linux-kernel - Re: [GIT pull] x86 vdso updates

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Message-ID: <BANLkTi=UEJqGxAs5p2tA=KzddNOrXCfXfQ@mail.gmail.com>
Date:	Fri, 27 May 2011 13:59:14 +0200
From:	richard -rw- weinberger <richard.weinberger@...il.com>
To:	Andrew Lutomirski <luto@....edu>
Cc:	Ingo Molnar <mingo@...e.hu>, Thomas Gleixner <tglx@...utronix.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>, x86@...nel.org,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [GIT pull] x86 vdso updates

On Fri, May 27, 2011 at 1:36 PM, Andrew Lutomirski <luto@....edu> wrote:
> On Fri, May 27, 2011 at 2:12 AM, Ingo Molnar <mingo@...e.hu> wrote:
>>
>> * Andy Lutomirski <luto@....edu> wrote:
>>
>>> On 05/26/2011 02:50 PM, Thomas Gleixner wrote:
>>> >       x86-64: Add time to vDSO
>>>
>>> And here's the glibc bug:
>>>
>>> http://sourceware.org/bugzilla/show_bug.cgi?id=12813
>>>
>>> Let the deprecation of the vsyscall page begin :)
>>
>> Yeah :-)
>>
>> On a related note, now that these bits are upstream, what are your
>> rough plans for doing the int81 vsyscall emulation patch?
>>
>> The int81 patch would actually be (much!) more important to the
>> average Linux user than getting rid of the vsyscall from static
>> binaries: the vsyscall is the last predictable executable address in
>> PIE daemons with a dangerous SYSENTER instruction in it ...
>>
>> I'd actually consider accelerating it into v2.6.40.
>
> Working on it slowly.  In principle I'm writing my thesis right now on
> things that have very little to do with software :)
>
> My rough plans for the near-term stuff are:
>
> 1. Move vvars out of the vsyscall page.  Otherwise we have at least
> one predictable syscall instruction every 1<<16 seconds because the
> time is executable.  It's prettier that way, too.
>
> 2. Remove the vsyscall64 sysctl.  That will reduce the number of
> vsyscalls that require the kernel's help to one.  (This is a bit
> unfortunate for UML users, but I'm not sure what to do about that.
> UML vgetcpu is already terminally broken.)

Can you please be a bit more precise on that?
When there is anything I can do, let me know...

-- 
Thanks,
//richard
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