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fio.nasm
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;; Copyright (c) 2020, Florian Büstgens
;; All rights reserved.
;;
;; Redistribution and use in source and binary forms, with or without
;; modification, are permitted provided that the following conditions are met:
;; 1. Redistributions of source code must retain the above copyright
;; notice, this list of conditions and the following disclaimer.
;;
;; 2. Redistributions in binary form must reproduce the above copyright notice,
;; this list of conditions and the following disclaimer in the
;; documentation and/or other materials provided with the distribution.
;;
;; THIS SOFTWARE IS PROVIDED BY <copyright holder> ''AS IS'' AND ANY
;; EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
;; WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
;; DISCLAIMED. IN NO EVENT SHALL <copyright holder> BE LIABLE FOR ANY
;; DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
;; (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
;; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
;; ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
;; (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
;; SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
;; fio.inc
;; Routines to find the kernel on a FAT32 partition
%include "fat32.nasm"
;; ----------------------------------------------------------
;; Find the kernel on a FAT32 drive
;; ----------------------------------------------------------
detect_kern:
push ax
push bx
push cx
call prepare_fs ; Preparing the bootloader to read the FAT32 drive
;; Getting file informations
mov di, 0x0200 + 0x20 ; Get first file entry
mov dx, WORD[di + 0x001A] ; Offset of the file entry
mov WORD[__cluster], dx
;; Preparing kernel location
mov ax, 0x0100 ; Location
mov es, ax ; Setting extra segment
xor bx, bx
;; Reading kernel cluster
mov cx, 0x0008
mov ax, WORD[__cluster]
call _lba_conv
call _read_disk_sectors
pop cx
pop bx
pop ax
ret
__cluster: dw 0x0000