Test Executive Stack Corruption Detection and Safety Buffers

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Solution Overview

Problem

Test executive sequences face challenges in detecting and preventing errors, particularly stack corruption and uninitialized local variable bugs, caused by user-supplied code modules, which are difficult to reproduce and diagnose due to their intermittent nature, leading to misattribution of issues to vendor bugs and increased debugging complexity.

Innovation Solution

The implementation of automatic stack corruption detection and utilization of stack safety buffers, as well as initialization of unused stack space to identify and mitigate uninitialized local variable bugs, within the test executive engine to detect and prevent errors before and after executing user-supplied code modules.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If user-supplied code modules are executed in the test executive sequence, then test functionality and versatility are improved, but stack corruption errors and uninitialized variable bugs occur causing system instability

Engineering Contradiction:

Improvetest functionalityVSAvoidsystem stability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent introduces a stack safety buffer as an intermediary layer between the user-supplied code module and the test executive engine's stack. This buffer acts as a mediator that detects stack corruption attempts by monitoring for specific patterns (such as 0xCCCCCD or 0xCCCCCE) that indicate unauthorized writes, thereby protecting the system stability while allowing user code execution

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent implements preliminary initialization of the stack safety buffer with detectable patterns before executing user-supplied code modules. This preliminary action enables the system to detect stack corruption in real-time during code execution, allowing early intervention before corruption propagates to critical system structures

Inventive Principle:

Principle #10Preliminary action

2Reliability

If stack corruption detection is implemented, then system reliability is improved, but device complexity and debugging overhead increase

Engineering Contradiction:

Improveerror detection capabilityVSAvoidtest executive engine complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent segments the stack into distinct regions: the user code's accessible stack frame and the protected stack safety buffer. This segmentation isolates the detection mechanism to a specific buffer region, reducing the overall complexity by limiting the scope of monitoring to only the boundary area rather than the entire stack

Inventive Principle:

Principle #1Segmentation

3Reliability

If stack safety buffers are allocated, then stack corruption is prevented, but memory usage and execution overhead increase

Engineering Contradiction:

Improvestack protectionVSAvoidmemory consumption

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The patent applies local quality by allocating stack safety buffers only at specific critical points where user-supplied code modules are invoked, rather than throughout the entire stack. Each buffer is localized to protect only the immediate stack frame of the called function, reducing overall memory consumption while maintaining protection where needed

Inventive Principle:

Principle #3Local quality

4Ease of repair

If automatic error detection is enabled, then debugging ease is improved, but execution time and productivity are reduced

Engineering Contradiction:

Improvedebugging easeVSAvoidexecution speed

Core Design Contradiction:

Ease of repairVSProductivity

Solution Approach 1:

The patent implements optional stack safety buffer checking that can be skipped in optimized execution paths. When user-supplied code modules are determined to be safe or when execution speed is prioritized, the detection overhead can be bypassed, allowing the system to rush through critical sections without the full detection burden while maintaining protection when needed

Inventive Principle:

Principle #21Skipping (Rushing through)

Data Source

PatentUS7613954B2Test executive with stack corruption detection, stack safety buffers, and increased determinism for uninitialized local variable bugs

Publication Date: 2009.11.03 NATIONAL INSTRUMENTS CORP

AI summary

A system and method for detecting and/or preventing execution problems caused by user-supplied code modules that are called by steps of a test executive sequence. The test executive sequence may include a plurality of test executive steps. At least a subset of the steps may be configured to call user-supplied code modules. The test executive sequence may be executed on a host computer under control of a test executive engine. For each step that calls a user-supplied code module, the test executive engine may perform certain actions to detect and/or prevent execution problems caused by the user-supplied code module. For example, the test executive engine may be operable to automatically detect stack corruption caused by the user-supplied code module, may be operable to utilize stack safety buffers to avoid stack corruption problems caused by the user-supplied code module, and/or may include features for aiding a user in determining whether the user-supplied code module contains an uninitialized local variable.