2023-04-19 03:44:10 +00:00
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global start
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extern kmain
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bits 32
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; base, limit, access, flags
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%macro gdt_entry 4
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2023-04-21 13:39:35 +00:00
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db %2 & 0xff
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db (%2 >> 8) & 0xff
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db %1 & 0xff
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db (%1 >> 8) & 0xff
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db (%1 >> 16) & 0xff
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db %3
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db ((%2 >> 16) & 0x0f) | (%4 << 4)
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db (%1 >> 24) & 0xff
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2023-04-19 03:44:10 +00:00
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%endmacro
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2023-04-21 13:39:35 +00:00
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section .multiboot
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2023-04-19 03:44:10 +00:00
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align 8
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mb_start:
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2023-04-21 13:39:35 +00:00
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; header
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2023-04-19 03:44:10 +00:00
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dd 0xe85250d6
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dd 0
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dd mb_end - mb_start
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dd 0x100000000 - (0xe85250d6 + (mb_end - mb_start))
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; null tag
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2023-04-19 03:44:10 +00:00
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dw 0
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dw 0
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dd 8
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;
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mb_end:
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section .bss
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align 16
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stack_start:
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resb 16384
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stack_end:
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section .rodata
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align 16
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gdt_start:
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gdt_entry 0, 0, 0, 0
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gdt_entry 0, 0xFFFFF, 0x9A, 0xC
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gdt_entry 0, 0xFFFFF, 0x92, 0xC
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gdt_end:
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gdt_descriptor:
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2023-04-21 13:39:35 +00:00
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dw gdt_end - gdt_start - 1
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dd gdt_start
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2023-04-19 03:44:10 +00:00
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section .text
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align 8
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start:
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2023-04-21 13:39:35 +00:00
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cli
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lgdt [gdt_descriptor]
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jmp 0x08:after_lgdt
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2023-04-19 03:44:10 +00:00
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after_lgdt:
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mov ax, 0x10
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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 fs, ax
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mov gs, ax
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mov esp, stack_end
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mov ebp, stack_end
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sti
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push ebx
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call kmain
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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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