X86: In non 64bit mode, throw a fault when a NULL segment is accessed.

diff --git a/src/arch/x86/tlb.cc b/src/arch/x86/tlb.cc
index f5e214a88f2576dd575a3c0275c38df4dca15447..5d101a5ae05945115c8b31affeb03b71e01fa959 100644 (file)
--- a/src/arch/x86/tlb.cc
+++ b/src/arch/x86/tlb.cc
@@ -571,6 +571,9 @@ TLB::translate(RequestPtr &req, ThreadContext *tc, bool write, bool execute)
         // If we're not in 64-bit mode, do protection/limit checks
         if (!efer.lma || !csAttr.longMode) {
             DPRINTF(TLB, "Not in long mode. Checking segment protection.\n");
+            // Check for a NULL segment selector.
+            if (!tc->readMiscRegNoEffect(MISCREG_SEG_SEL(seg)))
+                return new GeneralProtection(0);
             SegAttr attr = tc->readMiscRegNoEffect(MISCREG_SEG_ATTR(seg));
             if (!attr.writable && write)
                 return new GeneralProtection(0);