drivers/char/raw.c - linux - Git at Google

 /*
  * linux/drivers/char/raw.c
  *
  * Front-end raw character devices.  These can be bound to any block
  * devices to provide genuine Unix raw character device semantics.
  *
  * We reserve minor number 0 for a control interface.  ioctl()s on this
  * device are used to bind the other minor numbers to block devices.
  */

 #include <linux/init.h>
 #include <linux/fs.h>
 #include <linux/major.h>
 #include <linux/blkdev.h>
 #include <linux/module.h>
 #include <linux/raw.h>
 #include <linux/capability.h>
 #include <linux/uio.h>
 #include <linux/cdev.h>
 #include <linux/device.h>
 #include <linux/mutex.h>
 #include <linux/smp_lock.h>

 #include <asm/uaccess.h>

 struct raw_device_data {
 	struct block_device *binding;
 	int inuse;
 };

 static struct class *raw_class;
 static struct raw_device_data raw_devices[MAX_RAW_MINORS];
 static DEFINE_MUTEX(raw_mutex);
 static const struct file_operations raw_ctl_fops; /* forward declaration */

 /*
  * Open/close code for raw IO.
  *
  * We just rewrite the i_mapping for the /dev/raw/rawN file descriptor to
  * point at the blockdev's address_space and set the file handle to use
  * O_DIRECT.
  *
  * Set the device's soft blocksize to the minimum possible.  This gives the
  * finest possible alignment and has no adverse impact on performance.
  */
 static int raw_open(struct inode *inode, struct file *filp)
 {
 	const int minor = iminor(inode);
 	struct block_device *bdev;
 	int err;

 	if (minor == 0) {	/* It is the control device */
 		filp->f_op = &raw_ctl_fops;
 		return 0;
 	}

 	lock_kernel();
 	mutex_lock(&raw_mutex);

 	/*
 	 * All we need to do on open is check that the device is bound.
 	 */
 	bdev = raw_devices[minor].binding;
 	err = -ENODEV;
 	if (!bdev)
 		goto out;
 	igrab(bdev->bd_inode);
 	err = blkdev_get(bdev, filp->f_mode);
 	if (err)
 		goto out;
 	err = bd_claim(bdev, raw_open);
 	if (err)
 		goto out1;
 	err = set_blocksize(bdev, bdev_logical_block_size(bdev));
 	if (err)
 		goto out2;
 	filp->f_flags |= O_DIRECT;
 	filp->f_mapping = bdev->bd_inode->i_mapping;
 	if (++raw_devices[minor].inuse == 1)
 		filp->f_path.dentry->d_inode->i_mapping =
 			bdev->bd_inode->i_mapping;
 	filp->private_data = bdev;
 	mutex_unlock(&raw_mutex);
 	unlock_kernel();
 	return 0;

 out2:
 	bd_release(bdev);
 out1:
 	blkdev_put(bdev, filp->f_mode);
 out:
 	mutex_unlock(&raw_mutex);
 	unlock_kernel();
 	return err;
 }

 /*
  * When the final fd which refers to this character-special node is closed, we
  * make its ->mapping point back at its own i_data.
  */
 static int raw_release(struct inode *inode, struct file *filp)
 {
 	const int minor= iminor(inode);
 	struct block_device *bdev;

 	mutex_lock(&raw_mutex);
 	bdev = raw_devices[minor].binding;
 	if (--raw_devices[minor].inuse == 0) {
 		/* Here  inode->i_mapping == bdev->bd_inode->i_mapping  */
 		inode->i_mapping = &inode->i_data;
 		inode->i_mapping->backing_dev_info = &default_backing_dev_info;
 	}
 	mutex_unlock(&raw_mutex);

 	bd_release(bdev);
 	blkdev_put(bdev, filp->f_mode);
 	return 0;
 }

 /*
  * Forward ioctls to the underlying block device.
  */
 static int
 raw_ioctl(struct inode *inode, struct file *filp,
 		  unsigned int command, unsigned long arg)
 {
 	struct block_device *bdev = filp->private_data;

 	return blkdev_ioctl(bdev, 0, command, arg);
 }

 static void bind_device(struct raw_config_request *rq)
 {
 	device_destroy(raw_class, MKDEV(RAW_MAJOR, rq->raw_minor));
 	device_create(raw_class, NULL, MKDEV(RAW_MAJOR, rq->raw_minor), NULL,
 		      "raw%d", rq->raw_minor);
 }

 /*
  * Deal with ioctls against the raw-device control interface, to bind
  * and unbind other raw devices.
  */
 static int raw_ctl_ioctl(struct inode *inode, struct file *filp,
 			unsigned int command, unsigned long arg)
 {
 	struct raw_config_request rq;
 	struct raw_device_data *rawdev;
 	int err = 0;

 	switch (command) {
 	case RAW_SETBIND:
 	case RAW_GETBIND:

 		/* First, find out which raw minor we want */

 		if (copy_from_user(&rq, (void __user *) arg, sizeof(rq))) {
 			err = -EFAULT;
 			goto out;
 		}

 		if (rq.raw_minor <= 0 || rq.raw_minor >= MAX_RAW_MINORS) {
 			err = -EINVAL;
 			goto out;
 		}
 		rawdev = &raw_devices[rq.raw_minor];

 		if (command == RAW_SETBIND) {
 			dev_t dev;

 			/*
 			 * This is like making block devices, so demand the
 			 * same capability
 			 */
 			if (!capable(CAP_SYS_ADMIN)) {
 				err = -EPERM;
 				goto out;
 			}

 			/*
 			 * For now, we don't need to check that the underlying
 			 * block device is present or not: we can do that when
 			 * the raw device is opened.  Just check that the
 			 * major/minor numbers make sense.
 			 */

 			dev = MKDEV(rq.block_major, rq.block_minor);
 			if ((rq.block_major == 0 && rq.block_minor != 0) ||
 					MAJOR(dev) != rq.block_major ||
 					MINOR(dev) != rq.block_minor) {
 				err = -EINVAL;
 				goto out;
 			}

 			mutex_lock(&raw_mutex);
 			if (rawdev->inuse) {
 				mutex_unlock(&raw_mutex);
 				err = -EBUSY;
 				goto out;
 			}
 			if (rawdev->binding) {
 				bdput(rawdev->binding);
 				module_put(THIS_MODULE);
 			}
 			if (rq.block_major == 0 && rq.block_minor == 0) {
 				/* unbind */
 				rawdev->binding = NULL;
 				device_destroy(raw_class,
 						MKDEV(RAW_MAJOR, rq.raw_minor));
 			} else {
 				rawdev->binding = bdget(dev);
 				if (rawdev->binding == NULL)
 					err = -ENOMEM;
 				else {
 					__module_get(THIS_MODULE);
 					bind_device(&rq);
 				}
 			}
 			mutex_unlock(&raw_mutex);
 		} else {
 			struct block_device *bdev;

 			mutex_lock(&raw_mutex);
 			bdev = rawdev->binding;
 			if (bdev) {
 				rq.block_major = MAJOR(bdev->bd_dev);
 				rq.block_minor = MINOR(bdev->bd_dev);
 			} else {
 				rq.block_major = rq.block_minor = 0;
 			}
 			mutex_unlock(&raw_mutex);
 			if (copy_to_user((void __user *)arg, &rq, sizeof(rq))) {
 				err = -EFAULT;
 				goto out;
 			}
 		}
 		break;
 	default:
 		err = -EINVAL;
 		break;
 	}
 out:
 	return err;
 }

 static const struct file_operations raw_fops = {
 	.read	=	do_sync_read,
 	.aio_read = 	generic_file_aio_read,
 	.write	=	do_sync_write,
 	.aio_write =	blkdev_aio_write,
 	.open	=	raw_open,
 	.release=	raw_release,
 	.ioctl	=	raw_ioctl,
 	.owner	=	THIS_MODULE,
 };

 static const struct file_operations raw_ctl_fops = {
 	.ioctl	=	raw_ctl_ioctl,
 	.open	=	raw_open,
 	.owner	=	THIS_MODULE,
 };

 static struct cdev raw_cdev;

 static char *raw_nodename(struct device *dev)
 {
 	return kasprintf(GFP_KERNEL, "raw/%s", dev_name(dev));
 }

 static int __init raw_init(void)
 {
 	dev_t dev = MKDEV(RAW_MAJOR, 0);
 	int ret;

 	ret = register_chrdev_region(dev, MAX_RAW_MINORS, "raw");
 	if (ret)
 		goto error;

 	cdev_init(&raw_cdev, &raw_fops);
 	ret = cdev_add(&raw_cdev, dev, MAX_RAW_MINORS);
 	if (ret) {
 		kobject_put(&raw_cdev.kobj);
 		goto error_region;
 	}

 	raw_class = class_create(THIS_MODULE, "raw");
 	if (IS_ERR(raw_class)) {
 		printk(KERN_ERR "Error creating raw class.\n");
 		cdev_del(&raw_cdev);
 		ret = PTR_ERR(raw_class);
 		goto error_region;
 	}
 	raw_class->nodename = raw_nodename;
 	device_create(raw_class, NULL, MKDEV(RAW_MAJOR, 0), NULL, "rawctl");

 	return 0;

 error_region:
 	unregister_chrdev_region(dev, MAX_RAW_MINORS);
 error:
 	return ret;
 }

 static void __exit raw_exit(void)
 {
 	device_destroy(raw_class, MKDEV(RAW_MAJOR, 0));
 	class_destroy(raw_class);
 	cdev_del(&raw_cdev);
 	unregister_chrdev_region(MKDEV(RAW_MAJOR, 0), MAX_RAW_MINORS);
 }

 module_init(raw_init);
 module_exit(raw_exit);
 MODULE_LICENSE("GPL");
	/*
	* linux/drivers/char/raw.c
	*
	* Front-end raw character devices. These can be bound to any block
	* devices to provide genuine Unix raw character device semantics.
	*
	* We reserve minor number 0 for a control interface. ioctl()s on this
	* device are used to bind the other minor numbers to block devices.
	*/

	#include <linux/init.h>
	#include <linux/fs.h>
	#include <linux/major.h>
	#include <linux/blkdev.h>
	#include <linux/module.h>
	#include <linux/raw.h>
	#include <linux/capability.h>
	#include <linux/uio.h>
	#include <linux/cdev.h>
	#include <linux/device.h>
	#include <linux/mutex.h>
	#include <linux/smp_lock.h>

	#include <asm/uaccess.h>

	struct raw_device_data {
	struct block_device *binding;
	int inuse;
	};

	static struct class *raw_class;
	static struct raw_device_data raw_devices[MAX_RAW_MINORS];
	static DEFINE_MUTEX(raw_mutex);
	static const struct file_operations raw_ctl_fops; /* forward declaration */

	/*
	* Open/close code for raw IO.
	*
	* We just rewrite the i_mapping for the /dev/raw/rawN file descriptor to
	* point at the blockdev's address_space and set the file handle to use
	* O_DIRECT.
	*
	* Set the device's soft blocksize to the minimum possible. This gives the
	* finest possible alignment and has no adverse impact on performance.
	*/
	static int raw_open(struct inode inode, struct file filp)
	{
	const int minor = iminor(inode);
	struct block_device *bdev;
	int err;

	if (minor == 0) { /* It is the control device */
	filp->f_op = &raw_ctl_fops;
	return 0;
	}

	lock_kernel();
	mutex_lock(&raw_mutex);

	/*
	* All we need to do on open is check that the device is bound.
	*/
	bdev = raw_devices[minor].binding;
	err = -ENODEV;
	if (!bdev)
	goto out;
	igrab(bdev->bd_inode);
	err = blkdev_get(bdev, filp->f_mode);
	if (err)
	goto out;
	err = bd_claim(bdev, raw_open);
	if (err)
	goto out1;
	err = set_blocksize(bdev, bdev_logical_block_size(bdev));
	if (err)
	goto out2;
	filp->f_flags \|= O_DIRECT;
	filp->f_mapping = bdev->bd_inode->i_mapping;
	if (++raw_devices[minor].inuse == 1)
	filp->f_path.dentry->d_inode->i_mapping =
	bdev->bd_inode->i_mapping;
	filp->private_data = bdev;
	mutex_unlock(&raw_mutex);
	unlock_kernel();
	return 0;

	out2:
	bd_release(bdev);
	out1:
	blkdev_put(bdev, filp->f_mode);
	out:
	mutex_unlock(&raw_mutex);
	unlock_kernel();
	return err;
	}

	/*
	* When the final fd which refers to this character-special node is closed, we
	* make its ->mapping point back at its own i_data.
	*/
	static int raw_release(struct inode inode, struct file filp)
	{
	const int minor= iminor(inode);
	struct block_device *bdev;

	mutex_lock(&raw_mutex);
	bdev = raw_devices[minor].binding;
	if (--raw_devices[minor].inuse == 0) {
	/* Here inode->i_mapping == bdev->bd_inode->i_mapping */
	inode->i_mapping = &inode->i_data;
	inode->i_mapping->backing_dev_info = &default_backing_dev_info;
	}
	mutex_unlock(&raw_mutex);

	bd_release(bdev);
	blkdev_put(bdev, filp->f_mode);
	return 0;
	}

	/*
	* Forward ioctls to the underlying block device.
	*/
	static int
	raw_ioctl(struct inode inode, struct file filp,
	unsigned int command, unsigned long arg)
	{
	struct block_device *bdev = filp->private_data;

	return blkdev_ioctl(bdev, 0, command, arg);
	}

	static void bind_device(struct raw_config_request *rq)
	{
	device_destroy(raw_class, MKDEV(RAW_MAJOR, rq->raw_minor));
	device_create(raw_class, NULL, MKDEV(RAW_MAJOR, rq->raw_minor), NULL,
	"raw%d", rq->raw_minor);
	}

	/*
	* Deal with ioctls against the raw-device control interface, to bind
	* and unbind other raw devices.
	*/
	static int raw_ctl_ioctl(struct inode inode, struct file filp,
	unsigned int command, unsigned long arg)
	{
	struct raw_config_request rq;
	struct raw_device_data *rawdev;
	int err = 0;

	switch (command) {
	case RAW_SETBIND:
	case RAW_GETBIND:

	/* First, find out which raw minor we want */

	if (copy_from_user(&rq, (void __user *) arg, sizeof(rq))) {
	err = -EFAULT;
	goto out;
	}

	if (rq.raw_minor <= 0 \|\| rq.raw_minor >= MAX_RAW_MINORS) {
	err = -EINVAL;
	goto out;
	}
	rawdev = &raw_devices[rq.raw_minor];

	if (command == RAW_SETBIND) {
	dev_t dev;

	/*
	* This is like making block devices, so demand the
	* same capability
	*/
	if (!capable(CAP_SYS_ADMIN)) {
	err = -EPERM;
	goto out;
	}

	/*
	* For now, we don't need to check that the underlying
	* block device is present or not: we can do that when
	* the raw device is opened. Just check that the
	* major/minor numbers make sense.
	*/

	dev = MKDEV(rq.block_major, rq.block_minor);
	if ((rq.block_major == 0 && rq.block_minor != 0) \|\|
	MAJOR(dev) != rq.block_major \|\|
	MINOR(dev) != rq.block_minor) {
	err = -EINVAL;
	goto out;
	}

	mutex_lock(&raw_mutex);
	if (rawdev->inuse) {
	mutex_unlock(&raw_mutex);
	err = -EBUSY;
	goto out;
	}
	if (rawdev->binding) {
	bdput(rawdev->binding);
	module_put(THIS_MODULE);
	}
	if (rq.block_major == 0 && rq.block_minor == 0) {
	/* unbind */
	rawdev->binding = NULL;
	device_destroy(raw_class,
	MKDEV(RAW_MAJOR, rq.raw_minor));
	} else {
	rawdev->binding = bdget(dev);
	if (rawdev->binding == NULL)
	err = -ENOMEM;
	else {
	__module_get(THIS_MODULE);
	bind_device(&rq);
	}
	}
	mutex_unlock(&raw_mutex);
	} else {
	struct block_device *bdev;

	mutex_lock(&raw_mutex);
	bdev = rawdev->binding;
	if (bdev) {
	rq.block_major = MAJOR(bdev->bd_dev);
	rq.block_minor = MINOR(bdev->bd_dev);
	} else {
	rq.block_major = rq.block_minor = 0;
	}
	mutex_unlock(&raw_mutex);
	if (copy_to_user((void __user *)arg, &rq, sizeof(rq))) {
	err = -EFAULT;
	goto out;
	}
	}
	break;
	default:
	err = -EINVAL;
	break;
	}
	out:
	return err;
	}

	static const struct file_operations raw_fops = {
	.read = do_sync_read,
	.aio_read = generic_file_aio_read,
	.write = do_sync_write,
	.aio_write = blkdev_aio_write,
	.open = raw_open,
	.release= raw_release,
	.ioctl = raw_ioctl,
	.owner = THIS_MODULE,
	};

	static const struct file_operations raw_ctl_fops = {
	.ioctl = raw_ctl_ioctl,
	.open = raw_open,
	.owner = THIS_MODULE,
	};

	static struct cdev raw_cdev;

	static char raw_nodename(struct device dev)
	{
	return kasprintf(GFP_KERNEL, "raw/%s", dev_name(dev));
	}

	static int __init raw_init(void)
	{
	dev_t dev = MKDEV(RAW_MAJOR, 0);
	int ret;

	ret = register_chrdev_region(dev, MAX_RAW_MINORS, "raw");
	if (ret)
	goto error;

	cdev_init(&raw_cdev, &raw_fops);
	ret = cdev_add(&raw_cdev, dev, MAX_RAW_MINORS);
	if (ret) {
	kobject_put(&raw_cdev.kobj);
	goto error_region;
	}

	raw_class = class_create(THIS_MODULE, "raw");
	if (IS_ERR(raw_class)) {
	printk(KERN_ERR "Error creating raw class.\n");
	cdev_del(&raw_cdev);
	ret = PTR_ERR(raw_class);
	goto error_region;
	}
	raw_class->nodename = raw_nodename;
	device_create(raw_class, NULL, MKDEV(RAW_MAJOR, 0), NULL, "rawctl");

	return 0;

	error_region:
	unregister_chrdev_region(dev, MAX_RAW_MINORS);
	error:
	return ret;
	}

	static void __exit raw_exit(void)
	{
	device_destroy(raw_class, MKDEV(RAW_MAJOR, 0));
	class_destroy(raw_class);
	cdev_del(&raw_cdev);
	unregister_chrdev_region(MKDEV(RAW_MAJOR, 0), MAX_RAW_MINORS);
	}

	module_init(raw_init);
	module_exit(raw_exit);
	MODULE_LICENSE("GPL");