Basic Launch of Higher half kernel
We now can launch the kernel at 0xC0000000 (or 3 GiB mark) with paging enabled. A lot of early main is currently not executed to keep debugging as simple as possible during the initial testing of higher half kernel loading. A lot of the implementation is straight from wiki.osdev.org/Higher_Half_x86_Bare_Bones. Thanks to all the folks who keep that wiki updated, its really resourceful.
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9
Makefile
9
Makefile
@ -3,7 +3,7 @@ EMULATOR = qemu-system-i386
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AS = ${HOME}/opt/cross/bin/i686-elf-as
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CC = ${HOME}/opt/cross/bin/i686-elf-gcc
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CPP = ${HOME}/opt/cross/bin/i686-elf-g++
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CFLAGS = -ffreestanding -O2 -Wall -Wextra
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CFLAGS = -ffreestanding -Og -ggdb -Wall -Wextra
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OFILES =$(BUILD_DIR)/boot.o $(BUILD_DIR)/kterm.o $(BUILD_DIR)/kernel.o $(BUILD_DIR)/memory.o $(BUILD_DIR)/paging.o $(BUILD_DIR)/pit.o $(BUILD_DIR)/time.o $(BUILD_DIR)/keyboard.o $(BUILD_DIR)/io.o $(BUILD_DIR)/gdtc.o $(BUILD_DIR)/idt.o $(BUILD_DIR)/pic.o $(BUILD_DIR)/sv-terminal.o $(BUILD_DIR)/string.o
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@ -34,11 +34,14 @@ iso: clean_iso clean build
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grub-mkrescue -o build/barinkOS.iso root
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run: all
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$(EMULATOR) -kernel $(BUILD_DIR)/myos.bin -serial stdio -vga std -display gtk -m 2G -cpu core2duo
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$(EMULATOR) -cdrom build/barinkOS.iso -serial stdio -vga std -display gtk -m 2G -cpu core2duo
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debug: all
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$(EMULATOR) -cdrom build/barinkOS.iso -serial stdio -vga std -display gtk -m 2G -cpu core2duo -s -d int
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build_kernel: $(OBJ_LINK_LIST)
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$(CC) -T $(SRC_DIR)/kernel//linker.ld -o $(BUILD_DIR)/myos.bin \
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-ffreestanding -O2 -nostdlib $(OBJ_LINK_LIST) -lgcc
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-ffreestanding -ggdb -Og -nostdlib $(OBJ_LINK_LIST) -lgcc
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build_x86_64:
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$(AS) $(SRC_DIR)/cgc/x86_64/crti.s -o $(BUILD_DIR)/crti_64.o
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@ -7,30 +7,104 @@
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.set MAGIC, 0x1BADB002 /* 'magic number' lets bootloader find the header */
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.set CHECKSUM, -(MAGIC + FLAGS) /* checksum of above, to prove we are multiboot */
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.section .multiboot
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.section .multiboot.data, "aw"
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.align 4
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.long MAGIC
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.long FLAGS
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.long CHECKSUM
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.section .bss
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.align 16
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/*
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* Allocate initial stack
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*/
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.section .bootstrap_stack, "aw", @nobits
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stack_bottom:
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.skip 16384 # 16 KiB
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stack_top:
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.section .text
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.include "./src/kernel/Memory/GDT/gdt.s"
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.include "./src/kernel/irs_table.s"
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.include "./src/kernel/irq_table.s"
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.include "./src/kernel/Interrupts/idt/idt.s"
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.include "./src/kernel/Memory/paging.s"
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.include "./src/kernel/cpu.s"
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/*
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* Preallocate a couple pages to get us bootstrapped
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* Being carefull to not use any address the bootloader might
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* be using for its multiboot structures
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*/
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.section .bss, "aw", @nobits
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.align 4096
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boot_page_directory:
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.skip 4096
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boot_page_table:
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.skip 4096
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# More page tables may be required
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# Entry point
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.section .multiboot.text, "a"
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.global _start
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.type _start, @function
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.type _start, @function
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_start:
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# Get physical address of the boot_page_table
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movl $(boot_page_table - 0xC0000000), %edi
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# Map address 0
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movl $0, %esi
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# Map 1023 pages the 1024th being the VGA text buffer
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movl $1023, %ecx
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1: # Map the kernel
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cmpl $_kernel_start, %esi
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jl 2f
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cmpl $(_kernel_end - 0xC0000000), %esi
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jge 3f
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# Map physical address as "present and writable"
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movl %esi, %edx
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orl $0x003, %edx
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movl %edx, (%edi)
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2: # Size of page is 4096 bytes
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addl $4096, %esi
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# Size of entries in boot_page_table is 4 bytes
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addl $4, %edi
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# Loop to the next entry if we haven't finished.
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loop 1b
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3: # Map VGA video memory to 0xC03FF00 as "present, writable"
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movl $(0x000B8000 | 0x003), boot_page_table - 0xC0000000 + 1023 * 4
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# IMPORTANT NOTE FROM WIKI.OSDEV.ORG/HIGHER_HALF_X86_BARE_BONES
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# The page table is used at both page directory entry 0 (virtually from 0x0
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# to 0x3FFFFF) (thus identity mapping the kernel) and page directory entry
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# 768 (virtually from 0xC0000000 to 0xC03FFFFF) (thus mapping it in the
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# higher half). The kernel is identity mapped because enabling paging does
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# not change the next instruction, which continues to be physical. The CPU
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# would instead page fault if there was no identity mapping.\
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# Map the page table to both virtual addresss 0x00000000 and 0xC0000000
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movl $(boot_page_table - 0xC0000000 + 0x003), boot_page_directory - 0xC0000000 + 0
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movl $(boot_page_table - 0xC0000000 + 0x003), boot_page_directory - 0xC0000000 + 768 * 4
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# Set cr3 to the address of the boot_page_directory
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movl $(boot_page_directory - 0xC0000000), %ecx
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movl %ecx, %cr3
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# Enable paging and the write-protect bit
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movl %cr0, %ecx
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orl $0x80010000, %ecx
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movl %ecx, %cr0
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# Jump to higher half with an absolute jump
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lea 4f, %ecx
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jmp *%ecx
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.section .text
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4:
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# At this point, paging is fully set up and enabled
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isPaging:
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# Unmap the identity mapping as it is now unnecessary
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movl $0, boot_page_directory + 0
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# Reload cr3 to force tlb flush
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movl %cr3, %ecx
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movl %ecx, %cr3
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/*Setup the stack pointer to point to the beginning of our stack */
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/* I believe its a high address growing down to lower adress for the stack on x86*/
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mov $stack_top, %esp
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@ -44,16 +118,15 @@ _start:
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/* push the magic value */
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pushl %eax
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call early_main
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call early_main
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mov %cr0, %eax
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or $1, %eax
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mov %eax, %cr0
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mov %eax, %cr0
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call kernel_main
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//call kernel_main
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cli
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@ -61,6 +134,11 @@ _start:
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jmp 1b
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.size _start, . - _start
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.include "./src/kernel/Memory/GDT/gdt.s"
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.include "./src/kernel/irs_table.s"
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.include "./src/kernel/irq_table.s"
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.include "./src/kernel/Interrupts/idt/idt.s"
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.include "./src/kernel/Memory/paging.s"
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.include "./src/kernel/cpu.s"
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@ -21,7 +21,7 @@ void kterm_init () {
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kterm_row = 0;
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kterm_column = 0;
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kterm_color = vga_entry_color ( VGA_COLOR_LIGHT_GREY , VGA_COLOR_BLACK);
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kterm_buffer = (uint16_t*) 0xB8000;
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kterm_buffer = (uint16_t*) 0xC03FF000;
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for (size_t y = 0; y < VGA_HEIGHT; y++ ){
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for( size_t x = 0; x < VGA_WIDTH; x++){
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const size_t index = y * VGA_WIDTH + x;
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@ -1,11 +1,9 @@
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#include "kernel.h"
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extern "C" void kernel_main (BootInfo* bootinfo) {
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init_serial();
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pit_initialise();
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//InitializePaging();
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//Enable();
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//pit_initialise();
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startSuperVisorTerminal(bootinfo);
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}
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@ -16,8 +14,12 @@ extern "C" void early_main(unsigned long magic, unsigned long addr){
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* Initialize terminal interface
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* NOTE: This should be done later on , the magic value should be checked first.
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*/
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initGDT();
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kterm_init();
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init_serial();
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print_serial("Hello Higher half kernel!");
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printf("DDDDDDDDDDDDDDDD");
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return;
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/**
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* Check Multiboot magic number
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* NOTE: Printf call should not be a thing this early on ...
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@ -31,7 +33,7 @@ extern "C" void early_main(unsigned long magic, unsigned long addr){
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* Show a little banner for cuteness
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*/
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printf("|=== BarinkOS ===|\n");
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printf("Kernel Begin AT(0x%x)", kernel_begin);
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/**
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* Use the address given as an argument as the pointer
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@ -107,17 +109,17 @@ extern "C" void early_main(unsigned long magic, unsigned long addr){
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//memAlloc.free_block((void*) memory);
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//InitializePaging();
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IdentityMap();
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Enable();
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//IdentityMap();
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//Enable();
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}
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initGDT();
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init_idt();
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//initGDT();
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//init_idt();
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// Enable interrupts
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asm volatile("STI");
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//asm volatile("STI");
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CheckMBT( (multiboot_info_t *) addr);
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//CheckMBT( (multiboot_info_t *) addr);
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kernel_main(&bootinfo);
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@ -1,47 +1,45 @@
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/* The bootloader will look at this image and start execution at the symbol
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designated as the entry point. */
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ENTRY(_start)
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/* Tell where the various sections of the object files will be put in the final
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kernel image. */
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SECTIONS
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{
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/* Begin putting sections at 1 MiB, a conventional place for kernels to be
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loaded at by the bootloader. */
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. = 1M;
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kernel_begin = .;
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/* First put the multiboot header, as it is required to be put very early
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early in the image or the bootloader won't recognize the file format.
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Next we'll put the .text section. */
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.text BLOCK(4K) : ALIGN(4K)
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. = 0x00100000; /* place code at 1MB mark*/
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_kernel_start = .;
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kernel_begin = .; /* For legacy reasons */
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.multiboot.data : {
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*(.multiboot.data)
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}
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.multiboot.text : {
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*(multiboot.text)
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}
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. += 0xC0000000; /* Addresses in the following code need to be above the 3Gb mark */
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.text ALIGN (4K) : AT (ADDR (.text) - 0xC0000000)
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{
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*(.multiboot)
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*(.text)
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}
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/* Read-only data. */
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.rodata BLOCK(4K) : ALIGN(4K)
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.rodata ALIGN (4K) : AT (ADDR (.rodata) - 0xC0000000)
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{
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*(.rodata)
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}
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/* Read-write data (initialized) */
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.data BLOCK(4K) : ALIGN(4K)
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.data ALIGN (4K) : AT (ADDR (.data) - 0xC0000000)
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{
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*(.data)
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}
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/* Read-write data (uninitialized) and stack */
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.bss BLOCK(4K) : ALIGN(4K)
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.bss ALIGN (4K) : AT (ADDR (.bss) - 0xC0000000)
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{
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*(COMMON)
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*(.bss)
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*(.bootstrap_stack)
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}
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/* The compiler may produce other sections, by default it will put them in
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a segment with the same name. Simply add stuff here as needed. */
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kernel_end = .;
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_kernel_end = .;
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kernel_end = .; /* For legacy reasons */
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}
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