1 /*
2 * Copyright (c) 2003, 2024, 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.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "cds/cdsConfig.hpp"
27 #include "cds/metaspaceShared.hpp"
28 #include "classfile/classFileStream.hpp"
29 #include "classfile/classLoaderDataGraph.hpp"
30 #include "classfile/classLoadInfo.hpp"
31 #include "classfile/javaClasses.inline.hpp"
32 #include "classfile/metadataOnStackMark.hpp"
33 #include "classfile/symbolTable.hpp"
34 #include "classfile/klassFactory.hpp"
35 #include "classfile/verifier.hpp"
36 #include "classfile/vmClasses.hpp"
37 #include "classfile/vmSymbols.hpp"
38 #include "code/codeCache.hpp"
39 #include "compiler/compileBroker.hpp"
40 #include "interpreter/oopMapCache.hpp"
41 #include "interpreter/rewriter.hpp"
42 #include "jfr/jfrEvents.hpp"
43 #include "logging/logStream.hpp"
44 #include "memory/metadataFactory.hpp"
45 #include "memory/resourceArea.hpp"
46 #include "memory/universe.hpp"
47 #include "oops/annotations.hpp"
48 #include "oops/constantPool.hpp"
49 #include "oops/fieldStreams.inline.hpp"
50 #include "oops/klass.inline.hpp"
51 #include "oops/klassVtable.hpp"
52 #include "oops/method.hpp"
53 #include "oops/oop.inline.hpp"
54 #include "oops/recordComponent.hpp"
55 #include "prims/jvmtiImpl.hpp"
56 #include "prims/jvmtiRedefineClasses.hpp"
57 #include "prims/jvmtiThreadState.inline.hpp"
58 #include "prims/resolvedMethodTable.hpp"
59 #include "prims/methodComparator.hpp"
60 #include "runtime/atomic.hpp"
61 #include "runtime/deoptimization.hpp"
62 #include "runtime/handles.inline.hpp"
63 #include "runtime/jniHandles.inline.hpp"
64 #include "runtime/relocator.hpp"
65 #include "runtime/safepointVerifiers.hpp"
66 #include "utilities/bitMap.inline.hpp"
67 #include "utilities/checkedCast.hpp"
68 #include "utilities/events.hpp"
69 #include "utilities/macros.hpp"
70
71 Array<Method*>* VM_RedefineClasses::_old_methods = nullptr;
72 Array<Method*>* VM_RedefineClasses::_new_methods = nullptr;
73 Method** VM_RedefineClasses::_matching_old_methods = nullptr;
74 Method** VM_RedefineClasses::_matching_new_methods = nullptr;
75 Method** VM_RedefineClasses::_deleted_methods = nullptr;
76 Method** VM_RedefineClasses::_added_methods = nullptr;
77 int VM_RedefineClasses::_matching_methods_length = 0;
78 int VM_RedefineClasses::_deleted_methods_length = 0;
79 int VM_RedefineClasses::_added_methods_length = 0;
80
81 // This flag is global as the constructor does not reset it:
82 bool VM_RedefineClasses::_has_redefined_Object = false;
83 u8 VM_RedefineClasses::_id_counter = 0;
84
85 VM_RedefineClasses::VM_RedefineClasses(jint class_count,
86 const jvmtiClassDefinition *class_defs,
87 JvmtiClassLoadKind class_load_kind) {
88 _class_count = class_count;
89 _class_defs = class_defs;
90 _class_load_kind = class_load_kind;
91 _any_class_has_resolved_methods = false;
92 _res = JVMTI_ERROR_NONE;
93 _the_class = nullptr;
94 _id = next_id();
95 }
96
97 static inline InstanceKlass* get_ik(jclass def) {
98 oop mirror = JNIHandles::resolve_non_null(def);
99 return InstanceKlass::cast(java_lang_Class::as_Klass(mirror));
100 }
101
102 // If any of the classes are being redefined, wait
103 // Parallel constant pool merging leads to indeterminate constant pools.
104 void VM_RedefineClasses::lock_classes() {
105 JvmtiThreadState *state = JvmtiThreadState::state_for(JavaThread::current());
106 GrowableArray<Klass*>* redef_classes = state->get_classes_being_redefined();
107
108 MonitorLocker ml(RedefineClasses_lock);
109
110 if (redef_classes == nullptr) {
111 redef_classes = new (mtClass) GrowableArray<Klass*>(1, mtClass);
112 state->set_classes_being_redefined(redef_classes);
113 }
114
115 bool has_redefined;
116 do {
117 has_redefined = false;
118 // Go through classes each time until none are being redefined. Skip
119 // the ones that are being redefined by this thread currently. Class file
120 // load hook event may trigger new class redefine when we are redefining
121 // a class (after lock_classes()).
122 for (int i = 0; i < _class_count; i++) {
123 InstanceKlass* ik = get_ik(_class_defs[i].klass);
124 // Check if we are currently redefining the class in this thread already.
125 if (redef_classes->contains(ik)) {
126 assert(ik->is_being_redefined(), "sanity");
127 } else {
128 if (ik->is_being_redefined()) {
129 ml.wait();
130 has_redefined = true;
131 break; // for loop
132 }
133 }
134 }
135 } while (has_redefined);
136
137 for (int i = 0; i < _class_count; i++) {
138 InstanceKlass* ik = get_ik(_class_defs[i].klass);
139 redef_classes->push(ik); // Add to the _classes_being_redefined list
140 ik->set_is_being_redefined(true);
141 }
142 ml.notify_all();
143 }
144
145 void VM_RedefineClasses::unlock_classes() {
146 JvmtiThreadState *state = JvmtiThreadState::state_for(JavaThread::current());
147 GrowableArray<Klass*>* redef_classes = state->get_classes_being_redefined();
148 assert(redef_classes != nullptr, "_classes_being_redefined is not allocated");
149
150 MonitorLocker ml(RedefineClasses_lock);
151
152 for (int i = _class_count - 1; i >= 0; i--) {
153 InstanceKlass* def_ik = get_ik(_class_defs[i].klass);
154 if (redef_classes->length() > 0) {
155 // Remove the class from _classes_being_redefined list
156 Klass* k = redef_classes->pop();
157 assert(def_ik == k, "unlocking wrong class");
158 }
159 assert(def_ik->is_being_redefined(),
160 "should be being redefined to get here");
161
162 // Unlock after we finish all redefines for this class within
163 // the thread. Same class can be pushed to the list multiple
164 // times (not more than once by each recursive redefinition).
165 if (!redef_classes->contains(def_ik)) {
166 def_ik->set_is_being_redefined(false);
167 }
168 }
169 ml.notify_all();
170 }
171
172 bool VM_RedefineClasses::doit_prologue() {
173 if (_class_count == 0) {
174 _res = JVMTI_ERROR_NONE;
175 return false;
176 }
177 if (_class_defs == nullptr) {
178 _res = JVMTI_ERROR_NULL_POINTER;
179 return false;
180 }
181
182 for (int i = 0; i < _class_count; i++) {
183 if (_class_defs[i].klass == nullptr) {
184 _res = JVMTI_ERROR_INVALID_CLASS;
185 return false;
186 }
187 if (_class_defs[i].class_byte_count == 0) {
188 _res = JVMTI_ERROR_INVALID_CLASS_FORMAT;
189 return false;
190 }
191 if (_class_defs[i].class_bytes == nullptr) {
192 _res = JVMTI_ERROR_NULL_POINTER;
193 return false;
194 }
195
196 oop mirror = JNIHandles::resolve_non_null(_class_defs[i].klass);
197 // classes for primitives, arrays, and hidden classes
198 // cannot be redefined.
199 if (!is_modifiable_class(mirror)) {
200 _res = JVMTI_ERROR_UNMODIFIABLE_CLASS;
201 return false;
202 }
203 }
204
205 // Start timer after all the sanity checks; not quite accurate, but
206 // better than adding a bunch of stop() calls.
207 if (log_is_enabled(Info, redefine, class, timer)) {
208 _timer_vm_op_prologue.start();
209 }
210
211 lock_classes();
212 // We first load new class versions in the prologue, because somewhere down the
213 // call chain it is required that the current thread is a Java thread.
214 _res = load_new_class_versions();
215 if (_res != JVMTI_ERROR_NONE) {
216 // free any successfully created classes, since none are redefined
217 for (int i = 0; i < _class_count; i++) {
218 if (_scratch_classes[i] != nullptr) {
219 ClassLoaderData* cld = _scratch_classes[i]->class_loader_data();
220 // Free the memory for this class at class unloading time. Not before
221 // because CMS might think this is still live.
222 InstanceKlass* ik = get_ik(_class_defs[i].klass);
223 if (ik->get_cached_class_file() == _scratch_classes[i]->get_cached_class_file()) {
224 // Don't double-free cached_class_file copied from the original class if error.
225 _scratch_classes[i]->set_cached_class_file(nullptr);
226 }
227 cld->add_to_deallocate_list(InstanceKlass::cast(_scratch_classes[i]));
228 }
229 }
230 // Free os::malloc allocated memory in load_new_class_version.
231 os::free(_scratch_classes);
232 _timer_vm_op_prologue.stop();
233 unlock_classes();
234 return false;
235 }
236
237 _timer_vm_op_prologue.stop();
238 return true;
239 }
240
241 void VM_RedefineClasses::doit() {
242 Thread* current = Thread::current();
243
244 if (log_is_enabled(Info, redefine, class, timer)) {
245 _timer_vm_op_doit.start();
246 }
247
248 #if INCLUDE_CDS
249 if (CDSConfig::is_using_archive()) {
250 // Sharing is enabled so we remap the shared readonly space to
251 // shared readwrite, private just in case we need to redefine
252 // a shared class. We do the remap during the doit() phase of
253 // the safepoint to be safer.
254 if (!MetaspaceShared::remap_shared_readonly_as_readwrite()) {
255 log_info(redefine, class, load)("failed to remap shared readonly space to readwrite, private");
256 _res = JVMTI_ERROR_INTERNAL;
257 _timer_vm_op_doit.stop();
258 return;
259 }
260 }
261 #endif
262
263 // Mark methods seen on stack and everywhere else so old methods are not
264 // cleaned up if they're on the stack.
265 MetadataOnStackMark md_on_stack(/*walk_all_metadata*/true, /*redefinition_walk*/true);
266 HandleMark hm(current); // make sure any handles created are deleted
267 // before the stack walk again.
268
269 for (int i = 0; i < _class_count; i++) {
270 redefine_single_class(current, _class_defs[i].klass, _scratch_classes[i]);
271 }
272
273 // Flush all compiled code that depends on the classes redefined.
274 flush_dependent_code();
275
276 // Adjust constantpool caches and vtables for all classes
277 // that reference methods of the evolved classes.
278 // Have to do this after all classes are redefined and all methods that
279 // are redefined are marked as old.
280 AdjustAndCleanMetadata adjust_and_clean_metadata(current);
281 ClassLoaderDataGraph::classes_do(&adjust_and_clean_metadata);
282
283 // JSR-292 support
284 if (_any_class_has_resolved_methods) {
285 bool trace_name_printed = false;
286 ResolvedMethodTable::adjust_method_entries(&trace_name_printed);
287 }
288
289 // Increment flag indicating that some invariants are no longer true.
290 // See jvmtiExport.hpp for detailed explanation.
291 JvmtiExport::increment_redefinition_count();
292
293 // check_class() is optionally called for product bits, but is
294 // always called for non-product bits.
295 #ifdef PRODUCT
296 if (log_is_enabled(Trace, redefine, class, obsolete, metadata)) {
297 #endif
298 log_trace(redefine, class, obsolete, metadata)("calling check_class");
299 CheckClass check_class(current);
300 ClassLoaderDataGraph::classes_do(&check_class);
301 #ifdef PRODUCT
302 }
303 #endif
304
305 // Clean up any metadata now unreferenced while MetadataOnStackMark is set.
306 ClassLoaderDataGraph::clean_deallocate_lists(false);
307
308 _timer_vm_op_doit.stop();
309 }
310
311 void VM_RedefineClasses::doit_epilogue() {
312 unlock_classes();
313
314 // Free os::malloc allocated memory.
315 os::free(_scratch_classes);
316
317 // Reset the_class to null for error printing.
318 _the_class = nullptr;
319
320 if (log_is_enabled(Info, redefine, class, timer)) {
321 // Used to have separate timers for "doit" and "all", but the timer
322 // overhead skewed the measurements.
323 julong doit_time = _timer_vm_op_doit.milliseconds();
324 julong all_time = _timer_vm_op_prologue.milliseconds() + doit_time;
325
326 log_info(redefine, class, timer)
327 ("vm_op: all=" JULONG_FORMAT " prologue=" JULONG_FORMAT " doit=" JULONG_FORMAT,
328 all_time, (julong)_timer_vm_op_prologue.milliseconds(), doit_time);
329 log_info(redefine, class, timer)
330 ("redefine_single_class: phase1=" JULONG_FORMAT " phase2=" JULONG_FORMAT,
331 (julong)_timer_rsc_phase1.milliseconds(), (julong)_timer_rsc_phase2.milliseconds());
332 }
333 }
334
335 bool VM_RedefineClasses::is_modifiable_class(oop klass_mirror) {
336 // classes for primitives cannot be redefined
337 if (java_lang_Class::is_primitive(klass_mirror)) {
338 return false;
339 }
340 Klass* k = java_lang_Class::as_Klass(klass_mirror);
341 // classes for arrays cannot be redefined
342 if (k == nullptr || !k->is_instance_klass()) {
343 return false;
344 }
345
346 // Cannot redefine or retransform a hidden class.
347 if (InstanceKlass::cast(k)->is_hidden()) {
348 return false;
349 }
350 if (InstanceKlass::cast(k) == vmClasses::Object_klass()) {
351 return false;
352 }
353 if (InstanceKlass::cast(k) == vmClasses::Continuation_klass()) {
354 // Don't redefine Continuation class. See 8302779.
355 return false;
356 }
357 return true;
358 }
359
360 // Append the current entry at scratch_i in scratch_cp to *merge_cp_p
361 // where the end of *merge_cp_p is specified by *merge_cp_length_p. For
362 // direct CP entries, there is just the current entry to append. For
363 // indirect and double-indirect CP entries, there are zero or more
364 // referenced CP entries along with the current entry to append.
365 // Indirect and double-indirect CP entries are handled by recursive
366 // calls to append_entry() as needed. The referenced CP entries are
367 // always appended to *merge_cp_p before the referee CP entry. These
368 // referenced CP entries may already exist in *merge_cp_p in which case
369 // there is nothing extra to append and only the current entry is
370 // appended.
371 void VM_RedefineClasses::append_entry(const constantPoolHandle& scratch_cp,
372 int scratch_i, constantPoolHandle *merge_cp_p, int *merge_cp_length_p) {
373
374 // append is different depending on entry tag type
375 switch (scratch_cp->tag_at(scratch_i).value()) {
376
377 // The old verifier is implemented outside the VM. It loads classes,
378 // but does not resolve constant pool entries directly so we never
379 // see Class entries here with the old verifier. Similarly the old
380 // verifier does not like Class entries in the input constant pool.
381 // The split-verifier is implemented in the VM so it can optionally
382 // and directly resolve constant pool entries to load classes. The
383 // split-verifier can accept either Class entries or UnresolvedClass
384 // entries in the input constant pool. We revert the appended copy
385 // back to UnresolvedClass so that either verifier will be happy
386 // with the constant pool entry.
387 //
388 // this is an indirect CP entry so it needs special handling
389 case JVM_CONSTANT_Class:
390 case JVM_CONSTANT_UnresolvedClass:
391 {
392 int name_i = scratch_cp->klass_name_index_at(scratch_i);
393 int new_name_i = find_or_append_indirect_entry(scratch_cp, name_i, merge_cp_p,
394 merge_cp_length_p);
395
396 if (new_name_i != name_i) {
397 log_trace(redefine, class, constantpool)
398 ("Class entry@%d name_index change: %d to %d",
399 *merge_cp_length_p, name_i, new_name_i);
400 }
401
402 (*merge_cp_p)->temp_unresolved_klass_at_put(*merge_cp_length_p, new_name_i);
403 if (scratch_i != *merge_cp_length_p) {
404 // The new entry in *merge_cp_p is at a different index than
405 // the new entry in scratch_cp so we need to map the index values.
406 map_index(scratch_cp, scratch_i, *merge_cp_length_p);
407 }
408 (*merge_cp_length_p)++;
409 } break;
410
411 // these are direct CP entries so they can be directly appended,
412 // but double and long take two constant pool entries
413 case JVM_CONSTANT_Double: // fall through
414 case JVM_CONSTANT_Long:
415 {
416 ConstantPool::copy_entry_to(scratch_cp, scratch_i, *merge_cp_p, *merge_cp_length_p);
417
418 if (scratch_i != *merge_cp_length_p) {
419 // The new entry in *merge_cp_p is at a different index than
420 // the new entry in scratch_cp so we need to map the index values.
421 map_index(scratch_cp, scratch_i, *merge_cp_length_p);
422 }
423 (*merge_cp_length_p) += 2;
424 } break;
425
426 // these are direct CP entries so they can be directly appended
427 case JVM_CONSTANT_Float: // fall through
428 case JVM_CONSTANT_Integer: // fall through
429 case JVM_CONSTANT_Utf8: // fall through
430
431 // This was an indirect CP entry, but it has been changed into
432 // Symbol*s so this entry can be directly appended.
433 case JVM_CONSTANT_String: // fall through
434 {
435 ConstantPool::copy_entry_to(scratch_cp, scratch_i, *merge_cp_p, *merge_cp_length_p);
436
437 if (scratch_i != *merge_cp_length_p) {
438 // The new entry in *merge_cp_p is at a different index than
439 // the new entry in scratch_cp so we need to map the index values.
440 map_index(scratch_cp, scratch_i, *merge_cp_length_p);
441 }
442 (*merge_cp_length_p)++;
443 } break;
444
445 // this is an indirect CP entry so it needs special handling
446 case JVM_CONSTANT_NameAndType:
447 {
448 int name_ref_i = scratch_cp->name_ref_index_at(scratch_i);
449 int new_name_ref_i = find_or_append_indirect_entry(scratch_cp, name_ref_i, merge_cp_p,
450 merge_cp_length_p);
451
452 int signature_ref_i = scratch_cp->signature_ref_index_at(scratch_i);
453 int new_signature_ref_i = find_or_append_indirect_entry(scratch_cp, signature_ref_i,
454 merge_cp_p, merge_cp_length_p);
455
456 // If the referenced entries already exist in *merge_cp_p, then
457 // both new_name_ref_i and new_signature_ref_i will both be 0.
458 // In that case, all we are appending is the current entry.
459 if (new_name_ref_i != name_ref_i) {
460 log_trace(redefine, class, constantpool)
461 ("NameAndType entry@%d name_ref_index change: %d to %d",
462 *merge_cp_length_p, name_ref_i, new_name_ref_i);
463 }
464 if (new_signature_ref_i != signature_ref_i) {
465 log_trace(redefine, class, constantpool)
466 ("NameAndType entry@%d signature_ref_index change: %d to %d",
467 *merge_cp_length_p, signature_ref_i, new_signature_ref_i);
468 }
469
470 (*merge_cp_p)->name_and_type_at_put(*merge_cp_length_p,
471 new_name_ref_i, new_signature_ref_i);
472 if (scratch_i != *merge_cp_length_p) {
473 // The new entry in *merge_cp_p is at a different index than
474 // the new entry in scratch_cp so we need to map the index values.
475 map_index(scratch_cp, scratch_i, *merge_cp_length_p);
476 }
477 (*merge_cp_length_p)++;
478 } break;
479
480 // this is a double-indirect CP entry so it needs special handling
481 case JVM_CONSTANT_Fieldref: // fall through
482 case JVM_CONSTANT_InterfaceMethodref: // fall through
483 case JVM_CONSTANT_Methodref:
484 {
485 int klass_ref_i = scratch_cp->uncached_klass_ref_index_at(scratch_i);
486 int new_klass_ref_i = find_or_append_indirect_entry(scratch_cp, klass_ref_i,
487 merge_cp_p, merge_cp_length_p);
488
489 int name_and_type_ref_i = scratch_cp->uncached_name_and_type_ref_index_at(scratch_i);
490 int new_name_and_type_ref_i = find_or_append_indirect_entry(scratch_cp, name_and_type_ref_i,
491 merge_cp_p, merge_cp_length_p);
492
493 const char *entry_name = nullptr;
494 switch (scratch_cp->tag_at(scratch_i).value()) {
495 case JVM_CONSTANT_Fieldref:
496 entry_name = "Fieldref";
497 (*merge_cp_p)->field_at_put(*merge_cp_length_p, new_klass_ref_i,
498 new_name_and_type_ref_i);
499 break;
500 case JVM_CONSTANT_InterfaceMethodref:
501 entry_name = "IFMethodref";
502 (*merge_cp_p)->interface_method_at_put(*merge_cp_length_p,
503 new_klass_ref_i, new_name_and_type_ref_i);
504 break;
505 case JVM_CONSTANT_Methodref:
506 entry_name = "Methodref";
507 (*merge_cp_p)->method_at_put(*merge_cp_length_p, new_klass_ref_i,
508 new_name_and_type_ref_i);
509 break;
510 default:
511 guarantee(false, "bad switch");
512 break;
513 }
514
515 if (klass_ref_i != new_klass_ref_i) {
516 log_trace(redefine, class, constantpool)
517 ("%s entry@%d class_index changed: %d to %d", entry_name, *merge_cp_length_p, klass_ref_i, new_klass_ref_i);
518 }
519 if (name_and_type_ref_i != new_name_and_type_ref_i) {
520 log_trace(redefine, class, constantpool)
521 ("%s entry@%d name_and_type_index changed: %d to %d",
522 entry_name, *merge_cp_length_p, name_and_type_ref_i, new_name_and_type_ref_i);
523 }
524
525 if (scratch_i != *merge_cp_length_p) {
526 // The new entry in *merge_cp_p is at a different index than
527 // the new entry in scratch_cp so we need to map the index values.
528 map_index(scratch_cp, scratch_i, *merge_cp_length_p);
529 }
530 (*merge_cp_length_p)++;
531 } break;
532
533 // this is an indirect CP entry so it needs special handling
534 case JVM_CONSTANT_MethodType:
535 {
536 int ref_i = scratch_cp->method_type_index_at(scratch_i);
537 int new_ref_i = find_or_append_indirect_entry(scratch_cp, ref_i, merge_cp_p,
538 merge_cp_length_p);
539 if (new_ref_i != ref_i) {
540 log_trace(redefine, class, constantpool)
541 ("MethodType entry@%d ref_index change: %d to %d", *merge_cp_length_p, ref_i, new_ref_i);
542 }
543 (*merge_cp_p)->method_type_index_at_put(*merge_cp_length_p, new_ref_i);
544 if (scratch_i != *merge_cp_length_p) {
545 // The new entry in *merge_cp_p is at a different index than
546 // the new entry in scratch_cp so we need to map the index values.
547 map_index(scratch_cp, scratch_i, *merge_cp_length_p);
548 }
549 (*merge_cp_length_p)++;
550 } break;
551
552 // this is an indirect CP entry so it needs special handling
553 case JVM_CONSTANT_MethodHandle:
554 {
555 int ref_kind = scratch_cp->method_handle_ref_kind_at(scratch_i);
556 int ref_i = scratch_cp->method_handle_index_at(scratch_i);
557 int new_ref_i = find_or_append_indirect_entry(scratch_cp, ref_i, merge_cp_p,
558 merge_cp_length_p);
559 if (new_ref_i != ref_i) {
560 log_trace(redefine, class, constantpool)
561 ("MethodHandle entry@%d ref_index change: %d to %d", *merge_cp_length_p, ref_i, new_ref_i);
562 }
563 (*merge_cp_p)->method_handle_index_at_put(*merge_cp_length_p, ref_kind, new_ref_i);
564 if (scratch_i != *merge_cp_length_p) {
565 // The new entry in *merge_cp_p is at a different index than
566 // the new entry in scratch_cp so we need to map the index values.
567 map_index(scratch_cp, scratch_i, *merge_cp_length_p);
568 }
569 (*merge_cp_length_p)++;
570 } break;
571
572 // this is an indirect CP entry so it needs special handling
573 case JVM_CONSTANT_Dynamic: // fall through
574 case JVM_CONSTANT_InvokeDynamic:
575 {
576 // Index of the bootstrap specifier in the operands array
577 int old_bs_i = scratch_cp->bootstrap_methods_attribute_index(scratch_i);
578 int new_bs_i = find_or_append_operand(scratch_cp, old_bs_i, merge_cp_p,
579 merge_cp_length_p);
580 // The bootstrap method NameAndType_info index
581 int old_ref_i = scratch_cp->bootstrap_name_and_type_ref_index_at(scratch_i);
582 int new_ref_i = find_or_append_indirect_entry(scratch_cp, old_ref_i, merge_cp_p,
583 merge_cp_length_p);
584 if (new_bs_i != old_bs_i) {
585 log_trace(redefine, class, constantpool)
586 ("Dynamic entry@%d bootstrap_method_attr_index change: %d to %d",
587 *merge_cp_length_p, old_bs_i, new_bs_i);
588 }
589 if (new_ref_i != old_ref_i) {
590 log_trace(redefine, class, constantpool)
591 ("Dynamic entry@%d name_and_type_index change: %d to %d", *merge_cp_length_p, old_ref_i, new_ref_i);
592 }
593
594 if (scratch_cp->tag_at(scratch_i).is_dynamic_constant())
595 (*merge_cp_p)->dynamic_constant_at_put(*merge_cp_length_p, new_bs_i, new_ref_i);
596 else
597 (*merge_cp_p)->invoke_dynamic_at_put(*merge_cp_length_p, new_bs_i, new_ref_i);
598 if (scratch_i != *merge_cp_length_p) {
599 // The new entry in *merge_cp_p is at a different index than
600 // the new entry in scratch_cp so we need to map the index values.
601 map_index(scratch_cp, scratch_i, *merge_cp_length_p);
602 }
603 (*merge_cp_length_p)++;
604 } break;
605
606 // At this stage, Class or UnresolvedClass could be in scratch_cp, but not
607 // ClassIndex
608 case JVM_CONSTANT_ClassIndex: // fall through
609
610 // Invalid is used as the tag for the second constant pool entry
611 // occupied by JVM_CONSTANT_Double or JVM_CONSTANT_Long. It should
612 // not be seen by itself.
613 case JVM_CONSTANT_Invalid: // fall through
614
615 // At this stage, String could be here, but not StringIndex
616 case JVM_CONSTANT_StringIndex: // fall through
617
618 // At this stage JVM_CONSTANT_UnresolvedClassInError should not be
619 // here
620 case JVM_CONSTANT_UnresolvedClassInError: // fall through
621
622 default:
623 {
624 // leave a breadcrumb
625 jbyte bad_value = scratch_cp->tag_at(scratch_i).value();
626 ShouldNotReachHere();
627 } break;
628 } // end switch tag value
629 } // end append_entry()
630
631
632 u2 VM_RedefineClasses::find_or_append_indirect_entry(const constantPoolHandle& scratch_cp,
633 int ref_i, constantPoolHandle *merge_cp_p, int *merge_cp_length_p) {
634
635 int new_ref_i = ref_i;
636 bool match = (ref_i < *merge_cp_length_p) &&
637 scratch_cp->compare_entry_to(ref_i, *merge_cp_p, ref_i);
638
639 if (!match) {
640 // forward reference in *merge_cp_p or not a direct match
641 int found_i = scratch_cp->find_matching_entry(ref_i, *merge_cp_p);
642 if (found_i != 0) {
643 guarantee(found_i != ref_i, "compare_entry_to() and find_matching_entry() do not agree");
644 // Found a matching entry somewhere else in *merge_cp_p so just need a mapping entry.
645 new_ref_i = found_i;
646 map_index(scratch_cp, ref_i, found_i);
647 } else {
648 // no match found so we have to append this entry to *merge_cp_p
649 append_entry(scratch_cp, ref_i, merge_cp_p, merge_cp_length_p);
650 // The above call to append_entry() can only append one entry
651 // so the post call query of *merge_cp_length_p is only for
652 // the sake of consistency.
653 new_ref_i = *merge_cp_length_p - 1;
654 }
655 }
656
657 // constant pool indices are u2, unless the merged constant pool overflows which
658 // we don't check for.
659 return checked_cast<u2>(new_ref_i);
660 } // end find_or_append_indirect_entry()
661
662
663 // Append a bootstrap specifier into the merge_cp operands that is semantically equal
664 // to the scratch_cp operands bootstrap specifier passed by the old_bs_i index.
665 // Recursively append new merge_cp entries referenced by the new bootstrap specifier.
666 void VM_RedefineClasses::append_operand(const constantPoolHandle& scratch_cp, int old_bs_i,
667 constantPoolHandle *merge_cp_p, int *merge_cp_length_p) {
668
669 u2 old_ref_i = scratch_cp->operand_bootstrap_method_ref_index_at(old_bs_i);
670 u2 new_ref_i = find_or_append_indirect_entry(scratch_cp, old_ref_i, merge_cp_p,
671 merge_cp_length_p);
672 if (new_ref_i != old_ref_i) {
673 log_trace(redefine, class, constantpool)
674 ("operands entry@%d bootstrap method ref_index change: %d to %d", _operands_cur_length, old_ref_i, new_ref_i);
675 }
676
677 Array<u2>* merge_ops = (*merge_cp_p)->operands();
678 int new_bs_i = _operands_cur_length;
679 // We have _operands_cur_length == 0 when the merge_cp operands is empty yet.
680 // However, the operand_offset_at(0) was set in the extend_operands() call.
681 int new_base = (new_bs_i == 0) ? (*merge_cp_p)->operand_offset_at(0)
682 : (*merge_cp_p)->operand_next_offset_at(new_bs_i - 1);
683 u2 argc = scratch_cp->operand_argument_count_at(old_bs_i);
684
685 ConstantPool::operand_offset_at_put(merge_ops, _operands_cur_length, new_base);
686 merge_ops->at_put(new_base++, new_ref_i);
687 merge_ops->at_put(new_base++, argc);
688
689 for (int i = 0; i < argc; i++) {
690 u2 old_arg_ref_i = scratch_cp->operand_argument_index_at(old_bs_i, i);
691 u2 new_arg_ref_i = find_or_append_indirect_entry(scratch_cp, old_arg_ref_i, merge_cp_p,
692 merge_cp_length_p);
693 merge_ops->at_put(new_base++, new_arg_ref_i);
694 if (new_arg_ref_i != old_arg_ref_i) {
695 log_trace(redefine, class, constantpool)
696 ("operands entry@%d bootstrap method argument ref_index change: %d to %d",
697 _operands_cur_length, old_arg_ref_i, new_arg_ref_i);
698 }
699 }
700 if (old_bs_i != _operands_cur_length) {
701 // The bootstrap specifier in *merge_cp_p is at a different index than
702 // that in scratch_cp so we need to map the index values.
703 map_operand_index(old_bs_i, new_bs_i);
704 }
705 _operands_cur_length++;
706 } // end append_operand()
707
708
709 int VM_RedefineClasses::find_or_append_operand(const constantPoolHandle& scratch_cp,
710 int old_bs_i, constantPoolHandle *merge_cp_p, int *merge_cp_length_p) {
711
712 int new_bs_i = old_bs_i; // bootstrap specifier index
713 bool match = (old_bs_i < _operands_cur_length) &&
714 scratch_cp->compare_operand_to(old_bs_i, *merge_cp_p, old_bs_i);
715
716 if (!match) {
717 // forward reference in *merge_cp_p or not a direct match
718 int found_i = scratch_cp->find_matching_operand(old_bs_i, *merge_cp_p,
719 _operands_cur_length);
720 if (found_i != -1) {
721 guarantee(found_i != old_bs_i, "compare_operand_to() and find_matching_operand() disagree");
722 // found a matching operand somewhere else in *merge_cp_p so just need a mapping
723 new_bs_i = found_i;
724 map_operand_index(old_bs_i, found_i);
725 } else {
726 // no match found so we have to append this bootstrap specifier to *merge_cp_p
727 append_operand(scratch_cp, old_bs_i, merge_cp_p, merge_cp_length_p);
728 new_bs_i = _operands_cur_length - 1;
729 }
730 }
731 return new_bs_i;
732 } // end find_or_append_operand()
733
734
735 void VM_RedefineClasses::finalize_operands_merge(const constantPoolHandle& merge_cp, TRAPS) {
736 if (merge_cp->operands() == nullptr) {
737 return;
738 }
739 // Shrink the merge_cp operands
740 merge_cp->shrink_operands(_operands_cur_length, CHECK);
741
742 if (log_is_enabled(Trace, redefine, class, constantpool)) {
743 // don't want to loop unless we are tracing
744 int count = 0;
745 for (int i = 1; i < _operands_index_map_p->length(); i++) {
746 int value = _operands_index_map_p->at(i);
747 if (value != -1) {
748 log_trace(redefine, class, constantpool)("operands_index_map[%d]: old=%d new=%d", count, i, value);
749 count++;
750 }
751 }
752 }
753 // Clean-up
754 _operands_index_map_p = nullptr;
755 _operands_cur_length = 0;
756 _operands_index_map_count = 0;
757 } // end finalize_operands_merge()
758
759 // Symbol* comparator for qsort
760 // The caller must have an active ResourceMark.
761 static int symcmp(const void* a, const void* b) {
762 char* astr = (*(Symbol**)a)->as_C_string();
763 char* bstr = (*(Symbol**)b)->as_C_string();
764 return strcmp(astr, bstr);
765 }
766
767 // The caller must have an active ResourceMark.
768 static jvmtiError check_attribute_arrays(const char* attr_name,
769 InstanceKlass* the_class, InstanceKlass* scratch_class,
770 Array<u2>* the_array, Array<u2>* scr_array) {
771 bool the_array_exists = the_array != Universe::the_empty_short_array();
772 bool scr_array_exists = scr_array != Universe::the_empty_short_array();
773
774 int array_len = the_array->length();
775 if (the_array_exists && scr_array_exists) {
776 if (array_len != scr_array->length()) {
777 log_trace(redefine, class)
778 ("redefined class %s attribute change error: %s len=%d changed to len=%d",
779 the_class->external_name(), attr_name, array_len, scr_array->length());
780 return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
781 }
782
783 // The order of entries in the attribute array is not specified so we
784 // have to explicitly check for the same contents. We do this by copying
785 // the referenced symbols into their own arrays, sorting them and then
786 // comparing each element pair.
787
788 Symbol** the_syms = NEW_RESOURCE_ARRAY_RETURN_NULL(Symbol*, array_len);
789 Symbol** scr_syms = NEW_RESOURCE_ARRAY_RETURN_NULL(Symbol*, array_len);
790
791 if (the_syms == nullptr || scr_syms == nullptr) {
792 return JVMTI_ERROR_OUT_OF_MEMORY;
793 }
794
795 for (int i = 0; i < array_len; i++) {
796 int the_cp_index = the_array->at(i);
797 int scr_cp_index = scr_array->at(i);
798 the_syms[i] = the_class->constants()->klass_name_at(the_cp_index);
799 scr_syms[i] = scratch_class->constants()->klass_name_at(scr_cp_index);
800 }
801
802 qsort(the_syms, array_len, sizeof(Symbol*), symcmp);
803 qsort(scr_syms, array_len, sizeof(Symbol*), symcmp);
804
805 for (int i = 0; i < array_len; i++) {
806 if (the_syms[i] != scr_syms[i]) {
807 log_info(redefine, class)
808 ("redefined class %s attribute change error: %s[%d]: %s changed to %s",
809 the_class->external_name(), attr_name, i,
810 the_syms[i]->as_C_string(), scr_syms[i]->as_C_string());
811 return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
812 }
813 }
814 } else if (the_array_exists ^ scr_array_exists) {
815 const char* action_str = (the_array_exists) ? "removed" : "added";
816 log_info(redefine, class)
817 ("redefined class %s attribute change error: %s attribute %s",
818 the_class->external_name(), attr_name, action_str);
819 return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
820 }
821 return JVMTI_ERROR_NONE;
822 }
823
824 static jvmtiError check_nest_attributes(InstanceKlass* the_class,
825 InstanceKlass* scratch_class) {
826 // Check whether the class NestHost attribute has been changed.
827 Thread* thread = Thread::current();
828 ResourceMark rm(thread);
829 u2 the_nest_host_idx = the_class->nest_host_index();
830 u2 scr_nest_host_idx = scratch_class->nest_host_index();
831
832 if (the_nest_host_idx != 0 && scr_nest_host_idx != 0) {
833 Symbol* the_sym = the_class->constants()->klass_name_at(the_nest_host_idx);
834 Symbol* scr_sym = scratch_class->constants()->klass_name_at(scr_nest_host_idx);
835 if (the_sym != scr_sym) {
836 log_info(redefine, class, nestmates)
837 ("redefined class %s attribute change error: NestHost class: %s replaced with: %s",
838 the_class->external_name(), the_sym->as_C_string(), scr_sym->as_C_string());
839 return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
840 }
841 } else if ((the_nest_host_idx == 0) ^ (scr_nest_host_idx == 0)) {
842 const char* action_str = (the_nest_host_idx != 0) ? "removed" : "added";
843 log_info(redefine, class, nestmates)
844 ("redefined class %s attribute change error: NestHost attribute %s",
845 the_class->external_name(), action_str);
846 return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
847 }
848
849 // Check whether the class NestMembers attribute has been changed.
850 return check_attribute_arrays("NestMembers",
851 the_class, scratch_class,
852 the_class->nest_members(),
853 scratch_class->nest_members());
854 }
855
856 // Return an error status if the class Record attribute was changed.
857 static jvmtiError check_record_attribute(InstanceKlass* the_class, InstanceKlass* scratch_class) {
858 // Get lists of record components.
859 Array<RecordComponent*>* the_record = the_class->record_components();
860 Array<RecordComponent*>* scr_record = scratch_class->record_components();
861 bool the_record_exists = the_record != nullptr;
862 bool scr_record_exists = scr_record != nullptr;
863
864 if (the_record_exists && scr_record_exists) {
865 int the_num_components = the_record->length();
866 int scr_num_components = scr_record->length();
867 if (the_num_components != scr_num_components) {
868 log_info(redefine, class, record)
869 ("redefined class %s attribute change error: Record num_components=%d changed to num_components=%d",
870 the_class->external_name(), the_num_components, scr_num_components);
871 return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
872 }
873
874 // Compare each field in each record component.
875 ConstantPool* the_cp = the_class->constants();
876 ConstantPool* scr_cp = scratch_class->constants();
877 for (int x = 0; x < the_num_components; x++) {
878 RecordComponent* the_component = the_record->at(x);
879 RecordComponent* scr_component = scr_record->at(x);
880 const Symbol* const the_name = the_cp->symbol_at(the_component->name_index());
881 const Symbol* const scr_name = scr_cp->symbol_at(scr_component->name_index());
882 const Symbol* const the_descr = the_cp->symbol_at(the_component->descriptor_index());
883 const Symbol* const scr_descr = scr_cp->symbol_at(scr_component->descriptor_index());
884 if (the_name != scr_name || the_descr != scr_descr) {
885 log_info(redefine, class, record)
886 ("redefined class %s attribute change error: Record name_index, descriptor_index, and/or attributes_count changed",
887 the_class->external_name());
888 return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
889 }
890
891 int the_gen_sig = the_component->generic_signature_index();
892 int scr_gen_sig = scr_component->generic_signature_index();
893 const Symbol* const the_gen_sig_sym = (the_gen_sig == 0 ? nullptr :
894 the_cp->symbol_at(the_component->generic_signature_index()));
895 const Symbol* const scr_gen_sig_sym = (scr_gen_sig == 0 ? nullptr :
896 scr_cp->symbol_at(scr_component->generic_signature_index()));
897 if (the_gen_sig_sym != scr_gen_sig_sym) {
898 log_info(redefine, class, record)
899 ("redefined class %s attribute change error: Record generic_signature attribute changed",
900 the_class->external_name());
901 return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
902 }
903
904 // It's okay if a record component's annotations were changed.
905 }
906
907 } else if (the_record_exists ^ scr_record_exists) {
908 const char* action_str = (the_record_exists) ? "removed" : "added";
909 log_info(redefine, class, record)
910 ("redefined class %s attribute change error: Record attribute %s",
911 the_class->external_name(), action_str);
912 return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
913 }
914
915 return JVMTI_ERROR_NONE;
916 }
917
918
919 static jvmtiError check_permitted_subclasses_attribute(InstanceKlass* the_class,
920 InstanceKlass* scratch_class) {
921 Thread* thread = Thread::current();
922 ResourceMark rm(thread);
923
924 // Check whether the class PermittedSubclasses attribute has been changed.
925 return check_attribute_arrays("PermittedSubclasses",
926 the_class, scratch_class,
927 the_class->permitted_subclasses(),
928 scratch_class->permitted_subclasses());
929 }
930
931 static bool can_add_or_delete(Method* m) {
932 // Compatibility mode
933 return (AllowRedefinitionToAddDeleteMethods &&
934 (m->is_private() && (m->is_static() || m->is_final())));
935 }
936
937 jvmtiError VM_RedefineClasses::compare_and_normalize_class_versions(
938 InstanceKlass* the_class,
939 InstanceKlass* scratch_class) {
940 int i;
941
942 // Check superclasses, or rather their names, since superclasses themselves can be
943 // requested to replace.
944 // Check for null superclass first since this might be java.lang.Object
945 if (the_class->super() != scratch_class->super() &&
946 (the_class->super() == nullptr || scratch_class->super() == nullptr ||
947 the_class->super()->name() !=
948 scratch_class->super()->name())) {
949 log_info(redefine, class, normalize)
950 ("redefined class %s superclass change error: superclass changed from %s to %s.",
951 the_class->external_name(),
952 the_class->super() == nullptr ? "null" : the_class->super()->external_name(),
953 scratch_class->super() == nullptr ? "null" : scratch_class->super()->external_name());
954 return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_HIERARCHY_CHANGED;
955 }
956
957 // Check if the number, names and order of directly implemented interfaces are the same.
958 // I think in principle we should just check if the sets of names of directly implemented
959 // interfaces are the same, i.e. the order of declaration (which, however, if changed in the
960 // .java file, also changes in .class file) should not matter. However, comparing sets is
961 // technically a bit more difficult, and, more importantly, I am not sure at present that the
962 // order of interfaces does not matter on the implementation level, i.e. that the VM does not
963 // rely on it somewhere.
964 Array<InstanceKlass*>* k_interfaces = the_class->local_interfaces();
965 Array<InstanceKlass*>* k_new_interfaces = scratch_class->local_interfaces();
966 int n_intfs = k_interfaces->length();
967 if (n_intfs != k_new_interfaces->length()) {
968 log_info(redefine, class, normalize)
969 ("redefined class %s interfaces change error: number of implemented interfaces changed from %d to %d.",
970 the_class->external_name(), n_intfs, k_new_interfaces->length());
971 return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_HIERARCHY_CHANGED;
972 }
973 for (i = 0; i < n_intfs; i++) {
974 if (k_interfaces->at(i)->name() !=
975 k_new_interfaces->at(i)->name()) {
976 log_info(redefine, class, normalize)
977 ("redefined class %s interfaces change error: interface changed from %s to %s.",
978 the_class->external_name(),
979 k_interfaces->at(i)->external_name(), k_new_interfaces->at(i)->external_name());
980 return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_HIERARCHY_CHANGED;
981 }
982 }
983
984 // Check whether class is in the error init state.
985 if (the_class->is_in_error_state()) {
986 log_info(redefine, class, normalize)
987 ("redefined class %s is in error init state.", the_class->external_name());
988 // TBD #5057930: special error code is needed in 1.6
989 return JVMTI_ERROR_INVALID_CLASS;
990 }
991
992 // Check whether the nest-related attributes have been changed.
993 jvmtiError err = check_nest_attributes(the_class, scratch_class);
994 if (err != JVMTI_ERROR_NONE) {
995 return err;
996 }
997
998 // Check whether the Record attribute has been changed.
999 err = check_record_attribute(the_class, scratch_class);
1000 if (err != JVMTI_ERROR_NONE) {
1001 return err;
1002 }
1003
1004 // Check whether the PermittedSubclasses attribute has been changed.
1005 err = check_permitted_subclasses_attribute(the_class, scratch_class);
1006 if (err != JVMTI_ERROR_NONE) {
1007 return err;
1008 }
1009
1010 // Check whether class modifiers are the same.
1011 jushort old_flags = (jushort) the_class->access_flags().get_flags();
1012 jushort new_flags = (jushort) scratch_class->access_flags().get_flags();
1013 if (old_flags != new_flags) {
1014 log_info(redefine, class, normalize)
1015 ("redefined class %s modifiers change error: modifiers changed from %d to %d.",
1016 the_class->external_name(), old_flags, new_flags);
1017 return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_MODIFIERS_CHANGED;
1018 }
1019
1020 // Check if the number, names, types and order of fields declared in these classes
1021 // are the same.
1022 JavaFieldStream old_fs(the_class);
1023 JavaFieldStream new_fs(scratch_class);
1024 for (; !old_fs.done() && !new_fs.done(); old_fs.next(), new_fs.next()) {
1025 // name and signature
1026 Symbol* name_sym1 = the_class->constants()->symbol_at(old_fs.name_index());
1027 Symbol* sig_sym1 = the_class->constants()->symbol_at(old_fs.signature_index());
1028 Symbol* name_sym2 = scratch_class->constants()->symbol_at(new_fs.name_index());
1029 Symbol* sig_sym2 = scratch_class->constants()->symbol_at(new_fs.signature_index());
1030 if (name_sym1 != name_sym2 || sig_sym1 != sig_sym2) {
1031 log_info(redefine, class, normalize)
1032 ("redefined class %s fields change error: field %s %s changed to %s %s.",
1033 the_class->external_name(),
1034 sig_sym1->as_C_string(), name_sym1->as_C_string(),
1035 sig_sym2->as_C_string(), name_sym2->as_C_string());
1036 return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_SCHEMA_CHANGED;
1037 }
1038 // offset
1039 if (old_fs.offset() != new_fs.offset()) {
1040 log_info(redefine, class, normalize)
1041 ("redefined class %s field %s change error: offset changed from %d to %d.",
1042 the_class->external_name(), name_sym2->as_C_string(), old_fs.offset(), new_fs.offset());
1043 return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_SCHEMA_CHANGED;
1044 }
1045 // access
1046 old_flags = old_fs.access_flags().as_short();
1047 new_flags = new_fs.access_flags().as_short();
1048 if ((old_flags ^ new_flags) & JVM_RECOGNIZED_FIELD_MODIFIERS) {
1049 log_info(redefine, class, normalize)
1050 ("redefined class %s field %s change error: modifiers changed from %d to %d.",
1051 the_class->external_name(), name_sym2->as_C_string(), old_flags, new_flags);
1052 return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_SCHEMA_CHANGED;
1053 }
1054 }
1055
1056 // If both streams aren't done then we have a differing number of
1057 // fields.
1058 if (!old_fs.done() || !new_fs.done()) {
1059 const char* action = old_fs.done() ? "added" : "deleted";
1060 log_info(redefine, class, normalize)
1061 ("redefined class %s fields change error: some fields were %s.",
1062 the_class->external_name(), action);
1063 return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_SCHEMA_CHANGED;
1064 }
1065
1066 // Do a parallel walk through the old and new methods. Detect
1067 // cases where they match (exist in both), have been added in
1068 // the new methods, or have been deleted (exist only in the
1069 // old methods). The class file parser places methods in order
1070 // by method name, but does not order overloaded methods by
1071 // signature. In order to determine what fate befell the methods,
1072 // this code places the overloaded new methods that have matching
1073 // old methods in the same order as the old methods and places
1074 // new overloaded methods at the end of overloaded methods of
1075 // that name. The code for this order normalization is adapted
1076 // from the algorithm used in InstanceKlass::find_method().
1077 // Since we are swapping out of order entries as we find them,
1078 // we only have to search forward through the overloaded methods.
1079 // Methods which are added and have the same name as an existing
1080 // method (but different signature) will be put at the end of
1081 // the methods with that name, and the name mismatch code will
1082 // handle them.
1083 Array<Method*>* k_old_methods(the_class->methods());
1084 Array<Method*>* k_new_methods(scratch_class->methods());
1085 int n_old_methods = k_old_methods->length();
1086 int n_new_methods = k_new_methods->length();
1087 Thread* thread = Thread::current();
1088
1089 int ni = 0;
1090 int oi = 0;
1091 while (true) {
1092 Method* k_old_method;
1093 Method* k_new_method;
1094 enum { matched, added, deleted, undetermined } method_was = undetermined;
1095
1096 if (oi >= n_old_methods) {
1097 if (ni >= n_new_methods) {
1098 break; // we've looked at everything, done
1099 }
1100 // New method at the end
1101 k_new_method = k_new_methods->at(ni);
1102 method_was = added;
1103 } else if (ni >= n_new_methods) {
1104 // Old method, at the end, is deleted
1105 k_old_method = k_old_methods->at(oi);
1106 method_was = deleted;
1107 } else {
1108 // There are more methods in both the old and new lists
1109 k_old_method = k_old_methods->at(oi);
1110 k_new_method = k_new_methods->at(ni);
1111 if (k_old_method->name() != k_new_method->name()) {
1112 // Methods are sorted by method name, so a mismatch means added
1113 // or deleted
1114 if (k_old_method->name()->fast_compare(k_new_method->name()) > 0) {
1115 method_was = added;
1116 } else {
1117 method_was = deleted;
1118 }
1119 } else if (k_old_method->signature() == k_new_method->signature()) {
1120 // Both the name and signature match
1121 method_was = matched;
1122 } else {
1123 // The name matches, but the signature doesn't, which means we have to
1124 // search forward through the new overloaded methods.
1125 int nj; // outside the loop for post-loop check
1126 for (nj = ni + 1; nj < n_new_methods; nj++) {
1127 Method* m = k_new_methods->at(nj);
1128 if (k_old_method->name() != m->name()) {
1129 // reached another method name so no more overloaded methods
1130 method_was = deleted;
1131 break;
1132 }
1133 if (k_old_method->signature() == m->signature()) {
1134 // found a match so swap the methods
1135 k_new_methods->at_put(ni, m);
1136 k_new_methods->at_put(nj, k_new_method);
1137 k_new_method = m;
1138 method_was = matched;
1139 break;
1140 }
1141 }
1142
1143 if (nj >= n_new_methods) {
1144 // reached the end without a match; so method was deleted
1145 method_was = deleted;
1146 }
1147 }
1148 }
1149
1150 switch (method_was) {
1151 case matched:
1152 // methods match, be sure modifiers do too
1153 old_flags = (jushort) k_old_method->access_flags().get_flags();
1154 new_flags = (jushort) k_new_method->access_flags().get_flags();
1155 if ((old_flags ^ new_flags) & ~(JVM_ACC_NATIVE)) {
1156 log_info(redefine, class, normalize)
1157 ("redefined class %s method %s modifiers error: modifiers changed from %d to %d",
1158 the_class->external_name(), k_old_method->name_and_sig_as_C_string(), old_flags, new_flags);
1159 return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_METHOD_MODIFIERS_CHANGED;
1160 }
1161 {
1162 u2 new_num = k_new_method->method_idnum();
1163 u2 old_num = k_old_method->method_idnum();
1164 if (new_num != old_num) {
1165 Method* idnum_owner = scratch_class->method_with_idnum(old_num);
1166 if (idnum_owner != nullptr) {
1167 // There is already a method assigned this idnum -- switch them
1168 // Take current and original idnum from the new_method
1169 idnum_owner->set_method_idnum(new_num);
1170 idnum_owner->set_orig_method_idnum(k_new_method->orig_method_idnum());
1171 }
1172 // Take current and original idnum from the old_method
1173 k_new_method->set_method_idnum(old_num);
1174 k_new_method->set_orig_method_idnum(k_old_method->orig_method_idnum());
1175 if (thread->has_pending_exception()) {
1176 return JVMTI_ERROR_OUT_OF_MEMORY;
1177 }
1178 }
1179 }
1180 JFR_ONLY(k_new_method->copy_trace_flags(*k_old_method->trace_flags_addr());)
1181 log_trace(redefine, class, normalize)
1182 ("Method matched: new: %s [%d] == old: %s [%d]",
1183 k_new_method->name_and_sig_as_C_string(), ni, k_old_method->name_and_sig_as_C_string(), oi);
1184 // advance to next pair of methods
1185 ++oi;
1186 ++ni;
1187 break;
1188 case added:
1189 // method added, see if it is OK
1190 if (!can_add_or_delete(k_new_method)) {
1191 log_info(redefine, class, normalize)
1192 ("redefined class %s methods error: added method: %s [%d]",
1193 the_class->external_name(), k_new_method->name_and_sig_as_C_string(), ni);
1194 return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_METHOD_ADDED;
1195 }
1196 {
1197 u2 num = the_class->next_method_idnum();
1198 if (num == ConstMethod::UNSET_IDNUM) {
1199 // cannot add any more methods
1200 log_info(redefine, class, normalize)
1201 ("redefined class %s methods error: can't create ID for new method %s [%d]",
1202 the_class->external_name(), k_new_method->name_and_sig_as_C_string(), ni);
1203 return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_METHOD_ADDED;
1204 }
1205 u2 new_num = k_new_method->method_idnum();
1206 Method* idnum_owner = scratch_class->method_with_idnum(num);
1207 if (idnum_owner != nullptr) {
1208 // There is already a method assigned this idnum -- switch them
1209 // Take current and original idnum from the new_method
1210 idnum_owner->set_method_idnum(new_num);
1211 idnum_owner->set_orig_method_idnum(k_new_method->orig_method_idnum());
1212 }
1213 k_new_method->set_method_idnum(num);
1214 k_new_method->set_orig_method_idnum(num);
1215 if (thread->has_pending_exception()) {
1216 return JVMTI_ERROR_OUT_OF_MEMORY;
1217 }
1218 }
1219 log_trace(redefine, class, normalize)
1220 ("Method added: new: %s [%d]", k_new_method->name_and_sig_as_C_string(), ni);
1221 ++ni; // advance to next new method
1222 break;
1223 case deleted:
1224 // method deleted, see if it is OK
1225 if (!can_add_or_delete(k_old_method)) {
1226 log_info(redefine, class, normalize)
1227 ("redefined class %s methods error: deleted method %s [%d]",
1228 the_class->external_name(), k_old_method->name_and_sig_as_C_string(), oi);
1229 return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_METHOD_DELETED;
1230 }
1231 log_trace(redefine, class, normalize)
1232 ("Method deleted: old: %s [%d]", k_old_method->name_and_sig_as_C_string(), oi);
1233 ++oi; // advance to next old method
1234 break;
1235 default:
1236 ShouldNotReachHere();
1237 }
1238 }
1239
1240 return JVMTI_ERROR_NONE;
1241 }
1242
1243
1244 // Find new constant pool index value for old constant pool index value
1245 // by searching the index map. Returns zero (0) if there is no mapped
1246 // value for the old constant pool index.
1247 u2 VM_RedefineClasses::find_new_index(int old_index) {
1248 if (_index_map_count == 0) {
1249 // map is empty so nothing can be found
1250 return 0;
1251 }
1252
1253 if (old_index < 1 || old_index >= _index_map_p->length()) {
1254 // The old_index is out of range so it is not mapped. This should
1255 // not happen in regular constant pool merging use, but it can
1256 // happen if a corrupt annotation is processed.
1257 return 0;
1258 }
1259
1260 int value = _index_map_p->at(old_index);
1261 if (value == -1) {
1262 // the old_index is not mapped
1263 return 0;
1264 }
1265
1266 // constant pool indices are u2, unless the merged constant pool overflows which
1267 // we don't check for.
1268 return checked_cast<u2>(value);
1269 } // end find_new_index()
1270
1271
1272 // Find new bootstrap specifier index value for old bootstrap specifier index
1273 // value by searching the index map. Returns unused index (-1) if there is
1274 // no mapped value for the old bootstrap specifier index.
1275 int VM_RedefineClasses::find_new_operand_index(int old_index) {
1276 if (_operands_index_map_count == 0) {
1277 // map is empty so nothing can be found
1278 return -1;
1279 }
1280
1281 if (old_index == -1 || old_index >= _operands_index_map_p->length()) {
1282 // The old_index is out of range so it is not mapped.
1283 // This should not happen in regular constant pool merging use.
1284 return -1;
1285 }
1286
1287 int value = _operands_index_map_p->at(old_index);
1288 if (value == -1) {
1289 // the old_index is not mapped
1290 return -1;
1291 }
1292
1293 return value;
1294 } // end find_new_operand_index()
1295
1296
1297 // The bug 6214132 caused the verification to fail.
1298 // 1. What's done in RedefineClasses() before verification:
1299 // a) A reference to the class being redefined (_the_class) and a
1300 // reference to new version of the class (_scratch_class) are
1301 // saved here for use during the bytecode verification phase of
1302 // RedefineClasses.
1303 // b) The _java_mirror field from _the_class is copied to the
1304 // _java_mirror field in _scratch_class. This means that a jclass
1305 // returned for _the_class or _scratch_class will refer to the
1306 // same Java mirror. The verifier will see the "one true mirror"
1307 // for the class being verified.
1308 // 2. See comments in JvmtiThreadState for what is done during verification.
1309
1310 class RedefineVerifyMark : public StackObj {
1311 private:
1312 JvmtiThreadState* _state;
1313 Klass* _scratch_class;
1314 OopHandle _scratch_mirror;
1315
1316 public:
1317
1318 RedefineVerifyMark(Klass* the_class, Klass* scratch_class,
1319 JvmtiThreadState* state) : _state(state), _scratch_class(scratch_class)
1320 {
1321 _state->set_class_versions_map(the_class, scratch_class);
1322 _scratch_mirror = the_class->java_mirror_handle(); // this is a copy that is swapped
1323 _scratch_class->swap_java_mirror_handle(_scratch_mirror);
1324 }
1325
1326 ~RedefineVerifyMark() {
1327 // Restore the scratch class's mirror, so when scratch_class is removed
1328 // the correct mirror pointing to it can be cleared.
1329 _scratch_class->swap_java_mirror_handle(_scratch_mirror);
1330 _state->clear_class_versions_map();
1331 }
1332 };
1333
1334
1335 jvmtiError VM_RedefineClasses::load_new_class_versions() {
1336
1337 // For consistency allocate memory using os::malloc wrapper.
1338 _scratch_classes = (InstanceKlass**)
1339 os::malloc(sizeof(InstanceKlass*) * _class_count, mtClass);
1340 if (_scratch_classes == nullptr) {
1341 return JVMTI_ERROR_OUT_OF_MEMORY;
1342 }
1343 // Zero initialize the _scratch_classes array.
1344 for (int i = 0; i < _class_count; i++) {
1345 _scratch_classes[i] = nullptr;
1346 }
1347
1348 JavaThread* current = JavaThread::current();
1349 ResourceMark rm(current);
1350
1351 JvmtiThreadState *state = JvmtiThreadState::state_for(current);
1352 // state can only be null if the current thread is exiting which
1353 // should not happen since we're trying to do a RedefineClasses
1354 guarantee(state != nullptr, "exiting thread calling load_new_class_versions");
1355 for (int i = 0; i < _class_count; i++) {
1356 // Create HandleMark so that any handles created while loading new class
1357 // versions are deleted. Constant pools are deallocated while merging
1358 // constant pools
1359 HandleMark hm(current);
1360 InstanceKlass* the_class = get_ik(_class_defs[i].klass);
1361
1362 log_debug(redefine, class, load)
1363 ("loading name=%s kind=%d (avail_mem=" UINT64_FORMAT "K)",
1364 the_class->external_name(), _class_load_kind, os::available_memory() >> 10);
1365
1366 ClassFileStream st((u1*)_class_defs[i].class_bytes,
1367 _class_defs[i].class_byte_count,
1368 "__VM_RedefineClasses__",
1369 ClassFileStream::verify);
1370
1371 // Set redefined class handle in JvmtiThreadState class.
1372 // This redefined class is sent to agent event handler for class file
1373 // load hook event.
1374 state->set_class_being_redefined(the_class, _class_load_kind);
1375
1376 JavaThread* THREAD = current; // For exception macros.
1377 ExceptionMark em(THREAD);
1378 Handle protection_domain(THREAD, the_class->protection_domain());
1379 ClassLoadInfo cl_info(protection_domain);
1380 // Parse and create a class from the bytes, but this class isn't added
1381 // to the dictionary, so do not call resolve_from_stream.
1382 InstanceKlass* scratch_class = KlassFactory::create_from_stream(&st,
1383 the_class->name(),
1384 the_class->class_loader_data(),
1385 cl_info,
1386 THREAD);
1387
1388 // Clear class_being_redefined just to be sure.
1389 state->clear_class_being_redefined();
1390
1391 // TODO: if this is retransform, and nothing changed we can skip it
1392
1393 // Need to clean up allocated InstanceKlass if there's an error so assign
1394 // the result here. Caller deallocates all the scratch classes in case of
1395 // an error.
1396 _scratch_classes[i] = scratch_class;
1397
1398 if (HAS_PENDING_EXCEPTION) {
1399 Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1400 log_info(redefine, class, load, exceptions)("create_from_stream exception: '%s'", ex_name->as_C_string());
1401 CLEAR_PENDING_EXCEPTION;
1402
1403 if (ex_name == vmSymbols::java_lang_UnsupportedClassVersionError()) {
1404 return JVMTI_ERROR_UNSUPPORTED_VERSION;
1405 } else if (ex_name == vmSymbols::java_lang_ClassFormatError()) {
1406 return JVMTI_ERROR_INVALID_CLASS_FORMAT;
1407 } else if (ex_name == vmSymbols::java_lang_ClassCircularityError()) {
1408 return JVMTI_ERROR_CIRCULAR_CLASS_DEFINITION;
1409 } else if (ex_name == vmSymbols::java_lang_NoClassDefFoundError()) {
1410 // The message will be "XXX (wrong name: YYY)"
1411 return JVMTI_ERROR_NAMES_DONT_MATCH;
1412 } else if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1413 return JVMTI_ERROR_OUT_OF_MEMORY;
1414 } else { // Just in case more exceptions can be thrown..
1415 return JVMTI_ERROR_FAILS_VERIFICATION;
1416 }
1417 }
1418
1419 // Ensure class is linked before redefine
1420 if (!the_class->is_linked()) {
1421 the_class->link_class(THREAD);
1422 if (HAS_PENDING_EXCEPTION) {
1423 Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1424 oop message = java_lang_Throwable::message(PENDING_EXCEPTION);
1425 if (message != nullptr) {
1426 char* ex_msg = java_lang_String::as_utf8_string(message);
1427 log_info(redefine, class, load, exceptions)("link_class exception: '%s %s'",
1428 ex_name->as_C_string(), ex_msg);
1429 } else {
1430 log_info(redefine, class, load, exceptions)("link_class exception: '%s'",
1431 ex_name->as_C_string());
1432 }
1433 CLEAR_PENDING_EXCEPTION;
1434 if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1435 return JVMTI_ERROR_OUT_OF_MEMORY;
1436 } else if (ex_name == vmSymbols::java_lang_NoClassDefFoundError()) {
1437 return JVMTI_ERROR_INVALID_CLASS;
1438 } else {
1439 return JVMTI_ERROR_INTERNAL;
1440 }
1441 }
1442 }
1443
1444 // Do the validity checks in compare_and_normalize_class_versions()
1445 // before verifying the byte codes. By doing these checks first, we
1446 // limit the number of functions that require redirection from
1447 // the_class to scratch_class. In particular, we don't have to
1448 // modify JNI GetSuperclass() and thus won't change its performance.
1449 jvmtiError res = compare_and_normalize_class_versions(the_class,
1450 scratch_class);
1451 if (res != JVMTI_ERROR_NONE) {
1452 return res;
1453 }
1454
1455 // verify what the caller passed us
1456 {
1457 // The bug 6214132 caused the verification to fail.
1458 // Information about the_class and scratch_class is temporarily
1459 // recorded into jvmtiThreadState. This data is used to redirect
1460 // the_class to scratch_class in the JVM_* functions called by the
1461 // verifier. Please, refer to jvmtiThreadState.hpp for the detailed
1462 // description.
1463 RedefineVerifyMark rvm(the_class, scratch_class, state);
1464 Verifier::verify(scratch_class, true, THREAD);
1465 }
1466
1467 if (HAS_PENDING_EXCEPTION) {
1468 Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1469 log_info(redefine, class, load, exceptions)("verify_byte_codes exception: '%s'", ex_name->as_C_string());
1470 CLEAR_PENDING_EXCEPTION;
1471 if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1472 return JVMTI_ERROR_OUT_OF_MEMORY;
1473 } else {
1474 // tell the caller the bytecodes are bad
1475 return JVMTI_ERROR_FAILS_VERIFICATION;
1476 }
1477 }
1478
1479 res = merge_cp_and_rewrite(the_class, scratch_class, THREAD);
1480 if (HAS_PENDING_EXCEPTION) {
1481 Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1482 log_info(redefine, class, load, exceptions)("merge_cp_and_rewrite exception: '%s'", ex_name->as_C_string());
1483 CLEAR_PENDING_EXCEPTION;
1484 if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1485 return JVMTI_ERROR_OUT_OF_MEMORY;
1486 } else {
1487 return JVMTI_ERROR_INTERNAL;
1488 }
1489 }
1490
1491 #ifdef ASSERT
1492 {
1493 // verify what we have done during constant pool merging
1494 {
1495 RedefineVerifyMark rvm(the_class, scratch_class, state);
1496 Verifier::verify(scratch_class, true, THREAD);
1497 }
1498
1499 if (HAS_PENDING_EXCEPTION) {
1500 Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1501 log_info(redefine, class, load, exceptions)
1502 ("verify_byte_codes post merge-CP exception: '%s'", ex_name->as_C_string());
1503 CLEAR_PENDING_EXCEPTION;
1504 if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1505 return JVMTI_ERROR_OUT_OF_MEMORY;
1506 } else {
1507 // tell the caller that constant pool merging screwed up
1508 return JVMTI_ERROR_INTERNAL;
1509 }
1510 }
1511 }
1512 #endif // ASSERT
1513
1514 Rewriter::rewrite(scratch_class, THREAD);
1515 if (!HAS_PENDING_EXCEPTION) {
1516 scratch_class->link_methods(THREAD);
1517 }
1518 if (HAS_PENDING_EXCEPTION) {
1519 Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1520 log_info(redefine, class, load, exceptions)
1521 ("Rewriter::rewrite or link_methods exception: '%s'", ex_name->as_C_string());
1522 CLEAR_PENDING_EXCEPTION;
1523 if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1524 return JVMTI_ERROR_OUT_OF_MEMORY;
1525 } else {
1526 return JVMTI_ERROR_INTERNAL;
1527 }
1528 }
1529
1530 log_debug(redefine, class, load)
1531 ("loaded name=%s (avail_mem=" UINT64_FORMAT "K)", the_class->external_name(), os::available_memory() >> 10);
1532 }
1533
1534 return JVMTI_ERROR_NONE;
1535 }
1536
1537
1538 // Map old_index to new_index as needed. scratch_cp is only needed
1539 // for log calls.
1540 void VM_RedefineClasses::map_index(const constantPoolHandle& scratch_cp,
1541 int old_index, int new_index) {
1542 if (find_new_index(old_index) != 0) {
1543 // old_index is already mapped
1544 return;
1545 }
1546
1547 if (old_index == new_index) {
1548 // no mapping is needed
1549 return;
1550 }
1551
1552 _index_map_p->at_put(old_index, new_index);
1553 _index_map_count++;
1554
1555 log_trace(redefine, class, constantpool)
1556 ("mapped tag %d at index %d to %d", scratch_cp->tag_at(old_index).value(), old_index, new_index);
1557 } // end map_index()
1558
1559
1560 // Map old_index to new_index as needed.
1561 void VM_RedefineClasses::map_operand_index(int old_index, int new_index) {
1562 if (find_new_operand_index(old_index) != -1) {
1563 // old_index is already mapped
1564 return;
1565 }
1566
1567 if (old_index == new_index) {
1568 // no mapping is needed
1569 return;
1570 }
1571
1572 _operands_index_map_p->at_put(old_index, new_index);
1573 _operands_index_map_count++;
1574
1575 log_trace(redefine, class, constantpool)("mapped bootstrap specifier at index %d to %d", old_index, new_index);
1576 } // end map_index()
1577
1578
1579 // Merge old_cp and scratch_cp and return the results of the merge via
1580 // merge_cp_p. The number of entries in *merge_cp_p is returned via
1581 // merge_cp_length_p. The entries in old_cp occupy the same locations
1582 // in *merge_cp_p. Also creates a map of indices from entries in
1583 // scratch_cp to the corresponding entry in *merge_cp_p. Index map
1584 // entries are only created for entries in scratch_cp that occupy a
1585 // different location in *merged_cp_p.
1586 bool VM_RedefineClasses::merge_constant_pools(const constantPoolHandle& old_cp,
1587 const constantPoolHandle& scratch_cp, constantPoolHandle *merge_cp_p,
1588 int *merge_cp_length_p, TRAPS) {
1589
1590 if (merge_cp_p == nullptr) {
1591 assert(false, "caller must provide scratch constantPool");
1592 return false; // robustness
1593 }
1594 if (merge_cp_length_p == nullptr) {
1595 assert(false, "caller must provide scratch CP length");
1596 return false; // robustness
1597 }
1598 // Worst case we need old_cp->length() + scratch_cp()->length(),
1599 // but the caller might be smart so make sure we have at least
1600 // the minimum.
1601 if ((*merge_cp_p)->length() < old_cp->length()) {
1602 assert(false, "merge area too small");
1603 return false; // robustness
1604 }
1605
1606 log_info(redefine, class, constantpool)("old_cp_len=%d, scratch_cp_len=%d", old_cp->length(), scratch_cp->length());
1607
1608 {
1609 // Pass 0:
1610 // The old_cp is copied to *merge_cp_p; this means that any code
1611 // using old_cp does not have to change. This work looks like a
1612 // perfect fit for ConstantPool*::copy_cp_to(), but we need to
1613 // handle one special case:
1614 // - revert JVM_CONSTANT_Class to JVM_CONSTANT_UnresolvedClass
1615 // This will make verification happy.
1616
1617 int old_i; // index into old_cp
1618
1619 // index zero (0) is not used in constantPools
1620 for (old_i = 1; old_i < old_cp->length(); old_i++) {
1621 // leave debugging crumb
1622 jbyte old_tag = old_cp->tag_at(old_i).value();
1623 switch (old_tag) {
1624 case JVM_CONSTANT_Class:
1625 case JVM_CONSTANT_UnresolvedClass:
1626 // revert the copy to JVM_CONSTANT_UnresolvedClass
1627 // May be resolving while calling this so do the same for
1628 // JVM_CONSTANT_UnresolvedClass (klass_name_at() deals with transition)
1629 (*merge_cp_p)->temp_unresolved_klass_at_put(old_i,
1630 old_cp->klass_name_index_at(old_i));
1631 break;
1632
1633 case JVM_CONSTANT_Double:
1634 case JVM_CONSTANT_Long:
1635 // just copy the entry to *merge_cp_p, but double and long take
1636 // two constant pool entries
1637 ConstantPool::copy_entry_to(old_cp, old_i, *merge_cp_p, old_i);
1638 old_i++;
1639 break;
1640
1641 default:
1642 // just copy the entry to *merge_cp_p
1643 ConstantPool::copy_entry_to(old_cp, old_i, *merge_cp_p, old_i);
1644 break;
1645 }
1646 } // end for each old_cp entry
1647
1648 ConstantPool::copy_operands(old_cp, *merge_cp_p, CHECK_false);
1649 (*merge_cp_p)->extend_operands(scratch_cp, CHECK_false);
1650
1651 // We don't need to sanity check that *merge_cp_length_p is within
1652 // *merge_cp_p bounds since we have the minimum on-entry check above.
1653 (*merge_cp_length_p) = old_i;
1654 }
1655
1656 // merge_cp_len should be the same as old_cp->length() at this point
1657 // so this trace message is really a "warm-and-breathing" message.
1658 log_debug(redefine, class, constantpool)("after pass 0: merge_cp_len=%d", *merge_cp_length_p);
1659
1660 int scratch_i; // index into scratch_cp
1661 {
1662 // Pass 1a:
1663 // Compare scratch_cp entries to the old_cp entries that we have
1664 // already copied to *merge_cp_p. In this pass, we are eliminating
1665 // exact duplicates (matching entry at same index) so we only
1666 // compare entries in the common indice range.
1667 int increment = 1;
1668 int pass1a_length = MIN2(old_cp->length(), scratch_cp->length());
1669 for (scratch_i = 1; scratch_i < pass1a_length; scratch_i += increment) {
1670 switch (scratch_cp->tag_at(scratch_i).value()) {
1671 case JVM_CONSTANT_Double:
1672 case JVM_CONSTANT_Long:
1673 // double and long take two constant pool entries
1674 increment = 2;
1675 break;
1676
1677 default:
1678 increment = 1;
1679 break;
1680 }
1681
1682 bool match = scratch_cp->compare_entry_to(scratch_i, *merge_cp_p, scratch_i);
1683 if (match) {
1684 // found a match at the same index so nothing more to do
1685 continue;
1686 }
1687
1688 int found_i = scratch_cp->find_matching_entry(scratch_i, *merge_cp_p);
1689 if (found_i != 0) {
1690 guarantee(found_i != scratch_i,
1691 "compare_entry_to() and find_matching_entry() do not agree");
1692
1693 // Found a matching entry somewhere else in *merge_cp_p so
1694 // just need a mapping entry.
1695 map_index(scratch_cp, scratch_i, found_i);
1696 continue;
1697 }
1698
1699 // No match found so we have to append this entry and any unique
1700 // referenced entries to *merge_cp_p.
1701 append_entry(scratch_cp, scratch_i, merge_cp_p, merge_cp_length_p);
1702 }
1703 }
1704
1705 log_debug(redefine, class, constantpool)
1706 ("after pass 1a: merge_cp_len=%d, scratch_i=%d, index_map_len=%d",
1707 *merge_cp_length_p, scratch_i, _index_map_count);
1708
1709 if (scratch_i < scratch_cp->length()) {
1710 // Pass 1b:
1711 // old_cp is smaller than scratch_cp so there are entries in
1712 // scratch_cp that we have not yet processed. We take care of
1713 // those now.
1714 int increment = 1;
1715 for (; scratch_i < scratch_cp->length(); scratch_i += increment) {
1716 switch (scratch_cp->tag_at(scratch_i).value()) {
1717 case JVM_CONSTANT_Double:
1718 case JVM_CONSTANT_Long:
1719 // double and long take two constant pool entries
1720 increment = 2;
1721 break;
1722
1723 default:
1724 increment = 1;
1725 break;
1726 }
1727
1728 int found_i =
1729 scratch_cp->find_matching_entry(scratch_i, *merge_cp_p);
1730 if (found_i != 0) {
1731 // Found a matching entry somewhere else in *merge_cp_p so
1732 // just need a mapping entry.
1733 map_index(scratch_cp, scratch_i, found_i);
1734 continue;
1735 }
1736
1737 // No match found so we have to append this entry and any unique
1738 // referenced entries to *merge_cp_p.
1739 append_entry(scratch_cp, scratch_i, merge_cp_p, merge_cp_length_p);
1740 }
1741
1742 log_debug(redefine, class, constantpool)
1743 ("after pass 1b: merge_cp_len=%d, scratch_i=%d, index_map_len=%d",
1744 *merge_cp_length_p, scratch_i, _index_map_count);
1745 }
1746 finalize_operands_merge(*merge_cp_p, CHECK_false);
1747
1748 return true;
1749 } // end merge_constant_pools()
1750
1751
1752 // Scoped object to clean up the constant pool(s) created for merging
1753 class MergeCPCleaner {
1754 ClassLoaderData* _loader_data;
1755 ConstantPool* _cp;
1756 ConstantPool* _scratch_cp;
1757 public:
1758 MergeCPCleaner(ClassLoaderData* loader_data, ConstantPool* merge_cp) :
1759 _loader_data(loader_data), _cp(merge_cp), _scratch_cp(nullptr) {}
1760 ~MergeCPCleaner() {
1761 _loader_data->add_to_deallocate_list(_cp);
1762 if (_scratch_cp != nullptr) {
1763 _loader_data->add_to_deallocate_list(_scratch_cp);
1764 }
1765 }
1766 void add_scratch_cp(ConstantPool* scratch_cp) { _scratch_cp = scratch_cp; }
1767 };
1768
1769 // Merge constant pools between the_class and scratch_class and
1770 // potentially rewrite bytecodes in scratch_class to use the merged
1771 // constant pool.
1772 jvmtiError VM_RedefineClasses::merge_cp_and_rewrite(
1773 InstanceKlass* the_class, InstanceKlass* scratch_class,
1774 TRAPS) {
1775 // worst case merged constant pool length is old and new combined
1776 int merge_cp_length = the_class->constants()->length()
1777 + scratch_class->constants()->length();
1778
1779 // Constant pools are not easily reused so we allocate a new one
1780 // each time.
1781 // merge_cp is created unsafe for concurrent GC processing. It
1782 // should be marked safe before discarding it. Even though
1783 // garbage, if it crosses a card boundary, it may be scanned
1784 // in order to find the start of the first complete object on the card.
1785 ClassLoaderData* loader_data = the_class->class_loader_data();
1786 ConstantPool* merge_cp_oop =
1787 ConstantPool::allocate(loader_data,
1788 merge_cp_length,
1789 CHECK_(JVMTI_ERROR_OUT_OF_MEMORY));
1790 MergeCPCleaner cp_cleaner(loader_data, merge_cp_oop);
1791
1792 HandleMark hm(THREAD); // make sure handles are cleared before
1793 // MergeCPCleaner clears out merge_cp_oop
1794 constantPoolHandle merge_cp(THREAD, merge_cp_oop);
1795
1796 // Get constants() from the old class because it could have been rewritten
1797 // while we were at a safepoint allocating a new constant pool.
1798 constantPoolHandle old_cp(THREAD, the_class->constants());
1799 constantPoolHandle scratch_cp(THREAD, scratch_class->constants());
1800
1801 // If the length changed, the class was redefined out from under us. Return
1802 // an error.
1803 if (merge_cp_length != the_class->constants()->length()
1804 + scratch_class->constants()->length()) {
1805 return JVMTI_ERROR_INTERNAL;
1806 }
1807
1808 // Update the version number of the constant pools (may keep scratch_cp)
1809 merge_cp->increment_and_save_version(old_cp->version());
1810 scratch_cp->increment_and_save_version(old_cp->version());
1811
1812 ResourceMark rm(THREAD);
1813 _index_map_count = 0;
1814 _index_map_p = new intArray(scratch_cp->length(), scratch_cp->length(), -1);
1815
1816 _operands_cur_length = ConstantPool::operand_array_length(old_cp->operands());
1817 _operands_index_map_count = 0;
1818 int operands_index_map_len = ConstantPool::operand_array_length(scratch_cp->operands());
1819 _operands_index_map_p = new intArray(operands_index_map_len, operands_index_map_len, -1);
1820
1821 // reference to the cp holder is needed for copy_operands()
1822 merge_cp->set_pool_holder(scratch_class);
1823 bool result = merge_constant_pools(old_cp, scratch_cp, &merge_cp,
1824 &merge_cp_length, THREAD);
1825 merge_cp->set_pool_holder(nullptr);
1826
1827 if (!result) {
1828 // The merge can fail due to memory allocation failure or due
1829 // to robustness checks.
1830 return JVMTI_ERROR_INTERNAL;
1831 }
1832
1833 // ensure merged constant pool size does not overflow u2
1834 if (merge_cp_length > 0xFFFF) {
1835 log_warning(redefine, class, constantpool)("Merged constant pool overflow: %d entries", merge_cp_length);
1836 return JVMTI_ERROR_INTERNAL;
1837 }
1838
1839 // Set dynamic constants attribute from the original CP.
1840 if (old_cp->has_dynamic_constant()) {
1841 scratch_cp->set_has_dynamic_constant();
1842 }
1843
1844 log_info(redefine, class, constantpool)("merge_cp_len=%d, index_map_len=%d", merge_cp_length, _index_map_count);
1845
1846 if (_index_map_count == 0) {
1847 // there is nothing to map between the new and merged constant pools
1848
1849 // Copy attributes from scratch_cp to merge_cp
1850 merge_cp->copy_fields(scratch_cp());
1851
1852 if (old_cp->length() == scratch_cp->length()) {
1853 // The old and new constant pools are the same length and the
1854 // index map is empty. This means that the three constant pools
1855 // are equivalent (but not the same). Unfortunately, the new
1856 // constant pool has not gone through link resolution nor have
1857 // the new class bytecodes gone through constant pool cache
1858 // rewriting so we can't use the old constant pool with the new
1859 // class.
1860
1861 // toss the merged constant pool at return
1862 } else if (old_cp->length() < scratch_cp->length()) {
1863 // The old constant pool has fewer entries than the new constant
1864 // pool and the index map is empty. This means the new constant
1865 // pool is a superset of the old constant pool. However, the old
1866 // class bytecodes have already gone through constant pool cache
1867 // rewriting so we can't use the new constant pool with the old
1868 // class.
1869
1870 // toss the merged constant pool at return
1871 } else {
1872 // The old constant pool has more entries than the new constant
1873 // pool and the index map is empty. This means that both the old
1874 // and merged constant pools are supersets of the new constant
1875 // pool.
1876
1877 // Replace the new constant pool with a shrunken copy of the
1878 // merged constant pool
1879 set_new_constant_pool(loader_data, scratch_class, merge_cp, merge_cp_length,
1880 CHECK_(JVMTI_ERROR_OUT_OF_MEMORY));
1881 // The new constant pool replaces scratch_cp so have cleaner clean it up.
1882 // It can't be cleaned up while there are handles to it.
1883 cp_cleaner.add_scratch_cp(scratch_cp());
1884 }
1885 } else {
1886 if (log_is_enabled(Trace, redefine, class, constantpool)) {
1887 // don't want to loop unless we are tracing
1888 int count = 0;
1889 for (int i = 1; i < _index_map_p->length(); i++) {
1890 int value = _index_map_p->at(i);
1891
1892 if (value != -1) {
1893 log_trace(redefine, class, constantpool)("index_map[%d]: old=%d new=%d", count, i, value);
1894 count++;
1895 }
1896 }
1897 }
1898
1899 // We have entries mapped between the new and merged constant pools
1900 // so we have to rewrite some constant pool references.
1901 if (!rewrite_cp_refs(scratch_class)) {
1902 return JVMTI_ERROR_INTERNAL;
1903 }
1904
1905 // Copy attributes from scratch_cp to merge_cp (should be done after rewrite_cp_refs())
1906 merge_cp->copy_fields(scratch_cp());
1907
1908 // Replace the new constant pool with a shrunken copy of the
1909 // merged constant pool so now the rewritten bytecodes have
1910 // valid references; the previous new constant pool will get
1911 // GCed.
1912 set_new_constant_pool(loader_data, scratch_class, merge_cp, merge_cp_length,
1913 CHECK_(JVMTI_ERROR_OUT_OF_MEMORY));
1914 // The new constant pool replaces scratch_cp so have cleaner clean it up.
1915 // It can't be cleaned up while there are handles to it.
1916 cp_cleaner.add_scratch_cp(scratch_cp());
1917 }
1918
1919 return JVMTI_ERROR_NONE;
1920 } // end merge_cp_and_rewrite()
1921
1922
1923 // Rewrite constant pool references in klass scratch_class.
1924 bool VM_RedefineClasses::rewrite_cp_refs(InstanceKlass* scratch_class) {
1925
1926 // rewrite constant pool references in the nest attributes:
1927 if (!rewrite_cp_refs_in_nest_attributes(scratch_class)) {
1928 // propagate failure back to caller
1929 return false;
1930 }
1931
1932 // rewrite constant pool references in the Record attribute:
1933 if (!rewrite_cp_refs_in_record_attribute(scratch_class)) {
1934 // propagate failure back to caller
1935 return false;
1936 }
1937
1938 // rewrite constant pool references in the PermittedSubclasses attribute:
1939 if (!rewrite_cp_refs_in_permitted_subclasses_attribute(scratch_class)) {
1940 // propagate failure back to caller
1941 return false;
1942 }
1943
1944 // rewrite constant pool references in the methods:
1945 if (!rewrite_cp_refs_in_methods(scratch_class)) {
1946 // propagate failure back to caller
1947 return false;
1948 }
1949
1950 // rewrite constant pool references in the class_annotations:
1951 if (!rewrite_cp_refs_in_class_annotations(scratch_class)) {
1952 // propagate failure back to caller
1953 return false;
1954 }
1955
1956 // rewrite constant pool references in the fields_annotations:
1957 if (!rewrite_cp_refs_in_fields_annotations(scratch_class)) {
1958 // propagate failure back to caller
1959 return false;
1960 }
1961
1962 // rewrite constant pool references in the methods_annotations:
1963 if (!rewrite_cp_refs_in_methods_annotations(scratch_class)) {
1964 // propagate failure back to caller
1965 return false;
1966 }
1967
1968 // rewrite constant pool references in the methods_parameter_annotations:
1969 if (!rewrite_cp_refs_in_methods_parameter_annotations(scratch_class)) {
1970 // propagate failure back to caller
1971 return false;
1972 }
1973
1974 // rewrite constant pool references in the methods_default_annotations:
1975 if (!rewrite_cp_refs_in_methods_default_annotations(scratch_class)) {
1976 // propagate failure back to caller
1977 return false;
1978 }
1979
1980 // rewrite constant pool references in the class_type_annotations:
1981 if (!rewrite_cp_refs_in_class_type_annotations(scratch_class)) {
1982 // propagate failure back to caller
1983 return false;
1984 }
1985
1986 // rewrite constant pool references in the fields_type_annotations:
1987 if (!rewrite_cp_refs_in_fields_type_annotations(scratch_class)) {
1988 // propagate failure back to caller
1989 return false;
1990 }
1991
1992 // rewrite constant pool references in the methods_type_annotations:
1993 if (!rewrite_cp_refs_in_methods_type_annotations(scratch_class)) {
1994 // propagate failure back to caller
1995 return false;
1996 }
1997
1998 // There can be type annotations in the Code part of a method_info attribute.
1999 // These annotations are not accessible, even by reflection.
2000 // Currently they are not even parsed by the ClassFileParser.
2001 // If runtime access is added they will also need to be rewritten.
2002
2003 // rewrite source file name index:
2004 u2 source_file_name_idx = scratch_class->source_file_name_index();
2005 if (source_file_name_idx != 0) {
2006 u2 new_source_file_name_idx = find_new_index(source_file_name_idx);
2007 if (new_source_file_name_idx != 0) {
2008 scratch_class->set_source_file_name_index(new_source_file_name_idx);
2009 }
2010 }
2011
2012 // rewrite class generic signature index:
2013 u2 generic_signature_index = scratch_class->generic_signature_index();
2014 if (generic_signature_index != 0) {
2015 u2 new_generic_signature_index = find_new_index(generic_signature_index);
2016 if (new_generic_signature_index != 0) {
2017 scratch_class->set_generic_signature_index(new_generic_signature_index);
2018 }
2019 }
2020
2021 return true;
2022 } // end rewrite_cp_refs()
2023
2024 // Rewrite constant pool references in the NestHost and NestMembers attributes.
2025 bool VM_RedefineClasses::rewrite_cp_refs_in_nest_attributes(
2026 InstanceKlass* scratch_class) {
2027
2028 u2 cp_index = scratch_class->nest_host_index();
2029 if (cp_index != 0) {
2030 scratch_class->set_nest_host_index(find_new_index(cp_index));
2031 }
2032 Array<u2>* nest_members = scratch_class->nest_members();
2033 for (int i = 0; i < nest_members->length(); i++) {
2034 u2 cp_index = nest_members->at(i);
2035 nest_members->at_put(i, find_new_index(cp_index));
2036 }
2037 return true;
2038 }
2039
2040 // Rewrite constant pool references in the Record attribute.
2041 bool VM_RedefineClasses::rewrite_cp_refs_in_record_attribute(InstanceKlass* scratch_class) {
2042 Array<RecordComponent*>* components = scratch_class->record_components();
2043 if (components != nullptr) {
2044 for (int i = 0; i < components->length(); i++) {
2045 RecordComponent* component = components->at(i);
2046 u2 cp_index = component->name_index();
2047 component->set_name_index(find_new_index(cp_index));
2048 cp_index = component->descriptor_index();
2049 component->set_descriptor_index(find_new_index(cp_index));
2050 cp_index = component->generic_signature_index();
2051 if (cp_index != 0) {
2052 component->set_generic_signature_index(find_new_index(cp_index));
2053 }
2054
2055 AnnotationArray* annotations = component->annotations();
2056 if (annotations != nullptr && annotations->length() != 0) {
2057 int byte_i = 0; // byte index into annotations
2058 if (!rewrite_cp_refs_in_annotations_typeArray(annotations, byte_i)) {
2059 log_debug(redefine, class, annotation)("bad record_component_annotations at %d", i);
2060 // propagate failure back to caller
2061 return false;
2062 }
2063 }
2064
2065 AnnotationArray* type_annotations = component->type_annotations();
2066 if (type_annotations != nullptr && type_annotations->length() != 0) {
2067 int byte_i = 0; // byte index into annotations
2068 if (!rewrite_cp_refs_in_annotations_typeArray(type_annotations, byte_i)) {
2069 log_debug(redefine, class, annotation)("bad record_component_type_annotations at %d", i);
2070 // propagate failure back to caller
2071 return false;
2072 }
2073 }
2074 }
2075 }
2076 return true;
2077 }
2078
2079 // Rewrite constant pool references in the PermittedSubclasses attribute.
2080 bool VM_RedefineClasses::rewrite_cp_refs_in_permitted_subclasses_attribute(
2081 InstanceKlass* scratch_class) {
2082
2083 Array<u2>* permitted_subclasses = scratch_class->permitted_subclasses();
2084 assert(permitted_subclasses != nullptr, "unexpected null permitted_subclasses");
2085 for (int i = 0; i < permitted_subclasses->length(); i++) {
2086 u2 cp_index = permitted_subclasses->at(i);
2087 permitted_subclasses->at_put(i, find_new_index(cp_index));
2088 }
2089 return true;
2090 }
2091
2092 // Rewrite constant pool references in the methods.
2093 bool VM_RedefineClasses::rewrite_cp_refs_in_methods(InstanceKlass* scratch_class) {
2094
2095 Array<Method*>* methods = scratch_class->methods();
2096
2097 if (methods == nullptr || methods->length() == 0) {
2098 // no methods so nothing to do
2099 return true;
2100 }
2101
2102 JavaThread* THREAD = JavaThread::current(); // For exception macros.
2103 ExceptionMark em(THREAD);
2104
2105 // rewrite constant pool references in the methods:
2106 for (int i = methods->length() - 1; i >= 0; i--) {
2107 methodHandle method(THREAD, methods->at(i));
2108 methodHandle new_method;
2109 rewrite_cp_refs_in_method(method, &new_method, THREAD);
2110 if (!new_method.is_null()) {
2111 // the method has been replaced so save the new method version
2112 // even in the case of an exception. original method is on the
2113 // deallocation list.
2114 methods->at_put(i, new_method());
2115 }
2116 if (HAS_PENDING_EXCEPTION) {
2117 Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
2118 log_info(redefine, class, load, exceptions)("rewrite_cp_refs_in_method exception: '%s'", ex_name->as_C_string());
2119 // Need to clear pending exception here as the super caller sets
2120 // the JVMTI_ERROR_INTERNAL if the returned value is false.
2121 CLEAR_PENDING_EXCEPTION;
2122 return false;
2123 }
2124 }
2125
2126 return true;
2127 }
2128
2129
2130 // Rewrite constant pool references in the specific method. This code
2131 // was adapted from Rewriter::rewrite_method().
2132 void VM_RedefineClasses::rewrite_cp_refs_in_method(methodHandle method,
2133 methodHandle *new_method_p, TRAPS) {
2134
2135 *new_method_p = methodHandle(); // default is no new method
2136
2137 // We cache a pointer to the bytecodes here in code_base. If GC
2138 // moves the Method*, then the bytecodes will also move which
2139 // will likely cause a crash. We create a NoSafepointVerifier
2140 // object to detect whether we pass a possible safepoint in this
2141 // code block.
2142 NoSafepointVerifier nsv;
2143
2144 // Bytecodes and their length
2145 address code_base = method->code_base();
2146 int code_length = method->code_size();
2147
2148 int bc_length;
2149 for (int bci = 0; bci < code_length; bci += bc_length) {
2150 address bcp = code_base + bci;
2151 Bytecodes::Code c = (Bytecodes::Code)(*bcp);
2152
2153 bc_length = Bytecodes::length_for(c);
2154 if (bc_length == 0) {
2155 // More complicated bytecodes report a length of zero so
2156 // we have to try again a slightly different way.
2157 bc_length = Bytecodes::length_at(method(), bcp);
2158 }
2159
2160 assert(bc_length != 0, "impossible bytecode length");
2161
2162 switch (c) {
2163 case Bytecodes::_ldc:
2164 {
2165 u1 cp_index = *(bcp + 1);
2166 u2 new_index = find_new_index(cp_index);
2167
2168 if (StressLdcRewrite && new_index == 0) {
2169 // If we are stressing ldc -> ldc_w rewriting, then we
2170 // always need a new_index value.
2171 new_index = cp_index;
2172 }
2173 if (new_index != 0) {
2174 // the original index is mapped so we have more work to do
2175 if (!StressLdcRewrite && new_index <= max_jubyte) {
2176 // The new value can still use ldc instead of ldc_w
2177 // unless we are trying to stress ldc -> ldc_w rewriting
2178 log_trace(redefine, class, constantpool)
2179 ("%s@" INTPTR_FORMAT " old=%d, new=%d", Bytecodes::name(c), p2i(bcp), cp_index, new_index);
2180 // We checked that new_index fits in a u1 so this cast is safe
2181 *(bcp + 1) = (u1)new_index;
2182 } else {
2183 log_trace(redefine, class, constantpool)
2184 ("%s->ldc_w@" INTPTR_FORMAT " old=%d, new=%d", Bytecodes::name(c), p2i(bcp), cp_index, new_index);
2185 // the new value needs ldc_w instead of ldc
2186 u_char inst_buffer[4]; // max instruction size is 4 bytes
2187 bcp = (address)inst_buffer;
2188 // construct new instruction sequence
2189 *bcp = Bytecodes::_ldc_w;
2190 bcp++;
2191 // Rewriter::rewrite_method() does not rewrite ldc -> ldc_w.
2192 // See comment below for difference between put_Java_u2()
2193 // and put_native_u2().
2194 Bytes::put_Java_u2(bcp, new_index);
2195
2196 Relocator rc(method, nullptr /* no RelocatorListener needed */);
2197 methodHandle m;
2198 {
2199 PauseNoSafepointVerifier pnsv(&nsv);
2200
2201 // ldc is 2 bytes and ldc_w is 3 bytes
2202 m = rc.insert_space_at(bci, 3, inst_buffer, CHECK);
2203 }
2204
2205 // return the new method so that the caller can update
2206 // the containing class
2207 *new_method_p = method = m;
2208 // switch our bytecode processing loop from the old method
2209 // to the new method
2210 code_base = method->code_base();
2211 code_length = method->code_size();
2212 bcp = code_base + bci;
2213 c = (Bytecodes::Code)(*bcp);
2214 bc_length = Bytecodes::length_for(c);
2215 assert(bc_length != 0, "sanity check");
2216 } // end we need ldc_w instead of ldc
2217 } // end if there is a mapped index
2218 } break;
2219
2220 // these bytecodes have a two-byte constant pool index
2221 case Bytecodes::_anewarray : // fall through
2222 case Bytecodes::_checkcast : // fall through
2223 case Bytecodes::_getfield : // fall through
2224 case Bytecodes::_getstatic : // fall through
2225 case Bytecodes::_instanceof : // fall through
2226 case Bytecodes::_invokedynamic : // fall through
2227 case Bytecodes::_invokeinterface: // fall through
2228 case Bytecodes::_invokespecial : // fall through
2229 case Bytecodes::_invokestatic : // fall through
2230 case Bytecodes::_invokevirtual : // fall through
2231 case Bytecodes::_ldc_w : // fall through
2232 case Bytecodes::_ldc2_w : // fall through
2233 case Bytecodes::_multianewarray : // fall through
2234 case Bytecodes::_new : // fall through
2235 case Bytecodes::_putfield : // fall through
2236 case Bytecodes::_putstatic :
2237 {
2238 address p = bcp + 1;
2239 int cp_index = Bytes::get_Java_u2(p);
2240 u2 new_index = find_new_index(cp_index);
2241 if (new_index != 0) {
2242 // the original index is mapped so update w/ new value
2243 log_trace(redefine, class, constantpool)
2244 ("%s@" INTPTR_FORMAT " old=%d, new=%d", Bytecodes::name(c),p2i(bcp), cp_index, new_index);
2245 // Rewriter::rewrite_method() uses put_native_u2() in this
2246 // situation because it is reusing the constant pool index
2247 // location for a native index into the ConstantPoolCache.
2248 // Since we are updating the constant pool index prior to
2249 // verification and ConstantPoolCache initialization, we
2250 // need to keep the new index in Java byte order.
2251 Bytes::put_Java_u2(p, new_index);
2252 }
2253 } break;
2254 default:
2255 break;
2256 }
2257 } // end for each bytecode
2258 } // end rewrite_cp_refs_in_method()
2259
2260
2261 // Rewrite constant pool references in the class_annotations field.
2262 bool VM_RedefineClasses::rewrite_cp_refs_in_class_annotations(InstanceKlass* scratch_class) {
2263
2264 AnnotationArray* class_annotations = scratch_class->class_annotations();
2265 if (class_annotations == nullptr || class_annotations->length() == 0) {
2266 // no class_annotations so nothing to do
2267 return true;
2268 }
2269
2270 log_debug(redefine, class, annotation)("class_annotations length=%d", class_annotations->length());
2271
2272 int byte_i = 0; // byte index into class_annotations
2273 return rewrite_cp_refs_in_annotations_typeArray(class_annotations, byte_i);
2274 }
2275
2276
2277 // Rewrite constant pool references in an annotations typeArray. This
2278 // "structure" is adapted from the RuntimeVisibleAnnotations_attribute
2279 // that is described in section 4.8.15 of the 2nd-edition of the VM spec:
2280 //
2281 // annotations_typeArray {
2282 // u2 num_annotations;
2283 // annotation annotations[num_annotations];
2284 // }
2285 //
2286 bool VM_RedefineClasses::rewrite_cp_refs_in_annotations_typeArray(
2287 AnnotationArray* annotations_typeArray, int &byte_i_ref) {
2288
2289 if ((byte_i_ref + 2) > annotations_typeArray->length()) {
2290 // not enough room for num_annotations field
2291 log_debug(redefine, class, annotation)("length() is too small for num_annotations field");
2292 return false;
2293 }
2294
2295 u2 num_annotations = Bytes::get_Java_u2((address)
2296 annotations_typeArray->adr_at(byte_i_ref));
2297 byte_i_ref += 2;
2298
2299 log_debug(redefine, class, annotation)("num_annotations=%d", num_annotations);
2300
2301 int calc_num_annotations = 0;
2302 for (; calc_num_annotations < num_annotations; calc_num_annotations++) {
2303 if (!rewrite_cp_refs_in_annotation_struct(annotations_typeArray, byte_i_ref)) {
2304 log_debug(redefine, class, annotation)("bad annotation_struct at %d", calc_num_annotations);
2305 // propagate failure back to caller
2306 return false;
2307 }
2308 }
2309 assert(num_annotations == calc_num_annotations, "sanity check");
2310
2311 return true;
2312 } // end rewrite_cp_refs_in_annotations_typeArray()
2313
2314
2315 // Rewrite constant pool references in the annotation struct portion of
2316 // an annotations_typeArray. This "structure" is from section 4.8.15 of
2317 // the 2nd-edition of the VM spec:
2318 //
2319 // struct annotation {
2320 // u2 type_index;
2321 // u2 num_element_value_pairs;
2322 // {
2323 // u2 element_name_index;
2324 // element_value value;
2325 // } element_value_pairs[num_element_value_pairs];
2326 // }
2327 //
2328 bool VM_RedefineClasses::rewrite_cp_refs_in_annotation_struct(
2329 AnnotationArray* annotations_typeArray, int &byte_i_ref) {
2330 if ((byte_i_ref + 2 + 2) > annotations_typeArray->length()) {
2331 // not enough room for smallest annotation_struct
2332 log_debug(redefine, class, annotation)("length() is too small for annotation_struct");
2333 return false;
2334 }
2335
2336 u2 type_index = rewrite_cp_ref_in_annotation_data(annotations_typeArray,
2337 byte_i_ref, "type_index");
2338
2339 u2 num_element_value_pairs = Bytes::get_Java_u2((address)
2340 annotations_typeArray->adr_at(byte_i_ref));
2341 byte_i_ref += 2;
2342
2343 log_debug(redefine, class, annotation)
2344 ("type_index=%d num_element_value_pairs=%d", type_index, num_element_value_pairs);
2345
2346 int calc_num_element_value_pairs = 0;
2347 for (; calc_num_element_value_pairs < num_element_value_pairs;
2348 calc_num_element_value_pairs++) {
2349 if ((byte_i_ref + 2) > annotations_typeArray->length()) {
2350 // not enough room for another element_name_index, let alone
2351 // the rest of another component
2352 log_debug(redefine, class, annotation)("length() is too small for element_name_index");
2353 return false;
2354 }
2355
2356 u2 element_name_index = rewrite_cp_ref_in_annotation_data(
2357 annotations_typeArray, byte_i_ref,
2358 "element_name_index");
2359
2360 log_debug(redefine, class, annotation)("element_name_index=%d", element_name_index);
2361
2362 if (!rewrite_cp_refs_in_element_value(annotations_typeArray, byte_i_ref)) {
2363 log_debug(redefine, class, annotation)("bad element_value at %d", calc_num_element_value_pairs);
2364 // propagate failure back to caller
2365 return false;
2366 }
2367 } // end for each component
2368 assert(num_element_value_pairs == calc_num_element_value_pairs,
2369 "sanity check");
2370
2371 return true;
2372 } // end rewrite_cp_refs_in_annotation_struct()
2373
2374
2375 // Rewrite a constant pool reference at the current position in
2376 // annotations_typeArray if needed. Returns the original constant
2377 // pool reference if a rewrite was not needed or the new constant
2378 // pool reference if a rewrite was needed.
2379 u2 VM_RedefineClasses::rewrite_cp_ref_in_annotation_data(
2380 AnnotationArray* annotations_typeArray, int &byte_i_ref,
2381 const char * trace_mesg) {
2382
2383 address cp_index_addr = (address)
2384 annotations_typeArray->adr_at(byte_i_ref);
2385 u2 old_cp_index = Bytes::get_Java_u2(cp_index_addr);
2386 u2 new_cp_index = find_new_index(old_cp_index);
2387 if (new_cp_index != 0) {
2388 log_debug(redefine, class, annotation)("mapped old %s=%d", trace_mesg, old_cp_index);
2389 Bytes::put_Java_u2(cp_index_addr, new_cp_index);
2390 old_cp_index = new_cp_index;
2391 }
2392 byte_i_ref += 2;
2393 return old_cp_index;
2394 }
2395
2396
2397 // Rewrite constant pool references in the element_value portion of an
2398 // annotations_typeArray. This "structure" is from section 4.8.15.1 of
2399 // the 2nd-edition of the VM spec:
2400 //
2401 // struct element_value {
2402 // u1 tag;
2403 // union {
2404 // u2 const_value_index;
2405 // {
2406 // u2 type_name_index;
2407 // u2 const_name_index;
2408 // } enum_const_value;
2409 // u2 class_info_index;
2410 // annotation annotation_value;
2411 // struct {
2412 // u2 num_values;
2413 // element_value values[num_values];
2414 // } array_value;
2415 // } value;
2416 // }
2417 //
2418 bool VM_RedefineClasses::rewrite_cp_refs_in_element_value(
2419 AnnotationArray* annotations_typeArray, int &byte_i_ref) {
2420
2421 if ((byte_i_ref + 1) > annotations_typeArray->length()) {
2422 // not enough room for a tag let alone the rest of an element_value
2423 log_debug(redefine, class, annotation)("length() is too small for a tag");
2424 return false;
2425 }
2426
2427 u1 tag = annotations_typeArray->at(byte_i_ref);
2428 byte_i_ref++;
2429 log_debug(redefine, class, annotation)("tag='%c'", tag);
2430
2431 switch (tag) {
2432 // These BaseType tag values are from Table 4.2 in VM spec:
2433 case JVM_SIGNATURE_BYTE:
2434 case JVM_SIGNATURE_CHAR:
2435 case JVM_SIGNATURE_DOUBLE:
2436 case JVM_SIGNATURE_FLOAT:
2437 case JVM_SIGNATURE_INT:
2438 case JVM_SIGNATURE_LONG:
2439 case JVM_SIGNATURE_SHORT:
2440 case JVM_SIGNATURE_BOOLEAN:
2441
2442 // The remaining tag values are from Table 4.8 in the 2nd-edition of
2443 // the VM spec:
2444 case 's':
2445 {
2446 // For the above tag values (including the BaseType values),
2447 // value.const_value_index is right union field.
2448
2449 if ((byte_i_ref + 2) > annotations_typeArray->length()) {
2450 // not enough room for a const_value_index
2451 log_debug(redefine, class, annotation)("length() is too small for a const_value_index");
2452 return false;
2453 }
2454
2455 u2 const_value_index = rewrite_cp_ref_in_annotation_data(
2456 annotations_typeArray, byte_i_ref,
2457 "const_value_index");
2458
2459 log_debug(redefine, class, annotation)("const_value_index=%d", const_value_index);
2460 } break;
2461
2462 case 'e':
2463 {
2464 // for the above tag value, value.enum_const_value is right union field
2465
2466 if ((byte_i_ref + 4) > annotations_typeArray->length()) {
2467 // not enough room for a enum_const_value
2468 log_debug(redefine, class, annotation)("length() is too small for a enum_const_value");
2469 return false;
2470 }
2471
2472 u2 type_name_index = rewrite_cp_ref_in_annotation_data(
2473 annotations_typeArray, byte_i_ref,
2474 "type_name_index");
2475
2476 u2 const_name_index = rewrite_cp_ref_in_annotation_data(
2477 annotations_typeArray, byte_i_ref,
2478 "const_name_index");
2479
2480 log_debug(redefine, class, annotation)
2481 ("type_name_index=%d const_name_index=%d", type_name_index, const_name_index);
2482 } break;
2483
2484 case 'c':
2485 {
2486 // for the above tag value, value.class_info_index is right union field
2487
2488 if ((byte_i_ref + 2) > annotations_typeArray->length()) {
2489 // not enough room for a class_info_index
2490 log_debug(redefine, class, annotation)("length() is too small for a class_info_index");
2491 return false;
2492 }
2493
2494 u2 class_info_index = rewrite_cp_ref_in_annotation_data(
2495 annotations_typeArray, byte_i_ref,
2496 "class_info_index");
2497
2498 log_debug(redefine, class, annotation)("class_info_index=%d", class_info_index);
2499 } break;
2500
2501 case '@':
2502 // For the above tag value, value.attr_value is the right union
2503 // field. This is a nested annotation.
2504 if (!rewrite_cp_refs_in_annotation_struct(annotations_typeArray, byte_i_ref)) {
2505 // propagate failure back to caller
2506 return false;
2507 }
2508 break;
2509
2510 case JVM_SIGNATURE_ARRAY:
2511 {
2512 if ((byte_i_ref + 2) > annotations_typeArray->length()) {
2513 // not enough room for a num_values field
2514 log_debug(redefine, class, annotation)("length() is too small for a num_values field");
2515 return false;
2516 }
2517
2518 // For the above tag value, value.array_value is the right union
2519 // field. This is an array of nested element_value.
2520 u2 num_values = Bytes::get_Java_u2((address)
2521 annotations_typeArray->adr_at(byte_i_ref));
2522 byte_i_ref += 2;
2523 log_debug(redefine, class, annotation)("num_values=%d", num_values);
2524
2525 int calc_num_values = 0;
2526 for (; calc_num_values < num_values; calc_num_values++) {
2527 if (!rewrite_cp_refs_in_element_value(annotations_typeArray, byte_i_ref)) {
2528 log_debug(redefine, class, annotation)("bad nested element_value at %d", calc_num_values);
2529 // propagate failure back to caller
2530 return false;
2531 }
2532 }
2533 assert(num_values == calc_num_values, "sanity check");
2534 } break;
2535
2536 default:
2537 log_debug(redefine, class, annotation)("bad tag=0x%x", tag);
2538 return false;
2539 } // end decode tag field
2540
2541 return true;
2542 } // end rewrite_cp_refs_in_element_value()
2543
2544
2545 // Rewrite constant pool references in a fields_annotations field.
2546 bool VM_RedefineClasses::rewrite_cp_refs_in_fields_annotations(
2547 InstanceKlass* scratch_class) {
2548
2549 Array<AnnotationArray*>* fields_annotations = scratch_class->fields_annotations();
2550
2551 if (fields_annotations == nullptr || fields_annotations->length() == 0) {
2552 // no fields_annotations so nothing to do
2553 return true;
2554 }
2555
2556 log_debug(redefine, class, annotation)("fields_annotations length=%d", fields_annotations->length());
2557
2558 for (int i = 0; i < fields_annotations->length(); i++) {
2559 AnnotationArray* field_annotations = fields_annotations->at(i);
2560 if (field_annotations == nullptr || field_annotations->length() == 0) {
2561 // this field does not have any annotations so skip it
2562 continue;
2563 }
2564
2565 int byte_i = 0; // byte index into field_annotations
2566 if (!rewrite_cp_refs_in_annotations_typeArray(field_annotations, byte_i)) {
2567 log_debug(redefine, class, annotation)("bad field_annotations at %d", i);
2568 // propagate failure back to caller
2569 return false;
2570 }
2571 }
2572
2573 return true;
2574 } // end rewrite_cp_refs_in_fields_annotations()
2575
2576
2577 // Rewrite constant pool references in a methods_annotations field.
2578 bool VM_RedefineClasses::rewrite_cp_refs_in_methods_annotations(
2579 InstanceKlass* scratch_class) {
2580
2581 for (int i = 0; i < scratch_class->methods()->length(); i++) {
2582 Method* m = scratch_class->methods()->at(i);
2583 AnnotationArray* method_annotations = m->constMethod()->method_annotations();
2584
2585 if (method_annotations == nullptr || method_annotations->length() == 0) {
2586 // this method does not have any annotations so skip it
2587 continue;
2588 }
2589
2590 int byte_i = 0; // byte index into method_annotations
2591 if (!rewrite_cp_refs_in_annotations_typeArray(method_annotations, byte_i)) {
2592 log_debug(redefine, class, annotation)("bad method_annotations at %d", i);
2593 // propagate failure back to caller
2594 return false;
2595 }
2596 }
2597
2598 return true;
2599 } // end rewrite_cp_refs_in_methods_annotations()
2600
2601
2602 // Rewrite constant pool references in a methods_parameter_annotations
2603 // field. This "structure" is adapted from the
2604 // RuntimeVisibleParameterAnnotations_attribute described in section
2605 // 4.8.17 of the 2nd-edition of the VM spec:
2606 //
2607 // methods_parameter_annotations_typeArray {
2608 // u1 num_parameters;
2609 // {
2610 // u2 num_annotations;
2611 // annotation annotations[num_annotations];
2612 // } parameter_annotations[num_parameters];
2613 // }
2614 //
2615 bool VM_RedefineClasses::rewrite_cp_refs_in_methods_parameter_annotations(
2616 InstanceKlass* scratch_class) {
2617
2618 for (int i = 0; i < scratch_class->methods()->length(); i++) {
2619 Method* m = scratch_class->methods()->at(i);
2620 AnnotationArray* method_parameter_annotations = m->constMethod()->parameter_annotations();
2621 if (method_parameter_annotations == nullptr
2622 || method_parameter_annotations->length() == 0) {
2623 // this method does not have any parameter annotations so skip it
2624 continue;
2625 }
2626
2627 if (method_parameter_annotations->length() < 1) {
2628 // not enough room for a num_parameters field
2629 log_debug(redefine, class, annotation)("length() is too small for a num_parameters field at %d", i);
2630 return false;
2631 }
2632
2633 int byte_i = 0; // byte index into method_parameter_annotations
2634
2635 u1 num_parameters = method_parameter_annotations->at(byte_i);
2636 byte_i++;
2637
2638 log_debug(redefine, class, annotation)("num_parameters=%d", num_parameters);
2639
2640 int calc_num_parameters = 0;
2641 for (; calc_num_parameters < num_parameters; calc_num_parameters++) {
2642 if (!rewrite_cp_refs_in_annotations_typeArray(method_parameter_annotations, byte_i)) {
2643 log_debug(redefine, class, annotation)("bad method_parameter_annotations at %d", calc_num_parameters);
2644 // propagate failure back to caller
2645 return false;
2646 }
2647 }
2648 assert(num_parameters == calc_num_parameters, "sanity check");
2649 }
2650
2651 return true;
2652 } // end rewrite_cp_refs_in_methods_parameter_annotations()
2653
2654
2655 // Rewrite constant pool references in a methods_default_annotations
2656 // field. This "structure" is adapted from the AnnotationDefault_attribute
2657 // that is described in section 4.8.19 of the 2nd-edition of the VM spec:
2658 //
2659 // methods_default_annotations_typeArray {
2660 // element_value default_value;
2661 // }
2662 //
2663 bool VM_RedefineClasses::rewrite_cp_refs_in_methods_default_annotations(
2664 InstanceKlass* scratch_class) {
2665
2666 for (int i = 0; i < scratch_class->methods()->length(); i++) {
2667 Method* m = scratch_class->methods()->at(i);
2668 AnnotationArray* method_default_annotations = m->constMethod()->default_annotations();
2669 if (method_default_annotations == nullptr
2670 || method_default_annotations->length() == 0) {
2671 // this method does not have any default annotations so skip it
2672 continue;
2673 }
2674
2675 int byte_i = 0; // byte index into method_default_annotations
2676
2677 if (!rewrite_cp_refs_in_element_value(
2678 method_default_annotations, byte_i)) {
2679 log_debug(redefine, class, annotation)("bad default element_value at %d", i);
2680 // propagate failure back to caller
2681 return false;
2682 }
2683 }
2684
2685 return true;
2686 } // end rewrite_cp_refs_in_methods_default_annotations()
2687
2688
2689 // Rewrite constant pool references in a class_type_annotations field.
2690 bool VM_RedefineClasses::rewrite_cp_refs_in_class_type_annotations(
2691 InstanceKlass* scratch_class) {
2692
2693 AnnotationArray* class_type_annotations = scratch_class->class_type_annotations();
2694 if (class_type_annotations == nullptr || class_type_annotations->length() == 0) {
2695 // no class_type_annotations so nothing to do
2696 return true;
2697 }
2698
2699 log_debug(redefine, class, annotation)("class_type_annotations length=%d", class_type_annotations->length());
2700
2701 int byte_i = 0; // byte index into class_type_annotations
2702 return rewrite_cp_refs_in_type_annotations_typeArray(class_type_annotations,
2703 byte_i, "ClassFile");
2704 } // end rewrite_cp_refs_in_class_type_annotations()
2705
2706
2707 // Rewrite constant pool references in a fields_type_annotations field.
2708 bool VM_RedefineClasses::rewrite_cp_refs_in_fields_type_annotations(InstanceKlass* scratch_class) {
2709
2710 Array<AnnotationArray*>* fields_type_annotations = scratch_class->fields_type_annotations();
2711 if (fields_type_annotations == nullptr || fields_type_annotations->length() == 0) {
2712 // no fields_type_annotations so nothing to do
2713 return true;
2714 }
2715
2716 log_debug(redefine, class, annotation)("fields_type_annotations length=%d", fields_type_annotations->length());
2717
2718 for (int i = 0; i < fields_type_annotations->length(); i++) {
2719 AnnotationArray* field_type_annotations = fields_type_annotations->at(i);
2720 if (field_type_annotations == nullptr || field_type_annotations->length() == 0) {
2721 // this field does not have any annotations so skip it
2722 continue;
2723 }
2724
2725 int byte_i = 0; // byte index into field_type_annotations
2726 if (!rewrite_cp_refs_in_type_annotations_typeArray(field_type_annotations,
2727 byte_i, "field_info")) {
2728 log_debug(redefine, class, annotation)("bad field_type_annotations at %d", i);
2729 // propagate failure back to caller
2730 return false;
2731 }
2732 }
2733
2734 return true;
2735 } // end rewrite_cp_refs_in_fields_type_annotations()
2736
2737
2738 // Rewrite constant pool references in a methods_type_annotations field.
2739 bool VM_RedefineClasses::rewrite_cp_refs_in_methods_type_annotations(
2740 InstanceKlass* scratch_class) {
2741
2742 for (int i = 0; i < scratch_class->methods()->length(); i++) {
2743 Method* m = scratch_class->methods()->at(i);
2744 AnnotationArray* method_type_annotations = m->constMethod()->type_annotations();
2745
2746 if (method_type_annotations == nullptr || method_type_annotations->length() == 0) {
2747 // this method does not have any annotations so skip it
2748 continue;
2749 }
2750
2751 log_debug(redefine, class, annotation)("methods type_annotations length=%d", method_type_annotations->length());
2752
2753 int byte_i = 0; // byte index into method_type_annotations
2754 if (!rewrite_cp_refs_in_type_annotations_typeArray(method_type_annotations,
2755 byte_i, "method_info")) {
2756 log_debug(redefine, class, annotation)("bad method_type_annotations at %d", i);
2757 // propagate failure back to caller
2758 return false;
2759 }
2760 }
2761
2762 return true;
2763 } // end rewrite_cp_refs_in_methods_type_annotations()
2764
2765
2766 // Rewrite constant pool references in a type_annotations
2767 // field. This "structure" is adapted from the
2768 // RuntimeVisibleTypeAnnotations_attribute described in
2769 // section 4.7.20 of the Java SE 8 Edition of the VM spec:
2770 //
2771 // type_annotations_typeArray {
2772 // u2 num_annotations;
2773 // type_annotation annotations[num_annotations];
2774 // }
2775 //
2776 bool VM_RedefineClasses::rewrite_cp_refs_in_type_annotations_typeArray(
2777 AnnotationArray* type_annotations_typeArray, int &byte_i_ref,
2778 const char * location_mesg) {
2779
2780 if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
2781 // not enough room for num_annotations field
2782 log_debug(redefine, class, annotation)("length() is too small for num_annotations field");
2783 return false;
2784 }
2785
2786 u2 num_annotations = Bytes::get_Java_u2((address)
2787 type_annotations_typeArray->adr_at(byte_i_ref));
2788 byte_i_ref += 2;
2789
2790 log_debug(redefine, class, annotation)("num_type_annotations=%d", num_annotations);
2791
2792 int calc_num_annotations = 0;
2793 for (; calc_num_annotations < num_annotations; calc_num_annotations++) {
2794 if (!rewrite_cp_refs_in_type_annotation_struct(type_annotations_typeArray,
2795 byte_i_ref, location_mesg)) {
2796 log_debug(redefine, class, annotation)("bad type_annotation_struct at %d", calc_num_annotations);
2797 // propagate failure back to caller
2798 return false;
2799 }
2800 }
2801 assert(num_annotations == calc_num_annotations, "sanity check");
2802
2803 if (byte_i_ref != type_annotations_typeArray->length()) {
2804 log_debug(redefine, class, annotation)
2805 ("read wrong amount of bytes at end of processing type_annotations_typeArray (%d of %d bytes were read)",
2806 byte_i_ref, type_annotations_typeArray->length());
2807 return false;
2808 }
2809
2810 return true;
2811 } // end rewrite_cp_refs_in_type_annotations_typeArray()
2812
2813
2814 // Rewrite constant pool references in a type_annotation
2815 // field. This "structure" is adapted from the
2816 // RuntimeVisibleTypeAnnotations_attribute described in
2817 // section 4.7.20 of the Java SE 8 Edition of the VM spec:
2818 //
2819 // type_annotation {
2820 // u1 target_type;
2821 // union {
2822 // type_parameter_target;
2823 // supertype_target;
2824 // type_parameter_bound_target;
2825 // empty_target;
2826 // method_formal_parameter_target;
2827 // throws_target;
2828 // localvar_target;
2829 // catch_target;
2830 // offset_target;
2831 // type_argument_target;
2832 // } target_info;
2833 // type_path target_path;
2834 // annotation anno;
2835 // }
2836 //
2837 bool VM_RedefineClasses::rewrite_cp_refs_in_type_annotation_struct(
2838 AnnotationArray* type_annotations_typeArray, int &byte_i_ref,
2839 const char * location_mesg) {
2840
2841 if (!skip_type_annotation_target(type_annotations_typeArray,
2842 byte_i_ref, location_mesg)) {
2843 return false;
2844 }
2845
2846 if (!skip_type_annotation_type_path(type_annotations_typeArray, byte_i_ref)) {
2847 return false;
2848 }
2849
2850 if (!rewrite_cp_refs_in_annotation_struct(type_annotations_typeArray, byte_i_ref)) {
2851 return false;
2852 }
2853
2854 return true;
2855 } // end rewrite_cp_refs_in_type_annotation_struct()
2856
2857
2858 // Read, verify and skip over the target_type and target_info part
2859 // so that rewriting can continue in the later parts of the struct.
2860 //
2861 // u1 target_type;
2862 // union {
2863 // type_parameter_target;
2864 // supertype_target;
2865 // type_parameter_bound_target;
2866 // empty_target;
2867 // method_formal_parameter_target;
2868 // throws_target;
2869 // localvar_target;
2870 // catch_target;
2871 // offset_target;
2872 // type_argument_target;
2873 // } target_info;
2874 //
2875 bool VM_RedefineClasses::skip_type_annotation_target(
2876 AnnotationArray* type_annotations_typeArray, int &byte_i_ref,
2877 const char * location_mesg) {
2878
2879 if ((byte_i_ref + 1) > type_annotations_typeArray->length()) {
2880 // not enough room for a target_type let alone the rest of a type_annotation
2881 log_debug(redefine, class, annotation)("length() is too small for a target_type");
2882 return false;
2883 }
2884
2885 u1 target_type = type_annotations_typeArray->at(byte_i_ref);
2886 byte_i_ref += 1;
2887 log_debug(redefine, class, annotation)("target_type=0x%.2x", target_type);
2888 log_debug(redefine, class, annotation)("location=%s", location_mesg);
2889
2890 // Skip over target_info
2891 switch (target_type) {
2892 case 0x00:
2893 // kind: type parameter declaration of generic class or interface
2894 // location: ClassFile
2895 case 0x01:
2896 // kind: type parameter declaration of generic method or constructor
2897 // location: method_info
2898
2899 {
2900 // struct:
2901 // type_parameter_target {
2902 // u1 type_parameter_index;
2903 // }
2904 //
2905 if ((byte_i_ref + 1) > type_annotations_typeArray->length()) {
2906 log_debug(redefine, class, annotation)("length() is too small for a type_parameter_target");
2907 return false;
2908 }
2909
2910 u1 type_parameter_index = type_annotations_typeArray->at(byte_i_ref);
2911 byte_i_ref += 1;
2912
2913 log_debug(redefine, class, annotation)("type_parameter_target: type_parameter_index=%d", type_parameter_index);
2914 } break;
2915
2916 case 0x10:
2917 // kind: type in extends clause of class or interface declaration
2918 // or in implements clause of interface declaration
2919 // location: ClassFile
2920
2921 {
2922 // struct:
2923 // supertype_target {
2924 // u2 supertype_index;
2925 // }
2926 //
2927 if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
2928 log_debug(redefine, class, annotation)("length() is too small for a supertype_target");
2929 return false;
2930 }
2931
2932 u2 supertype_index = Bytes::get_Java_u2((address)
2933 type_annotations_typeArray->adr_at(byte_i_ref));
2934 byte_i_ref += 2;
2935
2936 log_debug(redefine, class, annotation)("supertype_target: supertype_index=%d", supertype_index);
2937 } break;
2938
2939 case 0x11:
2940 // kind: type in bound of type parameter declaration of generic class or interface
2941 // location: ClassFile
2942 case 0x12:
2943 // kind: type in bound of type parameter declaration of generic method or constructor
2944 // location: method_info
2945
2946 {
2947 // struct:
2948 // type_parameter_bound_target {
2949 // u1 type_parameter_index;
2950 // u1 bound_index;
2951 // }
2952 //
2953 if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
2954 log_debug(redefine, class, annotation)("length() is too small for a type_parameter_bound_target");
2955 return false;
2956 }
2957
2958 u1 type_parameter_index = type_annotations_typeArray->at(byte_i_ref);
2959 byte_i_ref += 1;
2960 u1 bound_index = type_annotations_typeArray->at(byte_i_ref);
2961 byte_i_ref += 1;
2962
2963 log_debug(redefine, class, annotation)
2964 ("type_parameter_bound_target: type_parameter_index=%d, bound_index=%d", type_parameter_index, bound_index);
2965 } break;
2966
2967 case 0x13:
2968 // kind: type in field declaration
2969 // location: field_info
2970 case 0x14:
2971 // kind: return type of method, or type of newly constructed object
2972 // location: method_info
2973 case 0x15:
2974 // kind: receiver type of method or constructor
2975 // location: method_info
2976
2977 {
2978 // struct:
2979 // empty_target {
2980 // }
2981 //
2982 log_debug(redefine, class, annotation)("empty_target");
2983 } break;
2984
2985 case 0x16:
2986 // kind: type in formal parameter declaration of method, constructor, or lambda expression
2987 // location: method_info
2988
2989 {
2990 // struct:
2991 // formal_parameter_target {
2992 // u1 formal_parameter_index;
2993 // }
2994 //
2995 if ((byte_i_ref + 1) > type_annotations_typeArray->length()) {
2996 log_debug(redefine, class, annotation)("length() is too small for a formal_parameter_target");
2997 return false;
2998 }
2999
3000 u1 formal_parameter_index = type_annotations_typeArray->at(byte_i_ref);
3001 byte_i_ref += 1;
3002
3003 log_debug(redefine, class, annotation)
3004 ("formal_parameter_target: formal_parameter_index=%d", formal_parameter_index);
3005 } break;
3006
3007 case 0x17:
3008 // kind: type in throws clause of method or constructor
3009 // location: method_info
3010
3011 {
3012 // struct:
3013 // throws_target {
3014 // u2 throws_type_index
3015 // }
3016 //
3017 if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
3018 log_debug(redefine, class, annotation)("length() is too small for a throws_target");
3019 return false;
3020 }
3021
3022 u2 throws_type_index = Bytes::get_Java_u2((address)
3023 type_annotations_typeArray->adr_at(byte_i_ref));
3024 byte_i_ref += 2;
3025
3026 log_debug(redefine, class, annotation)("throws_target: throws_type_index=%d", throws_type_index);
3027 } break;
3028
3029 case 0x40:
3030 // kind: type in local variable declaration
3031 // location: Code
3032 case 0x41:
3033 // kind: type in resource variable declaration
3034 // location: Code
3035
3036 {
3037 // struct:
3038 // localvar_target {
3039 // u2 table_length;
3040 // struct {
3041 // u2 start_pc;
3042 // u2 length;
3043 // u2 index;
3044 // } table[table_length];
3045 // }
3046 //
3047 if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
3048 // not enough room for a table_length let alone the rest of a localvar_target
3049 log_debug(redefine, class, annotation)("length() is too small for a localvar_target table_length");
3050 return false;
3051 }
3052
3053 u2 table_length = Bytes::get_Java_u2((address)
3054 type_annotations_typeArray->adr_at(byte_i_ref));
3055 byte_i_ref += 2;
3056
3057 log_debug(redefine, class, annotation)("localvar_target: table_length=%d", table_length);
3058
3059 int table_struct_size = 2 + 2 + 2; // 3 u2 variables per table entry
3060 int table_size = table_length * table_struct_size;
3061
3062 if ((byte_i_ref + table_size) > type_annotations_typeArray->length()) {
3063 // not enough room for a table
3064 log_debug(redefine, class, annotation)("length() is too small for a table array of length %d", table_length);
3065 return false;
3066 }
3067
3068 // Skip over table
3069 byte_i_ref += table_size;
3070 } break;
3071
3072 case 0x42:
3073 // kind: type in exception parameter declaration
3074 // location: Code
3075
3076 {
3077 // struct:
3078 // catch_target {
3079 // u2 exception_table_index;
3080 // }
3081 //
3082 if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
3083 log_debug(redefine, class, annotation)("length() is too small for a catch_target");
3084 return false;
3085 }
3086
3087 u2 exception_table_index = Bytes::get_Java_u2((address)
3088 type_annotations_typeArray->adr_at(byte_i_ref));
3089 byte_i_ref += 2;
3090
3091 log_debug(redefine, class, annotation)("catch_target: exception_table_index=%d", exception_table_index);
3092 } break;
3093
3094 case 0x43:
3095 // kind: type in instanceof expression
3096 // location: Code
3097 case 0x44:
3098 // kind: type in new expression
3099 // location: Code
3100 case 0x45:
3101 // kind: type in method reference expression using ::new
3102 // location: Code
3103 case 0x46:
3104 // kind: type in method reference expression using ::Identifier
3105 // location: Code
3106
3107 {
3108 // struct:
3109 // offset_target {
3110 // u2 offset;
3111 // }
3112 //
3113 if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
3114 log_debug(redefine, class, annotation)("length() is too small for a offset_target");
3115 return false;
3116 }
3117
3118 u2 offset = Bytes::get_Java_u2((address)
3119 type_annotations_typeArray->adr_at(byte_i_ref));
3120 byte_i_ref += 2;
3121
3122 log_debug(redefine, class, annotation)("offset_target: offset=%d", offset);
3123 } break;
3124
3125 case 0x47:
3126 // kind: type in cast expression
3127 // location: Code
3128 case 0x48:
3129 // kind: type argument for generic constructor in new expression or
3130 // explicit constructor invocation statement
3131 // location: Code
3132 case 0x49:
3133 // kind: type argument for generic method in method invocation expression
3134 // location: Code
3135 case 0x4A:
3136 // kind: type argument for generic constructor in method reference expression using ::new
3137 // location: Code
3138 case 0x4B:
3139 // kind: type argument for generic method in method reference expression using ::Identifier
3140 // location: Code
3141
3142 {
3143 // struct:
3144 // type_argument_target {
3145 // u2 offset;
3146 // u1 type_argument_index;
3147 // }
3148 //
3149 if ((byte_i_ref + 3) > type_annotations_typeArray->length()) {
3150 log_debug(redefine, class, annotation)("length() is too small for a type_argument_target");
3151 return false;
3152 }
3153
3154 u2 offset = Bytes::get_Java_u2((address)
3155 type_annotations_typeArray->adr_at(byte_i_ref));
3156 byte_i_ref += 2;
3157 u1 type_argument_index = type_annotations_typeArray->at(byte_i_ref);
3158 byte_i_ref += 1;
3159
3160 log_debug(redefine, class, annotation)
3161 ("type_argument_target: offset=%d, type_argument_index=%d", offset, type_argument_index);
3162 } break;
3163
3164 default:
3165 log_debug(redefine, class, annotation)("unknown target_type");
3166 #ifdef ASSERT
3167 ShouldNotReachHere();
3168 #endif
3169 return false;
3170 }
3171
3172 return true;
3173 } // end skip_type_annotation_target()
3174
3175
3176 // Read, verify and skip over the type_path part so that rewriting
3177 // can continue in the later parts of the struct.
3178 //
3179 // type_path {
3180 // u1 path_length;
3181 // {
3182 // u1 type_path_kind;
3183 // u1 type_argument_index;
3184 // } path[path_length];
3185 // }
3186 //
3187 bool VM_RedefineClasses::skip_type_annotation_type_path(
3188 AnnotationArray* type_annotations_typeArray, int &byte_i_ref) {
3189
3190 if ((byte_i_ref + 1) > type_annotations_typeArray->length()) {
3191 // not enough room for a path_length let alone the rest of the type_path
3192 log_debug(redefine, class, annotation)("length() is too small for a type_path");
3193 return false;
3194 }
3195
3196 u1 path_length = type_annotations_typeArray->at(byte_i_ref);
3197 byte_i_ref += 1;
3198
3199 log_debug(redefine, class, annotation)("type_path: path_length=%d", path_length);
3200
3201 int calc_path_length = 0;
3202 for (; calc_path_length < path_length; calc_path_length++) {
3203 if ((byte_i_ref + 1 + 1) > type_annotations_typeArray->length()) {
3204 // not enough room for a path
3205 log_debug(redefine, class, annotation)
3206 ("length() is too small for path entry %d of %d", calc_path_length, path_length);
3207 return false;
3208 }
3209
3210 u1 type_path_kind = type_annotations_typeArray->at(byte_i_ref);
3211 byte_i_ref += 1;
3212 u1 type_argument_index = type_annotations_typeArray->at(byte_i_ref);
3213 byte_i_ref += 1;
3214
3215 log_debug(redefine, class, annotation)
3216 ("type_path: path[%d]: type_path_kind=%d, type_argument_index=%d",
3217 calc_path_length, type_path_kind, type_argument_index);
3218
3219 if (type_path_kind > 3 || (type_path_kind != 3 && type_argument_index != 0)) {
3220 // not enough room for a path
3221 log_debug(redefine, class, annotation)("inconsistent type_path values");
3222 return false;
3223 }
3224 }
3225 assert(path_length == calc_path_length, "sanity check");
3226
3227 return true;
3228 } // end skip_type_annotation_type_path()
3229
3230
3231 // Rewrite constant pool references in the method's stackmap table.
3232 // These "structures" are adapted from the StackMapTable_attribute that
3233 // is described in section 4.8.4 of the 6.0 version of the VM spec
3234 // (dated 2005.10.26):
3235 // file:///net/quincunx.sfbay/export/gbracha/ClassFile-Java6.pdf
3236 //
3237 // stack_map {
3238 // u2 number_of_entries;
3239 // stack_map_frame entries[number_of_entries];
3240 // }
3241 //
3242 void VM_RedefineClasses::rewrite_cp_refs_in_stack_map_table(
3243 const methodHandle& method) {
3244
3245 if (!method->has_stackmap_table()) {
3246 return;
3247 }
3248
3249 AnnotationArray* stackmap_data = method->stackmap_data();
3250 address stackmap_p = (address)stackmap_data->adr_at(0);
3251 address stackmap_end = stackmap_p + stackmap_data->length();
3252
3253 assert(stackmap_p + 2 <= stackmap_end, "no room for number_of_entries");
3254 u2 number_of_entries = Bytes::get_Java_u2(stackmap_p);
3255 stackmap_p += 2;
3256
3257 log_debug(redefine, class, stackmap)("number_of_entries=%u", number_of_entries);
3258
3259 // walk through each stack_map_frame
3260 u2 calc_number_of_entries = 0;
3261 for (; calc_number_of_entries < number_of_entries; calc_number_of_entries++) {
3262 // The stack_map_frame structure is a u1 frame_type followed by
3263 // 0 or more bytes of data:
3264 //
3265 // union stack_map_frame {
3266 // same_frame;
3267 // same_locals_1_stack_item_frame;
3268 // same_locals_1_stack_item_frame_extended;
3269 // chop_frame;
3270 // same_frame_extended;
3271 // append_frame;
3272 // full_frame;
3273 // }
3274
3275 assert(stackmap_p + 1 <= stackmap_end, "no room for frame_type");
3276 u1 frame_type = *stackmap_p;
3277 stackmap_p++;
3278
3279 // same_frame {
3280 // u1 frame_type = SAME; /* 0-63 */
3281 // }
3282 if (frame_type <= 63) {
3283 // nothing more to do for same_frame
3284 }
3285
3286 // same_locals_1_stack_item_frame {
3287 // u1 frame_type = SAME_LOCALS_1_STACK_ITEM; /* 64-127 */
3288 // verification_type_info stack[1];
3289 // }
3290 else if (frame_type >= 64 && frame_type <= 127) {
3291 rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
3292 calc_number_of_entries, frame_type);
3293 }
3294
3295 // reserved for future use
3296 else if (frame_type >= 128 && frame_type <= 246) {
3297 // nothing more to do for reserved frame_types
3298 }
3299
3300 // same_locals_1_stack_item_frame_extended {
3301 // u1 frame_type = SAME_LOCALS_1_STACK_ITEM_EXTENDED; /* 247 */
3302 // u2 offset_delta;
3303 // verification_type_info stack[1];
3304 // }
3305 else if (frame_type == 247) {
3306 stackmap_p += 2;
3307 rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
3308 calc_number_of_entries, frame_type);
3309 }
3310
3311 // chop_frame {
3312 // u1 frame_type = CHOP; /* 248-250 */
3313 // u2 offset_delta;
3314 // }
3315 else if (frame_type >= 248 && frame_type <= 250) {
3316 stackmap_p += 2;
3317 }
3318
3319 // same_frame_extended {
3320 // u1 frame_type = SAME_FRAME_EXTENDED; /* 251*/
3321 // u2 offset_delta;
3322 // }
3323 else if (frame_type == 251) {
3324 stackmap_p += 2;
3325 }
3326
3327 // append_frame {
3328 // u1 frame_type = APPEND; /* 252-254 */
3329 // u2 offset_delta;
3330 // verification_type_info locals[frame_type - 251];
3331 // }
3332 else if (frame_type >= 252 && frame_type <= 254) {
3333 assert(stackmap_p + 2 <= stackmap_end,
3334 "no room for offset_delta");
3335 stackmap_p += 2;
3336 u1 len = frame_type - 251;
3337 for (u1 i = 0; i < len; i++) {
3338 rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
3339 calc_number_of_entries, frame_type);
3340 }
3341 }
3342
3343 // full_frame {
3344 // u1 frame_type = FULL_FRAME; /* 255 */
3345 // u2 offset_delta;
3346 // u2 number_of_locals;
3347 // verification_type_info locals[number_of_locals];
3348 // u2 number_of_stack_items;
3349 // verification_type_info stack[number_of_stack_items];
3350 // }
3351 else if (frame_type == 255) {
3352 assert(stackmap_p + 2 + 2 <= stackmap_end,
3353 "no room for smallest full_frame");
3354 stackmap_p += 2;
3355
3356 u2 number_of_locals = Bytes::get_Java_u2(stackmap_p);
3357 stackmap_p += 2;
3358
3359 for (u2 locals_i = 0; locals_i < number_of_locals; locals_i++) {
3360 rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
3361 calc_number_of_entries, frame_type);
3362 }
3363
3364 // Use the largest size for the number_of_stack_items, but only get
3365 // the right number of bytes.
3366 u2 number_of_stack_items = Bytes::get_Java_u2(stackmap_p);
3367 stackmap_p += 2;
3368
3369 for (u2 stack_i = 0; stack_i < number_of_stack_items; stack_i++) {
3370 rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
3371 calc_number_of_entries, frame_type);
3372 }
3373 }
3374 } // end while there is a stack_map_frame
3375 assert(number_of_entries == calc_number_of_entries, "sanity check");
3376 } // end rewrite_cp_refs_in_stack_map_table()
3377
3378
3379 // Rewrite constant pool references in the verification type info
3380 // portion of the method's stackmap table. These "structures" are
3381 // adapted from the StackMapTable_attribute that is described in
3382 // section 4.8.4 of the 6.0 version of the VM spec (dated 2005.10.26):
3383 // file:///net/quincunx.sfbay/export/gbracha/ClassFile-Java6.pdf
3384 //
3385 // The verification_type_info structure is a u1 tag followed by 0 or
3386 // more bytes of data:
3387 //
3388 // union verification_type_info {
3389 // Top_variable_info;
3390 // Integer_variable_info;
3391 // Float_variable_info;
3392 // Long_variable_info;
3393 // Double_variable_info;
3394 // Null_variable_info;
3395 // UninitializedThis_variable_info;
3396 // Object_variable_info;
3397 // Uninitialized_variable_info;
3398 // }
3399 //
3400 void VM_RedefineClasses::rewrite_cp_refs_in_verification_type_info(
3401 address& stackmap_p_ref, address stackmap_end, u2 frame_i,
3402 u1 frame_type) {
3403
3404 assert(stackmap_p_ref + 1 <= stackmap_end, "no room for tag");
3405 u1 tag = *stackmap_p_ref;
3406 stackmap_p_ref++;
3407
3408 switch (tag) {
3409 // Top_variable_info {
3410 // u1 tag = ITEM_Top; /* 0 */
3411 // }
3412 // verificationType.hpp has zero as ITEM_Bogus instead of ITEM_Top
3413 case 0: // fall through
3414
3415 // Integer_variable_info {
3416 // u1 tag = ITEM_Integer; /* 1 */
3417 // }
3418 case ITEM_Integer: // fall through
3419
3420 // Float_variable_info {
3421 // u1 tag = ITEM_Float; /* 2 */
3422 // }
3423 case ITEM_Float: // fall through
3424
3425 // Double_variable_info {
3426 // u1 tag = ITEM_Double; /* 3 */
3427 // }
3428 case ITEM_Double: // fall through
3429
3430 // Long_variable_info {
3431 // u1 tag = ITEM_Long; /* 4 */
3432 // }
3433 case ITEM_Long: // fall through
3434
3435 // Null_variable_info {
3436 // u1 tag = ITEM_Null; /* 5 */
3437 // }
3438 case ITEM_Null: // fall through
3439
3440 // UninitializedThis_variable_info {
3441 // u1 tag = ITEM_UninitializedThis; /* 6 */
3442 // }
3443 case ITEM_UninitializedThis:
3444 // nothing more to do for the above tag types
3445 break;
3446
3447 // Object_variable_info {
3448 // u1 tag = ITEM_Object; /* 7 */
3449 // u2 cpool_index;
3450 // }
3451 case ITEM_Object:
3452 {
3453 assert(stackmap_p_ref + 2 <= stackmap_end, "no room for cpool_index");
3454 u2 cpool_index = Bytes::get_Java_u2(stackmap_p_ref);
3455 u2 new_cp_index = find_new_index(cpool_index);
3456 if (new_cp_index != 0) {
3457 log_debug(redefine, class, stackmap)("mapped old cpool_index=%d", cpool_index);
3458 Bytes::put_Java_u2(stackmap_p_ref, new_cp_index);
3459 cpool_index = new_cp_index;
3460 }
3461 stackmap_p_ref += 2;
3462
3463 log_debug(redefine, class, stackmap)
3464 ("frame_i=%u, frame_type=%u, cpool_index=%d", frame_i, frame_type, cpool_index);
3465 } break;
3466
3467 // Uninitialized_variable_info {
3468 // u1 tag = ITEM_Uninitialized; /* 8 */
3469 // u2 offset;
3470 // }
3471 case ITEM_Uninitialized:
3472 assert(stackmap_p_ref + 2 <= stackmap_end, "no room for offset");
3473 stackmap_p_ref += 2;
3474 break;
3475
3476 default:
3477 log_debug(redefine, class, stackmap)("frame_i=%u, frame_type=%u, bad tag=0x%x", frame_i, frame_type, tag);
3478 ShouldNotReachHere();
3479 break;
3480 } // end switch (tag)
3481 } // end rewrite_cp_refs_in_verification_type_info()
3482
3483
3484 // Change the constant pool associated with klass scratch_class to scratch_cp.
3485 // scratch_cp_length elements are copied from scratch_cp to a smaller constant pool
3486 // and the smaller constant pool is associated with scratch_class.
3487 void VM_RedefineClasses::set_new_constant_pool(
3488 ClassLoaderData* loader_data,
3489 InstanceKlass* scratch_class, constantPoolHandle scratch_cp,
3490 int scratch_cp_length, TRAPS) {
3491 assert(scratch_cp->length() >= scratch_cp_length, "sanity check");
3492
3493 // scratch_cp is a merged constant pool and has enough space for a
3494 // worst case merge situation. We want to associate the minimum
3495 // sized constant pool with the klass to save space.
3496 ConstantPool* cp = ConstantPool::allocate(loader_data, scratch_cp_length, CHECK);
3497 constantPoolHandle smaller_cp(THREAD, cp);
3498
3499 // preserve version() value in the smaller copy
3500 int version = scratch_cp->version();
3501 assert(version != 0, "sanity check");
3502 smaller_cp->set_version(version);
3503
3504 // attach klass to new constant pool
3505 // reference to the cp holder is needed for copy_operands()
3506 smaller_cp->set_pool_holder(scratch_class);
3507
3508 smaller_cp->copy_fields(scratch_cp());
3509
3510 scratch_cp->copy_cp_to(1, scratch_cp_length - 1, smaller_cp, 1, THREAD);
3511 if (HAS_PENDING_EXCEPTION) {
3512 // Exception is handled in the caller
3513 loader_data->add_to_deallocate_list(smaller_cp());
3514 return;
3515 }
3516 scratch_cp = smaller_cp;
3517
3518 // attach new constant pool to klass
3519 scratch_class->set_constants(scratch_cp());
3520 scratch_cp->initialize_unresolved_klasses(loader_data, CHECK);
3521
3522 int i; // for portability
3523
3524 // update each field in klass to use new constant pool indices as needed
3525 int java_fields;
3526 int injected_fields;
3527 bool update_required = false;
3528 GrowableArray<FieldInfo>* fields = FieldInfoStream::create_FieldInfoArray(scratch_class->fieldinfo_stream(), &java_fields, &injected_fields);
3529 for (int i = 0; i < java_fields; i++) {
3530 FieldInfo* fi = fields->adr_at(i);
3531 jshort cur_index = fi->name_index();
3532 jshort new_index = find_new_index(cur_index);
3533 if (new_index != 0) {
3534 log_trace(redefine, class, constantpool)("field-name_index change: %d to %d", cur_index, new_index);
3535 fi->set_name_index(new_index);
3536 update_required = true;
3537 }
3538 cur_index = fi->signature_index();
3539 new_index = find_new_index(cur_index);
3540 if (new_index != 0) {
3541 log_trace(redefine, class, constantpool)("field-signature_index change: %d to %d", cur_index, new_index);
3542 fi->set_signature_index(new_index);
3543 update_required = true;
3544 }
3545 cur_index = fi->initializer_index();
3546 new_index = find_new_index(cur_index);
3547 if (new_index != 0) {
3548 log_trace(redefine, class, constantpool)("field-initval_index change: %d to %d", cur_index, new_index);
3549 fi->set_initializer_index(new_index);
3550 update_required = true;
3551 }
3552 cur_index = fi->generic_signature_index();
3553 new_index = find_new_index(cur_index);
3554 if (new_index != 0) {
3555 log_trace(redefine, class, constantpool)("field-generic_signature change: %d to %d", cur_index, new_index);
3556 fi->set_generic_signature_index(new_index);
3557 update_required = true;
3558 }
3559 }
3560 if (update_required) {
3561 Array<u1>* old_stream = scratch_class->fieldinfo_stream();
3562 assert(fields->length() == (java_fields + injected_fields), "Must be");
3563 Array<u1>* new_fis = FieldInfoStream::create_FieldInfoStream(fields, java_fields, injected_fields, scratch_class->class_loader_data(), CHECK);
3564 scratch_class->set_fieldinfo_stream(new_fis);
3565 MetadataFactory::free_array<u1>(scratch_class->class_loader_data(), old_stream);
3566 }
3567
3568 // Update constant pool indices in the inner classes info to use
3569 // new constant indices as needed. The inner classes info is a
3570 // quadruple:
3571 // (inner_class_info, outer_class_info, inner_name, inner_access_flags)
3572 InnerClassesIterator iter(scratch_class);
3573 for (; !iter.done(); iter.next()) {
3574 int cur_index = iter.inner_class_info_index();
3575 if (cur_index == 0) {
3576 continue; // JVM spec. allows null inner class refs so skip it
3577 }
3578 u2 new_index = find_new_index(cur_index);
3579 if (new_index != 0) {
3580 log_trace(redefine, class, constantpool)("inner_class_info change: %d to %d", cur_index, new_index);
3581 iter.set_inner_class_info_index(new_index);
3582 }
3583 cur_index = iter.outer_class_info_index();
3584 new_index = find_new_index(cur_index);
3585 if (new_index != 0) {
3586 log_trace(redefine, class, constantpool)("outer_class_info change: %d to %d", cur_index, new_index);
3587 iter.set_outer_class_info_index(new_index);
3588 }
3589 cur_index = iter.inner_name_index();
3590 new_index = find_new_index(cur_index);
3591 if (new_index != 0) {
3592 log_trace(redefine, class, constantpool)("inner_name change: %d to %d", cur_index, new_index);
3593 iter.set_inner_name_index(new_index);
3594 }
3595 } // end for each inner class
3596
3597 // Attach each method in klass to the new constant pool and update
3598 // to use new constant pool indices as needed:
3599 Array<Method*>* methods = scratch_class->methods();
3600 for (i = methods->length() - 1; i >= 0; i--) {
3601 methodHandle method(THREAD, methods->at(i));
3602 method->set_constants(scratch_cp());
3603
3604 u2 new_index = find_new_index(method->name_index());
3605 if (new_index != 0) {
3606 log_trace(redefine, class, constantpool)
3607 ("method-name_index change: %d to %d", method->name_index(), new_index);
3608 method->set_name_index(new_index);
3609 }
3610 new_index = find_new_index(method->signature_index());
3611 if (new_index != 0) {
3612 log_trace(redefine, class, constantpool)
3613 ("method-signature_index change: %d to %d", method->signature_index(), new_index);
3614 method->set_signature_index(new_index);
3615 }
3616 new_index = find_new_index(method->generic_signature_index());
3617 if (new_index != 0) {
3618 log_trace(redefine, class, constantpool)
3619 ("method-generic_signature_index change: %d to %d", method->generic_signature_index(), new_index);
3620 method->constMethod()->set_generic_signature_index(new_index);
3621 }
3622
3623 // Update constant pool indices in the method's checked exception
3624 // table to use new constant indices as needed.
3625 int cext_length = method->checked_exceptions_length();
3626 if (cext_length > 0) {
3627 CheckedExceptionElement * cext_table =
3628 method->checked_exceptions_start();
3629 for (int j = 0; j < cext_length; j++) {
3630 int cur_index = cext_table[j].class_cp_index;
3631 int new_index = find_new_index(cur_index);
3632 if (new_index != 0) {
3633 log_trace(redefine, class, constantpool)("cext-class_cp_index change: %d to %d", cur_index, new_index);
3634 cext_table[j].class_cp_index = (u2)new_index;
3635 }
3636 } // end for each checked exception table entry
3637 } // end if there are checked exception table entries
3638
3639 // Update each catch type index in the method's exception table
3640 // to use new constant pool indices as needed. The exception table
3641 // holds quadruple entries of the form:
3642 // (beg_bci, end_bci, handler_bci, klass_index)
3643
3644 ExceptionTable ex_table(method());
3645 int ext_length = ex_table.length();
3646
3647 for (int j = 0; j < ext_length; j ++) {
3648 int cur_index = ex_table.catch_type_index(j);
3649 u2 new_index = find_new_index(cur_index);
3650 if (new_index != 0) {
3651 log_trace(redefine, class, constantpool)("ext-klass_index change: %d to %d", cur_index, new_index);
3652 ex_table.set_catch_type_index(j, new_index);
3653 }
3654 } // end for each exception table entry
3655
3656 // Update constant pool indices in the method's local variable
3657 // table to use new constant indices as needed. The local variable
3658 // table hold sextuple entries of the form:
3659 // (start_pc, length, name_index, descriptor_index, signature_index, slot)
3660 int lvt_length = method->localvariable_table_length();
3661 if (lvt_length > 0) {
3662 LocalVariableTableElement * lv_table =
3663 method->localvariable_table_start();
3664 for (int j = 0; j < lvt_length; j++) {
3665 int cur_index = lv_table[j].name_cp_index;
3666 int new_index = find_new_index(cur_index);
3667 if (new_index != 0) {
3668 log_trace(redefine, class, constantpool)("lvt-name_cp_index change: %d to %d", cur_index, new_index);
3669 lv_table[j].name_cp_index = (u2)new_index;
3670 }
3671 cur_index = lv_table[j].descriptor_cp_index;
3672 new_index = find_new_index(cur_index);
3673 if (new_index != 0) {
3674 log_trace(redefine, class, constantpool)("lvt-descriptor_cp_index change: %d to %d", cur_index, new_index);
3675 lv_table[j].descriptor_cp_index = (u2)new_index;
3676 }
3677 cur_index = lv_table[j].signature_cp_index;
3678 new_index = find_new_index(cur_index);
3679 if (new_index != 0) {
3680 log_trace(redefine, class, constantpool)("lvt-signature_cp_index change: %d to %d", cur_index, new_index);
3681 lv_table[j].signature_cp_index = (u2)new_index;
3682 }
3683 } // end for each local variable table entry
3684 } // end if there are local variable table entries
3685
3686 // Update constant pool indices in the method's method_parameters.
3687 int mp_length = method->method_parameters_length();
3688 if (mp_length > 0) {
3689 MethodParametersElement* elem = method->method_parameters_start();
3690 for (int j = 0; j < mp_length; j++) {
3691 const int cp_index = elem[j].name_cp_index;
3692 const int new_cp_index = find_new_index(cp_index);
3693 if (new_cp_index != 0) {
3694 elem[j].name_cp_index = (u2)new_cp_index;
3695 }
3696 }
3697 }
3698
3699 rewrite_cp_refs_in_stack_map_table(method);
3700 } // end for each method
3701 } // end set_new_constant_pool()
3702
3703
3704 // Unevolving classes may point to methods of the_class directly
3705 // from their constant pool caches, itables, and/or vtables. We
3706 // use the ClassLoaderDataGraph::classes_do() facility and this helper
3707 // to fix up these pointers. MethodData also points to old methods and
3708 // must be cleaned.
3709
3710 // Adjust cpools and vtables closure
3711 void VM_RedefineClasses::AdjustAndCleanMetadata::do_klass(Klass* k) {
3712
3713 // This is a very busy routine. We don't want too much tracing
3714 // printed out.
3715 bool trace_name_printed = false;
3716
3717 // If the class being redefined is java.lang.Object, we need to fix all
3718 // array class vtables also. The _has_redefined_Object flag is global.
3719 // Once the java.lang.Object has been redefined (by the current or one
3720 // of the previous VM_RedefineClasses operations) we have to always
3721 // adjust method entries for array classes.
3722 if (k->is_array_klass() && _has_redefined_Object) {
3723 k->vtable().adjust_method_entries(&trace_name_printed);
3724
3725 } else if (k->is_instance_klass()) {
3726 HandleMark hm(_thread);
3727 InstanceKlass *ik = InstanceKlass::cast(k);
3728
3729 // Clean MethodData of this class's methods so they don't refer to
3730 // old methods that are no longer running.
3731 Array<Method*>* methods = ik->methods();
3732 int num_methods = methods->length();
3733 for (int index = 0; index < num_methods; ++index) {
3734 if (methods->at(index)->method_data() != nullptr) {
3735 methods->at(index)->method_data()->clean_weak_method_links();
3736 }
3737 }
3738
3739 // Adjust all vtables, default methods and itables, to clean out old methods.
3740 ResourceMark rm(_thread);
3741 if (ik->vtable_length() > 0) {
3742 ik->vtable().adjust_method_entries(&trace_name_printed);
3743 ik->adjust_default_methods(&trace_name_printed);
3744 }
3745
3746 if (ik->itable_length() > 0) {
3747 ik->itable().adjust_method_entries(&trace_name_printed);
3748 }
3749
3750 // The constant pools in other classes (other_cp) can refer to
3751 // old methods. We have to update method information in
3752 // other_cp's cache. If other_cp has a previous version, then we
3753 // have to repeat the process for each previous version. The
3754 // constant pool cache holds the Method*s for non-virtual
3755 // methods and for virtual, final methods.
3756 //
3757 // Special case: if the current class is being redefined by the current
3758 // VM_RedefineClasses operation, then new_cp has already been attached
3759 // to the_class and old_cp has already been added as a previous version.
3760 // The new_cp doesn't have any cached references to old methods so it
3761 // doesn't need to be updated and we could optimize by skipping it.
3762 // However, the current class can be marked as being redefined by another
3763 // VM_RedefineClasses operation which has already executed its doit_prologue
3764 // and needs cpcache method entries adjusted. For simplicity, the cpcache
3765 // update is done unconditionally. It should result in doing nothing for
3766 // classes being redefined by the current VM_RedefineClasses operation.
3767 // Method entries in the previous version(s) are adjusted as well.
3768 ConstantPoolCache* cp_cache;
3769
3770 // this klass' constant pool cache may need adjustment
3771 ConstantPool* other_cp = ik->constants();
3772 cp_cache = other_cp->cache();
3773 if (cp_cache != nullptr) {
3774 cp_cache->adjust_method_entries(&trace_name_printed);
3775 }
3776
3777 // the previous versions' constant pool caches may need adjustment
3778 for (InstanceKlass* pv_node = ik->previous_versions();
3779 pv_node != nullptr;
3780 pv_node = pv_node->previous_versions()) {
3781 cp_cache = pv_node->constants()->cache();
3782 if (cp_cache != nullptr) {
3783 cp_cache->adjust_method_entries(&trace_name_printed);
3784 }
3785 }
3786 }
3787 }
3788
3789 void VM_RedefineClasses::update_jmethod_ids() {
3790 for (int j = 0; j < _matching_methods_length; ++j) {
3791 Method* old_method = _matching_old_methods[j];
3792 jmethodID jmid = old_method->find_jmethod_id_or_null();
3793 if (jmid != nullptr) {
3794 // There is a jmethodID, change it to point to the new method
3795 Method* new_method = _matching_new_methods[j];
3796 Method::change_method_associated_with_jmethod_id(jmid, new_method);
3797 assert(Method::resolve_jmethod_id(jmid) == _matching_new_methods[j],
3798 "should be replaced");
3799 }
3800 }
3801 }
3802
3803 int VM_RedefineClasses::check_methods_and_mark_as_obsolete() {
3804 int emcp_method_count = 0;
3805 int obsolete_count = 0;
3806 int old_index = 0;
3807 for (int j = 0; j < _matching_methods_length; ++j, ++old_index) {
3808 Method* old_method = _matching_old_methods[j];
3809 Method* new_method = _matching_new_methods[j];
3810 Method* old_array_method;
3811
3812 // Maintain an old_index into the _old_methods array by skipping
3813 // deleted methods
3814 while ((old_array_method = _old_methods->at(old_index)) != old_method) {
3815 ++old_index;
3816 }
3817
3818 if (MethodComparator::methods_EMCP(old_method, new_method)) {
3819 // The EMCP definition from JSR-163 requires the bytecodes to be
3820 // the same with the exception of constant pool indices which may
3821 // differ. However, the constants referred to by those indices
3822 // must be the same.
3823 //
3824 // We use methods_EMCP() for comparison since constant pool
3825 // merging can remove duplicate constant pool entries that were
3826 // present in the old method and removed from the rewritten new
3827 // method. A faster binary comparison function would consider the
3828 // old and new methods to be different when they are actually
3829 // EMCP.
3830 //
3831 // The old and new methods are EMCP and you would think that we
3832 // could get rid of one of them here and now and save some space.
3833 // However, the concept of EMCP only considers the bytecodes and
3834 // the constant pool entries in the comparison. Other things,
3835 // e.g., the line number table (LNT) or the local variable table
3836 // (LVT) don't count in the comparison. So the new (and EMCP)
3837 // method can have a new LNT that we need so we can't just
3838 // overwrite the new method with the old method.
3839 //
3840 // When this routine is called, we have already attached the new
3841 // methods to the_class so the old methods are effectively
3842 // overwritten. However, if an old method is still executing,
3843 // then the old method cannot be collected until sometime after
3844 // the old method call has returned. So the overwriting of old
3845 // methods by new methods will save us space except for those
3846 // (hopefully few) old methods that are still executing.
3847 //
3848 // A method refers to a ConstMethod* and this presents another
3849 // possible avenue to space savings. The ConstMethod* in the
3850 // new method contains possibly new attributes (LNT, LVT, etc).
3851 // At first glance, it seems possible to save space by replacing
3852 // the ConstMethod* in the old method with the ConstMethod*
3853 // from the new method. The old and new methods would share the
3854 // same ConstMethod* and we would save the space occupied by
3855 // the old ConstMethod*. However, the ConstMethod* contains
3856 // a back reference to the containing method. Sharing the
3857 // ConstMethod* between two methods could lead to confusion in
3858 // the code that uses the back reference. This would lead to
3859 // brittle code that could be broken in non-obvious ways now or
3860 // in the future.
3861 //
3862 // Another possibility is to copy the ConstMethod* from the new
3863 // method to the old method and then overwrite the new method with
3864 // the old method. Since the ConstMethod* contains the bytecodes
3865 // for the method embedded in the oop, this option would change
3866 // the bytecodes out from under any threads executing the old
3867 // method and make the thread's bcp invalid. Since EMCP requires
3868 // that the bytecodes be the same modulo constant pool indices, it
3869 // is straight forward to compute the correct new bcp in the new
3870 // ConstMethod* from the old bcp in the old ConstMethod*. The
3871 // time consuming part would be searching all the frames in all
3872 // of the threads to find all of the calls to the old method.
3873 //
3874 // It looks like we will have to live with the limited savings
3875 // that we get from effectively overwriting the old methods
3876 // when the new methods are attached to the_class.
3877
3878 // Count number of methods that are EMCP. The method will be marked
3879 // old but not obsolete if it is EMCP.
3880 emcp_method_count++;
3881
3882 // An EMCP method is _not_ obsolete. An obsolete method has a
3883 // different jmethodID than the current method. An EMCP method
3884 // has the same jmethodID as the current method. Having the
3885 // same jmethodID for all EMCP versions of a method allows for
3886 // a consistent view of the EMCP methods regardless of which
3887 // EMCP method you happen to have in hand. For example, a
3888 // breakpoint set in one EMCP method will work for all EMCP
3889 // versions of the method including the current one.
3890 } else {
3891 // mark obsolete methods as such
3892 old_method->set_is_obsolete();
3893 obsolete_count++;
3894
3895 // obsolete methods need a unique idnum so they become new entries in
3896 // the jmethodID cache in InstanceKlass
3897 assert(old_method->method_idnum() == new_method->method_idnum(), "must match");
3898 u2 num = InstanceKlass::cast(_the_class)->next_method_idnum();
3899 if (num != ConstMethod::UNSET_IDNUM) {
3900 old_method->set_method_idnum(num);
3901 }
3902
3903 // With tracing we try not to "yack" too much. The position of
3904 // this trace assumes there are fewer obsolete methods than
3905 // EMCP methods.
3906 if (log_is_enabled(Trace, redefine, class, obsolete, mark)) {
3907 ResourceMark rm;
3908 log_trace(redefine, class, obsolete, mark)
3909 ("mark %s(%s) as obsolete", old_method->name()->as_C_string(), old_method->signature()->as_C_string());
3910 }
3911 }
3912 old_method->set_is_old();
3913 }
3914 for (int i = 0; i < _deleted_methods_length; ++i) {
3915 Method* old_method = _deleted_methods[i];
3916
3917 assert(!old_method->has_vtable_index(),
3918 "cannot delete methods with vtable entries");;
3919
3920 // Mark all deleted methods as old, obsolete and deleted
3921 old_method->set_is_deleted();
3922 old_method->set_is_old();
3923 old_method->set_is_obsolete();
3924 ++obsolete_count;
3925 // With tracing we try not to "yack" too much. The position of
3926 // this trace assumes there are fewer obsolete methods than
3927 // EMCP methods.
3928 if (log_is_enabled(Trace, redefine, class, obsolete, mark)) {
3929 ResourceMark rm;
3930 log_trace(redefine, class, obsolete, mark)
3931 ("mark deleted %s(%s) as obsolete", old_method->name()->as_C_string(), old_method->signature()->as_C_string());
3932 }
3933 }
3934 assert((emcp_method_count + obsolete_count) == _old_methods->length(),
3935 "sanity check");
3936 log_trace(redefine, class, obsolete, mark)("EMCP_cnt=%d, obsolete_cnt=%d", emcp_method_count, obsolete_count);
3937 return emcp_method_count;
3938 }
3939
3940 // This internal class transfers the native function registration from old methods
3941 // to new methods. It is designed to handle both the simple case of unchanged
3942 // native methods and the complex cases of native method prefixes being added and/or
3943 // removed.
3944 // It expects only to be used during the VM_RedefineClasses op (a safepoint).
3945 //
3946 // This class is used after the new methods have been installed in "the_class".
3947 //
3948 // So, for example, the following must be handled. Where 'm' is a method and
3949 // a number followed by an underscore is a prefix.
3950 //
3951 // Old Name New Name
3952 // Simple transfer to new method m -> m
3953 // Add prefix m -> 1_m
3954 // Remove prefix 1_m -> m
3955 // Simultaneous add of prefixes m -> 3_2_1_m
3956 // Simultaneous removal of prefixes 3_2_1_m -> m
3957 // Simultaneous add and remove 1_m -> 2_m
3958 // Same, caused by prefix removal only 3_2_1_m -> 3_2_m
3959 //
3960 class TransferNativeFunctionRegistration {
3961 private:
3962 InstanceKlass* the_class;
3963 int prefix_count;
3964 char** prefixes;
3965
3966 // Recursively search the binary tree of possibly prefixed method names.
3967 // Iteration could be used if all agents were well behaved. Full tree walk is
3968 // more resilent to agents not cleaning up intermediate methods.
3969 // Branch at each depth in the binary tree is:
3970 // (1) without the prefix.
3971 // (2) with the prefix.
3972 // where 'prefix' is the prefix at that 'depth' (first prefix, second prefix,...)
3973 Method* search_prefix_name_space(int depth, char* name_str, size_t name_len,
3974 Symbol* signature) {
3975 TempNewSymbol name_symbol = SymbolTable::probe(name_str, (int)name_len);
3976 if (name_symbol != nullptr) {
3977 Method* method = the_class->lookup_method(name_symbol, signature);
3978 if (method != nullptr) {
3979 // Even if prefixed, intermediate methods must exist.
3980 if (method->is_native()) {
3981 // Wahoo, we found a (possibly prefixed) version of the method, return it.
3982 return method;
3983 }
3984 if (depth < prefix_count) {
3985 // Try applying further prefixes (other than this one).
3986 method = search_prefix_name_space(depth+1, name_str, name_len, signature);
3987 if (method != nullptr) {
3988 return method; // found
3989 }
3990
3991 // Try adding this prefix to the method name and see if it matches
3992 // another method name.
3993 char* prefix = prefixes[depth];
3994 size_t prefix_len = strlen(prefix);
3995 size_t trial_len = name_len + prefix_len;
3996 char* trial_name_str = NEW_RESOURCE_ARRAY(char, trial_len + 1);
3997 strcpy(trial_name_str, prefix);
3998 strcat(trial_name_str, name_str);
3999 method = search_prefix_name_space(depth+1, trial_name_str, trial_len,
4000 signature);
4001 if (method != nullptr) {
4002 // If found along this branch, it was prefixed, mark as such
4003 method->set_is_prefixed_native();
4004 return method; // found
4005 }
4006 }
4007 }
4008 }
4009 return nullptr; // This whole branch bore nothing
4010 }
4011
4012 // Return the method name with old prefixes stripped away.
4013 char* method_name_without_prefixes(Method* method) {
4014 Symbol* name = method->name();
4015 char* name_str = name->as_utf8();
4016
4017 // Old prefixing may be defunct, strip prefixes, if any.
4018 for (int i = prefix_count-1; i >= 0; i--) {
4019 char* prefix = prefixes[i];
4020 size_t prefix_len = strlen(prefix);
4021 if (strncmp(prefix, name_str, prefix_len) == 0) {
4022 name_str += prefix_len;
4023 }
4024 }
4025 return name_str;
4026 }
4027
4028 // Strip any prefixes off the old native method, then try to find a
4029 // (possibly prefixed) new native that matches it.
4030 Method* strip_and_search_for_new_native(Method* method) {
4031 ResourceMark rm;
4032 char* name_str = method_name_without_prefixes(method);
4033 return search_prefix_name_space(0, name_str, strlen(name_str),
4034 method->signature());
4035 }
4036
4037 public:
4038
4039 // Construct a native method transfer processor for this class.
4040 TransferNativeFunctionRegistration(InstanceKlass* _the_class) {
4041 assert(SafepointSynchronize::is_at_safepoint(), "sanity check");
4042
4043 the_class = _the_class;
4044 prefixes = JvmtiExport::get_all_native_method_prefixes(&prefix_count);
4045 }
4046
4047 // Attempt to transfer any of the old or deleted methods that are native
4048 void transfer_registrations(Method** old_methods, int methods_length) {
4049 for (int j = 0; j < methods_length; j++) {
4050 Method* old_method = old_methods[j];
4051
4052 if (old_method->is_native() && old_method->has_native_function()) {
4053 Method* new_method = strip_and_search_for_new_native(old_method);
4054 if (new_method != nullptr) {
4055 // Actually set the native function in the new method.
4056 // Redefine does not send events (except CFLH), certainly not this
4057 // behind the scenes re-registration.
4058 new_method->set_native_function(old_method->native_function(),
4059 !Method::native_bind_event_is_interesting);
4060 }
4061 }
4062 }
4063 }
4064 };
4065
4066 // Don't lose the association between a native method and its JNI function.
4067 void VM_RedefineClasses::transfer_old_native_function_registrations(InstanceKlass* the_class) {
4068 TransferNativeFunctionRegistration transfer(the_class);
4069 transfer.transfer_registrations(_deleted_methods, _deleted_methods_length);
4070 transfer.transfer_registrations(_matching_old_methods, _matching_methods_length);
4071 }
4072
4073 // Deoptimize all compiled code that depends on the classes redefined.
4074 //
4075 // If the can_redefine_classes capability is obtained in the onload
4076 // phase or 'AlwaysRecordEvolDependencies' is true, then the compiler has
4077 // recorded all dependencies from startup. In that case we need only
4078 // deoptimize and throw away all compiled code that depends on the class.
4079 //
4080 // If can_redefine_classes is obtained sometime after the onload phase
4081 // (and 'AlwaysRecordEvolDependencies' is false) then the dependency
4082 // information may be incomplete. In that case the first call to
4083 // RedefineClasses causes all compiled code to be thrown away. As
4084 // can_redefine_classes has been obtained then all future compilations will
4085 // record dependencies so second and subsequent calls to RedefineClasses
4086 // need only throw away code that depends on the class.
4087 //
4088
4089 void VM_RedefineClasses::flush_dependent_code() {
4090 assert(SafepointSynchronize::is_at_safepoint(), "sanity check");
4091 assert(JvmtiExport::all_dependencies_are_recorded() || !AlwaysRecordEvolDependencies, "sanity check");
4092
4093 DeoptimizationScope deopt_scope;
4094
4095 // This is the first redefinition, mark all the nmethods for deoptimization
4096 if (!JvmtiExport::all_dependencies_are_recorded()) {
4097 CodeCache::mark_all_nmethods_for_evol_deoptimization(&deopt_scope);
4098 log_debug(redefine, class, nmethod)("Marked all nmethods for deopt");
4099 } else {
4100 CodeCache::mark_dependents_for_evol_deoptimization(&deopt_scope);
4101 log_debug(redefine, class, nmethod)("Marked dependent nmethods for deopt");
4102 }
4103
4104 deopt_scope.deoptimize_marked();
4105
4106 // From now on we know that the dependency information is complete
4107 JvmtiExport::set_all_dependencies_are_recorded(true);
4108 }
4109
4110 void VM_RedefineClasses::compute_added_deleted_matching_methods() {
4111 Method* old_method;
4112 Method* new_method;
4113
4114 _matching_old_methods = NEW_RESOURCE_ARRAY(Method*, _old_methods->length());
4115 _matching_new_methods = NEW_RESOURCE_ARRAY(Method*, _old_methods->length());
4116 _added_methods = NEW_RESOURCE_ARRAY(Method*, _new_methods->length());
4117 _deleted_methods = NEW_RESOURCE_ARRAY(Method*, _old_methods->length());
4118
4119 _matching_methods_length = 0;
4120 _deleted_methods_length = 0;
4121 _added_methods_length = 0;
4122
4123 int nj = 0;
4124 int oj = 0;
4125 while (true) {
4126 if (oj >= _old_methods->length()) {
4127 if (nj >= _new_methods->length()) {
4128 break; // we've looked at everything, done
4129 }
4130 // New method at the end
4131 new_method = _new_methods->at(nj);
4132 _added_methods[_added_methods_length++] = new_method;
4133 ++nj;
4134 } else if (nj >= _new_methods->length()) {
4135 // Old method, at the end, is deleted
4136 old_method = _old_methods->at(oj);
4137 _deleted_methods[_deleted_methods_length++] = old_method;
4138 ++oj;
4139 } else {
4140 old_method = _old_methods->at(oj);
4141 new_method = _new_methods->at(nj);
4142 if (old_method->name() == new_method->name()) {
4143 if (old_method->signature() == new_method->signature()) {
4144 _matching_old_methods[_matching_methods_length ] = old_method;
4145 _matching_new_methods[_matching_methods_length++] = new_method;
4146 ++nj;
4147 ++oj;
4148 } else {
4149 // added overloaded have already been moved to the end,
4150 // so this is a deleted overloaded method
4151 _deleted_methods[_deleted_methods_length++] = old_method;
4152 ++oj;
4153 }
4154 } else { // names don't match
4155 if (old_method->name()->fast_compare(new_method->name()) > 0) {
4156 // new method
4157 _added_methods[_added_methods_length++] = new_method;
4158 ++nj;
4159 } else {
4160 // deleted method
4161 _deleted_methods[_deleted_methods_length++] = old_method;
4162 ++oj;
4163 }
4164 }
4165 }
4166 }
4167 assert(_matching_methods_length + _deleted_methods_length == _old_methods->length(), "sanity");
4168 assert(_matching_methods_length + _added_methods_length == _new_methods->length(), "sanity");
4169 }
4170
4171
4172 void VM_RedefineClasses::swap_annotations(InstanceKlass* the_class,
4173 InstanceKlass* scratch_class) {
4174 // Swap annotation fields values
4175 Annotations* old_annotations = the_class->annotations();
4176 the_class->set_annotations(scratch_class->annotations());
4177 scratch_class->set_annotations(old_annotations);
4178 }
4179
4180
4181 // Install the redefinition of a class:
4182 // - house keeping (flushing breakpoints and caches, deoptimizing
4183 // dependent compiled code)
4184 // - replacing parts in the_class with parts from scratch_class
4185 // - adding a weak reference to track the obsolete but interesting
4186 // parts of the_class
4187 // - adjusting constant pool caches and vtables in other classes
4188 // that refer to methods in the_class. These adjustments use the
4189 // ClassLoaderDataGraph::classes_do() facility which only allows
4190 // a helper method to be specified. The interesting parameters
4191 // that we would like to pass to the helper method are saved in
4192 // static global fields in the VM operation.
4193 void VM_RedefineClasses::redefine_single_class(Thread* current, jclass the_jclass,
4194 InstanceKlass* scratch_class) {
4195
4196 HandleMark hm(current); // make sure handles from this call are freed
4197
4198 if (log_is_enabled(Info, redefine, class, timer)) {
4199 _timer_rsc_phase1.start();
4200 }
4201
4202 InstanceKlass* the_class = get_ik(the_jclass);
4203
4204 // Set a flag to control and optimize adjusting method entries
4205 _has_redefined_Object |= the_class == vmClasses::Object_klass();
4206
4207 // Remove all breakpoints in methods of this class
4208 JvmtiBreakpoints& jvmti_breakpoints = JvmtiCurrentBreakpoints::get_jvmti_breakpoints();
4209 jvmti_breakpoints.clearall_in_class_at_safepoint(the_class);
4210
4211 _old_methods = the_class->methods();
4212 _new_methods = scratch_class->methods();
4213 _the_class = the_class;
4214 compute_added_deleted_matching_methods();
4215 update_jmethod_ids();
4216
4217 _any_class_has_resolved_methods = the_class->has_resolved_methods() || _any_class_has_resolved_methods;
4218
4219 // Attach new constant pool to the original klass. The original
4220 // klass still refers to the old constant pool (for now).
4221 scratch_class->constants()->set_pool_holder(the_class);
4222
4223 #if 0
4224 // In theory, with constant pool merging in place we should be able
4225 // to save space by using the new, merged constant pool in place of
4226 // the old constant pool(s). By "pool(s)" I mean the constant pool in
4227 // the klass version we are replacing now and any constant pool(s) in
4228 // previous versions of klass. Nice theory, doesn't work in practice.
4229 // When this code is enabled, even simple programs throw NullPointer
4230 // exceptions. I'm guessing that this is caused by some constant pool
4231 // cache difference between the new, merged constant pool and the
4232 // constant pool that was just being used by the klass. I'm keeping
4233 // this code around to archive the idea, but the code has to remain
4234 // disabled for now.
4235
4236 // Attach each old method to the new constant pool. This can be
4237 // done here since we are past the bytecode verification and
4238 // constant pool optimization phases.
4239 for (int i = _old_methods->length() - 1; i >= 0; i--) {
4240 Method* method = _old_methods->at(i);
4241 method->set_constants(scratch_class->constants());
4242 }
4243
4244 // NOTE: this doesn't work because you can redefine the same class in two
4245 // threads, each getting their own constant pool data appended to the
4246 // original constant pool. In order for the new methods to work when they
4247 // become old methods, they need to keep their updated copy of the constant pool.
4248
4249 {
4250 // walk all previous versions of the klass
4251 InstanceKlass *ik = the_class;
4252 PreviousVersionWalker pvw(ik);
4253 do {
4254 ik = pvw.next_previous_version();
4255 if (ik != nullptr) {
4256
4257 // attach previous version of klass to the new constant pool
4258 ik->set_constants(scratch_class->constants());
4259
4260 // Attach each method in the previous version of klass to the
4261 // new constant pool
4262 Array<Method*>* prev_methods = ik->methods();
4263 for (int i = prev_methods->length() - 1; i >= 0; i--) {
4264 Method* method = prev_methods->at(i);
4265 method->set_constants(scratch_class->constants());
4266 }
4267 }
4268 } while (ik != nullptr);
4269 }
4270 #endif
4271
4272 // Replace methods and constantpool
4273 the_class->set_methods(_new_methods);
4274 scratch_class->set_methods(_old_methods); // To prevent potential GCing of the old methods,
4275 // and to be able to undo operation easily.
4276
4277 Array<int>* old_ordering = the_class->method_ordering();
4278 the_class->set_method_ordering(scratch_class->method_ordering());
4279 scratch_class->set_method_ordering(old_ordering);
4280
4281 ConstantPool* old_constants = the_class->constants();
4282 the_class->set_constants(scratch_class->constants());
4283 scratch_class->set_constants(old_constants); // See the previous comment.
4284 #if 0
4285 // We are swapping the guts of "the new class" with the guts of "the
4286 // class". Since the old constant pool has just been attached to "the
4287 // new class", it seems logical to set the pool holder in the old
4288 // constant pool also. However, doing this will change the observable
4289 // class hierarchy for any old methods that are still executing. A
4290 // method can query the identity of its "holder" and this query uses
4291 // the method's constant pool link to find the holder. The change in
4292 // holding class from "the class" to "the new class" can confuse
4293 // things.
4294 //
4295 // Setting the old constant pool's holder will also cause
4296 // verification done during vtable initialization below to fail.
4297 // During vtable initialization, the vtable's class is verified to be
4298 // a subtype of the method's holder. The vtable's class is "the
4299 // class" and the method's holder is gotten from the constant pool
4300 // link in the method itself. For "the class"'s directly implemented
4301 // methods, the method holder is "the class" itself (as gotten from
4302 // the new constant pool). The check works fine in this case. The
4303 // check also works fine for methods inherited from super classes.
4304 //
4305 // Miranda methods are a little more complicated. A miranda method is
4306 // provided by an interface when the class implementing the interface
4307 // does not provide its own method. These interfaces are implemented
4308 // internally as an InstanceKlass. These special instanceKlasses
4309 // share the constant pool of the class that "implements" the
4310 // interface. By sharing the constant pool, the method holder of a
4311 // miranda method is the class that "implements" the interface. In a
4312 // non-redefine situation, the subtype check works fine. However, if
4313 // the old constant pool's pool holder is modified, then the check
4314 // fails because there is no class hierarchy relationship between the
4315 // vtable's class and "the new class".
4316
4317 old_constants->set_pool_holder(scratch_class());
4318 #endif
4319
4320 // track number of methods that are EMCP for add_previous_version() call below
4321 int emcp_method_count = check_methods_and_mark_as_obsolete();
4322 transfer_old_native_function_registrations(the_class);
4323
4324 if (scratch_class->get_cached_class_file() != the_class->get_cached_class_file()) {
4325 // 1. the_class doesn't have a cache yet, scratch_class does have a cache.
4326 // 2. The same class can be present twice in the scratch classes list or there
4327 // are multiple concurrent RetransformClasses calls on different threads.
4328 // the_class and scratch_class have the same cached bytes, but different buffers.
4329 // In such cases we need to deallocate one of the buffers.
4330 // 3. RedefineClasses and the_class has cached bytes from a previous transformation.
4331 // In the case we need to use class bytes from scratch_class.
4332 if (the_class->get_cached_class_file() != nullptr) {
4333 os::free(the_class->get_cached_class_file());
4334 }
4335 the_class->set_cached_class_file(scratch_class->get_cached_class_file());
4336 }
4337
4338 // null out in scratch class to not delete twice. The class to be redefined
4339 // always owns these bytes.
4340 scratch_class->set_cached_class_file(nullptr);
4341
4342 // Replace inner_classes
4343 Array<u2>* old_inner_classes = the_class->inner_classes();
4344 the_class->set_inner_classes(scratch_class->inner_classes());
4345 scratch_class->set_inner_classes(old_inner_classes);
4346
4347 // Initialize the vtable and interface table after
4348 // methods have been rewritten
4349 // no exception should happen here since we explicitly
4350 // do not check loader constraints.
4351 // compare_and_normalize_class_versions has already checked:
4352 // - classloaders unchanged, signatures unchanged
4353 // - all instanceKlasses for redefined classes reused & contents updated
4354 the_class->vtable().initialize_vtable();
4355 the_class->itable().initialize_itable();
4356
4357 // Update jmethodID cache if present.
4358 the_class->update_methods_jmethod_cache();
4359
4360 // Copy the "source debug extension" attribute from new class version
4361 the_class->set_source_debug_extension(
4362 scratch_class->source_debug_extension(),
4363 scratch_class->source_debug_extension() == nullptr ? 0 :
4364 (int)strlen(scratch_class->source_debug_extension()));
4365
4366 // Use of javac -g could be different in the old and the new
4367 if (scratch_class->has_localvariable_table() !=
4368 the_class->has_localvariable_table()) {
4369 the_class->set_has_localvariable_table(scratch_class->has_localvariable_table());
4370 }
4371
4372 swap_annotations(the_class, scratch_class);
4373
4374 // Replace minor version number of class file
4375 u2 old_minor_version = the_class->constants()->minor_version();
4376 the_class->constants()->set_minor_version(scratch_class->constants()->minor_version());
4377 scratch_class->constants()->set_minor_version(old_minor_version);
4378
4379 // Replace major version number of class file
4380 u2 old_major_version = the_class->constants()->major_version();
4381 the_class->constants()->set_major_version(scratch_class->constants()->major_version());
4382 scratch_class->constants()->set_major_version(old_major_version);
4383
4384 // Replace CP indexes for class and name+type of enclosing method
4385 u2 old_class_idx = the_class->enclosing_method_class_index();
4386 u2 old_method_idx = the_class->enclosing_method_method_index();
4387 the_class->set_enclosing_method_indices(
4388 scratch_class->enclosing_method_class_index(),
4389 scratch_class->enclosing_method_method_index());
4390 scratch_class->set_enclosing_method_indices(old_class_idx, old_method_idx);
4391
4392 if (!the_class->has_been_redefined()) {
4393 the_class->set_has_been_redefined();
4394 }
4395
4396 // Scratch class is unloaded but still needs cleaning, and skipping for CDS.
4397 scratch_class->set_is_scratch_class();
4398
4399 // keep track of previous versions of this class
4400 the_class->add_previous_version(scratch_class, emcp_method_count);
4401
4402 _timer_rsc_phase1.stop();
4403 if (log_is_enabled(Info, redefine, class, timer)) {
4404 _timer_rsc_phase2.start();
4405 }
4406
4407 if (the_class->oop_map_cache() != nullptr) {
4408 // Flush references to any obsolete methods from the oop map cache
4409 // so that obsolete methods are not pinned.
4410 the_class->oop_map_cache()->flush_obsolete_entries();
4411 }
4412
4413 increment_class_counter(the_class);
4414
4415 if (EventClassRedefinition::is_enabled()) {
4416 EventClassRedefinition event;
4417 event.set_classModificationCount(java_lang_Class::classRedefinedCount(the_class->java_mirror()));
4418 event.set_redefinedClass(the_class);
4419 event.set_redefinitionId(_id);
4420 event.commit();
4421 }
4422
4423 {
4424 ResourceMark rm(current);
4425 // increment the classRedefinedCount field in the_class and in any
4426 // direct and indirect subclasses of the_class
4427 log_info(redefine, class, load)
4428 ("redefined name=%s, count=%d (avail_mem=" UINT64_FORMAT "K)",
4429 the_class->external_name(), java_lang_Class::classRedefinedCount(the_class->java_mirror()), os::available_memory() >> 10);
4430 Events::log_redefinition(current, "redefined class name=%s, count=%d",
4431 the_class->external_name(),
4432 java_lang_Class::classRedefinedCount(the_class->java_mirror()));
4433
4434 }
4435 _timer_rsc_phase2.stop();
4436
4437 } // end redefine_single_class()
4438
4439
4440 // Increment the classRedefinedCount field in the specific InstanceKlass
4441 // and in all direct and indirect subclasses.
4442 void VM_RedefineClasses::increment_class_counter(InstanceKlass* ik) {
4443 for (ClassHierarchyIterator iter(ik); !iter.done(); iter.next()) {
4444 // Only update instanceKlasses
4445 Klass* sub = iter.klass();
4446 if (sub->is_instance_klass()) {
4447 oop class_mirror = InstanceKlass::cast(sub)->java_mirror();
4448 Klass* class_oop = java_lang_Class::as_Klass(class_mirror);
4449 int new_count = java_lang_Class::classRedefinedCount(class_mirror) + 1;
4450 java_lang_Class::set_classRedefinedCount(class_mirror, new_count);
4451
4452 if (class_oop != _the_class) {
4453 // _the_class count is printed at end of redefine_single_class()
4454 log_debug(redefine, class, subclass)("updated count in subclass=%s to %d", ik->external_name(), new_count);
4455 }
4456 }
4457 }
4458 }
4459
4460 void VM_RedefineClasses::CheckClass::do_klass(Klass* k) {
4461 bool no_old_methods = true; // be optimistic
4462
4463 // Both array and instance classes have vtables.
4464 // a vtable should never contain old or obsolete methods
4465 ResourceMark rm(_thread);
4466 if (k->vtable_length() > 0 &&
4467 !k->vtable().check_no_old_or_obsolete_entries()) {
4468 if (log_is_enabled(Trace, redefine, class, obsolete, metadata)) {
4469 log_trace(redefine, class, obsolete, metadata)
4470 ("klassVtable::check_no_old_or_obsolete_entries failure -- OLD or OBSOLETE method found -- class: %s",
4471 k->signature_name());
4472 k->vtable().dump_vtable();
4473 }
4474 no_old_methods = false;
4475 }
4476
4477 if (k->is_instance_klass()) {
4478 HandleMark hm(_thread);
4479 InstanceKlass *ik = InstanceKlass::cast(k);
4480
4481 // an itable should never contain old or obsolete methods
4482 if (ik->itable_length() > 0 &&
4483 !ik->itable().check_no_old_or_obsolete_entries()) {
4484 if (log_is_enabled(Trace, redefine, class, obsolete, metadata)) {
4485 log_trace(redefine, class, obsolete, metadata)
4486 ("klassItable::check_no_old_or_obsolete_entries failure -- OLD or OBSOLETE method found -- class: %s",
4487 ik->signature_name());
4488 ik->itable().dump_itable();
4489 }
4490 no_old_methods = false;
4491 }
4492
4493 // the constant pool cache should never contain non-deleted old or obsolete methods
4494 if (ik->constants() != nullptr &&
4495 ik->constants()->cache() != nullptr &&
4496 !ik->constants()->cache()->check_no_old_or_obsolete_entries()) {
4497 if (log_is_enabled(Trace, redefine, class, obsolete, metadata)) {
4498 log_trace(redefine, class, obsolete, metadata)
4499 ("cp-cache::check_no_old_or_obsolete_entries failure -- OLD or OBSOLETE method found -- class: %s",
4500 ik->signature_name());
4501 ik->constants()->cache()->dump_cache();
4502 }
4503 no_old_methods = false;
4504 }
4505 }
4506
4507 // print and fail guarantee if old methods are found.
4508 if (!no_old_methods) {
4509 if (log_is_enabled(Trace, redefine, class, obsolete, metadata)) {
4510 dump_methods();
4511 } else {
4512 log_trace(redefine, class)("Use the '-Xlog:redefine+class*:' option "
4513 "to see more info about the following guarantee() failure.");
4514 }
4515 guarantee(false, "OLD and/or OBSOLETE method(s) found");
4516 }
4517 }
4518
4519 u8 VM_RedefineClasses::next_id() {
4520 while (true) {
4521 u8 id = _id_counter;
4522 u8 next_id = id + 1;
4523 u8 result = Atomic::cmpxchg(&_id_counter, id, next_id);
4524 if (result == id) {
4525 return next_id;
4526 }
4527 }
4528 }
4529
4530 void VM_RedefineClasses::dump_methods() {
4531 int j;
4532 log_trace(redefine, class, dump)("_old_methods --");
4533 for (j = 0; j < _old_methods->length(); ++j) {
4534 LogStreamHandle(Trace, redefine, class, dump) log_stream;
4535 Method* m = _old_methods->at(j);
4536 log_stream.print("%4d (%5d) ", j, m->vtable_index());
4537 m->access_flags().print_on(&log_stream);
4538 log_stream.print(" -- ");
4539 m->print_name(&log_stream);
4540 log_stream.cr();
4541 }
4542 log_trace(redefine, class, dump)("_new_methods --");
4543 for (j = 0; j < _new_methods->length(); ++j) {
4544 LogStreamHandle(Trace, redefine, class, dump) log_stream;
4545 Method* m = _new_methods->at(j);
4546 log_stream.print("%4d (%5d) ", j, m->vtable_index());
4547 m->access_flags().print_on(&log_stream);
4548 log_stream.print(" -- ");
4549 m->print_name(&log_stream);
4550 log_stream.cr();
4551 }
4552 log_trace(redefine, class, dump)("_matching_methods --");
4553 for (j = 0; j < _matching_methods_length; ++j) {
4554 LogStreamHandle(Trace, redefine, class, dump) log_stream;
4555 Method* m = _matching_old_methods[j];
4556 log_stream.print("%4d (%5d) ", j, m->vtable_index());
4557 m->access_flags().print_on(&log_stream);
4558 log_stream.print(" -- ");
4559 m->print_name();
4560 log_stream.cr();
4561
4562 m = _matching_new_methods[j];
4563 log_stream.print(" (%5d) ", m->vtable_index());
4564 m->access_flags().print_on(&log_stream);
4565 log_stream.cr();
4566 }
4567 log_trace(redefine, class, dump)("_deleted_methods --");
4568 for (j = 0; j < _deleted_methods_length; ++j) {
4569 LogStreamHandle(Trace, redefine, class, dump) log_stream;
4570 Method* m = _deleted_methods[j];
4571 log_stream.print("%4d (%5d) ", j, m->vtable_index());
4572 m->access_flags().print_on(&log_stream);
4573 log_stream.print(" -- ");
4574 m->print_name(&log_stream);
4575 log_stream.cr();
4576 }
4577 log_trace(redefine, class, dump)("_added_methods --");
4578 for (j = 0; j < _added_methods_length; ++j) {
4579 LogStreamHandle(Trace, redefine, class, dump) log_stream;
4580 Method* m = _added_methods[j];
4581 log_stream.print("%4d (%5d) ", j, m->vtable_index());
4582 m->access_flags().print_on(&log_stream);
4583 log_stream.print(" -- ");
4584 m->print_name(&log_stream);
4585 log_stream.cr();
4586 }
4587 }
4588
4589 void VM_RedefineClasses::print_on_error(outputStream* st) const {
4590 VM_Operation::print_on_error(st);
4591 if (_the_class != nullptr) {
4592 ResourceMark rm;
4593 st->print_cr(", redefining class %s", _the_class->external_name());
4594 }
4595 }