Import backup from 2003-08-09

bootdef.inc

@@ -0,0 +1,7 @@
+
+%define FAT_SEG 0x07E0			;right after boot sector
+%define ROOT_SEG 0x0900			;right after FAT
+%define STAGE2_SEG 0x0AC0		;right after ROOT_DIR
+%define KERNEL_ADD 0x100000		;final pmode kernel destination - physical
+
+

kernel.asm

@@ -1,10 +1,14 @@
 
-bits 32
+bits 16
 
-org	0x100000
+org	0xac00
 
-	mov	esi, msg
+	mov	ax, 0xb800
-	mov	edi, 0xb8000
+	mov	es, ax
+	xor	ax, ax
+	mov	ds, ax
+	mov	si, msg
+	xor	di, di
 
 msg_loop:
 	lodsb

stage1.asm

@@ -0,0 +1,233 @@
+
+%include "bootdef.inc"
+
+[bits 16]
+
+org 0x7c00
+
+	jmp short start
+
+; --------------------------------------------------
+; data portion of the "DOS BOOT RECORD"
+; ----------------------------------------------------------------------
+brINT13Flag     DB      90H             ; 0002h - 0EH for INT13 AH=42 READ
+brOEM           DB      'MSDOS5.0'      ; 0003h - OEM ID - Windows 95B
+brBPS           DW      512             ; 000Bh - Bytes per sector
+brSPC           DB      1               ; 000Dh - Sector per cluster
+brSc_b4_fat	DW      1               ; 000Eh - Reserved sectors
+brFATs          DB      2               ; 0010h - FAT copies
+brRootEntries   DW      0E0H		; 0011h - Root directory entries
+brSectorCount   DW      2880		; 0013h - Sectors in volume, < 32MB
+brMedia         DB      240		; 0015h - Media descriptor
+brSPF           DW      9               ; 0016h - Sectors per FAT
+brSc_p_trk	DW      18              ; 0018h - Sectors per head/track
+brHPC           DW      2		; 001Ah - Heads per cylinder
+brSc_b4_prt	DD      0               ; 001Ch - Hidden sectors
+brSectors       DD      0	        ; 0020h - Total number of sectors
+brDrive		DB      0               ; 0024h - Physical drive no.
+		DB      0               ; 0025h - Reserved (FAT32)
+		DB      29H             ; 0026h - Extended boot record sig (FAT32)
+brSerialNum     DD      404418EAH       ; 0027h - Volume serial number
+brLabel         DB      'HOS 0.1.1  '   ; 002Bh - Volume label
+brFSID          DB      'FAT12   '      ; 0036h - File System ID
+;------------------------------------------------------------------------
+
+start:
+	;dl=drive number, save it!
+	mov	[brDrive], dl
+	cli
+	xor	ax, ax
+	mov	ss, ax
+	mov	sp, 0x7Bfe		;right under boot sector
+	sti
+
+	mov	ax, 0xb800
+	mov	ds, ax
+	mov	es, ax
+
+	xor	di, di
+	mov	ax, 0x0700
+	mov	cx, 2000
+cls:
+	stosw
+	loop	cls
+
+enable_a20:
+	in	al, 0x64
+	test	al, 2
+	jnz	enable_a20
+	mov	al, 0xD1
+	out	0x64, al
+ea20_2:	in	al, 0x64
+	and	ax, byte 2
+	jnz	ea20_2
+	mov	al, 0xDF
+	out	0x60, al
+
+unreal:
+	xor	ax, ax
+	mov	es, ax
+	mov	ds, ax
+
+	lgdt	[gdtr]		;load gdt
+	cli
+	push	es
+	push	ds		;save segment values
+	mov	ebx, cr0
+	inc	bl
+	mov	cr0, ebx	;pmode!
+	mov	ax, KERNEL_DATA
+	mov	es, ax
+	mov	ds, ax		;load segment limits
+	dec	bl
+	mov	cr0, ebx	;back to real mode!
+	pop	ds
+	pop	es		;segments back, with 4gb limits!
+	sti
+
+;now lets read in the FAT and root directory so we can search for the kernel file...
+	mov	ax, 0x0209		;FAT1
+	mov	cx, 0x0002
+	xor	dh, dh
+	mov	dl, [brDrive]
+	mov	bx, FAT_SEG
+	mov	es, bx
+	xor	bx, bx
+	int	0x13
+
+	mov	ax, 0x020E		;root directory
+	mov	cx, 0x0002		;cyl/sect
+	mov	dh, 0x01		;head
+	mov	dl, [brDrive]		;drive
+	mov	bx, ROOT_SEG
+	mov	es, bx
+	xor	bx, bx
+	int	0x13
+
+;k now read root directory
+	mov	bx, ROOT_SEG
+	mov	ds, bx
+	xor	si, si			;k now ds:si points to beginning of root directory
+	mov	es, si
+	mov	cx, 224			;max root entries
+loop_compare:
+	mov	di, stage2
+	push	cx
+	push	si			;save pointer to root dir entry
+	mov	cx, 11
+loop_name:
+	cmpsb
+	loopz	loop_name
+	;cmp	cx, 0
+	jnz	goon			;cx didn't get to zero, bad file
+	pop	si
+	pop	cx
+	jmp	found_file		;good file, ds:si points to start of root directory entry
+goon:
+	pop	si
+	pop	cx
+	add	si, 32
+	loop	loop_compare
+
+error:
+	jmp	$			;halt! no kernel file found!
+
+found_file:				;ds:si points to root dir entry
+	mov	ax, STAGE2_SEG
+	mov	es, ax
+
+	mov	ax, [ds:si+26]
+	mov	bx, FAT_SEG
+	mov	ds, bx			;ds points to beginning of FAT
+	xor	bx, bx
+	xor	di, di
+
+readstage2_loop:
+	cmp	ax, 0xff7
+	jg	readstage2_done
+	inc	di
+	push	ax
+	push	bx
+	call	getCHSfromCluster
+	pop	bx
+	push	bx
+	mov	ax, 0x0201
+	mov	dl, [brDrive]
+	int	0x13
+	pop	bx
+	add	bx, 512
+	cmp	bx, 0
+	jne	readstage2_goon
+	mov	bx, es
+	add	bx, 0x0100
+	mov	es, bx
+	xor	bx, bx
+readstage2_goon:
+	pop	ax			;current logical cluster #
+
+	mov	cx, ax			;cx=logical cluster
+	mov	dx, 3
+	mul	dx
+	shr	ax, 1			;ax=logical cluster * 3 / 2
+	mov	si, ax
+	test	cl, 1			;is bit0 set?
+	jnz	odd_cluster
+even_cluster:
+	lodsw
+	and	ax, 0x0fff
+	jmp	got_cluster
+odd_cluster:
+	lodsw
+	shr	ax, 4
+got_cluster:
+	jmp	readstage2_loop
+
+readstage2_done:
+
+	jmp	0:(STAGE2_SEG*16)
+
+;------------------------------------------------------
+getCHSfromCluster:
+	;input: ax=lba of sector on floppy (0-2879)
+	add	ax, 31			;convert logical cluster# to lba#
+	xor	dx, dx			;lba->chs
+	mov	bx, 18
+	div	bx
+	inc	dx
+	mov	cl, dl			;sector# (1-18)
+	xor	dx, dx
+	mov	bx, 2
+	div	bx
+	mov	ch, al			;cylinder# (0-79)
+	mov	dh, dl			;head# (0-1)
+	ret
+
+
+;-------------------------------------------------------
+gdtr:
+	dw	gdt_end-gdt-1
+	dd	gdt
+gdt:
+	dd	0
+	dd	0
+
+KERNEL_DATA equ $-gdt
+	db	0xff		;segment 16 = 4gb data
+	db	0xff
+	db	0x00
+	db	0x00
+	db	0x00
+	db	0x92
+	db	0xcf		;cf
+	db	0x00
+
+gdt_end:
+
+
+
+stage2:	db	"STAGE2  BIN"
+
+times 510-($-$$)	db 0
+
+db	0x55, 0xaa
+