diff --git a/arch/sparc64/lib/mcount.S b/arch/sparc64/lib/mcount.S
index 7735a7a..734caf0 100644
--- a/arch/sparc64/lib/mcount.S
+++ b/arch/sparc64/lib/mcount.S
@@ -48,12 +48,23 @@
 	sub		%g3, STACK_BIAS, %g3
 	cmp		%sp, %g3
 	bg,pt		%xcc, 1f
-	 sethi		%hi(panicstring), %g3
+	 nop
+	/* If we are already on ovstack, don't hop onto it
+	 * again, we are already trying to output the stack overflow
+	 * message.
+	 */
 	sethi		%hi(ovstack), %g7		! cant move to panic stack fast enough
 	 or		%g7, %lo(ovstack), %g7
-	add		%g7, OVSTACKSIZE, %g7
+	add		%g7, OVSTACKSIZE, %g3
+	sub		%g3, STACK_BIAS + 192, %g3
 	sub		%g7, STACK_BIAS, %g7
-	mov		%g7, %sp
+	cmp		%sp, %g7
+	blu,pn		%xcc, 2f
+	 cmp		%sp, %g3
+	bleu,pn		%xcc, 1f
+	 nop
+2:	mov		%g3, %sp
+	sethi		%hi(panicstring), %g3
 	call		prom_printf
 	 or		%g3, %lo(panicstring), %o0
 	call		prom_halt