[Linux内核驱动]ioctl

ioctl()命令

更多详细内容在我的github中

ioctl 是设备驱动程序中设备控制接口函数，一个字符设备驱动通常会实现设备打开、关闭、读、写等功能，在一些需要细分的情境下，如果需要扩展新的功能，通常以增设 ioctl() 命令的方式实现。

Linux建议以下面的格式定义ioctl()命令：

设备类型序列号方向数据尺寸8位8位2位13/14位

• 设别类型（type）：是一个幻数，可以是0-0xff中的任意值。内核中的ioctl-number.txt给出了已经被使用的幻数。
• 序列号（nr）：可以为任意 unsigned char 型数据，取值范围 0~255，如果定义了多个 ioctl 命令，通常从 0 开始编号递增

• 方向（dir）：数据传送的方向，可以为 _IOC_NONE、_IOC_READ、_IOC_WRITE、_IOC_READ

  _IOC_WRITE，分别指示了四种访问模式：无数据、读数据、写数据、读写数据

• 数据尺寸（size）：占据 13bit 或者 14bit（体系相关，arm 架构一般为 14 位），指定了 arg 的数据类型及长度

在内核中，我们可以使用下面几个宏来定义 ioctl 命令：

// 分别对应不同的访问模式
#define _IO(type,nr) _IOC(_IOC_NONE,(type),(nr),0)
#define _IOR(type,nr,size) _IOC(_IOC_READ,(type),(nr),\
 (_IOC_TYPECHECK(size)))
#define _IOW(type,nr,size) _IOC(_IOC_WRITE,(type),(nr),\
 (_IOC_TYPECHECK(size)))
#define _IOWR(type,nr,size) _IOC(_IOC_READ|_IOC_WRITE,(type),(nr),\
 (_IOC_TYPECHECK(size)))

在ioctl()函数的实现中，可以使用下面的宏对命令进行检查：

_IOC_TYPE(unsigned int cmd) // 获取幻数
_IOC_NR(unsigned int cmd) // 获取序列号
_IOC_DIR(unsigned int cmd) // 获取命令方向

代码

ioctl.c

/*
 * @Date: 2024-05-07 15:45:31
 * @author: lidonghang-02 [email protected]
 * @LastEditTime: 2024-05-29 16:21:05
 */
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/cdev.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <linux/sched.h>
#include <linux/device.h>

#include <linux/semaphore.h>
#include <linux/mutex.h>

#include "ioctl.h"

#define LOCK_USE 1

#define IOCTL_SIZE 0x1000

#define IOCTL_MAJOR 0
#define IOCTL_MINOT 0
#define IOCTL_NR_DEVS 1

static int ioctl_major = IOCTL_MAJOR;
static int ioctl_minor = IOCTL_MINOT;
static int ioctl_nr_devs = IOCTL_NR_DEVS;

struct ioctl_dev
{
 struct cdev cdev;
 struct device *class_dev;
 unsigned int len;
 unsigned char buf[IOCTL_SIZE];

 struct semaphore sema;
 struct mutex mutex;
};
static struct class *ioctl_cls;
static struct ioctl_dev *ioctl_devp;

static int ioctl_open_func(struct inode *inode, struct file *filp)
{
 struct ioctl_dev *dev = container_of(inode->i_cdev, struct ioctl_dev, cdev);
 filp->private_data = dev;
 printk(KERN_INFO "ioctl_open\n");
 return 0;
}

static int ioctl_release_func(struct inode *inode, struct file *filp)
{
 printk(KERN_INFO "ioctl_release\n");
 return 0;
}

static ssize_t ioctl_read_func(struct file *filp, char __user *buf, size_t count, loff_t *f_pos)
{
 struct ioctl_dev *dev = filp->private_data;
 int ret = 0;
 if (*f_pos >= dev->len)
 {
 ret = -ENOMEM;
 printk(KERN_INFO "read beyond end of device\n");
 goto out_err_1;
 }
 if (count > dev->len - *f_pos)
 count = dev->len - *f_pos;

#if (LOCK_USE == 0)
 if (down_interruptible(&dev->sema))
 return -ERESTARTSYS;
#endif
#if (LOCK_USE == 1)
 if (mutex_lock_interruptible(&dev->mutex))
 return -ERESTARTSYS;
#endif

 if (copy_to_user(buf, dev->buf + *f_pos, count))
 ret = -EFAULT;
 else
 {
 *f_pos += count;
 ret = count;
 }

#if (LOCK_USE == 0)
 up(&dev->sema);
#endif
#if (LOCK_USE == 1)
 mutex_unlock(&dev->mutex);
#endif

out_err_1:
 return ret;
}

static ssize_t ioctl_write_func(struct file *filp, const char __user *buf, size_t count, loff_t *f_pos)
{
 struct ioctl_dev *dev = filp->private_data;
 int ret = 0;

 if (*f_pos >= dev->len)
 {
 printk(KERN_INFO "write beyond end of device\n");
 ret = -ENOMEM;
 goto out_err_1;
 }
 if (count > dev->len - *f_pos)
 count = dev->len - *f_pos;

#if (LOCK_USE == 0)
 if (down_interruptible(&dev->sema))
 return -ERESTARTSYS;
#endif
#if (LOCK_USE == 1)
 if (mutex_lock_interruptible(&dev->mutex))
 return -ERESTARTSYS;
#endif

 if (copy_from_user(dev->buf + *f_pos, buf, count))
 ret = -EFAULT;
 else
 {
 *f_pos += count;
 ret = count;
 }

#if (LOCK_USE == 0)
 up(&dev->sema);
#endif
#if (LOCK_USE == 1)
 mutex_unlock(&dev->mutex);

#endif

out_err_1:
 return ret;
}

static long ioctl_ioctl_func(struct file *filp, unsigned int cmd, unsigned long arg)
{
 struct ioctl_dev *dev = filp->private_data;
 int ret = 0;
 unsigned int tmp = 0;

 // 检查幻数(返回值POSIX标准规定，也用-EINVAL)
 if (_IOC_TYPE(cmd) != IOCTL_CHR_MAGIC)
 return -ENOTTY;
 // 检查命令编号
 if (_IOC_NR(cmd) > IOCTL_MAXNR)
 return -ENOTTY;
 // 检查命令方向，并验证用户空间指针的访问权限。
 if (_IOC_DIR(cmd) & _IOC_READ)
 ret = !access_ok(VERIFY_WRITE, (void __user *)arg, _IOC_SIZE(cmd));
 else if (_IOC_DIR(cmd) & _IOC_WRITE)
 ret = !access_ok(VERIFY_READ, (void __user *)arg, _IOC_SIZE(cmd));

 if (ret)
 return -EFAULT;

 switch (cmd)
 {
 case IOCTL_CLEAN:
 memset(dev->buf, 0, dev->len);
 printk(KERN_INFO "clean ioctl_dev\n");
 break;
 case IOCTL_GET_LEN:
 if (put_user(dev->len, (unsigned int __user *)arg))
 ret = -EFAULT;
 printk(KERN_INFO "get ioctl_dev len %u\n", dev->len);
 break;
 case IOCTL_SET_LEN:
 if (!capable(CAP_SYS_ADMIN))
 return -EPERM;
 if (get_user(tmp, (unsigned int __user *)arg))
 {
 printk(KERN_INFO "get_user failed\n");
 ret = -EFAULT;
 }
 else
 {
 if (tmp > IOCTL_SIZE)
 tmp = IOCTL_SIZE;
 dev->len = tmp;
 }
 printk(KERN_INFO "set ioctl_dev len to %u\n", dev->len);
 break;
 default:
 return -ENOTTY;
 }

 return ret;
}

struct file_operations ioctl_fops = {
 .owner = THIS_MODULE,
 .open = ioctl_open_func,
 .release = ioctl_release_func,
 .read = ioctl_read_func,
 .write = ioctl_write_func,
 .unlocked_ioctl = ioctl_ioctl_func,
};

static int __init ioctl_init_module(void)
{
 int ret = 0;
 dev_t devno = MKDEV(ioctl_major, 0);
 int i;

 // 注册设备号
 if (ioctl_major)
 ret = register_chrdev_region(devno, ioctl_nr_devs, "ioctl");
 else
 {
 ret = alloc_chrdev_region(&devno, 0, ioctl_nr_devs, "ioctl");
 ioctl_major = MAJOR(devno);
 }

 if (ret < 0)
 return ret;

 ioctl_devp = kzalloc(sizeof(struct ioctl_dev) * ioctl_nr_devs, GFP_KERNEL);
 if (!ioctl_devp)
 {
 printk(KERN_WARNING "alloc mem failed");
 ret = -ENOMEM;
 goto out_err_1;
 }
 // 创建一个类
 ioctl_cls = class_create(THIS_MODULE, "ioctl");
 if (IS_ERR(ioctl_cls))
 {
 printk(KERN_WARNING "Error creating class for ioctl");
 goto out_err_2;
 }

 for (i = 0; i < ioctl_nr_devs; i++)
 {
 cdev_init(&ioctl_devp[i].cdev, &ioctl_fops);
 ioctl_devp[i].cdev.owner = THIS_MODULE;
 ret = cdev_add(&ioctl_devp[i].cdev, MKDEV(ioctl_major, i), 1);
 if (ret)
 printk(KERN_WARNING "fail add hc_dev%d", i);
 else
 {
 ioctl_devp[i].len = 0;
 ioctl_devp[i].class_dev = device_create(ioctl_cls, NULL, MKDEV(ioctl_major, i), NULL, "ioctl%d", i);
 if (IS_ERR(ioctl_devp[i].class_dev))
 {
 printk(KERN_NOTICE "Error creating device for ioctl%d", i);
 }
 }
#if (LOCK_USE == 0)
 sema_init(&ioctl_devp[i].sema, 1); // 初始化信号量
#elif (LOCK_USE == 1)
 mutex_init(&ioctl_devp[i].mutex); // 初始化互斥量
#endif
 }

 printk(KERN_INFO "ioctl module init\n");
 return 0;
out_err_2:
 kfree(ioctl_devp);
out_err_1:
 unregister_chrdev_region(devno, ioctl_nr_devs);
 return ret;
}

static void __exit ioctl_exit_module(void)
{
 int i;
 for (i = 0; i < ioctl_nr_devs; i++)
 {
 device_destroy(ioctl_cls, MKDEV(ioctl_major, i));
 cdev_del(&ioctl_devp[i].cdev);
 }
 class_destroy(ioctl_cls);

 kfree(ioctl_devp);
 unregister_chrdev_region(MKDEV(ioctl_major, 0), ioctl_nr_devs);
 printk(KERN_INFO "ioctl module exit\n");
}

module_param(ioctl_major, int, S_IRUGO);
module_param(ioctl_minor, int, S_IRUGO);
module_param(ioctl_nr_devs, int, S_IRUGO);

module_init(ioctl_init_module);
module_exit(ioctl_exit_module);

MODULE_AUTHOR("lidonghang-02");
MODULE_LICENSE("GPL");

ioctl.h

#ifndef _IOCTL_CHR_H_
#define _IOCTL_CHR_H_

#define IOCTL_CHR_MAGIC 'c'

#define IOCTL_CLEAN _IO(IOCTL_CHR_MAGIC, 0)
#define IOCTL_GET_LEN _IOR(IOCTL_CHR_MAGIC, 1, unsigned int)
#define IOCTL_SET_LEN _IOW(IOCTL_CHR_MAGIC, 2, unsigned int)

#define IOCTL_MAXNR 2

#endif // _IOCTL_CHR_H_

test.c

/*
 * @Date: 2024-05-07 16:54:27
 * @author: lidonghang-02 [email protected]
 * @LastEditTime: 2024-05-19 19:54:51
 */
#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>
#include <sys/ioctl.h>
#include <errno.h>
#include "ioctl.h"
int main(int argc, char* argv[])
{
 unsigned int n;
 int fd;
 fd = open("/dev/ioctl0", O_RDWR);
 switch (argv[1][0])
 {
 case '0':
 ioctl(fd, IOCTL_CLEAN);
 printf("rclean mem\n");
 break;
 case '1':
 ioctl(fd, IOCTL_GET_LEN, &n);
 printf("get lens value = %u\n", n);
 break;
 case '2':
 n = atoi(argv[2]);
 ioctl(fd, IOCTL_SET_LEN, &n);
 printf("set lens value = %u\n", n);
 break;
 }
 close(fd);

 return 0;
}