bpf, btf: Add check_btf_kconfigs helper

This patch extracts duplicate code on error path when btf_get_module_btf()
returns NULL from the functions __register_btf_kfunc_id_set() and
register_btf_id_dtor_kfuncs() into a new helper named check_btf_kconfigs()
to check CONFIG_DEBUG_INFO_BTF and CONFIG_DEBUG_INFO_BTF_MODULES in it.
Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/fa5537fc55f1e4d0bfd686598c81b7ab9dbd82b7.1707373307.git.tanggeliang@kylinos.cnSigned-off-by: Martin KaFai Lau <martin.lau@kernel.org>

kernel/bpf/btf.c

@@ -7738,6 +7738,17 @@ static struct btf *btf_get_module_btf(const struct module *module)
 	return btf;
 }
 
+static int check_btf_kconfigs(const struct module *module, const char *feature)
+{
+	if (!module && IS_ENABLED(CONFIG_DEBUG_INFO_BTF)) {
+		pr_err("missing vmlinux BTF, cannot register %s\n", feature);
+		return -ENOENT;
+	}
+	if (module && IS_ENABLED(CONFIG_DEBUG_INFO_BTF_MODULES))
+		pr_warn("missing module BTF, cannot register %s\n", feature);
+	return 0;
+}
+
 BPF_CALL_4(bpf_btf_find_by_name_kind, char *, name, int, name_sz, u32, kind, int, flags)
 {
 	struct btf *btf = NULL;
@@ -8098,15 +8109,8 @@ static int __register_btf_kfunc_id_set(enum btf_kfunc_hook hook,
 	int ret, i;
 
 	btf = btf_get_module_btf(kset->owner);
-	if (!btf) {
-		if (!kset->owner && IS_ENABLED(CONFIG_DEBUG_INFO_BTF)) {
-			pr_err("missing vmlinux BTF, cannot register kfuncs\n");
-			return -ENOENT;
-		}
-		if (kset->owner && IS_ENABLED(CONFIG_DEBUG_INFO_BTF_MODULES))
-			pr_warn("missing module BTF, cannot register kfuncs\n");
-		return 0;
-	}
+	if (!btf)
+		return check_btf_kconfigs(kset->owner, "kfunc");
 	if (IS_ERR(btf))
 		return PTR_ERR(btf);
 
@@ -8214,15 +8218,8 @@ int register_btf_id_dtor_kfuncs(const struct btf_id_dtor_kfunc *dtors, u32 add_c
 	int ret;
 
 	btf = btf_get_module_btf(owner);
-	if (!btf) {
-		if (!owner && IS_ENABLED(CONFIG_DEBUG_INFO_BTF)) {
-			pr_err("missing vmlinux BTF, cannot register dtor kfuncs\n");
-			return -ENOENT;
-		}
-		if (owner && IS_ENABLED(CONFIG_DEBUG_INFO_BTF_MODULES))
-			pr_warn("missing module BTF, cannot register dtor kfuncs\n");
-		return 0;
-	}
+	if (!btf)
+		return check_btf_kconfigs(owner, "dtor kfuncs");
 	if (IS_ERR(btf))
 		return PTR_ERR(btf);