summaryrefslogtreecommitdiff
path: root/isolinux.asm
blob: 0be751f1976c391395721f9b103534d36b1f4dec (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
; -*- fundamental -*- (asm-mode sucks)
; ****************************************************************************
;
;  isolinux.asm
;
;  A program to boot Linux kernels off a CD-ROM using the El Torito
;  boot standard in "no emulation" mode, making the entire filesystem
;  available.  It is based on the SYSLINUX boot loader for MS-DOS
;  floppies.
;
;   Copyright (C) 1994-2006  H. Peter Anvin
;
;  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, Inc., 53 Temple Place Ste 330,
;  Boston MA 02111-1307, USA; either version 2 of the License, or
;  (at your option) any later version; incorporated herein by reference.
;
; ****************************************************************************

%define IS_ISOLINUX 1
%include "head.inc"

;
; Some semi-configurable constants... change on your own risk.
;
my_id		equ isolinux_id
FILENAME_MAX_LG2 equ 8			; log2(Max filename size Including final null)
FILENAME_MAX	equ (1 << FILENAME_MAX_LG2)
NULLFILE	equ 0			; Zero byte == null file name
NULLOFFSET	equ 0			; Position in which to look
retry_count	equ 6			; How patient are we with the BIOS?
%assign HIGHMEM_SLOP 128*1024		; Avoid this much memory near the top
MAX_OPEN_LG2	equ 6			; log2(Max number of open files)
MAX_OPEN	equ (1 << MAX_OPEN_LG2)
SECTOR_SHIFT	equ 11			; 2048 bytes/sector (El Torito requirement)
SECTOR_SIZE	equ (1 << SECTOR_SHIFT)

;
; This is what we need to do when idle
;
%macro	RESET_IDLE 0
	; Nothing
%endmacro
%macro	DO_IDLE 0
	; Nothing
%endmacro

;
; The following structure is used for "virtual kernels"; i.e. LILO-style
; option labels.  The options we permit here are `kernel' and `append
; Since there is no room in the bottom 64K for all of these, we
; stick them at vk_seg:0000 and copy them down before we need them.
;
		struc vkernel
vk_vname:	resb FILENAME_MAX	; Virtual name **MUST BE FIRST!**
vk_rname:	resb FILENAME_MAX	; Real name
vk_appendlen:	resw 1
vk_type:	resb 1			; Type of file
		alignb 4
vk_append:	resb max_cmd_len+1	; Command line
		alignb 4
vk_end:		equ $			; Should be <= vk_size
		endstruc

;
; Segment assignments in the bottom 640K
; 0000h - main code/data segment (and BIOS segment)
;
real_mode_seg	equ 3000h
vk_seg          equ 2000h		; Virtual kernels
xfer_buf_seg	equ 1000h		; Bounce buffer for I/O to high mem
comboot_seg	equ real_mode_seg	; COMBOOT image loading zone

;
; File structure.  This holds the information for each currently open file.
;
		struc open_file_t
file_sector	resd 1			; Sector pointer (0 = structure free)
file_left	resd 1			; Number of sectors left
		endstruc

%ifndef DEPEND
%if (open_file_t_size & (open_file_t_size-1))
%error "open_file_t is not a power of 2"
%endif
%endif

		struc dir_t
dir_lba		resd 1			; Directory start (LBA)
dir_len		resd 1			; Length in bytes
dir_clust	resd 1			; Length in clusters
		endstruc

; ---------------------------------------------------------------------------
;   BEGIN CODE
; ---------------------------------------------------------------------------

;
; Memory below this point is reserved for the BIOS and the MBR
;
		section .earlybss
trackbufsize	equ 8192
trackbuf	resb trackbufsize	; Track buffer goes here
getcbuf		resb trackbufsize
;		ends at 4800h

		; Some of these are touched before the whole image
		; is loaded.  DO NOT move this to .uibss.
		section .bss1
		alignb 4
ISOFileName	resb 64			; ISO filename canonicalization buffer
ISOFileNameEnd	equ $
CurDir		resb dir_t_size		; Current directory
RootDir		resb dir_t_size		; Root directory
FirstSecSum	resd 1			; Checksum of bytes 64-2048
ImageDwords	resd 1			; isolinux.bin size, dwords
InitStack	resd 1			; Initial stack pointer (SS:SP)
DiskSys		resw 1			; Last INT 13h call
ImageSectors	resw 1			; isolinux.bin size, sectors
DiskError	resb 1			; Error code for disk I/O
DriveNumber		resb 1			; CD-ROM BIOS drive number
ISOFlags	resb 1			; Flags for ISO directory search
RetryCount      resb 1			; Used for disk access retries

_spec_start	equ $

;
; El Torito spec packet
;

		alignb 8
spec_packet:	resb 1				; Size of packet
sp_media:	resb 1				; Media type
sp_drive:	resb 1				; Drive number
sp_controller:	resb 1				; Controller index
sp_lba:		resd 1				; LBA for emulated disk image
sp_devspec:	resw 1				; IDE/SCSI information
sp_buffer:	resw 1				; User-provided buffer
sp_loadseg:	resw 1				; Load segment
sp_sectors:	resw 1				; Sector count
sp_chs:		resb 3				; Simulated CHS geometry
sp_dummy:	resb 1				; Scratch, safe to overwrite

;
; EBIOS drive parameter packet
;
		alignb 8
drive_params:	resw 1				; Buffer size
dp_flags:	resw 1				; Information flags
dp_cyl:		resd 1				; Physical cylinders
dp_head:	resd 1				; Physical heads
dp_sec:		resd 1				; Physical sectors/track
dp_totalsec:	resd 2				; Total sectors
dp_secsize:	resw 1				; Bytes per sector
dp_dpte:	resd 1				; Device Parameter Table
dp_dpi_key:	resw 1				; 0BEDDh if rest valid
dp_dpi_len:	resb 1				; DPI len
		resb 1
		resw 1
dp_bus:		resb 4				; Host bus type
dp_interface:	resb 8				; Interface type
db_i_path:	resd 2				; Interface path
db_d_path:	resd 2				; Device path
		resb 1
db_dpi_csum:	resb 1				; Checksum for DPI info

;
; EBIOS disk address packet
;
		alignb 8
dapa:		resw 1				; Packet size
.count:		resw 1				; Block count
.off:		resw 1				; Offset of buffer
.seg:		resw 1				; Segment of buffer
.lba:		resd 2				; LBA (LSW, MSW)

;
; Spec packet for disk image emulation
;
		alignb 8
dspec_packet:	resb 1				; Size of packet
dsp_media:	resb 1				; Media type
dsp_drive:	resb 1				; Drive number
dsp_controller:	resb 1				; Controller index
dsp_lba:	resd 1				; LBA for emulated disk image
dsp_devspec:	resw 1				; IDE/SCSI information
dsp_buffer:	resw 1				; User-provided buffer
dsp_loadseg:	resw 1				; Load segment
dsp_sectors:	resw 1				; Sector count
dsp_chs:	resb 3				; Simulated CHS geometry
dsp_dummy:	resb 1				; Scratch, safe to overwrite

		alignb 4
_spec_end	equ $
_spec_len	equ _spec_end - _spec_start

		alignb open_file_t_size
Files		resb MAX_OPEN*open_file_t_size

;
; Constants for the xfer_buf_seg
;
; The xfer_buf_seg is also used to store message file buffers.  We
; need two trackbuffers (text and graphics), plus a work buffer
; for the graphics decompressor.
;
xbs_textbuf	equ 0			; Also hard-coded, do not change
xbs_vgabuf	equ trackbufsize
xbs_vgatmpbuf	equ 2*trackbufsize

		section .text
;;
;; Primary entry point.  Because BIOSes are buggy, we only load the first
;; CD-ROM sector (2K) of the file, so the number one priority is actually
;; loading the rest.
;;
StackBuf	equ $-44		; 44 bytes needed for
					; the bootsector chainloading
					; code!
OrigESDI	equ StackBuf-4          ; The high dword on the stack

bootsec		equ $

_start:		; Far jump makes sure we canonicalize the address
		cli
		jmp 0:_start1
		times 8-($-$$) nop		; Pad to file offset 8

		; This table hopefully gets filled in by mkisofs using the
		; -boot-info-table option.  If not, the values in this
		; table are default values that we can use to get us what
		; we need, at least under a certain set of assumptions.
bi_pvd:		dd 16				; LBA of primary volume descriptor
bi_file:	dd 0				; LBA of boot file
bi_length:	dd 0xdeadbeef			; Length of boot file
bi_csum:	dd 0xdeadbeef			; Checksum of boot file
bi_reserved:	times 10 dd 0xdeadbeef		; Reserved

_start1:	mov [cs:InitStack],sp		; Save initial stack pointer
		mov [cs:InitStack+2],ss
		xor ax,ax
		mov ss,ax
		mov sp,StackBuf			; Set up stack
		push es			; Save initial ES:DI -> $PnP pointer
		push di
		mov ds,ax
		mov es,ax
		mov fs,ax
		mov gs,ax
		sti

		cld
		; Show signs of life
		mov si,syslinux_banner
		call writestr
%ifdef DEBUG_MESSAGES
		mov si,copyright_str
		call writestr
%endif

		;
		; Before modifying any memory, get the checksum of bytes
		; 64-2048
		;
initial_csum:	xor edi,edi
		mov si,_start1
		mov cx,(SECTOR_SIZE-64) >> 2
.loop:		lodsd
		add edi,eax
		loop .loop
		mov [FirstSecSum],edi

		mov [DriveNumber],dl
%ifdef DEBUG_MESSAGES
		mov si,startup_msg
		call writemsg
		mov al,dl
		call writehex2
		call crlf
%endif
		;
		; Initialize spec packet buffers
		;
		mov di,_spec_start
		mov cx,_spec_len >> 2
		xor eax,eax
		rep stosd

		; Initialize length field of the various packets
		mov byte [spec_packet],13h
		mov byte [drive_params],30
		mov byte [dapa],16
		mov byte [dspec_packet],13h

		; Other nonzero fields
		inc word [dsp_sectors]

		; Now figure out what we're actually doing
		; Note: use passed-in DL value rather than 7Fh because
		; at least some BIOSes will get the wrong value otherwise
		mov ax,4B01h			; Get disk emulation status
		mov dl,[DriveNumber]
		mov si,spec_packet
		call int13
		jc award_hack			; changed for BrokenAwardHack
		mov dl,[DriveNumber]
		cmp [sp_drive],dl		; Should contain the drive number
		jne spec_query_failed

%ifdef DEBUG_MESSAGES
		mov si,spec_ok_msg
		call writemsg
		mov al,byte [sp_drive]
		call writehex2
		call crlf
%endif

found_drive:
		; Alright, we have found the drive.  Now, try to find the
		; boot file itself.  If we have a boot info table, life is
		; good; if not, we have to make some assumptions, and try
		; to figure things out ourselves.  In particular, the
		; assumptions we have to make are:
		; - single session only
		; - only one boot entry (no menu or other alternatives)

		cmp dword [bi_file],0		; Address of code to load
		jne found_file			; Boot info table present :)

%ifdef DEBUG_MESSAGES
		mov si,noinfotable_msg
		call writemsg
%endif

		; No such luck.  See if the the spec packet contained one.
		mov eax,[sp_lba]
		and eax,eax
		jz set_file			; Good enough

%ifdef DEBUG_MESSAGES
		mov si,noinfoinspec_msg
		call writemsg
%endif

		; No such luck.  Get the Boot Record Volume, assuming single
		; session disk, and that we're the first entry in the chain
		mov eax,17			; Assumed address of BRV
		mov bx,trackbuf
		call getonesec

		mov eax,[trackbuf+47h]		; Get boot catalog address
		mov bx,trackbuf
		call getonesec			; Get boot catalog

		mov eax,[trackbuf+28h]		; First boot entry
		; And hope and pray this is us...

		; Some BIOSes apparently have limitations on the size
		; that may be loaded (despite the El Torito spec being very
		; clear on the fact that it must all be loaded.)  Therefore,
		; we load it ourselves, and *bleep* the BIOS.

set_file:
		mov [bi_file],eax

found_file:
		; Set up boot file sizes
		mov eax,[bi_length]
		sub eax,SECTOR_SIZE-3
		shr eax,2			; bytes->dwords
		mov [ImageDwords],eax		; boot file dwords
		add eax,(2047 >> 2)
		shr eax,9			; dwords->sectors
		mov [ImageSectors],ax		; boot file sectors

		mov eax,[bi_file]		; Address of code to load
		inc eax				; Don't reload bootstrap code
%ifdef DEBUG_MESSAGES
		mov si,offset_msg
		call writemsg
		call writehex8
		call crlf
%endif

		; Just in case some BIOSes have problems with
		; segment wraparound, use the normalized address
		mov bx,((7C00h+2048) >> 4)
		mov es,bx
		xor bx,bx
		mov bp,[ImageSectors]
%ifdef DEBUG_MESSAGES
		push ax
		mov si,size_msg
		call writemsg
		mov ax,bp
		call writehex4
		call crlf
		pop ax
%endif
		call getlinsec

		push ds
		pop es

%ifdef DEBUG_MESSAGES
		mov si,loaded_msg
		call writemsg
%endif

		; Verify the checksum on the loaded image.
verify_image:
		mov si,7C00h+2048
		mov bx,es
		mov ecx,[ImageDwords]
		mov edi,[FirstSecSum]		; First sector checksum
.loop		es lodsd
		add edi,eax
		dec ecx
		jz .done
		and si,si
		jnz .loop
		; SI wrapped around, advance ES
		add bx,1000h
		mov es,bx
		jmp short .loop
.done:		mov ax,ds
		mov es,ax
		cmp [bi_csum],edi
		je integrity_ok

		mov si,checkerr_msg
		call writemsg
		jmp kaboom

integrity_ok:
%ifdef DEBUG_MESSAGES
		mov si,allread_msg
		call writemsg
%endif
		jmp all_read			; Jump to main code

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; Start of BrokenAwardHack --- 10-nov-2002           Knut_Petersen@t-online.de
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;
;; There is a problem with certain versions of the AWARD BIOS ...
;; the boot sector will be loaded and executed correctly, but, because the
;; int 13 vector points to the wrong code in the BIOS, every attempt to
;; load the spec packet will fail. We scan for the equivalent of
;;
;;	mov	ax,0201h
;;	mov	bx,7c00h
;;	mov	cx,0006h
;;	mov	dx,0180h
;;	pushf
;;	call	<direct far>
;;
;; and use <direct far> as the new vector for int 13. The code above is
;; used to load the boot code into ram, and there should be no reason
;; for anybody to change it now or in the future. There are no opcodes
;; that use encodings relativ to IP, so scanning is easy. If we find the
;; code above in the BIOS code we can be pretty sure to run on a machine
;; with an broken AWARD BIOS ...
;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
									     ;;
%ifdef DEBUG_MESSAGES							     ;;
									     ;;
award_notice	db	"Trying BrokenAwardHack first ...",CR,LF,0	     ;;
award_not_orig	db	"BAH: Original Int 13 vector   : ",0		     ;;
award_not_new	db	"BAH: Int 13 vector changed to : ",0		     ;;
award_not_succ	db	"BAH: SUCCESS",CR,LF,0				     ;;
award_not_fail	db	"BAH: FAILURE"					     ;;
award_not_crlf	db	CR,LF,0						     ;;
									     ;;
%endif									     ;;
									     ;;
award_oldint13	dd	0						     ;;
award_string	db	0b8h,1,2,0bbh,0,7ch,0b9h,6,0,0bah,80h,1,09ch,09ah    ;;
									     ;;
						;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
award_hack:	mov	si,spec_err_msg		; Moved to this place from
		call	writemsg		; spec_query_faild
						;
%ifdef DEBUG_MESSAGES				;
						;
		mov	si,award_notice		; display our plan
		call	writemsg		;
		mov	si,award_not_orig	; display original int 13
		call	writemsg		; vector
%endif						;
		mov	eax,[13h*4]		;
		mov	[award_oldint13],eax	;
						;
%ifdef DEBUG_MESSAGES				;
						;
		call	writehex8		;
		mov	si,award_not_crlf	;
		call	writestr		;
%endif						;
		push	es			; save ES
		mov	ax,0f000h		; ES = BIOS Seg
		mov	es,ax			;
		cld				;
		xor	di,di			; start at ES:DI = f000:0
award_loop:	push	di			; save DI
		mov	si,award_string		; scan for award_string
		mov	cx,7			; length of award_string = 7dw
		repz	cmpsw			; compare
		pop	di			; restore DI
		jcxz	award_found		; jmp if found
		inc	di			; not found, inc di
		jno	award_loop		;
						;
award_failed:	pop	es			; No, not this way :-((
award_fail2:					;
						;
%ifdef DEBUG_MESSAGES				;
						;
		mov	si,award_not_fail	; display failure ...
		call	writemsg		;
%endif						;
		mov	eax,[award_oldint13]	; restore the original int
		or	eax,eax			; 13 vector if there is one
		jz	spec_query_failed	; and try other workarounds
		mov	[13h*4],eax		;
		jmp	spec_query_failed	;
						;
award_found:	mov	eax,[es:di+0eh]		; load possible int 13 addr
		pop	es			; restore ES
						;
		cmp	eax,[award_oldint13]	; give up if this is the
		jz	award_failed		; active int 13 vector,
		mov	[13h*4],eax		; otherwise change 0:13h*4
						;
						;
%ifdef DEBUG_MESSAGES				;
						;
		push	eax			; display message and
		mov	si,award_not_new	; new vector address
		call	writemsg		;
		pop	eax			;
		call	writehex8		;
		mov	si,award_not_crlf	;
		call	writestr		;
%endif						;
		mov	ax,4B01h		; try to read the spec packet
		mov	dl,[DriveNumber]	; now ... it should not fail
		mov	si,spec_packet		; any longer
		int	13h			;
		jc	award_fail2		;
						;
%ifdef DEBUG_MESSAGES				;
						;
		mov	si,award_not_succ	; display our SUCCESS
		call	writemsg		;
%endif						;
		jmp	found_drive		; and leave error recovery code
						;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; End of BrokenAwardHack ----            10-nov-2002 Knut_Petersen@t-online.de
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;


		; INT 13h, AX=4B01h, DL=<passed in value> failed.
		; Try to scan the entire 80h-FFh from the end.

spec_query_failed:

		; some code moved to BrokenAwardHack

		mov dl,0FFh
.test_loop:	pusha
		mov ax,4B01h
		mov si,spec_packet
		mov byte [si],13		; Size of buffer
		call int13
		popa
		jc .still_broken

		mov si,maybe_msg
		call writemsg
		mov al,dl
		call writehex2
		call crlf

		cmp byte [sp_drive],dl
		jne .maybe_broken

		; Okay, good enough...
		mov si,alright_msg
		call writemsg
		mov [DriveNumber],dl
.found_drive:	jmp found_drive

		; Award BIOS 4.51 apparently passes garbage in sp_drive,
		; but if this was the drive number originally passed in
		; DL then consider it "good enough"
.maybe_broken:
		cmp byte [DriveNumber],dl
		je .found_drive

.still_broken:	dec dx
		cmp dl, 80h
		jnb .test_loop

		; No spec packet anywhere.  Some particularly pathetic
		; BIOSes apparently don't even implement function
		; 4B01h, so we can't query a spec packet no matter
		; what.  If we got a drive number in DL, then try to
		; use it, and if it works, then well...
		mov dl,[DriveNumber]
		cmp dl,81h			; Should be 81-FF at least
		jb fatal_error			; If not, it's hopeless

		; Write a warning to indicate we're on *very* thin ice now
		mov si,nospec_msg
		call writemsg
		mov al,dl
		call writehex2
		call crlf
		mov si,trysbm_msg
		call writemsg
		jmp .found_drive		; Pray that this works...

fatal_error:
		mov si,nothing_msg
		call writemsg

.norge:		jmp short .norge

		; Information message (DS:SI) output
		; Prefix with "isolinux: "
		;
writemsg:	push ax
		push si
		mov si,isolinux_str
		call writestr
		pop si
		call writestr
		pop ax
		ret

;
; Write a character to the screen.  There is a more "sophisticated"
; version of this in the subsequent code, so we patch the pointer
; when appropriate.
;

writechr:
		jmp near writechr_simple	; 3-byte jump

writechr_simple:
		pushfd
		pushad
		mov ah,0Eh
		xor bx,bx
		int 10h
		popad
		popfd
		ret

;
; int13: save all the segment registers and call INT 13h
;	 Some CD-ROM BIOSes have been found to corrupt segment registers.
;
int13:

		push ds
		push es
		push fs
		push gs
		int 13h
		pop gs
		pop fs
		pop es
		pop ds
		ret

;
; Get one sector.  Convenience entry point.
;
getonesec:
		mov bp,1
		; Fall through to getlinsec

;
; Get linear sectors - EBIOS LBA addressing, 2048-byte sectors.
;
; Note that we can't always do this as a single request, because at least
; Phoenix BIOSes has a 127-sector limit.  To be on the safe side, stick
; to 32 sectors (64K) per request.
;
; Input:
;	EAX	- Linear sector number
;	ES:BX	- Target buffer
;	BP	- Sector count
;
getlinsec:
		mov si,dapa			; Load up the DAPA
		mov [si+4],bx
		mov bx,es
		mov [si+6],bx
		mov [si+8],eax
.loop:
		push bp				; Sectors left
		cmp bp,[MaxTransfer]
		jbe .bp_ok
		mov bp,[MaxTransfer]
.bp_ok:
		mov [si+2],bp
		push si
		mov dl,[DriveNumber]
		mov ah,42h			; Extended Read
		call xint13
		pop si
		pop bp
		movzx eax,word [si+2]		; Sectors we read
		add [si+8],eax			; Advance sector pointer
		sub bp,ax			; Sectors left
		shl ax,SECTOR_SHIFT-4		; 2048-byte sectors -> segment
		add [si+6],ax			; Advance buffer pointer
		and bp,bp
		jnz .loop
		mov eax,[si+8]			; Next sector
		ret

		; INT 13h with retry
xint13:		mov byte [RetryCount],retry_count
.try:		pushad
		call int13
		jc .error
		add sp,byte 8*4			; Clean up stack
		ret
.error:
		mov [DiskError],ah		; Save error code
		popad
		mov [DiskSys],ax		; Save system call number
		dec byte [RetryCount]
		jz .real_error
		push ax
		mov al,[RetryCount]
		mov ah,[dapa+2]			; Sector transfer count
		cmp al,2			; Only 2 attempts left
		ja .nodanger
		mov ah,1			; Drop transfer size to 1
		jmp short .setsize
.nodanger:
		cmp al,retry_count-2
		ja .again			; First time, just try again
		shr ah,1			; Otherwise, try to reduce
		adc ah,0			; the max transfer size, but not to 0
.setsize:
		mov [MaxTransfer],ah
		mov [dapa+2],ah
.again:
		pop ax
		jmp .try

.real_error:	mov si,diskerr_msg
		call writemsg
		mov al,[DiskError]
		call writehex2
		mov si,oncall_str
		call writestr
		mov ax,[DiskSys]
		call writehex4
		mov si,ondrive_str
		call writestr
		mov al,dl
		call writehex2
		call crlf
		; Fall through to kaboom

;
; kaboom: write a message and bail out.  Wait for a user keypress,
;	  then do a hard reboot.
;
kaboom:
		RESET_STACK_AND_SEGS AX
		mov si,err_bootfailed
		call cwritestr
		call getchar
		cli
		mov word [BIOS_magic],0	; Cold reboot
		jmp 0F000h:0FFF0h	; Reset vector address

; -----------------------------------------------------------------------------
;  Common modules needed in the first sector
; -----------------------------------------------------------------------------

%include "writestr.inc"		; String output
writestr	equ cwritestr
%include "writehex.inc"		; Hexadecimal output

; -----------------------------------------------------------------------------
; Data that needs to be in the first sector
; -----------------------------------------------------------------------------

syslinux_banner	db CR, LF, 'ISOLINUX ', version_str, ' ', date, ' ', 0
copyright_str   db ' Copyright (C) 1994-', year, ' H. Peter Anvin'
		db CR, LF, 0
isolinux_str	db 'isolinux: ', 0
%ifdef DEBUG_MESSAGES
startup_msg:	db 'Starting up, DL = ', 0
spec_ok_msg:	db 'Loaded spec packet OK, drive = ', 0
secsize_msg:	db 'Sector size appears to be ', 0
offset_msg:	db 'Loading main image from LBA = ', 0
size_msg:	db 'Sectors to load = ', 0
loaded_msg:	db 'Loaded boot image, verifying...', CR, LF, 0
verify_msg:	db 'Image checksum verified.', CR, LF, 0
allread_msg	db 'Main image read, jumping to main code...', CR, LF, 0
%endif
noinfotable_msg	db 'No boot info table, assuming single session disk...', CR, LF, 0
noinfoinspec_msg db 'Spec packet missing LBA information, trying to wing it...', CR, LF, 0
spec_err_msg:	db 'Loading spec packet failed, trying to wing it...', CR, LF, 0
maybe_msg:	db 'Found something at drive = ', 0
alright_msg:	db 'Looks like it might be right, continuing...', CR, LF, 0
nospec_msg	db 'Extremely broken BIOS detected, last ditch attempt with drive = ', 0
nothing_msg:	db 'Failed to locate CD-ROM device; boot failed.', CR, LF
trysbm_msg	db 'See http://syslinux.zytor.com/sbm for more information.', CR, LF, 0
diskerr_msg:	db 'Disk error ', 0
oncall_str:	db ', AX = ',0
ondrive_str:	db ', drive ', 0
checkerr_msg:	db 'Image checksum error, sorry...', CR, LF, 0

err_bootfailed	db CR, LF, 'Boot failed: press a key to retry...'
bailmsg		equ err_bootfailed
crlf_msg	db CR, LF
null_msg	db 0

		alignb 4, db 0
MaxTransfer	dw 32				; Max sectors per transfer

rl_checkpt	equ $				; Must be <= 800h

rl_checkpt_off	equ ($-$$)
;%ifndef DEPEND
;%if rl_checkpt_off > 0x800
;%error "Sector 0 overflow"
;%endif
;%endif

; ----------------------------------------------------------------------------
;  End of code and data that have to be in the first sector
; ----------------------------------------------------------------------------

all_read:

; Test tracers
		TRACER 'T'
		TRACER '>'

;
; Common initialization code
;
%include "init.inc"
%include "cpuinit.inc"

		; Patch the writechr routine to point to the full code
		mov word [writechr+1], writechr_full-(writechr+3)

; Tell the user we got this far...
%ifndef DEBUG_MESSAGES			; Gets messy with debugging on
		mov si,copyright_str
		call writestr
%endif

;
; Now we're all set to start with our *real* business.	First load the
; configuration file (if any) and parse it.
;
; In previous versions I avoided using 32-bit registers because of a
; rumour some BIOSes clobbered the upper half of 32-bit registers at
; random.  I figure, though, that if there are any of those still left
; they probably won't be trying to install Linux on them...
;
; The code is still ripe with 16-bitisms, though.  Not worth the hassle
; to take'm out.  In fact, we may want to put them back if we're going
; to boot ELKS at some point.
;

;
; Now, we need to sniff out the actual filesystem data structures.
; mkisofs gave us a pointer to the primary volume descriptor
; (which will be at 16 only for a single-session disk!); from the PVD
; we should be able to find the rest of what we need to know.
;
get_fs_structures:
		mov eax,[bi_pvd]
		mov bx,trackbuf
		call getonesec

		mov eax,[trackbuf+156+2]
		mov [RootDir+dir_lba],eax
		mov [CurDir+dir_lba],eax
%ifdef DEBUG_MESSAGES
		mov si,dbg_rootdir_msg
		call writemsg
		call writehex8
		call crlf
%endif
		mov eax,[trackbuf+156+10]
		mov [RootDir+dir_len],eax
		mov [CurDir+dir_len],eax
		add eax,SECTOR_SIZE-1
		shr eax,SECTOR_SHIFT
		mov [RootDir+dir_clust],eax
		mov [CurDir+dir_clust],eax

		; Look for an isolinux directory, and if found,
		; make it the current directory instead of the root
		; directory.
		mov di,boot_dir			; Search for /boot/isolinux
		mov al,02h
		call searchdir_iso
		jnz .found_dir
		mov di,isolinux_dir
		mov al,02h			; Search for /isolinux
		call searchdir_iso
		jz .no_isolinux_dir
.found_dir:
		mov [CurDir+dir_len],eax
		mov eax,[si+file_left]
		mov [CurDir+dir_clust],eax
		xor eax,eax			; Free this file pointer entry
		xchg eax,[si+file_sector]
		mov [CurDir+dir_lba],eax
%ifdef DEBUG_MESSAGES
		push si
		mov si,dbg_isodir_msg
		call writemsg
		pop si
		call writehex8
		call crlf
%endif
.no_isolinux_dir:

;
; Locate the configuration file
;
load_config:
%ifdef DEBUG_MESSAGES
		mov si,dbg_config_msg
		call writemsg
%endif

		mov si,config_name
		mov di,ConfigName
		call strcpy

		mov di,ConfigName
		call open
		jz no_config_file		; Not found or empty

%ifdef DEBUG_MESSAGES
		mov si,dbg_configok_msg
		call writemsg
%endif

;
; Now we have the config file open.  Parse the config file and
; run the user interface.
;
%include "ui.inc"

;
; Enable disk emulation.  The kind of disk we emulate is dependent on the size of
; the file: 1200K, 1440K or 2880K floppy, otherwise harddisk.
;
is_disk_image:
		TRACER CR
		TRACER LF
		TRACER 'D'
		TRACER ':'

		shl edx,16
		mov dx,ax			; Set EDX <- file size
		mov di,img_table
		mov cx,img_table_count
		mov eax,[si+file_sector]	; Starting LBA of file
		mov [dsp_lba],eax		; Location of file
		mov byte [dsp_drive], 0		; 00h floppy, 80h hard disk
.search_table:
		TRACER 't'
		mov eax,[di+4]
		cmp edx,[di]
		je .type_found
		add di,8
		loop .search_table

		; Hard disk image.  Need to examine the partition table
		; in order to deduce the C/H/S geometry.  Sigh.
.hard_disk_image:
		TRACER 'h'
		cmp edx,512
		jb .bad_image

		mov bx,trackbuf
		mov cx,1			; Load 1 sector
		call getfssec

		cmp word [trackbuf+510],0aa55h	; Boot signature
		jne .bad_image		; Image not bootable

		mov cx,4			; 4 partition entries
		mov di,trackbuf+446		; Start of partition table

		xor ax,ax			; Highest sector(al) head(ah)

.part_scan:
		cmp byte [di+4], 0
		jz .part_loop
		lea si,[di+1]
		call .hs_check
		add si,byte 4
		call .hs_check
.part_loop:
		add di,byte 16
		loop .part_scan

		push eax			; H/S
		push edx			; File size
		mov bl,ah
		xor bh,bh
		inc bx				; # of heads in BX
		xor ah,ah			; # of sectors in AX
		cwde				; EAX[31:16] <- 0
		mul bx
		shl eax,9			; Convert to bytes
		; Now eax contains the number of bytes per cylinder
		pop ebx				; File size
		xor edx,edx
		div ebx
		and edx,edx
		jz .no_remainder
		inc eax				; Fractional cylinder...
		; Now (e)ax contains the number of cylinders
.no_remainder:	cmp eax,1024
		jna .ok_cyl
		mov ax,1024			; Max possible #
.ok_cyl:	dec ax				; Convert to max cylinder no
		pop ebx				; S(bl) H(bh)
		shl ah,6
		or bl,ah
		xchg ax,bx
		shl eax,16
		mov ah,bl
		mov al,4			; Hard disk boot
		mov byte [dsp_drive], 80h	; Drive 80h = hard disk

.type_found:
		TRACER 'T'
		mov bl,[sp_media]
		and bl,0F0h			; Copy controller info bits
		or al,bl
		mov [dsp_media],al		; Emulation type
		shr eax,8
		mov [dsp_chs],eax		; C/H/S geometry
		mov ax,[sp_devspec]		; Copy device spec
		mov [dsp_devspec],ax
		mov al,[sp_controller]		; Copy controller index
		mov [dsp_controller],al

		TRACER 'V'
		call vgaclearmode		; Reset video

		mov ax,4C00h			; Enable emulation and boot
		mov si,dspec_packet
		mov dl,[DriveNumber]
		lss sp,[InitStack]
		TRACER 'X'

		call int13

		; If this returns, we have problems
.bad_image:
		mov si,err_disk_image
		call cwritestr
		jmp enter_command

;
; Look for the highest seen H/S geometry
; We compute cylinders separately
;
.hs_check:
		mov bl,[si]			; Head #
		cmp bl,ah
		jna .done_track
		mov ah,bl			; New highest head #
.done_track:	mov bl,[si+1]
		and bl,3Fh			; Sector #
		cmp bl,al
		jna .done_sector
		mov al,bl
.done_sector:	ret

;
; Boot a specified local disk.  AX specifies the BIOS disk number; or
; 0xFFFF in case we should execute INT 18h ("next device.")
;
local_boot:
		call vgaclearmode
		lss sp,[cs:Stack]		; Restore stack pointer
		xor dx,dx
		mov ds,dx
		mov es,dx
		mov fs,dx
		mov gs,dx
		mov si,localboot_msg
		call writestr
		cmp ax,-1
		je .int18

		; Load boot sector from the specified BIOS device and jump to it.
		mov dl,al
		xor dh,dh
		push dx
		xor ax,ax			; Reset drive
		call xint13
		mov ax,0201h			; Read one sector
		mov cx,0001h			; C/H/S = 0/0/1 (first sector)
		mov bx,trackbuf
		call xint13
		pop dx
		cli				; Abandon hope, ye who enter here
		mov si,trackbuf
		mov di,07C00h
		mov cx,512			; Probably overkill, but should be safe
		rep movsd
		lss sp,[cs:InitStack]
		jmp 0:07C00h			; Jump to new boot sector

.int18:
		int 18h				; Hope this does the right thing...
		jmp kaboom			; If we returned, oh boy...

;
; close_file:
;	     Deallocates a file structure (pointer in SI)
;	     Assumes CS == DS.
;
close_file:
		and si,si
		jz .closed
		mov dword [si],0		; First dword == file_left
.closed:	ret

;
; searchdir:
;
;	Open a file
;
;	     On entry:
;		DS:DI	= filename
;	     If successful:
;		ZF clear
;		SI		= file pointer
;		DX:AX or EAX	= file length in bytes
;	     If unsuccessful
;		ZF set
;
; Assumes CS == DS == ES, and trashes BX and CX.
;
; searchdir_iso is a special entry point for ISOLINUX only.  In addition
; to the above, searchdir_iso passes a file flag mask in AL.  This is useful
; for searching for directories.
;
alloc_failure:
		xor ax,ax			; ZF <- 1
		ret

searchdir:
		xor al,al
searchdir_iso:
		mov [ISOFlags],al
		TRACER 'S'
		call allocate_file		; Temporary file structure for directory
		jnz alloc_failure
		push es
		push ds
		pop es				; ES = DS
		mov si,CurDir
		cmp byte [di],'/'		; If filename begins with slash
		jne .not_rooted
		inc di				; Skip leading slash
		mov si,RootDir			; Reference root directory instead
.not_rooted:
		mov eax,[si+dir_clust]
		mov [bx+file_left],eax
		mov eax,[si+dir_lba]
		mov [bx+file_sector],eax
		mov edx,[si+dir_len]

.look_for_slash:
		mov ax,di
.scan:
		mov cl,[di]
		inc di
		and cl,cl
		jz .isfile
		cmp cl,'/'
		jne .scan
		mov [di-1],byte 0		; Terminate at directory name
		mov cl,02h			; Search for directory
		xchg cl,[ISOFlags]

		push di				; Save these...
		push cx

		; Create recursion stack frame...
		push word .resume		; Where to "return" to
		push es
.isfile:	xchg ax,di

.getsome:
		; Get a chunk of the directory
		; This relies on the fact that ISOLINUX doesn't change SI
		mov si,trackbuf
		TRACER 'g'
		pushad
		xchg bx,si
		mov cx,[BufSafe]
		call getfssec
		popad

.compare:
		movzx eax,byte [si]		; Length of directory entry
		cmp al,33
		jb .next_sector
		TRACER 'c'
		mov cl,[si+25]
		xor cl,[ISOFlags]
		test cl, byte 8Eh		; Unwanted file attributes!
		jnz .not_file
		pusha
		movzx cx,byte [si+32]		; File identifier length
		add si,byte 33			; File identifier offset
		TRACER 'i'
		call iso_compare_names
		popa
		je .success
.not_file:
		sub edx,eax			; Decrease bytes left
		jbe .failure
		add si,ax			; Advance pointer

.check_overrun:
		; Did we finish the buffer?
		cmp si,trackbuf+trackbufsize
		jb .compare			; No, keep going

		jmp short .getsome		; Get some more directory

.next_sector:
		; Advance to the beginning of next sector
		lea ax,[si+SECTOR_SIZE-1]
		and ax,~(SECTOR_SIZE-1)
		sub ax,si
		jmp short .not_file		; We still need to do length checks

.failure:	xor eax,eax			; ZF = 1
		mov [bx+file_sector],eax
		pop es
		ret

.success:
		mov eax,[si+2]			; Location of extent
		mov [bx+file_sector],eax
		mov eax,[si+10]			; Data length
		push eax
		add eax,SECTOR_SIZE-1
		shr eax,SECTOR_SHIFT
		mov [bx+file_left],eax
		pop eax
		mov edx,eax
		shr edx,16
		and bx,bx			; ZF = 0
		mov si,bx
		pop es
		ret

.resume:	; We get here if we were only doing part of a lookup
		; This relies on the fact that .success returns bx == si
		xchg edx,eax			; Directory length in edx
		pop cx				; Old ISOFlags
		pop di				; Next filename pointer
		mov byte [di-1], '/'		; Restore slash
		mov [ISOFlags],cl		; Restore the flags
		jz .failure			; Did we fail?  If so fail for real!
		jmp .look_for_slash		; Otherwise, next level

;
; allocate_file: Allocate a file structure
;
;		If successful:
;		  ZF set
;		  BX = file pointer
;		In unsuccessful:
;		  ZF clear
;
allocate_file:
		TRACER 'a'
		push cx
		mov bx,Files
		mov cx,MAX_OPEN
.check:		cmp dword [bx], byte 0
		je .found
		add bx,open_file_t_size		; ZF = 0
		loop .check
		; ZF = 0 if we fell out of the loop
.found:		pop cx
		ret

;
; iso_compare_names:
;	Compare the names DS:SI and DS:DI and report if they are
;	equal from an ISO 9660 perspective.  SI is the name from
;	the filesystem; CX indicates its length, and ';' terminates.
;	DI is expected to end with a null.
;
;	Note: clobbers AX, CX, SI, DI; assumes DS == ES == base segment
;

iso_compare_names:
		; First, terminate and canonicalize input filename
		push di
		mov di,ISOFileName
.canon_loop:	jcxz .canon_end
		lodsb
		dec cx
		cmp al,';'
		je .canon_end
		and al,al
		je .canon_end
		stosb
		cmp di,ISOFileNameEnd-1		; Guard against buffer overrun
		jb .canon_loop
.canon_end:
		cmp di,ISOFileName
		jbe .canon_done
		cmp byte [di-1],'.'		; Remove terminal dots
		jne .canon_done
		dec di
		jmp short .canon_end
.canon_done:
		mov [di],byte 0			; Null-terminate string
		pop di
		mov si,ISOFileName
.compare:
		lodsb
		mov ah,[di]
		inc di
		and ax,ax
		jz .success			; End of string for both
		and al,al			; Is either one end of string?
		jz .failure			; If so, failure
		and ah,ah
		jz .failure
		or ax,2020h			; Convert to lower case
		cmp al,ah
		je .compare
.failure:	and ax,ax			; ZF = 0 (at least one will be nonzero)
.success:	ret

;
; mangle_name: Mangle a filename pointed to by DS:SI into a buffer pointed
;	       to by ES:DI; ends on encountering any whitespace.
;	       DI is preserved.
;
;	       This verifies that a filename is < FILENAME_MAX characters,
;	       doesn't contain whitespace, zero-pads the output buffer,
;	       and removes trailing dots and redundant slashes,
;	       so "repe cmpsb" can do a compare, and the
;	       path-searching routine gets a bit of an easier job.
;
mangle_name:
		push di
		push bx
		xor ax,ax
		mov cx,FILENAME_MAX-1
		mov bx,di

.mn_loop:
		lodsb
		cmp al,' '			; If control or space, end
		jna .mn_end
		cmp al,ah			; Repeated slash?
		je .mn_skip
		xor ah,ah
		cmp al,'/'
		jne .mn_ok
		mov ah,al
.mn_ok		stosb
.mn_skip:	loop .mn_loop
.mn_end:
		cmp bx,di			; At the beginning of the buffer?
		jbe .mn_zero
		cmp byte [es:di-1],'.'		; Terminal dot?
		je .mn_kill
		cmp byte [es:di-1],'/'		; Terminal slash?
		jne .mn_zero
.mn_kill:	dec di				; If so, remove it
		inc cx
		jmp short .mn_end
.mn_zero:
		inc cx				; At least one null byte
		xor ax,ax			; Zero-fill name
		rep stosb
		pop bx
		pop di
		ret				; Done

;
; unmangle_name: Does the opposite of mangle_name; converts a DOS-mangled
;                filename to the conventional representation.  This is needed
;                for the BOOT_IMAGE= parameter for the kernel.
;                NOTE: A 13-byte buffer is mandatory, even if the string is
;                known to be shorter.
;
;                DS:SI -> input mangled file name
;                ES:DI -> output buffer
;
;                On return, DI points to the first byte after the output name,
;                which is set to a null byte.
;
unmangle_name:	call strcpy
		dec di				; Point to final null byte
		ret

;
; getfssec: Get multiple clusters from a file, given the file pointer.
;
;  On entry:
;	ES:BX	-> Buffer
;	SI	-> File pointer
;	CX	-> Cluster count
;  On exit:
;	SI	-> File pointer (or 0 on EOF)
;	CF = 1	-> Hit EOF
;
getfssec:
		TRACER 'F'

		push ds
		push cs
		pop ds				; DS <- CS

		movzx ecx,cx
		cmp ecx,[si+file_left]
		jna .ok_size
		mov ecx,[si+file_left]
.ok_size:

		mov bp,cx
		push cx
		push si
		mov eax,[si+file_sector]
		TRACER 'l'
		call getlinsec
		xor ecx,ecx
		pop si
		pop cx

		add [si+file_sector],ecx
		sub [si+file_left],ecx
		ja .not_eof			; CF = 0

		xor ecx,ecx
		mov [si+file_sector],ecx	; Mark as unused
		xor si,si
		stc

.not_eof:
		pop ds
		TRACER 'f'
		ret

; -----------------------------------------------------------------------------
;  Common modules
; -----------------------------------------------------------------------------

%include "getc.inc"		; getc et al
%include "conio.inc"		; Console I/O
%include "configinit.inc"	; Initialize configuration
%include "parseconfig.inc"	; High-level config file handling
%include "parsecmd.inc"		; Low-level config file handling
%include "bcopy32.inc"		; 32-bit bcopy
%include "loadhigh.inc"		; Load a file into high memory
%include "font.inc"		; VGA font stuff
%include "graphics.inc"		; VGA graphics
%include "highmem.inc"		; High memory sizing
%include "strcpy.inc"		; strcpy()
%include "rawcon.inc"		; Console I/O w/o using the console functions
%include "adv.inc"		; Auxillary Data Vector

; -----------------------------------------------------------------------------
;  Begin data section
; -----------------------------------------------------------------------------

		section .data

localboot_msg	db 'Booting from local disk...', CR, LF, 0
default_str	db 'default', 0
default_len	equ ($-default_str)
boot_dir	db '/boot'			; /boot/isolinux
isolinux_dir	db '/isolinux', 0
config_name	db 'isolinux.cfg', 0
err_disk_image	db 'Cannot load disk image (invalid file)?', CR, LF, 0

%ifdef DEBUG_MESSAGES
dbg_rootdir_msg	db 'Root directory at LBA = ', 0
dbg_isodir_msg	db 'isolinux directory at LBA = ', 0
dbg_config_msg	db 'About to load config file...', CR, LF, 0
dbg_configok_msg	db 'Configuration file opened...', CR, LF, 0
%endif
;
; Command line options we'd like to take a look at
;
; mem= and vga= are handled as normal 32-bit integer values
initrd_cmd	db 'initrd='
initrd_cmd_len	equ 7

;
; Config file keyword table
;
%include "keywords.inc"

;
; Extensions to search for (in *forward* order).
;
		align 4, db 0
exten_table:	db '.cbt'		; COMBOOT (specific)
		db '.img'		; Disk image
		db '.bin'		; CD boot sector
		db '.com'		; COMBOOT (same as DOS)
		db '.c32'		; COM32
exten_table_end:
		dd 0, 0			; Need 8 null bytes here

;
; Floppy image table
;
		align 4, db 0
img_table_count	equ 3
img_table:
		dd 1200*1024		; 1200K floppy
		db 1			; Emulation type
		db 80-1			; Max cylinder
		db 15			; Max sector
		db 2-1			; Max head

		dd 1440*1024		; 1440K floppy
		db 2			; Emulation type
		db 80-1			; Max cylinder
		db 18			; Max sector
		db 2-1			; Max head

		dd 2880*1024		; 2880K floppy
		db 3			; Emulation type
		db 80-1			; Max cylinder
		db 36			; Max sector
		db 2-1			; Max head

;
; Misc initialized (data) variables
;

;
; Variables that are uninitialized in SYSLINUX but initialized here
;
; **** ISOLINUX:: We may have to make this flexible, based on what the
; **** BIOS expects our "sector size" to be.
;
		alignb 4, db 0
BufSafe		dw trackbufsize/SECTOR_SIZE	; Clusters we can load into trackbuf
BufSafeBytes	dw trackbufsize		; = how many bytes?
%ifndef DEPEND
%if ( trackbufsize % SECTOR_SIZE ) != 0
%error trackbufsize must be a multiple of SECTOR_SIZE
%endif
%endif