[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: Mon, 21 Oct 2013 13:31:01 +0400
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!
>
--
Respectfully
Azat Khuzhin
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