src/dyldLibSystemGlue.c

   1 /* -*- mode: C++; c-basic-offset: 4; tab-width: 4 -*-
   2  *
   3  * Copyright (c) 2009-2010 Apple Inc. All rights reserved.
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   7  * This file contains Original Code and/or Modifications of Original Code
   8  * as defined in and that are subject to the Apple Public Source License
   9  * Version 2.0 (the 'License'). You may not use this file except in
  10  * compliance with the License. Please obtain a copy of the License at
  11  * http://www.opensource.apple.com/apsl/ and read it before using this
  12  * file.
  13  *
  14  * The Original Code and all software distributed under the License are
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  24
  25 #include <Availability.h>
  26 #include <stddef.h>
  27 #include <TargetConditionals.h>
  28
  29
  30 //
  31 // This is the temporary private interface between libSystem.B.dylib and dyld
  32 //
  33
  34
  35 int          NXArgc = 0;
  36 const char** NXArgv = NULL;
  37 const char** environ = NULL;
  38 const char*  __progname = NULL;
  39
  40
  41
  42 //
  43 // Long ago, the compiler driver added -ldylib1.o to every dylib which caused a
  44 // __DATA,__dyld section to be added every dylib.  The new LINKEDIT format no longer requires
  45 // images to have a __DATA,__dyld section.  But until libdyld.dylib and dyld update
  46 // to some sort of vtable based interface, libdyld still needs a __DATA,__dyld section.
  47 // The code below adds that section.
  48 //
  49 struct __DATA__dyld {
  50         long                    lazy;
  51         void *lookup;
  52         // ProgramVars
  53         const void*             mh;
  54         int*                    NXArgcPtr;
  55         const char***   NXArgvPtr;
  56         const char***   environPtr;
  57         const char**    __prognamePtr;
  58 };
  59
  60 static volatile struct __DATA__dyld  myDyldSection __attribute__ ((section ("__DATA,__dyld")))
  61         = { 0, 0, NULL, &NXArgc, &NXArgv, &environ, &__progname };
  62
  63 #if __arm__ && TARGET_OS_OSX
  64 // <rdar://problem/8755380>
  65 // For historical reasons, gcc and llvm-gcc added -ldylib1.o to the link line of armv6
  66 // dylibs when targeting MacOSX (but not iOS).  clang cleans up that mistake, but doing
  67 // so would break the libdyld build.  Making _dyld_func_lookup weak,hidden means if
  68 // dylib1.o is used, it overrides this, otherwise this implementation is used.
  69 __attribute__((weak))
  70 #endif
  71 __attribute__((visibility("hidden")))
  72 int _dyld_func_lookup(const char* dyld_func_name, void **address)
  73 {
  74         // Cast lookup function here to resign from dyld's 0-discriminator to a real
  75         // function pointer if needed.
  76         int (*lookupFn)(const char*, void**) = myDyldSection.lookup;
  77         return lookupFn(dyld_func_name, address);
  78 }
  79
  80 #if TARGET_OS_IOS && !TARGET_OS_SIMULATOR
  81 __attribute__((visibility("hidden")))
  82 void setLookupFunc(void* ptr) {
  83     myDyldSection.lookup = ptr;
  84 }
  85 #endif