/* Copyright (C) 1994-2018 Free Software Foundation, Inc.

   This file is part of the GNU C Library.

   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 <errno.h>

#include <stddef.h>

#include <stdio.h>

#include <unistd.h>

#include <fcntl.h>

#include <sys/stat.h>

#include <sysdep.h>

#include <sys/syscall.h>

#include <kernel-features.h>

/* Execute the file FD refers to, overlaying the running program image.

   ARGV and ENVP are passed to the new program, as for `execve'.  */

int

fexecve (int fd, char *const argv[], char *const envp[])

{

  if (fd < 0 || argv == NULL || envp == NULL)

    {

      __set_errno (EINVAL);

      return -1;

    }

#ifdef __NR_execveat

  /* Avoid implicit array coercion in syscall macros.  */

  INLINE_SYSCALL (execveat, 5, fd, "", &argv[0], &envp[0], AT_EMPTY_PATH);

# ifndef __ASSUME_EXECVEAT

  if (errno != ENOSYS)

    return -1;

# endif

#endif

#ifndef __ASSUME_EXECVEAT

  /* We use the /proc filesystem to get the information.  If it is not

     mounted we fail.  */

  char buf[sizeof "/proc/self/fd/" + sizeof (int) * 3];

  __snprintf (buf, sizeof (buf), "/proc/self/fd/%d", fd);

  /* We do not need the return value.  */

  __execve (buf, argv, envp);

  int save = errno;

  /* We come here only if the 'execve' call fails.  Determine whether

     /proc is mounted.  If not we return ENOSYS.  */

  struct stat st;

  if (stat ("/proc/self/fd", &st) != 0 && errno == ENOENT)

    save = ENOSYS;

  __set_errno (save);

#endif

  return -1;

}