Dead or Alive: Finding Zombie Features in the Linux Kernel

Variability management in operating systems is an error-prone and tedious task. This is especially true for the Linux operating system, which provides a specialized tool called Kconfig for users to customize kernels from an impressive amount of selectable features. However, the lack of a dedicated tool for kernel developers leads to inconsistencies between the implementation and the variant model described by Kconfig. This results in real bugs like features that cannot be either enabled or disabled at all; the so called zombie features. For both in the implementation and the variant model, these inconsistencies can be categorized in referential and semantic problems. We therefore propose a tool approach to check the variability described by conditional compilation in the implementation with the variant model for both kinds of consistency. Our analysis of the variation points show that our approach is feasible for the amount of variability found in the Linux kernel.