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

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Date:	Fri, 20 Dec 2013 16:31:13 +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 12:42 PM, Masami Hiramatsu
<masami.hiramatsu.pt@...achi.com> wrote:
> (2013/12/20 12:07), Jovi Zhangwei wrote:
>> 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
>
> Hmm, I've added some debugging options.
>
> CONFIG_SLUB_DEBUG=y
> CONFIG_X86_DEBUGCTLMSR=y
> CONFIG_PNP_DEBUG_MESSAGES=y
> CONFIG_DEBUG_INFO=y
> CONFIG_DEBUG_FS=y
> CONFIG_DEBUG_KERNEL=y
> CONFIG_DEBUG_STACK_USAGE=y
> CONFIG_DEBUG_MEMORY_INIT=y
> CONFIG_DEBUG_STACKOVERFLOW=y
> CONFIG_DEBUG_SPINLOCK=y
> CONFIG_DEBUG_MUTEXES=y
> CONFIG_DEBUG_LOCK_ALLOC=y
> CONFIG_DEBUG_LOCKDEP=y
> CONFIG_DEBUG_BUGVERBOSE=y
> CONFIG_DEBUG_RODATA=y
> CONFIG_DEBUG_BOOT_PARAMS=y
>
> I guess some of them might cause it.
>
I recompiled the kernel with those config enabled, unfortunately still no crash,
I tested on 3.13.0-rc4, a fedora kvm box.

Jovi
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