/* kernel_thread.S: kernel thread creation
   *
   * Copyright (C) 2003 Red Hat, Inc. All Rights Reserved.
   * Written by David Howells (dhowells@redhat.com)
   *
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of the GNU General Public License
   * as published by the Free Software Foundation; either version
   * 2 of the License, or (at your option) any later version.
   */
  
  #include <linux/linkage.h>
  #include <asm/unistd.h>
  
  #define CLONE_VM	0x00000100	/* set if VM shared between processes */
  #define	KERN_ERR	"<3>"
  
  	.section .rodata
  kernel_thread_emsg:
  	.asciz	KERN_ERR "failed to create kernel thread: error=%d
  "
  
  	.text
  	.balign		4
  
  ###############################################################################
  #
  # Create a kernel thread
  #
  # int kernel_thread(int (*fn)(void *), void * arg, unsigned long flags)
  #
  ###############################################################################
  	.globl		kernel_thread
  	.type		kernel_thread,@function
  kernel_thread:
  	or.p		gr8,gr0,gr4
  	or		gr9,gr0,gr5
  
  	# start by forking the current process, but with shared VM
  	setlos.p	#__NR_clone,gr7		; syscall number
  	ori		gr10,#CLONE_VM,gr8	; first syscall arg	[clone_flags]
  	sethi.p		#0xe4e4,gr9		; second syscall arg	[newsp]
  	setlo		#0xe4e4,gr9
  	setlos.p	#0,gr10			; third syscall arg	[parent_tidptr]
  	setlos		#0,gr11			; fourth syscall arg	[child_tidptr]
  	tira		gr0,#0
  	setlos.p	#4095,gr7
  	andcc		gr8,gr8,gr0,icc0
  	addcc.p		gr8,gr7,gr0,icc1
  	bnelr		icc0,#2
  	bc		icc1,#0,kernel_thread_error
  
  	# now invoke the work function
  	or		gr5,gr0,gr8
  	calll		@(gr4,gr0)
  
  	# and finally exit the thread
  	setlos		#__NR_exit,gr7		; syscall number
  	tira		gr0,#0
  
  kernel_thread_error:
  	subi		sp,#8,sp
  	movsg		lr,gr4
  	sti		gr8,@(sp,#0)
  	sti.p		gr4,@(sp,#4)
  
  	or		gr8,gr0,gr9
  	sethi.p		%hi(kernel_thread_emsg),gr8
  	setlo		%lo(kernel_thread_emsg),gr8
  
  	call		printk
  
  	ldi		@(sp,#4),gr4
  	ldi		@(sp,#0),gr8
  	subi		sp,#8,sp
  	jmpl		@(gr4,gr0)
  
  	.size		kernel_thread,.-kernel_thread