tests/lib/libc/arch/i386/exec_prot_support.c

   1 /*      $NetBSD: exec_prot_support.c,v 1.1 2011/07/18 23:16:09 jym Exp $ */
   2
   3 /*-
   4  * Copyright (c) 2011 The NetBSD Foundation, Inc.
   5  * All rights reserved.
   6  *
   7  * This code is derived from software contributed to The NetBSD Foundation
   8  * by Jean-Yves Migeon.
   9  *
  10  * Redistribution and use in source and binary forms, with or without
  11  * modification, are permitted provided that the following conditions
  12  * are met:
  13  * 1. Redistributions of source code must retain the above copyright
  14  *    notice, this list of conditions and the following disclaimer.
  15  * 2. Redistributions in binary form must reproduce the above copyright
  16  *    notice, this list of conditions and the following disclaimer in the
  17  *    documentation and/or other materials provided with the distribution.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
  20  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
  21  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  22  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
  23  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  24  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  25  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  26  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  27  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  28  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  29  * POSSIBILITY OF SUCH DAMAGE.
  30  */
  31
  32 #include <sys/cdefs.h>
  33 __RCSID("$NetBSD: exec_prot_support.c,v 1.1 2011/07/18 23:16:09 jym Exp $");
  34
  35 #include <stdlib.h>
  36 #include <sys/sysctl.h>
  37
  38 #include "../../common/exec_prot.h"
  39
  40 /*
  41  * Support for executable space protection has always been erratic under i386.
  42  * Originally IA-32 can't do per-page execute permission, so it is
  43  * implemented using different executable segments for %cs (code segment).
  44  * This only allows coarse grained protection, especially when memory starts
  45  * being fragmented.
  46  * Later, PAE was introduced together with a NX/XD bit in the page table
  47  * entry to offer per-page permission.
  48  */
  49 int
  50 exec_prot_support(void)
  51 {
  52         int pae;
  53         size_t pae_len = sizeof(pae);
  54
  55         if (sysctlbyname("machdep.pae", &pae, &pae_len, NULL, 0) == -1)
  56                 return PARTIAL_XP;
  57
  58         if (pae == 1) {
  59                 if (system("cpuctl identify 0 | grep -q NOX") == 0 ||
  60                     system("cpuctl identify 0 | grep -q XD") == 0)
  61                         return PERPAGE_XP;
  62         }
  63
  64         return PARTIAL_XP;
  65 }