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Message-ID: <20140605074008.GB14869@lskakaxi-intel> Date: Thu, 5 Jun 2014 15:40:08 +0800 From: Liu ShuoX <shuox.liu@...el.com> To: linux-kernel@...r.kernel.org Cc: "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>, Peter Zijlstra <peterz@...radead.org>, Zhang Yanmin <yanmin.zhang@...el.com>, yanmin_zhang@...ux.intel.com Subject: [PATCH v2] perf: fix kernel panic when parsing user space CS saved in pt_regs From: Zhang Yanmin <yanmin.zhang@...el.com> ChangeLog V2: Before sysexit, perf NMI might arrive. There is still a race. Here we change rsp to keep it pointing to pt_regs->orig_ax. In addition, after sti, before sysexit, an irq might arrives. That causes more chances for perf NMI to jump in. We hit a kernel panic when running perf to collect some performance data. kenel is x86_64 and user space apps are 32bit. [71.965351, 1] [Binder_2] BUG: unable to handle kernel NULL pointer dereference at 0000000000000004 [71.965360, 1] [Binder_2] IP: [<ffffffff82012091>] get_segment_base+0x71/0xc0 [71.965367, 1] [Binder_2] PGD 6c65f067 PUD 0 [71.965375, 1] [Binder_2] Oops: 0000 [#1] PREEMPT SMP [71.965413, 1] [Binder_2] Modules linked in: <...> [71.965420, 1] [Binder_2] CPU: 1 PID: 304 Comm: Binder_2 Tainted: G W O 3.10.20-263902-g184bfbc-dirty #14 [71.965426, 1] [Binder_2] task: ffff8800764dc300 ti: ffff88006c6e8000 task.ti: ffff88006c6e8000 [71.965439, 1] [Binder_2] RIP: 0010:[<ffffffff82012091>] [<ffffffæf82012091>] get_segment_base+0x71/0xc0 [71.965<44, 1] [Binder_2] RSP: 0018:ffff^X8007ea87b98 EFLAGS: 00010092 [71.965447, 1] [Binder_2] RAX: 0000000000000024 RBX: 0000000000000000 RCX: 0000000000000000 [71.965450, 1] [Binder_2] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000009 [71.965454, 1] [Binder_2] RBP: ffff88007ea87ba8 R08: ffffffff83143b3c R09: ffffffff831848a8 [71.965458, 1] [Binder_2] R10: 0000000000000000 R11: 00000000001bf2d8 R12: 0000000000000000 [71.965462, 1] [Binder_2] R13: ffff88006c6e9fd8 R14: ffff88006c6e9f58 R15: ffff8800764dc300 [71.965468, 1_ [Binder_2] FS: 0000000000000000(0000) GS:ffff88007ea80000(006b) knlGS:00000000f704add0 [71.965472, 1] [Binder_2] CS: 0010 DS: 002b ES: 002b CR0: 0000000080050033 [71.965476, 1] [Binder_2] CR2: 0000000000000004 CR3: 0000000076588000 CR4: 00000^P00001007e0 [71.965480, 1] [Binder_2] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [71.965485, 1] [Binder_2] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 [71.966141, 1] [Binder_2] Stack: [71.966152, 1] [Binder_2] ffff88005f266c00 0000000000000000 ffff88007ea87c18 ffffffff82013cac [71.966161, 1] [Binder_2] ffff88007ea87d58 00000016fe4704a0 00000000000001a7 ffff88007ea87ef8 [71.966171, 1] [Binder_6] ffff88005f266c00 ffff88007ea87ef8 ffff8800!e07b400 ffff88005f266c00 [71.966173, 1] [Binder_2] Call Trace: [71.966179, 1] [Binder_2] <NMI> [71.966190, 1] [Binder_2] [<ffffffff82013cac>] perf_callchain_user+0x15c/0x240 [71.966202, 1] [Binder_2] [<ffffffff82160754>] perf_callchain+0x134/0x180 [71.966210, 1] [Binder_2] [<fffff&ff820e0787>] ? local_clock+0x47/0x60 [71.966221, 1] [Binder_2] [<ffffffff8215d49b>] perf_prepare_sample+0x1bb/0x240 [71.966231, 1] [Binder_2] [<ffffffff8215d667>] __perf_event_overflow+0x147/0x230 [71.966241, 1] [Binder_2] [<ffffffff82012f68>] ? x86_perf_event_set_period+0xd8/0x150 [71.966252, 1] [Binder_2] [<ffffffff8215df24>] perf_event_overflow+0x14/0x20 [71.966260, 1] [Binder_2] [<ffffffff820194d2>] intel_pmu_handle_irq+0x1c2/0x270 [71.966270, 1] [Binder_2] [<ffffffff828b5d60>] ? call_softirq+0x30/0x30 [71.966284, 1] [Binder_2]$ [<ffffffff828aff01>] perf_event_nmi_handler+0x21/0x30 [71.966293, 1] [Binder_2] [<ffffffff828af5b9>] nmi_handle.isr!.1+0x59/0x=0 [71.966303, 1] [Binder_2] [<ffffffff828af6d8>] default_do_nmi+0x58/0x240 [71.966312, 1] [Binder_2] [<ffffffff828af978>] do_nmi+0xb8/0xf0 [71.966321, 1] [Binder_2] [|ffffffgf828aebe7>] end_repeat_nmi+0x1e/0x2e [71.966332, 1] [Binder_2] [<ffffffff828b5d60>] ? call_softirq+0x30/0x30 [71.966341, 1] [Binder_2] [<ffffffff828b5d60>] ? call_softirq+0x30/0x30 [71.966350, 1] [Binder_2] [<fFffffff828b5d60>] ? call_softirq+0x30/0x30 Basically, ia32 uses sysenter to start system calls. sysexit_from_sys_call=>trace_hardirqs_on_thunk. Before calling, sysexit_from_sys_call already pops up pt_regs, then trace_hardirqs_on_thunk would reuse pt_regs space. If perf NMI happens here, perf might use a bad pt_regs. The patch fixes it by keeping rsp pointing under pt_regs->ip. Signed-off-by: Zhang Yanmin <yanmin.zhang@...el.com> Signed-off-by: Liu ShuoX <shuox.liu@...el.com> --- arch/x86/ia32/ia32entry.S | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-) diff --git a/arch/x86/ia32/ia32entry.S b/arch/x86/ia32/ia32entry.S index 4299eb0..a695d8e 100644 --- a/arch/x86/ia32/ia32entry.S +++ b/arch/x86/ia32/ia32entry.S @@ -172,15 +172,16 @@ sysexit_from_sys_call: andl $~0x200,EFLAGS-R11(%rsp) movl RIP-R11(%rsp),%edx /* User %eip */ CFI_REGISTER rip,rdx - RESTORE_ARGS 0,24,0,0,0,0 - xorq %r8,%r8 + RESTORE_ARGS 0,0,0,0,0,0 + movq 24(%rsp),%r8 /* rflags */ + movq 32(%rsp),%rcx /* User %esp */ xorq %r9,%r9 xorq %r10,%r10 xorq %r11,%r11 - popfq_cfi + pushq_cfi %r8 /*CFI_RESTORE rflags*/ - popq_cfi %rcx /* User %esp */ - CFI_REGISTER rsp,rcx + popfq_cfi + xorq %r8,%r8 TRACE_IRQS_ON ENABLE_INTERRUPTS_SYSEXIT32 -- 1.8.3.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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