drivers/hv/hv_utils_transport.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Kernel/userspace transport abstraction for Hyper-V util driver.
   4  *
   5  * Copyright (C) 2015, Vitaly Kuznetsov <vkuznets@redhat.com>
   6  */
   7
   8 #include <linux/slab.h>
   9 #include <linux/fs.h>
  10 #include <linux/poll.h>
  11
  12 #include "hyperv_vmbus.h"
  13 #include "hv_utils_transport.h"
  14
  15 static DEFINE_SPINLOCK(hvt_list_lock);
  16 static struct list_head hvt_list = LIST_HEAD_INIT(hvt_list);
  17
  18 static void hvt_reset(struct hvutil_transport *hvt)
  19 {
  20         kfree(hvt->outmsg);
  21         hvt->outmsg = NULL;
  22         hvt->outmsg_len = 0;
  23         if (hvt->on_reset)
  24                 hvt->on_reset();
  25 }
  26
  27 static ssize_t hvt_op_read(struct file *file, char __user *buf,
  28                            size_t count, loff_t *ppos)
  29 {
  30         struct hvutil_transport *hvt;
  31         int ret;
  32
  33         hvt = container_of(file->f_op, struct hvutil_transport, fops);
  34
  35         if (wait_event_interruptible(hvt->outmsg_q, hvt->outmsg_len > 0 ||
  36                                      hvt->mode != HVUTIL_TRANSPORT_CHARDEV))
  37                 return -EINTR;
  38
  39         mutex_lock(&hvt->lock);
  40
  41         if (hvt->mode == HVUTIL_TRANSPORT_DESTROY) {
  42                 ret = -EBADF;
  43                 goto out_unlock;
  44         }
  45
  46         if (!hvt->outmsg) {
  47                 ret = -EAGAIN;
  48                 goto out_unlock;
  49         }
  50
  51         if (count < hvt->outmsg_len) {
  52                 ret = -EINVAL;
  53                 goto out_unlock;
  54         }
  55
  56         if (!copy_to_user(buf, hvt->outmsg, hvt->outmsg_len))
  57                 ret = hvt->outmsg_len;
  58         else
  59                 ret = -EFAULT;
  60
  61         kfree(hvt->outmsg);
  62         hvt->outmsg = NULL;
  63         hvt->outmsg_len = 0;
  64
  65         if (hvt->on_read)
  66                 hvt->on_read();
  67         hvt->on_read = NULL;
  68
  69 out_unlock:
  70         mutex_unlock(&hvt->lock);
  71         return ret;
  72 }
  73
  74 static ssize_t hvt_op_write(struct file *file, const char __user *buf,
  75                             size_t count, loff_t *ppos)
  76 {
  77         struct hvutil_transport *hvt;
  78         u8 *inmsg;
  79         int ret;
  80
  81         hvt = container_of(file->f_op, struct hvutil_transport, fops);
  82
  83         inmsg = memdup_user(buf, count);
  84         if (IS_ERR(inmsg))
  85                 return PTR_ERR(inmsg);
  86
  87         if (hvt->mode == HVUTIL_TRANSPORT_DESTROY)
  88                 ret = -EBADF;
  89         else
  90                 ret = hvt->on_msg(inmsg, count);
  91
  92         kfree(inmsg);
  93
  94         return ret ? ret : count;
  95 }
  96
  97 static __poll_t hvt_op_poll(struct file *file, poll_table *wait)
  98 {
  99         struct hvutil_transport *hvt;
 100
 101         hvt = container_of(file->f_op, struct hvutil_transport, fops);
 102
 103         poll_wait(file, &hvt->outmsg_q, wait);
 104
 105         if (hvt->mode == HVUTIL_TRANSPORT_DESTROY)
 106                 return EPOLLERR | EPOLLHUP;
 107
 108         if (hvt->outmsg_len > 0)
 109                 return EPOLLIN | EPOLLRDNORM;
 110
 111         return 0;
 112 }
 113
 114 static int hvt_op_open(struct inode *inode, struct file *file)
 115 {
 116         struct hvutil_transport *hvt;
 117         int ret = 0;
 118         bool issue_reset = false;
 119
 120         hvt = container_of(file->f_op, struct hvutil_transport, fops);
 121
 122         mutex_lock(&hvt->lock);
 123
 124         if (hvt->mode == HVUTIL_TRANSPORT_DESTROY) {
 125                 ret = -EBADF;
 126         } else if (hvt->mode == HVUTIL_TRANSPORT_INIT) {
 127                 /*
 128                  * Switching to CHARDEV mode. We switch bach to INIT when
 129                  * device gets released.
 130                  */
 131                 hvt->mode = HVUTIL_TRANSPORT_CHARDEV;
 132         }
 133         else if (hvt->mode == HVUTIL_TRANSPORT_NETLINK) {
 134                 /*
 135                  * We're switching from netlink communication to using char
 136                  * device. Issue the reset first.
 137                  */
 138                 issue_reset = true;
 139                 hvt->mode = HVUTIL_TRANSPORT_CHARDEV;
 140         } else {
 141                 ret = -EBUSY;
 142         }
 143
 144         if (issue_reset)
 145                 hvt_reset(hvt);
 146
 147         mutex_unlock(&hvt->lock);
 148
 149         return ret;
 150 }
 151
 152 static void hvt_transport_free(struct hvutil_transport *hvt)
 153 {
 154         misc_deregister(&hvt->mdev);
 155         kfree(hvt->outmsg);
 156         kfree(hvt);
 157 }
 158
 159 static int hvt_op_release(struct inode *inode, struct file *file)
 160 {
 161         struct hvutil_transport *hvt;
 162         int mode_old;
 163
 164         hvt = container_of(file->f_op, struct hvutil_transport, fops);
 165
 166         mutex_lock(&hvt->lock);
 167         mode_old = hvt->mode;
 168         if (hvt->mode != HVUTIL_TRANSPORT_DESTROY)
 169                 hvt->mode = HVUTIL_TRANSPORT_INIT;
 170         /*
 171          * Cleanup message buffers to avoid spurious messages when the daemon
 172          * connects back.
 173          */
 174         hvt_reset(hvt);
 175
 176         if (mode_old == HVUTIL_TRANSPORT_DESTROY)
 177                 complete(&hvt->release);
 178
 179         mutex_unlock(&hvt->lock);
 180
 181         return 0;
 182 }
 183
 184 static void hvt_cn_callback(struct cn_msg *msg, struct netlink_skb_parms *nsp)
 185 {
 186         struct hvutil_transport *hvt, *hvt_found = NULL;
 187
 188         spin_lock(&hvt_list_lock);
 189         list_for_each_entry(hvt, &hvt_list, list) {
 190                 if (hvt->cn_id.idx == msg->id.idx &&
 191                     hvt->cn_id.val == msg->id.val) {
 192                         hvt_found = hvt;
 193                         break;
 194                 }
 195         }
 196         spin_unlock(&hvt_list_lock);
 197         if (!hvt_found) {
 198                 pr_warn("hvt_cn_callback: spurious message received!\n");
 199                 return;
 200         }
 201
 202         /*
 203          * Switching to NETLINK mode. Switching to CHARDEV happens when someone
 204          * opens the device.
 205          */
 206         mutex_lock(&hvt->lock);
 207         if (hvt->mode == HVUTIL_TRANSPORT_INIT)
 208                 hvt->mode = HVUTIL_TRANSPORT_NETLINK;
 209
 210         if (hvt->mode == HVUTIL_TRANSPORT_NETLINK)
 211                 hvt_found->on_msg(msg->data, msg->len);
 212         else
 213                 pr_warn("hvt_cn_callback: unexpected netlink message!\n");
 214         mutex_unlock(&hvt->lock);
 215 }
 216
 217 int hvutil_transport_send(struct hvutil_transport *hvt, void *msg, int len,
 218                           void (*on_read_cb)(void))
 219 {
 220         struct cn_msg *cn_msg;
 221         int ret = 0;
 222
 223         if (hvt->mode == HVUTIL_TRANSPORT_INIT ||
 224             hvt->mode == HVUTIL_TRANSPORT_DESTROY) {
 225                 return -EINVAL;
 226         } else if (hvt->mode == HVUTIL_TRANSPORT_NETLINK) {
 227                 cn_msg = kzalloc(sizeof(*cn_msg) + len, GFP_ATOMIC);
 228                 if (!cn_msg)
 229                         return -ENOMEM;
 230                 cn_msg->id.idx = hvt->cn_id.idx;
 231                 cn_msg->id.val = hvt->cn_id.val;
 232                 cn_msg->len = len;
 233                 memcpy(cn_msg->data, msg, len);
 234                 ret = cn_netlink_send(cn_msg, 0, 0, GFP_ATOMIC);
 235                 kfree(cn_msg);
 236                 /*
 237                  * We don't know when netlink messages are delivered but unlike
 238                  * in CHARDEV mode we're not blocked and we can send next
 239                  * messages right away.
 240                  */
 241                 if (on_read_cb)
 242                         on_read_cb();
 243                 return ret;
 244         }
 245         /* HVUTIL_TRANSPORT_CHARDEV */
 246         mutex_lock(&hvt->lock);
 247         if (hvt->mode != HVUTIL_TRANSPORT_CHARDEV) {
 248                 ret = -EINVAL;
 249                 goto out_unlock;
 250         }
 251
 252         if (hvt->outmsg) {
 253                 /* Previous message wasn't received */
 254                 ret = -EFAULT;
 255                 goto out_unlock;
 256         }
 257         hvt->outmsg = kzalloc(len, GFP_KERNEL);
 258         if (hvt->outmsg) {
 259                 memcpy(hvt->outmsg, msg, len);
 260                 hvt->outmsg_len = len;
 261                 hvt->on_read = on_read_cb;
 262                 wake_up_interruptible(&hvt->outmsg_q);
 263         } else
 264                 ret = -ENOMEM;
 265 out_unlock:
 266         mutex_unlock(&hvt->lock);
 267         return ret;
 268 }
 269
 270 struct hvutil_transport *hvutil_transport_init(const char *name,
 271                                                u32 cn_idx, u32 cn_val,
 272                                                int (*on_msg)(void *, int),
 273                                                void (*on_reset)(void))
 274 {
 275         struct hvutil_transport *hvt;
 276
 277         hvt = kzalloc(sizeof(*hvt), GFP_KERNEL);
 278         if (!hvt)
 279                 return NULL;
 280
 281         hvt->cn_id.idx = cn_idx;
 282         hvt->cn_id.val = cn_val;
 283
 284         hvt->mdev.minor = MISC_DYNAMIC_MINOR;
 285         hvt->mdev.name = name;
 286
 287         hvt->fops.owner = THIS_MODULE;
 288         hvt->fops.read = hvt_op_read;
 289         hvt->fops.write = hvt_op_write;
 290         hvt->fops.poll = hvt_op_poll;
 291         hvt->fops.open = hvt_op_open;
 292         hvt->fops.release = hvt_op_release;
 293
 294         hvt->mdev.fops = &hvt->fops;
 295
 296         init_waitqueue_head(&hvt->outmsg_q);
 297         mutex_init(&hvt->lock);
 298         init_completion(&hvt->release);
 299
 300         spin_lock(&hvt_list_lock);
 301         list_add(&hvt->list, &hvt_list);
 302         spin_unlock(&hvt_list_lock);
 303
 304         hvt->on_msg = on_msg;
 305         hvt->on_reset = on_reset;
 306
 307         if (misc_register(&hvt->mdev))
 308                 goto err_free_hvt;
 309
 310         /* Use cn_id.idx/cn_id.val to determine if we need to setup netlink */
 311         if (hvt->cn_id.idx > 0 && hvt->cn_id.val > 0 &&
 312             cn_add_callback(&hvt->cn_id, name, hvt_cn_callback))
 313                 goto err_free_hvt;
 314
 315         return hvt;
 316
 317 err_free_hvt:
 318         spin_lock(&hvt_list_lock);
 319         list_del(&hvt->list);
 320         spin_unlock(&hvt_list_lock);
 321         kfree(hvt);
 322         return NULL;
 323 }
 324
 325 void hvutil_transport_destroy(struct hvutil_transport *hvt)
 326 {
 327         int mode_old;
 328
 329         mutex_lock(&hvt->lock);
 330         mode_old = hvt->mode;
 331         hvt->mode = HVUTIL_TRANSPORT_DESTROY;
 332         wake_up_interruptible(&hvt->outmsg_q);
 333         mutex_unlock(&hvt->lock);
 334
 335         /*
 336          * In case we were in 'chardev' mode we still have an open fd so we
 337          * have to defer freeing the device. Netlink interface can be freed
 338          * now.
 339          */
 340         spin_lock(&hvt_list_lock);
 341         list_del(&hvt->list);
 342         spin_unlock(&hvt_list_lock);
 343         if (hvt->cn_id.idx > 0 && hvt->cn_id.val > 0)
 344                 cn_del_callback(&hvt->cn_id);
 345
 346         if (mode_old == HVUTIL_TRANSPORT_CHARDEV)
 347                 wait_for_completion(&hvt->release);
 348
 349         hvt_transport_free(hvt);
 350 }