SBSFU Firewall reset in User App when writing to SFR's.

RBurg.2 · ‎2022-03-25

Hi All,

I am almost finished integrating the SBSFU into my project. I can run the SBSFU and user app and update the processor, STM32L4R9VITx, successfully while no protections are enabled. When I enable firewall protection it boots into my application but fails on the first write to a special function register. The SBSFU restarts with a firewall reset detected and retries the application.

My application uses FreeRTOS and the freeRTOS SVC and PendSVC handlers.

Any ideas as to why I cant write to the SFR's?

SBSFU Linker files and pictures of the debugger instructions below.

mapping_sbsfu.ld
/* SE Code region protected by firewall */
VECTOR_SIZE = 0x200;
__ICFEDIT_SE_Code_region_ROM_start__       = 0x08000000 + VECTOR_SIZE;
__ICFEDIT_SE_CallGate_region_ROM_start__   = __ICFEDIT_SE_Code_region_ROM_start__ + 0x4;
__ICFEDIT_SE_CallGate_region_ROM_end__     = __ICFEDIT_SE_Code_region_ROM_start__ + 0x1FF;
 
/* SE key region protected by firewall */
__ICFEDIT_SE_Key_region_ROM_start__        = __ICFEDIT_SE_CallGate_region_ROM_end__ + 0x1;
__ICFEDIT_SE_Key_region_ROM_end__          = __ICFEDIT_SE_Key_region_ROM_start__ + 0xFF;
 
/* SE Startup: call before enabling firewall*/
__ICFEDIT_SE_Startup_region_ROM_start__    = __ICFEDIT_SE_Key_region_ROM_end__ + 0x1;
__ICFEDIT_SE_Code_nokey_region_ROM_start__ = __ICFEDIT_SE_Startup_region_ROM_start__ + 0x100;
__ICFEDIT_SE_Code_region_ROM_end__         = __ICFEDIT_SE_Startup_region_ROM_start__ + 0x52FF;
 
/* SE IF ROM: used to locate Secure Engine interface code out of firewall */
__ICFEDIT_SE_IF_region_ROM_start__         = __ICFEDIT_SE_Code_region_ROM_end__ + 1;
__ICFEDIT_SE_IF_region_ROM_end__           = __ICFEDIT_SE_IF_region_ROM_start__ + 0x66F;
 
/* SBSFU Code region */
__ICFEDIT_SB_region_ROM_start__            = __ICFEDIT_SE_IF_region_ROM_end__ + 0x1;
__ICFEDIT_SB_region_ROM_end__              = 0x0800FFFF;
 
SE_Entry_Secure_ROM_Region_Length = __ICFEDIT_SE_CallGate_region_ROM_end__ - __ICFEDIT_SE_CallGate_region_ROM_start__ + 1;
SE_Key_region_ROM_Length          = __ICFEDIT_SE_Key_region_ROM_end__ - __ICFEDIT_SE_Key_region_ROM_start__ + 1;
SE_Startup_region_ROM_Length      = __ICFEDIT_SE_Code_nokey_region_ROM_start__ - __ICFEDIT_SE_Startup_region_ROM_start__ ;
SE_ROM_region_Length              = __ICFEDIT_SE_Code_region_ROM_end__ - __ICFEDIT_SE_Code_nokey_region_ROM_start__ + 1;
SE_IF_region_ROM_Length           = __ICFEDIT_SE_IF_region_ROM_end__ - __ICFEDIT_SE_IF_region_ROM_start__ + 1;
SB_ROM_region_Length              = __ICFEDIT_SB_region_ROM_end__ - __ICFEDIT_SB_region_ROM_start__ + 1;
 
/* SE stack is placed 1st in RAM, stack overflow does not write on other RAM area */
__ICFEDIT_SE_region_RAM_start__     = 0x20000000;
__ICFEDIT_SE_region_RAM_stack_top__ = 0x20000400;
__ICFEDIT_SE_region_RAM_end__       = 0x20000FFF;
 
/* SBSFU RAM1 region */
__ICFEDIT_SB_region_RAM_start__     = 0x20041000;
__ICFEDIT_SB_region_RAM_end__       = 0x2007FFFF;
 
SE_RAM_region_Length = __ICFEDIT_SE_region_RAM_end__ - __ICFEDIT_SE_region_RAM_stack_top__ + 1;
SB_RAM_region_Length = __ICFEDIT_SB_region_RAM_end__ - __ICFEDIT_SB_region_RAM_start__ + 1;
 
MEMORY
{
 SE_Entry_Secure_ROM_Region (rx)     : ORIGIN = __ICFEDIT_SE_CallGate_region_ROM_start__, LENGTH = SE_Entry_Secure_ROM_Region_Length
 SE_Key_region_ROM (rx)              : ORIGIN = __ICFEDIT_SE_Key_region_ROM_start__, LENGTH = SE_Key_region_ROM_Length
 SE_Startup_region_ROM (rx)          : ORIGIN = __ICFEDIT_SE_Startup_region_ROM_start__, LENGTH = SE_Startup_region_ROM_Length
 SE_ROM_region (rx)                  : ORIGIN = __ICFEDIT_SE_Code_nokey_region_ROM_start__, LENGTH = SE_ROM_region_Length
 SE_IF_region_ROM (rx)               : ORIGIN = __ICFEDIT_SE_IF_region_ROM_start__, LENGTH = SE_IF_region_ROM_Length
 SB_ROM_region (rx)                  : ORIGIN = __ICFEDIT_SB_region_ROM_start__, LENGTH = SB_ROM_region_Length
 SE_RAM_region (xrw)               : ORIGIN = __ICFEDIT_SE_region_RAM_stack_top__, LENGTH = SE_RAM_region_Length
 SB_RAM_region (xrw)               : ORIGIN = __ICFEDIT_SB_region_RAM_start__, LENGTH = SB_RAM_region_Length
}

mapping_fwimg.ld
/* swap (24 kbytes) */
__ICFEDIT_SWAP_start__           = 0x081FA000;
__ICFEDIT_SWAP_end__             = 0x081FFFFF;
 
/* Active slot #1 (960 kbytes)*/
__ICFEDIT_SLOT_Active_1_start__  = 0x08106000;
__ICFEDIT_SLOT_Active_1_end__    = 0x081F5FFF;
__ICFEDIT_SLOT_Active_1_header__ = __ICFEDIT_SLOT_Active_1_start__;
 
/* Dwl slot #1 (960 kbytes)*/
__ICFEDIT_SLOT_Dwl_1_start__     = 0x08010000;
__ICFEDIT_SLOT_Dwl_1_end__       = 0x080FFFFF;

Fred · ‎2022-04-08

Hi @RBurg.2,

the RM clearly states: "A segment defined with a length equal to 0 is not considered as protected by the Firewall. As a consequence, there is no reset generation from the Firewall when an access to the base address of this segment is performed." so what you describe should not happen.

Please let me report it to the designers and come back yo you.

Thanks & Regards,

Fred

RBurg.2 · ‎2022-04-11

Thanks. I do still have the SBSFU flash segments protected by firewall, so I'm thinking there may be a problematic access somewhere either in my code or touchgfx, wish I could set up an interrupt and breakpoint to narrow it down.