diff options
author | Andrii Nakryiko <andrii@kernel.org> | 2022-05-08 17:41:42 -0700 |
---|---|---|
committer | Daniel Borkmann <daniel@iogearbox.net> | 2022-05-09 17:15:28 +0200 |
commit | 73d0280f6b79c936770698250549ba9f62682a45 (patch) | |
tree | 0b3c7c9d504dd815a680296af39eec24cd801cd4 /tools/lib | |
parent | 8e2f618e8be66f74e6e088281ca72deb5c87cf04 (diff) | |
download | linux-73d0280f6b79c936770698250549ba9f62682a45.tar.bz2 |
libbpf: Improve usability of field-based CO-RE helpers
Allow to specify field reference in two ways:
- if user has variable of necessary type, they can use variable-based
reference (my_var.my_field or my_var_ptr->my_field). This was the
only supported syntax up till now.
- now, bpf_core_field_exists() and bpf_core_field_size() support also
specifying field in a fashion similar to offsetof() macro, by
specifying type of the containing struct/union separately and field
name separately: bpf_core_field_exists(struct my_type, my_field).
This forms is quite often more convenient in practice and it matches
type-based CO-RE helpers that support specifying type by its name
without requiring any variables.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20220509004148.1801791-4-andrii@kernel.org
Diffstat (limited to 'tools/lib')
-rw-r--r-- | tools/lib/bpf/bpf_core_read.h | 25 |
1 files changed, 21 insertions, 4 deletions
diff --git a/tools/lib/bpf/bpf_core_read.h b/tools/lib/bpf/bpf_core_read.h index e4aa9996a550..5ad415f9051f 100644 --- a/tools/lib/bpf/bpf_core_read.h +++ b/tools/lib/bpf/bpf_core_read.h @@ -110,21 +110,38 @@ enum bpf_enum_value_kind { val; \ }) +#define ___bpf_field_ref1(field) (field) +#define ___bpf_field_ref2(type, field) (((typeof(type) *)0)->field) +#define ___bpf_field_ref(args...) \ + ___bpf_apply(___bpf_field_ref, ___bpf_narg(args))(args) + /* * 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. + * + * Supports two forms: + * - field reference through variable access: + * bpf_core_field_exists(p->my_field); + * - field reference through type and field names: + * bpf_core_field_exists(struct my_type, my_field). */ -#define bpf_core_field_exists(field) \ - __builtin_preserve_field_info(field, BPF_FIELD_EXISTS) +#define bpf_core_field_exists(field...) \ + __builtin_preserve_field_info(___bpf_field_ref(field), BPF_FIELD_EXISTS) /* * Convenience macro to get the byte size of a field. Works for integers, * struct/unions, pointers, arrays, and enums. + * + * Supports two forms: + * - field reference through variable access: + * bpf_core_field_size(p->my_field); + * - field reference through type and field names: + * bpf_core_field_size(struct my_type, my_field). */ -#define bpf_core_field_size(field) \ - __builtin_preserve_field_info(field, BPF_FIELD_BYTE_SIZE) +#define bpf_core_field_size(field...) \ + __builtin_preserve_field_info(___bpf_field_ref(field), BPF_FIELD_BYTE_SIZE) /* * Convenience macro to get BTF type ID of a specified type, using a local BTF |