Control Flow Checking or Not? (for Soft Errors).

Huge leaps in performance and power improvements of computing systems are driven by rapid technology scaling, but technology scaling has also rendered computing systems susceptible to soft errors. Among the soft error protection techniques, Control Flow Checking (CFC) based techniques have gained a reputation of being lightweight yet effective. The main idea behind CFCs is to check if the program is executing the instructions in the right order. In order to validate the protection claims of existing CFCs, we develop a systematic and quantitative method to evaluate the protection achieved by CFCs using the metric of vulnerability. Our quantitative analysis indicates that existing CFC techniques are not only ineffective in providing protection from soft faults, but incur additional performance and power overheads. Our results show that software-only CFC protection schemes increase system vulnerability by 18%--21% with 17%--38% performance overhead and hybrid CFC protection increases vulnerability by 5%. Although the vulnerability remains almost the same for hardware-only CFC protection, they incur overheads of design cost, area, and power due to the hardware modifications required for their implementations.