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/*-
 * Copyright (c) 1998 Michael Smith <msmith@freebsd.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD: release/9.1.0/sys/boot/i386/libi386/biosmem.c 229501 2012-01-04 16:39:39Z jhb $");

/*
 * Obtain memory configuration information from the BIOS
 */
#include <stand.h>
#include <machine/pc/bios.h>
#include "libi386.h"
#include "btxv86.h"

vm_offset_t	memtop, memtop_copyin, high_heap_base;
uint32_t	bios_basemem, bios_extmem, high_heap_size;

static struct bios_smap smap;

/*
 * The minimum amount of memory to reserve in bios_extmem for the heap.
 */
#define	HEAP_MIN	(3 * 1024 * 1024)

void
bios_getmem(void)
{
    uint64_t size;

    /* Parse system memory map */
    v86.ebx = 0;
    do {
	v86.ctl = V86_FLAGS;
	v86.addr = 0x15;		/* int 0x15 function 0xe820*/
	v86.eax = 0xe820;
	v86.ecx = sizeof(struct bios_smap);
	v86.edx = SMAP_SIG;
	v86.es = VTOPSEG(&smap);
	v86.edi = VTOPOFF(&smap);
	v86int();
	if ((V86_CY(v86.efl)) || (v86.eax != SMAP_SIG))
	    break;
	/* look for a low-memory segment that's large enough */
	if ((smap.type == SMAP_TYPE_MEMORY) && (smap.base == 0) &&
	    (smap.length >= (512 * 1024)))
	    bios_basemem = smap.length;
	/* look for the first segment in 'extended' memory */
	if ((smap.type == SMAP_TYPE_MEMORY) && (smap.base == 0x100000)) {
	    bios_extmem = smap.length;
	}

	/*
	 * Look for the largest segment in 'extended' memory beyond
	 * 1MB but below 4GB.
	 */
	if ((smap.type == SMAP_TYPE_MEMORY) && (smap.base > 0x100000) &&
	    (smap.base < 0x100000000ull)) {
	    size = smap.length;

	    /*
	     * If this segment crosses the 4GB boundary, truncate it.
	     */
	    if (smap.base + size > 0x100000000ull)
		size = 0x100000000ull - smap.base;

	    if (size > high_heap_size) {
		high_heap_size = size;
		high_heap_base = smap.base;
	    }
	}
    } while (v86.ebx != 0);

    /* Fall back to the old compatibility function for base memory */
    if (bios_basemem == 0) {
	v86.ctl = 0;
	v86.addr = 0x12;		/* int 0x12 */
	v86int();
	
	bios_basemem = (v86.eax & 0xffff) * 1024;
    }

    /* Fall back through several compatibility functions for extended memory */
    if (bios_extmem == 0) {
	v86.ctl = V86_FLAGS;
	v86.addr = 0x15;		/* int 0x15 function 0xe801*/
	v86.eax = 0xe801;
	v86int();
	if (!(V86_CY(v86.efl))) {
	    bios_extmem = ((v86.ecx & 0xffff) + ((v86.edx & 0xffff) * 64)) * 1024;
	}
    }
    if (bios_extmem == 0) {
	v86.ctl = 0;
	v86.addr = 0x15;		/* int 0x15 function 0x88*/
	v86.eax = 0x8800;
	v86int();
	bios_extmem = (v86.eax & 0xffff) * 1024;
    }

    /* Set memtop to actual top of memory */
    memtop = memtop_copyin = 0x100000 + bios_extmem;

    /*
     * If we have extended memory and did not find a suitable heap
     * region in the SMAP, use the last 3MB of 'extended' memory as a
     * high heap candidate.
     */
    if (bios_extmem >= HEAP_MIN && high_heap_size < HEAP_MIN) {
	high_heap_size = HEAP_MIN;
	high_heap_base = memtop - HEAP_MIN;
    }
}