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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/dma-fence-unwrap.h>
19#include <linux/anon_inodes.h>
20#include <linux/export.h>
21#include <linux/debugfs.h>
22#include <linux/module.h>
23#include <linux/seq_file.h>
24#include <linux/sync_file.h>
25#include <linux/poll.h>
26#include <linux/dma-resv.h>
27#include <linux/mm.h>
28#include <linux/mount.h>
29#include <linux/pseudo_fs.h>
30
31#include <uapi/linux/dma-buf.h>
32#include <uapi/linux/magic.h>
33
34#include "dma-buf-sysfs-stats.h"
35
36static inline int is_dma_buf_file(struct file *);
37
38#if IS_ENABLED(CONFIG_DEBUG_FS)
39static DEFINE_MUTEX(debugfs_list_mutex);
40static LIST_HEAD(debugfs_list);
41
42static void __dma_buf_debugfs_list_add(struct dma_buf *dmabuf)
43{
44 mutex_lock(&debugfs_list_mutex);
45 list_add(&dmabuf->list_node, &debugfs_list);
46 mutex_unlock(&debugfs_list_mutex);
47}
48
49static void __dma_buf_debugfs_list_del(struct dma_buf *dmabuf)
50{
51 if (!dmabuf)
52 return;
53
54 mutex_lock(&debugfs_list_mutex);
55 list_del(&dmabuf->list_node);
56 mutex_unlock(&debugfs_list_mutex);
57}
58#else
59static void __dma_buf_debugfs_list_add(struct dma_buf *dmabuf)
60{
61}
62
63static void __dma_buf_debugfs_list_del(struct dma_buf *dmabuf)
64{
65}
66#endif
67
68static char *dmabuffs_dname(struct dentry *dentry, char *buffer, int buflen)
69{
70 struct dma_buf *dmabuf;
71 char name[DMA_BUF_NAME_LEN];
72 ssize_t ret = 0;
73
74 dmabuf = dentry->d_fsdata;
75 spin_lock(&dmabuf->name_lock);
76 if (dmabuf->name)
77 ret = strscpy(name, dmabuf->name, sizeof(name));
78 spin_unlock(&dmabuf->name_lock);
79
80 return dynamic_dname(buffer, buflen, "/%s:%s",
81 dentry->d_name.name, ret > 0 ? name : "");
82}
83
84static void dma_buf_release(struct dentry *dentry)
85{
86 struct dma_buf *dmabuf;
87
88 dmabuf = dentry->d_fsdata;
89 if (unlikely(!dmabuf))
90 return;
91
92 BUG_ON(dmabuf->vmapping_counter);
93
94 /*
95 * If you hit this BUG() it could mean:
96 * * There's a file reference imbalance in dma_buf_poll / dma_buf_poll_cb or somewhere else
97 * * dmabuf->cb_in/out.active are non-0 despite no pending fence callback
98 */
99 BUG_ON(dmabuf->cb_in.active || dmabuf->cb_out.active);
100
101 dma_buf_stats_teardown(dmabuf);
102 dmabuf->ops->release(dmabuf);
103
104 if (dmabuf->resv == (struct dma_resv *)&dmabuf[1])
105 dma_resv_fini(dmabuf->resv);
106
107 WARN_ON(!list_empty(&dmabuf->attachments));
108 module_put(dmabuf->owner);
109 kfree(dmabuf->name);
110 kfree(dmabuf);
111}
112
113static int dma_buf_file_release(struct inode *inode, struct file *file)
114{
115 if (!is_dma_buf_file(file))
116 return -EINVAL;
117
118 __dma_buf_debugfs_list_del(file->private_data);
119
120 return 0;
121}
122
123static const struct dentry_operations dma_buf_dentry_ops = {
124 .d_dname = dmabuffs_dname,
125 .d_release = dma_buf_release,
126};
127
128static struct vfsmount *dma_buf_mnt;
129
130static int dma_buf_fs_init_context(struct fs_context *fc)
131{
132 struct pseudo_fs_context *ctx;
133
134 ctx = init_pseudo(fc, DMA_BUF_MAGIC);
135 if (!ctx)
136 return -ENOMEM;
137 ctx->dops = &dma_buf_dentry_ops;
138 return 0;
139}
140
141static struct file_system_type dma_buf_fs_type = {
142 .name = "dmabuf",
143 .init_fs_context = dma_buf_fs_init_context,
144 .kill_sb = kill_anon_super,
145};
146
147static int dma_buf_mmap_internal(struct file *file, struct vm_area_struct *vma)
148{
149 struct dma_buf *dmabuf;
150
151 if (!is_dma_buf_file(file))
152 return -EINVAL;
153
154 dmabuf = file->private_data;
155
156 /* check if buffer supports mmap */
157 if (!dmabuf->ops->mmap)
158 return -EINVAL;
159
160 /* check for overflowing the buffer's size */
161 if (vma->vm_pgoff + vma_pages(vma) >
162 dmabuf->size >> PAGE_SHIFT)
163 return -EINVAL;
164
165 return dmabuf->ops->mmap(dmabuf, vma);
166}
167
168static loff_t dma_buf_llseek(struct file *file, loff_t offset, int whence)
169{
170 struct dma_buf *dmabuf;
171 loff_t base;
172
173 if (!is_dma_buf_file(file))
174 return -EBADF;
175
176 dmabuf = file->private_data;
177
178 /* only support discovering the end of the buffer,
179 * but also allow SEEK_SET to maintain the idiomatic
180 * SEEK_END(0), SEEK_CUR(0) pattern.
181 */
182 if (whence == SEEK_END)
183 base = dmabuf->size;
184 else if (whence == SEEK_SET)
185 base = 0;
186 else
187 return -EINVAL;
188
189 if (offset != 0)
190 return -EINVAL;
191
192 return base + offset;
193}
194
195/**
196 * DOC: implicit fence polling
197 *
198 * To support cross-device and cross-driver synchronization of buffer access
199 * implicit fences (represented internally in the kernel with &struct dma_fence)
200 * can be attached to a &dma_buf. The glue for that and a few related things are
201 * provided in the &dma_resv structure.
202 *
203 * Userspace can query the state of these implicitly tracked fences using poll()
204 * and related system calls:
205 *
206 * - Checking for EPOLLIN, i.e. read access, can be use to query the state of the
207 * most recent write or exclusive fence.
208 *
209 * - Checking for EPOLLOUT, i.e. write access, can be used to query the state of
210 * all attached fences, shared and exclusive ones.
211 *
212 * Note that this only signals the completion of the respective fences, i.e. the
213 * DMA transfers are complete. Cache flushing and any other necessary
214 * preparations before CPU access can begin still need to happen.
215 *
216 * As an alternative to poll(), the set of fences on DMA buffer can be
217 * exported as a &sync_file using &dma_buf_sync_file_export.
218 */
219
220static void dma_buf_poll_cb(struct dma_fence *fence, struct dma_fence_cb *cb)
221{
222 struct dma_buf_poll_cb_t *dcb = (struct dma_buf_poll_cb_t *)cb;
223 struct dma_buf *dmabuf = container_of(dcb->poll, struct dma_buf, poll);
224 unsigned long flags;
225
226 spin_lock_irqsave(&dcb->poll->lock, flags);
227 wake_up_locked_poll(dcb->poll, dcb->active);
228 dcb->active = 0;
229 spin_unlock_irqrestore(&dcb->poll->lock, flags);
230 dma_fence_put(fence);
231 /* Paired with get_file in dma_buf_poll */
232 fput(dmabuf->file);
233}
234
235static bool dma_buf_poll_add_cb(struct dma_resv *resv, bool write,
236 struct dma_buf_poll_cb_t *dcb)
237{
238 struct dma_resv_iter cursor;
239 struct dma_fence *fence;
240 int r;
241
242 dma_resv_for_each_fence(&cursor, resv, dma_resv_usage_rw(write),
243 fence) {
244 dma_fence_get(fence);
245 r = dma_fence_add_callback(fence, &dcb->cb, dma_buf_poll_cb);
246 if (!r)
247 return true;
248 dma_fence_put(fence);
249 }
250
251 return false;
252}
253
254static __poll_t dma_buf_poll(struct file *file, poll_table *poll)
255{
256 struct dma_buf *dmabuf;
257 struct dma_resv *resv;
258 __poll_t events;
259
260 dmabuf = file->private_data;
261 if (!dmabuf || !dmabuf->resv)
262 return EPOLLERR;
263
264 resv = dmabuf->resv;
265
266 poll_wait(file, &dmabuf->poll, poll);
267
268 events = poll_requested_events(poll) & (EPOLLIN | EPOLLOUT);
269 if (!events)
270 return 0;
271
272 dma_resv_lock(resv, NULL);
273
274 if (events & EPOLLOUT) {
275 struct dma_buf_poll_cb_t *dcb = &dmabuf->cb_out;
276
277 /* Check that callback isn't busy */
278 spin_lock_irq(&dmabuf->poll.lock);
279 if (dcb->active)
280 events &= ~EPOLLOUT;
281 else
282 dcb->active = EPOLLOUT;
283 spin_unlock_irq(&dmabuf->poll.lock);
284
285 if (events & EPOLLOUT) {
286 /* Paired with fput in dma_buf_poll_cb */
287 get_file(dmabuf->file);
288
289 if (!dma_buf_poll_add_cb(resv, true, dcb))
290 /* No callback queued, wake up any other waiters */
291 dma_buf_poll_cb(NULL, &dcb->cb);
292 else
293 events &= ~EPOLLOUT;
294 }
295 }
296
297 if (events & EPOLLIN) {
298 struct dma_buf_poll_cb_t *dcb = &dmabuf->cb_in;
299
300 /* Check that callback isn't busy */
301 spin_lock_irq(&dmabuf->poll.lock);
302 if (dcb->active)
303 events &= ~EPOLLIN;
304 else
305 dcb->active = EPOLLIN;
306 spin_unlock_irq(&dmabuf->poll.lock);
307
308 if (events & EPOLLIN) {
309 /* Paired with fput in dma_buf_poll_cb */
310 get_file(dmabuf->file);
311
312 if (!dma_buf_poll_add_cb(resv, false, dcb))
313 /* No callback queued, wake up any other waiters */
314 dma_buf_poll_cb(NULL, &dcb->cb);
315 else
316 events &= ~EPOLLIN;
317 }
318 }
319
320 dma_resv_unlock(resv);
321 return events;
322}
323
324/**
325 * dma_buf_set_name - Set a name to a specific dma_buf to track the usage.
326 * It could support changing the name of the dma-buf if the same
327 * piece of memory is used for multiple purpose between different devices.
328 *
329 * @dmabuf: [in] dmabuf buffer that will be renamed.
330 * @buf: [in] A piece of userspace memory that contains the name of
331 * the dma-buf.
332 *
333 * Returns 0 on success. If the dma-buf buffer is already attached to
334 * devices, return -EBUSY.
335 *
336 */
337static long dma_buf_set_name(struct dma_buf *dmabuf, const char __user *buf)
338{
339 char *name = strndup_user(buf, DMA_BUF_NAME_LEN);
340
341 if (IS_ERR(name))
342 return PTR_ERR(name);
343
344 spin_lock(&dmabuf->name_lock);
345 kfree(dmabuf->name);
346 dmabuf->name = name;
347 spin_unlock(&dmabuf->name_lock);
348
349 return 0;
350}
351
352#if IS_ENABLED(CONFIG_SYNC_FILE)
353static long dma_buf_export_sync_file(struct dma_buf *dmabuf,
354 void __user *user_data)
355{
356 struct dma_buf_export_sync_file arg;
357 enum dma_resv_usage usage;
358 struct dma_fence *fence = NULL;
359 struct sync_file *sync_file;
360 int fd, ret;
361
362 if (copy_from_user(&arg, user_data, sizeof(arg)))
363 return -EFAULT;
364
365 if (arg.flags & ~DMA_BUF_SYNC_RW)
366 return -EINVAL;
367
368 if ((arg.flags & DMA_BUF_SYNC_RW) == 0)
369 return -EINVAL;
370
371 fd = get_unused_fd_flags(O_CLOEXEC);
372 if (fd < 0)
373 return fd;
374
375 usage = dma_resv_usage_rw(arg.flags & DMA_BUF_SYNC_WRITE);
376 ret = dma_resv_get_singleton(dmabuf->resv, usage, &fence);
377 if (ret)
378 goto err_put_fd;
379
380 if (!fence)
381 fence = dma_fence_get_stub();
382
383 sync_file = sync_file_create(fence);
384
385 dma_fence_put(fence);
386
387 if (!sync_file) {
388 ret = -ENOMEM;
389 goto err_put_fd;
390 }
391
392 arg.fd = fd;
393 if (copy_to_user(user_data, &arg, sizeof(arg))) {
394 ret = -EFAULT;
395 goto err_put_file;
396 }
397
398 fd_install(fd, sync_file->file);
399
400 return 0;
401
402err_put_file:
403 fput(sync_file->file);
404err_put_fd:
405 put_unused_fd(fd);
406 return ret;
407}
408
409static long dma_buf_import_sync_file(struct dma_buf *dmabuf,
410 const void __user *user_data)
411{
412 struct dma_buf_import_sync_file arg;
413 struct dma_fence *fence, *f;
414 enum dma_resv_usage usage;
415 struct dma_fence_unwrap iter;
416 unsigned int num_fences;
417 int ret = 0;
418
419 if (copy_from_user(&arg, user_data, sizeof(arg)))
420 return -EFAULT;
421
422 if (arg.flags & ~DMA_BUF_SYNC_RW)
423 return -EINVAL;
424
425 if ((arg.flags & DMA_BUF_SYNC_RW) == 0)
426 return -EINVAL;
427
428 fence = sync_file_get_fence(arg.fd);
429 if (!fence)
430 return -EINVAL;
431
432 usage = (arg.flags & DMA_BUF_SYNC_WRITE) ? DMA_RESV_USAGE_WRITE :
433 DMA_RESV_USAGE_READ;
434
435 num_fences = 0;
436 dma_fence_unwrap_for_each(f, &iter, fence)
437 ++num_fences;
438
439 if (num_fences > 0) {
440 dma_resv_lock(dmabuf->resv, NULL);
441
442 ret = dma_resv_reserve_fences(dmabuf->resv, num_fences);
443 if (!ret) {
444 dma_fence_unwrap_for_each(f, &iter, fence)
445 dma_resv_add_fence(dmabuf->resv, f, usage);
446 }
447
448 dma_resv_unlock(dmabuf->resv);
449 }
450
451 dma_fence_put(fence);
452
453 return ret;
454}
455#endif
456
457static long dma_buf_ioctl(struct file *file,
458 unsigned int cmd, unsigned long arg)
459{
460 struct dma_buf *dmabuf;
461 struct dma_buf_sync sync;
462 enum dma_data_direction direction;
463 int ret;
464
465 dmabuf = file->private_data;
466
467 switch (cmd) {
468 case DMA_BUF_IOCTL_SYNC:
469 if (copy_from_user(&sync, (void __user *) arg, sizeof(sync)))
470 return -EFAULT;
471
472 if (sync.flags & ~DMA_BUF_SYNC_VALID_FLAGS_MASK)
473 return -EINVAL;
474
475 switch (sync.flags & DMA_BUF_SYNC_RW) {
476 case DMA_BUF_SYNC_READ:
477 direction = DMA_FROM_DEVICE;
478 break;
479 case DMA_BUF_SYNC_WRITE:
480 direction = DMA_TO_DEVICE;
481 break;
482 case DMA_BUF_SYNC_RW:
483 direction = DMA_BIDIRECTIONAL;
484 break;
485 default:
486 return -EINVAL;
487 }
488
489 if (sync.flags & DMA_BUF_SYNC_END)
490 ret = dma_buf_end_cpu_access(dmabuf, direction);
491 else
492 ret = dma_buf_begin_cpu_access(dmabuf, direction);
493
494 return ret;
495
496 case DMA_BUF_SET_NAME_A:
497 case DMA_BUF_SET_NAME_B:
498 return dma_buf_set_name(dmabuf, (const char __user *)arg);
499
500#if IS_ENABLED(CONFIG_SYNC_FILE)
501 case DMA_BUF_IOCTL_EXPORT_SYNC_FILE:
502 return dma_buf_export_sync_file(dmabuf, (void __user *)arg);
503 case DMA_BUF_IOCTL_IMPORT_SYNC_FILE:
504 return dma_buf_import_sync_file(dmabuf, (const void __user *)arg);
505#endif
506
507 default:
508 return -ENOTTY;
509 }
510}
511
512static void dma_buf_show_fdinfo(struct seq_file *m, struct file *file)
513{
514 struct dma_buf *dmabuf = file->private_data;
515
516 seq_printf(m, "size:\t%zu\n", dmabuf->size);
517 /* Don't count the temporary reference taken inside procfs seq_show */
518 seq_printf(m, "count:\t%ld\n", file_count(dmabuf->file) - 1);
519 seq_printf(m, "exp_name:\t%s\n", dmabuf->exp_name);
520 spin_lock(&dmabuf->name_lock);
521 if (dmabuf->name)
522 seq_printf(m, "name:\t%s\n", dmabuf->name);
523 spin_unlock(&dmabuf->name_lock);
524}
525
526static const struct file_operations dma_buf_fops = {
527 .release = dma_buf_file_release,
528 .mmap = dma_buf_mmap_internal,
529 .llseek = dma_buf_llseek,
530 .poll = dma_buf_poll,
531 .unlocked_ioctl = dma_buf_ioctl,
532 .compat_ioctl = compat_ptr_ioctl,
533 .show_fdinfo = dma_buf_show_fdinfo,
534};
535
536/*
537 * is_dma_buf_file - Check if struct file* is associated with dma_buf
538 */
539static inline int is_dma_buf_file(struct file *file)
540{
541 return file->f_op == &dma_buf_fops;
542}
543
544static struct file *dma_buf_getfile(size_t size, int flags)
545{
546 static atomic64_t dmabuf_inode = ATOMIC64_INIT(0);
547 struct inode *inode = alloc_anon_inode(dma_buf_mnt->mnt_sb);
548 struct file *file;
549
550 if (IS_ERR(inode))
551 return ERR_CAST(inode);
552
553 inode->i_size = size;
554 inode_set_bytes(inode, size);
555
556 /*
557 * The ->i_ino acquired from get_next_ino() is not unique thus
558 * not suitable for using it as dentry name by dmabuf stats.
559 * Override ->i_ino with the unique and dmabuffs specific
560 * value.
561 */
562 inode->i_ino = atomic64_inc_return(&dmabuf_inode);
563 flags &= O_ACCMODE | O_NONBLOCK;
564 file = alloc_file_pseudo(inode, dma_buf_mnt, "dmabuf",
565 flags, &dma_buf_fops);
566 if (IS_ERR(file))
567 goto err_alloc_file;
568
569 return file;
570
571err_alloc_file:
572 iput(inode);
573 return file;
574}
575
576/**
577 * DOC: dma buf device access
578 *
579 * For device DMA access to a shared DMA buffer the usual sequence of operations
580 * is fairly simple:
581 *
582 * 1. The exporter defines his exporter instance using
583 * DEFINE_DMA_BUF_EXPORT_INFO() and calls dma_buf_export() to wrap a private
584 * buffer object into a &dma_buf. It then exports that &dma_buf to userspace
585 * as a file descriptor by calling dma_buf_fd().
586 *
587 * 2. Userspace passes this file-descriptors to all drivers it wants this buffer
588 * to share with: First the file descriptor is converted to a &dma_buf using
589 * dma_buf_get(). Then the buffer is attached to the device using
590 * dma_buf_attach().
591 *
592 * Up to this stage the exporter is still free to migrate or reallocate the
593 * backing storage.
594 *
595 * 3. Once the buffer is attached to all devices userspace can initiate DMA
596 * access to the shared buffer. In the kernel this is done by calling
597 * dma_buf_map_attachment() and dma_buf_unmap_attachment().
598 *
599 * 4. Once a driver is done with a shared buffer it needs to call
600 * dma_buf_detach() (after cleaning up any mappings) and then release the
601 * reference acquired with dma_buf_get() by calling dma_buf_put().
602 *
603 * For the detailed semantics exporters are expected to implement see
604 * &dma_buf_ops.
605 */
606
607/**
608 * dma_buf_export - Creates a new dma_buf, and associates an anon file
609 * with this buffer, so it can be exported.
610 * Also connect the allocator specific data and ops to the buffer.
611 * Additionally, provide a name string for exporter; useful in debugging.
612 *
613 * @exp_info: [in] holds all the export related information provided
614 * by the exporter. see &struct dma_buf_export_info
615 * for further details.
616 *
617 * Returns, on success, a newly created struct dma_buf object, which wraps the
618 * supplied private data and operations for struct dma_buf_ops. On either
619 * missing ops, or error in allocating struct dma_buf, will return negative
620 * error.
621 *
622 * For most cases the easiest way to create @exp_info is through the
623 * %DEFINE_DMA_BUF_EXPORT_INFO macro.
624 */
625struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info)
626{
627 struct dma_buf *dmabuf;
628 struct dma_resv *resv = exp_info->resv;
629 struct file *file;
630 size_t alloc_size = sizeof(struct dma_buf);
631 int ret;
632
633 if (WARN_ON(!exp_info->priv || !exp_info->ops
634 || !exp_info->ops->map_dma_buf
635 || !exp_info->ops->unmap_dma_buf
636 || !exp_info->ops->release))
637 return ERR_PTR(-EINVAL);
638
639 if (WARN_ON(exp_info->ops->cache_sgt_mapping &&
640 (exp_info->ops->pin || exp_info->ops->unpin)))
641 return ERR_PTR(-EINVAL);
642
643 if (WARN_ON(!exp_info->ops->pin != !exp_info->ops->unpin))
644 return ERR_PTR(-EINVAL);
645
646 if (!try_module_get(exp_info->owner))
647 return ERR_PTR(-ENOENT);
648
649 file = dma_buf_getfile(exp_info->size, exp_info->flags);
650 if (IS_ERR(file)) {
651 ret = PTR_ERR(file);
652 goto err_module;
653 }
654
655 if (!exp_info->resv)
656 alloc_size += sizeof(struct dma_resv);
657 else
658 /* prevent &dma_buf[1] == dma_buf->resv */
659 alloc_size += 1;
660 dmabuf = kzalloc(alloc_size, GFP_KERNEL);
661 if (!dmabuf) {
662 ret = -ENOMEM;
663 goto err_file;
664 }
665
666 dmabuf->priv = exp_info->priv;
667 dmabuf->ops = exp_info->ops;
668 dmabuf->size = exp_info->size;
669 dmabuf->exp_name = exp_info->exp_name;
670 dmabuf->owner = exp_info->owner;
671 spin_lock_init(&dmabuf->name_lock);
672 init_waitqueue_head(&dmabuf->poll);
673 dmabuf->cb_in.poll = dmabuf->cb_out.poll = &dmabuf->poll;
674 dmabuf->cb_in.active = dmabuf->cb_out.active = 0;
675 INIT_LIST_HEAD(&dmabuf->attachments);
676
677 if (!resv) {
678 dmabuf->resv = (struct dma_resv *)&dmabuf[1];
679 dma_resv_init(dmabuf->resv);
680 } else {
681 dmabuf->resv = resv;
682 }
683
684 ret = dma_buf_stats_setup(dmabuf, file);
685 if (ret)
686 goto err_dmabuf;
687
688 file->private_data = dmabuf;
689 file->f_path.dentry->d_fsdata = dmabuf;
690 dmabuf->file = file;
691
692 __dma_buf_debugfs_list_add(dmabuf);
693
694 return dmabuf;
695
696err_dmabuf:
697 if (!resv)
698 dma_resv_fini(dmabuf->resv);
699 kfree(dmabuf);
700err_file:
701 fput(file);
702err_module:
703 module_put(exp_info->owner);
704 return ERR_PTR(ret);
705}
706EXPORT_SYMBOL_NS_GPL(dma_buf_export, "DMA_BUF");
707
708/**
709 * dma_buf_fd - returns a file descriptor for the given struct dma_buf
710 * @dmabuf: [in] pointer to dma_buf for which fd is required.
711 * @flags: [in] flags to give to fd
712 *
713 * On success, returns an associated 'fd'. Else, returns error.
714 */
715int dma_buf_fd(struct dma_buf *dmabuf, int flags)
716{
717 int fd;
718
719 if (!dmabuf || !dmabuf->file)
720 return -EINVAL;
721
722 fd = get_unused_fd_flags(flags);
723 if (fd < 0)
724 return fd;
725
726 fd_install(fd, dmabuf->file);
727
728 return fd;
729}
730EXPORT_SYMBOL_NS_GPL(dma_buf_fd, "DMA_BUF");
731
732/**
733 * dma_buf_get - returns the struct dma_buf related to an fd
734 * @fd: [in] fd associated with the struct dma_buf to be returned
735 *
736 * On success, returns the struct dma_buf associated with an fd; uses
737 * file's refcounting done by fget to increase refcount. returns ERR_PTR
738 * otherwise.
739 */
740struct dma_buf *dma_buf_get(int fd)
741{
742 struct file *file;
743
744 file = fget(fd);
745
746 if (!file)
747 return ERR_PTR(-EBADF);
748
749 if (!is_dma_buf_file(file)) {
750 fput(file);
751 return ERR_PTR(-EINVAL);
752 }
753
754 return file->private_data;
755}
756EXPORT_SYMBOL_NS_GPL(dma_buf_get, "DMA_BUF");
757
758/**
759 * dma_buf_put - decreases refcount of the buffer
760 * @dmabuf: [in] buffer to reduce refcount of
761 *
762 * Uses file's refcounting done implicitly by fput().
763 *
764 * If, as a result of this call, the refcount becomes 0, the 'release' file
765 * operation related to this fd is called. It calls &dma_buf_ops.release vfunc
766 * in turn, and frees the memory allocated for dmabuf when exported.
767 */
768void dma_buf_put(struct dma_buf *dmabuf)
769{
770 if (WARN_ON(!dmabuf || !dmabuf->file))
771 return;
772
773 fput(dmabuf->file);
774}
775EXPORT_SYMBOL_NS_GPL(dma_buf_put, "DMA_BUF");
776
777static void mangle_sg_table(struct sg_table *sg_table)
778{
779#ifdef CONFIG_DMABUF_DEBUG
780 int i;
781 struct scatterlist *sg;
782
783 /* To catch abuse of the underlying struct page by importers mix
784 * up the bits, but take care to preserve the low SG_ bits to
785 * not corrupt the sgt. The mixing is undone in __unmap_dma_buf
786 * before passing the sgt back to the exporter.
787 */
788 for_each_sgtable_sg(sg_table, sg, i)
789 sg->page_link ^= ~0xffUL;
790#endif
791
792}
793static struct sg_table *__map_dma_buf(struct dma_buf_attachment *attach,
794 enum dma_data_direction direction)
795{
796 struct sg_table *sg_table;
797 signed long ret;
798
799 sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction);
800 if (IS_ERR_OR_NULL(sg_table))
801 return sg_table;
802
803 if (!dma_buf_attachment_is_dynamic(attach)) {
804 ret = dma_resv_wait_timeout(attach->dmabuf->resv,
805 DMA_RESV_USAGE_KERNEL, true,
806 MAX_SCHEDULE_TIMEOUT);
807 if (ret < 0) {
808 attach->dmabuf->ops->unmap_dma_buf(attach, sg_table,
809 direction);
810 return ERR_PTR(ret);
811 }
812 }
813
814 mangle_sg_table(sg_table);
815 return sg_table;
816}
817
818/**
819 * DOC: locking convention
820 *
821 * In order to avoid deadlock situations between dma-buf exports and importers,
822 * all dma-buf API users must follow the common dma-buf locking convention.
823 *
824 * Convention for importers
825 *
826 * 1. Importers must hold the dma-buf reservation lock when calling these
827 * functions:
828 *
829 * - dma_buf_pin()
830 * - dma_buf_unpin()
831 * - dma_buf_map_attachment()
832 * - dma_buf_unmap_attachment()
833 * - dma_buf_vmap()
834 * - dma_buf_vunmap()
835 *
836 * 2. Importers must not hold the dma-buf reservation lock when calling these
837 * functions:
838 *
839 * - dma_buf_attach()
840 * - dma_buf_dynamic_attach()
841 * - dma_buf_detach()
842 * - dma_buf_export()
843 * - dma_buf_fd()
844 * - dma_buf_get()
845 * - dma_buf_put()
846 * - dma_buf_mmap()
847 * - dma_buf_begin_cpu_access()
848 * - dma_buf_end_cpu_access()
849 * - dma_buf_map_attachment_unlocked()
850 * - dma_buf_unmap_attachment_unlocked()
851 * - dma_buf_vmap_unlocked()
852 * - dma_buf_vunmap_unlocked()
853 *
854 * Convention for exporters
855 *
856 * 1. These &dma_buf_ops callbacks are invoked with unlocked dma-buf
857 * reservation and exporter can take the lock:
858 *
859 * - &dma_buf_ops.attach()
860 * - &dma_buf_ops.detach()
861 * - &dma_buf_ops.release()
862 * - &dma_buf_ops.begin_cpu_access()
863 * - &dma_buf_ops.end_cpu_access()
864 * - &dma_buf_ops.mmap()
865 *
866 * 2. These &dma_buf_ops callbacks are invoked with locked dma-buf
867 * reservation and exporter can't take the lock:
868 *
869 * - &dma_buf_ops.pin()
870 * - &dma_buf_ops.unpin()
871 * - &dma_buf_ops.map_dma_buf()
872 * - &dma_buf_ops.unmap_dma_buf()
873 * - &dma_buf_ops.vmap()
874 * - &dma_buf_ops.vunmap()
875 *
876 * 3. Exporters must hold the dma-buf reservation lock when calling these
877 * functions:
878 *
879 * - dma_buf_move_notify()
880 */
881
882/**
883 * dma_buf_dynamic_attach - Add the device to dma_buf's attachments list
884 * @dmabuf: [in] buffer to attach device to.
885 * @dev: [in] device to be attached.
886 * @importer_ops: [in] importer operations for the attachment
887 * @importer_priv: [in] importer private pointer for the attachment
888 *
889 * Returns struct dma_buf_attachment pointer for this attachment. Attachments
890 * must be cleaned up by calling dma_buf_detach().
891 *
892 * Optionally this calls &dma_buf_ops.attach to allow device-specific attach
893 * functionality.
894 *
895 * Returns:
896 *
897 * A pointer to newly created &dma_buf_attachment on success, or a negative
898 * error code wrapped into a pointer on failure.
899 *
900 * Note that this can fail if the backing storage of @dmabuf is in a place not
901 * accessible to @dev, and cannot be moved to a more suitable place. This is
902 * indicated with the error code -EBUSY.
903 */
904struct dma_buf_attachment *
905dma_buf_dynamic_attach(struct dma_buf *dmabuf, struct device *dev,
906 const struct dma_buf_attach_ops *importer_ops,
907 void *importer_priv)
908{
909 struct dma_buf_attachment *attach;
910 int ret;
911
912 if (WARN_ON(!dmabuf || !dev))
913 return ERR_PTR(-EINVAL);
914
915 if (WARN_ON(importer_ops && !importer_ops->move_notify))
916 return ERR_PTR(-EINVAL);
917
918 attach = kzalloc(sizeof(*attach), GFP_KERNEL);
919 if (!attach)
920 return ERR_PTR(-ENOMEM);
921
922 attach->dev = dev;
923 attach->dmabuf = dmabuf;
924 if (importer_ops)
925 attach->peer2peer = importer_ops->allow_peer2peer;
926 attach->importer_ops = importer_ops;
927 attach->importer_priv = importer_priv;
928
929 if (dmabuf->ops->attach) {
930 ret = dmabuf->ops->attach(dmabuf, attach);
931 if (ret)
932 goto err_attach;
933 }
934 dma_resv_lock(dmabuf->resv, NULL);
935 list_add(&attach->node, &dmabuf->attachments);
936 dma_resv_unlock(dmabuf->resv);
937
938 /* When either the importer or the exporter can't handle dynamic
939 * mappings we cache the mapping here to avoid issues with the
940 * reservation object lock.
941 */
942 if (dma_buf_attachment_is_dynamic(attach) !=
943 dma_buf_is_dynamic(dmabuf)) {
944 struct sg_table *sgt;
945
946 dma_resv_lock(attach->dmabuf->resv, NULL);
947 if (dma_buf_is_dynamic(attach->dmabuf)) {
948 ret = dmabuf->ops->pin(attach);
949 if (ret)
950 goto err_unlock;
951 }
952
953 sgt = __map_dma_buf(attach, DMA_BIDIRECTIONAL);
954 if (!sgt)
955 sgt = ERR_PTR(-ENOMEM);
956 if (IS_ERR(sgt)) {
957 ret = PTR_ERR(sgt);
958 goto err_unpin;
959 }
960 dma_resv_unlock(attach->dmabuf->resv);
961 attach->sgt = sgt;
962 attach->dir = DMA_BIDIRECTIONAL;
963 }
964
965 return attach;
966
967err_attach:
968 kfree(attach);
969 return ERR_PTR(ret);
970
971err_unpin:
972 if (dma_buf_is_dynamic(attach->dmabuf))
973 dmabuf->ops->unpin(attach);
974
975err_unlock:
976 dma_resv_unlock(attach->dmabuf->resv);
977
978 dma_buf_detach(dmabuf, attach);
979 return ERR_PTR(ret);
980}
981EXPORT_SYMBOL_NS_GPL(dma_buf_dynamic_attach, "DMA_BUF");
982
983/**
984 * dma_buf_attach - Wrapper for dma_buf_dynamic_attach
985 * @dmabuf: [in] buffer to attach device to.
986 * @dev: [in] device to be attached.
987 *
988 * Wrapper to call dma_buf_dynamic_attach() for drivers which still use a static
989 * mapping.
990 */
991struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
992 struct device *dev)
993{
994 return dma_buf_dynamic_attach(dmabuf, dev, NULL, NULL);
995}
996EXPORT_SYMBOL_NS_GPL(dma_buf_attach, "DMA_BUF");
997
998static void __unmap_dma_buf(struct dma_buf_attachment *attach,
999 struct sg_table *sg_table,
1000 enum dma_data_direction direction)
1001{
1002 /* uses XOR, hence this unmangles */
1003 mangle_sg_table(sg_table);
1004
1005 attach->dmabuf->ops->unmap_dma_buf(attach, sg_table, direction);
1006}
1007
1008/**
1009 * dma_buf_detach - Remove the given attachment from dmabuf's attachments list
1010 * @dmabuf: [in] buffer to detach from.
1011 * @attach: [in] attachment to be detached; is free'd after this call.
1012 *
1013 * Clean up a device attachment obtained by calling dma_buf_attach().
1014 *
1015 * Optionally this calls &dma_buf_ops.detach for device-specific detach.
1016 */
1017void dma_buf_detach(struct dma_buf *dmabuf, struct dma_buf_attachment *attach)
1018{
1019 if (WARN_ON(!dmabuf || !attach || dmabuf != attach->dmabuf))
1020 return;
1021
1022 dma_resv_lock(dmabuf->resv, NULL);
1023
1024 if (attach->sgt) {
1025
1026 __unmap_dma_buf(attach, attach->sgt, attach->dir);
1027
1028 if (dma_buf_is_dynamic(attach->dmabuf))
1029 dmabuf->ops->unpin(attach);
1030 }
1031 list_del(&attach->node);
1032
1033 dma_resv_unlock(dmabuf->resv);
1034
1035 if (dmabuf->ops->detach)
1036 dmabuf->ops->detach(dmabuf, attach);
1037
1038 kfree(attach);
1039}
1040EXPORT_SYMBOL_NS_GPL(dma_buf_detach, "DMA_BUF");
1041
1042/**
1043 * dma_buf_pin - Lock down the DMA-buf
1044 * @attach: [in] attachment which should be pinned
1045 *
1046 * Only dynamic importers (who set up @attach with dma_buf_dynamic_attach()) may
1047 * call this, and only for limited use cases like scanout and not for temporary
1048 * pin operations. It is not permitted to allow userspace to pin arbitrary
1049 * amounts of buffers through this interface.
1050 *
1051 * Buffers must be unpinned by calling dma_buf_unpin().
1052 *
1053 * Returns:
1054 * 0 on success, negative error code on failure.
1055 */
1056int dma_buf_pin(struct dma_buf_attachment *attach)
1057{
1058 struct dma_buf *dmabuf = attach->dmabuf;
1059 int ret = 0;
1060
1061 WARN_ON(!dma_buf_attachment_is_dynamic(attach));
1062
1063 dma_resv_assert_held(dmabuf->resv);
1064
1065 if (dmabuf->ops->pin)
1066 ret = dmabuf->ops->pin(attach);
1067
1068 return ret;
1069}
1070EXPORT_SYMBOL_NS_GPL(dma_buf_pin, "DMA_BUF");
1071
1072/**
1073 * dma_buf_unpin - Unpin a DMA-buf
1074 * @attach: [in] attachment which should be unpinned
1075 *
1076 * This unpins a buffer pinned by dma_buf_pin() and allows the exporter to move
1077 * any mapping of @attach again and inform the importer through
1078 * &dma_buf_attach_ops.move_notify.
1079 */
1080void dma_buf_unpin(struct dma_buf_attachment *attach)
1081{
1082 struct dma_buf *dmabuf = attach->dmabuf;
1083
1084 WARN_ON(!dma_buf_attachment_is_dynamic(attach));
1085
1086 dma_resv_assert_held(dmabuf->resv);
1087
1088 if (dmabuf->ops->unpin)
1089 dmabuf->ops->unpin(attach);
1090}
1091EXPORT_SYMBOL_NS_GPL(dma_buf_unpin, "DMA_BUF");
1092
1093/**
1094 * dma_buf_map_attachment - Returns the scatterlist table of the attachment;
1095 * mapped into _device_ address space. Is a wrapper for map_dma_buf() of the
1096 * dma_buf_ops.
1097 * @attach: [in] attachment whose scatterlist is to be returned
1098 * @direction: [in] direction of DMA transfer
1099 *
1100 * Returns sg_table containing the scatterlist to be returned; returns ERR_PTR
1101 * on error. May return -EINTR if it is interrupted by a signal.
1102 *
1103 * On success, the DMA addresses and lengths in the returned scatterlist are
1104 * PAGE_SIZE aligned.
1105 *
1106 * A mapping must be unmapped by using dma_buf_unmap_attachment(). Note that
1107 * the underlying backing storage is pinned for as long as a mapping exists,
1108 * therefore users/importers should not hold onto a mapping for undue amounts of
1109 * time.
1110 *
1111 * Important: Dynamic importers must wait for the exclusive fence of the struct
1112 * dma_resv attached to the DMA-BUF first.
1113 */
1114struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
1115 enum dma_data_direction direction)
1116{
1117 struct sg_table *sg_table;
1118 int r;
1119
1120 might_sleep();
1121
1122 if (WARN_ON(!attach || !attach->dmabuf))
1123 return ERR_PTR(-EINVAL);
1124
1125 dma_resv_assert_held(attach->dmabuf->resv);
1126
1127 if (attach->sgt) {
1128 /*
1129 * Two mappings with different directions for the same
1130 * attachment are not allowed.
1131 */
1132 if (attach->dir != direction &&
1133 attach->dir != DMA_BIDIRECTIONAL)
1134 return ERR_PTR(-EBUSY);
1135
1136 return attach->sgt;
1137 }
1138
1139 if (dma_buf_is_dynamic(attach->dmabuf)) {
1140 if (!IS_ENABLED(CONFIG_DMABUF_MOVE_NOTIFY)) {
1141 r = attach->dmabuf->ops->pin(attach);
1142 if (r)
1143 return ERR_PTR(r);
1144 }
1145 }
1146
1147 sg_table = __map_dma_buf(attach, direction);
1148 if (!sg_table)
1149 sg_table = ERR_PTR(-ENOMEM);
1150
1151 if (IS_ERR(sg_table) && dma_buf_is_dynamic(attach->dmabuf) &&
1152 !IS_ENABLED(CONFIG_DMABUF_MOVE_NOTIFY))
1153 attach->dmabuf->ops->unpin(attach);
1154
1155 if (!IS_ERR(sg_table) && attach->dmabuf->ops->cache_sgt_mapping) {
1156 attach->sgt = sg_table;
1157 attach->dir = direction;
1158 }
1159
1160#ifdef CONFIG_DMA_API_DEBUG
1161 if (!IS_ERR(sg_table)) {
1162 struct scatterlist *sg;
1163 u64 addr;
1164 int len;
1165 int i;
1166
1167 for_each_sgtable_dma_sg(sg_table, sg, i) {
1168 addr = sg_dma_address(sg);
1169 len = sg_dma_len(sg);
1170 if (!PAGE_ALIGNED(addr) || !PAGE_ALIGNED(len)) {
1171 pr_debug("%s: addr %llx or len %x is not page aligned!\n",
1172 __func__, addr, len);
1173 }
1174 }
1175 }
1176#endif /* CONFIG_DMA_API_DEBUG */
1177 return sg_table;
1178}
1179EXPORT_SYMBOL_NS_GPL(dma_buf_map_attachment, "DMA_BUF");
1180
1181/**
1182 * dma_buf_map_attachment_unlocked - Returns the scatterlist table of the attachment;
1183 * mapped into _device_ address space. Is a wrapper for map_dma_buf() of the
1184 * dma_buf_ops.
1185 * @attach: [in] attachment whose scatterlist is to be returned
1186 * @direction: [in] direction of DMA transfer
1187 *
1188 * Unlocked variant of dma_buf_map_attachment().
1189 */
1190struct sg_table *
1191dma_buf_map_attachment_unlocked(struct dma_buf_attachment *attach,
1192 enum dma_data_direction direction)
1193{
1194 struct sg_table *sg_table;
1195
1196 might_sleep();
1197
1198 if (WARN_ON(!attach || !attach->dmabuf))
1199 return ERR_PTR(-EINVAL);
1200
1201 dma_resv_lock(attach->dmabuf->resv, NULL);
1202 sg_table = dma_buf_map_attachment(attach, direction);
1203 dma_resv_unlock(attach->dmabuf->resv);
1204
1205 return sg_table;
1206}
1207EXPORT_SYMBOL_NS_GPL(dma_buf_map_attachment_unlocked, "DMA_BUF");
1208
1209/**
1210 * dma_buf_unmap_attachment - unmaps and decreases usecount of the buffer;might
1211 * deallocate the scatterlist associated. Is a wrapper for unmap_dma_buf() of
1212 * dma_buf_ops.
1213 * @attach: [in] attachment to unmap buffer from
1214 * @sg_table: [in] scatterlist info of the buffer to unmap
1215 * @direction: [in] direction of DMA transfer
1216 *
1217 * This unmaps a DMA mapping for @attached obtained by dma_buf_map_attachment().
1218 */
1219void dma_buf_unmap_attachment(struct dma_buf_attachment *attach,
1220 struct sg_table *sg_table,
1221 enum dma_data_direction direction)
1222{
1223 might_sleep();
1224
1225 if (WARN_ON(!attach || !attach->dmabuf || !sg_table))
1226 return;
1227
1228 dma_resv_assert_held(attach->dmabuf->resv);
1229
1230 if (attach->sgt == sg_table)
1231 return;
1232
1233 __unmap_dma_buf(attach, sg_table, direction);
1234
1235 if (dma_buf_is_dynamic(attach->dmabuf) &&
1236 !IS_ENABLED(CONFIG_DMABUF_MOVE_NOTIFY))
1237 dma_buf_unpin(attach);
1238}
1239EXPORT_SYMBOL_NS_GPL(dma_buf_unmap_attachment, "DMA_BUF");
1240
1241/**
1242 * dma_buf_unmap_attachment_unlocked - unmaps and decreases usecount of the buffer;might
1243 * deallocate the scatterlist associated. Is a wrapper for unmap_dma_buf() of
1244 * dma_buf_ops.
1245 * @attach: [in] attachment to unmap buffer from
1246 * @sg_table: [in] scatterlist info of the buffer to unmap
1247 * @direction: [in] direction of DMA transfer
1248 *
1249 * Unlocked variant of dma_buf_unmap_attachment().
1250 */
1251void dma_buf_unmap_attachment_unlocked(struct dma_buf_attachment *attach,
1252 struct sg_table *sg_table,
1253 enum dma_data_direction direction)
1254{
1255 might_sleep();
1256
1257 if (WARN_ON(!attach || !attach->dmabuf || !sg_table))
1258 return;
1259
1260 dma_resv_lock(attach->dmabuf->resv, NULL);
1261 dma_buf_unmap_attachment(attach, sg_table, direction);
1262 dma_resv_unlock(attach->dmabuf->resv);
1263}
1264EXPORT_SYMBOL_NS_GPL(dma_buf_unmap_attachment_unlocked, "DMA_BUF");
1265
1266/**
1267 * dma_buf_move_notify - notify attachments that DMA-buf is moving
1268 *
1269 * @dmabuf: [in] buffer which is moving
1270 *
1271 * Informs all attachments that they need to destroy and recreate all their
1272 * mappings.
1273 */
1274void dma_buf_move_notify(struct dma_buf *dmabuf)
1275{
1276 struct dma_buf_attachment *attach;
1277
1278 dma_resv_assert_held(dmabuf->resv);
1279
1280 list_for_each_entry(attach, &dmabuf->attachments, node)
1281 if (attach->importer_ops)
1282 attach->importer_ops->move_notify(attach);
1283}
1284EXPORT_SYMBOL_NS_GPL(dma_buf_move_notify, "DMA_BUF");
1285
1286/**
1287 * DOC: cpu access
1288 *
1289 * There are multiple reasons for supporting CPU access to a dma buffer object:
1290 *
1291 * - Fallback operations in the kernel, for example when a device is connected
1292 * over USB and the kernel needs to shuffle the data around first before
1293 * sending it away. Cache coherency is handled by bracketing any transactions
1294 * with calls to dma_buf_begin_cpu_access() and dma_buf_end_cpu_access()
1295 * access.
1296 *
1297 * Since for most kernel internal dma-buf accesses need the entire buffer, a
1298 * vmap interface is introduced. Note that on very old 32-bit architectures
1299 * vmalloc space might be limited and result in vmap calls failing.
1300 *
1301 * Interfaces:
1302 *
1303 * .. code-block:: c
1304 *
1305 * void *dma_buf_vmap(struct dma_buf *dmabuf, struct iosys_map *map)
1306 * void dma_buf_vunmap(struct dma_buf *dmabuf, struct iosys_map *map)
1307 *
1308 * The vmap call can fail if there is no vmap support in the exporter, or if
1309 * it runs out of vmalloc space. Note that the dma-buf layer keeps a reference
1310 * count for all vmap access and calls down into the exporter's vmap function
1311 * only when no vmapping exists, and only unmaps it once. Protection against
1312 * concurrent vmap/vunmap calls is provided by taking the &dma_buf.lock mutex.
1313 *
1314 * - For full compatibility on the importer side with existing userspace
1315 * interfaces, which might already support mmap'ing buffers. This is needed in
1316 * many processing pipelines (e.g. feeding a software rendered image into a
1317 * hardware pipeline, thumbnail creation, snapshots, ...). Also, Android's ION
1318 * framework already supported this and for DMA buffer file descriptors to
1319 * replace ION buffers mmap support was needed.
1320 *
1321 * There is no special interfaces, userspace simply calls mmap on the dma-buf
1322 * fd. But like for CPU access there's a need to bracket the actual access,
1323 * which is handled by the ioctl (DMA_BUF_IOCTL_SYNC). Note that
1324 * DMA_BUF_IOCTL_SYNC can fail with -EAGAIN or -EINTR, in which case it must
1325 * be restarted.
1326 *
1327 * Some systems might need some sort of cache coherency management e.g. when
1328 * CPU and GPU domains are being accessed through dma-buf at the same time.
1329 * To circumvent this problem there are begin/end coherency markers, that
1330 * forward directly to existing dma-buf device drivers vfunc hooks. Userspace
1331 * can make use of those markers through the DMA_BUF_IOCTL_SYNC ioctl. The
1332 * sequence would be used like following:
1333 *
1334 * - mmap dma-buf fd
1335 * - for each drawing/upload cycle in CPU 1. SYNC_START ioctl, 2. read/write
1336 * to mmap area 3. SYNC_END ioctl. This can be repeated as often as you
1337 * want (with the new data being consumed by say the GPU or the scanout
1338 * device)
1339 * - munmap once you don't need the buffer any more
1340 *
1341 * For correctness and optimal performance, it is always required to use
1342 * SYNC_START and SYNC_END before and after, respectively, when accessing the
1343 * mapped address. Userspace cannot rely on coherent access, even when there
1344 * are systems where it just works without calling these ioctls.
1345 *
1346 * - And as a CPU fallback in userspace processing pipelines.
1347 *
1348 * Similar to the motivation for kernel cpu access it is again important that
1349 * the userspace code of a given importing subsystem can use the same
1350 * interfaces with a imported dma-buf buffer object as with a native buffer
1351 * object. This is especially important for drm where the userspace part of
1352 * contemporary OpenGL, X, and other drivers is huge, and reworking them to
1353 * use a different way to mmap a buffer rather invasive.
1354 *
1355 * The assumption in the current dma-buf interfaces is that redirecting the
1356 * initial mmap is all that's needed. A survey of some of the existing
1357 * subsystems shows that no driver seems to do any nefarious thing like
1358 * syncing up with outstanding asynchronous processing on the device or
1359 * allocating special resources at fault time. So hopefully this is good
1360 * enough, since adding interfaces to intercept pagefaults and allow pte
1361 * shootdowns would increase the complexity quite a bit.
1362 *
1363 * Interface:
1364 *
1365 * .. code-block:: c
1366 *
1367 * int dma_buf_mmap(struct dma_buf *, struct vm_area_struct *, unsigned long);
1368 *
1369 * If the importing subsystem simply provides a special-purpose mmap call to
1370 * set up a mapping in userspace, calling do_mmap with &dma_buf.file will
1371 * equally achieve that for a dma-buf object.
1372 */
1373
1374static int __dma_buf_begin_cpu_access(struct dma_buf *dmabuf,
1375 enum dma_data_direction direction)
1376{
1377 bool write = (direction == DMA_BIDIRECTIONAL ||
1378 direction == DMA_TO_DEVICE);
1379 struct dma_resv *resv = dmabuf->resv;
1380 long ret;
1381
1382 /* Wait on any implicit rendering fences */
1383 ret = dma_resv_wait_timeout(resv, dma_resv_usage_rw(write),
1384 true, MAX_SCHEDULE_TIMEOUT);
1385 if (ret < 0)
1386 return ret;
1387
1388 return 0;
1389}
1390
1391/**
1392 * dma_buf_begin_cpu_access - Must be called before accessing a dma_buf from the
1393 * cpu in the kernel context. Calls begin_cpu_access to allow exporter-specific
1394 * preparations. Coherency is only guaranteed in the specified range for the
1395 * specified access direction.
1396 * @dmabuf: [in] buffer to prepare cpu access for.
1397 * @direction: [in] direction of access.
1398 *
1399 * After the cpu access is complete the caller should call
1400 * dma_buf_end_cpu_access(). Only when cpu access is bracketed by both calls is
1401 * it guaranteed to be coherent with other DMA access.
1402 *
1403 * This function will also wait for any DMA transactions tracked through
1404 * implicit synchronization in &dma_buf.resv. For DMA transactions with explicit
1405 * synchronization this function will only ensure cache coherency, callers must
1406 * ensure synchronization with such DMA transactions on their own.
1407 *
1408 * Can return negative error values, returns 0 on success.
1409 */
1410int dma_buf_begin_cpu_access(struct dma_buf *dmabuf,
1411 enum dma_data_direction direction)
1412{
1413 int ret = 0;
1414
1415 if (WARN_ON(!dmabuf))
1416 return -EINVAL;
1417
1418 might_lock(&dmabuf->resv->lock.base);
1419
1420 if (dmabuf->ops->begin_cpu_access)
1421 ret = dmabuf->ops->begin_cpu_access(dmabuf, direction);
1422
1423 /* Ensure that all fences are waited upon - but we first allow
1424 * the native handler the chance to do so more efficiently if it
1425 * chooses. A double invocation here will be reasonably cheap no-op.
1426 */
1427 if (ret == 0)
1428 ret = __dma_buf_begin_cpu_access(dmabuf, direction);
1429
1430 return ret;
1431}
1432EXPORT_SYMBOL_NS_GPL(dma_buf_begin_cpu_access, "DMA_BUF");
1433
1434/**
1435 * dma_buf_end_cpu_access - Must be called after accessing a dma_buf from the
1436 * cpu in the kernel context. Calls end_cpu_access to allow exporter-specific
1437 * actions. Coherency is only guaranteed in the specified range for the
1438 * specified access direction.
1439 * @dmabuf: [in] buffer to complete cpu access for.
1440 * @direction: [in] direction of access.
1441 *
1442 * This terminates CPU access started with dma_buf_begin_cpu_access().
1443 *
1444 * Can return negative error values, returns 0 on success.
1445 */
1446int dma_buf_end_cpu_access(struct dma_buf *dmabuf,
1447 enum dma_data_direction direction)
1448{
1449 int ret = 0;
1450
1451 WARN_ON(!dmabuf);
1452
1453 might_lock(&dmabuf->resv->lock.base);
1454
1455 if (dmabuf->ops->end_cpu_access)
1456 ret = dmabuf->ops->end_cpu_access(dmabuf, direction);
1457
1458 return ret;
1459}
1460EXPORT_SYMBOL_NS_GPL(dma_buf_end_cpu_access, "DMA_BUF");
1461
1462
1463/**
1464 * dma_buf_mmap - Setup up a userspace mmap with the given vma
1465 * @dmabuf: [in] buffer that should back the vma
1466 * @vma: [in] vma for the mmap
1467 * @pgoff: [in] offset in pages where this mmap should start within the
1468 * dma-buf buffer.
1469 *
1470 * This function adjusts the passed in vma so that it points at the file of the
1471 * dma_buf operation. It also adjusts the starting pgoff and does bounds
1472 * checking on the size of the vma. Then it calls the exporters mmap function to
1473 * set up the mapping.
1474 *
1475 * Can return negative error values, returns 0 on success.
1476 */
1477int dma_buf_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma,
1478 unsigned long pgoff)
1479{
1480 if (WARN_ON(!dmabuf || !vma))
1481 return -EINVAL;
1482
1483 /* check if buffer supports mmap */
1484 if (!dmabuf->ops->mmap)
1485 return -EINVAL;
1486
1487 /* check for offset overflow */
1488 if (pgoff + vma_pages(vma) < pgoff)
1489 return -EOVERFLOW;
1490
1491 /* check for overflowing the buffer's size */
1492 if (pgoff + vma_pages(vma) >
1493 dmabuf->size >> PAGE_SHIFT)
1494 return -EINVAL;
1495
1496 /* readjust the vma */
1497 vma_set_file(vma, dmabuf->file);
1498 vma->vm_pgoff = pgoff;
1499
1500 return dmabuf->ops->mmap(dmabuf, vma);
1501}
1502EXPORT_SYMBOL_NS_GPL(dma_buf_mmap, "DMA_BUF");
1503
1504/**
1505 * dma_buf_vmap - Create virtual mapping for the buffer object into kernel
1506 * address space. Same restrictions as for vmap and friends apply.
1507 * @dmabuf: [in] buffer to vmap
1508 * @map: [out] returns the vmap pointer
1509 *
1510 * This call may fail due to lack of virtual mapping address space.
1511 * These calls are optional in drivers. The intended use for them
1512 * is for mapping objects linear in kernel space for high use objects.
1513 *
1514 * To ensure coherency users must call dma_buf_begin_cpu_access() and
1515 * dma_buf_end_cpu_access() around any cpu access performed through this
1516 * mapping.
1517 *
1518 * Returns 0 on success, or a negative errno code otherwise.
1519 */
1520int dma_buf_vmap(struct dma_buf *dmabuf, struct iosys_map *map)
1521{
1522 struct iosys_map ptr;
1523 int ret;
1524
1525 iosys_map_clear(map);
1526
1527 if (WARN_ON(!dmabuf))
1528 return -EINVAL;
1529
1530 dma_resv_assert_held(dmabuf->resv);
1531
1532 if (!dmabuf->ops->vmap)
1533 return -EINVAL;
1534
1535 if (dmabuf->vmapping_counter) {
1536 dmabuf->vmapping_counter++;
1537 BUG_ON(iosys_map_is_null(&dmabuf->vmap_ptr));
1538 *map = dmabuf->vmap_ptr;
1539 return 0;
1540 }
1541
1542 BUG_ON(iosys_map_is_set(&dmabuf->vmap_ptr));
1543
1544 ret = dmabuf->ops->vmap(dmabuf, &ptr);
1545 if (WARN_ON_ONCE(ret))
1546 return ret;
1547
1548 dmabuf->vmap_ptr = ptr;
1549 dmabuf->vmapping_counter = 1;
1550
1551 *map = dmabuf->vmap_ptr;
1552
1553 return 0;
1554}
1555EXPORT_SYMBOL_NS_GPL(dma_buf_vmap, "DMA_BUF");
1556
1557/**
1558 * dma_buf_vmap_unlocked - Create virtual mapping for the buffer object into kernel
1559 * address space. Same restrictions as for vmap and friends apply.
1560 * @dmabuf: [in] buffer to vmap
1561 * @map: [out] returns the vmap pointer
1562 *
1563 * Unlocked version of dma_buf_vmap()
1564 *
1565 * Returns 0 on success, or a negative errno code otherwise.
1566 */
1567int dma_buf_vmap_unlocked(struct dma_buf *dmabuf, struct iosys_map *map)
1568{
1569 int ret;
1570
1571 iosys_map_clear(map);
1572
1573 if (WARN_ON(!dmabuf))
1574 return -EINVAL;
1575
1576 dma_resv_lock(dmabuf->resv, NULL);
1577 ret = dma_buf_vmap(dmabuf, map);
1578 dma_resv_unlock(dmabuf->resv);
1579
1580 return ret;
1581}
1582EXPORT_SYMBOL_NS_GPL(dma_buf_vmap_unlocked, "DMA_BUF");
1583
1584/**
1585 * dma_buf_vunmap - Unmap a vmap obtained by dma_buf_vmap.
1586 * @dmabuf: [in] buffer to vunmap
1587 * @map: [in] vmap pointer to vunmap
1588 */
1589void dma_buf_vunmap(struct dma_buf *dmabuf, struct iosys_map *map)
1590{
1591 if (WARN_ON(!dmabuf))
1592 return;
1593
1594 dma_resv_assert_held(dmabuf->resv);
1595
1596 BUG_ON(iosys_map_is_null(&dmabuf->vmap_ptr));
1597 BUG_ON(dmabuf->vmapping_counter == 0);
1598 BUG_ON(!iosys_map_is_equal(&dmabuf->vmap_ptr, map));
1599
1600 if (--dmabuf->vmapping_counter == 0) {
1601 if (dmabuf->ops->vunmap)
1602 dmabuf->ops->vunmap(dmabuf, map);
1603 iosys_map_clear(&dmabuf->vmap_ptr);
1604 }
1605}
1606EXPORT_SYMBOL_NS_GPL(dma_buf_vunmap, "DMA_BUF");
1607
1608/**
1609 * dma_buf_vunmap_unlocked - Unmap a vmap obtained by dma_buf_vmap.
1610 * @dmabuf: [in] buffer to vunmap
1611 * @map: [in] vmap pointer to vunmap
1612 */
1613void dma_buf_vunmap_unlocked(struct dma_buf *dmabuf, struct iosys_map *map)
1614{
1615 if (WARN_ON(!dmabuf))
1616 return;
1617
1618 dma_resv_lock(dmabuf->resv, NULL);
1619 dma_buf_vunmap(dmabuf, map);
1620 dma_resv_unlock(dmabuf->resv);
1621}
1622EXPORT_SYMBOL_NS_GPL(dma_buf_vunmap_unlocked, "DMA_BUF");
1623
1624#ifdef CONFIG_DEBUG_FS
1625static int dma_buf_debug_show(struct seq_file *s, void *unused)
1626{
1627 struct dma_buf *buf_obj;
1628 struct dma_buf_attachment *attach_obj;
1629 int count = 0, attach_count;
1630 size_t size = 0;
1631 int ret;
1632
1633 ret = mutex_lock_interruptible(&debugfs_list_mutex);
1634
1635 if (ret)
1636 return ret;
1637
1638 seq_puts(s, "\nDma-buf Objects:\n");
1639 seq_printf(s, "%-8s\t%-8s\t%-8s\t%-8s\texp_name\t%-8s\tname\n",
1640 "size", "flags", "mode", "count", "ino");
1641
1642 list_for_each_entry(buf_obj, &debugfs_list, list_node) {
1643
1644 ret = dma_resv_lock_interruptible(buf_obj->resv, NULL);
1645 if (ret)
1646 goto error_unlock;
1647
1648
1649 spin_lock(&buf_obj->name_lock);
1650 seq_printf(s, "%08zu\t%08x\t%08x\t%08ld\t%s\t%08lu\t%s\n",
1651 buf_obj->size,
1652 buf_obj->file->f_flags, buf_obj->file->f_mode,
1653 file_count(buf_obj->file),
1654 buf_obj->exp_name,
1655 file_inode(buf_obj->file)->i_ino,
1656 buf_obj->name ?: "<none>");
1657 spin_unlock(&buf_obj->name_lock);
1658
1659 dma_resv_describe(buf_obj->resv, s);
1660
1661 seq_puts(s, "\tAttached Devices:\n");
1662 attach_count = 0;
1663
1664 list_for_each_entry(attach_obj, &buf_obj->attachments, node) {
1665 seq_printf(s, "\t%s\n", dev_name(attach_obj->dev));
1666 attach_count++;
1667 }
1668 dma_resv_unlock(buf_obj->resv);
1669
1670 seq_printf(s, "Total %d devices attached\n\n",
1671 attach_count);
1672
1673 count++;
1674 size += buf_obj->size;
1675 }
1676
1677 seq_printf(s, "\nTotal %d objects, %zu bytes\n", count, size);
1678
1679 mutex_unlock(&debugfs_list_mutex);
1680 return 0;
1681
1682error_unlock:
1683 mutex_unlock(&debugfs_list_mutex);
1684 return ret;
1685}
1686
1687DEFINE_SHOW_ATTRIBUTE(dma_buf_debug);
1688
1689static struct dentry *dma_buf_debugfs_dir;
1690
1691static int dma_buf_init_debugfs(void)
1692{
1693 struct dentry *d;
1694 int err = 0;
1695
1696 d = debugfs_create_dir("dma_buf", NULL);
1697 if (IS_ERR(d))
1698 return PTR_ERR(d);
1699
1700 dma_buf_debugfs_dir = d;
1701
1702 d = debugfs_create_file("bufinfo", 0444, dma_buf_debugfs_dir,
1703 NULL, &dma_buf_debug_fops);
1704 if (IS_ERR(d)) {
1705 pr_debug("dma_buf: debugfs: failed to create node bufinfo\n");
1706 debugfs_remove_recursive(dma_buf_debugfs_dir);
1707 dma_buf_debugfs_dir = NULL;
1708 err = PTR_ERR(d);
1709 }
1710
1711 return err;
1712}
1713
1714static void dma_buf_uninit_debugfs(void)
1715{
1716 debugfs_remove_recursive(dma_buf_debugfs_dir);
1717}
1718#else
1719static inline int dma_buf_init_debugfs(void)
1720{
1721 return 0;
1722}
1723static inline void dma_buf_uninit_debugfs(void)
1724{
1725}
1726#endif
1727
1728static int __init dma_buf_init(void)
1729{
1730 int ret;
1731
1732 ret = dma_buf_init_sysfs_statistics();
1733 if (ret)
1734 return ret;
1735
1736 dma_buf_mnt = kern_mount(&dma_buf_fs_type);
1737 if (IS_ERR(dma_buf_mnt))
1738 return PTR_ERR(dma_buf_mnt);
1739
1740 dma_buf_init_debugfs();
1741 return 0;
1742}
1743subsys_initcall(dma_buf_init);
1744
1745static void __exit dma_buf_deinit(void)
1746{
1747 dma_buf_uninit_debugfs();
1748 kern_unmount(dma_buf_mnt);
1749 dma_buf_uninit_sysfs_statistics();
1750}
1751__exitcall(dma_buf_deinit);