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

#define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt

#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 <linux/moduleparam.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/interface/hvm/dm_op.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)

static unsigned int privcmd_dm_op_max_num = 16;
module_param_named(dm_op_max_nr_bufs, privcmd_dm_op_max_num, uint, 0644);
MODULE_PARM_DESC(dm_op_max_nr_bufs,
                 "Maximum number of buffers per dm_op hypercall");

static unsigned int privcmd_dm_op_buf_max_size = 4096;
module_param_named(dm_op_buf_max_size, privcmd_dm_op_buf_max_size, uint,
                   0644);
MODULE_PARM_DESC(dm_op_buf_max_size,
                 "Maximum size of a dm_op hypercall buffer");

struct privcmd_data {
        domid_t domid;
};

static int privcmd_vma_range_is_mapped(
               struct vm_area_struct *vma,
               unsigned long addr,
               unsigned long nr_pages);

static long privcmd_ioctl_hypercall(struct file *file, void __user *udata)
{
        struct privcmd_data *data = file->private_data;
        struct privcmd_hypercall hypercall;
        long ret;

        /* Disallow arbitrary hypercalls if restricted */
        if (data->domid != DOMID_INVALID)
                return -EPERM;

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

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

        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;
}

/*
 * Similar to traverse_pages, but use each page as a "block" of
 * data to be processed as one unit.
 */
static int traverse_pages_block(unsigned nelem, size_t size,
                                struct list_head *pos,
                                int (*fn)(void *data, int nr, void *state),
                                void *state)
{
        void *pagedata;
        int ret = 0;

        BUG_ON(size > PAGE_SIZE);

        while (nelem) {
                int nr = (PAGE_SIZE/size);
                struct page *page;
                if (nr > nelem)
                        nr = nelem;
                pos = pos->next;
                page = list_entry(pos, struct page, lru);
                pagedata = page_address(page);
                ret = (*fn)(pagedata, nr, state);
                if (ret)
                        break;
                nelem -= nr;
        }

        return ret;
}

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

static int mmap_gfn_range(void *data, void *state)
{
        struct privcmd_mmap_entry *msg = data;
        struct mmap_gfn_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_gfn_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(struct file *file, void __user *udata)
{
        struct privcmd_data *data = file->private_data;
        struct privcmd_mmap mmapcmd;
        struct mm_struct *mm = current->mm;
        struct vm_area_struct *vma;
        int rc;
        LIST_HEAD(pagelist);
        struct mmap_gfn_state state;

        /* 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;

        /* If restriction is in place, check the domid matches */
        if (data->domid != DOMID_INVALID && data->domid != mmapcmd.dom)
                return -EPERM;

        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) || vma->vm_private_data)
                        goto out_up;
                vma->vm_private_data = PRIV_VMA_LOCKED;
        }

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

        rc = traverse_pages(mmapcmd.num, sizeof(struct privcmd_mmap_entry),
                            &pagelist,
                            mmap_gfn_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;
        int version;

        /* User-space gfn array to store errors in the second pass for V1. */
        xen_pfn_t __user *user_gfn;
        /* User-space int array to store errors in the second pass for V2. */
        int __user *user_err;
};

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

        if (xen_feature(XENFEAT_auto_translated_physmap))
                cur_pages = &pages[st->index];

        BUG_ON(nr < 0);
        ret = xen_remap_domain_gfn_array(st->vma, st->va & PAGE_MASK, gfnp, nr,
                                         (int *)gfnp, st->vma->vm_page_prot,
                                         st->domain, cur_pages);

        /* Adjust the global_error? */
        if (ret != nr) {
                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 += XEN_PAGE_SIZE * nr;
        st->index += nr / XEN_PFN_PER_PAGE;

        return 0;
}

static int mmap_return_error(int err, struct mmap_batch_state *st)
{
        int ret;

        if (st->version == 1) {
                if (err) {
                        xen_pfn_t gfn;

                        ret = get_user(gfn, st->user_gfn);
                        if (ret < 0)
                                return ret;
                        /*
                         * V1 encodes the error codes in the 32bit top
                         * nibble of the gfn (with its known
                         * limitations vis-a-vis 64 bit callers).
                         */
                        gfn |= (err == -ENOENT) ?
                                PRIVCMD_MMAPBATCH_PAGED_ERROR :
                                PRIVCMD_MMAPBATCH_MFN_ERROR;
                        return __put_user(gfn, st->user_gfn++);
                } else
                        st->user_gfn++;
        } else { /* st->version == 2 */
                if (err)
                        return __put_user(err, st->user_err++);
                else
                        st->user_err++;
        }

        return 0;
}

static int mmap_return_errors(void *data, int nr, void *state)
{
        struct mmap_batch_state *st = state;
        int *errs = data;
        int i;
        int ret;

        for (i = 0; i < nr; i++) {
                ret = mmap_return_error(errs[i], st);
                if (ret < 0)
                        return ret;
        }
        return 0;
}

/* Allocate pfns that are then mapped with gfns 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);
        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 != NULL);
        vma->vm_private_data = pages;

        return 0;
}

static const struct vm_operations_struct privcmd_vm_ops;

static long privcmd_ioctl_mmap_batch(
        struct file *file, void __user *udata, int version)
{
        struct privcmd_data *data = file->private_data;
        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);
        struct mmap_batch_state state;

        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;
        }

        /* If restriction is in place, check the domid matches */
        if (data->domid != DOMID_INVALID && data->domid != m.dom)
                return -EPERM;

        nr_pages = DIV_ROUND_UP(m.num, XEN_PFN_PER_PAGE);
        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;
        }

        if (version == 2) {
                /* Zero error array now to only copy back actual errors. */
                if (clear_user(m.err, sizeof(int) * m.num)) {
                        ret = -EFAULT;
                        goto out;
                }
        }

        down_write(&mm->mmap_sem);

        vma = find_vma(mm, m.addr);
        if (!vma ||
            vma->vm_ops != &privcmd_vm_ops) {
                ret = -EINVAL;
                goto out_unlock;
        }

        /*
         * Caller must either:
         *
         * Map the whole VMA range, which will also allocate all the
         * pages required for the auto_translated_physmap case.
         *
         * Or
         *
         * Map unmapped holes left from a previous map attempt (e.g.,
         * because those foreign frames were previously paged out).
         */
        if (vma->vm_private_data == NULL) {
                if (m.addr != vma->vm_start ||
                    m.addr + (nr_pages << PAGE_SHIFT) != vma->vm_end) {
                        ret = -EINVAL;
                        goto out_unlock;
                }
                if (xen_feature(XENFEAT_auto_translated_physmap)) {
                        ret = alloc_empty_pages(vma, nr_pages);
                        if (ret < 0)
                                goto out_unlock;
                } else
                        vma->vm_private_data = PRIV_VMA_LOCKED;
        } else {
                if (m.addr < vma->vm_start ||
                    m.addr + (nr_pages << PAGE_SHIFT) > vma->vm_end) {
                        ret = -EINVAL;
                        goto out_unlock;
                }
                if (privcmd_vma_range_is_mapped(vma, m.addr, nr_pages)) {
                        ret = -EINVAL;
                        goto out_unlock;
                }
        }

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

        BUILD_BUG_ON(((PAGE_SIZE / sizeof(xen_pfn_t)) % XEN_PFN_PER_PAGE) != 0);
        /* mmap_batch_fn guarantees ret == 0 */
        BUG_ON(traverse_pages_block(m.num, sizeof(xen_pfn_t),
                                    &pagelist, mmap_batch_fn, &state));

        up_write(&mm->mmap_sem);

        if (state.global_error) {
                /* Write back errors in second pass. */
                state.user_gfn = (xen_pfn_t *)m.arr;
                state.user_err = m.err;
                ret = traverse_pages_block(m.num, sizeof(xen_pfn_t),
                                           &pagelist, mmap_return_errors, &state);
        } else
                ret = 0;

        /* 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:
        free_page_list(&pagelist);
        return ret;

out_unlock:
        up_write(&mm->mmap_sem);
        goto out;
}

static int lock_pages(
        struct privcmd_dm_op_buf kbufs[], unsigned int num,
        struct page *pages[], unsigned int nr_pages)
{
        unsigned int i;

        for (i = 0; i < num; i++) {
                unsigned int requested;
                int pinned;

                requested = DIV_ROUND_UP(
                        offset_in_page(kbufs[i].uptr) + kbufs[i].size,
                        PAGE_SIZE);
                if (requested > nr_pages)
                        return -ENOSPC;

                pinned = get_user_pages_fast(
                        (unsigned long) kbufs[i].uptr,
                        requested, FOLL_WRITE, pages);
                if (pinned < 0)
                        return pinned;

                nr_pages -= pinned;
                pages += pinned;
        }

        return 0;
}

static void unlock_pages(struct page *pages[], unsigned int nr_pages)
{
        unsigned int i;

        if (!pages)
                return;

        for (i = 0; i < nr_pages; i++) {
                if (pages[i])
                        put_page(pages[i]);
        }
}

static long privcmd_ioctl_dm_op(struct file *file, void __user *udata)
{
        struct privcmd_data *data = file->private_data;
        struct privcmd_dm_op kdata;
        struct privcmd_dm_op_buf *kbufs;
        unsigned int nr_pages = 0;
        struct page **pages = NULL;
        struct xen_dm_op_buf *xbufs = NULL;
        unsigned int i;
        long rc;

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

        /* If restriction is in place, check the domid matches */
        if (data->domid != DOMID_INVALID && data->domid != kdata.dom)
                return -EPERM;

        if (kdata.num == 0)
                return 0;

        if (kdata.num > privcmd_dm_op_max_num)
                return -E2BIG;

        kbufs = kcalloc(kdata.num, sizeof(*kbufs), GFP_KERNEL);
        if (!kbufs)
                return -ENOMEM;

        if (copy_from_user(kbufs, kdata.ubufs,
                           sizeof(*kbufs) * kdata.num)) {
                rc = -EFAULT;
                goto out;
        }

        for (i = 0; i < kdata.num; i++) {
                if (kbufs[i].size > privcmd_dm_op_buf_max_size) {
                        rc = -E2BIG;
                        goto out;
                }

                if (!access_ok(VERIFY_WRITE, kbufs[i].uptr,
                               kbufs[i].size)) {
                        rc = -EFAULT;
                        goto out;
                }

                nr_pages += DIV_ROUND_UP(
                        offset_in_page(kbufs[i].uptr) + kbufs[i].size,
                        PAGE_SIZE);
        }

        pages = kcalloc(nr_pages, sizeof(*pages), GFP_KERNEL);
        if (!pages) {
                rc = -ENOMEM;
                goto out;
        }

        xbufs = kcalloc(kdata.num, sizeof(*xbufs), GFP_KERNEL);
        if (!xbufs) {
                rc = -ENOMEM;
                goto out;
        }

        rc = lock_pages(kbufs, kdata.num, pages, nr_pages);
        if (rc)
                goto out;

        for (i = 0; i < kdata.num; i++) {
                set_xen_guest_handle(xbufs[i].h, kbufs[i].uptr);
                xbufs[i].size = kbufs[i].size;
        }

        xen_preemptible_hcall_begin();
        rc = HYPERVISOR_dm_op(kdata.dom, kdata.num, xbufs);
        xen_preemptible_hcall_end();

out:
        unlock_pages(pages, nr_pages);
        kfree(xbufs);
        kfree(pages);
        kfree(kbufs);

        return rc;
}

static long privcmd_ioctl_restrict(struct file *file, void __user *udata)
{
        struct privcmd_data *data = file->private_data;
        domid_t dom;

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

        /* Set restriction to the specified domain, or check it matches */
        if (data->domid == DOMID_INVALID)
                data->domid = dom;
        else if (data->domid != dom)
                return -EINVAL;

        return 0;
}

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

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

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

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

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

        case IOCTL_PRIVCMD_DM_OP:
                ret = privcmd_ioctl_dm_op(file, udata);
                break;

        case IOCTL_PRIVCMD_RESTRICT:
                ret = privcmd_ioctl_restrict(file, udata);
                break;

        default:
                break;
        }

        return ret;
}

static int privcmd_open(struct inode *ino, struct file *file)
{
        struct privcmd_data *data = kzalloc(sizeof(*data), GFP_KERNEL);

        if (!data)
                return -ENOMEM;

        /* DOMID_INVALID implies no restriction */
        data->domid = DOMID_INVALID;

        file->private_data = data;
        return 0;
}

static int privcmd_release(struct inode *ino, struct file *file)
{
        struct privcmd_data *data = file->private_data;

        kfree(data);
        return 0;
}

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

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

        rc = xen_unmap_domain_gfn_range(vma, numgfns, pages);
        if (rc == 0)
                free_xenballooned_pages(numpgs, pages);
        else
                pr_crit("unable to unmap MFN range: leaking %d pages. rc=%d\n",
                        numpgs, rc);
        kfree(pages);
}

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

        return VM_FAULT_SIGBUS;
}

static const 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;
}

/*
 * For MMAPBATCH*. This allows asserting the singleshot mapping
 * on a per pfn/pte basis. Mapping calls that fail with ENOENT
 * can be then retried until success.
 */
static int is_mapped_fn(pte_t *pte, struct page *pmd_page,
                        unsigned long addr, void *data)
{
        return pte_none(*pte) ? 0 : -EBUSY;
}

static int privcmd_vma_range_is_mapped(
                   struct vm_area_struct *vma,
                   unsigned long addr,
                   unsigned long nr_pages)
{
        return apply_to_page_range(vma->vm_mm, addr, nr_pages << PAGE_SHIFT,
                                   is_mapped_fn, NULL) != 0;
}

const struct file_operations xen_privcmd_fops = {
        .owner = THIS_MODULE,
        .unlocked_ioctl = privcmd_ioctl,
        .open = privcmd_open,
        .release = privcmd_release,
        .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) {
                pr_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);