[U-Boot] [PATCH] arm: prevent using movt/movw address loads

[Albert ARIBAUD <albert.u.boot@aribaud.net>]

Hi Jeroen,

On Sat, 24 Aug 2013 13:55:38 +0200, Jeroen Hofstee
<jeroen@myspectrum.nl> wrote:

> The movt/movw instruction can be used to hardcode an
> memory location in the instruction itself. The linker
> starts complaining about this if the compiler decides
> to do so: "relocation R_ARM_MOVW_ABS_NC against `a local
> symbol' can not be used" and it is not support by U-boot
> as well. Prevent their use by requiring word relocations.
> This allows u-boot to be build at other optimalization
> levels then -Os.
> 
> Signed-off-by: Jeroen Hofstee <jeroen@myspectrum.nl>
> Cc: TigerLiu at viatech.com.cn
> Cc: Albert ARIBAUD <albert.u.boot@aribaud.net>
> ---
>  arch/arm/config.mk | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm/config.mk b/arch/arm/config.mk
> index 540a119..2277c82 100644
> --- a/arch/arm/config.mk
> +++ b/arch/arm/config.mk
> @@ -94,7 +94,11 @@ PLATFORM_RELFLAGS += -fno-optimize-sibling-calls
>  endif
>  endif
>  
> -# check that only R_ARM_RELATIVE relocations are generated
>  ifneq ($(CONFIG_SPL_BUILD),y)
> -ALL-y	+= checkarmreloc
> +# Check that only R_ARM_RELATIVE relocations are generated.
> +ALL-y += checkarmreloc
> +# The movt / movw can hardcode 16 bit parts of the addresses in the
> +# instruction. Relocation is not supported for that case, so disable
> +# such usage by requiring word relocations.
> +PLATFORM_CPPFLAGS += $(call cc-option, -mword-relocations)
>  endif

Applied as a bugfix to u-boot-arm/master, thanks!

Amicalement,
-- 
Albert.