ppbus_insarg
int opcode, union ppbus_insarg param1, union ppbus_insarg param2,
union ppbus_insarg param3, int * ret)
union ppbus_insarg, /* param1 */
union ppbus_insarg, /* param2 */
union ppbus_insarg, /* param3 */
union ppbus_insarg arg[PPBUS_MS_MAXARGS]; /* arguments */