/*

   * 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_ioctl_create_fence 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_ioctl_create_fence
   * @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 fence_ops timeline_fence_ops;
  
  static inline struct sync_pt *fence_to_sync_pt(struct 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.
   */

  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 = fence_context_alloc(1);
  	strlcpy(obj->name, name, sizeof(obj->name));

  
  	INIT_LIST_HEAD(&obj->child_list_head);
  	INIT_LIST_HEAD(&obj->active_list_head);
  	spin_lock_init(&obj->child_list_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);
  }
  
  /**

   * 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)
  {
  	unsigned long flags;
  	struct sync_pt *pt, *next;
  
  	trace_sync_timeline(obj);
  
  	spin_lock_irqsave(&obj->child_list_lock, flags);
  
  	obj->value += inc;
  
  	list_for_each_entry_safe(pt, next, &obj->active_list_head,
  				 active_list) {
  		if (fence_is_signaled_locked(&pt->base))
  			list_del_init(&pt->active_list);
  	}
  
  	spin_unlock_irqrestore(&obj->child_list_lock, flags);
  }
  
  /**
   * sync_pt_create() - creates a sync pt
   * @parent:	fence's parent sync_timeline
   * @size:	size to allocate for this pt
   * @inc:	value of the fence
   *
   * Creates a new sync_pt 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, int size,
  			     unsigned int value)
  {
  	unsigned long flags;
  	struct sync_pt *pt;
  
  	if (size < sizeof(*pt))
  		return NULL;
  
  	pt = kzalloc(size, GFP_KERNEL);
  	if (!pt)
  		return NULL;
  
  	spin_lock_irqsave(&obj->child_list_lock, flags);
  	sync_timeline_get(obj);
  	fence_init(&pt->base, &timeline_fence_ops, &obj->child_list_lock,
  		   obj->context, value);
  	list_add_tail(&pt->child_list, &obj->child_list_head);
  	INIT_LIST_HEAD(&pt->active_list);
  	spin_unlock_irqrestore(&obj->child_list_lock, flags);
  	return pt;
  }
  
  static const char *timeline_fence_get_driver_name(struct fence *fence)
  {

  	return "sw_sync";

  }
  
  static const char *timeline_fence_get_timeline_name(struct fence *fence)
  {
  	struct sync_timeline *parent = fence_parent(fence);
  
  	return parent->name;
  }
  
  static void timeline_fence_release(struct fence *fence)
  {
  	struct sync_pt *pt = fence_to_sync_pt(fence);
  	struct sync_timeline *parent = fence_parent(fence);
  	unsigned long flags;
  
  	spin_lock_irqsave(fence->lock, flags);
  	list_del(&pt->child_list);

  	if (!list_empty(&pt->active_list))

  		list_del(&pt->active_list);
  	spin_unlock_irqrestore(fence->lock, flags);
  
  	sync_timeline_put(parent);
  	fence_free(fence);
  }
  
  static bool timeline_fence_signaled(struct fence *fence)
  {
  	struct sync_timeline *parent = fence_parent(fence);
  
  	return (fence->seqno > parent->value) ? false : true;
  }
  
  static bool timeline_fence_enable_signaling(struct fence *fence)
  {
  	struct sync_pt *pt = fence_to_sync_pt(fence);
  	struct sync_timeline *parent = fence_parent(fence);
  
  	if (timeline_fence_signaled(fence))
  		return false;
  
  	list_add_tail(&pt->active_list, &parent->active_list_head);
  	return true;
  }
  
  static void timeline_fence_value_str(struct fence *fence,
  				    char *str, int size)
  {
  	snprintf(str, size, "%d", fence->seqno);
  }
  
  static void timeline_fence_timeline_value_str(struct fence *fence,
  					     char *str, int size)
  {
  	struct sync_timeline *parent = fence_parent(fence);
  
  	snprintf(str, size, "%d", parent->value);
  }
  
  static const struct 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,
  	.wait = fence_default_wait,
  	.release = timeline_fence_release,
  	.fence_value_str = timeline_fence_value_str,
  	.timeline_value_str = timeline_fence_timeline_value_str,
  };

  /*
   * *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;

  	smp_wmb();
  
  	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, sizeof(*pt), data.value);
  	if (!pt) {
  		err = -ENOMEM;
  		goto err;
  	}
  
  	sync_file = sync_file_create(&pt->base);
  	if (!sync_file) {
  		fence_put(&pt->base);
  		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;
  
  	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,
  };