1 files changed, 9 insertions, 0 deletions
diff --git a/target/nios2/op_helper.c b/target/nios2/op_helper.c
index 08ed3b4598..49fccf2c2c 100644
--- a/target/nios2/op_helper.c
+++ b/target/nios2/op_helper.c
@@ -34,6 +34,15 @@ void helper_raise_exception(CPUNios2State *env, uint32_t index)
 #ifndef CONFIG_USER_ONLY
 void helper_eret(CPUNios2State *env, uint32_t new_status, uint32_t new_pc)
 {
+    Nios2CPU *cpu = env_archcpu(env);
+
+    /*
+     * Both estatus and bstatus have no constraints on write;
+     * do not allow reserved fields in status to be set.
+     * TODO: more than this is required for shadow registers.
+     */
+    new_status &= cpu->cr_state[CR_STATUS].writable;
+
     env->ctrl[CR_STATUS] = new_status;
     env->pc = new_pc;
     cpu_loop_exit(env_cpu(env));