_R_S1
uc.uc_mcontext.__gregs[_REG_S1] = sc->sc_regs[_R_S1];
{ "s1", (long *)&ddb_regs.r_regs[_R_S1], DB_SETF_REGS, NULL },
gdb_regs[17] = regs->r_regs[_R_S1]; /* S1 */
case _R_S1: /* s1 */
tf->tf_regs[_R_S0], tf->tf_regs[_R_S1], tf->tf_regs[_R_S2]);