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

   1 /* Find path of executable.
   2    Copyright (C) 1998-2014 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 Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the 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    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, see
  18    <http://www.gnu.org/licenses/>.  */
  19
  20 #include <assert.h>
  21 #include <stdlib.h>
  22 #include <string.h>
  23 #include <unistd.h>
  24 #include <sys/param.h>
  25 #include <ldsodefs.h>
  26 #include <sysdep.h>
  27
  28 #include <dl-dst.h>
  29
  30 /* On Linux >= 2.1 systems which have the dcache implementation we can get
  31    the path of the application from the /proc/self/exe symlink.  Try this
  32    first and fall back on the generic method if necessary.  */
  33
  34 const char *
  35 _dl_get_origin (void)
  36 {
  37   char linkval[PATH_MAX];
  38   char *result;
  39   int len;
  40   INTERNAL_SYSCALL_DECL (err);
  41
  42   len = INTERNAL_SYSCALL (readlink, err, 3, "/proc/self/exe", linkval,
  43                           sizeof (linkval));
  44   if (! INTERNAL_SYSCALL_ERROR_P (len, err) && len > 0 && linkval[0] != '[')
  45     {
  46       /* We can use this value.  */
  47       assert (linkval[0] == '/');
  48       while (len > 1 && linkval[len - 1] != '/')
  49         --len;
  50       result = (char *) malloc (len + 1);
  51       if (result == NULL)
  52         result = (char *) -1;
  53       else if (len == 1)
  54         memcpy (result, "/", 2);
  55       else
  56         *((char *) __mempcpy (result, linkval, len - 1)) = '\0';
  57     }
  58   else
  59     {
  60       result = (char *) -1;
  61       /* We use the environment variable LD_ORIGIN_PATH.  If it is set make
  62          a copy and strip out trailing slashes.  */
  63       if (GLRO(dl_origin_path) != NULL)
  64         {
  65           size_t len = strlen (GLRO(dl_origin_path));
  66           result = (char *) malloc (len + 1);
  67           if (result == NULL)
  68             result = (char *) -1;
  69           else
  70             {
  71               char *cp = __mempcpy (result, GLRO(dl_origin_path), len);
  72               while (cp > result + 1 && cp[-1] == '/')
  73                 --cp;
  74               *cp = '\0';
  75             }
  76         }
  77     }
  78
  79   return result;
  80 }