drivers/connector/connector.c

   1 /*
   2  *      connector.c
   3  *
   4  * 2004+ Copyright (c) Evgeniy Polyakov <zbr@ioremap.net>
   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/slab.h>
  30 #include <linux/mutex.h>
  31 #include <linux/proc_fs.h>
  32 #include <linux/spinlock.h>
  33
  34 #include <net/sock.h>
  35
  36 MODULE_LICENSE("GPL");
  37 MODULE_AUTHOR("Evgeniy Polyakov <zbr@ioremap.net>");
  38 MODULE_DESCRIPTION("Generic userspace <-> kernelspace connector.");
  39
  40 static struct cn_dev cdev;
  41
  42 static int cn_already_initialized;
  43
  44 /*
  45  * msg->seq and msg->ack are used to determine message genealogy.
  46  * When someone sends message it puts there locally unique sequence
  47  * and random acknowledge numbers.  Sequence number may be copied into
  48  * nlmsghdr->nlmsg_seq too.
  49  *
  50  * Sequence number is incremented with each message to be sent.
  51  *
  52  * If we expect reply to our message then the sequence number in
  53  * received message MUST be the same as in original message, and
  54  * acknowledge number MUST be the same + 1.
  55  *
  56  * If we receive a message and its sequence number is not equal to the
  57  * one we are expecting then it is a new message.
  58  *
  59  * If we receive a message and its sequence number is the same as one
  60  * we are expecting but it's acknowledgement number is not equal to
  61  * the acknowledgement number in the original message + 1, then it is
  62  * a new message.
  63  *
  64  */
  65 int cn_netlink_send(struct cn_msg *msg, u32 __group, gfp_t gfp_mask)
  66 {
  67         struct cn_callback_entry *__cbq;
  68         unsigned int size;
  69         struct sk_buff *skb;
  70         struct nlmsghdr *nlh;
  71         struct cn_msg *data;
  72         struct cn_dev *dev = &cdev;
  73         u32 group = 0;
  74         int found = 0;
  75
  76         if (!__group) {
  77                 spin_lock_bh(&dev->cbdev->queue_lock);
  78                 list_for_each_entry(__cbq, &dev->cbdev->queue_list,
  79                                     callback_entry) {
  80                         if (cn_cb_equal(&__cbq->id.id, &msg->id)) {
  81                                 found = 1;
  82                                 group = __cbq->group;
  83                                 break;
  84                         }
  85                 }
  86                 spin_unlock_bh(&dev->cbdev->queue_lock);
  87
  88                 if (!found)
  89                         return -ENODEV;
  90         } else {
  91                 group = __group;
  92         }
  93
  94         if (!netlink_has_listeners(dev->nls, group))
  95                 return -ESRCH;
  96
  97         size = NLMSG_SPACE(sizeof(*msg) + msg->len);
  98
  99         skb = alloc_skb(size, gfp_mask);
 100         if (!skb)
 101                 return -ENOMEM;
 102
 103         nlh = NLMSG_PUT(skb, 0, msg->seq, NLMSG_DONE, size - sizeof(*nlh));
 104
 105         data = NLMSG_DATA(nlh);
 106
 107         memcpy(data, msg, sizeof(*data) + msg->len);
 108
 109         NETLINK_CB(skb).dst_group = group;
 110
 111         return netlink_broadcast(dev->nls, skb, 0, group, gfp_mask);
 112
 113 nlmsg_failure:
 114         kfree_skb(skb);
 115         return -EINVAL;
 116 }
 117 EXPORT_SYMBOL_GPL(cn_netlink_send);
 118
 119 /*
 120  * Callback helper - queues work and setup destructor for given data.
 121  */
 122 static int cn_call_callback(struct sk_buff *skb)
 123 {
 124         struct cn_callback_entry *__cbq, *__new_cbq;
 125         struct cn_dev *dev = &cdev;
 126         struct cn_msg *msg = NLMSG_DATA(nlmsg_hdr(skb));
 127         int err = -ENODEV;
 128
 129         spin_lock_bh(&dev->cbdev->queue_lock);
 130         list_for_each_entry(__cbq, &dev->cbdev->queue_list, callback_entry) {
 131                 if (cn_cb_equal(&__cbq->id.id, &msg->id)) {
 132                         if (likely(!work_pending(&__cbq->work) &&
 133                                         __cbq->data.skb == NULL)) {
 134                                 __cbq->data.skb = skb;
 135
 136                                 if (queue_work(dev->cbdev->cn_queue,
 137                                                &__cbq->work))
 138                                         err = 0;
 139                                 else
 140                                         err = -EINVAL;
 141                         } else {
 142                                 struct cn_callback_data *d;
 143
 144                                 err = -ENOMEM;
 145                                 __new_cbq = kzalloc(sizeof(struct cn_callback_entry), GFP_ATOMIC);
 146                                 if (__new_cbq) {
 147                                         d = &__new_cbq->data;
 148                                         d->skb = skb;
 149                                         d->callback = __cbq->data.callback;
 150                                         d->free = __new_cbq;
 151
 152                                         INIT_WORK(&__new_cbq->work,
 153                                                         &cn_queue_wrapper);
 154
 155                                         if (queue_work(dev->cbdev->cn_queue,
 156                                                        &__new_cbq->work))
 157                                                 err = 0;
 158                                         else {
 159                                                 kfree(__new_cbq);
 160                                                 err = -EINVAL;
 161                                         }
 162                                 }
 163                         }
 164                         break;
 165                 }
 166         }
 167         spin_unlock_bh(&dev->cbdev->queue_lock);
 168
 169         return err;
 170 }
 171
 172 /*
 173  * Main netlink receiving function.
 174  *
 175  * It checks skb, netlink header and msg sizes, and calls callback helper.
 176  */
 177 static void cn_rx_skb(struct sk_buff *__skb)
 178 {
 179         struct nlmsghdr *nlh;
 180         int err;
 181         struct sk_buff *skb;
 182
 183         skb = skb_get(__skb);
 184
 185         if (skb->len >= NLMSG_SPACE(0)) {
 186                 nlh = nlmsg_hdr(skb);
 187
 188                 if (nlh->nlmsg_len < sizeof(struct cn_msg) ||
 189                     skb->len < nlh->nlmsg_len ||
 190                     nlh->nlmsg_len > CONNECTOR_MAX_MSG_SIZE) {
 191                         kfree_skb(skb);
 192                         return;
 193                 }
 194
 195                 err = cn_call_callback(skb);
 196                 if (err < 0)
 197                         kfree_skb(skb);
 198         }
 199 }
 200
 201 /*
 202  * Callback add routing - adds callback with given ID and name.
 203  * If there is registered callback with the same ID it will not be added.
 204  *
 205  * May sleep.
 206  */
 207 int cn_add_callback(struct cb_id *id, char *name,
 208                     void (*callback)(struct cn_msg *, struct netlink_skb_parms *))
 209 {
 210         int err;
 211         struct cn_dev *dev = &cdev;
 212
 213         if (!cn_already_initialized)
 214                 return -EAGAIN;
 215
 216         err = cn_queue_add_callback(dev->cbdev, name, id, callback);
 217         if (err)
 218                 return err;
 219
 220         return 0;
 221 }
 222 EXPORT_SYMBOL_GPL(cn_add_callback);
 223
 224 /*
 225  * Callback remove routing - removes callback
 226  * with given ID.
 227  * If there is no registered callback with given
 228  * ID nothing happens.
 229  *
 230  * May sleep while waiting for reference counter to become zero.
 231  */
 232 void cn_del_callback(struct cb_id *id)
 233 {
 234         struct cn_dev *dev = &cdev;
 235
 236         cn_queue_del_callback(dev->cbdev, id);
 237 }
 238 EXPORT_SYMBOL_GPL(cn_del_callback);
 239
 240 static int cn_proc_show(struct seq_file *m, void *v)
 241 {
 242         struct cn_queue_dev *dev = cdev.cbdev;
 243         struct cn_callback_entry *cbq;
 244
 245         seq_printf(m, "Name            ID\n");
 246
 247         spin_lock_bh(&dev->queue_lock);
 248
 249         list_for_each_entry(cbq, &dev->queue_list, callback_entry) {
 250                 seq_printf(m, "%-15s %u:%u\n",
 251                            cbq->id.name,
 252                            cbq->id.id.idx,
 253                            cbq->id.id.val);
 254         }
 255
 256         spin_unlock_bh(&dev->queue_lock);
 257
 258         return 0;
 259 }
 260
 261 static int cn_proc_open(struct inode *inode, struct file *file)
 262 {
 263         return single_open(file, cn_proc_show, NULL);
 264 }
 265
 266 static const struct file_operations cn_file_ops = {
 267         .owner   = THIS_MODULE,
 268         .open    = cn_proc_open,
 269         .read    = seq_read,
 270         .llseek  = seq_lseek,
 271         .release = single_release
 272 };
 273
 274 static int __devinit cn_init(void)
 275 {
 276         struct cn_dev *dev = &cdev;
 277
 278         dev->input = cn_rx_skb;
 279
 280         dev->nls = netlink_kernel_create(&init_net, NETLINK_CONNECTOR,
 281                                          CN_NETLINK_USERS + 0xf,
 282                                          dev->input, NULL, THIS_MODULE);
 283         if (!dev->nls)
 284                 return -EIO;
 285
 286         dev->cbdev = cn_queue_alloc_dev("cqueue", dev->nls);
 287         if (!dev->cbdev) {
 288                 netlink_kernel_release(dev->nls);
 289                 return -EINVAL;
 290         }
 291
 292         cn_already_initialized = 1;
 293
 294         proc_net_fops_create(&init_net, "connector", S_IRUGO, &cn_file_ops);
 295
 296         return 0;
 297 }
 298
 299 static void __devexit cn_fini(void)
 300 {
 301         struct cn_dev *dev = &cdev;
 302
 303         cn_already_initialized = 0;
 304
 305         proc_net_remove(&init_net, "connector");
 306
 307         cn_queue_free_dev(dev->cbdev);
 308         netlink_kernel_release(dev->nls);
 309 }
 310
 311 subsys_initcall(cn_init);
 312 module_exit(cn_fini);