1 /*
2 * linux/drivers/char/raw.c
3 *
4 * Front-end raw character devices. These can be bound to any block
5 * devices to provide genuine Unix raw character device semantics.
6 *
7 * We reserve minor number 0 for a control interface. ioctl()s on this
8 * device are used to bind the other minor numbers to block devices.
9 */
10
11 #include <linux/init.h>
12 #include <linux/fs.h>
13 #include <linux/major.h>
14 #include <linux/blkdev.h>
15 #include <linux/module.h>
16 #include <linux/raw.h>
17 #include <linux/capability.h>
18 #include <linux/uio.h>
19 #include <linux/cdev.h>
20 #include <linux/device.h>
21 #include <linux/mutex.h>
22 #include <linux/gfp.h>
23 #include <linux/compat.h>
24 #include <linux/vmalloc.h>
25
26 #include <asm/uaccess.h>
27
28 struct raw_device_data {
29 struct block_device *binding;
30 int inuse;
31 };
32
33 static struct class *raw_class;
34 static struct raw_device_data *raw_devices;
35 static DEFINE_MUTEX(raw_mutex);
36 static const struct file_operations raw_ctl_fops; /* forward declaration */
37
38 static int max_raw_minors = MAX_RAW_MINORS;
39
40 module_param(max_raw_minors, int, 0);
41 MODULE_PARM_DESC(max_raw_minors, "Maximum number of raw devices (1-65536)");
42
43 /*
44 * Open/close code for raw IO.
45 *
46 * We just rewrite the i_mapping for the /dev/raw/rawN file descriptor to
47 * point at the blockdev's address_space and set the file handle to use
48 * O_DIRECT.
49 *
50 * Set the device's soft blocksize to the minimum possible. This gives the
51 * finest possible alignment and has no adverse impact on performance.
52 */
raw_open(struct inode * inode,struct file * filp)53 static int raw_open(struct inode *inode, struct file *filp)
54 {
55 const int minor = iminor(inode);
56 struct block_device *bdev;
57 int err;
58
59 if (minor == 0) { /* It is the control device */
60 filp->f_op = &raw_ctl_fops;
61 return 0;
62 }
63
64 mutex_lock(&raw_mutex);
65
66 /*
67 * All we need to do on open is check that the device is bound.
68 */
69 bdev = raw_devices[minor].binding;
70 err = -ENODEV;
71 if (!bdev)
72 goto out;
73 igrab(bdev->bd_inode);
74 err = blkdev_get(bdev, filp->f_mode | FMODE_EXCL, raw_open);
75 if (err)
76 goto out;
77 err = set_blocksize(bdev, bdev_logical_block_size(bdev));
78 if (err)
79 goto out1;
80 filp->f_flags |= O_DIRECT;
81 filp->f_mapping = bdev->bd_inode->i_mapping;
82 if (++raw_devices[minor].inuse == 1)
83 file_inode(filp)->i_mapping =
84 bdev->bd_inode->i_mapping;
85 filp->private_data = bdev;
86 mutex_unlock(&raw_mutex);
87 return 0;
88
89 out1:
90 blkdev_put(bdev, filp->f_mode | FMODE_EXCL);
91 out:
92 mutex_unlock(&raw_mutex);
93 return err;
94 }
95
96 /*
97 * When the final fd which refers to this character-special node is closed, we
98 * make its ->mapping point back at its own i_data.
99 */
raw_release(struct inode * inode,struct file * filp)100 static int raw_release(struct inode *inode, struct file *filp)
101 {
102 const int minor= iminor(inode);
103 struct block_device *bdev;
104
105 mutex_lock(&raw_mutex);
106 bdev = raw_devices[minor].binding;
107 if (--raw_devices[minor].inuse == 0)
108 /* Here inode->i_mapping == bdev->bd_inode->i_mapping */
109 inode->i_mapping = &inode->i_data;
110 mutex_unlock(&raw_mutex);
111
112 blkdev_put(bdev, filp->f_mode | FMODE_EXCL);
113 return 0;
114 }
115
116 /*
117 * Forward ioctls to the underlying block device.
118 */
119 static long
raw_ioctl(struct file * filp,unsigned int command,unsigned long arg)120 raw_ioctl(struct file *filp, unsigned int command, unsigned long arg)
121 {
122 struct block_device *bdev = filp->private_data;
123 return blkdev_ioctl(bdev, 0, command, arg);
124 }
125
bind_set(int number,u64 major,u64 minor)126 static int bind_set(int number, u64 major, u64 minor)
127 {
128 dev_t dev = MKDEV(major, minor);
129 struct raw_device_data *rawdev;
130 int err = 0;
131
132 if (number <= 0 || number >= max_raw_minors)
133 return -EINVAL;
134
135 if (MAJOR(dev) != major || MINOR(dev) != minor)
136 return -EINVAL;
137
138 rawdev = &raw_devices[number];
139
140 /*
141 * This is like making block devices, so demand the
142 * same capability
143 */
144 if (!capable(CAP_SYS_ADMIN))
145 return -EPERM;
146
147 /*
148 * For now, we don't need to check that the underlying
149 * block device is present or not: we can do that when
150 * the raw device is opened. Just check that the
151 * major/minor numbers make sense.
152 */
153
154 if (MAJOR(dev) == 0 && dev != 0)
155 return -EINVAL;
156
157 mutex_lock(&raw_mutex);
158 if (rawdev->inuse) {
159 mutex_unlock(&raw_mutex);
160 return -EBUSY;
161 }
162 if (rawdev->binding) {
163 bdput(rawdev->binding);
164 module_put(THIS_MODULE);
165 }
166 if (!dev) {
167 /* unbind */
168 rawdev->binding = NULL;
169 device_destroy(raw_class, MKDEV(RAW_MAJOR, number));
170 } else {
171 rawdev->binding = bdget(dev);
172 if (rawdev->binding == NULL) {
173 err = -ENOMEM;
174 } else {
175 dev_t raw = MKDEV(RAW_MAJOR, number);
176 __module_get(THIS_MODULE);
177 device_destroy(raw_class, raw);
178 device_create(raw_class, NULL, raw, NULL,
179 "raw%d", number);
180 }
181 }
182 mutex_unlock(&raw_mutex);
183 return err;
184 }
185
bind_get(int number,dev_t * dev)186 static int bind_get(int number, dev_t *dev)
187 {
188 struct raw_device_data *rawdev;
189 struct block_device *bdev;
190
191 if (number <= 0 || number >= max_raw_minors)
192 return -EINVAL;
193
194 rawdev = &raw_devices[number];
195
196 mutex_lock(&raw_mutex);
197 bdev = rawdev->binding;
198 *dev = bdev ? bdev->bd_dev : 0;
199 mutex_unlock(&raw_mutex);
200 return 0;
201 }
202
203 /*
204 * Deal with ioctls against the raw-device control interface, to bind
205 * and unbind other raw devices.
206 */
raw_ctl_ioctl(struct file * filp,unsigned int command,unsigned long arg)207 static long raw_ctl_ioctl(struct file *filp, unsigned int command,
208 unsigned long arg)
209 {
210 struct raw_config_request rq;
211 dev_t dev;
212 int err;
213
214 switch (command) {
215 case RAW_SETBIND:
216 if (copy_from_user(&rq, (void __user *) arg, sizeof(rq)))
217 return -EFAULT;
218
219 return bind_set(rq.raw_minor, rq.block_major, rq.block_minor);
220
221 case RAW_GETBIND:
222 if (copy_from_user(&rq, (void __user *) arg, sizeof(rq)))
223 return -EFAULT;
224
225 err = bind_get(rq.raw_minor, &dev);
226 if (err)
227 return err;
228
229 rq.block_major = MAJOR(dev);
230 rq.block_minor = MINOR(dev);
231
232 if (copy_to_user((void __user *)arg, &rq, sizeof(rq)))
233 return -EFAULT;
234
235 return 0;
236 }
237
238 return -EINVAL;
239 }
240
241 #ifdef CONFIG_COMPAT
242 struct raw32_config_request {
243 compat_int_t raw_minor;
244 compat_u64 block_major;
245 compat_u64 block_minor;
246 };
247
raw_ctl_compat_ioctl(struct file * file,unsigned int cmd,unsigned long arg)248 static long raw_ctl_compat_ioctl(struct file *file, unsigned int cmd,
249 unsigned long arg)
250 {
251 struct raw32_config_request __user *user_req = compat_ptr(arg);
252 struct raw32_config_request rq;
253 dev_t dev;
254 int err = 0;
255
256 switch (cmd) {
257 case RAW_SETBIND:
258 if (copy_from_user(&rq, user_req, sizeof(rq)))
259 return -EFAULT;
260
261 return bind_set(rq.raw_minor, rq.block_major, rq.block_minor);
262
263 case RAW_GETBIND:
264 if (copy_from_user(&rq, user_req, sizeof(rq)))
265 return -EFAULT;
266
267 err = bind_get(rq.raw_minor, &dev);
268 if (err)
269 return err;
270
271 rq.block_major = MAJOR(dev);
272 rq.block_minor = MINOR(dev);
273
274 if (copy_to_user(user_req, &rq, sizeof(rq)))
275 return -EFAULT;
276
277 return 0;
278 }
279
280 return -EINVAL;
281 }
282 #endif
283
284 static const struct file_operations raw_fops = {
285 .read_iter = blkdev_read_iter,
286 .write_iter = blkdev_write_iter,
287 .fsync = blkdev_fsync,
288 .open = raw_open,
289 .release = raw_release,
290 .unlocked_ioctl = raw_ioctl,
291 .llseek = default_llseek,
292 .owner = THIS_MODULE,
293 };
294
295 static const struct file_operations raw_ctl_fops = {
296 .unlocked_ioctl = raw_ctl_ioctl,
297 #ifdef CONFIG_COMPAT
298 .compat_ioctl = raw_ctl_compat_ioctl,
299 #endif
300 .open = raw_open,
301 .owner = THIS_MODULE,
302 .llseek = noop_llseek,
303 };
304
305 static struct cdev raw_cdev;
306
raw_devnode(struct device * dev,umode_t * mode)307 static char *raw_devnode(struct device *dev, umode_t *mode)
308 {
309 return kasprintf(GFP_KERNEL, "raw/%s", dev_name(dev));
310 }
311
raw_init(void)312 static int __init raw_init(void)
313 {
314 dev_t dev = MKDEV(RAW_MAJOR, 0);
315 int ret;
316
317 if (max_raw_minors < 1 || max_raw_minors > 65536) {
318 printk(KERN_WARNING "raw: invalid max_raw_minors (must be"
319 " between 1 and 65536), using %d\n", MAX_RAW_MINORS);
320 max_raw_minors = MAX_RAW_MINORS;
321 }
322
323 raw_devices = vzalloc(sizeof(struct raw_device_data) * max_raw_minors);
324 if (!raw_devices) {
325 printk(KERN_ERR "Not enough memory for raw device structures\n");
326 ret = -ENOMEM;
327 goto error;
328 }
329
330 ret = register_chrdev_region(dev, max_raw_minors, "raw");
331 if (ret)
332 goto error;
333
334 cdev_init(&raw_cdev, &raw_fops);
335 ret = cdev_add(&raw_cdev, dev, max_raw_minors);
336 if (ret) {
337 goto error_region;
338 }
339
340 raw_class = class_create(THIS_MODULE, "raw");
341 if (IS_ERR(raw_class)) {
342 printk(KERN_ERR "Error creating raw class.\n");
343 cdev_del(&raw_cdev);
344 ret = PTR_ERR(raw_class);
345 goto error_region;
346 }
347 raw_class->devnode = raw_devnode;
348 device_create(raw_class, NULL, MKDEV(RAW_MAJOR, 0), NULL, "rawctl");
349
350 return 0;
351
352 error_region:
353 unregister_chrdev_region(dev, max_raw_minors);
354 error:
355 vfree(raw_devices);
356 return ret;
357 }
358
raw_exit(void)359 static void __exit raw_exit(void)
360 {
361 device_destroy(raw_class, MKDEV(RAW_MAJOR, 0));
362 class_destroy(raw_class);
363 cdev_del(&raw_cdev);
364 unregister_chrdev_region(MKDEV(RAW_MAJOR, 0), max_raw_minors);
365 }
366
367 module_init(raw_init);
368 module_exit(raw_exit);
369 MODULE_LICENSE("GPL");
370