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

[Jisheng Zhang]

On Mon, 22 Aug 2016 15:53:07 +0200 Ard Biesheuvel  wrote:

> On 22 August 2016 at 15:48, Will Deacon 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>

Thanks for this patch. I also suspected the errata isn't really work arounded
before and queried this in June ;)

http://lists.infradead.org/pipermail/linux-arm-kernel/2016-June/434057.html

Thanks,
Jisheng

> 
> > ---
> >  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
> >  
> 
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