WARNING - OLD ARCHIVES

This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
   
 
 
Xen 
 
Home Products Support Community News
 
   
 

xen-devel

Re: [Xen-devel] Page fault on mapped pages with reserved bits set

To: Trammell Hudson <hudson@xxxxxxxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] Page fault on mapped pages with reserved bits set
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Wed, 20 Jun 2007 23:10:14 +0100
Delivery-date: Wed, 20 Jun 2007 15:05:45 -0700
Envelope-to: www-data@xxxxxxxxxxxxxxxxxx
In-reply-to: <20070620215910.GE13971@xxxxxxxxxxxxxx>
List-help: <mailto:xen-devel-request@lists.xensource.com?subject=help>
List-id: Xen developer discussion <xen-devel.lists.xensource.com>
List-post: <mailto:xen-devel@lists.xensource.com>
List-subscribe: <http://lists.xensource.com/cgi-bin/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/cgi-bin/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
Thread-index: Acezh8bDBVhndB97EdyVpQAWy6hiGQ==
Thread-topic: [Xen-devel] Page fault on mapped pages with reserved bits set
User-agent: Microsoft-Entourage/11.3.3.061214
On 20/6/07 22:59, "Trammell Hudson" <hudson@xxxxxxxxxxxxxx> wrote:

> I can't handle the page fault, since my kernel's page fault routine
> faults if it tries to do anything that writes to memory, such as
> push a return address on the stack.  To generate the error message
> above I had to disable my kernel's trap table to let Xen handle it.
> Otherwise the fault address is in my handler rather than in the
> instruction after setting MMUEXT_BASE_PTR.
> 
> Any suggestions on things to try?

It's a protection violation on a write, because none of your page directory
entries have bit 1 (_PAGE_RW) set. That bit gets ANDed down the entire page
walk, so it needs to be set at every level for the page to actually be
writable.

 -- Keir



_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel

<Prev in Thread] Current Thread [Next in Thread>