67 lines
767 B
ArmAsm
67 lines
767 B
ArmAsm
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[BITS 32]
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section .text
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global setup_gdt
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setup_gdt:
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lgdt [gdt_ptr]
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jmp 0x08:.flush_cs
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.flush_cs:
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mov ax, 0x10
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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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ret
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section .data
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gdt_ptr:
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dw gdt_entries.end - gdt_entries - 1
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dd gdt_entries
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gdt_entries:
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;; null descriptor
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dw 0x0 ; limit
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dw 0x0 ; base (low)
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db 0x0 ; base (mid)
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db 0x0 ; access
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db 0x0 ; granularity
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db 0x0 ; base (high)
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;; kernel mode code segment
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dw 0xFFFF
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dw 0x00
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db 0x00
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db 0x9A
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db 0xCF
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db 0x00
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;; kernel mode data segment
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dw 0xFFFF
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dw 0x00
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db 0x00
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db 0x92
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db 0xCF
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db 0x00
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;; user mode code segment
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dw 0xFFFF
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dw 0x00
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db 0x00
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db 0xFA
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db 0xCF
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db 0x00
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;; user mode data segment
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dw 0xFFFF
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dw 0x00
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db 0x00
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db 0xF2
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db 0xCF
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db 0x00
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;; TSS
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.end:
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