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 #include <TargetConditionals.h>
  27
  28 #if TARGET_IPHONE_SIMULATOR
  29 extern pid_t (*_host_fork)(void);
  30 #else
  31 extern pid_t __fork(void);
  32 #endif
  33
  34 static void (*_libSystem_atfork_prepare)(void) = 0;
  35 static void (*_libSystem_atfork_parent)(void) = 0;
  36 static void (*_libSystem_atfork_child)(void) = 0;
  37
  38 #if !TARGET_IPHONE_SIMULATOR
  39 __private_extern__
  40 #endif
  41 void _libc_fork_init(void (*prepare)(void), void (*parent)(void), void (*child)(void))
  42 {
  43         _libSystem_atfork_prepare = prepare;
  44         _libSystem_atfork_parent = parent;
  45         _libSystem_atfork_child = child;
  46 }
  47
  48 /*
  49  * fork stub
  50  */
  51 pid_t
  52 fork(void)
  53 {
  54         int ret;
  55
  56         _libSystem_atfork_prepare();
  57         // Reader beware: this __fork() call is yet another wrapper around the actual syscall
  58         // and lives inside libsyscall. The fork syscall needs some cuddling by asm before it's
  59         // allowed to see the big wide C world.
  60 #if TARGET_IPHONE_SIMULATOR
  61         // _host_fork is yet another layer of wrapping that lives in the simulator's libSystem
  62         ret = _host_fork();
  63 #else
  64         ret = __fork();
  65 #endif
  66         if (-1 == ret)
  67         {
  68                 // __fork already set errno for us
  69                 _libSystem_atfork_parent();
  70                 return ret;
  71         }
  72
  73         if (0 == ret)
  74         {
  75                 // We're the child in this part.
  76                 _libSystem_atfork_child();
  77                 return 0;
  78         }
  79
  80         _libSystem_atfork_parent();
  81         return ret;
  82 }
  83