__noinit in tfm

[Cla]

I understand, it is possible to add variables to a section of ram, that will not be initialized (zeroed) at boot (see for example: https://github.com/nrfconnect/sdk-zephyr/blob/main/samples/boards/nrf/system_off/src/retained.c#L131)
To do this, the variable has to be marked using `__noinit`.

Is it possible to do so in the `tfm` region?
If so, how? When I just move the otherwise working code, then I get compiler errors.

Thanks in advance.

[Hieu]

Hi Cla,

Could you please let me know what you are trying to achieve first? It is quite atypical to add some variables to TF-M, more so when you need it to be no-init.

Hieu

[Cla]

I would like to implement a stateful custom tfm-service, that retains its state across resets.

[Hieu]

Is PSA Protected Storage not a better solution for this use case?

My colleague Sigurd wrote an overview of it here: https://devzone.nordicsemi.com/nordic/nordic-blog/b/blog/posts/persistent-storage-of-keys-and-data-using-the-nrf-connect-sdk#PSA-Protected-Storage