Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!att!pacbell.com!ames!sgi!shinobu!odin!wiltse
From: wiltse@sgi.com (Wiltse Carpenter)
Newsgroups: comp.sys.mips
Subject: Re: MIPS floating-exception/illegal instruction bug?
Summary: SGI to fix in next release
Keywords: fpu,panic
Message-ID: <1990Dec15.193433.8356@odin.corp.sgi.com>
Date: 15 Dec 90 19:34:33 GMT
References: <1990Nov29.182320.24295@cs.umn.edu>
Sender: news@odin.corp.sgi.com (Net News)
Organization: Silicon Graphics, Inc., Mountain View, CA
Lines: 22

In article <1990Nov29.182320.24295@cs.umn.edu> slevy@poincare.geom.umn.edu (Stuart Levy) writes:
>A few months back someone posted (on comp.sys.mips) a 3-instruction program
>to cause a MIPS kernel panic.  I tried it on an Iris; it paniced their
>kernel too.  It was something about a branch whose delay-slot was filled
>by an illegal floating-point-type instruction, and whose target was
>another such instruction, or one causing a floating exception.

Actually, the panic happens when you have a floating point instruction
in the branch delay slot of an illegal branch instruction and the fp
instruction causes an interrupt.  The kernel tries to emulate the
branch and upon seeing that it is not really a legal branch, panics.

>Anyway, I now need a way to get a crash dump from one of our Irises,
>which occasionally misbehaves.  SGI customer support can't tell me any
way >to do this, but I think that program might save the day.  Can
anyone out >there tell me the magic recipe?

This will be fixed in the next major release of Irix, no need to open
another call on it.  Processes exhibiting such behaviour will be sent
the appropriate signal.

	-Wiltse Carpenter