mirror of
https://github.com/reactos/reactos.git
synced 2024-11-09 16:20:37 +00:00
179 lines
4.8 KiB
NASM
179 lines
4.8 KiB
NASM
;
|
|
; normal DOS boot sector
|
|
;
|
|
; Ported to nasm from FreeDOS fdisk 1.2.0 by:
|
|
; Casper Hornstrup (chorns@users.sourceforge.net)
|
|
;
|
|
|
|
align 2, db 0
|
|
|
|
global _bootnormal_code
|
|
_bootnormal_code:
|
|
|
|
;-----------------------------------------------------------------------
|
|
; ENTRY (copied from freedos bootsector)
|
|
;
|
|
; IN: DL = boot drive
|
|
;OUT: DL = boot drive
|
|
;
|
|
;-----------------------------------------------------------------------
|
|
|
|
real_start: cli
|
|
cld
|
|
xor ax, ax
|
|
mov ss, ax ; initialize stack
|
|
mov ds, ax
|
|
mov bp, 0x7c00
|
|
lea sp, [bp-0x20]
|
|
sti
|
|
|
|
mov ax, 0x1FE0
|
|
mov es, ax
|
|
mov si, bp
|
|
mov di, bp
|
|
mov cx, 0x0100
|
|
rep movsw
|
|
|
|
jmp word 0x1FE0:0x7c00+ cont-real_start
|
|
|
|
cont: mov ds, ax
|
|
mov ss, ax
|
|
xor ax,ax
|
|
mov es,ax
|
|
|
|
|
|
; search for active partition
|
|
lea di, [bp+0x1be] ; start of partition table
|
|
test_next_for_active:
|
|
test byte [di],0x80
|
|
jne active_partition_found
|
|
add di,0x10 ; next table
|
|
cmp di, 07c00h+0x1fe; scanned beyond end of table ??
|
|
jb test_next_for_active
|
|
|
|
;*****************************************************************
|
|
call print
|
|
db 'no active partition found',0
|
|
|
|
WAIT_FOR_REBOOT:
|
|
jmp $
|
|
|
|
|
|
;*****************************************************************
|
|
trouble_reading_drive:
|
|
call print
|
|
db 'read error while reading drive',0
|
|
jmp WAIT_FOR_REBOOT
|
|
|
|
;*****************************************************************
|
|
|
|
invalid_partition_code:
|
|
call print
|
|
db 'partition signature != 55AA',0
|
|
|
|
jmp WAIT_FOR_REBOOT
|
|
|
|
|
|
;*****************************************************************
|
|
|
|
active_partition_found:
|
|
; call print
|
|
; db 'loading active partition',0
|
|
|
|
call read_boot_sector
|
|
|
|
jc trouble_reading_drive
|
|
|
|
cmp word [es:0x7c00+0x1fe],0xaa55
|
|
jne invalid_partition_code
|
|
|
|
jmp word 0x0:0x7c00 ; and jump to boot sector code
|
|
|
|
|
|
;*****************************
|
|
; read_boot_sector
|
|
;
|
|
; IN: DI--> partition info
|
|
;OUT:CARRY
|
|
;*****************************
|
|
|
|
read_boot_sector:
|
|
; /* check for LBA support */
|
|
mov bx,0x55aa
|
|
mov ah,0x41
|
|
int 0x13
|
|
|
|
jc StandardBios ; if (regs.b.x != 0xaa55 || (regs.flags & 0x01))
|
|
cmp bx,0xaa55 ; goto StandardBios;
|
|
jne StandardBios
|
|
|
|
; /* if DAP cannot be used, don't use LBA */
|
|
; if ((regs.c.x & 1) == 0)
|
|
; goto StandardBios;
|
|
test cl,1
|
|
jz StandardBios
|
|
|
|
jmp short LBABios
|
|
|
|
|
|
_bios_LBA_address_packet:
|
|
db 0x10
|
|
db 0
|
|
db 4 ; read four sectors - why not
|
|
db 0
|
|
dw 0x7c00 ; fixed boot address for DOS sector
|
|
dw 0x0000
|
|
_bios_LBA_low dw 0
|
|
_bios_LBA_high dw 0
|
|
dw 0,0
|
|
|
|
|
|
LBABios:
|
|
; copy start address of partition to DAP
|
|
mov ax,[di+8]
|
|
mov [0x7c00+ (_bios_LBA_low-real_start)],ax
|
|
mov ax,[di+8+2]
|
|
mov [0x7c00+ (_bios_LBA_high-real_start)],ax
|
|
|
|
mov ax,0x4200 ; regs.a.x = LBA_READ;
|
|
mov si,0x7c00+ (_bios_LBA_address_packet-real_start); regs.si = FP_OFF(&dap);
|
|
|
|
int 0x13
|
|
ret
|
|
|
|
;*****************************************************************
|
|
; read disk, using standard BIOS
|
|
;
|
|
StandardBios:
|
|
mov ax,0x0204 ; regs.a.x = 0x0201;
|
|
mov bx,0x7c00 ; regs.b.x = FP_OFF(buffer);
|
|
mov cx,[di+2] ; regs.c.x =
|
|
; ((chs.Cylinder & 0xff) << 8) + ((chs.Cylinder & 0x300) >> 2) +
|
|
; chs.Sector;
|
|
; that was easy ;-)
|
|
mov dh,[di+1] ; regs.d.b.h = chs.Head;
|
|
; regs.es = FP_SEG(buffer);
|
|
int 0x13
|
|
ret
|
|
|
|
|
|
|
|
;****** PRINT
|
|
; prints text after call to this function.
|
|
|
|
print_1char:
|
|
xor bx, bx ; video page 0
|
|
mov ah, 0x0E ; else print it
|
|
int 0x10 ; via TTY mode
|
|
print: pop si ; this is the first character
|
|
print1: lodsb ; get token
|
|
push si ; stack up potential return address
|
|
cmp al, 0 ; end of string?
|
|
jne print_1char ; until done
|
|
ret ; and jump to it
|
|
|
|
|
|
|
|
times 0x1fe-$+$$ db 0
|
|
db 0x55,0xaa
|
|
|