Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Wed, 19 Apr 2023 08:43:35 -0700
From:   Josh Poimboeuf <jpoimboe@kernel.org>
To:     Chen Zhongjin <chenzhongjin@huawei.com>
Cc:     x86@kernel.org, linux-kernel@vger.kernel.org, tglx@linutronix.de,
        mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com,
        hpa@zytor.com, akpm@linux-foudation.org, ben-linux@fluff.org,
        wuchi.zero@gmail.com
Subject: Re: [PATCH 1/2] x86: profiling: remove lock functions hack for
 !FRAME_POINTER
Message-ID: <20230419154335.4vc7rouxl4gsynzm@treble>
References: <20230410022226.181812-1-chenzhongjin@huawei.com>
 <20230410022226.181812-2-chenzhongjin@huawei.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
In-Reply-To: <20230410022226.181812-2-chenzhongjin@huawei.com>
Precedence: bulk

On Mon, Apr 10, 2023 at 10:22:25AM +0800, Chen Zhongjin wrote:
> Syzbot has been reporting the problem of stack-out-of-bounds in
> profile_pc for a long time:
> https://syzkaller.appspot.com/bug?extid=84fe685c02cd112a2ac3
> 
> profile_pc tries to get pc if current regs is inside lock function. For
> !CONFIG_FRAME_POINTER it used a hack way to get the pc from stack, which
> is not work with ORC. It makes profile_pc read illeagal address, return
> wrong result, and frequently triggers KASAN.
> 
> Since lock profiling can be handled with much better other tools, It's
> reasonable to remove lock functions hack for !FRAME_POINTER kernel.
> 
> Suggested-by: Andi Kleen <ak@linux.intel.com>
> Signed-off-by: Chen Zhongjin <chenzhongjin@huawei.com>
> ---
>  arch/x86/kernel/time.c | 14 +-------------
>  1 file changed, 1 insertion(+), 13 deletions(-)
> 
> diff --git a/arch/x86/kernel/time.c b/arch/x86/kernel/time.c
> index e42faa792c07..e08fac7bb71e 100644
> --- a/arch/x86/kernel/time.c
> +++ b/arch/x86/kernel/time.c
> @@ -29,22 +29,10 @@ unsigned long profile_pc(struct pt_regs *regs)
>  {
>  	unsigned long pc = instruction_pointer(regs);
>  
> -	if (!user_mode(regs) && in_lock_functions(pc)) {
>  #ifdef CONFIG_FRAME_POINTER
> +	if (!user_mode(regs) && in_lock_functions(pc))

If lock profiling is no longer useful then we should just remove it
altogether, not just for ORC.

-- 
Josh