1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Framework for buffer objects that can be shared across devices/subsystems.
4  *
5  * Copyright(C) 2011 Linaro Limited. All rights reserved.
6  * Author: Sumit Semwal <sumit.semwal@ti.com>
7  *
8  * Many thanks to linaro-mm-sig list, and specially
9  * Arnd Bergmann <arnd@arndb.de>, Rob Clark <rob@ti.com> and
10  * Daniel Vetter <daniel@ffwll.ch> for their support in creation and
11  * refining of this idea.
12  */
13 
14 #include <linux/fs.h>
15 #include <linux/slab.h>
16 #include <linux/dma-buf.h>
17 #include <linux/dma-fence.h>
18 #include <linux/anon_inodes.h>
19 #include <linux/export.h>
20 #include <linux/debugfs.h>
21 #include <linux/module.h>
22 #include <linux/seq_file.h>
23 #include <linux/poll.h>
24 #include <linux/dma-resv.h>
25 #include <linux/mm.h>
26 #include <linux/mount.h>
27 #include <linux/pseudo_fs.h>
28 
29 #include <uapi/linux/dma-buf.h>
30 #include <uapi/linux/magic.h>
31 
32 #include "dma-buf-sysfs-stats.h"
33 
34 static inline int is_dma_buf_file(struct file *);
35 
36 struct dma_buf_list {
37 	struct list_head head;
38 	struct mutex lock;
39 };
40 
41 static struct dma_buf_list db_list;
42 
dmabuffs_dname(struct dentry * dentry,char * buffer,int buflen)43 static char *dmabuffs_dname(struct dentry *dentry, char *buffer, int buflen)
44 {
45 	struct dma_buf *dmabuf;
46 	char name[DMA_BUF_NAME_LEN];
47 	size_t ret = 0;
48 
49 	dmabuf = dentry->d_fsdata;
50 	spin_lock(&dmabuf->name_lock);
51 	if (dmabuf->name)
52 		ret = strlcpy(name, dmabuf->name, DMA_BUF_NAME_LEN);
53 	spin_unlock(&dmabuf->name_lock);
54 
55 	return dynamic_dname(dentry, buffer, buflen, "/%s:%s",
56 			     dentry->d_name.name, ret > 0 ? name : "");
57 }
58 
dma_buf_release(struct dentry * dentry)59 static void dma_buf_release(struct dentry *dentry)
60 {
61 	struct dma_buf *dmabuf;
62 
63 	dmabuf = dentry->d_fsdata;
64 	if (unlikely(!dmabuf))
65 		return;
66 
67 	BUG_ON(dmabuf->vmapping_counter);
68 
69 	/*
70 	 * If you hit this BUG() it could mean:
71 	 * * There's a file reference imbalance in dma_buf_poll / dma_buf_poll_cb or somewhere else
72 	 * * dmabuf->cb_in/out.active are non-0 despite no pending fence callback
73 	 */
74 	BUG_ON(dmabuf->cb_in.active || dmabuf->cb_out.active);
75 
76 	dma_buf_stats_teardown(dmabuf);
77 	dmabuf->ops->release(dmabuf);
78 
79 	if (dmabuf->resv == (struct dma_resv *)&dmabuf[1])
80 		dma_resv_fini(dmabuf->resv);
81 
82 	WARN_ON(!list_empty(&dmabuf->attachments));
83 	module_put(dmabuf->owner);
84 	kfree(dmabuf->name);
85 	kfree(dmabuf);
86 }
87 
dma_buf_file_release(struct inode * inode,struct file * file)88 static int dma_buf_file_release(struct inode *inode, struct file *file)
89 {
90 	struct dma_buf *dmabuf;
91 
92 	if (!is_dma_buf_file(file))
93 		return -EINVAL;
94 
95 	dmabuf = file->private_data;
96 
97 	mutex_lock(&db_list.lock);
98 	list_del(&dmabuf->list_node);
99 	mutex_unlock(&db_list.lock);
100 
101 	return 0;
102 }
103 
104 static const struct dentry_operations dma_buf_dentry_ops = {
105 	.d_dname = dmabuffs_dname,
106 	.d_release = dma_buf_release,
107 };
108 
109 static struct vfsmount *dma_buf_mnt;
110 
dma_buf_fs_init_context(struct fs_context * fc)111 static int dma_buf_fs_init_context(struct fs_context *fc)
112 {
113 	struct pseudo_fs_context *ctx;
114 
115 	ctx = init_pseudo(fc, DMA_BUF_MAGIC);
116 	if (!ctx)
117 		return -ENOMEM;
118 	ctx->dops = &dma_buf_dentry_ops;
119 	return 0;
120 }
121 
122 static struct file_system_type dma_buf_fs_type = {
123 	.name = "dmabuf",
124 	.init_fs_context = dma_buf_fs_init_context,
125 	.kill_sb = kill_anon_super,
126 };
127 
dma_buf_mmap_internal(struct file * file,struct vm_area_struct * vma)128 static int dma_buf_mmap_internal(struct file *file, struct vm_area_struct *vma)
129 {
130 	struct dma_buf *dmabuf;
131 
132 	if (!is_dma_buf_file(file))
133 		return -EINVAL;
134 
135 	dmabuf = file->private_data;
136 
137 	/* check if buffer supports mmap */
138 	if (!dmabuf->ops->mmap)
139 		return -EINVAL;
140 
141 	/* check for overflowing the buffer's size */
142 	if (vma->vm_pgoff + vma_pages(vma) >
143 	    dmabuf->size >> PAGE_SHIFT)
144 		return -EINVAL;
145 
146 	return dmabuf->ops->mmap(dmabuf, vma);
147 }
148 
dma_buf_llseek(struct file * file,loff_t offset,int whence)149 static loff_t dma_buf_llseek(struct file *file, loff_t offset, int whence)
150 {
151 	struct dma_buf *dmabuf;
152 	loff_t base;
153 
154 	if (!is_dma_buf_file(file))
155 		return -EBADF;
156 
157 	dmabuf = file->private_data;
158 
159 	/* only support discovering the end of the buffer,
160 	   but also allow SEEK_SET to maintain the idiomatic
161 	   SEEK_END(0), SEEK_CUR(0) pattern */
162 	if (whence == SEEK_END)
163 		base = dmabuf->size;
164 	else if (whence == SEEK_SET)
165 		base = 0;
166 	else
167 		return -EINVAL;
168 
169 	if (offset != 0)
170 		return -EINVAL;
171 
172 	return base + offset;
173 }
174 
175 /**
176  * DOC: implicit fence polling
177  *
178  * To support cross-device and cross-driver synchronization of buffer access
179  * implicit fences (represented internally in the kernel with &struct dma_fence)
180  * can be attached to a &dma_buf. The glue for that and a few related things are
181  * provided in the &dma_resv structure.
182  *
183  * Userspace can query the state of these implicitly tracked fences using poll()
184  * and related system calls:
185  *
186  * - Checking for EPOLLIN, i.e. read access, can be use to query the state of the
187  *   most recent write or exclusive fence.
188  *
189  * - Checking for EPOLLOUT, i.e. write access, can be used to query the state of
190  *   all attached fences, shared and exclusive ones.
191  *
192  * Note that this only signals the completion of the respective fences, i.e. the
193  * DMA transfers are complete. Cache flushing and any other necessary
194  * preparations before CPU access can begin still need to happen.
195  */
196 
dma_buf_poll_cb(struct dma_fence * fence,struct dma_fence_cb * cb)197 static void dma_buf_poll_cb(struct dma_fence *fence, struct dma_fence_cb *cb)
198 {
199 	struct dma_buf_poll_cb_t *dcb = (struct dma_buf_poll_cb_t *)cb;
200 	struct dma_buf *dmabuf = container_of(dcb->poll, struct dma_buf, poll);
201 	unsigned long flags;
202 
203 	spin_lock_irqsave(&dcb->poll->lock, flags);
204 	wake_up_locked_poll(dcb->poll, dcb->active);
205 	dcb->active = 0;
206 	spin_unlock_irqrestore(&dcb->poll->lock, flags);
207 	dma_fence_put(fence);
208 	/* Paired with get_file in dma_buf_poll */
209 	fput(dmabuf->file);
210 }
211 
dma_buf_poll_add_cb(struct dma_resv * resv,bool write,struct dma_buf_poll_cb_t * dcb)212 static bool dma_buf_poll_add_cb(struct dma_resv *resv, bool write,
213 				struct dma_buf_poll_cb_t *dcb)
214 {
215 	struct dma_resv_iter cursor;
216 	struct dma_fence *fence;
217 	int r;
218 
219 	dma_resv_for_each_fence(&cursor, resv, dma_resv_usage_rw(write),
220 				fence) {
221 		dma_fence_get(fence);
222 		r = dma_fence_add_callback(fence, &dcb->cb, dma_buf_poll_cb);
223 		if (!r)
224 			return true;
225 		dma_fence_put(fence);
226 	}
227 
228 	return false;
229 }
230 
dma_buf_poll(struct file * file,poll_table * poll)231 static __poll_t dma_buf_poll(struct file *file, poll_table *poll)
232 {
233 	struct dma_buf *dmabuf;
234 	struct dma_resv *resv;
235 	__poll_t events;
236 
237 	dmabuf = file->private_data;
238 	if (!dmabuf || !dmabuf->resv)
239 		return EPOLLERR;
240 
241 	resv = dmabuf->resv;
242 
243 	poll_wait(file, &dmabuf->poll, poll);
244 
245 	events = poll_requested_events(poll) & (EPOLLIN | EPOLLOUT);
246 	if (!events)
247 		return 0;
248 
249 	dma_resv_lock(resv, NULL);
250 
251 	if (events & EPOLLOUT) {
252 		struct dma_buf_poll_cb_t *dcb = &dmabuf->cb_out;
253 
254 		/* Check that callback isn't busy */
255 		spin_lock_irq(&dmabuf->poll.lock);
256 		if (dcb->active)
257 			events &= ~EPOLLOUT;
258 		else
259 			dcb->active = EPOLLOUT;
260 		spin_unlock_irq(&dmabuf->poll.lock);
261 
262 		if (events & EPOLLOUT) {
263 			/* Paired with fput in dma_buf_poll_cb */
264 			get_file(dmabuf->file);
265 
266 			if (!dma_buf_poll_add_cb(resv, true, dcb))
267 				/* No callback queued, wake up any other waiters */
268 				dma_buf_poll_cb(NULL, &dcb->cb);
269 			else
270 				events &= ~EPOLLOUT;
271 		}
272 	}
273 
274 	if (events & EPOLLIN) {
275 		struct dma_buf_poll_cb_t *dcb = &dmabuf->cb_in;
276 
277 		/* Check that callback isn't busy */
278 		spin_lock_irq(&dmabuf->poll.lock);
279 		if (dcb->active)
280 			events &= ~EPOLLIN;
281 		else
282 			dcb->active = EPOLLIN;
283 		spin_unlock_irq(&dmabuf->poll.lock);
284 
285 		if (events & EPOLLIN) {
286 			/* Paired with fput in dma_buf_poll_cb */
287 			get_file(dmabuf->file);
288 
289 			if (!dma_buf_poll_add_cb(resv, false, dcb))
290 				/* No callback queued, wake up any other waiters */
291 				dma_buf_poll_cb(NULL, &dcb->cb);
292 			else
293 				events &= ~EPOLLIN;
294 		}
295 	}
296 
297 	dma_resv_unlock(resv);
298 	return events;
299 }
300 
301 /**
302  * dma_buf_set_name - Set a name to a specific dma_buf to track the usage.
303  * It could support changing the name of the dma-buf if the same
304  * piece of memory is used for multiple purpose between different devices.
305  *
306  * @dmabuf: [in]     dmabuf buffer that will be renamed.
307  * @buf:    [in]     A piece of userspace memory that contains the name of
308  *                   the dma-buf.
309  *
310  * Returns 0 on success. If the dma-buf buffer is already attached to
311  * devices, return -EBUSY.
312  *
313  */
dma_buf_set_name(struct dma_buf * dmabuf,const char __user * buf)314 static long dma_buf_set_name(struct dma_buf *dmabuf, const char __user *buf)
315 {
316 	char *name = strndup_user(buf, DMA_BUF_NAME_LEN);
317 
318 	if (IS_ERR(name))
319 		return PTR_ERR(name);
320 
321 	spin_lock(&dmabuf->name_lock);
322 	kfree(dmabuf->name);
323 	dmabuf->name = name;
324 	spin_unlock(&dmabuf->name_lock);
325 
326 	return 0;
327 }
328 
dma_buf_ioctl(struct file * file,unsigned int cmd,unsigned long arg)329 static long dma_buf_ioctl(struct file *file,
330 			  unsigned int cmd, unsigned long arg)
331 {
332 	struct dma_buf *dmabuf;
333 	struct dma_buf_sync sync;
334 	enum dma_data_direction direction;
335 	int ret;
336 
337 	dmabuf = file->private_data;
338 
339 	switch (cmd) {
340 	case DMA_BUF_IOCTL_SYNC:
341 		if (copy_from_user(&sync, (void __user *) arg, sizeof(sync)))
342 			return -EFAULT;
343 
344 		if (sync.flags & ~DMA_BUF_SYNC_VALID_FLAGS_MASK)
345 			return -EINVAL;
346 
347 		switch (sync.flags & DMA_BUF_SYNC_RW) {
348 		case DMA_BUF_SYNC_READ:
349 			direction = DMA_FROM_DEVICE;
350 			break;
351 		case DMA_BUF_SYNC_WRITE:
352 			direction = DMA_TO_DEVICE;
353 			break;
354 		case DMA_BUF_SYNC_RW:
355 			direction = DMA_BIDIRECTIONAL;
356 			break;
357 		default:
358 			return -EINVAL;
359 		}
360 
361 		if (sync.flags & DMA_BUF_SYNC_END)
362 			ret = dma_buf_end_cpu_access(dmabuf, direction);
363 		else
364 			ret = dma_buf_begin_cpu_access(dmabuf, direction);
365 
366 		return ret;
367 
368 	case DMA_BUF_SET_NAME_A:
369 	case DMA_BUF_SET_NAME_B:
370 		return dma_buf_set_name(dmabuf, (const char __user *)arg);
371 
372 	default:
373 		return -ENOTTY;
374 	}
375 }
376 
dma_buf_show_fdinfo(struct seq_file * m,struct file * file)377 static void dma_buf_show_fdinfo(struct seq_file *m, struct file *file)
378 {
379 	struct dma_buf *dmabuf = file->private_data;
380 
381 	seq_printf(m, "size:\t%zu\n", dmabuf->size);
382 	/* Don't count the temporary reference taken inside procfs seq_show */
383 	seq_printf(m, "count:\t%ld\n", file_count(dmabuf->file) - 1);
384 	seq_printf(m, "exp_name:\t%s\n", dmabuf->exp_name);
385 	spin_lock(&dmabuf->name_lock);
386 	if (dmabuf->name)
387 		seq_printf(m, "name:\t%s\n", dmabuf->name);
388 	spin_unlock(&dmabuf->name_lock);
389 }
390 
391 static const struct file_operations dma_buf_fops = {
392 	.release	= dma_buf_file_release,
393 	.mmap		= dma_buf_mmap_internal,
394 	.llseek		= dma_buf_llseek,
395 	.poll		= dma_buf_poll,
396 	.unlocked_ioctl	= dma_buf_ioctl,
397 	.compat_ioctl	= compat_ptr_ioctl,
398 	.show_fdinfo	= dma_buf_show_fdinfo,
399 };
400 
401 /*
402  * is_dma_buf_file - Check if struct file* is associated with dma_buf
403  */
is_dma_buf_file(struct file * file)404 static inline int is_dma_buf_file(struct file *file)
405 {
406 	return file->f_op == &dma_buf_fops;
407 }
408 
dma_buf_getfile(struct dma_buf * dmabuf,int flags)409 static struct file *dma_buf_getfile(struct dma_buf *dmabuf, int flags)
410 {
411 	static atomic64_t dmabuf_inode = ATOMIC64_INIT(0);
412 	struct file *file;
413 	struct inode *inode = alloc_anon_inode(dma_buf_mnt->mnt_sb);
414 
415 	if (IS_ERR(inode))
416 		return ERR_CAST(inode);
417 
418 	inode->i_size = dmabuf->size;
419 	inode_set_bytes(inode, dmabuf->size);
420 
421 	/*
422 	 * The ->i_ino acquired from get_next_ino() is not unique thus
423 	 * not suitable for using it as dentry name by dmabuf stats.
424 	 * Override ->i_ino with the unique and dmabuffs specific
425 	 * value.
426 	 */
427 	inode->i_ino = atomic64_add_return(1, &dmabuf_inode);
428 	file = alloc_file_pseudo(inode, dma_buf_mnt, "dmabuf",
429 				 flags, &dma_buf_fops);
430 	if (IS_ERR(file))
431 		goto err_alloc_file;
432 	file->f_flags = flags & (O_ACCMODE | O_NONBLOCK);
433 	file->private_data = dmabuf;
434 	file->f_path.dentry->d_fsdata = dmabuf;
435 
436 	return file;
437 
438 err_alloc_file:
439 	iput(inode);
440 	return file;
441 }
442 
443 /**
444  * DOC: dma buf device access
445  *
446  * For device DMA access to a shared DMA buffer the usual sequence of operations
447  * is fairly simple:
448  *
449  * 1. The exporter defines his exporter instance using
450  *    DEFINE_DMA_BUF_EXPORT_INFO() and calls dma_buf_export() to wrap a private
451  *    buffer object into a &dma_buf. It then exports that &dma_buf to userspace
452  *    as a file descriptor by calling dma_buf_fd().
453  *
454  * 2. Userspace passes this file-descriptors to all drivers it wants this buffer
455  *    to share with: First the file descriptor is converted to a &dma_buf using
456  *    dma_buf_get(). Then the buffer is attached to the device using
457  *    dma_buf_attach().
458  *
459  *    Up to this stage the exporter is still free to migrate or reallocate the
460  *    backing storage.
461  *
462  * 3. Once the buffer is attached to all devices userspace can initiate DMA
463  *    access to the shared buffer. In the kernel this is done by calling
464  *    dma_buf_map_attachment() and dma_buf_unmap_attachment().
465  *
466  * 4. Once a driver is done with a shared buffer it needs to call
467  *    dma_buf_detach() (after cleaning up any mappings) and then release the
468  *    reference acquired with dma_buf_get() by calling dma_buf_put().
469  *
470  * For the detailed semantics exporters are expected to implement see
471  * &dma_buf_ops.
472  */
473 
474 /**
475  * dma_buf_export - Creates a new dma_buf, and associates an anon file
476  * with this buffer, so it can be exported.
477  * Also connect the allocator specific data and ops to the buffer.
478  * Additionally, provide a name string for exporter; useful in debugging.
479  *
480  * @exp_info:	[in]	holds all the export related information provided
481  *			by the exporter. see &struct dma_buf_export_info
482  *			for further details.
483  *
484  * Returns, on success, a newly created struct dma_buf object, which wraps the
485  * supplied private data and operations for struct dma_buf_ops. On either
486  * missing ops, or error in allocating struct dma_buf, will return negative
487  * error.
488  *
489  * For most cases the easiest way to create @exp_info is through the
490  * %DEFINE_DMA_BUF_EXPORT_INFO macro.
491  */
dma_buf_export(const struct dma_buf_export_info * exp_info)492 struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info)
493 {
494 	struct dma_buf *dmabuf;
495 	struct dma_resv *resv = exp_info->resv;
496 	struct file *file;
497 	size_t alloc_size = sizeof(struct dma_buf);
498 	int ret;
499 
500 	if (!exp_info->resv)
501 		alloc_size += sizeof(struct dma_resv);
502 	else
503 		/* prevent &dma_buf[1] == dma_buf->resv */
504 		alloc_size += 1;
505 
506 	if (WARN_ON(!exp_info->priv
507 			  || !exp_info->ops
508 			  || !exp_info->ops->map_dma_buf
509 			  || !exp_info->ops->unmap_dma_buf
510 			  || !exp_info->ops->release)) {
511 		return ERR_PTR(-EINVAL);
512 	}
513 
514 	if (WARN_ON(exp_info->ops->cache_sgt_mapping &&
515 		    (exp_info->ops->pin || exp_info->ops->unpin)))
516 		return ERR_PTR(-EINVAL);
517 
518 	if (WARN_ON(!exp_info->ops->pin != !exp_info->ops->unpin))
519 		return ERR_PTR(-EINVAL);
520 
521 	if (!try_module_get(exp_info->owner))
522 		return ERR_PTR(-ENOENT);
523 
524 	dmabuf = kzalloc(alloc_size, GFP_KERNEL);
525 	if (!dmabuf) {
526 		ret = -ENOMEM;
527 		goto err_module;
528 	}
529 
530 	dmabuf->priv = exp_info->priv;
531 	dmabuf->ops = exp_info->ops;
532 	dmabuf->size = exp_info->size;
533 	dmabuf->exp_name = exp_info->exp_name;
534 	dmabuf->owner = exp_info->owner;
535 	spin_lock_init(&dmabuf->name_lock);
536 	init_waitqueue_head(&dmabuf->poll);
537 	dmabuf->cb_in.poll = dmabuf->cb_out.poll = &dmabuf->poll;
538 	dmabuf->cb_in.active = dmabuf->cb_out.active = 0;
539 
540 	if (!resv) {
541 		resv = (struct dma_resv *)&dmabuf[1];
542 		dma_resv_init(resv);
543 	}
544 	dmabuf->resv = resv;
545 
546 	file = dma_buf_getfile(dmabuf, exp_info->flags);
547 	if (IS_ERR(file)) {
548 		ret = PTR_ERR(file);
549 		goto err_dmabuf;
550 	}
551 
552 	file->f_mode |= FMODE_LSEEK;
553 	dmabuf->file = file;
554 
555 	mutex_init(&dmabuf->lock);
556 	INIT_LIST_HEAD(&dmabuf->attachments);
557 
558 	mutex_lock(&db_list.lock);
559 	list_add(&dmabuf->list_node, &db_list.head);
560 	mutex_unlock(&db_list.lock);
561 
562 	ret = dma_buf_stats_setup(dmabuf);
563 	if (ret)
564 		goto err_sysfs;
565 
566 	return dmabuf;
567 
568 err_sysfs:
569 	/*
570 	 * Set file->f_path.dentry->d_fsdata to NULL so that when
571 	 * dma_buf_release() gets invoked by dentry_ops, it exits
572 	 * early before calling the release() dma_buf op.
573 	 */
574 	file->f_path.dentry->d_fsdata = NULL;
575 	fput(file);
576 err_dmabuf:
577 	kfree(dmabuf);
578 err_module:
579 	module_put(exp_info->owner);
580 	return ERR_PTR(ret);
581 }
582 EXPORT_SYMBOL_NS_GPL(dma_buf_export, DMA_BUF);
583 
584 /**
585  * dma_buf_fd - returns a file descriptor for the given struct dma_buf
586  * @dmabuf:	[in]	pointer to dma_buf for which fd is required.
587  * @flags:      [in]    flags to give to fd
588  *
589  * On success, returns an associated 'fd'. Else, returns error.
590  */
dma_buf_fd(struct dma_buf * dmabuf,int flags)591 int dma_buf_fd(struct dma_buf *dmabuf, int flags)
592 {
593 	int fd;
594 
595 	if (!dmabuf || !dmabuf->file)
596 		return -EINVAL;
597 
598 	fd = get_unused_fd_flags(flags);
599 	if (fd < 0)
600 		return fd;
601 
602 	fd_install(fd, dmabuf->file);
603 
604 	return fd;
605 }
606 EXPORT_SYMBOL_NS_GPL(dma_buf_fd, DMA_BUF);
607 
608 /**
609  * dma_buf_get - returns the struct dma_buf related to an fd
610  * @fd:	[in]	fd associated with the struct dma_buf to be returned
611  *
612  * On success, returns the struct dma_buf associated with an fd; uses
613  * file's refcounting done by fget to increase refcount. returns ERR_PTR
614  * otherwise.
615  */
dma_buf_get(int fd)616 struct dma_buf *dma_buf_get(int fd)
617 {
618 	struct file *file;
619 
620 	file = fget(fd);
621 
622 	if (!file)
623 		return ERR_PTR(-EBADF);
624 
625 	if (!is_dma_buf_file(file)) {
626 		fput(file);
627 		return ERR_PTR(-EINVAL);
628 	}
629 
630 	return file->private_data;
631 }
632 EXPORT_SYMBOL_NS_GPL(dma_buf_get, DMA_BUF);
633 
634 /**
635  * dma_buf_put - decreases refcount of the buffer
636  * @dmabuf:	[in]	buffer to reduce refcount of
637  *
638  * Uses file's refcounting done implicitly by fput().
639  *
640  * If, as a result of this call, the refcount becomes 0, the 'release' file
641  * operation related to this fd is called. It calls &dma_buf_ops.release vfunc
642  * in turn, and frees the memory allocated for dmabuf when exported.
643  */
dma_buf_put(struct dma_buf * dmabuf)644 void dma_buf_put(struct dma_buf *dmabuf)
645 {
646 	if (WARN_ON(!dmabuf || !dmabuf->file))
647 		return;
648 
649 	fput(dmabuf->file);
650 }
651 EXPORT_SYMBOL_NS_GPL(dma_buf_put, DMA_BUF);
652 
mangle_sg_table(struct sg_table * sg_table)653 static void mangle_sg_table(struct sg_table *sg_table)
654 {
655 #ifdef CONFIG_DMABUF_DEBUG
656 	int i;
657 	struct scatterlist *sg;
658 
659 	/* To catch abuse of the underlying struct page by importers mix
660 	 * up the bits, but take care to preserve the low SG_ bits to
661 	 * not corrupt the sgt. The mixing is undone in __unmap_dma_buf
662 	 * before passing the sgt back to the exporter. */
663 	for_each_sgtable_sg(sg_table, sg, i)
664 		sg->page_link ^= ~0xffUL;
665 #endif
666 
667 }
__map_dma_buf(struct dma_buf_attachment * attach,enum dma_data_direction direction)668 static struct sg_table * __map_dma_buf(struct dma_buf_attachment *attach,
669 				       enum dma_data_direction direction)
670 {
671 	struct sg_table *sg_table;
672 	signed long ret;
673 
674 	sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction);
675 	if (IS_ERR_OR_NULL(sg_table))
676 		return sg_table;
677 
678 	if (!dma_buf_attachment_is_dynamic(attach)) {
679 		ret = dma_resv_wait_timeout(attach->dmabuf->resv,
680 					    DMA_RESV_USAGE_KERNEL, true,
681 					    MAX_SCHEDULE_TIMEOUT);
682 		if (ret < 0) {
683 			attach->dmabuf->ops->unmap_dma_buf(attach, sg_table,
684 							   direction);
685 			return ERR_PTR(ret);
686 		}
687 	}
688 
689 	mangle_sg_table(sg_table);
690 	return sg_table;
691 }
692 
693 /**
694  * dma_buf_dynamic_attach - Add the device to dma_buf's attachments list
695  * @dmabuf:		[in]	buffer to attach device to.
696  * @dev:		[in]	device to be attached.
697  * @importer_ops:	[in]	importer operations for the attachment
698  * @importer_priv:	[in]	importer private pointer for the attachment
699  *
700  * Returns struct dma_buf_attachment pointer for this attachment. Attachments
701  * must be cleaned up by calling dma_buf_detach().
702  *
703  * Optionally this calls &dma_buf_ops.attach to allow device-specific attach
704  * functionality.
705  *
706  * Returns:
707  *
708  * A pointer to newly created &dma_buf_attachment on success, or a negative
709  * error code wrapped into a pointer on failure.
710  *
711  * Note that this can fail if the backing storage of @dmabuf is in a place not
712  * accessible to @dev, and cannot be moved to a more suitable place. This is
713  * indicated with the error code -EBUSY.
714  */
715 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)716 dma_buf_dynamic_attach(struct dma_buf *dmabuf, struct device *dev,
717 		       const struct dma_buf_attach_ops *importer_ops,
718 		       void *importer_priv)
719 {
720 	struct dma_buf_attachment *attach;
721 	int ret;
722 
723 	if (WARN_ON(!dmabuf || !dev))
724 		return ERR_PTR(-EINVAL);
725 
726 	if (WARN_ON(importer_ops && !importer_ops->move_notify))
727 		return ERR_PTR(-EINVAL);
728 
729 	attach = kzalloc(sizeof(*attach), GFP_KERNEL);
730 	if (!attach)
731 		return ERR_PTR(-ENOMEM);
732 
733 	attach->dev = dev;
734 	attach->dmabuf = dmabuf;
735 	if (importer_ops)
736 		attach->peer2peer = importer_ops->allow_peer2peer;
737 	attach->importer_ops = importer_ops;
738 	attach->importer_priv = importer_priv;
739 
740 	if (dmabuf->ops->attach) {
741 		ret = dmabuf->ops->attach(dmabuf, attach);
742 		if (ret)
743 			goto err_attach;
744 	}
745 	dma_resv_lock(dmabuf->resv, NULL);
746 	list_add(&attach->node, &dmabuf->attachments);
747 	dma_resv_unlock(dmabuf->resv);
748 
749 	/* When either the importer or the exporter can't handle dynamic
750 	 * mappings we cache the mapping here to avoid issues with the
751 	 * reservation object lock.
752 	 */
753 	if (dma_buf_attachment_is_dynamic(attach) !=
754 	    dma_buf_is_dynamic(dmabuf)) {
755 		struct sg_table *sgt;
756 
757 		if (dma_buf_is_dynamic(attach->dmabuf)) {
758 			dma_resv_lock(attach->dmabuf->resv, NULL);
759 			ret = dmabuf->ops->pin(attach);
760 			if (ret)
761 				goto err_unlock;
762 		}
763 
764 		sgt = __map_dma_buf(attach, DMA_BIDIRECTIONAL);
765 		if (!sgt)
766 			sgt = ERR_PTR(-ENOMEM);
767 		if (IS_ERR(sgt)) {
768 			ret = PTR_ERR(sgt);
769 			goto err_unpin;
770 		}
771 		if (dma_buf_is_dynamic(attach->dmabuf))
772 			dma_resv_unlock(attach->dmabuf->resv);
773 		attach->sgt = sgt;
774 		attach->dir = DMA_BIDIRECTIONAL;
775 	}
776 
777 	return attach;
778 
779 err_attach:
780 	kfree(attach);
781 	return ERR_PTR(ret);
782 
783 err_unpin:
784 	if (dma_buf_is_dynamic(attach->dmabuf))
785 		dmabuf->ops->unpin(attach);
786 
787 err_unlock:
788 	if (dma_buf_is_dynamic(attach->dmabuf))
789 		dma_resv_unlock(attach->dmabuf->resv);
790 
791 	dma_buf_detach(dmabuf, attach);
792 	return ERR_PTR(ret);
793 }
794 EXPORT_SYMBOL_NS_GPL(dma_buf_dynamic_attach, DMA_BUF);
795 
796 /**
797  * dma_buf_attach - Wrapper for dma_buf_dynamic_attach
798  * @dmabuf:	[in]	buffer to attach device to.
799  * @dev:	[in]	device to be attached.
800  *
801  * Wrapper to call dma_buf_dynamic_attach() for drivers which still use a static
802  * mapping.
803  */
dma_buf_attach(struct dma_buf * dmabuf,struct device * dev)804 struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
805 					  struct device *dev)
806 {
807 	return dma_buf_dynamic_attach(dmabuf, dev, NULL, NULL);
808 }
809 EXPORT_SYMBOL_NS_GPL(dma_buf_attach, DMA_BUF);
810 
__unmap_dma_buf(struct dma_buf_attachment * attach,struct sg_table * sg_table,enum dma_data_direction direction)811 static void __unmap_dma_buf(struct dma_buf_attachment *attach,
812 			    struct sg_table *sg_table,
813 			    enum dma_data_direction direction)
814 {
815 	/* uses XOR, hence this unmangles */
816 	mangle_sg_table(sg_table);
817 
818 	attach->dmabuf->ops->unmap_dma_buf(attach, sg_table, direction);
819 }
820 
821 /**
822  * dma_buf_detach - Remove the given attachment from dmabuf's attachments list
823  * @dmabuf:	[in]	buffer to detach from.
824  * @attach:	[in]	attachment to be detached; is free'd after this call.
825  *
826  * Clean up a device attachment obtained by calling dma_buf_attach().
827  *
828  * Optionally this calls &dma_buf_ops.detach for device-specific detach.
829  */
dma_buf_detach(struct dma_buf * dmabuf,struct dma_buf_attachment * attach)830 void dma_buf_detach(struct dma_buf *dmabuf, struct dma_buf_attachment *attach)
831 {
832 	if (WARN_ON(!dmabuf || !attach))
833 		return;
834 
835 	if (attach->sgt) {
836 		if (dma_buf_is_dynamic(attach->dmabuf))
837 			dma_resv_lock(attach->dmabuf->resv, NULL);
838 
839 		__unmap_dma_buf(attach, attach->sgt, attach->dir);
840 
841 		if (dma_buf_is_dynamic(attach->dmabuf)) {
842 			dmabuf->ops->unpin(attach);
843 			dma_resv_unlock(attach->dmabuf->resv);
844 		}
845 	}
846 
847 	dma_resv_lock(dmabuf->resv, NULL);
848 	list_del(&attach->node);
849 	dma_resv_unlock(dmabuf->resv);
850 	if (dmabuf->ops->detach)
851 		dmabuf->ops->detach(dmabuf, attach);
852 
853 	kfree(attach);
854 }
855 EXPORT_SYMBOL_NS_GPL(dma_buf_detach, DMA_BUF);
856 
857 /**
858  * dma_buf_pin - Lock down the DMA-buf
859  * @attach:	[in]	attachment which should be pinned
860  *
861  * Only dynamic importers (who set up @attach with dma_buf_dynamic_attach()) may
862  * call this, and only for limited use cases like scanout and not for temporary
863  * pin operations. It is not permitted to allow userspace to pin arbitrary
864  * amounts of buffers through this interface.
865  *
866  * Buffers must be unpinned by calling dma_buf_unpin().
867  *
868  * Returns:
869  * 0 on success, negative error code on failure.
870  */
dma_buf_pin(struct dma_buf_attachment * attach)871 int dma_buf_pin(struct dma_buf_attachment *attach)
872 {
873 	struct dma_buf *dmabuf = attach->dmabuf;
874 	int ret = 0;
875 
876 	WARN_ON(!dma_buf_attachment_is_dynamic(attach));
877 
878 	dma_resv_assert_held(dmabuf->resv);
879 
880 	if (dmabuf->ops->pin)
881 		ret = dmabuf->ops->pin(attach);
882 
883 	return ret;
884 }
885 EXPORT_SYMBOL_NS_GPL(dma_buf_pin, DMA_BUF);
886 
887 /**
888  * dma_buf_unpin - Unpin a DMA-buf
889  * @attach:	[in]	attachment which should be unpinned
890  *
891  * This unpins a buffer pinned by dma_buf_pin() and allows the exporter to move
892  * any mapping of @attach again and inform the importer through
893  * &dma_buf_attach_ops.move_notify.
894  */
dma_buf_unpin(struct dma_buf_attachment * attach)895 void dma_buf_unpin(struct dma_buf_attachment *attach)
896 {
897 	struct dma_buf *dmabuf = attach->dmabuf;
898 
899 	WARN_ON(!dma_buf_attachment_is_dynamic(attach));
900 
901 	dma_resv_assert_held(dmabuf->resv);
902 
903 	if (dmabuf->ops->unpin)
904 		dmabuf->ops->unpin(attach);
905 }
906 EXPORT_SYMBOL_NS_GPL(dma_buf_unpin, DMA_BUF);
907 
908 /**
909  * dma_buf_map_attachment - Returns the scatterlist table of the attachment;
910  * mapped into _device_ address space. Is a wrapper for map_dma_buf() of the
911  * dma_buf_ops.
912  * @attach:	[in]	attachment whose scatterlist is to be returned
913  * @direction:	[in]	direction of DMA transfer
914  *
915  * Returns sg_table containing the scatterlist to be returned; returns ERR_PTR
916  * on error. May return -EINTR if it is interrupted by a signal.
917  *
918  * On success, the DMA addresses and lengths in the returned scatterlist are
919  * PAGE_SIZE aligned.
920  *
921  * A mapping must be unmapped by using dma_buf_unmap_attachment(). Note that
922  * the underlying backing storage is pinned for as long as a mapping exists,
923  * therefore users/importers should not hold onto a mapping for undue amounts of
924  * time.
925  *
926  * Important: Dynamic importers must wait for the exclusive fence of the struct
927  * dma_resv attached to the DMA-BUF first.
928  */
dma_buf_map_attachment(struct dma_buf_attachment * attach,enum dma_data_direction direction)929 struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
930 					enum dma_data_direction direction)
931 {
932 	struct sg_table *sg_table;
933 	int r;
934 
935 	might_sleep();
936 
937 	if (WARN_ON(!attach || !attach->dmabuf))
938 		return ERR_PTR(-EINVAL);
939 
940 	if (dma_buf_attachment_is_dynamic(attach))
941 		dma_resv_assert_held(attach->dmabuf->resv);
942 
943 	if (attach->sgt) {
944 		/*
945 		 * Two mappings with different directions for the same
946 		 * attachment are not allowed.
947 		 */
948 		if (attach->dir != direction &&
949 		    attach->dir != DMA_BIDIRECTIONAL)
950 			return ERR_PTR(-EBUSY);
951 
952 		return attach->sgt;
953 	}
954 
955 	if (dma_buf_is_dynamic(attach->dmabuf)) {
956 		dma_resv_assert_held(attach->dmabuf->resv);
957 		if (!IS_ENABLED(CONFIG_DMABUF_MOVE_NOTIFY)) {
958 			r = attach->dmabuf->ops->pin(attach);
959 			if (r)
960 				return ERR_PTR(r);
961 		}
962 	}
963 
964 	sg_table = __map_dma_buf(attach, direction);
965 	if (!sg_table)
966 		sg_table = ERR_PTR(-ENOMEM);
967 
968 	if (IS_ERR(sg_table) && dma_buf_is_dynamic(attach->dmabuf) &&
969 	     !IS_ENABLED(CONFIG_DMABUF_MOVE_NOTIFY))
970 		attach->dmabuf->ops->unpin(attach);
971 
972 	if (!IS_ERR(sg_table) && attach->dmabuf->ops->cache_sgt_mapping) {
973 		attach->sgt = sg_table;
974 		attach->dir = direction;
975 	}
976 
977 #ifdef CONFIG_DMA_API_DEBUG
978 	if (!IS_ERR(sg_table)) {
979 		struct scatterlist *sg;
980 		u64 addr;
981 		int len;
982 		int i;
983 
984 		for_each_sgtable_dma_sg(sg_table, sg, i) {
985 			addr = sg_dma_address(sg);
986 			len = sg_dma_len(sg);
987 			if (!PAGE_ALIGNED(addr) || !PAGE_ALIGNED(len)) {
988 				pr_debug("%s: addr %llx or len %x is not page aligned!\n",
989 					 __func__, addr, len);
990 			}
991 		}
992 	}
993 #endif /* CONFIG_DMA_API_DEBUG */
994 	return sg_table;
995 }
996 EXPORT_SYMBOL_NS_GPL(dma_buf_map_attachment, DMA_BUF);
997 
998 /**
999  * dma_buf_unmap_attachment - unmaps and decreases usecount of the buffer;might
1000  * deallocate the scatterlist associated. Is a wrapper for unmap_dma_buf() of
1001  * dma_buf_ops.
1002  * @attach:	[in]	attachment to unmap buffer from
1003  * @sg_table:	[in]	scatterlist info of the buffer to unmap
1004  * @direction:  [in]    direction of DMA transfer
1005  *
1006  * This unmaps a DMA mapping for @attached obtained by dma_buf_map_attachment().
1007  */
dma_buf_unmap_attachment(struct dma_buf_attachment * attach,struct sg_table * sg_table,enum dma_data_direction direction)1008 void dma_buf_unmap_attachment(struct dma_buf_attachment *attach,
1009 				struct sg_table *sg_table,
1010 				enum dma_data_direction direction)
1011 {
1012 	might_sleep();
1013 
1014 	if (WARN_ON(!attach || !attach->dmabuf || !sg_table))
1015 		return;
1016 
1017 	if (dma_buf_attachment_is_dynamic(attach))
1018 		dma_resv_assert_held(attach->dmabuf->resv);
1019 
1020 	if (attach->sgt == sg_table)
1021 		return;
1022 
1023 	if (dma_buf_is_dynamic(attach->dmabuf))
1024 		dma_resv_assert_held(attach->dmabuf->resv);
1025 
1026 	__unmap_dma_buf(attach, sg_table, direction);
1027 
1028 	if (dma_buf_is_dynamic(attach->dmabuf) &&
1029 	    !IS_ENABLED(CONFIG_DMABUF_MOVE_NOTIFY))
1030 		dma_buf_unpin(attach);
1031 }
1032 EXPORT_SYMBOL_NS_GPL(dma_buf_unmap_attachment, DMA_BUF);
1033 
1034 /**
1035  * dma_buf_move_notify - notify attachments that DMA-buf is moving
1036  *
1037  * @dmabuf:	[in]	buffer which is moving
1038  *
1039  * Informs all attachmenst that they need to destroy and recreated all their
1040  * mappings.
1041  */
dma_buf_move_notify(struct dma_buf * dmabuf)1042 void dma_buf_move_notify(struct dma_buf *dmabuf)
1043 {
1044 	struct dma_buf_attachment *attach;
1045 
1046 	dma_resv_assert_held(dmabuf->resv);
1047 
1048 	list_for_each_entry(attach, &dmabuf->attachments, node)
1049 		if (attach->importer_ops)
1050 			attach->importer_ops->move_notify(attach);
1051 }
1052 EXPORT_SYMBOL_NS_GPL(dma_buf_move_notify, DMA_BUF);
1053 
1054 /**
1055  * DOC: cpu access
1056  *
1057  * There are mutliple reasons for supporting CPU access to a dma buffer object:
1058  *
1059  * - Fallback operations in the kernel, for example when a device is connected
1060  *   over USB and the kernel needs to shuffle the data around first before
1061  *   sending it away. Cache coherency is handled by braketing any transactions
1062  *   with calls to dma_buf_begin_cpu_access() and dma_buf_end_cpu_access()
1063  *   access.
1064  *
1065  *   Since for most kernel internal dma-buf accesses need the entire buffer, a
1066  *   vmap interface is introduced. Note that on very old 32-bit architectures
1067  *   vmalloc space might be limited and result in vmap calls failing.
1068  *
1069  *   Interfaces::
1070  *
1071  *      void \*dma_buf_vmap(struct dma_buf \*dmabuf, struct iosys_map \*map)
1072  *      void dma_buf_vunmap(struct dma_buf \*dmabuf, struct iosys_map \*map)
1073  *
1074  *   The vmap call can fail if there is no vmap support in the exporter, or if
1075  *   it runs out of vmalloc space. Note that the dma-buf layer keeps a reference
1076  *   count for all vmap access and calls down into the exporter's vmap function
1077  *   only when no vmapping exists, and only unmaps it once. Protection against
1078  *   concurrent vmap/vunmap calls is provided by taking the &dma_buf.lock mutex.
1079  *
1080  * - For full compatibility on the importer side with existing userspace
1081  *   interfaces, which might already support mmap'ing buffers. This is needed in
1082  *   many processing pipelines (e.g. feeding a software rendered image into a
1083  *   hardware pipeline, thumbnail creation, snapshots, ...). Also, Android's ION
1084  *   framework already supported this and for DMA buffer file descriptors to
1085  *   replace ION buffers mmap support was needed.
1086  *
1087  *   There is no special interfaces, userspace simply calls mmap on the dma-buf
1088  *   fd. But like for CPU access there's a need to braket the actual access,
1089  *   which is handled by the ioctl (DMA_BUF_IOCTL_SYNC). Note that
1090  *   DMA_BUF_IOCTL_SYNC can fail with -EAGAIN or -EINTR, in which case it must
1091  *   be restarted.
1092  *
1093  *   Some systems might need some sort of cache coherency management e.g. when
1094  *   CPU and GPU domains are being accessed through dma-buf at the same time.
1095  *   To circumvent this problem there are begin/end coherency markers, that
1096  *   forward directly to existing dma-buf device drivers vfunc hooks. Userspace
1097  *   can make use of those markers through the DMA_BUF_IOCTL_SYNC ioctl. The
1098  *   sequence would be used like following:
1099  *
1100  *     - mmap dma-buf fd
1101  *     - for each drawing/upload cycle in CPU 1. SYNC_START ioctl, 2. read/write
1102  *       to mmap area 3. SYNC_END ioctl. This can be repeated as often as you
1103  *       want (with the new data being consumed by say the GPU or the scanout
1104  *       device)
1105  *     - munmap once you don't need the buffer any more
1106  *
1107  *    For correctness and optimal performance, it is always required to use
1108  *    SYNC_START and SYNC_END before and after, respectively, when accessing the
1109  *    mapped address. Userspace cannot rely on coherent access, even when there
1110  *    are systems where it just works without calling these ioctls.
1111  *
1112  * - And as a CPU fallback in userspace processing pipelines.
1113  *
1114  *   Similar to the motivation for kernel cpu access it is again important that
1115  *   the userspace code of a given importing subsystem can use the same
1116  *   interfaces with a imported dma-buf buffer object as with a native buffer
1117  *   object. This is especially important for drm where the userspace part of
1118  *   contemporary OpenGL, X, and other drivers is huge, and reworking them to
1119  *   use a different way to mmap a buffer rather invasive.
1120  *
1121  *   The assumption in the current dma-buf interfaces is that redirecting the
1122  *   initial mmap is all that's needed. A survey of some of the existing
1123  *   subsystems shows that no driver seems to do any nefarious thing like
1124  *   syncing up with outstanding asynchronous processing on the device or
1125  *   allocating special resources at fault time. So hopefully this is good
1126  *   enough, since adding interfaces to intercept pagefaults and allow pte
1127  *   shootdowns would increase the complexity quite a bit.
1128  *
1129  *   Interface::
1130  *
1131  *      int dma_buf_mmap(struct dma_buf \*, struct vm_area_struct \*,
1132  *		       unsigned long);
1133  *
1134  *   If the importing subsystem simply provides a special-purpose mmap call to
1135  *   set up a mapping in userspace, calling do_mmap with &dma_buf.file will
1136  *   equally achieve that for a dma-buf object.
1137  */
1138 
__dma_buf_begin_cpu_access(struct dma_buf * dmabuf,enum dma_data_direction direction)1139 static int __dma_buf_begin_cpu_access(struct dma_buf *dmabuf,
1140 				      enum dma_data_direction direction)
1141 {
1142 	bool write = (direction == DMA_BIDIRECTIONAL ||
1143 		      direction == DMA_TO_DEVICE);
1144 	struct dma_resv *resv = dmabuf->resv;
1145 	long ret;
1146 
1147 	/* Wait on any implicit rendering fences */
1148 	ret = dma_resv_wait_timeout(resv, dma_resv_usage_rw(write),
1149 				    true, MAX_SCHEDULE_TIMEOUT);
1150 	if (ret < 0)
1151 		return ret;
1152 
1153 	return 0;
1154 }
1155 
1156 /**
1157  * dma_buf_begin_cpu_access - Must be called before accessing a dma_buf from the
1158  * cpu in the kernel context. Calls begin_cpu_access to allow exporter-specific
1159  * preparations. Coherency is only guaranteed in the specified range for the
1160  * specified access direction.
1161  * @dmabuf:	[in]	buffer to prepare cpu access for.
1162  * @direction:	[in]	length of range for cpu access.
1163  *
1164  * After the cpu access is complete the caller should call
1165  * dma_buf_end_cpu_access(). Only when cpu access is braketed by both calls is
1166  * it guaranteed to be coherent with other DMA access.
1167  *
1168  * This function will also wait for any DMA transactions tracked through
1169  * implicit synchronization in &dma_buf.resv. For DMA transactions with explicit
1170  * synchronization this function will only ensure cache coherency, callers must
1171  * ensure synchronization with such DMA transactions on their own.
1172  *
1173  * Can return negative error values, returns 0 on success.
1174  */
dma_buf_begin_cpu_access(struct dma_buf * dmabuf,enum dma_data_direction direction)1175 int dma_buf_begin_cpu_access(struct dma_buf *dmabuf,
1176 			     enum dma_data_direction direction)
1177 {
1178 	int ret = 0;
1179 
1180 	if (WARN_ON(!dmabuf))
1181 		return -EINVAL;
1182 
1183 	might_lock(&dmabuf->resv->lock.base);
1184 
1185 	if (dmabuf->ops->begin_cpu_access)
1186 		ret = dmabuf->ops->begin_cpu_access(dmabuf, direction);
1187 
1188 	/* Ensure that all fences are waited upon - but we first allow
1189 	 * the native handler the chance to do so more efficiently if it
1190 	 * chooses. A double invocation here will be reasonably cheap no-op.
1191 	 */
1192 	if (ret == 0)
1193 		ret = __dma_buf_begin_cpu_access(dmabuf, direction);
1194 
1195 	return ret;
1196 }
1197 EXPORT_SYMBOL_NS_GPL(dma_buf_begin_cpu_access, DMA_BUF);
1198 
1199 /**
1200  * dma_buf_end_cpu_access - Must be called after accessing a dma_buf from the
1201  * cpu in the kernel context. Calls end_cpu_access to allow exporter-specific
1202  * actions. Coherency is only guaranteed in the specified range for the
1203  * specified access direction.
1204  * @dmabuf:	[in]	buffer to complete cpu access for.
1205  * @direction:	[in]	length of range for cpu access.
1206  *
1207  * This terminates CPU access started with dma_buf_begin_cpu_access().
1208  *
1209  * Can return negative error values, returns 0 on success.
1210  */
dma_buf_end_cpu_access(struct dma_buf * dmabuf,enum dma_data_direction direction)1211 int dma_buf_end_cpu_access(struct dma_buf *dmabuf,
1212 			   enum dma_data_direction direction)
1213 {
1214 	int ret = 0;
1215 
1216 	WARN_ON(!dmabuf);
1217 
1218 	might_lock(&dmabuf->resv->lock.base);
1219 
1220 	if (dmabuf->ops->end_cpu_access)
1221 		ret = dmabuf->ops->end_cpu_access(dmabuf, direction);
1222 
1223 	return ret;
1224 }
1225 EXPORT_SYMBOL_NS_GPL(dma_buf_end_cpu_access, DMA_BUF);
1226 
1227 
1228 /**
1229  * dma_buf_mmap - Setup up a userspace mmap with the given vma
1230  * @dmabuf:	[in]	buffer that should back the vma
1231  * @vma:	[in]	vma for the mmap
1232  * @pgoff:	[in]	offset in pages where this mmap should start within the
1233  *			dma-buf buffer.
1234  *
1235  * This function adjusts the passed in vma so that it points at the file of the
1236  * dma_buf operation. It also adjusts the starting pgoff and does bounds
1237  * checking on the size of the vma. Then it calls the exporters mmap function to
1238  * set up the mapping.
1239  *
1240  * Can return negative error values, returns 0 on success.
1241  */
dma_buf_mmap(struct dma_buf * dmabuf,struct vm_area_struct * vma,unsigned long pgoff)1242 int dma_buf_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma,
1243 		 unsigned long pgoff)
1244 {
1245 	if (WARN_ON(!dmabuf || !vma))
1246 		return -EINVAL;
1247 
1248 	/* check if buffer supports mmap */
1249 	if (!dmabuf->ops->mmap)
1250 		return -EINVAL;
1251 
1252 	/* check for offset overflow */
1253 	if (pgoff + vma_pages(vma) < pgoff)
1254 		return -EOVERFLOW;
1255 
1256 	/* check for overflowing the buffer's size */
1257 	if (pgoff + vma_pages(vma) >
1258 	    dmabuf->size >> PAGE_SHIFT)
1259 		return -EINVAL;
1260 
1261 	/* readjust the vma */
1262 	vma_set_file(vma, dmabuf->file);
1263 	vma->vm_pgoff = pgoff;
1264 
1265 	return dmabuf->ops->mmap(dmabuf, vma);
1266 }
1267 EXPORT_SYMBOL_NS_GPL(dma_buf_mmap, DMA_BUF);
1268 
1269 /**
1270  * dma_buf_vmap - Create virtual mapping for the buffer object into kernel
1271  * address space. Same restrictions as for vmap and friends apply.
1272  * @dmabuf:	[in]	buffer to vmap
1273  * @map:	[out]	returns the vmap pointer
1274  *
1275  * This call may fail due to lack of virtual mapping address space.
1276  * These calls are optional in drivers. The intended use for them
1277  * is for mapping objects linear in kernel space for high use objects.
1278  *
1279  * To ensure coherency users must call dma_buf_begin_cpu_access() and
1280  * dma_buf_end_cpu_access() around any cpu access performed through this
1281  * mapping.
1282  *
1283  * Returns 0 on success, or a negative errno code otherwise.
1284  */
dma_buf_vmap(struct dma_buf * dmabuf,struct iosys_map * map)1285 int dma_buf_vmap(struct dma_buf *dmabuf, struct iosys_map *map)
1286 {
1287 	struct iosys_map ptr;
1288 	int ret = 0;
1289 
1290 	iosys_map_clear(map);
1291 
1292 	if (WARN_ON(!dmabuf))
1293 		return -EINVAL;
1294 
1295 	if (!dmabuf->ops->vmap)
1296 		return -EINVAL;
1297 
1298 	mutex_lock(&dmabuf->lock);
1299 	if (dmabuf->vmapping_counter) {
1300 		dmabuf->vmapping_counter++;
1301 		BUG_ON(iosys_map_is_null(&dmabuf->vmap_ptr));
1302 		*map = dmabuf->vmap_ptr;
1303 		goto out_unlock;
1304 	}
1305 
1306 	BUG_ON(iosys_map_is_set(&dmabuf->vmap_ptr));
1307 
1308 	ret = dmabuf->ops->vmap(dmabuf, &ptr);
1309 	if (WARN_ON_ONCE(ret))
1310 		goto out_unlock;
1311 
1312 	dmabuf->vmap_ptr = ptr;
1313 	dmabuf->vmapping_counter = 1;
1314 
1315 	*map = dmabuf->vmap_ptr;
1316 
1317 out_unlock:
1318 	mutex_unlock(&dmabuf->lock);
1319 	return ret;
1320 }
1321 EXPORT_SYMBOL_NS_GPL(dma_buf_vmap, DMA_BUF);
1322 
1323 /**
1324  * dma_buf_vunmap - Unmap a vmap obtained by dma_buf_vmap.
1325  * @dmabuf:	[in]	buffer to vunmap
1326  * @map:	[in]	vmap pointer to vunmap
1327  */
dma_buf_vunmap(struct dma_buf * dmabuf,struct iosys_map * map)1328 void dma_buf_vunmap(struct dma_buf *dmabuf, struct iosys_map *map)
1329 {
1330 	if (WARN_ON(!dmabuf))
1331 		return;
1332 
1333 	BUG_ON(iosys_map_is_null(&dmabuf->vmap_ptr));
1334 	BUG_ON(dmabuf->vmapping_counter == 0);
1335 	BUG_ON(!iosys_map_is_equal(&dmabuf->vmap_ptr, map));
1336 
1337 	mutex_lock(&dmabuf->lock);
1338 	if (--dmabuf->vmapping_counter == 0) {
1339 		if (dmabuf->ops->vunmap)
1340 			dmabuf->ops->vunmap(dmabuf, map);
1341 		iosys_map_clear(&dmabuf->vmap_ptr);
1342 	}
1343 	mutex_unlock(&dmabuf->lock);
1344 }
1345 EXPORT_SYMBOL_NS_GPL(dma_buf_vunmap, DMA_BUF);
1346 
1347 #ifdef CONFIG_DEBUG_FS
dma_buf_debug_show(struct seq_file * s,void * unused)1348 static int dma_buf_debug_show(struct seq_file *s, void *unused)
1349 {
1350 	struct dma_buf *buf_obj;
1351 	struct dma_buf_attachment *attach_obj;
1352 	int count = 0, attach_count;
1353 	size_t size = 0;
1354 	int ret;
1355 
1356 	ret = mutex_lock_interruptible(&db_list.lock);
1357 
1358 	if (ret)
1359 		return ret;
1360 
1361 	seq_puts(s, "\nDma-buf Objects:\n");
1362 	seq_printf(s, "%-8s\t%-8s\t%-8s\t%-8s\texp_name\t%-8s\n",
1363 		   "size", "flags", "mode", "count", "ino");
1364 
1365 	list_for_each_entry(buf_obj, &db_list.head, list_node) {
1366 
1367 		ret = dma_resv_lock_interruptible(buf_obj->resv, NULL);
1368 		if (ret)
1369 			goto error_unlock;
1370 
1371 
1372 		spin_lock(&buf_obj->name_lock);
1373 		seq_printf(s, "%08zu\t%08x\t%08x\t%08ld\t%s\t%08lu\t%s\n",
1374 				buf_obj->size,
1375 				buf_obj->file->f_flags, buf_obj->file->f_mode,
1376 				file_count(buf_obj->file),
1377 				buf_obj->exp_name,
1378 				file_inode(buf_obj->file)->i_ino,
1379 				buf_obj->name ?: "");
1380 		spin_unlock(&buf_obj->name_lock);
1381 
1382 		dma_resv_describe(buf_obj->resv, s);
1383 
1384 		seq_puts(s, "\tAttached Devices:\n");
1385 		attach_count = 0;
1386 
1387 		list_for_each_entry(attach_obj, &buf_obj->attachments, node) {
1388 			seq_printf(s, "\t%s\n", dev_name(attach_obj->dev));
1389 			attach_count++;
1390 		}
1391 		dma_resv_unlock(buf_obj->resv);
1392 
1393 		seq_printf(s, "Total %d devices attached\n\n",
1394 				attach_count);
1395 
1396 		count++;
1397 		size += buf_obj->size;
1398 	}
1399 
1400 	seq_printf(s, "\nTotal %d objects, %zu bytes\n", count, size);
1401 
1402 	mutex_unlock(&db_list.lock);
1403 	return 0;
1404 
1405 error_unlock:
1406 	mutex_unlock(&db_list.lock);
1407 	return ret;
1408 }
1409 
1410 DEFINE_SHOW_ATTRIBUTE(dma_buf_debug);
1411 
1412 static struct dentry *dma_buf_debugfs_dir;
1413 
dma_buf_init_debugfs(void)1414 static int dma_buf_init_debugfs(void)
1415 {
1416 	struct dentry *d;
1417 	int err = 0;
1418 
1419 	d = debugfs_create_dir("dma_buf", NULL);
1420 	if (IS_ERR(d))
1421 		return PTR_ERR(d);
1422 
1423 	dma_buf_debugfs_dir = d;
1424 
1425 	d = debugfs_create_file("bufinfo", S_IRUGO, dma_buf_debugfs_dir,
1426 				NULL, &dma_buf_debug_fops);
1427 	if (IS_ERR(d)) {
1428 		pr_debug("dma_buf: debugfs: failed to create node bufinfo\n");
1429 		debugfs_remove_recursive(dma_buf_debugfs_dir);
1430 		dma_buf_debugfs_dir = NULL;
1431 		err = PTR_ERR(d);
1432 	}
1433 
1434 	return err;
1435 }
1436 
dma_buf_uninit_debugfs(void)1437 static void dma_buf_uninit_debugfs(void)
1438 {
1439 	debugfs_remove_recursive(dma_buf_debugfs_dir);
1440 }
1441 #else
dma_buf_init_debugfs(void)1442 static inline int dma_buf_init_debugfs(void)
1443 {
1444 	return 0;
1445 }
dma_buf_uninit_debugfs(void)1446 static inline void dma_buf_uninit_debugfs(void)
1447 {
1448 }
1449 #endif
1450 
dma_buf_init(void)1451 static int __init dma_buf_init(void)
1452 {
1453 	int ret;
1454 
1455 	ret = dma_buf_init_sysfs_statistics();
1456 	if (ret)
1457 		return ret;
1458 
1459 	dma_buf_mnt = kern_mount(&dma_buf_fs_type);
1460 	if (IS_ERR(dma_buf_mnt))
1461 		return PTR_ERR(dma_buf_mnt);
1462 
1463 	mutex_init(&db_list.lock);
1464 	INIT_LIST_HEAD(&db_list.head);
1465 	dma_buf_init_debugfs();
1466 	return 0;
1467 }
1468 subsys_initcall(dma_buf_init);
1469 
dma_buf_deinit(void)1470 static void __exit dma_buf_deinit(void)
1471 {
1472 	dma_buf_uninit_debugfs();
1473 	kern_unmount(dma_buf_mnt);
1474 	dma_buf_uninit_sysfs_statistics();
1475 }
1476 __exitcall(dma_buf_deinit);
1477