--- kernel/system_call.s	2015-09-03 20:21:09.000000000 +0800
+++ kernel/system_call.s	2021-07-06 14:18:56.000000000 +0800
@@ -91,6 +91,11 @@
 	mov %dx,%es
 	movl $0x17,%edx		# fs points to local data space
 	mov %dx,%fs
+
+	pushl %eax   #by wyj
+	call print_nr
+	popl %eax
+
 	call sys_call_table(,%eax,4)
 	pushl %eax
 	movl current,%eax