KAISER: hiding the kernel from user space

Yes, this could be done, at least theoretically. But, the contexts where we have to decide to "do KAISER" or not are very tricky. We don't have a stack and don't have registers to clobber, so it's tricky to pull off.

You would essentially need to keep a bit of per-cpu data that was consulted very early in assembly at kernel entry. It would have to be updated at every context switch, probably from some flag in the task_struct. Again, doable, but far from trivial.