/* libio vtable validation.

   Copyright (C) 2016-2018 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 <dlfcn.h>

#include <libioP.h>

#include <stdio.h>

#include <ldsodefs.h>

#ifdef SHARED

void (*IO_accept_foreign_vtables) (void) attribute_hidden;

/* Used to detected multiple libcs.  */

extern struct dl_open_hook *_dl_open_hook;

libc_hidden_proto (_dl_open_hook);

#else  /* !SHARED */

/* Used to check whether static dlopen support is needed.  */

# pragma weak __dlopen

#endif

void attribute_hidden

_IO_vtable_check (void)

{

#ifdef SHARED

  /* Honor the compatibility flag.  */

  void (*flag) (void) = atomic_load_relaxed (&IO_accept_foreign_vtables);

#ifdef PTR_DEMANGLE

  PTR_DEMANGLE (flag);

#endif

  if (flag == &_IO_vtable_check)

    return;

  /* In case this libc copy is in a non-default namespace, we always

     need to accept foreign vtables because there is always a

     possibility that FILE * objects are passed across the linking

     boundary.  */

  {

    Dl_info di;

    struct link_map *l;

    if (!rtld_active ()

        || (_dl_addr (_IO_vtable_check, &di, &l, NULL) != 0

            && l->l_ns != LM_ID_BASE))

      return;

  }

#else /* !SHARED */

  /* We cannot perform vtable validation in the static dlopen case

     because FILE * handles might be passed back and forth across the

     boundary.  Therefore, we disable checking in this case.  */

  if (__dlopen != NULL)

    return;

#endif

  __libc_fatal ("Fatal error: glibc detected an invalid stdio handle\n");

}

/* Some variants of libstdc++ interpose _IO_2_1_stdin_ etc. and

   install their own vtables directly, without calling _IO_init or

   other functions.  Detect this by looking at the vtables values

   during startup, and disable vtable validation in this case.  */

#ifdef SHARED

__attribute__ ((constructor))

static void

check_stdfiles_vtables (void)

{

  if (_IO_2_1_stdin_.vtable != &_IO_file_jumps

      || _IO_2_1_stdout_.vtable != &_IO_file_jumps

      || _IO_2_1_stderr_.vtable != &_IO_file_jumps)

    IO_set_accept_foreign_vtables (&_IO_vtable_check);

}

#endif