#if 0
; first.S - LILO first stage boot loader with LBA32 support */
Copyright 1992-1998 Werner Almesberger.
Copyright 1999-2003 John Coffman.
All rights reserved.
Licensed under the terms contained in the file 'COPYING' in the
source directory.
#endif
#define LILO_ASM
#include "lilo.h"
get common.s /* as86 "include" will bypass the CPP */
#define VALIDATE 1 /* adds 13h bytes */
#define SECOND_CHECK 1 /* adds 5h bytes */
#define CYL1023 0 /* subs 8h bytes */
#if VERSION_MINOR>=50
# define DEBUG_NEW
# undef VIDEO_ENABLE
# define VIDEO_ENABLE 3
#endif
! VIDEO_ENABLE for those systems that disable the video on boot
! = 0 first stage does not enable video
! = 1 use get vid mode/set vid mode to enable
! = 2 use VGA enable call to enable video
! (cannot use, as code gets too big)
! = 3 use direct mode set (mode 3, CGA, EGA, VGA)
! = 7 use direct mode set (mode 7, MDA)
!
#ifndef VIDEO_ENABLE
# if VALIDATE==0
# define VIDEO_ENABLE 2
# else
# define VIDEO_ENABLE 2
# endif
#endif
! do not change the following -- it must correspond to the code in bsect.c
#define RELOCATABLE -1
.text
.globl _main
.org 0
zero:
_main: cli ! NT 4 blows up if this is missing
jmp start
stage: .byte STAGE_FIRST
.org 4
reloc:
#if RELOCATABLE
.word theend-zero ! size of the code & params
#else
.word 0 ! no size indication
#endif
.org 6
! Boot device parameters. They are set by the installer.
sig: .ascii "LILO"
vers: .word VERSION
mapstamp: .long 0 ! map timestamp
length = *-sig ! for the stage 1 vs stage 2 comparison
raid: .long 0 ! raid sector offset
tstamp: .long 0 ! timestamp
map_serial_no: .long 0 ! volume S/N containing map file
prompt: .byte 0 ! indicates whether to always enter prompt
! contains many other flags, too
d_dev: .byte 0x80 ! map file device code
d_flag: .byte 0 ! disk addressing flags
d_addr: .long 0 ! disk addr of second stage index sector
edd_packet = 0
;;; .word 16 ! size of packet
;;; .word 1 ! count of bytes to read
edd_addr = 4
;;; .word map2 ! where to read
;;; .word *-* ! segment where to read
edd_d_addr = 8
;;; .long 1 ! low address or CX,DX (geometric)
! start at sector 1 for search in geo mode
;;; .long 0 ! hi address
#if 0
! These locations are referenced as EX_OFF
! (they used to be at CODE_START_1)
ext_si: .word 0 ! external interface
ext_es: .word 0 ! these locations are referenced in second.S
ext_bx: .word 0 ! do not disturb the ordering
ext_dl: .byte 0 ! second.S will check this magic number
ext_dh: .byte 0 ! not referenced, but must align stack
ext_stack:
#endif
/***************************************************/
! The following instruction MUST be
! first instruction after the CLI/JMP short
! at the start of the file; otherwise
! the boot sector relocation fails.
!
start:
mov ax,#BOOTSEG ! use DS,ES,SS = 0x07C0
/***************************************************/
mov ss,ax
mov sp,#SETUP_STACKSIZE ! set the stack for First Stage
sti ! now it is safe
push dx ! set ext_dl (and ext_dh, which is not used)
push bx ! WATCH the order of pushes
push es ! set ext_es
push si ! set ext_si
#ifdef DEBUG_NEW
push ds
push es ! just not enough space with debug turned on
#endif
#define JRC_DS_EQ_SS
cld ! do not forget to do this !!!
mov ds,ax ! address data area
xor bp,bp ! shorted addressing
#if VIDEO_ENABLE
! a BIOS has been found where the video interrupt (0x10) trashes DX
! so, we had better be very paranoid about DX
!
# if VIDEO_ENABLE==2
pusha ! protect DX
# endif
# if VIDEO_ENABLE > 2
mov ax,#VIDEO_ENABLE ! set video mode 3 or 7
# elif VIDEO_ENABLE==1
mov ah,#15 ! get video mode
int 0x10
cbw
# else /* VIDEO_ENABLE==2 */
mov ax,#0x1200 ! enable video (VGA)
mov bl,#0x36 ! (probably a nop on EGA or MDA)
# endif
int 0x10 ! video call
# if VIDEO_ENABLE==2
popa ! restore DX
# endif
#endif
#if (VIDEO_ENABLE&1) == 0
mov al,#0x0d ! gimme a CR ...
call display
; the suspect call for trashing DX on one BIOS:
mov al,#0x0a ! ... an LF ...
call display
#endif
#if defined(DEBUG_NEW)
mov ah,dl
call bout ! code in AH
#endif
mov al,#0x4c ! ... an 'L' ...
call display
pusha ! preserve all the registers for restart
lagain:
push ds
pop es ! use buffer at end of boot sector
cmp dl,#EX_DL_MAG ! possible boot command line (chain.S)
jne boot_in_dl
mov dl,dh ! code passed in DH instead
boot_in_dl:
mov bx,#map2 ! buffer for volume search
mov dh,[d_dev](bp) ! map device to DH
#if VALIDATE
mov ax,dx ! copy device code to AL
and ah,#0x80 ! AH = 00 or 80
xor al,ah ! hi-bits must be the same
js use_installed
cmp al,#MAX_BIOS_DEVICES ! limit the device code
jae use_installed ! jump if DL is not valid
! map is on boot device for RAID1, and if so marked; viz.,
test byte ptr [prompt](bp),#FLAG_MAP_ON_BOOT
jnz use_boot ! as passed in from BIOS or MBR loader
#endif
use_installed:
mov dl,dh ! device code to DL
mov edi,[map_serial_no](bp) ! to search for
or edi,edi
jz done_search
push dx ! save flags
mov ah,#8 ! get number of hard disks
mov dl,#0x80
int 0x13
jc error
#if 0
movzx cx,dl ! extend to word in CX
#else
xchg ax,dx ! AL = device count
cbw ! AX = device count
xchg ax,cx ! CX = device count
#endif
mov dx,#0x80-1 ! device 80, flags=0
vagain:
inc dx
xor eax,eax
inc ax
call disk_read ! read
;;; jc error
cmp edi,[PART_TABLE_OFFSET-6](bx)
je vol_found
loop vagain
pop dx ! restore specified BIOS code
! AX and DX are identical at this point
vol_found:
! uses value in DX, stack may have extra value
done_search:
use_boot:
push bx ! save map2 for later
mov dh,[d_flag](bp) ! get device flags to DH
mov si,#d_addr
call pread ! increments BX
mov ah,#0x99 ! possible error code
cmp dword (bx-4),#EX_MAG_HL ! "LILO"
jne error
pop si ! point at #map2
push #SETUP_STACKSIZE/16 + BOOTSEG + SECTOR_SIZE/16*2
pop es
xor bx,bx
sload:
call pread ! read using map at DS:SI
jnz sload ! into memory at ES:BX (auto increment)
! Verify second stage loader signature
mov si,#sig ! pointer to signature area
mov di,si
mov cx,#length ! number of bytes to compare
repe
cmpsb ! check Signature 1 & 2
jne no2nd_err ! check Signature 2
#if SECOND_CHECK
/* it would be nice to re-incorporate this check */
mov al,#STAGE_SECOND
scasb
jne no2nd_err
#endif
! Start the second stage loader DS=location of Params
push es ! segment of second stage
push bp ! BP==0
mov al,#0x49 ! display an 'I'
call display
retf ! Jump to ES:BP
! error exits below
no2nd_err:
mov ah,#0x9A
! no return from error
error:
#ifndef LCF_NO1STDIAG
mov al,#32 ! display a space
call display
call bout
#endif
dec byte [zero](bp) ! CLI == 0xFA == 250
jz zzz
#ifndef DEBUG_NEW
mov sp,#SETUP_STACKSIZE-4*2-8*2 ! set the stack for First Stage
#else
mov sp,#SETUP_STACKSIZE-4*2-2*2-8*2 ! set the stack for First Stage
#endif
popa ! restore registers for restart
pusha
jmp near lagain ! redo from start
zzz:
#ifndef DEBUG_NEW
hlt
#endif
jmp zzz ! spin; wait for Ctrl-Alt-Del
! Pointer Read -- read using pointer in DS:SI
pread:
lodsd ! get address
or eax,eax
jz done
add eax,[raid](bp) ! reloc is 0 on non-raid
call disk_read
;;; jc error ! error, complain
add bh,#SECTOR_SIZE/256 ! next sector
done:
ret
! packet read routine
disk_read:
#ifndef JRC_DS_EQ_SS
push ds
#endif
pusha
#ifndef JRC_DS_EQ_SS
push ss
pop ds
#endif
;;;; push dword #0 ! high order disk address
push bp
push bp
push eax ! low order disk address
push es ! memory segment ES
push bx ! memory offset BX
push #1 ! sector count
push #16 ! size of packet = 16 bytes
mov si,sp ! address of packet DS:SI
push bx
test dh,#LINEAR_FLAG|LBA32_FLAG
jz disk_geometric
test dh,#LBA32_FLAG
jz disk_convert ; it must be LINEAR
mov bx,#0x55AA ;magic number
mov ah,#0x41
int 0x13
jc disk_convert
cmp bx,#0xAA55 ;changed?
jne disk_convert
test cl,#EDD_PACKET ;EDD packet calls supported
jnz disk_edd
disk_convert:
push dx
push es ! protect on floppies
mov ah,#8 ! get geometry
int 0x13
pop es
jc disk_error12
#if !CYL1023
push cx
shr cl,#6 ;;;;
xchg cl,ch ;CX is max cylinder number
mov di,cx ;DI saves it
pop cx
#endif
shr dx,#8
xchg ax,dx ;AX <- DX
inc ax ;AX is number of heads (256 allowed)
and cx,#0x003f ;CX is number of sectors
mul cx ; kills DX also
xchg ax,bx ;save in BX
mov ax,[edd_d_addr](si) ;low part of address
mov dx,[edd_d_addr+2](si) ;hi part of address
cmp dx,bx
jae disk_error2 ;prevent division error
div bx ;AX is cyl, DX is head/sect
#if CYL1023
cmp ax,#1023
#else
cmp ax,di
#endif
ja disk_error2 ;cyl is too big
shl ah,#6 ; save hi 2 bits
xchg al,ah
xchg ax,dx
div cl ;AH = sec-1, AL = head
or dl,ah ;form Cyl/Sec
mov cx,dx
inc cx ; sector is 1 based
pop dx ! restore device code
mov dh,al ! set head#
jmp disk_read2
disk_geometric:
push eax
pop cx
pop ax
mov dh,ah
disk_read2:
mov ax,#0x201 ;read, count of 1
jmp disk_int13
disk_edd:
mov ah,#0x42
disk_int13:
pop bx
mov bp,#5
disk_retry:
pusha
int 0x13
jnc disk_okay
dec bp
jz disk_err
xor ax,ax ! reset the disk controller
int 0x13
popa ! reset AX,BX,CX,DX,SI
jmp disk_retry
disk_error2:
mov ah,#0x40 ; signal seek error
disk_error12:
disk_err:
jmp near error
disk_okay:
; the pusha block is implicitly removed below
disk_ret:
mov (si+2*16-1),ah ! set error code
lea sp,(si+16) ! do not touch carry;
popa
#ifndef JRC_DS_EQ_SS
pop ds
#endif
ret
#ifndef LCF_NO1STDIAG
bout: rol ax,#4 ! bring hi-nibble to position
call nout
rol ax,#4 ! bring lo-nibble to position
nout: and al,#0x0F ! display one nibble
daa ! shorter conversion routine
add al,#0xF0
adc al,#0x40 ! is now a hex char 0..9A..F
#endif
; display - write byte in AL to console
; preserves all register contents
;
display: pusha ! make sure no register is changed
mov bx,#7 ! BH=0, BL=07
;;; xor bh,bh ! BH=0, page to write to
mov ah,#14
int 0x10
popa ! restore all the registers
ret
theend:
!
! If 'first' loads as the MBR, then there must be space for the partition
! table. If 'first' loads as the boot record of some partition, then
! the space reserved below is not used. But we must reserve the area
! as a hedge against the first case.
!
!
.org MAX_BOOT_SIZE !
.word 0,0,0,0 ! space for NT, DRDOS, and LILO volume S/N
! .org 0x1be ! spot for the partition table
p_table:
.blkb 16
.blkb 16
.blkb 16
.blkb 16
#ifdef FIRST
.org *-2
.long FIRST ! boot block check
#else
.word 0xAA55 ! boot block signature
#endif
! Better be exactly 0x200
map2 equ * ! addressed as ES:[map2]
--
Some people claim that the UNIX learning curve is steep, but at least you
only have to climb it once.
Andres Roldan <[EMAIL PROTECTED]>
http://people.fluidsignal.com/~aroldan
