31 lines
876 B
NASM
31 lines
876 B
NASM
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[bits 16]
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switch16_to_32:
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cli ; disable interrupts until we finish setup, since the
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; 16-bit interrupt vector will be invalid
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lgdt [gdt_flat_descriptor] ; load the GDT which defines the flat code and data segments
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mov eax, cr0 ; move the control register to eax so we can modify it
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or eax, 0x1 ; set the 1st bit to enable 32-bit pm
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mov cr0, eax ; write the modified control value back
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jmp i_gdt_code_segment:initialize32 ; far-jump to our new 32-bit code, forcing CPU to clear the pipeline of 16-bit instructions
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[bits 32]
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initialize32:
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; Set up registers and stack once in 32-bit protected mode
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mov ax, i_gdt_data_segment ; point the segment registers to the new data segment in 32-bit
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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 ebp, 0x90000 ; update stack position to be at the top of free space
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mov esp, ebp
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call main32
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