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Feat: FULLY IN 64-BIT MODE

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AfonsoCMSousa 2025-11-18 21:45:22 +00:00
parent c5cc6a0d8d
commit c1068d34e2
1 changed files with 131 additions and 83 deletions
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214
boot.asm
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@ -3,10 +3,15 @@
[bits 16] ; We start in 16-bit Real Mode
start:
mov bp, 0x7c00
mov sp, bp
xor ax, ax
mov ds, ax
mov es, ax
mov ss, ax
mov sp, 0x7c00
call clear_screen
mov ah, 0x00
mov al, 0x03
int 0x10
mov si, real_msg
call print_string
@ -36,116 +41,169 @@ print_string:
popa
ret
; --- Helper: Clear Screen ---
clear_screen:
pusha
mov ah, 0x00 ; Set Video Mode function
mov al, 0x03 ; 80x25 Text Mode
int 0x10
popa
ret
real_msg: db '[REAL] - Loaded successfully.', 0x0D, 0x0A, 0
; --- GDT (Global Descriptor Table) ---
align 8
gdt_start:
gdt_null: ; 8 bytes of zeros
dd 0x0
dd 0x0
gdt_null:
dq 0x0
gdt_code: ; Code Segment (0x08)
; Base=0, Limit=0xFFFFF, Access=0x9A, Flags=0xC
dw 0xffff ; Limit (bits 0-15)
dw 0x0 ; Base (bits 0-15)
db 0x0 ; Base (bits 16-23)
db 10011010b ; Access Byte (0x9A)
db 11001111b ; Flags (0xC) + Limit (bits 16-19)
db 0x0 ; Base (bits 24-31)
gdt_code32: ; 32-bit code segment (selector 0x08)
dw 0xffff ; Limit 0:15
dw 0x0000 ; Base 0:15
db 0x00 ; Base 16:23
db 10011010b ; Access: present, ring 0, code, executable, readable
db 11001111b ; Flags: 4KB granularity, 32-bit | Limit 16:19
db 0x00 ; Base 24:31
gdt_data: ; Data Segment (0x10)
; Base=0, Limit=0xFFFFF, Access=0x92, Flags=0xC
gdt_data32: ; 32-bit data segment (selector 0x10)
dw 0xffff
dw 0x0
db 0x0
db 10010010b ; Access Byte (0x92)
db 11001111b ; Flags (0xC) + Limit
db 0x0
dw 0x0000
db 0x00
db 10010010b ; Access: present, ring 0, data, writable
db 11001111b
db 0x00
gdt_code64: ; 64-bit code segment (selector 0x18)
dw 0xffff
dw 0x0000
db 0x00
db 10011010b ; Access: present, ring 0, code, executable, readable
db 10101111b ; Flags: 4KB granularity, 64-bit, limit 16:19
db 0x00
gdt_data64: ; 64-bit data segment (selector 0x20)
dw 0xffff
dw 0x0000
db 0x00
db 10010010b
db 10101111b
db 0x00
gdt_end:
gdt_descriptor:
dw gdt_end - gdt_start - 1 ; Size (Limit)
dd gdt_start ; Start Address
dw gdt_end - gdt_start - 1
dd gdt_start
; ==================================================
; 32-BIT PROTECTED MODE
; ==================================================
[bits 32]
init_pm:
; 5. Update Segment Registers
; Now that we are in 32-bit, we must point all segment registers
; to our new Data Segment (0x10)
; Set up segments
mov ax, 0x10
mov ds, ax
mov ss, ax
mov es, ax
mov fs, ax
mov gs, ax
mov ss, ax
mov esp, 0x90000
mov ebp, 0x90000 ; Update stack to a safe 32-bit area
mov esp, ebp
; Print message in Protected Mode
; Print to VGA memory
mov edi, 0xb8000
mov al, 'P'
mov ah, 0x0f
mov [edi], ax
add edi, 2
mov al, 'M'
mov [edi], ax
add edi, 2
mov al, '3'
mov [edi], ax
add edi, 2
mov al, '2'
mov [edi], ax
; 2. Set up Paging
mov eax, pml4_table
; Set up page tables for identity mapping first 2MB
; PML4[0] -> PDPT
mov edi, 0x1000
mov dword [edi], 0x2003 ; Present, Writable, points to 0x2000
add edi, 4
mov dword [edi], 0
; PDPT[0] -> PD
mov edi, 0x2000
mov dword [edi], 0x3003 ; Present, Writable, points to 0x3000
add edi, 4
mov dword [edi], 0
; PD[0] -> 2MB page at physical 0x0
mov edi, 0x3000
mov dword [edi], 0x83 ; Present, Writable, Page Size (2MB)
add edi, 4
mov dword [edi], 0
; Load CR3 with PML4 address
mov eax, 0x1000
mov cr3, eax
; Link PML4 -> PDPT
mov dword [pml4_table], pdpt_table + 0x3
mov dword [pml4_table + 4], 0x0
; Link PDPT -> PD
mov dword [pdpt_table], pd_table + 0x3
mov dword [pdpt_table + 4], 0x0
; Link PD -> 2MB Physical Page 0
mov dword [pd_table], 0x83
mov dword [pd_table + 4], 0x0
; 3. Enable PAE
; Enable PAE (Physical Address Extension)
mov eax, cr4
or eax, 0x20
mov cr4, eax
; 4. Enable Long Mode in EFER
; Enable Long Mode in EFER MSR
mov ecx, 0xC0000080
rdmsr
or eax, 0x00000100
or eax, 0x100
wrmsr
; 5. Enable Paging
; Enable Paging (activates Long Mode)
mov eax, cr0
or eax, 0x80000000
mov cr0, eax
; 6. Print "SoraOS Protected" directly to Video Memory
; We can't use BIOS interrupts anymore! We must write to 0xB8000.
mov ebx, 0xb8000
mov byte [ebx], 'S'
mov byte [ebx+1], 0x0f ; White on Black
mov byte [ebx+2], 'O'
mov byte [ebx+3], 0x0f
mov byte [ebx+4], 'R'
mov byte [ebx+5], 0x0f
mov byte [ebx+6], 'A'
mov byte [ebx+7], 0x0f
mov byte [ebx+8], ' '
mov byte [ebx+9], 0x0f
mov byte [ebx+10], 'P'
mov byte [ebx+11], 0x0f
mov byte [ebx+12], 'M'
mov byte [ebx+13], 0x0f
; Far jump to 64-bit code
jmp 0x18:long_mode_start
jmp $
; --- 64-bit Long Mode ---
[bits 64]
long_mode_start:
; Set up segments (most are ignored in 64-bit mode)
mov ax, 0x20
mov ds, ax
mov es, ax
mov fs, ax
mov gs, ax
mov ss, ax
; Set up stack
mov rsp, 0x90000
; Clear screen and print "SORA OS 64"
mov rdi, 0xb8000
mov rcx, 80*25
mov ax, 0x0f20 ; White space
rep stosw
; Print message
mov rdi, 0xb8000
mov rsi, long_msg
call print_string_64
; Hang
jmp $
; --- 64-bit Print String ---
print_string_64:
mov ah, 0x0f ; White on black
.loop:
lodsb
test al, al
jz .done
stosw ; Write character + attribute
jmp .loop
.done:
ret
long_msg: db 'SoraOS 64-BIT', 0
; --- The Magic Boot Sector Footer ---
; Fill the rest of the 512 bytes with zeros
times 510-($-$$) db 0
@ -161,13 +219,3 @@ pdpt_table:
pd_table:
resb 4096
section .data
gdt_ptr:
dw (gdt_end - gdt_start - 1)
dq gdt_start
gdt_start:
dq 0x0000000000000000
dq 0x00AF9A000000FFFF ; Code
dq 0x00AF92000000FFFF ; Data
gdt_end: