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         mutex_lock(&hvt->outmsg_lock);
  31         kfree(hvt->outmsg);
  32         hvt->outmsg = NULL;
  33         hvt->outmsg_len = 0;
  34         mutex_unlock(&hvt->outmsg_lock);
  35         if (hvt->on_reset)
  36                 hvt->on_reset();
  37 }
  38
  39 static ssize_t hvt_op_read(struct file *file, char __user *buf,
  40                            size_t count, loff_t *ppos)
  41 {
  42         struct hvutil_transport *hvt;
  43         int ret;
  44
  45         hvt = container_of(file->f_op, struct hvutil_transport, fops);
  46
  47         if (wait_event_interruptible(hvt->outmsg_q, hvt->outmsg_len > 0))
  48                 return -EINTR;
  49
  50         mutex_lock(&hvt->outmsg_lock);
  51         if (!hvt->outmsg) {
  52                 ret = -EAGAIN;
  53                 goto out_unlock;
  54         }
  55
  56         if (count < hvt->outmsg_len) {
  57                 ret = -EINVAL;
  58                 goto out_unlock;
  59         }
  60
  61         if (!copy_to_user(buf, hvt->outmsg, hvt->outmsg_len))
  62                 ret = hvt->outmsg_len;
  63         else
  64                 ret = -EFAULT;
  65
  66         kfree(hvt->outmsg);
  67         hvt->outmsg = NULL;
  68         hvt->outmsg_len = 0;
  69
  70 out_unlock:
  71         mutex_unlock(&hvt->outmsg_lock);
  72         return ret;
  73 }
  74
  75 static ssize_t hvt_op_write(struct file *file, const char __user *buf,
  76                             size_t count, loff_t *ppos)
  77 {
  78         struct hvutil_transport *hvt;
  79         u8 *inmsg;
  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->on_msg(inmsg, count))
  88                 return -EFAULT;
  89         kfree(inmsg);
  90
  91         return count;
  92 }
  93
  94 static unsigned int hvt_op_poll(struct file *file, poll_table *wait)
  95 {
  96         struct hvutil_transport *hvt;
  97
  98         hvt = container_of(file->f_op, struct hvutil_transport, fops);
  99
 100         poll_wait(file, &hvt->outmsg_q, wait);
 101         if (hvt->outmsg_len > 0)
 102                 return POLLIN | POLLRDNORM;
 103
 104         return 0;
 105 }
 106
 107 static int hvt_op_open(struct inode *inode, struct file *file)
 108 {
 109         struct hvutil_transport *hvt;
 110
 111         hvt = container_of(file->f_op, struct hvutil_transport, fops);
 112
 113         /*
 114          * Switching to CHARDEV mode. We switch bach to INIT when device
 115          * gets released.
 116          */
 117         if (hvt->mode == HVUTIL_TRANSPORT_INIT)
 118                 hvt->mode = HVUTIL_TRANSPORT_CHARDEV;
 119         else if (hvt->mode == HVUTIL_TRANSPORT_NETLINK) {
 120                 /*
 121                  * We're switching from netlink communication to using char
 122                  * device. Issue the reset first.
 123                  */
 124                 hvt_reset(hvt);
 125                 hvt->mode = HVUTIL_TRANSPORT_CHARDEV;
 126         } else
 127                 return -EBUSY;
 128
 129         return 0;
 130 }
 131
 132 static int hvt_op_release(struct inode *inode, struct file *file)
 133 {
 134         struct hvutil_transport *hvt;
 135
 136         hvt = container_of(file->f_op, struct hvutil_transport, fops);
 137
 138         hvt->mode = HVUTIL_TRANSPORT_INIT;
 139         /*
 140          * Cleanup message buffers to avoid spurious messages when the daemon
 141          * connects back.
 142          */
 143         hvt_reset(hvt);
 144
 145         return 0;
 146 }
 147
 148 static void hvt_cn_callback(struct cn_msg *msg, struct netlink_skb_parms *nsp)
 149 {
 150         struct hvutil_transport *hvt, *hvt_found = NULL;
 151
 152         spin_lock(&hvt_list_lock);
 153         list_for_each_entry(hvt, &hvt_list, list) {
 154                 if (hvt->cn_id.idx == msg->id.idx &&
 155                     hvt->cn_id.val == msg->id.val) {
 156                         hvt_found = hvt;
 157                         break;
 158                 }
 159         }
 160         spin_unlock(&hvt_list_lock);
 161         if (!hvt_found) {
 162                 pr_warn("hvt_cn_callback: spurious message received!\n");
 163                 return;
 164         }
 165
 166         /*
 167          * Switching to NETLINK mode. Switching to CHARDEV happens when someone
 168          * opens the device.
 169          */
 170         if (hvt->mode == HVUTIL_TRANSPORT_INIT)
 171                 hvt->mode = HVUTIL_TRANSPORT_NETLINK;
 172
 173         if (hvt->mode == HVUTIL_TRANSPORT_NETLINK)
 174                 hvt_found->on_msg(msg->data, msg->len);
 175         else
 176                 pr_warn("hvt_cn_callback: unexpected netlink message!\n");
 177 }
 178
 179 int hvutil_transport_send(struct hvutil_transport *hvt, void *msg, int len)
 180 {
 181         struct cn_msg *cn_msg;
 182         int ret = 0;
 183
 184         if (hvt->mode == HVUTIL_TRANSPORT_INIT) {
 185                 return -EINVAL;
 186         } else if (hvt->mode == HVUTIL_TRANSPORT_NETLINK) {
 187                 cn_msg = kzalloc(sizeof(*cn_msg) + len, GFP_ATOMIC);
 188                 if (!cn_msg)
 189                         return -ENOMEM;
 190                 cn_msg->id.idx = hvt->cn_id.idx;
 191                 cn_msg->id.val = hvt->cn_id.val;
 192                 cn_msg->len = len;
 193                 memcpy(cn_msg->data, msg, len);
 194                 ret = cn_netlink_send(cn_msg, 0, 0, GFP_ATOMIC);
 195                 kfree(cn_msg);
 196                 return ret;
 197         }
 198         /* HVUTIL_TRANSPORT_CHARDEV */
 199         mutex_lock(&hvt->outmsg_lock);
 200         if (hvt->outmsg) {
 201                 /* Previous message wasn't received */
 202                 ret = -EFAULT;
 203                 goto out_unlock;
 204         }
 205         hvt->outmsg = kzalloc(len, GFP_KERNEL);
 206         if (hvt->outmsg) {
 207                 memcpy(hvt->outmsg, msg, len);
 208                 hvt->outmsg_len = len;
 209                 wake_up_interruptible(&hvt->outmsg_q);
 210         } else
 211                 ret = -ENOMEM;
 212 out_unlock:
 213         mutex_unlock(&hvt->outmsg_lock);
 214         return ret;
 215 }
 216
 217 struct hvutil_transport *hvutil_transport_init(const char *name,
 218                                                u32 cn_idx, u32 cn_val,
 219                                                int (*on_msg)(void *, int),
 220                                                void (*on_reset)(void))
 221 {
 222         struct hvutil_transport *hvt;
 223
 224         hvt = kzalloc(sizeof(*hvt), GFP_KERNEL);
 225         if (!hvt)
 226                 return NULL;
 227
 228         hvt->cn_id.idx = cn_idx;
 229         hvt->cn_id.val = cn_val;
 230
 231         hvt->mdev.minor = MISC_DYNAMIC_MINOR;
 232         hvt->mdev.name = name;
 233
 234         hvt->fops.owner = THIS_MODULE;
 235         hvt->fops.read = hvt_op_read;
 236         hvt->fops.write = hvt_op_write;
 237         hvt->fops.poll = hvt_op_poll;
 238         hvt->fops.open = hvt_op_open;
 239         hvt->fops.release = hvt_op_release;
 240
 241         hvt->mdev.fops = &hvt->fops;
 242
 243         init_waitqueue_head(&hvt->outmsg_q);
 244         mutex_init(&hvt->outmsg_lock);
 245
 246         spin_lock(&hvt_list_lock);
 247         list_add(&hvt->list, &hvt_list);
 248         spin_unlock(&hvt_list_lock);
 249
 250         hvt->on_msg = on_msg;
 251         hvt->on_reset = on_reset;
 252
 253         if (misc_register(&hvt->mdev))
 254                 goto err_free_hvt;
 255
 256         /* Use cn_id.idx/cn_id.val to determine if we need to setup netlink */
 257         if (hvt->cn_id.idx > 0 && hvt->cn_id.val > 0 &&
 258             cn_add_callback(&hvt->cn_id, name, hvt_cn_callback))
 259                 goto err_free_hvt;
 260
 261         return hvt;
 262
 263 err_free_hvt:
 264         kfree(hvt);
 265         return NULL;
 266 }
 267
 268 void hvutil_transport_destroy(struct hvutil_transport *hvt)
 269 {
 270         spin_lock(&hvt_list_lock);
 271         list_del(&hvt->list);
 272         spin_unlock(&hvt_list_lock);
 273         if (hvt->cn_id.idx > 0 && hvt->cn_id.val > 0)
 274                 cn_del_callback(&hvt->cn_id);
 275         misc_deregister(&hvt->mdev);
 276         kfree(hvt->outmsg);
 277         kfree(hvt);
 278 }