user-level port

Andreas Rottmann a.rottmann at
Tue Jun 25 21:38:49 CEST 2002

Michael Hohmuth <hohmuth at> writes:

> Andreas Rottmann <a.rottmann at> writes:
> > I have read on the Fiasco homepage that Fiasco is beeing/was ported to
> > run as a user-level process under Unix. What is the state of this
> > project? 
> This project is well underway.  User-mode Fiasco (Fiasco/UX) works on
> Linux, runs nearly unmodified versions of Sigma0 and Rmgr, and runs
> virtually unmodified simple L4 programs such as the ping-pong IPC
> benchmark.

> It still lacks a number of features that would make it really useful,
> such as some pseudo device drivers that would enable L4Linux to run on
> top of it.
I plan to extend my programming knowledge/experience in the OS
area. Thus I'm interested in helping in that area, altough I must
admit that I have little experience with kernel/OS programming. I plan
to walk through the relevant docs and finally join the people doing
the Hurd/L4 port.

> Fiasco/UX's main developer, Udo Steinberg, currently is on a vacation;
> he will be back in August.  When he returns, he will write a term
> paper about it, explaining its architecture in detail.
I look forward to that. :-)

> Udo chose to use a different route, similar to the one used by
> User-mode Linux: Fiasco/UX uses ptrace(2) to control user binaries,
> allowing unmodified L4 binaries to run on top of it.  Inside the
> ``kernel,'' Fiasco/UX emulates i386 instructions _after_ they occurred
> (that is, in a signal handler), not _before_ (i.e., at the API level,
> as with a386).  This design allows us to debug even machine-specific
> low-level code under Unix.
This, of course, can be quite valuable and quite worth the performance
hit (which will be minor, I think), I guess.

Regards, Andy
Andreas Rottmann         | Dru at ICQ        | 118634484 at ICQ | a.rottmann at | GnuPG Key:
Fingerprint              | DFB4 4EB4 78A4 5EEE 6219  F228 F92F CFC5 01FD 5B62

More information about the l4-hackers mailing list