[PATCH 22/23] target/arm: Implement MDCR_EL2.TDCC and MDCR_EL3.TDCC traps

[Peter Maydell]

FEAT_FGT also implements an extra trap bit in the MDCR_EL2 and
MDCR_EL3 registers: bit TDCC enables trapping of use of the Debug
Comms Channel registers OSDTRRX_EL1, OSDTRTX_EL1, MDCCSR_EL0,
MDCCINT_EL0, DBGDTR_EL0, DBGDTRRX_EL0 and DBGDTRTX_EL0 (and their
AArch32 equivalents).  This trapping is independent of whether
fine-grained traps are enabled or not.

Implement these extra traps.  (We don't implement DBGDTR_EL0,
DBGDTRRX_EL0 and DBGDTRTX_EL0.)

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 target/arm/debug_helper.c | 35 +++++++++++++++++++++++++++++++----
 1 file changed, 31 insertions(+), 4 deletions(-)

diff --git a/target/arm/debug_helper.c b/target/arm/debug_helper.c
index b106746b0e1..3c671c88c1a 100644
--- a/target/arm/debug_helper.c
+++ b/target/arm/debug_helper.c
@@ -599,6 +599,33 @@ static CPAccessResult access_tda(CPUARMState *env, const 
ARMCPRegInfo *ri,
     return CP_ACCESS_OK;
 }
 
+/*
+ * Check for traps to Debug Comms Channel registers. If FEAT_FGT
+ * is implemented then these are controlled by MDCR_EL2.TDCC for
+ * EL2 and MDCR_EL3.TDCC for EL3. They are also controlled by
+ * the general debug access trap bits MDCR_EL2.TDA and MDCR_EL3.TDA.
+ */
+static CPAccessResult access_tdcc(CPUARMState *env, const ARMCPRegInfo *ri,
+                                  bool isread)
+{
+    int el = arm_current_el(env);
+    uint64_t mdcr_el2 = arm_mdcr_el2_eff(env);
+    bool mdcr_el2_tda = (mdcr_el2 & MDCR_TDA) || (mdcr_el2 & MDCR_TDE) ||
+        (arm_hcr_el2_eff(env) & HCR_TGE);
+    bool mdcr_el2_tdcc = cpu_isar_feature(aa64_fgt, env_archcpu(env)) &&
+                                          (mdcr_el2 & MDCR_TDCC);
+    bool mdcr_el3_tdcc = cpu_isar_feature(aa64_fgt, env_archcpu(env)) &&
+                                          (env->cp15.mdcr_el3 & MDCR_TDCC);
+
+    if (el < 2 && (mdcr_el2_tda || mdcr_el2_tdcc)) {
+        return CP_ACCESS_TRAP_EL2;
+    }
+    if (el < 3 && ((env->cp15.mdcr_el3 & MDCR_TDA) || mdcr_el3_tdcc)) {
+        return CP_ACCESS_TRAP_EL3;
+    }
+    return CP_ACCESS_OK;
+}
+
 static void oslar_write(CPUARMState *env, const ARMCPRegInfo *ri,
                         uint64_t value)
 {
@@ -681,7 +708,7 @@ static const ARMCPRegInfo debug_cp_reginfo[] = {
      */
     { .name = "MDCCSR_EL0", .state = ARM_CP_STATE_AA64,
       .opc0 = 2, .opc1 = 3, .crn = 0, .crm = 1, .opc2 = 0,
-      .access = PL0_R, .accessfn = access_tda,
+      .access = PL0_R, .accessfn = access_tdcc,
       .type = ARM_CP_CONST, .resetvalue = 0 },
     /*
      * OSDTRRX_EL1/OSDTRTX_EL1 are used for save and restore of DBGDTRRX_EL0.
@@ -689,11 +716,11 @@ static const ARMCPRegInfo debug_cp_reginfo[] = {
      */
     { .name = "OSDTRRX_EL1", .state = ARM_CP_STATE_BOTH, .cp = 14,
       .opc0 = 2, .opc1 = 0, .crn = 0, .crm = 0, .opc2 = 2,
-      .access = PL1_RW, .accessfn = access_tda,
+      .access = PL1_RW, .accessfn = access_tdcc,
       .type = ARM_CP_CONST, .resetvalue = 0 },
     { .name = "OSDTRTX_EL1", .state = ARM_CP_STATE_BOTH, .cp = 14,
       .opc0 = 2, .opc1 = 0, .crn = 0, .crm = 3, .opc2 = 2,
-      .access = PL1_RW, .accessfn = access_tda,
+      .access = PL1_RW, .accessfn = access_tdcc,
       .type = ARM_CP_CONST, .resetvalue = 0 },
     /*
      * OSECCR_EL1 provides a mechanism for an operating system
@@ -757,7 +784,7 @@ static const ARMCPRegInfo debug_cp_reginfo[] = {
      */
     { .name = "MDCCINT_EL1", .state = ARM_CP_STATE_BOTH,
       .cp = 14, .opc0 = 2, .opc1 = 0, .crn = 0, .crm = 2, .opc2 = 0,
-      .access = PL1_RW, .accessfn = access_tda,
+      .access = PL1_RW, .accessfn = access_tdcc,
       .type = ARM_CP_NOP },
     /*
      * Dummy DBGCLAIM registers.
-- 
2.34.1