change behaviour on too large argument

Makefile

@@ -2,13 +2,17 @@
 ifneq ($(KERNELRELEASE),)
 # kbuild part of makefile
 obj-m   := hello1.o hello2.o
-ccflags-y := -I$(obj)/inc
+ccflags-y := -I$(obj)/inc -g
 else
 # normal makefile
 KDIR ?= /lib/modules/`uname -r`/build
 
 default:
 	$(MAKE) -C $(KDIR) M=$$PWD
+	cp hello1.ko hello1.ko.unstripped
+	$(CROSS_COMPILE)strip -g hello1.ko
+
 clean:
 	$(MAKE) -C $(KDIR) M=$$PWD clean
+
 endif

hello1.c

@@ -45,8 +45,9 @@ struct TimingList {
 };
 
 static struct TimingList *tl_head;
+static unsigned int bug_generator;
 
-static struct TimingList* write_first_node(void)
+static struct TimingList *write_first_node(void)
 {
 	tl_head = kmalloc(sizeof(struct TimingList), GFP_KERNEL);
 	tl_head->next = NULL;
@@ -54,18 +55,22 @@ static struct TimingList* write_first_node(void)
 	return tl_head;
 }
 
-static struct TimingList* insert_next_node(struct TimingList *tail)
+static struct TimingList *insert_next_node(struct TimingList *tail)
 {
 	struct TimingList *new_tl_node = kmalloc(sizeof(struct TimingList),
 						GFP_KERNEL);
 
-	tail->next = new_tl_node;
-	new_tl_node->next = NULL;
+	if (bug_generator == 2) {
+		new_tl_node = NULL;
+	} else {
+		tail->next = new_tl_node;
+		new_tl_node->next = NULL;
+	}
 
 	return new_tl_node;
 }
 
-static struct TimingList* add_new_node(struct TimingList *tail)
+static struct TimingList *add_new_node(struct TimingList *tail)
 {
 	if (tail == NULL)
 		return write_first_node();
@@ -93,6 +98,7 @@ void destroy_list(void)
 		curr_tl = next_tl;
 	}
 }
+EXPORT_SYMBOL(destroy_list);
 
 static int __init hello_init(void)
 {
@@ -105,6 +111,8 @@ void print_hello(int msg_count)
 	struct TimingList *current_tail = tl_head;
 
 	for (i = 0; i < msg_count; i++) {
+		bug_generator = i;
+
 		current_tail = add_new_node(current_tail);
 
 		current_tail->t_before = ktime_get();
@@ -112,14 +120,13 @@ void print_hello(int msg_count)
 		current_tail->t_after = ktime_get();
 	}
 }
+EXPORT_SYMBOL(print_hello);
 
 static void __exit hello_exit(void)
 {
 	destroy_list();
 }
 
-EXPORT_SYMBOL(print_hello);
-EXPORT_SYMBOL(destroy_list);
 
 module_init(hello_init);
 module_exit(hello_exit);

hello2.c

@@ -44,14 +44,10 @@ static unsigned int msg_count = 1;
 
 static int __init hello_init(void)
 {
-	if (msg_count > 10) {
-		pr_err("Error: msg_count too large (%d > 10)\n", msg_count);
-		return -EINVAL;
-	}
+	BUG_ON(msg_count > 10);
 
-	if (msg_count == 0 || msg_count >= 5) {
+	if (msg_count == 0 || msg_count >= 5)
 		pr_warn("Warning: msg_count = %d (msg_count == 0 or 5 <= msg_count <= 10)\n", msg_count);
-	}
 
 	print_hello(msg_count);
 	return 0;

inc/hello1.h

@@ -1,2 +1,2 @@
-void print_hello(int);
+void print_hello(int msg_count);
 void destroy_list(void);