bpf: fix register_btf_kfunc_id_set for !CONFIG_DEBUG_INFO_BTF

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>

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index a1c44c1..b2a2489 100644 (file)
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -6740,8 +6740,19 @@ int register_btf_kfunc_id_set(enum bpf_prog_type prog_type,
        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);