1 /*
2  * Framework for buffer objects that can be shared across devices/subsystems.
3  *
4  * Copyright(C) 2011 Linaro Limited. All rights reserved.
5  * Author: Sumit Semwal <sumit.semwal@ti.com>
6  *
7  * Many thanks to linaro-mm-sig list, and specially
8  * Arnd Bergmann <arnd@arndb.de>, Rob Clark <rob@ti.com> and
9  * Daniel Vetter <daniel@ffwll.ch> for their support in creation and
10  * refining of this idea.
11  *
12  * This program is free software; you can redistribute it and/or modify it
13  * under the terms of the GNU General Public License version 2 as published by
14  * the Free Software Foundation.
15  *
16  * This program is distributed in the hope that it will be useful, but WITHOUT
17  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
18  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
19  * more details.
20  *
21  * You should have received a copy of the GNU General Public License along with
22  * this program.  If not, see <http://www.gnu.org/licenses/>.
23  */
24 
25 #include <linux/fs.h>
26 #include <linux/slab.h>
27 #include <linux/dma-buf.h>
28 #include <linux/dma-fence.h>
29 #include <linux/anon_inodes.h>
30 #include <linux/export.h>
31 #include <linux/debugfs.h>
32 #include <linux/module.h>
33 #include <linux/seq_file.h>
34 #include <linux/poll.h>
35 #include <linux/reservation.h>
36 #include <linux/mm.h>
37 
38 #include <uapi/linux/dma-buf.h>
39 
40 static inline int is_dma_buf_file(struct file *);
41 
42 struct dma_buf_list {
43 	struct list_head head;
44 	struct mutex lock;
45 };
46 
47 static struct dma_buf_list db_list;
48 
dma_buf_release(struct inode * inode,struct file * file)49 static int dma_buf_release(struct inode *inode, struct file *file)
50 {
51 	struct dma_buf *dmabuf;
52 
53 	if (!is_dma_buf_file(file))
54 		return -EINVAL;
55 
56 	dmabuf = file->private_data;
57 
58 	BUG_ON(dmabuf->vmapping_counter);
59 
60 	/*
61 	 * Any fences that a dma-buf poll can wait on should be signaled
62 	 * before releasing dma-buf. This is the responsibility of each
63 	 * driver that uses the reservation objects.
64 	 *
65 	 * If you hit this BUG() it means someone dropped their ref to the
66 	 * dma-buf while still having pending operation to the buffer.
67 	 */
68 	BUG_ON(dmabuf->cb_shared.active || dmabuf->cb_excl.active);
69 
70 	dmabuf->ops->release(dmabuf);
71 
72 	mutex_lock(&db_list.lock);
73 	list_del(&dmabuf->list_node);
74 	mutex_unlock(&db_list.lock);
75 
76 	if (dmabuf->resv == (struct reservation_object *)&dmabuf[1])
77 		reservation_object_fini(dmabuf->resv);
78 
79 	module_put(dmabuf->owner);
80 	kfree(dmabuf);
81 	return 0;
82 }
83 
dma_buf_mmap_internal(struct file * file,struct vm_area_struct * vma)84 static int dma_buf_mmap_internal(struct file *file, struct vm_area_struct *vma)
85 {
86 	struct dma_buf *dmabuf;
87 
88 	if (!is_dma_buf_file(file))
89 		return -EINVAL;
90 
91 	dmabuf = file->private_data;
92 
93 	/* check for overflowing the buffer's size */
94 	if (vma->vm_pgoff + vma_pages(vma) >
95 	    dmabuf->size >> PAGE_SHIFT)
96 		return -EINVAL;
97 
98 	return dmabuf->ops->mmap(dmabuf, vma);
99 }
100 
dma_buf_llseek(struct file * file,loff_t offset,int whence)101 static loff_t dma_buf_llseek(struct file *file, loff_t offset, int whence)
102 {
103 	struct dma_buf *dmabuf;
104 	loff_t base;
105 
106 	if (!is_dma_buf_file(file))
107 		return -EBADF;
108 
109 	dmabuf = file->private_data;
110 
111 	/* only support discovering the end of the buffer,
112 	   but also allow SEEK_SET to maintain the idiomatic
113 	   SEEK_END(0), SEEK_CUR(0) pattern */
114 	if (whence == SEEK_END)
115 		base = dmabuf->size;
116 	else if (whence == SEEK_SET)
117 		base = 0;
118 	else
119 		return -EINVAL;
120 
121 	if (offset != 0)
122 		return -EINVAL;
123 
124 	return base + offset;
125 }
126 
127 /**
128  * DOC: fence polling
129  *
130  * To support cross-device and cross-driver synchronization of buffer access
131  * implicit fences (represented internally in the kernel with &struct fence) can
132  * be attached to a &dma_buf. The glue for that and a few related things are
133  * provided in the &reservation_object structure.
134  *
135  * Userspace can query the state of these implicitly tracked fences using poll()
136  * and related system calls:
137  *
138  * - Checking for EPOLLIN, i.e. read access, can be use to query the state of the
139  *   most recent write or exclusive fence.
140  *
141  * - Checking for EPOLLOUT, i.e. write access, can be used to query the state of
142  *   all attached fences, shared and exclusive ones.
143  *
144  * Note that this only signals the completion of the respective fences, i.e. the
145  * DMA transfers are complete. Cache flushing and any other necessary
146  * preparations before CPU access can begin still need to happen.
147  */
148 
dma_buf_poll_cb(struct dma_fence * fence,struct dma_fence_cb * cb)149 static void dma_buf_poll_cb(struct dma_fence *fence, struct dma_fence_cb *cb)
150 {
151 	struct dma_buf_poll_cb_t *dcb = (struct dma_buf_poll_cb_t *)cb;
152 	unsigned long flags;
153 
154 	spin_lock_irqsave(&dcb->poll->lock, flags);
155 	wake_up_locked_poll(dcb->poll, dcb->active);
156 	dcb->active = 0;
157 	spin_unlock_irqrestore(&dcb->poll->lock, flags);
158 }
159 
dma_buf_poll(struct file * file,poll_table * poll)160 static __poll_t dma_buf_poll(struct file *file, poll_table *poll)
161 {
162 	struct dma_buf *dmabuf;
163 	struct reservation_object *resv;
164 	struct reservation_object_list *fobj;
165 	struct dma_fence *fence_excl;
166 	__poll_t events;
167 	unsigned shared_count, seq;
168 
169 	dmabuf = file->private_data;
170 	if (!dmabuf || !dmabuf->resv)
171 		return EPOLLERR;
172 
173 	resv = dmabuf->resv;
174 
175 	poll_wait(file, &dmabuf->poll, poll);
176 
177 	events = poll_requested_events(poll) & (EPOLLIN | EPOLLOUT);
178 	if (!events)
179 		return 0;
180 
181 retry:
182 	seq = read_seqcount_begin(&resv->seq);
183 	rcu_read_lock();
184 
185 	fobj = rcu_dereference(resv->fence);
186 	if (fobj)
187 		shared_count = fobj->shared_count;
188 	else
189 		shared_count = 0;
190 	fence_excl = rcu_dereference(resv->fence_excl);
191 	if (read_seqcount_retry(&resv->seq, seq)) {
192 		rcu_read_unlock();
193 		goto retry;
194 	}
195 
196 	if (fence_excl && (!(events & EPOLLOUT) || shared_count == 0)) {
197 		struct dma_buf_poll_cb_t *dcb = &dmabuf->cb_excl;
198 		__poll_t pevents = EPOLLIN;
199 
200 		if (shared_count == 0)
201 			pevents |= EPOLLOUT;
202 
203 		spin_lock_irq(&dmabuf->poll.lock);
204 		if (dcb->active) {
205 			dcb->active |= pevents;
206 			events &= ~pevents;
207 		} else
208 			dcb->active = pevents;
209 		spin_unlock_irq(&dmabuf->poll.lock);
210 
211 		if (events & pevents) {
212 			if (!dma_fence_get_rcu(fence_excl)) {
213 				/* force a recheck */
214 				events &= ~pevents;
215 				dma_buf_poll_cb(NULL, &dcb->cb);
216 			} else if (!dma_fence_add_callback(fence_excl, &dcb->cb,
217 							   dma_buf_poll_cb)) {
218 				events &= ~pevents;
219 				dma_fence_put(fence_excl);
220 			} else {
221 				/*
222 				 * No callback queued, wake up any additional
223 				 * waiters.
224 				 */
225 				dma_fence_put(fence_excl);
226 				dma_buf_poll_cb(NULL, &dcb->cb);
227 			}
228 		}
229 	}
230 
231 	if ((events & EPOLLOUT) && shared_count > 0) {
232 		struct dma_buf_poll_cb_t *dcb = &dmabuf->cb_shared;
233 		int i;
234 
235 		/* Only queue a new callback if no event has fired yet */
236 		spin_lock_irq(&dmabuf->poll.lock);
237 		if (dcb->active)
238 			events &= ~EPOLLOUT;
239 		else
240 			dcb->active = EPOLLOUT;
241 		spin_unlock_irq(&dmabuf->poll.lock);
242 
243 		if (!(events & EPOLLOUT))
244 			goto out;
245 
246 		for (i = 0; i < shared_count; ++i) {
247 			struct dma_fence *fence = rcu_dereference(fobj->shared[i]);
248 
249 			if (!dma_fence_get_rcu(fence)) {
250 				/*
251 				 * fence refcount dropped to zero, this means
252 				 * that fobj has been freed
253 				 *
254 				 * call dma_buf_poll_cb and force a recheck!
255 				 */
256 				events &= ~EPOLLOUT;
257 				dma_buf_poll_cb(NULL, &dcb->cb);
258 				break;
259 			}
260 			if (!dma_fence_add_callback(fence, &dcb->cb,
261 						    dma_buf_poll_cb)) {
262 				dma_fence_put(fence);
263 				events &= ~EPOLLOUT;
264 				break;
265 			}
266 			dma_fence_put(fence);
267 		}
268 
269 		/* No callback queued, wake up any additional waiters. */
270 		if (i == shared_count)
271 			dma_buf_poll_cb(NULL, &dcb->cb);
272 	}
273 
274 out:
275 	rcu_read_unlock();
276 	return events;
277 }
278 
dma_buf_ioctl(struct file * file,unsigned int cmd,unsigned long arg)279 static long dma_buf_ioctl(struct file *file,
280 			  unsigned int cmd, unsigned long arg)
281 {
282 	struct dma_buf *dmabuf;
283 	struct dma_buf_sync sync;
284 	enum dma_data_direction direction;
285 	int ret;
286 
287 	dmabuf = file->private_data;
288 
289 	switch (cmd) {
290 	case DMA_BUF_IOCTL_SYNC:
291 		if (copy_from_user(&sync, (void __user *) arg, sizeof(sync)))
292 			return -EFAULT;
293 
294 		if (sync.flags & ~DMA_BUF_SYNC_VALID_FLAGS_MASK)
295 			return -EINVAL;
296 
297 		switch (sync.flags & DMA_BUF_SYNC_RW) {
298 		case DMA_BUF_SYNC_READ:
299 			direction = DMA_FROM_DEVICE;
300 			break;
301 		case DMA_BUF_SYNC_WRITE:
302 			direction = DMA_TO_DEVICE;
303 			break;
304 		case DMA_BUF_SYNC_RW:
305 			direction = DMA_BIDIRECTIONAL;
306 			break;
307 		default:
308 			return -EINVAL;
309 		}
310 
311 		if (sync.flags & DMA_BUF_SYNC_END)
312 			ret = dma_buf_end_cpu_access(dmabuf, direction);
313 		else
314 			ret = dma_buf_begin_cpu_access(dmabuf, direction);
315 
316 		return ret;
317 	default:
318 		return -ENOTTY;
319 	}
320 }
321 
322 static const struct file_operations dma_buf_fops = {
323 	.release	= dma_buf_release,
324 	.mmap		= dma_buf_mmap_internal,
325 	.llseek		= dma_buf_llseek,
326 	.poll		= dma_buf_poll,
327 	.unlocked_ioctl	= dma_buf_ioctl,
328 #ifdef CONFIG_COMPAT
329 	.compat_ioctl	= dma_buf_ioctl,
330 #endif
331 };
332 
333 /*
334  * is_dma_buf_file - Check if struct file* is associated with dma_buf
335  */
is_dma_buf_file(struct file * file)336 static inline int is_dma_buf_file(struct file *file)
337 {
338 	return file->f_op == &dma_buf_fops;
339 }
340 
341 /**
342  * DOC: dma buf device access
343  *
344  * For device DMA access to a shared DMA buffer the usual sequence of operations
345  * is fairly simple:
346  *
347  * 1. The exporter defines his exporter instance using
348  *    DEFINE_DMA_BUF_EXPORT_INFO() and calls dma_buf_export() to wrap a private
349  *    buffer object into a &dma_buf. It then exports that &dma_buf to userspace
350  *    as a file descriptor by calling dma_buf_fd().
351  *
352  * 2. Userspace passes this file-descriptors to all drivers it wants this buffer
353  *    to share with: First the filedescriptor is converted to a &dma_buf using
354  *    dma_buf_get(). Then the buffer is attached to the device using
355  *    dma_buf_attach().
356  *
357  *    Up to this stage the exporter is still free to migrate or reallocate the
358  *    backing storage.
359  *
360  * 3. Once the buffer is attached to all devices userspace can initiate DMA
361  *    access to the shared buffer. In the kernel this is done by calling
362  *    dma_buf_map_attachment() and dma_buf_unmap_attachment().
363  *
364  * 4. Once a driver is done with a shared buffer it needs to call
365  *    dma_buf_detach() (after cleaning up any mappings) and then release the
366  *    reference acquired with dma_buf_get by calling dma_buf_put().
367  *
368  * For the detailed semantics exporters are expected to implement see
369  * &dma_buf_ops.
370  */
371 
372 /**
373  * dma_buf_export - Creates a new dma_buf, and associates an anon file
374  * with this buffer, so it can be exported.
375  * Also connect the allocator specific data and ops to the buffer.
376  * Additionally, provide a name string for exporter; useful in debugging.
377  *
378  * @exp_info:	[in]	holds all the export related information provided
379  *			by the exporter. see &struct dma_buf_export_info
380  *			for further details.
381  *
382  * Returns, on success, a newly created dma_buf object, which wraps the
383  * supplied private data and operations for dma_buf_ops. On either missing
384  * ops, or error in allocating struct dma_buf, will return negative error.
385  *
386  * For most cases the easiest way to create @exp_info is through the
387  * %DEFINE_DMA_BUF_EXPORT_INFO macro.
388  */
dma_buf_export(const struct dma_buf_export_info * exp_info)389 struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info)
390 {
391 	struct dma_buf *dmabuf;
392 	struct reservation_object *resv = exp_info->resv;
393 	struct file *file;
394 	size_t alloc_size = sizeof(struct dma_buf);
395 	int ret;
396 
397 	if (!exp_info->resv)
398 		alloc_size += sizeof(struct reservation_object);
399 	else
400 		/* prevent &dma_buf[1] == dma_buf->resv */
401 		alloc_size += 1;
402 
403 	if (WARN_ON(!exp_info->priv
404 			  || !exp_info->ops
405 			  || !exp_info->ops->map_dma_buf
406 			  || !exp_info->ops->unmap_dma_buf
407 			  || !exp_info->ops->release
408 			  || !exp_info->ops->map
409 			  || !exp_info->ops->mmap)) {
410 		return ERR_PTR(-EINVAL);
411 	}
412 
413 	if (!try_module_get(exp_info->owner))
414 		return ERR_PTR(-ENOENT);
415 
416 	dmabuf = kzalloc(alloc_size, GFP_KERNEL);
417 	if (!dmabuf) {
418 		ret = -ENOMEM;
419 		goto err_module;
420 	}
421 
422 	dmabuf->priv = exp_info->priv;
423 	dmabuf->ops = exp_info->ops;
424 	dmabuf->size = exp_info->size;
425 	dmabuf->exp_name = exp_info->exp_name;
426 	dmabuf->owner = exp_info->owner;
427 	init_waitqueue_head(&dmabuf->poll);
428 	dmabuf->cb_excl.poll = dmabuf->cb_shared.poll = &dmabuf->poll;
429 	dmabuf->cb_excl.active = dmabuf->cb_shared.active = 0;
430 
431 	if (!resv) {
432 		resv = (struct reservation_object *)&dmabuf[1];
433 		reservation_object_init(resv);
434 	}
435 	dmabuf->resv = resv;
436 
437 	file = anon_inode_getfile("dmabuf", &dma_buf_fops, dmabuf,
438 					exp_info->flags);
439 	if (IS_ERR(file)) {
440 		ret = PTR_ERR(file);
441 		goto err_dmabuf;
442 	}
443 
444 	file->f_mode |= FMODE_LSEEK;
445 	dmabuf->file = file;
446 
447 	mutex_init(&dmabuf->lock);
448 	INIT_LIST_HEAD(&dmabuf->attachments);
449 
450 	mutex_lock(&db_list.lock);
451 	list_add(&dmabuf->list_node, &db_list.head);
452 	mutex_unlock(&db_list.lock);
453 
454 	return dmabuf;
455 
456 err_dmabuf:
457 	kfree(dmabuf);
458 err_module:
459 	module_put(exp_info->owner);
460 	return ERR_PTR(ret);
461 }
462 EXPORT_SYMBOL_GPL(dma_buf_export);
463 
464 /**
465  * dma_buf_fd - returns a file descriptor for the given dma_buf
466  * @dmabuf:	[in]	pointer to dma_buf for which fd is required.
467  * @flags:      [in]    flags to give to fd
468  *
469  * On success, returns an associated 'fd'. Else, returns error.
470  */
dma_buf_fd(struct dma_buf * dmabuf,int flags)471 int dma_buf_fd(struct dma_buf *dmabuf, int flags)
472 {
473 	int fd;
474 
475 	if (!dmabuf || !dmabuf->file)
476 		return -EINVAL;
477 
478 	fd = get_unused_fd_flags(flags);
479 	if (fd < 0)
480 		return fd;
481 
482 	fd_install(fd, dmabuf->file);
483 
484 	return fd;
485 }
486 EXPORT_SYMBOL_GPL(dma_buf_fd);
487 
488 /**
489  * dma_buf_get - returns the dma_buf structure related to an fd
490  * @fd:	[in]	fd associated with the dma_buf to be returned
491  *
492  * On success, returns the dma_buf structure associated with an fd; uses
493  * file's refcounting done by fget to increase refcount. returns ERR_PTR
494  * otherwise.
495  */
dma_buf_get(int fd)496 struct dma_buf *dma_buf_get(int fd)
497 {
498 	struct file *file;
499 
500 	file = fget(fd);
501 
502 	if (!file)
503 		return ERR_PTR(-EBADF);
504 
505 	if (!is_dma_buf_file(file)) {
506 		fput(file);
507 		return ERR_PTR(-EINVAL);
508 	}
509 
510 	return file->private_data;
511 }
512 EXPORT_SYMBOL_GPL(dma_buf_get);
513 
514 /**
515  * dma_buf_put - decreases refcount of the buffer
516  * @dmabuf:	[in]	buffer to reduce refcount of
517  *
518  * Uses file's refcounting done implicitly by fput().
519  *
520  * If, as a result of this call, the refcount becomes 0, the 'release' file
521  * operation related to this fd is called. It calls &dma_buf_ops.release vfunc
522  * in turn, and frees the memory allocated for dmabuf when exported.
523  */
dma_buf_put(struct dma_buf * dmabuf)524 void dma_buf_put(struct dma_buf *dmabuf)
525 {
526 	if (WARN_ON(!dmabuf || !dmabuf->file))
527 		return;
528 
529 	fput(dmabuf->file);
530 }
531 EXPORT_SYMBOL_GPL(dma_buf_put);
532 
533 /**
534  * dma_buf_attach - Add the device to dma_buf's attachments list; optionally,
535  * calls attach() of dma_buf_ops to allow device-specific attach functionality
536  * @dmabuf:	[in]	buffer to attach device to.
537  * @dev:	[in]	device to be attached.
538  *
539  * Returns struct dma_buf_attachment pointer for this attachment. Attachments
540  * must be cleaned up by calling dma_buf_detach().
541  *
542  * Returns:
543  *
544  * A pointer to newly created &dma_buf_attachment on success, or a negative
545  * error code wrapped into a pointer on failure.
546  *
547  * Note that this can fail if the backing storage of @dmabuf is in a place not
548  * accessible to @dev, and cannot be moved to a more suitable place. This is
549  * indicated with the error code -EBUSY.
550  */
dma_buf_attach(struct dma_buf * dmabuf,struct device * dev)551 struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
552 					  struct device *dev)
553 {
554 	struct dma_buf_attachment *attach;
555 	int ret;
556 
557 	if (WARN_ON(!dmabuf || !dev))
558 		return ERR_PTR(-EINVAL);
559 
560 	attach = kzalloc(sizeof(*attach), GFP_KERNEL);
561 	if (!attach)
562 		return ERR_PTR(-ENOMEM);
563 
564 	attach->dev = dev;
565 	attach->dmabuf = dmabuf;
566 
567 	mutex_lock(&dmabuf->lock);
568 
569 	if (dmabuf->ops->attach) {
570 		ret = dmabuf->ops->attach(dmabuf, attach);
571 		if (ret)
572 			goto err_attach;
573 	}
574 	list_add(&attach->node, &dmabuf->attachments);
575 
576 	mutex_unlock(&dmabuf->lock);
577 	return attach;
578 
579 err_attach:
580 	kfree(attach);
581 	mutex_unlock(&dmabuf->lock);
582 	return ERR_PTR(ret);
583 }
584 EXPORT_SYMBOL_GPL(dma_buf_attach);
585 
586 /**
587  * dma_buf_detach - Remove the given attachment from dmabuf's attachments list;
588  * optionally calls detach() of dma_buf_ops for device-specific detach
589  * @dmabuf:	[in]	buffer to detach from.
590  * @attach:	[in]	attachment to be detached; is free'd after this call.
591  *
592  * Clean up a device attachment obtained by calling dma_buf_attach().
593  */
dma_buf_detach(struct dma_buf * dmabuf,struct dma_buf_attachment * attach)594 void dma_buf_detach(struct dma_buf *dmabuf, struct dma_buf_attachment *attach)
595 {
596 	if (WARN_ON(!dmabuf || !attach))
597 		return;
598 
599 	mutex_lock(&dmabuf->lock);
600 	list_del(&attach->node);
601 	if (dmabuf->ops->detach)
602 		dmabuf->ops->detach(dmabuf, attach);
603 
604 	mutex_unlock(&dmabuf->lock);
605 	kfree(attach);
606 }
607 EXPORT_SYMBOL_GPL(dma_buf_detach);
608 
609 /**
610  * dma_buf_map_attachment - Returns the scatterlist table of the attachment;
611  * mapped into _device_ address space. Is a wrapper for map_dma_buf() of the
612  * dma_buf_ops.
613  * @attach:	[in]	attachment whose scatterlist is to be returned
614  * @direction:	[in]	direction of DMA transfer
615  *
616  * Returns sg_table containing the scatterlist to be returned; returns ERR_PTR
617  * on error. May return -EINTR if it is interrupted by a signal.
618  *
619  * A mapping must be unmapped by using dma_buf_unmap_attachment(). Note that
620  * the underlying backing storage is pinned for as long as a mapping exists,
621  * therefore users/importers should not hold onto a mapping for undue amounts of
622  * time.
623  */
dma_buf_map_attachment(struct dma_buf_attachment * attach,enum dma_data_direction direction)624 struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
625 					enum dma_data_direction direction)
626 {
627 	struct sg_table *sg_table;
628 
629 	might_sleep();
630 
631 	if (WARN_ON(!attach || !attach->dmabuf))
632 		return ERR_PTR(-EINVAL);
633 
634 	sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction);
635 	if (!sg_table)
636 		sg_table = ERR_PTR(-ENOMEM);
637 
638 	return sg_table;
639 }
640 EXPORT_SYMBOL_GPL(dma_buf_map_attachment);
641 
642 /**
643  * dma_buf_unmap_attachment - unmaps and decreases usecount of the buffer;might
644  * deallocate the scatterlist associated. Is a wrapper for unmap_dma_buf() of
645  * dma_buf_ops.
646  * @attach:	[in]	attachment to unmap buffer from
647  * @sg_table:	[in]	scatterlist info of the buffer to unmap
648  * @direction:  [in]    direction of DMA transfer
649  *
650  * This unmaps a DMA mapping for @attached obtained by dma_buf_map_attachment().
651  */
dma_buf_unmap_attachment(struct dma_buf_attachment * attach,struct sg_table * sg_table,enum dma_data_direction direction)652 void dma_buf_unmap_attachment(struct dma_buf_attachment *attach,
653 				struct sg_table *sg_table,
654 				enum dma_data_direction direction)
655 {
656 	might_sleep();
657 
658 	if (WARN_ON(!attach || !attach->dmabuf || !sg_table))
659 		return;
660 
661 	attach->dmabuf->ops->unmap_dma_buf(attach, sg_table,
662 						direction);
663 }
664 EXPORT_SYMBOL_GPL(dma_buf_unmap_attachment);
665 
666 /**
667  * DOC: cpu access
668  *
669  * There are mutliple reasons for supporting CPU access to a dma buffer object:
670  *
671  * - Fallback operations in the kernel, for example when a device is connected
672  *   over USB and the kernel needs to shuffle the data around first before
673  *   sending it away. Cache coherency is handled by braketing any transactions
674  *   with calls to dma_buf_begin_cpu_access() and dma_buf_end_cpu_access()
675  *   access.
676  *
677  *   To support dma_buf objects residing in highmem cpu access is page-based
678  *   using an api similar to kmap. Accessing a dma_buf is done in aligned chunks
679  *   of PAGE_SIZE size. Before accessing a chunk it needs to be mapped, which
680  *   returns a pointer in kernel virtual address space. Afterwards the chunk
681  *   needs to be unmapped again. There is no limit on how often a given chunk
682  *   can be mapped and unmapped, i.e. the importer does not need to call
683  *   begin_cpu_access again before mapping the same chunk again.
684  *
685  *   Interfaces::
686  *      void \*dma_buf_kmap(struct dma_buf \*, unsigned long);
687  *      void dma_buf_kunmap(struct dma_buf \*, unsigned long, void \*);
688  *
689  *   Implementing the functions is optional for exporters and for importers all
690  *   the restrictions of using kmap apply.
691  *
692  *   dma_buf kmap calls outside of the range specified in begin_cpu_access are
693  *   undefined. If the range is not PAGE_SIZE aligned, kmap needs to succeed on
694  *   the partial chunks at the beginning and end but may return stale or bogus
695  *   data outside of the range (in these partial chunks).
696  *
697  *   For some cases the overhead of kmap can be too high, a vmap interface
698  *   is introduced. This interface should be used very carefully, as vmalloc
699  *   space is a limited resources on many architectures.
700  *
701  *   Interfaces::
702  *      void \*dma_buf_vmap(struct dma_buf \*dmabuf)
703  *      void dma_buf_vunmap(struct dma_buf \*dmabuf, void \*vaddr)
704  *
705  *   The vmap call can fail if there is no vmap support in the exporter, or if
706  *   it runs out of vmalloc space. Fallback to kmap should be implemented. Note
707  *   that the dma-buf layer keeps a reference count for all vmap access and
708  *   calls down into the exporter's vmap function only when no vmapping exists,
709  *   and only unmaps it once. Protection against concurrent vmap/vunmap calls is
710  *   provided by taking the dma_buf->lock mutex.
711  *
712  * - For full compatibility on the importer side with existing userspace
713  *   interfaces, which might already support mmap'ing buffers. This is needed in
714  *   many processing pipelines (e.g. feeding a software rendered image into a
715  *   hardware pipeline, thumbnail creation, snapshots, ...). Also, Android's ION
716  *   framework already supported this and for DMA buffer file descriptors to
717  *   replace ION buffers mmap support was needed.
718  *
719  *   There is no special interfaces, userspace simply calls mmap on the dma-buf
720  *   fd. But like for CPU access there's a need to braket the actual access,
721  *   which is handled by the ioctl (DMA_BUF_IOCTL_SYNC). Note that
722  *   DMA_BUF_IOCTL_SYNC can fail with -EAGAIN or -EINTR, in which case it must
723  *   be restarted.
724  *
725  *   Some systems might need some sort of cache coherency management e.g. when
726  *   CPU and GPU domains are being accessed through dma-buf at the same time.
727  *   To circumvent this problem there are begin/end coherency markers, that
728  *   forward directly to existing dma-buf device drivers vfunc hooks. Userspace
729  *   can make use of those markers through the DMA_BUF_IOCTL_SYNC ioctl. The
730  *   sequence would be used like following:
731  *
732  *     - mmap dma-buf fd
733  *     - for each drawing/upload cycle in CPU 1. SYNC_START ioctl, 2. read/write
734  *       to mmap area 3. SYNC_END ioctl. This can be repeated as often as you
735  *       want (with the new data being consumed by say the GPU or the scanout
736  *       device)
737  *     - munmap once you don't need the buffer any more
738  *
739  *    For correctness and optimal performance, it is always required to use
740  *    SYNC_START and SYNC_END before and after, respectively, when accessing the
741  *    mapped address. Userspace cannot rely on coherent access, even when there
742  *    are systems where it just works without calling these ioctls.
743  *
744  * - And as a CPU fallback in userspace processing pipelines.
745  *
746  *   Similar to the motivation for kernel cpu access it is again important that
747  *   the userspace code of a given importing subsystem can use the same
748  *   interfaces with a imported dma-buf buffer object as with a native buffer
749  *   object. This is especially important for drm where the userspace part of
750  *   contemporary OpenGL, X, and other drivers is huge, and reworking them to
751  *   use a different way to mmap a buffer rather invasive.
752  *
753  *   The assumption in the current dma-buf interfaces is that redirecting the
754  *   initial mmap is all that's needed. A survey of some of the existing
755  *   subsystems shows that no driver seems to do any nefarious thing like
756  *   syncing up with outstanding asynchronous processing on the device or
757  *   allocating special resources at fault time. So hopefully this is good
758  *   enough, since adding interfaces to intercept pagefaults and allow pte
759  *   shootdowns would increase the complexity quite a bit.
760  *
761  *   Interface::
762  *      int dma_buf_mmap(struct dma_buf \*, struct vm_area_struct \*,
763  *		       unsigned long);
764  *
765  *   If the importing subsystem simply provides a special-purpose mmap call to
766  *   set up a mapping in userspace, calling do_mmap with dma_buf->file will
767  *   equally achieve that for a dma-buf object.
768  */
769 
__dma_buf_begin_cpu_access(struct dma_buf * dmabuf,enum dma_data_direction direction)770 static int __dma_buf_begin_cpu_access(struct dma_buf *dmabuf,
771 				      enum dma_data_direction direction)
772 {
773 	bool write = (direction == DMA_BIDIRECTIONAL ||
774 		      direction == DMA_TO_DEVICE);
775 	struct reservation_object *resv = dmabuf->resv;
776 	long ret;
777 
778 	/* Wait on any implicit rendering fences */
779 	ret = reservation_object_wait_timeout_rcu(resv, write, true,
780 						  MAX_SCHEDULE_TIMEOUT);
781 	if (ret < 0)
782 		return ret;
783 
784 	return 0;
785 }
786 
787 /**
788  * dma_buf_begin_cpu_access - Must be called before accessing a dma_buf from the
789  * cpu in the kernel context. Calls begin_cpu_access to allow exporter-specific
790  * preparations. Coherency is only guaranteed in the specified range for the
791  * specified access direction.
792  * @dmabuf:	[in]	buffer to prepare cpu access for.
793  * @direction:	[in]	length of range for cpu access.
794  *
795  * After the cpu access is complete the caller should call
796  * dma_buf_end_cpu_access(). Only when cpu access is braketed by both calls is
797  * it guaranteed to be coherent with other DMA access.
798  *
799  * Can return negative error values, returns 0 on success.
800  */
dma_buf_begin_cpu_access(struct dma_buf * dmabuf,enum dma_data_direction direction)801 int dma_buf_begin_cpu_access(struct dma_buf *dmabuf,
802 			     enum dma_data_direction direction)
803 {
804 	int ret = 0;
805 
806 	if (WARN_ON(!dmabuf))
807 		return -EINVAL;
808 
809 	if (dmabuf->ops->begin_cpu_access)
810 		ret = dmabuf->ops->begin_cpu_access(dmabuf, direction);
811 
812 	/* Ensure that all fences are waited upon - but we first allow
813 	 * the native handler the chance to do so more efficiently if it
814 	 * chooses. A double invocation here will be reasonably cheap no-op.
815 	 */
816 	if (ret == 0)
817 		ret = __dma_buf_begin_cpu_access(dmabuf, direction);
818 
819 	return ret;
820 }
821 EXPORT_SYMBOL_GPL(dma_buf_begin_cpu_access);
822 
823 /**
824  * dma_buf_end_cpu_access - Must be called after accessing a dma_buf from the
825  * cpu in the kernel context. Calls end_cpu_access to allow exporter-specific
826  * actions. Coherency is only guaranteed in the specified range for the
827  * specified access direction.
828  * @dmabuf:	[in]	buffer to complete cpu access for.
829  * @direction:	[in]	length of range for cpu access.
830  *
831  * This terminates CPU access started with dma_buf_begin_cpu_access().
832  *
833  * Can return negative error values, returns 0 on success.
834  */
dma_buf_end_cpu_access(struct dma_buf * dmabuf,enum dma_data_direction direction)835 int dma_buf_end_cpu_access(struct dma_buf *dmabuf,
836 			   enum dma_data_direction direction)
837 {
838 	int ret = 0;
839 
840 	WARN_ON(!dmabuf);
841 
842 	if (dmabuf->ops->end_cpu_access)
843 		ret = dmabuf->ops->end_cpu_access(dmabuf, direction);
844 
845 	return ret;
846 }
847 EXPORT_SYMBOL_GPL(dma_buf_end_cpu_access);
848 
849 /**
850  * dma_buf_kmap - Map a page of the buffer object into kernel address space. The
851  * same restrictions as for kmap and friends apply.
852  * @dmabuf:	[in]	buffer to map page from.
853  * @page_num:	[in]	page in PAGE_SIZE units to map.
854  *
855  * This call must always succeed, any necessary preparations that might fail
856  * need to be done in begin_cpu_access.
857  */
dma_buf_kmap(struct dma_buf * dmabuf,unsigned long page_num)858 void *dma_buf_kmap(struct dma_buf *dmabuf, unsigned long page_num)
859 {
860 	WARN_ON(!dmabuf);
861 
862 	if (!dmabuf->ops->map)
863 		return NULL;
864 	return dmabuf->ops->map(dmabuf, page_num);
865 }
866 EXPORT_SYMBOL_GPL(dma_buf_kmap);
867 
868 /**
869  * dma_buf_kunmap - Unmap a page obtained by dma_buf_kmap.
870  * @dmabuf:	[in]	buffer to unmap page from.
871  * @page_num:	[in]	page in PAGE_SIZE units to unmap.
872  * @vaddr:	[in]	kernel space pointer obtained from dma_buf_kmap.
873  *
874  * This call must always succeed.
875  */
dma_buf_kunmap(struct dma_buf * dmabuf,unsigned long page_num,void * vaddr)876 void dma_buf_kunmap(struct dma_buf *dmabuf, unsigned long page_num,
877 		    void *vaddr)
878 {
879 	WARN_ON(!dmabuf);
880 
881 	if (dmabuf->ops->unmap)
882 		dmabuf->ops->unmap(dmabuf, page_num, vaddr);
883 }
884 EXPORT_SYMBOL_GPL(dma_buf_kunmap);
885 
886 
887 /**
888  * dma_buf_mmap - Setup up a userspace mmap with the given vma
889  * @dmabuf:	[in]	buffer that should back the vma
890  * @vma:	[in]	vma for the mmap
891  * @pgoff:	[in]	offset in pages where this mmap should start within the
892  *			dma-buf buffer.
893  *
894  * This function adjusts the passed in vma so that it points at the file of the
895  * dma_buf operation. It also adjusts the starting pgoff and does bounds
896  * checking on the size of the vma. Then it calls the exporters mmap function to
897  * set up the mapping.
898  *
899  * Can return negative error values, returns 0 on success.
900  */
dma_buf_mmap(struct dma_buf * dmabuf,struct vm_area_struct * vma,unsigned long pgoff)901 int dma_buf_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma,
902 		 unsigned long pgoff)
903 {
904 	struct file *oldfile;
905 	int ret;
906 
907 	if (WARN_ON(!dmabuf || !vma))
908 		return -EINVAL;
909 
910 	/* check for offset overflow */
911 	if (pgoff + vma_pages(vma) < pgoff)
912 		return -EOVERFLOW;
913 
914 	/* check for overflowing the buffer's size */
915 	if (pgoff + vma_pages(vma) >
916 	    dmabuf->size >> PAGE_SHIFT)
917 		return -EINVAL;
918 
919 	/* readjust the vma */
920 	get_file(dmabuf->file);
921 	oldfile = vma->vm_file;
922 	vma->vm_file = dmabuf->file;
923 	vma->vm_pgoff = pgoff;
924 
925 	ret = dmabuf->ops->mmap(dmabuf, vma);
926 	if (ret) {
927 		/* restore old parameters on failure */
928 		vma->vm_file = oldfile;
929 		fput(dmabuf->file);
930 	} else {
931 		if (oldfile)
932 			fput(oldfile);
933 	}
934 	return ret;
935 
936 }
937 EXPORT_SYMBOL_GPL(dma_buf_mmap);
938 
939 /**
940  * dma_buf_vmap - Create virtual mapping for the buffer object into kernel
941  * address space. Same restrictions as for vmap and friends apply.
942  * @dmabuf:	[in]	buffer to vmap
943  *
944  * This call may fail due to lack of virtual mapping address space.
945  * These calls are optional in drivers. The intended use for them
946  * is for mapping objects linear in kernel space for high use objects.
947  * Please attempt to use kmap/kunmap before thinking about these interfaces.
948  *
949  * Returns NULL on error.
950  */
dma_buf_vmap(struct dma_buf * dmabuf)951 void *dma_buf_vmap(struct dma_buf *dmabuf)
952 {
953 	void *ptr;
954 
955 	if (WARN_ON(!dmabuf))
956 		return NULL;
957 
958 	if (!dmabuf->ops->vmap)
959 		return NULL;
960 
961 	mutex_lock(&dmabuf->lock);
962 	if (dmabuf->vmapping_counter) {
963 		dmabuf->vmapping_counter++;
964 		BUG_ON(!dmabuf->vmap_ptr);
965 		ptr = dmabuf->vmap_ptr;
966 		goto out_unlock;
967 	}
968 
969 	BUG_ON(dmabuf->vmap_ptr);
970 
971 	ptr = dmabuf->ops->vmap(dmabuf);
972 	if (WARN_ON_ONCE(IS_ERR(ptr)))
973 		ptr = NULL;
974 	if (!ptr)
975 		goto out_unlock;
976 
977 	dmabuf->vmap_ptr = ptr;
978 	dmabuf->vmapping_counter = 1;
979 
980 out_unlock:
981 	mutex_unlock(&dmabuf->lock);
982 	return ptr;
983 }
984 EXPORT_SYMBOL_GPL(dma_buf_vmap);
985 
986 /**
987  * dma_buf_vunmap - Unmap a vmap obtained by dma_buf_vmap.
988  * @dmabuf:	[in]	buffer to vunmap
989  * @vaddr:	[in]	vmap to vunmap
990  */
dma_buf_vunmap(struct dma_buf * dmabuf,void * vaddr)991 void dma_buf_vunmap(struct dma_buf *dmabuf, void *vaddr)
992 {
993 	if (WARN_ON(!dmabuf))
994 		return;
995 
996 	BUG_ON(!dmabuf->vmap_ptr);
997 	BUG_ON(dmabuf->vmapping_counter == 0);
998 	BUG_ON(dmabuf->vmap_ptr != vaddr);
999 
1000 	mutex_lock(&dmabuf->lock);
1001 	if (--dmabuf->vmapping_counter == 0) {
1002 		if (dmabuf->ops->vunmap)
1003 			dmabuf->ops->vunmap(dmabuf, vaddr);
1004 		dmabuf->vmap_ptr = NULL;
1005 	}
1006 	mutex_unlock(&dmabuf->lock);
1007 }
1008 EXPORT_SYMBOL_GPL(dma_buf_vunmap);
1009 
1010 #ifdef CONFIG_DEBUG_FS
dma_buf_debug_show(struct seq_file * s,void * unused)1011 static int dma_buf_debug_show(struct seq_file *s, void *unused)
1012 {
1013 	int ret;
1014 	struct dma_buf *buf_obj;
1015 	struct dma_buf_attachment *attach_obj;
1016 	struct reservation_object *robj;
1017 	struct reservation_object_list *fobj;
1018 	struct dma_fence *fence;
1019 	unsigned seq;
1020 	int count = 0, attach_count, shared_count, i;
1021 	size_t size = 0;
1022 
1023 	ret = mutex_lock_interruptible(&db_list.lock);
1024 
1025 	if (ret)
1026 		return ret;
1027 
1028 	seq_puts(s, "\nDma-buf Objects:\n");
1029 	seq_printf(s, "%-8s\t%-8s\t%-8s\t%-8s\texp_name\n",
1030 		   "size", "flags", "mode", "count");
1031 
1032 	list_for_each_entry(buf_obj, &db_list.head, list_node) {
1033 		ret = mutex_lock_interruptible(&buf_obj->lock);
1034 
1035 		if (ret) {
1036 			seq_puts(s,
1037 				 "\tERROR locking buffer object: skipping\n");
1038 			continue;
1039 		}
1040 
1041 		seq_printf(s, "%08zu\t%08x\t%08x\t%08ld\t%s\n",
1042 				buf_obj->size,
1043 				buf_obj->file->f_flags, buf_obj->file->f_mode,
1044 				file_count(buf_obj->file),
1045 				buf_obj->exp_name);
1046 
1047 		robj = buf_obj->resv;
1048 		while (true) {
1049 			seq = read_seqcount_begin(&robj->seq);
1050 			rcu_read_lock();
1051 			fobj = rcu_dereference(robj->fence);
1052 			shared_count = fobj ? fobj->shared_count : 0;
1053 			fence = rcu_dereference(robj->fence_excl);
1054 			if (!read_seqcount_retry(&robj->seq, seq))
1055 				break;
1056 			rcu_read_unlock();
1057 		}
1058 
1059 		if (fence)
1060 			seq_printf(s, "\tExclusive fence: %s %s %ssignalled\n",
1061 				   fence->ops->get_driver_name(fence),
1062 				   fence->ops->get_timeline_name(fence),
1063 				   dma_fence_is_signaled(fence) ? "" : "un");
1064 		for (i = 0; i < shared_count; i++) {
1065 			fence = rcu_dereference(fobj->shared[i]);
1066 			if (!dma_fence_get_rcu(fence))
1067 				continue;
1068 			seq_printf(s, "\tShared fence: %s %s %ssignalled\n",
1069 				   fence->ops->get_driver_name(fence),
1070 				   fence->ops->get_timeline_name(fence),
1071 				   dma_fence_is_signaled(fence) ? "" : "un");
1072 			dma_fence_put(fence);
1073 		}
1074 		rcu_read_unlock();
1075 
1076 		seq_puts(s, "\tAttached Devices:\n");
1077 		attach_count = 0;
1078 
1079 		list_for_each_entry(attach_obj, &buf_obj->attachments, node) {
1080 			seq_printf(s, "\t%s\n", dev_name(attach_obj->dev));
1081 			attach_count++;
1082 		}
1083 
1084 		seq_printf(s, "Total %d devices attached\n\n",
1085 				attach_count);
1086 
1087 		count++;
1088 		size += buf_obj->size;
1089 		mutex_unlock(&buf_obj->lock);
1090 	}
1091 
1092 	seq_printf(s, "\nTotal %d objects, %zu bytes\n", count, size);
1093 
1094 	mutex_unlock(&db_list.lock);
1095 	return 0;
1096 }
1097 
dma_buf_debug_open(struct inode * inode,struct file * file)1098 static int dma_buf_debug_open(struct inode *inode, struct file *file)
1099 {
1100 	return single_open(file, dma_buf_debug_show, NULL);
1101 }
1102 
1103 static const struct file_operations dma_buf_debug_fops = {
1104 	.open           = dma_buf_debug_open,
1105 	.read           = seq_read,
1106 	.llseek         = seq_lseek,
1107 	.release        = single_release,
1108 };
1109 
1110 static struct dentry *dma_buf_debugfs_dir;
1111 
dma_buf_init_debugfs(void)1112 static int dma_buf_init_debugfs(void)
1113 {
1114 	struct dentry *d;
1115 	int err = 0;
1116 
1117 	d = debugfs_create_dir("dma_buf", NULL);
1118 	if (IS_ERR(d))
1119 		return PTR_ERR(d);
1120 
1121 	dma_buf_debugfs_dir = d;
1122 
1123 	d = debugfs_create_file("bufinfo", S_IRUGO, dma_buf_debugfs_dir,
1124 				NULL, &dma_buf_debug_fops);
1125 	if (IS_ERR(d)) {
1126 		pr_debug("dma_buf: debugfs: failed to create node bufinfo\n");
1127 		debugfs_remove_recursive(dma_buf_debugfs_dir);
1128 		dma_buf_debugfs_dir = NULL;
1129 		err = PTR_ERR(d);
1130 	}
1131 
1132 	return err;
1133 }
1134 
dma_buf_uninit_debugfs(void)1135 static void dma_buf_uninit_debugfs(void)
1136 {
1137 	debugfs_remove_recursive(dma_buf_debugfs_dir);
1138 }
1139 #else
dma_buf_init_debugfs(void)1140 static inline int dma_buf_init_debugfs(void)
1141 {
1142 	return 0;
1143 }
dma_buf_uninit_debugfs(void)1144 static inline void dma_buf_uninit_debugfs(void)
1145 {
1146 }
1147 #endif
1148 
dma_buf_init(void)1149 static int __init dma_buf_init(void)
1150 {
1151 	mutex_init(&db_list.lock);
1152 	INIT_LIST_HEAD(&db_list.head);
1153 	dma_buf_init_debugfs();
1154 	return 0;
1155 }
1156 subsys_initcall(dma_buf_init);
1157 
dma_buf_deinit(void)1158 static void __exit dma_buf_deinit(void)
1159 {
1160 	dma_buf_uninit_debugfs();
1161 }
1162 __exitcall(dma_buf_deinit);
1163