Someone in Russia was working on a source-level debugger for L4, I noticed, but I didn't see much else in the list archives relating to my question. (I searched for "[Dd]ebug" in the subject lines.)
Has anyone investigated L4 as a foundation for interactive application and OS debugging? On UNIX (which I am most familiar with) program debugging is easy enough but kernel debugging is very disruptive. It would be interesting to see a system allowing most of itself to be changed while, in some sense e.g. for other tasks, it continues to run. Is L4 suited to building a system like that? What if portability was also a goal?
L4 has jdb/kdb, but they stop the microkernel as I recall. However, that may not be a problem in my case. Ideally L4 would be small enough, and bug-free, so that my hypothetical new OS would never need to affect L4 proper.
-- Derek