ipc/glue/SharedMemory_posix.cpp

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #include <sys/mman.h>  // mprotect
   8 #include <unistd.h>    // sysconf
   9
  10 #include "mozilla/ipc/SharedMemory.h"
  11
  12 #if defined(XP_MACOSX) && defined(__x86_64__)
  13 #  include "prenv.h"
  14 #endif
  15
  16 namespace mozilla {
  17 namespace ipc {
  18
  19 #if defined(XP_MACOSX) && defined(__x86_64__)
  20 std::atomic<size_t> sPageSizeOverride = 0;
  21 #endif
  22
  23 void SharedMemory::SystemProtect(char* aAddr, size_t aSize, int aRights) {
  24   if (!SystemProtectFallible(aAddr, aSize, aRights)) {
  25     MOZ_CRASH("can't mprotect()");
  26   }
  27 }
  28
  29 bool SharedMemory::SystemProtectFallible(char* aAddr, size_t aSize,
  30                                          int aRights) {
  31   int flags = 0;
  32   if (aRights & RightsRead) flags |= PROT_READ;
  33   if (aRights & RightsWrite) flags |= PROT_WRITE;
  34   if (RightsNone == aRights) flags = PROT_NONE;
  35
  36   return 0 == mprotect(aAddr, aSize, flags);
  37 }
  38
  39 size_t SharedMemory::SystemPageSize() {
  40 #if defined(XP_MACOSX) && defined(__x86_64__)
  41   if (sPageSizeOverride == 0) {
  42     if (PR_GetEnv("MOZ_SHMEM_PAGESIZE_16K")) {
  43       sPageSizeOverride = 16 * 1024;
  44     } else {
  45       sPageSizeOverride = sysconf(_SC_PAGESIZE);
  46     }
  47   }
  48   return sPageSizeOverride;
  49 #else
  50   return sysconf(_SC_PAGESIZE);
  51 #endif
  52 }
  53
  54 }  // namespace ipc
  55 }  // namespace mozilla