_R_S2
uc.uc_mcontext.__gregs[_REG_S2] = sc->sc_regs[_R_S2];
{ "s2", (long *)&ddb_regs.r_regs[_R_S2], DB_SETF_REGS, NULL },
gdb_regs[18] = regs->r_regs[_R_S2]; /* S2 */
case _R_S2: /* s2 */
tf->tf_regs[_R_S0], tf->tf_regs[_R_S1], tf->tf_regs[_R_S2]);