// SPDX-License-Identifier: GPL-2.0-only
/*
 * drivers/dma-buf/sync_file.c
 *
 * Copyright (C) 2012 Google, Inc.
 */

#include <linux/dma-fence-unwrap.h>
#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 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 dma_fence *a_fence, *b_fence, **fences;
        struct dma_fence_unwrap a_iter, b_iter;
        unsigned int index, num_fences;
        struct sync_file *sync_file;

        sync_file = sync_file_alloc();
        if (!sync_file)
                return NULL;

        num_fences = 0;
        dma_fence_unwrap_for_each(a_fence, &a_iter, a->fence)
                ++num_fences;
        dma_fence_unwrap_for_each(b_fence, &b_iter, b->fence)
                ++num_fences;

        if (num_fences > INT_MAX)
                goto err_free_sync_file;

        fences = kcalloc(num_fences, sizeof(*fences), GFP_KERNEL);
        if (!fences)
                goto err_free_sync_file;

        /*
         * We can't guarantee that fences in both a and b are ordered, but it is
         * still quite likely.
         *
         * So attempt to order the fences as we pass over them and merge fences
         * with the same context.
         */

        index = 0;
        for (a_fence = dma_fence_unwrap_first(a->fence, &a_iter),
             b_fence = dma_fence_unwrap_first(b->fence, &b_iter);
             a_fence || b_fence; ) {

                if (!b_fence) {
                        add_fence(fences, &index, a_fence);
                        a_fence = dma_fence_unwrap_next(&a_iter);

                } else if (!a_fence) {
                        add_fence(fences, &index, b_fence);
                        b_fence = dma_fence_unwrap_next(&b_iter);

                } else if (a_fence->context < b_fence->context) {
                        add_fence(fences, &index, a_fence);
                        a_fence = dma_fence_unwrap_next(&a_iter);

                } else if (b_fence->context < a_fence->context) {
                        add_fence(fences, &index, b_fence);
                        b_fence = dma_fence_unwrap_next(&b_iter);

                } else if (__dma_fence_is_later(a_fence->seqno, b_fence->seqno,
                                                a_fence->ops)) {
                        add_fence(fences, &index, a_fence);
                        a_fence = dma_fence_unwrap_next(&a_iter);
                        b_fence = dma_fence_unwrap_next(&b_iter);

                } else {
                        add_fence(fences, &index, b_fence);
                        a_fence = dma_fence_unwrap_next(&a_iter);
                        b_fence = dma_fence_unwrap_next(&b_iter);
                }
        }

        if (index == 0)
                fences[index++] = dma_fence_get_stub();

        if (num_fences > index) {
                struct dma_fence **tmp;

                /* Keep going even when reducing the size failed */
                tmp = krealloc_array(fences, index, sizeof(*fences),
                                     GFP_KERNEL);
                if (tmp)
                        fences = tmp;
        }

        if (sync_file_set_fence(sync_file, fences, index) < 0)
                goto err_put_fences;

        strlcpy(sync_file->user_name, name, sizeof(sync_file->user_name));
        return sync_file;

err_put_fences:
        while (index)
                dma_fence_put(fences[--index]);
        kfree(fences);

err_free_sync_file:
        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_fence_info *fence_info = NULL;
        struct dma_fence_unwrap iter;
        struct sync_file_info info;
        unsigned int num_fences;
        struct dma_fence *fence;
        int ret;
        __u32 size;

        if (copy_from_user(&info, (void __user *)arg, sizeof(info)))
                return -EFAULT;

        if (info.flags || info.pad)
                return -EINVAL;

        num_fences = 0;
        dma_fence_unwrap_for_each(fence, &iter, sync_file->fence)
                ++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;

        num_fences = 0;
        dma_fence_unwrap_for_each(fence, &iter, sync_file->fence) {
                int status;

                status = sync_fill_fence_info(fence, &fence_info[num_fences++]);
                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,
};