[ktap] Re: "BUG: unable to handle kernel paging request" after ktap script to trace SyS_write
- From: Azat Khuzhin <a3at.mail@xxxxxxxxx>
- To: ktap <ktap@xxxxxxxxxxxxx>
- Date: Tue, 22 Oct 2013 08:10:07 +0400
On Tue, Oct 22, 2013 at 1:00 AM, Azat Khuzhin <a3at.mail@xxxxxxxxx> wrote:
> On Mon, Oct 21, 2013 at 1:31 PM, Azat Khuzhin <a3at.mail@xxxxxxxxx> wrote:
>> On Mon, Oct 21, 2013 at 12:50 PM, Jovi Zhangwei <jovi.zhangwei@xxxxxxxxx>
>> wrote:
>>> On Mon, Oct 21, 2013 at 4:13 PM, Azat Khuzhin <a3at.mail@xxxxxxxxx> wrote:
>>>> On Mon, Oct 21, 2013 at 11:31 AM, Jovi Zhangwei <jovi.zhangwei@xxxxxxxxx>
>>>> wrote:
>>>>> On Mon, Oct 21, 2013 at 1:15 PM, Azat Khuzhin <a3at.mail@xxxxxxxxx> wrote:
>>>>>> On Mon, Oct 21, 2013 at 7:55 AM, Jovi Zhangwei <jovi.zhangwei@xxxxxxxxx>
>>>>>> wrote:
>>>>>>> On Mon, Oct 21, 2013 at 12:01 AM, Azat Khuzhin <a3at.mail@xxxxxxxxx>
>>>>>>> wrote:
>>>>>>>> On Sun, Oct 20, 2013 at 7:27 PM, Jovi Zhangwei
>>>>>>>> <jovi.zhangwei@xxxxxxxxx> wrote:
>>>>>>>>> On Sun, Oct 20, 2013 at 10:22 PM, Azat Khuzhin <a3at.mail@xxxxxxxxx>
>>>>>>>>> wrote:
>>>>>>>>>> On Sun, Oct 20, 2013 at 12:50 PM, Jovi Zhangwei
>>>>>>>>>> <jovi.zhangwei@xxxxxxxxx> wrote:
>>>>>>>>>>> On Sat, Oct 19, 2013 at 5:06 PM, Azat Khuzhin <a3at.mail@xxxxxxxxx>
>>>>>>>>>>> wrote:
>>>>>>>>>>>> Hi all,
>>>>>>>>>>>>
>>>>>>>>>>>> I used next script, and after a few seconds of working, I have all
>>>>>>>>>>>> ssh
>>>>>>>>>>>> sessions killed.
>>>>>>>>>>>> #! /usr/bin/env ktap
>>>>>>>>>>>> trace probe:SyS_write {
>>>>>>>>>>>> print(backtrace(0, 100))
>>>>>>>>>>>> }
>>>>>>>>>>>>
>>>>>>>>>>>> However, I can login after this, and have next messages in dmesg:
>>>>>>>>>>>>
>>>>>>>>>>> Hi Azat,
>>>>>>>>>>
>>>>>>>>>> Hi Jovi,
>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> Thanks for your reporting, could you help to check if below two
>>>>>>>>>>> scripts works correctly?
>>>>>>>>>>>
>>>>>>>>>>> #! /usr/bin/env ktap
>>>>>>>>>>> trace probe:SyS_write {
>>>>>>>>>>> print_backtrace(0, 100)
>>>>>>>>>>> }
>>>>>>>>>>
>>>>>>>>>> [ 107.416689] BUG: unable to handle kernel paging request at
>>>>>>>>>> ffffffff621ee2b5
>>>>>>>>>> [ 107.417774] IP: [<ffffffff621ee2b5>] 0xffffffff621ee2b4
>>>>>>>>>> [ 107.418569] PGD 160c067 PUD 0
>>>>>>>>>> [ 107.419409] Oops: 0010 [#3] PREEMPT SMP
>>>>>>>>>> [ 107.420038] Modules linked in: ktapvm(O) nfsd auth_rpcgss
>>>>>>>>>> oid_registry nfs_acl nfs lockd fscache sunrpc loop fuse joydev
>>>>>>>>>> hid_generic usbhid hid snd_pcm microcode snd_page_alloc snd_timer snd
>>>>>>>>>> soundcore ohci_pci ohci_hcd ehci_hcd psmouse usbcore i2c_piix4
>>>>>>>>>> processor ac ther
>>>>>>>>>> mal_sys serio_raw pcspkr parport_pc usb_common evdev parport button
>>>>>>>>>> i2c_core ext4 crc16 jbd2 mbcache sd_mod sg crc_t10dif sr_mod cdrom
>>>>>>>>>> crct10dif_common ata_generic ahci libahci ata_piix libata e1000
>>>>>>>>>> scsi_mod
>>>>>>>>>> [ 107.420038] CPU: 1 PID: 2654 Comm: less Tainted: G D O
>>>>>>>>>> 3.12.0-rc5+ #40
>>>>>>>>>> [ 107.420038] Hardware name: innotek GmbH VirtualBox/VirtualBox,
>>>>>>>>>> BIOS
>>>>>>>>>> VirtualBox 12/01/2006
>>>>>>>>>> [ 107.420038] task: ffff88007a911790 ti: ffff88007a05c000 task.ti:
>>>>>>>>>> ffff88007a05c000
>>>>>>>>>> [ 107.420038] RIP: 0010:[<ffffffff621ee2b5>] [<ffffffff621ee2b5>]
>>>>>>>>>> 0xffffffff621ee2b4
>>>>>>>>>> [ 107.420038] RSP: 0018:ffff88007a05df78 EFLAGS: 00010293
>>>>>>>>>> [ 107.420038] RAX: 0000000000000001 RBX: 00000000000003ff RCX:
>>>>>>>>>> 0000000000000001
>>>>>>>>>> [ 107.420038] RDX: 00000000000003ff RSI: 0000000000628940 RDI:
>>>>>>>>>> 0000000000000001
>>>>>>>>>> [ 107.420038] RBP: 000000000000005f R08: 0000000001e49c20 R09:
>>>>>>>>>> 0000000000000000
>>>>>>>>>> [ 107.420038] R10: 0000000000000001 R11: 0000000000000246 R12:
>>>>>>>>>> 0000000000000000
>>>>>>>>>> [ 107.420038] R13: 0000000000000043 R14: 0000000000000000 R15:
>>>>>>>>>> 0000000000000000
>>>>>>>>>> [ 107.420038] FS: 00007ff4a1bda700(0000) GS:ffff88007fd00000(0000)
>>>>>>>>>> knlGS:0000000000000000
>>>>>>>>>> [ 107.420038] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
>>>>>>>>>> [ 107.420038] CR2: ffffffff621ee2b5 CR3: 000000007b91a000 CR4:
>>>>>>>>>> 00000000000006e0
>>>>>>>>>> [ 107.420038] Stack:
>>>>>>>>>> [ 107.420038] 000000000000005f ffffffff813b2b22 0000000000000246
>>>>>>>>>> 0000000000000001
>>>>>>>>>> [ 107.420038] 0000000000000000 0000000001e49c20 0000000000000001
>>>>>>>>>> 0000000000000023
>>>>>>>>>> [ 107.420038] 00000000000003ff 0000000000628940 0000000000000001
>>>>>>>>>> 0000000000000001
>>>>>>>>>> [ 107.420038] Call Trace:
>>>>>>>>>> [ 107.420038] [<ffffffff813b2b22>] ? system_call_fastpath+0x16/0x1b
>>>>>>>>>> [ 107.420038] Code: Bad RIP value.
>>>>>>>>>> [ 107.420038] RIP [<ffffffff621ee2b5>] 0xffffffff621ee2b4
>>>>>>>>>> [ 107.420038] RSP <ffff88007a05df78>
>>>>>>>>>> [ 107.420038] CR2: ffffffff621ee2b5
>>>>>>>>>> [ 107.420038] ---[ end trace fe1cc133ae0119a3 ]---
>>>>>>>>>>
>>>>>>>>>> And others.
>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> #! /usr/bin/env ktap
>>>>>>>>>>> trace probe:schedule {
>>>>>>>>>>> print(backtrace(0, 100))
>>>>>>>>>>> }
>>>>>>>>>>
>>>>>>>>>> This one printed message about 10 tines
>>>>>>>>>> and after this system hangs.
>>>>>>>>>>
>>>>>>>>>> In debugger attached to kernel:
>>>>>>>>>> Program received signal SIGSEGV, Segmentation fault.
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>> Thanks. It seems the kernel crash doesn't caused by backtrace(), but
>>>>>>>>> ktapvm core or kernel side.
>>>>>>>>
>>>>>>>> Yes, I already test another script (without backtrace), that also have
>>>>>>>> some problems.
>>>>>>>> Do you have this issue?
>>>>>>>>
>>>>>>>>>
>>>>>>>>> Would you please check below scripts again?
>>>>>>>>>
>>>>>>>>> -------------------------------------------------
>>>>>>>>> #!/usr/bin/env ktap
>>>>>>>>>
>>>>>>>>> trace probe:SyS_write {
>>>>>>>>> print("testing")
>>>>>>>>> }
>>>>>>>>
>>>>>>>> page fault.
>>>>>>>>
>>>>>>>>> --------------------------------------------------
>>>>>>>>> #!/usr/bin/env ktap
>>>>>>>>>
>>>>>>>>> trace probe:SyS_write {
>>>>>>>>> }
>>>>>>>>
>>>>>>>> page fault.
>>>>>>>>
>>>>>>>>> --------------------------------------------------
>>>>>>>>> #!/usr/bin/env ktap
>>>>>>>>>
>>>>>>>>> trace probe:schedule {
>>>>>>>>> }
>>>>>>>>
>>>>>>>> Just after this command, I ran dmesg, and received page fault.
>>>>>>>> And system hanged.
>>>>>>>>
>>>>>>>>> -------------------------------------------------
>>>>>>>>> #!/usr/bin/env ktap
>>>>>>>>>
>>>>>>>>> trace syscalls:sys_write_enter {
>>>>>>>>> }
>>>>>>>>
>>>>>>>> "s/sys_write_enter/sys_enter_write/"
>>>>>>>> Seems works fine.
>>>>>>>>
>>>>>>>>> -------------------------------------------------
>>>>>>>>> ./ktap test/arith.kp
>>>>>>>>
>>>>>>>> No output. No errors in kern.log
>>>>>>>>
>>>>>>>>> -------------------------------------------------
>>>>>>>>>
>>>>>>>>> And your hardware is x86-64 or ARM-64?
>>>>>>>>
>>>>>>>> x86-64
>>>>>>>>
>>>>>>> Unfortunately I cannot reproduce the crash in my local x86-64
>>>>>>> box(whatever any kernel version, include 3.12-rc6).
>>>>>>>
>>>>>>> Things to be clear now, kernel will crash only using ktap kprobe,
>>>>>>> tracepoint and other ktap basic operation is fine.
>>>>>>> It have a little strange that actually ktapvm doesn't know tracepoint
>>>>>>> or kprobe in kernel side, ktapvm just treat them as a id,
>>>>>>> so it's weird that tracepoint is fine but kprobe is not working.
>>>>>>>
>>>>>>> I guess you ran vanilla kernel (3.12-rc6) with no additional patch,
>>>>>>> could you post your kernel config file?
>>>>>>
>>>>>> Yes, it is vanilla kernel, but with some debug patches.
>>>>>> (printk's, and one patch to btrfs, I don't think that this actually
>>>>>> play some role)
>>>>>> I will try to reproduce this issue using the latest tar balls version
>>>>>> tomorrow (I hope).
>>>>>>
>>>>>> Here is my kernel config
>>>>>> https://gist.github.com/azat/7078890
>>>>>>
>>>>> Still cannot reproduce kernel crash when using your kernel config.
>>>>
>>>> Did you try to run something while that ktap script is running?
>>>> (another login, dmesg without head/tail)
>>>>
>>> Yes, whatever I do to system, nothing happened.
>>>
>>>>> What's confused me much is that tracepoint is working but kprobe not
>>>>> working.
>>>>
>>>> It works first N times however.
>>>>
>>>>>
>>>>> Can you apply below patch then run script again?
>>>>
>>>> I've just ran it, and I also have page fault.
>>>>
>>> Then it's interesting now, it seems caused by kernel kprobe, not ktapvm,
>>> because it never execute into kprobe perf callback in below code.
>>>
>>> static void ktap_overflow_callback(struct perf_event *event,
>>> struct perf_sample_data *data,
>>> struct pt_regs *regs)
>>> {
>>> return;
>>> ...
>>> }
>>>
>>> void kp_perf_event_register(ktap_state *ks, struct perf_event_attr *attr,
>>> struct task_struct *task, char *filter,
>>> ktap_closure *cl)
>>> {
>>> ...
>>> event = perf_event_create_kernel_counter(attr, cpu, task,
>>>
>>> ktap_overflow_callback,
>>> ktap_pevent);
>>> }
>>>
>>> So let's ignore ktap for a while, just check if kprobe works fine or not.
>>> Please try below command:
>>>
>>> #echo 'p:kprobes/kp0 SyS_write' > /sys/kernel/debug/tracing/kprobe_events
>>>
>>> #echo 1 > /sys/kernel/debug/tracing/events/kprobes/kp0/enable
>>>
>>> #cat /sys/kernel/debug/tracing/trace
>>
>> root:~# mount -t debugfs debugfs /sys/kernel/debug/
>> root:~# echo 'p:kprobes/kp0 SyS_write' >|
>> /sys/kernel/debug/tracing/kprobe_events
>> root:~# cat /sys/kernel/debug/tracing/kprobe_events
>> p:kprobes/kp0 SyS_write
>> root:~# cat /sys/kernel/debug/tracing/kprobe_profile
>> kp0 0 >> 0
>> root:~# echo 1 >| /sys/kernel/debug/tracing/events/kprobes/kp0/enable
>> root:~# cat /sys/kernel/debug/tracing/kprobe_profile
>> kp0 82 >> 0
>> root:~# cat /sys/kernel/debug/tracing/kprobe_profile
>> kp0 97 >> 0
>> root:~# cat /sys/kernel/debug/tracing/trace
>> root:~# cat /sys/kernel/debug/tracing/trace
>> # tracer: nop
>> #
>> # entries-in-buffer/entries-written: 175/175 #P:1
>> #
>> # _-----=> irqs-off
>> # / _----=> need-resched
>> # | / _---=> hardirq/softirq
>> # || / _--=> preempt-depth
>> # ||| / delay
>> # TASK-PID CPU# |||| TIMESTAMP FUNCTION
>> # | | | |||| | |
>> bash-2209 [000] d..1 121.488682: kp0: (SyS_write+0x0/0x74)
>> which-2475 [000] d..1 121.491036: kp0: (SyS_write+0x0/0x74)
>> git-2478 [000] d..1 121.494698: kp0: (SyS_write+0x0/0x74)
>> git-2481 [000] d..1 121.497838: kp0: (SyS_write+0x0/0x74)
>> wc-2486 [000] d..1 121.501778: kp0: (SyS_write+0x0/0x74)
>> bash-2209 [000] d..1 121.502462: kp0: (SyS_write+0x0/0x74)
>> sshd-2067 [000] d..1 121.502516: kp0: (SyS_write+0x0/0x74)
>> sshd-2067 [000] d..1 126.008965: kp0: (SyS_write+0x0/0x74)
>> bash-2209 [000] d..1 126.009187: kp0: (SyS_write+0x0/0x74)
>> sshd-2067 [000] d..1 126.009238: kp0: (SyS_write+0x0/0x74)
>> sshd-2067 [000] d..1 126.240849: kp0: (SyS_write+0x0/0x74)
>> .................
>>
>> In another console:
>> dmesg > /dev/null # fine
>> dmesg # all sessions logged out
>>
>> azat$ ssh -p2204 root@localhost # vm
>> root@localhost's password:
>> .....
>> Connection to localhost closed.
>>
>> Hm.. that is very interesting. I will try to debug this in evening/tomorrow.
>> Thanks!
>
> I've just tested on _another_ vm (fedora 19) with
> 3.11.4-201.fc19.x86_64.debug and ktap works correct.
>
> Right now I'm building kernel from -
> https://www.kernel.org/pub/linux/kernel/v3.x/linux-3.11.6.tar.xz
> I will let you know.
This one also trigger page fault.
>
> Thanks.
>
>>
>>>
>>
>>
>>
>> --
>> Respectfully
>> Azat Khuzhin
>
>
>
> --
> Respectfully
> Azat Khuzhin
--
Respectfully
Azat Khuzhin
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