/*
 * Sync File validation framework
 *
 * 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/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);

        if (!list_empty(&pt->link)) {
                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);
}

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, "%d", 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)
{
        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;

                list_del_init(&pt->link);
                rb_erase(&pt->node, &obj->pt_tree);

                /*
                 * A signal callback may release the last reference to this
                 * fence, causing it to be freed. That operation has to be
                 * last to avoid a use after free inside this loop, and must
                 * be after we remove the fence from the timeline in order to
                 * prevent deadlocking on timeline->lock inside
                 * timeline_fence_release().
                 */
                dma_fence_signal_locked(&pt->base);
        }

        spin_unlock_irq(&obj->lock);
}

/**
 * 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)) {
                                        dma_fence_put(&pt->base);
                                        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   = sw_sync_ioctl,
};