i386/sys/vfork.s

   1 /*
   2  * Copyright (c) 1999-2003 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. Please obtain a copy of the License at
  10  * http://www.opensource.apple.com/apsl/ and read it before using this
  11  * file.
  12  *
  13  * The Original Code and all software distributed under the License are
  14  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  15  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  16  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  18  * Please see the License for the specific language governing rights and
  19  * limitations under the License.
  20  *
  21  * @APPLE_LICENSE_HEADER_END@
  22  */
  23 /*
  24  * Copyright (c) 1995 NeXT Computer, Inc. All Rights Reserved
  25  */
  26 #include "SYS.h"
  27
  28 #if defined(__DYNAMIC__)
  29 #define GET_CURRENT_PID PICIFY(__current_pid)
  30
  31         NON_LAZY_STUB(__current_pid)
  32 #define __current_pid   (%edx)
  33 #else
  34 #define GET_CURRENT_PID
  35 #endif
  36
  37 /*
  38  * If __current_pid >= 0, we want to put a -1 in there
  39  * otherwise we just decrement it
  40  */
  41
  42 LEAF(_vfork, 0)
  43         GET_CURRENT_PID
  44         movl            __current_pid, %eax
  45 0:
  46         xorl            %ecx, %ecx
  47         testl           %eax, %eax
  48         cmovs           %eax, %ecx
  49         decl            %ecx
  50         lock
  51         cmpxchgl        %ecx, __current_pid
  52         jne             0b
  53         popl            %ecx
  54         movl            $(SYS_vfork), %eax      // code for vfork -> eax
  55         UNIX_SYSCALL_TRAP                       // do the system call
  56         jnb             L1                      // jump if CF==0
  57         GET_CURRENT_PID
  58         lock
  59         incl            __current_pid
  60         pushl           %ecx
  61         BRANCH_EXTERN(cerror)
  62
  63 L1:
  64         testl           %edx, %edx              // CF=OF=0,  ZF set if zero result
  65         jz              L2                      // parent, since r1 == 0 in parent, 1 in child
  66         xorl            %eax, %eax              // zero eax
  67         jmp             *%ecx
  68
  69 L2:
  70         GET_CURRENT_PID
  71         lock
  72         incl            __current_pid
  73         jmp             *%ecx