/* Find path of executable.

   Copyright (C) 1998-2018 Free Software Foundation, Inc.

   This file is part of the GNU C Library.

   Contributed by Ulrich Drepper <drepper@cygnus.com>, 1998.

   The GNU C Library is free software; you can redistribute it and/or

   modify it under the terms of the GNU Lesser General Public

   License as published by the Free Software Foundation; either

   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,

   but WITHOUT ANY WARRANTY; without even the implied warranty of

   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public

   License along with the GNU C Library.  If not, see

   <http://www.gnu.org/licenses/>.  */

#include <assert.h>

#include <stdlib.h>

#include <string.h>

#include <unistd.h>

#include <fcntl.h>

#include <sys/param.h>

#include <ldsodefs.h>

#include <sysdep.h>

#include <dl-dst.h>

/* On Linux >= 2.1 systems which have the dcache implementation we can get

   the path of the application from the /proc/self/exe symlink.  Try this

   first and fall back on the generic method if necessary.  */

const char *

_dl_get_origin (void)

{

  char linkval[PATH_MAX];

  char *result;

  int len;

  INTERNAL_SYSCALL_DECL (err);

  len = INTERNAL_SYSCALL (readlinkat, err, 4, AT_FDCWD, "/proc/self/exe",

                          linkval, sizeof (linkval));

  if (! INTERNAL_SYSCALL_ERROR_P (len, err) && len > 0 && linkval[0] != '[')

    {

      /* We can use this value.  */

      assert (linkval[0] == '/');

      while (len > 1 && linkval[len - 1] != '/')

	--len;

      result = (char *) malloc (len + 1);

      if (result == NULL)

	result = (char *) -1;

      else if (len == 1)

	memcpy (result, "/", 2);

      else

	*((char *) __mempcpy (result, linkval, len - 1)) = '\0';

    }

  else

    {

      result = (char *) -1;

      /* We use the environment variable LD_ORIGIN_PATH.  If it is set make

	 a copy and strip out trailing slashes.  */

      if (GLRO(dl_origin_path) != NULL)

	{

	  size_t len = strlen (GLRO(dl_origin_path));

	  result = (char *) malloc (len + 1);

	  if (result == NULL)

	    result = (char *) -1;

	  else

	    {

	      char *cp = __mempcpy (result, GLRO(dl_origin_path), len);

	      while (cp > result + 1 && cp[-1] == '/')

		--cp;

	      *cp = '\0';

	    }

	}

    }

  return result;

}