bpf: Use BTF_ID to resolve bpf_ctx_convert struct

This way the ID is resolved during compile time,
and we can remove the runtime name search.

Signed-off-by: Jiri Olsa <[e-mail]>
Signed-off-by: Alexei Starovoitov <[e-mail]>
Tested-by: Andrii Nakryiko <[e-mail]>
Acked-by: Andrii Nakryiko <[e-mail]>
Link: https://lore.kernel.org/bpf/[e-mail]

kernel/bpf/btf.c

···
 #include <linux/sort.h>
 #include <linux/bpf_verifier.h>
 #include <linux/btf.h>
+#include <linux/btf_ids.h>
 #include <linux/skmsg.h>
 #include <linux/perf_event.h>
 #include <net/sock.h>
···
 	return kern_ctx_type->type;
 }
 
+BTF_ID_LIST(bpf_ctx_convert_btf_id)
+BTF_ID(struct, bpf_ctx_convert)
+
 struct btf *btf_parse_vmlinux(void)
 {
 	struct btf_verifier_env *env = NULL;
 	struct bpf_verifier_log *log;
 	struct btf *btf = NULL;
-	int err, btf_id;
+	int err;
 
 	env = kzalloc(sizeof(*env), GFP_KERNEL | __GFP_NOWARN);
 	if (!env)
···
 	if (err)
 		goto errout;
 
-	/* find struct bpf_ctx_convert for type checking later */
-	btf_id = btf_find_by_name_kind(btf, "bpf_ctx_convert", BTF_KIND_STRUCT);
-	if (btf_id < 0) {
-		err = btf_id;
-		goto errout;
-	}
 	/* btf_parse_vmlinux() runs under bpf_verifier_lock */
-	bpf_ctx_convert.t = btf_type_by_id(btf, btf_id);
+	bpf_ctx_convert.t = btf_type_by_id(btf, bpf_ctx_convert_btf_id[0]);
 
 	/* find bpf map structs for map_ptr access checking */
 	err = btf_vmlinux_map_ids_init(btf, log);