Package de.fraunhofer.aisec.cpg.passes

Class ControlFlowSensitiveDFGPass

java.lang.Object

de.fraunhofer.aisec.cpg.passes.Pass

de.fraunhofer.aisec.cpg.passes.ControlFlowSensitiveDFGPass

All Implemented Interfaces:

java.util.function.Consumer<TranslationResult>

public class ControlFlowSensitiveDFGPass
extends Pass

This pass tracks VariableDeclarations and values that are included in the graph by the DFG edge. For this pass we traverse the EOG as it represents our understanding of the execution order and can be used to remove the DFG edges that are not feasible.

Control Flow Sensitivity in the DFG is only performed on VariableDeclarations and not on FieldDeclarations. The reason for this being the fact, that the value of a field might be modified to a value that is not present in the method, thus it is not detected by our variable tracking

This pass will split up at every branch in the EOG. Because of the existence of loops and multiple paths being able to run to through the same Declared reference expression we have to keep track of the set of values (assignments) associated to a variable at JoinPoints. If the set reaching a Joinpoint is not adding new values to one variable the path does not have to be further explored. This ensures that the algorithm terminates and scales with the number of different paths in the program finally reaching a fixpoint.

This is only feasible because the values associate to a variable at fix-points is the location assignment and not its symbolically executed value, in which case we could not ensure termination for the algorithm.

We here do not solve the problem of Exception-Handling, for this we will need additional semantics on Edges.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
protected class	ControlFlowSensitiveDFGPass.FunctionLevelFixpointIterator
protected static interface	ControlFlowSensitiveDFGPass.IterationFunction

Field Summary

Fields inherited from class de.fraunhofer.aisec.cpg.passes.Pass

lang, log, name

Constructor Summary

Constructors

Constructor	Description
ControlFlowSensitiveDFGPass()

Method Summary

Modifier and Type	Method	Description
void	accept(TranslationResult translationResult)
void	cleanup()
protected void	handle(de.fraunhofer.aisec.cpg.graph.Node node)	ControlFlowSensitiveDFG Pass is performed on every method.
protected void	removeValues(ControlFlowSensitiveDFGPass.FunctionLevelFixpointIterator fixDFGs)	Removes unrefined DFG edges

Methods inherited from class de.fraunhofer.aisec.cpg.passes.Pass

getLang, getName, setLang, supportsLanguageFrontend

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface java.util.function.Consumer

andThen

Constructor Details

ControlFlowSensitiveDFGPass

public ControlFlowSensitiveDFGPass()

Method Details

cleanup

public void cleanup()

Specified by:

cleanup in class Pass

accept

public void accept(TranslationResult translationResult)

removeValues

protected void removeValues(ControlFlowSensitiveDFGPass.FunctionLevelFixpointIterator fixDFGs)

Removes unrefined DFG edges

Parameters:

fixDFGs - ControlFlowSensitiveDFG of entire Method

handle

protected void handle(de.fraunhofer.aisec.cpg.graph.Node node)

ControlFlowSensitiveDFG Pass is performed on every method.

Parameters:

node - every node in the TranslationResult