[bits 16]
; Sets up the GDT for the switch to 32-bit protected mode

gdt_setup_flat:
	gdt_flat_null:  ; mandatory null descriptor
		dd 0x0  ; dd means define double-word (i.e. 4 bytes)
		dd 0x0

	gdt_flat_code_section:
		; base: 0x0, limit: 0xfffff
		; 1st flags: (present) 1 (privilege) 00 (descriptor type) 1 -> 1001b
		; Type flags: (code) 1 (conforming) 0 (readable) 1 (accessed) 0 -> 1010b
		; 2nd flags: (granularity) 1 (32-bit default) 1 (64-bit segment) 0 (AVL) 0 -> 1100b
		dw 0xffff  ; limit (bits 0 - 15)
		dw 0x0  ; base (bits 0 - 15)
		db 0x0  ; base (bits 16 - 23)
		db 10011010b  ; 1st flags, type flags
		db 11001111b  ; 2nd flags, limit (bits 16 - 19)
		db 0x0  ; base (bits 24 - 31)

	gdt_flat_data_section:
		; Same as code segment except for the type flags:
		; type flags: (code) 0 (expand down) 0 (writable) 1 (accessed) 0 -> 0010b
		dw 0xffff  ; limit (bits 0 - 15)
		dw 0x0  ; base (bits 0 - 15)
		db 0x0  ; base (bits 16 - 23)
		db 10010010b  ; 1st flags, type flags
		db 11001111b  ; 2nd flags, limit (bits 16 - 19)
		db 0x0  ; base (bits 24 - 31)

	gdt_flat_end:  ; so the assembler can calculate the size of the gdt section

	gdt_flat_descriptor:
		dw gdt_flat_end - gdt_setup_flat - 1  ; size of our GDT, always less 1 of the true size
		dd gdt_setup_flat  ; start address of the gdt

	i_gdt_code_segment equ gdt_flat_code_section - gdt_setup_flat
	i_gdt_data_segment equ gdt_flat_data_section - gdt_setup_flat