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DexTrapStackFixer.java
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88 lines (79 loc) · 2.79 KB
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package soot.dexpler;
/*-
* #%L
* Soot - a J*va Optimization Framework
* %%
* Copyright (C) 1997 - 2018 Raja Vallée-Rai and others
* %%
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as
* published by the Free Software Foundation, either version 2.1 of the
* License, or (at your option) any later version.
*
* This program 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 Lesser Public License for more details.
*
* You should have received a copy of the GNU General Lesser Public
* License along with this program. If not, see
* <http://www.gnu.org/licenses/lgpl-2.1.html>.
* #L%
*/
import java.util.Map;
import soot.Body;
import soot.BodyTransformer;
import soot.Local;
import soot.Scene;
import soot.Trap;
import soot.Unit;
import soot.jimple.CaughtExceptionRef;
import soot.jimple.IdentityStmt;
import soot.jimple.Jimple;
import soot.jimple.Stmt;
/**
* Transformer to ensure that all exception handlers pull the exception object. In other words, if an exception handler must
* always have a unit like
*
* $r10 = @caughtexception
*
* This is especially important if the dex code is later to be translated into Java bytecode. If no one ever accesses the
* exception object, it will reside on the stack forever, potentially leading to mismatching stack heights.
*
* @author Steven Arzt
*
*/
public class DexTrapStackFixer extends BodyTransformer {
public static DexTrapStackFixer v() {
return new DexTrapStackFixer();
}
@Override
protected void internalTransform(Body b, String phaseName, Map<String, String> options) {
for (Trap t : b.getTraps()) {
// If the first statement already catches the exception, we're fine
if (isCaughtExceptionRef(t.getHandlerUnit())) {
continue;
}
// Add the exception reference
Local l = Scene.v().createLocalGenerator(b).generateLocal(t.getException().getType());
Stmt caughtStmt = Jimple.v().newIdentityStmt(l, Jimple.v().newCaughtExceptionRef());
b.getUnits().add(caughtStmt);
b.getUnits().add(Jimple.v().newGotoStmt(t.getHandlerUnit()));
t.setHandlerUnit(caughtStmt);
}
}
/**
* Checks whether the given statement stores an exception reference
*
* @param handlerUnit
* The statement to check
* @return True if the given statement stores an exception reference, otherwise false
*/
private boolean isCaughtExceptionRef(Unit handlerUnit) {
if (!(handlerUnit instanceof IdentityStmt)) {
return false;
}
IdentityStmt stmt = (IdentityStmt) handlerUnit;
return stmt.getRightOp() instanceof CaughtExceptionRef;
}
}