From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeremy Fitzhardinge Subject: Re: vcpu_info Date: Fri, 10 Oct 2008 10:26:38 -0700 Message-ID: <48EF904E.6070004@goop.org> References: <48EF8579.4040201@goop.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: pallavi jk Cc: George Dunlap , xen-devel@lists.xensource.com List-Id: xen-devel@lists.xenproject.org pallavi jk wrote: > Hi Jeremy, > > Yes, I am planning to modify xen and the guest OS as well. > > I need to trap every entry into the guest OS from user mode because I > need to perform some checks in the hypervisor before transferring > control to the guest OS. If you run a 64-bit hypervisor, this will happen automatically. Only 32-on-32 supports directly trapping from guest usermode to kernel. > So I need to avoid fast handlers which would directly transfer control > to the guest OS, as I want to trap this entry first in the hypervisor. > I need to do this as I intend to protect applications from a possibly > malicious OS, so I want to perform some checks in the hypervisor. > > I have just started studying the code. Can you please provide me > guidelines about which source files and functions I should concentrate > on? arch/x86/**/traps.c is the first point to look at. Also entry.S which does the actual transfer of control between the various modes. There are several variants of each file for different modes (32, 64, 32 compat on 64), so make sure you target the right ones. J