sysdeps/unix/sysv/linux/dl-origin.c

   1 /* Find path of executable.
   2    Copyright (C) 1998, 1999, 2000 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1998.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Library General Public License as
   8    published by the Free Software Foundation; either version 2 of the
   9    License, or (at your option) any later version.
  10
  11    The GNU C Library 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 GNU
  14    Library General Public License for more details.
  15
  16    You should have received a copy of the GNU Library General Public
  17    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  18    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  19    Boston, MA 02111-1307, USA.  */
  20
  21 #include <stdlib.h>
  22 #include <string.h>
  23 #include <unistd.h>
  24 #include <sys/param.h>
  25 #include <ldsodefs.h>
  26
  27 #include <dl-dst.h>
  28
  29 /* On Linux >= 2.1 systems which have the dcache implementation we can get
  30    the path of the application from the /proc/self/exe symlink.  Try this
  31    first and fall back on the generic method if necessary.  */
  32 extern const char *_dl_origin_path;
  33
  34 const char *
  35 _dl_get_origin (void)
  36 {
  37   char linkval[PATH_MAX];
  38   char *result;
  39
  40   if (__readlink ("/proc/self/exe", linkval, PATH_MAX) != -1
  41       && linkval[0] != '[')
  42     {
  43       /* We can use this value.  */
  44       char *last_slash = strrchr (linkval, '/');
  45       result = (char *) malloc (last_slash - linkval + 1);
  46       if (result == NULL)
  47         result = (char *) -1;
  48       else if (last_slash == linkval)
  49         memcpy (result, "/", 2);
  50       else
  51         *((char *) __mempcpy (result, linkval, last_slash - linkval)) = '\0';
  52     }
  53   else
  54     {
  55       result = (char *) -1;
  56       /* We use the environment variable LD_ORIGIN_PATH.  If it is set make
  57          a copy and strip out trailing slashes.  */
  58       if (_dl_origin_path != NULL)
  59         {
  60           size_t len = strlen (_dl_origin_path);
  61           result = malloc (len + 1);
  62           if (result == NULL)
  63             result = (char *) -1;
  64           else
  65             {
  66               char *cp = __mempcpy (result, _dl_origin_path, len);
  67               while (cp > result + 1 && cp[-1] == '/')
  68                 --cp;
  69               *cp = '\0';
  70             }
  71         }
  72     }
  73
  74   return result;
  75 }