linux ioctl 应用程序,ioctl使用（驱动层和应用层）简介-优快云博客

在用户空间，ioctl系调用具有如下原型：

int ioctl(int fd, unsigned long cmd, ...);

这里的第三个参数，...在unix系统中一般代表可变参数，但是这里代表可选参数。

在驱动空间，ioctl方法的原型如下：

long (*unlocked_ioctl) (struct file *, unsigned int, unsigned long);

定义ioctl命令号码使用了4个字段，具体字段的操作宏方法定义在中。

type：幻数，这个字段有8位宽(_IO_TYPEBITS)

number：序数，这个字段也是8位宽(_IO_NRBITS)

direction：命令传输方向，这个字段是2位宽度(_IOC_DIRBITS)

size：所涉及用户数据大小，这个字段通常是14位(_IOC_SIZEBITS)

在中定义了构造命令编号的宏：

#d#define _IOC(dir,type,nr,size) \

(((dir) <

((type) <

((nr) <

((size) <

/* used to create numbers */

#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)))

/* used to decode ioctl numbers.. */

#define _IOC_DIR(nr) (((nr) >> _IOC_DIRSHIFT) & _IOC_DIRMASK)

#define _IOC_TYPE(nr) (((nr) >> _IOC_TYPESHIFT) & _IOC_TYPEMASK)

#define _IOC_NR(nr) (((nr) >> _IOC_NRSHIFT) & _IOC_NRMASK)

#define _IOC_SIZE(nr) (((nr) >> _IOC_SIZESHIFT) & _IOC_SIZEMASK)

在涉及用户空间和系统空间安全交换数据时，使用copy_from_user和copy_to_user函数，但是比较耗费资源。ioctl通常是传输小数据，可以通过其他更有效的方法来传递数据，因此需要通过函数access_ok验证地址的合法性，该函数在中声明：

int access_ok(int type, const void *addr, unsigned long size);

第一个参数应该是VERIFY_READ或VERIFY_WRITE，取决于要执行的动作是读取还是写入用户空间

第二个参数是一个用户空间地址

第三个参数是用户空间地址的大小

驱动ioctl代码：

* 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,

* T means "Tell" directly with the argument value

* G means "Get": reply by setting throught a pointer

* Q means "Query": response is on the return value

* x means "eXchange": switch G and S atomically

* H means "sHift" switch T and Q atmoically

#define SCULL_IOCSQUANTUM _IOW(SCULL_IOC_MAGIC, 1, int)

#define SCULL_IOCSQSET _IOW(SCULL_IOC_MAGIC, 2, int)

#define SCULL_IOCTQUANTUM _IO(SCULL_IOC_MAGIC, 3)

#define SCULL_IOCTQSET _IO(SCULL_IOC_MAGIC, 4)

#define SCULL_IOCGQUANTUM _IOR(SCULL_IOC_MAGIC, 5, int)

#define SCULL_IOCGQSET _IOR(SCULL_IOC_MAGIC, 6, int)

#define SCULL_IOCQQUANTUM _IO(SCULL_IOC_MAGIC, 7)

#define SCULL_IOCQQSET _IO(SCULL_IOC_MAGIC, 8)

#define SCULL_IOCXQUANTUM _IOWR(SCULL_IOC_MAGIC, 9, int)

#define SCULL_IOCXQSET _IOWR(SCULL_IOC_MAGIC, 10, int)

#define SCULL_IOCHQUANTUM _IO(SCULL_IOC_MAGIC, 11)

#define SCULL_IOCHQSET _IO(SCULL_IOC_MAGIC, 12)

#define SCULL_IOC_MAXNR 12

* The ioctl() implementation

long scull_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)

{

int err = 0, tmp;

int retval = 0;

* extract the type and number bitfields, and don't decode

* wrong cmds: return ENOTTY (inappropriate ioctl) before access_ok()

if (_IOC_TYPE(cmd) != SCULL_IOC_MAGIC) return -ENOTTY;

if (_IOC_NR(cmd) > SCULL_IOC_MAXNR) return -ENOTTY;

* the direct is bitmask, and VERIFY_WRITE catches R/W

* transfers. 'TYPE' is user-oriented, while

* access_ok is kernel-eriented, so the concept of "read" and

* "write" is reversed

if (_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 */

printk(KERN_NOTICE "ioctl switch SCULL_IOCSQUANTUM\n");

if (!capable(CAP_SYS_ADMIN)) {

return -EPERM;

}

retval = __get_user(scull_quantum, (int __user *)arg);

break;

case SCULL_IOCTQUANTUM: /* Tell: arg is the value */

printk(KERN_NOTICE "ioctl switch SCULL_IOCTQUANTUM\n");

if (!capable(CAP_SYS_ADMIN)) {

return -EPERM;

}

scull_quantum = arg;

break;

case SCULL_IOCGQUANTUM: /* Get: arg is point to result */

if (!capable(CAP_SYS_ADMIN)) {

return -EPERM;

}

retval = __put_user(scull_quantum, (int __user *)arg);

break;

case SCULL_IOCQQUANTUM: /* Querry: return it (it's positive) */

return scull_quantum;

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_IOCHQUANTUM: /* sHift: like Tell + Query */

if (!capable(CAP_SYS_ADMIN)) {

return -EPERM;

}

tmp = scull_quantum;

scull_quantum = arg;

return tmp;

case SCULL_IOCSQSET:

if (!capable(CAP_SYS_ADMIN)) {

return -EPERM;

}

break;

case SCULL_IOCTQSET:

if (!capable(CAP_SYS_ADMIN)) {

return -EPERM;

}

scull_qset = arg;

break;

case SCULL_IOCGQSET:

retval = __put_user(scull_qset, (int __user *)arg);

break;

case SCULL_IOCQQSET:

return scull_qset;

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;

case SCULL_IOCHQSET:

if (!capable(CAP_SYS_ADMIN)) {

return -EPERM;

}

tmp = scull_qset;

scull_qset = arg;

return tmp;

default:

return -ENOTTY;

}

return retval;

}

struct file_operations scull_fops = {

.owner = THIS_MODULE,

.read = scull_read,

.write = scull_write,

.unlocked_ioctl = scull_ioctl,

.open = scull_open,

.release = scull_release,

};

应用程序ioctl测试代码：

/*************************************************************************

> File Name: scull_test.c

> Author: liangqi

> Mail: 715147009@qq.com

> Created Time: 2015年08月17日星期一 09时12分13秒

************************************************************************/

#include

/* Use 'k' as magic number */

#define SCULL_IOC_MAGIC 'k'

#define SCULL_IOCSQUANTUM _IOW(SCULL_IOC_MAGIC, 1, int)

#define SCULL_IOCSQSET _IOW(SCULL_IOC_MAGIC, 2, int)

#define SCULL_IOCTQUANTUM _IO(SCULL_IOC_MAGIC, 3)

#define SCULL_IOCTQSET _IO(SCULL_IOC_MAGIC, 4)

#define SCULL_IOCGQUANTUM _IOR(SCULL_IOC_MAGIC, 5, int)

#define SCULL_IOCGQSET _IOR(SCULL_IOC_MAGIC, 6, int)

#define SCULL_IOCQQUANTUM _IO(SCULL_IOC_MAGIC, 7)

#define SCULL_IOCQQSET _IO(SCULL_IOC_MAGIC, 8)

#define SCULL_IOCXQUANTUM _IOWR(SCULL_IOC_MAGIC, 9, int)

#define SCULL_IOCXQSET _IOWR(SCULL_IOC_MAGIC, 10, int)

#define SCULL_IOCHQUANTUM _IO(SCULL_IOC_MAGIC, 11)

#define SCULL_IOCHQSET _IO(SCULL_IOC_MAGIC, 12)

#define SCULL_IOC_MAXNR 12

char *deviceName = "/dev/scull0";

int deviceHandler = 0;

int scull_quantum = 4000;

int scull_qset = 1000;

int main(int argc, char **argv)

{

/* open scull device */

deviceHandler = open(deviceName, O_RDWR);

if (deviceHandler == -1) {

printf("can't open %s:", deviceName);

}

scull_quantum = 5000;

if(ioctl(deviceHandler, SCULL_IOCSQUANTUM, &scull_quantum) == -1) {

printf("ioctl SCULL_IOCSQUANTUM failed\n");

}

printf("ioctl SCULL_IOCQQUANTUM get scull_quantum = %d\n",

ioctl(deviceHandler, SCULL_IOCQQUANTUM));

scull_quantum = 6000;

if(ioctl(deviceHandler, SCULL_IOCTQUANTUM, scull_quantum) == -1) {

printf("ioctl SCULL_IOCTQUANTUM failed\n");

}

printf("ioctl SCULL_IOCQQUANTUM get scull_quantum = %d\n",

ioctl(deviceHandler, SCULL_IOCQQUANTUM));

}

makefile文件：

# # Comment/uncommnet the following line to disable/enable debugging

# DEBUG = y

# Add your debugging flay (or not) to CFLAGS

ifeq ($(DEBUG),y)

DEBFLAGS = -O -g -DSCULL_DEBUG # "-O" is needed to expand inlines

else

DEBFLAGS = -O2

endif

ifneq ($(KERNELRELEASE),)

# call from kernel build system

scull-objs := main.o

obj-m := scull.o

else

KERNELDIR ?= /lib/modules/$(shell uname -r)/build

PWD := $(shell pwd)

.PHONY:all

all:scull_test modules

scull_test:scull_test.o

$(CC) $(CFLAGS) scull_test.o -o scull_test

modules:

$(MAKE) -C $(KERNELDIR) M=$(PWD) modules

endif

clean:

rm -rf *.o *~ core .depend .*.cmd *.ko *.mod.c .tmp_versions scull_test

运行结果：

# root@K2450:/home/liangqi/workspace/driver/scull# ./scull_test

ioctl SCULL_IOCQQUANTUM get scull_quantum = 5000

ioctl SCULL_IOCQQUANTUM get scull_quantum = 6000

root@K2450:/home/liangqi/workspace/driver/scull# dmesg | tail

[185903.939965] ioctl switch SCULL_IOCSQUANTUM

[185903.940068] ioctl switch SCULL_IOCTQUANTUM