/*
 * drivers/dma-buf/sync_file.c
 *
 * Copyright (C) 2012 Google, Inc.
 *
 * This software is licensed under the terms of the GNU General Public
 * License version 2, as published by the Free Software Foundation, and
 * may be copied, distributed, and modified under those terms.
 *
 * 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.
 *
 */

#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);

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(struct sync_file *a,
					 struct sync_file *b)
{
	struct sync_file *sync_file;
	struct dma_fence **fences, **nfences, **a_fences, **b_fences;
	int i, 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 = 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 (pt_a->seqno - pt_b->seqno <= INT_MAX)
				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) {
		kfree(fences);
		goto err;
	}

	return sync_file;

err:
	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 unsigned int 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) ? POLLIN : 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;
	size_t len;

	if (fd < 0)
		return fd;

	arg += offsetof(typeof(data), fd2);
	len = sizeof(data) - offsetof(typeof(data), fd2);
	if (copy_from_user(&data.fd2, (void __user *)arg, len)) {
		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;
	}

	fence3 = sync_file_merge(sync_file, fence2);
	if (!fence3) {
		err = -ENOMEM;
		goto err_put_fence2;
	}

	data.fence = fd;
	if (copy_to_user((void __user *)arg, &data.fd2, len)) {
		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)
{
	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 dma_fence **fences;
	size_t len, offset;
	int num_fences, i;

	arg += offsetof(typeof(info), status);
	len = sizeof(info) - offsetof(typeof(info), status);
	if (copy_from_user(&info.status, (void __user *)arg, len))
		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_is_signaled(sync_file->fence);
		goto no_fences;
	} else {
		info.status = 1;
	}

	if (info.num_fences < num_fences)
		return -EINVAL;

	offset = offsetof(struct sync_fence_info, status);
	for (i = 0; i < num_fences; i++) {
		struct {
			__s32	status;
			__u32	flags;
			__u64	timestamp_ns;
		} fence_info;
		struct sync_fence_info *finfo = (void *)&fence_info - offset;
		int status = sync_fill_fence_info(fences[i], finfo);
		u64 dest;

		/* Don't leak kernel memory to userspace via finfo->flags */
		finfo->flags = 0;
		info.status = info.status <= 0 ? info.status : status;
		dest = info.sync_fence_info + i * sizeof(*finfo) + offset;
		if (copy_to_user(u64_to_user_ptr(dest), &fence_info,
				 sizeof(fence_info)))
			return -EFAULT;
	}

no_fences:
	info.num_fences = num_fences;
	if (copy_to_user((void __user *)arg, &info.status, len))
		return -EFAULT;
	return 0;
}

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 = sync_file_ioctl,
};