Supporting Flexible Safety and Sharing in Multi-threaded Environments

There is increasing interest in extensible systems (such as extensible operating systems, mobile code runtime systems, Internet browsers and servers) that allow external programs to be downloaded and executed directly within the system. While appealing from system design and extensibility points of view, extensible systems are vulnerable to aberrant behaviors of external programs. External programs can interfere with executions of other programs by reading and writing into their memory locations. In this paper, we present an approach for providing safe execution of external programs through a safe threads mechanism. The approach also provides a novel technique for safe sharing among external programs. The paper also describes the design and implementation of the safe threads.