1 /*
2 * Copyright (c) 2008, 2019, 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.access.JavaLangAccess;
29 import jdk.internal.access.SharedSecrets;
30 import jdk.internal.ref.CleanerFactory;
31 import sun.invoke.util.Wrapper;
32
33 import java.lang.invoke.MethodHandles.Lookup;
34 import java.lang.reflect.Field;
35
36 import static java.lang.invoke.MethodHandleNatives.Constants.*;
37 import static java.lang.invoke.MethodHandleStatics.TRACE_METHOD_LINKAGE;
38 import static java.lang.invoke.MethodHandles.Lookup.IMPL_LOOKUP;
39
40 /**
41 * The JVM interface for the method handles package is all here.
42 * This is an interface internal and private to an implementation of JSR 292.
43 * <em>This class is not part of the JSR 292 standard.</em>
44 * @author jrose
45 */
46 class MethodHandleNatives {
47
48 private MethodHandleNatives() { } // static only
49
50 /// MemberName support
51
52 static native void init(MemberName self, Object ref);
53 static native void expand(MemberName self);
54 static native MemberName resolve(MemberName self, Class<?> caller,
55 boolean speculativeResolve) throws LinkageError, ClassNotFoundException;
56 static native int getMembers(Class<?> defc, String matchName, String matchSig,
57 int matchFlags, Class<?> caller, int skip, MemberName[] results);
58
59 /// Field layout queries parallel to jdk.internal.misc.Unsafe:
60 static native long objectFieldOffset(MemberName self); // e.g., returns vmindex
61 static native long staticFieldOffset(MemberName self); // e.g., returns vmindex
62 static native Object staticFieldBase(MemberName self); // e.g., returns clazz
63 static native Object getMemberVMInfo(MemberName self); // returns {vmindex,vmtarget}
64
65 /// CallSite support
66
67 /** Tell the JVM that we need to change the target of a CallSite. */
68 static native void setCallSiteTargetNormal(CallSite site, MethodHandle target);
69 static native void setCallSiteTargetVolatile(CallSite site, MethodHandle target);
70
71 static native void copyOutBootstrapArguments(Class<?> caller, int[] indexInfo,
72 int start, int end,
73 Object[] buf, int pos,
74 boolean resolve,
75 Object ifNotAvailable);
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_REFERENCE_KIND_SHIFT = 24, // refKind
122 MN_REFERENCE_KIND_MASK = 0x0F000000 >> MN_REFERENCE_KIND_SHIFT,
123 // The SEARCH_* bits are not for MN.flags but for the matchFlags argument of MHN.getMembers:
124 MN_SEARCH_SUPERCLASSES = 0x00100000,
125 MN_SEARCH_INTERFACES = 0x00200000;
126
127 /**
128 * Constant pool reference-kind codes, as used by CONSTANT_MethodHandle CP entries.
129 */
130 static final byte
131 REF_NONE = 0, // null value
132 REF_getField = 1,
133 REF_getStatic = 2,
134 REF_putField = 3,
135 REF_putStatic = 4,
136 REF_invokeVirtual = 5,
137 REF_invokeStatic = 6,
138 REF_invokeSpecial = 7,
139 REF_newInvokeSpecial = 8,
140 REF_invokeInterface = 9,
141 REF_LIMIT = 10;
142
143 /**
144 * Flags for Lookup.ClassOptions
145 */
146 static final int
147 NESTMATE_CLASS = 0x00000001,
148 HIDDEN_CLASS = 0x00000002,
149 STRONG_LOADER_LINK = 0x00000004,
150 ACCESS_VM_ANNOTATIONS = 0x00000008;
151 }
152
153 static boolean refKindIsValid(int refKind) {
154 return (refKind > REF_NONE && refKind < REF_LIMIT);
155 }
156 static boolean refKindIsField(byte refKind) {
157 assert(refKindIsValid(refKind));
158 return (refKind <= REF_putStatic);
159 }
160 static boolean refKindIsGetter(byte refKind) {
161 assert(refKindIsValid(refKind));
162 return (refKind <= REF_getStatic);
163 }
164 static boolean refKindIsSetter(byte refKind) {
165 return refKindIsField(refKind) && !refKindIsGetter(refKind);
166 }
167 static boolean refKindIsMethod(byte refKind) {
168 return !refKindIsField(refKind) && (refKind != REF_newInvokeSpecial);
169 }
170 static boolean refKindIsConstructor(byte refKind) {
171 return (refKind == REF_newInvokeSpecial);
172 }
173 static boolean refKindHasReceiver(byte refKind) {
174 assert(refKindIsValid(refKind));
175 return (refKind & 1) != 0;
176 }
177 static boolean refKindIsStatic(byte refKind) {
178 return !refKindHasReceiver(refKind) && (refKind != REF_newInvokeSpecial);
179 }
180 static boolean refKindDoesDispatch(byte refKind) {
181 assert(refKindIsValid(refKind));
182 return (refKind == REF_invokeVirtual ||
183 refKind == REF_invokeInterface);
184 }
185 static {
186 final int HR_MASK = ((1 << REF_getField) |
187 (1 << REF_putField) |
188 (1 << REF_invokeVirtual) |
189 (1 << REF_invokeSpecial) |
190 (1 << REF_invokeInterface)
191 );
192 for (byte refKind = REF_NONE+1; refKind < REF_LIMIT; refKind++) {
193 assert(refKindHasReceiver(refKind) == (((1<<refKind) & HR_MASK) != 0)) : refKind;
194 }
195 }
196 static String refKindName(byte refKind) {
197 assert(refKindIsValid(refKind));
198 switch (refKind) {
199 case REF_getField: return "getField";
200 case REF_getStatic: return "getStatic";
201 case REF_putField: return "putField";
202 case REF_putStatic: return "putStatic";
203 case REF_invokeVirtual: return "invokeVirtual";
204 case REF_invokeStatic: return "invokeStatic";
205 case REF_invokeSpecial: return "invokeSpecial";
206 case REF_newInvokeSpecial: return "newInvokeSpecial";
207 case REF_invokeInterface: return "invokeInterface";
208 default: return "REF_???";
209 }
210 }
211
212 private static native int getNamedCon(int which, Object[] name);
213 static boolean verifyConstants() {
214 Object[] box = { null };
215 for (int i = 0; ; i++) {
216 box[0] = null;
217 int vmval = getNamedCon(i, box);
218 if (box[0] == null) break;
219 String name = (String) box[0];
220 try {
221 Field con = Constants.class.getDeclaredField(name);
222 int jval = con.getInt(null);
223 if (jval == vmval) continue;
224 String err = (name+": JVM has "+vmval+" while Java has "+jval);
225 if (name.equals("CONV_OP_LIMIT")) {
226 System.err.println("warning: "+err);
227 continue;
228 }
229 throw new InternalError(err);
230 } catch (NoSuchFieldException | IllegalAccessException ex) {
231 String err = (name+": JVM has "+vmval+" which Java does not define");
232 // ignore exotic ops the JVM cares about; we just wont issue them
233 //System.err.println("warning: "+err);
234 continue;
235 }
236 }
237 return true;
238 }
239 static {
240 assert(verifyConstants());
241 }
242
243 // Up-calls from the JVM.
244 // These must NOT be public.
245
246 /**
247 * The JVM is linking an invokedynamic instruction. Create a reified call site for it.
248 */
249 static MemberName linkCallSite(Object callerObj,
250 int indexInCP,
251 Object bootstrapMethodObj,
252 Object nameObj, Object typeObj,
253 Object staticArguments,
254 Object[] appendixResult) {
255 MethodHandle bootstrapMethod = (MethodHandle)bootstrapMethodObj;
256 Class<?> caller = (Class<?>)callerObj;
257 String name = nameObj.toString().intern();
258 MethodType type = (MethodType)typeObj;
259 if (!TRACE_METHOD_LINKAGE)
260 return linkCallSiteImpl(caller, bootstrapMethod, name, type,
261 staticArguments, appendixResult);
262 return linkCallSiteTracing(caller, bootstrapMethod, name, type,
263 staticArguments, appendixResult);
264 }
265 static MemberName linkCallSiteImpl(Class<?> caller,
266 MethodHandle bootstrapMethod,
267 String name, MethodType type,
268 Object staticArguments,
269 Object[] appendixResult) {
270 CallSite callSite = CallSite.makeSite(bootstrapMethod,
271 name,
272 type,
273 staticArguments,
274 caller);
275 if (callSite instanceof ConstantCallSite) {
276 appendixResult[0] = callSite.dynamicInvoker();
277 return Invokers.linkToTargetMethod(type);
278 } else {
279 appendixResult[0] = callSite;
280 return Invokers.linkToCallSiteMethod(type);
281 }
282 }
283 // Tracing logic:
284 static MemberName linkCallSiteTracing(Class<?> caller,
285 MethodHandle bootstrapMethod,
286 String name, MethodType type,
287 Object staticArguments,
288 Object[] appendixResult) {
289 Object bsmReference = bootstrapMethod.internalMemberName();
290 if (bsmReference == null) bsmReference = bootstrapMethod;
291 String staticArglist = staticArglistForTrace(staticArguments);
292 System.out.println("linkCallSite "+caller.getName()+" "+
293 bsmReference+" "+
294 name+type+"/"+staticArglist);
295 try {
296 MemberName res = linkCallSiteImpl(caller, bootstrapMethod, name, type,
297 staticArguments, appendixResult);
298 System.out.println("linkCallSite => "+res+" + "+appendixResult[0]);
299 return res;
300 } catch (Throwable ex) {
301 ex.printStackTrace(); // print now in case exception is swallowed
302 System.out.println("linkCallSite => throw "+ex);
303 throw ex;
304 }
305 }
306
307 // this implements the upcall from the JVM, MethodHandleNatives.linkDynamicConstant:
308 static Object linkDynamicConstant(Object callerObj,
309 int indexInCP,
310 Object bootstrapMethodObj,
311 Object nameObj, Object typeObj,
312 Object staticArguments) {
313 MethodHandle bootstrapMethod = (MethodHandle)bootstrapMethodObj;
314 Class<?> caller = (Class<?>)callerObj;
315 String name = nameObj.toString().intern();
316 Class<?> type = (Class<?>)typeObj;
317 if (!TRACE_METHOD_LINKAGE)
318 return linkDynamicConstantImpl(caller, bootstrapMethod, name, type, staticArguments);
319 return linkDynamicConstantTracing(caller, bootstrapMethod, name, type, staticArguments);
320 }
321
322 static Object linkDynamicConstantImpl(Class<?> caller,
323 MethodHandle bootstrapMethod,
324 String name, Class<?> type,
325 Object staticArguments) {
326 return ConstantBootstraps.makeConstant(bootstrapMethod, name, type, staticArguments, caller);
327 }
328
329 private static String staticArglistForTrace(Object staticArguments) {
330 if (staticArguments instanceof Object[])
331 return "BSA="+java.util.Arrays.asList((Object[]) staticArguments);
332 if (staticArguments instanceof int[])
333 return "BSA@"+java.util.Arrays.toString((int[]) staticArguments);
334 if (staticArguments == null)
335 return "BSA0=null";
336 return "BSA1="+staticArguments;
337 }
338
339 // Tracing logic:
340 static Object linkDynamicConstantTracing(Class<?> caller,
341 MethodHandle bootstrapMethod,
342 String name, Class<?> type,
343 Object staticArguments) {
344 Object bsmReference = bootstrapMethod.internalMemberName();
345 if (bsmReference == null) bsmReference = bootstrapMethod;
346 String staticArglist = staticArglistForTrace(staticArguments);
347 System.out.println("linkDynamicConstant "+caller.getName()+" "+
348 bsmReference+" "+
349 name+type+"/"+staticArglist);
350 try {
351 Object res = linkDynamicConstantImpl(caller, bootstrapMethod, name, type, staticArguments);
352 System.out.println("linkDynamicConstantImpl => "+res);
353 return res;
354 } catch (Throwable ex) {
355 ex.printStackTrace(); // print now in case exception is swallowed
356 System.out.println("linkDynamicConstant => throw "+ex);
357 throw ex;
358 }
359 }
360
361 /** The JVM is requesting pull-mode bootstrap when it provides
362 * a tuple of the form int[]{ argc, vmindex }.
363 * The BSM is expected to call back to the JVM using the caller
364 * class and vmindex to resolve the static arguments.
365 */
366 static boolean staticArgumentsPulled(Object staticArguments) {
367 return staticArguments instanceof int[];
368 }
369
370 /** A BSM runs in pull-mode if and only if its sole arguments
371 * are (Lookup, BootstrapCallInfo), or can be converted pairwise
372 * to those types, and it is not of variable arity.
373 * Excluding error cases, we can just test that the arity is a constant 2.
374 *
375 * NOTE: This method currently returns false, since pulling is not currently
376 * exposed to a BSM. When pull mode is supported the method block will be
377 * replaced with currently commented out code.
378 */
379 static boolean isPullModeBSM(MethodHandle bsm) {
380 return false;
381 // return bsm.type().parameterCount() == 2 && !bsm.isVarargsCollector();
382 }
383
384 /**
385 * The JVM wants a pointer to a MethodType. Oblige it by finding or creating one.
386 */
387 static MethodType findMethodHandleType(Class<?> rtype, Class<?>[] ptypes) {
388 return MethodType.makeImpl(rtype, ptypes, true);
389 }
390
391 /**
392 * The JVM wants to link a call site that requires a dynamic type check.
393 * Name is a type-checking invoker, invokeExact or invoke.
394 * Return a JVM method (MemberName) to handle the invoking.
395 * The method assumes the following arguments on the stack:
396 * 0: the method handle being invoked
397 * 1-N: the arguments to the method handle invocation
398 * N+1: an optional, implicitly added argument (typically the given MethodType)
399 * <p>
400 * The nominal method at such a call site is an instance of
401 * a signature-polymorphic method (see @PolymorphicSignature).
402 * Such method instances are user-visible entities which are
403 * "split" from the generic placeholder method in {@code MethodHandle}.
404 * (Note that the placeholder method is not identical with any of
405 * its instances. If invoked reflectively, is guaranteed to throw an
406 * {@code UnsupportedOperationException}.)
407 * If the signature-polymorphic method instance is ever reified,
408 * it appears as a "copy" of the original placeholder
409 * (a native final member of {@code MethodHandle}) except
410 * that its type descriptor has shape required by the instance,
411 * and the method instance is <em>not</em> varargs.
412 * The method instance is also marked synthetic, since the
413 * method (by definition) does not appear in Java source code.
414 * <p>
415 * The JVM is allowed to reify this method as instance metadata.
416 * For example, {@code invokeBasic} is always reified.
417 * But the JVM may instead call {@code linkMethod}.
418 * If the result is an * ordered pair of a {@code (method, appendix)},
419 * the method gets all the arguments (0..N inclusive)
420 * plus the appendix (N+1), and uses the appendix to complete the call.
421 * In this way, one reusable method (called a "linker method")
422 * can perform the function of any number of polymorphic instance
423 * methods.
424 * <p>
425 * Linker methods are allowed to be weakly typed, with any or
426 * all references rewritten to {@code Object} and any primitives
427 * (except {@code long}/{@code float}/{@code double})
428 * rewritten to {@code int}.
429 * A linker method is trusted to return a strongly typed result,
430 * according to the specific method type descriptor of the
431 * signature-polymorphic instance it is emulating.
432 * This can involve (as necessary) a dynamic check using
433 * data extracted from the appendix argument.
434 * <p>
435 * The JVM does not inspect the appendix, other than to pass
436 * it verbatim to the linker method at every call.
437 * This means that the JDK runtime has wide latitude
438 * for choosing the shape of each linker method and its
439 * corresponding appendix.
440 * Linker methods should be generated from {@code LambdaForm}s
441 * so that they do not become visible on stack traces.
442 * <p>
443 * The {@code linkMethod} call is free to omit the appendix
444 * (returning null) and instead emulate the required function
445 * completely in the linker method.
446 * As a corner case, if N==255, no appendix is possible.
447 * In this case, the method returned must be custom-generated to
448 * perform any needed type checking.
449 * <p>
450 * If the JVM does not reify a method at a call site, but instead
451 * calls {@code linkMethod}, the corresponding call represented
452 * in the bytecodes may mention a valid method which is not
453 * representable with a {@code MemberName}.
454 * Therefore, use cases for {@code linkMethod} tend to correspond to
455 * special cases in reflective code such as {@code findVirtual}
456 * or {@code revealDirect}.
457 */
458 static MemberName linkMethod(Class<?> callerClass, int refKind,
459 Class<?> defc, String name, Object type,
460 Object[] appendixResult) {
461 if (!TRACE_METHOD_LINKAGE)
462 return linkMethodImpl(callerClass, refKind, defc, name, type, appendixResult);
463 return linkMethodTracing(callerClass, refKind, defc, name, type, appendixResult);
464 }
465 static MemberName linkMethodImpl(Class<?> callerClass, int refKind,
466 Class<?> defc, String name, Object type,
467 Object[] appendixResult) {
468 try {
469 if (refKind == REF_invokeVirtual) {
470 if (defc == MethodHandle.class) {
471 return Invokers.methodHandleInvokeLinkerMethod(
472 name, fixMethodType(callerClass, type), appendixResult);
473 } else if (defc == VarHandle.class) {
474 return varHandleOperationLinkerMethod(
475 name, fixMethodType(callerClass, type), appendixResult);
476 }
477 }
478 } catch (Error e) {
479 // Pass through an Error, including say StackOverflowError or
480 // OutOfMemoryError
481 throw e;
482 } catch (Throwable ex) {
483 // Wrap anything else in LinkageError
484 throw new LinkageError(ex.getMessage(), ex);
485 }
486 throw new LinkageError("no such method "+defc.getName()+"."+name+type);
487 }
488 private static MethodType fixMethodType(Class<?> callerClass, Object type) {
489 if (type instanceof MethodType)
490 return (MethodType) type;
491 else
492 return MethodType.fromDescriptor((String)type, callerClass.getClassLoader());
493 }
494 // Tracing logic:
495 static MemberName linkMethodTracing(Class<?> callerClass, int refKind,
496 Class<?> defc, String name, Object type,
497 Object[] appendixResult) {
498 System.out.println("linkMethod "+defc.getName()+"."+
499 name+type+"/"+Integer.toHexString(refKind));
500 try {
501 MemberName res = linkMethodImpl(callerClass, refKind, defc, name, type, appendixResult);
502 System.out.println("linkMethod => "+res+" + "+appendixResult[0]);
503 return res;
504 } catch (Throwable ex) {
505 System.out.println("linkMethod => throw "+ex);
506 throw ex;
507 }
508 }
509
510 /**
511 * Obtain the method to link to the VarHandle operation.
512 * This method is located here and not in Invokers to avoid
513 * intializing that and other classes early on in VM bootup.
514 */
515 private static MemberName varHandleOperationLinkerMethod(String name,
516 MethodType mtype,
517 Object[] appendixResult) {
518 // Get the signature method type
519 final MethodType sigType = mtype.basicType();
520
521 // Get the access kind from the method name
522 VarHandle.AccessMode ak;
523 try {
524 ak = VarHandle.AccessMode.valueFromMethodName(name);
525 } catch (IllegalArgumentException e) {
526 throw MethodHandleStatics.newInternalError(e);
527 }
528
529 // Create the appendix descriptor constant
530 VarHandle.AccessDescriptor ad = new VarHandle.AccessDescriptor(mtype, ak.at.ordinal(), ak.ordinal());
531 appendixResult[0] = ad;
532
533 if (MethodHandleStatics.VAR_HANDLE_GUARDS) {
534 // If not polymorphic in the return type, such as the compareAndSet
535 // methods that return boolean
536 Class<?> guardReturnType = sigType.returnType();
537 if (ak.at.isMonomorphicInReturnType) {
538 if (ak.at.returnType != mtype.returnType()) {
539 // The caller contains a different return type than that
540 // defined by the method
541 throw newNoSuchMethodErrorOnVarHandle(name, mtype);
542 }
543 // Adjust the return type of the signature method type
544 guardReturnType = ak.at.returnType;
545 }
546
547 // Get the guard method type for linking
548 final Class<?>[] guardParams = new Class<?>[sigType.parameterCount() + 2];
549 // VarHandle at start
550 guardParams[0] = VarHandle.class;
551 for (int i = 0; i < sigType.parameterCount(); i++) {
552 guardParams[i + 1] = sigType.parameterType(i);
553 }
554 // Access descriptor at end
555 guardParams[guardParams.length - 1] = VarHandle.AccessDescriptor.class;
556 MethodType guardType = MethodType.makeImpl(guardReturnType, guardParams, true);
557
558 MemberName linker = new MemberName(
559 VarHandleGuards.class, getVarHandleGuardMethodName(guardType),
560 guardType, REF_invokeStatic);
561
562 linker = MemberName.getFactory().resolveOrNull(REF_invokeStatic, linker,
563 VarHandleGuards.class);
564 if (linker != null) {
565 return linker;
566 }
567 // Fall back to lambda form linkage if guard method is not available
568 // TODO Optionally log fallback ?
569 }
570 return Invokers.varHandleInvokeLinkerMethod(ak, mtype);
571 }
572 static String getVarHandleGuardMethodName(MethodType guardType) {
573 String prefix = "guard_";
574 StringBuilder sb = new StringBuilder(prefix.length() + guardType.parameterCount());
575
576 sb.append(prefix);
577 for (int i = 1; i < guardType.parameterCount() - 1; i++) {
578 Class<?> pt = guardType.parameterType(i);
579 sb.append(getCharType(pt));
580 }
581 sb.append('_').append(getCharType(guardType.returnType()));
582 return sb.toString();
583 }
584 static char getCharType(Class<?> pt) {
585 return Wrapper.forBasicType(pt).basicTypeChar();
586 }
587 static NoSuchMethodError newNoSuchMethodErrorOnVarHandle(String name, MethodType mtype) {
588 return new NoSuchMethodError("VarHandle." + name + mtype);
589 }
590
591 /**
592 * The JVM is resolving a CONSTANT_MethodHandle CP entry. And it wants our help.
593 * It will make an up-call to this method. (Do not change the name or signature.)
594 * The type argument is a Class for field requests and a MethodType for non-fields.
595 * <p>
596 * Recent versions of the JVM may also pass a resolved MemberName for the type.
597 * In that case, the name is ignored and may be null.
598 */
599 static MethodHandle linkMethodHandleConstant(Class<?> callerClass, int refKind,
600 Class<?> defc, String name, Object type) {
601 try {
602 Lookup lookup = IMPL_LOOKUP.in(callerClass);
603 assert(refKindIsValid(refKind));
604 return lookup.linkMethodHandleConstant((byte) refKind, defc, name, type);
605 } catch (ReflectiveOperationException ex) {
606 throw mapLookupExceptionToError(ex);
607 }
608 }
609
610 /**
611 * Map a reflective exception to a linkage error.
612 */
613 static LinkageError mapLookupExceptionToError(ReflectiveOperationException ex) {
614 LinkageError err;
615 if (ex instanceof IllegalAccessException) {
616 Throwable cause = ex.getCause();
617 if (cause instanceof AbstractMethodError) {
618 return (AbstractMethodError) cause;
619 } else {
620 err = new IllegalAccessError(ex.getMessage());
621 }
622 } else if (ex instanceof NoSuchMethodException) {
623 err = new NoSuchMethodError(ex.getMessage());
624 } else if (ex instanceof NoSuchFieldException) {
625 err = new NoSuchFieldError(ex.getMessage());
626 } else {
627 err = new IncompatibleClassChangeError();
628 }
629 return initCauseFrom(err, ex);
630 }
631
632 /**
633 * Use best possible cause for err.initCause(), substituting the
634 * cause for err itself if the cause has the same (or better) type.
635 */
636 static <E extends Error> E initCauseFrom(E err, Exception ex) {
637 Throwable th = ex.getCause();
638 @SuppressWarnings("unchecked")
639 final Class<E> Eclass = (Class<E>) err.getClass();
640 if (Eclass.isInstance(th))
641 return Eclass.cast(th);
642 err.initCause(th == null ? ex : th);
643 return err;
644 }
645
646 /**
647 * Is this method a caller-sensitive method?
648 * I.e., does it call Reflection.getCallerClass or a similar method
649 * to ask about the identity of its caller?
650 */
651 static boolean isCallerSensitive(MemberName mem) {
652 if (!mem.isInvocable()) return false; // fields are not caller sensitive
653
654 return mem.isCallerSensitive() || canBeCalledVirtual(mem);
655 }
656
657 static boolean canBeCalledVirtual(MemberName mem) {
658 assert(mem.isInvocable());
659 switch (mem.getName()) {
660 case "getContextClassLoader":
661 return canBeCalledVirtual(mem, java.lang.Thread.class);
662 }
663 return false;
664 }
665
666 static boolean canBeCalledVirtual(MemberName symbolicRef, Class<?> definingClass) {
667 Class<?> symbolicRefClass = symbolicRef.getDeclaringClass();
668 if (symbolicRefClass == definingClass) return true;
669 if (symbolicRef.isStatic() || symbolicRef.isPrivate()) return false;
670 return (definingClass.isAssignableFrom(symbolicRefClass) || // Msym overrides Mdef
671 symbolicRefClass.isInterface()); // Mdef implements Msym
672 }
673
674 private static final JavaLangAccess JLA = SharedSecrets.getJavaLangAccess();
675 /*
676 * A convenient method for LambdaForms to get the class data of a given class.
677 * LambdaForms cannot use condy via MethodHandles.classData
678 */
679 static Object classData(Class<?> c) {
680 return JLA.classData(c);
681 }
682 }