biosmem.c revision 64187 
1/*-
2 * Copyright (c) 1998 Michael Smith <msmith@freebsd.org>
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 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24 * SUCH DAMAGE.
25 *
26 * $FreeBSD: head/sys/boot/i386/libi386/biosmem.c 64187 2000-08-03 09:14:02Z jhb $
27 */
28
29/*
30 * Obtain memory configuration information from the BIOS
31 */
32#include <stand.h>
33#include "libi386.h"
34#include "btxv86.h"
35
36vm_offset_t	memtop;
37u_int32_t	bios_basemem, bios_extmem;
38
39#define SMAPSIG	0x534D4150
40
41struct smap {
42    u_int64_t	base;
43    u_int64_t	length;
44    u_int32_t	type;
45} __attribute__ ((packed));
46
47static struct smap smap;
48
49void
50bios_getmem(void)
51{
52
53    /* Parse system memory map */
54    v86.ebx = 0;
55    do {
56	v86.ctl = V86_FLAGS;
57	v86.addr = 0x15;		/* int 0x15 function 0xe820*/
58	v86.eax = 0xe820;
59	v86.ecx = sizeof(struct smap);
60	v86.edx = SMAPSIG;
61	v86.es = VTOPSEG(&smap);
62	v86.edi = VTOPOFF(&smap);
63	v86int();
64	if ((v86.efl & 1) || (v86.eax != SMAPSIG))
65	    break;
66	/* look for a low-memory segment that's large enough */
67	if ((smap.type == 1) && (smap.base == 0) && (smap.length >= (512 * 1024)))
68	    bios_basemem = smap.length;
69	/* look for the first segment in 'extended' memory */
70	if ((smap.type == 1) && (smap.base == 0x100000)) {
71	    bios_extmem = smap.length;
72	}
73    } while (v86.ebx != 0);
74
75    /* Fall back to the old compatibility function for base memory */
76    if (bios_basemem == 0) {
77	v86.ctl = 0;
78	v86.addr = 0x12;		/* int 0x12 */
79	v86int();
80
81	bios_basemem = (v86.eax & 0xffff) * 1024;
82    }
83
84    /* Fall back through several compatibility functions for extended memory */
85    if (bios_extmem == 0) {
86	v86.ctl = V86_FLAGS;
87	v86.addr = 0x15;		/* int 0x15 function 0xe801*/
88	v86.eax = 0xe801;
89	v86int();
90	if (!(v86.efl & 1)) {
91	    bios_extmem = ((v86.ecx & 0xffff) + ((v86.edx & 0xffff) * 64)) * 1024;
92	}
93    }
94    if (bios_extmem == 0) {
95	v86.ctl = 0;
96	v86.addr = 0x15;		/* int 0x15 function 0x88*/
97	v86.eax = 0x8800;
98	v86int();
99	bios_extmem = (v86.eax & 0xffff) * 1024;
100    }
101
102    /* Set memtop to actual top of memory */
103    memtop = 0x100000 + bios_extmem;
104
105}
106
107