Verification of Operating System Monolithic Kernels Without Extensions

Abstract

Most widely used, general-purpose operating systems are built on top of monolithic kernels to achieve maximum performance. These monolithic kernels are written in the C/C++ programming language primarily and they may exceed one million lines of code in size even without optional extensions or loadable kernel modules such as device drivers and file systems. In addition, they evolve rapidly for supporting new functionality and due to continuous optimizations and elimination of defects. Since operating systems and, in turn, applications strongly depend on monolithic kernels, requirements for their functionality, security, reliability and performance are ones of the highest. Currently used approaches to software quality assurance help to reveal quite many defects in monolithic kernels, but none of them aims at detecting all violations of checked requirements and alongside providing guarantees that target programs always operate correctly. This paper presents a new method that is based on the software verification technique and that enables thorough checking and finding hard-to-detect faults in various versions of monolithic kernels. One of its key features is the possibility to avoid considerable efforts for configuring tools and developing specifications to obtain valuable verification results while one still can steadily improve their quality. We implemented the suggested method within software verification framework Klever and evaluated it on subsystems of the Linux monolithic kernel.