arm64/idreg: Add overrride for GCS

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>
Link: https://lore.kernel.org/r/20241001-arm64-gcs-v13-17-222b78d87eee@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 1518343bbe2237f1d577df5656339d6224b769be..c1b00f70973437c0575b7543df9be25eff4b4958 100644 (file)
--- 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 29d4b6244a6f630515a01ba13cd9c64b26187f07..2bb709d78405198708c7094f1ebd340af9d695b7 100644 (file)
--- 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 "