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Tejun Heo151060a2009-04-14 10:54:54 +09001/*
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>
Tejun Heo5a0e3ad2010-03-24 17:04:11 +090047#include <linux/slab.h>
Tejun Heo151060a2009-04-14 10:54:54 +090048#include <linux/spinlock.h>
49#include <linux/stat.h>
50
51#include "fuse_i.h"
52
53#define CUSE_CONNTBL_LEN 64
54
55struct 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
65static DEFINE_SPINLOCK(cuse_lock); /* protects cuse_conntbl */
66static struct list_head cuse_conntbl[CUSE_CONNTBL_LEN];
67static struct class *cuse_class;
68
69static struct cuse_conn *fc_to_cc(struct fuse_conn *fc)
70{
71 return container_of(fc, struct cuse_conn, fc);
72}
73
74static 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
90static 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
98static 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
109static 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
139static 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
150static 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
163static 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
176static 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,
Arnd Bergmann6038f372010-08-15 18:52:59 +0200185 .llseek = noop_llseek,
Tejun Heo151060a2009-04-14 10:54:54 +0900186};
187
188
189/**************************************************************************
190 * CUSE channel initialization and destruction
191 */
192
193struct cuse_devinfo {
194 const char *name;
195};
196
197/**
198 * cuse_parse_one - parse one key=value pair
199 * @pp: i/o parameter for the current position
200 * @end: points to one past the end of the packed string
201 * @keyp: out parameter for key
202 * @valp: out parameter for value
203 *
204 * *@pp points to packed strings - "key0=val0\0key1=val1\0" which ends
205 * at @end - 1. This function parses one pair and set *@keyp to the
206 * start of the key and *@valp to the start of the value. Note that
207 * the original string is modified such that the key string is
208 * terminated with '\0'. *@pp is updated to point to the next string.
209 *
210 * RETURNS:
211 * 1 on successful parse, 0 on EOF, -errno on failure.
212 */
213static int cuse_parse_one(char **pp, char *end, char **keyp, char **valp)
214{
215 char *p = *pp;
216 char *key, *val;
217
218 while (p < end && *p == '\0')
219 p++;
220 if (p == end)
221 return 0;
222
223 if (end[-1] != '\0') {
224 printk(KERN_ERR "CUSE: info not properly terminated\n");
225 return -EINVAL;
226 }
227
228 key = val = p;
229 p += strlen(p);
230
231 if (valp) {
232 strsep(&val, "=");
233 if (!val)
234 val = key + strlen(key);
235 key = strstrip(key);
236 val = strstrip(val);
237 } else
238 key = strstrip(key);
239
240 if (!strlen(key)) {
241 printk(KERN_ERR "CUSE: zero length info key specified\n");
242 return -EINVAL;
243 }
244
245 *pp = p;
246 *keyp = key;
247 if (valp)
248 *valp = val;
249
250 return 1;
251}
252
253/**
254 * cuse_parse_dev_info - parse device info
255 * @p: device info string
256 * @len: length of device info string
257 * @devinfo: out parameter for parsed device info
258 *
259 * Parse @p to extract device info and store it into @devinfo. String
260 * pointed to by @p is modified by parsing and @devinfo points into
261 * them, so @p shouldn't be freed while @devinfo is in use.
262 *
263 * RETURNS:
264 * 0 on success, -errno on failure.
265 */
266static int cuse_parse_devinfo(char *p, size_t len, struct cuse_devinfo *devinfo)
267{
268 char *end = p + len;
269 char *key, *val;
270 int rc;
271
272 while (true) {
273 rc = cuse_parse_one(&p, end, &key, &val);
274 if (rc < 0)
275 return rc;
276 if (!rc)
277 break;
278 if (strcmp(key, "DEVNAME") == 0)
279 devinfo->name = val;
280 else
281 printk(KERN_WARNING "CUSE: unknown device info \"%s\"\n",
282 key);
283 }
284
285 if (!devinfo->name || !strlen(devinfo->name)) {
286 printk(KERN_ERR "CUSE: DEVNAME unspecified\n");
287 return -EINVAL;
288 }
289
290 return 0;
291}
292
293static void cuse_gendev_release(struct device *dev)
294{
295 kfree(dev);
296}
297
298/**
299 * cuse_process_init_reply - finish initializing CUSE channel
300 *
301 * This function creates the character device and sets up all the
302 * required data structures for it. Please read the comment at the
303 * top of this file for high level overview.
304 */
305static void cuse_process_init_reply(struct fuse_conn *fc, struct fuse_req *req)
306{
307 struct cuse_conn *cc = fc_to_cc(fc);
308 struct cuse_init_out *arg = &req->misc.cuse_init_out;
309 struct page *page = req->pages[0];
310 struct cuse_devinfo devinfo = { };
311 struct device *dev;
312 struct cdev *cdev;
313 dev_t devt;
314 int rc;
315
316 if (req->out.h.error ||
317 arg->major != FUSE_KERNEL_VERSION || arg->minor < 11) {
318 goto err;
319 }
320
321 fc->minor = arg->minor;
322 fc->max_read = max_t(unsigned, arg->max_read, 4096);
323 fc->max_write = max_t(unsigned, arg->max_write, 4096);
324
325 /* parse init reply */
326 cc->unrestricted_ioctl = arg->flags & CUSE_UNRESTRICTED_IOCTL;
327
328 rc = cuse_parse_devinfo(page_address(page), req->out.args[1].size,
329 &devinfo);
330 if (rc)
331 goto err;
332
333 /* determine and reserve devt */
334 devt = MKDEV(arg->dev_major, arg->dev_minor);
335 if (!MAJOR(devt))
336 rc = alloc_chrdev_region(&devt, MINOR(devt), 1, devinfo.name);
337 else
338 rc = register_chrdev_region(devt, 1, devinfo.name);
339 if (rc) {
340 printk(KERN_ERR "CUSE: failed to register chrdev region\n");
341 goto err;
342 }
343
344 /* devt determined, create device */
345 rc = -ENOMEM;
346 dev = kzalloc(sizeof(*dev), GFP_KERNEL);
347 if (!dev)
348 goto err_region;
349
350 device_initialize(dev);
351 dev_set_uevent_suppress(dev, 1);
352 dev->class = cuse_class;
353 dev->devt = devt;
354 dev->release = cuse_gendev_release;
355 dev_set_drvdata(dev, cc);
356 dev_set_name(dev, "%s", devinfo.name);
357
358 rc = device_add(dev);
359 if (rc)
360 goto err_device;
361
362 /* register cdev */
363 rc = -ENOMEM;
364 cdev = cdev_alloc();
365 if (!cdev)
366 goto err_device;
367
368 cdev->owner = THIS_MODULE;
369 cdev->ops = &cuse_frontend_fops;
370
371 rc = cdev_add(cdev, devt, 1);
372 if (rc)
373 goto err_cdev;
374
375 cc->dev = dev;
376 cc->cdev = cdev;
377
378 /* make the device available */
379 spin_lock(&cuse_lock);
380 list_add(&cc->list, cuse_conntbl_head(devt));
381 spin_unlock(&cuse_lock);
382
383 /* announce device availability */
384 dev_set_uevent_suppress(dev, 0);
385 kobject_uevent(&dev->kobj, KOBJ_ADD);
386out:
387 __free_page(page);
388 return;
389
390err_cdev:
391 cdev_del(cdev);
392err_device:
393 put_device(dev);
394err_region:
395 unregister_chrdev_region(devt, 1);
396err:
397 fc->conn_error = 1;
398 goto out;
399}
400
401static int cuse_send_init(struct cuse_conn *cc)
402{
403 int rc;
404 struct fuse_req *req;
405 struct page *page;
406 struct fuse_conn *fc = &cc->fc;
407 struct cuse_init_in *arg;
408
409 BUILD_BUG_ON(CUSE_INIT_INFO_MAX > PAGE_SIZE);
410
411 req = fuse_get_req(fc);
412 if (IS_ERR(req)) {
413 rc = PTR_ERR(req);
414 goto err;
415 }
416
417 rc = -ENOMEM;
418 page = alloc_page(GFP_KERNEL | __GFP_ZERO);
419 if (!page)
420 goto err_put_req;
421
422 arg = &req->misc.cuse_init_in;
423 arg->major = FUSE_KERNEL_VERSION;
424 arg->minor = FUSE_KERNEL_MINOR_VERSION;
425 arg->flags |= CUSE_UNRESTRICTED_IOCTL;
426 req->in.h.opcode = CUSE_INIT;
427 req->in.numargs = 1;
428 req->in.args[0].size = sizeof(struct cuse_init_in);
429 req->in.args[0].value = arg;
430 req->out.numargs = 2;
431 req->out.args[0].size = sizeof(struct cuse_init_out);
432 req->out.args[0].value = &req->misc.cuse_init_out;
433 req->out.args[1].size = CUSE_INIT_INFO_MAX;
434 req->out.argvar = 1;
435 req->out.argpages = 1;
436 req->pages[0] = page;
437 req->num_pages = 1;
438 req->end = cuse_process_init_reply;
439 fuse_request_send_background(fc, req);
440
441 return 0;
442
443err_put_req:
444 fuse_put_request(fc, req);
445err:
446 return rc;
447}
448
449static void cuse_fc_release(struct fuse_conn *fc)
450{
451 struct cuse_conn *cc = fc_to_cc(fc);
452 kfree(cc);
453}
454
455/**
456 * cuse_channel_open - open method for /dev/cuse
457 * @inode: inode for /dev/cuse
458 * @file: file struct being opened
459 *
460 * Userland CUSE server can create a CUSE device by opening /dev/cuse
Paul Bolle8272f4c2011-02-15 00:05:34 +0100461 * and replying to the initialization request kernel sends. This
Tejun Heo151060a2009-04-14 10:54:54 +0900462 * function is responsible for handling CUSE device initialization.
463 * Because the fd opened by this function is used during
464 * initialization, this function only creates cuse_conn and sends
465 * init. The rest is delegated to a kthread.
466 *
467 * RETURNS:
468 * 0 on success, -errno on failure.
469 */
470static int cuse_channel_open(struct inode *inode, struct file *file)
471{
472 struct cuse_conn *cc;
473 int rc;
474
475 /* set up cuse_conn */
476 cc = kzalloc(sizeof(*cc), GFP_KERNEL);
477 if (!cc)
478 return -ENOMEM;
479
480 fuse_conn_init(&cc->fc);
481
482 INIT_LIST_HEAD(&cc->list);
483 cc->fc.release = cuse_fc_release;
484
485 cc->fc.connected = 1;
486 cc->fc.blocked = 0;
487 rc = cuse_send_init(cc);
488 if (rc) {
489 fuse_conn_put(&cc->fc);
490 return rc;
491 }
492 file->private_data = &cc->fc; /* channel owns base reference to cc */
493
494 return 0;
495}
496
497/**
498 * cuse_channel_release - release method for /dev/cuse
499 * @inode: inode for /dev/cuse
500 * @file: file struct being closed
501 *
502 * Disconnect the channel, deregister CUSE device and initiate
503 * destruction by putting the default reference.
504 *
505 * RETURNS:
506 * 0 on success, -errno on failure.
507 */
508static int cuse_channel_release(struct inode *inode, struct file *file)
509{
510 struct cuse_conn *cc = fc_to_cc(file->private_data);
511 int rc;
512
513 /* remove from the conntbl, no more access from this point on */
514 spin_lock(&cuse_lock);
515 list_del_init(&cc->list);
516 spin_unlock(&cuse_lock);
517
518 /* remove device */
519 if (cc->dev)
520 device_unregister(cc->dev);
521 if (cc->cdev) {
522 unregister_chrdev_region(cc->cdev->dev, 1);
523 cdev_del(cc->cdev);
524 }
525
526 /* kill connection and shutdown channel */
527 fuse_conn_kill(&cc->fc);
528 rc = fuse_dev_release(inode, file); /* puts the base reference */
529
530 return rc;
531}
532
533static struct file_operations cuse_channel_fops; /* initialized during init */
534
535
536/**************************************************************************
537 * Misc stuff and module initializatiion
538 *
539 * CUSE exports the same set of attributes to sysfs as fusectl.
540 */
541
542static ssize_t cuse_class_waiting_show(struct device *dev,
543 struct device_attribute *attr, char *buf)
544{
545 struct cuse_conn *cc = dev_get_drvdata(dev);
546
547 return sprintf(buf, "%d\n", atomic_read(&cc->fc.num_waiting));
548}
549
550static ssize_t cuse_class_abort_store(struct device *dev,
551 struct device_attribute *attr,
552 const char *buf, size_t count)
553{
554 struct cuse_conn *cc = dev_get_drvdata(dev);
555
556 fuse_abort_conn(&cc->fc);
557 return count;
558}
559
560static struct device_attribute cuse_class_dev_attrs[] = {
561 __ATTR(waiting, S_IFREG | 0400, cuse_class_waiting_show, NULL),
562 __ATTR(abort, S_IFREG | 0200, NULL, cuse_class_abort_store),
563 { }
564};
565
566static struct miscdevice cuse_miscdev = {
567 .minor = MISC_DYNAMIC_MINOR,
568 .name = "cuse",
569 .fops = &cuse_channel_fops,
570};
571
572static int __init cuse_init(void)
573{
574 int i, rc;
575
576 /* init conntbl */
577 for (i = 0; i < CUSE_CONNTBL_LEN; i++)
578 INIT_LIST_HEAD(&cuse_conntbl[i]);
579
580 /* inherit and extend fuse_dev_operations */
581 cuse_channel_fops = fuse_dev_operations;
582 cuse_channel_fops.owner = THIS_MODULE;
583 cuse_channel_fops.open = cuse_channel_open;
584 cuse_channel_fops.release = cuse_channel_release;
585
586 cuse_class = class_create(THIS_MODULE, "cuse");
587 if (IS_ERR(cuse_class))
588 return PTR_ERR(cuse_class);
589
590 cuse_class->dev_attrs = cuse_class_dev_attrs;
591
592 rc = misc_register(&cuse_miscdev);
593 if (rc) {
594 class_destroy(cuse_class);
595 return rc;
596 }
597
598 return 0;
599}
600
601static void __exit cuse_exit(void)
602{
603 misc_deregister(&cuse_miscdev);
604 class_destroy(cuse_class);
605}
606
607module_init(cuse_init);
608module_exit(cuse_exit);
609
610MODULE_AUTHOR("Tejun Heo <tj@kernel.org>");
611MODULE_DESCRIPTION("Character device in Userspace");
612MODULE_LICENSE("GPL");