Merge branch 'bpf: add support for BTF_KIND_DECL_TAG typedef'

Yonghong Song says:

====================

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
====================
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

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,

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;
 		}

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[] */
 
@@ -6841,11 +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 = {
@@ -6869,11 +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,
@@ -7168,6 +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,
+	},
+},
 
 };
 

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);