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

[Greg Ungerer <gerg@snapgear.com>]

Hi Bob,

On 07/06/11 16:19, Bob Liu wrote:
> On Fri, Jun 3, 2011 at 2:37 PM, Greg Ungerer<gerg@snapgear.com>  wrote:
>> Hi Bob,
>>
>> On 06/05/11 16:03, Bob Liu wrote:
>>>
>>> Currently on nommu arch mmap(),mremap() and munmap() doesn't do
>>> page_align()
>>> which isn't consist with mmu arch and cause some issues.
>>>
>>> First, some drivers' mmap() function depends on vma->vm_end - vma->start
>>> is
>>> page aligned which is true on mmu arch but not on nommu. eg: uvc camera
>>> driver.
>>>
>>> Second munmap() may return -EINVAL[split file] error in cases when end is
>>> not
>>> page aligned(passed into from userspace) but vma->vm_end is aligned dure
>>> to
>>> split or driver's mmap() ops.
>>>
>>> This patch add page align to fix those issues.
>>
>> This is actually causing me problems on head at the moment.
>> git bisected to this patch as the cause.
>>
>> When booting on a ColdFire (m68knommu) target the init process (or
>> there abouts at least) fails. Last console messages are:
>>
>> á...
>> áVFS: Mounted root (romfs filesystem) readonly on device 31:0.
>> áFreeing unused kernel memory: 52k freed (0x401aa000 - 0x401b6000)
>> áUnable 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)
   ==> do_mmap_pgoff(,0,6780,5,1002,0)
   <== do_mmap_pgoff() = -22
   Unable to mmap process text, errno 22

I can confirm that the PAGE_ALIGN(len) change in do_mmap_pgoff()
is enough to cause this too.

Regards
Greg




>> I haven't really debugged it any further yet. But that error message
>> comes from fs/binfmt_flat.c, it is reporting a failed do_mmap() call.
>>
>> Reverting that this patch and no more problem.
>>
>> Regards
>> Greg
>>

------------------------------------------------------------------------
Greg Ungerer  --  Principal Engineer        EMAIL:     gerg@snapgear.com
SnapGear Group, McAfee                      PHONE:       +61 7 3435 2888
8 Gardner Close                             FAX:         +61 7 3217 5323
Milton, QLD, 4064, Australia                WEB: http://www.SnapGear.com

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