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

From: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
To: Jovi Zhangwei <jovi.zhangwei@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>,
	linux-arch@vger.kernel.org,
	Ananth N Mavinakayanahalli <ananth@in.ibm.com>,
	Sandeepa Prabhu <sandeepa.prabhu@linaro.org>,
	x86@kernel.org, lkml <linux-kernel@vger.kernel.org>,
	"Steven Rostedt (Red Hat)" <rostedt@goodmis.org>,
	Ingo Molnar <mingo@redhat.com>,
	systemtap@sourceware.org, "H. Peter Anvin" <hpa@zytor.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	"David S. Miller" <davem@davemloft.net>
Subject: Re: Re: Re: [PATCH -tip v6 06/22] [BUGFIX] x86: Prohibit probing on memcpy/memset
Date: Mon, 23 Dec 2013 19:59:27 +0900	[thread overview]
Message-ID: <52B8178F.5020607@hitachi.com> (raw)
In-Reply-To: <CAGdX0WECaJBSX29-+fC=0XLJfAh0JvFyLTW2V8yM616L45iCQQ@mail.gmail.com>

(2013/12/23 13:51), Jovi Zhangwei wrote:
> On Fri, Dec 20, 2013 at 5:21 PM, Masami Hiramatsu
> <masami.hiramatsu.pt@hitachi.com> wrote:
>> (2013/12/20 17:31), Jovi Zhangwei wrote:
>>> On Fri, Dec 20, 2013 at 12:42 PM, Masami Hiramatsu
>>> <masami.hiramatsu.pt@hitachi.com> wrote:
>>>> (2013/12/20 12:07), Jovi Zhangwei wrote:
>>>>> On Fri, Dec 20, 2013 at 10:37 AM, Masami Hiramatsu
>>>>> <masami.hiramatsu.pt@hitachi.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@hitachi.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.
>>
>> Hmm, it's very odd. I'm running 3.13.0-rc4 x86-64 on the fedora
>> kvm box too. here is the full of my kconfig.
>>
> That configuration is still working for me, no crash for memcpy kprobe test.

Would you do __memcpy test? or memcpy test? I only had a crash on the
__memcpy(__memset).

Thank you,

> 
> I also posted my kernel configration at:
>     https://gist.github.com/ktap/8091293
> 
> I compared two configs, no clue found yet.
> 
> Thanks,
> 
> Jovi
> 

-- 
Masami HIRAMATSU
IT Management Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@hitachi.com