drivers/xen/gntdev.c - kernel/msm-4.9 - Gitiles

 /******************************************************************************
  * gntdev.c
  *
  * Device for accessing (in user-space) pages that have been granted by other
  * domains.
  *
  * Copyright (c) 2006-2007, D G Murray.
  *           (c) 2009 Gerd Hoffmann <kraxel@redhat.com>
  *
  * 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.
  *
  * You should have received a copy of the GNU General Public License
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  */

 #undef DEBUG

 #include <linux/module.h>
 #include <linux/kernel.h>
 #include <linux/init.h>
 #include <linux/miscdevice.h>
 #include <linux/fs.h>
 #include <linux/mm.h>
 #include <linux/mman.h>
 #include <linux/mmu_notifier.h>
 #include <linux/types.h>
 #include <linux/uaccess.h>
 #include <linux/sched.h>
 #include <linux/spinlock.h>
 #include <linux/slab.h>
 #include <linux/highmem.h>

 #include <xen/xen.h>
 #include <xen/grant_table.h>
 #include <xen/balloon.h>
 #include <xen/gntdev.h>
 #include <xen/events.h>
 #include <asm/xen/hypervisor.h>
 #include <asm/xen/hypercall.h>
 #include <asm/xen/page.h>

 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Derek G. Murray <Derek.Murray@cl.cam.ac.uk>, "
 	      "Gerd Hoffmann <kraxel@redhat.com>");
 MODULE_DESCRIPTION("User-space granted page access driver");

 static int limit = 1024*1024;
 module_param(limit, int, 0644);
 MODULE_PARM_DESC(limit, "Maximum number of grants that may be mapped by "
 		"the gntdev device");

 static atomic_t pages_mapped = ATOMIC_INIT(0);

 static int use_ptemod;
 #define populate_freeable_maps use_ptemod

 struct gntdev_priv {
 	/* maps with visible offsets in the file descriptor */
 	struct list_head maps;
 	/* maps that are not visible; will be freed on munmap.
 	 * Only populated if populate_freeable_maps == 1 */
 	struct list_head freeable_maps;
 	/* lock protects maps and freeable_maps */
 	spinlock_t lock;
 	struct mm_struct *mm;
 	struct mmu_notifier mn;
 };

 struct unmap_notify {
 	int flags;
 	/* Address relative to the start of the grant_map */
 	int addr;
 	int event;
 };

 struct grant_map {
 	struct list_head next;
 	struct vm_area_struct *vma;
 	int index;
 	int count;
 	int flags;
 	atomic_t users;
 	struct unmap_notify notify;
 	struct ioctl_gntdev_grant_ref *grants;
 	struct gnttab_map_grant_ref   *map_ops;
 	struct gnttab_unmap_grant_ref *unmap_ops;
 	struct gnttab_map_grant_ref   *kmap_ops;
 	struct page **pages;
 };

 static int unmap_grant_pages(struct grant_map *map, int offset, int pages);

 /* ------------------------------------------------------------------ */

 static void gntdev_print_maps(struct gntdev_priv *priv,
 			      char *text, int text_index)
 {
 #ifdef DEBUG
 	struct grant_map *map;

 	pr_debug("%s: maps list (priv %p)\n", __func__, priv);
 	list_for_each_entry(map, &priv->maps, next)
 		pr_debug("  index %2d, count %2d %s\n",
 		       map->index, map->count,
 		       map->index == text_index && text ? text : "");
 #endif
 }

 static void gntdev_free_map(struct grant_map *map)
 {
 	if (map == NULL)
 		return;

 	if (map->pages)
 		free_xenballooned_pages(map->count, map->pages);
 	kfree(map->pages);
 	kfree(map->grants);
 	kfree(map->map_ops);
 	kfree(map->unmap_ops);
 	kfree(map->kmap_ops);
 	kfree(map);
 }

 static struct grant_map *gntdev_alloc_map(struct gntdev_priv *priv, int count)
 {
 	struct grant_map *add;
 	int i;

 	add = kzalloc(sizeof(struct grant_map), GFP_KERNEL);
 	if (NULL == add)
 		return NULL;

 	add->grants    = kcalloc(count, sizeof(add->grants[0]), GFP_KERNEL);
 	add->map_ops   = kcalloc(count, sizeof(add->map_ops[0]), GFP_KERNEL);
 	add->unmap_ops = kcalloc(count, sizeof(add->unmap_ops[0]), GFP_KERNEL);
 	add->kmap_ops  = kcalloc(count, sizeof(add->kmap_ops[0]), GFP_KERNEL);
 	add->pages     = kcalloc(count, sizeof(add->pages[0]), GFP_KERNEL);
 	if (NULL == add->grants    ||
 	    NULL == add->map_ops   ||
 	    NULL == add->unmap_ops ||
 	    NULL == add->kmap_ops  ||
 	    NULL == add->pages)
 		goto err;

 	if (alloc_xenballooned_pages(count, add->pages, false /* lowmem */))
 		goto err;

 	for (i = 0; i < count; i++) {
 		add->map_ops[i].handle = -1;
 		add->unmap_ops[i].handle = -1;
 		add->kmap_ops[i].handle = -1;
 	}

 	add->index = 0;
 	add->count = count;
 	atomic_set(&add->users, 1);

 	return add;

 err:
 	gntdev_free_map(add);
 	return NULL;
 }

 static void gntdev_add_map(struct gntdev_priv *priv, struct grant_map *add)
 {
 	struct grant_map *map;

 	list_for_each_entry(map, &priv->maps, next) {
 		if (add->index + add->count < map->index) {
 			list_add_tail(&add->next, &map->next);
 			goto done;
 		}
 		add->index = map->index + map->count;
 	}
 	list_add_tail(&add->next, &priv->maps);

 done:
 	gntdev_print_maps(priv, "[new]", add->index);
 }

 static struct grant_map *gntdev_find_map_index(struct gntdev_priv *priv,
 		int index, int count)
 {
 	struct grant_map *map;

 	list_for_each_entry(map, &priv->maps, next) {
 		if (map->index != index)
 			continue;
 		if (count && map->count != count)
 			continue;
 		return map;
 	}
 	return NULL;
 }

 static void gntdev_put_map(struct gntdev_priv *priv, struct grant_map *map)
 {
 	if (!map)
 		return;

 	if (!atomic_dec_and_test(&map->users))
 		return;

 	atomic_sub(map->count, &pages_mapped);

 	if (map->notify.flags & UNMAP_NOTIFY_SEND_EVENT) {
 		notify_remote_via_evtchn(map->notify.event);
 		evtchn_put(map->notify.event);
 	}

 	if (populate_freeable_maps && priv) {
 		spin_lock(&priv->lock);
 		list_del(&map->next);
 		spin_unlock(&priv->lock);
 	}

 	if (map->pages && !use_ptemod)
 		unmap_grant_pages(map, 0, map->count);
 	gntdev_free_map(map);
 }

 /* ------------------------------------------------------------------ */

 static int find_grant_ptes(pte_t *pte, pgtable_t token,
 		unsigned long addr, void *data)
 {
 	struct grant_map *map = data;
 	unsigned int pgnr = (addr - map->vma->vm_start) >> PAGE_SHIFT;
 	int flags = map->flags | GNTMAP_application_map | GNTMAP_contains_pte;
 	u64 pte_maddr;

 	BUG_ON(pgnr >= map->count);
 	pte_maddr = arbitrary_virt_to_machine(pte).maddr;

 	gnttab_set_map_op(&map->map_ops[pgnr], pte_maddr, flags,
 			  map->grants[pgnr].ref,
 			  map->grants[pgnr].domid);
 	gnttab_set_unmap_op(&map->unmap_ops[pgnr], pte_maddr, flags,
 			    -1 /* handle */);
 	return 0;
 }

 static int map_grant_pages(struct grant_map *map)
 {
 	int i, err = 0;

 	if (!use_ptemod) {
 		/* Note: it could already be mapped */
 		if (map->map_ops[0].handle != -1)
 			return 0;
 		for (i = 0; i < map->count; i++) {
 			unsigned long addr = (unsigned long)
 				pfn_to_kaddr(page_to_pfn(map->pages[i]));
 			gnttab_set_map_op(&map->map_ops[i], addr, map->flags,
 				map->grants[i].ref,
 				map->grants[i].domid);
 			gnttab_set_unmap_op(&map->unmap_ops[i], addr,
 				map->flags, -1 /* handle */);
 		}
 	} else {
 		/*
 		 * Setup the map_ops corresponding to the pte entries pointing
 		 * to the kernel linear addresses of the struct pages.
 		 * These ptes are completely different from the user ptes dealt
 		 * with find_grant_ptes.
 		 */
 		for (i = 0; i < map->count; i++) {
 			unsigned level;
 			unsigned long address = (unsigned long)
 				pfn_to_kaddr(page_to_pfn(map->pages[i]));
 			pte_t *ptep;
 			u64 pte_maddr = 0;
 			BUG_ON(PageHighMem(map->pages[i]));

 			ptep = lookup_address(address, &level);
 			pte_maddr = arbitrary_virt_to_machine(ptep).maddr;
 			gnttab_set_map_op(&map->kmap_ops[i], pte_maddr,
 				map->flags |
 				GNTMAP_host_map |
 				GNTMAP_contains_pte,
 				map->grants[i].ref,
 				map->grants[i].domid);
 		}
 	}

 	pr_debug("map %d+%d\n", map->index, map->count);
 	err = gnttab_map_refs(map->map_ops, use_ptemod ? map->kmap_ops : NULL,
 			map->pages, map->count);
 	if (err)
 		return err;

 	for (i = 0; i < map->count; i++) {
 		if (map->map_ops[i].status)
 			err = -EINVAL;
 		else {
 			BUG_ON(map->map_ops[i].handle == -1);
 			map->unmap_ops[i].handle = map->map_ops[i].handle;
 			pr_debug("map handle=%d\n", map->map_ops[i].handle);
 		}
 	}
 	return err;
 }

 static int __unmap_grant_pages(struct grant_map *map, int offset, int pages)
 {
 	int i, err = 0;

 	if (map->notify.flags & UNMAP_NOTIFY_CLEAR_BYTE) {
 		int pgno = (map->notify.addr >> PAGE_SHIFT);
 		if (pgno >= offset && pgno < offset + pages) {
 			/* No need for kmap, pages are in lowmem */
 			uint8_t *tmp = pfn_to_kaddr(page_to_pfn(map->pages[pgno]));
 			tmp[map->notify.addr & (PAGE_SIZE-1)] = 0;
 			map->notify.flags &= ~UNMAP_NOTIFY_CLEAR_BYTE;
 		}
 	}

 	err = gnttab_unmap_refs(map->unmap_ops + offset,
 			use_ptemod ? map->kmap_ops + offset : NULL, map->pages + offset,
 			pages);
 	if (err)
 		return err;

 	for (i = 0; i < pages; i++) {
 		if (map->unmap_ops[offset+i].status)
 			err = -EINVAL;
 		pr_debug("unmap handle=%d st=%d\n",
 			map->unmap_ops[offset+i].handle,
 			map->unmap_ops[offset+i].status);
 		map->unmap_ops[offset+i].handle = -1;
 	}
 	return err;
 }

 static int unmap_grant_pages(struct grant_map *map, int offset, int pages)
 {
 	int range, err = 0;

 	pr_debug("unmap %d+%d [%d+%d]\n", map->index, map->count, offset, pages);

 	/* It is possible the requested range will have a "hole" where we
 	 * already unmapped some of the grants. Only unmap valid ranges.
 	 */
 	while (pages && !err) {
 		while (pages && map->unmap_ops[offset].handle == -1) {
 			offset++;
 			pages--;
 		}
 		range = 0;
 		while (range < pages) {
 			if (map->unmap_ops[offset+range].handle == -1) {
 				range--;
 				break;
 			}
 			range++;
 		}
 		err = __unmap_grant_pages(map, offset, range);
 		offset += range;
 		pages -= range;
 	}

 	return err;
 }

 /* ------------------------------------------------------------------ */

 static void gntdev_vma_open(struct vm_area_struct *vma)
 {
 	struct grant_map *map = vma->vm_private_data;

 	pr_debug("gntdev_vma_open %p\n", vma);
 	atomic_inc(&map->users);
 }

 static void gntdev_vma_close(struct vm_area_struct *vma)
 {
 	struct grant_map *map = vma->vm_private_data;
 	struct file *file = vma->vm_file;
 	struct gntdev_priv *priv = file->private_data;

 	pr_debug("gntdev_vma_close %p\n", vma);
 	if (use_ptemod) {
 		/* It is possible that an mmu notifier could be running
 		 * concurrently, so take priv->lock to ensure that the vma won't
 		 * vanishing during the unmap_grant_pages call, since we will
 		 * spin here until that completes. Such a concurrent call will
 		 * not do any unmapping, since that has been done prior to
 		 * closing the vma, but it may still iterate the unmap_ops list.
 		 */
 		spin_lock(&priv->lock);
 		map->vma = NULL;
 		spin_unlock(&priv->lock);
 	}
 	vma->vm_private_data = NULL;
 	gntdev_put_map(priv, map);
 }

 static struct vm_operations_struct gntdev_vmops = {
 	.open = gntdev_vma_open,
 	.close = gntdev_vma_close,
 };

 /* ------------------------------------------------------------------ */

 static void unmap_if_in_range(struct grant_map *map,
 			      unsigned long start, unsigned long end)
 {
 	unsigned long mstart, mend;
 	int err;

 	if (!map->vma)
 		return;
 	if (map->vma->vm_start >= end)
 		return;
 	if (map->vma->vm_end <= start)
 		return;
 	mstart = max(start, map->vma->vm_start);
 	mend   = min(end,   map->vma->vm_end);
 	pr_debug("map %d+%d (%lx %lx), range %lx %lx, mrange %lx %lx\n",
 			map->index, map->count,
 			map->vma->vm_start, map->vma->vm_end,
 			start, end, mstart, mend);
 	err = unmap_grant_pages(map,
 				(mstart - map->vma->vm_start) >> PAGE_SHIFT,
 				(mend - mstart) >> PAGE_SHIFT);
 	WARN_ON(err);
 }

 static void mn_invl_range_start(struct mmu_notifier *mn,
 				struct mm_struct *mm,
 				unsigned long start, unsigned long end)
 {
 	struct gntdev_priv *priv = container_of(mn, struct gntdev_priv, mn);
 	struct grant_map *map;

 	spin_lock(&priv->lock);
 	list_for_each_entry(map, &priv->maps, next) {
 		unmap_if_in_range(map, start, end);
 	}
 	list_for_each_entry(map, &priv->freeable_maps, next) {
 		unmap_if_in_range(map, start, end);
 	}
 	spin_unlock(&priv->lock);
 }

 static void mn_invl_page(struct mmu_notifier *mn,
 			 struct mm_struct *mm,
 			 unsigned long address)
 {
 	mn_invl_range_start(mn, mm, address, address + PAGE_SIZE);
 }

 static void mn_release(struct mmu_notifier *mn,
 		       struct mm_struct *mm)
 {
 	struct gntdev_priv *priv = container_of(mn, struct gntdev_priv, mn);
 	struct grant_map *map;
 	int err;

 	spin_lock(&priv->lock);
 	list_for_each_entry(map, &priv->maps, next) {
 		if (!map->vma)
 			continue;
 		pr_debug("map %d+%d (%lx %lx)\n",
 				map->index, map->count,
 				map->vma->vm_start, map->vma->vm_end);
 		err = unmap_grant_pages(map, /* offset */ 0, map->count);
 		WARN_ON(err);
 	}
 	list_for_each_entry(map, &priv->freeable_maps, next) {
 		if (!map->vma)
 			continue;
 		pr_debug("map %d+%d (%lx %lx)\n",
 				map->index, map->count,
 				map->vma->vm_start, map->vma->vm_end);
 		err = unmap_grant_pages(map, /* offset */ 0, map->count);
 		WARN_ON(err);
 	}
 	spin_unlock(&priv->lock);
 }

 static struct mmu_notifier_ops gntdev_mmu_ops = {
 	.release                = mn_release,
 	.invalidate_page        = mn_invl_page,
 	.invalidate_range_start = mn_invl_range_start,
 };

 /* ------------------------------------------------------------------ */

 static int gntdev_open(struct inode *inode, struct file *flip)
 {
 	struct gntdev_priv *priv;
 	int ret = 0;

 	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
 	if (!priv)
 		return -ENOMEM;

 	INIT_LIST_HEAD(&priv->maps);
 	INIT_LIST_HEAD(&priv->freeable_maps);
 	spin_lock_init(&priv->lock);

 	if (use_ptemod) {
 		priv->mm = get_task_mm(current);
 		if (!priv->mm) {
 			kfree(priv);
 			return -ENOMEM;
 		}
 		priv->mn.ops = &gntdev_mmu_ops;
 		ret = mmu_notifier_register(&priv->mn, priv->mm);
 		mmput(priv->mm);
 	}

 	if (ret) {
 		kfree(priv);
 		return ret;
 	}

 	flip->private_data = priv;
 	pr_debug("priv %p\n", priv);

 	return 0;
 }

 static int gntdev_release(struct inode *inode, struct file *flip)
 {
 	struct gntdev_priv *priv = flip->private_data;
 	struct grant_map *map;

 	pr_debug("priv %p\n", priv);

 	while (!list_empty(&priv->maps)) {
 		map = list_entry(priv->maps.next, struct grant_map, next);
 		list_del(&map->next);
 		gntdev_put_map(NULL /* already removed */, map);
 	}
 	WARN_ON(!list_empty(&priv->freeable_maps));

 	if (use_ptemod)
 		mmu_notifier_unregister(&priv->mn, priv->mm);
 	kfree(priv);
 	return 0;
 }

 static long gntdev_ioctl_map_grant_ref(struct gntdev_priv *priv,
 				       struct ioctl_gntdev_map_grant_ref __user *u)
 {
 	struct ioctl_gntdev_map_grant_ref op;
 	struct grant_map *map;
 	int err;

 	if (copy_from_user(&op, u, sizeof(op)) != 0)
 		return -EFAULT;
 	pr_debug("priv %p, add %d\n", priv, op.count);
 	if (unlikely(op.count <= 0))
 		return -EINVAL;

 	err = -ENOMEM;
 	map = gntdev_alloc_map(priv, op.count);
 	if (!map)
 		return err;

 	if (unlikely(atomic_add_return(op.count, &pages_mapped) > limit)) {
 		pr_debug("can't map: over limit\n");
 		gntdev_put_map(NULL, map);
 		return err;
 	}

 	if (copy_from_user(map->grants, &u->refs,
 			   sizeof(map->grants[0]) * op.count) != 0) {
 		gntdev_put_map(NULL, map);
 		return -EFAULT;
 	}

 	spin_lock(&priv->lock);
 	gntdev_add_map(priv, map);
 	op.index = map->index << PAGE_SHIFT;
 	spin_unlock(&priv->lock);

 	if (copy_to_user(u, &op, sizeof(op)) != 0)
 		return -EFAULT;

 	return 0;
 }

 static long gntdev_ioctl_unmap_grant_ref(struct gntdev_priv *priv,
 					 struct ioctl_gntdev_unmap_grant_ref __user *u)
 {
 	struct ioctl_gntdev_unmap_grant_ref op;
 	struct grant_map *map;
 	int err = -ENOENT;

 	if (copy_from_user(&op, u, sizeof(op)) != 0)
 		return -EFAULT;
 	pr_debug("priv %p, del %d+%d\n", priv, (int)op.index, (int)op.count);

 	spin_lock(&priv->lock);
 	map = gntdev_find_map_index(priv, op.index >> PAGE_SHIFT, op.count);
 	if (map) {
 		list_del(&map->next);
 		if (populate_freeable_maps)
 			list_add_tail(&map->next, &priv->freeable_maps);
 		err = 0;
 	}
 	spin_unlock(&priv->lock);
 	if (map)
 		gntdev_put_map(priv, map);
 	return err;
 }

 static long gntdev_ioctl_get_offset_for_vaddr(struct gntdev_priv *priv,
 					      struct ioctl_gntdev_get_offset_for_vaddr __user *u)
 {
 	struct ioctl_gntdev_get_offset_for_vaddr op;
 	struct vm_area_struct *vma;
 	struct grant_map *map;
 	int rv = -EINVAL;

 	if (copy_from_user(&op, u, sizeof(op)) != 0)
 		return -EFAULT;
 	pr_debug("priv %p, offset for vaddr %lx\n", priv, (unsigned long)op.vaddr);

 	down_read(&current->mm->mmap_sem);
 	vma = find_vma(current->mm, op.vaddr);
 	if (!vma || vma->vm_ops != &gntdev_vmops)
 		goto out_unlock;

 	map = vma->vm_private_data;
 	if (!map)
 		goto out_unlock;

 	op.offset = map->index << PAGE_SHIFT;
 	op.count = map->count;
 	rv = 0;

  out_unlock:
 	up_read(&current->mm->mmap_sem);

 	if (rv == 0 && copy_to_user(u, &op, sizeof(op)) != 0)
 		return -EFAULT;
 	return rv;
 }

 static long gntdev_ioctl_notify(struct gntdev_priv *priv, void __user *u)
 {
 	struct ioctl_gntdev_unmap_notify op;
 	struct grant_map *map;
 	int rc;
 	int out_flags;
 	unsigned int out_event;

 	if (copy_from_user(&op, u, sizeof(op)))
 		return -EFAULT;

 	if (op.action & ~(UNMAP_NOTIFY_CLEAR_BYTE|UNMAP_NOTIFY_SEND_EVENT))
 		return -EINVAL;

 	/* We need to grab a reference to the event channel we are going to use
 	 * to send the notify before releasing the reference we may already have
 	 * (if someone has called this ioctl twice). This is required so that
 	 * it is possible to change the clear_byte part of the notification
 	 * without disturbing the event channel part, which may now be the last
 	 * reference to that event channel.
 	 */
 	if (op.action & UNMAP_NOTIFY_SEND_EVENT) {
 		if (evtchn_get(op.event_channel_port))
 			return -EINVAL;
 	}

 	out_flags = op.action;
 	out_event = op.event_channel_port;

 	spin_lock(&priv->lock);

 	list_for_each_entry(map, &priv->maps, next) {
 		uint64_t begin = map->index << PAGE_SHIFT;
 		uint64_t end = (map->index + map->count) << PAGE_SHIFT;
 		if (op.index >= begin && op.index < end)
 			goto found;
 	}
 	rc = -ENOENT;
 	goto unlock_out;

  found:
 	if ((op.action & UNMAP_NOTIFY_CLEAR_BYTE) &&
 			(map->flags & GNTMAP_readonly)) {
 		rc = -EINVAL;
 		goto unlock_out;
 	}

 	out_flags = map->notify.flags;
 	out_event = map->notify.event;

 	map->notify.flags = op.action;
 	map->notify.addr = op.index - (map->index << PAGE_SHIFT);
 	map->notify.event = op.event_channel_port;

 	rc = 0;

  unlock_out:
 	spin_unlock(&priv->lock);

 	/* Drop the reference to the event channel we did not save in the map */
 	if (out_flags & UNMAP_NOTIFY_SEND_EVENT)
 		evtchn_put(out_event);

 	return rc;
 }

 static long gntdev_ioctl(struct file *flip,
 			 unsigned int cmd, unsigned long arg)
 {
 	struct gntdev_priv *priv = flip->private_data;
 	void __user *ptr = (void __user *)arg;

 	switch (cmd) {
 	case IOCTL_GNTDEV_MAP_GRANT_REF:
 		return gntdev_ioctl_map_grant_ref(priv, ptr);

 	case IOCTL_GNTDEV_UNMAP_GRANT_REF:
 		return gntdev_ioctl_unmap_grant_ref(priv, ptr);

 	case IOCTL_GNTDEV_GET_OFFSET_FOR_VADDR:
 		return gntdev_ioctl_get_offset_for_vaddr(priv, ptr);

 	case IOCTL_GNTDEV_SET_UNMAP_NOTIFY:
 		return gntdev_ioctl_notify(priv, ptr);

 	default:
 		pr_debug("priv %p, unknown cmd %x\n", priv, cmd);
 		return -ENOIOCTLCMD;
 	}

 	return 0;
 }

 static int gntdev_mmap(struct file *flip, struct vm_area_struct *vma)
 {
 	struct gntdev_priv *priv = flip->private_data;
 	int index = vma->vm_pgoff;
 	int count = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
 	struct grant_map *map;
 	int i, err = -EINVAL;

 	if ((vma->vm_flags & VM_WRITE) && !(vma->vm_flags & VM_SHARED))
 		return -EINVAL;

 	pr_debug("map %d+%d at %lx (pgoff %lx)\n",
 			index, count, vma->vm_start, vma->vm_pgoff);

 	spin_lock(&priv->lock);
 	map = gntdev_find_map_index(priv, index, count);
 	if (!map)
 		goto unlock_out;
 	if (use_ptemod && map->vma)
 		goto unlock_out;
 	if (use_ptemod && priv->mm != vma->vm_mm) {
 		printk(KERN_WARNING "Huh? Other mm?\n");
 		goto unlock_out;
 	}

 	atomic_inc(&map->users);

 	vma->vm_ops = &gntdev_vmops;

 	vma->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP;

 	if (use_ptemod)
 		vma->vm_flags |= VM_DONTCOPY;

 	vma->vm_private_data = map;

 	if (use_ptemod)
 		map->vma = vma;

 	if (map->flags) {
 		if ((vma->vm_flags & VM_WRITE) &&
 				(map->flags & GNTMAP_readonly))
 			goto out_unlock_put;
 	} else {
 		map->flags = GNTMAP_host_map;
 		if (!(vma->vm_flags & VM_WRITE))
 			map->flags |= GNTMAP_readonly;
 	}

 	spin_unlock(&priv->lock);

 	if (use_ptemod) {
 		err = apply_to_page_range(vma->vm_mm, vma->vm_start,
 					  vma->vm_end - vma->vm_start,
 					  find_grant_ptes, map);
 		if (err) {
 			printk(KERN_WARNING "find_grant_ptes() failure.\n");
 			goto out_put_map;
 		}
 	}

 	err = map_grant_pages(map);
 	if (err)
 		goto out_put_map;

 	if (!use_ptemod) {
 		for (i = 0; i < count; i++) {
 			err = vm_insert_page(vma, vma->vm_start + i*PAGE_SIZE,
 				map->pages[i]);
 			if (err)
 				goto out_put_map;
 		}
 	}

 	return 0;

 unlock_out:
 	spin_unlock(&priv->lock);
 	return err;

 out_unlock_put:
 	spin_unlock(&priv->lock);
 out_put_map:
 	if (use_ptemod)
 		map->vma = NULL;
 	gntdev_put_map(priv, map);
 	return err;
 }

 static const struct file_operations gntdev_fops = {
 	.owner = THIS_MODULE,
 	.open = gntdev_open,
 	.release = gntdev_release,
 	.mmap = gntdev_mmap,
 	.unlocked_ioctl = gntdev_ioctl
 };

 static struct miscdevice gntdev_miscdev = {
 	.minor        = MISC_DYNAMIC_MINOR,
 	.name         = "xen/gntdev",
 	.fops         = &gntdev_fops,
 };

 /* ------------------------------------------------------------------ */

 static int __init gntdev_init(void)
 {
 	int err;

 	if (!xen_domain())
 		return -ENODEV;

 	use_ptemod = xen_pv_domain();

 	err = misc_register(&gntdev_miscdev);
 	if (err != 0) {
 		printk(KERN_ERR "Could not register gntdev device\n");
 		return err;
 	}
 	return 0;
 }

 static void __exit gntdev_exit(void)
 {
 	misc_deregister(&gntdev_miscdev);
 }

 module_init(gntdev_init);
 module_exit(gntdev_exit);

 /* ------------------------------------------------------------------ */
	/******************************************************************************
	* gntdev.c
	*
	* Device for accessing (in user-space) pages that have been granted by other
	* domains.
	*
	* Copyright (c) 2006-2007, D G Murray.
	* (c) 2009 Gerd Hoffmann <kraxel@redhat.com>
	*
	* 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.
	*
	* You should have received a copy of the GNU General Public License
	* along with this program; if not, write to the Free Software
	* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
	*/

	#undef DEBUG

	#include <linux/module.h>
	#include <linux/kernel.h>
	#include <linux/init.h>
	#include <linux/miscdevice.h>
	#include <linux/fs.h>
	#include <linux/mm.h>
	#include <linux/mman.h>
	#include <linux/mmu_notifier.h>
	#include <linux/types.h>
	#include <linux/uaccess.h>
	#include <linux/sched.h>
	#include <linux/spinlock.h>
	#include <linux/slab.h>
	#include <linux/highmem.h>

	#include <xen/xen.h>
	#include <xen/grant_table.h>
	#include <xen/balloon.h>
	#include <xen/gntdev.h>
	#include <xen/events.h>
	#include <asm/xen/hypervisor.h>
	#include <asm/xen/hypercall.h>
	#include <asm/xen/page.h>

	MODULE_LICENSE("GPL");
	MODULE_AUTHOR("Derek G. Murray <Derek.Murray@cl.cam.ac.uk>, "
	"Gerd Hoffmann <kraxel@redhat.com>");
	MODULE_DESCRIPTION("User-space granted page access driver");

	static int limit = 1024*1024;
	module_param(limit, int, 0644);
	MODULE_PARM_DESC(limit, "Maximum number of grants that may be mapped by "
	"the gntdev device");

	static atomic_t pages_mapped = ATOMIC_INIT(0);

	static int use_ptemod;
	#define populate_freeable_maps use_ptemod

	struct gntdev_priv {
	/* maps with visible offsets in the file descriptor */
	struct list_head maps;
	/* maps that are not visible; will be freed on munmap.
	* Only populated if populate_freeable_maps == 1 */
	struct list_head freeable_maps;
	/* lock protects maps and freeable_maps */
	spinlock_t lock;
	struct mm_struct *mm;
	struct mmu_notifier mn;
	};

	struct unmap_notify {
	int flags;
	/* Address relative to the start of the grant_map */
	int addr;
	int event;
	};

	struct grant_map {
	struct list_head next;
	struct vm_area_struct *vma;
	int index;
	int count;
	int flags;
	atomic_t users;
	struct unmap_notify notify;
	struct ioctl_gntdev_grant_ref *grants;
	struct gnttab_map_grant_ref *map_ops;
	struct gnttab_unmap_grant_ref *unmap_ops;
	struct gnttab_map_grant_ref *kmap_ops;
	struct page **pages;
	};

	static int unmap_grant_pages(struct grant_map *map, int offset, int pages);

	/* ------------------------------------------------------------------ */

	static void gntdev_print_maps(struct gntdev_priv *priv,
	char *text, int text_index)
	{
	#ifdef DEBUG
	struct grant_map *map;

	pr_debug("%s: maps list (priv %p)\n", __func__, priv);
	list_for_each_entry(map, &priv->maps, next)
	pr_debug(" index %2d, count %2d %s\n",
	map->index, map->count,
	map->index == text_index && text ? text : "");
	#endif
	}

	static void gntdev_free_map(struct grant_map *map)
	{
	if (map == NULL)
	return;

	if (map->pages)
	free_xenballooned_pages(map->count, map->pages);
	kfree(map->pages);
	kfree(map->grants);
	kfree(map->map_ops);
	kfree(map->unmap_ops);
	kfree(map->kmap_ops);
	kfree(map);
	}

	static struct grant_map gntdev_alloc_map(struct gntdev_priv priv, int count)
	{
	struct grant_map *add;
	int i;

	add = kzalloc(sizeof(struct grant_map), GFP_KERNEL);
	if (NULL == add)
	return NULL;

	add->grants = kcalloc(count, sizeof(add->grants[0]), GFP_KERNEL);
	add->map_ops = kcalloc(count, sizeof(add->map_ops[0]), GFP_KERNEL);
	add->unmap_ops = kcalloc(count, sizeof(add->unmap_ops[0]), GFP_KERNEL);
	add->kmap_ops = kcalloc(count, sizeof(add->kmap_ops[0]), GFP_KERNEL);
	add->pages = kcalloc(count, sizeof(add->pages[0]), GFP_KERNEL);
	if (NULL == add->grants \|\|
	NULL == add->map_ops \|\|
	NULL == add->unmap_ops \|\|
	NULL == add->kmap_ops \|\|
	NULL == add->pages)
	goto err;

	if (alloc_xenballooned_pages(count, add->pages, false /* lowmem */))
	goto err;

	for (i = 0; i < count; i++) {
	add->map_ops[i].handle = -1;
	add->unmap_ops[i].handle = -1;
	add->kmap_ops[i].handle = -1;
	}

	add->index = 0;
	add->count = count;
	atomic_set(&add->users, 1);

	return add;

	err:
	gntdev_free_map(add);
	return NULL;
	}

	static void gntdev_add_map(struct gntdev_priv priv, struct grant_map add)
	{
	struct grant_map *map;

	list_for_each_entry(map, &priv->maps, next) {
	if (add->index + add->count < map->index) {
	list_add_tail(&add->next, &map->next);
	goto done;
	}
	add->index = map->index + map->count;
	}
	list_add_tail(&add->next, &priv->maps);

	done:
	gntdev_print_maps(priv, "[new]", add->index);
	}

	static struct grant_map gntdev_find_map_index(struct gntdev_priv priv,
	int index, int count)
	{
	struct grant_map *map;

	list_for_each_entry(map, &priv->maps, next) {
	if (map->index != index)
	continue;
	if (count && map->count != count)
	continue;
	return map;
	}
	return NULL;
	}

	static void gntdev_put_map(struct gntdev_priv priv, struct grant_map map)
	{
	if (!map)
	return;

	if (!atomic_dec_and_test(&map->users))
	return;

	atomic_sub(map->count, &pages_mapped);

	if (map->notify.flags & UNMAP_NOTIFY_SEND_EVENT) {
	notify_remote_via_evtchn(map->notify.event);
	evtchn_put(map->notify.event);
	}

	if (populate_freeable_maps && priv) {
	spin_lock(&priv->lock);
	list_del(&map->next);
	spin_unlock(&priv->lock);
	}

	if (map->pages && !use_ptemod)
	unmap_grant_pages(map, 0, map->count);
	gntdev_free_map(map);
	}

	/* ------------------------------------------------------------------ */

	static int find_grant_ptes(pte_t *pte, pgtable_t token,
	unsigned long addr, void *data)
	{
	struct grant_map *map = data;
	unsigned int pgnr = (addr - map->vma->vm_start) >> PAGE_SHIFT;
	int flags = map->flags \| GNTMAP_application_map \| GNTMAP_contains_pte;
	u64 pte_maddr;

	BUG_ON(pgnr >= map->count);
	pte_maddr = arbitrary_virt_to_machine(pte).maddr;

	gnttab_set_map_op(&map->map_ops[pgnr], pte_maddr, flags,
	map->grants[pgnr].ref,
	map->grants[pgnr].domid);
	gnttab_set_unmap_op(&map->unmap_ops[pgnr], pte_maddr, flags,
	-1 /* handle */);
	return 0;
	}

	static int map_grant_pages(struct grant_map *map)
	{
	int i, err = 0;

	if (!use_ptemod) {
	/* Note: it could already be mapped */
	if (map->map_ops[0].handle != -1)
	return 0;
	for (i = 0; i < map->count; i++) {
	unsigned long addr = (unsigned long)
	pfn_to_kaddr(page_to_pfn(map->pages[i]));
	gnttab_set_map_op(&map->map_ops[i], addr, map->flags,
	map->grants[i].ref,
	map->grants[i].domid);
	gnttab_set_unmap_op(&map->unmap_ops[i], addr,
	map->flags, -1 /* handle */);
	}
	} else {
	/*
	* Setup the map_ops corresponding to the pte entries pointing
	* to the kernel linear addresses of the struct pages.
	* These ptes are completely different from the user ptes dealt
	* with find_grant_ptes.
	*/
	for (i = 0; i < map->count; i++) {
	unsigned level;
	unsigned long address = (unsigned long)
	pfn_to_kaddr(page_to_pfn(map->pages[i]));
	pte_t *ptep;
	u64 pte_maddr = 0;
	BUG_ON(PageHighMem(map->pages[i]));

	ptep = lookup_address(address, &level);
	pte_maddr = arbitrary_virt_to_machine(ptep).maddr;
	gnttab_set_map_op(&map->kmap_ops[i], pte_maddr,
	map->flags \|
	GNTMAP_host_map \|
	GNTMAP_contains_pte,
	map->grants[i].ref,
	map->grants[i].domid);
	}
	}

	pr_debug("map %d+%d\n", map->index, map->count);
	err = gnttab_map_refs(map->map_ops, use_ptemod ? map->kmap_ops : NULL,
	map->pages, map->count);
	if (err)
	return err;

	for (i = 0; i < map->count; i++) {
	if (map->map_ops[i].status)
	err = -EINVAL;
	else {
	BUG_ON(map->map_ops[i].handle == -1);
	map->unmap_ops[i].handle = map->map_ops[i].handle;
	pr_debug("map handle=%d\n", map->map_ops[i].handle);
	}
	}
	return err;
	}

	static int __unmap_grant_pages(struct grant_map *map, int offset, int pages)
	{
	int i, err = 0;

	if (map->notify.flags & UNMAP_NOTIFY_CLEAR_BYTE) {
	int pgno = (map->notify.addr >> PAGE_SHIFT);
	if (pgno >= offset && pgno < offset + pages) {
	/* No need for kmap, pages are in lowmem */
	uint8_t *tmp = pfn_to_kaddr(page_to_pfn(map->pages[pgno]));
	tmp[map->notify.addr & (PAGE_SIZE-1)] = 0;
	map->notify.flags &= ~UNMAP_NOTIFY_CLEAR_BYTE;
	}
	}

	err = gnttab_unmap_refs(map->unmap_ops + offset,
	use_ptemod ? map->kmap_ops + offset : NULL, map->pages + offset,
	pages);
	if (err)
	return err;

	for (i = 0; i < pages; i++) {
	if (map->unmap_ops[offset+i].status)
	err = -EINVAL;
	pr_debug("unmap handle=%d st=%d\n",
	map->unmap_ops[offset+i].handle,
	map->unmap_ops[offset+i].status);
	map->unmap_ops[offset+i].handle = -1;
	}
	return err;
	}

	static int unmap_grant_pages(struct grant_map *map, int offset, int pages)
	{
	int range, err = 0;

	pr_debug("unmap %d+%d [%d+%d]\n", map->index, map->count, offset, pages);

	/* It is possible the requested range will have a "hole" where we
	* already unmapped some of the grants. Only unmap valid ranges.
	*/
	while (pages && !err) {
	while (pages && map->unmap_ops[offset].handle == -1) {
	offset++;
	pages--;
	}
	range = 0;
	while (range < pages) {
	if (map->unmap_ops[offset+range].handle == -1) {
	range--;
	break;
	}
	range++;
	}
	err = __unmap_grant_pages(map, offset, range);
	offset += range;
	pages -= range;
	}

	return err;
	}

	/* ------------------------------------------------------------------ */

	static void gntdev_vma_open(struct vm_area_struct *vma)
	{
	struct grant_map *map = vma->vm_private_data;

	pr_debug("gntdev_vma_open %p\n", vma);
	atomic_inc(&map->users);
	}

	static void gntdev_vma_close(struct vm_area_struct *vma)
	{
	struct grant_map *map = vma->vm_private_data;
	struct file *file = vma->vm_file;
	struct gntdev_priv *priv = file->private_data;

	pr_debug("gntdev_vma_close %p\n", vma);
	if (use_ptemod) {
	/* It is possible that an mmu notifier could be running
	* concurrently, so take priv->lock to ensure that the vma won't
	* vanishing during the unmap_grant_pages call, since we will
	* spin here until that completes. Such a concurrent call will
	* not do any unmapping, since that has been done prior to
	* closing the vma, but it may still iterate the unmap_ops list.
	*/
	spin_lock(&priv->lock);
	map->vma = NULL;
	spin_unlock(&priv->lock);
	}
	vma->vm_private_data = NULL;
	gntdev_put_map(priv, map);
	}

	static struct vm_operations_struct gntdev_vmops = {
	.open = gntdev_vma_open,
	.close = gntdev_vma_close,
	};

	/* ------------------------------------------------------------------ */

	static void unmap_if_in_range(struct grant_map *map,
	unsigned long start, unsigned long end)
	{
	unsigned long mstart, mend;
	int err;

	if (!map->vma)
	return;
	if (map->vma->vm_start >= end)
	return;
	if (map->vma->vm_end <= start)
	return;
	mstart = max(start, map->vma->vm_start);
	mend = min(end, map->vma->vm_end);
	pr_debug("map %d+%d (%lx %lx), range %lx %lx, mrange %lx %lx\n",
	map->index, map->count,
	map->vma->vm_start, map->vma->vm_end,
	start, end, mstart, mend);
	err = unmap_grant_pages(map,
	(mstart - map->vma->vm_start) >> PAGE_SHIFT,
	(mend - mstart) >> PAGE_SHIFT);
	WARN_ON(err);
	}

	static void mn_invl_range_start(struct mmu_notifier *mn,
	struct mm_struct *mm,
	unsigned long start, unsigned long end)
	{
	struct gntdev_priv *priv = container_of(mn, struct gntdev_priv, mn);
	struct grant_map *map;

	spin_lock(&priv->lock);
	list_for_each_entry(map, &priv->maps, next) {
	unmap_if_in_range(map, start, end);
	}
	list_for_each_entry(map, &priv->freeable_maps, next) {
	unmap_if_in_range(map, start, end);
	}
	spin_unlock(&priv->lock);
	}

	static void mn_invl_page(struct mmu_notifier *mn,
	struct mm_struct *mm,
	unsigned long address)
	{
	mn_invl_range_start(mn, mm, address, address + PAGE_SIZE);
	}

	static void mn_release(struct mmu_notifier *mn,
	struct mm_struct *mm)
	{
	struct gntdev_priv *priv = container_of(mn, struct gntdev_priv, mn);
	struct grant_map *map;
	int err;

	spin_lock(&priv->lock);
	list_for_each_entry(map, &priv->maps, next) {
	if (!map->vma)
	continue;
	pr_debug("map %d+%d (%lx %lx)\n",
	map->index, map->count,
	map->vma->vm_start, map->vma->vm_end);
	err = unmap_grant_pages(map, /* offset */ 0, map->count);
	WARN_ON(err);
	}
	list_for_each_entry(map, &priv->freeable_maps, next) {
	if (!map->vma)
	continue;
	pr_debug("map %d+%d (%lx %lx)\n",
	map->index, map->count,
	map->vma->vm_start, map->vma->vm_end);
	err = unmap_grant_pages(map, /* offset */ 0, map->count);
	WARN_ON(err);
	}
	spin_unlock(&priv->lock);
	}

	static struct mmu_notifier_ops gntdev_mmu_ops = {
	.release = mn_release,
	.invalidate_page = mn_invl_page,
	.invalidate_range_start = mn_invl_range_start,
	};

	/* ------------------------------------------------------------------ */

	static int gntdev_open(struct inode inode, struct file flip)
	{
	struct gntdev_priv *priv;
	int ret = 0;

	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
	if (!priv)
	return -ENOMEM;

	INIT_LIST_HEAD(&priv->maps);
	INIT_LIST_HEAD(&priv->freeable_maps);
	spin_lock_init(&priv->lock);

	if (use_ptemod) {
	priv->mm = get_task_mm(current);
	if (!priv->mm) {
	kfree(priv);
	return -ENOMEM;
	}
	priv->mn.ops = &gntdev_mmu_ops;
	ret = mmu_notifier_register(&priv->mn, priv->mm);
	mmput(priv->mm);
	}

	if (ret) {
	kfree(priv);
	return ret;
	}

	flip->private_data = priv;
	pr_debug("priv %p\n", priv);

	return 0;
	}

	static int gntdev_release(struct inode inode, struct file flip)
	{
	struct gntdev_priv *priv = flip->private_data;
	struct grant_map *map;

	pr_debug("priv %p\n", priv);

	while (!list_empty(&priv->maps)) {
	map = list_entry(priv->maps.next, struct grant_map, next);
	list_del(&map->next);
	gntdev_put_map(NULL /* already removed */, map);
	}
	WARN_ON(!list_empty(&priv->freeable_maps));

	if (use_ptemod)
	mmu_notifier_unregister(&priv->mn, priv->mm);
	kfree(priv);
	return 0;
	}

	static long gntdev_ioctl_map_grant_ref(struct gntdev_priv *priv,
	struct ioctl_gntdev_map_grant_ref __user *u)
	{
	struct ioctl_gntdev_map_grant_ref op;
	struct grant_map *map;
	int err;

	if (copy_from_user(&op, u, sizeof(op)) != 0)
	return -EFAULT;
	pr_debug("priv %p, add %d\n", priv, op.count);
	if (unlikely(op.count <= 0))
	return -EINVAL;

	err = -ENOMEM;
	map = gntdev_alloc_map(priv, op.count);
	if (!map)
	return err;

	if (unlikely(atomic_add_return(op.count, &pages_mapped) > limit)) {
	pr_debug("can't map: over limit\n");
	gntdev_put_map(NULL, map);
	return err;
	}

	if (copy_from_user(map->grants, &u->refs,
	sizeof(map->grants[0]) * op.count) != 0) {
	gntdev_put_map(NULL, map);
	return -EFAULT;
	}

	spin_lock(&priv->lock);
	gntdev_add_map(priv, map);
	op.index = map->index << PAGE_SHIFT;
	spin_unlock(&priv->lock);

	if (copy_to_user(u, &op, sizeof(op)) != 0)
	return -EFAULT;

	return 0;
	}

	static long gntdev_ioctl_unmap_grant_ref(struct gntdev_priv *priv,
	struct ioctl_gntdev_unmap_grant_ref __user *u)
	{
	struct ioctl_gntdev_unmap_grant_ref op;
	struct grant_map *map;
	int err = -ENOENT;

	if (copy_from_user(&op, u, sizeof(op)) != 0)
	return -EFAULT;
	pr_debug("priv %p, del %d+%d\n", priv, (int)op.index, (int)op.count);

	spin_lock(&priv->lock);
	map = gntdev_find_map_index(priv, op.index >> PAGE_SHIFT, op.count);
	if (map) {
	list_del(&map->next);
	if (populate_freeable_maps)
	list_add_tail(&map->next, &priv->freeable_maps);
	err = 0;
	}
	spin_unlock(&priv->lock);
	if (map)
	gntdev_put_map(priv, map);
	return err;
	}

	static long gntdev_ioctl_get_offset_for_vaddr(struct gntdev_priv *priv,
	struct ioctl_gntdev_get_offset_for_vaddr __user *u)
	{
	struct ioctl_gntdev_get_offset_for_vaddr op;
	struct vm_area_struct *vma;
	struct grant_map *map;
	int rv = -EINVAL;

	if (copy_from_user(&op, u, sizeof(op)) != 0)
	return -EFAULT;
	pr_debug("priv %p, offset for vaddr %lx\n", priv, (unsigned long)op.vaddr);

	down_read(&current->mm->mmap_sem);
	vma = find_vma(current->mm, op.vaddr);
	if (!vma \|\| vma->vm_ops != &gntdev_vmops)
	goto out_unlock;

	map = vma->vm_private_data;
	if (!map)
	goto out_unlock;

	op.offset = map->index << PAGE_SHIFT;
	op.count = map->count;
	rv = 0;

	out_unlock:
	up_read(&current->mm->mmap_sem);

	if (rv == 0 && copy_to_user(u, &op, sizeof(op)) != 0)
	return -EFAULT;
	return rv;
	}

	static long gntdev_ioctl_notify(struct gntdev_priv priv, void __user u)
	{
	struct ioctl_gntdev_unmap_notify op;
	struct grant_map *map;
	int rc;
	int out_flags;
	unsigned int out_event;

	if (copy_from_user(&op, u, sizeof(op)))
	return -EFAULT;

	if (op.action & ~(UNMAP_NOTIFY_CLEAR_BYTE\|UNMAP_NOTIFY_SEND_EVENT))
	return -EINVAL;

	/* We need to grab a reference to the event channel we are going to use
	* to send the notify before releasing the reference we may already have
	* (if someone has called this ioctl twice). This is required so that
	* it is possible to change the clear_byte part of the notification
	* without disturbing the event channel part, which may now be the last
	* reference to that event channel.
	*/
	if (op.action & UNMAP_NOTIFY_SEND_EVENT) {
	if (evtchn_get(op.event_channel_port))
	return -EINVAL;
	}

	out_flags = op.action;
	out_event = op.event_channel_port;

	spin_lock(&priv->lock);

	list_for_each_entry(map, &priv->maps, next) {
	uint64_t begin = map->index << PAGE_SHIFT;
	uint64_t end = (map->index + map->count) << PAGE_SHIFT;
	if (op.index >= begin && op.index < end)
	goto found;
	}
	rc = -ENOENT;
	goto unlock_out;

	found:
	if ((op.action & UNMAP_NOTIFY_CLEAR_BYTE) &&
	(map->flags & GNTMAP_readonly)) {
	rc = -EINVAL;
	goto unlock_out;
	}

	out_flags = map->notify.flags;
	out_event = map->notify.event;

	map->notify.flags = op.action;
	map->notify.addr = op.index - (map->index << PAGE_SHIFT);
	map->notify.event = op.event_channel_port;

	rc = 0;

	unlock_out:
	spin_unlock(&priv->lock);

	/* Drop the reference to the event channel we did not save in the map */
	if (out_flags & UNMAP_NOTIFY_SEND_EVENT)
	evtchn_put(out_event);

	return rc;
	}

	static long gntdev_ioctl(struct file *flip,
	unsigned int cmd, unsigned long arg)
	{
	struct gntdev_priv *priv = flip->private_data;
	void __user ptr = (void __user )arg;

	switch (cmd) {
	case IOCTL_GNTDEV_MAP_GRANT_REF:
	return gntdev_ioctl_map_grant_ref(priv, ptr);

	case IOCTL_GNTDEV_UNMAP_GRANT_REF:
	return gntdev_ioctl_unmap_grant_ref(priv, ptr);

	case IOCTL_GNTDEV_GET_OFFSET_FOR_VADDR:
	return gntdev_ioctl_get_offset_for_vaddr(priv, ptr);

	case IOCTL_GNTDEV_SET_UNMAP_NOTIFY:
	return gntdev_ioctl_notify(priv, ptr);

	default:
	pr_debug("priv %p, unknown cmd %x\n", priv, cmd);
	return -ENOIOCTLCMD;
	}

	return 0;
	}

	static int gntdev_mmap(struct file flip, struct vm_area_struct vma)
	{
	struct gntdev_priv *priv = flip->private_data;
	int index = vma->vm_pgoff;
	int count = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
	struct grant_map *map;
	int i, err = -EINVAL;

	if ((vma->vm_flags & VM_WRITE) && !(vma->vm_flags & VM_SHARED))
	return -EINVAL;

	pr_debug("map %d+%d at %lx (pgoff %lx)\n",
	index, count, vma->vm_start, vma->vm_pgoff);

	spin_lock(&priv->lock);
	map = gntdev_find_map_index(priv, index, count);
	if (!map)
	goto unlock_out;
	if (use_ptemod && map->vma)
	goto unlock_out;
	if (use_ptemod && priv->mm != vma->vm_mm) {
	printk(KERN_WARNING "Huh? Other mm?\n");
	goto unlock_out;
	}

	atomic_inc(&map->users);

	vma->vm_ops = &gntdev_vmops;

	vma->vm_flags \|= VM_DONTEXPAND \| VM_DONTDUMP;

	if (use_ptemod)
	vma->vm_flags \|= VM_DONTCOPY;

	vma->vm_private_data = map;

	if (use_ptemod)
	map->vma = vma;

	if (map->flags) {
	if ((vma->vm_flags & VM_WRITE) &&
	(map->flags & GNTMAP_readonly))
	goto out_unlock_put;
	} else {
	map->flags = GNTMAP_host_map;
	if (!(vma->vm_flags & VM_WRITE))
	map->flags \|= GNTMAP_readonly;
	}

	spin_unlock(&priv->lock);

	if (use_ptemod) {
	err = apply_to_page_range(vma->vm_mm, vma->vm_start,
	vma->vm_end - vma->vm_start,
	find_grant_ptes, map);
	if (err) {
	printk(KERN_WARNING "find_grant_ptes() failure.\n");
	goto out_put_map;
	}
	}

	err = map_grant_pages(map);
	if (err)
	goto out_put_map;

	if (!use_ptemod) {
	for (i = 0; i < count; i++) {
	err = vm_insert_page(vma, vma->vm_start + i*PAGE_SIZE,
	map->pages[i]);
	if (err)
	goto out_put_map;
	}
	}

	return 0;

	unlock_out:
	spin_unlock(&priv->lock);
	return err;

	out_unlock_put:
	spin_unlock(&priv->lock);
	out_put_map:
	if (use_ptemod)
	map->vma = NULL;
	gntdev_put_map(priv, map);
	return err;
	}

	static const struct file_operations gntdev_fops = {
	.owner = THIS_MODULE,
	.open = gntdev_open,
	.release = gntdev_release,
	.mmap = gntdev_mmap,
	.unlocked_ioctl = gntdev_ioctl
	};

	static struct miscdevice gntdev_miscdev = {
	.minor = MISC_DYNAMIC_MINOR,
	.name = "xen/gntdev",
	.fops = &gntdev_fops,
	};

	/* ------------------------------------------------------------------ */

	static int __init gntdev_init(void)
	{
	int err;

	if (!xen_domain())
	return -ENODEV;

	use_ptemod = xen_pv_domain();

	err = misc_register(&gntdev_miscdev);
	if (err != 0) {
	printk(KERN_ERR "Could not register gntdev device\n");
	return err;
	}
	return 0;
	}

	static void __exit gntdev_exit(void)
	{
	misc_deregister(&gntdev_miscdev);
	}

	module_init(gntdev_init);
	module_exit(gntdev_exit);

	/* ------------------------------------------------------------------ */