/*
* AlternatingStateTransformerFactory.java - This file is part of the Jakstab project.
* Copyright 2007-2012 Johannes Kinder <jk@jakstab.org>
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, see <http://www.gnu.org/licenses/>.
*/
package org.jakstab.cfa;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;
import org.jakstab.Options;
import org.jakstab.Program;
import org.jakstab.analysis.AbstractState;
import org.jakstab.analysis.UnderApproximateState;
import org.jakstab.analysis.composite.DualCompositeState;
import org.jakstab.asm.AbsoluteAddress;
import org.jakstab.cfa.CFAEdge.Kind;
import org.jakstab.rtl.Context;
import org.jakstab.cfa.Location;
import org.jakstab.rtl.expressions.ExpressionFactory;
import org.jakstab.rtl.expressions.RTLExpression;
import org.jakstab.rtl.expressions.RTLNumber;
import org.jakstab.rtl.statements.*;
import org.jakstab.util.FastSet;
import org.jakstab.util.Logger;
import org.jakstab.util.Tuple;
/**
* Provides state transformers without assumptions about procedures. Call instructions
* are treated as push / jmp combinations and return instructions as indirect jumps. If
* the target of a jump cannot be resolved, plug in values from an under-approximation
* to create MUST edges.
*
* For regular statements, produces MUST edges if there is an under-approximate witness.
*
* @author Johannes Kinder
*/
public class AlternatingStateTransformerFactory extends ResolvingTransformerFactory {
@SuppressWarnings("unused")
private static final Logger logger = Logger.getLogger(AlternatingStateTransformerFactory.class);
private Map<RTLNumber, RTLNumber> realToStub = new HashMap<RTLNumber, RTLNumber>();
private Map<RTLNumber, RTLNumber> stubToReal = new HashMap<RTLNumber, RTLNumber>();
private Program program = Program.getProgram();
@Override
public Set<CFAEdge> getTransformers(final AbstractState a) {
RTLStatement stmt = Program.getProgram().getStatement(a.getLocation());
Set<CFAEdge> transformers = stmt.accept(new DefaultStatementVisitor<Set<CFAEdge>>() {
@Override
protected Set<CFAEdge> visitDefault(RTLStatement stmt) {
CFAEdge.Kind edgeKind = Kind.MAY;
// If any under-approximate component is not BOT, then we have a witness
// and this is a MUST edge.
DualCompositeState dcs = (DualCompositeState)a;
for (int i = 0; i < dcs.numComponents(); i++) {
AbstractState componentState = dcs.getComponent(i);
if (componentState instanceof UnderApproximateState &&
!componentState.isBot()) {
edgeKind = Kind.MUST;
break;
}
}
return Collections.singleton(new CFAEdge(stmt.getLabel(), stmt.getNextLabel(), stmt, edgeKind));
}
@Override
public Set<CFAEdge> visit(RTLGoto stmt) {
assert stmt.getCondition() != null;
Set<CFAEdge> results = new FastSet<CFAEdge>();
if (Options.procedureAbstraction.getValue() == 2) {
// Calls always get a fallthrough edge in optimistic mode
if (stmt.getType() == RTLGoto.Type.CALL) {
Location nextLabel = stmt.getNextLabel();
if (Program.getProgram().getHarness().contains(stmt.getAddress())) {
nextLabel = new Location(Program.getProgram().getHarness().getFallthroughAddress(stmt.getAddress()));
}
if (nextLabel != null) {
RTLUnknownProcedureCall unknownCallEdge = new RTLUnknownProcedureCall(stmt);
unknownCallEdge.setLabel(stmt.getLabel());
unknownCallEdge.setNextLabel(nextLabel);
results.add(new CFAEdge(stmt.getLabel(), nextLabel, unknownCallEdge));
sound = false;
}
}
// Replace return with halt, since control flow passes over calls anyway
else if (stmt.getType() == RTLGoto.Type.RETURN) {
sound = false;
return Collections.emptySet();
}
}
DualCompositeState dcs = (DualCompositeState)a;
// Add all edges from over-approximation
for (Tuple<RTLNumber> pair : dcs.projectionFromConcretization(stmt.getCondition(), stmt.getTargetExpression())) {
RTLNumber conditionValue = pair.get(0);
RTLNumber targetValue = pair.get(1);
Location nextLabel;
// Start building the assume expression: assume correct condition case
assert conditionValue != null;
RTLExpression assumption =
ExpressionFactory.createEqual(stmt.getCondition(), conditionValue);
if (conditionValue.equals(ExpressionFactory.FALSE)) {
// assume (condition = false), and set next statement to fallthrough
nextLabel = stmt.getNextLabel();
} else {
if (targetValue == null) {
logger.debug("No value from MAY-analysis at " + stmt.getLabel());
sound = false;
unresolvedBranches.add(stmt.getLabel());
continue;
}
// assume (condition = true AND targetExpression = targetValue)
assumption = ExpressionFactory.createAnd(
assumption,
ExpressionFactory.createEqual(
stmt.getTargetExpression(),
targetValue)
);
// set next label to jump target
nextLabel = new Location(new AbsoluteAddress(targetValue));
}
assumption = assumption.evaluate(new Context());
RTLAssume assume = new RTLAssume(assumption, stmt);
assume.setLabel(stmt.getLabel());
assume.setNextLabel(nextLabel);
// Target address sanity check
if (nextLabel.getAddress().getValue() < 10L) {
logger.warn("Control flow from " + stmt.getLabel() + " reaches address " + nextLabel.getAddress() + "!");
}
results.add(new CFAEdge(assume.getLabel(), assume.getNextLabel(), assume, Kind.MAY));
}
// Add all edges from under-approximation
for (Tuple<RTLNumber> pair : dcs.projection(stmt.getCondition(), stmt.getTargetExpression())) {
RTLNumber conditionValue = pair.get(0);
RTLNumber targetValue = pair.get(1);
Location nextLabel;
// Start building the assume expression: assume correct condition case
assert conditionValue != null;
RTLExpression assumption =
ExpressionFactory.createEqual(stmt.getCondition(), conditionValue);
if (conditionValue.equals(ExpressionFactory.FALSE)) {
// assume (condition = false), and set next statement to fallthrough
nextLabel = stmt.getNextLabel();
} else {
assert targetValue != null;
// Translate real library addresses into stub addresses. Necessary because the static analysis component
// does not know about concrete import addresses, so it uses a stub system.
if (!isProgramAddress(targetValue)) {
logger.debug(dcs.getLocation() + ": Jumping out of module to " + targetValue.toHexString());
// Attempt to map this out-of-module location to a stub
if (realToStub.containsKey(targetValue)) {
// If we saw this concrete address before, replace it by the known stub
logger.debug("Replacing concrete target " + targetValue.toHexString() + " with stub to " + program.getSymbolFor(new AbsoluteAddress(realToStub.get(targetValue))));
targetValue = realToStub.get(targetValue);
} else {
// Check the statically produced edges for one that is not yet mapped to a concrete address.
// If the over-approximation resolved an import to a stub, it's going to be contained.
boolean foundStub = false;
for (CFAEdge e : results) {
RTLNumber staticTarget = e.getTarget().getAddress().toNumericConstant();
if (!isProgramAddress(staticTarget) && !stubToReal.containsKey(staticTarget)) {
// Take the first one that's neither taken nor in the program
// TODO: This could map the wrong addresses in some (hopefully) rare cases depending on analysis order
stubToReal.put(staticTarget, targetValue);
realToStub.put(targetValue, staticTarget);
targetValue = staticTarget;
foundStub = true;
break;
}
}
if (!foundStub) {
// If we have not found anything suitable, we need to create a new stub
// FIXME: The new stub will likely have incorrect stack height adjustment.
// We should extract that information from the trace.
logger.info(dcs.getLocation() + ": Creating new stub for unknown function at " + targetValue.toHexString());
RTLNumber stubTarget = Program.getProgram().getProcAddress("JAK_UNKNOWN", "proc" + targetValue.toHexString()).toNumericConstant();
stubToReal.put(stubTarget, targetValue);
realToStub.put(targetValue, stubTarget);
targetValue = stubTarget;
}
}
}
// assume (condition = true AND targetExpression = targetValue)
assumption = ExpressionFactory.createAnd(
assumption,
ExpressionFactory.createEqual(
stmt.getTargetExpression(),
targetValue)
);
// set next label to jump target
nextLabel = new Location(new AbsoluteAddress(targetValue));
}
assumption = assumption.evaluate(new Context());
RTLAssume assume = new RTLAssume(assumption, stmt);
assume.setLabel(stmt.getLabel());
assume.setNextLabel(nextLabel);
results.add(new CFAEdge(assume.getLabel(), assume.getNextLabel(), assume, Kind.MUST));
}
return results;
}
@Override
public Set<CFAEdge> visit(RTLHalt stmt) {
return Collections.emptySet();
}
});
saveNewEdges(transformers, a.getLocation());
return transformers;
}
@Override
protected void saveNewEdges(Set<CFAEdge> transformers, Location l) {
// Make sure we only add new edges. Edges are mutable so we cannot just implement
// hashCode and equals and add everything into a HashSet.
for (CFAEdge edge : transformers) {
boolean found = false;
// We check for this in the loop, because transformers may contain duplicate edges
// that only differ in their kind. So we check them against each other for upgrading
if (outEdges.containsKey(l)) {
for (CFAEdge existingEdge : outEdges.get(l)) {
if (existingEdge.getTarget().equals(edge.getTarget())) {
// There is an edge with the same target
found = true;
// Different kinds of edges
if (!existingEdge.getKind().equals(edge.getKind())) {
if (existingEdge.getKind().lessOrEqual(edge.getKind())) {
// If the new kind is greater than the existing, upgrade to new kind
//logger.debug("Upgrading existing edge " + existingEdge + " from " + existingEdge.getKind() + " to " + edge.getKind());
existingEdge.setKind(edge.getKind());
} else if (edge.getKind().lessOrEqual(existingEdge.getKind())) {
// If the existing kind is greater than the new one, upgrade new one
//logger.debug("Upgrading new edge " + edge + " from " + edge.getKind() + " to " + existingEdge.getKind());
edge.setKind(existingEdge.getKind());
} else {
// Incomparable edge kinds cannot happen with current logic
assert false : "Incomparable edge kinds!";
}
}
//break;
}
}
}
if (!found) outEdges.put(l, edge);
}
}
@Override
protected Set<CFAEdge> resolveGoto(AbstractState a, RTLGoto stmt) {
throw new UnsupportedOperationException("Not used");
}
private boolean isProgramAddress(RTLNumber n) {
return program.getModule(new AbsoluteAddress(n.longValue())) != null;
}
}