Re: [PATCH v8 9/9] vmcore: support mmap() on /proc/vmcore

[HATAYAMA Daisuke]

(2013/06/07 6:31), Arnd Bergmann wrote:
> On Thursday 23 May 2013 14:25:48 HATAYAMA Daisuke wrote:
> > This patch introduces mmap_vmcore().
> >
> > Don't permit writable nor executable mapping even with mprotect()
> > because this mmap() is aimed at reading crash dump memory.
> > Non-writable mapping is also requirement of remap_pfn_range() when
> > mapping linear pages on non-consecutive physical pages; see
> > is_cow_mapping().
> >
> > Set VM_MIXEDMAP flag to remap memory by remap_pfn_range and by
> > remap_vmalloc_range_pertial at the same time for a single
> > vma. do_munmap() can correctly clean partially remapped vma with two
> > functions in abnormal case. See zap_pte_range(), vm_normal_page() and
> > their comments for details.
> >
> > On x86-32 PAE kernels, mmap() supports at most 16TB memory only. This
> > limitation comes from the fact that the third argument of
> > remap_pfn_range(), pfn, is of 32-bit length on x86-32: unsigned long.
> >
> > Signed-off-by: HATAYAMA Daisuke <d.hatayama@xxxxxxxxxxxxxx>
> > Acked-by: Vivek Goyal <vgoyal@xxxxxxxxxx>
>
> I get build errors on 'make randconfig' from this, when building
> NOMMU kernels on ARM. I suppose the new feature should be hidden
> in #ifdef CONFIG_MMU.
>
> 	Arnd

Thanks for trying the build and your report!

OTOH, I don't have no-MMU architectures; x86 box only. I cannot reproduce this build error. Could you give me your build log? I want to use it to detect what part depends on CONFIG_MMU.

--
Thanks.
HATAYAMA, Daisuke

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