1#
2# Copyright (c) 2001 John Baldwin <jhb@FreeBSD.org>
3# All rights reserved.
4#
5# Redistribution and use in source and binary forms, with or without
6# modification, are permitted provided that the following conditions
7# are met:
8# 1. Redistributions of source code must retain the above copyright
9#    notice, this list of conditions and the following disclaimer.
10# 2. Redistributions in binary form must reproduce the above copyright
11#    notice, this list of conditions and the following disclaimer in the
12#    documentation and/or other materials provided with the distribution.
13# 3. Neither the name of the author nor the names of any co-contributors
14#    may be used to endorse or promote products derived from this software
15#    without specific prior written permission.
16#
17# THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
18# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20# ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
21# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23# OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27# SUCH DAMAGE.
28#
29
30# $FreeBSD$
31
32#
33# This program is a freestanding boot program to load an a.out binary
34# from a CD-ROM booted with no emulation mode as described by the El
35# Torito standard.  Due to broken BIOSen that do not load the desired
36# number of sectors, we try to fit this in as small a space as possible.
37#
38# Basically, we first create a set of boot arguments to pass to the loaded
39# binary.  Then we attempt to load /boot/loader from the CD we were booted
40# off of.
41#
42
43#include <bootargs.h>
44
45#
46# Memory locations.
47#
48		.set MEM_PAGE_SIZE,0x1000	# memory page size, 4k
49		.set MEM_ARG,0x900		# Arguments at start
50		.set MEM_ARG_BTX,0xa100		# Where we move them to so the
51						#  BTX client can see them
52		.set MEM_ARG_SIZE,0x18		# Size of the arguments
53		.set MEM_BTX_ADDRESS,0x9000	# where BTX lives
54		.set MEM_BTX_ENTRY,0x9010	# where BTX starts to execute
55		.set MEM_BTX_OFFSET,MEM_PAGE_SIZE # offset of BTX in the loader
56		.set MEM_BTX_CLIENT,0xa000	# where BTX clients live
57#
58# a.out header fields
59#
60		.set AOUT_TEXT,0x04		# text segment size
61		.set AOUT_DATA,0x08		# data segment size
62		.set AOUT_BSS,0x0c		# zero'd BSS size
63		.set AOUT_SYMBOLS,0x10		# symbol table
64		.set AOUT_ENTRY,0x14		# entry point
65		.set AOUT_HEADER,MEM_PAGE_SIZE	# size of the a.out header
66#
67# Segment selectors.
68#
69		.set SEL_SDATA,0x8		# Supervisor data
70		.set SEL_RDATA,0x10		# Real mode data
71		.set SEL_SCODE,0x18		# PM-32 code
72		.set SEL_SCODE16,0x20		# PM-16 code
73#
74# BTX constants
75#
76		.set INT_SYS,0x30		# BTX syscall interrupt
77#
78# Constants for reading from the CD.
79#
80		.set ERROR_TIMEOUT,0x80		# BIOS timeout on read
81		.set NUM_RETRIES,3		# Num times to retry
82		.set SECTOR_SIZE,0x800		# size of a sector
83		.set SECTOR_SHIFT,11		# number of place to shift
84		.set BUFFER_LEN,0x100		# number of sectors in buffer
85		.set MAX_READ,0x10000		# max we can read at a time
86		.set MAX_READ_SEC,MAX_READ >> SECTOR_SHIFT
87		.set MEM_READ_BUFFER,0x9000	# buffer to read from CD
88		.set MEM_VOLDESC,MEM_READ_BUFFER # volume descriptor
89		.set MEM_DIR,MEM_VOLDESC+SECTOR_SIZE # Lookup buffer
90		.set VOLDESC_LBA,0x10		# LBA of vol descriptor
91		.set VD_PRIMARY,1		# Primary VD
92		.set VD_END,255			# VD Terminator
93		.set VD_ROOTDIR,156		# Offset of Root Dir Record
94		.set DIR_LEN,0			# Offset of Dir Record length
95		.set DIR_EA_LEN,1		# Offset of EA length
96		.set DIR_EXTENT,2		# Offset of 64-bit LBA
97		.set DIR_SIZE,10		# Offset of 64-bit length
98		.set DIR_NAMELEN,32		# Offset of 8-bit name len
99		.set DIR_NAME,33		# Offset of dir name
100#
101# We expect to be loaded by the BIOS at 0x7c00 (standard boot loader entry
102# point)
103#
104		.code16
105		.globl start
106		.org 0x0, 0x0
107#
108# Program start.
109#
110start:		cld				# string ops inc
111		xor %ax,%ax			# zero %ax
112		mov %ax,%ss			# setup the
113		mov $start,%sp			#  stack
114		mov %ax,%ds			# setup the
115		mov %ax,%es			#  data segments
116		mov %dl,drive			# Save BIOS boot device
117		mov $msg_welcome,%si		# %ds:(%si) -> welcome message
118		call putstr			# display the welcome message
119#
120# Setup the arguments that the loader is expecting from boot[12]
121#
122		mov $msg_bootinfo,%si		# %ds:(%si) -> boot args message
123		call putstr			# display the message
124		mov $MEM_ARG,%bx		# %ds:(%bx) -> boot args
125		mov %bx,%di			# %es:(%di) -> boot args
126		xor %eax,%eax			# zero %eax
127		mov $(MEM_ARG_SIZE/4),%cx	# Size of arguments in 32-bit
128						#  dwords
129		rep				# Clear the arguments
130		stosl				#  to zero
131		mov drive,%dl			# Store BIOS boot device
132		mov %dl,0x4(%bx)		#  in kargs->bootdev
133		or $KARGS_FLAGS_CD,0x8(%bx)	# kargs->bootflags |=
134						#  KARGS_FLAGS_CD
135#
136# Load Volume Descriptor
137#
138		mov $VOLDESC_LBA,%eax		# Set LBA of first VD
139load_vd:	push %eax			# Save %eax
140		mov $1,%dh			# One sector
141		mov $MEM_VOLDESC,%ebx		# Destination
142		call read			# Read it in
143		cmpb $VD_PRIMARY,(%bx)		# Primary VD?
144		je have_vd			# Yes
145		pop %eax			# Prepare to
146		inc %eax			#  try next
147		cmpb $VD_END,(%bx)		# Last VD?
148		jne load_vd			# No, read next
149		mov $msg_novd,%si		# No VD
150		jmp error			# Halt
151have_vd:					# Have Primary VD
152#
153# Try to look up the loader binary using the paths in the loader_paths
154# array.
155#
156		mov $loader_paths,%si		# Point to start of array
157lookup_path:	push %si			# Save file name pointer
158		call lookup			# Try to find file
159		pop %di				# Restore file name pointer
160		jnc lookup_found		# Found this file
161		xor %al,%al			# Look for next
162		mov $0xffff,%cx			#  path name by
163		repnz				#  scanning for
164		scasb				#  nul char
165		mov %di,%si			# Point %si at next path
166		mov (%si),%al			# Get first char of next path
167		or %al,%al			# Is it double nul?
168		jnz lookup_path			# No, try it.
169		mov $msg_failed,%si		# Failed message
170		jmp error			# Halt
171lookup_found:					# Found a loader file
172#
173# Load the binary into the buffer.  Due to real mode addressing limitations
174# we have to read it in 64k chunks.
175#
176		mov DIR_SIZE(%bx),%eax		# Read file length
177		add $SECTOR_SIZE-1,%eax		# Convert length to sectors
178		shr $SECTOR_SHIFT,%eax
179		cmp $BUFFER_LEN,%eax
180		jbe load_sizeok
181		mov $msg_load2big,%si		# Error message
182		call error
183load_sizeok:	movzbw %al,%cx			# Num sectors to read
184		mov DIR_EXTENT(%bx),%eax	# Load extent
185		xor %edx,%edx
186		mov DIR_EA_LEN(%bx),%dl
187		add %edx,%eax			# Skip extended
188		mov $MEM_READ_BUFFER,%ebx	# Read into the buffer
189load_loop:	mov %cl,%dh
190		cmp $MAX_READ_SEC,%cl		# Truncate to max read size
191		jbe load_notrunc
192		mov $MAX_READ_SEC,%dh
193load_notrunc:	sub %dh,%cl			# Update count
194		push %eax			# Save
195		call read			# Read it in
196		pop %eax			# Restore
197		add $MAX_READ_SEC,%eax		# Update LBA
198		add $MAX_READ,%ebx		# Update dest addr
199		jcxz load_done			# Done?
200		jmp load_loop			# Keep going
201load_done:
202#
203# Turn on the A20 address line
204#
205		call seta20			# Turn A20 on
206#
207# Relocate the loader and BTX using a very lazy protected mode
208#
209		mov $msg_relocate,%si		# Display the
210		call putstr			#  relocation message
211		mov MEM_READ_BUFFER+AOUT_ENTRY,%edi # %edi is the destination
212		mov $(MEM_READ_BUFFER+AOUT_HEADER),%esi	# %esi is
213						#  the start of the text
214						#  segment
215		mov MEM_READ_BUFFER+AOUT_TEXT,%ecx # %ecx = length of the text
216						#  segment
217		push %edi			# Save entry point for later
218		lgdt gdtdesc			# setup our own gdt
219		cli				# turn off interrupts
220		mov %cr0,%eax			# Turn on
221		or $0x1,%al			#  protected
222		mov %eax,%cr0			#  mode
223		ljmp $SEL_SCODE,$pm_start	# long jump to clear the
224						#  instruction pre-fetch queue
225		.code32
226pm_start:	mov $SEL_SDATA,%ax		# Initialize
227		mov %ax,%ds			#  %ds and
228		mov %ax,%es			#  %es to a flat selector
229		rep				# Relocate the
230		movsb				#  text segment
231		add $(MEM_PAGE_SIZE - 1),%edi	# pad %edi out to a new page
232		and $~(MEM_PAGE_SIZE - 1),%edi #  for the data segment
233		mov MEM_READ_BUFFER+AOUT_DATA,%ecx # size of the data segment
234		rep				# Relocate the
235		movsb				#  data segment
236		mov MEM_READ_BUFFER+AOUT_BSS,%ecx # size of the bss
237		xor %eax,%eax			# zero %eax
238		add $3,%cl			# round %ecx up to
239		shr $2,%ecx			#  a multiple of 4
240		rep				# zero the
241		stosl				#  bss
242		mov MEM_READ_BUFFER+AOUT_ENTRY,%esi # %esi -> relocated loader
243		add $MEM_BTX_OFFSET,%esi	# %esi -> BTX in the loader
244		mov $MEM_BTX_ADDRESS,%edi	# %edi -> where BTX needs to go
245		movzwl 0xa(%esi),%ecx		# %ecx -> length of BTX
246		rep				# Relocate
247		movsb				#  BTX
248		ljmp $SEL_SCODE16,$pm_16	# Jump to 16-bit PM
249		.code16
250pm_16:		mov $SEL_RDATA,%ax		# Initialize
251		mov %ax,%ds			#  %ds and
252		mov %ax,%es			#  %es to a real mode selector
253		mov %cr0,%eax			# Turn off
254		and $~0x1,%al			#  protected
255		mov %eax,%cr0			#  mode
256		ljmp $0,$pm_end			# Long jump to clear the
257						#  instruction pre-fetch queue
258pm_end:		sti				# Turn interrupts back on now
259#
260# Copy the BTX client to MEM_BTX_CLIENT
261#
262		xor %ax,%ax			# zero %ax and set
263		mov %ax,%ds			#  %ds and %es
264		mov %ax,%es			#  to segment 0
265		mov $MEM_BTX_CLIENT,%di		# Prepare to relocate
266		mov $btx_client,%si		#  the simple btx client
267		mov $(btx_client_end-btx_client),%cx # length of btx client
268		rep				# Relocate the
269		movsb				#  simple BTX client
270#
271# Copy the boot[12] args to where the BTX client can see them
272#
273		mov $MEM_ARG,%si		# where the args are at now
274		mov $MEM_ARG_BTX,%di		# where the args are moving to
275		mov $(MEM_ARG_SIZE/4),%cx	# size of the arguments in longs
276		rep				# Relocate
277		movsl				#  the words
278#
279# Save the entry point so the client can get to it later on
280#
281		pop %eax			# Restore saved entry point
282		stosl				#  and add it to the end of
283						#  the arguments
284#
285# Now we just start up BTX and let it do the rest
286#
287		mov $msg_jump,%si		# Display the
288		call putstr			#  jump message
289		ljmp $0,$MEM_BTX_ENTRY		# Jump to the BTX entry point
290
291#
292# Lookup the file in the path at [SI] from the root directory.
293#
294# Trashes: All but BX
295# Returns: CF = 0 (success), BX = pointer to record
296#          CF = 1 (not found)
297#
298lookup:		mov $VD_ROOTDIR+MEM_VOLDESC,%bx	# Root directory record
299		push %si
300		mov $msg_lookup,%si		# Display lookup message
301		call putstr
302		pop %si
303		push %si
304		call putstr
305		mov $msg_lookup2,%si
306		call putstr
307		pop %si
308lookup_dir:	lodsb				# Get first char of path
309		cmp $0,%al			# Are we done?
310		je lookup_done			# Yes
311		cmp $'/',%al			# Skip path separator.
312		je lookup_dir
313		dec %si				# Undo lodsb side effect
314		call find_file			# Lookup first path item
315		jnc lookup_dir			# Try next component
316		mov $msg_lookupfail,%si		# Not found message
317		call putstr
318		stc				# Set carry
319		ret
320		jmp error
321lookup_done:	mov $msg_lookupok,%si		# Success message
322		call putstr
323		clc				# Clear carry
324		ret
325
326#
327# Lookup file at [SI] in directory whose record is at [BX].
328#
329# Trashes: All but returns
330# Returns: CF = 0 (success), BX = pointer to record, SI = next path item
331#          CF = 1 (not found), SI = preserved
332#
333find_file:	mov DIR_EXTENT(%bx),%eax	# Load extent
334		xor %edx,%edx
335		mov DIR_EA_LEN(%bx),%dl
336		add %edx,%eax			# Skip extended attributes
337		mov %eax,rec_lba		# Save LBA
338		mov DIR_SIZE(%bx),%eax		# Save size
339		mov %eax,rec_size
340		xor %cl,%cl			# Zero length
341		push %si			# Save
342ff.namelen:	inc %cl				# Update length
343		lodsb				# Read char
344		cmp $0,%al			# Nul?
345		je ff.namedone			# Yes
346		cmp $'/',%al			# Path separator?
347		jnz ff.namelen			# No, keep going
348ff.namedone:	dec %cl				# Adjust length and save
349		mov %cl,name_len
350		pop %si				# Restore
351ff.load:	mov rec_lba,%eax		# Load LBA
352		mov $MEM_DIR,%ebx		# Address buffer
353		mov $1,%dh			# One sector
354		call read			# Read directory block
355		incl rec_lba			# Update LBA to next block
356ff.scan:	mov %ebx,%edx			# Check for EOF
357		sub $MEM_DIR,%edx
358		cmp %edx,rec_size
359		ja ff.scan.1
360		stc				# EOF reached
361		ret
362ff.scan.1:	cmpb $0,DIR_LEN(%bx)		# Last record in block?
363		je ff.nextblock
364		push %si			# Save
365		movzbw DIR_NAMELEN(%bx),%si	# Find end of string
366ff.checkver:	cmpb $'0',DIR_NAME-1(%bx,%si)	# Less than '0'?
367		jb ff.checkver.1
368		cmpb $'9',DIR_NAME-1(%bx,%si)	# Greater than '9'?
369		ja ff.checkver.1
370		dec %si				# Next char
371		jnz ff.checkver
372		jmp ff.checklen			# All numbers in name, so
373						#  no version
374ff.checkver.1:	movzbw DIR_NAMELEN(%bx),%cx
375		cmp %cx,%si			# Did we find any digits?
376		je ff.checkdot			# No
377		cmpb $';',DIR_NAME-1(%bx,%si)	# Check for semicolon
378		jne ff.checkver.2
379		dec %si				# Skip semicolon
380		mov %si,%cx
381		mov %cl,DIR_NAMELEN(%bx)	# Adjust length
382		jmp ff.checkdot
383ff.checkver.2:	mov %cx,%si			# Restore %si to end of string
384ff.checkdot:	cmpb $'.',DIR_NAME-1(%bx,%si)	# Trailing dot?
385		jne ff.checklen			# No
386		decb DIR_NAMELEN(%bx)		# Adjust length
387ff.checklen:	pop %si				# Restore
388		movzbw name_len,%cx		# Load length of name
389		cmp %cl,DIR_NAMELEN(%bx)	# Does length match?
390		je ff.checkname			# Yes, check name
391ff.nextrec:	add DIR_LEN(%bx),%bl		# Next record
392		adc $0,%bh
393		jmp ff.scan
394ff.nextblock:	subl $SECTOR_SIZE,rec_size	# Adjust size
395		jnc ff.load			# If subtract ok, keep going
396		ret				# End of file, so not found
397ff.checkname:	lea DIR_NAME(%bx),%di		# Address name in record
398		push %si			# Save
399		repe cmpsb			# Compare name
400		je ff.match			# We have a winner!
401		pop %si				# Restore
402		jmp ff.nextrec			# Keep looking.
403ff.match:	add $2,%sp			# Discard saved %si
404		clc				# Clear carry
405		ret
406
407#
408# Load DH sectors starting at LBA EAX into [EBX].
409#
410# Trashes: EAX
411#
412read:		push %si			# Save
413		push %cx			# Save since some BIOSs trash
414		mov %eax,edd_lba		# LBA to read from
415		mov %ebx,%eax			# Convert address
416		shr $4,%eax			#  to segment
417		mov %ax,edd_addr+0x2		#  and store
418read.retry:	call twiddle			# Entertain the user
419		push %dx			# Save
420		mov $edd_packet,%si		# Address Packet
421		mov %dh,edd_len			# Set length
422		mov drive,%dl			# BIOS Device
423		mov $0x42,%ah			# BIOS: Extended Read
424		int $0x13			# Call BIOS
425		pop %dx				# Restore
426		jc read.fail			# Worked?
427		pop %cx				# Restore
428		pop %si
429		ret				# Return
430read.fail:	cmp $ERROR_TIMEOUT,%ah		# Timeout?
431		je read.retry			# Yes, Retry.
432read.error:	mov %ah,%al			# Save error
433		mov $hex_error,%di		# Format it
434		call hex8			#  as hex
435		mov $msg_badread,%si		# Display Read error message
436
437#
438# Display error message at [SI] and halt.
439#
440error:		call putstr			# Display message
441halt:		hlt
442		jmp halt			# Spin
443
444#
445# Display a null-terminated string.
446#
447# Trashes: AX, SI
448#
449putstr:		push %bx			# Save
450putstr.load:	lodsb				# load %al from %ds:(%si)
451		test %al,%al			# stop at null
452		jnz putstr.putc			# if the char != null, output it
453		pop %bx				# Restore
454		ret				# return when null is hit
455putstr.putc:	call putc			# output char
456		jmp putstr.load			# next char
457
458#
459# Display a single char.
460#
461putc:		mov $0x7,%bx			# attribute for output
462		mov $0xe,%ah			# BIOS: put_char
463		int $0x10			# call BIOS, print char in %al
464		ret				# Return to caller
465
466#
467# Output the "twiddle"
468#
469twiddle:	push %ax			# Save
470		push %bx			# Save
471		mov twiddle_index,%al		# Load index
472		mov $twiddle_chars,%bx		# Address table
473		inc %al				# Next
474		and $3,%al			#  char
475		mov %al,twiddle_index		# Save index for next call
476		xlat				# Get char
477		call putc			# Output it
478		mov $8,%al			# Backspace
479		call putc			# Output it
480		pop %bx				# Restore
481		pop %ax				# Restore
482		ret
483
484#
485# Enable A20. Put an upper limit on the amount of time we wait for the
486# keyboard controller to get ready (65K x ISA access time). If
487# we wait more than that amount, the hardware is probably
488# legacy-free and simply doesn't have a keyboard controller.
489# Thus, the A20 line is already enabled.
490#
491seta20: 	cli				# Disable interrupts
492		xor %cx,%cx			# Clear
493seta20.1:	inc %cx				# Increment, overflow?
494		jz seta20.3			# Yes
495		in $0x64,%al			# Get status
496		test $0x2,%al			# Busy?
497		jnz seta20.1			# Yes
498		mov $0xd1,%al			# Command: Write
499		out %al,$0x64			#  output port
500seta20.2:	in $0x64,%al			# Get status
501		test $0x2,%al			# Busy?
502		jnz seta20.2			# Yes
503		mov $0xdf,%al			# Enable
504		out %al,$0x60			#  A20
505seta20.3:	sti				# Enable interrupts
506		ret				# To caller
507
508#
509# Convert AL to hex, saving the result to [EDI].
510#
511hex8:		pushl %eax			# Save
512		shrb $0x4,%al			# Do upper
513		call hex8.1			#  4
514		popl %eax			# Restore
515hex8.1: 	andb $0xf,%al			# Get lower 4
516		cmpb $0xa,%al			# Convert
517		sbbb $0x69,%al			#  to hex
518		das				#  digit
519		orb $0x20,%al			# To lower case
520		stosb				# Save char
521		ret				# (Recursive)
522
523#
524# BTX client to start btxldr
525#
526		.code32
527btx_client:	mov $(MEM_ARG_BTX-MEM_BTX_CLIENT+MEM_ARG_SIZE-4), %esi
528						# %ds:(%esi) -> end
529						#  of boot[12] args
530		mov $(MEM_ARG_SIZE/4),%ecx	# Number of words to push
531		std				# Go backwards
532push_arg:	lodsl				# Read argument
533		push %eax			# Push it onto the stack
534		loop push_arg			# Push all of the arguments
535		cld				# In case anyone depends on this
536		pushl MEM_ARG_BTX-MEM_BTX_CLIENT+MEM_ARG_SIZE # Entry point of
537						#  the loader
538		push %eax			# Emulate a near call
539		mov $0x1,%eax			# 'exec' system call
540		int $INT_SYS			# BTX system call
541btx_client_end:
542		.code16
543
544		.p2align 4
545#
546# Global descriptor table.
547#
548gdt:		.word 0x0,0x0,0x0,0x0		# Null entry
549		.word 0xffff,0x0,0x9200,0xcf	# SEL_SDATA
550		.word 0xffff,0x0,0x9200,0x0	# SEL_RDATA
551		.word 0xffff,0x0,0x9a00,0xcf	# SEL_SCODE (32-bit)
552		.word 0xffff,0x0,0x9a00,0x8f	# SEL_SCODE16 (16-bit)
553gdt.1:
554#
555# Pseudo-descriptors.
556#
557gdtdesc:	.word gdt.1-gdt-1		# Limit
558		.long gdt			# Base
559#
560# EDD Packet
561#
562edd_packet:	.byte 0x10			# Length
563		.byte 0				# Reserved
564edd_len:	.byte 0x0			# Num to read
565		.byte 0				# Reserved
566edd_addr:	.word 0x0,0x0			# Seg:Off
567edd_lba:	.quad 0x0			# LBA
568
569drive:		.byte 0
570
571#
572# State for searching dir
573#
574rec_lba:	.long 0x0			# LBA (adjusted for EA)
575rec_size:	.long 0x0			# File size
576name_len:	.byte 0x0			# Length of current name
577
578twiddle_index:	.byte 0x0
579
580msg_welcome:	.asciz	"CD Loader 1.2\r\n\n"
581msg_bootinfo:	.asciz	"Building the boot loader arguments\r\n"
582msg_relocate:	.asciz	"Relocating the loader and the BTX\r\n"
583msg_jump:	.asciz	"Starting the BTX loader\r\n"
584msg_badread:	.ascii  "Read Error: 0x"
585hex_error:	.asciz	"00\r\n"
586msg_novd:	.asciz  "Could not find Primary Volume Descriptor\r\n"
587msg_lookup:	.asciz  "Looking up "
588msg_lookup2:	.asciz  "... "
589msg_lookupok:	.asciz  "Found\r\n"
590msg_lookupfail:	.asciz  "File not found\r\n"
591msg_load2big:	.asciz  "File too big\r\n"
592msg_failed:	.asciz	"Boot failed\r\n"
593twiddle_chars:	.ascii	"|/-\\"
594loader_paths:	.asciz  "/BOOT/LOADER"
595		.asciz	"/boot/loader"
596		.byte 0
597
598