22 Mar
2016
22 Mar
'16
6:27 a.m.
On Monday, 21 March 2016 at 15:57:24 -0700, scj(a)yaccman.com wrote:
But the closest I came to being murdered was ... it also turned out
that when -.25 was so "executed", it took the CPU into the power
down sequence, and it turned the machine off!
Not that I haven't done that sort of thing myself, but my favourite
one was a Tandem customer whose programmers had come from a different
system, and they knew that the correct way to terminate a program was
to jump to absolute location 0. And how about that, it worked!
One day we received a problem report that CPU 4 of their system would
reliably fail at 16:04 every day. We spent a long time puzzling over
it: there was kernel data corruption of a kind we had never seen
before. TL;DR: it seems that the jump to 0, in combination with a
kernel library bug, had interpreted the "instruction" at location 0 to
modify this particular location in kernel memory. More details at
http://www.lemis.com/grog/warstories/CPU-4-at-16-04.php
Greg
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