Method and system for on demand control of hardware support for software pointer authentification in a computing system

A system for executing instructions in a software application, the system comprising:

• a processor having circuitry and logic for executing the instructions, the processor comprising:
• a decode unit comprising circuitry and logic for decoding the instructions, the decode unit having a control register;
• an issue unit comprising circuitry and logic for receiving the decoded instructions and issuing decoded instructions,
• an execution unit comprising circuitry and logic for executing decoded instructions issued by the issue unit;
• and
• a non-transitory computer-readable medium having program instructions embodied therewith, the program instructions executable by the processor to cause the processor to:
• operate, in response to a value set in a bit field of the control register, in either a secure mode or a performance mode,
• wherein in the secure mode, the processor:
• upon encountering a secure mode entry instruction, computes an entry hash value using a hash function and stores the entry hash value in a first memory location;
• and
• upon encountering a secure mode exit instruction, computes an exit hash value using the same hash used when computing the entry hash value, loads the entry hash value from the first memory location, and determines whether the entry hash value is the same as the exit hash value, and
• wherein in the performance mode, the processor:
• upon encountering the secure mode entry instruction, executes the secure mode entry instruction as a no-operation;
• and
• upon encountering the secure mode exit instruction, executes the secure mode exit instruction as a no-operation.