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
23 #include <asm/uaccess.h>
24
25 struct raw_device_data {
26 struct block_device *binding;
27 int inuse;
28 };
29
30 static struct class *raw_class;
31 static struct raw_device_data raw_devices[MAX_RAW_MINORS];
32 static DEFINE_MUTEX(raw_mutex);
33 static const struct file_operations raw_ctl_fops; /* forward declaration */
34
35 /*
36 * Open/close code for raw IO.
37 *
38 * We just rewrite the i_mapping for the /dev/raw/rawN file descriptor to
39 * point at the blockdev's address_space and set the file handle to use
40 * O_DIRECT.
41 *
42 * Set the device's soft blocksize to the minimum possible. This gives the
43 * finest possible alignment and has no adverse impact on performance.
44 */
45 static int raw_open(struct inode *inode, struct file *filp)
46 {
47 const int minor = iminor(inode);
48 struct block_device *bdev;
49 int err;
50
51 if (minor == 0) { /* It is the control device */
52 filp->f_op = &raw_ctl_fops;
53 return 0;
54 }
55
56 mutex_lock(&raw_mutex);
57
58 /*
59 * All we need to do on open is check that the device is bound.
60 */
61 bdev = raw_devices[minor].binding;
62 err = -ENODEV;
63 if (!bdev)
64 goto out;
65 igrab(bdev->bd_inode);
66 err = blkdev_get(bdev, filp->f_mode, 0);
67 if (err)
68 goto out;
69 err = bd_claim(bdev, raw_open);
70 if (err)
71 goto out1;
72 err = set_blocksize(bdev, bdev_hardsect_size(bdev));
73 if (err)
74 goto out2;
75 filp->f_flags |= O_DIRECT;
76 filp->f_mapping = bdev->bd_inode->i_mapping;
77 if (++raw_devices[minor].inuse == 1)
78 filp->f_path.dentry->d_inode->i_mapping =
79 bdev->bd_inode->i_mapping;
80 filp->private_data = bdev;
81 mutex_unlock(&raw_mutex);
82 return 0;
83
84 out2:
85 bd_release(bdev);
86 out1:
87 blkdev_put(bdev);
88 out:
89 mutex_unlock(&raw_mutex);
90 return err;
91 }
92
93 /*
94 * When the final fd which refers to this character-special node is closed, we
95 * make its ->mapping point back at its own i_data.
96 */
97 static int raw_release(struct inode *inode, struct file *filp)
98 {
99 const int minor= iminor(inode);
100 struct block_device *bdev;
101
102 mutex_lock(&raw_mutex);
103 bdev = raw_devices[minor].binding;
104 if (--raw_devices[minor].inuse == 0) {
105 /* Here inode->i_mapping == bdev->bd_inode->i_mapping */
106 inode->i_mapping = &inode->i_data;
107 inode->i_mapping->backing_dev_info = &default_backing_dev_info;
108 }
109 mutex_unlock(&raw_mutex);
110
111 bd_release(bdev);
112 blkdev_put(bdev);
113 return 0;
114 }
115
116 /*
117 * Forward ioctls to the underlying block device.
118 */
119 static int
120 raw_ioctl(struct inode *inode, struct file *filp,
121 unsigned int command, unsigned long arg)
122 {
123 struct block_device *bdev = filp->private_data;
124
125 return blkdev_ioctl(bdev->bd_inode, NULL, command, arg);
126 }
127
128 static void bind_device(struct raw_config_request *rq)
129 {
130 device_destroy(raw_class, MKDEV(RAW_MAJOR, rq->raw_minor));
131 device_create(raw_class, NULL, MKDEV(RAW_MAJOR, rq->raw_minor),
132 "raw%d", rq->raw_minor);
133 }
134
135 /*
136 * Deal with ioctls against the raw-device control interface, to bind
137 * and unbind other raw devices.
138 */
139 static int raw_ctl_ioctl(struct inode *inode, struct file *filp,
140 unsigned int command, unsigned long arg)
141 {
142 struct raw_config_request rq;
143 struct raw_device_data *rawdev;
144 int err = 0;
145
146 switch (command) {
147 case RAW_SETBIND:
148 case RAW_GETBIND:
149
150 /* First, find out which raw minor we want */
151
152 if (copy_from_user(&rq, (void __user *) arg, sizeof(rq))) {
153 err = -EFAULT;
154 goto out;
155 }
156
157 if (rq.raw_minor <= 0 || rq.raw_minor >= MAX_RAW_MINORS) {
158 err = -EINVAL;
159 goto out;
160 }
161 rawdev = &raw_devices[rq.raw_minor];
162
163 if (command == RAW_SETBIND) {
164 dev_t dev;
165
166 /*
167 * This is like making block devices, so demand the
168 * same capability
169 */
170 if (!capable(CAP_SYS_ADMIN)) {
171 err = -EPERM;
172 goto out;
173 }
174
175 /*
176 * For now, we don't need to check that the underlying
177 * block device is present or not: we can do that when
178 * the raw device is opened. Just check that the
179 * major/minor numbers make sense.
180 */
181
182 dev = MKDEV(rq.block_major, rq.block_minor);
183 if ((rq.block_major == 0 && rq.block_minor != 0) ||
184 MAJOR(dev) != rq.block_major ||
185 MINOR(dev) != rq.block_minor) {
186 err = -EINVAL;
187 goto out;
188 }
189
190 mutex_lock(&raw_mutex);
191 if (rawdev->inuse) {
192 mutex_unlock(&raw_mutex);
193 err = -EBUSY;
194 goto out;
195 }
196 if (rawdev->binding) {
197 bdput(rawdev->binding);
198 module_put(THIS_MODULE);
199 }
200 if (rq.block_major == 0 && rq.block_minor == 0) {
201 /* unbind */
202 rawdev->binding = NULL;
203 device_destroy(raw_class,
204 MKDEV(RAW_MAJOR, rq.raw_minor));
205 } else {
206 rawdev->binding = bdget(dev);
207 if (rawdev->binding == NULL)
208 err = -ENOMEM;
209 else {
210 __module_get(THIS_MODULE);
211 bind_device(&rq);
212 }
213 }
214 mutex_unlock(&raw_mutex);
215 } else {
216 struct block_device *bdev;
217
218 mutex_lock(&raw_mutex);
219 bdev = rawdev->binding;
220 if (bdev) {
221 rq.block_major = MAJOR(bdev->bd_dev);
222 rq.block_minor = MINOR(bdev->bd_dev);
223 } else {
224 rq.block_major = rq.block_minor = 0;
225 }
226 mutex_unlock(&raw_mutex);
227 if (copy_to_user((void __user *)arg, &rq, sizeof(rq))) {
228 err = -EFAULT;
229 goto out;
230 }
231 }
232 break;
233 default:
234 err = -EINVAL;
235 break;
236 }
237 out:
238 return err;
239 }
240
241 static const struct file_operations raw_fops = {
242 .read = do_sync_read,
243 .aio_read = generic_file_aio_read,
244 .write = do_sync_write,
245 .aio_write = generic_file_aio_write_nolock,
246 .open = raw_open,
247 .release= raw_release,
248 .ioctl = raw_ioctl,
249 .owner = THIS_MODULE,
250 };
251
252 static const struct file_operations raw_ctl_fops = {
253 .ioctl = raw_ctl_ioctl,
254 .open = raw_open,
255 .owner = THIS_MODULE,
256 };
257
258 static struct cdev raw_cdev;
259
260 static int __init raw_init(void)
261 {
262 dev_t dev = MKDEV(RAW_MAJOR, 0);
263 int ret;
264
265 ret = register_chrdev_region(dev, MAX_RAW_MINORS, "raw");
266 if (ret)
267 goto error;
268
269 cdev_init(&raw_cdev, &raw_fops);
270 ret = cdev_add(&raw_cdev, dev, MAX_RAW_MINORS);
271 if (ret) {
272 kobject_put(&raw_cdev.kobj);
273 goto error_region;
274 }
275
276 raw_class = class_create(THIS_MODULE, "raw");
277 if (IS_ERR(raw_class)) {
278 printk(KERN_ERR "Error creating raw class.\n");
279 cdev_del(&raw_cdev);
280 ret = PTR_ERR(raw_class);
281 goto error_region;
282 }
283 device_create(raw_class, NULL, MKDEV(RAW_MAJOR, 0), "rawctl");
284
285 return 0;
286
287 error_region:
288 unregister_chrdev_region(dev, MAX_RAW_MINORS);
289 error:
290 return ret;
291 }
292
293 static void __exit raw_exit(void)
294 {
295 device_destroy(raw_class, MKDEV(RAW_MAJOR, 0));
296 class_destroy(raw_class);
297 cdev_del(&raw_cdev);
298 unregister_chrdev_region(MKDEV(RAW_MAJOR, 0), MAX_RAW_MINORS);
299 }
300
301 module_init(raw_init);
302 module_exit(raw_exit);
303 MODULE_LICENSE("GPL");
304
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