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// Copyright (C) 2017 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
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// See the License for the specific language governing permissions and
// limitations under the License.
// This class implements a FilesystemInterface, which lets the caller obtain
// basic information about what files are in the filesystem and where are they
// located in the disk, but not full access to the uncompressed contents of
// these files. This class uses the definitions found in
// fs/squashfs/squashfs_fs.h in the kernel header tree. This class supports
// squashfs version 4 in little-endian format only.
#include <memory>
#include <string>
#include <vector>
#include <brillo/secure_blob.h>
#include "update_engine/payload_consumer/file_descriptor.h"
#include "update_engine/payload_generator/extent_utils.h"
#include "update_engine/payload_generator/filesystem_interface.h"
namespace chromeos_update_engine {
class SquashfsFilesystem : public FilesystemInterface {
// From an squashfs image we need: (offset, bytes)
// - magic: (0, 4)
// * Acceptable value is: 0x73717368
// - block size: (12, 4)
// - compression type: (20, 2)
// * 1 is for zlib, gzip
// - major number: (28, 2)
// * We only support version 4 for now.
struct SquashfsHeader {
uint32_t magic;
uint32_t block_size;
uint16_t compression_type;
uint16_t major_version;
~SquashfsFilesystem() override = default;
// Creates the file system from the Squashfs file itself. If
// |extract_deflates| is true, it will process files to find location of all
// deflate streams.
static std::unique_ptr<SquashfsFilesystem> CreateFromFile(
const std::string& sqfs_path, bool extract_deflates, bool load_settings);
// Creates the file system from a file map |filemap| which is a multi-line
// string with each line with the following format:
// file_path start_byte compressed_size_1 ... compressed_size_2
// file_path: The name of the file inside the Squashfs File.
// start_byte: The byte address of the start of the file.
// compressed_size_i: The compressed size of the ith block of the file.
// The 25th bit of compressed_size_i is set if the block is uncompressed.
// |size| is the size of the Squashfs image.
static std::unique_ptr<SquashfsFilesystem> CreateFromFileMap(
const std::string& filemap, size_t size, const SquashfsHeader& header);
// FilesystemInterface overrides.
size_t GetBlockSize() const override;
size_t GetBlockCount() const override;
// Returns one FilesystemInterface::File for every file (that is not added to
// fragments) in the squashfs image.
// It also returns the following metadata files:
// <fragment-i>: The ith fragment in the Sqauashfs file.
// <metadata-i>: The part of the file system that does not belong to any
// file. Normally, there is only two: one for superblock and
// one for the metadata at the end.
bool GetFiles(std::vector<File>* files) const override;
// Squashfs image does not support this yet.
bool LoadSettings(brillo::KeyValueStore* store) const override;
// Returns true if the first few bytes of a file indicates a valid Squashfs
// image. The size of the |blob| should be at least
// sizeof(SquashfsHeader) or for now 96 bytes.
static bool IsSquashfsImage(const brillo::Blob& blob);
SquashfsFilesystem() = default;
// Initialize and populates the files in the file system.
bool Init(const std::string& map,
const std::string& sqfs_path,
size_t size,
const SquashfsHeader& header,
bool extract_deflates);
// The size of the image in bytes.
size_t size_;
// All the files in the filesystem.
std::vector<File> files_;
// The content of /etc/update_engine.conf.
std::string update_engine_config_;
} // namespace chromeos_update_engine