x86, pkeys: add self-tests

From: Dave Hansen <dave.hansen@linux.intel.com>

This code should be a good demonstration of how to use the new
system calls as well as how to use protection keys in general.

This code shows how to:
1. Manipulate the Protection Keys Rights User (PKRU) register with
   sys_pkey_get/set()
2. Set a protection key on memory
3. Fetch and/or modify PKRU from the signal XSAVE state
4. Read the kernel-provided protection key in the siginfo
5. Set up an execute-only mapping

There are currently 13 tests:

        test_read_of_write_disabled_region
        test_read_of_access_disabled_region
        test_write_of_write_disabled_region
        test_write_of_access_disabled_region
        test_kernel_write_of_access_disabled_region
        test_kernel_write_of_write_disabled_region
        test_kernel_gup_of_access_disabled_region
        test_kernel_gup_write_to_write_disabled_region
        test_executing_on_unreadable_memory
        test_ptrace_of_child
        test_pkey_syscalls_on_non_allocated_pkey
        test_pkey_syscalls_bad_args
	test_pkey_alloc_exhaust

Each of the tests is run with plain memory (via mmap(MAP_ANON)),
transparent huge pages, and hugetlb.

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: shuahkh@osg.samsung.com
Cc: linux-api@vger.kernel.org
Cc: linux-mm@kvack.org
Cc: x86@kernel.org
Cc: torvalds@linux-foundation.org
Cc: akpm@linux-foundation.org
3 files changed