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#
# Copyright (c) 1998 Robert Nordier
# All rights reserved.
#
# Redistribution and use in source and binary forms are freely
# permitted provided that the above copyright notice and this
# paragraph and the following disclaimer are duplicated in all
# such forms.
#
# This software is provided "AS IS" and without any express or
# implied warranties, including, without limitation, the implied
# warranties of merchantability and fitness for a particular
# purpose.
#
# $Id: boot0.s,v 1.1.1.1 1998/10/05 10:08:37 rnordier Exp $
# A 512-byte boot manager.
.set LOAD,0x7c00 # Load address
.set ORIGIN,0x600 # Relocation address
.set PRT_OFF,0x1be # Partition table
.set FAKE,0x810 # Partition entry
.set MNUOPT,0x81c # Menu options
.globl start # Entry point
start: cld # String ops inc
xorl %eax,%eax # Zero
movl %eax,%es # Address
movl %eax,%ds # data
movl %eax,%ss # Set up
movwir(LOAD,_sp) # stack
movl %esp,%esi # Source
movwir(start,_di) # Destination
movwir(0x100,_cx) # Word count
rep # Relocate
movsl # code
movb $0x10,%cl # Words to clear
rep # Zero
stosl # then
incb1(-0xe,_di_) # Sector number
jmpnwi(main-LOAD+ORIGIN) # To relocated code
main: movbrm(_dl,FAKE) # Save drive number
callwi(putn) # To new line
movwir(partbl,_bx) # Partition table
xorl %edx,%edx # Item
main.1: movbr0(_dh,_bx_) # Mark inactive
movb1r(0x4,_bx_,_al) # Load type
movwir(table0,_di) # Exclusion table
movb $0x3,%cl # Entries
repne # Exclude
scasb # partition?
je main.3 # Yes
movb $0xa,%cl # Entries
repne # Known
scasb # type?
jne main.2 # No
leaw1r(0xa,_di_,_di) # Name table
main.2: movwir(item,_si) # Display start
callwi(putkey) # of menu item
movl %edi,%esi # Set pointer
lodsb # to
cwde # partition
add %eax,%esi # description
callwi(puts) # Display it
btswrm(_dx,MNUOPT) # Flag option enabled
main.3: addb $0x10,%bl # Next entry
incl %edx # Next item
cmpb $0x4,%dl # Done?
jb main.1 # No
movwir(prompt,_si) # Display
callwi(putstr) # prompt
movbmr(opt,_dl) # Display
decl %esi # default
callwi(putkey) # key
xorb %ah,%ah # BIOS: Get
int $0x1a # system time
movl %edx,%edi # Save
main.4: movb $0x1,%ah # BIOS: Check
int $0x16 # for keypress
jnz main.6 # Have one
xorb %ah,%ah # BIOS: Get
int $0x1a # system time
subl %edi,%edx # Elapsed time
cmpwmr(ticks,_dx) # Timeout?
jb main.4 # No
jmp main.7 # Join common code
main.5: movb $0x7,%al # Signal
callwi(putchr) # error
main.6: xorb %ah,%ah # BIOS: Get
int $0x16 # keypress
movb %ah,%al # Scan code
cmpb $0x1c,%al # Enter pressed?
jne main.8 # No
main.7: movbma(opt) # Load
jmp main.9 # default
main.8: subb $0x3b,%al # Less F1 scan code
jb main.5 # Not a function key
main.9: cmpb $0x4,%al # F1..F5?
ja main.5 # No
movwir(FAKE,_si) # Partition entry
movb0r(_si_,_dl) # Load drive number
jne main.10 # If not F5
xorb $0x1,%dl # Toggle drive
jmp main.11 # number
main.10: cwtl # Option
btwrm(_ax,MNUOPT) # enabled?
jnc main.5 # No
movbam(opt) # Save option
shlb $0x4,%al # Point to
addwia(partbl) # partition
xchgl %esi,%eax # entry
movbi0(0x80,_si_) # Flag active
pushl %esi # Save
movl %eax,%esi # Fake partition entry
movwir(start,_bx) # Data to write
movwir(0x301,_ax) # Write sector
callwi(intx13) # to disk
popl %esi # Restore
jc main.5 # If error
main.11: movwir(LOAD,_bx) # Address for read
movwir(0x201,_ax) # Read sector
callwi(intx13) # from disk
jc main.5 # If error
cmpwi2(0xaa55,0x1fe,_bx_) # Bootable?
jne main.5 # No
callwi(putn) # To next line
jmp *%ebx # Invoke bootstrap
# Display routines
putkey: movb $'F',%al # Display
callwi(putchr) # 'F'
movb $'1',%al # Prepare
addb %dl,%al # digit
jmp putstr.1 # Display the rest
puts: callwi(putstr) # Display string
putn: movwir(crlf,_si) # To next line
putstr: lodsb # Get byte
testb $0x80,%al # End of string?
jnz putstr.2 # Yes
putstr.1: callwi(putchr) # Display char
jmp putstr # Continue
putstr.2: andb $~0x80,%al # Clear MSB
putchr: pushl %ebx # Save
movwir(0x7,_bx) # Page:attribute
movb $0xe,%ah # BIOS: Display
int $0x10 # character
popl %ebx # Restore
ret # To caller
# Disk I/O
intx13: movb1r(0x1,_si_,_dh) # Load head
movw1r(0x2,_si_,_cx) # Load cylinder:sector
o16 # Load
movw1r(0x8,_si_,_di) # offset
pushl %ecx # Save
pushl %ebx # caller's
movwir(0x55aa,_bx) # Magic
pushl %eax # Save
movb $0x41,%ah # BIOS: EDD extensions
int $0x13 # present?
popl %eax # Restore
jc intx13.1 # No
cmpwir(0xaa55,_bx) # Magic?
jne intx13.1 # No
testb $0x1,%cl # Use packet?
jz intx13.1 # No
orb $0x40,%ah # Use EDD
intx13.1: popl %ebx # Restore
popl %ecx # caller's
testb $0x40,%ah # Use EDD?
jz intx13.2 # No
movwir(break,_si) # Packet pointer
movbi0(0x10,_si_) # Packet size
movbr1(_al,0x2,_si_) # Block count
movwr1(_bx,0x4,_si_) # Transfer
movws1(_es,0x6,_si_) # buffer
o16 # LBA
movwr1(_di,0x8,_si_) # address
xorb %al,%al # Verify off
intx13.2: int $0x13 # BIOS: Disk I/O
ret # To caller
# Menu strings
crlf: .ascii "\r"; .byte '\n'|0x80
item: .ascii " "; .byte ' '|0x80
prompt: .ascii "\nDefault:"; .byte ' '|0x80
# Partition type tables
table0: .byte 0x0, 0x5, 0xf
table1: .byte 0x1, 0x4, 0x6, 0xb, 0xc, 0xe, 0x63, 0x83
.byte 0xa5, 0xa6
.byte os_misc-.-1 # Unknown
.byte os_dos-.-1 # DOS
.byte os_dos-.-1 # DOS
.byte os_dos-.-1 # DOS
.byte os_dos-.-1 # Windows
.byte os_dos-.-1 # Windows
.byte os_dos-.-1 # Windows
.byte os_unix-.-1 # UNIX
.byte os_linux-.-1 # Linux
.byte os_freebsd-.-1 # FreeBSD
.byte os_bsd-.-1 # OpenBSD
os_misc: .ascii "?"; .byte '?'|0x80
os_dos: .ascii "DO"; .byte 'S'|0x80
os_unix: .ascii "UNI"; .byte 'X'|0x80
os_linux: .ascii "Linu"; .byte 'x'|0x80
os_freebsd: .ascii "Free"
os_bsd: .ascii "BS"; .byte 'D'|0x80
.org PRT_OFF-0x3,0x90
opt: .byte 0x1 # Option
ticks: .word 0xb6 # Delay
partbl: .fill 0x40,0x1,0x0 # Partition table
.word 0xaa55 # Magic number
break: # Uninitialized data
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