Verification of a Virtual Filesystem Switch

Abstract. This work presents part of our verification effort to construct a correct file system for Flash memory. As a blueprint we use UBIFS, which is part of Linux. As all file systems in Linux, UBIFS implements the Virtual Filesystem Switch (VFS) interface. VFS in turn implements specification of POSIX and a realistic model of VFS by ASM refinement. The models and proofs are mechanized in the interactive theorem prover KIV. Algebraic directory trees are mapped to the pointer structures of VFS using Separation Logic. We consider hard-links, file handles and the partitioning of file content into pages