From: Stanislav Fomichev <sdf@google.com>
Date: Tue, 25 Jan 2022 16:13:40 -0800
Subject: bpf: fix register_btf_kfunc_id_set for !CONFIG_DEBUG_INFO_BTF
Patch-mainline: v5.18-rc1
Git-commit: c446fdacb10dcb3b9a9ed3b91d91e72d71d94b03
References: jsc#PED-1377

Commit dee872e124e8 ("bpf: Populate kfunc BTF ID sets in struct btf")
breaks loading of some modules when CONFIG_DEBUG_INFO_BTF is not set.
register_btf_kfunc_id_set returns -ENOENT to the callers when
there is no module btf. Let's return 0 (success) instead to let
those modules work in !CONFIG_DEBUG_INFO_BTF cases.

Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Fixes: dee872e124e8 ("bpf: Populate kfunc BTF ID sets in struct btf")
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Link: https://lore.kernel.org/r/20220126001340.1573649-1-sdf@google.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
---
 kernel/bpf/btf.c |   15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -6741,8 +6741,19 @@ int register_btf_kfunc_id_set(enum bpf_p
 	int ret;
 
 	btf = btf_get_module_btf(kset->owner);
-	if (IS_ERR_OR_NULL(btf))
-		return btf ? PTR_ERR(btf) : -ENOENT;
+	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_err("missing module BTF, cannot register kfuncs\n");
+			return -ENOENT;
+		}
+		return 0;
+	}
+	if (IS_ERR(btf))
+		return PTR_ERR(btf);
 
 	hook = bpf_prog_type_to_kfunc_hook(prog_type);
 	ret = btf_populate_kfunc_set(btf, hook, kset);