Merge branch 'x86/mpx' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 cpufeature and mpx updates from Peter Anvin:
 "This includes the basic infrastructure for MPX (Memory Protection
  Extensions) support, but does not include MPX support itself.  It is,
  however, a prerequisite for KVM support for MPX, which I believe will
  be pushed later this merge window by the KVM team.

  This includes moving the functionality in
  futex_atomic_cmpxchg_inatomic() into a new function in uaccess.h so it
  can be reused - this will be used by the final MPX patches.

  The actual MPX functionality (map management and so on) will be pushed
  in a future merge window, when ready"

* 'x86/mpx' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/intel/mpx: Remove unused LWP structure
  x86, mpx: Add MPX related opcodes to the x86 opcode map
  x86: replace futex_atomic_cmpxchg_inatomic() with user_atomic_cmpxchg_inatomic
  x86: add user_atomic_cmpxchg_inatomic at uaccess.h
  x86, xsave: Support eager-only xsave features, add MPX support
  x86, cpufeature: Define the Intel MPX feature flag

arch/x86/include/asm/uaccess.h

@@ -533,6 +533,98 @@ extern __must_check long strnlen_user(const char __user *str, long n);
 unsigned long __must_check clear_user(void __user *mem, unsigned long len);
 unsigned long __must_check __clear_user(void __user *mem, unsigned long len);
 
+extern void __cmpxchg_wrong_size(void)
+	__compiletime_error("Bad argument size for cmpxchg");
+
+#define __user_atomic_cmpxchg_inatomic(uval, ptr, old, new, size)	\
+({									\
+	int __ret = 0;							\
+	__typeof__(ptr) __uval = (uval);				\
+	__typeof__(*(ptr)) __old = (old);				\
+	__typeof__(*(ptr)) __new = (new);				\
+	switch (size) {							\
+	case 1:								\
+	{								\
+		asm volatile("\t" ASM_STAC "\n"				\
+			"1:\t" LOCK_PREFIX "cmpxchgb %4, %2\n"		\
+			"2:\t" ASM_CLAC "\n"				\
+			"\t.section .fixup, \"ax\"\n"			\
+			"3:\tmov     %3, %0\n"				\
+			"\tjmp     2b\n"				\
+			"\t.previous\n"					\
+			_ASM_EXTABLE(1b, 3b)				\
+			: "+r" (__ret), "=a" (__old), "+m" (*(ptr))	\
+			: "i" (-EFAULT), "q" (__new), "1" (__old)	\
+			: "memory"					\
+		);							\
+		break;							\
+	}								\
+	case 2:								\
+	{								\
+		asm volatile("\t" ASM_STAC "\n"				\
+			"1:\t" LOCK_PREFIX "cmpxchgw %4, %2\n"		\
+			"2:\t" ASM_CLAC "\n"				\
+			"\t.section .fixup, \"ax\"\n"			\
+			"3:\tmov     %3, %0\n"				\
+			"\tjmp     2b\n"				\
+			"\t.previous\n"					\
+			_ASM_EXTABLE(1b, 3b)				\
+			: "+r" (__ret), "=a" (__old), "+m" (*(ptr))	\
+			: "i" (-EFAULT), "r" (__new), "1" (__old)	\
+			: "memory"					\
+		);							\
+		break;							\
+	}								\
+	case 4:								\
+	{								\
+		asm volatile("\t" ASM_STAC "\n"				\
+			"1:\t" LOCK_PREFIX "cmpxchgl %4, %2\n"		\
+			"2:\t" ASM_CLAC "\n"				\
+			"\t.section .fixup, \"ax\"\n"			\
+			"3:\tmov     %3, %0\n"				\
+			"\tjmp     2b\n"				\
+			"\t.previous\n"					\
+			_ASM_EXTABLE(1b, 3b)				\
+			: "+r" (__ret), "=a" (__old), "+m" (*(ptr))	\
+			: "i" (-EFAULT), "r" (__new), "1" (__old)	\
+			: "memory"					\
+		);							\
+		break;							\
+	}								\
+	case 8:								\
+	{								\
+		if (!IS_ENABLED(CONFIG_X86_64))				\
+			__cmpxchg_wrong_size();				\
+									\
+		asm volatile("\t" ASM_STAC "\n"				\
+			"1:\t" LOCK_PREFIX "cmpxchgq %4, %2\n"		\
+			"2:\t" ASM_CLAC "\n"				\
+			"\t.section .fixup, \"ax\"\n"			\
+			"3:\tmov     %3, %0\n"				\
+			"\tjmp     2b\n"				\
+			"\t.previous\n"					\
+			_ASM_EXTABLE(1b, 3b)				\
+			: "+r" (__ret), "=a" (__old), "+m" (*(ptr))	\
+			: "i" (-EFAULT), "r" (__new), "1" (__old)	\
+			: "memory"					\
+		);							\
+		break;							\
+	}								\
+	default:							\
+		__cmpxchg_wrong_size();					\
+	}								\
+	*__uval = __old;						\
+	__ret;								\
+})
+
+#define user_atomic_cmpxchg_inatomic(uval, ptr, old, new)		\
+({									\
+	access_ok(VERIFY_WRITE, (ptr), sizeof(*(ptr))) ?		\
+		__user_atomic_cmpxchg_inatomic((uval), (ptr),		\
+				(old), (new), sizeof(*(ptr))) :		\
+		-EFAULT;						\
+})
+
 /*
  * movsl can be slow when source and dest are not both 8-byte aligned
  */