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Date: Thu, 12 May 2016 10:26:40 +0800 From: Li Bin <huawei.libin@...wei.com> To: James Morse <james.morse@....com>, David Long <dave.long@...aro.org> CC: Mark Rutland <mark.rutland@....com>, Petr Mladek <pmladek@...e.com>, "Feng Kan" <fkan@....com>, Catalin Marinas <catalin.marinas@....com>, Will Deacon <will.deacon@....com>, Viresh Kumar <viresh.kumar@...aro.org>, John Blackwood <john.blackwood@...r.com>, Pratyush Anand <panand@...hat.com>, Zi Shen Lim <zlim.lnx@...il.com>, Dave P Martin <Dave.Martin@....com>, Yang Shi <yang.shi@...aro.org>, Vladimir Murzin <Vladimir.Murzin@....com>, "Steve Capper" <steve.capper@...aro.org>, Kees Cook <keescook@...omium.org>, "Suzuki K. Poulose" <suzuki.poulose@....com>, Marc Zyngier <marc.zyngier@....com>, Mark Brown <broonie@...nel.org>, Sandeepa Prabhu <sandeepa.s.prabhu@...il.com>, William Cohen <wcohen@...hat.com>, Alex Bennée <alex.bennee@...aro.org>, <linux-arm-kernel@...ts.infradead.org>, Ard Biesheuvel <ard.biesheuvel@...aro.org>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, <linux-kernel@...r.kernel.org>, Mark Salyzyn <salyzyn@...roid.com>, Balamurugan Shanmugam <bshanmugam@....com>, Andrew Morton <akpm@...ux-foundation.org>, Robin Murphy <Robin.Murphy@....com>, "Jens Wiklander" <jens.wiklander@...aro.org>, Christoffer Dall <christoffer.dall@...aro.org> Subject: Re: [PATCH v12 00/10] arm64: Add kernel probes (kprobes) support on 2016/5/11 23:33, James Morse wrote: > Hi David, > > On 27/04/16 19:52, David Long wrote: >> From: "David A. Long" <dave.long@...aro.org> >> >> 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@...ntu:/sys/kernel/debug/tracing# insmod /root/jprobe_example.ko > Planted jprobe at ffffff80080c8f20, handler addr ffffff8000bb3000 > root@...ntu:/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 > > > > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@...ts.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel > > . >
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