linux-kernel - Re: [PATCH -tip v6 06/22] [BUGFIX] x86: Prohibit probing on memcpy/memset

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Message-ID: <CAGdX0WENxTPhFDtcEW6LFhk1SNZc6mEK+JsCDOJmfK8_PS1rxg@mail.gmail.com>
Date:	Fri, 20 Dec 2013 11:07:51 +0800
From:	Jovi Zhangwei <jovi.zhangwei@...il.com>
To:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Cc:	Ingo Molnar <mingo@...nel.org>, linux-arch@...r.kernel.org,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Sandeepa Prabhu <sandeepa.prabhu@...aro.org>, x86@...nel.org,
	lkml <linux-kernel@...r.kernel.org>,
	"Steven Rostedt (Red Hat)" <rostedt@...dmis.org>,
	Ingo Molnar <mingo@...hat.com>, systemtap@...rceware.org,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH -tip v6 06/22] [BUGFIX] x86: Prohibit probing on memcpy/memset

On Fri, Dec 20, 2013 at 10:37 AM, Masami Hiramatsu
<masami.hiramatsu.pt@...achi.com> wrote:
> Hi Jovi,
>
> (2013/12/19 18:37), Jovi Zhangwei wrote:
>> Hi Masami,
>>
>> On Thu, Dec 19, 2013 at 5:04 PM, Masami Hiramatsu
>> <masami.hiramatsu.pt@...achi.com> wrote:
>>> memcpy/memset functions are fundamental functions and
>>> those are involved in kprobe's exception handling.
>>> Prohibit probing on them to avoid kernel crash.
>>>
>> Would you please let me know the LKML link of that bugfix, I cannot
>> find it in my LKML fold.
>
> Yeah, that was found in my testing environment.
>
>> No objection on this patch. :) just want to know more, It seems there
>> have no problem to probe memcpy in my box, maybe I didn't hit the
>> crash code path.
>
> Ah, I see. Originally the problem happened when I put a probe on
> __memcpy. And it looks the instances of memcpy and __memcpy are
> same on x86-64. Thus I decided to blacklist both. (memset/__memset too)
> Have you ever tried to probe __memcpy on your box?
>
Hmm, still no crash, __memcpy and __memset are both tested.

I use below kprobe related config:

CONFIG_KPROBES=y
CONFIG_JUMP_LABEL=y
CONFIG_OPTPROBES=y
CONFIG_KPROBES_ON_FTRACE=y

Thanks,

Jovi.
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