feat(brbe): add BRBE support for NS world
This patch enables access to the branch record buffer control registers
in non-secure EL2 and EL1 using the new build option ENABLE_BRBE_FOR_NS.
It is disabled for all secure world, and cannot be used with ENABLE_RME.
This option is disabled by default, however, the FVP platform makefile
enables it for FVP builds.
Signed-off-by: John Powell <john.powell@arm.com>
Change-Id: I576a49d446a8a73286ea6417c16bd0b8de71fca0
diff --git a/lib/extensions/brbe/brbe.c b/lib/extensions/brbe/brbe.c
new file mode 100644
index 0000000..6975b04
--- /dev/null
+++ b/lib/extensions/brbe/brbe.c
@@ -0,0 +1,35 @@
+/*
+ * Copyright (c) 2022, Arm Limited. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <arch.h>
+#include <arch_helpers.h>
+
+static bool brbe_supported(void)
+{
+ uint64_t features;
+
+ features = read_id_aa64dfr0_el1() >> ID_AA64DFR0_BRBE_SHIFT;
+ return ((features & ID_AA64DFR0_BRBE_MASK) ==
+ ID_AA64DFR0_BRBE_SUPPORTED);
+}
+
+void brbe_enable(void)
+{
+ uint64_t val;
+
+ if (brbe_supported()) {
+ /*
+ * MDCR_EL3.SBRBE = 0b01
+ *
+ * Allows BRBE usage in non-secure world and prohibited in
+ * secure world.
+ */
+ val = read_mdcr_el3();
+ val &= ~(MDCR_SBRBE_MASK << MDCR_SBRBE_SHIFT);
+ val |= (0x1UL << MDCR_SBRBE_SHIFT);
+ write_mdcr_el3(val);
+ }
+}