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Path: utzoo!linus!philabs!seismo!rlgvax!guy
From: guy@rlgvax.UUCP (Guy Harris)
Newsgroups: net.unix-wizards
Subject: Re: Zero Based Program Query - (nf)
Message-ID: <1189@rlgvax.UUCP>
Date: Fri, 23-Sep-83 01:05:03 EDT
Article-I.D.: rlgvax.1189
Posted: Fri Sep 23 01:05:03 1983
Date-Received: Mon, 26-Sep-83 00:00:12 EDT
References: <1909@hp-pcd.UUCP>
Organization: CCI Office Systems Group, Reston, VA
Lines: 14

Our Power 5 machines (MC68000-based) start the user's address space at
0x800000, and run all the System III utilities except for a few like
the system activities package and the error logging code, so none of those
utilities cannot be fixed to work in such an address space.  In fact, I would
vote that any system which can start the user's address space at a point
higher than zero and which have enough address space that this isn't wasteful
should do so in order to trap nasty programs which attempt to dereference
null pointers (a lot of UNIX utilities assume that 0 points to a null string,
which is nasty beyond belief, and many of those that don't still don't check
that a pointer which may be null isn't before dereferencing it).  I could
dig up what we did to "fsck" if you want.

	Guy Harris
	{seismo,mcnc,we13,brl-bmd,allegra}!rlgvax!guy