runtime/vm/kernel_binary.cc

// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.
#if !defined(DART_PRECOMPILED_RUNTIME)

#include "vm/kernel_binary.h"

#include <memory>

#include "platform/globals.h"
#include "vm/compiler/frontend/kernel_to_il.h"
#include "vm/dart_api_impl.h"
#include "vm/flags.h"
#include "vm/growable_array.h"
#include "vm/kernel.h"
#include "vm/object.h"
#include "vm/os.h"
#include "vm/version.h"

namespace dart {

namespace kernel {

const char* Reader::TagName(Tag tag) {
  switch (tag) {
#define CASE(Name, value)                                                      \
  case k##Name:                                                                \
    return #Name;
    KERNEL_TAG_LIST(CASE)
#undef CASE
    default:
      break;
  }
  return "Unknown";
}

TypedDataPtr Reader::ReadLineStartsData(intptr_t line_start_count) {
  const intptr_t start_offset = offset();

  // Choose representation between Uint16 and Uint32 typed data.
  intptr_t max_start = 0;
  for (intptr_t i = 0; i < line_start_count; ++i) {
    const intptr_t delta = ReadUInt();
    max_start += delta;
  }

  const intptr_t cid = (max_start <= kMaxUint16) ? kTypedDataUint16ArrayCid
                                                 : kTypedDataUint32ArrayCid;
  const TypedData& line_starts_data =
      TypedData::Handle(TypedData::New(cid, line_start_count, Heap::kOld));

  set_offset(start_offset);
  intptr_t current_start = 0;
  for (intptr_t i = 0; i < line_start_count; ++i) {
    const intptr_t delta = ReadUInt();
    current_start += delta;
    if (cid == kTypedDataUint16ArrayCid) {
      line_starts_data.SetUint16(i << 1, static_cast<uint16_t>(current_start));
    } else {
      line_starts_data.SetUint32(i << 2, current_start);
    }
  }

  return line_starts_data.ptr();
}

const char* kKernelInvalidFilesize =
    "File size is too small to be a valid kernel file";
const char* kKernelInvalidMagicIdentifier = "Invalid magic identifier";
const char* kKernelInvalidBinaryFormatVersion =
    "Invalid kernel binary format version (expected %" Pu32 ", found %" Pu32
    ")";
const char* kKernelInvalidSizeIndicated =
    "Invalid kernel binary: Indicated size is invalid";
const char* kKernelInvalidSdkHash = "Invalid SDK hash";

const int kSdkHashSizeInBytes = 10;
const char* kSdkHashNull = "0000000000";

bool IsValidSdkHash(const uint8_t* sdk_hash) {
  if (memcmp(Version::SdkHash(), kSdkHashNull, kSdkHashSizeInBytes) != 0 &&
      memcmp(sdk_hash, kSdkHashNull, kSdkHashSizeInBytes) != 0 &&
      memcmp(sdk_hash, Version::SdkHash(), kSdkHashSizeInBytes) != 0) {
    return false;
  }
  return true;
}

std::unique_ptr<Program> Program::ReadFrom(Reader* reader, const char** error) {
  if (reader->size() < 70) {
    // A kernel file (v43) currently contains at least the following:
    //   * Magic number (32)
    //   * Kernel version (32)
    //   * SDK Hash (10 * 8)
    //   * List of problems (8)
    //   * Length of source map (32)
    //   * Length of canonical name table (8)
    //   * Metadata length (32)
    //   * Length of string table (8)
    //   * Length of constant table (8)
    //   * Component index (11 * 32)
    //
    // so is at least 74 bytes.
    // (Technically it will also contain an empty entry in both source map and
    // string table, taking up another 8 bytes.)
    if (error != nullptr) {
      *error = kKernelInvalidFilesize;
    }
    return nullptr;
  }

  uint32_t magic = reader->ReadUInt32();
  if (magic != kMagicProgramFile) {
    if (error != nullptr) {
      *error = kKernelInvalidMagicIdentifier;
    }
    return nullptr;
  }

  const uint32_t format_version = reader->ReadUInt32();
  if (format_version != kSupportedKernelFormatVersion) {
    if (error != nullptr) {
      *error = OS::SCreate(Thread::Current()->zone(),
                           kKernelInvalidBinaryFormatVersion,
                           kSupportedKernelFormatVersion, format_version);
    }
    return nullptr;
  }

  if (!IsValidSdkHash(reader->BufferAt(reader->offset()))) {
    if (error != nullptr) {
      *error = kKernelInvalidSdkHash;
    }
    return nullptr;
  }
  reader->set_offset(reader->offset() + kSdkHashSizeInBytes);

  std::unique_ptr<Program> program(new Program(reader->typed_data()));

  // Dill files can be concatenated (e.g. cat a.dill b.dill > c.dill). Find out
  // if this dill contains more than one program.
  int subprogram_count = 0;
  reader->set_offset(reader->size() - 4);
  while (reader->offset() > 0) {
    intptr_t size = reader->ReadUInt32();
    intptr_t start = reader->offset() - size;
    if (start < 0 || size <= 0) {
      if (error != nullptr) {
        *error = kKernelInvalidSizeIndicated;
      }
      return nullptr;
    }
    ++subprogram_count;
    if (subprogram_count > 1) break;
    reader->set_offset(start - 4);
  }
  program->single_program_ = subprogram_count == 1;

  // Read backwards at the end.
  program->library_count_ = reader->ReadSingleFieldFromIndexNoReset(
      reader->size_, KernelFixedFieldsAfterLibraries);
  program->source_table_offset_ = reader->ReadSingleFieldFromIndexNoReset(
      reader->size_, KernelNumberOfFixedFields(program->library_count_));
  program->constant_table_offset_ = reader->ReadUInt32();
  reader->ReadUInt32();  // offset for constant table index.
  program->name_table_offset_ = reader->ReadUInt32();
  program->metadata_payloads_offset_ = reader->ReadUInt32();
  program->metadata_mappings_offset_ = reader->ReadUInt32();
  program->string_table_offset_ = reader->ReadUInt32();
  // The below includes any 8-bit alignment; denotes the end of the previous
  // block.
  program->component_index_offset_ = reader->ReadUInt32();

  program->main_method_reference_ = NameIndex(reader->ReadUInt32() - 1);

  return program;
}

std::unique_ptr<Program> Program::ReadFromBuffer(const uint8_t* buffer,
                                                 intptr_t buffer_length,
                                                 const char** error) {
  // Whoever called this method (e.g. embedder) has to ensure the buffer stays
  // alive until the VM is done with the last usage (e.g. isolate shutdown).
  const auto& binary = ExternalTypedData::Handle(ExternalTypedData::New(
      kExternalTypedDataUint8ArrayCid, const_cast<uint8_t*>(buffer),
      buffer_length, Heap::kNew));
  kernel::Reader reader(binary);
  return kernel::Program::ReadFrom(&reader, error);
}

std::unique_ptr<Program> Program::ReadFromTypedData(
    const ExternalTypedData& typed_data,
    const char** error) {
  kernel::Reader reader(typed_data);
  return kernel::Program::ReadFrom(&reader, error);
}

}  // namespace kernel
}  // namespace dart
#endif  // !defined(DART_PRECOMPILED_RUNTIME)