[PATCH] xen: x86_64: Add macro for debugreg

Add 2 macros to set and get debugreg on x86_64.  This is useful for Xen
because it will need only to redefine each macro to a hypervisor call.

Signed-off-by: Vincent Hanquez <vincent.hanquez@cl.cam.ac.uk>
Cc: Ian Pratt <m+Ian.Pratt@cl.cam.ac.uk>
Cc: Andi Kleen <ak@muc.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/arch/x86_64/kernel/signal.c b/arch/x86_64/kernel/signal.c
index 3c5f308..0446e8b 100644
--- a/arch/x86_64/kernel/signal.c
+++ b/arch/x86_64/kernel/signal.c
@@ -439,7 +439,7 @@
 		 * inside the kernel.
 		 */
 		if (current->thread.debugreg7)
-			asm volatile("movq %0,%%db7"	: : "r" (current->thread.debugreg7));
+			set_debugreg(current->thread.debugreg7, 7);
 
 		/* Whee!  Actually deliver the signal.  */
 		return handle_signal(signr, &info, &ka, oldset, regs);