arm64: mte: Kconfig entry

Add Memory Tagging Extension support to the arm64 kbuild.
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Co-developed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>

arch/arm64/Kconfig

@@ -1664,6 +1664,39 @@ config ARCH_RANDOM
 	  provides a high bandwidth, cryptographically secure
 	  hardware random number generator.
 
+config ARM64_AS_HAS_MTE
+	# Initial support for MTE went in binutils 2.32.0, checked with
+	# ".arch armv8.5-a+memtag" below. However, this was incomplete
+	# as a late addition to the final architecture spec (LDGM/STGM)
+	# is only supported in the newer 2.32.x and 2.33 binutils
+	# versions, hence the extra "stgm" instruction check below.
+	def_bool $(as-instr,.arch armv8.5-a+memtag\nstgm xzr$(comma)[x0])
+
+config ARM64_MTE
+	bool "Memory Tagging Extension support"
+	default y
+	depends on ARM64_AS_HAS_MTE && ARM64_TAGGED_ADDR_ABI
+	select ARCH_USES_HIGH_VMA_FLAGS
+	help
+	  Memory Tagging (part of the ARMv8.5 Extensions) provides
+	  architectural support for run-time, always-on detection of
+	  various classes of memory error to aid with software debugging
+	  to eliminate vulnerabilities arising from memory-unsafe
+	  languages.
+
+	  This option enables the support for the Memory Tagging
+	  Extension at EL0 (i.e. for userspace).
+
+	  Selecting this option allows the feature to be detected at
+	  runtime. Any secondary CPU not implementing this feature will
+	  not be allowed a late bring-up.
+
+	  Userspace binaries that want to use this feature must
+	  explicitly opt in. The mechanism for the userspace is
+	  described in:
+
+	  Documentation/arm64/memory-tagging-extension.rst.
+
 endmenu
 
 config ARM64_SVE