LXR linux/drivers/hv/hv_utils

   1/*
   2 * Kernel/userspace transport abstraction for Hyper-V util driver.
   3 *
   4 * Copyright (C) 2015, Vitaly Kuznetsov <vkuznets@redhat.com>
   5 *
   6 * This program is free software; you can redistribute it and/or modify it
   7 * under the terms of the GNU General Public License version 2 as published
   8 * by the Free Software Foundation.
   9 *
  10 * This program is distributed in the hope that it will be useful, but
  11 * WITHOUT ANY WARRANTY; without even the implied warranty of
  12 * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
  13 * NON INFRINGEMENT.  See the GNU General Public License for more
  14 * details.
  15 *
  16 */
  17
  18#include <linux/slab.h>
  19#include <linux/fs.h>
  20#include <linux/poll.h>
  21
  22#include "hyperv_vmbus.h"
  23#include "hv_utils_transport.h"
  24
  25static DEFINE_SPINLOCK(hvt_list_lock);
  26static struct list_head hvt_list = LIST_HEAD_INIT(hvt_list);
  27
  28static void hvt_reset(struct hvutil_transport *hvt)
  29{
  30        kfree(hvt->outmsg);
  31        hvt->outmsg = NULL;
  32        hvt->outmsg_len = 0;
  33        if (hvt->on_reset)
  34                hvt->on_reset();
  35}
  36
  37static ssize_t hvt_op_read(struct file *file, char __user *buf,
  38                           size_t count, loff_t *ppos)
  39{
  40        struct hvutil_transport *hvt;
  41        int ret;
  42
  43        hvt = container_of(file->f_op, struct hvutil_transport, fops);
  44
  45        if (wait_event_interruptible(hvt->outmsg_q, hvt->outmsg_len > 0 ||
  46                                     hvt->mode != HVUTIL_TRANSPORT_CHARDEV))
  47                return -EINTR;
  48
  49        mutex_lock(&hvt->lock);
  50
  51        if (hvt->mode == HVUTIL_TRANSPORT_DESTROY) {
  52                ret = -EBADF;
  53                goto out_unlock;
  54        }
  55
  56        if (!hvt->outmsg) {
  57                ret = -EAGAIN;
  58                goto out_unlock;
  59        }
  60
  61        if (count < hvt->outmsg_len) {
  62                ret = -EINVAL;
  63                goto out_unlock;
  64        }
  65
  66        if (!copy_to_user(buf, hvt->outmsg, hvt->outmsg_len))
  67                ret = hvt->outmsg_len;
  68        else
  69                ret = -EFAULT;
  70
  71        kfree(hvt->outmsg);
  72        hvt->outmsg = NULL;
  73        hvt->outmsg_len = 0;
  74
  75        if (hvt->on_read)
  76                hvt->on_read();
  77        hvt->on_read = NULL;
  78
  79out_unlock:
  80        mutex_unlock(&hvt->lock);
  81        return ret;
  82}
  83
  84static ssize_t hvt_op_write(struct file *file, const char __user *buf,
  85                            size_t count, loff_t *ppos)
  86{
  87        struct hvutil_transport *hvt;
  88        u8 *inmsg;
  89        int ret;
  90
  91        hvt = container_of(file->f_op, struct hvutil_transport, fops);
  92
  93        inmsg = memdup_user(buf, count);
  94        if (IS_ERR(inmsg))
  95                return PTR_ERR(inmsg);
  96
  97        if (hvt->mode == HVUTIL_TRANSPORT_DESTROY)
  98                ret = -EBADF;
  99        else
 100                ret = hvt->on_msg(inmsg, count);
 101
 102        kfree(inmsg);
 103
 104        return ret ? ret : count;
 105}
 106
 107static unsigned int hvt_op_poll(struct file *file, poll_table *wait)
 108{
 109        struct hvutil_transport *hvt;
 110
 111        hvt = container_of(file->f_op, struct hvutil_transport, fops);
 112
 113        poll_wait(file, &hvt->outmsg_q, wait);
 114
 115        if (hvt->mode == HVUTIL_TRANSPORT_DESTROY)
 116                return POLLERR | POLLHUP;
 117
 118        if (hvt->outmsg_len > 0)
 119                return POLLIN | POLLRDNORM;
 120
 121        return 0;
 122}
 123
 124static int hvt_op_open(struct inode *inode, struct file *file)
 125{
 126        struct hvutil_transport *hvt;
 127        int ret = 0;
 128        bool issue_reset = false;
 129
 130        hvt = container_of(file->f_op, struct hvutil_transport, fops);
 131
 132        mutex_lock(&hvt->lock);
 133
 134        if (hvt->mode == HVUTIL_TRANSPORT_DESTROY) {
 135                ret = -EBADF;
 136        } else if (hvt->mode == HVUTIL_TRANSPORT_INIT) {
 137                /*
 138                 * Switching to CHARDEV mode. We switch bach to INIT when
 139                 * device gets released.
 140                 */
 141                hvt->mode = HVUTIL_TRANSPORT_CHARDEV;
 142        }
 143        else if (hvt->mode == HVUTIL_TRANSPORT_NETLINK) {
 144                /*
 145                 * We're switching from netlink communication to using char
 146                 * device. Issue the reset first.
 147                 */
 148                issue_reset = true;
 149                hvt->mode = HVUTIL_TRANSPORT_CHARDEV;
 150        } else {
 151                ret = -EBUSY;
 152        }
 153
 154        if (issue_reset)
 155                hvt_reset(hvt);
 156
 157        mutex_unlock(&hvt->lock);
 158
 159        return ret;
 160}
 161
 162static void hvt_transport_free(struct hvutil_transport *hvt)
 163{
 164        misc_deregister(&hvt->mdev);
 165        kfree(hvt->outmsg);
 166        kfree(hvt);
 167}
 168
 169static int hvt_op_release(struct inode *inode, struct file *file)
 170{
 171        struct hvutil_transport *hvt;
 172        int mode_old;
 173
 174        hvt = container_of(file->f_op, struct hvutil_transport, fops);
 175
 176        mutex_lock(&hvt->lock);
 177        mode_old = hvt->mode;
 178        if (hvt->mode != HVUTIL_TRANSPORT_DESTROY)
 179                hvt->mode = HVUTIL_TRANSPORT_INIT;
 180        /*
 181         * Cleanup message buffers to avoid spurious messages when the daemon
 182         * connects back.
 183         */
 184        hvt_reset(hvt);
 185
 186        if (mode_old == HVUTIL_TRANSPORT_DESTROY)
 187                complete(&hvt->release);
 188
 189        mutex_unlock(&hvt->lock);
 190
 191        return 0;
 192}
 193
 194static void hvt_cn_callback(struct cn_msg *msg, struct netlink_skb_parms *nsp)
 195{
 196        struct hvutil_transport *hvt, *hvt_found = NULL;
 197
 198        spin_lock(&hvt_list_lock);
 199        list_for_each_entry(hvt, &hvt_list, list) {
 200                if (hvt->cn_id.idx == msg->id.idx &&
 201                    hvt->cn_id.val == msg->id.val) {
 202                        hvt_found = hvt;
 203                        break;
 204                }
 205        }
 206        spin_unlock(&hvt_list_lock);
 207        if (!hvt_found) {
 208                pr_warn("hvt_cn_callback: spurious message received!\n");
 209                return;
 210        }
 211
 212        /*
 213         * Switching to NETLINK mode. Switching to CHARDEV happens when someone
 214         * opens the device.
 215         */
 216        mutex_lock(&hvt->lock);
 217        if (hvt->mode == HVUTIL_TRANSPORT_INIT)
 218                hvt->mode = HVUTIL_TRANSPORT_NETLINK;
 219
 220        if (hvt->mode == HVUTIL_TRANSPORT_NETLINK)
 221                hvt_found->on_msg(msg->data, msg->len);
 222        else
 223                pr_warn("hvt_cn_callback: unexpected netlink message!\n");
 224        mutex_unlock(&hvt->lock);
 225}
 226
 227int hvutil_transport_send(struct hvutil_transport *hvt, void *msg, int len,
 228                          void (*on_read_cb)(void))
 229{
 230        struct cn_msg *cn_msg;
 231        int ret = 0;
 232
 233        if (hvt->mode == HVUTIL_TRANSPORT_INIT ||
 234            hvt->mode == HVUTIL_TRANSPORT_DESTROY) {
 235                return -EINVAL;
 236        } else if (hvt->mode == HVUTIL_TRANSPORT_NETLINK) {
 237                cn_msg = kzalloc(sizeof(*cn_msg) + len, GFP_ATOMIC);
 238                if (!cn_msg)
 239                        return -ENOMEM;
 240                cn_msg->id.idx = hvt->cn_id.idx;
 241                cn_msg->id.val = hvt->cn_id.val;
 242                cn_msg->len = len;
 243                memcpy(cn_msg->data, msg, len);
 244                ret = cn_netlink_send(cn_msg, 0, 0, GFP_ATOMIC);
 245                kfree(cn_msg);
 246                /*
 247                 * We don't know when netlink messages are delivered but unlike
 248                 * in CHARDEV mode we're not blocked and we can send next
 249                 * messages right away.
 250                 */
 251                if (on_read_cb)
 252                        on_read_cb();
 253                return ret;
 254        }
 255        /* HVUTIL_TRANSPORT_CHARDEV */
 256        mutex_lock(&hvt->lock);
 257        if (hvt->mode != HVUTIL_TRANSPORT_CHARDEV) {
 258                ret = -EINVAL;
 259                goto out_unlock;
 260        }
 261
 262        if (hvt->outmsg) {
 263                /* Previous message wasn't received */
 264                ret = -EFAULT;
 265                goto out_unlock;
 266        }
 267        hvt->outmsg = kzalloc(len, GFP_KERNEL);
 268        if (hvt->outmsg) {
 269                memcpy(hvt->outmsg, msg, len);
 270                hvt->outmsg_len = len;
 271                hvt->on_read = on_read_cb;
 272                wake_up_interruptible(&hvt->outmsg_q);
 273        } else
 274                ret = -ENOMEM;
 275out_unlock:
 276        mutex_unlock(&hvt->lock);
 277        return ret;
 278}
 279
 280struct hvutil_transport *hvutil_transport_init(const char *name,
 281                                               u32 cn_idx, u32 cn_val,
 282                                               int (*on_msg)(void *, int),
 283                                               void (*on_reset)(void))
 284{
 285        struct hvutil_transport *hvt;
 286
 287        hvt = kzalloc(sizeof(*hvt), GFP_KERNEL);
 288        if (!hvt)
 289                return NULL;
 290
 291        hvt->cn_id.idx = cn_idx;
 292        hvt->cn_id.val = cn_val;
 293
 294        hvt->mdev.minor = MISC_DYNAMIC_MINOR;
 295        hvt->mdev.name = name;
 296
 297        hvt->fops.owner = THIS_MODULE;
 298        hvt->fops.read = hvt_op_read;
 299        hvt->fops.write = hvt_op_write;
 300        hvt->fops.poll = hvt_op_poll;
 301        hvt->fops.open = hvt_op_open;
 302        hvt->fops.release = hvt_op_release;
 303
 304        hvt->mdev.fops = &hvt->fops;
 305
 306        init_waitqueue_head(&hvt->outmsg_q);
 307        mutex_init(&hvt->lock);
 308        init_completion(&hvt->release);
 309
 310        spin_lock(&hvt_list_lock);
 311        list_add(&hvt->list, &hvt_list);
 312        spin_unlock(&hvt_list_lock);
 313
 314        hvt->on_msg = on_msg;
 315        hvt->on_reset = on_reset;
 316
 317        if (misc_register(&hvt->mdev))
 318                goto err_free_hvt;
 319
 320        /* Use cn_id.idx/cn_id.val to determine if we need to setup netlink */
 321        if (hvt->cn_id.idx > 0 && hvt->cn_id.val > 0 &&
 322            cn_add_callback(&hvt->cn_id, name, hvt_cn_callback))
 323                goto err_free_hvt;
 324
 325        return hvt;
 326
 327err_free_hvt:
 328        spin_lock(&hvt_list_lock);
 329        list_del(&hvt->list);
 330        spin_unlock(&hvt_list_lock);
 331        kfree(hvt);
 332        return NULL;
 333}
 334
 335void hvutil_transport_destroy(struct hvutil_transport *hvt)
 336{
 337        int mode_old;
 338
 339        mutex_lock(&hvt->lock);
 340        mode_old = hvt->mode;
 341        hvt->mode = HVUTIL_TRANSPORT_DESTROY;
 342        wake_up_interruptible(&hvt->outmsg_q);
 343        mutex_unlock(&hvt->lock);
 344
 345        /*
 346         * In case we were in 'chardev' mode we still have an open fd so we
 347         * have to defer freeing the device. Netlink interface can be freed
 348         * now.
 349         */
 350        spin_lock(&hvt_list_lock);
 351        list_del(&hvt->list);
 352        spin_unlock(&hvt_list_lock);
 353        if (hvt->cn_id.idx > 0 && hvt->cn_id.val > 0)
 354                cn_del_callback(&hvt->cn_id);
 355
 356        if (mode_old == HVUTIL_TRANSPORT_CHARDEV)
 357                wait_for_completion(&hvt->release);
 358
 359        hvt_transport_free(hvt);
 360}
 361