1 // Copyright 2013 The Chromium Authors
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 <windows.h>
8
9 #include <stddef.h>
10 #include <stdint.h>
11 #include <winnt.h>
12
13 #include <limits>
14 #include <string>
15
16 #include "base/files/file_path.h"
17 #include "base/logging.h"
18 #include "base/numerics/checked_math.h"
19 #include "base/numerics/safe_conversions.h"
20 #include "base/threading/scoped_blocking_call.h"
21 #include "base/win/pe_image.h"
22
23 namespace base {
24
25 MemoryMappedFile::MemoryMappedFile() = default;
26
MapImageToMemory(Access access)27 bool MemoryMappedFile::MapImageToMemory(Access access) {
28 ScopedBlockingCall scoped_blocking_call(FROM_HERE, BlockingType::MAY_BLOCK);
29
30 // The arguments to the calls of ::CreateFile(), ::CreateFileMapping(), and
31 // ::MapViewOfFile() need to be self consistent as far as access rights and
32 // type of mapping or one or more of them will fail in non-obvious ways.
33
34 if (!file_.IsValid())
35 return false;
36
37 file_mapping_.Set(::CreateFileMapping(file_.GetPlatformFile(), nullptr,
38 PAGE_READONLY | SEC_IMAGE_NO_EXECUTE, 0,
39 0, NULL));
40 if (!file_mapping_.is_valid())
41 return false;
42
43 auto* ptr = static_cast<uint8_t*>(
44 ::MapViewOfFile(file_mapping_.get(), FILE_MAP_READ, 0, 0, 0));
45 if (!ptr) {
46 return false;
47 }
48
49 // We need to know how large the mapped file is.
50 base::win::PEImage pe_image(ptr);
51 size_t len = pe_image.GetNTHeaders()->OptionalHeader.SizeOfImage;
52 if (len == 0u) {
53 // Consistent cross-platform behaviour, an empty `bytes_` indicates nothing
54 // is mapped.
55 return false;
56 }
57
58 // SAFETY: The `len` is the size of the image at `ptr`.
59 bytes_ = UNSAFE_BUFFERS(base::span(ptr, len));
60 return true;
61 }
62
MapFileRegionToMemory(const MemoryMappedFile::Region & region,Access access)63 bool MemoryMappedFile::MapFileRegionToMemory(
64 const MemoryMappedFile::Region& region,
65 Access access) {
66 ScopedBlockingCall scoped_blocking_call(FROM_HERE, BlockingType::MAY_BLOCK);
67
68 DCHECK(access != READ_CODE_IMAGE || region == Region::kWholeFile);
69
70 if (!file_.IsValid())
71 return false;
72
73 DWORD view_access;
74 DWORD flags = 0;
75 ULARGE_INTEGER size = {};
76 switch (access) {
77 case READ_ONLY:
78 flags |= PAGE_READONLY;
79 view_access = FILE_MAP_READ;
80 break;
81 case READ_WRITE:
82 flags |= PAGE_READWRITE;
83 view_access = FILE_MAP_WRITE;
84 break;
85 case READ_WRITE_COPY:
86 flags |= PAGE_WRITECOPY;
87 view_access = FILE_MAP_COPY;
88 break;
89 case READ_WRITE_EXTEND:
90 flags |= PAGE_READWRITE;
91 view_access = FILE_MAP_WRITE;
92 size.QuadPart = region.size;
93 break;
94 case READ_CODE_IMAGE:
95 return MapImageToMemory(access);
96 }
97
98 file_mapping_.Set(::CreateFileMapping(file_.GetPlatformFile(), NULL, flags,
99 size.HighPart, size.LowPart, NULL));
100 if (!file_mapping_.is_valid())
101 return false;
102
103 ULARGE_INTEGER map_start = {};
104 SIZE_T map_size = 0u;
105 int32_t data_offset = 0;
106 size_t byte_size = 0u;
107
108 if (region == MemoryMappedFile::Region::kWholeFile) {
109 DCHECK_NE(READ_WRITE_EXTEND, access);
110 int64_t file_len = file_.GetLength();
111 if (file_len <= 0 || !IsValueInRangeForNumericType<size_t>(file_len)) {
112 return false;
113 }
114 byte_size = base::checked_cast<size_t>(file_len);
115 } else {
116 // The region can be arbitrarily aligned. MapViewOfFile, instead, requires
117 // that the start address is aligned to the VM granularity (which is
118 // typically larger than a page size, for instance 32k).
119 // Also, conversely to POSIX's mmap, the |map_size| doesn't have to be
120 // aligned and must be less than or equal the mapped file size.
121 // We map here the outer region [|aligned_start|, |aligned_start+size|]
122 // which contains |region| and then add up the |data_offset| displacement.
123 int64_t aligned_start = 0;
124 size_t ignored = 0u;
125 CalculateVMAlignedBoundaries(region.offset, region.size, &aligned_start,
126 &ignored, &data_offset);
127 base::CheckedNumeric<SIZE_T> full_map_size = region.size;
128 full_map_size += data_offset;
129
130 // Ensure that the casts below in the MapViewOfFile call are sane.
131 if (aligned_start < 0 || !full_map_size.IsValid()) {
132 DLOG(ERROR) << "Region bounds are not valid for MapViewOfFile";
133 return false;
134 }
135 map_start.QuadPart = static_cast<uint64_t>(aligned_start);
136 map_size = full_map_size.ValueOrDie();
137 byte_size = region.size;
138
139 if (map_size == 0u) {
140 // Consistent cross-platform behaviour, an empty `bytes_` indicates
141 // nothing is mapped.
142 return false;
143 }
144 }
145
146 auto* ptr = static_cast<uint8_t*>(
147 ::MapViewOfFile(file_mapping_.get(), view_access, map_start.HighPart,
148 map_start.LowPart, map_size));
149 if (ptr == nullptr) {
150 return false;
151 }
152
153 // SAFETY: For the span construction to be valid, `ptr` needs to point to at
154 // least `data_size + byte_size` many bytes. The MapViewOfFile() will return a
155 // pointer of `map_size` bytes, unless it's 0 in which case it returns a
156 // pointer to all bytes in the file after the offset.
157 //
158 // If the mapping is of the whole file, `map_size == 0`, so `file_len` bytes
159 // are mapped. `byte_size == file_len` and `data_offset == 0`, so
160 // `data_offset + byte_size <= file_len` is trivially satisfied.
161 //
162 // If the mapping is a sub-range of the file, `map_size > 0` and `map_size`
163 // many bytes are mapped:
164 // - `aligned_start` is page aligned and <= `start`.
165 // - `map_size` is a multiple of the VM granularity and >=
166 // `byte_size`.
167 // - `data_offset` is the displacement of `start` w.r.t `aligned_start`.
168 // |..................|xxxxxxxxxxxxxxxxxx|.................|
169 // ^ aligned start ^ start | |
170 // ^------------------^ data_offset | |
171 // ^------------------^ byte_size |
172 // ^-------------------------------------------------------^ map_size
173 //
174 // The `data_offset` undoes the alignment of start. The `map_size` contains
175 // the padding before and after the mapped region to satisfy alignment. So
176 // the `data_offset + byte_size <= map_size`.
177 bytes_ = UNSAFE_BUFFERS(base::span(ptr + data_offset, byte_size));
178 return true;
179 }
180
CloseHandles()181 void MemoryMappedFile::CloseHandles() {
182 if (!bytes_.empty()) {
183 ::UnmapViewOfFile(bytes_.data());
184 }
185 if (file_mapping_.is_valid())
186 file_mapping_.Close();
187 if (file_.IsValid())
188 file_.Close();
189
190 bytes_ = base::span<uint8_t>();
191 }
192
193 } // namespace base
194