// SPDX-License-Identifier: GPL-2.0-only /* * Framework for buffer objects that can be shared across devices/subsystems. * * Copyright(C) 2011 Linaro Limited. All rights reserved. * Author: Sumit Semwal * * Many thanks to linaro-mm-sig list, and specially * Arnd Bergmann , Rob Clark and * Daniel Vetter for their support in creation and * refining of this idea. */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include static inline int is_dma_buf_file(struct file *); struct dma_buf_list { struct list_head head; struct mutex lock; }; static struct dma_buf_list db_list; static char *dmabuffs_dname(struct dentry *dentry, char *buffer, int buflen) { struct dma_buf *dmabuf; char name[DMA_BUF_NAME_LEN]; size_t ret = 0; dmabuf = dentry->d_fsdata; spin_lock(&dmabuf->name_lock); if (dmabuf->name) ret = strlcpy(name, dmabuf->name, DMA_BUF_NAME_LEN); spin_unlock(&dmabuf->name_lock); return dynamic_dname(dentry, buffer, buflen, "/%s:%s", dentry->d_name.name, ret > 0 ? name : ""); } static void dma_buf_release(struct dentry *dentry) { struct dma_buf *dmabuf; dmabuf = dentry->d_fsdata; BUG_ON(dmabuf->vmapping_counter); /* * Any fences that a dma-buf poll can wait on should be signaled * before releasing dma-buf. This is the responsibility of each * driver that uses the reservation objects. * * If you hit this BUG() it means someone dropped their ref to the * dma-buf while still having pending operation to the buffer. */ BUG_ON(dmabuf->cb_shared.active || dmabuf->cb_excl.active); dmabuf->ops->release(dmabuf); mutex_lock(&db_list.lock); list_del(&dmabuf->list_node); mutex_unlock(&db_list.lock); if (dmabuf->resv == (struct dma_resv *)&dmabuf[1]) dma_resv_fini(dmabuf->resv); module_put(dmabuf->owner); kfree(dmabuf->name); kfree(dmabuf); } static const struct dentry_operations dma_buf_dentry_ops = { .d_dname = dmabuffs_dname, .d_release = dma_buf_release, }; static struct vfsmount *dma_buf_mnt; static int dma_buf_fs_init_context(struct fs_context *fc) { struct pseudo_fs_context *ctx; ctx = init_pseudo(fc, DMA_BUF_MAGIC); if (!ctx) return -ENOMEM; ctx->dops = &dma_buf_dentry_ops; return 0; } static struct file_system_type dma_buf_fs_type = { .name = "dmabuf", .init_fs_context = dma_buf_fs_init_context, .kill_sb = kill_anon_super, }; static int dma_buf_mmap_internal(struct file *file, struct vm_area_struct *vma) { struct dma_buf *dmabuf; if (!is_dma_buf_file(file)) return -EINVAL; dmabuf = file->private_data; /* check if buffer supports mmap */ if (!dmabuf->ops->mmap) return -EINVAL; /* check for overflowing the buffer's size */ if (vma->vm_pgoff + vma_pages(vma) > dmabuf->size >> PAGE_SHIFT) return -EINVAL; return dmabuf->ops->mmap(dmabuf, vma); } static loff_t dma_buf_llseek(struct file *file, loff_t offset, int whence) { struct dma_buf *dmabuf; loff_t base; if (!is_dma_buf_file(file)) return -EBADF; dmabuf = file->private_data; /* only support discovering the end of the buffer, but also allow SEEK_SET to maintain the idiomatic SEEK_END(0), SEEK_CUR(0) pattern */ if (whence == SEEK_END) base = dmabuf->size; else if (whence == SEEK_SET) base = 0; else return -EINVAL; if (offset != 0) return -EINVAL; return base + offset; } /** * DOC: implicit fence polling * * To support cross-device and cross-driver synchronization of buffer access * implicit fences (represented internally in the kernel with &struct dma_fence) * can be attached to a &dma_buf. The glue for that and a few related things are * provided in the &dma_resv structure. * * Userspace can query the state of these implicitly tracked fences using poll() * and related system calls: * * - Checking for EPOLLIN, i.e. read access, can be use to query the state of the * most recent write or exclusive fence. * * - Checking for EPOLLOUT, i.e. write access, can be used to query the state of * all attached fences, shared and exclusive ones. * * Note that this only signals the completion of the respective fences, i.e. the * DMA transfers are complete. Cache flushing and any other necessary * preparations before CPU access can begin still need to happen. */ static void dma_buf_poll_cb(struct dma_fence *fence, struct dma_fence_cb *cb) { struct dma_buf_poll_cb_t *dcb = (struct dma_buf_poll_cb_t *)cb; unsigned long flags; spin_lock_irqsave(&dcb->poll->lock, flags); wake_up_locked_poll(dcb->poll, dcb->active); dcb->active = 0; spin_unlock_irqrestore(&dcb->poll->lock, flags); } static __poll_t dma_buf_poll(struct file *file, poll_table *poll) { struct dma_buf *dmabuf; struct dma_resv *resv; struct dma_resv_list *fobj; struct dma_fence *fence_excl; __poll_t events; unsigned shared_count, seq; dmabuf = file->private_data; if (!dmabuf || !dmabuf->resv) return EPOLLERR; resv = dmabuf->resv; poll_wait(file, &dmabuf->poll, poll); events = poll_requested_events(poll) & (EPOLLIN | EPOLLOUT); if (!events) return 0; retry: seq = read_seqcount_begin(&resv->seq); rcu_read_lock(); fobj = rcu_dereference(resv->fence); if (fobj) shared_count = fobj->shared_count; else shared_count = 0; fence_excl = rcu_dereference(resv->fence_excl); if (read_seqcount_retry(&resv->seq, seq)) { rcu_read_unlock(); goto retry; } if (fence_excl && (!(events & EPOLLOUT) || shared_count == 0)) { struct dma_buf_poll_cb_t *dcb = &dmabuf->cb_excl; __poll_t pevents = EPOLLIN; if (shared_count == 0) pevents |= EPOLLOUT; spin_lock_irq(&dmabuf->poll.lock); if (dcb->active) { dcb->active |= pevents; events &= ~pevents; } else dcb->active = pevents; spin_unlock_irq(&dmabuf->poll.lock); if (events & pevents) { if (!dma_fence_get_rcu(fence_excl)) { /* force a recheck */ events &= ~pevents; dma_buf_poll_cb(NULL, &dcb->cb); } else if (!dma_fence_add_callback(fence_excl, &dcb->cb, dma_buf_poll_cb)) { events &= ~pevents; dma_fence_put(fence_excl); } else { /* * No callback queued, wake up any additional * waiters. */ dma_fence_put(fence_excl); dma_buf_poll_cb(NULL, &dcb->cb); } } } if ((events & EPOLLOUT) && shared_count > 0) { struct dma_buf_poll_cb_t *dcb = &dmabuf->cb_shared; int i; /* Only queue a new callback if no event has fired yet */ spin_lock_irq(&dmabuf->poll.lock); if (dcb->active) events &= ~EPOLLOUT; else dcb->active = EPOLLOUT; spin_unlock_irq(&dmabuf->poll.lock); if (!(events & EPOLLOUT)) goto out; for (i = 0; i < shared_count; ++i) { struct dma_fence *fence = rcu_dereference(fobj->shared[i]); if (!dma_fence_get_rcu(fence)) { /* * fence refcount dropped to zero, this means * that fobj has been freed * * call dma_buf_poll_cb and force a recheck! */ events &= ~EPOLLOUT; dma_buf_poll_cb(NULL, &dcb->cb); break; } if (!dma_fence_add_callback(fence, &dcb->cb, dma_buf_poll_cb)) { dma_fence_put(fence); events &= ~EPOLLOUT; break; } dma_fence_put(fence); } /* No callback queued, wake up any additional waiters. */ if (i == shared_count) dma_buf_poll_cb(NULL, &dcb->cb); } out: rcu_read_unlock(); return events; } /** * dma_buf_set_name - Set a name to a specific dma_buf to track the usage. * The name of the dma-buf buffer can only be set when the dma-buf is not * attached to any devices. It could theoritically support changing the * name of the dma-buf if the same piece of memory is used for multiple * purpose between different devices. * * @dmabuf: [in] dmabuf buffer that will be renamed. * @buf: [in] A piece of userspace memory that contains the name of * the dma-buf. * * Returns 0 on success. If the dma-buf buffer is already attached to * devices, return -EBUSY. * */ static long dma_buf_set_name(struct dma_buf *dmabuf, const char __user *buf) { char *name = strndup_user(buf, DMA_BUF_NAME_LEN); long ret = 0; if (IS_ERR(name)) return PTR_ERR(name); dma_resv_lock(dmabuf->resv, NULL); if (!list_empty(&dmabuf->attachments)) { ret = -EBUSY; kfree(name); goto out_unlock; } spin_lock(&dmabuf->name_lock); kfree(dmabuf->name); dmabuf->name = name; spin_unlock(&dmabuf->name_lock); out_unlock: dma_resv_unlock(dmabuf->resv); return ret; } static long dma_buf_ioctl(struct file *file, unsigned int cmd, unsigned long arg) { struct dma_buf *dmabuf; struct dma_buf_sync sync; enum dma_data_direction direction; int ret; dmabuf = file->private_data; switch (cmd) { case DMA_BUF_IOCTL_SYNC: if (copy_from_user(&sync, (void __user *) arg, sizeof(sync))) return -EFAULT; if (sync.flags & ~DMA_BUF_SYNC_VALID_FLAGS_MASK) return -EINVAL; switch (sync.flags & DMA_BUF_SYNC_RW) { case DMA_BUF_SYNC_READ: direction = DMA_FROM_DEVICE; break; case DMA_BUF_SYNC_WRITE: direction = DMA_TO_DEVICE; break; case DMA_BUF_SYNC_RW: direction = DMA_BIDIRECTIONAL; break; default: return -EINVAL; } if (sync.flags & DMA_BUF_SYNC_END) ret = dma_buf_end_cpu_access(dmabuf, direction); else ret = dma_buf_begin_cpu_access(dmabuf, direction); return ret; case DMA_BUF_SET_NAME_A: case DMA_BUF_SET_NAME_B: return dma_buf_set_name(dmabuf, (const char __user *)arg); default: return -ENOTTY; } } static void dma_buf_show_fdinfo(struct seq_file *m, struct file *file) { struct dma_buf *dmabuf = file->private_data; seq_printf(m, "size:\t%zu\n", dmabuf->size); /* Don't count the temporary reference taken inside procfs seq_show */ seq_printf(m, "count:\t%ld\n", file_count(dmabuf->file) - 1); seq_printf(m, "exp_name:\t%s\n", dmabuf->exp_name); spin_lock(&dmabuf->name_lock); if (dmabuf->name) seq_printf(m, "name:\t%s\n", dmabuf->name); spin_unlock(&dmabuf->name_lock); } static const struct file_operations dma_buf_fops = { .mmap = dma_buf_mmap_internal, .llseek = dma_buf_llseek, .poll = dma_buf_poll, .unlocked_ioctl = dma_buf_ioctl, .compat_ioctl = compat_ptr_ioctl, .show_fdinfo = dma_buf_show_fdinfo, }; /* * is_dma_buf_file - Check if struct file* is associated with dma_buf */ static inline int is_dma_buf_file(struct file *file) { return file->f_op == &dma_buf_fops; } static struct file *dma_buf_getfile(struct dma_buf *dmabuf, int flags) { struct file *file; struct inode *inode = alloc_anon_inode(dma_buf_mnt->mnt_sb); if (IS_ERR(inode)) return ERR_CAST(inode); inode->i_size = dmabuf->size; inode_set_bytes(inode, dmabuf->size); file = alloc_file_pseudo(inode, dma_buf_mnt, "dmabuf", flags, &dma_buf_fops); if (IS_ERR(file)) goto err_alloc_file; file->f_flags = flags & (O_ACCMODE | O_NONBLOCK); file->private_data = dmabuf; file->f_path.dentry->d_fsdata = dmabuf; return file; err_alloc_file: iput(inode); return file; } /** * DOC: dma buf device access * * For device DMA access to a shared DMA buffer the usual sequence of operations * is fairly simple: * * 1. The exporter defines his exporter instance using * DEFINE_DMA_BUF_EXPORT_INFO() and calls dma_buf_export() to wrap a private * buffer object into a &dma_buf. It then exports that &dma_buf to userspace * as a file descriptor by calling dma_buf_fd(). * * 2. Userspace passes this file-descriptors to all drivers it wants this buffer * to share with: First the filedescriptor is converted to a &dma_buf using * dma_buf_get(). Then the buffer is attached to the device using * dma_buf_attach(). * * Up to this stage the exporter is still free to migrate or reallocate the * backing storage. * * 3. Once the buffer is attached to all devices userspace can initiate DMA * access to the shared buffer. In the kernel this is done by calling * dma_buf_map_attachment() and dma_buf_unmap_attachment(). * * 4. Once a driver is done with a shared buffer it needs to call * dma_buf_detach() (after cleaning up any mappings) and then release the * reference acquired with dma_buf_get by calling dma_buf_put(). * * For the detailed semantics exporters are expected to implement see * &dma_buf_ops. */ /** * dma_buf_export - Creates a new dma_buf, and associates an anon file * with this buffer, so it can be exported. * Also connect the allocator specific data and ops to the buffer. * Additionally, provide a name string for exporter; useful in debugging. * * @exp_info: [in] holds all the export related information provided * by the exporter. see &struct dma_buf_export_info * for further details. * * Returns, on success, a newly created dma_buf object, which wraps the * supplied private data and operations for dma_buf_ops. On either missing * ops, or error in allocating struct dma_buf, will return negative error. * * For most cases the easiest way to create @exp_info is through the * %DEFINE_DMA_BUF_EXPORT_INFO macro. */ struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info) { struct dma_buf *dmabuf; struct dma_resv *resv = exp_info->resv; struct file *file; size_t alloc_size = sizeof(struct dma_buf); int ret; if (!exp_info->resv) alloc_size += sizeof(struct dma_resv); else /* prevent &dma_buf[1] == dma_buf->resv */ alloc_size += 1; if (WARN_ON(!exp_info->priv || !exp_info->ops || !exp_info->ops->map_dma_buf || !exp_info->ops->unmap_dma_buf || !exp_info->ops->release)) { return ERR_PTR(-EINVAL); } if (WARN_ON(exp_info->ops->cache_sgt_mapping && (exp_info->ops->pin || exp_info->ops->unpin))) return ERR_PTR(-EINVAL); if (WARN_ON(!exp_info->ops->pin != !exp_info->ops->unpin)) return ERR_PTR(-EINVAL); if (!try_module_get(exp_info->owner)) return ERR_PTR(-ENOENT); dmabuf = kzalloc(alloc_size, GFP_KERNEL); if (!dmabuf) { ret = -ENOMEM; goto err_module; } dmabuf->priv = exp_info->priv; dmabuf->ops = exp_info->ops; dmabuf->size = exp_info->size; dmabuf->exp_name = exp_info->exp_name; dmabuf->owner = exp_info->owner; spin_lock_init(&dmabuf->name_lock); init_waitqueue_head(&dmabuf->poll); dmabuf->cb_excl.poll = dmabuf->cb_shared.poll = &dmabuf->poll; dmabuf->cb_excl.active = dmabuf->cb_shared.active = 0; if (!resv) { resv = (struct dma_resv *)&dmabuf[1]; dma_resv_init(resv); } dmabuf->resv = resv; file = dma_buf_getfile(dmabuf, exp_info->flags); if (IS_ERR(file)) { ret = PTR_ERR(file); goto err_dmabuf; } file->f_mode |= FMODE_LSEEK; dmabuf->file = file; mutex_init(&dmabuf->lock); INIT_LIST_HEAD(&dmabuf->attachments); mutex_lock(&db_list.lock); list_add(&dmabuf->list_node, &db_list.head); mutex_unlock(&db_list.lock); return dmabuf; err_dmabuf: kfree(dmabuf); err_module: module_put(exp_info->owner); return ERR_PTR(ret); } EXPORT_SYMBOL_GPL(dma_buf_export); /** * dma_buf_fd - returns a file descriptor for the given dma_buf * @dmabuf: [in] pointer to dma_buf for which fd is required. * @flags: [in] flags to give to fd * * On success, returns an associated 'fd'. Else, returns error. */ int dma_buf_fd(struct dma_buf *dmabuf, int flags) { int fd; if (!dmabuf || !dmabuf->file) return -EINVAL; fd = get_unused_fd_flags(flags); if (fd < 0) return fd; fd_install(fd, dmabuf->file); return fd; } EXPORT_SYMBOL_GPL(dma_buf_fd); /** * dma_buf_get - returns the dma_buf structure related to an fd * @fd: [in] fd associated with the dma_buf to be returned * * On success, returns the dma_buf structure associated with an fd; uses * file's refcounting done by fget to increase refcount. returns ERR_PTR * otherwise. */ struct dma_buf *dma_buf_get(int fd) { struct file *file; file = fget(fd); if (!file) return ERR_PTR(-EBADF); if (!is_dma_buf_file(file)) { fput(file); return ERR_PTR(-EINVAL); } return file->private_data; } EXPORT_SYMBOL_GPL(dma_buf_get); /** * dma_buf_put - decreases refcount of the buffer * @dmabuf: [in] buffer to reduce refcount of * * Uses file's refcounting done implicitly by fput(). * * If, as a result of this call, the refcount becomes 0, the 'release' file * operation related to this fd is called. It calls &dma_buf_ops.release vfunc * in turn, and frees the memory allocated for dmabuf when exported. */ void dma_buf_put(struct dma_buf *dmabuf) { if (WARN_ON(!dmabuf || !dmabuf->file)) return; fput(dmabuf->file); } EXPORT_SYMBOL_GPL(dma_buf_put); /** * dma_buf_dynamic_attach - Add the device to dma_buf's attachments list; optionally, * calls attach() of dma_buf_ops to allow device-specific attach functionality * @dmabuf: [in] buffer to attach device to. * @dev: [in] device to be attached. * @importer_ops: [in] importer operations for the attachment * @importer_priv: [in] importer private pointer for the attachment * * Returns struct dma_buf_attachment pointer for this attachment. Attachments * must be cleaned up by calling dma_buf_detach(). * * Returns: * * A pointer to newly created &dma_buf_attachment on success, or a negative * error code wrapped into a pointer on failure. * * Note that this can fail if the backing storage of @dmabuf is in a place not * accessible to @dev, and cannot be moved to a more suitable place. This is * indicated with the error code -EBUSY. */ 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) { struct dma_buf_attachment *attach; int ret; if (WARN_ON(!dmabuf || !dev)) return ERR_PTR(-EINVAL); if (WARN_ON(importer_ops && !importer_ops->move_notify)) return ERR_PTR(-EINVAL); attach = kzalloc(sizeof(*attach), GFP_KERNEL); if (!attach) return ERR_PTR(-ENOMEM); attach->dev = dev; attach->dmabuf = dmabuf; if (importer_ops) attach->peer2peer = importer_ops->allow_peer2peer; attach->importer_ops = importer_ops; attach->importer_priv = importer_priv; if (dmabuf->ops->attach) { ret = dmabuf->ops->attach(dmabuf, attach); if (ret) goto err_attach; } dma_resv_lock(dmabuf->resv, NULL); list_add(&attach->node, &dmabuf->attachments); dma_resv_unlock(dmabuf->resv); /* When either the importer or the exporter can't handle dynamic * mappings we cache the mapping here to avoid issues with the * reservation object lock. */ if (dma_buf_attachment_is_dynamic(attach) != dma_buf_is_dynamic(dmabuf)) { struct sg_table *sgt; if (dma_buf_is_dynamic(attach->dmabuf)) { dma_resv_lock(attach->dmabuf->resv, NULL); ret = dma_buf_pin(attach); if (ret) goto err_unlock; } sgt = dmabuf->ops->map_dma_buf(attach, DMA_BIDIRECTIONAL); if (!sgt) sgt = ERR_PTR(-ENOMEM); if (IS_ERR(sgt)) { ret = PTR_ERR(sgt); goto err_unpin; } if (dma_buf_is_dynamic(attach->dmabuf)) dma_resv_unlock(attach->dmabuf->resv); attach->sgt = sgt; attach->dir = DMA_BIDIRECTIONAL; } return attach; err_attach: kfree(attach); return ERR_PTR(ret); err_unpin: if (dma_buf_is_dynamic(attach->dmabuf)) dma_buf_unpin(attach); err_unlock: if (dma_buf_is_dynamic(attach->dmabuf)) dma_resv_unlock(attach->dmabuf->resv); dma_buf_detach(dmabuf, attach); return ERR_PTR(ret); } EXPORT_SYMBOL_GPL(dma_buf_dynamic_attach); /** * dma_buf_attach - Wrapper for dma_buf_dynamic_attach * @dmabuf: [in] buffer to attach device to. * @dev: [in] device to be attached. * * Wrapper to call dma_buf_dynamic_attach() for drivers which still use a static * mapping. */ struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf, struct device *dev) { return dma_buf_dynamic_attach(dmabuf, dev, NULL, NULL); } EXPORT_SYMBOL_GPL(dma_buf_attach); /** * dma_buf_detach - Remove the given attachment from dmabuf's attachments list; * optionally calls detach() of dma_buf_ops for device-specific detach * @dmabuf: [in] buffer to detach from. * @attach: [in] attachment to be detached; is free'd after this call. * * Clean up a device attachment obtained by calling dma_buf_attach(). */ void dma_buf_detach(struct dma_buf *dmabuf, struct dma_buf_attachment *attach) { if (WARN_ON(!dmabuf || !attach)) return; if (attach->sgt) { if (dma_buf_is_dynamic(attach->dmabuf)) dma_resv_lock(attach->dmabuf->resv, NULL); dmabuf->ops->unmap_dma_buf(attach, attach->sgt, attach->dir); if (dma_buf_is_dynamic(attach->dmabuf)) { dma_buf_unpin(attach); dma_resv_unlock(attach->dmabuf->resv); } } dma_resv_lock(dmabuf->resv, NULL); list_del(&attach->node); dma_resv_unlock(dmabuf->resv); if (dmabuf->ops->detach) dmabuf->ops->detach(dmabuf, attach); kfree(attach); } EXPORT_SYMBOL_GPL(dma_buf_detach); /** * dma_buf_pin - Lock down the DMA-buf * * @attach: [in] attachment which should be pinned * * Returns: * 0 on success, negative error code on failure. */ int dma_buf_pin(struct dma_buf_attachment *attach) { struct dma_buf *dmabuf = attach->dmabuf; int ret = 0; dma_resv_assert_held(dmabuf->resv); if (dmabuf->ops->pin) ret = dmabuf->ops->pin(attach); return ret; } EXPORT_SYMBOL_GPL(dma_buf_pin); /** * dma_buf_unpin - Remove lock from DMA-buf * * @attach: [in] attachment which should be unpinned */ void dma_buf_unpin(struct dma_buf_attachment *attach) { struct dma_buf *dmabuf = attach->dmabuf; dma_resv_assert_held(dmabuf->resv); if (dmabuf->ops->unpin) dmabuf->ops->unpin(attach); } EXPORT_SYMBOL_GPL(dma_buf_unpin); /** * dma_buf_map_attachment - Returns the scatterlist table of the attachment; * mapped into _device_ address space. Is a wrapper for map_dma_buf() of the * dma_buf_ops. * @attach: [in] attachment whose scatterlist is to be returned * @direction: [in] direction of DMA transfer * * Returns sg_table containing the scatterlist to be returned; returns ERR_PTR * on error. May return -EINTR if it is interrupted by a signal. * * A mapping must be unmapped by using dma_buf_unmap_attachment(). Note that * the underlying backing storage is pinned for as long as a mapping exists, * therefore users/importers should not hold onto a mapping for undue amounts of * time. */ struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach, enum dma_data_direction direction) { struct sg_table *sg_table; int r; might_sleep(); if (WARN_ON(!attach || !attach->dmabuf)) return ERR_PTR(-EINVAL); if (dma_buf_attachment_is_dynamic(attach)) dma_resv_assert_held(attach->dmabuf->resv); if (attach->sgt) { /* * Two mappings with different directions for the same * attachment are not allowed. */ if (attach->dir != direction && attach->dir != DMA_BIDIRECTIONAL) return ERR_PTR(-EBUSY); return attach->sgt; } if (dma_buf_is_dynamic(attach->dmabuf)) { dma_resv_assert_held(attach->dmabuf->resv); if (!IS_ENABLED(CONFIG_DMABUF_MOVE_NOTIFY)) { r = dma_buf_pin(attach); if (r) return ERR_PTR(r); } } sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction); if (!sg_table) sg_table = ERR_PTR(-ENOMEM); if (IS_ERR(sg_table) && dma_buf_is_dynamic(attach->dmabuf) && !IS_ENABLED(CONFIG_DMABUF_MOVE_NOTIFY)) dma_buf_unpin(attach); if (!IS_ERR(sg_table) && attach->dmabuf->ops->cache_sgt_mapping) { attach->sgt = sg_table; attach->dir = direction; } return sg_table; } EXPORT_SYMBOL_GPL(dma_buf_map_attachment); /** * dma_buf_unmap_attachment - unmaps and decreases usecount of the buffer;might * deallocate the scatterlist associated. Is a wrapper for unmap_dma_buf() of * dma_buf_ops. * @attach: [in] attachment to unmap buffer from * @sg_table: [in] scatterlist info of the buffer to unmap * @direction: [in] direction of DMA transfer * * This unmaps a DMA mapping for @attached obtained by dma_buf_map_attachment(). */ void dma_buf_unmap_attachment(struct dma_buf_attachment *attach, struct sg_table *sg_table, enum dma_data_direction direction) { might_sleep(); if (WARN_ON(!attach || !attach->dmabuf || !sg_table)) return; if (dma_buf_attachment_is_dynamic(attach)) dma_resv_assert_held(attach->dmabuf->resv); if (attach->sgt == sg_table) return; if (dma_buf_is_dynamic(attach->dmabuf)) dma_resv_assert_held(attach->dmabuf->resv); attach->dmabuf->ops->unmap_dma_buf(attach, sg_table, direction); if (dma_buf_is_dynamic(attach->dmabuf) && !IS_ENABLED(CONFIG_DMABUF_MOVE_NOTIFY)) dma_buf_unpin(attach); } EXPORT_SYMBOL_GPL(dma_buf_unmap_attachment); /** * dma_buf_move_notify - notify attachments that DMA-buf is moving * * @dmabuf: [in] buffer which is moving * * Informs all attachmenst that they need to destroy and recreated all their * mappings. */ void dma_buf_move_notify(struct dma_buf *dmabuf) { struct dma_buf_attachment *attach; dma_resv_assert_held(dmabuf->resv); list_for_each_entry(attach, &dmabuf->attachments, node) if (attach->importer_ops) attach->importer_ops->move_notify(attach); } EXPORT_SYMBOL_GPL(dma_buf_move_notify); /** * DOC: cpu access * * There are mutliple reasons for supporting CPU access to a dma buffer object: * * - Fallback operations in the kernel, for example when a device is connected * over USB and the kernel needs to shuffle the data around first before * sending it away. Cache coherency is handled by braketing any transactions * with calls to dma_buf_begin_cpu_access() and dma_buf_end_cpu_access() * access. * * Since for most kernel internal dma-buf accesses need the entire buffer, a * vmap interface is introduced. Note that on very old 32-bit architectures * vmalloc space might be limited and result in vmap calls failing. * * Interfaces:: * void \*dma_buf_vmap(struct dma_buf \*dmabuf) * void dma_buf_vunmap(struct dma_buf \*dmabuf, void \*vaddr) * * The vmap call can fail if there is no vmap support in the exporter, or if * it runs out of vmalloc space. Fallback to kmap should be implemented. Note * that the dma-buf layer keeps a reference count for all vmap access and * calls down into the exporter's vmap function only when no vmapping exists, * and only unmaps it once. Protection against concurrent vmap/vunmap calls is * provided by taking the dma_buf->lock mutex. * * - For full compatibility on the importer side with existing userspace * interfaces, which might already support mmap'ing buffers. This is needed in * many processing pipelines (e.g. feeding a software rendered image into a * hardware pipeline, thumbnail creation, snapshots, ...). Also, Android's ION * framework already supported this and for DMA buffer file descriptors to * replace ION buffers mmap support was needed. * * There is no special interfaces, userspace simply calls mmap on the dma-buf * fd. But like for CPU access there's a need to braket the actual access, * which is handled by the ioctl (DMA_BUF_IOCTL_SYNC). Note that * DMA_BUF_IOCTL_SYNC can fail with -EAGAIN or -EINTR, in which case it must * be restarted. * * Some systems might need some sort of cache coherency management e.g. when * CPU and GPU domains are being accessed through dma-buf at the same time. * To circumvent this problem there are begin/end coherency markers, that * forward directly to existing dma-buf device drivers vfunc hooks. Userspace * can make use of those markers through the DMA_BUF_IOCTL_SYNC ioctl. The * sequence would be used like following: * * - mmap dma-buf fd * - for each drawing/upload cycle in CPU 1. SYNC_START ioctl, 2. read/write * to mmap area 3. SYNC_END ioctl. This can be repeated as often as you * want (with the new data being consumed by say the GPU or the scanout * device) * - munmap once you don't need the buffer any more * * For correctness and optimal performance, it is always required to use * SYNC_START and SYNC_END before and after, respectively, when accessing the * mapped address. Userspace cannot rely on coherent access, even when there * are systems where it just works without calling these ioctls. * * - And as a CPU fallback in userspace processing pipelines. * * Similar to the motivation for kernel cpu access it is again important that * the userspace code of a given importing subsystem can use the same * interfaces with a imported dma-buf buffer object as with a native buffer * object. This is especially important for drm where the userspace part of * contemporary OpenGL, X, and other drivers is huge, and reworking them to * use a different way to mmap a buffer rather invasive. * * The assumption in the current dma-buf interfaces is that redirecting the * initial mmap is all that's needed. A survey of some of the existing * subsystems shows that no driver seems to do any nefarious thing like * syncing up with outstanding asynchronous processing on the device or * allocating special resources at fault time. So hopefully this is good * enough, since adding interfaces to intercept pagefaults and allow pte * shootdowns would increase the complexity quite a bit. * * Interface:: * int dma_buf_mmap(struct dma_buf \*, struct vm_area_struct \*, * unsigned long); * * If the importing subsystem simply provides a special-purpose mmap call to * set up a mapping in userspace, calling do_mmap with dma_buf->file will * equally achieve that for a dma-buf object. */ static int __dma_buf_begin_cpu_access(struct dma_buf *dmabuf, enum dma_data_direction direction) { bool write = (direction == DMA_BIDIRECTIONAL || direction == DMA_TO_DEVICE); struct dma_resv *resv = dmabuf->resv; long ret; /* Wait on any implicit rendering fences */ ret = dma_resv_wait_timeout_rcu(resv, write, true, MAX_SCHEDULE_TIMEOUT); if (ret < 0) return ret; return 0; } /** * dma_buf_begin_cpu_access - Must be called before accessing a dma_buf from the * cpu in the kernel context. Calls begin_cpu_access to allow exporter-specific * preparations. Coherency is only guaranteed in the specified range for the * specified access direction. * @dmabuf: [in] buffer to prepare cpu access for. * @direction: [in] length of range for cpu access. * * After the cpu access is complete the caller should call * dma_buf_end_cpu_access(). Only when cpu access is braketed by both calls is * it guaranteed to be coherent with other DMA access. * * Can return negative error values, returns 0 on success. */ int dma_buf_begin_cpu_access(struct dma_buf *dmabuf, enum dma_data_direction direction) { int ret = 0; if (WARN_ON(!dmabuf)) return -EINVAL; if (dmabuf->ops->begin_cpu_access) ret = dmabuf->ops->begin_cpu_access(dmabuf, direction); /* Ensure that all fences are waited upon - but we first allow * the native handler the chance to do so more efficiently if it * chooses. A double invocation here will be reasonably cheap no-op. */ if (ret == 0) ret = __dma_buf_begin_cpu_access(dmabuf, direction); return ret; } EXPORT_SYMBOL_GPL(dma_buf_begin_cpu_access); /** * dma_buf_end_cpu_access - Must be called after accessing a dma_buf from the * cpu in the kernel context. Calls end_cpu_access to allow exporter-specific * actions. Coherency is only guaranteed in the specified range for the * specified access direction. * @dmabuf: [in] buffer to complete cpu access for. * @direction: [in] length of range for cpu access. * * This terminates CPU access started with dma_buf_begin_cpu_access(). * * Can return negative error values, returns 0 on success. */ int dma_buf_end_cpu_access(struct dma_buf *dmabuf, enum dma_data_direction direction) { int ret = 0; WARN_ON(!dmabuf); if (dmabuf->ops->end_cpu_access) ret = dmabuf->ops->end_cpu_access(dmabuf, direction); return ret; } EXPORT_SYMBOL_GPL(dma_buf_end_cpu_access); /** * dma_buf_mmap - Setup up a userspace mmap with the given vma * @dmabuf: [in] buffer that should back the vma * @vma: [in] vma for the mmap * @pgoff: [in] offset in pages where this mmap should start within the * dma-buf buffer. * * This function adjusts the passed in vma so that it points at the file of the * dma_buf operation. It also adjusts the starting pgoff and does bounds * checking on the size of the vma. Then it calls the exporters mmap function to * set up the mapping. * * Can return negative error values, returns 0 on success. */ int dma_buf_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma, unsigned long pgoff) { struct file *oldfile; int ret; if (WARN_ON(!dmabuf || !vma)) return -EINVAL; /* check if buffer supports mmap */ if (!dmabuf->ops->mmap) return -EINVAL; /* check for offset overflow */ if (pgoff + vma_pages(vma) < pgoff) return -EOVERFLOW; /* check for overflowing the buffer's size */ if (pgoff + vma_pages(vma) > dmabuf->size >> PAGE_SHIFT) return -EINVAL; /* readjust the vma */ get_file(dmabuf->file); oldfile = vma->vm_file; vma->vm_file = dmabuf->file; vma->vm_pgoff = pgoff; ret = dmabuf->ops->mmap(dmabuf, vma); if (ret) { /* restore old parameters on failure */ vma->vm_file = oldfile; fput(dmabuf->file); } else { if (oldfile) fput(oldfile); } return ret; } EXPORT_SYMBOL_GPL(dma_buf_mmap); /** * dma_buf_vmap - Create virtual mapping for the buffer object into kernel * address space. Same restrictions as for vmap and friends apply. * @dmabuf: [in] buffer to vmap * * This call may fail due to lack of virtual mapping address space. * These calls are optional in drivers. The intended use for them * is for mapping objects linear in kernel space for high use objects. * Please attempt to use kmap/kunmap before thinking about these interfaces. * * Returns NULL on error. */ void *dma_buf_vmap(struct dma_buf *dmabuf) { void *ptr; if (WARN_ON(!dmabuf)) return NULL; if (!dmabuf->ops->vmap) return NULL; mutex_lock(&dmabuf->lock); if (dmabuf->vmapping_counter) { dmabuf->vmapping_counter++; BUG_ON(dma_buf_map_is_null(&dmabuf->vmap_ptr)); ptr = dmabuf->vmap_ptr.vaddr; goto out_unlock; } BUG_ON(dma_buf_map_is_set(&dmabuf->vmap_ptr)); ptr = dmabuf->ops->vmap(dmabuf); if (WARN_ON_ONCE(IS_ERR(ptr))) ptr = NULL; if (!ptr) goto out_unlock; dmabuf->vmap_ptr.vaddr = ptr; dmabuf->vmapping_counter = 1; out_unlock: mutex_unlock(&dmabuf->lock); return ptr; } EXPORT_SYMBOL_GPL(dma_buf_vmap); /** * dma_buf_vunmap - Unmap a vmap obtained by dma_buf_vmap. * @dmabuf: [in] buffer to vunmap * @vaddr: [in] vmap to vunmap */ void dma_buf_vunmap(struct dma_buf *dmabuf, void *vaddr) { if (WARN_ON(!dmabuf)) return; BUG_ON(dma_buf_map_is_null(&dmabuf->vmap_ptr)); BUG_ON(dmabuf->vmapping_counter == 0); BUG_ON(!dma_buf_map_is_vaddr(&dmabuf->vmap_ptr, vaddr)); mutex_lock(&dmabuf->lock); if (--dmabuf->vmapping_counter == 0) { if (dmabuf->ops->vunmap) dmabuf->ops->vunmap(dmabuf, vaddr); dma_buf_map_clear(&dmabuf->vmap_ptr); } mutex_unlock(&dmabuf->lock); } EXPORT_SYMBOL_GPL(dma_buf_vunmap); #ifdef CONFIG_DEBUG_FS static int dma_buf_debug_show(struct seq_file *s, void *unused) { int ret; struct dma_buf *buf_obj; struct dma_buf_attachment *attach_obj; struct dma_resv *robj; struct dma_resv_list *fobj; struct dma_fence *fence; unsigned seq; int count = 0, attach_count, shared_count, i; size_t size = 0; ret = mutex_lock_interruptible(&db_list.lock); if (ret) return ret; seq_puts(s, "\nDma-buf Objects:\n"); seq_printf(s, "%-8s\t%-8s\t%-8s\t%-8s\texp_name\t%-8s\n", "size", "flags", "mode", "count", "ino"); list_for_each_entry(buf_obj, &db_list.head, list_node) { ret = dma_resv_lock_interruptible(buf_obj->resv, NULL); if (ret) goto error_unlock; seq_printf(s, "%08zu\t%08x\t%08x\t%08ld\t%s\t%08lu\t%s\n", buf_obj->size, buf_obj->file->f_flags, buf_obj->file->f_mode, file_count(buf_obj->file), buf_obj->exp_name, file_inode(buf_obj->file)->i_ino, buf_obj->name ?: ""); robj = buf_obj->resv; while (true) { seq = read_seqcount_begin(&robj->seq); rcu_read_lock(); fobj = rcu_dereference(robj->fence); shared_count = fobj ? fobj->shared_count : 0; fence = rcu_dereference(robj->fence_excl); if (!read_seqcount_retry(&robj->seq, seq)) break; rcu_read_unlock(); } if (fence) seq_printf(s, "\tExclusive fence: %s %s %ssignalled\n", fence->ops->get_driver_name(fence), fence->ops->get_timeline_name(fence), dma_fence_is_signaled(fence) ? "" : "un"); for (i = 0; i < shared_count; i++) { fence = rcu_dereference(fobj->shared[i]); if (!dma_fence_get_rcu(fence)) continue; seq_printf(s, "\tShared fence: %s %s %ssignalled\n", fence->ops->get_driver_name(fence), fence->ops->get_timeline_name(fence), dma_fence_is_signaled(fence) ? "" : "un"); dma_fence_put(fence); } rcu_read_unlock(); seq_puts(s, "\tAttached Devices:\n"); attach_count = 0; list_for_each_entry(attach_obj, &buf_obj->attachments, node) { seq_printf(s, "\t%s\n", dev_name(attach_obj->dev)); attach_count++; } dma_resv_unlock(buf_obj->resv); seq_printf(s, "Total %d devices attached\n\n", attach_count); count++; size += buf_obj->size; } seq_printf(s, "\nTotal %d objects, %zu bytes\n", count, size); mutex_unlock(&db_list.lock); return 0; error_unlock: mutex_unlock(&db_list.lock); return ret; } DEFINE_SHOW_ATTRIBUTE(dma_buf_debug); static struct dentry *dma_buf_debugfs_dir; static int dma_buf_init_debugfs(void) { struct dentry *d; int err = 0; d = debugfs_create_dir("dma_buf", NULL); if (IS_ERR(d)) return PTR_ERR(d); dma_buf_debugfs_dir = d; d = debugfs_create_file("bufinfo", S_IRUGO, dma_buf_debugfs_dir, NULL, &dma_buf_debug_fops); if (IS_ERR(d)) { pr_debug("dma_buf: debugfs: failed to create node bufinfo\n"); debugfs_remove_recursive(dma_buf_debugfs_dir); dma_buf_debugfs_dir = NULL; err = PTR_ERR(d); } return err; } static void dma_buf_uninit_debugfs(void) { debugfs_remove_recursive(dma_buf_debugfs_dir); } #else static inline int dma_buf_init_debugfs(void) { return 0; } static inline void dma_buf_uninit_debugfs(void) { } #endif static int __init dma_buf_init(void) { dma_buf_mnt = kern_mount(&dma_buf_fs_type); if (IS_ERR(dma_buf_mnt)) return PTR_ERR(dma_buf_mnt); mutex_init(&db_list.lock); INIT_LIST_HEAD(&db_list.head); dma_buf_init_debugfs(); return 0; } subsys_initcall(dma_buf_init); static void __exit dma_buf_deinit(void) { dma_buf_uninit_debugfs(); kern_unmount(dma_buf_mnt); } __exitcall(dma_buf_deinit);