x86, 32-bit: Use same regs as 64-bit for kernel_thread_helper

The arg should be in %eax, but that is clobbered by the return value
of clone.  The function pointer can be in any register.  Also, don't
push args onto the stack, since regparm(3) is the normal calling
convention now.
Signed-off-by: Brian Gerst <brgerst@gmail.com>
LKML-Reference: <1260380084-3707-4-git-send-email-brgerst@gmail.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

arch/x86/kernel/entry_32.S

@@ -1047,12 +1047,8 @@ END(spurious_interrupt_bug)
 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
+	movl %edi,%eax
+	call *%esi
 	call do_exit
 	ud2			# padding for call trace
 	CFI_ENDPROC

arch/x86/kernel/process_32.c

@@ -193,8 +193,8 @@ void show_regs(struct pt_regs *regs)
 }
 
 /*
- * This gets run with %bx containing the
- * function to call, and %dx containing
+ * This gets run with %si containing the
+ * function to call, and %di containing
  * the "args".
  */
 extern void kernel_thread_helper(void);
@@ -208,8 +208,8 @@ int kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
 
 	memset(&regs, 0, sizeof(regs));
 
-	regs.bx = (unsigned long) fn;
-	regs.dx = (unsigned long) arg;
+	regs.si = (unsigned long) fn;
+	regs.di = (unsigned long) arg;
 
 	regs.ds = __USER_DS;
 	regs.es = __USER_DS;