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Subject[PATCH v3 23/39] arm64: Enable armv8.5-a asm-arch option
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From: Vincenzo Frascino <vincenzo.frascino@arm.com>

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@arm.com>
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
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 e875db8e1c86..192544fcd1a5 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -1600,6 +1600,9 @@ 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
@@ -1676,6 +1679,7 @@ 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 130569f90c54..afcd61f7d2b0 100644
--- a/arch/arm64/Makefile
+++ b/arch/arm64/Makefile
@@ -94,6 +94,11 @@ 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)"'
--
2.28.0.681.g6f77f65b4e-goog
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