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libbpf: Refactor BTF map definition parsing

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Refactor BTF-defined maps parsing logic to allow it to be nicely reused by BPF
static linker. Further, at least for BPF static linker, it's important to know
which attributes of a BPF map were defined explicitly, so provide a bit set
for each known portion of BTF map definition. This allows BPF static linker to
do a simple check when dealing with extern map declarations.

The same capabilities allow to distinguish attributes explicitly set to zero
(e.g., __uint(max_entries, 0)) vs the case of not specifying it at all (no
max_entries attribute at all). Libbpf is currently not utilizing that, but it
could be useful for backwards compatibility reasons later.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20210423181348.1801389-7-andrii@kernel.org
This commit is contained in:
Andrii Nakryiko
2021-04-23 11:13:36 -07:00
committed by Andrii Nakryiko
parent 7b106ea4b1
commit d9b9d4a43a
2 changed files with 178 additions and 111 deletions
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32
src/libbpf_internal.h
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@@ -138,6 +138,38 @@ static inline __u32 btf_type_info(int kind, int vlen, int kflag)
return (kflag << 31) | (kind << 24) | vlen;
}
enum map_def_parts {
MAP_DEF_MAP_TYPE = 0x001,
MAP_DEF_KEY_TYPE = 0x002,
MAP_DEF_KEY_SIZE = 0x004,
MAP_DEF_VALUE_TYPE = 0x008,
MAP_DEF_VALUE_SIZE = 0x010,
MAP_DEF_MAX_ENTRIES = 0x020,
MAP_DEF_MAP_FLAGS = 0x040,
MAP_DEF_NUMA_NODE = 0x080,
MAP_DEF_PINNING = 0x100,
MAP_DEF_INNER_MAP = 0x200,
MAP_DEF_ALL = 0x3ff, /* combination of all above */
};
struct btf_map_def {
enum map_def_parts parts;
__u32 map_type;
__u32 key_type_id;
__u32 key_size;
__u32 value_type_id;
__u32 value_size;
__u32 max_entries;
__u32 map_flags;
__u32 numa_node;
__u32 pinning;
};
int parse_btf_map_def(const char *map_name, struct btf *btf,
const struct btf_type *def_t, bool strict,
struct btf_map_def *map_def, struct btf_map_def *inner_def);
void *libbpf_add_mem(void **data, size_t *cap_cnt, size_t elem_sz,
size_t cur_cnt, size_t max_cnt, size_t add_cnt);
int libbpf_ensure_mem(void **data, size_t *cap_cnt, size_t elem_sz, size_t need_cnt);