ports/sysdeps/unix/sysv/linux/generic/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 <fcntl.h>
  25 #include <sys/param.h>
  26 #include <ldsodefs.h>
  27 #include <sysdep.h>
  28
  29 #include <dl-dst.h>
  30
  31 /* On Linux >= 2.1 systems which have the dcache implementation we can get
  32    the path of the application from the /proc/self/exe symlink.  Try this
  33    first and fall back on the generic method if necessary.  */
  34
  35 const char *
  36 _dl_get_origin (void)
  37 {
  38   char linkval[PATH_MAX];
  39   char *result;
  40   int len;
  41   INTERNAL_SYSCALL_DECL (err);
  42
  43   len = INTERNAL_SYSCALL (readlinkat, err, 4, AT_FDCWD, "/proc/self/exe",
  44                           linkval, sizeof (linkval));
  45   if (! INTERNAL_SYSCALL_ERROR_P (len, err) && len > 0 && linkval[0] != '[')
  46     {
  47       /* We can use this value.  */
  48       assert (linkval[0] == '/');
  49       while (len > 1 && linkval[len - 1] != '/')
  50         --len;
  51       result = (char *) malloc (len + 1);
  52       if (result == NULL)
  53         result = (char *) -1;
  54       else if (len == 1)
  55         memcpy (result, "/", 2);
  56       else
  57         *((char *) __mempcpy (result, linkval, len - 1)) = '\0';
  58     }
  59   else
  60     {
  61       result = (char *) -1;
  62       /* We use the environment variable LD_ORIGIN_PATH.  If it is set make
  63          a copy and strip out trailing slashes.  */
  64       if (GLRO(dl_origin_path) != NULL)
  65         {
  66           size_t len = strlen (GLRO(dl_origin_path));
  67           result = (char *) malloc (len + 1);
  68           if (result == NULL)
  69             result = (char *) -1;
  70           else
  71             {
  72               char *cp = __mempcpy (result, GLRO(dl_origin_path), len);
  73               while (cp > result + 1 && cp[-1] == '/')
  74                 --cp;
  75               *cp = '\0';
  76             }
  77         }
  78     }
  79
  80   return result;
  81 }