Re: [PATCH 3/3] ARM: tegra: make sure the pointer on 4 byte align when THUMB2_KERNEL enabled

[Dave Martin <dave.martin-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>]

On Mon, Apr 15, 2013 at 04:50:55PM -0600, Stephen Warren wrote:
> From: Joseph Lo <josephl-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
> 
> When building kernel with CONFIG_THUMB2_KERNEL, the data pointer in the
> assembly may not on the 4 byte alignment. Then causing a data abort when
> accessing the pointer. This patch add a ".align" flag in the head of the
> pointer. And always using 32-bit ADR Thumb instruction to make sure it
> won't build failure.
> 
> Signed-off-by: Joseph Lo <josephl-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
> Signed-off-by: Stephen Warren <swarren-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
> ---
>  arch/arm/mach-tegra/reset-handler.S |    1 +
>  arch/arm/mach-tegra/sleep.h         |    3 ++-
>  2 files changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm/mach-tegra/reset-handler.S b/arch/arm/mach-tegra/reset-handler.S
> index e6de88a..519a8c5 100644
> --- a/arch/arm/mach-tegra/reset-handler.S
> +++ b/arch/arm/mach-tegra/reset-handler.S
> @@ -83,6 +83,7 @@ ENDPROC(tegra_resume)
>  
>  #ifdef CONFIG_CACHE_L2X0
>  	.globl	l2x0_saved_regs_addr
> +	.align
>  l2x0_saved_regs_addr:
>  	.long	0
>  #endif
> diff --git a/arch/arm/mach-tegra/sleep.h b/arch/arm/mach-tegra/sleep.h
> index 4ffae54..8e9b6af 100644
> --- a/arch/arm/mach-tegra/sleep.h
> +++ b/arch/arm/mach-tegra/sleep.h
> @@ -92,7 +92,8 @@
>  
>  #ifdef CONFIG_CACHE_L2X0
>  .macro l2_cache_resume, tmp1, tmp2, tmp3, phys_l2x0_saved_regs
> -	adr	\tmp1, \phys_l2x0_saved_regs
> + ARM(	adr	\tmp1, \phys_l2x0_saved_regs )
> + THUMB(	adr.w	\tmp1, \phys_l2x0_saved_regs )

Can you give an example of the assembler error you get without this?

The target symbol is local and the assembler can see where it is,
so it should choose the correct variant for the adr instruction
with no need for the ".w" suffix.

If not, it could mean that there is a bug in the version of the
assembler you're using.


If it's definitely needed, you can append a Thumb-only .w suffix with

	W(adr)	\tmp1, \phys_l2x0_saved_regs

...which is slightly neater.

Cheers
---Dave

>  	ldr	\tmp1, [\tmp1]
>  	ldr	\tmp2, [\tmp1, #L2X0_R_PHY_BASE]
>  	ldr	\tmp3, [\tmp2, #L2X0_CTRL]
> -- 
> 1.7.10.4
> 
> 
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel