Issue with SBSFU integration with custom user application

[kaur]

 

Hi,

I am trying to integrate custom user application with SBSFU bootloader for p-nucleo-WB55 and I was wondering in case anyone saw the following issue.

When I try to use the Secure Engine functions for validation in my user application, the program gets stuck and watchdog resets after timeout sometimes. Here is the call stack flow when I come across this issue:

Reset_Handler() at startup_stm32wb55xx_cm4.s:52 0x8000640
<signal handler called>() at 0xffffffe9
memcmp() at 0x80027b4
SE_IMG_GetActiveFwState() at se_fwimg.c:354 0x8001d5e
SE_CallGateService() at se_callgate.c:1,213 0x80017b6
SE_CallGate() at se_callgate.c:319 0x80002d0
SE_APP_GetActiveFwState() at se_interface_application.c:185 0x8003978
 

I don't see this issue consistently so I am a bit lost on where the issue could be. Highly appreciate you taking the time to read this. Thanks.

[Bubbles]

Hello @kaur,

do you test the integration with SECBOOT_DISABLE_SECURITY_IPS defined in app_sfu.h?

what project was your starting point, 1_image or 2_image?

When you say it's not consistent, do you mean that sometimes it passes, or you rather see different error in other cases?

BR,

J

[kaur]

Hi Bubbles,

Thanks for your prompt response. Yes, I have SECBOOT_DISABLE_SECURITY_IPS defined in app_sfu.h.

The starting point was 2_image and I modified mapping_fwimg.ld to expand active slot and Dwl slot to 320 KB from original 208 KB.

Sometimes, the SE_IMG_GetActiveFwState() returns as expected and I don't see this issue. However, sometimes I come across the issue I mentioned. I don't see a different error. 

Also, I had trouble generating se_interface_app.o so I ended up using se_interface_application.o, se_interface_bootloader.o and se_interface_common.o in my UserApp application for the SE interface functions.

[Bubbles]

Hi @kaur,

looking at the default linker file, I fail to see where you could have found the additional >200kB.

But obviously you are having trouble with the SE interface in the first place. I don't think the provision you use for the SE interface will work with security enabled.

BR,

J

[kaur]

Hi @Bubbles,

I am using stm32wb55rg which has 1MB flash as a result of which I am able to use 320K KB image slots.

Could you please clarify which security you are referring to. I have ENABLE_IMAGE_STATE_HANDELING and SECBOOT_DISABLE_SECURITY_IPS defined in app_sfu.h which should be sufficient for using SE_APP_GetActiveFwState() for image validation in my understanding.

[Bubbles]

Hi @kaur,

the default memory mapping in the ST delivered SBSFU is for 1MB device. If you need larger FW slots, you need to use a single image variant of the SBSFU, external flash or forfeit some of the functionality. Please look at AN5056 and AN5185.

BR,

J

[kaur]

Hi Bubbles,

I suspect that this issue could be due to some misconfiguration in porting the P-NUCLEO-WB55.Nucleo/Applications/2_Images project to the STM32WB55CG MCU that I am using. Could you please help me with the steps that need to be taken to port the default SBSFU code for STM32WB55CG.

[Bubbles]

Hi @kaur,

both RG and CG have the same 1MB flash memory. just the package is different.

BR,

J

[kaur]

Hi Bubbles, 

Thank for your support. I am unable to reproduce this issue. I am still not sure what caused it but I will update this thread if I discover the root cause.