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 object constructor)
114 MN_IS_CONSTRUCTOR = 0x00020000, // object 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_HIDDEN_MEMBER = 0x00400000, // members defined in a hidden class or with @Hidden
120 MN_FLAT_FIELD = 0x00800000, // flat field
121 MN_NULL_RESTRICTED = 0x01000000, // null-restricted field
122 MN_REFERENCE_KIND_SHIFT = 26, // refKind
123 MN_REFERENCE_KIND_MASK = 0x3C000000 >> MN_REFERENCE_KIND_SHIFT;
124
125 /**
126 * Constant pool reference-kind codes, as used by CONSTANT_MethodHandle CP entries.
127 */
128 static final byte
129 REF_NONE = 0, // null value
130 REF_getField = 1,
131 REF_getStatic = 2,
132 REF_putField = 3,
133 REF_putStatic = 4,
134 REF_invokeVirtual = 5,
135 REF_invokeStatic = 6,
136 REF_invokeSpecial = 7,
137 REF_newInvokeSpecial = 8,
138 REF_invokeInterface = 9,
139 REF_LIMIT = 10;
140
141 /**
142 * Flags for Lookup.ClassOptions
143 */
144 static final int
145 NESTMATE_CLASS = 0x00000001,
146 HIDDEN_CLASS = 0x00000002,
147 STRONG_LOADER_LINK = 0x00000004,
148 ACCESS_VM_ANNOTATIONS = 0x00000008;
149
150 /**
151 * Lookup modes
152 */
153 static final int
154 LM_MODULE = Lookup.MODULE,
155 LM_UNCONDITIONAL = Lookup.UNCONDITIONAL,
156 LM_TRUSTED = -1;
157
158 }
159
160 static boolean refKindIsValid(int refKind) {
161 return (refKind > REF_NONE && refKind < REF_LIMIT);
162 }
163 static boolean refKindIsField(byte refKind) {
164 assert(refKindIsValid(refKind));
165 return (refKind <= REF_putStatic);
166 }
167 static boolean refKindIsGetter(byte refKind) {
168 assert(refKindIsValid(refKind));
169 return (refKind <= REF_getStatic);
170 }
171 static boolean refKindIsSetter(byte refKind) {
172 return refKindIsField(refKind) && !refKindIsGetter(refKind);
173 }
174 static boolean refKindIsMethod(byte refKind) {
175 return !refKindIsField(refKind) && (refKind != REF_newInvokeSpecial);
176 }
177 static boolean refKindIsConstructor(byte refKind) {
178 return (refKind == REF_newInvokeSpecial);
179 }
180 static boolean refKindHasReceiver(byte refKind) {
181 assert(refKindIsValid(refKind));
182 return (refKind & 1) != 0;
183 }
184 static boolean refKindIsStatic(byte refKind) {
185 return !refKindHasReceiver(refKind) && (refKind != REF_newInvokeSpecial);
186 }
187 static boolean refKindDoesDispatch(byte refKind) {
188 assert(refKindIsValid(refKind));
189 return (refKind == REF_invokeVirtual ||
190 refKind == REF_invokeInterface);
191 }
192 static {
193 final int HR_MASK = ((1 << REF_getField) |
194 (1 << REF_putField) |
195 (1 << REF_invokeVirtual) |
196 (1 << REF_invokeSpecial) |
197 (1 << REF_invokeInterface)
198 );
199 for (byte refKind = REF_NONE+1; refKind < REF_LIMIT; refKind++) {
200 assert(refKindHasReceiver(refKind) == (((1<<refKind) & HR_MASK) != 0)) : refKind;
201 }
202 }
203 static String refKindName(byte refKind) {
204 assert(refKindIsValid(refKind));
205 return switch (refKind) {
206 case REF_getField -> "getField";
207 case REF_getStatic -> "getStatic";
208 case REF_putField -> "putField";
209 case REF_putStatic -> "putStatic";
210 case REF_invokeVirtual -> "invokeVirtual";
211 case REF_invokeStatic -> "invokeStatic";
212 case REF_invokeSpecial -> "invokeSpecial";
213 case REF_newInvokeSpecial -> "newInvokeSpecial";
214 case REF_invokeInterface -> "invokeInterface";
215 default -> "REF_???";
216 };
217 }
218
219 private static native int getNamedCon(int which, Object[] name);
220 static boolean verifyConstants() {
221 Object[] box = { null };
222 for (int i = 0; ; i++) {
223 box[0] = null;
224 int vmval = getNamedCon(i, box);
225 if (box[0] == null) break;
226 String name = (String) box[0];
227 try {
228 Field con = Constants.class.getDeclaredField(name);
229 int jval = con.getInt(null);
230 if (jval == vmval) continue;
231 String err = (name+": JVM has "+vmval+" while Java has "+jval);
232 if (name.equals("CONV_OP_LIMIT")) {
233 System.err.println("warning: "+err);
234 continue;
235 }
236 throw new InternalError(err);
237 } catch (NoSuchFieldException | IllegalAccessException ex) {
238 String err = (name+": JVM has "+vmval+" which Java does not define");
239 // ignore exotic ops the JVM cares about; we just won't issue them
240 //System.err.println("warning: "+err);
241 continue;
242 }
243 }
244 return true;
245 }
246 static {
247 VM.setJavaLangInvokeInited();
248 assert(verifyConstants());
249 }
250
251 // Up-calls from the JVM.
252 // These must NOT be public.
253
254 /**
255 * The JVM is linking an invokedynamic instruction. Create a reified call site for it.
256 */
257 static MemberName linkCallSite(Object callerObj,
258 Object bootstrapMethodObj,
259 Object nameObj, Object typeObj,
260 Object staticArguments,
261 Object[] appendixResult) {
262 MethodHandle bootstrapMethod = (MethodHandle)bootstrapMethodObj;
263 Class<?> caller = (Class<?>)callerObj;
264 String name = nameObj.toString().intern();
265 MethodType type = (MethodType)typeObj;
266 if (!TRACE_METHOD_LINKAGE)
267 return linkCallSiteImpl(caller, bootstrapMethod, name, type,
268 staticArguments, appendixResult);
269 return linkCallSiteTracing(caller, bootstrapMethod, name, type,
270 staticArguments, appendixResult);
271 }
272 static MemberName linkCallSiteImpl(Class<?> caller,
273 MethodHandle bootstrapMethod,
274 String name, MethodType type,
275 Object staticArguments,
276 Object[] appendixResult) {
277 CallSite callSite = CallSite.makeSite(bootstrapMethod,
278 name,
279 type,
280 staticArguments,
281 caller);
282 if (TRACE_METHOD_LINKAGE) {
283 MethodHandle target = callSite.getTarget();
284 System.out.println("linkCallSite target class => " + target.getClass().getName());
285 System.out.println("linkCallSite target => " + target.debugString(0));
286 }
287
288 if (callSite instanceof ConstantCallSite) {
289 appendixResult[0] = callSite.dynamicInvoker();
290 return Invokers.linkToTargetMethod(type);
291 } else {
292 appendixResult[0] = callSite;
293 return Invokers.linkToCallSiteMethod(type);
294 }
295 }
296 // Tracing logic:
297 static MemberName linkCallSiteTracing(Class<?> caller,
298 MethodHandle bootstrapMethod,
299 String name, MethodType type,
300 Object staticArguments,
301 Object[] appendixResult) {
302 Object bsmReference = bootstrapMethod.internalMemberName();
303 if (bsmReference == null) bsmReference = bootstrapMethod;
304 String staticArglist = staticArglistForTrace(staticArguments);
305 System.out.println("linkCallSite "+getCallerInfo(caller)+" "+
306 bsmReference+" "+
307 name+type+"/"+staticArglist);
308 try {
309 MemberName res = linkCallSiteImpl(caller, bootstrapMethod, name, type,
310 staticArguments, appendixResult);
311 System.out.println("linkCallSite linkage => "+res+" + "+appendixResult[0]);
312 return res;
313 } catch (Throwable ex) {
314 ex.printStackTrace(); // print now in case exception is swallowed
315 System.out.println("linkCallSite => throw "+ex);
316 throw ex;
317 }
318 }
319
320 /**
321 * Return a human-readable description of the caller. Something like
322 * "java.base/java.security.Security.<clinit>(Security.java:82)"
323 */
324 private static String getCallerInfo(Class<?> caller) {
325 for (StackTraceElement e : Thread.currentThread().getStackTrace()) {
326 if (e.getClassName().equals(caller.getName())) {
327 return e.toString();
328 }
329 }
330 // fallback if the caller is somehow missing from the stack.
331 return caller.getName();
332 }
333
334 // this implements the upcall from the JVM, MethodHandleNatives.linkDynamicConstant:
335 static Object linkDynamicConstant(Object callerObj,
336 Object bootstrapMethodObj,
337 Object nameObj, Object typeObj,
338 Object staticArguments) {
339 MethodHandle bootstrapMethod = (MethodHandle)bootstrapMethodObj;
340 Class<?> caller = (Class<?>)callerObj;
341 String name = nameObj.toString().intern();
342 Class<?> type = (Class<?>)typeObj;
343 if (!TRACE_METHOD_LINKAGE)
344 return linkDynamicConstantImpl(caller, bootstrapMethod, name, type, staticArguments);
345 return linkDynamicConstantTracing(caller, bootstrapMethod, name, type, staticArguments);
346 }
347
348 static Object linkDynamicConstantImpl(Class<?> caller,
349 MethodHandle bootstrapMethod,
350 String name, Class<?> type,
351 Object staticArguments) {
352 return ConstantBootstraps.makeConstant(bootstrapMethod, name, type, staticArguments, caller);
353 }
354
355 private static String staticArglistForTrace(Object staticArguments) {
356 if (staticArguments instanceof Object[] array)
357 return "BSA="+java.util.Arrays.asList(array);
358 if (staticArguments instanceof int[] array)
359 return "BSA@"+java.util.Arrays.toString(array);
360 if (staticArguments == null)
361 return "BSA0=null";
362 return "BSA1="+staticArguments;
363 }
364
365 // Tracing logic:
366 static Object linkDynamicConstantTracing(Class<?> caller,
367 MethodHandle bootstrapMethod,
368 String name, Class<?> type,
369 Object staticArguments) {
370 Object bsmReference = bootstrapMethod.internalMemberName();
371 if (bsmReference == null) bsmReference = bootstrapMethod;
372 String staticArglist = staticArglistForTrace(staticArguments);
373 System.out.println("linkDynamicConstant "+caller.getName()+" "+
374 bsmReference+" "+
375 name+type+"/"+staticArglist);
376 try {
377 Object res = linkDynamicConstantImpl(caller, bootstrapMethod, name, type, staticArguments);
378 System.out.println("linkDynamicConstantImpl => "+res);
379 return res;
380 } catch (Throwable ex) {
381 ex.printStackTrace(); // print now in case exception is swallowed
382 System.out.println("linkDynamicConstant => throw "+ex);
383 throw ex;
384 }
385 }
386
387 /** The JVM is requesting pull-mode bootstrap when it provides
388 * a tuple of the form int[]{ argc, vmindex }.
389 * The BSM is expected to call back to the JVM using the caller
390 * class and vmindex to resolve the static arguments.
391 */
392 static boolean staticArgumentsPulled(Object staticArguments) {
393 return staticArguments instanceof int[];
394 }
395
396 /** A BSM runs in pull-mode if and only if its sole arguments
397 * are (Lookup, BootstrapCallInfo), or can be converted pairwise
398 * to those types, and it is not of variable arity.
399 * Excluding error cases, we can just test that the arity is a constant 2.
400 *
401 * NOTE: This method currently returns false, since pulling is not currently
402 * exposed to a BSM. When pull mode is supported the method block will be
403 * replaced with currently commented out code.
404 */
405 static boolean isPullModeBSM(MethodHandle bsm) {
406 return false;
407 // return bsm.type().parameterCount() == 2 && !bsm.isVarargsCollector();
408 }
409
410 /**
411 * The JVM wants a pointer to a MethodType. Oblige it by finding or creating one.
412 */
413 static MethodType findMethodHandleType(Class<?> rtype, Class<?>[] ptypes) {
414 return MethodType.methodType(rtype, ptypes, true);
415 }
416
417 /**
418 * The JVM wants to link a call site that requires a dynamic type check.
419 * Name is a type-checking invoker, invokeExact or invoke.
420 * Return a JVM method (MemberName) to handle the invoking.
421 * The method assumes the following arguments on the stack:
422 * 0: the method handle being invoked
423 * 1-N: the arguments to the method handle invocation
424 * N+1: an optional, implicitly added argument (typically the given MethodType)
425 * <p>
426 * The nominal method at such a call site is an instance of
427 * a signature-polymorphic method (see @PolymorphicSignature).
428 * Such method instances are user-visible entities which are
429 * "split" from the generic placeholder method in {@code MethodHandle}.
430 * (Note that the placeholder method is not identical with any of
431 * its instances. If invoked reflectively, is guaranteed to throw an
432 * {@code UnsupportedOperationException}.)
433 * If the signature-polymorphic method instance is ever reified,
434 * it appears as a "copy" of the original placeholder
435 * (a native final member of {@code MethodHandle}) except
436 * that its type descriptor has shape required by the instance,
437 * and the method instance is <em>not</em> varargs.
438 * The method instance is also marked synthetic, since the
439 * method (by definition) does not appear in Java source code.
440 * <p>
441 * The JVM is allowed to reify this method as instance metadata.
442 * For example, {@code invokeBasic} is always reified.
443 * But the JVM may instead call {@code linkMethod}.
444 * If the result is an * ordered pair of a {@code (method, appendix)},
445 * the method gets all the arguments (0..N inclusive)
446 * plus the appendix (N+1), and uses the appendix to complete the call.
447 * In this way, one reusable method (called a "linker method")
448 * can perform the function of any number of polymorphic instance
449 * methods.
450 * <p>
451 * Linker methods are allowed to be weakly typed, with any or
452 * all references rewritten to {@code Object} and any primitives
453 * (except {@code long}/{@code float}/{@code double})
454 * rewritten to {@code int}.
455 * A linker method is trusted to return a strongly typed result,
456 * according to the specific method type descriptor of the
457 * signature-polymorphic instance it is emulating.
458 * This can involve (as necessary) a dynamic check using
459 * data extracted from the appendix argument.
460 * <p>
461 * The JVM does not inspect the appendix, other than to pass
462 * it verbatim to the linker method at every call.
463 * This means that the JDK runtime has wide latitude
464 * for choosing the shape of each linker method and its
465 * corresponding appendix.
466 * Linker methods should be generated from {@code LambdaForm}s
467 * so that they do not become visible on stack traces.
468 * <p>
469 * The {@code linkMethod} call is free to omit the appendix
470 * (returning null) and instead emulate the required function
471 * completely in the linker method.
472 * As a corner case, if N==255, no appendix is possible.
473 * In this case, the method returned must be custom-generated to
474 * perform any needed type checking.
475 * <p>
476 * If the JVM does not reify a method at a call site, but instead
477 * calls {@code linkMethod}, the corresponding call represented
478 * in the bytecodes may mention a valid method which is not
479 * representable with a {@code MemberName}.
480 * Therefore, use cases for {@code linkMethod} tend to correspond to
481 * special cases in reflective code such as {@code findVirtual}
482 * or {@code revealDirect}.
483 */
484 static MemberName linkMethod(Class<?> callerClass, int refKind,
485 Class<?> defc, String name, Object type,
486 Object[] appendixResult) {
487 if (!TRACE_METHOD_LINKAGE)
488 return linkMethodImpl(callerClass, refKind, defc, name, type, appendixResult);
489 return linkMethodTracing(callerClass, refKind, defc, name, type, appendixResult);
490 }
491 static MemberName linkMethodImpl(Class<?> callerClass, int refKind,
492 Class<?> defc, String name, Object type,
493 Object[] appendixResult) {
494 try {
495 if (refKind == REF_invokeVirtual) {
496 if (defc == MethodHandle.class) {
497 return Invokers.methodHandleInvokeLinkerMethod(
498 name, fixMethodType(callerClass, type), appendixResult);
499 } else if (defc == VarHandle.class) {
500 return varHandleOperationLinkerMethod(
501 name, fixMethodType(callerClass, type), appendixResult);
502 }
503 }
504 } catch (Error e) {
505 // Pass through an Error, including say StackOverflowError or
506 // OutOfMemoryError
507 throw e;
508 } catch (Throwable ex) {
509 // Wrap anything else in LinkageError
510 throw new LinkageError(ex.getMessage(), ex);
511 }
512 throw new LinkageError("no such method "+defc.getName()+"."+name+type);
513 }
514 private static MethodType fixMethodType(Class<?> callerClass, Object type) {
515 if (type instanceof MethodType mt)
516 return mt;
517 else
518 return MethodType.fromDescriptor((String)type, callerClass.getClassLoader());
519 }
520 // Tracing logic:
521 static MemberName linkMethodTracing(Class<?> callerClass, int refKind,
522 Class<?> defc, String name, Object type,
523 Object[] appendixResult) {
524 System.out.println("linkMethod "+defc.getName()+"."+
525 name+type+"/"+Integer.toHexString(refKind));
526 try {
527 MemberName res = linkMethodImpl(callerClass, refKind, defc, name, type, appendixResult);
528 System.out.println("linkMethod => "+res+" + "+appendixResult[0]);
529 return res;
530 } catch (Throwable ex) {
531 System.out.println("linkMethod => throw "+ex);
532 throw ex;
533 }
534 }
535
536 /**
537 * Obtain the method to link to the VarHandle operation.
538 * This method is located here and not in Invokers to avoid
539 * initializing that and other classes early on in VM bootup.
540 */
541 private static MemberName varHandleOperationLinkerMethod(String name,
542 MethodType mtype,
543 Object[] appendixResult) {
544 // Get the signature method type
545 final MethodType sigType = mtype.basicType();
546
547 // Get the access kind from the method name
548 VarHandle.AccessMode ak;
549 try {
550 ak = VarHandle.AccessMode.valueFromMethodName(name);
551 } catch (IllegalArgumentException e) {
552 throw MethodHandleStatics.newInternalError(e);
553 }
554
555 // Create the appendix descriptor constant
556 VarHandle.AccessDescriptor ad = new VarHandle.AccessDescriptor(mtype, ak.at.ordinal(), ak.ordinal());
557 appendixResult[0] = ad;
558
559 if (MethodHandleStatics.VAR_HANDLE_GUARDS) {
560 // If not polymorphic in the return type, such as the compareAndSet
561 // methods that return boolean
562 Class<?> guardReturnType = sigType.returnType();
563 if (ak.at.isMonomorphicInReturnType) {
564 if (ak.at.returnType != mtype.returnType()) {
565 // The caller contains a different return type than that
566 // defined by the method
567 throw newNoSuchMethodErrorOnVarHandle(name, mtype);
568 }
569 // Adjust the return type of the signature method type
570 guardReturnType = ak.at.returnType;
571 }
572
573 // Get the guard method type for linking
574 final Class<?>[] guardParams = new Class<?>[sigType.parameterCount() + 2];
575 // VarHandle at start
576 guardParams[0] = VarHandle.class;
577 for (int i = 0; i < sigType.parameterCount(); i++) {
578 guardParams[i + 1] = sigType.parameterType(i);
579 }
580 // Access descriptor at end
581 guardParams[guardParams.length - 1] = VarHandle.AccessDescriptor.class;
582 MethodType guardType = MethodType.methodType(guardReturnType, guardParams, true);
583
584 MemberName linker = new MemberName(
585 VarHandleGuards.class, getVarHandleGuardMethodName(guardType),
586 guardType, REF_invokeStatic);
587
588 linker = MemberName.getFactory().resolveOrNull(REF_invokeStatic, linker,
589 VarHandleGuards.class, LM_TRUSTED);
590 if (linker != null) {
591 return linker;
592 }
593 // Fall back to lambda form linkage if guard method is not available
594 // TODO Optionally log fallback ?
595 }
596 return Invokers.varHandleInvokeLinkerMethod(mtype);
597 }
598 static String getVarHandleGuardMethodName(MethodType guardType) {
599 String prefix = "guard_";
600 StringBuilder sb = new StringBuilder(prefix.length() + guardType.parameterCount());
601
602 sb.append(prefix);
603 for (int i = 1; i < guardType.parameterCount() - 1; i++) {
604 Class<?> pt = guardType.parameterType(i);
605 sb.append(getCharType(pt));
606 }
607 sb.append('_').append(getCharType(guardType.returnType()));
608 return sb.toString();
609 }
610 static char getCharType(Class<?> pt) {
611 return Wrapper.forBasicType(pt).basicTypeChar();
612 }
613 static NoSuchMethodError newNoSuchMethodErrorOnVarHandle(String name, MethodType mtype) {
614 return new NoSuchMethodError("VarHandle." + name + mtype);
615 }
616
617 /**
618 * The JVM is resolving a CONSTANT_MethodHandle CP entry. And it wants our help.
619 * It will make an up-call to this method. (Do not change the name or signature.)
620 * The type argument is a Class for field requests and a MethodType for non-fields.
621 * <p>
622 * Recent versions of the JVM may also pass a resolved MemberName for the type.
623 * In that case, the name is ignored and may be null.
624 */
625 static MethodHandle linkMethodHandleConstant(Class<?> callerClass, int refKind,
626 Class<?> defc, String name, Object type) {
627 try {
628 Lookup lookup = IMPL_LOOKUP.in(callerClass);
629 assert(refKindIsValid(refKind));
630 return lookup.linkMethodHandleConstant((byte) refKind, defc, name, type);
631 } catch (ReflectiveOperationException ex) {
632 throw mapLookupExceptionToError(ex);
633 }
634 }
635
636 /**
637 * Map a reflective exception to a linkage error.
638 */
639 static LinkageError mapLookupExceptionToError(ReflectiveOperationException ex) {
640 LinkageError err;
641 if (ex instanceof IllegalAccessException) {
642 Throwable cause = ex.getCause();
643 if (cause instanceof AbstractMethodError ame) {
644 return ame;
645 } else {
646 err = new IllegalAccessError(ex.getMessage());
647 }
648 } else if (ex instanceof NoSuchMethodException) {
649 err = new NoSuchMethodError(ex.getMessage());
650 } else if (ex instanceof NoSuchFieldException) {
651 err = new NoSuchFieldError(ex.getMessage());
652 } else {
653 err = new IncompatibleClassChangeError();
654 }
655 return initCauseFrom(err, ex);
656 }
657
658 /**
659 * Use best possible cause for err.initCause(), substituting the
660 * cause for err itself if the cause has the same (or better) type.
661 */
662 static <E extends Error> E initCauseFrom(E err, Exception ex) {
663 Throwable th = ex.getCause();
664 @SuppressWarnings("unchecked")
665 final Class<E> Eclass = (Class<E>) err.getClass();
666 if (Eclass.isInstance(th))
667 return Eclass.cast(th);
668 err.initCause(th == null ? ex : th);
669 return err;
670 }
671
672 /**
673 * Is this method a caller-sensitive method?
674 * I.e., does it call Reflection.getCallerClass or a similar method
675 * to ask about the identity of its caller?
676 */
677 static boolean isCallerSensitive(MemberName mem) {
678 if (!mem.isInvocable()) return false; // fields are not caller sensitive
679
680 return mem.isCallerSensitive() || canBeCalledVirtual(mem);
681 }
682
683 static boolean canBeCalledVirtual(MemberName mem) {
684 assert(mem.isInvocable());
685 return mem.getName().equals("getContextClassLoader") && canBeCalledVirtual(mem, java.lang.Thread.class);
686 }
687
688 static boolean canBeCalledVirtual(MemberName symbolicRef, Class<?> definingClass) {
689 Class<?> symbolicRefClass = symbolicRef.getDeclaringClass();
690 if (symbolicRefClass == definingClass) return true;
691 if (symbolicRef.isStatic() || symbolicRef.isPrivate()) return false;
692 return (definingClass.isAssignableFrom(symbolicRefClass) || // Msym overrides Mdef
693 symbolicRefClass.isInterface()); // Mdef implements Msym
694 }
695 }