linux-kernel - Re: unable to handle kernel paging request when inserting FAT32 formatted flash media

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Date:	Tue, 03 May 2011 10:52:34 +0900
From:	OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
To:	linux-kernel@...r.kernel.org
Cc:	Rusty Russell <rusty@...tcorp.com.au>
Subject: Re: unable to handle kernel paging request when inserting FAT32 formatted flash media

OGAWA Hirofumi <hirofumi@...l.parknet.co.jp> writes:

>> It seems to be interesting exception.
>>
>> before relocation (from fat.ko)
>>     8656:	74 51                	je     86a9 <fat_build_inode+0x2e9>
>>     8658:	49 c7 c6 00 00 00 00 	mov    $0x0,%r14
>>     865f:	b2 b6                	mov    $0xb6,%dl
>>     8661:	80 3d 00 00 00 00 00 	cmpb   $0x0,0x0(%rip) <-- exception
>>     8668:	74 3f                	je     86a9 <fat_build_inode+0x2e9>
>>     866a:	49 8d 44 24 08       	lea    0x8(%r12),%rax
>>
>> after relocation (from oops)
>>
>>   20:	74 51                	je     73 <a+0x73>
>>   22:	49 c7 c6 d8 91 13 a0 	mov    $0xffffffffa01391d8,%r14
>>   29:	b2 b6                	mov    $0xb6,%dl
>>   2b:	3d fc 9b 00 00       	cmp    $0x9bfc,%eax
>>   30:	00 74 3f 49          	add    %dh,0x49(%rdi,%rdi,1)
>>   34:	8d 44 24 08          	lea    0x8(%rsp),%eax
>>
> relocation info should be this
>
>   0x0000000000008663  X86_64_PC32     0x000000000000927c      -5 .LC55

Hm. It seems to be 0x80 was gone somehow. If I added 0x80 at 0x8661, it
seems to be sane code.

  20:	74 51                	je     73 <a+0x73>
  22:	49 c7 c6 d8 91 13 a0 	mov    $0xffffffffa01391d8,%r14
  29:	b2 b6                	mov    $0xb6,%dl
  2b:	80 3d fc 9b 00 00 00 	cmpb   $0x0,0x9bfc(%rip) <- here is 0x8661
  32:	74 3f                	je     73 <a+0x73>
  34:	49 8d 44 24 08       	lea    0x8(%r12),%rax

I have no idea how this happened for now. This would be needed to trace
when happened.

At first, it would be module load time. If you had time to debug and
trace, I may be able to help to debug it.

Cc: to module maintainer.

Any idea?

Thanks.
-- 
OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
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