mirror of
https://github.com/pbatard/rufus.git
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101 lines
4.2 KiB
ArmAsm
101 lines
4.2 KiB
ArmAsm
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/********************************************************************************/
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/* GPT - A protective MBR that displays a notice if a user attempts to boot a */
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/* GPT drive in BIOS/Legacy mode. */
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/* */
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/* Copyright (c) 2019 Pete Batard <pete@akeo.ie> */
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/* */
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/* This program is free software; you can redistribute it and/or modify it */
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/* under the terms of the GNU General Public License as published by the Free */
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/* Software Foundation, either version 3 of the License, or (at your option) */
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/* any later version. */
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/* */
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/* This program is distributed in the hope that it will be useful, but WITHOUT */
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/* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or */
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/* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for */
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/* more details. */
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/* */
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/* You should have received a copy of the GNU General Public License along with */
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/* this program; if not, see <http://www.gnu.org/licenses/>. */
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/* */
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/********************************************************************************/
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/********************************************************************************/
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/* GNU Assembler Settings: */
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/********************************************************************************/
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.intel_syntax noprefix
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.code16
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/********************************************************************************/
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/********************************************************************************/
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/* Constants: */
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/********************************************************************************/
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MBR_ADDR = 0x7c00
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MBR_SIZE = 0x200
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MBR_RESERVED = 0x1b8 # Start of the reserved section (partition table, etc.)
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PT_MAX = 0x04 # Number of partition entries in the partition table
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PT_ENTRY_SIZE = 0x10 # Size of a partition entry in the partition table
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/********************************************************************************/
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/* MBR: This section resides at 0x00007c00 and is exactly 512 bytes */
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/********************************************************************************/
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.section main, "ax"
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.globl mbr
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mbr:
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inc cx
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dec bx
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inc bp
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dec di
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cld
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xor ax, ax
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mov ds, ax
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mov si, offset sep
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call print_string
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mov si, offset hdr
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call print_string
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mov si, offset sep
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call print_string
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mov si, offset txt
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call print_string
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hlt
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print_string:
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lodsb
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cmp al, 0x00
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jz 0f
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mov ah, 0x0e
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mov bx, 0x0007
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int 0x10
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jmp print_string
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0: ret
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/********************************************************************************/
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/* Data section */
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/********************************************************************************/
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sep:
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.string "****************************************\r\n"
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hdr:
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.string "*** ERROR: LEGACY BOOT OF UEFI MEDIA ***\r\n"
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txt:
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.ascii "\r\n" \
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"This drive can only boot in UEFI mode.\r\n" \
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"It can not boot in BIOS/Legacy mode.\r\n" \
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"\r\n" \
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"If you want to boot this drive in BIOS/Legacy mode, you\r\n" \
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"should recreate it in Rufus using the following settings:\r\n" \
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"* Partition scheme -> MBR\r\n" \
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"* Target system -> BIOS...\r\n" \
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"\0"
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/********************************************************************************/
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/* From offset 0x1b8, the MBR contains the partition table and signature data */
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/********************************************************************************/
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.org MBR_RESERVED
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disk_signature:
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.space 0x04
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filler:
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.space 0x02
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partition_table:
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.space PT_ENTRY_SIZE * PT_MAX
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mbr_signature:
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.word 0xAA55
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