;  mapper.S  -  LILO chain loader subroutine;; Copyright 2003-2004 John Coffman.; All rights reserved.;; Licensed under the terms contained in the file 'COPYING' in the ; source directory.;; Check for presence of existing drive mapper;;	Enter with  DS == CS,  SS == 0000	  (chain loader);	Enter with  DS == CS == ES,  SS != 0000   (second stage);;	If a previous drive mapper exists, ES:DI points at the  drvmap;		and ZF=0	(DI != 0);;	If no recognizable drive map exists, DI == 0  and  ZF==1;		ES is indeterminate;;;is_prev_mapper:	push	cx	push	si#ifndef CHAIN_LOADER	push	#0	pop	es	seg es#else	seg ss#endif	  les	di,[4*0x13]	; vector to int 0x13	or	di,di	jnz	is_p_no_mapper	; our mappers start at offset 0	mov	di,es	cmp	di,#0xA000	; start of system reserved locations	jae	is_p_no_mapper	cmp	di,#0x0060	; VERY conservative	jb	is_p_no_mapper; first test for new mapper	xor	di,di	mov	cx,#new13_length	mov	si,#new13	repe	  cmpsb	jne	is_p_try_old; found new (v.22) mapper	seg es	  mov	di,[new13_drvmap_offset]#if defined CHAIN_LOADER && defined DEBUG_NEW	mov	si,#msg_new	call	say#endif	jmp	is_prev_retis_p_try_old:	xor	di,di	mov	cx,#new13_old_length	mov	si,#new13_old	repe	  cmpsb	jne	is_p_no_mapper; likely old (<=v.21) mapper	seg es	  mov	di,(di)		cmp	di,#new13_old_min_offs	; validate the range of values	jb	is_p_no_mapper	cmp	di,#new13_old_max_offs	; validate the range of values#if defined CHAIN_LOADER && defined DEBUG_NEW	ja	is_p_no_mapper	mov	si,#msg_old	call	say	jmp	is_prev_ret#else	jbe	is_prev_ret#endifis_p_no_mapper:	xor	di,di		; set DI = 0, ZF=1is_prev_ret:	or	di,di		; set ZF by DI	pop	si	pop	cx	ret/* LILO version 21 (and maybe earlier) drive map header signature code */new13_old:	push	ax		! save AX (contains function code in AH)	push	bp		! need BP to mess with stack	mov	bp,sp	pushf			! push flags (to act like interrupt)	push	si	mov	si,#drvmap-new13new13_old_drvmap_offs	=	* - new13_old - 2new13_old_length	=	new13_old_drvmap_offsnew13_old_min_offs	=	0x46	; min seen in old code is 0x49new13_old_max_offs	=	0x50	; maxed out at  21.7.5 at 0x4d	.even			! this is very importantnew13:	push	ax		! save AX (contains function code in AH)	push	bp		! need BP to mess with stack	mov	bp,sp	jmp	new13a		! make space for signature	.org	new13+6	.ascii	"LILO"	.word	STAGE_DRIVE_MAPnew13_length		=	*-new13		; max compare length	.word	VERSIONnew13_drvmap_offset	=	* - new13	.word	drvmap-new13	! relative pointer to drive mapnew13a:#ifdef CHAIN_LOADER	! Stack layout:	!	!   +8	INT flags	!   +6	INT CS	!   +4	INT IP	!   +2	AX	! BP+0 BP	pushf			! push flags (to act like interrupt)	push	si	mov	si,#drvmap-new13mapfl:	seg	cs		! get next entry	 mov	ax,(si) 	! do not depend on DIRECTION flag	lea	si,(si+2)	! **	or	ax,ax		! at end ?	jz	nomap		! yes -> do not map	cmp	dl,al		! match ?	jne	mapfl		! no -> continue	mov	dl,ah		! map drivenomap:	pop	si		! restore SI	mov	8(bp),ax	! overwrite old flags (to remember mapping)	mov	ax,2(bp)	! restore AX	mov	bp,(bp)		! restore BPold13of	=	*+1old13sg	=	*+3	callf	0,0	push	bp		! save BP again	mov	bp,sp	! New stack layout:	!	!   +10	mapping (was flags)	!   +8	INT CS	!   +6	INT IP	!   +4	AX	!   +2  obsolete BP	! BP+0  BP	xchg	ax,4(bp)	! save AX and get command	pushf			! fix driver number, if necessary	cmp	ah,#8 ! do not fix	je	done13	cmp	ah,#0x15 ! do not fix	je	done13	mov	ax,10(bp)	! no mapping ?	or	ax,ax	jz	done13	mov	dl,al		! fix mappingdone13:	mov	ax,4(bp)	! restore AX	pop	10(bp)		! restore flags	pop	bp		! get BP	add	sp,#4		! fix SP	iret			! done		.evendrvmap:	.blkw	DRVMAP_SIZE+1new13end:#endif#ifdef SECOND_STAGE_LOADERdrvmap:#endif/* end of mapper.S  */