Write to QEMU guest system registers & memory?

Question

How do you write to the processor registers and specific memory addresses of a virtual system running in QEMU?

My desire would be to accomplish this from a user space p

Answer 1

GDB server within QEMU Monitor seems to be the best for your purpose. One of your options is implementing a gdb protocol, another one is driving gdb itself through its command line.

I've tested it a bit: attaching, reading and writing memory seems to work (I read what I write); jumping to another address seems to work too. (If you may call injected code, you can do anything, theoretically). Writing to text-mode video memory doesn't work (I don't even read what I wrote, and nothing changes on display).