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, 

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

[Håkon Alseth]

Hi,

 

You need to expand the partition in order to write larger asset sizes, and you also need to set a different TFM profile.

This is the configuration I am using now:

CONFIG_BUILD_WITH_TFM=y
#CONFIG_TFM_PROFILE_TYPE_NOT_SET=y
CONFIG_TFM_PROFILE_TYPE_MEDIUM=y
CONFIG_TFM_PS_MAX_ASSET_SIZE=4000
CONFIG_MAIN_STACK_SIZE=4096

 

And here is a larger pm_static.yml (store as pm_static.yml this in your project and delete build folder and regenerate the project):

app:
  address: 0x40000
  end_address: 0xf4000
  region: flash_primary
  size: 0xb4000
otp:
  address: 0xff8100
  end_address: 0xff83fc
  region: otp
  size: 0x2fc
rpmsg_nrf53_sram:
  address: 0x20070000
  end_address: 0x20080000
  placement:
    before:
    - end
  region: sram_primary
  size: 0x10000
sram_nonsecure:
  address: 0x20030000
  end_address: 0x20080000
  orig_span: &id001
  - sram_primary
  - rpmsg_nrf53_sram
  region: sram_primary
  size: 0x50000
  span: *id001
sram_primary:
  address: 0x20030000
  end_address: 0x20070000
  region: sram_primary
  size: 0x40000
sram_secure:
  address: 0x20000000
  end_address: 0x20030000
  orig_span: &id002
  - tfm_sram
  region: sram_primary
  size: 0x30000
  span: *id002
tfm:
  address: 0x0
  end_address: 0x40000
  placement:
    before:
    - app
  region: flash_primary
  size: 0x40000
tfm_its:
  address: 0xf4000
  end_address: 0xf6000
  inside:
  - tfm_storage
  placement:
    align:
      start: 0x4000
    before:
    - tfm_otp_nv_counters
  region: flash_primary
  size: 0x2000
tfm_nonsecure:
  address: 0x40000
  end_address: 0xf4000
  orig_span: &id003
  - app
  region: flash_primary
  size: 0xb4000
  span: *id003
tfm_otp_nv_counters:
  address: 0xf6000
  end_address: 0xf8000
  inside:
  - tfm_storage
  placement:
    align:
      start: 0x4000
    before:
    - tfm_ps
  region: flash_primary
  size: 0x2000
tfm_ps:
  address: 0xf8000
  end_address: 0x100000
  inside:
  - tfm_storage
  placement:
    align:
      start: 0x4000
    before:
    - end
  region: flash_primary
  size: 0x8000
tfm_secure:
  address: 0x0
  end_address: 0x40000
  orig_span: &id004
  - tfm
  region: flash_primary
  size: 0x40000
  span: *id004
tfm_sram:
  address: 0x20000000
  end_address: 0x20030000
  inside:
  - sram_secure
  placement:
    after:
    - start
  region: sram_primary
  size: 0x30000
tfm_storage:
  address: 0xf4000
  end_address: 0x100000
  orig_span: &id005
  - tfm_ps
  - tfm_its
  - tfm_otp_nv_counters
  region: flash_primary
  size: 0xc000
  span: *id005

 

Kind regards,

Håkon

[Jithin A]

Hi Håkon,

Thank you for the response.

The above suggestion did not work for me, I am seeing the same -132 error when I run the code.

I removed build directory and rebuilt the project, yet the same result.

I can confirm the partitions.yml in build/zephyr/partition.yml updated your setup.

[Håkon Alseth]

Hi,

 

Sorry about this, I forgot to erase the partitions when testing, so it had the layout of a former flashed firmware.

This was my working configuration. I see that there is a problem with the PS partition size, which is for some reason set to 0x4000, while the partition size is actually 0x8000, so I set it explicitly:

CONFIG_BUILD_WITH_TFM=y
# CONFIG_TFM_PROFILE_TYPE_NOT_SET=y
# CONFIG_TFM_PROFILE_TYPE_MEDIUM=y
CONFIG_TFM_PROFILE_TYPE_SMALL=y
CONFIG_TFM_PS_MAX_ASSET_SIZE=3800
CONFIG_MAIN_STACK_SIZE=4096
CONFIG_PM_PARTITION_SIZE_TFM_PROTECTED_STORAGE=0x8000

 

Kind regards,

Håkon

[Jithin A]

Hi Håkon

Thank you that worked for me.

One last question, I found this TF-M profile table and I see TFM PROTECTED STORAGE is set to OFF in the SMALL profile. If so, how is it working on our setup.

If I set to any other profile except SMALL, I get -132 error and why is so?

[Håkon Alseth]

Hi,

 

My deepest apologies for sharing incorrect information.

Note that we recommend to either use minimal or full TFM profile, as shown here:

https://docs.nordicsemi.com/bundle/ncs-2.7.0/page/nrf/security/tfm.html#minimal_build

  

If you have CONFIG_TFM_PROFILE_TYPE_NOT_SET that implies a "full" implementation, and you need to adjust this configuration:

# Adjust even higher if storing larger files
CONFIG_TFM_CRYPTO_IOVEC_BUFFER_SIZE=6400

Jithin A said:

I found this TF-M profile table and I see TFM PROTECTED STORAGE is set to OFF in the SMALL profile.

I think there's an issue with how kconfig shows the tfm subsys vs. what is actually set in the cmake files to the TFM build. I see that the configuration is greyed out, but it does indeed pass this to the tfm image:

build/$IMAGE_NAME/tfm/CMakeCache.txt:TFM_PARTITION_PROTECTED_STORAGE:BOOL=ON

 

Sorry for all the back-and-forth in this matter.

 

Kind regards,

Håkon

[Jithin A]

Hi,

Thank you for letting me know, will test above and let you know.