262 lines
4.2 KiB
NASM
262 lines
4.2 KiB
NASM
%define MAGIC 0x1BADB002
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%define ALIGN 1<<0
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%define MMAP 1<<1
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%define VID 1<<2
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%define FLAGS (ALIGN | MMAP | VID)
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section .multiboot.data
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dd MAGIC
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dd FLAGS
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dd -(MAGIC + FLAGS)
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dd 0 ; header_addr
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dd 0 ; load_addr
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dd 0 ; load_end_addr
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dd 0 ; bss_end_addr
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dd 0 ; entry_addr
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dd 1 ; mode_type
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dd 80 ; width
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dd 25 ; height
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dd 0 ; depth
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section .multiboot.text
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global _start
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_start:
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cli
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; Check if EAX contains this magic value that our bootloader should've set
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cmp eax, 0x2BADB002
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jne halt
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; Setup table
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; Identity page 0-4 mib
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mov eax, 0
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mov edx, 0
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.fill_table:
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mov ecx, edx
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or ecx, 7
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mov [boot_page_tab-0xC0000000+eax*4], ecx
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add edx, 0x1000
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inc eax
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cmp eax, 1024
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jne .fill_table
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mov ecx, boot_page_tab
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sub ecx, 0xC0000000
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or ecx, 7
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mov [boot_page_dir-0xC0000000], ecx
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mov [boot_page_dir-0xC0000000+768*4], ecx
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; Enable paging
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mov eax, boot_page_dir
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sub eax, 0xC0000000
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mov cr3, eax
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mov eax, cr0
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or eax, (1<<31)
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mov cr0, eax
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jmp higher_half
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section .text
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higher_half:
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; Un-identity-map kernel
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mov dword [boot_page_dir], 2
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; Add KERNEL_VMA to the address of the multiboot info struct
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add ebx, 0xC0000000
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; Load GDT
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lgdt [gdtp]
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; Offset to kernel data descriptor
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mov ax, 0x10
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mov es, ax
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mov ds, 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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; Offset to kernel code descriptor
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jmp 0x8:.use_code_seg
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.use_code_seg:
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mov esp, stack_bottom
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mov ebp, esp
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push ebx
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extern kernel
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call kernel
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cli
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halt:
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hlt
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jmp halt
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global pit_isr
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pit_isr:
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extern pit_handler
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call pit_handler
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iret
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global jmp_user_mode
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jmp_user_mode:
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mov ax, (4*8) | 3
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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 ; SS is handled by iret
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mov eax, [esp+4] ; esp arg
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mov edx, [esp+8] ; eip arg
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push (4*8) | 3
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push eax
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pushf
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push (3*8) | 3
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push edx
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iret
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global flush_tss
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flush_tss:
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ltr [esp+4]
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ret
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extern ctx
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global task_switch
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task_switch:
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push ebx
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push esi
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push edi
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push ebp
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mov esi, [ctx+28]
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; Return if only one process is running
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mov eax, [esi+12]
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cmp eax, 0
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je ret
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; Check if using same virtual memory
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cmp [esi+8], [eax+8]
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je .ret
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mov ecx, [eax+8]
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mov cr3, ecx
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.ret:
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pop ebp
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pop edi
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pop esi
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pop ebx
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ret
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extern exception_handler
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%macro isr_err_stub 1
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isr_stub_%+%1:
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cli
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push %1
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pusha
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call exception_handler
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popa
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add esp, 8
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iret
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%endmacro
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%macro isr_no_err_stub 1
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isr_stub_%+%1:
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cli
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push 0
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push %1
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pusha
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call exception_handler
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popa
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add esp, 12
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iret
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%endmacro
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isr_no_err_stub 0
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isr_no_err_stub 1
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isr_no_err_stub 2
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isr_no_err_stub 3
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isr_no_err_stub 4
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isr_no_err_stub 5
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isr_no_err_stub 6
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isr_no_err_stub 7
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isr_err_stub 8
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isr_no_err_stub 9
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isr_err_stub 10
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isr_err_stub 11
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isr_err_stub 12
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isr_err_stub 13
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isr_err_stub 14
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isr_no_err_stub 15
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isr_no_err_stub 16
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isr_err_stub 17
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isr_no_err_stub 18
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isr_no_err_stub 19
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isr_no_err_stub 20
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isr_no_err_stub 21
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isr_no_err_stub 22
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isr_no_err_stub 23
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isr_no_err_stub 24
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isr_no_err_stub 25
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isr_no_err_stub 26
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isr_no_err_stub 27
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isr_no_err_stub 28
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isr_no_err_stub 29
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isr_err_stub 30
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isr_no_err_stub 31
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global isr_stub_table
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isr_stub_table:
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%assign i 0
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%rep 32
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dd isr_stub_%+i
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%assign i i+1
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%endrep
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section .data
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; GDT for a flat memory layout
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; We get access to all memory and can utilize paging
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global gdt
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gdt:
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gdt_null:
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dq 0
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gdt_kern_code:
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dw 0xffff
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dw 0x0000
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db 0x00
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db 0b10011010
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db 0b11001111
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db 0x00
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gdt_kern_data:
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dw 0xffff
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dw 0x0000
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db 0x00
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db 0b10010010
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db 0b11001111
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db 0x00
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gdt_user_code:
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dw 0xffff
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dw 0x0000
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db 0x00
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db 0b11111010
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db 0b11001111
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db 0x00
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gdt_user_data:
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dw 0xffff
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dw 0x0000
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db 0x00
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db 0b11110010
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db 0b11001111
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db 0x00
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tss:
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dq 0
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gdt_end:
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gdtp:
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dw gdt_end - gdt - 1
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dd gdt
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global boot_page_dir
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align 0x1000
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boot_page_dir: times 1024 dd 0
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global boot_page_tab
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align 0x1000
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boot_page_tab: times 1024 dd 0
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section .bss
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align 16
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stack_top:
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resb 16384
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stack_bottom:
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