[Qemu-devel] Developing new user-level target?

[Patrick Mackinlay]

In searching across the net, I've managed to stumble across QEMU, which may 
be the best starting point for a project I have in mind. I'd like some 
feedback on the difficulty of doing what I propose, or if there are any more 
appropriate systems that people are aware of that may better satisfy my 
requirements.

Essentially, I have an interest in some older (mid to late 80's) UNIX 
computer systems. The one I'm particularly interested in used the CLIPPER 
processor (one of the first fully commercialised RISC CPUs) and a version of 
SVR3 named CLIX.

I'm interested in adding support for this system to QEMU. In the first 
instance, I'd like to get a user-level target working. Without having looked 
at any of the source yet, can someone comment on the difficulty of adding 
support for a new CPU? Following that, my next biggest concern is supporting 
not only the COFF executable format (does QEMU support only ELF at the 
moment?), but the translation from the native to Linux system calls.

As a final complexity, I'd like to (eventually) host all this on Windows - 
either natively under Win32, or more probably under the Interix subsystem 
included in Microsoft's Services For Unix (SFU). Again, the question arises 
regarding the system call translation component - how much work is involved 
in adapting this to suit a different (although still UNIX) target and a 
non-Linux host?

BTW, before anyone asks, I'm specifically interested in the user-level 
target right now. Producing a full system level emulation is interesting, 
but I have almost no documentation of the other system hardware and I think 
it's going to be quite an exercise in reverse-engineering to figure out 
enough to write emulation code.

Regards,
Pat Mackinlay.