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
36 static inline int is_dma_buf_file(struct file *);
37
38 #if IS_ENABLED(CONFIG_DEBUG_FS)
39 static DEFINE_MUTEX(debugfs_list_mutex);
40 static LIST_HEAD(debugfs_list);
41
__dma_buf_debugfs_list_add(struct dma_buf * dmabuf)42 static 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
__dma_buf_debugfs_list_del(struct dma_buf * dmabuf)49 static 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
__dma_buf_debugfs_list_add(struct dma_buf * dmabuf)59 static void __dma_buf_debugfs_list_add(struct dma_buf *dmabuf)
60 {
61 }
62
__dma_buf_debugfs_list_del(struct file * file)63 static void __dma_buf_debugfs_list_del(struct file *file)
64 {
65 }
66 #endif
67
dmabuffs_dname(struct dentry * dentry,char * buffer,int buflen)68 static 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
dma_buf_release(struct dentry * dentry)84 static 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
dma_buf_file_release(struct inode * inode,struct file * file)113 static 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
123 static const struct dentry_operations dma_buf_dentry_ops = {
124 .d_dname = dmabuffs_dname,
125 .d_release = dma_buf_release,
126 };
127
128 static struct vfsmount *dma_buf_mnt;
129
dma_buf_fs_init_context(struct fs_context * fc)130 static 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
141 static 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
dma_buf_mmap_internal(struct file * file,struct vm_area_struct * vma)147 static 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
dma_buf_llseek(struct file * file,loff_t offset,int whence)168 static 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 if (whence == SEEK_END)
182 base = dmabuf->size;
183 else if (whence == SEEK_SET)
184 base = 0;
185 else
186 return -EINVAL;
187
188 if (offset != 0)
189 return -EINVAL;
190
191 return base + offset;
192 }
193
194 /**
195 * DOC: implicit fence polling
196 *
197 * To support cross-device and cross-driver synchronization of buffer access
198 * implicit fences (represented internally in the kernel with &struct dma_fence)
199 * can be attached to a &dma_buf. The glue for that and a few related things are
200 * provided in the &dma_resv structure.
201 *
202 * Userspace can query the state of these implicitly tracked fences using poll()
203 * and related system calls:
204 *
205 * - Checking for EPOLLIN, i.e. read access, can be use to query the state of the
206 * most recent write or exclusive fence.
207 *
208 * - Checking for EPOLLOUT, i.e. write access, can be used to query the state of
209 * all attached fences, shared and exclusive ones.
210 *
211 * Note that this only signals the completion of the respective fences, i.e. the
212 * DMA transfers are complete. Cache flushing and any other necessary
213 * preparations before CPU access can begin still need to happen.
214 *
215 * As an alternative to poll(), the set of fences on DMA buffer can be
216 * exported as a &sync_file using &dma_buf_sync_file_export.
217 */
218
dma_buf_poll_cb(struct dma_fence * fence,struct dma_fence_cb * cb)219 static void dma_buf_poll_cb(struct dma_fence *fence, struct dma_fence_cb *cb)
220 {
221 struct dma_buf_poll_cb_t *dcb = (struct dma_buf_poll_cb_t *)cb;
222 struct dma_buf *dmabuf = container_of(dcb->poll, struct dma_buf, poll);
223 unsigned long flags;
224
225 spin_lock_irqsave(&dcb->poll->lock, flags);
226 wake_up_locked_poll(dcb->poll, dcb->active);
227 dcb->active = 0;
228 spin_unlock_irqrestore(&dcb->poll->lock, flags);
229 dma_fence_put(fence);
230 /* Paired with get_file in dma_buf_poll */
231 fput(dmabuf->file);
232 }
233
dma_buf_poll_add_cb(struct dma_resv * resv,bool write,struct dma_buf_poll_cb_t * dcb)234 static bool dma_buf_poll_add_cb(struct dma_resv *resv, bool write,
235 struct dma_buf_poll_cb_t *dcb)
236 {
237 struct dma_resv_iter cursor;
238 struct dma_fence *fence;
239 int r;
240
241 dma_resv_for_each_fence(&cursor, resv, dma_resv_usage_rw(write),
242 fence) {
243 dma_fence_get(fence);
244 r = dma_fence_add_callback(fence, &dcb->cb, dma_buf_poll_cb);
245 if (!r)
246 return true;
247 dma_fence_put(fence);
248 }
249
250 return false;
251 }
252
dma_buf_poll(struct file * file,poll_table * poll)253 static __poll_t dma_buf_poll(struct file *file, poll_table *poll)
254 {
255 struct dma_buf *dmabuf;
256 struct dma_resv *resv;
257 __poll_t events;
258
259 dmabuf = file->private_data;
260 if (!dmabuf || !dmabuf->resv)
261 return EPOLLERR;
262
263 resv = dmabuf->resv;
264
265 poll_wait(file, &dmabuf->poll, poll);
266
267 events = poll_requested_events(poll) & (EPOLLIN | EPOLLOUT);
268 if (!events)
269 return 0;
270
271 dma_resv_lock(resv, NULL);
272
273 if (events & EPOLLOUT) {
274 struct dma_buf_poll_cb_t *dcb = &dmabuf->cb_out;
275
276 /* Check that callback isn't busy */
277 spin_lock_irq(&dmabuf->poll.lock);
278 if (dcb->active)
279 events &= ~EPOLLOUT;
280 else
281 dcb->active = EPOLLOUT;
282 spin_unlock_irq(&dmabuf->poll.lock);
283
284 if (events & EPOLLOUT) {
285 /* Paired with fput in dma_buf_poll_cb */
286 get_file(dmabuf->file);
287
288 if (!dma_buf_poll_add_cb(resv, true, dcb))
289 /* No callback queued, wake up any other waiters */
290 dma_buf_poll_cb(NULL, &dcb->cb);
291 else
292 events &= ~EPOLLOUT;
293 }
294 }
295
296 if (events & EPOLLIN) {
297 struct dma_buf_poll_cb_t *dcb = &dmabuf->cb_in;
298
299 /* Check that callback isn't busy */
300 spin_lock_irq(&dmabuf->poll.lock);
301 if (dcb->active)
302 events &= ~EPOLLIN;
303 else
304 dcb->active = EPOLLIN;
305 spin_unlock_irq(&dmabuf->poll.lock);
306
307 if (events & EPOLLIN) {
308 /* Paired with fput in dma_buf_poll_cb */
309 get_file(dmabuf->file);
310
311 if (!dma_buf_poll_add_cb(resv, false, dcb))
312 /* No callback queued, wake up any other waiters */
313 dma_buf_poll_cb(NULL, &dcb->cb);
314 else
315 events &= ~EPOLLIN;
316 }
317 }
318
319 dma_resv_unlock(resv);
320 return events;
321 }
322
323 /**
324 * dma_buf_set_name - Set a name to a specific dma_buf to track the usage.
325 * It could support changing the name of the dma-buf if the same
326 * piece of memory is used for multiple purpose between different devices.
327 *
328 * @dmabuf: [in] dmabuf buffer that will be renamed.
329 * @buf: [in] A piece of userspace memory that contains the name of
330 * the dma-buf.
331 *
332 * Returns 0 on success. If the dma-buf buffer is already attached to
333 * devices, return -EBUSY.
334 *
335 */
dma_buf_set_name(struct dma_buf * dmabuf,const char __user * buf)336 static long dma_buf_set_name(struct dma_buf *dmabuf, const char __user *buf)
337 {
338 char *name = strndup_user(buf, DMA_BUF_NAME_LEN);
339
340 if (IS_ERR(name))
341 return PTR_ERR(name);
342
343 spin_lock(&dmabuf->name_lock);
344 kfree(dmabuf->name);
345 dmabuf->name = name;
346 spin_unlock(&dmabuf->name_lock);
347
348 return 0;
349 }
350
351 #if IS_ENABLED(CONFIG_SYNC_FILE)
dma_buf_export_sync_file(struct dma_buf * dmabuf,void __user * user_data)352 static long dma_buf_export_sync_file(struct dma_buf *dmabuf,
353 void __user *user_data)
354 {
355 struct dma_buf_export_sync_file arg;
356 enum dma_resv_usage usage;
357 struct dma_fence *fence = NULL;
358 struct sync_file *sync_file;
359 int fd, ret;
360
361 if (copy_from_user(&arg, user_data, sizeof(arg)))
362 return -EFAULT;
363
364 if (arg.flags & ~DMA_BUF_SYNC_RW)
365 return -EINVAL;
366
367 if ((arg.flags & DMA_BUF_SYNC_RW) == 0)
368 return -EINVAL;
369
370 fd = get_unused_fd_flags(O_CLOEXEC);
371 if (fd < 0)
372 return fd;
373
374 usage = dma_resv_usage_rw(arg.flags & DMA_BUF_SYNC_WRITE);
375 ret = dma_resv_get_singleton(dmabuf->resv, usage, &fence);
376 if (ret)
377 goto err_put_fd;
378
379 if (!fence)
380 fence = dma_fence_get_stub();
381
382 sync_file = sync_file_create(fence);
383
384 dma_fence_put(fence);
385
386 if (!sync_file) {
387 ret = -ENOMEM;
388 goto err_put_fd;
389 }
390
391 arg.fd = fd;
392 if (copy_to_user(user_data, &arg, sizeof(arg))) {
393 ret = -EFAULT;
394 goto err_put_file;
395 }
396
397 fd_install(fd, sync_file->file);
398
399 return 0;
400
401 err_put_file:
402 fput(sync_file->file);
403 err_put_fd:
404 put_unused_fd(fd);
405 return ret;
406 }
407
dma_buf_import_sync_file(struct dma_buf * dmabuf,const void __user * user_data)408 static long dma_buf_import_sync_file(struct dma_buf *dmabuf,
409 const void __user *user_data)
410 {
411 struct dma_buf_import_sync_file arg;
412 struct dma_fence *fence, *f;
413 enum dma_resv_usage usage;
414 struct dma_fence_unwrap iter;
415 unsigned int num_fences;
416 int ret = 0;
417
418 if (copy_from_user(&arg, user_data, sizeof(arg)))
419 return -EFAULT;
420
421 if (arg.flags & ~DMA_BUF_SYNC_RW)
422 return -EINVAL;
423
424 if ((arg.flags & DMA_BUF_SYNC_RW) == 0)
425 return -EINVAL;
426
427 fence = sync_file_get_fence(arg.fd);
428 if (!fence)
429 return -EINVAL;
430
431 usage = (arg.flags & DMA_BUF_SYNC_WRITE) ? DMA_RESV_USAGE_WRITE :
432 DMA_RESV_USAGE_READ;
433
434 num_fences = 0;
435 dma_fence_unwrap_for_each(f, &iter, fence)
436 ++num_fences;
437
438 if (num_fences > 0) {
439 dma_resv_lock(dmabuf->resv, NULL);
440
441 ret = dma_resv_reserve_fences(dmabuf->resv, num_fences);
442 if (!ret) {
443 dma_fence_unwrap_for_each(f, &iter, fence)
444 dma_resv_add_fence(dmabuf->resv, f, usage);
445 }
446
447 dma_resv_unlock(dmabuf->resv);
448 }
449
450 dma_fence_put(fence);
451
452 return ret;
453 }
454 #endif
455
dma_buf_ioctl(struct file * file,unsigned int cmd,unsigned long arg)456 static long dma_buf_ioctl(struct file *file,
457 unsigned int cmd, unsigned long arg)
458 {
459 struct dma_buf *dmabuf;
460 struct dma_buf_sync sync;
461 enum dma_data_direction direction;
462 int ret;
463
464 dmabuf = file->private_data;
465
466 switch (cmd) {
467 case DMA_BUF_IOCTL_SYNC:
468 if (copy_from_user(&sync, (void __user *) arg, sizeof(sync)))
469 return -EFAULT;
470
471 if (sync.flags & ~DMA_BUF_SYNC_VALID_FLAGS_MASK)
472 return -EINVAL;
473
474 switch (sync.flags & DMA_BUF_SYNC_RW) {
475 case DMA_BUF_SYNC_READ:
476 direction = DMA_FROM_DEVICE;
477 break;
478 case DMA_BUF_SYNC_WRITE:
479 direction = DMA_TO_DEVICE;
480 break;
481 case DMA_BUF_SYNC_RW:
482 direction = DMA_BIDIRECTIONAL;
483 break;
484 default:
485 return -EINVAL;
486 }
487
488 if (sync.flags & DMA_BUF_SYNC_END)
489 ret = dma_buf_end_cpu_access(dmabuf, direction);
490 else
491 ret = dma_buf_begin_cpu_access(dmabuf, direction);
492
493 return ret;
494
495 case DMA_BUF_SET_NAME_A:
496 case DMA_BUF_SET_NAME_B:
497 return dma_buf_set_name(dmabuf, (const char __user *)arg);
498
499 #if IS_ENABLED(CONFIG_SYNC_FILE)
500 case DMA_BUF_IOCTL_EXPORT_SYNC_FILE:
501 return dma_buf_export_sync_file(dmabuf, (void __user *)arg);
502 case DMA_BUF_IOCTL_IMPORT_SYNC_FILE:
503 return dma_buf_import_sync_file(dmabuf, (const void __user *)arg);
504 #endif
505
506 default:
507 return -ENOTTY;
508 }
509 }
510
dma_buf_show_fdinfo(struct seq_file * m,struct file * file)511 static void dma_buf_show_fdinfo(struct seq_file *m, struct file *file)
512 {
513 struct dma_buf *dmabuf = file->private_data;
514
515 seq_printf(m, "size:\t%zu\n", dmabuf->size);
516 /* Don't count the temporary reference taken inside procfs seq_show */
517 seq_printf(m, "count:\t%ld\n", file_count(dmabuf->file) - 1);
518 seq_printf(m, "exp_name:\t%s\n", dmabuf->exp_name);
519 spin_lock(&dmabuf->name_lock);
520 if (dmabuf->name)
521 seq_printf(m, "name:\t%s\n", dmabuf->name);
522 spin_unlock(&dmabuf->name_lock);
523 }
524
525 static const struct file_operations dma_buf_fops = {
526 .release = dma_buf_file_release,
527 .mmap = dma_buf_mmap_internal,
528 .llseek = dma_buf_llseek,
529 .poll = dma_buf_poll,
530 .unlocked_ioctl = dma_buf_ioctl,
531 .compat_ioctl = compat_ptr_ioctl,
532 .show_fdinfo = dma_buf_show_fdinfo,
533 };
534
535 /*
536 * is_dma_buf_file - Check if struct file* is associated with dma_buf
537 */
is_dma_buf_file(struct file * file)538 static inline int is_dma_buf_file(struct file *file)
539 {
540 return file->f_op == &dma_buf_fops;
541 }
542
dma_buf_getfile(size_t size,int flags)543 static struct file *dma_buf_getfile(size_t size, int flags)
544 {
545 static atomic64_t dmabuf_inode = ATOMIC64_INIT(0);
546 struct inode *inode = alloc_anon_inode(dma_buf_mnt->mnt_sb);
547 struct file *file;
548
549 if (IS_ERR(inode))
550 return ERR_CAST(inode);
551
552 inode->i_size = size;
553 inode_set_bytes(inode, size);
554
555 /*
556 * The ->i_ino acquired from get_next_ino() is not unique thus
557 * not suitable for using it as dentry name by dmabuf stats.
558 * Override ->i_ino with the unique and dmabuffs specific
559 * value.
560 */
561 inode->i_ino = atomic64_add_return(1, &dmabuf_inode);
562 flags &= O_ACCMODE | O_NONBLOCK;
563 file = alloc_file_pseudo(inode, dma_buf_mnt, "dmabuf",
564 flags, &dma_buf_fops);
565 if (IS_ERR(file))
566 goto err_alloc_file;
567
568 return file;
569
570 err_alloc_file:
571 iput(inode);
572 return file;
573 }
574
575 /**
576 * DOC: dma buf device access
577 *
578 * For device DMA access to a shared DMA buffer the usual sequence of operations
579 * is fairly simple:
580 *
581 * 1. The exporter defines his exporter instance using
582 * DEFINE_DMA_BUF_EXPORT_INFO() and calls dma_buf_export() to wrap a private
583 * buffer object into a &dma_buf. It then exports that &dma_buf to userspace
584 * as a file descriptor by calling dma_buf_fd().
585 *
586 * 2. Userspace passes this file-descriptors to all drivers it wants this buffer
587 * to share with: First the file descriptor is converted to a &dma_buf using
588 * dma_buf_get(). Then the buffer is attached to the device using
589 * dma_buf_attach().
590 *
591 * Up to this stage the exporter is still free to migrate or reallocate the
592 * backing storage.
593 *
594 * 3. Once the buffer is attached to all devices userspace can initiate DMA
595 * access to the shared buffer. In the kernel this is done by calling
596 * dma_buf_map_attachment() and dma_buf_unmap_attachment().
597 *
598 * 4. Once a driver is done with a shared buffer it needs to call
599 * dma_buf_detach() (after cleaning up any mappings) and then release the
600 * reference acquired with dma_buf_get() by calling dma_buf_put().
601 *
602 * For the detailed semantics exporters are expected to implement see
603 * &dma_buf_ops.
604 */
605
606 /**
607 * dma_buf_export - Creates a new dma_buf, and associates an anon file
608 * with this buffer, so it can be exported.
609 * Also connect the allocator specific data and ops to the buffer.
610 * Additionally, provide a name string for exporter; useful in debugging.
611 *
612 * @exp_info: [in] holds all the export related information provided
613 * by the exporter. see &struct dma_buf_export_info
614 * for further details.
615 *
616 * Returns, on success, a newly created struct dma_buf object, which wraps the
617 * supplied private data and operations for struct dma_buf_ops. On either
618 * missing ops, or error in allocating struct dma_buf, will return negative
619 * error.
620 *
621 * For most cases the easiest way to create @exp_info is through the
622 * %DEFINE_DMA_BUF_EXPORT_INFO macro.
623 */
dma_buf_export(const struct dma_buf_export_info * exp_info)624 struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info)
625 {
626 struct dma_buf *dmabuf;
627 struct dma_resv *resv = exp_info->resv;
628 struct file *file;
629 size_t alloc_size = sizeof(struct dma_buf);
630 int ret;
631
632 if (WARN_ON(!exp_info->priv || !exp_info->ops
633 || !exp_info->ops->map_dma_buf
634 || !exp_info->ops->unmap_dma_buf
635 || !exp_info->ops->release))
636 return ERR_PTR(-EINVAL);
637
638 if (WARN_ON(exp_info->ops->cache_sgt_mapping &&
639 (exp_info->ops->pin || exp_info->ops->unpin)))
640 return ERR_PTR(-EINVAL);
641
642 if (WARN_ON(!exp_info->ops->pin != !exp_info->ops->unpin))
643 return ERR_PTR(-EINVAL);
644
645 if (!try_module_get(exp_info->owner))
646 return ERR_PTR(-ENOENT);
647
648 file = dma_buf_getfile(exp_info->size, exp_info->flags);
649 if (IS_ERR(file)) {
650 ret = PTR_ERR(file);
651 goto err_module;
652 }
653
654 if (!exp_info->resv)
655 alloc_size += sizeof(struct dma_resv);
656 else
657 /* prevent &dma_buf[1] == dma_buf->resv */
658 alloc_size += 1;
659 dmabuf = kzalloc(alloc_size, GFP_KERNEL);
660 if (!dmabuf) {
661 ret = -ENOMEM;
662 goto err_file;
663 }
664
665 dmabuf->priv = exp_info->priv;
666 dmabuf->ops = exp_info->ops;
667 dmabuf->size = exp_info->size;
668 dmabuf->exp_name = exp_info->exp_name;
669 dmabuf->owner = exp_info->owner;
670 spin_lock_init(&dmabuf->name_lock);
671 init_waitqueue_head(&dmabuf->poll);
672 dmabuf->cb_in.poll = dmabuf->cb_out.poll = &dmabuf->poll;
673 dmabuf->cb_in.active = dmabuf->cb_out.active = 0;
674 INIT_LIST_HEAD(&dmabuf->attachments);
675
676 if (!resv) {
677 dmabuf->resv = (struct dma_resv *)&dmabuf[1];
678 dma_resv_init(dmabuf->resv);
679 } else {
680 dmabuf->resv = resv;
681 }
682
683 ret = dma_buf_stats_setup(dmabuf, file);
684 if (ret)
685 goto err_dmabuf;
686
687 file->private_data = dmabuf;
688 file->f_path.dentry->d_fsdata = dmabuf;
689 dmabuf->file = file;
690
691 __dma_buf_debugfs_list_add(dmabuf);
692
693 return dmabuf;
694
695 err_dmabuf:
696 if (!resv)
697 dma_resv_fini(dmabuf->resv);
698 kfree(dmabuf);
699 err_file:
700 fput(file);
701 err_module:
702 module_put(exp_info->owner);
703 return ERR_PTR(ret);
704 }
705 EXPORT_SYMBOL_NS_GPL(dma_buf_export, DMA_BUF);
706
707 /**
708 * dma_buf_fd - returns a file descriptor for the given struct dma_buf
709 * @dmabuf: [in] pointer to dma_buf for which fd is required.
710 * @flags: [in] flags to give to fd
711 *
712 * On success, returns an associated 'fd'. Else, returns error.
713 */
dma_buf_fd(struct dma_buf * dmabuf,int flags)714 int dma_buf_fd(struct dma_buf *dmabuf, int flags)
715 {
716 int fd;
717
718 if (!dmabuf || !dmabuf->file)
719 return -EINVAL;
720
721 fd = get_unused_fd_flags(flags);
722 if (fd < 0)
723 return fd;
724
725 fd_install(fd, dmabuf->file);
726
727 return fd;
728 }
729 EXPORT_SYMBOL_NS_GPL(dma_buf_fd, DMA_BUF);
730
731 /**
732 * dma_buf_get - returns the struct dma_buf related to an fd
733 * @fd: [in] fd associated with the struct dma_buf to be returned
734 *
735 * On success, returns the struct dma_buf associated with an fd; uses
736 * file's refcounting done by fget to increase refcount. returns ERR_PTR
737 * otherwise.
738 */
dma_buf_get(int fd)739 struct dma_buf *dma_buf_get(int fd)
740 {
741 struct file *file;
742
743 file = fget(fd);
744
745 if (!file)
746 return ERR_PTR(-EBADF);
747
748 if (!is_dma_buf_file(file)) {
749 fput(file);
750 return ERR_PTR(-EINVAL);
751 }
752
753 return file->private_data;
754 }
755 EXPORT_SYMBOL_NS_GPL(dma_buf_get, DMA_BUF);
756
757 /**
758 * dma_buf_put - decreases refcount of the buffer
759 * @dmabuf: [in] buffer to reduce refcount of
760 *
761 * Uses file's refcounting done implicitly by fput().
762 *
763 * If, as a result of this call, the refcount becomes 0, the 'release' file
764 * operation related to this fd is called. It calls &dma_buf_ops.release vfunc
765 * in turn, and frees the memory allocated for dmabuf when exported.
766 */
dma_buf_put(struct dma_buf * dmabuf)767 void dma_buf_put(struct dma_buf *dmabuf)
768 {
769 if (WARN_ON(!dmabuf || !dmabuf->file))
770 return;
771
772 fput(dmabuf->file);
773 }
774 EXPORT_SYMBOL_NS_GPL(dma_buf_put, DMA_BUF);
775
mangle_sg_table(struct sg_table * sg_table)776 static void mangle_sg_table(struct sg_table *sg_table)
777 {
778 #ifdef CONFIG_DMABUF_DEBUG
779 int i;
780 struct scatterlist *sg;
781
782 /* To catch abuse of the underlying struct page by importers mix
783 * up the bits, but take care to preserve the low SG_ bits to
784 * not corrupt the sgt. The mixing is undone in __unmap_dma_buf
785 * before passing the sgt back to the exporter. */
786 for_each_sgtable_sg(sg_table, sg, i)
787 sg->page_link ^= ~0xffUL;
788 #endif
789
790 }
__map_dma_buf(struct dma_buf_attachment * attach,enum dma_data_direction direction)791 static struct sg_table * __map_dma_buf(struct dma_buf_attachment *attach,
792 enum dma_data_direction direction)
793 {
794 struct sg_table *sg_table;
795 signed long ret;
796
797 sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction);
798 if (IS_ERR_OR_NULL(sg_table))
799 return sg_table;
800
801 if (!dma_buf_attachment_is_dynamic(attach)) {
802 ret = dma_resv_wait_timeout(attach->dmabuf->resv,
803 DMA_RESV_USAGE_KERNEL, true,
804 MAX_SCHEDULE_TIMEOUT);
805 if (ret < 0) {
806 attach->dmabuf->ops->unmap_dma_buf(attach, sg_table,
807 direction);
808 return ERR_PTR(ret);
809 }
810 }
811
812 mangle_sg_table(sg_table);
813 return sg_table;
814 }
815
816 /**
817 * DOC: locking convention
818 *
819 * In order to avoid deadlock situations between dma-buf exports and importers,
820 * all dma-buf API users must follow the common dma-buf locking convention.
821 *
822 * Convention for importers
823 *
824 * 1. Importers must hold the dma-buf reservation lock when calling these
825 * functions:
826 *
827 * - dma_buf_pin()
828 * - dma_buf_unpin()
829 * - dma_buf_map_attachment()
830 * - dma_buf_unmap_attachment()
831 * - dma_buf_vmap()
832 * - dma_buf_vunmap()
833 *
834 * 2. Importers must not hold the dma-buf reservation lock when calling these
835 * functions:
836 *
837 * - dma_buf_attach()
838 * - dma_buf_dynamic_attach()
839 * - dma_buf_detach()
840 * - dma_buf_export()
841 * - dma_buf_fd()
842 * - dma_buf_get()
843 * - dma_buf_put()
844 * - dma_buf_mmap()
845 * - dma_buf_begin_cpu_access()
846 * - dma_buf_end_cpu_access()
847 * - dma_buf_map_attachment_unlocked()
848 * - dma_buf_unmap_attachment_unlocked()
849 * - dma_buf_vmap_unlocked()
850 * - dma_buf_vunmap_unlocked()
851 *
852 * Convention for exporters
853 *
854 * 1. These &dma_buf_ops callbacks are invoked with unlocked dma-buf
855 * reservation and exporter can take the lock:
856 *
857 * - &dma_buf_ops.attach()
858 * - &dma_buf_ops.detach()
859 * - &dma_buf_ops.release()
860 * - &dma_buf_ops.begin_cpu_access()
861 * - &dma_buf_ops.end_cpu_access()
862 * - &dma_buf_ops.mmap()
863 *
864 * 2. These &dma_buf_ops callbacks are invoked with locked dma-buf
865 * reservation and exporter can't take the lock:
866 *
867 * - &dma_buf_ops.pin()
868 * - &dma_buf_ops.unpin()
869 * - &dma_buf_ops.map_dma_buf()
870 * - &dma_buf_ops.unmap_dma_buf()
871 * - &dma_buf_ops.vmap()
872 * - &dma_buf_ops.vunmap()
873 *
874 * 3. Exporters must hold the dma-buf reservation lock when calling these
875 * functions:
876 *
877 * - dma_buf_move_notify()
878 */
879
880 /**
881 * dma_buf_dynamic_attach - Add the device to dma_buf's attachments list
882 * @dmabuf: [in] buffer to attach device to.
883 * @dev: [in] device to be attached.
884 * @importer_ops: [in] importer operations for the attachment
885 * @importer_priv: [in] importer private pointer for the attachment
886 *
887 * Returns struct dma_buf_attachment pointer for this attachment. Attachments
888 * must be cleaned up by calling dma_buf_detach().
889 *
890 * Optionally this calls &dma_buf_ops.attach to allow device-specific attach
891 * functionality.
892 *
893 * Returns:
894 *
895 * A pointer to newly created &dma_buf_attachment on success, or a negative
896 * error code wrapped into a pointer on failure.
897 *
898 * Note that this can fail if the backing storage of @dmabuf is in a place not
899 * accessible to @dev, and cannot be moved to a more suitable place. This is
900 * indicated with the error code -EBUSY.
901 */
902 struct dma_buf_attachment *
dma_buf_dynamic_attach(struct dma_buf * dmabuf,struct device * dev,const struct dma_buf_attach_ops * importer_ops,void * importer_priv)903 dma_buf_dynamic_attach(struct dma_buf *dmabuf, struct device *dev,
904 const struct dma_buf_attach_ops *importer_ops,
905 void *importer_priv)
906 {
907 struct dma_buf_attachment *attach;
908 int ret;
909
910 if (WARN_ON(!dmabuf || !dev))
911 return ERR_PTR(-EINVAL);
912
913 if (WARN_ON(importer_ops && !importer_ops->move_notify))
914 return ERR_PTR(-EINVAL);
915
916 attach = kzalloc(sizeof(*attach), GFP_KERNEL);
917 if (!attach)
918 return ERR_PTR(-ENOMEM);
919
920 attach->dev = dev;
921 attach->dmabuf = dmabuf;
922 if (importer_ops)
923 attach->peer2peer = importer_ops->allow_peer2peer;
924 attach->importer_ops = importer_ops;
925 attach->importer_priv = importer_priv;
926
927 if (dmabuf->ops->attach) {
928 ret = dmabuf->ops->attach(dmabuf, attach);
929 if (ret)
930 goto err_attach;
931 }
932 dma_resv_lock(dmabuf->resv, NULL);
933 list_add(&attach->node, &dmabuf->attachments);
934 dma_resv_unlock(dmabuf->resv);
935
936 /* When either the importer or the exporter can't handle dynamic
937 * mappings we cache the mapping here to avoid issues with the
938 * reservation object lock.
939 */
940 if (dma_buf_attachment_is_dynamic(attach) !=
941 dma_buf_is_dynamic(dmabuf)) {
942 struct sg_table *sgt;
943
944 dma_resv_lock(attach->dmabuf->resv, NULL);
945 if (dma_buf_is_dynamic(attach->dmabuf)) {
946 ret = dmabuf->ops->pin(attach);
947 if (ret)
948 goto err_unlock;
949 }
950
951 sgt = __map_dma_buf(attach, DMA_BIDIRECTIONAL);
952 if (!sgt)
953 sgt = ERR_PTR(-ENOMEM);
954 if (IS_ERR(sgt)) {
955 ret = PTR_ERR(sgt);
956 goto err_unpin;
957 }
958 dma_resv_unlock(attach->dmabuf->resv);
959 attach->sgt = sgt;
960 attach->dir = DMA_BIDIRECTIONAL;
961 }
962
963 return attach;
964
965 err_attach:
966 kfree(attach);
967 return ERR_PTR(ret);
968
969 err_unpin:
970 if (dma_buf_is_dynamic(attach->dmabuf))
971 dmabuf->ops->unpin(attach);
972
973 err_unlock:
974 dma_resv_unlock(attach->dmabuf->resv);
975
976 dma_buf_detach(dmabuf, attach);
977 return ERR_PTR(ret);
978 }
979 EXPORT_SYMBOL_NS_GPL(dma_buf_dynamic_attach, DMA_BUF);
980
981 /**
982 * dma_buf_attach - Wrapper for dma_buf_dynamic_attach
983 * @dmabuf: [in] buffer to attach device to.
984 * @dev: [in] device to be attached.
985 *
986 * Wrapper to call dma_buf_dynamic_attach() for drivers which still use a static
987 * mapping.
988 */
dma_buf_attach(struct dma_buf * dmabuf,struct device * dev)989 struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
990 struct device *dev)
991 {
992 return dma_buf_dynamic_attach(dmabuf, dev, NULL, NULL);
993 }
994 EXPORT_SYMBOL_NS_GPL(dma_buf_attach, DMA_BUF);
995
__unmap_dma_buf(struct dma_buf_attachment * attach,struct sg_table * sg_table,enum dma_data_direction direction)996 static void __unmap_dma_buf(struct dma_buf_attachment *attach,
997 struct sg_table *sg_table,
998 enum dma_data_direction direction)
999 {
1000 /* uses XOR, hence this unmangles */
1001 mangle_sg_table(sg_table);
1002
1003 attach->dmabuf->ops->unmap_dma_buf(attach, sg_table, direction);
1004 }
1005
1006 /**
1007 * dma_buf_detach - Remove the given attachment from dmabuf's attachments list
1008 * @dmabuf: [in] buffer to detach from.
1009 * @attach: [in] attachment to be detached; is free'd after this call.
1010 *
1011 * Clean up a device attachment obtained by calling dma_buf_attach().
1012 *
1013 * Optionally this calls &dma_buf_ops.detach for device-specific detach.
1014 */
dma_buf_detach(struct dma_buf * dmabuf,struct dma_buf_attachment * attach)1015 void dma_buf_detach(struct dma_buf *dmabuf, struct dma_buf_attachment *attach)
1016 {
1017 if (WARN_ON(!dmabuf || !attach || dmabuf != attach->dmabuf))
1018 return;
1019
1020 dma_resv_lock(dmabuf->resv, NULL);
1021
1022 if (attach->sgt) {
1023
1024 __unmap_dma_buf(attach, attach->sgt, attach->dir);
1025
1026 if (dma_buf_is_dynamic(attach->dmabuf))
1027 dmabuf->ops->unpin(attach);
1028 }
1029 list_del(&attach->node);
1030
1031 dma_resv_unlock(dmabuf->resv);
1032
1033 if (dmabuf->ops->detach)
1034 dmabuf->ops->detach(dmabuf, attach);
1035
1036 kfree(attach);
1037 }
1038 EXPORT_SYMBOL_NS_GPL(dma_buf_detach, DMA_BUF);
1039
1040 /**
1041 * dma_buf_pin - Lock down the DMA-buf
1042 * @attach: [in] attachment which should be pinned
1043 *
1044 * Only dynamic importers (who set up @attach with dma_buf_dynamic_attach()) may
1045 * call this, and only for limited use cases like scanout and not for temporary
1046 * pin operations. It is not permitted to allow userspace to pin arbitrary
1047 * amounts of buffers through this interface.
1048 *
1049 * Buffers must be unpinned by calling dma_buf_unpin().
1050 *
1051 * Returns:
1052 * 0 on success, negative error code on failure.
1053 */
dma_buf_pin(struct dma_buf_attachment * attach)1054 int dma_buf_pin(struct dma_buf_attachment *attach)
1055 {
1056 struct dma_buf *dmabuf = attach->dmabuf;
1057 int ret = 0;
1058
1059 WARN_ON(!dma_buf_attachment_is_dynamic(attach));
1060
1061 dma_resv_assert_held(dmabuf->resv);
1062
1063 if (dmabuf->ops->pin)
1064 ret = dmabuf->ops->pin(attach);
1065
1066 return ret;
1067 }
1068 EXPORT_SYMBOL_NS_GPL(dma_buf_pin, DMA_BUF);
1069
1070 /**
1071 * dma_buf_unpin - Unpin a DMA-buf
1072 * @attach: [in] attachment which should be unpinned
1073 *
1074 * This unpins a buffer pinned by dma_buf_pin() and allows the exporter to move
1075 * any mapping of @attach again and inform the importer through
1076 * &dma_buf_attach_ops.move_notify.
1077 */
dma_buf_unpin(struct dma_buf_attachment * attach)1078 void dma_buf_unpin(struct dma_buf_attachment *attach)
1079 {
1080 struct dma_buf *dmabuf = attach->dmabuf;
1081
1082 WARN_ON(!dma_buf_attachment_is_dynamic(attach));
1083
1084 dma_resv_assert_held(dmabuf->resv);
1085
1086 if (dmabuf->ops->unpin)
1087 dmabuf->ops->unpin(attach);
1088 }
1089 EXPORT_SYMBOL_NS_GPL(dma_buf_unpin, DMA_BUF);
1090
1091 /**
1092 * dma_buf_map_attachment - Returns the scatterlist table of the attachment;
1093 * mapped into _device_ address space. Is a wrapper for map_dma_buf() of the
1094 * dma_buf_ops.
1095 * @attach: [in] attachment whose scatterlist is to be returned
1096 * @direction: [in] direction of DMA transfer
1097 *
1098 * Returns sg_table containing the scatterlist to be returned; returns ERR_PTR
1099 * on error. May return -EINTR if it is interrupted by a signal.
1100 *
1101 * On success, the DMA addresses and lengths in the returned scatterlist are
1102 * PAGE_SIZE aligned.
1103 *
1104 * A mapping must be unmapped by using dma_buf_unmap_attachment(). Note that
1105 * the underlying backing storage is pinned for as long as a mapping exists,
1106 * therefore users/importers should not hold onto a mapping for undue amounts of
1107 * time.
1108 *
1109 * Important: Dynamic importers must wait for the exclusive fence of the struct
1110 * dma_resv attached to the DMA-BUF first.
1111 */
dma_buf_map_attachment(struct dma_buf_attachment * attach,enum dma_data_direction direction)1112 struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
1113 enum dma_data_direction direction)
1114 {
1115 struct sg_table *sg_table;
1116 int r;
1117
1118 might_sleep();
1119
1120 if (WARN_ON(!attach || !attach->dmabuf))
1121 return ERR_PTR(-EINVAL);
1122
1123 dma_resv_assert_held(attach->dmabuf->resv);
1124
1125 if (attach->sgt) {
1126 /*
1127 * Two mappings with different directions for the same
1128 * attachment are not allowed.
1129 */
1130 if (attach->dir != direction &&
1131 attach->dir != DMA_BIDIRECTIONAL)
1132 return ERR_PTR(-EBUSY);
1133
1134 return attach->sgt;
1135 }
1136
1137 if (dma_buf_is_dynamic(attach->dmabuf)) {
1138 if (!IS_ENABLED(CONFIG_DMABUF_MOVE_NOTIFY)) {
1139 r = attach->dmabuf->ops->pin(attach);
1140 if (r)
1141 return ERR_PTR(r);
1142 }
1143 }
1144
1145 sg_table = __map_dma_buf(attach, direction);
1146 if (!sg_table)
1147 sg_table = ERR_PTR(-ENOMEM);
1148
1149 if (IS_ERR(sg_table) && dma_buf_is_dynamic(attach->dmabuf) &&
1150 !IS_ENABLED(CONFIG_DMABUF_MOVE_NOTIFY))
1151 attach->dmabuf->ops->unpin(attach);
1152
1153 if (!IS_ERR(sg_table) && attach->dmabuf->ops->cache_sgt_mapping) {
1154 attach->sgt = sg_table;
1155 attach->dir = direction;
1156 }
1157
1158 #ifdef CONFIG_DMA_API_DEBUG
1159 if (!IS_ERR(sg_table)) {
1160 struct scatterlist *sg;
1161 u64 addr;
1162 int len;
1163 int i;
1164
1165 for_each_sgtable_dma_sg(sg_table, sg, i) {
1166 addr = sg_dma_address(sg);
1167 len = sg_dma_len(sg);
1168 if (!PAGE_ALIGNED(addr) || !PAGE_ALIGNED(len)) {
1169 pr_debug("%s: addr %llx or len %x is not page aligned!\n",
1170 __func__, addr, len);
1171 }
1172 }
1173 }
1174 #endif /* CONFIG_DMA_API_DEBUG */
1175 return sg_table;
1176 }
1177 EXPORT_SYMBOL_NS_GPL(dma_buf_map_attachment, DMA_BUF);
1178
1179 /**
1180 * dma_buf_map_attachment_unlocked - Returns the scatterlist table of the attachment;
1181 * mapped into _device_ address space. Is a wrapper for map_dma_buf() of the
1182 * dma_buf_ops.
1183 * @attach: [in] attachment whose scatterlist is to be returned
1184 * @direction: [in] direction of DMA transfer
1185 *
1186 * Unlocked variant of dma_buf_map_attachment().
1187 */
1188 struct sg_table *
dma_buf_map_attachment_unlocked(struct dma_buf_attachment * attach,enum dma_data_direction direction)1189 dma_buf_map_attachment_unlocked(struct dma_buf_attachment *attach,
1190 enum dma_data_direction direction)
1191 {
1192 struct sg_table *sg_table;
1193
1194 might_sleep();
1195
1196 if (WARN_ON(!attach || !attach->dmabuf))
1197 return ERR_PTR(-EINVAL);
1198
1199 dma_resv_lock(attach->dmabuf->resv, NULL);
1200 sg_table = dma_buf_map_attachment(attach, direction);
1201 dma_resv_unlock(attach->dmabuf->resv);
1202
1203 return sg_table;
1204 }
1205 EXPORT_SYMBOL_NS_GPL(dma_buf_map_attachment_unlocked, DMA_BUF);
1206
1207 /**
1208 * dma_buf_unmap_attachment - unmaps and decreases usecount of the buffer;might
1209 * deallocate the scatterlist associated. Is a wrapper for unmap_dma_buf() of
1210 * dma_buf_ops.
1211 * @attach: [in] attachment to unmap buffer from
1212 * @sg_table: [in] scatterlist info of the buffer to unmap
1213 * @direction: [in] direction of DMA transfer
1214 *
1215 * This unmaps a DMA mapping for @attached obtained by dma_buf_map_attachment().
1216 */
dma_buf_unmap_attachment(struct dma_buf_attachment * attach,struct sg_table * sg_table,enum dma_data_direction direction)1217 void dma_buf_unmap_attachment(struct dma_buf_attachment *attach,
1218 struct sg_table *sg_table,
1219 enum dma_data_direction direction)
1220 {
1221 might_sleep();
1222
1223 if (WARN_ON(!attach || !attach->dmabuf || !sg_table))
1224 return;
1225
1226 dma_resv_assert_held(attach->dmabuf->resv);
1227
1228 if (attach->sgt == sg_table)
1229 return;
1230
1231 __unmap_dma_buf(attach, sg_table, direction);
1232
1233 if (dma_buf_is_dynamic(attach->dmabuf) &&
1234 !IS_ENABLED(CONFIG_DMABUF_MOVE_NOTIFY))
1235 dma_buf_unpin(attach);
1236 }
1237 EXPORT_SYMBOL_NS_GPL(dma_buf_unmap_attachment, DMA_BUF);
1238
1239 /**
1240 * dma_buf_unmap_attachment_unlocked - unmaps and decreases usecount of the buffer;might
1241 * deallocate the scatterlist associated. Is a wrapper for unmap_dma_buf() of
1242 * dma_buf_ops.
1243 * @attach: [in] attachment to unmap buffer from
1244 * @sg_table: [in] scatterlist info of the buffer to unmap
1245 * @direction: [in] direction of DMA transfer
1246 *
1247 * Unlocked variant of dma_buf_unmap_attachment().
1248 */
dma_buf_unmap_attachment_unlocked(struct dma_buf_attachment * attach,struct sg_table * sg_table,enum dma_data_direction direction)1249 void dma_buf_unmap_attachment_unlocked(struct dma_buf_attachment *attach,
1250 struct sg_table *sg_table,
1251 enum dma_data_direction direction)
1252 {
1253 might_sleep();
1254
1255 if (WARN_ON(!attach || !attach->dmabuf || !sg_table))
1256 return;
1257
1258 dma_resv_lock(attach->dmabuf->resv, NULL);
1259 dma_buf_unmap_attachment(attach, sg_table, direction);
1260 dma_resv_unlock(attach->dmabuf->resv);
1261 }
1262 EXPORT_SYMBOL_NS_GPL(dma_buf_unmap_attachment_unlocked, DMA_BUF);
1263
1264 /**
1265 * dma_buf_move_notify - notify attachments that DMA-buf is moving
1266 *
1267 * @dmabuf: [in] buffer which is moving
1268 *
1269 * Informs all attachments that they need to destroy and recreate all their
1270 * mappings.
1271 */
dma_buf_move_notify(struct dma_buf * dmabuf)1272 void dma_buf_move_notify(struct dma_buf *dmabuf)
1273 {
1274 struct dma_buf_attachment *attach;
1275
1276 dma_resv_assert_held(dmabuf->resv);
1277
1278 list_for_each_entry(attach, &dmabuf->attachments, node)
1279 if (attach->importer_ops)
1280 attach->importer_ops->move_notify(attach);
1281 }
1282 EXPORT_SYMBOL_NS_GPL(dma_buf_move_notify, DMA_BUF);
1283
1284 /**
1285 * DOC: cpu access
1286 *
1287 * There are multiple reasons for supporting CPU access to a dma buffer object:
1288 *
1289 * - Fallback operations in the kernel, for example when a device is connected
1290 * over USB and the kernel needs to shuffle the data around first before
1291 * sending it away. Cache coherency is handled by bracketing any transactions
1292 * with calls to dma_buf_begin_cpu_access() and dma_buf_end_cpu_access()
1293 * access.
1294 *
1295 * Since for most kernel internal dma-buf accesses need the entire buffer, a
1296 * vmap interface is introduced. Note that on very old 32-bit architectures
1297 * vmalloc space might be limited and result in vmap calls failing.
1298 *
1299 * Interfaces::
1300 *
1301 * void \*dma_buf_vmap(struct dma_buf \*dmabuf, struct iosys_map \*map)
1302 * void dma_buf_vunmap(struct dma_buf \*dmabuf, struct iosys_map \*map)
1303 *
1304 * The vmap call can fail if there is no vmap support in the exporter, or if
1305 * it runs out of vmalloc space. Note that the dma-buf layer keeps a reference
1306 * count for all vmap access and calls down into the exporter's vmap function
1307 * only when no vmapping exists, and only unmaps it once. Protection against
1308 * concurrent vmap/vunmap calls is provided by taking the &dma_buf.lock mutex.
1309 *
1310 * - For full compatibility on the importer side with existing userspace
1311 * interfaces, which might already support mmap'ing buffers. This is needed in
1312 * many processing pipelines (e.g. feeding a software rendered image into a
1313 * hardware pipeline, thumbnail creation, snapshots, ...). Also, Android's ION
1314 * framework already supported this and for DMA buffer file descriptors to
1315 * replace ION buffers mmap support was needed.
1316 *
1317 * There is no special interfaces, userspace simply calls mmap on the dma-buf
1318 * fd. But like for CPU access there's a need to bracket the actual access,
1319 * which is handled by the ioctl (DMA_BUF_IOCTL_SYNC). Note that
1320 * DMA_BUF_IOCTL_SYNC can fail with -EAGAIN or -EINTR, in which case it must
1321 * be restarted.
1322 *
1323 * Some systems might need some sort of cache coherency management e.g. when
1324 * CPU and GPU domains are being accessed through dma-buf at the same time.
1325 * To circumvent this problem there are begin/end coherency markers, that
1326 * forward directly to existing dma-buf device drivers vfunc hooks. Userspace
1327 * can make use of those markers through the DMA_BUF_IOCTL_SYNC ioctl. The
1328 * sequence would be used like following:
1329 *
1330 * - mmap dma-buf fd
1331 * - for each drawing/upload cycle in CPU 1. SYNC_START ioctl, 2. read/write
1332 * to mmap area 3. SYNC_END ioctl. This can be repeated as often as you
1333 * want (with the new data being consumed by say the GPU or the scanout
1334 * device)
1335 * - munmap once you don't need the buffer any more
1336 *
1337 * For correctness and optimal performance, it is always required to use
1338 * SYNC_START and SYNC_END before and after, respectively, when accessing the
1339 * mapped address. Userspace cannot rely on coherent access, even when there
1340 * are systems where it just works without calling these ioctls.
1341 *
1342 * - And as a CPU fallback in userspace processing pipelines.
1343 *
1344 * Similar to the motivation for kernel cpu access it is again important that
1345 * the userspace code of a given importing subsystem can use the same
1346 * interfaces with a imported dma-buf buffer object as with a native buffer
1347 * object. This is especially important for drm where the userspace part of
1348 * contemporary OpenGL, X, and other drivers is huge, and reworking them to
1349 * use a different way to mmap a buffer rather invasive.
1350 *
1351 * The assumption in the current dma-buf interfaces is that redirecting the
1352 * initial mmap is all that's needed. A survey of some of the existing
1353 * subsystems shows that no driver seems to do any nefarious thing like
1354 * syncing up with outstanding asynchronous processing on the device or
1355 * allocating special resources at fault time. So hopefully this is good
1356 * enough, since adding interfaces to intercept pagefaults and allow pte
1357 * shootdowns would increase the complexity quite a bit.
1358 *
1359 * Interface::
1360 *
1361 * int dma_buf_mmap(struct dma_buf \*, struct vm_area_struct \*,
1362 * unsigned long);
1363 *
1364 * If the importing subsystem simply provides a special-purpose mmap call to
1365 * set up a mapping in userspace, calling do_mmap with &dma_buf.file will
1366 * equally achieve that for a dma-buf object.
1367 */
1368
__dma_buf_begin_cpu_access(struct dma_buf * dmabuf,enum dma_data_direction direction)1369 static int __dma_buf_begin_cpu_access(struct dma_buf *dmabuf,
1370 enum dma_data_direction direction)
1371 {
1372 bool write = (direction == DMA_BIDIRECTIONAL ||
1373 direction == DMA_TO_DEVICE);
1374 struct dma_resv *resv = dmabuf->resv;
1375 long ret;
1376
1377 /* Wait on any implicit rendering fences */
1378 ret = dma_resv_wait_timeout(resv, dma_resv_usage_rw(write),
1379 true, MAX_SCHEDULE_TIMEOUT);
1380 if (ret < 0)
1381 return ret;
1382
1383 return 0;
1384 }
1385
1386 /**
1387 * dma_buf_begin_cpu_access - Must be called before accessing a dma_buf from the
1388 * cpu in the kernel context. Calls begin_cpu_access to allow exporter-specific
1389 * preparations. Coherency is only guaranteed in the specified range for the
1390 * specified access direction.
1391 * @dmabuf: [in] buffer to prepare cpu access for.
1392 * @direction: [in] direction of access.
1393 *
1394 * After the cpu access is complete the caller should call
1395 * dma_buf_end_cpu_access(). Only when cpu access is bracketed by both calls is
1396 * it guaranteed to be coherent with other DMA access.
1397 *
1398 * This function will also wait for any DMA transactions tracked through
1399 * implicit synchronization in &dma_buf.resv. For DMA transactions with explicit
1400 * synchronization this function will only ensure cache coherency, callers must
1401 * ensure synchronization with such DMA transactions on their own.
1402 *
1403 * Can return negative error values, returns 0 on success.
1404 */
dma_buf_begin_cpu_access(struct dma_buf * dmabuf,enum dma_data_direction direction)1405 int dma_buf_begin_cpu_access(struct dma_buf *dmabuf,
1406 enum dma_data_direction direction)
1407 {
1408 int ret = 0;
1409
1410 if (WARN_ON(!dmabuf))
1411 return -EINVAL;
1412
1413 might_lock(&dmabuf->resv->lock.base);
1414
1415 if (dmabuf->ops->begin_cpu_access)
1416 ret = dmabuf->ops->begin_cpu_access(dmabuf, direction);
1417
1418 /* Ensure that all fences are waited upon - but we first allow
1419 * the native handler the chance to do so more efficiently if it
1420 * chooses. A double invocation here will be reasonably cheap no-op.
1421 */
1422 if (ret == 0)
1423 ret = __dma_buf_begin_cpu_access(dmabuf, direction);
1424
1425 return ret;
1426 }
1427 EXPORT_SYMBOL_NS_GPL(dma_buf_begin_cpu_access, DMA_BUF);
1428
1429 /**
1430 * dma_buf_end_cpu_access - Must be called after accessing a dma_buf from the
1431 * cpu in the kernel context. Calls end_cpu_access to allow exporter-specific
1432 * actions. Coherency is only guaranteed in the specified range for the
1433 * specified access direction.
1434 * @dmabuf: [in] buffer to complete cpu access for.
1435 * @direction: [in] direction of access.
1436 *
1437 * This terminates CPU access started with dma_buf_begin_cpu_access().
1438 *
1439 * Can return negative error values, returns 0 on success.
1440 */
dma_buf_end_cpu_access(struct dma_buf * dmabuf,enum dma_data_direction direction)1441 int dma_buf_end_cpu_access(struct dma_buf *dmabuf,
1442 enum dma_data_direction direction)
1443 {
1444 int ret = 0;
1445
1446 WARN_ON(!dmabuf);
1447
1448 might_lock(&dmabuf->resv->lock.base);
1449
1450 if (dmabuf->ops->end_cpu_access)
1451 ret = dmabuf->ops->end_cpu_access(dmabuf, direction);
1452
1453 return ret;
1454 }
1455 EXPORT_SYMBOL_NS_GPL(dma_buf_end_cpu_access, DMA_BUF);
1456
1457
1458 /**
1459 * dma_buf_mmap - Setup up a userspace mmap with the given vma
1460 * @dmabuf: [in] buffer that should back the vma
1461 * @vma: [in] vma for the mmap
1462 * @pgoff: [in] offset in pages where this mmap should start within the
1463 * dma-buf buffer.
1464 *
1465 * This function adjusts the passed in vma so that it points at the file of the
1466 * dma_buf operation. It also adjusts the starting pgoff and does bounds
1467 * checking on the size of the vma. Then it calls the exporters mmap function to
1468 * set up the mapping.
1469 *
1470 * Can return negative error values, returns 0 on success.
1471 */
dma_buf_mmap(struct dma_buf * dmabuf,struct vm_area_struct * vma,unsigned long pgoff)1472 int dma_buf_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma,
1473 unsigned long pgoff)
1474 {
1475 if (WARN_ON(!dmabuf || !vma))
1476 return -EINVAL;
1477
1478 /* check if buffer supports mmap */
1479 if (!dmabuf->ops->mmap)
1480 return -EINVAL;
1481
1482 /* check for offset overflow */
1483 if (pgoff + vma_pages(vma) < pgoff)
1484 return -EOVERFLOW;
1485
1486 /* check for overflowing the buffer's size */
1487 if (pgoff + vma_pages(vma) >
1488 dmabuf->size >> PAGE_SHIFT)
1489 return -EINVAL;
1490
1491 /* readjust the vma */
1492 vma_set_file(vma, dmabuf->file);
1493 vma->vm_pgoff = pgoff;
1494
1495 return dmabuf->ops->mmap(dmabuf, vma);
1496 }
1497 EXPORT_SYMBOL_NS_GPL(dma_buf_mmap, DMA_BUF);
1498
1499 /**
1500 * dma_buf_vmap - Create virtual mapping for the buffer object into kernel
1501 * address space. Same restrictions as for vmap and friends apply.
1502 * @dmabuf: [in] buffer to vmap
1503 * @map: [out] returns the vmap pointer
1504 *
1505 * This call may fail due to lack of virtual mapping address space.
1506 * These calls are optional in drivers. The intended use for them
1507 * is for mapping objects linear in kernel space for high use objects.
1508 *
1509 * To ensure coherency users must call dma_buf_begin_cpu_access() and
1510 * dma_buf_end_cpu_access() around any cpu access performed through this
1511 * mapping.
1512 *
1513 * Returns 0 on success, or a negative errno code otherwise.
1514 */
dma_buf_vmap(struct dma_buf * dmabuf,struct iosys_map * map)1515 int dma_buf_vmap(struct dma_buf *dmabuf, struct iosys_map *map)
1516 {
1517 struct iosys_map ptr;
1518 int ret;
1519
1520 iosys_map_clear(map);
1521
1522 if (WARN_ON(!dmabuf))
1523 return -EINVAL;
1524
1525 dma_resv_assert_held(dmabuf->resv);
1526
1527 if (!dmabuf->ops->vmap)
1528 return -EINVAL;
1529
1530 if (dmabuf->vmapping_counter) {
1531 dmabuf->vmapping_counter++;
1532 BUG_ON(iosys_map_is_null(&dmabuf->vmap_ptr));
1533 *map = dmabuf->vmap_ptr;
1534 return 0;
1535 }
1536
1537 BUG_ON(iosys_map_is_set(&dmabuf->vmap_ptr));
1538
1539 ret = dmabuf->ops->vmap(dmabuf, &ptr);
1540 if (WARN_ON_ONCE(ret))
1541 return ret;
1542
1543 dmabuf->vmap_ptr = ptr;
1544 dmabuf->vmapping_counter = 1;
1545
1546 *map = dmabuf->vmap_ptr;
1547
1548 return 0;
1549 }
1550 EXPORT_SYMBOL_NS_GPL(dma_buf_vmap, DMA_BUF);
1551
1552 /**
1553 * dma_buf_vmap_unlocked - Create virtual mapping for the buffer object into kernel
1554 * address space. Same restrictions as for vmap and friends apply.
1555 * @dmabuf: [in] buffer to vmap
1556 * @map: [out] returns the vmap pointer
1557 *
1558 * Unlocked version of dma_buf_vmap()
1559 *
1560 * Returns 0 on success, or a negative errno code otherwise.
1561 */
dma_buf_vmap_unlocked(struct dma_buf * dmabuf,struct iosys_map * map)1562 int dma_buf_vmap_unlocked(struct dma_buf *dmabuf, struct iosys_map *map)
1563 {
1564 int ret;
1565
1566 iosys_map_clear(map);
1567
1568 if (WARN_ON(!dmabuf))
1569 return -EINVAL;
1570
1571 dma_resv_lock(dmabuf->resv, NULL);
1572 ret = dma_buf_vmap(dmabuf, map);
1573 dma_resv_unlock(dmabuf->resv);
1574
1575 return ret;
1576 }
1577 EXPORT_SYMBOL_NS_GPL(dma_buf_vmap_unlocked, DMA_BUF);
1578
1579 /**
1580 * dma_buf_vunmap - Unmap a vmap obtained by dma_buf_vmap.
1581 * @dmabuf: [in] buffer to vunmap
1582 * @map: [in] vmap pointer to vunmap
1583 */
dma_buf_vunmap(struct dma_buf * dmabuf,struct iosys_map * map)1584 void dma_buf_vunmap(struct dma_buf *dmabuf, struct iosys_map *map)
1585 {
1586 if (WARN_ON(!dmabuf))
1587 return;
1588
1589 dma_resv_assert_held(dmabuf->resv);
1590
1591 BUG_ON(iosys_map_is_null(&dmabuf->vmap_ptr));
1592 BUG_ON(dmabuf->vmapping_counter == 0);
1593 BUG_ON(!iosys_map_is_equal(&dmabuf->vmap_ptr, map));
1594
1595 if (--dmabuf->vmapping_counter == 0) {
1596 if (dmabuf->ops->vunmap)
1597 dmabuf->ops->vunmap(dmabuf, map);
1598 iosys_map_clear(&dmabuf->vmap_ptr);
1599 }
1600 }
1601 EXPORT_SYMBOL_NS_GPL(dma_buf_vunmap, DMA_BUF);
1602
1603 /**
1604 * dma_buf_vunmap_unlocked - Unmap a vmap obtained by dma_buf_vmap.
1605 * @dmabuf: [in] buffer to vunmap
1606 * @map: [in] vmap pointer to vunmap
1607 */
dma_buf_vunmap_unlocked(struct dma_buf * dmabuf,struct iosys_map * map)1608 void dma_buf_vunmap_unlocked(struct dma_buf *dmabuf, struct iosys_map *map)
1609 {
1610 if (WARN_ON(!dmabuf))
1611 return;
1612
1613 dma_resv_lock(dmabuf->resv, NULL);
1614 dma_buf_vunmap(dmabuf, map);
1615 dma_resv_unlock(dmabuf->resv);
1616 }
1617 EXPORT_SYMBOL_NS_GPL(dma_buf_vunmap_unlocked, DMA_BUF);
1618
1619 #ifdef CONFIG_DEBUG_FS
dma_buf_debug_show(struct seq_file * s,void * unused)1620 static int dma_buf_debug_show(struct seq_file *s, void *unused)
1621 {
1622 struct dma_buf *buf_obj;
1623 struct dma_buf_attachment *attach_obj;
1624 int count = 0, attach_count;
1625 size_t size = 0;
1626 int ret;
1627
1628 ret = mutex_lock_interruptible(&debugfs_list_mutex);
1629
1630 if (ret)
1631 return ret;
1632
1633 seq_puts(s, "\nDma-buf Objects:\n");
1634 seq_printf(s, "%-8s\t%-8s\t%-8s\t%-8s\texp_name\t%-8s\tname\n",
1635 "size", "flags", "mode", "count", "ino");
1636
1637 list_for_each_entry(buf_obj, &debugfs_list, list_node) {
1638
1639 ret = dma_resv_lock_interruptible(buf_obj->resv, NULL);
1640 if (ret)
1641 goto error_unlock;
1642
1643
1644 spin_lock(&buf_obj->name_lock);
1645 seq_printf(s, "%08zu\t%08x\t%08x\t%08ld\t%s\t%08lu\t%s\n",
1646 buf_obj->size,
1647 buf_obj->file->f_flags, buf_obj->file->f_mode,
1648 file_count(buf_obj->file),
1649 buf_obj->exp_name,
1650 file_inode(buf_obj->file)->i_ino,
1651 buf_obj->name ?: "<none>");
1652 spin_unlock(&buf_obj->name_lock);
1653
1654 dma_resv_describe(buf_obj->resv, s);
1655
1656 seq_puts(s, "\tAttached Devices:\n");
1657 attach_count = 0;
1658
1659 list_for_each_entry(attach_obj, &buf_obj->attachments, node) {
1660 seq_printf(s, "\t%s\n", dev_name(attach_obj->dev));
1661 attach_count++;
1662 }
1663 dma_resv_unlock(buf_obj->resv);
1664
1665 seq_printf(s, "Total %d devices attached\n\n",
1666 attach_count);
1667
1668 count++;
1669 size += buf_obj->size;
1670 }
1671
1672 seq_printf(s, "\nTotal %d objects, %zu bytes\n", count, size);
1673
1674 mutex_unlock(&debugfs_list_mutex);
1675 return 0;
1676
1677 error_unlock:
1678 mutex_unlock(&debugfs_list_mutex);
1679 return ret;
1680 }
1681
1682 DEFINE_SHOW_ATTRIBUTE(dma_buf_debug);
1683
1684 static struct dentry *dma_buf_debugfs_dir;
1685
dma_buf_init_debugfs(void)1686 static int dma_buf_init_debugfs(void)
1687 {
1688 struct dentry *d;
1689 int err = 0;
1690
1691 d = debugfs_create_dir("dma_buf", NULL);
1692 if (IS_ERR(d))
1693 return PTR_ERR(d);
1694
1695 dma_buf_debugfs_dir = d;
1696
1697 d = debugfs_create_file("bufinfo", S_IRUGO, dma_buf_debugfs_dir,
1698 NULL, &dma_buf_debug_fops);
1699 if (IS_ERR(d)) {
1700 pr_debug("dma_buf: debugfs: failed to create node bufinfo\n");
1701 debugfs_remove_recursive(dma_buf_debugfs_dir);
1702 dma_buf_debugfs_dir = NULL;
1703 err = PTR_ERR(d);
1704 }
1705
1706 return err;
1707 }
1708
dma_buf_uninit_debugfs(void)1709 static void dma_buf_uninit_debugfs(void)
1710 {
1711 debugfs_remove_recursive(dma_buf_debugfs_dir);
1712 }
1713 #else
dma_buf_init_debugfs(void)1714 static inline int dma_buf_init_debugfs(void)
1715 {
1716 return 0;
1717 }
dma_buf_uninit_debugfs(void)1718 static inline void dma_buf_uninit_debugfs(void)
1719 {
1720 }
1721 #endif
1722
dma_buf_init(void)1723 static int __init dma_buf_init(void)
1724 {
1725 int ret;
1726
1727 ret = dma_buf_init_sysfs_statistics();
1728 if (ret)
1729 return ret;
1730
1731 dma_buf_mnt = kern_mount(&dma_buf_fs_type);
1732 if (IS_ERR(dma_buf_mnt))
1733 return PTR_ERR(dma_buf_mnt);
1734
1735 dma_buf_init_debugfs();
1736 return 0;
1737 }
1738 subsys_initcall(dma_buf_init);
1739
dma_buf_deinit(void)1740 static void __exit dma_buf_deinit(void)
1741 {
1742 dma_buf_uninit_debugfs();
1743 kern_unmount(dma_buf_mnt);
1744 dma_buf_uninit_sysfs_statistics();
1745 }
1746 __exitcall(dma_buf_deinit);
1747