From mboxrd@z Thu Jan 1 00:00:00 1970 From: brad at anduin.eldar.org (Brad Spencer) Date: Tue, 10 Nov 2020 21:03:15 -0500 Subject: [COFF] Building OS from source in the olden days In-Reply-To: (message from Dave Horsfall on Wed, 11 Nov 2020 12:01:40 +1100 (EST)) Message-ID: Dave Horsfall writes: > On Wed, 11 Nov 2020, Greg 'groggy' Lehey wrote: > >> 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 > _______________________________________________ > COFF mailing list > COFF at minnie.tuhs.org > https://minnie.tuhs.org/cgi-bin/mailman/listinfo/coff 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 at anduin.eldar.org - KC8VKS - http://anduin.eldar.org