xref: /linux/block/bsg.c (revision 7505576d1c1ac0cfe85fdf90999433dd8b673012) 
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * bsg.c - block layer implementation of the sg v4 interface
4  */
5 #include <linux/module.h>
6 #include <linux/init.h>
7 #include <linux/file.h>
8 #include <linux/blkdev.h>
9 #include <linux/cdev.h>
10 #include <linux/jiffies.h>
11 #include <linux/percpu.h>
12 #include <linux/idr.h>
13 #include <linux/bsg.h>
14 #include <linux/slab.h>
15 
16 #include <scsi/scsi.h>
17 #include <scsi/scsi_ioctl.h>
18 #include <scsi/scsi_cmnd.h>
19 #include <scsi/scsi_device.h>
20 #include <scsi/scsi_driver.h>
21 #include <scsi/sg.h>
22 
23 #define BSG_DESCRIPTION	"Block layer SCSI generic (bsg) driver"
24 #define BSG_VERSION	"0.4"
25 
26 #define bsg_dbg(bd, fmt, ...) \
27 	pr_debug("%s: " fmt, (bd)->name, ##__VA_ARGS__)
28 
29 struct bsg_device {
30 	struct request_queue *queue;
31 	spinlock_t lock;
32 	struct hlist_node dev_list;
33 	refcount_t ref_count;
34 	char name[20];
35 	int max_queue;
36 };
37 
38 #define BSG_DEFAULT_CMDS	64
39 #define BSG_MAX_DEVS		32768
40 
41 static DEFINE_MUTEX(bsg_mutex);
42 static DEFINE_IDR(bsg_minor_idr);
43 
44 #define BSG_LIST_ARRAY_SIZE	8
45 static struct hlist_head bsg_device_list[BSG_LIST_ARRAY_SIZE];
46 
47 static struct class *bsg_class;
48 static int bsg_major;
49 
50 static inline struct hlist_head *bsg_dev_idx_hash(int index)
51 {
52 	return &bsg_device_list[index & (BSG_LIST_ARRAY_SIZE - 1)];
53 }
54 
55 #define uptr64(val) ((void __user *)(uintptr_t)(val))
56 
57 static int bsg_scsi_check_proto(struct sg_io_v4 *hdr)
58 {
59 	if (hdr->protocol != BSG_PROTOCOL_SCSI  ||
60 	    hdr->subprotocol != BSG_SUB_PROTOCOL_SCSI_CMD)
61 		return -EINVAL;
62 	return 0;
63 }
64 
65 static int bsg_scsi_fill_hdr(struct request *rq, struct sg_io_v4 *hdr,
66 		fmode_t mode)
67 {
68 	struct scsi_request *sreq = scsi_req(rq);
69 
70 	if (hdr->dout_xfer_len && hdr->din_xfer_len) {
71 		pr_warn_once("BIDI support in bsg has been removed.\n");
72 		return -EOPNOTSUPP;
73 	}
74 
75 	sreq->cmd_len = hdr->request_len;
76 	if (sreq->cmd_len > BLK_MAX_CDB) {
77 		sreq->cmd = kzalloc(sreq->cmd_len, GFP_KERNEL);
78 		if (!sreq->cmd)
79 			return -ENOMEM;
80 	}
81 
82 	if (copy_from_user(sreq->cmd, uptr64(hdr->request), sreq->cmd_len))
83 		return -EFAULT;
84 	if (blk_verify_command(sreq->cmd, mode))
85 		return -EPERM;
86 	return 0;
87 }
88 
89 static int bsg_scsi_complete_rq(struct request *rq, struct sg_io_v4 *hdr)
90 {
91 	struct scsi_request *sreq = scsi_req(rq);
92 	int ret = 0;
93 
94 	/*
95 	 * fill in all the output members
96 	 */
97 	hdr->device_status = sreq->result & 0xff;
98 	hdr->transport_status = host_byte(sreq->result);
99 	hdr->driver_status = driver_byte(sreq->result);
100 	hdr->info = 0;
101 	if (hdr->device_status || hdr->transport_status || hdr->driver_status)
102 		hdr->info |= SG_INFO_CHECK;
103 	hdr->response_len = 0;
104 
105 	if (sreq->sense_len && hdr->response) {
106 		int len = min_t(unsigned int, hdr->max_response_len,
107 					sreq->sense_len);
108 
109 		if (copy_to_user(uptr64(hdr->response), sreq->sense, len))
110 			ret = -EFAULT;
111 		else
112 			hdr->response_len = len;
113 	}
114 
115 	if (rq_data_dir(rq) == READ)
116 		hdr->din_resid = sreq->resid_len;
117 	else
118 		hdr->dout_resid = sreq->resid_len;
119 
120 	return ret;
121 }
122 
123 static void bsg_scsi_free_rq(struct request *rq)
124 {
125 	scsi_req_free_cmd(scsi_req(rq));
126 }
127 
128 static const struct bsg_ops bsg_scsi_ops = {
129 	.check_proto		= bsg_scsi_check_proto,
130 	.fill_hdr		= bsg_scsi_fill_hdr,
131 	.complete_rq		= bsg_scsi_complete_rq,
132 	.free_rq		= bsg_scsi_free_rq,
133 };
134 
135 static int bsg_sg_io(struct request_queue *q, fmode_t mode, void __user *uarg)
136 {
137 	struct request *rq;
138 	struct bio *bio;
139 	struct sg_io_v4 hdr;
140 	int ret;
141 
142 	if (copy_from_user(&hdr, uarg, sizeof(hdr)))
143 		return -EFAULT;
144 
145 	if (!q->bsg_dev.class_dev)
146 		return -ENXIO;
147 
148 	if (hdr.guard != 'Q')
149 		return -EINVAL;
150 	ret = q->bsg_dev.ops->check_proto(&hdr);
151 	if (ret)
152 		return ret;
153 
154 	rq = blk_get_request(q, hdr.dout_xfer_len ?
155 			REQ_OP_SCSI_OUT : REQ_OP_SCSI_IN, 0);
156 	if (IS_ERR(rq))
157 		return PTR_ERR(rq);
158 
159 	ret = q->bsg_dev.ops->fill_hdr(rq, &hdr, mode);
160 	if (ret)
161 		return ret;
162 
163 	rq->timeout = msecs_to_jiffies(hdr.timeout);
164 	if (!rq->timeout)
165 		rq->timeout = q->sg_timeout;
166 	if (!rq->timeout)
167 		rq->timeout = BLK_DEFAULT_SG_TIMEOUT;
168 	if (rq->timeout < BLK_MIN_SG_TIMEOUT)
169 		rq->timeout = BLK_MIN_SG_TIMEOUT;
170 
171 	if (hdr.dout_xfer_len) {
172 		ret = blk_rq_map_user(q, rq, NULL, uptr64(hdr.dout_xferp),
173 				hdr.dout_xfer_len, GFP_KERNEL);
174 	} else if (hdr.din_xfer_len) {
175 		ret = blk_rq_map_user(q, rq, NULL, uptr64(hdr.din_xferp),
176 				hdr.din_xfer_len, GFP_KERNEL);
177 	}
178 
179 	if (ret)
180 		goto out_free_rq;
181 
182 	bio = rq->bio;
183 
184 	blk_execute_rq(q, NULL, rq, !(hdr.flags & BSG_FLAG_Q_AT_TAIL));
185 	ret = rq->q->bsg_dev.ops->complete_rq(rq, &hdr);
186 	blk_rq_unmap_user(bio);
187 
188 out_free_rq:
189 	rq->q->bsg_dev.ops->free_rq(rq);
190 	blk_put_request(rq);
191 	if (!ret && copy_to_user(uarg, &hdr, sizeof(hdr)))
192 		return -EFAULT;
193 	return ret;
194 }
195 
196 static struct bsg_device *bsg_alloc_device(void)
197 {
198 	struct bsg_device *bd;
199 
200 	bd = kzalloc(sizeof(struct bsg_device), GFP_KERNEL);
201 	if (unlikely(!bd))
202 		return NULL;
203 
204 	spin_lock_init(&bd->lock);
205 	bd->max_queue = BSG_DEFAULT_CMDS;
206 	INIT_HLIST_NODE(&bd->dev_list);
207 	return bd;
208 }
209 
210 static int bsg_put_device(struct bsg_device *bd)
211 {
212 	struct request_queue *q = bd->queue;
213 
214 	mutex_lock(&bsg_mutex);
215 
216 	if (!refcount_dec_and_test(&bd->ref_count)) {
217 		mutex_unlock(&bsg_mutex);
218 		return 0;
219 	}
220 
221 	hlist_del(&bd->dev_list);
222 	mutex_unlock(&bsg_mutex);
223 
224 	bsg_dbg(bd, "tearing down\n");
225 
226 	/*
227 	 * close can always block
228 	 */
229 	kfree(bd);
230 	blk_put_queue(q);
231 	return 0;
232 }
233 
234 static struct bsg_device *bsg_add_device(struct inode *inode,
235 					 struct request_queue *rq,
236 					 struct file *file)
237 {
238 	struct bsg_device *bd;
239 	unsigned char buf[32];
240 
241 	lockdep_assert_held(&bsg_mutex);
242 
243 	if (!blk_get_queue(rq))
244 		return ERR_PTR(-ENXIO);
245 
246 	bd = bsg_alloc_device();
247 	if (!bd) {
248 		blk_put_queue(rq);
249 		return ERR_PTR(-ENOMEM);
250 	}
251 
252 	bd->queue = rq;
253 
254 	refcount_set(&bd->ref_count, 1);
255 	hlist_add_head(&bd->dev_list, bsg_dev_idx_hash(iminor(inode)));
256 
257 	strncpy(bd->name, dev_name(rq->bsg_dev.class_dev), sizeof(bd->name) - 1);
258 	bsg_dbg(bd, "bound to <%s>, max queue %d\n",
259 		format_dev_t(buf, inode->i_rdev), bd->max_queue);
260 
261 	return bd;
262 }
263 
264 static struct bsg_device *__bsg_get_device(int minor, struct request_queue *q)
265 {
266 	struct bsg_device *bd;
267 
268 	lockdep_assert_held(&bsg_mutex);
269 
270 	hlist_for_each_entry(bd, bsg_dev_idx_hash(minor), dev_list) {
271 		if (bd->queue == q) {
272 			refcount_inc(&bd->ref_count);
273 			goto found;
274 		}
275 	}
276 	bd = NULL;
277 found:
278 	return bd;
279 }
280 
281 static struct bsg_device *bsg_get_device(struct inode *inode, struct file *file)
282 {
283 	struct bsg_device *bd;
284 	struct bsg_class_device *bcd;
285 
286 	/*
287 	 * find the class device
288 	 */
289 	mutex_lock(&bsg_mutex);
290 	bcd = idr_find(&bsg_minor_idr, iminor(inode));
291 
292 	if (!bcd) {
293 		bd = ERR_PTR(-ENODEV);
294 		goto out_unlock;
295 	}
296 
297 	bd = __bsg_get_device(iminor(inode), bcd->queue);
298 	if (!bd)
299 		bd = bsg_add_device(inode, bcd->queue, file);
300 
301 out_unlock:
302 	mutex_unlock(&bsg_mutex);
303 	return bd;
304 }
305 
306 static int bsg_open(struct inode *inode, struct file *file)
307 {
308 	struct bsg_device *bd;
309 
310 	bd = bsg_get_device(inode, file);
311 
312 	if (IS_ERR(bd))
313 		return PTR_ERR(bd);
314 
315 	file->private_data = bd;
316 	return 0;
317 }
318 
319 static int bsg_release(struct inode *inode, struct file *file)
320 {
321 	struct bsg_device *bd = file->private_data;
322 
323 	file->private_data = NULL;
324 	return bsg_put_device(bd);
325 }
326 
327 static int bsg_get_command_q(struct bsg_device *bd, int __user *uarg)
328 {
329 	return put_user(bd->max_queue, uarg);
330 }
331 
332 static int bsg_set_command_q(struct bsg_device *bd, int __user *uarg)
333 {
334 	int queue;
335 
336 	if (get_user(queue, uarg))
337 		return -EFAULT;
338 	if (queue < 1)
339 		return -EINVAL;
340 
341 	spin_lock_irq(&bd->lock);
342 	bd->max_queue = queue;
343 	spin_unlock_irq(&bd->lock);
344 	return 0;
345 }
346 
347 static long bsg_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
348 {
349 	struct bsg_device *bd = file->private_data;
350 	void __user *uarg = (void __user *) arg;
351 
352 	switch (cmd) {
353 	/*
354 	 * Our own ioctls
355 	 */
356 	case SG_GET_COMMAND_Q:
357 		return bsg_get_command_q(bd, uarg);
358 	case SG_SET_COMMAND_Q:
359 		return bsg_set_command_q(bd, uarg);
360 
361 	/*
362 	 * SCSI/sg ioctls
363 	 */
364 	case SG_GET_VERSION_NUM:
365 	case SCSI_IOCTL_GET_IDLUN:
366 	case SCSI_IOCTL_GET_BUS_NUMBER:
367 	case SG_SET_TIMEOUT:
368 	case SG_GET_TIMEOUT:
369 	case SG_GET_RESERVED_SIZE:
370 	case SG_SET_RESERVED_SIZE:
371 	case SG_EMULATED_HOST:
372 	case SCSI_IOCTL_SEND_COMMAND:
373 		return scsi_cmd_ioctl(bd->queue, NULL, file->f_mode, cmd, uarg);
374 	case SG_IO:
375 		return bsg_sg_io(bd->queue, file->f_mode, uarg);
376 	default:
377 		return -ENOTTY;
378 	}
379 }
380 
381 static const struct file_operations bsg_fops = {
382 	.open		=	bsg_open,
383 	.release	=	bsg_release,
384 	.unlocked_ioctl	=	bsg_ioctl,
385 	.owner		=	THIS_MODULE,
386 	.llseek		=	default_llseek,
387 };
388 
389 void bsg_unregister_queue(struct request_queue *q)
390 {
391 	struct bsg_class_device *bcd = &q->bsg_dev;
392 
393 	if (!bcd->class_dev)
394 		return;
395 
396 	mutex_lock(&bsg_mutex);
397 	idr_remove(&bsg_minor_idr, bcd->minor);
398 	if (q->kobj.sd)
399 		sysfs_remove_link(&q->kobj, "bsg");
400 	device_unregister(bcd->class_dev);
401 	bcd->class_dev = NULL;
402 	mutex_unlock(&bsg_mutex);
403 }
404 EXPORT_SYMBOL_GPL(bsg_unregister_queue);
405 
406 int bsg_register_queue(struct request_queue *q, struct device *parent,
407 		const char *name, const struct bsg_ops *ops)
408 {
409 	struct bsg_class_device *bcd;
410 	dev_t dev;
411 	int ret;
412 	struct device *class_dev = NULL;
413 
414 	/*
415 	 * we need a proper transport to send commands, not a stacked device
416 	 */
417 	if (!queue_is_mq(q))
418 		return 0;
419 
420 	bcd = &q->bsg_dev;
421 	memset(bcd, 0, sizeof(*bcd));
422 
423 	mutex_lock(&bsg_mutex);
424 
425 	ret = idr_alloc(&bsg_minor_idr, bcd, 0, BSG_MAX_DEVS, GFP_KERNEL);
426 	if (ret < 0) {
427 		if (ret == -ENOSPC) {
428 			printk(KERN_ERR "bsg: too many bsg devices\n");
429 			ret = -EINVAL;
430 		}
431 		goto unlock;
432 	}
433 
434 	bcd->minor = ret;
435 	bcd->queue = q;
436 	bcd->ops = ops;
437 	dev = MKDEV(bsg_major, bcd->minor);
438 	class_dev = device_create(bsg_class, parent, dev, NULL, "%s", name);
439 	if (IS_ERR(class_dev)) {
440 		ret = PTR_ERR(class_dev);
441 		goto idr_remove;
442 	}
443 	bcd->class_dev = class_dev;
444 
445 	if (q->kobj.sd) {
446 		ret = sysfs_create_link(&q->kobj, &bcd->class_dev->kobj, "bsg");
447 		if (ret)
448 			goto unregister_class_dev;
449 	}
450 
451 	mutex_unlock(&bsg_mutex);
452 	return 0;
453 
454 unregister_class_dev:
455 	device_unregister(class_dev);
456 idr_remove:
457 	idr_remove(&bsg_minor_idr, bcd->minor);
458 unlock:
459 	mutex_unlock(&bsg_mutex);
460 	return ret;
461 }
462 
463 int bsg_scsi_register_queue(struct request_queue *q, struct device *parent)
464 {
465 	if (!blk_queue_scsi_passthrough(q)) {
466 		WARN_ONCE(true, "Attempt to register a non-SCSI queue\n");
467 		return -EINVAL;
468 	}
469 
470 	return bsg_register_queue(q, parent, dev_name(parent), &bsg_scsi_ops);
471 }
472 EXPORT_SYMBOL_GPL(bsg_scsi_register_queue);
473 
474 static struct cdev bsg_cdev;
475 
476 static char *bsg_devnode(struct device *dev, umode_t *mode)
477 {
478 	return kasprintf(GFP_KERNEL, "bsg/%s", dev_name(dev));
479 }
480 
481 static int __init bsg_init(void)
482 {
483 	int ret, i;
484 	dev_t devid;
485 
486 	for (i = 0; i < BSG_LIST_ARRAY_SIZE; i++)
487 		INIT_HLIST_HEAD(&bsg_device_list[i]);
488 
489 	bsg_class = class_create(THIS_MODULE, "bsg");
490 	if (IS_ERR(bsg_class))
491 		return PTR_ERR(bsg_class);
492 	bsg_class->devnode = bsg_devnode;
493 
494 	ret = alloc_chrdev_region(&devid, 0, BSG_MAX_DEVS, "bsg");
495 	if (ret)
496 		goto destroy_bsg_class;
497 
498 	bsg_major = MAJOR(devid);
499 
500 	cdev_init(&bsg_cdev, &bsg_fops);
501 	ret = cdev_add(&bsg_cdev, MKDEV(bsg_major, 0), BSG_MAX_DEVS);
502 	if (ret)
503 		goto unregister_chrdev;
504 
505 	printk(KERN_INFO BSG_DESCRIPTION " version " BSG_VERSION
506 	       " loaded (major %d)\n", bsg_major);
507 	return 0;
508 unregister_chrdev:
509 	unregister_chrdev_region(MKDEV(bsg_major, 0), BSG_MAX_DEVS);
510 destroy_bsg_class:
511 	class_destroy(bsg_class);
512 	return ret;
513 }
514 
515 MODULE_AUTHOR("Jens Axboe");
516 MODULE_DESCRIPTION(BSG_DESCRIPTION);
517 MODULE_LICENSE("GPL");
518 
519 device_initcall(bsg_init);
520