fs_mgr/liblp/images.cpp - android-core - Git at Google

 /*
  * Copyright (C) 2018 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 "images.h"

 #include <limits.h>

 #include <android-base/file.h>

 #include "reader.h"
 #include "utility.h"
 #include "writer.h"

 namespace android {
 namespace fs_mgr {

 using android::base::unique_fd;

 #if defined(_WIN32)
 static const int O_NOFOLLOW = 0;
 #endif

 std::unique_ptr<LpMetadata> ReadFromImageFile(int fd) {
     std::unique_ptr<uint8_t[]> buffer = std::make_unique<uint8_t[]>(LP_METADATA_GEOMETRY_SIZE);
     if (SeekFile64(fd, 0, SEEK_SET) < 0) {
         PERROR << __PRETTY_FUNCTION__ << " lseek failed";
         return nullptr;
     }
     if (!android::base::ReadFully(fd, buffer.get(), LP_METADATA_GEOMETRY_SIZE)) {
         PERROR << __PRETTY_FUNCTION__ << " read failed";
         return nullptr;
     }
     LpMetadataGeometry geometry;
     if (!ParseGeometry(buffer.get(), &geometry)) {
         return nullptr;
     }
     return ParseMetadata(geometry, fd);
 }

 std::unique_ptr<LpMetadata> ReadFromImageBlob(const void* data, size_t bytes) {
     if (bytes < LP_METADATA_GEOMETRY_SIZE) {
         LERROR << __PRETTY_FUNCTION__ << ": " << bytes << " is smaller than geometry header";
         return nullptr;
     }

     LpMetadataGeometry geometry;
     if (!ParseGeometry(data, &geometry)) {
         return nullptr;
     }

     const uint8_t* metadata_buffer =
             reinterpret_cast<const uint8_t*>(data) + LP_METADATA_GEOMETRY_SIZE;
     size_t metadata_buffer_size = bytes - LP_METADATA_GEOMETRY_SIZE;
     return ParseMetadata(geometry, metadata_buffer, metadata_buffer_size);
 }

 std::unique_ptr<LpMetadata> ReadFromImageFile(const std::string& image_file) {
     unique_fd fd = GetControlFileOrOpen(image_file.c_str(), O_RDONLY | O_CLOEXEC);
     if (fd < 0) {
         PERROR << __PRETTY_FUNCTION__ << " open failed: " << image_file;
         return nullptr;
     }
     return ReadFromImageFile(fd);
 }

 bool WriteToImageFile(int fd, const LpMetadata& input) {
     std::string geometry = SerializeGeometry(input.geometry);
     std::string metadata = SerializeMetadata(input);

     std::string everything = geometry + metadata;

     if (!android::base::WriteFully(fd, everything.data(), everything.size())) {
         PERROR << __PRETTY_FUNCTION__ << " write " << everything.size() << " bytes failed";
         return false;
     }
     return true;
 }

 bool WriteToImageFile(const char* file, const LpMetadata& input) {
     unique_fd fd(open(file, O_CREAT | O_RDWR | O_TRUNC | O_CLOEXEC, 0644));
     if (fd < 0) {
         PERROR << __PRETTY_FUNCTION__ << " open failed: " << file;
         return false;
     }
     return WriteToImageFile(fd, input);
 }

 ImageBuilder::ImageBuilder(const LpMetadata& metadata, uint32_t block_size,
                            const std::map<std::string, std::string>& images, bool sparsify)
     : metadata_(metadata),
       geometry_(metadata.geometry),
       block_size_(block_size),
       sparsify_(sparsify),
       images_(images) {
     uint64_t total_size = GetTotalSuperPartitionSize(metadata);
     if (block_size % LP_SECTOR_SIZE != 0) {
         LERROR << "Block size must be a multiple of the sector size, " << LP_SECTOR_SIZE;
         return;
     }
     if (total_size % block_size != 0) {
         LERROR << "Device size must be a multiple of the block size, " << block_size;
         return;
     }
     if (metadata.geometry.metadata_max_size % block_size != 0) {
         LERROR << "Metadata max size must be a multiple of the block size, " << block_size;
         return;
     }
     if (LP_METADATA_GEOMETRY_SIZE % block_size != 0) {
         LERROR << "Geometry size is not a multiple of the block size, " << block_size;
         return;
     }
     if (LP_PARTITION_RESERVED_BYTES % block_size != 0) {
         LERROR << "Reserved size is not a multiple of the block size, " << block_size;
         return;
     }

     uint64_t num_blocks = total_size / block_size;
     if (num_blocks >= UINT_MAX) {
         // libsparse counts blocks in unsigned 32-bit integers, so we check to
         // make sure we're not going to overflow.
         LERROR << "Block device is too large to encode with libsparse.";
         return;
     }

     for (const auto& block_device : metadata.block_devices) {
         SparsePtr file(sparse_file_new(block_size_, block_device.size), sparse_file_destroy);
         if (!file) {
             LERROR << "Could not allocate sparse file of size " << block_device.size;
             return;
         }
         device_images_.emplace_back(std::move(file));
     }
 }

 bool ImageBuilder::IsValid() const {
     return device_images_.size() == metadata_.block_devices.size();
 }

 bool ImageBuilder::Export(const char* file) {
     unique_fd fd(open(file, O_CREAT | O_RDWR | O_TRUNC | O_CLOEXEC, 0644));
     if (fd < 0) {
         PERROR << "open failed: " << file;
         return false;
     }
     if (device_images_.size() > 1) {
         LERROR << "Cannot export to a single image on retrofit builds.";
         return false;
     }
     // No gzip compression; no checksum.
     int ret = sparse_file_write(device_images_[0].get(), fd, false, sparsify_, false);
     if (ret != 0) {
         LERROR << "sparse_file_write failed (error code " << ret << ")";
         return false;
     }
     return true;
 }

 bool ImageBuilder::ExportFiles(const std::string& output_dir) {
     for (size_t i = 0; i < device_images_.size(); i++) {
         std::string name = GetBlockDevicePartitionName(metadata_.block_devices[i]);
         std::string file_name = "super_" + name + ".img";
         std::string file_path = output_dir + "/" + file_name;

         static const int kOpenFlags = O_CREAT | O_RDWR | O_TRUNC | O_CLOEXEC | O_NOFOLLOW;
         unique_fd fd(open(file_path.c_str(), kOpenFlags, 0644));
         if (fd < 0) {
             PERROR << "open failed: " << file_path;
             return false;
         }
         // No gzip compression; no checksum.
         int ret = sparse_file_write(device_images_[i].get(), fd, false, sparsify_, false);
         if (ret != 0) {
             LERROR << "sparse_file_write failed (error code " << ret << ")";
             return false;
         }
     }
     return true;
 }

 bool ImageBuilder::AddData(sparse_file* file, const std::string& blob, uint64_t sector) {
     uint32_t block;
     if (!SectorToBlock(sector, &block)) {
         return false;
     }
     void* data = const_cast<char*>(blob.data());
     int ret = sparse_file_add_data(file, data, blob.size(), block);
     if (ret != 0) {
         LERROR << "sparse_file_add_data failed (error code " << ret << ")";
         return false;
     }
     return true;
 }

 bool ImageBuilder::SectorToBlock(uint64_t sector, uint32_t* block) {
     // The caller must ensure that the metadata has an alignment that is a
     // multiple of the block size. liblp will take care of the rest, ensuring
     // that all partitions are on an aligned boundary. Therefore all writes
     // should be block-aligned, and if they are not, the table was misconfigured.
     // Note that the default alignment is 1MiB, which is a multiple of the
     // default block size (4096).
     if ((sector * LP_SECTOR_SIZE) % block_size_ != 0) {
         LERROR << "sector " << sector << " is not aligned to block size " << block_size_;
         return false;
     }
     *block = (sector * LP_SECTOR_SIZE) / block_size_;
     return true;
 }

 uint64_t ImageBuilder::BlockToSector(uint64_t block) const {
     return (block * block_size_) / LP_SECTOR_SIZE;
 }

 bool ImageBuilder::Build() {
     if (sparse_file_add_fill(device_images_[0].get(), 0, LP_PARTITION_RESERVED_BYTES, 0) < 0) {
         LERROR << "Could not add initial sparse block for reserved zeroes";
         return false;
     }

     std::string geometry_blob = SerializeGeometry(geometry_);
     std::string metadata_blob = SerializeMetadata(metadata_);
     metadata_blob.resize(geometry_.metadata_max_size);

     // Two copies of geometry, then two copies of each metadata slot.
     all_metadata_ += geometry_blob + geometry_blob;
     for (size_t i = 0; i < geometry_.metadata_slot_count * 2; i++) {
         all_metadata_ += metadata_blob;
     }

     uint64_t first_sector = LP_PARTITION_RESERVED_BYTES / LP_SECTOR_SIZE;
     if (!AddData(device_images_[0].get(), all_metadata_, first_sector)) {
         return false;
     }

     if (!CheckExtentOrdering()) {
         return false;
     }

     for (const auto& partition : metadata_.partitions) {
         auto iter = images_.find(GetPartitionName(partition));
         if (iter == images_.end()) {
             continue;
         }
         if (!AddPartitionImage(partition, iter->second)) {
             return false;
         }
         images_.erase(iter);
     }

     if (!images_.empty()) {
         LERROR << "Partition image was specified but no partition was found.";
         return false;
     }
     return true;
 }

 static inline bool HasFillValue(uint32_t* buffer, size_t count) {
     uint32_t fill_value = buffer[0];
     for (size_t i = 1; i < count; i++) {
         if (fill_value != buffer[i]) {
             return false;
         }
     }
     return true;
 }

 bool ImageBuilder::AddPartitionImage(const LpMetadataPartition& partition,
                                      const std::string& file) {
     // Track which extent we're processing.
     uint32_t extent_index = partition.first_extent_index;

     const LpMetadataExtent& extent = metadata_.extents[extent_index];
     if (extent.target_type != LP_TARGET_TYPE_LINEAR) {
         LERROR << "Partition should only have linear extents: " << GetPartitionName(partition);
         return false;
     }

     int fd = OpenImageFile(file);
     if (fd < 0) {
         LERROR << "Could not open image for partition: " << GetPartitionName(partition);
         return false;
     }

     // Make sure the image does not exceed the partition size.
     uint64_t file_length;
     if (!GetDescriptorSize(fd, &file_length)) {
         LERROR << "Could not compute image size";
         return false;
     }
     uint64_t partition_size = ComputePartitionSize(partition);
     if (file_length > partition_size) {
         LERROR << "Image for partition '" << GetPartitionName(partition)
                << "' is greater than its size (" << file_length << ", expected " << partition_size
                << ")";
         return false;
     }
     if (SeekFile64(fd, 0, SEEK_SET)) {
         PERROR << "lseek failed";
         return false;
     }

     // We track the current logical sector and the position the current extent
     // ends at.
     uint64_t output_sector = 0;
     uint64_t extent_last_sector = extent.num_sectors;

     // We also track the output device and the current output block within that
     // device.
     uint32_t output_block;
     if (!SectorToBlock(extent.target_data, &output_block)) {
         return false;
     }
     sparse_file* output_device = device_images_[extent.target_source].get();

     // Proceed to read the file and build sparse images.
     uint64_t pos = 0;
     uint64_t remaining = file_length;
     while (remaining) {
         // Check if we need to advance to the next extent.
         if (output_sector == extent_last_sector) {
             extent_index++;
             if (extent_index >= partition.first_extent_index + partition.num_extents) {
                 LERROR << "image is larger than extent table";
                 return false;
             }

             const LpMetadataExtent& extent = metadata_.extents[extent_index];
             extent_last_sector += extent.num_sectors;
             output_device = device_images_[extent.target_source].get();
             if (!SectorToBlock(extent.target_data, &output_block)) {
                 return false;
             }
         }

         uint32_t buffer[block_size_ / sizeof(uint32_t)];
         size_t read_size = remaining >= sizeof(buffer) ? sizeof(buffer) : size_t(remaining);
         if (!android::base::ReadFully(fd, buffer, sizeof(buffer))) {
             PERROR << "read failed";
             return false;
         }
         if (read_size != sizeof(buffer) || !HasFillValue(buffer, read_size / sizeof(uint32_t))) {
             int rv = sparse_file_add_fd(output_device, fd, pos, read_size, output_block);
             if (rv) {
                 LERROR << "sparse_file_add_fd failed with code: " << rv;
                 return false;
             }
         } else {
             int rv = sparse_file_add_fill(output_device, buffer[0], read_size, output_block);
             if (rv) {
                 LERROR << "sparse_file_add_fill failed with code: " << rv;
                 return false;
             }
         }
         pos += read_size;
         remaining -= read_size;
         output_sector += block_size_ / LP_SECTOR_SIZE;
         output_block++;
     }

     return true;
 }

 uint64_t ImageBuilder::ComputePartitionSize(const LpMetadataPartition& partition) const {
     uint64_t sectors = 0;
     for (size_t i = 0; i < partition.num_extents; i++) {
         sectors += metadata_.extents[partition.first_extent_index + i].num_sectors;
     }
     return sectors * LP_SECTOR_SIZE;
 }

 // For simplicity, we don't allow serializing any configuration: extents must
 // be ordered, such that any extent at position I in the table occurs *before*
 // any extent after position I, for the same block device. We validate that
 // here.
 //
 // Without this, it would be more difficult to find the appropriate extent for
 // an output block. With this guarantee it is a linear walk.
 bool ImageBuilder::CheckExtentOrdering() {
     std::vector<uint64_t> last_sectors(metadata_.block_devices.size());

     for (const auto& extent : metadata_.extents) {
         if (extent.target_type != LP_TARGET_TYPE_LINEAR) {
             LERROR << "Extents must all be type linear.";
             return false;
         }
         if (extent.target_data <= last_sectors[extent.target_source]) {
             LERROR << "Extents must appear in increasing order.";
             return false;
         }
         if ((extent.num_sectors * LP_SECTOR_SIZE) % block_size_ != 0) {
             LERROR << "Extents must be aligned to the block size.";
             return false;
         }
         last_sectors[extent.target_source] = extent.target_data;
     }
     return true;
 }

 int ImageBuilder::OpenImageFile(const std::string& file) {
     android::base::unique_fd source_fd = GetControlFileOrOpen(file.c_str(), O_RDONLY | O_CLOEXEC);
     if (source_fd < 0) {
         PERROR << "open image file failed: " << file;
         return -1;
     }

     SparsePtr source(sparse_file_import(source_fd, true, true), sparse_file_destroy);
     if (!source) {
         int fd = source_fd.get();
         temp_fds_.push_back(std::move(source_fd));
         return fd;
     }

     TemporaryFile tf;
     if (tf.fd < 0) {
         PERROR << "make temporary file failed";
         return -1;
     }

     // We temporarily unsparse the file, rather than try to merge its chunks.
     int rv = sparse_file_write(source.get(), tf.fd, false, false, false);
     if (rv) {
         LERROR << "sparse_file_write failed with code: " << rv;
         return -1;
     }
     temp_fds_.push_back(android::base::unique_fd(tf.release()));
     return temp_fds_.back().get();
 }

 bool WriteToImageFile(const char* file, const LpMetadata& metadata, uint32_t block_size,
                       const std::map<std::string, std::string>& images, bool sparsify) {
     ImageBuilder builder(metadata, block_size, images, sparsify);
     return builder.IsValid() && builder.Build() && builder.Export(file);
 }

 bool WriteSplitImageFiles(const std::string& output_dir, const LpMetadata& metadata,
                           uint32_t block_size, const std::map<std::string, std::string>& images,
                           bool sparsify) {
     ImageBuilder builder(metadata, block_size, images, sparsify);
     return builder.IsValid() && builder.Build() && builder.ExportFiles(output_dir);
 }

 }  // namespace fs_mgr
 }  // namespace android
	/*
	* Copyright (C) 2018 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 "images.h"

	#include <limits.h>

	#include <android-base/file.h>

	#include "reader.h"
	#include "utility.h"
	#include "writer.h"

	namespace android {
	namespace fs_mgr {

	using android::base::unique_fd;

	#if defined(_WIN32)
	static const int O_NOFOLLOW = 0;
	#endif

	std::unique_ptr<LpMetadata> ReadFromImageFile(int fd) {
	std::unique_ptr<uint8_t[]> buffer = std::make_unique<uint8_t[]>(LP_METADATA_GEOMETRY_SIZE);
	if (SeekFile64(fd, 0, SEEK_SET) < 0) {
	PERROR << __PRETTY_FUNCTION__ << " lseek failed";
	return nullptr;
	}
	if (!android::base::ReadFully(fd, buffer.get(), LP_METADATA_GEOMETRY_SIZE)) {
	PERROR << __PRETTY_FUNCTION__ << " read failed";
	return nullptr;
	}
	LpMetadataGeometry geometry;
	if (!ParseGeometry(buffer.get(), &geometry)) {
	return nullptr;
	}
	return ParseMetadata(geometry, fd);
	}

	std::unique_ptr<LpMetadata> ReadFromImageBlob(const void* data, size_t bytes) {
	if (bytes < LP_METADATA_GEOMETRY_SIZE) {
	LERROR << __PRETTY_FUNCTION__ << ": " << bytes << " is smaller than geometry header";
	return nullptr;
	}

	LpMetadataGeometry geometry;
	if (!ParseGeometry(data, &geometry)) {
	return nullptr;
	}

	const uint8_t* metadata_buffer =
	reinterpret_cast<const uint8_t*>(data) + LP_METADATA_GEOMETRY_SIZE;
	size_t metadata_buffer_size = bytes - LP_METADATA_GEOMETRY_SIZE;
	return ParseMetadata(geometry, metadata_buffer, metadata_buffer_size);
	}

	std::unique_ptr<LpMetadata> ReadFromImageFile(const std::string& image_file) {
	unique_fd fd = GetControlFileOrOpen(image_file.c_str(), O_RDONLY \| O_CLOEXEC);
	if (fd < 0) {
	PERROR << __PRETTY_FUNCTION__ << " open failed: " << image_file;
	return nullptr;
	}
	return ReadFromImageFile(fd);
	}

	bool WriteToImageFile(int fd, const LpMetadata& input) {
	std::string geometry = SerializeGeometry(input.geometry);
	std::string metadata = SerializeMetadata(input);

	std::string everything = geometry + metadata;

	if (!android::base::WriteFully(fd, everything.data(), everything.size())) {
	PERROR << __PRETTY_FUNCTION__ << " write " << everything.size() << " bytes failed";
	return false;
	}
	return true;
	}

	bool WriteToImageFile(const char* file, const LpMetadata& input) {
	unique_fd fd(open(file, O_CREAT \| O_RDWR \| O_TRUNC \| O_CLOEXEC, 0644));
	if (fd < 0) {
	PERROR << __PRETTY_FUNCTION__ << " open failed: " << file;
	return false;
	}
	return WriteToImageFile(fd, input);
	}

	ImageBuilder::ImageBuilder(const LpMetadata& metadata, uint32_t block_size,
	const std::map<std::string, std::string>& images, bool sparsify)
	: metadata_(metadata),
	geometry_(metadata.geometry),
	block_size_(block_size),
	sparsify_(sparsify),
	images_(images) {
	uint64_t total_size = GetTotalSuperPartitionSize(metadata);
	if (block_size % LP_SECTOR_SIZE != 0) {
	LERROR << "Block size must be a multiple of the sector size, " << LP_SECTOR_SIZE;
	return;
	}
	if (total_size % block_size != 0) {
	LERROR << "Device size must be a multiple of the block size, " << block_size;
	return;
	}
	if (metadata.geometry.metadata_max_size % block_size != 0) {
	LERROR << "Metadata max size must be a multiple of the block size, " << block_size;
	return;
	}
	if (LP_METADATA_GEOMETRY_SIZE % block_size != 0) {
	LERROR << "Geometry size is not a multiple of the block size, " << block_size;
	return;
	}
	if (LP_PARTITION_RESERVED_BYTES % block_size != 0) {
	LERROR << "Reserved size is not a multiple of the block size, " << block_size;
	return;
	}

	uint64_t num_blocks = total_size / block_size;
	if (num_blocks >= UINT_MAX) {
	// libsparse counts blocks in unsigned 32-bit integers, so we check to
	// make sure we're not going to overflow.
	LERROR << "Block device is too large to encode with libsparse.";
	return;
	}

	for (const auto& block_device : metadata.block_devices) {
	SparsePtr file(sparse_file_new(block_size_, block_device.size), sparse_file_destroy);
	if (!file) {
	LERROR << "Could not allocate sparse file of size " << block_device.size;
	return;
	}
	device_images_.emplace_back(std::move(file));
	}
	}

	bool ImageBuilder::IsValid() const {
	return device_images_.size() == metadata_.block_devices.size();
	}

	bool ImageBuilder::Export(const char* file) {
	unique_fd fd(open(file, O_CREAT \| O_RDWR \| O_TRUNC \| O_CLOEXEC, 0644));
	if (fd < 0) {
	PERROR << "open failed: " << file;
	return false;
	}
	if (device_images_.size() > 1) {
	LERROR << "Cannot export to a single image on retrofit builds.";
	return false;
	}
	// No gzip compression; no checksum.
	int ret = sparse_file_write(device_images_[0].get(), fd, false, sparsify_, false);
	if (ret != 0) {
	LERROR << "sparse_file_write failed (error code " << ret << ")";
	return false;
	}
	return true;
	}

	bool ImageBuilder::ExportFiles(const std::string& output_dir) {
	for (size_t i = 0; i < device_images_.size(); i++) {
	std::string name = GetBlockDevicePartitionName(metadata_.block_devices[i]);
	std::string file_name = "super_" + name + ".img";
	std::string file_path = output_dir + "/" + file_name;

	static const int kOpenFlags = O_CREAT \| O_RDWR \| O_TRUNC \| O_CLOEXEC \| O_NOFOLLOW;
	unique_fd fd(open(file_path.c_str(), kOpenFlags, 0644));
	if (fd < 0) {
	PERROR << "open failed: " << file_path;
	return false;
	}
	// No gzip compression; no checksum.
	int ret = sparse_file_write(device_images_[i].get(), fd, false, sparsify_, false);
	if (ret != 0) {
	LERROR << "sparse_file_write failed (error code " << ret << ")";
	return false;
	}
	}
	return true;
	}

	bool ImageBuilder::AddData(sparse_file* file, const std::string& blob, uint64_t sector) {
	uint32_t block;
	if (!SectorToBlock(sector, &block)) {
	return false;
	}
	void* data = const_cast<char*>(blob.data());
	int ret = sparse_file_add_data(file, data, blob.size(), block);
	if (ret != 0) {
	LERROR << "sparse_file_add_data failed (error code " << ret << ")";
	return false;
	}
	return true;
	}

	bool ImageBuilder::SectorToBlock(uint64_t sector, uint32_t* block) {
	// The caller must ensure that the metadata has an alignment that is a
	// multiple of the block size. liblp will take care of the rest, ensuring
	// that all partitions are on an aligned boundary. Therefore all writes
	// should be block-aligned, and if they are not, the table was misconfigured.
	// Note that the default alignment is 1MiB, which is a multiple of the
	// default block size (4096).
	if ((sector * LP_SECTOR_SIZE) % block_size_ != 0) {
	LERROR << "sector " << sector << " is not aligned to block size " << block_size_;
	return false;
	}
	block = (sector LP_SECTOR_SIZE) / block_size_;
	return true;
	}

	uint64_t ImageBuilder::BlockToSector(uint64_t block) const {
	return (block * block_size_) / LP_SECTOR_SIZE;
	}

	bool ImageBuilder::Build() {
	if (sparse_file_add_fill(device_images_[0].get(), 0, LP_PARTITION_RESERVED_BYTES, 0) < 0) {
	LERROR << "Could not add initial sparse block for reserved zeroes";
	return false;
	}

	std::string geometry_blob = SerializeGeometry(geometry_);
	std::string metadata_blob = SerializeMetadata(metadata_);
	metadata_blob.resize(geometry_.metadata_max_size);

	// Two copies of geometry, then two copies of each metadata slot.
	all_metadata_ += geometry_blob + geometry_blob;
	for (size_t i = 0; i < geometry_.metadata_slot_count * 2; i++) {
	all_metadata_ += metadata_blob;
	}

	uint64_t first_sector = LP_PARTITION_RESERVED_BYTES / LP_SECTOR_SIZE;
	if (!AddData(device_images_[0].get(), all_metadata_, first_sector)) {
	return false;
	}

	if (!CheckExtentOrdering()) {
	return false;
	}

	for (const auto& partition : metadata_.partitions) {
	auto iter = images_.find(GetPartitionName(partition));
	if (iter == images_.end()) {
	continue;
	}
	if (!AddPartitionImage(partition, iter->second)) {
	return false;
	}
	images_.erase(iter);
	}

	if (!images_.empty()) {
	LERROR << "Partition image was specified but no partition was found.";
	return false;
	}
	return true;
	}

	static inline bool HasFillValue(uint32_t* buffer, size_t count) {
	uint32_t fill_value = buffer[0];
	for (size_t i = 1; i < count; i++) {
	if (fill_value != buffer[i]) {
	return false;
	}
	}
	return true;
	}

	bool ImageBuilder::AddPartitionImage(const LpMetadataPartition& partition,
	const std::string& file) {
	// Track which extent we're processing.
	uint32_t extent_index = partition.first_extent_index;

	const LpMetadataExtent& extent = metadata_.extents[extent_index];
	if (extent.target_type != LP_TARGET_TYPE_LINEAR) {
	LERROR << "Partition should only have linear extents: " << GetPartitionName(partition);
	return false;
	}

	int fd = OpenImageFile(file);
	if (fd < 0) {
	LERROR << "Could not open image for partition: " << GetPartitionName(partition);
	return false;
	}

	// Make sure the image does not exceed the partition size.
	uint64_t file_length;
	if (!GetDescriptorSize(fd, &file_length)) {
	LERROR << "Could not compute image size";
	return false;
	}
	uint64_t partition_size = ComputePartitionSize(partition);
	if (file_length > partition_size) {
	LERROR << "Image for partition '" << GetPartitionName(partition)
	<< "' is greater than its size (" << file_length << ", expected " << partition_size
	<< ")";
	return false;
	}
	if (SeekFile64(fd, 0, SEEK_SET)) {
	PERROR << "lseek failed";
	return false;
	}

	// We track the current logical sector and the position the current extent
	// ends at.
	uint64_t output_sector = 0;
	uint64_t extent_last_sector = extent.num_sectors;

	// We also track the output device and the current output block within that
	// device.
	uint32_t output_block;
	if (!SectorToBlock(extent.target_data, &output_block)) {
	return false;
	}
	sparse_file* output_device = device_images_[extent.target_source].get();

	// Proceed to read the file and build sparse images.
	uint64_t pos = 0;
	uint64_t remaining = file_length;
	while (remaining) {
	// Check if we need to advance to the next extent.
	if (output_sector == extent_last_sector) {
	extent_index++;
	if (extent_index >= partition.first_extent_index + partition.num_extents) {
	LERROR << "image is larger than extent table";
	return false;
	}

	const LpMetadataExtent& extent = metadata_.extents[extent_index];
	extent_last_sector += extent.num_sectors;
	output_device = device_images_[extent.target_source].get();
	if (!SectorToBlock(extent.target_data, &output_block)) {
	return false;
	}
	}

	uint32_t buffer[block_size_ / sizeof(uint32_t)];
	size_t read_size = remaining >= sizeof(buffer) ? sizeof(buffer) : size_t(remaining);
	if (!android::base::ReadFully(fd, buffer, sizeof(buffer))) {
	PERROR << "read failed";
	return false;
	}
	if (read_size != sizeof(buffer) \|\| !HasFillValue(buffer, read_size / sizeof(uint32_t))) {
	int rv = sparse_file_add_fd(output_device, fd, pos, read_size, output_block);
	if (rv) {
	LERROR << "sparse_file_add_fd failed with code: " << rv;
	return false;
	}
	} else {
	int rv = sparse_file_add_fill(output_device, buffer[0], read_size, output_block);
	if (rv) {
	LERROR << "sparse_file_add_fill failed with code: " << rv;
	return false;
	}
	}
	pos += read_size;
	remaining -= read_size;
	output_sector += block_size_ / LP_SECTOR_SIZE;
	output_block++;
	}

	return true;
	}

	uint64_t ImageBuilder::ComputePartitionSize(const LpMetadataPartition& partition) const {
	uint64_t sectors = 0;
	for (size_t i = 0; i < partition.num_extents; i++) {
	sectors += metadata_.extents[partition.first_extent_index + i].num_sectors;
	}
	return sectors * LP_SECTOR_SIZE;
	}

	// For simplicity, we don't allow serializing any configuration: extents must
	// be ordered, such that any extent at position I in the table occurs before
	// any extent after position I, for the same block device. We validate that
	// here.
	//
	// Without this, it would be more difficult to find the appropriate extent for
	// an output block. With this guarantee it is a linear walk.
	bool ImageBuilder::CheckExtentOrdering() {
	std::vector<uint64_t> last_sectors(metadata_.block_devices.size());

	for (const auto& extent : metadata_.extents) {
	if (extent.target_type != LP_TARGET_TYPE_LINEAR) {
	LERROR << "Extents must all be type linear.";
	return false;
	}
	if (extent.target_data <= last_sectors[extent.target_source]) {
	LERROR << "Extents must appear in increasing order.";
	return false;
	}
	if ((extent.num_sectors * LP_SECTOR_SIZE) % block_size_ != 0) {
	LERROR << "Extents must be aligned to the block size.";
	return false;
	}
	last_sectors[extent.target_source] = extent.target_data;
	}
	return true;
	}

	int ImageBuilder::OpenImageFile(const std::string& file) {
	android::base::unique_fd source_fd = GetControlFileOrOpen(file.c_str(), O_RDONLY \| O_CLOEXEC);
	if (source_fd < 0) {
	PERROR << "open image file failed: " << file;
	return -1;
	}

	SparsePtr source(sparse_file_import(source_fd, true, true), sparse_file_destroy);
	if (!source) {
	int fd = source_fd.get();
	temp_fds_.push_back(std::move(source_fd));
	return fd;
	}

	TemporaryFile tf;
	if (tf.fd < 0) {
	PERROR << "make temporary file failed";
	return -1;
	}

	// We temporarily unsparse the file, rather than try to merge its chunks.
	int rv = sparse_file_write(source.get(), tf.fd, false, false, false);
	if (rv) {
	LERROR << "sparse_file_write failed with code: " << rv;
	return -1;
	}
	temp_fds_.push_back(android::base::unique_fd(tf.release()));
	return temp_fds_.back().get();
	}

	bool WriteToImageFile(const char* file, const LpMetadata& metadata, uint32_t block_size,
	const std::map<std::string, std::string>& images, bool sparsify) {
	ImageBuilder builder(metadata, block_size, images, sparsify);
	return builder.IsValid() && builder.Build() && builder.Export(file);
	}

	bool WriteSplitImageFiles(const std::string& output_dir, const LpMetadata& metadata,
	uint32_t block_size, const std::map<std::string, std::string>& images,
	bool sparsify) {
	ImageBuilder builder(metadata, block_size, images, sparsify);
	return builder.IsValid() && builder.Build() && builder.ExportFiles(output_dir);
	}

	} // namespace fs_mgr
	} // namespace android