/*
 * Copyright © 2008 Intel Corporation
 *
 * 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, sublicense,
 * 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 NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS 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:
 *    Eric Anholt <eric@anholt.net>
 *
 */

#include <linux/types.h>
#include <linux/slab.h>
#include <linux/mm.h>
#include <linux/uaccess.h>
#include <linux/fs.h>
#include <linux/file.h>
#include <linux/module.h>
#include <linux/mman.h>
#include <linux/pagemap.h>
#include <linux/shmem_fs.h>
#include "drmP.h"

/** @file drm_gem.c
 *
 * This file provides some of the base ioctls and library routines for
 * the graphics memory manager implemented by each device driver.
 *
 * Because various devices have different requirements in terms of
 * synchronization and migration strategies, implementing that is left up to
 * the driver, and all that the general API provides should be generic --
 * allocating objects, reading/writing data with the cpu, freeing objects.
 * Even there, platform-dependent optimizations for reading/writing data with
 * the CPU mean we'll likely hook those out to driver-specific calls.  However,
 * the DRI2 implementation wants to have at least allocate/mmap be generic.
 *
 * The goal was to have swap-backed object allocation managed through
 * struct file.  However, file descriptors as handles to a struct file have
 * two major failings:
 * - Process limits prevent more than 1024 or so being used at a time by
 *   default.
 * - Inability to allocate high fds will aggravate the X Server's select()
 *   handling, and likely that of many GL client applications as well.
 *
 * This led to a plan of using our own integer IDs (called handles, following
 * DRM terminology) to mimic fds, and implement the fd syscalls we need as
 * ioctls.  The objects themselves will still include the struct file so
 * that we can transition to fds if the required kernel infrastructure shows
 * up at a later date, and as our interface with shmfs for memory allocation.
 */

/*
 * We make up offsets for buffer objects so we can recognize them at
 * mmap time.
 */

/* pgoff in mmap is an unsigned long, so we need to make sure that
 * the faked up offset will fit
 */

#if BITS_PER_LONG == 64
#define DRM_FILE_PAGE_OFFSET_START ((0xFFFFFFFFUL >> PAGE_SHIFT) + 1)
#define DRM_FILE_PAGE_OFFSET_SIZE ((0xFFFFFFFFUL >> PAGE_SHIFT) * 16)
#else
#define DRM_FILE_PAGE_OFFSET_START ((0xFFFFFFFUL >> PAGE_SHIFT) + 1)
#define DRM_FILE_PAGE_OFFSET_SIZE ((0xFFFFFFFUL >> PAGE_SHIFT) * 16)
#endif

/**
 * Initialize the GEM device fields
 */

int
drm_gem_init(struct drm_device *dev)
{
        struct drm_gem_mm *mm;

        spin_lock_init(&dev->object_name_lock);
        idr_init(&dev->object_name_idr);

        mm = kzalloc(sizeof(struct drm_gem_mm), GFP_KERNEL);
        if (!mm) {
                DRM_ERROR("out of memory\n");
                return -ENOMEM;
        }

        dev->mm_private = mm;

        if (drm_ht_create(&mm->offset_hash, 12)) {
                kfree(mm);
                return -ENOMEM;
        }

        if (drm_mm_init(&mm->offset_manager, DRM_FILE_PAGE_OFFSET_START,
                        DRM_FILE_PAGE_OFFSET_SIZE)) {
                drm_ht_remove(&mm->offset_hash);
                kfree(mm);
                return -ENOMEM;
        }

        return 0;
}

void
drm_gem_destroy(struct drm_device *dev)
{
        struct drm_gem_mm *mm = dev->mm_private;

        drm_mm_takedown(&mm->offset_manager);
        drm_ht_remove(&mm->offset_hash);
        kfree(mm);
        dev->mm_private = NULL;
}

/**
 * Initialize an already allocated GEM object of the specified size with
 * shmfs backing store.
 */
int drm_gem_object_init(struct drm_device *dev,
                        struct drm_gem_object *obj, size_t size)
{
        BUG_ON((size & (PAGE_SIZE - 1)) != 0);

        obj->dev = dev;
        obj->filp = shmem_file_setup("drm mm object", size, VM_NORESERVE);
        if (IS_ERR(obj->filp))
                return -ENOMEM;

        kref_init(&obj->refcount);
        atomic_set(&obj->handle_count, 0);
        obj->size = size;

        return 0;
}
EXPORT_SYMBOL(drm_gem_object_init);

/**
 * Initialize an already allocated GEM object of the specified size with
 * no GEM provided backing store. Instead the caller is responsible for
 * backing the object and handling it.
 */
int drm_gem_private_object_init(struct drm_device *dev,
                        struct drm_gem_object *obj, size_t size)
{
        BUG_ON((size & (PAGE_SIZE - 1)) != 0);

        obj->dev = dev;
        obj->filp = NULL;

        kref_init(&obj->refcount);
        atomic_set(&obj->handle_count, 0);
        obj->size = size;

        return 0;
}
EXPORT_SYMBOL(drm_gem_private_object_init);

/**
 * Allocate a GEM object of the specified size with shmfs backing store
 */
struct drm_gem_object *
drm_gem_object_alloc(struct drm_device *dev, size_t size)
{
        struct drm_gem_object *obj;

        obj = kzalloc(sizeof(*obj), GFP_KERNEL);
        if (!obj)
                goto free;

        if (drm_gem_object_init(dev, obj, size) != 0)
                goto free;

        if (dev->driver->gem_init_object != NULL &&
            dev->driver->gem_init_object(obj) != 0) {
                goto fput;
        }
        return obj;
fput:
        /* Object_init mangles the global counters - readjust them. */
        fput(obj->filp);
free:
        kfree(obj);
        return NULL;
}
EXPORT_SYMBOL(drm_gem_object_alloc);

/**
 * Removes the mapping from handle to filp for this object.
 */
int
drm_gem_handle_delete(struct drm_file *filp, u32 handle)
{
        struct drm_device *dev;
        struct drm_gem_object *obj;

        /* This is gross. The idr system doesn't let us try a delete and
         * return an error code.  It just spews if you fail at deleting.
         * So, we have to grab a lock around finding the object and then
         * doing the delete on it and dropping the refcount, or the user
         * could race us to double-decrement the refcount and cause a
         * use-after-free later.  Given the frequency of our handle lookups,
         * we may want to use ida for number allocation and a hash table
         * for the pointers, anyway.
         */
        spin_lock(&filp->table_lock);

        /* Check if we currently have a reference on the object */
        obj = idr_find(&filp->object_idr, handle);
        if (obj == NULL) {
                spin_unlock(&filp->table_lock);
                return -EINVAL;
        }
        dev = obj->dev;

        /* Release reference and decrement refcount. */
        idr_remove(&filp->object_idr, handle);
        spin_unlock(&filp->table_lock);

        if (dev->driver->gem_close_object)
                dev->driver->gem_close_object(obj, filp);
        drm_gem_object_handle_unreference_unlocked(obj);

        return 0;
}
EXPORT_SYMBOL(drm_gem_handle_delete);

/**
 * Create a handle for this object. This adds a handle reference
 * to the object, which includes a regular reference count. Callers
 * will likely want to dereference the object afterwards.
 */
int
drm_gem_handle_create(struct drm_file *file_priv,
                       struct drm_gem_object *obj,
                       u32 *handlep)
{
        struct drm_device *dev = obj->dev;
        int ret;

        /*
         * Get the user-visible handle using idr.
         */
again:
        /* ensure there is space available to allocate a handle */
        if (idr_pre_get(&file_priv->object_idr, GFP_KERNEL) == 0)
                return -ENOMEM;

        /* do the allocation under our spinlock */
        spin_lock(&file_priv->table_lock);
        ret = idr_get_new_above(&file_priv->object_idr, obj, 1, (int *)handlep);
        spin_unlock(&file_priv->table_lock);
        if (ret == -EAGAIN)
                goto again;

        if (ret != 0)
                return ret;

        drm_gem_object_handle_reference(obj);

        if (dev->driver->gem_open_object) {
                ret = dev->driver->gem_open_object(obj, file_priv);
                if (ret) {
                        drm_gem_handle_delete(file_priv, *handlep);
                        return ret;
                }
        }

        return 0;
}
EXPORT_SYMBOL(drm_gem_handle_create);


/**
 * drm_gem_free_mmap_offset - release a fake mmap offset for an object
 * @obj: obj in question
 *
 * This routine frees fake offsets allocated by drm_gem_create_mmap_offset().
 */
void
drm_gem_free_mmap_offset(struct drm_gem_object *obj)
{
        struct drm_device *dev = obj->dev;
        struct drm_gem_mm *mm = dev->mm_private;
        struct drm_map_list *list = &obj->map_list;

        drm_ht_remove_item(&mm->offset_hash, &list->hash);
        drm_mm_put_block(list->file_offset_node);
        kfree(list->map);
        list->map = NULL;
}
EXPORT_SYMBOL(drm_gem_free_mmap_offset);

/**
 * drm_gem_create_mmap_offset - create a fake mmap offset for an object
 * @obj: obj in question
 *
 * GEM memory mapping works by handing back to userspace a fake mmap offset
 * it can use in a subsequent mmap(2) call.  The DRM core code then looks
 * up the object based on the offset and sets up the various memory mapping
 * structures.
 *
 * This routine allocates and attaches a fake offset for @obj.
 */
int
drm_gem_create_mmap_offset(struct drm_gem_object *obj)
{
        struct drm_device *dev = obj->dev;
        struct drm_gem_mm *mm = dev->mm_private;
        struct drm_map_list *list;
        struct drm_local_map *map;
        int ret = 0;

        /* Set the object up for mmap'ing */
        list = &obj->map_list;
        list->map = kzalloc(sizeof(struct drm_map_list), GFP_KERNEL);
        if (!list->map)
                return -ENOMEM;

        map = list->map;
        map->type = _DRM_GEM;
        map->size = obj->size;
        map->handle = obj;

        /* Get a DRM GEM mmap offset allocated... */
        list->file_offset_node = drm_mm_search_free(&mm->offset_manager,
                        obj->size / PAGE_SIZE, 0, 0);

        if (!list->file_offset_node) {
                DRM_ERROR("failed to allocate offset for bo %d\n", obj->name);
                ret = -ENOSPC;
                goto out_free_list;
        }

        list->file_offset_node = drm_mm_get_block(list->file_offset_node,
                        obj->size / PAGE_SIZE, 0);
        if (!list->file_offset_node) {
                ret = -ENOMEM;
                goto out_free_list;
        }

        list->hash.key = list->file_offset_node->start;
        ret = drm_ht_insert_item(&mm->offset_hash, &list->hash);
        if (ret) {
                DRM_ERROR("failed to add to map hash\n");
                goto out_free_mm;
        }

        return 0;

out_free_mm:
        drm_mm_put_block(list->file_offset_node);
out_free_list:
        kfree(list->map);
        list->map = NULL;

        return ret;
}
EXPORT_SYMBOL(drm_gem_create_mmap_offset);

/** Returns a reference to the object named by the handle. */
struct drm_gem_object *
drm_gem_object_lookup(struct drm_device *dev, struct drm_file *filp,
                      u32 handle)
{
        struct drm_gem_object *obj;

        spin_lock(&filp->table_lock);

        /* Check if we currently have a reference on the object */
        obj = idr_find(&filp->object_idr, handle);
        if (obj == NULL) {
                spin_unlock(&filp->table_lock);
                return NULL;
        }

        drm_gem_object_reference(obj);

        spin_unlock(&filp->table_lock);

        return obj;
}
EXPORT_SYMBOL(drm_gem_object_lookup);

/**
 * Releases the handle to an mm object.
 */
int
drm_gem_close_ioctl(struct drm_device *dev, void *data,
                    struct drm_file *file_priv)
{
        struct drm_gem_close *args = data;
        int ret;

        if (!(dev->driver->driver_features & DRIVER_GEM))
                return -ENODEV;

        ret = drm_gem_handle_delete(file_priv, args->handle);

        return ret;
}

/**
 * Create a global name for an object, returning the name.
 *
 * Note that the name does not hold a reference; when the object
 * is freed, the name goes away.
 */
int
drm_gem_flink_ioctl(struct drm_device *dev, void *data,
                    struct drm_file *file_priv)
{
        struct drm_gem_flink *args = data;
        struct drm_gem_object *obj;
        int ret;

        if (!(dev->driver->driver_features & DRIVER_GEM))
                return -ENODEV;

        obj = drm_gem_object_lookup(dev, file_priv, args->handle);
        if (obj == NULL)
                return -ENOENT;

again:
        if (idr_pre_get(&dev->object_name_idr, GFP_KERNEL) == 0) {
                ret = -ENOMEM;
                goto err;
        }

        spin_lock(&dev->object_name_lock);
        if (!obj->name) {
                ret = idr_get_new_above(&dev->object_name_idr, obj, 1,
                                        &obj->name);
                args->name = (uint64_t) obj->name;
                spin_unlock(&dev->object_name_lock);

                if (ret == -EAGAIN)
                        goto again;

                if (ret != 0)
                        goto err;

                /* Allocate a reference for the name table.  */
                drm_gem_object_reference(obj);
        } else {
                args->name = (uint64_t) obj->name;
                spin_unlock(&dev->object_name_lock);
                ret = 0;
        }

err:
        drm_gem_object_unreference_unlocked(obj);
        return ret;
}

/**
 * Open an object using the global name, returning a handle and the size.
 *
 * This handle (of course) holds a reference to the object, so the object
 * will not go away until the handle is deleted.
 */
int
drm_gem_open_ioctl(struct drm_device *dev, void *data,
                   struct drm_file *file_priv)
{
        struct drm_gem_open *args = data;
        struct drm_gem_object *obj;
        int ret;
        u32 handle;

        if (!(dev->driver->driver_features & DRIVER_GEM))
                return -ENODEV;

        spin_lock(&dev->object_name_lock);
        obj = idr_find(&dev->object_name_idr, (int) args->name);
        if (obj)
                drm_gem_object_reference(obj);
        spin_unlock(&dev->object_name_lock);
        if (!obj)
                return -ENOENT;

        ret = drm_gem_handle_create(file_priv, obj, &handle);
        drm_gem_object_unreference_unlocked(obj);
        if (ret)
                return ret;

        args->handle = handle;
        args->size = obj->size;

        return 0;
}

/**
 * Called at device open time, sets up the structure for handling refcounting
 * of mm objects.
 */
void
drm_gem_open(struct drm_device *dev, struct drm_file *file_private)
{
        idr_init(&file_private->object_idr);
        spin_lock_init(&file_private->table_lock);
}

/**
 * Called at device close to release the file's
 * handle references on objects.
 */
static int
drm_gem_object_release_handle(int id, void *ptr, void *data)
{
        struct drm_file *file_priv = data;
        struct drm_gem_object *obj = ptr;
        struct drm_device *dev = obj->dev;

        if (dev->driver->gem_close_object)
                dev->driver->gem_close_object(obj, file_priv);

        drm_gem_object_handle_unreference_unlocked(obj);

        return 0;
}

/**
 * Called at close time when the filp is going away.
 *
 * Releases any remaining references on objects by this filp.
 */
void
drm_gem_release(struct drm_device *dev, struct drm_file *file_private)
{
        idr_for_each(&file_private->object_idr,
                     &drm_gem_object_release_handle, file_private);

        idr_remove_all(&file_private->object_idr);
        idr_destroy(&file_private->object_idr);
}

void
drm_gem_object_release(struct drm_gem_object *obj)
{
        if (obj->filp)
            fput(obj->filp);
}
EXPORT_SYMBOL(drm_gem_object_release);

/**
 * Called after the last reference to the object has been lost.
 * Must be called holding struct_ mutex
 *
 * Frees the object
 */
void
drm_gem_object_free(struct kref *kref)
{
        struct drm_gem_object *obj = (struct drm_gem_object *) kref;
        struct drm_device *dev = obj->dev;

        BUG_ON(!mutex_is_locked(&dev->struct_mutex));

        if (dev->driver->gem_free_object != NULL)
                dev->driver->gem_free_object(obj);
}
EXPORT_SYMBOL(drm_gem_object_free);

static void drm_gem_object_ref_bug(struct kref *list_kref)
{
        BUG();
}

/**
 * Called after the last handle to the object has been closed
 *
 * Removes any name for the object. Note that this must be
 * called before drm_gem_object_free or we'll be touching
 * freed memory
 */
void drm_gem_object_handle_free(struct drm_gem_object *obj)
{
        struct drm_device *dev = obj->dev;

        /* Remove any name for this object */
        spin_lock(&dev->object_name_lock);
        if (obj->name) {
                idr_remove(&dev->object_name_idr, obj->name);
                obj->name = 0;
                spin_unlock(&dev->object_name_lock);
                /*
                 * The object name held a reference to this object, drop
                 * that now.
                *
                * This cannot be the last reference, since the handle holds one too.
                 */
                kref_put(&obj->refcount, drm_gem_object_ref_bug);
        } else
                spin_unlock(&dev->object_name_lock);

}
EXPORT_SYMBOL(drm_gem_object_handle_free);

void drm_gem_vm_open(struct vm_area_struct *vma)
{
        struct drm_gem_object *obj = vma->vm_private_data;

        drm_gem_object_reference(obj);

        mutex_lock(&obj->dev->struct_mutex);
        drm_vm_open_locked(vma);
        mutex_unlock(&obj->dev->struct_mutex);
}
EXPORT_SYMBOL(drm_gem_vm_open);

void drm_gem_vm_close(struct vm_area_struct *vma)
{
        struct drm_gem_object *obj = vma->vm_private_data;
        struct drm_device *dev = obj->dev;

        mutex_lock(&dev->struct_mutex);
        drm_vm_close_locked(vma);
        drm_gem_object_unreference(obj);
        mutex_unlock(&dev->struct_mutex);
}
EXPORT_SYMBOL(drm_gem_vm_close);


/**
 * drm_gem_mmap - memory map routine for GEM objects
 * @filp: DRM file pointer
 * @vma: VMA for the area to be mapped
 *
 * If a driver supports GEM object mapping, mmap calls on the DRM file
 * descriptor will end up here.
 *
 * If we find the object based on the offset passed in (vma->vm_pgoff will
 * contain the fake offset we created when the GTT map ioctl was called on
 * the object), we set up the driver fault handler so that any accesses
 * to the object can be trapped, to perform migration, GTT binding, surface
 * register allocation, or performance monitoring.
 */
int drm_gem_mmap(struct file *filp, struct vm_area_struct *vma)
{
        struct drm_file *priv = filp->private_data;
        struct drm_device *dev = priv->minor->dev;
        struct drm_gem_mm *mm = dev->mm_private;
        struct drm_local_map *map = NULL;
        struct drm_gem_object *obj;
        struct drm_hash_item *hash;
        int ret = 0;

        mutex_lock(&dev->struct_mutex);

        if (drm_ht_find_item(&mm->offset_hash, vma->vm_pgoff, &hash)) {
                mutex_unlock(&dev->struct_mutex);
                return drm_mmap(filp, vma);
        }

        map = drm_hash_entry(hash, struct drm_map_list, hash)->map;
        if (!map ||
            ((map->flags & _DRM_RESTRICTED) && !capable(CAP_SYS_ADMIN))) {
                ret =  -EPERM;
                goto out_unlock;
        }

        /* Check for valid size. */
        if (map->size < vma->vm_end - vma->vm_start) {
                ret = -EINVAL;
                goto out_unlock;
        }

        obj = map->handle;
        if (!obj->dev->driver->gem_vm_ops) {
                ret = -EINVAL;
                goto out_unlock;
        }

        vma->vm_flags |= VM_RESERVED | VM_IO | VM_PFNMAP | VM_DONTEXPAND;
        vma->vm_ops = obj->dev->driver->gem_vm_ops;
        vma->vm_private_data = map->handle;
        vma->vm_page_prot =  pgprot_writecombine(vm_get_page_prot(vma->vm_flags));

        /* Take a ref for this mapping of the object, so that the fault
         * handler can dereference the mmap offset's pointer to the object.
         * This reference is cleaned up by the corresponding vm_close
         * (which should happen whether the vma was created by this call, or
         * by a vm_open due to mremap or partial unmap or whatever).
         */
        drm_gem_object_reference(obj);

        vma->vm_file = filp;    /* Needed for drm_vm_open() */
        drm_vm_open_locked(vma);

out_unlock:
        mutex_unlock(&dev->struct_mutex);

        return ret;
}
EXPORT_SYMBOL(drm_gem_mmap);