Embedded Software 

Abstract: In NAND flash-based storage systems, an intermediate software layer called a flash translation layer (FTL)is usually employed to hide the erase-before-write characteristics of NAND flash memory. This paper proposes a novel superblockbased FTL scheme, which combines a set of adjacent logical blocks into a superblock. In the proposed FTL scheme, superblocks are mapped at coarse granularity,while pages inside the superblock are mapped freely at fine granularity to any location in several physical blocks. To reduce extra storage and flash memory operations, the fine-grain mapping information is stored in the spare area of NAND flash memory. This hybrid mapping technique has the flexibility provided by fine-grain address translation, while reducing the memory overhead to the level of coarse-grain address translation. Our experimental results show that the proposed FTL scheme decreases the garbage collection overhead up to 40% compared to previous FTL schemes.

Abstract: We classify component-based models of computation into component models and interface models. A component model specifies for each component howthe component behaves in an arbitrary environment; an interface model specifies for each component what the component expects from the environment. Component models support compositional abstraction, and therefore component-based verification. Interface models support compositional refinement, and therefore componentbased design. Many aspects of interface models, such as compatibility and refinement checking between interfaces, are properly viewed in a gametheoretic setting, where the input and output values of an interface are chosen by different players.

Abstract: Middleware for robotics development must meet demanding requirements in real-time distributed embedded systems. The Robot Operating System (ROS), open-source middleware, has been widely used for robotics applications. However, the ROS is not suitable for real-time embedded systems because it does not satisfy real-time requirements and only runs on a few OSs. To address this problem, ROS1 will undergo a significant upgrade to ROS2 by utilizing the Data Distribution Service (DDS). DDS is suitable for real-time distributed embedded systems due to its various transport configurations (e.g., deadline and fault-tolerance) and scalability. ROS2 must convert data for DDS and abstract DDS from its users; however, this incurs additional overhead, which is examined in this study. Transport latencies between ROS2 nodes vary depending on the use cases, data size, configurations, and DDS vendors. We conduct proof of concept for DDS approach to ROS and arrange DDS characteristic and guidelines from various evaluations. By highlighting the DDS capabilities, we explore and evaluate the potential and constraints of DDS and ROS2.

Abstract: Runtime property checking (as implemented in tools like Purify or Valgrind) checks whether a program execution satisfies a property. Active property checking extends runtime checking by checking whether the property is satisfied by all program executions that follow the same program path. This check is performed on a symbolic execution of the given program path using a constraint solver. If the check fails, the constraint solver generates an alternative program input triggering a new program execution that follows the same program path but exhibits a property violation. Combined with systematic dynamic test generation, which attempts to exercise all feasible paths in a program, active property checking defines a new form of dynamic software model checking (program verification). In this paper, we formalize and study active property checking. We show how static and dynamic type checking can be extended with active type checking. Then, we discuss how to implement active property checking efficiently. Finally, we discuss results of experiments with media playing applications on Windows, where active property checking was able to detect several new security-related bugs.