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libbpf: Introduce kflag for type_tags and decl_tags in BTF

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Add the following functions to libbpf API:
  * btf__add_type_attr()
  * btf__add_decl_attr()

These functions allow to add to BTF the type tags and decl tags with
info->kflag set to 1. The kflag indicates that the tag directly
encodes an __attribute__ and not a normal tag.

See Documentation/bpf/btf.rst changes in the subsequent patch for
details on the semantics.

Suggested-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Ihor Solodrai <ihor.solodrai@linux.dev>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Reviewed-by: Alan Maguire <alan.maguire@oracle.com>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20250130201239.1429648-2-ihor.solodrai@linux.dev
This commit is contained in:
Ihor Solodrai
2025-01-30 12:12:34 -08:00
committed by Andrii Nakryiko
parent 71208c3362
commit 32bda80136
3 changed files with 68 additions and 23 deletions
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86
src/btf.c
View File

@@ -2090,7 +2090,7 @@ static int validate_type_id(int id)
} }
/* generic append function for PTR, TYPEDEF, CONST/VOLATILE/RESTRICT */ /* generic append function for PTR, TYPEDEF, CONST/VOLATILE/RESTRICT */
static int btf_add_ref_kind(struct btf *btf, int kind, const char *name, int ref_type_id) static int btf_add_ref_kind(struct btf *btf, int kind, const char *name, int ref_type_id, int kflag)
{ {
struct btf_type *t; struct btf_type *t;
int sz, name_off = 0; int sz, name_off = 0;
@@ -2113,7 +2113,7 @@ static int btf_add_ref_kind(struct btf *btf, int kind, const char *name, int ref
} }
t->name_off = name_off; t->name_off = name_off;
t->info = btf_type_info(kind, 0, 0); t->info = btf_type_info(kind, 0, kflag);
t->type = ref_type_id; t->type = ref_type_id;
return btf_commit_type(btf, sz); return btf_commit_type(btf, sz);
@@ -2128,7 +2128,7 @@ static int btf_add_ref_kind(struct btf *btf, int kind, const char *name, int ref
*/ */
int btf__add_ptr(struct btf *btf, int ref_type_id) int btf__add_ptr(struct btf *btf, int ref_type_id)
{ {
return btf_add_ref_kind(btf, BTF_KIND_PTR, NULL, ref_type_id); return btf_add_ref_kind(btf, BTF_KIND_PTR, NULL, ref_type_id, 0);
} }
/* /*
@@ -2506,7 +2506,7 @@ int btf__add_fwd(struct btf *btf, const char *name, enum btf_fwd_kind fwd_kind)
struct btf_type *t; struct btf_type *t;
int id; int id;
id = btf_add_ref_kind(btf, BTF_KIND_FWD, name, 0); id = btf_add_ref_kind(btf, BTF_KIND_FWD, name, 0, 0);
if (id <= 0) if (id <= 0)
return id; return id;
t = btf_type_by_id(btf, id); t = btf_type_by_id(btf, id);
@@ -2536,7 +2536,7 @@ int btf__add_typedef(struct btf *btf, const char *name, int ref_type_id)
if (!name || !name[0]) if (!name || !name[0])
return libbpf_err(-EINVAL); return libbpf_err(-EINVAL);
return btf_add_ref_kind(btf, BTF_KIND_TYPEDEF, name, ref_type_id); return btf_add_ref_kind(btf, BTF_KIND_TYPEDEF, name, ref_type_id, 0);
} }
/* /*
@@ -2548,7 +2548,7 @@ int btf__add_typedef(struct btf *btf, const char *name, int ref_type_id)
*/ */
int btf__add_volatile(struct btf *btf, int ref_type_id) int btf__add_volatile(struct btf *btf, int ref_type_id)
{ {
return btf_add_ref_kind(btf, BTF_KIND_VOLATILE, NULL, ref_type_id); return btf_add_ref_kind(btf, BTF_KIND_VOLATILE, NULL, ref_type_id, 0);
} }
/* /*
@@ -2560,7 +2560,7 @@ int btf__add_volatile(struct btf *btf, int ref_type_id)
*/ */
int btf__add_const(struct btf *btf, int ref_type_id) int btf__add_const(struct btf *btf, int ref_type_id)
{ {
return btf_add_ref_kind(btf, BTF_KIND_CONST, NULL, ref_type_id); return btf_add_ref_kind(btf, BTF_KIND_CONST, NULL, ref_type_id, 0);
} }
/* /*
@@ -2572,7 +2572,7 @@ int btf__add_const(struct btf *btf, int ref_type_id)
*/ */
int btf__add_restrict(struct btf *btf, int ref_type_id) int btf__add_restrict(struct btf *btf, int ref_type_id)
{ {
return btf_add_ref_kind(btf, BTF_KIND_RESTRICT, NULL, ref_type_id); return btf_add_ref_kind(btf, BTF_KIND_RESTRICT, NULL, ref_type_id, 0);
} }
/* /*
@@ -2588,7 +2588,24 @@ int btf__add_type_tag(struct btf *btf, const char *value, int ref_type_id)
if (!value || !value[0]) if (!value || !value[0])
return libbpf_err(-EINVAL); return libbpf_err(-EINVAL);
return btf_add_ref_kind(btf, BTF_KIND_TYPE_TAG, value, ref_type_id); return btf_add_ref_kind(btf, BTF_KIND_TYPE_TAG, value, ref_type_id, 0);
}
/*
* 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;
* Set info->kflag to 1, indicating this tag is an __attribute__
* Returns:
* - >0, type ID of newly added BTF type;
* - <0, on error.
*/
int btf__add_type_attr(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, 1);
} }
/* /*
@@ -2610,7 +2627,7 @@ int btf__add_func(struct btf *btf, const char *name,
linkage != BTF_FUNC_EXTERN) linkage != BTF_FUNC_EXTERN)
return libbpf_err(-EINVAL); return libbpf_err(-EINVAL);
id = btf_add_ref_kind(btf, BTF_KIND_FUNC, name, proto_type_id); id = btf_add_ref_kind(btf, BTF_KIND_FUNC, name, proto_type_id, 0);
if (id > 0) { if (id > 0) {
struct btf_type *t = btf_type_by_id(btf, id); struct btf_type *t = btf_type_by_id(btf, id);
@@ -2845,18 +2862,8 @@ int btf__add_datasec_var_info(struct btf *btf, int var_type_id, __u32 offset, __
return 0; return 0;
} }
/* static int btf_add_decl_tag(struct btf *btf, const char *value, int ref_type_id,
* Append new BTF_KIND_DECL_TAG type with: int component_idx, int kflag)
* - *value* - non-empty/non-NULL string;
* - *ref_type_id* - referenced type ID, it might not exist yet;
* - *component_idx* - -1 for tagging reference type, otherwise struct/union
* member or function argument index;
* Returns:
* - >0, type ID of newly added BTF type;
* - <0, on error.
*/
int btf__add_decl_tag(struct btf *btf, const char *value, int ref_type_id,
int component_idx)
{ {
struct btf_type *t; struct btf_type *t;
int sz, value_off; int sz, value_off;
@@ -2880,13 +2887,46 @@ int btf__add_decl_tag(struct btf *btf, const char *value, int ref_type_id,
return value_off; return value_off;
t->name_off = value_off; t->name_off = value_off;
t->info = btf_type_info(BTF_KIND_DECL_TAG, 0, false); t->info = btf_type_info(BTF_KIND_DECL_TAG, 0, kflag);
t->type = ref_type_id; t->type = ref_type_id;
btf_decl_tag(t)->component_idx = component_idx; btf_decl_tag(t)->component_idx = component_idx;
return btf_commit_type(btf, sz); return btf_commit_type(btf, sz);
} }
/*
* Append new BTF_KIND_DECL_TAG type with:
* - *value* - non-empty/non-NULL string;
* - *ref_type_id* - referenced type ID, it might not exist yet;
* - *component_idx* - -1 for tagging reference type, otherwise struct/union
* member or function argument index;
* Returns:
* - >0, type ID of newly added BTF type;
* - <0, on error.
*/
int btf__add_decl_tag(struct btf *btf, const char *value, int ref_type_id,
int component_idx)
{
return btf_add_decl_tag(btf, value, ref_type_id, component_idx, 0);
}
/*
* Append new BTF_KIND_DECL_TAG type with:
* - *value* - non-empty/non-NULL string;
* - *ref_type_id* - referenced type ID, it might not exist yet;
* - *component_idx* - -1 for tagging reference type, otherwise struct/union
* member or function argument index;
* Set info->kflag to 1, indicating this tag is an __attribute__
* Returns:
* - >0, type ID of newly added BTF type;
* - <0, on error.
*/
int btf__add_decl_attr(struct btf *btf, const char *value, int ref_type_id,
int component_idx)
{
return btf_add_decl_tag(btf, value, ref_type_id, component_idx, 1);
}
struct btf_ext_sec_info_param { struct btf_ext_sec_info_param {
__u32 off; __u32 off;
__u32 len; __u32 len;

3
src/btf.h
View File

@@ -227,6 +227,7 @@ 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_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_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); LIBBPF_API int btf__add_type_tag(struct btf *btf, const char *value, int ref_type_id);
LIBBPF_API int btf__add_type_attr(struct btf *btf, const char *value, int ref_type_id);
/* func and func_proto construction APIs */ /* func and func_proto construction APIs */
LIBBPF_API int btf__add_func(struct btf *btf, const char *name, LIBBPF_API int btf__add_func(struct btf *btf, const char *name,
@@ -243,6 +244,8 @@ LIBBPF_API int btf__add_datasec_var_info(struct btf *btf, int var_type_id,
/* tag construction API */ /* tag construction API */
LIBBPF_API int btf__add_decl_tag(struct btf *btf, const char *value, int ref_type_id, LIBBPF_API int btf__add_decl_tag(struct btf *btf, const char *value, int ref_type_id,
int component_idx); int component_idx);
LIBBPF_API int btf__add_decl_attr(struct btf *btf, const char *value, int ref_type_id,
int component_idx);
struct btf_dedup_opts { struct btf_dedup_opts {
size_t sz; size_t sz;

2
src/libbpf.map
View File

@@ -436,4 +436,6 @@ LIBBPF_1.6.0 {
bpf_linker__add_buf; bpf_linker__add_buf;
bpf_linker__add_fd; bpf_linker__add_fd;
bpf_linker__new_fd; bpf_linker__new_fd;
btf__add_decl_attr;
btf__add_type_attr;
} LIBBPF_1.5.0; } LIBBPF_1.5.0;