kernel panic about kernel unaligned access

kernel panic about kernel unaligned access

[loody]

Dear all:
I use kernel 2.6.18 and I get the kernel panic as below:
Unhandled kernel unaligned access[#1]:
Cpu 0
$ 0   : 00000000 11000001 0000040a 8721f0d8
$ 4   : 874a6c00 80001d18 00000000 00000000
$ 8   : 00000000 ffffa438 00000000 874c2000
$12   : 00000000 00000000 00005800 00011000
$16   : 80001d10 874a6c40 874a6c00 87d7bf00
$20   : 874a6c78 871a0000 87370000 874a6c80
$24   : 00000000 2aacc770
$28   : 87d7a000 87d7be88 ffffa438 8709ed20
Hi    : 00000000
Lo    : 00000000
epc   : 8709e72c sync_sb_inodes+0x9c/0x320     Not tainted
ra    : 8709ed20 writeback_inodes+0xb4/0x160
Status: 11000003    KERNEL EXL IE
Cause : 00808010
BadVA : 00000442
PrId  : 00019654
Modules linked in:
Process pdflush (pid: 38, threadinfo=87d7a000, task=87d695b8)
Stack : ffffffff ffffffff 871c0000 87cae4d8 874a6c00 874a6c40 87d7bf00 871c4290
        87d7bf64 871a0000 87370000 00000000 00000000 8709ed20 ffffffff ffffffff
        8735e380 874bb8a8 00000400 0000034b ffffa62c 87d7bf00 87057f9c 00000000
        87189270 87188b20 00000000 87189564 ffff9880 87362d58 00000000 00000000
        87d7bef8 00000400 00000000 00000000 00000000 00000000 00000000 00000000
        ...
Call Trace:
 [<8709ed20>] writeback_inodes+0xb4/0x160
 [<87057f9c>] wb_kupdate+0xb8/0x154
 [<87189270>] __schedule+0x998/0xb34
 [<87188b20>] __schedule+0x248/0xb34
 [<87189564>] preempt_schedule+0x68/0xac
 [<87058d74>] pdflush+0x188/0x284
 [<87058cfc>] pdflush+0x110/0x284
 [<8703b9e4>] kthread+0x14c/0x1b8
 [<87057ee4>] wb_kupdate+0x0/0x154
 [<87058bec>] pdflush+0x0/0x284
 [<8703ba00>] kthread+0x168/0x1b8
 [<87003398>] kernel_thread_helper+0x10/0x18
 [<87003388>] kernel_thread_helper+0x0/0x18


Code: 8e450084  24b0fff8  8e02009c <8c510038> 8e220008  30420002
1040000f  00000000  8ca20000
note: pdflush[38] exited with preempt_count 1

my questions are:
1. what does "Not tainted" mean?
2. I grep the kernel and I find the above message comes from do_ade in
unaligned.c, If I guess correctly.
    but from the call trace I cannot find out who call it.
    who and how kernel pass the information to do_ade?
3. as far as i know, inode is the data structure we used to record file.
From what information in the inode I can find out the file name the
writeback_inodes try to write?
appreciate your help,
miloody

kernel panic about kernel unaligned access

[loody]

Dear all:
I use kernel 2.6.18 and I get the kernel panic as below:
Unhandled kernel unaligned access[#1]:
Cpu 0
$ 0   : 00000000 11000001 0000040a 8721f0d8
$ 4   : 874a6c00 80001d18 00000000 00000000
$ 8   : 00000000 ffffa438 00000000 874c2000
$12   : 00000000 00000000 00005800 00011000
$16   : 80001d10 874a6c40 874a6c00 87d7bf00
$20   : 874a6c78 871a0000 87370000 874a6c80
$24   : 00000000 2aacc770
$28   : 87d7a000 87d7be88 ffffa438 8709ed20
Hi    : 00000000
Lo    : 00000000
epc   : 8709e72c sync_sb_inodes+0x9c/0x320     Not tainted
ra    : 8709ed20 writeback_inodes+0xb4/0x160
Status: 11000003    KERNEL EXL IE
Cause : 00808010
BadVA : 00000442
PrId  : 00019654
Modules linked in:
Process pdflush (pid: 38, threadinfo=87d7a000, task=87d695b8)
Stack : ffffffff ffffffff 871c0000 87cae4d8 874a6c00 874a6c40 87d7bf00 871c4290
        87d7bf64 871a0000 87370000 00000000 00000000 8709ed20 ffffffff ffffffff
        8735e380 874bb8a8 00000400 0000034b ffffa62c 87d7bf00 87057f9c 00000000
        87189270 87188b20 00000000 87189564 ffff9880 87362d58 00000000 00000000
        87d7bef8 00000400 00000000 00000000 00000000 00000000 00000000 00000000
        ...
Call Trace:
 [<8709ed20>] writeback_inodes+0xb4/0x160
 [<87057f9c>] wb_kupdate+0xb8/0x154
 [<87189270>] __schedule+0x998/0xb34
 [<87188b20>] __schedule+0x248/0xb34
 [<87189564>] preempt_schedule+0x68/0xac
 [<87058d74>] pdflush+0x188/0x284
 [<87058cfc>] pdflush+0x110/0x284
 [<8703b9e4>] kthread+0x14c/0x1b8
 [<87057ee4>] wb_kupdate+0x0/0x154
 [<87058bec>] pdflush+0x0/0x284
 [<8703ba00>] kthread+0x168/0x1b8
 [<87003398>] kernel_thread_helper+0x10/0x18
 [<87003388>] kernel_thread_helper+0x0/0x18


Code: 8e450084  24b0fff8  8e02009c <8c510038> 8e220008  30420002
1040000f  00000000  8ca20000
note: pdflush[38] exited with preempt_count 1

my questions are:
1. what does "Not tainted" mean?
2. I grep the kernel and I find the above message comes from do_ade in
unaligned.c, If I guess correctly.
    but from the call trace I cannot find out who call it.
    who and how kernel pass the information to do_ade?
3. as far as i know, inode is the data structure we used to record file.

Re: kernel panic about kernel unaligned access

[Xiangfu Liu]

vinit dhatrak wrote:
>> my questions are:
>> 1. what does "Not tainted" mean?
>> 2. I grep the kernel and I find the above message comes from do_ade in
>> unaligned.c, If I guess correctly.
>>    but from the call trace I cannot find out who call it.
>>    who and how kernel pass the information to do_ade?
>> 3. as far as i know, inode is the data structure we used to record file.
>> From what information in the inode I can find out the file name the
>> writeback_inodes try to write?
>> appreciate your help,
>> miloody
>>
> 
> I can answer your first question. Loading a proprietary or
> non-GPL-compatible module will 'taint' the running kernel—meaning that
> any problems or bugs experienced will be less likely to be
> investigated by the maintainers. See this "Tainted Kernel" document
> from Novell.
> http://www.novell.com/support/viewContent.do?externalId=3582750&sliceId=1
> 
> In your case, it seems that your kernel is not tainted by any external code.
> Also, what you see as call trace is actually just stack dump, not
> exactly a backtrace.

Hi I also got similar panic in my board (ben nanonote). the process is "Process ksoftirqd/0"
Q: how to get the backtrace? 

Re: kernel panic about kernel unaligned access

[Mulyadi Santosa]

Hi...

On Tue, Oct 27, 2009 at 8:27 PM, loody <miloody@gmail.com> wrote:
> Dear all:
> I use kernel 2.6.18 and I get the kernel panic as below:
> Unhandled kernel unaligned access[#1]:
> Cpu 0
> $ 0   : 00000000 11000001 0000040a 8721f0d8
> $ 4   : 874a6c00 80001d18 00000000 00000000
> $ 8   : 00000000 ffffa438 00000000 874c2000
> $12   : 00000000 00000000 00005800 00011000
> $16   : 80001d10 874a6c40 874a6c00 87d7bf00
> $20   : 874a6c78 871a0000 87370000 874a6c80
> $24   : 00000000 2aacc770
> $28   : 87d7a000 87d7be88 ffffa438 8709ed20
> Hi    : 00000000
> Lo    : 00000000
> epc   : 8709e72c sync_sb_inodes+0x9c/0x320     Not tainted
> ra    : 8709ed20 writeback_inodes+0xb4/0x160

Hmmm, your machine is not x86, is it? So, I guess this panic is caused
by unaligned memory access.

AFAIK, in certain architecture, accessing memory at address not a
multiple of its word size might cause trap. So, for example if it is a
CPU with 4 byte word size, then accessing memory at 0x00000005 will
cause panic.


> my questions are:
> 1. what does "Not tainted" mean?

AFAIK, it means no non GPL-ed kernel module are currently inserted.

> 2. I grep the kernel and I find the above message comes from do_ade in
> unaligned.c, If I guess correctly.
>    but from the call trace I cannot find out who call it.
>    who and how kernel pass the information to do_ade?

Likely it is part of trap handler.... thus it is installed as interrupt handler.


-- 
regards,

Mulyadi Santosa
Freelance Linux trainer and consultant

blog: the-hydra.blogspot.com
training: mulyaditraining.blogspot.com

Re: kernel panic about kernel unaligned access

[loody]

hi

2009/10/28 Mulyadi Santosa <mulyadi.santosa@gmail.com>:
> Hi...
>
> On Tue, Oct 27, 2009 at 8:27 PM, loody <miloody@gmail.com> wrote:
>> Dear all:
>> I use kernel 2.6.18 and I get the kernel panic as below:
>> Unhandled kernel unaligned access[#1]:
>> Cpu 0
>> $ 0   : 00000000 11000001 0000040a 8721f0d8
>> $ 4   : 874a6c00 80001d18 00000000 00000000
>> $ 8   : 00000000 ffffa438 00000000 874c2000
>> $12   : 00000000 00000000 00005800 00011000
>> $16   : 80001d10 874a6c40 874a6c00 87d7bf00
>> $20   : 874a6c78 871a0000 87370000 874a6c80
>> $24   : 00000000 2aacc770
>> $28   : 87d7a000 87d7be88 ffffa438 8709ed20
>> Hi    : 00000000
>> Lo    : 00000000
>> epc   : 8709e72c sync_sb_inodes+0x9c/0x320     Not tainted
>> ra    : 8709ed20 writeback_inodes+0xb4/0x160
>
> Hmmm, your machine is not x86, is it? So, I guess this panic is caused
> by unaligned memory access.
Yes, my machine is mips machine.
if do_ade in unaligned.c is a trap, where do  we register it?
I grep the source code but I only find the definition but cannot get
the place where we register the trap.
Does it have any relationship with the word 'asmlinkage'?
I know init is the keyword for init section.
but what does asmlinkage mean?

> AFAIK, in certain architecture, accessing memory at address not a
> multiple of its word size might cause trap. So, for example if it is a
> CPU with 4 byte word size, then accessing memory at 0x00000005 will
> cause panic.
>
>
>> my questions are:
>> 1. what does "Not tainted" mean?
>
> AFAIK, it means no non GPL-ed kernel module are currently inserted.
>
>> 2. I grep the kernel and I find the above message comes from do_ade in
>> unaligned.c, If I guess correctly.
>>    but from the call trace I cannot find out who call it.
>>    who and how kernel pass the information to do_ade?
>
> Likely it is part of trap handler.... thus it is installed as interrupt handler.
>
>
> --
appreciate your help,
miloody

Re: kernel panic about kernel unaligned access

[David Daney]

loody wrote:
> hi
> 
> 2009/10/28 Mulyadi Santosa <mulyadi.santosa@gmail.com>:
>> Hi...
>>
>> On Tue, Oct 27, 2009 at 8:27 PM, loody <miloody@gmail.com> wrote:
>>> Dear all:
>>> I use kernel 2.6.18 and I get the kernel panic as below:
>>> Unhandled kernel unaligned access[#1]:
>>> Cpu 0
>>> $ 0   : 00000000 11000001 0000040a 8721f0d8
>>> $ 4   : 874a6c00 80001d18 00000000 00000000
>>> $ 8   : 00000000 ffffa438 00000000 874c2000
>>> $12   : 00000000 00000000 00005800 00011000
>>> $16   : 80001d10 874a6c40 874a6c00 87d7bf00
>>> $20   : 874a6c78 871a0000 87370000 874a6c80
>>> $24   : 00000000 2aacc770
>>> $28   : 87d7a000 87d7be88 ffffa438 8709ed20
>>> Hi    : 00000000
>>> Lo    : 00000000
>>> epc   : 8709e72c sync_sb_inodes+0x9c/0x320     Not tainted
>>> ra    : 8709ed20 writeback_inodes+0xb4/0x160
>> Hmmm, your machine is not x86, is it? So, I guess this panic is caused
>> by unaligned memory access.
> Yes, my machine is mips machine.
> if do_ade in unaligned.c is a trap, where do  we register it?
> I grep the source code but I only find the definition but cannot get
> the place where we register the trap.


Look in genex.S for lines like:

	BUILD_HANDLER adel ade ade silent		/* #4  */
	BUILD_HANDLER ades ade ade silent		/* #5  */

And also in traps.c for lines like:

	set_except_vector(4, handle_adel);
	set_except_vector(5, handle_ades);


David Daney

Re: kernel panic about kernel unaligned access

[loody]

Hi:
thanks for all your kind help.
2009/10/28 David Daney <ddaney@caviumnetworks.com>:
> loody wrote:
>>
>> hi
>>
>> 2009/10/28 Mulyadi Santosa <mulyadi.santosa@gmail.com>:
>>>
>>> Hi...
>>>
>>> On Tue, Oct 27, 2009 at 8:27 PM, loody <miloody@gmail.com> wrote:
>>>>
>>>> Dear all:
>>>> I use kernel 2.6.18 and I get the kernel panic as below:
>>>> Unhandled kernel unaligned access[#1]:
>>>> Cpu 0
>>>> $ 0   : 00000000 11000001 0000040a 8721f0d8
>>>> $ 4   : 874a6c00 80001d18 00000000 00000000
>>>> $ 8   : 00000000 ffffa438 00000000 874c2000
>>>> $12   : 00000000 00000000 00005800 00011000
>>>> $16   : 80001d10 874a6c40 874a6c00 87d7bf00
>>>> $20   : 874a6c78 871a0000 87370000 874a6c80
>>>> $24   : 00000000 2aacc770
>>>> $28   : 87d7a000 87d7be88 ffffa438 8709ed20
>>>> Hi    : 00000000
>>>> Lo    : 00000000
>>>> epc   : 8709e72c sync_sb_inodes+0x9c/0x320     Not tainted
>>>> ra    : 8709ed20 writeback_inodes+0xb4/0x160
>>>
>>> Hmmm, your machine is not x86, is it? So, I guess this panic is caused
>>> by unaligned memory access.
>>
>> Yes, my machine is mips machine.
>> if do_ade in unaligned.c is a trap, where do  we register it?
>> I grep the source code but I only find the definition but cannot get
>> the place where we register the trap.
>
>
> Look in genex.S for lines like:
>
>        BUILD_HANDLER adel ade ade silent               /* #4  */
>        BUILD_HANDLER ades ade ade silent               /* #5  */
>
> And also in traps.c for lines like:
>
>        set_except_vector(4, handle_adel);
>        set_except_vector(5, handle_ades);
Take  "8709ed20 writeback_inodes+0xb4/0x160" for example, what does
0x160, the last hex mean? The value of parameter?
appreciate your help,
miloody

Re: kernel panic about kernel unaligned access

[Anupam Kapoor]

> Take  "8709ed20 writeback_inodes+0xb4/0x160" for example, what does
> 0x160, the last hex mean? The value of parameter?
first-number       i.e 0xb4   means that EIP was as many bytes into
the 'writeback_inodes' function when this happened.
second-number  i.e 0x160 mean that the function is '0x160' bytes long.

anupam
-- 
In the beginning was the lambda, and the lambda was with Emacs, and
Emacs was the lambda.