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| author | Yonghong Song <yhs@fb.com> | 2022-01-27 07:46:27 -0800 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2022-01-27 12:03:47 -0800 |
| commit | b72903847af014342e0a22d8b595ad09a7eb45a0 (patch) | |
| tree | b5a49bb16e2922c3da51888003fff2391259cf33 | |
| parent | 67ef7e1a759e4268e2102e7aa93c226eb75589f4 (diff) | |
| download | linux-b72903847af014342e0a22d8b595ad09a7eb45a0.tar.bz2 | |
docs/bpf: clarify how btf_type_tag gets encoded in the type chain
Clarify where the BTF_KIND_TYPE_TAG gets encoded in the type chain,
so applications and kernel can properly parse them.
Signed-off-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/r/20220127154627.665163-1-yhs@fb.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
| -rw-r--r-- | Documentation/bpf/btf.rst | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/Documentation/bpf/btf.rst b/Documentation/bpf/btf.rst index ab08852e53ae..7940da9bc6c1 100644 --- a/Documentation/bpf/btf.rst +++ b/Documentation/bpf/btf.rst @@ -503,6 +503,19 @@ valid index (starting from 0) pointing to a member or an argument. * ``info.vlen``: 0 * ``type``: the type with ``btf_type_tag`` attribute +Currently, ``BTF_KIND_TYPE_TAG`` is only emitted for pointer types. +It has the following btf type chain: +:: + + ptr -> [type_tag]* + -> [const | volatile | restrict | typedef]* + -> base_type + +Basically, a pointer type points to zero or more +type_tag, then zero or more const/volatile/restrict/typedef +and finally the base type. The base type is one of +int, ptr, array, struct, union, enum, func_proto and float types. + 3. BTF Kernel API ================= |