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 1.4 2004/06/26 02:26:22 dillon Exp $
30 * Obtain memory configuration information from the BIOS
37 u_int32_t bios_basemem, bios_extmem, bios_howmem;
39 #define SMAPSIG 0x534D4150
47 static struct smap smap;
54 /* Parse system memory map */
57 #ifdef COMCONSOLE_DEBUG
58 printf("GET SMAP %d: ", v86.ebx);
61 v86.addr = 0x15; /* int 0x15 function 0xe820*/
63 v86.ecx = sizeof(struct smap);
65 v86.es = VTOPSEG(&smap);
66 v86.edi = VTOPOFF(&smap);
68 #ifdef COMCONSOLE_DEBUG
69 printf("RESULT: EFL=%04x EAX=%08x SMAPTYPE %d BASE %08x%08x LEN %08x%08x\n",
70 v86.efl, v86.eax, smap.type,
71 (int)(smap.base >> 32), (int)smap.base,
72 (int)(smap.length >> 32), (int)smap.length);
74 if ((v86.efl & 1) || (v86.eax != SMAPSIG))
76 /* look for a low-memory segment that's large enough */
77 if ((smap.type == 1) && (smap.base == 0) && (smap.length >= (512 * 1024))) {
78 bios_basemem = smap.length;
81 /* look for the first segment in 'extended' memory */
82 if ((smap.type == 1) && (smap.base == 0x100000)) {
83 bios_extmem = smap.length;
85 } while (v86.ebx != 0);
87 /* Fall back to the old compatibility function for base memory */
88 if (bios_basemem == 0) {
90 v86.addr = 0x12; /* int 0x12 */
93 bios_basemem = (v86.eax & 0xffff) * 1024;
97 /* Fall back through several compatibility functions for extended memory */
98 if (bios_extmem == 0) {
100 v86.addr = 0x15; /* int 0x15 function 0xe801*/
103 if (!(v86.efl & 1)) {
104 v = ((v86.ecx & 0xffff) +
105 ((int64_t)(v86.edx & 0xffff) * 64)) * 1024;
111 if (bios_extmem == 0) {
113 v86.addr = 0x15; /* int 0x15 function 0x88*/
116 bios_extmem = (v86.eax & 0xffff) * 1024;
120 * Set memtop to actual top of memory
122 * This is broken because the boot loader generally needs more than 16MB
123 * now but the extmem usually calculates to ~14-16MB (which is the fully
124 * segmented limit). Disk I/O will use bounce buffers.
128 memtop = 0x100000 + bios_extmem; /* XXX ignored */
129 memtop = 64 * 1024 * 1024;