first commit

src/bootload/longm.asm

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+; 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
+