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[Xen-devel] [RFC] x86_64 and protection

To: xen-devel@xxxxxxxxxxxxxxxxxxx
Subject: [Xen-devel] [RFC] x86_64 and protection
From: Mathieu Ropert <mro@xxxxxxxxxx>
Date: Fri, 24 Mar 2006 13:05:44 +0100
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Hi,

i'm trying to understand how protection with Xen on x86_64 has kernel and user code run on the same privilege level.

Things i'm wondering:
- As all kernel pages must mapped with USER bit, how do i make sure user process can't access them? Unmap all before switching to user mode? - How Xen makes the difference between a kernel and a user process? I think it use a software flag or something to handle syscall instruction properly (ie: processing hypercall or give control to kernel syscalls management depending on the caller).

Some documentations on this would be great for future attempts to port other OS to Xen.


Regards,

Mathieu

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