UREG_G2
childregs->u_regs[UREG_G2] = (unsigned long) args->fn_arg;
t->kregs->u_regs[UREG_G2] = (unsigned long) args->fn_arg;
err |= __put_user(regs->u_regs[UREG_G2], &((*grp)[MC_G2]));
err |= __get_user(regs->u_regs[UREG_G2], (&(*grp)[MC_G2]));