child_process_host.h revision 2a99a7e74a7f215066514fe81d2bfa6639d9eddd 
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 content {
17
18class ChildProcessHostDelegate;
19
20// This represents a non-browser process. This can include traditional child
21// processes like plugins, or an embedder could even use this for long lived
22// processes that run independent of the browser process.
23class CONTENT_EXPORT ChildProcessHost : public IPC::Sender {
24 public:
25  virtual ~ChildProcessHost() {}
26
27  // Used to create a child process host. The delegate must outlive this object.
28  static ChildProcessHost* Create(
29      ChildProcessHostDelegate* delegate);
30
31  // These flags may be passed to GetChildPath in order to alter its behavior,
32  // causing it to return a child path more suited to a specific task.
33  enum {
34    // No special behavior requested.
35    CHILD_NORMAL = 0,
36
37#if defined(OS_LINUX)
38    // Indicates that the child execed after forking may be execced from
39    // /proc/self/exe rather than using the "real" app path. This prevents
40    // autoupdate from confusing us if it changes the file out from under us.
41    // You will generally want to set this on Linux, except when there is an
42    // override to the command line (for example, we're forking a renderer in
43    // gdb). In this case, you'd use GetChildPath to get the real executable
44    // file name, and then prepend the GDB command to the command line.
45    CHILD_ALLOW_SELF = 1 << 0,
46#elif defined(OS_MACOSX)
47
48    // Requests that the child run in a process that does not have the
49    // PIE (position-independent executable) bit set, effectively disabling
50    // ASLR. For process types that need to allocate a large contiguous
51    // region, ASLR may not leave a large enough "hole" for the purpose. This
52    // option should be used sparingly, and only when absolutely necessary.
53    // This option is currently incompatible with CHILD_ALLOW_HEAP_EXECUTION.
54    CHILD_NO_PIE = 1 << 1,
55
56    // Requests that the child run in a process that does not protect the
57    // heap against execution. Normally, heap pages may be made executable
58    // with mprotect, so this mode should be used sparingly. It is intended
59    // for processes that may host plug-ins that expect an executable heap
60    // without having to call mprotect. This option is currently incompatible
61    // with CHILD_NO_PIE.
62    CHILD_ALLOW_HEAP_EXECUTION = 1 << 2,
63#endif
64  };
65
66  // Returns the pathname to be used for a child process.  If a subprocess
67  // pathname was specified on the command line, that will be used.  Otherwise,
68  // the default child process pathname will be returned.  On most platforms,
69  // this will be the same as the currently-executing process.
70  //
71  // The |flags| argument accepts one or more flags such as CHILD_ALLOW_SELF
72  // and CHILD_ALLOW_HEAP_EXECUTION as defined above. Pass only CHILD_NORMAL
73  // if none of these special behaviors are required.
74  //
75  // On failure, returns an empty FilePath.
76  static base::FilePath GetChildPath(int flags);
77
78  // Send the shutdown message to the child process.
79  // Does not check with the delegate's CanShutdown.
80  virtual void ForceShutdown() = 0;
81
82  // Creates the IPC channel.  Returns the channel id if it succeeded, an
83  // empty string otherwise
84  virtual std::string CreateChannel() = 0;
85
86  // Returns true iff the IPC channel is currently being opened;
87  virtual bool IsChannelOpening() = 0;
88
89  // Adds an IPC message filter.  A reference will be kept to the filter.
90  virtual void AddFilter(IPC::ChannelProxy::MessageFilter* filter) = 0;
91
92#if defined(OS_POSIX)
93  // See IPC::Channel::TakeClientFileDescriptor.
94  virtual int TakeClientFileDescriptor() = 0;
95#endif
96};
97
98};  // namespace content
99
100#endif  // CONTENT_PULIC_COMMON_CHILD_PROCESS_HOST_H_
101