From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753472AbcEMUCS (ORCPT ); Fri, 13 May 2016 16:02:18 -0400 Received: from mail-qg0-f45.google.com ([209.85.192.45]:36528 "EHLO mail-qg0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751969AbcEMUCQ (ORCPT ); Fri, 13 May 2016 16:02:16 -0400 Subject: Re: [PATCH v12 00/10] arm64: Add kernel probes (kprobes) support To: Li Bin , James Morse References: <1461783185-9056-1-git-send-email-dave.long@linaro.org> <573350B2.4010701@arm.com> <5733E9E0.1060504@huawei.com> Cc: Mark Rutland , Petr Mladek , Feng Kan , Catalin Marinas , Will Deacon , Viresh Kumar , John Blackwood , Pratyush Anand , Zi Shen Lim , Dave P Martin , Yang Shi , Vladimir Murzin , Steve Capper , Kees Cook , "Suzuki K. Poulose" , Marc Zyngier , Mark Brown , Sandeepa Prabhu , William Cohen , =?UTF-8?Q?Alex_Benn=c3=a9e?= , linux-arm-kernel@lists.infradead.org, Ard Biesheuvel , Greg Kroah-Hartman , linux-kernel@vger.kernel.org, Mark Salyzyn , Balamurugan Shanmugam , Andrew Morton , Robin Murphy , Jens Wiklander , Christoffer Dall From: David Long Message-ID: <573632C4.9010501@linaro.org> Date: Fri, 13 May 2016 16:02:12 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.3.0 MIME-Version: 1.0 In-Reply-To: <5733E9E0.1060504@huawei.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05/11/2016 10:26 PM, Li Bin wrote: > > > on 2016/5/11 23:33, James Morse wrote: >> Hi David, >> >> On 27/04/16 19:52, David Long wrote: >>> From: "David A. Long" >>> >>> This patchset is heavily based on Sandeepa Prabhu's ARM v8 kprobes patches, >>> first seen in October 2013. This version attempts to address concerns raised by >>> reviewers and also fixes problems discovered during testing. >>> >>> This patchset adds support for kernel probes(kprobes), jump probes(jprobes) >>> and return probes(kretprobes) support for ARM64. >>> >>> The kprobes mechanism makes use of software breakpoint and single stepping >>> support available in the ARM v8 kernel. >> >> I applied this series on v4.6-rc7, and built the sample kprobes. They work fine, >> unless I throw ftrace into the mix too. >> >> I enabled the function_graph tracer, then tried to load the jprobe example module: >> -------------------------%<------------------------- >> root@ubuntu:/sys/kernel/debug/tracing# insmod /root/jprobe_example.ko >> Planted jprobe at ffffff80080c8f20, handler addr ffffff8000bb3000 >> root@ubuntu:/sys/kernel/debug/tracing# jprobe: clone_flags = 0x1200011, stack_st >> art = 0x0 stack_size = 0x0 >> Bad mode in Synchronous Abort handler detected, code 0x86000005 -- IABT (current >> EL) >> CPU: 5 PID: 1047 Comm: systemd-udevd Not tainted 4.6.0-rc7+ #4064 >> Hardware name: ARM Juno development board (r1) (DT) >> task: ffffffc975948300 ti: ffffffc974e4c000 task.ti: ffffffc974e4c000 >> PC is at 0x0 >> LR is at 0x0 >> >> pc : [<0000000000000000>] lr : [<0000000000000000>] pstate: 60000145 >> sp : ffffffc974e4ff00 >> x29: 0000000001200011 x28: ffffffc974e4c000 >> x27: ffffff80088d0000 x26: 00000000000000dc >> x25: 0000000000000120 x24: 0000000000000015 >> x23: 0000000060000000 x22: 0000007fa1b40e60 >> x21: 0000007fa1ce70d0 x20: 0000000000000000 >> x19: 0000000000000000 x18: 0000000000000a03 >> x17: 0000007fa1b40d90 x16: ffffff80080c9708 >> x15: 003b9aca00000000 x14: 0000007fddb7e5c0 >> x13: 0000007fa1b40e2c x12: 0000000000d00ff0 >> x11: ffffff8009c4d000 x10: ffffff800920c000 >> x9 : ffffff8008f5c000 x8 : ffffffc976c06800 >> x7 : 000000000006daf2 x6 : 0000000000000015 >> x5 : 0000000000000004 x4 : ffffffc96e8690a0 >> x3 : 0000001ed7cbab74 x2 : ffffffc96e869000 >> x1 : 0000000000000000 x0 : 0000000000000000 >> >> Internal error: Oops - bad mode: 0 [#1] PREEMPT SMP >> Modules linked in: jprobe_example >> CPU: 5 PID: 1047 Comm: systemd-udevd Not tainted 4.6.0-rc7+ #4064 >> Hardware name: ARM Juno development board (r1) (DT) >> task: ffffffc975948300 ti: ffffffc974e4c000 task.ti: ffffffc974e4c000 >> PC is at 0x0 >> LR is at 0x0 >> >> pc : [<0000000000000000>] lr : [<0000000000000000>] pstate: 60000145 >> sp : ffffffc974e4ff00 >> x29: 0000000001200011 x28: ffffffc974e4c000 >> x27: ffffff80088d0000 x26: 00000000000000dc >> x25: 0000000000000120 x24: 0000000000000015 >> x23: 0000000060000000 x22: 0000007fa1b40e60 >> x21: 0000007fa1ce70d0 x20: 0000000000000000 >> x19: 0000000000000000 x18: 0000000000000a03 >> x17: 0000007fa1b40d90 x16: ffffff80080c9708 >> x15: 003b9aca00000000 x14: 0000007fddb7e5c0 >> x13: 0000007fa1b40e2c x12: 0000000000d00ff0 >> x11: ffffff8009c4d000 x10: ffffff800920c000 >> x9 : ffffff8008f5c000 x8 : ffffffc976c06800 >> x7 : 000000000006daf2 x6 : 0000000000000015 >> x5 : 0000000000000004 x4 : ffffffc96e8690a0 >> x3 : 0000001ed7cbab74 x2 : ffffffc96e869000 >> x1 : 0000000000000000 x0 : 0000000000000000 >> >> Process systemd-udevd (pid: 1047, stack limit = 0xffffffc974e4c020) >> Stack: (0xffffffc974e4ff00 to 0xffffffc974e50000) >> ff00: 0000000000000417 0000007fa1ce76f0 00000000000000dc 0000000000000417 >> ff20: 00000000ffffffff 0000007fddb7ecf8 0000000000000005 ffffffffffffffff >> ff40: 00000000ff000001 003b9aca00000000 000000555b3868b0 0000007fa1b40d90 >> ff60: 0000000000000a03 0000007fddb7e5c0 0000000000000000 0000007fddb7e5e0 >> ff80: 000000555b358000 000000558f56f0e0 0000000000000000 000000558f574f00 >> ffa0: 000000558f574f00 00000000000004fa 000000558f56f010 0000007fddb7e600 >> ffc0: 0000007fa1b40e2c 0000007fddb7e5c0 0000007fa1b40e60 0000000060000000 >> ffe0: 0000000001200011 00000000000000dc 0004000084000200 0800000002000000 >> Call trace: >> [< (null)>] (null) >> Code: bad PC value >> ---[ end trace 35d24aad799c2941 ]--- >> -------------------------%<------------------------- >> > > To solve this, it should pause function tracing before the jprobe handler is called > and unpause it before it returns back to the function it probed. > > diff --git a/arch/arm64/kernel/kprobes.c b/arch/arm64/kernel/kprobes.c > index db2d95c..b21ed00 100644 > --- a/arch/arm64/kernel/kprobes.c > +++ b/arch/arm64/kernel/kprobes.c > @@ -714,6 +714,7 @@ int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs) > > instruction_pointer_set(regs, (long)jp->entry); > preempt_disable(); > + pause_graph_tracing(); > return 1; > } > > @@ -757,6 +758,7 @@ int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs) > show_regs(regs); > BUG(); > } > + unpause_graph_tracing(); > *regs = kcb->jprobe_saved_regs; > memcpy((void *)stack_addr, kcb->jprobes_stack, > MIN_STACK_SIZE(stack_addr)); > > > Li Bin > >> >> Thanks, >> >> >> James Thanks for the suggested fix. -dl