/* Return true if the process can perform a chroot operation.

   Copyright (C) 2017-2018 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 <stdio.h>

#include <support/check.h>

#include <support/namespace.h>

#include <support/support.h>

#include <support/xunistd.h>

#include <sys/stat.h>

#include <unistd.h>

static void

callback (void *closure)

{

  int *result = closure;

  struct stat64 before;

  xstat ("/dev", &before);

  if (chroot ("/dev") != 0)

    {

      *result = errno;

      return;

    }

  struct stat64 after;

  xstat ("/", &after);

  TEST_VERIFY (before.st_dev == after.st_dev);

  TEST_VERIFY (before.st_ino == after.st_ino);

  *result = 0;

}

bool

support_can_chroot (void)

{

  int *result = support_shared_allocate (sizeof (*result));

  *result = 0;

  support_isolate_in_subprocess (callback, result);

  bool ok = *result == 0;

  if (!ok)

    {

      static bool already_warned;

      if (!already_warned)

        {

          already_warned = true;

          errno = *result;

          printf ("warning: this process does not support chroot: %m\n");

        }

    }

  support_shared_free (result);

  return ok;

}