[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 01:00:13 +0400
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.
Thanks.
>
>>
>
>
>
> --
> Respectfully
> Azat Khuzhin
--
Respectfully
Azat Khuzhin
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