[ktap] Re: KTAP

  • From: "zhangwei(Jovi)" <jovi.zhangwei@xxxxxxxxxx>
  • To: Oded Gabbay <ogabbay@xxxxxxxxxxxxxxx>
  • Date: Fri, 24 May 2013 10:41:52 +0800

On 2013/5/23 19:52, Oded Gabbay wrote:
> 
> On 23/05/13 13:39, zhangwei(Jovi) wrote:
>> On 2013/5/23 17:36, Oded Gabbay wrote:
>>> On 23/05/13 12:13, zhangwei(Jovi) wrote:
>>>> On 2013/5/23 16:48, Oded Gabbay wrote:
>>>>> Hi Jovi,
>>>>>
>>>>> I read today about the ktap release in LWN and tried to give it a go on 
>>>>> my custom board, which contains a powerpc processor from Freescale called 
>>>>> P2020 (e500v2 core).
>>>>>
>>>>> I have two comments and a question:
>>>>>
>>>>> 1. I needed to enable CONFIG_RELAY in the kernel configuration, although 
>>>>> this is not mentioned in the requirements. Maybe you should add it.
>>>>>
>>>> Involve ktap mailing list :)
>>>>
>>>> Thanks, you are right, I will add it.
>>>>
>>>>> 2. I needed to add #include <linux/vmalloc.h> to ktap.c for compilation
>>>>>
>>>> which kernel version of the board? currently ktap can support kernel 3.1 
>>>> or later, older kernel need some patch to run ktap.
>>>> I haven't compile ktap in powerpc, so might you are right.
>>> My kernel version is 3.4.41.
>>>>> I now arrived to a situation where I insmod the ktapvm.ko on my board, 
>>>>> but when I run:
>>>>> ./ktap scripts/syscalls.kp
>>>>>
>>>>> I get the following error:
>>>>> open /sys/kernel/debug/ktap/ktapvm failed: No such file or directory
>>>>>
>>>>> I checked and indeed there is no /sys/kernel/debug/ktap folder (debug 
>>>>> folder is empty).
>>>> I guess you are missing mount debugfs?
>>>>
>>>> mount -t debugfs none /sys/kernel/debug/
>>>>
>>>> Also I will add this into ktap doc.
>>> Yes, I was missing the mount. Thanks :)
>>>> Note that currently ktap is not stable enough to running in production 
>>>> system, but I'm trying to make it more stable :)
>>> I'm aware of that and I'm not putting it in production, but thanks for the 
>>> warning.
>>> After I fixed the mount issue, I was able to run the syscalls script but 
>>> the kernel immediately crashed...
>>> I will try to look into it.
>>> This was the message from the kernel:
>>>
>>> [cj:/usr/local/ktap] # ./ktap scripts/syscalls.kp
>>> Unable to handle kernel paging request for data at address 0x00000000
>>> Faulting instruction address: 0xf1eb5dcc
>>> Oops: Kernel access of bad area, sig: 11 [#1]
>>> PREEMPT SMP NR_CPUS=2 P2020 FSP150
>>> Modules linked in: ktapvm(O) mdio(O) hardware_version(PO) clipresent(PO) 
>>> monotonic(O) restartcause(PO) panic_buffer(O) [last unloaded: ktapvm]
>>> NIP: f1eb5dcc LR: f1eb5d90 CTR: c0265f04
>>> REGS: eedd5c90 TRAP: 0300   Tainted: P           O 
>>> (3.4.41-dev_ogabbay-105684*)
>>> MSR: 00029000 <CE,EE,ME>  CR: 44000482  XER: 20000000
>>> DEAR: 00000000, ESR: 00000000
>>> TASK = ef0c6820[2097] 'ktap' THREAD: eedd4000 CPU: 1
>>> GPR00: 00000000 eedd5d40 ef0c6820 eedd5d4c f1eb801c 00000016 eedd5d6a 
>>> 0000003a
>>> GPR08: eedd5d54 00000000 00000000 f1eb801d c0265f04 1002cacc 00000005 
>>> 00000003
>>> GPR16: 00000001 eede9628 00000001 eede9600 00000000 eee6e640 00000000 
>>> 00000000
>>> GPR24: 00000000 eedd5d4c f1ec0000 eede9200 ffffffff eede8600 eedd5d4c 
>>> eedd5db8
>>> NIP [f1eb5dcc] ftrace_on_event_call.clone.6+0xb4/0x1fc [ktapvm]
>>> LR [f1eb5d90] ftrace_on_event_call.clone.6+0x78/0x1fc [ktapvm]
>>> Call Trace:
>>> [eedd5d40] [f1eb0824] kp_tstring_newlstr+0xdc/0x164 [ktapvm] (unreliable)
>>> [eedd5db0] [f1eb5ff4] ktap_lib_probe+0xe0/0x198 [ktapvm]
>>> [eedd5de0] [f1eb2a90] precall+0x1e4/0x318 [ktapvm]
>>> [eedd5e00] [f1eb3244] kp_call+0x680/0x1180 [ktapvm]
>>> [eedd5e60] [f1eaf2c0] ktap_ioctl+0x20c/0x30c [ktapvm]
>>> [eedd5ea0] [c010d4f4] do_vfs_ioctl+0xa0/0x754
>>> [eedd5f10] [c010dc44] sys_ioctl+0x9c/0xa4
>>> [eedd5f40] [c000f3a0] ret_from_syscall+0x0/0x3c
>>> --- Exception: c01 at 0xff1e254
>>>      LR = 0xffb2c0c
>>> Instruction dump:
>>> 419e0024 88030000 2f800000 409e0148 88180000 2f800000 409e011c 3b200000
>>> 3b000000 3f40f1ec 3ac00000 813a93a0 <83c90000> 7f89f000 419e00c0 3b5a93a0
>>> ---[ end trace b87e7dec14e55ffe ]---
>>>
>>> cannot lookup ftrace_events in kallsyms
>>> Kernel panic - not syncing: Fatal exception
>>> Rebooting in 5 seconds..
>> Please pull latest ktap from github, I just figure out I missed function 
>> return value check.
>> Then there will have no panic, I assume.
> Yes, now there is no panic
>>
>> But I'm still curious on why your kernel didn't exported "ftrace_events", 
>> CONFIG_KALLSYMS not enabled?
> CONFIG_KALLSYMS is enabled. CONFIG_EVENT_TRACING is also enabled. But, when I 
> do:
> grep ftrace_events /proc/kallsyms
> I don't get any results.
> When I look at kernel/trace/trace_events.c, I don't see that "ftrace_events" 
> is exported...

Sorry, what I said have a little misleading, global variable ftrace_events is 
not exported,
so ktap use kallsyms_lookup_name to get address of ftrace_events.

It's so weird that you cannot found ftrace_events in /proc/kallsyms, it just is 
a normal global variable,
it seems this is another bug in powerpc or some kernel configuration problem.

>>
>>>> Thanks.
>>>>> I thought maybe you would have any idea how to fix this and save me time.
>>>>>
>>>>> -- 




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