rdos/boot/kernel.asm

		cpu 8086
		org 0x0700

%include	"inc/bpb.asm"
%include	"inc/mbr.asm"
%include	"inc/dpt.asm"

init:		cli
		xor ax, ax
		mov ds, ax
		mov es, ax
		mov ss, ax
		mov sp, ax

		mov si, 0x7C00
		; relocate to 00700
		mov di, text_start
		mov cx, text_length + rodata_length + data_length
		rep movsb
		; clear out bss section
		mov cx, bss_length
		rep stosb
		; jump to copy
		call 0:relinit

section .rodata

%define V 0x %+ VERSION
version:	dd V

section .text

relinit:	; print banner
		push word [version]
		push word [version+2]
		call printf
		db "RDOS ",2,2, 0x0A, 0x0D, 0
		; initialize the disk i/o
		call dinit
		; init 21h vector
		mov word [0x21*4], int21
		mov word [0x21*4+2], cs
		; set current PSP, directly after us
		mov ax, stack
		mov cl, 4
		shr ax, cl
		mov word [curpsp], ax
		; also the DTA
		mov bx, dta
		call setdta
		; set current drive to boot drive
		mov al, dl
		rol al, 1
		rol al, 1
		or dl, al
		and dl, 3
		call setdd

		mov bx, testfcb
		call fndfst

restart:
hlt:		hlt
		jmp hlt

%include	"kernel/psp.asm"
%include	"kernel/syscall.asm"
%include	"kernel/char.asm"
%include	"kernel/fcb.asm"
%include	"kernel/drive.asm"
%include	"kernel/printf.asm"

section .bss

dta:		resb 128

section .data

testfcb:	db 0
		db "HELLO   ", "COM"
		times 30 db 0

section .text

text_start	equ  $$
text_length	equ  $-$$

section .rodata

rodata_start	equ  $$
rodata_length	equ  $-$$

section .data

data_start	equ  $$
data_length	equ  $-$$

section .bss

		resw 256 ; 512b kern stack
		alignb 16
stack:		; stack grows into this ^
		; this is also the end marker
		; programs with their psp start here

bss_start	equ  $$
bss_length	equ  $-$$