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      1 /*
      2  * libjingle
      3  * Copyright 2004--2010, Google Inc.
      4  *
      5  * Redistribution and use in source and binary forms, with or without
      6  * modification, are permitted provided that the following conditions are met:
      7  *
      8  *  1. Redistributions of source code must retain the above copyright notice,
      9  *     this list of conditions and the following disclaimer.
     10  *  2. Redistributions in binary form must reproduce the above copyright notice,
     11  *     this list of conditions and the following disclaimer in the documentation
     12  *     and/or other materials provided with the distribution.
     13  *  3. The name of the author may not be used to endorse or promote products
     14  *     derived from this software without specific prior written permission.
     15  *
     16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
     17  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
     18  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
     19  * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
     20  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
     21  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
     22  * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
     23  * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
     24  * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
     25  * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     26  */
     27 
     28 #include "talk/base/latebindingsymboltable.h"
     29 
     30 #ifdef POSIX
     31 #include <dlfcn.h>
     32 #endif
     33 
     34 #include "talk/base/logging.h"
     35 
     36 namespace talk_base {
     37 
     38 #ifdef POSIX
     39 static const DllHandle kInvalidDllHandle = NULL;
     40 #else
     41 #error Not implemented
     42 #endif
     43 
     44 static const char *GetDllError() {
     45 #ifdef POSIX
     46   const char *err = dlerror();
     47   if (err) {
     48     return err;
     49   } else {
     50     return "No error";
     51   }
     52 #else
     53 #error Not implemented
     54 #endif
     55 }
     56 
     57 static bool LoadSymbol(DllHandle handle,
     58                        const char *symbol_name,
     59                        void **symbol) {
     60 #ifdef POSIX
     61   *symbol = dlsym(handle, symbol_name);
     62   const char *err = dlerror();
     63   if (err) {
     64     LOG(LS_ERROR) << "Error loading symbol " << symbol_name << ": " << err;
     65     return false;
     66   } else if (!*symbol) {
     67     // ELF allows for symbols to be NULL, but that should never happen for our
     68     // usage.
     69     LOG(LS_ERROR) << "Symbol " << symbol_name << " is NULL";
     70     return false;
     71   }
     72   return true;
     73 #else
     74 #error Not implemented
     75 #endif
     76 }
     77 
     78 LateBindingSymbolTable::LateBindingSymbolTable(const TableInfo *info,
     79     void **table)
     80     : info_(info),
     81       table_(table),
     82       handle_(kInvalidDllHandle),
     83       undefined_symbols_(false) {
     84   ClearSymbols();
     85 }
     86 
     87 LateBindingSymbolTable::~LateBindingSymbolTable() {
     88   Unload();
     89 }
     90 
     91 bool LateBindingSymbolTable::IsLoaded() const {
     92   return handle_ != kInvalidDllHandle;
     93 }
     94 
     95 bool LateBindingSymbolTable::Load() {
     96   ASSERT(info_->dll_name != NULL);
     97   return LoadFromPath(info_->dll_name);
     98 }
     99 
    100 bool LateBindingSymbolTable::LoadFromPath(const char *dll_path) {
    101   if (IsLoaded()) {
    102     return true;
    103   }
    104   if (undefined_symbols_) {
    105     // We do not attempt to load again because repeated attempts are not
    106     // likely to succeed and DLL loading is costly.
    107     LOG(LS_ERROR) << "We know there are undefined symbols";
    108     return false;
    109   }
    110 
    111 #ifdef POSIX
    112   handle_ = dlopen(dll_path,
    113                    // RTLD_NOW front-loads symbol resolution so that errors are
    114                    // caught early instead of causing a process abort later.
    115                    // RTLD_LOCAL prevents other modules from automatically
    116                    // seeing symbol definitions in the newly-loaded tree. This
    117                    // is necessary for same-named symbols in different ABI
    118                    // versions of the same library to not explode.
    119                    RTLD_NOW|RTLD_LOCAL
    120 #ifdef LINUX
    121                    // RTLD_DEEPBIND makes symbol dependencies in the
    122                    // newly-loaded tree prefer to resolve to definitions within
    123                    // that tree (the default on OS X). This is necessary for
    124                    // same-named symbols in different ABI versions of the same
    125                    // library to not explode.
    126                    |RTLD_DEEPBIND
    127 #endif
    128                    );  // NOLINT
    129 #else
    130 #error Not implemented
    131 #endif
    132 
    133   if (handle_ == kInvalidDllHandle) {
    134     LOG(LS_WARNING) << "Can't load " << dll_path << ": "
    135                     << GetDllError();
    136     return false;
    137   }
    138 #ifdef POSIX
    139   // Clear any old errors.
    140   dlerror();
    141 #endif
    142   for (int i = 0; i < info_->num_symbols; ++i) {
    143     if (!LoadSymbol(handle_, info_->symbol_names[i], &table_[i])) {
    144       undefined_symbols_ = true;
    145       Unload();
    146       return false;
    147     }
    148   }
    149   return true;
    150 }
    151 
    152 void LateBindingSymbolTable::Unload() {
    153   if (!IsLoaded()) {
    154     return;
    155   }
    156 
    157 #ifdef POSIX
    158   if (dlclose(handle_) != 0) {
    159     LOG(LS_ERROR) << GetDllError();
    160   }
    161 #else
    162 #error Not implemented
    163 #endif
    164 
    165   handle_ = kInvalidDllHandle;
    166   ClearSymbols();
    167 }
    168 
    169 void LateBindingSymbolTable::ClearSymbols() {
    170   memset(table_, 0, sizeof(void *) * info_->num_symbols);
    171 }
    172 
    173 }  // namespace talk_base
    174