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;; Method: load_FAT_data
;;--------------------------------------
;; di => where to load
;;--------------------------------------
;; Loads the boot sector, FATs, and root directory
;; of the FAT filesystem on disk 0x80 to di. di must
;; point to enough space. Returns the number of sectors
;; read.
load_FAT_data:
	push	ebp
	mov	ebp,	esp
	sub	esp,	4	;; space for return value
	pusha
	push	fs

lfd_read_bpb:
	xor	ecx,	ecx
	mov	bx,	di	;; offset to read to
	xor	eax,	eax	;; reading the first sector
	mov	fs,	ax	;; no segment variable
	mov	cx,	1	;; only reading bpb sector
	call	read_sectors
	add	word [ebp - 4],	cx	;; for return value

lfd_read_FATs:
	mov	ax,	word [di + 22]	;; sectors per FAT
	mul	byte [di + 16]	   	;; number of FATs
	mov	cx,  	ax 		;; that's how many sectors we need load
	
	mov	ax,	word [di + 14]	;; FATs start right after the reserved sectors
	
	add	bx,	0x200		;; read to sector after bpb
	call	read_sectors		
	add	word [ebp - 4],	cx	;; for return value

lfd_read_rootdir:
	add	ax,	cx		;; rootdir is right after FATs, so add number just loaded
	push	ax			;; save ax so we can use it for calculations
	
	mov	cx,	ax		;; num sectors loaded last
	mov	dx,	0x200		;; size of a sector
	mul	dx			;; number of bytes loaded last
	add	bx,	ax		;; add to memory index
	
	mov	ax,	word [di + 17]	;; # of rootdir entries
	mov	dx,	0x20 	   	;; 32-byte entry
	mul	dx
	mov	edx,	0x200		;; # of bytes per sector
	div	edx ;; <- this is the instruction that freezes it
	mov	cx,	ax

	pop	ax
	call	read_sectors
	add	word [ebp - 4],	cx	;; return value
	
	pop	fs
	popa
	mov	ax,	word [ebp - 4]	;; return value
	mov	esp,	ebp
	pop	ebp
	ret

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eax: 0x00004000 16384
ecx: 0x00000080 128
edx: 0x00000200 512
ebx: 0x00009e00 40448
esp: 0x00009be1 39905
ebp: 0x00009bf9 39929
esi: 0x00008ea5 36517
edi: 0x00009c00 39936
eip: 0x00008d95
eflags 0x00000206
id vip vif ac vm rf nt IOPL=0 of df IF tf sf zf af PF cf

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mov edx, 0
mov ecx, 0x200
div ecx

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shr eax, 0x9