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/i386/kernel/traps.c	2005-10-28 02:02:08.000000000 +0200
+++ 2.6.14-i386-bound/arch/i386/kernel/traps.c	2005-11-04 17:00:47.000000000 +0100
@@ -1081,9 +1081,9 @@ void __init trap_init(void)
 	set_trap_gate(0,&divide_error);
 	set_intr_gate(1,&debug);
 	set_intr_gate(2,&nmi);
-	set_system_intr_gate(3, &int3); /* int3-5 can be called from all */
+	set_system_intr_gate(3, &int3); /* int3/4 can be called from all */
 	set_system_gate(4,&overflow);
-	set_system_gate(5,&bounds);
+	set_trap_gate(5,&bounds);
 	set_trap_gate(6,&invalid_op);
 	set_trap_gate(7,&device_not_available);
 	set_task_gate(8,GDT_ENTRY_DOUBLEFAULT_TSS);