Joey,
I don't think you can access the ARM L2 Cache as internal SRAM. And I think the ARM local RAM 64KB is only accessible from the ARM, not the DSP.
You might try asking this question in a hardware forum. Try the following one:
DM814x and AM387x Processors Forum
http://e2e.ti.com/support/dsp/davinci_digital_media_processors/f/716.aspx
~Ramsey