NULL pointer protection with ARM Cortex-M MPU

NULL pointer protection with ARM Cortex-M MPU

Miro Samek

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This post explains how you can set up the ARM Cortex-M MPU (Memory Protection Unit) to protect thy code from dragons, demons, core dumps, and numberless other foul creatures awaiting thee after thou dereference the NULL pointer.

Summary

Miro Samek's blog explains how to use the ARM Cortex-M Memory Protection Unit (MPU) to protect firmware from NULL pointer dereferences. Readers will learn practical, step-by-step techniques to reserve the NULL page, configure MPU regions, and connect fault handlers for better detection and debugging of NULL-related faults.

Key Takeaways

Configure the MPU to reserve a zero (NULL) page and mark it non-accessible to trap NULL dereferences.
Align MPU region sizes and addresses to meet Cortex-M alignment and size constraints.
Implement and enrich HardFault/UsageFault handlers to detect, report, and diagnose NULL pointer faults.
Integrate MPU setup with the linker script and RTOS user-thread model to maintain protection across boot and context switches.
Validate protection with hardware debugging and targeted fault-injection tests to ensure reliable behavior in the field.

Who Should Read This

Intermediate firmware engineers and embedded developers working on ARM Cortex-M systems who need to harden firmware against NULL dereferences and memory faults, particularly in RTOS or safety-conscious projects.

Still RelevantIntermediate