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 EXPORT_SYMBOL_GPL(cn_netlink_send);
 125
 126 /*
 127  * Callback helper - queues work and setup destructor for given data.
 128  */
 129 static int cn_call_callback(struct cn_msg *msg, void (*destruct_data)(void *), void *data)
 130 {
 131         struct cn_callback_entry *__cbq, *__new_cbq;
 132         struct cn_dev *dev = &cdev;
 133         int err = -ENODEV;
 134
 135         spin_lock_bh(&dev->cbdev->queue_lock);
 136         list_for_each_entry(__cbq, &dev->cbdev->queue_list, callback_entry) {
 137                 if (cn_cb_equal(&__cbq->id.id, &msg->id)) {
 138                         if (likely(!work_pending(&__cbq->work) &&
 139                                         __cbq->data.ddata == NULL)) {
 140                                 __cbq->data.callback_priv = msg;
 141
 142                                 __cbq->data.ddata = data;
 143                                 __cbq->data.destruct_data = destruct_data;
 144
 145                                 if (queue_work(dev->cbdev->cn_queue,
 146                                                         &__cbq->work))
 147                                         err = 0;
 148                         } else {
 149                                 struct cn_callback_data *d;
 150
 151                                 err = -ENOMEM;
 152                                 __new_cbq = kzalloc(sizeof(struct cn_callback_entry), GFP_ATOMIC);
 153                                 if (__new_cbq) {
 154                                         d = &__new_cbq->data;
 155                                         d->callback_priv = msg;
 156                                         d->callback = __cbq->data.callback;
 157                                         d->ddata = data;
 158                                         d->destruct_data = destruct_data;
 159                                         d->free = __new_cbq;
 160
 161                                         INIT_WORK(&__new_cbq->work,
 162                                                         &cn_queue_wrapper);
 163
 164                                         if (queue_work(dev->cbdev->cn_queue,
 165                                                     &__new_cbq->work))
 166                                                 err = 0;
 167                                         else {
 168                                                 kfree(__new_cbq);
 169                                                 err = -EINVAL;
 170                                         }
 171                                 }
 172                         }
 173                         break;
 174                 }
 175         }
 176         spin_unlock_bh(&dev->cbdev->queue_lock);
 177
 178         return err;
 179 }
 180
 181 /*
 182  * Skb receive helper - checks skb and msg size and calls callback
 183  * helper.
 184  */
 185 static int __cn_rx_skb(struct sk_buff *skb, struct nlmsghdr *nlh)
 186 {
 187         u32 pid, uid, seq, group;
 188         struct cn_msg *msg;
 189
 190         pid = NETLINK_CREDS(skb)->pid;
 191         uid = NETLINK_CREDS(skb)->uid;
 192         seq = nlh->nlmsg_seq;
 193         group = NETLINK_CB((skb)).dst_group;
 194         msg = NLMSG_DATA(nlh);
 195
 196         return cn_call_callback(msg, (void (*)(void *))kfree_skb, skb);
 197 }
 198
 199 /*
 200  * Main netlink receiving function.
 201  *
 202  * It checks skb and netlink header sizes and calls the skb receive
 203  * helper with a shared skb.
 204  */
 205 static void cn_rx_skb(struct sk_buff *__skb)
 206 {
 207         struct nlmsghdr *nlh;
 208         u32 len;
 209         int err;
 210         struct sk_buff *skb;
 211
 212         skb = skb_get(__skb);
 213
 214         if (skb->len >= NLMSG_SPACE(0)) {
 215                 nlh = (struct nlmsghdr *)skb->data;
 216
 217                 if (nlh->nlmsg_len < sizeof(struct cn_msg) ||
 218                     skb->len < nlh->nlmsg_len ||
 219                     nlh->nlmsg_len > CONNECTOR_MAX_MSG_SIZE) {
 220                         kfree_skb(skb);
 221                         goto out;
 222                 }
 223
 224                 len = NLMSG_ALIGN(nlh->nlmsg_len);
 225                 if (len > skb->len)
 226                         len = skb->len;
 227
 228                 err = __cn_rx_skb(skb, nlh);
 229                 if (err < 0)
 230                         kfree_skb(skb);
 231         }
 232
 233 out:
 234         kfree_skb(__skb);
 235 }
 236
 237 /*
 238  * Netlink socket input callback - dequeues the skbs and calls the
 239  * main netlink receiving function.
 240  */
 241 static void cn_input(struct sock *sk, int len)
 242 {
 243         struct sk_buff *skb;
 244
 245         while ((skb = skb_dequeue(&sk->sk_receive_queue)) != NULL)
 246                 cn_rx_skb(skb);
 247 }
 248
 249 /*
 250  * Notification routing.
 251  *
 252  * Gets id and checks if there are notification request for it's idx
 253  * and val.  If there are such requests notify the listeners with the
 254  * given notify event.
 255  *
 256  */
 257 static void cn_notify(struct cb_id *id, u32 notify_event)
 258 {
 259         struct cn_ctl_entry *ent;
 260
 261         mutex_lock(&notify_lock);
 262         list_for_each_entry(ent, &notify_list, notify_entry) {
 263                 int i;
 264                 struct cn_notify_req *req;
 265                 struct cn_ctl_msg *ctl = ent->msg;
 266                 int idx_found, val_found;
 267
 268                 idx_found = val_found = 0;
 269
 270                 req = (struct cn_notify_req *)ctl->data;
 271                 for (i = 0; i < ctl->idx_notify_num; ++i, ++req) {
 272                         if (id->idx >= req->first &&
 273                                         id->idx < req->first + req->range) {
 274                                 idx_found = 1;
 275                                 break;
 276                         }
 277                 }
 278
 279                 for (i = 0; i < ctl->val_notify_num; ++i, ++req) {
 280                         if (id->val >= req->first &&
 281                                         id->val < req->first + req->range) {
 282                                 val_found = 1;
 283                                 break;
 284                         }
 285                 }
 286
 287                 if (idx_found && val_found) {
 288                         struct cn_msg m = { .ack = notify_event, };
 289
 290                         memcpy(&m.id, id, sizeof(m.id));
 291                         cn_netlink_send(&m, ctl->group, GFP_KERNEL);
 292                 }
 293         }
 294         mutex_unlock(&notify_lock);
 295 }
 296
 297 /*
 298  * Callback add routing - adds callback with given ID and name.
 299  * If there is registered callback with the same ID it will not be added.
 300  *
 301  * May sleep.
 302  */
 303 int cn_add_callback(struct cb_id *id, char *name, void (*callback)(void *))
 304 {
 305         int err;
 306         struct cn_dev *dev = &cdev;
 307
 308         if (!cn_already_initialized)
 309                 return -EAGAIN;
 310
 311         err = cn_queue_add_callback(dev->cbdev, name, id, callback);
 312         if (err)
 313                 return err;
 314
 315         cn_notify(id, 0);
 316
 317         return 0;
 318 }
 319 EXPORT_SYMBOL_GPL(cn_add_callback);
 320
 321 /*
 322  * Callback remove routing - removes callback
 323  * with given ID.
 324  * If there is no registered callback with given
 325  * ID nothing happens.
 326  *
 327  * May sleep while waiting for reference counter to become zero.
 328  */
 329 void cn_del_callback(struct cb_id *id)
 330 {
 331         struct cn_dev *dev = &cdev;
 332
 333         cn_queue_del_callback(dev->cbdev, id);
 334         cn_notify(id, 1);
 335 }
 336 EXPORT_SYMBOL_GPL(cn_del_callback);
 337
 338 /*
 339  * Checks two connector's control messages to be the same.
 340  * Returns 1 if they are the same or if the first one is corrupted.
 341  */
 342 static int cn_ctl_msg_equals(struct cn_ctl_msg *m1, struct cn_ctl_msg *m2)
 343 {
 344         int i;
 345         struct cn_notify_req *req1, *req2;
 346
 347         if (m1->idx_notify_num != m2->idx_notify_num)
 348                 return 0;
 349
 350         if (m1->val_notify_num != m2->val_notify_num)
 351                 return 0;
 352
 353         if (m1->len != m2->len)
 354                 return 0;
 355
 356         if ((m1->idx_notify_num + m1->val_notify_num) * sizeof(*req1) !=
 357             m1->len)
 358                 return 1;
 359
 360         req1 = (struct cn_notify_req *)m1->data;
 361         req2 = (struct cn_notify_req *)m2->data;
 362
 363         for (i = 0; i < m1->idx_notify_num; ++i) {
 364                 if (req1->first != req2->first || req1->range != req2->range)
 365                         return 0;
 366                 req1++;
 367                 req2++;
 368         }
 369
 370         for (i = 0; i < m1->val_notify_num; ++i) {
 371                 if (req1->first != req2->first || req1->range != req2->range)
 372                         return 0;
 373                 req1++;
 374                 req2++;
 375         }
 376
 377         return 1;
 378 }
 379
 380 /*
 381  * Main connector device's callback.
 382  *
 383  * Used for notification of a request's processing.
 384  */
 385 static void cn_callback(void *data)
 386 {
 387         struct cn_msg *msg = data;
 388         struct cn_ctl_msg *ctl;
 389         struct cn_ctl_entry *ent;
 390         u32 size;
 391
 392         if (msg->len < sizeof(*ctl))
 393                 return;
 394
 395         ctl = (struct cn_ctl_msg *)msg->data;
 396
 397         size = (sizeof(*ctl) + ((ctl->idx_notify_num +
 398                                  ctl->val_notify_num) *
 399                                 sizeof(struct cn_notify_req)));
 400
 401         if (msg->len != size)
 402                 return;
 403
 404         if (ctl->len + sizeof(*ctl) != msg->len)
 405                 return;
 406
 407         /*
 408          * Remove notification.
 409          */
 410         if (ctl->group == 0) {
 411                 struct cn_ctl_entry *n;
 412
 413                 mutex_lock(&notify_lock);
 414                 list_for_each_entry_safe(ent, n, &notify_list, notify_entry) {
 415                         if (cn_ctl_msg_equals(ent->msg, ctl)) {
 416                                 list_del(&ent->notify_entry);
 417                                 kfree(ent);
 418                         }
 419                 }
 420                 mutex_unlock(&notify_lock);
 421
 422                 return;
 423         }
 424
 425         size += sizeof(*ent);
 426
 427         ent = kzalloc(size, GFP_KERNEL);
 428         if (!ent)
 429                 return;
 430
 431         ent->msg = (struct cn_ctl_msg *)(ent + 1);
 432
 433         memcpy(ent->msg, ctl, size - sizeof(*ent));
 434
 435         mutex_lock(&notify_lock);
 436         list_add(&ent->notify_entry, &notify_list);
 437         mutex_unlock(&notify_lock);
 438 }
 439
 440 static int __devinit cn_init(void)
 441 {
 442         struct cn_dev *dev = &cdev;
 443         int err;
 444
 445         dev->input = cn_input;
 446         dev->id.idx = cn_idx;
 447         dev->id.val = cn_val;
 448
 449         dev->nls = netlink_kernel_create(NETLINK_CONNECTOR,
 450                                          CN_NETLINK_USERS + 0xf,
 451                                          dev->input, THIS_MODULE);
 452         if (!dev->nls)
 453                 return -EIO;
 454
 455         dev->cbdev = cn_queue_alloc_dev("cqueue", dev->nls);
 456         if (!dev->cbdev) {
 457                 if (dev->nls->sk_socket)
 458                         sock_release(dev->nls->sk_socket);
 459                 return -EINVAL;
 460         }
 461
 462         cn_already_initialized = 1;
 463
 464         err = cn_add_callback(&dev->id, "connector", &cn_callback);
 465         if (err) {
 466                 cn_already_initialized = 0;
 467                 cn_queue_free_dev(dev->cbdev);
 468                 if (dev->nls->sk_socket)
 469                         sock_release(dev->nls->sk_socket);
 470                 return -EINVAL;
 471         }
 472
 473         return 0;
 474 }
 475
 476 static void __devexit cn_fini(void)
 477 {
 478         struct cn_dev *dev = &cdev;
 479
 480         cn_already_initialized = 0;
 481
 482         cn_del_callback(&dev->id);
 483         cn_queue_free_dev(dev->cbdev);
 484         if (dev->nls->sk_socket)
 485                 sock_release(dev->nls->sk_socket);
 486 }
 487
 488 subsys_initcall(cn_init);
 489 module_exit(cn_fini);