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authorYonghong Song <yhs@fb.com>2021-09-15 01:31:03 +0300
committerAlexei Starovoitov <ast@kernel.org>2021-09-15 04:45:53 +0300
commit48f5a6c4162706f94523d7a0d828e4aee77d17e7 (patch)
tree53d112f3c22f0cbbe30868ee6922ea5e1e15e906 /Documentation/bpf/btf.rst
parentc240ba28789063690077d282f8f89e03f31037d0 (diff)
downloadlinux-48f5a6c4162706f94523d7a0d828e4aee77d17e7.tar.xz
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/bpf/btf.rst')
-rw-r--r--Documentation/bpf/btf.rst29
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
*****************