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# RCC-Project
#
# Copyright (C) 2026 Richard Qin
#
# This file is part of RCC-Project.
#
# RCC-Project 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.
#
# RCC-Project 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
# RCC-Project; see the file COPYING. If not see
# <http://www.gnu.org/licenses/>.
.intel_syntax noprefix
.code16
.equ MBR_LOAD_SEGMENT, 0x0000
.equ MBR_LOAD_OFFSET, 0x7C00
.equ BOOT_DRIVE_SLOT, 0x7FFC
.extern enter_protected_mode
.section .text16.entry, "ax"
.global reset_entry
.type reset_entry, @function
reset_entry:
cli
cld
xor ax, ax
mov ds, ax
mov es, ax
mov ss, ax
mov sp, 0x8000
mov byte ptr [BOOT_DRIVE_SLOT], dl
call enter_protected_mode
cli
mov dl, byte ptr [BOOT_DRIVE_SLOT]
xor ax, ax
mov ds, ax
mov es, ax
mov ss, ax
mov sp, MBR_LOAD_OFFSET
cld
.byte 0xEA
.word MBR_LOAD_OFFSET
.word MBR_LOAD_SEGMENT
reset_halt:
sti
reset_halt_loop:
hlt
jmp reset_halt_loop
.section .reset, "ax"
.global reset_vector
reset_vector:
cli
/*
* The linker places .text16 at physical address 0xF0000.
* F000:0000 therefore reaches the first 16-bit entry.
*/
.byte 0xEA
.word 0x0000
.word 0xF000
.fill 16 - (. - reset_vector), 1, 0x90
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