This patch makes it possible to make memory regions non-readable. This is enforced using the "present" bit in the page tables. A process that hits an not-present page fault in a non-readable region will be crashed.
Processes will now crash with SIGSEGV if they attempt making a syscall from PROT_WRITE memory. This neat idea comes from OpenBSD. :^)
It ain't much, but it's honest work!
