Re: [PATCH master] ARM: stm32mp: much enlarge very early stack size

[Sascha Hauer <sha@pengutronix.de>]

On Fri, Feb 17, 2023 at 06:51:24PM +0100, Ahmad Fatoum wrote:
> The barebox stack is always located at a fixed offset from the end of
> SDRAM. To determine end of SDRAM, barebox may need a stack setup, so
> at that early time, either stack pointer set up by BootROM is reused
> or we set up a temporary stack on some on-chip SRAM .
> 
> On STM32MP1, TF-A runs after BootROM, so barebox runs in normal world
> without prepared stack and TF-A is located on on-chip SRAM.
> 
> So what we did so far was have a small stack of 64 bytes starting behind
> end of barebox image to cover the first function call to determine
> actual memory size. This may have been chosen that small with the thought
> that an overflow would give an error message anyway, because of failed
> decompression. An overflow of exactly 4 bytes overwrites just the barebox
> proper image size though located at the end of the barebox image, thereby
> overflowing the size and leading to out-of-bounds access during decompression
> in 1 of 4 cases depending on barebox size, because we align barebox
> proper size to 16 bytes...
> 
> Let's just use a fully sized stack even in the early state. That's
> usually 32K and we expect a barebox loaded into DRAM to always have
> that much bytes following it. Another way would've been to use
> some of the other SRAMs, but I decided to leave those alone, as not
> to clobber data used by the coprocessor, when reloading barebox.
> 
> Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
> ---
>  arch/arm/mach-stm32mp/include/mach/entry.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Applied, thanks

Sascha

> 
> diff --git a/arch/arm/mach-stm32mp/include/mach/entry.h b/arch/arm/mach-stm32mp/include/mach/entry.h
> index f8d981cca7cd..8d3adb4bdaf9 100644
> --- a/arch/arm/mach-stm32mp/include/mach/entry.h
> +++ b/arch/arm/mach-stm32mp/include/mach/entry.h
> @@ -11,7 +11,7 @@ static __always_inline void stm32mp_cpu_lowlevel_init(void)
>  	unsigned long stack_top;
>  	arm_cpu_lowlevel_init();
>  
> -	stack_top = (unsigned long)__image_end + get_runtime_offset() + 64;
> +	stack_top = (unsigned long)__image_end + get_runtime_offset() + CONFIG_STACK_SIZE;
>  	stack_top = ALIGN(stack_top, 16);
>  	arm_setup_stack(stack_top);
>  }
> -- 
> 2.30.2
> 
> 
> 

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