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From:   Mark Brown <broonie@kernel.org>
Date:   Wed, 22 Nov 2023 09:42:37 +0000
Subject: [PATCH v7 27/39] arm64: Add Kconfig for Guarded Control Stack
 (GCS)
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To:     Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>,
        Jonathan Corbet <corbet@lwn.net>,
        Andrew Morton <akpm@linux-foundation.org>,
        Marc Zyngier <maz@kernel.org>,
        Oliver Upton <oliver.upton@linux.dev>,
        James Morse <james.morse@arm.com>,
        Suzuki K Poulose <suzuki.poulose@arm.com>,
        Arnd Bergmann <arnd@arndb.de>, Oleg Nesterov <oleg@redhat.com>,
        Eric Biederman <ebiederm@xmission.com>,
        Kees Cook <keescook@chromium.org>,
        Shuah Khan <shuah@kernel.org>,
        "Rick P. Edgecombe" <rick.p.edgecombe@intel.com>,
        Deepak Gupta <debug@rivosinc.com>,
        Ard Biesheuvel <ardb@kernel.org>,
        Szabolcs Nagy <Szabolcs.Nagy@arm.com>
Cc:     "H.J. Lu" <hjl.tools@gmail.com>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        Florian Weimer <fweimer@redhat.com>,
        Christian Brauner <brauner@kernel.org>,
        Thiago Jung Bauermann <thiago.bauermann@linaro.org>,
        linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org,
        kvmarm@lists.linux.dev, linux-fsdevel@vger.kernel.org,
        linux-arch@vger.kernel.org, linux-mm@kvack.org,
        linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-riscv@lists.infradead.org, Mark Brown <broonie@kernel.org>
Precedence: bulk

Provide a Kconfig option allowing the user to select if GCS support is
built into the kernel.

Signed-off-by: Mark Brown <broonie@kernel.org>
---
 arch/arm64/Kconfig | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 7b071a00425d..05cffc0f5786 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -2078,6 +2078,26 @@ config ARM64_EPAN
 	  if the cpu does not implement the feature.
 endmenu # "ARMv8.7 architectural features"
 
+menu "v9.4 architectural features"
+
+config ARM64_GCS
+	bool "Enable support for Guarded Control Stack (GCS)"
+	default y
+	select ARCH_HAS_USER_SHADOW_STACK
+	select ARCH_USES_HIGH_VMA_FLAGS
+	help
+	  Guarded Control Stack (GCS) provides support for a separate
+	  stack with restricted access which contains only return
+	  addresses.  This can be used to harden against some attacks
+	  by comparing return address used by the program with what is
+	  stored in the GCS, and may also be used to efficiently obtain
+	  the call stack for applications such as profiling.
+
+	  The feature is detected at runtime, and will remain disabled
+	  if the system does not implement the feature.
+
+endmenu # "v9.4 architectural features"
+
 config ARM64_SVE
 	bool "ARM Scalable Vector Extension support"
 	default y

-- 
2.39.2