How to reduce the code size of TF-M

[Tide]

After porting the application to sdk v2.4.0, I get the following error after compiling the code:

"opt/zephyr-sdk/arm-zephyr-eabi/bin/... /lib/gcc/arm-zephyr-eabi/12.2.0/... /... /... /... /arm-zephyr-eabi/bin/ld.bfd.exe: region `FLASH' overflow 47368 bytes"

The partitions I use are as follows:

flash_primary (0x100000 - 1024kB):
+--------------------------------------------------+
| 0x0: mcuboot (0xc000 - 48kB) |
| 0xc000: EMPTY_0 (0x4000 - 16kB) |
+---0x10000: mcuboot_primary (0x68000 - 416kB)-----+
+---0x10000: tfm_secure (0x40000 - 256kB)----------+
| 0x10000: mcuboot_pad (0x200 - 512B) |
+---0x10200: mcuboot_primary_app (0x67e00 - 415kB)-+
| 0x10200: tfm (0x3fe00 - 255kB) |
+---0x50000: tfm_nonsecure (0x28000 - 160kB)-------+
| 0x50000: app (0x28000 - 160kB) |
+--------------------------------------------------+
| 0x78000: mcuboot_secondary (0x68000 - 416kB) |
| 0xe0000: EMPTY_3 (0x8000 - 32kB) |
+---0xe8000: nonsecure_storage (0x6000 - 24kB)-----+
| 0xe8000: nvs_storage (0x6000 - 24kB) |
+--------------------------------------------------+
| 0xee000: EMPTY_2 (0x6000 - 24kB) |
+---0xf4000: tfm_storage (0x8000 - 32kB)-----------+
| 0xf4000: tfm_its (0x2000 - 8kB) |
| 0xf6000: tfm_otp_nv_counters (0x2000 - 8kB) |
| 0xf8000: tfm_ps (0x4000 - 16kB) |
+--------------------------------------------------+
| 0xfc000: EMPTY_1 (0x4000 - 16kB) |
+--------------------------------------------------+

otp (0x2f4 - 756B):
+------------------------------+
| 0xff8108: otp (0x2f4 - 756B) |
+------------------------------+

sram_primary (0x40000 - 256kB):
+--------------------------------------------------+
+---0x20000000: mcuboot_sram (0x16000 - 88kB)------+
+---0x20000000: sram_secure (0x16000 - 88kB)-------+
| 0x20000000: tfm_sram (0x16000 - 88kB) |
+---0x20016000: sram_nonsecure (0x2a000 - 168kB)---+
+---0x20016000: nrf_modem_lib_sram (0x7ce8 - 31kB)-+
| 0x20016000: nrf_modem_lib_ctrl (0x4e8 - 1kB) |
| 0x200164e8: nrf_modem_lib_tx (0x5800 - 22kB) |
| 0x2001bce8: nrf_modem_lib_rx (0x2000 - 8kB) |
+--------------------------------------------------+
| 0x2001dce8: sram_primary (0x22318 - 136kB) |
+--------------------------------------------------+

Only 160K bytes are reserved for app, TF-M uses 255K bytes of flash.  I only use secp256k1 crypto in my application, how do I configure TF-M to reduce the TF-M code size ?

[Håkon Alseth]

Hi,

 

Unfortunately, it is not trivial to configure one specific cipher support only with TFM at this time. I've tried to get it slimmed down, but ended up hitting several issues wrt. missing settings in mbedtls.

I have created an internal jira ticket to improve this configuration setting.

 

Kind regards,

Håkon

[Tide]

Thank you for your reply and I look forward to more exciting results from you.

[Tide]

Hi,

For this issue, please sync any progress on your end to this ticket and look forward to your progress.

[Tide]

Hi,
Is there any progress on this issue? We urgently need tf-m that can reduce the code size.

[Håkon Alseth]

Hi,

 

I am sorry, but the task is still open internally.

We have been able to set a "medium" configuration, here based on the samples/tfm/tfm_hello_world/ with a manual operation to reduce the "tfm" partition from 0x40000 -> 0x30000:

tfm_hello_world_medium_size_ncs240.zip

 

Please note the pm_static.yml file which statically defines the whole partition layout, as well as prj.conf::CONFIG_TFM_PROFILE_TYPE_MEDIUM=y.

 

Could you try this and see if this helps with the flash usage at your end as well?

 

Kind regards,

Håkon