1 /*
2 * CUSE: Character device in Userspace
3 *
4 * Copyright (C) 2008-2009 SUSE Linux Products GmbH
5 * Copyright (C) 2008-2009 Tejun Heo <tj@kernel.org>
6 *
7 * This file is released under the GPLv2.
8 *
9 * CUSE enables character devices to be implemented from userland much
10 * like FUSE allows filesystems. On initialization /dev/cuse is
11 * created. By opening the file and replying to the CUSE_INIT request
12 * userland CUSE server can create a character device. After that the
13 * operation is very similar to FUSE.
14 *
15 * A CUSE instance involves the following objects.
16 *
17 * cuse_conn : contains fuse_conn and serves as bonding structure
18 * channel : file handle connected to the userland CUSE server
19 * cdev : the implemented character device
20 * dev : generic device for cdev
21 *
22 * Note that 'channel' is what 'dev' is in FUSE. As CUSE deals with
23 * devices, it's called 'channel' to reduce confusion.
24 *
25 * channel determines when the character device dies. When channel is
26 * closed, everything begins to destruct. The cuse_conn is taken off
27 * the lookup table preventing further access from cdev, cdev and
28 * generic device are removed and the base reference of cuse_conn is
29 * put.
30 *
31 * On each open, the matching cuse_conn is looked up and if found an
32 * additional reference is taken which is released when the file is
33 * closed.
34 */
35
36 #include <linux/fuse.h>
37 #include <linux/cdev.h>
38 #include <linux/device.h>
39 #include <linux/file.h>
40 #include <linux/fs.h>
41 #include <linux/kdev_t.h>
42 #include <linux/kthread.h>
43 #include <linux/list.h>
44 #include <linux/magic.h>
45 #include <linux/miscdevice.h>
46 #include <linux/mutex.h>
47 #include <linux/spinlock.h>
48 #include <linux/stat.h>
49
50 #include "fuse_i.h"
51
52 #define CUSE_CONNTBL_LEN 64
53
54 struct cuse_conn {
55 struct list_head list; /* linked on cuse_conntbl */
56 struct fuse_conn fc; /* fuse connection */
57 struct cdev *cdev; /* associated character device */
58 struct device *dev; /* device representing @cdev */
59
60 /* init parameters, set once during initialization */
61 bool unrestricted_ioctl;
62 };
63
64 static DEFINE_SPINLOCK(cuse_lock); /* protects cuse_conntbl */
65 static struct list_head cuse_conntbl[CUSE_CONNTBL_LEN];
66 static struct class *cuse_class;
67
68 static struct cuse_conn *fc_to_cc(struct fuse_conn *fc)
69 {
70 return container_of(fc, struct cuse_conn, fc);
71 }
72
73 static struct list_head *cuse_conntbl_head(dev_t devt)
74 {
75 return &cuse_conntbl[(MAJOR(devt) + MINOR(devt)) % CUSE_CONNTBL_LEN];
76 }
77
78
79 /**************************************************************************
80 * CUSE frontend operations
81 *
82 * These are file operations for the character device.
83 *
84 * On open, CUSE opens a file from the FUSE mnt and stores it to
85 * private_data of the open file. All other ops call FUSE ops on the
86 * FUSE file.
87 */
88
89 static ssize_t cuse_read(struct file *file, char __user *buf, size_t count,
90 loff_t *ppos)
91 {
92 loff_t pos = 0;
93
94 return fuse_direct_io(file, buf, count, &pos, 0);
95 }
96
97 static ssize_t cuse_write(struct file *file, const char __user *buf,
98 size_t count, loff_t *ppos)
99 {
100 loff_t pos = 0;
101 /*
102 * No locking or generic_write_checks(), the server is
103 * responsible for locking and sanity checks.
104 */
105 return fuse_direct_io(file, buf, count, &pos, 1);
106 }
107
108 static int cuse_open(struct inode *inode, struct file *file)
109 {
110 dev_t devt = inode->i_cdev->dev;
111 struct cuse_conn *cc = NULL, *pos;
112 int rc;
113
114 /* look up and get the connection */
115 spin_lock(&cuse_lock);
116 list_for_each_entry(pos, cuse_conntbl_head(devt), list)
117 if (pos->dev->devt == devt) {
118 fuse_conn_get(&pos->fc);
119 cc = pos;
120 break;
121 }
122 spin_unlock(&cuse_lock);
123
124 /* dead? */
125 if (!cc)
126 return -ENODEV;
127
128 /*
129 * Generic permission check is already done against the chrdev
130 * file, proceed to open.
131 */
132 rc = fuse_do_open(&cc->fc, 0, file, 0);
133 if (rc)
134 fuse_conn_put(&cc->fc);
135 return rc;
136 }
137
138 static int cuse_release(struct inode *inode, struct file *file)
139 {
140 struct fuse_file *ff = file->private_data;
141 struct fuse_conn *fc = ff->fc;
142
143 fuse_sync_release(ff, file->f_flags);
144 fuse_conn_put(fc);
145
146 return 0;
147 }
148
149 static long cuse_file_ioctl(struct file *file, unsigned int cmd,
150 unsigned long arg)
151 {
152 struct fuse_file *ff = file->private_data;
153 struct cuse_conn *cc = fc_to_cc(ff->fc);
154 unsigned int flags = 0;
155
156 if (cc->unrestricted_ioctl)
157 flags |= FUSE_IOCTL_UNRESTRICTED;
158
159 return fuse_do_ioctl(file, cmd, arg, flags);
160 }
161
162 static long cuse_file_compat_ioctl(struct file *file, unsigned int cmd,
163 unsigned long arg)
164 {
165 struct fuse_file *ff = file->private_data;
166 struct cuse_conn *cc = fc_to_cc(ff->fc);
167 unsigned int flags = FUSE_IOCTL_COMPAT;
168
169 if (cc->unrestricted_ioctl)
170 flags |= FUSE_IOCTL_UNRESTRICTED;
171
172 return fuse_do_ioctl(file, cmd, arg, flags);
173 }
174
175 static const struct file_operations cuse_frontend_fops = {
176 .owner = THIS_MODULE,
177 .read = cuse_read,
178 .write = cuse_write,
179 .open = cuse_open,
180 .release = cuse_release,
181 .unlocked_ioctl = cuse_file_ioctl,
182 .compat_ioctl = cuse_file_compat_ioctl,
183 .poll = fuse_file_poll,
184 };
185
186
187 /**************************************************************************
188 * CUSE channel initialization and destruction
189 */
190
191 struct cuse_devinfo {
192 const char *name;
193 };
194
195 /**
196 * cuse_parse_one - parse one key=value pair
197 * @pp: i/o parameter for the current position
198 * @end: points to one past the end of the packed string
199 * @keyp: out parameter for key
200 * @valp: out parameter for value
201 *
202 * *@pp points to packed strings - "key0=val0\0key1=val1\0" which ends
203 * at @end - 1. This function parses one pair and set *@keyp to the
204 * start of the key and *@valp to the start of the value. Note that
205 * the original string is modified such that the key string is
206 * terminated with '\0'. *@pp is updated to point to the next string.
207 *
208 * RETURNS:
209 * 1 on successful parse, 0 on EOF, -errno on failure.
210 */
211 static int cuse_parse_one(char **pp, char *end, char **keyp, char **valp)
212 {
213 char *p = *pp;
214 char *key, *val;
215
216 while (p < end && *p == '\0')
217 p++;
218 if (p == end)
219 return 0;
220
221 if (end[-1] != '\0') {
222 printk(KERN_ERR "CUSE: info not properly terminated\n");
223 return -EINVAL;
224 }
225
226 key = val = p;
227 p += strlen(p);
228
229 if (valp) {
230 strsep(&val, "=");
231 if (!val)
232 val = key + strlen(key);
233 key = strstrip(key);
234 val = strstrip(val);
235 } else
236 key = strstrip(key);
237
238 if (!strlen(key)) {
239 printk(KERN_ERR "CUSE: zero length info key specified\n");
240 return -EINVAL;
241 }
242
243 *pp = p;
244 *keyp = key;
245 if (valp)
246 *valp = val;
247
248 return 1;
249 }
250
251 /**
252 * cuse_parse_dev_info - parse device info
253 * @p: device info string
254 * @len: length of device info string
255 * @devinfo: out parameter for parsed device info
256 *
257 * Parse @p to extract device info and store it into @devinfo. String
258 * pointed to by @p is modified by parsing and @devinfo points into
259 * them, so @p shouldn't be freed while @devinfo is in use.
260 *
261 * RETURNS:
262 * 0 on success, -errno on failure.
263 */
264 static int cuse_parse_devinfo(char *p, size_t len, struct cuse_devinfo *devinfo)
265 {
266 char *end = p + len;
267 char *key, *val;
268 int rc;
269
270 while (true) {
271 rc = cuse_parse_one(&p, end, &key, &val);
272 if (rc < 0)
273 return rc;
274 if (!rc)
275 break;
276 if (strcmp(key, "DEVNAME") == 0)
277 devinfo->name = val;
278 else
279 printk(KERN_WARNING "CUSE: unknown device info \"%s\"\n",
280 key);
281 }
282
283 if (!devinfo->name || !strlen(devinfo->name)) {
284 printk(KERN_ERR "CUSE: DEVNAME unspecified\n");
285 return -EINVAL;
286 }
287
288 return 0;
289 }
290
291 static void cuse_gendev_release(struct device *dev)
292 {
293 kfree(dev);
294 }
295
296 /**
297 * cuse_process_init_reply - finish initializing CUSE channel
298 *
299 * This function creates the character device and sets up all the
300 * required data structures for it. Please read the comment at the
301 * top of this file for high level overview.
302 */
303 static void cuse_process_init_reply(struct fuse_conn *fc, struct fuse_req *req)
304 {
305 struct cuse_conn *cc = fc_to_cc(fc);
306 struct cuse_init_out *arg = &req->misc.cuse_init_out;
307 struct page *page = req->pages[0];
308 struct cuse_devinfo devinfo = { };
309 struct device *dev;
310 struct cdev *cdev;
311 dev_t devt;
312 int rc;
313
314 if (req->out.h.error ||
315 arg->major != FUSE_KERNEL_VERSION || arg->minor < 11) {
316 goto err;
317 }
318
319 fc->minor = arg->minor;
320 fc->max_read = max_t(unsigned, arg->max_read, 4096);
321 fc->max_write = max_t(unsigned, arg->max_write, 4096);
322
323 /* parse init reply */
324 cc->unrestricted_ioctl = arg->flags & CUSE_UNRESTRICTED_IOCTL;
325
326 rc = cuse_parse_devinfo(page_address(page), req->out.args[1].size,
327 &devinfo);
328 if (rc)
329 goto err;
330
331 /* determine and reserve devt */
332 devt = MKDEV(arg->dev_major, arg->dev_minor);
333 if (!MAJOR(devt))
334 rc = alloc_chrdev_region(&devt, MINOR(devt), 1, devinfo.name);
335 else
336 rc = register_chrdev_region(devt, 1, devinfo.name);
337 if (rc) {
338 printk(KERN_ERR "CUSE: failed to register chrdev region\n");
339 goto err;
340 }
341
342 /* devt determined, create device */
343 rc = -ENOMEM;
344 dev = kzalloc(sizeof(*dev), GFP_KERNEL);
345 if (!dev)
346 goto err_region;
347
348 device_initialize(dev);
349 dev_set_uevent_suppress(dev, 1);
350 dev->class = cuse_class;
351 dev->devt = devt;
352 dev->release = cuse_gendev_release;
353 dev_set_drvdata(dev, cc);
354 dev_set_name(dev, "%s", devinfo.name);
355
356 rc = device_add(dev);
357 if (rc)
358 goto err_device;
359
360 /* register cdev */
361 rc = -ENOMEM;
362 cdev = cdev_alloc();
363 if (!cdev)
364 goto err_device;
365
366 cdev->owner = THIS_MODULE;
367 cdev->ops = &cuse_frontend_fops;
368
369 rc = cdev_add(cdev, devt, 1);
370 if (rc)
371 goto err_cdev;
372
373 cc->dev = dev;
374 cc->cdev = cdev;
375
376 /* make the device available */
377 spin_lock(&cuse_lock);
378 list_add(&cc->list, cuse_conntbl_head(devt));
379 spin_unlock(&cuse_lock);
380
381 /* announce device availability */
382 dev_set_uevent_suppress(dev, 0);
383 kobject_uevent(&dev->kobj, KOBJ_ADD);
384 out:
385 __free_page(page);
386 return;
387
388 err_cdev:
389 cdev_del(cdev);
390 err_device:
391 put_device(dev);
392 err_region:
393 unregister_chrdev_region(devt, 1);
394 err:
395 fc->conn_error = 1;
396 goto out;
397 }
398
399 static int cuse_send_init(struct cuse_conn *cc)
400 {
401 int rc;
402 struct fuse_req *req;
403 struct page *page;
404 struct fuse_conn *fc = &cc->fc;
405 struct cuse_init_in *arg;
406
407 BUILD_BUG_ON(CUSE_INIT_INFO_MAX > PAGE_SIZE);
408
409 req = fuse_get_req(fc);
410 if (IS_ERR(req)) {
411 rc = PTR_ERR(req);
412 goto err;
413 }
414
415 rc = -ENOMEM;
416 page = alloc_page(GFP_KERNEL | __GFP_ZERO);
417 if (!page)
418 goto err_put_req;
419
420 arg = &req->misc.cuse_init_in;
421 arg->major = FUSE_KERNEL_VERSION;
422 arg->minor = FUSE_KERNEL_MINOR_VERSION;
423 arg->flags |= CUSE_UNRESTRICTED_IOCTL;
424 req->in.h.opcode = CUSE_INIT;
425 req->in.numargs = 1;
426 req->in.args[0].size = sizeof(struct cuse_init_in);
427 req->in.args[0].value = arg;
428 req->out.numargs = 2;
429 req->out.args[0].size = sizeof(struct cuse_init_out);
430 req->out.args[0].value = &req->misc.cuse_init_out;
431 req->out.args[1].size = CUSE_INIT_INFO_MAX;
432 req->out.argvar = 1;
433 req->out.argpages = 1;
434 req->pages[0] = page;
435 req->num_pages = 1;
436 req->end = cuse_process_init_reply;
437 fuse_request_send_background(fc, req);
438
439 return 0;
440
441 err_put_req:
442 fuse_put_request(fc, req);
443 err:
444 return rc;
445 }
446
447 static void cuse_fc_release(struct fuse_conn *fc)
448 {
449 struct cuse_conn *cc = fc_to_cc(fc);
450 kfree(cc);
451 }
452
453 /**
454 * cuse_channel_open - open method for /dev/cuse
455 * @inode: inode for /dev/cuse
456 * @file: file struct being opened
457 *
458 * Userland CUSE server can create a CUSE device by opening /dev/cuse
459 * and replying to the initilaization request kernel sends. This
460 * function is responsible for handling CUSE device initialization.
461 * Because the fd opened by this function is used during
462 * initialization, this function only creates cuse_conn and sends
463 * init. The rest is delegated to a kthread.
464 *
465 * RETURNS:
466 * 0 on success, -errno on failure.
467 */
468 static int cuse_channel_open(struct inode *inode, struct file *file)
469 {
470 struct cuse_conn *cc;
471 int rc;
472
473 /* set up cuse_conn */
474 cc = kzalloc(sizeof(*cc), GFP_KERNEL);
475 if (!cc)
476 return -ENOMEM;
477
478 fuse_conn_init(&cc->fc);
479
480 INIT_LIST_HEAD(&cc->list);
481 cc->fc.release = cuse_fc_release;
482
483 cc->fc.connected = 1;
484 cc->fc.blocked = 0;
485 rc = cuse_send_init(cc);
486 if (rc) {
487 fuse_conn_put(&cc->fc);
488 return rc;
489 }
490 file->private_data = &cc->fc; /* channel owns base reference to cc */
491
492 return 0;
493 }
494
495 /**
496 * cuse_channel_release - release method for /dev/cuse
497 * @inode: inode for /dev/cuse
498 * @file: file struct being closed
499 *
500 * Disconnect the channel, deregister CUSE device and initiate
501 * destruction by putting the default reference.
502 *
503 * RETURNS:
504 * 0 on success, -errno on failure.
505 */
506 static int cuse_channel_release(struct inode *inode, struct file *file)
507 {
508 struct cuse_conn *cc = fc_to_cc(file->private_data);
509 int rc;
510
511 /* remove from the conntbl, no more access from this point on */
512 spin_lock(&cuse_lock);
513 list_del_init(&cc->list);
514 spin_unlock(&cuse_lock);
515
516 /* remove device */
517 if (cc->dev)
518 device_unregister(cc->dev);
519 if (cc->cdev) {
520 unregister_chrdev_region(cc->cdev->dev, 1);
521 cdev_del(cc->cdev);
522 }
523
524 /* kill connection and shutdown channel */
525 fuse_conn_kill(&cc->fc);
526 rc = fuse_dev_release(inode, file); /* puts the base reference */
527
528 return rc;
529 }
530
531 static struct file_operations cuse_channel_fops; /* initialized during init */
532
533
534 /**************************************************************************
535 * Misc stuff and module initializatiion
536 *
537 * CUSE exports the same set of attributes to sysfs as fusectl.
538 */
539
540 static ssize_t cuse_class_waiting_show(struct device *dev,
541 struct device_attribute *attr, char *buf)
542 {
543 struct cuse_conn *cc = dev_get_drvdata(dev);
544
545 return sprintf(buf, "%d\n", atomic_read(&cc->fc.num_waiting));
546 }
547
548 static ssize_t cuse_class_abort_store(struct device *dev,
549 struct device_attribute *attr,
550 const char *buf, size_t count)
551 {
552 struct cuse_conn *cc = dev_get_drvdata(dev);
553
554 fuse_abort_conn(&cc->fc);
555 return count;
556 }
557
558 static struct device_attribute cuse_class_dev_attrs[] = {
559 __ATTR(waiting, S_IFREG | 0400, cuse_class_waiting_show, NULL),
560 __ATTR(abort, S_IFREG | 0200, NULL, cuse_class_abort_store),
561 { }
562 };
563
564 static struct miscdevice cuse_miscdev = {
565 .minor = MISC_DYNAMIC_MINOR,
566 .name = "cuse",
567 .fops = &cuse_channel_fops,
568 };
569
570 static int __init cuse_init(void)
571 {
572 int i, rc;
573
574 /* init conntbl */
575 for (i = 0; i < CUSE_CONNTBL_LEN; i++)
576 INIT_LIST_HEAD(&cuse_conntbl[i]);
577
578 /* inherit and extend fuse_dev_operations */
579 cuse_channel_fops = fuse_dev_operations;
580 cuse_channel_fops.owner = THIS_MODULE;
581 cuse_channel_fops.open = cuse_channel_open;
582 cuse_channel_fops.release = cuse_channel_release;
583
584 cuse_class = class_create(THIS_MODULE, "cuse");
585 if (IS_ERR(cuse_class))
586 return PTR_ERR(cuse_class);
587
588 cuse_class->dev_attrs = cuse_class_dev_attrs;
589
590 rc = misc_register(&cuse_miscdev);
591 if (rc) {
592 class_destroy(cuse_class);
593 return rc;
594 }
595
596 return 0;
597 }
598
599 static void __exit cuse_exit(void)
600 {
601 misc_deregister(&cuse_miscdev);
602 class_destroy(cuse_class);
603 }
604
605 module_init(cuse_init);
606 module_exit(cuse_exit);
607
608 MODULE_AUTHOR("Tejun Heo <tj@kernel.org>");
609 MODULE_DESCRIPTION("Character device in Userspace");
610 MODULE_LICENSE("GPL");
611
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