I was part of the KSOS (later KSOS-11 and KSOS-32) team at LOGICON, which picked up a follow-on contract to use KSOS-11 in a true multi-level-secure production environment. Our target was SYSTEM_LOW as TOP SECRET.

Yes, we used that compiler for all the KSOS kernel and all the trusted user-space code.

KSOS-11 only ran on PDP-11/70, and it did use split I&D.

I have access to the KSOS-11 source code, and have been trying to rebuild that OS, BUT I haven't been able to find that Modula compiler.

KSOS-11 was a very small kernel, but there was a set of libraries that presented a UNIX system call interface, so it could run some PWB userspace tools, if they were re-compiled.

I'm using the term KSOS-11, as there was a follow-on project (KSOS-32) that ported the original PDP KSOS to 11/780. I wrote a completely new (simpler) scheduler, the bootstrap and memory management layer for that one.

And, for "reasons", the entire KSOS project at Logicon was shut down just a week or so after the first user login to KSOS-32.

KSOS-11 itself and some multi-level applications did ship to DoD customers, and it ran MLS applications for the Navy and USAFE.

--tep

ps. Jon was kind enough to remind me that we had corresponded about this in the past -and- to remind me to send to the list, and not just him :-)