Protypical implementation of DPT copying

boot/kernel.asm

@@ -4,6 +4,7 @@
 %include	"inc/bpb.asm"
 %include	"inc/mbr.asm"
 %include	"inc/fcb.asm"
+%include	"inc/dpt.asm"
 
 		; kernel stack size in words
 %define		stacksize 512
@@ -36,6 +37,7 @@ print_banner:	mov si, banner
 hlt:		hlt
 		jmp hlt
 
+%include	"kernel/far.asm"
 %include	"kernel/fcb.asm"
 %include        "kernel/drive.asm"
 

inc/dpt.asm

@@ -1,13 +1,5 @@
-struc dpt
-.steprate	resb 1
-.dmahdld	resb 1
-.motoroff	resb 1
-.sectorsize	resb 1
-.lastsector	resb 1
-.gaplen		resb 1
-.dtl		resb 1
-.gapfmt		resb 1
-.fillchar	resb 1
-.hdsettle	resb 1
-.motoron	resb 1
-endstruc
+DPTMTT	equ 2
+DPTSS	equ 3
+DPTSPT	equ 4
+
+DPTSIZE	equ 11

kernel/drive.asm

@@ -8,24 +8,37 @@ dskseek:	resd 1
 		; disk buffer for I/O operations
 dskbuf:		resb 512
 
+dpt:		resb DPTSIZE
+
 section .text
 
 ret:		ret
 
+		; Convert drive number into DL for int 13h
+		; IN	dl	dos drive number
+		; OUT	dl	bios drive number
+getdl:		cmp dl, 2
+		jc ret
+		mov dl, 0x80
+		ret
+
 		; select drive
 		; IN	dl	drive number
-dsksel:		cmp dl, 1
-		jnc ret
-		mov al, dl
-		and al, 0x02
-		ror dl, 1
-		ror dl, 1
-		cmp dl, byte [dsknum]
+dsksel:		cmp dl, byte [dsknum]
 		je ret
 
 		call dskrst
 
-		int 3
+		call getdl
+		mov ah, 8
+		les di, [0x1E*4]
+		int 0x13
+
+		; copy dpt
+		mov bx, di
+		mov dx, dpt
+		mov cx, DPTSIZE
+		call lod
 
 		ret
 

kernel/far.asm

@@ -0,0 +1,52 @@
+; far pointer load
+; IN	ES:BX	far pointer to data
+;	CX	number of bytes to copy
+;	0:DX	destination buffer
+; only CX is trashed
+
+lod:	push si
+	push di
+	push es
+
+	; ES:DI := DS:DX
+	mov ax, ds
+	mov es, ax
+	mov di, dx
+	; DS:SI := 0:BX
+	xor ax, ax
+	mov ds, ax
+	mov si, bx
+	; copy
+	pushf
+	cld
+	rep movsb
+	popf
+	; reset DS to kernel data
+	mov ds, cx
+
+	pop es
+	pop di
+	pop si
+	ret
+
+; far pointer store
+; IN	ES:BX	far ptr
+;	CX	number of bytes
+;	0:DX	source buffer
+; only CX is trashed
+
+sto:	push si
+	push di
+
+	mov si, dx
+	mov di, bx
+
+	; do the copy
+	pushf
+	cld
+	rep movsb
+	popf
+
+	pop di
+	pop si
+	ret