bpf: Rename BTF_KIND_TAG to BTF_KIND_DECL_TAG

Patch set [1] introduced BTF_KIND_TAG to allow tagging
declarations for struct/union, struct/union field, var, func
and func arguments and these tags will be encoded into
dwarf. They are also encoded to btf by llvm for the bpf target.

After BTF_KIND_TAG is introduced, we intended to use it
for kernel __user attributes. But kernel __user is actually
a type attribute. Upstream and internal discussion showed
it is not a good idea to mix declaration attribute and
type attribute. So we proposed to introduce btf_type_tag
as a type attribute and existing btf_tag renamed to
btf_decl_tag ([2]).

This patch renamed BTF_KIND_TAG to BTF_KIND_DECL_TAG and some
other declarations with *_tag to *_decl_tag to make it clear
the tag is for declaration. In the future, BTF_KIND_TYPE_TAG
might be introduced per [3].

 [1] https://lore.kernel.org/bpf/[email protected]/
 [2] https://reviews.llvm.org/D111588
 [3] https://reviews.llvm.org/D111199

Fixes: b5ea834 ("bpf: Support for new btf kind BTF_KIND_TAG")
Fixes: 5b84bd1 ("libbpf: Add support for BTF_KIND_TAG")
Fixes: 5c07f2f ("bpftool: Add support for BTF_KIND_TAG")
Signed-off-by: Yonghong Song <[email protected]>
Signed-off-by: Alexei Starovoitov <[email protected]>
Link: https://lore.kernel.org/bpf/[email protected]

Author: yonghong-song

Documentation/bpf/btf.rst

@@ -85,7 +85,7 @@ sequentially and type id is assigned to each recognized type starting from id
     #define BTF_KIND_VAR            14      /* Variable     */
     #define BTF_KIND_DATASEC        15      /* Section      */
     #define BTF_KIND_FLOAT          16      /* Floating point       */
-    #define BTF_KIND_TAG            17      /* Tag          */
+    #define BTF_KIND_DECL_TAG       17      /* Decl 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 +107,7 @@ 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 TAG.
+         * FUNC, FUNC_PROTO and DECL_TAG.
          * "type" is a type_id referring to another type.
          */
         union {
@@ -466,30 +466,30 @@ map definition.
 
 No additional type data follow ``btf_type``.
 
-2.2.17 BTF_KIND_TAG
-~~~~~~~~~~~~~~~~~~~
+2.2.17 BTF_KIND_DECL_TAG
+~~~~~~~~~~~~~~~~~~~~~~~~
 
 ``struct btf_type`` encoding requirement:
  * ``name_off``: offset to a non-empty string
  * ``info.kind_flag``: 0
- * ``info.kind``: BTF_KIND_TAG
+ * ``info.kind``: BTF_KIND_DECL_TAG
  * ``info.vlen``: 0
  * ``type``: ``struct``, ``union``, ``func`` or ``var``
 
-``btf_type`` is followed by ``struct btf_tag``.::
+``btf_type`` is followed by ``struct btf_decl_tag``.::
 
-    struct btf_tag {
+    struct btf_decl_tag {
         __u32   component_idx;
     };
 
-The ``name_off`` encodes btf_tag attribute string.
+The ``name_off`` encodes btf_decl_tag attribute string.
 The ``type`` should be ``struct``, ``union``, ``func`` or ``var``.
-For ``var`` type, ``btf_tag.component_idx`` must be ``-1``.
-For the other three types, if the btf_tag attribute is
+For ``var`` 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_tag.component_idx`` must be ``-1``. Otherwise,
+``btf_decl_tag.component_idx`` must be ``-1``. Otherwise,
 the attribute is applied to a ``struct``/``union`` member or
-a ``func`` argument, and ``btf_tag.component_idx`` should be a
+a ``func`` argument, and ``btf_decl_tag.component_idx`` should be a
 valid index (starting from 0) pointing to a member or an argument.
 
 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 TAG.
+	 * FUNC, FUNC_PROTO, VAR and DECL_TAG.
 	 * "type" is a type_id referring to another type.
 	 */
 	union {
@@ -74,7 +74,7 @@ enum {
 	BTF_KIND_VAR		= 14,	/* Variable	*/
 	BTF_KIND_DATASEC	= 15,	/* Section	*/
 	BTF_KIND_FLOAT		= 16,	/* Floating point	*/
-	BTF_KIND_TAG		= 17,	/* Tag */
+	BTF_KIND_DECL_TAG	= 17,	/* Decl Tag */
 
 	NR_BTF_KINDS,
 	BTF_KIND_MAX		= NR_BTF_KINDS - 1,
@@ -174,14 +174,14 @@ struct btf_var_secinfo {
 	__u32	size;
 };
 
-/* BTF_KIND_TAG is followed by a single "struct btf_tag" to describe
+/* BTF_KIND_DECL_TAG is followed by a single "struct btf_decl_tag" to describe
  * additional information related to the tag applied location.
  * If component_idx == -1, the tag is applied to a struct, union,
  * variable or function. Otherwise, it is applied to a struct/union
  * member or a func argument, and component_idx indicates which member
  * or argument (0 ... vlen-1).
  */
-struct btf_tag {
+struct btf_decl_tag {
        __s32   component_idx;
 };
 

kernel/bpf/btf.c

@@ -281,7 +281,7 @@ static const char * const btf_kind_str[NR_BTF_KINDS] = {
 	[BTF_KIND_VAR]		= "VAR",
 	[BTF_KIND_DATASEC]	= "DATASEC",
 	[BTF_KIND_FLOAT]	= "FLOAT",
-	[BTF_KIND_TAG]		= "TAG",
+	[BTF_KIND_DECL_TAG]	= "DECL_TAG",
 };
 
 const char *btf_type_str(const struct btf_type *t)
@@ -460,12 +460,12 @@ static bool btf_type_is_datasec(const struct btf_type *t)
 	return BTF_INFO_KIND(t->info) == BTF_KIND_DATASEC;
 }
 
-static bool btf_type_is_tag(const struct btf_type *t)
+static bool btf_type_is_decl_tag(const struct btf_type *t)
 {
-	return BTF_INFO_KIND(t->info) == BTF_KIND_TAG;
+	return BTF_INFO_KIND(t->info) == BTF_KIND_DECL_TAG;
 }
 
-static bool btf_type_is_tag_target(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);
@@ -549,7 +549,7 @@ const struct btf_type *btf_type_resolve_func_ptr(const struct btf *btf,
 static bool btf_type_is_resolve_source_only(const struct btf_type *t)
 {
 	return btf_type_is_var(t) ||
-	       btf_type_is_tag(t) ||
+	       btf_type_is_decl_tag(t) ||
 	       btf_type_is_datasec(t);
 }
 
@@ -576,7 +576,7 @@ static bool btf_type_needs_resolve(const struct btf_type *t)
 	       btf_type_is_struct(t) ||
 	       btf_type_is_array(t) ||
 	       btf_type_is_var(t) ||
-	       btf_type_is_tag(t) ||
+	       btf_type_is_decl_tag(t) ||
 	       btf_type_is_datasec(t);
 }
 
@@ -630,9 +630,9 @@ static const struct btf_var *btf_type_var(const struct btf_type *t)
 	return (const struct btf_var *)(t + 1);
 }
 
-static const struct btf_tag *btf_type_tag(const struct btf_type *t)
+static const struct btf_decl_tag *btf_type_decl_tag(const struct btf_type *t)
 {
-	return (const struct btf_tag *)(t + 1);
+	return (const struct btf_decl_tag *)(t + 1);
 }
 
 static const struct btf_kind_operations *btf_type_ops(const struct btf_type *t)
@@ -3820,11 +3820,11 @@ static const struct btf_kind_operations float_ops = {
 	.show = btf_df_show,
 };
 
-static s32 btf_tag_check_meta(struct btf_verifier_env *env,
+static s32 btf_decl_tag_check_meta(struct btf_verifier_env *env,
 			      const struct btf_type *t,
 			      u32 meta_left)
 {
-	const struct btf_tag *tag;
+	const struct btf_decl_tag *tag;
 	u32 meta_needed = sizeof(*tag);
 	s32 component_idx;
 	const char *value;
@@ -3852,7 +3852,7 @@ static s32 btf_tag_check_meta(struct btf_verifier_env *env,
 		return -EINVAL;
 	}
 
-	component_idx = btf_type_tag(t)->component_idx;
+	component_idx = btf_type_decl_tag(t)->component_idx;
 	if (component_idx < -1) {
 		btf_verifier_log_type(env, t, "Invalid component_idx");
 		return -EINVAL;
@@ -3863,7 +3863,7 @@ static s32 btf_tag_check_meta(struct btf_verifier_env *env,
 	return meta_needed;
 }
 
-static int btf_tag_resolve(struct btf_verifier_env *env,
+static int btf_decl_tag_resolve(struct btf_verifier_env *env,
 			   const struct resolve_vertex *v)
 {
 	const struct btf_type *next_type;
@@ -3874,7 +3874,7 @@ static int btf_tag_resolve(struct btf_verifier_env *env,
 	u32 vlen;
 
 	next_type = btf_type_by_id(btf, next_type_id);
-	if (!next_type || !btf_type_is_tag_target(next_type)) {
+	if (!next_type || !btf_type_is_decl_tag_target(next_type)) {
 		btf_verifier_log_type(env, v->t, "Invalid type_id");
 		return -EINVAL;
 	}
@@ -3883,7 +3883,7 @@ static int btf_tag_resolve(struct btf_verifier_env *env,
 	    !env_type_is_resolved(env, next_type_id))
 		return env_stack_push(env, next_type, next_type_id);
 
-	component_idx = btf_type_tag(t)->component_idx;
+	component_idx = btf_type_decl_tag(t)->component_idx;
 	if (component_idx != -1) {
 		if (btf_type_is_var(next_type)) {
 			btf_verifier_log_type(env, v->t, "Invalid component_idx");
@@ -3909,18 +3909,18 @@ static int btf_tag_resolve(struct btf_verifier_env *env,
 	return 0;
 }
 
-static void btf_tag_log(struct btf_verifier_env *env, const struct btf_type *t)
+static void btf_decl_tag_log(struct btf_verifier_env *env, const struct btf_type *t)
 {
 	btf_verifier_log(env, "type=%u component_idx=%d", t->type,
-			 btf_type_tag(t)->component_idx);
+			 btf_type_decl_tag(t)->component_idx);
 }
 
-static const struct btf_kind_operations tag_ops = {
-	.check_meta = btf_tag_check_meta,
-	.resolve = btf_tag_resolve,
+static const struct btf_kind_operations decl_tag_ops = {
+	.check_meta = btf_decl_tag_check_meta,
+	.resolve = btf_decl_tag_resolve,
 	.check_member = btf_df_check_member,
 	.check_kflag_member = btf_df_check_kflag_member,
-	.log_details = btf_tag_log,
+	.log_details = btf_decl_tag_log,
 	.show = btf_df_show,
 };
 
@@ -4058,7 +4058,7 @@ static const struct btf_kind_operations * const kind_ops[NR_BTF_KINDS] = {
 	[BTF_KIND_VAR] = &var_ops,
 	[BTF_KIND_DATASEC] = &datasec_ops,
 	[BTF_KIND_FLOAT] = &float_ops,
-	[BTF_KIND_TAG] = &tag_ops,
+	[BTF_KIND_DECL_TAG] = &decl_tag_ops,
 };
 
 static s32 btf_check_meta(struct btf_verifier_env *env,
@@ -4143,7 +4143,7 @@ static bool btf_resolve_valid(struct btf_verifier_env *env,
 		return !btf_resolved_type_id(btf, type_id) &&
 		       !btf_resolved_type_size(btf, type_id);
 
-	if (btf_type_is_tag(t))
+	if (btf_type_is_decl_tag(t))
 		return btf_resolved_type_id(btf, type_id) &&
 		       !btf_resolved_type_size(btf, type_id);
 

tools/bpf/bpftool/btf.c

@@ -37,7 +37,7 @@ static const char * const btf_kind_str[NR_BTF_KINDS] = {
 	[BTF_KIND_VAR]		= "VAR",
 	[BTF_KIND_DATASEC]	= "DATASEC",
 	[BTF_KIND_FLOAT]	= "FLOAT",
-	[BTF_KIND_TAG]		= "TAG",
+	[BTF_KIND_DECL_TAG]	= "DECL_TAG",
 };
 
 struct btf_attach_table {
@@ -348,8 +348,8 @@ static int dump_btf_type(const struct btf *btf, __u32 id,
 			printf(" size=%u", t->size);
 		break;
 	}
-	case BTF_KIND_TAG: {
-		const struct btf_tag *tag = (const void *)(t + 1);
+	case BTF_KIND_DECL_TAG: {
+		const struct btf_decl_tag *tag = (const void *)(t + 1);
 
 		if (json_output) {
 			jsonw_uint_field(w, "type_id", t->type);

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 TAG.
+	 * FUNC, FUNC_PROTO, VAR and DECL_TAG.
 	 * "type" is a type_id referring to another type.
 	 */
 	union {
@@ -74,7 +74,7 @@ enum {
 	BTF_KIND_VAR		= 14,	/* Variable	*/
 	BTF_KIND_DATASEC	= 15,	/* Section	*/
 	BTF_KIND_FLOAT		= 16,	/* Floating point	*/
-	BTF_KIND_TAG		= 17,	/* Tag */
+	BTF_KIND_DECL_TAG	= 17,	/* Decl Tag */
 
 	NR_BTF_KINDS,
 	BTF_KIND_MAX		= NR_BTF_KINDS - 1,
@@ -174,14 +174,14 @@ struct btf_var_secinfo {
 	__u32	size;
 };
 
-/* BTF_KIND_TAG is followed by a single "struct btf_tag" to describe
+/* BTF_KIND_DECL_TAG is followed by a single "struct btf_decl_tag" to describe
  * additional information related to the tag applied location.
  * If component_idx == -1, the tag is applied to a struct, union,
  * variable or function. Otherwise, it is applied to a struct/union
  * member or a func argument, and component_idx indicates which member
  * or argument (0 ... vlen-1).
  */
-struct btf_tag {
+struct btf_decl_tag {
        __s32   component_idx;
 };