mirror of
https://git.FreeBSD.org/src.git
synced 2024-12-26 11:47:31 +00:00
828c68cf7a
Since msdosfs is part of the base system, it's not wise to rely on something like mtools to provide this functionality. This utility is the agreed fix for PR # misc/804 fdformat did not ...
102 lines
3.2 KiB
NASM
102 lines
3.2 KiB
NASM
;;; Hello emacs, this looks like -*- asm -*- code, doesn't it?
|
|
;;;
|
|
;;; This forms a simple dummy boot program for use with a tool to
|
|
;;; format DOS floppies. All it does is displaying a message, and
|
|
;;; recover gracefully by re-initializing the CPU.
|
|
;;;
|
|
;;; Written by Joerg Wunsch, Dresden. Placed in the public domain.
|
|
;;; This software is provided as is, neither kind of warranty applies.
|
|
;;; Use at your own risk.
|
|
;;;
|
|
;;; (This is written in as86 syntax. as86 is part of Bruce Evans'
|
|
;;; bcc package.)
|
|
;;;
|
|
;;; $Id$
|
|
;;;
|
|
;;; This code must be linked to address 0x7c00 in order to function
|
|
;;; correctly (the BIOS boot address).
|
|
;;;
|
|
;;; It's 16-bit code, and we don't care for a data segment.
|
|
use16
|
|
.text
|
|
|
|
entry _begin
|
|
_begin: jmp init ; jump to boot prog
|
|
nop ; historical baggage ;-)
|
|
;;;
|
|
;;; Reserve space for the "BIOS parameter block".
|
|
;;; This will be overwritten by the actual formatting routine.
|
|
;;;
|
|
bpb: .ascii "BSD 4.4" ; "OEM" name
|
|
.word 512 ; sector size
|
|
.byte 2 ; cluster size
|
|
.word 1 ; reserved sectors (just the boot sector)
|
|
.byte 2 ; FAT count
|
|
.word 112 ; # of entries in root dir
|
|
.word 1440 ; total number of sectors, MSDOS 3.3 or below
|
|
.byte 0xf9 ; "media descriptor"
|
|
.word 3 ; FAT size (sectors)
|
|
.word 9 ; sectors per track
|
|
.word 2 ; heads per cylinder
|
|
.word 0 ; hidden sectors
|
|
;; MSDOS 4.0++ -- only valid iff total number of sectors == 0
|
|
.word 0 ; unused
|
|
.long 0 ; total number of sectors
|
|
.short 0 ; physical drive (0, 1, ..., 0x80) %-)
|
|
.byte 0 ; "extented boot signature"
|
|
.long 0 ; volume serial number (i.e., garbage :)
|
|
.ascii " " ; label -- same as vol label in root dir
|
|
.ascii "FAT12 " ; file system ID
|
|
;;;
|
|
;;; Executable code starts here.
|
|
;;;
|
|
init:
|
|
;; First, display our message.
|
|
mov si, *message
|
|
lp1: seg cs
|
|
movb al, [si]
|
|
inc si
|
|
testb al, al
|
|
jz lp2 ; null-terminated string
|
|
movb bl, *7 ; display with regular attribute
|
|
movb ah, *0x0e ; int 0x10, fnc 0x0e -- emulate tty
|
|
int 0x10
|
|
jmp lp1
|
|
lp2: xorb ah, ah ; int 0x16, fnc 0x00 -- wait for keystroke
|
|
int 0x16
|
|
mov ax, *0x40 ; write 0x1234 to address 0x472 --
|
|
push ax ; tell the BIOS that this is a warm boot
|
|
pop dx
|
|
mov 0x72, *0x1234
|
|
jmpf 0xfff0,0xf000 ; jump to CPU initialization code
|
|
|
|
message:
|
|
.byte 7
|
|
.byte 0xc9
|
|
.byte 0xcd,0xcd,0xcd,0xcd,0xcd,0xcd,0xcd,0xcd,0xcd,0xcd
|
|
.byte 0xcd,0xcd,0xcd,0xcd,0xcd,0xcd,0xcd,0xcd,0xcd,0xcd
|
|
.byte 0xcd,0xcd,0xcd,0xcd,0xcd,0xcd,0xcd,0xcd,0xcd,0xcd
|
|
.byte 0xcd,0xcd,0xcd,0xcd,0xcd,0xcd,0xcd,0xcd,0xcd,0xcd
|
|
.byte 0xcd,0xcd,0xcd,0xcd,0xcd,0xcd
|
|
.byte 0xbb, 13, 10, 0xba
|
|
.ascii " Sorry, this disc does actually not contain "
|
|
.byte 0xba, 13, 10, 0xba
|
|
.ascii " a bootable system. "
|
|
.byte 0xba, 13, 10, 0xba
|
|
.ascii " Press any key to reboot. "
|
|
.byte 0xba, 13, 10, 0xc8
|
|
.byte 0xcd,0xcd,0xcd,0xcd,0xcd,0xcd,0xcd,0xcd,0xcd,0xcd
|
|
.byte 0xcd,0xcd,0xcd,0xcd,0xcd,0xcd,0xcd,0xcd,0xcd,0xcd
|
|
.byte 0xcd,0xcd,0xcd,0xcd,0xcd,0xcd,0xcd,0xcd,0xcd,0xcd
|
|
.byte 0xcd,0xcd,0xcd,0xcd,0xcd,0xcd,0xcd,0xcd,0xcd,0xcd
|
|
.byte 0xcd,0xcd,0xcd,0xcd,0xcd,0xcd
|
|
.byte 0xbc, 13,10
|
|
.byte 0
|
|
|
|
;; Adjust the value below after changing the length of
|
|
;; the code above!
|
|
.space 0x1fe-0x161 ; pad to 512 bytes
|
|
|
|
.byte 0x55, 0xaa ; yes, we are bootable (cheating :)
|
|
end
|
|
|