Linux's simplest kernel module Hello World example, linuxhello

Linux's simplest kernel module Hello World example, linuxhello

Note:If you want to follow this practice, you need an arm Development Board and a kernel of the corresponding version (If You Want To compile and run it on a Linux host, refer to the end of this ArticleAppendix 1)

1. Create the following file in the drivers directory of the kernel of the corresponding version:

Module file tree

The file code is as follows:
/*Hello. c*/

#include <linux/init.h>#include <linux/module.h>static int hello_init(void){    printk(KERN_INFO "[init] Can you feel me?\n");    return 0;}static void hello_exit(void){    printk(KERN_INFO "[exit] Yes.\n");}module_init(hello_init);module_exit(hello_exit);MODULE_AUTHOR("Alan Wang <alan@wrcode.com>");MODULE_LICENSE("GPL");MODULE_DESCRIPTION("A simple Hello World Module");MODULE_ALIAS("A simple module");

/*Kconfig*/

# drivers/alan_test/Kconfigmenu "ALAN_TEST Driver "comment "ALAN_TEST Driver comment"config ALAN_TEST    bool "ALAN_TEST support"config HELLO    tristate "hello module test"    depends on ALAN_TESTendmenu

/*Makefile*/

# drivers/alan_test/Makefile# makefile for the ALAN_TESTobj-$(CONFIG_HELLO)    += hello.o

2. Modify the Kconfig Makefie in the upper-level directory:

Under driversKconfigAdd a row before endmenu

source "drivers/alan_test/Kconfig"endmenu

Under driversMakefileAdd a line at the end

obj-$(CONFIG_ALAN_TEST)        += alan_test/

3. make menuconfig Add the newly written module to the kernel:

In sequence: Device Drivers -->
ALAN_TEST Driver -->
* ** ALAN_TEST Driver comment ***
[*] ALAN_TEST support
<M> hello module test

ExitSaveMenuconfig

4. Compile the kernel:

UseMakeCompile
GeneratedZImage(Arch/arm/boot/zImage) is written to the corresponding position of the Development Board.
GeneratedHello. koCopy (drivers/alan_test/hello. ko) to a directory in the Linux System of the Development Board.

5. Insert the kernel module:

Insmod

6. Use modinfo to view the module information:

Modinfo

Appendix 1: The compilation module runs on the PC

Put hello. c and Makefile in the same directory
/*Makefile*/

KERNEL_VER = $(shell uname -r)# kernel modulesobj-m += hello.o# specify flags for the module compilationEXTRA_CFLAGS = -g -O0build: kernel_moduleskernel_modules:    make -C /lib/modules/$(KERNEL_VER)/build M=$(CURDIR) modulesclean:    make -C /lib/modules/$(KERNEL_VER)/build M=$(CURDIR) clean

Compile and runThe steps are as follows:
Compile and run the hello module on the PC