Line data Source code
1 : // Copyright 2012 the V8 project authors. All rights reserved.
2 : // Use of this source code is governed by a BSD-style license that can be
3 : // found in the LICENSE file.
4 :
5 : #include "src/handles.h"
6 :
7 : #include "src/address-map.h"
8 : #include "src/base/logging.h"
9 : #include "src/identity-map.h"
10 : #include "src/objects-inl.h"
11 :
12 : namespace v8 {
13 : namespace internal {
14 :
15 : #ifdef DEBUG
16 : bool HandleBase::IsDereferenceAllowed(DereferenceCheckMode mode) const {
17 : DCHECK_NOT_NULL(location_);
18 : Object* object = *location_;
19 : if (object->IsSmi()) return true;
20 : HeapObject* heap_object = HeapObject::cast(object);
21 : Heap* heap = heap_object->GetHeap();
22 : Object** roots_array_start = heap->roots_array_start();
23 : if (roots_array_start <= location_ &&
24 : location_ < roots_array_start + Heap::kStrongRootListLength &&
25 : heap->RootCanBeTreatedAsConstant(
26 : static_cast<Heap::RootListIndex>(location_ - roots_array_start))) {
27 : return true;
28 : }
29 : if (!AllowHandleDereference::IsAllowed()) return false;
30 : if (mode == INCLUDE_DEFERRED_CHECK &&
31 : !AllowDeferredHandleDereference::IsAllowed()) {
32 : // Accessing cells, maps and internalized strings is safe.
33 : if (heap_object->IsCell()) return true;
34 : if (heap_object->IsMap()) return true;
35 : if (heap_object->IsInternalizedString()) return true;
36 : return !heap->isolate()->IsDeferredHandle(location_);
37 : }
38 : return true;
39 : }
40 : #endif
41 :
42 :
43 7068 : int HandleScope::NumberOfHandles(Isolate* isolate) {
44 : HandleScopeImplementer* impl = isolate->handle_scope_implementer();
45 7068 : int n = impl->blocks()->length();
46 7068 : if (n == 0) return 0;
47 14094 : return ((n - 1) * kHandleBlockSize) + static_cast<int>(
48 21141 : (isolate->handle_scope_data()->next - impl->blocks()->last()));
49 : }
50 :
51 :
52 3668214 : Object** HandleScope::Extend(Isolate* isolate) {
53 : HandleScopeData* current = isolate->handle_scope_data();
54 :
55 1834107 : Object** result = current->next;
56 :
57 : DCHECK(result == current->limit);
58 : // Make sure there's at least one scope on the stack and that the
59 : // top of the scope stack isn't a barrier.
60 1834107 : if (!Utils::ApiCheck(current->level != current->sealed_level,
61 : "v8::HandleScope::CreateHandle()",
62 1834107 : "Cannot create a handle without a HandleScope")) {
63 : return NULL;
64 : }
65 : HandleScopeImplementer* impl = isolate->handle_scope_implementer();
66 : // If there's more room in the last block, we use that. This is used
67 : // for fast creation of scopes after scope barriers.
68 1834107 : if (!impl->blocks()->is_empty()) {
69 : Object** limit = &impl->blocks()->last()[kHandleBlockSize];
70 985003 : if (current->limit != limit) {
71 0 : current->limit = limit;
72 : DCHECK(limit - current->next < kHandleBlockSize);
73 : }
74 : }
75 :
76 : // If we still haven't found a slot for the handle, we extend the
77 : // current handle scope by allocating a new handle block.
78 1834107 : if (result == current->limit) {
79 : // If there's a spare block, use it for growing the current scope.
80 : result = impl->GetSpareOrNewBlock();
81 : // Add the extension to the global list of blocks, but count the
82 : // extension as part of the current scope.
83 1834107 : impl->blocks()->Add(result);
84 1834106 : current->limit = &result[kHandleBlockSize];
85 : }
86 :
87 1834106 : return result;
88 : }
89 :
90 :
91 3092644 : void HandleScope::DeleteExtensions(Isolate* isolate) {
92 : HandleScopeData* current = isolate->handle_scope_data();
93 3092644 : isolate->handle_scope_implementer()->DeleteExtensions(current->limit);
94 1546321 : }
95 :
96 :
97 : #ifdef ENABLE_HANDLE_ZAPPING
98 1373800819 : void HandleScope::ZapRange(Object** start, Object** end) {
99 : DCHECK(end - start <= kHandleBlockSize);
100 6171871944 : for (Object** p = start; p != end; p++) {
101 4798071125 : *reinterpret_cast<Address*>(p) = kHandleZapValue;
102 : }
103 1373800819 : }
104 : #endif
105 :
106 :
107 67172 : Address HandleScope::current_level_address(Isolate* isolate) {
108 67172 : return reinterpret_cast<Address>(&isolate->handle_scope_data()->level);
109 : }
110 :
111 :
112 67172 : Address HandleScope::current_next_address(Isolate* isolate) {
113 67172 : return reinterpret_cast<Address>(&isolate->handle_scope_data()->next);
114 : }
115 :
116 :
117 67172 : Address HandleScope::current_limit_address(Isolate* isolate) {
118 67172 : return reinterpret_cast<Address>(&isolate->handle_scope_data()->limit);
119 : }
120 :
121 789452 : CanonicalHandleScope::CanonicalHandleScope(Isolate* isolate)
122 789452 : : isolate_(isolate), zone_(isolate->allocator(), ZONE_NAME) {
123 394726 : HandleScopeData* handle_scope_data = isolate_->handle_scope_data();
124 394726 : prev_canonical_scope_ = handle_scope_data->canonical_scope;
125 394726 : handle_scope_data->canonical_scope = this;
126 394726 : root_index_map_ = new RootIndexMap(isolate);
127 : identity_map_ = new IdentityMap<Object**, ZoneAllocationPolicy>(
128 789452 : isolate->heap(), ZoneAllocationPolicy(&zone_));
129 394726 : canonical_level_ = handle_scope_data->level;
130 394726 : }
131 :
132 :
133 789449 : CanonicalHandleScope::~CanonicalHandleScope() {
134 394723 : delete root_index_map_;
135 394726 : delete identity_map_;
136 394726 : isolate_->handle_scope_data()->canonical_scope = prev_canonical_scope_;
137 394726 : }
138 :
139 :
140 27223819 : Object** CanonicalHandleScope::Lookup(Object* object) {
141 : DCHECK_LE(canonical_level_, isolate_->handle_scope_data()->level);
142 27223819 : if (isolate_->handle_scope_data()->level != canonical_level_) {
143 : // We are in an inner handle scope. Do not canonicalize since we will leave
144 : // this handle scope while still being in the canonical scope.
145 288431 : return HandleScope::CreateHandle(isolate_, object);
146 : }
147 26935388 : if (object->IsHeapObject()) {
148 22961758 : int index = root_index_map_->Lookup(HeapObject::cast(object));
149 22961805 : if (index != RootIndexMap::kInvalidRootIndex) {
150 : return isolate_->heap()
151 1323501 : ->root_handle(static_cast<Heap::RootListIndex>(index))
152 : .location();
153 : }
154 : }
155 25611934 : Object*** entry = identity_map_->Get(object);
156 25611870 : if (*entry == nullptr) {
157 : // Allocate new handle location.
158 28935857 : *entry = HandleScope::CreateHandle(isolate_, object);
159 : }
160 25611869 : return reinterpret_cast<Object**>(*entry);
161 : }
162 :
163 :
164 150613 : DeferredHandleScope::DeferredHandleScope(Isolate* isolate)
165 150613 : : impl_(isolate->handle_scope_implementer()) {
166 301226 : impl_->BeginDeferredScope();
167 150613 : HandleScopeData* data = impl_->isolate()->handle_scope_data();
168 : Object** new_next = impl_->GetSpareOrNewBlock();
169 150613 : Object** new_limit = &new_next[kHandleBlockSize];
170 : // Check that at least one HandleScope exists, see the class description.
171 : DCHECK(!impl_->blocks()->is_empty());
172 : // Check that we are not in a SealedHandleScope.
173 : DCHECK(data->limit == &impl_->blocks()->last()[kHandleBlockSize]);
174 150613 : impl_->blocks()->Add(new_next);
175 :
176 : #ifdef DEBUG
177 : prev_level_ = data->level;
178 : #endif
179 150613 : data->level++;
180 150613 : prev_limit_ = data->limit;
181 150613 : prev_next_ = data->next;
182 150613 : data->next = new_next;
183 150613 : data->limit = new_limit;
184 150613 : }
185 :
186 :
187 150613 : DeferredHandleScope::~DeferredHandleScope() {
188 150613 : impl_->isolate()->handle_scope_data()->level--;
189 : DCHECK(handles_detached_);
190 : DCHECK(impl_->isolate()->handle_scope_data()->level == prev_level_);
191 150613 : }
192 :
193 :
194 150613 : DeferredHandles* DeferredHandleScope::Detach() {
195 301226 : DeferredHandles* deferred = impl_->Detach(prev_limit_);
196 150613 : HandleScopeData* data = impl_->isolate()->handle_scope_data();
197 150613 : data->next = prev_next_;
198 150613 : data->limit = prev_limit_;
199 : #ifdef DEBUG
200 : handles_detached_ = true;
201 : #endif
202 150613 : return deferred;
203 : }
204 :
205 : } // namespace internal
206 : } // namespace v8
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