Path: utzoo!attcan!uunet!lll-winken!lll-tis!ames!mailrus!ncar!tank!oddjob!mimsy!chris
From: chris@mimsy.UUCP (Chris Torek)
Newsgroups: comp.lang.c
Subject: Re: (multiuser) protection via compiler
Message-ID: <13483@mimsy.UUCP>
Date: 10 Sep 88 16:56:11 GMT
References: <664@lindy.Stanford.EDU> <6758@megaron.arizona.edu> <718@gtx.com> <1450@ficc.uu.net>
Organization: U of Maryland, Dept. of Computer Science, Coll. Pk., MD 20742
Lines: 22

>In article <13454@mimsy.UUCP> I noted that for such an odd machine,
>>Whenever the compiler is forced to generate `iffy' code, it also generates
>>tests such as tags to make sure that you do not do something like this.

In article <1450@ficc.uu.net> peter@ficc.uu.net (Peter da Silva) writes:
>So what's to stop me from writing out a load module and subverting
>the protection mechanism, as I noted in my (deleted) footnote?

The O/S, of course, which cooperates with the compiler as to these tags
or region markers or whatever.  In fact, the only way to subvert the
system, if the system is done right, is to take it apart and either
rewire it, or move its disks to another machine and rewrite them, or
something along those lines---i.e., something software is physically
unable to protect against.  (I thought this whole line of reasoning was
obvious.  [proof by intimidation :-) ])

>I would think that the perversions necessary to make 'C' safe to run
>on this machine would make it sufficiently useless ...

Probably.
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7163)
Domain:	chris@mimsy.umd.edu	Path:	uunet!mimsy!chris