c - Linux 内核模块 - IOCTL 使用返回 ENOTTY

Question

我正在研究小内核模块。我正在尝试使用 IOCTL(在 ioctl_add 中)，但是当我调用它时我得到了 ENOTTY，这是在 main 底部的开关中检查的。代码如下。有谁知道我做错了什么吗？

用户.c:

#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/ioctl.h>
#include <linux/ioctl.h>
#include <sys/stat.h>
#include <sys/poll.h>
#include <fcntl.h>
#include <string.h>
#include <errno.h>

#define IOCTL_TYPE (100)
#define IOCTL_ADD (_IO(IOCTL_TYPE, 1))

void cleanup()
{
  if(f>=0) {
    close(f);
  }
}

int ioctl_add(int f)
{
    int ret;
    ret = ioctl(f, IOCTL_ADD);
    printf("Add \n");
    return ret;
}

int main(int argc, char * argv[])
{

        int fd;
        int *ptr;
        fd = open(argv[1], O_RDWR);

        if (fd < 0) {
                perror("error");
        }
        posix_memalign((void **)&ptr, 4096, 4096);
        * ptr = atoi(argv[2]); 
        write(fd, ptr, 4096);

        ioctl_add(fd);

        printf("data is %d\n", *ptr);  

        close(fd);

    switch(errno){
        case EBADF:
        printf("errno: EBADF \n");
        break;

        case EFAULT:
        printf("errno: EFAULT \n");
        break;

        case EINVAL:
        printf("errno: EINVAL \n");
        break;

        case ENOTTY:
        printf("errno: ENOTTY \n");
        break;

        default:
        printf("errno: none \n");

        return 0;
    }

    return 0;
}

模块.c:

#include <linux/kernel.h>  
#include <linux/module.h>
#include <linux/spinlock.h>
#include <linux/sched.h>

#include <linux/device.h>
#include <linux/fs.h>
#include <linux/cdev.h>
//#include <linux/mm.h>
//#include <linux/config.h>
#include <linux/ioport.h>
#include <linux/interrupt.h>
#include <linux/poll.h>
#include <asm/io.h>
#include <asm/bitops.h>

#include <linux/ioctl.h>
#define IOCTL_TYPE (100)
#define IOCTL_ADD (_IO(IOCTL_TYPE, 1))

#include <linux/mm.h>
#include <linux/pagemap.h>


#define DEVICE_NAME "acc_priv"
MODULE_LICENSE("GPL v2");

int ress, tmp;
struct  page *page;
int    *myaddr;

ssize_t acc_read(struct file *filp,
           char __user *buf, size_t count,loff_t * off)
{
  printk (KERN_ALERT "Opened\n\r");
  return 0; 
}  

ssize_t acc_write(struct file *filp,
            const char __user *buf, size_t count,loff_t * off)
{

  printk (KERN_ALERT "Write\n\r");

  printk(KERN_INFO "%s\n", __FUNCTION__);
  down_read(&current->mm->mmap_sem);
  ress = get_user_pages(current, current->mm,(unsigned long)buf,1,1,1,&page,NULL);
        if (ress) {
                printk(KERN_INFO "Got mmaped.\n");
                myaddr = kmap(page);
                printk(KERN_INFO "%d\n", *myaddr);

                tmp = *myaddr;   

                tmp = tmp * 2;
                printk(KERN_INFO "the result of multiplying: %d\n", tmp);

                * myaddr = tmp;
                page_cache_release(page);
        }
        up_read(&current->mm->mmap_sem);
        return (0);
}


static int acc_open(struct inode *inode,
              struct file *file)
{
  printk(KERN_INFO "Opened inode:%p, file:%p\n", inode, file);
  return 0;
}


long acc_ioctl(struct file *filp,
         unsigned int cmd,unsigned long arg)
{
      if(cmd == IOCTL_ADD)
        printk(KERN_INFO "Do specified job \n");

      return 0;
{

int acc_release(struct inode *inode,
          struct file *file)
{

  printk (KERN_INFO "device_release(%p,%p)\n", inode, file);

  return 0;
}

struct file_operations Fops = {
  .owner=THIS_MODULE,
  .read=acc_read, 
  .write=acc_write,
  .open=acc_open,
  .unlocked_ioctl=acc_ioctl,
  .release=acc_release, 
};

dev_t my_dev=0;
struct cdev * my_cdev = NULL;
static struct class *class_acc_priv = NULL;


void  clean_up(void)
{

  if(my_dev && class_acc_priv) {
    device_destroy(class_acc_priv,my_dev);
  }
  if(my_cdev) {
    cdev_del(my_cdev);
    my_cdev=NULL;
  }
  if(my_dev) {
    unregister_chrdev_region(my_dev, 1);
  }
  if(class_acc_priv) {
    class_destroy(class_acc_priv);
    class_acc_priv=NULL;
  }
}


int init_acc_priv(void)
{
  int res=0;
  res=alloc_chrdev_region(&my_dev, 0, 1, DEVICE_NAME);
  if(res) {
    printk (KERN_ALERT "Alocation of the device number for %s failed\n",
            DEVICE_NAME);
    return res;
  };

  class_acc_priv = class_create(THIS_MODULE, "acc_class");
  if (IS_ERR(class_acc_priv)) {
    printk(KERN_ERR "Error creating rs_class.\n");
    res=PTR_ERR(class_acc_priv);
    goto err1;
  }

  my_cdev = cdev_alloc( );
  my_cdev->ops = &Fops;
  my_cdev->owner = THIS_MODULE;
  res=cdev_add(my_cdev, my_dev, 1);
  if(res) {
    printk (KERN_ALERT "Registration of the device number for %s failed\n",
            DEVICE_NAME);
    res=-EFAULT;
    goto err1;
  };

  device_create(class_acc_priv,NULL,my_dev,NULL,"acc_priv%d",MINOR(my_dev));
  printk (KERN_ALERT "%s The major device number is %d.\n",
      "Registeration is a success.",
      MAJOR(my_dev));
  return res;
 err1:
  clean_up();
  return res;
}
module_init(init_acc_priv);


void cleanup_acc_priv( void )
{
  clean_up();
}
module_exit(cleanup_acc_priv);

Answer 1

当 32 位应用程序在 64 位操作系统上运行时，它使用 compat_ioctl 系统调用而不是 unlocked_ioctl 系统调用来执行 ioctl 命令。特殊系统调用的原因是 ioctl 参数的大小对于 64 位和 32 位应用程序可能不同。

所以需要实现.compat_ioctl文件操作。