State Caching In The Eros Kernel - Implementing Efficient Orthogonal Persistence In A Pure Capability System

EROS, the Extremely Reliable Operating System, addresses the issues of reliability and security by combining two ideas from earlier systems: capabilities and a persistent; single-level stare. Capabilities unify object naming with access control. Persistence extends this naming and access control uniformly across the memory hierarchy; main memory is viewed simply as a cache of the single-level store. The combination simplifies application design, allows programs to observe the ''principle of least privilege,'' and enables active objects to be constructed securely.Prior software capability implementations have suffered from poor performance. In EROS, cacheing techniques are used to implement authority checks efficiently and to preserve the state of active processes in a form optimized for the demands of the machine, The resulting system provides performance competative with conventional designs. This paper describes the EROS object model and the structures used to efficiently map this model onto one hardware implementation: the Intel 80x86 processor architecture.