Interrogative Virtual Machine Interface for Time Travel Debugging

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Solution Overview

Problem

Conventional debugging techniques for programs are inefficient, particularly in capturing and replaying program states, leading to high costs and resource overheads due to large virtual machine snapshots and event logs, which hinder effective debugging and forensics.

Innovation Solution

The implementation of an interrogative virtual machine interface (VMI) that captures minimal state and logs nondeterministic events, allowing for efficient snapshotting and event logging, enabling time travel debugging by replaying program execution based on snapshots and event logs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional virtual machine snapshotting is used to capture program state, then debugging capability is improved, but storage space and computational overhead increase significantly

Engineering Contradiction:

Improvedebugging capabilityVSAvoidsnapshot size

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The patent extracts only the essential state information needed for debugging from the complete virtual machine state. Instead of capturing the entire VM snapshot, it selectively captures minimal state data and nondeterministic events that are sufficient for reproduction and debugging, thereby reducing snapshot size while maintaining debugging capability

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent segments the debugging information into two distinct components: minimal state snapshots and nondeterministic event logs. This segmentation allows the system to capture only the necessary program state without including redundant information, reducing overall storage requirements while preserving debugging effectiveness

Inventive Principle:

Principle #1Segmentation

2Measurement precision

If x86-level virtualization is used to provide precise snapshots, then snapshot accuracy is improved, but storage space and logging overhead increase

Engineering Contradiction:

Improvesnapshot precisionVSAvoidevent log size

Core Design Contradiction:

Measurement precisionVSQuantity of substance

Solution Approach 1:

The patent applies local quality by capturing precise information only where necessary for debugging. Instead of uniformly logging all x86-level events, it selectively logs nondeterministic events that could affect program behavior, providing sufficient precision for debugging while reducing overall log volume

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent uses partial action by capturing only the essential subset of state information and events needed for debugging. Rather than implementing complete x86-level virtualization and logging, it captures minimal state and selective nondeterministic events, achieving adequate precision with reduced overhead

Inventive Principle:

Principle #16Partial or excessive action

3Productivity

If program execution is halted early during debugging, then debugging efficiency is improved, but hypothesis validation capability deteriorates

Engineering Contradiction:

Improvedebugging efficiencyVSAvoidhypothesis validation capability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent prepares debugging information in advance by capturing minimal state snapshots and logging nondeterministic events during program execution. This preliminary capture of debugging data allows developers to efficiently validate hypotheses by replaying execution from captured states without needing to halt execution at every potential debugging point

Inventive Principle:

Principle #10Preliminary action

4Adaptability or versatility

If program execution is restarted to return to an earlier point, then debugging flexibility is improved, but time and computational cost increase

Engineering Contradiction:

Improvedebugging flexibilityVSAvoidreexecution time

Core Design Contradiction:

Adaptability or versatilityVSLoss of time

Solution Approach 1:

The patent creates copies of program state at specific points during execution by capturing minimal state snapshots. These state copies enable developers to replay execution from earlier points without restarting the entire program, maintaining debugging flexibility while eliminating the time cost of full reexecution

Inventive Principle:

Principle #26Copying

Data Source

PatentUS9588870B2Time travel debugging for browser components

Publication Date: 2017.03.07 MICROSOFT TECHNOLOGY LICENSING LLC

AI summary

Various technologies described herein pertain to performing time travel debugging. A computer-executable program can be executed. The computer-executable program can be executable under control of a virtual machine. The virtual machine can interact with a browser system during execution of the computer-executable program. Moreover, nondeterministic events can be logged via an interrogative virtual machine interface (VMI) during the execution of the computer-executable program. The nondeterministic events can be logged as part of event logs. Moreover, the interrogative VMI is between the virtual machine and the browser system. Further, snapshots of the virtual machine can be captured during the execution of the computer-executable program. The snapshots can be captured via the interrogative VMI. At least a portion of the execution of the computer-executable program can be replayed based at least in part on a snapshot and at least a portion of the event logs.