1 // SPDX-License-Identifier: GPL-2.0-only
3 * linux/drivers/char/raw.c
5 * Front-end raw character devices. These can be bound to any block
6 * devices to provide genuine Unix raw character device semantics.
8 * We reserve minor number 0 for a control interface. ioctl()s on this
9 * device are used to bind the other minor numbers to block devices.
12 #include <linux/init.h>
14 #include <linux/major.h>
15 #include <linux/blkdev.h>
16 #include <linux/backing-dev.h>
17 #include <linux/module.h>
18 #include <linux/raw.h>
19 #include <linux/capability.h>
20 #include <linux/uio.h>
21 #include <linux/cdev.h>
22 #include <linux/device.h>
23 #include <linux/mutex.h>
24 #include <linux/gfp.h>
25 #include <linux/compat.h>
26 #include <linux/vmalloc.h>
28 #include <linux/uaccess.h>
30 struct raw_device_data {
32 struct block_device *bdev;
36 static struct class *raw_class;
37 static struct raw_device_data *raw_devices;
38 static DEFINE_MUTEX(raw_mutex);
39 static const struct file_operations raw_ctl_fops; /* forward declaration */
41 static int max_raw_minors = CONFIG_MAX_RAW_DEVS;
43 module_param(max_raw_minors, int, 0);
44 MODULE_PARM_DESC(max_raw_minors, "Maximum number of raw devices (1-65536)");
47 * Open/close code for raw IO.
49 * We just rewrite the i_mapping for the /dev/raw/rawN file descriptor to
50 * point at the blockdev's address_space and set the file handle to use
53 * Set the device's soft blocksize to the minimum possible. This gives the
54 * finest possible alignment and has no adverse impact on performance.
56 static int raw_open(struct inode *inode, struct file *filp)
58 const int minor = iminor(inode);
59 struct block_device *bdev;
62 if (minor == 0) { /* It is the control device */
63 filp->f_op = &raw_ctl_fops;
68 "process %s (pid %d) is using the deprecated raw device\n"
69 "support will be removed in Linux 5.14.\n",
70 current->comm, current->pid);
72 mutex_lock(&raw_mutex);
75 * All we need to do on open is check that the device is bound.
78 if (!raw_devices[minor].binding)
80 bdev = blkdev_get_by_dev(raw_devices[minor].binding,
81 filp->f_mode | FMODE_EXCL, raw_open);
86 err = set_blocksize(bdev, bdev_logical_block_size(bdev));
89 filp->f_flags |= O_DIRECT;
90 filp->f_mapping = bdev->bd_inode->i_mapping;
91 if (++raw_devices[minor].inuse == 1)
92 file_inode(filp)->i_mapping =
93 bdev->bd_inode->i_mapping;
94 filp->private_data = bdev;
95 raw_devices[minor].bdev = bdev;
96 mutex_unlock(&raw_mutex);
100 blkdev_put(bdev, filp->f_mode | FMODE_EXCL);
102 mutex_unlock(&raw_mutex);
107 * When the final fd which refers to this character-special node is closed, we
108 * make its ->mapping point back at its own i_data.
110 static int raw_release(struct inode *inode, struct file *filp)
112 const int minor= iminor(inode);
113 struct block_device *bdev;
115 mutex_lock(&raw_mutex);
116 bdev = raw_devices[minor].bdev;
117 if (--raw_devices[minor].inuse == 0)
118 /* Here inode->i_mapping == bdev->bd_inode->i_mapping */
119 inode->i_mapping = &inode->i_data;
120 mutex_unlock(&raw_mutex);
122 blkdev_put(bdev, filp->f_mode | FMODE_EXCL);
127 * Forward ioctls to the underlying block device.
130 raw_ioctl(struct file *filp, unsigned int command, unsigned long arg)
132 struct block_device *bdev = filp->private_data;
133 return blkdev_ioctl(bdev, 0, command, arg);
136 static int bind_set(int number, u64 major, u64 minor)
138 dev_t dev = MKDEV(major, minor);
139 dev_t raw = MKDEV(RAW_MAJOR, number);
140 struct raw_device_data *rawdev;
143 if (number <= 0 || number >= max_raw_minors)
146 if (MAJOR(dev) != major || MINOR(dev) != minor)
149 rawdev = &raw_devices[number];
152 * This is like making block devices, so demand the
155 if (!capable(CAP_SYS_ADMIN))
159 * For now, we don't need to check that the underlying
160 * block device is present or not: we can do that when
161 * the raw device is opened. Just check that the
162 * major/minor numbers make sense.
165 if (MAJOR(dev) == 0 && dev != 0)
168 mutex_lock(&raw_mutex);
170 mutex_unlock(&raw_mutex);
174 module_put(THIS_MODULE);
176 rawdev->binding = dev;
179 device_destroy(raw_class, raw);
181 __module_get(THIS_MODULE);
182 device_destroy(raw_class, raw);
183 device_create(raw_class, NULL, raw, NULL, "raw%d", number);
185 mutex_unlock(&raw_mutex);
189 static int bind_get(int number, dev_t *dev)
191 if (number <= 0 || number >= max_raw_minors)
193 *dev = raw_devices[number].binding;
198 * Deal with ioctls against the raw-device control interface, to bind
199 * and unbind other raw devices.
201 static long raw_ctl_ioctl(struct file *filp, unsigned int command,
204 struct raw_config_request rq;
210 if (copy_from_user(&rq, (void __user *) arg, sizeof(rq)))
213 return bind_set(rq.raw_minor, rq.block_major, rq.block_minor);
216 if (copy_from_user(&rq, (void __user *) arg, sizeof(rq)))
219 err = bind_get(rq.raw_minor, &dev);
223 rq.block_major = MAJOR(dev);
224 rq.block_minor = MINOR(dev);
226 if (copy_to_user((void __user *)arg, &rq, sizeof(rq)))
236 struct raw32_config_request {
237 compat_int_t raw_minor;
238 compat_u64 block_major;
239 compat_u64 block_minor;
242 static long raw_ctl_compat_ioctl(struct file *file, unsigned int cmd,
245 struct raw32_config_request __user *user_req = compat_ptr(arg);
246 struct raw32_config_request rq;
252 if (copy_from_user(&rq, user_req, sizeof(rq)))
255 return bind_set(rq.raw_minor, rq.block_major, rq.block_minor);
258 if (copy_from_user(&rq, user_req, sizeof(rq)))
261 err = bind_get(rq.raw_minor, &dev);
265 rq.block_major = MAJOR(dev);
266 rq.block_minor = MINOR(dev);
268 if (copy_to_user(user_req, &rq, sizeof(rq)))
278 static const struct file_operations raw_fops = {
279 .read_iter = blkdev_read_iter,
280 .write_iter = blkdev_write_iter,
281 .fsync = blkdev_fsync,
283 .release = raw_release,
284 .unlocked_ioctl = raw_ioctl,
285 .llseek = default_llseek,
286 .owner = THIS_MODULE,
289 static const struct file_operations raw_ctl_fops = {
290 .unlocked_ioctl = raw_ctl_ioctl,
292 .compat_ioctl = raw_ctl_compat_ioctl,
295 .owner = THIS_MODULE,
296 .llseek = noop_llseek,
299 static struct cdev raw_cdev;
301 static char *raw_devnode(struct device *dev, umode_t *mode)
303 return kasprintf(GFP_KERNEL, "raw/%s", dev_name(dev));
306 static int __init raw_init(void)
308 dev_t dev = MKDEV(RAW_MAJOR, 0);
311 if (max_raw_minors < 1 || max_raw_minors > 65536) {
312 pr_warn("raw: invalid max_raw_minors (must be between 1 and 65536), using %d\n",
313 CONFIG_MAX_RAW_DEVS);
314 max_raw_minors = CONFIG_MAX_RAW_DEVS;
317 raw_devices = vzalloc(array_size(max_raw_minors,
318 sizeof(struct raw_device_data)));
320 printk(KERN_ERR "Not enough memory for raw device structures\n");
325 ret = register_chrdev_region(dev, max_raw_minors, "raw");
329 cdev_init(&raw_cdev, &raw_fops);
330 ret = cdev_add(&raw_cdev, dev, max_raw_minors);
333 raw_class = class_create(THIS_MODULE, "raw");
334 if (IS_ERR(raw_class)) {
335 printk(KERN_ERR "Error creating raw class.\n");
337 ret = PTR_ERR(raw_class);
340 raw_class->devnode = raw_devnode;
341 device_create(raw_class, NULL, MKDEV(RAW_MAJOR, 0), NULL, "rawctl");
346 unregister_chrdev_region(dev, max_raw_minors);
352 static void __exit raw_exit(void)
354 device_destroy(raw_class, MKDEV(RAW_MAJOR, 0));
355 class_destroy(raw_class);
357 unregister_chrdev_region(MKDEV(RAW_MAJOR, 0), max_raw_minors);
360 module_init(raw_init);
361 module_exit(raw_exit);
362 MODULE_LICENSE("GPL");