Window Canaries: Re-thinking Stack Canaries for Architectures with Register Windows

This paper presents Window Canaries, a novel approach to Stack Canaries for architectures with a register window that protects return addresses and stack pointers without the need of adding additional instruction to each potentially vulnerable function. Instead, placement and check of the canary word is moved to window exception handlers that are responsible to handle register window overflows and underflows. The approach offers low performance overhead while guaranteeing that return addresses are protected by stack buffer overflows without relying on a heuristic that decides which functions to instrument. The contributions of this paper are a complete implementation of the approach for the Xtensa LX architecture with register window option as well as a performance evaluation and discussion of advantages and drawbacks.