Worst-case execution time analysis of the RTEMS real-time operating system

An important issue in building operating systems for hard real-time applications is to compute the worst-case execution times (WCET) of the operating system activities. Traditionally, this has been achieved by an exhaustive testing of the operating system, with a careful attention on the testing conditions to reproduce the worst-case execution scenario. In this paper we explore the alternative approach of using static analysis to predict off-line the WCET of the system calls of a real-time kernel, the RTEMS kernel. We give qualitative and quantitative results on the analysis of RTEMS, and draw some conclusions on the extent to which static analysis can be used on operating system code.