Formal specification and verification of a microkernel

Abstract

This thesis basically splits up into two parts. The first part introduces the abstract model of the Vamos kernel. The Vamos kernel provides the infrastructure for process and memory management, priority-based round-robin scheduling, communication with external devices, as well as inter-process communication. In the second part, we formulate a simulation theorem between the abstract Vamos model and the concrete Vamos implementation. The crucial points of the theorem are, on the one hand, the abstraction relation connecting the datastructures of the implementation with those of the model and, on the other hand, the implementation invariant formulating validity statements on the datastructures. Besides the exact formal definitions of the abstraction relation and the implementation invariant, we prove substantial parts of the simulation theorem. This work is part of the Verisoft project which aims at the pervasive formal verification of computer systems. For the modelling and the verification of the Vamos kernel this entails the integration of various computational models, for instance, Communicating Virtual Machines (Cvm) encapsulating the hardware-specific low-level functionality, and devices. The models and proofs presented in this thesis are formalized in the uniform logical framework of the interactive theorem prover Isabelle/HOL, and hence, it is rigorously checked that all verification results fit together.