[Windows Sandbox] MITIGATION_EXTENSION_POINT_DISABLE support for children.

sandbox/win/tests/integration_tests/hooking_dll.cc

+// 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.
+
+#include <stdio.h>
+#include <windows.h>
+
+#define _DLL_EXPORTING
+#include "integration_tests_common.h"
+
+// This data section creates a common area that is accessible
+// to all instances of the DLL (in every process).  They map to
+// the same physical memory location.
+// **Note that each instance of this DLL runs in the context of
+// the process it's injected into, so things like pointers and
+// addresses won't work.
+// **Note that any variables must be initialized to put them in
+// the specified segment, otherwise they will end up in the
+// default data segment.
+#pragma data_seg(".hook")
+HHOOK hook = NULL;
+bool hook_called = false;
+#pragma data_seg()
+#pragma comment(linker, "/SECTION:.hook,RWS")
+
+namespace {
+
+HANDLE event = NULL;
+}
+
+void SetHook(HHOOK hook_handle) {
+  hook = hook_handle;
+
+  return;
+}
+
+bool WasHookCalled() {
+  return hook_called;
+}
+
+LRESULT HookProc(int code, WPARAM w_param, LPARAM l_param) {
+  hook_called = true;
+  ::SetEvent(event);
+
+  // Recent versions of Windows do not require the HHOOK to be passed along,
+  // but I'm doing it here to show the shared use of the HHOOK variable in
+  // the shared data segment.  It is set by the instance of the DLL in the
+  // main test process.
+  return CallNextHookEx(hook, code, w_param, l_param);
+}
+
+BOOL WINAPI DllMain(HINSTANCE instance, DWORD reason, LPVOID reserved) {
+  if (reason == DLL_PROCESS_ATTACH) {
+    // The testing process should have set up this named event already.
+    event = ::OpenEventW(EVENT_MODIFY_STATE, FALSE, g_hook_event);
+    if (event == NULL || event == INVALID_HANDLE_VALUE)
+      return false;
+  }
+
+  if (reason == DLL_PROCESS_DETACH)
+    ::CloseHandle(event);
+
+  return TRUE;
+}