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bpf: Introduce KF_ARG_PTR_TO_CONST_STR

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Similar to ARG_PTR_TO_CONST_STR for BPF helpers, KF_ARG_PTR_TO_CONST_STR
specifies kfunc args that point to const strings. Annotation "__str" is
used to specify kfunc arg of type KF_ARG_PTR_TO_CONST_STR. Also, add
documentation for the "__str" annotation.

bpf_get_file_xattr() will be the first kfunc that uses this type.

Signed-off-by: Song Liu <song@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Vadim Fedorenko <vadim.fedorenko@linux.dev>
Link: https://lore.kernel.org/bpf/20231107045725.2278852-4-song@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Song Liu
2023-11-06 20:57:25 -08:00
committed by Alexei Starovoitov
parent 0b51940729
commit 045edee19d
2 changed files with 43 additions and 0 deletions
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Documentation/bpf/kfuncs.rst
+24
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@@ -135,6 +135,30 @@ Either way, the returned buffer is either NULL, or of size buffer_szk. Without t
annotation, the verifier will reject the program if a null pointer is passed in with
a nonzero size.
2.2.5 __str Annotation
----------------------------
This annotation is used to indicate that the argument is a constant string.
An example is given below::
__bpf_kfunc bpf_get_file_xattr(..., const char *name__str, ...)
{
...
}
In this case, ``bpf_get_file_xattr()`` can be called as::
bpf_get_file_xattr(..., "xattr_name", ...);
Or::
const char name[] = "xattr_name"; /* This need to be global */
int BPF_PROG(...)
{
...
bpf_get_file_xattr(..., name, ...);
...
}
.. _BPF_kfunc_nodef: