Re: [PATCH mm v10 24/42] arm64: Enable armv8.5-a asm-arch option

From: Alexander Potapenko
Date: Wed Nov 18 2020 - 10:48:28 EST


On Fri, Nov 13, 2020 at 11:17 PM Andrey Konovalov <andreyknvl@xxxxxxxxxx> wrote:
>
> From: Vincenzo Frascino <vincenzo.frascino@xxxxxxx>
>
> Hardware tag-based KASAN relies on Memory Tagging Extension (MTE) which
> is an armv8.5-a architecture extension.
>
> Enable the correct asm option when the compiler supports it in order to
> allow the usage of ALTERNATIVE()s with MTE instructions.
>
> Signed-off-by: Vincenzo Frascino <vincenzo.frascino@xxxxxxx>
> Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
> Reviewed-by: Catalin Marinas <catalin.marinas@xxxxxxx>
Reviewed-by: Alexander Potapenko <glider@xxxxxxxxxx>
> ---
> Change-Id: I172e15e4c189f073e4c14a10276b276092e76536
> ---
> arch/arm64/Kconfig | 4 ++++
> arch/arm64/Makefile | 5 +++++
> 2 files changed, 9 insertions(+)
>
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index c999da4f2bdd..b7d1f1a5705d 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -1591,6 +1591,9 @@ endmenu
>
> menu "ARMv8.5 architectural features"
>
> +config AS_HAS_ARMV8_5
> + def_bool $(cc-option,-Wa$(comma)-march=armv8.5-a)
> +
> config ARM64_BTI
> bool "Branch Target Identification support"
> default y
> @@ -1665,6 +1668,7 @@ config ARM64_MTE
> bool "Memory Tagging Extension support"
> default y
> depends on ARM64_AS_HAS_MTE && ARM64_TAGGED_ADDR_ABI
> + depends on AS_HAS_ARMV8_5
> select ARCH_USES_HIGH_VMA_FLAGS
> help
> Memory Tagging (part of the ARMv8.5 Extensions) provides
> diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
> index 5789c2d18d43..50ad9cbccb51 100644
> --- a/arch/arm64/Makefile
> +++ b/arch/arm64/Makefile
> @@ -100,6 +100,11 @@ ifeq ($(CONFIG_AS_HAS_ARMV8_4), y)
> asm-arch := armv8.4-a
> endif
>
> +ifeq ($(CONFIG_AS_HAS_ARMV8_5), y)
> +# make sure to pass the newest target architecture to -march.
> +asm-arch := armv8.5-a
> +endif
> +
> ifdef asm-arch
> KBUILD_CFLAGS += -Wa,-march=$(asm-arch) \
> -DARM64_ASM_ARCH='"$(asm-arch)"'
> --
> 2.29.2.299.gdc1121823c-goog
>


--
Alexander Potapenko
Software Engineer

Google Germany GmbH
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