content/public/common/child_process_host.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_CHILD_PROCESS_HOST_H_
   6 #define CONTENT_PUBLIC_COMMON_CHILD_PROCESS_HOST_H_
   7
   8 #include "base/files/scoped_file.h"
   9 #include "build/build_config.h"
  10 #include "content/common/content_export.h"
  11 #include "ipc/attachment_broker_privileged.h"
  12 #include "ipc/ipc_channel_proxy.h"
  13
  14 namespace base {
  15 class FilePath;
  16 }
  17
  18 namespace IPC {
  19 class MessageFilter;
  20 }
  21
  22 namespace content {
  23
  24 class ChildProcessHostDelegate;
  25
  26 // This represents a non-browser process. This can include traditional child
  27 // processes like plugins, or an embedder could even use this for long lived
  28 // processes that run independent of the browser process.
  29 class CONTENT_EXPORT ChildProcessHost : public IPC::Sender {
  30  public:
  31   ~ChildProcessHost() override {}
  32
  33   // This is a value never returned as the unique id of any child processes of
  34   // any kind, including the values returned by RenderProcessHost::GetID().
  35   static int kInvalidUniqueID;
  36
  37   // This value is used as the tracing id of the browser process for identifying
  38   // cross-process shared memory segments when tracing.
  39   // Note: In single-process mode all the clients of tracing will use this id.
  40   static uint64 kBrowserTracingProcessId;
  41
  42   // Used to create a child process host. The delegate must outlive this object.
  43   static ChildProcessHost* Create(ChildProcessHostDelegate* delegate);
  44
  45   // These flags may be passed to GetChildPath in order to alter its behavior,
  46   // causing it to return a child path more suited to a specific task.
  47   enum {
  48     // No special behavior requested.
  49     CHILD_NORMAL = 0,
  50
  51 #if defined(OS_LINUX)
  52     // Indicates that the child execed after forking may be execced from
  53     // /proc/self/exe rather than using the "real" app path. This prevents
  54     // autoupdate from confusing us if it changes the file out from under us.
  55     // You will generally want to set this on Linux, except when there is an
  56     // override to the command line (for example, we're forking a renderer in
  57     // gdb). In this case, you'd use GetChildPath to get the real executable
  58     // file name, and then prepend the GDB command to the command line.
  59     CHILD_ALLOW_SELF = 1 << 0,
  60 #elif defined(OS_MACOSX)
  61
  62     // Requests that the child run in a process that does not have the
  63     // PIE (position-independent executable) bit set, effectively disabling
  64     // ASLR. For process types that need to allocate a large contiguous
  65     // region, ASLR may not leave a large enough "hole" for the purpose. This
  66     // option should be used sparingly, and only when absolutely necessary.
  67     // This option is currently incompatible with CHILD_ALLOW_HEAP_EXECUTION.
  68     CHILD_NO_PIE = 1 << 1,
  69
  70     // Requests that the child run in a process that does not protect the
  71     // heap against execution. Normally, heap pages may be made executable
  72     // with mprotect, so this mode should be used sparingly. It is intended
  73     // for processes that may host plugins that expect an executable heap
  74     // without having to call mprotect. This option is currently incompatible
  75     // with CHILD_NO_PIE.
  76     CHILD_ALLOW_HEAP_EXECUTION = 1 << 2,
  77 #endif
  78   };
  79
  80   // Returns the pathname to be used for a child process.  If a subprocess
  81   // pathname was specified on the command line, that will be used.  Otherwise,
  82   // the default child process pathname will be returned.  On most platforms,
  83   // this will be the same as the currently-executing process.
  84   //
  85   // The |flags| argument accepts one or more flags such as CHILD_ALLOW_SELF
  86   // and CHILD_ALLOW_HEAP_EXECUTION as defined above. Pass only CHILD_NORMAL
  87   // if none of these special behaviors are required.
  88   //
  89   // On failure, returns an empty FilePath.
  90   static base::FilePath GetChildPath(int flags);
  91
  92   // Returns an AttachmentBroker used to broker attachments of IPC messages to
  93   // child processes.
  94   static IPC::AttachmentBrokerPrivileged* GetAttachmentBroker();
  95
  96   // Send the shutdown message to the child process.
  97   // Does not check with the delegate's CanShutdown.
  98   virtual void ForceShutdown() = 0;
  99
 100   // Creates the IPC channel.  Returns the channel id if it succeeded, an
 101   // empty string otherwise
 102   virtual std::string CreateChannel() = 0;
 103
 104   // Returns true iff the IPC channel is currently being opened;
 105   virtual bool IsChannelOpening() = 0;
 106
 107   // Adds an IPC message filter.  A reference will be kept to the filter.
 108   virtual void AddFilter(IPC::MessageFilter* filter) = 0;
 109
 110 #if defined(OS_POSIX)
 111   // See IPC::Channel::TakeClientFileDescriptor.
 112   virtual base::ScopedFD TakeClientFileDescriptor() = 0;
 113 #endif
 114 };
 115
 116 };  // namespace content
 117
 118 #endif  // CONTENT_PUBLIC_COMMON_CHILD_PROCESS_HOST_H_