高级字符驱动程序操作之ioctl（实践篇）

为了简单，我在“字符设备驱动程序（实践篇）”的基础上进行修改，来掩饰ioctl的用法。

 

1. scull.h 其中添加ioctl用到的命令

#ifndef _SCULL_H_#define _SCULL_H_#ifndef SCULL_MAJOR#define SCULL_MAJOR 0 /* dynamic major by default */#endif#ifndef SCULL_NR_DEVS#define SCULL_NR_DEVS 4 /* scull0 through scull3 */#endif#ifndef SCULL_QUANTUM#define SCULL_QUANTUM 4000#endif#ifndef SCULL_QSET#define SCULL_QSET 1000#endif/* * Representation of scull quantum sets. */struct scull_qset {void **data;struct scull_qset *next;};struct scull_dev {struct scull_qset *data; /* Pointer to first quantum set */int quantum; /* the current quantum size */int qset; /* the current array size */unsigned long size; /* amount of data stored here */unsigned int access_key; /* used by sculluid and scullpriv */struct semaphore sem; /* mutual exclusion semaphore */struct cdev cdev; /* Char device structure*/};/* * The different configurable parameters */extern int scull_major; /* main.c */extern int scull_nr_devs;extern int scull_quantum;extern int scull_qset;/* * Ioctl definitions *//* Use 'k' as magic number */#define SCULL_IOC_MAGIC 'k'/* Please use a different 8-bit number in your code */#define SCULL_IOCRESET _IO(SCULL_IOC_MAGIC, 0)/* * S means "Set" through a ptr, * G means "Get": reply by setting through a pointer * X means "eXchange": switch G and S atomically */#define SCULL_IOCSQUANTUM _IOW(SCULL_IOC_MAGIC, 1, int)#define SCULL_IOCSQSET _IOW(SCULL_IOC_MAGIC, 2, int)#define SCULL_IOCGQUANTUM _IOR(SCULL_IOC_MAGIC, 3, int)#define SCULL_IOCGQSET _IOR(SCULL_IOC_MAGIC, 4, int)#define SCULL_IOCXQUANTUM _IOWR(SCULL_IOC_MAGIC, 5, int)#define SCULL_IOCXQSET _IOWR(SCULL_IOC_MAGIC, 6, int)#define SCULL_IOC_MAXNR 6#endif /* _SCULL_H_ */

 

 

2. scull.c 添加ioctl函数，修改scull_fops

 

#include <linux/module.h>#include <linux/moduleparam.h>#include <linux/init.h>#include <linux/kernel.h>/* printk() */#include <linux/slab.h>/* kmalloc() */#include <linux/fs.h>/* everything... */#include <linux/errno.h>/* error codes */#include <linux/types.h>/* size_t */#include <linux/proc_fs.h>#include <linux/fcntl.h>/* O_ACCMODE */#include <linux/seq_file.h>#include <linux/cdev.h>#include <asm/system.h>/* cli(), *_flags */#include <asm/uaccess.h>/* copy_*_user */#include "scull.h"/* local definitions *//* * Our parameters which can be set at load time. */int scull_major = SCULL_MAJOR;int scull_minor = 0;int scull_nr_devs = SCULL_NR_DEVS;/* number of bare scull devices */int scull_quantum = SCULL_QUANTUM;int scull_qset = SCULL_QSET;module_param(scull_major, int, S_IRUGO);module_param(scull_minor, int, S_IRUGO);module_param(scull_nr_devs, int, S_IRUGO);module_param(scull_quantum, int, S_IRUGO);module_param(scull_qset, int, S_IRUGO);MODULE_AUTHOR("victorsummer");MODULE_LICENSE("Dual BSD/GPL");struct scull_dev *scull_devices;/* allocated in scull_init_module *//* * Empty out the scull device; must be called with the device * semaphore held. */int scull_trim(struct scull_dev *dev){struct scull_qset *next, *dptr;int qset = dev->qset; /* "dev" is not-null */int i;for (dptr = dev->data; dptr; dptr = next) { /* all the list items */if (dptr->data) {for (i = 0; i < qset; i++)kfree(dptr->data[i]);kfree(dptr->data);dptr->data = NULL;}next = dptr->next;kfree(dptr);}dev->size = 0;dev->quantum = scull_quantum;dev->qset = scull_qset;dev->data = NULL;return 0;}/* * Open and close */int scull_open(struct inode *inode, struct file *filp){struct scull_dev *dev; /* device information */dev = container_of(inode->i_cdev, struct scull_dev, cdev);filp->private_data = dev; /* for other methods *//* now trim to 0 the length of the device if open was write-only */if ( (filp->f_flags & O_ACCMODE) == O_WRONLY) {if (down_interruptible(&dev->sem))return -ERESTARTSYS;scull_trim(dev); /* ignore errors */up(&dev->sem);}return 0; /* success */}int scull_release(struct inode *inode, struct file *filp){return 0;}/* * Follow the list */struct scull_qset *scull_follow(struct scull_dev *dev, int n){struct scull_qset *qs = dev->data; /* Allocate first qset explicitly if need be */if (! qs) {qs = dev->data = kmalloc(sizeof(struct scull_qset), GFP_KERNEL);if (qs == NULL)return NULL; /* Never mind */memset(qs, 0, sizeof(struct scull_qset));}/* Then follow the list */while (n--) {if (!qs->next) {qs->next = kmalloc(sizeof(struct scull_qset), GFP_KERNEL);if (qs->next == NULL)return NULL; /* Never mind */memset(qs->next, 0, sizeof(struct scull_qset));}qs = qs->next;continue;}return qs;}/* * Data management: read and write */ssize_t scull_read(struct file *filp, char __user *buf, size_t count, loff_t *f_pos){struct scull_dev *dev = filp->private_data; struct scull_qset *dptr;/* the first listitem */int quantum = dev->quantum, qset = dev->qset;int itemsize = quantum * qset; /* how many bytes in the listitem */int item, s_pos, q_pos, rest;ssize_t retval = 0;if (down_interruptible(&dev->sem))return -ERESTARTSYS;if (*f_pos >= dev->size)goto out;if (*f_pos + count > dev->size)count = dev->size - *f_pos;/* find listitem, qset index, and offset in the quantum */item = (long)*f_pos / itemsize;rest = (long)*f_pos % itemsize;s_pos = rest / quantum; q_pos = rest % quantum;/* follow the list up to the right position (defined elsewhere) */dptr = scull_follow(dev, item);if (dptr == NULL || !dptr->data || ! dptr->data[s_pos])goto out; /* don't fill holes *//* read only up to the end of this quantum */if (count > quantum - q_pos)count = quantum - q_pos;if (copy_to_user(buf, dptr->data[s_pos] + q_pos, count)) {retval = -EFAULT;goto out;}*f_pos += count;retval = count; out:up(&dev->sem);return retval;}ssize_t scull_write(struct file *filp, const char __user *buf, size_t count, loff_t *f_pos){struct scull_dev *dev = filp->private_data;struct scull_qset *dptr;int quantum = dev->quantum, qset = dev->qset;int itemsize = quantum * qset;int item, s_pos, q_pos, rest;ssize_t retval = -ENOMEM; /* value used in "goto out" statements */if (down_interruptible(&dev->sem))return -ERESTARTSYS;/* find listitem, qset index and offset in the quantum */item = (long)*f_pos / itemsize;rest = (long)*f_pos % itemsize;s_pos = rest / quantum; q_pos = rest % quantum;/* follow the list up to the right position */dptr = scull_follow(dev, item);if (dptr == NULL)goto out;if (!dptr->data) {dptr->data = kmalloc(qset * sizeof(char *), GFP_KERNEL);if (!dptr->data)goto out;memset(dptr->data, 0, qset * sizeof(char *));}if (!dptr->data[s_pos]) {dptr->data[s_pos] = kmalloc(quantum, GFP_KERNEL);if (!dptr->data[s_pos])goto out;}/* write only up to the end of this quantum */if (count > quantum - q_pos)count = quantum - q_pos;if (copy_from_user(dptr->data[s_pos]+q_pos, buf, count)) {retval = -EFAULT;goto out;}*f_pos += count;retval = count; /* update the size */if (dev->size < *f_pos)dev->size = *f_pos; out:up(&dev->sem);return retval;}/* * The ioctl() implementation */int scull_ioctl(struct inode *inode, struct file *filp, unsigned int cmd, unsigned long arg){int err = 0, tmp;int retval = 0;if (_IOC_TYPE(cmd) != SCULL_IOC_MAGIC) return -ENOTTY;if (_IOC_NR(cmd) > SCULL_IOC_MAXNR) return -ENOTTY;// check memory before __put_user and __get_userif (_IOC_DIR(cmd) & _IOC_READ)err = !access_ok(VERIFY_WRITE, (void __user *)arg, _IOC_SIZE(cmd));else if (_IOC_DIR(cmd) & _IOC_WRITE)err = !access_ok(VERIFY_READ, (void __user *)arg, _IOC_SIZE(cmd));if (err) return -EFAULT;switch(cmd) { case SCULL_IOCRESET:scull_quantum = SCULL_QUANTUM;scull_qset = SCULL_QSET;break; case SCULL_IOCSQUANTUM: /* Set: arg points to the value */if (! capable (CAP_SYS_ADMIN))return -EPERM;retval = __get_user(scull_quantum, (int __user *)arg);break; case SCULL_IOCGQUANTUM: /* Get: arg is pointer to result */retval = __put_user(scull_quantum, (int __user *)arg);break; case SCULL_IOCXQUANTUM: /* eXchange: use arg as pointer */if (!capable(CAP_SYS_ADMIN))return -EPERM;tmp = scull_quantum;retval = __get_user(scull_quantum, (int __user *)arg);if (retval == 0)retval = __put_user(tmp, (int __user *)arg);break; case SCULL_IOCSQSET:if (! capable (CAP_SYS_ADMIN))return -EPERM;retval = __get_user(scull_qset, (int __user *)arg);break; case SCULL_IOCGQSET:retval = __put_user(scull_qset, (int __user *)arg);break; case SCULL_IOCXQSET:if (! capable (CAP_SYS_ADMIN))return -EPERM;tmp = scull_qset;retval = __get_user(scull_qset, (int __user *)arg);if (retval == 0)retval = put_user(tmp, (int __user *)arg);break; default: /* redundant, as cmd was checked against MAXNR */return -ENOTTY;}return retval;}struct file_operations scull_fops = {.owner = THIS_MODULE,.llseek = NULL,.read = scull_read,.write = scull_write,.ioctl = scull_ioctl,.open = scull_open,.release = scull_release,};/* * Finally, the module stuff *//* * The cleanup function is used to handle initialization failures as well. * Thefore, it must be careful to work correctly even if some of the items * have not been initialized */void scull_cleanup_module(void){int i;dev_t devno = MKDEV(scull_major, scull_minor);/* Get rid of our char dev entries */if (scull_devices) {for (i = 0; i < scull_nr_devs; i++) {scull_trim(scull_devices + i);cdev_del(&scull_devices[i].cdev);}kfree(scull_devices);}/* cleanup_module is never called if registering failed */unregister_chrdev_region(devno, scull_nr_devs);}/* * Set up the char_dev structure for this device. */static void scull_setup_cdev(struct scull_dev *dev, int index){int err, devno = MKDEV(scull_major, scull_minor + index); cdev_init(&dev->cdev, &scull_fops);dev->cdev.owner = THIS_MODULE;dev->cdev.ops = &scull_fops;err = cdev_add (&dev->cdev, devno, 1);/* Fail gracefully if need be */if (err)printk(KERN_NOTICE "Error %d adding scull%d", err, index);}int scull_init_module(void){int result, i;dev_t dev = 0;/* * Get a range of minor numbers to work with, asking for a dynamic * major unless directed otherwise at load time. */if (scull_major) {dev = MKDEV(scull_major, scull_minor);result = register_chrdev_region(dev, scull_nr_devs, "scull");} else {result = alloc_chrdev_region(&dev, scull_minor, scull_nr_devs,"scull");scull_major = MAJOR(dev);}if (result < 0) {printk(KERN_WARNING "scull: can't get major %d/n", scull_major);return result;} /* * allocate the devices -- we can't have them static, as the number * can be specified at load time */scull_devices = kmalloc(scull_nr_devs * sizeof(struct scull_dev), GFP_KERNEL);if (!scull_devices) {result = -ENOMEM;goto fail; /* Make this more graceful */}memset(scull_devices, 0, scull_nr_devs * sizeof(struct scull_dev)); /* Initialize each device. */for (i = 0; i < scull_nr_devs; i++) {scull_devices[i].quantum = scull_quantum;scull_devices[i].qset = scull_qset;init_MUTEX(&scull_devices[i].sem);scull_setup_cdev(&scull_devices[i], i);} /* At this point call the init function for any friend device */dev = MKDEV(scull_major, scull_minor + scull_nr_devs);return 0; /* succeed */ fail:scull_cleanup_module();return result;}module_init(scull_init_module);module_exit(scull_cleanup_module);

 

3. Makefile不变

 

KERNELDIR = /usr/src/linux-headers-2.6.31-14-genericPWD := $(shell pwd)obj-m := scull.o modules:$(MAKE) -C $(KERNELDIR) M=$(PWD) modul

 

 

4. make生成scull.ko

 

装载scull模块

sudo insmod scull.ko

查看主设备号 这里假设为251

cat /proc/devices

建立设备节点

sudo mknod /dev/scull0 c 251 0

sudo mknod /dev/scull1 c 251 1

sudo mknod /dev/scull2 c 251 2

sudo mknod /dev/scull3 c 251 3

更改权限

sudo chgrp staff /dev/scull[0-3]

sudo chmod 664 /dev/scull[0-3]

 

5. ioctl_test.c

 

#include <sys/ioctl.h>#include <fcntl.h>#include <stdlib.h>#include <stdio.h>#include "scull.h"int main(){int code = 0;int ioctl_fd = open("/dev/scull2", O_WRONLY);// test set quantumcode = 10;if(ioctl(ioctl_fd, SCULL_IOCSQUANTUM, &code) < 0) {printf("ioctl SCULL_IOCSQUANTUM error! /n"); exit(1);}// test get quantumcode = 0; if(ioctl(ioctl_fd, SCULL_IOCGQUANTUM, &code) < 0){printf("ioctl SCULL_IOCGQUANTUM error! /n");exit(1);}elseprintf("1. code should be 10, and actually code == %d /n", code);// test set and get quantumcode = 5;if(ioctl(ioctl_fd, SCULL_IOCXQUANTUM, &code) < 0){printf("ioctl SCULL_IOCXQUANTUM error! /n");exit(1);}elseprintf("2. code should be 10, and actually code == %d /n", code);if(ioctl(ioctl_fd, SCULL_IOCGQUANTUM, &code) < 0){printf("ioctl SCULL_IOCGQUANTUM error! /n");exit(1);}elseprintf("3. code should be 5, and actually code == %d /n", code);// test set qsetcode = 10;if(ioctl(ioctl_fd, SCULL_IOCSQSET, &code) < 0){printf("ioctl SCULL_IOCSQSET error! /n");exit(1);}// test get qsetcode = 0;if(ioctl(ioctl_fd, SCULL_IOCGQSET, &code) < 0){printf("ioctl SCULL_IOCGQSET error! /n");exit(1);}elseprintf("4. code should be 10, and actually code == %d /n", code);// test set and get qsetcode = 7;if(ioctl(ioctl_fd, SCULL_IOCXQSET, &code) < 0){printf("ioctl SCULL_IOCXQSET error! /n");exit(1);}else printf("5. code should be 10, and actually code == %d /n", code);if(ioctl(ioctl_fd, SCULL_IOCGQSET, &code) < 0){printf("ioctl SCULL_IOCGQSET error! /n");exit(1);}elseprintf("6. code should be 7, and actually code == %d /n", code);close(ioctl_fd); exit(0);}

 

6. 编译测试程序

gcc ioctl_test.c -o ioctl_test.o

 

开始测试啦

sudo ./ioctl_test.o

 

打印结果：

1. code should be 10, and actually code == 10
2. code should be 10, and actually code == 10
3. code should be 5, and actually code == 5
4. code should be 10, and actually code == 10
5. code should be 10, and actually code == 10
6. code should be 7, and actually code == 7