x86/mpx, selftests: Add MPX self test

I've had this code for a while, but never submitted it upstream.  Now
that Skylake hardware is out in the wild, folks can actually run this
for real.  It tests the following:

	1. The MPX hardware is enabled by the kernel and doing what it
	   is supposed to
	2. The MPX management code is present and enabled in the kernel
	3. MPX Signal handling
	4. The MPX bounds table population code (on-demand population)
	5. The MPX bounds table unmapping code (kernel-initiated freeing
	   when unused)

This has also caught bugs in the XSAVE code because MPX state is
saved/restored with XSAVE.

I'm submitting it now because it would have caught the recent issues
with the compat_siginfo code not being properly augmented when new
siginfo state is added.

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave@sr71.net>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Shuah Khan <shuahkh@osg.samsung.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20160608172535.5B40B0EE@viggo.jf.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

tools/testing/selftests/x86/Makefile

@@ -5,7 +5,7 @@ include ../lib.mk
 .PHONY: all all_32 all_64 warn_32bit_failure clean
 
 TARGETS_C_BOTHBITS := single_step_syscall sysret_ss_attrs syscall_nt ptrace_syscall \
-			check_initial_reg_state sigreturn ldt_gdt iopl
+			check_initial_reg_state sigreturn ldt_gdt iopl mpx-mini-test
 TARGETS_C_32BIT_ONLY := entry_from_vm86 syscall_arg_fault test_syscall_vdso unwind_vdso \
 			test_FCMOV test_FCOMI test_FISTTP \
 			vdso_restorer

tools/testing/selftests/x86/mpx-debug.h

@@ -0,0 +1,14 @@
+#ifndef _MPX_DEBUG_H
+#define _MPX_DEBUG_H
+
+#ifndef DEBUG_LEVEL
+#define DEBUG_LEVEL 0
+#endif
+#define dprintf_level(level, args...) do { if(level <= DEBUG_LEVEL) printf(args); } while(0)
+#define dprintf1(args...) dprintf_level(1, args)
+#define dprintf2(args...) dprintf_level(2, args)
+#define dprintf3(args...) dprintf_level(3, args)
+#define dprintf4(args...) dprintf_level(4, args)
+#define dprintf5(args...) dprintf_level(5, args)
+
+#endif /* _MPX_DEBUG_H */