PCP/M-86 loader for Apricot

bootcpm.com.asm

; nasm bootcpm.com.asm -fbin -o bootcpm.com
; runs from dos to load the bootloader from drive 0

CPU 8086
USE16

disklabeloff	equ	0x040a
disklabelseg	equ	0x040c
bootfrom	equ	0x0408
boot_locn	equ	0x1a
boot_size	equ	0x1e

section .text		start=0x100
	xor	ax, ax
	mov	es, ax		; bios data
	mov	word es:[bootfrom], 0
	mov	ax, ds
	mov	[bufseg], ax
	mov	es:[disklabelseg], ax
	mov	si, disklabel
	mov	es:[disklabeloff], si
	mov	[bufoff], si
	mov	word [sector], 0
	mov	word [sec_n], 1
	call	diskio

	mov	ax, disklabel
	shr	ax, 1
	shr	ax, 1
	shr	ax, 1
	shr	ax, 1
	mov	bx, ds
	add 	ax, bx
	mov	es, ax

	mov	si, loader
	mov	[bufoff], si
	mov	ax, word es:boot_locn
	mov	word [sector], ax
	mov	ax, es:boot_size
	mov	word [sec_n], ax
	call	diskio

	mov	ax, loader
	shr	ax, 1
	shr	ax, 1
	shr	ax, 1
	shr	ax, 1
	mov	bx, ds
	add 	ax, bx
	add 	ax, 8
	push	ax
	mov	es, ax

	; live-patching LOADER.SYS with new CPM3.SYS location
	mov 	ax, cpm3
	shr	ax, 1
	shr	ax, 1
	shr	ax, 1
	shr	ax, 1
	mov	bx, ds
	add 	ax, bx
	mov	es:[0xc8], ax
	mov	es:[0xec], ax
	mov	es:[0xef], ax
	add	ax, 0x8
	mov	es:[0x121], ax
	mov	es:[0x267], ax

	xor	ax, ax
	push	ax
	retf

diskio:
	push	bx
	push	cx
	mov	bx, 0x39
	mov	cx, 0x0b
	mov	dx, ds
	mov	si, diskio_s
	int	0xfc
	pop	cx
	pop	bx
	or	ax, ax
	ret

diskio_s:
drvn:	dw	0
op:	dw	0
sector:	dw	0
sec_n:	dw	0
bufoff: dw	0
bufseg:	dw	0

section .data align=0x10
disklabel:
loader	equ	disklabel + 0x200
cpm3	equ	loader + 0x600

loader.sys.asm

;
; ╔═════════════════════════════════════════════════════════════════════════╗
; ║	This file is generated by The Interactive Disassembler (IDA)	    ║
; ║	Copyright (c) 2000 by DataRescue sa/nv,	<ida@datarescue.com>	    ║
; ╚═════════════════════════════════════════════════════════════════════════╝
;
; LOADER.SYS from http://actapricot.org/disks/aprid5ks.htm#apr00301.dsk


; ═══════════════════════════════════════════════════════════════════════════

; Segment type:	Regular
interrupt	segment	byte private ''
		assume cs:interrupt
		assume es:nothing, ss:nothing, ds:nothing
		db 380h	dup(?)
intE0off	dw ?			;DATA XREF: _cpmentry+D↓w
					; _cpmentry+87↓w ...
intE0seg	dw ?			;DATA XREF: _cpmentry+13↓w
					; _cpmentry+8D↓w
		db 6Ch dup(?)
BIOSCtlDevInt	dw ?			;DATA XREF: cpmcode:61BE↓r
					; cpmcode:61F3↓r ...
		dw ?
		dd ?
ExecInt		dd ?			;DATA XREF: cpmcode:2BA0↓r
		dd ?
interrupt	ends

; ═══════════════════════════════════════════════════════════════════════════

; Segment type:	Regular
bios		segment	byte private ''
		assume cs:bios
		;org 400h
		assume es:nothing, ss:nothing, ds:nothing
		db 7
		public machinetype
machinetype	db 0			;DATA XREF: sub_158CE+2D↓r _entry+E↓r
		public ramsize
ramsize		dw 4000h		;DATA XREF: _entry+13↓r
		dd 56781234h
		public bootfrom
bootfrom	dw 0			;DATA XREF: read_disk+D↓r
		public disklabelptr
disklabelptr	dw 0B0h			;DATA XREF: _entry+1C↓r _entry+7D↓r ...
		dw 3E00h
		dd 0
		db 0
		db 0
		db 0
		db 0
		public n_flphdd
n_flphdd	dw 0			;DATA XREF: _entry+12F↓r _entry+14C↓r ...
floppybpbptr	dd 0
		dd 0
		dw 7FFFh
		public usercodearea
usercodearea	dw 0			;DATA XREF: _entry+1CC↓r _entry+216↓r
		dd 0
		db 0D8h	dup(0)
		dq 0FD100F040003h
		dq 0
		db 0F0h	dup(0)
db 0F9h	dup(0)
		dd 0
		dw 0
afontptroff	dw 0			;DATA XREF: _entry+5E↓w
afontptrseg	dw 0			;DATA XREF: _entry+69↓w
		dw 0
mfontptroff	dw 0			;DATA XREF: _entry+62↓w
mfontptrseg	dw 0			;DATA XREF: _entry+6D↓w
		dw 0
keytabptroff	dw 0			;DATA XREF: _entry+A6↓w
keytabptrseg	dw 0			;DATA XREF: _entry+AA↓w
		dw 0
		dd 0
		dw 0
		dd 0
		dd 0
		dd 0
		dd 0
		dd 0
		db 0CEh	dup(0)
bios		ends

; File Name   :	CPM3.SYS
; 
; included for the reference
; ═══════════════════════════════════════════════════════════════════════════

; Segment type:	Pure code
cpmhead		segment	byte private 'C86CMDHEAD'
		assume cs:cpmhead
		assume es:nothing, ss:nothing, ds:nothing
cpmcodesize	dw 88Ch			;DATA XREF: _entry+F3↓r
		dw seg cpmcode
		dw 88Ch
		dw 0
cpmdatasize	dw 65Ch			;DATA XREF: _entry+F7↓r
		dw seg cpmdata
		dw 723h
		dw 0
		db 6Eh dup(0)
cpmhead		ends

; ═══════════════════════════════════════════════════════════════════════════

; Segment type:	Pure code
cpmcode		segment	page private 'CODE'
		assume cs:cpmcode
		assume es:nothing, ss:nothing, ds:nothing

; ███████████████ S U B	R O U T	I N E ███████████████████████████████████████


_cpmentry	proc far
		jmp	loc_F088
; ───────────────────────────────────────────────────────────────────────────
		jmp	near ptr intE0
; ───────────────────────────────────────────────────────────────────────────
cpmdataseg	dw seg cpmdata		;DATA XREF: _cpmentry+17↓r intE0+1↓r ...
; ───────────────────────────────────────────────────────────────────────────

loc_F088:				;CODE XREF: _cpmentry↑j
		cli
		xor	ax, ax
		mov	ds, ax
		assume ds:bios
		mov	intE0off, offset intE0
		mov	intE0seg, cs
		mov	bx, cs:cpmdataseg
		mov	ds, bx
		assume ds:cpmdata
		mov	ax, stackseg
		mov	cl, 4
		shr	ax, cl
		add	ax, bx
		mov	stackseg, ax
		mov	word_17990, ax
		mov	word_1798A, ax
		mov	ss, ax
		mov	sp, 160h

loc_F0B5:				;CODE XREF: _cpmentry+53↓j
		mov	es, ax
		mov	word ptr es:70h, offset	word_F225
		mov	es:72h,	cs
		mov	ax, es:2
		test	ax, ax
		jz	loc_F0D5
		shr	ax, cl
		add	ax, bx
		mov	es:2, ax
		jmp	short loc_F0B5
; ───────────────────────────────────────────────────────────────────────────

loc_F0D5:				;CODE XREF: _cpmentry+49↑j
		mov	es, stackseg
		mov	es:54h,	cs
		cld
		push	dx
		mov	cx, 7
		mov	bx, 2

loc_F0E6:				;CODE XREF: _cpmentry+6F↓j
		push	bx
		push	cx
		call	word ptr [bx]
		pop	cx
		pop	bx
		add	bx, 4
		loop	loc_F0E6
		pop	dx
		call	dword ptr word_1796C
		sti
		mov	al, byte_179D2
		mov	es:36h,	al
		mov	byte_17AF6, al
		push	es
		xor	si, si
		push	ds
		mov	ds, si
		assume ds:bios
		mov	intE0off, offset intE0
		mov	intE0seg, cs
		mov	di, 56h	; 'V'
		mov	cx, 4
		repe movsw
		mov	cl, 4
		add	si, cx
		repe movsw
		mov	si, 380h
		mov	cl, 4
		repe movsw
		pop	es
		pop	ds
		assume ds:nothing
		mov	di, 2B9h
		mov	si, 56h	; 'V'
		mov	cl, 0Ch
		repe movsw
		xor	cx, cx
		mov	dx, cx
		int	0E0h		; ; CP/M interupt?
		retn
_cpmentry	endp

; ───────────────────────────────────────────────────────────────────────────
word_F225	dw 0E9CBh		;DATA XREF: _cpmentry+37↑o

; ───────────────────────────────────────────────────────────────────────────
cpmcode		ends

; ═══════════════════════════════════════════════════════════════════════════

; Segment type:	Pure data
cpmdata		segment	byte private 'DATA'
		assume cs:cpmdata
word_1796C	dw 0			;DATA XREF: _cpmentry+72↑r
off_17978	dd loc_FF31		;DATA XREF: cpmcode:62B2↑r
off_1797C	dd sub_1078B		;DATA XREF: cpmcode:6278↑r
word_1798A	dw 8A0h			;DATA XREF: _cpmentry+2D↑w
stackseg	dw 8A0h			;DATA XREF: _cpmentry+1E↑r
					; _cpmentry+27↑w ...
word_17990	dw 0			;DATA XREF: _cpmentry+2A↑w
word_17998	dw 10h			;DATA XREF: _entry+231↓r _entry+234↓w ...
word_1799A	dw 1000h		;DATA XREF: _entry+22B↓r
byte_179D2	db 0			;DATA XREF: _cpmentry+77↑r
byte_17AF6	db 0			;DATA XREF: _cpmentry+7E↑w
word_17C10	dw 0			;DATA XREF: read_disk+1F↓w
word_18888	dw 11F2h		;DATA XREF: cpmcode:6270↑r
byte_18B9A	db 0			;DATA XREF: cpmcode:6284↑w
cpmdata		ends

; File Name   :	LOADER.SYS
; Format      :	Binary File
; Base Address:	3E00h Range: 3E000h - 3E580h Loaded length: 0580h
; ═══════════════════════════════════════════════════════════════════════════

; Segment type:	Regular
head		segment	byte public 'C86CMDHEAD'
		assume cs:head
		assume es:nothing, ss:nothing, ds:nothing
		db 1
		dw 3Eh
		dw 0			; relocatable
		dw 3Eh
		dw 0
		db 2
		dw 10h
		dw 0			; relocatable
		dw 10h
		dw 0
		db 6Eh dup(0)
head		ends

; ═══════════════════════════════════════════════════════════════════════════

; Segment type:	Regular
code		segment	page public ''
		assume cs:code
		assume es:nothing, ss:nothing, ds:nothing

; ███████████████ S U B	R O U T	I N E ███████████████████████████████████████

; Attributes: noreturn static

		public _entry
_entry		proc far
		mov	ax, cs
		mov	ds, ax
		assume ds:stack
		mov	ss, ax
		assume ss:stack
		mov	sp, offset stacktop
		mov	ax, 0
		mov	es, ax
		assume es:bios
		mov	dl, es:machinetype
		mov	bx, es:ramsize
		mov	temp, bx
		les	di, dword ptr es:disklabelptr
		assume es:nothing
		mov	ax, es:[di+disklabel.CNF_FONT_sec]
		or	ax, ax
		jz	loadkeys
		mov	sector,	ax
		cmp	dl, 0		; if machine type is Xi
		jz	xifont
		add	sector,	10h
		mov	sec_n, 9
		sub	bx, 120h
		mov	bufseg,	bx
		jmp	short loadfont
; ───────────────────────────────────────────────────────────────────────────

xifont:					;CODE XREF: _entry+30↑j
		mov	bufseg,	80h
		mov	sec_n, 10h

loadfont:				;CODE XREF: _entry+45↑j
		call	read_disk
		or	ax, ax
		jnz	loadkeys
		xor	ax, ax
		mov	es, ax
		assume es:bios
		mov	es:afontptroff,	ax
		mov	es:mfontptroff,	ax
		mov	ax, bufseg
		mov	es:afontptrseg,	ax
		mov	es:mfontptrseg,	ax
		mov	temp, bx

loadkeys:				;CODE XREF: _entry+28↑j _entry+58↑j
		xor	ax, ax
		mov	es, ax
		mov	bx, temp
		les	di, dword ptr es:disklabelptr
		assume es:nothing
		mov	ax, es:[di+disklabel.CNF_KEYS_sec]
		or	ax, ax
		jz	loadcpmhead
		mov	sector,	ax
		mov	sec_n, 2
		sub	bx, 40h		; 2 sectors from the end of RAM
		mov	bufseg,	bx
		call	read_disk
		or	ax, ax
		jnz	loadcpmhead
		xor	ax, ax
		mov	es, ax
		assume es:bios
		mov	es:keytabptroff, ax
		mov	es:keytabptrseg, bx
		mov	temp, bx

loadcpmhead:				;CODE XREF: _entry+89↑j _entry+A0↑j
		xor	ax, ax
		mov	es, ax
		les	di, dword ptr es:disklabelptr
		mov	ax, es:[di+disklabel.CNF_DOS_sec]
		mov	sector,	ax
		mov	bufseg,	seg cpmhead
		mov	sec_n, 1
		call	read_disk
		or	ax, ax
		jz	$+2
		xor	ax, ax
		mov	es, ax
		les	di, dword ptr es:disklabelptr
		assume es:cpmhead
		mov	ax, es:[di+8Ah]
		mov	sector,	ax
		mov	bufseg,	seg cpmhead
		mov	ax, seg	cpmhead
		mov	es, ax
		mov	ax, es:cpmcodesize
		add	ax, es:cpmdatasize
		shr	ax, 1
		shr	ax, 1
		shr	ax, 1
		shr	ax, 1
		shr	ax, 1
		inc	ax
		inc	ax
		mov	sec_n, ax
		call	read_disk
		or	ax, ax
		jz	$+2		; delay	after reading the disk
		mov	si, 0F08h
		cmp	sec_n, 80h
		jb	fillfdds	; si=0C18h if CPM3.SYS > 80 sectors
		mov	si, 0C18h

fillfdds:				;CODE XREF: _entry+11B↑j
		mov	ax, seg	cpmcode
		mov	es, ax
		assume es:cpmcode
		mov	ax, es:cpmdataseg
		mov	ds, ax
		assume ds:cpmdata
		xor	ax, ax
		mov	es, ax
		assume es:bios
		mov	ax, es:n_flphdd
		test	al, al		; if no	floppies
		jz	fillhdds
		mov	bx, [si+4]
		push	ax
		call	sub_3E301
		call	sub_3E2EE
		pop	ax
		cmp	al, 1
		jz	fillhdds
		mov	bx, [si+6]
		call	sub_3E2EE

fillhdds:				;CODE XREF: _entry+135↑j _entry+144↑j
		mov	ax, es:n_flphdd
		test	ah, ah		; if no	hdds
		jz	setfdd2
		push	ax
		mov	bx, [si]
		call	sub_3E301
		call	sub_3E2EE
		mov	ax, [bx+0Eh]
		mov	bx, [si+4]
		mov	[bx+0Eh], ax
		mov	bx, [si+6]
		mov	[bx+0Eh], ax
		pop	ax
		cmp	ah, 1
		jz	setfdd2
		mov	bx, [si+2]
		call	sub_3E2EE

setfdd2:				;CODE XREF: _entry+152↑j _entry+170↑j
		mov	ax, es:n_flphdd
		cmp	al, 2		; 2 or more floppies
		jnb	setfdd1
		mov	word ptr [si+6], 0

setfdd1:				;CODE XREF: _entry+17E↑j
		cmp	al, 1		; 1 or more floppies
		jnb	sethdd2
		mov	word ptr [si+4], 0

sethdd2:				;CODE XREF: _entry+187↑j
		cmp	ah, 2		; 2 or more hdds
		jnb	sethdd1
		mov	cx, [si+4]
		mov	[si+2],	cx
		mov	cx, [si+6]
		mov	[si+4],	cx
		mov	word ptr [si+6], 0

sethdd1:				;CODE XREF: _entry+191↑j
		cmp	ah, 1		; 1 or more hdds
		jnb	loc_3E239
		mov	cx, [si+2]
		mov	[si], cx
		mov	cx, [si+4]
		mov	[si+2],	cx
		mov	word ptr [si+4], 0

loc_3E239:				;CODE XREF: _entry+1A7↑j
		cmp	cs:sec_n, 80h
		jnb	loc_3E28D
		mov	si, 0F56h	; if CPM3.SYS <	80s
		xor	ax, ax
		mov	es, ax
		mov	cx, 7
		cmp	es:usercodearea, 500h
		jnz	loc_3E25B
		dec	cx
		add	si, 6
		jmp	short loc_3E26C
; ───────────────────────────────────────────────────────────────────────────

loc_3E25B:				;CODE XREF: _entry+1D3↑j
		mov	ax, [si+6]
		mov	[si], ax
		mov	ax, [si+8]
		mov	[si+2],	ax
		mov	ax, [si+0Ah]
		mov	[si+4],	ax

loc_3E26C:				;CODE XREF: _entry+1D9↑j
		mov	ax, cs:temp
		sub	ax, [si]
		mov	[si+2],	ax
		add	si, 6

loc_3E278:				;CODE XREF: _entry+208↓j
		mov	word ptr [si], 0
		mov	word ptr [si+2], 0
		mov	byte ptr [si+4], 0FFh
		add	si, 6
		loop	loc_3E278
		jmp	boot
; ───────────────────────────────────────────────────────────────────────────

loc_3E28D:				;CODE XREF: _entry+1C0↑j
		xor	ax, ax		; if CPM3.SYS >= 80s
		mov	es, ax
		mov	cx, cs:temp
		mov	dx, es:usercodearea
		mov	bx, 5Ah

loc_3E29E:				;CODE XREF: _entry+229↓j
		mov	si, bx
		mov	bx, [bx]
		test	bx, bx
		jz	loc_3E2AB
		cmp	dx, [bx+2]
		ja	loc_3E29E

loc_3E2AB:				;CODE XREF: _entry+224↑j
		cmp	word_1799A, bx
		jz	loc_3E2BA
		mov	ax, word_17998
		mov	word_17998, bx
		mov	[si], ax

loc_3E2BA:				;CODE XREF: _entry+22F↑j
		mov	bx, 5Ah

loc_3E2BD:				;CODE XREF: _entry+24D↓j
		mov	si, bx
		mov	bx, [bx]
		test	bx, bx
		jz	boot
		mov	ax, [bx+2]
		add	ax, [bx+4]
		cmp	ax, cx
		jbe	loc_3E2BD
		mov	word ptr [si], 0
		mov	si, bx

loc_3E2D5:				;CODE XREF: _entry+25B↓j
		mov	di, bx
		mov	bx, [bx]
		test	bx, bx
		jnz	loc_3E2D5
		mov	ax, word_17998
		mov	word_17998, si
		mov	[di], ax

boot:					;CODE XREF: _entry+20A↑j _entry+243↑j
		mov	ax, seg	cpmcode
		push	ax
		xor	ax, ax
		push	ax
		retf
_entry		endp ; sp = -4


; ███████████████ S U B	R O U T	I N E ███████████████████████████████████████


sub_3E2EE	proc near		;CODE XREF: _entry+13E↑p _entry+149↑p ...
		push	si
		mov	dx, cs:temp
		sub	dx, [bx+12h]
		mov	[bx+12h], dx
		mov	cs:temp, dx
		pop	si
		retn
sub_3E2EE	endp


; ███████████████ S U B	R O U T	I N E ███████████████████████████████████████


sub_3E301	proc near		;CODE XREF: _entry+13B↑p _entry+157↑p
		push	si
		mov	si, [bx+10h]
		mov	si, [si]
		mov	dx, cs:temp

loc_3E30C:				;CODE XREF: sub_3E301+16↓j
		sub	dx, [si+0Ah]
		mov	[si+0Ah], dx
		mov	si, [si+0Ch]
		or	si, si
		jnz	loc_3E30C
		mov	cs:temp, dx
		pop	si
		retn
sub_3E301	endp


; ███████████████ S U B	R O U T	I N E ███████████████████████████████████████


read_disk	proc near		;CODE XREF: _entry+53↑p _entry+9B↑p ...
		push	bx
		push	cx
		push	es
		mov	bx, 39h		; DEV: FDD
		mov	cx, 0Bh		; COM: READ
		xor	ax, ax
		mov	es, ax
		mov	ax, es:bootfrom
		cmp	ax, 2		; if boot from id>=2, means hdd
		jb	loc_3E33F
		sub	ax, 2
		mov	bx, 40h		; DEV: HDD
		mov	cx, 5		; COM: READ

loc_3E33F:				;CODE XREF: read_disk+14↑j
		mov	word_17C10, ax
		mov	dx, ds
		mov	si, offset drive_no
		int	0FCh
		pop	es
		assume es:nothing
		pop	cx
		pop	bx
		or	ax, ax
		retn
read_disk	endp

; ───────────────────────────────────────────────────────────────────────────
		db 0
drive_no	dw 0			;DATA XREF: read_disk+24↑o
		dw 0
sector		dw 0			;DATA XREF: _entry+2A↑w _entry+32↑w ...
sec_n		dw 0			;DATA XREF: _entry+37↑w _entry+4D↑w ...
		dw 0
bufseg		dw seg bios		;DATA XREF: _entry+41↑w _entry+47↑w ...
temp		dw 0			;DATA XREF: _entry+18↑w _entry+71↑w ...
code		ends

; ═══════════════════════════════════════════════════════════════════════════

; Segment type:	Regular
stack		segment	byte public ''
		assume cs:stack
		;org 2DEh
		assume es:nothing, ss:nothing, ds:nothing
		db 100h	dup(0)
stacktop	db    0	;		;DATA XREF: _entry+6↑o
		db 121h	dup(0)
stack		ends


		end 

boot fails on loading CPM3.SYS fully in memory

went past this with patching CPM3.SYS location to bootcpm:cpm3

traced up until LOADER.SYS:code:0129