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heimskrheimskr
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Add initial code from Ring Zero and Lower
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‎.gitignore‎

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kernel
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iso
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# Prerequisites
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*.d
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‎CREDITS‎

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Thanks to Ring Zero and Lower for providing the base for this project:
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http://ringzeroandlower.com/2017/08/08/x86-64-kernel-boot.html

‎Makefile‎

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# Based on code by Ring Zero and Lower: http://ringzeroandlower.com/2017/08/08/x86-64-kernel-boot.html
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CC = x86_64-elf-g++
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AS = x86_64-elf-gcc
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SHARED_FLAGS = -fno-builtin -O2 -nostdinc -nostdlib -ffreestanding -g -Wall -Wextra -Werror -I. -MMD -mno-red-zone\
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-mcmodel=kernel -fno-pie
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CFLAGS = $(SHARED_FLAGS) -fno-exceptions -fno-rtti
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ASFLAGS = $(SHARED_FLAGS) -Wa,--divide
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GRUB ?= grub
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ASSEMBLED := boot.o
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COMPILED := kernel.o
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DFILES = $(patsubst %.o,%.d,$(ASSEMBLED) $(COMPILED))
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OBJS = $(ASSEMBLED) $(COMPILED)
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ISO_FILE := kernel.iso
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all: kernel
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define COMPILED_TEMPLATE
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$(1): $(patsubst %.o,%.cpp,$(1))
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$(CC) $(CFLAGS) -c $$< -o $$@
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endef
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define ASSEMBLED_TEMPLATE
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$(1): $(patsubst %.o,%.S,$(1))
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$(AS) $(ASFLAGS) -c $$< -o $$@
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endef
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$(foreach fname,$(COMPILED),$(eval $(call COMPILED_TEMPLATE,$(fname))))
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$(foreach fname,$(ASSEMBLED),$(eval $(call ASSEMBLED_TEMPLATE,$(fname))))
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kernel: $(OBJS) kernel.ld Makefile
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$(CC) -z max-page-size=0x1000 $(CFLAGS) -no-pie -Wl,--build-id=none -T kernel.ld -o $@ $(OBJS)
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iso: $(ISO_FILE)
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$(ISO_FILE): kernel
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mkdir -p iso/boot/grub
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cp grub.cfg iso/boot/grub/
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cp kernel iso/boot/
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$(GRUB)-mkrescue -o $(ISO_FILE) iso
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run: $(ISO_FILE)
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qemu-system-x86_64 -cdrom $(ISO_FILE) -serial stdio -m 1024M
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clean:
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find -name "*~" -delete
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rm -rf *.o **/*.o $(DFILES) kernel iso
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$(OBJS): Makefile
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-include $(DFILES)

‎arch/x86_64/control_register.h‎

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#ifndef _ARCH_X86_64_CONTROL_REGISTER_H_
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#define _ARCH_X86_64_CONTROL_REGISTER_H_
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#define CONTROL_REGISTER0_PROTECTED_MODE_ENABLED (1 << 0)
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#define CONTROL_REGISTER0_EXTENSION_TYPE (1 << 4)
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#define CONTROL_REGISTER0_PAGE (1 << 31)
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#define CONTROL_REGISTER4_PAGE_SIZE_EXTENSION (1 << 4)
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#define CONTROL_REGISTER4_PHYSICAL_ADDRESS_EXTENSION (1 << 5)
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#endif // _ARCH_X86_64_CONTROL_REGISTER_H_

‎arch/x86_64/gdt.h‎

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#ifndef _ARCH_X86_64_GDT_H_
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#define _ARCH_X86_64_GDT_H_
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#define GDT_ENTRY_SIZE 8
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#define GDT_FLAG_FOUR_KILOBYTE_GRANULARITY (1 << 3)
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#define GDT_FLAG_32BIT_PROTECTED_MODE (1 << 2)
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#define GDT_FLAG_64BIT_MODE (1 << 1)
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#define GDT_ACCESS_PRESENT (1 << 7)
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#define GDT_ACCESS_PRIVILEGE_RING0 (0x0 << 5)
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#define GDT_ACCESS_PRIVILEGE_RING1 (0x1 << 5)
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#define GDT_ACCESS_PRIVILEGE_RING2 (0x2 << 5)
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#define GDT_ACCESS_PRIVILEGE_RING3 (0x3 << 5)
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#define GDT_ACCESS_EXECUTABLE (1 << 3)
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#define GDT_ACCESS_DIRECTION_DOWN (1 << 2)
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#define GDT_ACCESS_READABLE_WRITABLE (1 << 1)
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#define DECLARE_GDT_ENTRY(base, limit, flags, access) \
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( \
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(((((base)) >> 24) & 0xFF) << 56) | \
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((((flags)) & 0xF) << 52) | \
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(((((limit)) >> 16) & 0xF) << 48) | \
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(((((access) | (1 << 4))) & 0xFF) << 40) | \
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((((base)) & 0xFFF) << 16) | \
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(((limit)) & 0xFFFF) \
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)
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#define GDT_FIRST_ENTRY 0
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#define GDT_KERNEL_ENTRY \
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DECLARE_GDT_ENTRY(0, 0, \
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GDT_FLAG_64BIT_MODE, \
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GDT_ACCESS_PRESENT | \
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GDT_ACCESS_PRIVILEGE_RING0 | \
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GDT_ACCESS_EXECUTABLE) \
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#define GDT_TABLE_ALIGNMENT 0x1000
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#define GDT_TABLE_SIZE 0x800
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#endif // _ARCH_X86_64_GDT_H_

‎arch/x86_64/kernel.h‎

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#ifndef _ARCH_X86_64_KERNEL_H_
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#define _ARCH_X86_64_KERNEL_H_
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#include <arch/x86_64/control_register.h>
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// START macros must have the same value in the kernel linker script
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#define KERNEL_PHYSICAL_START 0x0000000000400000
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#define KERNEL_VIRTUAL_START 0xFFFFFFFF80400000
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#define KERNEL_GDT_ENTRY 1
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#define KERNEL_CR0 \
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( \
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CONTROL_REGISTER0_PAGE | \
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CONTROL_REGISTER0_PROTECTED_MODE_ENABLED | \
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CONTROL_REGISTER0_EXTENSION_TYPE \
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)
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#define KERNEL_CR4 (CONTROL_REGISTER4_PHYSICAL_ADDRESS_EXTENSION)
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#endif // _ARCH_X86_64_KERNEL_H_

‎arch/x86_64/mmu.h‎

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#ifndef _ARCH_X86_64_MMU_H_
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#define _ARCH_X86_64_MMU_H_
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#define BOOT_PHYSICAL_VIRTUAL_OFFSET \
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(KERNEL_VIRTUAL_START - KERNEL_PHYSICAL_START)
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#define KERNEL_VIRTUAL_START_PAGE_DIRECTORY_ENTRY \
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(KERNEL_VIRTUAL_START / LEVEL_TWO_PAGE_SIZE)
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#define PML4_SIZE 0x1000
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#define PML4_ALIGNMENT 0x1000
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#define PML4_ENTRY_SIZE 8
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#define PML4_ADDR_TO_ENTRY_INDEX(addr) (((addr) >> 39) & 0x1FF)
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#define PDPT_SIZE 0x1000
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#define PDPT_ALIGNMENT 0x1000
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#define PDPT_ENTRY_SIZE 8
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#define PDPT_ADDR_TO_ENTRY_INDEX(addr) (((addr) >> 30) & 0x1FF)
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#define PAGE_DIRECTORY_SIZE 0x1000
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#define PAGE_DIRECTORY_ALIGNMENT 0x1000
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#define PAGE_DIRECTORY_ENTRY_SIZE 8
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#define PAGE_TABLE_SIZE 0x1000
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#define PAGE_TABLE_ALIGNMENT 0x1000
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#define PAGE_TABLE_ENTRY_SIZE 8
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#define MMU_PRESENT (1 << 0)
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#define MMU_WRITABLE (1 << 1)
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#define MMU_USER_MEMORY (1 << 2)
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#define MMU_PDE_TWO_MB (1 << 7)
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#endif // _ARCH_X86_64_MMU_H_

‎arch/x86_64/msr.h‎

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#ifndef _ARCH_I386_MSR_H_
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#define _ARCH_I386_MSR_H_
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#define MSR_EFER 0xC0000080
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#define MSR_EFER_LME (1 << 8)
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#endif // _ARCH_I386_MSR_H_

‎boot.S‎

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# Based on code by Ring Zero and Lower: http://ringzeroandlower.com/2017/08/08/x86-64-kernel-boot.html
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#include "arch/x86_64/gdt.h"
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#include "arch/x86_64/mmu.h"
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#include "kernel.h"
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#include "sizes.h"
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#include "multiboot2.h"
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#include "arch/x86_64/msr.h"
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.SET HEADER_LENGTH, header_end - header_start
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.SET CHECKSUM, -(MULTIBOOT2_HEADER_MAGIC + MULTIBOOT_ARCHITECTURE_I386 + HEADER_LENGTH)
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.section .multiboot
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header_start:
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.long MULTIBOOT2_HEADER_MAGIC
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.long MULTIBOOT_ARCHITECTURE_I386
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.long HEADER_LENGTH
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.long CHECKSUM
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# multiboot tags go here.
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.short MULTIBOOT_HEADER_TAG_END
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.short 0 # flags, none set
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.long 8 # size, including itself (short + short + long)
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header_end:
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.code32
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.section .bss
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.comm pml4, PML4_SIZE, PML4_ALIGNMENT
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.comm low_pdpt, PDPT_SIZE, PDPT_ALIGNMENT
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.comm high_pdpt, PDPT_SIZE, PDPT_ALIGNMENT
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.comm low_page_directory_table, PAGE_DIRECTORY_SIZE, PAGE_DIRECTORY_ALIGNMENT
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.comm high_page_directory_table, PAGE_DIRECTORY_SIZE, PAGE_DIRECTORY_ALIGNMENT
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.comm tmp_stack, KERNEL_BOOT_STACK_SIZE, KERNEL_BOOT_STACK_ALIGNMENT
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.data
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.align GDT_TABLE_ALIGNMENT
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gdt_table:
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.8byte GDT_FIRST_ENTRY
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.8byte GDT_KERNEL_ENTRY
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gdt_table_end:
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.skip (GDT_TABLE_SIZE - (gdt_table_end - gdt_table))
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gdt_ptr:
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.short GDT_TABLE_SIZE - 1
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.long gdt_table
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.section .text
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.global _start
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.type _start, @function
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_start:
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movl $tmp_stack + KERNEL_BOOT_STACK_SIZE, %esp
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movl $low_pdpt, %eax
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or $(MMU_PRESENT | MMU_WRITABLE), %eax
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movl %eax, pml4 + (PML4_ADDR_TO_ENTRY_INDEX(KERNEL_PHYSICAL_START) * PML4_ENTRY_SIZE)
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movl $high_pdpt, %eax
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or $(MMU_PRESENT | MMU_WRITABLE), %eax
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movl %eax, pml4 + (PML4_ADDR_TO_ENTRY_INDEX(KERNEL_VIRTUAL_START) * PML4_ENTRY_SIZE)
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movl $low_page_directory_table, %eax
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or $(MMU_PRESENT | MMU_WRITABLE), %eax
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movl %eax, low_pdpt + (PDPT_ADDR_TO_ENTRY_INDEX(KERNEL_PHYSICAL_START) * PDPT_ENTRY_SIZE)
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movl $high_page_directory_table, %eax
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or $(MMU_PRESENT | MMU_WRITABLE), %eax
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movl %eax, high_pdpt + (PDPT_ADDR_TO_ENTRY_INDEX(KERNEL_VIRTUAL_START) * PDPT_ENTRY_SIZE)
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mov $0, %ecx
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movl $_kernel_physical_end, %esi
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shrl $TWO_MEGABYTES_SHIFT, %esi
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addl $1, %esi
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page_directory_table_loop:
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movl $TWO_MEGABYTES, %eax
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mul %ecx
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or $(MMU_PRESENT | MMU_WRITABLE | MMU_PDE_TWO_MB), %eax
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movl %eax, low_page_directory_table(, %ecx, PAGE_DIRECTORY_ENTRY_SIZE)
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movl %eax, high_page_directory_table(, %ecx, PAGE_DIRECTORY_ENTRY_SIZE)
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inc %ecx
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cmp %esi, %ecx
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jne page_directory_table_loop # If not equal, redo loop
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movl $pml4, %eax
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movl %eax, %cr3
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movl $KERNEL_CR4, %eax
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movl %eax, %cr4
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movl $MSR_EFER, %ecx
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rdmsr
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or $MSR_EFER_LME, %eax
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wrmsr
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movl $KERNEL_CR0, %eax
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movl %eax, %cr0
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lgdt gdt_ptr
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ljmp $(KERNEL_GDT_ENTRY * GDT_ENTRY_SIZE), $_start64
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cli
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hlt
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.code64
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.global _start64
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.type _start64, @function
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_start64:
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# Setup segment selectors
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movw $0, %ax
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movw %ax, %ds
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movw %ax, %es
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movw %ax, %fs
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movw %ax, %gs
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movw %ax, %ss
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call _Z11kernel_mainv
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# Should never reach here
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cli
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hlt
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1:
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jmp 1b

‎grub.cfg‎

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set timeout=0
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set default=0
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menuentry "kernel" {
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multiboot2 /boot/kernel
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}

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