Hook up an override for GCS, allowing it to be disabled from the command
line by specifying arm64.nogcs in case there are problems.

Reviewed-by: Thiago Jung Bauermann <thiago.bauermann@linaro.org>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
---
 Documentation/admin-guide/kernel-parameters.txt | 3 +++
 arch/arm64/kernel/pi/idreg-override.c           | 2 ++
 2 files changed, 5 insertions(+)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 1518343bbe22..c1b00f709734 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -446,6 +446,9 @@
 	arm64.nobti	[ARM64] Unconditionally disable Branch Target
 			Identification support
 
+	arm64.nogcs	[ARM64] Unconditionally disable Guarded Control Stack
+			support
+
 	arm64.nomops	[ARM64] Unconditionally disable Memory Copy and Memory
 			Set instructions support
 
diff --git a/arch/arm64/kernel/pi/idreg-override.c b/arch/arm64/kernel/pi/idreg-override.c
index 29d4b6244a6f..2bb709d78405 100644
--- a/arch/arm64/kernel/pi/idreg-override.c
+++ b/arch/arm64/kernel/pi/idreg-override.c
@@ -133,6 +133,7 @@ static const struct ftr_set_desc pfr1 __prel64_initconst = {
 	.override	= &id_aa64pfr1_override,
 	.fields		= {
 		FIELD("bt", ID_AA64PFR1_EL1_BT_SHIFT, NULL ),
+		FIELD("gcs", ID_AA64PFR1_EL1_GCS_SHIFT, NULL),
 		FIELD("mte", ID_AA64PFR1_EL1_MTE_SHIFT, NULL),
 		FIELD("sme", ID_AA64PFR1_EL1_SME_SHIFT, pfr1_sme_filter),
 		{}
@@ -215,6 +216,7 @@ static const struct {
 	{ "arm64.nosve",		"id_aa64pfr0.sve=0" },
 	{ "arm64.nosme",		"id_aa64pfr1.sme=0" },
 	{ "arm64.nobti",		"id_aa64pfr1.bt=0" },
+	{ "arm64.nogcs",		"id_aa64pfr1.gcs=0" },
 	{ "arm64.nopauth",
 	  "id_aa64isar1.gpi=0 id_aa64isar1.gpa=0 "
 	  "id_aa64isar1.api=0 id_aa64isar1.apa=0 "

-- 
2.39.2