Hybrid Code Signature for Tracking Program Calling Context
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Solution Overview
Problem
Existing methods for capturing a program's control flow history are inefficient, requiring expensive instrumentation for software techniques and facing hardware limitations in dynamic runtime environments, such as high overhead and limited storage for branch instructions.
Innovation Solution
A hybrid code signature is generated using a processor to execute an application, profiling its execution by storing a reference signature and updating a working signature with a hashing function, which tracks function calls and returns to efficiently represent the calling context.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If software techniques are used to gather control flow information, then measurement precision is improved, but device complexity and overhead increase significantly
Solution Approach 1:
The patent replaces software-based instrumentation with hardware-based tracing mechanisms. Hardware tracing uses dedicated circuitry and registers to automatically capture control flow information without requiring software instrumentation, thereby achieving measurement precision while significantly reducing overhead and complexity.
Solution Approach 2:
The patent creates a simplified representation or copy of the control flow history using hardware registers and tracing mechanisms. Instead of fully instrumenting every software operation, the system copies essential control flow information (branch outcomes, function calls) into hardware structures for efficient analysis.
2Productivity
If hardware techniques are used to gather control flow information, then overhead is reduced, but storage area is consumed limiting the amount of branch instructions that can be recorded
Solution Approach 1:
The patent extracts only the essential information needed for control flow analysis from the complete instruction stream. Instead of storing all branch instructions and addresses, the system extracts and stores only the outcomes of branch instructions and key control flow events, significantly reducing storage requirements while maintaining tracing capability.
Solution Approach 2:
The patent segments the control flow information into distinct components (branch outcomes, function call/return events) and stores them separately in hardware registers. This segmentation allows efficient storage and processing of control flow history without requiring continuous storage of all instruction details.
3Measurement precision
If more branch instructions and target addresses are stored in hardware, then measurement precision is improved, but device complexity and area overhead increase
Solution Approach 1:
The patent applies partial action by storing only the necessary control flow information (branch outcomes and key events) rather than all possible instruction details. This selective storage approach provides sufficient measurement precision for calling context analysis while avoiding the complexity of storing complete instruction histories.
Data Source
AI summary
A method for a hybrid code signature including executing, via a processor, an application, the executing comprising executing a root instruction of the application; profiling, via the processor, the executing of the application, the profiling comprising storing a reference signature; determining, via the processor, a working signature of instructions executed subsequent to the executing of the root instruction, the determining comprising implementing a hashing function of the instructions in response to storing the reference signature; tracking the updating of the working signature by storing a value in a counter; and updating continuously, via the processor, the working signature with the hashing function while at least the working signature does not match the reference signature.