lib/libc/gen/getdevpath.c

   1 /*
   2  * Copyright (c) 2009 The DragonFly Project.  All rights reserved.
   3  *
   4  * This code is derived from software contributed to The DragonFly Project
   5  * by Matthew Dillon <dillon@backplane.com>
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  *
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in
  15  *    the documentation and/or other materials provided with the
  16  *    distribution.
  17  * 3. Neither the name of The DragonFly Project nor the names of its
  18  *    contributors may be used to endorse or promote products derived
  19  *    from this software without specific, prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  22  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  23  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  24  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
  25  * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  26  * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
  27  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  28  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
  29  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  30  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
  31  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  32  * SUCH DAMAGE.
  33  */
  34
  35 #include <sys/types.h>
  36 #include <sys/stat.h>
  37
  38 #include <stdio.h>
  39 #include <stdlib.h>
  40 #include <string.h>
  41 #include <unistd.h>
  42 #include <errno.h>
  43 #include <paths.h>
  44 #include <limits.h>
  45 #include <fstab.h>
  46
  47 static void finddevlabel(char **pathp, const char *devname);
  48 static int xlatedevpath(char **pathp, struct stat *st);
  49 static char *dodequote(char *base);
  50
  51 /*
  52  * Acquire device path.
  53  *
  54  */
  55 char *
  56 getdevpath(const char *devname, int flags)
  57 {
  58         struct stat st;
  59         char *path = NULL;
  60         int stgood = 0;
  61
  62         if (devname[0] == '/' || devname[0] == '.') {
  63                 asprintf(&path, "%s", devname);
  64         } else {
  65                 asprintf(&path, "/dev/%s", devname);
  66                 if (lstat(path, &st) < 0) {
  67                         free(path);
  68                         path = NULL;
  69                         finddevlabel(&path, devname);
  70                         if (path == NULL)
  71                                 asprintf(&path, "%s", devname);
  72                 } else {
  73                         stgood = 1;
  74                 }
  75         }
  76
  77         /*
  78          * Translate softlinks if requested.  If the lstat() of the
  79          * pre-translated path fails NULL is expected to be returned.
  80          * lstat() is not called on the post-translated path.
  81          */
  82         if ((flags & GETDEVPATH_RAWDEV) && path) {
  83                 if (stgood == 0 && lstat(path, &st) == 0)
  84                         stgood = 1;
  85                 if (stgood)
  86                         stgood = xlatedevpath(&path, &st);
  87                 if (stgood == 0) {
  88                         free(path);
  89                         path = NULL;
  90                 }
  91
  92         }
  93         if (path == NULL)
  94                 errno = ENOENT;
  95         return(path);
  96 }
  97
  98 static void
  99 finddevlabel(char **pathp, const char *devname)
 100 {
 101         const char *prefix = _PATH_DEVTAB_PATHS;
 102         const char *ptr1;
 103         const char *trailer;
 104         char *label;
 105         char *ptr2;
 106         char *ptr3;
 107         char *dtpath;
 108         char *bufp;
 109         char buf[256];
 110         FILE *fp;
 111         size_t len;     /* directory prefix length */
 112         size_t dlen;    /* devname length */
 113         size_t tlen;    /* devname length without trailer */
 114
 115         dlen = strlen(devname);
 116         if ((trailer = strrchr(devname, '.')) != NULL)
 117                 tlen = trailer - devname;
 118         else
 119                 tlen = 0;
 120
 121         while (*prefix && *pathp == NULL) {
 122                 /*
 123                  * Directory search path
 124                  */
 125                 ptr1 = strchr(prefix, ':');
 126                 len = (ptr1) ? (size_t)(ptr1 - prefix) : strlen(prefix);
 127                 asprintf(&dtpath, "%*.*s/devtab", len, len, prefix);
 128
 129                 /*
 130                  * Each devtab file
 131                  */
 132                 if ((fp = fopen(dtpath, "r")) != NULL) {
 133                         while (fgets(buf, sizeof(buf), fp) != NULL) {
 134                                 /*
 135                                  * Extract label field, check degenerate
 136                                  * cases.
 137                                  */
 138                                 label = strtok_r(buf, " \t\r\n", &bufp);
 139                                 if (label == NULL || *label == 0 ||
 140                                     *label == '#') {
 141                                         continue;
 142                                 }
 143
 144                                 /*
 145                                  * Match label, with or without the
 146                                  * trailer (aka ".s1a").  The trailer
 147                                  * is tacked on if the match is without
 148                                  * the trailer.
 149                                  */
 150                                 if (strcmp(devname, label) == 0) {
 151                                         trailer = "";
 152                                 } else if (tlen && strlen(label) == tlen &&
 153                                            strncmp(devname, label, tlen) == 0) {
 154                                         trailer = devname + tlen;
 155                                 } else {
 156                                         continue;
 157                                 }
 158
 159                                 /*
 160                                  * Match, extract and process remaining fields.
 161                                  */
 162                                 ptr2 = strtok_r(NULL, " \t\r\n", &bufp);
 163                                 ptr3 = strtok_r(NULL, " \t\r\n", &bufp);
 164                                 if (ptr2 == NULL || ptr3 == NULL)
 165                                         continue;
 166                                 if (*ptr2 == 0 || *ptr3 == 0)
 167                                         continue;
 168                                 ptr3 = dodequote(ptr3);
 169                                 if (strcmp(ptr2, "path") == 0) {
 170                                         asprintf(pathp, "%s%s", ptr3, trailer);
 171                                 } else {
 172                                         asprintf(pathp, "/dev/%s/%s%s",
 173                                                  ptr2, ptr3, trailer);
 174                                 }
 175                                 break;
 176                         }
 177                         fclose(fp);
 178                 }
 179                 free(dtpath);
 180                 prefix += len;
 181                 if (*prefix == ':')
 182                         ++prefix;
 183         }
 184 }
 185
 186 static int
 187 xlatedevpath(char **pathp, struct stat *st)
 188 {
 189         char *path;
 190         int n;
 191         int len;
 192
 193         /*
 194          * If not a softlink return unchanged.
 195          */
 196         if (!S_ISLNK(st->st_mode))
 197                 return(1);
 198
 199         /*
 200          * If the softlink isn't reasonable return bad (0)
 201          */
 202         len = (int)st->st_size;
 203         if (len < 0 || len > PATH_MAX)
 204                 return(0);
 205
 206         /*
 207          * Read the link, return if the result is not what we expected.
 208          */
 209         path = malloc(len + 1);
 210         n = readlink(*pathp, path, len);
 211         if (n < 0 || n > len) {
 212                 free(path);
 213                 return(0);
 214         }
 215
 216         /*
 217          * Success, replace (*pathp).
 218          */
 219         path[n] = 0;
 220         free(*pathp);
 221         *pathp = path;
 222         return(1);
 223 }
 224
 225 static char *
 226 dodequote(char *base)
 227 {
 228         int len = strlen(base);
 229
 230         if (len && base[0] == '\"' && base[len-1] == '\"') {
 231                 base[len - 1] = 0;
 232                 ++base;
 233         }
 234         return(base);
 235 }