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| author | Yonghong Song <yhs@fb.com> | 2021-09-15 00:31:03 +0200 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2021-09-15 03:45:53 +0200 |
| commit | 48f5a6c4162706f94523d7a0d828e4aee77d17e7 (patch) | |
| tree | 53d112f3c22f0cbbe30868ee6922ea5e1e15e906 /Documentation | |
| parent | selftests/bpf: Add a test with a bpf program with btf_tag attributes (diff) | |
| download | linux-48f5a6c4162706f94523d7a0d828e4aee77d17e7.tar.xz linux-48f5a6c4162706f94523d7a0d828e4aee77d17e7.zip | |
docs/bpf: Add documentation for BTF_KIND_TAG
Add BTF_KIND_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/20210914223103.249100-1-yhs@fb.com
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/bpf/btf.rst | 29 |
1 files changed, 28 insertions, 1 deletions
diff --git a/Documentation/bpf/btf.rst b/Documentation/bpf/btf.rst index 846354cd2d69..1bfe4072f5fc 100644 --- a/Documentation/bpf/btf.rst +++ b/Documentation/bpf/btf.rst @@ -85,6 +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 */ 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. @@ -106,7 +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 and FUNC_PROTO. + * FUNC, FUNC_PROTO and TAG. * "type" is a type_id referring to another type. */ union { @@ -465,6 +466,32 @@ map definition. No additional type data follow ``btf_type``. +2.2.17 BTF_KIND_TAG +~~~~~~~~~~~~~~~~~~~ + +``struct btf_type`` encoding requirement: + * ``name_off``: offset to a non-empty string + * ``info.kind_flag``: 0 + * ``info.kind``: BTF_KIND_TAG + * ``info.vlen``: 0 + * ``type``: ``struct``, ``union``, ``func`` or ``var`` + +``btf_type`` is followed by ``struct btf_tag``.:: + + struct btf_tag { + __u32 component_idx; + }; + +The ``name_off`` encodes btf_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 +applied to the ``struct``, ``union`` or ``func`` itself, +``btf_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 +valid index (starting from 0) pointing to a member or an argument. + 3. BTF Kernel API ***************** |