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;
 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(!test_bit(0, &__cbq->work.pending) &&
 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 work_struct *w;
 150                                 struct cn_callback_data *d;
 151
 152                                 w = kzalloc(sizeof(*w) + sizeof(*d), GFP_ATOMIC);
 153                                 if (w) {
 154                                         d = (struct cn_callback_data *)(w+1);
 155
 156                                         d->callback_priv = msg;
 157                                         d->callback = __cbq->data.callback;
 158                                         d->ddata = data;
 159                                         d->destruct_data = destruct_data;
 160                                         d->free = w;
 161
 162                                         INIT_LIST_HEAD(&w->entry);
 163                                         w->pending = 0;
 164                                         w->func = &cn_queue_wrapper;
 165                                         w->data = d;
 166                                         init_timer(&w->timer);
 167
 168                                         if (queue_work(dev->cbdev->cn_queue, w))
 169                                                 err = 0;
 170                                         else {
 171                                                 kfree(w);
 172                                                 err = -EINVAL;
 173                                         }
 174                                 } else
 175                                         err = -ENOMEM;
 176                         }
 177                         break;
 178                 }
 179         }
 180         spin_unlock_bh(&dev->cbdev->queue_lock);
 181
 182         return err;
 183 }
 184
 185 /*
 186  * Skb receive helper - checks skb and msg size and calls callback
 187  * helper.
 188  */
 189 static int __cn_rx_skb(struct sk_buff *skb, struct nlmsghdr *nlh)
 190 {
 191         u32 pid, uid, seq, group;
 192         struct cn_msg *msg;
 193
 194         pid = NETLINK_CREDS(skb)->pid;
 195         uid = NETLINK_CREDS(skb)->uid;
 196         seq = nlh->nlmsg_seq;
 197         group = NETLINK_CB((skb)).dst_group;
 198         msg = NLMSG_DATA(nlh);
 199
 200         return cn_call_callback(msg, (void (*)(void *))kfree_skb, skb);
 201 }
 202
 203 /*
 204  * Main netlink receiving function.
 205  *
 206  * It checks skb and netlink header sizes and calls the skb receive
 207  * helper with a shared skb.
 208  */
 209 static void cn_rx_skb(struct sk_buff *__skb)
 210 {
 211         struct nlmsghdr *nlh;
 212         u32 len;
 213         int err;
 214         struct sk_buff *skb;
 215
 216         skb = skb_get(__skb);
 217
 218         if (skb->len >= NLMSG_SPACE(0)) {
 219                 nlh = (struct nlmsghdr *)skb->data;
 220
 221                 if (nlh->nlmsg_len < sizeof(struct cn_msg) ||
 222                     skb->len < nlh->nlmsg_len ||
 223                     nlh->nlmsg_len > CONNECTOR_MAX_MSG_SIZE) {
 224                         kfree_skb(skb);
 225                         goto out;
 226                 }
 227
 228                 len = NLMSG_ALIGN(nlh->nlmsg_len);
 229                 if (len > skb->len)
 230                         len = skb->len;
 231
 232                 err = __cn_rx_skb(skb, nlh);
 233                 if (err < 0)
 234                         kfree_skb(skb);
 235         }
 236
 237 out:
 238         kfree_skb(__skb);
 239 }
 240
 241 /*
 242  * Netlink socket input callback - dequeues the skbs and calls the
 243  * main netlink receiving function.
 244  */
 245 static void cn_input(struct sock *sk, int len)
 246 {
 247         struct sk_buff *skb;
 248
 249         while ((skb = skb_dequeue(&sk->sk_receive_queue)) != NULL)
 250                 cn_rx_skb(skb);
 251 }
 252
 253 /*
 254  * Notification routing.
 255  *
 256  * Gets id and checks if there are notification request for it's idx
 257  * and val.  If there are such requests notify the listeners with the
 258  * given notify event.
 259  *
 260  */
 261 static void cn_notify(struct cb_id *id, u32 notify_event)
 262 {
 263         struct cn_ctl_entry *ent;
 264
 265         mutex_lock(&notify_lock);
 266         list_for_each_entry(ent, &notify_list, notify_entry) {
 267                 int i;
 268                 struct cn_notify_req *req;
 269                 struct cn_ctl_msg *ctl = ent->msg;
 270                 int idx_found, val_found;
 271
 272                 idx_found = val_found = 0;
 273
 274                 req = (struct cn_notify_req *)ctl->data;
 275                 for (i = 0; i < ctl->idx_notify_num; ++i, ++req) {
 276                         if (id->idx >= req->first &&
 277                                         id->idx < req->first + req->range) {
 278                                 idx_found = 1;
 279                                 break;
 280                         }
 281                 }
 282
 283                 for (i = 0; i < ctl->val_notify_num; ++i, ++req) {
 284                         if (id->val >= req->first &&
 285                                         id->val < req->first + req->range) {
 286                                 val_found = 1;
 287                                 break;
 288                         }
 289                 }
 290
 291                 if (idx_found && val_found) {
 292                         struct cn_msg m = { .ack = notify_event, };
 293
 294                         memcpy(&m.id, id, sizeof(m.id));
 295                         cn_netlink_send(&m, ctl->group, GFP_KERNEL);
 296                 }
 297         }
 298         mutex_unlock(&notify_lock);
 299 }
 300
 301 /*
 302  * Callback add routing - adds callback with given ID and name.
 303  * If there is registered callback with the same ID it will not be added.
 304  *
 305  * May sleep.
 306  */
 307 int cn_add_callback(struct cb_id *id, char *name, void (*callback)(void *))
 308 {
 309         int err;
 310         struct cn_dev *dev = &cdev;
 311
 312         if (!cn_already_initialized)
 313                 return -EAGAIN;
 314
 315         err = cn_queue_add_callback(dev->cbdev, name, id, callback);
 316         if (err)
 317                 return err;
 318
 319         cn_notify(id, 0);
 320
 321         return 0;
 322 }
 323 EXPORT_SYMBOL_GPL(cn_add_callback);
 324
 325 /*
 326  * Callback remove routing - removes callback
 327  * with given ID.
 328  * If there is no registered callback with given
 329  * ID nothing happens.
 330  *
 331  * May sleep while waiting for reference counter to become zero.
 332  */
 333 void cn_del_callback(struct cb_id *id)
 334 {
 335         struct cn_dev *dev = &cdev;
 336
 337         cn_queue_del_callback(dev->cbdev, id);
 338         cn_notify(id, 1);
 339 }
 340 EXPORT_SYMBOL_GPL(cn_del_callback);
 341
 342 /*
 343  * Checks two connector's control messages to be the same.
 344  * Returns 1 if they are the same or if the first one is corrupted.
 345  */
 346 static int cn_ctl_msg_equals(struct cn_ctl_msg *m1, struct cn_ctl_msg *m2)
 347 {
 348         int i;
 349         struct cn_notify_req *req1, *req2;
 350
 351         if (m1->idx_notify_num != m2->idx_notify_num)
 352                 return 0;
 353
 354         if (m1->val_notify_num != m2->val_notify_num)
 355                 return 0;
 356
 357         if (m1->len != m2->len)
 358                 return 0;
 359
 360         if ((m1->idx_notify_num + m1->val_notify_num) * sizeof(*req1) !=
 361             m1->len)
 362                 return 1;
 363
 364         req1 = (struct cn_notify_req *)m1->data;
 365         req2 = (struct cn_notify_req *)m2->data;
 366
 367         for (i = 0; i < m1->idx_notify_num; ++i) {
 368                 if (req1->first != req2->first || req1->range != req2->range)
 369                         return 0;
 370                 req1++;
 371                 req2++;
 372         }
 373
 374         for (i = 0; i < m1->val_notify_num; ++i) {
 375                 if (req1->first != req2->first || req1->range != req2->range)
 376                         return 0;
 377                 req1++;
 378                 req2++;
 379         }
 380
 381         return 1;
 382 }
 383
 384 /*
 385  * Main connector device's callback.
 386  *
 387  * Used for notification of a request's processing.
 388  */
 389 static void cn_callback(void *data)
 390 {
 391         struct cn_msg *msg = data;
 392         struct cn_ctl_msg *ctl;
 393         struct cn_ctl_entry *ent;
 394         u32 size;
 395
 396         if (msg->len < sizeof(*ctl))
 397                 return;
 398
 399         ctl = (struct cn_ctl_msg *)msg->data;
 400
 401         size = (sizeof(*ctl) + ((ctl->idx_notify_num +
 402                                  ctl->val_notify_num) *
 403                                 sizeof(struct cn_notify_req)));
 404
 405         if (msg->len != size)
 406                 return;
 407
 408         if (ctl->len + sizeof(*ctl) != msg->len)
 409                 return;
 410
 411         /*
 412          * Remove notification.
 413          */
 414         if (ctl->group == 0) {
 415                 struct cn_ctl_entry *n;
 416
 417                 mutex_lock(&notify_lock);
 418                 list_for_each_entry_safe(ent, n, &notify_list, notify_entry) {
 419                         if (cn_ctl_msg_equals(ent->msg, ctl)) {
 420                                 list_del(&ent->notify_entry);
 421                                 kfree(ent);
 422                         }
 423                 }
 424                 mutex_unlock(&notify_lock);
 425
 426                 return;
 427         }
 428
 429         size += sizeof(*ent);
 430
 431         ent = kzalloc(size, GFP_KERNEL);
 432         if (!ent)
 433                 return;
 434
 435         ent->msg = (struct cn_ctl_msg *)(ent + 1);
 436
 437         memcpy(ent->msg, ctl, size - sizeof(*ent));
 438
 439         mutex_lock(&notify_lock);
 440         list_add(&ent->notify_entry, &notify_list);
 441         mutex_unlock(&notify_lock);
 442 }
 443
 444 static int __devinit cn_init(void)
 445 {
 446         struct cn_dev *dev = &cdev;
 447         int err;
 448
 449         dev->input = cn_input;
 450         dev->id.idx = cn_idx;
 451         dev->id.val = cn_val;
 452
 453         dev->nls = netlink_kernel_create(NETLINK_CONNECTOR,
 454                                          CN_NETLINK_USERS + 0xf,
 455                                          dev->input, THIS_MODULE);
 456         if (!dev->nls)
 457                 return -EIO;
 458
 459         dev->cbdev = cn_queue_alloc_dev("cqueue", dev->nls);
 460         if (!dev->cbdev) {
 461                 if (dev->nls->sk_socket)
 462                         sock_release(dev->nls->sk_socket);
 463                 return -EINVAL;
 464         }
 465
 466         cn_already_initialized = 1;
 467
 468         err = cn_add_callback(&dev->id, "connector", &cn_callback);
 469         if (err) {
 470                 cn_already_initialized = 0;
 471                 cn_queue_free_dev(dev->cbdev);
 472                 if (dev->nls->sk_socket)
 473                         sock_release(dev->nls->sk_socket);
 474                 return -EINVAL;
 475         }
 476
 477         return 0;
 478 }
 479
 480 static void __devexit cn_fini(void)
 481 {
 482         struct cn_dev *dev = &cdev;
 483
 484         cn_already_initialized = 0;
 485
 486         cn_del_callback(&dev->id);
 487         cn_queue_free_dev(dev->cbdev);
 488         if (dev->nls->sk_socket)
 489                 sock_release(dev->nls->sk_socket);
 490 }
 491
 492 subsys_initcall(cn_init);
 493 module_exit(cn_fini);