Feat: FULLY IN 64-BIT MODE
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AfonsoCMSousa
parent
c5cc6a0d8d
commit
c1068d34e2
214
boot.asm
214
boot.asm
@ -3,10 +3,15 @@
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[bits 16] ; We start in 16-bit Real Mode
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[bits 16] ; We start in 16-bit Real Mode
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start:
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start:
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mov bp, 0x7c00
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xor ax, ax
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mov sp, bp
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mov ds, ax
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mov es, ax
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mov ss, ax
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mov sp, 0x7c00
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call clear_screen
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mov ah, 0x00
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mov al, 0x03
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int 0x10
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mov si, real_msg
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mov si, real_msg
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call print_string
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call print_string
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@ -36,116 +41,169 @@ print_string:
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popa
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popa
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ret
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ret
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; --- Helper: Clear Screen ---
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clear_screen:
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pusha
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mov ah, 0x00 ; Set Video Mode function
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mov al, 0x03 ; 80x25 Text Mode
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int 0x10
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popa
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ret
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real_msg: db '[REAL] - Loaded successfully.', 0x0D, 0x0A, 0
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real_msg: db '[REAL] - Loaded successfully.', 0x0D, 0x0A, 0
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; --- GDT (Global Descriptor Table) ---
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align 8
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gdt_start:
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gdt_start:
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gdt_null: ; 8 bytes of zeros
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gdt_null:
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dd 0x0
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dq 0x0
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dd 0x0
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gdt_code: ; Code Segment (0x08)
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gdt_code32: ; 32-bit code segment (selector 0x08)
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; Base=0, Limit=0xFFFFF, Access=0x9A, Flags=0xC
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dw 0xffff ; Limit 0:15
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dw 0xffff ; Limit (bits 0-15)
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dw 0x0000 ; Base 0:15
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dw 0x0 ; Base (bits 0-15)
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db 0x00 ; Base 16:23
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db 0x0 ; Base (bits 16-23)
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db 10011010b ; Access: present, ring 0, code, executable, readable
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db 10011010b ; Access Byte (0x9A)
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db 11001111b ; Flags: 4KB granularity, 32-bit | Limit 16:19
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db 11001111b ; Flags (0xC) + Limit (bits 16-19)
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db 0x00 ; Base 24:31
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db 0x0 ; Base (bits 24-31)
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gdt_data: ; Data Segment (0x10)
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gdt_data32: ; 32-bit data segment (selector 0x10)
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; Base=0, Limit=0xFFFFF, Access=0x92, Flags=0xC
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dw 0xffff
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dw 0xffff
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dw 0x0
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dw 0x0000
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db 0x0
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db 0x00
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db 10010010b ; Access Byte (0x92)
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db 10010010b ; Access: present, ring 0, data, writable
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db 11001111b ; Flags (0xC) + Limit
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db 11001111b
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db 0x0
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db 0x00
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gdt_code64: ; 64-bit code segment (selector 0x18)
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dw 0xffff
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dw 0x0000
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db 0x00
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db 10011010b ; Access: present, ring 0, code, executable, readable
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db 10101111b ; Flags: 4KB granularity, 64-bit, limit 16:19
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db 0x00
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gdt_data64: ; 64-bit data segment (selector 0x20)
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dw 0xffff
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dw 0x0000
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db 0x00
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db 10010010b
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db 10101111b
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db 0x00
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gdt_end:
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gdt_end:
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gdt_descriptor:
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gdt_descriptor:
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dw gdt_end - gdt_start - 1 ; Size (Limit)
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dw gdt_end - gdt_start - 1
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dd gdt_start ; Start Address
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dd gdt_start
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; ==================================================
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; ==================================================
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; 32-BIT PROTECTED MODE
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; 32-BIT PROTECTED MODE
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; ==================================================
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; ==================================================
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[bits 32]
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[bits 32]
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init_pm:
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init_pm:
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; 5. Update Segment Registers
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; Set up segments
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; Now that we are in 32-bit, we must point all segment registers
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; to our new Data Segment (0x10)
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mov ax, 0x10
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mov ax, 0x10
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mov ds, ax
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mov ds, ax
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mov ss, ax
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mov es, ax
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mov es, ax
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mov fs, ax
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mov fs, ax
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mov gs, ax
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mov gs, ax
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mov ss, ax
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mov esp, 0x90000
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mov ebp, 0x90000 ; Update stack to a safe 32-bit area
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; Print message in Protected Mode
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mov esp, ebp
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; Print to VGA memory
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mov edi, 0xb8000
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mov al, 'P'
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mov ah, 0x0f
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mov [edi], ax
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add edi, 2
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mov al, 'M'
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mov [edi], ax
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add edi, 2
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mov al, '3'
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mov [edi], ax
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add edi, 2
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mov al, '2'
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mov [edi], ax
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; 2. Set up Paging
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; Set up page tables for identity mapping first 2MB
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mov eax, pml4_table
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; PML4[0] -> PDPT
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mov edi, 0x1000
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mov dword [edi], 0x2003 ; Present, Writable, points to 0x2000
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add edi, 4
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mov dword [edi], 0
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; PDPT[0] -> PD
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mov edi, 0x2000
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mov dword [edi], 0x3003 ; Present, Writable, points to 0x3000
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add edi, 4
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mov dword [edi], 0
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; PD[0] -> 2MB page at physical 0x0
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mov edi, 0x3000
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mov dword [edi], 0x83 ; Present, Writable, Page Size (2MB)
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add edi, 4
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mov dword [edi], 0
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; Load CR3 with PML4 address
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mov eax, 0x1000
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mov cr3, eax
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mov cr3, eax
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; Link PML4 -> PDPT
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; Enable PAE (Physical Address Extension)
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mov dword [pml4_table], pdpt_table + 0x3
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mov dword [pml4_table + 4], 0x0
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; Link PDPT -> PD
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mov dword [pdpt_table], pd_table + 0x3
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mov dword [pdpt_table + 4], 0x0
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; Link PD -> 2MB Physical Page 0
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mov dword [pd_table], 0x83
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mov dword [pd_table + 4], 0x0
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; 3. Enable PAE
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mov eax, cr4
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mov eax, cr4
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or eax, 0x20
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or eax, 0x20
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mov cr4, eax
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mov cr4, eax
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; 4. Enable Long Mode in EFER
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; Enable Long Mode in EFER MSR
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mov ecx, 0xC0000080
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mov ecx, 0xC0000080
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rdmsr
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rdmsr
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or eax, 0x00000100
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or eax, 0x100
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wrmsr
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wrmsr
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; 5. Enable Paging
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; Enable Paging (activates Long Mode)
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mov eax, cr0
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mov eax, cr0
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or eax, 0x80000000
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or eax, 0x80000000
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mov cr0, eax
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mov cr0, eax
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; 6. Print "SoraOS Protected" directly to Video Memory
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; Far jump to 64-bit code
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; We can't use BIOS interrupts anymore! We must write to 0xB8000.
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jmp 0x18:long_mode_start
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mov ebx, 0xb8000
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mov byte [ebx], 'S'
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mov byte [ebx+1], 0x0f ; White on Black
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mov byte [ebx+2], 'O'
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mov byte [ebx+3], 0x0f
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mov byte [ebx+4], 'R'
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mov byte [ebx+5], 0x0f
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mov byte [ebx+6], 'A'
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mov byte [ebx+7], 0x0f
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mov byte [ebx+8], ' '
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mov byte [ebx+9], 0x0f
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mov byte [ebx+10], 'P'
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mov byte [ebx+11], 0x0f
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mov byte [ebx+12], 'M'
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mov byte [ebx+13], 0x0f
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jmp $
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jmp $
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; --- 64-bit Long Mode ---
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[bits 64]
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long_mode_start:
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; Set up segments (most are ignored in 64-bit mode)
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mov ax, 0x20
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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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; Set up stack
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mov rsp, 0x90000
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; Clear screen and print "SORA OS 64"
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mov rdi, 0xb8000
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mov rcx, 80*25
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mov ax, 0x0f20 ; White space
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rep stosw
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; Print message
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mov rdi, 0xb8000
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mov rsi, long_msg
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call print_string_64
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; Hang
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jmp $
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; --- 64-bit Print String ---
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print_string_64:
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mov ah, 0x0f ; White on black
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.loop:
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lodsb
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test al, al
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jz .done
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stosw ; Write character + attribute
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jmp .loop
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.done:
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ret
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long_msg: db 'SoraOS 64-BIT', 0
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; --- The Magic Boot Sector Footer ---
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; --- The Magic Boot Sector Footer ---
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; Fill the rest of the 512 bytes with zeros
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; Fill the rest of the 512 bytes with zeros
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times 510-($-$$) db 0
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times 510-($-$$) db 0
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@ -161,13 +219,3 @@ pdpt_table:
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pd_table:
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pd_table:
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resb 4096
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resb 4096
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section .data
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gdt_ptr:
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dw (gdt_end - gdt_start - 1)
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dq gdt_start
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gdt_start:
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dq 0x0000000000000000
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dq 0x00AF9A000000FFFF ; Code
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dq 0x00AF92000000FFFF ; Data
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gdt_end:
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