[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>

arch/x86_64/kernel/signal.c

@@ -439,7 +439,7 @@ int do_signal(struct pt_regs *regs, sigset_t *oldset)
 		 * 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);

arch/x86_64/kernel/traps.c

@@ -669,7 +669,7 @@ asmlinkage void do_debug(struct pt_regs * regs, unsigned long error_code)
        }
 #endif
 
-	asm("movq %%db6,%0" : "=r" (condition));
+	get_debugreg(condition, 6);
 
 	if (notify_die(DIE_DEBUG, "debug", regs, condition, error_code,
 						SIGTRAP) == NOTIFY_STOP)
@@ -721,7 +721,7 @@ asmlinkage void do_debug(struct pt_regs * regs, unsigned long error_code)
 	info.si_addr = (void __user *)regs->rip;
 	force_sig_info(SIGTRAP, &info, tsk);	
 clear_dr7:
-	asm volatile("movq %0,%%db7"::"r"(0UL));
+	set_debugreg(0UL, 7);
 	return;
 
 clear_TF_reenable:

include/asm-x86_64/processor.h

@@ -280,6 +280,14 @@ struct thread_struct {
 	set_fs(USER_DS);							 \
 } while(0) 
 
+#define get_debugreg(var, register)				\
+		__asm__("movq %%db" #register ", %0"		\
+			:"=r" (var))
+#define set_debugreg(value, register)			\
+		__asm__("movq %0,%%db" #register		\
+			: /* no output */			\
+			:"r" (value))
+
 struct task_struct;
 struct mm_struct;