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

[Bob Liu <lliubbo@gmail.com>]

Hi, Greg

On Wed, Jun 8, 2011 at 12:47 PM, Greg Ungerer <gerg@snapgear.com> wrote:
> 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
>

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()?

Thanks!

> 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
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>

-- 
Regards,
--Bob

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