		memset(dst + curr_off, 0, next_off - curr_off);
-		curr_off += map->off_arr->field_sz[i];
+		memset(dst + curr_off, 0, sz);
+		curr_off += map->field_offs->field_sz[i] + sz;
 	}
 	memset(dst + curr_off, 0, map->value_size - curr_off);
 }
@@ -1699,11 +1734,13 @@ void bpf_prog_put(struct bpf_prog *prog);
 void bpf_prog_free_id(struct bpf_prog *prog, bool do_idr_lock);
 void bpf_map_free_id(struct bpf_map *map, bool do_idr_lock);
 
-struct bpf_map_value_off_desc *bpf_map_kptr_off_contains(struct bpf_map *map, u32 offset);
-void bpf_map_free_kptr_off_tab(struct bpf_map *map);
-struct bpf_map_value_off *bpf_map_copy_kptr_off_tab(const struct bpf_map *map);
-bool bpf_map_equal_kptr_off_tab(const struct bpf_map *map_a, const struct bpf_map *map_b);
-void bpf_map_free_kptrs(struct bpf_map *map, void *map_value);
+struct btf_field *btf_record_find(const struct btf_record *rec,
+				  u32 offset, enum btf_field_type type);
+void btf_record_free(struct btf_record *rec);
+void bpf_map_free_record(struct bpf_map *map);
+struct btf_record *btf_record_dup(const struct btf_record *rec);
+bool btf_record_equal(const struct btf_record *rec_a, const struct btf_record *rec_b);
+void bpf_obj_free_fields(const struct btf_record *rec, void *obj);
 
 struct bpf_map *bpf_map_get(u32 ufd);
 struct bpf_map *bpf_map_get_with_uref(u32 ufd);
diff --git a/include/linux/btf.h b/include/linux/btf.h
index 86aad9b2ce02..9e62717cdc7a 100644
--- a/include/linux/btf.h
+++ b/include/linux/btf.h
@@ -163,8 +163,7 @@ bool btf_member_is_reg_int(const struct btf *btf, const struct btf_type *s,
 			   u32 expected_offset, u32 expected_size);
 int btf_find_spin_lock(const struct btf *btf, const struct btf_type *t);
 int btf_find_timer(const struct btf *btf, const struct btf_type *t);
-struct bpf_map_value_off *btf_parse_kptrs(const struct btf *btf,
-					  const struct btf_type *t);
+struct btf_record *btf_parse_fields(const struct btf *btf, const struct btf_type *t);
 bool btf_type_is_void(const struct btf_type *t);
 s32 btf_find_by_name_kind(const struct btf *btf, const char *name, u8 kind);
 const struct btf_type *btf_type_skip_modifiers(const struct btf *btf,
diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
index 832b2659e96e..417f84342e98 100644
--- a/kernel/bpf/arraymap.c
+++ b/kernel/bpf/arraymap.c
@@ -310,8 +310,7 @@ static void check_and_free_fields(struct bpf_array *arr, void *val)
 {
 	if (map_value_has_timer(&arr->map))
 		bpf_timer_cancel_and_free(val + arr->map.timer_off);
-	if (map_value_has_kptrs(&arr->map))
-		bpf_map_free_kptrs(&arr->map, val);
+	bpf_obj_free_fields(arr->map.record, val);
 }
 
 /* Called from syscall or from eBPF program */
@@ -409,7 +408,7 @@ static void array_map_free_timers(struct bpf_map *map)
 	struct bpf_array *array = container_of(map, struct bpf_array, map);
 	int i;
 
-	/* We don't reset or free kptr on uref dropping to zero. */
+	/* We don't reset or free fields other than timer on uref dropping to zero. */
 	if (!map_value_has_timer(map))
 		return;
 
@@ -423,22 +422,22 @@ static void array_map_free(struct bpf_map *map)
 	struct bpf_array *array = container_of(map, struct bpf_array, map);
 	int i;
 
-	if (map_value_has_kptrs(map)) {
+	if (!IS_ERR_OR_NULL(map->record)) {
 		if (array->map.map_type == BPF_MAP_TYPE_PERCPU_ARRAY) {
 			for (i = 0; i < array->map.max_entries; i++) {
 				void __percpu *pptr = array->pptrs[i & array->index_mask];
 				int cpu;
 
 				for_each_possible_cpu(cpu) {
-					bpf_map_free_kptrs(map, per_cpu_ptr(pptr, cpu));
+					bpf_obj_free_fields(map->record, per_cpu_ptr(pptr, cpu));
 					cond_resched();
 				}
 			}
 		} else {
 			for (i = 0; i < array->map.max_entries; i++)
-				bpf_map_free_kptrs(map, array_map_elem_ptr(array, i));
+				bpf_obj_free_fields(map->record, array_map_elem_ptr(array, i));
 		}
-		bpf_map_free_kptr_off_tab(map);
+		bpf_map_free_record(map);
 	}
 
 	if (array->map.map_type == BPF_MAP_TYPE_PERCPU_ARRAY)
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index f4d21eef6ebd..ffd687c7420d 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -3191,7 +3191,7 @@ static void btf_struct_log(struct btf_verifier_env *env,
 	btf_verifier_log(env, "size=%u vlen=%u", t->size, btf_type_vlen(t));
 }
 
-enum btf_field_type {
+enum btf_field_info_type {
 	BTF_FIELD_SPIN_LOCK,
 	BTF_FIELD_TIMER,
 	BTF_FIELD_KPTR,
@@ -3203,9 +3203,9 @@ enum {
 };
 
 struct btf_field_info {
-	u32 type_id;
+	enum btf_field_type type;
 	u32 off;
-	enum bpf_kptr_type type;
+	u32 type_id;
 };
 
 static int btf_find_struct(const struct btf *btf, const struct btf_type *t,
@@ -3222,7 +3222,7 @@ static int btf_find_struct(const struct btf *btf, const struct btf_type *t,
 static int btf_find_kptr(const struct btf *btf, const struct btf_type *t,
 			 u32 off, int sz, struct btf_field_info *info)
 {
-	enum bpf_kptr_type type;
+	enum btf_field_type type;
 	u32 res_id;
 
 	/* Permit modifiers on the pointer itself */
@@ -3259,7 +3259,7 @@ static int btf_find_kptr(const struct btf *btf, const struct btf_type *t,
 
 static int btf_find_struct_field(const struct btf *btf, const struct btf_type *t,
 				 const char *name, int sz, int align,
-				 enum btf_field_type field_type,
+				 enum btf_field_info_type field_type,
 				 struct btf_field_info *info, int info_cnt)
 {
 	const struct btf_member *member;
@@ -3311,7 +3311,7 @@ static int btf_find_struct_field(const struct btf *btf, const struct btf_type *t
 
 static int btf_find_datasec_var(const struct btf *btf, const struct btf_type *t,
 				const char *name, int sz, int align,
-				enum btf_field_type field_type,
+				enum btf_field_info_type field_type,
 				struct btf_field_info *info, int info_cnt)
 {
 	const struct btf_var_secinfo *vsi;
@@ -3360,7 +3360,7 @@ static int btf_find_datasec_var(const struct btf *btf, const struct btf_type *t,
 }
 
 static int btf_find_field(const struct btf *btf, const struct btf_type *t,
-			  enum btf_field_type field_type,
+			  enum btf_field_info_type field_type,
 			  struct btf_field_info *info, int info_cnt)
 {
 	const char *name;
@@ -3423,14 +3423,13 @@ int btf_find_timer(const struct btf *btf, const struct btf_type *t)
 	return info.off;
 }
 
-struct bpf_map_value_off *btf_parse_kptrs(const struct btf *btf,
-					  const struct btf_type *t)
+struct btf_record *btf_parse_fields(const struct btf *btf, const struct btf_type *t)
 {
-	struct btf_field_info info_arr[BPF_MAP_VALUE_OFF_MAX];
-	struct bpf_map_value_off *tab;
+	struct btf_field_info info_arr[BTF_FIELDS_MAX];
 	struct btf *kernel_btf = NULL;
 	struct module *mod = NULL;
-	int ret, i, nr_off;
+	struct btf_record *rec;
+	int ret, i, cnt;
 
 	ret = btf_find_field(btf, t, BTF_FIELD_KPTR, info_arr, ARRAY_SIZE(info_arr));
 	if (ret < 0)
@@ -3438,12 +3437,12 @@ struct bpf_map_value_off *btf_parse_kptrs(const struct btf *btf,
 	if (!ret)
 		return NULL;
 
-	nr_off = ret;
-	tab = kzalloc(offsetof(struct bpf_map_value_off, off[nr_off]), GFP_KERNEL | __GFP_NOWARN);
-	if (!tab)
+	cnt = ret;
+	rec = kzalloc(offsetof(struct btf_record, fields[cnt]), GFP_KERNEL | __GFP_NOWARN);
+	if (!rec)
 		return ERR_PTR(-ENOMEM);
-
-	for (i = 0; i < nr_off; i++) {
+	rec->cnt = 0;
+	for (i = 0; i < cnt; i++) {
 		const struct btf_type *t;
 		s32 id;
 
@@ -3500,28 +3499,24 @@ struct bpf_map_value_off *btf_parse_kptrs(const struct btf *btf,
 				ret = -EINVAL;
 				goto end_mod;
 			}
-			tab->off[i].kptr.dtor = (void *)addr;
+			rec->fields[i].kptr.dtor = (void *)addr;
 		}
 
-		tab->off[i].offset = info_arr[i].off;
-		tab->off[i].type = info_arr[i].type;
-		tab->off[i].kptr.btf_id = id;
-		tab->off[i].kptr.btf = kernel_btf;
-		tab->off[i].kptr.module = mod;
+		rec->fields[i].offset = info_arr[i].off;
+		rec->fields[i].type = info_arr[i].type;
+		rec->fields[i].kptr.btf_id = id;
+		rec->fields[i].kptr.btf = kernel_btf;
+		rec->fields[i].kptr.module = mod;
+		rec->cnt++;
 	}
-	tab->nr_off = nr_off;
-	return tab;
+	rec->cnt = cnt;
+	return rec;
 end_mod:
 	module_put(mod);
 end_btf:
 	btf_put(kernel_btf);
 end:
-	while (i--) {
-		btf_put(tab->off[i].kptr.btf);
-		if (tab->off[i].kptr.module)
-			module_put(tab->off[i].kptr.module);
-	}
-	kfree(tab);
+	btf_record_free(rec);
 	return ERR_PTR(ret);
 }
 
@@ -6370,7 +6365,7 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
 
 		/* kptr_get is only true for kfunc */
 		if (i == 0 && kptr_get) {
-			struct bpf_map_value_off_desc *off_desc;
+			struct btf_field *kptr_field;
 
 			if (reg->type != PTR_TO_MAP_VALUE) {
 				bpf_log(log, "arg#0 expected pointer to map value\n");
@@ -6386,8 +6381,8 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
 				return -EINVAL;
 			}
 
-			off_desc = bpf_map_kptr_off_contains(reg->map_ptr, reg->off + reg->var_off.value);
-			if (!off_desc || off_desc->type != BPF_KPTR_REF) {
+			kptr_field = btf_record_find(reg->map_ptr->record, reg->off + reg->var_off.value, BPF_KPTR);
+			if (!kptr_field || kptr_field->type != BPF_KPTR_REF) {
 				bpf_log(log, "arg#0 no referenced kptr at map value offset=%llu\n",
 					reg->off + reg->var_off.value);
 				return -EINVAL;
@@ -6406,8 +6401,8 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
 					func_name, i, btf_type_str(ref_t), ref_tname);
 				return -EINVAL;
 			}
-			if (!btf_struct_ids_match(log, btf, ref_id, 0, off_desc->kptr.btf,
-						  off_desc->kptr.btf_id, true)) {
+			if (!btf_struct_ids_match(log, btf, ref_id, 0, kptr_field->kptr.btf,
+						  kptr_field->kptr.btf_id, true)) {
 				bpf_log(log, "kernel function %s args#%d expected pointer to %s %s\n",
 					func_name, i, btf_type_str(ref_t), ref_tname);
 				return -EINVAL;
diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
index f39ee3e05589..c5ea8f9bb7a9 100644
--- a/kernel/bpf/hashtab.c
+++ b/kernel/bpf/hashtab.c
@@ -238,21 +238,20 @@ static void htab_free_prealloced_timers(struct bpf_htab *htab)
 	}
 }
 
-static void htab_free_prealloced_kptrs(struct bpf_htab *htab)
+static void htab_free_prealloced_fields(struct bpf_htab *htab)
 {
 	u32 num_entries = htab->map.max_entries;
 	int i;
 
-	if (!map_value_has_kptrs(&htab->map))
+	if (IS_ERR_OR_NULL(htab->map.record))
 		return;
 	if (htab_has_extra_elems(htab))
 		num_entries += num_possible_cpus();
-
 	for (i = 0; i < num_entries; i++) {
 		struct htab_elem *elem;
 
 		elem = get_htab_elem(htab, i);
-		bpf_map_free_kptrs(&htab->map, elem->key + round_up(htab->map.key_size, 8));
+		bpf_obj_free_fields(htab->map.record, elem->key + round_up(htab->map.key_size, 8));
 		cond_resched();
 	}
 }
@@ -766,8 +765,7 @@ static void check_and_free_fields(struct bpf_htab *htab,
 
 	if (map_value_has_timer(&htab->map))
 		bpf_timer_cancel_and_free(map_value + htab->map.timer_off);
-	if (map_value_has_kptrs(&htab->map))
-		bpf_map_free_kptrs(&htab->map, map_value);
+	bpf_obj_free_fields(htab->map.record, map_value);
 }
 
 /* It is called from the bpf_lru_list when the LRU needs to delete
@@ -1517,11 +1515,11 @@ static void htab_map_free(struct bpf_map *map)
 	if (!htab_is_prealloc(htab)) {
 		delete_all_elements(htab);
 	} else {
-		htab_free_prealloced_kptrs(htab);
+		htab_free_prealloced_fields(htab);
 		prealloc_destroy(htab);
 	}
 
-	bpf_map_free_kptr_off_tab(map);
+	bpf_map_free_record(map);
 	free_percpu(htab->extra_elems);
 	bpf_map_area_free(htab->buckets);
 	bpf_mem_alloc_destroy(&htab->pcpu_ma);
diff --git a/kernel/bpf/map_in_map.c b/kernel/bpf/map_in_map.c
index 135205d0d560..d6c662183f88 100644
--- a/kernel/bpf/map_in_map.c
+++ b/kernel/bpf/map_in_map.c
@@ -52,7 +52,15 @@ struct bpf_map *bpf_map_meta_alloc(int inner_map_ufd)
 	inner_map_meta->max_entries = inner_map->max_entries;
 	inner_map_meta->spin_lock_off = inner_map->spin_lock_off;
 	inner_map_meta->timer_off = inner_map->timer_off;
-	inner_map_meta->kptr_off_tab = bpf_map_copy_kptr_off_tab(inner_map);
+	inner_map_meta->record = btf_record_dup(inner_map->record);
+	if (IS_ERR(inner_map_meta->record)) {
+		/* btf_record_dup returns NULL or valid pointer in case of
+		 * invalid/empty/valid, but ERR_PTR in case of errors. During
+		 * equality NULL or IS_ERR is equivalent.
+		 */
+		fdput(f);
+		return ERR_CAST(inner_map_meta->record);
+	}
 	if (inner_map->btf) {
 		btf_get(inner_map->btf);
 		inner_map_meta->btf = inner_map->btf;
@@ -72,7 +80,7 @@ struct bpf_map *bpf_map_meta_alloc(int inner_map_ufd)
 
 void bpf_map_meta_free(struct bpf_map *map_meta)
 {
-	bpf_map_free_kptr_off_tab(map_meta);
+	bpf_map_free_record(map_meta);
 	btf_put(map_meta->btf);
 	kfree(map_meta);
 }
@@ -86,7 +94,7 @@ bool bpf_map_meta_equal(const struct bpf_map *meta0,
 		meta0->value_size == meta1->value_size &&
 		meta0->timer_off == meta1->timer_off &&
 		meta0->map_flags == meta1->map_flags &&
-		bpf_map_equal_kptr_off_tab(meta0, meta1);
+		btf_record_equal(meta0->record, meta1->record);
 }
 
 void *bpf_map_fd_get_ptr(struct bpf_map *map,
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 5887592eeb93..2d4bba45fd3c 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -495,114 +495,134 @@ static void bpf_map_release_memcg(struct bpf_map *map)
 }
 #endif
 
-static int bpf_map_kptr_off_cmp(const void *a, const void *b)
+static int btf_field_cmp(const void *a, const void *b)
 {
-	const struct bpf_map_value_off_desc *off_desc1 = a, *off_desc2 = b;
+	const struct btf_field *f1 = a, *f2 = b;
 
-	if (off_desc1->offset < off_desc2->offset)
+	if (f1->offset < f2->offset)
 		return -1;
-	else if (off_desc1->offset > off_desc2->offset)
+	else if (f1->offset > f2->offset)
 		return 1;
 	return 0;
 }
 
-struct bpf_map_value_off_desc *bpf_map_kptr_off_contains(struct bpf_map *map, u32 offset)
+struct btf_field *btf_record_find(const struct btf_record *rec, u32 offset,
+				  enum btf_field_type type)
 {
-	/* Since members are iterated in btf_find_field in increasing order,
-	 * offsets appended to kptr_off_tab are in increasing order, so we can
-	 * do bsearch to find exact match.
-	 */
-	struct bpf_map_value_off *tab;
+	struct btf_field *field;
 
-	if (!map_value_has_kptrs(map))
+	if (IS_ERR_OR_NULL(rec) || !(rec->field_mask & type))
+		return NULL;
+	field = bsearch(&offset, rec->fields, rec->cnt, sizeof(rec->fields[0]), btf_field_cmp);
+	if (!field || !(field->type & type))
 		return NULL;
-	tab = map->kptr_off_tab;
-	return bsearch(&offset, tab->off, tab->nr_off, sizeof(tab->off[0]), bpf_map_kptr_off_cmp);
+	return field;
 }
 
-void bpf_map_free_kptr_off_tab(struct bpf_map *map)
+void btf_record_free(struct btf_record *rec)
 {
-	struct bpf_map_value_off *tab = map->kptr_off_tab;
 	int i;
 
-	if (!map_value_has_kptrs(map))
+	if (IS_ERR_OR_NULL(rec))
 		return;
-	for (i = 0; i < tab->nr_off; i++) {
-		if (tab->off[i].kptr.module)
-			module_put(tab->off[i].kptr.module);
-		btf_put(tab->off[i].kptr.btf);
+	for (i = 0; i < rec->cnt; i++) {
+		switch (rec->fields[i].type) {
+		case BPF_KPTR_UNREF:
+		case BPF_KPTR_REF:
+			if (rec->fields[i].kptr.module)
+				module_put(rec->fields[i].kptr.module);
+			btf_put(rec->fields[i].kptr.btf);
+			break;
+		default:
+			WARN_ON_ONCE(1);
+			continue;
+		}
 	}
-	kfree(tab);
-	map->kptr_off_tab = NULL;
+	kfree(rec);
+}
+
+void bpf_map_free_record(struct bpf_map *map)
+{
+	btf_record_free(map->record);
+	map->record = NULL;
 }
 
-struct bpf_map_value_off *bpf_map_copy_kptr_off_tab(const struct bpf_map *map)
+struct btf_record *btf_record_dup(const struct btf_record *rec)
 {
-	struct bpf_map_value_off *tab = map->kptr_off_tab, *new_tab;
-	int size, i;
+	const struct btf_field *fields;
+	struct btf_record *new_rec;
+	int ret, size, i;
 
-	if (!map_value_has_kptrs(map))
-		return ERR_PTR(-ENOENT);
-	size = offsetof(struct bpf_map_value_off, off[tab->nr_off]);
-	new_tab = kmemdup(tab, size, GFP_KERNEL | __GFP_NOWARN);
-	if (!new_tab)
+	if (IS_ERR_OR_NULL(rec))
+		return NULL;
+	size = offsetof(struct btf_record, fields[rec->cnt]);
+	new_rec = kmemdup(rec, size, GFP_KERNEL | __GFP_NOWARN);
+	if (!new_rec)
 		return ERR_PTR(-ENOMEM);
-	/* Do a deep copy of the kptr_off_tab */
-	for (i = 0; i < tab->nr_off; i++) {
-		btf_get(tab->off[i].kptr.btf);
-		if (tab->off[i].kptr.module && !try_module_get(tab->off[i].kptr.module)) {
-			while (i--) {
-				if (tab->off[i].kptr.module)
-					module_put(tab->off[i].kptr.module);
-				btf_put(tab->off[i].kptr.btf);
+	/* Do a deep copy of the btf_record */
+	fields = rec->fields;
+	new_rec->cnt = 0;
+	for (i = 0; i < rec->cnt; i++) {
+		switch (fields[i].type) {
+		case BPF_KPTR_UNREF:
+		case BPF_KPTR_REF:
+			btf_get(fields[i].kptr.btf);
+			if (fields[i].kptr.module && !try_module_get(fields[i].kptr.module)) {
+				ret = -ENXIO;
+				goto free;
 			}
-			kfree(new_tab);
-			return ERR_PTR(-ENXIO);
+			break;
+		default:
+			ret = -EFAULT;
+			WARN_ON_ONCE(1);
+			goto free;
 		}
+		new_rec->cnt++;
 	}
-	return new_tab;
+	return new_rec;
+free:
+	btf_record_free(new_rec);
+	return ERR_PTR(ret);
 }
 
-bool bpf_map_equal_kptr_off_tab(const struct bpf_map *map_a, const struct bpf_map *map_b)
+bool btf_record_equal(const struct btf_record *rec_a, const struct btf_record *rec_b)
 {
-	struct bpf_map_value_off *tab_a = map_a->kptr_off_tab, *tab_b = map_b->kptr_off_tab;
-	bool a_has_kptr = map_value_has_kptrs(map_a), b_has_kptr = map_value_has_kptrs(map_b);
+	bool a_has_fields = !IS_ERR_OR_NULL(rec_a), b_has_fields = !IS_ERR_OR_NULL(rec_b);
 	int size;
 
-	if (!a_has_kptr && !b_has_kptr)
+	if (!a_has_fields && !b_has_fields)
 		return true;
-	if (a_has_kptr != b_has_kptr)
+	if (a_has_fields != b_has_fields)
 		return false;
-	if (tab_a->nr_off != tab_b->nr_off)
+	if (rec_a->cnt != rec_b->cnt)
 		return false;
-	size = offsetof(struct bpf_map_value_off, off[tab_a->nr_off]);
-	return !memcmp(tab_a, tab_b, size);
+	size = offsetof(struct btf_record, fields[rec_a->cnt]);
+	return !memcmp(rec_a, rec_b, size);
 }
 
-/* Caller must ensure map_value_has_kptrs is true. Note that this function can
- * be called on a map value while the map_value is visible to BPF programs, as
- * it ensures the correct synchronization, and we already enforce the same using
- * the bpf_kptr_xchg helper on the BPF program side for referenced kptrs.
- */
-void bpf_map_free_kptrs(struct bpf_map *map, void *map_value)
+void bpf_obj_free_fields(const struct btf_record *rec, void *obj)
 {
-	struct bpf_map_value_off *tab = map->kptr_off_tab;
-	unsigned long *btf_id_ptr;
+	const struct btf_field *fields;
 	int i;
 
-	for (i = 0; i < tab->nr_off; i++) {
-		struct bpf_map_value_off_desc *off_desc = &tab->off[i];
-		unsigned long old_ptr;
-
-		btf_id_ptr = map_value + off_desc->offset;
-		if (off_desc->type == BPF_KPTR_UNREF) {
-			u64 *p = (u64 *)btf_id_ptr;
-
-			WRITE_ONCE(*p, 0);
+	if (IS_ERR_OR_NULL(rec))
+		return;
+	fields = rec->fields;
+	for (i = 0; i < rec->cnt; i++) {
+		const struct btf_field *field = &fields[i];
+		void *field_ptr = obj + field->offset;
+
+		switch (fields[i].type) {
+		case BPF_KPTR_UNREF:
+			WRITE_ONCE(*(u64 *)field_ptr, 0);
+			break;
+		case BPF_KPTR_REF:
+			field->kptr.dtor((void *)xchg((unsigned long *)field_ptr, 0));
+			break;
+		default:
+			WARN_ON_ONCE(1);
 			continue;
 		}
-		old_ptr = xchg(btf_id_ptr, 0);
-		off_desc->kptr.dtor((void *)old_ptr);
 	}
 }
 
@@ -612,10 +632,10 @@ static void bpf_map_free_deferred(struct work_struct *work)
 	struct bpf_map *map = container_of(work, struct bpf_map, work);
 
 	security_bpf_map_free(map);
-	kfree(map->off_arr);
+	kfree(map->field_offs);
 	bpf_map_release_memcg(map);
 	/* implementation dependent freeing, map_free callback also does
-	 * bpf_map_free_kptr_off_tab, if needed.
+	 * bpf_map_free_record, if needed.
 	 */
 	map->ops->map_free(map);
 }
@@ -779,7 +799,7 @@ static int bpf_map_mmap(struct file *filp, struct vm_area_struct *vma)
 	int err;
 
 	if (!map->ops->map_mmap || map_value_has_spin_lock(map) ||
-	    map_value_has_timer(map) || map_value_has_kptrs(map))
+	    map_value_has_timer(map) || !IS_ERR_OR_NULL(map->record))
 		return -ENOTSUPP;
 
 	if (!(vma->vm_flags & VM_SHARED))
@@ -906,7 +926,7 @@ int map_check_no_btf(const struct bpf_map *map,
 	return -ENOTSUPP;
 }
 
-static int map_off_arr_cmp(const void *_a, const void *_b, const void *priv)
+static int map_field_offs_cmp(const void *_a, const void *_b, const void *priv)
 {
 	const u32 a = *(const u32 *)_a;
 	const u32 b = *(const u32 *)_b;
@@ -918,15 +938,15 @@ static int map_off_arr_cmp(const void *_a, const void *_b, const void *priv)
 	return 0;
 }
 
-static void map_off_arr_swap(void *_a, void *_b, int size, const void *priv)
+static void map_field_offs_swap(void *_a, void *_b, int size, const void *priv)
 {
 	struct bpf_map *map = (struct bpf_map *)priv;
-	u32 *off_base = map->off_arr->field_off;
+	u32 *off_base = map->field_offs->field_off;
 	u32 *a = _a, *b = _b;
 	u8 *sz_a, *sz_b;
 
-	sz_a = map->off_arr->field_sz + (a - off_base);
-	sz_b = map->off_arr->field_sz + (b - off_base);
+	sz_a = map->field_offs->field_sz + (a - off_base);
+	sz_b = map->field_offs->field_sz + (b - off_base);
 
 	swap(*a, *b);
 	swap(*sz_a, *sz_b);
@@ -936,51 +956,51 @@ static int bpf_map_alloc_off_arr(struct bpf_map *map)
 {
 	bool has_spin_lock = map_value_has_spin_lock(map);
 	bool has_timer = map_value_has_timer(map);
-	bool has_kptrs = map_value_has_kptrs(map);
-	struct bpf_map_off_arr *off_arr;
+	bool has_fields = !IS_ERR_OR_NULL(map);
+	struct btf_field_offs *fo;
 	u32 i;
 
-	if (!has_spin_lock && !has_timer && !has_kptrs) {
-		map->off_arr = NULL;
+	if (!has_spin_lock && !has_timer && !has_fields) {
+		map->field_offs = NULL;
 		return 0;
 	}
 
-	off_arr = kmalloc(sizeof(*map->off_arr), GFP_KERNEL | __GFP_NOWARN);
-	if (!off_arr)
+	fo = kmalloc(sizeof(*map->field_offs), GFP_KERNEL | __GFP_NOWARN);
+	if (!fo)
 		return -ENOMEM;
-	map->off_arr = off_arr;
+	map->field_offs = fo;
 
-	off_arr->cnt = 0;
+	fo->cnt = 0;
 	if (has_spin_lock) {
-		i = off_arr->cnt;
+		i = fo->cnt;
 
-		off_arr->field_off[i] = map->spin_lock_off;
-		off_arr->field_sz[i] = sizeof(struct bpf_spin_lock);
-		off_arr->cnt++;
+		fo->field_off[i] = map->spin_lock_off;
+		fo->field_sz[i] = sizeof(struct bpf_spin_lock);
+		fo->cnt++;
 	}
 	if (has_timer) {
-		i = off_arr->cnt;
+		i = fo->cnt;
 
-		off_arr->field_off[i] = map->timer_off;
-		off_arr->field_sz[i] = sizeof(struct bpf_timer);
-		off_arr->cnt++;
+		fo->field_off[i] = map->timer_off;
+		fo->field_sz[i] = sizeof(struct bpf_timer);
+		fo->cnt++;
 	}
-	if (has_kptrs) {
-		struct bpf_map_value_off *tab = map->kptr_off_tab;
-		u32 *off = &off_arr->field_off[off_arr->cnt];
-		u8 *sz = &off_arr->field_sz[off_arr->cnt];
+	if (has_fields) {
+		struct btf_record *rec = map->record;
+		u32 *off = &fo->field_off[fo->cnt];
+		u8 *sz = &fo->field_sz[fo->cnt];
 
-		for (i = 0; i < tab->nr_off; i++) {
-			*off++ = tab->off[i].offset;
-			*sz++ = sizeof(u64);
+		for (i = 0; i < rec->cnt; i++) {
+			*off++ = rec->fields[i].offset;
+			*sz++ = btf_field_type_size(rec->fields[i].type);
 		}
-		off_arr->cnt += tab->nr_off;
+		fo->cnt += rec->cnt;
 	}
 
-	if (off_arr->cnt == 1)
+	if (fo->cnt == 1)
 		return 0;
-	sort_r(off_arr->field_off, off_arr->cnt, sizeof(off_arr->field_off[0]),
-	       map_off_arr_cmp, map_off_arr_swap, map);
+	sort_r(fo->field_off, fo->cnt, sizeof(fo->field_off[0]),
+	       map_field_offs_cmp, map_field_offs_swap, map);
 	return 0;
 }
 
@@ -1038,8 +1058,10 @@ static int map_check_btf(struct bpf_map *map, const struct btf *btf,
 			return -EOPNOTSUPP;
 	}
 
-	map->kptr_off_tab = btf_parse_kptrs(btf, value_type);
-	if (map_value_has_kptrs(map)) {
+	map->record = btf_parse_fields(btf, value_type);
+	if (!IS_ERR_OR_NULL(map->record)) {
+		int i;
+
 		if (!bpf_capable()) {
 			ret = -EPERM;
 			goto free_map_tab;
@@ -1048,12 +1070,25 @@ static int map_check_btf(struct bpf_map *map, const struct btf *btf,
 			ret = -EACCES;
 			goto free_map_tab;
 		}
-		if (map->map_type != BPF_MAP_TYPE_HASH &&
-		    map->map_type != BPF_MAP_TYPE_LRU_HASH &&
-		    map->map_type != BPF_MAP_TYPE_ARRAY &&
-		    map->map_type != BPF_MAP_TYPE_PERCPU_ARRAY) {
-			ret = -EOPNOTSUPP;
-			goto free_map_tab;
+		for (i = 0; i < sizeof(map->record->field_mask) * 8; i++) {
+			switch (map->record->field_mask & (1 << i)) {
+			case 0:
+				continue;
+			case BPF_KPTR_UNREF:
+			case BPF_KPTR_REF:
+				if (map->map_type != BPF_MAP_TYPE_HASH &&
+				    map->map_type != BPF_MAP_TYPE_LRU_HASH &&
+				    map->map_type != BPF_MAP_TYPE_ARRAY &&
+				    map->map_type != BPF_MAP_TYPE_PERCPU_ARRAY) {
+					ret = -EOPNOTSUPP;
+					goto free_map_tab;
+				}
+				break;
+			default:
+				/* Fail if map_type checks are missing for a field type */
+				ret = -EOPNOTSUPP;
+				goto free_map_tab;
+			}
 		}
 	}
 
@@ -1065,7 +1100,7 @@ static int map_check_btf(struct bpf_map *map, const struct btf *btf,
 
 	return ret;
 free_map_tab:
-	bpf_map_free_kptr_off_tab(map);
+	bpf_map_free_record(map);
 	return ret;
 }
 
@@ -1186,7 +1221,7 @@ static int map_create(union bpf_attr *attr)
 free_map_sec:
 	security_bpf_map_free(map);
 free_map_off_arr:
-	kfree(map->off_arr);
+	kfree(map->field_offs);
 free_map:
 	btf_put(map->btf);
 	map->ops->map_free(map);
@@ -1883,7 +1918,7 @@ static int map_freeze(const union bpf_attr *attr)
 		return PTR_ERR(map);
 
 	if (map->map_type == BPF_MAP_TYPE_STRUCT_OPS ||
-	    map_value_has_timer(map) || map_value_has_kptrs(map)) {
+	    map_value_has_timer(map) || !IS_ERR_OR_NULL(map->record)) {
 		fdput(f);
 		return -ENOTSUPP;
 	}
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 14d350a25d5d..5ce5364ce898 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -262,7 +262,7 @@ struct bpf_call_arg_meta {
 	struct btf *ret_btf;
 	u32 ret_btf_id;
 	u32 subprogno;
-	struct bpf_map_value_off_desc *kptr_off_desc;
+	struct btf_field *kptr_field;
 	u8 uninit_dynptr_regno;
 };
 
@@ -3674,15 +3674,15 @@ int check_ptr_off_reg(struct bpf_verifier_env *env,
 }
 
 static int map_kptr_match_type(struct bpf_verifier_env *env,
-			       struct bpf_map_value_off_desc *off_desc,
+			       struct btf_field *kptr_field,
 			       struct bpf_reg_state *reg, u32 regno)
 {
-	const char *targ_name = kernel_type_name(off_desc->kptr.btf, off_desc->kptr.btf_id);
+	const char *targ_name = kernel_type_name(kptr_field->kptr.btf, kptr_field->kptr.btf_id);
 	int perm_flags = PTR_MAYBE_NULL;
 	const char *reg_name = "";
 
 	/* Only unreferenced case accepts untrusted pointers */
-	if (off_desc->type == BPF_KPTR_UNREF)
+	if (kptr_field->type == BPF_KPTR_UNREF)
 		perm_flags |= PTR_UNTRUSTED;
 
 	if (base_type(reg->type) != PTR_TO_BTF_ID || (type_flag(reg->type) & ~perm_flags))
@@ -3729,15 +3729,15 @@ static int map_kptr_match_type(struct bpf_verifier_env *env,
 	 * strict mode to true for type match.
 	 */
 	if (!btf_struct_ids_match(&env->log, reg->btf, reg->btf_id, reg->off,
-				  off_desc->kptr.btf, off_desc->kptr.btf_id,
-				  off_desc->type == BPF_KPTR_REF))
+				  kptr_field->kptr.btf, kptr_field->kptr.btf_id,
+				  kptr_field->type == BPF_KPTR_REF))
 		goto bad_type;
 	return 0;
 bad_type:
 	verbose(env, "invalid kptr access, R%d type=%s%s ", regno,
 		reg_type_str(env, reg->type), reg_name);
 	verbose(env, "expected=%s%s", reg_type_str(env, PTR_TO_BTF_ID), targ_name);
-	if (off_desc->type == BPF_KPTR_UNREF)
+	if (kptr_field->type == BPF_KPTR_UNREF)
 		verbose(env, " or %s%s\n", reg_type_str(env, PTR_TO_BTF_ID | PTR_UNTRUSTED),
 			targ_name);
 	else
@@ -3747,7 +3747,7 @@ static int map_kptr_match_type(struct bpf_verifier_env *env,
 
 static int check_map_kptr_access(struct bpf_verifier_env *env, u32 regno,
 				 int value_regno, int insn_idx,
-				 struct bpf_map_value_off_desc *off_desc)
+				 struct btf_field *kptr_field)
 {
 	struct bpf_insn *insn = &env->prog->insnsi[insn_idx];
 	int class = BPF_CLASS(insn->code);
@@ -3757,7 +3757,7 @@ static int check_map_kptr_access(struct bpf_verifier_env *env, u32 regno,
 	 *  - Reject cases where variable offset may touch kptr
 	 *  - size of access (must be BPF_DW)
 	 *  - tnum_is_const(reg->var_off)
-	 *  - off_desc->offset == off + reg->var_off.value
+	 *  - kptr_field->offset == off + reg->var_off.value
 	 */
 	/* Only BPF_[LDX,STX,ST] | BPF_MEM | BPF_DW is supported */
 	if (BPF_MODE(insn->code) != BPF_MEM) {
@@ -3768,7 +3768,7 @@ static int check_map_kptr_access(struct bpf_verifier_env *env, u32 regno,
 	/* We only allow loading referenced kptr, since it will be marked as
 	 * untrusted, similar to unreferenced kptr.
 	 */
-	if (class != BPF_LDX && off_desc->type == BPF_KPTR_REF) {
+	if (class != BPF_LDX && kptr_field->type == BPF_KPTR_REF) {
 		verbose(env, "store to referenced kptr disallowed\n");
 		return -EACCES;
 	}
@@ -3778,19 +3778,19 @@ static int check_map_kptr_access(struct bpf_verifier_env *env, u32 regno,
 		/* We can simply mark the value_regno receiving the pointer
 		 * value from map as PTR_TO_BTF_ID, with the correct type.
 		 */
-		mark_btf_ld_reg(env, cur_regs(env), value_regno, PTR_TO_BTF_ID, off_desc->kptr.btf,
-				off_desc->kptr.btf_id, PTR_MAYBE_NULL | PTR_UNTRUSTED);
+		mark_btf_ld_reg(env, cur_regs(env), value_regno, PTR_TO_BTF_ID, kptr_field->kptr.btf,
+				kptr_field->kptr.btf_id, PTR_MAYBE_NULL | PTR_UNTRUSTED);
 		/* For mark_ptr_or_null_reg */
 		val_reg->id = ++env->id_gen;
 	} else if (class == BPF_STX) {
 		val_reg = reg_state(env, value_regno);
 		if (!register_is_null(val_reg) &&
-		    map_kptr_match_type(env, off_desc, val_reg, value_regno))
+		    map_kptr_match_type(env, kptr_field, val_reg, value_regno))
 			return -EACCES;
 	} else if (class == BPF_ST) {
 		if (insn->imm) {
 			verbose(env, "BPF_ST imm must be 0 when storing to kptr at off=%u\n",
-				off_desc->offset);
+				kptr_field->offset);
 			return -EACCES;
 		}
 	} else {
@@ -3809,7 +3809,8 @@ static int check_map_access(struct bpf_verifier_env *env, u32 regno,
 	struct bpf_func_state *state = vstate->frame[vstate->curframe];
 	struct bpf_reg_state *reg = &state->regs[regno];
 	struct bpf_map *map = reg->map_ptr;
-	int err;
+	struct btf_record *rec;
+	int err, i;
 
 	err = check_mem_region_access(env, regno, off, size, map->value_size,
 				      zero_size_allowed);
@@ -3839,15 +3840,18 @@ static int check_map_access(struct bpf_verifier_env *env, u32 regno,
 			return -EACCES;
 		}
 	}
-	if (map_value_has_kptrs(map)) {
-		struct bpf_map_value_off *tab = map->kptr_off_tab;
-		int i;
-
-		for (i = 0; i < tab->nr_off; i++) {
-			u32 p = tab->off[i].offset;
-
-			if (reg->smin_value + off < p + sizeof(u64) &&
-			    p < reg->umax_value + off + size) {
+	if (IS_ERR_OR_NULL(map->record))
+		return 0;
+	rec = map->record;
+	for (i = 0; i < rec->cnt; i++) {
+		struct btf_field *field = &rec->fields[i];
+		u32 p = field->offset;
+
+		if (reg->smin_value + off < p + btf_field_type_size(field->type) &&
+		    p < reg->umax_value + off + size) {
+			switch (field->type) {
+			case BPF_KPTR_UNREF:
+			case BPF_KPTR_REF:
 				if (src != ACCESS_DIRECT) {
 					verbose(env, "kptr cannot be accessed indirectly by helper\n");
 					return -EACCES;
@@ -3866,10 +3870,13 @@ static int check_map_access(struct bpf_verifier_env *env, u32 regno,
 					return -EACCES;
 				}
 				break;
+			default:
+				verbose(env, "field cannot be accessed directly by load/store\n");
+				return -EACCES;
 			}
 		}
 	}
-	return err;
+	return 0;
 }
 
 #define MAX_PACKET_OFF 0xffff
@@ -4742,7 +4749,7 @@ static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regn
 		if (value_regno >= 0)
 			mark_reg_unknown(env, regs, value_regno);
 	} else if (reg->type == PTR_TO_MAP_VALUE) {
-		struct bpf_map_value_off_desc *kptr_off_desc = NULL;
+		struct btf_field *kptr_field = NULL;
 
 		if (t == BPF_WRITE && value_regno >= 0 &&
 		    is_pointer_value(env, value_regno)) {
@@ -4756,11 +4763,10 @@ static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regn
 		if (err)
 			return err;
 		if (tnum_is_const(reg->var_off))
-			kptr_off_desc = bpf_map_kptr_off_contains(reg->map_ptr,
-								  off + reg->var_off.value);
-		if (kptr_off_desc) {
-			err = check_map_kptr_access(env, regno, value_regno, insn_idx,
-						    kptr_off_desc);
+			kptr_field = btf_record_find(reg->map_ptr->record,
+						     off + reg->var_off.value, BPF_KPTR);
+		if (kptr_field) {
+			err = check_map_kptr_access(env, regno, value_regno, insn_idx, kptr_field);
 		} else if (t == BPF_READ && value_regno >= 0) {
 			struct bpf_map *map = reg->map_ptr;
 
@@ -5527,10 +5533,9 @@ static int process_kptr_func(struct bpf_verifier_env *env, int regno,
 			     struct bpf_call_arg_meta *meta)
 {
 	struct bpf_reg_state *regs = cur_regs(env), *reg = &regs[regno];
-	struct bpf_map_value_off_desc *off_desc;
 	struct bpf_map *map_ptr = reg->map_ptr;
+	struct btf_field *kptr_field;
 	u32 kptr_off;
-	int ret;
 
 	if (!tnum_is_const(reg->var_off)) {
 		verbose(env,
@@ -5543,30 +5548,23 @@ static int process_kptr_func(struct bpf_verifier_env *env, int regno,
 			map_ptr->name);
 		return -EINVAL;
 	}
-	if (!map_value_has_kptrs(map_ptr)) {
-		ret = PTR_ERR_OR_ZERO(map_ptr->kptr_off_tab);
-		if (ret == -E2BIG)
-			verbose(env, "map '%s' has more than %d kptr\n", map_ptr->name,
-				BPF_MAP_VALUE_OFF_MAX);
-		else if (ret == -EEXIST)
-			verbose(env, "map '%s' has repeating kptr BTF tags\n", map_ptr->name);
-		else
-			verbose(env, "map '%s' has no valid kptr\n", map_ptr->name);
+	if (!btf_record_has_field(map_ptr->record, BPF_KPTR)) {
+		verbose(env, "map '%s' has no valid kptr\n", map_ptr->name);
 		return -EINVAL;
 	}
 
 	meta->map_ptr = map_ptr;
 	kptr_off = reg->off + reg->var_off.value;
-	off_desc = bpf_map_kptr_off_contains(map_ptr, kptr_off);
-	if (!off_desc) {
+	kptr_field = btf_record_find(map_ptr->record, kptr_off, BPF_KPTR);
+	if (!kptr_field) {
 		verbose(env, "off=%d doesn't point to kptr\n", kptr_off);
 		return -EACCES;
 	}
-	if (off_desc->type != BPF_KPTR_REF) {
+	if (kptr_field->type != BPF_KPTR_REF) {
 		verbose(env, "off=%d kptr isn't referenced kptr\n", kptr_off);
 		return -EACCES;
 	}
-	meta->kptr_off_desc = off_desc;
+	meta->kptr_field = kptr_field;
 	return 0;
 }
 
@@ -5788,7 +5786,7 @@ static int check_reg_type(struct bpf_verifier_env *env, u32 regno,
 		}
 
 		if (meta->func_id == BPF_FUNC_kptr_xchg) {
-			if (map_kptr_match_type(env, meta->kptr_off_desc, reg, regno))
+			if (map_kptr_match_type(env, meta->kptr_field, reg, regno))
 				return -EACCES;
 		} else {
 			if (arg_btf_id == BPF_PTR_POISON) {
@@ -7536,8 +7534,8 @@ static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn
 		mark_reg_known_zero(env, regs, BPF_REG_0);
 		regs[BPF_REG_0].type = PTR_TO_BTF_ID | ret_flag;
 		if (func_id == BPF_FUNC_kptr_xchg) {
-			ret_btf = meta.kptr_off_desc->kptr.btf;
-			ret_btf_id = meta.kptr_off_desc->kptr.btf_id;
+			ret_btf = meta.kptr_field->kptr.btf;
+			ret_btf_id = meta.kptr_field->kptr.btf_id;
 		} else {
 			if (fn->ret_btf_id == BPF_PTR_POISON) {
 				verbose(env, "verifier internal error:");
-- 
2.38.1

[PATCH bpf-next v4 07/24] bpf: Consolidate spin_lock, timer management into btf_record

[Kumar Kartikeya Dwivedi]

Now that kptr_off_tab has been refactored into btf_record, and can hold
more than one specific field type, accomodate bpf_spin_lock and
bpf_timer as well.

While they don't require any more metadata than offset, having all
special fields in one place allows us to share the same code for
allocated user defined types and handle both map values and these
allocated objects in a similar fashion.

As an optimization, we still keep spin_lock_off and timer_off offsets in
the btf_record structure, just to avoid having to find the btf_field
struct each time their offset is needed. This is mostly needed to
manipulate such objects in a map value at runtime. It's ok to hardcode
just one offset as more than one field is disallowed.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 include/linux/bpf.h            |  53 +++---
 include/linux/btf.h            |   3 +-
 kernel/bpf/arraymap.c          |  19 +-
 kernel/bpf/bpf_local_storage.c |   2 +-
 kernel/bpf/btf.c               | 325 ++++++++++++++++++---------------
 kernel/bpf/hashtab.c           |  24 +--
 kernel/bpf/helpers.c           |   6 +-
 kernel/bpf/local_storage.c     |   2 +-
 kernel/bpf/map_in_map.c        |   5 +-
 kernel/bpf/syscall.c           | 133 ++++++--------
 kernel/bpf/verifier.c          |  82 +++------
 net/core/bpf_sk_storage.c      |   4 +-
 12 files changed, 314 insertions(+), 344 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 1440e7c3c510..d5c81b09577a 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -166,13 +166,13 @@ struct bpf_map_ops {
 
 enum {
 	/* Support at most 8 pointers in a BTF type */
-	BTF_FIELDS_MAX	      = 8,
-	BPF_MAP_OFF_ARR_MAX   = BTF_FIELDS_MAX +
-				1 + /* for bpf_spin_lock */
-				1,  /* for bpf_timer */
+	BTF_FIELDS_MAX	      = 10,
+	BPF_MAP_OFF_ARR_MAX   = BTF_FIELDS_MAX,
 };
 
 enum btf_field_type {
+	BPF_SPIN_LOCK  = (1 << 0),
+	BPF_TIMER      = (1 << 1),
 	BPF_KPTR_UNREF = (1 << 2),
 	BPF_KPTR_REF   = (1 << 3),
 	BPF_KPTR       = BPF_KPTR_UNREF | BPF_KPTR_REF,
@@ -196,6 +196,8 @@ struct btf_field {
 struct btf_record {
 	u32 cnt;
 	u32 field_mask;
+	int spin_lock_off;
+	int timer_off;
 	struct btf_field fields[];
 };
 
@@ -220,10 +222,8 @@ struct bpf_map {
 	u32 max_entries;
 	u64 map_extra; /* any per-map-type extra fields */
 	u32 map_flags;
-	int spin_lock_off; /* >=0 valid offset, <0 error */
-	struct btf_record *record;
-	int timer_off; /* >=0 valid offset, <0 error */
 	u32 id;
+	struct btf_record *record;
 	int numa_node;
 	u32 btf_key_type_id;
 	u32 btf_value_type_id;
@@ -257,9 +257,29 @@ struct bpf_map {
 	bool frozen; /* write-once; write-protected by freeze_mutex */
 };
 
+static inline const char *btf_field_type_name(enum btf_field_type type)
+{
+	switch (type) {
+	case BPF_SPIN_LOCK:
+		return "bpf_spin_lock";
+	case BPF_TIMER:
+		return "bpf_timer";
+	case BPF_KPTR_UNREF:
+	case BPF_KPTR_REF:
+		return "kptr";
+	default:
+		WARN_ON_ONCE(1);
+		return "unknown";
+	}
+}
+
 static inline u32 btf_field_type_size(enum btf_field_type type)
 {
 	switch (type) {
+	case BPF_SPIN_LOCK:
+		return sizeof(struct bpf_spin_lock);
+	case BPF_TIMER:
+		return sizeof(struct bpf_timer);
 	case BPF_KPTR_UNREF:
 	case BPF_KPTR_REF:
 		return sizeof(u64);
@@ -272,6 +292,10 @@ static inline u32 btf_field_type_size(enum btf_field_type type)
 static inline u32 btf_field_type_align(enum btf_field_type type)
 {
 	switch (type) {
+	case BPF_SPIN_LOCK:
+		return __alignof__(struct bpf_spin_lock);
+	case BPF_TIMER:
+		return __alignof__(struct bpf_timer);
 	case BPF_KPTR_UNREF:
 	case BPF_KPTR_REF:
 		return __alignof__(u64);
@@ -288,22 +312,8 @@ static inline bool btf_record_has_field(const struct btf_record *rec, enum btf_f
 	return rec->field_mask & type;
 }
 
-static inline bool map_value_has_spin_lock(const struct bpf_map *map)
-{
-	return map->spin_lock_off >= 0;
-}
-
-static inline bool map_value_has_timer(const struct bpf_map *map)
-{
-	return map->timer_off >= 0;
-}
-
 static inline void check_and_init_map_value(struct bpf_map *map, void *dst)
 {
-	if (unlikely(map_value_has_spin_lock(map)))
-		memset(dst + map->spin_lock_off, 0, sizeof(struct bpf_spin_lock));
-	if (unlikely(map_value_has_timer(map)))
-		memset(dst + map->timer_off, 0, sizeof(struct bpf_timer));
 	if (!IS_ERR_OR_NULL(map->record)) {
 		struct btf_field *fields = map->record->fields;
 		u32 cnt = map->record->cnt;
@@ -1740,6 +1750,7 @@ void btf_record_free(struct btf_record *rec);
 void bpf_map_free_record(struct bpf_map *map);
 struct btf_record *btf_record_dup(const struct btf_record *rec);
 bool btf_record_equal(const struct btf_record *rec_a, const struct btf_record *rec_b);
+void bpf_obj_free_timer(const struct btf_record *rec, void *obj);
 void bpf_obj_free_fields(const struct btf_record *rec, void *obj);
 
 struct bpf_map *bpf_map_get(u32 ufd);
diff --git a/include/linux/btf.h b/include/linux/btf.h
index 9e62717cdc7a..282006abd062 100644
--- a/include/linux/btf.h
+++ b/include/linux/btf.h
@@ -163,7 +163,8 @@ bool btf_member_is_reg_int(const struct btf *btf, const struct btf_type *s,
 			   u32 expected_offset, u32 expected_size);
 int btf_find_spin_lock(const struct btf *btf, const struct btf_type *t);
 int btf_find_timer(const struct btf *btf, const struct btf_type *t);
-struct btf_record *btf_parse_fields(const struct btf *btf, const struct btf_type *t);
+struct btf_record *btf_parse_fields(const struct btf *btf, const struct btf_type *t,
+				    u32 field_mask, u32 value_size);
 bool btf_type_is_void(const struct btf_type *t);
 s32 btf_find_by_name_kind(const struct btf *btf, const char *name, u8 kind);
 const struct btf_type *btf_type_skip_modifiers(const struct btf *btf,
diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
index 417f84342e98..672eb17ac421 100644
--- a/kernel/bpf/arraymap.c
+++ b/kernel/bpf/arraymap.c
@@ -306,13 +306,6 @@ static int array_map_get_next_key(struct bpf_map *map, void *key, void *next_key
 	return 0;
 }
 
-static void check_and_free_fields(struct bpf_array *arr, void *val)
-{
-	if (map_value_has_timer(&arr->map))
-		bpf_timer_cancel_and_free(val + arr->map.timer_off);
-	bpf_obj_free_fields(arr->map.record, val);
-}
-
 /* Called from syscall or from eBPF program */
 static int array_map_update_elem(struct bpf_map *map, void *key, void *value,
 				 u64 map_flags)
@@ -334,13 +327,13 @@ static int array_map_update_elem(struct bpf_map *map, void *key, void *value,
 		return -EEXIST;
 
 	if (unlikely((map_flags & BPF_F_LOCK) &&
-		     !map_value_has_spin_lock(map)))
+		     !btf_record_has_field(map->record, BPF_SPIN_LOCK)))
 		return -EINVAL;
 
 	if (array->map.map_type == BPF_MAP_TYPE_PERCPU_ARRAY) {
 		val = this_cpu_ptr(array->pptrs[index & array->index_mask]);
 		copy_map_value(map, val, value);
-		check_and_free_fields(array, val);
+		bpf_obj_free_fields(array->map.record, val);
 	} else {
 		val = array->value +
 			(u64)array->elem_size * (index & array->index_mask);
@@ -348,7 +341,7 @@ static int array_map_update_elem(struct bpf_map *map, void *key, void *value,
 			copy_map_value_locked(map, val, value, false);
 		else
 			copy_map_value(map, val, value);
-		check_and_free_fields(array, val);
+		bpf_obj_free_fields(array->map.record, val);
 	}
 	return 0;
 }
@@ -385,7 +378,7 @@ int bpf_percpu_array_update(struct bpf_map *map, void *key, void *value,
 	pptr = array->pptrs[index & array->index_mask];
 	for_each_possible_cpu(cpu) {
 		copy_map_value_long(map, per_cpu_ptr(pptr, cpu), value + off);
-		check_and_free_fields(array, per_cpu_ptr(pptr, cpu));
+		bpf_obj_free_fields(array->map.record, per_cpu_ptr(pptr, cpu));
 		off += size;
 	}
 	rcu_read_unlock();
@@ -409,11 +402,11 @@ static void array_map_free_timers(struct bpf_map *map)
 	int i;
 
 	/* We don't reset or free fields other than timer on uref dropping to zero. */
-	if (!map_value_has_timer(map))
+	if (!btf_record_has_field(map->record, BPF_TIMER))
 		return;
 
 	for (i = 0; i < array->map.max_entries; i++)
-		bpf_timer_cancel_and_free(array_map_elem_ptr(array, i) + map->timer_off);
+		bpf_obj_free_timer(map->record, array_map_elem_ptr(array, i));
 }
 
 /* Called when map->refcnt goes to zero, either from workqueue or from syscall */
diff --git a/kernel/bpf/bpf_local_storage.c b/kernel/bpf/bpf_local_storage.c
index 93d9b1b17bc8..37020078d1c1 100644
--- a/kernel/bpf/bpf_local_storage.c
+++ b/kernel/bpf/bpf_local_storage.c
@@ -382,7 +382,7 @@ bpf_local_storage_update(void *owner, struct bpf_local_storage_map *smap,
 	if (unlikely((map_flags & ~BPF_F_LOCK) > BPF_EXIST) ||
 	    /* BPF_F_LOCK can only be used in a value with spin_lock */
 	    unlikely((map_flags & BPF_F_LOCK) &&
-		     !map_value_has_spin_lock(&smap->map)))
+		     !btf_record_has_field(smap->map.record, BPF_SPIN_LOCK)))
 		return ERR_PTR(-EINVAL);
 
 	if (gfp_flags == GFP_KERNEL && (map_flags & ~BPF_F_LOCK) != BPF_NOEXIST)
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index ffd687c7420d..3dad828db13c 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -3205,16 +3205,20 @@ enum {
 struct btf_field_info {
 	enum btf_field_type type;
 	u32 off;
-	u32 type_id;
+	struct {
+		u32 type_id;
+	} kptr;
 };
 
 static int btf_find_struct(const struct btf *btf, const struct btf_type *t,
-			   u32 off, int sz, struct btf_field_info *info)
+			   u32 off, int sz, enum btf_field_type field_type,
+			   struct btf_field_info *info)
 {
 	if (!__btf_type_is_struct(t))
 		return BTF_FIELD_IGNORE;
 	if (t->size != sz)
 		return BTF_FIELD_IGNORE;
+	info->type = field_type;
 	info->off = off;
 	return BTF_FIELD_FOUND;
 }
@@ -3251,28 +3255,66 @@ static int btf_find_kptr(const struct btf *btf, const struct btf_type *t,
 	if (!__btf_type_is_struct(t))
 		return -EINVAL;
 
-	info->type_id = res_id;
-	info->off = off;
 	info->type = type;
+	info->off = off;
+	info->kptr.type_id = res_id;
 	return BTF_FIELD_FOUND;
 }
 
-static int btf_find_struct_field(const struct btf *btf, const struct btf_type *t,
-				 const char *name, int sz, int align,
-				 enum btf_field_info_type field_type,
+static int btf_get_field_type(const char *name, u32 field_mask, u32 *seen_mask,
+			      int *align, int *sz)
+{
+	int type = 0;
+
+	if (field_mask & BPF_SPIN_LOCK) {
+		if (!strcmp(name, "bpf_spin_lock")) {
+			if (*seen_mask & BPF_SPIN_LOCK)
+				return -E2BIG;
+			*seen_mask |= BPF_SPIN_LOCK;
+			type = BPF_SPIN_LOCK;
+			goto end;
+		}
+	}
+	if (field_mask & BPF_TIMER) {
+		if (!strcmp(name, "bpf_timer")) {
+			if (*seen_mask & BPF_TIMER)
+				return -E2BIG;
+			*seen_mask |= BPF_TIMER;
+			type = BPF_TIMER;
+			goto end;
+		}
+	}
+	/* Only return BPF_KPTR when all other types with matchable names fail */
+	if (field_mask & BPF_KPTR) {
+		type = BPF_KPTR_REF;
+		goto end;
+	}
+	return 0;
+end:
+	*sz = btf_field_type_size(type);
+	*align = btf_field_type_align(type);
+	return type;
+}
+
+static int btf_find_struct_field(const struct btf *btf,
+				 const struct btf_type *t, u32 field_mask,
 				 struct btf_field_info *info, int info_cnt)
 {
+	int ret, idx = 0, align, sz, field_type;
 	const struct btf_member *member;
 	struct btf_field_info tmp;
-	int ret, idx = 0;
-	u32 i, off;
+	u32 i, off, seen_mask = 0;
 
 	for_each_member(i, t, member) {
 		const struct btf_type *member_type = btf_type_by_id(btf,
 								    member->type);
 
-		if (name && strcmp(__btf_name_by_offset(btf, member_type->name_off), name))
+		field_type = btf_get_field_type(__btf_name_by_offset(btf, member_type->name_off),
+						field_mask, &seen_mask, &align, &sz);
+		if (field_type == 0)
 			continue;
+		if (field_type < 0)
+			return field_type;
 
 		off = __btf_member_bit_offset(t, member);
 		if (off % 8)
@@ -3280,17 +3322,18 @@ static int btf_find_struct_field(const struct btf *btf, const struct btf_type *t
 			return -EINVAL;
 		off /= 8;
 		if (off % align)
-			return -EINVAL;
+			continue;
 
 		switch (field_type) {
-		case BTF_FIELD_SPIN_LOCK:
-		case BTF_FIELD_TIMER:
-			ret = btf_find_struct(btf, member_type, off, sz,
+		case BPF_SPIN_LOCK:
+		case BPF_TIMER:
+			ret = btf_find_struct(btf, member_type, off, sz, field_type,
 					      idx < info_cnt ? &info[idx] : &tmp);
 			if (ret < 0)
 				return ret;
 			break;
-		case BTF_FIELD_KPTR:
+		case BPF_KPTR_UNREF:
+		case BPF_KPTR_REF:
 			ret = btf_find_kptr(btf, member_type, off, sz,
 					    idx < info_cnt ? &info[idx] : &tmp);
 			if (ret < 0)
@@ -3310,37 +3353,41 @@ static int btf_find_struct_field(const struct btf *btf, const struct btf_type *t
 }
 
 static int btf_find_datasec_var(const struct btf *btf, const struct btf_type *t,
-				const char *name, int sz, int align,
-				enum btf_field_info_type field_type,
-				struct btf_field_info *info, int info_cnt)
+				u32 field_mask, struct btf_field_info *info,
+				int info_cnt)
 {
+	int ret, idx = 0, align, sz, field_type;
 	const struct btf_var_secinfo *vsi;
 	struct btf_field_info tmp;
-	int ret, idx = 0;
-	u32 i, off;
+	u32 i, off, seen_mask = 0;
 
 	for_each_vsi(i, t, vsi) {
 		const struct btf_type *var = btf_type_by_id(btf, vsi->type);
 		const struct btf_type *var_type = btf_type_by_id(btf, var->type);
 
-		off = vsi->offset;
-
-		if (name && strcmp(__btf_name_by_offset(btf, var_type->name_off), name))
+		field_type = btf_get_field_type(__btf_name_by_offset(btf, var_type->name_off),
+						field_mask, &seen_mask, &align, &sz);
+		if (field_type == 0)
 			continue;
+		if (field_type < 0)
+			return field_type;
+
+		off = vsi->offset;
 		if (vsi->size != sz)
 			continue;
 		if (off % align)
-			return -EINVAL;
+			continue;
 
 		switch (field_type) {
-		case BTF_FIELD_SPIN_LOCK:
-		case BTF_FIELD_TIMER:
-			ret = btf_find_struct(btf, var_type, off, sz,
+		case BPF_SPIN_LOCK:
+		case BPF_TIMER:
+			ret = btf_find_struct(btf, var_type, off, sz, field_type,
 					      idx < info_cnt ? &info[idx] : &tmp);
 			if (ret < 0)
 				return ret;
 			break;
-		case BTF_FIELD_KPTR:
+		case BPF_KPTR_UNREF:
+		case BPF_KPTR_REF:
 			ret = btf_find_kptr(btf, var_type, off, sz,
 					    idx < info_cnt ? &info[idx] : &tmp);
 			if (ret < 0)
@@ -3360,78 +3407,98 @@ static int btf_find_datasec_var(const struct btf *btf, const struct btf_type *t,
 }
 
 static int btf_find_field(const struct btf *btf, const struct btf_type *t,
-			  enum btf_field_info_type field_type,
-			  struct btf_field_info *info, int info_cnt)
+			  u32 field_mask, struct btf_field_info *info,
+			  int info_cnt)
 {
-	const char *name;
-	int sz, align;
-
-	switch (field_type) {
-	case BTF_FIELD_SPIN_LOCK:
-		name = "bpf_spin_lock";
-		sz = sizeof(struct bpf_spin_lock);
-		align = __alignof__(struct bpf_spin_lock);
-		break;
-	case BTF_FIELD_TIMER:
-		name = "bpf_timer";
-		sz = sizeof(struct bpf_timer);
-		align = __alignof__(struct bpf_timer);
-		break;
-	case BTF_FIELD_KPTR:
-		name = NULL;
-		sz = sizeof(u64);
-		align = 8;
-		break;
-	default:
-		return -EFAULT;
-	}
-
 	if (__btf_type_is_struct(t))
-		return btf_find_struct_field(btf, t, name, sz, align, field_type, info, info_cnt);
+		return btf_find_struct_field(btf, t, field_mask, info, info_cnt);
 	else if (btf_type_is_datasec(t))
-		return btf_find_datasec_var(btf, t, name, sz, align, field_type, info, info_cnt);
+		return btf_find_datasec_var(btf, t, field_mask, info, info_cnt);
 	return -EINVAL;
 }
 
-/* find 'struct bpf_spin_lock' in map value.
- * return >= 0 offset if found
- * and < 0 in case of error
- */
-int btf_find_spin_lock(const struct btf *btf, const struct btf_type *t)
+static int btf_parse_kptr(const struct btf *btf, struct btf_field *field,
+			  struct btf_field_info *info)
 {
-	struct btf_field_info info;
+	struct module *mod = NULL;
+	const struct btf_type *t;
+	struct btf *kernel_btf;
 	int ret;
+	s32 id;
 
-	ret = btf_find_field(btf, t, BTF_FIELD_SPIN_LOCK, &info, 1);
-	if (ret < 0)
-		return ret;
-	if (!ret)
-		return -ENOENT;
-	return info.off;
-}
+	/* Find type in map BTF, and use it to look up the matching type
+	 * in vmlinux or module BTFs, by name and kind.
+	 */
+	t = btf_type_by_id(btf, info->kptr.type_id);
+	id = bpf_find_btf_id(__btf_name_by_offset(btf, t->name_off), BTF_INFO_KIND(t->info),
+			     &kernel_btf);
+	if (id < 0)
+		return id;
+
+	/* Find and stash the function pointer for the destruction function that
+	 * needs to be eventually invoked from the map free path.
+	 */
+	if (info->type == BPF_KPTR_REF) {
+		const struct btf_type *dtor_func;
+		const char *dtor_func_name;
+		unsigned long addr;
+		s32 dtor_btf_id;
+
+		/* This call also serves as a whitelist of allowed objects that
+		 * can be used as a referenced pointer and be stored in a map at
+		 * the same time.
+		 */
+		dtor_btf_id = btf_find_dtor_kfunc(kernel_btf, id);
+		if (dtor_btf_id < 0) {
+			ret = dtor_btf_id;
+			goto end_btf;
+		}
 
-int btf_find_timer(const struct btf *btf, const struct btf_type *t)
-{
-	struct btf_field_info info;
-	int ret;
+		dtor_func = btf_type_by_id(kernel_btf, dtor_btf_id);
+		if (!dtor_func) {
+			ret = -ENOENT;
+			goto end_btf;
+		}
 
-	ret = btf_find_field(btf, t, BTF_FIELD_TIMER, &info, 1);
-	if (ret < 0)
-		return ret;
-	if (!ret)
-		return -ENOENT;
-	return info.off;
+		if (btf_is_module(kernel_btf)) {
+			mod = btf_try_get_module(kernel_btf);
+			if (!mod) {
+				ret = -ENXIO;
+				goto end_btf;
+			}
+		}
+
+		/* We already verified dtor_func to be btf_type_is_func
+		 * in register_btf_id_dtor_kfuncs.
+		 */
+		dtor_func_name = __btf_name_by_offset(kernel_btf, dtor_func->name_off);
+		addr = kallsyms_lookup_name(dtor_func_name);
+		if (!addr) {
+			ret = -EINVAL;
+			goto end_mod;
+		}
+		field->kptr.dtor = (void *)addr;
+	}
+
+	field->kptr.btf_id = id;
+	field->kptr.btf = kernel_btf;
+	field->kptr.module = mod;
+	return 0;
+end_mod:
+	module_put(mod);
+end_btf:
+	btf_put(kernel_btf);
+	return ret;
 }
 
-struct btf_record *btf_parse_fields(const struct btf *btf, const struct btf_type *t)
+struct btf_record *btf_parse_fields(const struct btf *btf, const struct btf_type *t,
+				    u32 field_mask, u32 value_size)
 {
 	struct btf_field_info info_arr[BTF_FIELDS_MAX];
-	struct btf *kernel_btf = NULL;
-	struct module *mod = NULL;
 	struct btf_record *rec;
 	int ret, i, cnt;
 
-	ret = btf_find_field(btf, t, BTF_FIELD_KPTR, info_arr, ARRAY_SIZE(info_arr));
+	ret = btf_find_field(btf, t, field_mask, info_arr, ARRAY_SIZE(info_arr));
 	if (ret < 0)
 		return ERR_PTR(ret);
 	if (!ret)
@@ -3441,80 +3508,44 @@ struct btf_record *btf_parse_fields(const struct btf *btf, const struct btf_type
 	rec = kzalloc(offsetof(struct btf_record, fields[cnt]), GFP_KERNEL | __GFP_NOWARN);
 	if (!rec)
 		return ERR_PTR(-ENOMEM);
-	rec->cnt = 0;
-	for (i = 0; i < cnt; i++) {
-		const struct btf_type *t;
-		s32 id;
 
-		/* Find type in map BTF, and use it to look up the matching type
-		 * in vmlinux or module BTFs, by name and kind.
-		 */
-		t = btf_type_by_id(btf, info_arr[i].type_id);
-		id = bpf_find_btf_id(__btf_name_by_offset(btf, t->name_off), BTF_INFO_KIND(t->info),
-				     &kernel_btf);
-		if (id < 0) {
-			ret = id;
+	rec->spin_lock_off = -EINVAL;
+	rec->timer_off = -EINVAL;
+	for (i = 0; i < cnt; i++) {
+		if (info_arr[i].off + btf_field_type_size(info_arr[i].type) > value_size) {
+			WARN_ONCE(1, "verifier bug off %d size %d", info_arr[i].off, value_size);
+			ret = -EFAULT;
 			goto end;
 		}
 
-		/* Find and stash the function pointer for the destruction function that
-		 * needs to be eventually invoked from the map free path.
-		 */
-		if (info_arr[i].type == BPF_KPTR_REF) {
-			const struct btf_type *dtor_func;
-			const char *dtor_func_name;
-			unsigned long addr;
-			s32 dtor_btf_id;
-
-			/* This call also serves as a whitelist of allowed objects that
-			 * can be used as a referenced pointer and be stored in a map at
-			 * the same time.
-			 */
-			dtor_btf_id = btf_find_dtor_kfunc(kernel_btf, id);
-			if (dtor_btf_id < 0) {
-				ret = dtor_btf_id;
-				goto end_btf;
-			}
-
-			dtor_func = btf_type_by_id(kernel_btf, dtor_btf_id);
-			if (!dtor_func) {
-				ret = -ENOENT;
-				goto end_btf;
-			}
-
-			if (btf_is_module(kernel_btf)) {
-				mod = btf_try_get_module(kernel_btf);
-				if (!mod) {
-					ret = -ENXIO;
-					goto end_btf;
-				}
-			}
-
-			/* We already verified dtor_func to be btf_type_is_func
-			 * in register_btf_id_dtor_kfuncs.
-			 */
-			dtor_func_name = __btf_name_by_offset(kernel_btf, dtor_func->name_off);
-			addr = kallsyms_lookup_name(dtor_func_name);
-			if (!addr) {
-				ret = -EINVAL;
-				goto end_mod;
-			}
-			rec->fields[i].kptr.dtor = (void *)addr;
-		}
-
+		rec->field_mask |= info_arr[i].type;
 		rec->fields[i].offset = info_arr[i].off;
 		rec->fields[i].type = info_arr[i].type;
-		rec->fields[i].kptr.btf_id = id;
-		rec->fields[i].kptr.btf = kernel_btf;
-		rec->fields[i].kptr.module = mod;
+
+		switch (info_arr[i].type) {
+		case BPF_SPIN_LOCK:
+			WARN_ON_ONCE(rec->spin_lock_off >= 0);
+			/* Cache offset for faster lookup at runtime */
+			rec->spin_lock_off = rec->fields[i].offset;
+			break;
+		case BPF_TIMER:
+			WARN_ON_ONCE(rec->timer_off >= 0);
+			/* Cache offset for faster lookup at runtime */
+			rec->timer_off = rec->fields[i].offset;
+			break;
+		case BPF_KPTR_UNREF:
+		case BPF_KPTR_REF:
+			ret = btf_parse_kptr(btf, &rec->fields[i], &info_arr[i]);
+			if (ret < 0)
+				goto end;
+			break;
+		default:
+			ret = -EFAULT;
+			goto end;
+		}
 		rec->cnt++;
 	}
-	rec->cnt = cnt;
 	return rec;
-end_mod:
-	module_put(mod);
-end_btf:
-	btf_put(kernel_btf);
 end:
 	btf_record_free(rec);
 	return ERR_PTR(ret);
diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
index c5ea8f9bb7a9..50d254cd0709 100644
--- a/kernel/bpf/hashtab.c
+++ b/kernel/bpf/hashtab.c
@@ -222,7 +222,7 @@ static void htab_free_prealloced_timers(struct bpf_htab *htab)
 	u32 num_entries = htab->map.max_entries;
 	int i;
 
-	if (!map_value_has_timer(&htab->map))
+	if (!btf_record_has_field(htab->map.record, BPF_TIMER))
 		return;
 	if (htab_has_extra_elems(htab))
 		num_entries += num_possible_cpus();
@@ -231,9 +231,7 @@ static void htab_free_prealloced_timers(struct bpf_htab *htab)
 		struct htab_elem *elem;
 
 		elem = get_htab_elem(htab, i);
-		bpf_timer_cancel_and_free(elem->key +
-					  round_up(htab->map.key_size, 8) +
-					  htab->map.timer_off);
+		bpf_obj_free_timer(htab->map.record, elem->key + round_up(htab->map.key_size, 8));
 		cond_resched();
 	}
 }
@@ -763,8 +761,6 @@ static void check_and_free_fields(struct bpf_htab *htab,
 {
 	void *map_value = elem->key + round_up(htab->map.key_size, 8);
 
-	if (map_value_has_timer(&htab->map))
-		bpf_timer_cancel_and_free(map_value + htab->map.timer_off);
 	bpf_obj_free_fields(htab->map.record, map_value);
 }
 
@@ -1089,7 +1085,7 @@ static int htab_map_update_elem(struct bpf_map *map, void *key, void *value,
 	head = &b->head;
 
 	if (unlikely(map_flags & BPF_F_LOCK)) {
-		if (unlikely(!map_value_has_spin_lock(map)))
+		if (unlikely(!btf_record_has_field(map->record, BPF_SPIN_LOCK)))
 			return -EINVAL;
 		/* find an element without taking the bucket lock */
 		l_old = lookup_nulls_elem_raw(head, hash, key, key_size,
@@ -1472,12 +1468,8 @@ static void htab_free_malloced_timers(struct bpf_htab *htab)
 		struct htab_elem *l;
 
 		hlist_nulls_for_each_entry(l, n, head, hash_node) {
-			/* We don't reset or free kptr on uref dropping to zero,
-			 * hence just free timer.
-			 */
-			bpf_timer_cancel_and_free(l->key +
-						  round_up(htab->map.key_size, 8) +
-						  htab->map.timer_off);
+			/* We only free timer on uref dropping to zero */
+			bpf_obj_free_timer(htab->map.record, l->key + round_up(htab->map.key_size, 8));
 		}
 		cond_resched_rcu();
 	}
@@ -1488,8 +1480,8 @@ static void htab_map_free_timers(struct bpf_map *map)
 {
 	struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
 
-	/* We don't reset or free kptr on uref dropping to zero. */
-	if (!map_value_has_timer(&htab->map))
+	/* We only free timer on uref dropping to zero */
+	if (!btf_record_has_field(htab->map.record, BPF_TIMER))
 		return;
 	if (!htab_is_prealloc(htab))
 		htab_free_malloced_timers(htab);
@@ -1673,7 +1665,7 @@ __htab_map_lookup_and_delete_batch(struct bpf_map *map,
 
 	elem_map_flags = attr->batch.elem_flags;
 	if ((elem_map_flags & ~BPF_F_LOCK) ||
-	    ((elem_map_flags & BPF_F_LOCK) && !map_value_has_spin_lock(map)))
+	    ((elem_map_flags & BPF_F_LOCK) && !btf_record_has_field(map->record, BPF_SPIN_LOCK)))
 		return -EINVAL;
 
 	map_flags = attr->batch.flags;
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 124fd199ce5c..283f55bbeb70 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -366,9 +366,9 @@ void copy_map_value_locked(struct bpf_map *map, void *dst, void *src,
 	struct bpf_spin_lock *lock;
 
 	if (lock_src)
-		lock = src + map->spin_lock_off;
+		lock = src + map->record->spin_lock_off;
 	else
-		lock = dst + map->spin_lock_off;
+		lock = dst + map->record->spin_lock_off;
 	preempt_disable();
 	__bpf_spin_lock_irqsave(lock);
 	copy_map_value(map, dst, src);
@@ -1169,7 +1169,7 @@ BPF_CALL_3(bpf_timer_init, struct bpf_timer_kern *, timer, struct bpf_map *, map
 		ret = -ENOMEM;
 		goto out;
 	}
-	t->value = (void *)timer - map->timer_off;
+	t->value = (void *)timer - map->record->timer_off;
 	t->map = map;
 	t->prog = NULL;
 	rcu_assign_pointer(t->callback_fn, NULL);
diff --git a/kernel/bpf/local_storage.c b/kernel/bpf/local_storage.c
index 098cf336fae6..e90d9f63edc5 100644
--- a/kernel/bpf/local_storage.c
+++ b/kernel/bpf/local_storage.c
@@ -151,7 +151,7 @@ static int cgroup_storage_update_elem(struct bpf_map *map, void *key,
 		return -EINVAL;
 
 	if (unlikely((flags & BPF_F_LOCK) &&
-		     !map_value_has_spin_lock(map)))
+		     !btf_record_has_field(map->record, BPF_SPIN_LOCK)))
 		return -EINVAL;
 
 	storage = cgroup_storage_lookup((struct bpf_cgroup_storage_map *)map,
diff --git a/kernel/bpf/map_in_map.c b/kernel/bpf/map_in_map.c
index d6c662183f88..8ca0cca39d49 100644
--- a/kernel/bpf/map_in_map.c
+++ b/kernel/bpf/map_in_map.c
@@ -29,7 +29,7 @@ struct bpf_map *bpf_map_meta_alloc(int inner_map_ufd)
 		return ERR_PTR(-ENOTSUPP);
 	}
 
-	if (map_value_has_spin_lock(inner_map)) {
+	if (btf_record_has_field(inner_map->record, BPF_SPIN_LOCK)) {
 		fdput(f);
 		return ERR_PTR(-ENOTSUPP);
 	}
@@ -50,8 +50,6 @@ struct bpf_map *bpf_map_meta_alloc(int inner_map_ufd)
 	inner_map_meta->value_size = inner_map->value_size;
 	inner_map_meta->map_flags = inner_map->map_flags;
 	inner_map_meta->max_entries = inner_map->max_entries;
-	inner_map_meta->spin_lock_off = inner_map->spin_lock_off;
-	inner_map_meta->timer_off = inner_map->timer_off;
 	inner_map_meta->record = btf_record_dup(inner_map->record);
 	if (IS_ERR(inner_map_meta->record)) {
 		/* btf_record_dup returns NULL or valid pointer in case of
@@ -92,7 +90,6 @@ bool bpf_map_meta_equal(const struct bpf_map *meta0,
 	return meta0->map_type == meta1->map_type &&
 		meta0->key_size == meta1->key_size &&
 		meta0->value_size == meta1->value_size &&
-		meta0->timer_off == meta1->timer_off &&
 		meta0->map_flags == meta1->map_flags &&
 		btf_record_equal(meta0->record, meta1->record);
 }
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 2d4bba45fd3c..73822d36aa56 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -527,6 +527,9 @@ void btf_record_free(struct btf_record *rec)
 		return;
 	for (i = 0; i < rec->cnt; i++) {
 		switch (rec->fields[i].type) {
+		case BPF_SPIN_LOCK:
+		case BPF_TIMER:
+			break;
 		case BPF_KPTR_UNREF:
 		case BPF_KPTR_REF:
 			if (rec->fields[i].kptr.module)
@@ -564,6 +567,9 @@ struct btf_record *btf_record_dup(const struct btf_record *rec)
 	new_rec->cnt = 0;
 	for (i = 0; i < rec->cnt; i++) {
 		switch (fields[i].type) {
+		case BPF_SPIN_LOCK:
+		case BPF_TIMER:
+			break;
 		case BPF_KPTR_UNREF:
 		case BPF_KPTR_REF:
 			btf_get(fields[i].kptr.btf);
@@ -600,6 +606,13 @@ bool btf_record_equal(const struct btf_record *rec_a, const struct btf_record *r
 	return !memcmp(rec_a, rec_b, size);
 }
 
+void bpf_obj_free_timer(const struct btf_record *rec, void *obj)
+{
+	if (WARN_ON_ONCE(!btf_record_has_field(rec, BPF_TIMER)))
+		return;
+	bpf_timer_cancel_and_free(obj + rec->timer_off);
+}
+
 void bpf_obj_free_fields(const struct btf_record *rec, void *obj)
 {
 	const struct btf_field *fields;
@@ -613,6 +626,11 @@ void bpf_obj_free_fields(const struct btf_record *rec, void *obj)
 		void *field_ptr = obj + field->offset;
 
 		switch (fields[i].type) {
+		case BPF_SPIN_LOCK:
+			break;
+		case BPF_TIMER:
+			bpf_timer_cancel_and_free(field_ptr);
+			break;
 		case BPF_KPTR_UNREF:
 			WRITE_ONCE(*(u64 *)field_ptr, 0);
 			break;
@@ -798,8 +816,7 @@ static int bpf_map_mmap(struct file *filp, struct vm_area_struct *vma)
 	struct bpf_map *map = filp->private_data;
 	int err;
 
-	if (!map->ops->map_mmap || map_value_has_spin_lock(map) ||
-	    map_value_has_timer(map) || !IS_ERR_OR_NULL(map->record))
+	if (!map->ops->map_mmap || !IS_ERR_OR_NULL(map->record))
 		return -ENOTSUPP;
 
 	if (!(vma->vm_flags & VM_SHARED))
@@ -954,13 +971,13 @@ static void map_field_offs_swap(void *_a, void *_b, int size, const void *priv)
 
 static int bpf_map_alloc_off_arr(struct bpf_map *map)
 {
-	bool has_spin_lock = map_value_has_spin_lock(map);
-	bool has_timer = map_value_has_timer(map);
 	bool has_fields = !IS_ERR_OR_NULL(map);
 	struct btf_field_offs *fo;
-	u32 i;
+	struct btf_record *rec;
+	u32 i, *off;
+	u8 *sz;
 
-	if (!has_spin_lock && !has_timer && !has_fields) {
+	if (!has_fields) {
 		map->field_offs = NULL;
 		return 0;
 	}
@@ -970,32 +987,14 @@ static int bpf_map_alloc_off_arr(struct bpf_map *map)
 		return -ENOMEM;
 	map->field_offs = fo;
 
-	fo->cnt = 0;
-	if (has_spin_lock) {
-		i = fo->cnt;
-
-		fo->field_off[i] = map->spin_lock_off;
-		fo->field_sz[i] = sizeof(struct bpf_spin_lock);
-		fo->cnt++;
-	}
-	if (has_timer) {
-		i = fo->cnt;
-
-		fo->field_off[i] = map->timer_off;
-		fo->field_sz[i] = sizeof(struct bpf_timer);
-		fo->cnt++;
-	}
-	if (has_fields) {
-		struct btf_record *rec = map->record;
-		u32 *off = &fo->field_off[fo->cnt];
-		u8 *sz = &fo->field_sz[fo->cnt];
-
-		for (i = 0; i < rec->cnt; i++) {
-			*off++ = rec->fields[i].offset;
-			*sz++ = btf_field_type_size(rec->fields[i].type);
-		}
-		fo->cnt += rec->cnt;
+	rec = map->record;
+	off = &fo->field_off[fo->cnt];
+	sz = &fo->field_sz[fo->cnt];
+	for (i = 0; i < rec->cnt; i++) {
+		*off++ = rec->fields[i].offset;
+		*sz++ = btf_field_type_size(rec->fields[i].type);
 	}
+	fo->cnt = rec->cnt;
 
 	if (fo->cnt == 1)
 		return 0;
@@ -1026,39 +1025,8 @@ static int map_check_btf(struct bpf_map *map, const struct btf *btf,
 	if (!value_type || value_size != map->value_size)
 		return -EINVAL;
 
-	map->spin_lock_off = btf_find_spin_lock(btf, value_type);
-
-	if (map_value_has_spin_lock(map)) {
-		if (map->map_flags & BPF_F_RDONLY_PROG)
-			return -EACCES;
-		if (map->map_type != BPF_MAP_TYPE_HASH &&
-		    map->map_type != BPF_MAP_TYPE_ARRAY &&
-		    map->map_type != BPF_MAP_TYPE_CGROUP_STORAGE &&
-		    map->map_type != BPF_MAP_TYPE_SK_STORAGE &&
-		    map->map_type != BPF_MAP_TYPE_INODE_STORAGE &&
-		    map->map_type != BPF_MAP_TYPE_TASK_STORAGE &&
-		    map->map_type != BPF_MAP_TYPE_CGRP_STORAGE)
-			return -ENOTSUPP;
-		if (map->spin_lock_off + sizeof(struct bpf_spin_lock) >
-		    map->value_size) {
-			WARN_ONCE(1,
-				  "verifier bug spin_lock_off %d value_size %d\n",
-				  map->spin_lock_off, map->value_size);
-			return -EFAULT;
-		}
-	}
-
-	map->timer_off = btf_find_timer(btf, value_type);
-	if (map_value_has_timer(map)) {
-		if (map->map_flags & BPF_F_RDONLY_PROG)
-			return -EACCES;
-		if (map->map_type != BPF_MAP_TYPE_HASH &&
-		    map->map_type != BPF_MAP_TYPE_LRU_HASH &&
-		    map->map_type != BPF_MAP_TYPE_ARRAY)
-			return -EOPNOTSUPP;
-	}
-
-	map->record = btf_parse_fields(btf, value_type);
+	map->record = btf_parse_fields(btf, value_type, BPF_SPIN_LOCK | BPF_TIMER | BPF_KPTR,
+				       map->value_size);
 	if (!IS_ERR_OR_NULL(map->record)) {
 		int i;
 
@@ -1074,6 +1042,26 @@ static int map_check_btf(struct bpf_map *map, const struct btf *btf,
 			switch (map->record->field_mask & (1 << i)) {
 			case 0:
 				continue;
+			case BPF_SPIN_LOCK:
+				if (map->map_type != BPF_MAP_TYPE_HASH &&
+				    map->map_type != BPF_MAP_TYPE_ARRAY &&
+				    map->map_type != BPF_MAP_TYPE_CGROUP_STORAGE &&
+				    map->map_type != BPF_MAP_TYPE_SK_STORAGE &&
+				    map->map_type != BPF_MAP_TYPE_INODE_STORAGE &&
+				    map->map_type != BPF_MAP_TYPE_TASK_STORAGE &&
+				    map->map_type != BPF_MAP_TYPE_CGRP_STORAGE) {
+					ret = -EOPNOTSUPP;
+					goto free_map_tab;
+				}
+				break;
+			case BPF_TIMER:
+				if (map->map_type != BPF_MAP_TYPE_HASH &&
+				    map->map_type != BPF_MAP_TYPE_LRU_HASH &&
+				    map->map_type != BPF_MAP_TYPE_ARRAY) {
+					return -EOPNOTSUPP;
+					goto free_map_tab;
+				}
+				break;
 			case BPF_KPTR_UNREF:
 			case BPF_KPTR_REF:
 				if (map->map_type != BPF_MAP_TYPE_HASH &&
@@ -1153,8 +1141,6 @@ static int map_create(union bpf_attr *attr)
 	mutex_init(&map->freeze_mutex);
 	spin_lock_init(&map->owner.lock);
 
-	map->spin_lock_off = -EINVAL;
-	map->timer_off = -EINVAL;
 	if (attr->btf_key_type_id || attr->btf_value_type_id ||
 	    /* Even the map's value is a kernel's struct,
 	     * the bpf_prog.o must have BTF to begin with
@@ -1368,7 +1354,7 @@ static int map_lookup_elem(union bpf_attr *attr)
 	}
 
 	if ((attr->flags & BPF_F_LOCK) &&
-	    !map_value_has_spin_lock(map)) {
+	    !btf_record_has_field(map->record, BPF_SPIN_LOCK)) {
 		err = -EINVAL;
 		goto err_put;
 	}
@@ -1441,7 +1427,7 @@ static int map_update_elem(union bpf_attr *attr, bpfptr_t uattr)
 	}
 
 	if ((attr->flags & BPF_F_LOCK) &&
-	    !map_value_has_spin_lock(map)) {
+	    !btf_record_has_field(map->record, BPF_SPIN_LOCK)) {
 		err = -EINVAL;
 		goto err_put;
 	}
@@ -1604,7 +1590,7 @@ int generic_map_delete_batch(struct bpf_map *map,
 		return -EINVAL;
 
 	if ((attr->batch.elem_flags & BPF_F_LOCK) &&
-	    !map_value_has_spin_lock(map)) {
+	    !btf_record_has_field(map->record, BPF_SPIN_LOCK)) {
 		return -EINVAL;
 	}
 
@@ -1661,7 +1647,7 @@ int generic_map_update_batch(struct bpf_map *map,
 		return -EINVAL;
 
 	if ((attr->batch.elem_flags & BPF_F_LOCK) &&
-	    !map_value_has_spin_lock(map)) {
+	    !btf_record_has_field(map->record, BPF_SPIN_LOCK)) {
 		return -EINVAL;
 	}
 
@@ -1724,7 +1710,7 @@ int generic_map_lookup_batch(struct bpf_map *map,
 		return -EINVAL;
 
 	if ((attr->batch.elem_flags & BPF_F_LOCK) &&
-	    !map_value_has_spin_lock(map))
+	    !btf_record_has_field(map->record, BPF_SPIN_LOCK))
 		return -EINVAL;
 
 	value_size = bpf_map_value_size(map);
@@ -1846,7 +1832,7 @@ static int map_lookup_and_delete_elem(union bpf_attr *attr)
 	}
 
 	if ((attr->flags & BPF_F_LOCK) &&
-	    !map_value_has_spin_lock(map)) {
+	    !btf_record_has_field(map->record, BPF_SPIN_LOCK)) {
 		err = -EINVAL;
 		goto err_put;
 	}
@@ -1917,8 +1903,7 @@ static int map_freeze(const union bpf_attr *attr)
 	if (IS_ERR(map))
 		return PTR_ERR(map);
 
-	if (map->map_type == BPF_MAP_TYPE_STRUCT_OPS ||
-	    map_value_has_timer(map) || !IS_ERR_OR_NULL(map->record)) {
+	if (map->map_type == BPF_MAP_TYPE_STRUCT_OPS || !IS_ERR_OR_NULL(map->record)) {
 		fdput(f);
 		return -ENOTSUPP;
 	}
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 5ce5364ce898..73a3516f1a48 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -454,7 +454,7 @@ static bool reg_type_not_null(enum bpf_reg_type type)
 static bool reg_may_point_to_spin_lock(const struct bpf_reg_state *reg)
 {
 	return reg->type == PTR_TO_MAP_VALUE &&
-		map_value_has_spin_lock(reg->map_ptr);
+	       btf_record_has_field(reg->map_ptr->record, BPF_SPIN_LOCK);
 }
 
 static bool type_is_rdonly_mem(u32 type)
@@ -1388,7 +1388,7 @@ static void mark_ptr_not_null_reg(struct bpf_reg_state *reg)
 			/* transfer reg's id which is unique for every map_lookup_elem
 			 * as UID of the inner map.
 			 */
-			if (map_value_has_timer(map->inner_map_meta))
+			if (btf_record_has_field(map->inner_map_meta->record, BPF_TIMER))
 				reg->map_uid = reg->id;
 		} else if (map->map_type == BPF_MAP_TYPE_XSKMAP) {
 			reg->type = PTR_TO_XDP_SOCK;
@@ -3817,29 +3817,6 @@ static int check_map_access(struct bpf_verifier_env *env, u32 regno,
 	if (err)
 		return err;
 
-	if (map_value_has_spin_lock(map)) {
-		u32 lock = map->spin_lock_off;
-
-		/* if any part of struct bpf_spin_lock can be touched by
-		 * load/store reject this program.
-		 * To check that [x1, x2) overlaps with [y1, y2)
-		 * it is sufficient to check x1 < y2 && y1 < x2.
-		 */
-		if (reg->smin_value + off < lock + sizeof(struct bpf_spin_lock) &&
-		     lock < reg->umax_value + off + size) {
-			verbose(env, "bpf_spin_lock cannot be accessed directly by load/store\n");
-			return -EACCES;
-		}
-	}
-	if (map_value_has_timer(map)) {
-		u32 t = map->timer_off;
-
-		if (reg->smin_value + off < t + sizeof(struct bpf_timer) &&
-		     t < reg->umax_value + off + size) {
-			verbose(env, "bpf_timer cannot be accessed directly by load/store\n");
-			return -EACCES;
-		}
-	}
 	if (IS_ERR_OR_NULL(map->record))
 		return 0;
 	rec = map->record;
@@ -3847,6 +3824,10 @@ static int check_map_access(struct bpf_verifier_env *env, u32 regno,
 		struct btf_field *field = &rec->fields[i];
 		u32 p = field->offset;
 
+		/* If any part of a field  can be touched by load/store, reject
+		 * this program. To check that [x1, x2) overlaps with [y1, y2),
+		 * it is sufficient to check x1 < y2 && y1 < x2.
+		 */
 		if (reg->smin_value + off < p + btf_field_type_size(field->type) &&
 		    p < reg->umax_value + off + size) {
 			switch (field->type) {
@@ -3871,7 +3852,8 @@ static int check_map_access(struct bpf_verifier_env *env, u32 regno,
 				}
 				break;
 			default:
-				verbose(env, "field cannot be accessed directly by load/store\n");
+				verbose(env, "%s cannot be accessed directly by load/store\n",
+					btf_field_type_name(field->type));
 				return -EACCES;
 			}
 		}
@@ -5440,24 +5422,13 @@ static int process_spin_lock(struct bpf_verifier_env *env, int regno,
 			map->name);
 		return -EINVAL;
 	}
-	if (!map_value_has_spin_lock(map)) {
-		if (map->spin_lock_off == -E2BIG)
-			verbose(env,
-				"map '%s' has more than one 'struct bpf_spin_lock'\n",
-				map->name);
-		else if (map->spin_lock_off == -ENOENT)
-			verbose(env,
-				"map '%s' doesn't have 'struct bpf_spin_lock'\n",
-				map->name);
-		else
-			verbose(env,
-				"map '%s' is not a struct type or bpf_spin_lock is mangled\n",
-				map->name);
+	if (!btf_record_has_field(map->record, BPF_SPIN_LOCK)) {
+		verbose(env, "map '%s' has no valid bpf_spin_lock\n", map->name);
 		return -EINVAL;
 	}
-	if (map->spin_lock_off != val + reg->off) {
-		verbose(env, "off %lld doesn't point to 'struct bpf_spin_lock'\n",
-			val + reg->off);
+	if (map->record->spin_lock_off != val + reg->off) {
+		verbose(env, "off %lld doesn't point to 'struct bpf_spin_lock' that is at %d\n",
+			val + reg->off, map->record->spin_lock_off);
 		return -EINVAL;
 	}
 	if (is_lock) {
@@ -5500,24 +5471,13 @@ static int process_timer_func(struct bpf_verifier_env *env, int regno,
 			map->name);
 		return -EINVAL;
 	}
-	if (!map_value_has_timer(map)) {
-		if (map->timer_off == -E2BIG)
-			verbose(env,
-				"map '%s' has more than one 'struct bpf_timer'\n",
-				map->name);
-		else if (map->timer_off == -ENOENT)
-			verbose(env,
-				"map '%s' doesn't have 'struct bpf_timer'\n",
-				map->name);
-		else
-			verbose(env,
-				"map '%s' is not a struct type or bpf_timer is mangled\n",
-				map->name);
+	if (!btf_record_has_field(map->record, BPF_TIMER)) {
+		verbose(env, "map '%s' has no valid bpf_timer\n", map->name);
 		return -EINVAL;
 	}
-	if (map->timer_off != val + reg->off) {
+	if (map->record->timer_off != val + reg->off) {
 		verbose(env, "off %lld doesn't point to 'struct bpf_timer' that is at %d\n",
-			val + reg->off, map->timer_off);
+			val + reg->off, map->record->timer_off);
 		return -EINVAL;
 	}
 	if (meta->map_ptr) {
@@ -7470,7 +7430,7 @@ static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn
 		regs[BPF_REG_0].map_uid = meta.map_uid;
 		regs[BPF_REG_0].type = PTR_TO_MAP_VALUE | ret_flag;
 		if (!type_may_be_null(ret_type) &&
-		    map_value_has_spin_lock(meta.map_ptr)) {
+		    btf_record_has_field(meta.map_ptr->record, BPF_SPIN_LOCK)) {
 			regs[BPF_REG_0].id = ++env->id_gen;
 		}
 		break;
@@ -10381,7 +10341,7 @@ static int check_ld_imm(struct bpf_verifier_env *env, struct bpf_insn *insn)
 	    insn->src_reg == BPF_PSEUDO_MAP_IDX_VALUE) {
 		dst_reg->type = PTR_TO_MAP_VALUE;
 		dst_reg->off = aux->map_off;
-		if (map_value_has_spin_lock(map))
+		if (btf_record_has_field(map->record, BPF_SPIN_LOCK))
 			dst_reg->id = ++env->id_gen;
 	} else if (insn->src_reg == BPF_PSEUDO_MAP_FD ||
 		   insn->src_reg == BPF_PSEUDO_MAP_IDX) {
@@ -12659,7 +12619,7 @@ static int check_map_prog_compatibility(struct bpf_verifier_env *env,
 {
 	enum bpf_prog_type prog_type = resolve_prog_type(prog);
 
-	if (map_value_has_spin_lock(map)) {
+	if (btf_record_has_field(map->record, BPF_SPIN_LOCK)) {
 		if (prog_type == BPF_PROG_TYPE_SOCKET_FILTER) {
 			verbose(env, "socket filter progs cannot use bpf_spin_lock yet\n");
 			return -EINVAL;
@@ -12676,7 +12636,7 @@ static int check_map_prog_compatibility(struct bpf_verifier_env *env,
 		}
 	}
 
-	if (map_value_has_timer(map)) {
+	if (btf_record_has_field(map->record, BPF_TIMER)) {
 		if (is_tracing_prog_type(prog_type)) {
 			verbose(env, "tracing progs cannot use bpf_timer yet\n");
 			return -EINVAL;
diff --git a/net/core/bpf_sk_storage.c b/net/core/bpf_sk_storage.c
index 49884e7de080..9d2288c0736e 100644
--- a/net/core/bpf_sk_storage.c
+++ b/net/core/bpf_sk_storage.c
@@ -147,7 +147,7 @@ bpf_sk_storage_clone_elem(struct sock *newsk,
 	if (!copy_selem)
 		return NULL;
 
-	if (map_value_has_spin_lock(&smap->map))
+	if (btf_record_has_field(smap->map.record, BPF_SPIN_LOCK))
 		copy_map_value_locked(&smap->map, SDATA(copy_selem)->data,
 				      SDATA(selem)->data, true);
 	else
@@ -566,7 +566,7 @@ static int diag_get(struct bpf_local_storage_data *sdata, struct sk_buff *skb)
 	if (!nla_value)
 		goto errout;
 
-	if (map_value_has_spin_lock(&smap->map))
+	if (btf_record_has_field(smap->map.record, BPF_SPIN_LOCK))
 		copy_map_value_locked(&smap->map, nla_data(nla_value),
 				      sdata->data, true);
 	else
-- 
2.38.1

[PATCH bpf-next v4 08/24] bpf: Refactor map->off_arr handling

[Kumar Kartikeya Dwivedi]

Refactor map->off_arr handling into generic functions that can work on
their own without hardcoding map specific code. The btf_fields_offs
structure is now returned from btf_parse_field_offs, which can be reused
later for types in program BTF.

All functions like copy_map_value, zero_map_value call generic
underlying functions so that they can also be reused later for copying
to values allocated in programs which encode specific fields.

Later, some helper functions will also require access to this
btf_field_offs structure to be able to skip over special fields at
runtime.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 include/linux/bpf.h  | 41 ++++++++++++++-----------
 include/linux/btf.h  |  1 +
 kernel/bpf/btf.c     | 55 +++++++++++++++++++++++++++++++++
 kernel/bpf/syscall.c | 73 ++++++--------------------------------------
 4 files changed, 89 insertions(+), 81 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index d5c81b09577a..bb96bf947e53 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -341,57 +341,64 @@ static inline void bpf_long_memcpy(void *dst, const void *src, u32 size)
 }
 
 /* copy everything but bpf_spin_lock, bpf_timer, and kptrs. There could be one of each. */
-static inline void __copy_map_value(struct bpf_map *map, void *dst, void *src, bool long_memcpy)
+static inline void bpf_obj_memcpy(struct btf_field_offs *foffs,
+				  void *dst, void *src, u32 size,
+				  bool long_memcpy)
 {
 	u32 curr_off = 0;
 	int i;
 
-	if (likely(!map->field_offs)) {
+	if (likely(!foffs)) {
 		if (long_memcpy)
-			bpf_long_memcpy(dst, src, round_up(map->value_size, 8));
+			bpf_long_memcpy(dst, src, round_up(size, 8));
 		else
-			memcpy(dst, src, map->value_size);
+			memcpy(dst, src, size);
 		return;
 	}
 
-	for (i = 0; i < map->field_offs->cnt; i++) {
-		u32 next_off = map->field_offs->field_off[i];
+	for (i = 0; i < foffs->cnt; i++) {
+		u32 next_off = foffs->field_off[i];
 		u32 sz = next_off - curr_off;
 
 		memcpy(dst + curr_off, src + curr_off, sz);
-		curr_off += map->field_offs->field_sz[i] + sz;
+		curr_off += foffs->field_sz[i] + sz;
 	}
-	memcpy(dst + curr_off, src + curr_off, map->value_size - curr_off);
+	memcpy(dst + curr_off, src + curr_off, size - curr_off);
 }
 
 static inline void copy_map_value(struct bpf_map *map, void *dst, void *src)
 {
-	__copy_map_value(map, dst, src, false);
+	bpf_obj_memcpy(map->field_offs, dst, src, map->value_size, false);
 }
 
 static inline void copy_map_value_long(struct bpf_map *map, void *dst, void *src)
 {
-	__copy_map_value(map, dst, src, true);
+	bpf_obj_memcpy(map->field_offs, dst, src, map->value_size, true);
 }
 
-static inline void zero_map_value(struct bpf_map *map, void *dst)
+static inline void bpf_obj_memzero(struct btf_field_offs *foffs, void *dst, u32 size)
 {
 	u32 curr_off = 0;
 	int i;
 
-	if (likely(!map->field_offs)) {
-		memset(dst, 0, map->value_size);
+	if (likely(!foffs)) {
+		memset(dst, 0, size);
 		return;
 	}
 
-	for (i = 0; i < map->field_offs->cnt; i++) {
-		u32 next_off = map->field_offs->field_off[i];
+	for (i = 0; i < foffs->cnt; i++) {
+		u32 next_off = foffs->field_off[i];
 		u32 sz = next_off - curr_off;
 
 		memset(dst + curr_off, 0, sz);
-		curr_off += map->field_offs->field_sz[i] + sz;
+		curr_off += foffs->field_sz[i] + sz;
 	}
-	memset(dst + curr_off, 0, map->value_size - curr_off);
+	memset(dst + curr_off, 0, size - curr_off);
+}
+
+static inline void zero_map_value(struct bpf_map *map, void *dst)
+{
+	bpf_obj_memzero(map->field_offs, dst, map->value_size);
 }
 
 void copy_map_value_locked(struct bpf_map *map, void *dst, void *src,
diff --git a/include/linux/btf.h b/include/linux/btf.h
index 282006abd062..d80345fa566b 100644
--- a/include/linux/btf.h
+++ b/include/linux/btf.h
@@ -165,6 +165,7 @@ int btf_find_spin_lock(const struct btf *btf, const struct btf_type *t);
 int btf_find_timer(const struct btf *btf, const struct btf_type *t);
 struct btf_record *btf_parse_fields(const struct btf *btf, const struct btf_type *t,
 				    u32 field_mask, u32 value_size);
+struct btf_field_offs *btf_parse_field_offs(struct btf_record *rec);
 bool btf_type_is_void(const struct btf_type *t);
 s32 btf_find_by_name_kind(const struct btf *btf, const char *name, u8 kind);
 const struct btf_type *btf_type_skip_modifiers(const struct btf *btf,
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 3dad828db13c..197687c86dc1 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -3551,6 +3551,61 @@ struct btf_record *btf_parse_fields(const struct btf *btf, const struct btf_type
 	return ERR_PTR(ret);
 }
 
+static int btf_field_offs_cmp(const void *_a, const void *_b, const void *priv)
+{
+	const u32 a = *(const u32 *)_a;
+	const u32 b = *(const u32 *)_b;
+
+	if (a < b)
+		return -1;
+	else if (a > b)
+		return 1;
+	return 0;
+}
+
+static void btf_field_offs_swap(void *_a, void *_b, int size, const void *priv)
+{
+	struct btf_field_offs *foffs = (void *)priv;
+	u32 *off_base = foffs->field_off;
+	u32 *a = _a, *b = _b;
+	u8 *sz_a, *sz_b;
+
+	sz_a = foffs->field_sz + (a - off_base);
+	sz_b = foffs->field_sz + (b - off_base);
+
+	swap(*a, *b);
+	swap(*sz_a, *sz_b);
+}
+
+struct btf_field_offs *btf_parse_field_offs(struct btf_record *rec)
+{
+	struct btf_field_offs *foffs;
+	u32 i, *off;
+	u8 *sz;
+
+	BUILD_BUG_ON(ARRAY_SIZE(foffs->field_off) != ARRAY_SIZE(foffs->field_sz));
+	if (IS_ERR_OR_NULL(rec) || WARN_ON_ONCE(rec->cnt > sizeof(foffs->field_off)))
+		return NULL;
+
+	foffs = kzalloc(sizeof(*foffs), GFP_KERNEL | __GFP_NOWARN);
+	if (!foffs)
+		return ERR_PTR(-ENOMEM);
+
+	off = &foffs->field_off[0];
+	sz = &foffs->field_sz[0];
+	for (i = 0; i < rec->cnt; i++) {
+		off[i] = rec->fields[i].offset;
+		sz[i] = btf_field_type_size(rec->fields[i].type);
+	}
+	foffs->cnt = rec->cnt;
+
+	if (foffs->cnt == 1)
+		return foffs;
+	sort_r(foffs->field_off, foffs->cnt, sizeof(foffs->field_off[0]),
+	       btf_field_offs_cmp, btf_field_offs_swap, foffs);
+	return foffs;
+}
+
 static void __btf_struct_show(const struct btf *btf, const struct btf_type *t,
 			      u32 type_id, void *data, u8 bits_offset,
 			      struct btf_show *show)
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 73822d36aa56..85532d301124 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -943,66 +943,6 @@ int map_check_no_btf(const struct bpf_map *map,
 	return -ENOTSUPP;
 }
 
-static int map_field_offs_cmp(const void *_a, const void *_b, const void *priv)
-{
-	const u32 a = *(const u32 *)_a;
-	const u32 b = *(const u32 *)_b;
-
-	if (a < b)
-		return -1;
-	else if (a > b)
-		return 1;
-	return 0;
-}
-
-static void map_field_offs_swap(void *_a, void *_b, int size, const void *priv)
-{
-	struct bpf_map *map = (struct bpf_map *)priv;
-	u32 *off_base = map->field_offs->field_off;
-	u32 *a = _a, *b = _b;
-	u8 *sz_a, *sz_b;
-
-	sz_a = map->field_offs->field_sz + (a - off_base);
-	sz_b = map->field_offs->field_sz + (b - off_base);
-
-	swap(*a, *b);
-	swap(*sz_a, *sz_b);
-}
-
-static int bpf_map_alloc_off_arr(struct bpf_map *map)
-{
-	bool has_fields = !IS_ERR_OR_NULL(map);
-	struct btf_field_offs *fo;
-	struct btf_record *rec;
-	u32 i, *off;
-	u8 *sz;
-
-	if (!has_fields) {
-		map->field_offs = NULL;
-		return 0;
-	}
-
-	fo = kmalloc(sizeof(*map->field_offs), GFP_KERNEL | __GFP_NOWARN);
-	if (!fo)
-		return -ENOMEM;
-	map->field_offs = fo;
-
-	rec = map->record;
-	off = &fo->field_off[fo->cnt];
-	sz = &fo->field_sz[fo->cnt];
-	for (i = 0; i < rec->cnt; i++) {
-		*off++ = rec->fields[i].offset;
-		*sz++ = btf_field_type_size(rec->fields[i].type);
-	}
-	fo->cnt = rec->cnt;
-
-	if (fo->cnt == 1)
-		return 0;
-	sort_r(fo->field_off, fo->cnt, sizeof(fo->field_off[0]),
-	       map_field_offs_cmp, map_field_offs_swap, map);
-	return 0;
-}
-
 static int map_check_btf(struct bpf_map *map, const struct btf *btf,
 			 u32 btf_key_id, u32 btf_value_id)
 {
@@ -1097,6 +1037,7 @@ static int map_check_btf(struct bpf_map *map, const struct btf *btf,
 static int map_create(union bpf_attr *attr)
 {
 	int numa_node = bpf_map_attr_numa_node(attr);
+	struct btf_field_offs *foffs;
 	struct bpf_map *map;
 	int f_flags;
 	int err;
@@ -1176,13 +1117,17 @@ static int map_create(union bpf_attr *attr)
 			attr->btf_vmlinux_value_type_id;
 	}
 
-	err = bpf_map_alloc_off_arr(map);
-	if (err)
+
+	foffs = btf_parse_field_offs(map->record);
+	if (IS_ERR(foffs)) {
+		err = PTR_ERR(foffs);
 		goto free_map;
+	}
+	map->field_offs = foffs;
 
 	err = security_bpf_map_alloc(map);
 	if (err)
-		goto free_map_off_arr;
+		goto free_map_field_offs;
 
 	err = bpf_map_alloc_id(map);
 	if (err)
@@ -1206,7 +1151,7 @@ static int map_create(union bpf_attr *attr)
 
 free_map_sec:
 	security_bpf_map_free(map);
-free_map_off_arr:
+free_map_field_offs:
 	kfree(map->field_offs);
 free_map:
 	btf_put(map->btf);
-- 
2.38.1

[PATCH bpf-next v4 09/24] bpf: Support bpf_list_head in map values

[Kumar Kartikeya Dwivedi]

Add the basic support on the map side to parse, recognize, verify, and
build metadata table for a new special field of the type struct
bpf_list_head. To parameterize the bpf_list_head for a certain value
type and the list_node member it will accept in that value type, we use
BTF declaration tags.

The definition of bpf_list_head in a map value will be done as follows:

struct foo {
	struct bpf_list_node node;
	int data;
};

struct map_value {
	struct bpf_list_head head __contains(foo, node);
};

Then, the bpf_list_head only allows adding to the list 'head' using the
bpf_list_node 'node' for the type struct foo.

The 'contains' annotation is a BTF declaration tag composed of four
parts, "contains:name:node" where the name is then used to look up the
type in the map BTF, with its kind hardcoded to BTF_KIND_STRUCT during
the lookup. The node defines name of the member in this type that has
the type struct bpf_list_node, which is actually used for linking into
the linked list. For now, 'kind' part is hardcoded as struct.

This allows building intrusive linked lists in BPF, using container_of
to obtain pointer to entry, while being completely type safe from the
perspective of the verifier. The verifier knows exactly the type of the
nodes, and knows that list helpers return that type at some fixed offset
where the bpf_list_node member used for this list exists. The verifier
also uses this information to disallow adding types that are not
accepted by a certain list.

For now, no elements can be added to such lists. Support for that is
coming in future patches, hence draining and freeing items is done with
a TODO that will be resolved in a future patch.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 include/linux/bpf.h            |  17 ++++
 include/uapi/linux/bpf.h       |  10 +++
 kernel/bpf/btf.c               | 144 ++++++++++++++++++++++++++++++++-
 kernel/bpf/helpers.c           |  32 ++++++++
 kernel/bpf/syscall.c           |  22 ++++-
 kernel/bpf/verifier.c          |   7 ++
 tools/include/uapi/linux/bpf.h |  10 +++
 7 files changed, 238 insertions(+), 4 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index bb96bf947e53..2d9ebe9efcad 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -176,6 +176,7 @@ enum btf_field_type {
 	BPF_KPTR_UNREF = (1 << 2),
 	BPF_KPTR_REF   = (1 << 3),
 	BPF_KPTR       = BPF_KPTR_UNREF | BPF_KPTR_REF,
+	BPF_LIST_HEAD  = (1 << 4),
 };
 
 struct btf_field_kptr {
@@ -185,11 +186,18 @@ struct btf_field_kptr {
 	u32 btf_id;
 };
 
+struct btf_field_list_head {
+	struct btf *btf;
+	u32 value_btf_id;
+	u32 node_offset;
+};
+
 struct btf_field {
 	u32 offset;
 	enum btf_field_type type;
 	union {
 		struct btf_field_kptr kptr;
+		struct btf_field_list_head list_head;
 	};
 };
 
@@ -267,6 +275,8 @@ static inline const char *btf_field_type_name(enum btf_field_type type)
 	case BPF_KPTR_UNREF:
 	case BPF_KPTR_REF:
 		return "kptr";
+	case BPF_LIST_HEAD:
+		return "bpf_list_head";
 	default:
 		WARN_ON_ONCE(1);
 		return "unknown";
@@ -283,6 +293,8 @@ static inline u32 btf_field_type_size(enum btf_field_type type)
 	case BPF_KPTR_UNREF:
 	case BPF_KPTR_REF:
 		return sizeof(u64);
+	case BPF_LIST_HEAD:
+		return sizeof(struct bpf_list_head);
 	default:
 		WARN_ON_ONCE(1);
 		return 0;
@@ -299,6 +311,8 @@ static inline u32 btf_field_type_align(enum btf_field_type type)
 	case BPF_KPTR_UNREF:
 	case BPF_KPTR_REF:
 		return __alignof__(u64);
+	case BPF_LIST_HEAD:
+		return __alignof__(struct bpf_list_head);
 	default:
 		WARN_ON_ONCE(1);
 		return 0;
@@ -404,6 +418,9 @@ static inline void zero_map_value(struct bpf_map *map, void *dst)
 void copy_map_value_locked(struct bpf_map *map, void *dst, void *src,
 			   bool lock_src);
 void bpf_timer_cancel_and_free(void *timer);
+void bpf_list_head_free(const struct btf_field *field, void *list_head,
+			struct bpf_spin_lock *spin_lock);
+
 int bpf_obj_name_cpy(char *dst, const char *src, unsigned int size);
 
 struct bpf_offload_dev;
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 94659f6b3395..dd381086bad9 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -6887,6 +6887,16 @@ struct bpf_dynptr {
 	__u64 :64;
 } __attribute__((aligned(8)));
 
+struct bpf_list_head {
+	__u64 :64;
+	__u64 :64;
+} __attribute__((aligned(8)));
+
+struct bpf_list_node {
+	__u64 :64;
+	__u64 :64;
+} __attribute__((aligned(8)));
+
 struct bpf_sysctl {
 	__u32	write;		/* Sysctl is being read (= 0) or written (= 1).
 				 * Allows 1,2,4-byte read, but no write.
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 197687c86dc1..e56025505467 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -3205,9 +3205,15 @@ enum {
 struct btf_field_info {
 	enum btf_field_type type;
 	u32 off;
-	struct {
-		u32 type_id;
-	} kptr;
+	union {
+		struct {
+			u32 type_id;
+		} kptr;
+		struct {
+			const char *node_name;
+			u32 value_btf_id;
+		} list_head;
+	};
 };
 
 static int btf_find_struct(const struct btf *btf, const struct btf_type *t,
@@ -3261,6 +3267,66 @@ static int btf_find_kptr(const struct btf *btf, const struct btf_type *t,
 	return BTF_FIELD_FOUND;
 }
 
+static const char *btf_find_decl_tag_value(const struct btf *btf,
+					   const struct btf_type *pt,
+					   int comp_idx, const char *tag_key)
+{
+	int i;
+
+	for (i = 1; i < btf_nr_types(btf); i++) {
+		const struct btf_type *t = btf_type_by_id(btf, i);
+		int len = strlen(tag_key);
+
+		if (!btf_type_is_decl_tag(t))
+			continue;
+		/* TODO: Instead of btf_type pt, it would be much better if we had BTF
+		 * ID of the map value type. This would avoid btf_type_by_id call here.
+		 */
+		if (pt != btf_type_by_id(btf, t->type) ||
+		    btf_type_decl_tag(t)->component_idx != comp_idx)
+			continue;
+		if (strncmp(__btf_name_by_offset(btf, t->name_off), tag_key, len))
+			continue;
+		return __btf_name_by_offset(btf, t->name_off) + len;
+	}
+	return NULL;
+}
+
+static int btf_find_list_head(const struct btf *btf, const struct btf_type *pt,
+			      const struct btf_type *t, int comp_idx,
+			      u32 off, int sz, struct btf_field_info *info)
+{
+	const char *value_type;
+	const char *list_node;
+	s32 id;
+
+	if (!__btf_type_is_struct(t))
+		return BTF_FIELD_IGNORE;
+	if (t->size != sz)
+		return BTF_FIELD_IGNORE;
+	value_type = btf_find_decl_tag_value(btf, pt, comp_idx, "contains:");
+	if (!value_type)
+		return -EINVAL;
+	list_node = strstr(value_type, ":");
+	if (!list_node)
+		return -EINVAL;
+	value_type = kstrndup(value_type, list_node - value_type, GFP_KERNEL | __GFP_NOWARN);
+	if (!value_type)
+		return -ENOMEM;
+	id = btf_find_by_name_kind(btf, value_type, BTF_KIND_STRUCT);
+	kfree(value_type);
+	if (id < 0)
+		return id;
+	list_node++;
+	if (str_is_empty(list_node))
+		return -EINVAL;
+	info->type = BPF_LIST_HEAD;
+	info->off = off;
+	info->list_head.value_btf_id = id;
+	info->list_head.node_name = list_node;
+	return BTF_FIELD_FOUND;
+}
+
 static int btf_get_field_type(const char *name, u32 field_mask, u32 *seen_mask,
 			      int *align, int *sz)
 {
@@ -3284,6 +3350,12 @@ static int btf_get_field_type(const char *name, u32 field_mask, u32 *seen_mask,
 			goto end;
 		}
 	}
+	if (field_mask & BPF_LIST_HEAD) {
+		if (!strcmp(name, "bpf_list_head")) {
+			type = BPF_LIST_HEAD;
+			goto end;
+		}
+	}
 	/* Only return BPF_KPTR when all other types with matchable names fail */
 	if (field_mask & BPF_KPTR) {
 		type = BPF_KPTR_REF;
@@ -3317,6 +3389,8 @@ static int btf_find_struct_field(const struct btf *btf,
 			return field_type;
 
 		off = __btf_member_bit_offset(t, member);
+		if (i && !off)
+			return -EFAULT;
 		if (off % 8)
 			/* valid C code cannot generate such BTF */
 			return -EINVAL;
@@ -3339,6 +3413,12 @@ static int btf_find_struct_field(const struct btf *btf,
 			if (ret < 0)
 				return ret;
 			break;
+		case BPF_LIST_HEAD:
+			ret = btf_find_list_head(btf, t, member_type, i, off, sz,
+						 idx < info_cnt ? &info[idx] : &tmp);
+			if (ret < 0)
+				return ret;
+			break;
 		default:
 			return -EFAULT;
 		}
@@ -3373,6 +3453,8 @@ static int btf_find_datasec_var(const struct btf *btf, const struct btf_type *t,
 			return field_type;
 
 		off = vsi->offset;
+		if (i && !off)
+			return -EFAULT;
 		if (vsi->size != sz)
 			continue;
 		if (off % align)
@@ -3393,6 +3475,12 @@ static int btf_find_datasec_var(const struct btf *btf, const struct btf_type *t,
 			if (ret < 0)
 				return ret;
 			break;
+		case BPF_LIST_HEAD:
+			ret = btf_find_list_head(btf, var, var_type, -1, off, sz,
+						 idx < info_cnt ? &info[idx] : &tmp);
+			if (ret < 0)
+				return ret;
+			break;
 		default:
 			return -EFAULT;
 		}
@@ -3491,6 +3579,44 @@ static int btf_parse_kptr(const struct btf *btf, struct btf_field *field,
 	return ret;
 }
 
+static int btf_parse_list_head(const struct btf *btf, struct btf_field *field,
+			       struct btf_field_info *info)
+{
+	const struct btf_type *t, *n = NULL;
+	const struct btf_member *member;
+	u32 offset;
+	int i;
+
+	t = btf_type_by_id(btf, info->list_head.value_btf_id);
+	/* We've already checked that value_btf_id is a struct type. We
+	 * just need to figure out the offset of the list_node, and
+	 * verify its type.
+	 */
+	for_each_member(i, t, member) {
+		if (strcmp(info->list_head.node_name, __btf_name_by_offset(btf, member->name_off)))
+			continue;
+		/* Invalid BTF, two members with same name */
+		if (n)
+			return -EINVAL;
+		n = btf_type_by_id(btf, member->type);
+		if (!__btf_type_is_struct(n))
+			return -EINVAL;
+		if (strcmp("bpf_list_node", __btf_name_by_offset(btf, n->name_off)))
+			return -EINVAL;
+		offset = __btf_member_bit_offset(n, member);
+		if (offset % 8)
+			return -EINVAL;
+		offset /= 8;
+		if (offset % __alignof__(struct bpf_list_node))
+			return -EINVAL;
+
+		field->list_head.btf = (struct btf *)btf;
+		field->list_head.value_btf_id = info->list_head.value_btf_id;
+		field->list_head.node_offset = offset;
+	}
+	return 0;
+}
+
 struct btf_record *btf_parse_fields(const struct btf *btf, const struct btf_type *t,
 				    u32 field_mask, u32 value_size)
 {
@@ -3539,12 +3665,24 @@ struct btf_record *btf_parse_fields(const struct btf *btf, const struct btf_type
 			if (ret < 0)
 				goto end;
 			break;
+		case BPF_LIST_HEAD:
+			ret = btf_parse_list_head(btf, &rec->fields[i], &info_arr[i]);
+			if (ret < 0)
+				goto end;
+			break;
 		default:
 			ret = -EFAULT;
 			goto end;
 		}
 		rec->cnt++;
 	}
+
+	/* bpf_list_head requires bpf_spin_lock */
+	if (btf_record_has_field(rec, BPF_LIST_HEAD) && rec->spin_lock_off < 0) {
+		ret = -EINVAL;
+		goto end;
+	}
+
 	return rec;
 end:
 	btf_record_free(rec);
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 283f55bbeb70..339cce94b408 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -1706,6 +1706,38 @@ bpf_base_func_proto(enum bpf_func_id func_id)
 	}
 }
 
+void bpf_list_head_free(const struct btf_field *field, void *list_head,
+			struct bpf_spin_lock *spin_lock)
+{
+	struct list_head *head = list_head, *orig_head = head;
+	unsigned long flags;
+
+	BUILD_BUG_ON(sizeof(struct list_head) > sizeof(struct bpf_list_head));
+	BUILD_BUG_ON(__alignof__(struct list_head) > __alignof__(struct bpf_list_head));
+
+	/* __bpf_spin_lock_irqsave cannot be used here, as we may take a spin
+	 * lock again when we call bpf_obj_free_fields in the loop, and it will
+	 * overwrite the per-CPU local_irq_save state.
+	 */
+	local_irq_save(flags);
+	__bpf_spin_lock(spin_lock);
+	if (!head->next || list_empty(head))
+		goto unlock;
+	head = head->next;
+	while (head != orig_head) {
+		void *obj = head;
+
+		obj -= field->list_head.node_offset;
+		head = head->next;
+		/* TODO: Rework later */
+		kfree(obj);
+	}
+unlock:
+	INIT_LIST_HEAD(head);
+	__bpf_spin_unlock(spin_lock);
+	local_irq_restore(flags);
+}
+
 BTF_SET8_START(tracing_btf_ids)
 #ifdef CONFIG_KEXEC_CORE
 BTF_ID_FLAGS(func, crash_kexec, KF_DESTRUCTIVE)
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 85532d301124..fdbae52f463f 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -536,6 +536,9 @@ void btf_record_free(struct btf_record *rec)
 				module_put(rec->fields[i].kptr.module);
 			btf_put(rec->fields[i].kptr.btf);
 			break;
+		case BPF_LIST_HEAD:
+			/* Nothing to release for bpf_list_head */
+			break;
 		default:
 			WARN_ON_ONCE(1);
 			continue;
@@ -578,6 +581,9 @@ struct btf_record *btf_record_dup(const struct btf_record *rec)
 				goto free;
 			}
 			break;
+		case BPF_LIST_HEAD:
+			/* Nothing to acquire for bpf_list_head */
+			break;
 		default:
 			ret = -EFAULT;
 			WARN_ON_ONCE(1);
@@ -637,6 +643,11 @@ void bpf_obj_free_fields(const struct btf_record *rec, void *obj)
 		case BPF_KPTR_REF:
 			field->kptr.dtor((void *)xchg((unsigned long *)field_ptr, 0));
 			break;
+		case BPF_LIST_HEAD:
+			if (WARN_ON_ONCE(rec->spin_lock_off < 0))
+				continue;
+			bpf_list_head_free(field, field_ptr, obj + rec->spin_lock_off);
+			break;
 		default:
 			WARN_ON_ONCE(1);
 			continue;
@@ -965,7 +976,8 @@ static int map_check_btf(struct bpf_map *map, const struct btf *btf,
 	if (!value_type || value_size != map->value_size)
 		return -EINVAL;
 
-	map->record = btf_parse_fields(btf, value_type, BPF_SPIN_LOCK | BPF_TIMER | BPF_KPTR,
+	map->record = btf_parse_fields(btf, value_type,
+				       BPF_SPIN_LOCK | BPF_TIMER | BPF_KPTR | BPF_LIST_HEAD,
 				       map->value_size);
 	if (!IS_ERR_OR_NULL(map->record)) {
 		int i;
@@ -1012,6 +1024,14 @@ static int map_check_btf(struct bpf_map *map, const struct btf *btf,
 					goto free_map_tab;
 				}
 				break;
+			case BPF_LIST_HEAD:
+				if (map->map_type != BPF_MAP_TYPE_HASH &&
+				    map->map_type != BPF_MAP_TYPE_LRU_HASH &&
+				    map->map_type != BPF_MAP_TYPE_ARRAY) {
+					ret = -EOPNOTSUPP;
+					goto free_map_tab;
+				}
+				break;
 			default:
 				/* Fail if map_type checks are missing for a field type */
 				ret = -EOPNOTSUPP;
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 73a3516f1a48..168cd8bb9fd6 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -12643,6 +12643,13 @@ static int check_map_prog_compatibility(struct bpf_verifier_env *env,
 		}
 	}
 
+	if (btf_record_has_field(map->record, BPF_LIST_HEAD)) {
+		if (is_tracing_prog_type(prog_type)) {
+			verbose(env, "tracing progs cannot use bpf_list_head yet\n");
+			return -EINVAL;
+		}
+	}
+
 	if ((bpf_prog_is_dev_bound(prog->aux) || bpf_map_is_dev_bound(map)) &&
 	    !bpf_offload_prog_map_match(prog, map)) {
 		verbose(env, "offload device mismatch between prog and map\n");
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 94659f6b3395..dd381086bad9 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -6887,6 +6887,16 @@ struct bpf_dynptr {
 	__u64 :64;
 } __attribute__((aligned(8)));
 
+struct bpf_list_head {
+	__u64 :64;
+	__u64 :64;
+} __attribute__((aligned(8)));
+
+struct bpf_list_node {
+	__u64 :64;
+	__u64 :64;
+} __attribute__((aligned(8)));
+
 struct bpf_sysctl {
 	__u32	write;		/* Sysctl is being read (= 0) or written (= 1).
 				 * Allows 1,2,4-byte read, but no write.
-- 
2.38.1

[PATCH bpf-next v4 10/24] bpf: Introduce local kptrs

[Kumar Kartikeya Dwivedi]

Introduce local kptrs, i.e. PTR_TO_BTF_ID that point to a type in
program BTF. This is indicated by the presence of MEM_TYPE_LOCAL type
tag in reg->type to avoid having to check btf_is_kernel when trying to
match argument types in helpers.

Refactor btf_struct_access callback to just take bpf_reg_state instead
of btf and btf_type paramters. Note that the call site in
check_map_access now simulates access to a PTR_TO_BTF_ID by creating a
dummy reg on stack. Since only the type, btf, and btf_id of the register
matter for the checks, it can be done so without complicating the usual
cases elsewhere in the verifier where reg->btf and reg->btf_id is used
verbatim.

For now, these local kptrs will always be referenced in verifier
context, hence ref_obj_id == 0 for them is a bug. It is allowed to write
to such objects, as long fields that are special are not touched
(support for which will be added in subsequent patches). Note that once
such a local kptr is marked PTR_UNTRUSTED, it is no longer allowed to
write to it.

No PROBE_MEM handling is hence done unless PTR_UNTRUSTED is part of the
register type, since they can never be in an undefined state otherwise,
and their lifetime will always be valid.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 include/linux/bpf.h              | 28 ++++++++++++++++--------
 include/linux/filter.h           |  8 +++----
 kernel/bpf/btf.c                 | 16 ++++++++++----
 kernel/bpf/verifier.c            | 37 ++++++++++++++++++++++++++------
 net/bpf/bpf_dummy_struct_ops.c   | 14 ++++++------
 net/core/filter.c                | 34 ++++++++++++-----------------
 net/ipv4/bpf_tcp_ca.c            | 13 ++++++-----
 net/netfilter/nf_conntrack_bpf.c | 17 ++++++---------
 8 files changed, 99 insertions(+), 68 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 2d9ebe9efcad..bdd3adfcbe5f 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -527,6 +527,11 @@ enum bpf_type_flag {
 	/* Size is known at compile time. */
 	MEM_FIXED_SIZE		= BIT(10 + BPF_BASE_TYPE_BITS),
 
+	/* MEM is of a type from program BTF, not kernel BTF. This is used to
+	 * tag PTR_TO_BTF_ID allocated using bpf_kptr_alloc.
+	 */
+	MEM_TYPE_LOCAL		= BIT(11 + BPF_BASE_TYPE_BITS),
+
 	__BPF_TYPE_FLAG_MAX,
 	__BPF_TYPE_LAST_FLAG	= __BPF_TYPE_FLAG_MAX - 1,
 };
@@ -775,6 +780,7 @@ struct bpf_prog_ops {
 			union bpf_attr __user *uattr);
 };
 
+struct bpf_reg_state;
 struct bpf_verifier_ops {
 	/* return eBPF function prototype for verification */
 	const struct bpf_func_proto *
@@ -796,9 +802,8 @@ struct bpf_verifier_ops {
 				  struct bpf_insn *dst,
 				  struct bpf_prog *prog, u32 *target_size);
 	int (*btf_struct_access)(struct bpf_verifier_log *log,
-				 const struct btf *btf,
-				 const struct btf_type *t, int off, int size,
-				 enum bpf_access_type atype,
+				 const struct bpf_reg_state *reg,
+				 int off, int size, enum bpf_access_type atype,
 				 u32 *next_btf_id, enum bpf_type_flag *flag);
 };
 
@@ -2084,9 +2089,9 @@ static inline bool bpf_tracing_btf_ctx_access(int off, int size,
 	return btf_ctx_access(off, size, type, prog, info);
 }
 
-int btf_struct_access(struct bpf_verifier_log *log, const struct btf *btf,
-		      const struct btf_type *t, int off, int size,
-		      enum bpf_access_type atype,
+int btf_struct_access(struct bpf_verifier_log *log,
+		      const struct bpf_reg_state *reg,
+		      int off, int size, enum bpf_access_type atype,
 		      u32 *next_btf_id, enum bpf_type_flag *flag);
 bool btf_struct_ids_match(struct bpf_verifier_log *log,
 			  const struct btf *btf, u32 id, int off,
@@ -2337,9 +2342,8 @@ static inline struct bpf_prog *bpf_prog_by_id(u32 id)
 }
 
 static inline int btf_struct_access(struct bpf_verifier_log *log,
-				    const struct btf *btf,
-				    const struct btf_type *t, int off, int size,
-				    enum bpf_access_type atype,
+				    const struct bpf_reg_state *reg,
+				    int off, int size, enum bpf_access_type atype,
 				    u32 *next_btf_id, enum bpf_type_flag *flag)
 {
 	return -EACCES;
@@ -2796,4 +2800,10 @@ struct bpf_key {
 	bool has_ref;
 };
 #endif /* CONFIG_KEYS */
+
+static inline bool type_is_local_kptr(u32 type)
+{
+	return type & MEM_TYPE_LOCAL;
+}
+
 #endif /* _LINUX_BPF_H */
diff --git a/include/linux/filter.h b/include/linux/filter.h
index efc42a6e3aed..787d35dbf5b0 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -568,10 +568,10 @@ struct sk_filter {
 DECLARE_STATIC_KEY_FALSE(bpf_stats_enabled_key);
 
 extern struct mutex nf_conn_btf_access_lock;
-extern int (*nfct_btf_struct_access)(struct bpf_verifier_log *log, const struct btf *btf,
-				     const struct btf_type *t, int off, int size,
-				     enum bpf_access_type atype, u32 *next_btf_id,
-				     enum bpf_type_flag *flag);
+extern int (*nfct_btf_struct_access)(struct bpf_verifier_log *log,
+				     const struct bpf_reg_state *reg,
+				     int off, int size, enum bpf_access_type atype,
+				     u32 *next_btf_id, enum bpf_type_flag *flag);
 
 typedef unsigned int (*bpf_dispatcher_fn)(const void *ctx,
 					  const struct bpf_insn *insnsi,
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index e56025505467..2e0ec7307f73 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -6016,20 +6016,28 @@ static int btf_struct_walk(struct bpf_verifier_log *log, const struct btf *btf,
 	return -EINVAL;
 }
 
-int btf_struct_access(struct bpf_verifier_log *log, const struct btf *btf,
-		      const struct btf_type *t, int off, int size,
-		      enum bpf_access_type atype __maybe_unused,
+int btf_struct_access(struct bpf_verifier_log *log,
+		      const struct bpf_reg_state *reg,
+		      int off, int size, enum bpf_access_type atype __maybe_unused,
 		      u32 *next_btf_id, enum bpf_type_flag *flag)
 {
+	const struct btf *btf = reg->btf;
 	enum bpf_type_flag tmp_flag = 0;
+	const struct btf_type *t;
+	u32 id = reg->btf_id;
 	int err;
-	u32 id;
 
+	t = btf_type_by_id(btf, id);
 	do {
 		err = btf_struct_walk(log, btf, t, off, size, &id, &tmp_flag);
 
 		switch (err) {
 		case WALK_PTR:
+			/* For local types, the destination register cannot
+			 * become a pointer again.
+			 */
+			if (type_is_local_kptr(reg->type))
+				return SCALAR_VALUE;
 			/* If we found the pointer or scalar on t+off,
 			 * we're done.
 			 */
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 168cd8bb9fd6..4de72a4a39bb 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -4521,17 +4521,28 @@ static int check_ptr_to_btf_access(struct bpf_verifier_env *env,
 		return -EACCES;
 	}
 
-	if (env->ops->btf_struct_access) {
-		ret = env->ops->btf_struct_access(&env->log, reg->btf, t,
-						  off, size, atype, &btf_id, &flag);
+	if (env->ops->btf_struct_access && !type_is_local_kptr(reg->type)) {
+		if (!btf_is_kernel(reg->btf)) {
+			verbose(env, "verifier internal error: reg->btf must be kernel btf\n");
+			return -EFAULT;
+		}
+		ret = env->ops->btf_struct_access(&env->log, reg, off, size, atype, &btf_id, &flag);
 	} else {
-		if (atype != BPF_READ) {
+		/* Writes are permitted with default btf_struct_access for local
+		 * kptrs (which always have ref_obj_id > 0), but not for
+		 * _untrusted_ local kptrs.
+		 */
+		if (atype != BPF_READ && reg->type != (PTR_TO_BTF_ID | MEM_TYPE_LOCAL)) {
 			verbose(env, "only read is supported\n");
 			return -EACCES;
 		}
 
-		ret = btf_struct_access(&env->log, reg->btf, t, off, size,
-					atype, &btf_id, &flag);
+		if (type_is_local_kptr(reg->type) && !reg->ref_obj_id) {
+			verbose(env, "verifier internal error: ref_obj_id for local kptr must be non-zero\n");
+			return -EFAULT;
+		}
+
+		ret = btf_struct_access(&env->log, reg, off, size, atype, &btf_id, &flag);
 	}
 
 	if (ret < 0)
@@ -4557,6 +4568,7 @@ static int check_ptr_to_map_access(struct bpf_verifier_env *env,
 {
 	struct bpf_reg_state *reg = regs + regno;
 	struct bpf_map *map = reg->map_ptr;
+	struct bpf_reg_state map_reg;
 	enum bpf_type_flag flag = 0;
 	const struct btf_type *t;
 	const char *tname;
@@ -4595,7 +4607,10 @@ static int check_ptr_to_map_access(struct bpf_verifier_env *env,
 		return -EACCES;
 	}
 
-	ret = btf_struct_access(&env->log, btf_vmlinux, t, off, size, atype, &btf_id, &flag);
+	/* Simulate access to a PTR_TO_BTF_ID */
+	memset(&map_reg, 0, sizeof(map_reg));
+	mark_btf_ld_reg(env, &map_reg, 0, PTR_TO_BTF_ID, btf_vmlinux, *map->ops->map_btf_id, 0);
+	ret = btf_struct_access(&env->log, &map_reg, off, size, atype, &btf_id, &flag);
 	if (ret < 0)
 		return ret;
 
@@ -5805,6 +5820,7 @@ int check_func_arg_reg_off(struct bpf_verifier_env *env,
 	 * fixed offset.
 	 */
 	case PTR_TO_BTF_ID:
+	case PTR_TO_BTF_ID | MEM_TYPE_LOCAL:
 		/* When referenced PTR_TO_BTF_ID is passed to release function,
 		 * it's fixed offset must be 0.	In the other cases, fixed offset
 		 * can be non-zero.
@@ -13462,6 +13478,13 @@ static int convert_ctx_accesses(struct bpf_verifier_env *env)
 			break;
 		case PTR_TO_BTF_ID:
 		case PTR_TO_BTF_ID | PTR_UNTRUSTED:
+		/* PTR_TO_BTF_ID | MEM_TYPE_LOCAL always has a valid lifetime,
+		 * unlike PTR_TO_BTF_ID, and an active ref_obj_id, but the same
+		 * cannot be said once it is marked PTR_UNTRUSTED, hence we must
+		 * handle any faults for loads into such types. BPF_WRITE is
+		 * disallowed for this case.
+		 */
+		case PTR_TO_BTF_ID | MEM_TYPE_LOCAL | PTR_UNTRUSTED:
 			if (type == BPF_READ) {
 				insn->code = BPF_LDX | BPF_PROBE_MEM |
 					BPF_SIZE((insn)->code);
diff --git a/net/bpf/bpf_dummy_struct_ops.c b/net/bpf/bpf_dummy_struct_ops.c
index e78dadfc5829..2d434c1f4617 100644
--- a/net/bpf/bpf_dummy_struct_ops.c
+++ b/net/bpf/bpf_dummy_struct_ops.c
@@ -156,29 +156,29 @@ static bool bpf_dummy_ops_is_valid_access(int off, int size,
 }
 
 static int bpf_dummy_ops_btf_struct_access(struct bpf_verifier_log *log,
-					   const struct btf *btf,
-					   const struct btf_type *t, int off,
-					   int size, enum bpf_access_type atype,
+					   const struct bpf_reg_state *reg,
+					   int off, int size, enum bpf_access_type atype,
 					   u32 *next_btf_id,
 					   enum bpf_type_flag *flag)
 {
 	const struct btf_type *state;
+	const struct btf_type *t;
 	s32 type_id;
 	int err;
 
-	type_id = btf_find_by_name_kind(btf, "bpf_dummy_ops_state",
+	type_id = btf_find_by_name_kind(reg->btf, "bpf_dummy_ops_state",
 					BTF_KIND_STRUCT);
 	if (type_id < 0)
 		return -EINVAL;
 
-	state = btf_type_by_id(btf, type_id);
+	t = btf_type_by_id(reg->btf, reg->btf_id);
+	state = btf_type_by_id(reg->btf, type_id);
 	if (t != state) {
 		bpf_log(log, "only access to bpf_dummy_ops_state is supported\n");
 		return -EACCES;
 	}
 
-	err = btf_struct_access(log, btf, t, off, size, atype, next_btf_id,
-				flag);
+	err = btf_struct_access(log, reg, off, size, atype, next_btf_id, flag);
 	if (err < 0)
 		return err;
 
diff --git a/net/core/filter.c b/net/core/filter.c
index bb0136e7a8e4..1380828d67a3 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -8647,28 +8647,25 @@ static bool tc_cls_act_is_valid_access(int off, int size,
 DEFINE_MUTEX(nf_conn_btf_access_lock);
 EXPORT_SYMBOL_GPL(nf_conn_btf_access_lock);
 
-int (*nfct_btf_struct_access)(struct bpf_verifier_log *log, const struct btf *btf,
-			      const struct btf_type *t, int off, int size,
-			      enum bpf_access_type atype, u32 *next_btf_id,
-			      enum bpf_type_flag *flag);
+int (*nfct_btf_struct_access)(struct bpf_verifier_log *log,
+			      const struct bpf_reg_state *reg,
+			      int off, int size, enum bpf_access_type atype,
+			      u32 *next_btf_id, enum bpf_type_flag *flag);
 EXPORT_SYMBOL_GPL(nfct_btf_struct_access);
 
 static int tc_cls_act_btf_struct_access(struct bpf_verifier_log *log,
-					const struct btf *btf,
-					const struct btf_type *t, int off,
-					int size, enum bpf_access_type atype,
-					u32 *next_btf_id,
-					enum bpf_type_flag *flag)
+					const struct bpf_reg_state *reg,
+					int off, int size, enum bpf_access_type atype,
+					u32 *next_btf_id, enum bpf_type_flag *flag)
 {
 	int ret = -EACCES;
 
 	if (atype == BPF_READ)
-		return btf_struct_access(log, btf, t, off, size, atype, next_btf_id,
-					 flag);
+		return btf_struct_access(log, reg, off, size, atype, next_btf_id, flag);
 
 	mutex_lock(&nf_conn_btf_access_lock);
 	if (nfct_btf_struct_access)
-		ret = nfct_btf_struct_access(log, btf, t, off, size, atype, next_btf_id, flag);
+		ret = nfct_btf_struct_access(log, reg, off, size, atype, next_btf_id, flag);
 	mutex_unlock(&nf_conn_btf_access_lock);
 
 	return ret;
@@ -8734,21 +8731,18 @@ void bpf_warn_invalid_xdp_action(struct net_device *dev, struct bpf_prog *prog,
 EXPORT_SYMBOL_GPL(bpf_warn_invalid_xdp_action);
 
 static int xdp_btf_struct_access(struct bpf_verifier_log *log,
-				 const struct btf *btf,
-				 const struct btf_type *t, int off,
-				 int size, enum bpf_access_type atype,
-				 u32 *next_btf_id,
-				 enum bpf_type_flag *flag)
+				 const struct bpf_reg_state *reg,
+				 int off, int size, enum bpf_access_type atype,
+				 u32 *next_btf_id, enum bpf_type_flag *flag)
 {
 	int ret = -EACCES;
 
 	if (atype == BPF_READ)
-		return btf_struct_access(log, btf, t, off, size, atype, next_btf_id,
-					 flag);
+		return btf_struct_access(log, reg, off, size, atype, next_btf_id, flag);
 
 	mutex_lock(&nf_conn_btf_access_lock);
 	if (nfct_btf_struct_access)
-		ret = nfct_btf_struct_access(log, btf, t, off, size, atype, next_btf_id, flag);
+		ret = nfct_btf_struct_access(log, reg, off, size, atype, next_btf_id, flag);
 	mutex_unlock(&nf_conn_btf_access_lock);
 
 	return ret;
diff --git a/net/ipv4/bpf_tcp_ca.c b/net/ipv4/bpf_tcp_ca.c
index 6da16ae6a962..d15c91de995f 100644
--- a/net/ipv4/bpf_tcp_ca.c
+++ b/net/ipv4/bpf_tcp_ca.c
@@ -69,18 +69,17 @@ static bool bpf_tcp_ca_is_valid_access(int off, int size,
 }
 
 static int bpf_tcp_ca_btf_struct_access(struct bpf_verifier_log *log,
-					const struct btf *btf,
-					const struct btf_type *t, int off,
-					int size, enum bpf_access_type atype,
-					u32 *next_btf_id,
-					enum bpf_type_flag *flag)
+					const struct bpf_reg_state *reg,
+					int off, int size, enum bpf_access_type atype,
+					u32 *next_btf_id, enum bpf_type_flag *flag)
 {
+	const struct btf_type *t;
 	size_t end;
 
 	if (atype == BPF_READ)
-		return btf_struct_access(log, btf, t, off, size, atype, next_btf_id,
-					 flag);
+		return btf_struct_access(log, reg, off, size, atype, next_btf_id, flag);
 
+	t = btf_type_by_id(reg->btf, reg->btf_id);
 	if (t != tcp_sock_type) {
 		bpf_log(log, "only read is supported\n");
 		return -EACCES;
diff --git a/net/netfilter/nf_conntrack_bpf.c b/net/netfilter/nf_conntrack_bpf.c
index 8639e7efd0e2..24002bc61e07 100644
--- a/net/netfilter/nf_conntrack_bpf.c
+++ b/net/netfilter/nf_conntrack_bpf.c
@@ -191,19 +191,16 @@ BTF_ID(struct, nf_conn___init)
 
 /* Check writes into `struct nf_conn` */
 static int _nf_conntrack_btf_struct_access(struct bpf_verifier_log *log,
-					   const struct btf *btf,
-					   const struct btf_type *t, int off,
-					   int size, enum bpf_access_type atype,
-					   u32 *next_btf_id,
-					   enum bpf_type_flag *flag)
+					   const struct bpf_reg_state *reg,
+					   int off, int size, enum bpf_access_type atype,
+					   u32 *next_btf_id, enum bpf_type_flag *flag)
 {
-	const struct btf_type *ncit;
-	const struct btf_type *nct;
+	const struct btf_type *ncit, *nct, *t;
 	size_t end;
 
-	ncit = btf_type_by_id(btf, btf_nf_conn_ids[1]);
-	nct = btf_type_by_id(btf, btf_nf_conn_ids[0]);
-
+	ncit = btf_type_by_id(reg->btf, btf_nf_conn_ids[1]);
+	nct = btf_type_by_id(reg->btf, btf_nf_conn_ids[0]);
+	t = btf_type_by_id(reg->btf, reg->btf_id);
 	if (t != nct && t != ncit) {
 		bpf_log(log, "only read is supported\n");
 		return -EACCES;
-- 
2.38.1

[PATCH bpf-next v4 11/24] bpf: Recognize bpf_{spin_lock,list_head,list_node} in local kptrs

[Kumar Kartikeya Dwivedi]

Allow specifying bpf_spin_lock, bpf_list_head, bpf_list_node fields in a
local kptr.

A bpf_list_head allows implementing map-in-map style use cases, where
local kptr with bpf_list_head is linked into a list in a map value. This
would require embedding a bpf_list_node, support for which is also
included.

Lastly, while we strictly don't require to hold a bpf_spin_lock while
manipulating the bpf_list_head of a local kptr, as when have access to
it, we have complete ownership of the object, the locking constraint is
still kept and may be conditionally lifted in the future.

Note that the specification of such types can be done just like map
values, e.g.:

struct bar {
	struct bpf_list_node node;
};

struct foo {
	struct bpf_spin_lock lock;
	struct bpf_list_head head __contains(bar, node);
	struct bpf_list_node node;
};

struct map_value {
	struct bpf_spin_lock lock;
	struct bpf_list_head head __contains(foo, node);
};

To recognize such types in user BTF, we build a btf_struct_metas array
of metadata items corresponding to each BTF ID. This is done once during
the btf_parse stage to avoid having to do it each time during the
verification process's requirement to inspect the metadata.

Moreover, the computed metadata needs to be passed to some helpers in
future patches which requires allocating them and storing them in the
BTF that is pinned by the program itself, so that valid access can be
assumed to such data during program runtime.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 include/linux/bpf.h  |   7 ++
 include/linux/btf.h  |  35 ++++++++
 kernel/bpf/btf.c     | 196 +++++++++++++++++++++++++++++++++++++++----
 kernel/bpf/syscall.c |   4 +
 4 files changed, 224 insertions(+), 18 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index bdd3adfcbe5f..0797c467e894 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -177,6 +177,7 @@ enum btf_field_type {
 	BPF_KPTR_REF   = (1 << 3),
 	BPF_KPTR       = BPF_KPTR_UNREF | BPF_KPTR_REF,
 	BPF_LIST_HEAD  = (1 << 4),
+	BPF_LIST_NODE  = (1 << 5),
 };
 
 struct btf_field_kptr {
@@ -277,6 +278,8 @@ static inline const char *btf_field_type_name(enum btf_field_type type)
 		return "kptr";
 	case BPF_LIST_HEAD:
 		return "bpf_list_head";
+	case BPF_LIST_NODE:
+		return "bpf_list_node";
 	default:
 		WARN_ON_ONCE(1);
 		return "unknown";
@@ -295,6 +298,8 @@ static inline u32 btf_field_type_size(enum btf_field_type type)
 		return sizeof(u64);
 	case BPF_LIST_HEAD:
 		return sizeof(struct bpf_list_head);
+	case BPF_LIST_NODE:
+		return sizeof(struct bpf_list_node);
 	default:
 		WARN_ON_ONCE(1);
 		return 0;
@@ -313,6 +318,8 @@ static inline u32 btf_field_type_align(enum btf_field_type type)
 		return __alignof__(u64);
 	case BPF_LIST_HEAD:
 		return __alignof__(struct bpf_list_head);
+	case BPF_LIST_NODE:
+		return __alignof__(struct bpf_list_node);
 	default:
 		WARN_ON_ONCE(1);
 		return 0;
diff --git a/include/linux/btf.h b/include/linux/btf.h
index d80345fa566b..a01a8da20021 100644
--- a/include/linux/btf.h
+++ b/include/linux/btf.h
@@ -6,6 +6,8 @@
 
 #include <linux/types.h>
 #include <linux/bpfptr.h>
+#include <linux/bsearch.h>
+#include <linux/btf_ids.h>
 #include <uapi/linux/btf.h>
 #include <uapi/linux/bpf.h>
 
@@ -78,6 +80,17 @@ struct btf_id_dtor_kfunc {
 	u32 kfunc_btf_id;
 };
 
+struct btf_struct_meta {
+	u32 btf_id;
+	struct btf_record *record;
+	struct btf_field_offs *field_offs;
+};
+
+struct btf_struct_metas {
+	u32 cnt;
+	struct btf_struct_meta types[];
+};
+
 typedef void (*btf_dtor_kfunc_t)(void *);
 
 extern const struct file_operations btf_fops;
@@ -408,6 +421,23 @@ static inline struct btf_param *btf_params(const struct btf_type *t)
 	return (struct btf_param *)(t + 1);
 }
 
+static inline int btf_id_cmp_func(const void *a, const void *b)
+{
+	const int *pa = a, *pb = b;
+
+	return *pa - *pb;
+}
+
+static inline bool btf_id_set_contains(const struct btf_id_set *set, u32 id)
+{
+	return bsearch(&id, set->ids, set->cnt, sizeof(u32), btf_id_cmp_func) != NULL;
+}
+
+static inline void *btf_id_set8_contains(const struct btf_id_set8 *set, u32 id)
+{
+	return bsearch(&id, set->pairs, set->cnt, sizeof(set->pairs[0]), btf_id_cmp_func);
+}
+
 #ifdef CONFIG_BPF_SYSCALL
 struct bpf_prog;
 
@@ -423,6 +453,7 @@ int register_btf_kfunc_id_set(enum bpf_prog_type prog_type,
 s32 btf_find_dtor_kfunc(struct btf *btf, u32 btf_id);
 int register_btf_id_dtor_kfuncs(const struct btf_id_dtor_kfunc *dtors, u32 add_cnt,
 				struct module *owner);
+struct btf_struct_meta *btf_find_struct_meta(const struct btf *btf, u32 btf_id);
 #else
 static inline const struct btf_type *btf_type_by_id(const struct btf *btf,
 						    u32 type_id)
@@ -454,6 +485,10 @@ static inline int register_btf_id_dtor_kfuncs(const struct btf_id_dtor_kfunc *dt
 {
 	return 0;
 }
+static inline struct btf_struct_meta *btf_find_struct_meta(const struct btf *btf, u32 btf_id)
+{
+	return NULL;
+}
 #endif
 
 static inline bool btf_type_is_struct_ptr(struct btf *btf, const struct btf_type *t)
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 2e0ec7307f73..ffe9d5b182e6 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -237,6 +237,7 @@ struct btf {
 	struct rcu_head rcu;
 	struct btf_kfunc_set_tab *kfunc_set_tab;
 	struct btf_id_dtor_kfunc_tab *dtor_kfunc_tab;
+	struct btf_struct_metas *struct_meta_tab;
 
 	/* split BTF support */
 	struct btf *base_btf;
@@ -1642,8 +1643,30 @@ static void btf_free_dtor_kfunc_tab(struct btf *btf)
 	btf->dtor_kfunc_tab = NULL;
 }
 
+static void btf_struct_metas_free(struct btf_struct_metas *tab)
+{
+	int i;
+
+	if (!tab)
+		return;
+	for (i = 0; i < tab->cnt; i++) {
+		btf_record_free(tab->types[i].record);
+		kfree(tab->types[i].field_offs);
+	}
+	kfree(tab);
+}
+
+static void btf_free_struct_meta_tab(struct btf *btf)
+{
+	struct btf_struct_metas *tab = btf->struct_meta_tab;
+
+	btf_struct_metas_free(tab);
+	btf->struct_meta_tab = NULL;
+}
+
 static void btf_free(struct btf *btf)
 {
+	btf_free_struct_meta_tab(btf);
 	btf_free_dtor_kfunc_tab(btf);
 	btf_free_kfunc_set_tab(btf);
 	kvfree(btf->types);
@@ -3356,6 +3379,12 @@ static int btf_get_field_type(const char *name, u32 field_mask, u32 *seen_mask,
 			goto end;
 		}
 	}
+	if (field_mask & BPF_LIST_NODE) {
+		if (!strcmp(name, "bpf_list_node")) {
+			type = BPF_LIST_NODE;
+			goto end;
+		}
+	}
 	/* Only return BPF_KPTR when all other types with matchable names fail */
 	if (field_mask & BPF_KPTR) {
 		type = BPF_KPTR_REF;
@@ -3401,6 +3430,7 @@ static int btf_find_struct_field(const struct btf *btf,
 		switch (field_type) {
 		case BPF_SPIN_LOCK:
 		case BPF_TIMER:
+		case BPF_LIST_NODE:
 			ret = btf_find_struct(btf, member_type, off, sz, field_type,
 					      idx < info_cnt ? &info[idx] : &tmp);
 			if (ret < 0)
@@ -3463,6 +3493,7 @@ static int btf_find_datasec_var(const struct btf *btf, const struct btf_type *t,
 		switch (field_type) {
 		case BPF_SPIN_LOCK:
 		case BPF_TIMER:
+		case BPF_LIST_NODE:
 			ret = btf_find_struct(btf, var_type, off, sz, field_type,
 					      idx < info_cnt ? &info[idx] : &tmp);
 			if (ret < 0)
@@ -3670,6 +3701,8 @@ struct btf_record *btf_parse_fields(const struct btf *btf, const struct btf_type
 			if (ret < 0)
 				goto end;
 			break;
+		case BPF_LIST_NODE:
+			break;
 		default:
 			ret = -EFAULT;
 			goto end;
@@ -5140,6 +5173,118 @@ static int btf_parse_hdr(struct btf_verifier_env *env)
 	return btf_check_sec_info(env, btf_data_size);
 }
 
+static const char *local_kptr_fields[] = {
+	"bpf_spin_lock",
+	"bpf_list_head",
+	"bpf_list_node",
+};
+
+static struct btf_struct_metas *
+btf_parse_struct_metas(struct bpf_verifier_log *log, struct btf *btf)
+{
+	union {
+		struct btf_id_set set;
+		struct {
+			u32 _cnt;
+			u32 _ids[ARRAY_SIZE(local_kptr_fields)];
+		} _arr;
+	} lkf;
+	struct btf_struct_metas *tab = NULL;
+	int i, n, id, ret;
+
+	memset(&lkf, 0, sizeof(lkf));
+
+	for (i = 0; i < ARRAY_SIZE(local_kptr_fields); i++) {
+		/* Try to find whether this special type exists in user BTF, and
+		 * if so remember its ID so we can easily find it among members
+		 * of structs that we iterate in the next loop.
+		 */
+		id = btf_find_by_name_kind(btf, local_kptr_fields[i], BTF_KIND_STRUCT);
+		if (id < 0)
+			continue;
+		lkf.set.ids[lkf.set.cnt++] = id;
+	}
+
+	if (!lkf.set.cnt)
+		return NULL;
+	sort(&lkf.set.ids, lkf.set.cnt, sizeof(lkf.set.ids[0]), btf_id_cmp_func, NULL);
+
+	n = btf_nr_types(btf);
+	for (i = 1; i < n; i++) {
+		const struct btf_member *member;
+		struct btf_field_offs *foffs;
+		struct btf_struct_meta *type;
+		struct btf_record *record;
+		const struct btf_type *t;
+		int j;
+
+		t = btf_type_by_id(btf, i);
+		if (!t) {
+			ret = -EINVAL;
+			goto free;
+		}
+		if (!__btf_type_is_struct(t))
+			continue;
+
+		cond_resched();
+
+		for_each_member(j, t, member) {
+			if (btf_id_set_contains(&lkf.set, member->type))
+				goto parse;
+		}
+		continue;
+	parse:
+		if (!tab) {
+			tab = kzalloc(offsetof(struct btf_struct_metas, types[1]),
+				      GFP_KERNEL | __GFP_NOWARN);
+			if (!tab)
+				return ERR_PTR(-ENOMEM);
+		} else {
+			struct btf_struct_metas *new_tab;
+
+			new_tab = krealloc(tab, offsetof(struct btf_struct_metas, types[tab->cnt + 1]),
+					   GFP_KERNEL | __GFP_NOWARN);
+			if (!new_tab) {
+				ret = -ENOMEM;
+				goto free;
+			}
+			tab = new_tab;
+		}
+		type = &tab->types[tab->cnt];
+
+		type->btf_id = i;
+		record = btf_parse_fields(btf, t, BPF_SPIN_LOCK | BPF_LIST_HEAD | BPF_LIST_NODE, t->size);
+		if (IS_ERR_OR_NULL(record)) {
+			ret = PTR_ERR_OR_ZERO(record) ?: -EFAULT;
+			goto free;
+		}
+		foffs = btf_parse_field_offs(record);
+		if (WARN_ON_ONCE(IS_ERR_OR_NULL(foffs))) {
+			btf_record_free(record);
+			ret = -EFAULT;
+			goto free;
+		}
+		type->record = record;
+		type->field_offs = foffs;
+		tab->cnt++;
+	}
+	return tab;
+free:
+	btf_struct_metas_free(tab);
+	return ERR_PTR(ret);
+}
+
+struct btf_struct_meta *btf_find_struct_meta(const struct btf *btf, u32 btf_id)
+{
+	struct btf_struct_metas *tab;
+
+	BUILD_BUG_ON(offsetof(struct btf_struct_meta, btf_id) != 0);
+	tab = btf->struct_meta_tab;
+	if (!tab)
+		return NULL;
+	return bsearch(&btf_id, tab->types, tab->cnt, sizeof(tab->types[0]), btf_id_cmp_func);
+}
+
 static int btf_check_type_tags(struct btf_verifier_env *env,
 			       struct btf *btf, int start_id)
 {
@@ -5190,6 +5335,7 @@ static int btf_check_type_tags(struct btf_verifier_env *env,
 static struct btf *btf_parse(bpfptr_t btf_data, u32 btf_data_size,
 			     u32 log_level, char __user *log_ubuf, u32 log_size)
 {
+	struct btf_struct_metas *struct_meta_tab;
 	struct btf_verifier_env *env = NULL;
 	struct bpf_verifier_log *log;
 	struct btf *btf = NULL;
@@ -5258,15 +5404,24 @@ static struct btf *btf_parse(bpfptr_t btf_data, u32 btf_data_size,
 	if (err)
 		goto errout;
 
+	struct_meta_tab = btf_parse_struct_metas(log, btf);
+	if (IS_ERR(struct_meta_tab)) {
+		err = PTR_ERR(struct_meta_tab);
+		goto errout;
+	}
+	btf->struct_meta_tab = struct_meta_tab;
+
 	if (log->level && bpf_verifier_log_full(log)) {
 		err = -ENOSPC;
-		goto errout;
+		goto errout_meta;
 	}
 
 	btf_verifier_env_free(env);
 	refcount_set(&btf->refcnt, 1);
 	return btf;
 
+errout_meta:
+	btf_free_struct_meta_tab(btf);
 errout:
 	btf_verifier_env_free(env);
 	if (btf)
@@ -6027,6 +6182,28 @@ int btf_struct_access(struct bpf_verifier_log *log,
 	u32 id = reg->btf_id;
 	int err;
 
+	while (type_is_local_kptr(reg->type)) {
+		struct btf_struct_meta *meta;
+		struct btf_record *rec;
+		int i;
+
+		meta = btf_find_struct_meta(btf, id);
+		if (!meta)
+			break;
+		rec = meta->record;
+		for (i = 0; i < rec->cnt; i++) {
+			struct btf_field *field = &rec->fields[i];
+			u32 offset = field->offset;
+			if (off < offset + btf_field_type_size(field->type) && offset < off + size) {
+				bpf_log(log,
+					"direct access to %s is disallowed\n",
+					btf_field_type_name(field->type));
+				return -EACCES;
+			}
+		}
+		break;
+	}
+
 	t = btf_type_by_id(btf, id);
 	do {
 		err = btf_struct_walk(log, btf, t, off, size, &id, &tmp_flag);
@@ -7268,23 +7445,6 @@ bool btf_is_module(const struct btf *btf)
 	return btf->kernel_btf && strcmp(btf->name, "vmlinux") != 0;
 }
 
-static int btf_id_cmp_func(const void *a, const void *b)
-{
-	const int *pa = a, *pb = b;
-
-	return *pa - *pb;
-}
-
-bool btf_id_set_contains(const struct btf_id_set *set, u32 id)
-{
-	return bsearch(&id, set->ids, set->cnt, sizeof(u32), btf_id_cmp_func) != NULL;
-}
-
-static void *btf_id_set8_contains(const struct btf_id_set8 *set, u32 id)
-{
-	return bsearch(&id, set->pairs, set->cnt, sizeof(set->pairs[0]), btf_id_cmp_func);
-}
-
 enum {
 	BTF_MODULE_F_LIVE = (1 << 0),
 };
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index fdbae52f463f..c96039a4e57f 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -537,6 +537,7 @@ void btf_record_free(struct btf_record *rec)
 			btf_put(rec->fields[i].kptr.btf);
 			break;
 		case BPF_LIST_HEAD:
+		case BPF_LIST_NODE:
 			/* Nothing to release for bpf_list_head */
 			break;
 		default:
@@ -582,6 +583,7 @@ struct btf_record *btf_record_dup(const struct btf_record *rec)
 			}
 			break;
 		case BPF_LIST_HEAD:
+		case BPF_LIST_NODE:
 			/* Nothing to acquire for bpf_list_head */
 			break;
 		default:
@@ -648,6 +650,8 @@ void bpf_obj_free_fields(const struct btf_record *rec, void *obj)
 				continue;
 			bpf_list_head_free(field, field_ptr, obj + rec->spin_lock_off);
 			break;
+		case BPF_LIST_NODE:
+			break;
 		default:
 			WARN_ON_ONCE(1);
 			continue;
-- 
2.38.1

[PATCH bpf-next v4 12/24] bpf: Verify ownership relationships for user BTF types

[Kumar Kartikeya Dwivedi]

Ensure that there can be no ownership cycles among different types by
way of having owning objects that can hold some other type as their
element. For instance, a map value can only hold local kptrs, but these
are allowed to have another bpf_list_head. To prevent unbounded
recursion while freeing resources, elements of bpf_list_head in local
kptrs can never have a bpf_list_head which are part of list in a map
value.

Also, to make runtime destruction easier, once btf_struct_metas is fully
populated, we can stash the metadata of the value type directly in the
metadata of the list_head fields, as that allows easier access to the
value type's layout to destruct it at runtime from the btf_field entry
of the list head itself.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 include/linux/bpf.h  |  1 +
 include/linux/btf.h  |  1 +
 kernel/bpf/btf.c     | 71 ++++++++++++++++++++++++++++++++++++++++++++
 kernel/bpf/syscall.c |  4 +++
 4 files changed, 77 insertions(+)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 0797c467e894..fb2659c1c10c 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -191,6 +191,7 @@ struct btf_field_list_head {
 	struct btf *btf;
 	u32 value_btf_id;
 	u32 node_offset;
+	struct btf_record *value_rec;
 };
 
 struct btf_field {
diff --git a/include/linux/btf.h b/include/linux/btf.h
index a01a8da20021..42d8f3730a8d 100644
--- a/include/linux/btf.h
+++ b/include/linux/btf.h
@@ -178,6 +178,7 @@ int btf_find_spin_lock(const struct btf *btf, const struct btf_type *t);
 int btf_find_timer(const struct btf *btf, const struct btf_type *t);
 struct btf_record *btf_parse_fields(const struct btf *btf, const struct btf_type *t,
 				    u32 field_mask, u32 value_size);
+int btf_check_and_fixup_fields(const struct btf *btf, struct btf_record *rec);
 struct btf_field_offs *btf_parse_field_offs(struct btf_record *rec);
 bool btf_type_is_void(const struct btf_type *t);
 s32 btf_find_by_name_kind(const struct btf *btf, const char *name, u8 kind);
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index ffe9d5b182e6..514219a790f4 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -3722,6 +3722,67 @@ struct btf_record *btf_parse_fields(const struct btf *btf, const struct btf_type
 	return ERR_PTR(ret);
 }
 
+int btf_check_and_fixup_fields(const struct btf *btf, struct btf_record *rec)
+{
+	int i;
+
+	/* There are two owning types, kptr_ref and bpf_list_head. The former
+	 * only supports storing kernel types, which can never store references
+	 * to program allocated local types, atleast not yet. Hence we only need
+	 * to ensure that bpf_list_head ownership does not form cycles.
+	 */
+	if (IS_ERR_OR_NULL(rec) || !(rec->field_mask & BPF_LIST_HEAD))
+		return 0;
+	for (i = 0; i < rec->cnt; i++) {
+		struct btf_struct_meta *meta;
+		u32 btf_id;
+
+		if (!(rec->fields[i].type & BPF_LIST_HEAD))
+			continue;
+		btf_id = rec->fields[i].list_head.value_btf_id;
+		meta = btf_find_struct_meta(btf, btf_id);
+		if (!meta)
+			return -EFAULT;
+		rec->fields[i].list_head.value_rec = meta->record;
+
+		if (!(rec->field_mask & BPF_LIST_NODE))
+			continue;
+
+		/* We need to ensure ownership acyclicity among all types. The
+		 * proper way to do it would be to topologically sort all BTF
+		 * IDs based on the ownership edges, since there can be multiple
+		 * bpf_list_head in a type. Instead, we use the following
+		 * reasoning:
+		 *
+		 * - A type can only be owned by another type in user BTF if it
+		 *   has a bpf_list_node.
+		 * - A type can only _own_ another type in user BTF if it has a
+		 *   bpf_list_head.
+		 *
+		 * We ensure that if a type has both bpf_list_head and
+		 * bpf_list_node, its element types cannot be owning types.
+		 *
+		 * To ensure acyclicity:
+		 *
+		 * When A only has bpf_list_head, ownership chain can be:
+		 *	A -> B -> C
+		 * Where:
+		 * - B has both bpf_list_head and bpf_list_node.
+		 * - C only has bpf_list_node.
+		 *
+		 * When A has both bpf_list_head and bpf_list_node, some other
+		 * type already owns it in the BTF domain, hence it can not own
+		 * another owning type through any of the bpf_list_head edges.
+		 *	A -> B
+		 * Where:
+		 * - B only has bpf_list_node.
+		 */
+		if (meta->record->field_mask & BPF_LIST_HEAD)
+			return -ELOOP;
+	}
+	return 0;
+}
+
 static int btf_field_offs_cmp(const void *_a, const void *_b, const void *priv)
 {
 	const u32 a = *(const u32 *)_a;
@@ -5411,6 +5472,16 @@ static struct btf *btf_parse(bpfptr_t btf_data, u32 btf_data_size,
 	}
 	btf->struct_meta_tab = struct_meta_tab;
 
+	if (struct_meta_tab) {
+		int i;
+
+		for (i = 0; i < struct_meta_tab->cnt; i++) {
+			err = btf_check_and_fixup_fields(btf, struct_meta_tab->types[i].record);
+			if (err < 0)
+				goto errout_meta;
+		}
+	}
+
 	if (log->level && bpf_verifier_log_full(log)) {
 		err = -ENOSPC;
 		goto errout_meta;
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index c96039a4e57f..4669020bb47d 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -1044,6 +1044,10 @@ static int map_check_btf(struct bpf_map *map, const struct btf *btf,
 		}
 	}
 
+	ret = btf_check_and_fixup_fields(btf, map->record);
+	if (ret < 0)
+		goto free_map_tab;
+
 	if (map->ops->map_check_btf) {
 		ret = map->ops->map_check_btf(map, btf, key_type, value_type);
 		if (ret < 0)
-- 
2.38.1

[PATCH bpf-next v4 13/24] bpf: Support locking bpf_spin_lock in local kptr

[Kumar Kartikeya Dwivedi]

Allow locking a bpf_spin_lock embedded in local kptr, in addition to
already support map value pointers. The handling is similar to that of
map values, by just preserving the reg->id of local kptrs as well, and
adjusting process_spin_lock to work with non-PTR_TO_MAP_VALUE and
remember the id in verifier state.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 kernel/bpf/helpers.c  |  2 ++
 kernel/bpf/verifier.c | 70 ++++++++++++++++++++++++++++++++-----------
 2 files changed, 55 insertions(+), 17 deletions(-)

diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 339cce94b408..207f622ec70d 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -336,6 +336,7 @@ const struct bpf_func_proto bpf_spin_lock_proto = {
 	.gpl_only	= false,
 	.ret_type	= RET_VOID,
 	.arg1_type	= ARG_PTR_TO_SPIN_LOCK,
+	.arg1_btf_id    = BPF_PTR_POISON,
 };
 
 static inline void __bpf_spin_unlock_irqrestore(struct bpf_spin_lock *lock)
@@ -358,6 +359,7 @@ const struct bpf_func_proto bpf_spin_unlock_proto = {
 	.gpl_only	= false,
 	.ret_type	= RET_VOID,
 	.arg1_type	= ARG_PTR_TO_SPIN_LOCK,
+	.arg1_btf_id    = BPF_PTR_POISON,
 };
 
 void copy_map_value_locked(struct bpf_map *map, void *dst, void *src,
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 4de72a4a39bb..c31f20aed30c 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -453,8 +453,16 @@ static bool reg_type_not_null(enum bpf_reg_type type)
 
 static bool reg_may_point_to_spin_lock(const struct bpf_reg_state *reg)
 {
-	return reg->type == PTR_TO_MAP_VALUE &&
-	       btf_record_has_field(reg->map_ptr->record, BPF_SPIN_LOCK);
+	struct btf_record *rec = NULL;
+
+	if (reg->type == PTR_TO_MAP_VALUE) {
+		rec = reg->map_ptr->record;
+	} else if (reg->type == (PTR_TO_BTF_ID | MEM_TYPE_LOCAL)) {
+		struct btf_struct_meta *meta = btf_find_struct_meta(reg->btf, reg->btf_id);
+		if (meta)
+			rec = meta->record;
+	}
+	return btf_record_has_field(rec, BPF_SPIN_LOCK);
 }
 
 static bool type_is_rdonly_mem(u32 type)
@@ -5422,8 +5430,10 @@ static int process_spin_lock(struct bpf_verifier_env *env, int regno,
 	struct bpf_reg_state *regs = cur_regs(env), *reg = &regs[regno];
 	struct bpf_verifier_state *cur = env->cur_state;
 	bool is_const = tnum_is_const(reg->var_off);
-	struct bpf_map *map = reg->map_ptr;
 	u64 val = reg->var_off.value;
+	struct bpf_map *map = NULL;
+	struct btf_record *rec;
+	struct btf *btf = NULL;
 
 	if (!is_const) {
 		verbose(env,
@@ -5431,19 +5441,32 @@ static int process_spin_lock(struct bpf_verifier_env *env, int regno,
 			regno);
 		return -EINVAL;
 	}
-	if (!map->btf) {
-		verbose(env,
-			"map '%s' has to have BTF in order to use bpf_spin_lock\n",
-			map->name);
-		return -EINVAL;
+	if (reg->type == PTR_TO_MAP_VALUE) {
+		map = reg->map_ptr;
+		if (!map->btf) {
+			verbose(env,
+				"map '%s' has to have BTF in order to use bpf_spin_lock\n",
+				map->name);
+			return -EINVAL;
+		}
+		rec = map->record;
+	} else {
+		struct btf_struct_meta *meta;
+
+		btf = reg->btf;
+		meta = btf_find_struct_meta(reg->btf, reg->btf_id);
+		if (meta)
+			rec = meta->record;
 	}
-	if (!btf_record_has_field(map->record, BPF_SPIN_LOCK)) {
-		verbose(env, "map '%s' has no valid bpf_spin_lock\n", map->name);
+
+	if (!btf_record_has_field(rec, BPF_SPIN_LOCK)) {
+		verbose(env, "%s '%s' has no valid bpf_spin_lock\n", map ? "map" : "local",
+			map ? map->name : "kptr");
 		return -EINVAL;
 	}
-	if (map->record->spin_lock_off != val + reg->off) {
+	if (rec->spin_lock_off != val + reg->off) {
 		verbose(env, "off %lld doesn't point to 'struct bpf_spin_lock' that is at %d\n",
-			val + reg->off, map->record->spin_lock_off);
+			val + reg->off, rec->spin_lock_off);
 		return -EINVAL;
 	}
 	if (is_lock) {
@@ -5649,13 +5672,19 @@ static const struct bpf_reg_types int_ptr_types = {
 	},
 };
 
+static const struct bpf_reg_types spin_lock_types = {
+	.types = {
+		PTR_TO_MAP_VALUE,
+		PTR_TO_BTF_ID | MEM_TYPE_LOCAL,
+	}
+};
+
 static const struct bpf_reg_types fullsock_types = { .types = { PTR_TO_SOCKET } };
 static const struct bpf_reg_types scalar_types = { .types = { SCALAR_VALUE } };
 static const struct bpf_reg_types context_types = { .types = { PTR_TO_CTX } };
 static const struct bpf_reg_types alloc_mem_types = { .types = { PTR_TO_MEM | MEM_ALLOC } };
 static const struct bpf_reg_types const_map_ptr_types = { .types = { CONST_PTR_TO_MAP } };
 static const struct bpf_reg_types btf_ptr_types = { .types = { PTR_TO_BTF_ID } };
-static const struct bpf_reg_types spin_lock_types = { .types = { PTR_TO_MAP_VALUE } };
 static const struct bpf_reg_types percpu_btf_ptr_types = { .types = { PTR_TO_BTF_ID | MEM_PERCPU } };
 static const struct bpf_reg_types func_ptr_types = { .types = { PTR_TO_FUNC } };
 static const struct bpf_reg_types stack_ptr_types = { .types = { PTR_TO_STACK } };
@@ -5780,6 +5809,11 @@ static int check_reg_type(struct bpf_verifier_env *env, u32 regno,
 				return -EACCES;
 			}
 		}
+	} else if (reg->type == (PTR_TO_BTF_ID | MEM_TYPE_LOCAL)) {
+		if (meta->func_id != BPF_FUNC_spin_lock && meta->func_id != BPF_FUNC_spin_unlock) {
+			verbose(env, "verifier internal error: unimplemented handling of local kptr\n");
+			return -EFAULT;
+		}
 	}
 
 	return 0;
@@ -5896,7 +5930,8 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
 		goto skip_type_check;
 
 	/* arg_btf_id and arg_size are in a union. */
-	if (base_type(arg_type) == ARG_PTR_TO_BTF_ID)
+	if (base_type(arg_type) == ARG_PTR_TO_BTF_ID ||
+	    base_type(arg_type) == ARG_PTR_TO_SPIN_LOCK)
 		arg_btf_id = fn->arg_btf_id[arg];
 
 	err = check_reg_type(env, regno, arg_type, arg_btf_id, meta);
@@ -6514,9 +6549,10 @@ static bool check_btf_id_ok(const struct bpf_func_proto *fn)
 	int i;
 
 	for (i = 0; i < ARRAY_SIZE(fn->arg_type); i++) {
-		if (base_type(fn->arg_type[i]) == ARG_PTR_TO_BTF_ID && !fn->arg_btf_id[i])
-			return false;
-
+		if (base_type(fn->arg_type[i]) == ARG_PTR_TO_BTF_ID)
+			return !!fn->arg_btf_id[i];
+		if (base_type(fn->arg_type[i]) == ARG_PTR_TO_SPIN_LOCK)
+			return fn->arg_btf_id[i] == BPF_PTR_POISON;
 		if (base_type(fn->arg_type[i]) != ARG_PTR_TO_BTF_ID && fn->arg_btf_id[i] &&
 		    /* arg_btf_id and arg_size are in a union. */
 		    (base_type(fn->arg_type[i]) != ARG_PTR_TO_MEM ||
-- 
2.38.1

[PATCH bpf-next v4 14/24] bpf: Allow locking bpf_spin_lock global variables

[Kumar Kartikeya Dwivedi]

Global variables reside in maps accessible using direct_value_addr
callbacks, so giving each load instruction's rewrite a unique reg->id
disallows us from holding locks which are global.

This is not great, so refactor the active_spin_lock into two separate
fields, active_spin_lock_ptr and active_spin_lock_id, which is generic
enough to allow it for global variables, map lookups, and local kptr
registers at the same time.

Held vs non-held is indicated by active_spin_lock_ptr, which stores the
reg->map_ptr or reg->btf pointer of the register used for locking spin
lock. But the active_spin_lock_id also needs to be compared to ensure
whether bpf_spin_unlock is for the same register.

Next, pseudo load instructions are not given a unique reg->id, as they
are doing lookup for the same map value (max_entries is never greater
than 1).

Essentially, we consider that the tuple of (active_spin_lock_ptr,
active_spin_lock_id) will always be unique for any kind of argument to
bpf_spin_{lock,unlock}.

Note that this can be extended in the future to also remember offset
used for locking, so that we can introduce multiple bpf_spin_lock fields
in the same allocation.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 include/linux/bpf_verifier.h |  3 ++-
 kernel/bpf/verifier.c        | 39 +++++++++++++++++++++++++-----------
 2 files changed, 29 insertions(+), 13 deletions(-)

diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index 1a32baa78ce2..bb71c59f21f6 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -323,7 +323,8 @@ struct bpf_verifier_state {
 	u32 branches;
 	u32 insn_idx;
 	u32 curframe;
-	u32 active_spin_lock;
+	void *active_spin_lock_ptr;
+	u32 active_spin_lock_id;
 	bool speculative;
 
 	/* first and last insn idx of this verifier state */
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index c31f20aed30c..4a43cde0ff4c 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -1201,7 +1201,8 @@ static int copy_verifier_state(struct bpf_verifier_state *dst_state,
 	}
 	dst_state->speculative = src->speculative;
 	dst_state->curframe = src->curframe;
-	dst_state->active_spin_lock = src->active_spin_lock;
+	dst_state->active_spin_lock_ptr = src->active_spin_lock_ptr;
+	dst_state->active_spin_lock_id = src->active_spin_lock_id;
 	dst_state->branches = src->branches;
 	dst_state->parent = src->parent;
 	dst_state->first_insn_idx = src->first_insn_idx;
@@ -5470,22 +5471,35 @@ static int process_spin_lock(struct bpf_verifier_env *env, int regno,
 		return -EINVAL;
 	}
 	if (is_lock) {
-		if (cur->active_spin_lock) {
+		if (cur->active_spin_lock_ptr) {
 			verbose(env,
 				"Locking two bpf_spin_locks are not allowed\n");
 			return -EINVAL;
 		}
-		cur->active_spin_lock = reg->id;
+		if (map)
+			cur->active_spin_lock_ptr = map;
+		else
+			cur->active_spin_lock_ptr = btf;
+		cur->active_spin_lock_id = reg->id;
 	} else {
-		if (!cur->active_spin_lock) {
+		void *ptr;
+
+		if (map)
+			ptr = map;
+		else
+			ptr = btf;
+
+		if (!cur->active_spin_lock_ptr) {
 			verbose(env, "bpf_spin_unlock without taking a lock\n");
 			return -EINVAL;
 		}
-		if (cur->active_spin_lock != reg->id) {
+		if (cur->active_spin_lock_ptr != ptr ||
+		    cur->active_spin_lock_id != reg->id) {
 			verbose(env, "bpf_spin_unlock of different lock\n");
 			return -EINVAL;
 		}
-		cur->active_spin_lock = 0;
+		cur->active_spin_lock_ptr = NULL;
+		cur->active_spin_lock_id = 0;
 	}
 	return 0;
 }
@@ -10393,8 +10407,8 @@ static int check_ld_imm(struct bpf_verifier_env *env, struct bpf_insn *insn)
 	    insn->src_reg == BPF_PSEUDO_MAP_IDX_VALUE) {
 		dst_reg->type = PTR_TO_MAP_VALUE;
 		dst_reg->off = aux->map_off;
-		if (btf_record_has_field(map->record, BPF_SPIN_LOCK))
-			dst_reg->id = ++env->id_gen;
+		WARN_ON_ONCE(map->max_entries != 1);
+		/* We want reg->id to be same (0) as map_value is not distinct */
 	} else if (insn->src_reg == BPF_PSEUDO_MAP_FD ||
 		   insn->src_reg == BPF_PSEUDO_MAP_IDX) {
 		dst_reg->type = CONST_PTR_TO_MAP;
@@ -10472,7 +10486,7 @@ static int check_ld_abs(struct bpf_verifier_env *env, struct bpf_insn *insn)
 		return err;
 	}
 
-	if (env->cur_state->active_spin_lock) {
+	if (env->cur_state->active_spin_lock_ptr) {
 		verbose(env, "BPF_LD_[ABS|IND] cannot be used inside bpf_spin_lock-ed region\n");
 		return -EINVAL;
 	}
@@ -11738,7 +11752,8 @@ static bool states_equal(struct bpf_verifier_env *env,
 	if (old->speculative && !cur->speculative)
 		return false;
 
-	if (old->active_spin_lock != cur->active_spin_lock)
+	if (old->active_spin_lock_ptr != cur->active_spin_lock_ptr ||
+	    old->active_spin_lock_id != cur->active_spin_lock_id)
 		return false;
 
 	/* for states to be equal callsites have to be the same
@@ -12377,7 +12392,7 @@ static int do_check(struct bpf_verifier_env *env)
 					return -EINVAL;
 				}
 
-				if (env->cur_state->active_spin_lock &&
+				if (env->cur_state->active_spin_lock_ptr &&
 				    (insn->src_reg == BPF_PSEUDO_CALL ||
 				     insn->imm != BPF_FUNC_spin_unlock)) {
 					verbose(env, "function calls are not allowed while holding a lock\n");
@@ -12414,7 +12429,7 @@ static int do_check(struct bpf_verifier_env *env)
 					return -EINVAL;
 				}
 
-				if (env->cur_state->active_spin_lock) {
+				if (env->cur_state->active_spin_lock_ptr) {
 					verbose(env, "bpf_spin_unlock is missing\n");
 					return -EINVAL;
 				}
-- 
2.38.1

[PATCH bpf-next v4 15/24] bpf: Rewrite kfunc argument handling

[Kumar Kartikeya Dwivedi]

As we continue to add more features, argument types, kfunc flags, and
different extensions to kfuncs, the code to verify the correctness of
the kfunc prototype wrt the passed in registers has become ad-hoc and
ugly to read.

To make life easier, and make a very clear split between different
stages of argument processing, move all the code into verifier.c and
refactor into easier to read helpers and functions.

This also makes sharing code within the verifier easier with kfunc
argument processing. This will be more and more useful in later patches
as we are now moving to implement very core BPF helpers as kfuncs, to
keep them experimental before baking into UAPI.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 include/linux/btf.h                           |  31 +-
 kernel/bpf/btf.c                              |  16 +-
 kernel/bpf/verifier.c                         | 545 +++++++++++++++++-
 .../bpf/prog_tests/kfunc_dynptr_param.c       |   2 +-
 tools/testing/selftests/bpf/verifier/calls.c  |   4 +-
 .../selftests/bpf/verifier/ref_tracking.c     |   4 +-
 6 files changed, 568 insertions(+), 34 deletions(-)

diff --git a/include/linux/btf.h b/include/linux/btf.h
index 42d8f3730a8d..d5b26380a60f 100644
--- a/include/linux/btf.h
+++ b/include/linux/btf.h
@@ -338,6 +338,16 @@ static inline bool btf_type_is_struct(const struct btf_type *t)
 	return kind == BTF_KIND_STRUCT || kind == BTF_KIND_UNION;
 }
 
+static inline bool __btf_type_is_struct(const struct btf_type *t)
+{
+	return BTF_INFO_KIND(t->info) == BTF_KIND_STRUCT;
+}
+
+static inline bool btf_type_is_array(const struct btf_type *t)
+{
+	return BTF_INFO_KIND(t->info) == BTF_KIND_ARRAY;
+}
+
 static inline u16 btf_type_vlen(const struct btf_type *t)
 {
 	return BTF_INFO_VLEN(t->info);
@@ -439,9 +449,10 @@ static inline void *btf_id_set8_contains(const struct btf_id_set8 *set, u32 id)
 	return bsearch(&id, set->pairs, set->cnt, sizeof(set->pairs[0]), btf_id_cmp_func);
 }
 
-#ifdef CONFIG_BPF_SYSCALL
 struct bpf_prog;
+struct bpf_verifier_log;
 
+#ifdef CONFIG_BPF_SYSCALL
 const struct btf_type *btf_type_by_id(const struct btf *btf, u32 type_id);
 const char *btf_name_by_offset(const struct btf *btf, u32 offset);
 struct btf *btf_parse_vmlinux(void);
@@ -455,6 +466,12 @@ s32 btf_find_dtor_kfunc(struct btf *btf, u32 btf_id);
 int register_btf_id_dtor_kfuncs(const struct btf_id_dtor_kfunc *dtors, u32 add_cnt,
 				struct module *owner);
 struct btf_struct_meta *btf_find_struct_meta(const struct btf *btf, u32 btf_id);
+const struct btf_member *
+btf_get_prog_ctx_type(struct bpf_verifier_log *log, const struct btf *btf,
+		      const struct btf_type *t, enum bpf_prog_type prog_type,
+		      int arg);
+bool btf_types_are_same(const struct btf *btf1, u32 id1,
+			const struct btf *btf2, u32 id2);
 #else
 static inline const struct btf_type *btf_type_by_id(const struct btf *btf,
 						    u32 type_id)
@@ -490,6 +507,18 @@ static inline struct btf_struct_meta *btf_find_struct_meta(const struct btf *btf
 {
 	return NULL;
 }
+static inline const struct btf_member *
+btf_get_prog_ctx_type(struct bpf_verifier_log *log, const struct btf *btf,
+		      const struct btf_type *t, enum bpf_prog_type prog_type,
+		      int arg)
+{
+	return NULL;
+}
+static inline bool btf_types_are_same(const struct btf *btf1, u32 id1,
+				      const struct btf *btf2, u32 id2)
+{
+	return false;
+}
 #endif
 
 static inline bool btf_type_is_struct_ptr(struct btf *btf, const struct btf_type *t)
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 514219a790f4..7a66aaa02e6a 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -478,16 +478,6 @@ static bool btf_type_nosize_or_null(const struct btf_type *t)
 	return !t || btf_type_nosize(t);
 }
 
-static bool __btf_type_is_struct(const struct btf_type *t)
-{
-	return BTF_INFO_KIND(t->info) == BTF_KIND_STRUCT;
-}
-
-static bool btf_type_is_array(const struct btf_type *t)
-{
-	return BTF_INFO_KIND(t->info) == BTF_KIND_ARRAY;
-}
-
 static bool btf_type_is_datasec(const struct btf_type *t)
 {
 	return BTF_INFO_KIND(t->info) == BTF_KIND_DATASEC;
@@ -5534,7 +5524,7 @@ static u8 bpf_ctx_convert_map[] = {
 #undef BPF_MAP_TYPE
 #undef BPF_LINK_TYPE
 
-static const struct btf_member *
+const struct btf_member *
 btf_get_prog_ctx_type(struct bpf_verifier_log *log, const struct btf *btf,
 		      const struct btf_type *t, enum bpf_prog_type prog_type,
 		      int arg)
@@ -6320,8 +6310,8 @@ int btf_struct_access(struct bpf_verifier_log *log,
  * end up with two different module BTFs, but IDs point to the common type in
  * vmlinux BTF.
  */
-static bool btf_types_are_same(const struct btf *btf1, u32 id1,
-			       const struct btf *btf2, u32 id2)
+bool btf_types_are_same(const struct btf *btf1, u32 id1,
+			const struct btf *btf2, u32 id2)
 {
 	if (id1 != id2)
 		return false;
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 4a43cde0ff4c..5c2f5e61dde9 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -7675,19 +7675,521 @@ static void mark_btf_func_reg_size(struct bpf_verifier_env *env, u32 regno,
 	}
 }
 
+struct bpf_kfunc_call_arg_meta {
+	/* In parameters */
+	struct btf *btf;
+	u32 func_id;
+	u32 kfunc_flags;
+	const struct btf_type *func_proto;
+	const char *func_name;
+	/* Out parameters */
+	u32 ref_obj_id;
+	u8 release_regno;
+	bool r0_rdonly;
+	u64 r0_size;
+};
+
+static bool is_kfunc_acquire(struct bpf_kfunc_call_arg_meta *meta)
+{
+	return meta->kfunc_flags & KF_ACQUIRE;
+}
+
+static bool is_kfunc_ret_null(struct bpf_kfunc_call_arg_meta *meta)
+{
+	return meta->kfunc_flags & KF_RET_NULL;
+}
+
+static bool is_kfunc_release(struct bpf_kfunc_call_arg_meta *meta)
+{
+	return meta->kfunc_flags & KF_RELEASE;
+}
+
+static bool is_kfunc_trusted_args(struct bpf_kfunc_call_arg_meta *meta)
+{
+	return meta->kfunc_flags & KF_TRUSTED_ARGS;
+}
+
+static bool is_kfunc_sleepable(struct bpf_kfunc_call_arg_meta *meta)
+{
+	return meta->kfunc_flags & KF_SLEEPABLE;
+}
+
+static bool is_kfunc_destructive(struct bpf_kfunc_call_arg_meta *meta)
+{
+	return meta->kfunc_flags & KF_DESTRUCTIVE;
+}
+
+static bool is_kfunc_arg_kptr_get(struct bpf_kfunc_call_arg_meta *meta, int arg)
+{
+	return arg == 0 && (meta->kfunc_flags & KF_KPTR_GET);
+}
+
+static bool is_kfunc_arg_mem_size(const struct btf *btf,
+				  const struct btf_param *arg,
+				  const struct bpf_reg_state *reg)
+{
+	int len, sfx_len = sizeof("__sz") - 1;
+	const struct btf_type *t;
+	const char *param_name;
+
+	t = btf_type_skip_modifiers(btf, arg->type, NULL);
+	if (!btf_type_is_scalar(t) || reg->type != SCALAR_VALUE)
+		return false;
+
+	/* In the future, this can be ported to use BTF tagging */
+	param_name = btf_name_by_offset(btf, arg->name_off);
+	if (str_is_empty(param_name))
+		return false;
+	len = strlen(param_name);
+	if (len < sfx_len)
+		return false;
+	param_name += len - sfx_len;
+	if (strncmp(param_name, "__sz", sfx_len))
+		return false;
+
+	return true;
+}
+
+static bool is_kfunc_arg_ret_buf_size(const struct btf *btf,
+				      const struct btf_param *arg,
+				      const struct bpf_reg_state *reg,
+				      const char *name)
+{
+	int len, target_len = strlen(name);
+	const struct btf_type *t;
+	const char *param_name;
+
+	t = btf_type_skip_modifiers(btf, arg->type, NULL);
+	if (!btf_type_is_scalar(t) || reg->type != SCALAR_VALUE)
+		return false;
+
+	param_name = btf_name_by_offset(btf, arg->name_off);
+	if (str_is_empty(param_name))
+		return false;
+	len = strlen(param_name);
+	if (len != target_len)
+		return false;
+	if (strcmp(param_name, name))
+		return false;
+
+	return true;
+}
+
+enum {
+	KF_ARG_DYNPTR_ID,
+};
+
+BTF_ID_LIST(kf_arg_btf_ids)
+BTF_ID(struct, bpf_dynptr_kern)
+
+static bool is_kfunc_arg_dynptr(const struct btf *btf,
+				const struct btf_param *arg)
+{
+	const struct btf_type *t;
+	u32 res_id;
+
+	t = btf_type_skip_modifiers(btf, arg->type, NULL);
+	if (!t)
+		return false;
+	if (!btf_type_is_ptr(t))
+		return false;
+	t = btf_type_skip_modifiers(btf, t->type, &res_id);
+	if (!t)
+		return false;
+	return btf_types_are_same(btf, res_id, btf_vmlinux, kf_arg_btf_ids[KF_ARG_DYNPTR_ID]);
+}
+
+/* Returns true if struct is composed of scalars, 4 levels of nesting allowed */
+static bool __btf_type_is_scalar_struct(struct bpf_verifier_env *env,
+					const struct btf *btf,
+					const struct btf_type *t, int rec)
+{
+	const struct btf_type *member_type;
+	const struct btf_member *member;
+	u32 i;
+
+	if (!btf_type_is_struct(t))
+		return false;
+
+	for_each_member(i, t, member) {
+		const struct btf_array *array;
+
+		member_type = btf_type_skip_modifiers(btf, member->type, NULL);
+		if (btf_type_is_struct(member_type)) {
+			if (rec >= 3) {
+				verbose(env, "max struct nesting depth exceeded\n");
+				return false;
+			}
+			if (!__btf_type_is_scalar_struct(env, btf, member_type, rec + 1))
+				return false;
+			continue;
+		}
+		if (btf_type_is_array(member_type)) {
+			array = btf_array(member_type);
+			if (!array->nelems)
+				return false;
+			member_type = btf_type_skip_modifiers(btf, array->type, NULL);
+			if (!btf_type_is_scalar(member_type))
+				return false;
+			continue;
+		}
+		if (!btf_type_is_scalar(member_type))
+			return false;
+	}
+	return true;
+}
+
+
+static u32 *reg2btf_ids[__BPF_REG_TYPE_MAX] = {
+#ifdef CONFIG_NET
+	[PTR_TO_SOCKET] = &btf_sock_ids[BTF_SOCK_TYPE_SOCK],
+	[PTR_TO_SOCK_COMMON] = &btf_sock_ids[BTF_SOCK_TYPE_SOCK_COMMON],
+	[PTR_TO_TCP_SOCK] = &btf_sock_ids[BTF_SOCK_TYPE_TCP],
+#endif
+};
+
+enum kfunc_ptr_arg_type {
+	KF_ARG_PTR_TO_CTX,
+	KF_ARG_PTR_TO_BTF_ID,	     /* Also covers reg2btf_ids conversions */
+	KF_ARG_PTR_TO_KPTR_STRONG,   /* PTR_TO_KPTR but type specific */
+	KF_ARG_PTR_TO_DYNPTR,
+	KF_ARG_PTR_TO_MEM,
+	KF_ARG_PTR_TO_MEM_SIZE,	     /* Size derived from next argument, skip it */
+};
+
+static enum kfunc_ptr_arg_type
+get_kfunc_ptr_arg_type(struct bpf_verifier_env *env,
+		       struct bpf_kfunc_call_arg_meta *meta,
+		       const struct btf_type *t, const struct btf_type *ref_t,
+		       const char *ref_tname, const struct btf_param *args,
+		       int argno, int nargs)
+{
+	u32 regno = argno + 1;
+	struct bpf_reg_state *regs = cur_regs(env);
+	struct bpf_reg_state *reg = &regs[regno];
+	bool arg_mem_size = false;
+
+	/* In this function, we verify the kfunc's BTF as per the argument type,
+	 * leaving the rest of the verification with respect to the register
+	 * type to our caller. When a set of conditions hold in the BTF type of
+	 * arguments, we resolve it to a known kfunc_ptr_arg_type.
+	 */
+	if (btf_get_prog_ctx_type(&env->log, meta->btf, t, resolve_prog_type(env->prog), argno))
+		return KF_ARG_PTR_TO_CTX;
+
+	if ((base_type(reg->type) == PTR_TO_BTF_ID || reg2btf_ids[base_type(reg->type)])) {
+		if (!btf_type_is_struct(ref_t)) {
+			verbose(env, "kernel function %s args#%d pointer type %s %s is not supported\n",
+				meta->func_name, argno, btf_type_str(ref_t), ref_tname);
+			return -EINVAL;
+		}
+		return KF_ARG_PTR_TO_BTF_ID;
+	}
+
+	if (is_kfunc_arg_kptr_get(meta, argno)) {
+		if (!btf_type_is_ptr(ref_t)) {
+			verbose(env, "arg#0 BTF type must be a double pointer for kptr_get kfunc\n");
+			return -EINVAL;
+		}
+		ref_t = btf_type_by_id(meta->btf, ref_t->type);
+		ref_tname = btf_name_by_offset(meta->btf, ref_t->name_off);
+		if (!btf_type_is_struct(ref_t)) {
+			verbose(env, "kernel function %s args#0 pointer type %s %s is not supported\n",
+				meta->func_name, btf_type_str(ref_t), ref_tname);
+			return -EINVAL;
+		}
+		return KF_ARG_PTR_TO_KPTR_STRONG;
+	}
+
+	if (is_kfunc_arg_dynptr(meta->btf, &args[argno]))
+		return KF_ARG_PTR_TO_DYNPTR;
+
+	if (argno + 1 < nargs && is_kfunc_arg_mem_size(meta->btf, &args[argno + 1], &regs[regno + 1]))
+		arg_mem_size = true;
+
+	/* This is the catch all argument type of register types supported by
+	 * check_helper_mem_access. However, we only allow when argument type is
+	 * pointer to scalar, or struct composed (recursively) of scalars. When
+	 * arg_mem_size is true, the pointer can be void *.
+	 */
+	if (!btf_type_is_scalar(ref_t) && !__btf_type_is_scalar_struct(env, meta->btf, ref_t, 0) &&
+	    (arg_mem_size ? !btf_type_is_void(ref_t) : 1)) {
+		verbose(env, "arg#%d pointer type %s %s must point to %sscalar, or struct with scalar\n",
+			argno, btf_type_str(ref_t), ref_tname, arg_mem_size ? "void, " : "");
+		return -EINVAL;
+	}
+	return arg_mem_size ? KF_ARG_PTR_TO_MEM_SIZE : KF_ARG_PTR_TO_MEM;
+}
+
+static int process_kf_arg_ptr_to_btf_id(struct bpf_verifier_env *env,
+					struct bpf_reg_state *reg,
+					const struct btf_type *ref_t,
+					const char *ref_tname, u32 ref_id,
+					struct bpf_kfunc_call_arg_meta *meta,
+					int argno)
+{
+	const struct btf_type *reg_ref_t;
+	bool strict_type_match = false;
+	const struct btf *reg_btf;
+	const char *reg_ref_tname;
+	u32 reg_ref_id;
+
+	if (reg->type == PTR_TO_BTF_ID) {
+		reg_btf = reg->btf;
+		reg_ref_id = reg->btf_id;
+	} else {
+		reg_btf = btf_vmlinux;
+		reg_ref_id = *reg2btf_ids[base_type(reg->type)];
+	}
+
+	if (is_kfunc_trusted_args(meta) || (is_kfunc_release(meta) && reg->ref_obj_id))
+		strict_type_match = true;
+
+	reg_ref_t = btf_type_skip_modifiers(reg_btf, reg_ref_id, &reg_ref_id);
+	reg_ref_tname = btf_name_by_offset(reg_btf, reg_ref_t->name_off);
+	if (!btf_struct_ids_match(&env->log, reg_btf, reg_ref_id, reg->off, meta->btf, ref_id, strict_type_match)) {
+		verbose(env, "kernel function %s args#%d expected pointer to %s %s but R%d has a pointer to %s %s\n",
+			meta->func_name, argno, btf_type_str(ref_t), ref_tname, argno + 1,
+			btf_type_str(reg_ref_t), reg_ref_tname);
+		return -EINVAL;
+	}
+	return 0;
+}
+
+static int process_kf_arg_ptr_to_kptr_strong(struct bpf_verifier_env *env,
+					     struct bpf_reg_state *reg,
+					     const struct btf_type *ref_t,
+					     const char *ref_tname,
+					     struct bpf_kfunc_call_arg_meta *meta,
+					     int argno)
+{
+	struct btf_field *kptr_field;
+
+	/* check_func_arg_reg_off allows var_off for
+	 * PTR_TO_MAP_VALUE, but we need fixed offset to find
+	 * off_desc.
+	 */
+	if (!tnum_is_const(reg->var_off)) {
+		verbose(env, "arg#0 must have constant offset\n");
+		return -EINVAL;
+	}
+
+	kptr_field = btf_record_find(reg->map_ptr->record, reg->off + reg->var_off.value, BPF_KPTR);
+	if (!kptr_field || kptr_field->type != BPF_KPTR_REF) {
+		verbose(env, "arg#0 no referenced kptr at map value offset=%llu\n",
+			reg->off + reg->var_off.value);
+		return -EINVAL;
+	}
+
+	if (!btf_struct_ids_match(&env->log, meta->btf, ref_t->type, 0, kptr_field->kptr.btf,
+				  kptr_field->kptr.btf_id, true)) {
+		verbose(env, "kernel function %s args#%d expected pointer to %s %s\n",
+			meta->func_name, argno, btf_type_str(ref_t), ref_tname);
+		return -EINVAL;
+	}
+	return 0;
+}
+
+static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_arg_meta *meta)
+{
+	const char *func_name = meta->func_name, *ref_tname;
+	const struct btf *btf = meta->btf;
+	const struct btf_param *args;
+	u32 i, nargs;
+	int ret;
+
+	args = (const struct btf_param *)(meta->func_proto + 1);
+	nargs = btf_type_vlen(meta->func_proto);
+	if (nargs > MAX_BPF_FUNC_REG_ARGS) {
+		verbose(env, "Function %s has %d > %d args\n", func_name, nargs,
+			MAX_BPF_FUNC_REG_ARGS);
+		return -EINVAL;
+	}
+
+	/* Check that BTF function arguments match actual types that the
+	 * verifier sees.
+	 */
+	for (i = 0; i < nargs; i++) {
+		struct bpf_reg_state *regs = cur_regs(env), *reg = &regs[i + 1];
+		const struct btf_type *t, *ref_t, *resolve_ret;
+		enum bpf_arg_type arg_type = ARG_DONTCARE;
+		u32 regno = i + 1, ref_id, type_size;
+		bool is_ret_buf_sz = false;
+		int kf_arg_type;
+
+		t = btf_type_skip_modifiers(btf, args[i].type, NULL);
+		if (btf_type_is_scalar(t)) {
+			if (reg->type != SCALAR_VALUE) {
+				verbose(env, "R%d is not a scalar\n", regno);
+				return -EINVAL;
+			}
+			if (is_kfunc_arg_ret_buf_size(btf, &args[i], reg, "rdonly_buf_size")) {
+					meta->r0_rdonly = true;
+					is_ret_buf_sz = true;
+			} else if (is_kfunc_arg_ret_buf_size(btf, &args[i], reg, "rdwr_buf_size")) {
+					is_ret_buf_sz = true;
+			}
+
+			if (is_ret_buf_sz) {
+				if (meta->r0_size) {
+					verbose(env, "2 or more rdonly/rdwr_buf_size parameters for kfunc");
+					return -EINVAL;
+				}
+
+				if (!tnum_is_const(reg->var_off)) {
+					verbose(env, "R%d is not a const\n", regno);
+					return -EINVAL;
+				}
+
+				meta->r0_size = reg->var_off.value;
+				ret = mark_chain_precision(env, regno);
+				if (ret)
+					return ret;
+			}
+			continue;
+		}
+
+		if (!btf_type_is_ptr(t)) {
+			verbose(env, "Unrecognized arg#%d type %s\n", i, btf_type_str(t));
+			return -EINVAL;
+		}
+
+		if (reg->ref_obj_id) {
+			if (is_kfunc_release(meta) && meta->ref_obj_id) {
+				verbose(env, "verifier internal error: more than one arg with ref_obj_id R%d %u %u\n",
+					regno, reg->ref_obj_id,
+					meta->ref_obj_id);
+				return -EFAULT;
+			}
+			meta->ref_obj_id = reg->ref_obj_id;
+			if (is_kfunc_release(meta))
+				meta->release_regno = regno;
+		}
+
+		ref_t = btf_type_skip_modifiers(btf, t->type, &ref_id);
+		ref_tname = btf_name_by_offset(btf, ref_t->name_off);
+
+		kf_arg_type = get_kfunc_ptr_arg_type(env, meta, t, ref_t, ref_tname, args, i, nargs);
+		if (kf_arg_type < 0)
+			return kf_arg_type;
+
+		switch (kf_arg_type) {
+		case KF_ARG_PTR_TO_BTF_ID:
+			if (is_kfunc_trusted_args(meta) && !reg->ref_obj_id) {
+				verbose(env, "R%d must be referenced\n", regno);
+				return -EINVAL;
+			}
+			fallthrough;
+		case KF_ARG_PTR_TO_CTX:
+			/* Trusted arguments have the same offset checks as release arguments */
+			arg_type |= OBJ_RELEASE;
+			break;
+		case KF_ARG_PTR_TO_KPTR_STRONG:
+		case KF_ARG_PTR_TO_DYNPTR:
+		case KF_ARG_PTR_TO_MEM:
+		case KF_ARG_PTR_TO_MEM_SIZE:
+			/* Trusted by default */
+			break;
+		default:
+			WARN_ON_ONCE(1);
+			return -EFAULT;
+		}
+
+		if (is_kfunc_release(meta) && reg->ref_obj_id)
+			arg_type |= OBJ_RELEASE;
+		ret = check_func_arg_reg_off(env, reg, regno, arg_type);
+		if (ret < 0)
+			return ret;
+
+		switch (kf_arg_type) {
+		case KF_ARG_PTR_TO_CTX:
+			if (reg->type != PTR_TO_CTX) {
+				verbose(env, "arg#%d expected pointer to ctx, but got %s\n", i, btf_type_str(t));
+				return -EINVAL;
+			}
+			break;
+		case KF_ARG_PTR_TO_BTF_ID:
+			/* Only base_type is checked, further checks are done here */
+			if (reg->type != PTR_TO_BTF_ID &&
+			    (!reg2btf_ids[base_type(reg->type)] || type_flag(reg->type))) {
+				verbose(env, "arg#%d expected pointer to btf or socket\n", i);
+				return -EINVAL;
+			}
+			ret = process_kf_arg_ptr_to_btf_id(env, reg, ref_t, ref_tname, ref_id, meta, i);
+			if (ret < 0)
+				return ret;
+			break;
+		case KF_ARG_PTR_TO_KPTR_STRONG:
+			if (reg->type != PTR_TO_MAP_VALUE) {
+				verbose(env, "arg#0 expected pointer to map value\n");
+				return -EINVAL;
+			}
+			ret = process_kf_arg_ptr_to_kptr_strong(env, reg, ref_t, ref_tname, meta, i);
+			if (ret < 0)
+				return ret;
+			break;
+		case KF_ARG_PTR_TO_DYNPTR:
+			if (reg->type != PTR_TO_STACK) {
+				verbose(env, "arg#%d expected pointer to stack\n", i);
+				return -EINVAL;
+			}
+
+			if (!is_dynptr_reg_valid_init(env, reg)) {
+				verbose(env, "arg#%d pointer type %s %s must be valid and initialized\n",
+					i, btf_type_str(ref_t), ref_tname);
+				return -EINVAL;
+			}
+
+			if (!is_dynptr_type_expected(env, reg, ARG_PTR_TO_DYNPTR | DYNPTR_TYPE_LOCAL)) {
+				verbose(env, "arg#%d pointer type %s %s points to unsupported dynamic pointer type\n",
+					i, btf_type_str(ref_t), ref_tname);
+				return -EINVAL;
+			}
+			break;
+		case KF_ARG_PTR_TO_MEM:
+			resolve_ret = btf_resolve_size(btf, ref_t, &type_size);
+			if (IS_ERR(resolve_ret)) {
+				verbose(env, "arg#%d reference type('%s %s') size cannot be determined: %ld\n",
+					i, btf_type_str(ref_t), ref_tname, PTR_ERR(resolve_ret));
+				return -EINVAL;
+			}
+			ret = check_mem_reg(env, reg, regno, type_size);
+			if (ret < 0)
+				return ret;
+			break;
+		case KF_ARG_PTR_TO_MEM_SIZE:
+			ret = check_kfunc_mem_size_reg(env, &regs[regno + 1], regno + 1);
+			if (ret < 0) {
+				verbose(env, "arg#%d arg#%d memory, len pair leads to invalid memory access\n", i, i + 1);
+				return ret;
+			}
+			/* Skip next '__sz' argument */
+			i++;
+			break;
+		}
+	}
+
+	if (is_kfunc_release(meta) && !meta->release_regno) {
+		verbose(env, "release kernel function %s expects refcounted PTR_TO_BTF_ID\n",
+			func_name);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
 static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 			    int *insn_idx_p)
 {
 	const struct btf_type *t, *func, *func_proto, *ptr_type;
 	struct bpf_reg_state *regs = cur_regs(env);
-	struct bpf_kfunc_arg_meta meta = { 0 };
 	const char *func_name, *ptr_type_name;
+	struct bpf_kfunc_call_arg_meta meta;
 	u32 i, nargs, func_id, ptr_type_id;
 	int err, insn_idx = *insn_idx_p;
 	const struct btf_param *args;
 	struct btf *desc_btf;
 	u32 *kfunc_flags;
-	bool acq;
 
 	/* skip for now, but return error when we find this in fixup_kfunc_call */
 	if (!insn->imm)
@@ -7708,24 +8210,34 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 			func_name);
 		return -EACCES;
 	}
-	if (*kfunc_flags & KF_DESTRUCTIVE && !capable(CAP_SYS_BOOT)) {
-		verbose(env, "destructive kfunc calls require CAP_SYS_BOOT capabilities\n");
+
+	/* Prepare kfunc call metadata */
+	memset(&meta, 0, sizeof(meta));
+	meta.btf = desc_btf;
+	meta.func_id = func_id;
+	meta.kfunc_flags = *kfunc_flags;
+	meta.func_proto = func_proto;
+	meta.func_name = func_name;
+
+	if (is_kfunc_destructive(&meta) && !capable(CAP_SYS_BOOT)) {
+		verbose(env, "destructive kfunc calls require CAP_SYS_BOOT capability\n");
 		return -EACCES;
 	}
 
-	acq = *kfunc_flags & KF_ACQUIRE;
-
-	meta.flags = *kfunc_flags;
+	if (is_kfunc_sleepable(&meta) && !env->prog->aux->sleepable) {
+		verbose(env, "program must be sleepable to call sleepable kfunc %s\n", func_name);
+		return -EACCES;
+	}
 
 	/* Check the arguments */
-	err = btf_check_kfunc_arg_match(env, desc_btf, func_id, regs, &meta);
+	err = check_kfunc_args(env, &meta);
 	if (err < 0)
 		return err;
 	/* In case of release function, we get register number of refcounted
-	 * PTR_TO_BTF_ID back from btf_check_kfunc_arg_match, do the release now
+	 * PTR_TO_BTF_ID in bpf_kfunc_arg_meta, do the release now.
 	 */
-	if (err) {
-		err = release_reference(env, regs[err].ref_obj_id);
+	if (meta.release_regno) {
+		err = release_reference(env, regs[meta.release_regno].ref_obj_id);
 		if (err) {
 			verbose(env, "kfunc %s#%d reference has not been acquired before\n",
 				func_name, func_id);
@@ -7739,7 +8251,7 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 	/* Check return type */
 	t = btf_type_skip_modifiers(desc_btf, func_proto->type, NULL);
 
-	if (acq && !btf_type_is_struct_ptr(desc_btf, t)) {
+	if (is_kfunc_acquire(&meta) && !btf_type_is_struct_ptr(meta.btf, t)) {
 		verbose(env, "acquire kernel function does not return PTR_TO_BTF_ID\n");
 		return -EINVAL;
 	}
@@ -7778,20 +8290,23 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 			regs[BPF_REG_0].type = PTR_TO_BTF_ID;
 			regs[BPF_REG_0].btf_id = ptr_type_id;
 		}
-		if (*kfunc_flags & KF_RET_NULL) {
+		if (is_kfunc_ret_null(&meta)) {
 			regs[BPF_REG_0].type |= PTR_MAYBE_NULL;
 			/* For mark_ptr_or_null_reg, see 93c230e3f5bd6 */
 			regs[BPF_REG_0].id = ++env->id_gen;
 		}
 		mark_btf_func_reg_size(env, BPF_REG_0, sizeof(void *));
-		if (acq) {
+		if (is_kfunc_acquire(&meta)) {
 			int id = acquire_reference_state(env, insn_idx);
 
 			if (id < 0)
 				return id;
-			regs[BPF_REG_0].id = id;
+			if (is_kfunc_ret_null(&meta))
+				regs[BPF_REG_0].id = id;
 			regs[BPF_REG_0].ref_obj_id = id;
 		}
+		if (reg_may_point_to_spin_lock(&regs[BPF_REG_0]) && !regs[BPF_REG_0].id)
+			regs[BPF_REG_0].id = ++env->id_gen;
 	} /* else { add_kfunc_call() ensures it is btf_type_is_void(t) } */
 
 	nargs = btf_type_vlen(func_proto);
diff --git a/tools/testing/selftests/bpf/prog_tests/kfunc_dynptr_param.c b/tools/testing/selftests/bpf/prog_tests/kfunc_dynptr_param.c
index c210657d4d0a..55d641c1f126 100644
--- a/tools/testing/selftests/bpf/prog_tests/kfunc_dynptr_param.c
+++ b/tools/testing/selftests/bpf/prog_tests/kfunc_dynptr_param.c
@@ -22,7 +22,7 @@ static struct {
 	 "arg#0 pointer type STRUCT bpf_dynptr_kern points to unsupported dynamic pointer type", 0},
 	{"not_valid_dynptr",
 	 "arg#0 pointer type STRUCT bpf_dynptr_kern must be valid and initialized", 0},
-	{"not_ptr_to_stack", "arg#0 pointer type STRUCT bpf_dynptr_kern not to stack", 0},
+	{"not_ptr_to_stack", "arg#0 expected pointer to stack", 0},
 	{"dynptr_data_null", NULL, -EBADMSG},
 };
 
diff --git a/tools/testing/selftests/bpf/verifier/calls.c b/tools/testing/selftests/bpf/verifier/calls.c
index e1a937277b54..e349d85f7717 100644
--- a/tools/testing/selftests/bpf/verifier/calls.c
+++ b/tools/testing/selftests/bpf/verifier/calls.c
@@ -109,7 +109,7 @@
 	},
 	.prog_type = BPF_PROG_TYPE_SCHED_CLS,
 	.result = REJECT,
-	.errstr = "arg#0 pointer type STRUCT prog_test_ref_kfunc must point",
+	.errstr = "arg#0 expected pointer to btf or socket",
 	.fixup_kfunc_btf_id = {
 		{ "bpf_kfunc_call_test_acquire", 3 },
 		{ "bpf_kfunc_call_test_release", 5 },
@@ -181,7 +181,7 @@
 	},
 	.result_unpriv = REJECT,
 	.result = REJECT,
-	.errstr = "negative offset ptr_ ptr R1 off=-4 disallowed",
+	.errstr = "R1 must have zero offset when passed to release func",
 },
 {
 	"calls: invalid kfunc call: PTR_TO_BTF_ID with variable offset",
diff --git a/tools/testing/selftests/bpf/verifier/ref_tracking.c b/tools/testing/selftests/bpf/verifier/ref_tracking.c
index f18ce867271f..4784471b0b7f 100644
--- a/tools/testing/selftests/bpf/verifier/ref_tracking.c
+++ b/tools/testing/selftests/bpf/verifier/ref_tracking.c
@@ -142,7 +142,7 @@
 	.kfunc = "bpf",
 	.expected_attach_type = BPF_LSM_MAC,
 	.flags = BPF_F_SLEEPABLE,
-	.errstr = "arg#0 pointer type STRUCT bpf_key must point to scalar, or struct with scalar",
+	.errstr = "arg#0 expected pointer to btf or socket",
 	.fixup_kfunc_btf_id = {
 		{ "bpf_lookup_user_key", 2 },
 		{ "bpf_key_put", 4 },
@@ -163,7 +163,7 @@
 	.kfunc = "bpf",
 	.expected_attach_type = BPF_LSM_MAC,
 	.flags = BPF_F_SLEEPABLE,
-	.errstr = "arg#0 pointer type STRUCT bpf_key must point to scalar, or struct with scalar",
+	.errstr = "arg#0 expected pointer to btf or socket",
 	.fixup_kfunc_btf_id = {
 		{ "bpf_lookup_system_key", 1 },
 		{ "bpf_key_put", 3 },
-- 
2.38.1

[PATCH bpf-next v4 16/24] bpf: Drop kfunc bits from btf_check_func_arg_match

[Kumar Kartikeya Dwivedi]

Remove all kfunc related bits now from btf_check_func_arg_match, as
users have been converted away to refactored kfunc argument handling.

This is split into a separate commit to aid review, in order to compare
what has been preserved from the removed bits easily instead of mixing
removed hunks with previous patch.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 include/linux/bpf.h          |  11 --
 include/linux/bpf_verifier.h |   2 -
 kernel/bpf/btf.c             | 364 +----------------------------------
 kernel/bpf/verifier.c        |   4 +-
 4 files changed, 10 insertions(+), 371 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index fb2659c1c10c..5d9a786e0cef 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -2112,22 +2112,11 @@ int btf_distill_func_proto(struct bpf_verifier_log *log,
 			   const char *func_name,
 			   struct btf_func_model *m);
 
-struct bpf_kfunc_arg_meta {
-	u64 r0_size;
-	bool r0_rdonly;
-	int ref_obj_id;
-	u32 flags;
-};
-
 struct bpf_reg_state;
 int btf_check_subprog_arg_match(struct bpf_verifier_env *env, int subprog,
 				struct bpf_reg_state *regs);
 int btf_check_subprog_call(struct bpf_verifier_env *env, int subprog,
 			   struct bpf_reg_state *regs);
-int btf_check_kfunc_arg_match(struct bpf_verifier_env *env,
-			      const struct btf *btf, u32 func_id,
-			      struct bpf_reg_state *regs,
-			      struct bpf_kfunc_arg_meta *meta);
 int btf_prepare_func_args(struct bpf_verifier_env *env, int subprog,
 			  struct bpf_reg_state *reg);
 int btf_check_type_match(struct bpf_verifier_log *log, const struct bpf_prog *prog,
diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index bb71c59f21f6..8dad74432677 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -590,8 +590,6 @@ int check_ptr_off_reg(struct bpf_verifier_env *env,
 int check_func_arg_reg_off(struct bpf_verifier_env *env,
 			   const struct bpf_reg_state *reg, int regno,
 			   enum bpf_arg_type arg_type);
-int check_kfunc_mem_size_reg(struct bpf_verifier_env *env, struct bpf_reg_state *reg,
-			     u32 regno);
 int check_mem_reg(struct bpf_verifier_env *env, struct bpf_reg_state *reg,
 		   u32 regno, u32 mem_size);
 bool is_dynptr_reg_valid_init(struct bpf_verifier_env *env,
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 7a66aaa02e6a..a0ef746d19ae 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -6593,122 +6593,19 @@ int btf_check_type_match(struct bpf_verifier_log *log, const struct bpf_prog *pr
 	return btf_check_func_type_match(log, btf1, t1, btf2, t2);
 }
 
-static u32 *reg2btf_ids[__BPF_REG_TYPE_MAX] = {
-#ifdef CONFIG_NET
-	[PTR_TO_SOCKET] = &btf_sock_ids[BTF_SOCK_TYPE_SOCK],
-	[PTR_TO_SOCK_COMMON] = &btf_sock_ids[BTF_SOCK_TYPE_SOCK_COMMON],
-	[PTR_TO_TCP_SOCK] = &btf_sock_ids[BTF_SOCK_TYPE_TCP],
-#endif
-};
-
-/* Returns true if struct is composed of scalars, 4 levels of nesting allowed */
-static bool __btf_type_is_scalar_struct(struct bpf_verifier_log *log,
-					const struct btf *btf,
-					const struct btf_type *t, int rec)
-{
-	const struct btf_type *member_type;
-	const struct btf_member *member;
-	u32 i;
-
-	if (!btf_type_is_struct(t))
-		return false;
-
-	for_each_member(i, t, member) {
-		const struct btf_array *array;
-
-		member_type = btf_type_skip_modifiers(btf, member->type, NULL);
-		if (btf_type_is_struct(member_type)) {
-			if (rec >= 3) {
-				bpf_log(log, "max struct nesting depth exceeded\n");
-				return false;
-			}
-			if (!__btf_type_is_scalar_struct(log, btf, member_type, rec + 1))
-				return false;
-			continue;
-		}
-		if (btf_type_is_array(member_type)) {
-			array = btf_type_array(member_type);
-			if (!array->nelems)
-				return false;
-			member_type = btf_type_skip_modifiers(btf, array->type, NULL);
-			if (!btf_type_is_scalar(member_type))
-				return false;
-			continue;
-		}
-		if (!btf_type_is_scalar(member_type))
-			return false;
-	}
-	return true;
-}
-
-static bool is_kfunc_arg_mem_size(const struct btf *btf,
-				  const struct btf_param *arg,
-				  const struct bpf_reg_state *reg)
-{
-	int len, sfx_len = sizeof("__sz") - 1;
-	const struct btf_type *t;
-	const char *param_name;
-
-	t = btf_type_skip_modifiers(btf, arg->type, NULL);
-	if (!btf_type_is_scalar(t) || reg->type != SCALAR_VALUE)
-		return false;
-
-	/* In the future, this can be ported to use BTF tagging */
-	param_name = btf_name_by_offset(btf, arg->name_off);
-	if (str_is_empty(param_name))
-		return false;
-	len = strlen(param_name);
-	if (len < sfx_len)
-		return false;
-	param_name += len - sfx_len;
-	if (strncmp(param_name, "__sz", sfx_len))
-		return false;
-
-	return true;
-}
-
-static bool btf_is_kfunc_arg_mem_size(const struct btf *btf,
-				      const struct btf_param *arg,
-				      const struct bpf_reg_state *reg,
-				      const char *name)
-{
-	int len, target_len = strlen(name);
-	const struct btf_type *t;
-	const char *param_name;
-
-	t = btf_type_skip_modifiers(btf, arg->type, NULL);
-	if (!btf_type_is_scalar(t) || reg->type != SCALAR_VALUE)
-		return false;
-
-	param_name = btf_name_by_offset(btf, arg->name_off);
-	if (str_is_empty(param_name))
-		return false;
-	len = strlen(param_name);
-	if (len != target_len)
-		return false;
-	if (strcmp(param_name, name))
-		return false;
-
-	return true;
-}
-
 static int btf_check_func_arg_match(struct bpf_verifier_env *env,
 				    const struct btf *btf, u32 func_id,
 				    struct bpf_reg_state *regs,
 				    bool ptr_to_mem_ok,
-				    struct bpf_kfunc_arg_meta *kfunc_meta,
 				    bool processing_call)
 {
 	enum bpf_prog_type prog_type = resolve_prog_type(env->prog);
-	bool rel = false, kptr_get = false, trusted_args = false;
-	bool sleepable = false;
 	struct bpf_verifier_log *log = &env->log;
-	u32 i, nargs, ref_id, ref_obj_id = 0;
-	bool is_kfunc = btf_is_kernel(btf);
 	const char *func_name, *ref_tname;
 	const struct btf_type *t, *ref_t;
 	const struct btf_param *args;
-	int ref_regno = 0, ret;
+	u32 i, nargs, ref_id;
+	int ret;
 
 	t = btf_type_by_id(btf, func_id);
 	if (!t || !btf_type_is_func(t)) {
@@ -6734,14 +6631,6 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
 		return -EINVAL;
 	}
 
-	if (is_kfunc && kfunc_meta) {
-		/* Only kfunc can be release func */
-		rel = kfunc_meta->flags & KF_RELEASE;
-		kptr_get = kfunc_meta->flags & KF_KPTR_GET;
-		trusted_args = kfunc_meta->flags & KF_TRUSTED_ARGS;
-		sleepable = kfunc_meta->flags & KF_SLEEPABLE;
-	}
-
 	/* check that BTF function arguments match actual types that the
 	 * verifier sees.
 	 */
@@ -6749,42 +6638,9 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
 		enum bpf_arg_type arg_type = ARG_DONTCARE;
 		u32 regno = i + 1;
 		struct bpf_reg_state *reg = &regs[regno];
-		bool obj_ptr = false;
 
 		t = btf_type_skip_modifiers(btf, args[i].type, NULL);
 		if (btf_type_is_scalar(t)) {
-			if (is_kfunc && kfunc_meta) {
-				bool is_buf_size = false;
-
-				/* check for any const scalar parameter of name "rdonly_buf_size"
-				 * or "rdwr_buf_size"
-				 */
-				if (btf_is_kfunc_arg_mem_size(btf, &args[i], reg,
-							      "rdonly_buf_size")) {
-					kfunc_meta->r0_rdonly = true;
-					is_buf_size = true;
-				} else if (btf_is_kfunc_arg_mem_size(btf, &args[i], reg,
-								     "rdwr_buf_size"))
-					is_buf_size = true;
-
-				if (is_buf_size) {
-					if (kfunc_meta->r0_size) {
-						bpf_log(log, "2 or more rdonly/rdwr_buf_size parameters for kfunc");
-						return -EINVAL;
-					}
-
-					if (!tnum_is_const(reg->var_off)) {
-						bpf_log(log, "R%d is not a const\n", regno);
-						return -EINVAL;
-					}
-
-					kfunc_meta->r0_size = reg->var_off.value;
-					ret = mark_chain_precision(env, regno);
-					if (ret)
-						return ret;
-				}
-			}
-
 			if (reg->type == SCALAR_VALUE)
 				continue;
 			bpf_log(log, "R%d is not a scalar\n", regno);
@@ -6797,88 +6653,14 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
 			return -EINVAL;
 		}
 
-		/* These register types have special constraints wrt ref_obj_id
-		 * and offset checks. The rest of trusted args don't.
-		 */
-		obj_ptr = reg->type == PTR_TO_CTX || reg->type == PTR_TO_BTF_ID ||
-			  reg2btf_ids[base_type(reg->type)];
-
-		/* Check if argument must be a referenced pointer, args + i has
-		 * been verified to be a pointer (after skipping modifiers).
-		 * PTR_TO_CTX is ok without having non-zero ref_obj_id.
-		 */
-		if (is_kfunc && trusted_args && (obj_ptr && reg->type != PTR_TO_CTX) && !reg->ref_obj_id) {
-			bpf_log(log, "R%d must be referenced\n", regno);
-			return -EINVAL;
-		}
-
 		ref_t = btf_type_skip_modifiers(btf, t->type, &ref_id);
 		ref_tname = btf_name_by_offset(btf, ref_t->name_off);
 
-		/* Trusted args have the same offset checks as release arguments */
-		if ((trusted_args && obj_ptr) || (rel && reg->ref_obj_id))
-			arg_type |= OBJ_RELEASE;
 		ret = check_func_arg_reg_off(env, reg, regno, arg_type);
 		if (ret < 0)
 			return ret;
 
-		if (is_kfunc && reg->ref_obj_id) {
-			/* Ensure only one argument is referenced PTR_TO_BTF_ID */
-			if (ref_obj_id) {
-				bpf_log(log, "verifier internal error: more than one arg with ref_obj_id R%d %u %u\n",
-					regno, reg->ref_obj_id, ref_obj_id);
-				return -EFAULT;
-			}
-			ref_regno = regno;
-			ref_obj_id = reg->ref_obj_id;
-		}
-
-		/* kptr_get is only true for kfunc */
-		if (i == 0 && kptr_get) {
-			struct btf_field *kptr_field;
-
-			if (reg->type != PTR_TO_MAP_VALUE) {
-				bpf_log(log, "arg#0 expected pointer to map value\n");
-				return -EINVAL;
-			}
-
-			/* check_func_arg_reg_off allows var_off for
-			 * PTR_TO_MAP_VALUE, but we need fixed offset to find
-			 * off_desc.
-			 */
-			if (!tnum_is_const(reg->var_off)) {
-				bpf_log(log, "arg#0 must have constant offset\n");
-				return -EINVAL;
-			}
-
-			kptr_field = btf_record_find(reg->map_ptr->record, reg->off + reg->var_off.value, BPF_KPTR);
-			if (!kptr_field || kptr_field->type != BPF_KPTR_REF) {
-				bpf_log(log, "arg#0 no referenced kptr at map value offset=%llu\n",
-					reg->off + reg->var_off.value);
-				return -EINVAL;
-			}
-
-			if (!btf_type_is_ptr(ref_t)) {
-				bpf_log(log, "arg#0 BTF type must be a double pointer\n");
-				return -EINVAL;
-			}
-
-			ref_t = btf_type_skip_modifiers(btf, ref_t->type, &ref_id);
-			ref_tname = btf_name_by_offset(btf, ref_t->name_off);
-
-			if (!btf_type_is_struct(ref_t)) {
-				bpf_log(log, "kernel function %s args#%d pointer type %s %s is not supported\n",
-					func_name, i, btf_type_str(ref_t), ref_tname);
-				return -EINVAL;
-			}
-			if (!btf_struct_ids_match(log, btf, ref_id, 0, kptr_field->kptr.btf,
-						  kptr_field->kptr.btf_id, true)) {
-				bpf_log(log, "kernel function %s args#%d expected pointer to %s %s\n",
-					func_name, i, btf_type_str(ref_t), ref_tname);
-				return -EINVAL;
-			}
-			/* rest of the arguments can be anything, like normal kfunc */
-		} else if (btf_get_prog_ctx_type(log, btf, t, prog_type, i)) {
+		if (btf_get_prog_ctx_type(log, btf, t, prog_type, i)) {
 			/* If function expects ctx type in BTF check that caller
 			 * is passing PTR_TO_CTX.
 			 */
@@ -6888,109 +6670,10 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
 					i, btf_type_str(t));
 				return -EINVAL;
 			}
-		} else if (is_kfunc && (reg->type == PTR_TO_BTF_ID ||
-			   (reg2btf_ids[base_type(reg->type)] && !type_flag(reg->type)))) {
-			const struct btf_type *reg_ref_t;
-			const struct btf *reg_btf;
-			const char *reg_ref_tname;
-			u32 reg_ref_id;
-
-			if (!btf_type_is_struct(ref_t)) {
-				bpf_log(log, "kernel function %s args#%d pointer type %s %s is not supported\n",
-					func_name, i, btf_type_str(ref_t),
-					ref_tname);
-				return -EINVAL;
-			}
-
-			if (reg->type == PTR_TO_BTF_ID) {
-				reg_btf = reg->btf;
-				reg_ref_id = reg->btf_id;
-			} else {
-				reg_btf = btf_vmlinux;
-				reg_ref_id = *reg2btf_ids[base_type(reg->type)];
-			}
-
-			reg_ref_t = btf_type_skip_modifiers(reg_btf, reg_ref_id,
-							    &reg_ref_id);
-			reg_ref_tname = btf_name_by_offset(reg_btf,
-							   reg_ref_t->name_off);
-			if (!btf_struct_ids_match(log, reg_btf, reg_ref_id,
-						  reg->off, btf, ref_id,
-						  trusted_args || (rel && reg->ref_obj_id))) {
-				bpf_log(log, "kernel function %s args#%d expected pointer to %s %s but R%d has a pointer to %s %s\n",
-					func_name, i,
-					btf_type_str(ref_t), ref_tname,
-					regno, btf_type_str(reg_ref_t),
-					reg_ref_tname);
-				return -EINVAL;
-			}
 		} else if (ptr_to_mem_ok && processing_call) {
 			const struct btf_type *resolve_ret;
 			u32 type_size;
 
-			if (is_kfunc) {
-				bool arg_mem_size = i + 1 < nargs && is_kfunc_arg_mem_size(btf, &args[i + 1], &regs[regno + 1]);
-				bool arg_dynptr = btf_type_is_struct(ref_t) &&
-						  !strcmp(ref_tname,
-							  stringify_struct(bpf_dynptr_kern));
-
-				/* Permit pointer to mem, but only when argument
-				 * type is pointer to scalar, or struct composed
-				 * (recursively) of scalars.
-				 * When arg_mem_size is true, the pointer can be
-				 * void *.
-				 * Also permit initialized local dynamic pointers.
-				 */
-				if (!btf_type_is_scalar(ref_t) &&
-				    !__btf_type_is_scalar_struct(log, btf, ref_t, 0) &&
-				    !arg_dynptr &&
-				    (arg_mem_size ? !btf_type_is_void(ref_t) : 1)) {
-					bpf_log(log,
-						"arg#%d pointer type %s %s must point to %sscalar, or struct with scalar\n",
-						i, btf_type_str(ref_t), ref_tname, arg_mem_size ? "void, " : "");
-					return -EINVAL;
-				}
-
-				if (arg_dynptr) {
-					if (reg->type != PTR_TO_STACK) {
-						bpf_log(log, "arg#%d pointer type %s %s not to stack\n",
-							i, btf_type_str(ref_t),
-							ref_tname);
-						return -EINVAL;
-					}
-
-					if (!is_dynptr_reg_valid_init(env, reg)) {
-						bpf_log(log,
-							"arg#%d pointer type %s %s must be valid and initialized\n",
-							i, btf_type_str(ref_t),
-							ref_tname);
-						return -EINVAL;
-					}
-
-					if (!is_dynptr_type_expected(env, reg,
-							ARG_PTR_TO_DYNPTR | DYNPTR_TYPE_LOCAL)) {
-						bpf_log(log,
-							"arg#%d pointer type %s %s points to unsupported dynamic pointer type\n",
-							i, btf_type_str(ref_t),
-							ref_tname);
-						return -EINVAL;
-					}
-
-					continue;
-				}
-
-				/* Check for mem, len pair */
-				if (arg_mem_size) {
-					if (check_kfunc_mem_size_reg(env, &regs[regno + 1], regno + 1)) {
-						bpf_log(log, "arg#%d arg#%d memory, len pair leads to invalid memory access\n",
-							i, i + 1);
-						return -EINVAL;
-					}
-					i++;
-					continue;
-				}
-			}
-
 			resolve_ret = btf_resolve_size(btf, ref_t, &type_size);
 			if (IS_ERR(resolve_ret)) {
 				bpf_log(log,
@@ -7003,36 +6686,13 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
 			if (check_mem_reg(env, reg, regno, type_size))
 				return -EINVAL;
 		} else {
-			bpf_log(log, "reg type unsupported for arg#%d %sfunction %s#%d\n", i,
-				is_kfunc ? "kernel " : "", func_name, func_id);
+			bpf_log(log, "reg type unsupported for arg#%d function %s#%d\n", i,
+				func_name, func_id);
 			return -EINVAL;
 		}
 	}
 
-	/* Either both are set, or neither */
-	WARN_ON_ONCE((ref_obj_id && !ref_regno) || (!ref_obj_id && ref_regno));
-	/* We already made sure ref_obj_id is set only for one argument. We do
-	 * allow (!rel && ref_obj_id), so that passing such referenced
-	 * PTR_TO_BTF_ID to other kfuncs works. Note that rel is only true when
-	 * is_kfunc is true.
-	 */
-	if (rel && !ref_obj_id) {
-		bpf_log(log, "release kernel function %s expects refcounted PTR_TO_BTF_ID\n",
-			func_name);
-		return -EINVAL;
-	}
-
-	if (sleepable && !env->prog->aux->sleepable) {
-		bpf_log(log, "kernel function %s is sleepable but the program is not\n",
-			func_name);
-		return -EINVAL;
-	}
-
-	if (kfunc_meta && ref_obj_id)
-		kfunc_meta->ref_obj_id = ref_obj_id;
-
-	/* returns argument register number > 0 in case of reference release kfunc */
-	return rel ? ref_regno : 0;
+	return 0;
 }
 
 /* Compare BTF of a function declaration with given bpf_reg_state.
@@ -7062,7 +6722,7 @@ int btf_check_subprog_arg_match(struct bpf_verifier_env *env, int subprog,
 		return -EINVAL;
 
 	is_global = prog->aux->func_info_aux[subprog].linkage == BTF_FUNC_GLOBAL;
-	err = btf_check_func_arg_match(env, btf, btf_id, regs, is_global, NULL, false);
+	err = btf_check_func_arg_match(env, btf, btf_id, regs, is_global, false);
 
 	/* Compiler optimizations can remove arguments from static functions
 	 * or mismatched type can be passed into a global function.
@@ -7105,7 +6765,7 @@ int btf_check_subprog_call(struct bpf_verifier_env *env, int subprog,
 		return -EINVAL;
 
 	is_global = prog->aux->func_info_aux[subprog].linkage == BTF_FUNC_GLOBAL;
-	err = btf_check_func_arg_match(env, btf, btf_id, regs, is_global, NULL, true);
+	err = btf_check_func_arg_match(env, btf, btf_id, regs, is_global, true);
 
 	/* Compiler optimizations can remove arguments from static functions
 	 * or mismatched type can be passed into a global function.
@@ -7116,14 +6776,6 @@ int btf_check_subprog_call(struct bpf_verifier_env *env, int subprog,
 	return err;
 }
 
-int btf_check_kfunc_arg_match(struct bpf_verifier_env *env,
-			      const struct btf *btf, u32 func_id,
-			      struct bpf_reg_state *regs,
-			      struct bpf_kfunc_arg_meta *meta)
-{
-	return btf_check_func_arg_match(env, btf, func_id, regs, true, meta, true);
-}
-
 /* Convert BTF of a function into bpf_reg_state if possible
  * Returns:
  * EFAULT - there is a verifier bug. Abort verification.
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 5c2f5e61dde9..effc417cc086 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -5378,8 +5378,8 @@ int check_mem_reg(struct bpf_verifier_env *env, struct bpf_reg_state *reg,
 	return err;
 }
 
-int check_kfunc_mem_size_reg(struct bpf_verifier_env *env, struct bpf_reg_state *reg,
-			     u32 regno)
+static int check_kfunc_mem_size_reg(struct bpf_verifier_env *env, struct bpf_reg_state *reg,
+				    u32 regno)
 {
 	struct bpf_reg_state *mem_reg = &cur_regs(env)[regno - 1];
 	bool may_be_null = type_may_be_null(mem_reg->type);
-- 
2.38.1

[PATCH bpf-next v4 17/24] bpf: Support constant scalar arguments for kfuncs

[Kumar Kartikeya Dwivedi]

Allow passing known constant scalars as arguments to kfuncs that do not
represent a size parameter. This makes the search pruning optimization
of verifier more conservative for such kfunc calls, and each
non-distinct argument is considered unequivalent.

We will use this support to then expose a global bpf_kptr_alloc function
where it takes the local type ID in program BTF, and returns a
PTR_TO_BTF_ID to the local type. These will be called local kptrs, and
allows programs to allocate their own objects.

However, this is still not completely safe, as mark_chain_precision
logic is buggy without more work when the constant argument is not a
size, but still needs precise marker propagation for pruning checks.
Next patch will fix this problem.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 Documentation/bpf/kfuncs.rst | 30 ++++++++++++++++++
 kernel/bpf/verifier.c        | 59 +++++++++++++++++++++++++++---------
 2 files changed, 75 insertions(+), 14 deletions(-)

diff --git a/Documentation/bpf/kfuncs.rst b/Documentation/bpf/kfuncs.rst
index 0f858156371d..08f9a968d06d 100644
--- a/Documentation/bpf/kfuncs.rst
+++ b/Documentation/bpf/kfuncs.rst
@@ -72,6 +72,36 @@ argument as its size. By default, without __sz annotation, the size of the type
 of the pointer is used. Without __sz annotation, a kfunc cannot accept a void
 pointer.
 
+2.2.1 __k Annotation
+--------------------
+
+This annotation is only understood for scalar arguments, where it indicates that
+the verifier must check the scalar argument to be a known constant, which does
+not indicate a size parameter. This distinction is important, as when the scalar
+argument does not represent a size parameter, verifier is more conservative in
+state search pruning and does not consider two arguments equivalent for safety
+purposes if the already verified value was within range of the new one.
+
+This assumption holds well for sizes (as memory accessed within smaller bounds
+in old verified state will also work for bigger bounds in current to be explored
+state), but not for other constant arguments where each carries a distinct
+semantic effect.
+
+An example is given below::
+
+        void *bpf_mem_alloc(u32 local_type_id__k)
+        {
+        ...
+        }
+
+Here, bpf_mem_alloc uses local_type_id argument to find out the size of that
+type ID in program's BTF and return a sized pointer to it. Each type ID will
+have a distinct size, hence it is crucial to treat each such call as distinct
+when values don't match.
+
+Hence, whenever a constant scalar argument is accepted by a kfunc which is not a
+size parameter, __k suffix must be used.
+
 .. _BPF_kfunc_nodef:
 
 2.3 Using an existing kernel function
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index effc417cc086..b22ad48bbecd 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -7687,6 +7687,10 @@ struct bpf_kfunc_call_arg_meta {
 	u8 release_regno;
 	bool r0_rdonly;
 	u64 r0_size;
+	struct {
+		u64 value;
+		bool found;
+	} arg_constant;
 };
 
 static bool is_kfunc_acquire(struct bpf_kfunc_call_arg_meta *meta)
@@ -7724,30 +7728,40 @@ static bool is_kfunc_arg_kptr_get(struct bpf_kfunc_call_arg_meta *meta, int arg)
 	return arg == 0 && (meta->kfunc_flags & KF_KPTR_GET);
 }
 
-static bool is_kfunc_arg_mem_size(const struct btf *btf,
-				  const struct btf_param *arg,
-				  const struct bpf_reg_state *reg)
+static bool __kfunc_param_match_suffix(const struct btf *btf,
+				       const struct btf_param *arg,
+				       const char *suffix)
 {
-	int len, sfx_len = sizeof("__sz") - 1;
-	const struct btf_type *t;
+	int suffix_len = strlen(suffix), len;
 	const char *param_name;
 
-	t = btf_type_skip_modifiers(btf, arg->type, NULL);
-	if (!btf_type_is_scalar(t) || reg->type != SCALAR_VALUE)
-		return false;
-
 	/* In the future, this can be ported to use BTF tagging */
 	param_name = btf_name_by_offset(btf, arg->name_off);
 	if (str_is_empty(param_name))
 		return false;
 	len = strlen(param_name);
-	if (len < sfx_len)
+	if (len < suffix_len)
 		return false;
-	param_name += len - sfx_len;
-	if (strncmp(param_name, "__sz", sfx_len))
+	param_name += len - suffix_len;
+	return !strncmp(param_name, suffix, suffix_len);
+}
+
+static bool is_kfunc_arg_mem_size(const struct btf *btf,
+				  const struct btf_param *arg,
+				  const struct bpf_reg_state *reg)
+{
+	const struct btf_type *t;
+
+	t = btf_type_skip_modifiers(btf, arg->type, NULL);
+	if (!btf_type_is_scalar(t) || reg->type != SCALAR_VALUE)
 		return false;
 
-	return true;
+	return __kfunc_param_match_suffix(btf, arg, "__sz");
+}
+
+static bool is_kfunc_arg_sfx_constant(const struct btf *btf, const struct btf_param *arg)
+{
+	return __kfunc_param_match_suffix(btf, arg, "__k");
 }
 
 static bool is_kfunc_arg_ret_buf_size(const struct btf *btf,
@@ -8023,7 +8037,24 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_
 				verbose(env, "R%d is not a scalar\n", regno);
 				return -EINVAL;
 			}
-			if (is_kfunc_arg_ret_buf_size(btf, &args[i], reg, "rdonly_buf_size")) {
+			if (is_kfunc_arg_sfx_constant(meta->btf, &args[i])) {
+				/* kfunc is already bpf_capable() only, no need
+				 * to check it here.
+				 */
+				if (meta->arg_constant.found) {
+					verbose(env, "verifier internal error: only one constant argument permitted\n");
+					return -EFAULT;
+				}
+				if (!tnum_is_const(reg->var_off)) {
+					verbose(env, "R%d must be a known constant\n", regno);
+					return -EINVAL;
+				}
+				ret = mark_chain_precision(env, regno);
+				if (ret < 0)
+					return ret;
+				meta->arg_constant.found = true;
+				meta->arg_constant.value = reg->var_off.value;
+			} else if (is_kfunc_arg_ret_buf_size(btf, &args[i], reg, "rdonly_buf_size")) {
 					meta->r0_rdonly = true;
 					is_ret_buf_sz = true;
 			} else if (is_kfunc_arg_ret_buf_size(btf, &args[i], reg, "rdwr_buf_size")) {
-- 
2.38.1

[PATCH bpf-next v4 18/24] bpf: Teach verifier about non-size constant arguments

[Kumar Kartikeya Dwivedi]

Currently, the verifier has support for various arguments that either
describe the size of the memory being passed in to a helper, or describe
the size of the memory being returned. When a constant is passed in like
this, it is assumed for the purposes of precision tracking that if the
value in the already explored safe state is within the value in current
state, it would fine to prune the search.

While this holds well for size arguments, arguments where each value may
denote a distinct meaning and needs to be verified separately needs more
work. Search can only be pruned if both are constant values and both are
equal. In all other cases, it would be incorrect to treat those two
precise registers as equivalent if the new value satisfies the old one
(i.e. old <= cur).

Hence, make the register precision marker tri-state. There are now three
values that reg->precise takes: NOT_PRECISE, PRECISE, EXACT.

Both PRECISE and EXACT are 'true' values. EXACT affects how regsafe
decides whether both registers are equivalent for the purposes of
verifier state equivalence. When it sees that one register has
reg->precise == EXACT, unless both are absolute, it will return false.
When both are, it returns true only when both are const and both have
the same value. Otherwise, for PRECISE case it falls back to the default
check that is present now (i.e. thinking that we're talking about
sizes).

This is required as a future patch introduces a BPF memory allocator
interface, where we take the program BTF's type ID as an argument. Each
distinct type ID may result in the returned pointer obtaining a
different size, hence precision tracking is needed, and pruning cannot
just happen when the old value is within the current value. It must only
happen when the type ID is equal. The type ID will always correspond to
prog->aux->btf hence actual type match is not required.

Finally, change mark_chain_precision precision argument to EXACT for
kfuncs constant non-size scalar arguments (tagged with __k suffix).

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 include/linux/bpf_verifier.h |  10 ++--
 kernel/bpf/verifier.c        | 101 ++++++++++++++++++++++-------------
 2 files changed, 70 insertions(+), 41 deletions(-)

diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index 8dad74432677..2614892ca063 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -43,6 +43,12 @@ enum bpf_reg_liveness {
 	REG_LIVE_DONE = 0x8, /* liveness won't be updating this register anymore */
 };
 
+enum bpf_reg_precise {
+	NOT_PRECISE,
+	PRECISE,
+	EXACT,
+};
+
 struct bpf_reg_state {
 	/* Ordering of fields matters.  See states_equal() */
 	enum bpf_reg_type type;
@@ -180,7 +186,7 @@ struct bpf_reg_state {
 	s32 subreg_def;
 	enum bpf_reg_liveness live;
 	/* if (!precise && SCALAR_VALUE) min/max/tnum don't affect safety */
-	bool precise;
+	enum bpf_reg_precise precise;
 };
 
 enum bpf_stack_slot_type {
@@ -624,8 +630,6 @@ int bpf_check_attach_target(struct bpf_verifier_log *log,
 			    struct bpf_attach_target_info *tgt_info);
 void bpf_free_kfunc_btf_tab(struct bpf_kfunc_btf_tab *tab);
 
-int mark_chain_precision(struct bpf_verifier_env *env, int regno);
-
 #define BPF_BASE_TYPE_MASK	GENMASK(BPF_BASE_TYPE_BITS - 1, 0)
 
 /* extract base type from bpf_{arg, return, reg}_type. */
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index b22ad48bbecd..abb2df954f3f 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -855,7 +855,7 @@ static void print_verifier_state(struct bpf_verifier_env *env,
 		print_liveness(env, reg->live);
 		verbose(env, "=");
 		if (t == SCALAR_VALUE && reg->precise)
-			verbose(env, "P");
+			verbose(env, reg->precise == EXACT ? "E" : "P");
 		if ((t == SCALAR_VALUE || t == PTR_TO_STACK) &&
 		    tnum_is_const(reg->var_off)) {
 			/* reg->off should be 0 for SCALAR_VALUE */
@@ -952,7 +952,7 @@ static void print_verifier_state(struct bpf_verifier_env *env,
 			t = reg->type;
 			verbose(env, "=%s", t == SCALAR_VALUE ? "" : reg_type_str(env, t));
 			if (t == SCALAR_VALUE && reg->precise)
-				verbose(env, "P");
+				verbose(env, reg->precise == EXACT ? "E" : "P");
 			if (t == SCALAR_VALUE && tnum_is_const(reg->var_off))
 				verbose(env, "%lld", reg->var_off.value + reg->off);
 		} else {
@@ -1686,7 +1686,17 @@ static void __mark_reg_unknown(const struct bpf_verifier_env *env,
 	reg->type = SCALAR_VALUE;
 	reg->var_off = tnum_unknown;
 	reg->frameno = 0;
-	reg->precise = env->subprog_cnt > 1 || !env->bpf_capable;
+	/* Helpers requiring EXACT for constant arguments cannot be called from
+	 * programs without CAP_BPF. This is because we don't propagate
+	 * precision markers for when CAP_BPF is missing. If we allowed calling
+	 * such heleprs in those programs, the default would have to be EXACT
+	 * for them, which would be too aggresive.
+	 *
+	 * We still propagate EXACT when subprog_cnt > 1, hence those cases
+	 * would still override the default PRECISE value when we propagate the
+	 * precision markers.
+	 */
+	reg->precise = (env->subprog_cnt > 1 || !env->bpf_capable) ? PRECISE : NOT_PRECISE;
 	__mark_reg_unbounded(reg);
 }
 
@@ -2736,7 +2746,8 @@ static int backtrack_insn(struct bpf_verifier_env *env, int idx,
  * For now backtracking falls back into conservative marking.
  */
 static void mark_all_scalars_precise(struct bpf_verifier_env *env,
-				     struct bpf_verifier_state *st)
+				     struct bpf_verifier_state *st,
+				     enum bpf_reg_precise precise)
 {
 	struct bpf_func_state *func;
 	struct bpf_reg_state *reg;
@@ -2752,7 +2763,7 @@ static void mark_all_scalars_precise(struct bpf_verifier_env *env,
 				reg = &func->regs[j];
 				if (reg->type != SCALAR_VALUE)
 					continue;
-				reg->precise = true;
+				reg->precise = precise;
 			}
 			for (j = 0; j < func->allocated_stack / BPF_REG_SIZE; j++) {
 				if (!is_spilled_reg(&func->stack[j]))
@@ -2760,13 +2771,13 @@ static void mark_all_scalars_precise(struct bpf_verifier_env *env,
 				reg = &func->stack[j].spilled_ptr;
 				if (reg->type != SCALAR_VALUE)
 					continue;
-				reg->precise = true;
+				reg->precise = precise;
 			}
 		}
 }
 
 static int __mark_chain_precision(struct bpf_verifier_env *env, int regno,
-				  int spi)
+				  int spi, enum bpf_reg_precise precise)
 {
 	struct bpf_verifier_state *st = env->cur_state;
 	int first_idx = st->first_insn_idx;
@@ -2793,7 +2804,7 @@ static int __mark_chain_precision(struct bpf_verifier_env *env, int regno,
 			new_marks = true;
 		else
 			reg_mask = 0;
-		reg->precise = true;
+		reg->precise = precise;
 	}
 
 	while (spi >= 0) {
@@ -2810,7 +2821,7 @@ static int __mark_chain_precision(struct bpf_verifier_env *env, int regno,
 			new_marks = true;
 		else
 			stack_mask = 0;
-		reg->precise = true;
+		reg->precise = precise;
 		break;
 	}
 
@@ -2832,7 +2843,7 @@ static int __mark_chain_precision(struct bpf_verifier_env *env, int regno,
 				err = backtrack_insn(env, i, &reg_mask, &stack_mask);
 			}
 			if (err == -ENOTSUPP) {
-				mark_all_scalars_precise(env, st);
+				mark_all_scalars_precise(env, st, precise);
 				return 0;
 			} else if (err) {
 				return err;
@@ -2873,7 +2884,7 @@ static int __mark_chain_precision(struct bpf_verifier_env *env, int regno,
 			}
 			if (!reg->precise)
 				new_marks = true;
-			reg->precise = true;
+			reg->precise = precise;
 		}
 
 		bitmap_from_u64(mask, stack_mask);
@@ -2892,7 +2903,7 @@ static int __mark_chain_precision(struct bpf_verifier_env *env, int regno,
 				 * fp-8 and it's "unallocated" stack space.
 				 * In such case fallback to conservative.
 				 */
-				mark_all_scalars_precise(env, st);
+				mark_all_scalars_precise(env, st, precise);
 				return 0;
 			}
 
@@ -2907,7 +2918,7 @@ static int __mark_chain_precision(struct bpf_verifier_env *env, int regno,
 			}
 			if (!reg->precise)
 				new_marks = true;
-			reg->precise = true;
+			reg->precise = precise;
 		}
 		if (env->log.level & BPF_LOG_LEVEL2) {
 			verbose(env, "parent %s regs=%x stack=%llx marks:",
@@ -2927,14 +2938,16 @@ static int __mark_chain_precision(struct bpf_verifier_env *env, int regno,
 	return 0;
 }
 
-int mark_chain_precision(struct bpf_verifier_env *env, int regno)
+static int mark_chain_precision(struct bpf_verifier_env *env, int regno,
+				enum bpf_reg_precise precise)
 {
-	return __mark_chain_precision(env, regno, -1);
+	return __mark_chain_precision(env, regno, -1, precise);
 }
 
-static int mark_chain_precision_stack(struct bpf_verifier_env *env, int spi)
+static int mark_chain_precision_stack(struct bpf_verifier_env *env, int spi,
+				      enum bpf_reg_precise precise)
 {
-	return __mark_chain_precision(env, -1, spi);
+	return __mark_chain_precision(env, -1, spi, precise);
 }
 
 static bool is_spillable_regtype(enum bpf_reg_type type)
@@ -3069,7 +3082,7 @@ static int check_stack_write_fixed_off(struct bpf_verifier_env *env,
 			 * Backtrack from here and mark all registers as precise
 			 * that contributed into 'reg' being a constant.
 			 */
-			err = mark_chain_precision(env, value_regno);
+			err = mark_chain_precision(env, value_regno, PRECISE);
 			if (err)
 				return err;
 		}
@@ -3110,7 +3123,7 @@ static int check_stack_write_fixed_off(struct bpf_verifier_env *env,
 		/* when we zero initialize stack slots mark them as such */
 		if (reg && register_is_null(reg)) {
 			/* backtracking doesn't work for STACK_ZERO yet. */
-			err = mark_chain_precision(env, value_regno);
+			err = mark_chain_precision(env, value_regno, PRECISE);
 			if (err)
 				return err;
 			type = STACK_ZERO;
@@ -3226,7 +3239,7 @@ static int check_stack_write_var_off(struct bpf_verifier_env *env,
 	}
 	if (zero_used) {
 		/* backtracking doesn't work for STACK_ZERO yet. */
-		err = mark_chain_precision(env, value_regno);
+		err = mark_chain_precision(env, value_regno, PRECISE);
 		if (err)
 			return err;
 	}
@@ -3275,7 +3288,7 @@ static void mark_reg_stack_read(struct bpf_verifier_env *env,
 		 * backtracking. Any register that contributed
 		 * to const 0 was marked precise before spill.
 		 */
-		state->regs[dst_regno].precise = true;
+		state->regs[dst_regno].precise = PRECISE;
 	} else {
 		/* have read misc data from the stack */
 		mark_reg_unknown(env, state->regs, dst_regno);
@@ -5342,7 +5355,7 @@ static int check_mem_size_reg(struct bpf_verifier_env *env,
 				      reg->umax_value,
 				      zero_size_allowed, meta);
 	if (!err)
-		err = mark_chain_precision(env, regno);
+		err = mark_chain_precision(env, regno, PRECISE);
 	return err;
 }
 
@@ -6150,7 +6163,7 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
 			return -EACCES;
 		}
 		meta->mem_size = reg->var_off.value;
-		err = mark_chain_precision(env, regno);
+		err = mark_chain_precision(env, regno, PRECISE);
 		if (err)
 			return err;
 		break;
@@ -7128,7 +7141,7 @@ record_func_key(struct bpf_verifier_env *env, struct bpf_call_arg_meta *meta,
 		return 0;
 	}
 
-	err = mark_chain_precision(env, BPF_REG_3);
+	err = mark_chain_precision(env, BPF_REG_3, PRECISE);
 	if (err)
 		return err;
 	if (bpf_map_key_unseen(aux))
@@ -7228,7 +7241,7 @@ static bool loop_flag_is_zero(struct bpf_verifier_env *env)
 	bool reg_is_null = register_is_null(reg);
 
 	if (reg_is_null)
-		mark_chain_precision(env, BPF_REG_4);
+		mark_chain_precision(env, BPF_REG_4, PRECISE);
 
 	return reg_is_null;
 }
@@ -8049,7 +8062,7 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_
 					verbose(env, "R%d must be a known constant\n", regno);
 					return -EINVAL;
 				}
-				ret = mark_chain_precision(env, regno);
+				ret = mark_chain_precision(env, regno, EXACT);
 				if (ret < 0)
 					return ret;
 				meta->arg_constant.found = true;
@@ -8073,7 +8086,7 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_
 				}
 
 				meta->r0_size = reg->var_off.value;
-				ret = mark_chain_precision(env, regno);
+				ret = mark_chain_precision(env, regno, PRECISE);
 				if (ret)
 					return ret;
 			}
@@ -9752,7 +9765,7 @@ static int adjust_reg_min_max_vals(struct bpf_verifier_env *env,
 				 * This is legal, but we have to reverse our
 				 * src/dest handling in computing the range
 				 */
-				err = mark_chain_precision(env, insn->dst_reg);
+				err = mark_chain_precision(env, insn->dst_reg, PRECISE);
 				if (err)
 					return err;
 				return adjust_ptr_min_max_vals(env, insn,
@@ -9760,7 +9773,7 @@ static int adjust_reg_min_max_vals(struct bpf_verifier_env *env,
 			}
 		} else if (ptr_reg) {
 			/* pointer += scalar */
-			err = mark_chain_precision(env, insn->src_reg);
+			err = mark_chain_precision(env, insn->src_reg, PRECISE);
 			if (err)
 				return err;
 			return adjust_ptr_min_max_vals(env, insn,
@@ -10756,10 +10769,10 @@ static int check_cond_jmp_op(struct bpf_verifier_env *env,
 		 * above is_branch_taken() special cased the 0 comparison.
 		 */
 		if (!__is_pointer_value(false, dst_reg))
-			err = mark_chain_precision(env, insn->dst_reg);
+			err = mark_chain_precision(env, insn->dst_reg, PRECISE);
 		if (BPF_SRC(insn->code) == BPF_X && !err &&
 		    !__is_pointer_value(false, src_reg))
-			err = mark_chain_precision(env, insn->src_reg);
+			err = mark_chain_precision(env, insn->src_reg, PRECISE);
 		if (err)
 			return err;
 	}
@@ -12080,9 +12093,19 @@ static bool regsafe(struct bpf_verifier_env *env, struct bpf_reg_state *rold,
 		if (rcur->type == SCALAR_VALUE) {
 			if (!rold->precise && !rcur->precise)
 				return true;
-			/* new val must satisfy old val knowledge */
-			return range_within(rold, rcur) &&
-			       tnum_in(rold->var_off, rcur->var_off);
+			/* We can only determine safety when type of precision
+			 * needed is same. For EXACT, we need values to match
+			 * exactly, so simply return false as the memcmp above
+			 * failed already, otherwise current being within the
+			 * old value suffices.
+			 */
+			if (rold->precise == EXACT || rcur->precise == EXACT) {
+				return false;
+			} else {
+				/* new val must satisfy old val knowledge */
+				return range_within(rold, rcur) &&
+				       tnum_in(rold->var_off, rcur->var_off);
+			}
 		} else {
 			/* We're trying to use a pointer in place of a scalar.
 			 * Even if the scalar was unbounded, this could lead to
@@ -12411,8 +12434,9 @@ static int propagate_precision(struct bpf_verifier_env *env,
 		    !state_reg->precise)
 			continue;
 		if (env->log.level & BPF_LOG_LEVEL2)
-			verbose(env, "propagating r%d\n", i);
-		err = mark_chain_precision(env, i);
+			verbose(env, "propagating %sr%d\n",
+				state_reg->precise == EXACT ? "exact " : "", i);
+		err = mark_chain_precision(env, i, state_reg->precise);
 		if (err < 0)
 			return err;
 	}
@@ -12425,9 +12449,10 @@ static int propagate_precision(struct bpf_verifier_env *env,
 		    !state_reg->precise)
 			continue;
 		if (env->log.level & BPF_LOG_LEVEL2)
-			verbose(env, "propagating fp%d\n",
+			verbose(env, "propagating %sfp%d\n",
+				state_reg->precise == EXACT ? "exact " : "",
 				(-i - 1) * BPF_REG_SIZE);
-		err = mark_chain_precision_stack(env, i);
+		err = mark_chain_precision_stack(env, i, state_reg->precise);
 		if (err < 0)
 			return err;
 	}
-- 
2.38.1

[PATCH bpf-next v4 19/24] bpf: Introduce bpf_obj_new

[Kumar Kartikeya Dwivedi]

Introduce type safe memory allocator bpf_obj_new for BPF programs. The
kernel side kfunc is named bpf_obj_new_impl, as passing hidden arguments
to kfuncs still requires having them in prototype, unlike BPF helpers
which always take 5 arguments and have them checked using bpf_func_proto
in verifier, ignoring unset argument types.

Introduce __ign suffix to ignore a specific kfunc argument during type
checks, then use this to introduce support for passing type metadata to
the bpf_obj_new_impl kfunc.

The user passes BTF ID of the type it wants to allocates in program BTF,
the verifier then rewrites the first argument as the size of this type,
after performing some sanity checks (to ensure it exists and it is a
struct type).

The second argument is also fixed up and passed by the verifier. This is
the btf_struct_meta for the type being allocated. It would be needed
mostly for the offset array which is required for zero initializing
special fields while leaving the rest of storage in unitialized state.

It would also be needed in the next patch to perform proper destruction
of the object's special fields.

A convenience macro is included in the bpf_experimental.h header to hide
over the ugly details of the implementation, leading to user code
looking similar to a language level extension which allocates and
constructs fields of a user type.

struct bar {
	struct bpf_list_node node;
};

struct foo {
	struct bpf_spin_lock lock;
	struct bpf_list_head head __contains(bar, node);
};

void prog(void) {
	struct foo *f;

	f = bpf_obj_new(typeof(*f));
	if (!f)
		return;
	...
}

A key piece of this story is still missing, i.e. the free function,
which will come in the next patch.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 include/linux/bpf.h                           |  21 ++--
 include/linux/bpf_verifier.h                  |   2 +
 kernel/bpf/core.c                             |  16 +++
 kernel/bpf/helpers.c                          |  41 +++++--
 kernel/bpf/verifier.c                         | 107 ++++++++++++++++--
 .../testing/selftests/bpf/bpf_experimental.h  |  20 ++++
 6 files changed, 184 insertions(+), 23 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/bpf_experimental.h

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 5d9a786e0cef..efce66b2e220 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -54,6 +54,8 @@ struct cgroup;
 extern struct idr btf_idr;
 extern spinlock_t btf_idr_lock;
 extern struct kobject *btf_kobj;
+extern struct bpf_mem_alloc bpf_global_ma;
+extern bool bpf_global_ma_set;
 
 typedef u64 (*bpf_callback_t)(u64, u64, u64, u64, u64);
 typedef int (*bpf_iter_init_seq_priv_t)(void *private_data,
@@ -334,16 +336,19 @@ static inline bool btf_record_has_field(const struct btf_record *rec, enum btf_f
 	return rec->field_mask & type;
 }
 
-static inline void check_and_init_map_value(struct bpf_map *map, void *dst)
+static inline void bpf_obj_init(const struct btf_field_offs *foffs, void *obj)
 {
-	if (!IS_ERR_OR_NULL(map->record)) {
-		struct btf_field *fields = map->record->fields;
-		u32 cnt = map->record->cnt;
-		int i;
+	int i;
 
-		for (i = 0; i < cnt; i++)
-			memset(dst + fields[i].offset, 0, btf_field_type_size(fields[i].type));
-	}
+	if (!foffs)
+		return;
+	for (i = 0; i < foffs->cnt; i++)
+		memset(obj + foffs->field_off[i], 0, foffs->field_sz[i]);
+}
+
+static inline void check_and_init_map_value(struct bpf_map *map, void *dst)
+{
+	bpf_obj_init(map->field_offs, dst);
 }
 
 /* memcpy that is used with 8-byte aligned pointers, power-of-8 size and
diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index 2614892ca063..1e9c782e0974 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -426,6 +426,8 @@ struct bpf_insn_aux_data {
 		 */
 		struct bpf_loop_inline_state loop_inline_state;
 	};
+	u64 obj_new_size; /* remember the size of type passed to bpf_obj_new to rewrite R1 */
+	struct btf_struct_meta *kptr_struct_meta;
 	u64 map_key_state; /* constant (32 bit) key tracking for maps */
 	int ctx_field_size; /* the ctx field size for load insn, maybe 0 */
 	u32 seen; /* this insn was processed by the verifier at env->pass_cnt */
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 9c16338bcbe8..2e57fc839a5c 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -34,6 +34,7 @@
 #include <linux/log2.h>
 #include <linux/bpf_verifier.h>
 #include <linux/nodemask.h>
+#include <linux/bpf_mem_alloc.h>
 
 #include <asm/barrier.h>
 #include <asm/unaligned.h>
@@ -60,6 +61,9 @@
 #define CTX	regs[BPF_REG_CTX]
 #define IMM	insn->imm
 
+struct bpf_mem_alloc bpf_global_ma;
+bool bpf_global_ma_set;
+
 /* No hurry in this branch
  *
  * Exported for the bpf jit load helper.
@@ -2746,6 +2750,18 @@ int __weak bpf_arch_text_invalidate(void *dst, size_t len)
 	return -ENOTSUPP;
 }
 
+#ifdef CONFIG_BPF_SYSCALL
+static int __init bpf_global_ma_init(void)
+{
+	int ret;
+
+	ret = bpf_mem_alloc_init(&bpf_global_ma, 0, false);
+	bpf_global_ma_set = !ret;
+	return ret;
+}
+late_initcall(bpf_global_ma_init);
+#endif
+
 DEFINE_STATIC_KEY_FALSE(bpf_stats_enabled_key);
 EXPORT_SYMBOL(bpf_stats_enabled_key);
 
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 207f622ec70d..e10245e054e4 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -19,6 +19,7 @@
 #include <linux/proc_ns.h>
 #include <linux/security.h>
 #include <linux/btf_ids.h>
+#include <linux/bpf_mem_alloc.h>
 
 #include "../../lib/kstrtox.h"
 
@@ -1731,8 +1732,11 @@ void bpf_list_head_free(const struct btf_field *field, void *list_head,
 
 		obj -= field->list_head.node_offset;
 		head = head->next;
-		/* TODO: Rework later */
-		kfree(obj);
+		/* The contained type can also have resources, including a
+		 * bpf_list_head which needs to be freed.
+		 */
+		bpf_obj_free_fields(field->list_head.value_rec, obj);
+		bpf_mem_free(&bpf_global_ma, obj);
 	}
 unlock:
 	INIT_LIST_HEAD(head);
@@ -1740,20 +1744,43 @@ void bpf_list_head_free(const struct btf_field *field, void *list_head,
 	local_irq_restore(flags);
 }
 
-BTF_SET8_START(tracing_btf_ids)
+__diag_push();
+__diag_ignore_all("-Wmissing-prototypes",
+		  "Global functions as their definitions will be in vmlinux BTF");
+
+void *bpf_obj_new_impl(u64 local_type_id__k, void *meta__ign)
+{
+	struct btf_struct_meta *meta = meta__ign;
+	u64 size = local_type_id__k;
+	void *p;
+
+	if (unlikely(!bpf_global_ma_set))
+		return NULL;
+	p = bpf_mem_alloc(&bpf_global_ma, size);
+	if (!p)
+		return NULL;
+	if (meta)
+		bpf_obj_init(meta->field_offs, p);
+	return p;
+}
+
+__diag_pop();
+
+BTF_SET8_START(generic_btf_ids)
 #ifdef CONFIG_KEXEC_CORE
 BTF_ID_FLAGS(func, crash_kexec, KF_DESTRUCTIVE)
 #endif
-BTF_SET8_END(tracing_btf_ids)
+BTF_ID_FLAGS(func, bpf_obj_new_impl, KF_ACQUIRE | KF_RET_NULL)
+BTF_SET8_END(generic_btf_ids)
 
-static const struct btf_kfunc_id_set tracing_kfunc_set = {
+static const struct btf_kfunc_id_set generic_kfunc_set = {
 	.owner = THIS_MODULE,
-	.set   = &tracing_btf_ids,
+	.set   = &generic_btf_ids,
 };
 
 static int __init kfunc_init(void)
 {
-	return register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, &tracing_kfunc_set);
+	return register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, &generic_kfunc_set);
 }
 
 late_initcall(kfunc_init);
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index abb2df954f3f..c573282338e1 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -7777,6 +7777,11 @@ static bool is_kfunc_arg_sfx_constant(const struct btf *btf, const struct btf_pa
 	return __kfunc_param_match_suffix(btf, arg, "__k");
 }
 
+static bool is_kfunc_arg_sfx_ignore(const struct btf *btf, const struct btf_param *arg)
+{
+	return __kfunc_param_match_suffix(btf, arg, "__ign");
+}
+
 static bool is_kfunc_arg_ret_buf_size(const struct btf *btf,
 				      const struct btf_param *arg,
 				      const struct bpf_reg_state *reg,
@@ -8045,6 +8050,10 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_
 		int kf_arg_type;
 
 		t = btf_type_skip_modifiers(btf, args[i].type, NULL);
+
+		if (is_kfunc_arg_sfx_ignore(btf, &args[i]))
+			continue;
+
 		if (btf_type_is_scalar(t)) {
 			if (reg->type != SCALAR_VALUE) {
 				verbose(env, "R%d is not a scalar\n", regno);
@@ -8222,6 +8231,17 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_
 	return 0;
 }
 
+enum special_kfunc_type {
+	KF_bpf_obj_new_impl,
+};
+
+BTF_SET_START(special_kfunc_set)
+BTF_ID(func, bpf_obj_new_impl)
+BTF_SET_END(special_kfunc_set)
+
+BTF_ID_LIST(special_kfunc_list)
+BTF_ID(func, bpf_obj_new_impl)
+
 static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 			    int *insn_idx_p)
 {
@@ -8296,17 +8316,64 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 	t = btf_type_skip_modifiers(desc_btf, func_proto->type, NULL);
 
 	if (is_kfunc_acquire(&meta) && !btf_type_is_struct_ptr(meta.btf, t)) {
-		verbose(env, "acquire kernel function does not return PTR_TO_BTF_ID\n");
-		return -EINVAL;
+		/* Only exception is bpf_obj_new_impl */
+		if (meta.btf != btf_vmlinux || meta.func_id != special_kfunc_list[KF_bpf_obj_new_impl]) {
+			verbose(env, "acquire kernel function does not return PTR_TO_BTF_ID\n");
+			return -EINVAL;
+		}
 	}
 
 	if (btf_type_is_scalar(t)) {
 		mark_reg_unknown(env, regs, BPF_REG_0);
 		mark_btf_func_reg_size(env, BPF_REG_0, t->size);
 	} else if (btf_type_is_ptr(t)) {
-		ptr_type = btf_type_skip_modifiers(desc_btf, t->type,
-						   &ptr_type_id);
-		if (!btf_type_is_struct(ptr_type)) {
+		ptr_type = btf_type_skip_modifiers(desc_btf, t->type, &ptr_type_id);
+
+		if (meta.btf == btf_vmlinux && btf_id_set_contains(&special_kfunc_set, meta.func_id)) {
+			if (!btf_type_is_void(ptr_type)) {
+				verbose(env, "kernel function %s must have void * return type\n",
+					meta.func_name);
+				return -EINVAL;
+			}
+			if (meta.func_id == special_kfunc_list[KF_bpf_obj_new_impl]) {
+				const struct btf_type *ret_t;
+				struct btf *ret_btf;
+				u32 ret_btf_id;
+
+				if (((u64)(u32)meta.arg_constant.value) != meta.arg_constant.value) {
+					verbose(env, "local type ID argument must be in range [0, U32_MAX]\n");
+					return -EINVAL;
+				}
+
+				ret_btf = env->prog->aux->btf;
+				ret_btf_id = meta.arg_constant.value;
+
+				/* This may be NULL due to user not supplying a BTF */
+				if (!ret_btf) {
+					verbose(env, "bpf_obj_new requires prog BTF\n");
+					return -EINVAL;
+				}
+
+				ret_t = btf_type_by_id(ret_btf, ret_btf_id);
+				if (!ret_t || !__btf_type_is_struct(ret_t)) {
+					verbose(env, "bpf_obj_new type ID argument must be of a struct\n");
+					return -EINVAL;
+				}
+
+				mark_reg_known_zero(env, regs, BPF_REG_0);
+				regs[BPF_REG_0].type = PTR_TO_BTF_ID | MEM_TYPE_LOCAL;
+				regs[BPF_REG_0].btf = ret_btf;
+				regs[BPF_REG_0].btf_id = ret_btf_id;
+
+				env->insn_aux_data[insn_idx].obj_new_size = ret_t->size;
+				env->insn_aux_data[insn_idx].kptr_struct_meta =
+					btf_find_struct_meta(ret_btf, ret_btf_id);
+			} else {
+				verbose(env, "kernel function %s unhandled dynamic return type\n",
+					meta.func_name);
+				return -EFAULT;
+			}
+		} else if (!__btf_type_is_struct(ptr_type)) {
 			if (!meta.r0_size) {
 				ptr_type_name = btf_name_by_offset(desc_btf,
 								   ptr_type->name_off);
@@ -8334,6 +8401,7 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 			regs[BPF_REG_0].type = PTR_TO_BTF_ID;
 			regs[BPF_REG_0].btf_id = ptr_type_id;
 		}
+
 		if (is_kfunc_ret_null(&meta)) {
 			regs[BPF_REG_0].type |= PTR_MAYBE_NULL;
 			/* For mark_ptr_or_null_reg, see 93c230e3f5bd6 */
@@ -14472,8 +14540,8 @@ static int fixup_call_args(struct bpf_verifier_env *env)
 	return err;
 }
 
-static int fixup_kfunc_call(struct bpf_verifier_env *env,
-			    struct bpf_insn *insn)
+static int fixup_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
+			    struct bpf_insn *insn_buf, int insn_idx, int *cnt)
 {
 	const struct bpf_kfunc_desc *desc;
 
@@ -14492,8 +14560,21 @@ static int fixup_kfunc_call(struct bpf_verifier_env *env,
 		return -EFAULT;
 	}
 
+	*cnt = 0;
 	insn->imm = desc->imm;
+	if (insn->off)
+		return 0;
+	if (desc->func_id == special_kfunc_list[KF_bpf_obj_new_impl]) {
+		struct btf_struct_meta *kptr_struct_meta = env->insn_aux_data[insn_idx].kptr_struct_meta;
+		struct bpf_insn addr[2] = { BPF_LD_IMM64(BPF_REG_2, (long)kptr_struct_meta) };
+		u64 obj_new_size = env->insn_aux_data[insn_idx].obj_new_size;
 
+		insn_buf[0] = BPF_MOV64_IMM(BPF_REG_1, obj_new_size);
+		insn_buf[1] = addr[0];
+		insn_buf[2] = addr[1];
+		insn_buf[3] = *insn;
+		*cnt = 4;
+	}
 	return 0;
 }
 
@@ -14635,9 +14716,19 @@ static int do_misc_fixups(struct bpf_verifier_env *env)
 		if (insn->src_reg == BPF_PSEUDO_CALL)
 			continue;
 		if (insn->src_reg == BPF_PSEUDO_KFUNC_CALL) {
-			ret = fixup_kfunc_call(env, insn);
+			ret = fixup_kfunc_call(env, insn, insn_buf, i + delta, &cnt);
 			if (ret)
 				return ret;
+			if (cnt == 0)
+				continue;
+
+			new_prog = bpf_patch_insn_data(env, i + delta, insn_buf, cnt);
+			if (!new_prog)
+				return -ENOMEM;
+
+			delta	 += cnt - 1;
+			env->prog = prog = new_prog;
+			insn	  = new_prog->insnsi + i + delta;
 			continue;
 		}
 
diff --git a/tools/testing/selftests/bpf/bpf_experimental.h b/tools/testing/selftests/bpf/bpf_experimental.h
new file mode 100644
index 000000000000..1d3451084a68
--- /dev/null
+++ b/tools/testing/selftests/bpf/bpf_experimental.h
@@ -0,0 +1,20 @@
+#include <vmlinux.h>
+#include <bpf/bpf_tracing.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_core_read.h>
+
+/* Description
+ *	Allocates a local kptr of type represented by 'local_type_id' in program
+ *	BTF. User may use the bpf_core_type_id_local macro to pass the type ID
+ *	of a struct in program BTF.
+ *
+ *	The 'local_type_id' parameter must be a known constant.
+ *	The 'meta' parameter is a hidden argument that is ignored.
+ * Returns
+ *	A local kptr corresponding to passed in 'local_type_id', or NULL on
+ *	failure.
+ */
+extern void *bpf_obj_new_impl(__u64 local_type_id, void *meta) __ksym;
+
+/* Convenience macro to wrap over bpf_obj_new_impl */
+#define bpf_obj_new(type) bpf_obj_new_impl(bpf_core_type_id_local(type), NULL)
-- 
2.38.1

[PATCH bpf-next v4 20/24] bpf: Introduce bpf_obj_drop

[Kumar Kartikeya Dwivedi]

Introduce bpf_obj_drop, which is the kfunc used to free local kptrs
allocated using bpf_obj_new. Similar to bpf_obj_new, it implicitly
destructs the fields part of the local kptr automatically without user
intervention.

Just like the previous patch, btf_struct_meta that is needed to free up
the special fields is passed as a hidden argument to the kfunc.

For the user, a convenience macro hides over the kernel side kfunc which
is named bpf_obj_drop_impl.

Continuing the previous example:

void prog(void) {
	struct foo *f;

	f = bpf_obj_new(typeof(*f));
	if (!f)
		return;
	bpf_obj_drop(f);
}

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 kernel/bpf/helpers.c                          | 11 ++++
 kernel/bpf/verifier.c                         | 66 +++++++++++++++----
 .../testing/selftests/bpf/bpf_experimental.h  | 13 ++++
 3 files changed, 79 insertions(+), 11 deletions(-)

diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index e10245e054e4..a30f6573e805 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -1764,6 +1764,16 @@ void *bpf_obj_new_impl(u64 local_type_id__k, void *meta__ign)
 	return p;
 }
 
+void bpf_obj_drop_impl(void *p__lkptr, void *meta__ign)
+{
+	struct btf_struct_meta *meta = meta__ign;
+	void *p = p__lkptr;
+
+	if (meta)
+		bpf_obj_free_fields(meta->record, p);
+	bpf_mem_free(&bpf_global_ma, p);
+}
+
 __diag_pop();
 
 BTF_SET8_START(generic_btf_ids)
@@ -1771,6 +1781,7 @@ BTF_SET8_START(generic_btf_ids)
 BTF_ID_FLAGS(func, crash_kexec, KF_DESTRUCTIVE)
 #endif
 BTF_ID_FLAGS(func, bpf_obj_new_impl, KF_ACQUIRE | KF_RET_NULL)
+BTF_ID_FLAGS(func, bpf_kptr_drop_impl, KF_RELEASE)
 BTF_SET8_END(generic_btf_ids)
 
 static const struct btf_kfunc_id_set generic_kfunc_set = {
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index c573282338e1..1e72e559ea6b 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -7704,6 +7704,10 @@ struct bpf_kfunc_call_arg_meta {
 		u64 value;
 		bool found;
 	} arg_constant;
+	struct {
+		struct btf *btf;
+		u32 btf_id;
+	} arg_obj_drop;
 };
 
 static bool is_kfunc_acquire(struct bpf_kfunc_call_arg_meta *meta)
@@ -7782,6 +7786,11 @@ static bool is_kfunc_arg_sfx_ignore(const struct btf *btf, const struct btf_para
 	return __kfunc_param_match_suffix(btf, arg, "__ign");
 }
 
+static bool is_kfunc_arg_local_kptr(const struct btf *btf, const struct btf_param *arg)
+{
+	return __kfunc_param_match_suffix(btf, arg, "__lkptr");
+}
+
 static bool is_kfunc_arg_ret_buf_size(const struct btf *btf,
 				      const struct btf_param *arg,
 				      const struct bpf_reg_state *reg,
@@ -7882,6 +7891,7 @@ static u32 *reg2btf_ids[__BPF_REG_TYPE_MAX] = {
 
 enum kfunc_ptr_arg_type {
 	KF_ARG_PTR_TO_CTX,
+	KF_ARG_PTR_TO_LOCAL_BTF_ID,  /* Local kptr */
 	KF_ARG_PTR_TO_BTF_ID,	     /* Also covers reg2btf_ids conversions */
 	KF_ARG_PTR_TO_KPTR_STRONG,   /* PTR_TO_KPTR but type specific */
 	KF_ARG_PTR_TO_DYNPTR,
@@ -7889,6 +7899,20 @@ enum kfunc_ptr_arg_type {
 	KF_ARG_PTR_TO_MEM_SIZE,	     /* Size derived from next argument, skip it */
 };
 
+enum special_kfunc_type {
+	KF_bpf_obj_new_impl,
+	KF_bpf_obj_drop_impl,
+};
+
+BTF_SET_START(special_kfunc_set)
+BTF_ID(func, bpf_obj_new_impl)
+BTF_ID(func, bpf_obj_drop_impl)
+BTF_SET_END(special_kfunc_set)
+
+BTF_ID_LIST(special_kfunc_list)
+BTF_ID(func, bpf_obj_new_impl)
+BTF_ID(func, bpf_obj_drop_impl)
+
 static enum kfunc_ptr_arg_type
 get_kfunc_ptr_arg_type(struct bpf_verifier_env *env,
 		       struct bpf_kfunc_call_arg_meta *meta,
@@ -7909,6 +7933,9 @@ get_kfunc_ptr_arg_type(struct bpf_verifier_env *env,
 	if (btf_get_prog_ctx_type(&env->log, meta->btf, t, resolve_prog_type(env->prog), argno))
 		return KF_ARG_PTR_TO_CTX;
 
+	if (is_kfunc_arg_local_kptr(meta->btf, &args[argno]))
+		return KF_ARG_PTR_TO_LOCAL_BTF_ID;
+
 	if ((base_type(reg->type) == PTR_TO_BTF_ID || reg2btf_ids[base_type(reg->type)])) {
 		if (!btf_type_is_struct(ref_t)) {
 			verbose(env, "kernel function %s args#%d pointer type %s %s is not supported\n",
@@ -8127,6 +8154,7 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_
 			return kf_arg_type;
 
 		switch (kf_arg_type) {
+		case KF_ARG_PTR_TO_LOCAL_BTF_ID:
 		case KF_ARG_PTR_TO_BTF_ID:
 			if (is_kfunc_trusted_args(meta) && !reg->ref_obj_id) {
 				verbose(env, "R%d must be referenced\n", regno);
@@ -8161,6 +8189,21 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_
 				return -EINVAL;
 			}
 			break;
+		case KF_ARG_PTR_TO_LOCAL_BTF_ID:
+			if (reg->type != (PTR_TO_BTF_ID | MEM_TYPE_LOCAL)) {
+				verbose(env, "arg#%d expected point to local kptr\n", i);
+				return -EINVAL;
+			}
+			if (!reg->ref_obj_id) {
+				verbose(env, "local kptr must be referenced\n");
+				return -EINVAL;
+			}
+			if (meta->btf == btf_vmlinux &&
+			    meta->func_id == special_kfunc_list[KF_bpf_obj_drop_impl]) {
+				meta->arg_obj_drop.btf = reg->btf;
+				meta->arg_obj_drop.btf_id = reg->btf_id;
+			}
+			break;
 		case KF_ARG_PTR_TO_BTF_ID:
 			/* Only base_type is checked, further checks are done here */
 			if (reg->type != PTR_TO_BTF_ID &&
@@ -8231,17 +8274,6 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_
 	return 0;
 }
 
-enum special_kfunc_type {
-	KF_bpf_obj_new_impl,
-};
-
-BTF_SET_START(special_kfunc_set)
-BTF_ID(func, bpf_obj_new_impl)
-BTF_SET_END(special_kfunc_set)
-
-BTF_ID_LIST(special_kfunc_list)
-BTF_ID(func, bpf_obj_new_impl)
-
 static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 			    int *insn_idx_p)
 {
@@ -8368,6 +8400,10 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 				env->insn_aux_data[insn_idx].obj_new_size = ret_t->size;
 				env->insn_aux_data[insn_idx].kptr_struct_meta =
 					btf_find_struct_meta(ret_btf, ret_btf_id);
+			} else if (meta.func_id == special_kfunc_list[KF_bpf_obj_drop_impl]) {
+				env->insn_aux_data[insn_idx].kptr_struct_meta =
+					btf_find_struct_meta(meta.arg_obj_drop.btf,
+							     meta.arg_obj_drop.btf_id);
 			} else {
 				verbose(env, "kernel function %s unhandled dynamic return type\n",
 					meta.func_name);
@@ -14574,6 +14610,14 @@ static int fixup_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 		insn_buf[2] = addr[1];
 		insn_buf[3] = *insn;
 		*cnt = 4;
+	} else if (desc->func_id == special_kfunc_list[KF_bpf_obj_drop_impl]) {
+		struct btf_struct_meta *kptr_struct_meta = env->insn_aux_data[insn_idx].kptr_struct_meta;
+		struct bpf_insn addr[2] = { BPF_LD_IMM64(BPF_REG_2, (long)kptr_struct_meta) };
+
+		insn_buf[0] = addr[0];
+		insn_buf[1] = addr[1];
+		insn_buf[2] = *insn;
+		*cnt = 3;
 	}
 	return 0;
 }
diff --git a/tools/testing/selftests/bpf/bpf_experimental.h b/tools/testing/selftests/bpf/bpf_experimental.h
index 1d3451084a68..29a5520a4250 100644
--- a/tools/testing/selftests/bpf/bpf_experimental.h
+++ b/tools/testing/selftests/bpf/bpf_experimental.h
@@ -18,3 +18,16 @@ extern void *bpf_obj_new_impl(__u64 local_type_id, void *meta) __ksym;
 
 /* Convenience macro to wrap over bpf_obj_new_impl */
 #define bpf_obj_new(type) bpf_obj_new_impl(bpf_core_type_id_local(type), NULL)
+
+/* Description
+ *	Free a local kptr. All fields of local kptr that require destruction
+ *	will be destructed before the storage is freed.
+ *
+ *	The 'meta' parameter is a hidden argument that is ignored.
+ * Returns
+ *	Void.
+ */
+extern void bpf_obj_drop_impl(void *kptr, void *meta) __ksym;
+
+/* Convenience macro to wrap over bpf_obj_drop_impl */
+#define bpf_obj_drop(kptr) bpf_obj_drop_impl(kptr, NULL)
-- 
2.38.1

[PATCH bpf-next v4 21/24] bpf: Permit NULL checking pointer with non-zero fixed offset

[Kumar Kartikeya Dwivedi]

Pointer increment on seeing PTR_MAYBE_NULL is already protected against,
hence make an exception for local kptrs while still keeping the warning
for other unintended cases that might creep in.

bpf_list_del{,tail} helpers return a local kptr with incremented offset
pointing to bpf_list_node field. The user is supposed to then obtain the
pointer to the entry using container_of after NULL checking it. The
current restrictions trigger a warning when doing the NULL checking.
Revisiting the reason, it is meant as an assertion which seems to
actually work and catch the bad case.

Hence, under no other circumstances can reg->off be non-zero for a
register that has the PTR_MAYBE_NULL type flag set.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 kernel/bpf/verifier.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 1e72e559ea6b..58e58678382a 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -10622,15 +10622,20 @@ static void mark_ptr_or_null_reg(struct bpf_func_state *state,
 {
 	if (type_may_be_null(reg->type) && reg->id == id &&
 	    !WARN_ON_ONCE(!reg->id)) {
-		if (WARN_ON_ONCE(reg->smin_value || reg->smax_value ||
-				 !tnum_equals_const(reg->var_off, 0) ||
-				 reg->off)) {
+		if (reg->smin_value || reg->smax_value || !tnum_equals_const(reg->var_off, 0) || reg->off) {
 			/* Old offset (both fixed and variable parts) should
 			 * have been known-zero, because we don't allow pointer
 			 * arithmetic on pointers that might be NULL. If we
 			 * see this happening, don't convert the register.
+			 *
+			 * But in some cases, some helpers that return local
+			 * kptrs advance offset for the returned pointer.
+			 * In those cases, it is fine to expect to see reg->off.
 			 */
-			return;
+			if (WARN_ON_ONCE(reg->type != (PTR_TO_BTF_ID | MEM_TYPE_LOCAL | PTR_MAYBE_NULL)))
+				return;
+			if (WARN_ON_ONCE(reg->smin_value || reg->smax_value || !tnum_equals_const(reg->var_off, 0)))
+				return;
 		}
 		if (is_null) {
 			reg->type = SCALAR_VALUE;
-- 
2.38.1

[PATCH bpf-next v4 22/24] bpf: Introduce single ownership BPF linked list API

[Kumar Kartikeya Dwivedi]

Add a linked list API for use in BPF programs, where it expects
protection from the bpf_spin_lock in the same allocation as the
bpf_list_head. Future patches will extend the same infrastructure to
have different flavors with varying protection domains and visibility
(e.g. percpu variant with local_t protection, usable in NMI progs).

The following functions are added to kick things off:

bpf_list_push_front
bpf_list_push_back
bpf_list_pop_front
bpf_list_pop_back

The lock protecting the bpf_list_head needs to be taken for all
operations.

Once a node has been added to the list, it's pointer changes to
PTR_UNTRUSTED. However, it is only released once the lock protecting the
list is unlocked. For such local kptrs with PTR_UNTRUSTED set but an
active ref_obj_id, it is still permitted to read and write to them as
long as the lock is held.

bpf_list_pop_front and bpf_list_pop_back delete the first or last item
of the list respectively, and return pointer to the element at the
list_node offset. The user can then use container_of style macro to get
the actual entry type. The verifier however statically knows the actual
type, so the safety properties are still preserved.

With these additions, programs can now manage their own linked lists and
store their objects in them.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 include/linux/bpf_verifier.h                  |   5 +
 kernel/bpf/helpers.c                          |  50 ++-
 kernel/bpf/verifier.c                         | 377 ++++++++++++++++--
 .../testing/selftests/bpf/bpf_experimental.h  |  28 ++
 4 files changed, 425 insertions(+), 35 deletions(-)

diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index 1e9c782e0974..bde8f9e11132 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -229,6 +229,11 @@ struct bpf_reference_state {
 	 * exiting a callback function.
 	 */
 	int callback_ref;
+	/* Mark the reference state to release the registers sharing the same id
+	 * on bpf_spin_unlock (for nodes that we will lose ownership to but are
+	 * safe to access inside the critical section).
+	 */
+	bool release_on_unlock;
 };
 
 /* state of the program:
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index a30f6573e805..0acd87ed22fc 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -1774,6 +1774,50 @@ void bpf_obj_drop_impl(void *p__lkptr, void *meta__ign)
 	bpf_mem_free(&bpf_global_ma, p);
 }
 
+static void __bpf_list_add(struct bpf_list_node *node, struct bpf_list_head *head, bool tail)
+{
+	struct list_head *n = (void *)node, *h = (void *)head;
+
+	if (unlikely(!h->next))
+		INIT_LIST_HEAD(h);
+	if (unlikely(!n->next))
+		INIT_LIST_HEAD(n);
+	tail ? list_add_tail(n, h) : list_add(n, h);
+}
+
+void bpf_list_push_front(struct bpf_list_head *head, struct bpf_list_node *node)
+{
+	return __bpf_list_add(node, head, false);
+}
+
+void bpf_list_push_back(struct bpf_list_head *head, struct bpf_list_node *node)
+{
+	return __bpf_list_add(node, head, true);
+}
+
+static struct bpf_list_node *__bpf_list_del(struct bpf_list_head *head, bool tail)
+{
+	struct list_head *n, *h = (void *)head;
+
+	if (unlikely(!h->next))
+		INIT_LIST_HEAD(h);
+	if (list_empty(h))
+		return NULL;
+	n = tail ? h->prev : h->next;
+	list_del_init(n);
+	return (struct bpf_list_node *)n;
+}
+
+struct bpf_list_node *bpf_list_pop_front(struct bpf_list_head *head)
+{
+	return __bpf_list_del(head, false);
+}
+
+struct bpf_list_node *bpf_list_pop_back(struct bpf_list_head *head)
+{
+	return __bpf_list_del(head, true);
+}
+
 __diag_pop();
 
 BTF_SET8_START(generic_btf_ids)
@@ -1781,7 +1825,11 @@ BTF_SET8_START(generic_btf_ids)
 BTF_ID_FLAGS(func, crash_kexec, KF_DESTRUCTIVE)
 #endif
 BTF_ID_FLAGS(func, bpf_obj_new_impl, KF_ACQUIRE | KF_RET_NULL)
-BTF_ID_FLAGS(func, bpf_kptr_drop_impl, KF_RELEASE)
+BTF_ID_FLAGS(func, bpf_obj_drop_impl, KF_RELEASE)
+BTF_ID_FLAGS(func, bpf_list_push_front)
+BTF_ID_FLAGS(func, bpf_list_push_back)
+BTF_ID_FLAGS(func, bpf_list_pop_front, KF_ACQUIRE | KF_RET_NULL)
+BTF_ID_FLAGS(func, bpf_list_pop_back, KF_ACQUIRE | KF_RET_NULL)
 BTF_SET8_END(generic_btf_ids)
 
 static const struct btf_kfunc_id_set generic_kfunc_set = {
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 58e58678382a..c3675f858707 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -5495,7 +5495,9 @@ static int process_spin_lock(struct bpf_verifier_env *env, int regno,
 			cur->active_spin_lock_ptr = btf;
 		cur->active_spin_lock_id = reg->id;
 	} else {
+		struct bpf_func_state *fstate = cur_func(env);
 		void *ptr;
+		int i;
 
 		if (map)
 			ptr = map;
@@ -5513,6 +5515,16 @@ static int process_spin_lock(struct bpf_verifier_env *env, int regno,
 		}
 		cur->active_spin_lock_ptr = NULL;
 		cur->active_spin_lock_id = 0;
+
+		for (i = 0; i < fstate->acquired_refs; i++) {
+			/* WARN because this reference state cannot be freed
+			 * before this point, as bpf_spin_lock CS does not
+			 * allow functions that release the local kptr
+			 * immediately.
+			 */
+			if (fstate->refs[i].release_on_unlock)
+				WARN_ON_ONCE(release_reference(env, fstate->refs[i].id));
+		}
 	}
 	return 0;
 }
@@ -7708,6 +7720,9 @@ struct bpf_kfunc_call_arg_meta {
 		struct btf *btf;
 		u32 btf_id;
 	} arg_obj_drop;
+	struct {
+		struct btf_field *field;
+	} arg_list_head;
 };
 
 static bool is_kfunc_acquire(struct bpf_kfunc_call_arg_meta *meta)
@@ -7818,13 +7833,17 @@ static bool is_kfunc_arg_ret_buf_size(const struct btf *btf,
 
 enum {
 	KF_ARG_DYNPTR_ID,
+	KF_ARG_LIST_HEAD_ID,
+	KF_ARG_LIST_NODE_ID,
 };
 
 BTF_ID_LIST(kf_arg_btf_ids)
 BTF_ID(struct, bpf_dynptr_kern)
+BTF_ID(struct, bpf_list_head)
+BTF_ID(struct, bpf_list_node)
 
-static bool is_kfunc_arg_dynptr(const struct btf *btf,
-				const struct btf_param *arg)
+static bool __is_kfunc_ptr_arg_type(const struct btf *btf,
+				    const struct btf_param *arg, int type)
 {
 	const struct btf_type *t;
 	u32 res_id;
@@ -7837,7 +7856,22 @@ static bool is_kfunc_arg_dynptr(const struct btf *btf,
 	t = btf_type_skip_modifiers(btf, t->type, &res_id);
 	if (!t)
 		return false;
-	return btf_types_are_same(btf, res_id, btf_vmlinux, kf_arg_btf_ids[KF_ARG_DYNPTR_ID]);
+	return btf_types_are_same(btf, res_id, btf_vmlinux, kf_arg_btf_ids[type]);
+}
+
+static bool is_kfunc_arg_dynptr(const struct btf *btf, const struct btf_param *arg)
+{
+	return __is_kfunc_ptr_arg_type(btf, arg, KF_ARG_DYNPTR_ID);
+}
+
+static bool is_kfunc_arg_list_head(const struct btf *btf, const struct btf_param *arg)
+{
+	return __is_kfunc_ptr_arg_type(btf, arg, KF_ARG_LIST_HEAD_ID);
+}
+
+static bool is_kfunc_arg_list_node(const struct btf *btf, const struct btf_param *arg)
+{
+	return __is_kfunc_ptr_arg_type(btf, arg, KF_ARG_LIST_NODE_ID);
 }
 
 /* Returns true if struct is composed of scalars, 4 levels of nesting allowed */
@@ -7892,9 +7926,11 @@ static u32 *reg2btf_ids[__BPF_REG_TYPE_MAX] = {
 enum kfunc_ptr_arg_type {
 	KF_ARG_PTR_TO_CTX,
 	KF_ARG_PTR_TO_LOCAL_BTF_ID,  /* Local kptr */
-	KF_ARG_PTR_TO_BTF_ID,	     /* Also covers reg2btf_ids conversions */
 	KF_ARG_PTR_TO_KPTR_STRONG,   /* PTR_TO_KPTR but type specific */
 	KF_ARG_PTR_TO_DYNPTR,
+	KF_ARG_PTR_TO_LIST_HEAD,
+	KF_ARG_PTR_TO_LIST_NODE,
+	KF_ARG_PTR_TO_BTF_ID,	     /* Also covers reg2btf_ids conversions */
 	KF_ARG_PTR_TO_MEM,
 	KF_ARG_PTR_TO_MEM_SIZE,	     /* Size derived from next argument, skip it */
 };
@@ -7902,16 +7938,28 @@ enum kfunc_ptr_arg_type {
 enum special_kfunc_type {
 	KF_bpf_obj_new_impl,
 	KF_bpf_obj_drop_impl,
+	KF_bpf_list_push_front,
+	KF_bpf_list_push_back,
+	KF_bpf_list_pop_front,
+	KF_bpf_list_pop_back,
 };
 
 BTF_SET_START(special_kfunc_set)
 BTF_ID(func, bpf_obj_new_impl)
 BTF_ID(func, bpf_obj_drop_impl)
+BTF_ID(func, bpf_list_push_front)
+BTF_ID(func, bpf_list_push_back)
+BTF_ID(func, bpf_list_pop_front)
+BTF_ID(func, bpf_list_pop_back)
 BTF_SET_END(special_kfunc_set)
 
 BTF_ID_LIST(special_kfunc_list)
 BTF_ID(func, bpf_obj_new_impl)
 BTF_ID(func, bpf_obj_drop_impl)
+BTF_ID(func, bpf_list_push_front)
+BTF_ID(func, bpf_list_push_back)
+BTF_ID(func, bpf_list_pop_front)
+BTF_ID(func, bpf_list_pop_back)
 
 static enum kfunc_ptr_arg_type
 get_kfunc_ptr_arg_type(struct bpf_verifier_env *env,
@@ -7936,15 +7984,6 @@ get_kfunc_ptr_arg_type(struct bpf_verifier_env *env,
 	if (is_kfunc_arg_local_kptr(meta->btf, &args[argno]))
 		return KF_ARG_PTR_TO_LOCAL_BTF_ID;
 
-	if ((base_type(reg->type) == PTR_TO_BTF_ID || reg2btf_ids[base_type(reg->type)])) {
-		if (!btf_type_is_struct(ref_t)) {
-			verbose(env, "kernel function %s args#%d pointer type %s %s is not supported\n",
-				meta->func_name, argno, btf_type_str(ref_t), ref_tname);
-			return -EINVAL;
-		}
-		return KF_ARG_PTR_TO_BTF_ID;
-	}
-
 	if (is_kfunc_arg_kptr_get(meta, argno)) {
 		if (!btf_type_is_ptr(ref_t)) {
 			verbose(env, "arg#0 BTF type must be a double pointer for kptr_get kfunc\n");
@@ -7963,6 +8002,21 @@ get_kfunc_ptr_arg_type(struct bpf_verifier_env *env,
 	if (is_kfunc_arg_dynptr(meta->btf, &args[argno]))
 		return KF_ARG_PTR_TO_DYNPTR;
 
+	if (is_kfunc_arg_list_head(meta->btf, &args[argno]))
+		return KF_ARG_PTR_TO_LIST_HEAD;
+
+	if (is_kfunc_arg_list_node(meta->btf, &args[argno]))
+		return KF_ARG_PTR_TO_LIST_NODE;
+
+	if ((base_type(reg->type) == PTR_TO_BTF_ID || reg2btf_ids[base_type(reg->type)])) {
+		if (!btf_type_is_struct(ref_t)) {
+			verbose(env, "kernel function %s args#%d pointer type %s %s is not supported\n",
+				meta->func_name, argno, btf_type_str(ref_t), ref_tname);
+			return -EINVAL;
+		}
+		return KF_ARG_PTR_TO_BTF_ID;
+	}
+
 	if (argno + 1 < nargs && is_kfunc_arg_mem_size(meta->btf, &args[argno + 1], &regs[regno + 1]))
 		arg_mem_size = true;
 
@@ -8049,6 +8103,225 @@ static int process_kf_arg_ptr_to_kptr_strong(struct bpf_verifier_env *env,
 	return 0;
 }
 
+static int ref_set_release_on_unlock(struct bpf_verifier_env *env, u32 ref_obj_id)
+{
+	struct bpf_func_state *state = cur_func(env);
+	struct bpf_reg_state *reg;
+	int i;
+
+	/* bpf_spin_lock only allows calling list_push and list_pop, no BPF
+	 * subprogs, no global functions, so this acquired refs state will
+	 * remain unchanged till we find registers to kill on bpf_spin_unlock.
+	 *
+	 * The acquired refs state is therefore not modified inside the
+	 * bpf_spin_lock critical section by any means, nor is it copied into
+	 * another frame as subprog calls are disallowed.
+	 */
+	if (!ref_obj_id) {
+		verbose(env, "verifier internal error: ref_obj_id is zero for release_on_unlock\n");
+		return -EFAULT;
+	}
+	for (i = 0; i < state->acquired_refs; i++) {
+		if (state->refs[i].id == ref_obj_id) {
+			WARN_ON_ONCE(state->refs[i].release_on_unlock);
+			state->refs[i].release_on_unlock = true;
+			/* Now mark everyone sharing same ref_obj_id as untrusted */
+			bpf_for_each_reg_in_vstate(env->cur_state, state, reg, ({
+				if (reg->ref_obj_id == ref_obj_id)
+					reg->type |= PTR_UNTRUSTED;
+			}));
+			return 0;
+		}
+	}
+	verbose(env, "verifier internal error: ref state missing for ref_obj_id\n");
+	return -EFAULT;
+}
+
+/* Implementation details:
+ *
+ * Each register points to some region of memory, which we define as an
+ * allocation. Each allocation may embed a bpf_spin_lock which protects any
+ * special BPF objects (bpf_list_head, bpf_rb_root, etc.) part of the same
+ * allocation. The lock and the data it protects are co-located in the same
+ * memory region.
+ *
+ * Hence, everytime a register holds a pointer value pointing to such
+ * allocation, the verifier preserves a unique reg->id for it.
+ *
+ * The verifier remembers the lock 'class' and the lock 'id' whenever
+ * bpf_spin_lock is called.
+ *
+ * To enable this, lock state in the verifier captures two values:
+ *	active_spin_lock_ptr = A value identifying the register's class
+ *	active_spin_lock_id  = A unique ID for each register pointer value
+ *
+ * Currently, PTR_TO_MAP_VALUE and PTR_TO_BTF_ID | MEM_TYPE_LOCAL are the two
+ * supported register types.
+ *
+ * The active_spin_lock_ptr in case of map values is the reg->map_ptr, and in
+ * case of local kptrs is the reg->btf pointer.
+ *
+ * The active_spin_lock_id is non-unique for maps supporting direct_value_addr,
+ * as we can establish the provenance of the map value statically for each
+ * distinct lookup into such maps.
+ *
+ * In case of global variables, they use array maps with max_entries = 1, hence
+ * their active_spin_lock_ptr becomes map_ptr and id = 0 (since they all point
+ * into the same map value as max_entries is 1).
+ *
+ * In case of inner map lookups, the inner map pointer has same map_ptr as the
+ * outer map pointer (in verifier context), but each lookup into an inner map
+ * assigns a fresh reg->id to the lookup, so while lookups into distinct inner
+ * maps from the same outer map share the same map_ptr as active_spin_lock_ptr,
+ * they will get different reg->id assigned to each lookup.
+ *
+ * In case of local kptrs, active_spin_lock_ptr is the reg->btf, and the reg->id
+ * is a unique ID preserved after the NULL pointer check on the local kptr after
+ * its allocation using bpf_obj_new.
+ */
+static int check_reg_allocation_locked(struct bpf_verifier_env *env, struct bpf_reg_state *reg)
+{
+	void *ptr;
+	u32 id;
+
+	switch ((int)reg->type) {
+	case PTR_TO_MAP_VALUE:
+		ptr = reg->map_ptr;
+		break;
+	case PTR_TO_BTF_ID | MEM_TYPE_LOCAL:
+		ptr = reg->btf;
+		break;
+	default:
+		verbose(env, "verifier internal error: unknown reg type for lock check\n");
+		return -EFAULT;
+	}
+	id = reg->id;
+
+	if (env->cur_state->active_spin_lock_ptr != ptr ||
+	    env->cur_state->active_spin_lock_id != id) {
+		verbose(env, "mismatch between held lock and object allocation provenance\n");
+		return -EINVAL;
+	}
+	return 0;
+}
+
+static bool is_bpf_list_api_kfunc(u32 btf_id)
+{
+	return btf_id == special_kfunc_list[KF_bpf_list_push_front] ||
+	       btf_id == special_kfunc_list[KF_bpf_list_push_back] ||
+	       btf_id == special_kfunc_list[KF_bpf_list_pop_front] ||
+	       btf_id == special_kfunc_list[KF_bpf_list_pop_back];
+}
+
+static int process_kf_arg_ptr_to_list_head(struct bpf_verifier_env *env,
+					   struct bpf_reg_state *reg, u32 regno,
+					   struct bpf_kfunc_call_arg_meta *meta)
+{
+	struct btf_record *rec = NULL;
+	struct btf_field *field;
+	u32 list_head_off;
+
+	if (meta->btf != btf_vmlinux || !is_bpf_list_api_kfunc(meta->func_id)) {
+		verbose(env, "verifier internal error: bpf_list_head argument for unknown kfunc\n");
+		return -EFAULT;
+	}
+
+	if (reg->type == PTR_TO_MAP_VALUE) {
+		rec = reg->map_ptr->record;
+	} else /* PTR_TO_BTF_ID | MEM_TYPE_LOCAL */ {
+		struct btf_struct_meta *meta;
+
+		meta = btf_find_struct_meta(reg->btf, reg->btf_id);
+		if (!meta) {
+			verbose(env, "bpf_list_head not found for local kptr\n");
+			return -EINVAL;
+		}
+		rec = meta->record;
+	}
+
+	if (!tnum_is_const(reg->var_off)) {
+		verbose(env,
+			"R%d doesn't have constant offset. bpf_list_head has to be at the constant offset\n",
+			regno);
+		return -EINVAL;
+	}
+
+	list_head_off = reg->off + reg->var_off.value;
+	field = btf_record_find(rec, list_head_off, BPF_LIST_HEAD);
+	if (!field) {
+		verbose(env, "bpf_list_head not found at offset=%u\n", list_head_off);
+		return -EINVAL;
+	}
+
+	/* All functions require bpf_list_head to be protected using a bpf_spin_lock */
+	if (check_reg_allocation_locked(env, reg)) {
+		verbose(env, "bpf_spin_lock at off=%d must be held for manipulating bpf_list_head\n",
+			rec->spin_lock_off);
+		return -EINVAL;
+	}
+
+	if (meta->arg_list_head.field) {
+		verbose(env, "verifier internal error: repeating bpf_list_head arg\n");
+		return -EFAULT;
+	}
+	meta->arg_list_head.field = field;
+	return 0;
+}
+
+static int process_kf_arg_ptr_to_list_node(struct bpf_verifier_env *env,
+					   struct bpf_reg_state *reg, u32 regno,
+					   struct bpf_kfunc_call_arg_meta *meta)
+{
+	struct btf_struct_meta *struct_meta;
+	struct btf_field *field;
+	struct btf_record *rec;
+	u32 list_node_off;
+
+	if (meta->btf != btf_vmlinux ||
+	    (meta->func_id != special_kfunc_list[KF_bpf_list_push_front] &&
+	     meta->func_id != special_kfunc_list[KF_bpf_list_push_back])) {
+		verbose(env, "verifier internal error: bpf_list_head argument for unknown kfunc\n");
+		return -EFAULT;
+	}
+
+	if (!tnum_is_const(reg->var_off)) {
+		verbose(env,
+			"R%d doesn't have constant offset. bpf_list_head has to be at the constant offset\n",
+			regno);
+		return -EINVAL;
+	}
+
+	struct_meta = btf_find_struct_meta(reg->btf, reg->btf_id);
+	if (!struct_meta) {
+		verbose(env, "bpf_list_node not found for local kptr\n");
+		return -EINVAL;
+	}
+	rec = struct_meta->record;
+
+	list_node_off = reg->off + reg->var_off.value;
+	field = btf_record_find(rec, list_node_off, BPF_LIST_NODE);
+	if (!field || field->offset != list_node_off) {
+		verbose(env, "bpf_list_node not found at offset=%u\n", list_node_off);
+		return -EINVAL;
+	}
+
+	field = meta->arg_list_head.field;
+
+	if (!btf_struct_ids_match(&env->log, reg->btf, reg->btf_id, 0, field->list_head.btf,
+				  field->list_head.value_btf_id, true)) {
+		verbose(env, "bpf_list_head value type does not match arg#1\n");
+		return -EINVAL;
+	}
+
+	if (list_node_off != field->list_head.node_offset) {
+		verbose(env, "arg#1 offset must be for bpf_list_node at off=%d\n",
+			field->list_head.node_offset);
+		return -EINVAL;
+	}
+	/* Set arg#1 for expiration after unlock */
+	return ref_set_release_on_unlock(env, reg->ref_obj_id);
+}
+
 static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_arg_meta *meta)
 {
 	const char *func_name = meta->func_name, *ref_tname;
@@ -8167,6 +8440,8 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_
 			break;
 		case KF_ARG_PTR_TO_KPTR_STRONG:
 		case KF_ARG_PTR_TO_DYNPTR:
+		case KF_ARG_PTR_TO_LIST_HEAD:
+		case KF_ARG_PTR_TO_LIST_NODE:
 		case KF_ARG_PTR_TO_MEM:
 		case KF_ARG_PTR_TO_MEM_SIZE:
 			/* Trusted by default */
@@ -8204,17 +8479,6 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_
 				meta->arg_obj_drop.btf_id = reg->btf_id;
 			}
 			break;
-		case KF_ARG_PTR_TO_BTF_ID:
-			/* Only base_type is checked, further checks are done here */
-			if (reg->type != PTR_TO_BTF_ID &&
-			    (!reg2btf_ids[base_type(reg->type)] || type_flag(reg->type))) {
-				verbose(env, "arg#%d expected pointer to btf or socket\n", i);
-				return -EINVAL;
-			}
-			ret = process_kf_arg_ptr_to_btf_id(env, reg, ref_t, ref_tname, ref_id, meta, i);
-			if (ret < 0)
-				return ret;
-			break;
 		case KF_ARG_PTR_TO_KPTR_STRONG:
 			if (reg->type != PTR_TO_MAP_VALUE) {
 				verbose(env, "arg#0 expected pointer to map value\n");
@@ -8242,6 +8506,44 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_
 				return -EINVAL;
 			}
 			break;
+		case KF_ARG_PTR_TO_LIST_HEAD:
+			if (reg->type != PTR_TO_MAP_VALUE &&
+			    reg->type != (PTR_TO_BTF_ID | MEM_TYPE_LOCAL)) {
+				verbose(env, "arg#%d expected pointer to map value or local kptr\n", i);
+				return -EINVAL;
+			}
+			if (reg->type == (PTR_TO_BTF_ID | MEM_TYPE_LOCAL) && !reg->ref_obj_id) {
+				verbose(env, "local kptr must be referenced\n");
+				return -EINVAL;
+			}
+			ret = process_kf_arg_ptr_to_list_head(env, reg, regno, meta);
+			if (ret < 0)
+				return ret;
+			break;
+		case KF_ARG_PTR_TO_LIST_NODE:
+			if (reg->type != (PTR_TO_BTF_ID | MEM_TYPE_LOCAL)) {
+				verbose(env, "arg#%d expected point to local kptr\n", i);
+				return -EINVAL;
+			}
+			if (!reg->ref_obj_id) {
+				verbose(env, "local kptr must be referenced\n");
+				return -EINVAL;
+			}
+			ret = process_kf_arg_ptr_to_list_node(env, reg, regno, meta);
+			if (ret < 0)
+				return ret;
+			break;
+		case KF_ARG_PTR_TO_BTF_ID:
+			/* Only base_type is checked, further checks are done here */
+			if (reg->type != PTR_TO_BTF_ID &&
+			    (!reg2btf_ids[base_type(reg->type)] || type_flag(reg->type))) {
+				verbose(env, "arg#%d expected pointer to btf or socket\n", i);
+				return -EINVAL;
+			}
+			ret = process_kf_arg_ptr_to_btf_id(env, reg, ref_t, ref_tname, ref_id, meta, i);
+			if (ret < 0)
+				return ret;
+			break;
 		case KF_ARG_PTR_TO_MEM:
 			resolve_ret = btf_resolve_size(btf, ref_t, &type_size);
 			if (IS_ERR(resolve_ret)) {
@@ -8362,11 +8664,6 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 		ptr_type = btf_type_skip_modifiers(desc_btf, t->type, &ptr_type_id);
 
 		if (meta.btf == btf_vmlinux && btf_id_set_contains(&special_kfunc_set, meta.func_id)) {
-			if (!btf_type_is_void(ptr_type)) {
-				verbose(env, "kernel function %s must have void * return type\n",
-					meta.func_name);
-				return -EINVAL;
-			}
 			if (meta.func_id == special_kfunc_list[KF_bpf_obj_new_impl]) {
 				const struct btf_type *ret_t;
 				struct btf *ret_btf;
@@ -8404,6 +8701,15 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 				env->insn_aux_data[insn_idx].kptr_struct_meta =
 					btf_find_struct_meta(meta.arg_obj_drop.btf,
 							     meta.arg_obj_drop.btf_id);
+			} else if (meta.func_id == special_kfunc_list[KF_bpf_list_pop_front] ||
+				   meta.func_id == special_kfunc_list[KF_bpf_list_pop_back]) {
+				struct btf_field *field = meta.arg_list_head.field;
+
+				mark_reg_known_zero(env, regs, BPF_REG_0);
+				regs[BPF_REG_0].type = PTR_TO_BTF_ID | MEM_TYPE_LOCAL;
+				regs[BPF_REG_0].btf = field->list_head.btf;
+				regs[BPF_REG_0].btf_id = field->list_head.value_btf_id;
+				regs[BPF_REG_0].off = field->list_head.node_offset;
 			} else {
 				verbose(env, "kernel function %s unhandled dynamic return type\n",
 					meta.func_name);
@@ -13072,11 +13378,14 @@ static int do_check(struct bpf_verifier_env *env)
 					return -EINVAL;
 				}
 
-				if (env->cur_state->active_spin_lock_ptr &&
-				    (insn->src_reg == BPF_PSEUDO_CALL ||
-				     insn->imm != BPF_FUNC_spin_unlock)) {
-					verbose(env, "function calls are not allowed while holding a lock\n");
-					return -EINVAL;
+				if (env->cur_state->active_spin_lock_ptr) {
+					if ((insn->src_reg == BPF_REG_0 && insn->imm != BPF_FUNC_spin_unlock) ||
+					    (insn->src_reg == BPF_PSEUDO_CALL) ||
+					    (insn->src_reg == BPF_PSEUDO_KFUNC_CALL &&
+					     (insn->off != 0 || !is_bpf_list_api_kfunc(insn->imm)))) {
+						verbose(env, "function calls are not allowed while holding a lock\n");
+						return -EINVAL;
+					}
 				}
 				if (insn->src_reg == BPF_PSEUDO_CALL)
 					err = check_func_call(env, insn, &env->insn_idx);
diff --git a/tools/testing/selftests/bpf/bpf_experimental.h b/tools/testing/selftests/bpf/bpf_experimental.h
index 29a5520a4250..4a76c64e50ad 100644
--- a/tools/testing/selftests/bpf/bpf_experimental.h
+++ b/tools/testing/selftests/bpf/bpf_experimental.h
@@ -31,3 +31,31 @@ extern void bpf_obj_drop_impl(void *kptr, void *meta) __ksym;
 
 /* Convenience macro to wrap over bpf_obj_drop_impl */
 #define bpf_obj_drop(kptr) bpf_obj_drop_impl(kptr, NULL)
+
+/* Description
+ *	Add a new entry to the beginning of the BPF linked list.
+ * Returns
+ *	Void.
+ */
+extern void bpf_list_push_front(struct bpf_list_head *head, struct bpf_list_node *node) __ksym;
+
+/* Description
+ *	Add a new entry to the end of the BPF linked list.
+ * Returns
+ *	Void.
+ */
+extern void bpf_list_push_back(struct bpf_list_head *head, struct bpf_list_node *node) __ksym;
+
+/* Description
+ *	Remove the entry at the beginning of the BPF linked list.
+ * Returns
+ *	Pointer to bpf_list_node of deleted entry, or NULL if list is empty.
+ */
+extern struct bpf_list_node *bpf_list_pop_front(struct bpf_list_head *head) __ksym;
+
+/* Description
+ *	Remove the entry at the end of the BPF linked list.
+ * Returns
+ *	Pointer to bpf_list_node of deleted entry, or NULL if list is empty.
+ */
+extern struct bpf_list_node *bpf_list_pop_back(struct bpf_list_head *head) __ksym;
-- 
2.38.1

[PATCH bpf-next v4 23/24] selftests/bpf: Add __contains macro to bpf_experimental.h

[Kumar Kartikeya Dwivedi]

Add user facing __contains macro which provides a convenient wrapper
over the verbose kernel specific BTF declaration tag required to
annotate BPF list head structs in user types.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 tools/testing/selftests/bpf/bpf_experimental.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/tools/testing/selftests/bpf/bpf_experimental.h b/tools/testing/selftests/bpf/bpf_experimental.h
index 4a76c64e50ad..3db1578db2d9 100644
--- a/tools/testing/selftests/bpf/bpf_experimental.h
+++ b/tools/testing/selftests/bpf/bpf_experimental.h
@@ -3,6 +3,8 @@
 #include <bpf/bpf_helpers.h>
 #include <bpf/bpf_core_read.h>
 
+#define __contains(name, node) __attribute__((btf_decl_tag("contains:" #name ":" #node)))
+
 /* Description
  *	Allocates a local kptr of type represented by 'local_type_id' in program
  *	BTF. User may use the bpf_core_type_id_local macro to pass the type ID
-- 
2.38.1

[PATCH bpf-next v4 24/24] selftests/bpf: Add BPF linked list API tests

[Kumar Kartikeya Dwivedi]

Include various tests covering the success and failure cases. Also, run
the success cases at runtime to verify correctness of linked list
manipulation routines, in addition to ensuring successful verification.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 kernel/bpf/helpers.c                          |   5 +-
 tools/testing/selftests/bpf/DENYLIST.s390x    |   1 +
 .../selftests/bpf/prog_tests/linked_list.c    |  79 +++++
 .../testing/selftests/bpf/progs/linked_list.c | 330 ++++++++++++++++++
 4 files changed, 414 insertions(+), 1 deletion(-)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/linked_list.c
 create mode 100644 tools/testing/selftests/bpf/progs/linked_list.c

diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 0acd87ed22fc..db4398a5bb35 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -1839,7 +1839,10 @@ static const struct btf_kfunc_id_set generic_kfunc_set = {
 
 static int __init kfunc_init(void)
 {
-	return register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, &generic_kfunc_set);
+	int ret;
+
+	ret = register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, &generic_kfunc_set);
+	return ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_SCHED_CLS, &generic_kfunc_set);
 }
 
 late_initcall(kfunc_init);
diff --git a/tools/testing/selftests/bpf/DENYLIST.s390x b/tools/testing/selftests/bpf/DENYLIST.s390x
index be4e3d47ea3e..072243af93b0 100644
--- a/tools/testing/selftests/bpf/DENYLIST.s390x
+++ b/tools/testing/selftests/bpf/DENYLIST.s390x
@@ -33,6 +33,7 @@ ksyms_module                             # test_ksyms_module__open_and_load unex
 ksyms_module_libbpf                      # JIT does not support calling kernel function                                (kfunc)
 ksyms_module_lskel                       # test_ksyms_module_lskel__open_and_load unexpected error: -9                 (?)
 libbpf_get_fd_by_id_opts                 # failed to attach: ERROR: strerror_r(-524)=22                                (trampoline)
+linked_list				 # JIT does not support calling kernel function                                (kfunc)
 lookup_key                               # JIT does not support calling kernel function                                (kfunc)
 lru_bug                                  # prog 'printk': failed to auto-attach: -524
 map_kptr                                 # failed to open_and_load program: -524 (trampoline)
diff --git a/tools/testing/selftests/bpf/prog_tests/linked_list.c b/tools/testing/selftests/bpf/prog_tests/linked_list.c
new file mode 100644
index 000000000000..a017bc1b7b0a
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/linked_list.c
@@ -0,0 +1,79 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <test_progs.h>
+#include <network_helpers.h>
+
+#include "linked_list.skel.h"
+
+static void test_linked_list_success(void)
+{
+	LIBBPF_OPTS(bpf_test_run_opts, opts,
+		.data_in = &pkt_v4,
+		.data_size_in = sizeof(pkt_v4),
+		.repeat = 1,
+	);
+	struct linked_list *skel;
+	int key = 0, ret;
+	char buf[32];
+
+	skel = linked_list__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "linked_list__open_and_load"))
+		return;
+
+	ret = bpf_prog_test_run_opts(bpf_program__fd(skel->progs.map_list_push_pop), &opts);
+	ASSERT_OK(ret, "map_list_push_pop");
+	ASSERT_OK(opts.retval, "map_list_push_pop retval");
+
+	ret = bpf_prog_test_run_opts(bpf_program__fd(skel->progs.global_list_push_pop), &opts);
+	ASSERT_OK(ret, "global_list_push_pop");
+	ASSERT_OK(opts.retval, "global_list_push_pop retval");
+
+	ret = bpf_prog_test_run_opts(bpf_program__fd(skel->progs.global_list_push_pop_unclean), &opts);
+	ASSERT_OK(ret, "global_list_push_pop_unclean");
+	ASSERT_OK(opts.retval, "global_list_push_pop_unclean retval");
+
+	ASSERT_OK(bpf_map_update_elem(bpf_map__fd(skel->maps.data_A), &key, buf, 0),
+		  "check_and_free_fields");
+	ASSERT_OK(bpf_map_update_elem(bpf_map__fd(skel->maps.array_map), &key, buf, 0),
+		  "check_and_free_fields");
+
+	ret = bpf_prog_test_run_opts(bpf_program__fd(skel->progs.map_list_push_pop_multiple), &opts);
+	ASSERT_OK(ret, "map_list_push_pop_multiple");
+	ASSERT_OK(opts.retval, "map_list_push_pop_multiple retval");
+
+	ret = bpf_prog_test_run_opts(bpf_program__fd(skel->progs.global_list_push_pop_multiple), &opts);
+	ASSERT_OK(ret, "global_list_push_pop_multiple");
+	ASSERT_OK(opts.retval, "global_list_push_pop_multiple retval");
+
+	ret = bpf_prog_test_run_opts(bpf_program__fd(skel->progs.global_list_push_pop_multiple_unclean), &opts);
+	ASSERT_OK(ret, "global_list_push_pop_multiple_unclean");
+	ASSERT_OK(opts.retval, "global_list_push_pop_multiple_unclean retval");
+
+	ASSERT_OK(bpf_map_update_elem(bpf_map__fd(skel->maps.data_A), &key, buf, 0),
+		  "check_and_free_fields");
+	ASSERT_OK(bpf_map_update_elem(bpf_map__fd(skel->maps.array_map), &key, buf, 0),
+		  "check_and_free_fields");
+
+	ret = bpf_prog_test_run_opts(bpf_program__fd(skel->progs.map_list_in_list), &opts);
+	ASSERT_OK(ret, "map_list_in_list");
+	ASSERT_OK(opts.retval, "map_list_in_list retval");
+
+	ret = bpf_prog_test_run_opts(bpf_program__fd(skel->progs.global_list_in_list), &opts);
+	ASSERT_OK(ret, "global_list_in_list");
+	ASSERT_OK(opts.retval, "global_list_in_list retval");
+
+	ret = bpf_prog_test_run_opts(bpf_program__fd(skel->progs.global_list_in_list_unclean), &opts);
+	ASSERT_OK(ret, "global_list_in_list_unclean");
+	ASSERT_OK(opts.retval, "global_list_in_list_unclean retval");
+
+	ASSERT_OK(bpf_map_update_elem(bpf_map__fd(skel->maps.data_A), &key, buf, 0),
+		  "check_and_free_fields");
+	ASSERT_OK(bpf_map_update_elem(bpf_map__fd(skel->maps.array_map), &key, buf, 0),
+		  "check_and_free_fields");
+
+	linked_list__destroy(skel);
+}
+
+void test_linked_list(void)
+{
+	test_linked_list_success();
+}
diff --git a/tools/testing/selftests/bpf/progs/linked_list.c b/tools/testing/selftests/bpf/progs/linked_list.c
new file mode 100644
index 000000000000..eed0b2c1eb4a
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/linked_list.c
@@ -0,0 +1,330 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <vmlinux.h>
+#include <bpf/bpf_tracing.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_core_read.h>
+#include "bpf_experimental.h"
+
+#ifndef ARRAY_SIZE
+#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
+#endif
+
+struct bar {
+	struct bpf_list_node node;
+	int data;
+};
+
+struct foo {
+	struct bpf_list_node node;
+	struct bpf_list_head head __contains(bar, node);
+	struct bpf_spin_lock lock;
+	int data;
+};
+
+struct map_value {
+	struct bpf_list_head head __contains(foo, node);
+	struct bpf_spin_lock lock;
+	int data;
+};
+
+struct array_map {
+	__uint(type, BPF_MAP_TYPE_ARRAY);
+	__type(key, int);
+	__type(value, struct map_value);
+	__uint(max_entries, 1);
+} array_map SEC(".maps");
+
+#define private(name) SEC(".data." #name) __hidden __attribute__((aligned(8)))
+
+private(A) static struct bpf_spin_lock glock;
+private(A) static struct bpf_list_head ghead __contains(foo, node);
+private(A) static struct bpf_list_head gghead __contains(foo, node);
+
+static __always_inline int list_push_pop(struct bpf_spin_lock *lock,
+					 struct bpf_list_head *head, bool leave_in_map)
+{
+	struct bpf_list_node *n;
+	struct foo *f;
+
+	f = bpf_obj_new(typeof(*f));
+	if (!f)
+		return 2;
+
+	bpf_spin_lock(lock);
+	n = bpf_list_pop_front(head);
+	bpf_spin_unlock(lock);
+	if (n) {
+		bpf_obj_drop(container_of(n, struct foo, node));
+		bpf_obj_drop(f);
+		return 3;
+	}
+
+	bpf_spin_lock(lock);
+	n = bpf_list_pop_back(head);
+	bpf_spin_unlock(lock);
+	if (n) {
+		bpf_obj_drop(container_of(n, struct foo, node));
+		bpf_obj_drop(f);
+		return 4;
+	}
+
+
+	bpf_spin_lock(lock);
+	f->data = 42;
+	bpf_list_push_front(head, &f->node);
+	bpf_spin_unlock(lock);
+	if (leave_in_map)
+		return 0;
+	bpf_spin_lock(lock);
+	n = bpf_list_pop_back(head);
+	bpf_spin_unlock(lock);
+	if (!n)
+		return 5;
+	f = container_of(n, struct foo, node);
+	if (f->data != 42) {
+		bpf_obj_drop(f);
+		return 6;
+	}
+
+	bpf_spin_lock(lock);
+	f->data = 13;
+	bpf_list_push_front(head, &f->node);
+	bpf_spin_unlock(lock);
+	bpf_spin_lock(lock);
+	n = bpf_list_pop_front(head);
+	bpf_spin_unlock(lock);
+	if (!n)
+		return 7;
+	f = container_of(n, struct foo, node);
+	if (f->data != 13) {
+		bpf_obj_drop(f);
+		return 8;
+	}
+	bpf_obj_drop(f);
+
+	bpf_spin_lock(lock);
+	n = bpf_list_pop_front(head);
+	bpf_spin_unlock(lock);
+	if (n) {
+		bpf_obj_drop(container_of(n, struct foo, node));
+		return 9;
+	}
+
+	bpf_spin_lock(lock);
+	n = bpf_list_pop_back(head);
+	bpf_spin_unlock(lock);
+	if (n) {
+		bpf_obj_drop(container_of(n, struct foo, node));
+		return 10;
+	}
+	return 0;
+}
+
+
+static __always_inline int list_push_pop_multiple(struct bpf_spin_lock *lock,
+						  struct bpf_list_head *head, bool leave_in_map)
+{
+	struct bpf_list_node *n;
+	struct foo *f[8], *pf;
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(f); i++) {
+		f[i] = bpf_obj_new(typeof(**f));
+		if (!f[i])
+			return 2;
+		f[i]->data = i;
+		bpf_spin_lock(lock);
+		bpf_list_push_front(head, &f[i]->node);
+		bpf_spin_unlock(lock);
+	}
+
+	for (i = 0; i < ARRAY_SIZE(f); i++) {
+		bpf_spin_lock(lock);
+		n = bpf_list_pop_front(head);
+		bpf_spin_unlock(lock);
+		if (!n)
+			return 3;
+		pf = container_of(n, struct foo, node);
+		if (pf->data != (ARRAY_SIZE(f) - i - 1)) {
+			bpf_obj_drop(pf);
+			return 4;
+		}
+		bpf_spin_lock(lock);
+		bpf_list_push_back(head, &pf->node);
+		bpf_spin_unlock(lock);
+	}
+
+	if (leave_in_map)
+		return 0;
+
+	for (i = 0; i < ARRAY_SIZE(f); i++) {
+		bpf_spin_lock(lock);
+		n = bpf_list_pop_back(head);
+		bpf_spin_unlock(lock);
+		if (!n)
+			return 5;
+		pf = container_of(n, struct foo, node);
+		if (pf->data != i) {
+			bpf_obj_drop(pf);
+			return 6;
+		}
+		bpf_obj_drop(pf);
+	}
+	bpf_spin_lock(lock);
+	n = bpf_list_pop_back(head);
+	bpf_spin_unlock(lock);
+	if (n) {
+		bpf_obj_drop(container_of(n, struct foo, node));
+		return 7;
+	}
+
+	bpf_spin_lock(lock);
+	n = bpf_list_pop_front(head);
+	bpf_spin_unlock(lock);
+	if (n) {
+		bpf_obj_drop(container_of(n, struct foo, node));
+		return 8;
+	}
+	return 0;
+}
+
+static __always_inline int list_in_list(struct bpf_spin_lock *lock,
+					struct bpf_list_head *head, bool leave_in_map)
+{
+	struct bpf_list_node *n;
+	struct bar *ba[8], *b;
+	struct foo *f;
+	int i;
+
+	f = bpf_obj_new(typeof(*f));
+	if (!f)
+		return 2;
+	for (i = 0; i < ARRAY_SIZE(ba); i++) {
+		b = bpf_obj_new(typeof(*b));
+		if (!b) {
+			bpf_obj_drop(f);
+			return 3;
+		}
+		b->data = i;
+		bpf_spin_lock(&f->lock);
+		bpf_list_push_back(&f->head, &b->node);
+		bpf_spin_unlock(&f->lock);
+	}
+
+	bpf_spin_lock(lock);
+	f->data = 42;
+	bpf_list_push_front(head, &f->node);
+	bpf_spin_unlock(lock);
+
+	if (leave_in_map)
+		return 0;
+
+	bpf_spin_lock(lock);
+	n = bpf_list_pop_front(head);
+	bpf_spin_unlock(lock);
+	if (!n)
+		return 4;
+	f = container_of(n, struct foo, node);
+	if (f->data != 42) {
+		bpf_obj_drop(f);
+		return 5;
+	}
+
+	for (i = 0; i < ARRAY_SIZE(ba); i++) {
+		bpf_spin_lock(&f->lock);
+		n = bpf_list_pop_front(&f->head);
+		bpf_spin_unlock(&f->lock);
+		if (!n) {
+			bpf_obj_drop(f);
+			return 6;
+		}
+		b = container_of(n, struct bar, node);
+		if (b->data != i) {
+			bpf_obj_drop(f);
+			bpf_obj_drop(b);
+			return 7;
+		}
+		bpf_obj_drop(b);
+	}
+	bpf_spin_lock(&f->lock);
+	n = bpf_list_pop_front(&f->head);
+	bpf_spin_unlock(&f->lock);
+	if (n) {
+		bpf_obj_drop(f);
+		bpf_obj_drop(container_of(n, struct bar, node));
+		return 8;
+	}
+	bpf_obj_drop(f);
+	return 0;
+}
+
+SEC("tc")
+int map_list_push_pop(void *ctx)
+{
+	struct map_value *v;
+
+	v = bpf_map_lookup_elem(&array_map, &(int){0});
+	if (!v)
+		return 1;
+	return list_push_pop(&v->lock, &v->head, false);
+}
+
+SEC("tc")
+int global_list_push_pop(void *ctx)
+{
+	return list_push_pop(&glock, &ghead, false);
+}
+
+SEC("tc")
+int global_list_push_pop_unclean(void *ctx)
+{
+	return list_push_pop(&glock, &gghead, true);
+}
+
+SEC("tc")
+int map_list_push_pop_multiple(void *ctx)
+{
+	struct map_value *v;
+
+	v = bpf_map_lookup_elem(&array_map, &(int){0});
+	if (!v)
+		return 1;
+	return list_push_pop_multiple(&v->lock, &v->head, false);
+}
+
+SEC("tc")
+int global_list_push_pop_multiple(void *ctx)
+{
+	return list_push_pop_multiple(&glock, &ghead, false);
+}
+
+SEC("tc")
+int global_list_push_pop_multiple_unclean(void *ctx)
+{
+	return list_push_pop_multiple(&glock, &gghead, true);
+}
+
+SEC("tc")
+int map_list_in_list(void *ctx)
+{
+	struct map_value *v;
+
+	v = bpf_map_lookup_elem(&array_map, &(int){0});
+	if (!v)
+		return 1;
+	return list_in_list(&v->lock, &v->head, false);
+}
+
+SEC("tc")
+int global_list_in_list(void *ctx)
+{
+	return list_in_list(&glock, &ghead, false);
+}
+
+SEC("tc")
+int global_list_in_list_unclean(void *ctx)
+{
+	return list_in_list(&glock, &gghead, true);
+}
+
+char _license[] SEC("license") = "GPL";
-- 
2.38.1

Re: [PATCH bpf-next v4 01/24] bpf: Document UAPI details for special BPF types

[David Vernet]

On Fri, Nov 04, 2022 at 12:39:50AM +0530, Kumar Kartikeya Dwivedi wrote:
> The kernel recognizes some special BPF types in map values or local
> kptrs. Document that only bpf_spin_lock and bpf_timer will preserve
> backwards compatibility, and kptr will preserve backwards compatibility
> for the operations on the pointer, not the types supported for such
> kptrs.
> 
> For local kptrs, document that there are no stability guarantees at all.
> 
> Finally, document that 'bpf_' namespace is reserved for adding future
> special fields, hence BPF programs must not declare types with such
> names in their programs and still expect backwards compatibility.
> 
> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
> ---
>  Documentation/bpf/bpf_design_QA.rst | 44 +++++++++++++++++++++++++++++
>  1 file changed, 44 insertions(+)
> 
> diff --git a/Documentation/bpf/bpf_design_QA.rst b/Documentation/bpf/bpf_design_QA.rst
> index a210b8a4df00..b5273148497c 100644
> --- a/Documentation/bpf/bpf_design_QA.rst
> +++ b/Documentation/bpf/bpf_design_QA.rst
> @@ -298,3 +298,47 @@ A: NO.
>  
>  The BTF_ID macro does not cause a function to become part of the ABI
>  any more than does the EXPORT_SYMBOL_GPL macro.
> +
> +Q: What is the compatibility story for special BPF types in map values?
> +-----------------------------------------------------------------------
> +Q: Users are allowed to embed bpf_spin_lock, bpf_timer fields in their BPF map
> +values (when using BTF support for BPF maps). This allows to use helpers for
> +such objects on these fields inside map values. Users are also allowed to embed
> +pointers to some kernel types (with __kptr and __kptr_ref BTF tags). Will the
> +kernel preserve backwards compatibility for these features?
> +
> +A: It depends. For bpf_spin_lock, bpf_timer: YES, for kptr and everything else:
> +NO, but see below.
> +
> +For struct types that have been added already, like bpf_spin_lock and bpf_timer,
> +the kernel will preserve backwards compatibility, as they are part of UAPI.
> +
> +For kptrs, they are also part of UAPI, but only with respect to the kptr
> +mechanism. The types that you can use with a __kptr and __kptr_ref tagged
> +pointer in your struct is NOT part of the UAPI contract. The supported types can

s/is NOT/are NOT

> +and will change across kernel releases. However, operations like accessing kptr
> +fields and bpf_kptr_xchg() helper will continue to be supported across kernel
> +releases for the supported types.
> +
> +For any other supported struct type, unless explicitly stated in this document
> +and added to bpf.h UAPI header, such types can and will arbitrarily change their
> +size, type, and alignment, or any other user visible API or ABI detail across
> +kernel releases. The users must adapt their BPF programs to the new changes and
> +update them to make sure their programs continue to work correctly.
> +
> +NOTE: BPF subsystem specially reserves the 'bpf_' prefix for type names, in
> +order to introduce more special fields in the future. Hence, user programs must
> +avoid defining types with 'bpf_' prefix to not be broken in future releases. In
> +other words, no backwards compatibility is guaranteed if one using a type in BTF
> +with 'bpf_' prefix.
> +
> +Q: What is the compatibility story for special BPF types in local kptrs?
> +------------------------------------------------------------------------
> +Q: Same as above, but for local kptrs (i.e. pointers to objects allocated using
> +bpf_obj_new for user defined structures). Will the kernel preserve backwards
> +compatibility for these features?
> +
> +A: NO.
> +
> +Unlike map value types, there are no stability guarantees for this case. The
> +whole local kptr API itself is unstable (since it is exposed through kfuncs).
> -- 
> 2.38.1
> 

Looks good otherwise.

Acked-by: David Vernet <void@manifault.com>

Re: [PATCH bpf-next v4 02/24] bpf: Allow specifying volatile type modifier for kptrs

[David Vernet]

On Fri, Nov 04, 2022 at 12:39:51AM +0530, Kumar Kartikeya Dwivedi wrote:
> This is useful in particular to mark the pointer as volatile, so that
> compiler treats each load and store to the field as a volatile access.
> The alternative is having to define and use READ_ONCE and WRITE_ONCE in
> the BPF program.
> 
> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>

Acked-by: David Vernet <void@manifault.com>

Re: [PATCH bpf-next v4 05/24] bpf: Drop reg_type_may_be_refcounted_or_null

[David Vernet]

On Fri, Nov 04, 2022 at 12:39:54AM +0530, Kumar Kartikeya Dwivedi wrote:
> It is not scalable to maintain a list of types that can have non-zero
> ref_obj_id. It is never set for scalars anyway, so just remove the
> conditional on register types and print it whenever it is non-zero.
> 
> Acked-by: Dave Marchevsky <davemarchevsky@fb.com>
> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
> ---

Acked-by: David Vernet <void@manifault.com>

Re: [PATCH bpf-next v4 19/24] bpf: Introduce bpf_obj_new

[Dave Marchevsky]

On 11/3/22 3:10 PM, Kumar Kartikeya Dwivedi wrote:
> Introduce type safe memory allocator bpf_obj_new for BPF programs. The
> kernel side kfunc is named bpf_obj_new_impl, as passing hidden arguments
> to kfuncs still requires having them in prototype, unlike BPF helpers
> which always take 5 arguments and have them checked using bpf_func_proto
> in verifier, ignoring unset argument types.
> 
> Introduce __ign suffix to ignore a specific kfunc argument during type
> checks, then use this to introduce support for passing type metadata to
> the bpf_obj_new_impl kfunc.
> 
> The user passes BTF ID of the type it wants to allocates in program BTF,
> the verifier then rewrites the first argument as the size of this type,
> after performing some sanity checks (to ensure it exists and it is a
> struct type).
> 
> The second argument is also fixed up and passed by the verifier. This is
> the btf_struct_meta for the type being allocated. It would be needed
> mostly for the offset array which is required for zero initializing
> special fields while leaving the rest of storage in unitialized state.
> 
> It would also be needed in the next patch to perform proper destruction
> of the object's special fields.
> 
> A convenience macro is included in the bpf_experimental.h header to hide
> over the ugly details of the implementation, leading to user code
> looking similar to a language level extension which allocates and
> constructs fields of a user type.
> 
> struct bar {
> 	struct bpf_list_node node;
> };
> 
> struct foo {
> 	struct bpf_spin_lock lock;
> 	struct bpf_list_head head __contains(bar, node);
> };
> 
> void prog(void) {
> 	struct foo *f;
> 
> 	f = bpf_obj_new(typeof(*f));
> 	if (!f)
> 		return;
> 	...
> }
> 
> A key piece of this story is still missing, i.e. the free function,
> which will come in the next patch.
> 
> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
> ---

[...]

> diff --git a/tools/testing/selftests/bpf/bpf_experimental.h b/tools/testing/selftests/bpf/bpf_experimental.h
> new file mode 100644
> index 000000000000..1d3451084a68
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/bpf_experimental.h

Maybe bpf_experimental.h should go in libbpf as part of this series? If
including vmlinux.h is an issue - nothing in libbpf currently includes it - you
could rely on the BPF program including it, with a comment similar to "Note
that bpf programs need to include..." in lib/bpf/bpf_helpers.h .

> @@ -0,0 +1,20 @@
> +#include <vmlinux.h>
> +#include <bpf/bpf_tracing.h>
> +#include <bpf/bpf_helpers.h>
> +#include <bpf/bpf_core_read.h>
> +
> +/* Description
> + *	Allocates a local kptr of type represented by 'local_type_id' in program
> + *	BTF. User may use the bpf_core_type_id_local macro to pass the type ID
> + *	of a struct in program BTF.
> + *
> + *	The 'local_type_id' parameter must be a known constant.
> + *	The 'meta' parameter is a hidden argument that is ignored.
> + * Returns
> + *	A local kptr corresponding to passed in 'local_type_id', or NULL on
> + *	failure.
> + */
> +extern void *bpf_obj_new_impl(__u64 local_type_id, void *meta) __ksym;
> +
> +/* Convenience macro to wrap over bpf_obj_new_impl */
> +#define bpf_obj_new(type) bpf_obj_new_impl(bpf_core_type_id_local(type), NULL)

Re: [PATCH bpf-next v4 06/24] bpf: Refactor kptr_off_tab into btf_record

[Alexei Starovoitov]

On Fri, Nov 04, 2022 at 12:39:55AM +0530, Kumar Kartikeya Dwivedi wrote:
> @@ -936,51 +956,51 @@ static int bpf_map_alloc_off_arr(struct bpf_map *map)
>  {
>  	bool has_spin_lock = map_value_has_spin_lock(map);
>  	bool has_timer = map_value_has_timer(map);
> -	bool has_kptrs = map_value_has_kptrs(map);
> -	struct bpf_map_off_arr *off_arr;
> +	bool has_fields = !IS_ERR_OR_NULL(map);

should have been map->record.

> -	if (!map_value_has_kptrs(map_ptr)) {
> -		ret = PTR_ERR_OR_ZERO(map_ptr->kptr_off_tab);
> -		if (ret == -E2BIG)
> -			verbose(env, "map '%s' has more than %d kptr\n", map_ptr->name,
> -				BPF_MAP_VALUE_OFF_MAX);
> -		else if (ret == -EEXIST)
> -			verbose(env, "map '%s' has repeating kptr BTF tags\n", map_ptr->name);
> -		else
> -			verbose(env, "map '%s' has no valid kptr\n", map_ptr->name);
> +	if (!btf_record_has_field(map_ptr->record, BPF_KPTR)) {
> +		verbose(env, "map '%s' has no valid kptr\n", map_ptr->name);
>  		return -EINVAL;
>  	}

The loss of verbosity is annoying, but I see why you're doing it.

Re: [PATCH bpf-next v4 14/24] bpf: Allow locking bpf_spin_lock global variables

[Dave Marchevsky]

On 11/3/22 3:10 PM, Kumar Kartikeya Dwivedi wrote:
> Global variables reside in maps accessible using direct_value_addr
> callbacks, so giving each load instruction's rewrite a unique reg->id
> disallows us from holding locks which are global.
> 
> This is not great, so refactor the active_spin_lock into two separate
> fields, active_spin_lock_ptr and active_spin_lock_id, which is generic
> enough to allow it for global variables, map lookups, and local kptr
> registers at the same time.
> 
> Held vs non-held is indicated by active_spin_lock_ptr, which stores the
> reg->map_ptr or reg->btf pointer of the register used for locking spin
> lock. But the active_spin_lock_id also needs to be compared to ensure
> whether bpf_spin_unlock is for the same register.
> 
> Next, pseudo load instructions are not given a unique reg->id, as they
> are doing lookup for the same map value (max_entries is never greater
> than 1).
> 
> Essentially, we consider that the tuple of (active_spin_lock_ptr,
> active_spin_lock_id) will always be unique for any kind of argument to
> bpf_spin_{lock,unlock}.
> 
> Note that this can be extended in the future to also remember offset
> used for locking, so that we can introduce multiple bpf_spin_lock fields
> in the same allocation.
> 
> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
> ---
>  include/linux/bpf_verifier.h |  3 ++-
>  kernel/bpf/verifier.c        | 39 +++++++++++++++++++++++++-----------
>  2 files changed, 29 insertions(+), 13 deletions(-)
> 
> diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
> index 1a32baa78ce2..bb71c59f21f6 100644
> --- a/include/linux/bpf_verifier.h
> +++ b/include/linux/bpf_verifier.h
> @@ -323,7 +323,8 @@ struct bpf_verifier_state {
>  	u32 branches;
>  	u32 insn_idx;
>  	u32 curframe;
> -	u32 active_spin_lock;
> +	void *active_spin_lock_ptr;
> +	u32 active_spin_lock_id;
>  	bool speculative;
Back in first RFC of this series we talked about turning this "spin lock
identity" concept into a proper struct [0]. But to save you the click:

Dave:
"""
It would be good to make this "(lock_ptr, lock_id) is identifier for lock"
concept more concrete by grouping these fields in a struct w/ type enum + union,
or something similar. Will make it more obvious that they should be used / set
together.

But if you'd prefer to keep it as two fields, active_spin_lock_ptr is a
confusing name. In the future with no context as to what that field is, I'd
assume that it holds a pointer to a spin_lock instead of a "spin lock identity
pointer".
"""

Kumar: 
"""
That's a good point.

I'm thinking
struct active_lock {
  void *id_ptr;
  u32 offset;
  u32 reg_id;
};
How does that look?
"""

I didn't get back to you, but I think that looks reasonable, and "this can be
extended in the future to also remember offset used for locking" in this
patch summary supports the desire to group up those fields. (I agree that
offset isn't necessary for now, though).

  [0]: https://lore.kernel.org/bpf/311eb0d0-777a-4240-9fa0-59134344f051@fb.com/

Re: [PATCH bpf-next v4 06/24] bpf: Refactor kptr_off_tab into btf_record

[Alexei Starovoitov]

On Fri, Nov 04, 2022 at 12:39:55AM +0530, Kumar Kartikeya Dwivedi wrote:
>  		else
> @@ -311,11 +344,12 @@ static inline void __copy_map_value(struct bpf_map *map, void *dst, void *src, b
>  		return;
>  	}
>  
> -	for (i = 0; i < map->off_arr->cnt; i++) {
> -		u32 next_off = map->off_arr->field_off[i];
> +	for (i = 0; i < map->field_offs->cnt; i++) {
> +		u32 next_off = map->field_offs->field_off[i];
> +		u32 sz = next_off - curr_off;
>  
> -		memcpy(dst + curr_off, src + curr_off, next_off - curr_off);
> -		curr_off += map->off_arr->field_sz[i];
> +		memcpy(dst + curr_off, src + curr_off, sz);
> +		curr_off += map->field_offs->field_sz[i] + sz;

This is a clear bug. The kernel is crashing with this change.
How did you test this?

>  	}
>  	memcpy(dst + curr_off, src + curr_off, map->value_size - curr_off);
>  }
> @@ -335,16 +369,17 @@ static inline void zero_map_value(struct bpf_map *map, void *dst)
>  	u32 curr_off = 0;
>  	int i;
>  
> -	if (likely(!map->off_arr)) {
> +	if (likely(!map->field_offs)) {
>  		memset(dst, 0, map->value_size);
>  		return;
>  	}
>  
> -	for (i = 0; i < map->off_arr->cnt; i++) {
> -		u32 next_off = map->off_arr->field_off[i];
> +	for (i = 0; i < map->field_offs->cnt; i++) {
> +		u32 next_off = map->field_offs->field_off[i];
> +		u32 sz = next_off - curr_off;
>  
> -		memset(dst + curr_off, 0, next_off - curr_off);
> -		curr_off += map->off_arr->field_sz[i];
> +		memset(dst + curr_off, 0, sz);
> +		curr_off += map->field_offs->field_sz[i] + sz;

same thing

Re: [PATCH bpf-next v4 06/24] bpf: Refactor kptr_off_tab into btf_record

[Alexei Starovoitov]

On Fri, Nov 04, 2022 at 12:39:55AM +0530, Kumar Kartikeya Dwivedi wrote:
> -
> -	for (i = 0; i < nr_off; i++) {
> +	rec->cnt = 0;
> +	for (i = 0; i < cnt; i++) {
>  		const struct btf_type *t;
>  		s32 id;
>  
> @@ -3500,28 +3499,24 @@ struct bpf_map_value_off *btf_parse_kptrs(const struct btf *btf,
>  				ret = -EINVAL;
>  				goto end_mod;
>  			}
> -			tab->off[i].kptr.dtor = (void *)addr;
> +			rec->fields[i].kptr.dtor = (void *)addr;
>  		}
>  
> -		tab->off[i].offset = info_arr[i].off;
> -		tab->off[i].type = info_arr[i].type;
> -		tab->off[i].kptr.btf_id = id;
> -		tab->off[i].kptr.btf = kernel_btf;
> -		tab->off[i].kptr.module = mod;
> +		rec->fields[i].offset = info_arr[i].off;
> +		rec->fields[i].type = info_arr[i].type;
> +		rec->fields[i].kptr.btf_id = id;
> +		rec->fields[i].kptr.btf = kernel_btf;
> +		rec->fields[i].kptr.module = mod;
> +		rec->cnt++;
>  	}
> -	tab->nr_off = nr_off;
> -	return tab;
> +	rec->cnt = cnt;
> +	return rec;

This is weird. You also undo this assignment in the next patch.
What is the point of rec->cnt = 0;
followed by rec->cnt++
just to be overwritten with rec->cnt = cnt;
??

Re: [PATCH bpf-next v4 06/24] bpf: Refactor kptr_off_tab into btf_record

[Alexei Starovoitov]

On Fri, Nov 04, 2022 at 12:39:55AM +0530, Kumar Kartikeya Dwivedi wrote:
>  
> -enum bpf_kptr_type {
> -	BPF_KPTR_UNREF,
> -	BPF_KPTR_REF,
> +enum btf_field_type {
> +	BPF_KPTR_UNREF = (1 << 2),
> +	BPF_KPTR_REF   = (1 << 3),
> +	BPF_KPTR       = BPF_KPTR_UNREF | BPF_KPTR_REF,
>  };

...

> +		for (i = 0; i < sizeof(map->record->field_mask) * 8; i++) {
> +			switch (map->record->field_mask & (1 << i)) {
> +			case 0:
> +				continue;
> +			case BPF_KPTR_UNREF:
> +			case BPF_KPTR_REF:
> +				if (map->map_type != BPF_MAP_TYPE_HASH &&
> +				    map->map_type != BPF_MAP_TYPE_LRU_HASH &&
> +				    map->map_type != BPF_MAP_TYPE_ARRAY &&
> +				    map->map_type != BPF_MAP_TYPE_PERCPU_ARRAY) {
> +					ret = -EOPNOTSUPP;
> +					goto free_map_tab;
> +				}
> +				break;
> +			default:
> +				/* Fail if map_type checks are missing for a field type */
> +				ret = -EOPNOTSUPP;
> +				goto free_map_tab;
> +			}

With this patch alone this is also wrong.
And it breaks bisect.
Please make sure to do a full vmtest.sh for every patch in the series.

Re: [PATCH bpf-next v4 06/24] bpf: Refactor kptr_off_tab into btf_record

[Alexei Starovoitov]

On Thu, Nov 3, 2022 at 9:01 PM Alexei Starovoitov
<alexei.starovoitov@gmail.com> wrote:
>
> On Fri, Nov 04, 2022 at 12:39:55AM +0530, Kumar Kartikeya Dwivedi wrote:
> >
> > -enum bpf_kptr_type {
> > -     BPF_KPTR_UNREF,
> > -     BPF_KPTR_REF,
> > +enum btf_field_type {
> > +     BPF_KPTR_UNREF = (1 << 2),
> > +     BPF_KPTR_REF   = (1 << 3),
> > +     BPF_KPTR       = BPF_KPTR_UNREF | BPF_KPTR_REF,
> >  };
>
> ...
>
> > +             for (i = 0; i < sizeof(map->record->field_mask) * 8; i++) {
> > +                     switch (map->record->field_mask & (1 << i)) {
> > +                     case 0:
> > +                             continue;
> > +                     case BPF_KPTR_UNREF:
> > +                     case BPF_KPTR_REF:
> > +                             if (map->map_type != BPF_MAP_TYPE_HASH &&
> > +                                 map->map_type != BPF_MAP_TYPE_LRU_HASH &&
> > +                                 map->map_type != BPF_MAP_TYPE_ARRAY &&
> > +                                 map->map_type != BPF_MAP_TYPE_PERCPU_ARRAY) {
> > +                                     ret = -EOPNOTSUPP;
> > +                                     goto free_map_tab;
> > +                             }
> > +                             break;
> > +                     default:
> > +                             /* Fail if map_type checks are missing for a field type */
> > +                             ret = -EOPNOTSUPP;
> > +                             goto free_map_tab;
> > +                     }
>
> With this patch alone this is also wrong.

Actually this bit is probably fine. The bug is elsewhere.

The point below stands:


> And it breaks bisect.
> Please make sure to do a full vmtest.sh for every patch in the series.

Re: [PATCH bpf-next v4 07/24] bpf: Consolidate spin_lock, timer management into btf_record

[Alexei Starovoitov]

On Thu, Nov 3, 2022 at 12:11 PM Kumar Kartikeya Dwivedi
<memxor@gmail.com> wrote:
> +               rec->field_mask |= info_arr[i].type;
>                 rec->fields[i].offset = info_arr[i].off;
>                 rec->fields[i].type = info_arr[i].type;

I spent an hour to figure out that this hunk should have been
in the previous commit. Sigh.

Anyway, I fixed all the bugs I found in the patch 6 and
pushed the first 6 patches, since we really need to
make progress here quickly.
Too many people are waiting on this set.

Re: [PATCH bpf-next v4 00/24] Local kptrs, BPF linked lists

[patchwork-bot+netdevbpf]

Hello:

This series was applied to bpf/bpf-next.git (master)
by Alexei Starovoitov <ast@kernel.org>:

On Fri,  4 Nov 2022 00:39:49 +0530 you wrote:
> This series introduces user defined BPF objects, by introducing the idea
> of local kptrs. These are kptrs (strongly typed pointers) that refer to
> objects of a user defined type, hence called "local" kptrs. This allows
> BPF programs to allocate their own objects, build their own object
> hierarchies, and use the basic building blocks provided by BPF runtime
> to build their own data structures flexibly.
> 
> [...]

Here is the summary with links:
  - [bpf-next,v4,01/24] bpf: Document UAPI details for special BPF types
    https://git.kernel.org/bpf/bpf-next/c/9805af8d8a5b
  - [bpf-next,v4,02/24] bpf: Allow specifying volatile type modifier for kptrs
    https://git.kernel.org/bpf/bpf-next/c/23da464dd6b8
  - [bpf-next,v4,03/24] bpf: Clobber stack slot when writing over spilled PTR_TO_BTF_ID
    https://git.kernel.org/bpf/bpf-next/c/261f4664caff
  - [bpf-next,v4,04/24] bpf: Fix slot type check in check_stack_write_var_off
    https://git.kernel.org/bpf/bpf-next/c/f5e477a861e4
  - [bpf-next,v4,05/24] bpf: Drop reg_type_may_be_refcounted_or_null
    https://git.kernel.org/bpf/bpf-next/c/a28ace782e68
  - [bpf-next,v4,06/24] bpf: Refactor kptr_off_tab into btf_record
    https://git.kernel.org/bpf/bpf-next/c/aa3496accc41
  - [bpf-next,v4,07/24] bpf: Consolidate spin_lock, timer management into btf_record
    (no matching commit)
  - [bpf-next,v4,08/24] bpf: Refactor map->off_arr handling
    (no matching commit)
  - [bpf-next,v4,09/24] bpf: Support bpf_list_head in map values
    (no matching commit)
  - [bpf-next,v4,10/24] bpf: Introduce local kptrs
    (no matching commit)
  - [bpf-next,v4,11/24] bpf: Recognize bpf_{spin_lock,list_head,list_node} in local kptrs
    (no matching commit)
  - [bpf-next,v4,12/24] bpf: Verify ownership relationships for user BTF types
    (no matching commit)
  - [bpf-next,v4,13/24] bpf: Support locking bpf_spin_lock in local kptr
    (no matching commit)
  - [bpf-next,v4,14/24] bpf: Allow locking bpf_spin_lock global variables
    (no matching commit)
  - [bpf-next,v4,15/24] bpf: Rewrite kfunc argument handling
    (no matching commit)
  - [bpf-next,v4,16/24] bpf: Drop kfunc bits from btf_check_func_arg_match
    (no matching commit)
  - [bpf-next,v4,17/24] bpf: Support constant scalar arguments for kfuncs
    (no matching commit)
  - [bpf-next,v4,18/24] bpf: Teach verifier about non-size constant arguments
    (no matching commit)
  - [bpf-next,v4,19/24] bpf: Introduce bpf_obj_new
    (no matching commit)
  - [bpf-next,v4,20/24] bpf: Introduce bpf_obj_drop
    (no matching commit)
  - [bpf-next,v4,21/24] bpf: Permit NULL checking pointer with non-zero fixed offset
    (no matching commit)
  - [bpf-next,v4,22/24] bpf: Introduce single ownership BPF linked list API
    (no matching commit)
  - [bpf-next,v4,23/24] selftests/bpf: Add __contains macro to bpf_experimental.h
    (no matching commit)
  - [bpf-next,v4,24/24] selftests/bpf: Add BPF linked list API tests
    (no matching commit)

You are awesome, thank you!
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Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html

Re: [PATCH bpf-next v4 07/24] bpf: Consolidate spin_lock, timer management into btf_record

[Alexei Starovoitov]

On Thu, Nov 3, 2022 at 12:11 PM Kumar Kartikeya Dwivedi
<memxor@gmail.com> wrote:
>  static int bpf_map_alloc_off_arr(struct bpf_map *map)
>  {
> -       bool has_spin_lock = map_value_has_spin_lock(map);
> -       bool has_timer = map_value_has_timer(map);
>         bool has_fields = !IS_ERR_OR_NULL(map);
>         struct btf_field_offs *fo;
> -       u32 i;
> +       struct btf_record *rec;
> +       u32 i, *off;
> +       u8 *sz;
>
> -       if (!has_spin_lock && !has_timer && !has_fields) {
> +       if (!has_fields) {
>                 map->field_offs = NULL;
>                 return 0;
>         }
> @@ -970,32 +987,14 @@ static int bpf_map_alloc_off_arr(struct bpf_map *map)
>                 return -ENOMEM;
>         map->field_offs = fo;
>
> -       fo->cnt = 0;
> -       if (has_spin_lock) {
> -               i = fo->cnt;
> -
> -               fo->field_off[i] = map->spin_lock_off;
> -               fo->field_sz[i] = sizeof(struct bpf_spin_lock);
> -               fo->cnt++;
> -       }
> -       if (has_timer) {
> -               i = fo->cnt;
> -
> -               fo->field_off[i] = map->timer_off;
> -               fo->field_sz[i] = sizeof(struct bpf_timer);
> -               fo->cnt++;
> -       }
> -       if (has_fields) {
> -               struct btf_record *rec = map->record;
> -               u32 *off = &fo->field_off[fo->cnt];
> -               u8 *sz = &fo->field_sz[fo->cnt];
> -
> -               for (i = 0; i < rec->cnt; i++) {
> -                       *off++ = rec->fields[i].offset;
> -                       *sz++ = btf_field_type_size(rec->fields[i].type);
> -               }
> -               fo->cnt += rec->cnt;
> +       rec = map->record;
> +       off = &fo->field_off[fo->cnt];
> +       sz = &fo->field_sz[fo->cnt];

Another bug that would have been obvious if you run any tests.
(fo->cnt contains garbage)

I'm surprised by the amount of issues in the series.

> +       for (i = 0; i < rec->cnt; i++) {
> +               *off++ = rec->fields[i].offset;
> +               *sz++ = btf_field_type_size(rec->fields[i].type);
>         }

Anyway, pushed this patch as well after fixing this bug.

Re: [PATCH bpf-next v4 00/24] Local kptrs, BPF linked lists

[patchwork-bot+netdevbpf]

Hello:

This series was applied to bpf/bpf-next.git (master)
by Alexei Starovoitov <ast@kernel.org>:

On Fri,  4 Nov 2022 00:39:49 +0530 you wrote:
> This series introduces user defined BPF objects, by introducing the idea
> of local kptrs. These are kptrs (strongly typed pointers) that refer to
> objects of a user defined type, hence called "local" kptrs. This allows
> BPF programs to allocate their own objects, build their own object
> hierarchies, and use the basic building blocks provided by BPF runtime
> to build their own data structures flexibly.
> 
> [...]

Here is the summary with links:
  - [bpf-next,v4,01/24] bpf: Document UAPI details for special BPF types
    (no matching commit)
  - [bpf-next,v4,02/24] bpf: Allow specifying volatile type modifier for kptrs
    (no matching commit)
  - [bpf-next,v4,03/24] bpf: Clobber stack slot when writing over spilled PTR_TO_BTF_ID
    (no matching commit)
  - [bpf-next,v4,04/24] bpf: Fix slot type check in check_stack_write_var_off
    (no matching commit)
  - [bpf-next,v4,05/24] bpf: Drop reg_type_may_be_refcounted_or_null
    (no matching commit)
  - [bpf-next,v4,06/24] bpf: Refactor kptr_off_tab into btf_record
    (no matching commit)
  - [bpf-next,v4,07/24] bpf: Consolidate spin_lock, timer management into btf_record
    https://git.kernel.org/bpf/bpf-next/c/db559117828d
  - [bpf-next,v4,08/24] bpf: Refactor map->off_arr handling
    (no matching commit)
  - [bpf-next,v4,09/24] bpf: Support bpf_list_head in map values
    (no matching commit)
  - [bpf-next,v4,10/24] bpf: Introduce local kptrs
    (no matching commit)
  - [bpf-next,v4,11/24] bpf: Recognize bpf_{spin_lock,list_head,list_node} in local kptrs
    (no matching commit)
  - [bpf-next,v4,12/24] bpf: Verify ownership relationships for user BTF types
    (no matching commit)
  - [bpf-next,v4,13/24] bpf: Support locking bpf_spin_lock in local kptr
    (no matching commit)
  - [bpf-next,v4,14/24] bpf: Allow locking bpf_spin_lock global variables
    (no matching commit)
  - [bpf-next,v4,15/24] bpf: Rewrite kfunc argument handling
    (no matching commit)
  - [bpf-next,v4,16/24] bpf: Drop kfunc bits from btf_check_func_arg_match
    (no matching commit)
  - [bpf-next,v4,17/24] bpf: Support constant scalar arguments for kfuncs
    (no matching commit)
  - [bpf-next,v4,18/24] bpf: Teach verifier about non-size constant arguments
    (no matching commit)
  - [bpf-next,v4,19/24] bpf: Introduce bpf_obj_new
    (no matching commit)
  - [bpf-next,v4,20/24] bpf: Introduce bpf_obj_drop
    (no matching commit)
  - [bpf-next,v4,21/24] bpf: Permit NULL checking pointer with non-zero fixed offset
    (no matching commit)
  - [bpf-next,v4,22/24] bpf: Introduce single ownership BPF linked list API
    (no matching commit)
  - [bpf-next,v4,23/24] selftests/bpf: Add __contains macro to bpf_experimental.h
    (no matching commit)
  - [bpf-next,v4,24/24] selftests/bpf: Add BPF linked list API tests
    (no matching commit)

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
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Re: [PATCH bpf-next v4 22/24] bpf: Introduce single ownership BPF linked list API

[Dave Marchevsky]

On 11/3/22 3:10 PM, Kumar Kartikeya Dwivedi wrote:
> Add a linked list API for use in BPF programs, where it expects
> protection from the bpf_spin_lock in the same allocation as the
> bpf_list_head. Future patches will extend the same infrastructure to
> have different flavors with varying protection domains and visibility
> (e.g. percpu variant with local_t protection, usable in NMI progs).
> 
> The following functions are added to kick things off:
> 
> bpf_list_push_front
> bpf_list_push_back
> bpf_list_pop_front
> bpf_list_pop_back
> 
> The lock protecting the bpf_list_head needs to be taken for all
> operations.
> 
> Once a node has been added to the list, it's pointer changes to
> PTR_UNTRUSTED. However, it is only released once the lock protecting the
> list is unlocked. For such local kptrs with PTR_UNTRUSTED set but an
> active ref_obj_id, it is still permitted to read and write to them as
> long as the lock is held.

I think "still permitted to ... write to them" is not accurate
for this version of the series. In v2 you mentioned [0]:

"""
I have switched things a bit to disallow stores, which is a bug right now in
this set, because one can do this:

push_front(head, &p->node);
p2 = container_of(pop_front(head));
// p2 == p
bpf_obj_drop(p2);
p->data = ...;

One can always fully initialize the object _before_ inserting it into the list,
in some cases that will be the requirement (like adding to RCU protected lists)
for correctness.
"""

I confirmed this is currently the case by moving data write after
list_push in the selftest and running it:

@@ -87,8 +87,8 @@ static __always_inline int list_push_pop(struct bpf_spin_lock *lock,
        }

        bpf_spin_lock(lock);
-       f->data = 13;
        bpf_list_push_front(head, &f->node);
+       f->data = 13;
        bpf_spin_unlock(lock);

Got "only read is supported" from verifier.
I think it's fine to punt on supporting writes for now and do it in followups.

  [0]: https://lore.kernel.org/bpf/20221025190033.bqjr7466o7pdd3wo@apollo/

> 
> bpf_list_pop_front and bpf_list_pop_back delete the first or last item
> of the list respectively, and return pointer to the element at the
> list_node offset. The user can then use container_of style macro to get
> the actual entry type. The verifier however statically knows the actual
> type, so the safety properties are still preserved.
> 
> With these additions, programs can now manage their own linked lists and
> store their objects in them.
> 
> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
> ---

[...]

will comment on rest of patch in separate msg

Re: [PATCH bpf-next v4 10/24] bpf: Introduce local kptrs

[Alexei Starovoitov]

On Thu, Nov 3, 2022 at 12:11 PM Kumar Kartikeya Dwivedi
<memxor@gmail.com> wrote:
>
> Introduce local kptrs, i.e. PTR_TO_BTF_ID that point to a type in
> program BTF. This is indicated by the presence of MEM_TYPE_LOCAL type
> tag in reg->type to avoid having to check btf_is_kernel when trying to
> match argument types in helpers.
...
>
> +       /* MEM is of a type from program BTF, not kernel BTF. This is used to
> +        * tag PTR_TO_BTF_ID allocated using bpf_kptr_alloc.
> +        */
> +       MEM_TYPE_LOCAL          = BIT(11 + BPF_BASE_TYPE_BITS),
> +

I know we have bpf_core_type_id_local.
It sort-of makes sense in the context of the program.
type_id_local -> inside the program
type_id_kernel -> kernel

but in the context of the verifier "local kptr" doesn't read right.
Especially in MEM_TYPE_LOCAL.

Also, since it applies to PTR_TO_BTF_ID, should it prefix with PTR_?
Probably MEM_ is actually cleaner.
And we're not consistent already with MEM_PERCPU.
We can live with this inconsistency for now.

So how about we rename MEM_ALLOC to MEM_RINGBUF,
since it's special bpf_ringbuf_reserve() memory
and use MEM_ALLOC to indicate the memory that came from bpf_obj_new ?

... which made me realize that the comment above should
s/bpf_kptr_alloc/bpf_obj_new/

Re: [PATCH bpf-next v4 00/24] Local kptrs, BPF linked lists

[patchwork-bot+netdevbpf]

Hello:

This series was applied to bpf/bpf-next.git (master)
by Alexei Starovoitov <ast@kernel.org>:

On Fri,  4 Nov 2022 00:39:49 +0530 you wrote:
> This series introduces user defined BPF objects, by introducing the idea
> of local kptrs. These are kptrs (strongly typed pointers) that refer to
> objects of a user defined type, hence called "local" kptrs. This allows
> BPF programs to allocate their own objects, build their own object
> hierarchies, and use the basic building blocks provided by BPF runtime
> to build their own data structures flexibly.
> 
> [...]

Here is the summary with links:
  - [bpf-next,v4,01/24] bpf: Document UAPI details for special BPF types
    (no matching commit)
  - [bpf-next,v4,02/24] bpf: Allow specifying volatile type modifier for kptrs
    (no matching commit)
  - [bpf-next,v4,03/24] bpf: Clobber stack slot when writing over spilled PTR_TO_BTF_ID
    (no matching commit)
  - [bpf-next,v4,04/24] bpf: Fix slot type check in check_stack_write_var_off
    (no matching commit)
  - [bpf-next,v4,05/24] bpf: Drop reg_type_may_be_refcounted_or_null
    (no matching commit)
  - [bpf-next,v4,06/24] bpf: Refactor kptr_off_tab into btf_record
    (no matching commit)
  - [bpf-next,v4,07/24] bpf: Consolidate spin_lock, timer management into btf_record
    (no matching commit)
  - [bpf-next,v4,08/24] bpf: Refactor map->off_arr handling
    https://git.kernel.org/bpf/bpf-next/c/f71b2f64177a
  - [bpf-next,v4,09/24] bpf: Support bpf_list_head in map values
    (no matching commit)
  - [bpf-next,v4,10/24] bpf: Introduce local kptrs
    (no matching commit)
  - [bpf-next,v4,11/24] bpf: Recognize bpf_{spin_lock,list_head,list_node} in local kptrs
    (no matching commit)
  - [bpf-next,v4,12/24] bpf: Verify ownership relationships for user BTF types
    (no matching commit)
  - [bpf-next,v4,13/24] bpf: Support locking bpf_spin_lock in local kptr
    (no matching commit)
  - [bpf-next,v4,14/24] bpf: Allow locking bpf_spin_lock global variables
    (no matching commit)
  - [bpf-next,v4,15/24] bpf: Rewrite kfunc argument handling
    (no matching commit)
  - [bpf-next,v4,16/24] bpf: Drop kfunc bits from btf_check_func_arg_match
    (no matching commit)
  - [bpf-next,v4,17/24] bpf: Support constant scalar arguments for kfuncs
    (no matching commit)
  - [bpf-next,v4,18/24] bpf: Teach verifier about non-size constant arguments
    (no matching commit)
  - [bpf-next,v4,19/24] bpf: Introduce bpf_obj_new
    (no matching commit)
  - [bpf-next,v4,20/24] bpf: Introduce bpf_obj_drop
    (no matching commit)
  - [bpf-next,v4,21/24] bpf: Permit NULL checking pointer with non-zero fixed offset
    (no matching commit)
  - [bpf-next,v4,22/24] bpf: Introduce single ownership BPF linked list API
    (no matching commit)
  - [bpf-next,v4,23/24] selftests/bpf: Add __contains macro to bpf_experimental.h
    (no matching commit)
  - [bpf-next,v4,24/24] selftests/bpf: Add BPF linked list API tests
    (no matching commit)

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html

Re: [PATCH bpf-next v4 07/24] bpf: Consolidate spin_lock, timer management into btf_record

[Kumar Kartikeya Dwivedi]

On Fri, Nov 04, 2022 at 11:00:11AM IST, Alexei Starovoitov wrote:
> On Thu, Nov 3, 2022 at 12:11 PM Kumar Kartikeya Dwivedi
> <memxor@gmail.com> wrote:
> >  static int bpf_map_alloc_off_arr(struct bpf_map *map)
> >  {
> > -       bool has_spin_lock = map_value_has_spin_lock(map);
> > -       bool has_timer = map_value_has_timer(map);
> >         bool has_fields = !IS_ERR_OR_NULL(map);
> >         struct btf_field_offs *fo;
> > -       u32 i;
> > +       struct btf_record *rec;
> > +       u32 i, *off;
> > +       u8 *sz;
> >
> > -       if (!has_spin_lock && !has_timer && !has_fields) {
> > +       if (!has_fields) {
> >                 map->field_offs = NULL;
> >                 return 0;
> >         }
> > @@ -970,32 +987,14 @@ static int bpf_map_alloc_off_arr(struct bpf_map *map)
> >                 return -ENOMEM;
> >         map->field_offs = fo;
> >
> > -       fo->cnt = 0;
> > -       if (has_spin_lock) {
> > -               i = fo->cnt;
> > -
> > -               fo->field_off[i] = map->spin_lock_off;
> > -               fo->field_sz[i] = sizeof(struct bpf_spin_lock);
> > -               fo->cnt++;
> > -       }
> > -       if (has_timer) {
> > -               i = fo->cnt;
> > -
> > -               fo->field_off[i] = map->timer_off;
> > -               fo->field_sz[i] = sizeof(struct bpf_timer);
> > -               fo->cnt++;
> > -       }
> > -       if (has_fields) {
> > -               struct btf_record *rec = map->record;
> > -               u32 *off = &fo->field_off[fo->cnt];
> > -               u8 *sz = &fo->field_sz[fo->cnt];
> > -
> > -               for (i = 0; i < rec->cnt; i++) {
> > -                       *off++ = rec->fields[i].offset;
> > -                       *sz++ = btf_field_type_size(rec->fields[i].type);
> > -               }
> > -               fo->cnt += rec->cnt;
> > +       rec = map->record;
> > +       off = &fo->field_off[fo->cnt];
> > +       sz = &fo->field_sz[fo->cnt];
>
> Another bug that would have been obvious if you run any tests.
> (fo->cnt contains garbage)
>
> I'm surprised by the amount of issues in the series.
>

It's my bad, I deleted what was fo->cnt very recently and didn't give this a run
again, without realizing it's only the next patch that does kmalloc -> kzalloc.

Re: [PATCH bpf-next v4 07/24] bpf: Consolidate spin_lock, timer management into btf_record

[Kumar Kartikeya Dwivedi]

On Fri, Nov 04, 2022 at 12:13:45PM IST, Kumar Kartikeya Dwivedi wrote:
> On Fri, Nov 04, 2022 at 11:00:11AM IST, Alexei Starovoitov wrote:
> > On Thu, Nov 3, 2022 at 12:11 PM Kumar Kartikeya Dwivedi
> > <memxor@gmail.com> wrote:
> > >  static int bpf_map_alloc_off_arr(struct bpf_map *map)
> > >  {
> > > -       bool has_spin_lock = map_value_has_spin_lock(map);
> > > -       bool has_timer = map_value_has_timer(map);
> > >         bool has_fields = !IS_ERR_OR_NULL(map);
> > >         struct btf_field_offs *fo;
> > > -       u32 i;
> > > +       struct btf_record *rec;
> > > +       u32 i, *off;
> > > +       u8 *sz;
> > >
> > > -       if (!has_spin_lock && !has_timer && !has_fields) {
> > > +       if (!has_fields) {
> > >                 map->field_offs = NULL;
> > >                 return 0;
> > >         }
> > > @@ -970,32 +987,14 @@ static int bpf_map_alloc_off_arr(struct bpf_map *map)
> > >                 return -ENOMEM;
> > >         map->field_offs = fo;
> > >
> > > -       fo->cnt = 0;
> > > -       if (has_spin_lock) {
> > > -               i = fo->cnt;
> > > -
> > > -               fo->field_off[i] = map->spin_lock_off;
> > > -               fo->field_sz[i] = sizeof(struct bpf_spin_lock);
> > > -               fo->cnt++;
> > > -       }
> > > -       if (has_timer) {
> > > -               i = fo->cnt;
> > > -
> > > -               fo->field_off[i] = map->timer_off;
> > > -               fo->field_sz[i] = sizeof(struct bpf_timer);
> > > -               fo->cnt++;
> > > -       }
> > > -       if (has_fields) {
> > > -               struct btf_record *rec = map->record;
> > > -               u32 *off = &fo->field_off[fo->cnt];
> > > -               u8 *sz = &fo->field_sz[fo->cnt];
> > > -
> > > -               for (i = 0; i < rec->cnt; i++) {
> > > -                       *off++ = rec->fields[i].offset;
> > > -                       *sz++ = btf_field_type_size(rec->fields[i].type);
> > > -               }
> > > -               fo->cnt += rec->cnt;
> > > +       rec = map->record;
> > > +       off = &fo->field_off[fo->cnt];
> > > +       sz = &fo->field_sz[fo->cnt];
> >
> > Another bug that would have been obvious if you run any tests.
> > (fo->cnt contains garbage)
> >
> > I'm surprised by the amount of issues in the series.
> >
>
> It's my bad, I deleted what was fo->cnt very recently and didn't give this a run

deleted

> > > -       fo->cnt = 0;

Re: [PATCH bpf-next v4 06/24] bpf: Refactor kptr_off_tab into btf_record

[Kumar Kartikeya Dwivedi]

On Fri, Nov 04, 2022 at 08:30:28AM IST, Alexei Starovoitov wrote:
> On Fri, Nov 04, 2022 at 12:39:55AM +0530, Kumar Kartikeya Dwivedi wrote:
> >  		else
> > @@ -311,11 +344,12 @@ static inline void __copy_map_value(struct bpf_map *map, void *dst, void *src, b
> >  		return;
> >  	}
> >
> > -	for (i = 0; i < map->off_arr->cnt; i++) {
> > -		u32 next_off = map->off_arr->field_off[i];
> > +	for (i = 0; i < map->field_offs->cnt; i++) {
> > +		u32 next_off = map->field_offs->field_off[i];
> > +		u32 sz = next_off - curr_off;
> >
> > -		memcpy(dst + curr_off, src + curr_off, next_off - curr_off);
> > -		curr_off += map->off_arr->field_sz[i];
> > +		memcpy(dst + curr_off, src + curr_off, sz);
> > +		curr_off += map->field_offs->field_sz[i] + sz;
>
> This is a clear bug. The kernel is crashing with this change.
> How did you test this?
>

For me it is crashing at bpf-next now without this.

When for map value with size 48, having fields at:
off: 0, 16, 32
sz:  4, 16, 16

The above produces:

memcpy(dst + 0, src + 0, 0)
memcpy(dst + 4, src + 4, 12)
memcpy(dst + 32, src + 32, 0)
memcpy(dst + 48, src + 48, 0)

Without it, it becomes:

memcpy(dst + 0, src + 0, 0)
memcpy(dst + 4, src + 4, 12)
memcpy(dst + 20, src + 20, 12)
memcpy(dst + 36, src + 36, 12)

I will send a follow up fix.

> >  	}
> >  	memcpy(dst + curr_off, src + curr_off, map->value_size - curr_off);
> >  }
> > @@ -335,16 +369,17 @@ static inline void zero_map_value(struct bpf_map *map, void *dst)
> >  	u32 curr_off = 0;
> >  	int i;
> >
> > -	if (likely(!map->off_arr)) {
> > +	if (likely(!map->field_offs)) {
> >  		memset(dst, 0, map->value_size);
> >  		return;
> >  	}
> >
> > -	for (i = 0; i < map->off_arr->cnt; i++) {
> > -		u32 next_off = map->off_arr->field_off[i];
> > +	for (i = 0; i < map->field_offs->cnt; i++) {
> > +		u32 next_off = map->field_offs->field_off[i];
> > +		u32 sz = next_off - curr_off;
> >
> > -		memset(dst + curr_off, 0, next_off - curr_off);
> > -		curr_off += map->off_arr->field_sz[i];
> > +		memset(dst + curr_off, 0, sz);
> > +		curr_off += map->field_offs->field_sz[i] + sz;
>
> same thing

Re: [PATCH bpf-next v4 24/24] selftests/bpf: Add BPF linked list API tests

[Dave Marchevsky]

On 11/3/22 3:10 PM, Kumar Kartikeya Dwivedi wrote:
> Include various tests covering the success and failure cases. Also, run
> the success cases at runtime to verify correctness of linked list
> manipulation routines, in addition to ensuring successful verification.
> 
> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
> ---

[...]

> diff --git a/tools/testing/selftests/bpf/progs/linked_list.c b/tools/testing/selftests/bpf/progs/linked_list.c
> new file mode 100644
> index 000000000000..eed0b2c1eb4a
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/linked_list.c
> @@ -0,0 +1,330 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#include <vmlinux.h>
> +#include <bpf/bpf_tracing.h>
> +#include <bpf/bpf_helpers.h>
> +#include <bpf/bpf_core_read.h>
> +#include "bpf_experimental.h"
> +
> +#ifndef ARRAY_SIZE
> +#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
> +#endif
> +
> +struct bar {
> +	struct bpf_list_node node;
> +	int data;
> +};
> +
> +struct foo {
> +	struct bpf_list_node node;
> +	struct bpf_list_head head __contains(bar, node);
> +	struct bpf_spin_lock lock;
> +	int data;
> +};
> +
> +struct map_value {
> +	struct bpf_list_head head __contains(foo, node);
> +	struct bpf_spin_lock lock;
> +	int data;
> +};
> +
> +struct array_map {
> +	__uint(type, BPF_MAP_TYPE_ARRAY);
> +	__type(key, int);
> +	__type(value, struct map_value);
> +	__uint(max_entries, 1);
> +} array_map SEC(".maps");
> +
> +#define private(name) SEC(".data." #name) __hidden __attribute__((aligned(8)))

This __attribute__((aligned(8))) causes my clang to fail to build this selftest.
It fails with:

  fatal error: error in backend: unable to write nop sequence of 4 bytes

Tracked it down to llvm/lib/Target/BPF/MCTargetDesc/BPFAsmBackend.cpp:

  bool BPFAsmBackend::writeNopData(raw_ostream &OS, uint64_t Count,
                                   const MCSubtargetInfo *STI) const {
    if ((Count % 8) != 0)
      return false;

Presumably since ".data.A" section is PROGBITS the compiler tries to write
4 bytes of nop before / between the variables, but fails.

I'm using a clang built off of a very recent LLVM commit [0]. David Vernet
was able to successfully build the selftests with a clang built from
late August's tree, so maybe it's my clang version or some other toolchain
issue. Which clang did you use to build this?

[0]: github.com/llvm/llvm-project/commit/2a827e4a988b614bc6f70abe00308ceeb50dcd0a

Re: [PATCH bpf-next v4 24/24] selftests/bpf: Add BPF linked list API tests

[Kumar Kartikeya Dwivedi]

On Fri, Nov 04, 2022 at 12:33:46PM IST, Dave Marchevsky wrote:
> On 11/3/22 3:10 PM, Kumar Kartikeya Dwivedi wrote:
> > Include various tests covering the success and failure cases. Also, run
> > the success cases at runtime to verify correctness of linked list
> > manipulation routines, in addition to ensuring successful verification.
> >
> > Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
> > ---
>
> [...]
>
> > diff --git a/tools/testing/selftests/bpf/progs/linked_list.c b/tools/testing/selftests/bpf/progs/linked_list.c
> > new file mode 100644
> > index 000000000000..eed0b2c1eb4a
> > --- /dev/null
> > +++ b/tools/testing/selftests/bpf/progs/linked_list.c
> > @@ -0,0 +1,330 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +#include <vmlinux.h>
> > +#include <bpf/bpf_tracing.h>
> > +#include <bpf/bpf_helpers.h>
> > +#include <bpf/bpf_core_read.h>
> > +#include "bpf_experimental.h"
> > +
> > +#ifndef ARRAY_SIZE
> > +#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
> > +#endif
> > +
> > +struct bar {
> > +	struct bpf_list_node node;
> > +	int data;
> > +};
> > +
> > +struct foo {
> > +	struct bpf_list_node node;
> > +	struct bpf_list_head head __contains(bar, node);
> > +	struct bpf_spin_lock lock;
> > +	int data;
> > +};
> > +
> > +struct map_value {
> > +	struct bpf_list_head head __contains(foo, node);
> > +	struct bpf_spin_lock lock;
> > +	int data;
> > +};
> > +
> > +struct array_map {
> > +	__uint(type, BPF_MAP_TYPE_ARRAY);
> > +	__type(key, int);
> > +	__type(value, struct map_value);
> > +	__uint(max_entries, 1);
> > +} array_map SEC(".maps");
> > +
> > +#define private(name) SEC(".data." #name) __hidden __attribute__((aligned(8)))
>
> This __attribute__((aligned(8))) causes my clang to fail to build this selftest.
> It fails with:
>
>   fatal error: error in backend: unable to write nop sequence of 4 bytes
>
> Tracked it down to llvm/lib/Target/BPF/MCTargetDesc/BPFAsmBackend.cpp:
>
>   bool BPFAsmBackend::writeNopData(raw_ostream &OS, uint64_t Count,
>                                    const MCSubtargetInfo *STI) const {
>     if ((Count % 8) != 0)
>       return false;
>
> Presumably since ".data.A" section is PROGBITS the compiler tries to write
> 4 bytes of nop before / between the variables, but fails.
>
> I'm using a clang built off of a very recent LLVM commit [0]. David Vernet
> was able to successfully build the selftests with a clang built from
> late August's tree, so maybe it's my clang version or some other toolchain
> issue. Which clang did you use to build this?
>

Yes, I get the same ICE on clang nightly as well, specifically for linked_list
test. Then I rebuilt this with clang 14.0.6.

Also, that __attribute__ is necessary because the alignment info in UAPI bpf.h
is lost when it gets dumped to BTF and emitted to vmlinux.h. Since the struct
only has padding bits, the default alignment is 1. Adding named fields is
probably the better solution, which gives it __alignof__(u64).

> [0]: github.com/llvm/llvm-project/commit/2a827e4a988b614bc6f70abe00308ceeb50dcd0a

Re: [PATCH bpf-next v4 06/24] bpf: Refactor kptr_off_tab into btf_record

[Kumar Kartikeya Dwivedi]

On Fri, Nov 04, 2022 at 12:32:41PM IST, Kumar Kartikeya Dwivedi wrote:
> On Fri, Nov 04, 2022 at 08:30:28AM IST, Alexei Starovoitov wrote:
> > On Fri, Nov 04, 2022 at 12:39:55AM +0530, Kumar Kartikeya Dwivedi wrote:
> > >  		else
> > > @@ -311,11 +344,12 @@ static inline void __copy_map_value(struct bpf_map *map, void *dst, void *src, b
> > >  		return;
> > >  	}
> > >
> > > -	for (i = 0; i < map->off_arr->cnt; i++) {
> > > -		u32 next_off = map->off_arr->field_off[i];
> > > +	for (i = 0; i < map->field_offs->cnt; i++) {
> > > +		u32 next_off = map->field_offs->field_off[i];
> > > +		u32 sz = next_off - curr_off;
> > >
> > > -		memcpy(dst + curr_off, src + curr_off, next_off - curr_off);
> > > -		curr_off += map->off_arr->field_sz[i];
> > > +		memcpy(dst + curr_off, src + curr_off, sz);
> > > +		curr_off += map->field_offs->field_sz[i] + sz;
> >
> > This is a clear bug. The kernel is crashing with this change.
> > How did you test this?
> >
>
> For me it is crashing at bpf-next now without this.
>
> When for map value with size 48, having fields at:
> off: 0, 16, 32
> sz:  4, 16, 16
>
> The above produces:
>
> memcpy(dst + 0, src + 0, 0)
> memcpy(dst + 4, src + 4, 12)
> memcpy(dst + 32, src + 32, 0)
> memcpy(dst + 48, src + 48, 0)
>
> Without it, it becomes:
>
> memcpy(dst + 0, src + 0, 0)
> memcpy(dst + 4, src + 4, 12)
> memcpy(dst + 20, src + 20, 12)
> memcpy(dst + 36, src + 36, 12)
>
> I will send a follow up fix.
>

I think this is broken in the original code, I didn't realise this at first but
it's effectively the same in that commit. So it should have Fixes: tag for that.

Re: [PATCH bpf-next v4 06/24] bpf: Refactor kptr_off_tab into btf_record

[Kumar Kartikeya Dwivedi]

On Fri, Nov 04, 2022 at 09:39:22AM IST, Alexei Starovoitov wrote:
> On Thu, Nov 3, 2022 at 9:01 PM Alexei Starovoitov
> <alexei.starovoitov@gmail.com> wrote:
> >
> > On Fri, Nov 04, 2022 at 12:39:55AM +0530, Kumar Kartikeya Dwivedi wrote:
> > >
> > > -enum bpf_kptr_type {
> > > -     BPF_KPTR_UNREF,
> > > -     BPF_KPTR_REF,
> > > +enum btf_field_type {
> > > +     BPF_KPTR_UNREF = (1 << 2),
> > > +     BPF_KPTR_REF   = (1 << 3),
> > > +     BPF_KPTR       = BPF_KPTR_UNREF | BPF_KPTR_REF,
> > >  };
> >
> > ...
> >
> > > +             for (i = 0; i < sizeof(map->record->field_mask) * 8; i++) {
> > > +                     switch (map->record->field_mask & (1 << i)) {
> > > +                     case 0:
> > > +                             continue;
> > > +                     case BPF_KPTR_UNREF:
> > > +                     case BPF_KPTR_REF:
> > > +                             if (map->map_type != BPF_MAP_TYPE_HASH &&
> > > +                                 map->map_type != BPF_MAP_TYPE_LRU_HASH &&
> > > +                                 map->map_type != BPF_MAP_TYPE_ARRAY &&
> > > +                                 map->map_type != BPF_MAP_TYPE_PERCPU_ARRAY) {
> > > +                                     ret = -EOPNOTSUPP;
> > > +                                     goto free_map_tab;
> > > +                             }
> > > +                             break;
> > > +                     default:
> > > +                             /* Fail if map_type checks are missing for a field type */
> > > +                             ret = -EOPNOTSUPP;
> > > +                             goto free_map_tab;
> > > +                     }
> >
> > With this patch alone this is also wrong.
>
> Actually this bit is probably fine. The bug is elsewhere.
>
> The point below stands:
>
>
> > And it breaks bisect.
> > Please make sure to do a full vmtest.sh for every patch in the series.

I'm sorry. I made multiple small changes to these two and never retested them
again in isolation, and then it was 'fixed' by later changes. I'll make sure it
doesn't happen again.

Re: [PATCH bpf-next v4 22/24] bpf: Introduce single ownership BPF linked list API

[Kumar Kartikeya Dwivedi]

On Fri, Nov 04, 2022 at 11:26:39AM IST, Dave Marchevsky wrote:
> On 11/3/22 3:10 PM, Kumar Kartikeya Dwivedi wrote:
> > Add a linked list API for use in BPF programs, where it expects
> > protection from the bpf_spin_lock in the same allocation as the
> > bpf_list_head. Future patches will extend the same infrastructure to
> > have different flavors with varying protection domains and visibility
> > (e.g. percpu variant with local_t protection, usable in NMI progs).
> >
> > The following functions are added to kick things off:
> >
> > bpf_list_push_front
> > bpf_list_push_back
> > bpf_list_pop_front
> > bpf_list_pop_back
> >
> > The lock protecting the bpf_list_head needs to be taken for all
> > operations.
> >
> > Once a node has been added to the list, it's pointer changes to
> > PTR_UNTRUSTED. However, it is only released once the lock protecting the
> > list is unlocked. For such local kptrs with PTR_UNTRUSTED set but an
> > active ref_obj_id, it is still permitted to read and write to them as
> > long as the lock is held.
>
> I think "still permitted to ... write to them" is not accurate
> for this version of the series. In v2 you mentioned [0]:
>
> """
> I have switched things a bit to disallow stores, which is a bug right now in
> this set, because one can do this:
>
> push_front(head, &p->node);
> p2 = container_of(pop_front(head));
> // p2 == p
> bpf_obj_drop(p2);
> p->data = ...;
>
> One can always fully initialize the object _before_ inserting it into the list,
> in some cases that will be the requirement (like adding to RCU protected lists)
> for correctness.
> """
>
> I confirmed this is currently the case by moving data write after
> list_push in the selftest and running it:
>
> @@ -87,8 +87,8 @@ static __always_inline int list_push_pop(struct bpf_spin_lock *lock,
>         }
>
>         bpf_spin_lock(lock);
> -       f->data = 13;
>         bpf_list_push_front(head, &f->node);
> +       f->data = 13;
>         bpf_spin_unlock(lock);
>
> Got "only read is supported" from verifier.
> I think it's fine to punt on supporting writes for now and do it in followups.
>

Thanks for catching it, I'll fix up the commit message.

Also, just to manage the expectations I think enabling writes after pushing the
object won't be possible to make safe, unless the definition of "safe" is
twisted.

As shown in that example, we can reach a point where it has been freed but we
hold an untrusted pointer to it. Once it has been freed the object can be
reallocated and be in use again concurrently, possibly as a different type.

I was contemplating whether to simply drop this whole set_release_on_unlock
logic entirely. Not sure it's worth the added complexity, atleast for now. Once
you push you simply lose ownership of the object and any registers are
immediately killed.

Re: [PATCH bpf-next v4 10/24] bpf: Introduce local kptrs

[Kumar Kartikeya Dwivedi]

On Fri, Nov 04, 2022 at 11:27:04AM IST, Alexei Starovoitov wrote:
> On Thu, Nov 3, 2022 at 12:11 PM Kumar Kartikeya Dwivedi
> <memxor@gmail.com> wrote:
> >
> > Introduce local kptrs, i.e. PTR_TO_BTF_ID that point to a type in
> > program BTF. This is indicated by the presence of MEM_TYPE_LOCAL type
> > tag in reg->type to avoid having to check btf_is_kernel when trying to
> > match argument types in helpers.
> ...
> >
> > +       /* MEM is of a type from program BTF, not kernel BTF. This is used to
> > +        * tag PTR_TO_BTF_ID allocated using bpf_kptr_alloc.
> > +        */
> > +       MEM_TYPE_LOCAL          = BIT(11 + BPF_BASE_TYPE_BITS),
> > +
>
> I know we have bpf_core_type_id_local.
> It sort-of makes sense in the context of the program.
> type_id_local -> inside the program
> type_id_kernel -> kernel
>
> but in the context of the verifier "local kptr" doesn't read right.
> Especially in MEM_TYPE_LOCAL.

Yes, "local kptr" is not the best name. "kptr to local type" is too verbose
though, do you have any suggestions on what to call this?

>
> Also, since it applies to PTR_TO_BTF_ID, should it prefix with PTR_?
> Probably MEM_ is actually cleaner.
> And we're not consistent already with MEM_PERCPU.
> We can live with this inconsistency for now.
>
> So how about we rename MEM_ALLOC to MEM_RINGBUF,
> since it's special bpf_ringbuf_reserve() memory
> and use MEM_ALLOC to indicate the memory that came from bpf_obj_new ?
>

Yes, it makes sense. I think Andrii has expressed the same wish to rename it to
something similar to MEM_RINGBUF before in [0].

[0]: https://lore.kernel.org/bpf/CAEf4BzYK939fgyc3LwNvoz3vPk2avyskP_3wRZO344irubXPtg@mail.gmail.com

> ... which made me realize that the comment above should
> s/bpf_kptr_alloc/bpf_obj_new/

I'll fix the comment.

Re: [PATCH bpf-next v4 14/24] bpf: Allow locking bpf_spin_lock global variables

[Kumar Kartikeya Dwivedi]

On Fri, Nov 04, 2022 at 08:24:22AM IST, Dave Marchevsky wrote:
> On 11/3/22 3:10 PM, Kumar Kartikeya Dwivedi wrote:
> > Global variables reside in maps accessible using direct_value_addr
> > callbacks, so giving each load instruction's rewrite a unique reg->id
> > disallows us from holding locks which are global.
> >
> > This is not great, so refactor the active_spin_lock into two separate
> > fields, active_spin_lock_ptr and active_spin_lock_id, which is generic
> > enough to allow it for global variables, map lookups, and local kptr
> > registers at the same time.
> >
> > Held vs non-held is indicated by active_spin_lock_ptr, which stores the
> > reg->map_ptr or reg->btf pointer of the register used for locking spin
> > lock. But the active_spin_lock_id also needs to be compared to ensure
> > whether bpf_spin_unlock is for the same register.
> >
> > Next, pseudo load instructions are not given a unique reg->id, as they
> > are doing lookup for the same map value (max_entries is never greater
> > than 1).
> >
> > Essentially, we consider that the tuple of (active_spin_lock_ptr,
> > active_spin_lock_id) will always be unique for any kind of argument to
> > bpf_spin_{lock,unlock}.
> >
> > Note that this can be extended in the future to also remember offset
> > used for locking, so that we can introduce multiple bpf_spin_lock fields
> > in the same allocation.
> >
> > Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
> > ---
> >  include/linux/bpf_verifier.h |  3 ++-
> >  kernel/bpf/verifier.c        | 39 +++++++++++++++++++++++++-----------
> >  2 files changed, 29 insertions(+), 13 deletions(-)
> >
> > diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
> > index 1a32baa78ce2..bb71c59f21f6 100644
> > --- a/include/linux/bpf_verifier.h
> > +++ b/include/linux/bpf_verifier.h
> > @@ -323,7 +323,8 @@ struct bpf_verifier_state {
> >  	u32 branches;
> >  	u32 insn_idx;
> >  	u32 curframe;
> > -	u32 active_spin_lock;
> > +	void *active_spin_lock_ptr;
> > +	u32 active_spin_lock_id;
> >  	bool speculative;
> Back in first RFC of this series we talked about turning this "spin lock
> identity" concept into a proper struct [0]. But to save you the click:
>
> Dave:
> """
> It would be good to make this "(lock_ptr, lock_id) is identifier for lock"
> concept more concrete by grouping these fields in a struct w/ type enum + union,
> or something similar. Will make it more obvious that they should be used / set
> together.
>
> But if you'd prefer to keep it as two fields, active_spin_lock_ptr is a
> confusing name. In the future with no context as to what that field is, I'd
> assume that it holds a pointer to a spin_lock instead of a "spin lock identity
> pointer".
> """
>
> Kumar:
> """
> That's a good point.
>
> I'm thinking
> struct active_lock {
>   void *id_ptr;
>   u32 offset;
>   u32 reg_id;
> };
> How does that look?
> """
>
> I didn't get back to you, but I think that looks reasonable, and "this can be
> extended in the future to also remember offset used for locking" in this
> patch summary supports the desire to group up those fields. (I agree that
> offset isn't necessary for now, though).
>

I will make this change in v5.

However, do you have any suggestions on what we can call the id_ptr thing? In
patch 22 in the big comment above check_reg_allocation_locked I call it lock
class, but I'm not sure whether it helps or is more confusing for people.

In active_spin_lock_ptr, 'ptr' alone is confusing as you've pointed out before.

Re: [PATCH bpf-next v4 19/24] bpf: Introduce bpf_obj_new

[Kumar Kartikeya Dwivedi]

On Fri, Nov 04, 2022 at 08:07:25AM IST, Dave Marchevsky wrote:
> On 11/3/22 3:10 PM, Kumar Kartikeya Dwivedi wrote:
> > Introduce type safe memory allocator bpf_obj_new for BPF programs. The
> > kernel side kfunc is named bpf_obj_new_impl, as passing hidden arguments
> > to kfuncs still requires having them in prototype, unlike BPF helpers
> > which always take 5 arguments and have them checked using bpf_func_proto
> > in verifier, ignoring unset argument types.
> >
> > Introduce __ign suffix to ignore a specific kfunc argument during type
> > checks, then use this to introduce support for passing type metadata to
> > the bpf_obj_new_impl kfunc.
> >
> > The user passes BTF ID of the type it wants to allocates in program BTF,
> > the verifier then rewrites the first argument as the size of this type,
> > after performing some sanity checks (to ensure it exists and it is a
> > struct type).
> >
> > The second argument is also fixed up and passed by the verifier. This is
> > the btf_struct_meta for the type being allocated. It would be needed
> > mostly for the offset array which is required for zero initializing
> > special fields while leaving the rest of storage in unitialized state.
> >
> > It would also be needed in the next patch to perform proper destruction
> > of the object's special fields.
> >
> > A convenience macro is included in the bpf_experimental.h header to hide
> > over the ugly details of the implementation, leading to user code
> > looking similar to a language level extension which allocates and
> > constructs fields of a user type.
> >
> > struct bar {
> > 	struct bpf_list_node node;
> > };
> >
> > struct foo {
> > 	struct bpf_spin_lock lock;
> > 	struct bpf_list_head head __contains(bar, node);
> > };
> >
> > void prog(void) {
> > 	struct foo *f;
> >
> > 	f = bpf_obj_new(typeof(*f));
> > 	if (!f)
> > 		return;
> > 	...
> > }
> >
> > A key piece of this story is still missing, i.e. the free function,
> > which will come in the next patch.
> >
> > Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
> > ---
>
> [...]
>
> > diff --git a/tools/testing/selftests/bpf/bpf_experimental.h b/tools/testing/selftests/bpf/bpf_experimental.h
> > new file mode 100644
> > index 000000000000..1d3451084a68
> > --- /dev/null
> > +++ b/tools/testing/selftests/bpf/bpf_experimental.h
>
> Maybe bpf_experimental.h should go in libbpf as part of this series? If
> including vmlinux.h is an issue - nothing in libbpf currently includes it - you
> could rely on the BPF program including it, with a comment similar to "Note
> that bpf programs need to include..." in lib/bpf/bpf_helpers.h .
>

I don't have a problem with that, but I would like to also know Andrii's opinion
on this, since it won't work properly if people don't keep libbpf and kernel
version in sync.

Re: [PATCH bpf-next v4 10/24] bpf: Introduce local kptrs

[Alexei Starovoitov]

On Fri, Nov 4, 2022 at 12:51 AM Kumar Kartikeya Dwivedi
<memxor@gmail.com> wrote:
>
> On Fri, Nov 04, 2022 at 11:27:04AM IST, Alexei Starovoitov wrote:
> > On Thu, Nov 3, 2022 at 12:11 PM Kumar Kartikeya Dwivedi
> > <memxor@gmail.com> wrote:
> > >
> > > Introduce local kptrs, i.e. PTR_TO_BTF_ID that point to a type in
> > > program BTF. This is indicated by the presence of MEM_TYPE_LOCAL type
> > > tag in reg->type to avoid having to check btf_is_kernel when trying to
> > > match argument types in helpers.
> > ...
> > >
> > > +       /* MEM is of a type from program BTF, not kernel BTF. This is used to
> > > +        * tag PTR_TO_BTF_ID allocated using bpf_kptr_alloc.
> > > +        */
> > > +       MEM_TYPE_LOCAL          = BIT(11 + BPF_BASE_TYPE_BITS),
> > > +
> >
> > I know we have bpf_core_type_id_local.
> > It sort-of makes sense in the context of the program.
> > type_id_local -> inside the program
> > type_id_kernel -> kernel
> >
> > but in the context of the verifier "local kptr" doesn't read right.
> > Especially in MEM_TYPE_LOCAL.
>
> Yes, "local kptr" is not the best name. "kptr to local type" is too verbose
> though, do you have any suggestions on what to call this?
>
> >
> > Also, since it applies to PTR_TO_BTF_ID, should it prefix with PTR_?
> > Probably MEM_ is actually cleaner.
> > And we're not consistent already with MEM_PERCPU.
> > We can live with this inconsistency for now.
> >
> > So how about we rename MEM_ALLOC to MEM_RINGBUF,
> > since it's special bpf_ringbuf_reserve() memory
> > and use MEM_ALLOC to indicate the memory that came from bpf_obj_new ?
> >
>
> Yes, it makes sense. I think Andrii has expressed the same wish to rename it to
> something similar to MEM_RINGBUF before in [0].
>
> [0]: https://lore.kernel.org/bpf/CAEf4BzYK939fgyc3LwNvoz3vPk2avyskP_3wRZO344irubXPtg@mail.gmail.com

Great. Please rename then.
Also let's all of us agree and stop using this [0] notation
for links.
It's an email and not an academic paper.
Just insert the link.

Re: [PATCH bpf-next v4 19/24] bpf: Introduce bpf_obj_new

[Alexei Starovoitov]

On Fri, Nov 4, 2022 at 1:09 AM Kumar Kartikeya Dwivedi <memxor@gmail.com> wrote:
>
> On Fri, Nov 04, 2022 at 08:07:25AM IST, Dave Marchevsky wrote:
> > On 11/3/22 3:10 PM, Kumar Kartikeya Dwivedi wrote:
> > > Introduce type safe memory allocator bpf_obj_new for BPF programs. The
> > > kernel side kfunc is named bpf_obj_new_impl, as passing hidden arguments
> > > to kfuncs still requires having them in prototype, unlike BPF helpers
> > > which always take 5 arguments and have them checked using bpf_func_proto
> > > in verifier, ignoring unset argument types.
> > >
> > > Introduce __ign suffix to ignore a specific kfunc argument during type
> > > checks, then use this to introduce support for passing type metadata to
> > > the bpf_obj_new_impl kfunc.
> > >
> > > The user passes BTF ID of the type it wants to allocates in program BTF,
> > > the verifier then rewrites the first argument as the size of this type,
> > > after performing some sanity checks (to ensure it exists and it is a
> > > struct type).
> > >
> > > The second argument is also fixed up and passed by the verifier. This is
> > > the btf_struct_meta for the type being allocated. It would be needed
> > > mostly for the offset array which is required for zero initializing
> > > special fields while leaving the rest of storage in unitialized state.
> > >
> > > It would also be needed in the next patch to perform proper destruction
> > > of the object's special fields.
> > >
> > > A convenience macro is included in the bpf_experimental.h header to hide
> > > over the ugly details of the implementation, leading to user code
> > > looking similar to a language level extension which allocates and
> > > constructs fields of a user type.
> > >
> > > struct bar {
> > >     struct bpf_list_node node;
> > > };
> > >
> > > struct foo {
> > >     struct bpf_spin_lock lock;
> > >     struct bpf_list_head head __contains(bar, node);
> > > };
> > >
> > > void prog(void) {
> > >     struct foo *f;
> > >
> > >     f = bpf_obj_new(typeof(*f));
> > >     if (!f)
> > >             return;
> > >     ...
> > > }
> > >
> > > A key piece of this story is still missing, i.e. the free function,
> > > which will come in the next patch.
> > >
> > > Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
> > > ---
> >
> > [...]
> >
> > > diff --git a/tools/testing/selftests/bpf/bpf_experimental.h b/tools/testing/selftests/bpf/bpf_experimental.h
> > > new file mode 100644
> > > index 000000000000..1d3451084a68
> > > --- /dev/null
> > > +++ b/tools/testing/selftests/bpf/bpf_experimental.h
> >
> > Maybe bpf_experimental.h should go in libbpf as part of this series? If
> > including vmlinux.h is an issue - nothing in libbpf currently includes it - you
> > could rely on the BPF program including it, with a comment similar to "Note
> > that bpf programs need to include..." in lib/bpf/bpf_helpers.h .
> >
>
> I don't have a problem with that, but I would like to also know Andrii's opinion
> on this, since it won't work properly if people don't keep libbpf and kernel
> version in sync.

let's do the directory bikeshedding later.
bpf_experimental.h can be moved to libbpf dir in the follow up.

Re: [PATCH bpf-next v4 22/24] bpf: Introduce single ownership BPF linked list API

[Dave Marchevsky]

On 11/4/22 3:42 AM, Kumar Kartikeya Dwivedi wrote:
> On Fri, Nov 04, 2022 at 11:26:39AM IST, Dave Marchevsky wrote:
>> On 11/3/22 3:10 PM, Kumar Kartikeya Dwivedi wrote:
>>> Add a linked list API for use in BPF programs, where it expects
>>> protection from the bpf_spin_lock in the same allocation as the
>>> bpf_list_head. Future patches will extend the same infrastructure to
>>> have different flavors with varying protection domains and visibility
>>> (e.g. percpu variant with local_t protection, usable in NMI progs).
>>>
>>> The following functions are added to kick things off:
>>>
>>> bpf_list_push_front
>>> bpf_list_push_back
>>> bpf_list_pop_front
>>> bpf_list_pop_back
>>>
>>> The lock protecting the bpf_list_head needs to be taken for all
>>> operations.
>>>
>>> Once a node has been added to the list, it's pointer changes to
>>> PTR_UNTRUSTED. However, it is only released once the lock protecting the
>>> list is unlocked. For such local kptrs with PTR_UNTRUSTED set but an
>>> active ref_obj_id, it is still permitted to read and write to them as
>>> long as the lock is held.
>>
>> I think "still permitted to ... write to them" is not accurate
>> for this version of the series. In v2 you mentioned [0]:
>>
>> """
>> I have switched things a bit to disallow stores, which is a bug right now in
>> this set, because one can do this:
>>
>> push_front(head, &p->node);
>> p2 = container_of(pop_front(head));
>> // p2 == p
>> bpf_obj_drop(p2);
>> p->data = ...;
>>
>> One can always fully initialize the object _before_ inserting it into the list,
>> in some cases that will be the requirement (like adding to RCU protected lists)
>> for correctness.
>> """
>>
>> I confirmed this is currently the case by moving data write after
>> list_push in the selftest and running it:
>>
>> @@ -87,8 +87,8 @@ static __always_inline int list_push_pop(struct bpf_spin_lock *lock,
>>         }
>>
>>         bpf_spin_lock(lock);
>> -       f->data = 13;
>>         bpf_list_push_front(head, &f->node);
>> +       f->data = 13;
>>         bpf_spin_unlock(lock);
>>
>> Got "only read is supported" from verifier.
>> I think it's fine to punt on supporting writes for now and do it in followups.
>>
> 
> Thanks for catching it, I'll fix up the commit message.
> 
> Also, just to manage the expectations I think enabling writes after pushing the
> object won't be possible to make safe, unless the definition of "safe" is
> twisted.
> 
> As shown in that example, we can reach a point where it has been freed but we
> hold an untrusted pointer to it. Once it has been freed the object can be
> reallocated and be in use again concurrently, possibly as a different type.
I think this patchset prevents that example from passing verifier, provided
that bpf_spin_{lock,unlock} are added in the right places:

  p = bpf_obj_new(typeof(*p));
  if (!p)
    return;

  bpf_spin_lock(lock);
  push_front(head, &p->node);
  p2 = container_of(pop_front(head));
  // p2 == p
  if (!p2)
    return;
  bpf_spin_unlock(lock);

  bpf_obj_drop(p2);
  p->data = ...;

After bpf_obj_new R0 is of type ptr_or_null_BTF_TYPE with nonzero ref_obj_id,
let's say 1. 
After null check any regs holding p have _or_null removed.

After push_front any regs w/ ref_obj_id==1 become untrusted and have
release_on_unlock set. After pop_front R0 is ptr_or_null_BTF_TYPE with nonzero
ref_obj_id different than bpf_obj_new result, let's say 2.
Null check works same way as before.

After bpf_spin_unlock all release_on_unlock references are clobbered, so
p->data will result in "invalid mem access 'scalar'" verifier error.

Verifier requires list manipulation functions to be in a critical section
and doesn't allow bpf_obj_new or bpf_obj_drop in the critical section.
p2 == p but having different ref_obj_ids is OK because only p2 will escape
bpf_spin_unlock unclobbered to be released by bpf_obj_drop, and no free()s
are allowed until we're out of the critical section. So by the time we can
call bpf_obj_drop we only have one valid reference remaining ("trusted" one).

My OBJ_NON_OWNING_REF stuff in rbtree patchsets had same logic, IIRC
only difference is that my "add to datastructure" function was considered
a RELEASE func that also did an ACQUIRE of a release_on_unlock retval. But this
was before static lock checking discussions, so the RELEASE/ACQUIRE could fail.
I think directly modifying arg reg like you're doing in set_release_on_unlock
is cleaner.

> I was contemplating whether to simply drop this whole set_release_on_unlock
> logic entirely. Not sure it's worth the added complexity, atleast for now. Once
> you push you simply lose ownership of the object and any registers are
> immediately killed.

I think that being able to read / modify the datastructure node after it's been 
added is pretty critical, at least from a UX perspective. 

Totally fine with it being dropped from the series and experimented with
later, though.

Re: [PATCH bpf-next v4 10/24] bpf: Introduce local kptrs

[Dave Marchevsky]

On 11/4/22 3:51 AM, Kumar Kartikeya Dwivedi wrote:
> On Fri, Nov 04, 2022 at 11:27:04AM IST, Alexei Starovoitov wrote:
>> On Thu, Nov 3, 2022 at 12:11 PM Kumar Kartikeya Dwivedi
>> <memxor@gmail.com> wrote:
>>>
>>> Introduce local kptrs, i.e. PTR_TO_BTF_ID that point to a type in
>>> program BTF. This is indicated by the presence of MEM_TYPE_LOCAL type
>>> tag in reg->type to avoid having to check btf_is_kernel when trying to
>>> match argument types in helpers.
>> ...
>>>
>>> +       /* MEM is of a type from program BTF, not kernel BTF. This is used to
>>> +        * tag PTR_TO_BTF_ID allocated using bpf_kptr_alloc.
>>> +        */
>>> +       MEM_TYPE_LOCAL          = BIT(11 + BPF_BASE_TYPE_BITS),
>>> +
>>
>> I know we have bpf_core_type_id_local.
>> It sort-of makes sense in the context of the program.
>> type_id_local -> inside the program
>> type_id_kernel -> kernel
>>
>> but in the context of the verifier "local kptr" doesn't read right.
>> Especially in MEM_TYPE_LOCAL.
> 
> Yes, "local kptr" is not the best name. "kptr to local type" is too verbose
> though, do you have any suggestions on what to call this?
> 
>>
>> Also, since it applies to PTR_TO_BTF_ID, should it prefix with PTR_?
>> Probably MEM_ is actually cleaner.
>> And we're not consistent already with MEM_PERCPU.
>> We can live with this inconsistency for now.
>>
>> So how about we rename MEM_ALLOC to MEM_RINGBUF,
>> since it's special bpf_ringbuf_reserve() memory
>> and use MEM_ALLOC to indicate the memory that came from bpf_obj_new ?
>>
> 
> Yes, it makes sense. I think Andrii has expressed the same wish to rename it to
> something similar to MEM_RINGBUF before in [0].

I like this idea as well. I've been poking on a small refactoring patchset in
the background which will get rid of (current) MEM_ALLOC anyways.

> 
> [0]: https://lore.kernel.org/bpf/CAEf4BzYK939fgyc3LwNvoz3vPk2avyskP_3wRZO344irubXPtg@mail.gmail.com
> 
>> ... which made me realize that the comment above should
>> s/bpf_kptr_alloc/bpf_obj_new/
> 
> I'll fix the comment.

Re: [PATCH bpf-next v4 22/24] bpf: Introduce single ownership BPF linked list API

[Alexei Starovoitov]

On Fri, Nov 4, 2022 at 7:15 PM Dave Marchevsky <davemarchevsky@meta.com> wrote:
>
> > I was contemplating whether to simply drop this whole set_release_on_unlock
> > logic entirely. Not sure it's worth the added complexity, atleast for now. Once
> > you push you simply lose ownership of the object and any registers are
> > immediately killed.
>
> I think that being able to read / modify the datastructure node after it's been
> added is pretty critical, at least from a UX perspective.
>
> Totally fine with it being dropped from the series and experimented with
> later, though.

Kumar,
please split release_on_unlock logic into separate patch.
afaics it doesn't have to be introduced together with these kfuncs.

Re: [PATCH bpf-next v4 22/24] bpf: Introduce single ownership BPF linked list API

[Kumar Kartikeya Dwivedi]

On Sat, 5 Nov 2022 at 23:46, Alexei Starovoitov
<alexei.starovoitov@gmail.com> wrote:
>
> On Fri, Nov 4, 2022 at 7:15 PM Dave Marchevsky <davemarchevsky@meta.com> wrote:
> >
> > > I was contemplating whether to simply drop this whole set_release_on_unlock
> > > logic entirely. Not sure it's worth the added complexity, atleast for now. Once
> > > you push you simply lose ownership of the object and any registers are
> > > immediately killed.
> >
> > I think that being able to read / modify the datastructure node after it's been
> > added is pretty critical, at least from a UX perspective.
> >
> > Totally fine with it being dropped from the series and experimented with
> > later, though.
>
> Kumar,
> please split release_on_unlock logic into separate patch.
> afaics it doesn't have to be introduced together with these kfuncs.

Ack.