57 lines
1.2 KiB
NASM
57 lines
1.2 KiB
NASM
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SECTION .text
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USE32
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long_mode:
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.func: dq 0
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.page_table: dd 0
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.entry:
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; disable interrupts
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cli
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; disable paging
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mov eax, cr0
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and eax, 0x7FFFFFFF
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mov cr0, eax
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; enable FXSAVE/FXRSTOR, Page Global, Page Address Extension, and Page Size Extension
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mov eax, cr4
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or eax, 1 << 9 | 1 << 7 | 1 << 5 | 1 << 4
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mov cr4, eax
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; load long mode GDT
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lgdt [gdtr]
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; enable long mode
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mov ecx, 0xC0000080 ; Read from the EFER MSR.
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rdmsr
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or eax, 1 << 11 | 1 << 8 ; Set the Long-Mode-Enable and NXE bit.
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wrmsr
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; set page table
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mov eax, [.page_table]
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mov cr3, eax
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; enabling paging and protection simultaneously
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mov eax, cr0
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or eax, 1 << 31 | 1 << 16 | 1 ;Bit 31: Paging, Bit 16: write protect kernel, Bit 0: Protected Mode
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mov cr0, eax
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; far jump to enable Long Mode and load CS with 64 bit segment
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jmp gdt.lm64_code:.inner
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USE64
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.inner:
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; load all the other segments with 64 bit data segments
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mov rax, gdt.lm64_data
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mov ds, rax
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mov es, rax
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mov fs, rax
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mov gs, rax
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mov ss, rax
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; jump to specified function
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mov rax, [.func]
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jmp rax
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