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1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Framework for buffer objects that can be shared across devices/subsystems.
4 *
5 * Copyright(C) 2011 Linaro Limited. All rights reserved.
6 * Author: Sumit Semwal <sumit.semwal@ti.com>
7 *
8 * Many thanks to linaro-mm-sig list, and specially
9 * Arnd Bergmann <arnd@arndb.de>, Rob Clark <rob@ti.com> and
10 * Daniel Vetter <daniel@ffwll.ch> for their support in creation and
11 * refining of this idea.
12 */
13
14 #include <linux/fs.h>
15 #include <linux/slab.h>
16 #include <linux/dma-buf.h>
17 #include <linux/dma-fence.h>
18 #include <linux/anon_inodes.h>
19 #include <linux/export.h>
20 #include <linux/debugfs.h>
21 #include <linux/module.h>
22 #include <linux/seq_file.h>
23 #include <linux/poll.h>
24 #include <linux/dma-resv.h>
25 #include <linux/mm.h>
26 #include <linux/mount.h>
27 #include <linux/pseudo_fs.h>
28
29 #include <uapi/linux/dma-buf.h>
30 #include <uapi/linux/magic.h>
31
32 static inline int is_dma_buf_file(struct file *);
33
34 struct dma_buf_list {
35 struct list_head head;
36 struct mutex lock;
37 };
38
39 static struct dma_buf_list db_list;
40
41 static char *dmabuffs_dname(struct dentry *dentry, char *buffer, int buflen)
42 {
43 struct dma_buf *dmabuf;
44 char name[DMA_BUF_NAME_LEN];
45 size_t ret = 0;
46
47 dmabuf = dentry->d_fsdata;
48 dma_resv_lock(dmabuf->resv, NULL);
49 if (dmabuf->name)
50 ret = strlcpy(name, dmabuf->name, DMA_BUF_NAME_LEN);
51 dma_resv_unlock(dmabuf->resv);
52
53 return dynamic_dname(dentry, buffer, buflen, "/%s:%s",
54 dentry->d_name.name, ret > 0 ? name : "");
55 }
56
57 static const struct dentry_operations dma_buf_dentry_ops = {
58 .d_dname = dmabuffs_dname,
59 };
60
61 static struct vfsmount *dma_buf_mnt;
62
63 static int dma_buf_fs_init_context(struct fs_context *fc)
64 {
65 struct pseudo_fs_context *ctx;
66
67 ctx = init_pseudo(fc, DMA_BUF_MAGIC);
68 if (!ctx)
69 return -ENOMEM;
70 ctx->dops = &dma_buf_dentry_ops;
71 return 0;
72 }
73
74 static struct file_system_type dma_buf_fs_type = {
75 .name = "dmabuf",
76 .init_fs_context = dma_buf_fs_init_context,
77 .kill_sb = kill_anon_super,
78 };
79
80 static int dma_buf_release(struct inode *inode, struct file *file)
81 {
82 struct dma_buf *dmabuf;
83
84 if (!is_dma_buf_file(file))
85 return -EINVAL;
86
87 dmabuf = file->private_data;
88
89 BUG_ON(dmabuf->vmapping_counter);
90
91 /*
92 * Any fences that a dma-buf poll can wait on should be signaled
93 * before releasing dma-buf. This is the responsibility of each
94 * driver that uses the reservation objects.
95 *
96 * If you hit this BUG() it means someone dropped their ref to the
97 * dma-buf while still having pending operation to the buffer.
98 */
99 BUG_ON(dmabuf->cb_shared.active || dmabuf->cb_excl.active);
100
101 dmabuf->ops->release(dmabuf);
102
103 mutex_lock(&db_list.lock);
104 list_del(&dmabuf->list_node);
105 mutex_unlock(&db_list.lock);
106
107 if (dmabuf->resv == (struct dma_resv *)&dmabuf[1])
108 dma_resv_fini(dmabuf->resv);
109
110 module_put(dmabuf->owner);
111 kfree(dmabuf->name);
112 kfree(dmabuf);
113 return 0;
114 }
115
116 static int dma_buf_mmap_internal(struct file *file, struct vm_area_struct *vma)
117 {
118 struct dma_buf *dmabuf;
119
120 if (!is_dma_buf_file(file))
121 return -EINVAL;
122
123 dmabuf = file->private_data;
124
125 /* check if buffer supports mmap */
126 if (!dmabuf->ops->mmap)
127 return -EINVAL;
128
129 /* check for overflowing the buffer's size */
130 if (vma->vm_pgoff + vma_pages(vma) >
131 dmabuf->size >> PAGE_SHIFT)
132 return -EINVAL;
133
134 return dmabuf->ops->mmap(dmabuf, vma);
135 }
136
137 static loff_t dma_buf_llseek(struct file *file, loff_t offset, int whence)
138 {
139 struct dma_buf *dmabuf;
140 loff_t base;
141
142 if (!is_dma_buf_file(file))
143 return -EBADF;
144
145 dmabuf = file->private_data;
146
147 /* only support discovering the end of the buffer,
148 but also allow SEEK_SET to maintain the idiomatic
149 SEEK_END(0), SEEK_CUR(0) pattern */
150 if (whence == SEEK_END)
151 base = dmabuf->size;
152 else if (whence == SEEK_SET)
153 base = 0;
154 else
155 return -EINVAL;
156
157 if (offset != 0)
158 return -EINVAL;
159
160 return base + offset;
161 }
162
163 /**
164 * DOC: fence polling
165 *
166 * To support cross-device and cross-driver synchronization of buffer access
167 * implicit fences (represented internally in the kernel with &struct fence) can
168 * be attached to a &dma_buf. The glue for that and a few related things are
169 * provided in the &dma_resv structure.
170 *
171 * Userspace can query the state of these implicitly tracked fences using poll()
172 * and related system calls:
173 *
174 * - Checking for EPOLLIN, i.e. read access, can be use to query the state of the
175 * most recent write or exclusive fence.
176 *
177 * - Checking for EPOLLOUT, i.e. write access, can be used to query the state of
178 * all attached fences, shared and exclusive ones.
179 *
180 * Note that this only signals the completion of the respective fences, i.e. the
181 * DMA transfers are complete. Cache flushing and any other necessary
182 * preparations before CPU access can begin still need to happen.
183 */
184
185 static void dma_buf_poll_cb(struct dma_fence *fence, struct dma_fence_cb *cb)
186 {
187 struct dma_buf_poll_cb_t *dcb = (struct dma_buf_poll_cb_t *)cb;
188 unsigned long flags;
189
190 spin_lock_irqsave(&dcb->poll->lock, flags);
191 wake_up_locked_poll(dcb->poll, dcb->active);
192 dcb->active = 0;
193 spin_unlock_irqrestore(&dcb->poll->lock, flags);
194 }
195
196 static __poll_t dma_buf_poll(struct file *file, poll_table *poll)
197 {
198 struct dma_buf *dmabuf;
199 struct dma_resv *resv;
200 struct dma_resv_list *fobj;
201 struct dma_fence *fence_excl;
202 __poll_t events;
203 unsigned shared_count, seq;
204
205 dmabuf = file->private_data;
206 if (!dmabuf || !dmabuf->resv)
207 return EPOLLERR;
208
209 resv = dmabuf->resv;
210
211 poll_wait(file, &dmabuf->poll, poll);
212
213 events = poll_requested_events(poll) & (EPOLLIN | EPOLLOUT);
214 if (!events)
215 return 0;
216
217 retry:
218 seq = read_seqcount_begin(&resv->seq);
219 rcu_read_lock();
220
221 fobj = rcu_dereference(resv->fence);
222 if (fobj)
223 shared_count = fobj->shared_count;
224 else
225 shared_count = 0;
226 fence_excl = rcu_dereference(resv->fence_excl);
227 if (read_seqcount_retry(&resv->seq, seq)) {
228 rcu_read_unlock();
229 goto retry;
230 }
231
232 if (fence_excl && (!(events & EPOLLOUT) || shared_count == 0)) {
233 struct dma_buf_poll_cb_t *dcb = &dmabuf->cb_excl;
234 __poll_t pevents = EPOLLIN;
235
236 if (shared_count == 0)
237 pevents |= EPOLLOUT;
238
239 spin_lock_irq(&dmabuf->poll.lock);
240 if (dcb->active) {
241 dcb->active |= pevents;
242 events &= ~pevents;
243 } else
244 dcb->active = pevents;
245 spin_unlock_irq(&dmabuf->poll.lock);
246
247 if (events & pevents) {
248 if (!dma_fence_get_rcu(fence_excl)) {
249 /* force a recheck */
250 events &= ~pevents;
251 dma_buf_poll_cb(NULL, &dcb->cb);
252 } else if (!dma_fence_add_callback(fence_excl, &dcb->cb,
253 dma_buf_poll_cb)) {
254 events &= ~pevents;
255 dma_fence_put(fence_excl);
256 } else {
257 /*
258 * No callback queued, wake up any additional
259 * waiters.
260 */
261 dma_fence_put(fence_excl);
262 dma_buf_poll_cb(NULL, &dcb->cb);
263 }
264 }
265 }
266
267 if ((events & EPOLLOUT) && shared_count > 0) {
268 struct dma_buf_poll_cb_t *dcb = &dmabuf->cb_shared;
269 int i;
270
271 /* Only queue a new callback if no event has fired yet */
272 spin_lock_irq(&dmabuf->poll.lock);
273 if (dcb->active)
274 events &= ~EPOLLOUT;
275 else
276 dcb->active = EPOLLOUT;
277 spin_unlock_irq(&dmabuf->poll.lock);
278
279 if (!(events & EPOLLOUT))
280 goto out;
281
282 for (i = 0; i < shared_count; ++i) {
283 struct dma_fence *fence = rcu_dereference(fobj->shared[i]);
284
285 if (!dma_fence_get_rcu(fence)) {
286 /*
287 * fence refcount dropped to zero, this means
288 * that fobj has been freed
289 *
290 * call dma_buf_poll_cb and force a recheck!
291 */
292 events &= ~EPOLLOUT;
293 dma_buf_poll_cb(NULL, &dcb->cb);
294 break;
295 }
296 if (!dma_fence_add_callback(fence, &dcb->cb,
297 dma_buf_poll_cb)) {
298 dma_fence_put(fence);
299 events &= ~EPOLLOUT;
300 break;
301 }
302 dma_fence_put(fence);
303 }
304
305 /* No callback queued, wake up any additional waiters. */
306 if (i == shared_count)
307 dma_buf_poll_cb(NULL, &dcb->cb);
308 }
309
310 out:
311 rcu_read_unlock();
312 return events;
313 }
314
315 /**
316 * dma_buf_set_name - Set a name to a specific dma_buf to track the usage.
317 * The name of the dma-buf buffer can only be set when the dma-buf is not
318 * attached to any devices. It could theoritically support changing the
319 * name of the dma-buf if the same piece of memory is used for multiple
320 * purpose between different devices.
321 *
322 * @dmabuf [in] dmabuf buffer that will be renamed.
323 * @buf: [in] A piece of userspace memory that contains the name of
324 * the dma-buf.
325 *
326 * Returns 0 on success. If the dma-buf buffer is already attached to
327 * devices, return -EBUSY.
328 *
329 */
330 static long dma_buf_set_name(struct dma_buf *dmabuf, const char __user *buf)
331 {
332 char *name = strndup_user(buf, DMA_BUF_NAME_LEN);
333 long ret = 0;
334
335 if (IS_ERR(name))
336 return PTR_ERR(name);
337
338 dma_resv_lock(dmabuf->resv, NULL);
339 if (!list_empty(&dmabuf->attachments)) {
340 ret = -EBUSY;
341 kfree(name);
342 goto out_unlock;
343 }
344 kfree(dmabuf->name);
345 dmabuf->name = name;
346
347 out_unlock:
348 dma_resv_unlock(dmabuf->resv);
349 return ret;
350 }
351
352 static long dma_buf_ioctl(struct file *file,
353 unsigned int cmd, unsigned long arg)
354 {
355 struct dma_buf *dmabuf;
356 struct dma_buf_sync sync;
357 enum dma_data_direction direction;
358 int ret;
359
360 dmabuf = file->private_data;
361
362 switch (cmd) {
363 case DMA_BUF_IOCTL_SYNC:
364 if (copy_from_user(&sync, (void __user *) arg, sizeof(sync)))
365 return -EFAULT;
366
367 if (sync.flags & ~DMA_BUF_SYNC_VALID_FLAGS_MASK)
368 return -EINVAL;
369
370 switch (sync.flags & DMA_BUF_SYNC_RW) {
371 case DMA_BUF_SYNC_READ:
372 direction = DMA_FROM_DEVICE;
373 break;
374 case DMA_BUF_SYNC_WRITE:
375 direction = DMA_TO_DEVICE;
376 break;
377 case DMA_BUF_SYNC_RW:
378 direction = DMA_BIDIRECTIONAL;
379 break;
380 default:
381 return -EINVAL;
382 }
383
384 if (sync.flags & DMA_BUF_SYNC_END)
385 ret = dma_buf_end_cpu_access(dmabuf, direction);
386 else
387 ret = dma_buf_begin_cpu_access(dmabuf, direction);
388
389 return ret;
390
391 case DMA_BUF_SET_NAME:
392 return dma_buf_set_name(dmabuf, (const char __user *)arg);
393
394 default:
395 return -ENOTTY;
396 }
397 }
398
399 static void dma_buf_show_fdinfo(struct seq_file *m, struct file *file)
400 {
401 struct dma_buf *dmabuf = file->private_data;
402
403 seq_printf(m, "size:\t%zu\n", dmabuf->size);
404 /* Don't count the temporary reference taken inside procfs seq_show */
405 seq_printf(m, "count:\t%ld\n", file_count(dmabuf->file) - 1);
406 seq_printf(m, "exp_name:\t%s\n", dmabuf->exp_name);
407 dma_resv_lock(dmabuf->resv, NULL);
408 if (dmabuf->name)
409 seq_printf(m, "name:\t%s\n", dmabuf->name);
410 dma_resv_unlock(dmabuf->resv);
411 }
412
413 static const struct file_operations dma_buf_fops = {
414 .release = dma_buf_release,
415 .mmap = dma_buf_mmap_internal,
416 .llseek = dma_buf_llseek,
417 .poll = dma_buf_poll,
418 .unlocked_ioctl = dma_buf_ioctl,
419 .compat_ioctl = compat_ptr_ioctl,
420 .show_fdinfo = dma_buf_show_fdinfo,
421 };
422
423 /*
424 * is_dma_buf_file - Check if struct file* is associated with dma_buf
425 */
426 static inline int is_dma_buf_file(struct file *file)
427 {
428 return file->f_op == &dma_buf_fops;
429 }
430
431 static struct file *dma_buf_getfile(struct dma_buf *dmabuf, int flags)
432 {
433 struct file *file;
434 struct inode *inode = alloc_anon_inode(dma_buf_mnt->mnt_sb);
435
436 if (IS_ERR(inode))
437 return ERR_CAST(inode);
438
439 inode->i_size = dmabuf->size;
440 inode_set_bytes(inode, dmabuf->size);
441
442 file = alloc_file_pseudo(inode, dma_buf_mnt, "dmabuf",
443 flags, &dma_buf_fops);
444 if (IS_ERR(file))
445 goto err_alloc_file;
446 file->f_flags = flags & (O_ACCMODE | O_NONBLOCK);
447 file->private_data = dmabuf;
448 file->f_path.dentry->d_fsdata = dmabuf;
449
450 return file;
451
452 err_alloc_file:
453 iput(inode);
454 return file;
455 }
456
457 /**
458 * DOC: dma buf device access
459 *
460 * For device DMA access to a shared DMA buffer the usual sequence of operations
461 * is fairly simple:
462 *
463 * 1. The exporter defines his exporter instance using
464 * DEFINE_DMA_BUF_EXPORT_INFO() and calls dma_buf_export() to wrap a private
465 * buffer object into a &dma_buf. It then exports that &dma_buf to userspace
466 * as a file descriptor by calling dma_buf_fd().
467 *
468 * 2. Userspace passes this file-descriptors to all drivers it wants this buffer
469 * to share with: First the filedescriptor is converted to a &dma_buf using
470 * dma_buf_get(). Then the buffer is attached to the device using
471 * dma_buf_attach().
472 *
473 * Up to this stage the exporter is still free to migrate or reallocate the
474 * backing storage.
475 *
476 * 3. Once the buffer is attached to all devices userspace can initiate DMA
477 * access to the shared buffer. In the kernel this is done by calling
478 * dma_buf_map_attachment() and dma_buf_unmap_attachment().
479 *
480 * 4. Once a driver is done with a shared buffer it needs to call
481 * dma_buf_detach() (after cleaning up any mappings) and then release the
482 * reference acquired with dma_buf_get by calling dma_buf_put().
483 *
484 * For the detailed semantics exporters are expected to implement see
485 * &dma_buf_ops.
486 */
487
488 /**
489 * dma_buf_export - Creates a new dma_buf, and associates an anon file
490 * with this buffer, so it can be exported.
491 * Also connect the allocator specific data and ops to the buffer.
492 * Additionally, provide a name string for exporter; useful in debugging.
493 *
494 * @exp_info: [in] holds all the export related information provided
495 * by the exporter. see &struct dma_buf_export_info
496 * for further details.
497 *
498 * Returns, on success, a newly created dma_buf object, which wraps the
499 * supplied private data and operations for dma_buf_ops. On either missing
500 * ops, or error in allocating struct dma_buf, will return negative error.
501 *
502 * For most cases the easiest way to create @exp_info is through the
503 * %DEFINE_DMA_BUF_EXPORT_INFO macro.
504 */
505 struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info)
506 {
507 struct dma_buf *dmabuf;
508 struct dma_resv *resv = exp_info->resv;
509 struct file *file;
510 size_t alloc_size = sizeof(struct dma_buf);
511 int ret;
512
513 if (!exp_info->resv)
514 alloc_size += sizeof(struct dma_resv);
515 else
516 /* prevent &dma_buf[1] == dma_buf->resv */
517 alloc_size += 1;
518
519 if (WARN_ON(!exp_info->priv
520 || !exp_info->ops
521 || !exp_info->ops->map_dma_buf
522 || !exp_info->ops->unmap_dma_buf
523 || !exp_info->ops->release)) {
524 return ERR_PTR(-EINVAL);
525 }
526
527 if (WARN_ON(exp_info->ops->cache_sgt_mapping &&
528 exp_info->ops->dynamic_mapping))
529 return ERR_PTR(-EINVAL);
530
531 if (!try_module_get(exp_info->owner))
532 return ERR_PTR(-ENOENT);
533
534 dmabuf = kzalloc(alloc_size, GFP_KERNEL);
535 if (!dmabuf) {
536 ret = -ENOMEM;
537 goto err_module;
538 }
539
540 dmabuf->priv = exp_info->priv;
541 dmabuf->ops = exp_info->ops;
542 dmabuf->size = exp_info->size;
543 dmabuf->exp_name = exp_info->exp_name;
544 dmabuf->owner = exp_info->owner;
545 init_waitqueue_head(&dmabuf->poll);
546 dmabuf->cb_excl.poll = dmabuf->cb_shared.poll = &dmabuf->poll;
547 dmabuf->cb_excl.active = dmabuf->cb_shared.active = 0;
548
549 if (!resv) {
550 resv = (struct dma_resv *)&dmabuf[1];
551 dma_resv_init(resv);
552 }
553 dmabuf->resv = resv;
554
555 file = dma_buf_getfile(dmabuf, exp_info->flags);
556 if (IS_ERR(file)) {
557 ret = PTR_ERR(file);
558 goto err_dmabuf;
559 }
560
561 file->f_mode |= FMODE_LSEEK;
562 dmabuf->file = file;
563
564 mutex_init(&dmabuf->lock);
565 INIT_LIST_HEAD(&dmabuf->attachments);
566
567 mutex_lock(&db_list.lock);
568 list_add(&dmabuf->list_node, &db_list.head);
569 mutex_unlock(&db_list.lock);
570
571 return dmabuf;
572
573 err_dmabuf:
574 kfree(dmabuf);
575 err_module:
576 module_put(exp_info->owner);
577 return ERR_PTR(ret);
578 }
579 EXPORT_SYMBOL_GPL(dma_buf_export);
580
581 /**
582 * dma_buf_fd - returns a file descriptor for the given dma_buf
583 * @dmabuf: [in] pointer to dma_buf for which fd is required.
584 * @flags: [in] flags to give to fd
585 *
586 * On success, returns an associated 'fd'. Else, returns error.
587 */
588 int dma_buf_fd(struct dma_buf *dmabuf, int flags)
589 {
590 int fd;
591
592 if (!dmabuf || !dmabuf->file)
593 return -EINVAL;
594
595 fd = get_unused_fd_flags(flags);
596 if (fd < 0)
597 return fd;
598
599 fd_install(fd, dmabuf->file);
600
601 return fd;
602 }
603 EXPORT_SYMBOL_GPL(dma_buf_fd);
604
605 /**
606 * dma_buf_get - returns the dma_buf structure related to an fd
607 * @fd: [in] fd associated with the dma_buf to be returned
608 *
609 * On success, returns the dma_buf structure associated with an fd; uses
610 * file's refcounting done by fget to increase refcount. returns ERR_PTR
611 * otherwise.
612 */
613 struct dma_buf *dma_buf_get(int fd)
614 {
615 struct file *file;
616
617 file = fget(fd);
618
619 if (!file)
620 return ERR_PTR(-EBADF);
621
622 if (!is_dma_buf_file(file)) {
623 fput(file);
624 return ERR_PTR(-EINVAL);
625 }
626
627 return file->private_data;
628 }
629 EXPORT_SYMBOL_GPL(dma_buf_get);
630
631 /**
632 * dma_buf_put - decreases refcount of the buffer
633 * @dmabuf: [in] buffer to reduce refcount of
634 *
635 * Uses file's refcounting done implicitly by fput().
636 *
637 * If, as a result of this call, the refcount becomes 0, the 'release' file
638 * operation related to this fd is called. It calls &dma_buf_ops.release vfunc
639 * in turn, and frees the memory allocated for dmabuf when exported.
640 */
641 void dma_buf_put(struct dma_buf *dmabuf)
642 {
643 if (WARN_ON(!dmabuf || !dmabuf->file))
644 return;
645
646 fput(dmabuf->file);
647 }
648 EXPORT_SYMBOL_GPL(dma_buf_put);
649
650 /**
651 * dma_buf_dynamic_attach - Add the device to dma_buf's attachments list; optionally,
652 * calls attach() of dma_buf_ops to allow device-specific attach functionality
653 * @dmabuf: [in] buffer to attach device to.
654 * @dev: [in] device to be attached.
655 * @dynamic_mapping: [in] calling convention for map/unmap
656 *
657 * Returns struct dma_buf_attachment pointer for this attachment. Attachments
658 * must be cleaned up by calling dma_buf_detach().
659 *
660 * Returns:
661 *
662 * A pointer to newly created &dma_buf_attachment on success, or a negative
663 * error code wrapped into a pointer on failure.
664 *
665 * Note that this can fail if the backing storage of @dmabuf is in a place not
666 * accessible to @dev, and cannot be moved to a more suitable place. This is
667 * indicated with the error code -EBUSY.
668 */
669 struct dma_buf_attachment *
670 dma_buf_dynamic_attach(struct dma_buf *dmabuf, struct device *dev,
671 bool dynamic_mapping)
672 {
673 struct dma_buf_attachment *attach;
674 int ret;
675
676 if (WARN_ON(!dmabuf || !dev))
677 return ERR_PTR(-EINVAL);
678
679 attach = kzalloc(sizeof(*attach), GFP_KERNEL);
680 if (!attach)
681 return ERR_PTR(-ENOMEM);
682
683 attach->dev = dev;
684 attach->dmabuf = dmabuf;
685 attach->dynamic_mapping = dynamic_mapping;
686
687 if (dmabuf->ops->attach) {
688 ret = dmabuf->ops->attach(dmabuf, attach);
689 if (ret)
690 goto err_attach;
691 }
692 dma_resv_lock(dmabuf->resv, NULL);
693 list_add(&attach->node, &dmabuf->attachments);
694 dma_resv_unlock(dmabuf->resv);
695
696 /* When either the importer or the exporter can't handle dynamic
697 * mappings we cache the mapping here to avoid issues with the
698 * reservation object lock.
699 */
700 if (dma_buf_attachment_is_dynamic(attach) !=
701 dma_buf_is_dynamic(dmabuf)) {
702 struct sg_table *sgt;
703
704 if (dma_buf_is_dynamic(attach->dmabuf))
705 dma_resv_lock(attach->dmabuf->resv, NULL);
706
707 sgt = dmabuf->ops->map_dma_buf(attach, DMA_BIDIRECTIONAL);
708 if (!sgt)
709 sgt = ERR_PTR(-ENOMEM);
710 if (IS_ERR(sgt)) {
711 ret = PTR_ERR(sgt);
712 goto err_unlock;
713 }
714 if (dma_buf_is_dynamic(attach->dmabuf))
715 dma_resv_unlock(attach->dmabuf->resv);
716 attach->sgt = sgt;
717 attach->dir = DMA_BIDIRECTIONAL;
718 }
719
720 return attach;
721
722 err_attach:
723 kfree(attach);
724 return ERR_PTR(ret);
725
726 err_unlock:
727 if (dma_buf_is_dynamic(attach->dmabuf))
728 dma_resv_unlock(attach->dmabuf->resv);
729
730 dma_buf_detach(dmabuf, attach);
731 return ERR_PTR(ret);
732 }
733 EXPORT_SYMBOL_GPL(dma_buf_dynamic_attach);
734
735 /**
736 * dma_buf_attach - Wrapper for dma_buf_dynamic_attach
737 * @dmabuf: [in] buffer to attach device to.
738 * @dev: [in] device to be attached.
739 *
740 * Wrapper to call dma_buf_dynamic_attach() for drivers which still use a static
741 * mapping.
742 */
743 struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
744 struct device *dev)
745 {
746 return dma_buf_dynamic_attach(dmabuf, dev, false);
747 }
748 EXPORT_SYMBOL_GPL(dma_buf_attach);
749
750 /**
751 * dma_buf_detach - Remove the given attachment from dmabuf's attachments list;
752 * optionally calls detach() of dma_buf_ops for device-specific detach
753 * @dmabuf: [in] buffer to detach from.
754 * @attach: [in] attachment to be detached; is free'd after this call.
755 *
756 * Clean up a device attachment obtained by calling dma_buf_attach().
757 */
758 void dma_buf_detach(struct dma_buf *dmabuf, struct dma_buf_attachment *attach)
759 {
760 if (WARN_ON(!dmabuf || !attach))
761 return;
762
763 if (attach->sgt) {
764 if (dma_buf_is_dynamic(attach->dmabuf))
765 dma_resv_lock(attach->dmabuf->resv, NULL);
766
767 dmabuf->ops->unmap_dma_buf(attach, attach->sgt, attach->dir);
768
769 if (dma_buf_is_dynamic(attach->dmabuf))
770 dma_resv_unlock(attach->dmabuf->resv);
771 }
772
773 dma_resv_lock(dmabuf->resv, NULL);
774 list_del(&attach->node);
775 dma_resv_unlock(dmabuf->resv);
776 if (dmabuf->ops->detach)
777 dmabuf->ops->detach(dmabuf, attach);
778
779 kfree(attach);
780 }
781 EXPORT_SYMBOL_GPL(dma_buf_detach);
782
783 /**
784 * dma_buf_map_attachment - Returns the scatterlist table of the attachment;
785 * mapped into _device_ address space. Is a wrapper for map_dma_buf() of the
786 * dma_buf_ops.
787 * @attach: [in] attachment whose scatterlist is to be returned
788 * @direction: [in] direction of DMA transfer
789 *
790 * Returns sg_table containing the scatterlist to be returned; returns ERR_PTR
791 * on error. May return -EINTR if it is interrupted by a signal.
792 *
793 * A mapping must be unmapped by using dma_buf_unmap_attachment(). Note that
794 * the underlying backing storage is pinned for as long as a mapping exists,
795 * therefore users/importers should not hold onto a mapping for undue amounts of
796 * time.
797 */
798 struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
799 enum dma_data_direction direction)
800 {
801 struct sg_table *sg_table;
802
803 might_sleep();
804
805 if (WARN_ON(!attach || !attach->dmabuf))
806 return ERR_PTR(-EINVAL);
807
808 if (dma_buf_attachment_is_dynamic(attach))
809 dma_resv_assert_held(attach->dmabuf->resv);
810
811 if (attach->sgt) {
812 /*
813 * Two mappings with different directions for the same
814 * attachment are not allowed.
815 */
816 if (attach->dir != direction &&
817 attach->dir != DMA_BIDIRECTIONAL)
818 return ERR_PTR(-EBUSY);
819
820 return attach->sgt;
821 }
822
823 if (dma_buf_is_dynamic(attach->dmabuf))
824 dma_resv_assert_held(attach->dmabuf->resv);
825
826 sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction);
827 if (!sg_table)
828 sg_table = ERR_PTR(-ENOMEM);
829
830 if (!IS_ERR(sg_table) && attach->dmabuf->ops->cache_sgt_mapping) {
831 attach->sgt = sg_table;
832 attach->dir = direction;
833 }
834
835 return sg_table;
836 }
837 EXPORT_SYMBOL_GPL(dma_buf_map_attachment);
838
839 /**
840 * dma_buf_unmap_attachment - unmaps and decreases usecount of the buffer;might
841 * deallocate the scatterlist associated. Is a wrapper for unmap_dma_buf() of
842 * dma_buf_ops.
843 * @attach: [in] attachment to unmap buffer from
844 * @sg_table: [in] scatterlist info of the buffer to unmap
845 * @direction: [in] direction of DMA transfer
846 *
847 * This unmaps a DMA mapping for @attached obtained by dma_buf_map_attachment().
848 */
849 void dma_buf_unmap_attachment(struct dma_buf_attachment *attach,
850 struct sg_table *sg_table,
851 enum dma_data_direction direction)
852 {
853 might_sleep();
854
855 if (WARN_ON(!attach || !attach->dmabuf || !sg_table))
856 return;
857
858 if (dma_buf_attachment_is_dynamic(attach))
859 dma_resv_assert_held(attach->dmabuf->resv);
860
861 if (attach->sgt == sg_table)
862 return;
863
864 if (dma_buf_is_dynamic(attach->dmabuf))
865 dma_resv_assert_held(attach->dmabuf->resv);
866
867 attach->dmabuf->ops->unmap_dma_buf(attach, sg_table, direction);
868 }
869 EXPORT_SYMBOL_GPL(dma_buf_unmap_attachment);
870
871 /**
872 * DOC: cpu access
873 *
874 * There are mutliple reasons for supporting CPU access to a dma buffer object:
875 *
876 * - Fallback operations in the kernel, for example when a device is connected
877 * over USB and the kernel needs to shuffle the data around first before
878 * sending it away. Cache coherency is handled by braketing any transactions
879 * with calls to dma_buf_begin_cpu_access() and dma_buf_end_cpu_access()
880 * access.
881 *
882 * Since for most kernel internal dma-buf accesses need the entire buffer, a
883 * vmap interface is introduced. Note that on very old 32-bit architectures
884 * vmalloc space might be limited and result in vmap calls failing.
885 *
886 * Interfaces::
887 * void \*dma_buf_vmap(struct dma_buf \*dmabuf)
888 * void dma_buf_vunmap(struct dma_buf \*dmabuf, void \*vaddr)
889 *
890 * The vmap call can fail if there is no vmap support in the exporter, or if
891 * it runs out of vmalloc space. Fallback to kmap should be implemented. Note
892 * that the dma-buf layer keeps a reference count for all vmap access and
893 * calls down into the exporter's vmap function only when no vmapping exists,
894 * and only unmaps it once. Protection against concurrent vmap/vunmap calls is
895 * provided by taking the dma_buf->lock mutex.
896 *
897 * - For full compatibility on the importer side with existing userspace
898 * interfaces, which might already support mmap'ing buffers. This is needed in
899 * many processing pipelines (e.g. feeding a software rendered image into a
900 * hardware pipeline, thumbnail creation, snapshots, ...). Also, Android's ION
901 * framework already supported this and for DMA buffer file descriptors to
902 * replace ION buffers mmap support was needed.
903 *
904 * There is no special interfaces, userspace simply calls mmap on the dma-buf
905 * fd. But like for CPU access there's a need to braket the actual access,
906 * which is handled by the ioctl (DMA_BUF_IOCTL_SYNC). Note that
907 * DMA_BUF_IOCTL_SYNC can fail with -EAGAIN or -EINTR, in which case it must
908 * be restarted.
909 *
910 * Some systems might need some sort of cache coherency management e.g. when
911 * CPU and GPU domains are being accessed through dma-buf at the same time.
912 * To circumvent this problem there are begin/end coherency markers, that
913 * forward directly to existing dma-buf device drivers vfunc hooks. Userspace
914 * can make use of those markers through the DMA_BUF_IOCTL_SYNC ioctl. The
915 * sequence would be used like following:
916 *
917 * - mmap dma-buf fd
918 * - for each drawing/upload cycle in CPU 1. SYNC_START ioctl, 2. read/write
919 * to mmap area 3. SYNC_END ioctl. This can be repeated as often as you
920 * want (with the new data being consumed by say the GPU or the scanout
921 * device)
922 * - munmap once you don't need the buffer any more
923 *
924 * For correctness and optimal performance, it is always required to use
925 * SYNC_START and SYNC_END before and after, respectively, when accessing the
926 * mapped address. Userspace cannot rely on coherent access, even when there
927 * are systems where it just works without calling these ioctls.
928 *
929 * - And as a CPU fallback in userspace processing pipelines.
930 *
931 * Similar to the motivation for kernel cpu access it is again important that
932 * the userspace code of a given importing subsystem can use the same
933 * interfaces with a imported dma-buf buffer object as with a native buffer
934 * object. This is especially important for drm where the userspace part of
935 * contemporary OpenGL, X, and other drivers is huge, and reworking them to
936 * use a different way to mmap a buffer rather invasive.
937 *
938 * The assumption in the current dma-buf interfaces is that redirecting the
939 * initial mmap is all that's needed. A survey of some of the existing
940 * subsystems shows that no driver seems to do any nefarious thing like
941 * syncing up with outstanding asynchronous processing on the device or
942 * allocating special resources at fault time. So hopefully this is good
943 * enough, since adding interfaces to intercept pagefaults and allow pte
944 * shootdowns would increase the complexity quite a bit.
945 *
946 * Interface::
947 * int dma_buf_mmap(struct dma_buf \*, struct vm_area_struct \*,
948 * unsigned long);
949 *
950 * If the importing subsystem simply provides a special-purpose mmap call to
951 * set up a mapping in userspace, calling do_mmap with dma_buf->file will
952 * equally achieve that for a dma-buf object.
953 */
954
955 static int __dma_buf_begin_cpu_access(struct dma_buf *dmabuf,
956 enum dma_data_direction direction)
957 {
958 bool write = (direction == DMA_BIDIRECTIONAL ||
959 direction == DMA_TO_DEVICE);
960 struct dma_resv *resv = dmabuf->resv;
961 long ret;
962
963 /* Wait on any implicit rendering fences */
964 ret = dma_resv_wait_timeout_rcu(resv, write, true,
965 MAX_SCHEDULE_TIMEOUT);
966 if (ret < 0)
967 return ret;
968
969 return 0;
970 }
971
972 /**
973 * dma_buf_begin_cpu_access - Must be called before accessing a dma_buf from the
974 * cpu in the kernel context. Calls begin_cpu_access to allow exporter-specific
975 * preparations. Coherency is only guaranteed in the specified range for the
976 * specified access direction.
977 * @dmabuf: [in] buffer to prepare cpu access for.
978 * @direction: [in] length of range for cpu access.
979 *
980 * After the cpu access is complete the caller should call
981 * dma_buf_end_cpu_access(). Only when cpu access is braketed by both calls is
982 * it guaranteed to be coherent with other DMA access.
983 *
984 * Can return negative error values, returns 0 on success.
985 */
986 int dma_buf_begin_cpu_access(struct dma_buf *dmabuf,
987 enum dma_data_direction direction)
988 {
989 int ret = 0;
990
991 if (WARN_ON(!dmabuf))
992 return -EINVAL;
993
994 if (dmabuf->ops->begin_cpu_access)
995 ret = dmabuf->ops->begin_cpu_access(dmabuf, direction);
996
997 /* Ensure that all fences are waited upon - but we first allow
998 * the native handler the chance to do so more efficiently if it
999 * chooses. A double invocation here will be reasonably cheap no-op.
1000 */
1001 if (ret == 0)
1002 ret = __dma_buf_begin_cpu_access(dmabuf, direction);
1003
1004 return ret;
1005 }
1006 EXPORT_SYMBOL_GPL(dma_buf_begin_cpu_access);
1007
1008 /**
1009 * dma_buf_end_cpu_access - Must be called after accessing a dma_buf from the
1010 * cpu in the kernel context. Calls end_cpu_access to allow exporter-specific
1011 * actions. Coherency is only guaranteed in the specified range for the
1012 * specified access direction.
1013 * @dmabuf: [in] buffer to complete cpu access for.
1014 * @direction: [in] length of range for cpu access.
1015 *
1016 * This terminates CPU access started with dma_buf_begin_cpu_access().
1017 *
1018 * Can return negative error values, returns 0 on success.
1019 */
1020 int dma_buf_end_cpu_access(struct dma_buf *dmabuf,
1021 enum dma_data_direction direction)
1022 {
1023 int ret = 0;
1024
1025 WARN_ON(!dmabuf);
1026
1027 if (dmabuf->ops->end_cpu_access)
1028 ret = dmabuf->ops->end_cpu_access(dmabuf, direction);
1029
1030 return ret;
1031 }
1032 EXPORT_SYMBOL_GPL(dma_buf_end_cpu_access);
1033
1034
1035 /**
1036 * dma_buf_mmap - Setup up a userspace mmap with the given vma
1037 * @dmabuf: [in] buffer that should back the vma
1038 * @vma: [in] vma for the mmap
1039 * @pgoff: [in] offset in pages where this mmap should start within the
1040 * dma-buf buffer.
1041 *
1042 * This function adjusts the passed in vma so that it points at the file of the
1043 * dma_buf operation. It also adjusts the starting pgoff and does bounds
1044 * checking on the size of the vma. Then it calls the exporters mmap function to
1045 * set up the mapping.
1046 *
1047 * Can return negative error values, returns 0 on success.
1048 */
1049 int dma_buf_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma,
1050 unsigned long pgoff)
1051 {
1052 struct file *oldfile;
1053 int ret;
1054
1055 if (WARN_ON(!dmabuf || !vma))
1056 return -EINVAL;
1057
1058 /* check if buffer supports mmap */
1059 if (!dmabuf->ops->mmap)
1060 return -EINVAL;
1061
1062 /* check for offset overflow */
1063 if (pgoff + vma_pages(vma) < pgoff)
1064 return -EOVERFLOW;
1065
1066 /* check for overflowing the buffer's size */
1067 if (pgoff + vma_pages(vma) >
1068 dmabuf->size >> PAGE_SHIFT)
1069 return -EINVAL;
1070
1071 /* readjust the vma */
1072 get_file(dmabuf->file);
1073 oldfile = vma->vm_file;
1074 vma->vm_file = dmabuf->file;
1075 vma->vm_pgoff = pgoff;
1076
1077 ret = dmabuf->ops->mmap(dmabuf, vma);
1078 if (ret) {
1079 /* restore old parameters on failure */
1080 vma->vm_file = oldfile;
1081 fput(dmabuf->file);
1082 } else {
1083 if (oldfile)
1084 fput(oldfile);
1085 }
1086 return ret;
1087
1088 }
1089 EXPORT_SYMBOL_GPL(dma_buf_mmap);
1090
1091 /**
1092 * dma_buf_vmap - Create virtual mapping for the buffer object into kernel
1093 * address space. Same restrictions as for vmap and friends apply.
1094 * @dmabuf: [in] buffer to vmap
1095 *
1096 * This call may fail due to lack of virtual mapping address space.
1097 * These calls are optional in drivers. The intended use for them
1098 * is for mapping objects linear in kernel space for high use objects.
1099 * Please attempt to use kmap/kunmap before thinking about these interfaces.
1100 *
1101 * Returns NULL on error.
1102 */
1103 void *dma_buf_vmap(struct dma_buf *dmabuf)
1104 {
1105 void *ptr;
1106
1107 if (WARN_ON(!dmabuf))
1108 return NULL;
1109
1110 if (!dmabuf->ops->vmap)
1111 return NULL;
1112
1113 mutex_lock(&dmabuf->lock);
1114 if (dmabuf->vmapping_counter) {
1115 dmabuf->vmapping_counter++;
1116 BUG_ON(!dmabuf->vmap_ptr);
1117 ptr = dmabuf->vmap_ptr;
1118 goto out_unlock;
1119 }
1120
1121 BUG_ON(dmabuf->vmap_ptr);
1122
1123 ptr = dmabuf->ops->vmap(dmabuf);
1124 if (WARN_ON_ONCE(IS_ERR(ptr)))
1125 ptr = NULL;
1126 if (!ptr)
1127 goto out_unlock;
1128
1129 dmabuf->vmap_ptr = ptr;
1130 dmabuf->vmapping_counter = 1;
1131
1132 out_unlock:
1133 mutex_unlock(&dmabuf->lock);
1134 return ptr;
1135 }
1136 EXPORT_SYMBOL_GPL(dma_buf_vmap);
1137
1138 /**
1139 * dma_buf_vunmap - Unmap a vmap obtained by dma_buf_vmap.
1140 * @dmabuf: [in] buffer to vunmap
1141 * @vaddr: [in] vmap to vunmap
1142 */
1143 void dma_buf_vunmap(struct dma_buf *dmabuf, void *vaddr)
1144 {
1145 if (WARN_ON(!dmabuf))
1146 return;
1147
1148 BUG_ON(!dmabuf->vmap_ptr);
1149 BUG_ON(dmabuf->vmapping_counter == 0);
1150 BUG_ON(dmabuf->vmap_ptr != vaddr);
1151
1152 mutex_lock(&dmabuf->lock);
1153 if (--dmabuf->vmapping_counter == 0) {
1154 if (dmabuf->ops->vunmap)
1155 dmabuf->ops->vunmap(dmabuf, vaddr);
1156 dmabuf->vmap_ptr = NULL;
1157 }
1158 mutex_unlock(&dmabuf->lock);
1159 }
1160 EXPORT_SYMBOL_GPL(dma_buf_vunmap);
1161
1162 #ifdef CONFIG_DEBUG_FS
1163 static int dma_buf_debug_show(struct seq_file *s, void *unused)
1164 {
1165 int ret;
1166 struct dma_buf *buf_obj;
1167 struct dma_buf_attachment *attach_obj;
1168 struct dma_resv *robj;
1169 struct dma_resv_list *fobj;
1170 struct dma_fence *fence;
1171 unsigned seq;
1172 int count = 0, attach_count, shared_count, i;
1173 size_t size = 0;
1174
1175 ret = mutex_lock_interruptible(&db_list.lock);
1176
1177 if (ret)
1178 return ret;
1179
1180 seq_puts(s, "\nDma-buf Objects:\n");
1181 seq_printf(s, "%-8s\t%-8s\t%-8s\t%-8s\texp_name\t%-8s\n",
1182 "size", "flags", "mode", "count", "ino");
1183
1184 list_for_each_entry(buf_obj, &db_list.head, list_node) {
1185
1186 ret = dma_resv_lock_interruptible(buf_obj->resv, NULL);
1187 if (ret)
1188 goto error_unlock;
1189
1190 seq_printf(s, "%08zu\t%08x\t%08x\t%08ld\t%s\t%08lu\t%s\n",
1191 buf_obj->size,
1192 buf_obj->file->f_flags, buf_obj->file->f_mode,
1193 file_count(buf_obj->file),
1194 buf_obj->exp_name,
1195 file_inode(buf_obj->file)->i_ino,
1196 buf_obj->name ?: "");
1197
1198 robj = buf_obj->resv;
1199 while (true) {
1200 seq = read_seqcount_begin(&robj->seq);
1201 rcu_read_lock();
1202 fobj = rcu_dereference(robj->fence);
1203 shared_count = fobj ? fobj->shared_count : 0;
1204 fence = rcu_dereference(robj->fence_excl);
1205 if (!read_seqcount_retry(&robj->seq, seq))
1206 break;
1207 rcu_read_unlock();
1208 }
1209
1210 if (fence)
1211 seq_printf(s, "\tExclusive fence: %s %s %ssignalled\n",
1212 fence->ops->get_driver_name(fence),
1213 fence->ops->get_timeline_name(fence),
1214 dma_fence_is_signaled(fence) ? "" : "un");
1215 for (i = 0; i < shared_count; i++) {
1216 fence = rcu_dereference(fobj->shared[i]);
1217 if (!dma_fence_get_rcu(fence))
1218 continue;
1219 seq_printf(s, "\tShared fence: %s %s %ssignalled\n",
1220 fence->ops->get_driver_name(fence),
1221 fence->ops->get_timeline_name(fence),
1222 dma_fence_is_signaled(fence) ? "" : "un");
1223 dma_fence_put(fence);
1224 }
1225 rcu_read_unlock();
1226
1227 seq_puts(s, "\tAttached Devices:\n");
1228 attach_count = 0;
1229
1230 list_for_each_entry(attach_obj, &buf_obj->attachments, node) {
1231 seq_printf(s, "\t%s\n", dev_name(attach_obj->dev));
1232 attach_count++;
1233 }
1234 dma_resv_unlock(buf_obj->resv);
1235
1236 seq_printf(s, "Total %d devices attached\n\n",
1237 attach_count);
1238
1239 count++;
1240 size += buf_obj->size;
1241 }
1242
1243 seq_printf(s, "\nTotal %d objects, %zu bytes\n", count, size);
1244
1245 mutex_unlock(&db_list.lock);
1246 return 0;
1247
1248 error_unlock:
1249 mutex_unlock(&db_list.lock);
1250 return ret;
1251 }
1252
1253 DEFINE_SHOW_ATTRIBUTE(dma_buf_debug);
1254
1255 static struct dentry *dma_buf_debugfs_dir;
1256
1257 static int dma_buf_init_debugfs(void)
1258 {
1259 struct dentry *d;
1260 int err = 0;
1261
1262 d = debugfs_create_dir("dma_buf", NULL);
1263 if (IS_ERR(d))
1264 return PTR_ERR(d);
1265
1266 dma_buf_debugfs_dir = d;
1267
1268 d = debugfs_create_file("bufinfo", S_IRUGO, dma_buf_debugfs_dir,
1269 NULL, &dma_buf_debug_fops);
1270 if (IS_ERR(d)) {
1271 pr_debug("dma_buf: debugfs: failed to create node bufinfo\n");
1272 debugfs_remove_recursive(dma_buf_debugfs_dir);
1273 dma_buf_debugfs_dir = NULL;
1274 err = PTR_ERR(d);
1275 }
1276
1277 return err;
1278 }
1279
1280 static void dma_buf_uninit_debugfs(void)
1281 {
1282 debugfs_remove_recursive(dma_buf_debugfs_dir);
1283 }
1284 #else
1285 static inline int dma_buf_init_debugfs(void)
1286 {
1287 return 0;
1288 }
1289 static inline void dma_buf_uninit_debugfs(void)
1290 {
1291 }
1292 #endif
1293
1294 static int __init dma_buf_init(void)
1295 {
1296 dma_buf_mnt = kern_mount(&dma_buf_fs_type);
1297 if (IS_ERR(dma_buf_mnt))
1298 return PTR_ERR(dma_buf_mnt);
1299
1300 mutex_init(&db_list.lock);
1301 INIT_LIST_HEAD(&db_list.head);
1302 dma_buf_init_debugfs();
1303 return 0;
1304 }
1305 subsys_initcall(dma_buf_init);
1306
1307 static void __exit dma_buf_deinit(void)
1308 {
1309 dma_buf_uninit_debugfs();
1310 kern_unmount(dma_buf_mnt);
1311 }
1312 __exitcall(dma_buf_deinit);