1 /*
2 * Copyright (c) 2022, 2025, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package jdk.internal.classfile.impl;
27
28 import java.lang.classfile.BufWriter;
29 import java.lang.classfile.ClassModel;
30 import java.lang.classfile.ClassReader;
31 import java.lang.classfile.Label;
32 import java.lang.classfile.MethodModel;
33 import java.lang.classfile.attribute.StackMapFrameInfo;
34 import java.lang.classfile.attribute.StackMapFrameInfo.ObjectVerificationTypeInfo;
35 import java.lang.classfile.attribute.StackMapFrameInfo.SimpleVerificationTypeInfo;
36 import java.lang.classfile.attribute.StackMapFrameInfo.UninitializedVerificationTypeInfo;
37 import java.lang.classfile.attribute.StackMapFrameInfo.VerificationTypeInfo;
38 import java.lang.classfile.constantpool.ClassEntry;
39 import java.lang.classfile.constantpool.NameAndTypeEntry;
40 import java.lang.classfile.constantpool.PoolEntry;
41 import java.lang.classfile.constantpool.Utf8Entry;
42 import java.lang.constant.ConstantDescs;
43 import java.lang.constant.MethodTypeDesc;
44 import java.lang.reflect.AccessFlag;
45 import java.util.ArrayList;
46 import java.util.Arrays;
47 import java.util.Comparator;
48 import java.util.List;
49 import java.util.Objects;
50
51 import jdk.internal.access.SharedSecrets;
52
53 import static java.lang.classfile.ClassFile.*;
54 import static java.lang.classfile.attribute.StackMapFrameInfo.VerificationTypeInfo.*;
55 import static java.util.Objects.requireNonNull;
56
57 public class StackMapDecoder {
58
59 static final int
60 EARLY_LARVAL = 246,
61 SAME_LOCALS_1_STACK_ITEM_EXTENDED = 247,
62 SAME_EXTENDED = 251;
63 private static final int BASE_FRAMES_UPPER_LIMIT = SAME_LOCALS_1_STACK_ITEM_EXTENDED; // not inclusive
64 private static final StackMapFrameInfo[] NO_STACK_FRAME_INFOS = {};
65
66 private final ClassReader classReader;
67 private final int pos;
68 private final LabelContext ctx;
69 private final List<VerificationTypeInfo> initFrameLocals;
70 private final List<NameAndTypeEntry> initFrameUnsets;
71 private int p;
72
73 StackMapDecoder(ClassReader classReader, int pos, LabelContext ctx, List<VerificationTypeInfo> initFrameLocals,
74 List<NameAndTypeEntry> initFrameUnsets) {
75 this.classReader = classReader;
76 this.pos = pos;
77 this.ctx = ctx;
78 this.initFrameLocals = initFrameLocals;
79 this.initFrameUnsets = initFrameUnsets;
80 }
81
82 static List<VerificationTypeInfo> initFrameLocals(MethodModel method) {
83 return initFrameLocals(method.parent().orElseThrow().thisClass(),
84 method.methodName().stringValue(),
85 method.methodTypeSymbol(),
86 method.flags().has(AccessFlag.STATIC));
87 }
88
89 public static List<VerificationTypeInfo> initFrameLocals(ClassEntry thisClass, String methodName, MethodTypeDesc methodType, boolean isStatic) {
90 VerificationTypeInfo vtis[];
91 int i = 0;
92 if (!isStatic) {
93 vtis = new VerificationTypeInfo[methodType.parameterCount() + 1];
94 if ("<init>".equals(methodName) && !ConstantDescs.CD_Object.equals(thisClass.asSymbol())) {
95 vtis[i++] = SimpleVerificationTypeInfo.UNINITIALIZED_THIS;
96 } else {
97 vtis[i++] = new StackMapDecoder.ObjectVerificationTypeInfoImpl(thisClass);
98 }
99 } else {
100 vtis = new VerificationTypeInfo[methodType.parameterCount()];
101 }
102 for (int pi = 0; pi < methodType.parameterCount(); pi++) {
103 var arg = methodType.parameterType(pi);
104 vtis[i++] = switch (arg.descriptorString().charAt(0)) {
105 case 'I', 'S', 'C' ,'B', 'Z' -> SimpleVerificationTypeInfo.INTEGER;
106 case 'J' -> SimpleVerificationTypeInfo.LONG;
107 case 'F' -> SimpleVerificationTypeInfo.FLOAT;
108 case 'D' -> SimpleVerificationTypeInfo.DOUBLE;
109 case 'V' -> throw new IllegalArgumentException("Illegal method argument type: " + arg);
110 default -> new StackMapDecoder.ObjectVerificationTypeInfoImpl(TemporaryConstantPool.INSTANCE.classEntry(arg));
111 };
112 }
113 return List.of(vtis);
114 }
115
116 static List<NameAndTypeEntry> initFrameUnsets(MethodModel method) {
117 return initFrameUnsets(method.parent().orElseThrow(),
118 method.methodName());
119 }
120
121 private static List<NameAndTypeEntry> initFrameUnsets(ClassModel clazz, Utf8Entry methodName) {
122 if (!methodName.equalsString(ConstantDescs.INIT_NAME))
123 return List.of();
124 if (clazz.minorVersion() != PREVIEW_MINOR_VERSION || clazz.majorVersion() < Util.VALUE_OBJECTS_MAJOR)
125 return List.of();
126 var l = new ArrayList<NameAndTypeEntry>(clazz.fields().size());
127 for (var field : clazz.fields()) {
128 if ((field.flags().flagsMask() & (ACC_STATIC | ACC_STRICT_INIT)) == ACC_STRICT_INIT) { // instance strict
129 l.add(TemporaryConstantPool.INSTANCE.nameAndTypeEntry(field.fieldName(), field.fieldType()));
130 }
131 }
132 return List.copyOf(l);
133 }
134
135 private static List<NameAndTypeEntry> initFrameUnsets(MethodInfo mi, WritableField.UnsetField[] unsets) {
136 if (!mi.methodName().equalsString(ConstantDescs.INIT_NAME))
137 return List.of();
138 var l = new ArrayList<NameAndTypeEntry>(unsets.length);
139 for (var field : unsets) {
140 l.add(TemporaryConstantPool.INSTANCE.nameAndTypeEntry(field.name(), field.type()));
141 }
142 return List.copyOf(l);
143 }
144
145 public static void writeFrames(BufWriter b, List<StackMapFrameInfo> entries) {
146 var buf = (BufWriterImpl)b;
147 var dcb = (DirectCodeBuilder)buf.labelContext();
148 var mi = dcb.methodInfo();
149 var prevLocals = StackMapDecoder.initFrameLocals(buf.thisClass(),
150 mi.methodName().stringValue(),
151 mi.methodTypeSymbol(),
152 (mi.methodFlags() & ACC_STATIC) != 0);
153 var prevUnsets = initFrameUnsets(mi, buf.getStrictInstanceFields());
154 int prevOffset = -1;
155 // avoid using method handles due to early bootstrap
156 StackMapFrameInfo[] infos = entries.toArray(NO_STACK_FRAME_INFOS);
157 //sort by resolved label offsets first to allow unordered entries
158 Arrays.sort(infos, new Comparator<StackMapFrameInfo>() {
159 public int compare(final StackMapFrameInfo o1, final StackMapFrameInfo o2) {
160 return Integer.compare(dcb.labelToBci(o1.target()), dcb.labelToBci(o2.target()));
161 }
162 });
163 b.writeU2(infos.length);
164 for (var fr : infos) {
165 int offset = dcb.labelToBci(fr.target());
166 if (offset == prevOffset) {
167 throw new IllegalArgumentException("Duplicated stack frame bytecode index: " + offset);
168 }
169 writeFrame(buf, offset - prevOffset - 1, prevLocals, prevUnsets, fr);
170 prevOffset = offset;
171 prevLocals = fr.locals();
172 prevUnsets = fr.unsetFields();
173 }
174 }
175
176 // In sync with StackMapGenerator::needsLarvalFrame
177 private static boolean needsLarvalFrameForTransition(List<NameAndTypeEntry> prevUnsets, StackMapFrameInfo fr) {
178 if (prevUnsets.equals(fr.unsetFields()))
179 return false;
180 if (!fr.locals().contains(SimpleVerificationTypeInfo.UNINITIALIZED_THIS)) {
181 assert fr.unsetFields().isEmpty() : fr; // should be checked in StackMapFrameInfo constructor
182 return false;
183 }
184 return true;
185 }
186
187 private static void writeFrame(BufWriterImpl out, int offsetDelta, List<VerificationTypeInfo> prevLocals, List<NameAndTypeEntry> prevUnsets, StackMapFrameInfo fr) {
188 if (offsetDelta < 0) throw new IllegalArgumentException("Invalid stack map frames order");
189 // enclosing frames
190 if (needsLarvalFrameForTransition(prevUnsets, fr)) {
191 out.writeU1(EARLY_LARVAL);
192 Util.writeListIndices(out, fr.unsetFields());
193 }
194 // base frame
195 if (fr.stack().isEmpty()) {
196 int commonLocalsSize = Math.min(prevLocals.size(), fr.locals().size());
197 int diffLocalsSize = fr.locals().size() - prevLocals.size();
198 if (-3 <= diffLocalsSize && diffLocalsSize <= 3 && equals(fr.locals(), prevLocals, commonLocalsSize)) {
199 if (diffLocalsSize == 0 && offsetDelta < 64) { //same frame
200 out.writeU1(offsetDelta);
201 } else { //chop, same extended or append frame
202 out.writeU1U2(251 + diffLocalsSize, offsetDelta);
203 for (int i=commonLocalsSize; i<fr.locals().size(); i++) writeTypeInfo(out, fr.locals().get(i));
204 }
205 return;
206 }
207 } else if (fr.stack().size() == 1 && fr.locals().equals(prevLocals)) {
208 if (offsetDelta < 64) { //same locals 1 stack item frame
209 out.writeU1(64 + offsetDelta);
210 } else { //same locals 1 stack item extended frame
211 out.writeU1U2(247, offsetDelta);
212 }
213 writeTypeInfo(out, fr.stack().get(0));
214 return;
215 }
216 //full frame
217 out.writeU1U2U2(255, offsetDelta, fr.locals().size());
218 for (var l : fr.locals()) writeTypeInfo(out, l);
219 out.writeU2(fr.stack().size());
220 for (var s : fr.stack()) writeTypeInfo(out, s);
221 }
222
223 private static boolean equals(List<VerificationTypeInfo> l1, List<VerificationTypeInfo> l2, int compareSize) {
224 for (int i = 0; i < compareSize; i++) {
225 if (!l1.get(i).equals(l2.get(i))) return false;
226 }
227 return true;
228 }
229
230 private static void writeTypeInfo(BufWriterImpl bw, VerificationTypeInfo vti) {
231 int tag = vti.tag();
232 switch (tag) {
233 case ITEM_TOP, ITEM_INTEGER, ITEM_FLOAT, ITEM_DOUBLE, ITEM_LONG, ITEM_NULL,
234 ITEM_UNINITIALIZED_THIS ->
235 bw.writeU1(tag);
236 case ITEM_OBJECT ->
237 bw.writeU1U2(tag, bw.cpIndex(((ObjectVerificationTypeInfo)vti).className()));
238 case ITEM_UNINITIALIZED ->
239 bw.writeU1U2(tag, bw.labelContext().labelToBci(((UninitializedVerificationTypeInfo)vti).newTarget()));
240 default -> throw new IllegalArgumentException("Invalid verification type tag: " + vti.tag());
241 }
242 }
243
244 // Copied from BoundAttribute
245 <E extends PoolEntry> List<E> readEntryList(int p, Class<E> type) {
246 int cnt = classReader.readU2(p);
247 p += 2;
248 var entries = new Object[cnt];
249 int end = p + (cnt * 2);
250 for (int i = 0; p < end; i++, p += 2) {
251 entries[i] = classReader.readEntry(p, type);
252 }
253 return SharedSecrets.getJavaUtilCollectionAccess().listFromTrustedArray(entries);
254 }
255
256 List<StackMapFrameInfo> entries() {
257 p = pos;
258 List<VerificationTypeInfo> locals = initFrameLocals, stack = List.of();
259 List<NameAndTypeEntry> unsetFields = initFrameUnsets;
260 int bci = -1;
261 var entries = new StackMapFrameInfo[u2()];
262 for (int ei = 0; ei < entries.length; ei++) {
263 int actualFrameType = classReader.readU1(p++);
264 int frameType = actualFrameType; // effective frame type for parsing
265 // enclosing frames handling
266 if (frameType == EARLY_LARVAL) {
267 unsetFields = readEntryList(p, NameAndTypeEntry.class);
268 p += 2 + unsetFields.size() * 2;
269 frameType = classReader.readU1(p++);
270 }
271 // base frame handling
272 if (frameType < 64) {
273 bci += frameType + 1;
274 stack = List.of();
275 } else if (frameType < 128) {
276 bci += frameType - 63;
277 stack = List.of(readVerificationTypeInfo());
278 } else {
279 if (frameType < BASE_FRAMES_UPPER_LIMIT)
280 throw new IllegalArgumentException("Invalid base frame type: " + frameType);
281 bci += u2() + 1;
282 if (frameType == SAME_LOCALS_1_STACK_ITEM_EXTENDED) {
283 stack = List.of(readVerificationTypeInfo());
284 } else if (frameType < SAME_EXTENDED) {
285 locals = locals.subList(0, locals.size() + frameType - SAME_EXTENDED);
286 stack = List.of();
287 } else if (frameType == SAME_EXTENDED) {
288 stack = List.of();
289 } else if (frameType < SAME_EXTENDED + 4) {
290 int actSize = locals.size();
291 var newLocals = locals.toArray(new VerificationTypeInfo[actSize + frameType - SAME_EXTENDED]);
292 for (int i = actSize; i < newLocals.length; i++)
293 newLocals[i] = readVerificationTypeInfo();
294 locals = List.of(newLocals);
295 stack = List.of();
296 } else {
297 var newLocals = new VerificationTypeInfo[u2()];
298 for (int i=0; i<newLocals.length; i++)
299 newLocals[i] = readVerificationTypeInfo();
300 var newStack = new VerificationTypeInfo[u2()];
301 for (int i=0; i<newStack.length; i++)
302 newStack[i] = readVerificationTypeInfo();
303 locals = List.of(newLocals);
304 stack = List.of(newStack);
305 }
306 }
307 if (actualFrameType != EARLY_LARVAL && !unsetFields.isEmpty() && !locals.contains(SimpleVerificationTypeInfo.UNINITIALIZED_THIS)) {
308 // clear unsets post larval
309 unsetFields = List.of();
310 }
311 entries[ei] = new StackMapFrameImpl(actualFrameType,
312 ctx.getLabel(bci),
313 locals,
314 stack,
315 unsetFields);
316 }
317 return List.of(entries);
318 }
319
320 private VerificationTypeInfo readVerificationTypeInfo() {
321 int tag = classReader.readU1(p++);
322 return switch (tag) {
323 case ITEM_TOP -> SimpleVerificationTypeInfo.TOP;
324 case ITEM_INTEGER -> SimpleVerificationTypeInfo.INTEGER;
325 case ITEM_FLOAT -> SimpleVerificationTypeInfo.FLOAT;
326 case ITEM_DOUBLE -> SimpleVerificationTypeInfo.DOUBLE;
327 case ITEM_LONG -> SimpleVerificationTypeInfo.LONG;
328 case ITEM_NULL -> SimpleVerificationTypeInfo.NULL;
329 case ITEM_UNINITIALIZED_THIS -> SimpleVerificationTypeInfo.UNINITIALIZED_THIS;
330 case ITEM_OBJECT -> new ObjectVerificationTypeInfoImpl(classReader.entryByIndex(u2(), ClassEntry.class));
331 case ITEM_UNINITIALIZED -> new UninitializedVerificationTypeInfoImpl(ctx.getLabel(u2()));
332 default -> throw new IllegalArgumentException("Invalid verification type tag: " + tag);
333 };
334 }
335
336 public static record ObjectVerificationTypeInfoImpl(
337 ClassEntry className) implements ObjectVerificationTypeInfo {
338 public ObjectVerificationTypeInfoImpl {
339 requireNonNull(className);
340 }
341
342 @Override
343 public int tag() { return ITEM_OBJECT; }
344
345 @Override
346 public boolean equals(Object o) {
347 if (this == o) return true;
348 if (o instanceof ObjectVerificationTypeInfoImpl that) {
349 return Objects.equals(className, that.className);
350 }
351 return false;
352 }
353
354 @Override
355 public int hashCode() {
356 return Objects.hash(className);
357 }
358
359 @Override
360 public String toString() {
361 return className.asInternalName();
362 }
363 }
364
365 public static record UninitializedVerificationTypeInfoImpl(Label newTarget) implements UninitializedVerificationTypeInfo {
366 public UninitializedVerificationTypeInfoImpl {
367 requireNonNull(newTarget);
368 }
369
370 @Override
371 public int tag() { return ITEM_UNINITIALIZED; }
372
373 @Override
374 public String toString() {
375 return "UNINIT(" + newTarget +")";
376 }
377 }
378
379 private int u2() {
380 int v = classReader.readU2(p);
381 p += 2;
382 return v;
383 }
384
385 public static record StackMapFrameImpl(int frameType,
386 Label target,
387 List<VerificationTypeInfo> locals,
388 List<VerificationTypeInfo> stack,
389 List<NameAndTypeEntry> unsetFields)
390 implements StackMapFrameInfo {
391 public StackMapFrameImpl {
392 requireNonNull(target);
393 locals = Util.sanitizeU2List(locals);
394 stack = Util.sanitizeU2List(stack);
395 unsetFields = Util.sanitizeU2List(unsetFields);
396
397 uninitializedThisCheck:
398 if (!unsetFields.isEmpty()) {
399 for (var local : locals) {
400 if (local == SimpleVerificationTypeInfo.UNINITIALIZED_THIS) {
401 break uninitializedThisCheck;
402 }
403 }
404 throw new IllegalArgumentException("unset fields requires uninitializedThis in locals");
405 }
406 }
407
408 public StackMapFrameImpl(int frameType,
409 Label target,
410 List<VerificationTypeInfo> locals,
411 List<VerificationTypeInfo> stack) {
412 this(frameType, target, locals, stack, List.of());
413 }
414 }
415 }