xen: Add privcmd device driver

Access to arbitrary hypercalls is currently provided via xenfs. This
adds a standard character device to handle this. The support in xenfs
remains for backward compatibility and uses the device driver code.

Signed-off-by: Bastian Blank <waldi@debian.org>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

1 files changed, 437 insertions, 0 deletions

diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c
new file mode 100644
index 000000000000..4e8d3da89ad5
--- /dev/null
+++ b/drivers/xen/privcmd.c
@@ -0,0 +1,437 @@
+/******************************************************************************
+ * 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 "privcmd.h"
+
+MODULE_LICENSE("GPL");
+
+#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,
+                        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);
+        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;
+
+        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 err;
+
+        xen_pfn_t __user *user;
+};
+
+static int mmap_batch_fn(void *data, void *state)
+{
+        xen_pfn_t *mfnp = data;
+        struct mmap_batch_state *st = state;
+
+        if (xen_remap_domain_mfn_range(st->vma, st->va & PAGE_MASK, *mfnp, 1,
+                                       st->vma->vm_page_prot, st->domain) < 0) {
+                *mfnp |= 0xf0000000U;
+                st->err++;
+        }
+        st->va += PAGE_SIZE;
+
+        return 0;
+}
+
+static int mmap_return_errors(void *data, void *state)
+{
+        xen_pfn_t *mfnp = data;
+        struct mmap_batch_state *st = state;
+
+        return put_user(*mfnp, st->user++);
+}
+
+static struct vm_operations_struct privcmd_vm_ops;
+
+static long privcmd_ioctl_mmap_batch(void __user *udata)
+{
+        int ret;
+        struct privcmd_mmapbatch m;
+        struct mm_struct *mm = current->mm;
+        struct vm_area_struct *vma;
+        unsigned long nr_pages;
+        LIST_HEAD(pagelist);
+        struct mmap_batch_state state;
+
+        if (!xen_initial_domain())
+                return -EPERM;
+
+        if (copy_from_user(&m, udata, sizeof(m)))
+                return -EFAULT;
+
+        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 || list_empty(&pagelist))
+                goto out;
+
+        down_write(&mm->mmap_sem);
+
+        vma = find_vma(mm, m.addr);
+        ret = -EINVAL;
+        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);
+                goto out;
+        }
+
+        state.domain = m.dom;
+        state.vma = vma;
+        state.va = m.addr;
+        state.err = 0;
+
+        ret = traverse_pages(m.num, sizeof(xen_pfn_t),
+                             &pagelist, mmap_batch_fn, &state);
+
+        up_write(&mm->mmap_sem);
+
+        if (state.err > 0) {
+                state.user = m.arr;
+                ret = traverse_pages(m.num, sizeof(xen_pfn_t),
+                               &pagelist,
+                               mmap_return_errors, &state);
+        }
+
+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);
+                break;
+
+        default:
+                ret = -EINVAL;
+                break;
+        }
+
+        return ret;
+}
+
+#ifndef HAVE_ARCH_PRIVCMD_MMAP
+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 = {
+        .fault = privcmd_fault
+};
+
+static int privcmd_mmap(struct file *file, struct vm_area_struct *vma)
+{
+        /* Unsupported for auto-translate guests. */
+        if (xen_feature(XENFEAT_auto_translated_physmap))
+                return -ENOSYS;
+
+        /* DONTCOPY is essential for Xen because copy_page_range doesn't know
+         * how to recreate these mappings */
+        vma->vm_flags |= VM_RESERVED | VM_IO | VM_DONTCOPY | VM_PFNMAP;
+        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 (xchg(&vma->vm_private_data, (void *)1) == NULL);
+}
+#endif
+
+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);