From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751793Ab3LXIca (ORCPT ); Tue, 24 Dec 2013 03:32:30 -0500 Received: from mail9.hitachi.co.jp ([133.145.228.44]:52773 "EHLO mail9.hitachi.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751299Ab3LXIc2 (ORCPT ); Tue, 24 Dec 2013 03:32:28 -0500 Message-ID: <52B9468D.4060201@hitachi.com> Date: Tue, 24 Dec 2013 17:32:13 +0900 From: Masami Hiramatsu Organization: Hitachi, Ltd., Japan User-Agent: Mozilla/5.0 (Windows NT 5.2; rv:13.0) Gecko/20120614 Thunderbird/13.0.1 MIME-Version: 1.0 To: Jovi Zhangwei Cc: Ingo Molnar , linux-arch@vger.kernel.org, Ananth N Mavinakayanahalli , Sandeepa Prabhu , x86@kernel.org, lkml , "Steven Rostedt (Red Hat)" , Ingo Molnar , systemtap@sourceware.org, "H. Peter Anvin" , Thomas Gleixner , "David S. Miller" Subject: Re: Re: Re: Re: [PATCH -tip v6 06/22] [BUGFIX] x86: Prohibit probing on memcpy/memset References: <20131219090353.14309.15496.stgit@kbuild-fedora.novalocal> <20131219090409.14309.25677.stgit@kbuild-fedora.novalocal> <52B3AD7D.2020104@hitachi.com> <52B3CABE.1080903@hitachi.com> <52B40C00.2060401@hitachi.com> <52B8178F.5020607@hitachi.com> In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org (2013/12/24 15:39), Jovi Zhangwei wrote: > On Mon, Dec 23, 2013 at 6:59 PM, Masami Hiramatsu > wrote: >> (2013/12/23 13:51), Jovi Zhangwei wrote: >>> On Fri, Dec 20, 2013 at 5:21 PM, Masami Hiramatsu >>> wrote: >>>> (2013/12/20 17:31), Jovi Zhangwei wrote: >>>>> On Fri, Dec 20, 2013 at 12:42 PM, Masami Hiramatsu >>>>> wrote: >>>>>> (2013/12/20 12:07), Jovi Zhangwei wrote: >>>>>>> On Fri, Dec 20, 2013 at 10:37 AM, Masami Hiramatsu >>>>>>> wrote: >>>>>>>> Hi Jovi, >>>>>>>> >>>>>>>> (2013/12/19 18:37), Jovi Zhangwei wrote: >>>>>>>>> Hi Masami, >>>>>>>>> >>>>>>>>> On Thu, Dec 19, 2013 at 5:04 PM, Masami Hiramatsu >>>>>>>>> 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). >> > Still no crash, use your kernel config. > memcpy and __memcpy have same address in /proc/kallsyms. > > Looks like a interesting problem. Agreed. In my case, those have same address, but only probing __memcpy caused a kernel crash. I'm not sure why, but it is safe to disable probing on it. Thank you, -- Masami HIRAMATSU IT Management Research Dept. Linux Technology Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: masami.hiramatsu.pt@hitachi.com