target-arm: Implement MDCR_EL3.TDOSA and MDCR_EL2.TDOSA traps

Implement the traps to EL2 and EL3 controlled by the bits
MDCR_EL2.TDOSA MDCR_EL3.TDOSA. These can configurably trap
accesses to the "powerdown debug" registers.
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NSergey Fedorov <serge.fdrv@gmail.com>

target-arm/cpu.h

@@ -595,6 +595,18 @@ void pmccntr_sync(CPUARMState *env);
 #define CPTR_TTA      (1U << 20)
 #define CPTR_TFP      (1U << 10)
 
+#define MDCR_EPMAD    (1U << 21)
+#define MDCR_EDAD     (1U << 20)
+#define MDCR_SPME     (1U << 17)
+#define MDCR_SDD      (1U << 16)
+#define MDCR_TDRA     (1U << 11)
+#define MDCR_TDOSA    (1U << 10)
+#define MDCR_TDA      (1U << 9)
+#define MDCR_TDE      (1U << 8)
+#define MDCR_HPME     (1U << 7)
+#define MDCR_TPM      (1U << 6)
+#define MDCR_TPMCR    (1U << 5)
+
 #define CPSR_M (0x1fU)
 #define CPSR_T (1U << 5)
 #define CPSR_F (1U << 6)

target-arm/helper.c

@@ -385,6 +385,24 @@ static CPAccessResult access_trap_aa32s_el1(CPUARMState *env,
     return CP_ACCESS_TRAP_UNCATEGORIZED;
 }
 
+/* Check for traps to "powerdown debug" registers, which are controlled
+ * by MDCR.TDOSA
+ */
+static CPAccessResult access_tdosa(CPUARMState *env, const ARMCPRegInfo *ri,
+                                   bool isread)
+{
+    int el = arm_current_el(env);
+
+    if (el < 2 && (env->cp15.mdcr_el2 & MDCR_TDOSA)
+        && !arm_is_secure_below_el3(env)) {
+        return CP_ACCESS_TRAP_EL2;
+    }
+    if (el < 3 && (env->cp15.mdcr_el3 & MDCR_TDOSA)) {
+        return CP_ACCESS_TRAP_EL3;
+    }
+    return CP_ACCESS_OK;
+}
+
 static void dacr_write(CPUARMState *env, const ARMCPRegInfo *ri, uint64_t value)
 {
     ARMCPU *cpu = arm_env_get_cpu(env);
@@ -3778,15 +3796,18 @@ static const ARMCPRegInfo debug_cp_reginfo[] = {
     { .name = "OSLAR_EL1", .state = ARM_CP_STATE_BOTH,
       .cp = 14, .opc0 = 2, .opc1 = 0, .crn = 1, .crm = 0, .opc2 = 4,
       .access = PL1_W, .type = ARM_CP_NO_RAW,
+      .accessfn = access_tdosa,
       .writefn = oslar_write },
     { .name = "OSLSR_EL1", .state = ARM_CP_STATE_BOTH,
       .cp = 14, .opc0 = 2, .opc1 = 0, .crn = 1, .crm = 1, .opc2 = 4,
       .access = PL1_R, .resetvalue = 10,
+      .accessfn = access_tdosa,
       .fieldoffset = offsetof(CPUARMState, cp15.oslsr_el1) },
     /* Dummy OSDLR_EL1: 32-bit Linux will read this */
     { .name = "OSDLR_EL1", .state = ARM_CP_STATE_BOTH,
       .cp = 14, .opc0 = 2, .opc1 = 0, .crn = 1, .crm = 3, .opc2 = 4,
-      .access = PL1_RW, .type = ARM_CP_NOP },
+      .access = PL1_RW, .accessfn = access_tdosa,
+      .type = ARM_CP_NOP },
     /* Dummy DBGVCR: Linux wants to clear this on startup, but we don't
      * implement vector catch debug events yet.
      */