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From: m5d@bobkat.UUCP
Newsgroups: comp.os.minix
Subject: Re: Minix and compiler models
Message-ID: <533@bobkat.UUCP>
Date: Tue, 3-Feb-87 10:02:22 EST
Article-I.D.: bobkat.533
Posted: Tue Feb  3 10:02:22 1987
Date-Received: Wed, 4-Feb-87 07:22:31 EST
References: <966@ulowell.cs.ulowell.edu> <1565@cit-vax.Caltech.Edu> <500@bobkat.UUCP> <1151@husc6.UUCP>
Reply-To: m5d@bobkat.UUCP (Mike McNally (dlsh))
Organization: Digital Lynx, Inc; Dallas, TX
Lines: 32

In article <1151@husc6.UUCP> ddl@husc6.UUCP (Dan Lanciani) writes:
>MINIX may well support code, data, stack, and even more.  Just because C can't
>hack it...  There are also ways to use more memory while still preserving
>fork() semantics and swapability.  In OS I implememted two "extended"
>memory schemes:  A process usually starts out life with es=ds=ss.  There
>are system calls to allocate additional segments which are assigned
>descriptors (you know, small non-negative integers...) and a call to
>set your segment registers to use this memory.  This all works without
>giving up fork() and swapping because processes know only about these
>descriptors.  ...
>
>					Dan Lanciani
>					ddl@harvard.*

OK, OK, let me re-state my position.  I agree that given enough
run-time code, either called explicitly by the programmer (gag me, gag
me) or generated by the compiler, anything can happen.  The compiler
could even generate code to check pointer values every time a pointer
is dereferenced.  This begins to sound like a pseudo-code interpreter
approach.

Think of the overhead!  It makes my knees itch.  However, if you're
willing to live with it (which no doubt many people are to get a cheap
secure system on their machines), GREAT!  I don't mean to condemn.  I
was just trying to point out that with straight code it's bad to pin
memory locations.

-- 
Mike McNally, mercifully employed at Digital Lynx ---
    Where Plano Road the Mighty Flood of Forest Lane doth meet,
    And Garland fair, whose perfumed air flows soft about my feet...
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