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/* -*-Asm-*- */
/*
* GRUB -- GRand Unified Bootloader
* Copyright (C) 2008,2009 Free Software Foundation, Inc.
*
* GRUB is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* GRUB is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with GRUB. If not, see <http://www.gnu.org/licenses/>.
*/
#include <grub/symbol.h>
#include <grub/machine/boot.h>
#include <grub/machine/kernel.h>
#include <multiboot.h>
.file "cdboot.S"
#define CODE_ADDR 0x6000
#define DATA_ADDR ((GRUB_BOOT_MACHINE_KERNEL_ADDR) + 0x200)
#define CDSEC_SHIFT 11
#define CDBLK_LENG 16
.text
.code16
.globl start, _start
start:
_start:
call LOCAL(next)
LOCAL(next):
jmp 1f
.org 8
bi_pvd:
.long 0 /* LBA of primary volume descriptor. */
bi_file:
.long 0 /* LBA of boot file. */
bi_length:
.long 0 /* Length of boot file. */
bi_csum:
.long 0 /* Checksum of boot file */
bi_reserved:
.space (10*4) /* Reserved */
1:
popw %bx
/* Boot from CDROM. */
xorw %ax, %ax
movw %ax, %ss
movw $(CODE_ADDR), %sp
movw %ax, %ds
movw %ax, %es
movw $(0x7C00 + err_noboot_msg - start), %si
movl %cs: bi_length - LOCAL(next)(%bx), %ecx
orl %ecx, %ecx
jz LOCAL(fail)
addl $((1 << CDSEC_SHIFT) - 1), %ecx
shrl $CDSEC_SHIFT, %ecx
movl %cs: bi_file - LOCAL(next)(%bx), %esi
call LOCAL(read_cdrom)
ljmp $(DATA_ADDR >> 4), $0
/*
* Parameters:
* esi: start sector
* ecx: number of sectors
*/
LOCAL(read_cdrom):
xorl %eax, %eax
/* Number of blocks to read. */
pushw $CDBLK_LENG
/* Block number. */
incl %esi
pushl %eax
pushl %esi
/* Buffer address. */
pushw $((DATA_ADDR - 0x200)>> 4)
pushl %eax
pushw $0x10
xorl %edi, %edi
movw %sp, %si
1:
movw 0x10(%si), %di
cmpl %ecx, %edi
jbe 2f
movl %ecx, %edi
2:
mov %di, 2(%si)
pushl %ecx
movb $0x42, %ah
int $0x13
jnc 3f
movb $0x42, %ah /* Try again. */
int $0x13
jnc 3f
2:
shrw $1, %di /* Reduce transfer size. */
jz LOCAL(cdrom_fail)
movw %di, 0x10(%si)
movw %di, 2(%si)
movb $0x42, %ah
int $0x13
jc 2b
3:
movw %di, %ax
shlw $(CDSEC_SHIFT - 4), %ax
addw %ax, 6(%si)
addl %edi, 8(%si)
popl %ecx
subl %edi, %ecx
jnz 1b
addw $0x12, %sp
ret
LOCAL(cdrom_fail):
movw $(0x7C00 + err_cdfail_msg - start), %si
LOCAL(fail):
movb $0x0e, %ah
xorw %bx, %bx
1:
lodsb (%si), %al
int $0x10
cmpb $0, %al
jne 1b
1: jmp 1b
err_noboot_msg:
.ascii "no boot info\0"
err_cdfail_msg:
.ascii "cdrom read fails\0"
.org 0x7FF
.byte 0
|
