zygote_fork_delegate_linux.h revision 0529e5d033099cbfc42635f6f6183833b09dff6e 
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  // 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 next two are used in the protocol for discovering the
53    // child processes real PID from within the SUID sandbox. See
54    // http://code.google.com/p/chromium/wiki/LinuxZygote
55    kDummyFDIndex,
56    kParentFDIndex,
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_
85