> I have started an attempt to get uml working on FreeBSD.
> int sc_fpstate __aligned(16);
> I'm not quite sure how to proceed at this point.
You might proceed by just ignoring the fp state for now. UML will mostly
work if it doesn't save and restore it.
As Hans-Joerg pointed out, you ought to make sure you know how to intercept
Linux system calls on FreeBSD.
I have heard conflicting information on how it reacts to an int 0x80 syscall.
One thing I've heard is that it will segfault the process, in which case you
can intercept system calls from the UML segfault handler.
If this isn't true, then I think you have to install your own syscall handlers
in the FreeBSD kernel for UML which implement some sort of upcall to UML.
The system call tracing facility is hopelessly inadequate for UML's needs.