Bochs CPU fix: don't crash on weird memory accesses

Raising a GP exception may not be what a real x86 does, but it allows us
to catch this case in our experiments.

TODO: figure out correct reaction; backport to upstream

git-svn-id: https://www4.informatik.uni-erlangen.de/i4svn/danceos/trunk/devel/fail@1311 8c4709b5-6ec9-48aa-a5cd-a96041d1645a

bochs/cpu/cpu.cc

@@ -795,6 +795,9 @@ void BX_CPU_C::prefetch(void)
       else {
         BX_PANIC(("prefetch: getHostMemAddr vetoed direct read, pAddr=0x" FMT_PHY_ADDRX, pAddr));
       }
+      // DanceOS
+      // XXX how would this be handled on a real machine?
+      exception(BX_GP_EXCEPTION, 0);
     }
   }
 }