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