[PATCH] arm64: errata: Add -mpc-relative-literal-loads to erratum #843419 build flags

[Ard Biesheuvel]

On 23 January 2016 at 00:07, dann frazier <dann.frazier at canonical.com> wrote:
> GCC6 (and Linaro's 2015.12 snapshot of GCC5) has a new default that uses
> adrp/ldr or adrp/add to address literal pools. When CONFIG_ARM64_ERRATUM_843419
> is enabled, modules built with this toolchain fail to load:
>

(more context here https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63304)

Hi Dann,

I would prefer this new option to be set unconditionally (if
supported) both for the kernel and the modules, since we have no
requirement for supporting literals that are >1 MB away.

Thanks,
Ard.

>   [ 2.156817] module libahci: unsupported RELA relocation: 275
>
> Longterm, this will likely be superseded by -mfix-cortex-a53-843419, which
> should disable this optimization in the future.
>
> Cc: stable at vger.kernel.org
> Fixes: df057cc7b4fa ("arm64: errata: add module build workaround for erratum #843419")
> BugLink: http://bugs.launchpad.net/bugs/1533009
> Suggested-by: Christophe Lyon <christophe.lyon at linaro.org>
> Signed-off-by: dann frazier <dann.frazier at canonical.com>
> ---
>  arch/arm64/Makefile | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
> index cd822d8..08e794d 100644
> --- a/arch/arm64/Makefile
> +++ b/arch/arm64/Makefile
> @@ -43,6 +43,7 @@ CHECKFLAGS    += -D__aarch64__
>
>  ifeq ($(CONFIG_ARM64_ERRATUM_843419), y)
>  KBUILD_CFLAGS_MODULE   += -mcmodel=large
> +KBUILD_CFLAGS_MODULE   += $(call cc-option, -mpc-relative-literal-loads)
>  endif
>
>  # Default value
> --
> 2.7.0
>