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   1 /* kernel_thread.S: kernel thread creation
   2  *
   3  * Copyright (C) 2003 Red Hat, Inc. All Rights Reserved.
   4  * Written by David Howells (dhowells@redhat.com)
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public License
   8  * as published by the Free Software Foundation; either version
   9  * 2 of the License, or (at your option) any later version.
  10  */
  11
  12 #include <linux/linkage.h>
  13 #include <asm/unistd.h>
  14
  15 #define CLONE_VM        0x00000100      /* set if VM shared between processes */
  16 #define KERN_ERR        "<3>"
  17
  18         .section .rodata
  19 kernel_thread_emsg:
  20         .asciz  KERN_ERR "failed to create kernel thread: error=%d\n"
  21
  22         .text
  23         .balign         4
  24
  25 ###############################################################################
  26 #
  27 # Create a kernel thread
  28 #
  29 # int kernel_thread(int (*fn)(void *), void * arg, unsigned long flags)
  30 #
  31 ###############################################################################
  32         .globl          kernel_thread
  33         .type           kernel_thread,@function
  34 kernel_thread:
  35         or.p            gr8,gr0,gr4
  36         or              gr9,gr0,gr5
  37
  38         # start by forking the current process, but with shared VM
  39         setlos.p        #__NR_clone,gr7         ; syscall number
  40         ori             gr10,#CLONE_VM,gr8      ; first syscall arg     [clone_flags]
  41         sethi.p         #0xe4e4,gr9             ; second syscall arg    [newsp]
  42         setlo           #0xe4e4,gr9
  43         setlos.p        #0,gr10                 ; third syscall arg     [parent_tidptr]
  44         setlos          #0,gr11                 ; fourth syscall arg    [child_tidptr]
  45         tira            gr0,#0
  46         setlos.p        #4095,gr7
  47         andcc           gr8,gr8,gr0,icc0
  48         addcc.p         gr8,gr7,gr0,icc1
  49         bnelr           icc0,#2
  50         bc              icc1,#0,kernel_thread_error
  51
  52         # now invoke the work function
  53         or              gr5,gr0,gr8
  54         calll           @(gr4,gr0)
  55
  56         # and finally exit the thread
  57         setlos          #__NR_exit,gr7          ; syscall number
  58         tira            gr0,#0
  59
  60 kernel_thread_error:
  61         subi            sp,#8,sp
  62         movsg           lr,gr4
  63         sti             gr8,@(sp,#0)
  64         sti.p           gr4,@(sp,#4)
  65
  66         or              gr8,gr0,gr9
  67         sethi.p         %hi(kernel_thread_emsg),gr8
  68         setlo           %lo(kernel_thread_emsg),gr8
  69
  70         call            printk
  71
  72         ldi             @(sp,#4),gr4
  73         ldi             @(sp,#0),gr8
  74         subi            sp,#8,sp
  75         jmpl            @(gr4,gr0)
  76
  77         .size           kernel_thread,.-kernel_thread