my work on lab1_2 is done.

kernel/machine/mtrap.c

@@ -31,8 +31,8 @@ void handle_mtrap() {
     case CAUSE_ILLEGAL_INSTRUCTION:
       // TODO (lab1_2): call handle_illegal_instruction to implement illegal instruction
       // interception, and finish lab1_2.
-      panic( "call handle_illegal_instruction to accomplish illegal instruction interception for lab1_2.\n" );
-
+      // panic( "call handle_illegal_instruction to accomplish illegal instruction interception for lab1_2.\n" );
+      handle_illegal_instruction();  // 调用非法指令处理函数
       break;
     case CAUSE_MISALIGNED_LOAD:
       handle_misaligned_load();