It's not that hard to emulate the basic Linux system calls. If you have the user mode compiler and libc running, then you can get simple console applications up

It's not that hard to emulate the basic Linux system calls. If you have the user mode compiler and libc running, then you can get simple console applications up and running in a day or two. Having looked at qemu a bit, it feels like a bigger undertaking to understand the qemu internals enough to start modifying it. But if you can run qemu as-is, the core kernel is not that big if you have a very limited set of HW support and don't implement the more complicated system calls.