drivers/xen/privcmd.c - kernel/msm-4.19 - Gitiles

 /******************************************************************************
  * privcmd.c
  *
  * Interface to privileged domain-0 commands.
  *
  * Copyright (c) 2002-2004, K A Fraser, B Dragovic
  */

 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/sched.h>
 #include <linux/slab.h>
 #include <linux/string.h>
 #include <linux/errno.h>
 #include <linux/mm.h>
 #include <linux/mman.h>
 #include <linux/uaccess.h>
 #include <linux/swap.h>
 #include <linux/highmem.h>
 #include <linux/pagemap.h>
 #include <linux/seq_file.h>
 #include <linux/miscdevice.h>

 #include <asm/pgalloc.h>
 #include <asm/pgtable.h>
 #include <asm/tlb.h>
 #include <asm/xen/hypervisor.h>
 #include <asm/xen/hypercall.h>

 #include <xen/xen.h>
 #include <xen/privcmd.h>
 #include <xen/interface/xen.h>
 #include <xen/features.h>
 #include <xen/page.h>
 #include <xen/xen-ops.h>
 #include <xen/balloon.h>

 #include "privcmd.h"

 MODULE_LICENSE("GPL");

 #define PRIV_VMA_LOCKED ((void *)1)

 #ifndef HAVE_ARCH_PRIVCMD_MMAP
 static int privcmd_enforce_singleshot_mapping(struct vm_area_struct *vma);
 #endif

 static long privcmd_ioctl_hypercall(void __user *udata)
 {
 	struct privcmd_hypercall hypercall;
 	long ret;

 	if (copy_from_user(&hypercall, udata, sizeof(hypercall)))
 		return -EFAULT;

 	ret = privcmd_call(hypercall.op,
 			   hypercall.arg[0], hypercall.arg[1],
 			   hypercall.arg[2], hypercall.arg[3],
 			   hypercall.arg[4]);

 	return ret;
 }

 static void free_page_list(struct list_head *pages)
 {
 	struct page *p, *n;

 	list_for_each_entry_safe(p, n, pages, lru)
 		__free_page(p);

 	INIT_LIST_HEAD(pages);
 }

 /*
  * Given an array of items in userspace, return a list of pages
  * containing the data.  If copying fails, either because of memory
  * allocation failure or a problem reading user memory, return an
  * error code; its up to the caller to dispose of any partial list.
  */
 static int gather_array(struct list_head *pagelist,
 			unsigned nelem, size_t size,
 			const void __user *data)
 {
 	unsigned pageidx;
 	void *pagedata;
 	int ret;

 	if (size > PAGE_SIZE)
 		return 0;

 	pageidx = PAGE_SIZE;
 	pagedata = NULL;	/* quiet, gcc */
 	while (nelem--) {
 		if (pageidx > PAGE_SIZE-size) {
 			struct page *page = alloc_page(GFP_KERNEL);

 			ret = -ENOMEM;
 			if (page == NULL)
 				goto fail;

 			pagedata = page_address(page);

 			list_add_tail(&page->lru, pagelist);
 			pageidx = 0;
 		}

 		ret = -EFAULT;
 		if (copy_from_user(pagedata + pageidx, data, size))
 			goto fail;

 		data += size;
 		pageidx += size;
 	}

 	ret = 0;

 fail:
 	return ret;
 }

 /*
  * Call function "fn" on each element of the array fragmented
  * over a list of pages.
  */
 static int traverse_pages(unsigned nelem, size_t size,
 			  struct list_head *pos,
 			  int (*fn)(void *data, void *state),
 			  void *state)
 {
 	void *pagedata;
 	unsigned pageidx;
 	int ret = 0;

 	BUG_ON(size > PAGE_SIZE);

 	pageidx = PAGE_SIZE;
 	pagedata = NULL;	/* hush, gcc */

 	while (nelem--) {
 		if (pageidx > PAGE_SIZE-size) {
 			struct page *page;
 			pos = pos->next;
 			page = list_entry(pos, struct page, lru);
 			pagedata = page_address(page);
 			pageidx = 0;
 		}

 		ret = (*fn)(pagedata + pageidx, state);
 		if (ret)
 			break;
 		pageidx += size;
 	}

 	return ret;
 }

 struct mmap_mfn_state {
 	unsigned long va;
 	struct vm_area_struct *vma;
 	domid_t domain;
 };

 static int mmap_mfn_range(void *data, void *state)
 {
 	struct privcmd_mmap_entry *msg = data;
 	struct mmap_mfn_state *st = state;
 	struct vm_area_struct *vma = st->vma;
 	int rc;

 	/* Do not allow range to wrap the address space. */
 	if ((msg->npages > (LONG_MAX >> PAGE_SHIFT)) ||
 	    ((unsigned long)(msg->npages << PAGE_SHIFT) >= -st->va))
 		return -EINVAL;

 	/* Range chunks must be contiguous in va space. */
 	if ((msg->va != st->va) ||
 	    ((msg->va+(msg->npages<<PAGE_SHIFT)) > vma->vm_end))
 		return -EINVAL;

 	rc = xen_remap_domain_mfn_range(vma,
 					msg->va & PAGE_MASK,
 					msg->mfn, msg->npages,
 					vma->vm_page_prot,
 					st->domain, NULL);
 	if (rc < 0)
 		return rc;

 	st->va += msg->npages << PAGE_SHIFT;

 	return 0;
 }

 static long privcmd_ioctl_mmap(void __user *udata)
 {
 	struct privcmd_mmap mmapcmd;
 	struct mm_struct *mm = current->mm;
 	struct vm_area_struct *vma;
 	int rc;
 	LIST_HEAD(pagelist);
 	struct mmap_mfn_state state;

 	if (!xen_initial_domain())
 		return -EPERM;

 	/* We only support privcmd_ioctl_mmap_batch for auto translated. */
 	if (xen_feature(XENFEAT_auto_translated_physmap))
 		return -ENOSYS;

 	if (copy_from_user(&mmapcmd, udata, sizeof(mmapcmd)))
 		return -EFAULT;

 	rc = gather_array(&pagelist,
 			  mmapcmd.num, sizeof(struct privcmd_mmap_entry),
 			  mmapcmd.entry);

 	if (rc || list_empty(&pagelist))
 		goto out;

 	down_write(&mm->mmap_sem);

 	{
 		struct page *page = list_first_entry(&pagelist,
 						     struct page, lru);
 		struct privcmd_mmap_entry *msg = page_address(page);

 		vma = find_vma(mm, msg->va);
 		rc = -EINVAL;

 		if (!vma || (msg->va != vma->vm_start) ||
 		    !privcmd_enforce_singleshot_mapping(vma))
 			goto out_up;
 	}

 	state.va = vma->vm_start;
 	state.vma = vma;
 	state.domain = mmapcmd.dom;

 	rc = traverse_pages(mmapcmd.num, sizeof(struct privcmd_mmap_entry),
 			    &pagelist,
 			    mmap_mfn_range, &state);


 out_up:
 	up_write(&mm->mmap_sem);

 out:
 	free_page_list(&pagelist);

 	return rc;
 }

 struct mmap_batch_state {
 	domid_t domain;
 	unsigned long va;
 	struct vm_area_struct *vma;
 	int index;
 	/* A tristate:
 	 *      0 for no errors
 	 *      1 if at least one error has happened (and no
 	 *          -ENOENT errors have happened)
 	 *      -ENOENT if at least 1 -ENOENT has happened.
 	 */
 	int global_error;
 	/* An array for individual errors */
 	int *err;

 	/* User-space mfn array to store errors in the second pass for V1. */
 	xen_pfn_t __user *user_mfn;
 };

 /* auto translated dom0 note: if domU being created is PV, then mfn is
  * mfn(addr on bus). If it's auto xlated, then mfn is pfn (input to HAP).
  */
 static int mmap_batch_fn(void *data, void *state)
 {
 	xen_pfn_t *mfnp = data;
 	struct mmap_batch_state *st = state;
 	struct vm_area_struct *vma = st->vma;
 	struct page **pages = vma->vm_private_data;
 	struct page *cur_page = NULL;
 	int ret;

 	if (xen_feature(XENFEAT_auto_translated_physmap))
 		cur_page = pages[st->index++];

 	ret = xen_remap_domain_mfn_range(st->vma, st->va & PAGE_MASK, *mfnp, 1,
 					 st->vma->vm_page_prot, st->domain,
 					 &cur_page);

 	/* Store error code for second pass. */
 	*(st->err++) = ret;

 	/* And see if it affects the global_error. */
 	if (ret < 0) {
 		if (ret == -ENOENT)
 			st->global_error = -ENOENT;
 		else {
 			/* Record that at least one error has happened. */
 			if (st->global_error == 0)
 				st->global_error = 1;
 		}
 	}
 	st->va += PAGE_SIZE;

 	return 0;
 }

 static int mmap_return_errors_v1(void *data, void *state)
 {
 	xen_pfn_t *mfnp = data;
 	struct mmap_batch_state *st = state;
 	int err = *(st->err++);

 	/*
 	 * V1 encodes the error codes in the 32bit top nibble of the
 	 * mfn (with its known limitations vis-a-vis 64 bit callers).
 	 */
 	*mfnp |= (err == -ENOENT) ?
 				PRIVCMD_MMAPBATCH_PAGED_ERROR :
 				PRIVCMD_MMAPBATCH_MFN_ERROR;
 	return __put_user(*mfnp, st->user_mfn++);
 }

 /* Allocate pfns that are then mapped with gmfns from foreign domid. Update
  * the vma with the page info to use later.
  * Returns: 0 if success, otherwise -errno
  */
 static int alloc_empty_pages(struct vm_area_struct *vma, int numpgs)
 {
 	int rc;
 	struct page **pages;

 	pages = kcalloc(numpgs, sizeof(pages[0]), GFP_KERNEL);
 	if (pages == NULL)
 		return -ENOMEM;

 	rc = alloc_xenballooned_pages(numpgs, pages, 0);
 	if (rc != 0) {
 		pr_warn("%s Could not alloc %d pfns rc:%d\n", __func__,
 			numpgs, rc);
 		kfree(pages);
 		return -ENOMEM;
 	}
 	BUG_ON(vma->vm_private_data != PRIV_VMA_LOCKED);
 	vma->vm_private_data = pages;

 	return 0;
 }

 static struct vm_operations_struct privcmd_vm_ops;

 static long privcmd_ioctl_mmap_batch(void __user *udata, int version)
 {
 	int ret;
 	struct privcmd_mmapbatch_v2 m;
 	struct mm_struct *mm = current->mm;
 	struct vm_area_struct *vma;
 	unsigned long nr_pages;
 	LIST_HEAD(pagelist);
 	int *err_array = NULL;
 	struct mmap_batch_state state;

 	if (!xen_initial_domain())
 		return -EPERM;

 	switch (version) {
 	case 1:
 		if (copy_from_user(&m, udata, sizeof(struct privcmd_mmapbatch)))
 			return -EFAULT;
 		/* Returns per-frame error in m.arr. */
 		m.err = NULL;
 		if (!access_ok(VERIFY_WRITE, m.arr, m.num * sizeof(*m.arr)))
 			return -EFAULT;
 		break;
 	case 2:
 		if (copy_from_user(&m, udata, sizeof(struct privcmd_mmapbatch_v2)))
 			return -EFAULT;
 		/* Returns per-frame error code in m.err. */
 		if (!access_ok(VERIFY_WRITE, m.err, m.num * (sizeof(*m.err))))
 			return -EFAULT;
 		break;
 	default:
 		return -EINVAL;
 	}

 	nr_pages = m.num;
 	if ((m.num <= 0) || (nr_pages > (LONG_MAX >> PAGE_SHIFT)))
 		return -EINVAL;

 	ret = gather_array(&pagelist, m.num, sizeof(xen_pfn_t), m.arr);

 	if (ret)
 		goto out;
 	if (list_empty(&pagelist)) {
 		ret = -EINVAL;
 		goto out;
 	}

 	err_array = kcalloc(m.num, sizeof(int), GFP_KERNEL);
 	if (err_array == NULL) {
 		ret = -ENOMEM;
 		goto out;
 	}

 	down_write(&mm->mmap_sem);

 	vma = find_vma(mm, m.addr);
 	if (!vma ||
 	    vma->vm_ops != &privcmd_vm_ops ||
 	    (m.addr != vma->vm_start) ||
 	    ((m.addr + (nr_pages << PAGE_SHIFT)) != vma->vm_end) ||
 	    !privcmd_enforce_singleshot_mapping(vma)) {
 		up_write(&mm->mmap_sem);
 		ret = -EINVAL;
 		goto out;
 	}
 	if (xen_feature(XENFEAT_auto_translated_physmap)) {
 		ret = alloc_empty_pages(vma, m.num);
 		if (ret < 0) {
 			up_write(&mm->mmap_sem);
 			goto out;
 		}
 	}

 	state.domain        = m.dom;
 	state.vma           = vma;
 	state.va            = m.addr;
 	state.index         = 0;
 	state.global_error  = 0;
 	state.err           = err_array;

 	/* mmap_batch_fn guarantees ret == 0 */
 	BUG_ON(traverse_pages(m.num, sizeof(xen_pfn_t),
 			     &pagelist, mmap_batch_fn, &state));

 	up_write(&mm->mmap_sem);

 	if (version == 1) {
 		if (state.global_error) {
 			/* Write back errors in second pass. */
 			state.user_mfn = (xen_pfn_t *)m.arr;
 			state.err      = err_array;
 			ret = traverse_pages(m.num, sizeof(xen_pfn_t),
 					     &pagelist, mmap_return_errors_v1, &state);
 		} else
 			ret = 0;

 	} else if (version == 2) {
 		ret = __copy_to_user(m.err, err_array, m.num * sizeof(int));
 		if (ret)
 			ret = -EFAULT;
 	}

 	/* If we have not had any EFAULT-like global errors then set the global
 	 * error to -ENOENT if necessary. */
 	if ((ret == 0) && (state.global_error == -ENOENT))
 		ret = -ENOENT;

 out:
 	kfree(err_array);
 	free_page_list(&pagelist);

 	return ret;
 }

 static long privcmd_ioctl(struct file *file,
 			  unsigned int cmd, unsigned long data)
 {
 	int ret = -ENOSYS;
 	void __user *udata = (void __user *) data;

 	switch (cmd) {
 	case IOCTL_PRIVCMD_HYPERCALL:
 		ret = privcmd_ioctl_hypercall(udata);
 		break;

 	case IOCTL_PRIVCMD_MMAP:
 		ret = privcmd_ioctl_mmap(udata);
 		break;

 	case IOCTL_PRIVCMD_MMAPBATCH:
 		ret = privcmd_ioctl_mmap_batch(udata, 1);
 		break;

 	case IOCTL_PRIVCMD_MMAPBATCH_V2:
 		ret = privcmd_ioctl_mmap_batch(udata, 2);
 		break;

 	default:
 		ret = -EINVAL;
 		break;
 	}

 	return ret;
 }

 static void privcmd_close(struct vm_area_struct *vma)
 {
 	struct page **pages = vma->vm_private_data;
 	int numpgs = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;

 	if (!xen_feature(XENFEAT_auto_translated_physmap || !numpgs || !pages))
 		return;

 	xen_unmap_domain_mfn_range(vma, numpgs, pages);
 	free_xenballooned_pages(numpgs, pages);
 	kfree(pages);
 }

 static int privcmd_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
 {
 	printk(KERN_DEBUG "privcmd_fault: vma=%p %lx-%lx, pgoff=%lx, uv=%p\n",
 	       vma, vma->vm_start, vma->vm_end,
 	       vmf->pgoff, vmf->virtual_address);

 	return VM_FAULT_SIGBUS;
 }

 static struct vm_operations_struct privcmd_vm_ops = {
 	.close = privcmd_close,
 	.fault = privcmd_fault
 };

 static int privcmd_mmap(struct file *file, struct vm_area_struct *vma)
 {
 	/* DONTCOPY is essential for Xen because copy_page_range doesn't know
 	 * how to recreate these mappings */
 	vma->vm_flags |= VM_IO | VM_PFNMAP | VM_DONTCOPY |
 			 VM_DONTEXPAND | VM_DONTDUMP;
 	vma->vm_ops = &privcmd_vm_ops;
 	vma->vm_private_data = NULL;

 	return 0;
 }

 static int privcmd_enforce_singleshot_mapping(struct vm_area_struct *vma)
 {
 	return !cmpxchg(&vma->vm_private_data, NULL, PRIV_VMA_LOCKED);
 }

 const struct file_operations xen_privcmd_fops = {
 	.owner = THIS_MODULE,
 	.unlocked_ioctl = privcmd_ioctl,
 	.mmap = privcmd_mmap,
 };
 EXPORT_SYMBOL_GPL(xen_privcmd_fops);

 static struct miscdevice privcmd_dev = {
 	.minor = MISC_DYNAMIC_MINOR,
 	.name = "xen/privcmd",
 	.fops = &xen_privcmd_fops,
 };

 static int __init privcmd_init(void)
 {
 	int err;

 	if (!xen_domain())
 		return -ENODEV;

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

 static void __exit privcmd_exit(void)
 {
 	misc_deregister(&privcmd_dev);
 }

 module_init(privcmd_init);
 module_exit(privcmd_exit);
	/******************************************************************************
	* privcmd.c
	*
	* Interface to privileged domain-0 commands.
	*
	* Copyright (c) 2002-2004, K A Fraser, B Dragovic
	*/

	#include <linux/kernel.h>
	#include <linux/module.h>
	#include <linux/sched.h>
	#include <linux/slab.h>
	#include <linux/string.h>
	#include <linux/errno.h>
	#include <linux/mm.h>
	#include <linux/mman.h>
	#include <linux/uaccess.h>
	#include <linux/swap.h>
	#include <linux/highmem.h>
	#include <linux/pagemap.h>
	#include <linux/seq_file.h>
	#include <linux/miscdevice.h>

	#include <asm/pgalloc.h>
	#include <asm/pgtable.h>
	#include <asm/tlb.h>
	#include <asm/xen/hypervisor.h>
	#include <asm/xen/hypercall.h>

	#include <xen/xen.h>
	#include <xen/privcmd.h>
	#include <xen/interface/xen.h>
	#include <xen/features.h>
	#include <xen/page.h>
	#include <xen/xen-ops.h>
	#include <xen/balloon.h>

	#include "privcmd.h"

	MODULE_LICENSE("GPL");

	#define PRIV_VMA_LOCKED ((void *)1)

	#ifndef HAVE_ARCH_PRIVCMD_MMAP
	static int privcmd_enforce_singleshot_mapping(struct vm_area_struct *vma);
	#endif

	static long privcmd_ioctl_hypercall(void __user *udata)
	{
	struct privcmd_hypercall hypercall;
	long ret;

	if (copy_from_user(&hypercall, udata, sizeof(hypercall)))
	return -EFAULT;

	ret = privcmd_call(hypercall.op,
	hypercall.arg[0], hypercall.arg[1],
	hypercall.arg[2], hypercall.arg[3],
	hypercall.arg[4]);

	return ret;
	}

	static void free_page_list(struct list_head *pages)
	{
	struct page p, n;

	list_for_each_entry_safe(p, n, pages, lru)
	__free_page(p);

	INIT_LIST_HEAD(pages);
	}

	/*
	* Given an array of items in userspace, return a list of pages
	* containing the data. If copying fails, either because of memory
	* allocation failure or a problem reading user memory, return an
	* error code; its up to the caller to dispose of any partial list.
	*/
	static int gather_array(struct list_head *pagelist,
	unsigned nelem, size_t size,
	const void __user *data)
	{
	unsigned pageidx;
	void *pagedata;
	int ret;

	if (size > PAGE_SIZE)
	return 0;

	pageidx = PAGE_SIZE;
	pagedata = NULL; /* quiet, gcc */
	while (nelem--) {
	if (pageidx > PAGE_SIZE-size) {
	struct page *page = alloc_page(GFP_KERNEL);

	ret = -ENOMEM;
	if (page == NULL)
	goto fail;

	pagedata = page_address(page);

	list_add_tail(&page->lru, pagelist);
	pageidx = 0;
	}

	ret = -EFAULT;
	if (copy_from_user(pagedata + pageidx, data, size))
	goto fail;

	data += size;
	pageidx += size;
	}

	ret = 0;

	fail:
	return ret;
	}

	/*
	* Call function "fn" on each element of the array fragmented
	* over a list of pages.
	*/
	static int traverse_pages(unsigned nelem, size_t size,
	struct list_head *pos,
	int (fn)(void data, void *state),
	void *state)
	{
	void *pagedata;
	unsigned pageidx;
	int ret = 0;

	BUG_ON(size > PAGE_SIZE);

	pageidx = PAGE_SIZE;
	pagedata = NULL; /* hush, gcc */

	while (nelem--) {
	if (pageidx > PAGE_SIZE-size) {
	struct page *page;
	pos = pos->next;
	page = list_entry(pos, struct page, lru);
	pagedata = page_address(page);
	pageidx = 0;
	}

	ret = (*fn)(pagedata + pageidx, state);
	if (ret)
	break;
	pageidx += size;
	}

	return ret;
	}

	struct mmap_mfn_state {
	unsigned long va;
	struct vm_area_struct *vma;
	domid_t domain;
	};

	static int mmap_mfn_range(void data, void state)
	{
	struct privcmd_mmap_entry *msg = data;
	struct mmap_mfn_state *st = state;
	struct vm_area_struct *vma = st->vma;
	int rc;

	/* Do not allow range to wrap the address space. */
	if ((msg->npages > (LONG_MAX >> PAGE_SHIFT)) \|\|
	((unsigned long)(msg->npages << PAGE_SHIFT) >= -st->va))
	return -EINVAL;

	/* Range chunks must be contiguous in va space. */
	if ((msg->va != st->va) \|\|
	((msg->va+(msg->npages<<PAGE_SHIFT)) > vma->vm_end))
	return -EINVAL;

	rc = xen_remap_domain_mfn_range(vma,
	msg->va & PAGE_MASK,
	msg->mfn, msg->npages,
	vma->vm_page_prot,
	st->domain, NULL);
	if (rc < 0)
	return rc;

	st->va += msg->npages << PAGE_SHIFT;

	return 0;
	}

	static long privcmd_ioctl_mmap(void __user *udata)
	{
	struct privcmd_mmap mmapcmd;
	struct mm_struct *mm = current->mm;
	struct vm_area_struct *vma;
	int rc;
	LIST_HEAD(pagelist);
	struct mmap_mfn_state state;

	if (!xen_initial_domain())
	return -EPERM;

	/* We only support privcmd_ioctl_mmap_batch for auto translated. */
	if (xen_feature(XENFEAT_auto_translated_physmap))
	return -ENOSYS;

	if (copy_from_user(&mmapcmd, udata, sizeof(mmapcmd)))
	return -EFAULT;

	rc = gather_array(&pagelist,
	mmapcmd.num, sizeof(struct privcmd_mmap_entry),
	mmapcmd.entry);

	if (rc \|\| list_empty(&pagelist))
	goto out;

	down_write(&mm->mmap_sem);

	{
	struct page *page = list_first_entry(&pagelist,
	struct page, lru);
	struct privcmd_mmap_entry *msg = page_address(page);

	vma = find_vma(mm, msg->va);
	rc = -EINVAL;

	if (!vma \|\| (msg->va != vma->vm_start) \|\|
	!privcmd_enforce_singleshot_mapping(vma))
	goto out_up;
	}

	state.va = vma->vm_start;
	state.vma = vma;
	state.domain = mmapcmd.dom;

	rc = traverse_pages(mmapcmd.num, sizeof(struct privcmd_mmap_entry),
	&pagelist,
	mmap_mfn_range, &state);


	out_up:
	up_write(&mm->mmap_sem);

	out:
	free_page_list(&pagelist);

	return rc;
	}

	struct mmap_batch_state {
	domid_t domain;
	unsigned long va;
	struct vm_area_struct *vma;
	int index;
	/* A tristate:
	* 0 for no errors
	* 1 if at least one error has happened (and no
	* -ENOENT errors have happened)
	* -ENOENT if at least 1 -ENOENT has happened.
	*/
	int global_error;
	/* An array for individual errors */
	int *err;

	/* User-space mfn array to store errors in the second pass for V1. */
	xen_pfn_t __user *user_mfn;
	};

	/* auto translated dom0 note: if domU being created is PV, then mfn is
	* mfn(addr on bus). If it's auto xlated, then mfn is pfn (input to HAP).
	*/
	static int mmap_batch_fn(void data, void state)
	{
	xen_pfn_t *mfnp = data;
	struct mmap_batch_state *st = state;
	struct vm_area_struct *vma = st->vma;
	struct page **pages = vma->vm_private_data;
	struct page *cur_page = NULL;
	int ret;

	if (xen_feature(XENFEAT_auto_translated_physmap))
	cur_page = pages[st->index++];

	ret = xen_remap_domain_mfn_range(st->vma, st->va & PAGE_MASK, *mfnp, 1,
	st->vma->vm_page_prot, st->domain,
	&cur_page);

	/* Store error code for second pass. */
	*(st->err++) = ret;

	/* And see if it affects the global_error. */
	if (ret < 0) {
	if (ret == -ENOENT)
	st->global_error = -ENOENT;
	else {
	/* Record that at least one error has happened. */
	if (st->global_error == 0)
	st->global_error = 1;
	}
	}
	st->va += PAGE_SIZE;

	return 0;
	}

	static int mmap_return_errors_v1(void data, void state)
	{
	xen_pfn_t *mfnp = data;
	struct mmap_batch_state *st = state;
	int err = *(st->err++);

	/*
	* V1 encodes the error codes in the 32bit top nibble of the
	* mfn (with its known limitations vis-a-vis 64 bit callers).
	*/
	*mfnp \|= (err == -ENOENT) ?
	PRIVCMD_MMAPBATCH_PAGED_ERROR :
	PRIVCMD_MMAPBATCH_MFN_ERROR;
	return __put_user(*mfnp, st->user_mfn++);
	}

	/* Allocate pfns that are then mapped with gmfns from foreign domid. Update
	* the vma with the page info to use later.
	* Returns: 0 if success, otherwise -errno
	*/
	static int alloc_empty_pages(struct vm_area_struct *vma, int numpgs)
	{
	int rc;
	struct page **pages;

	pages = kcalloc(numpgs, sizeof(pages[0]), GFP_KERNEL);
	if (pages == NULL)
	return -ENOMEM;

	rc = alloc_xenballooned_pages(numpgs, pages, 0);
	if (rc != 0) {
	pr_warn("%s Could not alloc %d pfns rc:%d\n", __func__,
	numpgs, rc);
	kfree(pages);
	return -ENOMEM;
	}
	BUG_ON(vma->vm_private_data != PRIV_VMA_LOCKED);
	vma->vm_private_data = pages;

	return 0;
	}

	static struct vm_operations_struct privcmd_vm_ops;

	static long privcmd_ioctl_mmap_batch(void __user *udata, int version)
	{
	int ret;
	struct privcmd_mmapbatch_v2 m;
	struct mm_struct *mm = current->mm;
	struct vm_area_struct *vma;
	unsigned long nr_pages;
	LIST_HEAD(pagelist);
	int *err_array = NULL;
	struct mmap_batch_state state;

	if (!xen_initial_domain())
	return -EPERM;

	switch (version) {
	case 1:
	if (copy_from_user(&m, udata, sizeof(struct privcmd_mmapbatch)))
	return -EFAULT;
	/* Returns per-frame error in m.arr. */
	m.err = NULL;
	if (!access_ok(VERIFY_WRITE, m.arr, m.num * sizeof(*m.arr)))
	return -EFAULT;
	break;
	case 2:
	if (copy_from_user(&m, udata, sizeof(struct privcmd_mmapbatch_v2)))
	return -EFAULT;
	/* Returns per-frame error code in m.err. */
	if (!access_ok(VERIFY_WRITE, m.err, m.num * (sizeof(*m.err))))
	return -EFAULT;
	break;
	default:
	return -EINVAL;
	}

	nr_pages = m.num;
	if ((m.num <= 0) \|\| (nr_pages > (LONG_MAX >> PAGE_SHIFT)))
	return -EINVAL;

	ret = gather_array(&pagelist, m.num, sizeof(xen_pfn_t), m.arr);

	if (ret)
	goto out;
	if (list_empty(&pagelist)) {
	ret = -EINVAL;
	goto out;
	}

	err_array = kcalloc(m.num, sizeof(int), GFP_KERNEL);
	if (err_array == NULL) {
	ret = -ENOMEM;
	goto out;
	}

	down_write(&mm->mmap_sem);

	vma = find_vma(mm, m.addr);
	if (!vma \|\|
	vma->vm_ops != &privcmd_vm_ops \|\|
	(m.addr != vma->vm_start) \|\|
	((m.addr + (nr_pages << PAGE_SHIFT)) != vma->vm_end) \|\|
	!privcmd_enforce_singleshot_mapping(vma)) {
	up_write(&mm->mmap_sem);
	ret = -EINVAL;
	goto out;
	}
	if (xen_feature(XENFEAT_auto_translated_physmap)) {
	ret = alloc_empty_pages(vma, m.num);
	if (ret < 0) {
	up_write(&mm->mmap_sem);
	goto out;
	}
	}

	state.domain = m.dom;
	state.vma = vma;
	state.va = m.addr;
	state.index = 0;
	state.global_error = 0;
	state.err = err_array;

	/* mmap_batch_fn guarantees ret == 0 */
	BUG_ON(traverse_pages(m.num, sizeof(xen_pfn_t),
	&pagelist, mmap_batch_fn, &state));

	up_write(&mm->mmap_sem);

	if (version == 1) {
	if (state.global_error) {
	/* Write back errors in second pass. */
	state.user_mfn = (xen_pfn_t *)m.arr;
	state.err = err_array;
	ret = traverse_pages(m.num, sizeof(xen_pfn_t),
	&pagelist, mmap_return_errors_v1, &state);
	} else
	ret = 0;

	} else if (version == 2) {
	ret = __copy_to_user(m.err, err_array, m.num * sizeof(int));
	if (ret)
	ret = -EFAULT;
	}

	/* If we have not had any EFAULT-like global errors then set the global
	* error to -ENOENT if necessary. */
	if ((ret == 0) && (state.global_error == -ENOENT))
	ret = -ENOENT;

	out:
	kfree(err_array);
	free_page_list(&pagelist);

	return ret;
	}

	static long privcmd_ioctl(struct file *file,
	unsigned int cmd, unsigned long data)
	{
	int ret = -ENOSYS;
	void __user udata = (void __user ) data;

	switch (cmd) {
	case IOCTL_PRIVCMD_HYPERCALL:
	ret = privcmd_ioctl_hypercall(udata);
	break;

	case IOCTL_PRIVCMD_MMAP:
	ret = privcmd_ioctl_mmap(udata);
	break;

	case IOCTL_PRIVCMD_MMAPBATCH:
	ret = privcmd_ioctl_mmap_batch(udata, 1);
	break;

	case IOCTL_PRIVCMD_MMAPBATCH_V2:
	ret = privcmd_ioctl_mmap_batch(udata, 2);
	break;

	default:
	ret = -EINVAL;
	break;
	}

	return ret;
	}

	static void privcmd_close(struct vm_area_struct *vma)
	{
	struct page **pages = vma->vm_private_data;
	int numpgs = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;

	if (!xen_feature(XENFEAT_auto_translated_physmap \|\| !numpgs \|\| !pages))
	return;

	xen_unmap_domain_mfn_range(vma, numpgs, pages);
	free_xenballooned_pages(numpgs, pages);
	kfree(pages);
	}

	static int privcmd_fault(struct vm_area_struct vma, struct vm_fault vmf)
	{
	printk(KERN_DEBUG "privcmd_fault: vma=%p %lx-%lx, pgoff=%lx, uv=%p\n",
	vma, vma->vm_start, vma->vm_end,
	vmf->pgoff, vmf->virtual_address);

	return VM_FAULT_SIGBUS;
	}

	static struct vm_operations_struct privcmd_vm_ops = {
	.close = privcmd_close,
	.fault = privcmd_fault
	};

	static int privcmd_mmap(struct file file, struct vm_area_struct vma)
	{
	/* DONTCOPY is essential for Xen because copy_page_range doesn't know
	* how to recreate these mappings */
	vma->vm_flags \|= VM_IO \| VM_PFNMAP \| VM_DONTCOPY \|
	VM_DONTEXPAND \| VM_DONTDUMP;
	vma->vm_ops = &privcmd_vm_ops;
	vma->vm_private_data = NULL;

	return 0;
	}

	static int privcmd_enforce_singleshot_mapping(struct vm_area_struct *vma)
	{
	return !cmpxchg(&vma->vm_private_data, NULL, PRIV_VMA_LOCKED);
	}

	const struct file_operations xen_privcmd_fops = {
	.owner = THIS_MODULE,
	.unlocked_ioctl = privcmd_ioctl,
	.mmap = privcmd_mmap,
	};
	EXPORT_SYMBOL_GPL(xen_privcmd_fops);

	static struct miscdevice privcmd_dev = {
	.minor = MISC_DYNAMIC_MINOR,
	.name = "xen/privcmd",
	.fops = &xen_privcmd_fops,
	};

	static int __init privcmd_init(void)
	{
	int err;

	if (!xen_domain())
	return -ENODEV;

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

	static void __exit privcmd_exit(void)
	{
	misc_deregister(&privcmd_dev);
	}

	module_init(privcmd_init);
	module_exit(privcmd_exit);