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source: bootcd/isolinux/syslinux-6.03/dosutil/eltorito.asm @ 26ffad7

Last change on this file since 26ffad7 was e16e8f2, checked in by Edwin Eefting <edwin@datux.nl>, 3 years ago
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1
2	;-----------------------------------------------------------------------------
3	; ElTorito.asm
4	;
5	; El Torito Bootable CD-ROM driver which does not reset the CD-ROM drive upon
6	; loading, but instead accesses the drive through BIOS system calls
7	;
8	; MIT License
9	;
10	; (c) 2000 by Gary Tong
11	; (c) 2001-2009 by Bart Lagerweij
12	;
13	; Permission is hereby granted, free of charge, to any person obtaining a copy
14	; of this software and associated documentation files (the "Software"), to deal
15	; in the Software without restriction, including without limitation the rights
16	; to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
17	; copies of the Software, and to permit persons to whom the Software is
18	; furnished to do so, subject to the following conditions:
19	;
20	; The above copyright notice and this permission notice shall be included in
21	; all copies or substantial portions of the Software.
22	;
23	; THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
24	; IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
25	; FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
26	; AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
27	; LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
28	; OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
29	; THE SOFTWARE.
30	;
31	;-----------------------------------------------------------------------------
32
33	; To assemble and link, use these commands with NASM 2.x:
34	; nasm -Ox -f bin -o eltorito.sys eltorito.asm
35
36	; To enable Trace markers uncomment the line below
37	; DEBUG_TRACERS=1
38
39	; To enable debug info uncomment the line below
40	; DEBUG=1
41
42	%ifdef DEBUG_TRACERS
43	%macro TRACER 1
44	call debug_tracer
45	db %1
46	%endmacro
47	%else
48	%macro TRACER 1
49	%endmacro
50	%endif ; DEBUG_TRACERS
51
52	%define Ver '1.5'
53	%define CR 0DH, 0Ah
54	RPolyH equ 0EDB8h
55	RPolyL equ 08320h
56
57	section .text align=16
58	org 0
59
60	;=============================================================================
61
62	Cdrom:
63
64	NextDriver dd -1 ;-+
65	Attributes dw 0C800h ; \|
66	Pointers dw Strategy ; \|
67	dw Commands ; \| MSCDEX requires this
68	DeviceName db 'ELTORITO' ; \| data in these locations
69	dw 0 ; \|
70	DriveLetter db 0 ; \|
71	NumUnitsSupp db 1 ;-+
72
73	DriverName db 'El-Torito CD-ROM Device Driver',0
74	align 4, db 0
75	ReqHdrLoc dd 0
76	XferAddr dd 0
77	Checksum dd -1
78	DriveNumber db 0
79	ReadBytes db 0 ;0 --> 2048 bytes/sector
80	;1 --> 1024 bytes/sector
81	;2 --> 512 bytes/sector
82
83	Routines dw Init ;Init ;0
84	dw Unsupported ;MediaCheck ;1
85	dw Unsupported ;BuildBPB ;2
86	dw IoctlInput ;IoctlInput ;3
87	dw Unsupported ;Input ;4
88	dw Unsupported ;NonDesInput ;5
89	dw Unsupported ;InputStatus ;6
90	dw Unsupported ;InputFlush ;7
91	dw Unsupported ;Output ;8
92	dw Unsupported ;OutputVerify ;9
93	dw Unsupported ;OutputStatus ;10
94	dw Unsupported ;OutputFlush ;11
95	dw IoctlOutput ;IoctlOutput ;12
96	dw DoNothing ;DeviceOpen ;13
97	dw DoNothing ;DeviceClose ;14
98	dw ReadL ;ReadL ;128
99
100	IoctlICtrl dw Raddr ;Raddr ;0
101	dw Unsupported ;LocHead ;1
102	dw Unsupported ;(Reserved) ;2
103	dw Unsupported ;ErrStat ;3
104	dw Unsupported ;AudInfo ;4
105	dw DrvBytes ;DrvBytes ;5
106	dw DevStat ;DevStat ;6
107	dw SectSize ;SectSize ;7
108	dw VolSize ;VolSize ;8
109	dw MedChng ;MedChng ;9
110
111	SpecPkt times 19 db 0 ; offset 77h in 1.4
112	times 13 db 0 ; unknown extra 00s in 1.4
113
114	Greeting db 'El-Torito Bootable CD-ROM Driver for Dos v',Ver,', http://www.nu2.nu/eltorito/',CR
115	db ' (c) 2000 by Gary Tong',CR
116	db ' (c) 2001-2002 by Bart Lagerweij',CR,0
117	DblSpace db ' ',0
118
119	;=============================================================================
120
121	Strategy:
122
123	mov word [cs:ReqHdrLoc],bx
124	mov word [cs:ReqHdrLoc+2],es
125	retf
126
127
128	;=============================================================================
129
130	Commands:
131
132	push ax
133	push bx
134	push cx
135	push dx
136	push si
137	push di
138	push bp
139	; pushad
140	push ds
141	push es
142	TRACER 'C'
143
144	cld ;Clear direction
145	sti ;Enable interrupts
146
147	mov ax, cs ;ds=cs
148	mov ds, ax
149
150	les bx,[ReqHdrLoc] ;seg:offset ptr into es:bx
151	xor ax,ax
152	mov al,[es:bx+2] ;Get Command code
153	%ifdef DEBUG
154	call print_hex8
155	%endif
156	cmp al,15
157	jb Mult2 ;If 0-14
158	cmp al,128
159	jb UnknownCmd ;If 15-127
160	cmp al,129
161	jb ShiftDown ;If 128
162	UnknownCmd: mov al,121 ;8 = Unsupported (Reserved)
163	ShiftDown: sub al,113 ;128 --> 15, 121 --> 8
164	Mult2: shl al,1 ;Convert into offset (*2)
165	mov di,Routines
166	add di,ax
167	call word [di] ;Execute desired command
168	or ax,100h ;Set Return Status's Done bit
169	lds bx,[ReqHdrLoc] ;seg:offset ptr into ds:bx
170	mov [bx+3],ax ;Save Status
171
172	%ifdef DEBUG
173	cmp byte [cs:buffer+2048], 96h
174	je buffer_ok
175	mov al, '!'
176	call print_char
177	jmp $
178	buffer_ok:
179	%endif
180
181	TRACER 'c'
182	pop es
183	pop ds
184	; popad
185	pop bp
186	pop di
187	pop si
188	pop dx
189	pop cx
190	pop bx
191	pop ax
192	retf
193
194
195	;=============================================================================
196
197	Unsupported: ;Unsupported Command
198
199	mov ax,8003h ;Set Status Error bit,
200	TRACER 'U'
201	TRACER 'C'
202	retn ; Error 3 = Unknown Command
203
204
205	;=============================================================================
206
207	IoctlInput: ;IOCTL Input Routine
208
209	mov di,[es:bx+14] ;es:bx --> Request Header
210	mov es,[es:bx+16] ;Get Xfer Address into es:di
211	xor ax,ax ;Get Control Block Code
212	mov al,[es:di]
213	%ifdef DEBUG
214	TRACER 'I'
215	TRACER 'O'
216	call print_hex8
217	%endif
218	cmp al,10
219	jb UnkIoctlI ;If 0-9
220	mov al,2 ;Map to Unsupported
221	UnkIoctlI: shl al,1 ;Convert into offset (*2)
222	mov si,IoctlICtrl
223	add si,ax
224	call word [si] ;Execute desired command
225	retn
226
227
228	;=============================================================================
229
230	Raddr: ;Return Device Header Address
231
232	TRACER 'A'
233	mov word [es:di+1],0
234	mov [es:di+3],cs
235	xor ax, ax ;Set Return Status = success
236	TRACER 'a'
237	retn
238
239
240	;=============================================================================
241
242	DrvBytes: ;Read Drive Bytes
243
244	TRACER 'B'
245	push di ;Save original Xfer Addr
246	add di,2 ;Point to 1st dest byte
247	mov si,Greeting ;Point to Greeting
248	DrvB: movsb ;Copy over a byte
249	cmp byte [si],13 ;Is next char a CR?
250	jne DrvB ;Loop if not
251
252	sub di,2 ;Get #bytes copied into ax
253	mov ax,di
254	pop di ;Retrieve original Xfer Addr
255	sub ax,di
256	mov byte [es:di+1],al ;and save it
257	mov ax,0 ;Set Return Status = success
258	TRACER 'b'
259	retn
260
261
262	;=============================================================================
263
264	DevStat: ;Return Device Status
265
266	TRACER 'D'
267	mov word [es:di+1],202h ;Door closed
268	mov word [es:di+3],0 ;Door unlocked
269	;Supports only cooked reading
270	;Read only
271	;Data read only
272	;No interleaving
273	;No prefetching
274	;No audio channel manipulation
275	;Supports both HSG and Redbook
276	; addressing modes
277
278	xor ax, ax ;Set Return Status = success
279	TRACER 'd'
280	retn
281
282
283	;=============================================================================
284
285	SectSize: ;Return Sector Size
286
287	TRACER 'S'
288	mov word [es:di+2],2048
289	mov ax,0 ;Set Return Status = success
290	TRACER 's'
291	retn
292
293
294	;=============================================================================
295
296	VolSize: ;Return Volume Size
297
298	TRACER 'V'
299	call PriVolDesc ;Get and Check Primary Volume
300	; Descriptor
301	mov ax,800Fh ;Assume Invalid Disk Change
302	jc VolExit ;If Read Failure
303
304	mov ax,word [Buffer+80] ;Read Successful
305	mov word [es:di+1],ax ;Copy over Volume Size
306	mov ax,word [Buffer+82]
307	mov word [es:di+3],ax
308	mov ax,0 ;Set Return Status = success
309	VolExit:
310	TRACER 'v'
311	retn
312
313
314	;=============================================================================
315
316	MedChng: ;Return Media Changed Status
317
318	TRACER 'M'
319	call PriVolDesc ;Get and Check Primary Volume
320	; Descriptor
321	mov byte [es:di+1],-1 ;Assume Media Changed
322	mov ax,800Fh ; and Invalid Disk Change
323	jc MedExit ;If Media Changed or Bad
324
325	mov byte [es:di+1],1 ;Media has not changed
326	mov ax,0 ;Set Return Status = success
327	MedExit:
328	TRACER 'm'
329	retn
330
331
332	;=============================================================================
333
334	PriVolDesc: ;Get and Check Primary Volume
335	; Descriptor
336	TRACER 'P'
337	mov ax,cs ;Set ds:si --> SpecPkt
338	mov ds,ax
339
340	mov cx, 5
341	PriVolAgain:
342	mov byte [SpecPkt],16 ;SpecPkt Size
343	mov byte [SpecPkt+1],0 ;Reserved
344	mov word [SpecPkt+2],1 ;Transfer one 2048-byte sector
345	push cx
346	mov cl,byte [ReadBytes] ;Multiply by 4 if reading 512
347	shl word [SpecPkt+2],cl ; bytes at a time
348	pop cx
349	mov word [SpecPkt+6],cs ;Into our Buffer
350	mov word [SpecPkt+4], Buffer
351	mov word [SpecPkt+8],16 ;From CD Sector 16
352	mov word [SpecPkt+10],0
353	mov word [SpecPkt+12],0
354	mov word [SpecPkt+14],0
355
356	mov si, SpecPkt
357	mov dl, [DriveNumber]
358	mov ah, 42h ;Extended Read
359	int 13h
360	jnc PriVolPass ;If success
361
362	; TRACER '1'
363	; read error
364	loop PriVolAgain
365
366	TRACER '2'
367	; read retries exhausted
368	; flow into below
369	jmp PriReadErr
370
371	PriVolPass:
372	mov si,Buffer ;Point input to Buffer
373	mov ax,-1 ;Init Checksum registers
374	mov bx,ax ; bx,ax = 0FFFFFFFFh
375	jc PriNew ;If Read Failure
376
377	push di ;Read Successful,
378	; so Calculate Checksum
379	mov di,1024 ;Init Word counter
380	PriWord: mov dx,[cs:si] ;Grab next word from buffer
381	mov cx,16 ;Init bit counter
382	PriBit: shr dx,1 ;Shift everything right 1 bit
383	rcr bx,1
384	rcr ax,1
385	jnc NoMult ;If a zero shifted out
386
387	xor bx,RPolyH ;A one shifted out, so XOR
388	xor ax,RPolyL ; Checksum with RPoly
389	NoMult:
390	loop PriBit
391
392	add si,2 ;Inc Word Pointer
393	dec di
394	ja PriWord
395	TRACER '3'
396
397	pop di ;Checksum calculation complete
398	cmp bx,[Checksum+2] ;Has Checksum changed?
399	jne PriNew ;If Checksum Changed
400
401	cmp ax,[Checksum]
402	jne PriNew ;If Checksum Changed
403
404	clc ;Checksum not changed, CF=0
405	mov ax,0 ;Status = success
406	jmp PriOld
407
408	PriReadErr:
409	mov WORD [Checksum+2],bx ;Save New Checksum
410	mov [Checksum],ax ; or 0FFFFFFFFh if bad read
411	stc ;Checksum change, CF=1
412	mov ax, 800bh ;Status = read fault
413	jmp PriOld
414
415	PriNew: mov WORD [Checksum+2],bx ;Save New Checksum
416	mov [Checksum],ax ; or 0FFFFFFFFh if bad read
417	stc ;Checksum Changed, CF=1
418	mov ax,800Fh ;Status = Invalid Media Change
419	PriOld:
420	TRACER 'p'
421	retn
422
423
424	;=============================================================================
425
426	IoctlOutput: ;IOCTL Output Routine
427
428	TRACER 'O'
429	mov di,[es:bx+14] ;es:bx --> Request Header
430	mov es,[es:bx+16] ;Get Xfer Address into es:di
431	xor ax,ax ;Get Control Block Code
432	mov al,[es:di]
433	cmp al,2
434	jne UnkIoctlO ;If not 2 (ResetDrv)
435	call DoNothing ;Reset Drive
436	jmp IoctlODone
437	UnkIoctlO:
438	call Unsupported ;Unsupported command
439	IoctlODone:
440	TRACER 'o'
441	retn
442
443
444	;=============================================================================
445
446	DoNothing: ;Do Nothing Command
447
448	mov ax,0 ;Set Return Status = success
449	retn
450
451
452	;=============================================================================
453
454	ReadL: ;Read Long Command
455
456	TRACER 'R'
457	mov ax,cs ;Set ds=cs
458	mov ds,ax
459	;es:bx --> Request Header
460	cmp byte [es:bx+24],0 ;Check Data Read Mode
461	jne ReadLErr ;If Cooked Mode
462
463	cmp byte [es:bx+13],2 ;Check Addressing Mode
464	jb ReadLOK ;If HSG or Redbook Mode
465
466	ReadLErr:
467	TRACER '8'
468	mov ax,8003h ;Set Return Status = Unknown
469	jmp ReadLExit ; Command Error and exit
470
471	ReadLOK:
472	mov ax,[es:bx+20] ;Get Starting Sector Number,
473	mov dx,[es:bx+22] ; Assume HSG Addressing Mode
474	cmp byte [es:bx+13],0 ;Check Addressing Mode again
475	je ReadLHSG ;If HSG Addressing Mode
476
477	TRACER '7'
478	;Using Redbook Addressing Mode. Convert to HSG format
479	mov al,dl ;Get Minutes
480	mov dl,60
481	mul dl ;ax = Minutes * 60
482	add al,byte [es:bx+21] ;Add in Seconds
483	adc ah,0
484	mov dx,75 ;dx:ax =
485	mul dx ; ((Min * 60) + Sec) * 75
486	add al,byte [es:bx+20] ;Add in Frames
487	adc ah,0
488	adc dx,0
489	sub ax,150 ;Subtract 2-Second offset
490	sbb dx,0 ;dx:ax = HSG Starting Sector
491
492	ReadLHSG:
493	mov word [SpecPkt+8], ax ;Store Starting
494	mov word [SpecPkt+10], dx ; Sector Number
495	mov word [SpecPkt+12], 0 ; (HSG Format)
496	mov word [SpecPkt+14], 0
497
498	mov ax,[es:bx+14] ;Get Transfer Address
499	mov word [SpecPkt+4],ax
500	mov ax,[es:bx+16]
501	mov word [SpecPkt+6],ax
502
503	mov byte [SpecPkt],16 ;Size of Disk Address Packet
504	mov byte [SpecPkt+1],0 ;Reserved
505
506	mov cx, 5
507	ReadLAgain:
508	mov ax,[es:bx+18] ;Get number of sectors to read
509	mov word [SpecPkt+2],ax
510	cmp ax, 3FFFh ;Too large?
511	ja ReadLBad ;If yes
512
513	push cx
514	mov cl,byte [ReadBytes] ;Multiply by 4 if reading 512
515	shl word [SpecPkt+2],cl ; bytes at a time
516	pop cx
517
518	%ifdef DEBUG
519	push ax
520	push cx
521	push si
522	mov cx, 16
523	mov si,SpecPkt
524	ReadDump: mov al, ' '
525	call print_char
526	mov al, byte [si] ;Hexdump a SpecPkt byte
527	call print_hex8
528	inc si ;Point to next byte
529	loop ReadDump
530	pop si
531	pop cx
532	pop ax
533	%endif
534	mov si,SpecPkt
535	mov dl,[DriveNumber]
536	mov ah,42h ;Extended Read
537	int 13h
538	jnc ReadLGd ;If success
539
540	;hang:
541	; jmp hang
542	; TRACER '1'
543	loop ReadLAgain
544	TRACER '2'
545	jmp short ReadLBad
546	ReadLGd:
547	TRACER '3'
548	xor ax, ax ;Status 0 = success
549	jmp short ReadLExit
550
551	ReadLBad:
552	TRACER '9'
553	mov ax, 800Bh ;Set Read Fault Error
554	; flow into ReadLExit
555	ReadLExit:
556	TRACER 'r'
557	retn
558
559
560
561	%ifdef DEBUG_TRACERS
562	debug_tracer: pushad
563	pushfd
564
565	mov al, '['
566	mov ah,0Eh ;BIOS video teletype output
567	xor bh, bh
568	int 10h ;Print it
569
570	mov bp,sp
571	mov bx,[bp+9*4] ; Get return address
572	mov al,[cs:bx] ; Get data byte
573	inc word [bp+9*4] ; Return to after data byte
574
575	mov ah,0Eh ;BIOS video teletype output
576	xor bh, bh
577	int 10h ;Print it
578
579	mov al, ']'
580	mov ah,0Eh ;BIOS video teletype output
581	xor bh, bh
582	int 10h ;Print it
583
584	popfd
585	popad
586	retn
587	%endif
588
589	;-----------------------------------------------------------------------------
590	; PRINT_HEX4
591	;-----------------------------------------------------------------------------
592	; print a 4 bits integer in hex
593	;
594	; Input:
595	; AL - 4 bits integer to print (low)
596	;
597	; Output: None
598	;
599	; Registers destroyed: None
600	;
601	print_hex4:
602
603	push ax
604	and al, 0fh ; we only need the first nibble
605	cmp al, 10
606	jae hex_A_F
607	add al, '0'
608	jmp hex_0_9
609	hex_A_F:
610	add al, 'A'-10
611	hex_0_9:
612	call print_char
613	pop ax
614	retn
615
616
617	;-----------------------------------------------------------------------------
618	; print_hex8
619	;-----------------------------------------------------------------------------
620	; print a 8 bits integer in hex
621	;
622	; Input:
623	; AL - 8 bits integer to print
624	;
625	; Output: None
626	;
627	; Registers destroyed: None
628	;
629	print_hex8:
630
631	push ax
632	push bx
633
634	mov ah, al
635	shr al, 4
636	call print_hex4
637
638	mov al, ah
639	and al, 0fh
640	call print_hex4
641
642	pop bx
643	pop ax
644	retn
645
646
647	;=============================================================================
648	; print_hex16 - print a 16 bits integer in hex
649	;
650	; Input:
651	; AX - 16 bits integer to print
652	;
653	; Output: None
654	;
655	; Registers destroyed: None
656	;=============================================================================
657	print_hex16:
658
659	push ax
660	push bx
661	push cx
662
663	mov cx, 4
664	print_hex16_loop:
665	rol ax, 4
666	call print_hex4
667	loop print_hex16_loop
668
669	pop cx
670	pop bx
671	pop ax
672	retn
673
674	;=============================================================================
675	; print_hex32 - print a 32 bits integer in hex
676	;
677	; Input:
678	; EAX - 32 bits integer to print
679	;
680	; Output: None
681	;
682	; Registers destroyed: None
683	;=============================================================================
684	print_hex32:
685
686	push eax
687	push bx
688	push cx
689
690	mov cx, 8
691	print_hex32_loop:
692	rol eax, 4
693	call print_hex4
694	loop print_hex32_loop
695
696	pop cx
697	pop bx
698	pop eax
699	retn
700
701	;=============================================================================
702	; print_string - print string at current cursor location
703	;
704	; Input:
705	; DS:SI - ASCIIZ string to print
706	;
707	; Output: None
708	;
709	; Registers destroyed: None
710	;=============================================================================
711	print_string:
712	push ax
713	push si
714
715	print_string_again:
716	mov al, [si]
717	or al, al
718	jz print_string_exit
719	call print_char
720	inc si
721	jmp print_string_again
722
723	print_string_exit:
724	pop si
725	pop ax
726	retn
727
728	;-----------------------------------------------------------------------------
729	; PRINT_CHAR
730	;-----------------------------------------------------------------------------
731	; Print's a character at current cursor position
732	;
733	; Input:
734	; AL - Character to print
735	;
736	; Output: None
737	;
738	; Registers destroyed: None
739	;
740	print_char:
741
742	push ax
743	push bx
744
745	mov ah,0Eh ;BIOS video teletype output
746	xor bh, bh
747	int 10h ;Print it
748
749	print_char_exit:
750	pop bx
751	pop ax
752	retn
753
754
755	;=============================================================================
756
757	;This space is used as a 2048-byte read buffer plus one test byte.
758	;The 96h data is used for testing the number of bytes returned by an Extended
759	; CD-ROM sector read
760
761	align 16, db 0
762	Buffer times 2049 db 96h
763
764	;=============================================================================
765
766	Init: ;Initialization Routine
767
768	TRACER 'I'
769	mov ax,cs ;ds=cs
770	mov ds,ax
771
772	%ifdef DEBUG
773	; print CS value (load segment)
774	call print_hex16
775	%endif
776
777	mov si, Greeting ;Display Greeting
778	call print_string
779
780	mov ax,Unsupported ;Init is executed only once
781	mov [Routines],ax
782
783	mov ax, 5400h
784	int 13h ; Get diskemu status
785	jc FindBoot ; If CF=1 no diskemu loaded
786
787	mov [DriveNumber], cl ; Store drive number
788
789	call keyflag
790	and al, 8 ; alt key ?
791	jz extread
792
793	mov si, DrvNumMsg ; Display "drive number="
794	call print_string
795	mov al, [DriveNumber]
796	call print_hex8
797	mov si, LineEnd ; CR/LF
798	call print_string
799	jmp extread
800
801	; Diskemu is not loaded
802	; so loop to find drive number
803	; * start of 1.4 changes *
804	; ??? mov dl, 0ffh ;Start at Drive 0xff
805	; * FindBoot at c47 in 1.4, at c0c in 1.3 *
806	FindBoot: call ScanDrives ; call new helper in 1.4
807	jnc FoundBoot ; ded*df3
808	; mov si,offset SpecPkt ;Locate booted CD-ROM drive
809	; mov [SpecPkt],0 ;Clear 1st byte of SpecPkt
810	; mov ax,4B01h ;Get Bootable CD-ROM Status
811	; int 13h
812	; jnc FindPass ;If booted CD found
813	;
814	; Carry is not cleared in buggy Dell BIOSes,
815	; so I'm checking packet size byte
816	; some bogus bioses (Dell Inspiron 2500) returns packet size 0xff when failed
817	; Dell Dimension XPsT returns packet size 0x14 when OK
818
819	; cmp [SpecPkt], 0
820	; jne FoundBoot
821
822	; cmp [SpecPkt], 13h ; anything between 13h and 20h should be OK
823	; jb FindFail
824	; cmp [SpecPkt], 20h
825	; ja FindFail
826	; jmp short FoundBoot
827	;
828	; FindFail:
829	; dec dl ;Next drive
830	; cmp dl, 80h
831	; jae FindBoot ;Check from ffh..80h
832	; * end of 1.4 changes *
833
834	mov si,NoBootCD ;No booted CD found,
835	call print_string
836	jmp NoEndAddr ;Do not install driver
837
838	FoundBoot:
839	; mov dl, [SpecPkt+2] ; 1.4 change
840	; * next line at c57 in 1.4, at c3d in 1.3 *
841	mov [DriveNumber],dl ;Booted CD-ROM found,
842	; so save Drive #
843
844	call keyflag
845	and al, 8 ; alt key ?
846	jz extread
847
848	mov si, CDStat
849	call print_string
850	mov si, SpecPkt ;Point to returned CD SpecPkt
851	mov cx, 19 ; containing 19 bytes
852	StatDump: mov al, ' ' ;Print a space
853	call print_char
854	mov al, byte [si] ;Hexdump a SpecPkt byte
855	call print_hex8
856	inc si ;Point to next byte
857	loop StatDump
858
859	mov si, LineEnd ;Print a CR/LF
860	call print_string
861
862	extread:
863	;See how many CD Sector bytes are returned by an Extended Read
864	mov byte [SpecPkt],16 ;SpecPkt Size
865	mov byte [SpecPkt+1],0 ;Reserved
866	mov word [SpecPkt+2],1 ;Transfer one sector
867	mov word [SpecPkt+6],cs ;Into our Buffer
868	mov word [SpecPkt+4],Buffer
869	mov word [SpecPkt+8],16 ;From CD Sector 16
870	mov word [SpecPkt+10],0
871	mov word [SpecPkt+12],0
872	mov word [SpecPkt+14],0
873
874	mov si, SpecPkt ;Set ds:si --> SpecPkt
875	mov dl, [DriveNumber]
876	mov ah, 42h ;Extended Read
877	int 13h
878	jnc SecSize ;If success
879
880	mov ah, 42h ;Always make 2 read attempts
881	int 13h
882	;How many bytes did we get?
883	SecSize: std ;Count down
884	mov ax,cs ;Point to end of Buffer
885	mov es,ax
886	mov di,Buffer+2047 ;Find end of read data
887	mov si,Buffer+2048
888	mov cx,2049
889	repe cmpsb ;cx = number of bytes read
890
891	cld ;Restore count direction to up
892	mov si,CDBytes ;Display number of bytes read
893	call print_string
894
895	mov al, [DriveNumber]
896	call print_hex8
897
898	mov si,CDBytesA ;Remainder A of message
899	call print_string
900
901	mov al,ch ;Hex-dump cx
902	and al,0Fh ;Second nibble
903	call print_hex8 ; (don't need the First)
904	mov al,cl
905	call print_hex8 ; (don't need the First)
906
907	mov si,CDBytesB ;Remainder B of message
908	call print_string
909
910	cmp cx,2048 ;Did we read 2048 bytes?
911	je ParseParm ;If yes <-- O.K.
912
913	mov byte [ReadBytes],1
914	cmp cx,1024 ;Did we read 1024 bytes?
915	je ParseParm ;If yes <-- O.K.
916
917	mov byte [ReadBytes],2
918	cmp cx,512 ;Did we read 512 bytes?
919	jne NoEndAddr ;If not, do not load driver
920
921	ParseParm: mov bx,word [cs:ReqHdrLoc] ;Parse command line
922	mov es,word [cs:ReqHdrLoc+2] ; parameters
923	mov si,[es:bx+18] ;Get BPB array ptr into DS:SI
924	mov ds,[es:bx+20]
925	FindParm: inc si
926	FindParm1: cmp byte [si],0Dh ;CR? (End of parameters)
927	je EndOfParms
928
929	cmp byte [si],0Ah ;LF?
930	je EndOfParms
931
932	cmp byte [si],'/' ;A parameter?
933	jne FindParm
934
935	inc si
936	cmp byte [si],'D' ;Device Name parameter?
937	jne FindParm1
938
939	inc si
940	cmp byte [si],':'
941	jne FindParm1
942
943	;bbb
944	push si
945	mov si, DevName ;Device Name is at ds:si
946	push ds ;Keep ptr to Device Name
947	mov ax, cs
948	mov ds, ax
949	call print_string
950	pop ds ;Retrieve Device Name ptr
951	pop si
952	mov cx, 8 ;Get next 8 chars
953	inc si ; = Device Name
954	mov ax, cs
955	mov es, ax
956	mov di, DeviceName
957	NextChar: cmp byte [si],' '
958	ja AboveSpace
959
960	mov ax,cs ;Pad end of Device Name with
961	mov ds,ax ; spaces if necessary
962	mov si,DblSpace ;A space
963	AboveSpace: mov al, [si]
964	call print_char
965	movsb ;ds:[si] --> es:[di]
966	loop NextChar
967
968	mov si,LineEnd
969	mov ax,cs
970	mov ds,ax
971	call print_string
972
973	mov ax,Init-2 ;Last byte of driver to keep
974	jmp EndAddr ;Install driver
975
976	EndOfParms:
977	mov ax, cs ; Restore segment registers (fix)
978	mov ds, ax
979	mov es, ax
980
981	mov si,NoDevName ;No Device Name Found
982	call print_string
983
984	NoEndAddr: mov ax,0 ;Do not install driver
985
986	EndAddr: mov es,[ReqHdrLoc+2] ;Write End Address
987	mov bx,[ReqHdrLoc]
988	mov [es:bx+14],ax
989	mov [es:bx+16],cs
990	mov bx,ax ;Hold onto install status
991
992	mov si, DrvInst ;Display driver install status
993	call print_string
994	mov si, DrvInst1 ;Assume driver installed
995	cmp bx,0 ;Was driver installed?
996	jne DrvStatus ;If yes
997	mov si, NoDrvInst ;Driver not installed
998	DrvStatus: call print_string
999
1000	mov ax,0 ;Set Return Status = success
1001	cmp bx,0 ;Was INIT successful?
1002	jne InitStat ;If yes
1003	mov ax,800Ch ;Status = General Failure
1004	InitStat:
1005	push ax ;Save Return Status
1006
1007	call keyflag
1008	and al, 8 ; alt key ?
1009	jz InitExit
1010
1011	WaitHere:
1012	mov si, WaitMsg ;Display Halted message
1013	call print_string
1014
1015	AltWait:
1016	call keyflag
1017	and al, 8 ; Alt key?
1018	jnz AltWait ; Pressed? yes -> wait
1019
1020	InitExit:
1021	pop ax ;Retrieve Return Status
1022	TRACER 'i'
1023	retn ;That's it for Init!
1024
1025	; * start 1.4 changes at ded *
1026	SpecGo: mov si,SpecPkt
1027	int 13h
1028	retn
1029
1030	ScanDrives: push ax ; at df3 in 1.4
1031	push si
1032	mov dl, 7fh ;Start at Drive 0x80
1033	NextDrv: inc dl
1034	clc
1035	mov ax,4B01h ;Get Bootable CD-ROM Status
1036	mov BYTE [SpecPkt],0 ;Clear 1st byte of SpecPkt
1037	call SpecGo
1038	; Carry is not cleared in buggy Dell BIOSes,
1039	; so I'm checking packet size byte
1040	; some bogus bioses (Dell Inspiron 2500) returns packet size 0xff when failed
1041	; Dell Dimension XPsT returns packet size 0x14 when OK
1042
1043	cmp BYTE [SpecPkt], 13h ; anything between 13h and 20h should be OK
1044	jb FindFail
1045	cmp BYTE [SpecPkt], 20h
1046	ja FindFail ; in 1.4 at e16
1047	jmp short SendFound ; in 1.4 at e26
1048
1049	FindFail: cmp dl, 0ffh
1050	je SendFail ; Check from 80h..ffh
1051	jmp short NextDrv ;Next drive
1052	SendFail: xor dl,dl
1053	stc
1054	jmp short ThingDone
1055	SendFound: mov dl, [SpecPkt+2]
1056	clc
1057	ThingDone: pop si
1058	pop ax
1059	retn
1060	; * end 1.4 changes *
1061
1062	;=============================================================================
1063
1064	;------------------------------------------------------------
1065	; keyboard flags - return keyboard flags in AL
1066	; bit 3 = ALT key
1067	keyflag: ; at dbc in 1.3, at e2e in 1.4
1068	push bx
1069	mov ah, 2
1070	int 16h
1071	pop bx
1072	retn
1073
1074	;=============================================================================
1075
1076	DrvNumMsg db ' Diskemxx.bin returned drive number=', 0
1077	NoBootCD db ' No booted CD-ROM found.',CR,0
1078
1079	CDStat db ' INT 13h / AX=4B01h Specification Packet for '
1080	db 'Booted CD-ROM:',CR,' ', 0
1081
1082	CDBytes db ' Drive ', 0
1083	CDBytesA db ' returns ', 0
1084	CDBytesB db 'h bytes per Sector.',CR,0
1085
1086	DevName db ' Device Name: ', 0
1087	NoDevName db ' No Device Name found. '
1088	db 'Usage: device=eltorito.sys /D:<DevName>',CR,0
1089
1090	DrvInst db ' Driver ', 0
1091	NoDrvInst db 7,'not ' ;7 = Ctrl-G = Beep
1092	DrvInst1 db 'installed',CR,0
1093
1094	WaitMsg db ' Alt pressed, waiting...', CR, 0
1095	;ContMsg db ' Continuing...'
1096	LineEnd db CR,0
1097
1098
1099	;=============================================================================

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