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@xxxxxx> --- tools/lib/bpf/bpf_core_read.h | 24 +++++++++++++++++++++++- 1 file changed, 23 insertions(+), 1 deletion(-) 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 @@ -2,6 +2,28 @@ #ifndef __BPF_CORE_READ_H__ #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() @@ -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 -- 2.17.1
