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

To: xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: [Xen-devel] Changing semantics of ioperm() on Xen x86-64?
From: Anthony Liguori <aliguori@xxxxxxxxxx>
Date: Tue, 18 Apr 2006 16:50:09 -0500
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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.



Anthony Liguori

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