libbpf: Expose btf_type_by_id() internally

mainline inclusion
from mainline-5.13-rc1
commit e14ef4bf
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I5EUVD
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=e14ef4bf011192b61b48c4f3a35b3041140073ff

-------------------------------------------------

btf_type_by_id() is internal-only convenience API returning non-const pointer
to struct btf_type. Expose it outside of btf.c for re-use.
Signed-off-by: NAndrii Nakryiko <andrii@kernel.org>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210318194036.3521577-2-andrii@kernel.org
(cherry picked from commit e14ef4bf)
Signed-off-by: NWang Yufen <wangyufen@huawei.com>

tools/lib/bpf/btf.c

@@ -441,7 +441,7 @@ const struct btf *btf__base_btf(const struct btf *btf)
 }
 
 /* internal helper returning non-const pointer to a type */
-static struct btf_type *btf_type_by_id(struct btf *btf, __u32 type_id)
+struct btf_type *btf_type_by_id(struct btf *btf, __u32 type_id)
 {
 	if (type_id == 0)
 		return &btf_void;

tools/lib/bpf/libbpf_internal.h

@@ -107,6 +107,11 @@ static inline void *libbpf_reallocarray(void *ptr, size_t nmemb, size_t size)
 	return realloc(ptr, total);
 }
 
+struct btf;
+struct btf_type;
+
+struct btf_type *btf_type_by_id(struct btf *btf, __u32 type_id);
+
 void *btf_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 btf_ensure_mem(void **data, size_t *cap_cnt, size_t elem_sz, size_t need_cnt);