Incorrect SAU Configuration From MMT on STM32H573 with Backup RAM Enabled

[ben5050]

When using the memory management tool (MMT) on the STM32H573 to set the backup RAM as secure it generates an invalid secure attribution unit (SAU) config:

#define SAU_INIT_REGION5 1
#define SAU_INIT_START5 0x40000000 /* start address of SAU region 5 */
#define SAU_INIT_END5 0x400373FF /* end address of SAU region 5 */
#define SAU_INIT_NSC5 0

The above code is the last region the MMT defines for the SAU.

Typically the tool would define the region 0x40000000 to 0x4fffffff (the non-secure peripheral address space) as non-secure. However 0x40036400 is the start of the backup RAM address space which shouldn't be made non-secure.

Since this is the last SAU region, there is nothing configuring the region 0x40037400 to 0x4fffffff as non-secure, and so hard faults occur when e.g. trying to access the non-secure RCC address space.

I believe correctly generated code should look like the below:

#define SAU_INIT_REGION5 1
#define SAU_INIT_START5 0x40000000 /* start address of SAU region 5 */
#define SAU_INIT_END5 0x400363FF /* end address of SAU region 5 */
#define SAU_INIT_NSC5 0

#define SAU_INIT_REGION6 1
#define SAU_INIT_START6 0x40037400 /* start address of SAU region 6 */
#define SAU_INIT_END6 0x4FFFFFFF /* end address of SAU region 6 */
#define SAU_INIT_NSC6 0

Please can the MMT be updated to patch this? 

[Mahmoud Ben Romdhane]

Hello @ben5050 

Let me thank you for your post.

For more investigation, could you please provide your IOC.File.

Thanks

Mahmoud 

[ben5050]

Hi Mahmoud,

I've attached the IOC file.

Kind regards,

Ben

[Mahmoud Ben Romdhane]

Hello @ben5050 ,

 

After checking internally, the SAU configuration generated by the Memory Management Tool is correct and expected.

When Backup RAM is secure on STM32H573, CubeMX intentionally ends the non-secure peripheral SAU region before the Backup RAM start address.

As a result, the non-secure SAU region is limited to 0x40000000-0x400363FF and the remaining address space is not automatically configured as non-secure, in accordance with Trust Zone security model.

Any additional non-secure peripheral regions must be explicitly defined by the user if required.

 

Thanks

Mahmoud