; rmmod.asm
; real mode module for HOS
; Author: Josh Holtrop
; Date: 09/20/04

; the bootstrap process will jump us to 0x0:0x5010 so we'd better be ready for it
[org 0x5000]
[bits 16]
			;HOS module header, better be 16 bytes!
	dd	0x4D534F48	; magic identifier "HOSM"
	dd	1		; real mode module
	dd	start		; start address
	dd	0		; reserved

; ebx = return address
; ecx = where to store real mode parameter table
start:
	jmp	0:start_refreshed
start_refreshed:
	mov	ax, cs		; 0
	mov	ds, ax
	mov	es, ax
	mov	ss, ax
	mov	esp, 0x7000
	mov	[dat_rmadd], ecx
	mov	[dat_retn], ebx



	mov	ebx, [dat_retn]
	lgdt	[gdtrbs32]
	mov	eax, cr0
	or	eax, 0x01
	mov	cr0, eax
	jmp	KERNEL_CODE_BS32:segmented_start
[bits 32]
segmented_start:
	mov	cx, KERNEL_DATA_BS32
	mov	ss, cx
	mov	ds, cx
	mov	es, cx
	mov	gs, cx
	mov	fs, cx
	jmp	ebx


[bits 16]
; putString(int position, char *str)
putString:
	push	bp
	mov	bp, sp
	push	ds
	push	es
	push	edi
	push	esi
	push	eax

	mov	ax, 0xb800
	mov	es, ax
	xor	ax, ax
	mov	ds, ax
	mov	ax, [bp + 4]
	mov	di, ax
	shl	di, 1
	mov	ax, [bp + 6]
	mov	si, ax

putString_loop:
	lodsb
	stosb
	cmp	al, 0
	jz	putString_loop_done
	mov	al, 0x07
	stosb
	jmp	putString_loop
putString_loop_done:

	pop	eax
	pop	esi
	pop	edi
	pop	es
	pop	ds
	pop	bp
	ret

;-------------------------------------------------------
gdtrbs32:
	dw	gdt_endbs32-gdtbs32-1
	dd	gdtbs32
gdtbs32:				;null descriptor
	dd	0
	dd	0

	;a base of 0x4000_0000, when added to 0xC000_0000 will produce 0x0000_0000 physical before paging in effect
KERNEL_CODE_BS32 equ $-gdtbs32
	db	0xff		;limit	7:0
	db	0xff		;limit	15:8
	db	0x00		;base	7:0
	db	0x00		;base	15:8
	db	0x00		;base	23:16
	db	0x9a		;access
	db	0xcf		;flags / limit 19:16
	db	0x40		;base	31:24

KERNEL_DATA_BS32 equ $-gdtbs32
	db	0xff		;limit	7:0
	db	0xff		;limit	15:8
	db	0x00		;base	7:0
	db	0x00		;base	15:8
	db	0x00		;base	23:16
	db	0x92		;access
	db	0xcf		;flags / limit 19:16
	db	0x40		;base	31:24

gdt_endbs32:


dat_rmadd		dd	0
dat_initrd		dd	0
dat_retn		dd	0