x86: Invalidate LDT before handoff

stage23/lib/spinup.asm

@@ -12,6 +12,9 @@ common_spinup:
 
     lidt [invalid_idt]
 
+    xor eax, eax
+    lldt ax
+
     ; We don't need the return address
     add esp, 4
 

stage23/lib/spinup.asm64

@@ -53,6 +53,9 @@ bits 32
     mov gs, ax
     mov ss, ax
 
+    xor eax, eax
+    lldt ax
+
     mov eax, 0x00000011
     mov cr0, eax
 

stage23/sys/smp_trampoline.real

@@ -31,6 +31,9 @@ smp_trampoline:
     mov gs, ax
     mov ss, ax
 
+    xor eax, eax
+    lldt ax
+
     xor eax, eax
     mov cr4, eax