sys/fork.c

   1 /*
   2  * Copyright (c) 2010 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 #include <sys/types.h>
  24 #include <sys/stat.h>
  25 #include <errno.h>
  26
  27 extern pid_t __fork(void);
  28 extern void _cthread_fork_prepare();
  29 extern void _cthread_fork_parent();
  30 extern void _cthread_fork_child();
  31
  32 static void (*_libSystem_atfork_prepare)(void) = 0;
  33 static void (*_libSystem_atfork_parent)(void) = 0;
  34 static void (*_libSystem_atfork_child)(void) = 0;
  35
  36 __private_extern__ void _libc_fork_init(void (*prepare)(void), void (*parent)(void), void (*child)(void))
  37 {
  38         _libSystem_atfork_prepare = prepare;
  39         _libSystem_atfork_parent = parent;
  40         _libSystem_atfork_child = child;
  41 }
  42
  43 /*
  44  * fork stub
  45  */
  46 pid_t
  47 fork(void)
  48 {
  49         int ret;
  50
  51         _libSystem_atfork_prepare();
  52         // Reader beware: this __fork() call is yet another wrapper around the actual syscall
  53         // and lives inside libsyscall. The fork syscall needs some cuddling by asm before it's
  54         // allowed to see the big wide C world.
  55         ret = __fork();
  56         if (-1 == ret)
  57         {
  58                 // __fork already set errno for us
  59                 _libSystem_atfork_parent();
  60                 return ret;
  61         }
  62
  63         if (0 == ret)
  64         {
  65                 // We're the child in this part.
  66                 _libSystem_atfork_child();
  67                 return 0;
  68         }
  69
  70         _libSystem_atfork_parent();
  71         return ret;
  72 }
  73