#include <linux/init.h>

#include <linux/module.h>

MODULE_LICENSE("Dual BSD/GPL");

static int hello_init(void)

{

        printk(KERN_ALERT "Hello world\n");

        return ;

}

static void hello_exit(void)

{

        printk(KERN_ALERT "goodbye,cruel world\n");

}

module_init(hello_init);

module_exit(hello_exit);

 obj-m := helloworld.o

 CURRENT_DIR :=$(shell pwd)

 KERNEL_DIR := /usr/src/linux-headers-$(shell uname -r)

 all:

         $(MAKE) -C $(KERNEL_DIR) M=$(CURRENT_DIR) modules

 clean:

         rm -rf %.o

 ryan@Ryan-pc:/data1/Ryan/demo/helloworld$ make

 make -C /usr/src/linux-headers-3.13.--generic  M=/data1/Ryan/demo/helloworld modules

 make[]: Entering directory `/usr/src/linux-headers-3.13.--generic'

   Building modules, stage .

   MODPOST  modules

 make[]: Leaving directory `/usr/src/linux-headers-3.13.--generic'

 ryan@Ryan-pc:/data1/Ryan/demo/helloworld$ sudo insmod helloworld.ko

 ryan@Ryan-pc:/data1/Ryan/demo/helloworld$ 

 ryan@Ryan-pc:/data1/Ryan/demo/helloworld$ dmesg

 [178401.813566] sr :::: [sr0] Device not ready

 [178401.813570] sr :::: [sr0]

 [178401.813571] Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE

 [178401.813572] sr :::: [sr0]

 [178401.813573] Sense Key : Not Ready [current]

 [178401.813575] sr :::: [sr0]

 [178401.813577] Add. Sense: Medium not present - tray closed

 [178401.813579] sr :::: [sr0] CDB:

 [178401.813580] Read():      2f

 [178401.813584] end_request: I/O error, dev sr0, sector

 [179614.794066] helloworld: module verification failed: signature and/or  required key missing - tainting kernel

 [179614.794552] Hello world

 [180458.268623] goodbye,cruel world

 [180514.941519] Hello world

 [180549.136795] goodbye,cruel world

 [181244.193514] Hello world

 ryan@Ryan-pc:/data1/Ryan/demo/helloworld$ sudo rmmod helloworld

 ryan@Ryan-pc:/data1/Ryan/demo/helloworld$