An apparatus and method for managing a capability domain

A method of managing a capability domain within an apparatus having processing circuitry to execute instructions, the processing circuitry when in a default state being arranged to operate in the capability domain, the capability domain comprising capabilities used to constrain operations performed by the processing circuitry when executing said instructions, comprising:

• storing, within a program counter capability storage element, a program counter capability used by the processing circuitry to determine a program counter value, the program counter capability identifying a capability state for the processing circuitry;
• responsive to the capability state indicating said default state, operating the processing circuitry in the capability domain;
• and
• responsive to the capability state indicating an executive state, operating the processing circuitry in a manner less constrained than when in said default state so as to allow modification of the capability domain.

An apparatus comprising:

• processing means for executing instructions, the processing means, when in a default state, for operating in a capability domain comprising capabilities used to constrain operations performed by the processing means when executing said instructions;
• and
• program counter capability storage element means for storing a program counter capability used by the processing means to determine a program counter value, the program counter capability identifying a capability state for the processing means;
• the processing means, responsive to the capability state indicating said default state, for operating in the capability domain;
• and
• the processing means, responsive to the capability state indicating an executive state, for operating in a manner less constrained than when in said default state so as to allow modification of the capability domain.