bpf: get type information with BTF_ID_LIST

Get ready to remove bpf_struct_ops_init() in the future. By using
BTF_ID_LIST, it is possible to gather type information while building
instead of runtime.
Signed-off-by: Kui-Feng Lee <thinker.li@gmail.com>
Link: https://lore.kernel.org/r/20240119225005.668602-3-thinker.li@gmail.comSigned-off-by: Martin KaFai Lau <martin.lau@kernel.org>

kernel/bpf/bpf_struct_ops.c

@@ -108,7 +108,12 @@ const struct bpf_prog_ops bpf_struct_ops_prog_ops = {
 #endif
 };
 
-static const struct btf_type *module_type;
+BTF_ID_LIST(st_ops_ids)
+BTF_ID(struct, module)
+
+enum {
+	IDX_MODULE_ID,
+};
 
 static void bpf_struct_ops_init_one(struct bpf_struct_ops *st_ops,
 				    struct btf *btf,
@@ -197,7 +202,6 @@ static void bpf_struct_ops_init_one(struct bpf_struct_ops *st_ops,
 void bpf_struct_ops_init(struct btf *btf, struct bpf_verifier_log *log)
 {
 	struct bpf_struct_ops *st_ops;
-	s32 module_id;
 	u32 i;
 
 	/* Ensure BTF type is emitted for "struct bpf_struct_ops_##_name" */
@@ -205,13 +209,6 @@ void bpf_struct_ops_init(struct btf *btf, struct bpf_verifier_log *log)
 #include "bpf_struct_ops_types.h"
 #undef BPF_STRUCT_OPS_TYPE
 
-	module_id = btf_find_by_name_kind(btf, "module", BTF_KIND_STRUCT);
-	if (module_id < 0) {
-		pr_warn("Cannot find struct module in %s\n", btf_get_name(btf));
-		return;
-	}
-	module_type = btf_type_by_id(btf, module_id);
-
 	for (i = 0; i < ARRAY_SIZE(bpf_struct_ops); i++) {
 		st_ops = bpf_struct_ops[i];
 		bpf_struct_ops_init_one(st_ops, btf, log);
@@ -387,6 +384,7 @@ static long bpf_struct_ops_map_update_elem(struct bpf_map *map, void *key,
 	struct bpf_struct_ops_map *st_map = (struct bpf_struct_ops_map *)map;
 	const struct bpf_struct_ops *st_ops = st_map->st_ops;
 	struct bpf_struct_ops_value *uvalue, *kvalue;
+	const struct btf_type *module_type;
 	const struct btf_member *member;
 	const struct btf_type *t = st_ops->type;
 	struct bpf_tramp_links *tlinks;
@@ -434,6 +432,7 @@ static long bpf_struct_ops_map_update_elem(struct bpf_map *map, void *key,
 	image = st_map->image;
 	image_end = st_map->image + PAGE_SIZE;
 
+	module_type = btf_type_by_id(btf_vmlinux, st_ops_ids[IDX_MODULE_ID]);
 	for_each_member(i, t, member) {
 		const struct btf_type *mtype, *ptype;
 		struct bpf_prog *prog;