2 * Copyright (c) 1998 Michael Smith <msmith@freebsd.org>
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
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.
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
26 * $FreeBSD: src/sys/boot/i386/libi386/biosmem.c,v 1.7 2003/08/25 23:28:31 obrien Exp $
27 * $DragonFly: src/sys/boot/pc32/libi386/biosmem.c,v 1.3 2003/11/10 06:08:36 dillon Exp $
30 * Obtain memory configuration information from the BIOS
37 u_int32_t bios_basemem, bios_extmem;
39 #define SMAPSIG 0x534D4150
47 static struct smap smap;
53 /* Parse system memory map */
57 v86.addr = 0x15; /* int 0x15 function 0xe820*/
59 v86.ecx = sizeof(struct smap);
61 v86.es = VTOPSEG(&smap);
62 v86.edi = VTOPOFF(&smap);
64 if ((v86.efl & 1) || (v86.eax != SMAPSIG))
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;
73 } while (v86.ebx != 0);
75 /* Fall back to the old compatibility function for base memory */
76 if (bios_basemem == 0) {
78 v86.addr = 0x12; /* int 0x12 */
81 bios_basemem = (v86.eax & 0xffff) * 1024;
84 /* Fall back through several compatibility functions for extended memory */
85 if (bios_extmem == 0) {
87 v86.addr = 0x15; /* int 0x15 function 0xe801*/
91 bios_extmem = ((v86.ecx & 0xffff) + ((v86.edx & 0xffff) * 64)) * 1024;
94 if (bios_extmem == 0) {
96 v86.addr = 0x15; /* int 0x15 function 0x88*/
99 bios_extmem = (v86.eax & 0xffff) * 1024;
102 /* Set memtop to actual top of memory */
103 memtop = 0x100000 + bios_extmem;