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
exec_prot_support(void)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