From: Arjan van de Ven <arjan@infradead.org>
To: Eric Lacombe <goretux@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>, linux-kernel@vger.kernel.org
Subject: Re: [x86] do_arch_prctl - bug?
Date: Tue, 18 Nov 2008 06:45:56 -0800 [thread overview]
Message-ID: <20081118064556.6b7dc245@infradead.org> (raw)
In-Reply-To: <200811181533.33108.goretux@gmail.com>
On Tue, 18 Nov 2008 15:33:32 +0100
Eric Lacombe <goretux@gmail.com> wrote:
> Hello,
>
> I would like to know why the ARCH_SET_GS action of sys_arch_prctl,
> write the MSR MSR_KERNEL_GS_BASE and not the MSR MSR_GS_BASE when the
> variable "doit" equals 1? Is that a bug?
>
I don't think it is.
The trick is that we use "swapgs" on entering/leaving the kernel, and
that will "swap" gs with the MSR, so when we return to userspace, GS
gets loaded from the MSR_KERNEL_GS_BASE ...
--
Arjan van de Ven Intel Open Source Technology Centre
For development, discussion and tips for power savings,
visit http://www.lesswatts.org
next prev parent reply other threads:[~2008-11-18 14:45 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-11-18 14:33 [x86] do_arch_prctl - bug? Eric Lacombe
2008-11-18 14:45 ` Arjan van de Ven [this message]
[not found] ` <200811181820.04064.goretux@gmail.com>
2008-11-18 17:35 ` Eric Lacombe
-- strict thread matches above, loose matches on Subject: below --
2008-11-18 17:35 Eric Lacombe
2008-11-18 23:44 ` Eric Lacombe
2008-11-19 1:07 ` Jeremy Fitzhardinge
2008-11-19 9:23 ` Eric Lacombe
2008-11-19 21:06 ` Jeremy Fitzhardinge
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