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From: es1@cunixb.cc.columbia.edu (Ethan Solomita)
Newsgroups: comp.sys.amiga.tech
Subject: Re: Memory Protection
Message-ID: <1990Mar8.230916.23505@cunixf.cc.columbia.edu>
Date: 8 Mar 90 23:09:16 GMT
References: <7955.AA7955@caleb>
Sender: usenet@cunixf.cc.columbia.edu (The Network News)
Reply-To: es1@cunixb.cc.columbia.edu (Ethan Solomita)
Organization: Columbia University
Lines: 33

In article <7955.AA7955@caleb> jdp@caleb.UUCP (Jim Pritchett) writes:
>[]
>
>I have an idea for memory protection for the Amiga OS.  Step 1:  assume
>MMU.  Step 2:  all memory shared between multiple processes (i.e. OS
>stuff, messages, etc.) can only be written by an OS server process.
>When a user level process wants to write to shared memory, it asks
>the OS server to do so.  Any errant process trying to scribble outside
>of its area would cause the MMU to generate an error.  Is this reasonable?
>Basically, let anyone read anywhere they want (i.e. in the specially
>mapped shared area), but the MMU is used to prevent any user task from
>writing there.  This would be slower than now (MMU waits + server time)
>but I think that it could be made to work.
>
>Before you flame me, please remember that I am NOT an expert here.  This
>is basically just a response to all the "memory protection is impossible
>with the Amiga OS" posts.  I am curious as to why this would not be
>feasible.  (Of course, I am suggesting a very major change to the OS
>here.)
>

	The problem with that is that so many programs write to other
space intentionally, especially with interprocess communications. For
the gurus out there, how would this sound: Have all programs default
to as above, unable to write to other areas. However, there is a
library command that disables that as necessary. Also, a program which
is considered bug-free can shut it off for the speed increase. Perhaps
we would even see it show up in a program's preferences!
	-- Ethan

Ethan Solomita: es1@cunixb.cc.columbia.edu
Compu$erve    : 70137,3271
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