lib/kobject_uevent.c

   1 /*
   2  * kernel userspace event delivery
   3  *
   4  * Copyright (C) 2004 Red Hat, Inc.  All rights reserved.
   5  * Copyright (C) 2004 Novell, Inc.  All rights reserved.
   6  * Copyright (C) 2004 IBM, Inc. All rights reserved.
   7  *
   8  * Licensed under the GNU GPL v2.
   9  *
  10  * Authors:
  11  *      Robert Love             <rml@novell.com>
  12  *      Kay Sievers             <kay.sievers@vrfy.org>
  13  *      Arjan van de Ven        <arjanv@redhat.com>
  14  *      Greg Kroah-Hartman      <greg@kroah.com>
  15  */
  16
  17 #include <linux/spinlock.h>
  18 #include <linux/socket.h>
  19 #include <linux/skbuff.h>
  20 #include <linux/netlink.h>
  21 #include <linux/string.h>
  22 #include <linux/kobject.h>
  23 #include <net/sock.h>
  24
  25 #define BUFFER_SIZE     1024    /* buffer for the variables */
  26 #define NUM_ENVP        32      /* number of env pointers */
  27
  28 #if defined(CONFIG_HOTPLUG)
  29 char uevent_helper[UEVENT_HELPER_PATH_LEN] = "/sbin/hotplug";
  30 u64 uevent_seqnum;
  31 static DEFINE_SPINLOCK(sequence_lock);
  32 static struct sock *uevent_sock;
  33
  34 static char *action_to_string(enum kobject_action action)
  35 {
  36         switch (action) {
  37         case KOBJ_ADD:
  38                 return "add";
  39         case KOBJ_REMOVE:
  40                 return "remove";
  41         case KOBJ_CHANGE:
  42                 return "change";
  43         case KOBJ_OFFLINE:
  44                 return "offline";
  45         case KOBJ_ONLINE:
  46                 return "online";
  47         default:
  48                 return NULL;
  49         }
  50 }
  51
  52 /**
  53  * kobject_uevent - notify userspace by ending an uevent
  54  *
  55  * @action: action that is happening (usually KOBJ_ADD and KOBJ_REMOVE)
  56  * @kobj: struct kobject that the action is happening to
  57  */
  58 void kobject_uevent(struct kobject *kobj, enum kobject_action action)
  59 {
  60         char **envp;
  61         char *buffer;
  62         char *scratch;
  63         const char *action_string;
  64         const char *devpath = NULL;
  65         const char *subsystem;
  66         struct kobject *top_kobj;
  67         struct kset *kset;
  68         struct kset_uevent_ops *uevent_ops;
  69         u64 seq;
  70         char *seq_buff;
  71         int i = 0;
  72         int retval;
  73
  74         pr_debug("%s\n", __FUNCTION__);
  75
  76         action_string = action_to_string(action);
  77         if (!action_string)
  78                 return;
  79
  80         /* search the kset we belong to */
  81         top_kobj = kobj;
  82         if (!top_kobj->kset && top_kobj->parent) {
  83                 do {
  84                         top_kobj = top_kobj->parent;
  85                 } while (!top_kobj->kset && top_kobj->parent);
  86         }
  87         if (!top_kobj->kset)
  88                 return;
  89
  90         kset = top_kobj->kset;
  91         uevent_ops = kset->uevent_ops;
  92
  93         /*  skip the event, if the filter returns zero. */
  94         if (uevent_ops && uevent_ops->filter)
  95                 if (!uevent_ops->filter(kset, kobj))
  96                         return;
  97
  98         /* environment index */
  99         envp = kzalloc(NUM_ENVP * sizeof (char *), GFP_KERNEL);
 100         if (!envp)
 101                 return;
 102
 103         /* environment values */
 104         buffer = kmalloc(BUFFER_SIZE, GFP_KERNEL);
 105         if (!buffer)
 106                 goto exit;
 107
 108         /* complete object path */
 109         devpath = kobject_get_path(kobj, GFP_KERNEL);
 110         if (!devpath)
 111                 goto exit;
 112
 113         /* originating subsystem */
 114         if (uevent_ops && uevent_ops->name)
 115                 subsystem = uevent_ops->name(kset, kobj);
 116         else
 117                 subsystem = kobject_name(&kset->kobj);
 118
 119         /* event environemnt for helper process only */
 120         envp[i++] = "HOME=/";
 121         envp[i++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
 122
 123         /* default keys */
 124         scratch = buffer;
 125         envp [i++] = scratch;
 126         scratch += sprintf(scratch, "ACTION=%s", action_string) + 1;
 127         envp [i++] = scratch;
 128         scratch += sprintf (scratch, "DEVPATH=%s", devpath) + 1;
 129         envp [i++] = scratch;
 130         scratch += sprintf(scratch, "SUBSYSTEM=%s", subsystem) + 1;
 131
 132         /* just reserve the space, overwrite it after kset call has returned */
 133         envp[i++] = seq_buff = scratch;
 134         scratch += strlen("SEQNUM=18446744073709551616") + 1;
 135
 136         /* let the kset specific function add its stuff */
 137         if (uevent_ops && uevent_ops->uevent) {
 138                 retval = uevent_ops->uevent(kset, kobj,
 139                                   &envp[i], NUM_ENVP - i, scratch,
 140                                   BUFFER_SIZE - (scratch - buffer));
 141                 if (retval) {
 142                         pr_debug ("%s - uevent() returned %d\n",
 143                                   __FUNCTION__, retval);
 144                         goto exit;
 145                 }
 146         }
 147
 148         /* we will send an event, request a new sequence number */
 149         spin_lock(&sequence_lock);
 150         seq = ++uevent_seqnum;
 151         spin_unlock(&sequence_lock);
 152         sprintf(seq_buff, "SEQNUM=%llu", (unsigned long long)seq);
 153
 154         /* send netlink message */
 155         if (uevent_sock) {
 156                 struct sk_buff *skb;
 157                 size_t len;
 158
 159                 /* allocate message with the maximum possible size */
 160                 len = strlen(action_string) + strlen(devpath) + 2;
 161                 skb = alloc_skb(len + BUFFER_SIZE, GFP_KERNEL);
 162                 if (skb) {
 163                         /* add header */
 164                         scratch = skb_put(skb, len);
 165                         sprintf(scratch, "%s@%s", action_string, devpath);
 166
 167                         /* copy keys to our continuous event payload buffer */
 168                         for (i = 2; envp[i]; i++) {
 169                                 len = strlen(envp[i]) + 1;
 170                                 scratch = skb_put(skb, len);
 171                                 strcpy(scratch, envp[i]);
 172                         }
 173
 174                         NETLINK_CB(skb).dst_group = 1;
 175                         netlink_broadcast(uevent_sock, skb, 0, 1, GFP_KERNEL);
 176                 }
 177         }
 178
 179         /* call uevent_helper, usually only enabled during early boot */
 180         if (uevent_helper[0]) {
 181                 char *argv [3];
 182
 183                 argv [0] = uevent_helper;
 184                 argv [1] = (char *)subsystem;
 185                 argv [2] = NULL;
 186                 call_usermodehelper (argv[0], argv, envp, 0);
 187         }
 188
 189 exit:
 190         kfree(devpath);
 191         kfree(buffer);
 192         kfree(envp);
 193         return;
 194 }
 195 EXPORT_SYMBOL_GPL(kobject_uevent);
 196
 197 /**
 198  * add_uevent_var - helper for creating event variables
 199  * @envp: Pointer to table of environment variables, as passed into
 200  * uevent() method.
 201  * @num_envp: Number of environment variable slots available, as
 202  * passed into uevent() method.
 203  * @cur_index: Pointer to current index into @envp.  It should be
 204  * initialized to 0 before the first call to add_uevent_var(),
 205  * and will be incremented on success.
 206  * @buffer: Pointer to buffer for environment variables, as passed
 207  * into uevent() method.
 208  * @buffer_size: Length of @buffer, as passed into uevent() method.
 209  * @cur_len: Pointer to current length of space used in @buffer.
 210  * Should be initialized to 0 before the first call to
 211  * add_uevent_var(), and will be incremented on success.
 212  * @format: Format for creating environment variable (of the form
 213  * "XXX=%x") for snprintf().
 214  *
 215  * Returns 0 if environment variable was added successfully or -ENOMEM
 216  * if no space was available.
 217  */
 218 int add_uevent_var(char **envp, int num_envp, int *cur_index,
 219                    char *buffer, int buffer_size, int *cur_len,
 220                    const char *format, ...)
 221 {
 222         va_list args;
 223
 224         /*
 225          * We check against num_envp - 1 to make sure there is at
 226          * least one slot left after we return, since kobject_uevent()
 227          * needs to set the last slot to NULL.
 228          */
 229         if (*cur_index >= num_envp - 1)
 230                 return -ENOMEM;
 231
 232         envp[*cur_index] = buffer + *cur_len;
 233
 234         va_start(args, format);
 235         *cur_len += vsnprintf(envp[*cur_index],
 236                               max(buffer_size - *cur_len, 0),
 237                               format, args) + 1;
 238         va_end(args);
 239
 240         if (*cur_len > buffer_size)
 241                 return -ENOMEM;
 242
 243         (*cur_index)++;
 244         return 0;
 245 }
 246 EXPORT_SYMBOL_GPL(add_uevent_var);
 247
 248 static int __init kobject_uevent_init(void)
 249 {
 250         uevent_sock = netlink_kernel_create(NETLINK_KOBJECT_UEVENT, 1, NULL,
 251                                             THIS_MODULE);
 252
 253         if (!uevent_sock) {
 254                 printk(KERN_ERR
 255                        "kobject_uevent: unable to create netlink socket!\n");
 256                 return -ENODEV;
 257         }
 258
 259         return 0;
 260 }
 261
 262 postcore_initcall(kobject_uevent_init);
 263
 264 #endif /* CONFIG_HOTPLUG */