drivers/connector/connector.c

   1 /*
   2  *      connector.c
   3  *
   4  * 2004-2005 Copyright (c) Evgeniy Polyakov <johnpol@2ka.mipt.ru>
   5  * All rights reserved.
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License as published by
   9  * the Free Software Foundation; either version 2 of the License, or
  10  * (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program; if not, write to the Free Software
  19  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  20  */
  21
  22 #include <linux/kernel.h>
  23 #include <linux/module.h>
  24 #include <linux/list.h>
  25 #include <linux/skbuff.h>
  26 #include <linux/netlink.h>
  27 #include <linux/moduleparam.h>
  28 #include <linux/connector.h>
  29 #include <linux/mutex.h>
  30
  31 #include <net/sock.h>
  32
  33 MODULE_LICENSE("GPL");
  34 MODULE_AUTHOR("Evgeniy Polyakov <johnpol@2ka.mipt.ru>");
  35 MODULE_DESCRIPTION("Generic userspace <-> kernelspace connector.");
  36
  37 static u32 cn_idx = CN_IDX_CONNECTOR;
  38 static u32 cn_val = CN_VAL_CONNECTOR;
  39
  40 module_param(cn_idx, uint, 0);
  41 module_param(cn_val, uint, 0);
  42 MODULE_PARM_DESC(cn_idx, "Connector's main device idx.");
  43 MODULE_PARM_DESC(cn_val, "Connector's main device val.");
  44
  45 static DEFINE_MUTEX(notify_lock);
  46 static LIST_HEAD(notify_list);
  47
  48 static struct cn_dev cdev;
  49
  50 int cn_already_initialized = 0;
  51
  52 /*
  53  * msg->seq and msg->ack are used to determine message genealogy.
  54  * When someone sends message it puts there locally unique sequence
  55  * and random acknowledge numbers.  Sequence number may be copied into
  56  * nlmsghdr->nlmsg_seq too.
  57  *
  58  * Sequence number is incremented with each message to be sent.
  59  *
  60  * If we expect reply to our message then the sequence number in
  61  * received message MUST be the same as in original message, and
  62  * acknowledge number MUST be the same + 1.
  63  *
  64  * If we receive a message and its sequence number is not equal to the
  65  * one we are expecting then it is a new message.
  66  *
  67  * If we receive a message and its sequence number is the same as one
  68  * we are expecting but it's acknowledgement number is not equal to
  69  * the acknowledgement number in the original message + 1, then it is
  70  * a new message.
  71  *
  72  */
  73 int cn_netlink_send(struct cn_msg *msg, u32 __group, gfp_t gfp_mask)
  74 {
  75         struct cn_callback_entry *__cbq;
  76         unsigned int size;
  77         struct sk_buff *skb;
  78         struct nlmsghdr *nlh;
  79         struct cn_msg *data;
  80         struct cn_dev *dev = &cdev;
  81         u32 group = 0;
  82         int found = 0;
  83
  84         if (!__group) {
  85                 spin_lock_bh(&dev->cbdev->queue_lock);
  86                 list_for_each_entry(__cbq, &dev->cbdev->queue_list,
  87                                     callback_entry) {
  88                         if (cn_cb_equal(&__cbq->id.id, &msg->id)) {
  89                                 found = 1;
  90                                 group = __cbq->group;
  91                         }
  92                 }
  93                 spin_unlock_bh(&dev->cbdev->queue_lock);
  94
  95                 if (!found)
  96                         return -ENODEV;
  97         } else {
  98                 group = __group;
  99         }
 100
 101         if (!netlink_has_listeners(dev->nls, group))
 102                 return -ESRCH;
 103
 104         size = NLMSG_SPACE(sizeof(*msg) + msg->len);
 105
 106         skb = alloc_skb(size, gfp_mask);
 107         if (!skb)
 108                 return -ENOMEM;
 109
 110         nlh = NLMSG_PUT(skb, 0, msg->seq, NLMSG_DONE, size - sizeof(*nlh));
 111
 112         data = NLMSG_DATA(nlh);
 113
 114         memcpy(data, msg, sizeof(*data) + msg->len);
 115
 116         NETLINK_CB(skb).dst_group = group;
 117
 118         return netlink_broadcast(dev->nls, skb, 0, group, gfp_mask);
 119
 120 nlmsg_failure:
 121         kfree_skb(skb);
 122         return -EINVAL;
 123 }
 124
 125 /*
 126  * Callback helper - queues work and setup destructor for given data.
 127  */
 128 static int cn_call_callback(struct cn_msg *msg, void (*destruct_data)(void *), void *data)
 129 {
 130         struct cn_callback_entry *__cbq;
 131         struct cn_dev *dev = &cdev;
 132         int err = -ENODEV;
 133
 134         spin_lock_bh(&dev->cbdev->queue_lock);
 135         list_for_each_entry(__cbq, &dev->cbdev->queue_list, callback_entry) {
 136                 if (cn_cb_equal(&__cbq->id.id, &msg->id)) {
 137                         if (likely(!test_bit(0, &__cbq->work.pending) &&
 138                                         __cbq->data.ddata == NULL)) {
 139                                 __cbq->data.callback_priv = msg;
 140
 141                                 __cbq->data.ddata = data;
 142                                 __cbq->data.destruct_data = destruct_data;
 143
 144                                 if (queue_work(dev->cbdev->cn_queue,
 145                                                 &__cbq->work))
 146                                         err = 0;
 147                         } else {
 148                                 struct work_struct *w;
 149                                 struct cn_callback_data *d;
 150
 151                                 w = kzalloc(sizeof(*w) + sizeof(*d), GFP_ATOMIC);
 152                                 if (w) {
 153                                         d = (struct cn_callback_data *)(w+1);
 154
 155                                         d->callback_priv = msg;
 156                                         d->callback = __cbq->data.callback;
 157                                         d->ddata = data;
 158                                         d->destruct_data = destruct_data;
 159                                         d->free = w;
 160
 161                                         INIT_LIST_HEAD(&w->entry);
 162                                         w->pending = 0;
 163                                         w->func = &cn_queue_wrapper;
 164                                         w->data = d;
 165                                         init_timer(&w->timer);
 166
 167                                         if (queue_work(dev->cbdev->cn_queue, w))
 168                                                 err = 0;
 169                                         else {
 170                                                 kfree(w);
 171                                                 err = -EINVAL;
 172                                         }
 173                                 } else
 174                                         err = -ENOMEM;
 175                         }
 176                         break;
 177                 }
 178         }
 179         spin_unlock_bh(&dev->cbdev->queue_lock);
 180
 181         return err;
 182 }
 183
 184 /*
 185  * Skb receive helper - checks skb and msg size and calls callback
 186  * helper.
 187  */
 188 static int __cn_rx_skb(struct sk_buff *skb, struct nlmsghdr *nlh)
 189 {
 190         u32 pid, uid, seq, group;
 191         struct cn_msg *msg;
 192
 193         pid = NETLINK_CREDS(skb)->pid;
 194         uid = NETLINK_CREDS(skb)->uid;
 195         seq = nlh->nlmsg_seq;
 196         group = NETLINK_CB((skb)).dst_group;
 197         msg = NLMSG_DATA(nlh);
 198
 199         return cn_call_callback(msg, (void (*)(void *))kfree_skb, skb);
 200 }
 201
 202 /*
 203  * Main netlink receiving function.
 204  *
 205  * It checks skb and netlink header sizes and calls the skb receive
 206  * helper with a shared skb.
 207  */
 208 static void cn_rx_skb(struct sk_buff *__skb)
 209 {
 210         struct nlmsghdr *nlh;
 211         u32 len;
 212         int err;
 213         struct sk_buff *skb;
 214
 215         skb = skb_get(__skb);
 216
 217         if (skb->len >= NLMSG_SPACE(0)) {
 218                 nlh = (struct nlmsghdr *)skb->data;
 219
 220                 if (nlh->nlmsg_len < sizeof(struct cn_msg) ||
 221                     skb->len < nlh->nlmsg_len ||
 222                     nlh->nlmsg_len > CONNECTOR_MAX_MSG_SIZE) {
 223                         kfree_skb(skb);
 224                         goto out;
 225                 }
 226
 227                 len = NLMSG_ALIGN(nlh->nlmsg_len);
 228                 if (len > skb->len)
 229                         len = skb->len;
 230
 231                 err = __cn_rx_skb(skb, nlh);
 232                 if (err < 0)
 233                         kfree_skb(skb);
 234         }
 235
 236 out:
 237         kfree_skb(__skb);
 238 }
 239
 240 /*
 241  * Netlink socket input callback - dequeues the skbs and calls the
 242  * main netlink receiving function.
 243  */
 244 static void cn_input(struct sock *sk, int len)
 245 {
 246         struct sk_buff *skb;
 247
 248         while ((skb = skb_dequeue(&sk->sk_receive_queue)) != NULL)
 249                 cn_rx_skb(skb);
 250 }
 251
 252 /*
 253  * Notification routing.
 254  *
 255  * Gets id and checks if there are notification request for it's idx
 256  * and val.  If there are such requests notify the listeners with the
 257  * given notify event.
 258  *
 259  */
 260 static void cn_notify(struct cb_id *id, u32 notify_event)
 261 {
 262         struct cn_ctl_entry *ent;
 263
 264         mutex_lock(&notify_lock);
 265         list_for_each_entry(ent, &notify_list, notify_entry) {
 266                 int i;
 267                 struct cn_notify_req *req;
 268                 struct cn_ctl_msg *ctl = ent->msg;
 269                 int idx_found, val_found;
 270
 271                 idx_found = val_found = 0;
 272
 273                 req = (struct cn_notify_req *)ctl->data;
 274                 for (i = 0; i < ctl->idx_notify_num; ++i, ++req) {
 275                         if (id->idx >= req->first &&
 276                                         id->idx < req->first + req->range) {
 277                                 idx_found = 1;
 278                                 break;
 279                         }
 280                 }
 281
 282                 for (i = 0; i < ctl->val_notify_num; ++i, ++req) {
 283                         if (id->val >= req->first &&
 284                                         id->val < req->first + req->range) {
 285                                 val_found = 1;
 286                                 break;
 287                         }
 288                 }
 289
 290                 if (idx_found && val_found) {
 291                         struct cn_msg m = { .ack = notify_event, };
 292
 293                         memcpy(&m.id, id, sizeof(m.id));
 294                         cn_netlink_send(&m, ctl->group, GFP_KERNEL);
 295                 }
 296         }
 297         mutex_unlock(&notify_lock);
 298 }
 299
 300 /*
 301  * Callback add routing - adds callback with given ID and name.
 302  * If there is registered callback with the same ID it will not be added.
 303  *
 304  * May sleep.
 305  */
 306 int cn_add_callback(struct cb_id *id, char *name, void (*callback)(void *))
 307 {
 308         int err;
 309         struct cn_dev *dev = &cdev;
 310
 311         if (!cn_already_initialized)
 312                 return -EAGAIN;
 313
 314         err = cn_queue_add_callback(dev->cbdev, name, id, callback);
 315         if (err)
 316                 return err;
 317
 318         cn_notify(id, 0);
 319
 320         return 0;
 321 }
 322
 323 /*
 324  * Callback remove routing - removes callback
 325  * with given ID.
 326  * If there is no registered callback with given
 327  * ID nothing happens.
 328  *
 329  * May sleep while waiting for reference counter to become zero.
 330  */
 331 void cn_del_callback(struct cb_id *id)
 332 {
 333         struct cn_dev *dev = &cdev;
 334
 335         cn_queue_del_callback(dev->cbdev, id);
 336         cn_notify(id, 1);
 337 }
 338
 339 /*
 340  * Checks two connector's control messages to be the same.
 341  * Returns 1 if they are the same or if the first one is corrupted.
 342  */
 343 static int cn_ctl_msg_equals(struct cn_ctl_msg *m1, struct cn_ctl_msg *m2)
 344 {
 345         int i;
 346         struct cn_notify_req *req1, *req2;
 347
 348         if (m1->idx_notify_num != m2->idx_notify_num)
 349                 return 0;
 350
 351         if (m1->val_notify_num != m2->val_notify_num)
 352                 return 0;
 353
 354         if (m1->len != m2->len)
 355                 return 0;
 356
 357         if ((m1->idx_notify_num + m1->val_notify_num) * sizeof(*req1) !=
 358             m1->len)
 359                 return 1;
 360
 361         req1 = (struct cn_notify_req *)m1->data;
 362         req2 = (struct cn_notify_req *)m2->data;
 363
 364         for (i = 0; i < m1->idx_notify_num; ++i) {
 365                 if (req1->first != req2->first || req1->range != req2->range)
 366                         return 0;
 367                 req1++;
 368                 req2++;
 369         }
 370
 371         for (i = 0; i < m1->val_notify_num; ++i) {
 372                 if (req1->first != req2->first || req1->range != req2->range)
 373                         return 0;
 374                 req1++;
 375                 req2++;
 376         }
 377
 378         return 1;
 379 }
 380
 381 /*
 382  * Main connector device's callback.
 383  *
 384  * Used for notification of a request's processing.
 385  */
 386 static void cn_callback(void *data)
 387 {
 388         struct cn_msg *msg = data;
 389         struct cn_ctl_msg *ctl;
 390         struct cn_ctl_entry *ent;
 391         u32 size;
 392
 393         if (msg->len < sizeof(*ctl))
 394                 return;
 395
 396         ctl = (struct cn_ctl_msg *)msg->data;
 397
 398         size = (sizeof(*ctl) + ((ctl->idx_notify_num +
 399                                  ctl->val_notify_num) *
 400                                 sizeof(struct cn_notify_req)));
 401
 402         if (msg->len != size)
 403                 return;
 404
 405         if (ctl->len + sizeof(*ctl) != msg->len)
 406                 return;
 407
 408         /*
 409          * Remove notification.
 410          */
 411         if (ctl->group == 0) {
 412                 struct cn_ctl_entry *n;
 413
 414                 mutex_lock(&notify_lock);
 415                 list_for_each_entry_safe(ent, n, &notify_list, notify_entry) {
 416                         if (cn_ctl_msg_equals(ent->msg, ctl)) {
 417                                 list_del(&ent->notify_entry);
 418                                 kfree(ent);
 419                         }
 420                 }
 421                 mutex_unlock(&notify_lock);
 422
 423                 return;
 424         }
 425
 426         size += sizeof(*ent);
 427
 428         ent = kzalloc(size, GFP_KERNEL);
 429         if (!ent)
 430                 return;
 431
 432         ent->msg = (struct cn_ctl_msg *)(ent + 1);
 433
 434         memcpy(ent->msg, ctl, size - sizeof(*ent));
 435
 436         mutex_lock(&notify_lock);
 437         list_add(&ent->notify_entry, &notify_list);
 438         mutex_unlock(&notify_lock);
 439 }
 440
 441 static int __devinit cn_init(void)
 442 {
 443         struct cn_dev *dev = &cdev;
 444         int err;
 445
 446         dev->input = cn_input;
 447         dev->id.idx = cn_idx;
 448         dev->id.val = cn_val;
 449
 450         dev->nls = netlink_kernel_create(NETLINK_CONNECTOR,
 451                                          CN_NETLINK_USERS + 0xf,
 452                                          dev->input, THIS_MODULE);
 453         if (!dev->nls)
 454                 return -EIO;
 455
 456         dev->cbdev = cn_queue_alloc_dev("cqueue", dev->nls);
 457         if (!dev->cbdev) {
 458                 if (dev->nls->sk_socket)
 459                         sock_release(dev->nls->sk_socket);
 460                 return -EINVAL;
 461         }
 462
 463         cn_already_initialized = 1;
 464
 465         err = cn_add_callback(&dev->id, "connector", &cn_callback);
 466         if (err) {
 467                 cn_already_initialized = 0;
 468                 cn_queue_free_dev(dev->cbdev);
 469                 if (dev->nls->sk_socket)
 470                         sock_release(dev->nls->sk_socket);
 471                 return -EINVAL;
 472         }
 473
 474         return 0;
 475 }
 476
 477 static void __devexit cn_fini(void)
 478 {
 479         struct cn_dev *dev = &cdev;
 480
 481         cn_already_initialized = 0;
 482
 483         cn_del_callback(&dev->id);
 484         cn_queue_free_dev(dev->cbdev);
 485         if (dev->nls->sk_socket)
 486                 sock_release(dev->nls->sk_socket);
 487 }
 488
 489 subsys_initcall(cn_init);
 490 module_exit(cn_fini);
 491
 492 EXPORT_SYMBOL_GPL(cn_add_callback);
 493 EXPORT_SYMBOL_GPL(cn_del_callback);
 494 EXPORT_SYMBOL_GPL(cn_netlink_send);