Referencing through a null pointer

[Michael I. Bushnell]

You know, people love railing against VAX unix...but there is one
reason that you CAN'T make the bottom of "data" un-readable and thus
fix the problem.  The VAX has a linear address space (or the VM hardware
makes it look that way).  There isn't a distinction between a data 
address and a text address, except that one is less than _etext.  If you
marked the bottom page non-readable, you would have massive problems...
you couldn't read start and whatever else makes it into the beginning
of the text space. 

There is a problem; but there isn't an easy way to avoid it, short
of deciding that a unix process should be loaded starting at address
1024 and make the first page non-readable.


                N u m q u a m   G l o r i a   D e o 

			Michael I. Bushnell
			HASA - "A" division
14308 Skyline Rd NE				Computer Science Dept.
Albuquerque, NM  87123		OR		Farris Engineering Ctr.
	OR					University of New Mexico
mike at turing.unm.edu				Albuquerque, NM  87131
{ucbvax,gatech}!unmvax!turing.unm.edu!mike