include/mach-o/dyld-interposing.h

   1 /*
   2  * Copyright (c) 2005-2008 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 #if !defined(_DYLD_INTERPOSING_H_)
  25 #define _DYLD_INTERPOSING_H_
  26
  27 /*
  28  *  Example:
  29  *
  30  *  static
  31  *  int
  32  *  my_open(const char* path, int flags, mode_t mode)
  33  *  {
  34  *    int value;
  35  *    // do stuff before open (including changing the arguments)
  36  *    value = open(path, flags, mode);
  37  *    // do stuff after open (including changing the return value(s))
  38  *    return value;
  39  *  }
  40  *  DYLD_INTERPOSE(my_open, open)
  41  */
  42
  43 #define DYLD_INTERPOSE(_replacement,_replacee) \
  44    __attribute__((used)) static struct{ const void* replacement; const void* replacee; } _interpose_##_replacee \
  45             __attribute__ ((section ("__DATA,__interpose"))) = { (const void*)(unsigned long)&_replacement, (const void*)(unsigned long)&_replacee };
  46
  47 #endif