On-Chip MEM contents (in user peripheral) access??

A possible way should be :

dual port memory connected with one port to the peripheral, and the peripheral connected as avalon slave. Bring the other memory port of the memory to outside this verilog module (address, data, read, write, ...). Connect this peripheral as register slave in SOPC builder.

Make a new peripheral in SOPC builder (choose legacy for simplicity), be sure to use 'memory slave'. Choose the option 'export bus ports' in the 'Instantiation' page.

Connect the exported bus ports to the 'exported' memory ports of the slave itself.

Now you can access the slave functionality with the register slave, that contains the functionality to handle one port of the dual port memory, and the cpu can reach the dual port memory with the memory slave mapped to an other address range. If you have a DMA master in the system, the memory can be accessed with DMA if it is set up correctly.

I did these kind of things in a previous project, and I hope this is an answer to your question.

Stefaan.