Experimental evaluation of software-implemented fault injection at different levels of abstraction

Transient hardware faults caused by cosmic ray or alpha particle strikes in hardware components are increasing in frequency due to shrinking feature size and manufacturing variations. Fault injection (FI), where a fault is artificially introduced during a program's execution to observe its behaviour, is a commonly used experimental technique to evaluate the resilience of software techniques for tolerating hardware faults. Software-implemented FI can be performed at different levels of abstraction in the system stack, including at the compiler's intermediate representation (IR) of a program or at the assembly code level. IR-level FI has the advantage that it is closer to the source code of the program being evaluated and hence it is easier to derive insights for the design of fault-tolerance mechanisms. Unfortunately, it is not clear how accurate IR-level FI is vis-a-vis assembly-level FI, and prior work has presented contradictory findings. In this thesis, we first perform a thorough comparison study of two contradictory previous studies, and find that the inconsistent findings are due to an implementation detail regarding how candidate injection bits are selected. Further, we perform a comprehensive evaluation of the accuracy of IR-level FI across a range of benchmark programs and compiler optimization levels to supplement our findings. Our results show that IR-level FI can be as accurate as assembly-level FI for silent data corruptions (SDCs) across different benchmarks and optimization levels, but for crashes the accuracy depends on the optimization level (i.e., less accuracy when more optimizations are applied). Finally, we discuss why compiler optimizations may have an effect on the accuracy of IR-level FI for measuring crash probabilities, and present a machine learning-based technique to estimate crash probabilities that are as accurate as those measured using assembly-level FI, using only results from IR-level FI experiments. The proposed technique is shown to be capable of improving the accuracy of crash probabilities from IR-level FI by over 9 times; this allows IR-level FI to be used for accurately measuring both SDC and crash probabilities.Applied Science, Faculty ofElectrical and Computer Engineering, Department ofGraduat