btf: Make btf_set_contains take a const pointer

bsearch doesn't modify the contents of the array, so we can take a const pointer.
Signed-off-by: Lorenz Bauer <lmb@cloudflare.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200921121227.255763-2-lmb@cloudflare.com

include/linux/bpf.h

@@ -1905,6 +1905,6 @@ int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type t,
 		       void *addr1, void *addr2);
 
 struct btf_id_set;
-bool btf_id_set_contains(struct btf_id_set *set, u32 id);
+bool btf_id_set_contains(const struct btf_id_set *set, u32 id);
 
 #endif /* _LINUX_BPF_H */

kernel/bpf/btf.c

@@ -4772,7 +4772,7 @@ static int btf_id_cmp_func(const void *a, const void *b)
 	return *pa - *pb;
 }
 
-bool btf_id_set_contains(struct btf_id_set *set, u32 id)
+bool btf_id_set_contains(const struct btf_id_set *set, u32 id)
 {
 	return bsearch(&id, set->ids, set->cnt, sizeof(u32), btf_id_cmp_func) != NULL;
 }