; DEPRECATED!

CPUID_EXTENSIONS equ 0x80000000
CPUID_EXT_FEATURES equ 0x80000001
EFLAGS_ID equ 1 << 21
CPUID_EDX_EXT_FEAT_LM equ 1 << 29

enterlong:
	call .queryLongMode
	

.NoLongMode
	cli
	hlt
	jmp .NoLongMode

.checkCPUID:
    pushfd
    pop eax

    ; The original value should be saved for comparison and restoration later
    mov ecx, eax
    xor eax, EFLAGS_ID

    ; storing the eflags and then retrieving it again will show whether or not
    ; the bit could successfully be flipped
    push eax                    ; save to eflags
    popfd
    pushfd                      ; restore from eflags
    pop eax

    ; Restore EFLAGS to its original value
    push ecx
    popfd

    ; if the bit in eax was successfully flipped (eax != ecx), CPUID is supported.
    xor eax, ecx
    jnz .NoLongMode
	ret

.queryLongMode:
	call .checkCPUID

    mov eax, CPUID_EXTENSIONS
    cpuid
    cmp eax, CPUID_FEATURES
    jb .NoLongMode

	mov eax, CPUID_EXT_FEATURES
    cpuid
    test edx, CPUID_EDX_EXT_FEAT_LM
    jz .NoLongMode
	
	ret