An apparatus and method for controlling access to a set of memory mapped control registers

A method of controlling access to a set of memory mapped control registers within an apparatus, comprising:

• executing program code on processing circuitry to perform data processing operations;
• storing, within the set of memory mapped control registers, control information used to control operation of the processing circuitry when executing the program code;
• storing within a lockdown register a lockdown value;
• executing store instructions on the processing circuitry in order to perform write operations to a memory address space, the store instructions being of multiple types;
• and
• when the lockdown value is set, preventing a write operation being performed to change the control information in the memory mapped control registers unless that write operation occurs due to execution by the processing circuitry of a store instruction from a first subset of the multiple types of store instructions.

A computer program for controlling a host data processing apparatus to provide an instruction execution environment, comprising:

• processing program logic to execute program code to perform data processing operations;
• and
• control program logic to maintain a set of memory mapped control data structures to store control information used to control operation of the processing program logic when executing the program code, and to maintain a lockdown data structure to store a lockdown value;
• wherein:
• the processing program logic is arranged to execute store instructions in order to perform write operations to a memory address space, the store instructions being of multiple types;
• and
• the processing program logic is arranged, when the lockdown value is set, to prevent a write operation being performed to change the control information in the memory mapped control data structures unless that write operation occurs due to execution of a store instruction from a first subset of the multiple types of store instructions.