From: Brian Gerst <bgerst@didntduck.org>
To: Bjorn Wesen <bjorn@sparta.lu.se>
Cc: linux-kernel@vger.kernel.org
Subject: Re: meaning of vmalloc shortcut comment in fault.c
Date: Tue, 05 Jun 2001 11:11:06 -0400 [thread overview]
Message-ID: <3B1CF68A.65AB5108@didntduck.org> (raw)
In-Reply-To: <Pine.LNX.3.96.1010605145320.9033B-100000@medusa.sparta.lu.se>
Bjorn Wesen wrote:
>
> Can someone elaborate on why it's bad to refer to tsk directly below (this
> is a 2.4.5 change in x86) and why it's needed on x86 and not other archs..
>
> What should I do for an arch that does not have a "cr3" machine register
> to check with ?
%cr3 is the page table pointer on the x86. Changing the page table
pointer and changing the stack pointer (from which tsk is derived) is
not done atomically during a task switch. If an interrupt happens in
between and causes a page fault on a vmalloced area, using tsk may refer
to the wrong page tables. %cr3 by definition always has the current
page table pointer.
--
Brian Gerst
prev parent reply other threads:[~2001-06-05 15:12 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-06-05 12:56 meaning of vmalloc shortcut comment in fault.c Bjorn Wesen
2001-06-05 15:11 ` Brian Gerst [this message]
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