__register_btf_kfunc_id_set() assumes .BTF to be part of the module's .ko file if CONFIG_DEBUG_INFO_BTF is enabled. If that's not the case, the function prints an error message and return an error. As a result, such modules cannot be loaded.

However, the section could be stripped out during a build process. It would be better to let the modules loaded, because their basic functionalities have no problem[1], though the BTF functionalities will not be supported. Make the function to lower the level of the message from error to warn, and return no error.

[1] https://lore.kernel.org/bpf/20220219082037.ow2kbq5brktf4f2u@apollo.legion/

Reported-by: Alexander Egorenkov Alexander.Egorenkov@ibm.com Link: https://lore.kernel.org/bpf/87y228q66f.fsf@oc8242746057.ibm.com/ Suggested-by: Kumar Kartikeya Dwivedi memxor@gmail.com Link: https://lore.kernel.org/bpf/20220219082037.ow2kbq5brktf4f2u@apollo.legion/ Fixes: c446fdacb10d ("bpf: fix register_btf_kfunc_id_set for !CONFIG_DEBUG_INFO_BTF") Cc: stable@vger.kernel.org # 5.18.x Signed-off-by: SeongJae Park sj@kernel.org Acked-by: Jiri Olsa jolsa@kernel.org Signed-off-by: SeongJae Park sj@kernel.org ---

Changes from v2 (https://lore.kernel.org/bpf/20230628164611.83038-1-sj@kernel.org/) - Keep the error for vmlinux case. Changes from v1 (https://lore.kernel.org/all/20230626181120.7086-1-sj@kernel.org/) - Fix Fixes: tag (Jiri Olsa) - Add 'Acked-by: ' from Jiri Olsa

Notes - This is a fix. Hence, would better to merged into bpf tree, not bpf-next. - This doesn't cleanly applied on 6.1.y. I will send the backport to stable@ as soon as this is merged into the mainline.

kernel/bpf/btf.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index 29fe21099298..817204d53372 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -7891,10 +7891,8 @@ static int __register_btf_kfunc_id_set(enum btf_kfunc_hook hook, 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; - } + if (kset->owner && IS_ENABLED(CONFIG_DEBUG_INFO_BTF_MODULES)) + pr_warn("missing module BTF, cannot register kfuncs\n"); return 0; } if (IS_ERR(btf))