err |= __put_user(from->si_addr, &to->si_addr);
#ifdef __ARCH_SI_TRAPNO
err |= __put_user(from->si_trapno, &to->si_trapno);
+#endif
+#ifdef BUS_MCEERR_AO
+ /*
+ * Other callers might not initialize the si_lsb field,
+ * so check explicitely for the right codes here.
+ */
+ if (from->si_code == BUS_MCEERR_AR || from->si_code == BUS_MCEERR_AO)
+ err |= __put_user(from->si_addr_lsb, &to->si_addr_lsb);
#endif
break;
case __SI_CHLD: