arm64: enable armv8.5-a asm-arch option

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.

Link: https://lkml.kernel.org/r/d03d1157124ea3532eaeb77507988733f5734986.1606161801.git.andreyknvl@google.com
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Alexander Potapenko <glider@google.com>
Tested-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Branislav Rankov <Branislav.Rankov@arm.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Kevin Brodsky <kevin.brodsky@arm.com>
Cc: Marco Elver <elver@google.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 81463eb..69f968a 100644 (file)
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -1571,6 +1571,9 @@ 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
@@ -1645,6 +1648,7 @@ 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 6a87d59..05f46a6 100644 (file)
--- a/arch/arm64/Makefile
+++ b/arch/arm64/Makefile
@@ -96,6 +96,11 @@ 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)"'