text: // Copyright (c) 2012 The Chromium Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file.
  
  #ifndef CONTENT_ZYGOTE_ZYGOTE_LINUX_H_
  #define CONTENT_ZYGOTE_ZYGOTE_LINUX_H_
  
  #include <stddef.h>
  
  #include <memory>
  #include <string>
  #include <vector>
  
  #include "base/containers/small_map.h"
  #include "base/files/scoped_file.h"
  #include "base/posix/global_descriptors.h"
  #include "base/process/kill.h"
  #include "base/process/process.h"
  #include "base/process/process_handle.h"
  #include "base/time/time.h"
  
  namespace base {
  class PickleIterator;
  }
  
  namespace content {
  
  class ZygoteForkDelegate;
  
  // This is the object which implements the zygote. The ZygoteMain function,
  // which is called from ChromeMain, simply constructs one of these objects and
  // runs it.
  class Zygote {
   public:
    Zygote(int sandbox_flags,
           std::vector<std::unique_ptr<ZygoteForkDelegate>> helpers,
           const base::GlobalDescriptors::Descriptor& ipc_backchannel);
    ~Zygote();
  
    bool ProcessRequests();
  
   private:
    struct ZygoteProcessInfo {
      // Pid from inside the Zygote's PID namespace.
      base::ProcessHandle internal_pid;
      // Keeps track of which fork delegate helper the process was started from.
      ZygoteForkDelegate* started_from_helper;
      // Records when the browser requested the zygote to reap this process.
      base::TimeTicks time_of_reap_request;
      // Notes whether the zygote has sent SIGKILL to this process.
      bool sent_sigkill;
    };
    using ZygoteProcessMap =
        base::small_map<std::map<base::ProcessHandle, ZygoteProcessInfo>>;
  
    // Retrieve a ZygoteProcessInfo from the process_info_map_.
    // Returns true and write to process_info if |pid| can be found, return
    // false otherwise.
    bool GetProcessInfo(base::ProcessHandle pid, ZygoteProcessInfo* process_info);
  
    // Returns true if the SUID sandbox is active.
    bool UsingSUIDSandbox() const;
    // Returns true if the NS sandbox is active.
    bool UsingNSSandbox() const;
  
    // ---------------------------------------------------------------------------
    // Requests from the browser...
  
    // Read and process a request from the browser. Returns true if we are in a
    // new process and thus need to unwind back into ChromeMain.
    bool HandleRequestFromBrowser(int fd);
  
    void HandleReapRequest(int fd, base::PickleIterator iter);
  
    // Get the termination status of |real_pid|. |real_pid| is the PID as it
    // appears outside of the sandbox.
    // Return true if it managed to get the termination status and return the
    // status in |status| and the exit code in |exit_code|.
    bool GetTerminationStatus(base::ProcessHandle real_pid,
                              bool known_dead,
                              base::TerminationStatus* status,
                              int* exit_code);
  
    void HandleGetTerminationStatus(int fd, base::PickleIterator iter);
  
    // This is equivalent to fork(), except that, when using the SUID sandbox, it
    // returns the real PID of the child process as it appears outside the
    // sandbox, rather than returning the PID inside the sandbox.  The child's
    // real PID is determined by having it call
    // service_manager::SendZygoteChildPing(int) using the |pid_oracle|
    // descriptor.
    // Finally, when using a ZygoteForkDelegate helper, |uma_name|, |uma_sample|,
    // and |uma_boundary_value| may be set if the helper wants to make a UMA
    // report via UMA_HISTOGRAM_ENUMERATION.
    int ForkWithRealPid(const std::string& process_type,
                        const base::GlobalDescriptors::Mapping& fd_mapping,
                        base::ScopedFD pid_oracle,
                        std::string* uma_name,
                        int* uma_sample,
                        int* uma_boundary_value);
  
    // Unpacks process type and arguments from |iter| and forks a new process.
    // Returns -1 on error, otherwise returns twice, returning 0 to the child
    // process and the child process ID to the parent process, like fork().
    base::ProcessId ReadArgsAndFork(base::PickleIterator iter,
                                    std::vector<base::ScopedFD> fds,
                                    std::string* uma_name,
                                    int* uma_sample,
                                    int* uma_boundary_value);
  
    // Handle a 'fork' request from the browser: this means that the browser
    // wishes to start a new renderer. Returns true if we are in a new process,
    // otherwise writes the child_pid back to the browser via |fd|. Writes a
    // child_pid of -1 on error.
    bool HandleForkRequest(int fd,
                           base::PickleIterator iter,
                           std::vector<base::ScopedFD> fds);
  
    bool HandleGetSandboxStatus(int fd, base::PickleIterator iter);
  
    // Attempt to reap the child process by calling waitpid, and return
    // whether successful.  If the process has not terminated within
    // 2 seconds of its reap request, send it SIGKILL.
    bool ReapChild(const base::TimeTicks& now, ZygoteProcessInfo* child);
  
    // Attempt to reap all outstanding children in |to_reap_|.
    void ReapChildren();
  
    // The Zygote needs to keep some information about each process. Most
    // notably what the PID of the process is inside the PID namespace of
    // the Zygote and whether or not a process was started by the
    // ZygoteForkDelegate helper.
    ZygoteProcessMap process_info_map_;
  
    const int sandbox_flags_;
    std::vector<std::unique_ptr<ZygoteForkDelegate>> helpers_;
  
    // Count of how many fork delegates for which we've invoked InitialUMA().
    size_t initial_uma_index_;
  
    // The vector contains the child processes that need to be reaped.
    std::vector<ZygoteProcessInfo> to_reap_;
  
    // Sandbox IPC channel for renderers to invoke services from the browser. See
    // https://chromium.googlesource.com/chromium/src/+/master/docs/linux/sandbox_ipc.md
    base::GlobalDescriptors::Descriptor ipc_backchannel_;
  };
  
  }  // namespace content
  
  #endif  // CONTENT_ZYGOTE_ZYGOTE_LINUX_H_
  