mozglue/baseprofiler/lul/AutoObjectMapper.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>
   8 #include <unistd.h>
   9 #include <sys/types.h>
  10 #include <sys/stat.h>
  11 #include <fcntl.h>
  12
  13 #include "mozilla/Assertions.h"
  14 #include "mozilla/Sprintf.h"
  15
  16 #include "BaseProfiler.h"
  17 #include "PlatformMacros.h"
  18 #include "AutoObjectMapper.h"
  19
  20 // A helper function for creating failure error messages in
  21 // AutoObjectMapper*::Map.
  22 static void failedToMessage(void (*aLog)(const char*), const char* aHowFailed,
  23                             std::string aFileName) {
  24   char buf[300];
  25   SprintfLiteral(buf, "AutoObjectMapper::Map: Failed to %s \'%s\'", aHowFailed,
  26                  aFileName.c_str());
  27   buf[sizeof(buf) - 1] = 0;
  28   aLog(buf);
  29 }
  30
  31 AutoObjectMapperPOSIX::AutoObjectMapperPOSIX(void (*aLog)(const char*))
  32     : mImage(nullptr), mSize(0), mLog(aLog), mIsMapped(false) {}
  33
  34 AutoObjectMapperPOSIX::~AutoObjectMapperPOSIX() {
  35   if (!mIsMapped) {
  36     // There's nothing to do.
  37     MOZ_ASSERT(!mImage);
  38     MOZ_ASSERT(mSize == 0);
  39     return;
  40   }
  41   MOZ_ASSERT(mSize > 0);
  42   // The following assertion doesn't necessarily have to be true,
  43   // but we assume (reasonably enough) that no mmap facility would
  44   // be crazy enough to map anything at page zero.
  45   MOZ_ASSERT(mImage);
  46   munmap(mImage, mSize);
  47 }
  48
  49 bool AutoObjectMapperPOSIX::Map(/*OUT*/ void** start, /*OUT*/ size_t* length,
  50                                 std::string fileName) {
  51   MOZ_ASSERT(!mIsMapped);
  52
  53   int fd = open(fileName.c_str(), O_RDONLY);
  54   if (fd == -1) {
  55     failedToMessage(mLog, "open", fileName);
  56     return false;
  57   }
  58
  59   struct stat st;
  60   int err = fstat(fd, &st);
  61   size_t sz = (err == 0) ? st.st_size : 0;
  62   if (err != 0 || sz == 0) {
  63     failedToMessage(mLog, "fstat", fileName);
  64     close(fd);
  65     return false;
  66   }
  67
  68   void* image = mmap(nullptr, sz, PROT_READ, MAP_SHARED, fd, 0);
  69   if (image == MAP_FAILED) {
  70     failedToMessage(mLog, "mmap", fileName);
  71     close(fd);
  72     return false;
  73   }
  74
  75   close(fd);
  76   mIsMapped = true;
  77   mImage = *start = image;
  78   mSize = *length = sz;
  79   return true;
  80 }