/*
* JBoss, Home of Professional Open Source
* Copyright 2008-10 Red Hat and individual contributors
* by the @authors tag. See the copyright.txt in the distribution for a
* full listing of individual contributors.
*
* This 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 software 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this software; if not, write to the Free
* Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
* 02110-1301 USA, or see the FSF site: http://www.fsf.org.
*
* @authors Andrew Dinn
*/
package org.jboss.byteman.agent.adapter;
import org.jboss.byteman.agent.Location;
import org.jboss.byteman.agent.TransformContext;
import org.objectweb.asm.ClassVisitor;
import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.Opcodes;
/**
* asm Adapter class used to add a rule event trigger call to a method of som egiven class
*/
public class VariableAccessTriggerAdapter extends RuleTriggerAdapter
{
public VariableAccessTriggerAdapter(ClassVisitor cv, TransformContext transformContext,
String varName, int flags, int count, boolean whenComplete)
{
super(cv, transformContext);
this.varName = varName;
this.flags = flags;
this.count = count;
this.whenComplete = whenComplete;
}
public MethodVisitor visitMethod(
final int access,
final String name,
final String desc,
final String signature,
final String[] exceptions)
{
MethodVisitor mv = super.visitMethod(access, name, desc, signature, exceptions);
if (injectIntoMethod(name, desc)) {
if (name.equals("<init>")) {
return new VariableAccessTriggerConstructorAdapter(mv, getTransformContext(), access, name, desc, signature, exceptions);
} else {
return new VariableAccessTriggerMethodAdapter(mv, getTransformContext(), access, name, desc, signature, exceptions);
}
}
return mv;
}
/**
* a method visitor used to add a rule event trigger call to a method
*/
private class VariableAccessTriggerMethodAdapter extends RuleTriggerMethodAdapter implements LocalScopeMethodVisitor
{
/**
* flag used by subclass to avoid inserting trigger until after super constructor has been called
*/
protected boolean latched;
private int index;
private int visitedCount;
VariableAccessTriggerMethodAdapter(MethodVisitor mv, TransformContext transformContext, int access, String name, String descriptor, String signature, String[] exceptions)
{
super(mv, transformContext, access, name, descriptor, signature, exceptions);
// index -1 indicates that the var is not in scope
this.index = -1;
visitedCount = 0;
latched = false;
}
/**
* checks if the local var coming into scope is the one mentioned in the rule location and if so
* records which slot is now being used to store the variable. this is called by the BMJSRInliner
* which feeds this adapter because this adapter implements LocalScopeMethodVisitor
* @param name
* @param desc
* @param signature
* @param stackSlot
*/
public void visitLocalScopeStart(String name, String desc, String signature, int stackSlot, int startOffset) {
if (name.equals(varName)) {
// update the current var index so we track accesses correctly
index = stackSlot;
// if this is truly a local variable rather than a param and the event is a local WRITE
// then the var comes into scope just after it is initialised. so we count this point as
// the point where an AT WRITE 1 or AFTER WRITE 1 rule should be injected. That's not
// strictly correct for an AT WRITE 1 rule but then again we cannot expose the slot
// before it is initialised since it is nto a valid slot until that point
if (startOffset > 0 && (count == 0 || (visitedCount < count)) && ((flags & Location.ACCESS_WRITE) != 0)) {
// a relevant invocation occurs in the called method
visitedCount++;
if (!latched && (count == 0 || visitedCount == count)) {
injectTriggerPoint();
}
}
}
}
/**
* checks if the local var going out of scope is the one mentioned in the rule location and if so
* records that the slot is no longer active. this is called by the BMJSRInliner
* which feeds this adapter because this adapter implements LocalScopeMethodVisitor
* @param name
* @param desc
* @param signature
* @param stackSlot
*/
public void visitLocalScopeEnd(String name, String desc, String signature, int stackSlot, int endOffset) {
if (name.equals(varName)) {
// restore the previous var index so we know which index the var is now located at
index =-1;
}
}
@Override
public void visitVarInsn(int opcode, int var) {
// this instruction can be called during trigger injection
// if we in a trigger region then we don't want to re-enter
// trigger injection or count this visit
if (inBytemanTrigger()) {
super.visitVarInsn(opcode, var);
} else {
if (whenComplete) {
super.visitVarInsn(opcode, var);
}
if (var == index) {
if ((count == 0 || (visitedCount < count)) && matchCall(opcode)) {
// a relevant invocation occurs in the called method
visitedCount++;
if (!latched && (count == 0 || visitedCount == count)) {
injectTriggerPoint();
}
}
}
if (!whenComplete) {
super.visitVarInsn(opcode, var);
}
}
}
public void visitIincInsn(int var, int increment)
{
// IINC counts as a read and a write but we need to regard it as a read, increment and then write back
// so we trigger AT READ, AFTER READ and AT WRITE before the IINC and AFTER WRITE after the IINC
boolean ruleIsAfterWrite = ((flags & Location.ACCESS_WRITE) != 0 && whenComplete);
if (ruleIsAfterWrite) {
// trigger comes after the IINC
super.visitIincInsn(var, increment);
}
if (var == index) {
// n.b. no need to check if we are in a Byteman trigegr as we never inject IINC into trigger regions
if ((count == 0 || (visitedCount < count))) {
// a relevant invocation occurs in the called method
visitedCount++;
if (!latched && (count == 0 || visitedCount == count)) {
injectTriggerPoint();
}
}
}
if (!ruleIsAfterWrite) {
// trigger comes before the IINC
super.visitIincInsn(var, increment);
}
}
private boolean matchCall(int opcode)
{
if (opcode < Opcodes.ISTORE) {
// it's a load
return ((flags & Location.ACCESS_READ) != 0);
} else {
// it's a store
return ((flags & Location.ACCESS_WRITE) != 0);
}
}
}
/**
* a method visitor used to add a rule event trigger call to a constructor -- this has to make sure
* the super constructor has been called before allowing a trigger call to be compiled
*/
private class VariableAccessTriggerConstructorAdapter extends VariableAccessTriggerMethodAdapter
{
VariableAccessTriggerConstructorAdapter(MethodVisitor mv, TransformContext transformContext, int access, String name, String descriptor, String signature, String[] exceptions)
{
super(mv, transformContext, access, name, descriptor, signature, exceptions);
// ensure we don't transform calls before the super constructor is called
latched = true;
}
public void visitMethodInsn(
final int opcode,
final String owner,
final String name,
final String desc,
boolean itf)
{
super.visitMethodInsn(opcode, owner, name, desc, itf);
// hmm, this probably means the super constructor has been invoked :-)
if (latched && isSuperOrSiblingConstructorCall(opcode, owner, name)) {
latched = false;
}
}
}
private String varName;
private int flags;
private int count;
private boolean whenComplete;
}