wasm-serialization.cc

// Copyright 2017 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/wasm/wasm-serialization.h"

#include "src/assembler-inl.h"
#include "src/external-reference-table.h"
#include "src/objects-inl.h"
#include "src/objects.h"
#include "src/snapshot/code-serializer.h"
#include "src/snapshot/serializer-common.h"
#include "src/utils.h"
#include "src/version.h"
#include "src/wasm/function-compiler.h"
#include "src/wasm/module-compiler.h"
#include "src/wasm/module-decoder.h"
#include "src/wasm/wasm-code-manager.h"
#include "src/wasm/wasm-module.h"
#include "src/wasm/wasm-objects-inl.h"
#include "src/wasm/wasm-objects.h"
#include "src/wasm/wasm-result.h"

namespace v8 {
namespace internal {
namespace wasm {

namespace {

// TODO(bbudge) Try to unify the various implementations of readers and writers
// in WASM, e.g. StreamProcessor and ZoneBuffer, with these.
class Writer {
 public:
  explicit Writer(Vector<byte> buffer)
      : start_(buffer.start()), end_(buffer.end()), pos_(buffer.start()) {}

  size_t bytes_written() const { return pos_ - start_; }
  byte* current_location() const { return pos_; }
  size_t current_size() const { return end_ - pos_; }
  Vector<byte> current_buffer() const {
    return {current_location(), current_size()};
  }

  template <typename T>
  void Write(const T& value) {
    DCHECK_GE(current_size(), sizeof(T));
    WriteUnalignedValue(reinterpret_cast<Address>(current_location()), value);
    pos_ += sizeof(T);
    if (FLAG_trace_wasm_serialization) {
      StdoutStream{} << "wrote: " << static_cast<size_t>(value)
                     << " sized: " << sizeof(T) << std::endl;
    }
  }

  void WriteVector(const Vector<const byte> v) {
    DCHECK_GE(current_size(), v.size());
    if (v.size() > 0) {
      memcpy(current_location(), v.start(), v.size());
      pos_ += v.size();
    }
    if (FLAG_trace_wasm_serialization) {
      StdoutStream{} << "wrote vector of " << v.size() << " elements"
                     << std::endl;
    }
  }

  void Skip(size_t size) { pos_ += size; }

 private:
  byte* const start_;
  byte* const end_;
  byte* pos_;
};

class Reader {
 public:
  explicit Reader(Vector<const byte> buffer)
      : start_(buffer.start()), end_(buffer.end()), pos_(buffer.start()) {}

  size_t bytes_read() const { return pos_ - start_; }
  const byte* current_location() const { return pos_; }
  size_t current_size() const { return end_ - pos_; }
  Vector<const byte> current_buffer() const {
    return {current_location(), current_size()};
  }

  template <typename T>
  T Read() {
    DCHECK_GE(current_size(), sizeof(T));
    T value =
        ReadUnalignedValue<T>(reinterpret_cast<Address>(current_location()));
    pos_ += sizeof(T);
    if (FLAG_trace_wasm_serialization) {
      StdoutStream{} << "read: " << static_cast<size_t>(value)
                     << " sized: " << sizeof(T) << std::endl;
    }
    return value;
  }

  void ReadVector(Vector<byte> v) {
    if (v.size() > 0) {
      DCHECK_GE(current_size(), v.size());
      memcpy(v.start(), current_location(), v.size());
      pos_ += v.size();
    }
    if (FLAG_trace_wasm_serialization) {
      StdoutStream{} << "read vector of " << v.size() << " elements"
                     << std::endl;
    }
  }

  void Skip(size_t size) { pos_ += size; }

 private:
  const byte* const start_;
  const byte* const end_;
  const byte* pos_;
};

constexpr size_t kVersionSize = 4 * sizeof(uint32_t);

void WriteVersion(Isolate* isolate, Writer* writer) {
  writer->Write(
      SerializedData::ComputeMagicNumber(isolate->external_reference_table()));
  writer->Write(Version::Hash());
  writer->Write(static_cast<uint32_t>(CpuFeatures::SupportedFeatures()));
  writer->Write(FlagList::Hash());
}

// On Intel, call sites are encoded as a displacement. For linking and for
// serialization/deserialization, we want to store/retrieve a tag (the function
// index). On Intel, that means accessing the raw displacement.
// On ARM64, call sites are encoded as either a literal load or a direct branch.
// Other platforms simply require accessing the target address.
void SetWasmCalleeTag(RelocInfo* rinfo, uint32_t tag) {
#if V8_TARGET_ARCH_X64 || V8_TARGET_ARCH_IA32
  *(reinterpret_cast<uint32_t*>(rinfo->target_address_address())) = tag;
#elif V8_TARGET_ARCH_ARM64
  Instruction* instr = reinterpret_cast<Instruction*>(rinfo->pc());
  if (instr->IsLdrLiteralX()) {
    Memory<Address>(rinfo->constant_pool_entry_address()) =
        static_cast<Address>(tag);
  } else {
    DCHECK(instr->IsBranchAndLink() || instr->IsUnconditionalBranch());
    instr->SetBranchImmTarget(
        reinterpret_cast<Instruction*>(rinfo->pc() + tag * kInstrSize));
  }
#else
  Address addr = static_cast<Address>(tag);
  if (rinfo->rmode() == RelocInfo::EXTERNAL_REFERENCE) {
    rinfo->set_target_external_reference(addr, SKIP_ICACHE_FLUSH);
  } else if (rinfo->rmode() == RelocInfo::WASM_STUB_CALL) {
    rinfo->set_wasm_stub_call_address(addr, SKIP_ICACHE_FLUSH);
  } else {
    rinfo->set_target_address(addr, SKIP_WRITE_BARRIER, SKIP_ICACHE_FLUSH);
  }
#endif
}

uint32_t GetWasmCalleeTag(RelocInfo* rinfo) {
#if V8_TARGET_ARCH_X64 || V8_TARGET_ARCH_IA32
  return *(reinterpret_cast<uint32_t*>(rinfo->target_address_address()));
#elif V8_TARGET_ARCH_ARM64
  Instruction* instr = reinterpret_cast<Instruction*>(rinfo->pc());
  if (instr->IsLdrLiteralX()) {
    return static_cast<uint32_t>(
        Memory<Address>(rinfo->constant_pool_entry_address()));
  } else {
    DCHECK(instr->IsBranchAndLink() || instr->IsUnconditionalBranch());
    return static_cast<uint32_t>(instr->ImmPCOffset() / kInstrSize);
  }
#else
  Address addr;
  if (rinfo->rmode() == RelocInfo::EXTERNAL_REFERENCE) {
    addr = rinfo->target_external_reference();
  } else if (rinfo->rmode() == RelocInfo::WASM_STUB_CALL) {
    addr = rinfo->wasm_stub_call_address();
  } else {
    addr = rinfo->target_address();
  }
  return static_cast<uint32_t>(addr);
#endif
}

constexpr size_t kHeaderSize =
    sizeof(uint32_t) +  // total wasm function count
    sizeof(uint32_t);   // imported functions (index of first wasm function)

constexpr size_t kCodeHeaderSize =
    sizeof(size_t) +         // size of code section
    sizeof(size_t) +         // offset of constant pool
    sizeof(size_t) +         // offset of safepoint table
    sizeof(size_t) +         // offset of handler table
    sizeof(uint32_t) +       // stack slots
    sizeof(size_t) +         // code size
    sizeof(size_t) +         // reloc size
    sizeof(size_t) +         // source positions size
    sizeof(size_t) +         // protected instructions size
    sizeof(WasmCode::Tier);  // tier

}  // namespace

class V8_EXPORT_PRIVATE NativeModuleSerializer {
 public:
  NativeModuleSerializer() = delete;
  NativeModuleSerializer(Isolate*, const NativeModule*,
                         Vector<WasmCode* const>);

  size_t Measure() const;
  bool Write(Writer* writer);

 private:
  size_t MeasureCode(const WasmCode*) const;
  void WriteHeader(Writer* writer);
  void WriteCode(const WasmCode*, Writer* writer);

  Isolate* const isolate_;
  const NativeModule* const native_module_;
  Vector<WasmCode* const> code_table_;
  bool write_called_;

  // Reverse lookup tables for embedded addresses.
  std::map<Address, uint32_t> wasm_stub_targets_lookup_;
  std::map<Address, uint32_t> reference_table_lookup_;

  DISALLOW_COPY_AND_ASSIGN(NativeModuleSerializer);
};

NativeModuleSerializer::NativeModuleSerializer(
    Isolate* isolate, const NativeModule* module,
    Vector<WasmCode* const> code_table)
    : isolate_(isolate),
      native_module_(module),
      code_table_(code_table),
      write_called_(false) {
  DCHECK_NOT_NULL(isolate_);
  DCHECK_NOT_NULL(native_module_);
  // TODO(mtrofin): persist the export wrappers. Ideally, we'd only persist
  // the unique ones, i.e. the cache.
  for (uint32_t i = 0; i < WasmCode::kRuntimeStubCount; ++i) {
    Address addr =
        native_module_->runtime_stub(static_cast<WasmCode::RuntimeStubId>(i))
            ->instruction_start();
    wasm_stub_targets_lookup_.insert(std::make_pair(addr, i));
  }
  ExternalReferenceTable* table = isolate_->external_reference_table();
  for (uint32_t i = 0; i < table->size(); ++i) {
    Address addr = table->address(i);
    reference_table_lookup_.insert(std::make_pair(addr, i));
  }
}

size_t NativeModuleSerializer::MeasureCode(const WasmCode* code) const {
  if (code == nullptr) return sizeof(size_t);
  DCHECK_EQ(WasmCode::kFunction, code->kind());
  return kCodeHeaderSize + code->instructions().size() +
         code->reloc_info().size() + code->source_positions().size() +
         code->protected_instructions().size() *
             sizeof(trap_handler::ProtectedInstructionData);
}

size_t NativeModuleSerializer::Measure() const {
  size_t size = kHeaderSize;
  for (WasmCode* code : code_table_) {
    size += MeasureCode(code);
  }
  return size;
}

void NativeModuleSerializer::WriteHeader(Writer* writer) {
  // TODO(eholk): We need to properly preserve the flag whether the trap
  // handler was used or not when serializing.

  writer->Write(native_module_->num_functions());
  writer->Write(native_module_->num_imported_functions());
}

void NativeModuleSerializer::WriteCode(const WasmCode* code, Writer* writer) {
  if (code == nullptr) {
    writer->Write(size_t{0});
    return;
  }
  DCHECK_EQ(WasmCode::kFunction, code->kind());
  // Write the size of the entire code section, followed by the code header.
  writer->Write(MeasureCode(code));
  writer->Write(code->constant_pool_offset());
  writer->Write(code->safepoint_table_offset());
  writer->Write(code->handler_table_offset());
  writer->Write(code->stack_slots());
  writer->Write(code->instructions().size());
  writer->Write(code->reloc_info().size());
  writer->Write(code->source_positions().size());
  writer->Write(code->protected_instructions().size());
  writer->Write(code->tier());

  // Get a pointer to the destination buffer, to hold relocated code.
  byte* serialized_code_start = writer->current_buffer().start();
  byte* code_start = serialized_code_start;
  size_t code_size = code->instructions().size();
  writer->Skip(code_size);
  // Write the reloc info, source positions, and protected code.
  writer->WriteVector(code->reloc_info());
  writer->WriteVector(code->source_positions());
  writer->WriteVector(Vector<byte>::cast(code->protected_instructions()));
#if V8_TARGET_ARCH_MIPS || V8_TARGET_ARCH_MIPS64 || V8_TARGET_ARCH_ARM
  // On platforms that don't support misaligned word stores, copy to an aligned
  // buffer if necessary so we can relocate the serialized code.
  std::unique_ptr<byte[]> aligned_buffer;
  if (!IsAligned(reinterpret_cast<Address>(serialized_code_start),
                 kInt32Size)) {
    aligned_buffer.reset(new byte[code_size]);
    code_start = aligned_buffer.get();
  }
#endif
  memcpy(code_start, code->instructions().start(), code_size);
  // Relocate the code.
  int mask = RelocInfo::ModeMask(RelocInfo::WASM_CALL) |
             RelocInfo::ModeMask(RelocInfo::WASM_STUB_CALL) |
             RelocInfo::ModeMask(RelocInfo::EXTERNAL_REFERENCE) |
             RelocInfo::ModeMask(RelocInfo::INTERNAL_REFERENCE) |
             RelocInfo::ModeMask(RelocInfo::INTERNAL_REFERENCE_ENCODED);
  RelocIterator orig_iter(code->instructions(), code->reloc_info(),
                          code->constant_pool(), mask);
  for (RelocIterator iter(
           {code_start, code->instructions().size()}, code->reloc_info(),
           reinterpret_cast<Address>(code_start) + code->constant_pool_offset(),
           mask);
       !iter.done(); iter.next(), orig_iter.next()) {
    RelocInfo::Mode mode = orig_iter.rinfo()->rmode();
    switch (mode) {
      case RelocInfo::WASM_CALL: {
        Address orig_target = orig_iter.rinfo()->wasm_call_address();
        uint32_t tag =
            native_module_->GetFunctionIndexFromJumpTableSlot(orig_target);
        SetWasmCalleeTag(iter.rinfo(), tag);
      } break;
      case RelocInfo::WASM_STUB_CALL: {
        Address orig_target = orig_iter.rinfo()->wasm_stub_call_address();
        auto stub_iter = wasm_stub_targets_lookup_.find(orig_target);
        DCHECK(stub_iter != wasm_stub_targets_lookup_.end());
        uint32_t tag = stub_iter->second;
        SetWasmCalleeTag(iter.rinfo(), tag);
      } break;
      case RelocInfo::EXTERNAL_REFERENCE: {
        Address orig_target = orig_iter.rinfo()->target_external_reference();
        auto ref_iter = reference_table_lookup_.find(orig_target);
        DCHECK(ref_iter != reference_table_lookup_.end());
        uint32_t tag = ref_iter->second;
        SetWasmCalleeTag(iter.rinfo(), tag);
      } break;
      case RelocInfo::INTERNAL_REFERENCE:
      case RelocInfo::INTERNAL_REFERENCE_ENCODED: {
        Address orig_target = orig_iter.rinfo()->target_internal_reference();
        Address offset = orig_target - code->instruction_start();
        Assembler::deserialization_set_target_internal_reference_at(
            iter.rinfo()->pc(), offset, mode);
      } break;
      default:
        UNREACHABLE();
    }
  }
  // If we copied to an aligned buffer, copy code into serialized buffer.
  if (code_start != serialized_code_start) {
    memcpy(serialized_code_start, code_start, code_size);
  }
}

bool NativeModuleSerializer::Write(Writer* writer) {
  DCHECK(!write_called_);
  write_called_ = true;

  WriteHeader(writer);

  for (WasmCode* code : code_table_) {
    WriteCode(code, writer);
  }
  return true;
}

WasmSerializer::WasmSerializer(Isolate* isolate, NativeModule* native_module)
    : isolate_(isolate),
      native_module_(native_module),
      code_table_(native_module->SnapshotCodeTable()) {}

size_t WasmSerializer::GetSerializedNativeModuleSize() const {
  NativeModuleSerializer serializer(isolate_, native_module_,
                                    VectorOf(code_table_));
  return kVersionSize + serializer.Measure();
}

bool WasmSerializer::SerializeNativeModule(Vector<byte> buffer) const {
  NativeModuleSerializer serializer(isolate_, native_module_,
                                    VectorOf(code_table_));
  size_t measured_size = kVersionSize + serializer.Measure();
  if (buffer.size() < measured_size) return false;

  Writer writer(buffer);
  WriteVersion(isolate_, &writer);

  if (!serializer.Write(&writer)) return false;
  DCHECK_EQ(measured_size, writer.bytes_written());
  return true;
}

class V8_EXPORT_PRIVATE NativeModuleDeserializer {
 public:
  NativeModuleDeserializer() = delete;
  NativeModuleDeserializer(Isolate*, NativeModule*);

  bool Read(Reader* reader);

 private:
  bool ReadHeader(Reader* reader);
  bool ReadCode(uint32_t fn_index, Reader* reader);

  Isolate* const isolate_;
  NativeModule* const native_module_;
  bool read_called_;

  DISALLOW_COPY_AND_ASSIGN(NativeModuleDeserializer);
};

NativeModuleDeserializer::NativeModuleDeserializer(Isolate* isolate,
                                                   NativeModule* native_module)
    : isolate_(isolate), native_module_(native_module), read_called_(false) {}

bool NativeModuleDeserializer::Read(Reader* reader) {
  DCHECK(!read_called_);
  read_called_ = true;

  if (!ReadHeader(reader)) return false;
  uint32_t total_fns = native_module_->num_functions();
  uint32_t first_wasm_fn = native_module_->num_imported_functions();
  for (uint32_t i = first_wasm_fn; i < total_fns; ++i) {
    if (!ReadCode(i, reader)) return false;
  }
  return reader->current_size() == 0;
}

bool NativeModuleDeserializer::ReadHeader(Reader* reader) {
  size_t functions = reader->Read<uint32_t>();
  size_t imports = reader->Read<uint32_t>();
  return functions == native_module_->num_functions() &&
         imports == native_module_->num_imported_functions();
}

bool NativeModuleDeserializer::ReadCode(uint32_t fn_index, Reader* reader) {
  size_t code_section_size = reader->Read<size_t>();
  if (code_section_size == 0) return true;
  size_t constant_pool_offset = reader->Read<size_t>();
  size_t safepoint_table_offset = reader->Read<size_t>();
  size_t handler_table_offset = reader->Read<size_t>();
  uint32_t stack_slot_count = reader->Read<uint32_t>();
  size_t code_size = reader->Read<size_t>();
  size_t reloc_size = reader->Read<size_t>();
  size_t source_position_size = reader->Read<size_t>();
  size_t protected_instructions_size = reader->Read<size_t>();
  WasmCode::Tier tier = reader->Read<WasmCode::Tier>();

  Vector<const byte> code_buffer = {reader->current_location(), code_size};
  reader->Skip(code_size);

  OwnedVector<byte> reloc_info = OwnedVector<byte>::New(reloc_size);
  reader->ReadVector(reloc_info.as_vector());
  OwnedVector<byte> source_pos = OwnedVector<byte>::New(source_position_size);
  reader->ReadVector(source_pos.as_vector());
  auto protected_instructions =
      OwnedVector<trap_handler::ProtectedInstructionData>::New(
          protected_instructions_size);
  reader->ReadVector(Vector<byte>::cast(protected_instructions.as_vector()));

  WasmCode* code = native_module_->AddDeserializedCode(
      fn_index, code_buffer, stack_slot_count, safepoint_table_offset,
      handler_table_offset, constant_pool_offset,
      std::move(protected_instructions), std::move(reloc_info),
      std::move(source_pos), tier);

  // Relocate the code.
  int mask = RelocInfo::ModeMask(RelocInfo::WASM_CALL) |
             RelocInfo::ModeMask(RelocInfo::WASM_STUB_CALL) |
             RelocInfo::ModeMask(RelocInfo::EXTERNAL_REFERENCE) |
             RelocInfo::ModeMask(RelocInfo::INTERNAL_REFERENCE) |
             RelocInfo::ModeMask(RelocInfo::INTERNAL_REFERENCE_ENCODED);
  for (RelocIterator iter(code->instructions(), code->reloc_info(),
                          code->constant_pool(), mask);
       !iter.done(); iter.next()) {
    RelocInfo::Mode mode = iter.rinfo()->rmode();
    switch (mode) {
      case RelocInfo::WASM_CALL: {
        uint32_t tag = GetWasmCalleeTag(iter.rinfo());
        Address target = native_module_->GetCallTargetForFunction(tag);
        iter.rinfo()->set_wasm_call_address(target, SKIP_ICACHE_FLUSH);
        break;
      }
      case RelocInfo::WASM_STUB_CALL: {
        uint32_t tag = GetWasmCalleeTag(iter.rinfo());
        DCHECK_LT(tag, WasmCode::kRuntimeStubCount);
        Address target =
            native_module_
                ->runtime_stub(static_cast<WasmCode::RuntimeStubId>(tag))
                ->instruction_start();
        iter.rinfo()->set_wasm_stub_call_address(target, SKIP_ICACHE_FLUSH);
        break;
      }
      case RelocInfo::EXTERNAL_REFERENCE: {
        uint32_t tag = GetWasmCalleeTag(iter.rinfo());
        Address address = isolate_->external_reference_table()->address(tag);
        iter.rinfo()->set_target_external_reference(address, SKIP_ICACHE_FLUSH);
        break;
      }
      case RelocInfo::INTERNAL_REFERENCE:
      case RelocInfo::INTERNAL_REFERENCE_ENCODED: {
        Address offset = iter.rinfo()->target_internal_reference();
        Address target = code->instruction_start() + offset;
        Assembler::deserialization_set_target_internal_reference_at(
            iter.rinfo()->pc(), target, mode);
        break;
      }
      default:
        UNREACHABLE();
    }
  }

  if (FLAG_print_code || FLAG_print_wasm_code) code->Print();
  code->Validate();

  // Finally, flush the icache for that code.
  Assembler::FlushICache(code->instructions().start(),
                         code->instructions().size());

  return true;
}

bool IsSupportedVersion(Isolate* isolate, Vector<const byte> version) {
  if (version.size() < kVersionSize) return false;
  byte current_version[kVersionSize];
  Writer writer({current_version, kVersionSize});
  WriteVersion(isolate, &writer);
  return memcmp(version.start(), current_version, kVersionSize) == 0;
}

MaybeHandle<WasmModuleObject> DeserializeNativeModule(
    Isolate* isolate, Vector<const byte> data, Vector<const byte> wire_bytes) {
  if (!IsWasmCodegenAllowed(isolate, isolate->native_context())) {
    return {};
  }
  if (!IsSupportedVersion(isolate, data)) {
    return {};
  }
  // TODO(titzer): module features should be part of the serialization format.
  WasmFeatures enabled_features = WasmFeaturesFromIsolate(isolate);
  ModuleResult decode_result = DecodeWasmModule(
      enabled_features, wire_bytes.start(), wire_bytes.end(), false,
      i::wasm::kWasmOrigin, isolate->counters(), isolate->allocator());
  if (decode_result.failed()) return {};
  CHECK_NOT_NULL(decode_result.value());
  WasmModule* module = decode_result.value().get();
  Handle<Script> script =
      CreateWasmScript(isolate, wire_bytes, module->source_map_url);

  OwnedVector<uint8_t> wire_bytes_copy = OwnedVector<uint8_t>::Of(wire_bytes);

  Handle<WasmModuleObject> module_object = WasmModuleObject::New(
      isolate, enabled_features, std::move(decode_result).value(),
      std::move(wire_bytes_copy), script, Handle<ByteArray>::null());
  NativeModule* native_module = module_object->native_module();

  if (FLAG_wasm_lazy_compilation) {
    native_module->SetLazyBuiltin(BUILTIN_CODE(isolate, WasmCompileLazy));
  }
  NativeModuleDeserializer deserializer(isolate, native_module);

  Reader reader(data + kVersionSize);
  if (!deserializer.Read(&reader)) return {};

  CompileJsToWasmWrappers(isolate, native_module,
                          handle(module_object->export_wrappers(), isolate));

  // Log the code within the generated module for profiling.
  native_module->LogWasmCodes(isolate);

  return module_object;
}

}  // namespace wasm
}  // namespace internal
}  // namespace v8