Integrate the handle verifier from multiple modules (DLLs)

base/win/scoped_handle.cc

 // Copyright (c) 2012 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 "base/win/scoped_handle.h"
 
 #include <unordered_map>
 
 #include "base/debug/alias.h"
+#include "base/environment.h"

[Will Harris, 2015/04/04 19:17:48]

nit: this include is no longer needed

 #include "base/hash.h"
 #include "base/lazy_instance.h"
 #include "base/logging.h"
 #include "base/synchronization/lock_impl.h"
 
+extern "C" {
+__declspec(dllexport) void* GetHandleVerifier();
+typedef void* (*GetHandleVerifierFn)();
+}
+
 namespace {
 
 struct HandleHash {
   size_t operator()(const HANDLE& handle) const {
     char buffer[sizeof(handle)];
     memcpy(buffer, &handle, sizeof(handle));
     return base::Hash(buffer, sizeof(buffer));
   }
 };
 
 struct Info {
   const void* owner;
   const void* pc1;
   const void* pc2;
   DWORD thread_id;
 };
 typedef std::unordered_map<HANDLE, Info, HandleHash> HandleMap;
 
-// g_lock protects g_handle_map and g_closing.
+// g_lock protects the handle map and setting g_active_verifier.
 typedef base::internal::LockImpl NativeLock;
 base::LazyInstance<NativeLock>::Leaky g_lock = LAZY_INSTANCE_INITIALIZER;
-base::LazyInstance<HandleMap>::Leaky g_handle_map = LAZY_INSTANCE_INITIALIZER;
-bool g_closing = false;
-
-// g_verifier_enabled is not protected by g_lock because that would require
-// using the lock (hence, synchornizing multiple threads) even when the
-// verifier is not in use. Note that this variable is initialized to track all
-// handles, and it should only move to the disabled state, and never back to
-// enabled, because that would crash when seeing handles created while the
-// verifier was disabled. This also implies that it is OK if the value change is
-// not propagated immediately to all CPUs (as would happen with a lock).
-bool g_verifier_enabled = true;
 
 bool CloseHandleWrapper(HANDLE handle) {
   if (!::CloseHandle(handle))
     CHECK(false);
   return true;
 }
 
 // Simple automatic locking using a native critical section so it supports
 // recursive locking.
 class AutoNativeLock {
  public:
   explicit AutoNativeLock(NativeLock& lock) : lock_(lock) {
     lock_.Lock();
   }
 
   ~AutoNativeLock() {
     lock_.Unlock();
   }
 
  private:
   NativeLock& lock_;
   DISALLOW_COPY_AND_ASSIGN(AutoNativeLock);
 };
 
+// Implements the actual object that is verifying handles for this process.
+// The active instance is shared across the module boundary but there is no
+// way to delete this object from the wrong side of it (or any side, actually).
+class ActiveVerifier {
+ public:
+  explicit ActiveVerifier(bool enabled)
+      : enabled_(enabled), closing_(false), lock_(g_lock.Pointer()) {
+  }
+
+  // Retrieves the current verifier.
+  static ActiveVerifier* Get();
+
+  // The methods required by HandleTraits. They are virtual because we need to
+  // forward the call execution to another module, instead of letting the
+  // compiler call the version that is linked in the current module.
+  virtual bool CloseHandle(HANDLE handle);
+  virtual void StartTracking(HANDLE handle, const void* owner,
+                             const void* pc1, const void* pc2);
+  virtual void StopTracking(HANDLE handle, const void* owner,
+                            const void* pc1, const void* pc2);
+  virtual void Disable();
+  virtual void OnHandleBeingClosed(HANDLE handle);
+
+ private:
+  ~ActiveVerifier();  // Not implemented.
+
+  static void InstallVerifier();
+
+  bool enabled_;
+  bool closing_;
+  NativeLock* lock_;
+  HandleMap map_;
+  DISALLOW_COPY_AND_ASSIGN(ActiveVerifier);
+};
+ActiveVerifier* g_active_verifier = NULL;
+
+// static
+ActiveVerifier* ActiveVerifier::Get() {
+  if (!g_active_verifier)
+    ActiveVerifier::InstallVerifier();
+
+  return g_active_verifier;
+}
+
+// static
+void ActiveVerifier::InstallVerifier() {
+#if defined(COMPONENT_BUILD)
+  AutoNativeLock lock(g_lock.Get());
+  g_active_verifier = new ActiveVerifier(true);
+#else
+  // If you are reading this, wondering why your process seems deadlocked, take
+  // a look at your DllMain code and remove things that should not be done
+  // there, like doing whatever gave you that nice windows handle you are trying
+  // to store in a ScopedHandle.
+  HMODULE main_module = ::GetModuleHandle(NULL);
+  GetHandleVerifierFn get_handle_verifier =
+      reinterpret_cast<GetHandleVerifierFn>(::GetProcAddress(
+          main_module, "GetHandleVerifier"));
+
+  if (!get_handle_verifier) {
+    g_active_verifier = new ActiveVerifier(false);
+    return;
+  }
+
+  ActiveVerifier* verifier =
+      reinterpret_cast<ActiveVerifier*>(get_handle_verifier());
+
+  // This lock only protects against races in this module, which is fine.
+  AutoNativeLock lock(g_lock.Get());
+  g_active_verifier = verifier ? verifier : new ActiveVerifier(true);
+#endif
+}
+
+bool ActiveVerifier::CloseHandle(HANDLE handle) {
+  if (!enabled_)
+    return CloseHandleWrapper(handle);
+
+  AutoNativeLock lock(*lock_);
+  closing_ = true;
+  CloseHandleWrapper(handle);
+  closing_ = false;
+
+  return true;
+}
+
+void ActiveVerifier::StartTracking(HANDLE handle, const void* owner,
+                                   const void* pc1, const void* pc2) {
+  if (!enabled_)
+    return;
+
+  // Grab the thread id before the lock.
+  DWORD thread_id = GetCurrentThreadId();
+
+  AutoNativeLock lock(*lock_);
+
+  Info handle_info = { owner, pc1, pc2, thread_id };
+  std::pair<HANDLE, Info> item(handle, handle_info);
+  std::pair<HandleMap::iterator, bool> result = map_.insert(item);
+  if (!result.second) {
+    Info other = result.first->second;
+    base::debug::Alias(&other);
+    CHECK(false);
+  }
+}
+
+void ActiveVerifier::StopTracking(HANDLE handle, const void* owner,
+                                  const void* pc1, const void* pc2) {
+  if (!enabled_)
+    return;
+
+  AutoNativeLock lock(*lock_);
+  HandleMap::iterator i = map_.find(handle);
+  if (i == map_.end())
+    CHECK(false);
+
+  Info other = i->second;
+  if (other.owner != owner) {
+    base::debug::Alias(&other);
+    CHECK(false);
+  }
+
+  map_.erase(i);
+}
+
+void ActiveVerifier::Disable() {
+  enabled_ = false;
+}
+
+void ActiveVerifier::OnHandleBeingClosed(HANDLE handle) {
+  AutoNativeLock lock(*lock_);
+  if (closing_)
+    return;
+
+  HandleMap::iterator i = map_.find(handle);
+  if (i == map_.end())
+    return;
+
+  Info other = i->second;
+  base::debug::Alias(&other);
+  CHECK(false);
+}
+
 }  // namespace
 
+void* GetHandleVerifier() {
+  return g_active_verifier;
+}
+
 namespace base {
 namespace win {
 
 // Static.
 bool HandleTraits::CloseHandle(HANDLE handle) {
-  if (!g_verifier_enabled)
-    return CloseHandleWrapper(handle);
-
-  AutoNativeLock lock(g_lock.Get());
-  g_closing = true;
-  CloseHandleWrapper(handle);
-  g_closing = false;
-
-  return true;
+  return ActiveVerifier::Get()->CloseHandle(handle);
 }
 
 // Static.
 void VerifierTraits::StartTracking(HANDLE handle, const void* owner,
                                    const void* pc1, const void* pc2) {
-  if (!g_verifier_enabled)
-    return;
-
-  // Grab the thread id before the lock.
-  DWORD thread_id = GetCurrentThreadId();
-
-  AutoNativeLock lock(g_lock.Get());
-
-  Info handle_info = { owner, pc1, pc2, thread_id };
-  std::pair<HANDLE, Info> item(handle, handle_info);
-  std::pair<HandleMap::iterator, bool> result = g_handle_map.Get().insert(item);
-  if (!result.second) {
-    Info other = result.first->second;
-    debug::Alias(&other);
-    CHECK(false);
-  }
+  return ActiveVerifier::Get()->StartTracking(handle, owner, pc1, pc2);
 }
 
 // Static.
 void VerifierTraits::StopTracking(HANDLE handle, const void* owner,
                                   const void* pc1, const void* pc2) {
-  if (!g_verifier_enabled)
-    return;
-
-  AutoNativeLock lock(g_lock.Get());
-  HandleMap::iterator i = g_handle_map.Get().find(handle);
-  if (i == g_handle_map.Get().end())
-    CHECK(false);
-
-  Info other = i->second;
-  if (other.owner != owner) {
-    debug::Alias(&other);
-    CHECK(false);
-  }
-
-  g_handle_map.Get().erase(i);
+  return ActiveVerifier::Get()->StopTracking(handle, owner, pc1, pc2);
 }
 
 void DisableHandleVerifier() {
-  g_verifier_enabled = false;
+  return ActiveVerifier::Get()->Disable();
 }
 
 void OnHandleBeingClosed(HANDLE handle) {
-  AutoNativeLock lock(g_lock.Get());
-  if (g_closing)
-    return;
-
-  HandleMap::iterator i = g_handle_map.Get().find(handle);
-  if (i == g_handle_map.Get().end())
-    return;
-
-  Info other = i->second;
-  debug::Alias(&other);
-  CHECK(false);
+  return ActiveVerifier::Get()->OnHandleBeingClosed(handle);
 }
 
 }  // namespace win
 }  // namespace base