[PATCH] arm64: errata: Pass --fix-cortex-a53-843419 to ld if workaround enabled

[Ard Biesheuvel]

On 22 August 2016 at 15:48, Will Deacon <will.deacon at arm.com> wrote:
> Cortex-A53 erratum 843419 is worked around by the linker, although it is
> a configure-time option to GCC as to whether ld is actually asked to
> apply the workaround or not.
>
> This patch ensures that we pass --fix-cortex-a53-843419 to the linker
> when both CONFIG_ARM64_ERRATUM_843419=y and the linker supports the
> option.
>
> Signed-off-by: Will Deacon <will.deacon at arm.com>

Acked-by: Ard Biesheuvel <ard.biesheuvel at linaro.org>

> ---
>  arch/arm64/Kconfig  | 15 +++++----------
>  arch/arm64/Makefile |  9 +++++++++
>  2 files changed, 14 insertions(+), 10 deletions(-)
>
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index bc3f00f586f1..e4b7d10e8e1c 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -415,18 +415,13 @@ config ARM64_ERRATUM_845719
>
>  config ARM64_ERRATUM_843419
>         bool "Cortex-A53: 843419: A load or store might access an incorrect address"
> -       depends on MODULES
>         default y
> -       select ARM64_MODULE_CMODEL_LARGE
> +       select ARM64_MODULE_CMODEL_LARGE if MODULES
>         help
> -         This option builds kernel modules using the large memory model in
> -         order to avoid the use of the ADRP instruction, which can cause
> -         a subsequent memory access to use an incorrect address on Cortex-A53
> -         parts up to r0p4.
> -
> -         Note that the kernel itself must be linked with a version of ld
> -         which fixes potentially affected ADRP instructions through the
> -         use of veneers.
> +         This option links the kernel with '--fix-cortex-a53-843419' and
> +         builds modules using the large memory model in order to avoid the use
> +         of the ADRP instruction, which can cause a subsequent memory access
> +         to use an incorrect address on Cortex-A53 parts up to r0p4.
>
>           If unsure, say Y.
>
> diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
> index 5b54f8c021d8..c5ad4957e7ee 100644
> --- a/arch/arm64/Makefile
> +++ b/arch/arm64/Makefile
> @@ -18,6 +18,15 @@ ifneq ($(CONFIG_RELOCATABLE),)
>  LDFLAGS_vmlinux                += -pie -Bsymbolic
>  endif
>
> +ifeq ($(CONFIG_ARM64_ERRATUM_843419),y)
> +ld-843419-workaround := $(call ld-option, --fix-cortex-a53-843419)
> +  ifeq ($(ld-843419-workaround),)
> +$(warning ld does not support --fix-cortex-a53-843419; kernel may be susceptible to erratum)
> +  else
> +LDFLAGS_vmlinux        += --fix-cortex-a53-843419
> +  endif
> +endif
> +
>  KBUILD_DEFCONFIG := defconfig
>
>  # Check for binutils support for specific extensions
> --
> 2.1.4
>