/******************************************************************************
 * 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 <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;

        /* 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;
        int version;

        /* User-space mfn array to store errors in the second pass for V1. */
        xen_pfn_t __user *user_mfn;
        /* 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 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. */
        if (st->version == 1) {
                if (ret < 0) {
                        /*
                         * V1 encodes the error codes in the 32bit top nibble of the
                         * mfn (with its known limitations vis-a-vis 64 bit callers).
                         */
                        *mfnp |= (ret == -ENOENT) ?
                                                PRIVCMD_MMAPBATCH_PAGED_ERROR :
                                                PRIVCMD_MMAPBATCH_MFN_ERROR;
                }
        } else { /* st->version == 2 */
                *((int *) mfnp) = 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(void *data, void *state)
{
        struct mmap_batch_state *st = state;

        if (st->version == 1) {
                xen_pfn_t mfnp = *((xen_pfn_t *) data);
                if (mfnp & PRIVCMD_MMAPBATCH_MFN_ERROR)
                        return __put_user(mfnp, st->user_mfn++);
                else
                        st->user_mfn++;
        } else { /* st->version == 2 */
                int err = *((int *) data);
                if (err)
                        return __put_user(err, st->user_err++);
                else
                        st->user_err++;
        }

        return 0;
}

/* 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);
        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;
        }

        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;
        }

        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 ||
            (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.version       = version;

        /* 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 (state.global_error) {
                /* Write back errors in second pass. */
                state.user_mfn = (xen_pfn_t *)m.arr;
                state.user_err = m.err;
                ret = traverse_pages(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;
}

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) {
                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);