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

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Date:	Mon, 27 May 2013 10:49:27 +0900
From:	HATAYAMA Daisuke <d.hatayama@...fujitsu.com>
To:	Maxim Uvarov <muvarov@...il.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>, riel@...hat.com,
	hughd@...gle.com, jingbai.ma@...com,
	"kexec@...ts.infradead.org" <kexec@...ts.infradead.org>,
	linux-kernel@...r.kernel.org, lisa.mitchell@...com,
	linux-mm@...ck.org,
	Atsushi Kumagai <kumagai-atsushi@....nes.nec.co.jp>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	kosaki.motohiro@...fujitsu.com, zhangyanfei@...fujitsu.com,
	walken@...gle.com, Cliff Wickman <cpw@....com>,
	Vivek Goyal <vgoyal@...hat.com>
Subject: Re: [PATCH v8 9/9] vmcore: support mmap() on /proc/vmcore

(2013/05/24 18:02), Maxim Uvarov wrote:
>
>
>
> 2013/5/24 Andrew Morton <akpm@...ux-foundation.org <mailto:akpm@...ux-foundation.org>>
>
>     On Thu, 23 May 2013 14:25:48 +0900 HATAYAMA Daisuke <d.hatayama@...fujitsu.com <mailto:d.hatayama@...fujitsu.com>> 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.
>
>     More reviewing and testing, please.
>
>
> Do you have git pull for both kernel and userland changes? I would like to do some more testing on my machines.
>
> Maxim.

Thanks! That's very helpful.

-- 
Thanks.
HATAYAMA, Daisuke

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