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From:   Alexei Starovoitov <alexei.starovoitov@gmail.com>
Date:   Fri, 26 Mar 2021 07:24:33 -0700
Message-ID: <CAADnVQ+W79=L=jb0hcOa4E067_PnWbnWHdxqyw-9+Nz9wKkOCA@mail.gmail.com>
Subject: Re: [PATCH bpf-next] bpf: trace jit code when enable BPF_JIT_ALWAYS_ON
To:     Jianlin Lv <Jianlin.Lv@arm.com>
Cc:     bpf <bpf@vger.kernel.org>, "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Andrii Nakryiko <andrii@kernel.org>,
        Martin KaFai Lau <kafai@fb.com>,
        Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>,
        John Fastabend <john.fastabend@gmail.com>,
        KP Singh <kpsingh@kernel.org>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Andrey Ignatov <rdna@fb.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Nicolas Dichtel <nicolas.dichtel@6wind.com>,
        Kees Cook <keescook@chromium.org>,
        Masahiro Yamada <masahiroy@kernel.org>,
        Mahesh Bandewar <maheshb@google.com>,
        LKML <linux-kernel@vger.kernel.org>,
        Network Development <netdev@vger.kernel.org>,
        iecedge@gmail.com, nd <nd@arm.com>
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On Fri, Mar 26, 2021 at 5:40 AM Jianlin Lv <Jianlin.Lv@arm.com> wrote:
>
> When CONFIG_BPF_JIT_ALWAYS_ON is enabled, the value of bpf_jit_enable in
> /proc/sys is limited to SYSCTL_ONE. This is not convenient for debugging.
> This patch modifies the value of extra2 (max) to 2 that support developers
> to emit traces on kernel log.
>
> Signed-off-by: Jianlin Lv <Jianlin.Lv@arm.com>
> ---
>  net/core/sysctl_net_core.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/net/core/sysctl_net_core.c b/net/core/sysctl_net_core.c
> index d84c8a1b280e..aa16883ac445 100644
> --- a/net/core/sysctl_net_core.c
> +++ b/net/core/sysctl_net_core.c
> @@ -386,7 +386,7 @@ static struct ctl_table net_core_table[] = {
>                 .proc_handler   = proc_dointvec_minmax_bpf_enable,
>  # ifdef CONFIG_BPF_JIT_ALWAYS_ON
>                 .extra1         = SYSCTL_ONE,
> -               .extra2         = SYSCTL_ONE,
> +               .extra2         = &two,

"bpftool prog dump jited" is much better way to examine JITed dumps.
I'd rather remove bpf_jit_enable=2 altogether.