[PATCH bpf-next 0/5] bpf: add support for BTF_KIND_DECL_TAG typedef

[PATCH bpf-next 0/5] bpf: add support for BTF_KIND_DECL_TAG typedef

[Yonghong Song]

Latest upstream llvm-project added support for btf_decl_tag attributes
for typedef declarations ([1], [2]). Similar to other btf_decl_tag cases,
func/func_param/global_var/struct/union/field, btf_decl_tag with typedef
declaration can carry information from kernel source to clang compiler
and then to dwarf/BTF, for bpf verification or other use cases.

This patch set added kernel support for BTF_KIND_DECL_TAG to typedef
declaration (Patch 1). Additional selftests are added to cover
unit testing, dedup, or bpf program usage of btf_decl_tag with typedef.
(Patches 2, 3 and 4). The btf documentation is updated to include
BTF_KIND_DECL_TAG typedef (Patch 5).

  [1] https://reviews.llvm.org/D110127
  [2] https://reviews.llvm.org/D112259

Yonghong Song (5):
  bpf: add BTF_KIND_DECL_TAG typedef support
  selftests/bpf: add BTF_KIND_DECL_TAG typedef unit tests
  selftests/bpf: test deduplication for BTF_KIND_DECL_TAG typedef
  selftests/bpf: add BTF_KIND_DECL_TAG typedef example in tag.c
  docs/bpf: update documentation for BTF_KIND_DECL_TAG typedef support

 Documentation/bpf/btf.rst                    |  6 +-
 kernel/bpf/btf.c                             |  4 +-
 tools/testing/selftests/bpf/prog_tests/btf.c | 83 ++++++++++++++++++--
 tools/testing/selftests/bpf/progs/tag.c      |  9 ++-
 4 files changed, 89 insertions(+), 13 deletions(-)

-- 
2.30.2

[PATCH bpf-next 1/5] bpf: add BTF_KIND_DECL_TAG typedef support

[Yonghong Song]

The llvm patches ([1], [2]) added support to attach btf_decl_tag
attributes to typedef declarations. This patch added
support in kernel.

  [1] https://reviews.llvm.org/D110127
  [2] https://reviews.llvm.org/D112259

Signed-off-by: Yonghong Song <yhs@fb.com>
---
 kernel/bpf/btf.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 9059053088b9..dbc3ad07e21b 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -468,7 +468,7 @@ static bool btf_type_is_decl_tag(const struct btf_type *t)
 static bool btf_type_is_decl_tag_target(const struct btf_type *t)
 {
 	return btf_type_is_func(t) || btf_type_is_struct(t) ||
-	       btf_type_is_var(t);
+	       btf_type_is_var(t) || btf_type_is_typedef(t);
 }
 
 u32 btf_nr_types(const struct btf *btf)
@@ -3885,7 +3885,7 @@ static int btf_decl_tag_resolve(struct btf_verifier_env *env,
 
 	component_idx = btf_type_decl_tag(t)->component_idx;
 	if (component_idx != -1) {
-		if (btf_type_is_var(next_type)) {
+		if (btf_type_is_var(next_type) || btf_type_is_typedef(next_type)) {
 			btf_verifier_log_type(env, v->t, "Invalid component_idx");
 			return -EINVAL;
 		}
-- 
2.30.2

[PATCH bpf-next 2/5] selftests/bpf: add BTF_KIND_DECL_TAG typedef unit tests

[Yonghong Song]

Test good and bad variants of typedef BTF_KIND_DECL_TAG encoding.

Signed-off-by: Yonghong Song <yhs@fb.com>
---
 tools/testing/selftests/bpf/prog_tests/btf.c | 36 ++++++++++++++++++++
 1 file changed, 36 insertions(+)

diff --git a/tools/testing/selftests/bpf/prog_tests/btf.c b/tools/testing/selftests/bpf/prog_tests/btf.c
index fa67f25bbef5..a00418b8b252 100644
--- a/tools/testing/selftests/bpf/prog_tests/btf.c
+++ b/tools/testing/selftests/bpf/prog_tests/btf.c
@@ -3903,6 +3903,42 @@ static struct btf_raw_test raw_tests[] = {
 	.btf_load_err = true,
 	.err_str = "Invalid component_idx",
 },
+{
+	.descr = "decl_tag test #13, typedef, well-formed",
+	.raw_types = {
+		BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 32, 4),	/* [1] */
+		BTF_TYPEDEF_ENC(NAME_TBD, 1),			/* [2] */
+		BTF_DECL_TAG_ENC(NAME_TBD, 2, -1),
+		BTF_END_RAW,
+	},
+	BTF_STR_SEC("\0t\0tag"),
+	.map_type = BPF_MAP_TYPE_ARRAY,
+	.map_name = "tag_type_check_btf",
+	.key_size = sizeof(int),
+	.value_size = 4,
+	.key_type_id = 1,
+	.value_type_id = 1,
+	.max_entries = 1,
+},
+{
+	.descr = "decl_tag test #14, typedef, invalid component_idx",
+	.raw_types = {
+		BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 32, 4),	/* [1] */
+		BTF_TYPEDEF_ENC(NAME_TBD, 1),			/* [2] */
+		BTF_DECL_TAG_ENC(NAME_TBD, 2, 0),
+		BTF_END_RAW,
+	},
+	BTF_STR_SEC("\0local\0tag"),
+	.map_type = BPF_MAP_TYPE_ARRAY,
+	.map_name = "tag_type_check_btf",
+	.key_size = sizeof(int),
+	.value_size = 4,
+	.key_type_id = 1,
+	.value_type_id = 1,
+	.max_entries = 1,
+	.btf_load_err = true,
+	.err_str = "Invalid component_idx",
+},
 
 }; /* struct btf_raw_test raw_tests[] */
 
-- 
2.30.2

[PATCH bpf-next 3/5] selftests/bpf: test deduplication for BTF_KIND_DECL_TAG typedef

[Yonghong Song]

Add unit tests for deduplication of BTF_KIND_DECL_TAG to typedef types.
Also changed a few comments from "tag" to "decl_tag" to match
BTF_KIND_DECL_TAG enum value name.

Signed-off-by: Yonghong Song <yhs@fb.com>
---
 tools/testing/selftests/bpf/prog_tests/btf.c | 47 +++++++++++++++++---
 1 file changed, 41 insertions(+), 6 deletions(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/btf.c b/tools/testing/selftests/bpf/prog_tests/btf.c
index a00418b8b252..3477f272560f 100644
--- a/tools/testing/selftests/bpf/prog_tests/btf.c
+++ b/tools/testing/selftests/bpf/prog_tests/btf.c
@@ -6877,11 +6877,12 @@ const struct btf_dedup_test dedup_tests[] = {
 				BTF_FUNC_PROTO_ARG_ENC(NAME_TBD, 8),
 			BTF_FUNC_ENC(NAME_TBD, 12),					/* [13] func */
 			BTF_TYPE_FLOAT_ENC(NAME_TBD, 2),				/* [14] float */
-			BTF_DECL_TAG_ENC(NAME_TBD, 13, -1),				/* [15] tag */
-			BTF_DECL_TAG_ENC(NAME_TBD, 13, 1),				/* [16] tag */
+			BTF_DECL_TAG_ENC(NAME_TBD, 13, -1),				/* [15] decl_tag */
+			BTF_DECL_TAG_ENC(NAME_TBD, 13, 1),				/* [16] decl_tag */
+			BTF_DECL_TAG_ENC(NAME_TBD, 7, -1),				/* [17] decl_tag */
 			BTF_END_RAW,
 		},
-		BTF_STR_SEC("\0A\0B\0C\0D\0E\0F\0G\0H\0I\0J\0K\0L\0M\0N\0O\0P"),
+		BTF_STR_SEC("\0A\0B\0C\0D\0E\0F\0G\0H\0I\0J\0K\0L\0M\0N\0O\0P\0Q"),
 	},
 	.expect = {
 		.raw_types = {
@@ -6905,11 +6906,12 @@ const struct btf_dedup_test dedup_tests[] = {
 				BTF_FUNC_PROTO_ARG_ENC(NAME_TBD, 8),
 			BTF_FUNC_ENC(NAME_TBD, 12),					/* [13] func */
 			BTF_TYPE_FLOAT_ENC(NAME_TBD, 2),				/* [14] float */
-			BTF_DECL_TAG_ENC(NAME_TBD, 13, -1),				/* [15] tag */
-			BTF_DECL_TAG_ENC(NAME_TBD, 13, 1),				/* [16] tag */
+			BTF_DECL_TAG_ENC(NAME_TBD, 13, -1),				/* [15] decl_tag */
+			BTF_DECL_TAG_ENC(NAME_TBD, 13, 1),				/* [16] decl_tag */
+			BTF_DECL_TAG_ENC(NAME_TBD, 7, -1),				/* [17] decl_tag */
 			BTF_END_RAW,
 		},
-		BTF_STR_SEC("\0A\0B\0C\0D\0E\0F\0G\0H\0I\0J\0K\0L\0M\0N\0O\0P"),
+		BTF_STR_SEC("\0A\0B\0C\0D\0E\0F\0G\0H\0I\0J\0K\0L\0M\0N\0O\0P\0Q"),
 	},
 	.opts = {
 		.dont_resolve_fwds = false,
@@ -7204,6 +7206,39 @@ const struct btf_dedup_test dedup_tests[] = {
 		.dont_resolve_fwds = false,
 	},
 },
+{
+	.descr = "dedup: typedef tags",
+	.input = {
+		.raw_types = {
+			/* int */
+			BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 32, 4),	/* [1] */
+			BTF_TYPEDEF_ENC(NAME_NTH(1), 1),		/* [2] */
+			BTF_TYPEDEF_ENC(NAME_NTH(1), 1),		/* [3] */
+			/* tag -> t: tag1, tag2 */
+			BTF_DECL_TAG_ENC(NAME_NTH(2), 2, -1),		/* [4] */
+			BTF_DECL_TAG_ENC(NAME_NTH(3), 2, -1),		/* [5] */
+			/* tag -> t: tag1, tag3 */
+			BTF_DECL_TAG_ENC(NAME_NTH(2), 3, -1),		/* [6] */
+			BTF_DECL_TAG_ENC(NAME_NTH(4), 3, -1),		/* [7] */
+			BTF_END_RAW,
+		},
+		BTF_STR_SEC("\0t\0tag1\0tag2\0tag3"),
+	},
+	.expect = {
+		.raw_types = {
+			BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 32, 4),	/* [1] */
+			BTF_TYPEDEF_ENC(NAME_NTH(1), 1),		/* [2] */
+			BTF_DECL_TAG_ENC(NAME_NTH(2), 2, -1),		/* [3] */
+			BTF_DECL_TAG_ENC(NAME_NTH(3), 2, -1),		/* [4] */
+			BTF_DECL_TAG_ENC(NAME_NTH(4), 2, -1),		/* [5] */
+			BTF_END_RAW,
+		},
+		BTF_STR_SEC("\0t\0tag1\0tag2\0tag3"),
+	},
+	.opts = {
+		.dont_resolve_fwds = false,
+	},
+},
 
 };
 
-- 
2.30.2

[PATCH bpf-next 4/5] selftests/bpf: add BTF_KIND_DECL_TAG typedef example in tag.c

[Yonghong Song]

Change value type in progs/tag.c to a typedef with a btf_decl_tag.
With `bpftool btf dump file tag.o`, we have
  ...
  [14] TYPEDEF 'value_t' type_id=17
  [15] DECL_TAG 'tag1' type_id=14 component_idx=-1
  [16] DECL_TAG 'tag2' type_id=14 component_idx=-1
  [17] STRUCT '(anon)' size=8 vlen=2
        'a' type_id=2 bits_offset=0
        'b' type_id=2 bits_offset=32
  ...

The btf_tag selftest also succeeded:
  $ ./test_progs -t tag
    #21 btf_tag:OK
    Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED

Signed-off-by: Yonghong Song <yhs@fb.com>
---
 tools/testing/selftests/bpf/progs/tag.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/bpf/progs/tag.c b/tools/testing/selftests/bpf/progs/tag.c
index 672d19e7b120..1792f4eda095 100644
--- a/tools/testing/selftests/bpf/progs/tag.c
+++ b/tools/testing/selftests/bpf/progs/tag.c
@@ -24,18 +24,23 @@ struct key_t {
 	int c;
 } __tag1 __tag2;
 
+typedef struct {
+	int a;
+	int b;
+} value_t __tag1 __tag2;
+
 struct {
 	__uint(type, BPF_MAP_TYPE_HASH);
 	__uint(max_entries, 3);
 	__type(key, struct key_t);
-	__type(value, __u64);
+	__type(value, value_t);
 } hashmap1 SEC(".maps");
 
 
 static __noinline int foo(int x __tag1 __tag2) __tag1 __tag2
 {
 	struct key_t key;
-	__u64 val = 1;
+	value_t val = {};
 
 	key.a = key.b = key.c = x;
 	bpf_map_update_elem(&hashmap1, &key, &val, 0);
-- 
2.30.2

[PATCH bpf-next 5/5] docs/bpf: update documentation for BTF_KIND_DECL_TAG typedef support

[Yonghong Song]

Add BTF_KIND_DECL_TAG typedef support in btf.rst.

Signed-off-by: Yonghong Song <yhs@fb.com>
---
 Documentation/bpf/btf.rst | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/Documentation/bpf/btf.rst b/Documentation/bpf/btf.rst
index 9e5b4a98af76..9ad4218a751f 100644
--- a/Documentation/bpf/btf.rst
+++ b/Documentation/bpf/btf.rst
@@ -474,7 +474,7 @@ No additional type data follow ``btf_type``.
  * ``info.kind_flag``: 0
  * ``info.kind``: BTF_KIND_DECL_TAG
  * ``info.vlen``: 0
- * ``type``: ``struct``, ``union``, ``func`` or ``var``
+ * ``type``: ``struct``, ``union``, ``func``, ``var`` or ``typedef``
 
 ``btf_type`` is followed by ``struct btf_decl_tag``.::
 
@@ -483,8 +483,8 @@ No additional type data follow ``btf_type``.
     };
 
 The ``name_off`` encodes btf_decl_tag attribute string.
-The ``type`` should be ``struct``, ``union``, ``func`` or ``var``.
-For ``var`` type, ``btf_decl_tag.component_idx`` must be ``-1``.
+The ``type`` should be ``struct``, ``union``, ``func``, ``var`` or ``typedef``.
+For ``var`` or ``typedef`` type, ``btf_decl_tag.component_idx`` must be ``-1``.
 For the other three types, if the btf_decl_tag attribute is
 applied to the ``struct``, ``union`` or ``func`` itself,
 ``btf_decl_tag.component_idx`` must be ``-1``. Otherwise,
-- 
2.30.2

Re: [PATCH bpf-next 0/5] bpf: add support for BTF_KIND_DECL_TAG typedef

[Alexei Starovoitov]

On Thu, Oct 21, 2021 at 12:56 PM Yonghong Song <yhs@fb.com> wrote:
>
> Latest upstream llvm-project added support for btf_decl_tag attributes
> for typedef declarations ([1], [2]). Similar to other btf_decl_tag cases,
> func/func_param/global_var/struct/union/field, btf_decl_tag with typedef
> declaration can carry information from kernel source to clang compiler
> and then to dwarf/BTF, for bpf verification or other use cases.
>
> This patch set added kernel support for BTF_KIND_DECL_TAG to typedef
> declaration (Patch 1). Additional selftests are added to cover
> unit testing, dedup, or bpf program usage of btf_decl_tag with typedef.
> (Patches 2, 3 and 4). The btf documentation is updated to include
> BTF_KIND_DECL_TAG typedef (Patch 5).
>
>   [1] https://reviews.llvm.org/D110127
>   [2] https://reviews.llvm.org/D112259

Applied. Thanks