text: // Copyright 2021 The gVisor Authors.
  //
  // 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 GVISOR_TEST_UTIL_CGROUP_UTIL_H_
  #define GVISOR_TEST_UTIL_CGROUP_UTIL_H_
  
  #include <unistd.h>
  
  #include "absl/container/flat_hash_map.h"
  #include "absl/container/flat_hash_set.h"
  #include "absl/strings/string_view.h"
  #include "test/util/cleanup.h"
  #include "test/util/fs_util.h"
  #include "test/util/temp_path.h"
  
  namespace gvisor {
  namespace testing {
  
  // Cgroup represents a cgroup directory on a mounted cgroupfs.
  class Cgroup {
   public:
    Cgroup(std::string_view path);
  
    uint64_t id() const { return id_; }
  
    const std::string& Path() const { return cgroup_path_; }
  
    std::string Relpath(absl::string_view leaf) const {
      return JoinPath(cgroup_path_, leaf);
    }
  
    // Returns the contents of a cgroup control file with the given name.
    PosixErrorOr<std::string> ReadControlFile(absl::string_view name) const;
  
    // Reads the contents of a cgroup control with the given name, and attempts
    // to parse it as an integer.
    PosixErrorOr<int64_t> ReadIntegerControlFile(absl::string_view name) const;
  
    // Writes a string to a cgroup control file.
    PosixError WriteControlFile(absl::string_view name,
                                const std::string& value) const;
  
    // Writes an integer value to a cgroup control file.
    PosixError WriteIntegerControlFile(absl::string_view name,
                                       int64_t value) const;
  
    // Returns the thread ids of the leaders of thread groups managed by this
    // cgroup.
    PosixErrorOr<absl::flat_hash_set<pid_t>> Procs() const;
  
    PosixErrorOr<absl::flat_hash_set<pid_t>> Tasks() const;
  
    // ContainsCallingProcess checks whether the calling process is part of the
    PosixError ContainsCallingProcess() const;
  
   private:
    PosixErrorOr<absl::flat_hash_set<pid_t>> ParsePIDList(
        absl::string_view data) const;
  
    static int64_t next_id_;
    int64_t id_;
    const std::string cgroup_path_;
  };
  
  // Mounter is a utility for creating cgroupfs mounts. It automatically manages
  // the lifetime of created mounts.
  class Mounter {
   public:
    Mounter(TempPath root) : root_(std::move(root)) {}
  
    PosixErrorOr<Cgroup> MountCgroupfs(std::string mopts);
  
    PosixError Unmount(const Cgroup& c);
  
   private:
    // The destruction order of these members avoids errors during cleanup. We
    // first unmount (by executing the mounts_ cleanups), then delete the
    // mountpoint subdirs, then delete the root.
    TempPath root_;
    absl::flat_hash_map<int64_t, TempPath> mountpoints_;
    absl::flat_hash_map<int64_t, Cleanup> mounts_;
  };
  
  // Represents a line from /proc/cgroups.
  struct CgroupsEntry {
    std::string subsys_name;
    uint32_t hierarchy;
    uint64_t num_cgroups;
    bool enabled;
  };
  
  // Returns a parsed representation of /proc/cgroups.
  PosixErrorOr<absl::flat_hash_map<std::string, CgroupsEntry>>
  ProcCgroupsEntries();
  
  // Represents a line from /proc/<pid>/cgroup.
  struct PIDCgroupEntry {
    uint32_t hierarchy;
    std::string controllers;
    std::string path;
  };
  
  // Returns a parsed representation of /proc/<pid>/cgroup.
  PosixErrorOr<absl::flat_hash_map<std::string, PIDCgroupEntry>>
  ProcPIDCgroupEntries(pid_t pid);
  
  }  // namespace testing
  }  // namespace gvisor
  
  #endif  // GVISOR_TEST_UTIL_CGROUP_UTIL_H_
  