nRF5340: secure memory access and difference between NSC parameters.

[Buttman]

Hello!

I'm reading the functions that exist in SPU HAL.

The function nrf_spu_flashnsc_set is used to configuring non-secure callable flash region.
Which is great to use when accessing secure memory.

I have read the documentation, but I can't understand what the difference is between two parameters being the:

Non-secure callable flash region ID and the Flash region number.

What is the difference ?
According to the documentation, I assume that the non-secure callable flash region ID is between the numbers 0..63.
But I don't get what the flash region number is.

Another question is, what is the workflow to store data on the secure memory. Right now do I store variables on specific memory address and secure those memory address.
But that doesn't feel like a long term solution.
Is there any workflow how to store functions on the secure memory that has been configured and how to access them?

Best regards
Buttman

[Øivind]

Hi,

There can only be two non-secure callable regions, so the ID is either 0 or 1. The flash is divided into 64 flash regions, each with a size of 16 KiB. A section of a flash region can be configured as a non-secure callable region. If CONFIG_ARM_FIRMWARE_HAS_SECURE_ENTRY_FUNCS is set, the spm will create a non-secure callable region with ID 0.

For your second question, have you taken a look at this guide by Heidi? https://devzone.nordicsemi.com/nordic/nrf-connect-sdk-guides/b/software/posts/using-a-custom-secure-partition-manager-wtih-your-application

Does that answer your questions?

[Buttman]

The first question is definitely answered, thanks for that. The second question did I get an answer by looking more into ARM's TrustZone architecture. But thanks for the answers!