/* SPDX-License-Identifier: GPL-2.0 OR MIT */
/**************************************************************************
 *
 * Copyright (c) 2009-2023 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 "ttm_object.h"
#include "vmwgfx_drv.h"

#include <linux/list.h>
#include <linux/spinlock.h>
#include <linux/slab.h>
#include <linux/atomic.h>
#include <linux/module.h>
#include <linux/hashtable.h>

MODULE_IMPORT_NS("DMA_BUF");

#define VMW_TTM_OBJECT_REF_HT_ORDER 10

/**
 * 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;
        DECLARE_HASHTABLE(ref_hash, VMW_TTM_OBJECT_REF_HT_ORDER);
        struct kref refcount;
};

/*
 * struct ttm_object_device
 *
 * @object_lock: lock that protects idr.
 *
 * This is the per-device data structure needed for ttm object management.
 */

struct ttm_object_device {
        spinlock_t object_lock;
        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 int ttm_tfile_find_ref_rcu(struct ttm_object_file *tfile,
                                  uint64_t key,
                                  struct vmwgfx_hash_item **p_hash)
{
        struct vmwgfx_hash_item *hash;

        hash_for_each_possible_rcu(tfile->ref_hash, hash, head, key) {
                if (hash->key == key) {
                        *p_hash = hash;
                        return 0;
                }
        }
        return -EINVAL;
}

static int ttm_tfile_find_ref(struct ttm_object_file *tfile,
                              uint64_t key,
                              struct vmwgfx_hash_item **p_hash)
{
        struct vmwgfx_hash_item *hash;

        hash_for_each_possible(tfile->ref_hash, hash, head, key) {
                if (hash->key == key) {
                        *p_hash = hash;
                        return 0;
                }
        }
        return -EINVAL;
}

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);
}

struct ttm_base_object *ttm_base_object_lookup(struct ttm_object_file *tfile,
                                               uint64_t key)
{
        struct ttm_base_object *base = NULL;
        struct vmwgfx_hash_item *hash;
        int ret;

        spin_lock(&tfile->lock);
        ret = ttm_tfile_find_ref(tfile, key, &hash);

        if (likely(ret == 0)) {
                base = hlist_entry(hash, struct ttm_ref_object, hash)->obj;
                if (!kref_get_unless_zero(&base->refcount))
                        base = NULL;
        }
        spin_unlock(&tfile->lock);


        return base;
}

struct ttm_base_object *
ttm_base_object_lookup_for_ref(struct ttm_object_device *tdev, uint64_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 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 = ttm_tfile_find_ref_rcu(tfile, base->handle, &hash);

                if (ret == 0) {
                        ref = hlist_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_obj(*ref);
                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);
                hash_add_rcu(tfile->ref_hash, &ref->hash.head, ref->hash.key);
                ret = 0;

                list_add_tail(&ref->head, &tfile->ref_list);
                kref_get(&base->refcount);
                spin_unlock(&tfile->lock);
                if (existed != NULL)
                        *existed = false;
        }

        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;

        hash_del_rcu(&ref->hash.head);
        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 ttm_ref_object *ref;
        struct vmwgfx_hash_item *hash;
        int ret;

        spin_lock(&tfile->lock);
        ret = ttm_tfile_find_ref(tfile, key, &hash);
        if (unlikely(ret != 0)) {
                spin_unlock(&tfile->lock);
                return -EINVAL;
        }
        ref = hlist_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);

        ttm_object_file_unref(&tfile);
}

struct ttm_object_file *ttm_object_file_init(struct ttm_object_device *tdev)
{
        struct ttm_object_file *tfile = kmalloc_obj(*tfile);

        if (unlikely(tfile == NULL))
                return NULL;

        spin_lock_init(&tfile->lock);
        tfile->tdev = tdev;
        kref_init(&tfile->refcount);
        INIT_LIST_HEAD(&tfile->ref_list);

        hash_init(tfile->ref_hash);

        return tfile;
}

struct ttm_object_device *
ttm_object_device_init(const struct dma_buf_ops *ops)
{
        struct ttm_object_device *tdev = kmalloc_obj(*tdev);

        if (unlikely(tdev == NULL))
                return NULL;

        spin_lock_init(&tdev->object_lock);

        /*
         * 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;
}

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);

        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 file_ref_get(&dmabuf->file->f_ref);
}

/**
 * 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.
 * @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,
                          enum ttm_object_type type,
                          void (*refcount_release) (struct ttm_base_object **))
{
        bool shareable = !!(type == VMW_RES_SURFACE);
        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);
}