Institute ofComputing Jaca: a Reflective Fault

Injection Tool based on PatternsEliane Martins

Cecilia Rubira

Nelson Leme

Institute of Computing

State University of Campinas - Unicamp

Brasil

International Performance and Dependability Symposium — IPDS’2002Washington, D.C., USA • June 23 - 26, 2002

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Contents

• Context

• Motivation and Objective

• Jaca

• Preliminary Experiments

• Conclusions

• Future Works

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Fault Injection

• Deliberate introduction of faults into a system to observe its behavior– valuable approach to validate dependability properties

– useful to evaluate impact of error recovery mechanisms into performance

• Approaches:– simulation-based fault injection

– hardware fault injection software fault injection (SFI)

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• Static injection (compile-time)

– source or Assembler code alteration • no extra code is needed• faults triggered when altered code is accessed

• needs extra code: fault injector and monitor• needs fault trigger mechanism

SFI Approaches

• Dynamic injection (runtime)–special process–interrupt routines–trace mode–code insertion

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Motivation

• Typical runtime SFI tools work at machine code levelex.: corruption of CPU registers

useful to emulate consequences of hardware failures low intrusion into the target application great effort to emulate software faults

ex.: incorrect assignment of values to variables; incorrect array indexes; missing function

• Why is it important to emulate software faults ?• software faults are major cause of system failures

• COTS software components use is increasing, even for critical applications

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Our Goals

• Problem:– Runtime injection at source-code level, affecting

objects’ attributes and methods

– Separation of concerns: fault injection and monitoring code separated from application code

• Approach used:– computational reflection

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Computational Reflection• Capability of a system to reason

about or act upon itself

• Reflective systems manipulate – external data

– meta information: data representing system’s aspects

structural reflectionmanipulation of

structural aspectsex.: definition of a class or function

behavioral reflectionmanipulation of

system’s behaviorex.: method invocation

interception

• Reflective systems’

architecture:– base level: system’s functions

– meta level: interception and/or

alteration functions

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Behavioral Reflection and OO

metaobject

meta-level

base-level

object X : classattribute A : type, valuemethod M1 : name, parameters

M1A B

M2 M3

object X

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• Evolution of FIRE: runtime fault injection tool for

applications written in C++ showed feasibility of the approach source code dependency

• Main requirements:– validation of Java applications

– high portability

– source code independence

– ability to incorporate new fault models

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• Design based on the Fault Injection Pattern set:– reuse of architectural solutions

already used to implement fault injection tools

• Code is written in pure Java• Use of Javassist reflection library:

– extends Java reflection API– requires no modification to the

standard JVM– performs reflection at bytecode level

during load time

Development Aspects

• portability• source code independence

• modularity• extensibility

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Jaca’s Architecture

Interface

Controller

InjectorManager

Monitor Manager

ActivatorLogicalInjector

Logical Injector

LogicalMonitor

LogicalMonitor

… …

PhysicalInjector

PhysicalMonitor

…

Meta Level

Base LevelTarget Application

Fault List

Log File

Class List

Jaca

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Application Instrumentation

Application’s Class Files

Metaobjects’ ClassFiles

byte code

byte code

Javassist library

Activator(class loader)

byte code +

hooks to metaobjects

Metaobject

Physical Injector

Physical Monitor

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Preliminary Experiments• Experiments to show Jaca’s extensibility:

– Assembler-level fault injection

PhysicalInjector

JNIEXPORT void JNICALL Java_LowLevelRoutine (JNIEnv *param1, jobject param2){ int a, b, c, d, op, num ;

printf ( "\n###-> testing CPUID\n” ) ; op = 1;

asm ( "cpuid" : "=a" (a), "=b" (b), "=c" (c), "=d" (d) : "a" (op));

printf ( "\n###-> Register values: - EAX: %i, EBX: %i, ECX: %i, EDX: %i\n\n", a, b, c, d ) ;

... }

Low LevelFunctions

LowLevelRoutine( )

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Conclusions and Future Works• Jaca:

– an extensible, portable software fault injector

– faults affect attributes and methods of Java applications

– fault injection uses computational reflection source code independent but ... dependent on reflection toolkit used

• Further works:– validate real world applications

• COTS ODBMS is being tested

– extend Jaca’s functionalities

– use of other reflection toolkits: Guaraná, Kava

– explore Assembler-level fault injection features

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Thank you !

• Our emails:

eliane@ic.unicamp.br

cmrubira@ic.unicamp.br

nleme@post.com