i386: move kernel_thread_helper into entry.S

And add proper CFI annotation to it which was previously
impossible. This prevents "stuck" messages by the dwarf2 unwinder
when reaching the top of a kernel stack.

Includes feedback from Jan Beulich

Cc: jbeulich@novell.com
Signed-off-by: Andi Kleen <ak@suse.de>

---
 arch/i386/kernel/entry.S   |   13 +++++++++++++
 arch/i386/kernel/process.c |    9 ---------
 2 files changed, 13 insertions(+), 9 deletions(-)

Index: linux/arch/i386/kernel/entry.S
===================================================================
--- linux.orig/arch/i386/kernel/entry.S
+++ linux/arch/i386/kernel/entry.S
@@ -946,6 +946,19 @@ ENTRY(arch_unwind_init_running)
 ENDPROC(arch_unwind_init_running)
 #endif
 
+ENTRY(kernel_thread_helper)
+	pushl $0		# fake return address for unwinder
+	CFI_STARTPROC
+	movl %edx,%eax
+	push %edx
+	CFI_ADJUST_CFA_OFFSET 4
+	call *%ebx
+	push %eax
+	CFI_ADJUST_CFA_OFFSET 4
+	call do_exit
+	CFI_ENDPROC
+ENDPROC(kernel_thread_helper)
+
 .section .rodata,"a"
 #include "syscall_table.S"
 
Index: linux/arch/i386/kernel/process.c
===================================================================
--- linux.orig/arch/i386/kernel/process.c
+++ linux/arch/i386/kernel/process.c
@@ -321,15 +321,6 @@ void show_regs(struct pt_regs * regs)
  * the "args".
  */
 extern void kernel_thread_helper(void);
-__asm__(".section .text\n"
-	".align 4\n"
-	"kernel_thread_helper:\n\t"
-	"movl %edx,%eax\n\t"
-	"pushl %edx\n\t"
-	"call *%ebx\n\t"
-	"pushl %eax\n\t"
-	"call do_exit\n"
-	".previous");
 
 /*
  * Create a kernel thread