src/linux/dirs.c

   1 /*****************************************************************************
   2  * linux/dirs.c: Linux-specific directories
   3  *****************************************************************************
   4  * Copyright © 2008-2012 Rémi Denis-Courmont
   5  *
   6  * This program is free software; you can redistribute it and/or modify it
   7  * under the terms of the GNU Lesser General Public License as published by
   8  * the Free Software Foundation; either version 2.1 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  14  * GNU Lesser General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU Lesser General Public License
  17  * along with this program; if not, write to the Free Software Foundation,
  18  * Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
  19  *****************************************************************************/
  20
  21 #ifdef HAVE_CONFIG_H
  22 # include "config.h"
  23 #endif
  24
  25 #include <stdio.h>
  26 #include <string.h>
  27 #include <pthread.h>
  28 #include <linux/limits.h>
  29
  30 #include <vlc_common.h>
  31 #include "libvlc.h"
  32 #include "config/configuration.h"
  33
  34 static char *config_GetLibDirRaw(void)
  35 {
  36     char *path = NULL;
  37     /* Find the path to libvlc (i.e. ourselves) */
  38     FILE *maps = fopen ("/proc/self/maps", "rte");
  39     if (maps == NULL)
  40         goto error;
  41
  42     char *line = NULL;
  43     size_t linelen = 0;
  44     uintptr_t needle = (uintptr_t)config_GetLibDir;
  45
  46     for (;;)
  47     {
  48         ssize_t len = getline (&line, &linelen, maps);
  49         if (len == -1)
  50             break;
  51
  52         void *start, *end;
  53         if (sscanf (line, "%p-%p", &start, &end) < 2)
  54             continue;
  55         /* This mapping contains the address of this function. */
  56         if (needle < (uintptr_t)start || (uintptr_t)end <= needle)
  57             continue;
  58
  59         char *dir = strchr (line, '/');
  60         if (dir == NULL)
  61             continue;
  62
  63         char *file = strrchr (line, '/');
  64         if (end == NULL)
  65             continue;
  66         *file = '\0';
  67
  68         path = strdup(dir);
  69         break;
  70     }
  71
  72     free (line);
  73     fclose (maps);
  74 error:
  75     if (path == NULL)
  76         path = strdup(LIBDIR);
  77     return path;
  78 }
  79
  80 static char cached_path[PATH_MAX] = LIBDIR;
  81
  82 static void config_GetLibDirOnce(void)
  83 {
  84     char *path = config_GetLibDirRaw();
  85     if (likely(path != NULL && sizeof (cached_path) > strlen(path)))
  86         strcpy(cached_path, path);
  87     free(path);
  88 }
  89
  90 char *config_GetLibDir(void)
  91 {
  92     static pthread_once_t once = PTHREAD_ONCE_INIT;
  93
  94     /* Reading and parsing /proc/self/maps is slow, so cache the value since
  95      * it's guaranteed not to change during the life-time of the process. */
  96     pthread_once(&once, config_GetLibDirOnce);
  97     return strdup(cached_path);
  98 }