From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753865AbbJAP1u (ORCPT ); Thu, 1 Oct 2015 11:27:50 -0400 Received: from foss.arm.com ([217.140.101.70]:36656 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753554AbbJAP1o (ORCPT ); Thu, 1 Oct 2015 11:27:44 -0400 Date: Thu, 1 Oct 2015 16:27:39 +0100 From: Catalin Marinas To: AKASHI Takahiro Cc: Li Bin , will.deacon@arm.com, ard.biesheuvel@linaro.org, rostedt@goodmis.org, zhouchengming1@huawei.com, guohanjun@huawei.com, linux-kernel@vger.kernel.org, lizefan@huawei.com, dingtianhong@huawei.com, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH] arm64: ftrace: fix function_graph tracer panic Message-ID: <20151001152739.GI6963@e104818-lin.cambridge.arm.com> References: <1443581395-30088-1-git-send-email-huawei.libin@huawei.com> <560CCE91.3020407@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <560CCE91.3020407@linaro.org> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Oct 01, 2015 at 03:11:29PM +0900, AKASHI Takahiro wrote: > On 09/30/2015 11:49 AM, Li Bin wrote: > >When function graph tracer is enabled, the following operation > >will trigger panic: > > > >mount -t debugfs nodev /sys/kernel > >echo next_tgid > /sys/kernel/tracing/set_ftrace_filter > >echo function_graph > /sys/kernel/tracing/current_tracer > >ls /proc/ > > > >------------[ cut here ]------------ > >[ 198.501417] Unable to handle kernel paging request at virtual address cb88537fdc8ba316 > >[ 198.506126] pgd = ffffffc008f79000 > >[ 198.509363] [cb88537fdc8ba316] *pgd=00000000488c6003, *pud=00000000488c6003, *pmd=0000000000000000 > >[ 198.517726] Internal error: Oops: 94000005 [#1] SMP > >[ 198.518798] Modules linked in: > >[ 198.520582] CPU: 1 PID: 1388 Comm: ls Tainted: G > >[ 198.521800] Hardware name: linux,dummy-virt (DT) > >[ 198.522852] task: ffffffc0fa9e8000 ti: ffffffc0f9ab0000 task.ti: ffffffc0f9ab0000 > >[ 198.524306] PC is at next_tgid+0x30/0x100 > >[ 198.525205] LR is at return_to_handler+0x0/0x20 > >[ 198.526090] pc : [] lr : [] pstate: 60000145 > >[ 198.527392] sp : ffffffc0f9ab3d40 > >[ 198.528084] x29: ffffffc0f9ab3d40 x28: ffffffc0f9ab0000 > >[ 198.529406] x27: ffffffc000d6a000 x26: ffffffc000b786e8 > >[ 198.530659] x25: ffffffc0002a1900 x24: ffffffc0faf16c00 > >[ 198.531942] x23: ffffffc0f9ab3ea0 x22: 0000000000000002 > >[ 198.533202] x21: ffffffc000d85050 x20: 0000000000000002 > >[ 198.534446] x19: 0000000000000002 x18: 0000000000000000 > >[ 198.535719] x17: 000000000049fa08 x16: ffffffc000242efc > >[ 198.537030] x15: 0000007fa472b54c x14: ffffffffff000000 > >[ 198.538347] x13: ffffffc0fada84a0 x12: 0000000000000001 > >[ 198.539634] x11: ffffffc0f9ab3d70 x10: ffffffc0f9ab3d70 > >[ 198.540915] x9 : ffffffc0000907c0 x8 : ffffffc0f9ab3d40 > >[ 198.542215] x7 : 0000002e330f08f0 x6 : 0000000000000015 > >[ 198.543508] x5 : 0000000000000f08 x4 : ffffffc0f9835ec0 > >[ 198.544792] x3 : cb88537fdc8ba316 x2 : cb88537fdc8ba306 > >[ 198.546108] x1 : 0000000000000002 x0 : ffffffc000d85050 > >[ 198.547432] > >[ 198.547920] Process ls (pid: 1388, stack limit = 0xffffffc0f9ab0020) > >[ 198.549170] Stack: (0xffffffc0f9ab3d40 to 0xffffffc0f9ab4000) > >[ 198.582568] Call trace: > >[ 198.583313] [] next_tgid+0x30/0x100 > >[ 198.584359] [] ftrace_graph_caller+0x6c/0x70 > >[ 198.585503] [] ftrace_graph_caller+0x6c/0x70 > >[ 198.586574] [] ftrace_graph_caller+0x6c/0x70 > >[ 198.587660] [] ftrace_graph_caller+0x6c/0x70 > >[ 198.588896] Code: aa0003f5 2a0103f4 b4000102 91004043 (885f7c60) > >[ 198.591092] ---[ end trace 6a346f8f20949ac8 ]--- > > > >This is because when using function graph tracer, if the traced > >function return value is in multi regs ([0x-07]), return_to_handler > >may corrupt them. So in return_to_handler, the parameter regs should > >be protected properly. > > You're right. we should preserve x0-x7 around a call to ftrace_return_to_handler() > just in case they might be used as a "composite type" (ie. struct) of return value. Do I take this as an ack? I applied the patch locally and I'm going to send a pull request tomorrow. Thanks. -- Catalin