blob: 59821d785283b488f4aeebe17bd318a5abb14206 [file] [log] [blame]
// Copyright 2013 The Chromium Authors. All rights reserved.
// 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 <fcntl.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <unistd.h>
#include "base/logging.h"
#include "base/numerics/safe_conversions.h"
#include "base/threading/scoped_blocking_call.h"
#include "build/build_config.h"
#if defined(OS_ANDROID)
#include <android/api-level.h>
#include "starboard/types.h"
#endif
namespace base {
MemoryMappedFile::MemoryMappedFile() : data_(nullptr), length_(0) {}
#if !defined(OS_NACL)
bool MemoryMappedFile::MapFileRegionToMemory(
const MemoryMappedFile::Region& region,
Access access) {
ScopedBlockingCall scoped_blocking_call(BlockingType::MAY_BLOCK);
off_t map_start = 0;
size_t map_size = 0;
int32_t data_offset = 0;
if (region == MemoryMappedFile::Region::kWholeFile) {
int64_t file_len = file_.GetLength();
if (file_len < 0) {
DPLOG(ERROR) << "fstat " << file_.GetPlatformFile();
return false;
}
if (!IsValueInRangeForNumericType<size_t>(file_len))
return false;
map_size = static_cast<size_t>(file_len);
length_ = map_size;
} else {
// The region can be arbitrarily aligned. mmap, instead, requires both the
// start and size to be page-aligned. Hence, we map here the page-aligned
// 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 aligned_size = 0;
CalculateVMAlignedBoundaries(region.offset,
region.size,
&aligned_start,
&aligned_size,
&data_offset);
// Ensure that the casts in the mmap call below are sane.
if (aligned_start < 0 ||
!IsValueInRangeForNumericType<off_t>(aligned_start)) {
DLOG(ERROR) << "Region bounds are not valid for mmap";
return false;
}
map_start = static_cast<off_t>(aligned_start);
map_size = aligned_size;
length_ = region.size;
}
int flags = 0;
switch (access) {
case READ_ONLY:
flags |= PROT_READ;
break;
case READ_WRITE:
flags |= PROT_READ | PROT_WRITE;
break;
case READ_WRITE_EXTEND:
flags |= PROT_READ | PROT_WRITE;
const int64_t new_file_len = region.offset + region.size;
// POSIX won't auto-extend the file when it is written so it must first
// be explicitly extended to the maximum size. Zeros will fill the new
// space. It is assumed that the existing file is fully realized as
// otherwise the entire file would have to be read and possibly written.
const int64_t original_file_len = file_.GetLength();
if (original_file_len < 0) {
DPLOG(ERROR) << "fstat " << file_.GetPlatformFile();
return false;
}
// Increase the actual length of the file, if necessary. This can fail if
// the disk is full and the OS doesn't support sparse files.
if (!file_.SetLength(std::max(original_file_len, new_file_len))) {
DPLOG(ERROR) << "ftruncate " << file_.GetPlatformFile();
return false;
}
// Realize the extent of the file so that it can't fail (and crash) later
// when trying to write to a memory page that can't be created. This can
// fail if the disk is full and the file is sparse.
bool do_manual_extension = false;
#if defined(OS_ANDROID) && __ANDROID_API__ < 21
// Only Android API>=21 supports the fallocate call. Older versions need
// to manually extend the file by writing zeros at block intervals.
do_manual_extension = true;
#elif defined(OS_MACOSX)
// MacOS doesn't support fallocate even though their new APFS filesystem
// does support sparse files. It does, however, have the functionality
// available via fcntl.
// See also: https://openradar.appspot.com/32720223
fstore_t params = {F_ALLOCATEALL, F_PEOFPOSMODE, region.offset,
region.size, 0};
if (fcntl(file_.GetPlatformFile(), F_PREALLOCATE, &params) != 0) {
DPLOG(ERROR) << "F_PREALLOCATE";
// This can fail because the filesystem doesn't support it so don't
// give up just yet. Try the manual method below.
do_manual_extension = true;
}
#else
if (posix_fallocate(file_.GetPlatformFile(), region.offset,
region.size) != 0) {
DPLOG(ERROR) << "posix_fallocate";
// This can fail because the filesystem doesn't support it so don't
// give up just yet. Try the manual method below.
do_manual_extension = true;
}
#endif
// Manually realize the extended file by writing bytes to it at intervals.
if (do_manual_extension) {
int64_t block_size = 512; // Start with something safe.
struct stat statbuf;
if (fstat(file_.GetPlatformFile(), &statbuf) == 0 &&
statbuf.st_blksize > 0) {
block_size = statbuf.st_blksize;
}
// Write starting at the next block boundary after the old file length.
const int64_t extension_start =
(original_file_len + block_size - 1) & ~(block_size - 1);
for (int64_t i = extension_start; i < new_file_len; i += block_size) {
char existing_byte;
if (pread(file_.GetPlatformFile(), &existing_byte, 1, i) != 1)
return false; // Can't read? Not viable.
if (existing_byte != 0)
continue; // Block has data so must already exist.
if (pwrite(file_.GetPlatformFile(), &existing_byte, 1, i) != 1)
return false; // Can't write? Not viable.
}
}
break;
}
data_ = static_cast<uint8_t*>(mmap(nullptr, map_size, flags, MAP_SHARED,
file_.GetPlatformFile(), map_start));
if (data_ == MAP_FAILED) {
DPLOG(ERROR) << "mmap " << file_.GetPlatformFile();
return false;
}
data_ += data_offset;
return true;
}
#endif
void MemoryMappedFile::CloseHandles() {
ScopedBlockingCall scoped_blocking_call(BlockingType::MAY_BLOCK);
if (data_ != nullptr)
munmap(data_, length_);
file_.Close();
data_ = nullptr;
length_ = 0;
}
} // namespace base