1// Copyright 2013 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#include "base/files/memory_mapped_file.h"
6
7#include <sys/mman.h>
8#include <sys/stat.h>
9#include <unistd.h>
10
11#include "base/logging.h"
12#include "base/threading/thread_restrictions.h"
13
14namespace base {
15
16MemoryMappedFile::MemoryMappedFile() : data_(NULL), length_(0) {
17}
18
19bool MemoryMappedFile::MapFileRegionToMemory(
20    const MemoryMappedFile::Region& region) {
21  ThreadRestrictions::AssertIOAllowed();
22
23  off_t map_start = 0;
24  size_t map_size = 0;
25  int32 data_offset = 0;
26
27  if (region == MemoryMappedFile::Region::kWholeFile) {
28    int64 file_len = file_.GetLength();
29    if (file_len == -1) {
30      DPLOG(ERROR) << "fstat " << file_.GetPlatformFile();
31      return false;
32    }
33    map_size = static_cast<size_t>(file_len);
34    length_ = map_size;
35  } else {
36    // The region can be arbitrarily aligned. mmap, instead, requires both the
37    // start and size to be page-aligned. Hence, we map here the page-aligned
38    // outer region [|aligned_start|, |aligned_start| + |size|] which contains
39    // |region| and then add up the |data_offset| displacement.
40    int64 aligned_start = 0;
41    int64 aligned_size = 0;
42    CalculateVMAlignedBoundaries(region.offset,
43                                 region.size,
44                                 &aligned_start,
45                                 &aligned_size,
46                                 &data_offset);
47
48    // Ensure that the casts in the mmap call below are sane.
49    if (aligned_start < 0 || aligned_size < 0 ||
50        aligned_start > std::numeric_limits<off_t>::max() ||
51        static_cast<uint64>(aligned_size) >
52            std::numeric_limits<size_t>::max() ||
53        static_cast<uint64>(region.size) > std::numeric_limits<size_t>::max()) {
54      DLOG(ERROR) << "Region bounds are not valid for mmap";
55      return false;
56    }
57
58    map_start = static_cast<off_t>(aligned_start);
59    map_size = static_cast<size_t>(aligned_size);
60    length_ = static_cast<size_t>(region.size);
61  }
62
63  data_ = static_cast<uint8*>(mmap(NULL,
64                                   map_size,
65                                   PROT_READ,
66                                   MAP_SHARED,
67                                   file_.GetPlatformFile(),
68                                   map_start));
69  if (data_ == MAP_FAILED) {
70    DPLOG(ERROR) << "mmap " << file_.GetPlatformFile();
71    return false;
72  }
73
74  data_ += data_offset;
75  return true;
76}
77
78void MemoryMappedFile::CloseHandles() {
79  ThreadRestrictions::AssertIOAllowed();
80
81  if (data_ != NULL)
82    munmap(data_, length_);
83  file_.Close();
84
85  data_ = NULL;
86  length_ = 0;
87}
88
89}  // namespace base
90