11 Nov
2020
11 Nov
'20
2:03 a.m.
Dave Horsfall <dave(a)horsfall.org> writes:
On Wed, 11 Nov 2020, Greg 'groggy' Lehey
wrote:
Wow... you too... Back in the late 1980s or early 1990s I removed a
time bomb from a language compiler running on a Data General MV/10000
with AOS/VS as the OS while an undergrad. This particular bomb,
apparently, was put in by a disgruntled employee of the company that
provided the compiler, as I received the story. I honestly don't know
many of the details, beyond that. The effort required that I
disassemble the compiler with a assembly debugger and then patch the
machine code to defeat the bomb. I seem to remember that I just patched
out a jump instruction with a nop or two. I have mostly forgotten what
the compiler was for, but it may have been the commercial Simscript
compiler for the DG. We, that is myself and one of the professors, sent
the patch to the company that provided the compiler and I know that they
ended up giving the patch out as another university with the same bomb
problem sent me a thank you note. The only other work around was to set
the clock back on the system, as it literally was a time based bomb.
--
Brad Spencer - brad(a)anduin.eldar.org - KC8VKS - http://anduin.eldar.org
I'm currently reviewing a paper about Unix
and Linux, and I made the
comment that in the olden days the normal way to build an OS image for a
big computer was from source. Now I've been asked for a reference, and
I can't find one! Can anybody help?
Depends what you mean by "olden days" and "big computer". As I
recall we
(Uni of NSW) had the source to the 360/50 and the Cyber 72, but not for
the VMS stuff; binaries were patched with IEBUPDTE and later on SUPERZAP
(possibly written locally).
I got an official pat on the back for getting SPITBOL to work after its
time-bombs (yes, plural) expired[*]...
And we had the source to something called Unix Edition 5 & 6 etc, but they
were hardly mainframes :-)
[*]
The first bomb failed with an error message, so I patched that. It then
started crashing rather mysteriously, and I discovered that it was taking
an indirect jump to whatever was in R0 at the time (I think). Rather than
waste time digging them all out, I wrote a program that LOADed the binary,
scanned memory for a word that matched that date, and printed each address
so they could then be inspected by hand. There were something like six of
them... One big SUPERZAP later, and we had a working SPITBOL compiler
again; a bored CompSci student is terrible to behold.
-- Dave
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