i386_set_watch.c revision 66174 
1/*
2 * Copyright 2000  Brian S. Dean <bsd@bsdhome.com>
3 * All Rights Reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 *
9 * 1. Redistributions of source code must retain the above copyright
10 *    notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 *    notice, this list of conditions and the following disclaimer in the
13 *    documentation and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY BRIAN S. DEAN ``AS IS'' AND ANY
16 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
17 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
18 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL BRIAN S. DEAN BE LIABLE
19 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
20 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
21 * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
22 * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
23 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
24 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
25 * USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
26 * DAMAGE.
27 *
28 */
29
30/*
31 * $FreeBSD: head/lib/libc/i386/sys/i386_set_watch.c 66174 2000-09-21 17:07:27Z bsd $
32 */
33
34
35#include <machine/reg.h>
36#include <machine/sysarch.h>
37
38
39int
40i386_set_watch(int watchnum, unsigned int watchaddr, int size,
41               int access, struct dbreg * d)
42{
43	int i;
44	unsigned int mask;
45
46	if (watchnum == -1) {
47		for (i = 0, mask = 0x3; i < 4; i++, mask <<= 2)
48			if ((d->dr7 & mask) == 0)
49				break;
50		if (i < 4)
51			watchnum = i;
52		else
53			return -1;
54	}
55
56	switch (access) {
57	case DBREG_DR7_EXEC:
58		size = 1; /* size must be 1 for an execution breakpoint */
59		/* fall through */
60	case DBREG_DR7_WRONLY:
61	case DBREG_DR7_RDWR:
62		break;
63	default : return -1; break;
64	}
65
66	/*
67	 * we can watch a 1, 2, or 4 byte sized location
68	 */
69	switch (size) {
70	case 1  : mask = 0x00; break;
71	case 2  : mask = 0x01 << 2; break;
72	case 4  : mask = 0x03 << 2; break;
73	default : return -1; break;
74	}
75
76	mask |= access;
77
78	/* clear the bits we are about to affect */
79	d->dr7 &= ~((0x3 << (watchnum*2)) | (0x0f << (watchnum*4+16)));
80
81	/* set drN register to the address, N=watchnum */
82	DBREG_DRX(d,watchnum) = watchaddr;
83
84	/* enable the watchpoint */
85	d->dr7 |= (0x2 << (watchnum*2)) | (mask << (watchnum*4+16));
86
87	return watchnum;
88}
89