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/* first.S - LILO first stage boot loader */
/* Copyright 1992-1998 Werner Almesberger. See file COPYING for details. */
#define LILO_ASM
#include "lilo.h"
#ifndef LCF_NO1STDIAG
#define CYL_CHECK
#endif
.text
.globl _main
.org 0
_main: cli ! NT 4 blows up if this is missing
jmp start
.org 6
! Boot device parameters. They are set by the installer.
.ascii "LILO"
.word STAGE_FIRST
.word VERSION
timeout:.word 0 ! input timeout
delay: .word 0 ! boot delay
port: .byte 0 ! COM port (0 = unused, 1 = COM1, etc.)
sparam: .byte 0 ! serial port parameters (0 = unused)
tstamp: .long 0 ! timestamp
d1_cx: .word 0 ! first descriptor sector address
d1_dx: .word 0
d1_al: .byte 0 ! (unused)
d2_cx: .word 0 ! second descriptor sector address
d2_dx: .word 0
d2_al: .byte 0 ! (unused)
dc_cx: .word 0 ! default command-line sector address
dc_dx: .word 0
dc_al: .byte 0 ! (unused)
prompt: .byte 0 ! indicates whether to always enter prompt
! (also used as alignment byte)
ms_len: .word 0 ! initial greeting message
ms_cx: .word 0
ms_dx: .word 0
ms_al: .byte 0 ! (unused)
kt_cx: .word 0 ! keyboard translation table
kt_dx: .word 0
kt_al: .byte 0
d_addr: ! second stage sector addresses
.org CODE_START_1
ext_si: .word 0 ! external interface
ext_es: .word 0
ext_bx: .word 0
ext_dl: .byte 0
start: mov ax,#BOOTSEG ! set DS
mov ds,ax
mov ext_es,es ! copy possible external parameters
mov ext_si,si
mov ext_bx,bx
mov ext_dl,dl
mov ax,#FIRSTSEG ! beam us up ...
mov es,ax
mov cx,#256
sub si,si
sub di,di
cld
rep
movsw
jmpi go,FIRSTSEG
go: cli ! no interrupts
mov ds,ax ! AX is already set
mov es,ax ! (ES may be wrong when restarting)
mov sp,#STACK ! set the stack
mov ax,#STACKSEG
mov ss,ax
sti ! now it is safe
mov al,#0x0d ! gimme a CR ...
call display
mov al,#0x0a ! ... an LF ...
call display
mov al,#0x4c ! ... an 'L' ...
call display
lagain: mov si,#d_addr ! ready to load the second stage loader
mov bx,#SECOND
cld
sload: lodsw ! get CX
mov cx,ax
lodsw ! get DX
mov dx,ax
or ax,cx ! at EOF ?
jz done ! yes -> start it
inc si ! skip the length byte
call cread
jc error ! error -> start over again
add bx,#512 ! next sector
jmp sload
error:
#ifndef LCF_NO1STDIAG
push ax ! display a space
mov al,#32
call display
pop ax
mov al,ah ! display error code
call bout
#endif
xor ax,ax ! reset the FDC
mov dl,al
int 0x13
jmp lagain ! redo from start
done: mov al,#0x49 ! display an 'I'
call display
jmpi 0,SECONDSEG ! start the second stage loader
#ifndef LCF_NO1STDIAG
bout: push ax ! display one byte
shr al,#4
call nout
pop ax
nout: and al,#15 ! display one nibble
add al,#48
cmp al,#58
jb nokay
add al,#7
nokay: ! fall through
#endif
display:xor bh,bh ! display on screen
mov ah,#14
int 0x10
ret
linerr: pop dx ! discard stack contents
pop cx
pop bx
ret ! (carry is already set)
cread: test dl,#LINEAR_FLAG ! linear address ?
jz readsect ! no -> go on
and dl,#0xff-LINEAR_FLAG ! remove flag
!
! Translate the linear address into a sector/track/cylinder address
!
push bx ! BX is used as scratch
push cx ! LSW
push dx ! MSW with drive
mov ah,#8 ! get drive geometry (do not clobber ES:DI)
int 0x13
jc linerr ! error -> quit
mov al,dh ! AL <- #heads-1
pop dx ! get MSW
mov t_drive,dl ! save drive
mov dl,dh ! linear address (high) into DX
xor dh,dh
#ifdef CYL_CHECK
push cx ! compute #cyls-1
xchg ch,cl
rol ch,1
rol ch,1
and ch,#3
mov n_cyl,cx ! save #cyls-1
pop cx
#endif
and cx,#0x3f ! CX <- #secs
mul cl ! AX <- #secs/cyl
add ax,cx
xchg ax,bx
pop ax ! linear address (low) into AX
div bx ! DX <- cylinder, AX <- remaining secs
xchg ax,dx
div cl ! AL <- track, AH <- sector
inc ah
mov t_sector,ah
xchg ax,dx ! AX <- cylinder, DL <- track
mov dh,dl ! set up DX (head:drive)
mov dl,t_drive
#ifdef CYL_CHECK
cmp ax,n_cyl ! valid cylinder number ?
ja linerr3 ! no -> error
#endif
xchg ah,al ! build cylinder number
ror al,1
ror al,1
or al,t_sector
mov cx,ax
pop bx ! restore BX
readsect:
mov ax,#0x201 ! read one sector
int 0x13
ret ! quit, possibly with errors
#ifdef CYL_CHECK
linerr3:pop bx ! pop BX and linear address
xor ax,ax ! zero indicates internal error
stc ! error
ret
n_cyl: .word 0 ! temporary space
#endif
t_drive:.byte 0
t_sector:.byte 0
/* Here are at least 66 bytes of free space. This is reserved for the
partition table and the boot signature. */
theend:
|
