[bpf-next,v3,10/10] docs/bpf: Update documentation for BTF_KIND_TYPE_TAG support

Commit Message

Yonghong Song Nov. 12, 2021, 1:26 a.m. UTC

Add BTF_KIND_TYPE_TAG documentation in btf.rst.

Acked-by: Andrii Nakryiko <[e-mail]>
Signed-off-by: Yonghong Song <[e-mail]>
---
 Documentation/bpf/btf.rst | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

Patch

diff --git a/Documentation/bpf/btf.rst b/Documentation/bpf/btf.rst
index 9ad4218a751f..d0ec40d00c28 100644
--- a/Documentation/bpf/btf.rst
+++ b/Documentation/bpf/btf.rst
@@ -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
 *****************