1// Copyright 2016 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/snapshot/serializer.h"
6
7#include "src/macro-assembler.h"
8#include "src/snapshot/natives.h"
9
10namespace v8 {
11namespace internal {
12
13Serializer::Serializer(Isolate* isolate)
14    : isolate_(isolate),
15      external_reference_encoder_(isolate),
16      root_index_map_(isolate),
17      recursion_depth_(0),
18      code_address_map_(NULL),
19      large_objects_total_size_(0),
20      seen_large_objects_index_(0) {
21  // The serializer is meant to be used only to generate initial heap images
22  // from a context in which there is only one isolate.
23  for (int i = 0; i < kNumberOfPreallocatedSpaces; i++) {
24    pending_chunk_[i] = 0;
25    max_chunk_size_[i] = static_cast<uint32_t>(
26        MemoryAllocator::PageAreaSize(static_cast<AllocationSpace>(i)));
27  }
28
29#ifdef OBJECT_PRINT
30  if (FLAG_serialization_statistics) {
31    instance_type_count_ = NewArray<int>(kInstanceTypes);
32    instance_type_size_ = NewArray<size_t>(kInstanceTypes);
33    for (int i = 0; i < kInstanceTypes; i++) {
34      instance_type_count_[i] = 0;
35      instance_type_size_[i] = 0;
36    }
37  } else {
38    instance_type_count_ = NULL;
39    instance_type_size_ = NULL;
40  }
41#endif  // OBJECT_PRINT
42}
43
44Serializer::~Serializer() {
45  if (code_address_map_ != NULL) delete code_address_map_;
46#ifdef OBJECT_PRINT
47  if (instance_type_count_ != NULL) {
48    DeleteArray(instance_type_count_);
49    DeleteArray(instance_type_size_);
50  }
51#endif  // OBJECT_PRINT
52}
53
54#ifdef OBJECT_PRINT
55void Serializer::CountInstanceType(Map* map, int size) {
56  int instance_type = map->instance_type();
57  instance_type_count_[instance_type]++;
58  instance_type_size_[instance_type] += size;
59}
60#endif  // OBJECT_PRINT
61
62void Serializer::OutputStatistics(const char* name) {
63  if (!FLAG_serialization_statistics) return;
64  PrintF("%s:\n", name);
65  PrintF("  Spaces (bytes):\n");
66  for (int space = 0; space < kNumberOfSpaces; space++) {
67    PrintF("%16s", AllocationSpaceName(static_cast<AllocationSpace>(space)));
68  }
69  PrintF("\n");
70  for (int space = 0; space < kNumberOfPreallocatedSpaces; space++) {
71    size_t s = pending_chunk_[space];
72    for (uint32_t chunk_size : completed_chunks_[space]) s += chunk_size;
73    PrintF("%16" PRIuS, s);
74  }
75  PrintF("%16d\n", large_objects_total_size_);
76#ifdef OBJECT_PRINT
77  PrintF("  Instance types (count and bytes):\n");
78#define PRINT_INSTANCE_TYPE(Name)                                 \
79  if (instance_type_count_[Name]) {                               \
80    PrintF("%10d %10" PRIuS "  %s\n", instance_type_count_[Name], \
81           instance_type_size_[Name], #Name);                     \
82  }
83  INSTANCE_TYPE_LIST(PRINT_INSTANCE_TYPE)
84#undef PRINT_INSTANCE_TYPE
85  PrintF("\n");
86#endif  // OBJECT_PRINT
87}
88
89void Serializer::SerializeDeferredObjects() {
90  while (deferred_objects_.length() > 0) {
91    HeapObject* obj = deferred_objects_.RemoveLast();
92    ObjectSerializer obj_serializer(this, obj, &sink_, kPlain, kStartOfObject);
93    obj_serializer.SerializeDeferred();
94  }
95  sink_.Put(kSynchronize, "Finished with deferred objects");
96}
97
98void Serializer::VisitPointers(Object** start, Object** end) {
99  for (Object** current = start; current < end; current++) {
100    if ((*current)->IsSmi()) {
101      PutSmi(Smi::cast(*current));
102    } else {
103      SerializeObject(HeapObject::cast(*current), kPlain, kStartOfObject, 0);
104    }
105  }
106}
107
108void Serializer::EncodeReservations(
109    List<SerializedData::Reservation>* out) const {
110  for (int i = 0; i < kNumberOfPreallocatedSpaces; i++) {
111    for (int j = 0; j < completed_chunks_[i].length(); j++) {
112      out->Add(SerializedData::Reservation(completed_chunks_[i][j]));
113    }
114
115    if (pending_chunk_[i] > 0 || completed_chunks_[i].length() == 0) {
116      out->Add(SerializedData::Reservation(pending_chunk_[i]));
117    }
118    out->last().mark_as_last();
119  }
120
121  out->Add(SerializedData::Reservation(large_objects_total_size_));
122  out->last().mark_as_last();
123}
124
125#ifdef DEBUG
126bool Serializer::BackReferenceIsAlreadyAllocated(
127    SerializerReference reference) {
128  DCHECK(reference.is_back_reference());
129  AllocationSpace space = reference.space();
130  int chunk_index = reference.chunk_index();
131  if (space == LO_SPACE) {
132    return chunk_index == 0 &&
133           reference.large_object_index() < seen_large_objects_index_;
134  } else if (chunk_index == completed_chunks_[space].length()) {
135    return reference.chunk_offset() < pending_chunk_[space];
136  } else {
137    return chunk_index < completed_chunks_[space].length() &&
138           reference.chunk_offset() < completed_chunks_[space][chunk_index];
139  }
140}
141#endif  // DEBUG
142
143bool Serializer::SerializeHotObject(HeapObject* obj, HowToCode how_to_code,
144                                    WhereToPoint where_to_point, int skip) {
145  if (how_to_code != kPlain || where_to_point != kStartOfObject) return false;
146  // Encode a reference to a hot object by its index in the working set.
147  int index = hot_objects_.Find(obj);
148  if (index == HotObjectsList::kNotFound) return false;
149  DCHECK(index >= 0 && index < kNumberOfHotObjects);
150  if (FLAG_trace_serializer) {
151    PrintF(" Encoding hot object %d:", index);
152    obj->ShortPrint();
153    PrintF("\n");
154  }
155  if (skip != 0) {
156    sink_.Put(kHotObjectWithSkip + index, "HotObjectWithSkip");
157    sink_.PutInt(skip, "HotObjectSkipDistance");
158  } else {
159    sink_.Put(kHotObject + index, "HotObject");
160  }
161  return true;
162}
163bool Serializer::SerializeBackReference(HeapObject* obj, HowToCode how_to_code,
164                                        WhereToPoint where_to_point, int skip) {
165  SerializerReference reference = reference_map_.Lookup(obj);
166  if (!reference.is_valid()) return false;
167  // Encode the location of an already deserialized object in order to write
168  // its location into a later object.  We can encode the location as an
169  // offset fromthe start of the deserialized objects or as an offset
170  // backwards from thecurrent allocation pointer.
171  if (reference.is_attached_reference()) {
172    FlushSkip(skip);
173    if (FLAG_trace_serializer) {
174      PrintF(" Encoding attached reference %d\n",
175             reference.attached_reference_index());
176    }
177    PutAttachedReference(reference, how_to_code, where_to_point);
178  } else {
179    DCHECK(reference.is_back_reference());
180    if (FLAG_trace_serializer) {
181      PrintF(" Encoding back reference to: ");
182      obj->ShortPrint();
183      PrintF("\n");
184    }
185
186    PutAlignmentPrefix(obj);
187    AllocationSpace space = reference.space();
188    if (skip == 0) {
189      sink_.Put(kBackref + how_to_code + where_to_point + space, "BackRef");
190    } else {
191      sink_.Put(kBackrefWithSkip + how_to_code + where_to_point + space,
192                "BackRefWithSkip");
193      sink_.PutInt(skip, "BackRefSkipDistance");
194    }
195    PutBackReference(obj, reference);
196  }
197  return true;
198}
199
200void Serializer::PutRoot(int root_index, HeapObject* object,
201                         SerializerDeserializer::HowToCode how_to_code,
202                         SerializerDeserializer::WhereToPoint where_to_point,
203                         int skip) {
204  if (FLAG_trace_serializer) {
205    PrintF(" Encoding root %d:", root_index);
206    object->ShortPrint();
207    PrintF("\n");
208  }
209
210  if (how_to_code == kPlain && where_to_point == kStartOfObject &&
211      root_index < kNumberOfRootArrayConstants &&
212      !isolate()->heap()->InNewSpace(object)) {
213    if (skip == 0) {
214      sink_.Put(kRootArrayConstants + root_index, "RootConstant");
215    } else {
216      sink_.Put(kRootArrayConstantsWithSkip + root_index, "RootConstant");
217      sink_.PutInt(skip, "SkipInPutRoot");
218    }
219  } else {
220    FlushSkip(skip);
221    sink_.Put(kRootArray + how_to_code + where_to_point, "RootSerialization");
222    sink_.PutInt(root_index, "root_index");
223    hot_objects_.Add(object);
224  }
225}
226
227void Serializer::PutSmi(Smi* smi) {
228  sink_.Put(kOnePointerRawData, "Smi");
229  byte* bytes = reinterpret_cast<byte*>(&smi);
230  for (int i = 0; i < kPointerSize; i++) sink_.Put(bytes[i], "Byte");
231}
232
233void Serializer::PutBackReference(HeapObject* object,
234                                  SerializerReference reference) {
235  DCHECK(BackReferenceIsAlreadyAllocated(reference));
236  sink_.PutInt(reference.back_reference(), "BackRefValue");
237  hot_objects_.Add(object);
238}
239
240void Serializer::PutAttachedReference(SerializerReference reference,
241                                      HowToCode how_to_code,
242                                      WhereToPoint where_to_point) {
243  DCHECK(reference.is_attached_reference());
244  DCHECK((how_to_code == kPlain && where_to_point == kStartOfObject) ||
245         (how_to_code == kPlain && where_to_point == kInnerPointer) ||
246         (how_to_code == kFromCode && where_to_point == kInnerPointer));
247  sink_.Put(kAttachedReference + how_to_code + where_to_point, "AttachedRef");
248  sink_.PutInt(reference.attached_reference_index(), "AttachedRefIndex");
249}
250
251int Serializer::PutAlignmentPrefix(HeapObject* object) {
252  AllocationAlignment alignment = object->RequiredAlignment();
253  if (alignment != kWordAligned) {
254    DCHECK(1 <= alignment && alignment <= 3);
255    byte prefix = (kAlignmentPrefix - 1) + alignment;
256    sink_.Put(prefix, "Alignment");
257    return Heap::GetMaximumFillToAlign(alignment);
258  }
259  return 0;
260}
261
262SerializerReference Serializer::AllocateLargeObject(int size) {
263  // Large objects are allocated one-by-one when deserializing. We do not
264  // have to keep track of multiple chunks.
265  large_objects_total_size_ += size;
266  return SerializerReference::LargeObjectReference(seen_large_objects_index_++);
267}
268
269SerializerReference Serializer::Allocate(AllocationSpace space, int size) {
270  DCHECK(space >= 0 && space < kNumberOfPreallocatedSpaces);
271  DCHECK(size > 0 && size <= static_cast<int>(max_chunk_size(space)));
272  uint32_t new_chunk_size = pending_chunk_[space] + size;
273  if (new_chunk_size > max_chunk_size(space)) {
274    // The new chunk size would not fit onto a single page. Complete the
275    // current chunk and start a new one.
276    sink_.Put(kNextChunk, "NextChunk");
277    sink_.Put(space, "NextChunkSpace");
278    completed_chunks_[space].Add(pending_chunk_[space]);
279    pending_chunk_[space] = 0;
280    new_chunk_size = size;
281  }
282  uint32_t offset = pending_chunk_[space];
283  pending_chunk_[space] = new_chunk_size;
284  return SerializerReference::BackReference(
285      space, completed_chunks_[space].length(), offset);
286}
287
288void Serializer::Pad() {
289  // The non-branching GetInt will read up to 3 bytes too far, so we need
290  // to pad the snapshot to make sure we don't read over the end.
291  for (unsigned i = 0; i < sizeof(int32_t) - 1; i++) {
292    sink_.Put(kNop, "Padding");
293  }
294  // Pad up to pointer size for checksum.
295  while (!IsAligned(sink_.Position(), kPointerAlignment)) {
296    sink_.Put(kNop, "Padding");
297  }
298}
299
300void Serializer::InitializeCodeAddressMap() {
301  isolate_->InitializeLoggingAndCounters();
302  code_address_map_ = new CodeAddressMap(isolate_);
303}
304
305Code* Serializer::CopyCode(Code* code) {
306  code_buffer_.Rewind(0);  // Clear buffer without deleting backing store.
307  int size = code->CodeSize();
308  code_buffer_.AddAll(Vector<byte>(code->address(), size));
309  return Code::cast(HeapObject::FromAddress(&code_buffer_.first()));
310}
311
312bool Serializer::HasNotExceededFirstPageOfEachSpace() {
313  for (int i = 0; i < kNumberOfPreallocatedSpaces; i++) {
314    if (!completed_chunks_[i].is_empty()) return false;
315  }
316  return true;
317}
318
319void Serializer::ObjectSerializer::SerializePrologue(AllocationSpace space,
320                                                     int size, Map* map) {
321  if (serializer_->code_address_map_) {
322    const char* code_name =
323        serializer_->code_address_map_->Lookup(object_->address());
324    LOG(serializer_->isolate_,
325        CodeNameEvent(object_->address(), sink_->Position(), code_name));
326  }
327
328  SerializerReference back_reference;
329  if (space == LO_SPACE) {
330    sink_->Put(kNewObject + reference_representation_ + space,
331               "NewLargeObject");
332    sink_->PutInt(size >> kObjectAlignmentBits, "ObjectSizeInWords");
333    if (object_->IsCode()) {
334      sink_->Put(EXECUTABLE, "executable large object");
335    } else {
336      sink_->Put(NOT_EXECUTABLE, "not executable large object");
337    }
338    back_reference = serializer_->AllocateLargeObject(size);
339  } else {
340    int fill = serializer_->PutAlignmentPrefix(object_);
341    back_reference = serializer_->Allocate(space, size + fill);
342    sink_->Put(kNewObject + reference_representation_ + space, "NewObject");
343    sink_->PutInt(size >> kObjectAlignmentBits, "ObjectSizeInWords");
344  }
345
346#ifdef OBJECT_PRINT
347  if (FLAG_serialization_statistics) {
348    serializer_->CountInstanceType(map, size);
349  }
350#endif  // OBJECT_PRINT
351
352  // Mark this object as already serialized.
353  serializer_->reference_map()->Add(object_, back_reference);
354
355  // Serialize the map (first word of the object).
356  serializer_->SerializeObject(map, kPlain, kStartOfObject, 0);
357}
358
359void Serializer::ObjectSerializer::SerializeExternalString() {
360  // Instead of serializing this as an external string, we serialize
361  // an imaginary sequential string with the same content.
362  Isolate* isolate = serializer_->isolate();
363  DCHECK(object_->IsExternalString());
364  DCHECK(object_->map() != isolate->heap()->native_source_string_map());
365  ExternalString* string = ExternalString::cast(object_);
366  int length = string->length();
367  Map* map;
368  int content_size;
369  int allocation_size;
370  const byte* resource;
371  // Find the map and size for the imaginary sequential string.
372  bool internalized = object_->IsInternalizedString();
373  if (object_->IsExternalOneByteString()) {
374    map = internalized ? isolate->heap()->one_byte_internalized_string_map()
375                       : isolate->heap()->one_byte_string_map();
376    allocation_size = SeqOneByteString::SizeFor(length);
377    content_size = length * kCharSize;
378    resource = reinterpret_cast<const byte*>(
379        ExternalOneByteString::cast(string)->resource()->data());
380  } else {
381    map = internalized ? isolate->heap()->internalized_string_map()
382                       : isolate->heap()->string_map();
383    allocation_size = SeqTwoByteString::SizeFor(length);
384    content_size = length * kShortSize;
385    resource = reinterpret_cast<const byte*>(
386        ExternalTwoByteString::cast(string)->resource()->data());
387  }
388
389  AllocationSpace space = (allocation_size > Page::kMaxRegularHeapObjectSize)
390                              ? LO_SPACE
391                              : OLD_SPACE;
392  SerializePrologue(space, allocation_size, map);
393
394  // Output the rest of the imaginary string.
395  int bytes_to_output = allocation_size - HeapObject::kHeaderSize;
396
397  // Output raw data header. Do not bother with common raw length cases here.
398  sink_->Put(kVariableRawData, "RawDataForString");
399  sink_->PutInt(bytes_to_output, "length");
400
401  // Serialize string header (except for map).
402  Address string_start = string->address();
403  for (int i = HeapObject::kHeaderSize; i < SeqString::kHeaderSize; i++) {
404    sink_->PutSection(string_start[i], "StringHeader");
405  }
406
407  // Serialize string content.
408  sink_->PutRaw(resource, content_size, "StringContent");
409
410  // Since the allocation size is rounded up to object alignment, there
411  // maybe left-over bytes that need to be padded.
412  int padding_size = allocation_size - SeqString::kHeaderSize - content_size;
413  DCHECK(0 <= padding_size && padding_size < kObjectAlignment);
414  for (int i = 0; i < padding_size; i++) sink_->PutSection(0, "StringPadding");
415
416  sink_->Put(kSkip, "SkipAfterString");
417  sink_->PutInt(bytes_to_output, "SkipDistance");
418}
419
420// Clear and later restore the next link in the weak cell or allocation site.
421// TODO(all): replace this with proper iteration of weak slots in serializer.
422class UnlinkWeakNextScope {
423 public:
424  explicit UnlinkWeakNextScope(HeapObject* object) : object_(nullptr) {
425    if (object->IsWeakCell()) {
426      object_ = object;
427      next_ = WeakCell::cast(object)->next();
428      WeakCell::cast(object)->clear_next(object->GetHeap()->the_hole_value());
429    } else if (object->IsAllocationSite()) {
430      object_ = object;
431      next_ = AllocationSite::cast(object)->weak_next();
432      AllocationSite::cast(object)->set_weak_next(
433          object->GetHeap()->undefined_value());
434    }
435  }
436
437  ~UnlinkWeakNextScope() {
438    if (object_ != nullptr) {
439      if (object_->IsWeakCell()) {
440        WeakCell::cast(object_)->set_next(next_, UPDATE_WEAK_WRITE_BARRIER);
441      } else {
442        AllocationSite::cast(object_)->set_weak_next(next_,
443                                                     UPDATE_WEAK_WRITE_BARRIER);
444      }
445    }
446  }
447
448 private:
449  HeapObject* object_;
450  Object* next_;
451  DisallowHeapAllocation no_gc_;
452};
453
454void Serializer::ObjectSerializer::Serialize() {
455  if (FLAG_trace_serializer) {
456    PrintF(" Encoding heap object: ");
457    object_->ShortPrint();
458    PrintF("\n");
459  }
460
461  // We cannot serialize typed array objects correctly.
462  DCHECK(!object_->IsJSTypedArray());
463
464  // We don't expect fillers.
465  DCHECK(!object_->IsFiller());
466
467  if (object_->IsScript()) {
468    // Clear cached line ends.
469    Object* undefined = serializer_->isolate()->heap()->undefined_value();
470    Script::cast(object_)->set_line_ends(undefined);
471  }
472
473  if (object_->IsExternalString()) {
474    Heap* heap = serializer_->isolate()->heap();
475    if (object_->map() != heap->native_source_string_map()) {
476      // Usually we cannot recreate resources for external strings. To work
477      // around this, external strings are serialized to look like ordinary
478      // sequential strings.
479      // The exception are native source code strings, since we can recreate
480      // their resources. In that case we fall through and leave it to
481      // VisitExternalOneByteString further down.
482      SerializeExternalString();
483      return;
484    }
485  }
486
487  int size = object_->Size();
488  Map* map = object_->map();
489  AllocationSpace space =
490      MemoryChunk::FromAddress(object_->address())->owner()->identity();
491  SerializePrologue(space, size, map);
492
493  // Serialize the rest of the object.
494  CHECK_EQ(0, bytes_processed_so_far_);
495  bytes_processed_so_far_ = kPointerSize;
496
497  RecursionScope recursion(serializer_);
498  // Objects that are immediately post processed during deserialization
499  // cannot be deferred, since post processing requires the object content.
500  if (recursion.ExceedsMaximum() && CanBeDeferred(object_)) {
501    serializer_->QueueDeferredObject(object_);
502    sink_->Put(kDeferred, "Deferring object content");
503    return;
504  }
505
506  UnlinkWeakNextScope unlink_weak_next(object_);
507
508  object_->IterateBody(map->instance_type(), size, this);
509  OutputRawData(object_->address() + size);
510}
511
512void Serializer::ObjectSerializer::SerializeDeferred() {
513  if (FLAG_trace_serializer) {
514    PrintF(" Encoding deferred heap object: ");
515    object_->ShortPrint();
516    PrintF("\n");
517  }
518
519  int size = object_->Size();
520  Map* map = object_->map();
521  SerializerReference back_reference =
522      serializer_->reference_map()->Lookup(object_);
523  DCHECK(back_reference.is_back_reference());
524
525  // Serialize the rest of the object.
526  CHECK_EQ(0, bytes_processed_so_far_);
527  bytes_processed_so_far_ = kPointerSize;
528
529  serializer_->PutAlignmentPrefix(object_);
530  sink_->Put(kNewObject + back_reference.space(), "deferred object");
531  serializer_->PutBackReference(object_, back_reference);
532  sink_->PutInt(size >> kPointerSizeLog2, "deferred object size");
533
534  UnlinkWeakNextScope unlink_weak_next(object_);
535
536  object_->IterateBody(map->instance_type(), size, this);
537  OutputRawData(object_->address() + size);
538}
539
540void Serializer::ObjectSerializer::VisitPointers(Object** start, Object** end) {
541  Object** current = start;
542  while (current < end) {
543    while (current < end && (*current)->IsSmi()) current++;
544    if (current < end) OutputRawData(reinterpret_cast<Address>(current));
545
546    while (current < end && !(*current)->IsSmi()) {
547      HeapObject* current_contents = HeapObject::cast(*current);
548      int root_index = serializer_->root_index_map()->Lookup(current_contents);
549      // Repeats are not subject to the write barrier so we can only use
550      // immortal immovable root members. They are never in new space.
551      if (current != start && root_index != RootIndexMap::kInvalidRootIndex &&
552          Heap::RootIsImmortalImmovable(root_index) &&
553          current_contents == current[-1]) {
554        DCHECK(!serializer_->isolate()->heap()->InNewSpace(current_contents));
555        int repeat_count = 1;
556        while (&current[repeat_count] < end - 1 &&
557               current[repeat_count] == current_contents) {
558          repeat_count++;
559        }
560        current += repeat_count;
561        bytes_processed_so_far_ += repeat_count * kPointerSize;
562        if (repeat_count > kNumberOfFixedRepeat) {
563          sink_->Put(kVariableRepeat, "VariableRepeat");
564          sink_->PutInt(repeat_count, "repeat count");
565        } else {
566          sink_->Put(kFixedRepeatStart + repeat_count, "FixedRepeat");
567        }
568      } else {
569        serializer_->SerializeObject(current_contents, kPlain, kStartOfObject,
570                                     0);
571        bytes_processed_so_far_ += kPointerSize;
572        current++;
573      }
574    }
575  }
576}
577
578void Serializer::ObjectSerializer::VisitEmbeddedPointer(RelocInfo* rinfo) {
579  int skip = OutputRawData(rinfo->target_address_address(),
580                           kCanReturnSkipInsteadOfSkipping);
581  HowToCode how_to_code = rinfo->IsCodedSpecially() ? kFromCode : kPlain;
582  Object* object = rinfo->target_object();
583  serializer_->SerializeObject(HeapObject::cast(object), how_to_code,
584                               kStartOfObject, skip);
585  bytes_processed_so_far_ += rinfo->target_address_size();
586}
587
588void Serializer::ObjectSerializer::VisitExternalReference(Address* p) {
589  int skip = OutputRawData(reinterpret_cast<Address>(p),
590                           kCanReturnSkipInsteadOfSkipping);
591  sink_->Put(kExternalReference + kPlain + kStartOfObject, "ExternalRef");
592  sink_->PutInt(skip, "SkipB4ExternalRef");
593  Address target = *p;
594  sink_->PutInt(serializer_->EncodeExternalReference(target), "reference id");
595  bytes_processed_so_far_ += kPointerSize;
596}
597
598void Serializer::ObjectSerializer::VisitExternalReference(RelocInfo* rinfo) {
599  int skip = OutputRawData(rinfo->target_address_address(),
600                           kCanReturnSkipInsteadOfSkipping);
601  HowToCode how_to_code = rinfo->IsCodedSpecially() ? kFromCode : kPlain;
602  sink_->Put(kExternalReference + how_to_code + kStartOfObject, "ExternalRef");
603  sink_->PutInt(skip, "SkipB4ExternalRef");
604  Address target = rinfo->target_external_reference();
605  sink_->PutInt(serializer_->EncodeExternalReference(target), "reference id");
606  bytes_processed_so_far_ += rinfo->target_address_size();
607}
608
609void Serializer::ObjectSerializer::VisitInternalReference(RelocInfo* rinfo) {
610  // We can only reference to internal references of code that has been output.
611  DCHECK(object_->IsCode() && code_has_been_output_);
612  // We do not use skip from last patched pc to find the pc to patch, since
613  // target_address_address may not return addresses in ascending order when
614  // used for internal references. External references may be stored at the
615  // end of the code in the constant pool, whereas internal references are
616  // inline. That would cause the skip to be negative. Instead, we store the
617  // offset from code entry.
618  Address entry = Code::cast(object_)->entry();
619  intptr_t pc_offset = rinfo->target_internal_reference_address() - entry;
620  intptr_t target_offset = rinfo->target_internal_reference() - entry;
621  DCHECK(0 <= pc_offset &&
622         pc_offset <= Code::cast(object_)->instruction_size());
623  DCHECK(0 <= target_offset &&
624         target_offset <= Code::cast(object_)->instruction_size());
625  sink_->Put(rinfo->rmode() == RelocInfo::INTERNAL_REFERENCE
626                 ? kInternalReference
627                 : kInternalReferenceEncoded,
628             "InternalRef");
629  sink_->PutInt(static_cast<uintptr_t>(pc_offset), "internal ref address");
630  sink_->PutInt(static_cast<uintptr_t>(target_offset), "internal ref value");
631}
632
633void Serializer::ObjectSerializer::VisitRuntimeEntry(RelocInfo* rinfo) {
634  int skip = OutputRawData(rinfo->target_address_address(),
635                           kCanReturnSkipInsteadOfSkipping);
636  HowToCode how_to_code = rinfo->IsCodedSpecially() ? kFromCode : kPlain;
637  sink_->Put(kExternalReference + how_to_code + kStartOfObject, "ExternalRef");
638  sink_->PutInt(skip, "SkipB4ExternalRef");
639  Address target = rinfo->target_address();
640  sink_->PutInt(serializer_->EncodeExternalReference(target), "reference id");
641  bytes_processed_so_far_ += rinfo->target_address_size();
642}
643
644void Serializer::ObjectSerializer::VisitCodeTarget(RelocInfo* rinfo) {
645  int skip = OutputRawData(rinfo->target_address_address(),
646                           kCanReturnSkipInsteadOfSkipping);
647  Code* object = Code::GetCodeFromTargetAddress(rinfo->target_address());
648  serializer_->SerializeObject(object, kFromCode, kInnerPointer, skip);
649  bytes_processed_so_far_ += rinfo->target_address_size();
650}
651
652void Serializer::ObjectSerializer::VisitCodeEntry(Address entry_address) {
653  int skip = OutputRawData(entry_address, kCanReturnSkipInsteadOfSkipping);
654  Code* object = Code::cast(Code::GetObjectFromEntryAddress(entry_address));
655  serializer_->SerializeObject(object, kPlain, kInnerPointer, skip);
656  bytes_processed_so_far_ += kPointerSize;
657}
658
659void Serializer::ObjectSerializer::VisitCell(RelocInfo* rinfo) {
660  int skip = OutputRawData(rinfo->pc(), kCanReturnSkipInsteadOfSkipping);
661  Cell* object = Cell::cast(rinfo->target_cell());
662  serializer_->SerializeObject(object, kPlain, kInnerPointer, skip);
663  bytes_processed_so_far_ += kPointerSize;
664}
665
666bool Serializer::ObjectSerializer::SerializeExternalNativeSourceString(
667    int builtin_count,
668    v8::String::ExternalOneByteStringResource** resource_pointer,
669    FixedArray* source_cache, int resource_index) {
670  Isolate* isolate = serializer_->isolate();
671  for (int i = 0; i < builtin_count; i++) {
672    Object* source = source_cache->get(i);
673    if (!source->IsUndefined(isolate)) {
674      ExternalOneByteString* string = ExternalOneByteString::cast(source);
675      typedef v8::String::ExternalOneByteStringResource Resource;
676      const Resource* resource = string->resource();
677      if (resource == *resource_pointer) {
678        sink_->Put(resource_index, "NativesStringResource");
679        sink_->PutSection(i, "NativesStringResourceEnd");
680        bytes_processed_so_far_ += sizeof(resource);
681        return true;
682      }
683    }
684  }
685  return false;
686}
687
688void Serializer::ObjectSerializer::VisitExternalOneByteString(
689    v8::String::ExternalOneByteStringResource** resource_pointer) {
690  DCHECK_EQ(serializer_->isolate()->heap()->native_source_string_map(),
691            object_->map());
692  DCHECK(ExternalOneByteString::cast(object_)->is_short());
693  Address references_start = reinterpret_cast<Address>(resource_pointer);
694  OutputRawData(references_start);
695  if (SerializeExternalNativeSourceString(
696          Natives::GetBuiltinsCount(), resource_pointer,
697          Natives::GetSourceCache(serializer_->isolate()->heap()),
698          kNativesStringResource)) {
699    return;
700  }
701  if (SerializeExternalNativeSourceString(
702          ExtraNatives::GetBuiltinsCount(), resource_pointer,
703          ExtraNatives::GetSourceCache(serializer_->isolate()->heap()),
704          kExtraNativesStringResource)) {
705    return;
706  }
707  // One of the strings in the natives cache should match the resource.  We
708  // don't expect any other kinds of external strings here.
709  UNREACHABLE();
710}
711
712Address Serializer::ObjectSerializer::PrepareCode() {
713  Code* code = Code::cast(object_);
714  if (FLAG_predictable) {
715    // To make snapshots reproducible, we make a copy of the code object
716    // and wipe all pointers in the copy, which we then serialize.
717    code = serializer_->CopyCode(code);
718    int mode_mask = RelocInfo::kCodeTargetMask |
719                    RelocInfo::ModeMask(RelocInfo::EMBEDDED_OBJECT) |
720                    RelocInfo::ModeMask(RelocInfo::EXTERNAL_REFERENCE) |
721                    RelocInfo::ModeMask(RelocInfo::RUNTIME_ENTRY) |
722                    RelocInfo::ModeMask(RelocInfo::INTERNAL_REFERENCE) |
723                    RelocInfo::ModeMask(RelocInfo::INTERNAL_REFERENCE_ENCODED);
724    for (RelocIterator it(code, mode_mask); !it.done(); it.next()) {
725      RelocInfo* rinfo = it.rinfo();
726      rinfo->WipeOut();
727    }
728    // We need to wipe out the header fields *after* wiping out the
729    // relocations, because some of these fields are needed for the latter.
730    code->WipeOutHeader();
731  }
732  // Code age headers are not serializable.
733  code->MakeYoung(serializer_->isolate());
734  return code->address();
735}
736
737int Serializer::ObjectSerializer::OutputRawData(
738    Address up_to, Serializer::ObjectSerializer::ReturnSkip return_skip) {
739  Address object_start = object_->address();
740  int base = bytes_processed_so_far_;
741  int up_to_offset = static_cast<int>(up_to - object_start);
742  int to_skip = up_to_offset - bytes_processed_so_far_;
743  int bytes_to_output = to_skip;
744  bytes_processed_so_far_ += to_skip;
745  // This assert will fail if the reloc info gives us the target_address_address
746  // locations in a non-ascending order.  Luckily that doesn't happen.
747  DCHECK(to_skip >= 0);
748  bool outputting_code = false;
749  bool is_code_object = object_->IsCode();
750  if (to_skip != 0 && is_code_object && !code_has_been_output_) {
751    // Output the code all at once and fix later.
752    bytes_to_output = object_->Size() + to_skip - bytes_processed_so_far_;
753    outputting_code = true;
754    code_has_been_output_ = true;
755  }
756  if (bytes_to_output != 0 && (!is_code_object || outputting_code)) {
757    if (!outputting_code && bytes_to_output == to_skip &&
758        IsAligned(bytes_to_output, kPointerAlignment) &&
759        bytes_to_output <= kNumberOfFixedRawData * kPointerSize) {
760      int size_in_words = bytes_to_output >> kPointerSizeLog2;
761      sink_->PutSection(kFixedRawDataStart + size_in_words, "FixedRawData");
762      to_skip = 0;  // This instruction includes skip.
763    } else {
764      // We always end up here if we are outputting the code of a code object.
765      sink_->Put(kVariableRawData, "VariableRawData");
766      sink_->PutInt(bytes_to_output, "length");
767    }
768
769    if (is_code_object) object_start = PrepareCode();
770
771    const char* description = is_code_object ? "Code" : "Byte";
772    sink_->PutRaw(object_start + base, bytes_to_output, description);
773  }
774  if (to_skip != 0 && return_skip == kIgnoringReturn) {
775    sink_->Put(kSkip, "Skip");
776    sink_->PutInt(to_skip, "SkipDistance");
777    to_skip = 0;
778  }
779  return to_skip;
780}
781
782}  // namespace internal
783}  // namespace v8
784