Other than apparently commonly assumed, the bound instruction does not
require the corresponding IDT entry to have DPL 3.

From: Jan Beulich <jbeulich@novell.com>

--- 2.6.14/arch/x86_64/kernel/traps.c	2005-10-28 02:02:08.000000000 +0200
+++ 2.6.14-x86_64-bound/arch/x86_64/kernel/traps.c	2005-11-07 09:33:53.000000000 +0100
@@ -917,8 +917,8 @@ void __init trap_init(void)
 	set_intr_gate_ist(1,&debug,DEBUG_STACK);
 	set_intr_gate_ist(2,&nmi,NMI_STACK);
 	set_system_gate(3,&int3);
-	set_system_gate(4,&overflow);	/* int4-5 can be called from all */
-	set_system_gate(5,&bounds);
+	set_system_gate(4,&overflow);	/* int4 can be called from all */
+	set_intr_gate(5,&bounds);
 	set_intr_gate(6,&invalid_op);
 	set_intr_gate(7,&device_not_available);
 	set_intr_gate_ist(8,&double_fault, DOUBLEFAULT_STACK);