| // |
| // Copyright (C) 2020 The Android Open Source Project |
| // |
| // Licensed under the Apache License, Version 2.0 (the "License"); |
| // you may not use this file except in compliance with the License. |
| // You may obtain a copy of the License at |
| // |
| // http://www.apache.org/licenses/LICENSE-2.0 |
| // |
| // Unless required by applicable law or agreed to in writing, software |
| // distributed under the License is distributed on an "AS IS" BASIS, |
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| // See the License for the specific language governing permissions and |
| // limitations under the License. |
| // |
| |
| #include "snapshot_reader.h" |
| |
| #include <android-base/file.h> |
| #include <android-base/logging.h> |
| #include <ext4_utils/ext4_utils.h> |
| |
| namespace android { |
| namespace snapshot { |
| |
| using android::base::borrowed_fd; |
| |
| // Not supported. |
| bool ReadOnlyFileDescriptor::Open(const char*, int, mode_t) { |
| errno = EINVAL; |
| return false; |
| } |
| |
| bool ReadOnlyFileDescriptor::Open(const char*, int) { |
| errno = EINVAL; |
| return false; |
| } |
| |
| ssize_t ReadOnlyFileDescriptor::Write(const void*, size_t) { |
| errno = EINVAL; |
| return false; |
| } |
| |
| bool ReadOnlyFileDescriptor::BlkIoctl(int, uint64_t, uint64_t, int*) { |
| errno = EINVAL; |
| return false; |
| } |
| |
| ReadFdFileDescriptor::ReadFdFileDescriptor(android::base::unique_fd&& fd) : fd_(std::move(fd)) {} |
| |
| ssize_t ReadFdFileDescriptor::Read(void* buf, size_t count) { |
| return read(fd_.get(), buf, count); |
| } |
| |
| off64_t ReadFdFileDescriptor::Seek(off64_t offset, int whence) { |
| return lseek(fd_.get(), offset, whence); |
| } |
| |
| uint64_t ReadFdFileDescriptor::BlockDevSize() { |
| return get_block_device_size(fd_.get()); |
| } |
| |
| bool ReadFdFileDescriptor::Close() { |
| fd_ = {}; |
| return true; |
| } |
| |
| bool ReadFdFileDescriptor::IsSettingErrno() { |
| return true; |
| } |
| |
| bool ReadFdFileDescriptor::IsOpen() { |
| return fd_ >= 0; |
| } |
| |
| bool ReadFdFileDescriptor::Flush() { |
| return true; |
| } |
| |
| bool CompressedSnapshotReader::SetCow(std::unique_ptr<CowReader>&& cow) { |
| cow_ = std::move(cow); |
| |
| const auto& header = cow_->GetHeader(); |
| block_size_ = header.block_size; |
| |
| // Populate the operation map. |
| op_iter_ = cow_->GetOpIter(); |
| while (!op_iter_->AtEnd()) { |
| const CowOperation* op = op_iter_->Get(); |
| if (IsMetadataOp(*op)) { |
| op_iter_->Next(); |
| continue; |
| } |
| if (op->new_block >= ops_.size()) { |
| ops_.resize(op->new_block + 1, nullptr); |
| } |
| ops_[op->new_block] = op; |
| op_iter_->Next(); |
| } |
| |
| return true; |
| } |
| |
| void CompressedSnapshotReader::SetSourceDevice(const std::string& source_device) { |
| source_device_ = {source_device}; |
| } |
| |
| void CompressedSnapshotReader::SetBlockDeviceSize(uint64_t block_device_size) { |
| block_device_size_ = block_device_size; |
| } |
| |
| borrowed_fd CompressedSnapshotReader::GetSourceFd() { |
| if (source_fd_ < 0) { |
| if (!source_device_) { |
| LOG(ERROR) << "CompressedSnapshotReader needs source device, but none was set"; |
| errno = EINVAL; |
| return {-1}; |
| } |
| source_fd_.reset(open(source_device_->c_str(), O_RDONLY | O_CLOEXEC)); |
| if (source_fd_ < 0) { |
| PLOG(ERROR) << "open " << *source_device_; |
| return {-1}; |
| } |
| } |
| return source_fd_; |
| } |
| |
| ssize_t CompressedSnapshotReader::Read(void* buf, size_t count) { |
| // Find the start and end chunks, inclusive. |
| uint64_t start_chunk = offset_ / block_size_; |
| uint64_t end_chunk = (offset_ + count - 1) / block_size_; |
| |
| // Chop off the first N bytes if the position is not block-aligned. |
| size_t start_offset = offset_ % block_size_; |
| |
| uint8_t* buf_pos = reinterpret_cast<uint8_t*>(buf); |
| size_t buf_remaining = count; |
| |
| size_t initial_bytes = std::min(block_size_ - start_offset, buf_remaining); |
| ssize_t rv = ReadBlock(start_chunk, start_offset, buf_pos, initial_bytes); |
| if (rv < 0) { |
| return -1; |
| } |
| offset_ += rv; |
| buf_pos += rv; |
| buf_remaining -= rv; |
| |
| for (uint64_t chunk = start_chunk + 1; chunk < end_chunk; chunk++) { |
| ssize_t rv = ReadBlock(chunk, 0, buf_pos, buf_remaining); |
| if (rv < 0) { |
| return -1; |
| } |
| offset_ += rv; |
| buf_pos += rv; |
| buf_remaining -= rv; |
| } |
| |
| if (buf_remaining) { |
| ssize_t rv = ReadBlock(end_chunk, 0, buf_pos, buf_remaining); |
| if (rv < 0) { |
| return -1; |
| } |
| offset_ += rv; |
| buf_pos += rv; |
| buf_remaining -= rv; |
| } |
| |
| CHECK_EQ(buf_pos - reinterpret_cast<uint8_t*>(buf), count); |
| CHECK_EQ(buf_remaining, 0); |
| |
| errno = 0; |
| return count; |
| } |
| |
| ssize_t CompressedSnapshotReader::ReadBlock(uint64_t chunk, size_t start_offset, void* buffer, |
| size_t buffer_size) { |
| size_t bytes_to_read = std::min(static_cast<size_t>(block_size_), buffer_size); |
| |
| // The offset is relative to the chunk; we should be reading no more than |
| // one chunk. |
| CHECK(start_offset + bytes_to_read <= block_size_); |
| |
| const CowOperation* op = nullptr; |
| if (chunk < ops_.size()) { |
| op = ops_[chunk]; |
| } |
| |
| if (!op || op->type == kCowCopyOp) { |
| borrowed_fd fd = GetSourceFd(); |
| if (fd < 0) { |
| // GetSourceFd sets errno. |
| return -1; |
| } |
| |
| if (op) { |
| chunk = op->source; |
| } |
| |
| off64_t offset = (chunk * block_size_) + start_offset; |
| if (!android::base::ReadFullyAtOffset(fd, buffer, bytes_to_read, offset)) { |
| PLOG(ERROR) << "read " << *source_device_; |
| // ReadFullyAtOffset sets errno. |
| return -1; |
| } |
| } else if (op->type == kCowZeroOp) { |
| memset(buffer, 0, bytes_to_read); |
| } else if (op->type == kCowReplaceOp) { |
| if (cow_->ReadData(op, buffer, bytes_to_read, start_offset) < bytes_to_read) { |
| LOG(ERROR) << "CompressedSnapshotReader failed to read replace op"; |
| errno = EIO; |
| return -1; |
| } |
| } else if (op->type == kCowXorOp) { |
| borrowed_fd fd = GetSourceFd(); |
| if (fd < 0) { |
| // GetSourceFd sets errno. |
| return -1; |
| } |
| |
| off64_t offset = op->source + start_offset; |
| |
| std::string data(bytes_to_read, '\0'); |
| if (!android::base::ReadFullyAtOffset(fd, data.data(), data.size(), offset)) { |
| PLOG(ERROR) << "read " << *source_device_; |
| // ReadFullyAtOffset sets errno. |
| return -1; |
| } |
| |
| if (cow_->ReadData(op, buffer, bytes_to_read, start_offset) < bytes_to_read) { |
| LOG(ERROR) << "CompressedSnapshotReader failed to read xor op"; |
| errno = EIO; |
| return -1; |
| } |
| |
| for (size_t i = 0; i < bytes_to_read; i++) { |
| ((char*)buffer)[i] ^= data[i]; |
| } |
| } else { |
| LOG(ERROR) << "CompressedSnapshotReader unknown op type: " << uint32_t(op->type); |
| errno = EINVAL; |
| return -1; |
| } |
| |
| // MemoryByteSink doesn't do anything in ReturnBuffer, so don't bother calling it. |
| return bytes_to_read; |
| } |
| |
| off64_t CompressedSnapshotReader::Seek(off64_t offset, int whence) { |
| switch (whence) { |
| case SEEK_SET: |
| offset_ = offset; |
| break; |
| case SEEK_END: |
| offset_ = static_cast<off64_t>(block_device_size_) + offset; |
| break; |
| case SEEK_CUR: |
| offset_ += offset; |
| break; |
| default: |
| LOG(ERROR) << "Unrecognized seek whence: " << whence; |
| errno = EINVAL; |
| return -1; |
| } |
| return offset_; |
| } |
| |
| uint64_t CompressedSnapshotReader::BlockDevSize() { |
| return block_device_size_; |
| } |
| |
| bool CompressedSnapshotReader::Close() { |
| cow_ = nullptr; |
| source_fd_ = {}; |
| return true; |
| } |
| |
| bool CompressedSnapshotReader::IsSettingErrno() { |
| return true; |
| } |
| |
| bool CompressedSnapshotReader::IsOpen() { |
| return cow_ != nullptr; |
| } |
| |
| bool CompressedSnapshotReader::Flush() { |
| return true; |
| } |
| |
| } // namespace snapshot |
| } // namespace android |