x86, 64-bit: Move kernel_thread to C

Prepare for merging with 32-bit.

Signed-off-by: Brian Gerst <brgerst@gmail.com>
LKML-Reference: <1260380084-3707-2-git-send-email-brgerst@gmail.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

1 files changed, 3 insertions, 46 deletions

diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index 63bca794c8f9..73d9b2c0e217 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -1166,63 +1166,20 @@ bad_gs:
 	jmp  2b
 	.previous
 
-/*
- * Create a kernel thread.
- *
- * C extern interface:
- *	extern long kernel_thread(int (*fn)(void *), void * arg, unsigned long flags)
- *
- * asm input arguments:
- *	rdi: fn, rsi: arg, rdx: flags
- */
-ENTRY(kernel_thread)
-	CFI_STARTPROC
-	FAKE_STACK_FRAME $child_rip
-	SAVE_ALL
-
-	# rdi: flags, rsi: usp, rdx: will be &pt_regs
-	movq %rdx,%rdi
-	orq  kernel_thread_flags(%rip),%rdi
-	movq $-1, %rsi
-	movq %rsp, %rdx
-
-	xorl %r8d,%r8d
-	xorl %r9d,%r9d
-
-	# clone now
-	call do_fork
-	movq %rax,RAX(%rsp)
-	xorl %edi,%edi
-
-	/*
-	 * It isn't worth to check for reschedule here,
-	 * so internally to the x86_64 port you can rely on kernel_thread()
-	 * not to reschedule the child before returning, this avoids the need
-	 * of hacks for example to fork off the per-CPU idle tasks.
-	 * [Hopefully no generic code relies on the reschedule -AK]
-	 */
-	RESTORE_ALL
-	UNFAKE_STACK_FRAME
-	ret
-	CFI_ENDPROC
-END(kernel_thread)
-
-ENTRY(child_rip)
+ENTRY(kernel_thread_helper)
 	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.
 	 */
-	movq %rdi, %rax
-	movq %rsi, %rdi
-	call *%rax
+	call *%rsi
 	# exit
 	mov %eax, %edi
 	call do_exit
 	ud2			# padding for call trace
 	CFI_ENDPROC
-END(child_rip)
+END(kernel_thread_helper)
 
 /*
  * execve(). This function needs to use IRET, not SYSRET, to set up all state properly.