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Re: kernel panic about kernel unaligned access

To: loody <miloody@gmail.com>
Subject: Re: kernel panic about kernel unaligned access
From: Mulyadi Santosa <mulyadi.santosa@gmail.com>
Date: Wed, 28 Oct 2009 10:56:45 +0700
Cc: linux-mips <linux-mips@linux-mips.org>, Kernel Newbies <kernelnewbies@nl.linux.org>
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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

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