Method and apparatus for interrupt handling

A data processing device comprising:

• a plurality of system registers, comprising a set of interrupt handling registers for controlling handling of an incoming interrupt;
• processing means for executing software at a plurality of execution levels,
• interrupt controller means for routing said incoming interrupt to interrupt handling software configured to run at one of said plurality of execution levels;
• register access control means for dynamically controlling access to at least some of said interrupt handling registers in dependence upon said one of said plurality of execution levels that said incoming interrupt is routed to, such that interrupt handling software configured to run at said execution level has access to said at least some of said interrupt handling registers for handling said incoming interrupt, and such that said interrupt handling software configured to run at said execution level does not have access to interrupt handling registers for handling a second incoming interrupt routed to an interrupt handling software run at a more privileged execution level.

A device for routing an incoming interrupt to processing circuitry, said processing circuitry being configured to execute software at a plurality of execution levels, said device comprising:

• processor mode detection circuitry configured to detect a current execution mode of said processor;
• and
• input circuitry configured to receive said incoming interrupt intended for an interrupt handler configured to run at an intended execution mode and at an intended execution level;
• routing circuitry configured to route said incoming interrupt to interrupt handling software configured to run at a target execution level, said routing circuitry being configured to:
• respond to said received incoming interrupt having an intended execution mode that corresponds with said current execution mode of said processing circuitry to route said incoming interrupt to interrupt handling software configured to run at said intended execution level;
• and
• respond to said received incoming interrupt having an intended execution mode that does not correspond with said current execution mode of said processing circuitry, to route said incoming interrupt to interrupt handling software configured to run at a predetermined execution level that is more privileged than said intended execution level.

A method of routing an incoming interrupt to processing circuitry, said processing circuitry being configured to execute software at a plurality of execution levels, said method comprising the steps of:

• detecting a current execution mode of said processor;
• and
• receiving said incoming interrupt intended for an interrupt handler configured to run at an intended execution mode and at an intended execution level;
• routing said incoming interrupt to interrupt handling software configured to run at a target execution level, by:
• responding to said received incoming interrupt having an intended execution mode that corresponds with said current execution mode of said processing circuitry to route said incoming interrupt to interrupt handling software configured to run at said intended execution level;
• and
• responding to said received incoming interrupt having an intended execution mode that does not correspond with said current execution mode of said processing circuitry, to route said incoming interrupt to interrupt handling software configured to run at a predetermined execution level that is more privileged than said intended execution level.