Debugging Using Time Machines

Cyclic debugging is one of the most important and most commonly used activities in program development. During cyclic debugging, the program is repeatedly reexecuted to track down errors when a failure has been observed. This process necessitates reproducible program executions. Applying classical debugging techniques such using breakpoints or single stepping in real-time systems change the temporal behavior and make reproduction of the observed failure during debugging less likely, if not impossible. Consequently, these techniques are not directly applicable for cyclic debugging of real-time systems. In this paper we present how do you turn standard CPU instruction level simulator debuggers, JTAG/BDM debuggers or in circuit emulator debuggers into veritable time machines so you can debug your embedded application both forwards and backwards in time – repeatedly. By on-line recording significant system events, and off-line deterministically replaying them, we can inspect the real-time system in great detail while still preserving its real-time behavior.