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 for details on the semantics.
Suggested-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
Signed-off-by: Ihor Solodrai <ihor.solodrai@xxxxx>
---
Documentation/bpf/btf.rst | 27 +++++++++--
tools/include/uapi/linux/btf.h | 3 +-
tools/lib/bpf/btf.c | 87 +++++++++++++++++++++++++---------
tools/lib/bpf/btf.h | 3 ++
tools/lib/bpf/libbpf.map | 2 +
5 files changed, 93 insertions(+), 29 deletions(-)
diff --git a/Documentation/bpf/btf.rst b/Documentation/bpf/btf.rst
index 2478cef758f8..615ded7b2442 100644
--- a/Documentation/bpf/btf.rst
+++ b/Documentation/bpf/btf.rst
@@ -102,8 +102,9 @@ Each type contains the following common data::
* bits 24-28: kind (e.g. int, ptr, array...etc)
* bits 29-30: unused
* bit 31: kind_flag, currently used by
- * struct, union, fwd, enum and enum64.
- */
+ * struct, union, enum, fwd, enum64,
+ * DECL_TAG and TYPE_TAG
+ */
__u32 info;
/* "size" is used by INT, ENUM, STRUCT, UNION and ENUM64.
* "size" tells the size of the type it is describing.
@@ -478,7 +479,7 @@ No additional type data follow ``btf_type``.
``struct btf_type`` encoding requirement:
* ``name_off``: offset to a non-empty string
- * ``info.kind_flag``: 0
+ * ``info.kind_flag``: 0 or 1
* ``info.kind``: BTF_KIND_DECL_TAG
* ``info.vlen``: 0
* ``type``: ``struct``, ``union``, ``func``, ``var`` or ``typedef``
@@ -489,7 +490,6 @@ No additional type data follow ``btf_type``.
__u32 component_idx;
};
-The ``name_off`` encodes btf_decl_tag attribute string.
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
@@ -499,12 +499,21 @@ 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.
+If ``info.kind_flag`` is 0, then this is a normal decl tag, and the
+``name_off`` encodes btf_decl_tag attribute string.
+
+If ``info.kind_flag`` is 1, then the decl tag represents an arbitrary
+__attribute__. In this case, ``name_off`` encodes a string
+representing the attribute-list of the attribute specifier. For
+example, for an ``__attribute__((aligned(4)))`` the string's contents
+is ``aligned(4)``.
+
2.2.18 BTF_KIND_TYPE_TAG
~~~~~~~~~~~~~~~~~~~~~~~~
``struct btf_type`` encoding requirement:
* ``name_off``: offset to a non-empty string
- * ``info.kind_flag``: 0
+ * ``info.kind_flag``: 0 or 1
* ``info.kind``: BTF_KIND_TYPE_TAG
* ``info.vlen``: 0
* ``type``: the type with ``btf_type_tag`` attribute
@@ -522,6 +531,14 @@ type_tag, then zero or more const/volatile/restrict/typedef
and finally the base type. The base type is one of
int, ptr, array, struct, union, enum, func_proto and float types.
+Similarly to decl tags, if the ``info.kind_flag`` is 0, then this is a
+normal type tag, and the ``name_off`` encodes btf_type_tag attribute
+string.
+
+If ``info.kind_flag`` is 1, then the type tag represents an arbitrary
+__attribute__, and the ``name_off`` encodes a string representing the
+attribute-list of the attribute specifier.
+
2.2.19 BTF_KIND_ENUM64
~~~~~~~~~~~~~~~~~~~~~~
diff --git a/tools/include/uapi/linux/btf.h b/tools/include/uapi/linux/btf.h
index ec1798b6d3ff..d602c26a0c2a 100644
--- a/tools/include/uapi/linux/btf.h
+++ b/tools/include/uapi/linux/btf.h
@@ -36,7 +36,8 @@ struct btf_type {
* bits 24-28: kind (e.g. int, ptr, array...etc)
* bits 29-30: unused
* bit 31: kind_flag, currently used by
- * struct, union, enum, fwd and enum64
+ * struct, union, enum, fwd, enum64,
+ * DECL_TAG and TYPE_TAG
*/
__u32 info;
/* "size" is used by INT, ENUM, STRUCT, UNION, DATASEC and ENUM64.
diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index 48c66f3a9200..df2808cee009 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -2090,7 +2090,7 @@ static int validate_type_id(int id)
}
/* 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;
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->info = btf_type_info(kind, 0, 0);
+ t->info = btf_type_info(kind, 0, kflag);
t->type = ref_type_id;
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)
{
- 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;
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)
return 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])
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)
{
- 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)
{
- 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)
{
- 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])
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)
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) {
struct btf_type *t = btf_type_by_id(btf, id);
@@ -2845,18 +2862,9 @@ int btf__add_datasec_var_info(struct btf *btf, int var_type_id, __u32 offset, __
return 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;
- * 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)
+
+static int __btf__add_decl_tag(struct btf *btf, const char *value,
+ int ref_type_id, int component_idx, int kflag)
{
struct btf_type *t;
int sz, value_off;
@@ -2880,13 +2888,46 @@ int btf__add_decl_tag(struct btf *btf, const char *value, int ref_type_id,
return 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;
btf_decl_tag(t)->component_idx = component_idx;
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 {
__u32 off;
__u32 len;
diff --git a/tools/lib/bpf/btf.h b/tools/lib/bpf/btf.h
index 47ee8f6ac489..1c969a530a3e 100644
--- a/tools/lib/bpf/btf.h
+++ b/tools/lib/bpf/btf.h
@@ -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_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_attr(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,
@@ -243,6 +244,8 @@ LIBBPF_API int btf__add_datasec_var_info(struct btf *btf, int var_type_id,
/* tag construction API */
LIBBPF_API int btf__add_decl_tag(struct btf *btf, const char *value, int ref_type_id,
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 {
size_t sz;
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index a8b2936a1646..8616e10b3c1b 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -436,4 +436,6 @@ LIBBPF_1.6.0 {
bpf_linker__add_buf;
bpf_linker__add_fd;
bpf_linker__new_fd;
+ btf__add_decl_attr;
+ btf__add_type_attr;
} LIBBPF_1.5.0;
--
2.48.1
