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