linux-kernel - Re: [PATCH v3 1/4] rethook: use preempt_{disable, enable}_notrace in rethook_trampoline

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Date:   Wed, 17 May 2023 20:59:47 +0900
From:   Masami Hiramatsu (Google) <mhiramat@...nel.org>
To:     Ze Gao <zegao2021@...il.com>
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        Albert Ou <aou@...s.berkeley.edu>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Borislav Petkov <bp@...en8.de>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Sven Schnelle <svens@...ux.ibm.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Vasily Gorbik <gor@...ux.ibm.com>, x86@...nel.org,
        bpf@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-riscv@...ts.infradead.org, linux-s390@...r.kernel.org,
        linux-trace-kernel@...r.kernel.org,
        Conor Dooley <conor@...nel.org>, Jiri Olsa <jolsa@...nel.org>,
        Yonghong Song <yhs@...com>, Ze Gao <zegao@...cent.com>,
        stable@...r.kernel.org
Subject: Re: [PATCH v3 1/4] rethook: use preempt_{disable, enable}_notrace
 in rethook_trampoline_handler

Hi Ze Gao,

On Wed, 17 May 2023 11:45:06 +0800
Ze Gao <zegao2021@...il.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@...cent.com>
> Acked-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>
> Cc: <stable@...r.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 here because
> @@ -321,7 +321,7 @@ unsigned long rethook_trampoline_handler(struct pt_regs *regs,
>  		first = first->next;
>  		rethook_recycle(rhn);
>  	}
> -	preempt_enable();
> +	preempt_enable_notrace();
>  
>  	return correct_ret_addr;
>  }
> -- 
> 2.40.1
> 


-- 
Masami Hiramatsu (Google) <mhiramat@...nel.org>