kernel/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 = kzalloc(count, GFP_KERNEL);
  84         if (copy_from_user(inmsg, buf, count)) {
  85                 kfree(inmsg);
  86                 return -EFAULT;
  87         }
  88         if (hvt->on_msg(inmsg, count))
  89                 return -EFAULT;
  90         kfree(inmsg);
  91
  92         return count;
  93 }
  94
  95 static unsigned int hvt_op_poll(struct file *file, poll_table *wait)
  96 {
  97         struct hvutil_transport *hvt;
  98
  99         hvt = container_of(file->f_op, struct hvutil_transport, fops);
 100
 101         poll_wait(file, &hvt->outmsg_q, wait);
 102         if (hvt->outmsg_len > 0)
 103                 return POLLIN | POLLRDNORM;
 104
 105         return 0;
 106 }
 107
 108 static int hvt_op_open(struct inode *inode, struct file *file)
 109 {
 110         struct hvutil_transport *hvt;
 111
 112         hvt = container_of(file->f_op, struct hvutil_transport, fops);
 113
 114         /*
 115          * Switching to CHARDEV mode. We switch bach to INIT when device
 116          * gets released.
 117          */
 118         if (hvt->mode == HVUTIL_TRANSPORT_INIT)
 119                 hvt->mode = HVUTIL_TRANSPORT_CHARDEV;
 120         else if (hvt->mode == HVUTIL_TRANSPORT_NETLINK) {
 121                 /*
 122                  * We're switching from netlink communication to using char
 123                  * device. Issue the reset first.
 124                  */
 125                 hvt_reset(hvt);
 126                 hvt->mode = HVUTIL_TRANSPORT_CHARDEV;
 127         } else
 128                 return -EBUSY;
 129
 130         return 0;
 131 }
 132
 133 static int hvt_op_release(struct inode *inode, struct file *file)
 134 {
 135         struct hvutil_transport *hvt;
 136
 137         hvt = container_of(file->f_op, struct hvutil_transport, fops);
 138
 139         hvt->mode = HVUTIL_TRANSPORT_INIT;
 140         /*
 141          * Cleanup message buffers to avoid spurious messages when the daemon
 142          * connects back.
 143          */
 144         hvt_reset(hvt);
 145
 146         return 0;
 147 }
 148
 149 static void hvt_cn_callback(struct cn_msg *msg, struct netlink_skb_parms *nsp)
 150 {
 151         struct hvutil_transport *hvt, *hvt_found = NULL;
 152
 153         spin_lock(&hvt_list_lock);
 154         list_for_each_entry(hvt, &hvt_list, list) {
 155                 if (hvt->cn_id.idx == msg->id.idx &&
 156                     hvt->cn_id.val == msg->id.val) {
 157                         hvt_found = hvt;
 158                         break;
 159                 }
 160         }
 161         spin_unlock(&hvt_list_lock);
 162         if (!hvt_found) {
 163                 pr_warn("hvt_cn_callback: spurious message received!\n");
 164                 return;
 165         }
 166
 167         /*
 168          * Switching to NETLINK mode. Switching to CHARDEV happens when someone
 169          * opens the device.
 170          */
 171         if (hvt->mode == HVUTIL_TRANSPORT_INIT)
 172                 hvt->mode = HVUTIL_TRANSPORT_NETLINK;
 173
 174         if (hvt->mode == HVUTIL_TRANSPORT_NETLINK)
 175                 hvt_found->on_msg(msg->data, msg->len);
 176         else
 177                 pr_warn("hvt_cn_callback: unexpected netlink message!\n");
 178 }
 179
 180 int hvutil_transport_send(struct hvutil_transport *hvt, void *msg, int len)
 181 {
 182         struct cn_msg *cn_msg;
 183         int ret = 0;
 184
 185         if (hvt->mode == HVUTIL_TRANSPORT_INIT) {
 186                 return -EINVAL;
 187         } else if (hvt->mode == HVUTIL_TRANSPORT_NETLINK) {
 188                 cn_msg = kzalloc(sizeof(*cn_msg) + len, GFP_ATOMIC);
 189                 if (!cn_msg)
 190                         return -ENOMEM;
 191                 cn_msg->id.idx = hvt->cn_id.idx;
 192                 cn_msg->id.val = hvt->cn_id.val;
 193                 cn_msg->len = len;
 194                 memcpy(cn_msg->data, msg, len);
 195                 ret = cn_netlink_send(cn_msg, 0, 0, GFP_ATOMIC);
 196                 kfree(cn_msg);
 197                 return ret;
 198         }
 199         /* HVUTIL_TRANSPORT_CHARDEV */
 200         mutex_lock(&hvt->outmsg_lock);
 201         if (hvt->outmsg) {
 202                 /* Previous message wasn't received */
 203                 ret = -EFAULT;
 204                 goto out_unlock;
 205         }
 206         hvt->outmsg = kzalloc(len, GFP_KERNEL);
 207         memcpy(hvt->outmsg, msg, len);
 208         hvt->outmsg_len = len;
 209         wake_up_interruptible(&hvt->outmsg_q);
 210 out_unlock:
 211         mutex_unlock(&hvt->outmsg_lock);
 212         return ret;
 213 }
 214
 215 struct hvutil_transport *hvutil_transport_init(const char *name,
 216                                                u32 cn_idx, u32 cn_val,
 217                                                int (*on_msg)(void *, int),
 218                                                void (*on_reset)(void))
 219 {
 220         struct hvutil_transport *hvt;
 221
 222         hvt = kzalloc(sizeof(*hvt), GFP_KERNEL);
 223         if (!hvt)
 224                 return NULL;
 225
 226         hvt->cn_id.idx = cn_idx;
 227         hvt->cn_id.val = cn_val;
 228
 229         hvt->mdev.minor = MISC_DYNAMIC_MINOR;
 230         hvt->mdev.name = name;
 231
 232         hvt->fops.owner = THIS_MODULE;
 233         hvt->fops.read = hvt_op_read;
 234         hvt->fops.write = hvt_op_write;
 235         hvt->fops.poll = hvt_op_poll;
 236         hvt->fops.open = hvt_op_open;
 237         hvt->fops.release = hvt_op_release;
 238
 239         hvt->mdev.fops = &hvt->fops;
 240
 241         init_waitqueue_head(&hvt->outmsg_q);
 242         mutex_init(&hvt->outmsg_lock);
 243
 244         spin_lock(&hvt_list_lock);
 245         list_add(&hvt->list, &hvt_list);
 246         spin_unlock(&hvt_list_lock);
 247
 248         hvt->on_msg = on_msg;
 249         hvt->on_reset = on_reset;
 250
 251         if (misc_register(&hvt->mdev))
 252                 goto err_free_hvt;
 253
 254         /* Use cn_id.idx/cn_id.val to determine if we need to setup netlink */
 255         if (hvt->cn_id.idx > 0 && hvt->cn_id.val > 0 &&
 256             cn_add_callback(&hvt->cn_id, name, hvt_cn_callback))
 257                 goto err_free_hvt;
 258
 259         return hvt;
 260
 261 err_free_hvt:
 262         kfree(hvt);
 263         return NULL;
 264 }
 265
 266 void hvutil_transport_destroy(struct hvutil_transport *hvt)
 267 {
 268         spin_lock(&hvt_list_lock);
 269         list_del(&hvt->list);
 270         spin_unlock(&hvt_list_lock);
 271         if (hvt->cn_id.idx > 0 && hvt->cn_id.val > 0)
 272                 cn_del_callback(&hvt->cn_id);
 273         misc_deregister(&hvt->mdev);
 274         kfree(hvt->outmsg);
 275         kfree(hvt);
 276 }