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151060ac TH |
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"); |