mirror of
https://github.com/reactos/reactos.git
synced 2024-06-01 02:01:57 +00:00
188 lines
4.5 KiB
ArmAsm
188 lines
4.5 KiB
ArmAsm
/*
|
|
* COPYRIGHT: See COPYING in the top level directory
|
|
* PROJECT: ReactOS Bootsector for ISO file system
|
|
* PURPOSE: Normal DOS boot sector
|
|
* Ported to NASM from FreeDOS fdisk 1.2.0 by:
|
|
* PROGRAMMERS: Casper Hornstrup (chorns@users.sourceforge.net)
|
|
*/
|
|
|
|
/* INCLUDES ******************************************************************/
|
|
|
|
#include <asm.inc>
|
|
|
|
//-----------------------------------------------------------------------
|
|
// ENTRY (copied from freedos bootsector)
|
|
//
|
|
// IN: DL = boot drive
|
|
// OUT: DL = boot drive
|
|
//
|
|
//-----------------------------------------------------------------------
|
|
|
|
.code16
|
|
real_start:
|
|
cli
|
|
cld
|
|
xor ax, ax
|
|
mov ss, ax // initialize stack
|
|
mov ds, ax
|
|
mov bp, HEX(7c00)
|
|
lea sp, [bp-32]
|
|
sti
|
|
|
|
/* Copy 512 bytes of MBR to 1fe0:7c00 */
|
|
mov ax, HEX(1FE0)
|
|
mov es, ax
|
|
mov si, bp
|
|
mov di, bp
|
|
mov cx, 256
|
|
rep movsw
|
|
|
|
/* Jump into relocated code */
|
|
ljmp16 HEX(1FE0), cont
|
|
cont:
|
|
|
|
/* Setup segment registers */
|
|
mov ds, ax
|
|
mov ss, ax
|
|
xor ax, ax
|
|
mov es, ax
|
|
|
|
/* Search for active partition */
|
|
lea di, [bp + HEX(1be)] // start of partition table
|
|
test_next_for_active:
|
|
test byte ptr ds:[di], HEX(80)
|
|
jne active_partition_found
|
|
add di, 16 // next table
|
|
cmp di, HEX(07c00) + HEX(1fe) // scanned beyond end of table ??
|
|
jb test_next_for_active
|
|
|
|
/*****************************************************************/
|
|
call print
|
|
.asciz "No active partition found"
|
|
|
|
WAIT_FOR_REBOOT:
|
|
jmp WAIT_FOR_REBOOT
|
|
|
|
|
|
/*****************************************************************/
|
|
trouble_reading_drive:
|
|
call print
|
|
.asciz "Read error while reading drive"
|
|
jmp WAIT_FOR_REBOOT
|
|
|
|
/*****************************************************************/
|
|
|
|
invalid_partition_code:
|
|
call print
|
|
.asciz "Partition signature != 55AA"
|
|
|
|
jmp WAIT_FOR_REBOOT
|
|
|
|
/*****************************************************************/
|
|
|
|
active_partition_found:
|
|
// call print
|
|
// .asciz "Loading active partition"
|
|
|
|
call read_boot_sector
|
|
|
|
jc trouble_reading_drive
|
|
|
|
cmp word ptr es:[HEX(7c00)+HEX(1fe)], HEX(0aa55)
|
|
jne invalid_partition_code
|
|
|
|
ljmp16 0, HEX(7c00) // and jump to boot sector code
|
|
|
|
/*****************************
|
|
* read_boot_sector
|
|
*
|
|
* IN: DI--> partition info
|
|
* OUT:CARRY
|
|
*****************************/
|
|
read_boot_sector:
|
|
/* check for LBA support */
|
|
mov bx, HEX(55aa)
|
|
mov ah, HEX(41)
|
|
int HEX(13)
|
|
|
|
jc StandardBios // if (regs.b.x != 0xaa55 || (regs.flags & 0x01))
|
|
cmp bx, HEX(0aa55) // 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:
|
|
.byte 16
|
|
.byte 0
|
|
.byte 4 // read four sectors - why not
|
|
.byte 0
|
|
.word HEX(7c00) // fixed boot address for DOS sector
|
|
.word HEX(0000)
|
|
|
|
_bios_LBA_low:
|
|
.word 0
|
|
_bios_LBA_high:
|
|
.word 0
|
|
.word 0,0
|
|
|
|
|
|
LBABios:
|
|
// copy start address of partition to DAP
|
|
mov ax, [di + 8]
|
|
mov word ptr ds:[_bios_LBA_low], ax
|
|
mov ax,[di + 8 + 2]
|
|
mov word ptr ds:[_bios_LBA_high], ax
|
|
|
|
mov ax, HEX(4200) // regs.a.x = LBA_READ;
|
|
mov si, offset _bios_LBA_address_packet // regs.si = FP_OFF(&dap);
|
|
|
|
int HEX(13)
|
|
ret
|
|
|
|
/*****************************************************************
|
|
* read disk, using standard BIOS
|
|
*/
|
|
StandardBios:
|
|
mov ax, HEX(0204) // regs.a.x = 0x0201;
|
|
mov bx, HEX(7c00) // regs.b.x = FP_OFF(buffer);
|
|
|
|
/* regs.c.x =
|
|
((chs.Cylinder & 0xff) << 8) + ((chs.Cylinder & 0x300) >> 2) +
|
|
; chs.Sector;
|
|
that was easy ;-) */
|
|
mov cx, word ptr ds:[di + 2]
|
|
mov dh, byte ptr ds:[di + 1] // regs.d.b.h = chs.Head;
|
|
// regs.es = FP_SEG(buffer);
|
|
int HEX(13)
|
|
ret
|
|
|
|
/****** PRINT
|
|
* prints text after call to this function.
|
|
*/
|
|
print_1char:
|
|
xor bx, bx // video page 0
|
|
mov ah, HEX(0E) // else print it
|
|
int HEX(10) // 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
|
|
|
|
.org 510
|
|
.byte HEX(55), HEX(0aa)
|
|
|
|
.endcode16
|
|
|
|
END
|