util-linux/mdev.c

   1 /* vi:set ts=4:
   2  *
   3  * mdev - Mini udev for busybox
   4  *
   5  * Copyright 2005 Rob Landley <rob@landley.net>
   6  * Copyright 2005 Frank Sorenson <frank@tuxrocks.com>
   7  *
   8  * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
   9  */
  10
  11 #include <ctype.h>
  12 #include <dirent.h>
  13 #include <errno.h>
  14 #include <fcntl.h>
  15 #include <stdio.h>
  16 #include <string.h>
  17 #include <sys/mman.h>
  18 #include <sys/stat.h>
  19 #include <sys/sysmacros.h>
  20 #include <sys/types.h>
  21 #include <unistd.h>
  22 #include <stdlib.h>
  23 #include "busybox.h"
  24 #include "xregex.h"
  25
  26 #define DEV_PATH        "/dev"
  27 #define MDEV_CONF       "/etc/mdev.conf"
  28
  29 #include <busybox.h>
  30
  31 int root_major, root_minor;
  32
  33 /* mknod in /dev based on a path like "/sys/block/hda/hda1" */
  34 static void make_device(char *path)
  35 {
  36         char *device_name, *s;
  37         int major, minor, type, len, fd;
  38         int mode = 0660;
  39         uid_t uid = 0;
  40         gid_t gid = 0;
  41         char *temp = path + strlen(path);
  42
  43         /* Try to read major/minor string.  Note that the kernel puts \n after
  44          * the data, so we don't need to worry about null terminating the string
  45          * because sscanf() will stop at the first nondigit, which \n is.  We
  46          * also depend on path having writeable space after it. */
  47
  48         strcat(path, "/dev");
  49         fd = open(path, O_RDONLY);
  50         len = read(fd, temp + 1, 64);
  51         *temp++ = 0;
  52         close(fd);
  53         if (len < 1) return;
  54
  55         /* Determine device name, type, major and minor */
  56
  57         device_name = strrchr(path, '/') + 1;
  58         type = path[5]=='c' ? S_IFCHR : S_IFBLK;
  59         if (sscanf(temp, "%d:%d", &major, &minor) != 2) return;
  60
  61         /* If we have a config file, look up permissions for this device */
  62
  63         if (ENABLE_FEATURE_MDEV_CONF) {
  64                 char *conf, *pos, *end;
  65
  66                 /* mmap the config file */
  67                 if (-1 != (fd=open(MDEV_CONF,O_RDONLY))) {
  68                         len = lseek(fd, 0, SEEK_END);
  69                         conf = mmap(NULL, len, PROT_READ, MAP_PRIVATE, fd, 0);
  70                         if (conf) {
  71                                 int line = 0;
  72
  73                                 /* Loop through lines in mmaped file*/
  74                                 for (pos=conf; pos-conf<len;) {
  75                                         int field;
  76                                         char *end2;
  77
  78                                         line++;
  79                                         /* find end of this line */
  80                                         for(end=pos; end-conf<len && *end!='\n'; end++)
  81                                                 ;
  82
  83                                         /* Three fields: regex, uid:gid, mode */
  84                                         for (field=3; field; field--) {
  85                                                 /* Skip whitespace */
  86                                                 while (pos<end && isspace(*pos))
  87                                                         pos++;
  88                                                 if (pos==end || *pos=='#')
  89                                                         break;
  90                                                 for (end2=pos; end2<end && !isspace(*end2) && *end2!='#'; end2++)
  91                                                         ;
  92
  93                                                 switch (field) {
  94                                                         /* Regex to match this device */
  95                                                         case 3:
  96                                                         {
  97                                                                 char *regex = strndupa(pos,end2-pos);
  98                                                                 regex_t match;
  99                                                                 regmatch_t off;
 100                                                                 int result;
 101
 102                                                                 /* Is this it? */
 103                                                                 xregcomp(&match,regex,REG_EXTENDED);
 104                                                                 result = regexec(&match,device_name,1,&off,0);
 105                                                                 regfree(&match);
 106
 107                                                                 /* If not this device, skip rest of line */
 108                                                                 if (result || off.rm_so || off.rm_eo!=strlen(device_name))
 109                                                                         goto end_line;
 110
 111                                                                 break;
 112                                                         }
 113                                                         /* uid:gid */
 114                                                         case 2:
 115                                                         {
 116                                                                 char *s2;
 117
 118                                                                 /* Find : */
 119                                                                 for(s=pos; s<end2 && *s!=':'; s++)
 120                                                                         ;
 121                                                                 if (s == end2)
 122                                                                         goto end_line;
 123
 124                                                                 /* Parse UID */
 125                                                                 uid = strtoul(pos,&s2,10);
 126                                                                 if (s != s2) {
 127                                                                         struct passwd *pass;
 128                                                                         pass = getpwnam(strndupa(pos,s-pos));
 129                                                                         if (!pass)
 130                                                                                 goto end_line;
 131                                                                         uid = pass->pw_uid;
 132                                                                 }
 133                                                                 s++;
 134                                                                 /* parse GID */
 135                                                                 gid = strtoul(s,&s2,10);
 136                                                                 if (end2 != s2) {
 137                                                                         struct group *grp;
 138                                                                         grp = getgrnam(strndupa(s,end2-s));
 139                                                                         if (!grp)
 140                                                                                 goto end_line;
 141                                                                         gid = grp->gr_gid;
 142                                                                 }
 143                                                                 break;
 144                                                         }
 145                                                         /* mode */
 146                                                         case 1:
 147                                                         {
 148                                                                 mode = strtoul(pos,&pos,8);
 149                                                                 if (pos != end2)
 150                                                                         goto end_line;
 151                                                                 else
 152                                                                         goto found_device;
 153                                                         }
 154                                                 }
 155                                                 pos = end2;
 156                                         }
 157 end_line:
 158                                         /* Did everything parse happily? */
 159                                         if (field && field!=3)
 160                                                 bb_error_msg_and_die("Bad line %d",line);
 161
 162                                         /* Next line */
 163                                         pos = ++end;
 164                                 }
 165 found_device:
 166                                 munmap(conf, len);
 167                         }
 168                         close(fd);
 169                 }
 170         }
 171
 172         umask(0);
 173         if (mknod(device_name, mode | type, makedev(major, minor)) && errno != EEXIST)
 174                 bb_perror_msg_and_die("mknod %s failed", device_name);
 175
 176         if (major==root_major && minor==root_minor)
 177                 symlink(device_name, "root");
 178
 179         if (ENABLE_FEATURE_MDEV_CONF) chown(device_name, uid, gid);
 180 }
 181
 182 /* Recursive search of /sys/block or /sys/class.  path must be a writeable
 183  * buffer of size PATH_MAX containing the directory string to start at. */
 184
 185 static void find_dev(char *path)
 186 {
 187         DIR *dir;
 188         size_t len = strlen(path);
 189         struct dirent *entry;
 190
 191         if ((dir = opendir(path)) == NULL)
 192                 return;
 193
 194         while ((entry = readdir(dir)) != NULL) {
 195
 196                 /* Skip "." and ".." (also skips hidden files, which is ok) */
 197
 198                 if (entry->d_name[0] == '.')
 199                         continue;
 200
 201                 if (entry->d_type == DT_DIR) {
 202                         snprintf(path+len, PATH_MAX-len, "/%s", entry->d_name);
 203                         find_dev(path);
 204                         path[len] = 0;
 205                 }
 206
 207                 /* If there's a dev entry, mknod it */
 208
 209                 if (!strcmp(entry->d_name, "dev")) make_device(path);
 210         }
 211
 212         closedir(dir);
 213 }
 214
 215 int mdev_main(int argc, char *argv[])
 216 {
 217         char *action;
 218         char *env_path;
 219         RESERVE_CONFIG_BUFFER(temp,PATH_MAX);
 220
 221         bb_xchdir(DEV_PATH);
 222
 223         /* Scan */
 224
 225         if (argc == 2 && !strcmp(argv[1],"-s")) {
 226                 struct stat st;
 227
 228                 stat("/", &st);  // If this fails, we have bigger problems.
 229                 root_major=major(st.st_dev);
 230                 root_minor=minor(st.st_dev);
 231                 strcpy(temp,"/sys/block");
 232                 find_dev(temp);
 233                 strcpy(temp,"/sys/class");
 234                 find_dev(temp);
 235
 236         /* Hotplug */
 237
 238         } else {
 239                 action = getenv("ACTION");
 240                 env_path = getenv("DEVPATH");
 241             if (!action || !env_path)
 242                         bb_show_usage();
 243
 244                 if (!strcmp(action, "add")) {
 245                         sprintf(temp, "/sys%s", env_path);
 246                         make_device(temp);
 247                 } else if (!strcmp(action, "remove")) {
 248                         unlink(strrchr(env_path, '/') + 1);
 249                 }
 250         }
 251
 252         if (ENABLE_FEATURE_CLEAN_UP) RELEASE_CONFIG_BUFFER(temp);
 253         return 0;
 254 }