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Re: [f-cpu] More Dark and Dusty Corners

On Tue, Sep 04, 2001 at 08:38:57AM +0200, Reichelt wrote:
> > I said "register", so I guess I meant hardware ;)  Whether user mode
> > programs are allowed to read that register is currently unspecified.
> NO they should NOT be allowed to read that register.
> A virtual machine works by keeping the CPU in user mode while sometimes tricking 
> it into believing it is in supervisor mode. Instructions which would blow the 
> masquerade are handle in the trap handler.

For a VM, read access should be turned off, right.  But there may be
other situations where limited (read-only) access to selected special
registers is useful.

In a simple privilege model (user/supervisor only), the register should
be invisible.  In the capabilities model, there might be a bit that
turns access privileges on and off independently.

 Michael "Tired" Riepe <Michael.Riepe@stud.uni-hannover.de>
 "All I wanna do is have a little fun before I die"
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