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/
Home Products Support Community News


Re: [Xen-devel] Changing semantics of ioperm() on Xen x86-64?

To: Anthony Liguori <aliguori@xxxxxxxxxx>
Subject: Re: [Xen-devel] Changing semantics of ioperm() on Xen x86-64?
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Wed, 19 Apr 2006 08:26:58 +0100
Cc: xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>
Delivery-date: Wed, 19 Apr 2006 00:33:02 -0700
Envelope-to: www-data@xxxxxxxxxxxxxxxxxx
In-reply-to: <44455F11.8080007@xxxxxxxxxx>
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>
References: <44455F11.8080007@xxxxxxxxxx>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx

On 18 Apr 2006, at 22:50, Anthony Liguori wrote:

As part of the Xen x86-64 Linux port, we've changed the ioperm() syscall to always modify the IOPL instead of actually modifying the IO bitmap in the TSS like we do on x86-32. Is there a particular reason for doing this?

I'm completely guessing here that this may allow us to avoid changing the TR when changing from user/kernel mode but that doesn't seem like that huge of a gain.

I don't expect that there are many apps that would rely on using ioperm to restrict access to only certain ranges of ports so I don't think this is a security problem but it still is a little discomforting.

As Ian said, x86/64 port took an old snap of the i386 port and has gone stale in quite a few ways. It needs some maintenance TLC. i386 did the same thing with ioperm() until io bitmap support was added to Xen.

 -- Keir

Xen-devel mailing list

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