aboutsummaryrefslogtreecommitdiff
path: root/drivers/char/raw.c
blob: bfd59e6bf54ff1aa221b71e4f22d989e9ba98a1a (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
/*
 * linux/drivers/char/raw.c
 *
 * Front-end raw character devices.  These can be bound to any block
 * devices to provide genuine Unix raw character device semantics.
 *
 * We reserve minor number 0 for a control interface.  ioctl()s on this
 * device are used to bind the other minor numbers to block devices.
 */

#include <linux/init.h>
#include <linux/fs.h>
#include <linux/major.h>
#include <linux/blkdev.h>
#include <linux/module.h>
#include <linux/raw.h>
#include <linux/capability.h>
#include <linux/uio.h>
#include <linux/cdev.h>
#include <linux/device.h>
#include <linux/mutex.h>
#include <linux/smp_lock.h>

#include <asm/uaccess.h>

struct raw_device_data {
	struct block_device *binding;
	int inuse;
};

static struct class *raw_class;
static struct raw_device_data raw_devices[MAX_RAW_MINORS];
static DEFINE_MUTEX(raw_mutex);
static const struct file_operations raw_ctl_fops; /* forward declaration */

/*
 * Open/close code for raw IO.
 *
 * We just rewrite the i_mapping for the /dev/raw/rawN file descriptor to
 * point at the blockdev's address_space and set the file handle to use
 * O_DIRECT.
 *
 * Set the device's soft blocksize to the minimum possible.  This gives the
 * finest possible alignment and has no adverse impact on performance.
 */
static int raw_open(struct inode *inode, struct file *filp)
{
	const int minor = iminor(inode);
	struct block_device *bdev;
	int err;

	if (minor == 0) {	/* It is the control device */
		filp->f_op = &raw_ctl_fops;
		return 0;
	}

	lock_kernel();
	mutex_lock(&raw_mutex);

	/*
	 * All we need to do on open is check that the device is bound.
	 */
	bdev = raw_devices[minor].binding;
	err = -ENODEV;
	if (!bdev)
		goto out;
	igrab(bdev->bd_inode);
	err = blkdev_get(bdev, filp->f_mode, 0);
	if (err)
		goto out;
	err = bd_claim(bdev, raw_open);
	if (err)
		goto out1;
	err = set_blocksize(bdev, bdev_hardsect_size(bdev));
	if (err)
		goto out2;
	filp->f_flags |= O_DIRECT;
	filp->f_mapping = bdev->bd_inode->i_mapping;
	if (++raw_devices[minor].inuse == 1)
		filp->f_path.dentry->d_inode->i_mapping =
			bdev->bd_inode->i_mapping;
	filp->private_data = bdev;
	mutex_unlock(&raw_mutex);
	unlock_kernel();
	return 0;

out2:
	bd_release(bdev);
out1:
	blkdev_put(bdev, filp->f_mode);
out:
	mutex_unlock(&raw_mutex);
	return err;
}

/*
 * When the final fd which refers to this character-special node is closed, we
 * make its ->mapping point back at its own i_data.
 */
static int raw_release(struct inode *inode, struct file *filp)
{
	const int minor= iminor(inode);
	struct block_device *bdev;

	mutex_lock(&raw_mutex);
	bdev = raw_devices[minor].binding;
	if (--raw_devices[minor].inuse == 0) {
		/* Here  inode->i_mapping == bdev->bd_inode->i_mapping  */
		inode->i_mapping = &inode->i_data;
		inode->i_mapping->backing_dev_info = &default_backing_dev_info;
	}
	mutex_unlock(&raw_mutex);

	bd_release(bdev);
	blkdev_put(bdev, filp->f_mode);
	return 0;
}

/*
 * Forward ioctls to the underlying block device.
 */
static int
raw_ioctl(struct inode *inode, struct file *filp,
		  unsigned int command, unsigned long arg)
{
	struct block_device *bdev = filp->private_data;

	return blkdev_ioctl(bdev->bd_inode, NULL, command, arg);
}

static void bind_device(struct raw_config_request *rq)
{
	device_destroy(raw_class, MKDEV(RAW_MAJOR, rq->raw_minor));
	device_create(raw_class, NULL, MKDEV(RAW_MAJOR, rq->raw_minor), NULL,
		      "raw%d", rq->raw_minor);
}

/*
 * Deal with ioctls against the raw-device control interface, to bind
 * and unbind other raw devices.
 */
static int raw_ctl_ioctl(struct inode *inode, struct file *filp,
			unsigned int command, unsigned long arg)
{
	struct raw_config_request rq;
	struct raw_device_data *rawdev;
	int err = 0;

	switch (command) {
	case RAW_SETBIND:
	case RAW_GETBIND:

		/* First, find out which raw minor we want */

		if (copy_from_user(&rq, (void __user *) arg, sizeof(rq))) {
			err = -EFAULT;
			goto out;
		}

		if (rq.raw_minor <= 0 || rq.raw_minor >= MAX_RAW_MINORS) {
			err = -EINVAL;
			goto out;
		}
		rawdev = &raw_devices[rq.raw_minor];

		if (command == RAW_SETBIND) {
			dev_t dev;

			/*
			 * This is like making block devices, so demand the
			 * same capability
			 */
			if (!capable(CAP_SYS_ADMIN)) {
				err = -EPERM;
				goto out;
			}

			/*
			 * For now, we don't need to check that the underlying
			 * block device is present or not: we can do that when
			 * the raw device is opened.  Just check that the
			 * major/minor numbers make sense.
			 */

			dev = MKDEV(rq.block_major, rq.block_minor);
			if ((rq.block_major == 0 && rq.block_minor != 0) ||
					MAJOR(dev) != rq.block_major ||
					MINOR(dev) != rq.block_minor) {
				err = -EINVAL;
				goto out;
			}

			mutex_lock(&raw_mutex);
			if (rawdev->inuse) {
				mutex_unlock(&raw_mutex);
				err = -EBUSY;
				goto out;
			}
			if (rawdev->binding) {
				bdput(rawdev->binding);
				module_put(THIS_MODULE);
			}
			if (rq.block_major == 0 && rq.block_minor == 0) {
				/* unbind */
				rawdev->binding = NULL;
				device_destroy(raw_class,
						MKDEV(RAW_MAJOR, rq.raw_minor));
			} else {
				rawdev->binding = bdget(dev);
				if (rawdev->binding == NULL)
					err = -ENOMEM;
				else {
					__module_get(THIS_MODULE);
					bind_device(&rq);
				}
			}
			mutex_unlock(&raw_mutex);
		} else {
			struct block_device *bdev;

			mutex_lock(&raw_mutex);
			bdev = rawdev->binding;
			if (bdev) {
				rq.block_major = MAJOR(bdev->bd_dev);
				rq.block_minor = MINOR(bdev->bd_dev);
			} else {
				rq.block_major = rq.block_minor = 0;
			}
			mutex_unlock(&raw_mutex);
			if (copy_to_user((void __user *)arg, &rq, sizeof(rq))) {
				err = -EFAULT;
				goto out;
			}
		}
		break;
	default:
		err = -EINVAL;
		break;
	}
out:
	return err;
}

static const struct file_operations raw_fops = {
	.read	=	do_sync_read,
	.aio_read = 	generic_file_aio_read,
	.write	=	do_sync_write,
	.aio_write = 	generic_file_aio_write_nolock,
	.open	=	raw_open,
	.release=	raw_release,
	.ioctl	=	raw_ioctl,
	.owner	=	THIS_MODULE,
};

static const struct file_operations raw_ctl_fops = {
	.ioctl	=	raw_ctl_ioctl,
	.open	=	raw_open,
	.owner	=	THIS_MODULE,
};

static struct cdev raw_cdev;

static int __init raw_init(void)
{
	dev_t dev = MKDEV(RAW_MAJOR, 0);
	int ret;

	ret = register_chrdev_region(dev, MAX_RAW_MINORS, "raw");
	if (ret)
		goto error;

	cdev_init(&raw_cdev, &raw_fops);
	ret = cdev_add(&raw_cdev, dev, MAX_RAW_MINORS);
	if (ret) {
		kobject_put(&raw_cdev.kobj);
		goto error_region;
	}

	raw_class = class_create(THIS_MODULE, "raw");
	if (IS_ERR(raw_class)) {
		printk(KERN_ERR "Error creating raw class.\n");
		cdev_del(&raw_cdev);
		ret = PTR_ERR(raw_class);
		goto error_region;
	}
	device_create(raw_class, NULL, MKDEV(RAW_MAJOR, 0), NULL, "rawctl");

	return 0;

error_region:
	unregister_chrdev_region(dev, MAX_RAW_MINORS);
error:
	return ret;
}

static void __exit raw_exit(void)
{
	device_destroy(raw_class, MKDEV(RAW_MAJOR, 0));
	class_destroy(raw_class);
	cdev_del(&raw_cdev);
	unregister_chrdev_region(MKDEV(RAW_MAJOR, 0), MAX_RAW_MINORS);
}

module_init(raw_init);
module_exit(raw_exit);
MODULE_LICENSE("GPL");