[PATCH bpf-next v5 0/8] Typeless/weak ksym for gen_loader + misc fixups

[PATCH bpf-next v5 0/8] Typeless/weak ksym for gen_loader + misc fixups

[Kumar Kartikeya Dwivedi]

Patches (1,2,3,6) add typeless and weak ksym support to gen_loader. It is follow
up for the recent kfunc from modules series.

The later patches (7,8) are misc fixes for selftests, and patch 4 for libbpf
where we try to be careful to not end up with fds == 0, as libbpf assumes in
various places that they are greater than 0. Patch 5 fixes up missing O_CLOEXEC
in libbpf.

Changelog:
----------
v4 -> v5
v4: https://lore.kernel.org/bpf/20211020191526.2306852-1-memxor@gmail.com

 * Address feedback from Andrii
   * Drop use of ensure_good_fd in unneeded call sites
   * Add sys_bpf_fd
   * Add _lskel suffix to all light skeletons and change all current selftests
   * Drop early break in close loop for sk_lookup
   * Fix other nits

v3 -> v4
v3: https://lore.kernel.org/bpf/20211014205644.1837280-1-memxor@gmail.com

 * Remove gpl_only = true from bpf_kallsyms_lookup_name (Alexei)
 * Add bpf_dump_raw_ok check to ensure kptr_restrict isn't bypassed (Alexei)

v2 -> v3
v2: https://lore.kernel.org/bpf/20211013073348.1611155-1-memxor@gmail.com

 * Address feedback from Song
   * Move ksym logging to separate helper to avoid code duplication
   * Move src_reg mask stuff to separate helper
   * Fix various other nits, add acks
     * __builtin_expect is used instead of likely to as skel_internal.h is
       included in isolation.

v1 -> v2
v1: https://lore.kernel.org/bpf/20211006002853.308945-1-memxor@gmail.com

 * Remove redundant OOM checks in emit_bpf_kallsyms_lookup_name
 * Use designated initializer for sk_lookup fd array (Jakub)
 * Do fd check for all fd returning low level APIs (Andrii, Alexei)
 * Make Fixes: tag quote commit message, use selftests/bpf prefix (Song, Andrii)
 * Split typeless and weak ksym support into separate patches, expand commit
   message (Song)
 * Fix duplication in selftests stemming from use of LSKELS_EXTRA (Song)

Kumar Kartikeya Dwivedi (8):
  bpf: Add bpf_kallsyms_lookup_name helper
  libbpf: Add typeless ksym support to gen_loader
  libbpf: Add weak ksym support to gen_loader
  libbpf: Ensure that BPF syscall fds are never 0, 1, or 2
  libbpf: Use O_CLOEXEC uniformly when opening fds
  selftests/bpf: Add weak/typeless ksym test for light skeleton
  selftests/bpf: Fix fd cleanup in sk_lookup test
  selftests/bpf: Fix memory leak in test_ima

 include/linux/bpf.h                           |   1 +
 include/uapi/linux/bpf.h                      |  16 +++
 kernel/bpf/syscall.c                          |  27 ++++
 tools/include/uapi/linux/bpf.h                |  16 +++
 tools/lib/bpf/bpf.c                           |  35 +++--
 tools/lib/bpf/bpf_gen_internal.h              |  12 +-
 tools/lib/bpf/btf.c                           |   2 +-
 tools/lib/bpf/gen_loader.c                    | 132 ++++++++++++++++--
 tools/lib/bpf/libbpf.c                        |  19 ++-
 tools/lib/bpf/libbpf_internal.h               |  24 ++++
 tools/lib/bpf/libbpf_probes.c                 |   2 +-
 tools/lib/bpf/linker.c                        |   4 +-
 tools/lib/bpf/xsk.c                           |   6 +-
 tools/testing/selftests/bpf/Makefile          |   4 +-
 .../selftests/bpf/prog_tests/atomics.c        |  34 ++---
 .../selftests/bpf/prog_tests/fentry_fexit.c   |  16 +--
 .../selftests/bpf/prog_tests/fentry_test.c    |  14 +-
 .../selftests/bpf/prog_tests/fexit_sleep.c    |  12 +-
 .../selftests/bpf/prog_tests/fexit_test.c     |  14 +-
 .../selftests/bpf/prog_tests/kfunc_call.c     |   6 +-
 .../selftests/bpf/prog_tests/ksyms_btf.c      |  35 ++++-
 .../selftests/bpf/prog_tests/ksyms_module.c   |  40 +++++-
 .../bpf/prog_tests/ksyms_module_libbpf.c      |  28 ----
 .../selftests/bpf/prog_tests/ringbuf.c        |  12 +-
 .../selftests/bpf/prog_tests/sk_lookup.c      |   4 +-
 .../selftests/bpf/prog_tests/test_ima.c       |   3 +-
 .../selftests/bpf/prog_tests/trace_printk.c   |  14 +-
 .../selftests/bpf/prog_tests/trace_vprintk.c  |  12 +-
 .../selftests/bpf/prog_tests/verif_stats.c    |   6 +-
 .../selftests/bpf/progs/test_ksyms_weak.c     |   2 +-
 30 files changed, 393 insertions(+), 159 deletions(-)
 delete mode 100644 tools/testing/selftests/bpf/prog_tests/ksyms_module_libbpf.c

-- 
2.33.1

[PATCH bpf-next v5 1/8] bpf: Add bpf_kallsyms_lookup_name helper

[Kumar Kartikeya Dwivedi]

This helper allows us to get the address of a kernel symbol from inside
a BPF_PROG_TYPE_SYSCALL prog (used by gen_loader), so that we can
relocate typeless ksym vars.

Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 include/linux/bpf.h            |  1 +
 include/uapi/linux/bpf.h       | 16 ++++++++++++++++
 kernel/bpf/syscall.c           | 27 +++++++++++++++++++++++++++
 tools/include/uapi/linux/bpf.h | 16 ++++++++++++++++
 4 files changed, 60 insertions(+)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 31421c74ba08..05889394fe77 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -2109,6 +2109,7 @@ extern const struct bpf_func_proto bpf_for_each_map_elem_proto;
 extern const struct bpf_func_proto bpf_btf_find_by_name_kind_proto;
 extern const struct bpf_func_proto bpf_sk_setsockopt_proto;
 extern const struct bpf_func_proto bpf_sk_getsockopt_proto;
+extern const struct bpf_func_proto bpf_kallsyms_lookup_name_proto;
 
 const struct bpf_func_proto *tracing_prog_func_proto(
   enum bpf_func_id func_id, const struct bpf_prog *prog);
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index c10820037883..9aaa2d6a3db6 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -4915,6 +4915,21 @@ union bpf_attr {
  *		Dynamically cast a *sk* pointer to a *unix_sock* pointer.
  *	Return
  *		*sk* if casting is valid, or **NULL** otherwise.
+ *
+ * long bpf_kallsyms_lookup_name(const char *name, int name_sz, int flags, u64 *res)
+ *	Description
+ *		Get the address of a kernel symbol, returned in *res*. *res* is
+ *		set to 0 if the symbol is not found.
+ *	Return
+ *		On success, zero. On error, a negative value.
+ *
+ *		**-EINVAL** if *flags* is not zero.
+ *
+ *		**-EINVAL** if string *name* is not the same size as *name_sz*.
+ *
+ *		**-ENOENT** if symbol is not found.
+ *
+ *		**-EPERM** if caller does not have permission to obtain kernel address.
  */
 #define __BPF_FUNC_MAPPER(FN)		\
 	FN(unspec),			\
@@ -5096,6 +5111,7 @@ union bpf_attr {
 	FN(get_branch_snapshot),	\
 	FN(trace_vprintk),		\
 	FN(skc_to_unix_sock),		\
+	FN(kallsyms_lookup_name),	\
 	/* */
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 3e1c024ce3ed..c0f2dadd67c4 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -4763,6 +4763,31 @@ static const struct bpf_func_proto bpf_sys_close_proto = {
 	.arg1_type	= ARG_ANYTHING,
 };
 
+BPF_CALL_4(bpf_kallsyms_lookup_name, const char *, name, int, name_sz, int, flags, u64 *, res)
+{
+	if (flags)
+		return -EINVAL;
+
+	if (name_sz <= 1 || name[name_sz - 1])
+		return -EINVAL;
+
+	if (!bpf_dump_raw_ok(current_cred()))
+		return -EPERM;
+
+	*res = kallsyms_lookup_name(name);
+	return *res ? 0 : -ENOENT;
+}
+
+const struct bpf_func_proto bpf_kallsyms_lookup_name_proto = {
+	.func		= bpf_kallsyms_lookup_name,
+	.gpl_only	= false,
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_PTR_TO_MEM,
+	.arg2_type	= ARG_CONST_SIZE,
+	.arg3_type	= ARG_ANYTHING,
+	.arg4_type	= ARG_PTR_TO_LONG,
+};
+
 static const struct bpf_func_proto *
 syscall_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 {
@@ -4773,6 +4798,8 @@ syscall_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 		return &bpf_btf_find_by_name_kind_proto;
 	case BPF_FUNC_sys_close:
 		return &bpf_sys_close_proto;
+	case BPF_FUNC_kallsyms_lookup_name:
+		return &bpf_kallsyms_lookup_name_proto;
 	default:
 		return tracing_prog_func_proto(func_id, prog);
 	}
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index c10820037883..9aaa2d6a3db6 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -4915,6 +4915,21 @@ union bpf_attr {
  *		Dynamically cast a *sk* pointer to a *unix_sock* pointer.
  *	Return
  *		*sk* if casting is valid, or **NULL** otherwise.
+ *
+ * long bpf_kallsyms_lookup_name(const char *name, int name_sz, int flags, u64 *res)
+ *	Description
+ *		Get the address of a kernel symbol, returned in *res*. *res* is
+ *		set to 0 if the symbol is not found.
+ *	Return
+ *		On success, zero. On error, a negative value.
+ *
+ *		**-EINVAL** if *flags* is not zero.
+ *
+ *		**-EINVAL** if string *name* is not the same size as *name_sz*.
+ *
+ *		**-ENOENT** if symbol is not found.
+ *
+ *		**-EPERM** if caller does not have permission to obtain kernel address.
  */
 #define __BPF_FUNC_MAPPER(FN)		\
 	FN(unspec),			\
@@ -5096,6 +5111,7 @@ union bpf_attr {
 	FN(get_branch_snapshot),	\
 	FN(trace_vprintk),		\
 	FN(skc_to_unix_sock),		\
+	FN(kallsyms_lookup_name),	\
 	/* */
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper
-- 
2.33.1

[PATCH bpf-next v5 2/8] libbpf: Add typeless ksym support to gen_loader

[Kumar Kartikeya Dwivedi]

This uses the bpf_kallsyms_lookup_name helper added in previous patches
to relocate typeless ksyms. The return value ENOENT can be ignored, and
the value written to 'res' can be directly stored to the insn, as it is
overwritten to 0 on lookup failure. For repeating symbols, we can simply
copy the previously populated bpf_insn.

Also, we need to take care to not close fds for typeless ksym_desc, so
reuse the 'off' member's space to add a marker for typeless ksym and use
that to skip them in cleanup_relos.

We add a emit_ksym_relo_log helper that avoids duplicating common
logging instructions between typeless and weak ksym (for future commit).

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 tools/lib/bpf/bpf_gen_internal.h | 12 +++-
 tools/lib/bpf/gen_loader.c       | 97 ++++++++++++++++++++++++++++----
 tools/lib/bpf/libbpf.c           | 13 ++---
 3 files changed, 99 insertions(+), 23 deletions(-)

diff --git a/tools/lib/bpf/bpf_gen_internal.h b/tools/lib/bpf/bpf_gen_internal.h
index 70eccbffefb1..9f328d044636 100644
--- a/tools/lib/bpf/bpf_gen_internal.h
+++ b/tools/lib/bpf/bpf_gen_internal.h
@@ -8,13 +8,19 @@ struct ksym_relo_desc {
 	int kind;
 	int insn_idx;
 	bool is_weak;
+	bool is_typeless;
 };
 
 struct ksym_desc {
 	const char *name;
 	int ref;
 	int kind;
-	int off;
+	union {
+		/* used for kfunc */
+		int off;
+		/* used for typeless ksym */
+		bool typeless;
+	};
 	int insn;
 };
 
@@ -49,7 +55,7 @@ void bpf_gen__prog_load(struct bpf_gen *gen, struct bpf_prog_load_params *load_a
 void bpf_gen__map_update_elem(struct bpf_gen *gen, int map_idx, void *value, __u32 value_size);
 void bpf_gen__map_freeze(struct bpf_gen *gen, int map_idx);
 void bpf_gen__record_attach_target(struct bpf_gen *gen, const char *name, enum bpf_attach_type type);
-void bpf_gen__record_extern(struct bpf_gen *gen, const char *name, bool is_weak, int kind,
-			    int insn_idx);
+void bpf_gen__record_extern(struct bpf_gen *gen, const char *name, bool is_weak,
+			    bool is_typeless, int kind, int insn_idx);
 
 #endif
diff --git a/tools/lib/bpf/gen_loader.c b/tools/lib/bpf/gen_loader.c
index 937bfc7db41e..11172a868180 100644
--- a/tools/lib/bpf/gen_loader.c
+++ b/tools/lib/bpf/gen_loader.c
@@ -559,7 +559,7 @@ static void emit_find_attach_target(struct bpf_gen *gen)
 }
 
 void bpf_gen__record_extern(struct bpf_gen *gen, const char *name, bool is_weak,
-			    int kind, int insn_idx)
+			    bool is_typeless, int kind, int insn_idx)
 {
 	struct ksym_relo_desc *relo;
 
@@ -572,6 +572,7 @@ void bpf_gen__record_extern(struct bpf_gen *gen, const char *name, bool is_weak,
 	relo += gen->relo_cnt;
 	relo->name = name;
 	relo->is_weak = is_weak;
+	relo->is_typeless = is_typeless;
 	relo->kind = kind;
 	relo->insn_idx = insn_idx;
 	gen->relo_cnt++;
@@ -621,6 +622,29 @@ static void emit_bpf_find_by_name_kind(struct bpf_gen *gen, struct ksym_relo_des
 	debug_ret(gen, "find_by_name_kind(%s,%d)", relo->name, relo->kind);
 }
 
+/* Overwrites BPF_REG_{0, 1, 2, 3, 4, 7}
+ * Returns result in BPF_REG_7
+ * Returns u64 symbol addr in BPF_REG_9
+ */
+static void emit_bpf_kallsyms_lookup_name(struct bpf_gen *gen, struct ksym_relo_desc *relo)
+{
+	int name_off, len = strlen(relo->name) + 1, res_off;
+
+	name_off = add_data(gen, relo->name, len);
+	res_off = add_data(gen, NULL, 8); /* res is u64 */
+	emit2(gen, BPF_LD_IMM64_RAW_FULL(BPF_REG_1, BPF_PSEUDO_MAP_IDX_VALUE,
+					 0, 0, 0, name_off));
+	emit(gen, BPF_MOV64_IMM(BPF_REG_2, len));
+	emit(gen, BPF_MOV64_IMM(BPF_REG_3, 0));
+	emit2(gen, BPF_LD_IMM64_RAW_FULL(BPF_REG_4, BPF_PSEUDO_MAP_IDX_VALUE,
+					 0, 0, 0, res_off));
+	emit(gen, BPF_MOV64_REG(BPF_REG_7, BPF_REG_4));
+	emit(gen, BPF_EMIT_CALL(BPF_FUNC_kallsyms_lookup_name));
+	emit(gen, BPF_LDX_MEM(BPF_DW, BPF_REG_9, BPF_REG_7, 0));
+	emit(gen, BPF_MOV64_REG(BPF_REG_7, BPF_REG_0));
+	debug_ret(gen, "kallsyms_lookup_name(%s,%d)", relo->name, relo->kind);
+}
+
 /* Expects:
  * BPF_REG_8 - pointer to instruction
  *
@@ -700,6 +724,58 @@ static void emit_relo_kfunc_btf(struct bpf_gen *gen, struct ksym_relo_desc *relo
 		   relo->name, kdesc->ref);
 }
 
+static void emit_ksym_relo_log(struct bpf_gen *gen, struct ksym_relo_desc *relo,
+			       int ref)
+{
+	if (!gen->log_level)
+		return;
+	emit(gen, BPF_LDX_MEM(BPF_W, BPF_REG_7, BPF_REG_8,
+			      offsetof(struct bpf_insn, imm)));
+	emit(gen, BPF_LDX_MEM(BPF_H, BPF_REG_9, BPF_REG_8, sizeof(struct bpf_insn) +
+			      offsetof(struct bpf_insn, imm)));
+	debug_regs(gen, BPF_REG_7, BPF_REG_9, " var t=%d w=%d (%s:count=%d): imm[0]: %%d, imm[1]: %%d",
+		   relo->is_typeless, relo->is_weak, relo->name, ref);
+	emit(gen, BPF_LDX_MEM(BPF_B, BPF_REG_9, BPF_REG_8, offsetofend(struct bpf_insn, code)));
+	debug_regs(gen, BPF_REG_9, -1, " var t=%d w=%d (%s:count=%d): insn.reg",
+		   relo->is_typeless, relo->is_weak, relo->name, ref);
+}
+
+/* Expects:
+ * BPF_REG_8 - pointer to instruction
+ */
+static void emit_relo_ksym_typeless(struct bpf_gen *gen,
+				    struct ksym_relo_desc *relo, int insn)
+{
+	struct ksym_desc *kdesc;
+
+	kdesc = get_ksym_desc(gen, relo);
+	if (!kdesc)
+		return;
+	/* try to copy from existing ldimm64 insn */
+	if (kdesc->ref > 1) {
+		move_blob2blob(gen, insn + offsetof(struct bpf_insn, imm), 4,
+			       kdesc->insn + offsetof(struct bpf_insn, imm));
+		move_blob2blob(gen, insn + sizeof(struct bpf_insn) + offsetof(struct bpf_insn, imm), 4,
+			       kdesc->insn + sizeof(struct bpf_insn) + offsetof(struct bpf_insn, imm));
+		goto log;
+	}
+	/* remember insn offset, so we can copy ksym addr later */
+	kdesc->insn = insn;
+	/* skip typeless ksym_desc in fd closing loop in cleanup_relos */
+	kdesc->typeless = true;
+	emit_bpf_kallsyms_lookup_name(gen, relo);
+	emit(gen, BPF_JMP_IMM(BPF_JEQ, BPF_REG_7, -ENOENT, 1));
+	emit_check_err(gen);
+	/* store lower half of addr into insn[insn_idx].imm */
+	emit(gen, BPF_STX_MEM(BPF_W, BPF_REG_8, BPF_REG_9, offsetof(struct bpf_insn, imm)));
+	/* store upper half of addr into insn[insn_idx + 1].imm */
+	emit(gen, BPF_ALU64_IMM(BPF_RSH, BPF_REG_9, 32));
+	emit(gen, BPF_STX_MEM(BPF_W, BPF_REG_8, BPF_REG_9,
+		      sizeof(struct bpf_insn) + offsetof(struct bpf_insn, imm)));
+log:
+	emit_ksym_relo_log(gen, relo, kdesc->ref);
+}
+
 /* Expects:
  * BPF_REG_8 - pointer to instruction
  */
@@ -729,14 +805,7 @@ static void emit_relo_ksym_btf(struct bpf_gen *gen, struct ksym_relo_desc *relo,
 	emit(gen, BPF_STX_MEM(BPF_W, BPF_REG_8, BPF_REG_7,
 			      sizeof(struct bpf_insn) + offsetof(struct bpf_insn, imm)));
 log:
-	if (!gen->log_level)
-		return;
-	emit(gen, BPF_LDX_MEM(BPF_W, BPF_REG_7, BPF_REG_8,
-			      offsetof(struct bpf_insn, imm)));
-	emit(gen, BPF_LDX_MEM(BPF_H, BPF_REG_9, BPF_REG_8, sizeof(struct bpf_insn) +
-			      offsetof(struct bpf_insn, imm)));
-	debug_regs(gen, BPF_REG_7, BPF_REG_9, " var (%s:count=%d): imm: %%d, fd: %%d",
-		   relo->name, kdesc->ref);
+	emit_ksym_relo_log(gen, relo, kdesc->ref);
 }
 
 static void emit_relo(struct bpf_gen *gen, struct ksym_relo_desc *relo, int insns)
@@ -748,7 +817,10 @@ static void emit_relo(struct bpf_gen *gen, struct ksym_relo_desc *relo, int insn
 	emit2(gen, BPF_LD_IMM64_RAW_FULL(BPF_REG_8, BPF_PSEUDO_MAP_IDX_VALUE, 0, 0, 0, insn));
 	switch (relo->kind) {
 	case BTF_KIND_VAR:
-		emit_relo_ksym_btf(gen, relo, insn);
+		if (relo->is_typeless)
+			emit_relo_ksym_typeless(gen, relo, insn);
+		else
+			emit_relo_ksym_btf(gen, relo, insn);
 		break;
 	case BTF_KIND_FUNC:
 		emit_relo_kfunc_btf(gen, relo, insn);
@@ -773,12 +845,13 @@ static void cleanup_relos(struct bpf_gen *gen, int insns)
 	int i, insn;
 
 	for (i = 0; i < gen->nr_ksyms; i++) {
-		if (gen->ksyms[i].kind == BTF_KIND_VAR) {
+		/* only close fds for typed ksyms and kfuncs */
+		if (gen->ksyms[i].kind == BTF_KIND_VAR && !gen->ksyms[i].typeless) {
 			/* close fd recorded in insn[insn_idx + 1].imm */
 			insn = gen->ksyms[i].insn;
 			insn += sizeof(struct bpf_insn) + offsetof(struct bpf_insn, imm);
 			emit_sys_close_blob(gen, insn);
-		} else { /* BTF_KIND_FUNC */
+		} else if (gen->ksyms[i].kind == BTF_KIND_FUNC) {
 			emit_sys_close_blob(gen, blob_fd_array_off(gen, gen->ksyms[i].off));
 			if (gen->ksyms[i].off < MAX_FD_ARRAY_SZ)
 				gen->nr_fd_array--;
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 59d39ce9f375..61d666dc5646 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -6560,17 +6560,14 @@ static int bpf_program__record_externs(struct bpf_program *prog)
 		case RELO_EXTERN_VAR:
 			if (ext->type != EXT_KSYM)
 				continue;
-			if (!ext->ksym.type_id) {
-				pr_warn("typeless ksym %s is not supported yet\n",
-					ext->name);
-				return -ENOTSUP;
-			}
-			bpf_gen__record_extern(obj->gen_loader, ext->name, ext->is_weak,
+			bpf_gen__record_extern(obj->gen_loader, ext->name,
+					       ext->is_weak, !ext->ksym.type_id,
 					       BTF_KIND_VAR, relo->insn_idx);
 			break;
 		case RELO_EXTERN_FUNC:
-			bpf_gen__record_extern(obj->gen_loader, ext->name, ext->is_weak,
-					       BTF_KIND_FUNC, relo->insn_idx);
+			bpf_gen__record_extern(obj->gen_loader, ext->name,
+					       ext->is_weak, false, BTF_KIND_FUNC,
+					       relo->insn_idx);
 			break;
 		default:
 			continue;
-- 
2.33.1

[PATCH bpf-next v5 3/8] libbpf: Add weak ksym support to gen_loader

[Kumar Kartikeya Dwivedi]

This extends existing ksym relocation code to also support relocating
weak ksyms. Care needs to be taken to zero out the src_reg (currently
BPF_PSEUOD_BTF_ID, always set for gen_loader by bpf_object__relocate_data)
when the BTF ID lookup fails at runtime.  This is not a problem for
libbpf as it only sets ext->is_set when BTF ID lookup succeeds (and only
proceeds in case of failure if ext->is_weak, leading to src_reg
remaining as 0 for weak unresolved ksym).

A pattern similar to emit_relo_kfunc_btf is followed of first storing
the default values and then jumping over actual stores in case of an
error. For src_reg adjustment, we also need to perform it when copying
the populated instruction, so depending on if copied insn[0].imm is 0 or
not, we decide to jump over the adjustment.

We cannot reach that point unless the ksym was weak and resolved and
zeroed out, as the emit_check_err will cause us to jump to cleanup
label, so we do not need to recheck whether the ksym is weak before
doing the adjustment after copying BTF ID and BTF FD.

This is consistent with how libbpf relocates weak ksym. Logging
statements are added to show the relocation result and aid debugging.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 tools/lib/bpf/gen_loader.c | 35 ++++++++++++++++++++++++++++++++---
 1 file changed, 32 insertions(+), 3 deletions(-)

diff --git a/tools/lib/bpf/gen_loader.c b/tools/lib/bpf/gen_loader.c
index 11172a868180..1c404752e565 100644
--- a/tools/lib/bpf/gen_loader.c
+++ b/tools/lib/bpf/gen_loader.c
@@ -13,6 +13,7 @@
 #include "hashmap.h"
 #include "bpf_gen_internal.h"
 #include "skel_internal.h"
+#include <asm/byteorder.h>
 
 #define MAX_USED_MAPS	64
 #define MAX_USED_PROGS	32
@@ -776,12 +777,24 @@ static void emit_relo_ksym_typeless(struct bpf_gen *gen,
 	emit_ksym_relo_log(gen, relo, kdesc->ref);
 }
 
+static __u32 src_reg_mask(void)
+{
+#if defined(__LITTLE_ENDIAN_BITFIELD)
+	return 0x0f; /* src_reg,dst_reg,... */
+#elif defined(__BIG_ENDIAN_BITFIELD)
+	return 0xf0; /* dst_reg,src_reg,... */
+#else
+#error "Unsupported bit endianness, cannot proceed"
+#endif
+}
+
 /* Expects:
  * BPF_REG_8 - pointer to instruction
  */
 static void emit_relo_ksym_btf(struct bpf_gen *gen, struct ksym_relo_desc *relo, int insn)
 {
 	struct ksym_desc *kdesc;
+	__u32 reg_mask;
 
 	kdesc = get_ksym_desc(gen, relo);
 	if (!kdesc)
@@ -792,19 +805,35 @@ static void emit_relo_ksym_btf(struct bpf_gen *gen, struct ksym_relo_desc *relo,
 			       kdesc->insn + offsetof(struct bpf_insn, imm));
 		move_blob2blob(gen, insn + sizeof(struct bpf_insn) + offsetof(struct bpf_insn, imm), 4,
 			       kdesc->insn + sizeof(struct bpf_insn) + offsetof(struct bpf_insn, imm));
-		goto log;
+		emit(gen, BPF_LDX_MEM(BPF_W, BPF_REG_9, BPF_REG_8, offsetof(struct bpf_insn, imm)));
+		/* jump over src_reg adjustment if imm is not 0 */
+		emit(gen, BPF_JMP_IMM(BPF_JNE, BPF_REG_9, 0, 3));
+		goto clear_src_reg;
 	}
 	/* remember insn offset, so we can copy BTF ID and FD later */
 	kdesc->insn = insn;
 	emit_bpf_find_by_name_kind(gen, relo);
-	emit_check_err(gen);
+	if (!relo->is_weak)
+		emit_check_err(gen);
+	/* set default values as 0 */
+	emit(gen, BPF_ST_MEM(BPF_W, BPF_REG_8, offsetof(struct bpf_insn, imm), 0));
+	emit(gen, BPF_ST_MEM(BPF_W, BPF_REG_8, sizeof(struct bpf_insn) + offsetof(struct bpf_insn, imm), 0));
+	/* skip success case stores if ret < 0 */
+	emit(gen, BPF_JMP_IMM(BPF_JSLT, BPF_REG_7, 0, 4));
 	/* store btf_id into insn[insn_idx].imm */
 	emit(gen, BPF_STX_MEM(BPF_W, BPF_REG_8, BPF_REG_7, offsetof(struct bpf_insn, imm)));
 	/* store btf_obj_fd into insn[insn_idx + 1].imm */
 	emit(gen, BPF_ALU64_IMM(BPF_RSH, BPF_REG_7, 32));
 	emit(gen, BPF_STX_MEM(BPF_W, BPF_REG_8, BPF_REG_7,
 			      sizeof(struct bpf_insn) + offsetof(struct bpf_insn, imm)));
-log:
+	emit(gen, BPF_JMP_IMM(BPF_JSGE, BPF_REG_7, 0, 3));
+clear_src_reg:
+	/* clear bpf_object__relocate_data's src_reg assignment, otherwise we get a verifier failure */
+	reg_mask = src_reg_mask();
+	emit(gen, BPF_LDX_MEM(BPF_B, BPF_REG_9, BPF_REG_8, offsetofend(struct bpf_insn, code)));
+	emit(gen, BPF_ALU32_IMM(BPF_AND, BPF_REG_9, reg_mask));
+	emit(gen, BPF_STX_MEM(BPF_B, BPF_REG_8, BPF_REG_9, offsetofend(struct bpf_insn, code)));
+
 	emit_ksym_relo_log(gen, relo, kdesc->ref);
 }
 
-- 
2.33.1

[PATCH bpf-next v5 4/8] libbpf: Ensure that BPF syscall fds are never 0, 1, or 2

[Kumar Kartikeya Dwivedi]

Add a simple wrapper for passing an fd and getting a new one >= 3 if it
is one of 0, 1, or 2. There are two primary reasons to make this change:
First, libbpf relies on the assumption a certain BPF fd is never 0 (e.g.
most recently noticed in [0]). Second, Alexei pointed out in [1] that
some environments reset stdin, stdout, and stderr if they notice an
invalid fd at these numbers. To protect against both these cases, switch
all internal BPF syscall wrappers in libbpf to always return an fd >= 3.
We only need to modify the syscall wrappers and not other code that
assumes a valid fd by doing >= 0, to avoid pointless churn, and because
it is still a valid assumption. The cost paid is two additional syscalls
if fd is in range [0, 2].

  [0]: e31eec77e4ab ("bpf: selftests: Fix fd cleanup in get_branch_snapshot")
  [1]: https://lore.kernel.org/bpf/CAADnVQKVKY8o_3aU8Gzke443+uHa-eGoM0h7W4srChMXU1S4Bg@mail.gmail.com

Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 tools/lib/bpf/bpf.c             | 35 +++++++++++++++++++++------------
 tools/lib/bpf/libbpf_internal.h | 24 ++++++++++++++++++++++
 2 files changed, 46 insertions(+), 13 deletions(-)

diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index 7d1741ceaa32..53efbdb1b652 100644
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -65,13 +65,22 @@ static inline int sys_bpf(enum bpf_cmd cmd, union bpf_attr *attr,
 	return syscall(__NR_bpf, cmd, attr, size);
 }
 
+static inline int sys_bpf_fd(enum bpf_cmd cmd, union bpf_attr *attr,
+			     unsigned int size)
+{
+	int fd;
+
+	fd = sys_bpf(cmd, attr, size);
+	return ensure_good_fd(fd);
+}
+
 static inline int sys_bpf_prog_load(union bpf_attr *attr, unsigned int size)
 {
 	int retries = 5;
 	int fd;
 
 	do {
-		fd = sys_bpf(BPF_PROG_LOAD, attr, size);
+		fd = sys_bpf_fd(BPF_PROG_LOAD, attr, size);
 	} while (fd < 0 && errno == EAGAIN && retries-- > 0);
 
 	return fd;
@@ -103,7 +112,7 @@ int bpf_create_map_xattr(const struct bpf_create_map_attr *create_attr)
 	else
 		attr.inner_map_fd = create_attr->inner_map_fd;
 
-	fd = sys_bpf(BPF_MAP_CREATE, &attr, sizeof(attr));
+	fd = sys_bpf_fd(BPF_MAP_CREATE, &attr, sizeof(attr));
 	return libbpf_err_errno(fd);
 }
 
@@ -181,7 +190,7 @@ int bpf_create_map_in_map_node(enum bpf_map_type map_type, const char *name,
 		attr.numa_node = node;
 	}
 
-	fd = sys_bpf(BPF_MAP_CREATE, &attr, sizeof(attr));
+	fd = sys_bpf_fd(BPF_MAP_CREATE, &attr, sizeof(attr));
 	return libbpf_err_errno(fd);
 }
 
@@ -609,7 +618,7 @@ int bpf_obj_get(const char *pathname)
 	memset(&attr, 0, sizeof(attr));
 	attr.pathname = ptr_to_u64((void *)pathname);
 
-	fd = sys_bpf(BPF_OBJ_GET, &attr, sizeof(attr));
+	fd = sys_bpf_fd(BPF_OBJ_GET, &attr, sizeof(attr));
 	return libbpf_err_errno(fd);
 }
 
@@ -720,7 +729,7 @@ int bpf_link_create(int prog_fd, int target_fd,
 		break;
 	}
 proceed:
-	fd = sys_bpf(BPF_LINK_CREATE, &attr, sizeof(attr));
+	fd = sys_bpf_fd(BPF_LINK_CREATE, &attr, sizeof(attr));
 	return libbpf_err_errno(fd);
 }
 
@@ -763,7 +772,7 @@ int bpf_iter_create(int link_fd)
 	memset(&attr, 0, sizeof(attr));
 	attr.iter_create.link_fd = link_fd;
 
-	fd = sys_bpf(BPF_ITER_CREATE, &attr, sizeof(attr));
+	fd = sys_bpf_fd(BPF_ITER_CREATE, &attr, sizeof(attr));
 	return libbpf_err_errno(fd);
 }
 
@@ -921,7 +930,7 @@ int bpf_prog_get_fd_by_id(__u32 id)
 	memset(&attr, 0, sizeof(attr));
 	attr.prog_id = id;
 
-	fd = sys_bpf(BPF_PROG_GET_FD_BY_ID, &attr, sizeof(attr));
+	fd = sys_bpf_fd(BPF_PROG_GET_FD_BY_ID, &attr, sizeof(attr));
 	return libbpf_err_errno(fd);
 }
 
@@ -933,7 +942,7 @@ int bpf_map_get_fd_by_id(__u32 id)
 	memset(&attr, 0, sizeof(attr));
 	attr.map_id = id;
 
-	fd = sys_bpf(BPF_MAP_GET_FD_BY_ID, &attr, sizeof(attr));
+	fd = sys_bpf_fd(BPF_MAP_GET_FD_BY_ID, &attr, sizeof(attr));
 	return libbpf_err_errno(fd);
 }
 
@@ -945,7 +954,7 @@ int bpf_btf_get_fd_by_id(__u32 id)
 	memset(&attr, 0, sizeof(attr));
 	attr.btf_id = id;
 
-	fd = sys_bpf(BPF_BTF_GET_FD_BY_ID, &attr, sizeof(attr));
+	fd = sys_bpf_fd(BPF_BTF_GET_FD_BY_ID, &attr, sizeof(attr));
 	return libbpf_err_errno(fd);
 }
 
@@ -957,7 +966,7 @@ int bpf_link_get_fd_by_id(__u32 id)
 	memset(&attr, 0, sizeof(attr));
 	attr.link_id = id;
 
-	fd = sys_bpf(BPF_LINK_GET_FD_BY_ID, &attr, sizeof(attr));
+	fd = sys_bpf_fd(BPF_LINK_GET_FD_BY_ID, &attr, sizeof(attr));
 	return libbpf_err_errno(fd);
 }
 
@@ -988,7 +997,7 @@ int bpf_raw_tracepoint_open(const char *name, int prog_fd)
 	attr.raw_tracepoint.name = ptr_to_u64(name);
 	attr.raw_tracepoint.prog_fd = prog_fd;
 
-	fd = sys_bpf(BPF_RAW_TRACEPOINT_OPEN, &attr, sizeof(attr));
+	fd = sys_bpf_fd(BPF_RAW_TRACEPOINT_OPEN, &attr, sizeof(attr));
 	return libbpf_err_errno(fd);
 }
 
@@ -1008,7 +1017,7 @@ int bpf_load_btf(const void *btf, __u32 btf_size, char *log_buf, __u32 log_buf_s
 		attr.btf_log_buf = ptr_to_u64(log_buf);
 	}
 
-	fd = sys_bpf(BPF_BTF_LOAD, &attr, sizeof(attr));
+	fd = sys_bpf_fd(BPF_BTF_LOAD, &attr, sizeof(attr));
 
 	if (fd < 0 && !do_log && log_buf && log_buf_size) {
 		do_log = true;
@@ -1050,7 +1059,7 @@ int bpf_enable_stats(enum bpf_stats_type type)
 	memset(&attr, 0, sizeof(attr));
 	attr.enable_stats.type = type;
 
-	fd = sys_bpf(BPF_ENABLE_STATS, &attr, sizeof(attr));
+	fd = sys_bpf_fd(BPF_ENABLE_STATS, &attr, sizeof(attr));
 	return libbpf_err_errno(fd);
 }
 
diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h
index 13bc7950e304..14f135808f5c 100644
--- a/tools/lib/bpf/libbpf_internal.h
+++ b/tools/lib/bpf/libbpf_internal.h
@@ -13,6 +13,8 @@
 #include <limits.h>
 #include <errno.h>
 #include <linux/err.h>
+#include <fcntl.h>
+#include <unistd.h>
 #include "libbpf_legacy.h"
 #include "relo_core.h"
 
@@ -468,4 +470,26 @@ static inline bool is_ldimm64_insn(struct bpf_insn *insn)
 	return insn->code == (BPF_LD | BPF_IMM | BPF_DW);
 }
 
+/* if fd is stdin, stdout, or stderr, dup to a fd greater than 2
+ * Takes ownership of the fd passed in, and closes it if calling
+ * fcntl(fd, F_DUPFD_CLOEXEC, 3).
+ */
+static inline int ensure_good_fd(int fd)
+{
+	int old_fd = fd, saved_errno;
+
+	if (fd < 0)
+		return fd;
+	if (fd < 3) {
+		fd = fcntl(fd, F_DUPFD_CLOEXEC, 3);
+		saved_errno = errno;
+		close(old_fd);
+		if (fd < 0) {
+			pr_warn("failed to dup FD %d to FD > 2: %d\n", old_fd, -saved_errno);
+			errno = saved_errno;
+		}
+	}
+	return fd;
+}
+
 #endif /* __LIBBPF_LIBBPF_INTERNAL_H */
-- 
2.33.1

[PATCH bpf-next v5 5/8] libbpf: Use O_CLOEXEC uniformly when opening fds

[Kumar Kartikeya Dwivedi]

There are some instances where we don't use O_CLOEXEC when opening an
fd, fix these up. Otherwise, it is possible that a parallel fork causes
these fds to leak into a child process on execve.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 tools/lib/bpf/btf.c           | 2 +-
 tools/lib/bpf/libbpf.c        | 6 +++---
 tools/lib/bpf/libbpf_probes.c | 2 +-
 tools/lib/bpf/linker.c        | 4 ++--
 tools/lib/bpf/xsk.c           | 6 +++---
 5 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index 0c628c33e23b..7e4c5586bd87 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -897,7 +897,7 @@ static struct btf *btf_parse_elf(const char *path, struct btf *base_btf,
 		return ERR_PTR(-LIBBPF_ERRNO__LIBELF);
 	}
 
-	fd = open(path, O_RDONLY);
+	fd = open(path, O_RDONLY | O_CLOEXEC);
 	if (fd < 0) {
 		err = -errno;
 		pr_warn("failed to open %s: %s\n", path, strerror(errno));
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 61d666dc5646..f284c8ce83f1 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -1231,7 +1231,7 @@ static int bpf_object__elf_init(struct bpf_object *obj)
 		 */
 		elf = elf_memory((char *)obj->efile.obj_buf, obj->efile.obj_buf_sz);
 	} else {
-		obj->efile.fd = open(obj->path, O_RDONLY);
+		obj->efile.fd = open(obj->path, O_RDONLY | O_CLOEXEC);
 		if (obj->efile.fd < 0) {
 			char errmsg[STRERR_BUFSIZE], *cp;
 
@@ -9587,7 +9587,7 @@ static int append_to_file(const char *file, const char *fmt, ...)
 	int fd, n, err = 0;
 	va_list ap;
 
-	fd = open(file, O_WRONLY | O_APPEND, 0);
+	fd = open(file, O_WRONLY | O_APPEND | O_CLOEXEC, 0);
 	if (fd < 0)
 		return -errno;
 
@@ -11232,7 +11232,7 @@ int parse_cpu_mask_file(const char *fcpu, bool **mask, int *mask_sz)
 	int fd, err = 0, len;
 	char buf[128];
 
-	fd = open(fcpu, O_RDONLY);
+	fd = open(fcpu, O_RDONLY | O_CLOEXEC);
 	if (fd < 0) {
 		err = -errno;
 		pr_warn("Failed to open cpu mask file %s: %d\n", fcpu, err);
diff --git a/tools/lib/bpf/libbpf_probes.c b/tools/lib/bpf/libbpf_probes.c
index cd8c703dde71..68f2dbf364aa 100644
--- a/tools/lib/bpf/libbpf_probes.c
+++ b/tools/lib/bpf/libbpf_probes.c
@@ -33,7 +33,7 @@ static int get_vendor_id(int ifindex)
 
 	snprintf(path, sizeof(path), "/sys/class/net/%s/device/vendor", ifname);
 
-	fd = open(path, O_RDONLY);
+	fd = open(path, O_RDONLY | O_CLOEXEC);
 	if (fd < 0)
 		return -1;
 
diff --git a/tools/lib/bpf/linker.c b/tools/lib/bpf/linker.c
index ce0800e61dc7..f677dccdeae4 100644
--- a/tools/lib/bpf/linker.c
+++ b/tools/lib/bpf/linker.c
@@ -301,7 +301,7 @@ static int init_output_elf(struct bpf_linker *linker, const char *file)
 	if (!linker->filename)
 		return -ENOMEM;
 
-	linker->fd = open(file, O_WRONLY | O_CREAT | O_TRUNC, 0644);
+	linker->fd = open(file, O_WRONLY | O_CREAT | O_TRUNC | O_CLOEXEC, 0644);
 	if (linker->fd < 0) {
 		err = -errno;
 		pr_warn("failed to create '%s': %d\n", file, err);
@@ -556,7 +556,7 @@ static int linker_load_obj_file(struct bpf_linker *linker, const char *filename,
 
 	obj->filename = filename;
 
-	obj->fd = open(filename, O_RDONLY);
+	obj->fd = open(filename, O_RDONLY | O_CLOEXEC);
 	if (obj->fd < 0) {
 		err = -errno;
 		pr_warn("failed to open file '%s': %d\n", filename, err);
diff --git a/tools/lib/bpf/xsk.c b/tools/lib/bpf/xsk.c
index a2111696ba91..81f8fbc85e70 100644
--- a/tools/lib/bpf/xsk.c
+++ b/tools/lib/bpf/xsk.c
@@ -300,7 +300,7 @@ int xsk_umem__create_v0_0_4(struct xsk_umem **umem_ptr, void *umem_area,
 	if (!umem)
 		return -ENOMEM;
 
-	umem->fd = socket(AF_XDP, SOCK_RAW, 0);
+	umem->fd = socket(AF_XDP, SOCK_RAW | SOCK_CLOEXEC, 0);
 	if (umem->fd < 0) {
 		err = -errno;
 		goto out_umem_alloc;
@@ -549,7 +549,7 @@ static int xsk_get_max_queues(struct xsk_socket *xsk)
 	struct ifreq ifr = {};
 	int fd, err, ret;
 
-	fd = socket(AF_LOCAL, SOCK_DGRAM, 0);
+	fd = socket(AF_LOCAL, SOCK_DGRAM | SOCK_CLOEXEC, 0);
 	if (fd < 0)
 		return -errno;
 
@@ -1046,7 +1046,7 @@ int xsk_socket__create_shared(struct xsk_socket **xsk_ptr,
 	}
 
 	if (umem->refcount++ > 0) {
-		xsk->fd = socket(AF_XDP, SOCK_RAW, 0);
+		xsk->fd = socket(AF_XDP, SOCK_RAW | SOCK_CLOEXEC, 0);
 		if (xsk->fd < 0) {
 			err = -errno;
 			goto out_xsk_alloc;
-- 
2.33.1

[PATCH bpf-next v5 6/8] selftests/bpf: Add weak/typeless ksym test for light skeleton

[Kumar Kartikeya Dwivedi]

Also, avoid using CO-RE features, as lskel doesn't support CO-RE, yet.
Include both light and libbpf skeleton in same file to test both of them
together.

In c48e51c8b07a ("bpf: selftests: Add selftests for module kfunc support"),
I added support for generating both lskel and libbpf skel for a BPF
object, however the name parameter for bpftool caused collisions when
included in same file together. This meant that every test needed a
separate file for a libbpf/light skeleton separation instead of
subtests.

Change that by appending a "_lskel" suffix to the name for files using
light skeleton, and convert all existing users.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 tools/testing/selftests/bpf/Makefile          |  4 +-
 .../selftests/bpf/prog_tests/atomics.c        | 34 ++++++++--------
 .../selftests/bpf/prog_tests/fentry_fexit.c   | 16 ++++----
 .../selftests/bpf/prog_tests/fentry_test.c    | 14 +++----
 .../selftests/bpf/prog_tests/fexit_sleep.c    | 12 +++---
 .../selftests/bpf/prog_tests/fexit_test.c     | 14 +++----
 .../selftests/bpf/prog_tests/kfunc_call.c     |  6 +--
 .../selftests/bpf/prog_tests/ksyms_btf.c      | 35 +++++++++++++++-
 .../selftests/bpf/prog_tests/ksyms_module.c   | 40 +++++++++++++++++--
 .../bpf/prog_tests/ksyms_module_libbpf.c      | 28 -------------
 .../selftests/bpf/prog_tests/ringbuf.c        | 12 +++---
 .../selftests/bpf/prog_tests/trace_printk.c   | 14 +++----
 .../selftests/bpf/prog_tests/trace_vprintk.c  | 12 +++---
 .../selftests/bpf/prog_tests/verif_stats.c    |  6 +--
 .../selftests/bpf/progs/test_ksyms_weak.c     |  2 +-
 15 files changed, 142 insertions(+), 107 deletions(-)
 delete mode 100644 tools/testing/selftests/bpf/prog_tests/ksyms_module_libbpf.c

diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index ac47cf9760fc..70276cce949a 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -325,7 +325,7 @@ LINKED_SKELS := test_static_linked.skel.h linked_funcs.skel.h		\
 LSKELS := kfunc_call_test.c fentry_test.c fexit_test.c fexit_sleep.c \
 	test_ringbuf.c atomics.c trace_printk.c trace_vprintk.c
 # Generate both light skeleton and libbpf skeleton for these
-LSKELS_EXTRA := test_ksyms_module.c
+LSKELS_EXTRA := test_ksyms_module.c test_ksyms_weak.c
 SKEL_BLACKLIST += $$(LSKELS)
 
 test_static_linked.skel.h-deps := test_static_linked1.o test_static_linked2.o
@@ -404,7 +404,7 @@ $(TRUNNER_BPF_LSKELS): %.lskel.h: %.o $(BPFTOOL) | $(TRUNNER_OUTPUT)
 	$(Q)$$(BPFTOOL) gen object $$(<:.o=.linked2.o) $$(<:.o=.linked1.o)
 	$(Q)$$(BPFTOOL) gen object $$(<:.o=.linked3.o) $$(<:.o=.linked2.o)
 	$(Q)diff $$(<:.o=.linked2.o) $$(<:.o=.linked3.o)
-	$(Q)$$(BPFTOOL) gen skeleton -L $$(<:.o=.linked3.o) name $$(notdir $$(<:.o=)) > $$@
+	$(Q)$$(BPFTOOL) gen skeleton -L $$(<:.o=.linked3.o) name $$(notdir $$(<:.o=_lskel)) > $$@
 
 $(TRUNNER_BPF_SKELS_LINKED): $(TRUNNER_BPF_OBJS) $(BPFTOOL) | $(TRUNNER_OUTPUT)
 	$$(call msg,LINK-BPF,$(TRUNNER_BINARY),$$(@:.skel.h=.o))
diff --git a/tools/testing/selftests/bpf/prog_tests/atomics.c b/tools/testing/selftests/bpf/prog_tests/atomics.c
index 1486be5d3209..0f9525293881 100644
--- a/tools/testing/selftests/bpf/prog_tests/atomics.c
+++ b/tools/testing/selftests/bpf/prog_tests/atomics.c
@@ -4,13 +4,13 @@
 
 #include "atomics.lskel.h"
 
-static void test_add(struct atomics *skel)
+static void test_add(struct atomics_lskel *skel)
 {
 	int err, prog_fd;
 	__u32 duration = 0, retval;
 	int link_fd;
 
-	link_fd = atomics__add__attach(skel);
+	link_fd = atomics_lskel__add__attach(skel);
 	if (!ASSERT_GT(link_fd, 0, "attach(add)"))
 		return;
 
@@ -36,13 +36,13 @@ static void test_add(struct atomics *skel)
 	close(link_fd);
 }
 
-static void test_sub(struct atomics *skel)
+static void test_sub(struct atomics_lskel *skel)
 {
 	int err, prog_fd;
 	__u32 duration = 0, retval;
 	int link_fd;
 
-	link_fd = atomics__sub__attach(skel);
+	link_fd = atomics_lskel__sub__attach(skel);
 	if (!ASSERT_GT(link_fd, 0, "attach(sub)"))
 		return;
 
@@ -69,13 +69,13 @@ static void test_sub(struct atomics *skel)
 	close(link_fd);
 }
 
-static void test_and(struct atomics *skel)
+static void test_and(struct atomics_lskel *skel)
 {
 	int err, prog_fd;
 	__u32 duration = 0, retval;
 	int link_fd;
 
-	link_fd = atomics__and__attach(skel);
+	link_fd = atomics_lskel__and__attach(skel);
 	if (!ASSERT_GT(link_fd, 0, "attach(and)"))
 		return;
 
@@ -97,13 +97,13 @@ static void test_and(struct atomics *skel)
 	close(link_fd);
 }
 
-static void test_or(struct atomics *skel)
+static void test_or(struct atomics_lskel *skel)
 {
 	int err, prog_fd;
 	__u32 duration = 0, retval;
 	int link_fd;
 
-	link_fd = atomics__or__attach(skel);
+	link_fd = atomics_lskel__or__attach(skel);
 	if (!ASSERT_GT(link_fd, 0, "attach(or)"))
 		return;
 
@@ -126,13 +126,13 @@ static void test_or(struct atomics *skel)
 	close(link_fd);
 }
 
-static void test_xor(struct atomics *skel)
+static void test_xor(struct atomics_lskel *skel)
 {
 	int err, prog_fd;
 	__u32 duration = 0, retval;
 	int link_fd;
 
-	link_fd = atomics__xor__attach(skel);
+	link_fd = atomics_lskel__xor__attach(skel);
 	if (!ASSERT_GT(link_fd, 0, "attach(xor)"))
 		return;
 
@@ -154,13 +154,13 @@ static void test_xor(struct atomics *skel)
 	close(link_fd);
 }
 
-static void test_cmpxchg(struct atomics *skel)
+static void test_cmpxchg(struct atomics_lskel *skel)
 {
 	int err, prog_fd;
 	__u32 duration = 0, retval;
 	int link_fd;
 
-	link_fd = atomics__cmpxchg__attach(skel);
+	link_fd = atomics_lskel__cmpxchg__attach(skel);
 	if (!ASSERT_GT(link_fd, 0, "attach(cmpxchg)"))
 		return;
 
@@ -183,13 +183,13 @@ static void test_cmpxchg(struct atomics *skel)
 	close(link_fd);
 }
 
-static void test_xchg(struct atomics *skel)
+static void test_xchg(struct atomics_lskel *skel)
 {
 	int err, prog_fd;
 	__u32 duration = 0, retval;
 	int link_fd;
 
-	link_fd = atomics__xchg__attach(skel);
+	link_fd = atomics_lskel__xchg__attach(skel);
 	if (!ASSERT_GT(link_fd, 0, "attach(xchg)"))
 		return;
 
@@ -212,10 +212,10 @@ static void test_xchg(struct atomics *skel)
 
 void test_atomics(void)
 {
-	struct atomics *skel;
+	struct atomics_lskel *skel;
 	__u32 duration = 0;
 
-	skel = atomics__open_and_load();
+	skel = atomics_lskel__open_and_load();
 	if (CHECK(!skel, "skel_load", "atomics skeleton failed\n"))
 		return;
 
@@ -243,5 +243,5 @@ void test_atomics(void)
 		test_xchg(skel);
 
 cleanup:
-	atomics__destroy(skel);
+	atomics_lskel__destroy(skel);
 }
diff --git a/tools/testing/selftests/bpf/prog_tests/fentry_fexit.c b/tools/testing/selftests/bpf/prog_tests/fentry_fexit.c
index 91154c2ba256..4374ac8a8a91 100644
--- a/tools/testing/selftests/bpf/prog_tests/fentry_fexit.c
+++ b/tools/testing/selftests/bpf/prog_tests/fentry_fexit.c
@@ -6,23 +6,23 @@
 
 void test_fentry_fexit(void)
 {
-	struct fentry_test *fentry_skel = NULL;
-	struct fexit_test *fexit_skel = NULL;
+	struct fentry_test_lskel *fentry_skel = NULL;
+	struct fexit_test_lskel *fexit_skel = NULL;
 	__u64 *fentry_res, *fexit_res;
 	__u32 duration = 0, retval;
 	int err, prog_fd, i;
 
-	fentry_skel = fentry_test__open_and_load();
+	fentry_skel = fentry_test_lskel__open_and_load();
 	if (CHECK(!fentry_skel, "fentry_skel_load", "fentry skeleton failed\n"))
 		goto close_prog;
-	fexit_skel = fexit_test__open_and_load();
+	fexit_skel = fexit_test_lskel__open_and_load();
 	if (CHECK(!fexit_skel, "fexit_skel_load", "fexit skeleton failed\n"))
 		goto close_prog;
 
-	err = fentry_test__attach(fentry_skel);
+	err = fentry_test_lskel__attach(fentry_skel);
 	if (CHECK(err, "fentry_attach", "fentry attach failed: %d\n", err))
 		goto close_prog;
-	err = fexit_test__attach(fexit_skel);
+	err = fexit_test_lskel__attach(fexit_skel);
 	if (CHECK(err, "fexit_attach", "fexit attach failed: %d\n", err))
 		goto close_prog;
 
@@ -44,6 +44,6 @@ void test_fentry_fexit(void)
 	}
 
 close_prog:
-	fentry_test__destroy(fentry_skel);
-	fexit_test__destroy(fexit_skel);
+	fentry_test_lskel__destroy(fentry_skel);
+	fexit_test_lskel__destroy(fexit_skel);
 }
diff --git a/tools/testing/selftests/bpf/prog_tests/fentry_test.c b/tools/testing/selftests/bpf/prog_tests/fentry_test.c
index 174c89e7456e..12921b3850d2 100644
--- a/tools/testing/selftests/bpf/prog_tests/fentry_test.c
+++ b/tools/testing/selftests/bpf/prog_tests/fentry_test.c
@@ -3,19 +3,19 @@
 #include <test_progs.h>
 #include "fentry_test.lskel.h"
 
-static int fentry_test(struct fentry_test *fentry_skel)
+static int fentry_test(struct fentry_test_lskel *fentry_skel)
 {
 	int err, prog_fd, i;
 	__u32 duration = 0, retval;
 	int link_fd;
 	__u64 *result;
 
-	err = fentry_test__attach(fentry_skel);
+	err = fentry_test_lskel__attach(fentry_skel);
 	if (!ASSERT_OK(err, "fentry_attach"))
 		return err;
 
 	/* Check that already linked program can't be attached again. */
-	link_fd = fentry_test__test1__attach(fentry_skel);
+	link_fd = fentry_test_lskel__test1__attach(fentry_skel);
 	if (!ASSERT_LT(link_fd, 0, "fentry_attach_link"))
 		return -1;
 
@@ -31,7 +31,7 @@ static int fentry_test(struct fentry_test *fentry_skel)
 			return -1;
 	}
 
-	fentry_test__detach(fentry_skel);
+	fentry_test_lskel__detach(fentry_skel);
 
 	/* zero results for re-attach test */
 	memset(fentry_skel->bss, 0, sizeof(*fentry_skel->bss));
@@ -40,10 +40,10 @@ static int fentry_test(struct fentry_test *fentry_skel)
 
 void test_fentry_test(void)
 {
-	struct fentry_test *fentry_skel = NULL;
+	struct fentry_test_lskel *fentry_skel = NULL;
 	int err;
 
-	fentry_skel = fentry_test__open_and_load();
+	fentry_skel = fentry_test_lskel__open_and_load();
 	if (!ASSERT_OK_PTR(fentry_skel, "fentry_skel_load"))
 		goto cleanup;
 
@@ -55,5 +55,5 @@ void test_fentry_test(void)
 	ASSERT_OK(err, "fentry_second_attach");
 
 cleanup:
-	fentry_test__destroy(fentry_skel);
+	fentry_test_lskel__destroy(fentry_skel);
 }
diff --git a/tools/testing/selftests/bpf/prog_tests/fexit_sleep.c b/tools/testing/selftests/bpf/prog_tests/fexit_sleep.c
index 4e7f4b42ea29..f949647dbbc2 100644
--- a/tools/testing/selftests/bpf/prog_tests/fexit_sleep.c
+++ b/tools/testing/selftests/bpf/prog_tests/fexit_sleep.c
@@ -10,7 +10,7 @@
 
 static int do_sleep(void *skel)
 {
-	struct fexit_sleep *fexit_skel = skel;
+	struct fexit_sleep_lskel *fexit_skel = skel;
 	struct timespec ts1 = { .tv_nsec = 1 };
 	struct timespec ts2 = { .tv_sec = 10 };
 
@@ -25,16 +25,16 @@ static char child_stack[STACK_SIZE];
 
 void test_fexit_sleep(void)
 {
-	struct fexit_sleep *fexit_skel = NULL;
+	struct fexit_sleep_lskel *fexit_skel = NULL;
 	int wstatus, duration = 0;
 	pid_t cpid;
 	int err, fexit_cnt;
 
-	fexit_skel = fexit_sleep__open_and_load();
+	fexit_skel = fexit_sleep_lskel__open_and_load();
 	if (CHECK(!fexit_skel, "fexit_skel_load", "fexit skeleton failed\n"))
 		goto cleanup;
 
-	err = fexit_sleep__attach(fexit_skel);
+	err = fexit_sleep_lskel__attach(fexit_skel);
 	if (CHECK(err, "fexit_attach", "fexit attach failed: %d\n", err))
 		goto cleanup;
 
@@ -60,7 +60,7 @@ void test_fexit_sleep(void)
 	 */
 	close(fexit_skel->progs.nanosleep_fentry.prog_fd);
 	close(fexit_skel->progs.nanosleep_fexit.prog_fd);
-	fexit_sleep__detach(fexit_skel);
+	fexit_sleep_lskel__detach(fexit_skel);
 
 	/* kill the thread to unwind sys_nanosleep stack through the trampoline */
 	kill(cpid, 9);
@@ -78,5 +78,5 @@ void test_fexit_sleep(void)
 		goto cleanup;
 
 cleanup:
-	fexit_sleep__destroy(fexit_skel);
+	fexit_sleep_lskel__destroy(fexit_skel);
 }
diff --git a/tools/testing/selftests/bpf/prog_tests/fexit_test.c b/tools/testing/selftests/bpf/prog_tests/fexit_test.c
index af3dba726701..d4887d8bb396 100644
--- a/tools/testing/selftests/bpf/prog_tests/fexit_test.c
+++ b/tools/testing/selftests/bpf/prog_tests/fexit_test.c
@@ -3,19 +3,19 @@
 #include <test_progs.h>
 #include "fexit_test.lskel.h"
 
-static int fexit_test(struct fexit_test *fexit_skel)
+static int fexit_test(struct fexit_test_lskel *fexit_skel)
 {
 	int err, prog_fd, i;
 	__u32 duration = 0, retval;
 	int link_fd;
 	__u64 *result;
 
-	err = fexit_test__attach(fexit_skel);
+	err = fexit_test_lskel__attach(fexit_skel);
 	if (!ASSERT_OK(err, "fexit_attach"))
 		return err;
 
 	/* Check that already linked program can't be attached again. */
-	link_fd = fexit_test__test1__attach(fexit_skel);
+	link_fd = fexit_test_lskel__test1__attach(fexit_skel);
 	if (!ASSERT_LT(link_fd, 0, "fexit_attach_link"))
 		return -1;
 
@@ -31,7 +31,7 @@ static int fexit_test(struct fexit_test *fexit_skel)
 			return -1;
 	}
 
-	fexit_test__detach(fexit_skel);
+	fexit_test_lskel__detach(fexit_skel);
 
 	/* zero results for re-attach test */
 	memset(fexit_skel->bss, 0, sizeof(*fexit_skel->bss));
@@ -40,10 +40,10 @@ static int fexit_test(struct fexit_test *fexit_skel)
 
 void test_fexit_test(void)
 {
-	struct fexit_test *fexit_skel = NULL;
+	struct fexit_test_lskel *fexit_skel = NULL;
 	int err;
 
-	fexit_skel = fexit_test__open_and_load();
+	fexit_skel = fexit_test_lskel__open_and_load();
 	if (!ASSERT_OK_PTR(fexit_skel, "fexit_skel_load"))
 		goto cleanup;
 
@@ -55,5 +55,5 @@ void test_fexit_test(void)
 	ASSERT_OK(err, "fexit_second_attach");
 
 cleanup:
-	fexit_test__destroy(fexit_skel);
+	fexit_test_lskel__destroy(fexit_skel);
 }
diff --git a/tools/testing/selftests/bpf/prog_tests/kfunc_call.c b/tools/testing/selftests/bpf/prog_tests/kfunc_call.c
index 9611f2bc50df..5c9c0176991b 100644
--- a/tools/testing/selftests/bpf/prog_tests/kfunc_call.c
+++ b/tools/testing/selftests/bpf/prog_tests/kfunc_call.c
@@ -7,10 +7,10 @@
 
 static void test_main(void)
 {
-	struct kfunc_call_test *skel;
+	struct kfunc_call_test_lskel *skel;
 	int prog_fd, retval, err;
 
-	skel = kfunc_call_test__open_and_load();
+	skel = kfunc_call_test_lskel__open_and_load();
 	if (!ASSERT_OK_PTR(skel, "skel"))
 		return;
 
@@ -26,7 +26,7 @@ static void test_main(void)
 	ASSERT_OK(err, "bpf_prog_test_run(test2)");
 	ASSERT_EQ(retval, 3, "test2-retval");
 
-	kfunc_call_test__destroy(skel);
+	kfunc_call_test_lskel__destroy(skel);
 }
 
 static void test_subprog(void)
diff --git a/tools/testing/selftests/bpf/prog_tests/ksyms_btf.c b/tools/testing/selftests/bpf/prog_tests/ksyms_btf.c
index cf3acfa5a91d..79f6bd1e50d6 100644
--- a/tools/testing/selftests/bpf/prog_tests/ksyms_btf.c
+++ b/tools/testing/selftests/bpf/prog_tests/ksyms_btf.c
@@ -7,6 +7,7 @@
 #include "test_ksyms_btf.skel.h"
 #include "test_ksyms_btf_null_check.skel.h"
 #include "test_ksyms_weak.skel.h"
+#include "test_ksyms_weak.lskel.h"
 
 static int duration;
 
@@ -89,11 +90,11 @@ static void test_weak_syms(void)
 	int err;
 
 	skel = test_ksyms_weak__open_and_load();
-	if (CHECK(!skel, "test_ksyms_weak__open_and_load", "failed\n"))
+	if (!ASSERT_OK_PTR(skel, "test_ksyms_weak__open_and_load"))
 		return;
 
 	err = test_ksyms_weak__attach(skel);
-	if (CHECK(err, "test_ksyms_weak__attach", "skeleton attach failed: %d\n", err))
+	if (!ASSERT_OK(err, "test_ksyms_weak__attach"))
 		goto cleanup;
 
 	/* trigger tracepoint */
@@ -109,6 +110,33 @@ static void test_weak_syms(void)
 	test_ksyms_weak__destroy(skel);
 }
 
+static void test_weak_syms_lskel(void)
+{
+	struct test_ksyms_weak_lskel *skel;
+	struct test_ksyms_weak_lskel__data *data;
+	int err;
+
+	skel = test_ksyms_weak_lskel__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "test_ksyms_weak_lskel__open_and_load"))
+		return;
+
+	err = test_ksyms_weak_lskel__attach(skel);
+	if (!ASSERT_OK(err, "test_ksyms_weak_lskel__attach"))
+		goto cleanup;
+
+	/* trigger tracepoint */
+	usleep(1);
+
+	data = skel->data;
+	ASSERT_EQ(data->out__existing_typed, 0, "existing typed ksym");
+	ASSERT_NEQ(data->out__existing_typeless, -1, "existing typeless ksym");
+	ASSERT_EQ(data->out__non_existent_typeless, 0, "nonexistent typeless ksym");
+	ASSERT_EQ(data->out__non_existent_typed, 0, "nonexistent typed ksym");
+
+cleanup:
+	test_ksyms_weak_lskel__destroy(skel);
+}
+
 void test_ksyms_btf(void)
 {
 	int percpu_datasec;
@@ -136,4 +164,7 @@ void test_ksyms_btf(void)
 
 	if (test__start_subtest("weak_ksyms"))
 		test_weak_syms();
+
+	if (test__start_subtest("weak_ksyms_lskel"))
+		test_weak_syms_lskel();
 }
diff --git a/tools/testing/selftests/bpf/prog_tests/ksyms_module.c b/tools/testing/selftests/bpf/prog_tests/ksyms_module.c
index 831447878d7b..d490ad80eccb 100644
--- a/tools/testing/selftests/bpf/prog_tests/ksyms_module.c
+++ b/tools/testing/selftests/bpf/prog_tests/ksyms_module.c
@@ -4,10 +4,11 @@
 #include <test_progs.h>
 #include <network_helpers.h>
 #include "test_ksyms_module.lskel.h"
+#include "test_ksyms_module.skel.h"
 
-void test_ksyms_module(void)
+void test_ksyms_module_lskel(void)
 {
-	struct test_ksyms_module *skel;
+	struct test_ksyms_module_lskel *skel;
 	int retval;
 	int err;
 
@@ -16,8 +17,8 @@ void test_ksyms_module(void)
 		return;
 	}
 
-	skel = test_ksyms_module__open_and_load();
-	if (!ASSERT_OK_PTR(skel, "test_ksyms_module__open_and_load"))
+	skel = test_ksyms_module_lskel__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "test_ksyms_module_lskel__open_and_load"))
 		return;
 	err = bpf_prog_test_run(skel->progs.load.prog_fd, 1, &pkt_v4, sizeof(pkt_v4),
 				NULL, NULL, (__u32 *)&retval, NULL);
@@ -25,6 +26,37 @@ void test_ksyms_module(void)
 		goto cleanup;
 	ASSERT_EQ(retval, 0, "retval");
 	ASSERT_EQ(skel->bss->out_bpf_testmod_ksym, 42, "bpf_testmod_ksym");
+cleanup:
+	test_ksyms_module_lskel__destroy(skel);
+}
+
+void test_ksyms_module_libbpf(void)
+{
+	struct test_ksyms_module *skel;
+	int retval, err;
+
+	if (!env.has_testmod) {
+		test__skip();
+		return;
+	}
+
+	skel = test_ksyms_module__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "test_ksyms_module__open"))
+		return;
+	err = bpf_prog_test_run(bpf_program__fd(skel->progs.load), 1, &pkt_v4,
+				sizeof(pkt_v4), NULL, NULL, (__u32 *)&retval, NULL);
+	if (!ASSERT_OK(err, "bpf_prog_test_run"))
+		goto cleanup;
+	ASSERT_EQ(retval, 0, "retval");
+	ASSERT_EQ(skel->bss->out_bpf_testmod_ksym, 42, "bpf_testmod_ksym");
 cleanup:
 	test_ksyms_module__destroy(skel);
 }
+
+void test_ksyms_module(void)
+{
+	if (test__start_subtest("lskel"))
+		test_ksyms_module_lskel();
+	if (test__start_subtest("libbpf"))
+		test_ksyms_module_libbpf();
+}
diff --git a/tools/testing/selftests/bpf/prog_tests/ksyms_module_libbpf.c b/tools/testing/selftests/bpf/prog_tests/ksyms_module_libbpf.c
deleted file mode 100644
index e6343ef63af9..000000000000
--- a/tools/testing/selftests/bpf/prog_tests/ksyms_module_libbpf.c
+++ /dev/null
@@ -1,28 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0
-
-#include <test_progs.h>
-#include <network_helpers.h>
-#include "test_ksyms_module.skel.h"
-
-void test_ksyms_module_libbpf(void)
-{
-	struct test_ksyms_module *skel;
-	int retval, err;
-
-	if (!env.has_testmod) {
-		test__skip();
-		return;
-	}
-
-	skel = test_ksyms_module__open_and_load();
-	if (!ASSERT_OK_PTR(skel, "test_ksyms_module__open"))
-		return;
-	err = bpf_prog_test_run(bpf_program__fd(skel->progs.load), 1, &pkt_v4,
-				sizeof(pkt_v4), NULL, NULL, (__u32 *)&retval, NULL);
-	if (!ASSERT_OK(err, "bpf_prog_test_run"))
-		goto cleanup;
-	ASSERT_EQ(retval, 0, "retval");
-	ASSERT_EQ(skel->bss->out_bpf_testmod_ksym, 42, "bpf_testmod_ksym");
-cleanup:
-	test_ksyms_module__destroy(skel);
-}
diff --git a/tools/testing/selftests/bpf/prog_tests/ringbuf.c b/tools/testing/selftests/bpf/prog_tests/ringbuf.c
index 4706cee84360..9a80fe8a6427 100644
--- a/tools/testing/selftests/bpf/prog_tests/ringbuf.c
+++ b/tools/testing/selftests/bpf/prog_tests/ringbuf.c
@@ -58,7 +58,7 @@ static int process_sample(void *ctx, void *data, size_t len)
 	}
 }
 
-static struct test_ringbuf *skel;
+static struct test_ringbuf_lskel *skel;
 static struct ring_buffer *ringbuf;
 
 static void trigger_samples()
@@ -90,13 +90,13 @@ void test_ringbuf(void)
 	int page_size = getpagesize();
 	void *mmap_ptr, *tmp_ptr;
 
-	skel = test_ringbuf__open();
+	skel = test_ringbuf_lskel__open();
 	if (CHECK(!skel, "skel_open", "skeleton open failed\n"))
 		return;
 
 	skel->maps.ringbuf.max_entries = page_size;
 
-	err = test_ringbuf__load(skel);
+	err = test_ringbuf_lskel__load(skel);
 	if (CHECK(err != 0, "skel_load", "skeleton load failed\n"))
 		goto cleanup;
 
@@ -154,7 +154,7 @@ void test_ringbuf(void)
 	if (CHECK(!ringbuf, "ringbuf_create", "failed to create ringbuf\n"))
 		goto cleanup;
 
-	err = test_ringbuf__attach(skel);
+	err = test_ringbuf_lskel__attach(skel);
 	if (CHECK(err, "skel_attach", "skeleton attachment failed: %d\n", err))
 		goto cleanup;
 
@@ -292,8 +292,8 @@ void test_ringbuf(void)
 	CHECK(skel->bss->discarded != 1, "err_discarded", "exp %ld, got %ld\n",
 	      1L, skel->bss->discarded);
 
-	test_ringbuf__detach(skel);
+	test_ringbuf_lskel__detach(skel);
 cleanup:
 	ring_buffer__free(ringbuf);
-	test_ringbuf__destroy(skel);
+	test_ringbuf_lskel__destroy(skel);
 }
diff --git a/tools/testing/selftests/bpf/prog_tests/trace_printk.c b/tools/testing/selftests/bpf/prog_tests/trace_printk.c
index 3f7a7141265e..cade7f12315f 100644
--- a/tools/testing/selftests/bpf/prog_tests/trace_printk.c
+++ b/tools/testing/selftests/bpf/prog_tests/trace_printk.c
@@ -10,27 +10,27 @@
 
 void serial_test_trace_printk(void)
 {
+	struct trace_printk_lskel__bss *bss;
 	int err = 0, iter = 0, found = 0;
-	struct trace_printk__bss *bss;
-	struct trace_printk *skel;
+	struct trace_printk_lskel *skel;
 	char *buf = NULL;
 	FILE *fp = NULL;
 	size_t buflen;
 
-	skel = trace_printk__open();
+	skel = trace_printk_lskel__open();
 	if (!ASSERT_OK_PTR(skel, "trace_printk__open"))
 		return;
 
 	ASSERT_EQ(skel->rodata->fmt[0], 'T', "skel->rodata->fmt[0]");
 	skel->rodata->fmt[0] = 't';
 
-	err = trace_printk__load(skel);
+	err = trace_printk_lskel__load(skel);
 	if (!ASSERT_OK(err, "trace_printk__load"))
 		goto cleanup;
 
 	bss = skel->bss;
 
-	err = trace_printk__attach(skel);
+	err = trace_printk_lskel__attach(skel);
 	if (!ASSERT_OK(err, "trace_printk__attach"))
 		goto cleanup;
 
@@ -43,7 +43,7 @@ void serial_test_trace_printk(void)
 
 	/* wait for tracepoint to trigger */
 	usleep(1);
-	trace_printk__detach(skel);
+	trace_printk_lskel__detach(skel);
 
 	if (!ASSERT_GT(bss->trace_printk_ran, 0, "bss->trace_printk_ran"))
 		goto cleanup;
@@ -65,7 +65,7 @@ void serial_test_trace_printk(void)
 		goto cleanup;
 
 cleanup:
-	trace_printk__destroy(skel);
+	trace_printk_lskel__destroy(skel);
 	free(buf);
 	if (fp)
 		fclose(fp);
diff --git a/tools/testing/selftests/bpf/prog_tests/trace_vprintk.c b/tools/testing/selftests/bpf/prog_tests/trace_vprintk.c
index 46101270cb1a..7a4e313e8558 100644
--- a/tools/testing/selftests/bpf/prog_tests/trace_vprintk.c
+++ b/tools/testing/selftests/bpf/prog_tests/trace_vprintk.c
@@ -10,20 +10,20 @@
 
 void serial_test_trace_vprintk(void)
 {
+	struct trace_vprintk_lskel__bss *bss;
 	int err = 0, iter = 0, found = 0;
-	struct trace_vprintk__bss *bss;
-	struct trace_vprintk *skel;
+	struct trace_vprintk_lskel *skel;
 	char *buf = NULL;
 	FILE *fp = NULL;
 	size_t buflen;
 
-	skel = trace_vprintk__open_and_load();
+	skel = trace_vprintk_lskel__open_and_load();
 	if (!ASSERT_OK_PTR(skel, "trace_vprintk__open_and_load"))
 		goto cleanup;
 
 	bss = skel->bss;
 
-	err = trace_vprintk__attach(skel);
+	err = trace_vprintk_lskel__attach(skel);
 	if (!ASSERT_OK(err, "trace_vprintk__attach"))
 		goto cleanup;
 
@@ -36,7 +36,7 @@ void serial_test_trace_vprintk(void)
 
 	/* wait for tracepoint to trigger */
 	usleep(1);
-	trace_vprintk__detach(skel);
+	trace_vprintk_lskel__detach(skel);
 
 	if (!ASSERT_GT(bss->trace_vprintk_ran, 0, "bss->trace_vprintk_ran"))
 		goto cleanup;
@@ -61,7 +61,7 @@ void serial_test_trace_vprintk(void)
 		goto cleanup;
 
 cleanup:
-	trace_vprintk__destroy(skel);
+	trace_vprintk_lskel__destroy(skel);
 	free(buf);
 	if (fp)
 		fclose(fp);
diff --git a/tools/testing/selftests/bpf/prog_tests/verif_stats.c b/tools/testing/selftests/bpf/prog_tests/verif_stats.c
index b4bae1340cf1..a47e7c0e1ffd 100644
--- a/tools/testing/selftests/bpf/prog_tests/verif_stats.c
+++ b/tools/testing/selftests/bpf/prog_tests/verif_stats.c
@@ -8,11 +8,11 @@
 void test_verif_stats(void)
 {
 	__u32 len = sizeof(struct bpf_prog_info);
+	struct trace_vprintk_lskel *skel;
 	struct bpf_prog_info info = {};
-	struct trace_vprintk *skel;
 	int err;
 
-	skel = trace_vprintk__open_and_load();
+	skel = trace_vprintk_lskel__open_and_load();
 	if (!ASSERT_OK_PTR(skel, "trace_vprintk__open_and_load"))
 		goto cleanup;
 
@@ -24,5 +24,5 @@ void test_verif_stats(void)
 		goto cleanup;
 
 cleanup:
-	trace_vprintk__destroy(skel);
+	trace_vprintk_lskel__destroy(skel);
 }
diff --git a/tools/testing/selftests/bpf/progs/test_ksyms_weak.c b/tools/testing/selftests/bpf/progs/test_ksyms_weak.c
index 5f8379aadb29..8eadbd4caf7a 100644
--- a/tools/testing/selftests/bpf/progs/test_ksyms_weak.c
+++ b/tools/testing/selftests/bpf/progs/test_ksyms_weak.c
@@ -38,7 +38,7 @@ int pass_handler(const void *ctx)
 	/* tests existing symbols. */
 	rq = (struct rq *)bpf_per_cpu_ptr(&runqueues, 0);
 	if (rq)
-		out__existing_typed = rq->cpu;
+		out__existing_typed = 0;
 	out__existing_typeless = (__u64)&bpf_prog_active;
 
 	/* tests non-existent symbols. */
-- 
2.33.1

[PATCH bpf-next v5 7/8] selftests/bpf: Fix fd cleanup in sk_lookup test

[Kumar Kartikeya Dwivedi]

Similar to the fix in commit:
e31eec77e4ab ("bpf: selftests: Fix fd cleanup in get_branch_snapshot")

We use designated initializer to set fds to -1 without breaking on
future changes to MAX_SERVER constant denoting the array size.

The particular close(0) occurs on non-reuseport tests, so it can be seen
with -n 115/{2,3} but not 115/4. This can cause problems with future
tests if they depend on BTF fd never being acquired as fd 0, breaking
internal libbpf assumptions.

Fixes: 0ab5539f8584 ("selftests/bpf: Tests for BPF_SK_LOOKUP attach point")
Reviewed-by: Jakub Sitnicki <jakub@cloudflare.com>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 tools/testing/selftests/bpf/prog_tests/sk_lookup.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/sk_lookup.c b/tools/testing/selftests/bpf/prog_tests/sk_lookup.c
index aee41547e7f4..6db07401bc49 100644
--- a/tools/testing/selftests/bpf/prog_tests/sk_lookup.c
+++ b/tools/testing/selftests/bpf/prog_tests/sk_lookup.c
@@ -598,7 +598,7 @@ static void query_lookup_prog(struct test_sk_lookup *skel)
 
 static void run_lookup_prog(const struct test *t)
 {
-	int server_fds[MAX_SERVERS] = { -1 };
+	int server_fds[] = { [0 ... MAX_SERVERS - 1] = -1 };
 	int client_fd, reuse_conn_fd = -1;
 	struct bpf_link *lookup_link;
 	int i, err;
@@ -1053,7 +1053,7 @@ static void run_sk_assign(struct test_sk_lookup *skel,
 			  struct bpf_program *lookup_prog,
 			  const char *remote_ip, const char *local_ip)
 {
-	int server_fds[MAX_SERVERS] = { -1 };
+	int server_fds[] = { [0 ... MAX_SERVERS - 1] = -1 };
 	struct bpf_sk_lookup ctx;
 	__u64 server_cookie;
 	int i, err;
-- 
2.33.1

[PATCH bpf-next v5 8/8] selftests/bpf: Fix memory leak in test_ima

[Kumar Kartikeya Dwivedi]

The allocated ring buffer is never freed, do so in the cleanup path.

Fixes: f446b570ac7e ("bpf/selftests: Update the IMA test to use BPF ring buffer")
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 tools/testing/selftests/bpf/prog_tests/test_ima.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/test_ima.c b/tools/testing/selftests/bpf/prog_tests/test_ima.c
index 0252f61d611a..97d8a6f84f4a 100644
--- a/tools/testing/selftests/bpf/prog_tests/test_ima.c
+++ b/tools/testing/selftests/bpf/prog_tests/test_ima.c
@@ -43,7 +43,7 @@ static int process_sample(void *ctx, void *data, size_t len)
 void test_test_ima(void)
 {
 	char measured_dir_template[] = "/tmp/ima_measuredXXXXXX";
-	struct ring_buffer *ringbuf;
+	struct ring_buffer *ringbuf = NULL;
 	const char *measured_dir;
 	char cmd[256];
 
@@ -85,5 +85,6 @@ void test_test_ima(void)
 	err = system(cmd);
 	CHECK(err, "failed to run command", "%s, errno = %d\n", cmd, errno);
 close_prog:
+	ring_buffer__free(ringbuf);
 	ima__destroy(skel);
 }
-- 
2.33.1

Re: [PATCH bpf-next v5 4/8] libbpf: Ensure that BPF syscall fds are never 0, 1, or 2

[Andrii Nakryiko]

On Wed, Oct 27, 2021 at 11:35 PM Kumar Kartikeya Dwivedi
<memxor@gmail.com> wrote:
>
> Add a simple wrapper for passing an fd and getting a new one >= 3 if it
> is one of 0, 1, or 2. There are two primary reasons to make this change:
> First, libbpf relies on the assumption a certain BPF fd is never 0 (e.g.
> most recently noticed in [0]). Second, Alexei pointed out in [1] that
> some environments reset stdin, stdout, and stderr if they notice an
> invalid fd at these numbers. To protect against both these cases, switch
> all internal BPF syscall wrappers in libbpf to always return an fd >= 3.
> We only need to modify the syscall wrappers and not other code that
> assumes a valid fd by doing >= 0, to avoid pointless churn, and because
> it is still a valid assumption. The cost paid is two additional syscalls
> if fd is in range [0, 2].
>
>   [0]: e31eec77e4ab ("bpf: selftests: Fix fd cleanup in get_branch_snapshot")
>   [1]: https://lore.kernel.org/bpf/CAADnVQKVKY8o_3aU8Gzke443+uHa-eGoM0h7W4srChMXU1S4Bg@mail.gmail.com
>
> Acked-by: Song Liu <songliubraving@fb.com>
> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
> ---

LGTM, thanks.

Acked-by: Andrii Nakryiko <andrii@kernel.org>

>  tools/lib/bpf/bpf.c             | 35 +++++++++++++++++++++------------
>  tools/lib/bpf/libbpf_internal.h | 24 ++++++++++++++++++++++
>  2 files changed, 46 insertions(+), 13 deletions(-)
>

[...]

Re: [PATCH bpf-next v5 5/8] libbpf: Use O_CLOEXEC uniformly when opening fds

[Andrii Nakryiko]

On Wed, Oct 27, 2021 at 11:35 PM Kumar Kartikeya Dwivedi
<memxor@gmail.com> wrote:
>
> There are some instances where we don't use O_CLOEXEC when opening an
> fd, fix these up. Otherwise, it is possible that a parallel fork causes
> these fds to leak into a child process on execve.
>
> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
> ---

Acked-by: Andrii Nakryiko <andrii@kernel.org>

>  tools/lib/bpf/btf.c           | 2 +-
>  tools/lib/bpf/libbpf.c        | 6 +++---
>  tools/lib/bpf/libbpf_probes.c | 2 +-
>  tools/lib/bpf/linker.c        | 4 ++--
>  tools/lib/bpf/xsk.c           | 6 +++---
>  5 files changed, 10 insertions(+), 10 deletions(-)
>

[...]

Re: [PATCH bpf-next v5 6/8] selftests/bpf: Add weak/typeless ksym test for light skeleton

[Andrii Nakryiko]

On Wed, Oct 27, 2021 at 11:35 PM Kumar Kartikeya Dwivedi
<memxor@gmail.com> wrote:
>
> Also, avoid using CO-RE features, as lskel doesn't support CO-RE, yet.
> Include both light and libbpf skeleton in same file to test both of them
> together.
>
> In c48e51c8b07a ("bpf: selftests: Add selftests for module kfunc support"),
> I added support for generating both lskel and libbpf skel for a BPF
> object, however the name parameter for bpftool caused collisions when
> included in same file together. This meant that every test needed a
> separate file for a libbpf/light skeleton separation instead of
> subtests.
>
> Change that by appending a "_lskel" suffix to the name for files using
> light skeleton, and convert all existing users.
>
> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
> ---

I like the simplicity, thanks.

Acked-by: Andrii Nakryiko <andrii@kernel.org>

>  tools/testing/selftests/bpf/Makefile          |  4 +-
>  .../selftests/bpf/prog_tests/atomics.c        | 34 ++++++++--------
>  .../selftests/bpf/prog_tests/fentry_fexit.c   | 16 ++++----
>  .../selftests/bpf/prog_tests/fentry_test.c    | 14 +++----
>  .../selftests/bpf/prog_tests/fexit_sleep.c    | 12 +++---
>  .../selftests/bpf/prog_tests/fexit_test.c     | 14 +++----
>  .../selftests/bpf/prog_tests/kfunc_call.c     |  6 +--
>  .../selftests/bpf/prog_tests/ksyms_btf.c      | 35 +++++++++++++++-
>  .../selftests/bpf/prog_tests/ksyms_module.c   | 40 +++++++++++++++++--
>  .../bpf/prog_tests/ksyms_module_libbpf.c      | 28 -------------
>  .../selftests/bpf/prog_tests/ringbuf.c        | 12 +++---
>  .../selftests/bpf/prog_tests/trace_printk.c   | 14 +++----
>  .../selftests/bpf/prog_tests/trace_vprintk.c  | 12 +++---
>  .../selftests/bpf/prog_tests/verif_stats.c    |  6 +--
>  .../selftests/bpf/progs/test_ksyms_weak.c     |  2 +-
>  15 files changed, 142 insertions(+), 107 deletions(-)
>  delete mode 100644 tools/testing/selftests/bpf/prog_tests/ksyms_module_libbpf.c
>

[...]

Re: [PATCH bpf-next v5 1/8] bpf: Add bpf_kallsyms_lookup_name helper

[Andrii Nakryiko]

On Wed, Oct 27, 2021 at 11:35 PM Kumar Kartikeya Dwivedi
<memxor@gmail.com> wrote:
>
> This helper allows us to get the address of a kernel symbol from inside
> a BPF_PROG_TYPE_SYSCALL prog (used by gen_loader), so that we can
> relocate typeless ksym vars.
>
> Acked-by: Song Liu <songliubraving@fb.com>
> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
> ---
>  include/linux/bpf.h            |  1 +
>  include/uapi/linux/bpf.h       | 16 ++++++++++++++++
>  kernel/bpf/syscall.c           | 27 +++++++++++++++++++++++++++
>  tools/include/uapi/linux/bpf.h | 16 ++++++++++++++++
>  4 files changed, 60 insertions(+)
>

[...]

> +BPF_CALL_4(bpf_kallsyms_lookup_name, const char *, name, int, name_sz, int, flags, u64 *, res)
> +{
> +       if (flags)
> +               return -EINVAL;
> +
> +       if (name_sz <= 1 || name[name_sz - 1])
> +               return -EINVAL;
> +
> +       if (!bpf_dump_raw_ok(current_cred()))
> +               return -EPERM;
> +
> +       *res = kallsyms_lookup_name(name);
> +       return *res ? 0 : -ENOENT;
> +}
> +
> +const struct bpf_func_proto bpf_kallsyms_lookup_name_proto = {
> +       .func           = bpf_kallsyms_lookup_name,
> +       .gpl_only       = false,
> +       .ret_type       = RET_INTEGER,
> +       .arg1_type      = ARG_PTR_TO_MEM,
> +       .arg2_type      = ARG_CONST_SIZE,

can you make it ARG_CONST_SIZE_OR_ZERO? Not because zero makes sense,
but because it removes the need to prove to the verifier that the size
(which you can get at runtime) is > 0. Just less unnecessary fussing
with preventing Clang optimizations.

> +       .arg3_type      = ARG_ANYTHING,
> +       .arg4_type      = ARG_PTR_TO_LONG,
> +};
> +

[...]

Re: [PATCH bpf-next v5 3/8] libbpf: Add weak ksym support to gen_loader

[Alexei Starovoitov]

On Thu, Oct 28, 2021 at 12:04:56PM +0530, Kumar Kartikeya Dwivedi wrote:
> This extends existing ksym relocation code to also support relocating
> weak ksyms. Care needs to be taken to zero out the src_reg (currently
> BPF_PSEUOD_BTF_ID, always set for gen_loader by bpf_object__relocate_data)
> when the BTF ID lookup fails at runtime.  This is not a problem for
> libbpf as it only sets ext->is_set when BTF ID lookup succeeds (and only
> proceeds in case of failure if ext->is_weak, leading to src_reg
> remaining as 0 for weak unresolved ksym).
> 
> A pattern similar to emit_relo_kfunc_btf is followed of first storing
> the default values and then jumping over actual stores in case of an
> error. For src_reg adjustment, we also need to perform it when copying
> the populated instruction, so depending on if copied insn[0].imm is 0 or
> not, we decide to jump over the adjustment.
> 
> We cannot reach that point unless the ksym was weak and resolved and
> zeroed out, as the emit_check_err will cause us to jump to cleanup
> label, so we do not need to recheck whether the ksym is weak before
> doing the adjustment after copying BTF ID and BTF FD.
> 
> This is consistent with how libbpf relocates weak ksym. Logging
> statements are added to show the relocation result and aid debugging.
> 
> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
> ---
>  tools/lib/bpf/gen_loader.c | 35 ++++++++++++++++++++++++++++++++---
>  1 file changed, 32 insertions(+), 3 deletions(-)
> 
> diff --git a/tools/lib/bpf/gen_loader.c b/tools/lib/bpf/gen_loader.c
> index 11172a868180..1c404752e565 100644
> --- a/tools/lib/bpf/gen_loader.c
> +++ b/tools/lib/bpf/gen_loader.c
> @@ -13,6 +13,7 @@
>  #include "hashmap.h"
>  #include "bpf_gen_internal.h"
>  #include "skel_internal.h"
> +#include <asm/byteorder.h>
>  
>  #define MAX_USED_MAPS	64
>  #define MAX_USED_PROGS	32
> @@ -776,12 +777,24 @@ static void emit_relo_ksym_typeless(struct bpf_gen *gen,
>  	emit_ksym_relo_log(gen, relo, kdesc->ref);
>  }
>  
> +static __u32 src_reg_mask(void)
> +{
> +#if defined(__LITTLE_ENDIAN_BITFIELD)
> +	return 0x0f; /* src_reg,dst_reg,... */
> +#elif defined(__BIG_ENDIAN_BITFIELD)
> +	return 0xf0; /* dst_reg,src_reg,... */
> +#else
> +#error "Unsupported bit endianness, cannot proceed"
> +#endif
> +}
> +
>  /* Expects:
>   * BPF_REG_8 - pointer to instruction
>   */
>  static void emit_relo_ksym_btf(struct bpf_gen *gen, struct ksym_relo_desc *relo, int insn)
>  {
>  	struct ksym_desc *kdesc;
> +	__u32 reg_mask;
>  
>  	kdesc = get_ksym_desc(gen, relo);
>  	if (!kdesc)
> @@ -792,19 +805,35 @@ static void emit_relo_ksym_btf(struct bpf_gen *gen, struct ksym_relo_desc *relo,
>  			       kdesc->insn + offsetof(struct bpf_insn, imm));
>  		move_blob2blob(gen, insn + sizeof(struct bpf_insn) + offsetof(struct bpf_insn, imm), 4,
>  			       kdesc->insn + sizeof(struct bpf_insn) + offsetof(struct bpf_insn, imm));
> -		goto log;
> +		emit(gen, BPF_LDX_MEM(BPF_W, BPF_REG_9, BPF_REG_8, offsetof(struct bpf_insn, imm)));

Thanks a lot for working on this. I've applied the set.

The above load is redundant, right? BPF_REG_0 already has that value
and could have been used in the JNE below, right?

> +		/* jump over src_reg adjustment if imm is not 0 */
> +		emit(gen, BPF_JMP_IMM(BPF_JNE, BPF_REG_9, 0, 3));
> +		goto clear_src_reg;

Is there a test for this part of the code?
It's only for weak && unresolved && multi referenced ksym, right?
Or bpf_link_fops2 test_ksyms_weak.c fits this category?

>  	}
>  	/* remember insn offset, so we can copy BTF ID and FD later */
>  	kdesc->insn = insn;
>  	emit_bpf_find_by_name_kind(gen, relo);
> -	emit_check_err(gen);
> +	if (!relo->is_weak)
> +		emit_check_err(gen);
> +	/* set default values as 0 */
> +	emit(gen, BPF_ST_MEM(BPF_W, BPF_REG_8, offsetof(struct bpf_insn, imm), 0));
> +	emit(gen, BPF_ST_MEM(BPF_W, BPF_REG_8, sizeof(struct bpf_insn) + offsetof(struct bpf_insn, imm), 0));
> +	/* skip success case stores if ret < 0 */
> +	emit(gen, BPF_JMP_IMM(BPF_JSLT, BPF_REG_7, 0, 4));
>  	/* store btf_id into insn[insn_idx].imm */
>  	emit(gen, BPF_STX_MEM(BPF_W, BPF_REG_8, BPF_REG_7, offsetof(struct bpf_insn, imm)));
>  	/* store btf_obj_fd into insn[insn_idx + 1].imm */
>  	emit(gen, BPF_ALU64_IMM(BPF_RSH, BPF_REG_7, 32));
>  	emit(gen, BPF_STX_MEM(BPF_W, BPF_REG_8, BPF_REG_7,
>  			      sizeof(struct bpf_insn) + offsetof(struct bpf_insn, imm)));

The double store (first with zeros and then with real values) doesn't look pretty.
I think an extra jump over two stores would have been cleaner.

Re: [PATCH bpf-next v5 3/8] libbpf: Add weak ksym support to gen_loader

[Kumar Kartikeya Dwivedi]

On Fri, Oct 29, 2021 at 05:52:44AM IST, Alexei Starovoitov wrote:
> On Thu, Oct 28, 2021 at 12:04:56PM +0530, Kumar Kartikeya Dwivedi wrote:
> > This extends existing ksym relocation code to also support relocating
> > weak ksyms. Care needs to be taken to zero out the src_reg (currently
> > BPF_PSEUOD_BTF_ID, always set for gen_loader by bpf_object__relocate_data)
> > when the BTF ID lookup fails at runtime.  This is not a problem for
> > libbpf as it only sets ext->is_set when BTF ID lookup succeeds (and only
> > proceeds in case of failure if ext->is_weak, leading to src_reg
> > remaining as 0 for weak unresolved ksym).
> >
> > A pattern similar to emit_relo_kfunc_btf is followed of first storing
> > the default values and then jumping over actual stores in case of an
> > error. For src_reg adjustment, we also need to perform it when copying
> > the populated instruction, so depending on if copied insn[0].imm is 0 or
> > not, we decide to jump over the adjustment.
> >
> > We cannot reach that point unless the ksym was weak and resolved and
> > zeroed out, as the emit_check_err will cause us to jump to cleanup
> > label, so we do not need to recheck whether the ksym is weak before
> > doing the adjustment after copying BTF ID and BTF FD.
> >
> > This is consistent with how libbpf relocates weak ksym. Logging
> > statements are added to show the relocation result and aid debugging.
> >
> > Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
> > ---
> >  tools/lib/bpf/gen_loader.c | 35 ++++++++++++++++++++++++++++++++---
> >  1 file changed, 32 insertions(+), 3 deletions(-)
> >
> > diff --git a/tools/lib/bpf/gen_loader.c b/tools/lib/bpf/gen_loader.c
> > index 11172a868180..1c404752e565 100644
> > --- a/tools/lib/bpf/gen_loader.c
> > +++ b/tools/lib/bpf/gen_loader.c
> > @@ -13,6 +13,7 @@
> >  #include "hashmap.h"
> >  #include "bpf_gen_internal.h"
> >  #include "skel_internal.h"
> > +#include <asm/byteorder.h>
> >
> >  #define MAX_USED_MAPS	64
> >  #define MAX_USED_PROGS	32
> > @@ -776,12 +777,24 @@ static void emit_relo_ksym_typeless(struct bpf_gen *gen,
> >  	emit_ksym_relo_log(gen, relo, kdesc->ref);
> >  }
> >
> > +static __u32 src_reg_mask(void)
> > +{
> > +#if defined(__LITTLE_ENDIAN_BITFIELD)
> > +	return 0x0f; /* src_reg,dst_reg,... */
> > +#elif defined(__BIG_ENDIAN_BITFIELD)
> > +	return 0xf0; /* dst_reg,src_reg,... */
> > +#else
> > +#error "Unsupported bit endianness, cannot proceed"
> > +#endif
> > +}
> > +
> >  /* Expects:
> >   * BPF_REG_8 - pointer to instruction
> >   */
> >  static void emit_relo_ksym_btf(struct bpf_gen *gen, struct ksym_relo_desc *relo, int insn)
> >  {
> >  	struct ksym_desc *kdesc;
> > +	__u32 reg_mask;
> >
> >  	kdesc = get_ksym_desc(gen, relo);
> >  	if (!kdesc)
> > @@ -792,19 +805,35 @@ static void emit_relo_ksym_btf(struct bpf_gen *gen, struct ksym_relo_desc *relo,
> >  			       kdesc->insn + offsetof(struct bpf_insn, imm));
> >  		move_blob2blob(gen, insn + sizeof(struct bpf_insn) + offsetof(struct bpf_insn, imm), 4,
> >  			       kdesc->insn + sizeof(struct bpf_insn) + offsetof(struct bpf_insn, imm));
> > -		goto log;
> > +		emit(gen, BPF_LDX_MEM(BPF_W, BPF_REG_9, BPF_REG_8, offsetof(struct bpf_insn, imm)));
>
> Thanks a lot for working on this. I've applied the set.
>
> The above load is redundant, right? BPF_REG_0 already has that value
> and could have been used in the JNE below, right?
>

Hm, true, we could certainly avoid another load here.

> > +		/* jump over src_reg adjustment if imm is not 0 */
> > +		emit(gen, BPF_JMP_IMM(BPF_JNE, BPF_REG_9, 0, 3));
> > +		goto clear_src_reg;
>
> Is there a test for this part of the code?
> It's only for weak && unresolved && multi referenced ksym, right?

Correct.

> Or bpf_link_fops2 test_ksyms_weak.c fits this category?
>

Yes, the result of relocation is as follows (t=0 means typed, w=1 means weak):
find_by_name_kind(bpf_link_fops2,14) r=-2
var t=0 w=1 (bpf_link_fops2:count=1): imm[0]: 0, imm[1]: 0
var t=0 w=1 (bpf_link_fops2:count=1): insn.reg r=1
// goto clear_src_reg happens for this one
var t=0 w=1 (bpf_link_fops2:count=2): imm[0]: 0, imm[1]: 0
var t=0 w=1 (bpf_link_fops2:count=2): insn.reg r=1

> >  	}
> >  	/* remember insn offset, so we can copy BTF ID and FD later */
> >  	kdesc->insn = insn;
> >  	emit_bpf_find_by_name_kind(gen, relo);
> > -	emit_check_err(gen);
> > +	if (!relo->is_weak)
> > +		emit_check_err(gen);
> > +	/* set default values as 0 */
> > +	emit(gen, BPF_ST_MEM(BPF_W, BPF_REG_8, offsetof(struct bpf_insn, imm), 0));
> > +	emit(gen, BPF_ST_MEM(BPF_W, BPF_REG_8, sizeof(struct bpf_insn) + offsetof(struct bpf_insn, imm), 0));
> > +	/* skip success case stores if ret < 0 */
> > +	emit(gen, BPF_JMP_IMM(BPF_JSLT, BPF_REG_7, 0, 4));
> >  	/* store btf_id into insn[insn_idx].imm */
> >  	emit(gen, BPF_STX_MEM(BPF_W, BPF_REG_8, BPF_REG_7, offsetof(struct bpf_insn, imm)));
> >  	/* store btf_obj_fd into insn[insn_idx + 1].imm */
> >  	emit(gen, BPF_ALU64_IMM(BPF_RSH, BPF_REG_7, 32));
> >  	emit(gen, BPF_STX_MEM(BPF_W, BPF_REG_8, BPF_REG_7,
> >  			      sizeof(struct bpf_insn) + offsetof(struct bpf_insn, imm)));
>
> The double store (first with zeros and then with real values) doesn't look pretty.
> I think an extra jump over two stores would have been cleaner.

I will address all your (and Andrii's) points in another patch.

--
Kartikeya