/*      $NetBSD: biosmemx.S,v 1.13 2024/08/24 20:23:11 riastradh Exp $  */

/*
 * Copyright (c) 1997, 1999
 *      Matthias Drochner.  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 ``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 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 <machine/asm.h>

        .text

/*
 * int getextmem2(int buffer[2])
 *
 * return: 0=OK, -1=error
 * buffer[0]: extmem kBytes below 16M (max 15M/1024)
 * buffer[1]: extmem above 16M, in 64k units
 */
ENTRY(getextmem2)
        pushl   %ebp
        movl    %esp,%ebp
        pushl   %ebx
        pushl   %ecx
        pushl   %edx
        push    %esi
        push    %edi

        call    _C_LABEL(prot_to_real)
        .code16

        xorl    %ebx,%ebx
        movl    $0xe801,%eax
        int     $0x15
        pushf

        movw    %si,%ax
        orw     %si,%bx
        jz      1f              /* if zero use configured values */
        movw    %cx,%ax         /* k below 16M (max 0x3c00 = 15MB) */
        movw    %dx,%bx         /* 64k above 16M */
1:
        popf
        setc    %bl

        calll   _C_LABEL(real_to_prot)
        .code32

        movl    8(%ebp),%edi
        xorl    %eax,%eax
        movw    %cx,%ax
        stosl
        movw    %dx,%ax
        stosl
        movb    %bl,%al
        cbw

        pop     %edi
        pop     %esi
        popl    %edx
        popl    %ecx
        popl    %ebx
        popl    %ebp
        ret

/*
 * int getmementry(int *iterator, int buffer[6])
 *
 * return: 0=ok, else error
 * buffer[0]: start of memory chunk
 * buffer[2]: length (bytes)
 * buffer[4]: type
 * buffer[5]: ACPI 3.0 Extended Attributes bitfield (unused)
 *
 * Some buggy BIOSes may write to 24 bytes even if only 20 were requested.
 * Therefore, the buffer is defined for 6 elements to avoid stack buffer
 * overruns.  See PR install/49470.
 *
 * More details can be found in the:
 *
 *      Advanced Configuration and Power Interface (ACPI)
 *      Specification, Release 6.5, 2022-08-29, UEFI Forum, Inc.,
 *      Sec. 15.1 `INT 15H E820H - Query System Address Map',
 *      pp. 756-757
 *      https://uefi.org/sites/default/files/resources/ACPI_Spec_6_5_Aug29.pdf#page=824
 *      https://uefi.org/specs/ACPI/6.5/15_System_Address_Map_Interfaces.html#int-15h-e820h-query-system-address-map
 *
 * as well as this OSDev.org wiki page:
 *
 *      https://wiki.osdev.org/Detecting_Memory_(x86)#BIOS_Function:_INT_0x15,_EAX_=_0xE820
 */
ENTRY(getmementry)
        pushl   %ebp
        movl    %esp,%ebp
        pushl   %ebx
        pushl   %ecx
        pushl   %edx
        push    %esi
        push    %edi

        movl    8(%ebp),%eax
        movl    0(%eax),%ebx            /* index */
        movl    $20,%ecx                /* Buffer size */
        movl    $0x534d4150,%edx        /* "SMAP" */
        movl    12(%ebp),%edi           /* buffer address */

        call    _C_LABEL(prot_to_real)
        .code16

        push    %di
        shrl    $4,%edi
        mov     %ds,%ax
        add     %di,%ax
        mov     %ax,%es
        pop     %di
        and     $0xf,%di                /* buffer address now in ES:DI */

        movl    $0xe820,%eax            /* Some BIOS check EAX value */
        int     $0x15

        setc    %cl

        calll   _C_LABEL(real_to_prot)
        .code32

        movl    8(%ebp),%eax
        movl    %ebx,0(%eax)            /* updated index */
        xorl    %eax,%eax
        movb    %cl,%al

        pop     %edi
        pop     %esi
        popl    %edx
        popl    %ecx
        popl    %ebx
        popl    %ebp
        ret

/*
 * int biosA20(void)
 *
 * return: 0=ok, else error
 */
ENTRY(biosA20)
        pushl   %ebp
        movl    %esp,%ebp
        pushl   %ebx
        pushl   %ecx
        pushl   %edx
        push    %esi
        push    %edi

        call    _C_LABEL(prot_to_real)
        .code16

        movl    $0x2401,%eax
        int     $0x15
        setc    %cl

        calll   _C_LABEL(real_to_prot)
        .code32

        movzbl  %cl,%eax

        pop     %edi
        pop     %esi
        popl    %edx
        popl    %ecx
        popl    %ebx
        popl    %ebp
        ret