apexd/apex_database.h

/*
 * 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.
 */

#ifndef ANDROID_APEXD_APEX_DATABASE_H_
#define ANDROID_APEXD_APEX_DATABASE_H_

#include <map>
#include <string>
#include <unordered_set>

#include <android-base/logging.h>

namespace android {
namespace apex {

class MountedApexDatabase {
 public:
  // Stores associated low-level data for a mounted APEX. To conserve memory,
  // the APEX file isn't stored, but must be opened to retrieve specific data.
  struct MountedApexData {
    std::string loop_name;  // Loop device used (fs path).
    std::string full_path;  // Full path to the apex file.
    std::string mount_point;  // Path this apex is mounted on.
    std::string device_name;  // Name of the dm verity device.

    MountedApexData() {}
    MountedApexData(const std::string& loop_name, const std::string& full_path,
                    const std::string& mount_point,
                    const std::string& device_name)
        : loop_name(loop_name),
          full_path(full_path),
          mount_point(mount_point),
          device_name(device_name) {}

    inline bool operator<(const MountedApexData& rhs) const {
      int compare_val = loop_name.compare(rhs.loop_name);
      if (compare_val < 0) {
        return true;
      } else if (compare_val > 0) {
        return false;
      }
      compare_val = full_path.compare(rhs.full_path);
      if (compare_val < 0) {
        return true;
      } else if (compare_val > 0) {
        return false;
      }
      compare_val = mount_point.compare(rhs.mount_point);
      if (compare_val < 0) {
        return true;
      } else if (compare_val > 0) {
        return false;
      }
      return device_name < rhs.device_name;
    }
  };

  inline void CheckAtMostOneLatest() {
    for (const auto& apex_set : mounted_apexes_) {
      size_t count = 0;
      for (const auto& pair : apex_set.second) {
        if (pair.second) {
          count++;
        }
      }
      CHECK_LE(count, 1u) << apex_set.first;
    }
  }

  inline void CheckUniqueLoopDm() {
    std::unordered_set<std::string> loop_devices;
    std::unordered_set<std::string> dm_devices;
    for (const auto& apex_set : mounted_apexes_) {
      for (const auto& pair : apex_set.second) {
        if (pair.first.loop_name != "") {
          CHECK(loop_devices.insert(pair.first.loop_name).second)
              << "Duplicate loop device: " << pair.first.loop_name;
        }
        if (pair.first.device_name != "") {
          CHECK(dm_devices.insert(pair.first.device_name).second)
              << "Duplicate dm device: " << pair.first.device_name;
        }
      }
    }
  }

  template <typename... Args>
  inline void AddMountedApex(const std::string& package, bool latest,
                             Args&&... args) {
    auto it = mounted_apexes_.find(package);
    if (it == mounted_apexes_.end()) {
      auto insert_it =
          mounted_apexes_.emplace(package, std::map<MountedApexData, bool>());
      CHECK(insert_it.second);
      it = insert_it.first;
    }

    auto check_it = it->second.emplace(
        MountedApexData(std::forward<Args>(args)...), latest);
    CHECK(check_it.second);

    CheckAtMostOneLatest();
    CheckUniqueLoopDm();
  }

  inline void RemoveMountedApex(const std::string& package,
                                const std::string& full_path) {
    auto it = mounted_apexes_.find(package);
    if (it == mounted_apexes_.end()) {
      return;
    }

    auto& pkg_map = it->second;

    for (auto pkg_it = pkg_map.begin(); pkg_it != pkg_map.end(); ++pkg_it) {
      if (pkg_it->first.full_path == full_path) {
        pkg_map.erase(pkg_it);
        return;
      }
    }
  }

  inline void SetLatest(const std::string& package,
                        const std::string& full_path) {
    auto it = mounted_apexes_.find(package);
    CHECK(it != mounted_apexes_.end());

    auto& pkg_map = it->second;

    for (auto pkg_it = pkg_map.begin(); pkg_it != pkg_map.end(); ++pkg_it) {
      if (pkg_it->first.full_path == full_path) {
        pkg_it->second = true;
        for (auto reset_it = pkg_map.begin(); reset_it != pkg_map.end();
             ++reset_it) {
          if (reset_it != pkg_it) {
            reset_it->second = false;
          }
        }
        return;
      }
    }

    LOG(FATAL) << "Did not find " << package << " " << full_path;
  }

  inline void UnsetLatestForall(const std::string& package) {
    auto it = mounted_apexes_.find(package);
    if (it == mounted_apexes_.end()) {
      return;
    }
    for (auto& data : it->second) {
      data.second = false;
    }
  }

  template <typename T>
  inline void ForallMountedApexes(const std::string& package,
                                  const T& handler) const {
    auto it = mounted_apexes_.find(package);
    if (it == mounted_apexes_.end()) {
      return;
    }
    for (auto& pair : it->second) {
      handler(pair.first, pair.second);
    }
  }

  template <typename T>
  inline void ForallMountedApexes(const T& handler) const {
    for (const auto& pkg : mounted_apexes_) {
      for (const auto& pair : pkg.second) {
        handler(pkg.first, pair.first, pair.second);
      }
    }
  }

  void PopulateFromMounts();

 private:
  // A map from package name to mounted apexes.
  // Note: using std::maps to
  //         a) so we do not have to worry about iterator invalidation.
  //         b) do not have to const_cast (over std::set)
  // TODO: Eventually this structure (and functions) need to be guarded by
  // locks.
  std::map<std::string, std::map<MountedApexData, bool>> mounted_apexes_;
};

}  // namespace apex
}  // namespace android

#endif  // ANDROID_APEXD_APEX_DATABASE_H_