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From: tim@ism780c.UUCP (Tim Smith)
Newsgroups: comp.sys.m68k
Subject: Re: Virtual Machine (was: Apollo (was: MINIX port to A1000))
Message-ID: <7862@ism780c.UUCP>
Date: Wed, 11-Nov-87 14:40:36 EST
Article-I.D.: ism780c.7862
Posted: Wed Nov 11 14:40:36 1987
Date-Received: Sat, 14-Nov-87 05:23:38 EST
References: <8711050534.AA25885@jade.berkeley.edu>
Reply-To: tim@ism780c.UUCP (Tim Smith)
Organization: Interactive Systems Corp., Santa Monica CA
Lines: 14
Keywords: virtual machine, emulation, 68010

Maybe Motorola can write a working virtual machine for the 680xx, but
can anyone else? 

You have to have some way of making sure that long stack frames from
things like bus errors are valid before allowing them to be used.
These frames are full of undocumented fields that can can cause all
kinds of problems if they contain bad data.

Example: take a valid bus error stack frame, and change the return address,
and then return from the bus error.  This can cause the processor to go
off into hyperspace.
-- 
Tim Smith, Knowledgian		{sdcrdcf,uunet}!ism780c!tim
				tim@ism780c.isc.com