The technological progress in embedded system softwares increasingly requires the introduction of multiprocessor/multicore platforms for their considerable capacity and performances. This has introduced a large number of scientific researches in multiprocessor real-time scheduling but most of the results remain theoretical.Some implementations within real time operating systems have been studied, most of which are validated using simulation. However, simulation does not cover all the possible situations and does not take all the target constraints into account. This arises some questions about the confidence in implementing "sophisticated policies" and ensuring that the implemented schedulers behave exactly as they are specified in literature.For this reason, we introduce in this paper an innovative approach to formally verify the behavior of an implemented Global EDF scheduler in an OSEK/VDX real-time operating system called Trampoline. It’s a preliminary step since we intend to extend this study to other scheduling policies which are more complicated.