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 struct dma_buf_list { 39 struct list_head head; 40 struct mutex lock; 41 }; 42 43 static struct dma_buf_list db_list; 44 45 static char *dmabuffs_dname(struct dentry *dentry, char *buffer, int buflen) 46 { 47 struct dma_buf *dmabuf; 48 char name[DMA_BUF_NAME_LEN]; 49 size_t ret = 0; 50 51 dmabuf = dentry->d_fsdata; 52 spin_lock(&dmabuf->name_lock); 53 if (dmabuf->name) 54 ret = strlcpy(name, dmabuf->name, DMA_BUF_NAME_LEN); 55 spin_unlock(&dmabuf->name_lock); 56 57 return dynamic_dname(buffer, buflen, "/%s:%s", 58 dentry->d_name.name, ret > 0 ? name : ""); 59 } 60 61 static void dma_buf_release(struct dentry *dentry) 62 { 63 struct dma_buf *dmabuf; 64 65 dmabuf = dentry->d_fsdata; 66 if (unlikely(!dmabuf)) 67 return; 68 69 BUG_ON(dmabuf->vmapping_counter); 70 71 /* 72 * If you hit this BUG() it could mean: 73 * * There's a file reference imbalance in dma_buf_poll / dma_buf_poll_cb or somewhere else 74 * * dmabuf->cb_in/out.active are non-0 despite no pending fence callback 75 */ 76 BUG_ON(dmabuf->cb_in.active || dmabuf->cb_out.active); 77 78 dma_buf_stats_teardown(dmabuf); 79 dmabuf->ops->release(dmabuf); 80 81 if (dmabuf->resv == (struct dma_resv *)&dmabuf[1]) 82 dma_resv_fini(dmabuf->resv); 83 84 WARN_ON(!list_empty(&dmabuf->attachments)); 85 module_put(dmabuf->owner); 86 kfree(dmabuf->name); 87 kfree(dmabuf); 88 } 89 90 static int dma_buf_file_release(struct inode *inode, struct file *file) 91 { 92 struct dma_buf *dmabuf; 93 94 if (!is_dma_buf_file(file)) 95 return -EINVAL; 96 97 dmabuf = file->private_data; 98 if (dmabuf) { 99 mutex_lock(&db_list.lock); 100 list_del(&dmabuf->list_node); 101 mutex_unlock(&db_list.lock); 102 } 103 104 return 0; 105 } 106 107 static const struct dentry_operations dma_buf_dentry_ops = { 108 .d_dname = dmabuffs_dname, 109 .d_release = dma_buf_release, 110 }; 111 112 static struct vfsmount *dma_buf_mnt; 113 114 static int dma_buf_fs_init_context(struct fs_context *fc) 115 { 116 struct pseudo_fs_context *ctx; 117 118 ctx = init_pseudo(fc, DMA_BUF_MAGIC); 119 if (!ctx) 120 return -ENOMEM; 121 ctx->dops = &dma_buf_dentry_ops; 122 return 0; 123 } 124 125 static struct file_system_type dma_buf_fs_type = { 126 .name = "dmabuf", 127 .init_fs_context = dma_buf_fs_init_context, 128 .kill_sb = kill_anon_super, 129 }; 130 131 static int dma_buf_mmap_internal(struct file *file, struct vm_area_struct *vma) 132 { 133 struct dma_buf *dmabuf; 134 135 if (!is_dma_buf_file(file)) 136 return -EINVAL; 137 138 dmabuf = file->private_data; 139 140 /* check if buffer supports mmap */ 141 if (!dmabuf->ops->mmap) 142 return -EINVAL; 143 144 /* check for overflowing the buffer's size */ 145 if (vma->vm_pgoff + vma_pages(vma) > 146 dmabuf->size >> PAGE_SHIFT) 147 return -EINVAL; 148 149 return dmabuf->ops->mmap(dmabuf, vma); 150 } 151 152 static loff_t dma_buf_llseek(struct file *file, loff_t offset, int whence) 153 { 154 struct dma_buf *dmabuf; 155 loff_t base; 156 157 if (!is_dma_buf_file(file)) 158 return -EBADF; 159 160 dmabuf = file->private_data; 161 162 /* only support discovering the end of the buffer, 163 but also allow SEEK_SET to maintain the idiomatic 164 SEEK_END(0), SEEK_CUR(0) pattern */ 165 if (whence == SEEK_END) 166 base = dmabuf->size; 167 else if (whence == SEEK_SET) 168 base = 0; 169 else 170 return -EINVAL; 171 172 if (offset != 0) 173 return -EINVAL; 174 175 return base + offset; 176 } 177 178 /** 179 * DOC: implicit fence polling 180 * 181 * To support cross-device and cross-driver synchronization of buffer access 182 * implicit fences (represented internally in the kernel with &struct dma_fence) 183 * can be attached to a &dma_buf. The glue for that and a few related things are 184 * provided in the &dma_resv structure. 185 * 186 * Userspace can query the state of these implicitly tracked fences using poll() 187 * and related system calls: 188 * 189 * - Checking for EPOLLIN, i.e. read access, can be use to query the state of the 190 * most recent write or exclusive fence. 191 * 192 * - Checking for EPOLLOUT, i.e. write access, can be used to query the state of 193 * all attached fences, shared and exclusive ones. 194 * 195 * Note that this only signals the completion of the respective fences, i.e. the 196 * DMA transfers are complete. Cache flushing and any other necessary 197 * preparations before CPU access can begin still need to happen. 198 * 199 * As an alternative to poll(), the set of fences on DMA buffer can be 200 * exported as a &sync_file using &dma_buf_sync_file_export. 201 */ 202 203 static void dma_buf_poll_cb(struct dma_fence *fence, struct dma_fence_cb *cb) 204 { 205 struct dma_buf_poll_cb_t *dcb = (struct dma_buf_poll_cb_t *)cb; 206 struct dma_buf *dmabuf = container_of(dcb->poll, struct dma_buf, poll); 207 unsigned long flags; 208 209 spin_lock_irqsave(&dcb->poll->lock, flags); 210 wake_up_locked_poll(dcb->poll, dcb->active); 211 dcb->active = 0; 212 spin_unlock_irqrestore(&dcb->poll->lock, flags); 213 dma_fence_put(fence); 214 /* Paired with get_file in dma_buf_poll */ 215 fput(dmabuf->file); 216 } 217 218 static bool dma_buf_poll_add_cb(struct dma_resv *resv, bool write, 219 struct dma_buf_poll_cb_t *dcb) 220 { 221 struct dma_resv_iter cursor; 222 struct dma_fence *fence; 223 int r; 224 225 dma_resv_for_each_fence(&cursor, resv, dma_resv_usage_rw(write), 226 fence) { 227 dma_fence_get(fence); 228 r = dma_fence_add_callback(fence, &dcb->cb, dma_buf_poll_cb); 229 if (!r) 230 return true; 231 dma_fence_put(fence); 232 } 233 234 return false; 235 } 236 237 static __poll_t dma_buf_poll(struct file *file, poll_table *poll) 238 { 239 struct dma_buf *dmabuf; 240 struct dma_resv *resv; 241 __poll_t events; 242 243 dmabuf = file->private_data; 244 if (!dmabuf || !dmabuf->resv) 245 return EPOLLERR; 246 247 resv = dmabuf->resv; 248 249 poll_wait(file, &dmabuf->poll, poll); 250 251 events = poll_requested_events(poll) & (EPOLLIN | EPOLLOUT); 252 if (!events) 253 return 0; 254 255 dma_resv_lock(resv, NULL); 256 257 if (events & EPOLLOUT) { 258 struct dma_buf_poll_cb_t *dcb = &dmabuf->cb_out; 259 260 /* Check that callback isn't busy */ 261 spin_lock_irq(&dmabuf->poll.lock); 262 if (dcb->active) 263 events &= ~EPOLLOUT; 264 else 265 dcb->active = EPOLLOUT; 266 spin_unlock_irq(&dmabuf->poll.lock); 267 268 if (events & EPOLLOUT) { 269 /* Paired with fput in dma_buf_poll_cb */ 270 get_file(dmabuf->file); 271 272 if (!dma_buf_poll_add_cb(resv, true, dcb)) 273 /* No callback queued, wake up any other waiters */ 274 dma_buf_poll_cb(NULL, &dcb->cb); 275 else 276 events &= ~EPOLLOUT; 277 } 278 } 279 280 if (events & EPOLLIN) { 281 struct dma_buf_poll_cb_t *dcb = &dmabuf->cb_in; 282 283 /* Check that callback isn't busy */ 284 spin_lock_irq(&dmabuf->poll.lock); 285 if (dcb->active) 286 events &= ~EPOLLIN; 287 else 288 dcb->active = EPOLLIN; 289 spin_unlock_irq(&dmabuf->poll.lock); 290 291 if (events & EPOLLIN) { 292 /* Paired with fput in dma_buf_poll_cb */ 293 get_file(dmabuf->file); 294 295 if (!dma_buf_poll_add_cb(resv, false, dcb)) 296 /* No callback queued, wake up any other waiters */ 297 dma_buf_poll_cb(NULL, &dcb->cb); 298 else 299 events &= ~EPOLLIN; 300 } 301 } 302 303 dma_resv_unlock(resv); 304 return events; 305 } 306 307 /** 308 * dma_buf_set_name - Set a name to a specific dma_buf to track the usage. 309 * It could support changing the name of the dma-buf if the same 310 * piece of memory is used for multiple purpose between different devices. 311 * 312 * @dmabuf: [in] dmabuf buffer that will be renamed. 313 * @buf: [in] A piece of userspace memory that contains the name of 314 * the dma-buf. 315 * 316 * Returns 0 on success. If the dma-buf buffer is already attached to 317 * devices, return -EBUSY. 318 * 319 */ 320 static long dma_buf_set_name(struct dma_buf *dmabuf, const char __user *buf) 321 { 322 char *name = strndup_user(buf, DMA_BUF_NAME_LEN); 323 324 if (IS_ERR(name)) 325 return PTR_ERR(name); 326 327 spin_lock(&dmabuf->name_lock); 328 kfree(dmabuf->name); 329 dmabuf->name = name; 330 spin_unlock(&dmabuf->name_lock); 331 332 return 0; 333 } 334 335 #if IS_ENABLED(CONFIG_SYNC_FILE) 336 static long dma_buf_export_sync_file(struct dma_buf *dmabuf, 337 void __user *user_data) 338 { 339 struct dma_buf_export_sync_file arg; 340 enum dma_resv_usage usage; 341 struct dma_fence *fence = NULL; 342 struct sync_file *sync_file; 343 int fd, ret; 344 345 if (copy_from_user(&arg, user_data, sizeof(arg))) 346 return -EFAULT; 347 348 if (arg.flags & ~DMA_BUF_SYNC_RW) 349 return -EINVAL; 350 351 if ((arg.flags & DMA_BUF_SYNC_RW) == 0) 352 return -EINVAL; 353 354 fd = get_unused_fd_flags(O_CLOEXEC); 355 if (fd < 0) 356 return fd; 357 358 usage = dma_resv_usage_rw(arg.flags & DMA_BUF_SYNC_WRITE); 359 ret = dma_resv_get_singleton(dmabuf->resv, usage, &fence); 360 if (ret) 361 goto err_put_fd; 362 363 if (!fence) 364 fence = dma_fence_get_stub(); 365 366 sync_file = sync_file_create(fence); 367 368 dma_fence_put(fence); 369 370 if (!sync_file) { 371 ret = -ENOMEM; 372 goto err_put_fd; 373 } 374 375 arg.fd = fd; 376 if (copy_to_user(user_data, &arg, sizeof(arg))) { 377 ret = -EFAULT; 378 goto err_put_file; 379 } 380 381 fd_install(fd, sync_file->file); 382 383 return 0; 384 385 err_put_file: 386 fput(sync_file->file); 387 err_put_fd: 388 put_unused_fd(fd); 389 return ret; 390 } 391 392 static long dma_buf_import_sync_file(struct dma_buf *dmabuf, 393 const void __user *user_data) 394 { 395 struct dma_buf_import_sync_file arg; 396 struct dma_fence *fence, *f; 397 enum dma_resv_usage usage; 398 struct dma_fence_unwrap iter; 399 unsigned int num_fences; 400 int ret = 0; 401 402 if (copy_from_user(&arg, user_data, sizeof(arg))) 403 return -EFAULT; 404 405 if (arg.flags & ~DMA_BUF_SYNC_RW) 406 return -EINVAL; 407 408 if ((arg.flags & DMA_BUF_SYNC_RW) == 0) 409 return -EINVAL; 410 411 fence = sync_file_get_fence(arg.fd); 412 if (!fence) 413 return -EINVAL; 414 415 usage = (arg.flags & DMA_BUF_SYNC_WRITE) ? DMA_RESV_USAGE_WRITE : 416 DMA_RESV_USAGE_READ; 417 418 num_fences = 0; 419 dma_fence_unwrap_for_each(f, &iter, fence) 420 ++num_fences; 421 422 if (num_fences > 0) { 423 dma_resv_lock(dmabuf->resv, NULL); 424 425 ret = dma_resv_reserve_fences(dmabuf->resv, num_fences); 426 if (!ret) { 427 dma_fence_unwrap_for_each(f, &iter, fence) 428 dma_resv_add_fence(dmabuf->resv, f, usage); 429 } 430 431 dma_resv_unlock(dmabuf->resv); 432 } 433 434 dma_fence_put(fence); 435 436 return ret; 437 } 438 #endif 439 440 static long dma_buf_ioctl(struct file *file, 441 unsigned int cmd, unsigned long arg) 442 { 443 struct dma_buf *dmabuf; 444 struct dma_buf_sync sync; 445 enum dma_data_direction direction; 446 int ret; 447 448 dmabuf = file->private_data; 449 450 switch (cmd) { 451 case DMA_BUF_IOCTL_SYNC: 452 if (copy_from_user(&sync, (void __user *) arg, sizeof(sync))) 453 return -EFAULT; 454 455 if (sync.flags & ~DMA_BUF_SYNC_VALID_FLAGS_MASK) 456 return -EINVAL; 457 458 switch (sync.flags & DMA_BUF_SYNC_RW) { 459 case DMA_BUF_SYNC_READ: 460 direction = DMA_FROM_DEVICE; 461 break; 462 case DMA_BUF_SYNC_WRITE: 463 direction = DMA_TO_DEVICE; 464 break; 465 case DMA_BUF_SYNC_RW: 466 direction = DMA_BIDIRECTIONAL; 467 break; 468 default: 469 return -EINVAL; 470 } 471 472 if (sync.flags & DMA_BUF_SYNC_END) 473 ret = dma_buf_end_cpu_access(dmabuf, direction); 474 else 475 ret = dma_buf_begin_cpu_access(dmabuf, direction); 476 477 return ret; 478 479 case DMA_BUF_SET_NAME_A: 480 case DMA_BUF_SET_NAME_B: 481 return dma_buf_set_name(dmabuf, (const char __user *)arg); 482 483 #if IS_ENABLED(CONFIG_SYNC_FILE) 484 case DMA_BUF_IOCTL_EXPORT_SYNC_FILE: 485 return dma_buf_export_sync_file(dmabuf, (void __user *)arg); 486 case DMA_BUF_IOCTL_IMPORT_SYNC_FILE: 487 return dma_buf_import_sync_file(dmabuf, (const void __user *)arg); 488 #endif 489 490 default: 491 return -ENOTTY; 492 } 493 } 494 495 static void dma_buf_show_fdinfo(struct seq_file *m, struct file *file) 496 { 497 struct dma_buf *dmabuf = file->private_data; 498 499 seq_printf(m, "size:\t%zu\n", dmabuf->size); 500 /* Don't count the temporary reference taken inside procfs seq_show */ 501 seq_printf(m, "count:\t%ld\n", file_count(dmabuf->file) - 1); 502 seq_printf(m, "exp_name:\t%s\n", dmabuf->exp_name); 503 spin_lock(&dmabuf->name_lock); 504 if (dmabuf->name) 505 seq_printf(m, "name:\t%s\n", dmabuf->name); 506 spin_unlock(&dmabuf->name_lock); 507 } 508 509 static const struct file_operations dma_buf_fops = { 510 .release = dma_buf_file_release, 511 .mmap = dma_buf_mmap_internal, 512 .llseek = dma_buf_llseek, 513 .poll = dma_buf_poll, 514 .unlocked_ioctl = dma_buf_ioctl, 515 .compat_ioctl = compat_ptr_ioctl, 516 .show_fdinfo = dma_buf_show_fdinfo, 517 }; 518 519 /* 520 * is_dma_buf_file - Check if struct file* is associated with dma_buf 521 */ 522 static inline int is_dma_buf_file(struct file *file) 523 { 524 return file->f_op == &dma_buf_fops; 525 } 526 527 static struct file *dma_buf_getfile(size_t size, int flags) 528 { 529 static atomic64_t dmabuf_inode = ATOMIC64_INIT(0); 530 struct inode *inode = alloc_anon_inode(dma_buf_mnt->mnt_sb); 531 struct file *file; 532 533 if (IS_ERR(inode)) 534 return ERR_CAST(inode); 535 536 inode->i_size = size; 537 inode_set_bytes(inode, size); 538 539 /* 540 * The ->i_ino acquired from get_next_ino() is not unique thus 541 * not suitable for using it as dentry name by dmabuf stats. 542 * Override ->i_ino with the unique and dmabuffs specific 543 * value. 544 */ 545 inode->i_ino = atomic64_add_return(1, &dmabuf_inode); 546 flags &= O_ACCMODE | O_NONBLOCK; 547 file = alloc_file_pseudo(inode, dma_buf_mnt, "dmabuf", 548 flags, &dma_buf_fops); 549 if (IS_ERR(file)) 550 goto err_alloc_file; 551 552 return file; 553 554 err_alloc_file: 555 iput(inode); 556 return file; 557 } 558 559 /** 560 * DOC: dma buf device access 561 * 562 * For device DMA access to a shared DMA buffer the usual sequence of operations 563 * is fairly simple: 564 * 565 * 1. The exporter defines his exporter instance using 566 * DEFINE_DMA_BUF_EXPORT_INFO() and calls dma_buf_export() to wrap a private 567 * buffer object into a &dma_buf. It then exports that &dma_buf to userspace 568 * as a file descriptor by calling dma_buf_fd(). 569 * 570 * 2. Userspace passes this file-descriptors to all drivers it wants this buffer 571 * to share with: First the file descriptor is converted to a &dma_buf using 572 * dma_buf_get(). Then the buffer is attached to the device using 573 * dma_buf_attach(). 574 * 575 * Up to this stage the exporter is still free to migrate or reallocate the 576 * backing storage. 577 * 578 * 3. Once the buffer is attached to all devices userspace can initiate DMA 579 * access to the shared buffer. In the kernel this is done by calling 580 * dma_buf_map_attachment() and dma_buf_unmap_attachment(). 581 * 582 * 4. Once a driver is done with a shared buffer it needs to call 583 * dma_buf_detach() (after cleaning up any mappings) and then release the 584 * reference acquired with dma_buf_get() by calling dma_buf_put(). 585 * 586 * For the detailed semantics exporters are expected to implement see 587 * &dma_buf_ops. 588 */ 589 590 /** 591 * dma_buf_export - Creates a new dma_buf, and associates an anon file 592 * with this buffer, so it can be exported. 593 * Also connect the allocator specific data and ops to the buffer. 594 * Additionally, provide a name string for exporter; useful in debugging. 595 * 596 * @exp_info: [in] holds all the export related information provided 597 * by the exporter. see &struct dma_buf_export_info 598 * for further details. 599 * 600 * Returns, on success, a newly created struct dma_buf object, which wraps the 601 * supplied private data and operations for struct dma_buf_ops. On either 602 * missing ops, or error in allocating struct dma_buf, will return negative 603 * error. 604 * 605 * For most cases the easiest way to create @exp_info is through the 606 * %DEFINE_DMA_BUF_EXPORT_INFO macro. 607 */ 608 struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info) 609 { 610 struct dma_buf *dmabuf; 611 struct dma_resv *resv = exp_info->resv; 612 struct file *file; 613 size_t alloc_size = sizeof(struct dma_buf); 614 int ret; 615 616 if (WARN_ON(!exp_info->priv || !exp_info->ops 617 || !exp_info->ops->map_dma_buf 618 || !exp_info->ops->unmap_dma_buf 619 || !exp_info->ops->release)) 620 return ERR_PTR(-EINVAL); 621 622 if (WARN_ON(exp_info->ops->cache_sgt_mapping && 623 (exp_info->ops->pin || exp_info->ops->unpin))) 624 return ERR_PTR(-EINVAL); 625 626 if (WARN_ON(!exp_info->ops->pin != !exp_info->ops->unpin)) 627 return ERR_PTR(-EINVAL); 628 629 if (!try_module_get(exp_info->owner)) 630 return ERR_PTR(-ENOENT); 631 632 file = dma_buf_getfile(exp_info->size, exp_info->flags); 633 if (IS_ERR(file)) { 634 ret = PTR_ERR(file); 635 goto err_module; 636 } 637 638 if (!exp_info->resv) 639 alloc_size += sizeof(struct dma_resv); 640 else 641 /* prevent &dma_buf[1] == dma_buf->resv */ 642 alloc_size += 1; 643 dmabuf = kzalloc(alloc_size, GFP_KERNEL); 644 if (!dmabuf) { 645 ret = -ENOMEM; 646 goto err_file; 647 } 648 649 dmabuf->priv = exp_info->priv; 650 dmabuf->ops = exp_info->ops; 651 dmabuf->size = exp_info->size; 652 dmabuf->exp_name = exp_info->exp_name; 653 dmabuf->owner = exp_info->owner; 654 spin_lock_init(&dmabuf->name_lock); 655 init_waitqueue_head(&dmabuf->poll); 656 dmabuf->cb_in.poll = dmabuf->cb_out.poll = &dmabuf->poll; 657 dmabuf->cb_in.active = dmabuf->cb_out.active = 0; 658 INIT_LIST_HEAD(&dmabuf->attachments); 659 660 if (!resv) { 661 dmabuf->resv = (struct dma_resv *)&dmabuf[1]; 662 dma_resv_init(dmabuf->resv); 663 } else { 664 dmabuf->resv = resv; 665 } 666 667 ret = dma_buf_stats_setup(dmabuf, file); 668 if (ret) 669 goto err_dmabuf; 670 671 file->private_data = dmabuf; 672 file->f_path.dentry->d_fsdata = dmabuf; 673 dmabuf->file = file; 674 675 mutex_lock(&db_list.lock); 676 list_add(&dmabuf->list_node, &db_list.head); 677 mutex_unlock(&db_list.lock); 678 679 return dmabuf; 680 681 err_dmabuf: 682 if (!resv) 683 dma_resv_fini(dmabuf->resv); 684 kfree(dmabuf); 685 err_file: 686 fput(file); 687 err_module: 688 module_put(exp_info->owner); 689 return ERR_PTR(ret); 690 } 691 EXPORT_SYMBOL_NS_GPL(dma_buf_export, DMA_BUF); 692 693 /** 694 * dma_buf_fd - returns a file descriptor for the given struct dma_buf 695 * @dmabuf: [in] pointer to dma_buf for which fd is required. 696 * @flags: [in] flags to give to fd 697 * 698 * On success, returns an associated 'fd'. Else, returns error. 699 */ 700 int dma_buf_fd(struct dma_buf *dmabuf, int flags) 701 { 702 int fd; 703 704 if (!dmabuf || !dmabuf->file) 705 return -EINVAL; 706 707 fd = get_unused_fd_flags(flags); 708 if (fd < 0) 709 return fd; 710 711 fd_install(fd, dmabuf->file); 712 713 return fd; 714 } 715 EXPORT_SYMBOL_NS_GPL(dma_buf_fd, DMA_BUF); 716 717 /** 718 * dma_buf_get - returns the struct dma_buf related to an fd 719 * @fd: [in] fd associated with the struct dma_buf to be returned 720 * 721 * On success, returns the struct dma_buf associated with an fd; uses 722 * file's refcounting done by fget to increase refcount. returns ERR_PTR 723 * otherwise. 724 */ 725 struct dma_buf *dma_buf_get(int fd) 726 { 727 struct file *file; 728 729 file = fget(fd); 730 731 if (!file) 732 return ERR_PTR(-EBADF); 733 734 if (!is_dma_buf_file(file)) { 735 fput(file); 736 return ERR_PTR(-EINVAL); 737 } 738 739 return file->private_data; 740 } 741 EXPORT_SYMBOL_NS_GPL(dma_buf_get, DMA_BUF); 742 743 /** 744 * dma_buf_put - decreases refcount of the buffer 745 * @dmabuf: [in] buffer to reduce refcount of 746 * 747 * Uses file's refcounting done implicitly by fput(). 748 * 749 * If, as a result of this call, the refcount becomes 0, the 'release' file 750 * operation related to this fd is called. It calls &dma_buf_ops.release vfunc 751 * in turn, and frees the memory allocated for dmabuf when exported. 752 */ 753 void dma_buf_put(struct dma_buf *dmabuf) 754 { 755 if (WARN_ON(!dmabuf || !dmabuf->file)) 756 return; 757 758 fput(dmabuf->file); 759 } 760 EXPORT_SYMBOL_NS_GPL(dma_buf_put, DMA_BUF); 761 762 static void mangle_sg_table(struct sg_table *sg_table) 763 { 764 #ifdef CONFIG_DMABUF_DEBUG 765 int i; 766 struct scatterlist *sg; 767 768 /* To catch abuse of the underlying struct page by importers mix 769 * up the bits, but take care to preserve the low SG_ bits to 770 * not corrupt the sgt. The mixing is undone in __unmap_dma_buf 771 * before passing the sgt back to the exporter. */ 772 for_each_sgtable_sg(sg_table, sg, i) 773 sg->page_link ^= ~0xffUL; 774 #endif 775 776 } 777 static struct sg_table * __map_dma_buf(struct dma_buf_attachment *attach, 778 enum dma_data_direction direction) 779 { 780 struct sg_table *sg_table; 781 signed long ret; 782 783 sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction); 784 if (IS_ERR_OR_NULL(sg_table)) 785 return sg_table; 786 787 if (!dma_buf_attachment_is_dynamic(attach)) { 788 ret = dma_resv_wait_timeout(attach->dmabuf->resv, 789 DMA_RESV_USAGE_KERNEL, true, 790 MAX_SCHEDULE_TIMEOUT); 791 if (ret < 0) { 792 attach->dmabuf->ops->unmap_dma_buf(attach, sg_table, 793 direction); 794 return ERR_PTR(ret); 795 } 796 } 797 798 mangle_sg_table(sg_table); 799 return sg_table; 800 } 801 802 /** 803 * DOC: locking convention 804 * 805 * In order to avoid deadlock situations between dma-buf exports and importers, 806 * all dma-buf API users must follow the common dma-buf locking convention. 807 * 808 * Convention for importers 809 * 810 * 1. Importers must hold the dma-buf reservation lock when calling these 811 * functions: 812 * 813 * - dma_buf_pin() 814 * - dma_buf_unpin() 815 * - dma_buf_map_attachment() 816 * - dma_buf_unmap_attachment() 817 * - dma_buf_vmap() 818 * - dma_buf_vunmap() 819 * 820 * 2. Importers must not hold the dma-buf reservation lock when calling these 821 * functions: 822 * 823 * - dma_buf_attach() 824 * - dma_buf_dynamic_attach() 825 * - dma_buf_detach() 826 * - dma_buf_export() 827 * - dma_buf_fd() 828 * - dma_buf_get() 829 * - dma_buf_put() 830 * - dma_buf_mmap() 831 * - dma_buf_begin_cpu_access() 832 * - dma_buf_end_cpu_access() 833 * - dma_buf_map_attachment_unlocked() 834 * - dma_buf_unmap_attachment_unlocked() 835 * - dma_buf_vmap_unlocked() 836 * - dma_buf_vunmap_unlocked() 837 * 838 * Convention for exporters 839 * 840 * 1. These &dma_buf_ops callbacks are invoked with unlocked dma-buf 841 * reservation and exporter can take the lock: 842 * 843 * - &dma_buf_ops.attach() 844 * - &dma_buf_ops.detach() 845 * - &dma_buf_ops.release() 846 * - &dma_buf_ops.begin_cpu_access() 847 * - &dma_buf_ops.end_cpu_access() 848 * - &dma_buf_ops.mmap() 849 * 850 * 2. These &dma_buf_ops callbacks are invoked with locked dma-buf 851 * reservation and exporter can't take the lock: 852 * 853 * - &dma_buf_ops.pin() 854 * - &dma_buf_ops.unpin() 855 * - &dma_buf_ops.map_dma_buf() 856 * - &dma_buf_ops.unmap_dma_buf() 857 * - &dma_buf_ops.vmap() 858 * - &dma_buf_ops.vunmap() 859 * 860 * 3. Exporters must hold the dma-buf reservation lock when calling these 861 * functions: 862 * 863 * - dma_buf_move_notify() 864 */ 865 866 /** 867 * dma_buf_dynamic_attach - Add the device to dma_buf's attachments list 868 * @dmabuf: [in] buffer to attach device to. 869 * @dev: [in] device to be attached. 870 * @importer_ops: [in] importer operations for the attachment 871 * @importer_priv: [in] importer private pointer for the attachment 872 * 873 * Returns struct dma_buf_attachment pointer for this attachment. Attachments 874 * must be cleaned up by calling dma_buf_detach(). 875 * 876 * Optionally this calls &dma_buf_ops.attach to allow device-specific attach 877 * functionality. 878 * 879 * Returns: 880 * 881 * A pointer to newly created &dma_buf_attachment on success, or a negative 882 * error code wrapped into a pointer on failure. 883 * 884 * Note that this can fail if the backing storage of @dmabuf is in a place not 885 * accessible to @dev, and cannot be moved to a more suitable place. This is 886 * indicated with the error code -EBUSY. 887 */ 888 struct dma_buf_attachment * 889 dma_buf_dynamic_attach(struct dma_buf *dmabuf, struct device *dev, 890 const struct dma_buf_attach_ops *importer_ops, 891 void *importer_priv) 892 { 893 struct dma_buf_attachment *attach; 894 int ret; 895 896 if (WARN_ON(!dmabuf || !dev)) 897 return ERR_PTR(-EINVAL); 898 899 if (WARN_ON(importer_ops && !importer_ops->move_notify)) 900 return ERR_PTR(-EINVAL); 901 902 attach = kzalloc(sizeof(*attach), GFP_KERNEL); 903 if (!attach) 904 return ERR_PTR(-ENOMEM); 905 906 attach->dev = dev; 907 attach->dmabuf = dmabuf; 908 if (importer_ops) 909 attach->peer2peer = importer_ops->allow_peer2peer; 910 attach->importer_ops = importer_ops; 911 attach->importer_priv = importer_priv; 912 913 if (dmabuf->ops->attach) { 914 ret = dmabuf->ops->attach(dmabuf, attach); 915 if (ret) 916 goto err_attach; 917 } 918 dma_resv_lock(dmabuf->resv, NULL); 919 list_add(&attach->node, &dmabuf->attachments); 920 dma_resv_unlock(dmabuf->resv); 921 922 /* When either the importer or the exporter can't handle dynamic 923 * mappings we cache the mapping here to avoid issues with the 924 * reservation object lock. 925 */ 926 if (dma_buf_attachment_is_dynamic(attach) != 927 dma_buf_is_dynamic(dmabuf)) { 928 struct sg_table *sgt; 929 930 dma_resv_lock(attach->dmabuf->resv, NULL); 931 if (dma_buf_is_dynamic(attach->dmabuf)) { 932 ret = dmabuf->ops->pin(attach); 933 if (ret) 934 goto err_unlock; 935 } 936 937 sgt = __map_dma_buf(attach, DMA_BIDIRECTIONAL); 938 if (!sgt) 939 sgt = ERR_PTR(-ENOMEM); 940 if (IS_ERR(sgt)) { 941 ret = PTR_ERR(sgt); 942 goto err_unpin; 943 } 944 dma_resv_unlock(attach->dmabuf->resv); 945 attach->sgt = sgt; 946 attach->dir = DMA_BIDIRECTIONAL; 947 } 948 949 return attach; 950 951 err_attach: 952 kfree(attach); 953 return ERR_PTR(ret); 954 955 err_unpin: 956 if (dma_buf_is_dynamic(attach->dmabuf)) 957 dmabuf->ops->unpin(attach); 958 959 err_unlock: 960 dma_resv_unlock(attach->dmabuf->resv); 961 962 dma_buf_detach(dmabuf, attach); 963 return ERR_PTR(ret); 964 } 965 EXPORT_SYMBOL_NS_GPL(dma_buf_dynamic_attach, DMA_BUF); 966 967 /** 968 * dma_buf_attach - Wrapper for dma_buf_dynamic_attach 969 * @dmabuf: [in] buffer to attach device to. 970 * @dev: [in] device to be attached. 971 * 972 * Wrapper to call dma_buf_dynamic_attach() for drivers which still use a static 973 * mapping. 974 */ 975 struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf, 976 struct device *dev) 977 { 978 return dma_buf_dynamic_attach(dmabuf, dev, NULL, NULL); 979 } 980 EXPORT_SYMBOL_NS_GPL(dma_buf_attach, DMA_BUF); 981 982 static void __unmap_dma_buf(struct dma_buf_attachment *attach, 983 struct sg_table *sg_table, 984 enum dma_data_direction direction) 985 { 986 /* uses XOR, hence this unmangles */ 987 mangle_sg_table(sg_table); 988 989 attach->dmabuf->ops->unmap_dma_buf(attach, sg_table, direction); 990 } 991 992 /** 993 * dma_buf_detach - Remove the given attachment from dmabuf's attachments list 994 * @dmabuf: [in] buffer to detach from. 995 * @attach: [in] attachment to be detached; is free'd after this call. 996 * 997 * Clean up a device attachment obtained by calling dma_buf_attach(). 998 * 999 * Optionally this calls &dma_buf_ops.detach for device-specific detach. 1000 */ 1001 void dma_buf_detach(struct dma_buf *dmabuf, struct dma_buf_attachment *attach) 1002 { 1003 if (WARN_ON(!dmabuf || !attach || dmabuf != attach->dmabuf)) 1004 return; 1005 1006 dma_resv_lock(dmabuf->resv, NULL); 1007 1008 if (attach->sgt) { 1009 1010 __unmap_dma_buf(attach, attach->sgt, attach->dir); 1011 1012 if (dma_buf_is_dynamic(attach->dmabuf)) 1013 dmabuf->ops->unpin(attach); 1014 } 1015 list_del(&attach->node); 1016 1017 dma_resv_unlock(dmabuf->resv); 1018 1019 if (dmabuf->ops->detach) 1020 dmabuf->ops->detach(dmabuf, attach); 1021 1022 kfree(attach); 1023 } 1024 EXPORT_SYMBOL_NS_GPL(dma_buf_detach, DMA_BUF); 1025 1026 /** 1027 * dma_buf_pin - Lock down the DMA-buf 1028 * @attach: [in] attachment which should be pinned 1029 * 1030 * Only dynamic importers (who set up @attach with dma_buf_dynamic_attach()) may 1031 * call this, and only for limited use cases like scanout and not for temporary 1032 * pin operations. It is not permitted to allow userspace to pin arbitrary 1033 * amounts of buffers through this interface. 1034 * 1035 * Buffers must be unpinned by calling dma_buf_unpin(). 1036 * 1037 * Returns: 1038 * 0 on success, negative error code on failure. 1039 */ 1040 int dma_buf_pin(struct dma_buf_attachment *attach) 1041 { 1042 struct dma_buf *dmabuf = attach->dmabuf; 1043 int ret = 0; 1044 1045 WARN_ON(!dma_buf_attachment_is_dynamic(attach)); 1046 1047 dma_resv_assert_held(dmabuf->resv); 1048 1049 if (dmabuf->ops->pin) 1050 ret = dmabuf->ops->pin(attach); 1051 1052 return ret; 1053 } 1054 EXPORT_SYMBOL_NS_GPL(dma_buf_pin, DMA_BUF); 1055 1056 /** 1057 * dma_buf_unpin - Unpin a DMA-buf 1058 * @attach: [in] attachment which should be unpinned 1059 * 1060 * This unpins a buffer pinned by dma_buf_pin() and allows the exporter to move 1061 * any mapping of @attach again and inform the importer through 1062 * &dma_buf_attach_ops.move_notify. 1063 */ 1064 void dma_buf_unpin(struct dma_buf_attachment *attach) 1065 { 1066 struct dma_buf *dmabuf = attach->dmabuf; 1067 1068 WARN_ON(!dma_buf_attachment_is_dynamic(attach)); 1069 1070 dma_resv_assert_held(dmabuf->resv); 1071 1072 if (dmabuf->ops->unpin) 1073 dmabuf->ops->unpin(attach); 1074 } 1075 EXPORT_SYMBOL_NS_GPL(dma_buf_unpin, DMA_BUF); 1076 1077 /** 1078 * dma_buf_map_attachment - Returns the scatterlist table of the attachment; 1079 * mapped into _device_ address space. Is a wrapper for map_dma_buf() of the 1080 * dma_buf_ops. 1081 * @attach: [in] attachment whose scatterlist is to be returned 1082 * @direction: [in] direction of DMA transfer 1083 * 1084 * Returns sg_table containing the scatterlist to be returned; returns ERR_PTR 1085 * on error. May return -EINTR if it is interrupted by a signal. 1086 * 1087 * On success, the DMA addresses and lengths in the returned scatterlist are 1088 * PAGE_SIZE aligned. 1089 * 1090 * A mapping must be unmapped by using dma_buf_unmap_attachment(). Note that 1091 * the underlying backing storage is pinned for as long as a mapping exists, 1092 * therefore users/importers should not hold onto a mapping for undue amounts of 1093 * time. 1094 * 1095 * Important: Dynamic importers must wait for the exclusive fence of the struct 1096 * dma_resv attached to the DMA-BUF first. 1097 */ 1098 struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach, 1099 enum dma_data_direction direction) 1100 { 1101 struct sg_table *sg_table; 1102 int r; 1103 1104 might_sleep(); 1105 1106 if (WARN_ON(!attach || !attach->dmabuf)) 1107 return ERR_PTR(-EINVAL); 1108 1109 dma_resv_assert_held(attach->dmabuf->resv); 1110 1111 if (attach->sgt) { 1112 /* 1113 * Two mappings with different directions for the same 1114 * attachment are not allowed. 1115 */ 1116 if (attach->dir != direction && 1117 attach->dir != DMA_BIDIRECTIONAL) 1118 return ERR_PTR(-EBUSY); 1119 1120 return attach->sgt; 1121 } 1122 1123 if (dma_buf_is_dynamic(attach->dmabuf)) { 1124 if (!IS_ENABLED(CONFIG_DMABUF_MOVE_NOTIFY)) { 1125 r = attach->dmabuf->ops->pin(attach); 1126 if (r) 1127 return ERR_PTR(r); 1128 } 1129 } 1130 1131 sg_table = __map_dma_buf(attach, direction); 1132 if (!sg_table) 1133 sg_table = ERR_PTR(-ENOMEM); 1134 1135 if (IS_ERR(sg_table) && dma_buf_is_dynamic(attach->dmabuf) && 1136 !IS_ENABLED(CONFIG_DMABUF_MOVE_NOTIFY)) 1137 attach->dmabuf->ops->unpin(attach); 1138 1139 if (!IS_ERR(sg_table) && attach->dmabuf->ops->cache_sgt_mapping) { 1140 attach->sgt = sg_table; 1141 attach->dir = direction; 1142 } 1143 1144 #ifdef CONFIG_DMA_API_DEBUG 1145 if (!IS_ERR(sg_table)) { 1146 struct scatterlist *sg; 1147 u64 addr; 1148 int len; 1149 int i; 1150 1151 for_each_sgtable_dma_sg(sg_table, sg, i) { 1152 addr = sg_dma_address(sg); 1153 len = sg_dma_len(sg); 1154 if (!PAGE_ALIGNED(addr) || !PAGE_ALIGNED(len)) { 1155 pr_debug("%s: addr %llx or len %x is not page aligned!\n", 1156 __func__, addr, len); 1157 } 1158 } 1159 } 1160 #endif /* CONFIG_DMA_API_DEBUG */ 1161 return sg_table; 1162 } 1163 EXPORT_SYMBOL_NS_GPL(dma_buf_map_attachment, DMA_BUF); 1164 1165 /** 1166 * dma_buf_map_attachment_unlocked - Returns the scatterlist table of the attachment; 1167 * mapped into _device_ address space. Is a wrapper for map_dma_buf() of the 1168 * dma_buf_ops. 1169 * @attach: [in] attachment whose scatterlist is to be returned 1170 * @direction: [in] direction of DMA transfer 1171 * 1172 * Unlocked variant of dma_buf_map_attachment(). 1173 */ 1174 struct sg_table * 1175 dma_buf_map_attachment_unlocked(struct dma_buf_attachment *attach, 1176 enum dma_data_direction direction) 1177 { 1178 struct sg_table *sg_table; 1179 1180 might_sleep(); 1181 1182 if (WARN_ON(!attach || !attach->dmabuf)) 1183 return ERR_PTR(-EINVAL); 1184 1185 dma_resv_lock(attach->dmabuf->resv, NULL); 1186 sg_table = dma_buf_map_attachment(attach, direction); 1187 dma_resv_unlock(attach->dmabuf->resv); 1188 1189 return sg_table; 1190 } 1191 EXPORT_SYMBOL_NS_GPL(dma_buf_map_attachment_unlocked, DMA_BUF); 1192 1193 /** 1194 * dma_buf_unmap_attachment - unmaps and decreases usecount of the buffer;might 1195 * deallocate the scatterlist associated. Is a wrapper for unmap_dma_buf() of 1196 * dma_buf_ops. 1197 * @attach: [in] attachment to unmap buffer from 1198 * @sg_table: [in] scatterlist info of the buffer to unmap 1199 * @direction: [in] direction of DMA transfer 1200 * 1201 * This unmaps a DMA mapping for @attached obtained by dma_buf_map_attachment(). 1202 */ 1203 void dma_buf_unmap_attachment(struct dma_buf_attachment *attach, 1204 struct sg_table *sg_table, 1205 enum dma_data_direction direction) 1206 { 1207 might_sleep(); 1208 1209 if (WARN_ON(!attach || !attach->dmabuf || !sg_table)) 1210 return; 1211 1212 dma_resv_assert_held(attach->dmabuf->resv); 1213 1214 if (attach->sgt == sg_table) 1215 return; 1216 1217 __unmap_dma_buf(attach, sg_table, direction); 1218 1219 if (dma_buf_is_dynamic(attach->dmabuf) && 1220 !IS_ENABLED(CONFIG_DMABUF_MOVE_NOTIFY)) 1221 dma_buf_unpin(attach); 1222 } 1223 EXPORT_SYMBOL_NS_GPL(dma_buf_unmap_attachment, DMA_BUF); 1224 1225 /** 1226 * dma_buf_unmap_attachment_unlocked - unmaps and decreases usecount of the buffer;might 1227 * deallocate the scatterlist associated. Is a wrapper for unmap_dma_buf() of 1228 * dma_buf_ops. 1229 * @attach: [in] attachment to unmap buffer from 1230 * @sg_table: [in] scatterlist info of the buffer to unmap 1231 * @direction: [in] direction of DMA transfer 1232 * 1233 * Unlocked variant of dma_buf_unmap_attachment(). 1234 */ 1235 void dma_buf_unmap_attachment_unlocked(struct dma_buf_attachment *attach, 1236 struct sg_table *sg_table, 1237 enum dma_data_direction direction) 1238 { 1239 might_sleep(); 1240 1241 if (WARN_ON(!attach || !attach->dmabuf || !sg_table)) 1242 return; 1243 1244 dma_resv_lock(attach->dmabuf->resv, NULL); 1245 dma_buf_unmap_attachment(attach, sg_table, direction); 1246 dma_resv_unlock(attach->dmabuf->resv); 1247 } 1248 EXPORT_SYMBOL_NS_GPL(dma_buf_unmap_attachment_unlocked, DMA_BUF); 1249 1250 /** 1251 * dma_buf_move_notify - notify attachments that DMA-buf is moving 1252 * 1253 * @dmabuf: [in] buffer which is moving 1254 * 1255 * Informs all attachments that they need to destroy and recreate all their 1256 * mappings. 1257 */ 1258 void dma_buf_move_notify(struct dma_buf *dmabuf) 1259 { 1260 struct dma_buf_attachment *attach; 1261 1262 dma_resv_assert_held(dmabuf->resv); 1263 1264 list_for_each_entry(attach, &dmabuf->attachments, node) 1265 if (attach->importer_ops) 1266 attach->importer_ops->move_notify(attach); 1267 } 1268 EXPORT_SYMBOL_NS_GPL(dma_buf_move_notify, DMA_BUF); 1269 1270 /** 1271 * DOC: cpu access 1272 * 1273 * There are multiple reasons for supporting CPU access to a dma buffer object: 1274 * 1275 * - Fallback operations in the kernel, for example when a device is connected 1276 * over USB and the kernel needs to shuffle the data around first before 1277 * sending it away. Cache coherency is handled by bracketing any transactions 1278 * with calls to dma_buf_begin_cpu_access() and dma_buf_end_cpu_access() 1279 * access. 1280 * 1281 * Since for most kernel internal dma-buf accesses need the entire buffer, a 1282 * vmap interface is introduced. Note that on very old 32-bit architectures 1283 * vmalloc space might be limited and result in vmap calls failing. 1284 * 1285 * Interfaces:: 1286 * 1287 * void \*dma_buf_vmap(struct dma_buf \*dmabuf, struct iosys_map \*map) 1288 * void dma_buf_vunmap(struct dma_buf \*dmabuf, struct iosys_map \*map) 1289 * 1290 * The vmap call can fail if there is no vmap support in the exporter, or if 1291 * it runs out of vmalloc space. Note that the dma-buf layer keeps a reference 1292 * count for all vmap access and calls down into the exporter's vmap function 1293 * only when no vmapping exists, and only unmaps it once. Protection against 1294 * concurrent vmap/vunmap calls is provided by taking the &dma_buf.lock mutex. 1295 * 1296 * - For full compatibility on the importer side with existing userspace 1297 * interfaces, which might already support mmap'ing buffers. This is needed in 1298 * many processing pipelines (e.g. feeding a software rendered image into a 1299 * hardware pipeline, thumbnail creation, snapshots, ...). Also, Android's ION 1300 * framework already supported this and for DMA buffer file descriptors to 1301 * replace ION buffers mmap support was needed. 1302 * 1303 * There is no special interfaces, userspace simply calls mmap on the dma-buf 1304 * fd. But like for CPU access there's a need to bracket the actual access, 1305 * which is handled by the ioctl (DMA_BUF_IOCTL_SYNC). Note that 1306 * DMA_BUF_IOCTL_SYNC can fail with -EAGAIN or -EINTR, in which case it must 1307 * be restarted. 1308 * 1309 * Some systems might need some sort of cache coherency management e.g. when 1310 * CPU and GPU domains are being accessed through dma-buf at the same time. 1311 * To circumvent this problem there are begin/end coherency markers, that 1312 * forward directly to existing dma-buf device drivers vfunc hooks. Userspace 1313 * can make use of those markers through the DMA_BUF_IOCTL_SYNC ioctl. The 1314 * sequence would be used like following: 1315 * 1316 * - mmap dma-buf fd 1317 * - for each drawing/upload cycle in CPU 1. SYNC_START ioctl, 2. read/write 1318 * to mmap area 3. SYNC_END ioctl. This can be repeated as often as you 1319 * want (with the new data being consumed by say the GPU or the scanout 1320 * device) 1321 * - munmap once you don't need the buffer any more 1322 * 1323 * For correctness and optimal performance, it is always required to use 1324 * SYNC_START and SYNC_END before and after, respectively, when accessing the 1325 * mapped address. Userspace cannot rely on coherent access, even when there 1326 * are systems where it just works without calling these ioctls. 1327 * 1328 * - And as a CPU fallback in userspace processing pipelines. 1329 * 1330 * Similar to the motivation for kernel cpu access it is again important that 1331 * the userspace code of a given importing subsystem can use the same 1332 * interfaces with a imported dma-buf buffer object as with a native buffer 1333 * object. This is especially important for drm where the userspace part of 1334 * contemporary OpenGL, X, and other drivers is huge, and reworking them to 1335 * use a different way to mmap a buffer rather invasive. 1336 * 1337 * The assumption in the current dma-buf interfaces is that redirecting the 1338 * initial mmap is all that's needed. A survey of some of the existing 1339 * subsystems shows that no driver seems to do any nefarious thing like 1340 * syncing up with outstanding asynchronous processing on the device or 1341 * allocating special resources at fault time. So hopefully this is good 1342 * enough, since adding interfaces to intercept pagefaults and allow pte 1343 * shootdowns would increase the complexity quite a bit. 1344 * 1345 * Interface:: 1346 * 1347 * int dma_buf_mmap(struct dma_buf \*, struct vm_area_struct \*, 1348 * unsigned long); 1349 * 1350 * If the importing subsystem simply provides a special-purpose mmap call to 1351 * set up a mapping in userspace, calling do_mmap with &dma_buf.file will 1352 * equally achieve that for a dma-buf object. 1353 */ 1354 1355 static int __dma_buf_begin_cpu_access(struct dma_buf *dmabuf, 1356 enum dma_data_direction direction) 1357 { 1358 bool write = (direction == DMA_BIDIRECTIONAL || 1359 direction == DMA_TO_DEVICE); 1360 struct dma_resv *resv = dmabuf->resv; 1361 long ret; 1362 1363 /* Wait on any implicit rendering fences */ 1364 ret = dma_resv_wait_timeout(resv, dma_resv_usage_rw(write), 1365 true, MAX_SCHEDULE_TIMEOUT); 1366 if (ret < 0) 1367 return ret; 1368 1369 return 0; 1370 } 1371 1372 /** 1373 * dma_buf_begin_cpu_access - Must be called before accessing a dma_buf from the 1374 * cpu in the kernel context. Calls begin_cpu_access to allow exporter-specific 1375 * preparations. Coherency is only guaranteed in the specified range for the 1376 * specified access direction. 1377 * @dmabuf: [in] buffer to prepare cpu access for. 1378 * @direction: [in] direction of access. 1379 * 1380 * After the cpu access is complete the caller should call 1381 * dma_buf_end_cpu_access(). Only when cpu access is bracketed by both calls is 1382 * it guaranteed to be coherent with other DMA access. 1383 * 1384 * This function will also wait for any DMA transactions tracked through 1385 * implicit synchronization in &dma_buf.resv. For DMA transactions with explicit 1386 * synchronization this function will only ensure cache coherency, callers must 1387 * ensure synchronization with such DMA transactions on their own. 1388 * 1389 * Can return negative error values, returns 0 on success. 1390 */ 1391 int dma_buf_begin_cpu_access(struct dma_buf *dmabuf, 1392 enum dma_data_direction direction) 1393 { 1394 int ret = 0; 1395 1396 if (WARN_ON(!dmabuf)) 1397 return -EINVAL; 1398 1399 might_lock(&dmabuf->resv->lock.base); 1400 1401 if (dmabuf->ops->begin_cpu_access) 1402 ret = dmabuf->ops->begin_cpu_access(dmabuf, direction); 1403 1404 /* Ensure that all fences are waited upon - but we first allow 1405 * the native handler the chance to do so more efficiently if it 1406 * chooses. A double invocation here will be reasonably cheap no-op. 1407 */ 1408 if (ret == 0) 1409 ret = __dma_buf_begin_cpu_access(dmabuf, direction); 1410 1411 return ret; 1412 } 1413 EXPORT_SYMBOL_NS_GPL(dma_buf_begin_cpu_access, DMA_BUF); 1414 1415 /** 1416 * dma_buf_end_cpu_access - Must be called after accessing a dma_buf from the 1417 * cpu in the kernel context. Calls end_cpu_access to allow exporter-specific 1418 * actions. Coherency is only guaranteed in the specified range for the 1419 * specified access direction. 1420 * @dmabuf: [in] buffer to complete cpu access for. 1421 * @direction: [in] direction of access. 1422 * 1423 * This terminates CPU access started with dma_buf_begin_cpu_access(). 1424 * 1425 * Can return negative error values, returns 0 on success. 1426 */ 1427 int dma_buf_end_cpu_access(struct dma_buf *dmabuf, 1428 enum dma_data_direction direction) 1429 { 1430 int ret = 0; 1431 1432 WARN_ON(!dmabuf); 1433 1434 might_lock(&dmabuf->resv->lock.base); 1435 1436 if (dmabuf->ops->end_cpu_access) 1437 ret = dmabuf->ops->end_cpu_access(dmabuf, direction); 1438 1439 return ret; 1440 } 1441 EXPORT_SYMBOL_NS_GPL(dma_buf_end_cpu_access, DMA_BUF); 1442 1443 1444 /** 1445 * dma_buf_mmap - Setup up a userspace mmap with the given vma 1446 * @dmabuf: [in] buffer that should back the vma 1447 * @vma: [in] vma for the mmap 1448 * @pgoff: [in] offset in pages where this mmap should start within the 1449 * dma-buf buffer. 1450 * 1451 * This function adjusts the passed in vma so that it points at the file of the 1452 * dma_buf operation. It also adjusts the starting pgoff and does bounds 1453 * checking on the size of the vma. Then it calls the exporters mmap function to 1454 * set up the mapping. 1455 * 1456 * Can return negative error values, returns 0 on success. 1457 */ 1458 int dma_buf_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma, 1459 unsigned long pgoff) 1460 { 1461 if (WARN_ON(!dmabuf || !vma)) 1462 return -EINVAL; 1463 1464 /* check if buffer supports mmap */ 1465 if (!dmabuf->ops->mmap) 1466 return -EINVAL; 1467 1468 /* check for offset overflow */ 1469 if (pgoff + vma_pages(vma) < pgoff) 1470 return -EOVERFLOW; 1471 1472 /* check for overflowing the buffer's size */ 1473 if (pgoff + vma_pages(vma) > 1474 dmabuf->size >> PAGE_SHIFT) 1475 return -EINVAL; 1476 1477 /* readjust the vma */ 1478 vma_set_file(vma, dmabuf->file); 1479 vma->vm_pgoff = pgoff; 1480 1481 return dmabuf->ops->mmap(dmabuf, vma); 1482 } 1483 EXPORT_SYMBOL_NS_GPL(dma_buf_mmap, DMA_BUF); 1484 1485 /** 1486 * dma_buf_vmap - Create virtual mapping for the buffer object into kernel 1487 * address space. Same restrictions as for vmap and friends apply. 1488 * @dmabuf: [in] buffer to vmap 1489 * @map: [out] returns the vmap pointer 1490 * 1491 * This call may fail due to lack of virtual mapping address space. 1492 * These calls are optional in drivers. The intended use for them 1493 * is for mapping objects linear in kernel space for high use objects. 1494 * 1495 * To ensure coherency users must call dma_buf_begin_cpu_access() and 1496 * dma_buf_end_cpu_access() around any cpu access performed through this 1497 * mapping. 1498 * 1499 * Returns 0 on success, or a negative errno code otherwise. 1500 */ 1501 int dma_buf_vmap(struct dma_buf *dmabuf, struct iosys_map *map) 1502 { 1503 struct iosys_map ptr; 1504 int ret; 1505 1506 iosys_map_clear(map); 1507 1508 if (WARN_ON(!dmabuf)) 1509 return -EINVAL; 1510 1511 dma_resv_assert_held(dmabuf->resv); 1512 1513 if (!dmabuf->ops->vmap) 1514 return -EINVAL; 1515 1516 if (dmabuf->vmapping_counter) { 1517 dmabuf->vmapping_counter++; 1518 BUG_ON(iosys_map_is_null(&dmabuf->vmap_ptr)); 1519 *map = dmabuf->vmap_ptr; 1520 return 0; 1521 } 1522 1523 BUG_ON(iosys_map_is_set(&dmabuf->vmap_ptr)); 1524 1525 ret = dmabuf->ops->vmap(dmabuf, &ptr); 1526 if (WARN_ON_ONCE(ret)) 1527 return ret; 1528 1529 dmabuf->vmap_ptr = ptr; 1530 dmabuf->vmapping_counter = 1; 1531 1532 *map = dmabuf->vmap_ptr; 1533 1534 return 0; 1535 } 1536 EXPORT_SYMBOL_NS_GPL(dma_buf_vmap, DMA_BUF); 1537 1538 /** 1539 * dma_buf_vmap_unlocked - Create virtual mapping for the buffer object into kernel 1540 * address space. Same restrictions as for vmap and friends apply. 1541 * @dmabuf: [in] buffer to vmap 1542 * @map: [out] returns the vmap pointer 1543 * 1544 * Unlocked version of dma_buf_vmap() 1545 * 1546 * Returns 0 on success, or a negative errno code otherwise. 1547 */ 1548 int dma_buf_vmap_unlocked(struct dma_buf *dmabuf, struct iosys_map *map) 1549 { 1550 int ret; 1551 1552 iosys_map_clear(map); 1553 1554 if (WARN_ON(!dmabuf)) 1555 return -EINVAL; 1556 1557 dma_resv_lock(dmabuf->resv, NULL); 1558 ret = dma_buf_vmap(dmabuf, map); 1559 dma_resv_unlock(dmabuf->resv); 1560 1561 return ret; 1562 } 1563 EXPORT_SYMBOL_NS_GPL(dma_buf_vmap_unlocked, DMA_BUF); 1564 1565 /** 1566 * dma_buf_vunmap - Unmap a vmap obtained by dma_buf_vmap. 1567 * @dmabuf: [in] buffer to vunmap 1568 * @map: [in] vmap pointer to vunmap 1569 */ 1570 void dma_buf_vunmap(struct dma_buf *dmabuf, struct iosys_map *map) 1571 { 1572 if (WARN_ON(!dmabuf)) 1573 return; 1574 1575 dma_resv_assert_held(dmabuf->resv); 1576 1577 BUG_ON(iosys_map_is_null(&dmabuf->vmap_ptr)); 1578 BUG_ON(dmabuf->vmapping_counter == 0); 1579 BUG_ON(!iosys_map_is_equal(&dmabuf->vmap_ptr, map)); 1580 1581 if (--dmabuf->vmapping_counter == 0) { 1582 if (dmabuf->ops->vunmap) 1583 dmabuf->ops->vunmap(dmabuf, map); 1584 iosys_map_clear(&dmabuf->vmap_ptr); 1585 } 1586 } 1587 EXPORT_SYMBOL_NS_GPL(dma_buf_vunmap, DMA_BUF); 1588 1589 /** 1590 * dma_buf_vunmap_unlocked - Unmap a vmap obtained by dma_buf_vmap. 1591 * @dmabuf: [in] buffer to vunmap 1592 * @map: [in] vmap pointer to vunmap 1593 */ 1594 void dma_buf_vunmap_unlocked(struct dma_buf *dmabuf, struct iosys_map *map) 1595 { 1596 if (WARN_ON(!dmabuf)) 1597 return; 1598 1599 dma_resv_lock(dmabuf->resv, NULL); 1600 dma_buf_vunmap(dmabuf, map); 1601 dma_resv_unlock(dmabuf->resv); 1602 } 1603 EXPORT_SYMBOL_NS_GPL(dma_buf_vunmap_unlocked, DMA_BUF); 1604 1605 #ifdef CONFIG_DEBUG_FS 1606 static int dma_buf_debug_show(struct seq_file *s, void *unused) 1607 { 1608 struct dma_buf *buf_obj; 1609 struct dma_buf_attachment *attach_obj; 1610 int count = 0, attach_count; 1611 size_t size = 0; 1612 int ret; 1613 1614 ret = mutex_lock_interruptible(&db_list.lock); 1615 1616 if (ret) 1617 return ret; 1618 1619 seq_puts(s, "\nDma-buf Objects:\n"); 1620 seq_printf(s, "%-8s\t%-8s\t%-8s\t%-8s\texp_name\t%-8s\tname\n", 1621 "size", "flags", "mode", "count", "ino"); 1622 1623 list_for_each_entry(buf_obj, &db_list.head, list_node) { 1624 1625 ret = dma_resv_lock_interruptible(buf_obj->resv, NULL); 1626 if (ret) 1627 goto error_unlock; 1628 1629 1630 spin_lock(&buf_obj->name_lock); 1631 seq_printf(s, "%08zu\t%08x\t%08x\t%08ld\t%s\t%08lu\t%s\n", 1632 buf_obj->size, 1633 buf_obj->file->f_flags, buf_obj->file->f_mode, 1634 file_count(buf_obj->file), 1635 buf_obj->exp_name, 1636 file_inode(buf_obj->file)->i_ino, 1637 buf_obj->name ?: "<none>"); 1638 spin_unlock(&buf_obj->name_lock); 1639 1640 dma_resv_describe(buf_obj->resv, s); 1641 1642 seq_puts(s, "\tAttached Devices:\n"); 1643 attach_count = 0; 1644 1645 list_for_each_entry(attach_obj, &buf_obj->attachments, node) { 1646 seq_printf(s, "\t%s\n", dev_name(attach_obj->dev)); 1647 attach_count++; 1648 } 1649 dma_resv_unlock(buf_obj->resv); 1650 1651 seq_printf(s, "Total %d devices attached\n\n", 1652 attach_count); 1653 1654 count++; 1655 size += buf_obj->size; 1656 } 1657 1658 seq_printf(s, "\nTotal %d objects, %zu bytes\n", count, size); 1659 1660 mutex_unlock(&db_list.lock); 1661 return 0; 1662 1663 error_unlock: 1664 mutex_unlock(&db_list.lock); 1665 return ret; 1666 } 1667 1668 DEFINE_SHOW_ATTRIBUTE(dma_buf_debug); 1669 1670 static struct dentry *dma_buf_debugfs_dir; 1671 1672 static int dma_buf_init_debugfs(void) 1673 { 1674 struct dentry *d; 1675 int err = 0; 1676 1677 d = debugfs_create_dir("dma_buf", NULL); 1678 if (IS_ERR(d)) 1679 return PTR_ERR(d); 1680 1681 dma_buf_debugfs_dir = d; 1682 1683 d = debugfs_create_file("bufinfo", S_IRUGO, dma_buf_debugfs_dir, 1684 NULL, &dma_buf_debug_fops); 1685 if (IS_ERR(d)) { 1686 pr_debug("dma_buf: debugfs: failed to create node bufinfo\n"); 1687 debugfs_remove_recursive(dma_buf_debugfs_dir); 1688 dma_buf_debugfs_dir = NULL; 1689 err = PTR_ERR(d); 1690 } 1691 1692 return err; 1693 } 1694 1695 static void dma_buf_uninit_debugfs(void) 1696 { 1697 debugfs_remove_recursive(dma_buf_debugfs_dir); 1698 } 1699 #else 1700 static inline int dma_buf_init_debugfs(void) 1701 { 1702 return 0; 1703 } 1704 static inline void dma_buf_uninit_debugfs(void) 1705 { 1706 } 1707 #endif 1708 1709 static int __init dma_buf_init(void) 1710 { 1711 int ret; 1712 1713 ret = dma_buf_init_sysfs_statistics(); 1714 if (ret) 1715 return ret; 1716 1717 dma_buf_mnt = kern_mount(&dma_buf_fs_type); 1718 if (IS_ERR(dma_buf_mnt)) 1719 return PTR_ERR(dma_buf_mnt); 1720 1721 mutex_init(&db_list.lock); 1722 INIT_LIST_HEAD(&db_list.head); 1723 dma_buf_init_debugfs(); 1724 return 0; 1725 } 1726 subsys_initcall(dma_buf_init); 1727 1728 static void __exit dma_buf_deinit(void) 1729 { 1730 dma_buf_uninit_debugfs(); 1731 kern_unmount(dma_buf_mnt); 1732 dma_buf_uninit_sysfs_statistics(); 1733 } 1734 __exitcall(dma_buf_deinit); 1735