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authorYonghong Song <yhs@fb.com>2021-10-12 19:48:38 +0300
committerAlexei Starovoitov <ast@kernel.org>2021-10-19 04:35:36 +0300
commit223f903e9c832699f4e5f422281a60756c1c6cfe (patch)
tree3e6417cd43149323fe5c10bd25d234a82a6088dc /Documentation/bpf
parent431bfb9ee3e2ac0294d5ef58cee87683807299c0 (diff)
downloadlinux-223f903e9c832699f4e5f422281a60756c1c6cfe.tar.xz
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: b5ea834dde6b ("bpf: Support for new btf kind BTF_KIND_TAG") Fixes: 5b84bd10363e ("libbpf: Add support for BTF_KIND_TAG") Fixes: 5c07f2fec003 ("bpftool: Add support for BTF_KIND_TAG") Signed-off-by: Yonghong Song <yhs@fb.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20211012164838.3345699-1-yhs@fb.com
Diffstat (limited to 'Documentation/bpf')
-rw-r--r--Documentation/bpf/btf.rst24
1 files changed, 12 insertions, 12 deletions
diff --git a/Documentation/bpf/btf.rst b/Documentation/bpf/btf.rst
index 1bfe4072f5fc..9e5b4a98af76 100644
--- a/Documentation/bpf/btf.rst
+++ b/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