host/commands/launch/boot_image_unpacker.cc

/*
 * 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 "host/commands/launch/boot_image_unpacker.h"

#include <string.h>
#include <unistd.h>

#include <sstream>

#include <glog/logging.h>

#include "common/libs/utils/subprocess.h"
#include "host/commands/launch/bootimg.h"

namespace cvd {

namespace {

// Extracts size bytes from file, starting at offset bytes from the beginning to
// path.
bool ExtractFile(SharedFD source, off_t offset, size_t size,
                 const std::string& path) {
  auto dest = SharedFD::Open(path.c_str(), O_CREAT | O_RDWR, 0755);
  if (!dest->IsOpen()) {
    LOG(ERROR) << "Unable to open " << path;
    return false;
  }
  auto off = source->LSeek(offset, SEEK_SET);
  if (off != offset) {
    LOG(ERROR) << "Failed to lseek: " << source->StrError();
    return false;
  }
  return dest->CopyFrom(*source, size);
}
}  // namespace

std::unique_ptr<BootImageUnpacker> BootImageUnpacker::FromImage(
    const std::string& path) {
  auto boot_img = SharedFD::Open(path.c_str(), O_RDONLY);
  if (!boot_img->IsOpen()) {
    LOG(ERROR) << "Unable to open boot image (" << path
               << "): " << boot_img->StrError();
    return nullptr;
  }
  boot_img_hdr header;
  auto bytes_read = boot_img->Read(&header, sizeof(header));
  if (bytes_read != sizeof(header)) {
    LOG(ERROR) << "Error reading boot image header";
    return nullptr;
  }

  std::ostringstream cmdline;
  cmdline << reinterpret_cast<char*>(&header.cmdline[0]);
  if (header.extra_cmdline[0] != '\0') {
    cmdline << " ";
    cmdline << reinterpret_cast<char*>(&header.extra_cmdline[0]);
  }

  uint32_t page_size = header.page_size;
  // See system/core/mkbootimg/include/mkbootimg/bootimg.h for the origin of
  // these offset calculations
  uint32_t kernel_offset = page_size;
  uint32_t ramdisk_offset =
      kernel_offset +
      ((header.kernel_size + page_size - 1) / page_size) * page_size;

  std::unique_ptr<BootImageUnpacker> ret(new BootImageUnpacker(
      boot_img, cmdline.str(), header.kernel_size, kernel_offset,
      header.ramdisk_size, ramdisk_offset));

  return ret;
}

std::string BootImageUnpacker::kernel_command_line() const {
  return kernel_command_line_;
}

bool BootImageUnpacker::ExtractKernelImage(const std::string& path) const {
  if (kernel_image_size_ == 0) return false;
  return ExtractFile(boot_image_, kernel_image_offset_, kernel_image_size_,
                     path);
}
bool BootImageUnpacker::ExtractRamdiskImage(const std::string& path) const {
  if (ramdisk_image_size_ == 0) return false;
  return ExtractFile(boot_image_, ramdisk_image_offset_, ramdisk_image_size_,
                     path);
}

}  // namespace cvd