[PATCH] xen: x86: add macro for debugreg

Add 2 macros to set and get debugreg on x86.  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>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

include/asm-i386/processor.h

@@ -501,12 +501,16 @@ static inline void load_esp0(struct tss_struct *tss, struct thread_struct *threa
 } while (0)
 
 /*
- * This special macro can be used to load a debugging register
+ * These special macros can be used to get or set a debugging register
  */
-#define loaddebug(thread,register) \
-               __asm__("movl %0,%%db" #register  \
-                       : /* no output */ \
-                       :"r" ((thread)->debugreg[register]))
+#define get_debugreg(var, register)				\
+		__asm__("movl %%db" #register ", %0"		\
+			:"=r" (var))
+#define set_debugreg(value, register)			\
+		__asm__("movl %0,%%db" #register		\
+			: /* no output */			\
+			:"r" (value))
+
 
 /* Forward declaration, a strange C thing */
 struct task_struct;