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| author |   Andrii Nakryiko <andriin@fb.com> | 2019-10-15 11:28:48 -0700 |
|---|---|---|
| committer |   Alexei Starovoitov <ast@kernel.org> | 2019-10-15 16:06:05 -0700 |
| commit | 01340e31915bc73bf33a8f912ff1b74d514b8d79 (patch) | |
| tree | e808e372f8ec2a039ea6c72650982c6c2abdc295 /tools | |
| parent | libbpf: Add support for field existance CO-RE relocation (diff) | |
| download | linux-dev-01340e31915bc73bf33a8f912ff1b74d514b8d79.tar.xz linux-dev-01340e31915bc73bf33a8f912ff1b74d514b8d79.zip | |
libbpf: Add BPF-side definitions of supported field relocation kinds
Add enum definition for Clang's __builtin_preserve_field_info()
second argument (info_kind). Currently only byte offset and existence
are supported. Corresponding Clang changes introducing this built-in can
be found at [0]
[0] https://reviews.llvm.org/D67980
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20191015182849.3922287-5-andriin@fb.com
Diffstat (limited to 'tools')
| -rw-r--r-- | tools/lib/bpf/bpf_core_read.h | 24 |
1 files changed, 23 insertions, 1 deletions
diff --git a/tools/lib/bpf/bpf_core_read.h b/tools/lib/bpf/bpf_core_read.h index 4daf04c25493..a273df3784f4 100644 --- a/tools/lib/bpf/bpf_core_read.h +++ b/tools/lib/bpf/bpf_core_read.h @@ -3,6 +3,28 @@ #define __BPF_CORE_READ_H__ /* + * enum bpf_field_info_kind is passed as a second argument into + * __builtin_preserve_field_info() built-in to get a specific aspect of + * a field, captured as a first argument. __builtin_preserve_field_info(field, + * info_kind) returns __u32 integer and produces BTF field relocation, which + * is understood and processed by libbpf during BPF object loading. See + * selftests/bpf for examples. + */ +enum bpf_field_info_kind { + BPF_FIELD_BYTE_OFFSET = 0, /* field byte offset */ + BPF_FIELD_EXISTS = 2, /* field existence in target kernel */ +}; + +/* + * Convenience macro to check that field actually exists in target kernel's. + * Returns: + * 1, if matching field is present in target kernel; + * 0, if no matching field found. + */ +#define bpf_core_field_exists(field) \ + __builtin_preserve_field_info(field, BPF_FIELD_EXISTS) + +/* * bpf_core_read() abstracts away bpf_probe_read() call and captures offset * relocation for source address using __builtin_preserve_access_index() * built-in, provided by Clang. @@ -12,7 +34,7 @@ * a relocation, which records BTF type ID describing root struct/union and an * accessor string which describes exact embedded field that was used to take * an address. See detailed description of this relocation format and - * semantics in comments to struct bpf_offset_reloc in libbpf_internal.h. + * semantics in comments to struct bpf_field_reloc in libbpf_internal.h. * * This relocation allows libbpf to adjust BPF instruction to use correct * actual field offset, based on target kernel BTF type that matches original |