diff --git a/bochs/cpu/proc_ctrl.cc b/bochs/cpu/proc_ctrl.cc
index 2547c3d11..a25623519 100644
--- a/bochs/cpu/proc_ctrl.cc
+++ b/bochs/cpu/proc_ctrl.cc
@@ -1,5 +1,5 @@
 /////////////////////////////////////////////////////////////////////////
-// $Id: proc_ctrl.cc,v 1.218 2008-04-20 21:44:13 sshwarts Exp $
+// $Id: proc_ctrl.cc,v 1.219 2008-04-25 11:39:51 sshwarts Exp $
 /////////////////////////////////////////////////////////////////////////
 //
 //  Copyright (C) 2001  MandrakeSoft S.A.
@@ -1896,6 +1896,10 @@ void BX_CPP_AttrRegparmN(1) BX_CPU_C::WRMSR(bxInstruction_c *i)
       return;
 
     case BX_MSR_KERNELGSBASE:
+      if (! IsCanonical(val64)) {
+        BX_ERROR(("WRMSR: attempt to write non-canonical value to MSR_KERNELGSBASE !"));
+        exception(BX_GP_EXCEPTION, 0, 0);
+      }
       MSR_KERNELGSBASE = val64;
       return;
 
diff --git a/bochs/cpu/tasking.cc b/bochs/cpu/tasking.cc
index 6a5619b3f..122c382d0 100644
--- a/bochs/cpu/tasking.cc
+++ b/bochs/cpu/tasking.cc
@@ -1,5 +1,5 @@
 /////////////////////////////////////////////////////////////////////////
-// $Id: tasking.cc,v 1.54 2008-04-22 22:05:38 sshwarts Exp $
+// $Id: tasking.cc,v 1.55 2008-04-25 11:39:51 sshwarts Exp $
 /////////////////////////////////////////////////////////////////////////
 //
 //  Copyright (C) 2001  MandrakeSoft S.A.
@@ -186,6 +186,11 @@ void BX_CPU_C::task_switch(bx_selector_t *tss_selector,
     exception(BX_TS_EXCEPTION, tss_selector->value & 0xfffc, 0);
   }
 
+  if (old_TSS_limit < old_TSS_max) {
+    BX_ERROR(("task_switch(): old TSS limit < %d", old_TSS_max));
+    exception(BX_TS_EXCEPTION, BX_CPU_THIS_PTR tr.selector.value & 0xfffc, 0);
+  }
+
   if (obase32 == nbase32) {
     BX_INFO(("TASK SWITCH: switching to the same TSS !"));
   }