blob: a133edf879cd0c6f30ea6d1a8a6313193940a24f [file] [log] [blame]
/*
* Copyright (C) 2021 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 "ramdisk_utils.h"
#include <android-base/file.h>
#include <android-base/result.h>
#include <bootimg.h>
#include <iostream>
#include "cpio.h"
#include "lz4_legacy.h"
using android::base::ErrnoError;
using android::base::Error;
using android::base::ReadFullyAtOffset;
using android::base::WriteStringToFd;
namespace android {
namespace {
// Extract ramdisk from boot image / partition at |boot_path|.
// Return a temporary file storing the ramdisk section.
android::base::Result<std::unique_ptr<TemporaryFile>> ExtractRamdiskRaw(
std::string_view boot_path) {
android::base::unique_fd bootimg(
TEMP_FAILURE_RETRY(open(boot_path.data(), O_RDONLY)));
if (!bootimg.ok()) return ErrnoError() << "open(" << boot_path << ")";
boot_img_hdr_v3 hdr{};
if (!ReadFullyAtOffset(bootimg.get(), &hdr, sizeof(hdr), 0))
return ErrnoError() << "read header";
if (0 != memcmp(hdr.magic, BOOT_MAGIC, BOOT_MAGIC_SIZE))
return Error() << "Boot magic mismatch";
if (hdr.header_version < 3)
return Error() << "Unsupported header version V" << hdr.header_version;
if (hdr.ramdisk_size <= 0) {
return Error() << boot_path
<< " contains a valid bootimg header but no ramdisk";
}
// See bootimg.h
auto kernel_size_bytes = (hdr.kernel_size + 4096 - 1) / 4096 * 4096;
auto ramdisk_offset = 4096 + kernel_size_bytes;
std::string ramdisk_content(hdr.ramdisk_size, '\0');
if (!ReadFullyAtOffset(bootimg.get(), ramdisk_content.data(),
hdr.ramdisk_size, ramdisk_offset))
return ErrnoError() << "read ramdisk section";
auto ramdisk_content_file = std::make_unique<TemporaryFile>();
if (!WriteStringToFd(ramdisk_content, ramdisk_content_file->fd))
return ErrnoError() << "write ramdisk section to file";
fsync(ramdisk_content_file->fd);
return ramdisk_content_file;
}
} // namespace
// From the boot image / partition, extract the ramdisk section, decompress it,
// and extract from the cpio archive.
android::base::Result<std::unique_ptr<TemporaryDir>> ExtractRamdiskToDirectory(
std::string_view boot_path) {
auto raw_ramdisk_file = ExtractRamdiskRaw(boot_path);
if (!raw_ramdisk_file.ok()) return raw_ramdisk_file.error();
TemporaryFile decompressed;
auto decompress_res = android::Lz4DecompressLegacy((*raw_ramdisk_file)->path,
decompressed.path);
if (!decompress_res.ok()) return decompress_res.error();
return android::CpioExtract(decompressed.path);
}
} // namespace android