target/arm: Forbid unprivileged mode for M Baseline

MSR handling is the only place where CONTROL.nPRIV is modified.
Signed-off-by: NJulia Suvorova <jusual@mail.ru>
Message-id: 20180705222622.17139-1-jusual@mail.ru
Reviewed-by: NPeter Maydell <peter.maydell@linaro.org>
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

target/arm/helper.c

@@ -10728,8 +10728,10 @@ void HELPER(v7m_msr)(CPUARMState *env, uint32_t maskreg, uint32_t val)
             write_v7m_control_spsel_for_secstate(env,
                                                  val & R_V7M_CONTROL_SPSEL_MASK,
                                                  M_REG_NS);
-            env->v7m.control[M_REG_NS] &= ~R_V7M_CONTROL_NPRIV_MASK;
-            env->v7m.control[M_REG_NS] |= val & R_V7M_CONTROL_NPRIV_MASK;
+            if (arm_feature(env, ARM_FEATURE_M_MAIN)) {
+                env->v7m.control[M_REG_NS] &= ~R_V7M_CONTROL_NPRIV_MASK;
+                env->v7m.control[M_REG_NS] |= val & R_V7M_CONTROL_NPRIV_MASK;
+            }
             return;
         case 0x98: /* SP_NS */
         {
@@ -10822,8 +10824,10 @@ void HELPER(v7m_msr)(CPUARMState *env, uint32_t maskreg, uint32_t val)
             !arm_v7m_is_handler_mode(env)) {
             write_v7m_control_spsel(env, (val & R_V7M_CONTROL_SPSEL_MASK) != 0);
         }
-        env->v7m.control[env->v7m.secure] &= ~R_V7M_CONTROL_NPRIV_MASK;
-        env->v7m.control[env->v7m.secure] |= val & R_V7M_CONTROL_NPRIV_MASK;
+        if (arm_feature(env, ARM_FEATURE_M_MAIN)) {
+            env->v7m.control[env->v7m.secure] &= ~R_V7M_CONTROL_NPRIV_MASK;
+            env->v7m.control[env->v7m.secure] |= val & R_V7M_CONTROL_NPRIV_MASK;
+        }
         break;
     default:
     bad_reg: