With the goal of centralizing all tests in the system, this is a
first step to establish a Tests sub-tree. It will contain all of
the unit tests and test harnesses for the various components in the
system.
This patch fixes some issues with the mmap() and mprotect() syscalls,
neither of whom were checking the permission bits of the underlying
files when mapping an inode MAP_SHARED.
This made it possible to subvert execution of any running program
by simply memory-mapping its executable and replacing some of the code.
Test: Kernel/mmap-write-into-running-programs-executable-file.cpp