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      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 }
     66