Index: kernel/arch/ppc64/src/asm.S
===================================================================
--- kernel/arch/ppc64/src/asm.S	(revision e32e092d6f8bed442ecc81b18af9ef323bc4e650)
+++ kernel/arch/ppc64/src/asm.S	(revision 566987b0b136c4a5e4c99b9659c683aa5122e984)
@@ -67,4 +67,8 @@
 	mr sp, r4
 	
+	# %r3 is defined to hold pcb_ptr - set it to 0
+
+	xor r3, r3, r3
+
 	# jump to userspace