how to write your first linux device driver

 

0. environment

-ubuntu 1804 64bit

 

1. apt-get install linux-headers-$(uname -r)

 

 

2. code hello.c

#include 
     
      #include 
      
       MODULE_LICENSE("Dual BSD/GPL");static int hello_init(void){printk(KERN_ALERT "Hello, solidmango\n");return 0;}static void hello_exit(void){printk(KERN_ALERT "Goodbye, solidmango\n");}module_init(hello_init);module_exit(hello_exit);
      
     

 

3. Makefile

# If KERNELRELEASE is defined, we've been invoked from the# kernel build system and can use its language.ifneq ($(KERNELRELEASE),)obj-m := hello.o# Otherwise we were called directly from the command# line; invoke the kernel build system.elseKERNELDIR ?= /lib/modules/$(shell uname -r)/buildPWD := $(shell pwd)default:$(MAKE) -C $(KERNELDIR) M=$(PWD) modulesendif

 

4. sudo insmod hello.ko

 

5. sudo rmmod hello

 

6. view result

 

sm@ubuntu:~/dev$ cat /var/log/syslog|grep solidmangoSep 26 00:30:04 ubuntu kernel: [ 3041.143749] Hello, solidmangoSep 26 00:30:31 ubuntu kernel: [ 3068.192172] Goodbye, solidmango

 

7. sign your kernel module

/lib/modules/4.15.18/build/scripts/sign-file sha512 /lib/modules/4.15.18/build/certs/signing_key.pem /lib/modules/4.15.18/build/certs/signing_key.x509 hello.ko

 

signing_key.pem and signing_key.x509 files are generated when build the linux kernel

 

reference

https://wiki.gentoo.org/wiki/Signed_kernel_module_support#Enabling_module_signature_verification