The other main microkernel provided service is interprocess communication, normally abbreviated to IPC. Much of the IPC in Mach-based operating systems is already abstracted away from the raw Mach_Msg interface by MIG, the Mach Interface Generator. It is similar in action to Sun's rpcgen program in that it takes a high level representation of services provided into client and server stubs which can be linked against by ordinary programs. The operating systems group at Utah have written Flick [#!flick!#] which is intended to provide a replacement for many different generators of this sort, including MIG and rpcgen.
I don't think it is worth investigating porting MIG to generate L4 calls, since Flick would provide a much better basis for emulating Mach-style IPC. Flick generates code that is `between 2 and 17 times faster' [#!flick!#] than other generators. Flick already supports interface descriptions written in CORBA, ONC RPC and MIG, and will generate stubs for IIOP, ONC/TCP, Mach ports or Fluke IPC. The authors claim that it is extremely flexible and extensible so it should not be hard to provide a back end that generates L4 calls.