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 out_unlock:
  76         mutex_unlock(&hvt->lock);
  77         return ret;
  78 }
  79
  80 static ssize_t hvt_op_write(struct file *file, const char __user *buf,
  81                             size_t count, loff_t *ppos)
  82 {
  83         struct hvutil_transport *hvt;
  84         u8 *inmsg;
  85         int ret;
  86
  87         hvt = container_of(file->f_op, struct hvutil_transport, fops);
  88
  89         inmsg = memdup_user(buf, count);
  90         if (IS_ERR(inmsg))
  91                 return PTR_ERR(inmsg);
  92
  93         if (hvt->mode == HVUTIL_TRANSPORT_DESTROY)
  94                 ret = -EBADF;
  95         else
  96                 ret = hvt->on_msg(inmsg, count);
  97
  98         kfree(inmsg);
  99
 100         return ret ? ret : count;
 101 }
 102
 103 static unsigned int hvt_op_poll(struct file *file, poll_table *wait)
 104 {
 105         struct hvutil_transport *hvt;
 106
 107         hvt = container_of(file->f_op, struct hvutil_transport, fops);
 108
 109         poll_wait(file, &hvt->outmsg_q, wait);
 110
 111         if (hvt->mode == HVUTIL_TRANSPORT_DESTROY)
 112                 return POLLERR | POLLHUP;
 113
 114         if (hvt->outmsg_len > 0)
 115                 return POLLIN | POLLRDNORM;
 116
 117         return 0;
 118 }
 119
 120 static int hvt_op_open(struct inode *inode, struct file *file)
 121 {
 122         struct hvutil_transport *hvt;
 123         int ret = 0;
 124         bool issue_reset = false;
 125
 126         hvt = container_of(file->f_op, struct hvutil_transport, fops);
 127
 128         mutex_lock(&hvt->lock);
 129
 130         if (hvt->mode == HVUTIL_TRANSPORT_DESTROY) {
 131                 ret = -EBADF;
 132         } else if (hvt->mode == HVUTIL_TRANSPORT_INIT) {
 133                 /*
 134                  * Switching to CHARDEV mode. We switch bach to INIT when
 135                  * device gets released.
 136                  */
 137                 hvt->mode = HVUTIL_TRANSPORT_CHARDEV;
 138         }
 139         else if (hvt->mode == HVUTIL_TRANSPORT_NETLINK) {
 140                 /*
 141                  * We're switching from netlink communication to using char
 142                  * device. Issue the reset first.
 143                  */
 144                 issue_reset = true;
 145                 hvt->mode = HVUTIL_TRANSPORT_CHARDEV;
 146         } else {
 147                 ret = -EBUSY;
 148         }
 149
 150         if (issue_reset)
 151                 hvt_reset(hvt);
 152
 153         mutex_unlock(&hvt->lock);
 154
 155         return ret;
 156 }
 157
 158 static void hvt_transport_free(struct hvutil_transport *hvt)
 159 {
 160         misc_deregister(&hvt->mdev);
 161         kfree(hvt->outmsg);
 162         kfree(hvt);
 163 }
 164
 165 static int hvt_op_release(struct inode *inode, struct file *file)
 166 {
 167         struct hvutil_transport *hvt;
 168         int mode_old;
 169
 170         hvt = container_of(file->f_op, struct hvutil_transport, fops);
 171
 172         mutex_lock(&hvt->lock);
 173         mode_old = hvt->mode;
 174         if (hvt->mode != HVUTIL_TRANSPORT_DESTROY)
 175                 hvt->mode = HVUTIL_TRANSPORT_INIT;
 176         /*
 177          * Cleanup message buffers to avoid spurious messages when the daemon
 178          * connects back.
 179          */
 180         hvt_reset(hvt);
 181         mutex_unlock(&hvt->lock);
 182
 183         if (mode_old == HVUTIL_TRANSPORT_DESTROY)
 184                 hvt_transport_free(hvt);
 185
 186         return 0;
 187 }
 188
 189 static void hvt_cn_callback(struct cn_msg *msg, struct netlink_skb_parms *nsp)
 190 {
 191         struct hvutil_transport *hvt, *hvt_found = NULL;
 192
 193         spin_lock(&hvt_list_lock);
 194         list_for_each_entry(hvt, &hvt_list, list) {
 195                 if (hvt->cn_id.idx == msg->id.idx &&
 196                     hvt->cn_id.val == msg->id.val) {
 197                         hvt_found = hvt;
 198                         break;
 199                 }
 200         }
 201         spin_unlock(&hvt_list_lock);
 202         if (!hvt_found) {
 203                 pr_warn("hvt_cn_callback: spurious message received!\n");
 204                 return;
 205         }
 206
 207         /*
 208          * Switching to NETLINK mode. Switching to CHARDEV happens when someone
 209          * opens the device.
 210          */
 211         mutex_lock(&hvt->lock);
 212         if (hvt->mode == HVUTIL_TRANSPORT_INIT)
 213                 hvt->mode = HVUTIL_TRANSPORT_NETLINK;
 214
 215         if (hvt->mode == HVUTIL_TRANSPORT_NETLINK)
 216                 hvt_found->on_msg(msg->data, msg->len);
 217         else
 218                 pr_warn("hvt_cn_callback: unexpected netlink message!\n");
 219         mutex_unlock(&hvt->lock);
 220 }
 221
 222 int hvutil_transport_send(struct hvutil_transport *hvt, void *msg, int len)
 223 {
 224         struct cn_msg *cn_msg;
 225         int ret = 0;
 226
 227         if (hvt->mode == HVUTIL_TRANSPORT_INIT ||
 228             hvt->mode == HVUTIL_TRANSPORT_DESTROY) {
 229                 return -EINVAL;
 230         } else if (hvt->mode == HVUTIL_TRANSPORT_NETLINK) {
 231                 cn_msg = kzalloc(sizeof(*cn_msg) + len, GFP_ATOMIC);
 232                 if (!cn_msg)
 233                         return -ENOMEM;
 234                 cn_msg->id.idx = hvt->cn_id.idx;
 235                 cn_msg->id.val = hvt->cn_id.val;
 236                 cn_msg->len = len;
 237                 memcpy(cn_msg->data, msg, len);
 238                 ret = cn_netlink_send(cn_msg, 0, 0, GFP_ATOMIC);
 239                 kfree(cn_msg);
 240                 return ret;
 241         }
 242         /* HVUTIL_TRANSPORT_CHARDEV */
 243         mutex_lock(&hvt->lock);
 244         if (hvt->mode != HVUTIL_TRANSPORT_CHARDEV) {
 245                 ret = -EINVAL;
 246                 goto out_unlock;
 247         }
 248
 249         if (hvt->outmsg) {
 250                 /* Previous message wasn't received */
 251                 ret = -EFAULT;
 252                 goto out_unlock;
 253         }
 254         hvt->outmsg = kzalloc(len, GFP_KERNEL);
 255         if (hvt->outmsg) {
 256                 memcpy(hvt->outmsg, msg, len);
 257                 hvt->outmsg_len = len;
 258                 wake_up_interruptible(&hvt->outmsg_q);
 259         } else
 260                 ret = -ENOMEM;
 261 out_unlock:
 262         mutex_unlock(&hvt->lock);
 263         return ret;
 264 }
 265
 266 struct hvutil_transport *hvutil_transport_init(const char *name,
 267                                                u32 cn_idx, u32 cn_val,
 268                                                int (*on_msg)(void *, int),
 269                                                void (*on_reset)(void))
 270 {
 271         struct hvutil_transport *hvt;
 272
 273         hvt = kzalloc(sizeof(*hvt), GFP_KERNEL);
 274         if (!hvt)
 275                 return NULL;
 276
 277         hvt->cn_id.idx = cn_idx;
 278         hvt->cn_id.val = cn_val;
 279
 280         hvt->mdev.minor = MISC_DYNAMIC_MINOR;
 281         hvt->mdev.name = name;
 282
 283         hvt->fops.owner = THIS_MODULE;
 284         hvt->fops.read = hvt_op_read;
 285         hvt->fops.write = hvt_op_write;
 286         hvt->fops.poll = hvt_op_poll;
 287         hvt->fops.open = hvt_op_open;
 288         hvt->fops.release = hvt_op_release;
 289
 290         hvt->mdev.fops = &hvt->fops;
 291
 292         init_waitqueue_head(&hvt->outmsg_q);
 293         mutex_init(&hvt->lock);
 294
 295         spin_lock(&hvt_list_lock);
 296         list_add(&hvt->list, &hvt_list);
 297         spin_unlock(&hvt_list_lock);
 298
 299         hvt->on_msg = on_msg;
 300         hvt->on_reset = on_reset;
 301
 302         if (misc_register(&hvt->mdev))
 303                 goto err_free_hvt;
 304
 305         /* Use cn_id.idx/cn_id.val to determine if we need to setup netlink */
 306         if (hvt->cn_id.idx > 0 && hvt->cn_id.val > 0 &&
 307             cn_add_callback(&hvt->cn_id, name, hvt_cn_callback))
 308                 goto err_free_hvt;
 309
 310         return hvt;
 311
 312 err_free_hvt:
 313         spin_lock(&hvt_list_lock);
 314         list_del(&hvt->list);
 315         spin_unlock(&hvt_list_lock);
 316         kfree(hvt);
 317         return NULL;
 318 }
 319
 320 void hvutil_transport_destroy(struct hvutil_transport *hvt)
 321 {
 322         int mode_old;
 323
 324         mutex_lock(&hvt->lock);
 325         mode_old = hvt->mode;
 326         hvt->mode = HVUTIL_TRANSPORT_DESTROY;
 327         wake_up_interruptible(&hvt->outmsg_q);
 328         mutex_unlock(&hvt->lock);
 329
 330         /*
 331          * In case we were in 'chardev' mode we still have an open fd so we
 332          * have to defer freeing the device. Netlink interface can be freed
 333          * now.
 334          */
 335         spin_lock(&hvt_list_lock);
 336         list_del(&hvt->list);
 337         spin_unlock(&hvt_list_lock);
 338         if (hvt->cn_id.idx > 0 && hvt->cn_id.val > 0)
 339                 cn_del_callback(&hvt->cn_id);
 340
 341         if (mode_old != HVUTIL_TRANSPORT_CHARDEV)
 342                 hvt_transport_free(hvt);
 343 }