// Copyright 2013 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "base/files/memory_mapped_file.h"
#include <windows.h>
#include <stddef.h>
#include <stdint.h>
#include <winnt.h>
#include <limits>
#include <string>
#include "base/files/file_path.h"
#include "base/logging.h"
#include "base/numerics/checked_math.h"
#include "base/numerics/safe_conversions.h"
#include "base/threading/scoped_blocking_call.h"
#include "base/win/pe_image.h"
namespace base {
MemoryMappedFile::MemoryMappedFile() = default;
bool MemoryMappedFile::MapImageToMemory(Access access) {
ScopedBlockingCall scoped_blocking_call(FROM_HERE, BlockingType::MAY_BLOCK);
// The arguments to the calls of ::CreateFile(), ::CreateFileMapping(), and
// ::MapViewOfFile() need to be self consistent as far as access rights and
// type of mapping or one or more of them will fail in non-obvious ways.
if (!file_.IsValid())
return false;
file_mapping_.Set(::CreateFileMapping(file_.GetPlatformFile(), nullptr,
PAGE_READONLY | SEC_IMAGE_NO_EXECUTE, 0,
0, NULL));
if (!file_mapping_.is_valid())
return false;
auto* ptr = static_cast<uint8_t*>(
::MapViewOfFile(file_mapping_.get(), FILE_MAP_READ, 0, 0, 0));
if (!ptr) {
return false;
}
// We need to know how large the mapped file is.
base::win::PEImage pe_image(ptr);
size_t len = pe_image.GetNTHeaders()->OptionalHeader.SizeOfImage;
if (len == 0u) {
// Consistent cross-platform behaviour, an empty `bytes_` indicates nothing
// is mapped.
return false;
}
// SAFETY: The `len` is the size of the image at `ptr`.
bytes_ = UNSAFE_BUFFERS(base::span(ptr, len));
return true;
}
bool MemoryMappedFile::MapFileRegionToMemory(
const MemoryMappedFile::Region& region,
Access access) {
ScopedBlockingCall scoped_blocking_call(FROM_HERE, BlockingType::MAY_BLOCK);
DCHECK(access != READ_CODE_IMAGE || region == Region::kWholeFile);
if (!file_.IsValid())
return false;
DWORD view_access;
DWORD flags = 0;
ULARGE_INTEGER size = {};
switch (access) {
case READ_ONLY:
flags |= PAGE_READONLY;
view_access = FILE_MAP_READ;
break;
case READ_WRITE:
flags |= PAGE_READWRITE;
view_access = FILE_MAP_WRITE;
break;
case READ_WRITE_COPY:
flags |= PAGE_WRITECOPY;
view_access = FILE_MAP_COPY;
break;
case READ_WRITE_EXTEND:
flags |= PAGE_READWRITE;
view_access = FILE_MAP_WRITE;
size.QuadPart = region.size;
break;
case READ_CODE_IMAGE:
return MapImageToMemory(access);
}
file_mapping_.Set(::CreateFileMapping(file_.GetPlatformFile(), NULL, flags,
size.HighPart, size.LowPart, NULL));
if (!file_mapping_.is_valid())
return false;
ULARGE_INTEGER map_start = {};
SIZE_T map_size = 0u;
int32_t data_offset = 0;
size_t byte_size = 0u;
if (region == MemoryMappedFile::Region::kWholeFile) {
DCHECK_NE(READ_WRITE_EXTEND, access);
int64_t file_len = file_.GetLength();
if (file_len <= 0 || !IsValueInRangeForNumericType<size_t>(file_len)) {
return false;
}
byte_size = base::checked_cast<size_t>(file_len);
} else {
// The region can be arbitrarily aligned. MapViewOfFile, instead, requires
// that the start address is aligned to the VM granularity (which is
// typically larger than a page size, for instance 32k).
// Also, conversely to POSIX's mmap, the |map_size| doesn't have to be
// aligned and must be less than or equal the mapped file size.
// We map here the outer region [|aligned_start|, |aligned_start+size|]
// which contains |region| and then add up the |data_offset| displacement.
int64_t aligned_start = 0;
size_t ignored = 0u;
CalculateVMAlignedBoundaries(region.offset, region.size, &aligned_start,
&ignored, &data_offset);
base::CheckedNumeric<SIZE_T> full_map_size = region.size;
full_map_size += data_offset;
// Ensure that the casts below in the MapViewOfFile call are sane.
if (aligned_start < 0 || !full_map_size.IsValid()) {
DLOG(ERROR) << "Region bounds are not valid for MapViewOfFile";
return false;
}
map_start.QuadPart = static_cast<uint64_t>(aligned_start);
map_size = full_map_size.ValueOrDie();
byte_size = region.size;
if (map_size == 0u) {
// Consistent cross-platform behaviour, an empty `bytes_` indicates
// nothing is mapped.
return false;
}
}
auto* ptr = static_cast<uint8_t*>(
::MapViewOfFile(file_mapping_.get(), view_access, map_start.HighPart,
map_start.LowPart, map_size));
if (ptr == nullptr) {
return false;
}
// SAFETY: For the span construction to be valid, `ptr` needs to point to at
// least `data_size + byte_size` many bytes. The MapViewOfFile() will return a
// pointer of `map_size` bytes, unless it's 0 in which case it returns a
// pointer to all bytes in the file after the offset.
//
// If the mapping is of the whole file, `map_size == 0`, so `file_len` bytes
// are mapped. `byte_size == file_len` and `data_offset == 0`, so
// `data_offset + byte_size <= file_len` is trivially satisfied.
//
// If the mapping is a sub-range of the file, `map_size > 0` and `map_size`
// many bytes are mapped:
// - `aligned_start` is page aligned and <= `start`.
// - `map_size` is a multiple of the VM granularity and >=
// `byte_size`.
// - `data_offset` is the displacement of `start` w.r.t `aligned_start`.
// |..................|xxxxxxxxxxxxxxxxxx|.................|
// ^ aligned start ^ start | |
// ^------------------^ data_offset | |
// ^------------------^ byte_size |
// ^-------------------------------------------------------^ map_size
//
// The `data_offset` undoes the alignment of start. The `map_size` contains
// the padding before and after the mapped region to satisfy alignment. So
// the `data_offset + byte_size <= map_size`.
bytes_ = UNSAFE_BUFFERS(base::span(ptr + data_offset, byte_size));
return true;
}
void MemoryMappedFile::CloseHandles() {
if (!bytes_.empty()) {
::UnmapViewOfFile(bytes_.data());
}
if (file_mapping_.is_valid())
file_mapping_.Close();
if (file_.IsValid())
file_.Close();
bytes_ = base::span<uint8_t>();
}
} // namespace base
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