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From: "John S. Dyson" <toor@dyson.iquest.net>
Message-Id: <199610230537.AAA00161@dyson.iquest.net>
Subject: Re: Virtual memory question:  map first page?
To: johnson@charming.nrtc.northrop.com
Date: Wed, 23 Oct 1996 00:37:00 -0500 (EST)
Cc: questions@FreeBSD.ORG
In-Reply-To: <9610230515.AA02752@charming.nrtc.northrop.com> from "johnson@charming.nrtc.northrop.com" at Oct 22, 96 10:14:59 pm
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> 
> Is it possible to map the first page of linear memory?  What I would like
> to be able to do is set up a process in which linear addresses starting
> at 0 are mapped.
> 
Should be.

> When I modified imgact_aout.c to map the first linear page of memory as
> an experiment, and then ran a specially cooked executable to exercise that
> code, the machine immediately hung.
> 
> Is there something special on the first linear page of a user process?
> 
The only thing that I know of (off the top), and I might be corrected, is
that the first physical page is "special", but the first virtual page
should be safe...  (Specifically, there is an architectural bug in the
pmap code "today" that disables use of physical page 0.)  That bug is
probably not long for the world though.

John