Re: [PATCH v2] nommu: add page_align to mmap

[Greg Ungerer <gerg@snapgear.com>]

Hi Bob,

On 09/06/11 20:30, Bob Liu wrote:
> On Wed, Jun 8, 2011 at 6:19 PM, Greg Ungerer<gerg@snapgear.com>  wrote:
>>>>>> When booting on a ColdFire (m68knommu) target the init process (or
>>>>>> there abouts at least) fails. Last console messages are:
>>>>>>
>>>>>> ...
>>>>>> VFS: Mounted root (romfs filesystem) readonly on device 31:0.
>>>>>> Freeing unused kernel memory: 52k freed (0x401aa000 - 0x401b6000)
>>>>>> Unable to mmap process text, errno 22
>>>>>>
>>>>>
>>>>> Oh, bad news. I will try to reproduce it on my board.
>>>>> If you are free please enable debug in nommu.c and then we can see what
>>>>> caused the problem.
>>>>
>>>> Yep, with debug on:
>>>>
>>>> ­...
>>>> VFS: Mounted root (romfs filesystem) readonly on device 31:0.
>>>> Freeing unused kernel memory: 52k freed (0x4018c000 - 0x40198000)
>>>> ==>  ádo_mmap_pgoff(,0,6780,5,1002,0)
>>>> <== do_mmap_pgoff() = -22
>>>> Unable to mmap process text, errno 22
>>>>
>>>
>>> Since I can't reproduce this problem, could you please attach the
>>> whole dmesg log with nommu debug on or
>>> you can step into to see why errno 22 is returned, is it returned by
>>> do_mmap_private()?
>>
>> There was no other debug messages with debug turned on in nommu.c.
>> (I can give you the boot msgs before this if you want, but there
>> was no nommu.c debug in it).
>>
>> But I did trace it into do_mmap_pgoff() to see what was failing.
>> It fails based on the return value from:
>>
>> addr = file->f_op->get_unmapped_area(file, addr, len,
>>                                            ¡pgoff, flags);
>>
>
> Thanks for this information.
> But it's a callback function. I still can't know what's the problem maybe.
> Would you do me a favor to do more trace to see where it callback to,
> fs or some driver etc..?

Its calling to romfs_get_unmapped_area() [fs/romfs/mmap-nommu.c]. It is
being called with:

   romfs_get_unmapped_area(addr=0,len=7000,pgoff=0,flags=1002)

This is failing the first size check because isize comes back
as 0x6ca8, and this is smaller then len (0x7000). Thus returning
-EINVAL.

That code is trying to map the contents of the file /bin/init
directly from the romfs filesystem (which is in RAM). The init
binary is 0x6ca8 bytes in size (that is the isize above).

Regards
Greg


------------------------------------------------------------------------
Greg Ungerer  --  Principal Engineer        EMAIL:     gerg@snapgear.com
SnapGear Group, McAfee                      PHONE:       +61 7 3435 2888
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Milton, QLD, 4064, Australia                WEB: http://www.SnapGear.com

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