content/public/common/zygote_fork_delegate_linux.h

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef CONTENT_PUBLIC_COMMON_ZYGOTE_FORK_DELEGATE_LINUX_H_
   6 #define CONTENT_PUBLIC_COMMON_ZYGOTE_FORK_DELEGATE_LINUX_H_
   7
   8 #include <unistd.h>
   9
  10 #include <string>
  11 #include <vector>
  12
  13 // TODO(jln) base::TerminationStatus should be forward declared when switching
  14 // to C++11.
  15 #include "base/process/kill.h"
  16
  17 namespace content {
  18
  19 // The ZygoteForkDelegate allows the Chrome Linux zygote to delegate
  20 // fork operations to another class that knows how to do some
  21 // specialized version of fork.
  22 class ZygoteForkDelegate {
  23  public:
  24   // A ZygoteForkDelegate is created during Chrome linux zygote
  25   // initialization, and provides "fork()" functionality as an
  26   // alternative to forking the zygote.  A new delegate is passed in
  27   // as an argument to ZygoteMain().
  28   virtual ~ZygoteForkDelegate() {}
  29
  30   // Initialization happens in the zygote after it has been
  31   // started by ZygoteMain.
  32   // If |enable_layer1_sandbox| is true, the delegate must enable a
  33   // layer-1 sandbox such as the setuid sandbox.
  34   virtual void Init(int sandboxdesc, bool enable_layer1_sandbox) = 0;
  35
  36   // After Init, supply a UMA_HISTOGRAM_ENUMERATION the delegate
  37   // would like to supply on the first fork.
  38   virtual void InitialUMA(std::string* uma_name,
  39                           int* uma_sample,
  40                           int* uma_boundary_value) = 0;
  41
  42   // Returns 'true' if the delegate would like to handle a given fork
  43   // request.  Otherwise returns false.  Optionally, fills in uma_name et al
  44   // with a report the helper wants to make via UMA_HISTOGRAM_ENUMERATION.
  45   virtual bool CanHelp(const std::string& process_type, std::string* uma_name,
  46                        int* uma_sample, int* uma_boundary_value) = 0;
  47
  48   // Indexes of FDs in the vector passed to Fork().
  49   enum {
  50     // Used to pass in the descriptor for talking to the Browser
  51     kBrowserFDIndex,
  52     // The PID oracle is used in the protocol for discovering the
  53     // child process's real PID from within the SUID sandbox.
  54     // The child process is required to write to the socket after
  55     // successfully forking.
  56     kPIDOracleFDIndex,
  57     kNumPassedFDs  // Number of FDs in the vector passed to Fork().
  58   };
  59
  60   // Delegate forks, returning a -1 on failure. Outside the
  61   // suid sandbox, Fork() returns the Linux process ID.
  62   // This method is not aware of any potential pid namespaces, so it'll
  63   // return a raw pid just like fork() would.
  64   // Delegate is responsible for communicating the channel ID to the
  65   // newly created child process.
  66   virtual pid_t Fork(const std::string& process_type,
  67                      const std::vector<int>& fds,
  68                      const std::string& channel_id) = 0;
  69
  70   // The fork delegate must also assume the role of waiting for its children
  71   // since the caller will not be their parents and cannot do it. |pid| here
  72   // should be a pid that has been returned by the Fork() method. i.e. This
  73   // method is completely unaware of eventual PID namespaces due to sandboxing.
  74   // |known_dead| indicates that the process is already dead and that a
  75   // blocking wait() should be performed. In this case, GetTerminationStatus()
  76   // will send a SIGKILL to the target process first.
  77   virtual bool GetTerminationStatus(pid_t pid, bool known_dead,
  78                                     base::TerminationStatus* status,
  79                                     int* exit_code) = 0;
  80 };
  81
  82 }  // namespace content
  83
  84 #endif  // CONTENT_PUBLIC_COMMON_ZYGOTE_FORK_DELEGATE_LINUX_H_