From: Vivek Goyal <vgoyal@redhat.com>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: HATAYAMA Daisuke <d.hatayama@jp.fujitsu.com>,
cpw@sgi.com, kumagai-atsushi@mxc.nes.nec.co.jp,
lisa.mitchell@hp.com, heiko.carstens@de.ibm.com,
akpm@linux-foundation.org, kexec@lists.infradead.org,
linux-kernel@vger.kernel.org, zhangyanfei@cn.fujitsu.com
Subject: Re: [PATCH v3 18/21] vmcore: check if vmcore objects satify mmap()'s page-size boundary requirement
Date: Thu, 21 Mar 2013 11:21:24 -0400 [thread overview]
Message-ID: <20130321152124.GJ3934@redhat.com> (raw)
In-Reply-To: <87a9pxz0wv.fsf@xmission.com>
On Thu, Mar 21, 2013 at 12:07:12AM -0700, Eric W. Biederman wrote:
[..]
> I think the two having different contents violates the principle of
> least surprise.
>
> I think exporting the old memory as the ``extra data'' is the least
> surprising and the easiest way to go.
>
> I don't mind filling the extra data with zero's but I don't see the
> point.
I think only question would be if there is a problem in reading memory
areas which BIOS has kept reserved or possibly not exported. Are there
any surprises to be expected. (machines reboots while trying to reboot
a particular memory location etc).
So trying to zero the extra data can make theoritically make it somewhat
safer.
So if starting or end address of PT_LOAD header is not aligned, why
not we simply allocate a page. Copy the relevant data from old memory,
fill rest with zero. That way mmap and read view will be same. There
will be no surprises w.r.t reading old kernel memory beyond what's
specified by the headers.
And in practice I am not expecting many PT_LOAD ranges which are unaligned.
Just few. And allocating a few 4K pages should not be a big deal.
And vmcore_list will help us again map whether pfn lies in old memory
or new memory.
Thanks
Vivek
next prev parent reply other threads:[~2013-03-21 15:21 UTC|newest]
Thread overview: 76+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-03-16 4:00 [PATCH v3 00/21] kdump, vmcore: support mmap() on /proc/vmcore HATAYAMA Daisuke
2013-03-16 4:00 ` [PATCH v3 01/21] vmcore: reference e_phoff member explicitly to get position of program header table HATAYAMA Daisuke
2013-03-19 21:44 ` Eric W. Biederman
2013-03-21 2:50 ` HATAYAMA Daisuke
2013-03-21 6:11 ` Eric W. Biederman
2013-03-21 14:12 ` Vivek Goyal
2013-03-22 0:25 ` HATAYAMA Daisuke
2013-03-16 4:00 ` [PATCH v3 02/21] vmcore: clean up by removing unnecessary variable HATAYAMA Daisuke
2013-03-16 4:01 ` [PATCH v3 03/21] vmcore: rearrange program headers without assuming consequtive PT_NOTE entries HATAYAMA Daisuke
2013-03-19 21:59 ` Eric W. Biederman
2013-03-16 4:01 ` [PATCH v3 04/21] vmcore, sysfs: export ELF note segment size instead of vmcoreinfo data size HATAYAMA Daisuke
2013-03-16 4:01 ` [PATCH v3 05/21] vmcore: allocate buffer for ELF headers on page-size alignment HATAYAMA Daisuke
2013-03-16 4:01 ` [PATCH v3 06/21] vmcore: round up buffer size of ELF headers by PAGE_SIZE HATAYAMA Daisuke
2013-03-19 22:07 ` Eric W. Biederman
2013-03-16 4:01 ` [PATCH v3 07/21] vmcore, procfs: introduce a flag to distinguish objects copied in 2nd kernel HATAYAMA Daisuke
2013-03-19 19:35 ` Andrew Morton
2013-03-16 4:01 ` [PATCH v3 08/21] vmcore: copy non page-size aligned head and tail pages " HATAYAMA Daisuke
2013-03-19 19:37 ` Andrew Morton
2013-03-19 20:59 ` Eric W. Biederman
2013-03-19 21:22 ` Vivek Goyal
2013-03-19 23:35 ` Eric W. Biederman
2013-03-16 4:01 ` [PATCH v3 09/21] vmcore: modify vmcore clean-up function to free buffer on " HATAYAMA Daisuke
2013-03-16 4:01 ` [PATCH v3 10/21] vmcore: clean up read_vmcore() HATAYAMA Daisuke
2013-03-16 4:01 ` [PATCH v3 11/21] vmcore: read buffers for vmcore objects copied from old memory HATAYAMA Daisuke
2013-03-16 4:01 ` [PATCH v3 12/21] vmcore: allocate per-cpu crash_notes objects on page-size boundary HATAYAMA Daisuke
2013-03-19 21:06 ` Eric W. Biederman
2013-03-19 22:12 ` Eric W. Biederman
2013-03-20 13:48 ` Vivek Goyal
2013-03-20 20:48 ` Eric W. Biederman
2013-03-16 4:02 ` [PATCH v3 13/21] kexec: allocate vmcoreinfo note buffer " HATAYAMA Daisuke
2013-03-19 21:07 ` Eric W. Biederman
2013-03-19 22:12 ` Eric W. Biederman
2013-03-16 4:02 ` [PATCH v3 14/21] kexec, elf: introduce NT_VMCORE_DEBUGINFO note type HATAYAMA Daisuke
2013-03-16 4:02 ` [PATCH v3 15/21] elf: introduce NT_VMCORE_PAD type HATAYAMA Daisuke
2013-03-16 4:02 ` [PATCH v3 16/21] kexec: fill note buffers by NT_VMCORE_PAD notes in page-size boundary HATAYAMA Daisuke
2013-03-19 22:17 ` Eric W. Biederman
2013-03-16 4:02 ` [PATCH v3 17/21] vmcore: check NT_VMCORE_PAD as a mark indicating the end of ELF note buffer HATAYAMA Daisuke
2013-03-19 21:11 ` Eric W. Biederman
2013-03-21 2:59 ` HATAYAMA Daisuke
2013-03-21 3:54 ` Eric W. Biederman
2013-03-21 14:36 ` Vivek Goyal
2013-03-22 0:30 ` HATAYAMA Daisuke
2013-03-22 0:41 ` Eric W. Biederman
2013-03-19 22:20 ` Eric W. Biederman
2013-03-16 4:02 ` [PATCH v3 18/21] vmcore: check if vmcore objects satify mmap()'s page-size boundary requirement HATAYAMA Daisuke
2013-03-19 20:02 ` Andrew Morton
2013-03-19 21:22 ` Eric W. Biederman
2013-03-20 13:51 ` Vivek Goyal
2013-03-19 22:38 ` Eric W. Biederman
2013-03-20 13:57 ` Vivek Goyal
2013-03-20 20:55 ` Eric W. Biederman
2013-03-21 3:25 ` HATAYAMA Daisuke
2013-03-21 4:18 ` Eric W. Biederman
2013-03-21 6:14 ` HATAYAMA Daisuke
2013-03-21 6:29 ` Eric W. Biederman
2013-03-21 6:46 ` HATAYAMA Daisuke
2013-03-21 7:07 ` Eric W. Biederman
2013-03-21 15:21 ` Vivek Goyal [this message]
2013-03-21 15:27 ` Vivek Goyal
2013-03-22 0:43 ` HATAYAMA Daisuke
2013-03-22 0:54 ` Eric W. Biederman
2013-03-22 2:30 ` HATAYAMA Daisuke
2013-03-21 14:57 ` Vivek Goyal
2013-03-21 7:22 ` Eric W. Biederman
2013-03-21 14:49 ` Vivek Goyal
2013-03-22 7:11 ` HATAYAMA Daisuke
2013-03-21 13:50 ` Vivek Goyal
2013-03-16 4:02 ` [PATCH v3 19/21] vmcore: round-up offset of vmcore object in page-size boundary HATAYAMA Daisuke
2013-03-16 4:02 ` [PATCH v3 20/21] vmcore: count holes generated by round-up operation for vmcore size HATAYAMA Daisuke
2013-03-16 4:02 ` [PATCH v3 21/21] vmcore: introduce mmap_vmcore() HATAYAMA Daisuke
2013-03-19 19:30 ` [PATCH v3 00/21] kdump, vmcore: support mmap() on /proc/vmcore Andrew Morton
2013-03-21 3:52 ` HATAYAMA Daisuke
2013-03-21 6:16 ` Eric W. Biederman
2013-03-21 6:35 ` HATAYAMA Daisuke
2013-03-21 7:14 ` Eric W. Biederman
2013-03-19 23:16 ` Eric W. Biederman
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