Hi Roman,

many thanks for sharing those findings and fixes.
I'll try my best to take a look soon.

Can you please in the meantime open a gitlab issue: https://github.com/TrustedFirmware-M/trusted-firmware-m/issues
such that we can track its progress and port it to LTS?

Many thanks in advance.
Best regards,
Nick

From: Roman.Mazurak--- via TF-M <tf-m@lists.trustedfirmware.org>
Sent: 20 December 2024 18:25
To: tf-m@lists.trustedfirmware.org <tf-m@lists.trustedfirmware.org>
Subject: [TF-M] FPU S16-S31 registers
 

Hi all,

 

We found the problem with FPU S16-S31 registers if FPU is enabled and compiler uses S16-S31 FPU registers on CM33 non-secure code with TZ agent. SPM doesn’t save/restore S16-S31 registers properly nor by PendSV neither by FLIH SVC handler. I created a patch for this problem:

https://review.trustedfirmware.org/c/TF-M/trusted-firmware-m/+/34202

 

The second problem I found is related to lazy stacking. It’s possible that float point context will be stacked by MCU when FLIH is switching to/from background thread after a new boundary is applied. As result it’s possible that the non-privileged code will no have access to PSP stack of suspended partition because a new MPU settings are applied. Please review a patch for this problem:

https://review.trustedfirmware.org/c/TF-M/trusted-firmware-m/+/34203

 

Regards,

Roman.