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Dynamic scripting for the JVM
/*
* Copyright (C) 2007 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.snapscript.dx.dex.file;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import org.snapscript.dx.dex.code.DalvCode;
import org.snapscript.dx.dex.code.DalvInsnList;
import org.snapscript.dx.dex.code.LocalList;
import org.snapscript.dx.dex.code.PositionList;
import org.snapscript.dx.rop.cst.CstMethodRef;
import org.snapscript.dx.rop.cst.CstString;
import org.snapscript.dx.rop.type.Prototype;
import org.snapscript.dx.rop.type.StdTypeList;
import org.snapscript.dx.rop.type.Type;
import org.snapscript.dx.util.ByteArrayByteInput;
import org.snapscript.dx.util.ByteInput;
import org.snapscript.dx.util.ExceptionWithContext;
import org.snapscript.dx.util.Leb128Utils;
import static org.snapscript.dx.dex.file.DebugInfoConstants.*;
/**
* A decoder for the dex debug info state machine format.
* This code exists mostly as a reference implementation and test for
* for the {@code DebugInfoEncoder}
*/
public class DebugInfoDecoder {
/** encoded debug info */
private final byte[] encoded;
/** positions decoded */
private final ArrayList positions;
/** locals decoded */
private final ArrayList locals;
/** size of code block in code units */
private final int codesize;
/** indexed by register, the last local variable live in a reg */
private final LocalEntry[] lastEntryForReg;
/** method descriptor of method this debug info is for */
private final Prototype desc;
/** true if method is static */
private final boolean isStatic;
/** dex file this debug info will be stored in */
private final DexFile file;
/**
* register size, in register units, of the register space
* used by this method
*/
private final int regSize;
/** current decoding state: line number */
private int line = 1;
/** current decoding state: bytecode address */
private int address = 0;
/** string index of the string "this" */
private final int thisStringIdx;
/**
* Constructs an instance.
*
* @param encoded encoded debug info
* @param codesize size of code block in code units
* @param regSize register size, in register units, of the register space
* used by this method
* @param isStatic true if method is static
* @param ref method descriptor of method this debug info is for
* @param file dex file this debug info will be stored in
*/
DebugInfoDecoder(byte[] encoded, int codesize, int regSize,
boolean isStatic, CstMethodRef ref, DexFile file) {
if (encoded == null) {
throw new NullPointerException("encoded == null");
}
this.encoded = encoded;
this.isStatic = isStatic;
this.desc = ref.getPrototype();
this.file = file;
this.regSize = regSize;
positions = new ArrayList();
locals = new ArrayList();
this.codesize = codesize;
lastEntryForReg = new LocalEntry[regSize];
int idx = -1;
try {
idx = file.getStringIds().indexOf(new CstString("this"));
} catch (IllegalArgumentException ex) {
/*
* Silently tolerate not finding "this". It just means that
* no method has local variable info that looks like
* a standard instance method.
*/
}
thisStringIdx = idx;
}
/**
* An entry in the resulting postions table
*/
static private class PositionEntry {
/** bytecode address */
public int address;
/** line number */
public int line;
public PositionEntry(int address, int line) {
this.address = address;
this.line = line;
}
}
/**
* An entry in the resulting locals table
*/
static private class LocalEntry {
/** address of event */
public int address;
/** {@code true} iff it's a local start */
public boolean isStart;
/** register number */
public int reg;
/** index of name in strings table */
public int nameIndex;
/** index of type in types table */
public int typeIndex;
/** index of type signature in strings table */
public int signatureIndex;
public LocalEntry(int address, boolean isStart, int reg, int nameIndex,
int typeIndex, int signatureIndex) {
this.address = address;
this.isStart = isStart;
this.reg = reg;
this.nameIndex = nameIndex;
this.typeIndex = typeIndex;
this.signatureIndex = signatureIndex;
}
public String toString() {
return String.format("[%x %s v%d %04x %04x %04x]",
address, isStart ? "start" : "end", reg,
nameIndex, typeIndex, signatureIndex);
}
}
/**
* Gets the decoded positions list.
* Valid after calling {@code decode}.
*
* @return positions list in ascending address order.
*/
public List getPositionList() {
return positions;
}
/**
* Gets the decoded locals list, in ascending start-address order.
* Valid after calling {@code decode}.
*
* @return locals list in ascending address order.
*/
public List getLocals() {
return locals;
}
/**
* Decodes the debug info sequence.
*/
public void decode() {
try {
decode0();
} catch (Exception ex) {
throw ExceptionWithContext.withContext(ex,
"...while decoding debug info");
}
}
/**
* Reads a string index. String indicies are offset by 1, and a 0 value
* in the stream (-1 as returned by this method) means "null"
*
* @return index into file's string ids table, -1 means null
* @throws IOException
*/
private int readStringIndex(ByteInput bs) throws IOException {
int offsetIndex = Leb128Utils.readUnsignedLeb128(bs);
return offsetIndex - 1;
}
/**
* Gets the register that begins the method's parameter range (including
* the 'this' parameter for non-static methods). The range continues until
* {@code regSize}
*
* @return register as noted above.
*/
private int getParamBase() {
return regSize
- desc.getParameterTypes().getWordCount() - (isStatic? 0 : 1);
}
private void decode0() throws IOException {
ByteInput bs = new ByteArrayByteInput(encoded);
line = Leb128Utils.readUnsignedLeb128(bs);
int szParams = Leb128Utils.readUnsignedLeb128(bs);
StdTypeList params = desc.getParameterTypes();
int curReg = getParamBase();
if (szParams != params.size()) {
throw new RuntimeException(
"Mismatch between parameters_size and prototype");
}
if (!isStatic) {
// Start off with implicit 'this' entry
LocalEntry thisEntry =
new LocalEntry(0, true, curReg, thisStringIdx, 0, 0);
locals.add(thisEntry);
lastEntryForReg[curReg] = thisEntry;
curReg++;
}
for (int i = 0; i < szParams; i++) {
Type paramType = params.getType(i);
LocalEntry le;
int nameIdx = readStringIndex(bs);
if (nameIdx == -1) {
/*
* Unnamed parameter; often but not always filled in by an
* extended start op after the prologue
*/
le = new LocalEntry(0, true, curReg, -1, 0, 0);
} else {
// TODO: Final 0 should be idx of paramType.getDescriptor().
le = new LocalEntry(0, true, curReg, nameIdx, 0, 0);
}
locals.add(le);
lastEntryForReg[curReg] = le;
curReg += paramType.getCategory();
}
for (;;) {
int opcode = bs.readByte() & 0xff;
switch (opcode) {
case DBG_START_LOCAL: {
int reg = Leb128Utils.readUnsignedLeb128(bs);
int nameIdx = readStringIndex(bs);
int typeIdx = readStringIndex(bs);
LocalEntry le = new LocalEntry(
address, true, reg, nameIdx, typeIdx, 0);
locals.add(le);
lastEntryForReg[reg] = le;
}
break;
case DBG_START_LOCAL_EXTENDED: {
int reg = Leb128Utils.readUnsignedLeb128(bs);
int nameIdx = readStringIndex(bs);
int typeIdx = readStringIndex(bs);
int sigIdx = readStringIndex(bs);
LocalEntry le = new LocalEntry(
address, true, reg, nameIdx, typeIdx, sigIdx);
locals.add(le);
lastEntryForReg[reg] = le;
}
break;
case DBG_RESTART_LOCAL: {
int reg = Leb128Utils.readUnsignedLeb128(bs);
LocalEntry prevle;
LocalEntry le;
try {
prevle = lastEntryForReg[reg];
if (prevle.isStart) {
throw new RuntimeException("nonsensical "
+ "RESTART_LOCAL on live register v"
+ reg);
}
le = new LocalEntry(address, true, reg,
prevle.nameIndex, prevle.typeIndex, 0);
} catch (NullPointerException ex) {
throw new RuntimeException(
"Encountered RESTART_LOCAL on new v" + reg);
}
locals.add(le);
lastEntryForReg[reg] = le;
}
break;
case DBG_END_LOCAL: {
int reg = Leb128Utils.readUnsignedLeb128(bs);
LocalEntry prevle;
LocalEntry le;
try {
prevle = lastEntryForReg[reg];
if (!prevle.isStart) {
throw new RuntimeException("nonsensical "
+ "END_LOCAL on dead register v" + reg);
}
le = new LocalEntry(address, false, reg,
prevle.nameIndex, prevle.typeIndex,
prevle.signatureIndex);
} catch (NullPointerException ex) {
throw new RuntimeException(
"Encountered END_LOCAL on new v" + reg);
}
locals.add(le);
lastEntryForReg[reg] = le;
}
break;
case DBG_END_SEQUENCE:
// all done
return;
case DBG_ADVANCE_PC:
address += Leb128Utils.readUnsignedLeb128(bs);
break;
case DBG_ADVANCE_LINE:
line += Leb128Utils.readSignedLeb128(bs);
break;
case DBG_SET_PROLOGUE_END:
//TODO do something with this.
break;
case DBG_SET_EPILOGUE_BEGIN:
//TODO do something with this.
break;
case DBG_SET_FILE:
//TODO do something with this.
break;
default:
if (opcode < DBG_FIRST_SPECIAL) {
throw new RuntimeException(
"Invalid extended opcode encountered "
+ opcode);
}
int adjopcode = opcode - DBG_FIRST_SPECIAL;
address += adjopcode / DBG_LINE_RANGE;
line += DBG_LINE_BASE + (adjopcode % DBG_LINE_RANGE);
positions.add(new PositionEntry(address, line));
break;
}
}
}
/**
* Validates an encoded debug info stream against data used to encode it,
* throwing an exception if they do not match. Used to validate the
* encoder.
*
* @param info encoded debug info
* @param file {@code non-null;} file to refer to during decoding
* @param ref {@code non-null;} method whose info is being decoded
* @param code {@code non-null;} original code object that was encoded
* @param isStatic whether the method is static
*/
public static void validateEncode(byte[] info, DexFile file,
CstMethodRef ref, DalvCode code, boolean isStatic) {
PositionList pl = code.getPositions();
LocalList ll = code.getLocals();
DalvInsnList insns = code.getInsns();
int codeSize = insns.codeSize();
int countRegisters = insns.getRegistersSize();
try {
validateEncode0(info, codeSize, countRegisters,
isStatic, ref, file, pl, ll);
} catch (RuntimeException ex) {
System.err.println("instructions:");
insns.debugPrint(System.err, " ", true);
System.err.println("local list:");
ll.debugPrint(System.err, " ");
throw ExceptionWithContext.withContext(ex,
"while processing " + ref.toHuman());
}
}
private static void validateEncode0(byte[] info, int codeSize,
int countRegisters, boolean isStatic, CstMethodRef ref,
DexFile file, PositionList pl, LocalList ll) {
DebugInfoDecoder decoder
= new DebugInfoDecoder(info, codeSize, countRegisters,
isStatic, ref, file);
decoder.decode();
/*
* Go through the decoded position entries, matching up
* with original entries.
*/
List decodedEntries = decoder.getPositionList();
if (decodedEntries.size() != pl.size()) {
throw new RuntimeException(
"Decoded positions table not same size was "
+ decodedEntries.size() + " expected " + pl.size());
}
for (PositionEntry entry : decodedEntries) {
boolean found = false;
for (int i = pl.size() - 1; i >= 0; i--) {
PositionList.Entry ple = pl.get(i);
if (entry.line == ple.getPosition().getLine()
&& entry.address == ple.getAddress()) {
found = true;
break;
}
}
if (!found) {
throw new RuntimeException ("Could not match position entry: "
+ entry.address + ", " + entry.line);
}
}
/*
* Go through the original local list, in order, matching up
* with decoded entries.
*/
List decodedLocals = decoder.getLocals();
int thisStringIdx = decoder.thisStringIdx;
int decodedSz = decodedLocals.size();
int paramBase = decoder.getParamBase();
/*
* Preflight to fill in any parameters that were skipped in
* the prologue (including an implied "this") but then
* identified by full signature.
*/
for (int i = 0; i < decodedSz; i++) {
LocalEntry entry = decodedLocals.get(i);
int idx = entry.nameIndex;
if ((idx < 0) || (idx == thisStringIdx)) {
for (int j = i + 1; j < decodedSz; j++) {
LocalEntry e2 = decodedLocals.get(j);
if (e2.address != 0) {
break;
}
if ((entry.reg == e2.reg) && e2.isStart) {
decodedLocals.set(i, e2);
decodedLocals.remove(j);
decodedSz--;
break;
}
}
}
}
int origSz = ll.size();
int decodeAt = 0;
boolean problem = false;
for (int i = 0; i < origSz; i++) {
LocalList.Entry origEntry = ll.get(i);
if (origEntry.getDisposition()
== LocalList.Disposition.END_REPLACED) {
/*
* The encoded list doesn't represent replacements, so
* ignore them for the sake of comparison.
*/
continue;
}
LocalEntry decodedEntry;
do {
decodedEntry = decodedLocals.get(decodeAt);
if (decodedEntry.nameIndex >= 0) {
break;
}
/*
* A negative name index means this is an anonymous
* parameter, and we shouldn't expect to see it in the
* original list. So, skip it.
*/
decodeAt++;
} while (decodeAt < decodedSz);
int decodedAddress = decodedEntry.address;
if (decodedEntry.reg != origEntry.getRegister()) {
System.err.println("local register mismatch at orig " + i +
" / decoded " + decodeAt);
problem = true;
break;
}
if (decodedEntry.isStart != origEntry.isStart()) {
System.err.println("local start/end mismatch at orig " + i +
" / decoded " + decodeAt);
problem = true;
break;
}
/*
* The secondary check here accounts for the fact that a
* parameter might not be marked as starting at 0 in the
* original list.
*/
if ((decodedAddress != origEntry.getAddress())
&& !((decodedAddress == 0)
&& (decodedEntry.reg >= paramBase))) {
System.err.println("local address mismatch at orig " + i +
" / decoded " + decodeAt);
problem = true;
break;
}
decodeAt++;
}
if (problem) {
System.err.println("decoded locals:");
for (LocalEntry e : decodedLocals) {
System.err.println(" " + e);
}
throw new RuntimeException("local table problem");
}
}
}