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Re: [Xen-devel] getting domU current privlege level?

from [Ian Campbell]

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To:	"Kurtz, Ryan M." <Ryan.Kurtz@xxxxxxxxxx>
Subject:	Re: [Xen-devel] getting domU current privlege level?
From:	Ian Campbell <Ian.Campbell@xxxxxxxxxxxxx>
Date:	Wed, 09 Aug 2006 16:59:29 +0100
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On Wed, 2006-08-09 at 10:15 -0400, Kurtz, Ryan M. wrote:

> I am looking for a way to access the CPL of a running domU from a user
> program in dom0.  Is this possible?  I have looked at the
> vcpu_get_context structure, and noticed that a couple parts of the CS
> register can be accessed, but not the CPL.  Does anyone know if it is
> possible to access these lower 2 bits of the CS register?

Checkout tools/xentrace/xenctx.c (installed as /usr/lib/xen/bin/xenctx).

It uses xc_vcpu_getcontext() to populate vcpu_guest_context_t ctx (is
this what you are referring to by "vcpu_get_context structure" ???)

CS is found in ctx.user_regs.cs and appears to contain the correct CPL.
Using xenctx I've just observed CS values of 0x61 and 0x73 which
indicate Linux kernel vs. userspace.

Ian.



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