세상 간단한 Kernel module 예시 (C Linux Kernel)

TL;DR §

• hello.c

#include <linux/init.h>
#include <linux/module.h>
#include <linux/kernel.h>
 
void print_hello(void) {
	printk(KERN_INFO "Hello, kernel!\n");
}
 
void print_goodbye(void) {
	printk(KERN_INFO "Goodbye, kernel!\n");
}
 
static int __init hello_init(void) {
	print_hello();
	return 0;
}
 
static void __exit hello_exit(void) {
	print_goodbye();
}
 
MODULE_LICENSE("GPL");
module_init(hello_init);
module_exit(hello_exit);

• Makefile

TARGET := hello
KERNELDIR := /lib/modules/$(shell uname -r)/build
PWD := $(shell pwd)

obj-m := $(TARGET).o

default:
	$(MAKE) -C $(KERNELDIR) M=$(PWD) modules
clean:
	$(MAKE) -C $(KERNELDIR) M=$(PWD) clean
start:
	sudo insmod ./$(TARGET).ko
stop:
	sudo rmmod $(TARGET)

• 빌드

make

• 적재

make start

• 확인

sudo journalctl -kn1

• 해제

make stop