[handles] Sanitize Handle and friends.

src/handles.cc

 // Copyright 2012 the V8 project 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 "src/v8.h"
+#include "src/handles.h"
 
-#include "src/handles.h"
+#include "src/api.h"
+#include "src/isolate.h"
 
 namespace v8 {
 namespace internal {
 
+HandleBase::HandleBase(HeapObject* object)
+    : HandleBase(object, object->GetIsolate()) {}
 
+
+HandleBase::HandleBase(Object* object, Isolate* isolate)
+    : HandleBase(HandleScope::CreateHandle(isolate, object)) {}
+
+
+#ifdef DEBUG
+
+bool HandleBase::IsDereferenceAllowed(DereferenceCheckMode mode) const {
+  DCHECK_NOT_NULL(location_);
+  Object* const object = *location_;
+  if (object->IsSmi()) return true;
+  HeapObject* const heap_object = HeapObject::cast(object);
+  Heap* const heap = heap_object->GetHeap();
+  Object** roots_array_start = heap->roots_array_start();
+  if (roots_array_start <= location_ &&
+      location_ < roots_array_start + Heap::kStrongRootListLength &&
+      heap->RootCanBeTreatedAsConstant(
+          static_cast<Heap::RootListIndex>(location_ - roots_array_start))) {
+    return true;
+  }
+  if (!AllowHandleDereference::IsAllowed()) return false;
+  if (mode == INCLUDE_DEFERRED_CHECK &&
+      !AllowDeferredHandleDereference::IsAllowed()) {
+    // Accessing cells, maps and internalized strings is safe.
+    if (heap_object->IsCell()) return true;
+    if (heap_object->IsMap()) return true;
+    if (heap_object->IsInternalizedString()) return true;
+    return !heap->isolate()->IsDeferredHandle(location_);
+  }
+  return true;
+}
+
+#endif  // DEBUG
+
+
+HandleScope::HandleScope(Isolate* isolate) : isolate_(isolate) {
+  HandleScopeData* const current = isolate->handle_scope_data();
+  prev_next_ = current->next;
+  prev_limit_ = current->limit;
+  current->level++;
+}
+
+
+HandleScope::~HandleScope() { CloseScope(isolate_, prev_next_, prev_limit_); }
+
+
+// static
 int HandleScope::NumberOfHandles(Isolate* isolate) {
   HandleScopeImplementer* impl = isolate->handle_scope_implementer();
   int n = impl->blocks()->length();
   if (n == 0) return 0;
   return ((n - 1) * kHandleBlockSize) + static_cast<int>(
       (isolate->handle_scope_data()->next - impl->blocks()->last()));
 }
 
 
+// static
+Object** HandleScope::CreateHandle(Isolate* isolate, Object* value) {
+  DCHECK(AllowHandleAllocation::IsAllowed());
+  HandleScopeData* const current = isolate->handle_scope_data();
+
+  Object** result = current->next;
+  if (result == current->limit) result = Extend(isolate);
+  // Update the current next field, set the value in the created
+  // handle, and return the result.
+  DCHECK_LT(result, current->limit);
+  current->next = result + 1;
+
+  *result = value;
+  return result;
+}
+
+
+// static
+void HandleScope::DeleteExtensions(Isolate* isolate) {
+  HandleScopeData* const current = isolate->handle_scope_data();
+  isolate->handle_scope_implementer()->DeleteExtensions(current->limit);
+}
+
+
+Handle<Object> HandleScope::CloseAndEscape(Handle<Object> handle) {
+  HandleScopeData* const current = isolate_->handle_scope_data();
+
+  Object* value = *handle;
+  // Throw away all handles in the current scope.
+  CloseScope(isolate_, prev_next_, prev_limit_);
+  // Allocate one handle in the parent scope.
+  DCHECK_LT(0, current->level);
+  Handle<Object> result(CreateHandle(isolate_, value));
+  // Reinitialize the current scope (so that it's ready
+  // to be used or closed again).
+  prev_next_ = current->next;
+  prev_limit_ = current->limit;
+  current->level++;
+  return result;
+}
+
+
+// static
+void HandleScope::CloseScope(Isolate* isolate, Object** prev_next,
+                             Object** prev_limit) {
+  HandleScopeData* const current = isolate->handle_scope_data();
+
+  std::swap(current->next, prev_next);
+  current->level--;
+  if (current->limit != prev_limit) {
+    current->limit = prev_limit;
+    DeleteExtensions(isolate);
+#ifdef ENABLE_HANDLE_ZAPPING
+    ZapRange(current->next, prev_limit);
+  } else {
+    ZapRange(current->next, prev_next);
+#endif
+  }
+}
+
+
+// static
 Object** HandleScope::Extend(Isolate* isolate) {
   HandleScopeData* current = isolate->handle_scope_data();
 
   Object** result = current->next;
-
-  DCHECK(result == current->limit);
+  DCHECK_EQ(result, current->limit);
   // Make sure there's at least one scope on the stack and that the
   // top of the scope stack isn't a barrier.
   if (!Utils::ApiCheck(current->level != 0,
                        "v8::HandleScope::CreateHandle()",
                        "Cannot create a handle without a HandleScope")) {
     return NULL;
   }
   HandleScopeImplementer* impl = isolate->handle_scope_implementer();
   // If there's more room in the last block, we use that. This is used
   // for fast creation of scopes after scope barriers.
@@ skipping 13 matching lines @@
     // Add the extension to the global list of blocks, but count the
     // extension as part of the current scope.
     impl->blocks()->Add(result);
     current->limit = &result[kHandleBlockSize];
   }
 
   return result;
 }
 
 
-void HandleScope::DeleteExtensions(Isolate* isolate) {
-  HandleScopeData* current = isolate->handle_scope_data();
-  isolate->handle_scope_implementer()->DeleteExtensions(current->limit);
-}
-
-
 #ifdef ENABLE_HANDLE_ZAPPING
 void HandleScope::ZapRange(Object** start, Object** end) {
   DCHECK(end - start <= kHandleBlockSize);
   for (Object** p = start; p != end; p++) {
     *reinterpret_cast<Address*>(p) = v8::internal::kHandleZapValue;
   }
 }
 #endif
 
 
@@ skipping 43 matching lines @@
   DeferredHandles* deferred = impl_->Detach(prev_limit_);
   HandleScopeData* data = impl_->isolate()->handle_scope_data();
   data->next = prev_next_;
   data->limit = prev_limit_;
 #ifdef DEBUG
   handles_detached_ = true;
 #endif
   return deferred;
 }
 
-} }  // namespace v8::internal
+
+#ifdef DEBUG
+
+SealHandleScope::SealHandleScope(Isolate* isolate) : isolate_(isolate) {
+  // Make sure the current thread is allowed to create handles to begin with.
+  CHECK(AllowHandleAllocation::IsAllowed());
+  HandleScopeData* const current = isolate_->handle_scope_data();
+  // Shrink the current handle scope to make it impossible to do
+  // handle allocations without an explicit handle scope.
+  limit_ = current->limit;
+  current->limit = current->next;
+  level_ = current->level;
+  current->level = 0;
+}
+
+
+SealHandleScope::~SealHandleScope() {
+  // Restore state in current handle scope to re-enable handle
+  // allocations.
+  HandleScopeData* const current = isolate_->handle_scope_data();
+  DCHECK_EQ(0, current->level);
+  current->level = level_;
+  DCHECK_EQ(current->next, current->limit);
+  current->limit = limit_;
+}
+
+#endif  // DEBUG
+
+}  // namespace internal
+}  // namespace v8