Linux Cubed Series 7: Sunsite/Linux Cubed Series 7 - Sunsite Vol 1.iso/system/filesyst/xiafs/xiafspgm.8/xiafspgm/xiafspgm-0.8.1/secondary.s

Text File | 1993-03-21 | 6KB | 327 lines

!-----------------------------------------------------------------------!
! secondary.s                                !
!                                    !
!   Copyright (C) Q. Frank Xia, 1993.  All rights reserved.        !
!                                    !
! This software may be redistributed as per Linux copyright        !
!                                    !
!-----------------------------------------------------------------------!


SETUPSECTS     = 4        ! nr of setup sectors
BOOTSEG        = 0x07C0    ! original address of boot sector
INITSEG       = 0x9000    ! we move boot here - out of the way
SETUPSEG      = 0x9020    ! setup starts here
SYSSEG        = 0x1000    ! system loaded at 0x10000 (65536).
IMAGESEG      = 0        ! setup loaded at 0:0xf8000 first
IMAGEOFF      = 0xf800    ! then moved to SETUPSEG:0x0000

    .text
    .globl    _main
_main:


! move this 512 byte to INITSEG:0x0000

    mov    ax, #BOOTSEG
    mov    ds, ax
    mov    ax, #INITSEG
    mov    es, ax
    mov    cx, #256
    sub    si, si
    sub    di, di
    cld
    rep
    movsw
    jmpi    start, INITSEG


! set up the segment registers and the stack

start:
    mov    ax, cs        ! setup seg registers
    mov    ds, ax        ! put stack at INITSEG:0x4000-12.
    mov    es, ax
    mov    ss, ax
    mov    ax, #0x4000-12
    mov    sp, ax


! get disk drive parameters

    movb    boot_disk, dl    ! save root disk code

    testb    dl, #0x80    ! hd or floppy ?
    jz    floppy


! get hard disk drive parameters

    mov    di, sp        ! hard disk boot
    movb    ah, #0x08    ! find out the parameters of the hard disk
    int    0x13
die1:    jc    die1
    andb    cl, #0x3f
    movb    nr_sects, cl
    incb    dh
    movb    nr_heads, dh
    jmp    load_all


! get diskette drive parameters

floppy:
    xor    ax, ax
    mov    fs, ax
    mov    bx, #0x78        ! fs:bx is parameter table address
    seg fs
    lgs    si, (bx)        ! gs:si is source
    mov    di, dx            ! es:di is destination
    mov    cx, #6            ! copy 12 bytes
    cld
    rep
    seg gs
    movsw

    mov    di, dx
    movb    4(di), *18        ! patch sector count
    seg fs
    mov    (bx), di
    seg fs
    mov    2(bx), es
    mov    ax, cs
    mov    fs, ax
    mov    gs, ax
    xor    ah, ah            ! reset FDC
    xor    dl, dl
    int     0x13


! get parameters

    xor    dx, dx            ! drive 0, head 0
    mov    cx, #0x0012        ! sector 18, track 0
    mov    bx, #0x0200          ! address after setup (es = cs)
    mov    ax, #0x0201        ! service 2, 1 sector
    int    0x13
    jnc    params_got
    movb    cl, #0x0f        ! sector 15
    mov    ax, #0x0201        ! service 2, 1 sector
    int    0x13
    jnc    params_got
die2:    jmp    die2

params_got:
    movb    nr_sects, cl
    movb    nr_heads, #2


! load the kernel image

load_all:

    movb    al, nr_sects        ! calculate start cylinder,
    mulb    nr_heads        ! head, secot_read
    mov    cx, ax
    mov    ax, Istart_lo
    mov    dx, Istart_hi
    div    cx
    mov    cylinder, ax
    mov    ax, dx
    divb    nr_sects
    movb    head, al
    movb    sect_read, ah

    mov    bp, #msg_load        ! Print "loading"
    call    print_string

    mov    ax, #IMAGESEG        ! load Image to 0:IMAGEOFF
    mov    es, ax
    mov    bx, #IMAGEOFF
    call    do_load
    call    move_setup
    call    kill_motor
    mov    bp, #msg_crlf
    call    print_string

    mov    ax, root_dev        ! get root_dev device number
    or    ax, ax            ! major and minor.
    jne    root_defined
    mov    bx, nr_sects
    mov    ax, #0x0208        ! /dev/ps0 - 1.2Mb (2,8)
    cmp    bx, #15
    je    root_defined
    mov    ax, #0x021c        ! /dev/PS0 - 1.44Mb (2,28)
    cmp    bx, #18
    je    root_defined
    mov    ax, #0x0200        ! /dev/fd0 - autodetect

root_defined:
    mov    root_dev, ax

    jmpi    0, SETUPSEG        ! load done, jump to setup seg

do_load:
    mov     ax, es
    test     ax, #0x0fff
die3:    jne     die3            ! es must be at 64kB boundary

repeat_load:
    mov     ax, es
    cmp     ax, end_seg        ! have we loaded all yet?
    jb     do_load_1
    ret
do_load_1:
    movb     al, nr_sects
    subb     al, sect_read
    mov     cx, ax
    shl     cx, #9
    add     cx, bx
    jnc     do_load_2
    je     do_load_2
    xor     ax, ax
    sub     ax, bx
    shr     ax, #9
do_load_2:
    call     read_track
    movb     cl, al
    addb     al, sect_read
    cmpb     al, nr_sects
    jne     do_load_3
    mov     ax, #0
    incb     head
    movb    dl, head
    cmpb    dl, nr_heads
    jne    do_load_3
    movb    head, #0
    incb    cylinder
do_load_3:
    movb     sect_read, al
    shl     cx, #9
    add     bx, cx
    jnc     repeat_load
    mov     ax, es
    add     ah, #0x10
    mov     es, ax
    xor     bx, bx
    jmp     repeat_load

read_track:
    pusha
    pusha
    mov    ax, #0xe2e         ! print `.'
    mov    bx, #7
     int    0x10
    popa

    mov    dx, cylinder        ! al = # of sectors already loaded
    movb    cl, sect_read
    incb    cl            ! cl = sector, 1 related
    movb    ch, dl            ! ch = sylinder
    shlb    dh, #6            ! bit 6-7 of cl contains up 2 bits
    orb    cl, dh            ! of cylinder
    movb    dh, head        ! dh = head
    movb    dl, boot_disk        ! dl = disk code
    movb    ah, #2

    int    0x13
    jc    read_err
    popa
    ret

read_err:
    mov    bp, #msg_err
    call    print_string            ! ah = error, al = read

    xor     ah, ah
    xor     dl, dl
    int     0x13

    popa
    jmp     read_track

move_setup:
    pusha
    mov     ax, #IMAGESEG
    mov    ds, ax
    mov    si, #IMAGEOFF
    mov    ax, #SETUPSEG
    mov    es, ax
    xor    di, di
    mov    cx, #0x800
    cld
    rep
    movsw
    mov    ax, cx
    mov    ds, ax
    mov    es, ax
    popa
    ret


! print a string
! bp = address of the string to print

print_string:
    pusha
    push    bp
    mov    ah, #0x03        ! read cursor pos
    xor    bh, bh
    int    0x10
    pop    bp
    mov    cx, #9
    mov    bx, #0x0007        ! page 0, attribute 7 (normal)
    mov    ax, #0x1301        ! write string, move cursor
    int    0x10
    popa
    ret

! kill the floppy motor

kill_motor:
    push dx
    mov dx, #0x3f2
    xor al, al
    outb
    pop dx
    ret

msg_load:
    .byte 13, 10
    .ascii "loading"
msg_err:
    .byte 13, 10
    .ascii "retry"
msg_crlf:
    .byte 13, 10, 0

nr_sects:
    .byte 9
nr_heads:
    .byte 2

sect_read:
    .byte 0            ! sectors read of current track

.org 496
head:
Istart_lo:            ! Istart_lo, Istart_hi and end_seg
    .word 1            ! are filled by mkboot.
cylinder:
Istart_hi:
    .word 0
end_seg:
    .word 0x4000

swap_dev:            ! root_dev may changed by mkboot.
    .word 0            ! other feilds are copied from
ram_size:            ! kernel image.
    .word 0
vid_mode:
    .word 1
root_dev:
    .word 0
boot_disk:
boot_flag:
    .word 0xAA55