linux-kernel - Re: [PATCH 3/4] x86,mm: Improve _install_special

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Message-ID: <537B9C6D.7010705@zytor.com>
Date:	Tue, 20 May 2014 11:18:21 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Cyrill Gorcunov <gorcunov@...il.com>,
	Andy Lutomirski <luto@...capital.net>
CC:	X86 ML <x86@...nel.org>, Andrew Morton <akpm@...ux-foundation.org>,
	Sasha Levin <sasha.levin@...cle.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Dave Jones <davej@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Pavel Emelyanov <xemul@...allels.com>
Subject: Re: [PATCH 3/4] x86,mm: Improve _install_special_mapping and fix
 x86 vdso naming

On 05/20/2014 11:01 AM, Cyrill Gorcunov wrote:
>>
>> This patch should fix this issue, at least.  If there's still a way to
>> get a native vdso that doesn't say "[vdso]", please let me know/
> 
> Yes, having a native procfs way to detect vdso is much preferred!
> 

Is there any path by which we can end up with [vdso] without a leading
slash in /proc/self/maps?  Otherwise, why is that not "native"?

>>>   The situation get worse when task was dumped on one kernel and
>>> then restored on another kernel where vdso content is different
>>> from one save in image -- is such case as I mentioned we need
>>> that named vdso proxy which redirect calls to vdso of the system
>>> where task is restoring. And when such "restored" task get checkpointed
>>> second time we don't dump new living vdso but save only old vdso
>>> proxy on disk (detecting it is a different story, in short we
>>> inject a unique mark into elf header).
>>
>> Yuck.  But I don't know whether the kernel can help much here.
> 
> Some prctl which would tell kernel to put vdso at specifed address.
> We can live without it for now so not a big deal (yet ;)

mremap() will do this for you.

	-hpa

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