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From:   Alexei Starovoitov <alexei.starovoitov@gmail.com>
Date:   Tue, 9 Aug 2022 10:48:48 -0700
Message-ID: <CAADnVQKgOR0L0thz6HbkL1x7mwc4eSRHftwsrzE9AxufyGBYZg@mail.gmail.com>
Subject: Re: [PATCH bpf-next v4 2/3] bpf: export crash_kexec() as destructive kfunc
To:     Artem Savkov <asavkov@redhat.com>
Cc:     Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Andrii Nakryiko <andrii@kernel.org>, bpf <bpf@vger.kernel.org>,
        Network Development <netdev@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Daniel Vacek <dvacek@redhat.com>,
        Jiri Olsa <olsajiri@gmail.com>, Song Liu <song@kernel.org>,
        Daniel Xu <dxu@dxuuu.xyz>,
        Kumar Kartikeya Dwivedi <memxor@gmail.com>
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On Tue, Aug 9, 2022 at 3:53 AM Artem Savkov <asavkov@redhat.com> wrote:
>
> Allow properly marked bpf programs to call crash_kexec().
>
> Signed-off-by: Artem Savkov <asavkov@redhat.com>
> ---
>  kernel/bpf/helpers.c | 21 +++++++++++++++++++++
>  1 file changed, 21 insertions(+)
>
> diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
> index 1f961f9982d2..103dbddff41f 100644
> --- a/kernel/bpf/helpers.c
> +++ b/kernel/bpf/helpers.c
> @@ -1711,3 +1711,24 @@ bpf_base_func_proto(enum bpf_func_id func_id)
>                 return NULL;
>         }
>  }
> +
> +BTF_SET8_START(tracing_btf_ids)
> +#ifdef CONFIG_KEXEC_CORE
> +BTF_ID_FLAGS(func, crash_kexec, KF_DESTRUCTIVE)
> +#endif
> +BTF_SET8_END(tracing_btf_ids)
> +
> +static const struct btf_kfunc_id_set tracing_kfunc_set = {
> +       .owner = THIS_MODULE,
> +       .set   = &tracing_btf_ids,
> +};
> +
> +static int __init kfunc_init(void)
> +{
> +       if (register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, &tracing_kfunc_set))
> +               pr_warn("failed to register kfunc id set for BPF_PROG_TYPE_TRACING\n");

Please drop pr_warn. We don't have it in all other
places where we do registration.