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docs/bpf: Update documentation for BTF_KIND_TYPE_TAG support

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Add BTF_KIND_TYPE_TAG documentation in btf.rst.

Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20211112012656.1509082-1-yhs@fb.com
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Yonghong Song 2021-11-11 17:26:56 -08:00 committed by Alexei Starovoitov
parent 3f1d0dc0ba
commit d52f5c639d
1 changed files with 12 additions and 1 deletions
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Documentation/bpf/btf.rst
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@ -86,6 +86,7 @@ sequentially and type id is assigned to each recognized type starting from id
#define BTF_KIND_DATASEC 15 /* Section */
#define BTF_KIND_FLOAT 16 /* Floating point */
#define BTF_KIND_DECL_TAG 17 /* Decl Tag */
#define BTF_KIND_TYPE_TAG 18 /* Type 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 +108,7 @@ 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 DECL_TAG.
* FUNC, FUNC_PROTO, DECL_TAG and TYPE_TAG.
* "type" is a type_id referring to another type.
*/
union {
@ -492,6 +493,16 @@ 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.
2.2.17 BTF_KIND_TYPE_TAG
~~~~~~~~~~~~~~~~~~~~~~~~
``struct btf_type`` encoding requirement:
* ``name_off``: offset to a non-empty string
* ``info.kind_flag``: 0
* ``info.kind``: BTF_KIND_TYPE_TAG
* ``info.vlen``: 0
* ``type``: the type with ``btf_type_tag`` attribute
3. BTF Kernel API
*****************