zygote_fork_delegate_linux.h revision e5d81f57cb97b3b6b7fccc9c5610d21eb81db09d 
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
17namespace 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.
22class 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  virtual void Init(int sandboxdesc) = 0;
33
34  // After Init, supply a UMA_HISTOGRAM_ENUMERATION the delegate
35  // would like to supply on the first fork.
36  virtual void InitialUMA(std::string* uma_name,
37                          int* uma_sample,
38                          int* uma_boundary_value) = 0;
39
40  // Returns 'true' if the delegate would like to handle a given fork
41  // request.  Otherwise returns false.  Optionally, fills in uma_name et al
42  // with a report the helper wants to make via UMA_HISTOGRAM_ENUMERATION.
43  virtual bool CanHelp(const std::string& process_type, std::string* uma_name,
44                       int* uma_sample, int* uma_boundary_value) = 0;
45
46  // Indexes of FDs in the vector passed to Fork().
47  enum {
48    // Used to pass in the descriptor for talking to the Browser
49    kBrowserFDIndex,
50    // The next two are used in the protocol for discovering the
51    // child processes real PID from within the SUID sandbox. See
52    // http://code.google.com/p/chromium/wiki/LinuxZygote
53    kDummyFDIndex,
54    kParentFDIndex,
55    kNumPassedFDs  // Number of FDs in the vector passed to Fork().
56  };
57
58  // Delegate forks, returning a -1 on failure. Outside the
59  // suid sandbox, Fork() returns the Linux process ID.
60  // This method is not aware of any potential pid namespaces, so it'll
61  // return a raw pid just like fork() would.
62  virtual pid_t Fork(const std::string& process_type,
63                     const std::vector<int>& fds) = 0;
64
65  // After a successful fork, signal the child to indicate that
66  // the child's PID has been received. Also communicate the
67  // channel switch as a part of acknowledgement message.
68  virtual bool AckChild(int fd, const std::string& channel_switch) = 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_
85