feat(gcs): support guarded control stack
Arm v9.4 introduces support for Guarded Control Stack, providing
mitigations against some forms of RPO attacks and an efficient mechanism
for obtaining the current call stack without requiring a full stack
unwind. Enable access to this feature for EL2 and below, context
switching the newly added EL2 registers as appropriate.
Change the FVP platform to default to handling this as a dynamic option
so the right decision can be made by the code at runtime.
Signed-off-by: Mark Brown <broonie@kernel.org>
Change-Id: I691aa7c22e3547bb3abe98d96993baf18c5f0e7b
diff --git a/include/arch/aarch64/arch_features.h b/include/arch/aarch64/arch_features.h
index 840b117..16f4fb9 100644
--- a/include/arch/aarch64/arch_features.h
+++ b/include/arch/aarch64/arch_features.h
@@ -316,6 +316,24 @@
return is_feat_s1pie_supported() || is_feat_s2pie_supported();
}
+static unsigned int read_feat_gcs_id_field(void)
+{
+ return ISOLATE_FIELD(read_id_aa64pfr1_el1(), ID_AA64PFR1_EL1_GCS);
+}
+
+static inline bool is_feat_gcs_supported(void)
+{
+ if (ENABLE_FEAT_GCS == FEAT_STATE_DISABLED) {
+ return false;
+ }
+
+ if (ENABLE_FEAT_GCS == FEAT_STATE_ALWAYS) {
+ return true;
+ }
+
+ return read_feat_gcs_id_field() != 0U;
+}
+
/*******************************************************************************
* Functions to identify the presence of the Activity Monitors Extension
******************************************************************************/