Building self-debuggable system on L4?

[Derek Peschel]

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