src/dyldExceptions.c

   1 /* -*- mode: C++; c-basic-offset: 4; tab-width: 4 -*-
   2  *
   3  * Copyright (c) 2004-2011 Apple Inc. All rights reserved.
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   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 <stdlib.h>
  26 #include <string.h>
  27 #include <mach-o/loader.h>
  28 #include <unistd.h>
  29 #include <stdio.h>
  30 #include <stdbool.h>
  31 #include <stdarg.h>
  32 #include <pthread.h>
  33 #include <Availability.h>
  34 #include <mach-o/dyld_priv.h>
  35
  36 #include "dyldLibSystemInterface.h"
  37
  38
  39 extern void _ZN4dyld3logEPKcz(const char*, ...);
  40 extern struct LibSystemHelpers* _ZN4dyld17gLibSystemHelpersE;
  41
  42
  43 #if __LP64__
  44         #define LC_SEGMENT_COMMAND              LC_SEGMENT_64
  45         #define macho_header                    mach_header_64
  46         #define macho_segment_command   segment_command_64
  47         #define macho_section                   section_64
  48         #define getsectdatafromheader   getsectdatafromheader_64
  49 #else
  50         #define LC_SEGMENT_COMMAND              LC_SEGMENT
  51         #define macho_header                    mach_header
  52         #define macho_segment_command   segment_command
  53         #define macho_section                   section
  54 #endif
  55
  56
  57 //
  58 //  The standard versions of __cxa_get_globals*() from libstdc++-static.a cannot be used.
  59 //  On Mac OS X, they use keymgr which dyld does not implement.
  60 //  On iPhoneOS, they use pthread_key_create which dyld cannot use.
  61 //
  62 //   Implement these ourselves to make upcalls into libSystem to malloc and create a pthread key
  63 //
  64 static pthread_key_t                            sCxaKey = 0;
  65 static char                                                     sPreMainCxaGlobals[2*sizeof(long)];
  66
  67 // called by libstdc++.a
  68 char* __cxa_get_globals()
  69 {
  70         // if libSystem.dylib not yet initialized, or is old libSystem, use shared global
  71         if ( (_ZN4dyld17gLibSystemHelpersE == NULL) || (_ZN4dyld17gLibSystemHelpersE->version < 7) )
  72                 return sPreMainCxaGlobals;
  73
  74         if ( sCxaKey == 0 ) {
  75                 // create key
  76                 // we don't need a lock because only one thread can be in dyld at a time
  77                 _ZN4dyld17gLibSystemHelpersE->pthread_key_create(&sCxaKey, &free);
  78         }
  79         char* data = (char*)_ZN4dyld17gLibSystemHelpersE->pthread_getspecific(sCxaKey);
  80         if ( data == NULL ) {
  81         long* t = (long*)calloc(2,sizeof(long));
  82                 data = (char*)t;
  83                 _ZN4dyld17gLibSystemHelpersE->pthread_setspecific(sCxaKey, data);
  84         }
  85         return data;
  86 }
  87
  88 // called by libstdc++.a
  89 char* __cxa_get_globals_fast()
  90 {
  91         // if libSystem.dylib not yet initialized, or is old libSystem, use shared global
  92         if ( (_ZN4dyld17gLibSystemHelpersE == NULL) || (_ZN4dyld17gLibSystemHelpersE->version < 7) )
  93                 return sPreMainCxaGlobals;
  94
  95         return _ZN4dyld17gLibSystemHelpersE->pthread_getspecific(sCxaKey);
  96 }
  97
  98
  99
 100 #if !__USING_SJLJ_EXCEPTIONS__
 101 //
 102 //  When dyld uses zero-cost exceptions it just needs to implement
 103 //  _dyld_find_unwind_sections to return sections inside dyld proper.
 104 //
 105
 106 extern void*  ehStart  __asm("section$start$__TEXT$__eh_frame");
 107 extern void*  ehEnd    __asm("section$end$__TEXT$__eh_frame");
 108 extern void*  uwStart  __asm("section$start$__TEXT$__unwind_info");
 109 extern void*  uwEnd    __asm("section$end$__TEXT$__unwind_info");
 110
 111 extern void*  textStart __asm("section$start$__TEXT$__text");
 112 extern void*  textEnd   __asm("section$end$__TEXT$__text");
 113
 114 extern void* __dso_handle;
 115
 116 // called by libuwind code to find unwind information sections in dyld
 117 bool _dyld_find_unwind_sections(void* addr, struct dyld_unwind_sections* info)
 118 {
 119         if ( ((void*)&textStart < addr) && (addr < (void*)&textEnd) ) {
 120         info->mh = (struct mach_header*)&__dso_handle;
 121         info->dwarf_section = &ehStart;
 122         info->dwarf_section_length = ((char*)&ehEnd - (char*)&ehStart);
 123         info->compact_unwind_section = &uwStart;
 124         info->compact_unwind_section_length = ((char*)&uwEnd - (char*)&uwStart);
 125                 return true;
 126         }
 127         else {
 128                 return false;
 129         }
 130 }
 131
 132 #else
 133 //
 134 //  When dyld uses setjump-longjump exceptions it needs to implement
 135 //  routines to push and pop a stack of _Unwind_FunctionContext.
 136 //
 137
 138 struct _Unwind_FunctionContext
 139 {
 140         // next function in stack of handlers
 141         struct _Unwind_FunctionContext*         prev;
 142
 143 };
 144
 145
 146 static pthread_key_t                                            sThreadChainKey = 0;
 147 static struct _Unwind_FunctionContext*          sStaticThreadChain = NULL;
 148
 149 //
 150 // When libSystem's initializers are run, they call back into dyld's
 151 // registerThreadHelpers which creates a pthread key and calls
 152 //  __Unwind_SjLj_SetThreadKey().
 153 //
 154 void __Unwind_SjLj_SetThreadKey(pthread_key_t key)
 155 {
 156         sThreadChainKey = key;
 157         //_ZN4dyld3logEPKcz("__Unwind_SjLj_SetThreadKey(key=%d), sStaticThreadChain=%p\n", key, sStaticThreadChain);
 158         // switch static chain to be per thread
 159         _ZN4dyld17gLibSystemHelpersE->pthread_setspecific(sThreadChainKey, sStaticThreadChain);
 160         sStaticThreadChain = NULL;
 161         //_ZN4dyld3logEPKcz("__Unwind_SjLj_SetThreadKey(key=%d), result=%d, new top=%p\n", key, result, pthread_getspecific(sThreadChainKey));
 162 }
 163
 164
 165 //static void printChain()
 166 //{
 167 //      _ZN4dyld3logEPKcz("chain: ");
 168 //      struct _Unwind_FunctionContext* start = sStaticThreadChain;
 169 //      if ( sThreadChainKey != 0 ) {
 170 //              start = (struct _Unwind_FunctionContext*)pthread_getspecific(sThreadChainKey);
 171 //      }
 172 //      for (struct _Unwind_FunctionContext* p = start; p != NULL; p = p->prev) {
 173 //              _ZN4dyld3logEPKcz("%p -> ", p);
 174 //      }
 175 //      _ZN4dyld3logEPKcz("\n");
 176 //}
 177
 178
 179 struct _Unwind_FunctionContext* __Unwind_SjLj_GetTopOfFunctionStack()
 180 {
 181         //_ZN4dyld3logEPKcz("__Unwind_SjLj_GetTopOfFunctionStack(),           key=%d, ", sThreadChainKey);
 182         //printChain();
 183         if ( sThreadChainKey != 0 ) {
 184                 return (struct _Unwind_FunctionContext*)pthread_getspecific(sThreadChainKey);
 185         }
 186         else {
 187                 return sStaticThreadChain;
 188         }
 189 }
 190
 191 void __Unwind_SjLj_SetTopOfFunctionStack(struct _Unwind_FunctionContext* fc)
 192 {
 193         //_ZN4dyld3logEPKcz("__Unwind_SjLj_SetTopOfFunctionStack(%p), key=%d, prev=%p\n",
 194         //      fc, sThreadChainKey, (fc != NULL) ? fc->prev : NULL);
 195         if ( sThreadChainKey != 0 )
 196                 _ZN4dyld17gLibSystemHelpersE->pthread_setspecific(sThreadChainKey, fc);
 197         else
 198                 sStaticThreadChain = fc;
 199         //_ZN4dyld3logEPKcz("__Unwind_SjLj_SetTopOfFunctionStack(%p), key=%d, ", fc, sThreadChainKey);
 200         //printChain();
 201 }
 202
 203 #endif
 204
 205
 206