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
40static inline int is_dma_buf_file(struct file *);
41
42struct dma_buf_list {
43 struct list_head head;
44 struct mutex lock;
45};
46
47static struct dma_buf_list db_list;
48
49static 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
84static 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
101static 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
149static 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
160static __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
181retry:
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
274out:
275 rcu_read_unlock();
276 return events;
277}
278
279static 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
322static 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 */
336static 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 */
389struct 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->mmap)) {
409 return ERR_PTR(-EINVAL);
410 }
411
412 if (!try_module_get(exp_info->owner))
413 return ERR_PTR(-ENOENT);
414
415 dmabuf = kzalloc(alloc_size, GFP_KERNEL);
416 if (!dmabuf) {
417 ret = -ENOMEM;
418 goto err_module;
419 }
420
421 dmabuf->priv = exp_info->priv;
422 dmabuf->ops = exp_info->ops;
423 dmabuf->size = exp_info->size;
424 dmabuf->exp_name = exp_info->exp_name;
425 dmabuf->owner = exp_info->owner;
426 init_waitqueue_head(&dmabuf->poll);
427 dmabuf->cb_excl.poll = dmabuf->cb_shared.poll = &dmabuf->poll;
428 dmabuf->cb_excl.active = dmabuf->cb_shared.active = 0;
429
430 if (!resv) {
431 resv = (struct reservation_object *)&dmabuf[1];
432 reservation_object_init(resv);
433 }
434 dmabuf->resv = resv;
435
436 file = anon_inode_getfile("dmabuf", &dma_buf_fops, dmabuf,
437 exp_info->flags);
438 if (IS_ERR(file)) {
439 ret = PTR_ERR(file);
440 goto err_dmabuf;
441 }
442
443 file->f_mode |= FMODE_LSEEK;
444 dmabuf->file = file;
445
446 mutex_init(&dmabuf->lock);
447 INIT_LIST_HEAD(&dmabuf->attachments);
448
449 mutex_lock(&db_list.lock);
450 list_add(&dmabuf->list_node, &db_list.head);
451 mutex_unlock(&db_list.lock);
452
453 return dmabuf;
454
455err_dmabuf:
456 kfree(dmabuf);
457err_module:
458 module_put(exp_info->owner);
459 return ERR_PTR(ret);
460}
461EXPORT_SYMBOL_GPL(dma_buf_export);
462
463/**
464 * dma_buf_fd - returns a file descriptor for the given dma_buf
465 * @dmabuf: [in] pointer to dma_buf for which fd is required.
466 * @flags: [in] flags to give to fd
467 *
468 * On success, returns an associated 'fd'. Else, returns error.
469 */
470int dma_buf_fd(struct dma_buf *dmabuf, int flags)
471{
472 int fd;
473
474 if (!dmabuf || !dmabuf->file)
475 return -EINVAL;
476
477 fd = get_unused_fd_flags(flags);
478 if (fd < 0)
479 return fd;
480
481 fd_install(fd, dmabuf->file);
482
483 return fd;
484}
485EXPORT_SYMBOL_GPL(dma_buf_fd);
486
487/**
488 * dma_buf_get - returns the dma_buf structure related to an fd
489 * @fd: [in] fd associated with the dma_buf to be returned
490 *
491 * On success, returns the dma_buf structure associated with an fd; uses
492 * file's refcounting done by fget to increase refcount. returns ERR_PTR
493 * otherwise.
494 */
495struct dma_buf *dma_buf_get(int fd)
496{
497 struct file *file;
498
499 file = fget(fd);
500
501 if (!file)
502 return ERR_PTR(-EBADF);
503
504 if (!is_dma_buf_file(file)) {
505 fput(file);
506 return ERR_PTR(-EINVAL);
507 }
508
509 return file->private_data;
510}
511EXPORT_SYMBOL_GPL(dma_buf_get);
512
513/**
514 * dma_buf_put - decreases refcount of the buffer
515 * @dmabuf: [in] buffer to reduce refcount of
516 *
517 * Uses file's refcounting done implicitly by fput().
518 *
519 * If, as a result of this call, the refcount becomes 0, the 'release' file
520 * operation related to this fd is called. It calls &dma_buf_ops.release vfunc
521 * in turn, and frees the memory allocated for dmabuf when exported.
522 */
523void dma_buf_put(struct dma_buf *dmabuf)
524{
525 if (WARN_ON(!dmabuf || !dmabuf->file))
526 return;
527
528 fput(dmabuf->file);
529}
530EXPORT_SYMBOL_GPL(dma_buf_put);
531
532/**
533 * dma_buf_attach - Add the device to dma_buf's attachments list; optionally,
534 * calls attach() of dma_buf_ops to allow device-specific attach functionality
535 * @dmabuf: [in] buffer to attach device to.
536 * @dev: [in] device to be attached.
537 *
538 * Returns struct dma_buf_attachment pointer for this attachment. Attachments
539 * must be cleaned up by calling dma_buf_detach().
540 *
541 * Returns:
542 *
543 * A pointer to newly created &dma_buf_attachment on success, or a negative
544 * error code wrapped into a pointer on failure.
545 *
546 * Note that this can fail if the backing storage of @dmabuf is in a place not
547 * accessible to @dev, and cannot be moved to a more suitable place. This is
548 * indicated with the error code -EBUSY.
549 */
550struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
551 struct device *dev)
552{
553 struct dma_buf_attachment *attach;
554 int ret;
555
556 if (WARN_ON(!dmabuf || !dev))
557 return ERR_PTR(-EINVAL);
558
559 attach = kzalloc(sizeof(*attach), GFP_KERNEL);
560 if (!attach)
561 return ERR_PTR(-ENOMEM);
562
563 attach->dev = dev;
564 attach->dmabuf = dmabuf;
565
566 mutex_lock(&dmabuf->lock);
567
568 if (dmabuf->ops->attach) {
569 ret = dmabuf->ops->attach(dmabuf, attach);
570 if (ret)
571 goto err_attach;
572 }
573 list_add(&attach->node, &dmabuf->attachments);
574
575 mutex_unlock(&dmabuf->lock);
576 return attach;
577
578err_attach:
579 kfree(attach);
580 mutex_unlock(&dmabuf->lock);
581 return ERR_PTR(ret);
582}
583EXPORT_SYMBOL_GPL(dma_buf_attach);
584
585/**
586 * dma_buf_detach - Remove the given attachment from dmabuf's attachments list;
587 * optionally calls detach() of dma_buf_ops for device-specific detach
588 * @dmabuf: [in] buffer to detach from.
589 * @attach: [in] attachment to be detached; is free'd after this call.
590 *
591 * Clean up a device attachment obtained by calling dma_buf_attach().
592 */
593void dma_buf_detach(struct dma_buf *dmabuf, struct dma_buf_attachment *attach)
594{
595 if (WARN_ON(!dmabuf || !attach))
596 return;
597
598 mutex_lock(&dmabuf->lock);
599 list_del(&attach->node);
600 if (dmabuf->ops->detach)
601 dmabuf->ops->detach(dmabuf, attach);
602
603 mutex_unlock(&dmabuf->lock);
604 kfree(attach);
605}
606EXPORT_SYMBOL_GPL(dma_buf_detach);
607
608/**
609 * dma_buf_map_attachment - Returns the scatterlist table of the attachment;
610 * mapped into _device_ address space. Is a wrapper for map_dma_buf() of the
611 * dma_buf_ops.
612 * @attach: [in] attachment whose scatterlist is to be returned
613 * @direction: [in] direction of DMA transfer
614 *
615 * Returns sg_table containing the scatterlist to be returned; returns ERR_PTR
616 * on error. May return -EINTR if it is interrupted by a signal.
617 *
618 * A mapping must be unmapped by using dma_buf_unmap_attachment(). Note that
619 * the underlying backing storage is pinned for as long as a mapping exists,
620 * therefore users/importers should not hold onto a mapping for undue amounts of
621 * time.
622 */
623struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
624 enum dma_data_direction direction)
625{
626 struct sg_table *sg_table;
627
628 might_sleep();
629
630 if (WARN_ON(!attach || !attach->dmabuf))
631 return ERR_PTR(-EINVAL);
632
633 sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction);
634 if (!sg_table)
635 sg_table = ERR_PTR(-ENOMEM);
636
637 return sg_table;
638}
639EXPORT_SYMBOL_GPL(dma_buf_map_attachment);
640
641/**
642 * dma_buf_unmap_attachment - unmaps and decreases usecount of the buffer;might
643 * deallocate the scatterlist associated. Is a wrapper for unmap_dma_buf() of
644 * dma_buf_ops.
645 * @attach: [in] attachment to unmap buffer from
646 * @sg_table: [in] scatterlist info of the buffer to unmap
647 * @direction: [in] direction of DMA transfer
648 *
649 * This unmaps a DMA mapping for @attached obtained by dma_buf_map_attachment().
650 */
651void dma_buf_unmap_attachment(struct dma_buf_attachment *attach,
652 struct sg_table *sg_table,
653 enum dma_data_direction direction)
654{
655 might_sleep();
656
657 if (WARN_ON(!attach || !attach->dmabuf || !sg_table))
658 return;
659
660 attach->dmabuf->ops->unmap_dma_buf(attach, sg_table,
661 direction);
662}
663EXPORT_SYMBOL_GPL(dma_buf_unmap_attachment);
664
665/**
666 * DOC: cpu access
667 *
668 * There are mutliple reasons for supporting CPU access to a dma buffer object:
669 *
670 * - Fallback operations in the kernel, for example when a device is connected
671 * over USB and the kernel needs to shuffle the data around first before
672 * sending it away. Cache coherency is handled by braketing any transactions
673 * with calls to dma_buf_begin_cpu_access() and dma_buf_end_cpu_access()
674 * access.
675 *
676 * To support dma_buf objects residing in highmem cpu access is page-based
677 * using an api similar to kmap. Accessing a dma_buf is done in aligned chunks
678 * of PAGE_SIZE size. Before accessing a chunk it needs to be mapped, which
679 * returns a pointer in kernel virtual address space. Afterwards the chunk
680 * needs to be unmapped again. There is no limit on how often a given chunk
681 * can be mapped and unmapped, i.e. the importer does not need to call
682 * begin_cpu_access again before mapping the same chunk again.
683 *
684 * Interfaces::
685 * void \*dma_buf_kmap(struct dma_buf \*, unsigned long);
686 * void dma_buf_kunmap(struct dma_buf \*, unsigned long, void \*);
687 *
688 * Implementing the functions is optional for exporters and for importers all
689 * the restrictions of using kmap apply.
690 *
691 * dma_buf kmap calls outside of the range specified in begin_cpu_access are
692 * undefined. If the range is not PAGE_SIZE aligned, kmap needs to succeed on
693 * the partial chunks at the beginning and end but may return stale or bogus
694 * data outside of the range (in these partial chunks).
695 *
696 * For some cases the overhead of kmap can be too high, a vmap interface
697 * is introduced. This interface should be used very carefully, as vmalloc
698 * space is a limited resources on many architectures.
699 *
700 * Interfaces::
701 * void \*dma_buf_vmap(struct dma_buf \*dmabuf)
702 * void dma_buf_vunmap(struct dma_buf \*dmabuf, void \*vaddr)
703 *
704 * The vmap call can fail if there is no vmap support in the exporter, or if
705 * it runs out of vmalloc space. Fallback to kmap should be implemented. Note
706 * that the dma-buf layer keeps a reference count for all vmap access and
707 * calls down into the exporter's vmap function only when no vmapping exists,
708 * and only unmaps it once. Protection against concurrent vmap/vunmap calls is
709 * provided by taking the dma_buf->lock mutex.
710 *
711 * - For full compatibility on the importer side with existing userspace
712 * interfaces, which might already support mmap'ing buffers. This is needed in
713 * many processing pipelines (e.g. feeding a software rendered image into a
714 * hardware pipeline, thumbnail creation, snapshots, ...). Also, Android's ION
715 * framework already supported this and for DMA buffer file descriptors to
716 * replace ION buffers mmap support was needed.
717 *
718 * There is no special interfaces, userspace simply calls mmap on the dma-buf
719 * fd. But like for CPU access there's a need to braket the actual access,
720 * which is handled by the ioctl (DMA_BUF_IOCTL_SYNC). Note that
721 * DMA_BUF_IOCTL_SYNC can fail with -EAGAIN or -EINTR, in which case it must
722 * be restarted.
723 *
724 * Some systems might need some sort of cache coherency management e.g. when
725 * CPU and GPU domains are being accessed through dma-buf at the same time.
726 * To circumvent this problem there are begin/end coherency markers, that
727 * forward directly to existing dma-buf device drivers vfunc hooks. Userspace
728 * can make use of those markers through the DMA_BUF_IOCTL_SYNC ioctl. The
729 * sequence would be used like following:
730 *
731 * - mmap dma-buf fd
732 * - for each drawing/upload cycle in CPU 1. SYNC_START ioctl, 2. read/write
733 * to mmap area 3. SYNC_END ioctl. This can be repeated as often as you
734 * want (with the new data being consumed by say the GPU or the scanout
735 * device)
736 * - munmap once you don't need the buffer any more
737 *
738 * For correctness and optimal performance, it is always required to use
739 * SYNC_START and SYNC_END before and after, respectively, when accessing the
740 * mapped address. Userspace cannot rely on coherent access, even when there
741 * are systems where it just works without calling these ioctls.
742 *
743 * - And as a CPU fallback in userspace processing pipelines.
744 *
745 * Similar to the motivation for kernel cpu access it is again important that
746 * the userspace code of a given importing subsystem can use the same
747 * interfaces with a imported dma-buf buffer object as with a native buffer
748 * object. This is especially important for drm where the userspace part of
749 * contemporary OpenGL, X, and other drivers is huge, and reworking them to
750 * use a different way to mmap a buffer rather invasive.
751 *
752 * The assumption in the current dma-buf interfaces is that redirecting the
753 * initial mmap is all that's needed. A survey of some of the existing
754 * subsystems shows that no driver seems to do any nefarious thing like
755 * syncing up with outstanding asynchronous processing on the device or
756 * allocating special resources at fault time. So hopefully this is good
757 * enough, since adding interfaces to intercept pagefaults and allow pte
758 * shootdowns would increase the complexity quite a bit.
759 *
760 * Interface::
761 * int dma_buf_mmap(struct dma_buf \*, struct vm_area_struct \*,
762 * unsigned long);
763 *
764 * If the importing subsystem simply provides a special-purpose mmap call to
765 * set up a mapping in userspace, calling do_mmap with dma_buf->file will
766 * equally achieve that for a dma-buf object.
767 */
768
769static int __dma_buf_begin_cpu_access(struct dma_buf *dmabuf,
770 enum dma_data_direction direction)
771{
772 bool write = (direction == DMA_BIDIRECTIONAL ||
773 direction == DMA_TO_DEVICE);
774 struct reservation_object *resv = dmabuf->resv;
775 long ret;
776
777 /* Wait on any implicit rendering fences */
778 ret = reservation_object_wait_timeout_rcu(resv, write, true,
779 MAX_SCHEDULE_TIMEOUT);
780 if (ret < 0)
781 return ret;
782
783 return 0;
784}
785
786/**
787 * dma_buf_begin_cpu_access - Must be called before accessing a dma_buf from the
788 * cpu in the kernel context. Calls begin_cpu_access to allow exporter-specific
789 * preparations. Coherency is only guaranteed in the specified range for the
790 * specified access direction.
791 * @dmabuf: [in] buffer to prepare cpu access for.
792 * @direction: [in] length of range for cpu access.
793 *
794 * After the cpu access is complete the caller should call
795 * dma_buf_end_cpu_access(). Only when cpu access is braketed by both calls is
796 * it guaranteed to be coherent with other DMA access.
797 *
798 * Can return negative error values, returns 0 on success.
799 */
800int dma_buf_begin_cpu_access(struct dma_buf *dmabuf,
801 enum dma_data_direction direction)
802{
803 int ret = 0;
804
805 if (WARN_ON(!dmabuf))
806 return -EINVAL;
807
808 if (dmabuf->ops->begin_cpu_access)
809 ret = dmabuf->ops->begin_cpu_access(dmabuf, direction);
810
811 /* Ensure that all fences are waited upon - but we first allow
812 * the native handler the chance to do so more efficiently if it
813 * chooses. A double invocation here will be reasonably cheap no-op.
814 */
815 if (ret == 0)
816 ret = __dma_buf_begin_cpu_access(dmabuf, direction);
817
818 return ret;
819}
820EXPORT_SYMBOL_GPL(dma_buf_begin_cpu_access);
821
822/**
823 * dma_buf_end_cpu_access - Must be called after accessing a dma_buf from the
824 * cpu in the kernel context. Calls end_cpu_access to allow exporter-specific
825 * actions. Coherency is only guaranteed in the specified range for the
826 * specified access direction.
827 * @dmabuf: [in] buffer to complete cpu access for.
828 * @direction: [in] length of range for cpu access.
829 *
830 * This terminates CPU access started with dma_buf_begin_cpu_access().
831 *
832 * Can return negative error values, returns 0 on success.
833 */
834int dma_buf_end_cpu_access(struct dma_buf *dmabuf,
835 enum dma_data_direction direction)
836{
837 int ret = 0;
838
839 WARN_ON(!dmabuf);
840
841 if (dmabuf->ops->end_cpu_access)
842 ret = dmabuf->ops->end_cpu_access(dmabuf, direction);
843
844 return ret;
845}
846EXPORT_SYMBOL_GPL(dma_buf_end_cpu_access);
847
848/**
849 * dma_buf_kmap - Map a page of the buffer object into kernel address space. The
850 * same restrictions as for kmap and friends apply.
851 * @dmabuf: [in] buffer to map page from.
852 * @page_num: [in] page in PAGE_SIZE units to map.
853 *
854 * This call must always succeed, any necessary preparations that might fail
855 * need to be done in begin_cpu_access.
856 */
857void *dma_buf_kmap(struct dma_buf *dmabuf, unsigned long page_num)
858{
859 WARN_ON(!dmabuf);
860
861 if (!dmabuf->ops->map)
862 return NULL;
863 return dmabuf->ops->map(dmabuf, page_num);
864}
865EXPORT_SYMBOL_GPL(dma_buf_kmap);
866
867/**
868 * dma_buf_kunmap - Unmap a page obtained by dma_buf_kmap.
869 * @dmabuf: [in] buffer to unmap page from.
870 * @page_num: [in] page in PAGE_SIZE units to unmap.
871 * @vaddr: [in] kernel space pointer obtained from dma_buf_kmap.
872 *
873 * This call must always succeed.
874 */
875void dma_buf_kunmap(struct dma_buf *dmabuf, unsigned long page_num,
876 void *vaddr)
877{
878 WARN_ON(!dmabuf);
879
880 if (dmabuf->ops->unmap)
881 dmabuf->ops->unmap(dmabuf, page_num, vaddr);
882}
883EXPORT_SYMBOL_GPL(dma_buf_kunmap);
884
885
886/**
887 * dma_buf_mmap - Setup up a userspace mmap with the given vma
888 * @dmabuf: [in] buffer that should back the vma
889 * @vma: [in] vma for the mmap
890 * @pgoff: [in] offset in pages where this mmap should start within the
891 * dma-buf buffer.
892 *
893 * This function adjusts the passed in vma so that it points at the file of the
894 * dma_buf operation. It also adjusts the starting pgoff and does bounds
895 * checking on the size of the vma. Then it calls the exporters mmap function to
896 * set up the mapping.
897 *
898 * Can return negative error values, returns 0 on success.
899 */
900int dma_buf_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma,
901 unsigned long pgoff)
902{
903 struct file *oldfile;
904 int ret;
905
906 if (WARN_ON(!dmabuf || !vma))
907 return -EINVAL;
908
909 /* check for offset overflow */
910 if (pgoff + vma_pages(vma) < pgoff)
911 return -EOVERFLOW;
912
913 /* check for overflowing the buffer's size */
914 if (pgoff + vma_pages(vma) >
915 dmabuf->size >> PAGE_SHIFT)
916 return -EINVAL;
917
918 /* readjust the vma */
919 get_file(dmabuf->file);
920 oldfile = vma->vm_file;
921 vma->vm_file = dmabuf->file;
922 vma->vm_pgoff = pgoff;
923
924 ret = dmabuf->ops->mmap(dmabuf, vma);
925 if (ret) {
926 /* restore old parameters on failure */
927 vma->vm_file = oldfile;
928 fput(dmabuf->file);
929 } else {
930 if (oldfile)
931 fput(oldfile);
932 }
933 return ret;
934
935}
936EXPORT_SYMBOL_GPL(dma_buf_mmap);
937
938/**
939 * dma_buf_vmap - Create virtual mapping for the buffer object into kernel
940 * address space. Same restrictions as for vmap and friends apply.
941 * @dmabuf: [in] buffer to vmap
942 *
943 * This call may fail due to lack of virtual mapping address space.
944 * These calls are optional in drivers. The intended use for them
945 * is for mapping objects linear in kernel space for high use objects.
946 * Please attempt to use kmap/kunmap before thinking about these interfaces.
947 *
948 * Returns NULL on error.
949 */
950void *dma_buf_vmap(struct dma_buf *dmabuf)
951{
952 void *ptr;
953
954 if (WARN_ON(!dmabuf))
955 return NULL;
956
957 if (!dmabuf->ops->vmap)
958 return NULL;
959
960 mutex_lock(&dmabuf->lock);
961 if (dmabuf->vmapping_counter) {
962 dmabuf->vmapping_counter++;
963 BUG_ON(!dmabuf->vmap_ptr);
964 ptr = dmabuf->vmap_ptr;
965 goto out_unlock;
966 }
967
968 BUG_ON(dmabuf->vmap_ptr);
969
970 ptr = dmabuf->ops->vmap(dmabuf);
971 if (WARN_ON_ONCE(IS_ERR(ptr)))
972 ptr = NULL;
973 if (!ptr)
974 goto out_unlock;
975
976 dmabuf->vmap_ptr = ptr;
977 dmabuf->vmapping_counter = 1;
978
979out_unlock:
980 mutex_unlock(&dmabuf->lock);
981 return ptr;
982}
983EXPORT_SYMBOL_GPL(dma_buf_vmap);
984
985/**
986 * dma_buf_vunmap - Unmap a vmap obtained by dma_buf_vmap.
987 * @dmabuf: [in] buffer to vunmap
988 * @vaddr: [in] vmap to vunmap
989 */
990void dma_buf_vunmap(struct dma_buf *dmabuf, void *vaddr)
991{
992 if (WARN_ON(!dmabuf))
993 return;
994
995 BUG_ON(!dmabuf->vmap_ptr);
996 BUG_ON(dmabuf->vmapping_counter == 0);
997 BUG_ON(dmabuf->vmap_ptr != vaddr);
998
999 mutex_lock(&dmabuf->lock);
1000 if (--dmabuf->vmapping_counter == 0) {
1001 if (dmabuf->ops->vunmap)
1002 dmabuf->ops->vunmap(dmabuf, vaddr);
1003 dmabuf->vmap_ptr = NULL;
1004 }
1005 mutex_unlock(&dmabuf->lock);
1006}
1007EXPORT_SYMBOL_GPL(dma_buf_vunmap);
1008
1009#ifdef CONFIG_DEBUG_FS
1010static int dma_buf_debug_show(struct seq_file *s, void *unused)
1011{
1012 int ret;
1013 struct dma_buf *buf_obj;
1014 struct dma_buf_attachment *attach_obj;
1015 struct reservation_object *robj;
1016 struct reservation_object_list *fobj;
1017 struct dma_fence *fence;
1018 unsigned seq;
1019 int count = 0, attach_count, shared_count, i;
1020 size_t size = 0;
1021
1022 ret = mutex_lock_interruptible(&db_list.lock);
1023
1024 if (ret)
1025 return ret;
1026
1027 seq_puts(s, "\nDma-buf Objects:\n");
1028 seq_printf(s, "%-8s\t%-8s\t%-8s\t%-8s\texp_name\n",
1029 "size", "flags", "mode", "count");
1030
1031 list_for_each_entry(buf_obj, &db_list.head, list_node) {
1032 ret = mutex_lock_interruptible(&buf_obj->lock);
1033
1034 if (ret) {
1035 seq_puts(s,
1036 "\tERROR locking buffer object: skipping\n");
1037 continue;
1038 }
1039
1040 seq_printf(s, "%08zu\t%08x\t%08x\t%08ld\t%s\n",
1041 buf_obj->size,
1042 buf_obj->file->f_flags, buf_obj->file->f_mode,
1043 file_count(buf_obj->file),
1044 buf_obj->exp_name);
1045
1046 robj = buf_obj->resv;
1047 while (true) {
1048 seq = read_seqcount_begin(&robj->seq);
1049 rcu_read_lock();
1050 fobj = rcu_dereference(robj->fence);
1051 shared_count = fobj ? fobj->shared_count : 0;
1052 fence = rcu_dereference(robj->fence_excl);
1053 if (!read_seqcount_retry(&robj->seq, seq))
1054 break;
1055 rcu_read_unlock();
1056 }
1057
1058 if (fence)
1059 seq_printf(s, "\tExclusive fence: %s %s %ssignalled\n",
1060 fence->ops->get_driver_name(fence),
1061 fence->ops->get_timeline_name(fence),
1062 dma_fence_is_signaled(fence) ? "" : "un");
1063 for (i = 0; i < shared_count; i++) {
1064 fence = rcu_dereference(fobj->shared[i]);
1065 if (!dma_fence_get_rcu(fence))
1066 continue;
1067 seq_printf(s, "\tShared fence: %s %s %ssignalled\n",
1068 fence->ops->get_driver_name(fence),
1069 fence->ops->get_timeline_name(fence),
1070 dma_fence_is_signaled(fence) ? "" : "un");
1071 }
1072 rcu_read_unlock();
1073
1074 seq_puts(s, "\tAttached Devices:\n");
1075 attach_count = 0;
1076
1077 list_for_each_entry(attach_obj, &buf_obj->attachments, node) {
1078 seq_printf(s, "\t%s\n", dev_name(attach_obj->dev));
1079 attach_count++;
1080 }
1081
1082 seq_printf(s, "Total %d devices attached\n\n",
1083 attach_count);
1084
1085 count++;
1086 size += buf_obj->size;
1087 mutex_unlock(&buf_obj->lock);
1088 }
1089
1090 seq_printf(s, "\nTotal %d objects, %zu bytes\n", count, size);
1091
1092 mutex_unlock(&db_list.lock);
1093 return 0;
1094}
1095
1096DEFINE_SHOW_ATTRIBUTE(dma_buf_debug);
1097
1098static struct dentry *dma_buf_debugfs_dir;
1099
1100static int dma_buf_init_debugfs(void)
1101{
1102 struct dentry *d;
1103 int err = 0;
1104
1105 d = debugfs_create_dir("dma_buf", NULL);
1106 if (IS_ERR(d))
1107 return PTR_ERR(d);
1108
1109 dma_buf_debugfs_dir = d;
1110
1111 d = debugfs_create_file("bufinfo", S_IRUGO, dma_buf_debugfs_dir,
1112 NULL, &dma_buf_debug_fops);
1113 if (IS_ERR(d)) {
1114 pr_debug("dma_buf: debugfs: failed to create node bufinfo\n");
1115 debugfs_remove_recursive(dma_buf_debugfs_dir);
1116 dma_buf_debugfs_dir = NULL;
1117 err = PTR_ERR(d);
1118 }
1119
1120 return err;
1121}
1122
1123static void dma_buf_uninit_debugfs(void)
1124{
1125 debugfs_remove_recursive(dma_buf_debugfs_dir);
1126}
1127#else
1128static inline int dma_buf_init_debugfs(void)
1129{
1130 return 0;
1131}
1132static inline void dma_buf_uninit_debugfs(void)
1133{
1134}
1135#endif
1136
1137static int __init dma_buf_init(void)
1138{
1139 mutex_init(&db_list.lock);
1140 INIT_LIST_HEAD(&db_list.head);
1141 dma_buf_init_debugfs();
1142 return 0;
1143}
1144subsys_initcall(dma_buf_init);
1145
1146static void __exit dma_buf_deinit(void)
1147{
1148 dma_buf_uninit_debugfs();
1149}
1150__exitcall(dma_buf_deinit);
1151