Too bad that has it's own issues. Android/Google definitely has the clout to be able to call the shots (ie force the processor manufacturer to issue them a CA cert for their own use), but what would happen if ARM then became a dominant server arch?

Also, putting code signing in the processor wouldn't fix the problem: code signing already happens in higher levels (ie higher than userland), so moving the verification a level up would likely take the exploitable bugs with it. The problem remains.