When you say arbitrary code what do you mean? Are you wanting to put backend specific code there or a common post-amble of tcg ops? Can you give a bit more detail about your use case?
I'm trying to add a clock-synchronization library so that I can have two (or more) instances of QEMU run in a synchronized (deterministic) fashion. The "arbitrary code" is more or less a function call (i.e., callq) instruction to a function that uses shared semaphores to block execution.
Jack
