175 lines
2.9 KiB
ArmAsm
175 lines
2.9 KiB
ArmAsm
/* -*-Asm-*- */
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/*
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* GRUB -- GRand Unified Bootloader
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* Copyright (C) 2008 Free Software Foundation, Inc.
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*
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* GRUB is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* GRUB is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with GRUB. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <grub/boot.h>
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#include <grub/machine/boot.h>
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#include <grub/machine/kernel.h>
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#include <multiboot.h>
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.file "cdboot.S"
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#define CODE_ADDR 0x6000
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#define DATA_ADDR ((GRUB_BOOT_MACHINE_KERNEL_ADDR) + 0x200)
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#define CDSEC_SHIFT 11
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#define CDBLK_LENG 16
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.text
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.code16
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.globl start, _start
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start:
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_start:
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call next
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next:
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jmp 1f
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. = start + 8
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bi_pvd:
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.long 0 /* LBA of primary volume descript. */
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bi_file:
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.long 0 /* LBA of boot file. */
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bi_length:
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.long 0 /* Length of boot file. */
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bi_csum:
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.long 0 /* Checksum of boot file */
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bi_reserved:
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.space (10*4) /* Reserved */
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1:
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popw %bx
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/* Boot from CDROM. */
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xorw %ax, %ax
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movw %ax, %ss
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movw $(CODE_ADDR), %sp
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movw %ax, %ds
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movw %ax, %es
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movw $(0x7C00 + err_noboot_msg - start), %si
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movl %cs: bi_length - next(%bx), %ecx
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orl %ecx, %ecx
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jz fail
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addl $((1 << CDSEC_SHIFT) - 1), %ecx
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shrl $CDSEC_SHIFT, %ecx
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movl %cs: bi_file - next(%bx), %esi
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call read_cdrom
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/* Root drive will default to boot drive */
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movb $0xFF, %dh
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ljmp $(DATA_ADDR >> 4), $0
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/*
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* Parameters:
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* esi: start sector
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* ecx: number of sectors
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*/
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read_cdrom:
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xorl %eax, %eax
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/* Number of blocks to read. */
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pushw $CDBLK_LENG
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/* Block number. */
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pushl %eax
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pushl %esi
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/* Buffer address. */
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pushw $((DATA_ADDR - 0x400)>> 4)
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pushl %eax
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pushw $0x10
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xorl %edi, %edi
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movw %sp, %si
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1:
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movw 0x10(%si), %di
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cmpl %ecx, %edi
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jbe 2f
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movl %ecx, %edi
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2:
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mov %di, 2(%si)
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pushl %ecx
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movb $0x42, %ah
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int $0x13
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jnc 3f
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movb $0x42, %ah /* Try again. */
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int $0x13
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jnc 3f
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2:
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shrw $1, %di /* Reduce transfer size. */
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jz cdrom_fail
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movw %di, 0x10(%si)
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movw %di, 2(%si)
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movb $0x42, %ah
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int $0x13
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jc 2b
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3:
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movw %di, %ax
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shlw $(CDSEC_SHIFT - 4), %ax
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addw %ax, 6(%si)
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addl %edi, 8(%si)
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popl %ecx
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subl %edi, %ecx
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jnz 1b
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addw $0x12, %sp
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ret
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cdrom_fail:
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movw $(0x7C00 + err_cdfail_msg - start), %si
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fail:
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movb $0x0e, %ah
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xorw %bx, %bx
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1:
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lodsb (%si), %al
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int $0x10
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cmpb $0, %al
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jne 1b
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1: jmp 1b
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err_noboot_msg:
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.ascii "no boot info\0"
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err_cdfail_msg:
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.ascii "cdrom read fails\0"
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. = start + 0x1FF
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.byte 0
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