SnapshotCreator: start from existing snapshot if we have one

src/snapshot/code-serializer.cc

 // Copyright 2016 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/snapshot/code-serializer.h"
 
 #include <memory>
 
 #include "src/code-stubs.h"
 #include "src/counters.h"
@@ skipping 369 matching lines @@
   SetMagicNumber(cs->isolate());
   SetHeaderValue(kVersionHashOffset, Version::Hash());
   SetHeaderValue(kSourceHashOffset, cs->source_hash());
   SetHeaderValue(kCpuFeaturesOffset,
                  static_cast<uint32_t>(CpuFeatures::SupportedFeatures()));
   SetHeaderValue(kFlagHashOffset, FlagList::Hash());
   SetHeaderValue(kNumReservationsOffset, reservations.length());
   SetHeaderValue(kNumCodeStubKeysOffset, num_stub_keys);
   SetHeaderValue(kPayloadLengthOffset, payload->length());
 
+  // Zero out any padding in the header.
+  memset(data_ + kUnalignedHeaderSize, 0, kHeaderSize - kUnalignedHeaderSize);
+
   // Copy reservation chunk sizes.
   CopyBytes(data_ + kHeaderSize, reinterpret_cast<byte*>(reservations.begin()),
             reservation_size);
 
   // Copy code stub keys.
   CopyBytes(data_ + kHeaderSize + reservation_size,
             reinterpret_cast<byte*>(stub_keys->begin()), stub_keys_size);
 
+  // Zero out any padding before the payload.
   memset(data_ + payload_offset, 0, padded_payload_offset - payload_offset);
 
   // Copy serialized data.
   CopyBytes(data_ + padded_payload_offset, payload->begin(),
             static_cast<size_t>(payload->length()));
 
   Checksum checksum(DataWithoutHeader());
   SetHeaderValue(kChecksum1Offset, checksum.a());
   SetHeaderValue(kChecksum2Offset, checksum.b());
 }
 
 SerializedCodeData::SanityCheckResult SerializedCodeData::SanityCheck(
     Isolate* isolate, uint32_t expected_source_hash) const {
   if (this->size_ < kHeaderSize) return INVALID_HEADER;
   uint32_t magic_number = GetMagicNumber();
   if (magic_number != ComputeMagicNumber(isolate)) return MAGIC_NUMBER_MISMATCH;
+  if (GetExtraReferences() > GetExtraReferences(isolate)) {
+    return MAGIC_NUMBER_MISMATCH;
+  }
   uint32_t version_hash = GetHeaderValue(kVersionHashOffset);
   uint32_t source_hash = GetHeaderValue(kSourceHashOffset);
   uint32_t cpu_features = GetHeaderValue(kCpuFeaturesOffset);
   uint32_t flags_hash = GetHeaderValue(kFlagHashOffset);
+  uint32_t payload_length = GetHeaderValue(kPayloadLengthOffset);
   uint32_t c1 = GetHeaderValue(kChecksum1Offset);
   uint32_t c2 = GetHeaderValue(kChecksum2Offset);
   if (version_hash != Version::Hash()) return VERSION_MISMATCH;
   if (source_hash != expected_source_hash) return SOURCE_MISMATCH;
   if (cpu_features != static_cast<uint32_t>(CpuFeatures::SupportedFeatures())) {
     return CPU_FEATURES_MISMATCH;
   }
   if (flags_hash != FlagList::Hash()) return FLAGS_MISMATCH;
+  uint32_t max_payload_length =
+      this->size_ -
+      POINTER_SIZE_ALIGN(kHeaderSize +
+                         GetHeaderValue(kNumReservationsOffset) * kInt32Size +
+                         GetHeaderValue(kNumCodeStubKeysOffset) * kInt32Size);
+  if (payload_length > max_payload_length) return LENGTH_MISMATCH;
   if (!Checksum(DataWithoutHeader()).Check(c1, c2)) return CHECKSUM_MISMATCH;
   return CHECK_SUCCESS;
 }
 
 uint32_t SerializedCodeData::SourceHash(Handle<String> source) {
   return source->length();
 }
 
 // Return ScriptData object and relinquish ownership over it to the caller.
 ScriptData* SerializedCodeData::GetScriptData() {
@@ skipping 42 matching lines @@
   *rejection_result = scd.SanityCheck(isolate, expected_source_hash);
   if (*rejection_result != CHECK_SUCCESS) {
     cached_data->Reject();
     return SerializedCodeData(nullptr, 0);
   }
   return scd;
 }
 
 }  // namespace internal
 }  // namespace v8