Invalid pointer traps (S/6000)
Marc Brandis
brandis at inf.ethz.ch
Mon Feb 11 20:45:01 AEST 1991
I noticed that when a program under AIX on the S/6000 reads through an invalid
pointer, no exception is reported but instead the value 0 is returned. On write,
the exception is reported. This seems to be true for the whole address range
from 0 up to 7fffffff.
As I understand the hardware documentation, the MMU does in fact detect the
illegal access, so the whole thing can only be a matter of the operating system.
Is there a way to turn this off so that all accesses to unmapped pages report
an exception, not only writes?
Thanks for any pointers.
Marc-Michael Brandis
Computer Systems Laboratory, ETH-Zentrum (Swiss Federal Institute of Technology)
CH-8092 Zurich, Switzerland
email: brandis at inf.ethz.ch
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