Enable MTE support unilaterally for Normal World

This patch enables MTE for Normal world if the CPU suppors it. Enabling
MTE for secure world will be done later.

Change-Id: I9ef64460beaba15e9a9c20ab02da4fb2208b6f7d
Signed-off-by: Soby Mathew <soby.mathew@arm.com>

include/arch/aarch64/arch.h

@@ -219,6 +219,13 @@
 
 #define BTI_IMPLEMENTED		ULL(1)	/* The BTI mechanism is implemented */
 
+#define ID_AA64PFR1_EL1_MTE_SHIFT	U(8)
+#define ID_AA64PFR1_EL1_MTE_MASK	ULL(0xf)
+
+#define MTE_UNIMPLEMENTED	ULL(0)
+#define MTE_IMPLEMENTED_EL0	ULL(1)	/* MTE is only implemented at EL0 */
+#define MTE_IMPLEMENTED_ELX	ULL(2)	/* MTE is implemented at all ELs */
+
 /* ID_PFR1_EL1 definitions */
 #define ID_PFR1_VIRTEXT_SHIFT	U(12)
 #define ID_PFR1_VIRTEXT_MASK	U(0xf)
@@ -276,6 +283,7 @@
 
 /* SCR definitions */
 #define SCR_RES1_BITS		((U(1) << 4) | (U(1) << 5))
+#define SCR_ATA_BIT		(U(1) << 26)
 #define SCR_FIEN_BIT		(U(1) << 21)
 #define SCR_API_BIT		(U(1) << 17)
 #define SCR_APK_BIT		(U(1) << 16)

include/arch/aarch64/arch_features.h

@@ -54,4 +54,10 @@ static inline bool is_armv8_5_bti_present(void)
 		ID_AA64PFR1_EL1_BT_MASK) == BTI_IMPLEMENTED;
 }
 
+static inline unsigned int get_armv8_5_mte_support(void)
+{
+	return ((read_id_aa64pfr1_el1() >> ID_AA64PFR1_EL1_MTE_SHIFT) &
+		ID_AA64PFR1_EL1_MTE_MASK);
+}
+
 #endif /* ARCH_FEATURES_H */

lib/el3_runtime/aarch64/context_mgmt.c

@@ -12,6 +12,7 @@
 
 #include <arch.h>
 #include <arch_helpers.h>
+#include <arch_features.h>
 #include <bl31/interrupt_mgmt.h>
 #include <common/bl_common.h>
 #include <context.h>
@@ -136,6 +137,18 @@ void cm_setup_context(cpu_context_t *ctx, const entry_point_info_t *ep)
 		scr_el3 |= SCR_API_BIT | SCR_APK_BIT;
 #endif /* !CTX_INCLUDE_PAUTH_REGS */
 
+	unsigned int mte = get_armv8_5_mte_support();
+
+	/*
+	 * Enable MTE support unilaterally for normal world if the CPU supports
+	 * it.
+	 */
+	if (mte != MTE_UNIMPLEMENTED) {
+		if (security_state == NON_SECURE) {
+			scr_el3 |= SCR_ATA_BIT;
+		}
+	}
+
 #ifdef IMAGE_BL31
 	/*
 	 * SCR_EL3.IRQ, SCR_EL3.FIQ: Enable the physical FIQ and IRQ routing as