Merge branch 'typedef-func_proto'

Yonghong Song says:

====================
The current btf implementation disallows the typedef of
a func_proto type. This actually is allowed per C standard.
This patch fixed btf verification to permit such types.
Patch #1 fixed the kernel side and Patch #2 fixed
the tools test_btf test.
====================
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

kernel/bpf/btf.c

@@ -1459,7 +1459,8 @@ static int btf_modifier_resolve(struct btf_verifier_env *env,
 
 		/* "typedef void new_void", "const void"...etc */
 		if (!btf_type_is_void(next_type) &&
-		    !btf_type_is_fwd(next_type)) {
+		    !btf_type_is_fwd(next_type) &&
+		    !btf_type_is_func_proto(next_type)) {
 			btf_verifier_log_type(env, v->t, "Invalid type_id");
 			return -EINVAL;
 		}

tools/testing/selftests/bpf/test_btf.c

@@ -1881,13 +1881,12 @@ static struct btf_raw_test raw_tests[] = {
 },
 
 {
-	.descr = "func proto (CONST=>TYPEDEF=>FUNC_PROTO)",
+	.descr = "func proto (TYPEDEF=>FUNC_PROTO)",
 	.raw_types = {
 		BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 32, 4),	/* [1] */
 		BTF_TYPE_INT_ENC(0, 0, 0, 32, 4),		/* [2] */
-		BTF_CONST_ENC(4),				/* [3] */
-		BTF_TYPEDEF_ENC(NAME_TBD, 5),			/* [4] */
-		BTF_FUNC_PROTO_ENC(0, 2),			/* [5] */
+		BTF_TYPEDEF_ENC(NAME_TBD, 4),			/* [3] */
+		BTF_FUNC_PROTO_ENC(0, 2),			/* [4] */
 			BTF_FUNC_PROTO_ARG_ENC(0, 1),
 			BTF_FUNC_PROTO_ARG_ENC(0, 2),
 		BTF_END_RAW,
@@ -1901,8 +1900,6 @@ static struct btf_raw_test raw_tests[] = {
 	.key_type_id = 1,
 	.value_type_id = 1,
 	.max_entries = 4,
-	.btf_load_err = true,
-	.err_str = "Invalid type_id",
 },
 
 {