An implementation model for a multiprocessor operating system on a descriptor oriented architecture

Abstract

This thesis evolves a computer system which serves as the "basis for operating system design in a multiprocessor environment. The evolution presupposes the distinction between the 'mechanisms' and 'policies' which comprise an operating system and suggests an implementation for the set of mechanisms, which satisfy the criteria of flexibility and extensibility. The assumption is that the policy defining part of the operating system can be considered as a set of cooperating concurrent processes. The set of mechanisms, available to the system designer implementing the policy defining operating system, is termed as the 'nucleus' and is treated as a set of protected entities available to all processes in the system. The control of access is effected through a protection structure, which provides for the flexibility, extensibility and protected access. The protection structure uses a 'capability' model for protection and is supported by a descriptor oriented architecture. It is shown that the limited protection features of the supporting architecture cam be generalized to construct the protection structure, with respect to which, the nucleus can be appropriately specified. The nucleus is directed towards the delineation of as many features as possible, from a 'monitor' which is constrained to be used exclusively and which provides system wide functions.