1 /*
   2  * Copyright (c) 2003, 2025, 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 "cds/cdsConfig.hpp"
  26 #include "cds/metaspaceShared.hpp"
  27 #include "classfile/classFileStream.hpp"
  28 #include "classfile/classLoaderDataGraph.hpp"
  29 #include "classfile/classLoadInfo.hpp"
  30 #include "classfile/javaClasses.inline.hpp"
  31 #include "classfile/klassFactory.hpp"
  32 #include "classfile/metadataOnStackMark.hpp"
  33 #include "classfile/stackMapTable.hpp"
  34 #include "classfile/symbolTable.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/methodComparator.hpp"
  59 #include "prims/resolvedMethodTable.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 #if INCLUDE_JFR
  71 #include "jfr/jfr.hpp"
  72 #endif
  73 
  74 Array<Method*>* VM_RedefineClasses::_old_methods = nullptr;
  75 Array<Method*>* VM_RedefineClasses::_new_methods = nullptr;
  76 Method**  VM_RedefineClasses::_matching_old_methods = nullptr;
  77 Method**  VM_RedefineClasses::_matching_new_methods = nullptr;
  78 Method**  VM_RedefineClasses::_deleted_methods      = nullptr;
  79 Method**  VM_RedefineClasses::_added_methods        = nullptr;
  80 int       VM_RedefineClasses::_matching_methods_length = 0;
  81 int       VM_RedefineClasses::_deleted_methods_length  = 0;
  82 int       VM_RedefineClasses::_added_methods_length    = 0;
  83 
  84 // This flag is global as the constructor does not reset it:
  85 bool      VM_RedefineClasses::_has_redefined_Object = false;
  86 u8        VM_RedefineClasses::_id_counter = 0;
  87 
  88 VM_RedefineClasses::VM_RedefineClasses(jint class_count,
  89                                        const jvmtiClassDefinition *class_defs,
  90                                        JvmtiClassLoadKind class_load_kind) {
  91   _class_count = class_count;
  92   _class_defs = class_defs;
  93   _class_load_kind = class_load_kind;
  94   _any_class_has_resolved_methods = false;
  95   _res = JVMTI_ERROR_NONE;
  96   _the_class = nullptr;
  97   _id = next_id();
  98 }
  99 
 100 static inline InstanceKlass* get_ik(jclass def) {
 101   oop mirror = JNIHandles::resolve_non_null(def);
 102   return InstanceKlass::cast(java_lang_Class::as_Klass(mirror));
 103 }
 104 
 105 // If any of the classes are being redefined, wait
 106 // Parallel constant pool merging leads to indeterminate constant pools.
 107 void VM_RedefineClasses::lock_classes() {
 108   JvmtiThreadState *state = JvmtiThreadState::state_for(JavaThread::current());
 109   GrowableArray<Klass*>* redef_classes = state->get_classes_being_redefined();
 110 
 111   MonitorLocker ml(RedefineClasses_lock);
 112 
 113   if (redef_classes == nullptr) {
 114     redef_classes = new (mtClass) GrowableArray<Klass*>(1, mtClass);
 115     state->set_classes_being_redefined(redef_classes);
 116   }
 117 
 118   bool has_redefined;
 119   do {
 120     has_redefined = false;
 121     // Go through classes each time until none are being redefined. Skip
 122     // the ones that are being redefined by this thread currently. Class file
 123     // load hook event may trigger new class redefine when we are redefining
 124     // a class (after lock_classes()).
 125     for (int i = 0; i < _class_count; i++) {
 126       InstanceKlass* ik = get_ik(_class_defs[i].klass);
 127       // Check if we are currently redefining the class in this thread already.
 128       if (redef_classes->contains(ik)) {
 129         assert(ik->is_being_redefined(), "sanity");
 130       } else {
 131         if (ik->is_being_redefined()) {
 132           ml.wait();
 133           has_redefined = true;
 134           break;  // for loop
 135         }
 136       }
 137     }
 138   } while (has_redefined);
 139 
 140   for (int i = 0; i < _class_count; i++) {
 141     InstanceKlass* ik = get_ik(_class_defs[i].klass);
 142     redef_classes->push(ik); // Add to the _classes_being_redefined list
 143     ik->set_is_being_redefined(true);
 144   }
 145   ml.notify_all();
 146 }
 147 
 148 void VM_RedefineClasses::unlock_classes() {
 149   JvmtiThreadState *state = JvmtiThreadState::state_for(JavaThread::current());
 150   GrowableArray<Klass*>* redef_classes = state->get_classes_being_redefined();
 151   assert(redef_classes != nullptr, "_classes_being_redefined is not allocated");
 152 
 153   MonitorLocker ml(RedefineClasses_lock);
 154 
 155   for (int i = _class_count - 1; i >= 0; i--) {
 156     InstanceKlass* def_ik = get_ik(_class_defs[i].klass);
 157     if (redef_classes->length() > 0) {
 158       // Remove the class from _classes_being_redefined list
 159       Klass* k = redef_classes->pop();
 160       assert(def_ik == k, "unlocking wrong class");
 161     }
 162     assert(def_ik->is_being_redefined(),
 163            "should be being redefined to get here");
 164 
 165     // Unlock after we finish all redefines for this class within
 166     // the thread. Same class can be pushed to the list multiple
 167     // times (not more than once by each recursive redefinition).
 168     if (!redef_classes->contains(def_ik)) {
 169       def_ik->set_is_being_redefined(false);
 170     }
 171   }
 172   ml.notify_all();
 173 }
 174 
 175 bool VM_RedefineClasses::doit_prologue() {
 176   if (_class_count == 0) {
 177     _res = JVMTI_ERROR_NONE;
 178     return false;
 179   }
 180   if (_class_defs == nullptr) {
 181     _res = JVMTI_ERROR_NULL_POINTER;
 182     return false;
 183   }
 184 
 185   for (int i = 0; i < _class_count; i++) {
 186     if (_class_defs[i].klass == nullptr) {
 187       _res = JVMTI_ERROR_INVALID_CLASS;
 188       return false;
 189     }
 190     if (_class_defs[i].class_byte_count == 0) {
 191       _res = JVMTI_ERROR_INVALID_CLASS_FORMAT;
 192       return false;
 193     }
 194     if (_class_defs[i].class_bytes == nullptr) {
 195       _res = JVMTI_ERROR_NULL_POINTER;
 196       return false;
 197     }
 198 
 199     oop mirror = JNIHandles::resolve_non_null(_class_defs[i].klass);
 200     // classes for primitives, arrays, and hidden classes
 201     // cannot be redefined.
 202     if (!is_modifiable_class(mirror)) {
 203       _res = JVMTI_ERROR_UNMODIFIABLE_CLASS;
 204       return false;
 205     }
 206   }
 207 
 208   // Start timer after all the sanity checks; not quite accurate, but
 209   // better than adding a bunch of stop() calls.
 210   if (log_is_enabled(Info, redefine, class, timer)) {
 211     _timer_vm_op_prologue.start();
 212   }
 213 
 214   lock_classes();
 215   // We first load new class versions in the prologue, because somewhere down the
 216   // call chain it is required that the current thread is a Java thread.
 217   _res = load_new_class_versions();
 218   if (_res != JVMTI_ERROR_NONE) {
 219     // free any successfully created classes, since none are redefined
 220     for (int i = 0; i < _class_count; i++) {
 221       if (_scratch_classes[i] != nullptr) {
 222         ClassLoaderData* cld = _scratch_classes[i]->class_loader_data();
 223         // Free the memory for this class at class unloading time.  Not before
 224         // because CMS might think this is still live.
 225         InstanceKlass* ik = get_ik(_class_defs[i].klass);
 226         if (ik->get_cached_class_file() == _scratch_classes[i]->get_cached_class_file()) {
 227           // Don't double-free cached_class_file copied from the original class if error.
 228           _scratch_classes[i]->set_cached_class_file(nullptr);
 229         }
 230         cld->add_to_deallocate_list(InstanceKlass::cast(_scratch_classes[i]));
 231       }
 232     }
 233     // Free os::malloc allocated memory in load_new_class_version.
 234     os::free(_scratch_classes);
 235     _timer_vm_op_prologue.stop();
 236     unlock_classes();
 237     return false;
 238   }
 239 
 240   _timer_vm_op_prologue.stop();
 241   return true;
 242 }
 243 
 244 void VM_RedefineClasses::doit() {
 245   Thread* current = Thread::current();
 246 
 247   if (log_is_enabled(Info, redefine, class, timer)) {
 248     _timer_vm_op_doit.start();
 249   }
 250 
 251 #if INCLUDE_CDS
 252   if (CDSConfig::is_using_archive()) {
 253     // Sharing is enabled so we remap the shared readonly space to
 254     // shared readwrite, private just in case we need to redefine
 255     // a shared class. We do the remap during the doit() phase of
 256     // the safepoint to be safer.
 257     if (!MetaspaceShared::remap_shared_readonly_as_readwrite()) {
 258       log_info(redefine, class, load)("failed to remap shared readonly space to readwrite, private");
 259       _res = JVMTI_ERROR_INTERNAL;
 260       _timer_vm_op_doit.stop();
 261       return;
 262     }
 263   }
 264 #endif
 265 
 266   // Mark methods seen on stack and everywhere else so old methods are not
 267   // cleaned up if they're on the stack.
 268   MetadataOnStackMark md_on_stack(/*walk_all_metadata*/true, /*redefinition_walk*/true);
 269   HandleMark hm(current);   // make sure any handles created are deleted
 270                             // before the stack walk again.
 271 
 272   for (int i = 0; i < _class_count; i++) {
 273     redefine_single_class(current, _class_defs[i].klass, _scratch_classes[i]);
 274   }
 275 
 276   // Flush all compiled code that depends on the classes redefined.
 277   flush_dependent_code();
 278 
 279   // Adjust constantpool caches and vtables for all classes
 280   // that reference methods of the evolved classes.
 281   // Have to do this after all classes are redefined and all methods that
 282   // are redefined are marked as old.
 283   AdjustAndCleanMetadata adjust_and_clean_metadata(current);
 284   ClassLoaderDataGraph::classes_do(&adjust_and_clean_metadata);
 285 
 286   // JSR-292 support
 287   if (_any_class_has_resolved_methods) {
 288     bool trace_name_printed = false;
 289     ResolvedMethodTable::adjust_method_entries(&trace_name_printed);
 290   }
 291 
 292   // Increment flag indicating that some invariants are no longer true.
 293   // See jvmtiExport.hpp for detailed explanation.
 294   JvmtiExport::increment_redefinition_count();
 295 
 296   // check_class() is optionally called for product bits, but is
 297   // always called for non-product bits.
 298 #ifdef PRODUCT
 299   if (log_is_enabled(Trace, redefine, class, obsolete, metadata)) {
 300 #endif
 301     log_trace(redefine, class, obsolete, metadata)("calling check_class");
 302     CheckClass check_class(current);
 303     ClassLoaderDataGraph::classes_do(&check_class);
 304 #ifdef PRODUCT
 305   }
 306 #endif
 307 
 308   // Clean up any metadata now unreferenced while MetadataOnStackMark is set.
 309   ClassLoaderDataGraph::clean_deallocate_lists(false);
 310 
 311   _timer_vm_op_doit.stop();
 312 }
 313 
 314 void VM_RedefineClasses::doit_epilogue() {
 315   unlock_classes();
 316 
 317   // Free os::malloc allocated memory.
 318   os::free(_scratch_classes);
 319 
 320   // Reset the_class to null for error printing.
 321   _the_class = nullptr;
 322 
 323   if (log_is_enabled(Info, redefine, class, timer)) {
 324     // Used to have separate timers for "doit" and "all", but the timer
 325     // overhead skewed the measurements.
 326     julong doit_time = _timer_vm_op_doit.milliseconds();
 327     julong all_time = _timer_vm_op_prologue.milliseconds() + doit_time;
 328 
 329     log_info(redefine, class, timer)
 330       ("vm_op: all=" JULONG_FORMAT "  prologue=" JULONG_FORMAT "  doit=" JULONG_FORMAT,
 331        all_time, (julong)_timer_vm_op_prologue.milliseconds(), doit_time);
 332     log_info(redefine, class, timer)
 333       ("redefine_single_class: phase1=" JULONG_FORMAT "  phase2=" JULONG_FORMAT,
 334        (julong)_timer_rsc_phase1.milliseconds(), (julong)_timer_rsc_phase2.milliseconds());
 335   }
 336 }
 337 
 338 bool VM_RedefineClasses::is_modifiable_class(oop klass_mirror) {
 339   // classes for primitives cannot be redefined
 340   if (java_lang_Class::is_primitive(klass_mirror)) {
 341     return false;
 342   }
 343   Klass* k = java_lang_Class::as_Klass(klass_mirror);
 344   // classes for arrays cannot be redefined
 345   if (k == nullptr || !k->is_instance_klass()) {
 346     return false;
 347   }
 348 
 349   // Cannot redefine or retransform a hidden class.
 350   if (InstanceKlass::cast(k)->is_hidden()) {
 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, const int old_bs_i,
 667        constantPoolHandle *merge_cp_p, int *merge_cp_length_p) {
 668 
 669   BSMAttributeEntry* old_bsme = scratch_cp->bsm_attribute_entry(old_bs_i);
 670   u2 old_ref_i = old_bsme->bootstrap_method_index();
 671   u2 new_ref_i = find_or_append_indirect_entry(scratch_cp, old_ref_i, merge_cp_p,
 672                                                merge_cp_length_p);
 673   if (new_ref_i != old_ref_i) {
 674     log_trace(redefine, class, constantpool)
 675       ("operands entry@%d bootstrap method ref_index change: %d to %d", _operands_cur_length, old_ref_i, new_ref_i);
 676   }
 677 
 678   Array<u2>* merge_ops = (*merge_cp_p)->operands();
 679   int new_bs_i = _operands_cur_length;
 680   // We have _operands_cur_length == 0 when the merge_cp operands is empty yet.
 681   // However, the operand_offset_at(0) was set in the extend_operands() call.
 682   int new_base = (new_bs_i == 0) ? (*merge_cp_p)->operand_offset_at(0)
 683                                  : (*merge_cp_p)->operand_next_offset_at(new_bs_i - 1);
 684   u2 argc      = old_bsme->argument_count();
 685 
 686   ConstantPool::operand_offset_at_put(merge_ops, _operands_cur_length, new_base);
 687   merge_ops->at_put(new_base++, new_ref_i);
 688   merge_ops->at_put(new_base++, argc);
 689 
 690   for (int i = 0; i < argc; i++) {
 691     u2 old_arg_ref_i = old_bsme->argument_index(i);
 692     u2 new_arg_ref_i = find_or_append_indirect_entry(scratch_cp, old_arg_ref_i, merge_cp_p,
 693                                                      merge_cp_length_p);
 694     merge_ops->at_put(new_base++, new_arg_ref_i);
 695     if (new_arg_ref_i != old_arg_ref_i) {
 696       log_trace(redefine, class, constantpool)
 697         ("operands entry@%d bootstrap method argument ref_index change: %d to %d",
 698          _operands_cur_length, old_arg_ref_i, new_arg_ref_i);
 699     }
 700   }
 701   if (old_bs_i != _operands_cur_length) {
 702     // The bootstrap specifier in *merge_cp_p is at a different index than
 703     // that in scratch_cp so we need to map the index values.
 704     map_operand_index(old_bs_i, new_bs_i);
 705   }
 706   _operands_cur_length++;
 707 } // end append_operand()
 708 
 709 
 710 int VM_RedefineClasses::find_or_append_operand(const constantPoolHandle& scratch_cp,
 711       int old_bs_i, constantPoolHandle *merge_cp_p, int *merge_cp_length_p) {
 712 
 713   int new_bs_i = old_bs_i; // bootstrap specifier index
 714   bool match = (old_bs_i < _operands_cur_length) &&
 715                scratch_cp->compare_operand_to(old_bs_i, *merge_cp_p, old_bs_i);
 716 
 717   if (!match) {
 718     // forward reference in *merge_cp_p or not a direct match
 719     int found_i = scratch_cp->find_matching_operand(old_bs_i, *merge_cp_p,
 720                                                     _operands_cur_length);
 721     if (found_i != -1) {
 722       guarantee(found_i != old_bs_i, "compare_operand_to() and find_matching_operand() disagree");
 723       // found a matching operand somewhere else in *merge_cp_p so just need a mapping
 724       new_bs_i = found_i;
 725       map_operand_index(old_bs_i, found_i);
 726     } else {
 727       // no match found so we have to append this bootstrap specifier to *merge_cp_p
 728       append_operand(scratch_cp, old_bs_i, merge_cp_p, merge_cp_length_p);
 729       new_bs_i = _operands_cur_length - 1;
 730     }
 731   }
 732   return new_bs_i;
 733 } // end find_or_append_operand()
 734 
 735 
 736 void VM_RedefineClasses::finalize_operands_merge(const constantPoolHandle& merge_cp, TRAPS) {
 737   if (merge_cp->operands() == nullptr) {
 738     return;
 739   }
 740   // Shrink the merge_cp operands
 741   merge_cp->shrink_operands(_operands_cur_length, CHECK);
 742 
 743   if (log_is_enabled(Trace, redefine, class, constantpool)) {
 744     // don't want to loop unless we are tracing
 745     int count = 0;
 746     for (int i = 1; i < _operands_index_map_p->length(); i++) {
 747       int value = _operands_index_map_p->at(i);
 748       if (value != -1) {
 749         log_trace(redefine, class, constantpool)("operands_index_map[%d]: old=%d new=%d", count, i, value);
 750         count++;
 751       }
 752     }
 753   }
 754   // Clean-up
 755   _operands_index_map_p = nullptr;
 756   _operands_cur_length = 0;
 757   _operands_index_map_count = 0;
 758 } // end finalize_operands_merge()
 759 
 760 // Symbol* comparator for qsort
 761 // The caller must have an active ResourceMark.
 762 static int symcmp(const void* a, const void* b) {
 763   char* astr = (*(Symbol**)a)->as_C_string();
 764   char* bstr = (*(Symbol**)b)->as_C_string();
 765   return strcmp(astr, bstr);
 766 }
 767 
 768 // The caller must have an active ResourceMark.
 769 static jvmtiError check_attribute_arrays(const char* attr_name,
 770            InstanceKlass* the_class, InstanceKlass* scratch_class,
 771            Array<u2>* the_array, Array<u2>* scr_array) {
 772   bool the_array_exists = the_array != Universe::the_empty_short_array();
 773   bool scr_array_exists = scr_array != Universe::the_empty_short_array();
 774 
 775   int array_len = the_array->length();
 776   if (the_array_exists && scr_array_exists) {
 777     if (array_len != scr_array->length()) {
 778       log_trace(redefine, class)
 779         ("redefined class %s attribute change error: %s len=%d changed to len=%d",
 780          the_class->external_name(), attr_name, array_len, scr_array->length());
 781       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
 782     }
 783 
 784     // The order of entries in the attribute array is not specified so we
 785     // have to explicitly check for the same contents. We do this by copying
 786     // the referenced symbols into their own arrays, sorting them and then
 787     // comparing each element pair.
 788 
 789     Symbol** the_syms = NEW_RESOURCE_ARRAY_RETURN_NULL(Symbol*, array_len);
 790     Symbol** scr_syms = NEW_RESOURCE_ARRAY_RETURN_NULL(Symbol*, array_len);
 791 
 792     if (the_syms == nullptr || scr_syms == nullptr) {
 793       return JVMTI_ERROR_OUT_OF_MEMORY;
 794     }
 795 
 796     for (int i = 0; i < array_len; i++) {
 797       int the_cp_index = the_array->at(i);
 798       int scr_cp_index = scr_array->at(i);
 799       the_syms[i] = the_class->constants()->klass_name_at(the_cp_index);
 800       scr_syms[i] = scratch_class->constants()->klass_name_at(scr_cp_index);
 801     }
 802 
 803     qsort(the_syms, array_len, sizeof(Symbol*), symcmp);
 804     qsort(scr_syms, array_len, sizeof(Symbol*), symcmp);
 805 
 806     for (int i = 0; i < array_len; i++) {
 807       if (the_syms[i] != scr_syms[i]) {
 808         log_info(redefine, class)
 809           ("redefined class %s attribute change error: %s[%d]: %s changed to %s",
 810            the_class->external_name(), attr_name, i,
 811            the_syms[i]->as_C_string(), scr_syms[i]->as_C_string());
 812         return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
 813       }
 814     }
 815   } else if (the_array_exists ^ scr_array_exists) {
 816     const char* action_str = (the_array_exists) ? "removed" : "added";
 817     log_info(redefine, class)
 818       ("redefined class %s attribute change error: %s attribute %s",
 819        the_class->external_name(), attr_name, action_str);
 820     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
 821   }
 822   return JVMTI_ERROR_NONE;
 823 }
 824 
 825 static jvmtiError check_nest_attributes(InstanceKlass* the_class,
 826                                         InstanceKlass* scratch_class) {
 827   // Check whether the class NestHost attribute has been changed.
 828   Thread* thread = Thread::current();
 829   ResourceMark rm(thread);
 830   u2 the_nest_host_idx = the_class->nest_host_index();
 831   u2 scr_nest_host_idx = scratch_class->nest_host_index();
 832 
 833   if (the_nest_host_idx != 0 && scr_nest_host_idx != 0) {
 834     Symbol* the_sym = the_class->constants()->klass_name_at(the_nest_host_idx);
 835     Symbol* scr_sym = scratch_class->constants()->klass_name_at(scr_nest_host_idx);
 836     if (the_sym != scr_sym) {
 837       log_info(redefine, class, nestmates)
 838         ("redefined class %s attribute change error: NestHost class: %s replaced with: %s",
 839          the_class->external_name(), the_sym->as_C_string(), scr_sym->as_C_string());
 840       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
 841     }
 842   } else if ((the_nest_host_idx == 0) ^ (scr_nest_host_idx == 0)) {
 843     const char* action_str = (the_nest_host_idx != 0) ? "removed" : "added";
 844     log_info(redefine, class, nestmates)
 845       ("redefined class %s attribute change error: NestHost attribute %s",
 846        the_class->external_name(), action_str);
 847     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
 848   }
 849 
 850   // Check whether the class NestMembers attribute has been changed.
 851   return check_attribute_arrays("NestMembers",
 852                                 the_class, scratch_class,
 853                                 the_class->nest_members(),
 854                                 scratch_class->nest_members());
 855 }
 856 
 857 // Return an error status if the class Record attribute was changed.
 858 static jvmtiError check_record_attribute(InstanceKlass* the_class, InstanceKlass* scratch_class) {
 859   // Get lists of record components.
 860   Array<RecordComponent*>* the_record = the_class->record_components();
 861   Array<RecordComponent*>* scr_record = scratch_class->record_components();
 862   bool the_record_exists = the_record != nullptr;
 863   bool scr_record_exists = scr_record != nullptr;
 864 
 865   if (the_record_exists && scr_record_exists) {
 866     int the_num_components = the_record->length();
 867     int scr_num_components = scr_record->length();
 868     if (the_num_components != scr_num_components) {
 869       log_info(redefine, class, record)
 870         ("redefined class %s attribute change error: Record num_components=%d changed to num_components=%d",
 871          the_class->external_name(), the_num_components, scr_num_components);
 872       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
 873     }
 874 
 875     // Compare each field in each record component.
 876     ConstantPool* the_cp =  the_class->constants();
 877     ConstantPool* scr_cp =  scratch_class->constants();
 878     for (int x = 0; x < the_num_components; x++) {
 879       RecordComponent* the_component = the_record->at(x);
 880       RecordComponent* scr_component = scr_record->at(x);
 881       const Symbol* const the_name = the_cp->symbol_at(the_component->name_index());
 882       const Symbol* const scr_name = scr_cp->symbol_at(scr_component->name_index());
 883       const Symbol* const the_descr = the_cp->symbol_at(the_component->descriptor_index());
 884       const Symbol* const scr_descr = scr_cp->symbol_at(scr_component->descriptor_index());
 885       if (the_name != scr_name || the_descr != scr_descr) {
 886         log_info(redefine, class, record)
 887           ("redefined class %s attribute change error: Record name_index, descriptor_index, and/or attributes_count changed",
 888            the_class->external_name());
 889         return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
 890       }
 891 
 892       int the_gen_sig = the_component->generic_signature_index();
 893       int scr_gen_sig = scr_component->generic_signature_index();
 894       const Symbol* const the_gen_sig_sym = (the_gen_sig == 0 ? nullptr :
 895         the_cp->symbol_at(the_component->generic_signature_index()));
 896       const Symbol* const scr_gen_sig_sym = (scr_gen_sig == 0 ? nullptr :
 897         scr_cp->symbol_at(scr_component->generic_signature_index()));
 898       if (the_gen_sig_sym != scr_gen_sig_sym) {
 899         log_info(redefine, class, record)
 900           ("redefined class %s attribute change error: Record generic_signature attribute changed",
 901            the_class->external_name());
 902         return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
 903       }
 904 
 905       // It's okay if a record component's annotations were changed.
 906     }
 907 
 908   } else if (the_record_exists ^ scr_record_exists) {
 909     const char* action_str = (the_record_exists) ? "removed" : "added";
 910     log_info(redefine, class, record)
 911       ("redefined class %s attribute change error: Record attribute %s",
 912        the_class->external_name(), action_str);
 913     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
 914   }
 915 
 916   return JVMTI_ERROR_NONE;
 917 }
 918 
 919 
 920 static jvmtiError check_permitted_subclasses_attribute(InstanceKlass* the_class,
 921                                                        InstanceKlass* scratch_class) {
 922   Thread* thread = Thread::current();
 923   ResourceMark rm(thread);
 924 
 925   // Check whether the class PermittedSubclasses attribute has been changed.
 926   return check_attribute_arrays("PermittedSubclasses",
 927                                 the_class, scratch_class,
 928                                 the_class->permitted_subclasses(),
 929                                 scratch_class->permitted_subclasses());
 930 }
 931 
 932 static bool can_add_or_delete(Method* m) {
 933       // Compatibility mode
 934   return (AllowRedefinitionToAddDeleteMethods &&
 935           (m->is_private() && (m->is_static() || m->is_final())));
 936 }
 937 
 938 jvmtiError VM_RedefineClasses::compare_and_normalize_class_versions(
 939              InstanceKlass* the_class,
 940              InstanceKlass* scratch_class) {
 941   int i;
 942 
 943   // Check superclasses, or rather their names, since superclasses themselves can be
 944   // requested to replace.
 945   // Check for null superclass first since this might be java.lang.Object
 946   if (the_class->super() != scratch_class->super() &&
 947       (the_class->super() == nullptr || scratch_class->super() == nullptr ||
 948        the_class->super()->name() !=
 949        scratch_class->super()->name())) {
 950     log_info(redefine, class, normalize)
 951       ("redefined class %s superclass change error: superclass changed from %s to %s.",
 952        the_class->external_name(),
 953        the_class->super() == nullptr ? "null" : the_class->super()->external_name(),
 954        scratch_class->super() == nullptr ? "null" : scratch_class->super()->external_name());
 955     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_HIERARCHY_CHANGED;
 956   }
 957 
 958   // Check if the number, names and order of directly implemented interfaces are the same.
 959   // I think in principle we should just check if the sets of names of directly implemented
 960   // interfaces are the same, i.e. the order of declaration (which, however, if changed in the
 961   // .java file, also changes in .class file) should not matter. However, comparing sets is
 962   // technically a bit more difficult, and, more importantly, I am not sure at present that the
 963   // order of interfaces does not matter on the implementation level, i.e. that the VM does not
 964   // rely on it somewhere.
 965   Array<InstanceKlass*>* k_interfaces = the_class->local_interfaces();
 966   Array<InstanceKlass*>* k_new_interfaces = scratch_class->local_interfaces();
 967   int n_intfs = k_interfaces->length();
 968   if (n_intfs != k_new_interfaces->length()) {
 969     log_info(redefine, class, normalize)
 970       ("redefined class %s interfaces change error: number of implemented interfaces changed from %d to %d.",
 971        the_class->external_name(), n_intfs, k_new_interfaces->length());
 972     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_HIERARCHY_CHANGED;
 973   }
 974   for (i = 0; i < n_intfs; i++) {
 975     if (k_interfaces->at(i)->name() !=
 976         k_new_interfaces->at(i)->name()) {
 977       log_info(redefine, class, normalize)
 978           ("redefined class %s interfaces change error: interface changed from %s to %s.",
 979            the_class->external_name(),
 980            k_interfaces->at(i)->external_name(), k_new_interfaces->at(i)->external_name());
 981       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_HIERARCHY_CHANGED;
 982     }
 983   }
 984 
 985   // Check whether class is in the error init state.
 986   if (the_class->is_in_error_state()) {
 987     log_info(redefine, class, normalize)
 988       ("redefined class %s is in error init state.", the_class->external_name());
 989     // TBD #5057930: special error code is needed in 1.6
 990     return JVMTI_ERROR_INVALID_CLASS;
 991   }
 992 
 993   // Check whether the nest-related attributes have been changed.
 994   jvmtiError err = check_nest_attributes(the_class, scratch_class);
 995   if (err != JVMTI_ERROR_NONE) {
 996     return err;
 997   }
 998 
 999   // Check whether the Record attribute has been changed.
1000   err = check_record_attribute(the_class, scratch_class);
1001   if (err != JVMTI_ERROR_NONE) {
1002     return err;
1003   }
1004 
1005   // Check whether the PermittedSubclasses attribute has been changed.
1006   err = check_permitted_subclasses_attribute(the_class, scratch_class);
1007   if (err != JVMTI_ERROR_NONE) {
1008     return err;
1009   }
1010 
1011   // Check whether class modifiers are the same.
1012   u2 old_flags = the_class->access_flags().as_class_flags();
1013   u2 new_flags = scratch_class->access_flags().as_class_flags();
1014   if (old_flags != new_flags) {
1015     log_info(redefine, class, normalize)
1016         ("redefined class %s modifiers change error: modifiers changed from %d to %d.",
1017          the_class->external_name(), old_flags, new_flags);
1018     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_MODIFIERS_CHANGED;
1019   }
1020 
1021   // Check if the number, names, types and order of fields declared in these classes
1022   // are the same.
1023   JavaFieldStream old_fs(the_class);
1024   JavaFieldStream new_fs(scratch_class);
1025   for (; !old_fs.done() && !new_fs.done(); old_fs.next(), new_fs.next()) {
1026     // name and signature
1027     Symbol* name_sym1 = the_class->constants()->symbol_at(old_fs.name_index());
1028     Symbol* sig_sym1 = the_class->constants()->symbol_at(old_fs.signature_index());
1029     Symbol* name_sym2 = scratch_class->constants()->symbol_at(new_fs.name_index());
1030     Symbol* sig_sym2 = scratch_class->constants()->symbol_at(new_fs.signature_index());
1031     if (name_sym1 != name_sym2 || sig_sym1 != sig_sym2) {
1032       log_info(redefine, class, normalize)
1033           ("redefined class %s fields change error: field %s %s changed to %s %s.",
1034            the_class->external_name(),
1035            sig_sym1->as_C_string(), name_sym1->as_C_string(),
1036            sig_sym2->as_C_string(), name_sym2->as_C_string());
1037       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_SCHEMA_CHANGED;
1038     }
1039     // offset
1040     if (old_fs.offset() != new_fs.offset()) {
1041       log_info(redefine, class, normalize)
1042           ("redefined class %s field %s change error: offset changed from %d to %d.",
1043            the_class->external_name(), name_sym2->as_C_string(), old_fs.offset(), new_fs.offset());
1044       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_SCHEMA_CHANGED;
1045     }
1046     // access
1047     old_flags = old_fs.access_flags().as_field_flags();
1048     new_flags = new_fs.access_flags().as_field_flags();
1049     if (old_flags != new_flags) {
1050       log_info(redefine, class, normalize)
1051           ("redefined class %s field %s change error: modifiers changed from %d to %d.",
1052            the_class->external_name(), name_sym2->as_C_string(), old_flags, new_flags);
1053       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_SCHEMA_CHANGED;
1054     }
1055   }
1056 
1057   // If both streams aren't done then we have a differing number of
1058   // fields.
1059   if (!old_fs.done() || !new_fs.done()) {
1060     const char* action = old_fs.done() ? "added" : "deleted";
1061     log_info(redefine, class, normalize)
1062         ("redefined class %s fields change error: some fields were %s.",
1063          the_class->external_name(), action);
1064     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_SCHEMA_CHANGED;
1065   }
1066 
1067   // Do a parallel walk through the old and new methods. Detect
1068   // cases where they match (exist in both), have been added in
1069   // the new methods, or have been deleted (exist only in the
1070   // old methods).  The class file parser places methods in order
1071   // by method name, but does not order overloaded methods by
1072   // signature.  In order to determine what fate befell the methods,
1073   // this code places the overloaded new methods that have matching
1074   // old methods in the same order as the old methods and places
1075   // new overloaded methods at the end of overloaded methods of
1076   // that name. The code for this order normalization is adapted
1077   // from the algorithm used in InstanceKlass::find_method().
1078   // Since we are swapping out of order entries as we find them,
1079   // we only have to search forward through the overloaded methods.
1080   // Methods which are added and have the same name as an existing
1081   // method (but different signature) will be put at the end of
1082   // the methods with that name, and the name mismatch code will
1083   // handle them.
1084   Array<Method*>* k_old_methods(the_class->methods());
1085   Array<Method*>* k_new_methods(scratch_class->methods());
1086   int n_old_methods = k_old_methods->length();
1087   int n_new_methods = k_new_methods->length();
1088   Thread* thread = Thread::current();
1089 
1090   int ni = 0;
1091   int oi = 0;
1092   while (true) {
1093     Method* k_old_method;
1094     Method* k_new_method;
1095     enum { matched, added, deleted, undetermined } method_was = undetermined;
1096 
1097     if (oi >= n_old_methods) {
1098       if (ni >= n_new_methods) {
1099         break; // we've looked at everything, done
1100       }
1101       // New method at the end
1102       k_new_method = k_new_methods->at(ni);
1103       method_was = added;
1104     } else if (ni >= n_new_methods) {
1105       // Old method, at the end, is deleted
1106       k_old_method = k_old_methods->at(oi);
1107       method_was = deleted;
1108     } else {
1109       // There are more methods in both the old and new lists
1110       k_old_method = k_old_methods->at(oi);
1111       k_new_method = k_new_methods->at(ni);
1112       if (k_old_method->name() != k_new_method->name()) {
1113         // Methods are sorted by method name, so a mismatch means added
1114         // or deleted
1115         if (k_old_method->name()->fast_compare(k_new_method->name()) > 0) {
1116           method_was = added;
1117         } else {
1118           method_was = deleted;
1119         }
1120       } else if (k_old_method->signature() == k_new_method->signature()) {
1121         // Both the name and signature match
1122         method_was = matched;
1123       } else {
1124         // The name matches, but the signature doesn't, which means we have to
1125         // search forward through the new overloaded methods.
1126         int nj;  // outside the loop for post-loop check
1127         for (nj = ni + 1; nj < n_new_methods; nj++) {
1128           Method* m = k_new_methods->at(nj);
1129           if (k_old_method->name() != m->name()) {
1130             // reached another method name so no more overloaded methods
1131             method_was = deleted;
1132             break;
1133           }
1134           if (k_old_method->signature() == m->signature()) {
1135             // found a match so swap the methods
1136             k_new_methods->at_put(ni, m);
1137             k_new_methods->at_put(nj, k_new_method);
1138             k_new_method = m;
1139             method_was = matched;
1140             break;
1141           }
1142         }
1143 
1144         if (nj >= n_new_methods) {
1145           // reached the end without a match; so method was deleted
1146           method_was = deleted;
1147         }
1148       }
1149     }
1150 
1151     switch (method_was) {
1152     case matched:
1153       // methods match, be sure modifiers do too
1154       old_flags = k_old_method->access_flags().as_method_flags();
1155       new_flags = k_new_method->access_flags().as_method_flags();
1156       if ((old_flags ^ new_flags) & ~(JVM_ACC_NATIVE)) {
1157         log_info(redefine, class, normalize)
1158           ("redefined class %s  method %s modifiers error: modifiers changed from %d to %d",
1159            the_class->external_name(), k_old_method->name_and_sig_as_C_string(), old_flags, new_flags);
1160         return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_METHOD_MODIFIERS_CHANGED;
1161       }
1162       {
1163         u2 new_num = k_new_method->method_idnum();
1164         u2 old_num = k_old_method->method_idnum();
1165         if (new_num != old_num) {
1166           Method* idnum_owner = scratch_class->method_with_idnum(old_num);
1167           if (idnum_owner != nullptr) {
1168             // There is already a method assigned this idnum -- switch them
1169             // Take current and original idnum from the new_method
1170             idnum_owner->set_method_idnum(new_num);
1171             idnum_owner->set_orig_method_idnum(k_new_method->orig_method_idnum());
1172           }
1173           // Take current and original idnum from the old_method
1174           k_new_method->set_method_idnum(old_num);
1175           k_new_method->set_orig_method_idnum(k_old_method->orig_method_idnum());
1176           if (thread->has_pending_exception()) {
1177             return JVMTI_ERROR_OUT_OF_MEMORY;
1178           }
1179         }
1180       }
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     size_t avail_mem = 0;
1362     // Return value ignored - defaulting to 0 on failure.
1363     (void)os::available_memory(avail_mem);
1364     log_debug(redefine, class, load)
1365       ("loading name=%s kind=%d (avail_mem=%zuK)",
1366        the_class->external_name(), _class_load_kind, avail_mem >> 10);
1367 
1368     ClassFileStream st((u1*)_class_defs[i].class_bytes,
1369                        _class_defs[i].class_byte_count,
1370                        "__VM_RedefineClasses__");
1371 
1372     // Set redefined class handle in JvmtiThreadState class.
1373     // This redefined class is sent to agent event handler for class file
1374     // load hook event.
1375     state->set_class_being_redefined(the_class, _class_load_kind);
1376 
1377     JavaThread* THREAD = current; // For exception macros.
1378     ExceptionMark em(THREAD);
1379     Handle protection_domain(THREAD, the_class->protection_domain());
1380     ClassLoadInfo cl_info(protection_domain);
1381     // Parse and create a class from the bytes, but this class isn't added
1382     // to the dictionary, so do not call resolve_from_stream.
1383     InstanceKlass* scratch_class = KlassFactory::create_from_stream(&st,
1384                                                       the_class->name(),
1385                                                       the_class->class_loader_data(),
1386                                                       cl_info,
1387                                                       THREAD);
1388 
1389     // Clear class_being_redefined just to be sure.
1390     state->clear_class_being_redefined();
1391 
1392     // TODO: if this is retransform, and nothing changed we can skip it
1393 
1394     // Need to clean up allocated InstanceKlass if there's an error so assign
1395     // the result here. Caller deallocates all the scratch classes in case of
1396     // an error.
1397     _scratch_classes[i] = scratch_class;
1398 
1399     if (HAS_PENDING_EXCEPTION) {
1400       Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1401       log_info(redefine, class, load, exceptions)("create_from_stream exception: '%s'", ex_name->as_C_string());
1402       CLEAR_PENDING_EXCEPTION;
1403 
1404       if (ex_name == vmSymbols::java_lang_UnsupportedClassVersionError()) {
1405         return JVMTI_ERROR_UNSUPPORTED_VERSION;
1406       } else if (ex_name == vmSymbols::java_lang_ClassFormatError()) {
1407         return JVMTI_ERROR_INVALID_CLASS_FORMAT;
1408       } else if (ex_name == vmSymbols::java_lang_ClassCircularityError()) {
1409         return JVMTI_ERROR_CIRCULAR_CLASS_DEFINITION;
1410       } else if (ex_name == vmSymbols::java_lang_NoClassDefFoundError()) {
1411         // The message will be "XXX (wrong name: YYY)"
1412         return JVMTI_ERROR_NAMES_DONT_MATCH;
1413       } else if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1414         return JVMTI_ERROR_OUT_OF_MEMORY;
1415       } else {  // Just in case more exceptions can be thrown..
1416         return JVMTI_ERROR_FAILS_VERIFICATION;
1417       }
1418     }
1419 
1420     // Ensure class is linked before redefine
1421     if (!the_class->is_linked()) {
1422       the_class->link_class(THREAD);
1423       if (HAS_PENDING_EXCEPTION) {
1424         Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1425         oop message = java_lang_Throwable::message(PENDING_EXCEPTION);
1426         if (message != nullptr) {
1427           char* ex_msg = java_lang_String::as_utf8_string(message);
1428           log_info(redefine, class, load, exceptions)("link_class exception: '%s %s'",
1429                    ex_name->as_C_string(), ex_msg);
1430         } else {
1431           log_info(redefine, class, load, exceptions)("link_class exception: '%s'",
1432                    ex_name->as_C_string());
1433         }
1434         CLEAR_PENDING_EXCEPTION;
1435         if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1436           return JVMTI_ERROR_OUT_OF_MEMORY;
1437         } else if (ex_name == vmSymbols::java_lang_NoClassDefFoundError()) {
1438           return JVMTI_ERROR_INVALID_CLASS;
1439         } else {
1440           return JVMTI_ERROR_INTERNAL;
1441         }
1442       }
1443     }
1444 
1445     // Do the validity checks in compare_and_normalize_class_versions()
1446     // before verifying the byte codes. By doing these checks first, we
1447     // limit the number of functions that require redirection from
1448     // the_class to scratch_class. In particular, we don't have to
1449     // modify JNI GetSuperclass() and thus won't change its performance.
1450     jvmtiError res = compare_and_normalize_class_versions(the_class,
1451                        scratch_class);
1452     if (res != JVMTI_ERROR_NONE) {
1453       return res;
1454     }
1455 
1456     // verify what the caller passed us
1457     {
1458       // The bug 6214132 caused the verification to fail.
1459       // Information about the_class and scratch_class is temporarily
1460       // recorded into jvmtiThreadState. This data is used to redirect
1461       // the_class to scratch_class in the JVM_* functions called by the
1462       // verifier. Please, refer to jvmtiThreadState.hpp for the detailed
1463       // description.
1464       RedefineVerifyMark rvm(the_class, scratch_class, state);
1465       Verifier::verify(scratch_class, true, THREAD);
1466     }
1467 
1468     if (HAS_PENDING_EXCEPTION) {
1469       Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1470       log_info(redefine, class, load, exceptions)("verify_byte_codes exception: '%s'", ex_name->as_C_string());
1471       CLEAR_PENDING_EXCEPTION;
1472       if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1473         return JVMTI_ERROR_OUT_OF_MEMORY;
1474       } else {
1475         // tell the caller the bytecodes are bad
1476         return JVMTI_ERROR_FAILS_VERIFICATION;
1477       }
1478     }
1479 
1480     res = merge_cp_and_rewrite(the_class, scratch_class, THREAD);
1481     if (HAS_PENDING_EXCEPTION) {
1482       Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1483       log_info(redefine, class, load, exceptions)("merge_cp_and_rewrite exception: '%s'", ex_name->as_C_string());
1484       CLEAR_PENDING_EXCEPTION;
1485       if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1486         return JVMTI_ERROR_OUT_OF_MEMORY;
1487       } else {
1488         return JVMTI_ERROR_INTERNAL;
1489       }
1490     }
1491 
1492 #ifdef ASSERT
1493     {
1494       // verify what we have done during constant pool merging
1495       {
1496         RedefineVerifyMark rvm(the_class, scratch_class, state);
1497         Verifier::verify(scratch_class, true, THREAD);
1498       }
1499 
1500       if (HAS_PENDING_EXCEPTION) {
1501         Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1502         log_info(redefine, class, load, exceptions)
1503           ("verify_byte_codes post merge-CP exception: '%s'", ex_name->as_C_string());
1504         CLEAR_PENDING_EXCEPTION;
1505         if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1506           return JVMTI_ERROR_OUT_OF_MEMORY;
1507         } else {
1508           // tell the caller that constant pool merging screwed up
1509           return JVMTI_ERROR_INTERNAL;
1510         }
1511       }
1512     }
1513 #endif // ASSERT
1514 
1515     Rewriter::rewrite(scratch_class, THREAD);
1516     if (!HAS_PENDING_EXCEPTION) {
1517       scratch_class->link_methods(THREAD);
1518     }
1519     if (HAS_PENDING_EXCEPTION) {
1520       Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1521       log_info(redefine, class, load, exceptions)
1522         ("Rewriter::rewrite or link_methods exception: '%s'", ex_name->as_C_string());
1523       CLEAR_PENDING_EXCEPTION;
1524       if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1525         return JVMTI_ERROR_OUT_OF_MEMORY;
1526       } else {
1527         return JVMTI_ERROR_INTERNAL;
1528       }
1529     }
1530     // Return value ignored - defaulting to 0 on failure.
1531     (void)os::available_memory(avail_mem);
1532     log_debug(redefine, class, load)
1533       ("loaded name=%s (avail_mem=%zuK)", the_class->external_name(), avail_mem >> 10);
1534   }
1535 
1536   return JVMTI_ERROR_NONE;
1537 }
1538 
1539 
1540 // Map old_index to new_index as needed. scratch_cp is only needed
1541 // for log calls.
1542 void VM_RedefineClasses::map_index(const constantPoolHandle& scratch_cp,
1543        int old_index, int new_index) {
1544   if (find_new_index(old_index) != 0) {
1545     // old_index is already mapped
1546     return;
1547   }
1548 
1549   if (old_index == new_index) {
1550     // no mapping is needed
1551     return;
1552   }
1553 
1554   _index_map_p->at_put(old_index, new_index);
1555   _index_map_count++;
1556 
1557   log_trace(redefine, class, constantpool)
1558     ("mapped tag %d at index %d to %d", scratch_cp->tag_at(old_index).value(), old_index, new_index);
1559 } // end map_index()
1560 
1561 
1562 // Map old_index to new_index as needed.
1563 void VM_RedefineClasses::map_operand_index(int old_index, int new_index) {
1564   if (find_new_operand_index(old_index) != -1) {
1565     // old_index is already mapped
1566     return;
1567   }
1568 
1569   if (old_index == new_index) {
1570     // no mapping is needed
1571     return;
1572   }
1573 
1574   _operands_index_map_p->at_put(old_index, new_index);
1575   _operands_index_map_count++;
1576 
1577   log_trace(redefine, class, constantpool)("mapped bootstrap specifier at index %d to %d", old_index, new_index);
1578 } // end map_index()
1579 
1580 
1581 // Merge old_cp and scratch_cp and return the results of the merge via
1582 // merge_cp_p. The number of entries in merge_cp_p is returned via
1583 // merge_cp_length_p. The entries in old_cp occupy the same locations
1584 // in merge_cp_p. Also creates a map of indices from entries in
1585 // scratch_cp to the corresponding entry in merge_cp_p. Index map
1586 // entries are only created for entries in scratch_cp that occupy a
1587 // different location in merged_cp_p.
1588 bool VM_RedefineClasses::merge_constant_pools(const constantPoolHandle& old_cp,
1589        const constantPoolHandle& scratch_cp, constantPoolHandle& merge_cp_p,
1590        int& merge_cp_length_p, TRAPS) {
1591 
1592   // Worst case we need old_cp->length() + scratch_cp()->length(),
1593   // but the caller might be smart so make sure we have at least
1594   // the minimum.
1595   if (merge_cp_p->length() < old_cp->length()) {
1596     assert(false, "merge area too small");
1597     return false; // robustness
1598   }
1599 
1600   log_info(redefine, class, constantpool)("old_cp_len=%d, scratch_cp_len=%d", old_cp->length(), scratch_cp->length());
1601 
1602   {
1603     // Pass 0:
1604     // The old_cp is copied to *merge_cp_p; this means that any code
1605     // using old_cp does not have to change. This work looks like a
1606     // perfect fit for ConstantPool*::copy_cp_to(), but we need to
1607     // handle one special case:
1608     // - revert JVM_CONSTANT_Class to JVM_CONSTANT_UnresolvedClass
1609     // This will make verification happy.
1610 
1611     int old_i;  // index into old_cp
1612 
1613     // index zero (0) is not used in constantPools
1614     for (old_i = 1; old_i < old_cp->length(); old_i++) {
1615       // leave debugging crumb
1616       jbyte old_tag = old_cp->tag_at(old_i).value();
1617       switch (old_tag) {
1618       case JVM_CONSTANT_Class:
1619       case JVM_CONSTANT_UnresolvedClass:
1620         // revert the copy to JVM_CONSTANT_UnresolvedClass
1621         // May be resolving while calling this so do the same for
1622         // JVM_CONSTANT_UnresolvedClass (klass_name_at() deals with transition)
1623         merge_cp_p->temp_unresolved_klass_at_put(old_i,
1624           old_cp->klass_name_index_at(old_i));
1625         break;
1626 
1627       case JVM_CONSTANT_Double:
1628       case JVM_CONSTANT_Long:
1629         // just copy the entry to merge_cp_p, but double and long take
1630         // two constant pool entries
1631         ConstantPool::copy_entry_to(old_cp, old_i, merge_cp_p, old_i);
1632         old_i++;
1633         break;
1634 
1635       default:
1636         // just copy the entry to merge_cp_p
1637         ConstantPool::copy_entry_to(old_cp, old_i, merge_cp_p, old_i);
1638         break;
1639       }
1640     } // end for each old_cp entry
1641 
1642     ConstantPool::copy_operands(old_cp, merge_cp_p, CHECK_false);
1643     merge_cp_p->extend_operands(scratch_cp, CHECK_false);
1644 
1645     // We don't need to sanity check that *merge_cp_length_p is within
1646     // *merge_cp_p bounds since we have the minimum on-entry check above.
1647     merge_cp_length_p = old_i;
1648   }
1649 
1650   // merge_cp_len should be the same as old_cp->length() at this point
1651   // so this trace message is really a "warm-and-breathing" message.
1652   log_debug(redefine, class, constantpool)("after pass 0: merge_cp_len=%d", merge_cp_length_p);
1653 
1654   int scratch_i;  // index into scratch_cp
1655   {
1656     // Pass 1a:
1657     // Compare scratch_cp entries to the old_cp entries that we have
1658     // already copied to *merge_cp_p. In this pass, we are eliminating
1659     // exact duplicates (matching entry at same index) so we only
1660     // compare entries in the common indice range.
1661     int increment = 1;
1662     int pass1a_length = MIN2(old_cp->length(), scratch_cp->length());
1663     for (scratch_i = 1; scratch_i < pass1a_length; scratch_i += increment) {
1664       switch (scratch_cp->tag_at(scratch_i).value()) {
1665       case JVM_CONSTANT_Double:
1666       case JVM_CONSTANT_Long:
1667         // double and long take two constant pool entries
1668         increment = 2;
1669         break;
1670 
1671       default:
1672         increment = 1;
1673         break;
1674       }
1675 
1676       bool match = scratch_cp->compare_entry_to(scratch_i, merge_cp_p, scratch_i);
1677       if (match) {
1678         // found a match at the same index so nothing more to do
1679         continue;
1680       }
1681 
1682       int found_i = scratch_cp->find_matching_entry(scratch_i, merge_cp_p);
1683       if (found_i != 0) {
1684         guarantee(found_i != scratch_i,
1685           "compare_entry_to() and find_matching_entry() do not agree");
1686 
1687         // Found a matching entry somewhere else in *merge_cp_p so
1688         // just need a mapping entry.
1689         map_index(scratch_cp, scratch_i, found_i);
1690         continue;
1691       }
1692 
1693       // No match found so we have to append this entry and any unique
1694       // referenced entries to merge_cp_p.
1695       append_entry(scratch_cp, scratch_i, &merge_cp_p, &merge_cp_length_p);
1696     }
1697   }
1698 
1699   log_debug(redefine, class, constantpool)
1700     ("after pass 1a: merge_cp_len=%d, scratch_i=%d, index_map_len=%d",
1701      merge_cp_length_p, scratch_i, _index_map_count);
1702 
1703   if (scratch_i < scratch_cp->length()) {
1704     // Pass 1b:
1705     // old_cp is smaller than scratch_cp so there are entries in
1706     // scratch_cp that we have not yet processed. We take care of
1707     // those now.
1708     int increment = 1;
1709     for (; scratch_i < scratch_cp->length(); scratch_i += increment) {
1710       switch (scratch_cp->tag_at(scratch_i).value()) {
1711       case JVM_CONSTANT_Double:
1712       case JVM_CONSTANT_Long:
1713         // double and long take two constant pool entries
1714         increment = 2;
1715         break;
1716 
1717       default:
1718         increment = 1;
1719         break;
1720       }
1721 
1722       int found_i =
1723         scratch_cp->find_matching_entry(scratch_i, merge_cp_p);
1724       if (found_i != 0) {
1725         // Found a matching entry somewhere else in merge_cp_p so
1726         // just need a mapping entry.
1727         map_index(scratch_cp, scratch_i, found_i);
1728         continue;
1729       }
1730 
1731       // No match found so we have to append this entry and any unique
1732       // referenced entries to merge_cp_p.
1733       append_entry(scratch_cp, scratch_i, &merge_cp_p, &merge_cp_length_p);
1734     }
1735 
1736     log_debug(redefine, class, constantpool)
1737       ("after pass 1b: merge_cp_len=%d, scratch_i=%d, index_map_len=%d",
1738        merge_cp_length_p, scratch_i, _index_map_count);
1739   }
1740   finalize_operands_merge(merge_cp_p, CHECK_false);
1741 
1742   return true;
1743 } // end merge_constant_pools()
1744 
1745 
1746 // Scoped object to clean up the constant pool(s) created for merging
1747 class MergeCPCleaner {
1748   ClassLoaderData*   _loader_data;
1749   ConstantPool*      _cp;
1750   ConstantPool*      _scratch_cp;
1751  public:
1752   MergeCPCleaner(ClassLoaderData* loader_data, ConstantPool* merge_cp) :
1753                  _loader_data(loader_data), _cp(merge_cp), _scratch_cp(nullptr) {}
1754   ~MergeCPCleaner() {
1755     _loader_data->add_to_deallocate_list(_cp);
1756     if (_scratch_cp != nullptr) {
1757       _loader_data->add_to_deallocate_list(_scratch_cp);
1758     }
1759   }
1760   void add_scratch_cp(ConstantPool* scratch_cp) { _scratch_cp = scratch_cp; }
1761 };
1762 
1763 // Merge constant pools between the_class and scratch_class and
1764 // potentially rewrite bytecodes in scratch_class to use the merged
1765 // constant pool.
1766 jvmtiError VM_RedefineClasses::merge_cp_and_rewrite(
1767              InstanceKlass* the_class, InstanceKlass* scratch_class,
1768              TRAPS) {
1769   // worst case merged constant pool length is old and new combined
1770   int merge_cp_length = the_class->constants()->length()
1771         + scratch_class->constants()->length();
1772 
1773   // Constant pools are not easily reused so we allocate a new one
1774   // each time.
1775   // merge_cp is created unsafe for concurrent GC processing.  It
1776   // should be marked safe before discarding it. Even though
1777   // garbage,  if it crosses a card boundary, it may be scanned
1778   // in order to find the start of the first complete object on the card.
1779   ClassLoaderData* loader_data = the_class->class_loader_data();
1780   ConstantPool* merge_cp_oop =
1781     ConstantPool::allocate(loader_data,
1782                            merge_cp_length,
1783                            CHECK_(JVMTI_ERROR_OUT_OF_MEMORY));
1784   MergeCPCleaner cp_cleaner(loader_data, merge_cp_oop);
1785 
1786   HandleMark hm(THREAD);  // make sure handles are cleared before
1787                           // MergeCPCleaner clears out merge_cp_oop
1788   constantPoolHandle merge_cp(THREAD, merge_cp_oop);
1789 
1790   // Get constants() from the old class because it could have been rewritten
1791   // while we were at a safepoint allocating a new constant pool.
1792   constantPoolHandle old_cp(THREAD, the_class->constants());
1793   constantPoolHandle scratch_cp(THREAD, scratch_class->constants());
1794 
1795   // If the length changed, the class was redefined out from under us. Return
1796   // an error.
1797   if (merge_cp_length != the_class->constants()->length()
1798          + scratch_class->constants()->length()) {
1799     return JVMTI_ERROR_INTERNAL;
1800   }
1801 
1802   // Update the version number of the constant pools (may keep scratch_cp)
1803   merge_cp->increment_and_save_version(old_cp->version());
1804   scratch_cp->increment_and_save_version(old_cp->version());
1805 
1806   ResourceMark rm(THREAD);
1807   _index_map_count = 0;
1808   _index_map_p = new intArray(scratch_cp->length(), scratch_cp->length(), -1);
1809 
1810   _operands_cur_length = ConstantPool::operand_array_length(old_cp->operands());
1811   _operands_index_map_count = 0;
1812   int operands_index_map_len = ConstantPool::operand_array_length(scratch_cp->operands());
1813   _operands_index_map_p = new intArray(operands_index_map_len, operands_index_map_len, -1);
1814 
1815   // reference to the cp holder is needed for copy_operands()
1816   merge_cp->set_pool_holder(scratch_class);
1817   bool result = merge_constant_pools(old_cp, scratch_cp, merge_cp,
1818                   merge_cp_length, THREAD);
1819   merge_cp->set_pool_holder(nullptr);
1820 
1821   if (!result) {
1822     // The merge can fail due to memory allocation failure or due
1823     // to robustness checks.
1824     return JVMTI_ERROR_INTERNAL;
1825   }
1826 
1827   // ensure merged constant pool size does not overflow u2
1828   if (merge_cp_length > 0xFFFF) {
1829     log_warning(redefine, class, constantpool)("Merged constant pool overflow: %d entries", merge_cp_length);
1830     return JVMTI_ERROR_INTERNAL;
1831   }
1832 
1833   // Set dynamic constants attribute from the original CP.
1834   if (old_cp->has_dynamic_constant()) {
1835     scratch_cp->set_has_dynamic_constant();
1836   }
1837 
1838   log_info(redefine, class, constantpool)("merge_cp_len=%d, index_map_len=%d", merge_cp_length, _index_map_count);
1839 
1840   if (_index_map_count == 0) {
1841     // there is nothing to map between the new and merged constant pools
1842 
1843     // Copy attributes from scratch_cp to merge_cp
1844     merge_cp->copy_fields(scratch_cp());
1845 
1846     if (old_cp->length() == scratch_cp->length()) {
1847       // The old and new constant pools are the same length and the
1848       // index map is empty. This means that the three constant pools
1849       // are equivalent (but not the same). Unfortunately, the new
1850       // constant pool has not gone through link resolution nor have
1851       // the new class bytecodes gone through constant pool cache
1852       // rewriting so we can't use the old constant pool with the new
1853       // class.
1854 
1855       // toss the merged constant pool at return
1856     } else if (old_cp->length() < scratch_cp->length()) {
1857       // The old constant pool has fewer entries than the new constant
1858       // pool and the index map is empty. This means the new constant
1859       // pool is a superset of the old constant pool. However, the old
1860       // class bytecodes have already gone through constant pool cache
1861       // rewriting so we can't use the new constant pool with the old
1862       // class.
1863 
1864       // toss the merged constant pool at return
1865     } else {
1866       // The old constant pool has more entries than the new constant
1867       // pool and the index map is empty. This means that both the old
1868       // and merged constant pools are supersets of the new constant
1869       // pool.
1870 
1871       // Replace the new constant pool with a shrunken copy of the
1872       // merged constant pool
1873       set_new_constant_pool(loader_data, scratch_class, merge_cp, merge_cp_length,
1874                             CHECK_(JVMTI_ERROR_OUT_OF_MEMORY));
1875       // The new constant pool replaces scratch_cp so have cleaner clean it up.
1876       // It can't be cleaned up while there are handles to it.
1877       cp_cleaner.add_scratch_cp(scratch_cp());
1878     }
1879   } else {
1880     if (log_is_enabled(Trace, redefine, class, constantpool)) {
1881       // don't want to loop unless we are tracing
1882       int count = 0;
1883       for (int i = 1; i < _index_map_p->length(); i++) {
1884         int value = _index_map_p->at(i);
1885 
1886         if (value != -1) {
1887           log_trace(redefine, class, constantpool)("index_map[%d]: old=%d new=%d", count, i, value);
1888           count++;
1889         }
1890       }
1891     }
1892 
1893     // We have entries mapped between the new and merged constant pools
1894     // so we have to rewrite some constant pool references.
1895     if (!rewrite_cp_refs(scratch_class)) {
1896       return JVMTI_ERROR_INTERNAL;
1897     }
1898 
1899     // Copy attributes from scratch_cp to merge_cp (should be done after rewrite_cp_refs())
1900     merge_cp->copy_fields(scratch_cp());
1901 
1902     // Replace the new constant pool with a shrunken copy of the
1903     // merged constant pool so now the rewritten bytecodes have
1904     // valid references; the previous new constant pool will get
1905     // GCed.
1906     set_new_constant_pool(loader_data, scratch_class, merge_cp, merge_cp_length,
1907                           CHECK_(JVMTI_ERROR_OUT_OF_MEMORY));
1908     // The new constant pool replaces scratch_cp so have cleaner clean it up.
1909     // It can't be cleaned up while there are handles to it.
1910     cp_cleaner.add_scratch_cp(scratch_cp());
1911   }
1912 
1913   return JVMTI_ERROR_NONE;
1914 } // end merge_cp_and_rewrite()
1915 
1916 
1917 // Rewrite constant pool references in klass scratch_class.
1918 bool VM_RedefineClasses::rewrite_cp_refs(InstanceKlass* scratch_class) {
1919 
1920   // rewrite constant pool references in the nest attributes:
1921   if (!rewrite_cp_refs_in_nest_attributes(scratch_class)) {
1922     // propagate failure back to caller
1923     return false;
1924   }
1925 
1926   // rewrite constant pool references in the Record attribute:
1927   if (!rewrite_cp_refs_in_record_attribute(scratch_class)) {
1928     // propagate failure back to caller
1929     return false;
1930   }
1931 
1932   // rewrite constant pool references in the PermittedSubclasses attribute:
1933   if (!rewrite_cp_refs_in_permitted_subclasses_attribute(scratch_class)) {
1934     // propagate failure back to caller
1935     return false;
1936   }
1937 
1938   // rewrite constant pool references in the methods:
1939   if (!rewrite_cp_refs_in_methods(scratch_class)) {
1940     // propagate failure back to caller
1941     return false;
1942   }
1943 
1944   // rewrite constant pool references in the class_annotations:
1945   if (!rewrite_cp_refs_in_class_annotations(scratch_class)) {
1946     // propagate failure back to caller
1947     return false;
1948   }
1949 
1950   // rewrite constant pool references in the fields_annotations:
1951   if (!rewrite_cp_refs_in_fields_annotations(scratch_class)) {
1952     // propagate failure back to caller
1953     return false;
1954   }
1955 
1956   // rewrite constant pool references in the methods_annotations:
1957   if (!rewrite_cp_refs_in_methods_annotations(scratch_class)) {
1958     // propagate failure back to caller
1959     return false;
1960   }
1961 
1962   // rewrite constant pool references in the methods_parameter_annotations:
1963   if (!rewrite_cp_refs_in_methods_parameter_annotations(scratch_class)) {
1964     // propagate failure back to caller
1965     return false;
1966   }
1967 
1968   // rewrite constant pool references in the methods_default_annotations:
1969   if (!rewrite_cp_refs_in_methods_default_annotations(scratch_class)) {
1970     // propagate failure back to caller
1971     return false;
1972   }
1973 
1974   // rewrite constant pool references in the class_type_annotations:
1975   if (!rewrite_cp_refs_in_class_type_annotations(scratch_class)) {
1976     // propagate failure back to caller
1977     return false;
1978   }
1979 
1980   // rewrite constant pool references in the fields_type_annotations:
1981   if (!rewrite_cp_refs_in_fields_type_annotations(scratch_class)) {
1982     // propagate failure back to caller
1983     return false;
1984   }
1985 
1986   // rewrite constant pool references in the methods_type_annotations:
1987   if (!rewrite_cp_refs_in_methods_type_annotations(scratch_class)) {
1988     // propagate failure back to caller
1989     return false;
1990   }
1991 
1992   // There can be type annotations in the Code part of a method_info attribute.
1993   // These annotations are not accessible, even by reflection.
1994   // Currently they are not even parsed by the ClassFileParser.
1995   // If runtime access is added they will also need to be rewritten.
1996 
1997   // rewrite source file name index:
1998   u2 source_file_name_idx = scratch_class->source_file_name_index();
1999   if (source_file_name_idx != 0) {
2000     u2 new_source_file_name_idx = find_new_index(source_file_name_idx);
2001     if (new_source_file_name_idx != 0) {
2002       scratch_class->set_source_file_name_index(new_source_file_name_idx);
2003     }
2004   }
2005 
2006   // rewrite class generic signature index:
2007   u2 generic_signature_index = scratch_class->generic_signature_index();
2008   if (generic_signature_index != 0) {
2009     u2 new_generic_signature_index = find_new_index(generic_signature_index);
2010     if (new_generic_signature_index != 0) {
2011       scratch_class->set_generic_signature_index(new_generic_signature_index);
2012     }
2013   }
2014 
2015   return true;
2016 } // end rewrite_cp_refs()
2017 
2018 // Rewrite constant pool references in the NestHost and NestMembers attributes.
2019 bool VM_RedefineClasses::rewrite_cp_refs_in_nest_attributes(
2020        InstanceKlass* scratch_class) {
2021 
2022   u2 cp_index = scratch_class->nest_host_index();
2023   if (cp_index != 0) {
2024     scratch_class->set_nest_host_index(find_new_index(cp_index));
2025   }
2026   Array<u2>* nest_members = scratch_class->nest_members();
2027   for (int i = 0; i < nest_members->length(); i++) {
2028     u2 cp_index = nest_members->at(i);
2029     nest_members->at_put(i, find_new_index(cp_index));
2030   }
2031   return true;
2032 }
2033 
2034 // Rewrite constant pool references in the Record attribute.
2035 bool VM_RedefineClasses::rewrite_cp_refs_in_record_attribute(InstanceKlass* scratch_class) {
2036   Array<RecordComponent*>* components = scratch_class->record_components();
2037   if (components != nullptr) {
2038     for (int i = 0; i < components->length(); i++) {
2039       RecordComponent* component = components->at(i);
2040       u2 cp_index = component->name_index();
2041       component->set_name_index(find_new_index(cp_index));
2042       cp_index = component->descriptor_index();
2043       component->set_descriptor_index(find_new_index(cp_index));
2044       cp_index = component->generic_signature_index();
2045       if (cp_index != 0) {
2046         component->set_generic_signature_index(find_new_index(cp_index));
2047       }
2048 
2049       AnnotationArray* annotations = component->annotations();
2050       if (annotations != nullptr && annotations->length() != 0) {
2051         int byte_i = 0;  // byte index into annotations
2052         if (!rewrite_cp_refs_in_annotations_typeArray(annotations, byte_i)) {
2053           log_debug(redefine, class, annotation)("bad record_component_annotations at %d", i);
2054           // propagate failure back to caller
2055           return false;
2056         }
2057       }
2058 
2059       AnnotationArray* type_annotations = component->type_annotations();
2060       if (type_annotations != nullptr && type_annotations->length() != 0) {
2061         int byte_i = 0;  // byte index into annotations
2062         if (!rewrite_cp_refs_in_annotations_typeArray(type_annotations, byte_i)) {
2063           log_debug(redefine, class, annotation)("bad record_component_type_annotations at %d", i);
2064           // propagate failure back to caller
2065           return false;
2066         }
2067       }
2068     }
2069   }
2070   return true;
2071 }
2072 
2073 // Rewrite constant pool references in the PermittedSubclasses attribute.
2074 bool VM_RedefineClasses::rewrite_cp_refs_in_permitted_subclasses_attribute(
2075        InstanceKlass* scratch_class) {
2076 
2077   Array<u2>* permitted_subclasses = scratch_class->permitted_subclasses();
2078   assert(permitted_subclasses != nullptr, "unexpected null permitted_subclasses");
2079   for (int i = 0; i < permitted_subclasses->length(); i++) {
2080     u2 cp_index = permitted_subclasses->at(i);
2081     permitted_subclasses->at_put(i, find_new_index(cp_index));
2082   }
2083   return true;
2084 }
2085 
2086 // Rewrite constant pool references in the methods.
2087 bool VM_RedefineClasses::rewrite_cp_refs_in_methods(InstanceKlass* scratch_class) {
2088 
2089   Array<Method*>* methods = scratch_class->methods();
2090 
2091   if (methods == nullptr || methods->length() == 0) {
2092     // no methods so nothing to do
2093     return true;
2094   }
2095 
2096   JavaThread* THREAD = JavaThread::current(); // For exception macros.
2097   ExceptionMark em(THREAD);
2098 
2099   // rewrite constant pool references in the methods:
2100   for (int i = methods->length() - 1; i >= 0; i--) {
2101     methodHandle method(THREAD, methods->at(i));
2102     methodHandle new_method;
2103     rewrite_cp_refs_in_method(method, &new_method, THREAD);
2104     if (!new_method.is_null()) {
2105       // the method has been replaced so save the new method version
2106       // even in the case of an exception.  original method is on the
2107       // deallocation list.
2108       methods->at_put(i, new_method());
2109     }
2110     if (HAS_PENDING_EXCEPTION) {
2111       Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
2112       log_info(redefine, class, load, exceptions)("rewrite_cp_refs_in_method exception: '%s'", ex_name->as_C_string());
2113       // Need to clear pending exception here as the super caller sets
2114       // the JVMTI_ERROR_INTERNAL if the returned value is false.
2115       CLEAR_PENDING_EXCEPTION;
2116       return false;
2117     }
2118   }
2119 
2120   return true;
2121 }
2122 
2123 
2124 // Rewrite constant pool references in the specific method. This code
2125 // was adapted from Rewriter::rewrite_method().
2126 void VM_RedefineClasses::rewrite_cp_refs_in_method(methodHandle method,
2127        methodHandle *new_method_p, TRAPS) {
2128 
2129   *new_method_p = methodHandle();  // default is no new method
2130 
2131   // We cache a pointer to the bytecodes here in code_base. If GC
2132   // moves the Method*, then the bytecodes will also move which
2133   // will likely cause a crash. We create a NoSafepointVerifier
2134   // object to detect whether we pass a possible safepoint in this
2135   // code block.
2136   NoSafepointVerifier nsv;
2137 
2138   // Bytecodes and their length
2139   address code_base = method->code_base();
2140   int code_length = method->code_size();
2141 
2142   int bc_length;
2143   for (int bci = 0; bci < code_length; bci += bc_length) {
2144     address bcp = code_base + bci;
2145     Bytecodes::Code c = (Bytecodes::Code)(*bcp);
2146 
2147     bc_length = Bytecodes::length_for(c);
2148     if (bc_length == 0) {
2149       // More complicated bytecodes report a length of zero so
2150       // we have to try again a slightly different way.
2151       bc_length = Bytecodes::length_at(method(), bcp);
2152     }
2153 
2154     assert(bc_length != 0, "impossible bytecode length");
2155 
2156     switch (c) {
2157       case Bytecodes::_ldc:
2158       {
2159         u1 cp_index = *(bcp + 1);
2160         u2 new_index = find_new_index(cp_index);
2161 
2162         if (StressLdcRewrite && new_index == 0) {
2163           // If we are stressing ldc -> ldc_w rewriting, then we
2164           // always need a new_index value.
2165           new_index = cp_index;
2166         }
2167         if (new_index != 0) {
2168           // the original index is mapped so we have more work to do
2169           if (!StressLdcRewrite && new_index <= max_jubyte) {
2170             // The new value can still use ldc instead of ldc_w
2171             // unless we are trying to stress ldc -> ldc_w rewriting
2172             log_trace(redefine, class, constantpool)
2173               ("%s@" INTPTR_FORMAT " old=%d, new=%d", Bytecodes::name(c), p2i(bcp), cp_index, new_index);
2174             // We checked that new_index fits in a u1 so this cast is safe
2175             *(bcp + 1) = (u1)new_index;
2176           } else {
2177             log_trace(redefine, class, constantpool)
2178               ("%s->ldc_w@" INTPTR_FORMAT " old=%d, new=%d", Bytecodes::name(c), p2i(bcp), cp_index, new_index);
2179             // the new value needs ldc_w instead of ldc
2180             u_char inst_buffer[4]; // max instruction size is 4 bytes
2181             bcp = (address)inst_buffer;
2182             // construct new instruction sequence
2183             *bcp = Bytecodes::_ldc_w;
2184             bcp++;
2185             // Rewriter::rewrite_method() does not rewrite ldc -> ldc_w.
2186             // See comment below for difference between put_Java_u2()
2187             // and put_native_u2().
2188             Bytes::put_Java_u2(bcp, new_index);
2189 
2190             Relocator rc(method, nullptr /* no RelocatorListener needed */);
2191             methodHandle m;
2192             {
2193               PauseNoSafepointVerifier pnsv(&nsv);
2194 
2195               // ldc is 2 bytes and ldc_w is 3 bytes
2196               m = rc.insert_space_at(bci, 3, inst_buffer, CHECK);
2197             }
2198 
2199             // return the new method so that the caller can update
2200             // the containing class
2201             *new_method_p = method = m;
2202             // switch our bytecode processing loop from the old method
2203             // to the new method
2204             code_base = method->code_base();
2205             code_length = method->code_size();
2206             bcp = code_base + bci;
2207             c = (Bytecodes::Code)(*bcp);
2208             bc_length = Bytecodes::length_for(c);
2209             assert(bc_length != 0, "sanity check");
2210           } // end we need ldc_w instead of ldc
2211         } // end if there is a mapped index
2212       } break;
2213 
2214       // these bytecodes have a two-byte constant pool index
2215       case Bytecodes::_anewarray      : // fall through
2216       case Bytecodes::_checkcast      : // fall through
2217       case Bytecodes::_getfield       : // fall through
2218       case Bytecodes::_getstatic      : // fall through
2219       case Bytecodes::_instanceof     : // fall through
2220       case Bytecodes::_invokedynamic  : // fall through
2221       case Bytecodes::_invokeinterface: // fall through
2222       case Bytecodes::_invokespecial  : // fall through
2223       case Bytecodes::_invokestatic   : // fall through
2224       case Bytecodes::_invokevirtual  : // fall through
2225       case Bytecodes::_ldc_w          : // fall through
2226       case Bytecodes::_ldc2_w         : // fall through
2227       case Bytecodes::_multianewarray : // fall through
2228       case Bytecodes::_new            : // fall through
2229       case Bytecodes::_putfield       : // fall through
2230       case Bytecodes::_putstatic      :
2231       {
2232         address p = bcp + 1;
2233         int cp_index = Bytes::get_Java_u2(p);
2234         u2 new_index = find_new_index(cp_index);
2235         if (new_index != 0) {
2236           // the original index is mapped so update w/ new value
2237           log_trace(redefine, class, constantpool)
2238             ("%s@" INTPTR_FORMAT " old=%d, new=%d", Bytecodes::name(c),p2i(bcp), cp_index, new_index);
2239           // Rewriter::rewrite_method() uses put_native_u2() in this
2240           // situation because it is reusing the constant pool index
2241           // location for a native index into the ConstantPoolCache.
2242           // Since we are updating the constant pool index prior to
2243           // verification and ConstantPoolCache initialization, we
2244           // need to keep the new index in Java byte order.
2245           Bytes::put_Java_u2(p, new_index);
2246         }
2247       } break;
2248       default:
2249         break;
2250     }
2251   } // end for each bytecode
2252 } // end rewrite_cp_refs_in_method()
2253 
2254 
2255 // Rewrite constant pool references in the class_annotations field.
2256 bool VM_RedefineClasses::rewrite_cp_refs_in_class_annotations(InstanceKlass* scratch_class) {
2257 
2258   AnnotationArray* class_annotations = scratch_class->class_annotations();
2259   if (class_annotations == nullptr || class_annotations->length() == 0) {
2260     // no class_annotations so nothing to do
2261     return true;
2262   }
2263 
2264   log_debug(redefine, class, annotation)("class_annotations length=%d", class_annotations->length());
2265 
2266   int byte_i = 0;  // byte index into class_annotations
2267   return rewrite_cp_refs_in_annotations_typeArray(class_annotations, byte_i);
2268 }
2269 
2270 
2271 // Rewrite constant pool references in an annotations typeArray. This
2272 // "structure" is adapted from the RuntimeVisibleAnnotations_attribute
2273 // that is described in section 4.8.15 of the 2nd-edition of the VM spec:
2274 //
2275 // annotations_typeArray {
2276 //   u2 num_annotations;
2277 //   annotation annotations[num_annotations];
2278 // }
2279 //
2280 bool VM_RedefineClasses::rewrite_cp_refs_in_annotations_typeArray(
2281        AnnotationArray* annotations_typeArray, int &byte_i_ref) {
2282 
2283   if ((byte_i_ref + 2) > annotations_typeArray->length()) {
2284     // not enough room for num_annotations field
2285     log_debug(redefine, class, annotation)("length() is too small for num_annotations field");
2286     return false;
2287   }
2288 
2289   u2 num_annotations = Bytes::get_Java_u2((address)
2290                          annotations_typeArray->adr_at(byte_i_ref));
2291   byte_i_ref += 2;
2292 
2293   log_debug(redefine, class, annotation)("num_annotations=%d", num_annotations);
2294 
2295   int calc_num_annotations = 0;
2296   for (; calc_num_annotations < num_annotations; calc_num_annotations++) {
2297     if (!rewrite_cp_refs_in_annotation_struct(annotations_typeArray, byte_i_ref)) {
2298       log_debug(redefine, class, annotation)("bad annotation_struct at %d", calc_num_annotations);
2299       // propagate failure back to caller
2300       return false;
2301     }
2302   }
2303   assert(num_annotations == calc_num_annotations, "sanity check");
2304 
2305   return true;
2306 } // end rewrite_cp_refs_in_annotations_typeArray()
2307 
2308 
2309 // Rewrite constant pool references in the annotation struct portion of
2310 // an annotations_typeArray. This "structure" is from section 4.8.15 of
2311 // the 2nd-edition of the VM spec:
2312 //
2313 // struct annotation {
2314 //   u2 type_index;
2315 //   u2 num_element_value_pairs;
2316 //   {
2317 //     u2 element_name_index;
2318 //     element_value value;
2319 //   } element_value_pairs[num_element_value_pairs];
2320 // }
2321 //
2322 bool VM_RedefineClasses::rewrite_cp_refs_in_annotation_struct(
2323        AnnotationArray* annotations_typeArray, int &byte_i_ref) {
2324   if ((byte_i_ref + 2 + 2) > annotations_typeArray->length()) {
2325     // not enough room for smallest annotation_struct
2326     log_debug(redefine, class, annotation)("length() is too small for annotation_struct");
2327     return false;
2328   }
2329 
2330   u2 type_index = rewrite_cp_ref_in_annotation_data(annotations_typeArray,
2331                     byte_i_ref, "type_index");
2332 
2333   u2 num_element_value_pairs = Bytes::get_Java_u2((address)
2334                                  annotations_typeArray->adr_at(byte_i_ref));
2335   byte_i_ref += 2;
2336 
2337   log_debug(redefine, class, annotation)
2338     ("type_index=%d  num_element_value_pairs=%d", type_index, num_element_value_pairs);
2339 
2340   int calc_num_element_value_pairs = 0;
2341   for (; calc_num_element_value_pairs < num_element_value_pairs;
2342        calc_num_element_value_pairs++) {
2343     if ((byte_i_ref + 2) > annotations_typeArray->length()) {
2344       // not enough room for another element_name_index, let alone
2345       // the rest of another component
2346       log_debug(redefine, class, annotation)("length() is too small for element_name_index");
2347       return false;
2348     }
2349 
2350     u2 element_name_index = rewrite_cp_ref_in_annotation_data(
2351                               annotations_typeArray, byte_i_ref,
2352                               "element_name_index");
2353 
2354     log_debug(redefine, class, annotation)("element_name_index=%d", element_name_index);
2355 
2356     if (!rewrite_cp_refs_in_element_value(annotations_typeArray, byte_i_ref)) {
2357       log_debug(redefine, class, annotation)("bad element_value at %d", calc_num_element_value_pairs);
2358       // propagate failure back to caller
2359       return false;
2360     }
2361   } // end for each component
2362   assert(num_element_value_pairs == calc_num_element_value_pairs,
2363     "sanity check");
2364 
2365   return true;
2366 } // end rewrite_cp_refs_in_annotation_struct()
2367 
2368 
2369 // Rewrite a constant pool reference at the current position in
2370 // annotations_typeArray if needed. Returns the original constant
2371 // pool reference if a rewrite was not needed or the new constant
2372 // pool reference if a rewrite was needed.
2373 u2 VM_RedefineClasses::rewrite_cp_ref_in_annotation_data(
2374      AnnotationArray* annotations_typeArray, int &byte_i_ref,
2375      const char * trace_mesg) {
2376 
2377   address cp_index_addr = (address)
2378     annotations_typeArray->adr_at(byte_i_ref);
2379   u2 old_cp_index = Bytes::get_Java_u2(cp_index_addr);
2380   u2 new_cp_index = find_new_index(old_cp_index);
2381   if (new_cp_index != 0) {
2382     log_debug(redefine, class, annotation)("mapped old %s=%d", trace_mesg, old_cp_index);
2383     Bytes::put_Java_u2(cp_index_addr, new_cp_index);
2384     old_cp_index = new_cp_index;
2385   }
2386   byte_i_ref += 2;
2387   return old_cp_index;
2388 }
2389 
2390 
2391 // Rewrite constant pool references in the element_value portion of an
2392 // annotations_typeArray. This "structure" is from section 4.8.15.1 of
2393 // the 2nd-edition of the VM spec:
2394 //
2395 // struct element_value {
2396 //   u1 tag;
2397 //   union {
2398 //     u2 const_value_index;
2399 //     {
2400 //       u2 type_name_index;
2401 //       u2 const_name_index;
2402 //     } enum_const_value;
2403 //     u2 class_info_index;
2404 //     annotation annotation_value;
2405 //     struct {
2406 //       u2 num_values;
2407 //       element_value values[num_values];
2408 //     } array_value;
2409 //   } value;
2410 // }
2411 //
2412 bool VM_RedefineClasses::rewrite_cp_refs_in_element_value(
2413        AnnotationArray* annotations_typeArray, int &byte_i_ref) {
2414 
2415   if ((byte_i_ref + 1) > annotations_typeArray->length()) {
2416     // not enough room for a tag let alone the rest of an element_value
2417     log_debug(redefine, class, annotation)("length() is too small for a tag");
2418     return false;
2419   }
2420 
2421   u1 tag = annotations_typeArray->at(byte_i_ref);
2422   byte_i_ref++;
2423   log_debug(redefine, class, annotation)("tag='%c'", tag);
2424 
2425   switch (tag) {
2426     // These BaseType tag values are from Table 4.2 in VM spec:
2427     case JVM_SIGNATURE_BYTE:
2428     case JVM_SIGNATURE_CHAR:
2429     case JVM_SIGNATURE_DOUBLE:
2430     case JVM_SIGNATURE_FLOAT:
2431     case JVM_SIGNATURE_INT:
2432     case JVM_SIGNATURE_LONG:
2433     case JVM_SIGNATURE_SHORT:
2434     case JVM_SIGNATURE_BOOLEAN:
2435 
2436     // The remaining tag values are from Table 4.8 in the 2nd-edition of
2437     // the VM spec:
2438     case 's':
2439     {
2440       // For the above tag values (including the BaseType values),
2441       // value.const_value_index is right union field.
2442 
2443       if ((byte_i_ref + 2) > annotations_typeArray->length()) {
2444         // not enough room for a const_value_index
2445         log_debug(redefine, class, annotation)("length() is too small for a const_value_index");
2446         return false;
2447       }
2448 
2449       u2 const_value_index = rewrite_cp_ref_in_annotation_data(
2450                                annotations_typeArray, byte_i_ref,
2451                                "const_value_index");
2452 
2453       log_debug(redefine, class, annotation)("const_value_index=%d", const_value_index);
2454     } break;
2455 
2456     case 'e':
2457     {
2458       // for the above tag value, value.enum_const_value is right union field
2459 
2460       if ((byte_i_ref + 4) > annotations_typeArray->length()) {
2461         // not enough room for a enum_const_value
2462         log_debug(redefine, class, annotation)("length() is too small for a enum_const_value");
2463         return false;
2464       }
2465 
2466       u2 type_name_index = rewrite_cp_ref_in_annotation_data(
2467                              annotations_typeArray, byte_i_ref,
2468                              "type_name_index");
2469 
2470       u2 const_name_index = rewrite_cp_ref_in_annotation_data(
2471                               annotations_typeArray, byte_i_ref,
2472                               "const_name_index");
2473 
2474       log_debug(redefine, class, annotation)
2475         ("type_name_index=%d  const_name_index=%d", type_name_index, const_name_index);
2476     } break;
2477 
2478     case 'c':
2479     {
2480       // for the above tag value, value.class_info_index is right union field
2481 
2482       if ((byte_i_ref + 2) > annotations_typeArray->length()) {
2483         // not enough room for a class_info_index
2484         log_debug(redefine, class, annotation)("length() is too small for a class_info_index");
2485         return false;
2486       }
2487 
2488       u2 class_info_index = rewrite_cp_ref_in_annotation_data(
2489                               annotations_typeArray, byte_i_ref,
2490                               "class_info_index");
2491 
2492       log_debug(redefine, class, annotation)("class_info_index=%d", class_info_index);
2493     } break;
2494 
2495     case '@':
2496       // For the above tag value, value.attr_value is the right union
2497       // field. This is a nested annotation.
2498       if (!rewrite_cp_refs_in_annotation_struct(annotations_typeArray, byte_i_ref)) {
2499         // propagate failure back to caller
2500         return false;
2501       }
2502       break;
2503 
2504     case JVM_SIGNATURE_ARRAY:
2505     {
2506       if ((byte_i_ref + 2) > annotations_typeArray->length()) {
2507         // not enough room for a num_values field
2508         log_debug(redefine, class, annotation)("length() is too small for a num_values field");
2509         return false;
2510       }
2511 
2512       // For the above tag value, value.array_value is the right union
2513       // field. This is an array of nested element_value.
2514       u2 num_values = Bytes::get_Java_u2((address)
2515                         annotations_typeArray->adr_at(byte_i_ref));
2516       byte_i_ref += 2;
2517       log_debug(redefine, class, annotation)("num_values=%d", num_values);
2518 
2519       int calc_num_values = 0;
2520       for (; calc_num_values < num_values; calc_num_values++) {
2521         if (!rewrite_cp_refs_in_element_value(annotations_typeArray, byte_i_ref)) {
2522           log_debug(redefine, class, annotation)("bad nested element_value at %d", calc_num_values);
2523           // propagate failure back to caller
2524           return false;
2525         }
2526       }
2527       assert(num_values == calc_num_values, "sanity check");
2528     } break;
2529 
2530     default:
2531       log_debug(redefine, class, annotation)("bad tag=0x%x", tag);
2532       return false;
2533   } // end decode tag field
2534 
2535   return true;
2536 } // end rewrite_cp_refs_in_element_value()
2537 
2538 
2539 // Rewrite constant pool references in a fields_annotations field.
2540 bool VM_RedefineClasses::rewrite_cp_refs_in_fields_annotations(
2541        InstanceKlass* scratch_class) {
2542 
2543   Array<AnnotationArray*>* fields_annotations = scratch_class->fields_annotations();
2544 
2545   if (fields_annotations == nullptr || fields_annotations->length() == 0) {
2546     // no fields_annotations so nothing to do
2547     return true;
2548   }
2549 
2550   log_debug(redefine, class, annotation)("fields_annotations length=%d", fields_annotations->length());
2551 
2552   for (int i = 0; i < fields_annotations->length(); i++) {
2553     AnnotationArray* field_annotations = fields_annotations->at(i);
2554     if (field_annotations == nullptr || field_annotations->length() == 0) {
2555       // this field does not have any annotations so skip it
2556       continue;
2557     }
2558 
2559     int byte_i = 0;  // byte index into field_annotations
2560     if (!rewrite_cp_refs_in_annotations_typeArray(field_annotations, byte_i)) {
2561       log_debug(redefine, class, annotation)("bad field_annotations at %d", i);
2562       // propagate failure back to caller
2563       return false;
2564     }
2565   }
2566 
2567   return true;
2568 } // end rewrite_cp_refs_in_fields_annotations()
2569 
2570 
2571 // Rewrite constant pool references in a methods_annotations field.
2572 bool VM_RedefineClasses::rewrite_cp_refs_in_methods_annotations(
2573        InstanceKlass* scratch_class) {
2574 
2575   for (int i = 0; i < scratch_class->methods()->length(); i++) {
2576     Method* m = scratch_class->methods()->at(i);
2577     AnnotationArray* method_annotations = m->constMethod()->method_annotations();
2578 
2579     if (method_annotations == nullptr || method_annotations->length() == 0) {
2580       // this method does not have any annotations so skip it
2581       continue;
2582     }
2583 
2584     int byte_i = 0;  // byte index into method_annotations
2585     if (!rewrite_cp_refs_in_annotations_typeArray(method_annotations, byte_i)) {
2586       log_debug(redefine, class, annotation)("bad method_annotations at %d", i);
2587       // propagate failure back to caller
2588       return false;
2589     }
2590   }
2591 
2592   return true;
2593 } // end rewrite_cp_refs_in_methods_annotations()
2594 
2595 
2596 // Rewrite constant pool references in a methods_parameter_annotations
2597 // field. This "structure" is adapted from the
2598 // RuntimeVisibleParameterAnnotations_attribute described in section
2599 // 4.8.17 of the 2nd-edition of the VM spec:
2600 //
2601 // methods_parameter_annotations_typeArray {
2602 //   u1 num_parameters;
2603 //   {
2604 //     u2 num_annotations;
2605 //     annotation annotations[num_annotations];
2606 //   } parameter_annotations[num_parameters];
2607 // }
2608 //
2609 bool VM_RedefineClasses::rewrite_cp_refs_in_methods_parameter_annotations(
2610        InstanceKlass* scratch_class) {
2611 
2612   for (int i = 0; i < scratch_class->methods()->length(); i++) {
2613     Method* m = scratch_class->methods()->at(i);
2614     AnnotationArray* method_parameter_annotations = m->constMethod()->parameter_annotations();
2615     if (method_parameter_annotations == nullptr
2616         || method_parameter_annotations->length() == 0) {
2617       // this method does not have any parameter annotations so skip it
2618       continue;
2619     }
2620 
2621     if (method_parameter_annotations->length() < 1) {
2622       // not enough room for a num_parameters field
2623       log_debug(redefine, class, annotation)("length() is too small for a num_parameters field at %d", i);
2624       return false;
2625     }
2626 
2627     int byte_i = 0;  // byte index into method_parameter_annotations
2628 
2629     u1 num_parameters = method_parameter_annotations->at(byte_i);
2630     byte_i++;
2631 
2632     log_debug(redefine, class, annotation)("num_parameters=%d", num_parameters);
2633 
2634     int calc_num_parameters = 0;
2635     for (; calc_num_parameters < num_parameters; calc_num_parameters++) {
2636       if (!rewrite_cp_refs_in_annotations_typeArray(method_parameter_annotations, byte_i)) {
2637         log_debug(redefine, class, annotation)("bad method_parameter_annotations at %d", calc_num_parameters);
2638         // propagate failure back to caller
2639         return false;
2640       }
2641     }
2642     assert(num_parameters == calc_num_parameters, "sanity check");
2643   }
2644 
2645   return true;
2646 } // end rewrite_cp_refs_in_methods_parameter_annotations()
2647 
2648 
2649 // Rewrite constant pool references in a methods_default_annotations
2650 // field. This "structure" is adapted from the AnnotationDefault_attribute
2651 // that is described in section 4.8.19 of the 2nd-edition of the VM spec:
2652 //
2653 // methods_default_annotations_typeArray {
2654 //   element_value default_value;
2655 // }
2656 //
2657 bool VM_RedefineClasses::rewrite_cp_refs_in_methods_default_annotations(
2658        InstanceKlass* scratch_class) {
2659 
2660   for (int i = 0; i < scratch_class->methods()->length(); i++) {
2661     Method* m = scratch_class->methods()->at(i);
2662     AnnotationArray* method_default_annotations = m->constMethod()->default_annotations();
2663     if (method_default_annotations == nullptr
2664         || method_default_annotations->length() == 0) {
2665       // this method does not have any default annotations so skip it
2666       continue;
2667     }
2668 
2669     int byte_i = 0;  // byte index into method_default_annotations
2670 
2671     if (!rewrite_cp_refs_in_element_value(
2672            method_default_annotations, byte_i)) {
2673       log_debug(redefine, class, annotation)("bad default element_value at %d", i);
2674       // propagate failure back to caller
2675       return false;
2676     }
2677   }
2678 
2679   return true;
2680 } // end rewrite_cp_refs_in_methods_default_annotations()
2681 
2682 
2683 // Rewrite constant pool references in a class_type_annotations field.
2684 bool VM_RedefineClasses::rewrite_cp_refs_in_class_type_annotations(
2685        InstanceKlass* scratch_class) {
2686 
2687   AnnotationArray* class_type_annotations = scratch_class->class_type_annotations();
2688   if (class_type_annotations == nullptr || class_type_annotations->length() == 0) {
2689     // no class_type_annotations so nothing to do
2690     return true;
2691   }
2692 
2693   log_debug(redefine, class, annotation)("class_type_annotations length=%d", class_type_annotations->length());
2694 
2695   int byte_i = 0;  // byte index into class_type_annotations
2696   return rewrite_cp_refs_in_type_annotations_typeArray(class_type_annotations,
2697       byte_i, "ClassFile");
2698 } // end rewrite_cp_refs_in_class_type_annotations()
2699 
2700 
2701 // Rewrite constant pool references in a fields_type_annotations field.
2702 bool VM_RedefineClasses::rewrite_cp_refs_in_fields_type_annotations(InstanceKlass* scratch_class) {
2703 
2704   Array<AnnotationArray*>* fields_type_annotations = scratch_class->fields_type_annotations();
2705   if (fields_type_annotations == nullptr || fields_type_annotations->length() == 0) {
2706     // no fields_type_annotations so nothing to do
2707     return true;
2708   }
2709 
2710   log_debug(redefine, class, annotation)("fields_type_annotations length=%d", fields_type_annotations->length());
2711 
2712   for (int i = 0; i < fields_type_annotations->length(); i++) {
2713     AnnotationArray* field_type_annotations = fields_type_annotations->at(i);
2714     if (field_type_annotations == nullptr || field_type_annotations->length() == 0) {
2715       // this field does not have any annotations so skip it
2716       continue;
2717     }
2718 
2719     int byte_i = 0;  // byte index into field_type_annotations
2720     if (!rewrite_cp_refs_in_type_annotations_typeArray(field_type_annotations,
2721            byte_i, "field_info")) {
2722       log_debug(redefine, class, annotation)("bad field_type_annotations at %d", i);
2723       // propagate failure back to caller
2724       return false;
2725     }
2726   }
2727 
2728   return true;
2729 } // end rewrite_cp_refs_in_fields_type_annotations()
2730 
2731 
2732 // Rewrite constant pool references in a methods_type_annotations field.
2733 bool VM_RedefineClasses::rewrite_cp_refs_in_methods_type_annotations(
2734        InstanceKlass* scratch_class) {
2735 
2736   for (int i = 0; i < scratch_class->methods()->length(); i++) {
2737     Method* m = scratch_class->methods()->at(i);
2738     AnnotationArray* method_type_annotations = m->constMethod()->type_annotations();
2739 
2740     if (method_type_annotations == nullptr || method_type_annotations->length() == 0) {
2741       // this method does not have any annotations so skip it
2742       continue;
2743     }
2744 
2745     log_debug(redefine, class, annotation)("methods type_annotations length=%d", method_type_annotations->length());
2746 
2747     int byte_i = 0;  // byte index into method_type_annotations
2748     if (!rewrite_cp_refs_in_type_annotations_typeArray(method_type_annotations,
2749            byte_i, "method_info")) {
2750       log_debug(redefine, class, annotation)("bad method_type_annotations at %d", i);
2751       // propagate failure back to caller
2752       return false;
2753     }
2754   }
2755 
2756   return true;
2757 } // end rewrite_cp_refs_in_methods_type_annotations()
2758 
2759 
2760 // Rewrite constant pool references in a type_annotations
2761 // field. This "structure" is adapted from the
2762 // RuntimeVisibleTypeAnnotations_attribute described in
2763 // section 4.7.20 of the Java SE 8 Edition of the VM spec:
2764 //
2765 // type_annotations_typeArray {
2766 //   u2              num_annotations;
2767 //   type_annotation annotations[num_annotations];
2768 // }
2769 //
2770 bool VM_RedefineClasses::rewrite_cp_refs_in_type_annotations_typeArray(
2771        AnnotationArray* type_annotations_typeArray, int &byte_i_ref,
2772        const char * location_mesg) {
2773 
2774   if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
2775     // not enough room for num_annotations field
2776     log_debug(redefine, class, annotation)("length() is too small for num_annotations field");
2777     return false;
2778   }
2779 
2780   u2 num_annotations = Bytes::get_Java_u2((address)
2781                          type_annotations_typeArray->adr_at(byte_i_ref));
2782   byte_i_ref += 2;
2783 
2784   log_debug(redefine, class, annotation)("num_type_annotations=%d", num_annotations);
2785 
2786   int calc_num_annotations = 0;
2787   for (; calc_num_annotations < num_annotations; calc_num_annotations++) {
2788     if (!rewrite_cp_refs_in_type_annotation_struct(type_annotations_typeArray,
2789            byte_i_ref, location_mesg)) {
2790       log_debug(redefine, class, annotation)("bad type_annotation_struct at %d", calc_num_annotations);
2791       // propagate failure back to caller
2792       return false;
2793     }
2794   }
2795   assert(num_annotations == calc_num_annotations, "sanity check");
2796 
2797   if (byte_i_ref != type_annotations_typeArray->length()) {
2798     log_debug(redefine, class, annotation)
2799       ("read wrong amount of bytes at end of processing type_annotations_typeArray (%d of %d bytes were read)",
2800        byte_i_ref, type_annotations_typeArray->length());
2801     return false;
2802   }
2803 
2804   return true;
2805 } // end rewrite_cp_refs_in_type_annotations_typeArray()
2806 
2807 
2808 // Rewrite constant pool references in a type_annotation
2809 // field. This "structure" is adapted from the
2810 // RuntimeVisibleTypeAnnotations_attribute described in
2811 // section 4.7.20 of the Java SE 8 Edition of the VM spec:
2812 //
2813 // type_annotation {
2814 //   u1 target_type;
2815 //   union {
2816 //     type_parameter_target;
2817 //     supertype_target;
2818 //     type_parameter_bound_target;
2819 //     empty_target;
2820 //     method_formal_parameter_target;
2821 //     throws_target;
2822 //     localvar_target;
2823 //     catch_target;
2824 //     offset_target;
2825 //     type_argument_target;
2826 //   } target_info;
2827 //   type_path target_path;
2828 //   annotation anno;
2829 // }
2830 //
2831 bool VM_RedefineClasses::rewrite_cp_refs_in_type_annotation_struct(
2832        AnnotationArray* type_annotations_typeArray, int &byte_i_ref,
2833        const char * location_mesg) {
2834 
2835   if (!skip_type_annotation_target(type_annotations_typeArray,
2836          byte_i_ref, location_mesg)) {
2837     return false;
2838   }
2839 
2840   if (!skip_type_annotation_type_path(type_annotations_typeArray, byte_i_ref)) {
2841     return false;
2842   }
2843 
2844   if (!rewrite_cp_refs_in_annotation_struct(type_annotations_typeArray, byte_i_ref)) {
2845     return false;
2846   }
2847 
2848   return true;
2849 } // end rewrite_cp_refs_in_type_annotation_struct()
2850 
2851 
2852 // Read, verify and skip over the target_type and target_info part
2853 // so that rewriting can continue in the later parts of the struct.
2854 //
2855 // u1 target_type;
2856 // union {
2857 //   type_parameter_target;
2858 //   supertype_target;
2859 //   type_parameter_bound_target;
2860 //   empty_target;
2861 //   method_formal_parameter_target;
2862 //   throws_target;
2863 //   localvar_target;
2864 //   catch_target;
2865 //   offset_target;
2866 //   type_argument_target;
2867 // } target_info;
2868 //
2869 bool VM_RedefineClasses::skip_type_annotation_target(
2870        AnnotationArray* type_annotations_typeArray, int &byte_i_ref,
2871        const char * location_mesg) {
2872 
2873   if ((byte_i_ref + 1) > type_annotations_typeArray->length()) {
2874     // not enough room for a target_type let alone the rest of a type_annotation
2875     log_debug(redefine, class, annotation)("length() is too small for a target_type");
2876     return false;
2877   }
2878 
2879   u1 target_type = type_annotations_typeArray->at(byte_i_ref);
2880   byte_i_ref += 1;
2881   log_debug(redefine, class, annotation)("target_type=0x%.2x", target_type);
2882   log_debug(redefine, class, annotation)("location=%s", location_mesg);
2883 
2884   // Skip over target_info
2885   switch (target_type) {
2886     case 0x00:
2887     // kind: type parameter declaration of generic class or interface
2888     // location: ClassFile
2889     case 0x01:
2890     // kind: type parameter declaration of generic method or constructor
2891     // location: method_info
2892 
2893     {
2894       // struct:
2895       // type_parameter_target {
2896       //   u1 type_parameter_index;
2897       // }
2898       //
2899       if ((byte_i_ref + 1) > type_annotations_typeArray->length()) {
2900         log_debug(redefine, class, annotation)("length() is too small for a type_parameter_target");
2901         return false;
2902       }
2903 
2904       u1 type_parameter_index = type_annotations_typeArray->at(byte_i_ref);
2905       byte_i_ref += 1;
2906 
2907       log_debug(redefine, class, annotation)("type_parameter_target: type_parameter_index=%d", type_parameter_index);
2908     } break;
2909 
2910     case 0x10:
2911     // kind: type in extends clause of class or interface declaration
2912     //       or in implements clause of interface declaration
2913     // location: ClassFile
2914 
2915     {
2916       // struct:
2917       // supertype_target {
2918       //   u2 supertype_index;
2919       // }
2920       //
2921       if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
2922         log_debug(redefine, class, annotation)("length() is too small for a supertype_target");
2923         return false;
2924       }
2925 
2926       u2 supertype_index = Bytes::get_Java_u2((address)
2927                              type_annotations_typeArray->adr_at(byte_i_ref));
2928       byte_i_ref += 2;
2929 
2930       log_debug(redefine, class, annotation)("supertype_target: supertype_index=%d", supertype_index);
2931     } break;
2932 
2933     case 0x11:
2934     // kind: type in bound of type parameter declaration of generic class or interface
2935     // location: ClassFile
2936     case 0x12:
2937     // kind: type in bound of type parameter declaration of generic method or constructor
2938     // location: method_info
2939 
2940     {
2941       // struct:
2942       // type_parameter_bound_target {
2943       //   u1 type_parameter_index;
2944       //   u1 bound_index;
2945       // }
2946       //
2947       if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
2948         log_debug(redefine, class, annotation)("length() is too small for a type_parameter_bound_target");
2949         return false;
2950       }
2951 
2952       u1 type_parameter_index = type_annotations_typeArray->at(byte_i_ref);
2953       byte_i_ref += 1;
2954       u1 bound_index = type_annotations_typeArray->at(byte_i_ref);
2955       byte_i_ref += 1;
2956 
2957       log_debug(redefine, class, annotation)
2958         ("type_parameter_bound_target: type_parameter_index=%d, bound_index=%d", type_parameter_index, bound_index);
2959     } break;
2960 
2961     case 0x13:
2962     // kind: type in field declaration
2963     // location: field_info
2964     case 0x14:
2965     // kind: return type of method, or type of newly constructed object
2966     // location: method_info
2967     case 0x15:
2968     // kind: receiver type of method or constructor
2969     // location: method_info
2970 
2971     {
2972       // struct:
2973       // empty_target {
2974       // }
2975       //
2976       log_debug(redefine, class, annotation)("empty_target");
2977     } break;
2978 
2979     case 0x16:
2980     // kind: type in formal parameter declaration of method, constructor, or lambda expression
2981     // location: method_info
2982 
2983     {
2984       // struct:
2985       // formal_parameter_target {
2986       //   u1 formal_parameter_index;
2987       // }
2988       //
2989       if ((byte_i_ref + 1) > type_annotations_typeArray->length()) {
2990         log_debug(redefine, class, annotation)("length() is too small for a formal_parameter_target");
2991         return false;
2992       }
2993 
2994       u1 formal_parameter_index = type_annotations_typeArray->at(byte_i_ref);
2995       byte_i_ref += 1;
2996 
2997       log_debug(redefine, class, annotation)
2998         ("formal_parameter_target: formal_parameter_index=%d", formal_parameter_index);
2999     } break;
3000 
3001     case 0x17:
3002     // kind: type in throws clause of method or constructor
3003     // location: method_info
3004 
3005     {
3006       // struct:
3007       // throws_target {
3008       //   u2 throws_type_index
3009       // }
3010       //
3011       if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
3012         log_debug(redefine, class, annotation)("length() is too small for a throws_target");
3013         return false;
3014       }
3015 
3016       u2 throws_type_index = Bytes::get_Java_u2((address)
3017                                type_annotations_typeArray->adr_at(byte_i_ref));
3018       byte_i_ref += 2;
3019 
3020       log_debug(redefine, class, annotation)("throws_target: throws_type_index=%d", throws_type_index);
3021     } break;
3022 
3023     case 0x40:
3024     // kind: type in local variable declaration
3025     // location: Code
3026     case 0x41:
3027     // kind: type in resource variable declaration
3028     // location: Code
3029 
3030     {
3031       // struct:
3032       // localvar_target {
3033       //   u2 table_length;
3034       //   struct {
3035       //     u2 start_pc;
3036       //     u2 length;
3037       //     u2 index;
3038       //   } table[table_length];
3039       // }
3040       //
3041       if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
3042         // not enough room for a table_length let alone the rest of a localvar_target
3043         log_debug(redefine, class, annotation)("length() is too small for a localvar_target table_length");
3044         return false;
3045       }
3046 
3047       u2 table_length = Bytes::get_Java_u2((address)
3048                           type_annotations_typeArray->adr_at(byte_i_ref));
3049       byte_i_ref += 2;
3050 
3051       log_debug(redefine, class, annotation)("localvar_target: table_length=%d", table_length);
3052 
3053       int table_struct_size = 2 + 2 + 2; // 3 u2 variables per table entry
3054       int table_size = table_length * table_struct_size;
3055 
3056       if ((byte_i_ref + table_size) > type_annotations_typeArray->length()) {
3057         // not enough room for a table
3058         log_debug(redefine, class, annotation)("length() is too small for a table array of length %d", table_length);
3059         return false;
3060       }
3061 
3062       // Skip over table
3063       byte_i_ref += table_size;
3064     } break;
3065 
3066     case 0x42:
3067     // kind: type in exception parameter declaration
3068     // location: Code
3069 
3070     {
3071       // struct:
3072       // catch_target {
3073       //   u2 exception_table_index;
3074       // }
3075       //
3076       if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
3077         log_debug(redefine, class, annotation)("length() is too small for a catch_target");
3078         return false;
3079       }
3080 
3081       u2 exception_table_index = Bytes::get_Java_u2((address)
3082                                    type_annotations_typeArray->adr_at(byte_i_ref));
3083       byte_i_ref += 2;
3084 
3085       log_debug(redefine, class, annotation)("catch_target: exception_table_index=%d", exception_table_index);
3086     } break;
3087 
3088     case 0x43:
3089     // kind: type in instanceof expression
3090     // location: Code
3091     case 0x44:
3092     // kind: type in new expression
3093     // location: Code
3094     case 0x45:
3095     // kind: type in method reference expression using ::new
3096     // location: Code
3097     case 0x46:
3098     // kind: type in method reference expression using ::Identifier
3099     // location: Code
3100 
3101     {
3102       // struct:
3103       // offset_target {
3104       //   u2 offset;
3105       // }
3106       //
3107       if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
3108         log_debug(redefine, class, annotation)("length() is too small for a offset_target");
3109         return false;
3110       }
3111 
3112       u2 offset = Bytes::get_Java_u2((address)
3113                     type_annotations_typeArray->adr_at(byte_i_ref));
3114       byte_i_ref += 2;
3115 
3116       log_debug(redefine, class, annotation)("offset_target: offset=%d", offset);
3117     } break;
3118 
3119     case 0x47:
3120     // kind: type in cast expression
3121     // location: Code
3122     case 0x48:
3123     // kind: type argument for generic constructor in new expression or
3124     //       explicit constructor invocation statement
3125     // location: Code
3126     case 0x49:
3127     // kind: type argument for generic method in method invocation expression
3128     // location: Code
3129     case 0x4A:
3130     // kind: type argument for generic constructor in method reference expression using ::new
3131     // location: Code
3132     case 0x4B:
3133     // kind: type argument for generic method in method reference expression using ::Identifier
3134     // location: Code
3135 
3136     {
3137       // struct:
3138       // type_argument_target {
3139       //   u2 offset;
3140       //   u1 type_argument_index;
3141       // }
3142       //
3143       if ((byte_i_ref + 3) > type_annotations_typeArray->length()) {
3144         log_debug(redefine, class, annotation)("length() is too small for a type_argument_target");
3145         return false;
3146       }
3147 
3148       u2 offset = Bytes::get_Java_u2((address)
3149                     type_annotations_typeArray->adr_at(byte_i_ref));
3150       byte_i_ref += 2;
3151       u1 type_argument_index = type_annotations_typeArray->at(byte_i_ref);
3152       byte_i_ref += 1;
3153 
3154       log_debug(redefine, class, annotation)
3155         ("type_argument_target: offset=%d, type_argument_index=%d", offset, type_argument_index);
3156     } break;
3157 
3158     default:
3159       log_debug(redefine, class, annotation)("unknown target_type");
3160 #ifdef ASSERT
3161       ShouldNotReachHere();
3162 #endif
3163       return false;
3164   }
3165 
3166   return true;
3167 } // end skip_type_annotation_target()
3168 
3169 
3170 // Read, verify and skip over the type_path part so that rewriting
3171 // can continue in the later parts of the struct.
3172 //
3173 // type_path {
3174 //   u1 path_length;
3175 //   {
3176 //     u1 type_path_kind;
3177 //     u1 type_argument_index;
3178 //   } path[path_length];
3179 // }
3180 //
3181 bool VM_RedefineClasses::skip_type_annotation_type_path(
3182        AnnotationArray* type_annotations_typeArray, int &byte_i_ref) {
3183 
3184   if ((byte_i_ref + 1) > type_annotations_typeArray->length()) {
3185     // not enough room for a path_length let alone the rest of the type_path
3186     log_debug(redefine, class, annotation)("length() is too small for a type_path");
3187     return false;
3188   }
3189 
3190   u1 path_length = type_annotations_typeArray->at(byte_i_ref);
3191   byte_i_ref += 1;
3192 
3193   log_debug(redefine, class, annotation)("type_path: path_length=%d", path_length);
3194 
3195   int calc_path_length = 0;
3196   for (; calc_path_length < path_length; calc_path_length++) {
3197     if ((byte_i_ref + 1 + 1) > type_annotations_typeArray->length()) {
3198       // not enough room for a path
3199       log_debug(redefine, class, annotation)
3200         ("length() is too small for path entry %d of %d", calc_path_length, path_length);
3201       return false;
3202     }
3203 
3204     u1 type_path_kind = type_annotations_typeArray->at(byte_i_ref);
3205     byte_i_ref += 1;
3206     u1 type_argument_index = type_annotations_typeArray->at(byte_i_ref);
3207     byte_i_ref += 1;
3208 
3209     log_debug(redefine, class, annotation)
3210       ("type_path: path[%d]: type_path_kind=%d, type_argument_index=%d",
3211        calc_path_length, type_path_kind, type_argument_index);
3212 
3213     if (type_path_kind > 3 || (type_path_kind != 3 && type_argument_index != 0)) {
3214       // not enough room for a path
3215       log_debug(redefine, class, annotation)("inconsistent type_path values");
3216       return false;
3217     }
3218   }
3219   assert(path_length == calc_path_length, "sanity check");
3220 
3221   return true;
3222 } // end skip_type_annotation_type_path()
3223 
3224 
3225 // Rewrite constant pool references in the method's stackmap table.
3226 // These "structures" are adapted from the StackMapTable_attribute that
3227 // is described in section 4.8.4 of the 6.0 version of the VM spec
3228 // (dated 2005.10.26):
3229 // file:///net/quincunx.sfbay/export/gbracha/ClassFile-Java6.pdf
3230 //
3231 // stack_map {
3232 //   u2 number_of_entries;
3233 //   stack_map_frame entries[number_of_entries];
3234 // }
3235 //
3236 void VM_RedefineClasses::rewrite_cp_refs_in_stack_map_table(
3237        const methodHandle& method) {
3238 
3239   if (!method->has_stackmap_table()) {
3240     return;
3241   }
3242 
3243   AnnotationArray* stackmap_data = method->stackmap_data();
3244   address stackmap_p = (address)stackmap_data->adr_at(0);
3245   address stackmap_end = stackmap_p + stackmap_data->length();
3246 
3247   assert(stackmap_p + 2 <= stackmap_end, "no room for number_of_entries");
3248   u2 number_of_entries = Bytes::get_Java_u2(stackmap_p);
3249   stackmap_p += 2;
3250 
3251   log_debug(redefine, class, stackmap)("number_of_entries=%u", number_of_entries);
3252 
3253   // walk through each stack_map_frame
3254   u2 calc_number_of_entries = 0;
3255   for (; calc_number_of_entries < number_of_entries; calc_number_of_entries++) {
3256     // The stack_map_frame structure is a u1 frame_type followed by
3257     // 0 or more bytes of data:
3258     //
3259     // union stack_map_frame {
3260     //   same_frame;
3261     //   same_locals_1_stack_item_frame;
3262     //   same_locals_1_stack_item_frame_extended;
3263     //   chop_frame;
3264     //   same_frame_extended;
3265     //   append_frame;
3266     //   full_frame;
3267     // }
3268 
3269     assert(stackmap_p + 1 <= stackmap_end, "no room for frame_type");
3270     u1 frame_type = *stackmap_p;
3271     stackmap_p++;
3272 
3273     // same_frame {
3274     //   u1 frame_type = SAME; /* 0-63 */
3275     // }
3276     if (frame_type <= StackMapReader::SAME_FRAME_END) {
3277       // nothing more to do for same_frame
3278     }
3279 
3280     // same_locals_1_stack_item_frame {
3281     //   u1 frame_type = SAME_LOCALS_1_STACK_ITEM; /* 64-127 */
3282     //   verification_type_info stack[1];
3283     // }
3284     else if (frame_type >= StackMapReader::SAME_LOCALS_1_STACK_ITEM_FRAME_START &&
3285              frame_type <= StackMapReader::SAME_LOCALS_1_STACK_ITEM_FRAME_END) {
3286       rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
3287         calc_number_of_entries, frame_type);
3288     }
3289 
3290     // reserved for future use
3291     else if (frame_type >= StackMapReader::RESERVED_START &&
3292              frame_type <= StackMapReader::RESERVED_END) {
3293       // nothing more to do for reserved frame_types
3294     }
3295 
3296     // same_locals_1_stack_item_frame_extended {
3297     //   u1 frame_type = SAME_LOCALS_1_STACK_ITEM_EXTENDED; /* 247 */
3298     //   u2 offset_delta;
3299     //   verification_type_info stack[1];
3300     // }
3301     else if (frame_type == StackMapReader::SAME_LOCALS_1_STACK_ITEM_EXTENDED) {
3302       stackmap_p += 2;
3303       rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
3304         calc_number_of_entries, frame_type);
3305     }
3306 
3307     // chop_frame {
3308     //   u1 frame_type = CHOP; /* 248-250 */
3309     //   u2 offset_delta;
3310     // }
3311     else if (frame_type >= StackMapReader::CHOP_FRAME_START &&
3312              frame_type <= StackMapReader::CHOP_FRAME_END) {
3313       stackmap_p += 2;
3314     }
3315 
3316     // same_frame_extended {
3317     //   u1 frame_type = SAME_EXTENDED; /* 251 */
3318     //   u2 offset_delta;
3319     // }
3320     else if (frame_type == StackMapReader::SAME_FRAME_EXTENDED) {
3321       stackmap_p += 2;
3322     }
3323 
3324     // append_frame {
3325     //   u1 frame_type = APPEND; /* 252-254 */
3326     //   u2 offset_delta;
3327     //   verification_type_info locals[frame_type - SAME_EXTENDED];
3328     // }
3329     else if (frame_type >= StackMapReader::APPEND_FRAME_START &&
3330              frame_type <= StackMapReader::APPEND_FRAME_END) {
3331       assert(stackmap_p + 2 <= stackmap_end,
3332         "no room for offset_delta");
3333       stackmap_p += 2;
3334       u1 len = frame_type - StackMapReader::APPEND_FRAME_START + 1;
3335       for (u1 i = 0; i < len; i++) {
3336         rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
3337           calc_number_of_entries, frame_type);
3338       }
3339     }
3340 
3341     // full_frame {
3342     //   u1 frame_type = FULL_FRAME; /* 255 */
3343     //   u2 offset_delta;
3344     //   u2 number_of_locals;
3345     //   verification_type_info locals[number_of_locals];
3346     //   u2 number_of_stack_items;
3347     //   verification_type_info stack[number_of_stack_items];
3348     // }
3349     else if (frame_type == StackMapReader::FULL_FRAME) {
3350       assert(stackmap_p + 2 + 2 <= stackmap_end,
3351         "no room for smallest full_frame");
3352       stackmap_p += 2;
3353 
3354       u2 number_of_locals = Bytes::get_Java_u2(stackmap_p);
3355       stackmap_p += 2;
3356 
3357       for (u2 locals_i = 0; locals_i < number_of_locals; locals_i++) {
3358         rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
3359           calc_number_of_entries, frame_type);
3360       }
3361 
3362       // Use the largest size for the number_of_stack_items, but only get
3363       // the right number of bytes.
3364       u2 number_of_stack_items = Bytes::get_Java_u2(stackmap_p);
3365       stackmap_p += 2;
3366 
3367       for (u2 stack_i = 0; stack_i < number_of_stack_items; stack_i++) {
3368         rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
3369           calc_number_of_entries, frame_type);
3370       }
3371     }
3372   } // end while there is a stack_map_frame
3373   assert(number_of_entries == calc_number_of_entries, "sanity check");
3374 } // end rewrite_cp_refs_in_stack_map_table()
3375 
3376 
3377 // Rewrite constant pool references in the verification type info
3378 // portion of the method's stackmap table. These "structures" are
3379 // adapted from the StackMapTable_attribute that is described in
3380 // section 4.8.4 of the 6.0 version of the VM spec (dated 2005.10.26):
3381 // file:///net/quincunx.sfbay/export/gbracha/ClassFile-Java6.pdf
3382 //
3383 // The verification_type_info structure is a u1 tag followed by 0 or
3384 // more bytes of data:
3385 //
3386 // union verification_type_info {
3387 //   Top_variable_info;
3388 //   Integer_variable_info;
3389 //   Float_variable_info;
3390 //   Long_variable_info;
3391 //   Double_variable_info;
3392 //   Null_variable_info;
3393 //   UninitializedThis_variable_info;
3394 //   Object_variable_info;
3395 //   Uninitialized_variable_info;
3396 // }
3397 //
3398 void VM_RedefineClasses::rewrite_cp_refs_in_verification_type_info(
3399        address& stackmap_p_ref, address stackmap_end, u2 frame_i,
3400        u1 frame_type) {
3401 
3402   assert(stackmap_p_ref + 1 <= stackmap_end, "no room for tag");
3403   u1 tag = *stackmap_p_ref;
3404   stackmap_p_ref++;
3405 
3406   switch (tag) {
3407   // Top_variable_info {
3408   //   u1 tag = ITEM_Top; /* 0 */
3409   // }
3410   // verificationType.hpp has zero as ITEM_Bogus instead of ITEM_Top
3411   case 0:  // fall through
3412 
3413   // Integer_variable_info {
3414   //   u1 tag = ITEM_Integer; /* 1 */
3415   // }
3416   case ITEM_Integer:  // fall through
3417 
3418   // Float_variable_info {
3419   //   u1 tag = ITEM_Float; /* 2 */
3420   // }
3421   case ITEM_Float:  // fall through
3422 
3423   // Double_variable_info {
3424   //   u1 tag = ITEM_Double; /* 3 */
3425   // }
3426   case ITEM_Double:  // fall through
3427 
3428   // Long_variable_info {
3429   //   u1 tag = ITEM_Long; /* 4 */
3430   // }
3431   case ITEM_Long:  // fall through
3432 
3433   // Null_variable_info {
3434   //   u1 tag = ITEM_Null; /* 5 */
3435   // }
3436   case ITEM_Null:  // fall through
3437 
3438   // UninitializedThis_variable_info {
3439   //   u1 tag = ITEM_UninitializedThis; /* 6 */
3440   // }
3441   case ITEM_UninitializedThis:
3442     // nothing more to do for the above tag types
3443     break;
3444 
3445   // Object_variable_info {
3446   //   u1 tag = ITEM_Object; /* 7 */
3447   //   u2 cpool_index;
3448   // }
3449   case ITEM_Object:
3450   {
3451     assert(stackmap_p_ref + 2 <= stackmap_end, "no room for cpool_index");
3452     u2 cpool_index = Bytes::get_Java_u2(stackmap_p_ref);
3453     u2 new_cp_index = find_new_index(cpool_index);
3454     if (new_cp_index != 0) {
3455       log_debug(redefine, class, stackmap)("mapped old cpool_index=%d", cpool_index);
3456       Bytes::put_Java_u2(stackmap_p_ref, new_cp_index);
3457       cpool_index = new_cp_index;
3458     }
3459     stackmap_p_ref += 2;
3460 
3461     log_debug(redefine, class, stackmap)
3462       ("frame_i=%u, frame_type=%u, cpool_index=%d", frame_i, frame_type, cpool_index);
3463   } break;
3464 
3465   // Uninitialized_variable_info {
3466   //   u1 tag = ITEM_Uninitialized; /* 8 */
3467   //   u2 offset;
3468   // }
3469   case ITEM_Uninitialized:
3470     assert(stackmap_p_ref + 2 <= stackmap_end, "no room for offset");
3471     stackmap_p_ref += 2;
3472     break;
3473 
3474   default:
3475     log_debug(redefine, class, stackmap)("frame_i=%u, frame_type=%u, bad tag=0x%x", frame_i, frame_type, tag);
3476     ShouldNotReachHere();
3477     break;
3478   } // end switch (tag)
3479 } // end rewrite_cp_refs_in_verification_type_info()
3480 
3481 
3482 // Change the constant pool associated with klass scratch_class to scratch_cp.
3483 // scratch_cp_length elements are copied from scratch_cp to a smaller constant pool
3484 // and the smaller constant pool is associated with scratch_class.
3485 void VM_RedefineClasses::set_new_constant_pool(
3486        ClassLoaderData* loader_data,
3487        InstanceKlass* scratch_class, constantPoolHandle scratch_cp,
3488        int scratch_cp_length, TRAPS) {
3489   assert(scratch_cp->length() >= scratch_cp_length, "sanity check");
3490 
3491   // scratch_cp is a merged constant pool and has enough space for a
3492   // worst case merge situation. We want to associate the minimum
3493   // sized constant pool with the klass to save space.
3494   ConstantPool* cp = ConstantPool::allocate(loader_data, scratch_cp_length, CHECK);
3495   constantPoolHandle smaller_cp(THREAD, cp);
3496 
3497   // preserve version() value in the smaller copy
3498   int version = scratch_cp->version();
3499   assert(version != 0, "sanity check");
3500   smaller_cp->set_version(version);
3501 
3502   // attach klass to new constant pool
3503   // reference to the cp holder is needed for copy_operands()
3504   smaller_cp->set_pool_holder(scratch_class);
3505 
3506   smaller_cp->copy_fields(scratch_cp());
3507 
3508   scratch_cp->copy_cp_to(1, scratch_cp_length - 1, smaller_cp, 1, THREAD);
3509   if (HAS_PENDING_EXCEPTION) {
3510     // Exception is handled in the caller
3511     loader_data->add_to_deallocate_list(smaller_cp());
3512     return;
3513   }
3514   scratch_cp = smaller_cp;
3515 
3516   // attach new constant pool to klass
3517   scratch_class->set_constants(scratch_cp());
3518   scratch_cp->initialize_unresolved_klasses(loader_data, CHECK);
3519 
3520   int i;  // for portability
3521 
3522   // update each field in klass to use new constant pool indices as needed
3523   int java_fields;
3524   int injected_fields;
3525   bool update_required = false;
3526   GrowableArray<FieldInfo>* fields = FieldInfoStream::create_FieldInfoArray(scratch_class->fieldinfo_stream(), &java_fields, &injected_fields);
3527   for (int i = 0; i < java_fields; i++) {
3528     FieldInfo* fi = fields->adr_at(i);
3529     jshort cur_index = fi->name_index();
3530     jshort new_index = find_new_index(cur_index);
3531     if (new_index != 0) {
3532       log_trace(redefine, class, constantpool)("field-name_index change: %d to %d", cur_index, new_index);
3533       fi->set_name_index(new_index);
3534       update_required = true;
3535     }
3536     cur_index = fi->signature_index();
3537     new_index = find_new_index(cur_index);
3538     if (new_index != 0) {
3539       log_trace(redefine, class, constantpool)("field-signature_index change: %d to %d", cur_index, new_index);
3540       fi->set_signature_index(new_index);
3541       update_required = true;
3542     }
3543     cur_index = fi->initializer_index();
3544     new_index = find_new_index(cur_index);
3545     if (new_index != 0) {
3546       log_trace(redefine, class, constantpool)("field-initval_index change: %d to %d", cur_index, new_index);
3547       fi->set_initializer_index(new_index);
3548       update_required = true;
3549     }
3550     cur_index = fi->generic_signature_index();
3551     new_index = find_new_index(cur_index);
3552     if (new_index != 0) {
3553       log_trace(redefine, class, constantpool)("field-generic_signature change: %d to %d", cur_index, new_index);
3554       fi->set_generic_signature_index(new_index);
3555       update_required = true;
3556     }
3557   }
3558   if (update_required) {
3559     Array<u1>* old_stream = scratch_class->fieldinfo_stream();
3560     assert(fields->length() == (java_fields + injected_fields), "Must be");
3561     Array<u1>* new_fis = FieldInfoStream::create_FieldInfoStream(fields, java_fields, injected_fields, scratch_class->class_loader_data(), CHECK);
3562     scratch_class->set_fieldinfo_stream(new_fis);
3563     MetadataFactory::free_array<u1>(scratch_class->class_loader_data(), old_stream);
3564 
3565     Array<u1>* old_table = scratch_class->fieldinfo_search_table();
3566     Array<u1>* search_table = FieldInfoStream::create_search_table(scratch_class->constants(), new_fis, scratch_class->class_loader_data(), CHECK);
3567     scratch_class->set_fieldinfo_search_table(search_table);
3568     MetadataFactory::free_array<u1>(scratch_class->class_loader_data(), old_table);
3569 
3570     DEBUG_ONLY(FieldInfoStream::validate_search_table(scratch_class->constants(), new_fis, search_table));
3571   }
3572 
3573   // Update constant pool indices in the inner classes info to use
3574   // new constant indices as needed. The inner classes info is a
3575   // quadruple:
3576   // (inner_class_info, outer_class_info, inner_name, inner_access_flags)
3577   InnerClassesIterator iter(scratch_class);
3578   for (; !iter.done(); iter.next()) {
3579     int cur_index = iter.inner_class_info_index();
3580     if (cur_index == 0) {
3581       continue;  // JVM spec. allows null inner class refs so skip it
3582     }
3583     u2 new_index = find_new_index(cur_index);
3584     if (new_index != 0) {
3585       log_trace(redefine, class, constantpool)("inner_class_info change: %d to %d", cur_index, new_index);
3586       iter.set_inner_class_info_index(new_index);
3587     }
3588     cur_index = iter.outer_class_info_index();
3589     new_index = find_new_index(cur_index);
3590     if (new_index != 0) {
3591       log_trace(redefine, class, constantpool)("outer_class_info change: %d to %d", cur_index, new_index);
3592       iter.set_outer_class_info_index(new_index);
3593     }
3594     cur_index = iter.inner_name_index();
3595     new_index = find_new_index(cur_index);
3596     if (new_index != 0) {
3597       log_trace(redefine, class, constantpool)("inner_name change: %d to %d", cur_index, new_index);
3598       iter.set_inner_name_index(new_index);
3599     }
3600   } // end for each inner class
3601 
3602   // Attach each method in klass to the new constant pool and update
3603   // to use new constant pool indices as needed:
3604   Array<Method*>* methods = scratch_class->methods();
3605   for (i = methods->length() - 1; i >= 0; i--) {
3606     methodHandle method(THREAD, methods->at(i));
3607     method->set_constants(scratch_cp());
3608 
3609     u2 new_index = find_new_index(method->name_index());
3610     if (new_index != 0) {
3611       log_trace(redefine, class, constantpool)
3612         ("method-name_index change: %d to %d", method->name_index(), new_index);
3613       method->set_name_index(new_index);
3614     }
3615     new_index = find_new_index(method->signature_index());
3616     if (new_index != 0) {
3617       log_trace(redefine, class, constantpool)
3618         ("method-signature_index change: %d to %d", method->signature_index(), new_index);
3619       method->set_signature_index(new_index);
3620     }
3621     new_index = find_new_index(method->generic_signature_index());
3622     if (new_index != 0) {
3623       log_trace(redefine, class, constantpool)
3624         ("method-generic_signature_index change: %d to %d", method->generic_signature_index(), new_index);
3625       method->constMethod()->set_generic_signature_index(new_index);
3626     }
3627 
3628     // Update constant pool indices in the method's checked exception
3629     // table to use new constant indices as needed.
3630     int cext_length = method->checked_exceptions_length();
3631     if (cext_length > 0) {
3632       CheckedExceptionElement * cext_table =
3633         method->checked_exceptions_start();
3634       for (int j = 0; j < cext_length; j++) {
3635         int cur_index = cext_table[j].class_cp_index;
3636         int new_index = find_new_index(cur_index);
3637         if (new_index != 0) {
3638           log_trace(redefine, class, constantpool)("cext-class_cp_index change: %d to %d", cur_index, new_index);
3639           cext_table[j].class_cp_index = (u2)new_index;
3640         }
3641       } // end for each checked exception table entry
3642     } // end if there are checked exception table entries
3643 
3644     // Update each catch type index in the method's exception table
3645     // to use new constant pool indices as needed. The exception table
3646     // holds quadruple entries of the form:
3647     //   (beg_bci, end_bci, handler_bci, klass_index)
3648 
3649     ExceptionTable ex_table(method());
3650     int ext_length = ex_table.length();
3651 
3652     for (int j = 0; j < ext_length; j ++) {
3653       int cur_index = ex_table.catch_type_index(j);
3654       u2 new_index = find_new_index(cur_index);
3655       if (new_index != 0) {
3656         log_trace(redefine, class, constantpool)("ext-klass_index change: %d to %d", cur_index, new_index);
3657         ex_table.set_catch_type_index(j, new_index);
3658       }
3659     } // end for each exception table entry
3660 
3661     // Update constant pool indices in the method's local variable
3662     // table to use new constant indices as needed. The local variable
3663     // table hold sextuple entries of the form:
3664     // (start_pc, length, name_index, descriptor_index, signature_index, slot)
3665     int lvt_length = method->localvariable_table_length();
3666     if (lvt_length > 0) {
3667       LocalVariableTableElement * lv_table =
3668         method->localvariable_table_start();
3669       for (int j = 0; j < lvt_length; j++) {
3670         int cur_index = lv_table[j].name_cp_index;
3671         int new_index = find_new_index(cur_index);
3672         if (new_index != 0) {
3673           log_trace(redefine, class, constantpool)("lvt-name_cp_index change: %d to %d", cur_index, new_index);
3674           lv_table[j].name_cp_index = (u2)new_index;
3675         }
3676         cur_index = lv_table[j].descriptor_cp_index;
3677         new_index = find_new_index(cur_index);
3678         if (new_index != 0) {
3679           log_trace(redefine, class, constantpool)("lvt-descriptor_cp_index change: %d to %d", cur_index, new_index);
3680           lv_table[j].descriptor_cp_index = (u2)new_index;
3681         }
3682         cur_index = lv_table[j].signature_cp_index;
3683         new_index = find_new_index(cur_index);
3684         if (new_index != 0) {
3685           log_trace(redefine, class, constantpool)("lvt-signature_cp_index change: %d to %d", cur_index, new_index);
3686           lv_table[j].signature_cp_index = (u2)new_index;
3687         }
3688       } // end for each local variable table entry
3689     } // end if there are local variable table entries
3690 
3691     // Update constant pool indices in the method's method_parameters.
3692     int mp_length = method->method_parameters_length();
3693     if (mp_length > 0) {
3694       MethodParametersElement* elem = method->method_parameters_start();
3695       for (int j = 0; j < mp_length; j++) {
3696         const int cp_index = elem[j].name_cp_index;
3697         const int new_cp_index = find_new_index(cp_index);
3698         if (new_cp_index != 0) {
3699           elem[j].name_cp_index = (u2)new_cp_index;
3700         }
3701       }
3702     }
3703 
3704     rewrite_cp_refs_in_stack_map_table(method);
3705   } // end for each method
3706 } // end set_new_constant_pool()
3707 
3708 
3709 // Unevolving classes may point to methods of the_class directly
3710 // from their constant pool caches, itables, and/or vtables. We
3711 // use the ClassLoaderDataGraph::classes_do() facility and this helper
3712 // to fix up these pointers.  MethodData also points to old methods and
3713 // must be cleaned.
3714 
3715 // Adjust cpools and vtables closure
3716 void VM_RedefineClasses::AdjustAndCleanMetadata::do_klass(Klass* k) {
3717 
3718   // This is a very busy routine. We don't want too much tracing
3719   // printed out.
3720   bool trace_name_printed = false;
3721 
3722   // If the class being redefined is java.lang.Object, we need to fix all
3723   // array class vtables also. The _has_redefined_Object flag is global.
3724   // Once the java.lang.Object has been redefined (by the current or one
3725   // of the previous VM_RedefineClasses operations) we have to always
3726   // adjust method entries for array classes.
3727   if (k->is_array_klass() && _has_redefined_Object) {
3728     k->vtable().adjust_method_entries(&trace_name_printed);
3729 
3730   } else if (k->is_instance_klass()) {
3731     HandleMark hm(_thread);
3732     InstanceKlass *ik = InstanceKlass::cast(k);
3733 
3734     // Clean MethodData of this class's methods so they don't refer to
3735     // old methods that are no longer running.
3736     Array<Method*>* methods = ik->methods();
3737     int num_methods = methods->length();
3738     for (int index = 0; index < num_methods; ++index) {
3739       if (methods->at(index)->method_data() != nullptr) {
3740         methods->at(index)->method_data()->clean_weak_method_links();
3741       }
3742     }
3743 
3744     // Adjust all vtables, default methods and itables, to clean out old methods.
3745     ResourceMark rm(_thread);
3746     if (ik->vtable_length() > 0) {
3747       ik->vtable().adjust_method_entries(&trace_name_printed);
3748       ik->adjust_default_methods(&trace_name_printed);
3749     }
3750 
3751     if (ik->itable_length() > 0) {
3752       ik->itable().adjust_method_entries(&trace_name_printed);
3753     }
3754 
3755     // The constant pools in other classes (other_cp) can refer to
3756     // old methods.  We have to update method information in
3757     // other_cp's cache. If other_cp has a previous version, then we
3758     // have to repeat the process for each previous version. The
3759     // constant pool cache holds the Method*s for non-virtual
3760     // methods and for virtual, final methods.
3761     //
3762     // Special case: if the current class is being redefined by the current
3763     // VM_RedefineClasses operation, then new_cp has already been attached
3764     // to the_class and old_cp has already been added as a previous version.
3765     // The new_cp doesn't have any cached references to old methods so it
3766     // doesn't need to be updated and we could optimize by skipping it.
3767     // However, the current class can be marked as being redefined by another
3768     // VM_RedefineClasses operation which has already executed its doit_prologue
3769     // and needs cpcache method entries adjusted. For simplicity, the cpcache
3770     // update is done unconditionally. It should result in doing nothing for
3771     // classes being redefined by the current VM_RedefineClasses operation.
3772     // Method entries in the previous version(s) are adjusted as well.
3773     ConstantPoolCache* cp_cache;
3774 
3775     // this klass' constant pool cache may need adjustment
3776     ConstantPool* other_cp = ik->constants();
3777     cp_cache = other_cp->cache();
3778     if (cp_cache != nullptr) {
3779       cp_cache->adjust_method_entries(&trace_name_printed);
3780     }
3781 
3782     // the previous versions' constant pool caches may need adjustment
3783     for (InstanceKlass* pv_node = ik->previous_versions();
3784          pv_node != nullptr;
3785          pv_node = pv_node->previous_versions()) {
3786       cp_cache = pv_node->constants()->cache();
3787       if (cp_cache != nullptr) {
3788         cp_cache->adjust_method_entries(&trace_name_printed);
3789       }
3790     }
3791   }
3792 }
3793 
3794 void VM_RedefineClasses::update_jmethod_ids() {
3795   for (int j = 0; j < _matching_methods_length; ++j) {
3796     Method* old_method = _matching_old_methods[j];
3797     // The method_idnum should be within the range of 1..number-of-methods
3798     // until incremented later for obsolete methods.
3799     // The increment is so if a jmethodID is created for an old obsolete method
3800     // it gets a new jmethodID cache slot in the InstanceKlass.
3801     // They're cleaned out later when all methods of the previous version are purged.
3802     assert(old_method->method_idnum() <= _old_methods->length(),
3803            "shouldn't be incremented yet for obsolete methods");
3804     jmethodID jmid = old_method->find_jmethod_id_or_null();
3805     if (jmid != nullptr) {
3806       // There is a jmethodID, change it to point to the new method
3807       Method* new_method = _matching_new_methods[j];
3808       Method::change_method_associated_with_jmethod_id(jmid, new_method);
3809       assert(Method::resolve_jmethod_id(jmid) == _matching_new_methods[j],
3810              "should be replaced");
3811     }
3812   }
3813 }
3814 
3815 int VM_RedefineClasses::check_methods_and_mark_as_obsolete() {
3816   int emcp_method_count = 0;
3817   int obsolete_count = 0;
3818   int old_index = 0;
3819   for (int j = 0; j < _matching_methods_length; ++j, ++old_index) {
3820     Method* old_method = _matching_old_methods[j];
3821     Method* new_method = _matching_new_methods[j];
3822     Method* old_array_method;
3823 
3824     // Maintain an old_index into the _old_methods array by skipping
3825     // deleted methods
3826     while ((old_array_method = _old_methods->at(old_index)) != old_method) {
3827       ++old_index;
3828     }
3829 
3830     if (MethodComparator::methods_EMCP(old_method, new_method)) {
3831       // The EMCP definition from JSR-163 requires the bytecodes to be
3832       // the same with the exception of constant pool indices which may
3833       // differ. However, the constants referred to by those indices
3834       // must be the same.
3835       //
3836       // We use methods_EMCP() for comparison since constant pool
3837       // merging can remove duplicate constant pool entries that were
3838       // present in the old method and removed from the rewritten new
3839       // method. A faster binary comparison function would consider the
3840       // old and new methods to be different when they are actually
3841       // EMCP.
3842       //
3843       // The old and new methods are EMCP and you would think that we
3844       // could get rid of one of them here and now and save some space.
3845       // However, the concept of EMCP only considers the bytecodes and
3846       // the constant pool entries in the comparison. Other things,
3847       // e.g., the line number table (LNT) or the local variable table
3848       // (LVT) don't count in the comparison. So the new (and EMCP)
3849       // method can have a new LNT that we need so we can't just
3850       // overwrite the new method with the old method.
3851       //
3852       // When this routine is called, we have already attached the new
3853       // methods to the_class so the old methods are effectively
3854       // overwritten. However, if an old method is still executing,
3855       // then the old method cannot be collected until sometime after
3856       // the old method call has returned. So the overwriting of old
3857       // methods by new methods will save us space except for those
3858       // (hopefully few) old methods that are still executing.
3859       //
3860       // A method refers to a ConstMethod* and this presents another
3861       // possible avenue to space savings. The ConstMethod* in the
3862       // new method contains possibly new attributes (LNT, LVT, etc).
3863       // At first glance, it seems possible to save space by replacing
3864       // the ConstMethod* in the old method with the ConstMethod*
3865       // from the new method. The old and new methods would share the
3866       // same ConstMethod* and we would save the space occupied by
3867       // the old ConstMethod*. However, the ConstMethod* contains
3868       // a back reference to the containing method. Sharing the
3869       // ConstMethod* between two methods could lead to confusion in
3870       // the code that uses the back reference. This would lead to
3871       // brittle code that could be broken in non-obvious ways now or
3872       // in the future.
3873       //
3874       // Another possibility is to copy the ConstMethod* from the new
3875       // method to the old method and then overwrite the new method with
3876       // the old method. Since the ConstMethod* contains the bytecodes
3877       // for the method embedded in the oop, this option would change
3878       // the bytecodes out from under any threads executing the old
3879       // method and make the thread's bcp invalid. Since EMCP requires
3880       // that the bytecodes be the same modulo constant pool indices, it
3881       // is straight forward to compute the correct new bcp in the new
3882       // ConstMethod* from the old bcp in the old ConstMethod*. The
3883       // time consuming part would be searching all the frames in all
3884       // of the threads to find all of the calls to the old method.
3885       //
3886       // It looks like we will have to live with the limited savings
3887       // that we get from effectively overwriting the old methods
3888       // when the new methods are attached to the_class.
3889 
3890       // Count number of methods that are EMCP.  The method will be marked
3891       // old but not obsolete if it is EMCP.
3892       emcp_method_count++;
3893 
3894       // An EMCP method is _not_ obsolete. An obsolete method has a
3895       // different jmethodID than the current method. An EMCP method
3896       // has the same jmethodID as the current method. Having the
3897       // same jmethodID for all EMCP versions of a method allows for
3898       // a consistent view of the EMCP methods regardless of which
3899       // EMCP method you happen to have in hand. For example, a
3900       // breakpoint set in one EMCP method will work for all EMCP
3901       // versions of the method including the current one.
3902     } else {
3903       // mark obsolete methods as such
3904       old_method->set_is_obsolete();
3905       obsolete_count++;
3906 
3907       // obsolete methods need a unique idnum so they become new entries in
3908       // the jmethodID cache in InstanceKlass
3909       assert(old_method->method_idnum() == new_method->method_idnum(), "must match");
3910       u2 num = InstanceKlass::cast(_the_class)->next_method_idnum();
3911       if (num != ConstMethod::UNSET_IDNUM) {
3912         old_method->set_method_idnum(num);
3913       }
3914 
3915       // With tracing we try not to "yack" too much. The position of
3916       // this trace assumes there are fewer obsolete methods than
3917       // EMCP methods.
3918       if (log_is_enabled(Trace, redefine, class, obsolete, mark)) {
3919         ResourceMark rm;
3920         log_trace(redefine, class, obsolete, mark)
3921           ("mark %s(%s) as obsolete", old_method->name()->as_C_string(), old_method->signature()->as_C_string());
3922       }
3923     }
3924     old_method->set_is_old();
3925   }
3926   for (int i = 0; i < _deleted_methods_length; ++i) {
3927     Method* old_method = _deleted_methods[i];
3928 
3929     assert(!old_method->has_vtable_index(),
3930            "cannot delete methods with vtable entries");;
3931 
3932     // Mark all deleted methods as old, obsolete and deleted
3933     old_method->set_is_deleted();
3934     old_method->set_is_old();
3935     old_method->set_is_obsolete();
3936     ++obsolete_count;
3937     // With tracing we try not to "yack" too much. The position of
3938     // this trace assumes there are fewer obsolete methods than
3939     // EMCP methods.
3940     if (log_is_enabled(Trace, redefine, class, obsolete, mark)) {
3941       ResourceMark rm;
3942       log_trace(redefine, class, obsolete, mark)
3943         ("mark deleted %s(%s) as obsolete", old_method->name()->as_C_string(), old_method->signature()->as_C_string());
3944     }
3945   }
3946   assert((emcp_method_count + obsolete_count) == _old_methods->length(),
3947     "sanity check");
3948   log_trace(redefine, class, obsolete, mark)("EMCP_cnt=%d, obsolete_cnt=%d", emcp_method_count, obsolete_count);
3949   return emcp_method_count;
3950 }
3951 
3952 // This internal class transfers the native function registration from old methods
3953 // to new methods.  It is designed to handle both the simple case of unchanged
3954 // native methods and the complex cases of native method prefixes being added and/or
3955 // removed.
3956 // It expects only to be used during the VM_RedefineClasses op (a safepoint).
3957 //
3958 // This class is used after the new methods have been installed in "the_class".
3959 //
3960 // So, for example, the following must be handled.  Where 'm' is a method and
3961 // a number followed by an underscore is a prefix.
3962 //
3963 //                                      Old Name    New Name
3964 // Simple transfer to new method        m       ->  m
3965 // Add prefix                           m       ->  1_m
3966 // Remove prefix                        1_m     ->  m
3967 // Simultaneous add of prefixes         m       ->  3_2_1_m
3968 // Simultaneous removal of prefixes     3_2_1_m ->  m
3969 // Simultaneous add and remove          1_m     ->  2_m
3970 // Same, caused by prefix removal only  3_2_1_m ->  3_2_m
3971 //
3972 class TransferNativeFunctionRegistration {
3973  private:
3974   InstanceKlass* the_class;
3975   int prefix_count;
3976   char** prefixes;
3977 
3978   // Recursively search the binary tree of possibly prefixed method names.
3979   // Iteration could be used if all agents were well behaved. Full tree walk is
3980   // more resilent to agents not cleaning up intermediate methods.
3981   // Branch at each depth in the binary tree is:
3982   //    (1) without the prefix.
3983   //    (2) with the prefix.
3984   // where 'prefix' is the prefix at that 'depth' (first prefix, second prefix,...)
3985   Method* search_prefix_name_space(int depth, char* name_str, size_t name_len,
3986                                      Symbol* signature) {
3987     TempNewSymbol name_symbol = SymbolTable::probe(name_str, (int)name_len);
3988     if (name_symbol != nullptr) {
3989       Method* method = the_class->lookup_method(name_symbol, signature);
3990       if (method != nullptr) {
3991         // Even if prefixed, intermediate methods must exist.
3992         if (method->is_native()) {
3993           // Wahoo, we found a (possibly prefixed) version of the method, return it.
3994           return method;
3995         }
3996         if (depth < prefix_count) {
3997           // Try applying further prefixes (other than this one).
3998           method = search_prefix_name_space(depth+1, name_str, name_len, signature);
3999           if (method != nullptr) {
4000             return method; // found
4001           }
4002 
4003           // Try adding this prefix to the method name and see if it matches
4004           // another method name.
4005           char* prefix = prefixes[depth];
4006           size_t prefix_len = strlen(prefix);
4007           size_t trial_len = name_len + prefix_len;
4008           char* trial_name_str = NEW_RESOURCE_ARRAY(char, trial_len + 1);
4009           strcpy(trial_name_str, prefix);
4010           strcat(trial_name_str, name_str);
4011           method = search_prefix_name_space(depth+1, trial_name_str, trial_len,
4012                                             signature);
4013           if (method != nullptr) {
4014             // If found along this branch, it was prefixed, mark as such
4015             method->set_is_prefixed_native();
4016             return method; // found
4017           }
4018         }
4019       }
4020     }
4021     return nullptr;  // This whole branch bore nothing
4022   }
4023 
4024   // Return the method name with old prefixes stripped away.
4025   char* method_name_without_prefixes(Method* method) {
4026     Symbol* name = method->name();
4027     char* name_str = name->as_utf8();
4028 
4029     // Old prefixing may be defunct, strip prefixes, if any.
4030     for (int i = prefix_count-1; i >= 0; i--) {
4031       char* prefix = prefixes[i];
4032       size_t prefix_len = strlen(prefix);
4033       if (strncmp(prefix, name_str, prefix_len) == 0) {
4034         name_str += prefix_len;
4035       }
4036     }
4037     return name_str;
4038   }
4039 
4040   // Strip any prefixes off the old native method, then try to find a
4041   // (possibly prefixed) new native that matches it.
4042   Method* strip_and_search_for_new_native(Method* method) {
4043     ResourceMark rm;
4044     char* name_str = method_name_without_prefixes(method);
4045     return search_prefix_name_space(0, name_str, strlen(name_str),
4046                                     method->signature());
4047   }
4048 
4049  public:
4050 
4051   // Construct a native method transfer processor for this class.
4052   TransferNativeFunctionRegistration(InstanceKlass* _the_class) {
4053     assert(SafepointSynchronize::is_at_safepoint(), "sanity check");
4054 
4055     the_class = _the_class;
4056     prefixes = JvmtiExport::get_all_native_method_prefixes(&prefix_count);
4057   }
4058 
4059   // Attempt to transfer any of the old or deleted methods that are native
4060   void transfer_registrations(Method** old_methods, int methods_length) {
4061     for (int j = 0; j < methods_length; j++) {
4062       Method* old_method = old_methods[j];
4063 
4064       if (old_method->is_native() && old_method->has_native_function()) {
4065         Method* new_method = strip_and_search_for_new_native(old_method);
4066         if (new_method != nullptr) {
4067           // Actually set the native function in the new method.
4068           // Redefine does not send events (except CFLH), certainly not this
4069           // behind the scenes re-registration.
4070           new_method->set_native_function(old_method->native_function(),
4071                               !Method::native_bind_event_is_interesting);
4072         }
4073       }
4074     }
4075   }
4076 };
4077 
4078 // Don't lose the association between a native method and its JNI function.
4079 void VM_RedefineClasses::transfer_old_native_function_registrations(InstanceKlass* the_class) {
4080   TransferNativeFunctionRegistration transfer(the_class);
4081   transfer.transfer_registrations(_deleted_methods, _deleted_methods_length);
4082   transfer.transfer_registrations(_matching_old_methods, _matching_methods_length);
4083 }
4084 
4085 // Deoptimize all compiled code that depends on the classes redefined.
4086 //
4087 // If the can_redefine_classes capability is obtained in the onload
4088 // phase or 'AlwaysRecordEvolDependencies' is true, then the compiler has
4089 // recorded all dependencies from startup. In that case we need only
4090 // deoptimize and throw away all compiled code that depends on the class.
4091 //
4092 // If can_redefine_classes is obtained sometime after the onload phase
4093 // (and 'AlwaysRecordEvolDependencies' is false) then the dependency
4094 // information may be incomplete. In that case the first call to
4095 // RedefineClasses causes all compiled code to be thrown away. As
4096 // can_redefine_classes has been obtained then all future compilations will
4097 // record dependencies so second and subsequent calls to RedefineClasses
4098 // need only throw away code that depends on the class.
4099 //
4100 
4101 void VM_RedefineClasses::flush_dependent_code() {
4102   assert(SafepointSynchronize::is_at_safepoint(), "sanity check");
4103   assert(JvmtiExport::all_dependencies_are_recorded() || !AlwaysRecordEvolDependencies, "sanity check");
4104 
4105   DeoptimizationScope deopt_scope;
4106 
4107   // This is the first redefinition, mark all the nmethods for deoptimization
4108   if (!JvmtiExport::all_dependencies_are_recorded()) {
4109     CodeCache::mark_all_nmethods_for_evol_deoptimization(&deopt_scope);
4110     log_debug(redefine, class, nmethod)("Marked all nmethods for deopt");
4111   } else {
4112     CodeCache::mark_dependents_for_evol_deoptimization(&deopt_scope);
4113     log_debug(redefine, class, nmethod)("Marked dependent nmethods for deopt");
4114   }
4115 
4116   deopt_scope.deoptimize_marked();
4117 
4118   // From now on we know that the dependency information is complete
4119   JvmtiExport::set_all_dependencies_are_recorded(true);
4120 }
4121 
4122 void VM_RedefineClasses::compute_added_deleted_matching_methods() {
4123   Method* old_method;
4124   Method* new_method;
4125 
4126   _matching_old_methods = NEW_RESOURCE_ARRAY(Method*, _old_methods->length());
4127   _matching_new_methods = NEW_RESOURCE_ARRAY(Method*, _old_methods->length());
4128   _added_methods        = NEW_RESOURCE_ARRAY(Method*, _new_methods->length());
4129   _deleted_methods      = NEW_RESOURCE_ARRAY(Method*, _old_methods->length());
4130 
4131   _matching_methods_length = 0;
4132   _deleted_methods_length  = 0;
4133   _added_methods_length    = 0;
4134 
4135   int nj = 0;
4136   int oj = 0;
4137   while (true) {
4138     if (oj >= _old_methods->length()) {
4139       if (nj >= _new_methods->length()) {
4140         break; // we've looked at everything, done
4141       }
4142       // New method at the end
4143       new_method = _new_methods->at(nj);
4144       _added_methods[_added_methods_length++] = new_method;
4145       ++nj;
4146     } else if (nj >= _new_methods->length()) {
4147       // Old method, at the end, is deleted
4148       old_method = _old_methods->at(oj);
4149       _deleted_methods[_deleted_methods_length++] = old_method;
4150       ++oj;
4151     } else {
4152       old_method = _old_methods->at(oj);
4153       new_method = _new_methods->at(nj);
4154       if (old_method->name() == new_method->name()) {
4155         if (old_method->signature() == new_method->signature()) {
4156           _matching_old_methods[_matching_methods_length  ] = old_method;
4157           _matching_new_methods[_matching_methods_length++] = new_method;
4158           ++nj;
4159           ++oj;
4160         } else {
4161           // added overloaded have already been moved to the end,
4162           // so this is a deleted overloaded method
4163           _deleted_methods[_deleted_methods_length++] = old_method;
4164           ++oj;
4165         }
4166       } else { // names don't match
4167         if (old_method->name()->fast_compare(new_method->name()) > 0) {
4168           // new method
4169           _added_methods[_added_methods_length++] = new_method;
4170           ++nj;
4171         } else {
4172           // deleted method
4173           _deleted_methods[_deleted_methods_length++] = old_method;
4174           ++oj;
4175         }
4176       }
4177     }
4178   }
4179   assert(_matching_methods_length + _deleted_methods_length == _old_methods->length(), "sanity");
4180   assert(_matching_methods_length + _added_methods_length == _new_methods->length(), "sanity");
4181 }
4182 
4183 
4184 void VM_RedefineClasses::swap_annotations(InstanceKlass* the_class,
4185                                           InstanceKlass* scratch_class) {
4186   // Swap annotation fields values
4187   Annotations* old_annotations = the_class->annotations();
4188   the_class->set_annotations(scratch_class->annotations());
4189   scratch_class->set_annotations(old_annotations);
4190 }
4191 
4192 
4193 // Install the redefinition of a class:
4194 //    - house keeping (flushing breakpoints and caches, deoptimizing
4195 //      dependent compiled code)
4196 //    - replacing parts in the_class with parts from scratch_class
4197 //    - adding a weak reference to track the obsolete but interesting
4198 //      parts of the_class
4199 //    - adjusting constant pool caches and vtables in other classes
4200 //      that refer to methods in the_class. These adjustments use the
4201 //      ClassLoaderDataGraph::classes_do() facility which only allows
4202 //      a helper method to be specified. The interesting parameters
4203 //      that we would like to pass to the helper method are saved in
4204 //      static global fields in the VM operation.
4205 void VM_RedefineClasses::redefine_single_class(Thread* current, jclass the_jclass,
4206                                                InstanceKlass* scratch_class) {
4207 
4208   HandleMark hm(current);   // make sure handles from this call are freed
4209 
4210   if (log_is_enabled(Info, redefine, class, timer)) {
4211     _timer_rsc_phase1.start();
4212   }
4213 
4214   InstanceKlass* the_class = get_ik(the_jclass);
4215 
4216   // Set a flag to control and optimize adjusting method entries
4217   _has_redefined_Object |= the_class == vmClasses::Object_klass();
4218 
4219   // Remove all breakpoints in methods of this class
4220   JvmtiBreakpoints& jvmti_breakpoints = JvmtiCurrentBreakpoints::get_jvmti_breakpoints();
4221   jvmti_breakpoints.clearall_in_class_at_safepoint(the_class);
4222 
4223   _old_methods = the_class->methods();
4224   _new_methods = scratch_class->methods();
4225   _the_class = the_class;
4226   compute_added_deleted_matching_methods();
4227   update_jmethod_ids();
4228 
4229   _any_class_has_resolved_methods = the_class->has_resolved_methods() || _any_class_has_resolved_methods;
4230 
4231   // Attach new constant pool to the original klass. The original
4232   // klass still refers to the old constant pool (for now).
4233   scratch_class->constants()->set_pool_holder(the_class);
4234 
4235 #if 0
4236   // In theory, with constant pool merging in place we should be able
4237   // to save space by using the new, merged constant pool in place of
4238   // the old constant pool(s). By "pool(s)" I mean the constant pool in
4239   // the klass version we are replacing now and any constant pool(s) in
4240   // previous versions of klass. Nice theory, doesn't work in practice.
4241   // When this code is enabled, even simple programs throw NullPointer
4242   // exceptions. I'm guessing that this is caused by some constant pool
4243   // cache difference between the new, merged constant pool and the
4244   // constant pool that was just being used by the klass. I'm keeping
4245   // this code around to archive the idea, but the code has to remain
4246   // disabled for now.
4247 
4248   // Attach each old method to the new constant pool. This can be
4249   // done here since we are past the bytecode verification and
4250   // constant pool optimization phases.
4251   for (int i = _old_methods->length() - 1; i >= 0; i--) {
4252     Method* method = _old_methods->at(i);
4253     method->set_constants(scratch_class->constants());
4254   }
4255 
4256   // NOTE: this doesn't work because you can redefine the same class in two
4257   // threads, each getting their own constant pool data appended to the
4258   // original constant pool.  In order for the new methods to work when they
4259   // become old methods, they need to keep their updated copy of the constant pool.
4260 
4261   {
4262     // walk all previous versions of the klass
4263     InstanceKlass *ik = the_class;
4264     PreviousVersionWalker pvw(ik);
4265     do {
4266       ik = pvw.next_previous_version();
4267       if (ik != nullptr) {
4268 
4269         // attach previous version of klass to the new constant pool
4270         ik->set_constants(scratch_class->constants());
4271 
4272         // Attach each method in the previous version of klass to the
4273         // new constant pool
4274         Array<Method*>* prev_methods = ik->methods();
4275         for (int i = prev_methods->length() - 1; i >= 0; i--) {
4276           Method* method = prev_methods->at(i);
4277           method->set_constants(scratch_class->constants());
4278         }
4279       }
4280     } while (ik != nullptr);
4281   }
4282 #endif
4283 
4284   // Replace methods and constantpool
4285   the_class->set_methods(_new_methods);
4286   scratch_class->set_methods(_old_methods);     // To prevent potential GCing of the old methods,
4287                                           // and to be able to undo operation easily.
4288 
4289   Array<int>* old_ordering = the_class->method_ordering();
4290   the_class->set_method_ordering(scratch_class->method_ordering());
4291   scratch_class->set_method_ordering(old_ordering);
4292 
4293   ConstantPool* old_constants = the_class->constants();
4294   the_class->set_constants(scratch_class->constants());
4295   scratch_class->set_constants(old_constants);  // See the previous comment.
4296 #if 0
4297   // We are swapping the guts of "the new class" with the guts of "the
4298   // class". Since the old constant pool has just been attached to "the
4299   // new class", it seems logical to set the pool holder in the old
4300   // constant pool also. However, doing this will change the observable
4301   // class hierarchy for any old methods that are still executing. A
4302   // method can query the identity of its "holder" and this query uses
4303   // the method's constant pool link to find the holder. The change in
4304   // holding class from "the class" to "the new class" can confuse
4305   // things.
4306   //
4307   // Setting the old constant pool's holder will also cause
4308   // verification done during vtable initialization below to fail.
4309   // During vtable initialization, the vtable's class is verified to be
4310   // a subtype of the method's holder. The vtable's class is "the
4311   // class" and the method's holder is gotten from the constant pool
4312   // link in the method itself. For "the class"'s directly implemented
4313   // methods, the method holder is "the class" itself (as gotten from
4314   // the new constant pool). The check works fine in this case. The
4315   // check also works fine for methods inherited from super classes.
4316   //
4317   // Miranda methods are a little more complicated. A miranda method is
4318   // provided by an interface when the class implementing the interface
4319   // does not provide its own method.  These interfaces are implemented
4320   // internally as an InstanceKlass. These special instanceKlasses
4321   // share the constant pool of the class that "implements" the
4322   // interface. By sharing the constant pool, the method holder of a
4323   // miranda method is the class that "implements" the interface. In a
4324   // non-redefine situation, the subtype check works fine. However, if
4325   // the old constant pool's pool holder is modified, then the check
4326   // fails because there is no class hierarchy relationship between the
4327   // vtable's class and "the new class".
4328 
4329   old_constants->set_pool_holder(scratch_class());
4330 #endif
4331 
4332   // track number of methods that are EMCP for add_previous_version() call below
4333   int emcp_method_count = check_methods_and_mark_as_obsolete();
4334   transfer_old_native_function_registrations(the_class);
4335 
4336   if (scratch_class->get_cached_class_file() != the_class->get_cached_class_file()) {
4337     // 1. the_class doesn't have a cache yet, scratch_class does have a cache.
4338     // 2. The same class can be present twice in the scratch classes list or there
4339     // are multiple concurrent RetransformClasses calls on different threads.
4340     // the_class and scratch_class have the same cached bytes, but different buffers.
4341     // In such cases we need to deallocate one of the buffers.
4342     // 3. RedefineClasses and the_class has cached bytes from a previous transformation.
4343     // In the case we need to use class bytes from scratch_class.
4344     if (the_class->get_cached_class_file() != nullptr) {
4345       os::free(the_class->get_cached_class_file());
4346     }
4347     the_class->set_cached_class_file(scratch_class->get_cached_class_file());
4348   }
4349 
4350   // null out in scratch class to not delete twice.  The class to be redefined
4351   // always owns these bytes.
4352   scratch_class->set_cached_class_file(nullptr);
4353 
4354   // Replace inner_classes
4355   Array<u2>* old_inner_classes = the_class->inner_classes();
4356   the_class->set_inner_classes(scratch_class->inner_classes());
4357   scratch_class->set_inner_classes(old_inner_classes);
4358 
4359   // Initialize the vtable and interface table after
4360   // methods have been rewritten
4361   // no exception should happen here since we explicitly
4362   // do not check loader constraints.
4363   // compare_and_normalize_class_versions has already checked:
4364   //  - classloaders unchanged, signatures unchanged
4365   //  - all instanceKlasses for redefined classes reused & contents updated
4366   the_class->vtable().initialize_vtable();
4367   the_class->itable().initialize_itable();
4368 
4369   // Update jmethodID cache if present.
4370   the_class->update_methods_jmethod_cache();
4371 
4372   // Copy the "source debug extension" attribute from new class version
4373   the_class->set_source_debug_extension(
4374     scratch_class->source_debug_extension(),
4375     scratch_class->source_debug_extension() == nullptr ? 0 :
4376     (int)strlen(scratch_class->source_debug_extension()));
4377 
4378   // Use of javac -g could be different in the old and the new
4379   if (scratch_class->has_localvariable_table() !=
4380       the_class->has_localvariable_table()) {
4381     the_class->set_has_localvariable_table(scratch_class->has_localvariable_table());
4382   }
4383 
4384   swap_annotations(the_class, scratch_class);
4385 
4386   // Replace minor version number of class file
4387   u2 old_minor_version = the_class->constants()->minor_version();
4388   the_class->constants()->set_minor_version(scratch_class->constants()->minor_version());
4389   scratch_class->constants()->set_minor_version(old_minor_version);
4390 
4391   // Replace major version number of class file
4392   u2 old_major_version = the_class->constants()->major_version();
4393   the_class->constants()->set_major_version(scratch_class->constants()->major_version());
4394   scratch_class->constants()->set_major_version(old_major_version);
4395 
4396   // Replace CP indexes for class and name+type of enclosing method
4397   u2 old_class_idx  = the_class->enclosing_method_class_index();
4398   u2 old_method_idx = the_class->enclosing_method_method_index();
4399   the_class->set_enclosing_method_indices(
4400     scratch_class->enclosing_method_class_index(),
4401     scratch_class->enclosing_method_method_index());
4402   scratch_class->set_enclosing_method_indices(old_class_idx, old_method_idx);
4403 
4404   if (!the_class->has_been_redefined()) {
4405     the_class->set_has_been_redefined();
4406   }
4407 
4408   // Scratch class is unloaded but still needs cleaning, and skipping for CDS.
4409   scratch_class->set_is_scratch_class();
4410 
4411   // keep track of previous versions of this class
4412   the_class->add_previous_version(scratch_class, emcp_method_count);
4413 
4414   JFR_ONLY(Jfr::on_klass_redefinition(the_class, scratch_class);)
4415 
4416   _timer_rsc_phase1.stop();
4417   if (log_is_enabled(Info, redefine, class, timer)) {
4418     _timer_rsc_phase2.start();
4419   }
4420 
4421   if (the_class->oop_map_cache() != nullptr) {
4422     // Flush references to any obsolete methods from the oop map cache
4423     // so that obsolete methods are not pinned.
4424     the_class->oop_map_cache()->flush_obsolete_entries();
4425   }
4426 
4427   increment_class_counter(the_class);
4428 
4429   if (EventClassRedefinition::is_enabled()) {
4430     EventClassRedefinition event;
4431     event.set_classModificationCount(java_lang_Class::classRedefinedCount(the_class->java_mirror()));
4432     event.set_redefinedClass(the_class);
4433     event.set_redefinitionId(_id);
4434     event.commit();
4435   }
4436 
4437   {
4438     ResourceMark rm(current);
4439     // increment the classRedefinedCount field in the_class and in any
4440     // direct and indirect subclasses of the_class
4441     size_t avail_mem = 0;
4442     // Return value ignored - defaulting to 0 on failure.
4443     (void)os::available_memory(avail_mem);
4444     log_info(redefine, class, load)
4445       ("redefined name=%s, count=%d (avail_mem=%zuK)",
4446        the_class->external_name(), java_lang_Class::classRedefinedCount(the_class->java_mirror()), avail_mem >> 10);
4447     Events::log_redefinition(current, "redefined class name=%s, count=%d",
4448                              the_class->external_name(),
4449                              java_lang_Class::classRedefinedCount(the_class->java_mirror()));
4450 
4451   }
4452   _timer_rsc_phase2.stop();
4453 
4454 } // end redefine_single_class()
4455 
4456 
4457 // Increment the classRedefinedCount field in the specific InstanceKlass
4458 // and in all direct and indirect subclasses.
4459 void VM_RedefineClasses::increment_class_counter(InstanceKlass* ik) {
4460   for (ClassHierarchyIterator iter(ik); !iter.done(); iter.next()) {
4461     // Only update instanceKlasses
4462     Klass* sub = iter.klass();
4463     if (sub->is_instance_klass()) {
4464       oop class_mirror = InstanceKlass::cast(sub)->java_mirror();
4465       Klass* class_oop = java_lang_Class::as_Klass(class_mirror);
4466       int new_count = java_lang_Class::classRedefinedCount(class_mirror) + 1;
4467       java_lang_Class::set_classRedefinedCount(class_mirror, new_count);
4468 
4469       if (class_oop != _the_class) {
4470         // _the_class count is printed at end of redefine_single_class()
4471         log_debug(redefine, class, subclass)("updated count in subclass=%s to %d", ik->external_name(), new_count);
4472       }
4473     }
4474   }
4475 }
4476 
4477 void VM_RedefineClasses::CheckClass::do_klass(Klass* k) {
4478   bool no_old_methods = true;  // be optimistic
4479 
4480   // Both array and instance classes have vtables.
4481   // a vtable should never contain old or obsolete methods
4482   ResourceMark rm(_thread);
4483   if (k->vtable_length() > 0 &&
4484       !k->vtable().check_no_old_or_obsolete_entries()) {
4485     if (log_is_enabled(Trace, redefine, class, obsolete, metadata)) {
4486       log_trace(redefine, class, obsolete, metadata)
4487         ("klassVtable::check_no_old_or_obsolete_entries failure -- OLD or OBSOLETE method found -- class: %s",
4488          k->signature_name());
4489       k->vtable().dump_vtable();
4490     }
4491     no_old_methods = false;
4492   }
4493 
4494   if (k->is_instance_klass()) {
4495     HandleMark hm(_thread);
4496     InstanceKlass *ik = InstanceKlass::cast(k);
4497 
4498     // an itable should never contain old or obsolete methods
4499     if (ik->itable_length() > 0 &&
4500         !ik->itable().check_no_old_or_obsolete_entries()) {
4501       if (log_is_enabled(Trace, redefine, class, obsolete, metadata)) {
4502         log_trace(redefine, class, obsolete, metadata)
4503           ("klassItable::check_no_old_or_obsolete_entries failure -- OLD or OBSOLETE method found -- class: %s",
4504            ik->signature_name());
4505         ik->itable().dump_itable();
4506       }
4507       no_old_methods = false;
4508     }
4509 
4510     // the constant pool cache should never contain non-deleted old or obsolete methods
4511     if (ik->constants() != nullptr &&
4512         ik->constants()->cache() != nullptr &&
4513         !ik->constants()->cache()->check_no_old_or_obsolete_entries()) {
4514       if (log_is_enabled(Trace, redefine, class, obsolete, metadata)) {
4515         log_trace(redefine, class, obsolete, metadata)
4516           ("cp-cache::check_no_old_or_obsolete_entries failure -- OLD or OBSOLETE method found -- class: %s",
4517            ik->signature_name());
4518         ik->constants()->cache()->dump_cache();
4519       }
4520       no_old_methods = false;
4521     }
4522   }
4523 
4524   // print and fail guarantee if old methods are found.
4525   if (!no_old_methods) {
4526     if (log_is_enabled(Trace, redefine, class, obsolete, metadata)) {
4527       dump_methods();
4528     } else {
4529       log_trace(redefine, class)("Use the '-Xlog:redefine+class*:' option "
4530         "to see more info about the following guarantee() failure.");
4531     }
4532     guarantee(false, "OLD and/or OBSOLETE method(s) found");
4533   }
4534 }
4535 
4536 u8 VM_RedefineClasses::next_id() {
4537   while (true) {
4538     u8 id = _id_counter;
4539     u8 next_id = id + 1;
4540     u8 result = Atomic::cmpxchg(&_id_counter, id, next_id);
4541     if (result == id) {
4542       return next_id;
4543     }
4544   }
4545 }
4546 
4547 void VM_RedefineClasses::dump_methods() {
4548   int j;
4549   log_trace(redefine, class, dump)("_old_methods --");
4550   for (j = 0; j < _old_methods->length(); ++j) {
4551     LogStreamHandle(Trace, redefine, class, dump) log_stream;
4552     Method* m = _old_methods->at(j);
4553     log_stream.print("%4d  (%5d)  ", j, m->vtable_index());
4554     m->access_flags().print_on(&log_stream);
4555     log_stream.print(" --  ");
4556     m->print_name(&log_stream);
4557     log_stream.cr();
4558   }
4559   log_trace(redefine, class, dump)("_new_methods --");
4560   for (j = 0; j < _new_methods->length(); ++j) {
4561     LogStreamHandle(Trace, redefine, class, dump) log_stream;
4562     Method* m = _new_methods->at(j);
4563     log_stream.print("%4d  (%5d)  ", j, m->vtable_index());
4564     m->access_flags().print_on(&log_stream);
4565     log_stream.print(" --  ");
4566     m->print_name(&log_stream);
4567     log_stream.cr();
4568   }
4569   log_trace(redefine, class, dump)("_matching_methods --");
4570   for (j = 0; j < _matching_methods_length; ++j) {
4571     LogStreamHandle(Trace, redefine, class, dump) log_stream;
4572     Method* m = _matching_old_methods[j];
4573     log_stream.print("%4d  (%5d)  ", j, m->vtable_index());
4574     m->access_flags().print_on(&log_stream);
4575     log_stream.print(" --  ");
4576     m->print_name();
4577     log_stream.cr();
4578 
4579     m = _matching_new_methods[j];
4580     log_stream.print("      (%5d)  ", m->vtable_index());
4581     m->access_flags().print_on(&log_stream);
4582     log_stream.cr();
4583   }
4584   log_trace(redefine, class, dump)("_deleted_methods --");
4585   for (j = 0; j < _deleted_methods_length; ++j) {
4586     LogStreamHandle(Trace, redefine, class, dump) log_stream;
4587     Method* m = _deleted_methods[j];
4588     log_stream.print("%4d  (%5d)  ", j, m->vtable_index());
4589     m->access_flags().print_on(&log_stream);
4590     log_stream.print(" --  ");
4591     m->print_name(&log_stream);
4592     log_stream.cr();
4593   }
4594   log_trace(redefine, class, dump)("_added_methods --");
4595   for (j = 0; j < _added_methods_length; ++j) {
4596     LogStreamHandle(Trace, redefine, class, dump) log_stream;
4597     Method* m = _added_methods[j];
4598     log_stream.print("%4d  (%5d)  ", j, m->vtable_index());
4599     m->access_flags().print_on(&log_stream);
4600     log_stream.print(" --  ");
4601     m->print_name(&log_stream);
4602     log_stream.cr();
4603   }
4604 }
4605 
4606 void VM_RedefineClasses::print_on_error(outputStream* st) const {
4607   VM_Operation::print_on_error(st);
4608   if (_the_class != nullptr) {
4609     ResourceMark rm;
4610     st->print_cr(", redefining class %s", _the_class->external_name());
4611   }
4612 }