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 = nlmsg_hdr(skb);
 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                         return;
 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
 234 /*
 235  * Notification routing.
 236  *
 237  * Gets id and checks if there are notification request for it's idx
 238  * and val.  If there are such requests notify the listeners with the
 239  * given notify event.
 240  *
 241  */
 242 static void cn_notify(struct cb_id *id, u32 notify_event)
 243 {
 244         struct cn_ctl_entry *ent;
 245
 246         mutex_lock(&notify_lock);
 247         list_for_each_entry(ent, &notify_list, notify_entry) {
 248                 int i;
 249                 struct cn_notify_req *req;
 250                 struct cn_ctl_msg *ctl = ent->msg;
 251                 int idx_found, val_found;
 252
 253                 idx_found = val_found = 0;
 254
 255                 req = (struct cn_notify_req *)ctl->data;
 256                 for (i = 0; i < ctl->idx_notify_num; ++i, ++req) {
 257                         if (id->idx >= req->first &&
 258                                         id->idx < req->first + req->range) {
 259                                 idx_found = 1;
 260                                 break;
 261                         }
 262                 }
 263
 264                 for (i = 0; i < ctl->val_notify_num; ++i, ++req) {
 265                         if (id->val >= req->first &&
 266                                         id->val < req->first + req->range) {
 267                                 val_found = 1;
 268                                 break;
 269                         }
 270                 }
 271
 272                 if (idx_found && val_found) {
 273                         struct cn_msg m = { .ack = notify_event, };
 274
 275                         memcpy(&m.id, id, sizeof(m.id));
 276                         cn_netlink_send(&m, ctl->group, GFP_KERNEL);
 277                 }
 278         }
 279         mutex_unlock(&notify_lock);
 280 }
 281
 282 /*
 283  * Callback add routing - adds callback with given ID and name.
 284  * If there is registered callback with the same ID it will not be added.
 285  *
 286  * May sleep.
 287  */
 288 int cn_add_callback(struct cb_id *id, char *name, void (*callback)(void *))
 289 {
 290         int err;
 291         struct cn_dev *dev = &cdev;
 292
 293         if (!cn_already_initialized)
 294                 return -EAGAIN;
 295
 296         err = cn_queue_add_callback(dev->cbdev, name, id, callback);
 297         if (err)
 298                 return err;
 299
 300         cn_notify(id, 0);
 301
 302         return 0;
 303 }
 304 EXPORT_SYMBOL_GPL(cn_add_callback);
 305
 306 /*
 307  * Callback remove routing - removes callback
 308  * with given ID.
 309  * If there is no registered callback with given
 310  * ID nothing happens.
 311  *
 312  * May sleep while waiting for reference counter to become zero.
 313  */
 314 void cn_del_callback(struct cb_id *id)
 315 {
 316         struct cn_dev *dev = &cdev;
 317
 318         cn_queue_del_callback(dev->cbdev, id);
 319         cn_notify(id, 1);
 320 }
 321 EXPORT_SYMBOL_GPL(cn_del_callback);
 322
 323 /*
 324  * Checks two connector's control messages to be the same.
 325  * Returns 1 if they are the same or if the first one is corrupted.
 326  */
 327 static int cn_ctl_msg_equals(struct cn_ctl_msg *m1, struct cn_ctl_msg *m2)
 328 {
 329         int i;
 330         struct cn_notify_req *req1, *req2;
 331
 332         if (m1->idx_notify_num != m2->idx_notify_num)
 333                 return 0;
 334
 335         if (m1->val_notify_num != m2->val_notify_num)
 336                 return 0;
 337
 338         if (m1->len != m2->len)
 339                 return 0;
 340
 341         if ((m1->idx_notify_num + m1->val_notify_num) * sizeof(*req1) !=
 342             m1->len)
 343                 return 1;
 344
 345         req1 = (struct cn_notify_req *)m1->data;
 346         req2 = (struct cn_notify_req *)m2->data;
 347
 348         for (i = 0; i < m1->idx_notify_num; ++i) {
 349                 if (req1->first != req2->first || req1->range != req2->range)
 350                         return 0;
 351                 req1++;
 352                 req2++;
 353         }
 354
 355         for (i = 0; i < m1->val_notify_num; ++i) {
 356                 if (req1->first != req2->first || req1->range != req2->range)
 357                         return 0;
 358                 req1++;
 359                 req2++;
 360         }
 361
 362         return 1;
 363 }
 364
 365 /*
 366  * Main connector device's callback.
 367  *
 368  * Used for notification of a request's processing.
 369  */
 370 static void cn_callback(void *data)
 371 {
 372         struct cn_msg *msg = data;
 373         struct cn_ctl_msg *ctl;
 374         struct cn_ctl_entry *ent;
 375         u32 size;
 376
 377         if (msg->len < sizeof(*ctl))
 378                 return;
 379
 380         ctl = (struct cn_ctl_msg *)msg->data;
 381
 382         size = (sizeof(*ctl) + ((ctl->idx_notify_num +
 383                                  ctl->val_notify_num) *
 384                                 sizeof(struct cn_notify_req)));
 385
 386         if (msg->len != size)
 387                 return;
 388
 389         if (ctl->len + sizeof(*ctl) != msg->len)
 390                 return;
 391
 392         /*
 393          * Remove notification.
 394          */
 395         if (ctl->group == 0) {
 396                 struct cn_ctl_entry *n;
 397
 398                 mutex_lock(&notify_lock);
 399                 list_for_each_entry_safe(ent, n, &notify_list, notify_entry) {
 400                         if (cn_ctl_msg_equals(ent->msg, ctl)) {
 401                                 list_del(&ent->notify_entry);
 402                                 kfree(ent);
 403                         }
 404                 }
 405                 mutex_unlock(&notify_lock);
 406
 407                 return;
 408         }
 409
 410         size += sizeof(*ent);
 411
 412         ent = kzalloc(size, GFP_KERNEL);
 413         if (!ent)
 414                 return;
 415
 416         ent->msg = (struct cn_ctl_msg *)(ent + 1);
 417
 418         memcpy(ent->msg, ctl, size - sizeof(*ent));
 419
 420         mutex_lock(&notify_lock);
 421         list_add(&ent->notify_entry, &notify_list);
 422         mutex_unlock(&notify_lock);
 423 }
 424
 425 static int __devinit cn_init(void)
 426 {
 427         struct cn_dev *dev = &cdev;
 428         int err;
 429
 430         dev->input = cn_rx_skb;
 431         dev->id.idx = cn_idx;
 432         dev->id.val = cn_val;
 433
 434         dev->nls = netlink_kernel_create(&init_net, NETLINK_CONNECTOR,
 435                                          CN_NETLINK_USERS + 0xf,
 436                                          dev->input, NULL, THIS_MODULE);
 437         if (!dev->nls)
 438                 return -EIO;
 439
 440         dev->cbdev = cn_queue_alloc_dev("cqueue", dev->nls);
 441         if (!dev->cbdev) {
 442                 if (dev->nls->sk_socket)
 443                         sock_release(dev->nls->sk_socket);
 444                 return -EINVAL;
 445         }
 446
 447         cn_already_initialized = 1;
 448
 449         err = cn_add_callback(&dev->id, "connector", &cn_callback);
 450         if (err) {
 451                 cn_already_initialized = 0;
 452                 cn_queue_free_dev(dev->cbdev);
 453                 if (dev->nls->sk_socket)
 454                         sock_release(dev->nls->sk_socket);
 455                 return -EINVAL;
 456         }
 457
 458         return 0;
 459 }
 460
 461 static void __devexit cn_fini(void)
 462 {
 463         struct cn_dev *dev = &cdev;
 464
 465         cn_already_initialized = 0;
 466
 467         cn_del_callback(&dev->id);
 468         cn_queue_free_dev(dev->cbdev);
 469         if (dev->nls->sk_socket)
 470                 sock_release(dev->nls->sk_socket);
 471 }
 472
 473 subsys_initcall(cn_init);
 474 module_exit(cn_fini);