[PATCH v2] ARM: proc-v7.S: Adjust stack address when XIP_KERNEL

[Chris Brandt]

On 16 Feb 2016, Russell King - ARM Linux wrote:

> I keep looking at this patch, and I really find that I detest this
> PHYS_OFFSET_FIXUP thing - it's really not obvious what's going on here.
> It's taken a _long_ time to work this out, which _really_ isn't good
> going forward.
> 
> Let's instead change things to make it much more obvious - see the
> patch below.
> 
> 
> diff --git a/arch/arm/include/asm/memory.h b/arch/arm/include/asm/memory.h
>  index ebdaaf7dd19f..593e5613184d 100644
> --- a/arch/arm/include/asm/memory.h
> +++ b/arch/arm/include/asm/memory.h
> @@ -135,11 +135,18 @@
>  #define PLAT_PHYS_OFFSET	UL(CONFIG_PHYS_OFFSET)
>  
>  #ifdef CONFIG_XIP_KERNEL
> -#define PHYS_OFFSET_FIXUP \
> -	( XIP_VIRT_ADDR(CONFIG_XIP_PHYS_ADDR) - PAGE_OFFSET + \
> -	  PLAT_PHYS_OFFSET - CONFIG_XIP_PHYS_ADDR )
> +/*
> + * When referencing data in RAM from the XIP region in a relative 
> +manner
> + * with the MMU off, we need the relative offset between the two 
> +physical
> + * addresses.  The macro below achieves this, which is:
> + *    __pa(v_data) - __xip_pa(v_text)
> + */
> +#define PHYS_RELATIVE(v_data, v_text) \
> +	(((v_data) - PAGE_OFFSET + PLAT_PHYS_OFFSET) - \
> +	 ((v_text) - XIP_VIRT_ADDR(CONFIG_XIP_PHYS_ADDR) + \
> +          CONFIG_XIP_PHYS_ADDR))
>  #else
> -#define PHYS_OFFSET_FIXUP 0
> +#define PHYS_RELATIVE(v_data, v_text) (v_data) - (v_text)
>  #endif
>  
>  #ifndef __ASSEMBLY__
> diff --git a/arch/arm/mm/proc-v7.S b/arch/arm/mm/proc-v7.S index
>  1595fb29ec12..0f8963a7e7d9 100644
> --- a/arch/arm/mm/proc-v7.S
> +++ b/arch/arm/mm/proc-v7.S
> @@ -487,7 +487,7 @@ __errata_finish:
>  
>  	.align	2
>  __v7_setup_stack_ptr:
> -	.word	__v7_setup_stack - . + PHYS_OFFSET_FIXUP
> +	.word	PHYS_RELATIVE(__v7_setup_stack, .)
>  ENDPROC(__v7_setup)
>  
>  	.bss
>


This works fine for me (comes up with the same number either way).

Just tested it with my XIP_KERNEL ARMv7 system.


Chris