1 /*
   2  * Copyright (c) 2003, 2024, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "cds/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/metadataOnStackMark.hpp"
  32 #include "classfile/symbolTable.hpp"
  33 #include "classfile/klassFactory.hpp"
  34 #include "classfile/verifier.hpp"
  35 #include "classfile/vmClasses.hpp"
  36 #include "classfile/vmSymbols.hpp"
  37 #include "code/codeCache.hpp"
  38 #include "compiler/compileBroker.hpp"
  39 #include "interpreter/oopMapCache.hpp"
  40 #include "interpreter/rewriter.hpp"
  41 #include "jfr/jfrEvents.hpp"
  42 #include "logging/logStream.hpp"
  43 #include "memory/metadataFactory.hpp"
  44 #include "memory/resourceArea.hpp"
  45 #include "memory/universe.hpp"
  46 #include "oops/annotations.hpp"
  47 #include "oops/constantPool.hpp"
  48 #include "oops/fieldStreams.inline.hpp"
  49 #include "oops/klass.inline.hpp"
  50 #include "oops/klassVtable.hpp"
  51 #include "oops/method.hpp"
  52 #include "oops/oop.inline.hpp"
  53 #include "oops/recordComponent.hpp"
  54 #include "prims/jvmtiImpl.hpp"
  55 #include "prims/jvmtiRedefineClasses.hpp"
  56 #include "prims/jvmtiThreadState.inline.hpp"
  57 #include "prims/resolvedMethodTable.hpp"
  58 #include "prims/methodComparator.hpp"
  59 #include "runtime/atomic.hpp"
  60 #include "runtime/deoptimization.hpp"
  61 #include "runtime/handles.inline.hpp"
  62 #include "runtime/jniHandles.inline.hpp"
  63 #include "runtime/relocator.hpp"
  64 #include "runtime/safepointVerifiers.hpp"
  65 #include "utilities/bitMap.inline.hpp"
  66 #include "utilities/checkedCast.hpp"
  67 #include "utilities/events.hpp"
  68 #include "utilities/macros.hpp"
  69 
  70 Array<Method*>* VM_RedefineClasses::_old_methods = nullptr;
  71 Array<Method*>* VM_RedefineClasses::_new_methods = nullptr;
  72 Method**  VM_RedefineClasses::_matching_old_methods = nullptr;
  73 Method**  VM_RedefineClasses::_matching_new_methods = nullptr;
  74 Method**  VM_RedefineClasses::_deleted_methods      = nullptr;
  75 Method**  VM_RedefineClasses::_added_methods        = nullptr;
  76 int       VM_RedefineClasses::_matching_methods_length = 0;
  77 int       VM_RedefineClasses::_deleted_methods_length  = 0;
  78 int       VM_RedefineClasses::_added_methods_length    = 0;
  79 
  80 // This flag is global as the constructor does not reset it:
  81 bool      VM_RedefineClasses::_has_redefined_Object = false;
  82 u8        VM_RedefineClasses::_id_counter = 0;
  83 
  84 VM_RedefineClasses::VM_RedefineClasses(jint class_count,
  85                                        const jvmtiClassDefinition *class_defs,
  86                                        JvmtiClassLoadKind class_load_kind) {
  87   _class_count = class_count;
  88   _class_defs = class_defs;
  89   _class_load_kind = class_load_kind;
  90   _any_class_has_resolved_methods = false;
  91   _res = JVMTI_ERROR_NONE;
  92   _the_class = nullptr;
  93   _id = next_id();
  94 }
  95 
  96 static inline InstanceKlass* get_ik(jclass def) {
  97   oop mirror = JNIHandles::resolve_non_null(def);
  98   return InstanceKlass::cast(java_lang_Class::as_Klass(mirror));
  99 }
 100 
 101 // If any of the classes are being redefined, wait
 102 // Parallel constant pool merging leads to indeterminate constant pools.
 103 void VM_RedefineClasses::lock_classes() {
 104   JvmtiThreadState *state = JvmtiThreadState::state_for(JavaThread::current());
 105   GrowableArray<Klass*>* redef_classes = state->get_classes_being_redefined();
 106 
 107   MonitorLocker ml(RedefineClasses_lock);
 108 
 109   if (redef_classes == nullptr) {
 110     redef_classes = new (mtClass) GrowableArray<Klass*>(1, mtClass);
 111     state->set_classes_being_redefined(redef_classes);
 112   }
 113 
 114   bool has_redefined;
 115   do {
 116     has_redefined = false;
 117     // Go through classes each time until none are being redefined. Skip
 118     // the ones that are being redefined by this thread currently. Class file
 119     // load hook event may trigger new class redefine when we are redefining
 120     // a class (after lock_classes()).
 121     for (int i = 0; i < _class_count; i++) {
 122       InstanceKlass* ik = get_ik(_class_defs[i].klass);
 123       // Check if we are currently redefining the class in this thread already.
 124       if (redef_classes->contains(ik)) {
 125         assert(ik->is_being_redefined(), "sanity");
 126       } else {
 127         if (ik->is_being_redefined()) {
 128           ml.wait();
 129           has_redefined = true;
 130           break;  // for loop
 131         }
 132       }
 133     }
 134   } while (has_redefined);
 135 
 136   for (int i = 0; i < _class_count; i++) {
 137     InstanceKlass* ik = get_ik(_class_defs[i].klass);
 138     redef_classes->push(ik); // Add to the _classes_being_redefined list
 139     ik->set_is_being_redefined(true);
 140   }
 141   ml.notify_all();
 142 }
 143 
 144 void VM_RedefineClasses::unlock_classes() {
 145   JvmtiThreadState *state = JvmtiThreadState::state_for(JavaThread::current());
 146   GrowableArray<Klass*>* redef_classes = state->get_classes_being_redefined();
 147   assert(redef_classes != nullptr, "_classes_being_redefined is not allocated");
 148 
 149   MonitorLocker ml(RedefineClasses_lock);
 150 
 151   for (int i = _class_count - 1; i >= 0; i--) {
 152     InstanceKlass* def_ik = get_ik(_class_defs[i].klass);
 153     if (redef_classes->length() > 0) {
 154       // Remove the class from _classes_being_redefined list
 155       Klass* k = redef_classes->pop();
 156       assert(def_ik == k, "unlocking wrong class");
 157     }
 158     assert(def_ik->is_being_redefined(),
 159            "should be being redefined to get here");
 160 
 161     // Unlock after we finish all redefines for this class within
 162     // the thread. Same class can be pushed to the list multiple
 163     // times (not more than once by each recursive redefinition).
 164     if (!redef_classes->contains(def_ik)) {
 165       def_ik->set_is_being_redefined(false);
 166     }
 167   }
 168   ml.notify_all();
 169 }
 170 
 171 bool VM_RedefineClasses::doit_prologue() {
 172   if (_class_count == 0) {
 173     _res = JVMTI_ERROR_NONE;
 174     return false;
 175   }
 176   if (_class_defs == nullptr) {
 177     _res = JVMTI_ERROR_NULL_POINTER;
 178     return false;
 179   }
 180 
 181   for (int i = 0; i < _class_count; i++) {
 182     if (_class_defs[i].klass == nullptr) {
 183       _res = JVMTI_ERROR_INVALID_CLASS;
 184       return false;
 185     }
 186     if (_class_defs[i].class_byte_count == 0) {
 187       _res = JVMTI_ERROR_INVALID_CLASS_FORMAT;
 188       return false;
 189     }
 190     if (_class_defs[i].class_bytes == nullptr) {
 191       _res = JVMTI_ERROR_NULL_POINTER;
 192       return false;
 193     }
 194 
 195     oop mirror = JNIHandles::resolve_non_null(_class_defs[i].klass);
 196     // classes for primitives, arrays, and hidden classes
 197     // cannot be redefined.
 198     if (!is_modifiable_class(mirror)) {
 199       _res = JVMTI_ERROR_UNMODIFIABLE_CLASS;
 200       return false;
 201     }
 202   }
 203 
 204   // Start timer after all the sanity checks; not quite accurate, but
 205   // better than adding a bunch of stop() calls.
 206   if (log_is_enabled(Info, redefine, class, timer)) {
 207     _timer_vm_op_prologue.start();
 208   }
 209 
 210   lock_classes();
 211   // We first load new class versions in the prologue, because somewhere down the
 212   // call chain it is required that the current thread is a Java thread.
 213   _res = load_new_class_versions();
 214   if (_res != JVMTI_ERROR_NONE) {
 215     // free any successfully created classes, since none are redefined
 216     for (int i = 0; i < _class_count; i++) {
 217       if (_scratch_classes[i] != nullptr) {
 218         ClassLoaderData* cld = _scratch_classes[i]->class_loader_data();
 219         // Free the memory for this class at class unloading time.  Not before
 220         // because CMS might think this is still live.
 221         InstanceKlass* ik = get_ik(_class_defs[i].klass);
 222         if (ik->get_cached_class_file() == _scratch_classes[i]->get_cached_class_file()) {
 223           // Don't double-free cached_class_file copied from the original class if error.
 224           _scratch_classes[i]->set_cached_class_file(nullptr);
 225         }
 226         cld->add_to_deallocate_list(InstanceKlass::cast(_scratch_classes[i]));
 227       }
 228     }
 229     // Free os::malloc allocated memory in load_new_class_version.
 230     os::free(_scratch_classes);
 231     _timer_vm_op_prologue.stop();
 232     unlock_classes();
 233     return false;
 234   }
 235 
 236   _timer_vm_op_prologue.stop();
 237   return true;
 238 }
 239 
 240 void VM_RedefineClasses::doit() {
 241   Thread* current = Thread::current();
 242 
 243   if (log_is_enabled(Info, redefine, class, timer)) {
 244     _timer_vm_op_doit.start();
 245   }
 246 
 247 #if INCLUDE_CDS
 248   if (UseSharedSpaces) {
 249     // Sharing is enabled so we remap the shared readonly space to
 250     // shared readwrite, private just in case we need to redefine
 251     // a shared class. We do the remap during the doit() phase of
 252     // the safepoint to be safer.
 253     if (!MetaspaceShared::remap_shared_readonly_as_readwrite()) {
 254       log_info(redefine, class, load)("failed to remap shared readonly space to readwrite, private");
 255       _res = JVMTI_ERROR_INTERNAL;
 256       _timer_vm_op_doit.stop();
 257       return;
 258     }
 259   }
 260 #endif
 261 
 262   // Mark methods seen on stack and everywhere else so old methods are not
 263   // cleaned up if they're on the stack.
 264   MetadataOnStackMark md_on_stack(/*walk_all_metadata*/true, /*redefinition_walk*/true);
 265   HandleMark hm(current);   // make sure any handles created are deleted
 266                             // before the stack walk again.
 267 
 268   for (int i = 0; i < _class_count; i++) {
 269     redefine_single_class(current, _class_defs[i].klass, _scratch_classes[i]);
 270   }
 271 
 272   // Flush all compiled code that depends on the classes redefined.
 273   flush_dependent_code();
 274 
 275   // Adjust constantpool caches and vtables for all classes
 276   // that reference methods of the evolved classes.
 277   // Have to do this after all classes are redefined and all methods that
 278   // are redefined are marked as old.
 279   AdjustAndCleanMetadata adjust_and_clean_metadata(current);
 280   ClassLoaderDataGraph::classes_do(&adjust_and_clean_metadata);
 281 
 282   // JSR-292 support
 283   if (_any_class_has_resolved_methods) {
 284     bool trace_name_printed = false;
 285     ResolvedMethodTable::adjust_method_entries(&trace_name_printed);
 286   }
 287 
 288   // Increment flag indicating that some invariants are no longer true.
 289   // See jvmtiExport.hpp for detailed explanation.
 290   JvmtiExport::increment_redefinition_count();
 291 
 292   // check_class() is optionally called for product bits, but is
 293   // always called for non-product bits.
 294 #ifdef PRODUCT
 295   if (log_is_enabled(Trace, redefine, class, obsolete, metadata)) {
 296 #endif
 297     log_trace(redefine, class, obsolete, metadata)("calling check_class");
 298     CheckClass check_class(current);
 299     ClassLoaderDataGraph::classes_do(&check_class);
 300 #ifdef PRODUCT
 301   }
 302 #endif
 303 
 304   // Clean up any metadata now unreferenced while MetadataOnStackMark is set.
 305   ClassLoaderDataGraph::clean_deallocate_lists(false);
 306 
 307   _timer_vm_op_doit.stop();
 308 }
 309 
 310 void VM_RedefineClasses::doit_epilogue() {
 311   unlock_classes();
 312 
 313   // Free os::malloc allocated memory.
 314   os::free(_scratch_classes);
 315 
 316   // Reset the_class to null for error printing.
 317   _the_class = nullptr;
 318 
 319   if (log_is_enabled(Info, redefine, class, timer)) {
 320     // Used to have separate timers for "doit" and "all", but the timer
 321     // overhead skewed the measurements.
 322     julong doit_time = _timer_vm_op_doit.milliseconds();
 323     julong all_time = _timer_vm_op_prologue.milliseconds() + doit_time;
 324 
 325     log_info(redefine, class, timer)
 326       ("vm_op: all=" JULONG_FORMAT "  prologue=" JULONG_FORMAT "  doit=" JULONG_FORMAT,
 327        all_time, (julong)_timer_vm_op_prologue.milliseconds(), doit_time);
 328     log_info(redefine, class, timer)
 329       ("redefine_single_class: phase1=" JULONG_FORMAT "  phase2=" JULONG_FORMAT,
 330        (julong)_timer_rsc_phase1.milliseconds(), (julong)_timer_rsc_phase2.milliseconds());
 331   }
 332 }
 333 
 334 bool VM_RedefineClasses::is_modifiable_class(oop klass_mirror) {
 335   // classes for primitives cannot be redefined
 336   if (java_lang_Class::is_primitive(klass_mirror)) {
 337     return false;
 338   }
 339   Klass* k = java_lang_Class::as_Klass(klass_mirror);
 340   // classes for arrays cannot be redefined
 341   if (k == nullptr || !k->is_instance_klass()) {
 342     return false;
 343   }
 344 
 345   // Cannot redefine or retransform a hidden class.
 346   if (InstanceKlass::cast(k)->is_hidden()) {
 347     return false;
 348   }
 349   if (InstanceKlass::cast(k) == vmClasses::Continuation_klass()) {
 350     // Don't redefine Continuation class. See 8302779.
 351     return false;
 352   }
 353   return true;
 354 }
 355 
 356 // Append the current entry at scratch_i in scratch_cp to *merge_cp_p
 357 // where the end of *merge_cp_p is specified by *merge_cp_length_p. For
 358 // direct CP entries, there is just the current entry to append. For
 359 // indirect and double-indirect CP entries, there are zero or more
 360 // referenced CP entries along with the current entry to append.
 361 // Indirect and double-indirect CP entries are handled by recursive
 362 // calls to append_entry() as needed. The referenced CP entries are
 363 // always appended to *merge_cp_p before the referee CP entry. These
 364 // referenced CP entries may already exist in *merge_cp_p in which case
 365 // there is nothing extra to append and only the current entry is
 366 // appended.
 367 void VM_RedefineClasses::append_entry(const constantPoolHandle& scratch_cp,
 368        int scratch_i, constantPoolHandle *merge_cp_p, int *merge_cp_length_p) {
 369 
 370   // append is different depending on entry tag type
 371   switch (scratch_cp->tag_at(scratch_i).value()) {
 372 
 373     // The old verifier is implemented outside the VM. It loads classes,
 374     // but does not resolve constant pool entries directly so we never
 375     // see Class entries here with the old verifier. Similarly the old
 376     // verifier does not like Class entries in the input constant pool.
 377     // The split-verifier is implemented in the VM so it can optionally
 378     // and directly resolve constant pool entries to load classes. The
 379     // split-verifier can accept either Class entries or UnresolvedClass
 380     // entries in the input constant pool. We revert the appended copy
 381     // back to UnresolvedClass so that either verifier will be happy
 382     // with the constant pool entry.
 383     //
 384     // this is an indirect CP entry so it needs special handling
 385     case JVM_CONSTANT_Class:
 386     case JVM_CONSTANT_UnresolvedClass:
 387     {
 388       int name_i = scratch_cp->klass_name_index_at(scratch_i);
 389       int new_name_i = find_or_append_indirect_entry(scratch_cp, name_i, merge_cp_p,
 390                                                      merge_cp_length_p);
 391 
 392       if (new_name_i != name_i) {
 393         log_trace(redefine, class, constantpool)
 394           ("Class entry@%d name_index change: %d to %d",
 395            *merge_cp_length_p, name_i, new_name_i);
 396       }
 397 
 398       (*merge_cp_p)->temp_unresolved_klass_at_put(*merge_cp_length_p, new_name_i);
 399       if (scratch_i != *merge_cp_length_p) {
 400         // The new entry in *merge_cp_p is at a different index than
 401         // the new entry in scratch_cp so we need to map the index values.
 402         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 403       }
 404       (*merge_cp_length_p)++;
 405     } break;
 406 
 407     // these are direct CP entries so they can be directly appended,
 408     // but double and long take two constant pool entries
 409     case JVM_CONSTANT_Double:  // fall through
 410     case JVM_CONSTANT_Long:
 411     {
 412       ConstantPool::copy_entry_to(scratch_cp, scratch_i, *merge_cp_p, *merge_cp_length_p);
 413 
 414       if (scratch_i != *merge_cp_length_p) {
 415         // The new entry in *merge_cp_p is at a different index than
 416         // the new entry in scratch_cp so we need to map the index values.
 417         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 418       }
 419       (*merge_cp_length_p) += 2;
 420     } break;
 421 
 422     // these are direct CP entries so they can be directly appended
 423     case JVM_CONSTANT_Float:   // fall through
 424     case JVM_CONSTANT_Integer: // fall through
 425     case JVM_CONSTANT_Utf8:    // fall through
 426 
 427     // This was an indirect CP entry, but it has been changed into
 428     // Symbol*s so this entry can be directly appended.
 429     case JVM_CONSTANT_String:      // fall through
 430     {
 431       ConstantPool::copy_entry_to(scratch_cp, scratch_i, *merge_cp_p, *merge_cp_length_p);
 432 
 433       if (scratch_i != *merge_cp_length_p) {
 434         // The new entry in *merge_cp_p is at a different index than
 435         // the new entry in scratch_cp so we need to map the index values.
 436         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 437       }
 438       (*merge_cp_length_p)++;
 439     } break;
 440 
 441     // this is an indirect CP entry so it needs special handling
 442     case JVM_CONSTANT_NameAndType:
 443     {
 444       int name_ref_i = scratch_cp->name_ref_index_at(scratch_i);
 445       int new_name_ref_i = find_or_append_indirect_entry(scratch_cp, name_ref_i, merge_cp_p,
 446                                                          merge_cp_length_p);
 447 
 448       int signature_ref_i = scratch_cp->signature_ref_index_at(scratch_i);
 449       int new_signature_ref_i = find_or_append_indirect_entry(scratch_cp, signature_ref_i,
 450                                                               merge_cp_p, merge_cp_length_p);
 451 
 452       // If the referenced entries already exist in *merge_cp_p, then
 453       // both new_name_ref_i and new_signature_ref_i will both be 0.
 454       // In that case, all we are appending is the current entry.
 455       if (new_name_ref_i != name_ref_i) {
 456         log_trace(redefine, class, constantpool)
 457           ("NameAndType entry@%d name_ref_index change: %d to %d",
 458            *merge_cp_length_p, name_ref_i, new_name_ref_i);
 459       }
 460       if (new_signature_ref_i != signature_ref_i) {
 461         log_trace(redefine, class, constantpool)
 462           ("NameAndType entry@%d signature_ref_index change: %d to %d",
 463            *merge_cp_length_p, signature_ref_i, new_signature_ref_i);
 464       }
 465 
 466       (*merge_cp_p)->name_and_type_at_put(*merge_cp_length_p,
 467         new_name_ref_i, new_signature_ref_i);
 468       if (scratch_i != *merge_cp_length_p) {
 469         // The new entry in *merge_cp_p is at a different index than
 470         // the new entry in scratch_cp so we need to map the index values.
 471         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 472       }
 473       (*merge_cp_length_p)++;
 474     } break;
 475 
 476     // this is a double-indirect CP entry so it needs special handling
 477     case JVM_CONSTANT_Fieldref:           // fall through
 478     case JVM_CONSTANT_InterfaceMethodref: // fall through
 479     case JVM_CONSTANT_Methodref:
 480     {
 481       int klass_ref_i = scratch_cp->uncached_klass_ref_index_at(scratch_i);
 482       int new_klass_ref_i = find_or_append_indirect_entry(scratch_cp, klass_ref_i,
 483                                                           merge_cp_p, merge_cp_length_p);
 484 
 485       int name_and_type_ref_i = scratch_cp->uncached_name_and_type_ref_index_at(scratch_i);
 486       int new_name_and_type_ref_i = find_or_append_indirect_entry(scratch_cp, name_and_type_ref_i,
 487                                                           merge_cp_p, merge_cp_length_p);
 488 
 489       const char *entry_name = nullptr;
 490       switch (scratch_cp->tag_at(scratch_i).value()) {
 491       case JVM_CONSTANT_Fieldref:
 492         entry_name = "Fieldref";
 493         (*merge_cp_p)->field_at_put(*merge_cp_length_p, new_klass_ref_i,
 494           new_name_and_type_ref_i);
 495         break;
 496       case JVM_CONSTANT_InterfaceMethodref:
 497         entry_name = "IFMethodref";
 498         (*merge_cp_p)->interface_method_at_put(*merge_cp_length_p,
 499           new_klass_ref_i, new_name_and_type_ref_i);
 500         break;
 501       case JVM_CONSTANT_Methodref:
 502         entry_name = "Methodref";
 503         (*merge_cp_p)->method_at_put(*merge_cp_length_p, new_klass_ref_i,
 504           new_name_and_type_ref_i);
 505         break;
 506       default:
 507         guarantee(false, "bad switch");
 508         break;
 509       }
 510 
 511       if (klass_ref_i != new_klass_ref_i) {
 512         log_trace(redefine, class, constantpool)
 513           ("%s entry@%d class_index changed: %d to %d", entry_name, *merge_cp_length_p, klass_ref_i, new_klass_ref_i);
 514       }
 515       if (name_and_type_ref_i != new_name_and_type_ref_i) {
 516         log_trace(redefine, class, constantpool)
 517           ("%s entry@%d name_and_type_index changed: %d to %d",
 518            entry_name, *merge_cp_length_p, name_and_type_ref_i, new_name_and_type_ref_i);
 519       }
 520 
 521       if (scratch_i != *merge_cp_length_p) {
 522         // The new entry in *merge_cp_p is at a different index than
 523         // the new entry in scratch_cp so we need to map the index values.
 524         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 525       }
 526       (*merge_cp_length_p)++;
 527     } break;
 528 
 529     // this is an indirect CP entry so it needs special handling
 530     case JVM_CONSTANT_MethodType:
 531     {
 532       int ref_i = scratch_cp->method_type_index_at(scratch_i);
 533       int new_ref_i = find_or_append_indirect_entry(scratch_cp, ref_i, merge_cp_p,
 534                                                     merge_cp_length_p);
 535       if (new_ref_i != ref_i) {
 536         log_trace(redefine, class, constantpool)
 537           ("MethodType entry@%d ref_index change: %d to %d", *merge_cp_length_p, ref_i, new_ref_i);
 538       }
 539       (*merge_cp_p)->method_type_index_at_put(*merge_cp_length_p, new_ref_i);
 540       if (scratch_i != *merge_cp_length_p) {
 541         // The new entry in *merge_cp_p is at a different index than
 542         // the new entry in scratch_cp so we need to map the index values.
 543         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 544       }
 545       (*merge_cp_length_p)++;
 546     } break;
 547 
 548     // this is an indirect CP entry so it needs special handling
 549     case JVM_CONSTANT_MethodHandle:
 550     {
 551       int ref_kind = scratch_cp->method_handle_ref_kind_at(scratch_i);
 552       int ref_i = scratch_cp->method_handle_index_at(scratch_i);
 553       int new_ref_i = find_or_append_indirect_entry(scratch_cp, ref_i, merge_cp_p,
 554                                                     merge_cp_length_p);
 555       if (new_ref_i != ref_i) {
 556         log_trace(redefine, class, constantpool)
 557           ("MethodHandle entry@%d ref_index change: %d to %d", *merge_cp_length_p, ref_i, new_ref_i);
 558       }
 559       (*merge_cp_p)->method_handle_index_at_put(*merge_cp_length_p, ref_kind, new_ref_i);
 560       if (scratch_i != *merge_cp_length_p) {
 561         // The new entry in *merge_cp_p is at a different index than
 562         // the new entry in scratch_cp so we need to map the index values.
 563         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 564       }
 565       (*merge_cp_length_p)++;
 566     } break;
 567 
 568     // this is an indirect CP entry so it needs special handling
 569     case JVM_CONSTANT_Dynamic:  // fall through
 570     case JVM_CONSTANT_InvokeDynamic:
 571     {
 572       // Index of the bootstrap specifier in the operands array
 573       int old_bs_i = scratch_cp->bootstrap_methods_attribute_index(scratch_i);
 574       int new_bs_i = find_or_append_operand(scratch_cp, old_bs_i, merge_cp_p,
 575                                             merge_cp_length_p);
 576       // The bootstrap method NameAndType_info index
 577       int old_ref_i = scratch_cp->bootstrap_name_and_type_ref_index_at(scratch_i);
 578       int new_ref_i = find_or_append_indirect_entry(scratch_cp, old_ref_i, merge_cp_p,
 579                                                     merge_cp_length_p);
 580       if (new_bs_i != old_bs_i) {
 581         log_trace(redefine, class, constantpool)
 582           ("Dynamic entry@%d bootstrap_method_attr_index change: %d to %d",
 583            *merge_cp_length_p, old_bs_i, new_bs_i);
 584       }
 585       if (new_ref_i != old_ref_i) {
 586         log_trace(redefine, class, constantpool)
 587           ("Dynamic entry@%d name_and_type_index change: %d to %d", *merge_cp_length_p, old_ref_i, new_ref_i);
 588       }
 589 
 590       if (scratch_cp->tag_at(scratch_i).is_dynamic_constant())
 591         (*merge_cp_p)->dynamic_constant_at_put(*merge_cp_length_p, new_bs_i, new_ref_i);
 592       else
 593         (*merge_cp_p)->invoke_dynamic_at_put(*merge_cp_length_p, new_bs_i, new_ref_i);
 594       if (scratch_i != *merge_cp_length_p) {
 595         // The new entry in *merge_cp_p is at a different index than
 596         // the new entry in scratch_cp so we need to map the index values.
 597         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 598       }
 599       (*merge_cp_length_p)++;
 600     } break;
 601 
 602     // At this stage, Class or UnresolvedClass could be in scratch_cp, but not
 603     // ClassIndex
 604     case JVM_CONSTANT_ClassIndex: // fall through
 605 
 606     // Invalid is used as the tag for the second constant pool entry
 607     // occupied by JVM_CONSTANT_Double or JVM_CONSTANT_Long. It should
 608     // not be seen by itself.
 609     case JVM_CONSTANT_Invalid: // fall through
 610 
 611     // At this stage, String could be here, but not StringIndex
 612     case JVM_CONSTANT_StringIndex: // fall through
 613 
 614     // At this stage JVM_CONSTANT_UnresolvedClassInError should not be here
 615     case JVM_CONSTANT_UnresolvedClassInError: // fall through
 616 
 617     default:
 618     {
 619       // leave a breadcrumb
 620       jbyte bad_value = scratch_cp->tag_at(scratch_i).value();
 621       ShouldNotReachHere();
 622     } break;
 623   } // end switch tag value
 624 } // end append_entry()
 625 
 626 
 627 u2 VM_RedefineClasses::find_or_append_indirect_entry(const constantPoolHandle& scratch_cp,
 628       int ref_i, constantPoolHandle *merge_cp_p, int *merge_cp_length_p) {
 629 
 630   int new_ref_i = ref_i;
 631   bool match = (ref_i < *merge_cp_length_p) &&
 632                scratch_cp->compare_entry_to(ref_i, *merge_cp_p, ref_i);
 633 
 634   if (!match) {
 635     // forward reference in *merge_cp_p or not a direct match
 636     int found_i = scratch_cp->find_matching_entry(ref_i, *merge_cp_p);
 637     if (found_i != 0) {
 638       guarantee(found_i != ref_i, "compare_entry_to() and find_matching_entry() do not agree");
 639       // Found a matching entry somewhere else in *merge_cp_p so just need a mapping entry.
 640       new_ref_i = found_i;
 641       map_index(scratch_cp, ref_i, found_i);
 642     } else {
 643       // no match found so we have to append this entry to *merge_cp_p
 644       append_entry(scratch_cp, ref_i, merge_cp_p, merge_cp_length_p);
 645       // The above call to append_entry() can only append one entry
 646       // so the post call query of *merge_cp_length_p is only for
 647       // the sake of consistency.
 648       new_ref_i = *merge_cp_length_p - 1;
 649     }
 650   }
 651 
 652   // constant pool indices are u2, unless the merged constant pool overflows which
 653   // we don't check for.
 654   return checked_cast<u2>(new_ref_i);
 655 } // end find_or_append_indirect_entry()
 656 
 657 
 658 // Append a bootstrap specifier into the merge_cp operands that is semantically equal
 659 // to the scratch_cp operands bootstrap specifier passed by the old_bs_i index.
 660 // Recursively append new merge_cp entries referenced by the new bootstrap specifier.
 661 void VM_RedefineClasses::append_operand(const constantPoolHandle& scratch_cp, int old_bs_i,
 662        constantPoolHandle *merge_cp_p, int *merge_cp_length_p) {
 663 
 664   u2 old_ref_i = scratch_cp->operand_bootstrap_method_ref_index_at(old_bs_i);
 665   u2 new_ref_i = find_or_append_indirect_entry(scratch_cp, old_ref_i, merge_cp_p,
 666                                                merge_cp_length_p);
 667   if (new_ref_i != old_ref_i) {
 668     log_trace(redefine, class, constantpool)
 669       ("operands entry@%d bootstrap method ref_index change: %d to %d", _operands_cur_length, old_ref_i, new_ref_i);
 670   }
 671 
 672   Array<u2>* merge_ops = (*merge_cp_p)->operands();
 673   int new_bs_i = _operands_cur_length;
 674   // We have _operands_cur_length == 0 when the merge_cp operands is empty yet.
 675   // However, the operand_offset_at(0) was set in the extend_operands() call.
 676   int new_base = (new_bs_i == 0) ? (*merge_cp_p)->operand_offset_at(0)
 677                                  : (*merge_cp_p)->operand_next_offset_at(new_bs_i - 1);
 678   u2 argc      = scratch_cp->operand_argument_count_at(old_bs_i);
 679 
 680   ConstantPool::operand_offset_at_put(merge_ops, _operands_cur_length, new_base);
 681   merge_ops->at_put(new_base++, new_ref_i);
 682   merge_ops->at_put(new_base++, argc);
 683 
 684   for (int i = 0; i < argc; i++) {
 685     u2 old_arg_ref_i = scratch_cp->operand_argument_index_at(old_bs_i, i);
 686     u2 new_arg_ref_i = find_or_append_indirect_entry(scratch_cp, old_arg_ref_i, merge_cp_p,
 687                                                      merge_cp_length_p);
 688     merge_ops->at_put(new_base++, new_arg_ref_i);
 689     if (new_arg_ref_i != old_arg_ref_i) {
 690       log_trace(redefine, class, constantpool)
 691         ("operands entry@%d bootstrap method argument ref_index change: %d to %d",
 692          _operands_cur_length, old_arg_ref_i, new_arg_ref_i);
 693     }
 694   }
 695   if (old_bs_i != _operands_cur_length) {
 696     // The bootstrap specifier in *merge_cp_p is at a different index than
 697     // that in scratch_cp so we need to map the index values.
 698     map_operand_index(old_bs_i, new_bs_i);
 699   }
 700   _operands_cur_length++;
 701 } // end append_operand()
 702 
 703 
 704 int VM_RedefineClasses::find_or_append_operand(const constantPoolHandle& scratch_cp,
 705       int old_bs_i, constantPoolHandle *merge_cp_p, int *merge_cp_length_p) {
 706 
 707   int new_bs_i = old_bs_i; // bootstrap specifier index
 708   bool match = (old_bs_i < _operands_cur_length) &&
 709                scratch_cp->compare_operand_to(old_bs_i, *merge_cp_p, old_bs_i);
 710 
 711   if (!match) {
 712     // forward reference in *merge_cp_p or not a direct match
 713     int found_i = scratch_cp->find_matching_operand(old_bs_i, *merge_cp_p,
 714                                                     _operands_cur_length);
 715     if (found_i != -1) {
 716       guarantee(found_i != old_bs_i, "compare_operand_to() and find_matching_operand() disagree");
 717       // found a matching operand somewhere else in *merge_cp_p so just need a mapping
 718       new_bs_i = found_i;
 719       map_operand_index(old_bs_i, found_i);
 720     } else {
 721       // no match found so we have to append this bootstrap specifier to *merge_cp_p
 722       append_operand(scratch_cp, old_bs_i, merge_cp_p, merge_cp_length_p);
 723       new_bs_i = _operands_cur_length - 1;
 724     }
 725   }
 726   return new_bs_i;
 727 } // end find_or_append_operand()
 728 
 729 
 730 void VM_RedefineClasses::finalize_operands_merge(const constantPoolHandle& merge_cp, TRAPS) {
 731   if (merge_cp->operands() == nullptr) {
 732     return;
 733   }
 734   // Shrink the merge_cp operands
 735   merge_cp->shrink_operands(_operands_cur_length, CHECK);
 736 
 737   if (log_is_enabled(Trace, redefine, class, constantpool)) {
 738     // don't want to loop unless we are tracing
 739     int count = 0;
 740     for (int i = 1; i < _operands_index_map_p->length(); i++) {
 741       int value = _operands_index_map_p->at(i);
 742       if (value != -1) {
 743         log_trace(redefine, class, constantpool)("operands_index_map[%d]: old=%d new=%d", count, i, value);
 744         count++;
 745       }
 746     }
 747   }
 748   // Clean-up
 749   _operands_index_map_p = nullptr;
 750   _operands_cur_length = 0;
 751   _operands_index_map_count = 0;
 752 } // end finalize_operands_merge()
 753 
 754 // Symbol* comparator for qsort
 755 // The caller must have an active ResourceMark.
 756 static int symcmp(const void* a, const void* b) {
 757   char* astr = (*(Symbol**)a)->as_C_string();
 758   char* bstr = (*(Symbol**)b)->as_C_string();
 759   return strcmp(astr, bstr);
 760 }
 761 
 762 // The caller must have an active ResourceMark.
 763 static jvmtiError check_attribute_arrays(const char* attr_name,
 764            InstanceKlass* the_class, InstanceKlass* scratch_class,
 765            Array<u2>* the_array, Array<u2>* scr_array) {
 766   bool the_array_exists = the_array != Universe::the_empty_short_array();
 767   bool scr_array_exists = scr_array != Universe::the_empty_short_array();
 768 
 769   int array_len = the_array->length();
 770   if (the_array_exists && scr_array_exists) {
 771     if (array_len != scr_array->length()) {
 772       log_trace(redefine, class)
 773         ("redefined class %s attribute change error: %s len=%d changed to len=%d",
 774          the_class->external_name(), attr_name, array_len, scr_array->length());
 775       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
 776     }
 777 
 778     // The order of entries in the attribute array is not specified so we
 779     // have to explicitly check for the same contents. We do this by copying
 780     // the referenced symbols into their own arrays, sorting them and then
 781     // comparing each element pair.
 782 
 783     Symbol** the_syms = NEW_RESOURCE_ARRAY_RETURN_NULL(Symbol*, array_len);
 784     Symbol** scr_syms = NEW_RESOURCE_ARRAY_RETURN_NULL(Symbol*, array_len);
 785 
 786     if (the_syms == nullptr || scr_syms == nullptr) {
 787       return JVMTI_ERROR_OUT_OF_MEMORY;
 788     }
 789 
 790     for (int i = 0; i < array_len; i++) {
 791       int the_cp_index = the_array->at(i);
 792       int scr_cp_index = scr_array->at(i);
 793       the_syms[i] = the_class->constants()->klass_name_at(the_cp_index);
 794       scr_syms[i] = scratch_class->constants()->klass_name_at(scr_cp_index);
 795     }
 796 
 797     qsort(the_syms, array_len, sizeof(Symbol*), symcmp);
 798     qsort(scr_syms, array_len, sizeof(Symbol*), symcmp);
 799 
 800     for (int i = 0; i < array_len; i++) {
 801       if (the_syms[i] != scr_syms[i]) {
 802         log_info(redefine, class)
 803           ("redefined class %s attribute change error: %s[%d]: %s changed to %s",
 804            the_class->external_name(), attr_name, i,
 805            the_syms[i]->as_C_string(), scr_syms[i]->as_C_string());
 806         return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
 807       }
 808     }
 809   } else if (the_array_exists ^ scr_array_exists) {
 810     const char* action_str = (the_array_exists) ? "removed" : "added";
 811     log_info(redefine, class)
 812       ("redefined class %s attribute change error: %s attribute %s",
 813        the_class->external_name(), attr_name, action_str);
 814     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
 815   }
 816   return JVMTI_ERROR_NONE;
 817 }
 818 
 819 static jvmtiError check_nest_attributes(InstanceKlass* the_class,
 820                                         InstanceKlass* scratch_class) {
 821   // Check whether the class NestHost attribute has been changed.
 822   Thread* thread = Thread::current();
 823   ResourceMark rm(thread);
 824   u2 the_nest_host_idx = the_class->nest_host_index();
 825   u2 scr_nest_host_idx = scratch_class->nest_host_index();
 826 
 827   if (the_nest_host_idx != 0 && scr_nest_host_idx != 0) {
 828     Symbol* the_sym = the_class->constants()->klass_name_at(the_nest_host_idx);
 829     Symbol* scr_sym = scratch_class->constants()->klass_name_at(scr_nest_host_idx);
 830     if (the_sym != scr_sym) {
 831       log_info(redefine, class, nestmates)
 832         ("redefined class %s attribute change error: NestHost class: %s replaced with: %s",
 833          the_class->external_name(), the_sym->as_C_string(), scr_sym->as_C_string());
 834       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
 835     }
 836   } else if ((the_nest_host_idx == 0) ^ (scr_nest_host_idx == 0)) {
 837     const char* action_str = (the_nest_host_idx != 0) ? "removed" : "added";
 838     log_info(redefine, class, nestmates)
 839       ("redefined class %s attribute change error: NestHost attribute %s",
 840        the_class->external_name(), action_str);
 841     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
 842   }
 843 
 844   // Check whether the class NestMembers attribute has been changed.
 845   return check_attribute_arrays("NestMembers",
 846                                 the_class, scratch_class,
 847                                 the_class->nest_members(),
 848                                 scratch_class->nest_members());
 849 }
 850 
 851 // Return an error status if the class Record attribute was changed.
 852 static jvmtiError check_record_attribute(InstanceKlass* the_class, InstanceKlass* scratch_class) {
 853   // Get lists of record components.
 854   Array<RecordComponent*>* the_record = the_class->record_components();
 855   Array<RecordComponent*>* scr_record = scratch_class->record_components();
 856   bool the_record_exists = the_record != nullptr;
 857   bool scr_record_exists = scr_record != nullptr;
 858 
 859   if (the_record_exists && scr_record_exists) {
 860     int the_num_components = the_record->length();
 861     int scr_num_components = scr_record->length();
 862     if (the_num_components != scr_num_components) {
 863       log_info(redefine, class, record)
 864         ("redefined class %s attribute change error: Record num_components=%d changed to num_components=%d",
 865          the_class->external_name(), the_num_components, scr_num_components);
 866       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
 867     }
 868 
 869     // Compare each field in each record component.
 870     ConstantPool* the_cp =  the_class->constants();
 871     ConstantPool* scr_cp =  scratch_class->constants();
 872     for (int x = 0; x < the_num_components; x++) {
 873       RecordComponent* the_component = the_record->at(x);
 874       RecordComponent* scr_component = scr_record->at(x);
 875       const Symbol* const the_name = the_cp->symbol_at(the_component->name_index());
 876       const Symbol* const scr_name = scr_cp->symbol_at(scr_component->name_index());
 877       const Symbol* const the_descr = the_cp->symbol_at(the_component->descriptor_index());
 878       const Symbol* const scr_descr = scr_cp->symbol_at(scr_component->descriptor_index());
 879       if (the_name != scr_name || the_descr != scr_descr) {
 880         log_info(redefine, class, record)
 881           ("redefined class %s attribute change error: Record name_index, descriptor_index, and/or attributes_count changed",
 882            the_class->external_name());
 883         return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
 884       }
 885 
 886       int the_gen_sig = the_component->generic_signature_index();
 887       int scr_gen_sig = scr_component->generic_signature_index();
 888       const Symbol* const the_gen_sig_sym = (the_gen_sig == 0 ? nullptr :
 889         the_cp->symbol_at(the_component->generic_signature_index()));
 890       const Symbol* const scr_gen_sig_sym = (scr_gen_sig == 0 ? nullptr :
 891         scr_cp->symbol_at(scr_component->generic_signature_index()));
 892       if (the_gen_sig_sym != scr_gen_sig_sym) {
 893         log_info(redefine, class, record)
 894           ("redefined class %s attribute change error: Record generic_signature attribute changed",
 895            the_class->external_name());
 896         return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
 897       }
 898 
 899       // It's okay if a record component's annotations were changed.
 900     }
 901 
 902   } else if (the_record_exists ^ scr_record_exists) {
 903     const char* action_str = (the_record_exists) ? "removed" : "added";
 904     log_info(redefine, class, record)
 905       ("redefined class %s attribute change error: Record attribute %s",
 906        the_class->external_name(), action_str);
 907     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
 908   }
 909 
 910   return JVMTI_ERROR_NONE;
 911 }
 912 
 913 
 914 static jvmtiError check_permitted_subclasses_attribute(InstanceKlass* the_class,
 915                                                        InstanceKlass* scratch_class) {
 916   Thread* thread = Thread::current();
 917   ResourceMark rm(thread);
 918 
 919   // Check whether the class PermittedSubclasses attribute has been changed.
 920   return check_attribute_arrays("PermittedSubclasses",
 921                                 the_class, scratch_class,
 922                                 the_class->permitted_subclasses(),
 923                                 scratch_class->permitted_subclasses());
 924 }
 925 
 926 static bool can_add_or_delete(Method* m) {
 927       // Compatibility mode
 928   return (AllowRedefinitionToAddDeleteMethods &&
 929           (m->is_private() && (m->is_static() || m->is_final())));
 930 }
 931 
 932 jvmtiError VM_RedefineClasses::compare_and_normalize_class_versions(
 933              InstanceKlass* the_class,
 934              InstanceKlass* scratch_class) {
 935   int i;
 936 
 937   // Check superclasses, or rather their names, since superclasses themselves can be
 938   // requested to replace.
 939   // Check for null superclass first since this might be java.lang.Object
 940   if (the_class->super() != scratch_class->super() &&
 941       (the_class->super() == nullptr || scratch_class->super() == nullptr ||
 942        the_class->super()->name() !=
 943        scratch_class->super()->name())) {
 944     log_info(redefine, class, normalize)
 945       ("redefined class %s superclass change error: superclass changed from %s to %s.",
 946        the_class->external_name(),
 947        the_class->super() == nullptr ? "null" : the_class->super()->external_name(),
 948        scratch_class->super() == nullptr ? "null" : scratch_class->super()->external_name());
 949     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_HIERARCHY_CHANGED;
 950   }
 951 
 952   // Check if the number, names and order of directly implemented interfaces are the same.
 953   // I think in principle we should just check if the sets of names of directly implemented
 954   // interfaces are the same, i.e. the order of declaration (which, however, if changed in the
 955   // .java file, also changes in .class file) should not matter. However, comparing sets is
 956   // technically a bit more difficult, and, more importantly, I am not sure at present that the
 957   // order of interfaces does not matter on the implementation level, i.e. that the VM does not
 958   // rely on it somewhere.
 959   Array<InstanceKlass*>* k_interfaces = the_class->local_interfaces();
 960   Array<InstanceKlass*>* k_new_interfaces = scratch_class->local_interfaces();
 961   int n_intfs = k_interfaces->length();
 962   if (n_intfs != k_new_interfaces->length()) {
 963     log_info(redefine, class, normalize)
 964       ("redefined class %s interfaces change error: number of implemented interfaces changed from %d to %d.",
 965        the_class->external_name(), n_intfs, k_new_interfaces->length());
 966     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_HIERARCHY_CHANGED;
 967   }
 968   for (i = 0; i < n_intfs; i++) {
 969     if (k_interfaces->at(i)->name() !=
 970         k_new_interfaces->at(i)->name()) {
 971       log_info(redefine, class, normalize)
 972           ("redefined class %s interfaces change error: interface changed from %s to %s.",
 973            the_class->external_name(),
 974            k_interfaces->at(i)->external_name(), k_new_interfaces->at(i)->external_name());
 975       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_HIERARCHY_CHANGED;
 976     }
 977   }
 978 
 979   // Check whether class is in the error init state.
 980   if (the_class->is_in_error_state()) {
 981     log_info(redefine, class, normalize)
 982       ("redefined class %s is in error init state.", the_class->external_name());
 983     // TBD #5057930: special error code is needed in 1.6
 984     return JVMTI_ERROR_INVALID_CLASS;
 985   }
 986 
 987   // Check whether the nest-related attributes have been changed.
 988   jvmtiError err = check_nest_attributes(the_class, scratch_class);
 989   if (err != JVMTI_ERROR_NONE) {
 990     return err;
 991   }
 992 
 993   // Check whether the Record attribute has been changed.
 994   err = check_record_attribute(the_class, scratch_class);
 995   if (err != JVMTI_ERROR_NONE) {
 996     return err;
 997   }
 998 
 999   // Check whether the PermittedSubclasses attribute has been changed.
1000   err = check_permitted_subclasses_attribute(the_class, scratch_class);
1001   if (err != JVMTI_ERROR_NONE) {
1002     return err;
1003   }
1004 
1005   // Check whether class modifiers are the same.
1006   jushort old_flags = (jushort) the_class->access_flags().get_flags();
1007   jushort new_flags = (jushort) scratch_class->access_flags().get_flags();
1008   if (old_flags != new_flags) {
1009     log_info(redefine, class, normalize)
1010         ("redefined class %s modifiers change error: modifiers changed from %d to %d.",
1011          the_class->external_name(), old_flags, new_flags);
1012     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_MODIFIERS_CHANGED;
1013   }
1014 
1015   // Check if the number, names, types and order of fields declared in these classes
1016   // are the same.
1017   JavaFieldStream old_fs(the_class);
1018   JavaFieldStream new_fs(scratch_class);
1019   for (; !old_fs.done() && !new_fs.done(); old_fs.next(), new_fs.next()) {
1020     // name and signature
1021     Symbol* name_sym1 = the_class->constants()->symbol_at(old_fs.name_index());
1022     Symbol* sig_sym1 = the_class->constants()->symbol_at(old_fs.signature_index());
1023     Symbol* name_sym2 = scratch_class->constants()->symbol_at(new_fs.name_index());
1024     Symbol* sig_sym2 = scratch_class->constants()->symbol_at(new_fs.signature_index());
1025     if (name_sym1 != name_sym2 || sig_sym1 != sig_sym2) {
1026       log_info(redefine, class, normalize)
1027           ("redefined class %s fields change error: field %s %s changed to %s %s.",
1028            the_class->external_name(),
1029            sig_sym1->as_C_string(), name_sym1->as_C_string(),
1030            sig_sym2->as_C_string(), name_sym2->as_C_string());
1031       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_SCHEMA_CHANGED;
1032     }
1033     // offset
1034     if (old_fs.offset() != new_fs.offset()) {
1035       log_info(redefine, class, normalize)
1036           ("redefined class %s field %s change error: offset changed from %d to %d.",
1037            the_class->external_name(), name_sym2->as_C_string(), old_fs.offset(), new_fs.offset());
1038       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_SCHEMA_CHANGED;
1039     }
1040     // access
1041     old_flags = old_fs.access_flags().as_short();
1042     new_flags = new_fs.access_flags().as_short();
1043     if ((old_flags ^ new_flags) & JVM_RECOGNIZED_FIELD_MODIFIERS) {
1044       log_info(redefine, class, normalize)
1045           ("redefined class %s field %s change error: modifiers changed from %d to %d.",
1046            the_class->external_name(), name_sym2->as_C_string(), old_flags, new_flags);
1047       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_SCHEMA_CHANGED;
1048     }
1049   }
1050 
1051   // If both streams aren't done then we have a differing number of
1052   // fields.
1053   if (!old_fs.done() || !new_fs.done()) {
1054     const char* action = old_fs.done() ? "added" : "deleted";
1055     log_info(redefine, class, normalize)
1056         ("redefined class %s fields change error: some fields were %s.",
1057          the_class->external_name(), action);
1058     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_SCHEMA_CHANGED;
1059   }
1060 
1061   // Do a parallel walk through the old and new methods. Detect
1062   // cases where they match (exist in both), have been added in
1063   // the new methods, or have been deleted (exist only in the
1064   // old methods).  The class file parser places methods in order
1065   // by method name, but does not order overloaded methods by
1066   // signature.  In order to determine what fate befell the methods,
1067   // this code places the overloaded new methods that have matching
1068   // old methods in the same order as the old methods and places
1069   // new overloaded methods at the end of overloaded methods of
1070   // that name. The code for this order normalization is adapted
1071   // from the algorithm used in InstanceKlass::find_method().
1072   // Since we are swapping out of order entries as we find them,
1073   // we only have to search forward through the overloaded methods.
1074   // Methods which are added and have the same name as an existing
1075   // method (but different signature) will be put at the end of
1076   // the methods with that name, and the name mismatch code will
1077   // handle them.
1078   Array<Method*>* k_old_methods(the_class->methods());
1079   Array<Method*>* k_new_methods(scratch_class->methods());
1080   int n_old_methods = k_old_methods->length();
1081   int n_new_methods = k_new_methods->length();
1082   Thread* thread = Thread::current();
1083 
1084   int ni = 0;
1085   int oi = 0;
1086   while (true) {
1087     Method* k_old_method;
1088     Method* k_new_method;
1089     enum { matched, added, deleted, undetermined } method_was = undetermined;
1090 
1091     if (oi >= n_old_methods) {
1092       if (ni >= n_new_methods) {
1093         break; // we've looked at everything, done
1094       }
1095       // New method at the end
1096       k_new_method = k_new_methods->at(ni);
1097       method_was = added;
1098     } else if (ni >= n_new_methods) {
1099       // Old method, at the end, is deleted
1100       k_old_method = k_old_methods->at(oi);
1101       method_was = deleted;
1102     } else {
1103       // There are more methods in both the old and new lists
1104       k_old_method = k_old_methods->at(oi);
1105       k_new_method = k_new_methods->at(ni);
1106       if (k_old_method->name() != k_new_method->name()) {
1107         // Methods are sorted by method name, so a mismatch means added
1108         // or deleted
1109         if (k_old_method->name()->fast_compare(k_new_method->name()) > 0) {
1110           method_was = added;
1111         } else {
1112           method_was = deleted;
1113         }
1114       } else if (k_old_method->signature() == k_new_method->signature()) {
1115         // Both the name and signature match
1116         method_was = matched;
1117       } else {
1118         // The name matches, but the signature doesn't, which means we have to
1119         // search forward through the new overloaded methods.
1120         int nj;  // outside the loop for post-loop check
1121         for (nj = ni + 1; nj < n_new_methods; nj++) {
1122           Method* m = k_new_methods->at(nj);
1123           if (k_old_method->name() != m->name()) {
1124             // reached another method name so no more overloaded methods
1125             method_was = deleted;
1126             break;
1127           }
1128           if (k_old_method->signature() == m->signature()) {
1129             // found a match so swap the methods
1130             k_new_methods->at_put(ni, m);
1131             k_new_methods->at_put(nj, k_new_method);
1132             k_new_method = m;
1133             method_was = matched;
1134             break;
1135           }
1136         }
1137 
1138         if (nj >= n_new_methods) {
1139           // reached the end without a match; so method was deleted
1140           method_was = deleted;
1141         }
1142       }
1143     }
1144 
1145     switch (method_was) {
1146     case matched:
1147       // methods match, be sure modifiers do too
1148       old_flags = (jushort) k_old_method->access_flags().get_flags();
1149       new_flags = (jushort) k_new_method->access_flags().get_flags();
1150       if ((old_flags ^ new_flags) & ~(JVM_ACC_NATIVE)) {
1151         log_info(redefine, class, normalize)
1152           ("redefined class %s  method %s modifiers error: modifiers changed from %d to %d",
1153            the_class->external_name(), k_old_method->name_and_sig_as_C_string(), old_flags, new_flags);
1154         return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_METHOD_MODIFIERS_CHANGED;
1155       }
1156       {
1157         u2 new_num = k_new_method->method_idnum();
1158         u2 old_num = k_old_method->method_idnum();
1159         if (new_num != old_num) {
1160           Method* idnum_owner = scratch_class->method_with_idnum(old_num);
1161           if (idnum_owner != nullptr) {
1162             // There is already a method assigned this idnum -- switch them
1163             // Take current and original idnum from the new_method
1164             idnum_owner->set_method_idnum(new_num);
1165             idnum_owner->set_orig_method_idnum(k_new_method->orig_method_idnum());
1166           }
1167           // Take current and original idnum from the old_method
1168           k_new_method->set_method_idnum(old_num);
1169           k_new_method->set_orig_method_idnum(k_old_method->orig_method_idnum());
1170           if (thread->has_pending_exception()) {
1171             return JVMTI_ERROR_OUT_OF_MEMORY;
1172           }
1173         }
1174       }
1175       JFR_ONLY(k_new_method->copy_trace_flags(*k_old_method->trace_flags_addr());)
1176       log_trace(redefine, class, normalize)
1177         ("Method matched: new: %s [%d] == old: %s [%d]",
1178          k_new_method->name_and_sig_as_C_string(), ni, k_old_method->name_and_sig_as_C_string(), oi);
1179       // advance to next pair of methods
1180       ++oi;
1181       ++ni;
1182       break;
1183     case added:
1184       // method added, see if it is OK
1185       if (!can_add_or_delete(k_new_method)) {
1186         log_info(redefine, class, normalize)
1187           ("redefined class %s methods error: added method: %s [%d]",
1188            the_class->external_name(), k_new_method->name_and_sig_as_C_string(), ni);
1189         return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_METHOD_ADDED;
1190       }
1191       {
1192         u2 num = the_class->next_method_idnum();
1193         if (num == ConstMethod::UNSET_IDNUM) {
1194           // cannot add any more methods
1195           log_info(redefine, class, normalize)
1196             ("redefined class %s methods error: can't create ID for new method %s [%d]",
1197              the_class->external_name(), k_new_method->name_and_sig_as_C_string(), ni);
1198           return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_METHOD_ADDED;
1199         }
1200         u2 new_num = k_new_method->method_idnum();
1201         Method* idnum_owner = scratch_class->method_with_idnum(num);
1202         if (idnum_owner != nullptr) {
1203           // There is already a method assigned this idnum -- switch them
1204           // Take current and original idnum from the new_method
1205           idnum_owner->set_method_idnum(new_num);
1206           idnum_owner->set_orig_method_idnum(k_new_method->orig_method_idnum());
1207         }
1208         k_new_method->set_method_idnum(num);
1209         k_new_method->set_orig_method_idnum(num);
1210         if (thread->has_pending_exception()) {
1211           return JVMTI_ERROR_OUT_OF_MEMORY;
1212         }
1213       }
1214       log_trace(redefine, class, normalize)
1215         ("Method added: new: %s [%d]", k_new_method->name_and_sig_as_C_string(), ni);
1216       ++ni; // advance to next new method
1217       break;
1218     case deleted:
1219       // method deleted, see if it is OK
1220       if (!can_add_or_delete(k_old_method)) {
1221         log_info(redefine, class, normalize)
1222           ("redefined class %s methods error: deleted method %s [%d]",
1223            the_class->external_name(), k_old_method->name_and_sig_as_C_string(), oi);
1224         return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_METHOD_DELETED;
1225       }
1226       log_trace(redefine, class, normalize)
1227         ("Method deleted: old: %s [%d]", k_old_method->name_and_sig_as_C_string(), oi);
1228       ++oi; // advance to next old method
1229       break;
1230     default:
1231       ShouldNotReachHere();
1232     }
1233   }
1234 
1235   return JVMTI_ERROR_NONE;
1236 }
1237 
1238 
1239 // Find new constant pool index value for old constant pool index value
1240 // by searching the index map. Returns zero (0) if there is no mapped
1241 // value for the old constant pool index.
1242 u2 VM_RedefineClasses::find_new_index(int old_index) {
1243   if (_index_map_count == 0) {
1244     // map is empty so nothing can be found
1245     return 0;
1246   }
1247 
1248   if (old_index < 1 || old_index >= _index_map_p->length()) {
1249     // The old_index is out of range so it is not mapped. This should
1250     // not happen in regular constant pool merging use, but it can
1251     // happen if a corrupt annotation is processed.
1252     return 0;
1253   }
1254 
1255   int value = _index_map_p->at(old_index);
1256   if (value == -1) {
1257     // the old_index is not mapped
1258     return 0;
1259   }
1260 
1261   // constant pool indices are u2, unless the merged constant pool overflows which
1262   // we don't check for.
1263   return checked_cast<u2>(value);
1264 } // end find_new_index()
1265 
1266 
1267 // Find new bootstrap specifier index value for old bootstrap specifier index
1268 // value by searching the index map. Returns unused index (-1) if there is
1269 // no mapped value for the old bootstrap specifier index.
1270 int VM_RedefineClasses::find_new_operand_index(int old_index) {
1271   if (_operands_index_map_count == 0) {
1272     // map is empty so nothing can be found
1273     return -1;
1274   }
1275 
1276   if (old_index == -1 || old_index >= _operands_index_map_p->length()) {
1277     // The old_index is out of range so it is not mapped.
1278     // This should not happen in regular constant pool merging use.
1279     return -1;
1280   }
1281 
1282   int value = _operands_index_map_p->at(old_index);
1283   if (value == -1) {
1284     // the old_index is not mapped
1285     return -1;
1286   }
1287 
1288   return value;
1289 } // end find_new_operand_index()
1290 
1291 
1292 // The bug 6214132 caused the verification to fail.
1293 // 1. What's done in RedefineClasses() before verification:
1294 //  a) A reference to the class being redefined (_the_class) and a
1295 //     reference to new version of the class (_scratch_class) are
1296 //     saved here for use during the bytecode verification phase of
1297 //     RedefineClasses.
1298 //  b) The _java_mirror field from _the_class is copied to the
1299 //     _java_mirror field in _scratch_class. This means that a jclass
1300 //     returned for _the_class or _scratch_class will refer to the
1301 //     same Java mirror. The verifier will see the "one true mirror"
1302 //     for the class being verified.
1303 // 2. See comments in JvmtiThreadState for what is done during verification.
1304 
1305 class RedefineVerifyMark : public StackObj {
1306  private:
1307   JvmtiThreadState* _state;
1308   Klass*            _scratch_class;
1309   OopHandle         _scratch_mirror;
1310 
1311  public:
1312 
1313   RedefineVerifyMark(Klass* the_class, Klass* scratch_class,
1314                      JvmtiThreadState* state) : _state(state), _scratch_class(scratch_class)
1315   {
1316     _state->set_class_versions_map(the_class, scratch_class);
1317     _scratch_mirror = the_class->java_mirror_handle();  // this is a copy that is swapped
1318     _scratch_class->swap_java_mirror_handle(_scratch_mirror);
1319   }
1320 
1321   ~RedefineVerifyMark() {
1322     // Restore the scratch class's mirror, so when scratch_class is removed
1323     // the correct mirror pointing to it can be cleared.
1324     _scratch_class->swap_java_mirror_handle(_scratch_mirror);
1325     _state->clear_class_versions_map();
1326   }
1327 };
1328 
1329 
1330 jvmtiError VM_RedefineClasses::load_new_class_versions() {
1331 
1332   // For consistency allocate memory using os::malloc wrapper.
1333   _scratch_classes = (InstanceKlass**)
1334     os::malloc(sizeof(InstanceKlass*) * _class_count, mtClass);
1335   if (_scratch_classes == nullptr) {
1336     return JVMTI_ERROR_OUT_OF_MEMORY;
1337   }
1338   // Zero initialize the _scratch_classes array.
1339   for (int i = 0; i < _class_count; i++) {
1340     _scratch_classes[i] = nullptr;
1341   }
1342 
1343   JavaThread* current = JavaThread::current();
1344   ResourceMark rm(current);
1345 
1346   JvmtiThreadState *state = JvmtiThreadState::state_for(current);
1347   // state can only be null if the current thread is exiting which
1348   // should not happen since we're trying to do a RedefineClasses
1349   guarantee(state != nullptr, "exiting thread calling load_new_class_versions");
1350   for (int i = 0; i < _class_count; i++) {
1351     // Create HandleMark so that any handles created while loading new class
1352     // versions are deleted. Constant pools are deallocated while merging
1353     // constant pools
1354     HandleMark hm(current);
1355     InstanceKlass* the_class = get_ik(_class_defs[i].klass);
1356 
1357     log_debug(redefine, class, load)
1358       ("loading name=%s kind=%d (avail_mem=" UINT64_FORMAT "K)",
1359        the_class->external_name(), _class_load_kind, os::available_memory() >> 10);
1360 
1361     ClassFileStream st((u1*)_class_defs[i].class_bytes,
1362                        _class_defs[i].class_byte_count,
1363                        "__VM_RedefineClasses__",
1364                        ClassFileStream::verify);
1365 
1366     // Set redefined class handle in JvmtiThreadState class.
1367     // This redefined class is sent to agent event handler for class file
1368     // load hook event.
1369     state->set_class_being_redefined(the_class, _class_load_kind);
1370 
1371     JavaThread* THREAD = current; // For exception macros.
1372     ExceptionMark em(THREAD);
1373     Handle protection_domain(THREAD, the_class->protection_domain());
1374     ClassLoadInfo cl_info(protection_domain);
1375     // Parse and create a class from the bytes, but this class isn't added
1376     // to the dictionary, so do not call resolve_from_stream.
1377     InstanceKlass* scratch_class = KlassFactory::create_from_stream(&st,
1378                                                       the_class->name(),
1379                                                       the_class->class_loader_data(),
1380                                                       cl_info,
1381                                                       THREAD);
1382 
1383     // Clear class_being_redefined just to be sure.
1384     state->clear_class_being_redefined();
1385 
1386     // TODO: if this is retransform, and nothing changed we can skip it
1387 
1388     // Need to clean up allocated InstanceKlass if there's an error so assign
1389     // the result here. Caller deallocates all the scratch classes in case of
1390     // an error.
1391     _scratch_classes[i] = scratch_class;
1392 
1393     if (HAS_PENDING_EXCEPTION) {
1394       Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1395       log_info(redefine, class, load, exceptions)("create_from_stream exception: '%s'", ex_name->as_C_string());
1396       CLEAR_PENDING_EXCEPTION;
1397 
1398       if (ex_name == vmSymbols::java_lang_UnsupportedClassVersionError()) {
1399         return JVMTI_ERROR_UNSUPPORTED_VERSION;
1400       } else if (ex_name == vmSymbols::java_lang_ClassFormatError()) {
1401         return JVMTI_ERROR_INVALID_CLASS_FORMAT;
1402       } else if (ex_name == vmSymbols::java_lang_ClassCircularityError()) {
1403         return JVMTI_ERROR_CIRCULAR_CLASS_DEFINITION;
1404       } else if (ex_name == vmSymbols::java_lang_NoClassDefFoundError()) {
1405         // The message will be "XXX (wrong name: YYY)"
1406         return JVMTI_ERROR_NAMES_DONT_MATCH;
1407       } else if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1408         return JVMTI_ERROR_OUT_OF_MEMORY;
1409       } else {  // Just in case more exceptions can be thrown..
1410         return JVMTI_ERROR_FAILS_VERIFICATION;
1411       }
1412     }
1413 
1414     // Ensure class is linked before redefine
1415     if (!the_class->is_linked()) {
1416       the_class->link_class(THREAD);
1417       if (HAS_PENDING_EXCEPTION) {
1418         Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1419         oop message = java_lang_Throwable::message(PENDING_EXCEPTION);
1420         if (message != nullptr) {
1421           char* ex_msg = java_lang_String::as_utf8_string(message);
1422           log_info(redefine, class, load, exceptions)("link_class exception: '%s %s'",
1423                    ex_name->as_C_string(), ex_msg);
1424         } else {
1425           log_info(redefine, class, load, exceptions)("link_class exception: '%s'",
1426                    ex_name->as_C_string());
1427         }
1428         CLEAR_PENDING_EXCEPTION;
1429         if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1430           return JVMTI_ERROR_OUT_OF_MEMORY;
1431         } else if (ex_name == vmSymbols::java_lang_NoClassDefFoundError()) {
1432           return JVMTI_ERROR_INVALID_CLASS;
1433         } else {
1434           return JVMTI_ERROR_INTERNAL;
1435         }
1436       }
1437     }
1438 
1439     // Do the validity checks in compare_and_normalize_class_versions()
1440     // before verifying the byte codes. By doing these checks first, we
1441     // limit the number of functions that require redirection from
1442     // the_class to scratch_class. In particular, we don't have to
1443     // modify JNI GetSuperclass() and thus won't change its performance.
1444     jvmtiError res = compare_and_normalize_class_versions(the_class,
1445                        scratch_class);
1446     if (res != JVMTI_ERROR_NONE) {
1447       return res;
1448     }
1449 
1450     // verify what the caller passed us
1451     {
1452       // The bug 6214132 caused the verification to fail.
1453       // Information about the_class and scratch_class is temporarily
1454       // recorded into jvmtiThreadState. This data is used to redirect
1455       // the_class to scratch_class in the JVM_* functions called by the
1456       // verifier. Please, refer to jvmtiThreadState.hpp for the detailed
1457       // description.
1458       RedefineVerifyMark rvm(the_class, scratch_class, state);
1459       Verifier::verify(scratch_class, true, THREAD);
1460     }
1461 
1462     if (HAS_PENDING_EXCEPTION) {
1463       Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1464       log_info(redefine, class, load, exceptions)("verify_byte_codes exception: '%s'", ex_name->as_C_string());
1465       CLEAR_PENDING_EXCEPTION;
1466       if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1467         return JVMTI_ERROR_OUT_OF_MEMORY;
1468       } else {
1469         // tell the caller the bytecodes are bad
1470         return JVMTI_ERROR_FAILS_VERIFICATION;
1471       }
1472     }
1473 
1474     res = merge_cp_and_rewrite(the_class, scratch_class, THREAD);
1475     if (HAS_PENDING_EXCEPTION) {
1476       Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1477       log_info(redefine, class, load, exceptions)("merge_cp_and_rewrite exception: '%s'", ex_name->as_C_string());
1478       CLEAR_PENDING_EXCEPTION;
1479       if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1480         return JVMTI_ERROR_OUT_OF_MEMORY;
1481       } else {
1482         return JVMTI_ERROR_INTERNAL;
1483       }
1484     }
1485 
1486 #ifdef ASSERT
1487     {
1488       // verify what we have done during constant pool merging
1489       {
1490         RedefineVerifyMark rvm(the_class, scratch_class, state);
1491         Verifier::verify(scratch_class, true, THREAD);
1492       }
1493 
1494       if (HAS_PENDING_EXCEPTION) {
1495         Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1496         log_info(redefine, class, load, exceptions)
1497           ("verify_byte_codes post merge-CP exception: '%s'", ex_name->as_C_string());
1498         CLEAR_PENDING_EXCEPTION;
1499         if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1500           return JVMTI_ERROR_OUT_OF_MEMORY;
1501         } else {
1502           // tell the caller that constant pool merging screwed up
1503           return JVMTI_ERROR_INTERNAL;
1504         }
1505       }
1506     }
1507 #endif // ASSERT
1508 
1509     Rewriter::rewrite(scratch_class, THREAD);
1510     if (!HAS_PENDING_EXCEPTION) {
1511       scratch_class->link_methods(THREAD);
1512     }
1513     if (HAS_PENDING_EXCEPTION) {
1514       Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1515       log_info(redefine, class, load, exceptions)
1516         ("Rewriter::rewrite or link_methods exception: '%s'", ex_name->as_C_string());
1517       CLEAR_PENDING_EXCEPTION;
1518       if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1519         return JVMTI_ERROR_OUT_OF_MEMORY;
1520       } else {
1521         return JVMTI_ERROR_INTERNAL;
1522       }
1523     }
1524 
1525     log_debug(redefine, class, load)
1526       ("loaded name=%s (avail_mem=" UINT64_FORMAT "K)", the_class->external_name(), os::available_memory() >> 10);
1527   }
1528 
1529   return JVMTI_ERROR_NONE;
1530 }
1531 
1532 
1533 // Map old_index to new_index as needed. scratch_cp is only needed
1534 // for log calls.
1535 void VM_RedefineClasses::map_index(const constantPoolHandle& scratch_cp,
1536        int old_index, int new_index) {
1537   if (find_new_index(old_index) != 0) {
1538     // old_index is already mapped
1539     return;
1540   }
1541 
1542   if (old_index == new_index) {
1543     // no mapping is needed
1544     return;
1545   }
1546 
1547   _index_map_p->at_put(old_index, new_index);
1548   _index_map_count++;
1549 
1550   log_trace(redefine, class, constantpool)
1551     ("mapped tag %d at index %d to %d", scratch_cp->tag_at(old_index).value(), old_index, new_index);
1552 } // end map_index()
1553 
1554 
1555 // Map old_index to new_index as needed.
1556 void VM_RedefineClasses::map_operand_index(int old_index, int new_index) {
1557   if (find_new_operand_index(old_index) != -1) {
1558     // old_index is already mapped
1559     return;
1560   }
1561 
1562   if (old_index == new_index) {
1563     // no mapping is needed
1564     return;
1565   }
1566 
1567   _operands_index_map_p->at_put(old_index, new_index);
1568   _operands_index_map_count++;
1569 
1570   log_trace(redefine, class, constantpool)("mapped bootstrap specifier at index %d to %d", old_index, new_index);
1571 } // end map_index()
1572 
1573 
1574 // Merge old_cp and scratch_cp and return the results of the merge via
1575 // merge_cp_p. The number of entries in *merge_cp_p is returned via
1576 // merge_cp_length_p. The entries in old_cp occupy the same locations
1577 // in *merge_cp_p. Also creates a map of indices from entries in
1578 // scratch_cp to the corresponding entry in *merge_cp_p. Index map
1579 // entries are only created for entries in scratch_cp that occupy a
1580 // different location in *merged_cp_p.
1581 bool VM_RedefineClasses::merge_constant_pools(const constantPoolHandle& old_cp,
1582        const constantPoolHandle& scratch_cp, constantPoolHandle *merge_cp_p,
1583        int *merge_cp_length_p, TRAPS) {
1584 
1585   if (merge_cp_p == nullptr) {
1586     assert(false, "caller must provide scratch constantPool");
1587     return false; // robustness
1588   }
1589   if (merge_cp_length_p == nullptr) {
1590     assert(false, "caller must provide scratch CP length");
1591     return false; // robustness
1592   }
1593   // Worst case we need old_cp->length() + scratch_cp()->length(),
1594   // but the caller might be smart so make sure we have at least
1595   // the minimum.
1596   if ((*merge_cp_p)->length() < old_cp->length()) {
1597     assert(false, "merge area too small");
1598     return false; // robustness
1599   }
1600 
1601   log_info(redefine, class, constantpool)("old_cp_len=%d, scratch_cp_len=%d", old_cp->length(), scratch_cp->length());
1602 
1603   {
1604     // Pass 0:
1605     // The old_cp is copied to *merge_cp_p; this means that any code
1606     // using old_cp does not have to change. This work looks like a
1607     // perfect fit for ConstantPool*::copy_cp_to(), but we need to
1608     // handle one special case:
1609     // - revert JVM_CONSTANT_Class to JVM_CONSTANT_UnresolvedClass
1610     // This will make verification happy.
1611 
1612     int old_i;  // index into old_cp
1613 
1614     // index zero (0) is not used in constantPools
1615     for (old_i = 1; old_i < old_cp->length(); old_i++) {
1616       // leave debugging crumb
1617       jbyte old_tag = old_cp->tag_at(old_i).value();
1618       switch (old_tag) {
1619       case JVM_CONSTANT_Class:
1620       case JVM_CONSTANT_UnresolvedClass:
1621         // revert the copy to JVM_CONSTANT_UnresolvedClass
1622         // May be resolving while calling this so do the same for
1623         // JVM_CONSTANT_UnresolvedClass (klass_name_at() deals with transition)
1624         (*merge_cp_p)->temp_unresolved_klass_at_put(old_i,
1625           old_cp->klass_name_index_at(old_i));
1626         break;
1627 
1628       case JVM_CONSTANT_Double:
1629       case JVM_CONSTANT_Long:
1630         // just copy the entry to *merge_cp_p, but double and long take
1631         // two constant pool entries
1632         ConstantPool::copy_entry_to(old_cp, old_i, *merge_cp_p, old_i);
1633         old_i++;
1634         break;
1635 
1636       default:
1637         // just copy the entry to *merge_cp_p
1638         ConstantPool::copy_entry_to(old_cp, old_i, *merge_cp_p, old_i);
1639         break;
1640       }
1641     } // end for each old_cp entry
1642 
1643     ConstantPool::copy_operands(old_cp, *merge_cp_p, CHECK_false);
1644     (*merge_cp_p)->extend_operands(scratch_cp, CHECK_false);
1645 
1646     // We don't need to sanity check that *merge_cp_length_p is within
1647     // *merge_cp_p bounds since we have the minimum on-entry check above.
1648     (*merge_cp_length_p) = old_i;
1649   }
1650 
1651   // merge_cp_len should be the same as old_cp->length() at this point
1652   // so this trace message is really a "warm-and-breathing" message.
1653   log_debug(redefine, class, constantpool)("after pass 0: merge_cp_len=%d", *merge_cp_length_p);
1654 
1655   int scratch_i;  // index into scratch_cp
1656   {
1657     // Pass 1a:
1658     // Compare scratch_cp entries to the old_cp entries that we have
1659     // already copied to *merge_cp_p. In this pass, we are eliminating
1660     // exact duplicates (matching entry at same index) so we only
1661     // compare entries in the common indice range.
1662     int increment = 1;
1663     int pass1a_length = MIN2(old_cp->length(), scratch_cp->length());
1664     for (scratch_i = 1; scratch_i < pass1a_length; scratch_i += increment) {
1665       switch (scratch_cp->tag_at(scratch_i).value()) {
1666       case JVM_CONSTANT_Double:
1667       case JVM_CONSTANT_Long:
1668         // double and long take two constant pool entries
1669         increment = 2;
1670         break;
1671 
1672       default:
1673         increment = 1;
1674         break;
1675       }
1676 
1677       bool match = scratch_cp->compare_entry_to(scratch_i, *merge_cp_p, scratch_i);
1678       if (match) {
1679         // found a match at the same index so nothing more to do
1680         continue;
1681       }
1682 
1683       int found_i = scratch_cp->find_matching_entry(scratch_i, *merge_cp_p);
1684       if (found_i != 0) {
1685         guarantee(found_i != scratch_i,
1686           "compare_entry_to() and find_matching_entry() do not agree");
1687 
1688         // Found a matching entry somewhere else in *merge_cp_p so
1689         // just need a mapping entry.
1690         map_index(scratch_cp, scratch_i, found_i);
1691         continue;
1692       }
1693 
1694       // No match found so we have to append this entry and any unique
1695       // referenced entries to *merge_cp_p.
1696       append_entry(scratch_cp, scratch_i, merge_cp_p, merge_cp_length_p);
1697     }
1698   }
1699 
1700   log_debug(redefine, class, constantpool)
1701     ("after pass 1a: merge_cp_len=%d, scratch_i=%d, index_map_len=%d",
1702      *merge_cp_length_p, scratch_i, _index_map_count);
1703 
1704   if (scratch_i < scratch_cp->length()) {
1705     // Pass 1b:
1706     // old_cp is smaller than scratch_cp so there are entries in
1707     // scratch_cp that we have not yet processed. We take care of
1708     // those now.
1709     int increment = 1;
1710     for (; scratch_i < scratch_cp->length(); scratch_i += increment) {
1711       switch (scratch_cp->tag_at(scratch_i).value()) {
1712       case JVM_CONSTANT_Double:
1713       case JVM_CONSTANT_Long:
1714         // double and long take two constant pool entries
1715         increment = 2;
1716         break;
1717 
1718       default:
1719         increment = 1;
1720         break;
1721       }
1722 
1723       int found_i =
1724         scratch_cp->find_matching_entry(scratch_i, *merge_cp_p);
1725       if (found_i != 0) {
1726         // Found a matching entry somewhere else in *merge_cp_p so
1727         // just need a mapping entry.
1728         map_index(scratch_cp, scratch_i, found_i);
1729         continue;
1730       }
1731 
1732       // No match found so we have to append this entry and any unique
1733       // referenced entries to *merge_cp_p.
1734       append_entry(scratch_cp, scratch_i, merge_cp_p, merge_cp_length_p);
1735     }
1736 
1737     log_debug(redefine, class, constantpool)
1738       ("after pass 1b: merge_cp_len=%d, scratch_i=%d, index_map_len=%d",
1739        *merge_cp_length_p, scratch_i, _index_map_count);
1740   }
1741   finalize_operands_merge(*merge_cp_p, CHECK_false);
1742 
1743   return true;
1744 } // end merge_constant_pools()
1745 
1746 
1747 // Scoped object to clean up the constant pool(s) created for merging
1748 class MergeCPCleaner {
1749   ClassLoaderData*   _loader_data;
1750   ConstantPool*      _cp;
1751   ConstantPool*      _scratch_cp;
1752  public:
1753   MergeCPCleaner(ClassLoaderData* loader_data, ConstantPool* merge_cp) :
1754                  _loader_data(loader_data), _cp(merge_cp), _scratch_cp(nullptr) {}
1755   ~MergeCPCleaner() {
1756     _loader_data->add_to_deallocate_list(_cp);
1757     if (_scratch_cp != nullptr) {
1758       _loader_data->add_to_deallocate_list(_scratch_cp);
1759     }
1760   }
1761   void add_scratch_cp(ConstantPool* scratch_cp) { _scratch_cp = scratch_cp; }
1762 };
1763 
1764 // Merge constant pools between the_class and scratch_class and
1765 // potentially rewrite bytecodes in scratch_class to use the merged
1766 // constant pool.
1767 jvmtiError VM_RedefineClasses::merge_cp_and_rewrite(
1768              InstanceKlass* the_class, InstanceKlass* scratch_class,
1769              TRAPS) {
1770   // worst case merged constant pool length is old and new combined
1771   int merge_cp_length = the_class->constants()->length()
1772         + scratch_class->constants()->length();
1773 
1774   // Constant pools are not easily reused so we allocate a new one
1775   // each time.
1776   // merge_cp is created unsafe for concurrent GC processing.  It
1777   // should be marked safe before discarding it. Even though
1778   // garbage,  if it crosses a card boundary, it may be scanned
1779   // in order to find the start of the first complete object on the card.
1780   ClassLoaderData* loader_data = the_class->class_loader_data();
1781   ConstantPool* merge_cp_oop =
1782     ConstantPool::allocate(loader_data,
1783                            merge_cp_length,
1784                            CHECK_(JVMTI_ERROR_OUT_OF_MEMORY));
1785   MergeCPCleaner cp_cleaner(loader_data, merge_cp_oop);
1786 
1787   HandleMark hm(THREAD);  // make sure handles are cleared before
1788                           // MergeCPCleaner clears out merge_cp_oop
1789   constantPoolHandle merge_cp(THREAD, merge_cp_oop);
1790 
1791   // Get constants() from the old class because it could have been rewritten
1792   // while we were at a safepoint allocating a new constant pool.
1793   constantPoolHandle old_cp(THREAD, the_class->constants());
1794   constantPoolHandle scratch_cp(THREAD, scratch_class->constants());
1795 
1796   // If the length changed, the class was redefined out from under us. Return
1797   // an error.
1798   if (merge_cp_length != the_class->constants()->length()
1799          + scratch_class->constants()->length()) {
1800     return JVMTI_ERROR_INTERNAL;
1801   }
1802 
1803   // Update the version number of the constant pools (may keep scratch_cp)
1804   merge_cp->increment_and_save_version(old_cp->version());
1805   scratch_cp->increment_and_save_version(old_cp->version());
1806 
1807   ResourceMark rm(THREAD);
1808   _index_map_count = 0;
1809   _index_map_p = new intArray(scratch_cp->length(), scratch_cp->length(), -1);
1810 
1811   _operands_cur_length = ConstantPool::operand_array_length(old_cp->operands());
1812   _operands_index_map_count = 0;
1813   int operands_index_map_len = ConstantPool::operand_array_length(scratch_cp->operands());
1814   _operands_index_map_p = new intArray(operands_index_map_len, operands_index_map_len, -1);
1815 
1816   // reference to the cp holder is needed for copy_operands()
1817   merge_cp->set_pool_holder(scratch_class);
1818   bool result = merge_constant_pools(old_cp, scratch_cp, &merge_cp,
1819                   &merge_cp_length, THREAD);
1820   merge_cp->set_pool_holder(nullptr);
1821 
1822   if (!result) {
1823     // The merge can fail due to memory allocation failure or due
1824     // to robustness checks.
1825     return JVMTI_ERROR_INTERNAL;
1826   }
1827 
1828   // ensure merged constant pool size does not overflow u2
1829   if (merge_cp_length > 0xFFFF) {
1830     log_warning(redefine, class, constantpool)("Merged constant pool overflow: %d entries", merge_cp_length);
1831     return JVMTI_ERROR_INTERNAL;
1832   }
1833 
1834   // Set dynamic constants attribute from the original CP.
1835   if (old_cp->has_dynamic_constant()) {
1836     scratch_cp->set_has_dynamic_constant();
1837   }
1838 
1839   log_info(redefine, class, constantpool)("merge_cp_len=%d, index_map_len=%d", merge_cp_length, _index_map_count);
1840 
1841   if (_index_map_count == 0) {
1842     // there is nothing to map between the new and merged constant pools
1843 
1844     // Copy attributes from scratch_cp to merge_cp
1845     merge_cp->copy_fields(scratch_cp());
1846 
1847     if (old_cp->length() == scratch_cp->length()) {
1848       // The old and new constant pools are the same length and the
1849       // index map is empty. This means that the three constant pools
1850       // are equivalent (but not the same). Unfortunately, the new
1851       // constant pool has not gone through link resolution nor have
1852       // the new class bytecodes gone through constant pool cache
1853       // rewriting so we can't use the old constant pool with the new
1854       // class.
1855 
1856       // toss the merged constant pool at return
1857     } else if (old_cp->length() < scratch_cp->length()) {
1858       // The old constant pool has fewer entries than the new constant
1859       // pool and the index map is empty. This means the new constant
1860       // pool is a superset of the old constant pool. However, the old
1861       // class bytecodes have already gone through constant pool cache
1862       // rewriting so we can't use the new constant pool with the old
1863       // class.
1864 
1865       // toss the merged constant pool at return
1866     } else {
1867       // The old constant pool has more entries than the new constant
1868       // pool and the index map is empty. This means that both the old
1869       // and merged constant pools are supersets of the new constant
1870       // pool.
1871 
1872       // Replace the new constant pool with a shrunken copy of the
1873       // merged constant pool
1874       set_new_constant_pool(loader_data, scratch_class, merge_cp, merge_cp_length,
1875                             CHECK_(JVMTI_ERROR_OUT_OF_MEMORY));
1876       // The new constant pool replaces scratch_cp so have cleaner clean it up.
1877       // It can't be cleaned up while there are handles to it.
1878       cp_cleaner.add_scratch_cp(scratch_cp());
1879     }
1880   } else {
1881     if (log_is_enabled(Trace, redefine, class, constantpool)) {
1882       // don't want to loop unless we are tracing
1883       int count = 0;
1884       for (int i = 1; i < _index_map_p->length(); i++) {
1885         int value = _index_map_p->at(i);
1886 
1887         if (value != -1) {
1888           log_trace(redefine, class, constantpool)("index_map[%d]: old=%d new=%d", count, i, value);
1889           count++;
1890         }
1891       }
1892     }
1893 
1894     // We have entries mapped between the new and merged constant pools
1895     // so we have to rewrite some constant pool references.
1896     if (!rewrite_cp_refs(scratch_class)) {
1897       return JVMTI_ERROR_INTERNAL;
1898     }
1899 
1900     // Copy attributes from scratch_cp to merge_cp (should be done after rewrite_cp_refs())
1901     merge_cp->copy_fields(scratch_cp());
1902 
1903     // Replace the new constant pool with a shrunken copy of the
1904     // merged constant pool so now the rewritten bytecodes have
1905     // valid references; the previous new constant pool will get
1906     // GCed.
1907     set_new_constant_pool(loader_data, scratch_class, merge_cp, merge_cp_length,
1908                           CHECK_(JVMTI_ERROR_OUT_OF_MEMORY));
1909     // The new constant pool replaces scratch_cp so have cleaner clean it up.
1910     // It can't be cleaned up while there are handles to it.
1911     cp_cleaner.add_scratch_cp(scratch_cp());
1912   }
1913 
1914   return JVMTI_ERROR_NONE;
1915 } // end merge_cp_and_rewrite()
1916 
1917 
1918 // Rewrite constant pool references in klass scratch_class.
1919 bool VM_RedefineClasses::rewrite_cp_refs(InstanceKlass* scratch_class) {
1920 
1921   // rewrite constant pool references in the nest attributes:
1922   if (!rewrite_cp_refs_in_nest_attributes(scratch_class)) {
1923     // propagate failure back to caller
1924     return false;
1925   }
1926 
1927   // rewrite constant pool references in the Record attribute:
1928   if (!rewrite_cp_refs_in_record_attribute(scratch_class)) {
1929     // propagate failure back to caller
1930     return false;
1931   }
1932 
1933   // rewrite constant pool references in the PermittedSubclasses attribute:
1934   if (!rewrite_cp_refs_in_permitted_subclasses_attribute(scratch_class)) {
1935     // propagate failure back to caller
1936     return false;
1937   }
1938 
1939   // rewrite constant pool references in the Preload attribute:
1940   if (!rewrite_cp_refs_in_preload_attribute(scratch_class)) {
1941     // propagate failure back to caller
1942     return false;
1943   }
1944 
1945   // rewrite constant pool references in the methods:
1946   if (!rewrite_cp_refs_in_methods(scratch_class)) {
1947     // propagate failure back to caller
1948     return false;
1949   }
1950 
1951   // rewrite constant pool references in the class_annotations:
1952   if (!rewrite_cp_refs_in_class_annotations(scratch_class)) {
1953     // propagate failure back to caller
1954     return false;
1955   }
1956 
1957   // rewrite constant pool references in the fields_annotations:
1958   if (!rewrite_cp_refs_in_fields_annotations(scratch_class)) {
1959     // propagate failure back to caller
1960     return false;
1961   }
1962 
1963   // rewrite constant pool references in the methods_annotations:
1964   if (!rewrite_cp_refs_in_methods_annotations(scratch_class)) {
1965     // propagate failure back to caller
1966     return false;
1967   }
1968 
1969   // rewrite constant pool references in the methods_parameter_annotations:
1970   if (!rewrite_cp_refs_in_methods_parameter_annotations(scratch_class)) {
1971     // propagate failure back to caller
1972     return false;
1973   }
1974 
1975   // rewrite constant pool references in the methods_default_annotations:
1976   if (!rewrite_cp_refs_in_methods_default_annotations(scratch_class)) {
1977     // propagate failure back to caller
1978     return false;
1979   }
1980 
1981   // rewrite constant pool references in the class_type_annotations:
1982   if (!rewrite_cp_refs_in_class_type_annotations(scratch_class)) {
1983     // propagate failure back to caller
1984     return false;
1985   }
1986 
1987   // rewrite constant pool references in the fields_type_annotations:
1988   if (!rewrite_cp_refs_in_fields_type_annotations(scratch_class)) {
1989     // propagate failure back to caller
1990     return false;
1991   }
1992 
1993   // rewrite constant pool references in the methods_type_annotations:
1994   if (!rewrite_cp_refs_in_methods_type_annotations(scratch_class)) {
1995     // propagate failure back to caller
1996     return false;
1997   }
1998 
1999   // There can be type annotations in the Code part of a method_info attribute.
2000   // These annotations are not accessible, even by reflection.
2001   // Currently they are not even parsed by the ClassFileParser.
2002   // If runtime access is added they will also need to be rewritten.
2003 
2004   // rewrite source file name index:
2005   u2 source_file_name_idx = scratch_class->source_file_name_index();
2006   if (source_file_name_idx != 0) {
2007     u2 new_source_file_name_idx = find_new_index(source_file_name_idx);
2008     if (new_source_file_name_idx != 0) {
2009       scratch_class->set_source_file_name_index(new_source_file_name_idx);
2010     }
2011   }
2012 
2013   // rewrite class generic signature index:
2014   u2 generic_signature_index = scratch_class->generic_signature_index();
2015   if (generic_signature_index != 0) {
2016     u2 new_generic_signature_index = find_new_index(generic_signature_index);
2017     if (new_generic_signature_index != 0) {
2018       scratch_class->set_generic_signature_index(new_generic_signature_index);
2019     }
2020   }
2021 
2022   return true;
2023 } // end rewrite_cp_refs()
2024 
2025 // Rewrite constant pool references in the NestHost and NestMembers attributes.
2026 bool VM_RedefineClasses::rewrite_cp_refs_in_nest_attributes(
2027        InstanceKlass* scratch_class) {
2028 
2029   u2 cp_index = scratch_class->nest_host_index();
2030   if (cp_index != 0) {
2031     scratch_class->set_nest_host_index(find_new_index(cp_index));
2032   }
2033   Array<u2>* nest_members = scratch_class->nest_members();
2034   for (int i = 0; i < nest_members->length(); i++) {
2035     u2 cp_index = nest_members->at(i);
2036     nest_members->at_put(i, find_new_index(cp_index));
2037   }
2038   return true;
2039 }
2040 
2041 // Rewrite constant pool references in the Record attribute.
2042 bool VM_RedefineClasses::rewrite_cp_refs_in_record_attribute(InstanceKlass* scratch_class) {
2043   Array<RecordComponent*>* components = scratch_class->record_components();
2044   if (components != nullptr) {
2045     for (int i = 0; i < components->length(); i++) {
2046       RecordComponent* component = components->at(i);
2047       u2 cp_index = component->name_index();
2048       component->set_name_index(find_new_index(cp_index));
2049       cp_index = component->descriptor_index();
2050       component->set_descriptor_index(find_new_index(cp_index));
2051       cp_index = component->generic_signature_index();
2052       if (cp_index != 0) {
2053         component->set_generic_signature_index(find_new_index(cp_index));
2054       }
2055 
2056       AnnotationArray* annotations = component->annotations();
2057       if (annotations != nullptr && annotations->length() != 0) {
2058         int byte_i = 0;  // byte index into annotations
2059         if (!rewrite_cp_refs_in_annotations_typeArray(annotations, byte_i)) {
2060           log_debug(redefine, class, annotation)("bad record_component_annotations at %d", i);
2061           // propagate failure back to caller
2062           return false;
2063         }
2064       }
2065 
2066       AnnotationArray* type_annotations = component->type_annotations();
2067       if (type_annotations != nullptr && type_annotations->length() != 0) {
2068         int byte_i = 0;  // byte index into annotations
2069         if (!rewrite_cp_refs_in_annotations_typeArray(type_annotations, byte_i)) {
2070           log_debug(redefine, class, annotation)("bad record_component_type_annotations at %d", i);
2071           // propagate failure back to caller
2072           return false;
2073         }
2074       }
2075     }
2076   }
2077   return true;
2078 }
2079 
2080 // Rewrite constant pool references in the PermittedSubclasses attribute.
2081 bool VM_RedefineClasses::rewrite_cp_refs_in_permitted_subclasses_attribute(
2082        InstanceKlass* scratch_class) {
2083 
2084   Array<u2>* permitted_subclasses = scratch_class->permitted_subclasses();
2085   assert(permitted_subclasses != nullptr, "unexpected null permitted_subclasses");
2086   for (int i = 0; i < permitted_subclasses->length(); i++) {
2087     u2 cp_index = permitted_subclasses->at(i);
2088     permitted_subclasses->at_put(i, find_new_index(cp_index));
2089   }
2090   return true;
2091 }
2092 
2093 // Rewrite constant pool references in the Preload attribute.
2094 bool VM_RedefineClasses::rewrite_cp_refs_in_preload_attribute(
2095        InstanceKlass* scratch_class) {
2096 
2097   Array<u2>* loadable_descriptors = scratch_class->loadable_descriptors();
2098   assert(loadable_descriptors != nullptr, "unexpected null loadable_descriptors");
2099   for (int i = 0; i < loadable_descriptors->length(); i++) {
2100     u2 cp_index = loadable_descriptors->at(i);
2101     loadable_descriptors->at_put(i, find_new_index(cp_index));
2102   }
2103   return true;
2104 }
2105 
2106 // Rewrite constant pool references in the methods.
2107 bool VM_RedefineClasses::rewrite_cp_refs_in_methods(InstanceKlass* scratch_class) {
2108 
2109   Array<Method*>* methods = scratch_class->methods();
2110 
2111   if (methods == nullptr || methods->length() == 0) {
2112     // no methods so nothing to do
2113     return true;
2114   }
2115 
2116   JavaThread* THREAD = JavaThread::current(); // For exception macros.
2117   ExceptionMark em(THREAD);
2118 
2119   // rewrite constant pool references in the methods:
2120   for (int i = methods->length() - 1; i >= 0; i--) {
2121     methodHandle method(THREAD, methods->at(i));
2122     methodHandle new_method;
2123     rewrite_cp_refs_in_method(method, &new_method, THREAD);
2124     if (!new_method.is_null()) {
2125       // the method has been replaced so save the new method version
2126       // even in the case of an exception.  original method is on the
2127       // deallocation list.
2128       methods->at_put(i, new_method());
2129     }
2130     if (HAS_PENDING_EXCEPTION) {
2131       Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
2132       log_info(redefine, class, load, exceptions)("rewrite_cp_refs_in_method exception: '%s'", ex_name->as_C_string());
2133       // Need to clear pending exception here as the super caller sets
2134       // the JVMTI_ERROR_INTERNAL if the returned value is false.
2135       CLEAR_PENDING_EXCEPTION;
2136       return false;
2137     }
2138   }
2139 
2140   return true;
2141 }
2142 
2143 
2144 // Rewrite constant pool references in the specific method. This code
2145 // was adapted from Rewriter::rewrite_method().
2146 void VM_RedefineClasses::rewrite_cp_refs_in_method(methodHandle method,
2147        methodHandle *new_method_p, TRAPS) {
2148 
2149   *new_method_p = methodHandle();  // default is no new method
2150 
2151   // We cache a pointer to the bytecodes here in code_base. If GC
2152   // moves the Method*, then the bytecodes will also move which
2153   // will likely cause a crash. We create a NoSafepointVerifier
2154   // object to detect whether we pass a possible safepoint in this
2155   // code block.
2156   NoSafepointVerifier nsv;
2157 
2158   // Bytecodes and their length
2159   address code_base = method->code_base();
2160   int code_length = method->code_size();
2161 
2162   int bc_length;
2163   for (int bci = 0; bci < code_length; bci += bc_length) {
2164     address bcp = code_base + bci;
2165     Bytecodes::Code c = (Bytecodes::Code)(*bcp);
2166 
2167     bc_length = Bytecodes::length_for(c);
2168     if (bc_length == 0) {
2169       // More complicated bytecodes report a length of zero so
2170       // we have to try again a slightly different way.
2171       bc_length = Bytecodes::length_at(method(), bcp);
2172     }
2173 
2174     assert(bc_length != 0, "impossible bytecode length");
2175 
2176     switch (c) {
2177       case Bytecodes::_ldc:
2178       {
2179         u1 cp_index = *(bcp + 1);
2180         u2 new_index = find_new_index(cp_index);
2181 
2182         if (StressLdcRewrite && new_index == 0) {
2183           // If we are stressing ldc -> ldc_w rewriting, then we
2184           // always need a new_index value.
2185           new_index = cp_index;
2186         }
2187         if (new_index != 0) {
2188           // the original index is mapped so we have more work to do
2189           if (!StressLdcRewrite && new_index <= max_jubyte) {
2190             // The new value can still use ldc instead of ldc_w
2191             // unless we are trying to stress ldc -> ldc_w rewriting
2192             log_trace(redefine, class, constantpool)
2193               ("%s@" INTPTR_FORMAT " old=%d, new=%d", Bytecodes::name(c), p2i(bcp), cp_index, new_index);
2194             // We checked that new_index fits in a u1 so this cast is safe
2195             *(bcp + 1) = (u1)new_index;
2196           } else {
2197             log_trace(redefine, class, constantpool)
2198               ("%s->ldc_w@" INTPTR_FORMAT " old=%d, new=%d", Bytecodes::name(c), p2i(bcp), cp_index, new_index);
2199             // the new value needs ldc_w instead of ldc
2200             u_char inst_buffer[4]; // max instruction size is 4 bytes
2201             bcp = (address)inst_buffer;
2202             // construct new instruction sequence
2203             *bcp = Bytecodes::_ldc_w;
2204             bcp++;
2205             // Rewriter::rewrite_method() does not rewrite ldc -> ldc_w.
2206             // See comment below for difference between put_Java_u2()
2207             // and put_native_u2().
2208             Bytes::put_Java_u2(bcp, new_index);
2209 
2210             Relocator rc(method, nullptr /* no RelocatorListener needed */);
2211             methodHandle m;
2212             {
2213               PauseNoSafepointVerifier pnsv(&nsv);
2214 
2215               // ldc is 2 bytes and ldc_w is 3 bytes
2216               m = rc.insert_space_at(bci, 3, inst_buffer, CHECK);
2217             }
2218 
2219             // return the new method so that the caller can update
2220             // the containing class
2221             *new_method_p = method = m;
2222             // switch our bytecode processing loop from the old method
2223             // to the new method
2224             code_base = method->code_base();
2225             code_length = method->code_size();
2226             bcp = code_base + bci;
2227             c = (Bytecodes::Code)(*bcp);
2228             bc_length = Bytecodes::length_for(c);
2229             assert(bc_length != 0, "sanity check");
2230           } // end we need ldc_w instead of ldc
2231         } // end if there is a mapped index
2232       } break;
2233 
2234       // these bytecodes have a two-byte constant pool index
2235       case Bytecodes::_anewarray      : // fall through
2236       case Bytecodes::_checkcast      : // fall through
2237       case Bytecodes::_getfield       : // fall through
2238       case Bytecodes::_getstatic      : // fall through
2239       case Bytecodes::_instanceof     : // fall through
2240       case Bytecodes::_invokedynamic  : // fall through
2241       case Bytecodes::_invokeinterface: // fall through
2242       case Bytecodes::_invokespecial  : // fall through
2243       case Bytecodes::_invokestatic   : // fall through
2244       case Bytecodes::_invokevirtual  : // fall through
2245       case Bytecodes::_ldc_w          : // fall through
2246       case Bytecodes::_ldc2_w         : // fall through
2247       case Bytecodes::_multianewarray : // fall through
2248       case Bytecodes::_new            : // fall through
2249       case Bytecodes::_putfield       : // fall through
2250       case Bytecodes::_putstatic      :
2251       {
2252         address p = bcp + 1;
2253         int cp_index = Bytes::get_Java_u2(p);
2254         u2 new_index = find_new_index(cp_index);
2255         if (new_index != 0) {
2256           // the original index is mapped so update w/ new value
2257           log_trace(redefine, class, constantpool)
2258             ("%s@" INTPTR_FORMAT " old=%d, new=%d", Bytecodes::name(c),p2i(bcp), cp_index, new_index);
2259           // Rewriter::rewrite_method() uses put_native_u2() in this
2260           // situation because it is reusing the constant pool index
2261           // location for a native index into the ConstantPoolCache.
2262           // Since we are updating the constant pool index prior to
2263           // verification and ConstantPoolCache initialization, we
2264           // need to keep the new index in Java byte order.
2265           Bytes::put_Java_u2(p, new_index);
2266         }
2267       } break;
2268       default:
2269         break;
2270     }
2271   } // end for each bytecode
2272 } // end rewrite_cp_refs_in_method()
2273 
2274 
2275 // Rewrite constant pool references in the class_annotations field.
2276 bool VM_RedefineClasses::rewrite_cp_refs_in_class_annotations(InstanceKlass* scratch_class) {
2277 
2278   AnnotationArray* class_annotations = scratch_class->class_annotations();
2279   if (class_annotations == nullptr || class_annotations->length() == 0) {
2280     // no class_annotations so nothing to do
2281     return true;
2282   }
2283 
2284   log_debug(redefine, class, annotation)("class_annotations length=%d", class_annotations->length());
2285 
2286   int byte_i = 0;  // byte index into class_annotations
2287   return rewrite_cp_refs_in_annotations_typeArray(class_annotations, byte_i);
2288 }
2289 
2290 
2291 // Rewrite constant pool references in an annotations typeArray. This
2292 // "structure" is adapted from the RuntimeVisibleAnnotations_attribute
2293 // that is described in section 4.8.15 of the 2nd-edition of the VM spec:
2294 //
2295 // annotations_typeArray {
2296 //   u2 num_annotations;
2297 //   annotation annotations[num_annotations];
2298 // }
2299 //
2300 bool VM_RedefineClasses::rewrite_cp_refs_in_annotations_typeArray(
2301        AnnotationArray* annotations_typeArray, int &byte_i_ref) {
2302 
2303   if ((byte_i_ref + 2) > annotations_typeArray->length()) {
2304     // not enough room for num_annotations field
2305     log_debug(redefine, class, annotation)("length() is too small for num_annotations field");
2306     return false;
2307   }
2308 
2309   u2 num_annotations = Bytes::get_Java_u2((address)
2310                          annotations_typeArray->adr_at(byte_i_ref));
2311   byte_i_ref += 2;
2312 
2313   log_debug(redefine, class, annotation)("num_annotations=%d", num_annotations);
2314 
2315   int calc_num_annotations = 0;
2316   for (; calc_num_annotations < num_annotations; calc_num_annotations++) {
2317     if (!rewrite_cp_refs_in_annotation_struct(annotations_typeArray, byte_i_ref)) {
2318       log_debug(redefine, class, annotation)("bad annotation_struct at %d", calc_num_annotations);
2319       // propagate failure back to caller
2320       return false;
2321     }
2322   }
2323   assert(num_annotations == calc_num_annotations, "sanity check");
2324 
2325   return true;
2326 } // end rewrite_cp_refs_in_annotations_typeArray()
2327 
2328 
2329 // Rewrite constant pool references in the annotation struct portion of
2330 // an annotations_typeArray. This "structure" is from section 4.8.15 of
2331 // the 2nd-edition of the VM spec:
2332 //
2333 // struct annotation {
2334 //   u2 type_index;
2335 //   u2 num_element_value_pairs;
2336 //   {
2337 //     u2 element_name_index;
2338 //     element_value value;
2339 //   } element_value_pairs[num_element_value_pairs];
2340 // }
2341 //
2342 bool VM_RedefineClasses::rewrite_cp_refs_in_annotation_struct(
2343        AnnotationArray* annotations_typeArray, int &byte_i_ref) {
2344   if ((byte_i_ref + 2 + 2) > annotations_typeArray->length()) {
2345     // not enough room for smallest annotation_struct
2346     log_debug(redefine, class, annotation)("length() is too small for annotation_struct");
2347     return false;
2348   }
2349 
2350   u2 type_index = rewrite_cp_ref_in_annotation_data(annotations_typeArray,
2351                     byte_i_ref, "type_index");
2352 
2353   u2 num_element_value_pairs = Bytes::get_Java_u2((address)
2354                                  annotations_typeArray->adr_at(byte_i_ref));
2355   byte_i_ref += 2;
2356 
2357   log_debug(redefine, class, annotation)
2358     ("type_index=%d  num_element_value_pairs=%d", type_index, num_element_value_pairs);
2359 
2360   int calc_num_element_value_pairs = 0;
2361   for (; calc_num_element_value_pairs < num_element_value_pairs;
2362        calc_num_element_value_pairs++) {
2363     if ((byte_i_ref + 2) > annotations_typeArray->length()) {
2364       // not enough room for another element_name_index, let alone
2365       // the rest of another component
2366       log_debug(redefine, class, annotation)("length() is too small for element_name_index");
2367       return false;
2368     }
2369 
2370     u2 element_name_index = rewrite_cp_ref_in_annotation_data(
2371                               annotations_typeArray, byte_i_ref,
2372                               "element_name_index");
2373 
2374     log_debug(redefine, class, annotation)("element_name_index=%d", element_name_index);
2375 
2376     if (!rewrite_cp_refs_in_element_value(annotations_typeArray, byte_i_ref)) {
2377       log_debug(redefine, class, annotation)("bad element_value at %d", calc_num_element_value_pairs);
2378       // propagate failure back to caller
2379       return false;
2380     }
2381   } // end for each component
2382   assert(num_element_value_pairs == calc_num_element_value_pairs,
2383     "sanity check");
2384 
2385   return true;
2386 } // end rewrite_cp_refs_in_annotation_struct()
2387 
2388 
2389 // Rewrite a constant pool reference at the current position in
2390 // annotations_typeArray if needed. Returns the original constant
2391 // pool reference if a rewrite was not needed or the new constant
2392 // pool reference if a rewrite was needed.
2393 u2 VM_RedefineClasses::rewrite_cp_ref_in_annotation_data(
2394      AnnotationArray* annotations_typeArray, int &byte_i_ref,
2395      const char * trace_mesg) {
2396 
2397   address cp_index_addr = (address)
2398     annotations_typeArray->adr_at(byte_i_ref);
2399   u2 old_cp_index = Bytes::get_Java_u2(cp_index_addr);
2400   u2 new_cp_index = find_new_index(old_cp_index);
2401   if (new_cp_index != 0) {
2402     log_debug(redefine, class, annotation)("mapped old %s=%d", trace_mesg, old_cp_index);
2403     Bytes::put_Java_u2(cp_index_addr, new_cp_index);
2404     old_cp_index = new_cp_index;
2405   }
2406   byte_i_ref += 2;
2407   return old_cp_index;
2408 }
2409 
2410 
2411 // Rewrite constant pool references in the element_value portion of an
2412 // annotations_typeArray. This "structure" is from section 4.8.15.1 of
2413 // the 2nd-edition of the VM spec:
2414 //
2415 // struct element_value {
2416 //   u1 tag;
2417 //   union {
2418 //     u2 const_value_index;
2419 //     {
2420 //       u2 type_name_index;
2421 //       u2 const_name_index;
2422 //     } enum_const_value;
2423 //     u2 class_info_index;
2424 //     annotation annotation_value;
2425 //     struct {
2426 //       u2 num_values;
2427 //       element_value values[num_values];
2428 //     } array_value;
2429 //   } value;
2430 // }
2431 //
2432 bool VM_RedefineClasses::rewrite_cp_refs_in_element_value(
2433        AnnotationArray* annotations_typeArray, int &byte_i_ref) {
2434 
2435   if ((byte_i_ref + 1) > annotations_typeArray->length()) {
2436     // not enough room for a tag let alone the rest of an element_value
2437     log_debug(redefine, class, annotation)("length() is too small for a tag");
2438     return false;
2439   }
2440 
2441   u1 tag = annotations_typeArray->at(byte_i_ref);
2442   byte_i_ref++;
2443   log_debug(redefine, class, annotation)("tag='%c'", tag);
2444 
2445   switch (tag) {
2446     // These BaseType tag values are from Table 4.2 in VM spec:
2447     case JVM_SIGNATURE_BYTE:
2448     case JVM_SIGNATURE_CHAR:
2449     case JVM_SIGNATURE_DOUBLE:
2450     case JVM_SIGNATURE_FLOAT:
2451     case JVM_SIGNATURE_INT:
2452     case JVM_SIGNATURE_LONG:
2453     case JVM_SIGNATURE_SHORT:
2454     case JVM_SIGNATURE_BOOLEAN:
2455 
2456     // The remaining tag values are from Table 4.8 in the 2nd-edition of
2457     // the VM spec:
2458     case 's':
2459     {
2460       // For the above tag values (including the BaseType values),
2461       // value.const_value_index is right union field.
2462 
2463       if ((byte_i_ref + 2) > annotations_typeArray->length()) {
2464         // not enough room for a const_value_index
2465         log_debug(redefine, class, annotation)("length() is too small for a const_value_index");
2466         return false;
2467       }
2468 
2469       u2 const_value_index = rewrite_cp_ref_in_annotation_data(
2470                                annotations_typeArray, byte_i_ref,
2471                                "const_value_index");
2472 
2473       log_debug(redefine, class, annotation)("const_value_index=%d", const_value_index);
2474     } break;
2475 
2476     case 'e':
2477     {
2478       // for the above tag value, value.enum_const_value is right union field
2479 
2480       if ((byte_i_ref + 4) > annotations_typeArray->length()) {
2481         // not enough room for a enum_const_value
2482         log_debug(redefine, class, annotation)("length() is too small for a enum_const_value");
2483         return false;
2484       }
2485 
2486       u2 type_name_index = rewrite_cp_ref_in_annotation_data(
2487                              annotations_typeArray, byte_i_ref,
2488                              "type_name_index");
2489 
2490       u2 const_name_index = rewrite_cp_ref_in_annotation_data(
2491                               annotations_typeArray, byte_i_ref,
2492                               "const_name_index");
2493 
2494       log_debug(redefine, class, annotation)
2495         ("type_name_index=%d  const_name_index=%d", type_name_index, const_name_index);
2496     } break;
2497 
2498     case 'c':
2499     {
2500       // for the above tag value, value.class_info_index is right union field
2501 
2502       if ((byte_i_ref + 2) > annotations_typeArray->length()) {
2503         // not enough room for a class_info_index
2504         log_debug(redefine, class, annotation)("length() is too small for a class_info_index");
2505         return false;
2506       }
2507 
2508       u2 class_info_index = rewrite_cp_ref_in_annotation_data(
2509                               annotations_typeArray, byte_i_ref,
2510                               "class_info_index");
2511 
2512       log_debug(redefine, class, annotation)("class_info_index=%d", class_info_index);
2513     } break;
2514 
2515     case '@':
2516       // For the above tag value, value.attr_value is the right union
2517       // field. This is a nested annotation.
2518       if (!rewrite_cp_refs_in_annotation_struct(annotations_typeArray, byte_i_ref)) {
2519         // propagate failure back to caller
2520         return false;
2521       }
2522       break;
2523 
2524     case JVM_SIGNATURE_ARRAY:
2525     {
2526       if ((byte_i_ref + 2) > annotations_typeArray->length()) {
2527         // not enough room for a num_values field
2528         log_debug(redefine, class, annotation)("length() is too small for a num_values field");
2529         return false;
2530       }
2531 
2532       // For the above tag value, value.array_value is the right union
2533       // field. This is an array of nested element_value.
2534       u2 num_values = Bytes::get_Java_u2((address)
2535                         annotations_typeArray->adr_at(byte_i_ref));
2536       byte_i_ref += 2;
2537       log_debug(redefine, class, annotation)("num_values=%d", num_values);
2538 
2539       int calc_num_values = 0;
2540       for (; calc_num_values < num_values; calc_num_values++) {
2541         if (!rewrite_cp_refs_in_element_value(annotations_typeArray, byte_i_ref)) {
2542           log_debug(redefine, class, annotation)("bad nested element_value at %d", calc_num_values);
2543           // propagate failure back to caller
2544           return false;
2545         }
2546       }
2547       assert(num_values == calc_num_values, "sanity check");
2548     } break;
2549 
2550     default:
2551       log_debug(redefine, class, annotation)("bad tag=0x%x", tag);
2552       return false;
2553   } // end decode tag field
2554 
2555   return true;
2556 } // end rewrite_cp_refs_in_element_value()
2557 
2558 
2559 // Rewrite constant pool references in a fields_annotations field.
2560 bool VM_RedefineClasses::rewrite_cp_refs_in_fields_annotations(
2561        InstanceKlass* scratch_class) {
2562 
2563   Array<AnnotationArray*>* fields_annotations = scratch_class->fields_annotations();
2564 
2565   if (fields_annotations == nullptr || fields_annotations->length() == 0) {
2566     // no fields_annotations so nothing to do
2567     return true;
2568   }
2569 
2570   log_debug(redefine, class, annotation)("fields_annotations length=%d", fields_annotations->length());
2571 
2572   for (int i = 0; i < fields_annotations->length(); i++) {
2573     AnnotationArray* field_annotations = fields_annotations->at(i);
2574     if (field_annotations == nullptr || field_annotations->length() == 0) {
2575       // this field does not have any annotations so skip it
2576       continue;
2577     }
2578 
2579     int byte_i = 0;  // byte index into field_annotations
2580     if (!rewrite_cp_refs_in_annotations_typeArray(field_annotations, byte_i)) {
2581       log_debug(redefine, class, annotation)("bad field_annotations at %d", i);
2582       // propagate failure back to caller
2583       return false;
2584     }
2585   }
2586 
2587   return true;
2588 } // end rewrite_cp_refs_in_fields_annotations()
2589 
2590 
2591 // Rewrite constant pool references in a methods_annotations field.
2592 bool VM_RedefineClasses::rewrite_cp_refs_in_methods_annotations(
2593        InstanceKlass* scratch_class) {
2594 
2595   for (int i = 0; i < scratch_class->methods()->length(); i++) {
2596     Method* m = scratch_class->methods()->at(i);
2597     AnnotationArray* method_annotations = m->constMethod()->method_annotations();
2598 
2599     if (method_annotations == nullptr || method_annotations->length() == 0) {
2600       // this method does not have any annotations so skip it
2601       continue;
2602     }
2603 
2604     int byte_i = 0;  // byte index into method_annotations
2605     if (!rewrite_cp_refs_in_annotations_typeArray(method_annotations, byte_i)) {
2606       log_debug(redefine, class, annotation)("bad method_annotations at %d", i);
2607       // propagate failure back to caller
2608       return false;
2609     }
2610   }
2611 
2612   return true;
2613 } // end rewrite_cp_refs_in_methods_annotations()
2614 
2615 
2616 // Rewrite constant pool references in a methods_parameter_annotations
2617 // field. This "structure" is adapted from the
2618 // RuntimeVisibleParameterAnnotations_attribute described in section
2619 // 4.8.17 of the 2nd-edition of the VM spec:
2620 //
2621 // methods_parameter_annotations_typeArray {
2622 //   u1 num_parameters;
2623 //   {
2624 //     u2 num_annotations;
2625 //     annotation annotations[num_annotations];
2626 //   } parameter_annotations[num_parameters];
2627 // }
2628 //
2629 bool VM_RedefineClasses::rewrite_cp_refs_in_methods_parameter_annotations(
2630        InstanceKlass* scratch_class) {
2631 
2632   for (int i = 0; i < scratch_class->methods()->length(); i++) {
2633     Method* m = scratch_class->methods()->at(i);
2634     AnnotationArray* method_parameter_annotations = m->constMethod()->parameter_annotations();
2635     if (method_parameter_annotations == nullptr
2636         || method_parameter_annotations->length() == 0) {
2637       // this method does not have any parameter annotations so skip it
2638       continue;
2639     }
2640 
2641     if (method_parameter_annotations->length() < 1) {
2642       // not enough room for a num_parameters field
2643       log_debug(redefine, class, annotation)("length() is too small for a num_parameters field at %d", i);
2644       return false;
2645     }
2646 
2647     int byte_i = 0;  // byte index into method_parameter_annotations
2648 
2649     u1 num_parameters = method_parameter_annotations->at(byte_i);
2650     byte_i++;
2651 
2652     log_debug(redefine, class, annotation)("num_parameters=%d", num_parameters);
2653 
2654     int calc_num_parameters = 0;
2655     for (; calc_num_parameters < num_parameters; calc_num_parameters++) {
2656       if (!rewrite_cp_refs_in_annotations_typeArray(method_parameter_annotations, byte_i)) {
2657         log_debug(redefine, class, annotation)("bad method_parameter_annotations at %d", calc_num_parameters);
2658         // propagate failure back to caller
2659         return false;
2660       }
2661     }
2662     assert(num_parameters == calc_num_parameters, "sanity check");
2663   }
2664 
2665   return true;
2666 } // end rewrite_cp_refs_in_methods_parameter_annotations()
2667 
2668 
2669 // Rewrite constant pool references in a methods_default_annotations
2670 // field. This "structure" is adapted from the AnnotationDefault_attribute
2671 // that is described in section 4.8.19 of the 2nd-edition of the VM spec:
2672 //
2673 // methods_default_annotations_typeArray {
2674 //   element_value default_value;
2675 // }
2676 //
2677 bool VM_RedefineClasses::rewrite_cp_refs_in_methods_default_annotations(
2678        InstanceKlass* scratch_class) {
2679 
2680   for (int i = 0; i < scratch_class->methods()->length(); i++) {
2681     Method* m = scratch_class->methods()->at(i);
2682     AnnotationArray* method_default_annotations = m->constMethod()->default_annotations();
2683     if (method_default_annotations == nullptr
2684         || method_default_annotations->length() == 0) {
2685       // this method does not have any default annotations so skip it
2686       continue;
2687     }
2688 
2689     int byte_i = 0;  // byte index into method_default_annotations
2690 
2691     if (!rewrite_cp_refs_in_element_value(
2692            method_default_annotations, byte_i)) {
2693       log_debug(redefine, class, annotation)("bad default element_value at %d", i);
2694       // propagate failure back to caller
2695       return false;
2696     }
2697   }
2698 
2699   return true;
2700 } // end rewrite_cp_refs_in_methods_default_annotations()
2701 
2702 
2703 // Rewrite constant pool references in a class_type_annotations field.
2704 bool VM_RedefineClasses::rewrite_cp_refs_in_class_type_annotations(
2705        InstanceKlass* scratch_class) {
2706 
2707   AnnotationArray* class_type_annotations = scratch_class->class_type_annotations();
2708   if (class_type_annotations == nullptr || class_type_annotations->length() == 0) {
2709     // no class_type_annotations so nothing to do
2710     return true;
2711   }
2712 
2713   log_debug(redefine, class, annotation)("class_type_annotations length=%d", class_type_annotations->length());
2714 
2715   int byte_i = 0;  // byte index into class_type_annotations
2716   return rewrite_cp_refs_in_type_annotations_typeArray(class_type_annotations,
2717       byte_i, "ClassFile");
2718 } // end rewrite_cp_refs_in_class_type_annotations()
2719 
2720 
2721 // Rewrite constant pool references in a fields_type_annotations field.
2722 bool VM_RedefineClasses::rewrite_cp_refs_in_fields_type_annotations(InstanceKlass* scratch_class) {
2723 
2724   Array<AnnotationArray*>* fields_type_annotations = scratch_class->fields_type_annotations();
2725   if (fields_type_annotations == nullptr || fields_type_annotations->length() == 0) {
2726     // no fields_type_annotations so nothing to do
2727     return true;
2728   }
2729 
2730   log_debug(redefine, class, annotation)("fields_type_annotations length=%d", fields_type_annotations->length());
2731 
2732   for (int i = 0; i < fields_type_annotations->length(); i++) {
2733     AnnotationArray* field_type_annotations = fields_type_annotations->at(i);
2734     if (field_type_annotations == nullptr || field_type_annotations->length() == 0) {
2735       // this field does not have any annotations so skip it
2736       continue;
2737     }
2738 
2739     int byte_i = 0;  // byte index into field_type_annotations
2740     if (!rewrite_cp_refs_in_type_annotations_typeArray(field_type_annotations,
2741            byte_i, "field_info")) {
2742       log_debug(redefine, class, annotation)("bad field_type_annotations at %d", i);
2743       // propagate failure back to caller
2744       return false;
2745     }
2746   }
2747 
2748   return true;
2749 } // end rewrite_cp_refs_in_fields_type_annotations()
2750 
2751 
2752 // Rewrite constant pool references in a methods_type_annotations field.
2753 bool VM_RedefineClasses::rewrite_cp_refs_in_methods_type_annotations(
2754        InstanceKlass* scratch_class) {
2755 
2756   for (int i = 0; i < scratch_class->methods()->length(); i++) {
2757     Method* m = scratch_class->methods()->at(i);
2758     AnnotationArray* method_type_annotations = m->constMethod()->type_annotations();
2759 
2760     if (method_type_annotations == nullptr || method_type_annotations->length() == 0) {
2761       // this method does not have any annotations so skip it
2762       continue;
2763     }
2764 
2765     log_debug(redefine, class, annotation)("methods type_annotations length=%d", method_type_annotations->length());
2766 
2767     int byte_i = 0;  // byte index into method_type_annotations
2768     if (!rewrite_cp_refs_in_type_annotations_typeArray(method_type_annotations,
2769            byte_i, "method_info")) {
2770       log_debug(redefine, class, annotation)("bad method_type_annotations at %d", i);
2771       // propagate failure back to caller
2772       return false;
2773     }
2774   }
2775 
2776   return true;
2777 } // end rewrite_cp_refs_in_methods_type_annotations()
2778 
2779 
2780 // Rewrite constant pool references in a type_annotations
2781 // field. This "structure" is adapted from the
2782 // RuntimeVisibleTypeAnnotations_attribute described in
2783 // section 4.7.20 of the Java SE 8 Edition of the VM spec:
2784 //
2785 // type_annotations_typeArray {
2786 //   u2              num_annotations;
2787 //   type_annotation annotations[num_annotations];
2788 // }
2789 //
2790 bool VM_RedefineClasses::rewrite_cp_refs_in_type_annotations_typeArray(
2791        AnnotationArray* type_annotations_typeArray, int &byte_i_ref,
2792        const char * location_mesg) {
2793 
2794   if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
2795     // not enough room for num_annotations field
2796     log_debug(redefine, class, annotation)("length() is too small for num_annotations field");
2797     return false;
2798   }
2799 
2800   u2 num_annotations = Bytes::get_Java_u2((address)
2801                          type_annotations_typeArray->adr_at(byte_i_ref));
2802   byte_i_ref += 2;
2803 
2804   log_debug(redefine, class, annotation)("num_type_annotations=%d", num_annotations);
2805 
2806   int calc_num_annotations = 0;
2807   for (; calc_num_annotations < num_annotations; calc_num_annotations++) {
2808     if (!rewrite_cp_refs_in_type_annotation_struct(type_annotations_typeArray,
2809            byte_i_ref, location_mesg)) {
2810       log_debug(redefine, class, annotation)("bad type_annotation_struct at %d", calc_num_annotations);
2811       // propagate failure back to caller
2812       return false;
2813     }
2814   }
2815   assert(num_annotations == calc_num_annotations, "sanity check");
2816 
2817   if (byte_i_ref != type_annotations_typeArray->length()) {
2818     log_debug(redefine, class, annotation)
2819       ("read wrong amount of bytes at end of processing type_annotations_typeArray (%d of %d bytes were read)",
2820        byte_i_ref, type_annotations_typeArray->length());
2821     return false;
2822   }
2823 
2824   return true;
2825 } // end rewrite_cp_refs_in_type_annotations_typeArray()
2826 
2827 
2828 // Rewrite constant pool references in a type_annotation
2829 // field. This "structure" is adapted from the
2830 // RuntimeVisibleTypeAnnotations_attribute described in
2831 // section 4.7.20 of the Java SE 8 Edition of the VM spec:
2832 //
2833 // type_annotation {
2834 //   u1 target_type;
2835 //   union {
2836 //     type_parameter_target;
2837 //     supertype_target;
2838 //     type_parameter_bound_target;
2839 //     empty_target;
2840 //     method_formal_parameter_target;
2841 //     throws_target;
2842 //     localvar_target;
2843 //     catch_target;
2844 //     offset_target;
2845 //     type_argument_target;
2846 //   } target_info;
2847 //   type_path target_path;
2848 //   annotation anno;
2849 // }
2850 //
2851 bool VM_RedefineClasses::rewrite_cp_refs_in_type_annotation_struct(
2852        AnnotationArray* type_annotations_typeArray, int &byte_i_ref,
2853        const char * location_mesg) {
2854 
2855   if (!skip_type_annotation_target(type_annotations_typeArray,
2856          byte_i_ref, location_mesg)) {
2857     return false;
2858   }
2859 
2860   if (!skip_type_annotation_type_path(type_annotations_typeArray, byte_i_ref)) {
2861     return false;
2862   }
2863 
2864   if (!rewrite_cp_refs_in_annotation_struct(type_annotations_typeArray, byte_i_ref)) {
2865     return false;
2866   }
2867 
2868   return true;
2869 } // end rewrite_cp_refs_in_type_annotation_struct()
2870 
2871 
2872 // Read, verify and skip over the target_type and target_info part
2873 // so that rewriting can continue in the later parts of the struct.
2874 //
2875 // u1 target_type;
2876 // union {
2877 //   type_parameter_target;
2878 //   supertype_target;
2879 //   type_parameter_bound_target;
2880 //   empty_target;
2881 //   method_formal_parameter_target;
2882 //   throws_target;
2883 //   localvar_target;
2884 //   catch_target;
2885 //   offset_target;
2886 //   type_argument_target;
2887 // } target_info;
2888 //
2889 bool VM_RedefineClasses::skip_type_annotation_target(
2890        AnnotationArray* type_annotations_typeArray, int &byte_i_ref,
2891        const char * location_mesg) {
2892 
2893   if ((byte_i_ref + 1) > type_annotations_typeArray->length()) {
2894     // not enough room for a target_type let alone the rest of a type_annotation
2895     log_debug(redefine, class, annotation)("length() is too small for a target_type");
2896     return false;
2897   }
2898 
2899   u1 target_type = type_annotations_typeArray->at(byte_i_ref);
2900   byte_i_ref += 1;
2901   log_debug(redefine, class, annotation)("target_type=0x%.2x", target_type);
2902   log_debug(redefine, class, annotation)("location=%s", location_mesg);
2903 
2904   // Skip over target_info
2905   switch (target_type) {
2906     case 0x00:
2907     // kind: type parameter declaration of generic class or interface
2908     // location: ClassFile
2909     case 0x01:
2910     // kind: type parameter declaration of generic method or constructor
2911     // location: method_info
2912 
2913     {
2914       // struct:
2915       // type_parameter_target {
2916       //   u1 type_parameter_index;
2917       // }
2918       //
2919       if ((byte_i_ref + 1) > type_annotations_typeArray->length()) {
2920         log_debug(redefine, class, annotation)("length() is too small for a type_parameter_target");
2921         return false;
2922       }
2923 
2924       u1 type_parameter_index = type_annotations_typeArray->at(byte_i_ref);
2925       byte_i_ref += 1;
2926 
2927       log_debug(redefine, class, annotation)("type_parameter_target: type_parameter_index=%d", type_parameter_index);
2928     } break;
2929 
2930     case 0x10:
2931     // kind: type in extends clause of class or interface declaration
2932     //       or in implements clause of interface declaration
2933     // location: ClassFile
2934 
2935     {
2936       // struct:
2937       // supertype_target {
2938       //   u2 supertype_index;
2939       // }
2940       //
2941       if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
2942         log_debug(redefine, class, annotation)("length() is too small for a supertype_target");
2943         return false;
2944       }
2945 
2946       u2 supertype_index = Bytes::get_Java_u2((address)
2947                              type_annotations_typeArray->adr_at(byte_i_ref));
2948       byte_i_ref += 2;
2949 
2950       log_debug(redefine, class, annotation)("supertype_target: supertype_index=%d", supertype_index);
2951     } break;
2952 
2953     case 0x11:
2954     // kind: type in bound of type parameter declaration of generic class or interface
2955     // location: ClassFile
2956     case 0x12:
2957     // kind: type in bound of type parameter declaration of generic method or constructor
2958     // location: method_info
2959 
2960     {
2961       // struct:
2962       // type_parameter_bound_target {
2963       //   u1 type_parameter_index;
2964       //   u1 bound_index;
2965       // }
2966       //
2967       if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
2968         log_debug(redefine, class, annotation)("length() is too small for a type_parameter_bound_target");
2969         return false;
2970       }
2971 
2972       u1 type_parameter_index = type_annotations_typeArray->at(byte_i_ref);
2973       byte_i_ref += 1;
2974       u1 bound_index = type_annotations_typeArray->at(byte_i_ref);
2975       byte_i_ref += 1;
2976 
2977       log_debug(redefine, class, annotation)
2978         ("type_parameter_bound_target: type_parameter_index=%d, bound_index=%d", type_parameter_index, bound_index);
2979     } break;
2980 
2981     case 0x13:
2982     // kind: type in field declaration
2983     // location: field_info
2984     case 0x14:
2985     // kind: return type of method, or type of newly constructed object
2986     // location: method_info
2987     case 0x15:
2988     // kind: receiver type of method or constructor
2989     // location: method_info
2990 
2991     {
2992       // struct:
2993       // empty_target {
2994       // }
2995       //
2996       log_debug(redefine, class, annotation)("empty_target");
2997     } break;
2998 
2999     case 0x16:
3000     // kind: type in formal parameter declaration of method, constructor, or lambda expression
3001     // location: method_info
3002 
3003     {
3004       // struct:
3005       // formal_parameter_target {
3006       //   u1 formal_parameter_index;
3007       // }
3008       //
3009       if ((byte_i_ref + 1) > type_annotations_typeArray->length()) {
3010         log_debug(redefine, class, annotation)("length() is too small for a formal_parameter_target");
3011         return false;
3012       }
3013 
3014       u1 formal_parameter_index = type_annotations_typeArray->at(byte_i_ref);
3015       byte_i_ref += 1;
3016 
3017       log_debug(redefine, class, annotation)
3018         ("formal_parameter_target: formal_parameter_index=%d", formal_parameter_index);
3019     } break;
3020 
3021     case 0x17:
3022     // kind: type in throws clause of method or constructor
3023     // location: method_info
3024 
3025     {
3026       // struct:
3027       // throws_target {
3028       //   u2 throws_type_index
3029       // }
3030       //
3031       if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
3032         log_debug(redefine, class, annotation)("length() is too small for a throws_target");
3033         return false;
3034       }
3035 
3036       u2 throws_type_index = Bytes::get_Java_u2((address)
3037                                type_annotations_typeArray->adr_at(byte_i_ref));
3038       byte_i_ref += 2;
3039 
3040       log_debug(redefine, class, annotation)("throws_target: throws_type_index=%d", throws_type_index);
3041     } break;
3042 
3043     case 0x40:
3044     // kind: type in local variable declaration
3045     // location: Code
3046     case 0x41:
3047     // kind: type in resource variable declaration
3048     // location: Code
3049 
3050     {
3051       // struct:
3052       // localvar_target {
3053       //   u2 table_length;
3054       //   struct {
3055       //     u2 start_pc;
3056       //     u2 length;
3057       //     u2 index;
3058       //   } table[table_length];
3059       // }
3060       //
3061       if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
3062         // not enough room for a table_length let alone the rest of a localvar_target
3063         log_debug(redefine, class, annotation)("length() is too small for a localvar_target table_length");
3064         return false;
3065       }
3066 
3067       u2 table_length = Bytes::get_Java_u2((address)
3068                           type_annotations_typeArray->adr_at(byte_i_ref));
3069       byte_i_ref += 2;
3070 
3071       log_debug(redefine, class, annotation)("localvar_target: table_length=%d", table_length);
3072 
3073       int table_struct_size = 2 + 2 + 2; // 3 u2 variables per table entry
3074       int table_size = table_length * table_struct_size;
3075 
3076       if ((byte_i_ref + table_size) > type_annotations_typeArray->length()) {
3077         // not enough room for a table
3078         log_debug(redefine, class, annotation)("length() is too small for a table array of length %d", table_length);
3079         return false;
3080       }
3081 
3082       // Skip over table
3083       byte_i_ref += table_size;
3084     } break;
3085 
3086     case 0x42:
3087     // kind: type in exception parameter declaration
3088     // location: Code
3089 
3090     {
3091       // struct:
3092       // catch_target {
3093       //   u2 exception_table_index;
3094       // }
3095       //
3096       if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
3097         log_debug(redefine, class, annotation)("length() is too small for a catch_target");
3098         return false;
3099       }
3100 
3101       u2 exception_table_index = Bytes::get_Java_u2((address)
3102                                    type_annotations_typeArray->adr_at(byte_i_ref));
3103       byte_i_ref += 2;
3104 
3105       log_debug(redefine, class, annotation)("catch_target: exception_table_index=%d", exception_table_index);
3106     } break;
3107 
3108     case 0x43:
3109     // kind: type in instanceof expression
3110     // location: Code
3111     case 0x44:
3112     // kind: type in new expression
3113     // location: Code
3114     case 0x45:
3115     // kind: type in method reference expression using ::new
3116     // location: Code
3117     case 0x46:
3118     // kind: type in method reference expression using ::Identifier
3119     // location: Code
3120 
3121     {
3122       // struct:
3123       // offset_target {
3124       //   u2 offset;
3125       // }
3126       //
3127       if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
3128         log_debug(redefine, class, annotation)("length() is too small for a offset_target");
3129         return false;
3130       }
3131 
3132       u2 offset = Bytes::get_Java_u2((address)
3133                     type_annotations_typeArray->adr_at(byte_i_ref));
3134       byte_i_ref += 2;
3135 
3136       log_debug(redefine, class, annotation)("offset_target: offset=%d", offset);
3137     } break;
3138 
3139     case 0x47:
3140     // kind: type in cast expression
3141     // location: Code
3142     case 0x48:
3143     // kind: type argument for generic constructor in new expression or
3144     //       explicit constructor invocation statement
3145     // location: Code
3146     case 0x49:
3147     // kind: type argument for generic method in method invocation expression
3148     // location: Code
3149     case 0x4A:
3150     // kind: type argument for generic constructor in method reference expression using ::new
3151     // location: Code
3152     case 0x4B:
3153     // kind: type argument for generic method in method reference expression using ::Identifier
3154     // location: Code
3155 
3156     {
3157       // struct:
3158       // type_argument_target {
3159       //   u2 offset;
3160       //   u1 type_argument_index;
3161       // }
3162       //
3163       if ((byte_i_ref + 3) > type_annotations_typeArray->length()) {
3164         log_debug(redefine, class, annotation)("length() is too small for a type_argument_target");
3165         return false;
3166       }
3167 
3168       u2 offset = Bytes::get_Java_u2((address)
3169                     type_annotations_typeArray->adr_at(byte_i_ref));
3170       byte_i_ref += 2;
3171       u1 type_argument_index = type_annotations_typeArray->at(byte_i_ref);
3172       byte_i_ref += 1;
3173 
3174       log_debug(redefine, class, annotation)
3175         ("type_argument_target: offset=%d, type_argument_index=%d", offset, type_argument_index);
3176     } break;
3177 
3178     default:
3179       log_debug(redefine, class, annotation)("unknown target_type");
3180 #ifdef ASSERT
3181       ShouldNotReachHere();
3182 #endif
3183       return false;
3184   }
3185 
3186   return true;
3187 } // end skip_type_annotation_target()
3188 
3189 
3190 // Read, verify and skip over the type_path part so that rewriting
3191 // can continue in the later parts of the struct.
3192 //
3193 // type_path {
3194 //   u1 path_length;
3195 //   {
3196 //     u1 type_path_kind;
3197 //     u1 type_argument_index;
3198 //   } path[path_length];
3199 // }
3200 //
3201 bool VM_RedefineClasses::skip_type_annotation_type_path(
3202        AnnotationArray* type_annotations_typeArray, int &byte_i_ref) {
3203 
3204   if ((byte_i_ref + 1) > type_annotations_typeArray->length()) {
3205     // not enough room for a path_length let alone the rest of the type_path
3206     log_debug(redefine, class, annotation)("length() is too small for a type_path");
3207     return false;
3208   }
3209 
3210   u1 path_length = type_annotations_typeArray->at(byte_i_ref);
3211   byte_i_ref += 1;
3212 
3213   log_debug(redefine, class, annotation)("type_path: path_length=%d", path_length);
3214 
3215   int calc_path_length = 0;
3216   for (; calc_path_length < path_length; calc_path_length++) {
3217     if ((byte_i_ref + 1 + 1) > type_annotations_typeArray->length()) {
3218       // not enough room for a path
3219       log_debug(redefine, class, annotation)
3220         ("length() is too small for path entry %d of %d", calc_path_length, path_length);
3221       return false;
3222     }
3223 
3224     u1 type_path_kind = type_annotations_typeArray->at(byte_i_ref);
3225     byte_i_ref += 1;
3226     u1 type_argument_index = type_annotations_typeArray->at(byte_i_ref);
3227     byte_i_ref += 1;
3228 
3229     log_debug(redefine, class, annotation)
3230       ("type_path: path[%d]: type_path_kind=%d, type_argument_index=%d",
3231        calc_path_length, type_path_kind, type_argument_index);
3232 
3233     if (type_path_kind > 3 || (type_path_kind != 3 && type_argument_index != 0)) {
3234       // not enough room for a path
3235       log_debug(redefine, class, annotation)("inconsistent type_path values");
3236       return false;
3237     }
3238   }
3239   assert(path_length == calc_path_length, "sanity check");
3240 
3241   return true;
3242 } // end skip_type_annotation_type_path()
3243 
3244 
3245 // Rewrite constant pool references in the method's stackmap table.
3246 // These "structures" are adapted from the StackMapTable_attribute that
3247 // is described in section 4.8.4 of the 6.0 version of the VM spec
3248 // (dated 2005.10.26):
3249 // file:///net/quincunx.sfbay/export/gbracha/ClassFile-Java6.pdf
3250 //
3251 // stack_map {
3252 //   u2 number_of_entries;
3253 //   stack_map_frame entries[number_of_entries];
3254 // }
3255 //
3256 void VM_RedefineClasses::rewrite_cp_refs_in_stack_map_table(
3257        const methodHandle& method) {
3258 
3259   if (!method->has_stackmap_table()) {
3260     return;
3261   }
3262 
3263   AnnotationArray* stackmap_data = method->stackmap_data();
3264   address stackmap_p = (address)stackmap_data->adr_at(0);
3265   address stackmap_end = stackmap_p + stackmap_data->length();
3266 
3267   assert(stackmap_p + 2 <= stackmap_end, "no room for number_of_entries");
3268   u2 number_of_entries = Bytes::get_Java_u2(stackmap_p);
3269   stackmap_p += 2;
3270 
3271   log_debug(redefine, class, stackmap)("number_of_entries=%u", number_of_entries);
3272 
3273   // walk through each stack_map_frame
3274   u2 calc_number_of_entries = 0;
3275   for (; calc_number_of_entries < number_of_entries; calc_number_of_entries++) {
3276     // The stack_map_frame structure is a u1 frame_type followed by
3277     // 0 or more bytes of data:
3278     //
3279     // union stack_map_frame {
3280     //   same_frame;
3281     //   same_locals_1_stack_item_frame;
3282     //   same_locals_1_stack_item_frame_extended;
3283     //   chop_frame;
3284     //   same_frame_extended;
3285     //   append_frame;
3286     //   full_frame;
3287     // }
3288 
3289     assert(stackmap_p + 1 <= stackmap_end, "no room for frame_type");
3290     u1 frame_type = *stackmap_p;
3291     stackmap_p++;
3292 
3293     // same_frame {
3294     //   u1 frame_type = SAME; /* 0-63 */
3295     // }
3296     if (frame_type <= 63) {
3297       // nothing more to do for same_frame
3298     }
3299 
3300     // same_locals_1_stack_item_frame {
3301     //   u1 frame_type = SAME_LOCALS_1_STACK_ITEM; /* 64-127 */
3302     //   verification_type_info stack[1];
3303     // }
3304     else if (frame_type >= 64 && frame_type <= 127) {
3305       rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
3306         calc_number_of_entries, frame_type);
3307     }
3308 
3309     // reserved for future use
3310     else if (frame_type >= 128 && frame_type <= 246) {
3311       // nothing more to do for reserved frame_types
3312     }
3313 
3314     // same_locals_1_stack_item_frame_extended {
3315     //   u1 frame_type = SAME_LOCALS_1_STACK_ITEM_EXTENDED; /* 247 */
3316     //   u2 offset_delta;
3317     //   verification_type_info stack[1];
3318     // }
3319     else if (frame_type == 247) {
3320       stackmap_p += 2;
3321       rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
3322         calc_number_of_entries, frame_type);
3323     }
3324 
3325     // chop_frame {
3326     //   u1 frame_type = CHOP; /* 248-250 */
3327     //   u2 offset_delta;
3328     // }
3329     else if (frame_type >= 248 && frame_type <= 250) {
3330       stackmap_p += 2;
3331     }
3332 
3333     // same_frame_extended {
3334     //   u1 frame_type = SAME_FRAME_EXTENDED; /* 251*/
3335     //   u2 offset_delta;
3336     // }
3337     else if (frame_type == 251) {
3338       stackmap_p += 2;
3339     }
3340 
3341     // append_frame {
3342     //   u1 frame_type = APPEND; /* 252-254 */
3343     //   u2 offset_delta;
3344     //   verification_type_info locals[frame_type - 251];
3345     // }
3346     else if (frame_type >= 252 && frame_type <= 254) {
3347       assert(stackmap_p + 2 <= stackmap_end,
3348         "no room for offset_delta");
3349       stackmap_p += 2;
3350       u1 len = frame_type - 251;
3351       for (u1 i = 0; i < len; i++) {
3352         rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
3353           calc_number_of_entries, frame_type);
3354       }
3355     }
3356 
3357     // full_frame {
3358     //   u1 frame_type = FULL_FRAME; /* 255 */
3359     //   u2 offset_delta;
3360     //   u2 number_of_locals;
3361     //   verification_type_info locals[number_of_locals];
3362     //   u2 number_of_stack_items;
3363     //   verification_type_info stack[number_of_stack_items];
3364     // }
3365     else if (frame_type == 255) {
3366       assert(stackmap_p + 2 + 2 <= stackmap_end,
3367         "no room for smallest full_frame");
3368       stackmap_p += 2;
3369 
3370       u2 number_of_locals = Bytes::get_Java_u2(stackmap_p);
3371       stackmap_p += 2;
3372 
3373       for (u2 locals_i = 0; locals_i < number_of_locals; locals_i++) {
3374         rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
3375           calc_number_of_entries, frame_type);
3376       }
3377 
3378       // Use the largest size for the number_of_stack_items, but only get
3379       // the right number of bytes.
3380       u2 number_of_stack_items = Bytes::get_Java_u2(stackmap_p);
3381       stackmap_p += 2;
3382 
3383       for (u2 stack_i = 0; stack_i < number_of_stack_items; stack_i++) {
3384         rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
3385           calc_number_of_entries, frame_type);
3386       }
3387     }
3388   } // end while there is a stack_map_frame
3389   assert(number_of_entries == calc_number_of_entries, "sanity check");
3390 } // end rewrite_cp_refs_in_stack_map_table()
3391 
3392 
3393 // Rewrite constant pool references in the verification type info
3394 // portion of the method's stackmap table. These "structures" are
3395 // adapted from the StackMapTable_attribute that is described in
3396 // section 4.8.4 of the 6.0 version of the VM spec (dated 2005.10.26):
3397 // file:///net/quincunx.sfbay/export/gbracha/ClassFile-Java6.pdf
3398 //
3399 // The verification_type_info structure is a u1 tag followed by 0 or
3400 // more bytes of data:
3401 //
3402 // union verification_type_info {
3403 //   Top_variable_info;
3404 //   Integer_variable_info;
3405 //   Float_variable_info;
3406 //   Long_variable_info;
3407 //   Double_variable_info;
3408 //   Null_variable_info;
3409 //   UninitializedThis_variable_info;
3410 //   Object_variable_info;
3411 //   Uninitialized_variable_info;
3412 // }
3413 //
3414 void VM_RedefineClasses::rewrite_cp_refs_in_verification_type_info(
3415        address& stackmap_p_ref, address stackmap_end, u2 frame_i,
3416        u1 frame_type) {
3417 
3418   assert(stackmap_p_ref + 1 <= stackmap_end, "no room for tag");
3419   u1 tag = *stackmap_p_ref;
3420   stackmap_p_ref++;
3421 
3422   switch (tag) {
3423   // Top_variable_info {
3424   //   u1 tag = ITEM_Top; /* 0 */
3425   // }
3426   // verificationType.hpp has zero as ITEM_Bogus instead of ITEM_Top
3427   case 0:  // fall through
3428 
3429   // Integer_variable_info {
3430   //   u1 tag = ITEM_Integer; /* 1 */
3431   // }
3432   case ITEM_Integer:  // fall through
3433 
3434   // Float_variable_info {
3435   //   u1 tag = ITEM_Float; /* 2 */
3436   // }
3437   case ITEM_Float:  // fall through
3438 
3439   // Double_variable_info {
3440   //   u1 tag = ITEM_Double; /* 3 */
3441   // }
3442   case ITEM_Double:  // fall through
3443 
3444   // Long_variable_info {
3445   //   u1 tag = ITEM_Long; /* 4 */
3446   // }
3447   case ITEM_Long:  // fall through
3448 
3449   // Null_variable_info {
3450   //   u1 tag = ITEM_Null; /* 5 */
3451   // }
3452   case ITEM_Null:  // fall through
3453 
3454   // UninitializedThis_variable_info {
3455   //   u1 tag = ITEM_UninitializedThis; /* 6 */
3456   // }
3457   case ITEM_UninitializedThis:
3458     // nothing more to do for the above tag types
3459     break;
3460 
3461   // Object_variable_info {
3462   //   u1 tag = ITEM_Object; /* 7 */
3463   //   u2 cpool_index;
3464   // }
3465   case ITEM_Object:
3466   {
3467     assert(stackmap_p_ref + 2 <= stackmap_end, "no room for cpool_index");
3468     u2 cpool_index = Bytes::get_Java_u2(stackmap_p_ref);
3469     u2 new_cp_index = find_new_index(cpool_index);
3470     if (new_cp_index != 0) {
3471       log_debug(redefine, class, stackmap)("mapped old cpool_index=%d", cpool_index);
3472       Bytes::put_Java_u2(stackmap_p_ref, new_cp_index);
3473       cpool_index = new_cp_index;
3474     }
3475     stackmap_p_ref += 2;
3476 
3477     log_debug(redefine, class, stackmap)
3478       ("frame_i=%u, frame_type=%u, cpool_index=%d", frame_i, frame_type, cpool_index);
3479   } break;
3480 
3481   // Uninitialized_variable_info {
3482   //   u1 tag = ITEM_Uninitialized; /* 8 */
3483   //   u2 offset;
3484   // }
3485   case ITEM_Uninitialized:
3486     assert(stackmap_p_ref + 2 <= stackmap_end, "no room for offset");
3487     stackmap_p_ref += 2;
3488     break;
3489 
3490   default:
3491     log_debug(redefine, class, stackmap)("frame_i=%u, frame_type=%u, bad tag=0x%x", frame_i, frame_type, tag);
3492     ShouldNotReachHere();
3493     break;
3494   } // end switch (tag)
3495 } // end rewrite_cp_refs_in_verification_type_info()
3496 
3497 
3498 // Change the constant pool associated with klass scratch_class to scratch_cp.
3499 // scratch_cp_length elements are copied from scratch_cp to a smaller constant pool
3500 // and the smaller constant pool is associated with scratch_class.
3501 void VM_RedefineClasses::set_new_constant_pool(
3502        ClassLoaderData* loader_data,
3503        InstanceKlass* scratch_class, constantPoolHandle scratch_cp,
3504        int scratch_cp_length, TRAPS) {
3505   assert(scratch_cp->length() >= scratch_cp_length, "sanity check");
3506 
3507   // scratch_cp is a merged constant pool and has enough space for a
3508   // worst case merge situation. We want to associate the minimum
3509   // sized constant pool with the klass to save space.
3510   ConstantPool* cp = ConstantPool::allocate(loader_data, scratch_cp_length, CHECK);
3511   constantPoolHandle smaller_cp(THREAD, cp);
3512 
3513   // preserve version() value in the smaller copy
3514   int version = scratch_cp->version();
3515   assert(version != 0, "sanity check");
3516   smaller_cp->set_version(version);
3517 
3518   // attach klass to new constant pool
3519   // reference to the cp holder is needed for copy_operands()
3520   smaller_cp->set_pool_holder(scratch_class);
3521 
3522   smaller_cp->copy_fields(scratch_cp());
3523 
3524   scratch_cp->copy_cp_to(1, scratch_cp_length - 1, smaller_cp, 1, THREAD);
3525   if (HAS_PENDING_EXCEPTION) {
3526     // Exception is handled in the caller
3527     loader_data->add_to_deallocate_list(smaller_cp());
3528     return;
3529   }
3530   scratch_cp = smaller_cp;
3531 
3532   // attach new constant pool to klass
3533   scratch_class->set_constants(scratch_cp());
3534   scratch_cp->initialize_unresolved_klasses(loader_data, CHECK);
3535 
3536   int i;  // for portability
3537 
3538   // update each field in klass to use new constant pool indices as needed
3539   int java_fields;
3540   int injected_fields;
3541   bool update_required = false;
3542   GrowableArray<FieldInfo>* fields = FieldInfoStream::create_FieldInfoArray(scratch_class->fieldinfo_stream(), &java_fields, &injected_fields);
3543   for (int i = 0; i < java_fields; i++) {
3544     FieldInfo* fi = fields->adr_at(i);
3545     jshort cur_index = fi->name_index();
3546     jshort new_index = find_new_index(cur_index);
3547     if (new_index != 0) {
3548       log_trace(redefine, class, constantpool)("field-name_index change: %d to %d", cur_index, new_index);
3549       fi->set_name_index(new_index);
3550       update_required = true;
3551     }
3552     cur_index = fi->signature_index();
3553     new_index = find_new_index(cur_index);
3554     if (new_index != 0) {
3555       log_trace(redefine, class, constantpool)("field-signature_index change: %d to %d", cur_index, new_index);
3556       fi->set_signature_index(new_index);
3557       update_required = true;
3558     }
3559     cur_index = fi->initializer_index();
3560     new_index = find_new_index(cur_index);
3561     if (new_index != 0) {
3562       log_trace(redefine, class, constantpool)("field-initval_index change: %d to %d", cur_index, new_index);
3563       fi->set_initializer_index(new_index);
3564       update_required = true;
3565     }
3566     cur_index = fi->generic_signature_index();
3567     new_index = find_new_index(cur_index);
3568     if (new_index != 0) {
3569       log_trace(redefine, class, constantpool)("field-generic_signature change: %d to %d", cur_index, new_index);
3570       fi->set_generic_signature_index(new_index);
3571       update_required = true;
3572     }
3573   }
3574   if (update_required) {
3575     Array<u1>* old_stream = scratch_class->fieldinfo_stream();
3576     assert(fields->length() == (java_fields + injected_fields), "Must be");
3577     Array<u1>* new_fis = FieldInfoStream::create_FieldInfoStream(fields, java_fields, injected_fields, scratch_class->class_loader_data(), CHECK);
3578     scratch_class->set_fieldinfo_stream(new_fis);
3579     MetadataFactory::free_array<u1>(scratch_class->class_loader_data(), old_stream);
3580   }
3581 
3582   // Update constant pool indices in the inner classes info to use
3583   // new constant indices as needed. The inner classes info is a
3584   // quadruple:
3585   // (inner_class_info, outer_class_info, inner_name, inner_access_flags)
3586   InnerClassesIterator iter(scratch_class);
3587   for (; !iter.done(); iter.next()) {
3588     int cur_index = iter.inner_class_info_index();
3589     if (cur_index == 0) {
3590       continue;  // JVM spec. allows null inner class refs so skip it
3591     }
3592     u2 new_index = find_new_index(cur_index);
3593     if (new_index != 0) {
3594       log_trace(redefine, class, constantpool)("inner_class_info change: %d to %d", cur_index, new_index);
3595       iter.set_inner_class_info_index(new_index);
3596     }
3597     cur_index = iter.outer_class_info_index();
3598     new_index = find_new_index(cur_index);
3599     if (new_index != 0) {
3600       log_trace(redefine, class, constantpool)("outer_class_info change: %d to %d", cur_index, new_index);
3601       iter.set_outer_class_info_index(new_index);
3602     }
3603     cur_index = iter.inner_name_index();
3604     new_index = find_new_index(cur_index);
3605     if (new_index != 0) {
3606       log_trace(redefine, class, constantpool)("inner_name change: %d to %d", cur_index, new_index);
3607       iter.set_inner_name_index(new_index);
3608     }
3609   } // end for each inner class
3610 
3611   // Attach each method in klass to the new constant pool and update
3612   // to use new constant pool indices as needed:
3613   Array<Method*>* methods = scratch_class->methods();
3614   for (i = methods->length() - 1; i >= 0; i--) {
3615     methodHandle method(THREAD, methods->at(i));
3616     method->set_constants(scratch_cp());
3617 
3618     u2 new_index = find_new_index(method->name_index());
3619     if (new_index != 0) {
3620       log_trace(redefine, class, constantpool)
3621         ("method-name_index change: %d to %d", method->name_index(), new_index);
3622       method->set_name_index(new_index);
3623     }
3624     new_index = find_new_index(method->signature_index());
3625     if (new_index != 0) {
3626       log_trace(redefine, class, constantpool)
3627         ("method-signature_index change: %d to %d", method->signature_index(), new_index);
3628       method->set_signature_index(new_index);
3629     }
3630     new_index = find_new_index(method->generic_signature_index());
3631     if (new_index != 0) {
3632       log_trace(redefine, class, constantpool)
3633         ("method-generic_signature_index change: %d to %d", method->generic_signature_index(), new_index);
3634       method->constMethod()->set_generic_signature_index(new_index);
3635     }
3636 
3637     // Update constant pool indices in the method's checked exception
3638     // table to use new constant indices as needed.
3639     int cext_length = method->checked_exceptions_length();
3640     if (cext_length > 0) {
3641       CheckedExceptionElement * cext_table =
3642         method->checked_exceptions_start();
3643       for (int j = 0; j < cext_length; j++) {
3644         int cur_index = cext_table[j].class_cp_index;
3645         int new_index = find_new_index(cur_index);
3646         if (new_index != 0) {
3647           log_trace(redefine, class, constantpool)("cext-class_cp_index change: %d to %d", cur_index, new_index);
3648           cext_table[j].class_cp_index = (u2)new_index;
3649         }
3650       } // end for each checked exception table entry
3651     } // end if there are checked exception table entries
3652 
3653     // Update each catch type index in the method's exception table
3654     // to use new constant pool indices as needed. The exception table
3655     // holds quadruple entries of the form:
3656     //   (beg_bci, end_bci, handler_bci, klass_index)
3657 
3658     ExceptionTable ex_table(method());
3659     int ext_length = ex_table.length();
3660 
3661     for (int j = 0; j < ext_length; j ++) {
3662       int cur_index = ex_table.catch_type_index(j);
3663       u2 new_index = find_new_index(cur_index);
3664       if (new_index != 0) {
3665         log_trace(redefine, class, constantpool)("ext-klass_index change: %d to %d", cur_index, new_index);
3666         ex_table.set_catch_type_index(j, new_index);
3667       }
3668     } // end for each exception table entry
3669 
3670     // Update constant pool indices in the method's local variable
3671     // table to use new constant indices as needed. The local variable
3672     // table hold sextuple entries of the form:
3673     // (start_pc, length, name_index, descriptor_index, signature_index, slot)
3674     int lvt_length = method->localvariable_table_length();
3675     if (lvt_length > 0) {
3676       LocalVariableTableElement * lv_table =
3677         method->localvariable_table_start();
3678       for (int j = 0; j < lvt_length; j++) {
3679         int cur_index = lv_table[j].name_cp_index;
3680         int new_index = find_new_index(cur_index);
3681         if (new_index != 0) {
3682           log_trace(redefine, class, constantpool)("lvt-name_cp_index change: %d to %d", cur_index, new_index);
3683           lv_table[j].name_cp_index = (u2)new_index;
3684         }
3685         cur_index = lv_table[j].descriptor_cp_index;
3686         new_index = find_new_index(cur_index);
3687         if (new_index != 0) {
3688           log_trace(redefine, class, constantpool)("lvt-descriptor_cp_index change: %d to %d", cur_index, new_index);
3689           lv_table[j].descriptor_cp_index = (u2)new_index;
3690         }
3691         cur_index = lv_table[j].signature_cp_index;
3692         new_index = find_new_index(cur_index);
3693         if (new_index != 0) {
3694           log_trace(redefine, class, constantpool)("lvt-signature_cp_index change: %d to %d", cur_index, new_index);
3695           lv_table[j].signature_cp_index = (u2)new_index;
3696         }
3697       } // end for each local variable table entry
3698     } // end if there are local variable table entries
3699 
3700     // Update constant pool indices in the method's method_parameters.
3701     int mp_length = method->method_parameters_length();
3702     if (mp_length > 0) {
3703       MethodParametersElement* elem = method->method_parameters_start();
3704       for (int j = 0; j < mp_length; j++) {
3705         const int cp_index = elem[j].name_cp_index;
3706         const int new_cp_index = find_new_index(cp_index);
3707         if (new_cp_index != 0) {
3708           elem[j].name_cp_index = (u2)new_cp_index;
3709         }
3710       }
3711     }
3712 
3713     rewrite_cp_refs_in_stack_map_table(method);
3714   } // end for each method
3715 } // end set_new_constant_pool()
3716 
3717 
3718 // Unevolving classes may point to methods of the_class directly
3719 // from their constant pool caches, itables, and/or vtables. We
3720 // use the ClassLoaderDataGraph::classes_do() facility and this helper
3721 // to fix up these pointers.  MethodData also points to old methods and
3722 // must be cleaned.
3723 
3724 // Adjust cpools and vtables closure
3725 void VM_RedefineClasses::AdjustAndCleanMetadata::do_klass(Klass* k) {
3726 
3727   // This is a very busy routine. We don't want too much tracing
3728   // printed out.
3729   bool trace_name_printed = false;
3730 
3731   // If the class being redefined is java.lang.Object, we need to fix all
3732   // array class vtables also. The _has_redefined_Object flag is global.
3733   // Once the java.lang.Object has been redefined (by the current or one
3734   // of the previous VM_RedefineClasses operations) we have to always
3735   // adjust method entries for array classes.
3736   if (k->is_array_klass() && _has_redefined_Object) {
3737     k->vtable().adjust_method_entries(&trace_name_printed);
3738 
3739   } else if (k->is_instance_klass()) {
3740     HandleMark hm(_thread);
3741     InstanceKlass *ik = InstanceKlass::cast(k);
3742 
3743     // Clean MethodData of this class's methods so they don't refer to
3744     // old methods that are no longer running.
3745     Array<Method*>* methods = ik->methods();
3746     int num_methods = methods->length();
3747     for (int index = 0; index < num_methods; ++index) {
3748       if (methods->at(index)->method_data() != nullptr) {
3749         methods->at(index)->method_data()->clean_weak_method_links();
3750       }
3751     }
3752 
3753     // Adjust all vtables, default methods and itables, to clean out old methods.
3754     ResourceMark rm(_thread);
3755     if (ik->vtable_length() > 0) {
3756       ik->vtable().adjust_method_entries(&trace_name_printed);
3757       ik->adjust_default_methods(&trace_name_printed);
3758     }
3759 
3760     if (ik->itable_length() > 0) {
3761       ik->itable().adjust_method_entries(&trace_name_printed);
3762     }
3763 
3764     // The constant pools in other classes (other_cp) can refer to
3765     // old methods.  We have to update method information in
3766     // other_cp's cache. If other_cp has a previous version, then we
3767     // have to repeat the process for each previous version. The
3768     // constant pool cache holds the Method*s for non-virtual
3769     // methods and for virtual, final methods.
3770     //
3771     // Special case: if the current class is being redefined by the current
3772     // VM_RedefineClasses operation, then new_cp has already been attached
3773     // to the_class and old_cp has already been added as a previous version.
3774     // The new_cp doesn't have any cached references to old methods so it
3775     // doesn't need to be updated and we could optimize by skipping it.
3776     // However, the current class can be marked as being redefined by another
3777     // VM_RedefineClasses operation which has already executed its doit_prologue
3778     // and needs cpcache method entries adjusted. For simplicity, the cpcache
3779     // update is done unconditionally. It should result in doing nothing for
3780     // classes being redefined by the current VM_RedefineClasses operation.
3781     // Method entries in the previous version(s) are adjusted as well.
3782     ConstantPoolCache* cp_cache;
3783 
3784     // this klass' constant pool cache may need adjustment
3785     ConstantPool* other_cp = ik->constants();
3786     cp_cache = other_cp->cache();
3787     if (cp_cache != nullptr) {
3788       cp_cache->adjust_method_entries(&trace_name_printed);
3789     }
3790 
3791     // the previous versions' constant pool caches may need adjustment
3792     for (InstanceKlass* pv_node = ik->previous_versions();
3793          pv_node != nullptr;
3794          pv_node = pv_node->previous_versions()) {
3795       cp_cache = pv_node->constants()->cache();
3796       if (cp_cache != nullptr) {
3797         cp_cache->adjust_method_entries(&trace_name_printed);
3798       }
3799     }
3800   }
3801 }
3802 
3803 void VM_RedefineClasses::update_jmethod_ids() {
3804   for (int j = 0; j < _matching_methods_length; ++j) {
3805     Method* old_method = _matching_old_methods[j];
3806     jmethodID jmid = old_method->find_jmethod_id_or_null();
3807     if (jmid != nullptr) {
3808       // There is a jmethodID, change it to point to the new method
3809       Method* new_method = _matching_new_methods[j];
3810       Method::change_method_associated_with_jmethod_id(jmid, new_method);
3811       assert(Method::resolve_jmethod_id(jmid) == _matching_new_methods[j],
3812              "should be replaced");
3813     }
3814   }
3815 }
3816 
3817 int VM_RedefineClasses::check_methods_and_mark_as_obsolete() {
3818   int emcp_method_count = 0;
3819   int obsolete_count = 0;
3820   int old_index = 0;
3821   for (int j = 0; j < _matching_methods_length; ++j, ++old_index) {
3822     Method* old_method = _matching_old_methods[j];
3823     Method* new_method = _matching_new_methods[j];
3824     Method* old_array_method;
3825 
3826     // Maintain an old_index into the _old_methods array by skipping
3827     // deleted methods
3828     while ((old_array_method = _old_methods->at(old_index)) != old_method) {
3829       ++old_index;
3830     }
3831 
3832     if (MethodComparator::methods_EMCP(old_method, new_method)) {
3833       // The EMCP definition from JSR-163 requires the bytecodes to be
3834       // the same with the exception of constant pool indices which may
3835       // differ. However, the constants referred to by those indices
3836       // must be the same.
3837       //
3838       // We use methods_EMCP() for comparison since constant pool
3839       // merging can remove duplicate constant pool entries that were
3840       // present in the old method and removed from the rewritten new
3841       // method. A faster binary comparison function would consider the
3842       // old and new methods to be different when they are actually
3843       // EMCP.
3844       //
3845       // The old and new methods are EMCP and you would think that we
3846       // could get rid of one of them here and now and save some space.
3847       // However, the concept of EMCP only considers the bytecodes and
3848       // the constant pool entries in the comparison. Other things,
3849       // e.g., the line number table (LNT) or the local variable table
3850       // (LVT) don't count in the comparison. So the new (and EMCP)
3851       // method can have a new LNT that we need so we can't just
3852       // overwrite the new method with the old method.
3853       //
3854       // When this routine is called, we have already attached the new
3855       // methods to the_class so the old methods are effectively
3856       // overwritten. However, if an old method is still executing,
3857       // then the old method cannot be collected until sometime after
3858       // the old method call has returned. So the overwriting of old
3859       // methods by new methods will save us space except for those
3860       // (hopefully few) old methods that are still executing.
3861       //
3862       // A method refers to a ConstMethod* and this presents another
3863       // possible avenue to space savings. The ConstMethod* in the
3864       // new method contains possibly new attributes (LNT, LVT, etc).
3865       // At first glance, it seems possible to save space by replacing
3866       // the ConstMethod* in the old method with the ConstMethod*
3867       // from the new method. The old and new methods would share the
3868       // same ConstMethod* and we would save the space occupied by
3869       // the old ConstMethod*. However, the ConstMethod* contains
3870       // a back reference to the containing method. Sharing the
3871       // ConstMethod* between two methods could lead to confusion in
3872       // the code that uses the back reference. This would lead to
3873       // brittle code that could be broken in non-obvious ways now or
3874       // in the future.
3875       //
3876       // Another possibility is to copy the ConstMethod* from the new
3877       // method to the old method and then overwrite the new method with
3878       // the old method. Since the ConstMethod* contains the bytecodes
3879       // for the method embedded in the oop, this option would change
3880       // the bytecodes out from under any threads executing the old
3881       // method and make the thread's bcp invalid. Since EMCP requires
3882       // that the bytecodes be the same modulo constant pool indices, it
3883       // is straight forward to compute the correct new bcp in the new
3884       // ConstMethod* from the old bcp in the old ConstMethod*. The
3885       // time consuming part would be searching all the frames in all
3886       // of the threads to find all of the calls to the old method.
3887       //
3888       // It looks like we will have to live with the limited savings
3889       // that we get from effectively overwriting the old methods
3890       // when the new methods are attached to the_class.
3891 
3892       // Count number of methods that are EMCP.  The method will be marked
3893       // old but not obsolete if it is EMCP.
3894       emcp_method_count++;
3895 
3896       // An EMCP method is _not_ obsolete. An obsolete method has a
3897       // different jmethodID than the current method. An EMCP method
3898       // has the same jmethodID as the current method. Having the
3899       // same jmethodID for all EMCP versions of a method allows for
3900       // a consistent view of the EMCP methods regardless of which
3901       // EMCP method you happen to have in hand. For example, a
3902       // breakpoint set in one EMCP method will work for all EMCP
3903       // versions of the method including the current one.
3904     } else {
3905       // mark obsolete methods as such
3906       old_method->set_is_obsolete();
3907       obsolete_count++;
3908 
3909       // obsolete methods need a unique idnum so they become new entries in
3910       // the jmethodID cache in InstanceKlass
3911       assert(old_method->method_idnum() == new_method->method_idnum(), "must match");
3912       u2 num = InstanceKlass::cast(_the_class)->next_method_idnum();
3913       if (num != ConstMethod::UNSET_IDNUM) {
3914         old_method->set_method_idnum(num);
3915       }
3916 
3917       // With tracing we try not to "yack" too much. The position of
3918       // this trace assumes there are fewer obsolete methods than
3919       // EMCP methods.
3920       if (log_is_enabled(Trace, redefine, class, obsolete, mark)) {
3921         ResourceMark rm;
3922         log_trace(redefine, class, obsolete, mark)
3923           ("mark %s(%s) as obsolete", old_method->name()->as_C_string(), old_method->signature()->as_C_string());
3924       }
3925     }
3926     old_method->set_is_old();
3927   }
3928   for (int i = 0; i < _deleted_methods_length; ++i) {
3929     Method* old_method = _deleted_methods[i];
3930 
3931     assert(!old_method->has_vtable_index(),
3932            "cannot delete methods with vtable entries");;
3933 
3934     // Mark all deleted methods as old, obsolete and deleted
3935     old_method->set_is_deleted();
3936     old_method->set_is_old();
3937     old_method->set_is_obsolete();
3938     ++obsolete_count;
3939     // With tracing we try not to "yack" too much. The position of
3940     // this trace assumes there are fewer obsolete methods than
3941     // EMCP methods.
3942     if (log_is_enabled(Trace, redefine, class, obsolete, mark)) {
3943       ResourceMark rm;
3944       log_trace(redefine, class, obsolete, mark)
3945         ("mark deleted %s(%s) as obsolete", old_method->name()->as_C_string(), old_method->signature()->as_C_string());
3946     }
3947   }
3948   assert((emcp_method_count + obsolete_count) == _old_methods->length(),
3949     "sanity check");
3950   log_trace(redefine, class, obsolete, mark)("EMCP_cnt=%d, obsolete_cnt=%d", emcp_method_count, obsolete_count);
3951   return emcp_method_count;
3952 }
3953 
3954 // This internal class transfers the native function registration from old methods
3955 // to new methods.  It is designed to handle both the simple case of unchanged
3956 // native methods and the complex cases of native method prefixes being added and/or
3957 // removed.
3958 // It expects only to be used during the VM_RedefineClasses op (a safepoint).
3959 //
3960 // This class is used after the new methods have been installed in "the_class".
3961 //
3962 // So, for example, the following must be handled.  Where 'm' is a method and
3963 // a number followed by an underscore is a prefix.
3964 //
3965 //                                      Old Name    New Name
3966 // Simple transfer to new method        m       ->  m
3967 // Add prefix                           m       ->  1_m
3968 // Remove prefix                        1_m     ->  m
3969 // Simultaneous add of prefixes         m       ->  3_2_1_m
3970 // Simultaneous removal of prefixes     3_2_1_m ->  m
3971 // Simultaneous add and remove          1_m     ->  2_m
3972 // Same, caused by prefix removal only  3_2_1_m ->  3_2_m
3973 //
3974 class TransferNativeFunctionRegistration {
3975  private:
3976   InstanceKlass* the_class;
3977   int prefix_count;
3978   char** prefixes;
3979 
3980   // Recursively search the binary tree of possibly prefixed method names.
3981   // Iteration could be used if all agents were well behaved. Full tree walk is
3982   // more resilent to agents not cleaning up intermediate methods.
3983   // Branch at each depth in the binary tree is:
3984   //    (1) without the prefix.
3985   //    (2) with the prefix.
3986   // where 'prefix' is the prefix at that 'depth' (first prefix, second prefix,...)
3987   Method* search_prefix_name_space(int depth, char* name_str, size_t name_len,
3988                                      Symbol* signature) {
3989     TempNewSymbol name_symbol = SymbolTable::probe(name_str, (int)name_len);
3990     if (name_symbol != nullptr) {
3991       Method* method = the_class->lookup_method(name_symbol, signature);
3992       if (method != nullptr) {
3993         // Even if prefixed, intermediate methods must exist.
3994         if (method->is_native()) {
3995           // Wahoo, we found a (possibly prefixed) version of the method, return it.
3996           return method;
3997         }
3998         if (depth < prefix_count) {
3999           // Try applying further prefixes (other than this one).
4000           method = search_prefix_name_space(depth+1, name_str, name_len, signature);
4001           if (method != nullptr) {
4002             return method; // found
4003           }
4004 
4005           // Try adding this prefix to the method name and see if it matches
4006           // another method name.
4007           char* prefix = prefixes[depth];
4008           size_t prefix_len = strlen(prefix);
4009           size_t trial_len = name_len + prefix_len;
4010           char* trial_name_str = NEW_RESOURCE_ARRAY(char, trial_len + 1);
4011           strcpy(trial_name_str, prefix);
4012           strcat(trial_name_str, name_str);
4013           method = search_prefix_name_space(depth+1, trial_name_str, trial_len,
4014                                             signature);
4015           if (method != nullptr) {
4016             // If found along this branch, it was prefixed, mark as such
4017             method->set_is_prefixed_native();
4018             return method; // found
4019           }
4020         }
4021       }
4022     }
4023     return nullptr;  // This whole branch bore nothing
4024   }
4025 
4026   // Return the method name with old prefixes stripped away.
4027   char* method_name_without_prefixes(Method* method) {
4028     Symbol* name = method->name();
4029     char* name_str = name->as_utf8();
4030 
4031     // Old prefixing may be defunct, strip prefixes, if any.
4032     for (int i = prefix_count-1; i >= 0; i--) {
4033       char* prefix = prefixes[i];
4034       size_t prefix_len = strlen(prefix);
4035       if (strncmp(prefix, name_str, prefix_len) == 0) {
4036         name_str += prefix_len;
4037       }
4038     }
4039     return name_str;
4040   }
4041 
4042   // Strip any prefixes off the old native method, then try to find a
4043   // (possibly prefixed) new native that matches it.
4044   Method* strip_and_search_for_new_native(Method* method) {
4045     ResourceMark rm;
4046     char* name_str = method_name_without_prefixes(method);
4047     return search_prefix_name_space(0, name_str, strlen(name_str),
4048                                     method->signature());
4049   }
4050 
4051  public:
4052 
4053   // Construct a native method transfer processor for this class.
4054   TransferNativeFunctionRegistration(InstanceKlass* _the_class) {
4055     assert(SafepointSynchronize::is_at_safepoint(), "sanity check");
4056 
4057     the_class = _the_class;
4058     prefixes = JvmtiExport::get_all_native_method_prefixes(&prefix_count);
4059   }
4060 
4061   // Attempt to transfer any of the old or deleted methods that are native
4062   void transfer_registrations(Method** old_methods, int methods_length) {
4063     for (int j = 0; j < methods_length; j++) {
4064       Method* old_method = old_methods[j];
4065 
4066       if (old_method->is_native() && old_method->has_native_function()) {
4067         Method* new_method = strip_and_search_for_new_native(old_method);
4068         if (new_method != nullptr) {
4069           // Actually set the native function in the new method.
4070           // Redefine does not send events (except CFLH), certainly not this
4071           // behind the scenes re-registration.
4072           new_method->set_native_function(old_method->native_function(),
4073                               !Method::native_bind_event_is_interesting);
4074         }
4075       }
4076     }
4077   }
4078 };
4079 
4080 // Don't lose the association between a native method and its JNI function.
4081 void VM_RedefineClasses::transfer_old_native_function_registrations(InstanceKlass* the_class) {
4082   TransferNativeFunctionRegistration transfer(the_class);
4083   transfer.transfer_registrations(_deleted_methods, _deleted_methods_length);
4084   transfer.transfer_registrations(_matching_old_methods, _matching_methods_length);
4085 }
4086 
4087 // Deoptimize all compiled code that depends on the classes redefined.
4088 //
4089 // If the can_redefine_classes capability is obtained in the onload
4090 // phase or 'AlwaysRecordEvolDependencies' is true, then the compiler has
4091 // recorded all dependencies from startup. In that case we need only
4092 // deoptimize and throw away all compiled code that depends on the class.
4093 //
4094 // If can_redefine_classes is obtained sometime after the onload phase
4095 // (and 'AlwaysRecordEvolDependencies' is false) then the dependency
4096 // information may be incomplete. In that case the first call to
4097 // RedefineClasses causes all compiled code to be thrown away. As
4098 // can_redefine_classes has been obtained then all future compilations will
4099 // record dependencies so second and subsequent calls to RedefineClasses
4100 // need only throw away code that depends on the class.
4101 //
4102 
4103 void VM_RedefineClasses::flush_dependent_code() {
4104   assert(SafepointSynchronize::is_at_safepoint(), "sanity check");
4105   assert(JvmtiExport::all_dependencies_are_recorded() || !AlwaysRecordEvolDependencies, "sanity check");
4106 
4107   DeoptimizationScope deopt_scope;
4108 
4109   // This is the first redefinition, mark all the nmethods for deoptimization
4110   if (!JvmtiExport::all_dependencies_are_recorded()) {
4111     CodeCache::mark_all_nmethods_for_evol_deoptimization(&deopt_scope);
4112     log_debug(redefine, class, nmethod)("Marked all nmethods for deopt");
4113   } else {
4114     CodeCache::mark_dependents_for_evol_deoptimization(&deopt_scope);
4115     log_debug(redefine, class, nmethod)("Marked dependent nmethods for deopt");
4116   }
4117 
4118   deopt_scope.deoptimize_marked();
4119 
4120   // From now on we know that the dependency information is complete
4121   JvmtiExport::set_all_dependencies_are_recorded(true);
4122 }
4123 
4124 void VM_RedefineClasses::compute_added_deleted_matching_methods() {
4125   Method* old_method;
4126   Method* new_method;
4127 
4128   _matching_old_methods = NEW_RESOURCE_ARRAY(Method*, _old_methods->length());
4129   _matching_new_methods = NEW_RESOURCE_ARRAY(Method*, _old_methods->length());
4130   _added_methods        = NEW_RESOURCE_ARRAY(Method*, _new_methods->length());
4131   _deleted_methods      = NEW_RESOURCE_ARRAY(Method*, _old_methods->length());
4132 
4133   _matching_methods_length = 0;
4134   _deleted_methods_length  = 0;
4135   _added_methods_length    = 0;
4136 
4137   int nj = 0;
4138   int oj = 0;
4139   while (true) {
4140     if (oj >= _old_methods->length()) {
4141       if (nj >= _new_methods->length()) {
4142         break; // we've looked at everything, done
4143       }
4144       // New method at the end
4145       new_method = _new_methods->at(nj);
4146       _added_methods[_added_methods_length++] = new_method;
4147       ++nj;
4148     } else if (nj >= _new_methods->length()) {
4149       // Old method, at the end, is deleted
4150       old_method = _old_methods->at(oj);
4151       _deleted_methods[_deleted_methods_length++] = old_method;
4152       ++oj;
4153     } else {
4154       old_method = _old_methods->at(oj);
4155       new_method = _new_methods->at(nj);
4156       if (old_method->name() == new_method->name()) {
4157         if (old_method->signature() == new_method->signature()) {
4158           _matching_old_methods[_matching_methods_length  ] = old_method;
4159           _matching_new_methods[_matching_methods_length++] = new_method;
4160           ++nj;
4161           ++oj;
4162         } else {
4163           // added overloaded have already been moved to the end,
4164           // so this is a deleted overloaded method
4165           _deleted_methods[_deleted_methods_length++] = old_method;
4166           ++oj;
4167         }
4168       } else { // names don't match
4169         if (old_method->name()->fast_compare(new_method->name()) > 0) {
4170           // new method
4171           _added_methods[_added_methods_length++] = new_method;
4172           ++nj;
4173         } else {
4174           // deleted method
4175           _deleted_methods[_deleted_methods_length++] = old_method;
4176           ++oj;
4177         }
4178       }
4179     }
4180   }
4181   assert(_matching_methods_length + _deleted_methods_length == _old_methods->length(), "sanity");
4182   assert(_matching_methods_length + _added_methods_length == _new_methods->length(), "sanity");
4183 }
4184 
4185 
4186 void VM_RedefineClasses::swap_annotations(InstanceKlass* the_class,
4187                                           InstanceKlass* scratch_class) {
4188   // Swap annotation fields values
4189   Annotations* old_annotations = the_class->annotations();
4190   the_class->set_annotations(scratch_class->annotations());
4191   scratch_class->set_annotations(old_annotations);
4192 }
4193 
4194 
4195 // Install the redefinition of a class:
4196 //    - house keeping (flushing breakpoints and caches, deoptimizing
4197 //      dependent compiled code)
4198 //    - replacing parts in the_class with parts from scratch_class
4199 //    - adding a weak reference to track the obsolete but interesting
4200 //      parts of the_class
4201 //    - adjusting constant pool caches and vtables in other classes
4202 //      that refer to methods in the_class. These adjustments use the
4203 //      ClassLoaderDataGraph::classes_do() facility which only allows
4204 //      a helper method to be specified. The interesting parameters
4205 //      that we would like to pass to the helper method are saved in
4206 //      static global fields in the VM operation.
4207 void VM_RedefineClasses::redefine_single_class(Thread* current, jclass the_jclass,
4208                                                InstanceKlass* scratch_class) {
4209 
4210   HandleMark hm(current);   // make sure handles from this call are freed
4211 
4212   if (log_is_enabled(Info, redefine, class, timer)) {
4213     _timer_rsc_phase1.start();
4214   }
4215 
4216   InstanceKlass* the_class = get_ik(the_jclass);
4217 
4218   // Set a flag to control and optimize adjusting method entries
4219   _has_redefined_Object |= the_class == vmClasses::Object_klass();
4220 
4221   // Remove all breakpoints in methods of this class
4222   JvmtiBreakpoints& jvmti_breakpoints = JvmtiCurrentBreakpoints::get_jvmti_breakpoints();
4223   jvmti_breakpoints.clearall_in_class_at_safepoint(the_class);
4224 
4225   _old_methods = the_class->methods();
4226   _new_methods = scratch_class->methods();
4227   _the_class = the_class;
4228   compute_added_deleted_matching_methods();
4229   update_jmethod_ids();
4230 
4231   _any_class_has_resolved_methods = the_class->has_resolved_methods() || _any_class_has_resolved_methods;
4232 
4233   // Attach new constant pool to the original klass. The original
4234   // klass still refers to the old constant pool (for now).
4235   scratch_class->constants()->set_pool_holder(the_class);
4236 
4237 #if 0
4238   // In theory, with constant pool merging in place we should be able
4239   // to save space by using the new, merged constant pool in place of
4240   // the old constant pool(s). By "pool(s)" I mean the constant pool in
4241   // the klass version we are replacing now and any constant pool(s) in
4242   // previous versions of klass. Nice theory, doesn't work in practice.
4243   // When this code is enabled, even simple programs throw NullPointer
4244   // exceptions. I'm guessing that this is caused by some constant pool
4245   // cache difference between the new, merged constant pool and the
4246   // constant pool that was just being used by the klass. I'm keeping
4247   // this code around to archive the idea, but the code has to remain
4248   // disabled for now.
4249 
4250   // Attach each old method to the new constant pool. This can be
4251   // done here since we are past the bytecode verification and
4252   // constant pool optimization phases.
4253   for (int i = _old_methods->length() - 1; i >= 0; i--) {
4254     Method* method = _old_methods->at(i);
4255     method->set_constants(scratch_class->constants());
4256   }
4257 
4258   // NOTE: this doesn't work because you can redefine the same class in two
4259   // threads, each getting their own constant pool data appended to the
4260   // original constant pool.  In order for the new methods to work when they
4261   // become old methods, they need to keep their updated copy of the constant pool.
4262 
4263   {
4264     // walk all previous versions of the klass
4265     InstanceKlass *ik = the_class;
4266     PreviousVersionWalker pvw(ik);
4267     do {
4268       ik = pvw.next_previous_version();
4269       if (ik != nullptr) {
4270 
4271         // attach previous version of klass to the new constant pool
4272         ik->set_constants(scratch_class->constants());
4273 
4274         // Attach each method in the previous version of klass to the
4275         // new constant pool
4276         Array<Method*>* prev_methods = ik->methods();
4277         for (int i = prev_methods->length() - 1; i >= 0; i--) {
4278           Method* method = prev_methods->at(i);
4279           method->set_constants(scratch_class->constants());
4280         }
4281       }
4282     } while (ik != nullptr);
4283   }
4284 #endif
4285 
4286   // Replace methods and constantpool
4287   the_class->set_methods(_new_methods);
4288   scratch_class->set_methods(_old_methods);     // To prevent potential GCing of the old methods,
4289                                           // and to be able to undo operation easily.
4290 
4291   Array<int>* old_ordering = the_class->method_ordering();
4292   the_class->set_method_ordering(scratch_class->method_ordering());
4293   scratch_class->set_method_ordering(old_ordering);
4294 
4295   ConstantPool* old_constants = the_class->constants();
4296   the_class->set_constants(scratch_class->constants());
4297   scratch_class->set_constants(old_constants);  // See the previous comment.
4298 #if 0
4299   // We are swapping the guts of "the new class" with the guts of "the
4300   // class". Since the old constant pool has just been attached to "the
4301   // new class", it seems logical to set the pool holder in the old
4302   // constant pool also. However, doing this will change the observable
4303   // class hierarchy for any old methods that are still executing. A
4304   // method can query the identity of its "holder" and this query uses
4305   // the method's constant pool link to find the holder. The change in
4306   // holding class from "the class" to "the new class" can confuse
4307   // things.
4308   //
4309   // Setting the old constant pool's holder will also cause
4310   // verification done during vtable initialization below to fail.
4311   // During vtable initialization, the vtable's class is verified to be
4312   // a subtype of the method's holder. The vtable's class is "the
4313   // class" and the method's holder is gotten from the constant pool
4314   // link in the method itself. For "the class"'s directly implemented
4315   // methods, the method holder is "the class" itself (as gotten from
4316   // the new constant pool). The check works fine in this case. The
4317   // check also works fine for methods inherited from super classes.
4318   //
4319   // Miranda methods are a little more complicated. A miranda method is
4320   // provided by an interface when the class implementing the interface
4321   // does not provide its own method.  These interfaces are implemented
4322   // internally as an InstanceKlass. These special instanceKlasses
4323   // share the constant pool of the class that "implements" the
4324   // interface. By sharing the constant pool, the method holder of a
4325   // miranda method is the class that "implements" the interface. In a
4326   // non-redefine situation, the subtype check works fine. However, if
4327   // the old constant pool's pool holder is modified, then the check
4328   // fails because there is no class hierarchy relationship between the
4329   // vtable's class and "the new class".
4330 
4331   old_constants->set_pool_holder(scratch_class());
4332 #endif
4333 
4334   // track number of methods that are EMCP for add_previous_version() call below
4335   int emcp_method_count = check_methods_and_mark_as_obsolete();
4336   transfer_old_native_function_registrations(the_class);
4337 
4338   if (scratch_class->get_cached_class_file() != the_class->get_cached_class_file()) {
4339     // 1. the_class doesn't have a cache yet, scratch_class does have a cache.
4340     // 2. The same class can be present twice in the scratch classes list or there
4341     // are multiple concurrent RetransformClasses calls on different threads.
4342     // the_class and scratch_class have the same cached bytes, but different buffers.
4343     // In such cases we need to deallocate one of the buffers.
4344     // 3. RedefineClasses and the_class has cached bytes from a previous transformation.
4345     // In the case we need to use class bytes from scratch_class.
4346     if (the_class->get_cached_class_file() != nullptr) {
4347       os::free(the_class->get_cached_class_file());
4348     }
4349     the_class->set_cached_class_file(scratch_class->get_cached_class_file());
4350   }
4351 
4352   // null out in scratch class to not delete twice.  The class to be redefined
4353   // always owns these bytes.
4354   scratch_class->set_cached_class_file(nullptr);
4355 
4356   // Replace inner_classes
4357   Array<u2>* old_inner_classes = the_class->inner_classes();
4358   the_class->set_inner_classes(scratch_class->inner_classes());
4359   scratch_class->set_inner_classes(old_inner_classes);
4360 
4361   // Initialize the vtable and interface table after
4362   // methods have been rewritten
4363   // no exception should happen here since we explicitly
4364   // do not check loader constraints.
4365   // compare_and_normalize_class_versions has already checked:
4366   //  - classloaders unchanged, signatures unchanged
4367   //  - all instanceKlasses for redefined classes reused & contents updated
4368   the_class->vtable().initialize_vtable();
4369   the_class->itable().initialize_itable();
4370 
4371   // Leave arrays of jmethodIDs and itable index cache unchanged
4372 
4373   // Copy the "source debug extension" attribute from new class version
4374   the_class->set_source_debug_extension(
4375     scratch_class->source_debug_extension(),
4376     scratch_class->source_debug_extension() == nullptr ? 0 :
4377     (int)strlen(scratch_class->source_debug_extension()));
4378 
4379   // Use of javac -g could be different in the old and the new
4380   if (scratch_class->has_localvariable_table() !=
4381       the_class->has_localvariable_table()) {
4382     the_class->set_has_localvariable_table(scratch_class->has_localvariable_table());
4383   }
4384 
4385   swap_annotations(the_class, scratch_class);
4386 
4387   // Replace minor version number of class file
4388   u2 old_minor_version = the_class->constants()->minor_version();
4389   the_class->constants()->set_minor_version(scratch_class->constants()->minor_version());
4390   scratch_class->constants()->set_minor_version(old_minor_version);
4391 
4392   // Replace major version number of class file
4393   u2 old_major_version = the_class->constants()->major_version();
4394   the_class->constants()->set_major_version(scratch_class->constants()->major_version());
4395   scratch_class->constants()->set_major_version(old_major_version);
4396 
4397   // Replace CP indexes for class and name+type of enclosing method
4398   u2 old_class_idx  = the_class->enclosing_method_class_index();
4399   u2 old_method_idx = the_class->enclosing_method_method_index();
4400   the_class->set_enclosing_method_indices(
4401     scratch_class->enclosing_method_class_index(),
4402     scratch_class->enclosing_method_method_index());
4403   scratch_class->set_enclosing_method_indices(old_class_idx, old_method_idx);
4404 
4405   if (!the_class->has_been_redefined()) {
4406     the_class->set_has_been_redefined();
4407   }
4408 
4409   // Scratch class is unloaded but still needs cleaning, and skipping for CDS.
4410   scratch_class->set_is_scratch_class();
4411 
4412   // keep track of previous versions of this class
4413   the_class->add_previous_version(scratch_class, emcp_method_count);
4414 
4415   _timer_rsc_phase1.stop();
4416   if (log_is_enabled(Info, redefine, class, timer)) {
4417     _timer_rsc_phase2.start();
4418   }
4419 
4420   if (the_class->oop_map_cache() != nullptr) {
4421     // Flush references to any obsolete methods from the oop map cache
4422     // so that obsolete methods are not pinned.
4423     the_class->oop_map_cache()->flush_obsolete_entries();
4424   }
4425 
4426   increment_class_counter(the_class);
4427 
4428   if (EventClassRedefinition::is_enabled()) {
4429     EventClassRedefinition event;
4430     event.set_classModificationCount(java_lang_Class::classRedefinedCount(the_class->java_mirror()));
4431     event.set_redefinedClass(the_class);
4432     event.set_redefinitionId(_id);
4433     event.commit();
4434   }
4435 
4436   {
4437     ResourceMark rm(current);
4438     // increment the classRedefinedCount field in the_class and in any
4439     // direct and indirect subclasses of the_class
4440     log_info(redefine, class, load)
4441       ("redefined name=%s, count=%d (avail_mem=" UINT64_FORMAT "K)",
4442        the_class->external_name(), java_lang_Class::classRedefinedCount(the_class->java_mirror()), os::available_memory() >> 10);
4443     Events::log_redefinition(current, "redefined class name=%s, count=%d",
4444                              the_class->external_name(),
4445                              java_lang_Class::classRedefinedCount(the_class->java_mirror()));
4446 
4447   }
4448   _timer_rsc_phase2.stop();
4449 
4450 } // end redefine_single_class()
4451 
4452 
4453 // Increment the classRedefinedCount field in the specific InstanceKlass
4454 // and in all direct and indirect subclasses.
4455 void VM_RedefineClasses::increment_class_counter(InstanceKlass* ik) {
4456   for (ClassHierarchyIterator iter(ik); !iter.done(); iter.next()) {
4457     // Only update instanceKlasses
4458     Klass* sub = iter.klass();
4459     if (sub->is_instance_klass()) {
4460       oop class_mirror = InstanceKlass::cast(sub)->java_mirror();
4461       Klass* class_oop = java_lang_Class::as_Klass(class_mirror);
4462       int new_count = java_lang_Class::classRedefinedCount(class_mirror) + 1;
4463       java_lang_Class::set_classRedefinedCount(class_mirror, new_count);
4464 
4465       if (class_oop != _the_class) {
4466         // _the_class count is printed at end of redefine_single_class()
4467         log_debug(redefine, class, subclass)("updated count in subclass=%s to %d", ik->external_name(), new_count);
4468       }
4469     }
4470   }
4471 }
4472 
4473 void VM_RedefineClasses::CheckClass::do_klass(Klass* k) {
4474   bool no_old_methods = true;  // be optimistic
4475 
4476   // Both array and instance classes have vtables.
4477   // a vtable should never contain old or obsolete methods
4478   ResourceMark rm(_thread);
4479   if (k->vtable_length() > 0 &&
4480       !k->vtable().check_no_old_or_obsolete_entries()) {
4481     if (log_is_enabled(Trace, redefine, class, obsolete, metadata)) {
4482       log_trace(redefine, class, obsolete, metadata)
4483         ("klassVtable::check_no_old_or_obsolete_entries failure -- OLD or OBSOLETE method found -- class: %s",
4484          k->signature_name());
4485       k->vtable().dump_vtable();
4486     }
4487     no_old_methods = false;
4488   }
4489 
4490   if (k->is_instance_klass()) {
4491     HandleMark hm(_thread);
4492     InstanceKlass *ik = InstanceKlass::cast(k);
4493 
4494     // an itable should never contain old or obsolete methods
4495     if (ik->itable_length() > 0 &&
4496         !ik->itable().check_no_old_or_obsolete_entries()) {
4497       if (log_is_enabled(Trace, redefine, class, obsolete, metadata)) {
4498         log_trace(redefine, class, obsolete, metadata)
4499           ("klassItable::check_no_old_or_obsolete_entries failure -- OLD or OBSOLETE method found -- class: %s",
4500            ik->signature_name());
4501         ik->itable().dump_itable();
4502       }
4503       no_old_methods = false;
4504     }
4505 
4506     // the constant pool cache should never contain non-deleted old or obsolete methods
4507     if (ik->constants() != nullptr &&
4508         ik->constants()->cache() != nullptr &&
4509         !ik->constants()->cache()->check_no_old_or_obsolete_entries()) {
4510       if (log_is_enabled(Trace, redefine, class, obsolete, metadata)) {
4511         log_trace(redefine, class, obsolete, metadata)
4512           ("cp-cache::check_no_old_or_obsolete_entries failure -- OLD or OBSOLETE method found -- class: %s",
4513            ik->signature_name());
4514         ik->constants()->cache()->dump_cache();
4515       }
4516       no_old_methods = false;
4517     }
4518   }
4519 
4520   // print and fail guarantee if old methods are found.
4521   if (!no_old_methods) {
4522     if (log_is_enabled(Trace, redefine, class, obsolete, metadata)) {
4523       dump_methods();
4524     } else {
4525       log_trace(redefine, class)("Use the '-Xlog:redefine+class*:' option "
4526         "to see more info about the following guarantee() failure.");
4527     }
4528     guarantee(false, "OLD and/or OBSOLETE method(s) found");
4529   }
4530 }
4531 
4532 u8 VM_RedefineClasses::next_id() {
4533   while (true) {
4534     u8 id = _id_counter;
4535     u8 next_id = id + 1;
4536     u8 result = Atomic::cmpxchg(&_id_counter, id, next_id);
4537     if (result == id) {
4538       return next_id;
4539     }
4540   }
4541 }
4542 
4543 void VM_RedefineClasses::dump_methods() {
4544   int j;
4545   log_trace(redefine, class, dump)("_old_methods --");
4546   for (j = 0; j < _old_methods->length(); ++j) {
4547     LogStreamHandle(Trace, redefine, class, dump) log_stream;
4548     Method* m = _old_methods->at(j);
4549     log_stream.print("%4d  (%5d)  ", j, m->vtable_index());
4550     m->access_flags().print_on(&log_stream);
4551     log_stream.print(" --  ");
4552     m->print_name(&log_stream);
4553     log_stream.cr();
4554   }
4555   log_trace(redefine, class, dump)("_new_methods --");
4556   for (j = 0; j < _new_methods->length(); ++j) {
4557     LogStreamHandle(Trace, redefine, class, dump) log_stream;
4558     Method* m = _new_methods->at(j);
4559     log_stream.print("%4d  (%5d)  ", j, m->vtable_index());
4560     m->access_flags().print_on(&log_stream);
4561     log_stream.print(" --  ");
4562     m->print_name(&log_stream);
4563     log_stream.cr();
4564   }
4565   log_trace(redefine, class, dump)("_matching_methods --");
4566   for (j = 0; j < _matching_methods_length; ++j) {
4567     LogStreamHandle(Trace, redefine, class, dump) log_stream;
4568     Method* m = _matching_old_methods[j];
4569     log_stream.print("%4d  (%5d)  ", j, m->vtable_index());
4570     m->access_flags().print_on(&log_stream);
4571     log_stream.print(" --  ");
4572     m->print_name();
4573     log_stream.cr();
4574 
4575     m = _matching_new_methods[j];
4576     log_stream.print("      (%5d)  ", m->vtable_index());
4577     m->access_flags().print_on(&log_stream);
4578     log_stream.cr();
4579   }
4580   log_trace(redefine, class, dump)("_deleted_methods --");
4581   for (j = 0; j < _deleted_methods_length; ++j) {
4582     LogStreamHandle(Trace, redefine, class, dump) log_stream;
4583     Method* m = _deleted_methods[j];
4584     log_stream.print("%4d  (%5d)  ", j, m->vtable_index());
4585     m->access_flags().print_on(&log_stream);
4586     log_stream.print(" --  ");
4587     m->print_name(&log_stream);
4588     log_stream.cr();
4589   }
4590   log_trace(redefine, class, dump)("_added_methods --");
4591   for (j = 0; j < _added_methods_length; ++j) {
4592     LogStreamHandle(Trace, redefine, class, dump) log_stream;
4593     Method* m = _added_methods[j];
4594     log_stream.print("%4d  (%5d)  ", j, m->vtable_index());
4595     m->access_flags().print_on(&log_stream);
4596     log_stream.print(" --  ");
4597     m->print_name(&log_stream);
4598     log_stream.cr();
4599   }
4600 }
4601 
4602 void VM_RedefineClasses::print_on_error(outputStream* st) const {
4603   VM_Operation::print_on_error(st);
4604   if (_the_class != nullptr) {
4605     ResourceMark rm;
4606     st->print_cr(", redefining class %s", _the_class->external_name());
4607   }
4608 }