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|
/* chain.S - LILO boot chainer */
/* Copyright 1992-1997 Werner Almesberger. See file COPYING for details. */
#define LILO_ASM
#include "lilo.h"
.text
.globl _main
.org 0
_main: jmp start
.org 2
.ascii "LILO"
.word STAGE_CHAIN
.word VERSION
offset: .word 0
drive: .byte 0
.byte 0 ! head, always zero
start: cli ! set SS:SP to 0:7C00
xor ax,ax
mov ss,ax
mov ax,#0x7c00
mov sp,ax
sti
mov ax,#SETUPSEG ! move boot sector to default location
mov ds,ax
xor ax,ax
mov es,ax
mov cx,#256
mov si,#512
mov di,#BOOTSEG*16
rep
movsw
push bx ! save secret message
#ifdef DOS_D
#if 0
seg es
cmp byte ptr BOOTSEG*16+0x26,#0x29
je dos4
mov bx,#baddos ! complain
call say
mov ax,#FIRSTSEG ! restart LILO
jmpi #GO,FIRSTSEG
#endif
dos4: seg es
mov byte ptr BOOTSEG*16+0x24,#0x81
#endif
mov cx,#0x20 ! move partition table
mov si,#PART_TABLE_OFFSET
mov di,#PART_TABLE
rep
movsw
#if defined(SWAP_HD) || defined(SWAP_FD)
call swap13
#endif
! table entry
pop bx ! get secret message (active partition)
#ifdef LCF_REWRITE_TABLE
or bl,bl ! none set ?
jz tonopp ! yes -> do not patch
br tonopp
cmp bx,#0x81 ! valid code ?
jb towrfail ! no -> abort
cmp bx,#0x84
jna wrokay ! yes -> continue
towrfail:br wrfail
tonopp: br nopp
wrokay: push bx ! save BX
xor ax,ax ! ES becomes 0
mov es,ax
mov ax,#0x201 ! load partition table, one sector
mov dx,#0x80 ! first drive
mov cx,#1
mov bx,#PARTS_LOAD
int 0x13 ! load it
jc wrfail ! error -> abort
mov cx,#4 ! process all four entries
mov bx,#PART_TABLE
ptchpt: seg es ! clear all active flags
mov byte ptr (bx),#0
#if defined(LCF_FIX_TYPE) && defined(LCF_HIDE_DOS)
seg es
mov al,(bx+4) ! get partition type
cmp al,#PART_DOS12 ! hidden ?
je hideme ! no -> hide it
cmp al,#PART_DOS16
je hideme
cmp al,#PART_DOS32
jne nonrel ! already hidden -> continue
hideme: add al,#HIDDEN_OFF ! write back corrected value
seg es
mov (bx+4),al
#endif
nonrel: add bx,#16 ! next entry
loop ptchpt
pop bx ! compute active flag position
dec bx
shl bl,1
shl bx,1
shl bx,1
shl bx,1
cmp bx,offset ! right ?
jne wrfail ! no -> abort
seg es ! set active flag
mov byte ptr (bx+PART_TABLE),#0x80
#ifdef LCF_FIX_TYPE
seg es ! is this a
mov al,byte ptr (bx+PART_TABLE+4)
cmp al,#PART_HDOS12 ! hidden ?
je unhideme ! yes -> unhide it
cmp al,#PART_HDOS16
je unhideme
cmp al,#PART_HDOS32
jne nounhid ! not hidden -> continue
unhideme:sub al,#HIDDEN_OFF ! write back corrected value
seg es
mov (bx+PART_TABLE+4),al
#endif
nounhid:mov ax,#0x301 ! save it (restore all registers for
mov dx,#0x80 ! paranoia)
mov cx,#1
mov bx,#0x600
int 0x13 ! write ...
jc wrfail ! argl
mov bx,#passmsg ! confirm modification
call say
jmp nopp
wrfail: mov bx,#failmsg ! complain
call say
mov ax,#FIRSTSEG ! restart LILO
jmpi #GO,FIRSTSEG
#endif
nopp: mov si,offset ! DS:SI and ES:SI point to the partition
add si,#PART_TABLE
mov dx,drive ! initialize DX (drive and head)
xor ax,ax ! set DS and ES to zero
#ifdef XXX
mov ax,ds
mov es,ax
mov si,#lilosig
mov bx,#cmd
mov dl,#0xfe
#else
mov ds,ax
mov es,ax
#endif
mov bp,#0 ! might help some boot problems
mov ax,#0xaa55 ! boot signature (just in case ...)
jmpi #BOOTSEG*16,0 ! start boot sector
#ifdef XXX
lilosig:.ascii "LILO"
cmd: .ascii "98"
.byte 0
#endif
#if defined(DOS_D) || defined(LCF_REWRITE_TABLE)
! Display a NUL-terminated string on the console
say: mov al,(bx) ! get byte
or al,al ! NUL ?
jz aret ! yes -> done
push bx ! save pointer
mov ah,#14 ! display, tty-style
xor bh,bh
int 0x10
pop bx
inc bx ! next one
jmp say
aret: ret ! done
#ifdef DOS_D
baddos: .ascii "Need DOS version 4 or newer."
.byte 13,10,0
#endif
failmsg:.ascii "Rewrite error."
.byte 13,10,0
passmsg:.ascii "Rewrote the partition table."
.byte 13,10,0
#endif
#if defined(SWAP_HD) || defined(SWAP_FD)
swap13: seg es ! allocate 1 kB
dec word ptr [0x413]
int 0x12 ! get start segment
mov cl,#6
shl ax,cl
cli ! disable interrupts
xor bx,bx ! zero a few registers
mov di,bx
seg es ! change offset
xchg bx,[0x4c]
mov old13of,bx
mov bx,ax ! change segment
seg es
xchg bx,[0x4e]
mov old13sg,bx
mov es,ax ! move drive swapper
mov si,#new13
mov cx,#new13end-new13
rep
movsb
sti ! enable interrupts
ret ! done
new13: seg cs ! save function code
mov fcode-new13,ah
test dl,#0x80 ! hard disk drive ?
#ifdef SWAP_FD
jnz noswap ! yes -> go on
#else
jz noswap ! no -> go on
#endif
xor dl,#1 ! swap drive 0 and 1
noswap: pushf
.byte 0x9a ! CALL FAR
old13of:.word 0
old13sg:.word 0
pushf ! fix driver number, if necessary
seg cs
cmp byte ptr fcode-new13,#8 ! do not fix
je done13
seg cs
cmp byte ptr fcode-new13,#0x15 ! do not fix
je done13
test dl,#0x80 ! hard disk drive ?
#ifdef SWAP_FD
jnz done13 ! yes -> go on
#else
jz done13 ! no -> go on
#endif
xor dl,#1 ! fix it
done13: seg cs
mov tmpbx-new13,bx ! restore flags
mov bx,sp
seg ss
pop 6(bx)
seg cs
mov bx,tmpbx-new13
iret ! done
new13end:
fcode: .byte 0 ! function code
tmpbx: .word 0
#endif
theend:
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