【Android 逆向】ART 函数抽取加壳 ⑥ ( 函数抽取后续操作 “ 还原被抽取的函数 “ | LoadClass 类加载 | LoadClassMembers 类成员加载 )

void ClassLinker::LoadClass(Thread* self,
                            const DexFile& dex_file,
                            const DexFile::ClassDef& dex_class_def,
                            Handle<mirror::Class> klass) {
  const uint8_t* class_data = dex_file.GetClassData(dex_class_def);
  if (class_data == nullptr) {
    return;  // no fields or methods - for example a marker interface
  }
  LoadClassMembers(self, dex_file, class_data, klass);
}

LoadMethod(dex_file, it, klass, method);

void ClassLinker::LoadClassMembers(Thread* self,
                                   const DexFile& dex_file,
                                   const uint8_t* class_data,
                                   Handle<mirror::Class> klass) {
  {
    //注意：在设置字段和方法数组之前，我们不能暂停线程，否则
	//Class:：VisitFieldRoots可能缺少某些字段或方法。
    ScopedAssertNoThreadSuspension nts(__FUNCTION__);
    //加载静态字段。
	//我们允许class_data_item中相同字段的重复定义
	//但忽略此处的重复索引b/21868015。
    LinearAlloc* const allocator = GetAllocatorForClassLoader(klass->GetClassLoader());
    ClassDataItemIterator it(dex_file, class_data);
    LengthPrefixedArray<ArtField>* sfields = AllocArtFieldArray(self,
                                                                allocator,
                                                                it.NumStaticFields());
    size_t num_sfields = 0;
    uint32_t last_field_idx = 0u;
    for (; it.HasNextStaticField(); it.Next()) {
      uint32_t field_idx = it.GetMemberIndex();
      DCHECK_GE(field_idx, last_field_idx);  // Ordering enforced by DexFileVerifier.
      if (num_sfields == 0 || LIKELY(field_idx > last_field_idx)) {
        DCHECK_LT(num_sfields, it.NumStaticFields());
        LoadField(it, klass, &sfields->At(num_sfields));
        ++num_sfields;
        last_field_idx = field_idx;
      }
    }

    // 加载实例字段.
    LengthPrefixedArray<ArtField>* ifields = AllocArtFieldArray(self,
                                                                allocator,
                                                                it.NumInstanceFields());
    size_t num_ifields = 0u;
    last_field_idx = 0u;
    for (; it.HasNextInstanceField(); it.Next()) {
      uint32_t field_idx = it.GetMemberIndex();
      DCHECK_GE(field_idx, last_field_idx);  // Ordering enforced by DexFileVerifier.
      if (num_ifields == 0 || LIKELY(field_idx > last_field_idx)) {
        DCHECK_LT(num_ifields, it.NumInstanceFields());
        LoadField(it, klass, &ifields->At(num_ifields));
        ++num_ifields;
        last_field_idx = field_idx;
      }
    }

    if (UNLIKELY(num_sfields != it.NumStaticFields()) ||
        UNLIKELY(num_ifields != it.NumInstanceFields())) {
      LOG(WARNING) << "Duplicate fields in class " << klass->PrettyDescriptor()
          << " (unique static fields: " << num_sfields << "/" << it.NumStaticFields()
          << ", unique instance fields: " << num_ifields << "/" << it.NumInstanceFields() << ")";
      // 注意：不要缩小过度分配的sfields/ifield，只需设置大小即可。
      if (sfields != nullptr) {
        sfields->SetSize(num_sfields);
      }
      if (ifields != nullptr) {
        ifields->SetSize(num_ifields);
      }
    }
    // 设置字段数组。
    klass->SetSFieldsPtr(sfields);
    DCHECK_EQ(klass->NumStaticFields(), num_sfields);
    klass->SetIFieldsPtr(ifields);
    DCHECK_EQ(klass->NumInstanceFields(), num_ifields);
    // 加载方法.
    bool has_oat_class = false;
    const OatFile::OatClass oat_class =
        (Runtime::Current()->IsStarted() && !Runtime::Current()->IsAotCompiler())
            ? OatFile::FindOatClass(dex_file, klass->GetDexClassDefIndex(), &has_oat_class)
            : OatFile::OatClass::Invalid();
    const OatFile::OatClass* oat_class_ptr = has_oat_class ? &oat_class : nullptr;
    klass->SetMethodsPtr(
        AllocArtMethodArray(self, allocator, it.NumDirectMethods() + it.NumVirtualMethods()),
        it.NumDirectMethods(),
        it.NumVirtualMethods());
    size_t class_def_method_index = 0;
    uint32_t last_dex_method_index = DexFile::kDexNoIndex;
    size_t last_class_def_method_index = 0;
    // TODO 这些应该真正使用迭代器。
    for (size_t i = 0; it.HasNextDirectMethod(); i++, it.Next()) {
      // 新建 ArtMethod 对象 , 表示一个函数
      ArtMethod* method = klass->GetDirectMethodUnchecked(i, image_pointer_size_);
      LoadMethod(dex_file, it, klass, method);
      LinkCode(this, method, oat_class_ptr, class_def_method_index);
      uint32_t it_method_index = it.GetMemberIndex();
      if (last_dex_method_index == it_method_index) {
        // 重复案例
        method->SetMethodIndex(last_class_def_method_index);
      } else {
        method->SetMethodIndex(class_def_method_index);
        last_dex_method_index = it_method_index;
        last_class_def_method_index = class_def_method_index;
      }
      class_def_method_index++;
    }
    for (size_t i = 0; it.HasNextVirtualMethod(); i++, it.Next()) {
      ArtMethod* method = klass->GetVirtualMethodUnchecked(i, image_pointer_size_);
      LoadMethod(dex_file, it, klass, method);
      DCHECK_EQ(class_def_method_index, it.NumDirectMethods() + i);
      LinkCode(this, method, oat_class_ptr, class_def_method_index);
      class_def_method_index++;
    }
    DCHECK(!it.HasNext());
  }
  // 确保卡片上有标记，以便记住的套餐能够拾取本地根。
  Runtime::Current()->GetHeap()->WriteBarrierEveryFieldOf(klass.Get());
  self->AllowThreadSuspension();
}