Fast Execute-Only Memory for Embedded Systems

TL;DR

PicoXOM is a new execute-only memory system for ARM embedded devices that offers high security with minimal performance and size overhead by utilizing ARM's hardware features.

Contribution

It introduces PicoXOM, a fast and efficient XOM solution for ARMv7-M and ARMv8-M that leverages existing hardware features to reduce overhead.

Findings

Average 0.33% performance overhead

Average 5.89% code size overhead

Effective protection against remote code disclosure

Abstract

Remote code disclosure attacks threaten embedded systems as they allow attackers to steal intellectual property or to find reusable code for use in control-flow hijacking attacks. Execute-only memory (XOM) prevents remote code disclosures, but existing XOM solutions either require a memory management unit that is not available on ARM embedded systems or incur significant overhead. We present PicoXOM: a fast and novel XOM system for ARMv7-M and ARMv8-M devices which leverages ARM's Data Watchpoint and Tracing unit along with the processor's simplified memory protection hardware. On average, PicoXOM incurs 0.33% performance overhead and 5.89% code size overhead on two benchmark suites and five real-world applications.