sparc: Add kgdb support.

Current limitations:

1) On SMP single stepping has some fundamental issues,
   shared with other sw single-step architectures such
   as mips and arm.

2) On 32-bit sparc we don't support SMP kgdb yet.  That
   requires some reworking of the IPI mechanisms and
   infrastructure on that platform.

Signed-off-by: David S. Miller <davem@davemloft.net>

include/asm-sparc/head.h

@@ -52,6 +52,17 @@
 	nop; \
 	nop;
 
+#ifdef CONFIG_KGDB
+#define KGDB_TRAP(num) \
+	b kgdb_trap_low; \
+	rd %psr,%l0; \
+	nop; \
+	nop;
+#else
+#define KGDB_TRAP(num) \
+	BAD_TRAP(num)
+#endif
+
 /* The Get Condition Codes software trap for userland. */
 #define GETCC_TRAP \
         b getcc_trap_handler; mov %psr, %l0; nop; nop;