[Win] Create ModuleWatcher.

chrome/common/conflicts/module_watcher_win.h

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CHROME_COMMON_CONFLICTS_MODULE_WATCHER_WIN_H_
+#define CHROME_COMMON_CONFLICTS_MODULE_WATCHER_WIN_H_
+
+#include "base/callback.h"
+#include "base/files/file_path.h"
+#include "base/memory/ref_counted.h"
+#include "base/synchronization/lock.h"
+
+namespace base {
+template <class ObserverType>
+class ObserverListThreadSafe;
+}  // namespace base
+
+namespace conflicts {
+
+class ModuleWatcherTest;
+
+// This class observes modules as they are loaded and unloaded into a processes
+// address space. It works by installing a DllNotification callback, and
+// also enumerating all currently loaded modules at the time of its creation.
+class ModuleWatcher {
+ public:
+  // The types of events that are observed by the watcher.
+  enum EventType {
+    // The module was already loaded at the time of creation of the
+    // ModuleWatcher.
+    MODULE_ALREADY_LOADED,
+    // The module was not loaded at the time of creation of the ModuleWatcher
+    // and is being loaded.
+    MODULE_LOADED,
+    // The module is being unloaded.
+    MODULE_UNLOADED,
+  };
+
+  // A notification about a module being loaded or unloaded.
+  struct ModuleEvent {
+    // The type of event.
+    EventType event_type;
+    // The full path to the module being loaded or unloaded.
+    base::FilePath module_path;
+    // The load address of the module.
+    void* load_address;
+    // The size of the module in memory, in bytes.
+    size_t size;
+  };
+
+  // Clients may register callbacks with the following type in order to receive
+  // notifications.
+  using OnModuleEventCallback = base::Callback<void(const ModuleEvent& event)>;
+  class Observer;
+
+  ModuleWatcher();
+  ~ModuleWatcher();
+
+  // Registers a callback with this ModuleWatcher. The thread on which the
+  // callback is registered is the thread on which the callback will be invoked.
+  // To unregister the callback simply delete the resulting Observer object.
+  // Note that the observer must be destroyed on the same thread on which it
+  // was created. (See ObserverListThreadSafe::RemoveObserver for details.)
+  std::unique_ptr<Observer> RegisterCallback(

[Patrick Monette, 2016/11/03 20:18:15]

Seems like you are implementing base::CallbackList<> in a thread-safe way.

Maybe you could implement the CallbackListThreadSafe class in order to separate
this
responsability from ModuleWatcher, which would make its implementation quite a
bit simpler.

Feel free to ignore this suggestion.

[chrisha, 2016/11/04 15:32:42]

I am indeed. I'm not sure if anybody else needs this, so I'll punt on this for
now. I will, however, leave a comment with CallbackListThreadSafe so that people
find this code if they actually want such a thing.

+      const OnModuleEventCallback& callback);
+
+  // Starts the watcher. This enumerates all loaded modules and registers a
+  // DllNotification callback for continued notifications. This is threadsafe.
+  // Note that it is possible to receive duplicate notifications for some
+  // modules as the initial loaded module enumerations is racy with the
+  // installation of the callback. In this case you will receive both a
+  // MODULE_LOADED and a MODULE_ALREADY_LOADED event for the same module. Since
+  // the callback is installed first no modules will be missed.
+  void Start();
+
+  // Stops the watcher. The watcher may subsequently be restarted. Doesn't
+  // need to be called explicitly as ~ModuleWatcher will do so as well. This
+  // is thread-safe.
+  void Stop();
+
+  // Returns true if the watcher is currently running, false otherwise.
+  bool IsRunning();
+
+ protected:
+  // Used as a bridge between the operating system notifications and this class.
+  class Bridge;
+
+  // The Bridge requires access to Notify.
+  friend class Bridge;
+  // For unittesting.
+  friend class ModuleWatcherTest;
+  // Observers require access to |observer_list_|.
+  friend class Observer;
+
+  // Registers a Dll Notification callback with the OS. Returns true on success,
+  // false otherwise. Modifies |dll_notification_cookie_|.
+  bool RegisterDllNotificationCallback();
+
+  // Removes the installed Dll Notification callback. This should only
+  // be called if InstallDllNotificationCallback returned true. Returns true on
+  // success, false otherwise.
+  bool UnregisterDllNotificationCallback();
+
+  // Enumerates all currently loaded modules, firing off callbacks. Returns
+  // true on success, false otherwise.
+  bool EnumerateAlreadyLoadedModules();
+
+  // Invoked by ModuleWatcherHelper. Dispatches the provided ModuleEvent to all
+  // registered observers.
+  void Notify(const ModuleEvent& event);
+
+  // The list of registered observers. This is directly modified by
+  // ModuleWatcher::Observer.
+  scoped_refptr<base::ObserverListThreadSafe<Observer>> observer_list_;
+
+ private:
+  base::Lock lock_;
+  // Indicates whether or not the ModuleWatcher is currently started. Under
+  // lock_.
+  bool started_;
+  // Used by the DllNotification mechanism. Under lock_.
+  void* dll_notification_cookie_;
+
+  DISALLOW_COPY_AND_ASSIGN(ModuleWatcher);
+};
+
+// Observer class. This is all implementation detail, plumbing callbacks to
+// an ObserverListThreadSafe and handling automatic unregistration. Nothing to
+// see here.
+class ModuleWatcher::Observer {
+ public:
+  ~Observer();
+
+ protected:
+  friend ModuleWatcher;
+
+  // Constructor. To actually create one of these use
+  // ModuleWatcher::RegisterCallback
+  Observer(const OnModuleEventCallback& callback,
+           ModuleWatcher* module_watcher);
+
+  // Used by ModuleWatcher to dispatch events to this observer.
+  void Notify(const ModuleEvent& event);
+
+  // The bound callback.
+  OnModuleEventCallback callback_;
+  // The parent ModuleWatcher to which this observer belongs.
+  ModuleWatcher* module_watcher_;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(Observer);
+};
+
+}  // namespace conflicts
+
+#endif  // CHROME_COMMON_CONFLICTS_MODULE_WATCHER_WIN_H_