after calling __set_MSP the local variables get corrupted

[ELitv.2]

Hello,

First, I am sharing some basic information.

The target - STM32G0, compiler Keil C11.

I am trying to jump from a Bootloader to an application. The scenario is very frequent and there are many questions about that on the web, but unfortunately I failed to find a solution to my problem. One of the problems I haven't yet resolved is corruption of the local variables right before the jump as result of __set_MSP which stores in the stack the base address of the applicatio, where I am trying to jump to.

You see here 2 pictures.

On the 1st picture you can see that appJumpAddress is 0x800515D, which is correct.

On the 2nd picture , after calling __set_MSP, written in asm, you see that appJumpAddress is already wrong and therefore my BL jumps to the wrong place in Flash memory .

The operation is standard , described everywhere. What I might did wrong?

Thanks!

P.S.

If someone here has an implementation of such a jump in Keil, can you please share these 3-4 lines?

[Tesla DeLorean]

No kidding... half this stuff is coded by people who barely know what they are doing.

The use of statics/globals would have been safer.

Look, don't set the MSP here, it's not coming back. Explicitly load the SP as the first thing you do in the Reset_Handler of the *Application*. Some of the GNU startup.s examples do this.

Reset_Handler   PROC
                EXPORT  Reset_Handler             [WEAK]
                IMPORT  SystemInit
                IMPORT  __main
 
;                LDR     SP, =__initial_sp 
 
                LDR     R0, =__initial_sp ; Cortex-M0(+) method
                MOV    SP, R0
 
                LDR     R0, =SystemInit
                BLX     R0
 
                LDR     R0, =__main
                BX      R0
                ENDP

[Tesla DeLorean]

Also the interrupts shouldn't be disabled at the MCU level, nothing enables them again.

And don't change the SCB->VTOR here. That should be handled in the App side SystemInit() with a symbol the linker can fix up.

extern uint32_t *__Vectors;

SCB->VTOR = (uint32_t)(&__Vectors);

[Piranha]

A complete solution:

https://community.st.com/s/question/0D50X0000AFpTmUSQV/using-nvicsystemreset-in-bootloaderapplication-jumps

P.S. The line 229 perfectly describes almost all ST's firmware related code in general!

[ELitv.2]

Actually, SCB->VTOR I changed in the SystemInit in the App, because Keil changed it to the FLASH_BASE which is 0. Thus, setting VTOR before the jump is redundant.

Thank you for your help!

[ELitv.2]

Thank you!

[Pavel A.]

Loading MSP for the app is popular because of ARM (Keil) and IAR. Their startup files neglect to initialize MSP like gcc's.

https://github.com/STMicroelectronics/STM32CubeG0/blob/f4e8c0a878aebc1b873b8590fd29563404759694/Drivers/CMSIS/Device/ST/STM32G0xx/Source/Templates/arm/startup_stm32g030xx.s#L121

https://github.com/STMicroelectronics/STM32CubeG0/blob/f4e8c0a878aebc1b873b8590fd29563404759694/Drivers/CMSIS/Device/ST/STM32G0xx/Source/Templates/iar/startup_stm32g030xx.s#L114

As for SCB->VTOR: now I'm setting it in the beginning of main(). Just got tired patching SystemInit().

[Andrew Neil]

How to take screenshots on Windows:

https://www.techrepublic.com/article/how-to-take-screenshots-in-windows-10/

[ELitv.2]

You're right and I appologize for not providing pictures of good quality. It is because I asked the question with my phone and had these pictures because i discussed the issue with my friends on Telegram. Next time i will do a better job. Thank you!