aboutsummaryrefslogtreecommitdiff
path: root/fs/fuse/cuse.c
blob: eae2c11268bcb484075cfd08482beeb172dd66bc (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
/*
 * CUSE: Character device in Userspace
 *
 * Copyright (C) 2008-2009  SUSE Linux Products GmbH
 * Copyright (C) 2008-2009  Tejun Heo <tj@kernel.org>
 *
 * This file is released under the GPLv2.
 *
 * CUSE enables character devices to be implemented from userland much
 * like FUSE allows filesystems.  On initialization /dev/cuse is
 * created.  By opening the file and replying to the CUSE_INIT request
 * userland CUSE server can create a character device.  After that the
 * operation is very similar to FUSE.
 *
 * A CUSE instance involves the following objects.
 *
 * cuse_conn	: contains fuse_conn and serves as bonding structure
 * channel	: file handle connected to the userland CUSE server
 * cdev		: the implemented character device
 * dev		: generic device for cdev
 *
 * Note that 'channel' is what 'dev' is in FUSE.  As CUSE deals with
 * devices, it's called 'channel' to reduce confusion.
 *
 * channel determines when the character device dies.  When channel is
 * closed, everything begins to destruct.  The cuse_conn is taken off
 * the lookup table preventing further access from cdev, cdev and
 * generic device are removed and the base reference of cuse_conn is
 * put.
 *
 * On each open, the matching cuse_conn is looked up and if found an
 * additional reference is taken which is released when the file is
 * closed.
 */

#include <linux/fuse.h>
#include <linux/cdev.h>
#include <linux/device.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/kdev_t.h>
#include <linux/kthread.h>
#include <linux/list.h>
#include <linux/magic.h>
#include <linux/miscdevice.h>
#include <linux/mutex.h>
#include <linux/slab.h>
#include <linux/stat.h>
#include <linux/module.h>
#include <linux/uio.h>

#include "fuse_i.h"

#define CUSE_CONNTBL_LEN	64

struct cuse_conn {
	struct list_head	list;	/* linked on cuse_conntbl */
	struct fuse_conn	fc;	/* fuse connection */
	struct cdev		*cdev;	/* associated character device */
	struct device		*dev;	/* device representing @cdev */

	/* init parameters, set once during initialization */
	bool			unrestricted_ioctl;
};

static DEFINE_MUTEX(cuse_lock);		/* protects registration */
static struct list_head cuse_conntbl[CUSE_CONNTBL_LEN];
static struct class *cuse_class;

static struct cuse_conn *fc_to_cc(struct fuse_conn *fc)
{
	return container_of(fc, struct cuse_conn, fc);
}

static struct list_head *cuse_conntbl_head(dev_t devt)
{
	return &cuse_conntbl[(MAJOR(devt) + MINOR(devt)) % CUSE_CONNTBL_LEN];
}


/**************************************************************************
 * CUSE frontend operations
 *
 * These are file operations for the character device.
 *
 * On open, CUSE opens a file from the FUSE mnt and stores it to
 * private_data of the open file.  All other ops call FUSE ops on the
 * FUSE file.
 */

static ssize_t cuse_read_iter(struct kiocb *kiocb, struct iov_iter *to)
{
	struct fuse_io_priv io = { .async = 0, .file = kiocb->ki_filp };
	loff_t pos = 0;

	return fuse_direct_io(&io, to, &pos, FUSE_DIO_CUSE);
}

static ssize_t cuse_write_iter(struct kiocb *kiocb, struct iov_iter *from)
{
	struct fuse_io_priv io = { .async = 0, .file = kiocb->ki_filp };
	loff_t pos = 0;
	/*
	 * No locking or generic_write_checks(), the server is
	 * responsible for locking and sanity checks.
	 */
	return fuse_direct_io(&io, from, &pos,
			      FUSE_DIO_WRITE | FUSE_DIO_CUSE);
}

static int cuse_open(struct inode *inode, struct file *file)
{
	dev_t devt = inode->i_cdev->dev;
	struct cuse_conn *cc = NULL, *pos;
	int rc;

	/* look up and get the connection */
	mutex_lock(&cuse_lock);
	list_for_each_entry(pos, cuse_conntbl_head(devt), list)
		if (pos->dev->devt == devt) {
			fuse_conn_get(&pos->fc);
			cc = pos;
			break;
		}
	mutex_unlock(&cuse_lock);

	/* dead? */
	if (!cc)
		return -ENODEV;

	/*
	 * Generic permission check is already done against the chrdev
	 * file, proceed to open.
	 */
	rc = fuse_do_open(&cc->fc, 0, file, 0);
	if (rc)
		fuse_conn_put(&cc->fc);
	return rc;
}

static int cuse_release(struct inode *inode, struct file *file)
{
	struct fuse_file *ff = file->private_data;
	struct fuse_conn *fc = ff->fc;

	fuse_sync_release(ff, file->f_flags);
	fuse_conn_put(fc);

	return 0;
}

static long cuse_file_ioctl(struct file *file, unsigned int cmd,
			    unsigned long arg)
{
	struct fuse_file *ff = file->private_data;
	struct cuse_conn *cc = fc_to_cc(ff->fc);
	unsigned int flags = 0;

	if (cc->unrestricted_ioctl)
		flags |= FUSE_IOCTL_UNRESTRICTED;

	return fuse_do_ioctl(file, cmd, arg, flags);
}

static long cuse_file_compat_ioctl(struct file *file, unsigned int cmd,
				   unsigned long arg)
{
	struct fuse_file *ff = file->private_data;
	struct cuse_conn *cc = fc_to_cc(ff->fc);
	unsigned int flags = FUSE_IOCTL_COMPAT;

	if (cc->unrestricted_ioctl)
		flags |= FUSE_IOCTL_UNRESTRICTED;

	return fuse_do_ioctl(file, cmd, arg, flags);
}

static const struct file_operations cuse_frontend_fops = {
	.owner			= THIS_MODULE,
	.read_iter		= cuse_read_iter,
	.write_iter		= cuse_write_iter,
	.open			= cuse_open,
	.release		= cuse_release,
	.unlocked_ioctl		= cuse_file_ioctl,
	.compat_ioctl		= cuse_file_compat_ioctl,
	.poll			= fuse_file_poll,
	.llseek		= noop_llseek,
};


/**************************************************************************
 * CUSE channel initialization and destruction
 */

struct cuse_devinfo {
	const char		*name;
};

/**
 * cuse_parse_one - parse one key=value pair
 * @pp: i/o parameter for the current position
 * @end: points to one past the end of the packed string
 * @keyp: out parameter for key
 * @valp: out parameter for value
 *
 * *@pp points to packed strings - "key0=val0\0key1=val1\0" which ends
 * at @end - 1.  This function parses one pair and set *@keyp to the
 * start of the key and *@valp to the start of the value.  Note that
 * the original string is modified such that the key string is
 * terminated with '\0'.  *@pp is updated to point to the next string.
 *
 * RETURNS:
 * 1 on successful parse, 0 on EOF, -errno on failure.
 */
static int cuse_parse_one(char **pp, char *end, char **keyp, char **valp)
{
	char *p = *pp;
	char *key, *val;

	while (p < end && *p == '\0')
		p++;
	if (p == end)
		return 0;

	if (end[-1] != '\0') {
		printk(KERN_ERR "CUSE: info not properly terminated\n");
		return -EINVAL;
	}

	key = val = p;
	p += strlen(p);

	if (valp) {
		strsep(&val, "=");
		if (!val)
			val = key + strlen(key);
		key = strstrip(key);
		val = strstrip(val);
	} else
		key = strstrip(key);

	if (!strlen(key)) {
		printk(KERN_ERR "CUSE: zero length info key specified\n");
		return -EINVAL;
	}

	*pp = p;
	*keyp = key;
	if (valp)
		*valp = val;

	return 1;
}

/**
 * cuse_parse_dev_info - parse device info
 * @p: device info string
 * @len: length of device info string
 * @devinfo: out parameter for parsed device info
 *
 * Parse @p to extract device info and store it into @devinfo.  String
 * pointed to by @p is modified by parsing and @devinfo points into
 * them, so @p shouldn't be freed while @devinfo is in use.
 *
 * RETURNS:
 * 0 on success, -errno on failure.
 */
static int cuse_parse_devinfo(char *p, size_t len, struct cuse_devinfo *devinfo)
{
	char *end = p + len;
	char *uninitialized_var(key), *uninitialized_var(val);
	int rc;

	while (true) {
		rc = cuse_parse_one(&p, end, &key, &val);
		if (rc < 0)
			return rc;
		if (!rc)
			break;
		if (strcmp(key, "DEVNAME") == 0)
			devinfo->name = val;
		else
			printk(KERN_WARNING "CUSE: unknown device info \"%s\"\n",
			       key);
	}

	if (!devinfo->name || !strlen(devinfo->name)) {
		printk(KERN_ERR "CUSE: DEVNAME unspecified\n");
		return -EINVAL;
	}

	return 0;
}

static void cuse_gendev_release(struct device *dev)
{
	kfree(dev);
}

/**
 * cuse_process_init_reply - finish initializing CUSE channel
 *
 * This function creates the character device and sets up all the
 * required data structures for it.  Please read the comment at the
 * top of this file for high level overview.
 */
static void cuse_process_init_reply(struct fuse_conn *fc, struct fuse_req *req)
{
	struct cuse_conn *cc = fc_to_cc(fc), *pos;
	struct cuse_init_out *arg = req->out.args[0].value;
	struct page *page = req->pages[0];
	struct cuse_devinfo devinfo = { };
	struct device *dev;
	struct cdev *cdev;
	dev_t devt;
	int rc, i;

	if (req->out.h.error ||
	    arg->major != FUSE_KERNEL_VERSION || arg->minor < 11) {
		goto err;
	}

	fc->minor = arg->minor;
	fc->max_read = max_t(unsigned, arg->max_read, 4096);
	fc->max_write = max_t(unsigned, arg->max_write, 4096);

	/* parse init reply */
	cc->unrestricted_ioctl = arg->flags & CUSE_UNRESTRICTED_IOCTL;

	rc = cuse_parse_devinfo(page_address(page), req->out.args[1].size,
				&devinfo);
	if (rc)
		goto err;

	/* determine and reserve devt */
	devt = MKDEV(arg->dev_major, arg->dev_minor);
	if (!MAJOR(devt))
		rc = alloc_chrdev_region(&devt, MINOR(devt), 1, devinfo.name);
	else
		rc = register_chrdev_region(devt, 1, devinfo.name);
	if (rc) {
		printk(KERN_ERR "CUSE: failed to register chrdev region\n");
		goto err;
	}

	/* devt determined, create device */
	rc = -ENOMEM;
	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
	if (!dev)
		goto err_region;

	device_initialize(dev);
	dev_set_uevent_suppress(dev, 1);
	dev->class = cuse_class;
	dev->devt = devt;
	dev->release = cuse_gendev_release;
	dev_set_drvdata(dev, cc);
	dev_set_name(dev, "%s", devinfo.name);

	mutex_lock(&cuse_lock);

	/* make sure the device-name is unique */
	for (i = 0; i < CUSE_CONNTBL_LEN; ++i) {
		list_for_each_entry(pos, &cuse_conntbl[i], list)
			if (!strcmp(dev_name(pos->dev), dev_name(dev)))
				goto err_unlock;
	}

	rc = device_add(dev);
	if (rc)
		goto err_unlock;

	/* register cdev */
	rc = -ENOMEM;
	cdev = cdev_alloc();
	if (!cdev)
		goto err_unlock;

	cdev->owner = THIS_MODULE;
	cdev->ops = &cuse_frontend_fops;

	rc = cdev_add(cdev, devt, 1);
	if (rc)
		goto err_cdev;

	cc->dev = dev;
	cc->cdev = cdev;

	/* make the device available */
	list_add(&cc->list, cuse_conntbl_head(devt));
	mutex_unlock(&cuse_lock);

	/* announce device availability */
	dev_set_uevent_suppress(dev, 0);
	kobject_uevent(&dev->kobj, KOBJ_ADD);
out:
	kfree(arg);
	__free_page(page);
	return;

err_cdev:
	cdev_del(cdev);
err_unlock:
	mutex_unlock(&cuse_lock);
	put_device(dev);
err_region:
	unregister_chrdev_region(devt, 1);
err:
	fuse_abort_conn(fc);
	goto out;
}

static int cuse_send_init(struct cuse_conn *cc)
{
	int rc;
	struct fuse_req *req;
	struct page *page;
	struct fuse_conn *fc = &cc->fc;
	struct cuse_init_in *arg;
	void *outarg;

	BUILD_BUG_ON(CUSE_INIT_INFO_MAX > PAGE_SIZE);

	req = fuse_get_req_for_background(fc, 1);
	if (IS_ERR(req)) {
		rc = PTR_ERR(req);
		goto err;
	}

	rc = -ENOMEM;
	page = alloc_page(GFP_KERNEL | __GFP_ZERO);
	if (!page)
		goto err_put_req;

	outarg = kzalloc(sizeof(struct cuse_init_out), GFP_KERNEL);
	if (!outarg)
		goto err_free_page;

	arg = &req->misc.cuse_init_in;
	arg->major = FUSE_KERNEL_VERSION;
	arg->minor = FUSE_KERNEL_MINOR_VERSION;
	arg->flags |= CUSE_UNRESTRICTED_IOCTL;
	req->in.h.opcode = CUSE_INIT;
	req->in.numargs = 1;
	req->in.args[0].size = sizeof(struct cuse_init_in);
	req->in.args[0].value = arg;
	req->out.numargs = 2;
	req->out.args[0].size = sizeof(struct cuse_init_out);
	req->out.args[0].value = outarg;
	req->out.args[1].size = CUSE_INIT_INFO_MAX;
	req->out.argvar = 1;
	req->out.argpages = 1;
	req->pages[0] = page;
	req->page_descs[0].length = req->out.args[1].size;
	req->num_pages = 1;
	req->end = cuse_process_init_reply;
	fuse_request_send_background(fc, req);

	return 0;

err_free_page:
	__free_page(page);
err_put_req:
	fuse_put_request(fc, req);
err:
	return rc;
}

static void cuse_fc_release(struct fuse_conn *fc)
{
	struct cuse_conn *cc = fc_to_cc(fc);
	kfree_rcu(cc, fc.rcu);
}

/**
 * cuse_channel_open - open method for /dev/cuse
 * @inode: inode for /dev/cuse
 * @file: file struct being opened
 *
 * Userland CUSE server can create a CUSE device by opening /dev/cuse
 * and replying to the initialization request kernel sends.  This
 * function is responsible for handling CUSE device initialization.
 * Because the fd opened by this function is used during
 * initialization, this function only creates cuse_conn and sends
 * init.  The rest is delegated to a kthread.
 *
 * RETURNS:
 * 0 on success, -errno on failure.
 */
static int cuse_channel_open(struct inode *inode, struct file *file)
{
	struct fuse_dev *fud;
	struct cuse_conn *cc;
	int rc;

	/* set up cuse_conn */
	cc = kzalloc(sizeof(*cc), GFP_KERNEL);
	if (!cc)
		return -ENOMEM;

	fuse_conn_init(&cc->fc);

	fud = fuse_dev_alloc(&cc->fc);
	if (!fud) {
		kfree(cc);
		return -ENOMEM;
	}

	INIT_LIST_HEAD(&cc->list);
	cc->fc.release = cuse_fc_release;

	cc->fc.initialized = 1;
	rc = cuse_send_init(cc);
	if (rc) {
		fuse_dev_free(fud);
		return rc;
	}
	file->private_data = fud;

	return 0;
}

/**
 * cuse_channel_release - release method for /dev/cuse
 * @inode: inode for /dev/cuse
 * @file: file struct being closed
 *
 * Disconnect the channel, deregister CUSE device and initiate
 * destruction by putting the default reference.
 *
 * RETURNS:
 * 0 on success, -errno on failure.
 */
static int cuse_channel_release(struct inode *inode, struct file *file)
{
	struct fuse_dev *fud = file->private_data;
	struct cuse_conn *cc = fc_to_cc(fud->fc);
	int rc;

	/* remove from the conntbl, no more access from this point on */
	mutex_lock(&cuse_lock);
	list_del_init(&cc->list);
	mutex_unlock(&cuse_lock);

	/* remove device */
	if (cc->dev)
		device_unregister(cc->dev);
	if (cc->cdev) {
		unregister_chrdev_region(cc->cdev->dev, 1);
		cdev_del(cc->cdev);
	}

	rc = fuse_dev_release(inode, file);	/* puts the base reference */

	return rc;
}

static struct file_operations cuse_channel_fops; /* initialized during init */


/**************************************************************************
 * Misc stuff and module initializatiion
 *
 * CUSE exports the same set of attributes to sysfs as fusectl.
 */

static ssize_t cuse_class_waiting_show(struct device *dev,
				       struct device_attribute *attr, char *buf)
{
	struct cuse_conn *cc = dev_get_drvdata(dev);

	return sprintf(buf, "%d\n", atomic_read(&cc->fc.num_waiting));
}
static DEVICE_ATTR(waiting, 0400, cuse_class_waiting_show, NULL);

static ssize_t cuse_class_abort_store(struct device *dev,
				      struct device_attribute *attr,
				      const char *buf, size_t count)
{
	struct cuse_conn *cc = dev_get_drvdata(dev);

	fuse_abort_conn(&cc->fc);
	return count;
}
static DEVICE_ATTR(abort, 0200, NULL, cuse_class_abort_store);

static struct attribute *cuse_class_dev_attrs[] = {
	&dev_attr_waiting.attr,
	&dev_attr_abort.attr,
	NULL,
};
ATTRIBUTE_GROUPS(cuse_class_dev);

static struct miscdevice cuse_miscdev = {
	.minor		= CUSE_MINOR,
	.name		= "cuse",
	.fops		= &cuse_channel_fops,
};

MODULE_ALIAS_MISCDEV(CUSE_MINOR);
MODULE_ALIAS("devname:cuse");

static int __init cuse_init(void)
{
	int i, rc;

	/* init conntbl */
	for (i = 0; i < CUSE_CONNTBL_LEN; i++)
		INIT_LIST_HEAD(&cuse_conntbl[i]);

	/* inherit and extend fuse_dev_operations */
	cuse_channel_fops		= fuse_dev_operations;
	cuse_channel_fops.owner		= THIS_MODULE;
	cuse_channel_fops.open		= cuse_channel_open;
	cuse_channel_fops.release	= cuse_channel_release;

	cuse_class = class_create(THIS_MODULE, "cuse");
	if (IS_ERR(cuse_class))
		return PTR_ERR(cuse_class);

	cuse_class->dev_groups = cuse_class_dev_groups;

	rc = misc_register(&cuse_miscdev);
	if (rc) {
		class_destroy(cuse_class);
		return rc;
	}

	return 0;
}

static void __exit cuse_exit(void)
{
	misc_deregister(&cuse_miscdev);
	class_destroy(cuse_class);
}

module_init(cuse_init);
module_exit(cuse_exit);

MODULE_AUTHOR("Tejun Heo <tj@kernel.org>");
MODULE_DESCRIPTION("Character device in Userspace");
MODULE_LICENSE("GPL");