There’s a new blog post on the ARM blog, talking about Security Extensions and Privilege Levels in ARMv8-M Cortex systems:
Security Extensions and Privilege Levels
[…]
ARMv8-M introduces Security Extensions that provide hardware features for more secure devices. The Security Extensions allow the protection of trusted and system resources from untrusted handlers and applications. They can be executed without the additional software sandboxing overheads of reprogramming the MPU. The Security Extensions collaborates with the associated software model to provide a mechanism to restrict access to system resources and processes through well-defined interfaces similar to system calls, thereby ensuring a higher level of protection and also offering an implicit privilege-stack. […]
Firmware Security 