Setup secure storage memory for data storage inside TFM

[Jithin A]

Hi,

We are working on nrf5340 board with NS and TF-M setup and we have SDK v2.7.0

We need to have a flash partition to store the some secure data may be a size of 4KB inside the TF-M.

Please help us or direct us to any reference.

[Jithin A]

Hi, any one please guide us through the setup please.

I see they have an example psa_protected_storage. If I set any partition size to 1KB the example does not work, it just goes into  arch_system_halt().

How can I modify the partition size?

[Håkon Alseth]

Hi,

 

You seem to have found an example that provides what you are looking for:

Jithin A said:

example psa_protected_storage.

What exactly did you add here?

Jithin A said:

If I set any partition size to 1KB the example does not work, it just goes into  arch_system_halt().

And what is the assert output? 

I suspect that the data that you added is stacked memory. If yes, then try to adjust your CONFIG_MAIN_STACK_SIZE.

 

If you want to store larger than 2k objects, you should adjust the CONFIG_TFM_PS_MAX_ASSET_SIZE. This can max. be 4020 due to overhead, and aligning to a flash page.

 

Kind regards,

Håkon

[Jithin A]

Hi  Håkon Alseth,

Thank you for the response, please see below comments.

Håkon Alseth said:

What exactly did you add here?

--> Nothing, plain example as is.

Håkon Alseth said:

And what is the assert output?

--> Reason holds 2

Håkon Alseth said:

I suspect that the data that you added is stacked memory. If yes, then try to adjust your CONFIG_MAIN_STACK_SIZE.

--> I don't think so, the data is a string with only 20-30 chars defined global which I believe is not stacked.

I just adjusted the partition size to be 1000 instead and nothing else changed.

Håkon Alseth said:

If you want to store larger than 2k objects, you should adjust the CONFIG_TFM_PS_MAX_ASSET_SIZE. This can max. be 4020 due to overhead, and aligning to a flash page.

--> Yet the same result. For reference I have attached the logs screenshot.

You can see it's not able execute the application.

Please let me know if my setup is wrong or missing something.

Thank you.

[Håkon Alseth]

Hi,

 

Jithin A said:

I just adjusted the partition size to be 1000 instead and nothing else changed.

Can you share your changes?

 

Kind regards,

Håkon

[Jithin A]

Hi, 

PFA for the file you requested.

I have added a macro: SIZE_OF_TEST_STRING_1 in which I am modifying the partition size when setting.

Please correct me if my understanding is wrong.

Thank you.

 

psa_protected_storage.zip

[Håkon Alseth]

Hi,

 

By changing the sizeof, it does not make the string any larger. You are effectively reading outside of the pointer. This also uses stack memory, as it declares a char array of size 1000, so you will need to adjust the main stack size, as previously mentioned.

I would recommend that you instead declare a static/global array of your wanted size and store that.

 

Kind regards,

Håkon

[Jithin A]

Thank you for the quick response, let me try and get back to you shortly.

[Jithin A]

I tried the way you suggested and now I am getting PSA_ERROR_GENERIC_ERROR (-132) when writing. 

Also, I have set CONFIG_TFM_PS_MAX_ASSET_SIZE to 4020

Let me attach the changes here.

2727.psa_protected_storage.zip