[PATCH] x86_64: Add kernel thread stack frame termination for properly stopping stack unwinds.

One open question: Should these added pushes perhaps be made
conditional upon CONFIG_STACK_UNWIND or CONFIG_UNWIND_INFO?
[AK: Not needed -- these are all very slow paths]
Signed-off-by: NJan Beulich <jbeulich@novell.com>
Signed-off-by: NAndi Kleen <ak@suse.de>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

arch/x86_64/kernel/entry.S

@@ -973,6 +973,8 @@ ENTRY(kernel_thread)
 ENDPROC(kernel_thread)
 	
 child_rip:
+	pushq $0		# fake return address
+	CFI_STARTPROC
 	/*
 	 * Here we are in the child and the registers are set as they were
 	 * at kernel_thread() invocation in the parent.
@@ -983,6 +985,7 @@ child_rip:
 	# exit
 	xorl %edi, %edi
 	call do_exit
+	CFI_ENDPROC
 ENDPROC(child_rip)
 
 /*

arch/x86_64/kernel/head.S

@@ -191,6 +191,7 @@ startup_64:
 	 * jump
 	 */
 	movq	initial_code(%rip),%rax
+	pushq	$0		# fake return address
 	jmp	*%rax
 
 	/* SMP bootup changes these two */