Merge branch 'Support BTF_KIND_TYPE_TAG for btf_type_tag attributes'

Yonghong Song says:

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

LLVM patches ([1] for clang, [2] and [3] for BPF backend)
added support for btf_type_tag attributes. This patch
added support for the kernel.

The main motivation for btf_type_tag is to bring kernel
annotations __user, __rcu etc. to btf. With such information
available in btf, bpf verifier can detect mis-usages
and reject the program. For example, for __user tagged pointer,
developers can then use proper helper like bpf_probe_read_kernel()
etc. to read the data.

BTF_KIND_TYPE_TAG may also useful for other tracing
facility where instead of to require user to specify
kernel/user address type, the kernel can detect it
by itself with btf.

Patch 1 added support in kernel, Patch 2 for libbpf and Patch 3
for bpftool. Patches 4-9 are for bpf selftests and Patch 10
updated docs/bpf/btf.rst file with new btf kind.

  [1] https://reviews.llvm.org/D111199
  [2] https://reviews.llvm.org/D113222
  [3] https://reviews.llvm.org/D113496

Changelogs:
  v2 -> v3:
    - rebase to resolve merge conflicts.
  v1 -> v2:
    - add more dedup tests.
    - remove build requirement for LLVM=1.
    - remove testing macro __has_attribute in bpf programs
      as it is always defined in recent clang compilers.
====================
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Documentation/bpf/btf.rst

@@ -86,6 +86,7 @@ sequentially and type id is assigned to each recognized type starting from id
     #define BTF_KIND_DATASEC        15      /* Section      */
     #define BTF_KIND_FLOAT          16      /* Floating point       */
     #define BTF_KIND_DECL_TAG       17      /* Decl Tag     */
+    #define BTF_KIND_TYPE_TAG       18      /* Type Tag     */
 
 Note that the type section encodes debug info, not just pure types.
 ``BTF_KIND_FUNC`` is not a type, and it represents a defined subprogram.
@@ -107,7 +108,7 @@ Each type contains the following common data::
          * "size" tells the size of the type it is describing.
          *
          * "type" is used by PTR, TYPEDEF, VOLATILE, CONST, RESTRICT,
-         * FUNC, FUNC_PROTO and DECL_TAG.
+         * FUNC, FUNC_PROTO, DECL_TAG and TYPE_TAG.
          * "type" is a type_id referring to another type.
          */
         union {
@@ -492,6 +493,16 @@ the attribute is applied to a ``struct``/``union`` member or
 a ``func`` argument, and ``btf_decl_tag.component_idx`` should be a
 valid index (starting from 0) pointing to a member or an argument.
 
+2.2.17 BTF_KIND_TYPE_TAG
+~~~~~~~~~~~~~~~~~~~~~~~~
+
+``struct btf_type`` encoding requirement:
+ * ``name_off``: offset to a non-empty string
+ * ``info.kind_flag``: 0
+ * ``info.kind``: BTF_KIND_TYPE_TAG
+ * ``info.vlen``: 0
+ * ``type``: the type with ``btf_type_tag`` attribute
+
 3. BTF Kernel API
 *****************
 

include/uapi/linux/btf.h

@@ -43,7 +43,7 @@ struct btf_type {
 	 * "size" tells the size of the type it is describing.
 	 *
 	 * "type" is used by PTR, TYPEDEF, VOLATILE, CONST, RESTRICT,
-	 * FUNC, FUNC_PROTO, VAR and DECL_TAG.
+	 * FUNC, FUNC_PROTO, VAR, DECL_TAG and TYPE_TAG.
 	 * "type" is a type_id referring to another type.
 	 */
 	union {
@@ -75,6 +75,7 @@ enum {
 	BTF_KIND_DATASEC	= 15,	/* Section	*/
 	BTF_KIND_FLOAT		= 16,	/* Floating point	*/
 	BTF_KIND_DECL_TAG	= 17,	/* Decl Tag */
+	BTF_KIND_TYPE_TAG	= 18,	/* Type Tag */
 
 	NR_BTF_KINDS,
 	BTF_KIND_MAX		= NR_BTF_KINDS - 1,

kernel/bpf/btf.c

@@ -282,6 +282,7 @@ static const char * const btf_kind_str[NR_BTF_KINDS] = {
 	[BTF_KIND_DATASEC]	= "DATASEC",
 	[BTF_KIND_FLOAT]	= "FLOAT",
 	[BTF_KIND_DECL_TAG]	= "DECL_TAG",
+	[BTF_KIND_TYPE_TAG]	= "TYPE_TAG",
 };
 
 const char *btf_type_str(const struct btf_type *t)
@@ -418,6 +419,7 @@ static bool btf_type_is_modifier(const struct btf_type *t)
 	case BTF_KIND_VOLATILE:
 	case BTF_KIND_CONST:
 	case BTF_KIND_RESTRICT:
+	case BTF_KIND_TYPE_TAG:
 		return true;
 	}
 
@@ -1737,6 +1739,7 @@ __btf_resolve_size(const struct btf *btf, const struct btf_type *type,
 		case BTF_KIND_VOLATILE:
 		case BTF_KIND_CONST:
 		case BTF_KIND_RESTRICT:
+		case BTF_KIND_TYPE_TAG:
 			id = type->type;
 			type = btf_type_by_id(btf, type->type);
 			break;
@@ -2345,6 +2348,8 @@ static int btf_ref_type_check_meta(struct btf_verifier_env *env,
 				   const struct btf_type *t,
 				   u32 meta_left)
 {
+	const char *value;
+
 	if (btf_type_vlen(t)) {
 		btf_verifier_log_type(env, t, "vlen != 0");
 		return -EINVAL;
@@ -2360,7 +2365,7 @@ static int btf_ref_type_check_meta(struct btf_verifier_env *env,
 		return -EINVAL;
 	}
 
-	/* typedef type must have a valid name, and other ref types,
+	/* typedef/type_tag type must have a valid name, and other ref types,
 	 * volatile, const, restrict, should have a null name.
 	 */
 	if (BTF_INFO_KIND(t->info) == BTF_KIND_TYPEDEF) {
@@ -2369,6 +2374,12 @@ static int btf_ref_type_check_meta(struct btf_verifier_env *env,
 			btf_verifier_log_type(env, t, "Invalid name");
 			return -EINVAL;
 		}
+	} else if (BTF_INFO_KIND(t->info) == BTF_KIND_TYPE_TAG) {
+		value = btf_name_by_offset(env->btf, t->name_off);
+		if (!value || !value[0]) {
+			btf_verifier_log_type(env, t, "Invalid name");
+			return -EINVAL;
+		}
 	} else {
 		if (t->name_off) {
 			btf_verifier_log_type(env, t, "Invalid name");
@@ -4059,6 +4070,7 @@ static const struct btf_kind_operations * const kind_ops[NR_BTF_KINDS] = {
 	[BTF_KIND_DATASEC] = &datasec_ops,
 	[BTF_KIND_FLOAT] = &float_ops,
 	[BTF_KIND_DECL_TAG] = &decl_tag_ops,
+	[BTF_KIND_TYPE_TAG] = &modifier_ops,
 };
 
 static s32 btf_check_meta(struct btf_verifier_env *env,

tools/bpf/bpftool/btf.c

@@ -39,6 +39,7 @@ static const char * const btf_kind_str[NR_BTF_KINDS] = {
 	[BTF_KIND_DATASEC]	= "DATASEC",
 	[BTF_KIND_FLOAT]	= "FLOAT",
 	[BTF_KIND_DECL_TAG]	= "DECL_TAG",
+	[BTF_KIND_TYPE_TAG]	= "TYPE_TAG",
 };
 
 struct btf_attach_point {
@@ -142,6 +143,7 @@ static int dump_btf_type(const struct btf *btf, __u32 id,
 	case BTF_KIND_VOLATILE:
 	case BTF_KIND_RESTRICT:
 	case BTF_KIND_TYPEDEF:
+	case BTF_KIND_TYPE_TAG:
 		if (json_output)
 			jsonw_uint_field(w, "type_id", t->type);
 		else

tools/include/uapi/linux/btf.h

@@ -43,7 +43,7 @@ struct btf_type {
 	 * "size" tells the size of the type it is describing.
 	 *
 	 * "type" is used by PTR, TYPEDEF, VOLATILE, CONST, RESTRICT,
-	 * FUNC, FUNC_PROTO, VAR and DECL_TAG.
+	 * FUNC, FUNC_PROTO, VAR, DECL_TAG and TYPE_TAG.
 	 * "type" is a type_id referring to another type.
 	 */
 	union {
@@ -75,6 +75,7 @@ enum {
 	BTF_KIND_DATASEC	= 15,	/* Section	*/
 	BTF_KIND_FLOAT		= 16,	/* Floating point	*/
 	BTF_KIND_DECL_TAG	= 17,	/* Decl Tag */
+	BTF_KIND_TYPE_TAG	= 18,	/* Type Tag */
 
 	NR_BTF_KINDS,
 	BTF_KIND_MAX		= NR_BTF_KINDS - 1,

tools/lib/bpf/btf.c

@@ -299,6 +299,7 @@ static int btf_type_size(const struct btf_type *t)
 	case BTF_KIND_TYPEDEF:
 	case BTF_KIND_FUNC:
 	case BTF_KIND_FLOAT:
+	case BTF_KIND_TYPE_TAG:
 		return base_size;
 	case BTF_KIND_INT:
 		return base_size + sizeof(__u32);
@@ -349,6 +350,7 @@ static int btf_bswap_type_rest(struct btf_type *t)
 	case BTF_KIND_TYPEDEF:
 	case BTF_KIND_FUNC:
 	case BTF_KIND_FLOAT:
+	case BTF_KIND_TYPE_TAG:
 		return 0;
 	case BTF_KIND_INT:
 		*(__u32 *)(t + 1) = bswap_32(*(__u32 *)(t + 1));
@@ -649,6 +651,7 @@ int btf__align_of(const struct btf *btf, __u32 id)
 	case BTF_KIND_VOLATILE:
 	case BTF_KIND_CONST:
 	case BTF_KIND_RESTRICT:
+	case BTF_KIND_TYPE_TAG:
 		return btf__align_of(btf, t->type);
 	case BTF_KIND_ARRAY:
 		return btf__align_of(btf, btf_array(t)->type);
@@ -2235,6 +2238,22 @@ int btf__add_restrict(struct btf *btf, int ref_type_id)
 	return btf_add_ref_kind(btf, BTF_KIND_RESTRICT, NULL, ref_type_id);
 }
 
+/*
+ * Append new BTF_KIND_TYPE_TAG type with:
+ *   - *value*, non-empty/non-NULL tag value;
+ *   - *ref_type_id* - referenced type ID, it might not exist yet;
+ * Returns:
+ *   - >0, type ID of newly added BTF type;
+ *   - <0, on error.
+ */
+int btf__add_type_tag(struct btf *btf, const char *value, int ref_type_id)
+{
+	if (!value|| !value[0])
+		return libbpf_err(-EINVAL);
+
+	return btf_add_ref_kind(btf, BTF_KIND_TYPE_TAG, value, ref_type_id);
+}
+
 /*
  * Append new BTF_KIND_FUNC type with:
  *   - *name*, non-empty/non-NULL name;
@@ -3639,6 +3658,7 @@ static int btf_dedup_prep(struct btf_dedup *d)
 		case BTF_KIND_TYPEDEF:
 		case BTF_KIND_FUNC:
 		case BTF_KIND_FLOAT:
+		case BTF_KIND_TYPE_TAG:
 			h = btf_hash_common(t);
 			break;
 		case BTF_KIND_INT:
@@ -3699,6 +3719,7 @@ static int btf_dedup_prim_type(struct btf_dedup *d, __u32 type_id)
 	case BTF_KIND_VAR:
 	case BTF_KIND_DATASEC:
 	case BTF_KIND_DECL_TAG:
+	case BTF_KIND_TYPE_TAG:
 		return 0;
 
 	case BTF_KIND_INT:
@@ -4297,6 +4318,7 @@ static int btf_dedup_ref_type(struct btf_dedup *d, __u32 type_id)
 	case BTF_KIND_PTR:
 	case BTF_KIND_TYPEDEF:
 	case BTF_KIND_FUNC:
+	case BTF_KIND_TYPE_TAG:
 		ref_type_id = btf_dedup_ref_type(d, t->type);
 		if (ref_type_id < 0)
 			return ref_type_id;
@@ -4603,6 +4625,7 @@ int btf_type_visit_type_ids(struct btf_type *t, type_id_visit_fn visit, void *ct
 	case BTF_KIND_FUNC:
 	case BTF_KIND_VAR:
 	case BTF_KIND_DECL_TAG:
+	case BTF_KIND_TYPE_TAG:
 		return visit(&t->type, ctx);
 
 	case BTF_KIND_ARRAY: {

tools/lib/bpf/btf.h

@@ -227,6 +227,7 @@ LIBBPF_API int btf__add_typedef(struct btf *btf, const char *name, int ref_type_
 LIBBPF_API int btf__add_volatile(struct btf *btf, int ref_type_id);
 LIBBPF_API int btf__add_const(struct btf *btf, int ref_type_id);
 LIBBPF_API int btf__add_restrict(struct btf *btf, int ref_type_id);
+LIBBPF_API int btf__add_type_tag(struct btf *btf, const char *value, int ref_type_id);
 
 /* func and func_proto construction APIs */
 LIBBPF_API int btf__add_func(struct btf *btf, const char *name,
@@ -458,7 +459,8 @@ static inline bool btf_is_mod(const struct btf_type *t)
 
 	return kind == BTF_KIND_VOLATILE ||
 	       kind == BTF_KIND_CONST ||
-	       kind == BTF_KIND_RESTRICT;
+	       kind == BTF_KIND_RESTRICT ||
+	       kind == BTF_KIND_TYPE_TAG;
 }
 
 static inline bool btf_is_func(const struct btf_type *t)
@@ -491,6 +493,11 @@ static inline bool btf_is_decl_tag(const struct btf_type *t)
 	return btf_kind(t) == BTF_KIND_DECL_TAG;
 }
 
+static inline bool btf_is_type_tag(const struct btf_type *t)
+{
+	return btf_kind(t) == BTF_KIND_TYPE_TAG;
+}
+
 static inline __u8 btf_int_encoding(const struct btf_type *t)
 {
 	return BTF_INT_ENCODING(*(__u32 *)(t + 1));

tools/lib/bpf/btf_dump.c

@@ -330,6 +330,7 @@ static int btf_dump_mark_referenced(struct btf_dump *d)
 		case BTF_KIND_FUNC:
 		case BTF_KIND_VAR:
 		case BTF_KIND_DECL_TAG:
+		case BTF_KIND_TYPE_TAG:
 			d->type_states[t->type].referenced = 1;
 			break;
 
@@ -573,6 +574,7 @@ static int btf_dump_order_type(struct btf_dump *d, __u32 id, bool through_ptr)
 	case BTF_KIND_VOLATILE:
 	case BTF_KIND_CONST:
 	case BTF_KIND_RESTRICT:
+	case BTF_KIND_TYPE_TAG:
 		return btf_dump_order_type(d, t->type, through_ptr);
 
 	case BTF_KIND_FUNC_PROTO: {
@@ -747,6 +749,7 @@ static void btf_dump_emit_type(struct btf_dump *d, __u32 id, __u32 cont_id)
 	case BTF_KIND_VOLATILE:
 	case BTF_KIND_CONST:
 	case BTF_KIND_RESTRICT:
+	case BTF_KIND_TYPE_TAG:
 		btf_dump_emit_type(d, t->type, cont_id);
 		break;
 	case BTF_KIND_ARRAY:
@@ -1167,6 +1170,7 @@ static void btf_dump_emit_type_decl(struct btf_dump *d, __u32 id,
 		case BTF_KIND_CONST:
 		case BTF_KIND_RESTRICT:
 		case BTF_KIND_FUNC_PROTO:
+		case BTF_KIND_TYPE_TAG:
 			id = t->type;
 			break;
 		case BTF_KIND_ARRAY:
@@ -1335,6 +1339,11 @@ static void btf_dump_emit_type_chain(struct btf_dump *d,
 		case BTF_KIND_RESTRICT:
 			btf_dump_printf(d, " restrict");
 			break;
+		case BTF_KIND_TYPE_TAG:
+			btf_dump_emit_mods(d, decls);
+			name = btf_name_of(d, t->name_off);
+			btf_dump_printf(d, " __attribute__((btf_type_tag(\"%s\")))", name);
+			break;
 		case BTF_KIND_ARRAY: {
 			const struct btf_array *a = btf_array(t);
 			const struct btf_type *next_t;

tools/lib/bpf/libbpf.c

@@ -197,6 +197,8 @@ enum kern_feature_id {
 	FEAT_PERF_LINK,
 	/* BTF_KIND_DECL_TAG support */
 	FEAT_BTF_DECL_TAG,
+	/* BTF_KIND_TYPE_TAG support */
+	FEAT_BTF_TYPE_TAG,
 	__FEAT_CNT,
 };
 
@@ -2076,6 +2078,7 @@ static const char *__btf_kind_str(__u16 kind)
 	case BTF_KIND_DATASEC: return "datasec";
 	case BTF_KIND_FLOAT: return "float";
 	case BTF_KIND_DECL_TAG: return "decl_tag";
+	case BTF_KIND_TYPE_TAG: return "type_tag";
 	default: return "unknown";
 	}
 }
@@ -2588,8 +2591,10 @@ static bool btf_needs_sanitization(struct bpf_object *obj)
 	bool has_float = kernel_supports(obj, FEAT_BTF_FLOAT);
 	bool has_func = kernel_supports(obj, FEAT_BTF_FUNC);
 	bool has_decl_tag = kernel_supports(obj, FEAT_BTF_DECL_TAG);
+	bool has_type_tag = kernel_supports(obj, FEAT_BTF_TYPE_TAG);
 
-	return !has_func || !has_datasec || !has_func_global || !has_float || !has_decl_tag;
+	return !has_func || !has_datasec || !has_func_global || !has_float ||
+	       !has_decl_tag || !has_type_tag;
 }
 
 static void bpf_object__sanitize_btf(struct bpf_object *obj, struct btf *btf)
@@ -2599,6 +2604,7 @@ static void bpf_object__sanitize_btf(struct bpf_object *obj, struct btf *btf)
 	bool has_float = kernel_supports(obj, FEAT_BTF_FLOAT);
 	bool has_func = kernel_supports(obj, FEAT_BTF_FUNC);
 	bool has_decl_tag = kernel_supports(obj, FEAT_BTF_DECL_TAG);
+	bool has_type_tag = kernel_supports(obj, FEAT_BTF_TYPE_TAG);
 	struct btf_type *t;
 	int i, j, vlen;
 
@@ -2657,6 +2663,10 @@ static void bpf_object__sanitize_btf(struct bpf_object *obj, struct btf *btf)
 			 */
 			t->name_off = 0;
 			t->info = BTF_INFO_ENC(BTF_KIND_STRUCT, 0, 0);
+		} else if (!has_type_tag && btf_is_type_tag(t)) {
+			/* replace TYPE_TAG with a CONST */
+			t->name_off = 0;
+			t->info = BTF_INFO_ENC(BTF_KIND_CONST, 0, 0);
 		}
 	}
 }
@@ -4460,6 +4470,22 @@ static int probe_kern_btf_decl_tag(void)
 					     strs, sizeof(strs)));
 }
 
+static int probe_kern_btf_type_tag(void)
+{
+	static const char strs[] = "\0tag";
+	__u32 types[] = {
+		/* int */
+		BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 32, 4),		/* [1] */
+		/* attr */
+		BTF_TYPE_TYPE_TAG_ENC(1, 1),				/* [2] */
+		/* ptr */
+		BTF_TYPE_ENC(0, BTF_INFO_ENC(BTF_KIND_PTR, 0, 0), 2),	/* [3] */
+	};
+
+	return probe_fd(libbpf__load_raw_btf((char *)types, sizeof(types),
+					     strs, sizeof(strs)));
+}
+
 static int probe_kern_array_mmap(void)
 {
 	struct bpf_create_map_attr attr = {
@@ -4657,6 +4683,9 @@ static struct kern_feature_desc {
 	[FEAT_BTF_DECL_TAG] = {
 		"BTF_KIND_DECL_TAG support", probe_kern_btf_decl_tag,
 	},
+	[FEAT_BTF_TYPE_TAG] = {
+		"BTF_KIND_TYPE_TAG support", probe_kern_btf_type_tag,
+	},
 };
 
 static bool kernel_supports(const struct bpf_object *obj, enum kern_feature_id feat_id)

tools/lib/bpf/libbpf.map

@@ -403,6 +403,7 @@ LIBBPF_0.6.0 {
 		bpf_program__set_extra_flags;
 		btf__add_btf;
 		btf__add_decl_tag;
+		btf__add_type_tag;
 		btf__dedup;
 		btf__dedup_deprecated;
 		btf__raw_data;

tools/lib/bpf/libbpf_internal.h

@@ -73,6 +73,8 @@
 	BTF_TYPE_ENC(name, BTF_INFO_ENC(BTF_KIND_FLOAT, 0, 0), sz)
 #define BTF_TYPE_DECL_TAG_ENC(value, type, component_idx) \
 	BTF_TYPE_ENC(value, BTF_INFO_ENC(BTF_KIND_DECL_TAG, 0, 0), type), (component_idx)
+#define BTF_TYPE_TYPE_TAG_ENC(value, type) \
+	BTF_TYPE_ENC(value, BTF_INFO_ENC(BTF_KIND_TYPE_TAG, 0, 0), type)
 
 #ifndef likely
 #define likely(x) __builtin_expect(!!(x), 1)

tools/testing/selftests/bpf/README.rst

@@ -204,16 +204,17 @@ __ https://reviews.llvm.org/D93563
 btf_tag test and Clang version
 ==============================
 
-The btf_tag selftest require LLVM support to recognize the btf_decl_tag attribute.
-It was introduced in `Clang 14`__.
+The btf_tag selftest requires LLVM support to recognize the btf_decl_tag and
+btf_type_tag attributes. They are introduced in `Clang 14` [0_, 1_].
 
-Without it, the btf_tag selftest will be skipped and you will observe:
+Without them, the btf_tag selftest will be skipped and you will observe:
 
 .. code-block:: console
 
   #<test_num> btf_tag:SKIP
 
-__ https://reviews.llvm.org/D111588
+.. _0: https://reviews.llvm.org/D111588
+.. _1: https://reviews.llvm.org/D111199
 
 Clang dependencies for static linking tests
 ===========================================

tools/testing/selftests/bpf/btf_helpers.c

@@ -25,11 +25,12 @@ static const char * const btf_kind_str_mapping[] = {
 	[BTF_KIND_DATASEC]	= "DATASEC",
 	[BTF_KIND_FLOAT]	= "FLOAT",
 	[BTF_KIND_DECL_TAG]	= "DECL_TAG",
+	[BTF_KIND_TYPE_TAG]	= "TYPE_TAG",
 };
 
 static const char *btf_kind_str(__u16 kind)
 {
-	if (kind > BTF_KIND_DECL_TAG)
+	if (kind > BTF_KIND_TYPE_TAG)
 		return "UNKNOWN";
 	return btf_kind_str_mapping[kind];
 }
@@ -109,6 +110,7 @@ int fprintf_btf_type_raw(FILE *out, const struct btf *btf, __u32 id)
 	case BTF_KIND_VOLATILE:
 	case BTF_KIND_RESTRICT:
 	case BTF_KIND_TYPEDEF:
+	case BTF_KIND_TYPE_TAG:
 		fprintf(out, " type_id=%u", t->type);
 		break;
 	case BTF_KIND_ARRAY: {

tools/testing/selftests/bpf/prog_tests/btf.c

@@ -3939,6 +3939,23 @@ static struct btf_raw_test raw_tests[] = {
 	.btf_load_err = true,
 	.err_str = "Invalid component_idx",
 },
+{
+	.descr = "type_tag test #1",
+	.raw_types = {
+		BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 32, 4),	/* [1] */
+		BTF_TYPE_TAG_ENC(NAME_TBD, 1),			/* [2] */
+		BTF_PTR_ENC(2),					/* [3] */
+		BTF_END_RAW,
+	},
+	BTF_STR_SEC("\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,
+},
 
 }; /* struct btf_raw_test raw_tests[] */
 
@@ -6861,15 +6878,16 @@ static struct btf_dedup_test dedup_tests[] = {
 			BTF_RESTRICT_ENC(8),						/* [11] restrict */
 			BTF_FUNC_PROTO_ENC(1, 2),					/* [12] func_proto */
 				BTF_FUNC_PROTO_ARG_ENC(NAME_TBD, 1),
-				BTF_FUNC_PROTO_ARG_ENC(NAME_TBD, 8),
+				BTF_FUNC_PROTO_ARG_ENC(NAME_TBD, 18),
 			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] 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_TYPE_TAG_ENC(NAME_TBD, 8),					/* [18] type_tag */
 			BTF_END_RAW,
 		},
-		BTF_STR_SEC("\0A\0B\0C\0D\0E\0F\0G\0H\0I\0J\0K\0L\0M\0N\0O\0P\0Q"),
+		BTF_STR_SEC("\0A\0B\0C\0D\0E\0F\0G\0H\0I\0J\0K\0L\0M\0N\0O\0P\0Q\0R"),
 	},
 	.expect = {
 		.raw_types = {
@@ -6890,15 +6908,16 @@ static struct btf_dedup_test dedup_tests[] = {
 			BTF_RESTRICT_ENC(8),						/* [11] restrict */
 			BTF_FUNC_PROTO_ENC(1, 2),					/* [12] func_proto */
 				BTF_FUNC_PROTO_ARG_ENC(NAME_TBD, 1),
-				BTF_FUNC_PROTO_ARG_ENC(NAME_TBD, 8),
+				BTF_FUNC_PROTO_ARG_ENC(NAME_TBD, 18),
 			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] 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_TYPE_TAG_ENC(NAME_TBD, 8),					/* [18] type_tag */
 			BTF_END_RAW,
 		},
-		BTF_STR_SEC("\0A\0B\0C\0D\0E\0F\0G\0H\0I\0J\0K\0L\0M\0N\0O\0P\0Q"),
+		BTF_STR_SEC("\0A\0B\0C\0D\0E\0F\0G\0H\0I\0J\0K\0L\0M\0N\0O\0P\0Q\0R"),
 	},
 },
 {
@@ -7204,6 +7223,135 @@ static struct btf_dedup_test dedup_tests[] = {
 		BTF_STR_SEC("\0t\0tag1\0tag2\0tag3"),
 	},
 },
+{
+	.descr = "dedup: btf_type_tag #1",
+	.input = {
+		.raw_types = {
+			/* ptr -> tag2 -> tag1 -> int */
+			BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 32, 4),	/* [1] */
+			BTF_TYPE_TAG_ENC(NAME_NTH(1), 1),		/* [2] */
+			BTF_TYPE_TAG_ENC(NAME_NTH(2), 2),		/* [3] */
+			BTF_PTR_ENC(3),					/* [4] */
+			/* ptr -> tag2 -> tag1 -> int */
+			BTF_TYPE_TAG_ENC(NAME_NTH(1), 1),		/* [5] */
+			BTF_TYPE_TAG_ENC(NAME_NTH(2), 5),		/* [6] */
+			BTF_PTR_ENC(6),					/* [7] */
+			/* ptr -> tag1 -> int */
+			BTF_TYPE_TAG_ENC(NAME_NTH(1), 1),		/* [8] */
+			BTF_PTR_ENC(8),					/* [9] */
+			BTF_END_RAW,
+		},
+		BTF_STR_SEC("\0tag1\0tag2"),
+	},
+	.expect = {
+		.raw_types = {
+			/* ptr -> tag2 -> tag1 -> int */
+			BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 32, 4),	/* [1] */
+			BTF_TYPE_TAG_ENC(NAME_NTH(1), 1),		/* [2] */
+			BTF_TYPE_TAG_ENC(NAME_NTH(2), 2),		/* [3] */
+			BTF_PTR_ENC(3),					/* [4] */
+			/* ptr -> tag1 -> int */
+			BTF_PTR_ENC(2),					/* [5] */
+			BTF_END_RAW,
+		},
+		BTF_STR_SEC("\0tag1\0tag2"),
+	},
+},
+{
+	.descr = "dedup: btf_type_tag #2",
+	.input = {
+		.raw_types = {
+			/* ptr -> tag2 -> tag1 -> int */
+			BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 32, 4),	/* [1] */
+			BTF_TYPE_TAG_ENC(NAME_NTH(1), 1),		/* [2] */
+			BTF_TYPE_TAG_ENC(NAME_NTH(2), 2),		/* [3] */
+			BTF_PTR_ENC(3),					/* [4] */
+			/* ptr -> tag2 -> int */
+			BTF_TYPE_TAG_ENC(NAME_NTH(2), 1),		/* [5] */
+			BTF_PTR_ENC(5),					/* [6] */
+			BTF_END_RAW,
+		},
+		BTF_STR_SEC("\0tag1\0tag2"),
+	},
+	.expect = {
+		.raw_types = {
+			/* ptr -> tag2 -> tag1 -> int */
+			BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 32, 4),	/* [1] */
+			BTF_TYPE_TAG_ENC(NAME_NTH(1), 1),		/* [2] */
+			BTF_TYPE_TAG_ENC(NAME_NTH(2), 2),		/* [3] */
+			BTF_PTR_ENC(3),					/* [4] */
+			/* ptr -> tag2 -> int */
+			BTF_TYPE_TAG_ENC(NAME_NTH(2), 1),		/* [5] */
+			BTF_PTR_ENC(5),					/* [6] */
+			BTF_END_RAW,
+		},
+		BTF_STR_SEC("\0tag1\0tag2"),
+	},
+},
+{
+	.descr = "dedup: btf_type_tag #3",
+	.input = {
+		.raw_types = {
+			/* ptr -> tag2 -> tag1 -> int */
+			BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 32, 4),	/* [1] */
+			BTF_TYPE_TAG_ENC(NAME_NTH(1), 1),		/* [2] */
+			BTF_TYPE_TAG_ENC(NAME_NTH(2), 2),		/* [3] */
+			BTF_PTR_ENC(3),					/* [4] */
+			/* ptr -> tag1 -> tag2 -> int */
+			BTF_TYPE_TAG_ENC(NAME_NTH(2), 1),		/* [5] */
+			BTF_TYPE_TAG_ENC(NAME_NTH(1), 5),		/* [6] */
+			BTF_PTR_ENC(6),					/* [7] */
+			BTF_END_RAW,
+		},
+		BTF_STR_SEC("\0tag1\0tag2"),
+	},
+	.expect = {
+		.raw_types = {
+			/* ptr -> tag2 -> tag1 -> int */
+			BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 32, 4),	/* [1] */
+			BTF_TYPE_TAG_ENC(NAME_NTH(1), 1),		/* [2] */
+			BTF_TYPE_TAG_ENC(NAME_NTH(2), 2),		/* [3] */
+			BTF_PTR_ENC(3),					/* [4] */
+			/* ptr -> tag1 -> tag2 -> int */
+			BTF_TYPE_TAG_ENC(NAME_NTH(2), 1),		/* [5] */
+			BTF_TYPE_TAG_ENC(NAME_NTH(1), 5),		/* [6] */
+			BTF_PTR_ENC(6),					/* [7] */
+			BTF_END_RAW,
+		},
+		BTF_STR_SEC("\0tag1\0tag2"),
+	},
+},
+{
+	.descr = "dedup: btf_type_tag #4",
+	.input = {
+		.raw_types = {
+			/* ptr -> tag1 -> int */
+			BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 32, 4),	/* [1] */
+			BTF_TYPE_TAG_ENC(NAME_NTH(1), 1),		/* [2] */
+			BTF_PTR_ENC(2),					/* [3] */
+			/* ptr -> tag1 -> long */
+			BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 64, 8),	/* [4] */
+			BTF_TYPE_TAG_ENC(NAME_NTH(1), 4),		/* [5] */
+			BTF_PTR_ENC(5),					/* [6] */
+			BTF_END_RAW,
+		},
+		BTF_STR_SEC("\0tag1"),
+	},
+	.expect = {
+		.raw_types = {
+			/* ptr -> tag1 -> int */
+			BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 32, 4),	/* [1] */
+			BTF_TYPE_TAG_ENC(NAME_NTH(1), 1),		/* [2] */
+			BTF_PTR_ENC(2),					/* [3] */
+			/* ptr -> tag1 -> long */
+			BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 64, 8),	/* [4] */
+			BTF_TYPE_TAG_ENC(NAME_NTH(1), 4),		/* [5] */
+			BTF_PTR_ENC(5),					/* [6] */
+			BTF_END_RAW,
+		},
+		BTF_STR_SEC("\0tag1"),
+	},
+},
 
 };
 
@@ -7222,6 +7370,7 @@ static int btf_type_size(const struct btf_type *t)
 	case BTF_KIND_TYPEDEF:
 	case BTF_KIND_FUNC:
 	case BTF_KIND_FLOAT:
+	case BTF_KIND_TYPE_TAG:
 		return base_size;
 	case BTF_KIND_INT:
 		return base_size + sizeof(__u32);

tools/testing/selftests/bpf/prog_tests/btf_tag.c

 // SPDX-License-Identifier: GPL-2.0
 /* Copyright (c) 2021 Facebook */
 #include <test_progs.h>
-#include "tag.skel.h"
+#include "btf_decl_tag.skel.h"
 
-void test_btf_tag(void)
+/* struct btf_type_tag_test is referenced in btf_type_tag.skel.h */
+struct btf_type_tag_test {
+        int **p;
+};
+#include "btf_type_tag.skel.h"
+
+static void test_btf_decl_tag(void)
+{
+	struct btf_decl_tag *skel;
+
+	skel = btf_decl_tag__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "btf_decl_tag"))
+		return;
+
+	if (skel->rodata->skip_tests) {
+		printf("%s:SKIP: btf_decl_tag attribute not supported", __func__);
+		test__skip();
+	}
+
+	btf_decl_tag__destroy(skel);
+}
+
+static void test_btf_type_tag(void)
 {
-	struct tag *skel;
+	struct btf_type_tag *skel;
 
-	skel = tag__open_and_load();
-	if (!ASSERT_OK_PTR(skel, "btf_tag"))
+	skel = btf_type_tag__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "btf_type_tag"))
 		return;
 
 	if (skel->rodata->skip_tests) {
-		printf("%s:SKIP: btf_tag attribute not supported", __func__);
+		printf("%s:SKIP: btf_type_tag attribute not supported", __func__);
 		test__skip();
 	}
 
-	tag__destroy(skel);
+	btf_type_tag__destroy(skel);
+}
+
+void test_btf_tag(void)
+{
+	if (test__start_subtest("btf_decl_tag"))
+		test_btf_decl_tag();
+	if (test__start_subtest("btf_type_tag"))
+		test_btf_type_tag();
 }

tools/testing/selftests/bpf/prog_tests/btf_write.c

@@ -297,6 +297,16 @@ static void gen_btf(struct btf *btf)
 	ASSERT_EQ(btf_decl_tag(t)->component_idx, 1, "tag_component_idx");
 	ASSERT_STREQ(btf_type_raw_dump(btf, 19),
 		     "[19] DECL_TAG 'tag2' type_id=14 component_idx=1", "raw_dump");
+
+	/* TYPE_TAG */
+	id = btf__add_type_tag(btf, "tag1", 1);
+	ASSERT_EQ(id, 20, "tag_id");
+	t = btf__type_by_id(btf, 20);
+	ASSERT_STREQ(btf__str_by_offset(btf, t->name_off), "tag1", "tag_value");
+	ASSERT_EQ(btf_kind(t), BTF_KIND_TYPE_TAG, "tag_kind");
+	ASSERT_EQ(t->type, 1, "tag_type");
+	ASSERT_STREQ(btf_type_raw_dump(btf, 20),
+		     "[20] TYPE_TAG 'tag1' type_id=1", "raw_dump");
 }
 
 static void test_btf_add()
@@ -337,7 +347,8 @@ static void test_btf_add()
 		"[17] DATASEC 'datasec1' size=12 vlen=1\n"
 		"\ttype_id=1 offset=4 size=8",
 		"[18] DECL_TAG 'tag1' type_id=16 component_idx=-1",
-		"[19] DECL_TAG 'tag2' type_id=14 component_idx=1");
+		"[19] DECL_TAG 'tag2' type_id=14 component_idx=1",
+		"[20] TYPE_TAG 'tag1' type_id=1");
 
 	btf__free(btf);
 }
@@ -359,7 +370,7 @@ static void test_btf_add_btf()
 	gen_btf(btf2);
 
 	id = btf__add_btf(btf1, btf2);
-	if (!ASSERT_EQ(id, 20, "id"))
+	if (!ASSERT_EQ(id, 21, "id"))
 		goto cleanup;
 
 	VALIDATE_RAW_BTF(
@@ -391,35 +402,37 @@ static void test_btf_add_btf()
 		"\ttype_id=1 offset=4 size=8",
 		"[18] DECL_TAG 'tag1' type_id=16 component_idx=-1",
 		"[19] DECL_TAG 'tag2' type_id=14 component_idx=1",
+		"[20] TYPE_TAG 'tag1' type_id=1",
 
 		/* types appended from the second BTF */
-		"[20] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED",
-		"[21] PTR '(anon)' type_id=20",
-		"[22] CONST '(anon)' type_id=24",
-		"[23] VOLATILE '(anon)' type_id=22",
-		"[24] RESTRICT '(anon)' type_id=23",
-		"[25] ARRAY '(anon)' type_id=21 index_type_id=20 nr_elems=10",
-		"[26] STRUCT 's1' size=8 vlen=2\n"
-		"\t'f1' type_id=20 bits_offset=0\n"
-		"\t'f2' type_id=20 bits_offset=32 bitfield_size=16",
-		"[27] UNION 'u1' size=8 vlen=1\n"
-		"\t'f1' type_id=20 bits_offset=0 bitfield_size=16",
-		"[28] ENUM 'e1' size=4 vlen=2\n"
+		"[21] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED",
+		"[22] PTR '(anon)' type_id=21",
+		"[23] CONST '(anon)' type_id=25",
+		"[24] VOLATILE '(anon)' type_id=23",
+		"[25] RESTRICT '(anon)' type_id=24",
+		"[26] ARRAY '(anon)' type_id=22 index_type_id=21 nr_elems=10",
+		"[27] STRUCT 's1' size=8 vlen=2\n"
+		"\t'f1' type_id=21 bits_offset=0\n"
+		"\t'f2' type_id=21 bits_offset=32 bitfield_size=16",
+		"[28] UNION 'u1' size=8 vlen=1\n"
+		"\t'f1' type_id=21 bits_offset=0 bitfield_size=16",
+		"[29] ENUM 'e1' size=4 vlen=2\n"
 		"\t'v1' val=1\n"
 		"\t'v2' val=2",
-		"[29] FWD 'struct_fwd' fwd_kind=struct",
-		"[30] FWD 'union_fwd' fwd_kind=union",
-		"[31] ENUM 'enum_fwd' size=4 vlen=0",
-		"[32] TYPEDEF 'typedef1' type_id=20",
-		"[33] FUNC 'func1' type_id=34 linkage=global",
-		"[34] FUNC_PROTO '(anon)' ret_type_id=20 vlen=2\n"
-		"\t'p1' type_id=20\n"
-		"\t'p2' type_id=21",
-		"[35] VAR 'var1' type_id=20, linkage=global-alloc",
-		"[36] DATASEC 'datasec1' size=12 vlen=1\n"
-		"\ttype_id=20 offset=4 size=8",
-		"[37] DECL_TAG 'tag1' type_id=35 component_idx=-1",
-		"[38] DECL_TAG 'tag2' type_id=33 component_idx=1");
+		"[30] FWD 'struct_fwd' fwd_kind=struct",
+		"[31] FWD 'union_fwd' fwd_kind=union",
+		"[32] ENUM 'enum_fwd' size=4 vlen=0",
+		"[33] TYPEDEF 'typedef1' type_id=21",
+		"[34] FUNC 'func1' type_id=35 linkage=global",
+		"[35] FUNC_PROTO '(anon)' ret_type_id=21 vlen=2\n"
+		"\t'p1' type_id=21\n"
+		"\t'p2' type_id=22",
+		"[36] VAR 'var1' type_id=21, linkage=global-alloc",
+		"[37] DATASEC 'datasec1' size=12 vlen=1\n"
+		"\ttype_id=21 offset=4 size=8",
+		"[38] DECL_TAG 'tag1' type_id=36 component_idx=-1",
+		"[39] DECL_TAG 'tag2' type_id=34 component_idx=1",
+		"[40] TYPE_TAG 'tag1' type_id=21");
 
 cleanup:
 	btf__free(btf1);

tools/testing/selftests/bpf/progs/tag.c → tools/testing/selftests/bpf/progs/btf_decl_tag.c

@@ -4,10 +4,6 @@
 #include <bpf/bpf_helpers.h>
 #include <bpf/bpf_tracing.h>
 
-#ifndef __has_attribute
-#define __has_attribute(x) 0
-#endif
-
 #if __has_attribute(btf_decl_tag)
 #define __tag1 __attribute__((btf_decl_tag("tag1")))
 #define __tag2 __attribute__((btf_decl_tag("tag2")))

tools/testing/selftests/bpf/progs/btf_type_tag.c

+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2021 Facebook */
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+#if __has_attribute(btf_type_tag)
+#define __tag1 __attribute__((btf_type_tag("tag1")))
+#define __tag2 __attribute__((btf_type_tag("tag2")))
+volatile const bool skip_tests = false;
+#else
+#define __tag1
+#define __tag2
+volatile const bool skip_tests = true;
+#endif
+
+struct btf_type_tag_test {
+	int __tag1 * __tag1 __tag2 *p;
+} g;
+
+SEC("fentry/bpf_fentry_test1")
+int BPF_PROG(sub, int x)
+{
+  return 0;
+}

tools/testing/selftests/bpf/test_btf.h

@@ -72,4 +72,7 @@
 #define BTF_DECL_TAG_ENC(value, type, component_idx)	\
 	BTF_TYPE_ENC(value, BTF_INFO_ENC(BTF_KIND_DECL_TAG, 0, 0), type), (component_idx)
 
+#define BTF_TYPE_TAG_ENC(value, type)	\
+	BTF_TYPE_ENC(value, BTF_INFO_ENC(BTF_KIND_TYPE_TAG, 0, 0), type)
+
 #endif /* _TEST_BTF_H */