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

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * 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/backing-dev.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/gfp.h>
 #include <linux/compat.h>
 #include <linux/vmalloc.h>

 #include <linux/uaccess.h>

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

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

 static int max_raw_minors = CONFIG_MAX_RAW_DEVS;

 module_param(max_raw_minors, int, 0);
 MODULE_PARM_DESC(max_raw_minors, "Maximum number of raw devices (1-65536)");

 /*
  * 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;
 	}

 	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;
 	bdgrab(bdev);
 	err = blkdev_get(bdev, filp->f_mode | FMODE_EXCL, raw_open);
 	if (err)
 		goto out;
 	err = set_blocksize(bdev, bdev_logical_block_size(bdev));
 	if (err)
 		goto out1;
 	filp->f_flags |= O_DIRECT;
 	filp->f_mapping = bdev->bd_inode->i_mapping;
 	if (++raw_devices[minor].inuse == 1)
 		file_inode(filp)->i_mapping =
 			bdev->bd_inode->i_mapping;
 	filp->private_data = bdev;
 	mutex_unlock(&raw_mutex);
 	return 0;

 out1:
 	blkdev_put(bdev, filp->f_mode | FMODE_EXCL);
 out:
 	mutex_unlock(&raw_mutex);
 	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;
 	mutex_unlock(&raw_mutex);

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

 /*
  * Forward ioctls to the underlying block device.
  */
 static long
 raw_ioctl(struct file *filp, unsigned int command, unsigned long arg)
 {
 	struct block_device *bdev = filp->private_data;
 	return blkdev_ioctl(bdev, 0, command, arg);
 }

 static int bind_set(int number, u64 major, u64 minor)
 {
 	dev_t dev = MKDEV(major, minor);
 	struct raw_device_data *rawdev;
 	int err = 0;

 	if (number <= 0 || number >= max_raw_minors)
 		return -EINVAL;

 	if (MAJOR(dev) != major || MINOR(dev) != minor)
 		return -EINVAL;

 	rawdev = &raw_devices[number];

 	/*
 	 * This is like making block devices, so demand the
 	 * same capability
 	 */
 	if (!capable(CAP_SYS_ADMIN))
 		return -EPERM;

 	/*
 	 * 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.
 	 */

 	if (MAJOR(dev) == 0 && dev != 0)
 		return -EINVAL;

 	mutex_lock(&raw_mutex);
 	if (rawdev->inuse) {
 		mutex_unlock(&raw_mutex);
 		return -EBUSY;
 	}
 	if (rawdev->binding) {
 		bdput(rawdev->binding);
 		module_put(THIS_MODULE);
 	}
 	if (!dev) {
 		/* unbind */
 		rawdev->binding = NULL;
 		device_destroy(raw_class, MKDEV(RAW_MAJOR, number));
 	} else {
 		rawdev->binding = bdget(dev);
 		if (rawdev->binding == NULL) {
 			err = -ENOMEM;
 		} else {
 			dev_t raw = MKDEV(RAW_MAJOR, number);
 			__module_get(THIS_MODULE);
 			device_destroy(raw_class, raw);
 			device_create(raw_class, NULL, raw, NULL,
 				      "raw%d", number);
 		}
 	}
 	mutex_unlock(&raw_mutex);
 	return err;
 }

 static int bind_get(int number, dev_t *dev)
 {
 	struct raw_device_data *rawdev;
 	struct block_device *bdev;

 	if (number <= 0 || number >= max_raw_minors)
 		return -EINVAL;

 	rawdev = &raw_devices[number];

 	mutex_lock(&raw_mutex);
 	bdev = rawdev->binding;
 	*dev = bdev ? bdev->bd_dev : 0;
 	mutex_unlock(&raw_mutex);
 	return 0;
 }

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

 	switch (command) {
 	case RAW_SETBIND:
 		if (copy_from_user(&rq, (void __user *) arg, sizeof(rq)))
 			return -EFAULT;

 		return bind_set(rq.raw_minor, rq.block_major, rq.block_minor);

 	case RAW_GETBIND:
 		if (copy_from_user(&rq, (void __user *) arg, sizeof(rq)))
 			return -EFAULT;

 		err = bind_get(rq.raw_minor, &dev);
 		if (err)
 			return err;

 		rq.block_major = MAJOR(dev);
 		rq.block_minor = MINOR(dev);

 		if (copy_to_user((void __user *)arg, &rq, sizeof(rq)))
 			return -EFAULT;

 		return 0;
 	}

 	return -EINVAL;
 }

 #ifdef CONFIG_COMPAT
 struct raw32_config_request {
 	compat_int_t	raw_minor;
 	compat_u64	block_major;
 	compat_u64	block_minor;
 };

 static long raw_ctl_compat_ioctl(struct file *file, unsigned int cmd,
 				unsigned long arg)
 {
 	struct raw32_config_request __user *user_req = compat_ptr(arg);
 	struct raw32_config_request rq;
 	dev_t dev;
 	int err = 0;

 	switch (cmd) {
 	case RAW_SETBIND:
 		if (copy_from_user(&rq, user_req, sizeof(rq)))
 			return -EFAULT;

 		return bind_set(rq.raw_minor, rq.block_major, rq.block_minor);

 	case RAW_GETBIND:
 		if (copy_from_user(&rq, user_req, sizeof(rq)))
 			return -EFAULT;

 		err = bind_get(rq.raw_minor, &dev);
 		if (err)
 			return err;

 		rq.block_major = MAJOR(dev);
 		rq.block_minor = MINOR(dev);

 		if (copy_to_user(user_req, &rq, sizeof(rq)))
 			return -EFAULT;

 		return 0;
 	}

 	return -EINVAL;
 }
 #endif

 static const struct file_operations raw_fops = {
 	.read_iter	= blkdev_read_iter,
 	.write_iter	= blkdev_write_iter,
 	.fsync		= blkdev_fsync,
 	.open		= raw_open,
 	.release	= raw_release,
 	.unlocked_ioctl = raw_ioctl,
 	.llseek		= default_llseek,
 	.owner		= THIS_MODULE,
 };

 static const struct file_operations raw_ctl_fops = {
 	.unlocked_ioctl = raw_ctl_ioctl,
 #ifdef CONFIG_COMPAT
 	.compat_ioctl	= raw_ctl_compat_ioctl,
 #endif
 	.open		= raw_open,
 	.owner		= THIS_MODULE,
 	.llseek		= noop_llseek,
 };

 static struct cdev raw_cdev;

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

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

 	if (max_raw_minors < 1 || max_raw_minors > 65536) {
 		pr_warn("raw: invalid max_raw_minors (must be between 1 and 65536), using %d\n",
 			CONFIG_MAX_RAW_DEVS);
 		max_raw_minors = CONFIG_MAX_RAW_DEVS;
 	}

 	raw_devices = vzalloc(array_size(max_raw_minors,
 					 sizeof(struct raw_device_data)));
 	if (!raw_devices) {
 		printk(KERN_ERR "Not enough memory for raw device structures\n");
 		ret = -ENOMEM;
 		goto error;
 	}

 	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)
 		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->devnode = raw_devnode;
 	device_create(raw_class, NULL, MKDEV(RAW_MAJOR, 0), NULL, "rawctl");

 	return 0;

 error_region:
 	unregister_chrdev_region(dev, max_raw_minors);
 error:
 	vfree(raw_devices);
 	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");
	// SPDX-License-Identifier: GPL-2.0-only
	/*
	* 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/backing-dev.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/gfp.h>
	#include <linux/compat.h>
	#include <linux/vmalloc.h>

	#include <linux/uaccess.h>

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

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

	static int max_raw_minors = CONFIG_MAX_RAW_DEVS;

	module_param(max_raw_minors, int, 0);
	MODULE_PARM_DESC(max_raw_minors, "Maximum number of raw devices (1-65536)");

	/*
	* 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;
	}

	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;
	bdgrab(bdev);
	err = blkdev_get(bdev, filp->f_mode \| FMODE_EXCL, raw_open);
	if (err)
	goto out;
	err = set_blocksize(bdev, bdev_logical_block_size(bdev));
	if (err)
	goto out1;
	filp->f_flags \|= O_DIRECT;
	filp->f_mapping = bdev->bd_inode->i_mapping;
	if (++raw_devices[minor].inuse == 1)
	file_inode(filp)->i_mapping =
	bdev->bd_inode->i_mapping;
	filp->private_data = bdev;
	mutex_unlock(&raw_mutex);
	return 0;

	out1:
	blkdev_put(bdev, filp->f_mode \| FMODE_EXCL);
	out:
	mutex_unlock(&raw_mutex);
	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;
	mutex_unlock(&raw_mutex);

	blkdev_put(bdev, filp->f_mode \| FMODE_EXCL);
	return 0;
	}

	/*
	* Forward ioctls to the underlying block device.
	*/
	static long
	raw_ioctl(struct file *filp, unsigned int command, unsigned long arg)
	{
	struct block_device *bdev = filp->private_data;
	return blkdev_ioctl(bdev, 0, command, arg);
	}

	static int bind_set(int number, u64 major, u64 minor)
	{
	dev_t dev = MKDEV(major, minor);
	struct raw_device_data *rawdev;
	int err = 0;

	if (number <= 0 \|\| number >= max_raw_minors)
	return -EINVAL;

	if (MAJOR(dev) != major \|\| MINOR(dev) != minor)
	return -EINVAL;

	rawdev = &raw_devices[number];

	/*
	* This is like making block devices, so demand the
	* same capability
	*/
	if (!capable(CAP_SYS_ADMIN))
	return -EPERM;

	/*
	* 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.
	*/

	if (MAJOR(dev) == 0 && dev != 0)
	return -EINVAL;

	mutex_lock(&raw_mutex);
	if (rawdev->inuse) {
	mutex_unlock(&raw_mutex);
	return -EBUSY;
	}
	if (rawdev->binding) {
	bdput(rawdev->binding);
	module_put(THIS_MODULE);
	}
	if (!dev) {
	/* unbind */
	rawdev->binding = NULL;
	device_destroy(raw_class, MKDEV(RAW_MAJOR, number));
	} else {
	rawdev->binding = bdget(dev);
	if (rawdev->binding == NULL) {
	err = -ENOMEM;
	} else {
	dev_t raw = MKDEV(RAW_MAJOR, number);
	__module_get(THIS_MODULE);
	device_destroy(raw_class, raw);
	device_create(raw_class, NULL, raw, NULL,
	"raw%d", number);
	}
	}
	mutex_unlock(&raw_mutex);
	return err;
	}

	static int bind_get(int number, dev_t *dev)
	{
	struct raw_device_data *rawdev;
	struct block_device *bdev;

	if (number <= 0 \|\| number >= max_raw_minors)
	return -EINVAL;

	rawdev = &raw_devices[number];

	mutex_lock(&raw_mutex);
	bdev = rawdev->binding;
	*dev = bdev ? bdev->bd_dev : 0;
	mutex_unlock(&raw_mutex);
	return 0;
	}

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

	switch (command) {
	case RAW_SETBIND:
	if (copy_from_user(&rq, (void __user *) arg, sizeof(rq)))
	return -EFAULT;

	return bind_set(rq.raw_minor, rq.block_major, rq.block_minor);

	case RAW_GETBIND:
	if (copy_from_user(&rq, (void __user *) arg, sizeof(rq)))
	return -EFAULT;

	err = bind_get(rq.raw_minor, &dev);
	if (err)
	return err;

	rq.block_major = MAJOR(dev);
	rq.block_minor = MINOR(dev);

	if (copy_to_user((void __user *)arg, &rq, sizeof(rq)))
	return -EFAULT;

	return 0;
	}

	return -EINVAL;
	}

	#ifdef CONFIG_COMPAT
	struct raw32_config_request {
	compat_int_t raw_minor;
	compat_u64 block_major;
	compat_u64 block_minor;
	};

	static long raw_ctl_compat_ioctl(struct file *file, unsigned int cmd,
	unsigned long arg)
	{
	struct raw32_config_request __user *user_req = compat_ptr(arg);
	struct raw32_config_request rq;
	dev_t dev;
	int err = 0;

	switch (cmd) {
	case RAW_SETBIND:
	if (copy_from_user(&rq, user_req, sizeof(rq)))
	return -EFAULT;

	return bind_set(rq.raw_minor, rq.block_major, rq.block_minor);

	case RAW_GETBIND:
	if (copy_from_user(&rq, user_req, sizeof(rq)))
	return -EFAULT;

	err = bind_get(rq.raw_minor, &dev);
	if (err)
	return err;

	rq.block_major = MAJOR(dev);
	rq.block_minor = MINOR(dev);

	if (copy_to_user(user_req, &rq, sizeof(rq)))
	return -EFAULT;

	return 0;
	}

	return -EINVAL;
	}
	#endif

	static const struct file_operations raw_fops = {
	.read_iter = blkdev_read_iter,
	.write_iter = blkdev_write_iter,
	.fsync = blkdev_fsync,
	.open = raw_open,
	.release = raw_release,
	.unlocked_ioctl = raw_ioctl,
	.llseek = default_llseek,
	.owner = THIS_MODULE,
	};

	static const struct file_operations raw_ctl_fops = {
	.unlocked_ioctl = raw_ctl_ioctl,
	#ifdef CONFIG_COMPAT
	.compat_ioctl = raw_ctl_compat_ioctl,
	#endif
	.open = raw_open,
	.owner = THIS_MODULE,
	.llseek = noop_llseek,
	};

	static struct cdev raw_cdev;

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

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

	if (max_raw_minors < 1 \|\| max_raw_minors > 65536) {
	pr_warn("raw: invalid max_raw_minors (must be between 1 and 65536), using %d\n",
	CONFIG_MAX_RAW_DEVS);
	max_raw_minors = CONFIG_MAX_RAW_DEVS;
	}

	raw_devices = vzalloc(array_size(max_raw_minors,
	sizeof(struct raw_device_data)));
	if (!raw_devices) {
	printk(KERN_ERR "Not enough memory for raw device structures\n");
	ret = -ENOMEM;
	goto error;
	}

	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)
	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->devnode = raw_devnode;
	device_create(raw_class, NULL, MKDEV(RAW_MAJOR, 0), NULL, "rawctl");

	return 0;

	error_region:
	unregister_chrdev_region(dev, max_raw_minors);
	error:
	vfree(raw_devices);
	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");