Process isolation on the nRF52

[Carl]

Hello,

I am looking at using the nRF52832 for a safety-related purpose and therefore want to isolate the safety-related code away from the Bluetooth stack. The main concern is accidental threats such as buffer overruns, stack overflows, etc. that might corrupt critical data. I'm therefore looking for features that would allow the application to prevent or detect access to safety-related memory or peripherals by the stack.

What is the best I can achieve with the nRF52 series (either SoftDevice or Zephyr)? I'm aware that there is a "memory watch unit" (MWU) provided by the nRF52 and also a "memory protection unit" (MPU) provided by ARM M4. However, from this related question I understand the MWU cannot be used by the application with the SoftDevice:

Memory Watch Unit : Who implements MWU_IRQHandler? - Nordic Q&A - Nordic DevZone - Nordic DevZone (nordicsemi.com)

Is the same true of MPU? How does the situation change if I'm using Zephyr? Are there any other features I should be aware of that would allow me to effectively isolate my code from the stack?

Thanks,

Carl

[Kenneth]

Hi,

Not sure if I have a good suggestion for you here. The MWU is used by the softdevice controller, so it's not possible for the application to control. The MPU is not used by the softdevice, and can thereby be used by the application in the way that Vidar mention in his reply you link to ("stack guard" using MPU).

If you want a really good solution you should consider using the nRF5340, for instance the ble stack is then running on it's own networe core, and the application run on the application core. In addition the zephyr RTOS do also provide security features:
https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/zephyr/security/security-overview.html 

Best regards,
Kenneth

[Carl]

Thanks Kenneth.