drivers/hv/hv_utils_transport.c

   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
  25 static DEFINE_SPINLOCK(hvt_list_lock);
  26 static struct list_head hvt_list = LIST_HEAD_INIT(hvt_list);
  27
  28 static 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
  37 static 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
  79 out_unlock:
  80         mutex_unlock(&hvt->lock);
  81         return ret;
  82 }
  83
  84 static 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
 107 static __poll_t 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 EPOLLERR | EPOLLHUP;
 117
 118         if (hvt->outmsg_len > 0)
 119                 return EPOLLIN | EPOLLRDNORM;
 120
 121         return 0;
 122 }
 123
 124 static 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
 162 static void hvt_transport_free(struct hvutil_transport *hvt)
 163 {
 164         misc_deregister(&hvt->mdev);
 165         kfree(hvt->outmsg);
 166         kfree(hvt);
 167 }
 168
 169 static 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
 194 static 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
 227 int 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;
 275 out_unlock:
 276         mutex_unlock(&hvt->lock);
 277         return ret;
 278 }
 279
 280 struct 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
 327 err_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
 335 void 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 }