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
27 #include <sys/cdefs.h>
28 __FBSDID("$FreeBSD$");
31 * Obtain memory configuration information from the BIOS
34 #include <machine/pc/bios.h>
38 vm_offset_t memtop, memtop_copyin, high_heap_base;
39 uint32_t bios_basemem, bios_extmem, high_heap_size;
41 static struct bios_smap smap;
44 * The minimum amount of memory to reserve in bios_extmem for the heap.
46 #define HEAP_MIN (3 * 1024 * 1024)
53 /* Parse system memory map */
57 v86.addr = 0x15; /* int 0x15 function 0xe820*/
59 v86.ecx = sizeof(struct bios_smap);
61 v86.es = VTOPSEG(&smap);
62 v86.edi = VTOPOFF(&smap);
64 if ((v86.efl & 1) || (v86.eax != SMAP_SIG))
66 /* look for a low-memory segment that's large enough */
67 if ((smap.type == SMAP_TYPE_MEMORY) && (smap.base == 0) &&
68 (smap.length >= (512 * 1024)))
69 bios_basemem = smap.length;
70 /* look for the first segment in 'extended' memory */
71 if ((smap.type == SMAP_TYPE_MEMORY) && (smap.base == 0x100000)) {
72 bios_extmem = smap.length;
76 * Look for the largest segment in 'extended' memory beyond
79 if ((smap.type == SMAP_TYPE_MEMORY) && (smap.base > 0x100000) &&
80 (smap.base < 0x100000000ull)) {
84 * If this segment crosses the 4GB boundary, truncate it.
86 if (smap.base + size > 0x100000000ull)
87 size = 0x100000000ull - smap.base;
89 if (size > high_heap_size) {
90 high_heap_size = size;
91 high_heap_base = smap.base;
94 } while (v86.ebx != 0);
96 /* Fall back to the old compatibility function for base memory */
97 if (bios_basemem == 0) {
99 v86.addr = 0x12; /* int 0x12 */
102 bios_basemem = (v86.eax & 0xffff) * 1024;
105 /* Fall back through several compatibility functions for extended memory */
106 if (bios_extmem == 0) {
108 v86.addr = 0x15; /* int 0x15 function 0xe801*/
111 if (!(v86.efl & 1)) {
112 bios_extmem = ((v86.ecx & 0xffff) + ((v86.edx & 0xffff) * 64)) * 1024;
115 if (bios_extmem == 0) {
117 v86.addr = 0x15; /* int 0x15 function 0x88*/
120 bios_extmem = (v86.eax & 0xffff) * 1024;
123 /* Set memtop to actual top of memory */
124 memtop = memtop_copyin = 0x100000 + bios_extmem;
127 * If we have extended memory and did not find a suitable heap
128 * region in the SMAP, use the last 3MB of 'extended' memory as a
129 * high heap candidate.
131 if (bios_extmem >= HEAP_MIN && high_heap_size < HEAP_MIN) {
132 high_heap_size = HEAP_MIN;
133 high_heap_base = memtop - HEAP_MIN;