Coherence-based dynamic code rewriting, tracing and code coverage

A non-transitory computer-readable medium comprising instructions to be executed in a device which is connected to a processor via a coherence interconnect, wherein the processor executes code having code pages that are stored in a local memory of the device and the instructions when executed in the device causes the device to carry out a method of modifying a portion of the code, the method comprising:

• during execution of the code by the processor, monitoring the coherence interconnect for requests to access cache lines of code pages that are stored in the local memory of the device, and in response to a request to read a cache line of the code pages having a particular address, retrieving the cache line of the code pages having the particular address from the local memory, storing the cache line retrieved from the local memory in a buffer, modifying the cache line stored in the buffer, and transmitting the modified cache line to the processor in place of the cache line retrieved from the local memory.

A computer system comprising

• a processor;
• a device connected to the processor via a coherence interconnect, the device including local memory in which code pages of code to be executed in the processor are stored, wherein the device is configured to:
• during execution of the code by the processor, monitoring the coherence interconnect for requests to access cache lines of the code pages, and in response to a request to read a cache line of the code pages having a particular address, retrieving the cache line of the code pages having the particular address from the local memory, storing the cache line retrieved from the local memory in a buffer, modifying the cache line stored in the buffer, and transmitting the modified cache line to the processor in place of the cache line retrieved from the local memory.