When the Debugger Lies
Summary
This article investigates debugging embedded security on the Nordic nRF54LM20, focusing on how the KMU, SICR, and ARM CoreSight access ports interact with debuggers. It reveals how debugger caches and read strategies can yield stale memory values, demonstrates practical debugging steps with GDB and J-Link, and explains how to bypass caching to obtain accurate results. The discussion highlights the importance of understanding bus architecture and debugger behavior when testing hardware security features in embedded systems.