OSDev.org

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;; Header
0x10 0x00
;; Sectors
0x0001
;; Where?
0x0200
0x0100
;; Which?
0x00000000 00000001

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loadSector:
;; Save a couple of important registers
	push bp
	push si
;; Set the stack frame
	mov bp, sp
;; Align the stack to a dword boundary (I chose to 16 bytes)
	and sp, 0xFFF0
;; Put the structure on the stack
	push dword ebx
	push dword eax
	push es
	push di
	push cx
	push 16
;; Get the location of the structure
	mov si, sp
;; Save some more registers
	push dx
	push ds
;; Copy SS to DS for the int
;; because the structure is on the stack
	push ss
	pop ds
;; Which subfunction
	mov ax, 0x42
;; One last register
	push bp
;; Do it!
	int 13h

;; At this point, I can find nothing that I expect despite no errors reported

;; Restore the various registers
	pop bp
	pop ds
	pop dx
;; Remove the structure & alignment padding from the stack
	mov sp, bp
;; Restore the pointers
	pop si
	pop bp
	ret

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DAPACK:
		db	0x10
		db	0
blkcnt	dw	0						; int 13 resets this to # of blocks actually read/written
db_add	dw	0						; memory buffer destination address
db_seg	dw	0						; in memory page zero
d_lba	dd	1						; put the lba to read in this spot
		dd	0						; more storage bytes only for big lba's ( > 4 bytes )

ReadSectors:						; EBX is LBA to start, CX is sectors to read, ES:DI is destination address
	pushad
	mov si, WORD DAPACK
	mov [db_add], di
	mov [d_lba], ebx
	mov [blkcnt], cx
	mov [db_seg], es
	mov ah, 0x42
	movzx edx, BYTE [BootDrive]
	int 0x13
	jc .Error
	popad
	ret
	
	.Error:
		mov si, DiskErrorMsg
		call Error