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| author | Yonghong Song <yhs@fb.com> | 2022-11-20 20:54:37 +0100 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2022-11-21 00:45:26 +0100 |
| commit | a35b9af4ec2c7f69286ef861fd2074a577e354cb (patch) | |
| tree | 260c91a59720dc30887556f629b4851af8efedcb /kernel/bpf/helpers.c | |
| parent | bpf: Add a kfunc to type cast from bpf uapi ctx to kernel ctx (diff) | |
| download | linux-a35b9af4ec2c7f69286ef861fd2074a577e354cb.tar.xz linux-a35b9af4ec2c7f69286ef861fd2074a577e354cb.zip | |
bpf: Add a kfunc for generic type cast
Implement bpf_rdonly_cast() which tries to cast the object
to a specified type. This tries to support use case like below:
#define skb_shinfo(SKB) ((struct skb_shared_info *)(skb_end_pointer(SKB)))
where skb_end_pointer(SKB) is a 'unsigned char *' and needs to
be casted to 'struct skb_shared_info *'.
The signature of bpf_rdonly_cast() looks like
void *bpf_rdonly_cast(void *obj, __u32 btf_id)
The function returns the same 'obj' but with PTR_TO_BTF_ID with
btf_id. The verifier will ensure btf_id being a struct type.
Since the supported type cast may not reflect what the 'obj'
represents, the returned btf_id is marked as PTR_UNTRUSTED, so
the return value and subsequent pointer chasing cannot be
used as helper/kfunc arguments.
Signed-off-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/r/20221120195437.3114585-1-yhs@fb.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'kernel/bpf/helpers.c')
| -rw-r--r-- | kernel/bpf/helpers.c | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c index e45e72676f5a..9e8a5557ea8d 100644 --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -1884,6 +1884,11 @@ void *bpf_cast_to_kern_ctx(void *obj) return obj; } +void *bpf_rdonly_cast(void *obj__ign, u32 btf_id__k) +{ + return obj__ign; +} + __diag_pop(); BTF_SET8_START(generic_btf_ids) @@ -1913,6 +1918,7 @@ BTF_ID(func, bpf_task_release) BTF_SET8_START(common_btf_ids) BTF_ID_FLAGS(func, bpf_cast_to_kern_ctx) +BTF_ID_FLAGS(func, bpf_rdonly_cast) BTF_SET8_END(common_btf_ids) static const struct btf_kfunc_id_set common_kfunc_set = { |