Commit 223f903e authored by Yonghong Song's avatar Yonghong Song Committed by Alexei Starovoitov
Browse files

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/20210914223004.244411-1-yhs@fb.com/
 [2] https://reviews.llvm.org/D111588
 [3] https://reviews.llvm.org/D111199



Fixes: b5ea834d ("bpf: Support for new btf kind BTF_KIND_TAG")
Fixes: 5b84bd10 ("libbpf: Add support for BTF_KIND_TAG")
Fixes: 5c07f2fe ("bpftool: Add support for BTF_KIND_TAG")
Signed-off-by: default avatarYonghong Song <yhs@fb.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211012164838.3345699-1-yhs@fb.com
parent 431bfb9e

Documentation/bpf/btf.rst

+12 −12
Original line number Diff line number Diff line
@@ -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

+4 −4
Original line number Diff line number Diff line
@@ -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

+22 −22
Original line number Diff line number Diff line
@@ -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

+3 −3
Original line number Diff line number Diff line
@@ -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

+4 −4
Original line number Diff line number Diff line
@@ -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;

};