raw.c revision ff23eca3e8f613034e0d20ff86f6a89b62f5a14e 
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
25struct raw_device_data {
26	struct block_device *binding;
27	int inuse;
28};
29
30static struct class *raw_class;
31static struct raw_device_data raw_devices[MAX_RAW_MINORS];
32static DEFINE_MUTEX(raw_mutex);
33static 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 */
45static 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_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
84out2:
85	bd_release(bdev);
86out1:
87	blkdev_put(bdev);
88out:
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 */
97static 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 */
119static int
120raw_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
128static void bind_device(struct raw_config_request *rq)
129{
130	class_device_destroy(raw_class, MKDEV(RAW_MAJOR, rq->raw_minor));
131	class_device_create(raw_class, NULL, MKDEV(RAW_MAJOR, rq->raw_minor),
132				      NULL, "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 */
139static 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				class_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	}
237out:
238	return err;
239}
240
241static ssize_t raw_file_write(struct file *file, const char __user *buf,
242				   size_t count, loff_t *ppos)
243{
244	struct iovec local_iov = {
245		.iov_base = (char __user *)buf,
246		.iov_len = count
247	};
248
249	return generic_file_write_nolock(file, &local_iov, 1, ppos);
250}
251
252static ssize_t raw_file_aio_write(struct kiocb *iocb, const char __user *buf,
253					size_t count, loff_t pos)
254{
255	struct iovec local_iov = {
256		.iov_base = (char __user *)buf,
257		.iov_len = count
258	};
259
260	return generic_file_aio_write_nolock(iocb, &local_iov, 1, &iocb->ki_pos);
261}
262
263
264static struct file_operations raw_fops = {
265	.read	=	generic_file_read,
266	.aio_read = 	generic_file_aio_read,
267	.write	=	raw_file_write,
268	.aio_write = 	raw_file_aio_write,
269	.open	=	raw_open,
270	.release=	raw_release,
271	.ioctl	=	raw_ioctl,
272	.readv	= 	generic_file_readv,
273	.writev	= 	generic_file_writev,
274	.owner	=	THIS_MODULE,
275};
276
277static struct file_operations raw_ctl_fops = {
278	.ioctl	=	raw_ctl_ioctl,
279	.open	=	raw_open,
280	.owner	=	THIS_MODULE,
281};
282
283static struct cdev raw_cdev = {
284	.kobj	=	{.name = "raw", },
285	.owner	=	THIS_MODULE,
286};
287
288static int __init raw_init(void)
289{
290	dev_t dev = MKDEV(RAW_MAJOR, 0);
291
292	if (register_chrdev_region(dev, MAX_RAW_MINORS, "raw"))
293		goto error;
294
295	cdev_init(&raw_cdev, &raw_fops);
296	if (cdev_add(&raw_cdev, dev, MAX_RAW_MINORS)) {
297		kobject_put(&raw_cdev.kobj);
298		unregister_chrdev_region(dev, MAX_RAW_MINORS);
299		goto error;
300	}
301
302	raw_class = class_create(THIS_MODULE, "raw");
303	if (IS_ERR(raw_class)) {
304		printk(KERN_ERR "Error creating raw class.\n");
305		cdev_del(&raw_cdev);
306		unregister_chrdev_region(dev, MAX_RAW_MINORS);
307		goto error;
308	}
309	class_device_create(raw_class, NULL, MKDEV(RAW_MAJOR, 0), NULL, "rawctl");
310
311	return 0;
312
313error:
314	printk(KERN_ERR "error register raw device\n");
315	return 1;
316}
317
318static void __exit raw_exit(void)
319{
320	class_device_destroy(raw_class, MKDEV(RAW_MAJOR, 0));
321	class_destroy(raw_class);
322	cdev_del(&raw_cdev);
323	unregister_chrdev_region(MKDEV(RAW_MAJOR, 0), MAX_RAW_MINORS);
324}
325
326module_init(raw_init);
327module_exit(raw_exit);
328MODULE_LICENSE("GPL");
329