Start working on FAT32 bootloader

Makefile

@@ -9,7 +9,7 @@ QEMU = qemu-system-$(QEMU_ARCH)
 QEMU_ARGS = $(addprefix --option-rom ,$(ROMS))
 
 NASM = nasm
-NASM_ARGS = -s -I. -Ilib -w-macro-params
+NASM_ARGS = -s -I. -Ilib -w-macro-params -DFLOPPY=$(FLOPPY)
 
 EMUL = utils/emul
 
@@ -62,8 +62,12 @@ fdimage.img: fat.bs $(DISTFILES)
 	mformat -C -i $@ -f $(FLOPPY) -B fat.bs ::
 	mcopy -i $@ $(DISTFILES) ::
 
-hdimage.img: boot/mbr.bs fdimage.img
-	cat boot/mbr.bs fdimage.img >$@
+hdimage.img: mbr.bs fdimage.img
+	cat mbr.bs fdimage.img >$@
+
+part.img: fat32.bs
+	dd if=/dev/zero bs=1024 count=33k of=$@
+	mformat -F -i part.img -B fat32.bs ::
 
 clean:
 	rm -f *.com *.bs *.0 *.lst *.img *.bin *.rom
@@ -72,11 +76,11 @@ clean:
 qemu-floppy: fdimage.img $(ROMS)
 	$(QEMU) $(QEMU_ARGS) -boot a -fda fdimage.img
 
-qemu-hdd: hdimage.img $(ROMS)
-	$(QEMU) $(QEMU_ARGS) -boot c -hda hdimage.img
+qemu-hdd: part.img $(ROMS)
+	$(QEMU) $(QEMU_ARGS) -boot c -hda part.img
 
-qemu-pxe: pxe.bs $(ROMS)
+qemu-pxe: pxeboot.0 $(ROMS)
 	$(QEMU) $(QEMU_ARGS) -boot n \
 		-option-rom /usr/share/qemu/pxe-rtl8139.rom \
 		-device e1000,netdev=mynet0,mac=52:54:00:12:34:56 \
-		-netdev user,id=mynet0,net=192.168.76.0/24,dhcpstart=192.168.76.9,tftp=$(CURDIR),bootfile=pxe.bs
+		-netdev user,id=mynet0,net=192.168.76.0/24,dhcpstart=192.168.76.9,tftp=$(CURDIR),bootfile=pxeboot.0

fat32.asm

@@ -0,0 +1,125 @@
+	; Bootsector for FAT32 filesystems
+	org 0x0800
+	jmp near init
+
+	; WORD reserved sector count
+rsc:    equ ( $$ + 0x00E )
+	; BYTE number of FATs
+fn:	equ ( $$ + 0x010 )
+	; DWORD hidden sector count (partition offset)
+po:	equ ( $$ + 0x01C )
+	; DWORD sectors per FAT
+sf:	equ ( $$ + 0x024 )
+	; BYTE drive number (we set it from dl)
+dn:	equ ( $$ + 0x040 )
+
+	; Area for BPB
+	times (0x5A - ($-$$)) db 0
+
+init:	xor ax, ax
+	mov ds, ax
+	mov es, ax
+	mov ss, ax
+	mov sp, 0x7C00
+
+	mov si, sp
+	mov di, 0x0800
+	mov cx, 0x0100
+	rep movsw
+	jmp 0x0:main
+
+msg:	pop si
+mloop:	lodsb
+	test al, al
+	jz mend
+	mov ah, 0x0e
+	mov bx, 7
+	int 0x10
+	jmp mloop
+mend:	push si
+	ret
+
+err:	call msg
+	db "DISKERR", 0x0A, 0x0D, 0
+hlt:	hlt
+	jmp hlt
+
+	; Requires DWORD ptr and QWORD sector on the stack
+read:	pop bp
+	push cx
+	mov ax, 0x10
+	push ax
+	mov ah, 0x42
+	mov dl, 0x80
+	mov si, sp
+
+	int 0x13
+	jc err
+
+	pop ax
+	pop cx
+	push bp
+	ret
+
+	; Advances cluster number to next entry
+next:	; Upper two words for sector num
+	xor ax, ax
+	push ax
+	push ax
+
+	; Lower two words for sector num
+	mov ax, [clus]
+	mov dx, [clus+2]
+
+	; 32-bit >> 7
+	mov cl, 7
+shftl:	clc
+	rcr dx, 1
+	rcr ax, 1
+	loop shftl
+
+	; Add reserved sector count
+	add ax, word [rsc]
+	adc dx, 0
+
+	push dx
+	push ax
+
+	; target buffer
+	push cs
+	mov ax, buf
+	push ax
+
+	mov cx, 1
+	call read
+
+        ; Stow off offset in FAT sector
+        mov si, [clus]
+        sal si, 1
+        sal si, 1
+        and si, 0x1FF
+	add si, buf
+	mov di, clus
+	movsw
+	movsw
+
+	; 1x QWORD, 1x DWORD = 12 bytes
+	add sp, 12
+	ret
+
+main:	call next
+	mov ax, [clus]
+	mov dx, [clus+2]
+	int 3
+
+	xor ah,ah
+	int 0x16
+	int 0x19
+	jmp hlt
+
+clus:	dd 2
+
+	; Padding and signature
+	times (0x1FE - ($-$$)) db 0
+	dw 0xAA55
+buf: