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122 lines
2.6 KiB
ArmAsm
122 lines
2.6 KiB
ArmAsm
/*
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* GRUB -- GRand Unified Bootloader
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* Copyright (C) 2000 Free Software Foundation, Inc.
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*
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* This program 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 2 of the License, or
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* (at your option) any later version.
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*
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* This program 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 this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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#include <nbi.h>
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#include <diskless_size.h>
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.file "nbloader.S"
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.text
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.code16
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/* Just a dummy entry */
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.globl _start; _start:
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/*
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* netboot image header
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*/
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.long NBI_MAGIC
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.long 0x00000004
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/* load address of the first block */
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.word NBI_DEST_OFF
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.word NBI_DEST_SEG
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/* start addr of the relocation code */
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.word NBI_DEST_OFF + (relocate - _start)
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.word NBI_DEST_SEG
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.long 0x04000004
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.long NBI_DEST_ADDR + 0x0200
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.long DISKLESS_SIZE
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.long DISKLESS_SIZE
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relocate:
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/*
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* This code is for now located at 0x10000.
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* Relocate the code in two steps:
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* 1. Copy the first 32k to 0x8000 and jump to the relocated area.
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* 2. Copy the rest to 0x10000 (0x8000 + 32k).
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*/
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/* Copy the first 32k */
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movw $NBI_DEST_SEG, %ax
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movw %ax, %ds
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movw $RELOCATED_SEG, %ax
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movw %ax, %es
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xorw %si, %si
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xorw %di, %di
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/* Always copy 32k bytes */
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movw $0x4000, %cx
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cld
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rep
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movsw
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/* Jump to the relocated address */
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ljmp $0, $(RELOCATED_ADDR + copy_rest - _start)
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/* Copy the rest */
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copy_rest:
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/* Set %edx to the number of bytes */
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movl $(DISKLESS_SIZE + 0x200 - 0x8000), %edx
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copy_loop:
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/* Check the rest */
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orl %edx, %edx
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jz boot_stage2
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/* Copy by 32k, as that is easy to implement */
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movl $0x8000, %ecx
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cmpl %ecx, %edx
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jg copy
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movl %edx, %ecx
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copy:
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/* Update the number of rest bytes */
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subl %ecx, %edx
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/* Add 0x0800 (32k >> 4) into %es and %ds */
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movw %es, %ax
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addw $0x0800, %ax
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movw %ax, %es
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movw %ds, %ax
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addw $0x800, %ax
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movw %ax, %ds
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/* Zero the offsets */
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xorw %si, %si
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xorw %di, %di
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/* Use word-size copy */
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addw $1, %cx
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shrw $1, %cx
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/* The direction is already correct */
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rep
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movsw
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jmp copy_loop
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/* Jump to the stage2 */
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boot_stage2:
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ljmp $0, $STAGE2_START_ADDR
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/* This ensures that the length of this image will be 1 sector */
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. = _start + 0x200 - 1
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.byte 0
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