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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> | |
5a0e3ad6 | 47 | #include <linux/slab.h> |
151060ac TH |
48 | #include <linux/spinlock.h> |
49 | #include <linux/stat.h> | |
50 | ||
51 | #include "fuse_i.h" | |
52 | ||
53 | #define CUSE_CONNTBL_LEN 64 | |
54 | ||
55 | struct cuse_conn { | |
56 | struct list_head list; /* linked on cuse_conntbl */ | |
57 | struct fuse_conn fc; /* fuse connection */ | |
58 | struct cdev *cdev; /* associated character device */ | |
59 | struct device *dev; /* device representing @cdev */ | |
60 | ||
61 | /* init parameters, set once during initialization */ | |
62 | bool unrestricted_ioctl; | |
63 | }; | |
64 | ||
65 | static DEFINE_SPINLOCK(cuse_lock); /* protects cuse_conntbl */ | |
66 | static struct list_head cuse_conntbl[CUSE_CONNTBL_LEN]; | |
67 | static struct class *cuse_class; | |
68 | ||
69 | static struct cuse_conn *fc_to_cc(struct fuse_conn *fc) | |
70 | { | |
71 | return container_of(fc, struct cuse_conn, fc); | |
72 | } | |
73 | ||
74 | static struct list_head *cuse_conntbl_head(dev_t devt) | |
75 | { | |
76 | return &cuse_conntbl[(MAJOR(devt) + MINOR(devt)) % CUSE_CONNTBL_LEN]; | |
77 | } | |
78 | ||
79 | ||
80 | /************************************************************************** | |
81 | * CUSE frontend operations | |
82 | * | |
83 | * These are file operations for the character device. | |
84 | * | |
85 | * On open, CUSE opens a file from the FUSE mnt and stores it to | |
86 | * private_data of the open file. All other ops call FUSE ops on the | |
87 | * FUSE file. | |
88 | */ | |
89 | ||
90 | static ssize_t cuse_read(struct file *file, char __user *buf, size_t count, | |
91 | loff_t *ppos) | |
92 | { | |
93 | loff_t pos = 0; | |
94 | ||
95 | return fuse_direct_io(file, buf, count, &pos, 0); | |
96 | } | |
97 | ||
98 | static ssize_t cuse_write(struct file *file, const char __user *buf, | |
99 | size_t count, loff_t *ppos) | |
100 | { | |
101 | loff_t pos = 0; | |
102 | /* | |
103 | * No locking or generic_write_checks(), the server is | |
104 | * responsible for locking and sanity checks. | |
105 | */ | |
106 | return fuse_direct_io(file, buf, count, &pos, 1); | |
107 | } | |
108 | ||
109 | static int cuse_open(struct inode *inode, struct file *file) | |
110 | { | |
111 | dev_t devt = inode->i_cdev->dev; | |
112 | struct cuse_conn *cc = NULL, *pos; | |
113 | int rc; | |
114 | ||
115 | /* look up and get the connection */ | |
116 | spin_lock(&cuse_lock); | |
117 | list_for_each_entry(pos, cuse_conntbl_head(devt), list) | |
118 | if (pos->dev->devt == devt) { | |
119 | fuse_conn_get(&pos->fc); | |
120 | cc = pos; | |
121 | break; | |
122 | } | |
123 | spin_unlock(&cuse_lock); | |
124 | ||
125 | /* dead? */ | |
126 | if (!cc) | |
127 | return -ENODEV; | |
128 | ||
129 | /* | |
130 | * Generic permission check is already done against the chrdev | |
131 | * file, proceed to open. | |
132 | */ | |
133 | rc = fuse_do_open(&cc->fc, 0, file, 0); | |
134 | if (rc) | |
135 | fuse_conn_put(&cc->fc); | |
136 | return rc; | |
137 | } | |
138 | ||
139 | static int cuse_release(struct inode *inode, struct file *file) | |
140 | { | |
141 | struct fuse_file *ff = file->private_data; | |
142 | struct fuse_conn *fc = ff->fc; | |
143 | ||
144 | fuse_sync_release(ff, file->f_flags); | |
145 | fuse_conn_put(fc); | |
146 | ||
147 | return 0; | |
148 | } | |
149 | ||
150 | static long cuse_file_ioctl(struct file *file, unsigned int cmd, | |
151 | unsigned long arg) | |
152 | { | |
153 | struct fuse_file *ff = file->private_data; | |
154 | struct cuse_conn *cc = fc_to_cc(ff->fc); | |
155 | unsigned int flags = 0; | |
156 | ||
157 | if (cc->unrestricted_ioctl) | |
158 | flags |= FUSE_IOCTL_UNRESTRICTED; | |
159 | ||
160 | return fuse_do_ioctl(file, cmd, arg, flags); | |
161 | } | |
162 | ||
163 | static long cuse_file_compat_ioctl(struct file *file, unsigned int cmd, | |
164 | unsigned long arg) | |
165 | { | |
166 | struct fuse_file *ff = file->private_data; | |
167 | struct cuse_conn *cc = fc_to_cc(ff->fc); | |
168 | unsigned int flags = FUSE_IOCTL_COMPAT; | |
169 | ||
170 | if (cc->unrestricted_ioctl) | |
171 | flags |= FUSE_IOCTL_UNRESTRICTED; | |
172 | ||
173 | return fuse_do_ioctl(file, cmd, arg, flags); | |
174 | } | |
175 | ||
176 | static const struct file_operations cuse_frontend_fops = { | |
177 | .owner = THIS_MODULE, | |
178 | .read = cuse_read, | |
179 | .write = cuse_write, | |
180 | .open = cuse_open, | |
181 | .release = cuse_release, | |
182 | .unlocked_ioctl = cuse_file_ioctl, | |
183 | .compat_ioctl = cuse_file_compat_ioctl, | |
184 | .poll = fuse_file_poll, | |
185 | }; | |
186 | ||
187 | ||
188 | /************************************************************************** | |
189 | * CUSE channel initialization and destruction | |
190 | */ | |
191 | ||
192 | struct cuse_devinfo { | |
193 | const char *name; | |
194 | }; | |
195 | ||
196 | /** | |
197 | * cuse_parse_one - parse one key=value pair | |
198 | * @pp: i/o parameter for the current position | |
199 | * @end: points to one past the end of the packed string | |
200 | * @keyp: out parameter for key | |
201 | * @valp: out parameter for value | |
202 | * | |
203 | * *@pp points to packed strings - "key0=val0\0key1=val1\0" which ends | |
204 | * at @end - 1. This function parses one pair and set *@keyp to the | |
205 | * start of the key and *@valp to the start of the value. Note that | |
206 | * the original string is modified such that the key string is | |
207 | * terminated with '\0'. *@pp is updated to point to the next string. | |
208 | * | |
209 | * RETURNS: | |
210 | * 1 on successful parse, 0 on EOF, -errno on failure. | |
211 | */ | |
212 | static int cuse_parse_one(char **pp, char *end, char **keyp, char **valp) | |
213 | { | |
214 | char *p = *pp; | |
215 | char *key, *val; | |
216 | ||
217 | while (p < end && *p == '\0') | |
218 | p++; | |
219 | if (p == end) | |
220 | return 0; | |
221 | ||
222 | if (end[-1] != '\0') { | |
223 | printk(KERN_ERR "CUSE: info not properly terminated\n"); | |
224 | return -EINVAL; | |
225 | } | |
226 | ||
227 | key = val = p; | |
228 | p += strlen(p); | |
229 | ||
230 | if (valp) { | |
231 | strsep(&val, "="); | |
232 | if (!val) | |
233 | val = key + strlen(key); | |
234 | key = strstrip(key); | |
235 | val = strstrip(val); | |
236 | } else | |
237 | key = strstrip(key); | |
238 | ||
239 | if (!strlen(key)) { | |
240 | printk(KERN_ERR "CUSE: zero length info key specified\n"); | |
241 | return -EINVAL; | |
242 | } | |
243 | ||
244 | *pp = p; | |
245 | *keyp = key; | |
246 | if (valp) | |
247 | *valp = val; | |
248 | ||
249 | return 1; | |
250 | } | |
251 | ||
252 | /** | |
253 | * cuse_parse_dev_info - parse device info | |
254 | * @p: device info string | |
255 | * @len: length of device info string | |
256 | * @devinfo: out parameter for parsed device info | |
257 | * | |
258 | * Parse @p to extract device info and store it into @devinfo. String | |
259 | * pointed to by @p is modified by parsing and @devinfo points into | |
260 | * them, so @p shouldn't be freed while @devinfo is in use. | |
261 | * | |
262 | * RETURNS: | |
263 | * 0 on success, -errno on failure. | |
264 | */ | |
265 | static int cuse_parse_devinfo(char *p, size_t len, struct cuse_devinfo *devinfo) | |
266 | { | |
267 | char *end = p + len; | |
268 | char *key, *val; | |
269 | int rc; | |
270 | ||
271 | while (true) { | |
272 | rc = cuse_parse_one(&p, end, &key, &val); | |
273 | if (rc < 0) | |
274 | return rc; | |
275 | if (!rc) | |
276 | break; | |
277 | if (strcmp(key, "DEVNAME") == 0) | |
278 | devinfo->name = val; | |
279 | else | |
280 | printk(KERN_WARNING "CUSE: unknown device info \"%s\"\n", | |
281 | key); | |
282 | } | |
283 | ||
284 | if (!devinfo->name || !strlen(devinfo->name)) { | |
285 | printk(KERN_ERR "CUSE: DEVNAME unspecified\n"); | |
286 | return -EINVAL; | |
287 | } | |
288 | ||
289 | return 0; | |
290 | } | |
291 | ||
292 | static void cuse_gendev_release(struct device *dev) | |
293 | { | |
294 | kfree(dev); | |
295 | } | |
296 | ||
297 | /** | |
298 | * cuse_process_init_reply - finish initializing CUSE channel | |
299 | * | |
300 | * This function creates the character device and sets up all the | |
301 | * required data structures for it. Please read the comment at the | |
302 | * top of this file for high level overview. | |
303 | */ | |
304 | static void cuse_process_init_reply(struct fuse_conn *fc, struct fuse_req *req) | |
305 | { | |
306 | struct cuse_conn *cc = fc_to_cc(fc); | |
307 | struct cuse_init_out *arg = &req->misc.cuse_init_out; | |
308 | struct page *page = req->pages[0]; | |
309 | struct cuse_devinfo devinfo = { }; | |
310 | struct device *dev; | |
311 | struct cdev *cdev; | |
312 | dev_t devt; | |
313 | int rc; | |
314 | ||
315 | if (req->out.h.error || | |
316 | arg->major != FUSE_KERNEL_VERSION || arg->minor < 11) { | |
317 | goto err; | |
318 | } | |
319 | ||
320 | fc->minor = arg->minor; | |
321 | fc->max_read = max_t(unsigned, arg->max_read, 4096); | |
322 | fc->max_write = max_t(unsigned, arg->max_write, 4096); | |
323 | ||
324 | /* parse init reply */ | |
325 | cc->unrestricted_ioctl = arg->flags & CUSE_UNRESTRICTED_IOCTL; | |
326 | ||
327 | rc = cuse_parse_devinfo(page_address(page), req->out.args[1].size, | |
328 | &devinfo); | |
329 | if (rc) | |
330 | goto err; | |
331 | ||
332 | /* determine and reserve devt */ | |
333 | devt = MKDEV(arg->dev_major, arg->dev_minor); | |
334 | if (!MAJOR(devt)) | |
335 | rc = alloc_chrdev_region(&devt, MINOR(devt), 1, devinfo.name); | |
336 | else | |
337 | rc = register_chrdev_region(devt, 1, devinfo.name); | |
338 | if (rc) { | |
339 | printk(KERN_ERR "CUSE: failed to register chrdev region\n"); | |
340 | goto err; | |
341 | } | |
342 | ||
343 | /* devt determined, create device */ | |
344 | rc = -ENOMEM; | |
345 | dev = kzalloc(sizeof(*dev), GFP_KERNEL); | |
346 | if (!dev) | |
347 | goto err_region; | |
348 | ||
349 | device_initialize(dev); | |
350 | dev_set_uevent_suppress(dev, 1); | |
351 | dev->class = cuse_class; | |
352 | dev->devt = devt; | |
353 | dev->release = cuse_gendev_release; | |
354 | dev_set_drvdata(dev, cc); | |
355 | dev_set_name(dev, "%s", devinfo.name); | |
356 | ||
357 | rc = device_add(dev); | |
358 | if (rc) | |
359 | goto err_device; | |
360 | ||
361 | /* register cdev */ | |
362 | rc = -ENOMEM; | |
363 | cdev = cdev_alloc(); | |
364 | if (!cdev) | |
365 | goto err_device; | |
366 | ||
367 | cdev->owner = THIS_MODULE; | |
368 | cdev->ops = &cuse_frontend_fops; | |
369 | ||
370 | rc = cdev_add(cdev, devt, 1); | |
371 | if (rc) | |
372 | goto err_cdev; | |
373 | ||
374 | cc->dev = dev; | |
375 | cc->cdev = cdev; | |
376 | ||
377 | /* make the device available */ | |
378 | spin_lock(&cuse_lock); | |
379 | list_add(&cc->list, cuse_conntbl_head(devt)); | |
380 | spin_unlock(&cuse_lock); | |
381 | ||
382 | /* announce device availability */ | |
383 | dev_set_uevent_suppress(dev, 0); | |
384 | kobject_uevent(&dev->kobj, KOBJ_ADD); | |
385 | out: | |
386 | __free_page(page); | |
387 | return; | |
388 | ||
389 | err_cdev: | |
390 | cdev_del(cdev); | |
391 | err_device: | |
392 | put_device(dev); | |
393 | err_region: | |
394 | unregister_chrdev_region(devt, 1); | |
395 | err: | |
396 | fc->conn_error = 1; | |
397 | goto out; | |
398 | } | |
399 | ||
400 | static int cuse_send_init(struct cuse_conn *cc) | |
401 | { | |
402 | int rc; | |
403 | struct fuse_req *req; | |
404 | struct page *page; | |
405 | struct fuse_conn *fc = &cc->fc; | |
406 | struct cuse_init_in *arg; | |
407 | ||
408 | BUILD_BUG_ON(CUSE_INIT_INFO_MAX > PAGE_SIZE); | |
409 | ||
410 | req = fuse_get_req(fc); | |
411 | if (IS_ERR(req)) { | |
412 | rc = PTR_ERR(req); | |
413 | goto err; | |
414 | } | |
415 | ||
416 | rc = -ENOMEM; | |
417 | page = alloc_page(GFP_KERNEL | __GFP_ZERO); | |
418 | if (!page) | |
419 | goto err_put_req; | |
420 | ||
421 | arg = &req->misc.cuse_init_in; | |
422 | arg->major = FUSE_KERNEL_VERSION; | |
423 | arg->minor = FUSE_KERNEL_MINOR_VERSION; | |
424 | arg->flags |= CUSE_UNRESTRICTED_IOCTL; | |
425 | req->in.h.opcode = CUSE_INIT; | |
426 | req->in.numargs = 1; | |
427 | req->in.args[0].size = sizeof(struct cuse_init_in); | |
428 | req->in.args[0].value = arg; | |
429 | req->out.numargs = 2; | |
430 | req->out.args[0].size = sizeof(struct cuse_init_out); | |
431 | req->out.args[0].value = &req->misc.cuse_init_out; | |
432 | req->out.args[1].size = CUSE_INIT_INFO_MAX; | |
433 | req->out.argvar = 1; | |
434 | req->out.argpages = 1; | |
435 | req->pages[0] = page; | |
436 | req->num_pages = 1; | |
437 | req->end = cuse_process_init_reply; | |
438 | fuse_request_send_background(fc, req); | |
439 | ||
440 | return 0; | |
441 | ||
442 | err_put_req: | |
443 | fuse_put_request(fc, req); | |
444 | err: | |
445 | return rc; | |
446 | } | |
447 | ||
448 | static void cuse_fc_release(struct fuse_conn *fc) | |
449 | { | |
450 | struct cuse_conn *cc = fc_to_cc(fc); | |
451 | kfree(cc); | |
452 | } | |
453 | ||
454 | /** | |
455 | * cuse_channel_open - open method for /dev/cuse | |
456 | * @inode: inode for /dev/cuse | |
457 | * @file: file struct being opened | |
458 | * | |
459 | * Userland CUSE server can create a CUSE device by opening /dev/cuse | |
460 | * and replying to the initilaization request kernel sends. This | |
461 | * function is responsible for handling CUSE device initialization. | |
462 | * Because the fd opened by this function is used during | |
463 | * initialization, this function only creates cuse_conn and sends | |
464 | * init. The rest is delegated to a kthread. | |
465 | * | |
466 | * RETURNS: | |
467 | * 0 on success, -errno on failure. | |
468 | */ | |
469 | static int cuse_channel_open(struct inode *inode, struct file *file) | |
470 | { | |
471 | struct cuse_conn *cc; | |
472 | int rc; | |
473 | ||
474 | /* set up cuse_conn */ | |
475 | cc = kzalloc(sizeof(*cc), GFP_KERNEL); | |
476 | if (!cc) | |
477 | return -ENOMEM; | |
478 | ||
479 | fuse_conn_init(&cc->fc); | |
480 | ||
481 | INIT_LIST_HEAD(&cc->list); | |
482 | cc->fc.release = cuse_fc_release; | |
483 | ||
484 | cc->fc.connected = 1; | |
485 | cc->fc.blocked = 0; | |
486 | rc = cuse_send_init(cc); | |
487 | if (rc) { | |
488 | fuse_conn_put(&cc->fc); | |
489 | return rc; | |
490 | } | |
491 | file->private_data = &cc->fc; /* channel owns base reference to cc */ | |
492 | ||
493 | return 0; | |
494 | } | |
495 | ||
496 | /** | |
497 | * cuse_channel_release - release method for /dev/cuse | |
498 | * @inode: inode for /dev/cuse | |
499 | * @file: file struct being closed | |
500 | * | |
501 | * Disconnect the channel, deregister CUSE device and initiate | |
502 | * destruction by putting the default reference. | |
503 | * | |
504 | * RETURNS: | |
505 | * 0 on success, -errno on failure. | |
506 | */ | |
507 | static int cuse_channel_release(struct inode *inode, struct file *file) | |
508 | { | |
509 | struct cuse_conn *cc = fc_to_cc(file->private_data); | |
510 | int rc; | |
511 | ||
512 | /* remove from the conntbl, no more access from this point on */ | |
513 | spin_lock(&cuse_lock); | |
514 | list_del_init(&cc->list); | |
515 | spin_unlock(&cuse_lock); | |
516 | ||
517 | /* remove device */ | |
518 | if (cc->dev) | |
519 | device_unregister(cc->dev); | |
520 | if (cc->cdev) { | |
521 | unregister_chrdev_region(cc->cdev->dev, 1); | |
522 | cdev_del(cc->cdev); | |
523 | } | |
524 | ||
525 | /* kill connection and shutdown channel */ | |
526 | fuse_conn_kill(&cc->fc); | |
527 | rc = fuse_dev_release(inode, file); /* puts the base reference */ | |
528 | ||
529 | return rc; | |
530 | } | |
531 | ||
532 | static struct file_operations cuse_channel_fops; /* initialized during init */ | |
533 | ||
534 | ||
535 | /************************************************************************** | |
536 | * Misc stuff and module initializatiion | |
537 | * | |
538 | * CUSE exports the same set of attributes to sysfs as fusectl. | |
539 | */ | |
540 | ||
541 | static ssize_t cuse_class_waiting_show(struct device *dev, | |
542 | struct device_attribute *attr, char *buf) | |
543 | { | |
544 | struct cuse_conn *cc = dev_get_drvdata(dev); | |
545 | ||
546 | return sprintf(buf, "%d\n", atomic_read(&cc->fc.num_waiting)); | |
547 | } | |
548 | ||
549 | static ssize_t cuse_class_abort_store(struct device *dev, | |
550 | struct device_attribute *attr, | |
551 | const char *buf, size_t count) | |
552 | { | |
553 | struct cuse_conn *cc = dev_get_drvdata(dev); | |
554 | ||
555 | fuse_abort_conn(&cc->fc); | |
556 | return count; | |
557 | } | |
558 | ||
559 | static struct device_attribute cuse_class_dev_attrs[] = { | |
560 | __ATTR(waiting, S_IFREG | 0400, cuse_class_waiting_show, NULL), | |
561 | __ATTR(abort, S_IFREG | 0200, NULL, cuse_class_abort_store), | |
562 | { } | |
563 | }; | |
564 | ||
565 | static struct miscdevice cuse_miscdev = { | |
566 | .minor = MISC_DYNAMIC_MINOR, | |
567 | .name = "cuse", | |
568 | .fops = &cuse_channel_fops, | |
569 | }; | |
570 | ||
571 | static int __init cuse_init(void) | |
572 | { | |
573 | int i, rc; | |
574 | ||
575 | /* init conntbl */ | |
576 | for (i = 0; i < CUSE_CONNTBL_LEN; i++) | |
577 | INIT_LIST_HEAD(&cuse_conntbl[i]); | |
578 | ||
579 | /* inherit and extend fuse_dev_operations */ | |
580 | cuse_channel_fops = fuse_dev_operations; | |
581 | cuse_channel_fops.owner = THIS_MODULE; | |
582 | cuse_channel_fops.open = cuse_channel_open; | |
583 | cuse_channel_fops.release = cuse_channel_release; | |
584 | ||
585 | cuse_class = class_create(THIS_MODULE, "cuse"); | |
586 | if (IS_ERR(cuse_class)) | |
587 | return PTR_ERR(cuse_class); | |
588 | ||
589 | cuse_class->dev_attrs = cuse_class_dev_attrs; | |
590 | ||
591 | rc = misc_register(&cuse_miscdev); | |
592 | if (rc) { | |
593 | class_destroy(cuse_class); | |
594 | return rc; | |
595 | } | |
596 | ||
597 | return 0; | |
598 | } | |
599 | ||
600 | static void __exit cuse_exit(void) | |
601 | { | |
602 | misc_deregister(&cuse_miscdev); | |
603 | class_destroy(cuse_class); | |
604 | } | |
605 | ||
606 | module_init(cuse_init); | |
607 | module_exit(cuse_exit); | |
608 | ||
609 | MODULE_AUTHOR("Tejun Heo <tj@kernel.org>"); | |
610 | MODULE_DESCRIPTION("Character device in Userspace"); | |
611 | MODULE_LICENSE("GPL"); |