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 inode->i_mapping->backing_dev_info = &default_backing_dev_info;
111 }
112 mutex_unlock(&raw_mutex);
113
114 blkdev_put(bdev, filp->f_mode | FMODE_EXCL);
115 return 0;
116 }
117
118 /*
119 * Forward ioctls to the underlying block device.
120 */
121 static long
raw_ioctl(struct file * filp,unsigned int command,unsigned long arg)122 raw_ioctl(struct file *filp, unsigned int command, unsigned long arg)
123 {
124 struct block_device *bdev = filp->private_data;
125 return blkdev_ioctl(bdev, 0, command, arg);
126 }
127
bind_set(int number,u64 major,u64 minor)128 static int bind_set(int number, u64 major, u64 minor)
129 {
130 dev_t dev = MKDEV(major, minor);
131 struct raw_device_data *rawdev;
132 int err = 0;
133
134 if (number <= 0 || number >= max_raw_minors)
135 return -EINVAL;
136
137 if (MAJOR(dev) != major || MINOR(dev) != minor)
138 return -EINVAL;
139
140 rawdev = &raw_devices[number];
141
142 /*
143 * This is like making block devices, so demand the
144 * same capability
145 */
146 if (!capable(CAP_SYS_ADMIN))
147 return -EPERM;
148
149 /*
150 * For now, we don't need to check that the underlying
151 * block device is present or not: we can do that when
152 * the raw device is opened. Just check that the
153 * major/minor numbers make sense.
154 */
155
156 if (MAJOR(dev) == 0 && dev != 0)
157 return -EINVAL;
158
159 mutex_lock(&raw_mutex);
160 if (rawdev->inuse) {
161 mutex_unlock(&raw_mutex);
162 return -EBUSY;
163 }
164 if (rawdev->binding) {
165 bdput(rawdev->binding);
166 module_put(THIS_MODULE);
167 }
168 if (!dev) {
169 /* unbind */
170 rawdev->binding = NULL;
171 device_destroy(raw_class, MKDEV(RAW_MAJOR, number));
172 } else {
173 rawdev->binding = bdget(dev);
174 if (rawdev->binding == NULL) {
175 err = -ENOMEM;
176 } else {
177 dev_t raw = MKDEV(RAW_MAJOR, number);
178 __module_get(THIS_MODULE);
179 device_destroy(raw_class, raw);
180 device_create(raw_class, NULL, raw, NULL,
181 "raw%d", number);
182 }
183 }
184 mutex_unlock(&raw_mutex);
185 return err;
186 }
187
bind_get(int number,dev_t * dev)188 static int bind_get(int number, dev_t *dev)
189 {
190 struct raw_device_data *rawdev;
191 struct block_device *bdev;
192
193 if (number <= 0 || number >= MAX_RAW_MINORS)
194 return -EINVAL;
195
196 rawdev = &raw_devices[number];
197
198 mutex_lock(&raw_mutex);
199 bdev = rawdev->binding;
200 *dev = bdev ? bdev->bd_dev : 0;
201 mutex_unlock(&raw_mutex);
202 return 0;
203 }
204
205 /*
206 * Deal with ioctls against the raw-device control interface, to bind
207 * and unbind other raw devices.
208 */
raw_ctl_ioctl(struct file * filp,unsigned int command,unsigned long arg)209 static long raw_ctl_ioctl(struct file *filp, unsigned int command,
210 unsigned long arg)
211 {
212 struct raw_config_request rq;
213 dev_t dev;
214 int err;
215
216 switch (command) {
217 case RAW_SETBIND:
218 if (copy_from_user(&rq, (void __user *) arg, sizeof(rq)))
219 return -EFAULT;
220
221 return bind_set(rq.raw_minor, rq.block_major, rq.block_minor);
222
223 case RAW_GETBIND:
224 if (copy_from_user(&rq, (void __user *) arg, sizeof(rq)))
225 return -EFAULT;
226
227 err = bind_get(rq.raw_minor, &dev);
228 if (err)
229 return err;
230
231 rq.block_major = MAJOR(dev);
232 rq.block_minor = MINOR(dev);
233
234 if (copy_to_user((void __user *)arg, &rq, sizeof(rq)))
235 return -EFAULT;
236
237 return 0;
238 }
239
240 return -EINVAL;
241 }
242
243 #ifdef CONFIG_COMPAT
244 struct raw32_config_request {
245 compat_int_t raw_minor;
246 compat_u64 block_major;
247 compat_u64 block_minor;
248 };
249
raw_ctl_compat_ioctl(struct file * file,unsigned int cmd,unsigned long arg)250 static long raw_ctl_compat_ioctl(struct file *file, unsigned int cmd,
251 unsigned long arg)
252 {
253 struct raw32_config_request __user *user_req = compat_ptr(arg);
254 struct raw32_config_request rq;
255 dev_t dev;
256 int err = 0;
257
258 switch (cmd) {
259 case RAW_SETBIND:
260 if (copy_from_user(&rq, user_req, sizeof(rq)))
261 return -EFAULT;
262
263 return bind_set(rq.raw_minor, rq.block_major, rq.block_minor);
264
265 case RAW_GETBIND:
266 if (copy_from_user(&rq, user_req, sizeof(rq)))
267 return -EFAULT;
268
269 err = bind_get(rq.raw_minor, &dev);
270 if (err)
271 return err;
272
273 rq.block_major = MAJOR(dev);
274 rq.block_minor = MINOR(dev);
275
276 if (copy_to_user(user_req, &rq, sizeof(rq)))
277 return -EFAULT;
278
279 return 0;
280 }
281
282 return -EINVAL;
283 }
284 #endif
285
286 static const struct file_operations raw_fops = {
287 .read = do_sync_read,
288 .aio_read = generic_file_aio_read,
289 .write = do_sync_write,
290 .aio_write = blkdev_aio_write,
291 .fsync = blkdev_fsync,
292 .open = raw_open,
293 .release = raw_release,
294 .unlocked_ioctl = raw_ioctl,
295 .llseek = default_llseek,
296 .owner = THIS_MODULE,
297 };
298
299 static const struct file_operations raw_ctl_fops = {
300 .unlocked_ioctl = raw_ctl_ioctl,
301 #ifdef CONFIG_COMPAT
302 .compat_ioctl = raw_ctl_compat_ioctl,
303 #endif
304 .open = raw_open,
305 .owner = THIS_MODULE,
306 .llseek = noop_llseek,
307 };
308
309 static struct cdev raw_cdev;
310
raw_devnode(struct device * dev,umode_t * mode)311 static char *raw_devnode(struct device *dev, umode_t *mode)
312 {
313 return kasprintf(GFP_KERNEL, "raw/%s", dev_name(dev));
314 }
315
raw_init(void)316 static int __init raw_init(void)
317 {
318 dev_t dev = MKDEV(RAW_MAJOR, 0);
319 int ret;
320
321 if (max_raw_minors < 1 || max_raw_minors > 65536) {
322 printk(KERN_WARNING "raw: invalid max_raw_minors (must be"
323 " between 1 and 65536), using %d\n", MAX_RAW_MINORS);
324 max_raw_minors = MAX_RAW_MINORS;
325 }
326
327 raw_devices = vzalloc(sizeof(struct raw_device_data) * max_raw_minors);
328 if (!raw_devices) {
329 printk(KERN_ERR "Not enough memory for raw device structures\n");
330 ret = -ENOMEM;
331 goto error;
332 }
333
334 ret = register_chrdev_region(dev, max_raw_minors, "raw");
335 if (ret)
336 goto error;
337
338 cdev_init(&raw_cdev, &raw_fops);
339 ret = cdev_add(&raw_cdev, dev, max_raw_minors);
340 if (ret) {
341 goto error_region;
342 }
343
344 raw_class = class_create(THIS_MODULE, "raw");
345 if (IS_ERR(raw_class)) {
346 printk(KERN_ERR "Error creating raw class.\n");
347 cdev_del(&raw_cdev);
348 ret = PTR_ERR(raw_class);
349 goto error_region;
350 }
351 raw_class->devnode = raw_devnode;
352 device_create(raw_class, NULL, MKDEV(RAW_MAJOR, 0), NULL, "rawctl");
353
354 return 0;
355
356 error_region:
357 unregister_chrdev_region(dev, max_raw_minors);
358 error:
359 vfree(raw_devices);
360 return ret;
361 }
362
raw_exit(void)363 static void __exit raw_exit(void)
364 {
365 device_destroy(raw_class, MKDEV(RAW_MAJOR, 0));
366 class_destroy(raw_class);
367 cdev_del(&raw_cdev);
368 unregister_chrdev_region(MKDEV(RAW_MAJOR, 0), max_raw_minors);
369 }
370
371 module_init(raw_init);
372 module_exit(raw_exit);
373 MODULE_LICENSE("GPL");
374