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 /* SPDX-License-Identifier: GPL-2.0 OR MIT */
 /**************************************************************************
  *
  * Copyright (c) 2009-2013 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>
  *
  * While no substantial code is shared, the prime code is inspired by
  * drm_prime.c, with
  * Authors:
  *      Dave Airlie <airlied@redhat.com>
  *      Rob Clark <rob.clark@linaro.org>
  */
 /** @file ttm_ref_object.c
  *
  * Base- and reference object implementation for the various
  * ttm objects. Implements reference counting, minimal security checks
  * and release on file close.
  */
 
 
 #define pr_fmt(fmt) "[TTM] " fmt
 
 #include <linux/list.h>
 #include <linux/spinlock.h>
 #include <linux/slab.h>
 #include <linux/atomic.h>
 #include <linux/module.h>
 #include "ttm_object.h"
 #include "vmwgfx_drv.h"
 
 MODULE_IMPORT_NS(DMA_BUF);
 
 /**
  * struct ttm_object_file
  *
  * @tdev: Pointer to the ttm_object_device.
  *
  * @lock: Lock that protects the ref_list list and the
  * ref_hash hash tables.
  *
  * @ref_list: List of ttm_ref_objects to be destroyed at
  * file release.
  *
  * @ref_hash: Hash tables of ref objects, one per ttm_ref_type,
  * for fast lookup of ref objects given a base object.
  *
  * @refcount: reference/usage count
  */
 struct ttm_object_file {
     struct ttm_object_device *tdev;
     spinlock_t lock;
     struct list_head ref_list;
     struct vmwgfx_open_hash ref_hash;
     struct kref refcount;
 };
 
 /*
  * struct ttm_object_device
  *
  * @object_lock: lock that protects the object_hash hash table.
  *
  * @object_hash: hash table for fast lookup of object global names.
  *
  * @object_count: Per device object count.
  *
  * This is the per-device data structure needed for ttm object management.
  */
 
 struct ttm_object_device {
     spinlock_t object_lock;
     struct vmwgfx_open_hash object_hash;
     atomic_t object_count;
     struct dma_buf_ops ops;
     void (*dmabuf_release)(struct dma_buf *dma_buf);
     struct idr idr;
 };
 
 /*
  * struct ttm_ref_object
  *
  * @hash: Hash entry for the per-file object reference hash.
  *
  * @head: List entry for the per-file list of ref-objects.
  *
  * @kref: Ref count.
  *
  * @obj: Base object this ref object is referencing.
  *
  * @ref_type: Type of ref object.
  *
  * This is similar to an idr object, but it also has a hash table entry
  * that allows lookup with a pointer to the referenced object as a key. In
  * that way, one can easily detect whether a base object is referenced by
  * a particular ttm_object_file. It also carries a ref count to avoid creating
  * multiple ref objects if a ttm_object_file references the same base
  * object more than once.
  */
 
 struct ttm_ref_object {
     struct rcu_head rcu_head;
     struct vmwgfx_hash_item hash;
     struct list_head head;
     struct kref kref;
     struct ttm_base_object *obj;
     struct ttm_object_file *tfile;
 };
 
 static void ttm_prime_dmabuf_release(struct dma_buf *dma_buf);
 
 static inline struct ttm_object_file *
 ttm_object_file_ref(struct ttm_object_file *tfile)
 {
     kref_get(&tfile->refcount);
     return tfile;
 }
 
 static void ttm_object_file_destroy(struct kref *kref)
 {
     struct ttm_object_file *tfile =
         container_of(kref, struct ttm_object_file, refcount);
 
     kfree(tfile);
 }
 
 
 static inline void ttm_object_file_unref(struct ttm_object_file **p_tfile)
 {
     struct ttm_object_file *tfile = *p_tfile;
 
     *p_tfile = NULL;
     kref_put(&tfile->refcount, ttm_object_file_destroy);
 }
 
 
 int ttm_base_object_init(struct ttm_object_file *tfile,
              struct ttm_base_object *base,
              bool shareable,
              enum ttm_object_type object_type,
              void (*refcount_release) (struct ttm_base_object **))
 {
     struct ttm_object_device *tdev = tfile->tdev;
     int ret;
 
     base->shareable = shareable;
     base->tfile = ttm_object_file_ref(tfile);
     base->refcount_release = refcount_release;
     base->object_type = object_type;
     kref_init(&base->refcount);
     idr_preload(GFP_KERNEL);
     spin_lock(&tdev->object_lock);
     ret = idr_alloc(&tdev->idr, base, 1, 0, GFP_NOWAIT);
     spin_unlock(&tdev->object_lock);
     idr_preload_end();
     if (ret < 0)
         return ret;
 
     base->handle = ret;
     ret = ttm_ref_object_add(tfile, base, NULL, false);
     if (unlikely(ret != 0))
         goto out_err1;
 
     ttm_base_object_unref(&base);
 
     return 0;
 out_err1:
     spin_lock(&tdev->object_lock);
     idr_remove(&tdev->idr, base->handle);
     spin_unlock(&tdev->object_lock);
     return ret;
 }
 
 static void ttm_release_base(struct kref *kref)
 {
     struct ttm_base_object *base =
         container_of(kref, struct ttm_base_object, refcount);
     struct ttm_object_device *tdev = base->tfile->tdev;
 
     spin_lock(&tdev->object_lock);
     idr_remove(&tdev->idr, base->handle);
     spin_unlock(&tdev->object_lock);
 
     /*
      * Note: We don't use synchronize_rcu() here because it's far
      * too slow. It's up to the user to free the object using
      * call_rcu() or ttm_base_object_kfree().
      */
 
     ttm_object_file_unref(&base->tfile);
     if (base->refcount_release)
         base->refcount_release(&base);
 }
 
 void ttm_base_object_unref(struct ttm_base_object **p_base)
 {
     struct ttm_base_object *base = *p_base;
 
     *p_base = NULL;
 
     kref_put(&base->refcount, ttm_release_base);
 }
 
 /**
  * ttm_base_object_noref_lookup - look up a base object without reference
  * @tfile: The struct ttm_object_file the object is registered with.
  * @key: The object handle.
  *
  * This function looks up a ttm base object and returns a pointer to it
  * without refcounting the pointer. The returned pointer is only valid
  * until ttm_base_object_noref_release() is called, and the object
  * pointed to by the returned pointer may be doomed. Any persistent usage
  * of the object requires a refcount to be taken using kref_get_unless_zero().
  * Iff this function returns successfully it needs to be paired with
  * ttm_base_object_noref_release() and no sleeping- or scheduling functions
  * may be called inbetween these function callse.
  *
  * Return: A pointer to the object if successful or NULL otherwise.
  */
 struct ttm_base_object *
 ttm_base_object_noref_lookup(struct ttm_object_file *tfile, uint32_t key)
 {
     struct vmwgfx_hash_item *hash;
     struct vmwgfx_open_hash *ht = &tfile->ref_hash;
     int ret;
 
     rcu_read_lock();
     ret = vmwgfx_ht_find_item_rcu(ht, key, &hash);
     if (ret) {
         rcu_read_unlock();
         return NULL;
     }
 
     __release(RCU);
     return drm_hash_entry(hash, struct ttm_ref_object, hash)->obj;
 }
 EXPORT_SYMBOL(ttm_base_object_noref_lookup);
 
 struct ttm_base_object *ttm_base_object_lookup(struct ttm_object_file *tfile,
                            uint32_t key)
 {
     struct ttm_base_object *base = NULL;
     struct vmwgfx_hash_item *hash;
     struct vmwgfx_open_hash *ht = &tfile->ref_hash;
     int ret;
 
     rcu_read_lock();
     ret = vmwgfx_ht_find_item_rcu(ht, key, &hash);
 
     if (likely(ret == 0)) {
         base = drm_hash_entry(hash, struct ttm_ref_object, hash)->obj;
         if (!kref_get_unless_zero(&base->refcount))
             base = NULL;
     }
     rcu_read_unlock();
 
     return base;
 }
 
 struct ttm_base_object *
 ttm_base_object_lookup_for_ref(struct ttm_object_device *tdev, uint32_t key)
 {
     struct ttm_base_object *base;
 
     rcu_read_lock();
     base = idr_find(&tdev->idr, key);
 
     if (base && !kref_get_unless_zero(&base->refcount))
         base = NULL;
     rcu_read_unlock();
 
     return base;
 }
 
 int ttm_ref_object_add(struct ttm_object_file *tfile,
                struct ttm_base_object *base,
                bool *existed,
                bool require_existed)
 {
     struct vmwgfx_open_hash *ht = &tfile->ref_hash;
     struct ttm_ref_object *ref;
     struct vmwgfx_hash_item *hash;
     int ret = -EINVAL;
 
     if (base->tfile != tfile && !base->shareable)
         return -EPERM;
 
     if (existed != NULL)
         *existed = true;
 
     while (ret == -EINVAL) {
         rcu_read_lock();
         ret = vmwgfx_ht_find_item_rcu(ht, base->handle, &hash);
 
         if (ret == 0) {
             ref = drm_hash_entry(hash, struct ttm_ref_object, hash);
             if (kref_get_unless_zero(&ref->kref)) {
                 rcu_read_unlock();
                 break;
             }
         }
 
         rcu_read_unlock();
         if (require_existed)
             return -EPERM;
 
         ref = kmalloc(sizeof(*ref), GFP_KERNEL);
         if (unlikely(ref == NULL)) {
             return -ENOMEM;
         }
 
         ref->hash.key = base->handle;
         ref->obj = base;
         ref->tfile = tfile;
         kref_init(&ref->kref);
 
         spin_lock(&tfile->lock);
         ret = vmwgfx_ht_insert_item_rcu(ht, &ref->hash);
 
         if (likely(ret == 0)) {
             list_add_tail(&ref->head, &tfile->ref_list);
             kref_get(&base->refcount);
             spin_unlock(&tfile->lock);
             if (existed != NULL)
                 *existed = false;
             break;
         }
 
         spin_unlock(&tfile->lock);
         BUG_ON(ret != -EINVAL);
 
         kfree(ref);
     }
 
     return ret;
 }
 
 static void __releases(tfile->lock) __acquires(tfile->lock)
 ttm_ref_object_release(struct kref *kref)
 {
     struct ttm_ref_object *ref =
         container_of(kref, struct ttm_ref_object, kref);
     struct ttm_object_file *tfile = ref->tfile;
     struct vmwgfx_open_hash *ht;
 
     ht = &tfile->ref_hash;
     (void)vmwgfx_ht_remove_item_rcu(ht, &ref->hash);
     list_del(&ref->head);
     spin_unlock(&tfile->lock);
 
     ttm_base_object_unref(&ref->obj);
     kfree_rcu(ref, rcu_head);
     spin_lock(&tfile->lock);
 }
 
 int ttm_ref_object_base_unref(struct ttm_object_file *tfile,
                   unsigned long key)
 {
     struct vmwgfx_open_hash *ht = &tfile->ref_hash;
     struct ttm_ref_object *ref;
     struct vmwgfx_hash_item *hash;
     int ret;
 
     spin_lock(&tfile->lock);
     ret = vmwgfx_ht_find_item(ht, key, &hash);
     if (unlikely(ret != 0)) {
         spin_unlock(&tfile->lock);
         return -EINVAL;
     }
     ref = drm_hash_entry(hash, struct ttm_ref_object, hash);
     kref_put(&ref->kref, ttm_ref_object_release);
     spin_unlock(&tfile->lock);
     return 0;
 }
 
 void ttm_object_file_release(struct ttm_object_file **p_tfile)
 {
     struct ttm_ref_object *ref;
     struct list_head *list;
     struct ttm_object_file *tfile = *p_tfile;
 
     *p_tfile = NULL;
     spin_lock(&tfile->lock);
 
     /*
      * Since we release the lock within the loop, we have to
      * restart it from the beginning each time.
      */
 
     while (!list_empty(&tfile->ref_list)) {
         list = tfile->ref_list.next;
         ref = list_entry(list, struct ttm_ref_object, head);
         ttm_ref_object_release(&ref->kref);
     }
 
     spin_unlock(&tfile->lock);
     vmwgfx_ht_remove(&tfile->ref_hash);
 
     ttm_object_file_unref(&tfile);
 }
 
 struct ttm_object_file *ttm_object_file_init(struct ttm_object_device *tdev,
                          unsigned int hash_order)
 {
     struct ttm_object_file *tfile = kmalloc(sizeof(*tfile), GFP_KERNEL);
     int ret;
 
     if (unlikely(tfile == NULL))
         return NULL;
 
     spin_lock_init(&tfile->lock);
     tfile->tdev = tdev;
     kref_init(&tfile->refcount);
     INIT_LIST_HEAD(&tfile->ref_list);
 
     ret = vmwgfx_ht_create(&tfile->ref_hash, hash_order);
     if (ret)
         goto out_err;
 
     return tfile;
 out_err:
     vmwgfx_ht_remove(&tfile->ref_hash);
 
     kfree(tfile);
 
     return NULL;
 }
 
 struct ttm_object_device *
 ttm_object_device_init(unsigned int hash_order,
                const struct dma_buf_ops *ops)
 {
     struct ttm_object_device *tdev = kmalloc(sizeof(*tdev), GFP_KERNEL);
     int ret;
 
     if (unlikely(tdev == NULL))
         return NULL;
 
     spin_lock_init(&tdev->object_lock);
     atomic_set(&tdev->object_count, 0);
     ret = vmwgfx_ht_create(&tdev->object_hash, hash_order);
     if (ret != 0)
         goto out_no_object_hash;
 
     /*
      * Our base is at VMWGFX_NUM_MOB + 1 because we want to create
      * a seperate namespace for GEM handles (which are
      * 1..VMWGFX_NUM_MOB) and the surface handles. Some ioctl's
      * can take either handle as an argument so we want to
      * easily be able to tell whether the handle refers to a
      * GEM buffer or a surface.
      */
     idr_init_base(&tdev->idr, VMWGFX_NUM_MOB + 1);
     tdev->ops = *ops;
     tdev->dmabuf_release = tdev->ops.release;
     tdev->ops.release = ttm_prime_dmabuf_release;
     return tdev;
 
 out_no_object_hash:
     kfree(tdev);
     return NULL;
 }
 
 void ttm_object_device_release(struct ttm_object_device **p_tdev)
 {
     struct ttm_object_device *tdev = *p_tdev;
 
     *p_tdev = NULL;
 
     WARN_ON_ONCE(!idr_is_empty(&tdev->idr));
     idr_destroy(&tdev->idr);
     vmwgfx_ht_remove(&tdev->object_hash);
 
     kfree(tdev);
 }
 
 /**
  * get_dma_buf_unless_doomed - get a dma_buf reference if possible.
  *
  * @dmabuf: Non-refcounted pointer to a struct dma-buf.
  *
  * Obtain a file reference from a lookup structure that doesn't refcount
  * the file, but synchronizes with its release method to make sure it has
  * not been freed yet. See for example kref_get_unless_zero documentation.
  * Returns true if refcounting succeeds, false otherwise.
  *
  * Nobody really wants this as a public API yet, so let it mature here
  * for some time...
  */
 static bool __must_check get_dma_buf_unless_doomed(struct dma_buf *dmabuf)
 {
     return atomic_long_inc_not_zero(&dmabuf->file->f_count) != 0L;
 }
 
 /**
  * ttm_prime_refcount_release - refcount release method for a prime object.
  *
  * @p_base: Pointer to ttm_base_object pointer.
  *
  * This is a wrapper that calls the refcount_release founction of the
  * underlying object. At the same time it cleans up the prime object.
  * This function is called when all references to the base object we
  * derive from are gone.
  */
 static void ttm_prime_refcount_release(struct ttm_base_object **p_base)
 {
     struct ttm_base_object *base = *p_base;
     struct ttm_prime_object *prime;
 
     *p_base = NULL;
     prime = container_of(base, struct ttm_prime_object, base);
     BUG_ON(prime->dma_buf != NULL);
     mutex_destroy(&prime->mutex);
     if (prime->refcount_release)
         prime->refcount_release(&base);
 }
 
 /**
  * ttm_prime_dmabuf_release - Release method for the dma-bufs we export
  *
  * @dma_buf:
  *
  * This function first calls the dma_buf release method the driver
  * provides. Then it cleans up our dma_buf pointer used for lookup,
  * and finally releases the reference the dma_buf has on our base
  * object.
  */
 static void ttm_prime_dmabuf_release(struct dma_buf *dma_buf)
 {
     struct ttm_prime_object *prime =
         (struct ttm_prime_object *) dma_buf->priv;
     struct ttm_base_object *base = &prime->base;
     struct ttm_object_device *tdev = base->tfile->tdev;
 
     if (tdev->dmabuf_release)
         tdev->dmabuf_release(dma_buf);
     mutex_lock(&prime->mutex);
     if (prime->dma_buf == dma_buf)
         prime->dma_buf = NULL;
     mutex_unlock(&prime->mutex);
     ttm_base_object_unref(&base);
 }
 
 /**
  * ttm_prime_fd_to_handle - Get a base object handle from a prime fd
  *
  * @tfile: A struct ttm_object_file identifying the caller.
  * @fd: The prime / dmabuf fd.
  * @handle: The returned handle.
  *
  * This function returns a handle to an object that previously exported
  * a dma-buf. Note that we don't handle imports yet, because we simply
  * have no consumers of that implementation.
  */
 int ttm_prime_fd_to_handle(struct ttm_object_file *tfile,
                int fd, u32 *handle)
 {
     struct ttm_object_device *tdev = tfile->tdev;
     struct dma_buf *dma_buf;
     struct ttm_prime_object *prime;
     struct ttm_base_object *base;
     int ret;
 
     dma_buf = dma_buf_get(fd);
     if (IS_ERR(dma_buf))
         return PTR_ERR(dma_buf);
 
     if (dma_buf->ops != &tdev->ops)
         return -ENOSYS;
 
     prime = (struct ttm_prime_object *) dma_buf->priv;
     base = &prime->base;
     *handle = base->handle;
     ret = ttm_ref_object_add(tfile, base, NULL, false);
 
     dma_buf_put(dma_buf);
 
     return ret;
 }
 
 /**
  * ttm_prime_handle_to_fd - Return a dma_buf fd from a ttm prime object
  *
  * @tfile: Struct ttm_object_file identifying the caller.
  * @handle: Handle to the object we're exporting from.
  * @flags: flags for dma-buf creation. We just pass them on.
  * @prime_fd: The returned file descriptor.
  *
  */
 int ttm_prime_handle_to_fd(struct ttm_object_file *tfile,
                uint32_t handle, uint32_t flags,
                int *prime_fd)
 {
     struct ttm_object_device *tdev = tfile->tdev;
     struct ttm_base_object *base;
     struct dma_buf *dma_buf;
     struct ttm_prime_object *prime;
     int ret;
 
     base = ttm_base_object_lookup(tfile, handle);
     if (unlikely(base == NULL ||
              base->object_type != ttm_prime_type)) {
         ret = -ENOENT;
         goto out_unref;
     }
 
     prime = container_of(base, struct ttm_prime_object, base);
     if (unlikely(!base->shareable)) {
         ret = -EPERM;
         goto out_unref;
     }
 
     ret = mutex_lock_interruptible(&prime->mutex);
     if (unlikely(ret != 0)) {
         ret = -ERESTARTSYS;
         goto out_unref;
     }
 
     dma_buf = prime->dma_buf;
     if (!dma_buf || !get_dma_buf_unless_doomed(dma_buf)) {
         DEFINE_DMA_BUF_EXPORT_INFO(exp_info);
         exp_info.ops = &tdev->ops;
         exp_info.size = prime->size;
         exp_info.flags = flags;
         exp_info.priv = prime;
 
         /*
          * Need to create a new dma_buf
          */
 
         dma_buf = dma_buf_export(&exp_info);
         if (IS_ERR(dma_buf)) {
             ret = PTR_ERR(dma_buf);
             mutex_unlock(&prime->mutex);
             goto out_unref;
         }
 
         /*
          * dma_buf has taken the base object reference
          */
         base = NULL;
         prime->dma_buf = dma_buf;
     }
     mutex_unlock(&prime->mutex);
 
     ret = dma_buf_fd(dma_buf, flags);
     if (ret >= 0) {
         *prime_fd = ret;
         ret = 0;
     } else
         dma_buf_put(dma_buf);
 
 out_unref:
     if (base)
         ttm_base_object_unref(&base);
     return ret;
 }
 
 /**
  * ttm_prime_object_init - Initialize a ttm_prime_object
  *
  * @tfile: struct ttm_object_file identifying the caller
  * @size: The size of the dma_bufs we export.
  * @prime: The object to be initialized.
  * @shareable: See ttm_base_object_init
  * @type: See ttm_base_object_init
  * @refcount_release: See ttm_base_object_init
  *
  * Initializes an object which is compatible with the drm_prime model
  * for data sharing between processes and devices.
  */
 int ttm_prime_object_init(struct ttm_object_file *tfile, size_t size,
               struct ttm_prime_object *prime, bool shareable,
               enum ttm_object_type type,
               void (*refcount_release) (struct ttm_base_object **))
 {
     mutex_init(&prime->mutex);
     prime->size = PAGE_ALIGN(size);
     prime->real_type = type;
     prime->dma_buf = NULL;
     prime->refcount_release = refcount_release;
     return ttm_base_object_init(tfile, &prime->base, shareable,
                     ttm_prime_type,
                     ttm_prime_refcount_release);
 }

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