xen/gntdev: allow usermode to map granted pages (ab31523c) · Commits · e / devices / android_kernel_fairphone_FP3

drivers/xen/Kconfig

+7 −0

Original line number	Diff line number	Diff line
		@@ -62,6 +62,13 @@ config XEN_SYS_HYPERVISOR
		virtual environment, /sys/hypervisor will still be present,
		but will have no xen contents.

		config XEN_GNTDEV
		tristate "userspace grant access device driver"
		depends on XEN
		select MMU_NOTIFIER
		help
		Allows userspace processes to use grants.

		config XEN_PLATFORM_PCI
		tristate "xen platform pci device driver"
		depends on XEN_PVHVM

drivers/xen/Makefile

+2 −0

Original line number	Diff line number	Diff line
		@@ -9,6 +9,7 @@ obj-$(CONFIG_HOTPLUG_CPU) += cpu_hotplug.o
		obj-$(CONFIG_XEN_XENCOMM) += xencomm.o
		obj-$(CONFIG_XEN_BALLOON) += balloon.o
		obj-$(CONFIG_XEN_DEV_EVTCHN) += xen-evtchn.o
		obj-$(CONFIG_XEN_GNTDEV) += xen-gntdev.o
		obj-$(CONFIG_XENFS) += xenfs/
		obj-$(CONFIG_XEN_SYS_HYPERVISOR) += sys-hypervisor.o
		obj-$(CONFIG_XEN_PLATFORM_PCI) += platform-pci.o
		@@ -16,4 +17,5 @@ obj-$(CONFIG_SWIOTLB_XEN) += swiotlb-xen.o
		obj-$(CONFIG_XEN_DOM0) += pci.o

		xen-evtchn-y := evtchn.o
		xen-gntdev-y := gntdev.o

drivers/xen/gntdev.c

0 → 100644

+635 −0

Original line number	Diff line number	Diff line
		/******************************************************************************
		* 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 <xen/xen.h>
		#include <xen/grant_table.h>
		#include <xen/gntdev.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;
		module_param(limit, int, 0644);
		MODULE_PARM_DESC(limit, "Maximum number of grants that may be mapped at "
		"once by a gntdev instance");

		struct gntdev_priv {
		struct list_head maps;
		uint32_t used;
		uint32_t limit;
		/* lock protects maps from concurrent changes */
		spinlock_t lock;
		struct mm_struct *mm;
		struct mmu_notifier mn;
		};

		struct grant_map {
		struct list_head next;
		struct gntdev_priv *priv;
		struct vm_area_struct *vma;
		int index;
		int count;
		int flags;
		int is_mapped;
		struct ioctl_gntdev_grant_ref *grants;
		struct gnttab_map_grant_ref *map_ops;
		struct gnttab_unmap_grant_ref *unmap_ops;
		};

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

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

		pr_debug("maps list (priv %p, usage %d/%d)\n",
		priv, priv->used, priv->limit);

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

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

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

		add->index = 0;
		add->count = count;
		add->priv = priv;

		if (add->count + priv->used > priv->limit)
		goto err;

		return add;

		err:
		kfree(add->grants);
		kfree(add->map_ops);
		kfree(add->unmap_ops);
		kfree(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:
		priv->used += add->count;
		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 (map->count != count)
		continue;
		return map;
		}
		return NULL;
		}

		static struct grant_map gntdev_find_map_vaddr(struct gntdev_priv priv,
		unsigned long vaddr)
		{
		struct grant_map *map;

		list_for_each_entry(map, &priv->maps, next) {
		if (!map->vma)
		continue;
		if (vaddr < map->vma->vm_start)
		continue;
		if (vaddr >= map->vma->vm_end)
		continue;
		return map;
		}
		return NULL;
		}

		static int gntdev_del_map(struct grant_map *map)
		{
		int i;

		if (map->vma)
		return -EBUSY;
		for (i = 0; i < map->count; i++)
		if (map->unmap_ops[i].handle)
		return -EBUSY;

		map->priv->used -= map->count;
		list_del(&map->next);
		return 0;
		}

		static void gntdev_free_map(struct grant_map *map)
		{
		if (!map)
		return;
		kfree(map->grants);
		kfree(map->map_ops);
		kfree(map->unmap_ops);
		kfree(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;
		u64 pte_maddr;

		BUG_ON(pgnr >= map->count);
		pte_maddr = (u64)pfn_to_mfn(page_to_pfn(token)) << PAGE_SHIFT;
		pte_maddr += (unsigned long)pte & ~PAGE_MASK;
		gnttab_set_map_op(&map->map_ops[pgnr], pte_maddr, map->flags,
		map->grants[pgnr].ref,
		map->grants[pgnr].domid);
		gnttab_set_unmap_op(&map->unmap_ops[pgnr], pte_maddr, map->flags,
		0 /* handle */);
		return 0;
		}

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

		pr_debug("map %d+%d\n", map->index, map->count);
		err = HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref,
		map->map_ops, map->count);
		if (err)
		return err;

		for (i = 0; i < map->count; i++) {
		if (map->map_ops[i].status)
		err = -EINVAL;
		map->unmap_ops[i].handle = map->map_ops[i].handle;
		}
		return err;
		}

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

		pr_debug("map %d+%d [%d+%d]\n", map->index, map->count, offset, pages);
		err = HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref,
		map->unmap_ops + offset, pages);
		if (err)
		return err;

		for (i = 0; i < pages; i++) {
		if (map->unmap_ops[offset+i].status)
		err = -EINVAL;
		map->unmap_ops[offset+i].handle = 0;
		}
		return err;
		}

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

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

		pr_debug("close %p\n", vma);
		map->is_mapped = 0;
		map->vma = NULL;
		vma->vm_private_data = NULL;
		}

		static int gntdev_vma_fault(struct vm_area_struct vma, struct vm_fault vmf)
		{
		pr_debug("vaddr %p, pgoff %ld (shouldn't happen)\n",
		vmf->virtual_address, vmf->pgoff);
		vmf->flags = VM_FAULT_ERROR;
		return 0;
		}

		static struct vm_operations_struct gntdev_vmops = {
		.close = gntdev_vma_close,
		.fault = gntdev_vma_fault,
		};

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

		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;
		unsigned long mstart, mend;
		int err;

		spin_lock(&priv->lock);
		list_for_each_entry(map, &priv->maps, next) {
		if (!map->vma)
		continue;
		if (!map->is_mapped)
		continue;
		if (map->vma->vm_start >= end)
		continue;
		if (map->vma->vm_end <= start)
		continue;
		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);
		}
		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);
		}
		spin_unlock(&priv->lock);
		}

		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);
		spin_lock_init(&priv->lock);
		priv->limit = limit;

		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;
		int err;

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

		spin_lock(&priv->lock);
		while (!list_empty(&priv->maps)) {
		map = list_entry(priv->maps.next, struct grant_map, next);
		err = gntdev_del_map(map);
		if (WARN_ON(err))
		gntdev_free_map(map);

		}
		spin_unlock(&priv->lock);

		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;
		if (unlikely(op.count > priv->limit))
		return -EINVAL;

		err = -ENOMEM;
		map = gntdev_alloc_map(priv, op.count);
		if (!map)
		return err;
		if (copy_from_user(map->grants, &u->refs,
		sizeof(map->grants[0]) * op.count) != 0) {
		gntdev_free_map(map);
		return err;
		}

		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) {
		spin_lock(&priv->lock);
		gntdev_del_map(map);
		spin_unlock(&priv->lock);
		gntdev_free_map(map);
		return err;
		}
		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)
		err = gntdev_del_map(map);
		spin_unlock(&priv->lock);
		if (!err)
		gntdev_free_map(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 grant_map *map;

		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);

		spin_lock(&priv->lock);
		map = gntdev_find_map_vaddr(priv, op.vaddr);
		if (map == NULL \|\|
		map->vma->vm_start != op.vaddr) {
		spin_unlock(&priv->lock);
		return -EINVAL;
		}
		op.offset = map->index << PAGE_SHIFT;
		op.count = map->count;
		spin_unlock(&priv->lock);

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

		static long gntdev_ioctl_set_max_grants(struct gntdev_priv *priv,
		struct ioctl_gntdev_set_max_grants __user *u)
		{
		struct ioctl_gntdev_set_max_grants op;

		if (copy_from_user(&op, u, sizeof(op)) != 0)
		return -EFAULT;
		pr_debug("priv %p, limit %d\n", priv, op.count);
		if (op.count > limit)
		return -E2BIG;

		spin_lock(&priv->lock);
		priv->limit = op.count;
		spin_unlock(&priv->lock);
		return 0;
		}

		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_MAX_GRANTS:
		return gntdev_ioctl_set_max_grants(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 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 (map->vma)
		goto unlock_out;
		if (priv->mm != vma->vm_mm) {
		printk(KERN_WARNING "Huh? Other mm?\n");
		goto unlock_out;
		}

		vma->vm_ops = &gntdev_vmops;

		vma->vm_flags \|= VM_RESERVED\|VM_DONTCOPY\|VM_DONTEXPAND;

		vma->vm_private_data = map;
		map->vma = vma;

		map->flags = GNTMAP_host_map \| GNTMAP_application_map \| GNTMAP_contains_pte;
		if (!(vma->vm_flags & VM_WRITE))
		map->flags \|= GNTMAP_readonly;

		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 unlock_out;
		}

		err = map_grant_pages(map);
		if (err) {
		printk(KERN_WARNING "map_grant_pages() failure.\n");
		goto unlock_out;
		}
		map->is_mapped = 1;

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

		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);

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

include/xen/gntdev.h

0 → 100644

+119 −0

Original line number	Diff line number	Diff line
		/******************************************************************************
		* gntdev.h
		*
		* Interface to /dev/xen/gntdev.
		*
		* Copyright (c) 2007, D G Murray
		*
		* This program is free software; you can redistribute it and/or
		* modify it under the terms of the GNU General Public License version 2
		* as published by the Free Software Foundation; or, when distributed
		* separately from the Linux kernel or incorporated into other
		* software packages, subject to the following license:
		*
		* Permission is hereby granted, free of charge, to any person obtaining a copy
		* of this source file (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 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.
		*/

		#ifndef __LINUX_PUBLIC_GNTDEV_H__
		#define __LINUX_PUBLIC_GNTDEV_H__

		struct ioctl_gntdev_grant_ref {
		/* The domain ID of the grant to be mapped. */
		uint32_t domid;
		/* The grant reference of the grant to be mapped. */
		uint32_t ref;
		};

		/*
		* Inserts the grant references into the mapping table of an instance
		* of gntdev. N.B. This does not perform the mapping, which is deferred
		* until mmap() is called with @index as the offset.
		*/
		#define IOCTL_GNTDEV_MAP_GRANT_REF \
		_IOC(_IOC_NONE, 'G', 0, sizeof(struct ioctl_gntdev_map_grant_ref))
		struct ioctl_gntdev_map_grant_ref {
		/* IN parameters */
		/* The number of grants to be mapped. */
		uint32_t count;
		uint32_t pad;
		/* OUT parameters */
		/* The offset to be used on a subsequent call to mmap(). */
		uint64_t index;
		/* Variable IN parameter. */
		/* Array of grant references, of size @count. */
		struct ioctl_gntdev_grant_ref refs[1];
		};

		/*
		* Removes the grant references from the mapping table of an instance of
		* of gntdev. N.B. munmap() must be called on the relevant virtual address(es)
		* before this ioctl is called, or an error will result.
		*/
		#define IOCTL_GNTDEV_UNMAP_GRANT_REF \
		_IOC(_IOC_NONE, 'G', 1, sizeof(struct ioctl_gntdev_unmap_grant_ref))
		struct ioctl_gntdev_unmap_grant_ref {
		/* IN parameters */
		/* The offset was returned by the corresponding map operation. */
		uint64_t index;
		/* The number of pages to be unmapped. */
		uint32_t count;
		uint32_t pad;
		};

		/*
		* Returns the offset in the driver's address space that corresponds
		* to @vaddr. This can be used to perform a munmap(), followed by an
		* UNMAP_GRANT_REF ioctl, where no state about the offset is retained by
		* the caller. The number of pages that were allocated at the same time as
		* @vaddr is returned in @count.
		*
		* N.B. Where more than one page has been mapped into a contiguous range, the
		* supplied @vaddr must correspond to the start of the range; otherwise
		* an error will result. It is only possible to munmap() the entire
		* contiguously-allocated range at once, and not any subrange thereof.
		*/
		#define IOCTL_GNTDEV_GET_OFFSET_FOR_VADDR \
		_IOC(_IOC_NONE, 'G', 2, sizeof(struct ioctl_gntdev_get_offset_for_vaddr))
		struct ioctl_gntdev_get_offset_for_vaddr {
		/* IN parameters */
		/* The virtual address of the first mapped page in a range. */
		uint64_t vaddr;
		/* OUT parameters */
		/* The offset that was used in the initial mmap() operation. */
		uint64_t offset;
		/* The number of pages mapped in the VM area that begins at @vaddr. */
		uint32_t count;
		uint32_t pad;
		};

		/*
		* Sets the maximum number of grants that may mapped at once by this gntdev
		* instance.
		*
		* N.B. This must be called before any other ioctl is performed on the device.
		*/
		#define IOCTL_GNTDEV_SET_MAX_GRANTS \
		_IOC(_IOC_NONE, 'G', 3, sizeof(struct ioctl_gntdev_set_max_grants))
		struct ioctl_gntdev_set_max_grants {
		/* IN parameter */
		/* The maximum number of grants that may be mapped at once. */
		uint32_t count;
		};

		#endif /* __LINUX_PUBLIC_GNTDEV_H__ */