DHOOM: Reusing Design-for-Debug Hardware for Online Monitoring

Runtime verification employs dedicated hardware or software monitors to check whether program properties hold at runtime. However, these monitors often incur high area and performance overheads depending on whether they are implemented in hardware or software. In this work, we propose DHOOM, an architectural framework for runtime monitoring of program assertions, which exploits the combination of a reconfigurable fabric present alongside a processor core with the vestigial on-chip Design-for-Debug hardware. This combination of hardware features allows DHOOM to minimize the overall performance overhead of runtime verification, even when subject to a given area constraint. We present an algorithm for dynamically selecting an effective subset of assertion monitors that can be accommodated in the available programmable fabric, while instrumenting the remaining assertions in software. We show that our proposed strategy, while respecting area constraints, reduces the performance overhead of runtime verification by up to 32% when compared with a baseline of software-only monitors.