Revert of [debugger api] remove legacy JSON debug protocol. (patchset #2...

Revert of [debugger api] remove legacy JSON debug protocol. (patchset #2 id:20001 of https://codereview.chromium.org/2642253005/ )

Reason for revert:
Node.js relies on this

Original issue's description:
> [debugger api] remove legacy JSON debug protocol.
>
> R=jgruber@chromium.org
> BUG=v8:5530
>
> Review-Url: https://codereview.chromium.org/2642253005
> Cr-Commit-Position: refs/heads/master@{#42543}
> Committed: https://chromium.googlesource.com/v8/v8/+/e26a58e43c51a680a0a6363e0066886f4971a41f

TBR=jgruber@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=v8:5530

Review-Url: https://codereview.chromium.org/2644233003
Cr-Commit-Position: refs/heads/master@{#42549}

include/v8-debug.h

@@ -23,6 +23,68 @@ enum DebugEvent {
 
 class V8_EXPORT Debug {
  public:
+  /**
+   * A client object passed to the v8 debugger whose ownership will be taken by
+   * it. v8 is always responsible for deleting the object.
+   */
+  class ClientData {
+   public:
+    virtual ~ClientData() {}
+  };
+
+
+  /**
+   * A message object passed to the debug message handler.
+   */
+  class Message {
+   public:
+    /**
+     * Check type of message.
+     */
+    virtual bool IsEvent() const = 0;
+    virtual bool IsResponse() const = 0;
+    virtual DebugEvent GetEvent() const = 0;
+
+    /**
+     * Indicate whether this is a response to a continue command which will
+     * start the VM running after this is processed.
+     */
+    virtual bool WillStartRunning() const = 0;
+
+    /**
+     * Access to execution state and event data. Don't store these cross
+     * callbacks as their content becomes invalid. These objects are from the
+     * debugger event that started the debug message loop.
+     */
+    virtual Local<Object> GetExecutionState() const = 0;
+    virtual Local<Object> GetEventData() const = 0;
+
+    /**
+     * Get the debugger protocol JSON.
+     */
+    virtual Local<String> GetJSON() const = 0;
+
+    /**
+     * Get the context active when the debug event happened. Note this is not
+     * the current active context as the JavaScript part of the debugger is
+     * running in its own context which is entered at this point.
+     */
+    virtual Local<Context> GetEventContext() const = 0;
+
+    /**
+     * Client data passed with the corresponding request if any. This is the
+     * client_data data value passed into Debug::SendCommand along with the
+     * request that led to the message or NULL if the message is an event. The
+     * debugger takes ownership of the data and will delete it even if there is
+     * no message handler.
+     */
+    virtual ClientData* GetClientData() const = 0;
+
+    virtual Isolate* GetIsolate() const = 0;
+
+    virtual ~Message() {}
+  };
+
   /**
    * An event details object passed to the debug event listener.
    */
@@ -53,6 +115,13 @@ class V8_EXPORT Debug {
      */
     virtual Local<Value> GetCallbackData() const = 0;
 
+    /**
+     * Client data passed to DebugBreakForCommand function. The
+     * debugger takes ownership of the data and will delete it even if
+     * there is no message handler.
+     */
+    virtual ClientData* GetClientData() const = 0;
+
     virtual Isolate* GetIsolate() const = 0;
 
     virtual ~EventDetails() {}
@@ -63,11 +132,26 @@ class V8_EXPORT Debug {
    *
    * \param event_details object providing information about the debug event
    *
-   * A EventCallback does not take possession of the event data,
+   * A EventCallback2 does not take possession of the event data,
    * and must not rely on the data persisting after the handler returns.
    */
   typedef void (*EventCallback)(const EventDetails& event_details);
 
+  /**
+   * Debug message callback function.
+   *
+   * \param message the debug message handler message object
+   *
+   * A MessageHandler does not take possession of the message data,
+   * and must not rely on the data persisting after the handler returns.
+   */
+  typedef void (*MessageHandler)(const Message& message);
+
+  /**
+   * Callback function for the host to ensure debug messages are processed.
+   */
+  typedef void (*DebugMessageDispatchHandler)();
+
   static bool SetDebugEventListener(Isolate* isolate, EventCallback that,
                                     Local<Value> data = Local<Value>());
 
@@ -83,6 +167,16 @@ class V8_EXPORT Debug {
   V8_DEPRECATED("No longer supported",
                 static bool CheckDebugBreak(Isolate* isolate));
 
+  // Message based interface. The message protocol is JSON.
+  V8_DEPRECATED("No longer supported",
+                static void SetMessageHandler(Isolate* isolate,
+                                              MessageHandler handler));
+
+  V8_DEPRECATED("No longer supported",
+                static void SendCommand(Isolate* isolate,
+                                        const uint16_t* command, int length,
+                                        ClientData* client_data = NULL));
+
   /**
    * Run a JavaScript function in the debugger.
    * \param fun the function to call
@@ -113,6 +207,40 @@ class V8_EXPORT Debug {
                 static MaybeLocal<Value> GetMirror(Local<Context> context,
                                                    v8::Local<v8::Value> obj));
 
+  /**
+   * Makes V8 process all pending debug messages.
+   *
+   * From V8 point of view all debug messages come asynchronously (e.g. from
+   * remote debugger) but they all must be handled synchronously: V8 cannot
+   * do 2 things at one time so normal script execution must be interrupted
+   * for a while.
+   *
+   * Generally when message arrives V8 may be in one of 3 states:
+   * 1. V8 is running script; V8 will automatically interrupt and process all
+   * pending messages;
+   * 2. V8 is suspended on debug breakpoint; in this state V8 is dedicated
+   * to reading and processing debug messages;
+   * 3. V8 is not running at all or has called some long-working C++ function;
+   * by default it means that processing of all debug messages will be deferred
+   * until V8 gets control again; however, embedding application may improve
+   * this by manually calling this method.
+   *
+   * Technically this method in many senses is equivalent to executing empty
+   * script:
+   * 1. It does nothing except for processing all pending debug messages.
+   * 2. It should be invoked with the same precautions and from the same context
+   * as V8 script would be invoked from, because:
+   *   a. with "evaluate" command it can do whatever normal script can do,
+   *   including all native calls;
+   *   b. no other thread should call V8 while this method is running
+   *   (v8::Locker may be used here).
+   *
+   * "Evaluate" debug command behavior currently is not specified in scope
+   * of this method.
+   */
+  V8_DEPRECATED("No longer supported",
+                static void ProcessDebugMessages(Isolate* isolate));
+
   /**
    * Debugger is running in its own context which is entered while debugger
    * messages are being dispatched. This is an explicit getter for this

src/api.cc

@@ -8896,6 +8896,24 @@ bool Debug::CheckDebugBreak(Isolate* isolate) {
 }
 
 
+void Debug::SetMessageHandler(Isolate* isolate,
+                              v8::Debug::MessageHandler handler) {
+  i::Isolate* i_isolate = reinterpret_cast<i::Isolate*>(isolate);
+  ENTER_V8(i_isolate);
+  i_isolate->debug()->SetMessageHandler(handler);
+}
+
+
+void Debug::SendCommand(Isolate* isolate,
+                        const uint16_t* command,
+                        int length,
+                        ClientData* client_data) {
+  i::Isolate* internal_isolate = reinterpret_cast<i::Isolate*>(isolate);
+  internal_isolate->debug()->EnqueueCommandMessage(
+      i::Vector<const uint16_t>(command, length), client_data);
+}
+
+
 MaybeLocal<Value> Debug::Call(Local<Context> context,
                               v8::Local<v8::Function> fun,
                               v8::Local<v8::Value> data) {
@@ -8935,6 +8953,10 @@ MaybeLocal<Value> Debug::GetMirror(Local<Context> context,
   RETURN_ESCAPED(result);
 }
 
+void Debug::ProcessDebugMessages(Isolate* isolate) {
+  reinterpret_cast<i::Isolate*>(isolate)->debug()->ProcessDebugMessages(true);
+}
+
 
 Local<Context> Debug::GetDebugContext(Isolate* isolate) {
   return debug::GetDebugContext(isolate);

src/debug/debug.h

@@ -244,16 +244,62 @@ class DebugInfoListNode {
   DebugInfoListNode* next_;
 };
 
+// Message delivered to the message handler callback. This is either a debugger
+// event or the response to a command.
+class MessageImpl : public v8::Debug::Message {
+ public:
+  // Create a message object for a debug event.
+  static MessageImpl NewEvent(DebugEvent event, bool running,
+                              Handle<JSObject> exec_state,
+                              Handle<JSObject> event_data);
+
+  // Create a message object for the response to a debug command.
+  static MessageImpl NewResponse(DebugEvent event, bool running,
+                                 Handle<JSObject> exec_state,
+                                 Handle<JSObject> event_data,
+                                 Handle<String> response_json,
+                                 v8::Debug::ClientData* client_data);
+
+  // Implementation of interface v8::Debug::Message.
+  virtual bool IsEvent() const;
+  virtual bool IsResponse() const;
+  virtual DebugEvent GetEvent() const;
+  virtual bool WillStartRunning() const;
+  virtual v8::Local<v8::Object> GetExecutionState() const;
+  virtual v8::Local<v8::Object> GetEventData() const;
+  virtual v8::Local<v8::String> GetJSON() const;
+  virtual v8::Local<v8::Context> GetEventContext() const;
+  virtual v8::Debug::ClientData* GetClientData() const;
+  virtual v8::Isolate* GetIsolate() const;
+
+ private:
+  MessageImpl(bool is_event, DebugEvent event, bool running,
+              Handle<JSObject> exec_state, Handle<JSObject> event_data,
+              Handle<String> response_json, v8::Debug::ClientData* client_data);
+
+  bool is_event_;                 // Does this message represent a debug event?
+  DebugEvent event_;              // Debug event causing the break.
+  bool running_;                  // Will the VM start running after this event?
+  Handle<JSObject> exec_state_;   // Current execution state.
+  Handle<JSObject> event_data_;   // Data associated with the event.
+  Handle<String> response_json_;  // Response JSON if message holds a response.
+  v8::Debug::ClientData* client_data_;  // Client data passed with the request.
+};
+
 // Details of the debug event delivered to the debug event listener.
 class EventDetailsImpl : public v8::Debug::EventDetails {
  public:
-  EventDetailsImpl(DebugEvent event, Handle<JSObject> exec_state,
-                   Handle<JSObject> event_data, Handle<Object> callback_data);
+  EventDetailsImpl(DebugEvent event,
+                   Handle<JSObject> exec_state,
+                   Handle<JSObject> event_data,
+                   Handle<Object> callback_data,
+                   v8::Debug::ClientData* client_data);
   virtual DebugEvent GetEvent() const;
   virtual v8::Local<v8::Object> GetExecutionState() const;
   virtual v8::Local<v8::Object> GetEventData() const;
   virtual v8::Local<v8::Context> GetEventContext() const;
   virtual v8::Local<v8::Value> GetCallbackData() const;
+  virtual v8::Debug::ClientData* GetClientData() const;
   virtual v8::Isolate* GetIsolate() const;
 
  private:
@@ -262,8 +308,70 @@ class EventDetailsImpl : public v8::Debug::EventDetails {
   Handle<JSObject> event_data_;         // Data associated with the event.
   Handle<Object> callback_data_;        // User data passed with the callback
                                         // when it was registered.
+  v8::Debug::ClientData* client_data_;  // Data passed to DebugBreakForCommand.
 };
 
+// Message send by user to v8 debugger or debugger output message.
+// In addition to command text it may contain a pointer to some user data
+// which are expected to be passed along with the command reponse to message
+// handler.
+class CommandMessage {
+ public:
+  static CommandMessage New(const Vector<uint16_t>& command,
+                            v8::Debug::ClientData* data);
+  CommandMessage();
+
+  // Deletes user data and disposes of the text.
+  void Dispose();
+  Vector<uint16_t> text() const { return text_; }
+  v8::Debug::ClientData* client_data() const { return client_data_; }
+
+ private:
+  CommandMessage(const Vector<uint16_t>& text, v8::Debug::ClientData* data);
+
+  Vector<uint16_t> text_;
+  v8::Debug::ClientData* client_data_;
+};
+
+// A Queue of CommandMessage objects.  A thread-safe version is
+// LockingCommandMessageQueue, based on this class.
+class CommandMessageQueue BASE_EMBEDDED {
+ public:
+  explicit CommandMessageQueue(int size);
+  ~CommandMessageQueue();
+  bool IsEmpty() const { return start_ == end_; }
+  CommandMessage Get();
+  void Put(const CommandMessage& message);
+  void Clear() { start_ = end_ = 0; }  // Queue is empty after Clear().
+
+ private:
+  // Doubles the size of the message queue, and copies the messages.
+  void Expand();
+
+  CommandMessage* messages_;
+  int start_;
+  int end_;
+  int size_;  // The size of the queue buffer.  Queue can hold size-1 messages.
+};
+
+// LockingCommandMessageQueue is a thread-safe circular buffer of CommandMessage
+// messages.  The message data is not managed by LockingCommandMessageQueue.
+// Pointers to the data are passed in and out. Implemented by adding a
+// Mutex to CommandMessageQueue.  Includes logging of all puts and gets.
+class LockingCommandMessageQueue BASE_EMBEDDED {
+ public:
+  LockingCommandMessageQueue(Logger* logger, int size);
+  bool IsEmpty() const;
+  CommandMessage Get();
+  void Put(const CommandMessage& message);
+  void Clear();
+
+ private:
+  Logger* logger_;
+  CommandMessageQueue queue_;
+  mutable base::Mutex mutex_;
+  DISALLOW_COPY_AND_ASSIGN(LockingCommandMessageQueue);
+};
 
 class DebugFeatureTracker {
  public:
@@ -297,7 +405,7 @@ class DebugFeatureTracker {
 class Debug {
  public:
   // Debug event triggers.
-  void OnDebugBreak(Handle<Object> break_points_hit);
+  void OnDebugBreak(Handle<Object> break_points_hit, bool auto_continue);
 
   void OnThrow(Handle<Object> exception);
   void OnPromiseReject(Handle<Object> promise, Handle<Object> value);
@@ -307,10 +415,14 @@ class Debug {
 
   // API facing.
   void SetEventListener(Handle<Object> callback, Handle<Object> data);
+  void SetMessageHandler(v8::Debug::MessageHandler handler);
+  void EnqueueCommandMessage(Vector<const uint16_t> command,
+                             v8::Debug::ClientData* client_data = NULL);
   MUST_USE_RESULT MaybeHandle<Object> Call(Handle<Object> fun,
                                            Handle<Object> data);
   Handle<Context> GetDebugContext();
   void HandleDebugBreak();
+  void ProcessDebugMessages(bool debug_command_only);
 
   // Internal logic
   bool Load();
@@ -467,6 +579,8 @@ class Debug {
     thread_local_.break_id_ = ++thread_local_.break_count_;
   }
 
+  // Check whether there are commands in the command queue.
+  inline bool has_commands() const { return !command_queue_.IsEmpty(); }
   inline bool ignore_events() const {
     return is_suppressed_ || !is_active_ || isolate_->needs_side_effect_check();
   }
@@ -490,7 +604,8 @@ class Debug {
   // is presented. Other clients can install JavaScript event listener
   // (e.g. some of NodeJS module).
   bool non_inspector_listener_exists() const {
-    return !event_listener_.is_null() && !event_listener_->IsForeign();
+    return message_handler_ != nullptr ||
+           (!event_listener_.is_null() && !event_listener_->IsForeign());
   }
 
   void OnException(Handle<Object> exception, Handle<Object> promise);
@@ -511,8 +626,16 @@ class Debug {
   // Mirror cache handling.
   void ClearMirrorCache();
 
+  void CallEventCallback(v8::DebugEvent event,
+                         Handle<Object> exec_state,
+                         Handle<Object> event_data,
+                         v8::Debug::ClientData* client_data);
   void ProcessCompileEvent(v8::DebugEvent event, Handle<Script> script);
-  void ProcessDebugEvent(v8::DebugEvent event, Handle<JSObject> event_data);
+  void ProcessDebugEvent(v8::DebugEvent event, Handle<JSObject> event_data,
+                         bool auto_continue);
+  void NotifyMessageHandler(v8::DebugEvent event, Handle<JSObject> exec_state,
+                            Handle<JSObject> event_data, bool auto_continue);
+  void InvokeMessageHandler(MessageImpl message);
 
   // Find the closest source position for a break point for a given position.
   int FindBreakablePosition(Handle<DebugInfo> debug_info, int source_position,
@@ -553,8 +676,14 @@ class Debug {
   Handle<Object> event_listener_;
   Handle<Object> event_listener_data_;
 
+  v8::Debug::MessageHandler message_handler_;
+
   debug::DebugEventListener* debug_event_listener_ = nullptr;
 
+  static const int kQueueInitialSize = 4;
+  base::Semaphore command_received_;  // Signaled for each command received.
+  LockingCommandMessageQueue command_queue_;
+
   // Debugger is active, i.e. there is a debug event listener attached.
   bool is_active_;
   // Debugger needs to be notified on every new function call.

src/execution.cc

@@ -469,7 +469,7 @@ Object* StackGuard::HandleInterrupts() {
     isolate_->heap()->HandleGCRequest();
   }
 
-  if (CheckDebugBreak()) {
+  if (CheckDebugBreak() || CheckDebugCommand()) {
     isolate_->debug()->HandleDebugBreak();
   }
 

src/execution.h

@@ -86,11 +86,12 @@ class StackGuard final {
 
 #define INTERRUPT_LIST(V)                       \
   V(DEBUGBREAK, DebugBreak, 0)                  \
-  V(TERMINATE_EXECUTION, TerminateExecution, 1) \
-  V(GC_REQUEST, GC, 2)                          \
-  V(INSTALL_CODE, InstallCode, 3)               \
-  V(API_INTERRUPT, ApiInterrupt, 4)             \
-  V(DEOPT_MARKED_ALLOCATION_SITES, DeoptMarkedAllocationSites, 5)
+  V(DEBUGCOMMAND, DebugCommand, 1)              \
+  V(TERMINATE_EXECUTION, TerminateExecution, 2) \
+  V(GC_REQUEST, GC, 3)                          \
+  V(INSTALL_CODE, InstallCode, 4)               \
+  V(API_INTERRUPT, ApiInterrupt, 5)             \
+  V(DEOPT_MARKED_ALLOCATION_SITES, DeoptMarkedAllocationSites, 6)
 
 #define V(NAME, Name, id)                                          \
   inline bool Check##Name() { return CheckInterrupt(NAME); }  \

src/log.cc

@@ -1249,6 +1249,28 @@ void Logger::HeapSampleItemEvent(const char* type, int number, int bytes) {
 }
 
 
+void Logger::DebugTag(const char* call_site_tag) {
+  if (!log_->IsEnabled() || !FLAG_log) return;
+  Log::MessageBuilder msg(log_);
+  msg.Append("debug-tag,%s", call_site_tag);
+  msg.WriteToLogFile();
+}
+
+
+void Logger::DebugEvent(const char* event_type, Vector<uint16_t> parameter) {
+  if (!log_->IsEnabled() || !FLAG_log) return;
+  StringBuilder s(parameter.length() + 1);
+  for (int i = 0; i < parameter.length(); ++i) {
+    s.AddCharacter(static_cast<char>(parameter[i]));
+  }
+  char* parameter_string = s.Finalize();
+  Log::MessageBuilder msg(log_);
+  msg.Append("debug-queue-event,%s,%15.3f,%s", event_type,
+             base::OS::TimeCurrentMillis(), parameter_string);
+  DeleteArray(parameter_string);
+  msg.WriteToLogFile();
+}
+
 void Logger::RuntimeCallTimerEvent() {
   RuntimeCallStats* stats = isolate_->counters()->runtime_call_stats();
   RuntimeCallTimer* timer = stats->current_timer();

src/log.h

@@ -136,6 +136,12 @@ class Logger : public CodeEventListener {
   // object.
   void SuspectReadEvent(Name* name, Object* obj);
 
+  // Emits an event when a message is put on or read from a debugging queue.
+  // DebugTag lets us put a call-site specific label on the event.
+  void DebugTag(const char* call_site_tag);
+  void DebugEvent(const char* event_type, Vector<uint16_t> parameter);
+
+
   // ==== Events logged by --log-api. ====
   void ApiSecurityCheck();
   void ApiNamedPropertyAccess(const char* tag, JSObject* holder, Object* name);