/* Copyright (C) 2004-2018 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 <stdint.h>

#include <stdio.h>

#include <stdio_ext.h>

#include <stdlib.h>

#include <string.h>

#include "libio/libioP.h"

/* Return 1 if the whole area PTR .. PTR+SIZE is not writable.

   Return -1 if it is writable.  */

int

__readonly_area (const char *ptr, size_t size)

{

  const void *ptr_end = ptr + size;

  FILE *fp = fopen ("/proc/self/maps", "rce");

  if (fp == NULL)

    {

      /* It is the system administrator's choice to not have /proc

	 available to this process (e.g., because it runs in a chroot

	 environment.  Don't fail in this case.  */

      if (errno == ENOENT

	  /* The kernel has a bug in that a process is denied access

	     to the /proc filesystem if it is set[ug]id.  There has

	     been no willingness to change this in the kernel so

	     far.  */

	  || errno == EACCES)

	return 1;

      return -1;

    }

  /* We need no locking.  */

  __fsetlocking (fp, FSETLOCKING_BYCALLER);

  char *line = NULL;

  size_t linelen = 0;

  while (! __feof_unlocked (fp))

    {

      if (_IO_getdelim (&line, &linelen, '\n', fp) <= 0)

	break;

      char *p;

      uintptr_t from = strtoul (line, &p, 16);

      if (p == line || *p++ != '-')

	break;

      char *q;

      uintptr_t to = strtoul (p, &q, 16);

      if (q == p || *q++ != ' ')

	break;

      if (from < (uintptr_t) ptr_end && to > (uintptr_t) ptr)

	{

	  /* Found an entry that at least partially covers the area.  */

	  if (*q++ != 'r' || *q++ != '-')

	    break;

	  if (from <= (uintptr_t) ptr && to >= (uintptr_t) ptr_end)

	    {

	      size = 0;

	      break;

	    }

	  else if (from <= (uintptr_t) ptr)

	    size -= to - (uintptr_t) ptr;

	  else if (to >= (uintptr_t) ptr_end)

	    size -= (uintptr_t) ptr_end - from;

	  else

	    size -= to - from;

	  if (!size)

	    break;

	}

    }

  fclose (fp);

  free (line);

  /* If the whole area between ptr and ptr_end is covered by read-only

     VMAs, return 1.  Otherwise return -1.  */

  return size == 0 ? 1 : -1;

}