mozglue/interposers/env_interposer.cpp

   1 /* This Source Code Form is subject to the terms of the Mozilla Public
   2  * License, v. 2.0. If a copy of the MPL was not distributed with this
   3  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   4
   5 #include <pthread.h>
   6 #include <string.h>
   7 #include <unistd.h>
   8
   9 #include "InterposerHelper.h"
  10
  11 // The interposers in this file cover all the functions used to access the
  12 // environment (getenv(), putenv(), setenv(), unsetenv() and clearenv()). They
  13 // all use the mutex below for synchronization to prevent races that caused
  14 // startup crashes, see bug 1752703.
  15 static pthread_mutex_t gEnvLock = PTHREAD_MUTEX_INITIALIZER;
  16
  17 static char* internal_getenv(const char* aName) {
  18   if (environ == nullptr || aName[0] == '\0') {
  19     return nullptr;
  20   }
  21
  22   size_t len = strlen(aName);
  23   for (char** env_ptr = environ; *env_ptr != nullptr; ++env_ptr) {
  24     if ((aName[0] == (*env_ptr)[0]) && (strncmp(aName, *env_ptr, len) == 0) &&
  25         ((*env_ptr)[len] == '=')) {
  26       return *env_ptr + len + 1;
  27     }
  28   }
  29
  30   return nullptr;
  31 }
  32
  33 extern "C" {
  34
  35 MFBT_API char* getenv(const char* name) {
  36   pthread_mutex_lock(&gEnvLock);
  37   char* result = internal_getenv(name);
  38   pthread_mutex_unlock(&gEnvLock);
  39
  40   return result;
  41 }
  42
  43 MFBT_API int putenv(char* string) {
  44   static const auto real_putenv = GET_REAL_SYMBOL(putenv);
  45
  46   pthread_mutex_lock(&gEnvLock);
  47   int result = real_putenv(string);
  48   pthread_mutex_unlock(&gEnvLock);
  49   return result;
  50 }
  51
  52 MFBT_API int setenv(const char* name, const char* value, int replace) {
  53   static const auto real_setenv = GET_REAL_SYMBOL(setenv);
  54
  55   pthread_mutex_lock(&gEnvLock);
  56   int result = real_setenv(name, value, replace);
  57   pthread_mutex_unlock(&gEnvLock);
  58   return result;
  59 }
  60
  61 MFBT_API int unsetenv(const char* name) {
  62   static const auto real_unsetenv = GET_REAL_SYMBOL(unsetenv);
  63
  64   pthread_mutex_lock(&gEnvLock);
  65   int result = real_unsetenv(name);
  66   pthread_mutex_unlock(&gEnvLock);
  67   return result;
  68 }
  69
  70 MFBT_API int clearenv(void) {
  71   static const auto real_clearenv = GET_REAL_SYMBOL(clearenv);
  72
  73   pthread_mutex_lock(&gEnvLock);
  74   int result = real_clearenv();
  75   pthread_mutex_unlock(&gEnvLock);
  76   return result;
  77 }
  78
  79 }  // extern "C"