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 63bca794c8f..73d9b2c0e21 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.