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Date:      Fri, 14 Nov 1997 23:09:15 -0600
From:      Jonathan Lemon <jlemon@americantv.com>
To:        Joe Eykholt <jre@ipsilon.com>
Cc:        freebsd-hackers@FreeBSD.ORG
Subject:   Re: FreeBSD Pentium Bug fix (proposed)
Message-ID:  <19971114230915.12485@right.PCS>
In-Reply-To: <346D17BA.1B37ADEA@ipsilon.com>; from Joe Eykholt on Nov 11, 1997 at 07:32:10PM -0800
References:  <199711150115.RAA18627@hub.freebsd.org> <346D17BA.1B37ADEA@ipsilon.com>

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On Nov 11, 1997 at 07:32:10PM -0800, Joe Eykholt wrote:
> One point, though.  The segment length is at least one byte
> since the limit in the descriptor is the last valid offset
> in the segment, not the length.   That means that the address might
> be referenced.  The granularity should be 0 for bytes. 

The address within in the segment is specified by the vector address
contained within the IDT descriptor, so we don't have to worry about
that.


> so another, guaranteed-invalid address might be better, or you might
> leave the P bit off in that segment or (better) in the 
> IDT entry 6 descriptor, causing a segment-not-present fault.  
> (I haven't tried any of this). 

Leaving the `P'resent bit off does generate a segment-not-present fault.  
Unfortunately, this is of lower priority than a illegal instruction fault,
and doesn't work.  (This was the first thing I tried)
--
Jonathan



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