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>
diff --git a/arch/sparc64/kernel/smp.c b/arch/sparc64/kernel/smp.c
index 409dd71..8face0c 100644
--- a/arch/sparc64/kernel/smp.c
+++ b/arch/sparc64/kernel/smp.c
@@ -910,6 +910,9 @@
 extern unsigned long xcall_report_regs;
 extern unsigned long xcall_receive_signal;
 extern unsigned long xcall_new_mmu_context_version;
+#ifdef CONFIG_KGDB
+extern unsigned long xcall_kgdb_capture;
+#endif
 
 #ifdef DCACHE_ALIASING_POSSIBLE
 extern unsigned long xcall_flush_dcache_page_cheetah;
@@ -1079,6 +1082,13 @@
 	smp_cross_call(&xcall_new_mmu_context_version, 0, 0, 0);
 }
 
+#ifdef CONFIG_KGDB
+void kgdb_roundup_cpus(unsigned long flags)
+{
+	smp_cross_call(&xcall_kgdb_capture, 0, 0, 0);
+}
+#endif
+
 void smp_report_regs(void)
 {
 	smp_cross_call(&xcall_report_regs, 0, 0, 0);