Deterministic code fingerprinting for program flow monitoring

A method for monitoring the flow of a program, comprising:

• receiving a trigger to execute a set of instructions, wherein the set of instructions comprise a deterministic segment and a non-deterministic segment;
• executing the set of instructions by a processor, wherein the set of instructions is executed by fetching and executing the instructions from a memory according to a predefined order deterministically generating a fingerprint from accesses to the memory while executing the deterministic segment, but not from accesses to the memory while executing the non-deterministic segment;
• and
• comparing the generated fingerprint to an expected fingerprint to determine whether the set of instructions executed according to the predefined order.

A safety system, comprising:

• a monitored device;
• a safety monitoring unit configured to perform a test on the monitored device;
• a memory configured to store a set of instructions, wherein the set of instructions comprise a deterministic segment and a non-deterministic segment, and wherein the instructions are configured to trigger the test and are configured to be executed in a predefined order;
• a processor configured to execute the set of instructions by fetching and executing the instructions from the memory according to the predefined order;
• a program flow monitoring (PFM) unit configured to deterministically generate a fingerprint from accesses to the memory while executing the deterministic segment, but not from accesses to the memory while executing the non-deterministic segment;
• and
• a verification unit configured to compare the generated fingerprint to an expected fingerprint to determine whether the set of instructions executed in the predefined order.