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From:   Ze Gao <zegao2021@gmail.com>
Date:   Thu, 18 May 2023 10:40:49 +0800
Message-ID: <CAD8CoPCBKyADGuUAaR6E-aO4wyy1LnCaBhuxoKz3nrTvPdHLYA@mail.gmail.com>
Subject: Re: [PATCH v3 1/4] rethook: use preempt_{disable, enable}_notrace in rethook_trampoline_handler
To:     Masami Hiramatsu <mhiramat@kernel.org>
Cc:     Steven Rostedt <rostedt@goodmis.org>,
        Albert Ou <aou@eecs.berkeley.edu>,
        Alexander Gordeev <agordeev@linux.ibm.com>,
        Alexei Starovoitov <ast@kernel.org>,
        Borislav Petkov <bp@alien8.de>,
        Christian Borntraeger <borntraeger@linux.ibm.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Heiko Carstens <hca@linux.ibm.com>,
        "H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Sven Schnelle <svens@linux.ibm.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Vasily Gorbik <gor@linux.ibm.com>, x86@kernel.org,
        bpf@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org,
        linux-trace-kernel@vger.kernel.org,
        Conor Dooley <conor@kernel.org>, Jiri Olsa <jolsa@kernel.org>,
        Yonghong Song <yhs@fb.com>, Ze Gao <zegao@tencent.com>,
        stable@vger.kernel.org
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Great, thanks!

Regards,
Ze

On Wed, May 17, 2023 at 7:59=E2=80=AFPM Masami Hiramatsu <mhiramat@kernel.o=
rg> wrote:
>
> Hi Ze Gao,
>
> On Wed, 17 May 2023 11:45:06 +0800
> Ze Gao <zegao2021@gmail.com> wrote:
>
> > This patch replaces preempt_{disable, enable} with its corresponding
> > notrace version in rethook_trampoline_handler so no worries about stack
> > recursion or overflow introduced by preempt_count_{add, sub} under
> > fprobe + rethook context.
> >
> > Fixes: 54ecbe6f1ed5 ("rethook: Add a generic return hook")
> > Signed-off-by: Ze Gao <zegao@tencent.com>
> > Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
> > Cc: <stable@vger.kernel.org>
> > Link: https://lore.kernel.org/linux-trace-kernel/20230516071830.8190-2-=
zegao@tencent.com
>
> Note that you don't need to add Link tag of the previous version for each=
 patch.
> I'll add it when I pick it :)
>
> Thank you,
>
> > ---
> >  kernel/trace/rethook.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/kernel/trace/rethook.c b/kernel/trace/rethook.c
> > index 32c3dfdb4d6a..60f6cb2b486b 100644
> > --- a/kernel/trace/rethook.c
> > +++ b/kernel/trace/rethook.c
> > @@ -288,7 +288,7 @@ unsigned long rethook_trampoline_handler(struct pt_=
regs *regs,
> >        * These loops must be protected from rethook_free_rcu() because =
those
> >        * are accessing 'rhn->rethook'.
> >        */
> > -     preempt_disable();
> > +     preempt_disable_notrace();
> >
> >       /*
> >        * Run the handler on the shadow stack. Do not unlink the list he=
re because
> > @@ -321,7 +321,7 @@ unsigned long rethook_trampoline_handler(struct pt_=
regs *regs,
> >               first =3D first->next;
> >               rethook_recycle(rhn);
> >       }
> > -     preempt_enable();
> > +     preempt_enable_notrace();
> >
> >       return correct_ret_addr;
> >  }
> > --
> > 2.40.1
> >
>
>
> --
> Masami Hiramatsu (Google) <mhiramat@kernel.org>