1 /*
2 * Copyright (c) 2008, 2023, 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 java.lang.invoke;
27
28 import jdk.internal.misc.VM;
29 import jdk.internal.ref.CleanerFactory;
30 import sun.invoke.util.Wrapper;
31
32 import java.lang.invoke.MethodHandles.Lookup;
33 import java.lang.reflect.Field;
34
35 import static java.lang.invoke.MethodHandleNatives.Constants.*;
36 import static java.lang.invoke.MethodHandleStatics.TRACE_METHOD_LINKAGE;
37 import static java.lang.invoke.MethodHandles.Lookup.IMPL_LOOKUP;
38
39 /**
40 * The JVM interface for the method handles package is all here.
41 * This is an interface internal and private to an implementation of JSR 292.
42 * <em>This class is not part of the JSR 292 standard.</em>
43 * @author jrose
44 */
45 class MethodHandleNatives {
46
47 private MethodHandleNatives() { } // static only
48
49 /// MemberName support
50
51 static native void init(MemberName self, Object ref);
52 static native void expand(MemberName self);
53 static native MemberName resolve(MemberName self, Class<?> caller, int lookupMode,
54 boolean speculativeResolve) throws LinkageError, ClassNotFoundException;
55
56 /// Field layout queries parallel to jdk.internal.misc.Unsafe:
57 static native long objectFieldOffset(MemberName self); // e.g., returns vmindex
58 static native long staticFieldOffset(MemberName self); // e.g., returns vmindex
59 static native Object staticFieldBase(MemberName self); // e.g., returns clazz
60 static native Object getMemberVMInfo(MemberName self); // returns {vmindex,vmtarget}
61
62 /// CallSite support
63
64 /** Tell the JVM that we need to change the target of a CallSite. */
65 static native void setCallSiteTargetNormal(CallSite site, MethodHandle target);
66 static native void setCallSiteTargetVolatile(CallSite site, MethodHandle target);
67
68 static native void copyOutBootstrapArguments(Class<?> caller, int[] indexInfo,
69 int start, int end,
70 Object[] buf, int pos,
71 boolean resolve,
72 Object ifNotAvailable);
73
74 /// CDS support
75 static native void checkArchivable(Class<?> type);
76
77 /** Represents a context to track nmethod dependencies on CallSite instance target. */
78 static class CallSiteContext implements Runnable {
79 //@Injected JVM_nmethodBucket* vmdependencies;
80 //@Injected jlong last_cleanup;
81
82 static CallSiteContext make(CallSite cs) {
83 final CallSiteContext newContext = new CallSiteContext();
84 // CallSite instance is tracked by a Cleanable which clears native
85 // structures allocated for CallSite context. Though the CallSite can
86 // become unreachable, its Context is retained by the Cleanable instance
87 // (which is referenced from Cleaner instance which is referenced from
88 // CleanerFactory class) until cleanup is performed.
89 CleanerFactory.cleaner().register(cs, newContext);
90 return newContext;
91 }
92
93 @Override
94 public void run() {
95 MethodHandleNatives.clearCallSiteContext(this);
96 }
97 }
98
99 /** Invalidate all recorded nmethods. */
100 private static native void clearCallSiteContext(CallSiteContext context);
101
102 private static native void registerNatives();
103 static {
104 registerNatives();
105 }
106
107 /**
108 * Compile-time constants go here. This collection exists not only for
109 * reference from clients, but also for ensuring the VM and JDK agree on the
110 * values of these constants (see {@link #verifyConstants()}).
111 */
112 static class Constants {
113 Constants() { } // static only
114
115 static final int
116 MN_IS_METHOD = 0x00010000, // method (not constructor)
117 MN_IS_CONSTRUCTOR = 0x00020000, // constructor
118 MN_IS_FIELD = 0x00040000, // field
119 MN_IS_TYPE = 0x00080000, // nested type
120 MN_CALLER_SENSITIVE = 0x00100000, // @CallerSensitive annotation detected
121 MN_TRUSTED_FINAL = 0x00200000, // trusted final field
122 MN_HIDDEN_MEMBER = 0x00400000, // members defined in a hidden class or with @Hidden
123 MN_REFERENCE_KIND_SHIFT = 24, // refKind
124 MN_REFERENCE_KIND_MASK = 0x0F000000 >> MN_REFERENCE_KIND_SHIFT;
125
126 /**
127 * Constant pool reference-kind codes, as used by CONSTANT_MethodHandle CP entries.
128 */
129 static final byte
130 REF_NONE = 0, // null value
131 REF_getField = 1,
132 REF_getStatic = 2,
133 REF_putField = 3,
134 REF_putStatic = 4,
135 REF_invokeVirtual = 5,
136 REF_invokeStatic = 6,
137 REF_invokeSpecial = 7,
138 REF_newInvokeSpecial = 8,
139 REF_invokeInterface = 9,
140 REF_LIMIT = 10;
141
142 /**
143 * Flags for Lookup.ClassOptions
144 */
145 static final int
146 NESTMATE_CLASS = 0x00000001,
147 HIDDEN_CLASS = 0x00000002,
148 STRONG_LOADER_LINK = 0x00000004,
149 ACCESS_VM_ANNOTATIONS = 0x00000008;
150
151 /**
152 * Lookup modes
153 */
154 static final int
155 LM_MODULE = Lookup.MODULE,
156 LM_UNCONDITIONAL = Lookup.UNCONDITIONAL,
157 LM_TRUSTED = -1;
158
159 }
160
161 static boolean refKindIsValid(int refKind) {
162 return (refKind > REF_NONE && refKind < REF_LIMIT);
163 }
164 static boolean refKindIsField(byte refKind) {
165 assert(refKindIsValid(refKind));
166 return (refKind <= REF_putStatic);
167 }
168 static boolean refKindIsGetter(byte refKind) {
169 assert(refKindIsValid(refKind));
170 return (refKind <= REF_getStatic);
171 }
172 static boolean refKindIsSetter(byte refKind) {
173 return refKindIsField(refKind) && !refKindIsGetter(refKind);
174 }
175 static boolean refKindIsMethod(byte refKind) {
176 return !refKindIsField(refKind) && (refKind != REF_newInvokeSpecial);
177 }
178 static boolean refKindIsConstructor(byte refKind) {
179 return (refKind == REF_newInvokeSpecial);
180 }
181 static boolean refKindHasReceiver(byte refKind) {
182 assert(refKindIsValid(refKind));
183 return (refKind & 1) != 0;
184 }
185 static boolean refKindIsStatic(byte refKind) {
186 return !refKindHasReceiver(refKind) && (refKind != REF_newInvokeSpecial);
187 }
188 static boolean refKindDoesDispatch(byte refKind) {
189 assert(refKindIsValid(refKind));
190 return (refKind == REF_invokeVirtual ||
191 refKind == REF_invokeInterface);
192 }
193 static {
194 final int HR_MASK = ((1 << REF_getField) |
195 (1 << REF_putField) |
196 (1 << REF_invokeVirtual) |
197 (1 << REF_invokeSpecial) |
198 (1 << REF_invokeInterface)
199 );
200 for (byte refKind = REF_NONE+1; refKind < REF_LIMIT; refKind++) {
201 assert(refKindHasReceiver(refKind) == (((1<<refKind) & HR_MASK) != 0)) : refKind;
202 }
203 }
204 static String refKindName(byte refKind) {
205 assert(refKindIsValid(refKind));
206 return switch (refKind) {
207 case REF_getField -> "getField";
208 case REF_getStatic -> "getStatic";
209 case REF_putField -> "putField";
210 case REF_putStatic -> "putStatic";
211 case REF_invokeVirtual -> "invokeVirtual";
212 case REF_invokeStatic -> "invokeStatic";
213 case REF_invokeSpecial -> "invokeSpecial";
214 case REF_newInvokeSpecial -> "newInvokeSpecial";
215 case REF_invokeInterface -> "invokeInterface";
216 default -> "REF_???";
217 };
218 }
219
220 private static native int getNamedCon(int which, Object[] name);
221 static boolean verifyConstants() {
222 Object[] box = { null };
223 for (int i = 0; ; i++) {
224 box[0] = null;
225 int vmval = getNamedCon(i, box);
226 if (box[0] == null) break;
227 String name = (String) box[0];
228 try {
229 Field con = Constants.class.getDeclaredField(name);
230 int jval = con.getInt(null);
231 if (jval == vmval) continue;
232 String err = (name+": JVM has "+vmval+" while Java has "+jval);
233 if (name.equals("CONV_OP_LIMIT")) {
234 System.err.println("warning: "+err);
235 continue;
236 }
237 throw new InternalError(err);
238 } catch (NoSuchFieldException | IllegalAccessException ex) {
239 String err = (name+": JVM has "+vmval+" which Java does not define");
240 // ignore exotic ops the JVM cares about; we just won't issue them
241 //System.err.println("warning: "+err);
242 continue;
243 }
244 }
245 return true;
246 }
247 static {
248 VM.setJavaLangInvokeInited();
249 assert(verifyConstants());
250 }
251
252 // Up-calls from the JVM.
253 // These must NOT be public.
254
255 /**
256 * The JVM is linking an invokedynamic instruction. Create a reified call site for it.
257 */
258 static MemberName linkCallSite(Object callerObj,
259 Object bootstrapMethodObj,
260 Object nameObj, Object typeObj,
261 Object staticArguments,
262 Object[] appendixResult) {
263 MethodHandle bootstrapMethod = (MethodHandle)bootstrapMethodObj;
264 Class<?> caller = (Class<?>)callerObj;
265 String name = nameObj.toString().intern();
266 MethodType type = (MethodType)typeObj;
267 if (!TRACE_METHOD_LINKAGE)
268 return linkCallSiteImpl(caller, bootstrapMethod, name, type,
269 staticArguments, appendixResult);
270 return linkCallSiteTracing(caller, bootstrapMethod, name, type,
271 staticArguments, appendixResult);
272 }
273 static MemberName linkCallSiteImpl(Class<?> caller,
274 MethodHandle bootstrapMethod,
275 String name, MethodType type,
276 Object staticArguments,
277 Object[] appendixResult) {
278 CallSite callSite = CallSite.makeSite(bootstrapMethod,
279 name,
280 type,
281 staticArguments,
282 caller);
283 if (TRACE_METHOD_LINKAGE) {
284 MethodHandle target = callSite.getTarget();
285 System.out.println("linkCallSite target class => " + target.getClass().getName());
286 System.out.println("linkCallSite target => " + target.debugString(0));
287 }
288
289 if (callSite instanceof ConstantCallSite) {
290 appendixResult[0] = callSite.dynamicInvoker();
291 return Invokers.linkToTargetMethod(type);
292 } else {
293 appendixResult[0] = callSite;
294 return Invokers.linkToCallSiteMethod(type);
295 }
296 }
297 // Tracing logic:
298 static MemberName linkCallSiteTracing(Class<?> caller,
299 MethodHandle bootstrapMethod,
300 String name, MethodType type,
301 Object staticArguments,
302 Object[] appendixResult) {
303 Object bsmReference = bootstrapMethod.internalMemberName();
304 if (bsmReference == null) bsmReference = bootstrapMethod;
305 String staticArglist = staticArglistForTrace(staticArguments);
306 System.out.println("linkCallSite "+getCallerInfo(caller)+" "+
307 bsmReference+" "+
308 name+type+"/"+staticArglist);
309 try {
310 MemberName res = linkCallSiteImpl(caller, bootstrapMethod, name, type,
311 staticArguments, appendixResult);
312 System.out.println("linkCallSite linkage => "+res+" + "+appendixResult[0]);
313 return res;
314 } catch (Throwable ex) {
315 ex.printStackTrace(); // print now in case exception is swallowed
316 System.out.println("linkCallSite => throw "+ex);
317 throw ex;
318 }
319 }
320
321 /**
322 * Return a human-readable description of the caller. Something like
323 * "java.base/java.security.Security.<clinit>(Security.java:82)"
324 */
325 private static String getCallerInfo(Class<?> caller) {
326 for (StackTraceElement e : Thread.currentThread().getStackTrace()) {
327 if (e.getClassName().equals(caller.getName())) {
328 return e.toString();
329 }
330 }
331 // fallback if the caller is somehow missing from the stack.
332 return caller.getName();
333 }
334
335 // this implements the upcall from the JVM, MethodHandleNatives.linkDynamicConstant:
336 static Object linkDynamicConstant(Object callerObj,
337 Object bootstrapMethodObj,
338 Object nameObj, Object typeObj,
339 Object staticArguments) {
340 MethodHandle bootstrapMethod = (MethodHandle)bootstrapMethodObj;
341 Class<?> caller = (Class<?>)callerObj;
342 String name = nameObj.toString().intern();
343 Class<?> type = (Class<?>)typeObj;
344 if (!TRACE_METHOD_LINKAGE)
345 return linkDynamicConstantImpl(caller, bootstrapMethod, name, type, staticArguments);
346 return linkDynamicConstantTracing(caller, bootstrapMethod, name, type, staticArguments);
347 }
348
349 static Object linkDynamicConstantImpl(Class<?> caller,
350 MethodHandle bootstrapMethod,
351 String name, Class<?> type,
352 Object staticArguments) {
353 return ConstantBootstraps.makeConstant(bootstrapMethod, name, type, staticArguments, caller);
354 }
355
356 private static String staticArglistForTrace(Object staticArguments) {
357 if (staticArguments instanceof Object[] array)
358 return "BSA="+java.util.Arrays.asList(array);
359 if (staticArguments instanceof int[] array)
360 return "BSA@"+java.util.Arrays.toString(array);
361 if (staticArguments == null)
362 return "BSA0=null";
363 return "BSA1="+staticArguments;
364 }
365
366 // Tracing logic:
367 static Object linkDynamicConstantTracing(Class<?> caller,
368 MethodHandle bootstrapMethod,
369 String name, Class<?> type,
370 Object staticArguments) {
371 Object bsmReference = bootstrapMethod.internalMemberName();
372 if (bsmReference == null) bsmReference = bootstrapMethod;
373 String staticArglist = staticArglistForTrace(staticArguments);
374 System.out.println("linkDynamicConstant "+caller.getName()+" "+
375 bsmReference+" "+
376 name+type+"/"+staticArglist);
377 try {
378 Object res = linkDynamicConstantImpl(caller, bootstrapMethod, name, type, staticArguments);
379 System.out.println("linkDynamicConstantImpl => "+res);
380 return res;
381 } catch (Throwable ex) {
382 ex.printStackTrace(); // print now in case exception is swallowed
383 System.out.println("linkDynamicConstant => throw "+ex);
384 throw ex;
385 }
386 }
387
388 /** The JVM is requesting pull-mode bootstrap when it provides
389 * a tuple of the form int[]{ argc, vmindex }.
390 * The BSM is expected to call back to the JVM using the caller
391 * class and vmindex to resolve the static arguments.
392 */
393 static boolean staticArgumentsPulled(Object staticArguments) {
394 return staticArguments instanceof int[];
395 }
396
397 /** A BSM runs in pull-mode if and only if its sole arguments
398 * are (Lookup, BootstrapCallInfo), or can be converted pairwise
399 * to those types, and it is not of variable arity.
400 * Excluding error cases, we can just test that the arity is a constant 2.
401 *
402 * NOTE: This method currently returns false, since pulling is not currently
403 * exposed to a BSM. When pull mode is supported the method block will be
404 * replaced with currently commented out code.
405 */
406 static boolean isPullModeBSM(MethodHandle bsm) {
407 return false;
408 // return bsm.type().parameterCount() == 2 && !bsm.isVarargsCollector();
409 }
410
411 /**
412 * The JVM wants a pointer to a MethodType. Oblige it by finding or creating one.
413 */
414 static MethodType findMethodHandleType(Class<?> rtype, Class<?>[] ptypes) {
415 return MethodType.methodType(rtype, ptypes, true);
416 }
417
418 /**
419 * The JVM wants to link a call site that requires a dynamic type check.
420 * Name is a type-checking invoker, invokeExact or invoke.
421 * Return a JVM method (MemberName) to handle the invoking.
422 * The method assumes the following arguments on the stack:
423 * 0: the method handle being invoked
424 * 1-N: the arguments to the method handle invocation
425 * N+1: an optional, implicitly added argument (typically the given MethodType)
426 * <p>
427 * The nominal method at such a call site is an instance of
428 * a signature-polymorphic method (see @PolymorphicSignature).
429 * Such method instances are user-visible entities which are
430 * "split" from the generic placeholder method in {@code MethodHandle}.
431 * (Note that the placeholder method is not identical with any of
432 * its instances. If invoked reflectively, is guaranteed to throw an
433 * {@code UnsupportedOperationException}.)
434 * If the signature-polymorphic method instance is ever reified,
435 * it appears as a "copy" of the original placeholder
436 * (a native final member of {@code MethodHandle}) except
437 * that its type descriptor has shape required by the instance,
438 * and the method instance is <em>not</em> varargs.
439 * The method instance is also marked synthetic, since the
440 * method (by definition) does not appear in Java source code.
441 * <p>
442 * The JVM is allowed to reify this method as instance metadata.
443 * For example, {@code invokeBasic} is always reified.
444 * But the JVM may instead call {@code linkMethod}.
445 * If the result is an * ordered pair of a {@code (method, appendix)},
446 * the method gets all the arguments (0..N inclusive)
447 * plus the appendix (N+1), and uses the appendix to complete the call.
448 * In this way, one reusable method (called a "linker method")
449 * can perform the function of any number of polymorphic instance
450 * methods.
451 * <p>
452 * Linker methods are allowed to be weakly typed, with any or
453 * all references rewritten to {@code Object} and any primitives
454 * (except {@code long}/{@code float}/{@code double})
455 * rewritten to {@code int}.
456 * A linker method is trusted to return a strongly typed result,
457 * according to the specific method type descriptor of the
458 * signature-polymorphic instance it is emulating.
459 * This can involve (as necessary) a dynamic check using
460 * data extracted from the appendix argument.
461 * <p>
462 * The JVM does not inspect the appendix, other than to pass
463 * it verbatim to the linker method at every call.
464 * This means that the JDK runtime has wide latitude
465 * for choosing the shape of each linker method and its
466 * corresponding appendix.
467 * Linker methods should be generated from {@code LambdaForm}s
468 * so that they do not become visible on stack traces.
469 * <p>
470 * The {@code linkMethod} call is free to omit the appendix
471 * (returning null) and instead emulate the required function
472 * completely in the linker method.
473 * As a corner case, if N==255, no appendix is possible.
474 * In this case, the method returned must be custom-generated to
475 * perform any needed type checking.
476 * <p>
477 * If the JVM does not reify a method at a call site, but instead
478 * calls {@code linkMethod}, the corresponding call represented
479 * in the bytecodes may mention a valid method which is not
480 * representable with a {@code MemberName}.
481 * Therefore, use cases for {@code linkMethod} tend to correspond to
482 * special cases in reflective code such as {@code findVirtual}
483 * or {@code revealDirect}.
484 */
485 static MemberName linkMethod(Class<?> callerClass, int refKind,
486 Class<?> defc, String name, Object type,
487 Object[] appendixResult) {
488 if (!TRACE_METHOD_LINKAGE)
489 return linkMethodImpl(callerClass, refKind, defc, name, type, appendixResult);
490 return linkMethodTracing(callerClass, refKind, defc, name, type, appendixResult);
491 }
492 static MemberName linkMethodImpl(Class<?> callerClass, int refKind,
493 Class<?> defc, String name, Object type,
494 Object[] appendixResult) {
495 try {
496 if (refKind == REF_invokeVirtual) {
497 if (defc == MethodHandle.class) {
498 return Invokers.methodHandleInvokeLinkerMethod(
499 name, fixMethodType(callerClass, type), appendixResult);
500 } else if (defc == VarHandle.class) {
501 return varHandleOperationLinkerMethod(
502 name, fixMethodType(callerClass, type), appendixResult);
503 }
504 }
505 } catch (Error e) {
506 // Pass through an Error, including say StackOverflowError or
507 // OutOfMemoryError
508 throw e;
509 } catch (Throwable ex) {
510 // Wrap anything else in LinkageError
511 throw new LinkageError(ex.getMessage(), ex);
512 }
513 throw new LinkageError("no such method "+defc.getName()+"."+name+type);
514 }
515 private static MethodType fixMethodType(Class<?> callerClass, Object type) {
516 if (type instanceof MethodType mt)
517 return mt;
518 else
519 return MethodType.fromDescriptor((String)type, callerClass.getClassLoader());
520 }
521 // Tracing logic:
522 static MemberName linkMethodTracing(Class<?> callerClass, int refKind,
523 Class<?> defc, String name, Object type,
524 Object[] appendixResult) {
525 System.out.println("linkMethod "+defc.getName()+"."+
526 name+type+"/"+Integer.toHexString(refKind));
527 try {
528 MemberName res = linkMethodImpl(callerClass, refKind, defc, name, type, appendixResult);
529 System.out.println("linkMethod => "+res+" + "+appendixResult[0]);
530 return res;
531 } catch (Throwable ex) {
532 System.out.println("linkMethod => throw "+ex);
533 throw ex;
534 }
535 }
536
537 /**
538 * Obtain the method to link to the VarHandle operation.
539 * This method is located here and not in Invokers to avoid
540 * initializing that and other classes early on in VM bootup.
541 */
542 private static MemberName varHandleOperationLinkerMethod(String name,
543 MethodType mtype,
544 Object[] appendixResult) {
545 // Get the signature method type
546 final MethodType sigType = mtype.basicType();
547
548 // Get the access kind from the method name
549 VarHandle.AccessMode ak;
550 try {
551 ak = VarHandle.AccessMode.valueFromMethodName(name);
552 } catch (IllegalArgumentException e) {
553 throw MethodHandleStatics.newInternalError(e);
554 }
555
556 // Create the appendix descriptor constant
557 VarHandle.AccessDescriptor ad = new VarHandle.AccessDescriptor(mtype, ak.at.ordinal(), ak.ordinal());
558 appendixResult[0] = ad;
559
560 if (MethodHandleStatics.VAR_HANDLE_GUARDS) {
561 // If not polymorphic in the return type, such as the compareAndSet
562 // methods that return boolean
563 Class<?> guardReturnType = sigType.returnType();
564 if (ak.at.isMonomorphicInReturnType) {
565 if (ak.at.returnType != mtype.returnType()) {
566 // The caller contains a different return type than that
567 // defined by the method
568 throw newNoSuchMethodErrorOnVarHandle(name, mtype);
569 }
570 // Adjust the return type of the signature method type
571 guardReturnType = ak.at.returnType;
572 }
573
574 // Get the guard method type for linking
575 final Class<?>[] guardParams = new Class<?>[sigType.parameterCount() + 2];
576 // VarHandle at start
577 guardParams[0] = VarHandle.class;
578 for (int i = 0; i < sigType.parameterCount(); i++) {
579 guardParams[i + 1] = sigType.parameterType(i);
580 }
581 // Access descriptor at end
582 guardParams[guardParams.length - 1] = VarHandle.AccessDescriptor.class;
583 MethodType guardType = MethodType.methodType(guardReturnType, guardParams, true);
584
585 MemberName linker = new MemberName(
586 VarHandleGuards.class, getVarHandleGuardMethodName(guardType),
587 guardType, REF_invokeStatic);
588
589 linker = MemberName.getFactory().resolveOrNull(REF_invokeStatic, linker,
590 VarHandleGuards.class, LM_TRUSTED);
591 if (linker != null) {
592 return linker;
593 }
594 // Fall back to lambda form linkage if guard method is not available
595 // TODO Optionally log fallback ?
596 }
597 return Invokers.varHandleInvokeLinkerMethod(mtype);
598 }
599 static String getVarHandleGuardMethodName(MethodType guardType) {
600 String prefix = "guard_";
601 StringBuilder sb = new StringBuilder(prefix.length() + guardType.parameterCount());
602
603 sb.append(prefix);
604 for (int i = 1; i < guardType.parameterCount() - 1; i++) {
605 Class<?> pt = guardType.parameterType(i);
606 sb.append(getCharType(pt));
607 }
608 sb.append('_').append(getCharType(guardType.returnType()));
609 return sb.toString();
610 }
611 static char getCharType(Class<?> pt) {
612 return Wrapper.forBasicType(pt).basicTypeChar();
613 }
614 static NoSuchMethodError newNoSuchMethodErrorOnVarHandle(String name, MethodType mtype) {
615 return new NoSuchMethodError("VarHandle." + name + mtype);
616 }
617
618 /**
619 * The JVM is resolving a CONSTANT_MethodHandle CP entry. And it wants our help.
620 * It will make an up-call to this method. (Do not change the name or signature.)
621 * The type argument is a Class for field requests and a MethodType for non-fields.
622 * <p>
623 * Recent versions of the JVM may also pass a resolved MemberName for the type.
624 * In that case, the name is ignored and may be null.
625 */
626 static MethodHandle linkMethodHandleConstant(Class<?> callerClass, int refKind,
627 Class<?> defc, String name, Object type) {
628 try {
629 Lookup lookup = IMPL_LOOKUP.in(callerClass);
630 assert(refKindIsValid(refKind));
631 return lookup.linkMethodHandleConstant((byte) refKind, defc, name, type);
632 } catch (ReflectiveOperationException ex) {
633 throw mapLookupExceptionToError(ex);
634 }
635 }
636
637 /**
638 * Map a reflective exception to a linkage error.
639 */
640 static LinkageError mapLookupExceptionToError(ReflectiveOperationException ex) {
641 LinkageError err;
642 if (ex instanceof IllegalAccessException) {
643 Throwable cause = ex.getCause();
644 if (cause instanceof AbstractMethodError ame) {
645 return ame;
646 } else {
647 err = new IllegalAccessError(ex.getMessage());
648 }
649 } else if (ex instanceof NoSuchMethodException) {
650 err = new NoSuchMethodError(ex.getMessage());
651 } else if (ex instanceof NoSuchFieldException) {
652 err = new NoSuchFieldError(ex.getMessage());
653 } else {
654 err = new IncompatibleClassChangeError();
655 }
656 return initCauseFrom(err, ex);
657 }
658
659 /**
660 * Use best possible cause for err.initCause(), substituting the
661 * cause for err itself if the cause has the same (or better) type.
662 */
663 static <E extends Error> E initCauseFrom(E err, Exception ex) {
664 Throwable th = ex.getCause();
665 @SuppressWarnings("unchecked")
666 final Class<E> Eclass = (Class<E>) err.getClass();
667 if (Eclass.isInstance(th))
668 return Eclass.cast(th);
669 err.initCause(th == null ? ex : th);
670 return err;
671 }
672
673 /**
674 * Is this method a caller-sensitive method?
675 * I.e., does it call Reflection.getCallerClass or a similar method
676 * to ask about the identity of its caller?
677 */
678 static boolean isCallerSensitive(MemberName mem) {
679 if (!mem.isInvocable()) return false; // fields are not caller sensitive
680
681 return mem.isCallerSensitive() || canBeCalledVirtual(mem);
682 }
683
684 static boolean canBeCalledVirtual(MemberName mem) {
685 assert(mem.isInvocable());
686 return mem.getName().equals("getContextClassLoader") && canBeCalledVirtual(mem, java.lang.Thread.class);
687 }
688
689 static boolean canBeCalledVirtual(MemberName symbolicRef, Class<?> definingClass) {
690 Class<?> symbolicRefClass = symbolicRef.getDeclaringClass();
691 if (symbolicRefClass == definingClass) return true;
692 if (symbolicRef.isStatic() || symbolicRef.isPrivate()) return false;
693 return (definingClass.isAssignableFrom(symbolicRefClass) || // Msym overrides Mdef
694 symbolicRefClass.isInterface()); // Mdef implements Msym
695 }
696 }