There's no such feature in the rproc driver. Note: the rproc API changes two or three times a year. That's no stuff for productive code yet.
You can implement those functions in your code. Find the source in package am335x_pru_package in file
But why using rproc? uio_pruss privides what you desire.
Anyway, I'm not sure that mapped memory can fulfill you target (400Mbit/s), since all trafic is running over the OCP port. Better think about DMA transfer from fast PRU RAM (DRAM[1|2], SRAM) to ARM RAM.