CSE2410 Fall 2014 Bounce

// Copyright 2006-2008 the V8 project authors. All rights reserved.

// Redistribution and use in source and binary forms, with or without

// modification, are permitted provided that the following conditions are

// met:

//

//     * Redistributions of source code must retain the above copyright

//       notice, this list of conditions and the following disclaimer.

//     * Redistributions in binary form must reproduce the above

//       copyright notice, this list of conditions and the following

//       disclaimer in the documentation and/or other materials provided

//       with the distribution.

//     * Neither the name of Google Inc. nor the names of its

//       contributors may be used to endorse or promote products derived

//       from this software without specific prior written permission.

//

// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT

// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR

// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT

// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,

// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT

// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,

// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY

// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE

// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

#include "v8.h"

#include "api.h"

#include "arguments.h"

#include "bootstrapper.h"

#include "code-stubs.h"

#include "compiler.h"

#include "debug.h"

#include "execution.h"

#include "global-handles.h"

#include "natives.h"

#include "stub-cache.h"

#include "log.h"

namespace v8 { namespace internal {

static void PrintLn(v8::Local<v8::Value> value) {

  v8::Local<v8::String> s = value->ToString();

  char* data = NewArray<char>(s->Length() + 1);

  if (data == NULL) {

    V8::FatalProcessOutOfMemory("PrintLn");

    return;

  }

  s->WriteAscii(data);

  PrintF("%s\n", data);

  DeleteArray(data);

}

static Handle<Code> ComputeCallDebugBreak(int argc) {

  CALL_HEAP_FUNCTION(StubCache::ComputeCallDebugBreak(argc), Code);

}

static Handle<Code> ComputeCallDebugPrepareStepIn(int argc) {

  CALL_HEAP_FUNCTION(StubCache::ComputeCallDebugPrepareStepIn(argc), Code);

}

BreakLocationIterator::BreakLocationIterator(Handle<DebugInfo> debug_info,

                                             BreakLocatorType type) {

  debug_info_ = debug_info;

  type_ = type;

  reloc_iterator_ = NULL;

  reloc_iterator_original_ = NULL;

  Reset();  // Initialize the rest of the member variables.

}

BreakLocationIterator::~BreakLocationIterator() {

  ASSERT(reloc_iterator_ != NULL);

  ASSERT(reloc_iterator_original_ != NULL);

  delete reloc_iterator_;

  delete reloc_iterator_original_;

}

void BreakLocationIterator::Next() {

  AssertNoAllocation nogc;

  ASSERT(!RinfoDone());

  // Iterate through reloc info for code and original code stopping at each

  // breakable code target.

  bool first = break_point_ == -1;

  while (!RinfoDone()) {

    if (!first) RinfoNext();

    first = false;

    if (RinfoDone()) return;

    // Whenever a statement position or (plain) position is passed update the

    // current value of these.

    if (RelocInfo::IsPosition(rmode())) {

      if (RelocInfo::IsStatementPosition(rmode())) {

        statement_position_ =

            rinfo()->data() - debug_info_->shared()->start_position();

      }

      // Always update the position as we don't want that to be before the

      // statement position.

      position_ = rinfo()->data() - debug_info_->shared()->start_position();

      ASSERT(position_ >= 0);

      ASSERT(statement_position_ >= 0);

    }

    // Check for breakable code target. Look in the original code as setting

    // break points can cause the code targets in the running (debugged) code to

    // be of a different kind than in the original code.

    if (RelocInfo::IsCodeTarget(rmode())) {

      Address target = original_rinfo()->target_address();

      Code* code = Code::GetCodeFromTargetAddress(target);

      if (code->is_inline_cache_stub() || RelocInfo::IsConstructCall(rmode())) {

        break_point_++;

        return;

      }

      if (code->kind() == Code::STUB) {

        if (type_ == ALL_BREAK_LOCATIONS) {

          if (Debug::IsBreakStub(code)) {

            break_point_++;

            return;

          }

        } else {

          ASSERT(type_ == SOURCE_BREAK_LOCATIONS);

          if (Debug::IsSourceBreakStub(code)) {

            break_point_++;

            return;

          }

        }

      }

    }

    // Check for break at return.

    if (RelocInfo::IsJSReturn(rmode())) {

      // Set the positions to the end of the function.

      if (debug_info_->shared()->HasSourceCode()) {

        position_ = debug_info_->shared()->end_position() -

                    debug_info_->shared()->start_position();

      } else {

        position_ = 0;

      }

      statement_position_ = position_;

      break_point_++;

      return;

    }

  }

}

void BreakLocationIterator::Next(int count) {

  while (count > 0) {

    Next();

    count--;

  }

}

// Find the break point closest to the supplied address.

void BreakLocationIterator::FindBreakLocationFromAddress(Address pc) {

  // Run through all break points to locate the one closest to the address.

  int closest_break_point = 0;

  int distance = kMaxInt;

  while (!Done()) {

    // Check if this break point is closer that what was previously found.

    if (this->pc() < pc && pc - this->pc() < distance) {

      closest_break_point = break_point();

      distance = pc - this->pc();

      // Check whether we can't get any closer.

      if (distance == 0) break;

    }

    Next();

  }

  // Move to the break point found.

  Reset();

  Next(closest_break_point);

}

// Find the break point closest to the supplied source position.

void BreakLocationIterator::FindBreakLocationFromPosition(int position) {

  // Run through all break points to locate the one closest to the source

  // position.

  int closest_break_point = 0;

  int distance = kMaxInt;

  while (!Done()) {

    // Check if this break point is closer that what was previously found.

    if (position <= statement_position() &&

        statement_position() - position < distance) {

      closest_break_point = break_point();

      distance = statement_position() - position;

      // Check whether we can't get any closer.

      if (distance == 0) break;

    }

    Next();

  }

  // Move to the break point found.

  Reset();

  Next(closest_break_point);

}

void BreakLocationIterator::Reset() {

  // Create relocation iterators for the two code objects.

  if (reloc_iterator_ != NULL) delete reloc_iterator_;

  if (reloc_iterator_original_ != NULL) delete reloc_iterator_original_;

  reloc_iterator_ = new RelocIterator(debug_info_->code());

  reloc_iterator_original_ = new RelocIterator(debug_info_->original_code());

  // Position at the first break point.

  break_point_ = -1;

  position_ = 1;

  statement_position_ = 1;

  Next();

}

bool BreakLocationIterator::Done() const {

  return RinfoDone();

}

void BreakLocationIterator::SetBreakPoint(Handle<Object> break_point_object) {

  // If there is not already a real break point here patch code with debug

  // break.

  if (!HasBreakPoint()) {

    SetDebugBreak();

  }

  ASSERT(IsDebugBreak());

  // Set the break point information.

  DebugInfo::SetBreakPoint(debug_info_, code_position(),

                           position(), statement_position(),

                           break_point_object);

}

void BreakLocationIterator::ClearBreakPoint(Handle<Object> break_point_object) {

  // Clear the break point information.

  DebugInfo::ClearBreakPoint(debug_info_, code_position(), break_point_object);

  // If there are no more break points here remove the debug break.

  if (!HasBreakPoint()) {

    ClearDebugBreak();

    ASSERT(!IsDebugBreak());

  }

}

void BreakLocationIterator::SetOneShot() {

  // If there is a real break point here no more to do.

  if (HasBreakPoint()) {

    ASSERT(IsDebugBreak());

    return;

  }

  // Patch code with debug break.

  SetDebugBreak();

}

void BreakLocationIterator::ClearOneShot() {

  // If there is a real break point here no more to do.

  if (HasBreakPoint()) {

    ASSERT(IsDebugBreak());

    return;

  }

  // Patch code removing debug break.

  ClearDebugBreak();

  ASSERT(!IsDebugBreak());

}

void BreakLocationIterator::SetDebugBreak() {

  // If there is already a break point here just return. This might happen if

  // the same code is flooded with break points twice. Flooding the same

  // function twice might happen when stepping in a function with an exception

  // handler as the handler and the function is the same.

  if (IsDebugBreak()) {

    return;

  }

  if (RelocInfo::IsJSReturn(rmode())) {

    // Patch the frame exit code with a break point.

    SetDebugBreakAtReturn();

  } else {

    // Patch the original code with the current address as the current address

    // might have changed by the inline caching since the code was copied.

    original_rinfo()->set_target_address(rinfo()->target_address());

    // Patch the code to invoke the builtin debug break function matching the

    // calling convention used by the call site.

    Handle<Code> dbgbrk_code(Debug::FindDebugBreak(rinfo()));

    rinfo()->set_target_address(dbgbrk_code->entry());

  }

  ASSERT(IsDebugBreak());

}

void BreakLocationIterator::ClearDebugBreak() {

  if (RelocInfo::IsJSReturn(rmode())) {

    // Restore the frame exit code.

    ClearDebugBreakAtReturn();

  } else {

    // Patch the code to the original invoke.

    rinfo()->set_target_address(original_rinfo()->target_address());

  }

  ASSERT(!IsDebugBreak());

}

void BreakLocationIterator::PrepareStepIn() {

  HandleScope scope;

  // Step in can only be prepared if currently positioned on an IC call or

  // construct call.

  Address target = rinfo()->target_address();

  Code* code = Code::GetCodeFromTargetAddress(target);

  if (code->is_call_stub()) {

    // Step in through IC call is handled by the runtime system. Therefore make

    // sure that the any current IC is cleared and the runtime system is

    // called. If the executing code has a debug break at the location change

    // the call in the original code as it is the code there that will be

    // executed in place of the debug break call.

    Handle<Code> stub = ComputeCallDebugPrepareStepIn(code->arguments_count());

    if (IsDebugBreak()) {

      original_rinfo()->set_target_address(stub->entry());

    } else {

      rinfo()->set_target_address(stub->entry());

    }

  } else {

    // Step in through constructs call requires no changes to the running code.

    ASSERT(RelocInfo::IsConstructCall(rmode()));

  }

}

// Check whether the break point is at a position which will exit the function.

bool BreakLocationIterator::IsExit() const {

  return (RelocInfo::IsJSReturn(rmode()));

}

bool BreakLocationIterator::HasBreakPoint() {

  return debug_info_->HasBreakPoint(code_position());

}

// Check whether there is a debug break at the current position.

bool BreakLocationIterator::IsDebugBreak() {

  if (RelocInfo::IsJSReturn(rmode())) {

    return IsDebugBreakAtReturn();

  } else {

    return Debug::IsDebugBreak(rinfo()->target_address());

  }

}

Object* BreakLocationIterator::BreakPointObjects() {

  return debug_info_->GetBreakPointObjects(code_position());

}

// Clear out all the debug break code. This is ONLY supposed to be used when

// shutting down the debugger as it will leave the break point information in

// DebugInfo even though the code is patched back to the non break point state.

void BreakLocationIterator::ClearAllDebugBreak() {

  while (!Done()) {

    ClearDebugBreak();

    Next();

  }

}

bool BreakLocationIterator::RinfoDone() const {

  ASSERT(reloc_iterator_->done() == reloc_iterator_original_->done());

  return reloc_iterator_->done();

}

void BreakLocationIterator::RinfoNext() {

  reloc_iterator_->next();

  reloc_iterator_original_->next();

#ifdef DEBUG

  ASSERT(reloc_iterator_->done() == reloc_iterator_original_->done());

  if (!reloc_iterator_->done()) {

    ASSERT(rmode() == original_rmode());

  }

#endif

}

bool Debug::has_break_points_ = false;

DebugInfoListNode* Debug::debug_info_list_ = NULL;

// Threading support.

void Debug::ThreadInit() {

  thread_local_.break_count_ = 0;

  thread_local_.break_id_ = 0;

  thread_local_.break_frame_id_ = StackFrame::NO_ID;

  thread_local_.last_step_action_ = StepNone;

  thread_local_.last_statement_position_ = RelocInfo::kNoPosition;

  thread_local_.step_count_ = 0;

  thread_local_.last_fp_ = 0;

  thread_local_.step_into_fp_ = 0;

  thread_local_.after_break_target_ = 0;

  thread_local_.debugger_entry_ = NULL;

  thread_local_.preemption_pending_ = false;

}

JSCallerSavedBuffer Debug::registers_;

Debug::ThreadLocal Debug::thread_local_;

char* Debug::ArchiveDebug(char* storage) {

  char* to = storage;

  memcpy(to, reinterpret_cast<char*>(&thread_local_), sizeof(ThreadLocal));

  to += sizeof(ThreadLocal);

  memcpy(to, reinterpret_cast<char*>(&registers_), sizeof(registers_));

  ThreadInit();

  ASSERT(to <= storage + ArchiveSpacePerThread());

  return storage + ArchiveSpacePerThread();

}

char* Debug::RestoreDebug(char* storage) {

  char* from = storage;

  memcpy(reinterpret_cast<char*>(&thread_local_), from, sizeof(ThreadLocal));

  from += sizeof(ThreadLocal);

  memcpy(reinterpret_cast<char*>(&registers_), from, sizeof(registers_));

  ASSERT(from <= storage + ArchiveSpacePerThread());

  return storage + ArchiveSpacePerThread();

}

int Debug::ArchiveSpacePerThread() {

  return sizeof(ThreadLocal) + sizeof(registers_);

}

// Default break enabled.

bool Debug::disable_break_ = false;

// Default call debugger on uncaught exception.

bool Debug::break_on_exception_ = false;

bool Debug::break_on_uncaught_exception_ = true;

Handle<Context> Debug::debug_context_ = Handle<Context>();

Code* Debug::debug_break_return_entry_ = NULL;

Code* Debug::debug_break_return_ = NULL;

void Debug::HandleWeakDebugInfo(v8::Persistent<v8::Value> obj, void* data) {

  DebugInfoListNode* node = reinterpret_cast<DebugInfoListNode*>(data);

  RemoveDebugInfo(node->debug_info());

#ifdef DEBUG

  node = Debug::debug_info_list_;

  while (node != NULL) {

    ASSERT(node != reinterpret_cast<DebugInfoListNode*>(data));

    node = node->next();

  }

#endif

}

DebugInfoListNode::DebugInfoListNode(DebugInfo* debug_info): next_(NULL) {

  // Globalize the request debug info object and make it weak.

  debug_info_ = Handle<DebugInfo>::cast((GlobalHandles::Create(debug_info)));

  GlobalHandles::MakeWeak(reinterpret_cast<Object**>(debug_info_.location()),

                          this, Debug::HandleWeakDebugInfo);

}

DebugInfoListNode::~DebugInfoListNode() {

  GlobalHandles::Destroy(reinterpret_cast<Object**>(debug_info_.location()));

}

void Debug::Setup(bool create_heap_objects) {

  ThreadInit();

  if (create_heap_objects) {

    // Get code to handle entry to debug break on return.

    debug_break_return_entry_ =

        Builtins::builtin(Builtins::Return_DebugBreakEntry);

    ASSERT(debug_break_return_entry_->IsCode());

    // Get code to handle debug break on return.

    debug_break_return_ =

        Builtins::builtin(Builtins::Return_DebugBreak);

    ASSERT(debug_break_return_->IsCode());

  }

}

bool Debug::CompileDebuggerScript(int index) {

  HandleScope scope;

  // Bail out if the index is invalid.

  if (index == -1) {

    return false;

  }

  // Find source and name for the requested script.

  Handle<String> source_code = Bootstrapper::NativesSourceLookup(index);

  Vector<const char> name = Natives::GetScriptName(index);

  Handle<String> script_name = Factory::NewStringFromAscii(name);

  // Compile the script.

  bool allow_natives_syntax = FLAG_allow_natives_syntax;

  FLAG_allow_natives_syntax = true;

  Handle<JSFunction> boilerplate;

  boilerplate = Compiler::Compile(source_code, script_name, 0, 0, NULL, NULL);

  FLAG_allow_natives_syntax = allow_natives_syntax;

  // Silently ignore stack overflows during compilation.

  if (boilerplate.is_null()) {

    ASSERT(Top::has_pending_exception());

    Top::clear_pending_exception();

    return false;

  }

  // Execute the boilerplate function in the debugger context.

  Handle<Context> context = Top::global_context();

  bool caught_exception = false;

  Handle<JSFunction> function =

      Factory::NewFunctionFromBoilerplate(boilerplate, context);

  Handle<Object> result =

      Execution::TryCall(function, Handle<Object>(context->global()),

                         0, NULL, &caught_exception);

  // Check for caught exceptions.

  if (caught_exception) {

    Handle<Object> message = MessageHandler::MakeMessageObject(

        "error_loading_debugger", NULL, HandleVector<Object>(&result, 1),

        Handle<String>());

    MessageHandler::ReportMessage(NULL, message);

    return false;

  }

  // Mark this script as native and return successfully.

  Handle<Script> script(Script::cast(function->shared()->script()));

  script->set_type(Smi::FromInt(SCRIPT_TYPE_NATIVE));

  return true;

}

bool Debug::Load() {

  // Return if debugger is already loaded.

  if (IsLoaded()) return true;

  // Bail out if we're already in the process of compiling the native

  // JavaScript source code for the debugger.

  if (Debugger::compiling_natives() || Debugger::is_loading_debugger())

    return false;

  Debugger::set_loading_debugger(true);

  // Disable breakpoints and interrupts while compiling and running the

  // debugger scripts including the context creation code.

  DisableBreak disable(true);

  PostponeInterruptsScope postpone;

  // Create the debugger context.

  HandleScope scope;

  Handle<Context> context =

      Bootstrapper::CreateEnvironment(Handle<Object>::null(),

                                      v8::Handle<ObjectTemplate>(),

                                      NULL);

  // Use the debugger context.

  SaveContext save;

  Top::set_context(*context);

  // Expose the builtins object in the debugger context.

  Handle<String> key = Factory::LookupAsciiSymbol("builtins");

  Handle<GlobalObject> global = Handle<GlobalObject>(context->global());

  SetProperty(global, key, Handle<Object>(global->builtins()), NONE);

  // Compile the JavaScript for the debugger in the debugger context.

  Debugger::set_compiling_natives(true);

  bool caught_exception =

      !CompileDebuggerScript(Natives::GetIndex("mirror")) ||

      !CompileDebuggerScript(Natives::GetIndex("debug"));

  Debugger::set_compiling_natives(false);

  // Make sure we mark the debugger as not loading before we might

  // return.

  Debugger::set_loading_debugger(false);

  // Check for caught exceptions.

  if (caught_exception) return false;

  // Debugger loaded.

  debug_context_ = Handle<Context>::cast(GlobalHandles::Create(*context));

  return true;

}

void Debug::Unload() {

  // Return debugger is not loaded.

  if (!IsLoaded()) {

    return;

  }

  // Clear debugger context global handle.

  GlobalHandles::Destroy(reinterpret_cast<Object**>(debug_context_.location()));

  debug_context_ = Handle<Context>();

}

// Set the flag indicating that preemption happened during debugging.

void Debug::PreemptionWhileInDebugger() {

  ASSERT(InDebugger());

  Debug::set_preemption_pending(true);

}

void Debug::Iterate(ObjectVisitor* v) {

  v->VisitPointer(bit_cast<Object**, Code**>(&(debug_break_return_entry_)));

  v->VisitPointer(bit_cast<Object**, Code**>(&(debug_break_return_)));

}

Object* Debug::Break(Arguments args) {

  HandleScope scope;

  ASSERT(args.length() == 0);

  // Get the top-most JavaScript frame.

  JavaScriptFrameIterator it;

  JavaScriptFrame* frame = it.frame();

  // Just continue if breaks are disabled or debugger cannot be loaded.

  if (disable_break() || !Load()) {

    SetAfterBreakTarget(frame);

    return Heap::undefined_value();

  }

  // Enter the debugger.

  EnterDebugger debugger;

  if (debugger.FailedToEnter()) {

    return Heap::undefined_value();

  }

  // Postpone interrupt during breakpoint processing.

  PostponeInterruptsScope postpone;

  // Get the debug info (create it if it does not exist).

  Handle<SharedFunctionInfo> shared =

      Handle<SharedFunctionInfo>(JSFunction::cast(frame->function())->shared());

  Handle<DebugInfo> debug_info = GetDebugInfo(shared);

  // Find the break point where execution has stopped.

  BreakLocationIterator break_location_iterator(debug_info,

                                                ALL_BREAK_LOCATIONS);

  break_location_iterator.FindBreakLocationFromAddress(frame->pc());

  // Check whether step next reached a new statement.

  if (!StepNextContinue(&break_location_iterator, frame)) {

    // Decrease steps left if performing multiple steps.

    if (thread_local_.step_count_ > 0) {

      thread_local_.step_count_--;

    }

  }

  // If there is one or more real break points check whether any of these are

  // triggered.

  Handle<Object> break_points_hit(Heap::undefined_value());

  if (break_location_iterator.HasBreakPoint()) {

    Handle<Object> break_point_objects =

        Handle<Object>(break_location_iterator.BreakPointObjects());

    break_points_hit = CheckBreakPoints(break_point_objects);

  }

  // Notify debugger if a real break point is triggered or if performing single

  // stepping with no more steps to perform. Otherwise do another step.

  if (!break_points_hit->IsUndefined() ||

    (thread_local_.last_step_action_ != StepNone &&

     thread_local_.step_count_ == 0)) {

    // Clear all current stepping setup.

    ClearStepping();

    // Notify the debug event listeners.

    Debugger::OnDebugBreak(break_points_hit, false);

  } else if (thread_local_.last_step_action_ != StepNone) {

    // Hold on to last step action as it is cleared by the call to

    // ClearStepping.

    StepAction step_action = thread_local_.last_step_action_;

    int step_count = thread_local_.step_count_;

    // Clear all current stepping setup.

    ClearStepping();

    // Set up for the remaining steps.

    PrepareStep(step_action, step_count);

  }

  // Install jump to the call address which was overwritten.

  SetAfterBreakTarget(frame);

  return Heap::undefined_value();

}

// Check the break point objects for whether one or more are actually

// triggered. This function returns a JSArray with the break point objects

// which is triggered.

Handle<Object> Debug::CheckBreakPoints(Handle<Object> break_point_objects) {

  int break_points_hit_count = 0;

  Handle<JSArray> break_points_hit = Factory::NewJSArray(1);

  // If there are multiple break points they are in a FixedArray.

  ASSERT(!break_point_objects->IsUndefined());

  if (break_point_objects->IsFixedArray()) {

    Handle<FixedArray> array(FixedArray::cast(*break_point_objects));

    for (int i = 0; i < array->length(); i++) {

      Handle<Object> o(array->get(i));

      if (CheckBreakPoint(o)) {

        break_points_hit->SetElement(break_points_hit_count++, *o);

      }

    }

  } else {

    if (CheckBreakPoint(break_point_objects)) {

      break_points_hit->SetElement(break_points_hit_count++,

                                   *break_point_objects);

    }

  }

  // Return undefined if no break points where triggered.

  if (break_points_hit_count == 0) {

    return Factory::undefined_value();

  }

  return break_points_hit;

}

// Check whether a single break point object is triggered.

bool Debug::CheckBreakPoint(Handle<Object> break_point_object) {

  HandleScope scope;

  // Ignore check if break point object is not a JSObject.

  if (!break_point_object->IsJSObject()) return true;

  // Get the function CheckBreakPoint (defined in debug.js).

  Handle<JSFunction> check_break_point =

    Handle<JSFunction>(JSFunction::cast(

      debug_context()->global()->GetProperty(

          *Factory::LookupAsciiSymbol("IsBreakPointTriggered"))));

  // Get the break id as an object.

  Handle<Object> break_id = Factory::NewNumberFromInt(Debug::break_id());

  // Call HandleBreakPointx.

  bool caught_exception = false;

  const int argc = 2;

  Object** argv[argc] = {

    break_id.location(),

    reinterpret_cast<Object**>(break_point_object.location())

  };

  Handle<Object> result = Execution::TryCall(check_break_point,

                                             Top::builtins(), argc, argv,

                                             &caught_exception);

  // If exception or non boolean result handle as not triggered

  if (caught_exception || !result->IsBoolean()) {

    return false;

  }

  // Return whether the break point is triggered.

  return *result == Heap::true_value();

}

// Check whether the function has debug information.

bool Debug::HasDebugInfo(Handle<SharedFunctionInfo> shared) {

  return !shared->debug_info()->IsUndefined();

}

// Return the debug info for this function. EnsureDebugInfo must be called

// prior to ensure the debug info has been generated for shared.

Handle<DebugInfo> Debug::GetDebugInfo(Handle<SharedFunctionInfo> shared) {

  ASSERT(HasDebugInfo(shared));

  return Handle<DebugInfo>(DebugInfo::cast(shared->debug_info()));

}

void Debug::SetBreakPoint(Handle<SharedFunctionInfo> shared,

                          int source_position,

                          Handle<Object> break_point_object) {

  HandleScope scope;

  if (!EnsureDebugInfo(shared)) {

    // Return if retrieving debug info failed.

    return;

  }

  Handle<DebugInfo> debug_info = GetDebugInfo(shared);

  // Source positions starts with zero.

  ASSERT(source_position >= 0);

  // Find the break point and change it.

  BreakLocationIterator it(debug_info, SOURCE_BREAK_LOCATIONS);

  it.FindBreakLocationFromPosition(source_position);

  it.SetBreakPoint(break_point_object);

  // At least one active break point now.

  ASSERT(debug_info->GetBreakPointCount() > 0);

}

void Debug::ClearBreakPoint(Handle<Object> break_point_object) {

  HandleScope scope;

  DebugInfoListNode* node = debug_info_list_;

  while (node != NULL) {

    Object* result = DebugInfo::FindBreakPointInfo(node->debug_info(),

                                                   break_point_object);

    if (!result->IsUndefined()) {

      // Get information in the break point.

      BreakPointInfo* break_point_info = BreakPointInfo::cast(result);

      Handle<DebugInfo> debug_info = node->debug_info();

      Handle<SharedFunctionInfo> shared(debug_info->shared());

      int source_position =  break_point_info->statement_position()->value();

      // Source positions starts with zero.

      ASSERT(source_position >= 0);

      // Find the break point and clear it.

      BreakLocationIterator it(debug_info, SOURCE_BREAK_LOCATIONS);

      it.FindBreakLocationFromPosition(source_position);

      it.ClearBreakPoint(break_point_object);

      // If there are no more break points left remove the debug info for this

      // function.

      if (debug_info->GetBreakPointCount() == 0) {

        RemoveDebugInfo(debug_info);

      }

      return;

    }

    node = node->next();

  }

}

void Debug::ClearAllBreakPoints() {

  DebugInfoListNode* node = debug_info_list_;

  while (node != NULL) {

    // Remove all debug break code.

    BreakLocationIterator it(node->debug_info(), ALL_BREAK_LOCATIONS);

    it.ClearAllDebugBreak();

    node = node->next();

  }

  // Remove all debug info.

  while (debug_info_list_ != NULL) {

    RemoveDebugInfo(debug_info_list_->debug_info());

  }

}

void Debug::FloodWithOneShot(Handle<SharedFunctionInfo> shared) {

  // Make sure the function has setup the debug info.

  if (!EnsureDebugInfo(shared)) {

    // Return if we failed to retrieve the debug info.

    return;

  }

  // Flood the function with break points.

  BreakLocationIterator it(GetDebugInfo(shared), ALL_BREAK_LOCATIONS);

  while (!it.Done()) {

    it.SetOneShot();

    it.Next();

  }

}

void Debug::FloodHandlerWithOneShot() {

  // Iterate through the JavaScript stack looking for handlers.

  StackFrame::Id id = break_frame_id();

  if (id == StackFrame::NO_ID) {

    // If there is no JavaScript stack don't do anything.

    return;

  }

  for (JavaScriptFrameIterator it(id); !it.done(); it.Advance()) {

    JavaScriptFrame* frame = it.frame();

    if (frame->HasHandler()) {

      Handle<SharedFunctionInfo> shared =

          Handle<SharedFunctionInfo>(

              JSFunction::cast(frame->function())->shared());

      // Flood the function with the catch block with break points

      FloodWithOneShot(shared);

      return;

    }

  }

}

void Debug::ChangeBreakOnException(ExceptionBreakType type, bool enable) {

  if (type == BreakUncaughtException) {

    break_on_uncaught_exception_ = enable;

  } else {

    break_on_exception_ = enable;

  }

}

void Debug::PrepareStep(StepAction step_action, int step_count) {

  HandleScope scope;

  ASSERT(Debug::InDebugger());

  // Remember this step action and count.

  thread_local_.last_step_action_ = step_action;

  thread_local_.step_count_ = step_count;

  // Get the frame where the execution has stopped and skip the debug frame if

  // any. The debug frame will only be present if execution was stopped due to

  // hitting a break point. In other situations (e.g. unhandled exception) the

  // debug frame is not present.

  StackFrame::Id id = break_frame_id();

  if (id == StackFrame::NO_ID) {

    // If there is no JavaScript stack don't do anything.

    return;

  }

  JavaScriptFrameIterator frames_it(id);

  JavaScriptFrame* frame = frames_it.frame();

  // First of all ensure there is one-shot break points in the top handler

  // if any.

  FloodHandlerWithOneShot();

  // If the function on the top frame is unresolved perform step out. This will

  // be the case when calling unknown functions and having the debugger stopped

  // in an unhandled exception.

  if (!frame->function()->IsJSFunction()) {

    // Step out: Find the calling JavaScript frame and flood it with

    // breakpoints.

    frames_it.Advance();

    // Fill the function to return to with one-shot break points.

    JSFunction* function = JSFunction::cast(frames_it.frame()->function());

    FloodWithOneShot(Handle<SharedFunctionInfo>(function->shared()));

    return;

  }

  // Get the debug info (create it if it does not exist).

  Handle<SharedFunctionInfo> shared =

      Handle<SharedFunctionInfo>(JSFunction::cast(frame->function())->shared());

  if (!EnsureDebugInfo(shared)) {

    // Return if ensuring debug info failed.

    return;

  }

  Handle<DebugInfo> debug_info = GetDebugInfo(shared);

  // Find the break location where execution has stopped.

  BreakLocationIterator it(debug_info, ALL_BREAK_LOCATIONS);

  it.FindBreakLocationFromAddress(frame->pc());

  // Compute whether or not the target is a call target.

  bool is_call_target = false;

  if (RelocInfo::IsCodeTarget(it.rinfo()->rmode())) {

    Address target = it.rinfo()->target_address();

    Code* code = Code::GetCodeFromTargetAddress(target);

    if (code->is_call_stub()) is_call_target = true;

  }

  // If this is the last break code target step out is the only possibility.

  if (it.IsExit() || step_action == StepOut) {

    // Step out: If there is a JavaScript caller frame, we need to

    // flood it with breakpoints.

    frames_it.Advance();

    if (!frames_it.done()) {

      // Fill the function to return to with one-shot break points.

      JSFunction* function = JSFunction::cast(frames_it.frame()->function());

      FloodWithOneShot(Handle<SharedFunctionInfo>(function->shared()));

    }

  } else if (!(is_call_target || RelocInfo::IsConstructCall(it.rmode())) ||

             step_action == StepNext || step_action == StepMin) {

    // Step next or step min.

    // Fill the current function with one-shot break points.

    FloodWithOneShot(shared);

    // Remember source position and frame to handle step next.

    thread_local_.last_statement_position_ =

        debug_info->code()->SourceStatementPosition(frame->pc());

    thread_local_.last_fp_ = frame->fp();

  } else {

    // Fill the current function with one-shot break points even for step in on

    // a call target as the function called might be a native function for

    // which step in will not stop.

    FloodWithOneShot(shared);

    // Step in or Step in min

    it.PrepareStepIn();

    ActivateStepIn(frame);

  }

}

// Check whether the current debug break should be reported to the debugger. It

// is used to have step next and step in only report break back to the debugger

// if on a different frame or in a different statement. In some situations

// there will be several break points in the same statement when the code is

// flooded with one-shot break points. This function helps to perform several

// steps before reporting break back to the debugger.

bool Debug::StepNextContinue(BreakLocationIterator* break_location_iterator,

                             JavaScriptFrame* frame) {

  // If the step last action was step next or step in make sure that a new

  // statement is hit.

  if (thread_local_.last_step_action_ == StepNext ||

      thread_local_.last_step_action_ == StepIn) {

    // Never continue if returning from function.

    if (break_location_iterator->IsExit()) return false;

    // Continue if we are still on the same frame and in the same statement.

    int current_statement_position =

        break_location_iterator->code()->SourceStatementPosition(frame->pc());

    return thread_local_.last_fp_ == frame->fp() &&

        thread_local_.last_statement_position_ == current_statement_position;

  }

  // No step next action - don't continue.

  return false;

}

// Check whether the code object at the specified address is a debug break code

// object.

bool Debug::IsDebugBreak(Address addr) {

  Code* code = Code::GetCodeFromTargetAddress(addr);

  return code->ic_state() == DEBUG_BREAK;

}

// Check whether a code stub with the specified major key is a possible break

// point location when looking for source break locations.

bool Debug::IsSourceBreakStub(Code* code) {

  CodeStub::Major major_key = code->major_key();

  return major_key == CodeStub::CallFunction;

}

// Check whether a code stub with the specified major key is a possible break

// location.

bool Debug::IsBreakStub(Code* code) {

  CodeStub::Major major_key = code->major_key();

  return major_key == CodeStub::CallFunction ||

         major_key == CodeStub::StackCheck;

}

// Find the builtin to use for invoking the debug break

Handle<Code> Debug::FindDebugBreak(RelocInfo* rinfo) {

  // Find the builtin debug break function matching the calling convention

  // used by the call site.

  RelocInfo::Mode mode = rinfo->rmode();

  if (RelocInfo::IsCodeTarget(mode)) {

    Address target = rinfo->target_address();

    Code* code = Code::GetCodeFromTargetAddress(target);

    if (code->is_inline_cache_stub()) {

      if (code->is_call_stub()) {

        return ComputeCallDebugBreak(code->arguments_count());

      }

      if (code->is_load_stub()) {

        return Handle<Code>(Builtins::builtin(Builtins::LoadIC_DebugBreak));

      }

      if (code->is_store_stub()) {

        return Handle<Code>(Builtins::builtin(Builtins::StoreIC_DebugBreak));

      }

      if (code->is_keyed_load_stub()) {

        Handle<Code> result =

            Handle<Code>(Builtins::builtin(Builtins::KeyedLoadIC_DebugBreak));

        return result;

      }

      if (code->is_keyed_store_stub()) {

        Handle<Code> result =

            Handle<Code>(Builtins::builtin(Builtins::KeyedStoreIC_DebugBreak));

        return result;

      }

    }

    if (RelocInfo::IsConstructCall(mode)) {

      Handle<Code> result =

          Handle<Code>(Builtins::builtin(Builtins::ConstructCall_DebugBreak));

      return result;

    }

    if (code->kind() == Code::STUB) {

      ASSERT(code->major_key() == CodeStub::CallFunction ||

             code->major_key() == CodeStub::StackCheck);

      Handle<Code> result =

          Handle<Code>(Builtins::builtin(Builtins::StubNoRegisters_DebugBreak));

      return result;

    }

  }

  UNREACHABLE();

  return Handle<Code>::null();

}

// Simple function for returning the source positions for active break points.

Handle<Object> Debug::GetSourceBreakLocations(

    Handle<SharedFunctionInfo> shared) {

  if (!HasDebugInfo(shared)) return Handle<Object>(Heap::undefined_value());

  Handle<DebugInfo> debug_info = GetDebugInfo(shared);

  if (debug_info->GetBreakPointCount() == 0) {

    return Handle<Object>(Heap::undefined_value());

  }

  Handle<FixedArray> locations =

      Factory::NewFixedArray(debug_info->GetBreakPointCount());

  int count = 0;

  for (int i = 0; i < debug_info->break_points()->length(); i++) {

    if (!debug_info->break_points()->get(i)->IsUndefined()) {

      BreakPointInfo* break_point_info =

          BreakPointInfo::cast(debug_info->break_points()->get(i));

      if (break_point_info->GetBreakPointCount() > 0) {

        locations->set(count++, break_point_info->statement_position());

      }

    }

  }

  return locations;

}

void Debug::NewBreak(StackFrame::Id break_frame_id) {

  thread_local_.break_frame_id_ = break_frame_id;

  thread_local_.break_id_ = ++thread_local_.break_count_;

}

void Debug::SetBreak(StackFrame::Id break_frame_id, int break_id) {

  thread_local_.break_frame_id_ = break_frame_id;

  thread_local_.break_id_ = break_id;

}

// Handle stepping into a function.

void Debug::HandleStepIn(Handle<JSFunction> function,

                         Address fp,

                         bool is_constructor) {

  // If the frame pointer is not supplied by the caller find it.

  if (fp == 0) {

    StackFrameIterator it;

    it.Advance();

    // For constructor functions skip another frame.

    if (is_constructor) {

      ASSERT(it.frame()->is_construct());

      it.Advance();

    }

    fp = it.frame()->fp();

  }

  // Flood the function with one-shot break points if it is called from where

  // step into was requested.

  if (fp == Debug::step_in_fp()) {

    // Don't allow step into functions in the native context.

    if (function->context()->global() != Top::context()->builtins()) {

      if (function->shared()->code() ==

          Builtins::builtin(Builtins::FunctionApply) ||

          function->shared()->code() ==

          Builtins::builtin(Builtins::FunctionCall)) {

        // Handle function.apply and function.call separately to flood the

        // function to be called and not the code for Builtins::FunctionApply or

        // Builtins::FunctionCall. At the point of the call IC to call either

        // Builtins::FunctionApply or Builtins::FunctionCall the expression

        // stack has the following content:

        //   symbol "apply" or "call"

        //   function apply or call was called on

        //   receiver for apply or call (first parameter to apply or call)

        //   ... further arguments to apply or call.

        JavaScriptFrameIterator it;

        ASSERT(it.frame()->fp() == fp);

        ASSERT(it.frame()->GetExpression(1)->IsJSFunction());

        if (it.frame()->GetExpression(1)->IsJSFunction()) {

          Handle<JSFunction>

              actual_function(JSFunction::cast(it.frame()->GetExpression(1)));

          Handle<SharedFunctionInfo> actual_shared(actual_function->shared());

          Debug::FloodWithOneShot(actual_shared);

        }

      } else {

        Debug::FloodWithOneShot(Handle<SharedFunctionInfo>(function->shared()));

      }

    }

  }

}

void Debug::ClearStepping() {

  // Clear the various stepping setup.

  ClearOneShot();

  ClearStepIn();

  ClearStepNext();

  // Clear multiple step counter.

  thread_local_.step_count_ = 0;

}

// Clears all the one-shot break points that are currently set. Normally this

// function is called each time a break point is hit as one shot break points

// are used to support stepping.

void Debug::ClearOneShot() {

  // The current implementation just runs through all the breakpoints. When the

  // last break point for a function is removed that function is automatically

  // removed from the list.

  DebugInfoListNode* node = debug_info_list_;

  while (node != NULL) {

    BreakLocationIterator it(node->debug_info(), ALL_BREAK_LOCATIONS);

    while (!it.Done()) {

      it.ClearOneShot();

      it.Next();

    }

    node = node->next();

  }

}

void Debug::ActivateStepIn(StackFrame* frame) {

  thread_local_.step_into_fp_ = frame->fp();

}

void Debug::ClearStepIn() {

  thread_local_.step_into_fp_ = 0;

}

void Debug::ClearStepNext() {

  thread_local_.last_step_action_ = StepNone;

  thread_local_.last_statement_position_ = RelocInfo::kNoPosition;

  thread_local_.last_fp_ = 0;

}

bool Debug::EnsureCompiled(Handle<SharedFunctionInfo> shared) {

  if (shared->is_compiled()) return true;

  return CompileLazyShared(shared, CLEAR_EXCEPTION, 0);

}

// Ensures the debug information is present for shared.

bool Debug::EnsureDebugInfo(Handle<SharedFunctionInfo> shared) {

  // Return if we already have the debug info for shared.

  if (HasDebugInfo(shared)) return true;

  // Ensure shared in compiled. Return false if this failed.

  if (!EnsureCompiled(shared)) return false;

  // Create the debug info object.

  Handle<DebugInfo> debug_info = Factory::NewDebugInfo(shared);

  // Add debug info to the list.

  DebugInfoListNode* node = new DebugInfoListNode(*debug_info);

  node->set_next(debug_info_list_);

  debug_info_list_ = node;

  // Now there is at least one break point.

  has_break_points_ = true;

  return true;

}

void Debug::RemoveDebugInfo(Handle<DebugInfo> debug_info) {

  ASSERT(debug_info_list_ != NULL);

  // Run through the debug info objects to find this one and remove it.

  DebugInfoListNode* prev = NULL;

  DebugInfoListNode* current = debug_info_list_;

  while (current != NULL) {

    if (*current->debug_info() == *debug_info) {

      // Unlink from list. If prev is NULL we are looking at the first element.

      if (prev == NULL) {

        debug_info_list_ = current->next();

      } else {

        prev->set_next(current->next());

      }

      current->debug_info()->shared()->set_debug_info(Heap::undefined_value());

      delete current;

      // If there are no more debug info objects there are not more break

      // points.

      has_break_points_ = debug_info_list_ != NULL;

      return;

    }

    // Move to next in list.

    prev = current;

    current = current->next();

  }

  UNREACHABLE();

}

void Debug::SetAfterBreakTarget(JavaScriptFrame* frame) {

  HandleScope scope;

  // Get the executing function in which the debug break occurred.

  Handle<SharedFunctionInfo> shared =

      Handle<SharedFunctionInfo>(JSFunction::cast(frame->function())->shared());

  if (!EnsureDebugInfo(shared)) {

    // Return if we failed to retrieve the debug info.

    return;

  }

  Handle<DebugInfo> debug_info = GetDebugInfo(shared);

  Handle<Code> code(debug_info->code());

  Handle<Code> original_code(debug_info->original_code());

#ifdef DEBUG

  // Get the code which is actually executing.

  Handle<Code> frame_code(frame->code());

  ASSERT(frame_code.is_identical_to(code));

#endif

  // Find the call address in the running code. This address holds the call to

  // either a DebugBreakXXX or to the debug break return entry code if the

  // break point is still active after processing the break point.

  Address addr = frame->pc() - Assembler::kTargetAddrToReturnAddrDist;

  // Check if the location is at JS exit.

  bool at_js_exit = false;

  RelocIterator it(debug_info->code());

  while (!it.done()) {

    if (RelocInfo::IsJSReturn(it.rinfo()->rmode())) {

      at_js_exit = it.rinfo()->pc() == addr - 1;

    }

    it.next();

  }

  // Handle the jump to continue execution after break point depending on the

  // break location.

  if (at_js_exit) {

    // First check if the call in the code is still the debug break return

    // entry code. If it is the break point is still active. If not the break

    // point was removed during break point processing.

    if (Assembler::target_address_at(addr) ==

        debug_break_return_entry()->entry()) {

      // Break point still active. Jump to the corresponding place in the

      // original code.

      addr +=  original_code->instruction_start() - code->instruction_start();

    }

    // Move one byte back to where the call instruction was placed.

    thread_local_.after_break_target_ = addr - 1;

  } else {

    // Check if there still is a debug break call at the target address. If the

    // break point has been removed it will have disappeared. If it have

    // disappeared don't try to look in the original code as the running code

    // will have the right address. This takes care of the case where the last

    // break point is removed from the function and therefore no "original code"

    // is available. If the debug break call is still there find the address in

    // the original code.

    if (IsDebugBreak(Assembler::target_address_at(addr))) {

      // If the break point is still there find the call address which was

      // overwritten in the original code by the call to DebugBreakXXX.

      // Find the corresponding address in the original code.

      addr += original_code->instruction_start() - code->instruction_start();

    }

    // Install jump to the call address in the original code. This will be the

    // call which was overwritten by the call to DebugBreakXXX.

    thread_local_.after_break_target_ = Assembler::target_address_at(addr);

  }

}

bool Debug::IsDebugGlobal(GlobalObject* global) {

  return IsLoaded() && global == Debug::debug_context()->global();

}

void Debug::ClearMirrorCache() {

  HandleScope scope;

  ASSERT(Top::context() == *Debug::debug_context());

  // Clear the mirror cache.

  Handle<String> function_name =

      Factory::LookupSymbol(CStrVector("ClearMirrorCache"));

  Handle<Object> fun(Top::global()->GetProperty(*function_name));

  ASSERT(fun->IsJSFunction());

  bool caught_exception;

  Handle<Object> js_object = Execution::TryCall(

      Handle<JSFunction>::cast(fun),

      Handle<JSObject>(Debug::debug_context()->global()),

      0, NULL, &caught_exception);

}

Mutex* Debugger::debugger_access_ = OS::CreateMutex();

Handle<Object> Debugger::event_listener_ = Handle<Object>();

Handle<Object> Debugger::event_listener_data_ = Handle<Object>();

bool Debugger::compiling_natives_ = false;

bool Debugger::is_loading_debugger_ = false;

bool Debugger::never_unload_debugger_ = false;

DebugMessageThread* Debugger::message_thread_ = NULL;

v8::DebugMessageHandler Debugger::message_handler_ = NULL;

bool Debugger::message_handler_cleared_ = false;

void* Debugger::message_handler_data_ = NULL;

v8::DebugHostDispatchHandler Debugger::host_dispatch_handler_ = NULL;

void* Debugger::host_dispatch_handler_data_ = NULL;

DebuggerAgent* Debugger::agent_ = NULL;

LockingMessageQueue Debugger::command_queue_(kQueueInitialSize);

LockingMessageQueue Debugger::message_queue_(kQueueInitialSize);

Semaphore* Debugger::command_received_ = OS::CreateSemaphore(0);

Semaphore* Debugger::message_received_ = OS::CreateSemaphore(0);

Handle<Object> Debugger::MakeJSObject(Vector<const char> constructor_name,

                                      int argc, Object*** argv,

                                      bool* caught_exception) {

  ASSERT(Top::context() == *Debug::debug_context());

  // Create the execution state object.

  Handle<String> constructor_str = Factory::LookupSymbol(constructor_name);

  Handle<Object> constructor(Top::global()->GetProperty(*constructor_str));