[Crash-utility] dis command not correct in crash

[Lei Wen]

Per

On Tue, Mar 5, 2013 at 6:30 PM, Per Fransson <per.fransson.ml at gmail.com> wrote:
> Hi,
>
> On Tue, Mar 5, 2013 at 9:22 AM, Lei Wen <adrian.wenl at gmail.com> wrote:
>> Per,
>>
>> On Tue, Mar 5, 2013 at 3:25 PM, Per Fransson <per.fransson.ml at gmail.com> wrote:
>>> Hi Lei,
>>>
>>> On Tue, Mar 5, 2013 at 1:22 AM, Lei Wen <adrian.wenl at gmail.com> wrote:
>>>> Hi Per,
>>>>
>>>>
>>>> On Tue, Mar 5, 2013 at 4:38 AM, Per Fransson <per.fransson.ml at gmail.com>
>>>> wrote:
>>>>>
>>>>> Hi,
>>>>>
>>>>> On Mon, Mar 4, 2013 at 8:49 PM, Mika Westerberg <mika.westerberg at iki.fi>
>>>>> wrote:
>>>>> > On Mon, Mar 04, 2013 at 10:20:42AM +0800, Lei Wen wrote:
>>>>> >> I met "dis" command not correct issue when use the crash, any idea?
>>>>> >> For built-in "dis" command in crash:
>>>>> >> crash> dis task_rq_lock
>>>>> >> 0xc015a2d8 <task_rq_lock>:      rscsgt  r0, sp, r3, lsl #14
>>>>> >> 0xc015a2dc <task_rq_lock+4>:    mrcgt   8, 7, r0, cr2, cr13, {5}
>>>>> >> 0xc015a2e0 <task_rq_lock+8>:    mcrvc   8, 4, r3, cr13, cr3, {6}
>>>>> >> 0xc015a2e4 <task_rq_lock+12>:   lslsvc  r3, r10, r8
>>>>> >> 0xc015a2e8 <task_rq_lock+16>:   bl      0xc049fe34
>>>>> >> <__ip_route_output_key+220>
>>>>> >
>>>>> > Looks weird.
>>>>> >
>>>>> > What is the kernel version? Does the 'dis' command work for other
>>>>> > functions?
>>>>> >
>>>>>
>>>>> You could do a check on one of the instructions - the 'bl' comes to
>>>>> mind. Not sure, but I believe it should amount to:
>>>>>
>>>>> 0xeb000000 | (((0xc049fe34-0xc015a2f0) >> 2) & 0x00ffffff)
>>>>>
>>>>> i.e.
>>>>>
>>>>> 0xeb0d16d1
>>>>>
>>>>> Is that what you get with
>>>>>
>>>>> crash> rd 0xc015a2e8
>>>>>
>>>>> ?
>>>>>
>>>>> If not, try a
>>>>>
>>>>> crash> search 0xeb0d16d1
>>>>>
>>>>> and see if it turns up somewhere else.
>>>>
>>>>
>>>>
>>>>
>>>> Yes, it is that value.
>>>>
>>>> crash> rd 0xc015a2e8
>>>>
>>>> c015a2e8:  eb0d16d1                              ....
>>>>
>>>>
>>>>
>>>> While in gdb, show the same address's value, it would be:
>>>>
>>>> (gdb) x 0xc015a2e8
>>>>
>>>> 0xc015a2e8 <task_rq_lock+16>:   0xe1a05000
>>>>
>>>>
>>>>
>>>> Why it didn't match with each other? Any idea?
>>>>
>>>>
>>>
>>> Nope, no idea. When you're using gdb, do you feed it the coredump as
>>> well, or just the vmlinux? if you get the same strange result with
>>> gdb+vmlinux+coredump, I think you should try to match some known data,
>>> e.g. the 'bl' and see if the contents are offset somehow. Try the gdb
>>> search command on 0xeb0d16d1.
>>
>> Your hypothesis is correct.
>> When feed dump image with vmlinux to the gdb, I get exactly same result
>> as crash...
>>
>> How to use the search command in gdb?
>>
>
> Oh, it's 'find' in gdb. To look for 0xeb0d16d1 in the virtual interval
> 0xc0000000--0xe0000000 you would:
>
> (gdb) find /w 0xc0000000, +0x20000000, 0xeb0d16d1
>
> or use your favorite hex editor.
>
> If the dump isn't offset, it could be overwrites.

Here is the result:
(gdb) find /w 0xc0000000, +0x20000000, 0xeb0d16d1
0xc015a2e8 <task_rq_lock+16>
1 pattern found.

Seems its output is exactly as crash's rd command...

Thanks,
Lei