Control-flow checking by software signatures

TLDR

CFCSS is a pure software control‑flow monitoring technique that requires no dedicated hardware, unlike previous methods or watchdog tasks. The paper introduces CFCSS, a new signature‑based control‑flow checking method. CFCSS assigns unique signatures to each program graph node, embeds them at compile time, and compares them at run time, with an additional algorithm to reduce code size and overhead. Experimental fault injection showed that CFCSS reduced undetected branching‑fault errors from 33.7 % to 3.1 %, improving detection coverage by an order of magnitude.

Abstract

This paper presents a new signature monitoring technique, CFCSS (control flow checking by software signatures); CFCSS is a pure software method that checks the control flow of a program using assigned signatures. An algorithm assigns a unique signature to each node in the program graph and adds instructions for error detection. Signatures are embedded in the program during compilation time using the constant field of the instructions and compared with run-time signatures when the program is executed. Another algorithm reduces the code size and execution time overhead caused by checking instructions in CFCSS. A "branching fault injection experiment" was performed with benchmark programs. Without CFCSS, an average of 33.7 % of the injected branching faults produced undetected incorrect outputs; however, with CFCSS, only 3.1 % of branching faults produced undetected incorrect outputs. Thus it is possible to increase error detection coverage for control flow errors by an order of magnitude using CFCSS. The distinctive advantage of CFCSS over previous signature monitoring techniques is that CFCSS is a pure software method, i.e., it needs no dedicated hardware such as a watchdog processor for control flow checking. A watchdog task in multitasking environment also needs no extra hardware, but the advantage of CFCSS over a watchdog task is that CFCSS can be used even when the operating system does not support multitasking.