1. A data processing apparatus comprising: processing circuitry configured to perform data processing; a memory attribute unit comprising a plurality of storage regions, each storage region configured to store attribute data for controlling access to a corresponding memory address range by the processing circuitry; and wherein in response to a target memory address, the processing circuitry is configured to perform a region identifying operation to output a region identifying value for identifying which of said plurality of storage regions is a corresponding storage region indicated by the memory attribute unit as corresponding to a memory address range including said target memory address, wherein the target memory address is a physical address and the region identifying value is made available to at least some software executed by the data processing apparatus.