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シンプルなキャラクタ型デバイスドライバ作成メモ

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前提

  • 実行後にログを出力するだけのデバイスドライバ
  • register_chrdevを使用(カーネル2.6系以降は推奨されないらしい)
  • Ubuntu 16.04、Windows/VMWare
  • Linux ubuntu 4.4.0-91-generic #114-Ubuntu SMP Tue Aug 8 11:56:56 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux
  • エラーハンドリングは無し

メモ

コード

simple_kernelmodule.c
#include <linux/module.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/fs.h>

#define NODE_NAME "kuredev"
#define SUCCESS 0

MODULE_LICENSE("Dual BSD/GPL");

static int major_num = 0;

static int kure_open(struct inode *inode, struct file *file){
        printk("kure_open\n");
        return SUCCESS;
}

static int kure_release(struct inode *inode, struct file *file){
        printk("kure_release\n");
        return SUCCESS;
}

static ssize_t kure_read(struct file *file, char __user *buf, size_t count, loff_t *f_pos){
        printk("kure_read\n");
        return count;
}

static ssize_t kure_write(struct file *file, char __user *buf, size_t count,loff_t *f_pos){
        printk("kure_write\n");
        return count;
}

struct file_operations kure_fops = {
        .owner = THIS_MODULE,
        .read = kure_read,
        .write = kure_write,
        .open = kure_open,
        .release = kure_release
};

static int kure_init(void){
        major_num = register_chrdev(major_num, NODE_NAME, &kure_fops);
        printk("kure_init\n");
        return SUCCESS;
}

static void kure_exit(void){
        unregister_chrdev(major_num, NODE_NAME);
        printk("kure_exit\n");
}

module_init(kure_init);
module_exit(kure_exit);
Makefile
KERNEL_DIR = /lib/modules/$(shell uname -r)/build
BUILD_DIR := $(shell pwd)
VERBOSE   := 0
obj-m := simple_kernelmodule.o
all:
        make -C $(KERNEL_DIR) SUBDIRS=$(BUILD_DIR) KBUILD_VERBOSE=$(VERBOSE) modules
clean:
        rm -rf  *.o *.ko *.mod.c *.symvers *.order .tmp_versions .helloworld.*

実行結果

# make
# insmod simple_kernelmodule.ko
# cat /proc/devices | grep kure
246 kuredev
# mknod -m 666 /dev/kuredev c 246 0
# echo 0 > /dev/kuredev
# rmmod simple_kernelmodule

実行結果(syslog)

Aug 13 05:14:01 ubuntu kernel: [ 9907.393185] kure_init ★insmod
Aug 13 05:15:11 ubuntu kernel: [ 9978.162543] kure_open ★echo 
Aug 13 05:15:11 ubuntu kernel: [ 9978.162552] kure_write
Aug 13 05:15:11 ubuntu kernel: [ 9978.162554] kure_release
Aug 13 05:15:35 ubuntu kernel: [10002.117217] kure_exit ★rmmod

参考

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