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Date: Sat, 4 Oct 2014 19:24:56 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Fengguang Wu <fengguang.wu@...el.com>
Cc: Jet Chen <jet.chen@...el.com>, Su Tao <tao.su@...el.com>,
Yuanhan Liu <yuanhan.liu@...el.com>, LKP <lkp@...org>,
linux-kernel@...r.kernel.org
Subject: Re: [perf] BUG: unable to handle kernel NULL pointer dereference at
00000085
On Sat, Oct 04, 2014 at 09:46:22PM +0800, Fengguang Wu wrote:
> Hi Peter,
>
> 0day kernel testing robot got the below dmesg and the first bad commit is
>
> git://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git perf/core
>
> commit a54b3e27e27c1bb6d2610eade895c04934c2667e
> Author: Peter Zijlstra <peterz@...radead.org>
> AuthorDate: Wed Sep 24 13:48:42 2014 +0200
> Commit: Peter Zijlstra <peterz@...radead.org>
> CommitDate: Thu Oct 2 23:11:50 2014 +0200
>
> perf: improve perf_sample_data struct layout
>
> This patch reorders fields in the perf_sample_data
> struct in order to minimize the number of cachelines
> touched in perf_sample_data_init(). It also removes
> some intializations which are redundant with the
> code in kernel/events/core.c
>
> Cc: mingo@...e.hu
> Cc: ak@...ux.intel.com
> Cc: jolsa@...hat.com
> Cc: acme@...hat.com
> Cc: cebbert.lkml@...il.com
> Cc: peterz@...radead.org
>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> Link: http://lkml.kernel.org/r/1411559322-16548-7-git-send-email-eranian@google.com
>
> [ 267.547006] debug: unmapping init [mem 0xc28f9000-0xc2b03fff]
> [ 267.694378] random: init urandom read with 4 bits of entropy available
> [ 279.465522] sock: process `trinity-main' is using obsolete setsockopt SO_BSDCOMPAT
> [ 285.269144] BUG: unable to handle kernel NULL pointer dereference at 00000085
> [ 285.273002] IP: [<c11259a1>] perf_prepare_sample+0x33e/0x496
> [ 285.276062] *pde = 00000000
> [ 285.279106] Oops: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC
> [ 285.279106] Modules linked in:
> [ 285.279106] CPU: 1 PID: 1583 Comm: trinity-main Not tainted 3.17.0-rc4-00210-ga54b3e2 #1
> [ 285.279106] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.7.5-20140531_083030-gandalf 04/01/2014
> [ 285.279106] task: c9475e80 ti: c9670000 task.ti: c9670000
> [ 285.279106] EIP: 0060:[<c11259a1>] EFLAGS: 00010046 CPU: 1
> [ 285.279106] EIP is at perf_prepare_sample+0x33e/0x496
> [ 285.279106] EAX: 00000000 EBX: 00000000 ECX: 00000049 EDX: 00000000
> [ 285.279106] ESI: cfd71c40 EDI: cfd71b84 EBP: cfd71b58 ESP: cfd71b34
> [ 285.279106] DS: 007b ES: 007b FS: 00d8 GS: 0033 SS: 0068
> [ 285.279106] CR0: 80050033 CR2: 00000085 CR3: 095b4000 CR4: 000006d0
> [ 285.279106] DR0: 41000043 DR1: 00000000 DR2: 00000000 DR3: 00000000
> [ 285.279106] DR6: ffff0ff0 DR7: 00010602
Could you try the below patch to confirm it works?
> This script may reproduce the error.
>
> ----------------------------------------------------------------------------
> #!/bin/bash
>
> kernel=$1
> initrd=quantal-core-i386.cgz
>
> wget --no-clobber https://github.com/fengguang/reproduce-kernel-bug/raw/master/initrd/$initrd
>
> kvm=(
> qemu-system-x86_64
> -cpu kvm64
> -enable-kvm
> -kernel $kernel
> -initrd $initrd
> -m 320
> -smp 2
> -net nic,vlan=1,model=e1000
> -net user,vlan=1
> -boot order=nc
> -no-reboot
> -watchdog i6300esb
> -rtc base=localtime
> -serial stdio
> -display none
> -monitor null
> )
>
> append=(
> hung_task_panic=1
> earlyprintk=ttyS0,115200
> debug
> apic=debug
> sysrq_always_enabled
> rcupdate.rcu_cpu_stall_timeout=100
> panic=-1
> softlockup_panic=1
> nmi_watchdog=panic
> oops=panic
> load_ramdisk=2
> prompt_ramdisk=0
> console=ttyS0,115200
> console=tty0
> vga=normal
> root=/dev/ram0
> rw
> drbd.minor_count=8
> )
>
> "${kvm[@]}" --append "${append[*]}"
> ----------------------------------------------------------------------------
What is lacking is the actual .config.
Also the times above (~285 seconds) seem to suggest userspace needs to
do something ?
I tried with i386-defconfig and the above receptie gives me:
...
[ 4.887413] tsc: Refined TSC clocksource calibration: 2693.765 MHz
[ 5.257469] hwclock (874) used greatest stack depth: 6624 bytes left
[ 5.299754] input: ImExPS/2 Generic Explorer Mouse as /devices/platform/i8042/serio1/input/input3
[ 5.911225] Switched to clocksource tsc
[ 6.613714] init: Failed to create pty - disabling logging for job
[ 6.615490] init: Temporary process spawn error: No space left on device
[ 8.058431] initctl (926) used greatest stack depth: 6192 bytes left
[ 9.084036] init: plymouth-log main process (940) terminated with
status 1
Kernel tests: Boot OK!
[ 71.302525] reboot: Restarting system
Which I take is 'good', right?
---
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -4953,12 +4953,13 @@ void perf_prepare_sample(struct perf_eve
header->size += size;
}
+ if (sample_type & (PERF_SAMPLE_REGS_USER | PERF_SAMPLE_STACK_USER))
+ perf_sample_regs_user(&data->regs_user, regs);
+
if (sample_type & PERF_SAMPLE_REGS_USER) {
/* regs dump ABI info */
int size = sizeof(u64);
- perf_sample_regs_user(&data->regs_user, regs);
-
if (data->regs_user.regs) {
u64 mask = event->attr.sample_regs_user;
size += hweight64(mask) * sizeof(u64);
@@ -4974,15 +4975,11 @@ void perf_prepare_sample(struct perf_eve
* in case new sample type is added, because we could eat
* up the rest of the sample size.
*/
- struct perf_regs *uregs = &data->regs_user;
u16 stack_size = event->attr.sample_stack_user;
u16 size = sizeof(u64);
- if (!uregs->abi)
- perf_sample_regs_user(uregs, regs);
-
stack_size = perf_sample_ustack_size(stack_size, header->size,
- uregs->regs);
+ data->regs_user.regs);
/*
* If there is something to dump, add space for the dump
--
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