Evolution of Kconfig in the Linux Kernel: A Study on Parser Compatibility: Bachelor’s Thesis

Linux is an operating system with a high degree of variability, enabling it to run on a wide range of hardware platforms. This variability is managed through the Kconfig system, which has been in use since 2002 to support the configurability of the Linux kernel. Over time, Kconfig has also been adopted by various other open-source projects. Just like the Linux kernel itself, the Kconfig system has evolved significantly, its language has been extended with new keywords, faulty behaviors have been corrected, and refactorings have taken place. These changes have led to different implementations of Kconfig tooling over time (across versions) and space (across projects), both internally within the Linux tooling and externally through research-driven tooling. In this thesis, we study the evolution of the Kconfig parser shipped with the Linux kernel. By examining the core source files that implement the parser logic, we manually analyze 365 commits that modify these files and classify the types of changes made. Additionally, we investigate 13 open-source projects that have adopted Kconfig as their configuration system, identifying when they first integrated Kconfig and how they maintain their configuration infrastructure. Finally, we perform a comparative compatibility analysis, systematically testing the Kconfig parser from each kernel version against older and more recent 87 kernel versions. Our goal is to determine whether each parser version produces configurations identical to those generated by the corresponding contemporary parser. We identify precisely which versions fail to parse specific inputs and analyze the underlying reasons for these incompatibilities.