linux-kernel - Re: [PATCH v3] btf: warn but return no error for NULL btf from __register_btf_kfunc_id

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Date:   Mon, 3 Jul 2023 18:53:56 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     SeongJae Park <sj@...nel.org>
Cc:     Alexander.Egorenkov@....com, ast@...nel.org, jolsa@...nel.org,
        martin.lau@...ux.dev, memxor@...il.com, olsajiri@...il.com,
        bpf@...r.kernel.org, stable@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] btf: warn but return no error for NULL btf from
 __register_btf_kfunc_id_set()

On 7/1/23 7:14 PM, SeongJae Park wrote:
> __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@....com>
> Link: https://lore.kernel.org/bpf/87y228q66f.fsf@oc8242746057.ibm.com/
> Suggested-by: Kumar Kartikeya Dwivedi <memxor@...il.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@...r.kernel.org> # 5.18.x
> Signed-off-by: SeongJae Park <sj@...nel.org>
> Acked-by: Jiri Olsa <jolsa@...nel.org>
> Signed-off-by: SeongJae Park <sj@...nel.org>
> ---
> 
> Changes from v2
> (https://lore.kernel.org/bpf/20230628164611.83038-1-sj@kernel.org/)
> - Keep the error for vmlinux case.

Looks good, applied to bpf, thanks!