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