[SPARC64]: Fix show_stack() when stack argument is NULL.

It didn't handle that case at all, and now dump_stack()
can be implemented directly as show_stack(current, NULL)

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

arch/sparc64/kernel/traps.c

diff --git a/arch/sparc64/kernel/traps.c b/arch/sparc64/kernel/traps.c
index 6ef2d29..6ef42b8 100644
--- a/arch/sparc64/kernel/traps.c
+++ b/arch/sparc64/kernel/traps.c
@@ -2134,12 +2134,20 @@
 void show_stack(struct task_struct *tsk, unsigned long *_ksp)
 {
 	unsigned long pc, fp, thread_base, ksp;
-	void *tp = task_stack_page(tsk);
+	struct thread_info *tp;
 	struct reg_window *rw;
 	int count = 0;
 
 	ksp = (unsigned long) _ksp;
-
+	if (!tsk)
+		tsk = current;
+	tp = task_thread_info(tsk);
+	if (ksp == 0UL) {
+		if (tsk == current)
+			asm("mov %%fp, %0" : "=r" (ksp));
+		else
+			ksp = tp->ksp;
+	}
 	if (tp == current_thread_info())
 		flushw_all();
 
@@ -2168,11 +2176,7 @@
 
 void dump_stack(void)
 {
-	unsigned long *ksp;
-
-	__asm__ __volatile__("mov	%%fp, %0"
-			     : "=r" (ksp));
-	show_stack(current, ksp);
+	show_stack(current, NULL);
 }
 
 EXPORT_SYMBOL(dump_stack);