feat(trbe): introduce trbe_disable() function
This patch adds trbe_disable() which disables Trace buffer access
from lower ELs in all security state. This function makes Secure
state the owner of Trace buffer and access from EL2/EL1 generate
trap exceptions to EL3.
Signed-off-by: Arvind Ram Prakash <arvind.ramprakash@arm.com>
Change-Id: If3e3bd621684b3c28f44c3ed2fe3df30b143f8cd
diff --git a/include/lib/extensions/trbe.h b/include/lib/extensions/trbe.h
index 5db3316..2c488e0 100644
--- a/include/lib/extensions/trbe.h
+++ b/include/lib/extensions/trbe.h
@@ -10,9 +10,13 @@
#include <context.h>
#if ENABLE_TRBE_FOR_NS
+void trbe_disable(cpu_context_t *ctx);
void trbe_enable(cpu_context_t *ctx);
void trbe_init_el2_unused(void);
#else
+static inline void trbe_disable(cpu_context_t *ctx)
+{
+}
static inline void trbe_enable(cpu_context_t *ctx)
{
}
diff --git a/lib/extensions/trbe/trbe.c b/lib/extensions/trbe/trbe.c
index 9157734..8c1c421 100644
--- a/lib/extensions/trbe/trbe.c
+++ b/lib/extensions/trbe/trbe.c
@@ -39,6 +39,25 @@
write_ctx_reg(state, CTX_MDCR_EL3, mdcr_el3_val);
}
+void trbe_disable(cpu_context_t *ctx)
+{
+ el3_state_t *state = get_el3state_ctx(ctx);
+ u_register_t mdcr_el3_val = read_ctx_reg(state, CTX_MDCR_EL3);
+
+ /*
+ * MDCR_EL3.NSTBE = 0b0
+ * Trace Buffer owning Security state is secure state. If FEAT_RME
+ * is not implemented, this field is RES0.
+ *
+ * MDCR_EL3.NSTB = 0b00
+ * Clear these bits to disable access of trace buffer control registers
+ * from lower ELs in any security state.
+ */
+ mdcr_el3_val &= ~(MDCR_NSTB(MDCR_NSTB_EL1));
+ mdcr_el3_val &= ~(MDCR_NSTBE_BIT);
+ write_ctx_reg(state, CTX_MDCR_EL3, mdcr_el3_val);
+}
+
void trbe_init_el2_unused(void)
{
/*