[PATCH] perf: fix kernel panic when parsing user space CS saved in pt_regs

From: Liu ShuoX
Date: Wed Jun 04 2014 - 22:36:54 EST

From: Zhang Yanmin <yanmin.zhang@xxxxxxxxx>

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: ddrgx snd_merr_dpcm_wm8958 snd_intel_sst snd_soc_sst_platform snd_soc_wm8994 snd_soc_wm_hubs lm3559 imx1x5 atomisp_css2401a0_v21 libmsrlisthelper rmi4 bcm_bt_lpm videobuf_vmalloc videobuf_core fps_throttle hdmi_audio pn544(O) tngdisp bcm4335(O) cfg80211
[ 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>] [<ffffffÃf82012091>] 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 moving the calling to trace_hardirqs_on_thunk ahead of
the stack popup.

Change-Id: I6c4fc46b009ea056f2321ce5b8f54cf8769a7bdd
Signed-off-by: Zhang Yanmin <yanmin.zhang@xxxxxxxxx>
---
arch/x86/ia32/ia32entry.S | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/ia32/ia32entry.S b/arch/x86/ia32/ia32entry.S
index 4299eb0..df61fdb 100644
--- a/arch/x86/ia32/ia32entry.S
+++ b/arch/x86/ia32/ia32entry.S
@@ -167,6 +167,7 @@ sysenter_dispatch:
testl $_TIF_ALLWORK_MASK,TI_flags+THREAD_INFO(%rsp,RIP-ARGOFFSET)
jnz sysexit_audit
sysexit_from_sys_call:
+ TRACE_IRQS_ON
andl $~TS_COMPAT,TI_status+THREAD_INFO(%rsp,RIP-ARGOFFSET)
/* clear IF, that popfq doesn't enable interrupts early */
andl $~0x200,EFLAGS-R11(%rsp) @@ -181,7 +182,6 @@ sysexit_from_sys_call:
/*CFI_RESTORE rflags*/
popq_cfi %rcx /* User %esp */
CFI_REGISTER rsp,rcx
- TRACE_IRQS_ON
ENABLE_INTERRUPTS_SYSEXIT32
#ifdef CONFIG_AUDITSYSCALL
--
1.8.3.2

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