head	1.6;
access;
symbols
	MBR_1_1_3:1.6
	MBR_1_1_2:1.5
	MBR_1_1_1:1.4
	MBR_1_1_0:1.3
	MBR_1_0_1:1.2
	MBR_1_0_0:1.1;
locks
	neil:1.6; strict;
comment	@# @;


1.6
date	2001.09.14.22.09.41;	author neil;	state Exp;
branches;
next	1.5;

1.5
date	2001.09.14.22.09.41;	author neil;	state Exp;
branches;
next	1.4;

1.4
date	2001.09.14.22.09.41;	author neil;	state Exp;
branches;
next	1.3;

1.3
date	2001.09.14.22.09.41;	author neil;	state Exp;
branches;
next	1.2;

1.2
date	2001.09.14.22.09.41;	author neil;	state Exp;
branches;
next	1.1;

1.1
date	2001.09.14.22.09.40;	author neil;	state Exp;
branches;
next	;


desc
@@


1.6
log
@mbr-1.1.3.S86
@
text
@! mbr.S - a replacement master boot record
! Copyright (C) 1995,1999-2001 Neil Turton
! See the file AUTHORS for a list of contributors.
!
!    This program is free software; you can redistribute it and/or modify
!    it under the terms of the GNU General Public License as published by
!    the Free Software Foundation; either version 2 of the License, or
!    (at your option) any later version.
!
!    This program is distributed in the hope that it will be useful,
!    but WITHOUT ANY WARRANTY; without even the implied warranty of
!    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
!    GNU General Public License for more details.
!
!    You should have received a copy of the GNU General Public License
!    along with this program; if not, write to the Free Software
!    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
!
#define LOGO
#undef COMPAT
!
! We are loaded at 0:0x7c00 by the BIOS, but need to load boot sectors
! here, so we have got to move out of the way. We move to 0:DEST_ADDR
! 0x600 is as good a place as any.
#define LOAD_ADDR 0x7c00
#define DEST_ADDR 0x600
! The time when we started up.
stime	equ 0x800
.org DEST_ADDR
	! Do not use DL here; we need the value later.  It contains
	! the drive which the MBR was loaded from.
	cld
	xor ax,ax
	mov ss,ax
	xor sp,sp ! First word pushed goes to 0000:FFFE.
	mov ds,ax
	mov es,ax
	mov si,#LOAD_ADDR
#ifdef Y2KBUG
#undef LOGO
! We need dx and cx for locating and updating the MBR
	pusha	! MBR data: cx=cylinder/sector dx=head/drive si=address
#endif
	mov di,#DEST_ADDR ! Here will do
	mov cx,#0x100
	repz
	movsw
	mov si,#table+0x30 ! Set bootable flags from partition table
	mov al,#8 ! AH=0 is set from above
	jmp 0:cont ! Switch to the newly made copy. From now on labels work.
cont:
	cmpb drive,#0xFF ! If drive==0xFF, use the value in DL instead.
	jne ptloop
	mov drive,dl ! Now DL is free for use
ptloop:	cmpb [si],#0 ! Check for bootable flag
	jz l7
	or flags,al ! Set in flags
l7:	sub si,#0x10
	shr al,1
	jnc ptloop ! Repeat until bit gets shifted out of al

	int 0x1a ! AH=0: Get time
	mov stime,dx

#ifdef Y2KBUG
! Address the year in the loaded copy.
#define YEAR #(year-DEST_ADDR+LOAD_ADDR)

	mov ah,#4
	int 0x1a	! cx=year(bcd) dh=month(bcd) dl=day(bcd)
	mov si,YEAR
	lodsw		! DF=0 set before
	cmp [si],dh	! compare last month, against this month
	pushf
	mov [si],dh
	jbe setdate	! if CF=1 jump
	inc ax		! we need to enter here with CF=0, inc doe not set it
	daa
	xchg ah,al
	adc al,#0
	daa
	xchg ah,al
	mov [si-2],ax
setdate:
	mov cx,ax
	mov ah,#5
	int 0x1a
	popf
	popa
	je nowrite
	mov bx,si
	mov ax,#0x0301
	int 0x13
nowrite:

#endif

#ifdef LOGO
	call show_logo
#endif

	cmpb delay,#255
	jz l3 ! Immediate interrupt
l0:	testb def,#0x80 ! Key press interrupt allowed
	jz l1
	mov ah,#1
	int 0x16
	jnz l3 ! Interrupted
l1:	testb def,#0x40 ! Shift/Ctrl allowed
	jz l2
	test byte 0x417,#0xf ! Check shift status
	jnz l3 ! Interrupted
l2:	xor ax,ax ! Check timer.
	int 0x1a
	sub dx,stime ! This code gets confused at midnight (FIXME)
	sub dl,delay
	sbb dh,#0
	jb l0 ! Time not passed

l4:	mov al,def ! Boot default
	and al,#7
	cmp al,#7
	jnz boot2 ! Boot number al
	mov si,#table ! Boot first partition marked bootable
	mov al,#0
	mov cx,#4
l5:	cmpb [si],#0
boot2:	jnz boot
	inc al
	add si,#0x10
	loop l5 ! Try next partition

	! Display the prompt
l3:
#ifdef LOGO
	call show_logo
#else
	xor bx,bx
#endif
	mov ah,#0xe ! Print char
	mov si,#chars ! List of chars to print
	mov cl,flags ! Interrupted (or no default)
l9:	lodsb
	shr cl,#1 ! Shift next bit into carry
	jnb l8
	int 0x10
l8:	or cl,cl ! Any more bits set?
	jnz l9
	mov al,#0x3a ! Print a colon
	int 0x10
l11:	xor ax,ax ! Get user input
	int 0x16
	cmp al,#0
	jz l11 ! Skip extended chars
	cmp al,#13 ! RETURN pressed
	jz l4 ! Boot default
	cmp al,#'a ! CPP isn't quite compatible with as86
	jb l10
	cmp al,#'z ! ' This may make it a bit more obvious
	ja l10
	sub al,#0x20 ! Upper case input

l10:	mov bl,al
	mov si,#chars
	mov cl,flags
l12:	lodsb
	shr cl,#1
	jnb l13
	cmp bl,al
	jz l14
l13:	or cl,cl
	jnz l12
	jmp l11
l14:	mov ax,#0xe0d
	xor bx,bx
	int 0x10
	! FIXME: This could be shortened.
	lea ax, 0xff&-(chars+1)[si]
	cmp al,#7 ! Check if advanced mode selected
	jnz boot
	mov al,#0x1f
	mov flags,al
il3:	jmp l3
	
boot:	! Boot partition al
#ifdef LOGO
	! Re-display the logo, so the prompt is right if we get an
	! error.
	call show_logo
#endif
	xor dx,dx
	mov cx,#1
	cmp al,#4
	jz sdr ! Boot from floppy (DL=0)
	jnb il3 ! Illegal - interrupt

	xor ah,ah
	mov cl,#4
	shl al,cl
	mov si,#table
	add si,ax
	mov dl,drive

	! Entry:
	!  SI -> Partition record
	!  DL = Drive number
sread:	test dl, #0x80		! Only try the extended interface on
	je sdi			! hard disks.

	mov ah, #0x41
	mov bx, #0x55aa
	push si
	push dx
	int #0x13
	pop dx
	pop si
	jb sdi
	cmp bx, #0xaa55		! Check the signature
	jnz sdi
	test cl, #1		! Check the API support bitmap
	jz sdi

	! That will do.  The big disk extenstion is there.
	mov ax, 8[si]		
	mov bx, 10[si]
	mov si, #request
	mov 8[si], ax
	mov 10[si], bx
	mov ah, #0x42
	jmp cdi

	! Entry:
	!  SI -> Partition record
	!  DL = Drive number
sdi:	mov dh,[si+1]
	mov cx,[si+2]

	! Entry:
	! DH = head
	! CX = cylinder/sector
	! DL = Drive number
sdr:	mov ax,#0x201
	mov bx,#LOAD_ADDR
cdi:	mov di,#5 ! number of retries
l6:	push ax
	mov byte [request+2], #1	! Reset count to 1
	int 0x13
	pop ax
	jnb lbit
	dec di
	jnz l6
iil3:	jmp il3
lbit:	cmp 0x7dfe,#0xaa55
	jnz iil3
#ifdef LOGO
	! Start the next line.
	xor bx, bx
	mov ax, #0xe0d
	int 0x10
	mov al, #0xa
	int 0x10
#endif
	jmp 0:LOAD_ADDR

#ifdef LOGO
	! Corrupts si, cx.  Returns with bx=0
show_logo:
	! Code to print the word "MBR" at boot time, to let people
	! know that we are here. - Tom Rothamel <tom-10990@@onegeek.org>
	! Inspired by a discussion on debian-devel.
	push ax
	mov ax,#0xe0d ! Print char CR
	xor bx,bx
	int 0x10
	mov si,#logo
	mov cx,#logolen
logol:
	lodsb
	int 0x10
	loop logol
	pop ax
	ret

logo:  .ascii "MBR "
logo_end:
logolen equ logo_end-logo   ! The length of the logo string.
#endif

request:.byte 0x10, 0, 1, 0
	.word LOAD_ADDR, 0
	.word 0, 0, 0, 0
chars:	db '1,'2,'3,'4,'F,0,0,'A
	! The data area follows.  Access to this data area from
	! external code should be via the pointer at offset 0x1bc.
	! Check the signature and version numbers.  If the program
	! knows about version V, it may access the data if X<=V<=Y.
	! While the version is still 0.0, just check X against 0.0.
	!
	! There used to be 2 bytes for the version number.  I now see
	! this as overkill.  1 byte should be enough for the version
	! number.  The spare byte in the real version will be assembly
	! flags.  The spare byte in the compat version will be
	! reserved for future expansion.
data:	.ascii "NDTmbr" ! Sig string
	db 0 ! Reserved.  Zero so that old installers accept this.
	db 0 ! From version X=0   i.e. Compat version
#ifndef Y2KBUG
	db 0 ! Assembly flags: none
#else
	db 1 ! Assembly flags: y2k
#endif
	db 1 ! To version Y=1     i.e. Real version
#ifndef COMPAT
! Setup the flags with cool settings. Have no delay, but allow
! interrupt. We mark everything bootable, but default to booting
! the active partition.
flags:	db 0x90 ! Floppy bootable. Advanced mode available.
def:	db 0xc7 ! Interrupt by anything.
delay:	db 18 ! About 1 second
drive:	db 0x80 ! /dev/hda
#else
! Setup the flags to mimic standard MBRs unless interrupted
! flags:bits 0-4 marks partitions 1-4 and floppy bootable
!	bit 7 = unlocked
! def:	bits 0-2 default boot partition (0-3, 4=floppy or 7=active)
!	bits 6,7 interrupt on (shift/ctrl,key press)
flags:	db 0 ! No specially bootable partitions. Advanced mode disabled.
def:	db 7 ! Boot active partition
delay:	db 0 ! Delay in timer ticks. 0=>No delay. 255=>Interrupt.
drive:	db 0x80
#endif
#ifdef Y2KBUG
.org DEST_ADDR+0x1b9
year:	dw 0x2001 ! Year
	db 1 ! Month
#endif
.org DEST_ADDR+0x1bc
	dw data-DEST_ADDR ! Pointer to the data
! Format of partition table entry
!   00 byte Boot indicator
!   01 byte start head
!   02 byte start sector
!   03 byte start cylinder
!   04 byte type
!   05 byte end head
!   06 byte end sector
!   07 byte end cylinder
!   08 dw   sectors before partition
!   0c dw   sectors in partition
table:	.space 0x40 ! The partition table
	dw 0xaa55

! Local Variables:
! mode:asm
! End:
@


1.5
log
@mbr-1.1.2.S86
@
text
@d2 2
a3 1
! Copyright (C) 1995 Neil Turton
d25 1
d38 6
a43 1
	mov si,#0x7c00
d62 36
a103 2
	int 0x1a ! AH=0: Get time
	mov stime,dx
d243 1
a243 1
	mov bx,#0x7c00
d263 1
a263 1
	jmp 0:0x7c00
d290 1
a290 1
	.word 0x7c00, 0
d298 6
d305 8
a312 2
	db 0,0 ! From version X=0.0
	db 0,0 ! to version Y=0.0
d331 5
@


1.4
log
@mbr-1.1.1.S86
@
text
@d18 1
d44 2
a45 1
cont:	cmpb drive,#0xFF ! If drive==0xFF, use the value in DL instead.
d54 5
a61 1
	mov stime+2,cx
d74 1
a74 2
	sub dx,stime ! This code gets confused at midnight
	sbb cx,stime+2 ! (FIXME)
a76 1
	sbb cx,#0
d78 1
d91 9
a99 1
l3:	mov cl,flags ! Interrupted (or no default)
d101 1
a104 2
	mov ah,#0xe ! Print char
	xor bx,bx
d108 1
a108 2
	mov ax,#0xe3a ! Print a colon
	xor bx,bx
d121 1
d136 2
a137 2
	mov ax,si
	sub ax,#chars+1
d144 7
a150 1
boot:	xor dx,dx ! Boot partition al
d155 1
d204 1
a204 4
l6:	push cx
	push dx
	push di
	push ax
a207 3
	pop di
	pop dx
	pop cx
d211 1
a211 1
	jmp il3
d213 9
a221 1
	jnz il3
d223 25
@


1.3
log
@mbr-1.1.0.S86
@
text
@d158 1
a158 1
	cmp bx, #0xaa55
d160 2
d188 1
d191 1
@


1.2
log
@mbr-1.0.1.S86
@
text
@d64 1
a64 1
	test 0x417,#0xf ! Check shift status
d135 1
a135 1
	jz sread ! Boot from floppy
d143 31
a173 1
	mov dh,[si+1]
d175 8
a182 1
sread:	mov di,#5 ! number of retries
d186 1
a186 2
	mov ax,#0x201
	mov bx,#0x7c00
d189 1
a189 1
	pop bx
d198 3
d222 1
a222 1
! def:	bits 0-2 default boot partition (0-4 or 7=active)
d244 4
@


1.1
log
@mbr-1.0.0.S86
@
text
@d27 2
d31 2
d41 1
a41 1
	mov al,#8
d43 4
a46 1
cont:	cmpb [si],#0 ! Check for bootable flag
d51 1
a51 1
	jnc cont ! Repeat until bit gets shifted out of al
d54 1
a54 1
	int 0x1a ! Get time
d142 1
a142 1
	mov dl,#0x80
d145 1
a145 1
sread:	mov di,#5
d163 5
d169 2
a170 2
	db 0,0 ! From version 0.0
	db 0,0 ! to version 0.0
d178 1
a178 1
drive:	db 0x80 ! /dev/hda1
@