powerpc: BookE hardware watchpoint support

This patch implements support for HW based watchpoint via the
DBSR_DAC (Data Address Compare) facility of the BookE processors.

It does so by interfacing with the existing DABR breakpoint code
and adding the necessary bits and pieces for the new bits to
be properly set or cleared

Signed-off-by: Luis Machado <luisgpm@br.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
diff --git a/include/asm-powerpc/system.h b/include/asm-powerpc/system.h
index e6e25e2..d6648c143 100644
--- a/include/asm-powerpc/system.h
+++ b/include/asm-powerpc/system.h
@@ -110,6 +110,8 @@
 #endif
 
 extern int set_dabr(unsigned long dabr);
+extern void do_dabr(struct pt_regs *regs, unsigned long address,
+		    unsigned long error_code);
 extern void print_backtrace(unsigned long *);
 extern void show_regs(struct pt_regs * regs);
 extern void flush_instruction_cache(void);