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_PULIC_COMMON_CHILD_PROCESS_HOST_H_
6#define CONTENT_PULIC_COMMON_CHILD_PROCESS_HOST_H_
7
8#include "build/build_config.h"
9#include "content/common/content_export.h"
10#include "ipc/ipc_channel_proxy.h"
11
12namespace base {
13class FilePath;
14}
15
16namespace IPC {
17class MessageFilter;
18}
19
20namespace content {
21
22class ChildProcessHostDelegate;
23
24// This represents a non-browser process. This can include traditional child
25// processes like plugins, or an embedder could even use this for long lived
26// processes that run independent of the browser process.
27class CONTENT_EXPORT ChildProcessHost : public IPC::Sender {
28 public:
29  virtual ~ChildProcessHost() {}
30
31  // This is a value never returned as the unique id of any child processes of
32  // any kind, including the values returned by RenderProcessHost::GetID().
33  static int kInvalidUniqueID;
34
35  // Used to create a child process host. The delegate must outlive this object.
36  static ChildProcessHost* Create(ChildProcessHostDelegate* delegate);
37
38  // These flags may be passed to GetChildPath in order to alter its behavior,
39  // causing it to return a child path more suited to a specific task.
40  enum {
41    // No special behavior requested.
42    CHILD_NORMAL = 0,
43
44#if defined(OS_LINUX)
45    // Indicates that the child execed after forking may be execced from
46    // /proc/self/exe rather than using the "real" app path. This prevents
47    // autoupdate from confusing us if it changes the file out from under us.
48    // You will generally want to set this on Linux, except when there is an
49    // override to the command line (for example, we're forking a renderer in
50    // gdb). In this case, you'd use GetChildPath to get the real executable
51    // file name, and then prepend the GDB command to the command line.
52    CHILD_ALLOW_SELF = 1 << 0,
53#elif defined(OS_MACOSX)
54
55    // Requests that the child run in a process that does not have the
56    // PIE (position-independent executable) bit set, effectively disabling
57    // ASLR. For process types that need to allocate a large contiguous
58    // region, ASLR may not leave a large enough "hole" for the purpose. This
59    // option should be used sparingly, and only when absolutely necessary.
60    // This option is currently incompatible with CHILD_ALLOW_HEAP_EXECUTION.
61    CHILD_NO_PIE = 1 << 1,
62
63    // Requests that the child run in a process that does not protect the
64    // heap against execution. Normally, heap pages may be made executable
65    // with mprotect, so this mode should be used sparingly. It is intended
66    // for processes that may host plug-ins that expect an executable heap
67    // without having to call mprotect. This option is currently incompatible
68    // with CHILD_NO_PIE.
69    CHILD_ALLOW_HEAP_EXECUTION = 1 << 2,
70#endif
71  };
72
73  // Returns the pathname to be used for a child process.  If a subprocess
74  // pathname was specified on the command line, that will be used.  Otherwise,
75  // the default child process pathname will be returned.  On most platforms,
76  // this will be the same as the currently-executing process.
77  //
78  // The |flags| argument accepts one or more flags such as CHILD_ALLOW_SELF
79  // and CHILD_ALLOW_HEAP_EXECUTION as defined above. Pass only CHILD_NORMAL
80  // if none of these special behaviors are required.
81  //
82  // On failure, returns an empty FilePath.
83  static base::FilePath GetChildPath(int flags);
84
85  // Send the shutdown message to the child process.
86  // Does not check with the delegate's CanShutdown.
87  virtual void ForceShutdown() = 0;
88
89  // Creates the IPC channel.  Returns the channel id if it succeeded, an
90  // empty string otherwise
91  virtual std::string CreateChannel() = 0;
92
93  // Returns true iff the IPC channel is currently being opened;
94  virtual bool IsChannelOpening() = 0;
95
96  // Adds an IPC message filter.  A reference will be kept to the filter.
97  virtual void AddFilter(IPC::MessageFilter* filter) = 0;
98
99#if defined(OS_POSIX)
100  // See IPC::Channel::TakeClientFileDescriptor.
101  virtual int TakeClientFileDescriptor() = 0;
102#endif
103};
104
105};  // namespace content
106
107#endif  // CONTENT_PULIC_COMMON_CHILD_PROCESS_HOST_H_
108