Root/drivers/char/raw.c

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
28struct raw_device_data {
29    struct block_device *binding;
30    int inuse;
31};
32
33static struct class *raw_class;
34static struct raw_device_data *raw_devices;
35static DEFINE_MUTEX(raw_mutex);
36static const struct file_operations raw_ctl_fops; /* forward declaration */
37
38static int max_raw_minors = MAX_RAW_MINORS;
39
40module_param(max_raw_minors, int, 0);
41MODULE_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 */
53static 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
89out1:
90    blkdev_put(bdev, filp->f_mode | FMODE_EXCL);
91out:
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 */
100static 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 */
121static long
122raw_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
128static 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
188static 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 */
209static 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
244struct raw32_config_request {
245    compat_int_t raw_minor;
246    compat_u64 block_major;
247    compat_u64 block_minor;
248};
249
250static 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
286static 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
299static 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
309static struct cdev raw_cdev;
310
311static char *raw_devnode(struct device *dev, umode_t *mode)
312{
313    return kasprintf(GFP_KERNEL, "raw/%s", dev_name(dev));
314}
315
316static 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
356error_region:
357    unregister_chrdev_region(dev, max_raw_minors);
358error:
359    vfree(raw_devices);
360    return ret;
361}
362
363static 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
371module_init(raw_init);
372module_exit(raw_exit);
373MODULE_LICENSE("GPL");
374

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