mirror of
https://github.com/Fennix-Project/Kernel.git
synced 2025-05-30 00:08:03 +00:00
153 lines
2.6 KiB
NASM
153 lines
2.6 KiB
NASM
; https://wiki.osdev.org/Creating_a_64-bit_kernel
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; https://wiki.osdev.org/Entering_Long_Mode_Directly
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KERNEL_VIRTUAL_BASE equ 0xFFFFFFFF80000000 ; 512GB
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KERNEL_LMA equ 0x1000000 ; 16MB
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KERNEL_STACK_SIZE equ 0x4000 ; 16KB
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extern Multiboot2Entry
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extern BootPageTable
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extern UpdatePageTable
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extern UpdatePageTable64
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extern DetectCPUID
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extern Detect64Bit
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extern LoadGDT32
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global MB2_start
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extern MB2_start_c
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[bits 32]
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section .bootstrap.data
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global MB2_HeaderMagic
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MB2_HeaderMagic:
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times (0x64) dq 0
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global MB2_HeaderInfo
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MB2_HeaderInfo:
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times (0x64) dq 0
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section .bootstrap.text
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MB2_start:
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cli
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; mov word [0xb8F00], 0x072E ; .
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mov [MB2_HeaderMagic], eax
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mov [MB2_HeaderInfo], ebx
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; We need to check if the CPU supports 64-bit mode
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call DetectCPUID
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call Detect64Bit
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; mov word [0xb8F02], 0x072E ; .
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mov ecx, cr0
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and ecx, 0x7fffffff ; Clear PG
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mov cr0, ecx
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mov ecx, cr4
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or ecx, 0x10 ; Set PSE
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or ecx, 0x20 ; Set PAE
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mov cr4, ecx
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; Load the GDT and update the page table
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call LoadGDT32
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call UpdatePageTable
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; Load the new page table
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mov edi, BootPageTable
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mov cr3, edi
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; mov word [0xb8F04], 0x072E ; .
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; Enable long mode
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mov ecx, 0xC0000080 ; EFER
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rdmsr
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or eax, 0x800 | 0x100 | 0x1 ; Set LME, LMA, SCE
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wrmsr
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mov ecx, cr0
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or ecx, (0x80000000 | 0x1) ; Set PG and PE
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mov cr0, ecx
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lgdt [GDT64.Ptr]
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; xor eax, eax
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; sgdt [eax]
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; test eax, eax
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; jz .InvalidGDT
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; .InvalidGDT:
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; mov word [0xb8F07], 0x4 ; Red
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; hlt
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jmp GDT64.code:HigherHalfStart
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[bits 64]
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HigherHalfStart:
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cli
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; mov word [0xb8F06], 0x072E ; .
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call UpdatePageTable64
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; Load the new page table
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mov rdi, BootPageTable
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mov cr3, rdi
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mov ax, GDT64.data
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mov ds, ax
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mov es, ax
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mov fs, ax
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mov gs, ax
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mov ss, ax
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; mov word [0xb8F08], 0x072E ; .
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mov rsp, (KernelStack + KERNEL_STACK_SIZE)
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mov rbp, (KernelStack + KERNEL_STACK_SIZE)
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cld
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cli
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call Multiboot2Entry
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.Loop:
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hlt
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jmp .Loop
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section .bootstrap.bss
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align 16
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KernelStack:
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resb KERNEL_STACK_SIZE
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; Access bits
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PRESENT equ 1 << 7
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NOT_SYS equ 1 << 4
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EXEC equ 1 << 3
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DC equ 1 << 2
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RW equ 1 << 1
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ACCESSED equ 1 << 0
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; Flags bits
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GRAN_4K equ 1 << 7
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SZ_32 equ 1 << 6
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LONG_MODE equ 1 << 5
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section .bootstrap.data
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GDT64:
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.null: equ $ - GDT64
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dq 0
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.code: equ $ - GDT64
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dd 0xFFFF
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db 0
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db PRESENT | NOT_SYS | EXEC | RW
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db GRAN_4K | LONG_MODE | 0xF
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db 0
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.data: equ $ - GDT64
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dd 0xFFFF
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db 0
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db PRESENT | NOT_SYS | RW
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db GRAN_4K | SZ_32 | 0xF
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db 0
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.tss: equ $ - GDT64
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dd 0x00000068
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dd 0x00CF8900
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.Ptr:
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dw $ - GDT64 - 1
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dq GDT64
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