The structure of a type safe operating system

The architecture of traditional operating systems relies on address-based memory protection. To achieve flexibility at a low cost operating system research has recently started to explore alternative protection mechanisms, such as type safety. This dissertation presents an operating system architecture that completely replaces address-based protection with type-based protection. Replacing such an essential part of the system leads to a novel operating system architecture with im-The dissertation describes not only the design of such a system but also its prototype implementation and the performance of initial applications, such as a file system, a web server, a data base management system, and a network file server. The prototype, which is called JX, uses Java bytecode as its type-safe instruction set and is able to run existing Java programs without modifications. The system is based on a modular microkernel, which is the only part of the system that is written in an unsafe language. Lightweight protection domains replace the heavyweight process concept of traditional systems. These domains are the unit of protection, resource management, and termination. Code is organized in components that are loaded into domains. The portal mechanism—a fast inter-domain communication mechanism—allows mutually distrusting domains to cooperate in a secure way. This dissertation shows that it is possible to build a complete and efficient general purpose time-sharing operating system based on type safety. 1.1 Robustness, security, and reliability 2 1.2 Configurability, reusability, and dedicated systems 2 1.3 Extensibility and fine-grained protection 3