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memdisk.inc @ dd1be7c

Last change on this file since dd1be7c was e16e8f2, checked in by Edwin Eefting <edwin@datux.nl>, 3 years ago
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1	; -- fundamental -- (asm-mode sucks)
2	; ****************************************************************************
3	;
4	; memdisk.inc
5	;
6	; A program to emulate an INT 13h disk BIOS from a "disk" in extended
7	; memory.
8	;
9	; Copyright 2001-2009 H. Peter Anvin - All Rights Reserved
10	; Copyright 2009 Intel Corporation; author: H. Peter Anvin
11	; Portions copyright 2009 Shao Miller [El Torito code, mBFT, safe hook]
12	;
13	; This program is free software; you can redistribute it and/or modify
14	; it under the terms of the GNU General Public License as published by
15	; the Free Software Foundation, Inc., 53 Temple Place Ste 330,
16	; Boston MA 02111-1307, USA; either version 2 of the License, or
17	; (at your option) any later version; incorporated herein by reference.
18	;
19	; ****************************************************************************
20
21	%include "../version.gen"
22
23	; %define DEBUG_TRACERS ; Uncomment to get debugging tracers
24
25	%ifdef DEBUG_TRACERS
26
27	%macro TRACER 1
28	call debug_tracer
29	db %1
30	%endmacro
31	%macro WRITEHEX2 0-1 al
32	%ifnidni %1,al
33	push ax
34	mov al,%1
35	call writehex2
36	pop ax
37	%else
38	call writehex2
39	%endif
40	%endmacro
41	%macro WRITEHEX4 0-1 ax
42	%ifnidni %1,ax
43	push ax
44	mov ax,%1
45	call writehex4
46	pop ax
47	%else
48	call writehex4
49	%endif
50	%endmacro
51	%macro WRITEHEX8 0-1 eax
52	%ifnidni %1,eax
53	push eax
54	mov eax,%1
55	call writehex8
56	pop eax
57	%else
58	call writehex8
59	%endif
60	%endmacro
61
62	%else ; DEBUG_TRACERS
63
64	%macro TRACER 1
65	%endmacro
66	%macro WRITEHEX2 0-1
67	%endmacro
68	%macro WRITEHEX4 0-1
69	%endmacro
70	%macro WRITEHEX8 0-1
71	%endmacro
72
73	%endif ; DEBUG_TRACERS
74
75	; Flags we test our configuration against
76	%define CONFIG_READONLY 0x01
77	%define CONFIG_RAW 0x02
78	%define CONFIG_SAFEINT 0x04
79	%define CONFIG_BIGRAW 0x08 ; MUST be 8!
80
81	org 0h
82
83	%define SECTORSIZE (1 << SECTORSIZE_LG2)
84
85	; Parameter registers definition; this is the definition
86	; of the stack frame.
87	%define P_DS word [bp+34]
88	%define P_ES word [bp+32]
89	%define P_EAX dword [bp+28]
90	%define P_HAX word [bp+30]
91	%define P_AX word [bp+28]
92	%define P_AL byte [bp+28]
93	%define P_AH byte [bp+29]
94	%define P_ECX dword [bp+24]
95	%define P_HCX word [bp+26]
96	%define P_CX word [bp+24]
97	%define P_CL byte [bp+24]
98	%define P_CH byte [bp+25]
99	%define P_EDX dword [bp+20]
100	%define P_HDX word [bp+22]
101	%define P_DX word [bp+20]
102	%define P_DL byte [bp+20]
103	%define P_DH byte [bp+21]
104	%define P_EBX dword [bp+16]
105	%define P_HBX word [bp+18]
106	%define P_HBXL byte [bp+18]
107	%define P_BX word [bp+16]
108	%define P_BL byte [bp+16]
109	%define P_BH byte [bp+17]
110	%define P_EBP dword [bp+8]
111	%define P_BP word [bp+8]
112	%define P_ESI dword [bp+4]
113	%define P_SI word [bp+4]
114	%define P_EDI dword [bp]
115	%define P_DI word [bp]
116
117	section .text
118	; These pointers are used by the installer and
119	; must be first in the binary
120	Pointers: dw Int13Start
121	dw Int15Start
122	dw MemDisk_Info ; Portions are patched by installer
123	dw TotalSize
124	dw IretPtr
125
126	IretPtr equ Int13Start.iret
127	Int13Start:
128	jmp strict near .SafeHookEnd ; 3-byte jump
129	db '$INT13SF' ; Signature for "safe hook"
130	db 'MEMDISK ' ; Vendor ID
131	dd 0 ; SEG:OFF of previous INT 13h hook
132	; Must be filled in by installer
133	dd 0 ; "Safe hook" flags
134	; ---- "Safe hook" structure ends here ---
135
136	; This next field should be guaranteed at this position after the
137	; "safe hook" structure. This allows for a MEMDISK OS driver to
138	; immediately find out the particular parameters using the mBFT
139	; and MDI structures. This binary will have the offset to the mBFT
140	; in this field to begin with, so the installer knows where the mBFT
141	; is. This is akin to the "Pointers" section above. The installer
142	; will refill this field with the physical address of the mBFT for
143	; future consumers, such as OS drivers.
144	dd mBFT ; Offset from hook to the mBFT
145
146	.SafeHookEnd:
147	cmp word [cs:Recursive],0
148	jne recursive
149
150	; Swap stack
151	mov [cs:Stack],esp
152	mov [cs:Stack+4],ss
153	mov [cs:SavedAX],ax
154	mov ax,cs
155	mov ss,ax
156	mov sp,[cs:MyStack]
157
158	%if ELTORITO
159	cmp word [cs:SavedAX],4a00h ; El Torito function?
160	jae our_drive ; We grab it
161	%endif
162	; See if DL points to our class of device (FD, HD)
163	push dx
164	push dx
165	xor dl,[cs:DriveNo]
166	pop dx
167	js .nomatch ; If SF=0, we have a class match here
168	; 0x00 the sign bit for FD
169	; 0x80 the sign bit for HD
170	jz our_drive ; If ZF=1, we have an exact match
171	cmp dl,[cs:DriveNo]
172	jb .nomatch ; Drive < Our drive
173	cmp dl,[cs:DriveShiftLimit]
174	jae .nomatch ; Drive > The maximum drive
175	; number that we will shift for.
176	; This leaves any higher-up BIOS
177	; drives alone, such as an optical
178	; disc drive 0xA0 or 0xE0
179	dec dl ; Drive > Our drive, adjust drive #
180	.nomatch:
181	TRACER '!'
182	WRITEHEX2 dl
183	TRACER ','
184	mov ax,[cs:SavedAX]
185	WRITEHEX4
186	inc word [cs:Recursive]
187	pushf
188	call far [cs:OldInt13]
189	pushf
190	dec word [cs:Recursive]
191	push bp
192	mov bp,sp
193	cmp byte [cs:SavedAX+1],08h ; Get drive params function?
194	je .norestoredl ; DL = number of drives
195	cmp byte [cs:SavedAX+1],15h ; Get disk type function?
196	jne .restoredl
197	test byte [bp+4],80h ; Hard disk?
198	jnz .norestoredl ; CX:DX = size of device
199	.restoredl:
200	mov dl,[bp+4]
201	.norestoredl:
202	push ax
203	push ebx
204	push ds
205	mov ax,[bp+2] ; Flags
206	lds ebx,[cs:Stack]
207	mov [bx+4],al ; Arithmetic flags
208	pop ds
209	pop ebx
210	pop ax
211	pop bp
212	lss esp,[cs:Stack]
213	.iret: iret
214
215	recursive:
216	TRACER '@'
217	jmp_oldint13:
218	jmp far [cs:OldInt13]
219
220	our_drive:
221	; Set up standard entry frame
222	push ds
223	push es
224	mov ds,ax
225	mov es,ax
226	mov ax,[SavedAX]
227	pushad
228	mov bp,sp ; Point BP to the entry stack frame
229	TRACER 'F'
230	WRITEHEX4
231	; Note: AX == P_AX here
232	cmp ah,Int13FuncsCnt-1
233	ja Invalid_jump
234	%if ELTORITO
235	mov al,[CD_PKT.type] ; Check if we are in
236	cmp al,0 ; El Torito no emulation mode
237	ja .emulation ; No. We support the function
238	cmp ah,3fh ; Yes. We must not support functions
239	jbe Invalid_jump ; 0 through 3Fh. Check and decide
240	.emulation:
241	%endif
242	xor al,al ; AL = 0 is standard entry condition
243	mov di,ax
244	shr di,7 ; Convert AH to an offset in DI
245	call [Int13Funcs+di]
246
247	Done: ; Standard routine for return
248	mov P_AX,ax
249	DoneWeird:
250	TRACER 'D'
251	xor bx,bx
252	mov es,bx
253	mov bx,[StatusPtr]
254	mov [es:bx],ah ; Save status
255	and ah,ah
256
257	lds ebx,[Stack]
258	; This sets the low byte (the arithmetic flags) of the
259	; FLAGS on stack to either 00h (no flags) or 01h (CF)
260	; depending on if AH was zero or not.
261	setnz [bx+4] ; Set CF iff error
262	popad
263	pop es
264	pop ds
265	lss esp,[cs:Stack]
266	iret
267
268	Reset:
269	; Reset affects multiple drives, so we need to pass it on
270	TRACER 'R'
271	xor ax,ax ; Bottom of memory
272	mov es,ax
273	test dl,dl ; Always pass it on if we are
274	; resetting HD
275	js .hard_disk ; Bit 7 set
276	; Some BIOSes get very unhappy if we pass a reset floppy
277	; command to them and don't actually have any floppies.
278	; This is a bug, but we have to deal with it nontheless.
279	; Therefore, if we are the ONLY floppy drive, and the
280	; user didn't request HD reset, then just drop the command.
281	; BIOS equipment byte, top two bits + 1 == total # of floppies
282	test byte [es:0x410],0C0h
283	jz success
284	jmp .pass_on ; ... otherwise pass it to the BIOS
285	.hard_disk:
286	; ... same thing for hard disks, sigh ...
287	cmp byte [es:0x475],1 ; BIOS variable for number of hard
288	; disks
289	jbe success
290
291	.pass_on:
292	pop ax ; Drop return address
293	popad ; Restore all registers
294	pop es
295	pop ds
296	lss esp,[cs:Stack] ; Restore the stack
297	and dl,80h ; Clear all but the type bit
298	jmp jmp_oldint13
299
300
301	Invalid:
302	pop dx ; Drop return address
303	Invalid_jump:
304	TRACER 'I'
305	mov ah,01h ; Unsupported function
306	jmp short Done
307
308	GetDriveType:
309	test byte [DriveNo],80h
310	mov bl,02h ; Type 02h = floppy with changeline
311	jz .floppy
312	; Hard disks only! DO NOT set CX:DX for floppies...
313	; it apparently causes Win98SE DOS to go into an loop
314	; resetting the drive over and over. Sigh.
315	inc bx ; Type = 03h
316	mov dx,[DiskSize] ; Return the disk size in sectors
317	mov P_DX,dx
318	mov cx,[DiskSize+2]
319	mov P_CX,cx
320	.floppy:
321	mov P_AH,bl ; 02h floppy, 03h hard disk
322	pop ax ; Drop return address
323	xor ax,ax ; Success...
324	jmp DoneWeird ; But don't stick it into P_AX
325
326	GetStatus:
327	xor ax,ax
328	mov es,ax
329	mov bx,[StatusPtr]
330	mov ah,[bx] ; Copy last status
331	ret
332
333	ReadMult:
334	TRACER 'm'
335	Read:
336	TRACER 'R'
337	call setup_regs
338	do_copy:
339	TRACER '<'
340	call bcopy
341	TRACER '>'
342	movzx ax,P_AL ; AH = 0, AL = transfer count
343	ret
344
345	WriteMult:
346	TRACER 'M'
347	Write:
348	TRACER 'W'
349	test byte [ConfigFlags],CONFIG_READONLY
350	jnz .readonly
351	call setup_regs
352	xchg esi,edi ; Opposite direction of a Read!
353	jmp short do_copy
354	.readonly: mov ah,03h ; Write protected medium
355	ret
356
357	; Verify integrity; just bounds-check
358	Seek:
359	Verify:
360	call setup_regs ; Returns error if appropriate
361	; And fall through to success
362
363	CheckIfReady: ; These are always-successful noop functions
364	Recalibrate:
365	InitWithParms:
366	DetectChange:
367	EDDDetectChange:
368	EDDLock:
369	SetMode:
370	success:
371	xor ax,ax ; Always successful
372	ret
373
374	GetParms:
375	TRACER 'G'
376	mov dl,[DriveCnt] ; Cached data
377	mov P_DL,dl
378	test byte [DriveNo],80h
379	jnz .hd
380	mov P_DI,DPT
381	mov P_ES,cs
382	mov bl,[DriveType]
383	mov P_BL,bl
384	.hd:
385	mov ax,[Cylinders]
386	dec ax ; We report the highest #, not the count
387	xchg al,ah
388	shl al,6
389	or al,[Sectors]
390	mov P_CX,ax
391	mov ax,[Heads]
392	dec ax
393	mov P_DH,al
394
395	;
396	; Is this MEMDISK installation check?
397	;
398	cmp P_HAX,'ME'
399	jne .notic
400	cmp P_HCX,'MD'
401	jne .notic
402	cmp P_HDX,'IS'
403	jne .notic
404	cmp P_HBX,'K?'
405	jne .notic
406
407	; MEMDISK installation check...
408	mov P_HAX,'!M'
409	mov P_HCX,'EM'
410	mov P_HDX,'DI'
411	mov P_HBX,'SK'
412	mov P_ES,cs
413	mov P_DI,MemDisk_Info
414
415	.notic:
416	xor ax,ax
417	ret
418	;
419	; EDD functions -- only if enabled
420	;
421	%if EDD
422	EDDPresence:
423	TRACER 'E'
424	TRACER 'c'
425
426	cmp P_BX,55AAh
427	jne Invalid
428	mov P_BX,0AA55h ; EDD signature
429	mov P_AX,03000h ; EDD 3.0
430	mov P_CX,0007h ; Bit 0 - Fixed disk access subset
431	; Bit 1 - Locking and ejecting subset
432	; Bit 2 - EDD subset
433	pop ax ; Drop return address
434	xor ax,ax ; Success
435	jmp DoneWeird ; Success, but AH != 0, sigh...
436
437	EDDRead:
438	TRACER 'E'
439	TRACER 'r'
440
441	call edd_setup_regs
442	call bcopy
443	xor ax,ax
444	ret
445
446	EDDWrite:
447	TRACER 'E'
448	TRACER 'w'
449
450	call edd_setup_regs
451	xchg esi,edi ; Opposite direction of a Read!
452	call bcopy
453	xor ax,ax
454	ret
455
456	EDDVerify:
457	EDDSeek:
458	call edd_setup_regs ; Just bounds checking
459	xor ax,ax
460	ret
461
462	EDDGetParms:
463	TRACER 'E'
464	TRACER 'p'
465
466	mov es,P_DS
467	mov di,P_SI
468	mov si,EDD_DPT
469
470	lodsw ; Length of our DPT
471	mov cx,[es:di]
472	cmp cx,26 ; Minimum size
473	jb .overrun
474
475	cmp cx,ax
476	jb .oksize
477	mov cx,ax
478
479	.oksize:
480	mov ax,cx
481	stosw
482	dec cx
483	dec cx
484	rep movsb
485
486	xor ax,ax
487	ret
488
489	.overrun:
490	mov ax,0100h
491	ret
492	%endif ; EDD
493
494	; Set up registers as for a "Read", and compares against disk
495	; size.
496	; WARNING: This fails immediately, even if we can transfer some
497	; sectors. This isn't really the correct behaviour.
498	setup_regs:
499
500	; Convert a CHS address in P_CX/P_DH into an LBA in eax
501	; CH = cyl[7:0]
502	; CL[0:5] = sector (1-based) CL[7:6] = cyl[9:8]
503	; DH = head
504	movzx ecx,P_CX
505	movzx ebx,cl ; Sector number
506	and bl,3Fh
507	dec ebx ; Sector number is 1-based
508	cmp bx,[Sectors]
509	jae .overrun
510	movzx edi,P_DH ; Head number
511	movzx eax,word [Heads]
512	cmp di,ax
513	jae .overrun
514	shr cl,6
515	xchg cl,ch ; Now (E)CX <- cylinder number
516	mul ecx ; eax <- Heads*cyl# (edx <- 0)
517	add eax,edi
518	mul dword [Sectors]
519	add eax,ebx
520	; Now eax = LBA, edx = 0
521
522	;
523	; setup_regs continues...
524	;
525	; Note: edi[31:16] and ecx[31:16] = 0 already
526	mov di,P_BX ; Get linear address of target buffer
527	mov cx,P_ES
528	shl ecx,4
529	add edi,ecx ; EDI = address to fetch to
530	movzx ecx,P_AL ; Sector count
531	mov esi,eax
532	add eax,ecx ; LBA of final sector + 1
533	shl esi,SECTORSIZE_LG2 ; LBA -> byte offset
534	add esi,[DiskBuf] ; Get address in high memory
535	cmp eax,[DiskSize] ; Check the high mark against limit
536	ja .overrun
537	shl ecx,SECTORSIZE_LG2-2 ; Convert count to dwords
538	ret
539
540	.overrun: pop ax ; Drop setup_regs return address
541	mov ax,0200h ; Missing address mark
542	ret ; Return to Done
543
544	; Set up registers as for an EDD Read, and compares against disk size.
545	%if EDD
546	edd_setup_regs:
547	push es
548	mov si,P_SI ; DS:SI -> DAPA
549	mov es,P_DS
550
551	mov dx,[es:si]
552	cmp dx,16
553	jb .baddapa
554
555	cmp dword [es:si+4],-1
556	je .linear_address
557
558	movzx ebx,word [es:si+4] ; Offset
559	movzx edi,word [es:si+6] ; Segment
560	shl edi,4
561	add ebx,edi
562	jmp .got_address
563
564	.linear_address:
565	cmp dx,24 ; Must be large enough to hold
566	; linear address
567	jb .baddapa
568
569	cmp dword [es:si+20],0 ; > 4 GB addresses not supported
570	mov ax,0900h ; "Data boundary error" - bogus, but
571	; no really better code available
572	jne .error
573
574	mov ebx,[es:si+16]
575
576	.got_address:
577	cmp dword [es:si+12],0 ; LBA too large?
578	jne .overrun
579
580	movzx ecx, word [es:si+2] ; Sectors to transfer
581	mov esi,[es:si+8] ; Starting sector
582	mov eax,esi
583	add eax,ecx
584	jc .overrun
585	cmp eax,[DiskSize]
586	ja .overrun
587
588	shl ecx,SECTORSIZE_LG2-2 ; Convert to dwords
589	shl esi,SECTORSIZE_LG2 ; Convert to an offset
590	add esi,[DiskBuf]
591	mov edi,ebx
592	pop es
593	ret
594
595	.baddapa:
596	mov ax,0100h ; Invalid command
597	pop es
598	pop ax ; Drop setup_regs return address
599	ret
600
601	.overrun:
602	mov ax,0200h ; "Address mark not found" =
603	; LBA beyond end of disk
604	.error:
605	and word [es:si+2],0 ; No sectors transferred
606	pop es
607	pop ax
608	ret
609
610	EDDEject:
611	mov ax,0B200h ; Volume Not Removable
612	ret
613	%if ELTORITO
614	ElToritoTerminate:
615	TRACER 'T'
616	mov ax,[cs:SavedAX]
617	cmp al,1 ; We only support query, not terminate
618	jne ElToritoErr ; Fail
619	cmp dl,7fh ; Terminate all?
620	je .doit
621	cmp dl,[cs:DriveNo] ; Terminate our drive?
622	je .doit
623	jmp ElToritoErr ; Fail
624	.doit: mov es,P_DS ; Caller's DS:SI pointed to packet
625	mov di,P_SI ; We'll use ES:DI
626	mov si,CD_PKT.size ; First byte is packet size
627	xor cx,0 ; Empty our count
628	;mov cl,[ds:si] ; We'll copy that many bytes
629	mov cl,13h
630	rep movsb ; Copy until CX is zero
631	mov ax,0 ; Success
632	ret
633	ElToritoEmulate:
634	ElToritoBoot:
635	ElToritoCatalog:
636	ElToritoErr:
637	TRACER '!'
638	mov ax,100h ; Invalid parameter
639	ret
640	%endif ; ELTORITO
641	%endif ; EDD
642
643	;
644	; INT 15h intercept routines
645	;
646	int15_e820:
647	cmp edx,534D4150h ; "SMAP"
648	jne oldint15
649	cmp ecx,20 ; Need 20 bytes
650	jb err86
651	push ds
652	push cs
653	pop ds
654	push edx ; "SMAP"
655	and ebx,ebx
656	jne .renew
657	mov ebx,E820Table
658	.renew:
659	add bx,12 ; Advance to next
660	mov eax,[bx-4] ; Type
661	and eax,eax ; Null type?
662	jz .renew ; If so advance to next
663	mov [es:di+16],eax
664	mov eax,[bx-12] ; Start addr (low)
665	mov edx,[bx-8] ; Start addr (high)
666	mov [es:di],eax
667	mov [es:di+4],edx
668	mov eax,[bx] ; End addr (low)
669	mov edx,[bx+4] ; End addr (high)
670	sub eax,[bx-12] ; Derive the length
671	sbb edx,[bx-8]
672	mov [es:di+8],eax ; Length (low)
673	mov [es:di+12],edx ; Length (high)
674	cmp dword [bx+8],-1 ; Type of next = end?
675	jne .notdone
676	xor ebx,ebx ; Done with table
677	.notdone:
678	pop eax ; "SMAP"
679	mov edx,eax ; Some systems expect eax = edx = SMAP
680	mov ecx,20 ; Bytes loaded
681	pop ds
682	int15_success:
683	mov byte [bp+6], 02h ; Clear CF
684	pop bp
685	iret
686
687	err86:
688	mov byte [bp+6], 03h ; Set CF
689	mov ah,86h
690	pop bp
691	iret
692
693	Int15Start:
694	push bp
695	mov bp,sp
696	cmp ax,0E820h
697	je near int15_e820
698	cmp ax,0E801h
699	je int15_e801
700	cmp ax,0E881h
701	je int15_e881
702	cmp ah,88h
703	je int15_88
704	oldint15: pop bp
705	jmp far [cs:OldInt15]
706
707	int15_e801: ; Get mem size for > 64 MB config
708	mov ax,[cs:Mem1MB]
709	mov cx,ax
710	mov bx,[cs:Mem16MB]
711	mov dx,bx
712	jmp short int15_success
713
714	int15_e881: ; Get mem size for > 64 MB config
715	; 32-bit code
716	mov eax,[cs:Mem1MB]
717	mov ecx,eax
718	mov ebx,[cs:Mem16MB]
719	mov edx,ebx
720	jmp short int15_success
721
722	int15_88: ; Get extended mem size
723	mov ax,[cs:MemInt1588]
724	jmp short int15_success
725
726	;
727	; Routine to copy in/out of high memory
728	; esi = linear source address
729	; edi = linear target address
730	; ecx = 32-bit word count
731	;
732	; Assumes cs = ds = es
733	;
734	bcopy:
735	push eax
736	push ebx
737	push edx
738	push ebp
739
740	mov bx, real_int15_stub
741
742	test byte [ConfigFlags], CONFIG_RAW\|CONFIG_SAFEINT
743	jz .anymode ; Always do the real INT 15h
744
745	smsw ax ; Unprivileged!
746	test al,01h
747	jnz .protmode ; Protmode -> do real INT 15h
748
749	.realmode:
750	; Raw or Safeint mode, and we're in real mode...
751
752	test byte [ConfigFlags], CONFIG_SAFEINT
753	jnz .fakeint15
754
755	.raw:
756	TRACER 'r'
757	; We're in real mode, do it outselves
758
759	pushfd ; <A>
760	push ds ; <B>
761	push es ; <C>
762
763	cli
764	cld
765
766	xor ebx,ebx
767	mov bx,cs
768	shl ebx,4
769	lea edx,[Shaker+ebx]
770	mov [Shaker+2],edx
771
772	; Test to see if A20 is enabled or not
773	xor ax,ax
774	mov ds,ax
775	dec ax
776	mov es,ax
777
778	mov ax,[0]
779	mov bx,ax
780	xor bx,[es:10h]
781	not ax
782	mov [0],ax
783	mov dx,ax
784	xor dx,[es:10h]
785	not ax
786	mov [0],ax
787
788	or dx,bx
789	push dx ; <D> Save A20 status
790	jnz .skip_a20e
791
792	mov ax,2401h ; Enable A20
793	int 15h
794	.skip_a20e:
795	mov dl,[ConfigFlags]
796	and dx,CONFIG_BIGRAW
797	add dx,8
798	; DX = 16 for BIGRAW, 8 for RAW
799	; 8 is selector for a 64K flat segment,
800	; 16 is selector for a 4GB flat segment.
801
802	lgdt [cs:Shaker]
803	mov eax,cr0
804	or al,01h
805	mov cr0,eax
806
807	mov bx,16 ; Large flat segment
808	mov ds,bx
809	mov es,bx
810
811	a32 rep movsd
812
813	; DX has the appropriate value to put in
814	; the registers on return
815	mov ds,dx
816	mov es,dx
817
818	and al,~01h
819	mov cr0,eax
820
821	pop dx ; <D> A20 status
822	pop es ; <C>
823	pop ds ; <B>
824
825	and dx,dx
826	jnz .skip_a20d
827	mov ax,2400h ; Disable A20
828	int 15h
829	.skip_a20d:
830	popfd ; <A>
831	jmp .done
832
833	.fakeint15:
834	; We're in real mode with CONFIG_SAFEINT, invoke the
835	; original INT 15h vector. We used to test for the
836	; INT 15h vector being unchanged here, but that is
837	; us; however, the test was wrong for years (always
838	; negative) so instead of fixing the test do what we
839	; tested and don't bother probing.
840	mov bx, fake_int15_stub
841
842	.protmode:
843	TRACER 'p'
844	.anymode:
845
846	.copy_loop:
847	push esi
848	push edi
849	push ecx
850	cmp ecx,4000h
851	jna .safe_size
852	mov ecx,4000h
853	.safe_size:
854	push ecx ; Transfer size this cycle
855	mov eax, esi
856	mov [Mover_src1], si
857	shr eax, 16
858	mov [Mover_src1+2], al
859	mov [Mover_src2], ah
860	mov eax, edi
861	mov [Mover_dst1], di
862	shr eax, 16
863	mov [Mover_dst1+2], al
864	mov [Mover_dst2], ah
865	mov si,Mover
866	mov ah, 87h
867	shl cx,1 ; Convert to 16-bit words
868	call bx ; INT 15h stub
869	pop eax ; Transfer size this cycle
870	pop ecx
871	pop edi
872	pop esi
873	jc .error
874	lea esi,[esi+4*eax]
875	lea edi,[edi+4*eax]
876	sub ecx, eax
877	jnz .copy_loop
878	; CF = 0
879	.error:
880	.done:
881	pop ebp
882	pop edx
883	pop ebx
884	pop eax
885	ret
886
887	real_int15_stub:
888	int 15h
889	cli ; Some BIOSes enable interrupts on INT 15h
890	ret
891
892	fake_int15_stub:
893	pushf
894	call far [OldInt15]
895	cli
896	ret
897
898	%ifdef DEBUG_TRACERS
899	debug_tracer: pushad
900	pushfd
901	mov bp,sp
902	mov bx,[bp+9*4]
903	mov al,[cs:bx]
904	inc word [bp+9*4]
905	mov ah,0Eh
906	mov bx,7
907	int 10h
908	popfd
909	popad
910	ret
911
912	writehex2: pushad
913	pushfd
914	mov cx,2
915	ror eax,4
916	jmp writehex_common
917	writehex4: pushad
918	pushfd
919	mov cx,4
920	ror eax,12
921	jmp writehex_common
922	writehex8: pushad
923	pushfd
924	mov cx,8
925	ror eax,28
926	writehex_common:
927	.loop: push cx
928	push eax
929	and al,0Fh
930	cmp al,10
931	jb .isdec
932	add al,'a'-'0'-10
933	.isdec: add al,'0'
934	mov ah,0Eh
935	mov bx,7
936	int 10h
937	pop eax
938	rol eax,4
939	pop cx
940	loop .loop
941	popfd
942	popad
943	ret
944	%endif
945
946	section .data align=16
947	alignb 2
948	Int13Funcs dw Reset ; 00h - RESET
949	dw GetStatus ; 01h - GET STATUS
950	dw Read ; 02h - READ
951	dw Write ; 03h - WRITE
952	dw Verify ; 04h - VERIFY
953	dw Invalid ; 05h - FORMAT TRACK
954	dw Invalid ; 06h - FORMAT TRACK AND SET BAD FLAGS
955	dw Invalid ; 07h - FORMAT DRIVE AT TRACK
956	dw GetParms ; 08h - GET PARAMETERS
957	dw InitWithParms ; 09h - INITIALIZE CONTROLLER WITH
958	; DRIVE PARAMETERS
959	dw Invalid ; 0Ah
960	dw Invalid ; 0Bh
961	dw Seek ; 0Ch - SEEK TO CYLINDER
962	dw Reset ; 0Dh - RESET HARD DISKS
963	dw Invalid ; 0Eh
964	dw Invalid ; 0Fh
965	dw CheckIfReady ; 10h - CHECK IF READY
966	dw Recalibrate ; 11h - RECALIBRATE
967	dw Invalid ; 12h
968	dw Invalid ; 13h
969	dw Invalid ; 14h
970	dw GetDriveType ; 15h - GET DRIVE TYPE
971	dw DetectChange ; 16h - DETECT DRIVE CHANGE
972	%if EDD
973	dw Invalid ; 17h
974	dw Invalid ; 18h
975	dw Invalid ; 19h
976	dw Invalid ; 1Ah
977	dw Invalid ; 1Bh
978	dw Invalid ; 1Ch
979	dw Invalid ; 1Dh
980	dw Invalid ; 1Eh
981	dw Invalid ; 1Fh
982	dw Invalid ; 20h
983	dw ReadMult ; 21h - READ MULTIPLE
984	dw WriteMult ; 22h - WRITE MULTIPLE
985	dw SetMode ; 23h - SET CONTROLLER FEATURES
986	dw SetMode ; 24h - SET MULTIPLE MODE
987	dw Invalid ; 25h - IDENTIFY DRIVE
988	dw Invalid ; 26h
989	dw Invalid ; 27h
990	dw Invalid ; 28h
991	dw Invalid ; 29h
992	dw Invalid ; 2Ah
993	dw Invalid ; 2Bh
994	dw Invalid ; 2Ch
995	dw Invalid ; 2Dh
996	dw Invalid ; 2Eh
997	dw Invalid ; 2Fh
998	dw Invalid ; 30h
999	dw Invalid ; 31h
1000	dw Invalid ; 32h
1001	dw Invalid ; 33h
1002	dw Invalid ; 34h
1003	dw Invalid ; 35h
1004	dw Invalid ; 36h
1005	dw Invalid ; 37h
1006	dw Invalid ; 38h
1007	dw Invalid ; 39h
1008	dw Invalid ; 3Ah
1009	dw Invalid ; 3Bh
1010	dw Invalid ; 3Ch
1011	dw Invalid ; 3Dh
1012	dw Invalid ; 3Eh
1013	dw Invalid ; 3Fh
1014	dw Invalid ; 40h
1015	dw EDDPresence ; 41h - EDD PRESENCE DETECT
1016	dw EDDRead ; 42h - EDD READ
1017	dw EDDWrite ; 43h - EDD WRITE
1018	dw EDDVerify ; 44h - EDD VERIFY
1019	dw EDDLock ; 45h - EDD LOCK/UNLOCK MEDIA
1020	dw EDDEject ; 46h - EDD EJECT
1021	dw EDDSeek ; 47h - EDD SEEK
1022	dw EDDGetParms ; 48h - EDD GET PARAMETERS
1023	dw EDDDetectChange ; 49h - EDD MEDIA CHANGE STATUS
1024	%if ELTORITO ; EDD El Torito Functions
1025	; ELTORITO _must_ also have EDD
1026	dw ElToritoEmulate ; 4Ah - Initiate Disk Emulation
1027	dw ElToritoTerminate ; 4Bh - Terminate Disk Emulation
1028	dw ElToritoBoot ; 4Ch - Initiate Disk Emu. and Reboot
1029	dw ElToritoCatalog ; 4Dh - Return Boot Catalog
1030	%endif ; ELTORITO
1031	%endif ; EDD
1032
1033	Int13FuncsEnd equ $
1034	Int13FuncsCnt equ (Int13FuncsEnd-Int13Funcs) >> 1
1035
1036
1037	alignb 8, db 0
1038	Shaker dw ShakerEnd-$-1 ; Descriptor table limit
1039	dd 0 ; Pointer to self
1040	dw 0
1041
1042	Shaker_RMDS: dd 0x0000ffff ; 64K data segment
1043	dd 0x00009300
1044
1045	Shaker_DS: dd 0x0000ffff ; 4GB data segment
1046	dd 0x008f9300
1047
1048	ShakerEnd equ $
1049
1050	alignb 8, db 0
1051
1052	Mover dd 0, 0, 0, 0 ; Must be zero
1053	dw 0ffffh ; 64 K segment size
1054	Mover_src1: db 0, 0, 0 ; Low 24 bits of source addy
1055	db 93h ; Access rights
1056	db 00h ; Extended access rights
1057	Mover_src2: db 0 ; High 8 bits of source addy
1058	dw 0ffffh ; 64 K segment size
1059	Mover_dst1: db 0, 0, 0 ; Low 24 bits of target addy
1060	db 93h ; Access rights
1061	db 00h ; Extended access rights
1062	Mover_dst2: db 0 ; High 8 bits of source addy
1063	Mover_dummy2: dd 0, 0, 0, 0 ; More space for the BIOS
1064
1065	alignb 16, db 0
1066	mBFT:
1067	; Fields common to all ACPI tables
1068	dd ' ' ; ACPI signature ("mBFT")
1069	; This is filled-in by the installer
1070	; to avoid an accidentally valid mBFT
1071	dd mBFT_Len ; ACPI table length
1072	db 1 ; ACPI revision
1073	db 0 ; ACPI table checksum
1074	db 'MEMDSK' ; ACPI OEM ID
1075	db 'Syslinux' ; ACPI OEM table ID
1076	dd 0 ; ACPI OEM revision
1077	dd 0 ; ACPI ASL compiler vendor ID
1078	dd 0 ; ACPI ASL compiler revision
1079	; The next field is mBFT-specific and filled-in by the installer
1080	dd 0 ; "Safe hook" physical address
1081
1082	; Note that the above ends on a DWORD boundary.
1083	; The MDI has always started at such a boundary.
1084	; Portions of the MDI are patched by the installer
1085	MemDisk_Info equ $ ; Pointed to by installation check
1086	MDI_Bytes dw MDI_Len ; Total bytes in MDI structure
1087	MDI_Version db VERSION_MINOR, VERSION_MAJOR ; MEMDISK version
1088
1089	DiskBuf dd 0 ; Linear address of high memory disk
1090	DiskSize dd 0 ; Size of disk in blocks
1091	CommandLine dw 0, 0 ; Far pointer to saved command line
1092
1093	OldInt13 dd 0 ; INT 13h in chain
1094	OldInt15 dd 0 ; INT 15h in chain
1095
1096	OldDosMem dw 0 ; Old position of DOS mem end
1097	BootLoaderID db 0 ; Boot loader ID from header
1098	db 0 ; pad
1099
1100	DPT_ptr dw 0 ; If nonzero, pointer to DPT
1101	; Original DPT pointer follows
1102
1103	MDI_Len equ $-MemDisk_Info
1104	mBFT_Len equ $-mBFT ; mBFT includes the MDI
1105
1106	; ---- MDI structure ends here ---
1107	DriveShiftLimit db 0ffh ; Installer will probe for
1108	; a range of contiguous drives.
1109	; Any BIOS drives above this region
1110	; shall not be impacted by our
1111	; shifting behaviour
1112	db 0 ; pad to a DWORD
1113	dw 0 ; pad to a QWORD
1114	MemInt1588 dw 0 ; 1MB-65MB memory amount (1K)
1115
1116	Cylinders dw 0 ; Cylinder count
1117	Heads dw 0 ; Head count
1118	Sectors dd 0 ; Sector count (zero-extended)
1119
1120	Mem1MB dd 0 ; 1MB-16MB memory amount (1K)
1121	Mem16MB dd 0 ; 16MB-4G memory amount (64K)
1122
1123	DriveNo db 0 ; Our drive number
1124	DriveType db 0 ; Our drive type (floppies)
1125	DriveCnt db 0 ; Drive count (from the BIOS)
1126
1127	ConfigFlags db 0 ; Bit 0 - readonly
1128
1129	MyStack dw 0 ; Offset of stack
1130	StatusPtr dw 0 ; Where to save status (zeroseg ptr)
1131
1132	DPT times 16 db 0 ; BIOS parameter table pointer (floppies)
1133	OldInt1E dd 0 ; Previous INT 1E pointer (DPT)
1134
1135	%if EDD
1136	EDD_DPT:
1137	.length dw 30
1138	.info dw 0029h
1139	; Bit 0 - DMA boundaries handled transparently
1140	; Bit 3 - Device supports write verify
1141	; Bit 5 - Media is lockable
1142	.cylinders dd 0 ; Filled in by installer
1143	.heads dd 0 ; Filled in by installer
1144	.sectors dd 0 ; Filled in by installer
1145	.totalsize dd 0, 0 ; Filled in by installer
1146	.bytespersec dw SECTORSIZE
1147	.eddtable dw -1, -1 ; Invalid DPTE pointer
1148	.dpikey dw 0BEDDh ; Device Path Info magic
1149	.dpilen db 2ch ; DPI len
1150	.res1 db 0 ; Reserved
1151	.res2 dw 0 ; Reserved
1152	.bustype dd 'MEM ' ; Host bus type (4 bytes, space padded)
1153	.inttype dd 'MEMORY ' ; Interface type (8 bytes, spc. padded)
1154	.intpath dd 0, 0 ; Interface path
1155	.devpath dd 0, 0, 0, 0 ; Device path
1156	.res3 db 0 ; Reserved
1157	.chksum db 0 ; DPI checksum
1158
1159	%if ELTORITO
1160	; El Torito CD Specification Packet - mostly filled in by installer
1161	CD_PKT:
1162	.size db 13h ; Packet size (19 bytes)
1163	.type db 0 ; Boot media type (flags)
1164	.driveno db 0E0h ; INT 13h drive number
1165	.controller db 0 ; Controller index
1166	.start dd 0 ; Starting LBA of image
1167	.devno dw 0 ; Device number
1168	.user_buf dw 0 ; User buffer segment
1169	.load_seg dw 0 ; Load segment
1170	.sect_count dw 0 ; Emulated sectors to load
1171	.geom1 db 0 ; Cylinders bits 0 thru 7
1172	.geom2 db 0 ; Sects/track 0 thru 5, cyls 8, 9
1173	.geom3 db 0 ; Heads
1174	%endif ; ELTORITO
1175
1176	%endif ; EDD
1177
1178	; End patch area
1179
1180	alignb 4, db 0
1181	Stack dd 0 ; Saved SS:ESP on invocation
1182	dw 0
1183	SavedAX dw 0 ; AX saved on invocation
1184	Recursive dw 0 ; Recursion counter
1185
1186	alignb 4, db 0 ; We MUST end on a dword boundary
1187
1188	E820Table equ $ ; The installer loads the E820 table here
1189	TotalSize equ $ ; End pointer

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