SBSFU SFB update package size question

[sute]

Hello,

I am developing an application on STM32H7 MCU which uses SBSFU bootloader for secure firmware updates. I am trying to combine the SFB update package with some additional data in a single binary file that is sent for the firmware. To make this work, I need to determine where the SFB update package ends and the additional data starts in the binary. To this end, I check the firmware header of the update package. I noticed that the actual size of the SFB update package is 1024 bytes larger than the update size reported in the header. I expected SFB size to be larger than the firmware itself since the SFB package contains the header in addition to the update, but the header size is only 320 bytes.

So I am wondering what does the SFB update package contain and can I be sure that its size is awlays the firmware size in the header + 1024 bytes?

Thanks!

[sute · Accepted solution]

Found from sfu_fwimg_regions.h:

#define SFU_IMG_IMAGE_OFFSET ((uint32_t)1024U)

So it seems to be hard coded value indeed.