Adding upstream version 5.10.209.upstream/5.10.209upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

26 files changed, 7586 insertions, 0 deletions

diff --git a/drivers/dma-buf/Kconfig b/drivers/dma-buf/Kconfig
new file mode 100644
index 000000000..3ca7de37d
--- /dev/null
+++ b/drivers/dma-buf/Kconfig
@@ -0,0 +1,70 @@
+# SPDX-License-Identifier: GPL-2.0-only
+menu "DMABUF options"
+
+config SYNC_FILE
+	bool "Explicit Synchronization Framework"
+	default n
+	select DMA_SHARED_BUFFER
+	help
+	  The Sync File Framework adds explicit synchronization via
+	  userspace. It enables send/receive 'struct dma_fence' objects to/from
+	  userspace via Sync File fds for synchronization between drivers via
+	  userspace components. It has been ported from Android.
+
+	  The first and main user for this is graphics in which a fence is
+	  associated with a buffer. When a job is submitted to the GPU a fence
+	  is attached to the buffer and is transferred via userspace, using Sync
+	  Files fds, to the DRM driver for example. More details at
+	  Documentation/driver-api/sync_file.rst.
+
+config SW_SYNC
+	bool "Sync File Validation Framework"
+	default n
+	depends on SYNC_FILE
+	depends on DEBUG_FS
+	help
+	  A sync object driver that uses a 32bit counter to coordinate
+	  synchronization.  Useful when there is no hardware primitive backing
+	  the synchronization.
+
+	  WARNING: improper use of this can result in deadlocking kernel
+	  drivers from userspace. Intended for test and debug only.
+
+config UDMABUF
+	bool "userspace dmabuf misc driver"
+	default n
+	depends on DMA_SHARED_BUFFER
+	depends on MEMFD_CREATE || COMPILE_TEST
+	help
+	  A driver to let userspace turn memfd regions into dma-bufs.
+	  Qemu can use this to create host dmabufs for guest framebuffers.
+
+config DMABUF_MOVE_NOTIFY
+	bool "Move notify between drivers (EXPERIMENTAL)"
+	default n
+	depends on DMA_SHARED_BUFFER
+	help
+	  Don't pin buffers if the dynamic DMA-buf interface is available on
+	  both the exporter as well as the importer. This fixes a security
+	  problem where userspace is able to pin unrestricted amounts of memory
+	  through DMA-buf.
+	  This is marked experimental because we don't yet have a consistent
+	  execution context and memory management between drivers.
+
+config DMABUF_SELFTESTS
+	tristate "Selftests for the dma-buf interfaces"
+	default n
+	depends on DMA_SHARED_BUFFER
+
+menuconfig DMABUF_HEAPS
+	bool "DMA-BUF Userland Memory Heaps"
+	select DMA_SHARED_BUFFER
+	help
+	  Choose this option to enable the DMA-BUF userland memory heaps.
+	  This options creates per heap chardevs in /dev/dma_heap/ which
+	  allows userspace to allocate dma-bufs that can be shared
+	  between drivers.
+
+source "drivers/dma-buf/heaps/Kconfig"
+
+endmenu
diff --git a/drivers/dma-buf/Makefile b/drivers/dma-buf/Makefile
new file mode 100644
index 000000000..995e05f60
--- /dev/null
+++ b/drivers/dma-buf/Makefile
@@ -0,0 +1,15 @@
+# SPDX-License-Identifier: GPL-2.0-only
+obj-y := dma-buf.o dma-fence.o dma-fence-array.o dma-fence-chain.o \
+	 dma-resv.o seqno-fence.o
+obj-$(CONFIG_DMABUF_HEAPS)	+= dma-heap.o
+obj-$(CONFIG_DMABUF_HEAPS)	+= heaps/
+obj-$(CONFIG_SYNC_FILE)		+= sync_file.o
+obj-$(CONFIG_SW_SYNC)		+= sw_sync.o sync_debug.o
+obj-$(CONFIG_UDMABUF)		+= udmabuf.o
+
+dmabuf_selftests-y := \
+	selftest.o \
+	st-dma-fence.o \
+	st-dma-fence-chain.o
+
+obj-$(CONFIG_DMABUF_SELFTESTS)	+= dmabuf_selftests.o
diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
new file mode 100644
index 000000000..93e9bf738
--- /dev/null
+++ b/drivers/dma-buf/dma-buf.c
@@ -0,0 +1,1422 @@
+// 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 <sumit.semwal@ti.com>
+ *
+ * Many thanks to linaro-mm-sig list, and specially
+ * Arnd Bergmann <arnd@arndb.de>, Rob Clark <rob@ti.com> and
+ * Daniel Vetter <daniel@ffwll.ch> for their support in creation and
+ * refining of this idea.
+ */
+
+#include <linux/fs.h>
+#include <linux/slab.h>
+#include <linux/dma-buf.h>
+#include <linux/dma-fence.h>
+#include <linux/anon_inodes.h>
+#include <linux/export.h>
+#include <linux/debugfs.h>
+#include <linux/module.h>
+#include <linux/seq_file.h>
+#include <linux/poll.h>
+#include <linux/dma-resv.h>
+#include <linux/mm.h>
+#include <linux/mount.h>
+#include <linux/pseudo_fs.h>
+
+#include <uapi/linux/dma-buf.h>
+#include <uapi/linux/magic.h>
+
+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;
+	if (unlikely(!dmabuf))
+		return;
+
+	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);
+
+	if (dmabuf->resv == (struct dma_resv *)&dmabuf[1])
+		dma_resv_fini(dmabuf->resv);
+
+	WARN_ON(!list_empty(&dmabuf->attachments));
+	module_put(dmabuf->owner);
+	kfree(dmabuf->name);
+	kfree(dmabuf);
+}
+
+static int dma_buf_file_release(struct inode *inode, struct file *file)
+{
+	struct dma_buf *dmabuf;
+
+	if (!is_dma_buf_file(file))
+		return -EINVAL;
+
+	dmabuf = file->private_data;
+
+	mutex_lock(&db_list.lock);
+	list_del(&dmabuf->list_node);
+	mutex_unlock(&db_list.lock);
+
+	return 0;
+}
+
+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 = {
+	.release	= dma_buf_file_release,
+	.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(!dmabuf->vmap_ptr);
+		ptr = dmabuf->vmap_ptr;
+		goto out_unlock;
+	}
+
+	BUG_ON(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 = 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(!dmabuf->vmap_ptr);
+	BUG_ON(dmabuf->vmapping_counter == 0);
+	BUG_ON(dmabuf->vmap_ptr != vaddr);
+
+	mutex_lock(&dmabuf->lock);
+	if (--dmabuf->vmapping_counter == 0) {
+		if (dmabuf->ops->vunmap)
+			dmabuf->ops->vunmap(dmabuf, vaddr);
+		dmabuf->vmap_ptr = NULL;
+	}
+	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);
diff --git a/drivers/dma-buf/dma-fence-array.c b/drivers/dma-buf/dma-fence-array.c
new file mode 100644
index 000000000..3e07f961e
--- /dev/null
+++ b/drivers/dma-buf/dma-fence-array.c
@@ -0,0 +1,207 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * dma-fence-array: aggregate fences to be waited together
+ *
+ * Copyright (C) 2016 Collabora Ltd
+ * Copyright (C) 2016 Advanced Micro Devices, Inc.
+ * Authors:
+ *	Gustavo Padovan <gustavo@padovan.org>
+ *	Christian König <christian.koenig@amd.com>
+ */
+
+#include <linux/export.h>
+#include <linux/slab.h>
+#include <linux/dma-fence-array.h>
+
+#define PENDING_ERROR 1
+
+static const char *dma_fence_array_get_driver_name(struct dma_fence *fence)
+{
+	return "dma_fence_array";
+}
+
+static const char *dma_fence_array_get_timeline_name(struct dma_fence *fence)
+{
+	return "unbound";
+}
+
+static void dma_fence_array_set_pending_error(struct dma_fence_array *array,
+					      int error)
+{
+	/*
+	 * Propagate the first error reported by any of our fences, but only
+	 * before we ourselves are signaled.
+	 */
+	if (error)
+		cmpxchg(&array->base.error, PENDING_ERROR, error);
+}
+
+static void dma_fence_array_clear_pending_error(struct dma_fence_array *array)
+{
+	/* Clear the error flag if not actually set. */
+	cmpxchg(&array->base.error, PENDING_ERROR, 0);
+}
+
+static void irq_dma_fence_array_work(struct irq_work *wrk)
+{
+	struct dma_fence_array *array = container_of(wrk, typeof(*array), work);
+
+	dma_fence_array_clear_pending_error(array);
+
+	dma_fence_signal(&array->base);
+	dma_fence_put(&array->base);
+}
+
+static void dma_fence_array_cb_func(struct dma_fence *f,
+				    struct dma_fence_cb *cb)
+{
+	struct dma_fence_array_cb *array_cb =
+		container_of(cb, struct dma_fence_array_cb, cb);
+	struct dma_fence_array *array = array_cb->array;
+
+	dma_fence_array_set_pending_error(array, f->error);
+
+	if (atomic_dec_and_test(&array->num_pending))
+		irq_work_queue(&array->work);
+	else
+		dma_fence_put(&array->base);
+}
+
+static bool dma_fence_array_enable_signaling(struct dma_fence *fence)
+{
+	struct dma_fence_array *array = to_dma_fence_array(fence);
+	struct dma_fence_array_cb *cb = (void *)(&array[1]);
+	unsigned i;
+
+	for (i = 0; i < array->num_fences; ++i) {
+		cb[i].array = array;
+		/*
+		 * As we may report that the fence is signaled before all
+		 * callbacks are complete, we need to take an additional
+		 * reference count on the array so that we do not free it too
+		 * early. The core fence handling will only hold the reference
+		 * until we signal the array as complete (but that is now
+		 * insufficient).
+		 */
+		dma_fence_get(&array->base);
+		if (dma_fence_add_callback(array->fences[i], &cb[i].cb,
+					   dma_fence_array_cb_func)) {
+			int error = array->fences[i]->error;
+
+			dma_fence_array_set_pending_error(array, error);
+			dma_fence_put(&array->base);
+			if (atomic_dec_and_test(&array->num_pending)) {
+				dma_fence_array_clear_pending_error(array);
+				return false;
+			}
+		}
+	}
+
+	return true;
+}
+
+static bool dma_fence_array_signaled(struct dma_fence *fence)
+{
+	struct dma_fence_array *array = to_dma_fence_array(fence);
+
+	if (atomic_read(&array->num_pending) > 0)
+		return false;
+
+	dma_fence_array_clear_pending_error(array);
+	return true;
+}
+
+static void dma_fence_array_release(struct dma_fence *fence)
+{
+	struct dma_fence_array *array = to_dma_fence_array(fence);
+	unsigned i;
+
+	for (i = 0; i < array->num_fences; ++i)
+		dma_fence_put(array->fences[i]);
+
+	kfree(array->fences);
+	dma_fence_free(fence);
+}
+
+const struct dma_fence_ops dma_fence_array_ops = {
+	.get_driver_name = dma_fence_array_get_driver_name,
+	.get_timeline_name = dma_fence_array_get_timeline_name,
+	.enable_signaling = dma_fence_array_enable_signaling,
+	.signaled = dma_fence_array_signaled,
+	.release = dma_fence_array_release,
+};
+EXPORT_SYMBOL(dma_fence_array_ops);
+
+/**
+ * dma_fence_array_create - Create a custom fence array
+ * @num_fences:		[in]	number of fences to add in the array
+ * @fences:		[in]	array containing the fences
+ * @context:		[in]	fence context to use
+ * @seqno:		[in]	sequence number to use
+ * @signal_on_any:	[in]	signal on any fence in the array
+ *
+ * Allocate a dma_fence_array object and initialize the base fence with
+ * dma_fence_init().
+ * In case of error it returns NULL.
+ *
+ * The caller should allocate the fences array with num_fences size
+ * and fill it with the fences it wants to add to the object. Ownership of this
+ * array is taken and dma_fence_put() is used on each fence on release.
+ *
+ * If @signal_on_any is true the fence array signals if any fence in the array
+ * signals, otherwise it signals when all fences in the array signal.
+ */
+struct dma_fence_array *dma_fence_array_create(int num_fences,
+					       struct dma_fence **fences,
+					       u64 context, unsigned seqno,
+					       bool signal_on_any)
+{
+	struct dma_fence_array *array;
+	size_t size = sizeof(*array);
+
+	/* Allocate the callback structures behind the array. */
+	size += num_fences * sizeof(struct dma_fence_array_cb);
+	array = kzalloc(size, GFP_KERNEL);
+	if (!array)
+		return NULL;
+
+	spin_lock_init(&array->lock);
+	dma_fence_init(&array->base, &dma_fence_array_ops, &array->lock,
+		       context, seqno);
+	init_irq_work(&array->work, irq_dma_fence_array_work);
+
+	array->num_fences = num_fences;
+	atomic_set(&array->num_pending, signal_on_any ? 1 : num_fences);
+	array->fences = fences;
+
+	array->base.error = PENDING_ERROR;
+
+	return array;
+}
+EXPORT_SYMBOL(dma_fence_array_create);
+
+/**
+ * dma_fence_match_context - Check if all fences are from the given context
+ * @fence:		[in]	fence or fence array
+ * @context:		[in]	fence context to check all fences against
+ *
+ * Checks the provided fence or, for a fence array, all fences in the array
+ * against the given context. Returns false if any fence is from a different
+ * context.
+ */
+bool dma_fence_match_context(struct dma_fence *fence, u64 context)
+{
+	struct dma_fence_array *array = to_dma_fence_array(fence);
+	unsigned i;
+
+	if (!dma_fence_is_array(fence))
+		return fence->context == context;
+
+	for (i = 0; i < array->num_fences; i++) {
+		if (array->fences[i]->context != context)
+			return false;
+	}
+
+	return true;
+}
+EXPORT_SYMBOL(dma_fence_match_context);
diff --git a/drivers/dma-buf/dma-fence-chain.c b/drivers/dma-buf/dma-fence-chain.c
new file mode 100644
index 000000000..7d129e68a
--- /dev/null
+++ b/drivers/dma-buf/dma-fence-chain.c
@@ -0,0 +1,258 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * fence-chain: chain fences together in a timeline
+ *
+ * Copyright (C) 2018 Advanced Micro Devices, Inc.
+ * Authors:
+ *	Christian König <christian.koenig@amd.com>
+ */
+
+#include <linux/dma-fence-chain.h>
+
+static bool dma_fence_chain_enable_signaling(struct dma_fence *fence);
+
+/**
+ * dma_fence_chain_get_prev - use RCU to get a reference to the previous fence
+ * @chain: chain node to get the previous node from
+ *
+ * Use dma_fence_get_rcu_safe to get a reference to the previous fence of the
+ * chain node.
+ */
+static struct dma_fence *dma_fence_chain_get_prev(struct dma_fence_chain *chain)
+{
+	struct dma_fence *prev;
+
+	rcu_read_lock();
+	prev = dma_fence_get_rcu_safe(&chain->prev);
+	rcu_read_unlock();
+	return prev;
+}
+
+/**
+ * dma_fence_chain_walk - chain walking function
+ * @fence: current chain node
+ *
+ * Walk the chain to the next node. Returns the next fence or NULL if we are at
+ * the end of the chain. Garbage collects chain nodes which are already
+ * signaled.
+ */
+struct dma_fence *dma_fence_chain_walk(struct dma_fence *fence)
+{
+	struct dma_fence_chain *chain, *prev_chain;
+	struct dma_fence *prev, *replacement, *tmp;
+
+	chain = to_dma_fence_chain(fence);
+	if (!chain) {
+		dma_fence_put(fence);
+		return NULL;
+	}
+
+	while ((prev = dma_fence_chain_get_prev(chain))) {
+
+		prev_chain = to_dma_fence_chain(prev);
+		if (prev_chain) {
+			if (!dma_fence_is_signaled(prev_chain->fence))
+				break;
+
+			replacement = dma_fence_chain_get_prev(prev_chain);
+		} else {
+			if (!dma_fence_is_signaled(prev))
+				break;
+
+			replacement = NULL;
+		}
+
+		tmp = cmpxchg((struct dma_fence __force **)&chain->prev,
+			      prev, replacement);
+		if (tmp == prev)
+			dma_fence_put(tmp);
+		else
+			dma_fence_put(replacement);
+		dma_fence_put(prev);
+	}
+
+	dma_fence_put(fence);
+	return prev;
+}
+EXPORT_SYMBOL(dma_fence_chain_walk);
+
+/**
+ * dma_fence_chain_find_seqno - find fence chain node by seqno
+ * @pfence: pointer to the chain node where to start
+ * @seqno: the sequence number to search for
+ *
+ * Advance the fence pointer to the chain node which will signal this sequence
+ * number. If no sequence number is provided then this is a no-op.
+ *
+ * Returns EINVAL if the fence is not a chain node or the sequence number has
+ * not yet advanced far enough.
+ */
+int dma_fence_chain_find_seqno(struct dma_fence **pfence, uint64_t seqno)
+{
+	struct dma_fence_chain *chain;
+
+	if (!seqno)
+		return 0;
+
+	chain = to_dma_fence_chain(*pfence);
+	if (!chain || chain->base.seqno < seqno)
+		return -EINVAL;
+
+	dma_fence_chain_for_each(*pfence, &chain->base) {
+		if ((*pfence)->context != chain->base.context ||
+		    to_dma_fence_chain(*pfence)->prev_seqno < seqno)
+			break;
+	}
+	dma_fence_put(&chain->base);
+
+	return 0;
+}
+EXPORT_SYMBOL(dma_fence_chain_find_seqno);
+
+static const char *dma_fence_chain_get_driver_name(struct dma_fence *fence)
+{
+        return "dma_fence_chain";
+}
+
+static const char *dma_fence_chain_get_timeline_name(struct dma_fence *fence)
+{
+        return "unbound";
+}
+
+static void dma_fence_chain_irq_work(struct irq_work *work)
+{
+	struct dma_fence_chain *chain;
+
+	chain = container_of(work, typeof(*chain), work);
+
+	/* Try to rearm the callback */
+	if (!dma_fence_chain_enable_signaling(&chain->base))
+		/* Ok, we are done. No more unsignaled fences left */
+		dma_fence_signal(&chain->base);
+	dma_fence_put(&chain->base);
+}
+
+static void dma_fence_chain_cb(struct dma_fence *f, struct dma_fence_cb *cb)
+{
+	struct dma_fence_chain *chain;
+
+	chain = container_of(cb, typeof(*chain), cb);
+	irq_work_queue(&chain->work);
+	dma_fence_put(f);
+}
+
+static bool dma_fence_chain_enable_signaling(struct dma_fence *fence)
+{
+	struct dma_fence_chain *head = to_dma_fence_chain(fence);
+
+	dma_fence_get(&head->base);
+	dma_fence_chain_for_each(fence, &head->base) {
+		struct dma_fence_chain *chain = to_dma_fence_chain(fence);
+		struct dma_fence *f = chain ? chain->fence : fence;
+
+		dma_fence_get(f);
+		if (!dma_fence_add_callback(f, &head->cb, dma_fence_chain_cb)) {
+			dma_fence_put(fence);
+			return true;
+		}
+		dma_fence_put(f);
+	}
+	dma_fence_put(&head->base);
+	return false;
+}
+
+static bool dma_fence_chain_signaled(struct dma_fence *fence)
+{
+	dma_fence_chain_for_each(fence, fence) {
+		struct dma_fence_chain *chain = to_dma_fence_chain(fence);
+		struct dma_fence *f = chain ? chain->fence : fence;
+
+		if (!dma_fence_is_signaled(f)) {
+			dma_fence_put(fence);
+			return false;
+		}
+	}
+
+	return true;
+}
+
+static void dma_fence_chain_release(struct dma_fence *fence)
+{
+	struct dma_fence_chain *chain = to_dma_fence_chain(fence);
+	struct dma_fence *prev;
+
+	/* Manually unlink the chain as much as possible to avoid recursion
+	 * and potential stack overflow.
+	 */
+	while ((prev = rcu_dereference_protected(chain->prev, true))) {
+		struct dma_fence_chain *prev_chain;
+
+		if (kref_read(&prev->refcount) > 1)
+		       break;
+
+		prev_chain = to_dma_fence_chain(prev);
+		if (!prev_chain)
+			break;
+
+		/* No need for atomic operations since we hold the last
+		 * reference to prev_chain.
+		 */
+		chain->prev = prev_chain->prev;
+		RCU_INIT_POINTER(prev_chain->prev, NULL);
+		dma_fence_put(prev);
+	}
+	dma_fence_put(prev);
+
+	dma_fence_put(chain->fence);
+	dma_fence_free(fence);
+}
+
+const struct dma_fence_ops dma_fence_chain_ops = {
+	.use_64bit_seqno = true,
+	.get_driver_name = dma_fence_chain_get_driver_name,
+	.get_timeline_name = dma_fence_chain_get_timeline_name,
+	.enable_signaling = dma_fence_chain_enable_signaling,
+	.signaled = dma_fence_chain_signaled,
+	.release = dma_fence_chain_release,
+};
+EXPORT_SYMBOL(dma_fence_chain_ops);
+
+/**
+ * dma_fence_chain_init - initialize a fence chain
+ * @chain: the chain node to initialize
+ * @prev: the previous fence
+ * @fence: the current fence
+ * @seqno: the sequence number to use for the fence chain
+ *
+ * Initialize a new chain node and either start a new chain or add the node to
+ * the existing chain of the previous fence.
+ */
+void dma_fence_chain_init(struct dma_fence_chain *chain,
+			  struct dma_fence *prev,
+			  struct dma_fence *fence,
+			  uint64_t seqno)
+{
+	struct dma_fence_chain *prev_chain = to_dma_fence_chain(prev);
+	uint64_t context;
+
+	spin_lock_init(&chain->lock);
+	rcu_assign_pointer(chain->prev, prev);
+	chain->fence = fence;
+	chain->prev_seqno = 0;
+	init_irq_work(&chain->work, dma_fence_chain_irq_work);
+
+	/* Try to reuse the context of the previous chain node. */
+	if (prev_chain && __dma_fence_is_later(seqno, prev->seqno, prev->ops)) {
+		context = prev->context;
+		chain->prev_seqno = prev->seqno;
+	} else {
+		context = dma_fence_context_alloc(1);
+		/* Make sure that we always have a valid sequence number. */
+		if (prev_chain)
+			seqno = max(prev->seqno, seqno);
+	}
+
+	dma_fence_init(&chain->base, &dma_fence_chain_ops,
+		       &chain->lock, context, seqno);
+}
+EXPORT_SYMBOL(dma_fence_chain_init);
diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c
new file mode 100644
index 000000000..7475e09b0
--- /dev/null
+++ b/drivers/dma-buf/dma-fence.c
@@ -0,0 +1,865 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Fence mechanism for dma-buf and to allow for asynchronous dma access
+ *
+ * Copyright (C) 2012 Canonical Ltd
+ * Copyright (C) 2012 Texas Instruments
+ *
+ * Authors:
+ * Rob Clark <robdclark@gmail.com>
+ * Maarten Lankhorst <maarten.lankhorst@canonical.com>
+ */
+
+#include <linux/slab.h>
+#include <linux/export.h>
+#include <linux/atomic.h>
+#include <linux/dma-fence.h>
+#include <linux/sched/signal.h>
+
+#define CREATE_TRACE_POINTS
+#include <trace/events/dma_fence.h>
+
+EXPORT_TRACEPOINT_SYMBOL(dma_fence_emit);
+EXPORT_TRACEPOINT_SYMBOL(dma_fence_enable_signal);
+EXPORT_TRACEPOINT_SYMBOL(dma_fence_signaled);
+
+static DEFINE_SPINLOCK(dma_fence_stub_lock);
+static struct dma_fence dma_fence_stub;
+
+/*
+ * fence context counter: each execution context should have its own
+ * fence context, this allows checking if fences belong to the same
+ * context or not. One device can have multiple separate contexts,
+ * and they're used if some engine can run independently of another.
+ */
+static atomic64_t dma_fence_context_counter = ATOMIC64_INIT(1);
+
+/**
+ * DOC: DMA fences overview
+ *
+ * DMA fences, represented by &struct dma_fence, are the kernel internal
+ * synchronization primitive for DMA operations like GPU rendering, video
+ * encoding/decoding, or displaying buffers on a screen.
+ *
+ * A fence is initialized using dma_fence_init() and completed using
+ * dma_fence_signal(). Fences are associated with a context, allocated through
+ * dma_fence_context_alloc(), and all fences on the same context are
+ * fully ordered.
+ *
+ * Since the purposes of fences is to facilitate cross-device and
+ * cross-application synchronization, there's multiple ways to use one:
+ *
+ * - Individual fences can be exposed as a &sync_file, accessed as a file
+ *   descriptor from userspace, created by calling sync_file_create(). This is
+ *   called explicit fencing, since userspace passes around explicit
+ *   synchronization points.
+ *
+ * - Some subsystems also have their own explicit fencing primitives, like
+ *   &drm_syncobj. Compared to &sync_file, a &drm_syncobj allows the underlying
+ *   fence to be updated.
+ *
+ * - Then there's also implicit fencing, where the synchronization points are
+ *   implicitly passed around as part of shared &dma_buf instances. Such
+ *   implicit fences are stored in &struct dma_resv through the
+ *   &dma_buf.resv pointer.
+ */
+
+/**
+ * DOC: fence cross-driver contract
+ *
+ * Since &dma_fence provide a cross driver contract, all drivers must follow the
+ * same rules:
+ *
+ * * Fences must complete in a reasonable time. Fences which represent kernels
+ *   and shaders submitted by userspace, which could run forever, must be backed
+ *   up by timeout and gpu hang recovery code. Minimally that code must prevent
+ *   further command submission and force complete all in-flight fences, e.g.
+ *   when the driver or hardware do not support gpu reset, or if the gpu reset
+ *   failed for some reason. Ideally the driver supports gpu recovery which only
+ *   affects the offending userspace context, and no other userspace
+ *   submissions.
+ *
+ * * Drivers may have different ideas of what completion within a reasonable
+ *   time means. Some hang recovery code uses a fixed timeout, others a mix
+ *   between observing forward progress and increasingly strict timeouts.
+ *   Drivers should not try to second guess timeout handling of fences from
+ *   other drivers.
+ *
+ * * To ensure there's no deadlocks of dma_fence_wait() against other locks
+ *   drivers should annotate all code required to reach dma_fence_signal(),
+ *   which completes the fences, with dma_fence_begin_signalling() and
+ *   dma_fence_end_signalling().
+ *
+ * * Drivers are allowed to call dma_fence_wait() while holding dma_resv_lock().
+ *   This means any code required for fence completion cannot acquire a
+ *   &dma_resv lock. Note that this also pulls in the entire established
+ *   locking hierarchy around dma_resv_lock() and dma_resv_unlock().
+ *
+ * * Drivers are allowed to call dma_fence_wait() from their &shrinker
+ *   callbacks. This means any code required for fence completion cannot
+ *   allocate memory with GFP_KERNEL.
+ *
+ * * Drivers are allowed to call dma_fence_wait() from their &mmu_notifier
+ *   respectively &mmu_interval_notifier callbacks. This means any code required
+ *   for fence completeion cannot allocate memory with GFP_NOFS or GFP_NOIO.
+ *   Only GFP_ATOMIC is permissible, which might fail.
+ *
+ * Note that only GPU drivers have a reasonable excuse for both requiring
+ * &mmu_interval_notifier and &shrinker callbacks at the same time as having to
+ * track asynchronous compute work using &dma_fence. No driver outside of
+ * drivers/gpu should ever call dma_fence_wait() in such contexts.
+ */
+
+static const char *dma_fence_stub_get_name(struct dma_fence *fence)
+{
+        return "stub";
+}
+
+static const struct dma_fence_ops dma_fence_stub_ops = {
+	.get_driver_name = dma_fence_stub_get_name,
+	.get_timeline_name = dma_fence_stub_get_name,
+};
+
+/**
+ * dma_fence_get_stub - return a signaled fence
+ *
+ * Return a stub fence which is already signaled.
+ */
+struct dma_fence *dma_fence_get_stub(void)
+{
+	spin_lock(&dma_fence_stub_lock);
+	if (!dma_fence_stub.ops) {
+		dma_fence_init(&dma_fence_stub,
+			       &dma_fence_stub_ops,
+			       &dma_fence_stub_lock,
+			       0, 0);
+		dma_fence_signal_locked(&dma_fence_stub);
+	}
+	spin_unlock(&dma_fence_stub_lock);
+
+	return dma_fence_get(&dma_fence_stub);
+}
+EXPORT_SYMBOL(dma_fence_get_stub);
+
+/**
+ * dma_fence_context_alloc - allocate an array of fence contexts
+ * @num: amount of contexts to allocate
+ *
+ * This function will return the first index of the number of fence contexts
+ * allocated.  The fence context is used for setting &dma_fence.context to a
+ * unique number by passing the context to dma_fence_init().
+ */
+u64 dma_fence_context_alloc(unsigned num)
+{
+	WARN_ON(!num);
+	return atomic64_fetch_add(num, &dma_fence_context_counter);
+}
+EXPORT_SYMBOL(dma_fence_context_alloc);
+
+/**
+ * DOC: fence signalling annotation
+ *
+ * Proving correctness of all the kernel code around &dma_fence through code
+ * review and testing is tricky for a few reasons:
+ *
+ * * It is a cross-driver contract, and therefore all drivers must follow the
+ *   same rules for lock nesting order, calling contexts for various functions
+ *   and anything else significant for in-kernel interfaces. But it is also
+ *   impossible to test all drivers in a single machine, hence brute-force N vs.
+ *   N testing of all combinations is impossible. Even just limiting to the
+ *   possible combinations is infeasible.
+ *
+ * * There is an enormous amount of driver code involved. For render drivers
+ *   there's the tail of command submission, after fences are published,
+ *   scheduler code, interrupt and workers to process job completion,
+ *   and timeout, gpu reset and gpu hang recovery code. Plus for integration
+ *   with core mm with have &mmu_notifier, respectively &mmu_interval_notifier,
+ *   and &shrinker. For modesetting drivers there's the commit tail functions
+ *   between when fences for an atomic modeset are published, and when the
+ *   corresponding vblank completes, including any interrupt processing and
+ *   related workers. Auditing all that code, across all drivers, is not
+ *   feasible.
+ *
+ * * Due to how many other subsystems are involved and the locking hierarchies
+ *   this pulls in there is extremely thin wiggle-room for driver-specific
+ *   differences. &dma_fence interacts with almost all of the core memory
+ *   handling through page fault handlers via &dma_resv, dma_resv_lock() and
+ *   dma_resv_unlock(). On the other side it also interacts through all
+ *   allocation sites through &mmu_notifier and &shrinker.
+ *
+ * Furthermore lockdep does not handle cross-release dependencies, which means
+ * any deadlocks between dma_fence_wait() and dma_fence_signal() can't be caught
+ * at runtime with some quick testing. The simplest example is one thread
+ * waiting on a &dma_fence while holding a lock::
+ *
+ *     lock(A);
+ *     dma_fence_wait(B);
+ *     unlock(A);
+ *
+ * while the other thread is stuck trying to acquire the same lock, which
+ * prevents it from signalling the fence the previous thread is stuck waiting
+ * on::
+ *
+ *     lock(A);
+ *     unlock(A);
+ *     dma_fence_signal(B);
+ *
+ * By manually annotating all code relevant to signalling a &dma_fence we can
+ * teach lockdep about these dependencies, which also helps with the validation
+ * headache since now lockdep can check all the rules for us::
+ *
+ *    cookie = dma_fence_begin_signalling();
+ *    lock(A);
+ *    unlock(A);
+ *    dma_fence_signal(B);
+ *    dma_fence_end_signalling(cookie);
+ *
+ * For using dma_fence_begin_signalling() and dma_fence_end_signalling() to
+ * annotate critical sections the following rules need to be observed:
+ *
+ * * All code necessary to complete a &dma_fence must be annotated, from the
+ *   point where a fence is accessible to other threads, to the point where
+ *   dma_fence_signal() is called. Un-annotated code can contain deadlock issues,
+ *   and due to the very strict rules and many corner cases it is infeasible to
+ *   catch these just with review or normal stress testing.
+ *
+ * * &struct dma_resv deserves a special note, since the readers are only
+ *   protected by rcu. This means the signalling critical section starts as soon
+ *   as the new fences are installed, even before dma_resv_unlock() is called.
+ *
+ * * The only exception are fast paths and opportunistic signalling code, which
+ *   calls dma_fence_signal() purely as an optimization, but is not required to
+ *   guarantee completion of a &dma_fence. The usual example is a wait IOCTL
+ *   which calls dma_fence_signal(), while the mandatory completion path goes
+ *   through a hardware interrupt and possible job completion worker.
+ *
+ * * To aid composability of code, the annotations can be freely nested, as long
+ *   as the overall locking hierarchy is consistent. The annotations also work
+ *   both in interrupt and process context. Due to implementation details this
+ *   requires that callers pass an opaque cookie from
+ *   dma_fence_begin_signalling() to dma_fence_end_signalling().
+ *
+ * * Validation against the cross driver contract is implemented by priming
+ *   lockdep with the relevant hierarchy at boot-up. This means even just
+ *   testing with a single device is enough to validate a driver, at least as
+ *   far as deadlocks with dma_fence_wait() against dma_fence_signal() are
+ *   concerned.
+ */
+#ifdef CONFIG_LOCKDEP
+static struct lockdep_map dma_fence_lockdep_map = {
+	.name = "dma_fence_map"
+};
+
+/**
+ * dma_fence_begin_signalling - begin a critical DMA fence signalling section
+ *
+ * Drivers should use this to annotate the beginning of any code section
+ * required to eventually complete &dma_fence by calling dma_fence_signal().
+ *
+ * The end of these critical sections are annotated with
+ * dma_fence_end_signalling().
+ *
+ * Returns:
+ *
+ * Opaque cookie needed by the implementation, which needs to be passed to
+ * dma_fence_end_signalling().
+ */
+bool dma_fence_begin_signalling(void)
+{
+	/* explicitly nesting ... */
+	if (lock_is_held_type(&dma_fence_lockdep_map, 1))
+		return true;
+
+	/* rely on might_sleep check for soft/hardirq locks */
+	if (in_atomic())
+		return true;
+
+	/* ... and non-recursive readlock */
+	lock_acquire(&dma_fence_lockdep_map, 0, 0, 1, 1, NULL, _RET_IP_);
+
+	return false;
+}
+EXPORT_SYMBOL(dma_fence_begin_signalling);
+
+/**
+ * dma_fence_end_signalling - end a critical DMA fence signalling section
+ * @cookie: opaque cookie from dma_fence_begin_signalling()
+ *
+ * Closes a critical section annotation opened by dma_fence_begin_signalling().
+ */
+void dma_fence_end_signalling(bool cookie)
+{
+	if (cookie)
+		return;
+
+	lock_release(&dma_fence_lockdep_map, _RET_IP_);
+}
+EXPORT_SYMBOL(dma_fence_end_signalling);
+
+void __dma_fence_might_wait(void)
+{
+	bool tmp;
+
+	tmp = lock_is_held_type(&dma_fence_lockdep_map, 1);
+	if (tmp)
+		lock_release(&dma_fence_lockdep_map, _THIS_IP_);
+	lock_map_acquire(&dma_fence_lockdep_map);
+	lock_map_release(&dma_fence_lockdep_map);
+	if (tmp)
+		lock_acquire(&dma_fence_lockdep_map, 0, 0, 1, 1, NULL, _THIS_IP_);
+}
+#endif
+
+
+/**
+ * dma_fence_signal_locked - signal completion of a fence
+ * @fence: the fence to signal
+ *
+ * Signal completion for software callbacks on a fence, this will unblock
+ * dma_fence_wait() calls and run all the callbacks added with
+ * dma_fence_add_callback(). Can be called multiple times, but since a fence
+ * can only go from the unsignaled to the signaled state and not back, it will
+ * only be effective the first time.
+ *
+ * Unlike dma_fence_signal(), this function must be called with &dma_fence.lock
+ * held.
+ *
+ * Returns 0 on success and a negative error value when @fence has been
+ * signalled already.
+ */
+int dma_fence_signal_locked(struct dma_fence *fence)
+{
+	struct dma_fence_cb *cur, *tmp;
+	struct list_head cb_list;
+
+	lockdep_assert_held(fence->lock);
+
+	if (unlikely(test_and_set_bit(DMA_FENCE_FLAG_SIGNALED_BIT,
+				      &fence->flags)))
+		return -EINVAL;
+
+	/* Stash the cb_list before replacing it with the timestamp */
+	list_replace(&fence->cb_list, &cb_list);
+
+	fence->timestamp = ktime_get();
+	set_bit(DMA_FENCE_FLAG_TIMESTAMP_BIT, &fence->flags);
+	trace_dma_fence_signaled(fence);
+
+	list_for_each_entry_safe(cur, tmp, &cb_list, node) {
+		INIT_LIST_HEAD(&cur->node);
+		cur->func(fence, cur);
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL(dma_fence_signal_locked);
+
+/**
+ * dma_fence_signal - signal completion of a fence
+ * @fence: the fence to signal
+ *
+ * Signal completion for software callbacks on a fence, this will unblock
+ * dma_fence_wait() calls and run all the callbacks added with
+ * dma_fence_add_callback(). Can be called multiple times, but since a fence
+ * can only go from the unsignaled to the signaled state and not back, it will
+ * only be effective the first time.
+ *
+ * Returns 0 on success and a negative error value when @fence has been
+ * signalled already.
+ */
+int dma_fence_signal(struct dma_fence *fence)
+{
+	unsigned long flags;
+	int ret;
+	bool tmp;
+
+	if (!fence)
+		return -EINVAL;
+
+	tmp = dma_fence_begin_signalling();
+
+	spin_lock_irqsave(fence->lock, flags);
+	ret = dma_fence_signal_locked(fence);
+	spin_unlock_irqrestore(fence->lock, flags);
+
+	dma_fence_end_signalling(tmp);
+
+	return ret;
+}
+EXPORT_SYMBOL(dma_fence_signal);
+
+/**
+ * dma_fence_wait_timeout - sleep until the fence gets signaled
+ * or until timeout elapses
+ * @fence: the fence to wait on
+ * @intr: if true, do an interruptible wait
+ * @timeout: timeout value in jiffies, or MAX_SCHEDULE_TIMEOUT
+ *
+ * Returns -ERESTARTSYS if interrupted, 0 if the wait timed out, or the
+ * remaining timeout in jiffies on success. Other error values may be
+ * returned on custom implementations.
+ *
+ * Performs a synchronous wait on this fence. It is assumed the caller
+ * directly or indirectly (buf-mgr between reservation and committing)
+ * holds a reference to the fence, otherwise the fence might be
+ * freed before return, resulting in undefined behavior.
+ *
+ * See also dma_fence_wait() and dma_fence_wait_any_timeout().
+ */
+signed long
+dma_fence_wait_timeout(struct dma_fence *fence, bool intr, signed long timeout)
+{
+	signed long ret;
+
+	if (WARN_ON(timeout < 0))
+		return -EINVAL;
+
+	might_sleep();
+
+	__dma_fence_might_wait();
+
+	trace_dma_fence_wait_start(fence);
+	if (fence->ops->wait)
+		ret = fence->ops->wait(fence, intr, timeout);
+	else
+		ret = dma_fence_default_wait(fence, intr, timeout);
+	trace_dma_fence_wait_end(fence);
+	return ret;
+}
+EXPORT_SYMBOL(dma_fence_wait_timeout);
+
+/**
+ * dma_fence_release - default relese function for fences
+ * @kref: &dma_fence.recfount
+ *
+ * This is the default release functions for &dma_fence. Drivers shouldn't call
+ * this directly, but instead call dma_fence_put().
+ */
+void dma_fence_release(struct kref *kref)
+{
+	struct dma_fence *fence =
+		container_of(kref, struct dma_fence, refcount);
+
+	trace_dma_fence_destroy(fence);
+
+	if (WARN(!list_empty(&fence->cb_list) &&
+		 !test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags),
+		 "Fence %s:%s:%llx:%llx released with pending signals!\n",
+		 fence->ops->get_driver_name(fence),
+		 fence->ops->get_timeline_name(fence),
+		 fence->context, fence->seqno)) {
+		unsigned long flags;
+
+		/*
+		 * Failed to signal before release, likely a refcounting issue.
+		 *
+		 * This should never happen, but if it does make sure that we
+		 * don't leave chains dangling. We set the error flag first
+		 * so that the callbacks know this signal is due to an error.
+		 */
+		spin_lock_irqsave(fence->lock, flags);
+		fence->error = -EDEADLK;
+		dma_fence_signal_locked(fence);
+		spin_unlock_irqrestore(fence->lock, flags);
+	}
+
+	if (fence->ops->release)
+		fence->ops->release(fence);
+	else
+		dma_fence_free(fence);
+}
+EXPORT_SYMBOL(dma_fence_release);
+
+/**
+ * dma_fence_free - default release function for &dma_fence.
+ * @fence: fence to release
+ *
+ * This is the default implementation for &dma_fence_ops.release. It calls
+ * kfree_rcu() on @fence.
+ */
+void dma_fence_free(struct dma_fence *fence)
+{
+	kfree_rcu(fence, rcu);
+}
+EXPORT_SYMBOL(dma_fence_free);
+
+static bool __dma_fence_enable_signaling(struct dma_fence *fence)
+{
+	bool was_set;
+
+	lockdep_assert_held(fence->lock);
+
+	was_set = test_and_set_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT,
+				   &fence->flags);
+
+	if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))
+		return false;
+
+	if (!was_set && fence->ops->enable_signaling) {
+		trace_dma_fence_enable_signal(fence);
+
+		if (!fence->ops->enable_signaling(fence)) {
+			dma_fence_signal_locked(fence);
+			return false;
+		}
+	}
+
+	return true;
+}
+
+/**
+ * dma_fence_enable_sw_signaling - enable signaling on fence
+ * @fence: the fence to enable
+ *
+ * This will request for sw signaling to be enabled, to make the fence
+ * complete as soon as possible. This calls &dma_fence_ops.enable_signaling
+ * internally.
+ */
+void dma_fence_enable_sw_signaling(struct dma_fence *fence)
+{
+	unsigned long flags;
+
+	if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))
+		return;
+
+	spin_lock_irqsave(fence->lock, flags);
+	__dma_fence_enable_signaling(fence);
+	spin_unlock_irqrestore(fence->lock, flags);
+}
+EXPORT_SYMBOL(dma_fence_enable_sw_signaling);
+
+/**
+ * dma_fence_add_callback - add a callback to be called when the fence
+ * is signaled
+ * @fence: the fence to wait on
+ * @cb: the callback to register
+ * @func: the function to call
+ *
+ * @cb will be initialized by dma_fence_add_callback(), no initialization
+ * by the caller is required. Any number of callbacks can be registered
+ * to a fence, but a callback can only be registered to one fence at a time.
+ *
+ * Note that the callback can be called from an atomic context.  If
+ * fence is already signaled, this function will return -ENOENT (and
+ * *not* call the callback).
+ *
+ * Add a software callback to the fence. Same restrictions apply to
+ * refcount as it does to dma_fence_wait(), however the caller doesn't need to
+ * keep a refcount to fence afterward dma_fence_add_callback() has returned:
+ * when software access is enabled, the creator of the fence is required to keep
+ * the fence alive until after it signals with dma_fence_signal(). The callback
+ * itself can be called from irq context.
+ *
+ * Returns 0 in case of success, -ENOENT if the fence is already signaled
+ * and -EINVAL in case of error.
+ */
+int dma_fence_add_callback(struct dma_fence *fence, struct dma_fence_cb *cb,
+			   dma_fence_func_t func)
+{
+	unsigned long flags;
+	int ret = 0;
+
+	if (WARN_ON(!fence || !func))
+		return -EINVAL;
+
+	if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)) {
+		INIT_LIST_HEAD(&cb->node);
+		return -ENOENT;
+	}
+
+	spin_lock_irqsave(fence->lock, flags);
+
+	if (__dma_fence_enable_signaling(fence)) {
+		cb->func = func;
+		list_add_tail(&cb->node, &fence->cb_list);
+	} else {
+		INIT_LIST_HEAD(&cb->node);
+		ret = -ENOENT;
+	}
+
+	spin_unlock_irqrestore(fence->lock, flags);
+
+	return ret;
+}
+EXPORT_SYMBOL(dma_fence_add_callback);
+
+/**
+ * dma_fence_get_status - returns the status upon completion
+ * @fence: the dma_fence to query
+ *
+ * This wraps dma_fence_get_status_locked() to return the error status
+ * condition on a signaled fence. See dma_fence_get_status_locked() for more
+ * details.
+ *
+ * Returns 0 if the fence has not yet been signaled, 1 if the fence has
+ * been signaled without an error condition, or a negative error code
+ * if the fence has been completed in err.
+ */
+int dma_fence_get_status(struct dma_fence *fence)
+{
+	unsigned long flags;
+	int status;
+
+	spin_lock_irqsave(fence->lock, flags);
+	status = dma_fence_get_status_locked(fence);
+	spin_unlock_irqrestore(fence->lock, flags);
+
+	return status;
+}
+EXPORT_SYMBOL(dma_fence_get_status);
+
+/**
+ * dma_fence_remove_callback - remove a callback from the signaling list
+ * @fence: the fence to wait on
+ * @cb: the callback to remove
+ *
+ * Remove a previously queued callback from the fence. This function returns
+ * true if the callback is successfully removed, or false if the fence has
+ * already been signaled.
+ *
+ * *WARNING*:
+ * Cancelling a callback should only be done if you really know what you're
+ * doing, since deadlocks and race conditions could occur all too easily. For
+ * this reason, it should only ever be done on hardware lockup recovery,
+ * with a reference held to the fence.
+ *
+ * Behaviour is undefined if @cb has not been added to @fence using
+ * dma_fence_add_callback() beforehand.
+ */
+bool
+dma_fence_remove_callback(struct dma_fence *fence, struct dma_fence_cb *cb)
+{
+	unsigned long flags;
+	bool ret;
+
+	spin_lock_irqsave(fence->lock, flags);
+
+	ret = !list_empty(&cb->node);
+	if (ret)
+		list_del_init(&cb->node);
+
+	spin_unlock_irqrestore(fence->lock, flags);
+
+	return ret;
+}
+EXPORT_SYMBOL(dma_fence_remove_callback);
+
+struct default_wait_cb {
+	struct dma_fence_cb base;
+	struct task_struct *task;
+};
+
+static void
+dma_fence_default_wait_cb(struct dma_fence *fence, struct dma_fence_cb *cb)
+{
+	struct default_wait_cb *wait =
+		container_of(cb, struct default_wait_cb, base);
+
+	wake_up_state(wait->task, TASK_NORMAL);
+}
+
+/**
+ * dma_fence_default_wait - default sleep until the fence gets signaled
+ * or until timeout elapses
+ * @fence: the fence to wait on
+ * @intr: if true, do an interruptible wait
+ * @timeout: timeout value in jiffies, or MAX_SCHEDULE_TIMEOUT
+ *
+ * Returns -ERESTARTSYS if interrupted, 0 if the wait timed out, or the
+ * remaining timeout in jiffies on success. If timeout is zero the value one is
+ * returned if the fence is already signaled for consistency with other
+ * functions taking a jiffies timeout.
+ */
+signed long
+dma_fence_default_wait(struct dma_fence *fence, bool intr, signed long timeout)
+{
+	struct default_wait_cb cb;
+	unsigned long flags;
+	signed long ret = timeout ? timeout : 1;
+
+	if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))
+		return ret;
+
+	spin_lock_irqsave(fence->lock, flags);
+
+	if (intr && signal_pending(current)) {
+		ret = -ERESTARTSYS;
+		goto out;
+	}
+
+	if (!__dma_fence_enable_signaling(fence))
+		goto out;
+
+	if (!timeout) {
+		ret = 0;
+		goto out;
+	}
+
+	cb.base.func = dma_fence_default_wait_cb;
+	cb.task = current;
+	list_add(&cb.base.node, &fence->cb_list);
+
+	while (!test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags) && ret > 0) {
+		if (intr)
+			__set_current_state(TASK_INTERRUPTIBLE);
+		else
+			__set_current_state(TASK_UNINTERRUPTIBLE);
+		spin_unlock_irqrestore(fence->lock, flags);
+
+		ret = schedule_timeout(ret);
+
+		spin_lock_irqsave(fence->lock, flags);
+		if (ret > 0 && intr && signal_pending(current))
+			ret = -ERESTARTSYS;
+	}
+
+	if (!list_empty(&cb.base.node))
+		list_del(&cb.base.node);
+	__set_current_state(TASK_RUNNING);
+
+out:
+	spin_unlock_irqrestore(fence->lock, flags);
+	return ret;
+}
+EXPORT_SYMBOL(dma_fence_default_wait);
+
+static bool
+dma_fence_test_signaled_any(struct dma_fence **fences, uint32_t count,
+			    uint32_t *idx)
+{
+	int i;
+
+	for (i = 0; i < count; ++i) {
+		struct dma_fence *fence = fences[i];
+		if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)) {
+			if (idx)
+				*idx = i;
+			return true;
+		}
+	}
+	return false;
+}
+
+/**
+ * dma_fence_wait_any_timeout - sleep until any fence gets signaled
+ * or until timeout elapses
+ * @fences: array of fences to wait on
+ * @count: number of fences to wait on
+ * @intr: if true, do an interruptible wait
+ * @timeout: timeout value in jiffies, or MAX_SCHEDULE_TIMEOUT
+ * @idx: used to store the first signaled fence index, meaningful only on
+ *	positive return
+ *
+ * Returns -EINVAL on custom fence wait implementation, -ERESTARTSYS if
+ * interrupted, 0 if the wait timed out, or the remaining timeout in jiffies
+ * on success.
+ *
+ * Synchronous waits for the first fence in the array to be signaled. The
+ * caller needs to hold a reference to all fences in the array, otherwise a
+ * fence might be freed before return, resulting in undefined behavior.
+ *
+ * See also dma_fence_wait() and dma_fence_wait_timeout().
+ */
+signed long
+dma_fence_wait_any_timeout(struct dma_fence **fences, uint32_t count,
+			   bool intr, signed long timeout, uint32_t *idx)
+{
+	struct default_wait_cb *cb;
+	signed long ret = timeout;
+	unsigned i;
+
+	if (WARN_ON(!fences || !count || timeout < 0))
+		return -EINVAL;
+
+	if (timeout == 0) {
+		for (i = 0; i < count; ++i)
+			if (dma_fence_is_signaled(fences[i])) {
+				if (idx)
+					*idx = i;
+				return 1;
+			}
+
+		return 0;
+	}
+
+	cb = kcalloc(count, sizeof(struct default_wait_cb), GFP_KERNEL);
+	if (cb == NULL) {
+		ret = -ENOMEM;
+		goto err_free_cb;
+	}
+
+	for (i = 0; i < count; ++i) {
+		struct dma_fence *fence = fences[i];
+
+		cb[i].task = current;
+		if (dma_fence_add_callback(fence, &cb[i].base,
+					   dma_fence_default_wait_cb)) {
+			/* This fence is already signaled */
+			if (idx)
+				*idx = i;
+			goto fence_rm_cb;
+		}
+	}
+
+	while (ret > 0) {
+		if (intr)
+			set_current_state(TASK_INTERRUPTIBLE);
+		else
+			set_current_state(TASK_UNINTERRUPTIBLE);
+
+		if (dma_fence_test_signaled_any(fences, count, idx))
+			break;
+
+		ret = schedule_timeout(ret);
+
+		if (ret > 0 && intr && signal_pending(current))
+			ret = -ERESTARTSYS;
+	}
+
+	__set_current_state(TASK_RUNNING);
+
+fence_rm_cb:
+	while (i-- > 0)
+		dma_fence_remove_callback(fences[i], &cb[i].base);
+
+err_free_cb:
+	kfree(cb);
+
+	return ret;
+}
+EXPORT_SYMBOL(dma_fence_wait_any_timeout);
+
+/**
+ * dma_fence_init - Initialize a custom fence.
+ * @fence: the fence to initialize
+ * @ops: the dma_fence_ops for operations on this fence
+ * @lock: the irqsafe spinlock to use for locking this fence
+ * @context: the execution context this fence is run on
+ * @seqno: a linear increasing sequence number for this context
+ *
+ * Initializes an allocated fence, the caller doesn't have to keep its
+ * refcount after committing with this fence, but it will need to hold a
+ * refcount again if &dma_fence_ops.enable_signaling gets called.
+ *
+ * context and seqno are used for easy comparison between fences, allowing
+ * to check which fence is later by simply using dma_fence_later().
+ */
+void
+dma_fence_init(struct dma_fence *fence, const struct dma_fence_ops *ops,
+	       spinlock_t *lock, u64 context, u64 seqno)
+{
+	BUG_ON(!lock);
+	BUG_ON(!ops || !ops->get_driver_name || !ops->get_timeline_name);
+
+	kref_init(&fence->refcount);
+	fence->ops = ops;
+	INIT_LIST_HEAD(&fence->cb_list);
+	fence->lock = lock;
+	fence->context = context;
+	fence->seqno = seqno;
+	fence->flags = 0UL;
+	fence->error = 0;
+
+	trace_dma_fence_init(fence);
+}
+EXPORT_SYMBOL(dma_fence_init);
diff --git a/drivers/dma-buf/dma-heap.c b/drivers/dma-buf/dma-heap.c
new file mode 100644
index 000000000..dcbb023ac
--- /dev/null
+++ b/drivers/dma-buf/dma-heap.c
@@ -0,0 +1,302 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Framework for userspace DMA-BUF allocations
+ *
+ * Copyright (C) 2011 Google, Inc.
+ * Copyright (C) 2019 Linaro Ltd.
+ */
+
+#include <linux/cdev.h>
+#include <linux/debugfs.h>
+#include <linux/device.h>
+#include <linux/dma-buf.h>
+#include <linux/err.h>
+#include <linux/xarray.h>
+#include <linux/list.h>
+#include <linux/slab.h>
+#include <linux/nospec.h>
+#include <linux/uaccess.h>
+#include <linux/syscalls.h>
+#include <linux/dma-heap.h>
+#include <uapi/linux/dma-heap.h>
+
+#define DEVNAME "dma_heap"
+
+#define NUM_HEAP_MINORS 128
+
+/**
+ * struct dma_heap - represents a dmabuf heap in the system
+ * @name:		used for debugging/device-node name
+ * @ops:		ops struct for this heap
+ * @heap_devt		heap device node
+ * @list		list head connecting to list of heaps
+ * @heap_cdev		heap char device
+ *
+ * Represents a heap of memory from which buffers can be made.
+ */
+struct dma_heap {
+	const char *name;
+	const struct dma_heap_ops *ops;
+	void *priv;
+	dev_t heap_devt;
+	struct list_head list;
+	struct cdev heap_cdev;
+};
+
+static LIST_HEAD(heap_list);
+static DEFINE_MUTEX(heap_list_lock);
+static dev_t dma_heap_devt;
+static struct class *dma_heap_class;
+static DEFINE_XARRAY_ALLOC(dma_heap_minors);
+
+static int dma_heap_buffer_alloc(struct dma_heap *heap, size_t len,
+				 unsigned int fd_flags,
+				 unsigned int heap_flags)
+{
+	/*
+	 * Allocations from all heaps have to begin
+	 * and end on page boundaries.
+	 */
+	len = PAGE_ALIGN(len);
+	if (!len)
+		return -EINVAL;
+
+	return heap->ops->allocate(heap, len, fd_flags, heap_flags);
+}
+
+static int dma_heap_open(struct inode *inode, struct file *file)
+{
+	struct dma_heap *heap;
+
+	heap = xa_load(&dma_heap_minors, iminor(inode));
+	if (!heap) {
+		pr_err("dma_heap: minor %d unknown.\n", iminor(inode));
+		return -ENODEV;
+	}
+
+	/* instance data as context */
+	file->private_data = heap;
+	nonseekable_open(inode, file);
+
+	return 0;
+}
+
+static long dma_heap_ioctl_allocate(struct file *file, void *data)
+{
+	struct dma_heap_allocation_data *heap_allocation = data;
+	struct dma_heap *heap = file->private_data;
+	int fd;
+
+	if (heap_allocation->fd)
+		return -EINVAL;
+
+	if (heap_allocation->fd_flags & ~DMA_HEAP_VALID_FD_FLAGS)
+		return -EINVAL;
+
+	if (heap_allocation->heap_flags & ~DMA_HEAP_VALID_HEAP_FLAGS)
+		return -EINVAL;
+
+	fd = dma_heap_buffer_alloc(heap, heap_allocation->len,
+				   heap_allocation->fd_flags,
+				   heap_allocation->heap_flags);
+	if (fd < 0)
+		return fd;
+
+	heap_allocation->fd = fd;
+
+	return 0;
+}
+
+static unsigned int dma_heap_ioctl_cmds[] = {
+	DMA_HEAP_IOCTL_ALLOC,
+};
+
+static long dma_heap_ioctl(struct file *file, unsigned int ucmd,
+			   unsigned long arg)
+{
+	char stack_kdata[128];
+	char *kdata = stack_kdata;
+	unsigned int kcmd;
+	unsigned int in_size, out_size, drv_size, ksize;
+	int nr = _IOC_NR(ucmd);
+	int ret = 0;
+
+	if (nr >= ARRAY_SIZE(dma_heap_ioctl_cmds))
+		return -EINVAL;
+
+	nr = array_index_nospec(nr, ARRAY_SIZE(dma_heap_ioctl_cmds));
+	/* Get the kernel ioctl cmd that matches */
+	kcmd = dma_heap_ioctl_cmds[nr];
+
+	/* Figure out the delta between user cmd size and kernel cmd size */
+	drv_size = _IOC_SIZE(kcmd);
+	out_size = _IOC_SIZE(ucmd);
+	in_size = out_size;
+	if ((ucmd & kcmd & IOC_IN) == 0)
+		in_size = 0;
+	if ((ucmd & kcmd & IOC_OUT) == 0)
+		out_size = 0;
+	ksize = max(max(in_size, out_size), drv_size);
+
+	/* If necessary, allocate buffer for ioctl argument */
+	if (ksize > sizeof(stack_kdata)) {
+		kdata = kmalloc(ksize, GFP_KERNEL);
+		if (!kdata)
+			return -ENOMEM;
+	}
+
+	if (copy_from_user(kdata, (void __user *)arg, in_size) != 0) {
+		ret = -EFAULT;
+		goto err;
+	}
+
+	/* zero out any difference between the kernel/user structure size */
+	if (ksize > in_size)
+		memset(kdata + in_size, 0, ksize - in_size);
+
+	switch (kcmd) {
+	case DMA_HEAP_IOCTL_ALLOC:
+		ret = dma_heap_ioctl_allocate(file, kdata);
+		break;
+	default:
+		ret = -ENOTTY;
+		goto err;
+	}
+
+	if (copy_to_user((void __user *)arg, kdata, out_size) != 0)
+		ret = -EFAULT;
+err:
+	if (kdata != stack_kdata)
+		kfree(kdata);
+	return ret;
+}
+
+static const struct file_operations dma_heap_fops = {
+	.owner          = THIS_MODULE,
+	.open		= dma_heap_open,
+	.unlocked_ioctl = dma_heap_ioctl,
+#ifdef CONFIG_COMPAT
+	.compat_ioctl	= dma_heap_ioctl,
+#endif
+};
+
+/**
+ * dma_heap_get_drvdata() - get per-subdriver data for the heap
+ * @heap: DMA-Heap to retrieve private data for
+ *
+ * Returns:
+ * The per-subdriver data for the heap.
+ */
+void *dma_heap_get_drvdata(struct dma_heap *heap)
+{
+	return heap->priv;
+}
+
+struct dma_heap *dma_heap_add(const struct dma_heap_export_info *exp_info)
+{
+	struct dma_heap *heap, *h, *err_ret;
+	struct device *dev_ret;
+	unsigned int minor;
+	int ret;
+
+	if (!exp_info->name || !strcmp(exp_info->name, "")) {
+		pr_err("dma_heap: Cannot add heap without a name\n");
+		return ERR_PTR(-EINVAL);
+	}
+
+	if (!exp_info->ops || !exp_info->ops->allocate) {
+		pr_err("dma_heap: Cannot add heap with invalid ops struct\n");
+		return ERR_PTR(-EINVAL);
+	}
+
+	heap = kzalloc(sizeof(*heap), GFP_KERNEL);
+	if (!heap)
+		return ERR_PTR(-ENOMEM);
+
+	heap->name = exp_info->name;
+	heap->ops = exp_info->ops;
+	heap->priv = exp_info->priv;
+
+	/* Find unused minor number */
+	ret = xa_alloc(&dma_heap_minors, &minor, heap,
+		       XA_LIMIT(0, NUM_HEAP_MINORS - 1), GFP_KERNEL);
+	if (ret < 0) {
+		pr_err("dma_heap: Unable to get minor number for heap\n");
+		err_ret = ERR_PTR(ret);
+		goto err0;
+	}
+
+	/* Create device */
+	heap->heap_devt = MKDEV(MAJOR(dma_heap_devt), minor);
+
+	cdev_init(&heap->heap_cdev, &dma_heap_fops);
+	ret = cdev_add(&heap->heap_cdev, heap->heap_devt, 1);
+	if (ret < 0) {
+		pr_err("dma_heap: Unable to add char device\n");
+		err_ret = ERR_PTR(ret);
+		goto err1;
+	}
+
+	dev_ret = device_create(dma_heap_class,
+				NULL,
+				heap->heap_devt,
+				NULL,
+				heap->name);
+	if (IS_ERR(dev_ret)) {
+		pr_err("dma_heap: Unable to create device\n");
+		err_ret = ERR_CAST(dev_ret);
+		goto err2;
+	}
+
+	mutex_lock(&heap_list_lock);
+	/* check the name is unique */
+	list_for_each_entry(h, &heap_list, list) {
+		if (!strcmp(h->name, exp_info->name)) {
+			mutex_unlock(&heap_list_lock);
+			pr_err("dma_heap: Already registered heap named %s\n",
+			       exp_info->name);
+			err_ret = ERR_PTR(-EINVAL);
+			goto err3;
+		}
+	}
+
+	/* Add heap to the list */
+	list_add(&heap->list, &heap_list);
+	mutex_unlock(&heap_list_lock);
+
+	return heap;
+
+err3:
+	device_destroy(dma_heap_class, heap->heap_devt);
+err2:
+	cdev_del(&heap->heap_cdev);
+err1:
+	xa_erase(&dma_heap_minors, minor);
+err0:
+	kfree(heap);
+	return err_ret;
+}
+
+static char *dma_heap_devnode(struct device *dev, umode_t *mode)
+{
+	return kasprintf(GFP_KERNEL, "dma_heap/%s", dev_name(dev));
+}
+
+static int dma_heap_init(void)
+{
+	int ret;
+
+	ret = alloc_chrdev_region(&dma_heap_devt, 0, NUM_HEAP_MINORS, DEVNAME);
+	if (ret)
+		return ret;
+
+	dma_heap_class = class_create(THIS_MODULE, DEVNAME);
+	if (IS_ERR(dma_heap_class)) {
+		unregister_chrdev_region(dma_heap_devt, NUM_HEAP_MINORS);
+		return PTR_ERR(dma_heap_class);
+	}
+	dma_heap_class->devnode = dma_heap_devnode;
+
+	return 0;
+}
+subsys_initcall(dma_heap_init);
diff --git a/drivers/dma-buf/dma-resv.c b/drivers/dma-buf/dma-resv.c
new file mode 100644
index 000000000..1187e5e80
--- /dev/null
+++ b/drivers/dma-buf/dma-resv.c
@@ -0,0 +1,683 @@
+/*
+ * Copyright (C) 2012-2014 Canonical Ltd (Maarten Lankhorst)
+ *
+ * Based on bo.c which bears the following copyright notice,
+ * but is dual licensed:
+ *
+ * Copyright (c) 2006-2009 VMware, Inc., Palo Alto, CA., USA
+ * All Rights Reserved.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sub license, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the
+ * next paragraph) shall be included in all copies or substantial portions
+ * of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
+ * THE COPYRIGHT HOLDERS, AUTHORS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM,
+ * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+ * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
+ * USE OR OTHER DEALINGS IN THE SOFTWARE.
+ *
+ **************************************************************************/
+/*
+ * Authors: Thomas Hellstrom <thellstrom-at-vmware-dot-com>
+ */
+
+#include <linux/dma-resv.h>
+#include <linux/export.h>
+#include <linux/mm.h>
+#include <linux/sched/mm.h>
+#include <linux/mmu_notifier.h>
+
+/**
+ * DOC: Reservation Object Overview
+ *
+ * The reservation object provides a mechanism to manage shared and
+ * exclusive fences associated with a buffer.  A reservation object
+ * can have attached one exclusive fence (normally associated with
+ * write operations) or N shared fences (read operations).  The RCU
+ * mechanism is used to protect read access to fences from locked
+ * write-side updates.
+ */
+
+DEFINE_WD_CLASS(reservation_ww_class);
+EXPORT_SYMBOL(reservation_ww_class);
+
+/**
+ * dma_resv_list_alloc - allocate fence list
+ * @shared_max: number of fences we need space for
+ *
+ * Allocate a new dma_resv_list and make sure to correctly initialize
+ * shared_max.
+ */
+static struct dma_resv_list *dma_resv_list_alloc(unsigned int shared_max)
+{
+	struct dma_resv_list *list;
+
+	list = kmalloc(offsetof(typeof(*list), shared[shared_max]), GFP_KERNEL);
+	if (!list)
+		return NULL;
+
+	list->shared_max = (ksize(list) - offsetof(typeof(*list), shared)) /
+		sizeof(*list->shared);
+
+	return list;
+}
+
+/**
+ * dma_resv_list_free - free fence list
+ * @list: list to free
+ *
+ * Free a dma_resv_list and make sure to drop all references.
+ */
+static void dma_resv_list_free(struct dma_resv_list *list)
+{
+	unsigned int i;
+
+	if (!list)
+		return;
+
+	for (i = 0; i < list->shared_count; ++i)
+		dma_fence_put(rcu_dereference_protected(list->shared[i], true));
+
+	kfree_rcu(list, rcu);
+}
+
+#if IS_ENABLED(CONFIG_LOCKDEP)
+static int __init dma_resv_lockdep(void)
+{
+	struct mm_struct *mm = mm_alloc();
+	struct ww_acquire_ctx ctx;
+	struct dma_resv obj;
+	struct address_space mapping;
+	int ret;
+
+	if (!mm)
+		return -ENOMEM;
+
+	dma_resv_init(&obj);
+	address_space_init_once(&mapping);
+
+	mmap_read_lock(mm);
+	ww_acquire_init(&ctx, &reservation_ww_class);
+	ret = dma_resv_lock(&obj, &ctx);
+	if (ret == -EDEADLK)
+		dma_resv_lock_slow(&obj, &ctx);
+	fs_reclaim_acquire(GFP_KERNEL);
+	/* for unmap_mapping_range on trylocked buffer objects in shrinkers */
+	i_mmap_lock_write(&mapping);
+	i_mmap_unlock_write(&mapping);
+#ifdef CONFIG_MMU_NOTIFIER
+	lock_map_acquire(&__mmu_notifier_invalidate_range_start_map);
+	__dma_fence_might_wait();
+	lock_map_release(&__mmu_notifier_invalidate_range_start_map);
+#else
+	__dma_fence_might_wait();
+#endif
+	fs_reclaim_release(GFP_KERNEL);
+	ww_mutex_unlock(&obj.lock);
+	ww_acquire_fini(&ctx);
+	mmap_read_unlock(mm);
+	
+	mmput(mm);
+
+	return 0;
+}
+subsys_initcall(dma_resv_lockdep);
+#endif
+
+/**
+ * dma_resv_init - initialize a reservation object
+ * @obj: the reservation object
+ */
+void dma_resv_init(struct dma_resv *obj)
+{
+	ww_mutex_init(&obj->lock, &reservation_ww_class);
+	seqcount_ww_mutex_init(&obj->seq, &obj->lock);
+
+	RCU_INIT_POINTER(obj->fence, NULL);
+	RCU_INIT_POINTER(obj->fence_excl, NULL);
+}
+EXPORT_SYMBOL(dma_resv_init);
+
+/**
+ * dma_resv_fini - destroys a reservation object
+ * @obj: the reservation object
+ */
+void dma_resv_fini(struct dma_resv *obj)
+{
+	struct dma_resv_list *fobj;
+	struct dma_fence *excl;
+
+	/*
+	 * This object should be dead and all references must have
+	 * been released to it, so no need to be protected with rcu.
+	 */
+	excl = rcu_dereference_protected(obj->fence_excl, 1);
+	if (excl)
+		dma_fence_put(excl);
+
+	fobj = rcu_dereference_protected(obj->fence, 1);
+	dma_resv_list_free(fobj);
+	ww_mutex_destroy(&obj->lock);
+}
+EXPORT_SYMBOL(dma_resv_fini);
+
+/**
+ * dma_resv_reserve_shared - Reserve space to add shared fences to
+ * a dma_resv.
+ * @obj: reservation object
+ * @num_fences: number of fences we want to add
+ *
+ * Should be called before dma_resv_add_shared_fence().  Must
+ * be called with obj->lock held.
+ *
+ * RETURNS
+ * Zero for success, or -errno
+ */
+int dma_resv_reserve_shared(struct dma_resv *obj, unsigned int num_fences)
+{
+	struct dma_resv_list *old, *new;
+	unsigned int i, j, k, max;
+
+	dma_resv_assert_held(obj);
+
+	old = dma_resv_get_list(obj);
+
+	if (old && old->shared_max) {
+		if ((old->shared_count + num_fences) <= old->shared_max)
+			return 0;
+		else
+			max = max(old->shared_count + num_fences,
+				  old->shared_max * 2);
+	} else {
+		max = max(4ul, roundup_pow_of_two(num_fences));
+	}
+
+	new = dma_resv_list_alloc(max);
+	if (!new)
+		return -ENOMEM;
+
+	/*
+	 * no need to bump fence refcounts, rcu_read access
+	 * requires the use of kref_get_unless_zero, and the
+	 * references from the old struct are carried over to
+	 * the new.
+	 */
+	for (i = 0, j = 0, k = max; i < (old ? old->shared_count : 0); ++i) {
+		struct dma_fence *fence;
+
+		fence = rcu_dereference_protected(old->shared[i],
+						  dma_resv_held(obj));
+		if (dma_fence_is_signaled(fence))
+			RCU_INIT_POINTER(new->shared[--k], fence);
+		else
+			RCU_INIT_POINTER(new->shared[j++], fence);
+	}
+	new->shared_count = j;
+
+	/*
+	 * We are not changing the effective set of fences here so can
+	 * merely update the pointer to the new array; both existing
+	 * readers and new readers will see exactly the same set of
+	 * active (unsignaled) shared fences. Individual fences and the
+	 * old array are protected by RCU and so will not vanish under
+	 * the gaze of the rcu_read_lock() readers.
+	 */
+	rcu_assign_pointer(obj->fence, new);
+
+	if (!old)
+		return 0;
+
+	/* Drop the references to the signaled fences */
+	for (i = k; i < max; ++i) {
+		struct dma_fence *fence;
+
+		fence = rcu_dereference_protected(new->shared[i],
+						  dma_resv_held(obj));
+		dma_fence_put(fence);
+	}
+	kfree_rcu(old, rcu);
+
+	return 0;
+}
+EXPORT_SYMBOL(dma_resv_reserve_shared);
+
+/**
+ * dma_resv_add_shared_fence - Add a fence to a shared slot
+ * @obj: the reservation object
+ * @fence: the shared fence to add
+ *
+ * Add a fence to a shared slot, obj->lock must be held, and
+ * dma_resv_reserve_shared() has been called.
+ */
+void dma_resv_add_shared_fence(struct dma_resv *obj, struct dma_fence *fence)
+{
+	struct dma_resv_list *fobj;
+	struct dma_fence *old;
+	unsigned int i, count;
+
+	dma_fence_get(fence);
+
+	dma_resv_assert_held(obj);
+
+	fobj = dma_resv_get_list(obj);
+	count = fobj->shared_count;
+
+	write_seqcount_begin(&obj->seq);
+
+	for (i = 0; i < count; ++i) {
+
+		old = rcu_dereference_protected(fobj->shared[i],
+						dma_resv_held(obj));
+		if (old->context == fence->context ||
+		    dma_fence_is_signaled(old))
+			goto replace;
+	}
+
+	BUG_ON(fobj->shared_count >= fobj->shared_max);
+	old = NULL;
+	count++;
+
+replace:
+	RCU_INIT_POINTER(fobj->shared[i], fence);
+	/* pointer update must be visible before we extend the shared_count */
+	smp_store_mb(fobj->shared_count, count);
+
+	write_seqcount_end(&obj->seq);
+	dma_fence_put(old);
+}
+EXPORT_SYMBOL(dma_resv_add_shared_fence);
+
+/**
+ * dma_resv_add_excl_fence - Add an exclusive fence.
+ * @obj: the reservation object
+ * @fence: the shared fence to add
+ *
+ * Add a fence to the exclusive slot.  The obj->lock must be held.
+ */
+void dma_resv_add_excl_fence(struct dma_resv *obj, struct dma_fence *fence)
+{
+	struct dma_fence *old_fence = dma_resv_get_excl(obj);
+	struct dma_resv_list *old;
+	u32 i = 0;
+
+	dma_resv_assert_held(obj);
+
+	old = dma_resv_get_list(obj);
+	if (old)
+		i = old->shared_count;
+
+	if (fence)
+		dma_fence_get(fence);
+
+	write_seqcount_begin(&obj->seq);
+	/* write_seqcount_begin provides the necessary memory barrier */
+	RCU_INIT_POINTER(obj->fence_excl, fence);
+	if (old)
+		old->shared_count = 0;
+	write_seqcount_end(&obj->seq);
+
+	/* inplace update, no shared fences */
+	while (i--)
+		dma_fence_put(rcu_dereference_protected(old->shared[i],
+						dma_resv_held(obj)));
+
+	dma_fence_put(old_fence);
+}
+EXPORT_SYMBOL(dma_resv_add_excl_fence);
+
+/**
+* dma_resv_copy_fences - Copy all fences from src to dst.
+* @dst: the destination reservation object
+* @src: the source reservation object
+*
+* Copy all fences from src to dst. dst-lock must be held.
+*/
+int dma_resv_copy_fences(struct dma_resv *dst, struct dma_resv *src)
+{
+	struct dma_resv_list *src_list, *dst_list;
+	struct dma_fence *old, *new;
+	unsigned i;
+
+	dma_resv_assert_held(dst);
+
+	rcu_read_lock();
+	src_list = rcu_dereference(src->fence);
+
+retry:
+	if (src_list) {
+		unsigned shared_count = src_list->shared_count;
+
+		rcu_read_unlock();
+
+		dst_list = dma_resv_list_alloc(shared_count);
+		if (!dst_list)
+			return -ENOMEM;
+
+		rcu_read_lock();
+		src_list = rcu_dereference(src->fence);
+		if (!src_list || src_list->shared_count > shared_count) {
+			kfree(dst_list);
+			goto retry;
+		}
+
+		dst_list->shared_count = 0;
+		for (i = 0; i < src_list->shared_count; ++i) {
+			struct dma_fence *fence;
+
+			fence = rcu_dereference(src_list->shared[i]);
+			if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT,
+				     &fence->flags))
+				continue;
+
+			if (!dma_fence_get_rcu(fence)) {
+				dma_resv_list_free(dst_list);
+				src_list = rcu_dereference(src->fence);
+				goto retry;
+			}
+
+			if (dma_fence_is_signaled(fence)) {
+				dma_fence_put(fence);
+				continue;
+			}
+
+			rcu_assign_pointer(dst_list->shared[dst_list->shared_count++], fence);
+		}
+	} else {
+		dst_list = NULL;
+	}
+
+	new = dma_fence_get_rcu_safe(&src->fence_excl);
+	rcu_read_unlock();
+
+	src_list = dma_resv_get_list(dst);
+	old = dma_resv_get_excl(dst);
+
+	write_seqcount_begin(&dst->seq);
+	/* write_seqcount_begin provides the necessary memory barrier */
+	RCU_INIT_POINTER(dst->fence_excl, new);
+	RCU_INIT_POINTER(dst->fence, dst_list);
+	write_seqcount_end(&dst->seq);
+
+	dma_resv_list_free(src_list);
+	dma_fence_put(old);
+
+	return 0;
+}
+EXPORT_SYMBOL(dma_resv_copy_fences);
+
+/**
+ * dma_resv_get_fences_rcu - Get an object's shared and exclusive
+ * fences without update side lock held
+ * @obj: the reservation object
+ * @pfence_excl: the returned exclusive fence (or NULL)
+ * @pshared_count: the number of shared fences returned
+ * @pshared: the array of shared fence ptrs returned (array is krealloc'd to
+ * the required size, and must be freed by caller)
+ *
+ * Retrieve all fences from the reservation object. If the pointer for the
+ * exclusive fence is not specified the fence is put into the array of the
+ * shared fences as well. Returns either zero or -ENOMEM.
+ */
+int dma_resv_get_fences_rcu(struct dma_resv *obj,
+			    struct dma_fence **pfence_excl,
+			    unsigned *pshared_count,
+			    struct dma_fence ***pshared)
+{
+	struct dma_fence **shared = NULL;
+	struct dma_fence *fence_excl;
+	unsigned int shared_count;
+	int ret = 1;
+
+	do {
+		struct dma_resv_list *fobj;
+		unsigned int i, seq;
+		size_t sz = 0;
+
+		shared_count = i = 0;
+
+		rcu_read_lock();
+		seq = read_seqcount_begin(&obj->seq);
+
+		fence_excl = rcu_dereference(obj->fence_excl);
+		if (fence_excl && !dma_fence_get_rcu(fence_excl))
+			goto unlock;
+
+		fobj = rcu_dereference(obj->fence);
+		if (fobj)
+			sz += sizeof(*shared) * fobj->shared_max;
+
+		if (!pfence_excl && fence_excl)
+			sz += sizeof(*shared);
+
+		if (sz) {
+			struct dma_fence **nshared;
+
+			nshared = krealloc(shared, sz,
+					   GFP_NOWAIT | __GFP_NOWARN);
+			if (!nshared) {
+				rcu_read_unlock();
+
+				dma_fence_put(fence_excl);
+				fence_excl = NULL;
+
+				nshared = krealloc(shared, sz, GFP_KERNEL);
+				if (nshared) {
+					shared = nshared;
+					continue;
+				}
+
+				ret = -ENOMEM;
+				break;
+			}
+			shared = nshared;
+			shared_count = fobj ? fobj->shared_count : 0;
+			for (i = 0; i < shared_count; ++i) {
+				shared[i] = rcu_dereference(fobj->shared[i]);
+				if (!dma_fence_get_rcu(shared[i]))
+					break;
+			}
+		}
+
+		if (i != shared_count || read_seqcount_retry(&obj->seq, seq)) {
+			while (i--)
+				dma_fence_put(shared[i]);
+			dma_fence_put(fence_excl);
+			goto unlock;
+		}
+
+		ret = 0;
+unlock:
+		rcu_read_unlock();
+	} while (ret);
+
+	if (pfence_excl)
+		*pfence_excl = fence_excl;
+	else if (fence_excl)
+		shared[shared_count++] = fence_excl;
+
+	if (!shared_count) {
+		kfree(shared);
+		shared = NULL;
+	}
+
+	*pshared_count = shared_count;
+	*pshared = shared;
+	return ret;
+}
+EXPORT_SYMBOL_GPL(dma_resv_get_fences_rcu);
+
+/**
+ * dma_resv_wait_timeout_rcu - Wait on reservation's objects
+ * shared and/or exclusive fences.
+ * @obj: the reservation object
+ * @wait_all: if true, wait on all fences, else wait on just exclusive fence
+ * @intr: if true, do interruptible wait
+ * @timeout: timeout value in jiffies or zero to return immediately
+ *
+ * RETURNS
+ * Returns -ERESTARTSYS if interrupted, 0 if the wait timed out, or
+ * greater than zer on success.
+ */
+long dma_resv_wait_timeout_rcu(struct dma_resv *obj,
+			       bool wait_all, bool intr,
+			       unsigned long timeout)
+{
+	struct dma_fence *fence;
+	unsigned seq, shared_count;
+	long ret = timeout ? timeout : 1;
+	int i;
+
+retry:
+	shared_count = 0;
+	seq = read_seqcount_begin(&obj->seq);
+	rcu_read_lock();
+	i = -1;
+
+	fence = rcu_dereference(obj->fence_excl);
+	if (fence && !test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)) {
+		if (!dma_fence_get_rcu(fence))
+			goto unlock_retry;
+
+		if (dma_fence_is_signaled(fence)) {
+			dma_fence_put(fence);
+			fence = NULL;
+		}
+
+	} else {
+		fence = NULL;
+	}
+
+	if (wait_all) {
+		struct dma_resv_list *fobj = rcu_dereference(obj->fence);
+
+		if (fobj)
+			shared_count = fobj->shared_count;
+
+		for (i = 0; !fence && i < shared_count; ++i) {
+			struct dma_fence *lfence = rcu_dereference(fobj->shared[i]);
+
+			if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT,
+				     &lfence->flags))
+				continue;
+
+			if (!dma_fence_get_rcu(lfence))
+				goto unlock_retry;
+
+			if (dma_fence_is_signaled(lfence)) {
+				dma_fence_put(lfence);
+				continue;
+			}
+
+			fence = lfence;
+			break;
+		}
+	}
+
+	rcu_read_unlock();
+	if (fence) {
+		if (read_seqcount_retry(&obj->seq, seq)) {
+			dma_fence_put(fence);
+			goto retry;
+		}
+
+		ret = dma_fence_wait_timeout(fence, intr, ret);
+		dma_fence_put(fence);
+		if (ret > 0 && wait_all && (i + 1 < shared_count))
+			goto retry;
+	}
+	return ret;
+
+unlock_retry:
+	rcu_read_unlock();
+	goto retry;
+}
+EXPORT_SYMBOL_GPL(dma_resv_wait_timeout_rcu);
+
+
+static inline int dma_resv_test_signaled_single(struct dma_fence *passed_fence)
+{
+	struct dma_fence *fence, *lfence = passed_fence;
+	int ret = 1;
+
+	if (!test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &lfence->flags)) {
+		fence = dma_fence_get_rcu(lfence);
+		if (!fence)
+			return -1;
+
+		ret = !!dma_fence_is_signaled(fence);
+		dma_fence_put(fence);
+	}
+	return ret;
+}
+
+/**
+ * dma_resv_test_signaled_rcu - Test if a reservation object's
+ * fences have been signaled.
+ * @obj: the reservation object
+ * @test_all: if true, test all fences, otherwise only test the exclusive
+ * fence
+ *
+ * RETURNS
+ * true if all fences signaled, else false
+ */
+bool dma_resv_test_signaled_rcu(struct dma_resv *obj, bool test_all)
+{
+	unsigned seq, shared_count;
+	int ret;
+
+	rcu_read_lock();
+retry:
+	ret = true;
+	shared_count = 0;
+	seq = read_seqcount_begin(&obj->seq);
+
+	if (test_all) {
+		unsigned i;
+
+		struct dma_resv_list *fobj = rcu_dereference(obj->fence);
+
+		if (fobj)
+			shared_count = fobj->shared_count;
+
+		for (i = 0; i < shared_count; ++i) {
+			struct dma_fence *fence = rcu_dereference(fobj->shared[i]);
+
+			ret = dma_resv_test_signaled_single(fence);
+			if (ret < 0)
+				goto retry;
+			else if (!ret)
+				break;
+		}
+
+		if (read_seqcount_retry(&obj->seq, seq))
+			goto retry;
+	}
+
+	if (!shared_count) {
+		struct dma_fence *fence_excl = rcu_dereference(obj->fence_excl);
+
+		if (fence_excl) {
+			ret = dma_resv_test_signaled_single(fence_excl);
+			if (ret < 0)
+				goto retry;
+
+			if (read_seqcount_retry(&obj->seq, seq))
+				goto retry;
+		}
+	}
+
+	rcu_read_unlock();
+	return ret;
+}
+EXPORT_SYMBOL_GPL(dma_resv_test_signaled_rcu);
diff --git a/drivers/dma-buf/heaps/Kconfig b/drivers/dma-buf/heaps/Kconfig
new file mode 100644
index 000000000..a5eef06c4
--- /dev/null
+++ b/drivers/dma-buf/heaps/Kconfig
@@ -0,0 +1,14 @@
+config DMABUF_HEAPS_SYSTEM
+	bool "DMA-BUF System Heap"
+	depends on DMABUF_HEAPS
+	help
+	  Choose this option to enable the system dmabuf heap. The system heap
+	  is backed by pages from the buddy allocator. If in doubt, say Y.
+
+config DMABUF_HEAPS_CMA
+	bool "DMA-BUF CMA Heap"
+	depends on DMABUF_HEAPS && DMA_CMA
+	help
+	  Choose this option to enable dma-buf CMA heap. This heap is backed
+	  by the Contiguous Memory Allocator (CMA). If your system has these
+	  regions, you should say Y here.
diff --git a/drivers/dma-buf/heaps/Makefile b/drivers/dma-buf/heaps/Makefile
new file mode 100644
index 000000000..6e54cdec3
--- /dev/null
+++ b/drivers/dma-buf/heaps/Makefile
@@ -0,0 +1,4 @@
+# SPDX-License-Identifier: GPL-2.0
+obj-y					+= heap-helpers.o
+obj-$(CONFIG_DMABUF_HEAPS_SYSTEM)	+= system_heap.o
+obj-$(CONFIG_DMABUF_HEAPS_CMA)		+= cma_heap.o
diff --git a/drivers/dma-buf/heaps/cma_heap.c b/drivers/dma-buf/heaps/cma_heap.c
new file mode 100644
index 000000000..e55384dc1
--- /dev/null
+++ b/drivers/dma-buf/heaps/cma_heap.c
@@ -0,0 +1,177 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * DMABUF CMA heap exporter
+ *
+ * Copyright (C) 2012, 2019 Linaro Ltd.
+ * Author: <benjamin.gaignard@linaro.org> for ST-Ericsson.
+ */
+
+#include <linux/cma.h>
+#include <linux/device.h>
+#include <linux/dma-buf.h>
+#include <linux/dma-heap.h>
+#include <linux/dma-map-ops.h>
+#include <linux/err.h>
+#include <linux/errno.h>
+#include <linux/highmem.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/scatterlist.h>
+#include <linux/sched/signal.h>
+
+#include "heap-helpers.h"
+
+struct cma_heap {
+	struct dma_heap *heap;
+	struct cma *cma;
+};
+
+static void cma_heap_free(struct heap_helper_buffer *buffer)
+{
+	struct cma_heap *cma_heap = dma_heap_get_drvdata(buffer->heap);
+	unsigned long nr_pages = buffer->pagecount;
+	struct page *cma_pages = buffer->priv_virt;
+
+	/* free page list */
+	kfree(buffer->pages);
+	/* release memory */
+	cma_release(cma_heap->cma, cma_pages, nr_pages);
+	kfree(buffer);
+}
+
+/* dmabuf heap CMA operations functions */
+static int cma_heap_allocate(struct dma_heap *heap,
+			     unsigned long len,
+			     unsigned long fd_flags,
+			     unsigned long heap_flags)
+{
+	struct cma_heap *cma_heap = dma_heap_get_drvdata(heap);
+	struct heap_helper_buffer *helper_buffer;
+	struct page *cma_pages;
+	size_t size = PAGE_ALIGN(len);
+	unsigned long nr_pages = size >> PAGE_SHIFT;
+	unsigned long align = get_order(size);
+	struct dma_buf *dmabuf;
+	int ret = -ENOMEM;
+	pgoff_t pg;
+
+	if (align > CONFIG_CMA_ALIGNMENT)
+		align = CONFIG_CMA_ALIGNMENT;
+
+	helper_buffer = kzalloc(sizeof(*helper_buffer), GFP_KERNEL);
+	if (!helper_buffer)
+		return -ENOMEM;
+
+	init_heap_helper_buffer(helper_buffer, cma_heap_free);
+	helper_buffer->heap = heap;
+	helper_buffer->size = len;
+
+	cma_pages = cma_alloc(cma_heap->cma, nr_pages, align, false);
+	if (!cma_pages)
+		goto free_buf;
+
+	if (PageHighMem(cma_pages)) {
+		unsigned long nr_clear_pages = nr_pages;
+		struct page *page = cma_pages;
+
+		while (nr_clear_pages > 0) {
+			void *vaddr = kmap_atomic(page);
+
+			memset(vaddr, 0, PAGE_SIZE);
+			kunmap_atomic(vaddr);
+			/*
+			 * Avoid wasting time zeroing memory if the process
+			 * has been killed by by SIGKILL
+			 */
+			if (fatal_signal_pending(current))
+				goto free_cma;
+
+			page++;
+			nr_clear_pages--;
+		}
+	} else {
+		memset(page_address(cma_pages), 0, size);
+	}
+
+	helper_buffer->pagecount = nr_pages;
+	helper_buffer->pages = kmalloc_array(helper_buffer->pagecount,
+					     sizeof(*helper_buffer->pages),
+					     GFP_KERNEL);
+	if (!helper_buffer->pages) {
+		ret = -ENOMEM;
+		goto free_cma;
+	}
+
+	for (pg = 0; pg < helper_buffer->pagecount; pg++)
+		helper_buffer->pages[pg] = &cma_pages[pg];
+
+	/* create the dmabuf */
+	dmabuf = heap_helper_export_dmabuf(helper_buffer, fd_flags);
+	if (IS_ERR(dmabuf)) {
+		ret = PTR_ERR(dmabuf);
+		goto free_pages;
+	}
+
+	helper_buffer->dmabuf = dmabuf;
+	helper_buffer->priv_virt = cma_pages;
+
+	ret = dma_buf_fd(dmabuf, fd_flags);
+	if (ret < 0) {
+		dma_buf_put(dmabuf);
+		/* just return, as put will call release and that will free */
+		return ret;
+	}
+
+	return ret;
+
+free_pages:
+	kfree(helper_buffer->pages);
+free_cma:
+	cma_release(cma_heap->cma, cma_pages, nr_pages);
+free_buf:
+	kfree(helper_buffer);
+	return ret;
+}
+
+static const struct dma_heap_ops cma_heap_ops = {
+	.allocate = cma_heap_allocate,
+};
+
+static int __add_cma_heap(struct cma *cma, void *data)
+{
+	struct cma_heap *cma_heap;
+	struct dma_heap_export_info exp_info;
+
+	cma_heap = kzalloc(sizeof(*cma_heap), GFP_KERNEL);
+	if (!cma_heap)
+		return -ENOMEM;
+	cma_heap->cma = cma;
+
+	exp_info.name = cma_get_name(cma);
+	exp_info.ops = &cma_heap_ops;
+	exp_info.priv = cma_heap;
+
+	cma_heap->heap = dma_heap_add(&exp_info);
+	if (IS_ERR(cma_heap->heap)) {
+		int ret = PTR_ERR(cma_heap->heap);
+
+		kfree(cma_heap);
+		return ret;
+	}
+
+	return 0;
+}
+
+static int add_default_cma_heap(void)
+{
+	struct cma *default_cma = dev_get_cma_area(NULL);
+	int ret = 0;
+
+	if (default_cma)
+		ret = __add_cma_heap(default_cma, NULL);
+
+	return ret;
+}
+module_init(add_default_cma_heap);
+MODULE_DESCRIPTION("DMA-BUF CMA Heap");
+MODULE_LICENSE("GPL v2");
diff --git a/drivers/dma-buf/heaps/heap-helpers.c b/drivers/dma-buf/heaps/heap-helpers.c
new file mode 100644
index 000000000..d0696cf93
--- /dev/null
+++ b/drivers/dma-buf/heaps/heap-helpers.c
@@ -0,0 +1,270 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/device.h>
+#include <linux/dma-buf.h>
+#include <linux/err.h>
+#include <linux/highmem.h>
+#include <linux/idr.h>
+#include <linux/list.h>
+#include <linux/slab.h>
+#include <linux/uaccess.h>
+#include <linux/vmalloc.h>
+#include <uapi/linux/dma-heap.h>
+
+#include "heap-helpers.h"
+
+void init_heap_helper_buffer(struct heap_helper_buffer *buffer,
+			     void (*free)(struct heap_helper_buffer *))
+{
+	buffer->priv_virt = NULL;
+	mutex_init(&buffer->lock);
+	buffer->vmap_cnt = 0;
+	buffer->vaddr = NULL;
+	buffer->pagecount = 0;
+	buffer->pages = NULL;
+	INIT_LIST_HEAD(&buffer->attachments);
+	buffer->free = free;
+}
+
+struct dma_buf *heap_helper_export_dmabuf(struct heap_helper_buffer *buffer,
+					  int fd_flags)
+{
+	DEFINE_DMA_BUF_EXPORT_INFO(exp_info);
+
+	exp_info.ops = &heap_helper_ops;
+	exp_info.size = buffer->size;
+	exp_info.flags = fd_flags;
+	exp_info.priv = buffer;
+
+	return dma_buf_export(&exp_info);
+}
+
+static void *dma_heap_map_kernel(struct heap_helper_buffer *buffer)
+{
+	void *vaddr;
+
+	vaddr = vmap(buffer->pages, buffer->pagecount, VM_MAP, PAGE_KERNEL);
+	if (!vaddr)
+		return ERR_PTR(-ENOMEM);
+
+	return vaddr;
+}
+
+static void dma_heap_buffer_destroy(struct heap_helper_buffer *buffer)
+{
+	if (buffer->vmap_cnt > 0) {
+		WARN(1, "%s: buffer still mapped in the kernel\n", __func__);
+		vunmap(buffer->vaddr);
+	}
+
+	buffer->free(buffer);
+}
+
+static void *dma_heap_buffer_vmap_get(struct heap_helper_buffer *buffer)
+{
+	void *vaddr;
+
+	if (buffer->vmap_cnt) {
+		buffer->vmap_cnt++;
+		return buffer->vaddr;
+	}
+	vaddr = dma_heap_map_kernel(buffer);
+	if (IS_ERR(vaddr))
+		return vaddr;
+	buffer->vaddr = vaddr;
+	buffer->vmap_cnt++;
+	return vaddr;
+}
+
+static void dma_heap_buffer_vmap_put(struct heap_helper_buffer *buffer)
+{
+	if (!--buffer->vmap_cnt) {
+		vunmap(buffer->vaddr);
+		buffer->vaddr = NULL;
+	}
+}
+
+struct dma_heaps_attachment {
+	struct device *dev;
+	struct sg_table table;
+	struct list_head list;
+};
+
+static int dma_heap_attach(struct dma_buf *dmabuf,
+			   struct dma_buf_attachment *attachment)
+{
+	struct dma_heaps_attachment *a;
+	struct heap_helper_buffer *buffer = dmabuf->priv;
+	int ret;
+
+	a = kzalloc(sizeof(*a), GFP_KERNEL);
+	if (!a)
+		return -ENOMEM;
+
+	ret = sg_alloc_table_from_pages(&a->table, buffer->pages,
+					buffer->pagecount, 0,
+					buffer->pagecount << PAGE_SHIFT,
+					GFP_KERNEL);
+	if (ret) {
+		kfree(a);
+		return ret;
+	}
+
+	a->dev = attachment->dev;
+	INIT_LIST_HEAD(&a->list);
+
+	attachment->priv = a;
+
+	mutex_lock(&buffer->lock);
+	list_add(&a->list, &buffer->attachments);
+	mutex_unlock(&buffer->lock);
+
+	return 0;
+}
+
+static void dma_heap_detach(struct dma_buf *dmabuf,
+			    struct dma_buf_attachment *attachment)
+{
+	struct dma_heaps_attachment *a = attachment->priv;
+	struct heap_helper_buffer *buffer = dmabuf->priv;
+
+	mutex_lock(&buffer->lock);
+	list_del(&a->list);
+	mutex_unlock(&buffer->lock);
+
+	sg_free_table(&a->table);
+	kfree(a);
+}
+
+static
+struct sg_table *dma_heap_map_dma_buf(struct dma_buf_attachment *attachment,
+				      enum dma_data_direction direction)
+{
+	struct dma_heaps_attachment *a = attachment->priv;
+	struct sg_table *table = &a->table;
+	int ret;
+
+	ret = dma_map_sgtable(attachment->dev, table, direction, 0);
+	if (ret)
+		table = ERR_PTR(ret);
+	return table;
+}
+
+static void dma_heap_unmap_dma_buf(struct dma_buf_attachment *attachment,
+				   struct sg_table *table,
+				   enum dma_data_direction direction)
+{
+	dma_unmap_sgtable(attachment->dev, table, direction, 0);
+}
+
+static vm_fault_t dma_heap_vm_fault(struct vm_fault *vmf)
+{
+	struct vm_area_struct *vma = vmf->vma;
+	struct heap_helper_buffer *buffer = vma->vm_private_data;
+
+	if (vmf->pgoff > buffer->pagecount)
+		return VM_FAULT_SIGBUS;
+
+	vmf->page = buffer->pages[vmf->pgoff];
+	get_page(vmf->page);
+
+	return 0;
+}
+
+static const struct vm_operations_struct dma_heap_vm_ops = {
+	.fault = dma_heap_vm_fault,
+};
+
+static int dma_heap_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma)
+{
+	struct heap_helper_buffer *buffer = dmabuf->priv;
+
+	if ((vma->vm_flags & (VM_SHARED | VM_MAYSHARE)) == 0)
+		return -EINVAL;
+
+	vma->vm_ops = &dma_heap_vm_ops;
+	vma->vm_private_data = buffer;
+
+	return 0;
+}
+
+static void dma_heap_dma_buf_release(struct dma_buf *dmabuf)
+{
+	struct heap_helper_buffer *buffer = dmabuf->priv;
+
+	dma_heap_buffer_destroy(buffer);
+}
+
+static int dma_heap_dma_buf_begin_cpu_access(struct dma_buf *dmabuf,
+					     enum dma_data_direction direction)
+{
+	struct heap_helper_buffer *buffer = dmabuf->priv;
+	struct dma_heaps_attachment *a;
+	int ret = 0;
+
+	mutex_lock(&buffer->lock);
+
+	if (buffer->vmap_cnt)
+		invalidate_kernel_vmap_range(buffer->vaddr, buffer->size);
+
+	list_for_each_entry(a, &buffer->attachments, list) {
+		dma_sync_sg_for_cpu(a->dev, a->table.sgl, a->table.nents,
+				    direction);
+	}
+	mutex_unlock(&buffer->lock);
+
+	return ret;
+}
+
+static int dma_heap_dma_buf_end_cpu_access(struct dma_buf *dmabuf,
+					   enum dma_data_direction direction)
+{
+	struct heap_helper_buffer *buffer = dmabuf->priv;
+	struct dma_heaps_attachment *a;
+
+	mutex_lock(&buffer->lock);
+
+	if (buffer->vmap_cnt)
+		flush_kernel_vmap_range(buffer->vaddr, buffer->size);
+
+	list_for_each_entry(a, &buffer->attachments, list) {
+		dma_sync_sg_for_device(a->dev, a->table.sgl, a->table.nents,
+				       direction);
+	}
+	mutex_unlock(&buffer->lock);
+
+	return 0;
+}
+
+static void *dma_heap_dma_buf_vmap(struct dma_buf *dmabuf)
+{
+	struct heap_helper_buffer *buffer = dmabuf->priv;
+	void *vaddr;
+
+	mutex_lock(&buffer->lock);
+	vaddr = dma_heap_buffer_vmap_get(buffer);
+	mutex_unlock(&buffer->lock);
+
+	return vaddr;
+}
+
+static void dma_heap_dma_buf_vunmap(struct dma_buf *dmabuf, void *vaddr)
+{
+	struct heap_helper_buffer *buffer = dmabuf->priv;
+
+	mutex_lock(&buffer->lock);
+	dma_heap_buffer_vmap_put(buffer);
+	mutex_unlock(&buffer->lock);
+}
+
+const struct dma_buf_ops heap_helper_ops = {
+	.map_dma_buf = dma_heap_map_dma_buf,
+	.unmap_dma_buf = dma_heap_unmap_dma_buf,
+	.mmap = dma_heap_mmap,
+	.release = dma_heap_dma_buf_release,
+	.attach = dma_heap_attach,
+	.detach = dma_heap_detach,
+	.begin_cpu_access = dma_heap_dma_buf_begin_cpu_access,
+	.end_cpu_access = dma_heap_dma_buf_end_cpu_access,
+	.vmap = dma_heap_dma_buf_vmap,
+	.vunmap = dma_heap_dma_buf_vunmap,
+};
diff --git a/drivers/dma-buf/heaps/heap-helpers.h b/drivers/dma-buf/heaps/heap-helpers.h
new file mode 100644
index 000000000..805d2df88
--- /dev/null
+++ b/drivers/dma-buf/heaps/heap-helpers.h
@@ -0,0 +1,53 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * DMABUF Heaps helper code
+ *
+ * Copyright (C) 2011 Google, Inc.
+ * Copyright (C) 2019 Linaro Ltd.
+ */
+
+#ifndef _HEAP_HELPERS_H
+#define _HEAP_HELPERS_H
+
+#include <linux/dma-heap.h>
+#include <linux/list.h>
+
+/**
+ * struct heap_helper_buffer - helper buffer metadata
+ * @heap:		back pointer to the heap the buffer came from
+ * @dmabuf:		backing dma-buf for this buffer
+ * @size:		size of the buffer
+ * @priv_virt		pointer to heap specific private value
+ * @lock		mutext to protect the data in this structure
+ * @vmap_cnt		count of vmap references on the buffer
+ * @vaddr		vmap'ed virtual address
+ * @pagecount		number of pages in the buffer
+ * @pages		list of page pointers
+ * @attachments		list of device attachments
+ *
+ * @free		heap callback to free the buffer
+ */
+struct heap_helper_buffer {
+	struct dma_heap *heap;
+	struct dma_buf *dmabuf;
+	size_t size;
+
+	void *priv_virt;
+	struct mutex lock;
+	int vmap_cnt;
+	void *vaddr;
+	pgoff_t pagecount;
+	struct page **pages;
+	struct list_head attachments;
+
+	void (*free)(struct heap_helper_buffer *buffer);
+};
+
+void init_heap_helper_buffer(struct heap_helper_buffer *buffer,
+			     void (*free)(struct heap_helper_buffer *));
+
+struct dma_buf *heap_helper_export_dmabuf(struct heap_helper_buffer *buffer,
+					  int fd_flags);
+
+extern const struct dma_buf_ops heap_helper_ops;
+#endif /* _HEAP_HELPERS_H */
diff --git a/drivers/dma-buf/heaps/system_heap.c b/drivers/dma-buf/heaps/system_heap.c
new file mode 100644
index 000000000..0bf688e3c
--- /dev/null
+++ b/drivers/dma-buf/heaps/system_heap.c
@@ -0,0 +1,123 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * DMABUF System heap exporter
+ *
+ * Copyright (C) 2011 Google, Inc.
+ * Copyright (C) 2019 Linaro Ltd.
+ */
+
+#include <linux/dma-buf.h>
+#include <linux/dma-mapping.h>
+#include <linux/dma-heap.h>
+#include <linux/err.h>
+#include <linux/highmem.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/scatterlist.h>
+#include <linux/slab.h>
+#include <linux/sched/signal.h>
+#include <asm/page.h>
+
+#include "heap-helpers.h"
+
+struct dma_heap *sys_heap;
+
+static void system_heap_free(struct heap_helper_buffer *buffer)
+{
+	pgoff_t pg;
+
+	for (pg = 0; pg < buffer->pagecount; pg++)
+		__free_page(buffer->pages[pg]);
+	kfree(buffer->pages);
+	kfree(buffer);
+}
+
+static int system_heap_allocate(struct dma_heap *heap,
+				unsigned long len,
+				unsigned long fd_flags,
+				unsigned long heap_flags)
+{
+	struct heap_helper_buffer *helper_buffer;
+	struct dma_buf *dmabuf;
+	int ret = -ENOMEM;
+	pgoff_t pg;
+
+	helper_buffer = kzalloc(sizeof(*helper_buffer), GFP_KERNEL);
+	if (!helper_buffer)
+		return -ENOMEM;
+
+	init_heap_helper_buffer(helper_buffer, system_heap_free);
+	helper_buffer->heap = heap;
+	helper_buffer->size = len;
+
+	helper_buffer->pagecount = len / PAGE_SIZE;
+	helper_buffer->pages = kmalloc_array(helper_buffer->pagecount,
+					     sizeof(*helper_buffer->pages),
+					     GFP_KERNEL);
+	if (!helper_buffer->pages) {
+		ret = -ENOMEM;
+		goto err0;
+	}
+
+	for (pg = 0; pg < helper_buffer->pagecount; pg++) {
+		/*
+		 * Avoid trying to allocate memory if the process
+		 * has been killed by by SIGKILL
+		 */
+		if (fatal_signal_pending(current))
+			goto err1;
+
+		helper_buffer->pages[pg] = alloc_page(GFP_KERNEL | __GFP_ZERO);
+		if (!helper_buffer->pages[pg])
+			goto err1;
+	}
+
+	/* create the dmabuf */
+	dmabuf = heap_helper_export_dmabuf(helper_buffer, fd_flags);
+	if (IS_ERR(dmabuf)) {
+		ret = PTR_ERR(dmabuf);
+		goto err1;
+	}
+
+	helper_buffer->dmabuf = dmabuf;
+
+	ret = dma_buf_fd(dmabuf, fd_flags);
+	if (ret < 0) {
+		dma_buf_put(dmabuf);
+		/* just return, as put will call release and that will free */
+		return ret;
+	}
+
+	return ret;
+
+err1:
+	while (pg > 0)
+		__free_page(helper_buffer->pages[--pg]);
+	kfree(helper_buffer->pages);
+err0:
+	kfree(helper_buffer);
+
+	return ret;
+}
+
+static const struct dma_heap_ops system_heap_ops = {
+	.allocate = system_heap_allocate,
+};
+
+static int system_heap_create(void)
+{
+	struct dma_heap_export_info exp_info;
+	int ret = 0;
+
+	exp_info.name = "system";
+	exp_info.ops = &system_heap_ops;
+	exp_info.priv = NULL;
+
+	sys_heap = dma_heap_add(&exp_info);
+	if (IS_ERR(sys_heap))
+		ret = PTR_ERR(sys_heap);
+
+	return ret;
+}
+module_init(system_heap_create);
+MODULE_LICENSE("GPL v2");
diff --git a/drivers/dma-buf/selftest.c b/drivers/dma-buf/selftest.c
new file mode 100644
index 000000000..c60b6944b
--- /dev/null
+++ b/drivers/dma-buf/selftest.c
@@ -0,0 +1,167 @@
+/* SPDX-License-Identifier: MIT */
+
+/*
+ * Copyright © 2019 Intel Corporation
+ */
+
+#include <linux/compiler.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/sched/signal.h>
+#include <linux/slab.h>
+
+#include "selftest.h"
+
+enum {
+#define selftest(n, func) __idx_##n,
+#include "selftests.h"
+#undef selftest
+};
+
+#define selftest(n, f) [__idx_##n] = { .name = #n, .func = f },
+static struct selftest {
+	bool enabled;
+	const char *name;
+	int (*func)(void);
+} selftests[] = {
+#include "selftests.h"
+};
+#undef selftest
+
+/* Embed the line number into the parameter name so that we can order tests */
+#define param(n) __PASTE(igt__, __PASTE(__PASTE(__LINE__, __), n))
+#define selftest_0(n, func, id) \
+module_param_named(id, selftests[__idx_##n].enabled, bool, 0400);
+#define selftest(n, func) selftest_0(n, func, param(n))
+#include "selftests.h"
+#undef selftest
+
+int __sanitycheck__(void)
+{
+	pr_debug("Hello World!\n");
+	return 0;
+}
+
+static char *__st_filter;
+
+static bool apply_subtest_filter(const char *caller, const char *name)
+{
+	char *filter, *sep, *tok;
+	bool result = true;
+
+	filter = kstrdup(__st_filter, GFP_KERNEL);
+	for (sep = filter; (tok = strsep(&sep, ","));) {
+		bool allow = true;
+		char *sl;
+
+		if (*tok == '!') {
+			allow = false;
+			tok++;
+		}
+
+		if (*tok == '\0')
+			continue;
+
+		sl = strchr(tok, '/');
+		if (sl) {
+			*sl++ = '\0';
+			if (strcmp(tok, caller)) {
+				if (allow)
+					result = false;
+				continue;
+			}
+			tok = sl;
+		}
+
+		if (strcmp(tok, name)) {
+			if (allow)
+				result = false;
+			continue;
+		}
+
+		result = allow;
+		break;
+	}
+	kfree(filter);
+
+	return result;
+}
+
+int
+__subtests(const char *caller, const struct subtest *st, int count, void *data)
+{
+	int err;
+
+	for (; count--; st++) {
+		cond_resched();
+		if (signal_pending(current))
+			return -EINTR;
+
+		if (!apply_subtest_filter(caller, st->name))
+			continue;
+
+		pr_info("dma-buf: Running %s/%s\n", caller, st->name);
+
+		err = st->func(data);
+		if (err && err != -EINTR) {
+			pr_err("dma-buf/%s: %s failed with error %d\n",
+			       caller, st->name, err);
+			return err;
+		}
+	}
+
+	return 0;
+}
+
+static void set_default_test_all(struct selftest *st, unsigned long count)
+{
+	unsigned long i;
+
+	for (i = 0; i < count; i++)
+		if (st[i].enabled)
+			return;
+
+	for (i = 0; i < count; i++)
+		st[i].enabled = true;
+}
+
+static int run_selftests(struct selftest *st, unsigned long count)
+{
+	int err = 0;
+
+	set_default_test_all(st, count);
+
+	/* Tests are listed in natural order in selftests.h */
+	for (; count--; st++) {
+		if (!st->enabled)
+			continue;
+
+		pr_info("dma-buf: Running %s\n", st->name);
+		err = st->func();
+		if (err)
+			break;
+	}
+
+	if (WARN(err > 0 || err == -ENOTTY,
+		 "%s returned %d, conflicting with selftest's magic values!\n",
+		 st->name, err))
+		err = -1;
+
+	return err;
+}
+
+static int __init st_init(void)
+{
+	return run_selftests(selftests, ARRAY_SIZE(selftests));
+}
+
+static void __exit st_exit(void)
+{
+}
+
+module_param_named(st_filter, __st_filter, charp, 0400);
+module_init(st_init);
+module_exit(st_exit);
+
+MODULE_DESCRIPTION("Self-test harness for dma-buf");
+MODULE_LICENSE("GPL and additional rights");
diff --git a/drivers/dma-buf/selftest.h b/drivers/dma-buf/selftest.h
new file mode 100644
index 000000000..45793aff6
--- /dev/null
+++ b/drivers/dma-buf/selftest.h
@@ -0,0 +1,30 @@
+// SPDX-License-Identifier: MIT
+
+/*
+ * Copyright © 2019 Intel Corporation
+ */
+
+#ifndef __SELFTEST_H__
+#define __SELFTEST_H__
+
+#include <linux/compiler.h>
+
+#define selftest(name, func) int func(void);
+#include "selftests.h"
+#undef selftest
+
+struct subtest {
+	int (*func)(void *data);
+	const char *name;
+};
+
+int __subtests(const char *caller,
+	       const struct subtest *st,
+	       int count,
+	       void *data);
+#define subtests(T, data) \
+	__subtests(__func__, T, ARRAY_SIZE(T), data)
+
+#define SUBTEST(x) { x, #x }
+
+#endif /* __SELFTEST_H__ */
diff --git a/drivers/dma-buf/selftests.h b/drivers/dma-buf/selftests.h
new file mode 100644
index 000000000..bc8cea67b
--- /dev/null
+++ b/drivers/dma-buf/selftests.h
@@ -0,0 +1,14 @@
+/* SPDX-License-Identifier: MIT */
+/* List each unit test as selftest(name, function)
+ *
+ * The name is used as both an enum and expanded as subtest__name to create
+ * a module parameter. It must be unique and legal for a C identifier.
+ *
+ * The function should be of type int function(void). It may be conditionally
+ * compiled using #if IS_ENABLED(CONFIG_DRM_I915_SELFTEST).
+ *
+ * Tests are executed in order by igt/dmabuf_selftest
+ */
+selftest(sanitycheck, __sanitycheck__) /* keep first (igt selfcheck) */
+selftest(dma_fence, dma_fence)
+selftest(dma_fence_chain, dma_fence_chain)
diff --git a/drivers/dma-buf/seqno-fence.c b/drivers/dma-buf/seqno-fence.c
new file mode 100644
index 000000000..bfe14e94c
--- /dev/null
+++ b/drivers/dma-buf/seqno-fence.c
@@ -0,0 +1,71 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * seqno-fence, using a dma-buf to synchronize fencing
+ *
+ * Copyright (C) 2012 Texas Instruments
+ * Copyright (C) 2012-2014 Canonical Ltd
+ * Authors:
+ *   Rob Clark <robdclark@gmail.com>
+ *   Maarten Lankhorst <maarten.lankhorst@canonical.com>
+ */
+
+#include <linux/slab.h>
+#include <linux/export.h>
+#include <linux/seqno-fence.h>
+
+static const char *seqno_fence_get_driver_name(struct dma_fence *fence)
+{
+	struct seqno_fence *seqno_fence = to_seqno_fence(fence);
+
+	return seqno_fence->ops->get_driver_name(fence);
+}
+
+static const char *seqno_fence_get_timeline_name(struct dma_fence *fence)
+{
+	struct seqno_fence *seqno_fence = to_seqno_fence(fence);
+
+	return seqno_fence->ops->get_timeline_name(fence);
+}
+
+static bool seqno_enable_signaling(struct dma_fence *fence)
+{
+	struct seqno_fence *seqno_fence = to_seqno_fence(fence);
+
+	return seqno_fence->ops->enable_signaling(fence);
+}
+
+static bool seqno_signaled(struct dma_fence *fence)
+{
+	struct seqno_fence *seqno_fence = to_seqno_fence(fence);
+
+	return seqno_fence->ops->signaled && seqno_fence->ops->signaled(fence);
+}
+
+static void seqno_release(struct dma_fence *fence)
+{
+	struct seqno_fence *f = to_seqno_fence(fence);
+
+	dma_buf_put(f->sync_buf);
+	if (f->ops->release)
+		f->ops->release(fence);
+	else
+		dma_fence_free(&f->base);
+}
+
+static signed long seqno_wait(struct dma_fence *fence, bool intr,
+			      signed long timeout)
+{
+	struct seqno_fence *f = to_seqno_fence(fence);
+
+	return f->ops->wait(fence, intr, timeout);
+}
+
+const struct dma_fence_ops seqno_fence_ops = {
+	.get_driver_name = seqno_fence_get_driver_name,
+	.get_timeline_name = seqno_fence_get_timeline_name,
+	.enable_signaling = seqno_enable_signaling,
+	.signaled = seqno_signaled,
+	.wait = seqno_wait,
+	.release = seqno_release,
+};
+EXPORT_SYMBOL(seqno_fence_ops);
diff --git a/drivers/dma-buf/st-dma-fence-chain.c b/drivers/dma-buf/st-dma-fence-chain.c
new file mode 100644
index 000000000..9525f7f56
--- /dev/null
+++ b/drivers/dma-buf/st-dma-fence-chain.c
@@ -0,0 +1,714 @@
+// SPDX-License-Identifier: MIT
+
+/*
+ * Copyright © 2019 Intel Corporation
+ */
+
+#include <linux/delay.h>
+#include <linux/dma-fence.h>
+#include <linux/dma-fence-chain.h>
+#include <linux/kernel.h>
+#include <linux/kthread.h>
+#include <linux/mm.h>
+#include <linux/sched/signal.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/random.h>
+
+#include "selftest.h"
+
+#define CHAIN_SZ (4 << 10)
+
+static struct kmem_cache *slab_fences;
+
+static inline struct mock_fence {
+	struct dma_fence base;
+	spinlock_t lock;
+} *to_mock_fence(struct dma_fence *f) {
+	return container_of(f, struct mock_fence, base);
+}
+
+static const char *mock_name(struct dma_fence *f)
+{
+	return "mock";
+}
+
+static void mock_fence_release(struct dma_fence *f)
+{
+	kmem_cache_free(slab_fences, to_mock_fence(f));
+}
+
+static const struct dma_fence_ops mock_ops = {
+	.get_driver_name = mock_name,
+	.get_timeline_name = mock_name,
+	.release = mock_fence_release,
+};
+
+static struct dma_fence *mock_fence(void)
+{
+	struct mock_fence *f;
+
+	f = kmem_cache_alloc(slab_fences, GFP_KERNEL);
+	if (!f)
+		return NULL;
+
+	spin_lock_init(&f->lock);
+	dma_fence_init(&f->base, &mock_ops, &f->lock, 0, 0);
+
+	return &f->base;
+}
+
+static inline struct mock_chain {
+	struct dma_fence_chain base;
+} *to_mock_chain(struct dma_fence *f) {
+	return container_of(f, struct mock_chain, base.base);
+}
+
+static struct dma_fence *mock_chain(struct dma_fence *prev,
+				    struct dma_fence *fence,
+				    u64 seqno)
+{
+	struct mock_chain *f;
+
+	f = kmalloc(sizeof(*f), GFP_KERNEL);
+	if (!f)
+		return NULL;
+
+	dma_fence_chain_init(&f->base,
+			     dma_fence_get(prev),
+			     dma_fence_get(fence),
+			     seqno);
+
+	return &f->base.base;
+}
+
+static int sanitycheck(void *arg)
+{
+	struct dma_fence *f, *chain;
+	int err = 0;
+
+	f = mock_fence();
+	if (!f)
+		return -ENOMEM;
+
+	chain = mock_chain(NULL, f, 1);
+	if (!chain)
+		err = -ENOMEM;
+
+	dma_fence_signal(f);
+	dma_fence_put(f);
+
+	dma_fence_put(chain);
+
+	return err;
+}
+
+struct fence_chains {
+	unsigned int chain_length;
+	struct dma_fence **fences;
+	struct dma_fence **chains;
+
+	struct dma_fence *tail;
+};
+
+static uint64_t seqno_inc(unsigned int i)
+{
+	return i + 1;
+}
+
+static int fence_chains_init(struct fence_chains *fc, unsigned int count,
+			     uint64_t (*seqno_fn)(unsigned int))
+{
+	unsigned int i;
+	int err = 0;
+
+	fc->chains = kvmalloc_array(count, sizeof(*fc->chains),
+				    GFP_KERNEL | __GFP_ZERO);
+	if (!fc->chains)
+		return -ENOMEM;
+
+	fc->fences = kvmalloc_array(count, sizeof(*fc->fences),
+				    GFP_KERNEL | __GFP_ZERO);
+	if (!fc->fences) {
+		err = -ENOMEM;
+		goto err_chains;
+	}
+
+	fc->tail = NULL;
+	for (i = 0; i < count; i++) {
+		fc->fences[i] = mock_fence();
+		if (!fc->fences[i]) {
+			err = -ENOMEM;
+			goto unwind;
+		}
+
+		fc->chains[i] = mock_chain(fc->tail,
+					   fc->fences[i],
+					   seqno_fn(i));
+		if (!fc->chains[i]) {
+			err = -ENOMEM;
+			goto unwind;
+		}
+
+		fc->tail = fc->chains[i];
+	}
+
+	fc->chain_length = i;
+	return 0;
+
+unwind:
+	for (i = 0; i < count; i++) {
+		dma_fence_put(fc->fences[i]);
+		dma_fence_put(fc->chains[i]);
+	}
+	kvfree(fc->fences);
+err_chains:
+	kvfree(fc->chains);
+	return err;
+}
+
+static void fence_chains_fini(struct fence_chains *fc)
+{
+	unsigned int i;
+
+	for (i = 0; i < fc->chain_length; i++) {
+		dma_fence_signal(fc->fences[i]);
+		dma_fence_put(fc->fences[i]);
+	}
+	kvfree(fc->fences);
+
+	for (i = 0; i < fc->chain_length; i++)
+		dma_fence_put(fc->chains[i]);
+	kvfree(fc->chains);
+}
+
+static int find_seqno(void *arg)
+{
+	struct fence_chains fc;
+	struct dma_fence *fence;
+	int err;
+	int i;
+
+	err = fence_chains_init(&fc, 64, seqno_inc);
+	if (err)
+		return err;
+
+	fence = dma_fence_get(fc.tail);
+	err = dma_fence_chain_find_seqno(&fence, 0);
+	dma_fence_put(fence);
+	if (err) {
+		pr_err("Reported %d for find_seqno(0)!\n", err);
+		goto err;
+	}
+
+	for (i = 0; i < fc.chain_length; i++) {
+		fence = dma_fence_get(fc.tail);
+		err = dma_fence_chain_find_seqno(&fence, i + 1);
+		dma_fence_put(fence);
+		if (err) {
+			pr_err("Reported %d for find_seqno(%d:%d)!\n",
+			       err, fc.chain_length + 1, i + 1);
+			goto err;
+		}
+		if (fence != fc.chains[i]) {
+			pr_err("Incorrect fence reported by find_seqno(%d:%d)\n",
+			       fc.chain_length + 1, i + 1);
+			err = -EINVAL;
+			goto err;
+		}
+
+		dma_fence_get(fence);
+		err = dma_fence_chain_find_seqno(&fence, i + 1);
+		dma_fence_put(fence);
+		if (err) {
+			pr_err("Error reported for finding self\n");
+			goto err;
+		}
+		if (fence != fc.chains[i]) {
+			pr_err("Incorrect fence reported by find self\n");
+			err = -EINVAL;
+			goto err;
+		}
+
+		dma_fence_get(fence);
+		err = dma_fence_chain_find_seqno(&fence, i + 2);
+		dma_fence_put(fence);
+		if (!err) {
+			pr_err("Error not reported for future fence: find_seqno(%d:%d)!\n",
+			       i + 1, i + 2);
+			err = -EINVAL;
+			goto err;
+		}
+
+		dma_fence_get(fence);
+		err = dma_fence_chain_find_seqno(&fence, i);
+		dma_fence_put(fence);
+		if (err) {
+			pr_err("Error reported for previous fence!\n");
+			goto err;
+		}
+		if (i > 0 && fence != fc.chains[i - 1]) {
+			pr_err("Incorrect fence reported by find_seqno(%d:%d)\n",
+			       i + 1, i);
+			err = -EINVAL;
+			goto err;
+		}
+	}
+
+err:
+	fence_chains_fini(&fc);
+	return err;
+}
+
+static int find_signaled(void *arg)
+{
+	struct fence_chains fc;
+	struct dma_fence *fence;
+	int err;
+
+	err = fence_chains_init(&fc, 2, seqno_inc);
+	if (err)
+		return err;
+
+	dma_fence_signal(fc.fences[0]);
+
+	fence = dma_fence_get(fc.tail);
+	err = dma_fence_chain_find_seqno(&fence, 1);
+	dma_fence_put(fence);
+	if (err) {
+		pr_err("Reported %d for find_seqno()!\n", err);
+		goto err;
+	}
+
+	if (fence && fence != fc.chains[0]) {
+		pr_err("Incorrect chain-fence.seqno:%lld reported for completed seqno:1\n",
+		       fence->seqno);
+
+		dma_fence_get(fence);
+		err = dma_fence_chain_find_seqno(&fence, 1);
+		dma_fence_put(fence);
+		if (err)
+			pr_err("Reported %d for finding self!\n", err);
+
+		err = -EINVAL;
+	}
+
+err:
+	fence_chains_fini(&fc);
+	return err;
+}
+
+static int find_out_of_order(void *arg)
+{
+	struct fence_chains fc;
+	struct dma_fence *fence;
+	int err;
+
+	err = fence_chains_init(&fc, 3, seqno_inc);
+	if (err)
+		return err;
+
+	dma_fence_signal(fc.fences[1]);
+
+	fence = dma_fence_get(fc.tail);
+	err = dma_fence_chain_find_seqno(&fence, 2);
+	dma_fence_put(fence);
+	if (err) {
+		pr_err("Reported %d for find_seqno()!\n", err);
+		goto err;
+	}
+
+	/*
+	 * We signaled the middle fence (2) of the 1-2-3 chain. The behavior
+	 * of the dma-fence-chain is to make us wait for all the fences up to
+	 * the point we want. Since fence 1 is still not signaled, this what
+	 * we should get as fence to wait upon (fence 2 being garbage
+	 * collected during the traversal of the chain).
+	 */
+	if (fence != fc.chains[0]) {
+		pr_err("Incorrect chain-fence.seqno:%lld reported for completed seqno:2\n",
+		       fence ? fence->seqno : 0);
+
+		err = -EINVAL;
+	}
+
+err:
+	fence_chains_fini(&fc);
+	return err;
+}
+
+static uint64_t seqno_inc2(unsigned int i)
+{
+	return 2 * i + 2;
+}
+
+static int find_gap(void *arg)
+{
+	struct fence_chains fc;
+	struct dma_fence *fence;
+	int err;
+	int i;
+
+	err = fence_chains_init(&fc, 64, seqno_inc2);
+	if (err)
+		return err;
+
+	for (i = 0; i < fc.chain_length; i++) {
+		fence = dma_fence_get(fc.tail);
+		err = dma_fence_chain_find_seqno(&fence, 2 * i + 1);
+		dma_fence_put(fence);
+		if (err) {
+			pr_err("Reported %d for find_seqno(%d:%d)!\n",
+			       err, fc.chain_length + 1, 2 * i + 1);
+			goto err;
+		}
+		if (fence != fc.chains[i]) {
+			pr_err("Incorrect fence.seqno:%lld reported by find_seqno(%d:%d)\n",
+			       fence->seqno,
+			       fc.chain_length + 1,
+			       2 * i + 1);
+			err = -EINVAL;
+			goto err;
+		}
+
+		dma_fence_get(fence);
+		err = dma_fence_chain_find_seqno(&fence, 2 * i + 2);
+		dma_fence_put(fence);
+		if (err) {
+			pr_err("Error reported for finding self\n");
+			goto err;
+		}
+		if (fence != fc.chains[i]) {
+			pr_err("Incorrect fence reported by find self\n");
+			err = -EINVAL;
+			goto err;
+		}
+	}
+
+err:
+	fence_chains_fini(&fc);
+	return err;
+}
+
+struct find_race {
+	struct fence_chains fc;
+	atomic_t children;
+};
+
+static int __find_race(void *arg)
+{
+	struct find_race *data = arg;
+	int err = 0;
+
+	while (!kthread_should_stop()) {
+		struct dma_fence *fence = dma_fence_get(data->fc.tail);
+		int seqno;
+
+		seqno = prandom_u32_max(data->fc.chain_length) + 1;
+
+		err = dma_fence_chain_find_seqno(&fence, seqno);
+		if (err) {
+			pr_err("Failed to find fence seqno:%d\n",
+			       seqno);
+			dma_fence_put(fence);
+			break;
+		}
+		if (!fence)
+			goto signal;
+
+		/*
+		 * We can only find ourselves if we are on fence we were
+		 * looking for.
+		 */
+		if (fence->seqno == seqno) {
+			err = dma_fence_chain_find_seqno(&fence, seqno);
+			if (err) {
+				pr_err("Reported an invalid fence for find-self:%d\n",
+				       seqno);
+				dma_fence_put(fence);
+				break;
+			}
+		}
+
+		dma_fence_put(fence);
+
+signal:
+		seqno = prandom_u32_max(data->fc.chain_length - 1);
+		dma_fence_signal(data->fc.fences[seqno]);
+		cond_resched();
+	}
+
+	if (atomic_dec_and_test(&data->children))
+		wake_up_var(&data->children);
+	return err;
+}
+
+static int find_race(void *arg)
+{
+	struct find_race data;
+	int ncpus = num_online_cpus();
+	struct task_struct **threads;
+	unsigned long count;
+	int err;
+	int i;
+
+	err = fence_chains_init(&data.fc, CHAIN_SZ, seqno_inc);
+	if (err)
+		return err;
+
+	threads = kmalloc_array(ncpus, sizeof(*threads), GFP_KERNEL);
+	if (!threads) {
+		err = -ENOMEM;
+		goto err;
+	}
+
+	atomic_set(&data.children, 0);
+	for (i = 0; i < ncpus; i++) {
+		threads[i] = kthread_run(__find_race, &data, "dmabuf/%d", i);
+		if (IS_ERR(threads[i])) {
+			ncpus = i;
+			break;
+		}
+		atomic_inc(&data.children);
+		get_task_struct(threads[i]);
+	}
+
+	wait_var_event_timeout(&data.children,
+			       !atomic_read(&data.children),
+			       5 * HZ);
+
+	for (i = 0; i < ncpus; i++) {
+		int ret;
+
+		ret = kthread_stop(threads[i]);
+		if (ret && !err)
+			err = ret;
+		put_task_struct(threads[i]);
+	}
+	kfree(threads);
+
+	count = 0;
+	for (i = 0; i < data.fc.chain_length; i++)
+		if (dma_fence_is_signaled(data.fc.fences[i]))
+			count++;
+	pr_info("Completed %lu cycles\n", count);
+
+err:
+	fence_chains_fini(&data.fc);
+	return err;
+}
+
+static int signal_forward(void *arg)
+{
+	struct fence_chains fc;
+	int err;
+	int i;
+
+	err = fence_chains_init(&fc, 64, seqno_inc);
+	if (err)
+		return err;
+
+	for (i = 0; i < fc.chain_length; i++) {
+		dma_fence_signal(fc.fences[i]);
+
+		if (!dma_fence_is_signaled(fc.chains[i])) {
+			pr_err("chain[%d] not signaled!\n", i);
+			err = -EINVAL;
+			goto err;
+		}
+
+		if (i + 1 < fc.chain_length &&
+		    dma_fence_is_signaled(fc.chains[i + 1])) {
+			pr_err("chain[%d] is signaled!\n", i);
+			err = -EINVAL;
+			goto err;
+		}
+	}
+
+err:
+	fence_chains_fini(&fc);
+	return err;
+}
+
+static int signal_backward(void *arg)
+{
+	struct fence_chains fc;
+	int err;
+	int i;
+
+	err = fence_chains_init(&fc, 64, seqno_inc);
+	if (err)
+		return err;
+
+	for (i = fc.chain_length; i--; ) {
+		dma_fence_signal(fc.fences[i]);
+
+		if (i > 0 && dma_fence_is_signaled(fc.chains[i])) {
+			pr_err("chain[%d] is signaled!\n", i);
+			err = -EINVAL;
+			goto err;
+		}
+	}
+
+	for (i = 0; i < fc.chain_length; i++) {
+		if (!dma_fence_is_signaled(fc.chains[i])) {
+			pr_err("chain[%d] was not signaled!\n", i);
+			err = -EINVAL;
+			goto err;
+		}
+	}
+
+err:
+	fence_chains_fini(&fc);
+	return err;
+}
+
+static int __wait_fence_chains(void *arg)
+{
+	struct fence_chains *fc = arg;
+
+	if (dma_fence_wait(fc->tail, false))
+		return -EIO;
+
+	return 0;
+}
+
+static int wait_forward(void *arg)
+{
+	struct fence_chains fc;
+	struct task_struct *tsk;
+	int err;
+	int i;
+
+	err = fence_chains_init(&fc, CHAIN_SZ, seqno_inc);
+	if (err)
+		return err;
+
+	tsk = kthread_run(__wait_fence_chains, &fc, "dmabuf/wait");
+	if (IS_ERR(tsk)) {
+		err = PTR_ERR(tsk);
+		goto err;
+	}
+	get_task_struct(tsk);
+	yield_to(tsk, true);
+
+	for (i = 0; i < fc.chain_length; i++)
+		dma_fence_signal(fc.fences[i]);
+
+	err = kthread_stop(tsk);
+	put_task_struct(tsk);
+
+err:
+	fence_chains_fini(&fc);
+	return err;
+}
+
+static int wait_backward(void *arg)
+{
+	struct fence_chains fc;
+	struct task_struct *tsk;
+	int err;
+	int i;
+
+	err = fence_chains_init(&fc, CHAIN_SZ, seqno_inc);
+	if (err)
+		return err;
+
+	tsk = kthread_run(__wait_fence_chains, &fc, "dmabuf/wait");
+	if (IS_ERR(tsk)) {
+		err = PTR_ERR(tsk);
+		goto err;
+	}
+	get_task_struct(tsk);
+	yield_to(tsk, true);
+
+	for (i = fc.chain_length; i--; )
+		dma_fence_signal(fc.fences[i]);
+
+	err = kthread_stop(tsk);
+	put_task_struct(tsk);
+
+err:
+	fence_chains_fini(&fc);
+	return err;
+}
+
+static void randomise_fences(struct fence_chains *fc)
+{
+	unsigned int count = fc->chain_length;
+
+	/* Fisher-Yates shuffle courtesy of Knuth */
+	while (--count) {
+		unsigned int swp;
+
+		swp = prandom_u32_max(count + 1);
+		if (swp == count)
+			continue;
+
+		swap(fc->fences[count], fc->fences[swp]);
+	}
+}
+
+static int wait_random(void *arg)
+{
+	struct fence_chains fc;
+	struct task_struct *tsk;
+	int err;
+	int i;
+
+	err = fence_chains_init(&fc, CHAIN_SZ, seqno_inc);
+	if (err)
+		return err;
+
+	randomise_fences(&fc);
+
+	tsk = kthread_run(__wait_fence_chains, &fc, "dmabuf/wait");
+	if (IS_ERR(tsk)) {
+		err = PTR_ERR(tsk);
+		goto err;
+	}
+	get_task_struct(tsk);
+	yield_to(tsk, true);
+
+	for (i = 0; i < fc.chain_length; i++)
+		dma_fence_signal(fc.fences[i]);
+
+	err = kthread_stop(tsk);
+	put_task_struct(tsk);
+
+err:
+	fence_chains_fini(&fc);
+	return err;
+}
+
+int dma_fence_chain(void)
+{
+	static const struct subtest tests[] = {
+		SUBTEST(sanitycheck),
+		SUBTEST(find_seqno),
+		SUBTEST(find_signaled),
+		SUBTEST(find_out_of_order),
+		SUBTEST(find_gap),
+		SUBTEST(find_race),
+		SUBTEST(signal_forward),
+		SUBTEST(signal_backward),
+		SUBTEST(wait_forward),
+		SUBTEST(wait_backward),
+		SUBTEST(wait_random),
+	};
+	int ret;
+
+	pr_info("sizeof(dma_fence_chain)=%zu\n",
+		sizeof(struct dma_fence_chain));
+
+	slab_fences = KMEM_CACHE(mock_fence,
+				 SLAB_TYPESAFE_BY_RCU |
+				 SLAB_HWCACHE_ALIGN);
+	if (!slab_fences)
+		return -ENOMEM;
+
+	ret = subtests(tests, NULL);
+
+	kmem_cache_destroy(slab_fences);
+	return ret;
+}
diff --git a/drivers/dma-buf/st-dma-fence.c b/drivers/dma-buf/st-dma-fence.c
new file mode 100644
index 000000000..e59306434
--- /dev/null
+++ b/drivers/dma-buf/st-dma-fence.c
@@ -0,0 +1,574 @@
+/* SPDX-License-Identifier: MIT */
+
+/*
+ * Copyright © 2019 Intel Corporation
+ */
+
+#include <linux/delay.h>
+#include <linux/dma-fence.h>
+#include <linux/kernel.h>
+#include <linux/kthread.h>
+#include <linux/sched/signal.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+
+#include "selftest.h"
+
+static struct kmem_cache *slab_fences;
+
+static struct mock_fence {
+	struct dma_fence base;
+	struct spinlock lock;
+} *to_mock_fence(struct dma_fence *f) {
+	return container_of(f, struct mock_fence, base);
+}
+
+static const char *mock_name(struct dma_fence *f)
+{
+	return "mock";
+}
+
+static void mock_fence_release(struct dma_fence *f)
+{
+	kmem_cache_free(slab_fences, to_mock_fence(f));
+}
+
+struct wait_cb {
+	struct dma_fence_cb cb;
+	struct task_struct *task;
+};
+
+static void mock_wakeup(struct dma_fence *f, struct dma_fence_cb *cb)
+{
+	wake_up_process(container_of(cb, struct wait_cb, cb)->task);
+}
+
+static long mock_wait(struct dma_fence *f, bool intr, long timeout)
+{
+	const int state = intr ? TASK_INTERRUPTIBLE : TASK_UNINTERRUPTIBLE;
+	struct wait_cb cb = { .task = current };
+
+	if (dma_fence_add_callback(f, &cb.cb, mock_wakeup))
+		return timeout;
+
+	while (timeout) {
+		set_current_state(state);
+
+		if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &f->flags))
+			break;
+
+		if (signal_pending_state(state, current))
+			break;
+
+		timeout = schedule_timeout(timeout);
+	}
+	__set_current_state(TASK_RUNNING);
+
+	if (!dma_fence_remove_callback(f, &cb.cb))
+		return timeout;
+
+	if (signal_pending_state(state, current))
+		return -ERESTARTSYS;
+
+	return -ETIME;
+}
+
+static const struct dma_fence_ops mock_ops = {
+	.get_driver_name = mock_name,
+	.get_timeline_name = mock_name,
+	.wait = mock_wait,
+	.release = mock_fence_release,
+};
+
+static struct dma_fence *mock_fence(void)
+{
+	struct mock_fence *f;
+
+	f = kmem_cache_alloc(slab_fences, GFP_KERNEL);
+	if (!f)
+		return NULL;
+
+	spin_lock_init(&f->lock);
+	dma_fence_init(&f->base, &mock_ops, &f->lock, 0, 0);
+
+	return &f->base;
+}
+
+static int sanitycheck(void *arg)
+{
+	struct dma_fence *f;
+
+	f = mock_fence();
+	if (!f)
+		return -ENOMEM;
+
+	dma_fence_signal(f);
+	dma_fence_put(f);
+
+	return 0;
+}
+
+static int test_signaling(void *arg)
+{
+	struct dma_fence *f;
+	int err = -EINVAL;
+
+	f = mock_fence();
+	if (!f)
+		return -ENOMEM;
+
+	if (dma_fence_is_signaled(f)) {
+		pr_err("Fence unexpectedly signaled on creation\n");
+		goto err_free;
+	}
+
+	if (dma_fence_signal(f)) {
+		pr_err("Fence reported being already signaled\n");
+		goto err_free;
+	}
+
+	if (!dma_fence_is_signaled(f)) {
+		pr_err("Fence not reporting signaled\n");
+		goto err_free;
+	}
+
+	if (!dma_fence_signal(f)) {
+		pr_err("Fence reported not being already signaled\n");
+		goto err_free;
+	}
+
+	err = 0;
+err_free:
+	dma_fence_put(f);
+	return err;
+}
+
+struct simple_cb {
+	struct dma_fence_cb cb;
+	bool seen;
+};
+
+static void simple_callback(struct dma_fence *f, struct dma_fence_cb *cb)
+{
+	smp_store_mb(container_of(cb, struct simple_cb, cb)->seen, true);
+}
+
+static int test_add_callback(void *arg)
+{
+	struct simple_cb cb = {};
+	struct dma_fence *f;
+	int err = -EINVAL;
+
+	f = mock_fence();
+	if (!f)
+		return -ENOMEM;
+
+	if (dma_fence_add_callback(f, &cb.cb, simple_callback)) {
+		pr_err("Failed to add callback, fence already signaled!\n");
+		goto err_free;
+	}
+
+	dma_fence_signal(f);
+	if (!cb.seen) {
+		pr_err("Callback failed!\n");
+		goto err_free;
+	}
+
+	err = 0;
+err_free:
+	dma_fence_put(f);
+	return err;
+}
+
+static int test_late_add_callback(void *arg)
+{
+	struct simple_cb cb = {};
+	struct dma_fence *f;
+	int err = -EINVAL;
+
+	f = mock_fence();
+	if (!f)
+		return -ENOMEM;
+
+	dma_fence_signal(f);
+
+	if (!dma_fence_add_callback(f, &cb.cb, simple_callback)) {
+		pr_err("Added callback, but fence was already signaled!\n");
+		goto err_free;
+	}
+
+	dma_fence_signal(f);
+	if (cb.seen) {
+		pr_err("Callback called after failed attachment !\n");
+		goto err_free;
+	}
+
+	err = 0;
+err_free:
+	dma_fence_put(f);
+	return err;
+}
+
+static int test_rm_callback(void *arg)
+{
+	struct simple_cb cb = {};
+	struct dma_fence *f;
+	int err = -EINVAL;
+
+	f = mock_fence();
+	if (!f)
+		return -ENOMEM;
+
+	if (dma_fence_add_callback(f, &cb.cb, simple_callback)) {
+		pr_err("Failed to add callback, fence already signaled!\n");
+		goto err_free;
+	}
+
+	if (!dma_fence_remove_callback(f, &cb.cb)) {
+		pr_err("Failed to remove callback!\n");
+		goto err_free;
+	}
+
+	dma_fence_signal(f);
+	if (cb.seen) {
+		pr_err("Callback still signaled after removal!\n");
+		goto err_free;
+	}
+
+	err = 0;
+err_free:
+	dma_fence_put(f);
+	return err;
+}
+
+static int test_late_rm_callback(void *arg)
+{
+	struct simple_cb cb = {};
+	struct dma_fence *f;
+	int err = -EINVAL;
+
+	f = mock_fence();
+	if (!f)
+		return -ENOMEM;
+
+	if (dma_fence_add_callback(f, &cb.cb, simple_callback)) {
+		pr_err("Failed to add callback, fence already signaled!\n");
+		goto err_free;
+	}
+
+	dma_fence_signal(f);
+	if (!cb.seen) {
+		pr_err("Callback failed!\n");
+		goto err_free;
+	}
+
+	if (dma_fence_remove_callback(f, &cb.cb)) {
+		pr_err("Callback removal succeed after being executed!\n");
+		goto err_free;
+	}
+
+	err = 0;
+err_free:
+	dma_fence_put(f);
+	return err;
+}
+
+static int test_status(void *arg)
+{
+	struct dma_fence *f;
+	int err = -EINVAL;
+
+	f = mock_fence();
+	if (!f)
+		return -ENOMEM;
+
+	if (dma_fence_get_status(f)) {
+		pr_err("Fence unexpectedly has signaled status on creation\n");
+		goto err_free;
+	}
+
+	dma_fence_signal(f);
+	if (!dma_fence_get_status(f)) {
+		pr_err("Fence not reporting signaled status\n");
+		goto err_free;
+	}
+
+	err = 0;
+err_free:
+	dma_fence_put(f);
+	return err;
+}
+
+static int test_error(void *arg)
+{
+	struct dma_fence *f;
+	int err = -EINVAL;
+
+	f = mock_fence();
+	if (!f)
+		return -ENOMEM;
+
+	dma_fence_set_error(f, -EIO);
+
+	if (dma_fence_get_status(f)) {
+		pr_err("Fence unexpectedly has error status before signal\n");
+		goto err_free;
+	}
+
+	dma_fence_signal(f);
+	if (dma_fence_get_status(f) != -EIO) {
+		pr_err("Fence not reporting error status, got %d\n",
+		       dma_fence_get_status(f));
+		goto err_free;
+	}
+
+	err = 0;
+err_free:
+	dma_fence_put(f);
+	return err;
+}
+
+static int test_wait(void *arg)
+{
+	struct dma_fence *f;
+	int err = -EINVAL;
+
+	f = mock_fence();
+	if (!f)
+		return -ENOMEM;
+
+	if (dma_fence_wait_timeout(f, false, 0) != -ETIME) {
+		pr_err("Wait reported complete before being signaled\n");
+		goto err_free;
+	}
+
+	dma_fence_signal(f);
+
+	if (dma_fence_wait_timeout(f, false, 0) != 0) {
+		pr_err("Wait reported incomplete after being signaled\n");
+		goto err_free;
+	}
+
+	err = 0;
+err_free:
+	dma_fence_signal(f);
+	dma_fence_put(f);
+	return err;
+}
+
+struct wait_timer {
+	struct timer_list timer;
+	struct dma_fence *f;
+};
+
+static void wait_timer(struct timer_list *timer)
+{
+	struct wait_timer *wt = from_timer(wt, timer, timer);
+
+	dma_fence_signal(wt->f);
+}
+
+static int test_wait_timeout(void *arg)
+{
+	struct wait_timer wt;
+	int err = -EINVAL;
+
+	timer_setup_on_stack(&wt.timer, wait_timer, 0);
+
+	wt.f = mock_fence();
+	if (!wt.f)
+		return -ENOMEM;
+
+	if (dma_fence_wait_timeout(wt.f, false, 1) != -ETIME) {
+		pr_err("Wait reported complete before being signaled\n");
+		goto err_free;
+	}
+
+	mod_timer(&wt.timer, jiffies + 1);
+
+	if (dma_fence_wait_timeout(wt.f, false, 2) == -ETIME) {
+		if (timer_pending(&wt.timer)) {
+			pr_notice("Timer did not fire within the jiffie!\n");
+			err = 0; /* not our fault! */
+		} else {
+			pr_err("Wait reported incomplete after timeout\n");
+		}
+		goto err_free;
+	}
+
+	err = 0;
+err_free:
+	del_timer_sync(&wt.timer);
+	destroy_timer_on_stack(&wt.timer);
+	dma_fence_signal(wt.f);
+	dma_fence_put(wt.f);
+	return err;
+}
+
+static int test_stub(void *arg)
+{
+	struct dma_fence *f[64];
+	int err = -EINVAL;
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(f); i++) {
+		f[i] = dma_fence_get_stub();
+		if (!dma_fence_is_signaled(f[i])) {
+			pr_err("Obtained unsignaled stub fence!\n");
+			goto err;
+		}
+	}
+
+	err = 0;
+err:
+	while (i--)
+		dma_fence_put(f[i]);
+	return err;
+}
+
+/* Now off to the races! */
+
+struct race_thread {
+	struct dma_fence __rcu **fences;
+	struct task_struct *task;
+	bool before;
+	int id;
+};
+
+static void __wait_for_callbacks(struct dma_fence *f)
+{
+	spin_lock_irq(f->lock);
+	spin_unlock_irq(f->lock);
+}
+
+static int thread_signal_callback(void *arg)
+{
+	const struct race_thread *t = arg;
+	unsigned long pass = 0;
+	unsigned long miss = 0;
+	int err = 0;
+
+	while (!err && !kthread_should_stop()) {
+		struct dma_fence *f1, *f2;
+		struct simple_cb cb;
+
+		f1 = mock_fence();
+		if (!f1) {
+			err = -ENOMEM;
+			break;
+		}
+
+		rcu_assign_pointer(t->fences[t->id], f1);
+		smp_wmb();
+
+		rcu_read_lock();
+		do {
+			f2 = dma_fence_get_rcu_safe(&t->fences[!t->id]);
+		} while (!f2 && !kthread_should_stop());
+		rcu_read_unlock();
+
+		if (t->before)
+			dma_fence_signal(f1);
+
+		smp_store_mb(cb.seen, false);
+		if (!f2 || dma_fence_add_callback(f2, &cb.cb, simple_callback))
+			miss++, cb.seen = true;
+
+		if (!t->before)
+			dma_fence_signal(f1);
+
+		if (!cb.seen) {
+			dma_fence_wait(f2, false);
+			__wait_for_callbacks(f2);
+		}
+
+		if (!READ_ONCE(cb.seen)) {
+			pr_err("Callback not seen on thread %d, pass %lu (%lu misses), signaling %s add_callback; fence signaled? %s\n",
+			       t->id, pass, miss,
+			       t->before ? "before" : "after",
+			       dma_fence_is_signaled(f2) ? "yes" : "no");
+			err = -EINVAL;
+		}
+
+		dma_fence_put(f2);
+
+		rcu_assign_pointer(t->fences[t->id], NULL);
+		smp_wmb();
+
+		dma_fence_put(f1);
+
+		pass++;
+	}
+
+	pr_info("%s[%d] completed %lu passes, %lu misses\n",
+		__func__, t->id, pass, miss);
+	return err;
+}
+
+static int race_signal_callback(void *arg)
+{
+	struct dma_fence __rcu *f[2] = {};
+	int ret = 0;
+	int pass;
+
+	for (pass = 0; !ret && pass <= 1; pass++) {
+		struct race_thread t[2];
+		int i;
+
+		for (i = 0; i < ARRAY_SIZE(t); i++) {
+			t[i].fences = f;
+			t[i].id = i;
+			t[i].before = pass;
+			t[i].task = kthread_run(thread_signal_callback, &t[i],
+						"dma-fence:%d", i);
+			get_task_struct(t[i].task);
+		}
+
+		msleep(50);
+
+		for (i = 0; i < ARRAY_SIZE(t); i++) {
+			int err;
+
+			err = kthread_stop(t[i].task);
+			if (err && !ret)
+				ret = err;
+
+			put_task_struct(t[i].task);
+		}
+	}
+
+	return ret;
+}
+
+int dma_fence(void)
+{
+	static const struct subtest tests[] = {
+		SUBTEST(sanitycheck),
+		SUBTEST(test_signaling),
+		SUBTEST(test_add_callback),
+		SUBTEST(test_late_add_callback),
+		SUBTEST(test_rm_callback),
+		SUBTEST(test_late_rm_callback),
+		SUBTEST(test_status),
+		SUBTEST(test_error),
+		SUBTEST(test_wait),
+		SUBTEST(test_wait_timeout),
+		SUBTEST(test_stub),
+		SUBTEST(race_signal_callback),
+	};
+	int ret;
+
+	pr_info("sizeof(dma_fence)=%zu\n", sizeof(struct dma_fence));
+
+	slab_fences = KMEM_CACHE(mock_fence,
+				 SLAB_TYPESAFE_BY_RCU |
+				 SLAB_HWCACHE_ALIGN);
+	if (!slab_fences)
+		return -ENOMEM;
+
+	ret = subtests(tests, NULL);
+
+	kmem_cache_destroy(slab_fences);
+
+	return ret;
+}
diff --git a/drivers/dma-buf/sw_sync.c b/drivers/dma-buf/sw_sync.c
new file mode 100644
index 000000000..7f5ed1aa7
--- /dev/null
+++ b/drivers/dma-buf/sw_sync.c
@@ -0,0 +1,412 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Sync File validation framework
+ *
+ * Copyright (C) 2012 Google, Inc.
+ */
+
+#include <linux/file.h>
+#include <linux/fs.h>
+#include <linux/uaccess.h>
+#include <linux/slab.h>
+#include <linux/sync_file.h>
+
+#include "sync_debug.h"
+
+#define CREATE_TRACE_POINTS
+#include "sync_trace.h"
+
+/*
+ * SW SYNC validation framework
+ *
+ * A sync object driver that uses a 32bit counter to coordinate
+ * synchronization.  Useful when there is no hardware primitive backing
+ * the synchronization.
+ *
+ * To start the framework just open:
+ *
+ * <debugfs>/sync/sw_sync
+ *
+ * That will create a sync timeline, all fences created under this timeline
+ * file descriptor will belong to the this timeline.
+ *
+ * The 'sw_sync' file can be opened many times as to create different
+ * timelines.
+ *
+ * Fences can be created with SW_SYNC_IOC_CREATE_FENCE ioctl with struct
+ * sw_sync_create_fence_data as parameter.
+ *
+ * To increment the timeline counter, SW_SYNC_IOC_INC ioctl should be used
+ * with the increment as u32. This will update the last signaled value
+ * from the timeline and signal any fence that has a seqno smaller or equal
+ * to it.
+ *
+ * struct sw_sync_create_fence_data
+ * @value:	the seqno to initialise the fence with
+ * @name:	the name of the new sync point
+ * @fence:	return the fd of the new sync_file with the created fence
+ */
+struct sw_sync_create_fence_data {
+	__u32	value;
+	char	name[32];
+	__s32	fence; /* fd of new fence */
+};
+
+#define SW_SYNC_IOC_MAGIC	'W'
+
+#define SW_SYNC_IOC_CREATE_FENCE	_IOWR(SW_SYNC_IOC_MAGIC, 0,\
+		struct sw_sync_create_fence_data)
+
+#define SW_SYNC_IOC_INC			_IOW(SW_SYNC_IOC_MAGIC, 1, __u32)
+
+static const struct dma_fence_ops timeline_fence_ops;
+
+static inline struct sync_pt *dma_fence_to_sync_pt(struct dma_fence *fence)
+{
+	if (fence->ops != &timeline_fence_ops)
+		return NULL;
+	return container_of(fence, struct sync_pt, base);
+}
+
+/**
+ * sync_timeline_create() - creates a sync object
+ * @name:	sync_timeline name
+ *
+ * Creates a new sync_timeline. Returns the sync_timeline object or NULL in
+ * case of error.
+ */
+static struct sync_timeline *sync_timeline_create(const char *name)
+{
+	struct sync_timeline *obj;
+
+	obj = kzalloc(sizeof(*obj), GFP_KERNEL);
+	if (!obj)
+		return NULL;
+
+	kref_init(&obj->kref);
+	obj->context = dma_fence_context_alloc(1);
+	strlcpy(obj->name, name, sizeof(obj->name));
+
+	obj->pt_tree = RB_ROOT;
+	INIT_LIST_HEAD(&obj->pt_list);
+	spin_lock_init(&obj->lock);
+
+	sync_timeline_debug_add(obj);
+
+	return obj;
+}
+
+static void sync_timeline_free(struct kref *kref)
+{
+	struct sync_timeline *obj =
+		container_of(kref, struct sync_timeline, kref);
+
+	sync_timeline_debug_remove(obj);
+
+	kfree(obj);
+}
+
+static void sync_timeline_get(struct sync_timeline *obj)
+{
+	kref_get(&obj->kref);
+}
+
+static void sync_timeline_put(struct sync_timeline *obj)
+{
+	kref_put(&obj->kref, sync_timeline_free);
+}
+
+static const char *timeline_fence_get_driver_name(struct dma_fence *fence)
+{
+	return "sw_sync";
+}
+
+static const char *timeline_fence_get_timeline_name(struct dma_fence *fence)
+{
+	struct sync_timeline *parent = dma_fence_parent(fence);
+
+	return parent->name;
+}
+
+static void timeline_fence_release(struct dma_fence *fence)
+{
+	struct sync_pt *pt = dma_fence_to_sync_pt(fence);
+	struct sync_timeline *parent = dma_fence_parent(fence);
+	unsigned long flags;
+
+	spin_lock_irqsave(fence->lock, flags);
+	if (!list_empty(&pt->link)) {
+		list_del(&pt->link);
+		rb_erase(&pt->node, &parent->pt_tree);
+	}
+	spin_unlock_irqrestore(fence->lock, flags);
+
+	sync_timeline_put(parent);
+	dma_fence_free(fence);
+}
+
+static bool timeline_fence_signaled(struct dma_fence *fence)
+{
+	struct sync_timeline *parent = dma_fence_parent(fence);
+
+	return !__dma_fence_is_later(fence->seqno, parent->value, fence->ops);
+}
+
+static bool timeline_fence_enable_signaling(struct dma_fence *fence)
+{
+	return true;
+}
+
+static void timeline_fence_value_str(struct dma_fence *fence,
+				    char *str, int size)
+{
+	snprintf(str, size, "%lld", fence->seqno);
+}
+
+static void timeline_fence_timeline_value_str(struct dma_fence *fence,
+					     char *str, int size)
+{
+	struct sync_timeline *parent = dma_fence_parent(fence);
+
+	snprintf(str, size, "%d", parent->value);
+}
+
+static const struct dma_fence_ops timeline_fence_ops = {
+	.get_driver_name = timeline_fence_get_driver_name,
+	.get_timeline_name = timeline_fence_get_timeline_name,
+	.enable_signaling = timeline_fence_enable_signaling,
+	.signaled = timeline_fence_signaled,
+	.release = timeline_fence_release,
+	.fence_value_str = timeline_fence_value_str,
+	.timeline_value_str = timeline_fence_timeline_value_str,
+};
+
+/**
+ * sync_timeline_signal() - signal a status change on a sync_timeline
+ * @obj:	sync_timeline to signal
+ * @inc:	num to increment on timeline->value
+ *
+ * A sync implementation should call this any time one of it's fences
+ * has signaled or has an error condition.
+ */
+static void sync_timeline_signal(struct sync_timeline *obj, unsigned int inc)
+{
+	LIST_HEAD(signalled);
+	struct sync_pt *pt, *next;
+
+	trace_sync_timeline(obj);
+
+	spin_lock_irq(&obj->lock);
+
+	obj->value += inc;
+
+	list_for_each_entry_safe(pt, next, &obj->pt_list, link) {
+		if (!timeline_fence_signaled(&pt->base))
+			break;
+
+		dma_fence_get(&pt->base);
+
+		list_move_tail(&pt->link, &signalled);
+		rb_erase(&pt->node, &obj->pt_tree);
+
+		dma_fence_signal_locked(&pt->base);
+	}
+
+	spin_unlock_irq(&obj->lock);
+
+	list_for_each_entry_safe(pt, next, &signalled, link) {
+		list_del_init(&pt->link);
+		dma_fence_put(&pt->base);
+	}
+}
+
+/**
+ * sync_pt_create() - creates a sync pt
+ * @obj:	parent sync_timeline
+ * @value:	value of the fence
+ *
+ * Creates a new sync_pt (fence) as a child of @parent.  @size bytes will be
+ * allocated allowing for implementation specific data to be kept after
+ * the generic sync_timeline struct. Returns the sync_pt object or
+ * NULL in case of error.
+ */
+static struct sync_pt *sync_pt_create(struct sync_timeline *obj,
+				      unsigned int value)
+{
+	struct sync_pt *pt;
+
+	pt = kzalloc(sizeof(*pt), GFP_KERNEL);
+	if (!pt)
+		return NULL;
+
+	sync_timeline_get(obj);
+	dma_fence_init(&pt->base, &timeline_fence_ops, &obj->lock,
+		       obj->context, value);
+	INIT_LIST_HEAD(&pt->link);
+
+	spin_lock_irq(&obj->lock);
+	if (!dma_fence_is_signaled_locked(&pt->base)) {
+		struct rb_node **p = &obj->pt_tree.rb_node;
+		struct rb_node *parent = NULL;
+
+		while (*p) {
+			struct sync_pt *other;
+			int cmp;
+
+			parent = *p;
+			other = rb_entry(parent, typeof(*pt), node);
+			cmp = value - other->base.seqno;
+			if (cmp > 0) {
+				p = &parent->rb_right;
+			} else if (cmp < 0) {
+				p = &parent->rb_left;
+			} else {
+				if (dma_fence_get_rcu(&other->base)) {
+					sync_timeline_put(obj);
+					kfree(pt);
+					pt = other;
+					goto unlock;
+				}
+				p = &parent->rb_left;
+			}
+		}
+		rb_link_node(&pt->node, parent, p);
+		rb_insert_color(&pt->node, &obj->pt_tree);
+
+		parent = rb_next(&pt->node);
+		list_add_tail(&pt->link,
+			      parent ? &rb_entry(parent, typeof(*pt), node)->link : &obj->pt_list);
+	}
+unlock:
+	spin_unlock_irq(&obj->lock);
+
+	return pt;
+}
+
+/*
+ * *WARNING*
+ *
+ * improper use of this can result in deadlocking kernel drivers from userspace.
+ */
+
+/* opening sw_sync create a new sync obj */
+static int sw_sync_debugfs_open(struct inode *inode, struct file *file)
+{
+	struct sync_timeline *obj;
+	char task_comm[TASK_COMM_LEN];
+
+	get_task_comm(task_comm, current);
+
+	obj = sync_timeline_create(task_comm);
+	if (!obj)
+		return -ENOMEM;
+
+	file->private_data = obj;
+
+	return 0;
+}
+
+static int sw_sync_debugfs_release(struct inode *inode, struct file *file)
+{
+	struct sync_timeline *obj = file->private_data;
+	struct sync_pt *pt, *next;
+
+	spin_lock_irq(&obj->lock);
+
+	list_for_each_entry_safe(pt, next, &obj->pt_list, link) {
+		dma_fence_set_error(&pt->base, -ENOENT);
+		dma_fence_signal_locked(&pt->base);
+	}
+
+	spin_unlock_irq(&obj->lock);
+
+	sync_timeline_put(obj);
+	return 0;
+}
+
+static long sw_sync_ioctl_create_fence(struct sync_timeline *obj,
+				       unsigned long arg)
+{
+	int fd = get_unused_fd_flags(O_CLOEXEC);
+	int err;
+	struct sync_pt *pt;
+	struct sync_file *sync_file;
+	struct sw_sync_create_fence_data data;
+
+	if (fd < 0)
+		return fd;
+
+	if (copy_from_user(&data, (void __user *)arg, sizeof(data))) {
+		err = -EFAULT;
+		goto err;
+	}
+
+	pt = sync_pt_create(obj, data.value);
+	if (!pt) {
+		err = -ENOMEM;
+		goto err;
+	}
+
+	sync_file = sync_file_create(&pt->base);
+	dma_fence_put(&pt->base);
+	if (!sync_file) {
+		err = -ENOMEM;
+		goto err;
+	}
+
+	data.fence = fd;
+	if (copy_to_user((void __user *)arg, &data, sizeof(data))) {
+		fput(sync_file->file);
+		err = -EFAULT;
+		goto err;
+	}
+
+	fd_install(fd, sync_file->file);
+
+	return 0;
+
+err:
+	put_unused_fd(fd);
+	return err;
+}
+
+static long sw_sync_ioctl_inc(struct sync_timeline *obj, unsigned long arg)
+{
+	u32 value;
+
+	if (copy_from_user(&value, (void __user *)arg, sizeof(value)))
+		return -EFAULT;
+
+	while (value > INT_MAX)  {
+		sync_timeline_signal(obj, INT_MAX);
+		value -= INT_MAX;
+	}
+
+	sync_timeline_signal(obj, value);
+
+	return 0;
+}
+
+static long sw_sync_ioctl(struct file *file, unsigned int cmd,
+			  unsigned long arg)
+{
+	struct sync_timeline *obj = file->private_data;
+
+	switch (cmd) {
+	case SW_SYNC_IOC_CREATE_FENCE:
+		return sw_sync_ioctl_create_fence(obj, arg);
+
+	case SW_SYNC_IOC_INC:
+		return sw_sync_ioctl_inc(obj, arg);
+
+	default:
+		return -ENOTTY;
+	}
+}
+
+const struct file_operations sw_sync_debugfs_fops = {
+	.open           = sw_sync_debugfs_open,
+	.release        = sw_sync_debugfs_release,
+	.unlocked_ioctl = sw_sync_ioctl,
+	.compat_ioctl	= compat_ptr_ioctl,
+};
diff --git a/drivers/dma-buf/sync_debug.c b/drivers/dma-buf/sync_debug.c
new file mode 100644
index 000000000..101394f16
--- /dev/null
+++ b/drivers/dma-buf/sync_debug.c
@@ -0,0 +1,190 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Sync File validation framework and debug information
+ *
+ * Copyright (C) 2012 Google, Inc.
+ */
+
+#include <linux/debugfs.h>
+#include "sync_debug.h"
+
+static struct dentry *dbgfs;
+
+static LIST_HEAD(sync_timeline_list_head);
+static DEFINE_SPINLOCK(sync_timeline_list_lock);
+static LIST_HEAD(sync_file_list_head);
+static DEFINE_SPINLOCK(sync_file_list_lock);
+
+void sync_timeline_debug_add(struct sync_timeline *obj)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&sync_timeline_list_lock, flags);
+	list_add_tail(&obj->sync_timeline_list, &sync_timeline_list_head);
+	spin_unlock_irqrestore(&sync_timeline_list_lock, flags);
+}
+
+void sync_timeline_debug_remove(struct sync_timeline *obj)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&sync_timeline_list_lock, flags);
+	list_del(&obj->sync_timeline_list);
+	spin_unlock_irqrestore(&sync_timeline_list_lock, flags);
+}
+
+void sync_file_debug_add(struct sync_file *sync_file)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&sync_file_list_lock, flags);
+	list_add_tail(&sync_file->sync_file_list, &sync_file_list_head);
+	spin_unlock_irqrestore(&sync_file_list_lock, flags);
+}
+
+void sync_file_debug_remove(struct sync_file *sync_file)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&sync_file_list_lock, flags);
+	list_del(&sync_file->sync_file_list);
+	spin_unlock_irqrestore(&sync_file_list_lock, flags);
+}
+
+static const char *sync_status_str(int status)
+{
+	if (status < 0)
+		return "error";
+
+	if (status > 0)
+		return "signaled";
+
+	return "active";
+}
+
+static void sync_print_fence(struct seq_file *s,
+			     struct dma_fence *fence, bool show)
+{
+	struct sync_timeline *parent = dma_fence_parent(fence);
+	int status;
+
+	status = dma_fence_get_status_locked(fence);
+
+	seq_printf(s, "  %s%sfence %s",
+		   show ? parent->name : "",
+		   show ? "_" : "",
+		   sync_status_str(status));
+
+	if (test_bit(DMA_FENCE_FLAG_TIMESTAMP_BIT, &fence->flags)) {
+		struct timespec64 ts64 =
+			ktime_to_timespec64(fence->timestamp);
+
+		seq_printf(s, "@%lld.%09ld", (s64)ts64.tv_sec, ts64.tv_nsec);
+	}
+
+	if (fence->ops->timeline_value_str &&
+		fence->ops->fence_value_str) {
+		char value[64];
+		bool success;
+
+		fence->ops->fence_value_str(fence, value, sizeof(value));
+		success = strlen(value);
+
+		if (success) {
+			seq_printf(s, ": %s", value);
+
+			fence->ops->timeline_value_str(fence, value,
+						       sizeof(value));
+
+			if (strlen(value))
+				seq_printf(s, " / %s", value);
+		}
+	}
+
+	seq_putc(s, '\n');
+}
+
+static void sync_print_obj(struct seq_file *s, struct sync_timeline *obj)
+{
+	struct list_head *pos;
+
+	seq_printf(s, "%s: %d\n", obj->name, obj->value);
+
+	spin_lock_irq(&obj->lock);
+	list_for_each(pos, &obj->pt_list) {
+		struct sync_pt *pt = container_of(pos, struct sync_pt, link);
+		sync_print_fence(s, &pt->base, false);
+	}
+	spin_unlock_irq(&obj->lock);
+}
+
+static void sync_print_sync_file(struct seq_file *s,
+				  struct sync_file *sync_file)
+{
+	char buf[128];
+	int i;
+
+	seq_printf(s, "[%p] %s: %s\n", sync_file,
+		   sync_file_get_name(sync_file, buf, sizeof(buf)),
+		   sync_status_str(dma_fence_get_status(sync_file->fence)));
+
+	if (dma_fence_is_array(sync_file->fence)) {
+		struct dma_fence_array *array = to_dma_fence_array(sync_file->fence);
+
+		for (i = 0; i < array->num_fences; ++i)
+			sync_print_fence(s, array->fences[i], true);
+	} else {
+		sync_print_fence(s, sync_file->fence, true);
+	}
+}
+
+static int sync_info_debugfs_show(struct seq_file *s, void *unused)
+{
+	struct list_head *pos;
+
+	seq_puts(s, "objs:\n--------------\n");
+
+	spin_lock_irq(&sync_timeline_list_lock);
+	list_for_each(pos, &sync_timeline_list_head) {
+		struct sync_timeline *obj =
+			container_of(pos, struct sync_timeline,
+				     sync_timeline_list);
+
+		sync_print_obj(s, obj);
+		seq_putc(s, '\n');
+	}
+	spin_unlock_irq(&sync_timeline_list_lock);
+
+	seq_puts(s, "fences:\n--------------\n");
+
+	spin_lock_irq(&sync_file_list_lock);
+	list_for_each(pos, &sync_file_list_head) {
+		struct sync_file *sync_file =
+			container_of(pos, struct sync_file, sync_file_list);
+
+		sync_print_sync_file(s, sync_file);
+		seq_putc(s, '\n');
+	}
+	spin_unlock_irq(&sync_file_list_lock);
+	return 0;
+}
+
+DEFINE_SHOW_ATTRIBUTE(sync_info_debugfs);
+
+static __init int sync_debugfs_init(void)
+{
+	dbgfs = debugfs_create_dir("sync", NULL);
+
+	/*
+	 * The debugfs files won't ever get removed and thus, there is
+	 * no need to protect it against removal races. The use of
+	 * debugfs_create_file_unsafe() is actually safe here.
+	 */
+	debugfs_create_file_unsafe("info", 0444, dbgfs, NULL,
+				   &sync_info_debugfs_fops);
+	debugfs_create_file_unsafe("sw_sync", 0644, dbgfs, NULL,
+				   &sw_sync_debugfs_fops);
+
+	return 0;
+}
+late_initcall(sync_debugfs_init);
diff --git a/drivers/dma-buf/sync_debug.h b/drivers/dma-buf/sync_debug.h
new file mode 100644
index 000000000..6176e52ba
--- /dev/null
+++ b/drivers/dma-buf/sync_debug.h
@@ -0,0 +1,72 @@
+/*
+ * Sync File validation framework and debug infomation
+ *
+ * Copyright (C) 2012 Google, Inc.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#ifndef _LINUX_SYNC_H
+#define _LINUX_SYNC_H
+
+#include <linux/list.h>
+#include <linux/rbtree.h>
+#include <linux/spinlock.h>
+#include <linux/dma-fence.h>
+
+#include <linux/sync_file.h>
+#include <uapi/linux/sync_file.h>
+
+/**
+ * struct sync_timeline - sync object
+ * @kref:		reference count on fence.
+ * @name:		name of the sync_timeline. Useful for debugging
+ * @lock:		lock protecting @pt_list and @value
+ * @pt_tree:		rbtree of active (unsignaled/errored) sync_pts
+ * @pt_list:		list of active (unsignaled/errored) sync_pts
+ * @sync_timeline_list:	membership in global sync_timeline_list
+ */
+struct sync_timeline {
+	struct kref		kref;
+	char			name[32];
+
+	/* protected by lock */
+	u64			context;
+	int			value;
+
+	struct rb_root		pt_tree;
+	struct list_head	pt_list;
+	spinlock_t		lock;
+
+	struct list_head	sync_timeline_list;
+};
+
+static inline struct sync_timeline *dma_fence_parent(struct dma_fence *fence)
+{
+	return container_of(fence->lock, struct sync_timeline, lock);
+}
+
+/**
+ * struct sync_pt - sync_pt object
+ * @base: base fence object
+ * @link: link on the sync timeline's list
+ * @node: node in the sync timeline's tree
+ */
+struct sync_pt {
+	struct dma_fence base;
+	struct list_head link;
+	struct rb_node node;
+};
+
+extern const struct file_operations sw_sync_debugfs_fops;
+
+void sync_timeline_debug_add(struct sync_timeline *obj);
+void sync_timeline_debug_remove(struct sync_timeline *obj);
+void sync_file_debug_add(struct sync_file *fence);
+void sync_file_debug_remove(struct sync_file *fence);
+
+#endif /* _LINUX_SYNC_H */
diff --git a/drivers/dma-buf/sync_file.c b/drivers/dma-buf/sync_file.c
new file mode 100644
index 000000000..f0c822952
--- /dev/null
+++ b/drivers/dma-buf/sync_file.c
@@ -0,0 +1,485 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * drivers/dma-buf/sync_file.c
+ *
+ * Copyright (C) 2012 Google, Inc.
+ */
+
+#include <linux/export.h>
+#include <linux/file.h>
+#include <linux/fs.h>
+#include <linux/kernel.h>
+#include <linux/poll.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/uaccess.h>
+#include <linux/anon_inodes.h>
+#include <linux/sync_file.h>
+#include <uapi/linux/sync_file.h>
+
+static const struct file_operations sync_file_fops;
+
+static struct sync_file *sync_file_alloc(void)
+{
+	struct sync_file *sync_file;
+
+	sync_file = kzalloc(sizeof(*sync_file), GFP_KERNEL);
+	if (!sync_file)
+		return NULL;
+
+	sync_file->file = anon_inode_getfile("sync_file", &sync_file_fops,
+					     sync_file, 0);
+	if (IS_ERR(sync_file->file))
+		goto err;
+
+	init_waitqueue_head(&sync_file->wq);
+
+	INIT_LIST_HEAD(&sync_file->cb.node);
+
+	return sync_file;
+
+err:
+	kfree(sync_file);
+	return NULL;
+}
+
+static void fence_check_cb_func(struct dma_fence *f, struct dma_fence_cb *cb)
+{
+	struct sync_file *sync_file;
+
+	sync_file = container_of(cb, struct sync_file, cb);
+
+	wake_up_all(&sync_file->wq);
+}
+
+/**
+ * sync_file_create() - creates a sync file
+ * @fence:	fence to add to the sync_fence
+ *
+ * Creates a sync_file containg @fence. This function acquires and additional
+ * reference of @fence for the newly-created &sync_file, if it succeeds. The
+ * sync_file can be released with fput(sync_file->file). Returns the
+ * sync_file or NULL in case of error.
+ */
+struct sync_file *sync_file_create(struct dma_fence *fence)
+{
+	struct sync_file *sync_file;
+
+	sync_file = sync_file_alloc();
+	if (!sync_file)
+		return NULL;
+
+	sync_file->fence = dma_fence_get(fence);
+
+	return sync_file;
+}
+EXPORT_SYMBOL(sync_file_create);
+
+static struct sync_file *sync_file_fdget(int fd)
+{
+	struct file *file = fget(fd);
+
+	if (!file)
+		return NULL;
+
+	if (file->f_op != &sync_file_fops)
+		goto err;
+
+	return file->private_data;
+
+err:
+	fput(file);
+	return NULL;
+}
+
+/**
+ * sync_file_get_fence - get the fence related to the sync_file fd
+ * @fd:		sync_file fd to get the fence from
+ *
+ * Ensures @fd references a valid sync_file and returns a fence that
+ * represents all fence in the sync_file. On error NULL is returned.
+ */
+struct dma_fence *sync_file_get_fence(int fd)
+{
+	struct sync_file *sync_file;
+	struct dma_fence *fence;
+
+	sync_file = sync_file_fdget(fd);
+	if (!sync_file)
+		return NULL;
+
+	fence = dma_fence_get(sync_file->fence);
+	fput(sync_file->file);
+
+	return fence;
+}
+EXPORT_SYMBOL(sync_file_get_fence);
+
+/**
+ * sync_file_get_name - get the name of the sync_file
+ * @sync_file:		sync_file to get the fence from
+ * @buf:		destination buffer to copy sync_file name into
+ * @len:		available size of destination buffer.
+ *
+ * Each sync_file may have a name assigned either by the user (when merging
+ * sync_files together) or created from the fence it contains. In the latter
+ * case construction of the name is deferred until use, and so requires
+ * sync_file_get_name().
+ *
+ * Returns: a string representing the name.
+ */
+char *sync_file_get_name(struct sync_file *sync_file, char *buf, int len)
+{
+	if (sync_file->user_name[0]) {
+		strlcpy(buf, sync_file->user_name, len);
+	} else {
+		struct dma_fence *fence = sync_file->fence;
+
+		snprintf(buf, len, "%s-%s%llu-%lld",
+			 fence->ops->get_driver_name(fence),
+			 fence->ops->get_timeline_name(fence),
+			 fence->context,
+			 fence->seqno);
+	}
+
+	return buf;
+}
+
+static int sync_file_set_fence(struct sync_file *sync_file,
+			       struct dma_fence **fences, int num_fences)
+{
+	struct dma_fence_array *array;
+
+	/*
+	 * The reference for the fences in the new sync_file and held
+	 * in add_fence() during the merge procedure, so for num_fences == 1
+	 * we already own a new reference to the fence. For num_fence > 1
+	 * we own the reference of the dma_fence_array creation.
+	 */
+	if (num_fences == 1) {
+		sync_file->fence = fences[0];
+		kfree(fences);
+	} else {
+		array = dma_fence_array_create(num_fences, fences,
+					       dma_fence_context_alloc(1),
+					       1, false);
+		if (!array)
+			return -ENOMEM;
+
+		sync_file->fence = &array->base;
+	}
+
+	return 0;
+}
+
+static struct dma_fence **get_fences(struct sync_file *sync_file,
+				     int *num_fences)
+{
+	if (dma_fence_is_array(sync_file->fence)) {
+		struct dma_fence_array *array = to_dma_fence_array(sync_file->fence);
+
+		*num_fences = array->num_fences;
+		return array->fences;
+	}
+
+	*num_fences = 1;
+	return &sync_file->fence;
+}
+
+static void add_fence(struct dma_fence **fences,
+		      int *i, struct dma_fence *fence)
+{
+	fences[*i] = fence;
+
+	if (!dma_fence_is_signaled(fence)) {
+		dma_fence_get(fence);
+		(*i)++;
+	}
+}
+
+/**
+ * sync_file_merge() - merge two sync_files
+ * @name:	name of new fence
+ * @a:		sync_file a
+ * @b:		sync_file b
+ *
+ * Creates a new sync_file which contains copies of all the fences in both
+ * @a and @b.  @a and @b remain valid, independent sync_file. Returns the
+ * new merged sync_file or NULL in case of error.
+ */
+static struct sync_file *sync_file_merge(const char *name, struct sync_file *a,
+					 struct sync_file *b)
+{
+	struct sync_file *sync_file;
+	struct dma_fence **fences = NULL, **nfences, **a_fences, **b_fences;
+	int i = 0, i_a, i_b, num_fences, a_num_fences, b_num_fences;
+
+	sync_file = sync_file_alloc();
+	if (!sync_file)
+		return NULL;
+
+	a_fences = get_fences(a, &a_num_fences);
+	b_fences = get_fences(b, &b_num_fences);
+	if (a_num_fences > INT_MAX - b_num_fences)
+		goto err;
+
+	num_fences = a_num_fences + b_num_fences;
+
+	fences = kcalloc(num_fences, sizeof(*fences), GFP_KERNEL);
+	if (!fences)
+		goto err;
+
+	/*
+	 * Assume sync_file a and b are both ordered and have no
+	 * duplicates with the same context.
+	 *
+	 * If a sync_file can only be created with sync_file_merge
+	 * and sync_file_create, this is a reasonable assumption.
+	 */
+	for (i_a = i_b = 0; i_a < a_num_fences && i_b < b_num_fences; ) {
+		struct dma_fence *pt_a = a_fences[i_a];
+		struct dma_fence *pt_b = b_fences[i_b];
+
+		if (pt_a->context < pt_b->context) {
+			add_fence(fences, &i, pt_a);
+
+			i_a++;
+		} else if (pt_a->context > pt_b->context) {
+			add_fence(fences, &i, pt_b);
+
+			i_b++;
+		} else {
+			if (__dma_fence_is_later(pt_a->seqno, pt_b->seqno,
+						 pt_a->ops))
+				add_fence(fences, &i, pt_a);
+			else
+				add_fence(fences, &i, pt_b);
+
+			i_a++;
+			i_b++;
+		}
+	}
+
+	for (; i_a < a_num_fences; i_a++)
+		add_fence(fences, &i, a_fences[i_a]);
+
+	for (; i_b < b_num_fences; i_b++)
+		add_fence(fences, &i, b_fences[i_b]);
+
+	if (i == 0)
+		fences[i++] = dma_fence_get(a_fences[0]);
+
+	if (num_fences > i) {
+		nfences = krealloc(fences, i * sizeof(*fences),
+				  GFP_KERNEL);
+		if (!nfences)
+			goto err;
+
+		fences = nfences;
+	}
+
+	if (sync_file_set_fence(sync_file, fences, i) < 0)
+		goto err;
+
+	strlcpy(sync_file->user_name, name, sizeof(sync_file->user_name));
+	return sync_file;
+
+err:
+	while (i)
+		dma_fence_put(fences[--i]);
+	kfree(fences);
+	fput(sync_file->file);
+	return NULL;
+
+}
+
+static int sync_file_release(struct inode *inode, struct file *file)
+{
+	struct sync_file *sync_file = file->private_data;
+
+	if (test_bit(POLL_ENABLED, &sync_file->flags))
+		dma_fence_remove_callback(sync_file->fence, &sync_file->cb);
+	dma_fence_put(sync_file->fence);
+	kfree(sync_file);
+
+	return 0;
+}
+
+static __poll_t sync_file_poll(struct file *file, poll_table *wait)
+{
+	struct sync_file *sync_file = file->private_data;
+
+	poll_wait(file, &sync_file->wq, wait);
+
+	if (list_empty(&sync_file->cb.node) &&
+	    !test_and_set_bit(POLL_ENABLED, &sync_file->flags)) {
+		if (dma_fence_add_callback(sync_file->fence, &sync_file->cb,
+					   fence_check_cb_func) < 0)
+			wake_up_all(&sync_file->wq);
+	}
+
+	return dma_fence_is_signaled(sync_file->fence) ? EPOLLIN : 0;
+}
+
+static long sync_file_ioctl_merge(struct sync_file *sync_file,
+				  unsigned long arg)
+{
+	int fd = get_unused_fd_flags(O_CLOEXEC);
+	int err;
+	struct sync_file *fence2, *fence3;
+	struct sync_merge_data data;
+
+	if (fd < 0)
+		return fd;
+
+	if (copy_from_user(&data, (void __user *)arg, sizeof(data))) {
+		err = -EFAULT;
+		goto err_put_fd;
+	}
+
+	if (data.flags || data.pad) {
+		err = -EINVAL;
+		goto err_put_fd;
+	}
+
+	fence2 = sync_file_fdget(data.fd2);
+	if (!fence2) {
+		err = -ENOENT;
+		goto err_put_fd;
+	}
+
+	data.name[sizeof(data.name) - 1] = '\0';
+	fence3 = sync_file_merge(data.name, sync_file, fence2);
+	if (!fence3) {
+		err = -ENOMEM;
+		goto err_put_fence2;
+	}
+
+	data.fence = fd;
+	if (copy_to_user((void __user *)arg, &data, sizeof(data))) {
+		err = -EFAULT;
+		goto err_put_fence3;
+	}
+
+	fd_install(fd, fence3->file);
+	fput(fence2->file);
+	return 0;
+
+err_put_fence3:
+	fput(fence3->file);
+
+err_put_fence2:
+	fput(fence2->file);
+
+err_put_fd:
+	put_unused_fd(fd);
+	return err;
+}
+
+static int sync_fill_fence_info(struct dma_fence *fence,
+				 struct sync_fence_info *info)
+{
+	strlcpy(info->obj_name, fence->ops->get_timeline_name(fence),
+		sizeof(info->obj_name));
+	strlcpy(info->driver_name, fence->ops->get_driver_name(fence),
+		sizeof(info->driver_name));
+
+	info->status = dma_fence_get_status(fence);
+	while (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags) &&
+	       !test_bit(DMA_FENCE_FLAG_TIMESTAMP_BIT, &fence->flags))
+		cpu_relax();
+	info->timestamp_ns =
+		test_bit(DMA_FENCE_FLAG_TIMESTAMP_BIT, &fence->flags) ?
+		ktime_to_ns(fence->timestamp) :
+		ktime_set(0, 0);
+
+	return info->status;
+}
+
+static long sync_file_ioctl_fence_info(struct sync_file *sync_file,
+				       unsigned long arg)
+{
+	struct sync_file_info info;
+	struct sync_fence_info *fence_info = NULL;
+	struct dma_fence **fences;
+	__u32 size;
+	int num_fences, ret, i;
+
+	if (copy_from_user(&info, (void __user *)arg, sizeof(info)))
+		return -EFAULT;
+
+	if (info.flags || info.pad)
+		return -EINVAL;
+
+	fences = get_fences(sync_file, &num_fences);
+
+	/*
+	 * Passing num_fences = 0 means that userspace doesn't want to
+	 * retrieve any sync_fence_info. If num_fences = 0 we skip filling
+	 * sync_fence_info and return the actual number of fences on
+	 * info->num_fences.
+	 */
+	if (!info.num_fences) {
+		info.status = dma_fence_get_status(sync_file->fence);
+		goto no_fences;
+	} else {
+		info.status = 1;
+	}
+
+	if (info.num_fences < num_fences)
+		return -EINVAL;
+
+	size = num_fences * sizeof(*fence_info);
+	fence_info = kzalloc(size, GFP_KERNEL);
+	if (!fence_info)
+		return -ENOMEM;
+
+	for (i = 0; i < num_fences; i++) {
+		int status = sync_fill_fence_info(fences[i], &fence_info[i]);
+		info.status = info.status <= 0 ? info.status : status;
+	}
+
+	if (copy_to_user(u64_to_user_ptr(info.sync_fence_info), fence_info,
+			 size)) {
+		ret = -EFAULT;
+		goto out;
+	}
+
+no_fences:
+	sync_file_get_name(sync_file, info.name, sizeof(info.name));
+	info.num_fences = num_fences;
+
+	if (copy_to_user((void __user *)arg, &info, sizeof(info)))
+		ret = -EFAULT;
+	else
+		ret = 0;
+
+out:
+	kfree(fence_info);
+
+	return ret;
+}
+
+static long sync_file_ioctl(struct file *file, unsigned int cmd,
+			    unsigned long arg)
+{
+	struct sync_file *sync_file = file->private_data;
+
+	switch (cmd) {
+	case SYNC_IOC_MERGE:
+		return sync_file_ioctl_merge(sync_file, arg);
+
+	case SYNC_IOC_FILE_INFO:
+		return sync_file_ioctl_fence_info(sync_file, arg);
+
+	default:
+		return -ENOTTY;
+	}
+}
+
+static const struct file_operations sync_file_fops = {
+	.release = sync_file_release,
+	.poll = sync_file_poll,
+	.unlocked_ioctl = sync_file_ioctl,
+	.compat_ioctl = compat_ptr_ioctl,
+};
diff --git a/drivers/dma-buf/sync_trace.h b/drivers/dma-buf/sync_trace.h
new file mode 100644
index 000000000..06e468a21
--- /dev/null
+++ b/drivers/dma-buf/sync_trace.h
@@ -0,0 +1,33 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#undef TRACE_SYSTEM
+#define TRACE_INCLUDE_PATH ../../drivers/dma-buf
+#define TRACE_SYSTEM sync_trace
+
+#if !defined(_TRACE_SYNC_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_SYNC_H
+
+#include "sync_debug.h"
+#include <linux/tracepoint.h>
+
+TRACE_EVENT(sync_timeline,
+	TP_PROTO(struct sync_timeline *timeline),
+
+	TP_ARGS(timeline),
+
+	TP_STRUCT__entry(
+			__string(name, timeline->name)
+			__field(u32, value)
+	),
+
+	TP_fast_assign(
+			__assign_str(name, timeline->name);
+			__entry->value = timeline->value;
+	),
+
+	TP_printk("name=%s value=%d", __get_str(name), __entry->value)
+);
+
+#endif /* if !defined(_TRACE_SYNC_H) || defined(TRACE_HEADER_MULTI_READ) */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>
diff --git a/drivers/dma-buf/udmabuf.c b/drivers/dma-buf/udmabuf.c
new file mode 100644
index 000000000..e359c5c6c
--- /dev/null
+++ b/drivers/dma-buf/udmabuf.c
@@ -0,0 +1,361 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/cred.h>
+#include <linux/device.h>
+#include <linux/dma-buf.h>
+#include <linux/highmem.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/memfd.h>
+#include <linux/miscdevice.h>
+#include <linux/module.h>
+#include <linux/shmem_fs.h>
+#include <linux/slab.h>
+#include <linux/udmabuf.h>
+
+static const u32    list_limit = 1024;  /* udmabuf_create_list->count limit */
+static const size_t size_limit_mb = 64; /* total dmabuf size, in megabytes  */
+
+struct udmabuf {
+	pgoff_t pagecount;
+	struct page **pages;
+	struct sg_table *sg;
+	struct miscdevice *device;
+};
+
+static vm_fault_t udmabuf_vm_fault(struct vm_fault *vmf)
+{
+	struct vm_area_struct *vma = vmf->vma;
+	struct udmabuf *ubuf = vma->vm_private_data;
+	pgoff_t pgoff = vmf->pgoff;
+
+	if (pgoff >= ubuf->pagecount)
+		return VM_FAULT_SIGBUS;
+	vmf->page = ubuf->pages[pgoff];
+	get_page(vmf->page);
+	return 0;
+}
+
+static const struct vm_operations_struct udmabuf_vm_ops = {
+	.fault = udmabuf_vm_fault,
+};
+
+static int mmap_udmabuf(struct dma_buf *buf, struct vm_area_struct *vma)
+{
+	struct udmabuf *ubuf = buf->priv;
+
+	if ((vma->vm_flags & (VM_SHARED | VM_MAYSHARE)) == 0)
+		return -EINVAL;
+
+	vma->vm_ops = &udmabuf_vm_ops;
+	vma->vm_private_data = ubuf;
+	return 0;
+}
+
+static struct sg_table *get_sg_table(struct device *dev, struct dma_buf *buf,
+				     enum dma_data_direction direction)
+{
+	struct udmabuf *ubuf = buf->priv;
+	struct sg_table *sg;
+	int ret;
+
+	sg = kzalloc(sizeof(*sg), GFP_KERNEL);
+	if (!sg)
+		return ERR_PTR(-ENOMEM);
+	ret = sg_alloc_table_from_pages(sg, ubuf->pages, ubuf->pagecount,
+					0, ubuf->pagecount << PAGE_SHIFT,
+					GFP_KERNEL);
+	if (ret < 0)
+		goto err;
+	ret = dma_map_sgtable(dev, sg, direction, 0);
+	if (ret < 0)
+		goto err;
+	return sg;
+
+err:
+	sg_free_table(sg);
+	kfree(sg);
+	return ERR_PTR(ret);
+}
+
+static void put_sg_table(struct device *dev, struct sg_table *sg,
+			 enum dma_data_direction direction)
+{
+	dma_unmap_sgtable(dev, sg, direction, 0);
+	sg_free_table(sg);
+	kfree(sg);
+}
+
+static struct sg_table *map_udmabuf(struct dma_buf_attachment *at,
+				    enum dma_data_direction direction)
+{
+	return get_sg_table(at->dev, at->dmabuf, direction);
+}
+
+static void unmap_udmabuf(struct dma_buf_attachment *at,
+			  struct sg_table *sg,
+			  enum dma_data_direction direction)
+{
+	return put_sg_table(at->dev, sg, direction);
+}
+
+static void release_udmabuf(struct dma_buf *buf)
+{
+	struct udmabuf *ubuf = buf->priv;
+	struct device *dev = ubuf->device->this_device;
+	pgoff_t pg;
+
+	if (ubuf->sg)
+		put_sg_table(dev, ubuf->sg, DMA_BIDIRECTIONAL);
+
+	for (pg = 0; pg < ubuf->pagecount; pg++)
+		put_page(ubuf->pages[pg]);
+	kfree(ubuf->pages);
+	kfree(ubuf);
+}
+
+static int begin_cpu_udmabuf(struct dma_buf *buf,
+			     enum dma_data_direction direction)
+{
+	struct udmabuf *ubuf = buf->priv;
+	struct device *dev = ubuf->device->this_device;
+	int ret = 0;
+
+	if (!ubuf->sg) {
+		ubuf->sg = get_sg_table(dev, buf, direction);
+		if (IS_ERR(ubuf->sg)) {
+			ret = PTR_ERR(ubuf->sg);
+			ubuf->sg = NULL;
+		}
+	} else {
+		dma_sync_sg_for_cpu(dev, ubuf->sg->sgl, ubuf->sg->nents,
+				    direction);
+	}
+
+	return ret;
+}
+
+static int end_cpu_udmabuf(struct dma_buf *buf,
+			   enum dma_data_direction direction)
+{
+	struct udmabuf *ubuf = buf->priv;
+	struct device *dev = ubuf->device->this_device;
+
+	if (!ubuf->sg)
+		return -EINVAL;
+
+	dma_sync_sg_for_device(dev, ubuf->sg->sgl, ubuf->sg->nents, direction);
+	return 0;
+}
+
+static const struct dma_buf_ops udmabuf_ops = {
+	.cache_sgt_mapping = true,
+	.map_dma_buf	   = map_udmabuf,
+	.unmap_dma_buf	   = unmap_udmabuf,
+	.release	   = release_udmabuf,
+	.mmap		   = mmap_udmabuf,
+	.begin_cpu_access  = begin_cpu_udmabuf,
+	.end_cpu_access    = end_cpu_udmabuf,
+};
+
+#define SEALS_WANTED (F_SEAL_SHRINK)
+#define SEALS_DENIED (F_SEAL_WRITE)
+
+static long udmabuf_create(struct miscdevice *device,
+			   struct udmabuf_create_list *head,
+			   struct udmabuf_create_item *list)
+{
+	DEFINE_DMA_BUF_EXPORT_INFO(exp_info);
+	struct file *memfd = NULL;
+	struct udmabuf *ubuf;
+	struct dma_buf *buf;
+	pgoff_t pgoff, pgcnt, pgidx, pgbuf = 0, pglimit;
+	struct page *page;
+	int seals, ret = -EINVAL;
+	u32 i, flags;
+
+	ubuf = kzalloc(sizeof(*ubuf), GFP_KERNEL);
+	if (!ubuf)
+		return -ENOMEM;
+
+	pglimit = (size_limit_mb * 1024 * 1024) >> PAGE_SHIFT;
+	for (i = 0; i < head->count; i++) {
+		if (!IS_ALIGNED(list[i].offset, PAGE_SIZE))
+			goto err;
+		if (!IS_ALIGNED(list[i].size, PAGE_SIZE))
+			goto err;
+		ubuf->pagecount += list[i].size >> PAGE_SHIFT;
+		if (ubuf->pagecount > pglimit)
+			goto err;
+	}
+
+	if (!ubuf->pagecount)
+		goto err;
+
+	ubuf->pages = kmalloc_array(ubuf->pagecount, sizeof(*ubuf->pages),
+				    GFP_KERNEL);
+	if (!ubuf->pages) {
+		ret = -ENOMEM;
+		goto err;
+	}
+
+	pgbuf = 0;
+	for (i = 0; i < head->count; i++) {
+		ret = -EBADFD;
+		memfd = fget(list[i].memfd);
+		if (!memfd)
+			goto err;
+		if (!shmem_mapping(file_inode(memfd)->i_mapping))
+			goto err;
+		seals = memfd_fcntl(memfd, F_GET_SEALS, 0);
+		if (seals == -EINVAL)
+			goto err;
+		ret = -EINVAL;
+		if ((seals & SEALS_WANTED) != SEALS_WANTED ||
+		    (seals & SEALS_DENIED) != 0)
+			goto err;
+		pgoff = list[i].offset >> PAGE_SHIFT;
+		pgcnt = list[i].size   >> PAGE_SHIFT;
+		for (pgidx = 0; pgidx < pgcnt; pgidx++) {
+			page = shmem_read_mapping_page(
+				file_inode(memfd)->i_mapping, pgoff + pgidx);
+			if (IS_ERR(page)) {
+				ret = PTR_ERR(page);
+				goto err;
+			}
+			ubuf->pages[pgbuf++] = page;
+		}
+		fput(memfd);
+		memfd = NULL;
+	}
+
+	exp_info.ops  = &udmabuf_ops;
+	exp_info.size = ubuf->pagecount << PAGE_SHIFT;
+	exp_info.priv = ubuf;
+	exp_info.flags = O_RDWR;
+
+	ubuf->device = device;
+	buf = dma_buf_export(&exp_info);
+	if (IS_ERR(buf)) {
+		ret = PTR_ERR(buf);
+		goto err;
+	}
+
+	flags = 0;
+	if (head->flags & UDMABUF_FLAGS_CLOEXEC)
+		flags |= O_CLOEXEC;
+	return dma_buf_fd(buf, flags);
+
+err:
+	while (pgbuf > 0)
+		put_page(ubuf->pages[--pgbuf]);
+	if (memfd)
+		fput(memfd);
+	kfree(ubuf->pages);
+	kfree(ubuf);
+	return ret;
+}
+
+static long udmabuf_ioctl_create(struct file *filp, unsigned long arg)
+{
+	struct udmabuf_create create;
+	struct udmabuf_create_list head;
+	struct udmabuf_create_item list;
+
+	if (copy_from_user(&create, (void __user *)arg,
+			   sizeof(create)))
+		return -EFAULT;
+
+	head.flags  = create.flags;
+	head.count  = 1;
+	list.memfd  = create.memfd;
+	list.offset = create.offset;
+	list.size   = create.size;
+
+	return udmabuf_create(filp->private_data, &head, &list);
+}
+
+static long udmabuf_ioctl_create_list(struct file *filp, unsigned long arg)
+{
+	struct udmabuf_create_list head;
+	struct udmabuf_create_item *list;
+	int ret = -EINVAL;
+	u32 lsize;
+
+	if (copy_from_user(&head, (void __user *)arg, sizeof(head)))
+		return -EFAULT;
+	if (head.count > list_limit)
+		return -EINVAL;
+	lsize = sizeof(struct udmabuf_create_item) * head.count;
+	list = memdup_user((void __user *)(arg + sizeof(head)), lsize);
+	if (IS_ERR(list))
+		return PTR_ERR(list);
+
+	ret = udmabuf_create(filp->private_data, &head, list);
+	kfree(list);
+	return ret;
+}
+
+static long udmabuf_ioctl(struct file *filp, unsigned int ioctl,
+			  unsigned long arg)
+{
+	long ret;
+
+	switch (ioctl) {
+	case UDMABUF_CREATE:
+		ret = udmabuf_ioctl_create(filp, arg);
+		break;
+	case UDMABUF_CREATE_LIST:
+		ret = udmabuf_ioctl_create_list(filp, arg);
+		break;
+	default:
+		ret = -ENOTTY;
+		break;
+	}
+	return ret;
+}
+
+static const struct file_operations udmabuf_fops = {
+	.owner		= THIS_MODULE,
+	.unlocked_ioctl = udmabuf_ioctl,
+#ifdef CONFIG_COMPAT
+	.compat_ioctl   = udmabuf_ioctl,
+#endif
+};
+
+static struct miscdevice udmabuf_misc = {
+	.minor          = MISC_DYNAMIC_MINOR,
+	.name           = "udmabuf",
+	.fops           = &udmabuf_fops,
+};
+
+static int __init udmabuf_dev_init(void)
+{
+	int ret;
+
+	ret = misc_register(&udmabuf_misc);
+	if (ret < 0) {
+		pr_err("Could not initialize udmabuf device\n");
+		return ret;
+	}
+
+	ret = dma_coerce_mask_and_coherent(udmabuf_misc.this_device,
+					   DMA_BIT_MASK(64));
+	if (ret < 0) {
+		pr_err("Could not setup DMA mask for udmabuf device\n");
+		misc_deregister(&udmabuf_misc);
+		return ret;
+	}
+
+	return 0;
+}
+
+static void __exit udmabuf_dev_exit(void)
+{
+	misc_deregister(&udmabuf_misc);
+}
+
+module_init(udmabuf_dev_init)
+module_exit(udmabuf_dev_exit)
+
+MODULE_AUTHOR("Gerd Hoffmann <kraxel@redhat.com>");
+MODULE_LICENSE("GPL v2");