Bring back jhb's two sector (1024 bytes) 'boot0' [rev 1.22] as 'boot0ext'.

3 files changed, 981 insertions, 0 deletions

diff --git a/sys/boot/i386/boot0/boot0ext.S b/sys/boot/i386/boot0/boot0ext.S
new file mode 100644
index 0000000..90c0e5c
--- /dev/null
+++ b/sys/boot/i386/boot0/boot0ext.S
@@ -0,0 +1,487 @@
+#
+# 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.
+#
+
+# $FreeBSD$
+
+# A 1024-byte boot manager.
+
+		.set NHRDRV,0x475		# Number of hard drives
+		.set ORIGIN,0x600		# Execution address
+		.set SECTOR_SIZE,0x200		# Length of a sector
+		.set NUM_SECTORS,2		# Total length in sectors
+
+		.set FAKE,ORIGIN+(SECTOR_SIZE*NUM_SECTORS) # Partition entry
+		.set LOAD,0x7c00		# Load address
+
+		.set PRT_OFF,0x1be		# Partition table
+
+		.set TBL0SZ,table0_end-table0	# Table 0 size
+		.set TBL1SZ,table1_end-table1	# Table 1 size
+
+		.set MAGIC,0xaa55		# Magic: bootable
+
+		.set KEY_ENTER,0x1c		# Enter key scan code
+		.set KEY_F1,0x3b		# F1 key scan code
+
+#
+# Flag bits
+#
+		.set FL_PACKET,0x80		# Packet mode
+		.set FL_NOUPDATE,0x40		# Don't save selection
+		.set FL_SETDRV,0x20		# Override drive number
+#
+# Addresses in the sector of embedded data values.
+# Accessed with negative offsets from the end of the relocated sectors (%bp).
+#
+		.set _PRT_END,(FAKE-(ORIGIN+SECTOR_SIZE))
+		.set _NXTDRV,-(_PRT_END+0x48)	# Next drive
+		.set _OPT,-(_PRT_END+0x47)	# Default option
+		.set _SETDRV,-(_PRT_END+0x46)	# Drive to force
+		.set _FLAGS,-(_PRT_END+0x45)	# Flags
+		.set _TICKS,-(_PRT_END+0x44)	# Timeout ticks
+		.set _FAKE,0x0			# Fake partition entry
+		.set _MNUOPT,0xc		# Menu options
+
+		.globl start			# Entry point
+		.code16				# This runs in real mode
+
+#
+# Initialise segments and registers to known values.
+# segments start at 0.
+# The stack is immediately below the address we were loaded to.
+#
+# Note that this section of code is used as the first signature check in
+# boot0cfg(8).
+#
+start:		cld				# String ops inc
+		xorw %ax,%ax			# Zero
+		movw %ax,%es			# Address
+		movw %ax,%ds			#  data
+		movw %ax,%ss			# Set up
+		movw $LOAD,%sp			#  stack
+# 
+# End signature code
+# 
+#
+# Set address for variable space beyond code, and clear it.
+# Notice that this is also used to point to the values embedded in the block,
+# by using negative offsets.
+#
+		movw $fake,%bp			# Address variables
+		movw %bp,%di			# %di used in stosw
+		movw $0x8,%cx			# Words to clear
+		rep				# Zero
+		stosw				#  them
+		incb -0xe(%di)			# Sector number 1
+#
+# Reload all of boot0 (including the extra sectors) into memory at the
+# relocation address.  
+#
+		push %dx			# Save drive number
+		movw $start,%bx			# Origin we were linked for
+		movw %bp,%si			# Fake PTE
+		movw $0x200+NUM_SECTORS,%ax	# Read in all
+		callw intx13			#  of boot0
+		pop %dx				# Restore
+#
+# Relocate to the new copy of the code.
+#
+		jmp main+ORIGIN-LOAD		# To relocated code
+#
+# Check what flags were loaded with us; specifically, use a predefined Drive.
+# If what the bios gives us is bad, use the '0' in the block instead, as well.
+#
+main:		testb $FL_SETDRV,_FLAGS(%bp)	# Set number drive?
+		jnz main.1			# Yes
+		testb %dl,%dl			# Drive number valid?
+		js main.2			# Possibly (0x80 set)
+main.1: 	movb _SETDRV(%bp),%dl		# Drive number to use
+#
+# Whatever we decided to use, now store it into the fake
+# partition entry that lives in the data space above us.
+#
+main.2: 	movb %dl,_FAKE(%bp)		# Save drive number
+		callw putn			# To new line
+		pushw %dx			# Save drive number
+#
+# Start out with a pointer to the 4th byte of the first table entry
+# so that after 4 iterations it's beyond the end of the sector.
+# and beyond a 256 byte boundary and has overflowed 8 bits (see next comment).
+# (remember that the table starts 2 bytes earlier than you would expect
+# as the bootable flag is after it in the block)
+#
+		movw $(partbl+0x4),%bx		# Partition table (+4)
+		xorw %dx,%dx			# Item number
+#
+# Loop around on the partition table, printing values until we
+# pass a 256 byte boundary. The end of loop test is at main.5.
+#
+main.3: 	movb %ch,-0x4(%bx)		# Zero active flag (ch == 0)
+		btw %dx,_FLAGS(%bp)		# Entry enabled?
+		jnc main.5			# No
+#
+# If any of the entries in the table are
+# the same as the 'type' in the slice table entry,
+# then this is an empty or non bootable partition. Skip it.
+#
+		movb (%bx),%al			# Load type
+		movw $tables,%di		# Lookup tables
+		movb $TBL0SZ,%cl		# Number of entries
+		repne				# Exclude
+		scasb				#  partition?
+		je main.5			# Yes
+#
+# Now scan the table of known types
+#
+		movb $TBL1SZ,%cl		# Number of entries
+		repne				# Known
+		scasb				#  type?
+		jne main.4			# No
+#
+# If it matches get the matching element in the
+# next array.  If it doesn't, we are already
+# pointing at its first element which points to a "?".
+#
+		addw $TBL1SZ,%di		# Adjust
+main.4: 	movb (%di),%cl			# Partition
+		addw %cx,%di			#  description
+		callw putx			# Display it
+main.5: 	incw %dx			# Next item 
+		addb $0x10,%bl			# Next entry
+		jnc main.3			# Till done
+#
+# Passed a 256 byte boundary..
+# table is finished.
+# Add one to the drive number and check it is valid, 
+#
+		popw %ax			# Drive number
+		subb $0x80-0x1,%al		# Does next
+		cmpb NHRDRV,%al			#  drive exist? (from BIOS?)
+		jb main.6			# Yes
+# If not then if there is only one drive,
+# Don't display drive as an option.
+#
+		decw %ax			# Already drive 0?
+		jz main.7			# Yes
+# If it was illegal or we cycled through them,
+# then go back to drive 0.
+#
+		xorb %al,%al			# Drive 0
+#
+# Whatever drive we selected, make it an ascii digit and save it back
+# to the "next drive" location in the loaded block in case we
+# want to save it for next time.
+# This also is part of the printed drive string so add 0x80 to indicate
+# end of string.
+#
+main.6: 	addb $'0'|0x80,%al		# Save next
+		movb %al,_NXTDRV(%bp)		#  drive number
+		movw $drive,%di			# Display
+		callw putx			#  item
+#
+# Now that we've printed the drive (if we needed to), display a prompt.
+# Get ready for the input by noting the time.
+#
+main.7: 	movw $prompt,%si		# Display
+		callw putstr			#  prompt
+		movb _OPT(%bp),%dl		# Display
+		decw %si			#  default
+		callw putkey			#  key
+		xorb %ah,%ah			# BIOS: Get
+		int $0x1a			#  system time
+		movw %dx,%di			# Ticks when
+		addw _TICKS(%bp),%di	 	#  timeout
+# 
+# Busy loop, looking for keystrokes but
+# keeping one eye on the time.
+#
+main.8: 	movb $0x1,%ah			# BIOS: Check
+		int $0x16			#  for keypress
+		jnz main.11			# Have one
+		xorb %ah,%ah			# BIOS: Get
+		int $0x1a			#  system time
+		cmpw %di,%dx			# Timeout?
+		jb main.8			# No
+#
+# If timed out or defaulting, come here.
+#
+main.9: 	movb _OPT(%bp),%al		# Load default
+		jmp main.12			# Join common code
+#
+# User's last try was bad, beep in displeasure.
+# Since nothing was printed, just continue on as if the user
+# hadn't done anything. This gives the effect of the user getting a beep 
+# for all bad keystrokes but no action until either the timeout
+# occurs or the user hits a good key.
+#
+main.10:	movb $0x7,%al			# Signal
+		callw putchr			#  error
+#
+# Get the keystroke.
+#
+main.11:	xorb %ah,%ah			# BIOS: Get
+		int $0x16			#  keypress
+		movb %ah,%al			# Scan code
+#
+# If it's CR act as if timed out.
+#
+		cmpb $KEY_ENTER,%al		# Enter pressed?
+		je main.9			# Yes
+#
+# Otherwise check if legal
+# If not ask again.
+#
+		subb $KEY_F1,%al		# Less F1 scan code
+		cmpb $0x4,%al			# F1..F5?
+		ja main.10			# No
+#
+# We have a selection.
+# but if it's a bad selection go back to complain.
+# The bits in MNUOPT were set when the options were printed.
+# Anything not printed is not an option.
+#
+main.12:	cbtw				# Option
+		btw %ax,_MNUOPT(%bp)	 	#  enabled?
+		jnc main.10			# No
+#
+# Save the info in the original tables
+# for rewriting to the disk.
+#
+		movb %al,_OPT(%bp)		# Save option
+		movw $fake,%si			# Partition for write
+		movb (%si),%dl			# Drive number
+		movw %si,%bx			# Partition for read
+		cmpb $0x4,%al			# F5 pressed?
+		pushf				# Save
+		je main.13			# Yes
+		shlb $0x4,%al			# Point to
+		addw $partbl,%ax		#  selected
+		xchgw %bx,%ax	 		#  partition
+		movb $0x80,(%bx)		# Flag active
+#
+# If not asked to do a write-back (flags 0x40) don't do one.
+#
+main.13:	pushw %bx			# Save
+		testb $FL_NOUPDATE,_FLAGS(%bp)	# Skip update?
+		jnz main.14			# Yes
+		movw $start,%bx			# Data to write
+		movw $0x301,%ax			# Write 1 sector
+		callw intx13			#  to disk
+main.14:	popw %si			# Restore
+		popf				# Restore
+#
+# If going to next drive, replace drive with selected one.
+# Remember to un-ascii it. Hey 0x80 is already set, cool!
+#
+		jne main.15			# If not F5
+		movb _NXTDRV(%bp),%dl		# Next drive
+		subb $'0',%dl			#  number
+# 
+# load  selected bootsector to the LOAD location in RAM.
+# If it fails to read or isn't marked bootable, treat it
+# as a bad selection.
+#
+main.15:	movw $LOAD,%bx			# Address for read
+		movw $0x201,%ax			# Read 1 sector
+		callw intx13			#  from disk
+		jc main.10			# If error
+		cmpw $MAGIC,0x1fe(%bx)		# Bootable?
+		jne main.10			# No
+		callw putn			# Leave some space
+		jmp *%bx			# Invoke bootstrap
+
+#
+# Display routines
+#
+
+putkey: 	movb $'F',%al			# Display
+		callw putchr			#  'F'
+		movb $'1',%al			# Prepare
+		addb %dl,%al			#  digit
+		jmp putstr.1			# Display the rest
+
+#
+# Display the option and note that it is a valid option.
+# That last point is a bit tricky..
+#
+putx:		btsw %dx,_MNUOPT(%bp)		# Enable menu option
+		movw $item,%si			# Display
+		callw putkey			#  key
+		movw %di,%si			# Display the rest
+
+puts:		callw putstr			# Display string
+
+putn:		movw $crlf,%si			# To next line
+
+putstr: 	lodsb				# Get byte
+		testb $0x80,%al 		# End of string?
+		jnz putstr.2			# Yes
+putstr.1:	callw putchr			# Display char
+		jmp putstr			# Continue
+putstr.2:	andb $~0x80,%al 		# Clear MSB
+
+putchr: 	pushw %bx			# Save
+		movw $0x7,%bx	 		# Page:attribute
+		movb $0xe,%ah			# BIOS: Display
+		int $0x10			#  character
+		popw %bx			# Restore
+		retw				# To caller
+
+# One-sector disk I/O routine
+#
+# Calling conventions: (assumes %si -> partition table entry)
+#
+# 0x1(%si)	- byte - head
+# 0x2(%si)	- word - cylinder/sector
+# 0x8(%si)	- long - LBA to use if needed
+# %ah		- byte - operation, 2 = read, 3 = write
+# %al		- byte - sector count
+# %dl		- byte - drive number
+# %es:(%bx)	- void - buffer to use for transfer
+#
+# If the head == 0xff, and cylinder/sector == 0xffff, then try
+# to use the EDD stuff with the LBA offset instead of CHS.  However,
+# use CHS if at all possible.
+
+intx13: 	movb 0x1(%si),%dh		# Load head
+		movw 0x2(%si),%cx		# Load cylinder:sector
+		pushw %si			# Save
+		movw %sp,%di			# Save
+		cmpb $0xff,%dh			# Might we need LBA?
+		jne intx13.2			# No, just use CHS
+		cmpw $0xffff,%cx		# Do we need LBA?
+		jne intx13.2			# No
+		testb $FL_PACKET,_FLAGS(%bp)	# Try the packet interface?
+		jz intx13.2			# No
+		pushw %cx			# Save
+		pushw %bx			# Save
+		movw $0x55aa,%bx		# Magic
+		pushw %ax			# Save
+		movb $0x41,%ah			# BIOS: EDD extensions
+		int $0x13			#  present?
+		popw %ax			# Restore
+		jc intx13.1			# Not present, use CHS
+		cmpw $0xaa55,%bx		# Magic?
+		jne intx13.1			# Not present, use CHS
+		testb $0x1,%cl			# Packet mode available?
+		jz intx13.1			# No, use CHS
+		orb $0x40,%ah			# Use disk packet
+intx13.1:	popw %bx			# Restore
+		popw %cx			# Restore
+		testb $0x40,%ah			# Using packet mode?
+		jz intx13.2			# No, so skip the rest
+		pushl $0x0			# Set the
+		pushl 0x8(%si)			# LBA address
+		pushw %es			# Set the transfer
+		pushw %bx			#  buffer address
+		push $0x0			# Punch a hole in the stack
+		push $0x10			# Packet size
+		movw %sp,%si			# Packet pointer
+		xchgb %al,0x2(%si)		# Set the block count in the
+						#  packet and zero %al,
+						#  turning verify off for writes
+intx13.2:	int $0x13			# BIOS: Disk I/O
+		movw %di,%sp			# Restore
+		popw %si			# Restore
+		retw				# To caller
+
+		.org PRT_OFF-0xe,0x90
+#
+# These values are sometimes changed before writing back to the drive
+# Be especially careful that nxtdrv: must come after drive:, as it 
+# is part of the same string.
+#
+# Note that the 'drive' string variable is used as the second signature
+# check in boot0cfg(8).
+#
+version_minor:	.byte 0x1			# minor version
+version_major:	.byte 0x1			# major version	
+drive:		.ascii "Drive "
+nxtdrv: 	.byte 0x0			# Next drive number
+opt:		.byte 0x0			# Option
+setdrv: 	.byte 0x80			# Drive to force
+flags:		.byte FLAGS			# Flags
+ticks:		.word TICKS			# Delay
+
+#
+# here is the 64 byte partition table that fdisk would fiddle with.
+#
+partbl: 	.fill 0x40,0x1,0x0		# Partition table
+		.word MAGIC			# Magic number
+
+#
+# start of sector two.. ugh
+#
+		.org SECTOR_SIZE,0x90
+# Menu strings
+
+item:		.ascii "  ";	     .byte ' '|0x80
+prompt: 	.ascii "\nDefault:"; .byte ' '|0x80
+crlf:		.ascii "\r";	     .byte '\n'|0x80
+
+# Partition type tables
+
+tables:
+#
+# These entries identify invalid or NON BOOT types and partitions.
+#
+table0:		.byte 0x0, 0x5, 0xf
+table0_end:
+#
+# These values indicate bootable types we know the names of
+#
+table1:		.byte 0x1, 0x4, 0x6, 0x7, 0xb, 0xc, 0xe, 0x63, 0x83
+		.byte 0x9f, 0xa5, 0xa6, 0xa9
+table1_end:
+#
+# These are offsets that match the known names above and point to the strings
+# that will be printed.
+#
+		.byte os_misc-. 		# Unknown
+		.byte os_dos-.			# DOS
+		.byte os_dos-.			# DOS
+		.byte os_dos-.			# DOS
+		.byte os_nt-.			# NT or OS/2
+		.byte os_windows-.		# Windows
+		.byte os_windows-.		# Windows
+		.byte os_windows-.		# Windows
+		.byte os_unix-. 		# UNIX
+		.byte os_linux-.		# Linux
+		.byte os_bsdos-.		# BSD/OS
+		.byte os_freebsd-.		# FreeBSD
+		.byte os_openbsd-.		# OpenBSD
+		.byte os_netbsd-.		# NetBSD
+#
+# And here are the strings themselves. 0x80 or'd into a byte indicates 
+# the end of the string. (not so great for Russians but...)
+#
+os_misc:	.ascii "Unknow";	.byte 'n'|0x80
+os_dos: 	.ascii "DO";		.byte 'S'|0x80
+os_nt:		.ascii "Windows N";	.byte 'T'|0x80
+os_windows: 	.ascii "Window";	.byte 's'|0x80
+os_unix:	.ascii "UNI";		.byte 'X'|0x80
+os_linux:	.ascii "Linu";		.byte 'x'|0x80
+os_freebsd:	.ascii "FreeBS";	.byte 'D'|0x80
+os_openbsd:	.ascii "OpenBS";	.byte 'D'|0x80
+os_netbsd:	.ascii "NetBS";		.byte 'D'|0x80
+os_bsdos:	.ascii "BSD/O";		.byte 'S'|0x80
+
+#
+# Fake partition entry created at the end of the table used when loading
+# boot0 at the very beginning and when loading an MBR from another disk when
+# F5 is pressed.
+#
+		.org SECTOR_SIZE*NUM_SECTORS, 0x0
+fake:
diff --git a/sys/boot/i386/boot0/boot0ext.s b/sys/boot/i386/boot0/boot0ext.s
new file mode 100644
index 0000000..90c0e5c
--- /dev/null
+++ b/sys/boot/i386/boot0/boot0ext.s
@@ -0,0 +1,487 @@
+#
+# 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.
+#
+
+# $FreeBSD$
+
+# A 1024-byte boot manager.
+
+		.set NHRDRV,0x475		# Number of hard drives
+		.set ORIGIN,0x600		# Execution address
+		.set SECTOR_SIZE,0x200		# Length of a sector
+		.set NUM_SECTORS,2		# Total length in sectors
+
+		.set FAKE,ORIGIN+(SECTOR_SIZE*NUM_SECTORS) # Partition entry
+		.set LOAD,0x7c00		# Load address
+
+		.set PRT_OFF,0x1be		# Partition table
+
+		.set TBL0SZ,table0_end-table0	# Table 0 size
+		.set TBL1SZ,table1_end-table1	# Table 1 size
+
+		.set MAGIC,0xaa55		# Magic: bootable
+
+		.set KEY_ENTER,0x1c		# Enter key scan code
+		.set KEY_F1,0x3b		# F1 key scan code
+
+#
+# Flag bits
+#
+		.set FL_PACKET,0x80		# Packet mode
+		.set FL_NOUPDATE,0x40		# Don't save selection
+		.set FL_SETDRV,0x20		# Override drive number
+#
+# Addresses in the sector of embedded data values.
+# Accessed with negative offsets from the end of the relocated sectors (%bp).
+#
+		.set _PRT_END,(FAKE-(ORIGIN+SECTOR_SIZE))
+		.set _NXTDRV,-(_PRT_END+0x48)	# Next drive
+		.set _OPT,-(_PRT_END+0x47)	# Default option
+		.set _SETDRV,-(_PRT_END+0x46)	# Drive to force
+		.set _FLAGS,-(_PRT_END+0x45)	# Flags
+		.set _TICKS,-(_PRT_END+0x44)	# Timeout ticks
+		.set _FAKE,0x0			# Fake partition entry
+		.set _MNUOPT,0xc		# Menu options
+
+		.globl start			# Entry point
+		.code16				# This runs in real mode
+
+#
+# Initialise segments and registers to known values.
+# segments start at 0.
+# The stack is immediately below the address we were loaded to.
+#
+# Note that this section of code is used as the first signature check in
+# boot0cfg(8).
+#
+start:		cld				# String ops inc
+		xorw %ax,%ax			# Zero
+		movw %ax,%es			# Address
+		movw %ax,%ds			#  data
+		movw %ax,%ss			# Set up
+		movw $LOAD,%sp			#  stack
+# 
+# End signature code
+# 
+#
+# Set address for variable space beyond code, and clear it.
+# Notice that this is also used to point to the values embedded in the block,
+# by using negative offsets.
+#
+		movw $fake,%bp			# Address variables
+		movw %bp,%di			# %di used in stosw
+		movw $0x8,%cx			# Words to clear
+		rep				# Zero
+		stosw				#  them
+		incb -0xe(%di)			# Sector number 1
+#
+# Reload all of boot0 (including the extra sectors) into memory at the
+# relocation address.  
+#
+		push %dx			# Save drive number
+		movw $start,%bx			# Origin we were linked for
+		movw %bp,%si			# Fake PTE
+		movw $0x200+NUM_SECTORS,%ax	# Read in all
+		callw intx13			#  of boot0
+		pop %dx				# Restore
+#
+# Relocate to the new copy of the code.
+#
+		jmp main+ORIGIN-LOAD		# To relocated code
+#
+# Check what flags were loaded with us; specifically, use a predefined Drive.
+# If what the bios gives us is bad, use the '0' in the block instead, as well.
+#
+main:		testb $FL_SETDRV,_FLAGS(%bp)	# Set number drive?
+		jnz main.1			# Yes
+		testb %dl,%dl			# Drive number valid?
+		js main.2			# Possibly (0x80 set)
+main.1: 	movb _SETDRV(%bp),%dl		# Drive number to use
+#
+# Whatever we decided to use, now store it into the fake
+# partition entry that lives in the data space above us.
+#
+main.2: 	movb %dl,_FAKE(%bp)		# Save drive number
+		callw putn			# To new line
+		pushw %dx			# Save drive number
+#
+# Start out with a pointer to the 4th byte of the first table entry
+# so that after 4 iterations it's beyond the end of the sector.
+# and beyond a 256 byte boundary and has overflowed 8 bits (see next comment).
+# (remember that the table starts 2 bytes earlier than you would expect
+# as the bootable flag is after it in the block)
+#
+		movw $(partbl+0x4),%bx		# Partition table (+4)
+		xorw %dx,%dx			# Item number
+#
+# Loop around on the partition table, printing values until we
+# pass a 256 byte boundary. The end of loop test is at main.5.
+#
+main.3: 	movb %ch,-0x4(%bx)		# Zero active flag (ch == 0)
+		btw %dx,_FLAGS(%bp)		# Entry enabled?
+		jnc main.5			# No
+#
+# If any of the entries in the table are
+# the same as the 'type' in the slice table entry,
+# then this is an empty or non bootable partition. Skip it.
+#
+		movb (%bx),%al			# Load type
+		movw $tables,%di		# Lookup tables
+		movb $TBL0SZ,%cl		# Number of entries
+		repne				# Exclude
+		scasb				#  partition?
+		je main.5			# Yes
+#
+# Now scan the table of known types
+#
+		movb $TBL1SZ,%cl		# Number of entries
+		repne				# Known
+		scasb				#  type?
+		jne main.4			# No
+#
+# If it matches get the matching element in the
+# next array.  If it doesn't, we are already
+# pointing at its first element which points to a "?".
+#
+		addw $TBL1SZ,%di		# Adjust
+main.4: 	movb (%di),%cl			# Partition
+		addw %cx,%di			#  description
+		callw putx			# Display it
+main.5: 	incw %dx			# Next item 
+		addb $0x10,%bl			# Next entry
+		jnc main.3			# Till done
+#
+# Passed a 256 byte boundary..
+# table is finished.
+# Add one to the drive number and check it is valid, 
+#
+		popw %ax			# Drive number
+		subb $0x80-0x1,%al		# Does next
+		cmpb NHRDRV,%al			#  drive exist? (from BIOS?)
+		jb main.6			# Yes
+# If not then if there is only one drive,
+# Don't display drive as an option.
+#
+		decw %ax			# Already drive 0?
+		jz main.7			# Yes
+# If it was illegal or we cycled through them,
+# then go back to drive 0.
+#
+		xorb %al,%al			# Drive 0
+#
+# Whatever drive we selected, make it an ascii digit and save it back
+# to the "next drive" location in the loaded block in case we
+# want to save it for next time.
+# This also is part of the printed drive string so add 0x80 to indicate
+# end of string.
+#
+main.6: 	addb $'0'|0x80,%al		# Save next
+		movb %al,_NXTDRV(%bp)		#  drive number
+		movw $drive,%di			# Display
+		callw putx			#  item
+#
+# Now that we've printed the drive (if we needed to), display a prompt.
+# Get ready for the input by noting the time.
+#
+main.7: 	movw $prompt,%si		# Display
+		callw putstr			#  prompt
+		movb _OPT(%bp),%dl		# Display
+		decw %si			#  default
+		callw putkey			#  key
+		xorb %ah,%ah			# BIOS: Get
+		int $0x1a			#  system time
+		movw %dx,%di			# Ticks when
+		addw _TICKS(%bp),%di	 	#  timeout
+# 
+# Busy loop, looking for keystrokes but
+# keeping one eye on the time.
+#
+main.8: 	movb $0x1,%ah			# BIOS: Check
+		int $0x16			#  for keypress
+		jnz main.11			# Have one
+		xorb %ah,%ah			# BIOS: Get
+		int $0x1a			#  system time
+		cmpw %di,%dx			# Timeout?
+		jb main.8			# No
+#
+# If timed out or defaulting, come here.
+#
+main.9: 	movb _OPT(%bp),%al		# Load default
+		jmp main.12			# Join common code
+#
+# User's last try was bad, beep in displeasure.
+# Since nothing was printed, just continue on as if the user
+# hadn't done anything. This gives the effect of the user getting a beep 
+# for all bad keystrokes but no action until either the timeout
+# occurs or the user hits a good key.
+#
+main.10:	movb $0x7,%al			# Signal
+		callw putchr			#  error
+#
+# Get the keystroke.
+#
+main.11:	xorb %ah,%ah			# BIOS: Get
+		int $0x16			#  keypress
+		movb %ah,%al			# Scan code
+#
+# If it's CR act as if timed out.
+#
+		cmpb $KEY_ENTER,%al		# Enter pressed?
+		je main.9			# Yes
+#
+# Otherwise check if legal
+# If not ask again.
+#
+		subb $KEY_F1,%al		# Less F1 scan code
+		cmpb $0x4,%al			# F1..F5?
+		ja main.10			# No
+#
+# We have a selection.
+# but if it's a bad selection go back to complain.
+# The bits in MNUOPT were set when the options were printed.
+# Anything not printed is not an option.
+#
+main.12:	cbtw				# Option
+		btw %ax,_MNUOPT(%bp)	 	#  enabled?
+		jnc main.10			# No
+#
+# Save the info in the original tables
+# for rewriting to the disk.
+#
+		movb %al,_OPT(%bp)		# Save option
+		movw $fake,%si			# Partition for write
+		movb (%si),%dl			# Drive number
+		movw %si,%bx			# Partition for read
+		cmpb $0x4,%al			# F5 pressed?
+		pushf				# Save
+		je main.13			# Yes
+		shlb $0x4,%al			# Point to
+		addw $partbl,%ax		#  selected
+		xchgw %bx,%ax	 		#  partition
+		movb $0x80,(%bx)		# Flag active
+#
+# If not asked to do a write-back (flags 0x40) don't do one.
+#
+main.13:	pushw %bx			# Save
+		testb $FL_NOUPDATE,_FLAGS(%bp)	# Skip update?
+		jnz main.14			# Yes
+		movw $start,%bx			# Data to write
+		movw $0x301,%ax			# Write 1 sector
+		callw intx13			#  to disk
+main.14:	popw %si			# Restore
+		popf				# Restore
+#
+# If going to next drive, replace drive with selected one.
+# Remember to un-ascii it. Hey 0x80 is already set, cool!
+#
+		jne main.15			# If not F5
+		movb _NXTDRV(%bp),%dl		# Next drive
+		subb $'0',%dl			#  number
+# 
+# load  selected bootsector to the LOAD location in RAM.
+# If it fails to read or isn't marked bootable, treat it
+# as a bad selection.
+#
+main.15:	movw $LOAD,%bx			# Address for read
+		movw $0x201,%ax			# Read 1 sector
+		callw intx13			#  from disk
+		jc main.10			# If error
+		cmpw $MAGIC,0x1fe(%bx)		# Bootable?
+		jne main.10			# No
+		callw putn			# Leave some space
+		jmp *%bx			# Invoke bootstrap
+
+#
+# Display routines
+#
+
+putkey: 	movb $'F',%al			# Display
+		callw putchr			#  'F'
+		movb $'1',%al			# Prepare
+		addb %dl,%al			#  digit
+		jmp putstr.1			# Display the rest
+
+#
+# Display the option and note that it is a valid option.
+# That last point is a bit tricky..
+#
+putx:		btsw %dx,_MNUOPT(%bp)		# Enable menu option
+		movw $item,%si			# Display
+		callw putkey			#  key
+		movw %di,%si			# Display the rest
+
+puts:		callw putstr			# Display string
+
+putn:		movw $crlf,%si			# To next line
+
+putstr: 	lodsb				# Get byte
+		testb $0x80,%al 		# End of string?
+		jnz putstr.2			# Yes
+putstr.1:	callw putchr			# Display char
+		jmp putstr			# Continue
+putstr.2:	andb $~0x80,%al 		# Clear MSB
+
+putchr: 	pushw %bx			# Save
+		movw $0x7,%bx	 		# Page:attribute
+		movb $0xe,%ah			# BIOS: Display
+		int $0x10			#  character
+		popw %bx			# Restore
+		retw				# To caller
+
+# One-sector disk I/O routine
+#
+# Calling conventions: (assumes %si -> partition table entry)
+#
+# 0x1(%si)	- byte - head
+# 0x2(%si)	- word - cylinder/sector
+# 0x8(%si)	- long - LBA to use if needed
+# %ah		- byte - operation, 2 = read, 3 = write
+# %al		- byte - sector count
+# %dl		- byte - drive number
+# %es:(%bx)	- void - buffer to use for transfer
+#
+# If the head == 0xff, and cylinder/sector == 0xffff, then try
+# to use the EDD stuff with the LBA offset instead of CHS.  However,
+# use CHS if at all possible.
+
+intx13: 	movb 0x1(%si),%dh		# Load head
+		movw 0x2(%si),%cx		# Load cylinder:sector
+		pushw %si			# Save
+		movw %sp,%di			# Save
+		cmpb $0xff,%dh			# Might we need LBA?
+		jne intx13.2			# No, just use CHS
+		cmpw $0xffff,%cx		# Do we need LBA?
+		jne intx13.2			# No
+		testb $FL_PACKET,_FLAGS(%bp)	# Try the packet interface?
+		jz intx13.2			# No
+		pushw %cx			# Save
+		pushw %bx			# Save
+		movw $0x55aa,%bx		# Magic
+		pushw %ax			# Save
+		movb $0x41,%ah			# BIOS: EDD extensions
+		int $0x13			#  present?
+		popw %ax			# Restore
+		jc intx13.1			# Not present, use CHS
+		cmpw $0xaa55,%bx		# Magic?
+		jne intx13.1			# Not present, use CHS
+		testb $0x1,%cl			# Packet mode available?
+		jz intx13.1			# No, use CHS
+		orb $0x40,%ah			# Use disk packet
+intx13.1:	popw %bx			# Restore
+		popw %cx			# Restore
+		testb $0x40,%ah			# Using packet mode?
+		jz intx13.2			# No, so skip the rest
+		pushl $0x0			# Set the
+		pushl 0x8(%si)			# LBA address
+		pushw %es			# Set the transfer
+		pushw %bx			#  buffer address
+		push $0x0			# Punch a hole in the stack
+		push $0x10			# Packet size
+		movw %sp,%si			# Packet pointer
+		xchgb %al,0x2(%si)		# Set the block count in the
+						#  packet and zero %al,
+						#  turning verify off for writes
+intx13.2:	int $0x13			# BIOS: Disk I/O
+		movw %di,%sp			# Restore
+		popw %si			# Restore
+		retw				# To caller
+
+		.org PRT_OFF-0xe,0x90
+#
+# These values are sometimes changed before writing back to the drive
+# Be especially careful that nxtdrv: must come after drive:, as it 
+# is part of the same string.
+#
+# Note that the 'drive' string variable is used as the second signature
+# check in boot0cfg(8).
+#
+version_minor:	.byte 0x1			# minor version
+version_major:	.byte 0x1			# major version	
+drive:		.ascii "Drive "
+nxtdrv: 	.byte 0x0			# Next drive number
+opt:		.byte 0x0			# Option
+setdrv: 	.byte 0x80			# Drive to force
+flags:		.byte FLAGS			# Flags
+ticks:		.word TICKS			# Delay
+
+#
+# here is the 64 byte partition table that fdisk would fiddle with.
+#
+partbl: 	.fill 0x40,0x1,0x0		# Partition table
+		.word MAGIC			# Magic number
+
+#
+# start of sector two.. ugh
+#
+		.org SECTOR_SIZE,0x90
+# Menu strings
+
+item:		.ascii "  ";	     .byte ' '|0x80
+prompt: 	.ascii "\nDefault:"; .byte ' '|0x80
+crlf:		.ascii "\r";	     .byte '\n'|0x80
+
+# Partition type tables
+
+tables:
+#
+# These entries identify invalid or NON BOOT types and partitions.
+#
+table0:		.byte 0x0, 0x5, 0xf
+table0_end:
+#
+# These values indicate bootable types we know the names of
+#
+table1:		.byte 0x1, 0x4, 0x6, 0x7, 0xb, 0xc, 0xe, 0x63, 0x83
+		.byte 0x9f, 0xa5, 0xa6, 0xa9
+table1_end:
+#
+# These are offsets that match the known names above and point to the strings
+# that will be printed.
+#
+		.byte os_misc-. 		# Unknown
+		.byte os_dos-.			# DOS
+		.byte os_dos-.			# DOS
+		.byte os_dos-.			# DOS
+		.byte os_nt-.			# NT or OS/2
+		.byte os_windows-.		# Windows
+		.byte os_windows-.		# Windows
+		.byte os_windows-.		# Windows
+		.byte os_unix-. 		# UNIX
+		.byte os_linux-.		# Linux
+		.byte os_bsdos-.		# BSD/OS
+		.byte os_freebsd-.		# FreeBSD
+		.byte os_openbsd-.		# OpenBSD
+		.byte os_netbsd-.		# NetBSD
+#
+# And here are the strings themselves. 0x80 or'd into a byte indicates 
+# the end of the string. (not so great for Russians but...)
+#
+os_misc:	.ascii "Unknow";	.byte 'n'|0x80
+os_dos: 	.ascii "DO";		.byte 'S'|0x80
+os_nt:		.ascii "Windows N";	.byte 'T'|0x80
+os_windows: 	.ascii "Window";	.byte 's'|0x80
+os_unix:	.ascii "UNI";		.byte 'X'|0x80
+os_linux:	.ascii "Linu";		.byte 'x'|0x80
+os_freebsd:	.ascii "FreeBS";	.byte 'D'|0x80
+os_openbsd:	.ascii "OpenBS";	.byte 'D'|0x80
+os_netbsd:	.ascii "NetBS";		.byte 'D'|0x80
+os_bsdos:	.ascii "BSD/O";		.byte 'S'|0x80
+
+#
+# Fake partition entry created at the end of the table used when loading
+# boot0 at the very beginning and when loading an MBR from another disk when
+# F5 is pressed.
+#
+		.org SECTOR_SIZE*NUM_SECTORS, 0x0
+fake:
diff --git a/sys/boot/i386/boot0ext/Makefile b/sys/boot/i386/boot0ext/Makefile
new file mode 100644
index 0000000..3458fc1
--- /dev/null
+++ b/sys/boot/i386/boot0ext/Makefile
@@ -0,0 +1,7 @@
+# $FreeBSD$
+
+.PATH: ${.CURDIR}/../boot0
+
+BOOT=	boot0ext
+
+.include "${.CURDIR}/../boot0/Makefile"