Path: utzoo!attcan!uunet!mcvax!kth!sunic!kullmar!pkmab!ske
From: ske@pkmab.se (Kristoffer Eriksson)
Newsgroups: comp.sys.amiga.tech
Subject: Re: MEMF_PHYSICAL?
Message-ID: <1265@pkmab.se>
Date: 13 Jun 89 20:16:12 GMT
References: <8906120031.AA03511@jade.berkeley.edu>
Reply-To: ske@pkmab.UUCP (Kristoffer Eriksson)
Organization: Peridot Konsult i Mellansverige AB, Oerebro, Sweden
Lines: 27

In article <8906120031.AA03511@jade.berkeley.edu> 451061@UOTTAWA.BITNET (Valentin Pepelea) writes:
>Kristoffer Eriksson <ske@pkmab.se> writes in message <1251@pkmab.se>
>
>> How can the OS and MMU provide any protection, if they don't care what
>> program is using what memory?
>
>Hire me, and I'll tell you. Actually, tell Commodore to hire me, and then
>everybody can use my "Virtual Memroy, Memory Protection" handler. Heh. No
>Kidding.

The way I know protection, it means that when one program is executing, it
has access to some memory, and no access to the rest of the memory, and when
another program executes, that program does not have access to the same parts
of memory, at least not all of it. Thus something in the MMU setup must
change when execution transfers from one program to another. But if nothing
in the system cares about such things, I don't understand how it is going
to work.

In a system with a monolithic kernel (like UNIX), I could imagine a simple
way to protect the kernel from the user programs without protecting the user
programs from each other, but the Amiga has a lot of separate tasks in stead
of a single kernel, so that does not apply. And it would only be half a
protected system as I see it, anyway.
-- 
Kristoffer Eriksson, Peridot Konsult AB, Hagagatan 6, S-703 40 Oerebro, Sweden
Phone: +46 19-13 03 60  !  e-mail: ske@pkmab.se
Fax:   +46 19-11 51 03  !  or ...!{uunet,mcvax}!sunic.sunet.se!kullmar!pkmab!ske