1 /*
   2  * Copyright (c) 2003, 2023, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   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/oop.inline.hpp"
  52 #include "oops/recordComponent.hpp"
  53 #include "prims/jvmtiImpl.hpp"
  54 #include "prims/jvmtiRedefineClasses.hpp"
  55 #include "prims/jvmtiThreadState.inline.hpp"
  56 #include "prims/resolvedMethodTable.hpp"
  57 #include "prims/methodComparator.hpp"
  58 #include "runtime/atomic.hpp"
  59 #include "runtime/deoptimization.hpp"
  60 #include "runtime/handles.inline.hpp"
  61 #include "runtime/jniHandles.inline.hpp"
  62 #include "runtime/relocator.hpp"
  63 #include "runtime/safepointVerifiers.hpp"
  64 #include "utilities/bitMap.inline.hpp"
  65 #include "utilities/events.hpp"
  66 
  67 Array<Method*>* VM_RedefineClasses::_old_methods = nullptr;
  68 Array<Method*>* VM_RedefineClasses::_new_methods = nullptr;
  69 Method**  VM_RedefineClasses::_matching_old_methods = nullptr;
  70 Method**  VM_RedefineClasses::_matching_new_methods = nullptr;
  71 Method**  VM_RedefineClasses::_deleted_methods      = nullptr;
  72 Method**  VM_RedefineClasses::_added_methods        = nullptr;
  73 int       VM_RedefineClasses::_matching_methods_length = 0;
  74 int       VM_RedefineClasses::_deleted_methods_length  = 0;
  75 int       VM_RedefineClasses::_added_methods_length    = 0;
  76 
  77 // This flag is global as the constructor does not reset it:
  78 bool      VM_RedefineClasses::_has_redefined_Object = false;
  79 u8        VM_RedefineClasses::_id_counter = 0;
  80 
  81 VM_RedefineClasses::VM_RedefineClasses(jint class_count,
  82                                        const jvmtiClassDefinition *class_defs,
  83                                        JvmtiClassLoadKind class_load_kind) {
  84   _class_count = class_count;
  85   _class_defs = class_defs;
  86   _class_load_kind = class_load_kind;
  87   _any_class_has_resolved_methods = false;
  88   _res = JVMTI_ERROR_NONE;
  89   _the_class = nullptr;
  90   _id = next_id();
  91 }
  92 
  93 static inline InstanceKlass* get_ik(jclass def) {
  94   oop mirror = JNIHandles::resolve_non_null(def);
  95   return InstanceKlass::cast(java_lang_Class::as_Klass(mirror));
  96 }
  97 
  98 // If any of the classes are being redefined, wait
  99 // Parallel constant pool merging leads to indeterminate constant pools.
 100 void VM_RedefineClasses::lock_classes() {
 101   JvmtiThreadState *state = JvmtiThreadState::state_for(JavaThread::current());
 102   GrowableArray<Klass*>* redef_classes = state->get_classes_being_redefined();
 103 
 104   MonitorLocker ml(RedefineClasses_lock);
 105 
 106   if (redef_classes == nullptr) {
 107     redef_classes = new (mtClass) GrowableArray<Klass*>(1, mtClass);
 108     state->set_classes_being_redefined(redef_classes);
 109   }
 110 
 111   bool has_redefined;
 112   do {
 113     has_redefined = false;
 114     // Go through classes each time until none are being redefined. Skip
 115     // the ones that are being redefined by this thread currently. Class file
 116     // load hook event may trigger new class redefine when we are redefining
 117     // a class (after lock_classes()).
 118     for (int i = 0; i < _class_count; i++) {
 119       InstanceKlass* ik = get_ik(_class_defs[i].klass);
 120       // Check if we are currently redefining the class in this thread already.
 121       if (redef_classes->contains(ik)) {
 122         assert(ik->is_being_redefined(), "sanity");
 123       } else {
 124         if (ik->is_being_redefined()) {
 125           ml.wait();
 126           has_redefined = true;
 127           break;  // for loop
 128         }
 129       }
 130     }
 131   } while (has_redefined);
 132 
 133   for (int i = 0; i < _class_count; i++) {
 134     InstanceKlass* ik = get_ik(_class_defs[i].klass);
 135     redef_classes->push(ik); // Add to the _classes_being_redefined list
 136     ik->set_is_being_redefined(true);
 137   }
 138   ml.notify_all();
 139 }
 140 
 141 void VM_RedefineClasses::unlock_classes() {
 142   JvmtiThreadState *state = JvmtiThreadState::state_for(JavaThread::current());
 143   GrowableArray<Klass*>* redef_classes = state->get_classes_being_redefined();
 144   assert(redef_classes != nullptr, "_classes_being_redefined is not allocated");
 145 
 146   MonitorLocker ml(RedefineClasses_lock);
 147 
 148   for (int i = _class_count - 1; i >= 0; i--) {
 149     InstanceKlass* def_ik = get_ik(_class_defs[i].klass);
 150     if (redef_classes->length() > 0) {
 151       // Remove the class from _classes_being_redefined list
 152       Klass* k = redef_classes->pop();
 153       assert(def_ik == k, "unlocking wrong class");
 154     }
 155     assert(def_ik->is_being_redefined(),
 156            "should be being redefined to get here");
 157 
 158     // Unlock after we finish all redefines for this class within
 159     // the thread. Same class can be pushed to the list multiple
 160     // times (not more than once by each recursive redefinition).
 161     if (!redef_classes->contains(def_ik)) {
 162       def_ik->set_is_being_redefined(false);
 163     }
 164   }
 165   ml.notify_all();
 166 }
 167 
 168 bool VM_RedefineClasses::doit_prologue() {
 169   if (_class_count == 0) {
 170     _res = JVMTI_ERROR_NONE;
 171     return false;
 172   }
 173   if (_class_defs == nullptr) {
 174     _res = JVMTI_ERROR_NULL_POINTER;
 175     return false;
 176   }
 177 
 178   for (int i = 0; i < _class_count; i++) {
 179     if (_class_defs[i].klass == nullptr) {
 180       _res = JVMTI_ERROR_INVALID_CLASS;
 181       return false;
 182     }
 183     if (_class_defs[i].class_byte_count == 0) {
 184       _res = JVMTI_ERROR_INVALID_CLASS_FORMAT;
 185       return false;
 186     }
 187     if (_class_defs[i].class_bytes == nullptr) {
 188       _res = JVMTI_ERROR_NULL_POINTER;
 189       return false;
 190     }
 191 
 192     oop mirror = JNIHandles::resolve_non_null(_class_defs[i].klass);
 193     // classes for primitives, arrays, and hidden classes
 194     // cannot be redefined.
 195     if (!is_modifiable_class(mirror)) {
 196       _res = JVMTI_ERROR_UNMODIFIABLE_CLASS;
 197       return false;
 198     }
 199   }
 200 
 201   // Start timer after all the sanity checks; not quite accurate, but
 202   // better than adding a bunch of stop() calls.
 203   if (log_is_enabled(Info, redefine, class, timer)) {
 204     _timer_vm_op_prologue.start();
 205   }
 206 
 207   lock_classes();
 208   // We first load new class versions in the prologue, because somewhere down the
 209   // call chain it is required that the current thread is a Java thread.
 210   _res = load_new_class_versions();
 211   if (_res != JVMTI_ERROR_NONE) {
 212     // free any successfully created classes, since none are redefined
 213     for (int i = 0; i < _class_count; i++) {
 214       if (_scratch_classes[i] != nullptr) {
 215         ClassLoaderData* cld = _scratch_classes[i]->class_loader_data();
 216         // Free the memory for this class at class unloading time.  Not before
 217         // because CMS might think this is still live.
 218         InstanceKlass* ik = get_ik(_class_defs[i].klass);
 219         if (ik->get_cached_class_file() == _scratch_classes[i]->get_cached_class_file()) {
 220           // Don't double-free cached_class_file copied from the original class if error.
 221           _scratch_classes[i]->set_cached_class_file(nullptr);
 222         }
 223         cld->add_to_deallocate_list(InstanceKlass::cast(_scratch_classes[i]));
 224       }
 225     }
 226     // Free os::malloc allocated memory in load_new_class_version.
 227     os::free(_scratch_classes);
 228     _timer_vm_op_prologue.stop();
 229     unlock_classes();
 230     return false;
 231   }
 232 
 233   _timer_vm_op_prologue.stop();
 234   return true;
 235 }
 236 
 237 void VM_RedefineClasses::doit() {
 238   Thread* current = Thread::current();
 239 
 240   if (log_is_enabled(Info, redefine, class, timer)) {
 241     _timer_vm_op_doit.start();
 242   }
 243 
 244 #if INCLUDE_CDS
 245   if (UseSharedSpaces) {
 246     // Sharing is enabled so we remap the shared readonly space to
 247     // shared readwrite, private just in case we need to redefine
 248     // a shared class. We do the remap during the doit() phase of
 249     // the safepoint to be safer.
 250     if (!MetaspaceShared::remap_shared_readonly_as_readwrite()) {
 251       log_info(redefine, class, load)("failed to remap shared readonly space to readwrite, private");
 252       _res = JVMTI_ERROR_INTERNAL;
 253       _timer_vm_op_doit.stop();
 254       return;
 255     }
 256   }
 257 #endif
 258 
 259   // Mark methods seen on stack and everywhere else so old methods are not
 260   // cleaned up if they're on the stack.
 261   MetadataOnStackMark md_on_stack(/*walk_all_metadata*/true, /*redefinition_walk*/true);
 262   HandleMark hm(current);   // make sure any handles created are deleted
 263                             // before the stack walk again.
 264 
 265   for (int i = 0; i < _class_count; i++) {
 266     redefine_single_class(current, _class_defs[i].klass, _scratch_classes[i]);
 267   }
 268 
 269   // Flush all compiled code that depends on the classes redefined.
 270   flush_dependent_code();
 271 
 272   // Adjust constantpool caches and vtables for all classes
 273   // that reference methods of the evolved classes.
 274   // Have to do this after all classes are redefined and all methods that
 275   // are redefined are marked as old.
 276   AdjustAndCleanMetadata adjust_and_clean_metadata(current);
 277   ClassLoaderDataGraph::classes_do(&adjust_and_clean_metadata);
 278 
 279   // JSR-292 support
 280   if (_any_class_has_resolved_methods) {
 281     bool trace_name_printed = false;
 282     ResolvedMethodTable::adjust_method_entries(&trace_name_printed);
 283   }
 284 
 285   // Increment flag indicating that some invariants are no longer true.
 286   // See jvmtiExport.hpp for detailed explanation.
 287   JvmtiExport::increment_redefinition_count();
 288 
 289   // check_class() is optionally called for product bits, but is
 290   // always called for non-product bits.
 291 #ifdef PRODUCT
 292   if (log_is_enabled(Trace, redefine, class, obsolete, metadata)) {
 293 #endif
 294     log_trace(redefine, class, obsolete, metadata)("calling check_class");
 295     CheckClass check_class(current);
 296     ClassLoaderDataGraph::classes_do(&check_class);
 297 #ifdef PRODUCT
 298   }
 299 #endif
 300 
 301   // Clean up any metadata now unreferenced while MetadataOnStackMark is set.
 302   ClassLoaderDataGraph::clean_deallocate_lists(false);
 303 
 304   _timer_vm_op_doit.stop();
 305 }
 306 
 307 void VM_RedefineClasses::doit_epilogue() {
 308   unlock_classes();
 309 
 310   // Free os::malloc allocated memory.
 311   os::free(_scratch_classes);
 312 
 313   // Reset the_class to null for error printing.
 314   _the_class = nullptr;
 315 
 316   if (log_is_enabled(Info, redefine, class, timer)) {
 317     // Used to have separate timers for "doit" and "all", but the timer
 318     // overhead skewed the measurements.
 319     julong doit_time = _timer_vm_op_doit.milliseconds();
 320     julong all_time = _timer_vm_op_prologue.milliseconds() + doit_time;
 321 
 322     log_info(redefine, class, timer)
 323       ("vm_op: all=" JULONG_FORMAT "  prologue=" JULONG_FORMAT "  doit=" JULONG_FORMAT,
 324        all_time, (julong)_timer_vm_op_prologue.milliseconds(), doit_time);
 325     log_info(redefine, class, timer)
 326       ("redefine_single_class: phase1=" JULONG_FORMAT "  phase2=" JULONG_FORMAT,
 327        (julong)_timer_rsc_phase1.milliseconds(), (julong)_timer_rsc_phase2.milliseconds());
 328   }
 329 }
 330 
 331 bool VM_RedefineClasses::is_modifiable_class(oop klass_mirror) {
 332   // classes for primitives cannot be redefined
 333   if (java_lang_Class::is_primitive(klass_mirror)) {
 334     return false;
 335   }
 336   Klass* k = java_lang_Class::as_Klass(klass_mirror);
 337   // classes for arrays cannot be redefined
 338   if (k == nullptr || !k->is_instance_klass()) {
 339     return false;
 340   }
 341 
 342   // Cannot redefine or retransform a hidden class.
 343   if (InstanceKlass::cast(k)->is_hidden()) {
 344     return false;
 345   }
 346   if (InstanceKlass::cast(k) == vmClasses::Continuation_klass()) {
 347     // Don't redefine Continuation class. See 8302779.
 348     return false;
 349   }
 350   return true;
 351 }
 352 
 353 // Append the current entry at scratch_i in scratch_cp to *merge_cp_p
 354 // where the end of *merge_cp_p is specified by *merge_cp_length_p. For
 355 // direct CP entries, there is just the current entry to append. For
 356 // indirect and double-indirect CP entries, there are zero or more
 357 // referenced CP entries along with the current entry to append.
 358 // Indirect and double-indirect CP entries are handled by recursive
 359 // calls to append_entry() as needed. The referenced CP entries are
 360 // always appended to *merge_cp_p before the referee CP entry. These
 361 // referenced CP entries may already exist in *merge_cp_p in which case
 362 // there is nothing extra to append and only the current entry is
 363 // appended.
 364 void VM_RedefineClasses::append_entry(const constantPoolHandle& scratch_cp,
 365        int scratch_i, constantPoolHandle *merge_cp_p, int *merge_cp_length_p) {
 366 
 367   // append is different depending on entry tag type
 368   switch (scratch_cp->tag_at(scratch_i).value()) {
 369 
 370     // The old verifier is implemented outside the VM. It loads classes,
 371     // but does not resolve constant pool entries directly so we never
 372     // see Class entries here with the old verifier. Similarly the old
 373     // verifier does not like Class entries in the input constant pool.
 374     // The split-verifier is implemented in the VM so it can optionally
 375     // and directly resolve constant pool entries to load classes. The
 376     // split-verifier can accept either Class entries or UnresolvedClass
 377     // entries in the input constant pool. We revert the appended copy
 378     // back to UnresolvedClass so that either verifier will be happy
 379     // with the constant pool entry.
 380     //
 381     // this is an indirect CP entry so it needs special handling
 382     case JVM_CONSTANT_Class:
 383     case JVM_CONSTANT_UnresolvedClass:
 384     {
 385       int name_i = scratch_cp->klass_name_index_at(scratch_i);
 386       int new_name_i = find_or_append_indirect_entry(scratch_cp, name_i, merge_cp_p,
 387                                                      merge_cp_length_p);
 388 
 389       if (new_name_i != name_i) {
 390         log_trace(redefine, class, constantpool)
 391           ("Class entry@%d name_index change: %d to %d",
 392            *merge_cp_length_p, name_i, new_name_i);
 393       }
 394 
 395       (*merge_cp_p)->temp_unresolved_klass_at_put(*merge_cp_length_p, new_name_i);
 396       if (scratch_i != *merge_cp_length_p) {
 397         // The new entry in *merge_cp_p is at a different index than
 398         // the new entry in scratch_cp so we need to map the index values.
 399         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 400       }
 401       (*merge_cp_length_p)++;
 402     } break;
 403 
 404     // these are direct CP entries so they can be directly appended,
 405     // but double and long take two constant pool entries
 406     case JVM_CONSTANT_Double:  // fall through
 407     case JVM_CONSTANT_Long:
 408     {
 409       ConstantPool::copy_entry_to(scratch_cp, scratch_i, *merge_cp_p, *merge_cp_length_p);
 410 
 411       if (scratch_i != *merge_cp_length_p) {
 412         // The new entry in *merge_cp_p is at a different index than
 413         // the new entry in scratch_cp so we need to map the index values.
 414         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 415       }
 416       (*merge_cp_length_p) += 2;
 417     } break;
 418 
 419     // these are direct CP entries so they can be directly appended
 420     case JVM_CONSTANT_Float:   // fall through
 421     case JVM_CONSTANT_Integer: // fall through
 422     case JVM_CONSTANT_Utf8:    // fall through
 423 
 424     // This was an indirect CP entry, but it has been changed into
 425     // Symbol*s so this entry can be directly appended.
 426     case JVM_CONSTANT_String:      // fall through
 427     {
 428       ConstantPool::copy_entry_to(scratch_cp, scratch_i, *merge_cp_p, *merge_cp_length_p);
 429 
 430       if (scratch_i != *merge_cp_length_p) {
 431         // The new entry in *merge_cp_p is at a different index than
 432         // the new entry in scratch_cp so we need to map the index values.
 433         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 434       }
 435       (*merge_cp_length_p)++;
 436     } break;
 437 
 438     // this is an indirect CP entry so it needs special handling
 439     case JVM_CONSTANT_NameAndType:
 440     {
 441       int name_ref_i = scratch_cp->name_ref_index_at(scratch_i);
 442       int new_name_ref_i = find_or_append_indirect_entry(scratch_cp, name_ref_i, merge_cp_p,
 443                                                          merge_cp_length_p);
 444 
 445       int signature_ref_i = scratch_cp->signature_ref_index_at(scratch_i);
 446       int new_signature_ref_i = find_or_append_indirect_entry(scratch_cp, signature_ref_i,
 447                                                               merge_cp_p, merge_cp_length_p);
 448 
 449       // If the referenced entries already exist in *merge_cp_p, then
 450       // both new_name_ref_i and new_signature_ref_i will both be 0.
 451       // In that case, all we are appending is the current entry.
 452       if (new_name_ref_i != name_ref_i) {
 453         log_trace(redefine, class, constantpool)
 454           ("NameAndType entry@%d name_ref_index change: %d to %d",
 455            *merge_cp_length_p, name_ref_i, new_name_ref_i);
 456       }
 457       if (new_signature_ref_i != signature_ref_i) {
 458         log_trace(redefine, class, constantpool)
 459           ("NameAndType entry@%d signature_ref_index change: %d to %d",
 460            *merge_cp_length_p, signature_ref_i, new_signature_ref_i);
 461       }
 462 
 463       (*merge_cp_p)->name_and_type_at_put(*merge_cp_length_p,
 464         new_name_ref_i, new_signature_ref_i);
 465       if (scratch_i != *merge_cp_length_p) {
 466         // The new entry in *merge_cp_p is at a different index than
 467         // the new entry in scratch_cp so we need to map the index values.
 468         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 469       }
 470       (*merge_cp_length_p)++;
 471     } break;
 472 
 473     // this is a double-indirect CP entry so it needs special handling
 474     case JVM_CONSTANT_Fieldref:           // fall through
 475     case JVM_CONSTANT_InterfaceMethodref: // fall through
 476     case JVM_CONSTANT_Methodref:
 477     {
 478       int klass_ref_i = scratch_cp->uncached_klass_ref_index_at(scratch_i);
 479       int new_klass_ref_i = find_or_append_indirect_entry(scratch_cp, klass_ref_i,
 480                                                           merge_cp_p, merge_cp_length_p);
 481 
 482       int name_and_type_ref_i = scratch_cp->uncached_name_and_type_ref_index_at(scratch_i);
 483       int new_name_and_type_ref_i = find_or_append_indirect_entry(scratch_cp, name_and_type_ref_i,
 484                                                           merge_cp_p, merge_cp_length_p);
 485 
 486       const char *entry_name = nullptr;
 487       switch (scratch_cp->tag_at(scratch_i).value()) {
 488       case JVM_CONSTANT_Fieldref:
 489         entry_name = "Fieldref";
 490         (*merge_cp_p)->field_at_put(*merge_cp_length_p, new_klass_ref_i,
 491           new_name_and_type_ref_i);
 492         break;
 493       case JVM_CONSTANT_InterfaceMethodref:
 494         entry_name = "IFMethodref";
 495         (*merge_cp_p)->interface_method_at_put(*merge_cp_length_p,
 496           new_klass_ref_i, new_name_and_type_ref_i);
 497         break;
 498       case JVM_CONSTANT_Methodref:
 499         entry_name = "Methodref";
 500         (*merge_cp_p)->method_at_put(*merge_cp_length_p, new_klass_ref_i,
 501           new_name_and_type_ref_i);
 502         break;
 503       default:
 504         guarantee(false, "bad switch");
 505         break;
 506       }
 507 
 508       if (klass_ref_i != new_klass_ref_i) {
 509         log_trace(redefine, class, constantpool)
 510           ("%s entry@%d class_index changed: %d to %d", entry_name, *merge_cp_length_p, klass_ref_i, new_klass_ref_i);
 511       }
 512       if (name_and_type_ref_i != new_name_and_type_ref_i) {
 513         log_trace(redefine, class, constantpool)
 514           ("%s entry@%d name_and_type_index changed: %d to %d",
 515            entry_name, *merge_cp_length_p, name_and_type_ref_i, new_name_and_type_ref_i);
 516       }
 517 
 518       if (scratch_i != *merge_cp_length_p) {
 519         // The new entry in *merge_cp_p is at a different index than
 520         // the new entry in scratch_cp so we need to map the index values.
 521         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 522       }
 523       (*merge_cp_length_p)++;
 524     } break;
 525 
 526     // this is an indirect CP entry so it needs special handling
 527     case JVM_CONSTANT_MethodType:
 528     {
 529       int ref_i = scratch_cp->method_type_index_at(scratch_i);
 530       int new_ref_i = find_or_append_indirect_entry(scratch_cp, ref_i, merge_cp_p,
 531                                                     merge_cp_length_p);
 532       if (new_ref_i != ref_i) {
 533         log_trace(redefine, class, constantpool)
 534           ("MethodType entry@%d ref_index change: %d to %d", *merge_cp_length_p, ref_i, new_ref_i);
 535       }
 536       (*merge_cp_p)->method_type_index_at_put(*merge_cp_length_p, new_ref_i);
 537       if (scratch_i != *merge_cp_length_p) {
 538         // The new entry in *merge_cp_p is at a different index than
 539         // the new entry in scratch_cp so we need to map the index values.
 540         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 541       }
 542       (*merge_cp_length_p)++;
 543     } break;
 544 
 545     // this is an indirect CP entry so it needs special handling
 546     case JVM_CONSTANT_MethodHandle:
 547     {
 548       int ref_kind = scratch_cp->method_handle_ref_kind_at(scratch_i);
 549       int ref_i = scratch_cp->method_handle_index_at(scratch_i);
 550       int new_ref_i = find_or_append_indirect_entry(scratch_cp, ref_i, merge_cp_p,
 551                                                     merge_cp_length_p);
 552       if (new_ref_i != ref_i) {
 553         log_trace(redefine, class, constantpool)
 554           ("MethodHandle entry@%d ref_index change: %d to %d", *merge_cp_length_p, ref_i, new_ref_i);
 555       }
 556       (*merge_cp_p)->method_handle_index_at_put(*merge_cp_length_p, ref_kind, new_ref_i);
 557       if (scratch_i != *merge_cp_length_p) {
 558         // The new entry in *merge_cp_p is at a different index than
 559         // the new entry in scratch_cp so we need to map the index values.
 560         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 561       }
 562       (*merge_cp_length_p)++;
 563     } break;
 564 
 565     // this is an indirect CP entry so it needs special handling
 566     case JVM_CONSTANT_Dynamic:  // fall through
 567     case JVM_CONSTANT_InvokeDynamic:
 568     {
 569       // Index of the bootstrap specifier in the operands array
 570       int old_bs_i = scratch_cp->bootstrap_methods_attribute_index(scratch_i);
 571       int new_bs_i = find_or_append_operand(scratch_cp, old_bs_i, merge_cp_p,
 572                                             merge_cp_length_p);
 573       // The bootstrap method NameAndType_info index
 574       int old_ref_i = scratch_cp->bootstrap_name_and_type_ref_index_at(scratch_i);
 575       int new_ref_i = find_or_append_indirect_entry(scratch_cp, old_ref_i, merge_cp_p,
 576                                                     merge_cp_length_p);
 577       if (new_bs_i != old_bs_i) {
 578         log_trace(redefine, class, constantpool)
 579           ("Dynamic entry@%d bootstrap_method_attr_index change: %d to %d",
 580            *merge_cp_length_p, old_bs_i, new_bs_i);
 581       }
 582       if (new_ref_i != old_ref_i) {
 583         log_trace(redefine, class, constantpool)
 584           ("Dynamic entry@%d name_and_type_index change: %d to %d", *merge_cp_length_p, old_ref_i, new_ref_i);
 585       }
 586 
 587       if (scratch_cp->tag_at(scratch_i).is_dynamic_constant())
 588         (*merge_cp_p)->dynamic_constant_at_put(*merge_cp_length_p, new_bs_i, new_ref_i);
 589       else
 590         (*merge_cp_p)->invoke_dynamic_at_put(*merge_cp_length_p, new_bs_i, new_ref_i);
 591       if (scratch_i != *merge_cp_length_p) {
 592         // The new entry in *merge_cp_p is at a different index than
 593         // the new entry in scratch_cp so we need to map the index values.
 594         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 595       }
 596       (*merge_cp_length_p)++;
 597     } break;
 598 
 599     // At this stage, Class or UnresolvedClass could be in scratch_cp, but not
 600     // ClassIndex
 601     case JVM_CONSTANT_ClassIndex: // fall through
 602 
 603     // Invalid is used as the tag for the second constant pool entry
 604     // occupied by JVM_CONSTANT_Double or JVM_CONSTANT_Long. It should
 605     // not be seen by itself.
 606     case JVM_CONSTANT_Invalid: // fall through
 607 
 608     // At this stage, String could be here, but not StringIndex
 609     case JVM_CONSTANT_StringIndex: // fall through
 610 
 611     // At this stage JVM_CONSTANT_UnresolvedClassInError should not be here
 612     case JVM_CONSTANT_UnresolvedClassInError: // fall through
 613 
 614     default:
 615     {
 616       // leave a breadcrumb
 617       jbyte bad_value = scratch_cp->tag_at(scratch_i).value();
 618       ShouldNotReachHere();
 619     } break;
 620   } // end switch tag value
 621 } // end append_entry()
 622 
 623 
 624 int VM_RedefineClasses::find_or_append_indirect_entry(const constantPoolHandle& scratch_cp,
 625       int ref_i, constantPoolHandle *merge_cp_p, int *merge_cp_length_p) {
 626 
 627   int new_ref_i = ref_i;
 628   bool match = (ref_i < *merge_cp_length_p) &&
 629                scratch_cp->compare_entry_to(ref_i, *merge_cp_p, ref_i);
 630 
 631   if (!match) {
 632     // forward reference in *merge_cp_p or not a direct match
 633     int found_i = scratch_cp->find_matching_entry(ref_i, *merge_cp_p);
 634     if (found_i != 0) {
 635       guarantee(found_i != ref_i, "compare_entry_to() and find_matching_entry() do not agree");
 636       // Found a matching entry somewhere else in *merge_cp_p so just need a mapping entry.
 637       new_ref_i = found_i;
 638       map_index(scratch_cp, ref_i, found_i);
 639     } else {
 640       // no match found so we have to append this entry to *merge_cp_p
 641       append_entry(scratch_cp, ref_i, merge_cp_p, merge_cp_length_p);
 642       // The above call to append_entry() can only append one entry
 643       // so the post call query of *merge_cp_length_p is only for
 644       // the sake of consistency.
 645       new_ref_i = *merge_cp_length_p - 1;
 646     }
 647   }
 648 
 649   return new_ref_i;
 650 } // end find_or_append_indirect_entry()
 651 
 652 
 653 // Append a bootstrap specifier into the merge_cp operands that is semantically equal
 654 // to the scratch_cp operands bootstrap specifier passed by the old_bs_i index.
 655 // Recursively append new merge_cp entries referenced by the new bootstrap specifier.
 656 void VM_RedefineClasses::append_operand(const constantPoolHandle& scratch_cp, int old_bs_i,
 657        constantPoolHandle *merge_cp_p, int *merge_cp_length_p) {
 658 
 659   int old_ref_i = scratch_cp->operand_bootstrap_method_ref_index_at(old_bs_i);
 660   int new_ref_i = find_or_append_indirect_entry(scratch_cp, old_ref_i, merge_cp_p,
 661                                                 merge_cp_length_p);
 662   if (new_ref_i != old_ref_i) {
 663     log_trace(redefine, class, constantpool)
 664       ("operands entry@%d bootstrap method ref_index change: %d to %d", _operands_cur_length, old_ref_i, new_ref_i);
 665   }
 666 
 667   Array<u2>* merge_ops = (*merge_cp_p)->operands();
 668   int new_bs_i = _operands_cur_length;
 669   // We have _operands_cur_length == 0 when the merge_cp operands is empty yet.
 670   // However, the operand_offset_at(0) was set in the extend_operands() call.
 671   int new_base = (new_bs_i == 0) ? (*merge_cp_p)->operand_offset_at(0)
 672                                  : (*merge_cp_p)->operand_next_offset_at(new_bs_i - 1);
 673   int argc     = scratch_cp->operand_argument_count_at(old_bs_i);
 674 
 675   ConstantPool::operand_offset_at_put(merge_ops, _operands_cur_length, new_base);
 676   merge_ops->at_put(new_base++, new_ref_i);
 677   merge_ops->at_put(new_base++, argc);
 678 
 679   for (int i = 0; i < argc; i++) {
 680     int old_arg_ref_i = scratch_cp->operand_argument_index_at(old_bs_i, i);
 681     int new_arg_ref_i = find_or_append_indirect_entry(scratch_cp, old_arg_ref_i, merge_cp_p,
 682                                                       merge_cp_length_p);
 683     merge_ops->at_put(new_base++, new_arg_ref_i);
 684     if (new_arg_ref_i != old_arg_ref_i) {
 685       log_trace(redefine, class, constantpool)
 686         ("operands entry@%d bootstrap method argument ref_index change: %d to %d",
 687          _operands_cur_length, old_arg_ref_i, new_arg_ref_i);
 688     }
 689   }
 690   if (old_bs_i != _operands_cur_length) {
 691     // The bootstrap specifier in *merge_cp_p is at a different index than
 692     // that in scratch_cp so we need to map the index values.
 693     map_operand_index(old_bs_i, new_bs_i);
 694   }
 695   _operands_cur_length++;
 696 } // end append_operand()
 697 
 698 
 699 int VM_RedefineClasses::find_or_append_operand(const constantPoolHandle& scratch_cp,
 700       int old_bs_i, constantPoolHandle *merge_cp_p, int *merge_cp_length_p) {
 701 
 702   int new_bs_i = old_bs_i; // bootstrap specifier index
 703   bool match = (old_bs_i < _operands_cur_length) &&
 704                scratch_cp->compare_operand_to(old_bs_i, *merge_cp_p, old_bs_i);
 705 
 706   if (!match) {
 707     // forward reference in *merge_cp_p or not a direct match
 708     int found_i = scratch_cp->find_matching_operand(old_bs_i, *merge_cp_p,
 709                                                     _operands_cur_length);
 710     if (found_i != -1) {
 711       guarantee(found_i != old_bs_i, "compare_operand_to() and find_matching_operand() disagree");
 712       // found a matching operand somewhere else in *merge_cp_p so just need a mapping
 713       new_bs_i = found_i;
 714       map_operand_index(old_bs_i, found_i);
 715     } else {
 716       // no match found so we have to append this bootstrap specifier to *merge_cp_p
 717       append_operand(scratch_cp, old_bs_i, merge_cp_p, merge_cp_length_p);
 718       new_bs_i = _operands_cur_length - 1;
 719     }
 720   }
 721   return new_bs_i;
 722 } // end find_or_append_operand()
 723 
 724 
 725 void VM_RedefineClasses::finalize_operands_merge(const constantPoolHandle& merge_cp, TRAPS) {
 726   if (merge_cp->operands() == nullptr) {
 727     return;
 728   }
 729   // Shrink the merge_cp operands
 730   merge_cp->shrink_operands(_operands_cur_length, CHECK);
 731 
 732   if (log_is_enabled(Trace, redefine, class, constantpool)) {
 733     // don't want to loop unless we are tracing
 734     int count = 0;
 735     for (int i = 1; i < _operands_index_map_p->length(); i++) {
 736       int value = _operands_index_map_p->at(i);
 737       if (value != -1) {
 738         log_trace(redefine, class, constantpool)("operands_index_map[%d]: old=%d new=%d", count, i, value);
 739         count++;
 740       }
 741     }
 742   }
 743   // Clean-up
 744   _operands_index_map_p = nullptr;
 745   _operands_cur_length = 0;
 746   _operands_index_map_count = 0;
 747 } // end finalize_operands_merge()
 748 
 749 // Symbol* comparator for qsort
 750 // The caller must have an active ResourceMark.
 751 static int symcmp(const void* a, const void* b) {
 752   char* astr = (*(Symbol**)a)->as_C_string();
 753   char* bstr = (*(Symbol**)b)->as_C_string();
 754   return strcmp(astr, bstr);
 755 }
 756 
 757 // The caller must have an active ResourceMark.
 758 static jvmtiError check_attribute_arrays(const char* attr_name,
 759            InstanceKlass* the_class, InstanceKlass* scratch_class,
 760            Array<u2>* the_array, Array<u2>* scr_array) {
 761   bool the_array_exists = the_array != Universe::the_empty_short_array();
 762   bool scr_array_exists = scr_array != Universe::the_empty_short_array();
 763 
 764   int array_len = the_array->length();
 765   if (the_array_exists && scr_array_exists) {
 766     if (array_len != scr_array->length()) {
 767       log_trace(redefine, class)
 768         ("redefined class %s attribute change error: %s len=%d changed to len=%d",
 769          the_class->external_name(), attr_name, array_len, scr_array->length());
 770       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
 771     }
 772 
 773     // The order of entries in the attribute array is not specified so we
 774     // have to explicitly check for the same contents. We do this by copying
 775     // the referenced symbols into their own arrays, sorting them and then
 776     // comparing each element pair.
 777 
 778     Symbol** the_syms = NEW_RESOURCE_ARRAY_RETURN_NULL(Symbol*, array_len);
 779     Symbol** scr_syms = NEW_RESOURCE_ARRAY_RETURN_NULL(Symbol*, array_len);
 780 
 781     if (the_syms == nullptr || scr_syms == nullptr) {
 782       return JVMTI_ERROR_OUT_OF_MEMORY;
 783     }
 784 
 785     for (int i = 0; i < array_len; i++) {
 786       int the_cp_index = the_array->at(i);
 787       int scr_cp_index = scr_array->at(i);
 788       the_syms[i] = the_class->constants()->klass_name_at(the_cp_index);
 789       scr_syms[i] = scratch_class->constants()->klass_name_at(scr_cp_index);
 790     }
 791 
 792     qsort(the_syms, array_len, sizeof(Symbol*), symcmp);
 793     qsort(scr_syms, array_len, sizeof(Symbol*), symcmp);
 794 
 795     for (int i = 0; i < array_len; i++) {
 796       if (the_syms[i] != scr_syms[i]) {
 797         log_info(redefine, class)
 798           ("redefined class %s attribute change error: %s[%d]: %s changed to %s",
 799            the_class->external_name(), attr_name, i,
 800            the_syms[i]->as_C_string(), scr_syms[i]->as_C_string());
 801         return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
 802       }
 803     }
 804   } else if (the_array_exists ^ scr_array_exists) {
 805     const char* action_str = (the_array_exists) ? "removed" : "added";
 806     log_info(redefine, class)
 807       ("redefined class %s attribute change error: %s attribute %s",
 808        the_class->external_name(), attr_name, action_str);
 809     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
 810   }
 811   return JVMTI_ERROR_NONE;
 812 }
 813 
 814 static jvmtiError check_nest_attributes(InstanceKlass* the_class,
 815                                         InstanceKlass* scratch_class) {
 816   // Check whether the class NestHost attribute has been changed.
 817   Thread* thread = Thread::current();
 818   ResourceMark rm(thread);
 819   u2 the_nest_host_idx = the_class->nest_host_index();
 820   u2 scr_nest_host_idx = scratch_class->nest_host_index();
 821 
 822   if (the_nest_host_idx != 0 && scr_nest_host_idx != 0) {
 823     Symbol* the_sym = the_class->constants()->klass_name_at(the_nest_host_idx);
 824     Symbol* scr_sym = scratch_class->constants()->klass_name_at(scr_nest_host_idx);
 825     if (the_sym != scr_sym) {
 826       log_info(redefine, class, nestmates)
 827         ("redefined class %s attribute change error: NestHost class: %s replaced with: %s",
 828          the_class->external_name(), the_sym->as_C_string(), scr_sym->as_C_string());
 829       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
 830     }
 831   } else if ((the_nest_host_idx == 0) ^ (scr_nest_host_idx == 0)) {
 832     const char* action_str = (the_nest_host_idx != 0) ? "removed" : "added";
 833     log_info(redefine, class, nestmates)
 834       ("redefined class %s attribute change error: NestHost attribute %s",
 835        the_class->external_name(), action_str);
 836     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
 837   }
 838 
 839   // Check whether the class NestMembers attribute has been changed.
 840   return check_attribute_arrays("NestMembers",
 841                                 the_class, scratch_class,
 842                                 the_class->nest_members(),
 843                                 scratch_class->nest_members());
 844 }
 845 
 846 // Return an error status if the class Record attribute was changed.
 847 static jvmtiError check_record_attribute(InstanceKlass* the_class, InstanceKlass* scratch_class) {
 848   // Get lists of record components.
 849   Array<RecordComponent*>* the_record = the_class->record_components();
 850   Array<RecordComponent*>* scr_record = scratch_class->record_components();
 851   bool the_record_exists = the_record != nullptr;
 852   bool scr_record_exists = scr_record != nullptr;
 853 
 854   if (the_record_exists && scr_record_exists) {
 855     int the_num_components = the_record->length();
 856     int scr_num_components = scr_record->length();
 857     if (the_num_components != scr_num_components) {
 858       log_info(redefine, class, record)
 859         ("redefined class %s attribute change error: Record num_components=%d changed to num_components=%d",
 860          the_class->external_name(), the_num_components, scr_num_components);
 861       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
 862     }
 863 
 864     // Compare each field in each record component.
 865     ConstantPool* the_cp =  the_class->constants();
 866     ConstantPool* scr_cp =  scratch_class->constants();
 867     for (int x = 0; x < the_num_components; x++) {
 868       RecordComponent* the_component = the_record->at(x);
 869       RecordComponent* scr_component = scr_record->at(x);
 870       const Symbol* const the_name = the_cp->symbol_at(the_component->name_index());
 871       const Symbol* const scr_name = scr_cp->symbol_at(scr_component->name_index());
 872       const Symbol* const the_descr = the_cp->symbol_at(the_component->descriptor_index());
 873       const Symbol* const scr_descr = scr_cp->symbol_at(scr_component->descriptor_index());
 874       if (the_name != scr_name || the_descr != scr_descr) {
 875         log_info(redefine, class, record)
 876           ("redefined class %s attribute change error: Record name_index, descriptor_index, and/or attributes_count changed",
 877            the_class->external_name());
 878         return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
 879       }
 880 
 881       int the_gen_sig = the_component->generic_signature_index();
 882       int scr_gen_sig = scr_component->generic_signature_index();
 883       const Symbol* const the_gen_sig_sym = (the_gen_sig == 0 ? nullptr :
 884         the_cp->symbol_at(the_component->generic_signature_index()));
 885       const Symbol* const scr_gen_sig_sym = (scr_gen_sig == 0 ? nullptr :
 886         scr_cp->symbol_at(scr_component->generic_signature_index()));
 887       if (the_gen_sig_sym != scr_gen_sig_sym) {
 888         log_info(redefine, class, record)
 889           ("redefined class %s attribute change error: Record generic_signature attribute changed",
 890            the_class->external_name());
 891         return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
 892       }
 893 
 894       // It's okay if a record component's annotations were changed.
 895     }
 896 
 897   } else if (the_record_exists ^ scr_record_exists) {
 898     const char* action_str = (the_record_exists) ? "removed" : "added";
 899     log_info(redefine, class, record)
 900       ("redefined class %s attribute change error: Record attribute %s",
 901        the_class->external_name(), action_str);
 902     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
 903   }
 904 
 905   return JVMTI_ERROR_NONE;
 906 }
 907 
 908 
 909 static jvmtiError check_permitted_subclasses_attribute(InstanceKlass* the_class,
 910                                                        InstanceKlass* scratch_class) {
 911   Thread* thread = Thread::current();
 912   ResourceMark rm(thread);
 913 
 914   // Check whether the class PermittedSubclasses attribute has been changed.
 915   return check_attribute_arrays("PermittedSubclasses",
 916                                 the_class, scratch_class,
 917                                 the_class->permitted_subclasses(),
 918                                 scratch_class->permitted_subclasses());
 919 }
 920 
 921 static jvmtiError check_preload_attribute(InstanceKlass* the_class,
 922                                           InstanceKlass* scratch_class) {
 923   Thread* thread = Thread::current();
 924   ResourceMark rm(thread);
 925 
 926   // Check whether the class Preload attribute has been changed.
 927   return check_attribute_arrays("Preload",
 928                                 the_class, scratch_class,
 929                                 the_class->preload_classes(),
 930                                 scratch_class->preload_classes());
 931 }
 932 
 933 static bool can_add_or_delete(Method* m) {
 934       // Compatibility mode
 935   return (AllowRedefinitionToAddDeleteMethods &&
 936           (m->is_private() && (m->is_static() || m->is_final())));
 937 }
 938 
 939 jvmtiError VM_RedefineClasses::compare_and_normalize_class_versions(
 940              InstanceKlass* the_class,
 941              InstanceKlass* scratch_class) {
 942   int i;
 943 
 944   // Check superclasses, or rather their names, since superclasses themselves can be
 945   // requested to replace.
 946   // Check for null superclass first since this might be java.lang.Object
 947   if (the_class->super() != scratch_class->super() &&
 948       (the_class->super() == nullptr || scratch_class->super() == nullptr ||
 949        the_class->super()->name() !=
 950        scratch_class->super()->name())) {
 951     log_info(redefine, class, normalize)
 952       ("redefined class %s superclass change error: superclass changed from %s to %s.",
 953        the_class->external_name(),
 954        the_class->super() == nullptr ? "null" : the_class->super()->external_name(),
 955        scratch_class->super() == nullptr ? "null" : scratch_class->super()->external_name());
 956     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_HIERARCHY_CHANGED;
 957   }
 958 
 959   // Check if the number, names and order of directly implemented interfaces are the same.
 960   // I think in principle we should just check if the sets of names of directly implemented
 961   // interfaces are the same, i.e. the order of declaration (which, however, if changed in the
 962   // .java file, also changes in .class file) should not matter. However, comparing sets is
 963   // technically a bit more difficult, and, more importantly, I am not sure at present that the
 964   // order of interfaces does not matter on the implementation level, i.e. that the VM does not
 965   // rely on it somewhere.
 966   Array<InstanceKlass*>* k_interfaces = the_class->local_interfaces();
 967   Array<InstanceKlass*>* k_new_interfaces = scratch_class->local_interfaces();
 968   int n_intfs = k_interfaces->length();
 969   if (n_intfs != k_new_interfaces->length()) {
 970     log_info(redefine, class, normalize)
 971       ("redefined class %s interfaces change error: number of implemented interfaces changed from %d to %d.",
 972        the_class->external_name(), n_intfs, k_new_interfaces->length());
 973     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_HIERARCHY_CHANGED;
 974   }
 975   for (i = 0; i < n_intfs; i++) {
 976     if (k_interfaces->at(i)->name() !=
 977         k_new_interfaces->at(i)->name()) {
 978       log_info(redefine, class, normalize)
 979           ("redefined class %s interfaces change error: interface changed from %s to %s.",
 980            the_class->external_name(),
 981            k_interfaces->at(i)->external_name(), k_new_interfaces->at(i)->external_name());
 982       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_HIERARCHY_CHANGED;
 983     }
 984   }
 985 
 986   // Check whether class is in the error init state.
 987   if (the_class->is_in_error_state()) {
 988     log_info(redefine, class, normalize)
 989       ("redefined class %s is in error init state.", the_class->external_name());
 990     // TBD #5057930: special error code is needed in 1.6
 991     return JVMTI_ERROR_INVALID_CLASS;
 992   }
 993 
 994   // Check whether the nest-related attributes have been changed.
 995   jvmtiError err = check_nest_attributes(the_class, scratch_class);
 996   if (err != JVMTI_ERROR_NONE) {
 997     return err;
 998   }
 999 
1000   // Check whether the Record attribute has been changed.
1001   err = check_record_attribute(the_class, scratch_class);
1002   if (err != JVMTI_ERROR_NONE) {
1003     return err;
1004   }
1005 
1006   // Check whether the PermittedSubclasses attribute has been changed.
1007   err = check_permitted_subclasses_attribute(the_class, scratch_class);
1008   if (err != JVMTI_ERROR_NONE) {
1009     return err;
1010   }
1011 
1012   // Check whether the Preload attribute has been changed.
1013   err = check_preload_attribute(the_class, scratch_class);
1014   if (err != JVMTI_ERROR_NONE) {
1015     return err;
1016   }
1017 
1018   // Check whether class modifiers are the same.
1019   jushort old_flags = (jushort) the_class->access_flags().get_flags();
1020   jushort new_flags = (jushort) scratch_class->access_flags().get_flags();
1021   if (old_flags != new_flags) {
1022     log_info(redefine, class, normalize)
1023         ("redefined class %s modifiers change error: modifiers changed from %d to %d.",
1024          the_class->external_name(), old_flags, new_flags);
1025     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_MODIFIERS_CHANGED;
1026   }
1027 
1028   // Check if the number, names, types and order of fields declared in these classes
1029   // are the same.
1030   JavaFieldStream old_fs(the_class);
1031   JavaFieldStream new_fs(scratch_class);
1032   for (; !old_fs.done() && !new_fs.done(); old_fs.next(), new_fs.next()) {
1033     // name and signature
1034     Symbol* name_sym1 = the_class->constants()->symbol_at(old_fs.name_index());
1035     Symbol* sig_sym1 = the_class->constants()->symbol_at(old_fs.signature_index());
1036     Symbol* name_sym2 = scratch_class->constants()->symbol_at(new_fs.name_index());
1037     Symbol* sig_sym2 = scratch_class->constants()->symbol_at(new_fs.signature_index());
1038     if (name_sym1 != name_sym2 || sig_sym1 != sig_sym2) {
1039       log_info(redefine, class, normalize)
1040           ("redefined class %s fields change error: field %s %s changed to %s %s.",
1041            the_class->external_name(),
1042            sig_sym1->as_C_string(), name_sym1->as_C_string(),
1043            sig_sym2->as_C_string(), name_sym2->as_C_string());
1044       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_SCHEMA_CHANGED;
1045     }
1046     // offset
1047     if (old_fs.offset() != new_fs.offset()) {
1048       log_info(redefine, class, normalize)
1049           ("redefined class %s field %s change error: offset changed from %d to %d.",
1050            the_class->external_name(), name_sym2->as_C_string(), old_fs.offset(), new_fs.offset());
1051       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_SCHEMA_CHANGED;
1052     }
1053     // access
1054     old_flags = old_fs.access_flags().as_short();
1055     new_flags = new_fs.access_flags().as_short();
1056     if ((old_flags ^ new_flags) & JVM_RECOGNIZED_FIELD_MODIFIERS) {
1057       log_info(redefine, class, normalize)
1058           ("redefined class %s field %s change error: modifiers changed from %d to %d.",
1059            the_class->external_name(), name_sym2->as_C_string(), old_flags, new_flags);
1060       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_SCHEMA_CHANGED;
1061     }
1062   }
1063 
1064   // If both streams aren't done then we have a differing number of
1065   // fields.
1066   if (!old_fs.done() || !new_fs.done()) {
1067     const char* action = old_fs.done() ? "added" : "deleted";
1068     log_info(redefine, class, normalize)
1069         ("redefined class %s fields change error: some fields were %s.",
1070          the_class->external_name(), action);
1071     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_SCHEMA_CHANGED;
1072   }
1073 
1074   // Do a parallel walk through the old and new methods. Detect
1075   // cases where they match (exist in both), have been added in
1076   // the new methods, or have been deleted (exist only in the
1077   // old methods).  The class file parser places methods in order
1078   // by method name, but does not order overloaded methods by
1079   // signature.  In order to determine what fate befell the methods,
1080   // this code places the overloaded new methods that have matching
1081   // old methods in the same order as the old methods and places
1082   // new overloaded methods at the end of overloaded methods of
1083   // that name. The code for this order normalization is adapted
1084   // from the algorithm used in InstanceKlass::find_method().
1085   // Since we are swapping out of order entries as we find them,
1086   // we only have to search forward through the overloaded methods.
1087   // Methods which are added and have the same name as an existing
1088   // method (but different signature) will be put at the end of
1089   // the methods with that name, and the name mismatch code will
1090   // handle them.
1091   Array<Method*>* k_old_methods(the_class->methods());
1092   Array<Method*>* k_new_methods(scratch_class->methods());
1093   int n_old_methods = k_old_methods->length();
1094   int n_new_methods = k_new_methods->length();
1095   Thread* thread = Thread::current();
1096 
1097   int ni = 0;
1098   int oi = 0;
1099   while (true) {
1100     Method* k_old_method;
1101     Method* k_new_method;
1102     enum { matched, added, deleted, undetermined } method_was = undetermined;
1103 
1104     if (oi >= n_old_methods) {
1105       if (ni >= n_new_methods) {
1106         break; // we've looked at everything, done
1107       }
1108       // New method at the end
1109       k_new_method = k_new_methods->at(ni);
1110       method_was = added;
1111     } else if (ni >= n_new_methods) {
1112       // Old method, at the end, is deleted
1113       k_old_method = k_old_methods->at(oi);
1114       method_was = deleted;
1115     } else {
1116       // There are more methods in both the old and new lists
1117       k_old_method = k_old_methods->at(oi);
1118       k_new_method = k_new_methods->at(ni);
1119       if (k_old_method->name() != k_new_method->name()) {
1120         // Methods are sorted by method name, so a mismatch means added
1121         // or deleted
1122         if (k_old_method->name()->fast_compare(k_new_method->name()) > 0) {
1123           method_was = added;
1124         } else {
1125           method_was = deleted;
1126         }
1127       } else if (k_old_method->signature() == k_new_method->signature()) {
1128         // Both the name and signature match
1129         method_was = matched;
1130       } else {
1131         // The name matches, but the signature doesn't, which means we have to
1132         // search forward through the new overloaded methods.
1133         int nj;  // outside the loop for post-loop check
1134         for (nj = ni + 1; nj < n_new_methods; nj++) {
1135           Method* m = k_new_methods->at(nj);
1136           if (k_old_method->name() != m->name()) {
1137             // reached another method name so no more overloaded methods
1138             method_was = deleted;
1139             break;
1140           }
1141           if (k_old_method->signature() == m->signature()) {
1142             // found a match so swap the methods
1143             k_new_methods->at_put(ni, m);
1144             k_new_methods->at_put(nj, k_new_method);
1145             k_new_method = m;
1146             method_was = matched;
1147             break;
1148           }
1149         }
1150 
1151         if (nj >= n_new_methods) {
1152           // reached the end without a match; so method was deleted
1153           method_was = deleted;
1154         }
1155       }
1156     }
1157 
1158     switch (method_was) {
1159     case matched:
1160       // methods match, be sure modifiers do too
1161       old_flags = (jushort) k_old_method->access_flags().get_flags();
1162       new_flags = (jushort) k_new_method->access_flags().get_flags();
1163       if ((old_flags ^ new_flags) & ~(JVM_ACC_NATIVE)) {
1164         log_info(redefine, class, normalize)
1165           ("redefined class %s  method %s modifiers error: modifiers changed from %d to %d",
1166            the_class->external_name(), k_old_method->name_and_sig_as_C_string(), old_flags, new_flags);
1167         return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_METHOD_MODIFIERS_CHANGED;
1168       }
1169       {
1170         u2 new_num = k_new_method->method_idnum();
1171         u2 old_num = k_old_method->method_idnum();
1172         if (new_num != old_num) {
1173           Method* idnum_owner = scratch_class->method_with_idnum(old_num);
1174           if (idnum_owner != nullptr) {
1175             // There is already a method assigned this idnum -- switch them
1176             // Take current and original idnum from the new_method
1177             idnum_owner->set_method_idnum(new_num);
1178             idnum_owner->set_orig_method_idnum(k_new_method->orig_method_idnum());
1179           }
1180           // Take current and original idnum from the old_method
1181           k_new_method->set_method_idnum(old_num);
1182           k_new_method->set_orig_method_idnum(k_old_method->orig_method_idnum());
1183           if (thread->has_pending_exception()) {
1184             return JVMTI_ERROR_OUT_OF_MEMORY;
1185           }
1186         }
1187       }
1188       log_trace(redefine, class, normalize)
1189         ("Method matched: new: %s [%d] == old: %s [%d]",
1190          k_new_method->name_and_sig_as_C_string(), ni, k_old_method->name_and_sig_as_C_string(), oi);
1191       // advance to next pair of methods
1192       ++oi;
1193       ++ni;
1194       break;
1195     case added:
1196       // method added, see if it is OK
1197       if (!can_add_or_delete(k_new_method)) {
1198         log_info(redefine, class, normalize)
1199           ("redefined class %s methods error: added method: %s [%d]",
1200            the_class->external_name(), k_new_method->name_and_sig_as_C_string(), ni);
1201         return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_METHOD_ADDED;
1202       }
1203       {
1204         u2 num = the_class->next_method_idnum();
1205         if (num == ConstMethod::UNSET_IDNUM) {
1206           // cannot add any more methods
1207           log_info(redefine, class, normalize)
1208             ("redefined class %s methods error: can't create ID for new method %s [%d]",
1209              the_class->external_name(), k_new_method->name_and_sig_as_C_string(), ni);
1210           return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_METHOD_ADDED;
1211         }
1212         u2 new_num = k_new_method->method_idnum();
1213         Method* idnum_owner = scratch_class->method_with_idnum(num);
1214         if (idnum_owner != nullptr) {
1215           // There is already a method assigned this idnum -- switch them
1216           // Take current and original idnum from the new_method
1217           idnum_owner->set_method_idnum(new_num);
1218           idnum_owner->set_orig_method_idnum(k_new_method->orig_method_idnum());
1219         }
1220         k_new_method->set_method_idnum(num);
1221         k_new_method->set_orig_method_idnum(num);
1222         if (thread->has_pending_exception()) {
1223           return JVMTI_ERROR_OUT_OF_MEMORY;
1224         }
1225       }
1226       log_trace(redefine, class, normalize)
1227         ("Method added: new: %s [%d]", k_new_method->name_and_sig_as_C_string(), ni);
1228       ++ni; // advance to next new method
1229       break;
1230     case deleted:
1231       // method deleted, see if it is OK
1232       if (!can_add_or_delete(k_old_method)) {
1233         log_info(redefine, class, normalize)
1234           ("redefined class %s methods error: deleted method %s [%d]",
1235            the_class->external_name(), k_old_method->name_and_sig_as_C_string(), oi);
1236         return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_METHOD_DELETED;
1237       }
1238       log_trace(redefine, class, normalize)
1239         ("Method deleted: old: %s [%d]", k_old_method->name_and_sig_as_C_string(), oi);
1240       ++oi; // advance to next old method
1241       break;
1242     default:
1243       ShouldNotReachHere();
1244     }
1245   }
1246 
1247   return JVMTI_ERROR_NONE;
1248 }
1249 
1250 
1251 // Find new constant pool index value for old constant pool index value
1252 // by searching the index map. Returns zero (0) if there is no mapped
1253 // value for the old constant pool index.
1254 int VM_RedefineClasses::find_new_index(int old_index) {
1255   if (_index_map_count == 0) {
1256     // map is empty so nothing can be found
1257     return 0;
1258   }
1259 
1260   if (old_index < 1 || old_index >= _index_map_p->length()) {
1261     // The old_index is out of range so it is not mapped. This should
1262     // not happen in regular constant pool merging use, but it can
1263     // happen if a corrupt annotation is processed.
1264     return 0;
1265   }
1266 
1267   int value = _index_map_p->at(old_index);
1268   if (value == -1) {
1269     // the old_index is not mapped
1270     return 0;
1271   }
1272 
1273   return value;
1274 } // end find_new_index()
1275 
1276 
1277 // Find new bootstrap specifier index value for old bootstrap specifier index
1278 // value by searching the index map. Returns unused index (-1) if there is
1279 // no mapped value for the old bootstrap specifier index.
1280 int VM_RedefineClasses::find_new_operand_index(int old_index) {
1281   if (_operands_index_map_count == 0) {
1282     // map is empty so nothing can be found
1283     return -1;
1284   }
1285 
1286   if (old_index == -1 || old_index >= _operands_index_map_p->length()) {
1287     // The old_index is out of range so it is not mapped.
1288     // This should not happen in regular constant pool merging use.
1289     return -1;
1290   }
1291 
1292   int value = _operands_index_map_p->at(old_index);
1293   if (value == -1) {
1294     // the old_index is not mapped
1295     return -1;
1296   }
1297 
1298   return value;
1299 } // end find_new_operand_index()
1300 
1301 
1302 // Returns true if the current mismatch is due to a resolved/unresolved
1303 // class pair. Otherwise, returns false.
1304 bool VM_RedefineClasses::is_unresolved_class_mismatch(const constantPoolHandle& cp1,
1305        int index1, const constantPoolHandle& cp2, int index2) {
1306 
1307   jbyte t1 = cp1->tag_at(index1).value();
1308   if (t1 != JVM_CONSTANT_Class && t1 != JVM_CONSTANT_UnresolvedClass) {
1309     return false;  // wrong entry type; not our special case
1310   }
1311 
1312   jbyte t2 = cp2->tag_at(index2).value();
1313   if (t2 != JVM_CONSTANT_Class && t2 != JVM_CONSTANT_UnresolvedClass) {
1314     return false;  // wrong entry type; not our special case
1315   }
1316 
1317   if (t1 == t2) {
1318     return false;  // not a mismatch; not our special case
1319   }
1320 
1321   char *s1 = cp1->klass_name_at(index1)->as_C_string();
1322   char *s2 = cp2->klass_name_at(index2)->as_C_string();
1323   if (strcmp(s1, s2) != 0) {
1324     return false;  // strings don't match; not our special case
1325   }
1326 
1327   return true;  // made it through the gauntlet; this is our special case
1328 } // end is_unresolved_class_mismatch()
1329 
1330 
1331 // The bug 6214132 caused the verification to fail.
1332 // 1. What's done in RedefineClasses() before verification:
1333 //  a) A reference to the class being redefined (_the_class) and a
1334 //     reference to new version of the class (_scratch_class) are
1335 //     saved here for use during the bytecode verification phase of
1336 //     RedefineClasses.
1337 //  b) The _java_mirror field from _the_class is copied to the
1338 //     _java_mirror field in _scratch_class. This means that a jclass
1339 //     returned for _the_class or _scratch_class will refer to the
1340 //     same Java mirror. The verifier will see the "one true mirror"
1341 //     for the class being verified.
1342 // 2. See comments in JvmtiThreadState for what is done during verification.
1343 
1344 class RedefineVerifyMark : public StackObj {
1345  private:
1346   JvmtiThreadState* _state;
1347   Klass*            _scratch_class;
1348   OopHandle         _scratch_mirror;
1349 
1350  public:
1351 
1352   RedefineVerifyMark(Klass* the_class, Klass* scratch_class,
1353                      JvmtiThreadState* state) : _state(state), _scratch_class(scratch_class)
1354   {
1355     _state->set_class_versions_map(the_class, scratch_class);
1356     _scratch_mirror = the_class->java_mirror_handle();  // this is a copy that is swapped
1357     _scratch_class->swap_java_mirror_handle(_scratch_mirror);
1358   }
1359 
1360   ~RedefineVerifyMark() {
1361     // Restore the scratch class's mirror, so when scratch_class is removed
1362     // the correct mirror pointing to it can be cleared.
1363     _scratch_class->swap_java_mirror_handle(_scratch_mirror);
1364     _state->clear_class_versions_map();
1365   }
1366 };
1367 
1368 
1369 jvmtiError VM_RedefineClasses::load_new_class_versions() {
1370 
1371   // For consistency allocate memory using os::malloc wrapper.
1372   _scratch_classes = (InstanceKlass**)
1373     os::malloc(sizeof(InstanceKlass*) * _class_count, mtClass);
1374   if (_scratch_classes == nullptr) {
1375     return JVMTI_ERROR_OUT_OF_MEMORY;
1376   }
1377   // Zero initialize the _scratch_classes array.
1378   for (int i = 0; i < _class_count; i++) {
1379     _scratch_classes[i] = nullptr;
1380   }
1381 
1382   JavaThread* current = JavaThread::current();
1383   ResourceMark rm(current);
1384 
1385   JvmtiThreadState *state = JvmtiThreadState::state_for(current);
1386   // state can only be null if the current thread is exiting which
1387   // should not happen since we're trying to do a RedefineClasses
1388   guarantee(state != nullptr, "exiting thread calling load_new_class_versions");
1389   for (int i = 0; i < _class_count; i++) {
1390     // Create HandleMark so that any handles created while loading new class
1391     // versions are deleted. Constant pools are deallocated while merging
1392     // constant pools
1393     HandleMark hm(current);
1394     InstanceKlass* the_class = get_ik(_class_defs[i].klass);
1395 
1396     log_debug(redefine, class, load)
1397       ("loading name=%s kind=%d (avail_mem=" UINT64_FORMAT "K)",
1398        the_class->external_name(), _class_load_kind, os::available_memory() >> 10);
1399 
1400     ClassFileStream st((u1*)_class_defs[i].class_bytes,
1401                        _class_defs[i].class_byte_count,
1402                        "__VM_RedefineClasses__",
1403                        ClassFileStream::verify);
1404 
1405     // Set redefined class handle in JvmtiThreadState class.
1406     // This redefined class is sent to agent event handler for class file
1407     // load hook event.
1408     state->set_class_being_redefined(the_class, _class_load_kind);
1409 
1410     JavaThread* THREAD = current; // For exception macros.
1411     ExceptionMark em(THREAD);
1412     Handle protection_domain(THREAD, the_class->protection_domain());
1413     ClassLoadInfo cl_info(protection_domain);
1414     // Parse and create a class from the bytes, but this class isn't added
1415     // to the dictionary, so do not call resolve_from_stream.
1416     InstanceKlass* scratch_class = KlassFactory::create_from_stream(&st,
1417                                                       the_class->name(),
1418                                                       the_class->class_loader_data(),
1419                                                       cl_info,
1420                                                       THREAD);
1421 
1422     // Clear class_being_redefined just to be sure.
1423     state->clear_class_being_redefined();
1424 
1425     // TODO: if this is retransform, and nothing changed we can skip it
1426 
1427     // Need to clean up allocated InstanceKlass if there's an error so assign
1428     // the result here. Caller deallocates all the scratch classes in case of
1429     // an error.
1430     _scratch_classes[i] = scratch_class;
1431 
1432     if (HAS_PENDING_EXCEPTION) {
1433       Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1434       log_info(redefine, class, load, exceptions)("create_from_stream exception: '%s'", ex_name->as_C_string());
1435       CLEAR_PENDING_EXCEPTION;
1436 
1437       if (ex_name == vmSymbols::java_lang_UnsupportedClassVersionError()) {
1438         return JVMTI_ERROR_UNSUPPORTED_VERSION;
1439       } else if (ex_name == vmSymbols::java_lang_ClassFormatError()) {
1440         return JVMTI_ERROR_INVALID_CLASS_FORMAT;
1441       } else if (ex_name == vmSymbols::java_lang_ClassCircularityError()) {
1442         return JVMTI_ERROR_CIRCULAR_CLASS_DEFINITION;
1443       } else if (ex_name == vmSymbols::java_lang_NoClassDefFoundError()) {
1444         // The message will be "XXX (wrong name: YYY)"
1445         return JVMTI_ERROR_NAMES_DONT_MATCH;
1446       } else if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1447         return JVMTI_ERROR_OUT_OF_MEMORY;
1448       } else {  // Just in case more exceptions can be thrown..
1449         return JVMTI_ERROR_FAILS_VERIFICATION;
1450       }
1451     }
1452 
1453     // Ensure class is linked before redefine
1454     if (!the_class->is_linked()) {
1455       the_class->link_class(THREAD);
1456       if (HAS_PENDING_EXCEPTION) {
1457         Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1458         oop message = java_lang_Throwable::message(PENDING_EXCEPTION);
1459         if (message != nullptr) {
1460           char* ex_msg = java_lang_String::as_utf8_string(message);
1461           log_info(redefine, class, load, exceptions)("link_class exception: '%s %s'",
1462                    ex_name->as_C_string(), ex_msg);
1463         } else {
1464           log_info(redefine, class, load, exceptions)("link_class exception: '%s'",
1465                    ex_name->as_C_string());
1466         }
1467         CLEAR_PENDING_EXCEPTION;
1468         if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1469           return JVMTI_ERROR_OUT_OF_MEMORY;
1470         } else if (ex_name == vmSymbols::java_lang_NoClassDefFoundError()) {
1471           return JVMTI_ERROR_INVALID_CLASS;
1472         } else {
1473           return JVMTI_ERROR_INTERNAL;
1474         }
1475       }
1476     }
1477 
1478     // Do the validity checks in compare_and_normalize_class_versions()
1479     // before verifying the byte codes. By doing these checks first, we
1480     // limit the number of functions that require redirection from
1481     // the_class to scratch_class. In particular, we don't have to
1482     // modify JNI GetSuperclass() and thus won't change its performance.
1483     jvmtiError res = compare_and_normalize_class_versions(the_class,
1484                        scratch_class);
1485     if (res != JVMTI_ERROR_NONE) {
1486       return res;
1487     }
1488 
1489     // verify what the caller passed us
1490     {
1491       // The bug 6214132 caused the verification to fail.
1492       // Information about the_class and scratch_class is temporarily
1493       // recorded into jvmtiThreadState. This data is used to redirect
1494       // the_class to scratch_class in the JVM_* functions called by the
1495       // verifier. Please, refer to jvmtiThreadState.hpp for the detailed
1496       // description.
1497       RedefineVerifyMark rvm(the_class, scratch_class, state);
1498       Verifier::verify(scratch_class, true, THREAD);
1499     }
1500 
1501     if (HAS_PENDING_EXCEPTION) {
1502       Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1503       log_info(redefine, class, load, exceptions)("verify_byte_codes exception: '%s'", ex_name->as_C_string());
1504       CLEAR_PENDING_EXCEPTION;
1505       if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1506         return JVMTI_ERROR_OUT_OF_MEMORY;
1507       } else {
1508         // tell the caller the bytecodes are bad
1509         return JVMTI_ERROR_FAILS_VERIFICATION;
1510       }
1511     }
1512 
1513     res = merge_cp_and_rewrite(the_class, scratch_class, THREAD);
1514     if (HAS_PENDING_EXCEPTION) {
1515       Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1516       log_info(redefine, class, load, exceptions)("merge_cp_and_rewrite 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 #ifdef ASSERT
1526     {
1527       // verify what we have done during constant pool merging
1528       {
1529         RedefineVerifyMark rvm(the_class, scratch_class, state);
1530         Verifier::verify(scratch_class, true, THREAD);
1531       }
1532 
1533       if (HAS_PENDING_EXCEPTION) {
1534         Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1535         log_info(redefine, class, load, exceptions)
1536           ("verify_byte_codes post merge-CP exception: '%s'", ex_name->as_C_string());
1537         CLEAR_PENDING_EXCEPTION;
1538         if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1539           return JVMTI_ERROR_OUT_OF_MEMORY;
1540         } else {
1541           // tell the caller that constant pool merging screwed up
1542           return JVMTI_ERROR_INTERNAL;
1543         }
1544       }
1545     }
1546 #endif // ASSERT
1547 
1548     Rewriter::rewrite(scratch_class, THREAD);
1549     if (!HAS_PENDING_EXCEPTION) {
1550       scratch_class->link_methods(THREAD);
1551     }
1552     if (HAS_PENDING_EXCEPTION) {
1553       Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1554       log_info(redefine, class, load, exceptions)
1555         ("Rewriter::rewrite or link_methods exception: '%s'", ex_name->as_C_string());
1556       CLEAR_PENDING_EXCEPTION;
1557       if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1558         return JVMTI_ERROR_OUT_OF_MEMORY;
1559       } else {
1560         return JVMTI_ERROR_INTERNAL;
1561       }
1562     }
1563 
1564     log_debug(redefine, class, load)
1565       ("loaded name=%s (avail_mem=" UINT64_FORMAT "K)", the_class->external_name(), os::available_memory() >> 10);
1566   }
1567 
1568   return JVMTI_ERROR_NONE;
1569 }
1570 
1571 
1572 // Map old_index to new_index as needed. scratch_cp is only needed
1573 // for log calls.
1574 void VM_RedefineClasses::map_index(const constantPoolHandle& scratch_cp,
1575        int old_index, int new_index) {
1576   if (find_new_index(old_index) != 0) {
1577     // old_index is already mapped
1578     return;
1579   }
1580 
1581   if (old_index == new_index) {
1582     // no mapping is needed
1583     return;
1584   }
1585 
1586   _index_map_p->at_put(old_index, new_index);
1587   _index_map_count++;
1588 
1589   log_trace(redefine, class, constantpool)
1590     ("mapped tag %d at index %d to %d", scratch_cp->tag_at(old_index).value(), old_index, new_index);
1591 } // end map_index()
1592 
1593 
1594 // Map old_index to new_index as needed.
1595 void VM_RedefineClasses::map_operand_index(int old_index, int new_index) {
1596   if (find_new_operand_index(old_index) != -1) {
1597     // old_index is already mapped
1598     return;
1599   }
1600 
1601   if (old_index == new_index) {
1602     // no mapping is needed
1603     return;
1604   }
1605 
1606   _operands_index_map_p->at_put(old_index, new_index);
1607   _operands_index_map_count++;
1608 
1609   log_trace(redefine, class, constantpool)("mapped bootstrap specifier at index %d to %d", old_index, new_index);
1610 } // end map_index()
1611 
1612 
1613 // Merge old_cp and scratch_cp and return the results of the merge via
1614 // merge_cp_p. The number of entries in *merge_cp_p is returned via
1615 // merge_cp_length_p. The entries in old_cp occupy the same locations
1616 // in *merge_cp_p. Also creates a map of indices from entries in
1617 // scratch_cp to the corresponding entry in *merge_cp_p. Index map
1618 // entries are only created for entries in scratch_cp that occupy a
1619 // different location in *merged_cp_p.
1620 bool VM_RedefineClasses::merge_constant_pools(const constantPoolHandle& old_cp,
1621        const constantPoolHandle& scratch_cp, constantPoolHandle *merge_cp_p,
1622        int *merge_cp_length_p, TRAPS) {
1623 
1624   if (merge_cp_p == nullptr) {
1625     assert(false, "caller must provide scratch constantPool");
1626     return false; // robustness
1627   }
1628   if (merge_cp_length_p == nullptr) {
1629     assert(false, "caller must provide scratch CP length");
1630     return false; // robustness
1631   }
1632   // Worst case we need old_cp->length() + scratch_cp()->length(),
1633   // but the caller might be smart so make sure we have at least
1634   // the minimum.
1635   if ((*merge_cp_p)->length() < old_cp->length()) {
1636     assert(false, "merge area too small");
1637     return false; // robustness
1638   }
1639 
1640   log_info(redefine, class, constantpool)("old_cp_len=%d, scratch_cp_len=%d", old_cp->length(), scratch_cp->length());
1641 
1642   {
1643     // Pass 0:
1644     // The old_cp is copied to *merge_cp_p; this means that any code
1645     // using old_cp does not have to change. This work looks like a
1646     // perfect fit for ConstantPool*::copy_cp_to(), but we need to
1647     // handle one special case:
1648     // - revert JVM_CONSTANT_Class to JVM_CONSTANT_UnresolvedClass
1649     // This will make verification happy.
1650 
1651     int old_i;  // index into old_cp
1652 
1653     // index zero (0) is not used in constantPools
1654     for (old_i = 1; old_i < old_cp->length(); old_i++) {
1655       // leave debugging crumb
1656       jbyte old_tag = old_cp->tag_at(old_i).value();
1657       switch (old_tag) {
1658       case JVM_CONSTANT_Class:
1659       case JVM_CONSTANT_UnresolvedClass:
1660         // revert the copy to JVM_CONSTANT_UnresolvedClass
1661         // May be resolving while calling this so do the same for
1662         // JVM_CONSTANT_UnresolvedClass (klass_name_at() deals with transition)
1663         (*merge_cp_p)->temp_unresolved_klass_at_put(old_i,
1664           old_cp->klass_name_index_at(old_i));
1665         break;
1666 
1667       case JVM_CONSTANT_Double:
1668       case JVM_CONSTANT_Long:
1669         // just copy the entry to *merge_cp_p, but double and long take
1670         // two constant pool entries
1671         ConstantPool::copy_entry_to(old_cp, old_i, *merge_cp_p, old_i);
1672         old_i++;
1673         break;
1674 
1675       default:
1676         // just copy the entry to *merge_cp_p
1677         ConstantPool::copy_entry_to(old_cp, old_i, *merge_cp_p, old_i);
1678         break;
1679       }
1680     } // end for each old_cp entry
1681 
1682     ConstantPool::copy_operands(old_cp, *merge_cp_p, CHECK_false);
1683     (*merge_cp_p)->extend_operands(scratch_cp, CHECK_false);
1684 
1685     // We don't need to sanity check that *merge_cp_length_p is within
1686     // *merge_cp_p bounds since we have the minimum on-entry check above.
1687     (*merge_cp_length_p) = old_i;
1688   }
1689 
1690   // merge_cp_len should be the same as old_cp->length() at this point
1691   // so this trace message is really a "warm-and-breathing" message.
1692   log_debug(redefine, class, constantpool)("after pass 0: merge_cp_len=%d", *merge_cp_length_p);
1693 
1694   int scratch_i;  // index into scratch_cp
1695   {
1696     // Pass 1a:
1697     // Compare scratch_cp entries to the old_cp entries that we have
1698     // already copied to *merge_cp_p. In this pass, we are eliminating
1699     // exact duplicates (matching entry at same index) so we only
1700     // compare entries in the common indice range.
1701     int increment = 1;
1702     int pass1a_length = MIN2(old_cp->length(), scratch_cp->length());
1703     for (scratch_i = 1; scratch_i < pass1a_length; scratch_i += increment) {
1704       switch (scratch_cp->tag_at(scratch_i).value()) {
1705       case JVM_CONSTANT_Double:
1706       case JVM_CONSTANT_Long:
1707         // double and long take two constant pool entries
1708         increment = 2;
1709         break;
1710 
1711       default:
1712         increment = 1;
1713         break;
1714       }
1715 
1716       bool match = scratch_cp->compare_entry_to(scratch_i, *merge_cp_p, scratch_i);
1717       if (match) {
1718         // found a match at the same index so nothing more to do
1719         continue;
1720       } else if (is_unresolved_class_mismatch(scratch_cp, scratch_i,
1721                                               *merge_cp_p, scratch_i)) {
1722         // The mismatch in compare_entry_to() above is because of a
1723         // resolved versus unresolved class entry at the same index
1724         // with the same string value. Since Pass 0 reverted any
1725         // class entries to unresolved class entries in *merge_cp_p,
1726         // we go with the unresolved class entry.
1727         continue;
1728       }
1729 
1730       int found_i = scratch_cp->find_matching_entry(scratch_i, *merge_cp_p);
1731       if (found_i != 0) {
1732         guarantee(found_i != scratch_i,
1733           "compare_entry_to() and find_matching_entry() do not agree");
1734 
1735         // Found a matching entry somewhere else in *merge_cp_p so
1736         // just need a mapping entry.
1737         map_index(scratch_cp, scratch_i, found_i);
1738         continue;
1739       }
1740 
1741       // The find_matching_entry() call above could fail to find a match
1742       // due to a resolved versus unresolved class or string entry situation
1743       // like we solved above with the is_unresolved_*_mismatch() calls.
1744       // However, we would have to call is_unresolved_*_mismatch() over
1745       // all of *merge_cp_p (potentially) and that doesn't seem to be
1746       // worth the time.
1747 
1748       // No match found so we have to append this entry and any unique
1749       // referenced entries to *merge_cp_p.
1750       append_entry(scratch_cp, scratch_i, merge_cp_p, merge_cp_length_p);
1751     }
1752   }
1753 
1754   log_debug(redefine, class, constantpool)
1755     ("after pass 1a: merge_cp_len=%d, scratch_i=%d, index_map_len=%d",
1756      *merge_cp_length_p, scratch_i, _index_map_count);
1757 
1758   if (scratch_i < scratch_cp->length()) {
1759     // Pass 1b:
1760     // old_cp is smaller than scratch_cp so there are entries in
1761     // scratch_cp that we have not yet processed. We take care of
1762     // those now.
1763     int increment = 1;
1764     for (; scratch_i < scratch_cp->length(); scratch_i += increment) {
1765       switch (scratch_cp->tag_at(scratch_i).value()) {
1766       case JVM_CONSTANT_Double:
1767       case JVM_CONSTANT_Long:
1768         // double and long take two constant pool entries
1769         increment = 2;
1770         break;
1771 
1772       default:
1773         increment = 1;
1774         break;
1775       }
1776 
1777       int found_i =
1778         scratch_cp->find_matching_entry(scratch_i, *merge_cp_p);
1779       if (found_i != 0) {
1780         // Found a matching entry somewhere else in *merge_cp_p so
1781         // just need a mapping entry.
1782         map_index(scratch_cp, scratch_i, found_i);
1783         continue;
1784       }
1785 
1786       // No match found so we have to append this entry and any unique
1787       // referenced entries to *merge_cp_p.
1788       append_entry(scratch_cp, scratch_i, merge_cp_p, merge_cp_length_p);
1789     }
1790 
1791     log_debug(redefine, class, constantpool)
1792       ("after pass 1b: merge_cp_len=%d, scratch_i=%d, index_map_len=%d",
1793        *merge_cp_length_p, scratch_i, _index_map_count);
1794   }
1795   finalize_operands_merge(*merge_cp_p, CHECK_false);
1796 
1797   return true;
1798 } // end merge_constant_pools()
1799 
1800 
1801 // Scoped object to clean up the constant pool(s) created for merging
1802 class MergeCPCleaner {
1803   ClassLoaderData*   _loader_data;
1804   ConstantPool*      _cp;
1805   ConstantPool*      _scratch_cp;
1806  public:
1807   MergeCPCleaner(ClassLoaderData* loader_data, ConstantPool* merge_cp) :
1808                  _loader_data(loader_data), _cp(merge_cp), _scratch_cp(nullptr) {}
1809   ~MergeCPCleaner() {
1810     _loader_data->add_to_deallocate_list(_cp);
1811     if (_scratch_cp != nullptr) {
1812       _loader_data->add_to_deallocate_list(_scratch_cp);
1813     }
1814   }
1815   void add_scratch_cp(ConstantPool* scratch_cp) { _scratch_cp = scratch_cp; }
1816 };
1817 
1818 // Merge constant pools between the_class and scratch_class and
1819 // potentially rewrite bytecodes in scratch_class to use the merged
1820 // constant pool.
1821 jvmtiError VM_RedefineClasses::merge_cp_and_rewrite(
1822              InstanceKlass* the_class, InstanceKlass* scratch_class,
1823              TRAPS) {
1824   // worst case merged constant pool length is old and new combined
1825   int merge_cp_length = the_class->constants()->length()
1826         + scratch_class->constants()->length();
1827 
1828   // Constant pools are not easily reused so we allocate a new one
1829   // each time.
1830   // merge_cp is created unsafe for concurrent GC processing.  It
1831   // should be marked safe before discarding it. Even though
1832   // garbage,  if it crosses a card boundary, it may be scanned
1833   // in order to find the start of the first complete object on the card.
1834   ClassLoaderData* loader_data = the_class->class_loader_data();
1835   ConstantPool* merge_cp_oop =
1836     ConstantPool::allocate(loader_data,
1837                            merge_cp_length,
1838                            CHECK_(JVMTI_ERROR_OUT_OF_MEMORY));
1839   MergeCPCleaner cp_cleaner(loader_data, merge_cp_oop);
1840 
1841   HandleMark hm(THREAD);  // make sure handles are cleared before
1842                           // MergeCPCleaner clears out merge_cp_oop
1843   constantPoolHandle merge_cp(THREAD, merge_cp_oop);
1844 
1845   // Get constants() from the old class because it could have been rewritten
1846   // while we were at a safepoint allocating a new constant pool.
1847   constantPoolHandle old_cp(THREAD, the_class->constants());
1848   constantPoolHandle scratch_cp(THREAD, scratch_class->constants());
1849 
1850   // If the length changed, the class was redefined out from under us. Return
1851   // an error.
1852   if (merge_cp_length != the_class->constants()->length()
1853          + scratch_class->constants()->length()) {
1854     return JVMTI_ERROR_INTERNAL;
1855   }
1856 
1857   // Update the version number of the constant pools (may keep scratch_cp)
1858   merge_cp->increment_and_save_version(old_cp->version());
1859   scratch_cp->increment_and_save_version(old_cp->version());
1860 
1861   ResourceMark rm(THREAD);
1862   _index_map_count = 0;
1863   _index_map_p = new intArray(scratch_cp->length(), scratch_cp->length(), -1);
1864 
1865   _operands_cur_length = ConstantPool::operand_array_length(old_cp->operands());
1866   _operands_index_map_count = 0;
1867   int operands_index_map_len = ConstantPool::operand_array_length(scratch_cp->operands());
1868   _operands_index_map_p = new intArray(operands_index_map_len, operands_index_map_len, -1);
1869 
1870   // reference to the cp holder is needed for copy_operands()
1871   merge_cp->set_pool_holder(scratch_class);
1872   bool result = merge_constant_pools(old_cp, scratch_cp, &merge_cp,
1873                   &merge_cp_length, THREAD);
1874   merge_cp->set_pool_holder(nullptr);
1875 
1876   if (!result) {
1877     // The merge can fail due to memory allocation failure or due
1878     // to robustness checks.
1879     return JVMTI_ERROR_INTERNAL;
1880   }
1881 
1882   // Set dynamic constants attribute from the original CP.
1883   if (old_cp->has_dynamic_constant()) {
1884     scratch_cp->set_has_dynamic_constant();
1885   }
1886 
1887   log_info(redefine, class, constantpool)("merge_cp_len=%d, index_map_len=%d", merge_cp_length, _index_map_count);
1888 
1889   if (_index_map_count == 0) {
1890     // there is nothing to map between the new and merged constant pools
1891 
1892     // Copy attributes from scratch_cp to merge_cp
1893     merge_cp->copy_fields(scratch_cp());
1894 
1895     if (old_cp->length() == scratch_cp->length()) {
1896       // The old and new constant pools are the same length and the
1897       // index map is empty. This means that the three constant pools
1898       // are equivalent (but not the same). Unfortunately, the new
1899       // constant pool has not gone through link resolution nor have
1900       // the new class bytecodes gone through constant pool cache
1901       // rewriting so we can't use the old constant pool with the new
1902       // class.
1903 
1904       // toss the merged constant pool at return
1905     } else if (old_cp->length() < scratch_cp->length()) {
1906       // The old constant pool has fewer entries than the new constant
1907       // pool and the index map is empty. This means the new constant
1908       // pool is a superset of the old constant pool. However, the old
1909       // class bytecodes have already gone through constant pool cache
1910       // rewriting so we can't use the new constant pool with the old
1911       // class.
1912 
1913       // toss the merged constant pool at return
1914     } else {
1915       // The old constant pool has more entries than the new constant
1916       // pool and the index map is empty. This means that both the old
1917       // and merged constant pools are supersets of the new constant
1918       // pool.
1919 
1920       // Replace the new constant pool with a shrunken copy of the
1921       // merged constant pool
1922       set_new_constant_pool(loader_data, scratch_class, merge_cp, merge_cp_length,
1923                             CHECK_(JVMTI_ERROR_OUT_OF_MEMORY));
1924       // The new constant pool replaces scratch_cp so have cleaner clean it up.
1925       // It can't be cleaned up while there are handles to it.
1926       cp_cleaner.add_scratch_cp(scratch_cp());
1927     }
1928   } else {
1929     if (log_is_enabled(Trace, redefine, class, constantpool)) {
1930       // don't want to loop unless we are tracing
1931       int count = 0;
1932       for (int i = 1; i < _index_map_p->length(); i++) {
1933         int value = _index_map_p->at(i);
1934 
1935         if (value != -1) {
1936           log_trace(redefine, class, constantpool)("index_map[%d]: old=%d new=%d", count, i, value);
1937           count++;
1938         }
1939       }
1940     }
1941 
1942     // We have entries mapped between the new and merged constant pools
1943     // so we have to rewrite some constant pool references.
1944     if (!rewrite_cp_refs(scratch_class)) {
1945       return JVMTI_ERROR_INTERNAL;
1946     }
1947 
1948     // Copy attributes from scratch_cp to merge_cp (should be done after rewrite_cp_refs())
1949     merge_cp->copy_fields(scratch_cp());
1950 
1951     // Replace the new constant pool with a shrunken copy of the
1952     // merged constant pool so now the rewritten bytecodes have
1953     // valid references; the previous new constant pool will get
1954     // GCed.
1955     set_new_constant_pool(loader_data, scratch_class, merge_cp, merge_cp_length,
1956                           CHECK_(JVMTI_ERROR_OUT_OF_MEMORY));
1957     // The new constant pool replaces scratch_cp so have cleaner clean it up.
1958     // It can't be cleaned up while there are handles to it.
1959     cp_cleaner.add_scratch_cp(scratch_cp());
1960   }
1961 
1962   return JVMTI_ERROR_NONE;
1963 } // end merge_cp_and_rewrite()
1964 
1965 
1966 // Rewrite constant pool references in klass scratch_class.
1967 bool VM_RedefineClasses::rewrite_cp_refs(InstanceKlass* scratch_class) {
1968 
1969   // rewrite constant pool references in the nest attributes:
1970   if (!rewrite_cp_refs_in_nest_attributes(scratch_class)) {
1971     // propagate failure back to caller
1972     return false;
1973   }
1974 
1975   // rewrite constant pool references in the Record attribute:
1976   if (!rewrite_cp_refs_in_record_attribute(scratch_class)) {
1977     // propagate failure back to caller
1978     return false;
1979   }
1980 
1981   // rewrite constant pool references in the PermittedSubclasses attribute:
1982   if (!rewrite_cp_refs_in_permitted_subclasses_attribute(scratch_class)) {
1983     // propagate failure back to caller
1984     return false;
1985   }
1986 
1987   // rewrite constant pool references in the Preload attribute:
1988   if (!rewrite_cp_refs_in_preload_attribute(scratch_class)) {
1989     // propagate failure back to caller
1990     return false;
1991   }
1992 
1993   // rewrite constant pool references in the methods:
1994   if (!rewrite_cp_refs_in_methods(scratch_class)) {
1995     // propagate failure back to caller
1996     return false;
1997   }
1998 
1999   // rewrite constant pool references in the class_annotations:
2000   if (!rewrite_cp_refs_in_class_annotations(scratch_class)) {
2001     // propagate failure back to caller
2002     return false;
2003   }
2004 
2005   // rewrite constant pool references in the fields_annotations:
2006   if (!rewrite_cp_refs_in_fields_annotations(scratch_class)) {
2007     // propagate failure back to caller
2008     return false;
2009   }
2010 
2011   // rewrite constant pool references in the methods_annotations:
2012   if (!rewrite_cp_refs_in_methods_annotations(scratch_class)) {
2013     // propagate failure back to caller
2014     return false;
2015   }
2016 
2017   // rewrite constant pool references in the methods_parameter_annotations:
2018   if (!rewrite_cp_refs_in_methods_parameter_annotations(scratch_class)) {
2019     // propagate failure back to caller
2020     return false;
2021   }
2022 
2023   // rewrite constant pool references in the methods_default_annotations:
2024   if (!rewrite_cp_refs_in_methods_default_annotations(scratch_class)) {
2025     // propagate failure back to caller
2026     return false;
2027   }
2028 
2029   // rewrite constant pool references in the class_type_annotations:
2030   if (!rewrite_cp_refs_in_class_type_annotations(scratch_class)) {
2031     // propagate failure back to caller
2032     return false;
2033   }
2034 
2035   // rewrite constant pool references in the fields_type_annotations:
2036   if (!rewrite_cp_refs_in_fields_type_annotations(scratch_class)) {
2037     // propagate failure back to caller
2038     return false;
2039   }
2040 
2041   // rewrite constant pool references in the methods_type_annotations:
2042   if (!rewrite_cp_refs_in_methods_type_annotations(scratch_class)) {
2043     // propagate failure back to caller
2044     return false;
2045   }
2046 
2047   // There can be type annotations in the Code part of a method_info attribute.
2048   // These annotations are not accessible, even by reflection.
2049   // Currently they are not even parsed by the ClassFileParser.
2050   // If runtime access is added they will also need to be rewritten.
2051 
2052   // rewrite source file name index:
2053   u2 source_file_name_idx = scratch_class->source_file_name_index();
2054   if (source_file_name_idx != 0) {
2055     u2 new_source_file_name_idx = find_new_index(source_file_name_idx);
2056     if (new_source_file_name_idx != 0) {
2057       scratch_class->set_source_file_name_index(new_source_file_name_idx);
2058     }
2059   }
2060 
2061   // rewrite class generic signature index:
2062   u2 generic_signature_index = scratch_class->generic_signature_index();
2063   if (generic_signature_index != 0) {
2064     u2 new_generic_signature_index = find_new_index(generic_signature_index);
2065     if (new_generic_signature_index != 0) {
2066       scratch_class->set_generic_signature_index(new_generic_signature_index);
2067     }
2068   }
2069 
2070   return true;
2071 } // end rewrite_cp_refs()
2072 
2073 // Rewrite constant pool references in the NestHost and NestMembers attributes.
2074 bool VM_RedefineClasses::rewrite_cp_refs_in_nest_attributes(
2075        InstanceKlass* scratch_class) {
2076 
2077   u2 cp_index = scratch_class->nest_host_index();
2078   if (cp_index != 0) {
2079     scratch_class->set_nest_host_index(find_new_index(cp_index));
2080   }
2081   Array<u2>* nest_members = scratch_class->nest_members();
2082   for (int i = 0; i < nest_members->length(); i++) {
2083     u2 cp_index = nest_members->at(i);
2084     nest_members->at_put(i, find_new_index(cp_index));
2085   }
2086   return true;
2087 }
2088 
2089 // Rewrite constant pool references in the Record attribute.
2090 bool VM_RedefineClasses::rewrite_cp_refs_in_record_attribute(InstanceKlass* scratch_class) {
2091   Array<RecordComponent*>* components = scratch_class->record_components();
2092   if (components != nullptr) {
2093     for (int i = 0; i < components->length(); i++) {
2094       RecordComponent* component = components->at(i);
2095       u2 cp_index = component->name_index();
2096       component->set_name_index(find_new_index(cp_index));
2097       cp_index = component->descriptor_index();
2098       component->set_descriptor_index(find_new_index(cp_index));
2099       cp_index = component->generic_signature_index();
2100       if (cp_index != 0) {
2101         component->set_generic_signature_index(find_new_index(cp_index));
2102       }
2103 
2104       AnnotationArray* annotations = component->annotations();
2105       if (annotations != nullptr && annotations->length() != 0) {
2106         int byte_i = 0;  // byte index into annotations
2107         if (!rewrite_cp_refs_in_annotations_typeArray(annotations, byte_i)) {
2108           log_debug(redefine, class, annotation)("bad record_component_annotations at %d", i);
2109           // propagate failure back to caller
2110           return false;
2111         }
2112       }
2113 
2114       AnnotationArray* type_annotations = component->type_annotations();
2115       if (type_annotations != nullptr && type_annotations->length() != 0) {
2116         int byte_i = 0;  // byte index into annotations
2117         if (!rewrite_cp_refs_in_annotations_typeArray(type_annotations, byte_i)) {
2118           log_debug(redefine, class, annotation)("bad record_component_type_annotations at %d", i);
2119           // propagate failure back to caller
2120           return false;
2121         }
2122       }
2123     }
2124   }
2125   return true;
2126 }
2127 
2128 // Rewrite constant pool references in the PermittedSubclasses attribute.
2129 bool VM_RedefineClasses::rewrite_cp_refs_in_permitted_subclasses_attribute(
2130        InstanceKlass* scratch_class) {
2131 
2132   Array<u2>* permitted_subclasses = scratch_class->permitted_subclasses();
2133   assert(permitted_subclasses != nullptr, "unexpected null permitted_subclasses");
2134   for (int i = 0; i < permitted_subclasses->length(); i++) {
2135     u2 cp_index = permitted_subclasses->at(i);
2136     permitted_subclasses->at_put(i, find_new_index(cp_index));
2137   }
2138   return true;
2139 }
2140 
2141 // Rewrite constant pool references in the Preload attribute.
2142 bool VM_RedefineClasses::rewrite_cp_refs_in_preload_attribute(
2143        InstanceKlass* scratch_class) {
2144 
2145   Array<u2>* preload_classes = scratch_class->preload_classes();
2146   assert(preload_classes != NULL, "unexpected null preload_classes");
2147   for (int i = 0; i < preload_classes->length(); i++) {
2148     u2 cp_index = preload_classes->at(i);
2149     preload_classes->at_put(i, find_new_index(cp_index));
2150   }
2151   return true;
2152 }
2153 
2154 // Rewrite constant pool references in the methods.
2155 bool VM_RedefineClasses::rewrite_cp_refs_in_methods(InstanceKlass* scratch_class) {
2156 
2157   Array<Method*>* methods = scratch_class->methods();
2158 
2159   if (methods == nullptr || methods->length() == 0) {
2160     // no methods so nothing to do
2161     return true;
2162   }
2163 
2164   JavaThread* THREAD = JavaThread::current(); // For exception macros.
2165   ExceptionMark em(THREAD);
2166 
2167   // rewrite constant pool references in the methods:
2168   for (int i = methods->length() - 1; i >= 0; i--) {
2169     methodHandle method(THREAD, methods->at(i));
2170     methodHandle new_method;
2171     rewrite_cp_refs_in_method(method, &new_method, THREAD);
2172     if (!new_method.is_null()) {
2173       // the method has been replaced so save the new method version
2174       // even in the case of an exception.  original method is on the
2175       // deallocation list.
2176       methods->at_put(i, new_method());
2177     }
2178     if (HAS_PENDING_EXCEPTION) {
2179       Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
2180       log_info(redefine, class, load, exceptions)("rewrite_cp_refs_in_method exception: '%s'", ex_name->as_C_string());
2181       // Need to clear pending exception here as the super caller sets
2182       // the JVMTI_ERROR_INTERNAL if the returned value is false.
2183       CLEAR_PENDING_EXCEPTION;
2184       return false;
2185     }
2186   }
2187 
2188   return true;
2189 }
2190 
2191 
2192 // Rewrite constant pool references in the specific method. This code
2193 // was adapted from Rewriter::rewrite_method().
2194 void VM_RedefineClasses::rewrite_cp_refs_in_method(methodHandle method,
2195        methodHandle *new_method_p, TRAPS) {
2196 
2197   *new_method_p = methodHandle();  // default is no new method
2198 
2199   // We cache a pointer to the bytecodes here in code_base. If GC
2200   // moves the Method*, then the bytecodes will also move which
2201   // will likely cause a crash. We create a NoSafepointVerifier
2202   // object to detect whether we pass a possible safepoint in this
2203   // code block.
2204   NoSafepointVerifier nsv;
2205 
2206   // Bytecodes and their length
2207   address code_base = method->code_base();
2208   int code_length = method->code_size();
2209 
2210   int bc_length;
2211   for (int bci = 0; bci < code_length; bci += bc_length) {
2212     address bcp = code_base + bci;
2213     Bytecodes::Code c = (Bytecodes::Code)(*bcp);
2214 
2215     bc_length = Bytecodes::length_for(c);
2216     if (bc_length == 0) {
2217       // More complicated bytecodes report a length of zero so
2218       // we have to try again a slightly different way.
2219       bc_length = Bytecodes::length_at(method(), bcp);
2220     }
2221 
2222     assert(bc_length != 0, "impossible bytecode length");
2223 
2224     switch (c) {
2225       case Bytecodes::_ldc:
2226       {
2227         int cp_index = *(bcp + 1);
2228         int new_index = find_new_index(cp_index);
2229 
2230         if (StressLdcRewrite && new_index == 0) {
2231           // If we are stressing ldc -> ldc_w rewriting, then we
2232           // always need a new_index value.
2233           new_index = cp_index;
2234         }
2235         if (new_index != 0) {
2236           // the original index is mapped so we have more work to do
2237           if (!StressLdcRewrite && new_index <= max_jubyte) {
2238             // The new value can still use ldc instead of ldc_w
2239             // unless we are trying to stress ldc -> ldc_w rewriting
2240             log_trace(redefine, class, constantpool)
2241               ("%s@" INTPTR_FORMAT " old=%d, new=%d", Bytecodes::name(c), p2i(bcp), cp_index, new_index);
2242             *(bcp + 1) = new_index;
2243           } else {
2244             log_trace(redefine, class, constantpool)
2245               ("%s->ldc_w@" INTPTR_FORMAT " old=%d, new=%d", Bytecodes::name(c), p2i(bcp), cp_index, new_index);
2246             // the new value needs ldc_w instead of ldc
2247             u_char inst_buffer[4]; // max instruction size is 4 bytes
2248             bcp = (address)inst_buffer;
2249             // construct new instruction sequence
2250             *bcp = Bytecodes::_ldc_w;
2251             bcp++;
2252             // Rewriter::rewrite_method() does not rewrite ldc -> ldc_w.
2253             // See comment below for difference between put_Java_u2()
2254             // and put_native_u2().
2255             Bytes::put_Java_u2(bcp, new_index);
2256 
2257             Relocator rc(method, nullptr /* no RelocatorListener needed */);
2258             methodHandle m;
2259             {
2260               PauseNoSafepointVerifier pnsv(&nsv);
2261 
2262               // ldc is 2 bytes and ldc_w is 3 bytes
2263               m = rc.insert_space_at(bci, 3, inst_buffer, CHECK);
2264             }
2265 
2266             // return the new method so that the caller can update
2267             // the containing class
2268             *new_method_p = method = m;
2269             // switch our bytecode processing loop from the old method
2270             // to the new method
2271             code_base = method->code_base();
2272             code_length = method->code_size();
2273             bcp = code_base + bci;
2274             c = (Bytecodes::Code)(*bcp);
2275             bc_length = Bytecodes::length_for(c);
2276             assert(bc_length != 0, "sanity check");
2277           } // end we need ldc_w instead of ldc
2278         } // end if there is a mapped index
2279       } break;
2280 
2281       // these bytecodes have a two-byte constant pool index
2282       case Bytecodes::_anewarray      : // fall through
2283       case Bytecodes::_checkcast      : // fall through
2284       case Bytecodes::_getfield       : // fall through
2285       case Bytecodes::_getstatic      : // fall through
2286       case Bytecodes::_aconst_init   : // fall through
2287       case Bytecodes::_withfield      : // fall through
2288       case Bytecodes::_instanceof     : // fall through
2289       case Bytecodes::_invokedynamic  : // fall through
2290       case Bytecodes::_invokeinterface: // fall through
2291       case Bytecodes::_invokespecial  : // fall through
2292       case Bytecodes::_invokestatic   : // fall through
2293       case Bytecodes::_invokevirtual  : // fall through
2294       case Bytecodes::_ldc_w          : // fall through
2295       case Bytecodes::_ldc2_w         : // fall through
2296       case Bytecodes::_multianewarray : // fall through
2297       case Bytecodes::_new            : // fall through
2298       case Bytecodes::_putfield       : // fall through
2299       case Bytecodes::_putstatic      :
2300       {
2301         address p = bcp + 1;
2302         int cp_index = Bytes::get_Java_u2(p);
2303         int new_index = find_new_index(cp_index);
2304         if (new_index != 0) {
2305           // the original index is mapped so update w/ new value
2306           log_trace(redefine, class, constantpool)
2307             ("%s@" INTPTR_FORMAT " old=%d, new=%d", Bytecodes::name(c),p2i(bcp), cp_index, new_index);
2308           // Rewriter::rewrite_method() uses put_native_u2() in this
2309           // situation because it is reusing the constant pool index
2310           // location for a native index into the ConstantPoolCache.
2311           // Since we are updating the constant pool index prior to
2312           // verification and ConstantPoolCache initialization, we
2313           // need to keep the new index in Java byte order.
2314           Bytes::put_Java_u2(p, new_index);
2315         }
2316       } break;
2317       default:
2318         break;
2319     }
2320   } // end for each bytecode
2321 } // end rewrite_cp_refs_in_method()
2322 
2323 
2324 // Rewrite constant pool references in the class_annotations field.
2325 bool VM_RedefineClasses::rewrite_cp_refs_in_class_annotations(InstanceKlass* scratch_class) {
2326 
2327   AnnotationArray* class_annotations = scratch_class->class_annotations();
2328   if (class_annotations == nullptr || class_annotations->length() == 0) {
2329     // no class_annotations so nothing to do
2330     return true;
2331   }
2332 
2333   log_debug(redefine, class, annotation)("class_annotations length=%d", class_annotations->length());
2334 
2335   int byte_i = 0;  // byte index into class_annotations
2336   return rewrite_cp_refs_in_annotations_typeArray(class_annotations, byte_i);
2337 }
2338 
2339 
2340 // Rewrite constant pool references in an annotations typeArray. This
2341 // "structure" is adapted from the RuntimeVisibleAnnotations_attribute
2342 // that is described in section 4.8.15 of the 2nd-edition of the VM spec:
2343 //
2344 // annotations_typeArray {
2345 //   u2 num_annotations;
2346 //   annotation annotations[num_annotations];
2347 // }
2348 //
2349 bool VM_RedefineClasses::rewrite_cp_refs_in_annotations_typeArray(
2350        AnnotationArray* annotations_typeArray, int &byte_i_ref) {
2351 
2352   if ((byte_i_ref + 2) > annotations_typeArray->length()) {
2353     // not enough room for num_annotations field
2354     log_debug(redefine, class, annotation)("length() is too small for num_annotations field");
2355     return false;
2356   }
2357 
2358   u2 num_annotations = Bytes::get_Java_u2((address)
2359                          annotations_typeArray->adr_at(byte_i_ref));
2360   byte_i_ref += 2;
2361 
2362   log_debug(redefine, class, annotation)("num_annotations=%d", num_annotations);
2363 
2364   int calc_num_annotations = 0;
2365   for (; calc_num_annotations < num_annotations; calc_num_annotations++) {
2366     if (!rewrite_cp_refs_in_annotation_struct(annotations_typeArray, byte_i_ref)) {
2367       log_debug(redefine, class, annotation)("bad annotation_struct at %d", calc_num_annotations);
2368       // propagate failure back to caller
2369       return false;
2370     }
2371   }
2372   assert(num_annotations == calc_num_annotations, "sanity check");
2373 
2374   return true;
2375 } // end rewrite_cp_refs_in_annotations_typeArray()
2376 
2377 
2378 // Rewrite constant pool references in the annotation struct portion of
2379 // an annotations_typeArray. This "structure" is from section 4.8.15 of
2380 // the 2nd-edition of the VM spec:
2381 //
2382 // struct annotation {
2383 //   u2 type_index;
2384 //   u2 num_element_value_pairs;
2385 //   {
2386 //     u2 element_name_index;
2387 //     element_value value;
2388 //   } element_value_pairs[num_element_value_pairs];
2389 // }
2390 //
2391 bool VM_RedefineClasses::rewrite_cp_refs_in_annotation_struct(
2392        AnnotationArray* annotations_typeArray, int &byte_i_ref) {
2393   if ((byte_i_ref + 2 + 2) > annotations_typeArray->length()) {
2394     // not enough room for smallest annotation_struct
2395     log_debug(redefine, class, annotation)("length() is too small for annotation_struct");
2396     return false;
2397   }
2398 
2399   u2 type_index = rewrite_cp_ref_in_annotation_data(annotations_typeArray,
2400                     byte_i_ref, "type_index");
2401 
2402   u2 num_element_value_pairs = Bytes::get_Java_u2((address)
2403                                  annotations_typeArray->adr_at(byte_i_ref));
2404   byte_i_ref += 2;
2405 
2406   log_debug(redefine, class, annotation)
2407     ("type_index=%d  num_element_value_pairs=%d", type_index, num_element_value_pairs);
2408 
2409   int calc_num_element_value_pairs = 0;
2410   for (; calc_num_element_value_pairs < num_element_value_pairs;
2411        calc_num_element_value_pairs++) {
2412     if ((byte_i_ref + 2) > annotations_typeArray->length()) {
2413       // not enough room for another element_name_index, let alone
2414       // the rest of another component
2415       log_debug(redefine, class, annotation)("length() is too small for element_name_index");
2416       return false;
2417     }
2418 
2419     u2 element_name_index = rewrite_cp_ref_in_annotation_data(
2420                               annotations_typeArray, byte_i_ref,
2421                               "element_name_index");
2422 
2423     log_debug(redefine, class, annotation)("element_name_index=%d", element_name_index);
2424 
2425     if (!rewrite_cp_refs_in_element_value(annotations_typeArray, byte_i_ref)) {
2426       log_debug(redefine, class, annotation)("bad element_value at %d", calc_num_element_value_pairs);
2427       // propagate failure back to caller
2428       return false;
2429     }
2430   } // end for each component
2431   assert(num_element_value_pairs == calc_num_element_value_pairs,
2432     "sanity check");
2433 
2434   return true;
2435 } // end rewrite_cp_refs_in_annotation_struct()
2436 
2437 
2438 // Rewrite a constant pool reference at the current position in
2439 // annotations_typeArray if needed. Returns the original constant
2440 // pool reference if a rewrite was not needed or the new constant
2441 // pool reference if a rewrite was needed.
2442 u2 VM_RedefineClasses::rewrite_cp_ref_in_annotation_data(
2443      AnnotationArray* annotations_typeArray, int &byte_i_ref,
2444      const char * trace_mesg) {
2445 
2446   address cp_index_addr = (address)
2447     annotations_typeArray->adr_at(byte_i_ref);
2448   u2 old_cp_index = Bytes::get_Java_u2(cp_index_addr);
2449   u2 new_cp_index = find_new_index(old_cp_index);
2450   if (new_cp_index != 0) {
2451     log_debug(redefine, class, annotation)("mapped old %s=%d", trace_mesg, old_cp_index);
2452     Bytes::put_Java_u2(cp_index_addr, new_cp_index);
2453     old_cp_index = new_cp_index;
2454   }
2455   byte_i_ref += 2;
2456   return old_cp_index;
2457 }
2458 
2459 
2460 // Rewrite constant pool references in the element_value portion of an
2461 // annotations_typeArray. This "structure" is from section 4.8.15.1 of
2462 // the 2nd-edition of the VM spec:
2463 //
2464 // struct element_value {
2465 //   u1 tag;
2466 //   union {
2467 //     u2 const_value_index;
2468 //     {
2469 //       u2 type_name_index;
2470 //       u2 const_name_index;
2471 //     } enum_const_value;
2472 //     u2 class_info_index;
2473 //     annotation annotation_value;
2474 //     struct {
2475 //       u2 num_values;
2476 //       element_value values[num_values];
2477 //     } array_value;
2478 //   } value;
2479 // }
2480 //
2481 bool VM_RedefineClasses::rewrite_cp_refs_in_element_value(
2482        AnnotationArray* annotations_typeArray, int &byte_i_ref) {
2483 
2484   if ((byte_i_ref + 1) > annotations_typeArray->length()) {
2485     // not enough room for a tag let alone the rest of an element_value
2486     log_debug(redefine, class, annotation)("length() is too small for a tag");
2487     return false;
2488   }
2489 
2490   u1 tag = annotations_typeArray->at(byte_i_ref);
2491   byte_i_ref++;
2492   log_debug(redefine, class, annotation)("tag='%c'", tag);
2493 
2494   switch (tag) {
2495     // These BaseType tag values are from Table 4.2 in VM spec:
2496     case JVM_SIGNATURE_BYTE:
2497     case JVM_SIGNATURE_CHAR:
2498     case JVM_SIGNATURE_DOUBLE:
2499     case JVM_SIGNATURE_FLOAT:
2500     case JVM_SIGNATURE_INT:
2501     case JVM_SIGNATURE_LONG:
2502     case JVM_SIGNATURE_SHORT:
2503     case JVM_SIGNATURE_BOOLEAN:
2504 
2505     // The remaining tag values are from Table 4.8 in the 2nd-edition of
2506     // the VM spec:
2507     case 's':
2508     {
2509       // For the above tag values (including the BaseType values),
2510       // value.const_value_index is right union field.
2511 
2512       if ((byte_i_ref + 2) > annotations_typeArray->length()) {
2513         // not enough room for a const_value_index
2514         log_debug(redefine, class, annotation)("length() is too small for a const_value_index");
2515         return false;
2516       }
2517 
2518       u2 const_value_index = rewrite_cp_ref_in_annotation_data(
2519                                annotations_typeArray, byte_i_ref,
2520                                "const_value_index");
2521 
2522       log_debug(redefine, class, annotation)("const_value_index=%d", const_value_index);
2523     } break;
2524 
2525     case 'e':
2526     {
2527       // for the above tag value, value.enum_const_value is right union field
2528 
2529       if ((byte_i_ref + 4) > annotations_typeArray->length()) {
2530         // not enough room for a enum_const_value
2531         log_debug(redefine, class, annotation)("length() is too small for a enum_const_value");
2532         return false;
2533       }
2534 
2535       u2 type_name_index = rewrite_cp_ref_in_annotation_data(
2536                              annotations_typeArray, byte_i_ref,
2537                              "type_name_index");
2538 
2539       u2 const_name_index = rewrite_cp_ref_in_annotation_data(
2540                               annotations_typeArray, byte_i_ref,
2541                               "const_name_index");
2542 
2543       log_debug(redefine, class, annotation)
2544         ("type_name_index=%d  const_name_index=%d", type_name_index, const_name_index);
2545     } break;
2546 
2547     case 'c':
2548     {
2549       // for the above tag value, value.class_info_index is right union field
2550 
2551       if ((byte_i_ref + 2) > annotations_typeArray->length()) {
2552         // not enough room for a class_info_index
2553         log_debug(redefine, class, annotation)("length() is too small for a class_info_index");
2554         return false;
2555       }
2556 
2557       u2 class_info_index = rewrite_cp_ref_in_annotation_data(
2558                               annotations_typeArray, byte_i_ref,
2559                               "class_info_index");
2560 
2561       log_debug(redefine, class, annotation)("class_info_index=%d", class_info_index);
2562     } break;
2563 
2564     case '@':
2565       // For the above tag value, value.attr_value is the right union
2566       // field. This is a nested annotation.
2567       if (!rewrite_cp_refs_in_annotation_struct(annotations_typeArray, byte_i_ref)) {
2568         // propagate failure back to caller
2569         return false;
2570       }
2571       break;
2572 
2573     case JVM_SIGNATURE_ARRAY:
2574     {
2575       if ((byte_i_ref + 2) > annotations_typeArray->length()) {
2576         // not enough room for a num_values field
2577         log_debug(redefine, class, annotation)("length() is too small for a num_values field");
2578         return false;
2579       }
2580 
2581       // For the above tag value, value.array_value is the right union
2582       // field. This is an array of nested element_value.
2583       u2 num_values = Bytes::get_Java_u2((address)
2584                         annotations_typeArray->adr_at(byte_i_ref));
2585       byte_i_ref += 2;
2586       log_debug(redefine, class, annotation)("num_values=%d", num_values);
2587 
2588       int calc_num_values = 0;
2589       for (; calc_num_values < num_values; calc_num_values++) {
2590         if (!rewrite_cp_refs_in_element_value(annotations_typeArray, byte_i_ref)) {
2591           log_debug(redefine, class, annotation)("bad nested element_value at %d", calc_num_values);
2592           // propagate failure back to caller
2593           return false;
2594         }
2595       }
2596       assert(num_values == calc_num_values, "sanity check");
2597     } break;
2598 
2599     default:
2600       log_debug(redefine, class, annotation)("bad tag=0x%x", tag);
2601       return false;
2602   } // end decode tag field
2603 
2604   return true;
2605 } // end rewrite_cp_refs_in_element_value()
2606 
2607 
2608 // Rewrite constant pool references in a fields_annotations field.
2609 bool VM_RedefineClasses::rewrite_cp_refs_in_fields_annotations(
2610        InstanceKlass* scratch_class) {
2611 
2612   Array<AnnotationArray*>* fields_annotations = scratch_class->fields_annotations();
2613 
2614   if (fields_annotations == nullptr || fields_annotations->length() == 0) {
2615     // no fields_annotations so nothing to do
2616     return true;
2617   }
2618 
2619   log_debug(redefine, class, annotation)("fields_annotations length=%d", fields_annotations->length());
2620 
2621   for (int i = 0; i < fields_annotations->length(); i++) {
2622     AnnotationArray* field_annotations = fields_annotations->at(i);
2623     if (field_annotations == nullptr || field_annotations->length() == 0) {
2624       // this field does not have any annotations so skip it
2625       continue;
2626     }
2627 
2628     int byte_i = 0;  // byte index into field_annotations
2629     if (!rewrite_cp_refs_in_annotations_typeArray(field_annotations, byte_i)) {
2630       log_debug(redefine, class, annotation)("bad field_annotations at %d", i);
2631       // propagate failure back to caller
2632       return false;
2633     }
2634   }
2635 
2636   return true;
2637 } // end rewrite_cp_refs_in_fields_annotations()
2638 
2639 
2640 // Rewrite constant pool references in a methods_annotations field.
2641 bool VM_RedefineClasses::rewrite_cp_refs_in_methods_annotations(
2642        InstanceKlass* scratch_class) {
2643 
2644   for (int i = 0; i < scratch_class->methods()->length(); i++) {
2645     Method* m = scratch_class->methods()->at(i);
2646     AnnotationArray* method_annotations = m->constMethod()->method_annotations();
2647 
2648     if (method_annotations == nullptr || method_annotations->length() == 0) {
2649       // this method does not have any annotations so skip it
2650       continue;
2651     }
2652 
2653     int byte_i = 0;  // byte index into method_annotations
2654     if (!rewrite_cp_refs_in_annotations_typeArray(method_annotations, byte_i)) {
2655       log_debug(redefine, class, annotation)("bad method_annotations at %d", i);
2656       // propagate failure back to caller
2657       return false;
2658     }
2659   }
2660 
2661   return true;
2662 } // end rewrite_cp_refs_in_methods_annotations()
2663 
2664 
2665 // Rewrite constant pool references in a methods_parameter_annotations
2666 // field. This "structure" is adapted from the
2667 // RuntimeVisibleParameterAnnotations_attribute described in section
2668 // 4.8.17 of the 2nd-edition of the VM spec:
2669 //
2670 // methods_parameter_annotations_typeArray {
2671 //   u1 num_parameters;
2672 //   {
2673 //     u2 num_annotations;
2674 //     annotation annotations[num_annotations];
2675 //   } parameter_annotations[num_parameters];
2676 // }
2677 //
2678 bool VM_RedefineClasses::rewrite_cp_refs_in_methods_parameter_annotations(
2679        InstanceKlass* scratch_class) {
2680 
2681   for (int i = 0; i < scratch_class->methods()->length(); i++) {
2682     Method* m = scratch_class->methods()->at(i);
2683     AnnotationArray* method_parameter_annotations = m->constMethod()->parameter_annotations();
2684     if (method_parameter_annotations == nullptr
2685         || method_parameter_annotations->length() == 0) {
2686       // this method does not have any parameter annotations so skip it
2687       continue;
2688     }
2689 
2690     if (method_parameter_annotations->length() < 1) {
2691       // not enough room for a num_parameters field
2692       log_debug(redefine, class, annotation)("length() is too small for a num_parameters field at %d", i);
2693       return false;
2694     }
2695 
2696     int byte_i = 0;  // byte index into method_parameter_annotations
2697 
2698     u1 num_parameters = method_parameter_annotations->at(byte_i);
2699     byte_i++;
2700 
2701     log_debug(redefine, class, annotation)("num_parameters=%d", num_parameters);
2702 
2703     int calc_num_parameters = 0;
2704     for (; calc_num_parameters < num_parameters; calc_num_parameters++) {
2705       if (!rewrite_cp_refs_in_annotations_typeArray(method_parameter_annotations, byte_i)) {
2706         log_debug(redefine, class, annotation)("bad method_parameter_annotations at %d", calc_num_parameters);
2707         // propagate failure back to caller
2708         return false;
2709       }
2710     }
2711     assert(num_parameters == calc_num_parameters, "sanity check");
2712   }
2713 
2714   return true;
2715 } // end rewrite_cp_refs_in_methods_parameter_annotations()
2716 
2717 
2718 // Rewrite constant pool references in a methods_default_annotations
2719 // field. This "structure" is adapted from the AnnotationDefault_attribute
2720 // that is described in section 4.8.19 of the 2nd-edition of the VM spec:
2721 //
2722 // methods_default_annotations_typeArray {
2723 //   element_value default_value;
2724 // }
2725 //
2726 bool VM_RedefineClasses::rewrite_cp_refs_in_methods_default_annotations(
2727        InstanceKlass* scratch_class) {
2728 
2729   for (int i = 0; i < scratch_class->methods()->length(); i++) {
2730     Method* m = scratch_class->methods()->at(i);
2731     AnnotationArray* method_default_annotations = m->constMethod()->default_annotations();
2732     if (method_default_annotations == nullptr
2733         || method_default_annotations->length() == 0) {
2734       // this method does not have any default annotations so skip it
2735       continue;
2736     }
2737 
2738     int byte_i = 0;  // byte index into method_default_annotations
2739 
2740     if (!rewrite_cp_refs_in_element_value(
2741            method_default_annotations, byte_i)) {
2742       log_debug(redefine, class, annotation)("bad default element_value at %d", i);
2743       // propagate failure back to caller
2744       return false;
2745     }
2746   }
2747 
2748   return true;
2749 } // end rewrite_cp_refs_in_methods_default_annotations()
2750 
2751 
2752 // Rewrite constant pool references in a class_type_annotations field.
2753 bool VM_RedefineClasses::rewrite_cp_refs_in_class_type_annotations(
2754        InstanceKlass* scratch_class) {
2755 
2756   AnnotationArray* class_type_annotations = scratch_class->class_type_annotations();
2757   if (class_type_annotations == nullptr || class_type_annotations->length() == 0) {
2758     // no class_type_annotations so nothing to do
2759     return true;
2760   }
2761 
2762   log_debug(redefine, class, annotation)("class_type_annotations length=%d", class_type_annotations->length());
2763 
2764   int byte_i = 0;  // byte index into class_type_annotations
2765   return rewrite_cp_refs_in_type_annotations_typeArray(class_type_annotations,
2766       byte_i, "ClassFile");
2767 } // end rewrite_cp_refs_in_class_type_annotations()
2768 
2769 
2770 // Rewrite constant pool references in a fields_type_annotations field.
2771 bool VM_RedefineClasses::rewrite_cp_refs_in_fields_type_annotations(InstanceKlass* scratch_class) {
2772 
2773   Array<AnnotationArray*>* fields_type_annotations = scratch_class->fields_type_annotations();
2774   if (fields_type_annotations == nullptr || fields_type_annotations->length() == 0) {
2775     // no fields_type_annotations so nothing to do
2776     return true;
2777   }
2778 
2779   log_debug(redefine, class, annotation)("fields_type_annotations length=%d", fields_type_annotations->length());
2780 
2781   for (int i = 0; i < fields_type_annotations->length(); i++) {
2782     AnnotationArray* field_type_annotations = fields_type_annotations->at(i);
2783     if (field_type_annotations == nullptr || field_type_annotations->length() == 0) {
2784       // this field does not have any annotations so skip it
2785       continue;
2786     }
2787 
2788     int byte_i = 0;  // byte index into field_type_annotations
2789     if (!rewrite_cp_refs_in_type_annotations_typeArray(field_type_annotations,
2790            byte_i, "field_info")) {
2791       log_debug(redefine, class, annotation)("bad field_type_annotations at %d", i);
2792       // propagate failure back to caller
2793       return false;
2794     }
2795   }
2796 
2797   return true;
2798 } // end rewrite_cp_refs_in_fields_type_annotations()
2799 
2800 
2801 // Rewrite constant pool references in a methods_type_annotations field.
2802 bool VM_RedefineClasses::rewrite_cp_refs_in_methods_type_annotations(
2803        InstanceKlass* scratch_class) {
2804 
2805   for (int i = 0; i < scratch_class->methods()->length(); i++) {
2806     Method* m = scratch_class->methods()->at(i);
2807     AnnotationArray* method_type_annotations = m->constMethod()->type_annotations();
2808 
2809     if (method_type_annotations == nullptr || method_type_annotations->length() == 0) {
2810       // this method does not have any annotations so skip it
2811       continue;
2812     }
2813 
2814     log_debug(redefine, class, annotation)("methods type_annotations length=%d", method_type_annotations->length());
2815 
2816     int byte_i = 0;  // byte index into method_type_annotations
2817     if (!rewrite_cp_refs_in_type_annotations_typeArray(method_type_annotations,
2818            byte_i, "method_info")) {
2819       log_debug(redefine, class, annotation)("bad method_type_annotations at %d", i);
2820       // propagate failure back to caller
2821       return false;
2822     }
2823   }
2824 
2825   return true;
2826 } // end rewrite_cp_refs_in_methods_type_annotations()
2827 
2828 
2829 // Rewrite constant pool references in a type_annotations
2830 // field. This "structure" is adapted from the
2831 // RuntimeVisibleTypeAnnotations_attribute described in
2832 // section 4.7.20 of the Java SE 8 Edition of the VM spec:
2833 //
2834 // type_annotations_typeArray {
2835 //   u2              num_annotations;
2836 //   type_annotation annotations[num_annotations];
2837 // }
2838 //
2839 bool VM_RedefineClasses::rewrite_cp_refs_in_type_annotations_typeArray(
2840        AnnotationArray* type_annotations_typeArray, int &byte_i_ref,
2841        const char * location_mesg) {
2842 
2843   if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
2844     // not enough room for num_annotations field
2845     log_debug(redefine, class, annotation)("length() is too small for num_annotations field");
2846     return false;
2847   }
2848 
2849   u2 num_annotations = Bytes::get_Java_u2((address)
2850                          type_annotations_typeArray->adr_at(byte_i_ref));
2851   byte_i_ref += 2;
2852 
2853   log_debug(redefine, class, annotation)("num_type_annotations=%d", num_annotations);
2854 
2855   int calc_num_annotations = 0;
2856   for (; calc_num_annotations < num_annotations; calc_num_annotations++) {
2857     if (!rewrite_cp_refs_in_type_annotation_struct(type_annotations_typeArray,
2858            byte_i_ref, location_mesg)) {
2859       log_debug(redefine, class, annotation)("bad type_annotation_struct at %d", calc_num_annotations);
2860       // propagate failure back to caller
2861       return false;
2862     }
2863   }
2864   assert(num_annotations == calc_num_annotations, "sanity check");
2865 
2866   if (byte_i_ref != type_annotations_typeArray->length()) {
2867     log_debug(redefine, class, annotation)
2868       ("read wrong amount of bytes at end of processing type_annotations_typeArray (%d of %d bytes were read)",
2869        byte_i_ref, type_annotations_typeArray->length());
2870     return false;
2871   }
2872 
2873   return true;
2874 } // end rewrite_cp_refs_in_type_annotations_typeArray()
2875 
2876 
2877 // Rewrite constant pool references in a type_annotation
2878 // field. This "structure" is adapted from the
2879 // RuntimeVisibleTypeAnnotations_attribute described in
2880 // section 4.7.20 of the Java SE 8 Edition of the VM spec:
2881 //
2882 // type_annotation {
2883 //   u1 target_type;
2884 //   union {
2885 //     type_parameter_target;
2886 //     supertype_target;
2887 //     type_parameter_bound_target;
2888 //     empty_target;
2889 //     method_formal_parameter_target;
2890 //     throws_target;
2891 //     localvar_target;
2892 //     catch_target;
2893 //     offset_target;
2894 //     type_argument_target;
2895 //   } target_info;
2896 //   type_path target_path;
2897 //   annotation anno;
2898 // }
2899 //
2900 bool VM_RedefineClasses::rewrite_cp_refs_in_type_annotation_struct(
2901        AnnotationArray* type_annotations_typeArray, int &byte_i_ref,
2902        const char * location_mesg) {
2903 
2904   if (!skip_type_annotation_target(type_annotations_typeArray,
2905          byte_i_ref, location_mesg)) {
2906     return false;
2907   }
2908 
2909   if (!skip_type_annotation_type_path(type_annotations_typeArray, byte_i_ref)) {
2910     return false;
2911   }
2912 
2913   if (!rewrite_cp_refs_in_annotation_struct(type_annotations_typeArray, byte_i_ref)) {
2914     return false;
2915   }
2916 
2917   return true;
2918 } // end rewrite_cp_refs_in_type_annotation_struct()
2919 
2920 
2921 // Read, verify and skip over the target_type and target_info part
2922 // so that rewriting can continue in the later parts of the struct.
2923 //
2924 // u1 target_type;
2925 // union {
2926 //   type_parameter_target;
2927 //   supertype_target;
2928 //   type_parameter_bound_target;
2929 //   empty_target;
2930 //   method_formal_parameter_target;
2931 //   throws_target;
2932 //   localvar_target;
2933 //   catch_target;
2934 //   offset_target;
2935 //   type_argument_target;
2936 // } target_info;
2937 //
2938 bool VM_RedefineClasses::skip_type_annotation_target(
2939        AnnotationArray* type_annotations_typeArray, int &byte_i_ref,
2940        const char * location_mesg) {
2941 
2942   if ((byte_i_ref + 1) > type_annotations_typeArray->length()) {
2943     // not enough room for a target_type let alone the rest of a type_annotation
2944     log_debug(redefine, class, annotation)("length() is too small for a target_type");
2945     return false;
2946   }
2947 
2948   u1 target_type = type_annotations_typeArray->at(byte_i_ref);
2949   byte_i_ref += 1;
2950   log_debug(redefine, class, annotation)("target_type=0x%.2x", target_type);
2951   log_debug(redefine, class, annotation)("location=%s", location_mesg);
2952 
2953   // Skip over target_info
2954   switch (target_type) {
2955     case 0x00:
2956     // kind: type parameter declaration of generic class or interface
2957     // location: ClassFile
2958     case 0x01:
2959     // kind: type parameter declaration of generic method or constructor
2960     // location: method_info
2961 
2962     {
2963       // struct:
2964       // type_parameter_target {
2965       //   u1 type_parameter_index;
2966       // }
2967       //
2968       if ((byte_i_ref + 1) > type_annotations_typeArray->length()) {
2969         log_debug(redefine, class, annotation)("length() is too small for a type_parameter_target");
2970         return false;
2971       }
2972 
2973       u1 type_parameter_index = type_annotations_typeArray->at(byte_i_ref);
2974       byte_i_ref += 1;
2975 
2976       log_debug(redefine, class, annotation)("type_parameter_target: type_parameter_index=%d", type_parameter_index);
2977     } break;
2978 
2979     case 0x10:
2980     // kind: type in extends clause of class or interface declaration
2981     //       or in implements clause of interface declaration
2982     // location: ClassFile
2983 
2984     {
2985       // struct:
2986       // supertype_target {
2987       //   u2 supertype_index;
2988       // }
2989       //
2990       if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
2991         log_debug(redefine, class, annotation)("length() is too small for a supertype_target");
2992         return false;
2993       }
2994 
2995       u2 supertype_index = Bytes::get_Java_u2((address)
2996                              type_annotations_typeArray->adr_at(byte_i_ref));
2997       byte_i_ref += 2;
2998 
2999       log_debug(redefine, class, annotation)("supertype_target: supertype_index=%d", supertype_index);
3000     } break;
3001 
3002     case 0x11:
3003     // kind: type in bound of type parameter declaration of generic class or interface
3004     // location: ClassFile
3005     case 0x12:
3006     // kind: type in bound of type parameter declaration of generic method or constructor
3007     // location: method_info
3008 
3009     {
3010       // struct:
3011       // type_parameter_bound_target {
3012       //   u1 type_parameter_index;
3013       //   u1 bound_index;
3014       // }
3015       //
3016       if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
3017         log_debug(redefine, class, annotation)("length() is too small for a type_parameter_bound_target");
3018         return false;
3019       }
3020 
3021       u1 type_parameter_index = type_annotations_typeArray->at(byte_i_ref);
3022       byte_i_ref += 1;
3023       u1 bound_index = type_annotations_typeArray->at(byte_i_ref);
3024       byte_i_ref += 1;
3025 
3026       log_debug(redefine, class, annotation)
3027         ("type_parameter_bound_target: type_parameter_index=%d, bound_index=%d", type_parameter_index, bound_index);
3028     } break;
3029 
3030     case 0x13:
3031     // kind: type in field declaration
3032     // location: field_info
3033     case 0x14:
3034     // kind: return type of method, or type of newly constructed object
3035     // location: method_info
3036     case 0x15:
3037     // kind: receiver type of method or constructor
3038     // location: method_info
3039 
3040     {
3041       // struct:
3042       // empty_target {
3043       // }
3044       //
3045       log_debug(redefine, class, annotation)("empty_target");
3046     } break;
3047 
3048     case 0x16:
3049     // kind: type in formal parameter declaration of method, constructor, or lambda expression
3050     // location: method_info
3051 
3052     {
3053       // struct:
3054       // formal_parameter_target {
3055       //   u1 formal_parameter_index;
3056       // }
3057       //
3058       if ((byte_i_ref + 1) > type_annotations_typeArray->length()) {
3059         log_debug(redefine, class, annotation)("length() is too small for a formal_parameter_target");
3060         return false;
3061       }
3062 
3063       u1 formal_parameter_index = type_annotations_typeArray->at(byte_i_ref);
3064       byte_i_ref += 1;
3065 
3066       log_debug(redefine, class, annotation)
3067         ("formal_parameter_target: formal_parameter_index=%d", formal_parameter_index);
3068     } break;
3069 
3070     case 0x17:
3071     // kind: type in throws clause of method or constructor
3072     // location: method_info
3073 
3074     {
3075       // struct:
3076       // throws_target {
3077       //   u2 throws_type_index
3078       // }
3079       //
3080       if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
3081         log_debug(redefine, class, annotation)("length() is too small for a throws_target");
3082         return false;
3083       }
3084 
3085       u2 throws_type_index = Bytes::get_Java_u2((address)
3086                                type_annotations_typeArray->adr_at(byte_i_ref));
3087       byte_i_ref += 2;
3088 
3089       log_debug(redefine, class, annotation)("throws_target: throws_type_index=%d", throws_type_index);
3090     } break;
3091 
3092     case 0x40:
3093     // kind: type in local variable declaration
3094     // location: Code
3095     case 0x41:
3096     // kind: type in resource variable declaration
3097     // location: Code
3098 
3099     {
3100       // struct:
3101       // localvar_target {
3102       //   u2 table_length;
3103       //   struct {
3104       //     u2 start_pc;
3105       //     u2 length;
3106       //     u2 index;
3107       //   } table[table_length];
3108       // }
3109       //
3110       if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
3111         // not enough room for a table_length let alone the rest of a localvar_target
3112         log_debug(redefine, class, annotation)("length() is too small for a localvar_target table_length");
3113         return false;
3114       }
3115 
3116       u2 table_length = Bytes::get_Java_u2((address)
3117                           type_annotations_typeArray->adr_at(byte_i_ref));
3118       byte_i_ref += 2;
3119 
3120       log_debug(redefine, class, annotation)("localvar_target: table_length=%d", table_length);
3121 
3122       int table_struct_size = 2 + 2 + 2; // 3 u2 variables per table entry
3123       int table_size = table_length * table_struct_size;
3124 
3125       if ((byte_i_ref + table_size) > type_annotations_typeArray->length()) {
3126         // not enough room for a table
3127         log_debug(redefine, class, annotation)("length() is too small for a table array of length %d", table_length);
3128         return false;
3129       }
3130 
3131       // Skip over table
3132       byte_i_ref += table_size;
3133     } break;
3134 
3135     case 0x42:
3136     // kind: type in exception parameter declaration
3137     // location: Code
3138 
3139     {
3140       // struct:
3141       // catch_target {
3142       //   u2 exception_table_index;
3143       // }
3144       //
3145       if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
3146         log_debug(redefine, class, annotation)("length() is too small for a catch_target");
3147         return false;
3148       }
3149 
3150       u2 exception_table_index = Bytes::get_Java_u2((address)
3151                                    type_annotations_typeArray->adr_at(byte_i_ref));
3152       byte_i_ref += 2;
3153 
3154       log_debug(redefine, class, annotation)("catch_target: exception_table_index=%d", exception_table_index);
3155     } break;
3156 
3157     case 0x43:
3158     // kind: type in instanceof expression
3159     // location: Code
3160     case 0x44:
3161     // kind: type in new expression
3162     // location: Code
3163     case 0x45:
3164     // kind: type in method reference expression using ::new
3165     // location: Code
3166     case 0x46:
3167     // kind: type in method reference expression using ::Identifier
3168     // location: Code
3169 
3170     {
3171       // struct:
3172       // offset_target {
3173       //   u2 offset;
3174       // }
3175       //
3176       if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
3177         log_debug(redefine, class, annotation)("length() is too small for a offset_target");
3178         return false;
3179       }
3180 
3181       u2 offset = Bytes::get_Java_u2((address)
3182                     type_annotations_typeArray->adr_at(byte_i_ref));
3183       byte_i_ref += 2;
3184 
3185       log_debug(redefine, class, annotation)("offset_target: offset=%d", offset);
3186     } break;
3187 
3188     case 0x47:
3189     // kind: type in cast expression
3190     // location: Code
3191     case 0x48:
3192     // kind: type argument for generic constructor in new expression or
3193     //       explicit constructor invocation statement
3194     // location: Code
3195     case 0x49:
3196     // kind: type argument for generic method in method invocation expression
3197     // location: Code
3198     case 0x4A:
3199     // kind: type argument for generic constructor in method reference expression using ::new
3200     // location: Code
3201     case 0x4B:
3202     // kind: type argument for generic method in method reference expression using ::Identifier
3203     // location: Code
3204 
3205     {
3206       // struct:
3207       // type_argument_target {
3208       //   u2 offset;
3209       //   u1 type_argument_index;
3210       // }
3211       //
3212       if ((byte_i_ref + 3) > type_annotations_typeArray->length()) {
3213         log_debug(redefine, class, annotation)("length() is too small for a type_argument_target");
3214         return false;
3215       }
3216 
3217       u2 offset = Bytes::get_Java_u2((address)
3218                     type_annotations_typeArray->adr_at(byte_i_ref));
3219       byte_i_ref += 2;
3220       u1 type_argument_index = type_annotations_typeArray->at(byte_i_ref);
3221       byte_i_ref += 1;
3222 
3223       log_debug(redefine, class, annotation)
3224         ("type_argument_target: offset=%d, type_argument_index=%d", offset, type_argument_index);
3225     } break;
3226 
3227     default:
3228       log_debug(redefine, class, annotation)("unknown target_type");
3229 #ifdef ASSERT
3230       ShouldNotReachHere();
3231 #endif
3232       return false;
3233   }
3234 
3235   return true;
3236 } // end skip_type_annotation_target()
3237 
3238 
3239 // Read, verify and skip over the type_path part so that rewriting
3240 // can continue in the later parts of the struct.
3241 //
3242 // type_path {
3243 //   u1 path_length;
3244 //   {
3245 //     u1 type_path_kind;
3246 //     u1 type_argument_index;
3247 //   } path[path_length];
3248 // }
3249 //
3250 bool VM_RedefineClasses::skip_type_annotation_type_path(
3251        AnnotationArray* type_annotations_typeArray, int &byte_i_ref) {
3252 
3253   if ((byte_i_ref + 1) > type_annotations_typeArray->length()) {
3254     // not enough room for a path_length let alone the rest of the type_path
3255     log_debug(redefine, class, annotation)("length() is too small for a type_path");
3256     return false;
3257   }
3258 
3259   u1 path_length = type_annotations_typeArray->at(byte_i_ref);
3260   byte_i_ref += 1;
3261 
3262   log_debug(redefine, class, annotation)("type_path: path_length=%d", path_length);
3263 
3264   int calc_path_length = 0;
3265   for (; calc_path_length < path_length; calc_path_length++) {
3266     if ((byte_i_ref + 1 + 1) > type_annotations_typeArray->length()) {
3267       // not enough room for a path
3268       log_debug(redefine, class, annotation)
3269         ("length() is too small for path entry %d of %d", calc_path_length, path_length);
3270       return false;
3271     }
3272 
3273     u1 type_path_kind = type_annotations_typeArray->at(byte_i_ref);
3274     byte_i_ref += 1;
3275     u1 type_argument_index = type_annotations_typeArray->at(byte_i_ref);
3276     byte_i_ref += 1;
3277 
3278     log_debug(redefine, class, annotation)
3279       ("type_path: path[%d]: type_path_kind=%d, type_argument_index=%d",
3280        calc_path_length, type_path_kind, type_argument_index);
3281 
3282     if (type_path_kind > 3 || (type_path_kind != 3 && type_argument_index != 0)) {
3283       // not enough room for a path
3284       log_debug(redefine, class, annotation)("inconsistent type_path values");
3285       return false;
3286     }
3287   }
3288   assert(path_length == calc_path_length, "sanity check");
3289 
3290   return true;
3291 } // end skip_type_annotation_type_path()
3292 
3293 
3294 // Rewrite constant pool references in the method's stackmap table.
3295 // These "structures" are adapted from the StackMapTable_attribute that
3296 // is described in section 4.8.4 of the 6.0 version of the VM spec
3297 // (dated 2005.10.26):
3298 // file:///net/quincunx.sfbay/export/gbracha/ClassFile-Java6.pdf
3299 //
3300 // stack_map {
3301 //   u2 number_of_entries;
3302 //   stack_map_frame entries[number_of_entries];
3303 // }
3304 //
3305 void VM_RedefineClasses::rewrite_cp_refs_in_stack_map_table(
3306        const methodHandle& method) {
3307 
3308   if (!method->has_stackmap_table()) {
3309     return;
3310   }
3311 
3312   AnnotationArray* stackmap_data = method->stackmap_data();
3313   address stackmap_p = (address)stackmap_data->adr_at(0);
3314   address stackmap_end = stackmap_p + stackmap_data->length();
3315 
3316   assert(stackmap_p + 2 <= stackmap_end, "no room for number_of_entries");
3317   u2 number_of_entries = Bytes::get_Java_u2(stackmap_p);
3318   stackmap_p += 2;
3319 
3320   log_debug(redefine, class, stackmap)("number_of_entries=%u", number_of_entries);
3321 
3322   // walk through each stack_map_frame
3323   u2 calc_number_of_entries = 0;
3324   for (; calc_number_of_entries < number_of_entries; calc_number_of_entries++) {
3325     // The stack_map_frame structure is a u1 frame_type followed by
3326     // 0 or more bytes of data:
3327     //
3328     // union stack_map_frame {
3329     //   same_frame;
3330     //   same_locals_1_stack_item_frame;
3331     //   same_locals_1_stack_item_frame_extended;
3332     //   chop_frame;
3333     //   same_frame_extended;
3334     //   append_frame;
3335     //   full_frame;
3336     // }
3337 
3338     assert(stackmap_p + 1 <= stackmap_end, "no room for frame_type");
3339     u1 frame_type = *stackmap_p;
3340     stackmap_p++;
3341 
3342     // same_frame {
3343     //   u1 frame_type = SAME; /* 0-63 */
3344     // }
3345     if (frame_type <= 63) {
3346       // nothing more to do for same_frame
3347     }
3348 
3349     // same_locals_1_stack_item_frame {
3350     //   u1 frame_type = SAME_LOCALS_1_STACK_ITEM; /* 64-127 */
3351     //   verification_type_info stack[1];
3352     // }
3353     else if (frame_type >= 64 && frame_type <= 127) {
3354       rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
3355         calc_number_of_entries, frame_type);
3356     }
3357 
3358     // reserved for future use
3359     else if (frame_type >= 128 && frame_type <= 246) {
3360       // nothing more to do for reserved frame_types
3361     }
3362 
3363     // same_locals_1_stack_item_frame_extended {
3364     //   u1 frame_type = SAME_LOCALS_1_STACK_ITEM_EXTENDED; /* 247 */
3365     //   u2 offset_delta;
3366     //   verification_type_info stack[1];
3367     // }
3368     else if (frame_type == 247) {
3369       stackmap_p += 2;
3370       rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
3371         calc_number_of_entries, frame_type);
3372     }
3373 
3374     // chop_frame {
3375     //   u1 frame_type = CHOP; /* 248-250 */
3376     //   u2 offset_delta;
3377     // }
3378     else if (frame_type >= 248 && frame_type <= 250) {
3379       stackmap_p += 2;
3380     }
3381 
3382     // same_frame_extended {
3383     //   u1 frame_type = SAME_FRAME_EXTENDED; /* 251*/
3384     //   u2 offset_delta;
3385     // }
3386     else if (frame_type == 251) {
3387       stackmap_p += 2;
3388     }
3389 
3390     // append_frame {
3391     //   u1 frame_type = APPEND; /* 252-254 */
3392     //   u2 offset_delta;
3393     //   verification_type_info locals[frame_type - 251];
3394     // }
3395     else if (frame_type >= 252 && frame_type <= 254) {
3396       assert(stackmap_p + 2 <= stackmap_end,
3397         "no room for offset_delta");
3398       stackmap_p += 2;
3399       u1 len = frame_type - 251;
3400       for (u1 i = 0; i < len; i++) {
3401         rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
3402           calc_number_of_entries, frame_type);
3403       }
3404     }
3405 
3406     // full_frame {
3407     //   u1 frame_type = FULL_FRAME; /* 255 */
3408     //   u2 offset_delta;
3409     //   u2 number_of_locals;
3410     //   verification_type_info locals[number_of_locals];
3411     //   u2 number_of_stack_items;
3412     //   verification_type_info stack[number_of_stack_items];
3413     // }
3414     else if (frame_type == 255) {
3415       assert(stackmap_p + 2 + 2 <= stackmap_end,
3416         "no room for smallest full_frame");
3417       stackmap_p += 2;
3418 
3419       u2 number_of_locals = Bytes::get_Java_u2(stackmap_p);
3420       stackmap_p += 2;
3421 
3422       for (u2 locals_i = 0; locals_i < number_of_locals; locals_i++) {
3423         rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
3424           calc_number_of_entries, frame_type);
3425       }
3426 
3427       // Use the largest size for the number_of_stack_items, but only get
3428       // the right number of bytes.
3429       u2 number_of_stack_items = Bytes::get_Java_u2(stackmap_p);
3430       stackmap_p += 2;
3431 
3432       for (u2 stack_i = 0; stack_i < number_of_stack_items; stack_i++) {
3433         rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
3434           calc_number_of_entries, frame_type);
3435       }
3436     }
3437   } // end while there is a stack_map_frame
3438   assert(number_of_entries == calc_number_of_entries, "sanity check");
3439 } // end rewrite_cp_refs_in_stack_map_table()
3440 
3441 
3442 // Rewrite constant pool references in the verification type info
3443 // portion of the method's stackmap table. These "structures" are
3444 // adapted from the StackMapTable_attribute that is described in
3445 // section 4.8.4 of the 6.0 version of the VM spec (dated 2005.10.26):
3446 // file:///net/quincunx.sfbay/export/gbracha/ClassFile-Java6.pdf
3447 //
3448 // The verification_type_info structure is a u1 tag followed by 0 or
3449 // more bytes of data:
3450 //
3451 // union verification_type_info {
3452 //   Top_variable_info;
3453 //   Integer_variable_info;
3454 //   Float_variable_info;
3455 //   Long_variable_info;
3456 //   Double_variable_info;
3457 //   Null_variable_info;
3458 //   UninitializedThis_variable_info;
3459 //   Object_variable_info;
3460 //   Uninitialized_variable_info;
3461 // }
3462 //
3463 void VM_RedefineClasses::rewrite_cp_refs_in_verification_type_info(
3464        address& stackmap_p_ref, address stackmap_end, u2 frame_i,
3465        u1 frame_type) {
3466 
3467   assert(stackmap_p_ref + 1 <= stackmap_end, "no room for tag");
3468   u1 tag = *stackmap_p_ref;
3469   stackmap_p_ref++;
3470 
3471   switch (tag) {
3472   // Top_variable_info {
3473   //   u1 tag = ITEM_Top; /* 0 */
3474   // }
3475   // verificationType.hpp has zero as ITEM_Bogus instead of ITEM_Top
3476   case 0:  // fall through
3477 
3478   // Integer_variable_info {
3479   //   u1 tag = ITEM_Integer; /* 1 */
3480   // }
3481   case ITEM_Integer:  // fall through
3482 
3483   // Float_variable_info {
3484   //   u1 tag = ITEM_Float; /* 2 */
3485   // }
3486   case ITEM_Float:  // fall through
3487 
3488   // Double_variable_info {
3489   //   u1 tag = ITEM_Double; /* 3 */
3490   // }
3491   case ITEM_Double:  // fall through
3492 
3493   // Long_variable_info {
3494   //   u1 tag = ITEM_Long; /* 4 */
3495   // }
3496   case ITEM_Long:  // fall through
3497 
3498   // Null_variable_info {
3499   //   u1 tag = ITEM_Null; /* 5 */
3500   // }
3501   case ITEM_Null:  // fall through
3502 
3503   // UninitializedThis_variable_info {
3504   //   u1 tag = ITEM_UninitializedThis; /* 6 */
3505   // }
3506   case ITEM_UninitializedThis:
3507     // nothing more to do for the above tag types
3508     break;
3509 
3510   // Object_variable_info {
3511   //   u1 tag = ITEM_Object; /* 7 */
3512   //   u2 cpool_index;
3513   // }
3514   case ITEM_Object:
3515   {
3516     assert(stackmap_p_ref + 2 <= stackmap_end, "no room for cpool_index");
3517     u2 cpool_index = Bytes::get_Java_u2(stackmap_p_ref);
3518     u2 new_cp_index = find_new_index(cpool_index);
3519     if (new_cp_index != 0) {
3520       log_debug(redefine, class, stackmap)("mapped old cpool_index=%d", cpool_index);
3521       Bytes::put_Java_u2(stackmap_p_ref, new_cp_index);
3522       cpool_index = new_cp_index;
3523     }
3524     stackmap_p_ref += 2;
3525 
3526     log_debug(redefine, class, stackmap)
3527       ("frame_i=%u, frame_type=%u, cpool_index=%d", frame_i, frame_type, cpool_index);
3528   } break;
3529 
3530   // Uninitialized_variable_info {
3531   //   u1 tag = ITEM_Uninitialized; /* 8 */
3532   //   u2 offset;
3533   // }
3534   case ITEM_Uninitialized:
3535     assert(stackmap_p_ref + 2 <= stackmap_end, "no room for offset");
3536     stackmap_p_ref += 2;
3537     break;
3538 
3539   default:
3540     log_debug(redefine, class, stackmap)("frame_i=%u, frame_type=%u, bad tag=0x%x", frame_i, frame_type, tag);
3541     ShouldNotReachHere();
3542     break;
3543   } // end switch (tag)
3544 } // end rewrite_cp_refs_in_verification_type_info()
3545 
3546 
3547 // Change the constant pool associated with klass scratch_class to scratch_cp.
3548 // scratch_cp_length elements are copied from scratch_cp to a smaller constant pool
3549 // and the smaller constant pool is associated with scratch_class.
3550 void VM_RedefineClasses::set_new_constant_pool(
3551        ClassLoaderData* loader_data,
3552        InstanceKlass* scratch_class, constantPoolHandle scratch_cp,
3553        int scratch_cp_length, TRAPS) {
3554   assert(scratch_cp->length() >= scratch_cp_length, "sanity check");
3555 
3556   // scratch_cp is a merged constant pool and has enough space for a
3557   // worst case merge situation. We want to associate the minimum
3558   // sized constant pool with the klass to save space.
3559   ConstantPool* cp = ConstantPool::allocate(loader_data, scratch_cp_length, CHECK);
3560   constantPoolHandle smaller_cp(THREAD, cp);
3561 
3562   // preserve version() value in the smaller copy
3563   int version = scratch_cp->version();
3564   assert(version != 0, "sanity check");
3565   smaller_cp->set_version(version);
3566 
3567   // attach klass to new constant pool
3568   // reference to the cp holder is needed for copy_operands()
3569   smaller_cp->set_pool_holder(scratch_class);
3570 
3571   smaller_cp->copy_fields(scratch_cp());
3572 
3573   scratch_cp->copy_cp_to(1, scratch_cp_length - 1, smaller_cp, 1, THREAD);
3574   if (HAS_PENDING_EXCEPTION) {
3575     // Exception is handled in the caller
3576     loader_data->add_to_deallocate_list(smaller_cp());
3577     return;
3578   }
3579   scratch_cp = smaller_cp;
3580 
3581   // attach new constant pool to klass
3582   scratch_class->set_constants(scratch_cp());
3583   scratch_cp->initialize_unresolved_klasses(loader_data, CHECK);
3584 
3585   int i;  // for portability
3586 
3587   // update each field in klass to use new constant pool indices as needed
3588   int java_fields;
3589   int injected_fields;
3590   bool update_required = false;
3591   GrowableArray<FieldInfo>* fields = FieldInfoStream::create_FieldInfoArray(scratch_class->fieldinfo_stream(), &java_fields, &injected_fields);
3592   for (int i = 0; i < java_fields; i++) {
3593     FieldInfo* fi = fields->adr_at(i);
3594     jshort cur_index = fi->name_index();
3595     jshort new_index = find_new_index(cur_index);
3596     if (new_index != 0) {
3597       log_trace(redefine, class, constantpool)("field-name_index change: %d to %d", cur_index, new_index);
3598       fi->set_name_index(new_index);
3599       update_required = true;
3600     }
3601     cur_index = fi->signature_index();
3602     new_index = find_new_index(cur_index);
3603     if (new_index != 0) {
3604       log_trace(redefine, class, constantpool)("field-signature_index change: %d to %d", cur_index, new_index);
3605       fi->set_signature_index(new_index);
3606       update_required = true;
3607     }
3608     cur_index = fi->initializer_index();
3609     new_index = find_new_index(cur_index);
3610     if (new_index != 0) {
3611       log_trace(redefine, class, constantpool)("field-initval_index change: %d to %d", cur_index, new_index);
3612       fi->set_initializer_index(new_index);
3613       update_required = true;
3614     }
3615     cur_index = fi->generic_signature_index();
3616     new_index = find_new_index(cur_index);
3617     if (new_index != 0) {
3618       log_trace(redefine, class, constantpool)("field-generic_signature change: %d to %d", cur_index, new_index);
3619       fi->set_generic_signature_index(new_index);
3620       update_required = true;
3621     }
3622   }
3623   if (update_required) {
3624     Array<u1>* old_stream = scratch_class->fieldinfo_stream();
3625     assert(fields->length() == (java_fields + injected_fields), "Must be");
3626     Array<u1>* new_fis = FieldInfoStream::create_FieldInfoStream(fields, java_fields, injected_fields, scratch_class->class_loader_data(), CHECK);
3627     scratch_class->set_fieldinfo_stream(new_fis);
3628     MetadataFactory::free_array<u1>(scratch_class->class_loader_data(), old_stream);
3629   }
3630 
3631   // Update constant pool indices in the inner classes info to use
3632   // new constant indices as needed. The inner classes info is a
3633   // quadruple:
3634   // (inner_class_info, outer_class_info, inner_name, inner_access_flags)
3635   InnerClassesIterator iter(scratch_class);
3636   for (; !iter.done(); iter.next()) {
3637     int cur_index = iter.inner_class_info_index();
3638     if (cur_index == 0) {
3639       continue;  // JVM spec. allows null inner class refs so skip it
3640     }
3641     int new_index = find_new_index(cur_index);
3642     if (new_index != 0) {
3643       log_trace(redefine, class, constantpool)("inner_class_info change: %d to %d", cur_index, new_index);
3644       iter.set_inner_class_info_index(new_index);
3645     }
3646     cur_index = iter.outer_class_info_index();
3647     new_index = find_new_index(cur_index);
3648     if (new_index != 0) {
3649       log_trace(redefine, class, constantpool)("outer_class_info change: %d to %d", cur_index, new_index);
3650       iter.set_outer_class_info_index(new_index);
3651     }
3652     cur_index = iter.inner_name_index();
3653     new_index = find_new_index(cur_index);
3654     if (new_index != 0) {
3655       log_trace(redefine, class, constantpool)("inner_name change: %d to %d", cur_index, new_index);
3656       iter.set_inner_name_index(new_index);
3657     }
3658   } // end for each inner class
3659 
3660   // Attach each method in klass to the new constant pool and update
3661   // to use new constant pool indices as needed:
3662   Array<Method*>* methods = scratch_class->methods();
3663   for (i = methods->length() - 1; i >= 0; i--) {
3664     methodHandle method(THREAD, methods->at(i));
3665     method->set_constants(scratch_cp());
3666 
3667     int new_index = find_new_index(method->name_index());
3668     if (new_index != 0) {
3669       log_trace(redefine, class, constantpool)
3670         ("method-name_index change: %d to %d", method->name_index(), new_index);
3671       method->set_name_index(new_index);
3672     }
3673     new_index = find_new_index(method->signature_index());
3674     if (new_index != 0) {
3675       log_trace(redefine, class, constantpool)
3676         ("method-signature_index change: %d to %d", method->signature_index(), new_index);
3677       method->set_signature_index(new_index);
3678     }
3679     new_index = find_new_index(method->generic_signature_index());
3680     if (new_index != 0) {
3681       log_trace(redefine, class, constantpool)
3682         ("method-generic_signature_index change: %d to %d", method->generic_signature_index(), new_index);
3683       method->set_generic_signature_index(new_index);
3684     }
3685 
3686     // Update constant pool indices in the method's checked exception
3687     // table to use new constant indices as needed.
3688     int cext_length = method->checked_exceptions_length();
3689     if (cext_length > 0) {
3690       CheckedExceptionElement * cext_table =
3691         method->checked_exceptions_start();
3692       for (int j = 0; j < cext_length; j++) {
3693         int cur_index = cext_table[j].class_cp_index;
3694         int new_index = find_new_index(cur_index);
3695         if (new_index != 0) {
3696           log_trace(redefine, class, constantpool)("cext-class_cp_index change: %d to %d", cur_index, new_index);
3697           cext_table[j].class_cp_index = (u2)new_index;
3698         }
3699       } // end for each checked exception table entry
3700     } // end if there are checked exception table entries
3701 
3702     // Update each catch type index in the method's exception table
3703     // to use new constant pool indices as needed. The exception table
3704     // holds quadruple entries of the form:
3705     //   (beg_bci, end_bci, handler_bci, klass_index)
3706 
3707     ExceptionTable ex_table(method());
3708     int ext_length = ex_table.length();
3709 
3710     for (int j = 0; j < ext_length; j ++) {
3711       int cur_index = ex_table.catch_type_index(j);
3712       int new_index = find_new_index(cur_index);
3713       if (new_index != 0) {
3714         log_trace(redefine, class, constantpool)("ext-klass_index change: %d to %d", cur_index, new_index);
3715         ex_table.set_catch_type_index(j, new_index);
3716       }
3717     } // end for each exception table entry
3718 
3719     // Update constant pool indices in the method's local variable
3720     // table to use new constant indices as needed. The local variable
3721     // table hold sextuple entries of the form:
3722     // (start_pc, length, name_index, descriptor_index, signature_index, slot)
3723     int lvt_length = method->localvariable_table_length();
3724     if (lvt_length > 0) {
3725       LocalVariableTableElement * lv_table =
3726         method->localvariable_table_start();
3727       for (int j = 0; j < lvt_length; j++) {
3728         int cur_index = lv_table[j].name_cp_index;
3729         int new_index = find_new_index(cur_index);
3730         if (new_index != 0) {
3731           log_trace(redefine, class, constantpool)("lvt-name_cp_index change: %d to %d", cur_index, new_index);
3732           lv_table[j].name_cp_index = (u2)new_index;
3733         }
3734         cur_index = lv_table[j].descriptor_cp_index;
3735         new_index = find_new_index(cur_index);
3736         if (new_index != 0) {
3737           log_trace(redefine, class, constantpool)("lvt-descriptor_cp_index change: %d to %d", cur_index, new_index);
3738           lv_table[j].descriptor_cp_index = (u2)new_index;
3739         }
3740         cur_index = lv_table[j].signature_cp_index;
3741         new_index = find_new_index(cur_index);
3742         if (new_index != 0) {
3743           log_trace(redefine, class, constantpool)("lvt-signature_cp_index change: %d to %d", cur_index, new_index);
3744           lv_table[j].signature_cp_index = (u2)new_index;
3745         }
3746       } // end for each local variable table entry
3747     } // end if there are local variable table entries
3748 
3749     // Update constant pool indices in the method's method_parameters.
3750     int mp_length = method->method_parameters_length();
3751     if (mp_length > 0) {
3752       MethodParametersElement* elem = method->method_parameters_start();
3753       for (int j = 0; j < mp_length; j++) {
3754         const int cp_index = elem[j].name_cp_index;
3755         const int new_cp_index = find_new_index(cp_index);
3756         if (new_cp_index != 0) {
3757           elem[j].name_cp_index = (u2)new_cp_index;
3758         }
3759       }
3760     }
3761 
3762     rewrite_cp_refs_in_stack_map_table(method);
3763   } // end for each method
3764 } // end set_new_constant_pool()
3765 
3766 
3767 // Unevolving classes may point to methods of the_class directly
3768 // from their constant pool caches, itables, and/or vtables. We
3769 // use the ClassLoaderDataGraph::classes_do() facility and this helper
3770 // to fix up these pointers.  MethodData also points to old methods and
3771 // must be cleaned.
3772 
3773 // Adjust cpools and vtables closure
3774 void VM_RedefineClasses::AdjustAndCleanMetadata::do_klass(Klass* k) {
3775 
3776   // This is a very busy routine. We don't want too much tracing
3777   // printed out.
3778   bool trace_name_printed = false;
3779 
3780   // If the class being redefined is java.lang.Object, we need to fix all
3781   // array class vtables also. The _has_redefined_Object flag is global.
3782   // Once the java.lang.Object has been redefined (by the current or one
3783   // of the previous VM_RedefineClasses operations) we have to always
3784   // adjust method entries for array classes.
3785   if (k->is_array_klass() && _has_redefined_Object) {
3786     k->vtable().adjust_method_entries(&trace_name_printed);
3787 
3788   } else if (k->is_instance_klass()) {
3789     HandleMark hm(_thread);
3790     InstanceKlass *ik = InstanceKlass::cast(k);
3791 
3792     // Clean MethodData of this class's methods so they don't refer to
3793     // old methods that are no longer running.
3794     Array<Method*>* methods = ik->methods();
3795     int num_methods = methods->length();
3796     for (int index = 0; index < num_methods; ++index) {
3797       if (methods->at(index)->method_data() != nullptr) {
3798         methods->at(index)->method_data()->clean_weak_method_links();
3799       }
3800     }
3801 
3802     // Adjust all vtables, default methods and itables, to clean out old methods.
3803     ResourceMark rm(_thread);
3804     if (ik->vtable_length() > 0) {
3805       ik->vtable().adjust_method_entries(&trace_name_printed);
3806       ik->adjust_default_methods(&trace_name_printed);
3807     }
3808 
3809     if (ik->itable_length() > 0) {
3810       ik->itable().adjust_method_entries(&trace_name_printed);
3811     }
3812 
3813     // The constant pools in other classes (other_cp) can refer to
3814     // old methods.  We have to update method information in
3815     // other_cp's cache. If other_cp has a previous version, then we
3816     // have to repeat the process for each previous version. The
3817     // constant pool cache holds the Method*s for non-virtual
3818     // methods and for virtual, final methods.
3819     //
3820     // Special case: if the current class is being redefined by the current
3821     // VM_RedefineClasses operation, then new_cp has already been attached
3822     // to the_class and old_cp has already been added as a previous version.
3823     // The new_cp doesn't have any cached references to old methods so it
3824     // doesn't need to be updated and we could optimize by skipping it.
3825     // However, the current class can be marked as being redefined by another
3826     // VM_RedefineClasses operation which has already executed its doit_prologue
3827     // and needs cpcache method entries adjusted. For simplicity, the cpcache
3828     // update is done unconditionally. It should result in doing nothing for
3829     // classes being redefined by the current VM_RedefineClasses operation.
3830     // Method entries in the previous version(s) are adjusted as well.
3831     ConstantPoolCache* cp_cache;
3832 
3833     // this klass' constant pool cache may need adjustment
3834     ConstantPool* other_cp = ik->constants();
3835     cp_cache = other_cp->cache();
3836     if (cp_cache != nullptr) {
3837       cp_cache->adjust_method_entries(&trace_name_printed);
3838     }
3839 
3840     // the previous versions' constant pool caches may need adjustment
3841     for (InstanceKlass* pv_node = ik->previous_versions();
3842          pv_node != nullptr;
3843          pv_node = pv_node->previous_versions()) {
3844       cp_cache = pv_node->constants()->cache();
3845       if (cp_cache != nullptr) {
3846         cp_cache->adjust_method_entries(&trace_name_printed);
3847       }
3848     }
3849   }
3850 }
3851 
3852 void VM_RedefineClasses::update_jmethod_ids() {
3853   for (int j = 0; j < _matching_methods_length; ++j) {
3854     Method* old_method = _matching_old_methods[j];
3855     jmethodID jmid = old_method->find_jmethod_id_or_null();
3856     if (jmid != nullptr) {
3857       // There is a jmethodID, change it to point to the new method
3858       Method* new_method = _matching_new_methods[j];
3859       Method::change_method_associated_with_jmethod_id(jmid, new_method);
3860       assert(Method::resolve_jmethod_id(jmid) == _matching_new_methods[j],
3861              "should be replaced");
3862     }
3863   }
3864 }
3865 
3866 int VM_RedefineClasses::check_methods_and_mark_as_obsolete() {
3867   int emcp_method_count = 0;
3868   int obsolete_count = 0;
3869   int old_index = 0;
3870   for (int j = 0; j < _matching_methods_length; ++j, ++old_index) {
3871     Method* old_method = _matching_old_methods[j];
3872     Method* new_method = _matching_new_methods[j];
3873     Method* old_array_method;
3874 
3875     // Maintain an old_index into the _old_methods array by skipping
3876     // deleted methods
3877     while ((old_array_method = _old_methods->at(old_index)) != old_method) {
3878       ++old_index;
3879     }
3880 
3881     if (MethodComparator::methods_EMCP(old_method, new_method)) {
3882       // The EMCP definition from JSR-163 requires the bytecodes to be
3883       // the same with the exception of constant pool indices which may
3884       // differ. However, the constants referred to by those indices
3885       // must be the same.
3886       //
3887       // We use methods_EMCP() for comparison since constant pool
3888       // merging can remove duplicate constant pool entries that were
3889       // present in the old method and removed from the rewritten new
3890       // method. A faster binary comparison function would consider the
3891       // old and new methods to be different when they are actually
3892       // EMCP.
3893       //
3894       // The old and new methods are EMCP and you would think that we
3895       // could get rid of one of them here and now and save some space.
3896       // However, the concept of EMCP only considers the bytecodes and
3897       // the constant pool entries in the comparison. Other things,
3898       // e.g., the line number table (LNT) or the local variable table
3899       // (LVT) don't count in the comparison. So the new (and EMCP)
3900       // method can have a new LNT that we need so we can't just
3901       // overwrite the new method with the old method.
3902       //
3903       // When this routine is called, we have already attached the new
3904       // methods to the_class so the old methods are effectively
3905       // overwritten. However, if an old method is still executing,
3906       // then the old method cannot be collected until sometime after
3907       // the old method call has returned. So the overwriting of old
3908       // methods by new methods will save us space except for those
3909       // (hopefully few) old methods that are still executing.
3910       //
3911       // A method refers to a ConstMethod* and this presents another
3912       // possible avenue to space savings. The ConstMethod* in the
3913       // new method contains possibly new attributes (LNT, LVT, etc).
3914       // At first glance, it seems possible to save space by replacing
3915       // the ConstMethod* in the old method with the ConstMethod*
3916       // from the new method. The old and new methods would share the
3917       // same ConstMethod* and we would save the space occupied by
3918       // the old ConstMethod*. However, the ConstMethod* contains
3919       // a back reference to the containing method. Sharing the
3920       // ConstMethod* between two methods could lead to confusion in
3921       // the code that uses the back reference. This would lead to
3922       // brittle code that could be broken in non-obvious ways now or
3923       // in the future.
3924       //
3925       // Another possibility is to copy the ConstMethod* from the new
3926       // method to the old method and then overwrite the new method with
3927       // the old method. Since the ConstMethod* contains the bytecodes
3928       // for the method embedded in the oop, this option would change
3929       // the bytecodes out from under any threads executing the old
3930       // method and make the thread's bcp invalid. Since EMCP requires
3931       // that the bytecodes be the same modulo constant pool indices, it
3932       // is straight forward to compute the correct new bcp in the new
3933       // ConstMethod* from the old bcp in the old ConstMethod*. The
3934       // time consuming part would be searching all the frames in all
3935       // of the threads to find all of the calls to the old method.
3936       //
3937       // It looks like we will have to live with the limited savings
3938       // that we get from effectively overwriting the old methods
3939       // when the new methods are attached to the_class.
3940 
3941       // Count number of methods that are EMCP.  The method will be marked
3942       // old but not obsolete if it is EMCP.
3943       emcp_method_count++;
3944 
3945       // An EMCP method is _not_ obsolete. An obsolete method has a
3946       // different jmethodID than the current method. An EMCP method
3947       // has the same jmethodID as the current method. Having the
3948       // same jmethodID for all EMCP versions of a method allows for
3949       // a consistent view of the EMCP methods regardless of which
3950       // EMCP method you happen to have in hand. For example, a
3951       // breakpoint set in one EMCP method will work for all EMCP
3952       // versions of the method including the current one.
3953     } else {
3954       // mark obsolete methods as such
3955       old_method->set_is_obsolete();
3956       obsolete_count++;
3957 
3958       // obsolete methods need a unique idnum so they become new entries in
3959       // the jmethodID cache in InstanceKlass
3960       assert(old_method->method_idnum() == new_method->method_idnum(), "must match");
3961       u2 num = InstanceKlass::cast(_the_class)->next_method_idnum();
3962       if (num != ConstMethod::UNSET_IDNUM) {
3963         old_method->set_method_idnum(num);
3964       }
3965 
3966       // With tracing we try not to "yack" too much. The position of
3967       // this trace assumes there are fewer obsolete methods than
3968       // EMCP methods.
3969       if (log_is_enabled(Trace, redefine, class, obsolete, mark)) {
3970         ResourceMark rm;
3971         log_trace(redefine, class, obsolete, mark)
3972           ("mark %s(%s) as obsolete", old_method->name()->as_C_string(), old_method->signature()->as_C_string());
3973       }
3974     }
3975     old_method->set_is_old();
3976   }
3977   for (int i = 0; i < _deleted_methods_length; ++i) {
3978     Method* old_method = _deleted_methods[i];
3979 
3980     assert(!old_method->has_vtable_index(),
3981            "cannot delete methods with vtable entries");;
3982 
3983     // Mark all deleted methods as old, obsolete and deleted
3984     old_method->set_is_deleted();
3985     old_method->set_is_old();
3986     old_method->set_is_obsolete();
3987     ++obsolete_count;
3988     // With tracing we try not to "yack" too much. The position of
3989     // this trace assumes there are fewer obsolete methods than
3990     // EMCP methods.
3991     if (log_is_enabled(Trace, redefine, class, obsolete, mark)) {
3992       ResourceMark rm;
3993       log_trace(redefine, class, obsolete, mark)
3994         ("mark deleted %s(%s) as obsolete", old_method->name()->as_C_string(), old_method->signature()->as_C_string());
3995     }
3996   }
3997   assert((emcp_method_count + obsolete_count) == _old_methods->length(),
3998     "sanity check");
3999   log_trace(redefine, class, obsolete, mark)("EMCP_cnt=%d, obsolete_cnt=%d", emcp_method_count, obsolete_count);
4000   return emcp_method_count;
4001 }
4002 
4003 // This internal class transfers the native function registration from old methods
4004 // to new methods.  It is designed to handle both the simple case of unchanged
4005 // native methods and the complex cases of native method prefixes being added and/or
4006 // removed.
4007 // It expects only to be used during the VM_RedefineClasses op (a safepoint).
4008 //
4009 // This class is used after the new methods have been installed in "the_class".
4010 //
4011 // So, for example, the following must be handled.  Where 'm' is a method and
4012 // a number followed by an underscore is a prefix.
4013 //
4014 //                                      Old Name    New Name
4015 // Simple transfer to new method        m       ->  m
4016 // Add prefix                           m       ->  1_m
4017 // Remove prefix                        1_m     ->  m
4018 // Simultaneous add of prefixes         m       ->  3_2_1_m
4019 // Simultaneous removal of prefixes     3_2_1_m ->  m
4020 // Simultaneous add and remove          1_m     ->  2_m
4021 // Same, caused by prefix removal only  3_2_1_m ->  3_2_m
4022 //
4023 class TransferNativeFunctionRegistration {
4024  private:
4025   InstanceKlass* the_class;
4026   int prefix_count;
4027   char** prefixes;
4028 
4029   // Recursively search the binary tree of possibly prefixed method names.
4030   // Iteration could be used if all agents were well behaved. Full tree walk is
4031   // more resilent to agents not cleaning up intermediate methods.
4032   // Branch at each depth in the binary tree is:
4033   //    (1) without the prefix.
4034   //    (2) with the prefix.
4035   // where 'prefix' is the prefix at that 'depth' (first prefix, second prefix,...)
4036   Method* search_prefix_name_space(int depth, char* name_str, size_t name_len,
4037                                      Symbol* signature) {
4038     TempNewSymbol name_symbol = SymbolTable::probe(name_str, (int)name_len);
4039     if (name_symbol != nullptr) {
4040       Method* method = the_class->lookup_method(name_symbol, signature);
4041       if (method != nullptr) {
4042         // Even if prefixed, intermediate methods must exist.
4043         if (method->is_native()) {
4044           // Wahoo, we found a (possibly prefixed) version of the method, return it.
4045           return method;
4046         }
4047         if (depth < prefix_count) {
4048           // Try applying further prefixes (other than this one).
4049           method = search_prefix_name_space(depth+1, name_str, name_len, signature);
4050           if (method != nullptr) {
4051             return method; // found
4052           }
4053 
4054           // Try adding this prefix to the method name and see if it matches
4055           // another method name.
4056           char* prefix = prefixes[depth];
4057           size_t prefix_len = strlen(prefix);
4058           size_t trial_len = name_len + prefix_len;
4059           char* trial_name_str = NEW_RESOURCE_ARRAY(char, trial_len + 1);
4060           strcpy(trial_name_str, prefix);
4061           strcat(trial_name_str, name_str);
4062           method = search_prefix_name_space(depth+1, trial_name_str, trial_len,
4063                                             signature);
4064           if (method != nullptr) {
4065             // If found along this branch, it was prefixed, mark as such
4066             method->set_is_prefixed_native();
4067             return method; // found
4068           }
4069         }
4070       }
4071     }
4072     return nullptr;  // This whole branch bore nothing
4073   }
4074 
4075   // Return the method name with old prefixes stripped away.
4076   char* method_name_without_prefixes(Method* method) {
4077     Symbol* name = method->name();
4078     char* name_str = name->as_utf8();
4079 
4080     // Old prefixing may be defunct, strip prefixes, if any.
4081     for (int i = prefix_count-1; i >= 0; i--) {
4082       char* prefix = prefixes[i];
4083       size_t prefix_len = strlen(prefix);
4084       if (strncmp(prefix, name_str, prefix_len) == 0) {
4085         name_str += prefix_len;
4086       }
4087     }
4088     return name_str;
4089   }
4090 
4091   // Strip any prefixes off the old native method, then try to find a
4092   // (possibly prefixed) new native that matches it.
4093   Method* strip_and_search_for_new_native(Method* method) {
4094     ResourceMark rm;
4095     char* name_str = method_name_without_prefixes(method);
4096     return search_prefix_name_space(0, name_str, strlen(name_str),
4097                                     method->signature());
4098   }
4099 
4100  public:
4101 
4102   // Construct a native method transfer processor for this class.
4103   TransferNativeFunctionRegistration(InstanceKlass* _the_class) {
4104     assert(SafepointSynchronize::is_at_safepoint(), "sanity check");
4105 
4106     the_class = _the_class;
4107     prefixes = JvmtiExport::get_all_native_method_prefixes(&prefix_count);
4108   }
4109 
4110   // Attempt to transfer any of the old or deleted methods that are native
4111   void transfer_registrations(Method** old_methods, int methods_length) {
4112     for (int j = 0; j < methods_length; j++) {
4113       Method* old_method = old_methods[j];
4114 
4115       if (old_method->is_native() && old_method->has_native_function()) {
4116         Method* new_method = strip_and_search_for_new_native(old_method);
4117         if (new_method != nullptr) {
4118           // Actually set the native function in the new method.
4119           // Redefine does not send events (except CFLH), certainly not this
4120           // behind the scenes re-registration.
4121           new_method->set_native_function(old_method->native_function(),
4122                               !Method::native_bind_event_is_interesting);
4123         }
4124       }
4125     }
4126   }
4127 };
4128 
4129 // Don't lose the association between a native method and its JNI function.
4130 void VM_RedefineClasses::transfer_old_native_function_registrations(InstanceKlass* the_class) {
4131   TransferNativeFunctionRegistration transfer(the_class);
4132   transfer.transfer_registrations(_deleted_methods, _deleted_methods_length);
4133   transfer.transfer_registrations(_matching_old_methods, _matching_methods_length);
4134 }
4135 
4136 // Deoptimize all compiled code that depends on the classes redefined.
4137 //
4138 // If the can_redefine_classes capability is obtained in the onload
4139 // phase then the compiler has recorded all dependencies from startup.
4140 // In that case we need only deoptimize and throw away all compiled code
4141 // that depends on the class.
4142 //
4143 // If can_redefine_classes is obtained sometime after the onload
4144 // phase then the dependency information may be incomplete. In that case
4145 // the first call to RedefineClasses causes all compiled code to be
4146 // thrown away. As can_redefine_classes has been obtained then
4147 // all future compilations will record dependencies so second and
4148 // subsequent calls to RedefineClasses need only throw away code
4149 // that depends on the class.
4150 //
4151 
4152 void VM_RedefineClasses::flush_dependent_code() {
4153   assert(SafepointSynchronize::is_at_safepoint(), "sanity check");
4154 
4155   DeoptimizationScope deopt_scope;
4156 
4157   // This is the first redefinition, mark all the nmethods for deoptimization
4158   if (!JvmtiExport::all_dependencies_are_recorded()) {
4159     CodeCache::mark_all_nmethods_for_evol_deoptimization(&deopt_scope);
4160     log_debug(redefine, class, nmethod)("Marked all nmethods for deopt");
4161   } else {
4162     CodeCache::mark_dependents_for_evol_deoptimization(&deopt_scope);
4163     log_debug(redefine, class, nmethod)("Marked dependent nmethods for deopt");
4164   }
4165 
4166   deopt_scope.deoptimize_marked();
4167 
4168   // From now on we know that the dependency information is complete
4169   JvmtiExport::set_all_dependencies_are_recorded(true);
4170 }
4171 
4172 void VM_RedefineClasses::compute_added_deleted_matching_methods() {
4173   Method* old_method;
4174   Method* new_method;
4175 
4176   _matching_old_methods = NEW_RESOURCE_ARRAY(Method*, _old_methods->length());
4177   _matching_new_methods = NEW_RESOURCE_ARRAY(Method*, _old_methods->length());
4178   _added_methods        = NEW_RESOURCE_ARRAY(Method*, _new_methods->length());
4179   _deleted_methods      = NEW_RESOURCE_ARRAY(Method*, _old_methods->length());
4180 
4181   _matching_methods_length = 0;
4182   _deleted_methods_length  = 0;
4183   _added_methods_length    = 0;
4184 
4185   int nj = 0;
4186   int oj = 0;
4187   while (true) {
4188     if (oj >= _old_methods->length()) {
4189       if (nj >= _new_methods->length()) {
4190         break; // we've looked at everything, done
4191       }
4192       // New method at the end
4193       new_method = _new_methods->at(nj);
4194       _added_methods[_added_methods_length++] = new_method;
4195       ++nj;
4196     } else if (nj >= _new_methods->length()) {
4197       // Old method, at the end, is deleted
4198       old_method = _old_methods->at(oj);
4199       _deleted_methods[_deleted_methods_length++] = old_method;
4200       ++oj;
4201     } else {
4202       old_method = _old_methods->at(oj);
4203       new_method = _new_methods->at(nj);
4204       if (old_method->name() == new_method->name()) {
4205         if (old_method->signature() == new_method->signature()) {
4206           _matching_old_methods[_matching_methods_length  ] = old_method;
4207           _matching_new_methods[_matching_methods_length++] = new_method;
4208           ++nj;
4209           ++oj;
4210         } else {
4211           // added overloaded have already been moved to the end,
4212           // so this is a deleted overloaded method
4213           _deleted_methods[_deleted_methods_length++] = old_method;
4214           ++oj;
4215         }
4216       } else { // names don't match
4217         if (old_method->name()->fast_compare(new_method->name()) > 0) {
4218           // new method
4219           _added_methods[_added_methods_length++] = new_method;
4220           ++nj;
4221         } else {
4222           // deleted method
4223           _deleted_methods[_deleted_methods_length++] = old_method;
4224           ++oj;
4225         }
4226       }
4227     }
4228   }
4229   assert(_matching_methods_length + _deleted_methods_length == _old_methods->length(), "sanity");
4230   assert(_matching_methods_length + _added_methods_length == _new_methods->length(), "sanity");
4231 }
4232 
4233 
4234 void VM_RedefineClasses::swap_annotations(InstanceKlass* the_class,
4235                                           InstanceKlass* scratch_class) {
4236   // Swap annotation fields values
4237   Annotations* old_annotations = the_class->annotations();
4238   the_class->set_annotations(scratch_class->annotations());
4239   scratch_class->set_annotations(old_annotations);
4240 }
4241 
4242 
4243 // Install the redefinition of a class:
4244 //    - house keeping (flushing breakpoints and caches, deoptimizing
4245 //      dependent compiled code)
4246 //    - replacing parts in the_class with parts from scratch_class
4247 //    - adding a weak reference to track the obsolete but interesting
4248 //      parts of the_class
4249 //    - adjusting constant pool caches and vtables in other classes
4250 //      that refer to methods in the_class. These adjustments use the
4251 //      ClassLoaderDataGraph::classes_do() facility which only allows
4252 //      a helper method to be specified. The interesting parameters
4253 //      that we would like to pass to the helper method are saved in
4254 //      static global fields in the VM operation.
4255 void VM_RedefineClasses::redefine_single_class(Thread* current, jclass the_jclass,
4256                                                InstanceKlass* scratch_class) {
4257 
4258   HandleMark hm(current);   // make sure handles from this call are freed
4259 
4260   if (log_is_enabled(Info, redefine, class, timer)) {
4261     _timer_rsc_phase1.start();
4262   }
4263 
4264   InstanceKlass* the_class = get_ik(the_jclass);
4265 
4266   // Set a flag to control and optimize adjusting method entries
4267   _has_redefined_Object |= the_class == vmClasses::Object_klass();
4268 
4269   // Remove all breakpoints in methods of this class
4270   JvmtiBreakpoints& jvmti_breakpoints = JvmtiCurrentBreakpoints::get_jvmti_breakpoints();
4271   jvmti_breakpoints.clearall_in_class_at_safepoint(the_class);
4272 
4273   _old_methods = the_class->methods();
4274   _new_methods = scratch_class->methods();
4275   _the_class = the_class;
4276   compute_added_deleted_matching_methods();
4277   update_jmethod_ids();
4278 
4279   _any_class_has_resolved_methods = the_class->has_resolved_methods() || _any_class_has_resolved_methods;
4280 
4281   // Attach new constant pool to the original klass. The original
4282   // klass still refers to the old constant pool (for now).
4283   scratch_class->constants()->set_pool_holder(the_class);
4284 
4285 #if 0
4286   // In theory, with constant pool merging in place we should be able
4287   // to save space by using the new, merged constant pool in place of
4288   // the old constant pool(s). By "pool(s)" I mean the constant pool in
4289   // the klass version we are replacing now and any constant pool(s) in
4290   // previous versions of klass. Nice theory, doesn't work in practice.
4291   // When this code is enabled, even simple programs throw NullPointer
4292   // exceptions. I'm guessing that this is caused by some constant pool
4293   // cache difference between the new, merged constant pool and the
4294   // constant pool that was just being used by the klass. I'm keeping
4295   // this code around to archive the idea, but the code has to remain
4296   // disabled for now.
4297 
4298   // Attach each old method to the new constant pool. This can be
4299   // done here since we are past the bytecode verification and
4300   // constant pool optimization phases.
4301   for (int i = _old_methods->length() - 1; i >= 0; i--) {
4302     Method* method = _old_methods->at(i);
4303     method->set_constants(scratch_class->constants());
4304   }
4305 
4306   // NOTE: this doesn't work because you can redefine the same class in two
4307   // threads, each getting their own constant pool data appended to the
4308   // original constant pool.  In order for the new methods to work when they
4309   // become old methods, they need to keep their updated copy of the constant pool.
4310 
4311   {
4312     // walk all previous versions of the klass
4313     InstanceKlass *ik = the_class;
4314     PreviousVersionWalker pvw(ik);
4315     do {
4316       ik = pvw.next_previous_version();
4317       if (ik != nullptr) {
4318 
4319         // attach previous version of klass to the new constant pool
4320         ik->set_constants(scratch_class->constants());
4321 
4322         // Attach each method in the previous version of klass to the
4323         // new constant pool
4324         Array<Method*>* prev_methods = ik->methods();
4325         for (int i = prev_methods->length() - 1; i >= 0; i--) {
4326           Method* method = prev_methods->at(i);
4327           method->set_constants(scratch_class->constants());
4328         }
4329       }
4330     } while (ik != nullptr);
4331   }
4332 #endif
4333 
4334   // Replace methods and constantpool
4335   the_class->set_methods(_new_methods);
4336   scratch_class->set_methods(_old_methods);     // To prevent potential GCing of the old methods,
4337                                           // and to be able to undo operation easily.
4338 
4339   Array<int>* old_ordering = the_class->method_ordering();
4340   the_class->set_method_ordering(scratch_class->method_ordering());
4341   scratch_class->set_method_ordering(old_ordering);
4342 
4343   ConstantPool* old_constants = the_class->constants();
4344   the_class->set_constants(scratch_class->constants());
4345   scratch_class->set_constants(old_constants);  // See the previous comment.
4346 #if 0
4347   // We are swapping the guts of "the new class" with the guts of "the
4348   // class". Since the old constant pool has just been attached to "the
4349   // new class", it seems logical to set the pool holder in the old
4350   // constant pool also. However, doing this will change the observable
4351   // class hierarchy for any old methods that are still executing. A
4352   // method can query the identity of its "holder" and this query uses
4353   // the method's constant pool link to find the holder. The change in
4354   // holding class from "the class" to "the new class" can confuse
4355   // things.
4356   //
4357   // Setting the old constant pool's holder will also cause
4358   // verification done during vtable initialization below to fail.
4359   // During vtable initialization, the vtable's class is verified to be
4360   // a subtype of the method's holder. The vtable's class is "the
4361   // class" and the method's holder is gotten from the constant pool
4362   // link in the method itself. For "the class"'s directly implemented
4363   // methods, the method holder is "the class" itself (as gotten from
4364   // the new constant pool). The check works fine in this case. The
4365   // check also works fine for methods inherited from super classes.
4366   //
4367   // Miranda methods are a little more complicated. A miranda method is
4368   // provided by an interface when the class implementing the interface
4369   // does not provide its own method.  These interfaces are implemented
4370   // internally as an InstanceKlass. These special instanceKlasses
4371   // share the constant pool of the class that "implements" the
4372   // interface. By sharing the constant pool, the method holder of a
4373   // miranda method is the class that "implements" the interface. In a
4374   // non-redefine situation, the subtype check works fine. However, if
4375   // the old constant pool's pool holder is modified, then the check
4376   // fails because there is no class hierarchy relationship between the
4377   // vtable's class and "the new class".
4378 
4379   old_constants->set_pool_holder(scratch_class());
4380 #endif
4381 
4382   // track number of methods that are EMCP for add_previous_version() call below
4383   int emcp_method_count = check_methods_and_mark_as_obsolete();
4384   transfer_old_native_function_registrations(the_class);
4385 
4386   if (scratch_class->get_cached_class_file() != the_class->get_cached_class_file()) {
4387     // 1. the_class doesn't have a cache yet, scratch_class does have a cache.
4388     // 2. The same class can be present twice in the scratch classes list or there
4389     // are multiple concurrent RetransformClasses calls on different threads.
4390     // the_class and scratch_class have the same cached bytes, but different buffers.
4391     // In such cases we need to deallocate one of the buffers.
4392     // 3. RedefineClasses and the_class has cached bytes from a previous transformation.
4393     // In the case we need to use class bytes from scratch_class.
4394     if (the_class->get_cached_class_file() != nullptr) {
4395       os::free(the_class->get_cached_class_file());
4396     }
4397     the_class->set_cached_class_file(scratch_class->get_cached_class_file());
4398   }
4399 
4400   // null out in scratch class to not delete twice.  The class to be redefined
4401   // always owns these bytes.
4402   scratch_class->set_cached_class_file(nullptr);
4403 
4404   // Replace inner_classes
4405   Array<u2>* old_inner_classes = the_class->inner_classes();
4406   the_class->set_inner_classes(scratch_class->inner_classes());
4407   scratch_class->set_inner_classes(old_inner_classes);
4408 
4409   // Initialize the vtable and interface table after
4410   // methods have been rewritten
4411   // no exception should happen here since we explicitly
4412   // do not check loader constraints.
4413   // compare_and_normalize_class_versions has already checked:
4414   //  - classloaders unchanged, signatures unchanged
4415   //  - all instanceKlasses for redefined classes reused & contents updated
4416   the_class->vtable().initialize_vtable();
4417   the_class->itable().initialize_itable();
4418 
4419   // Leave arrays of jmethodIDs and itable index cache unchanged
4420 
4421   // Copy the "source debug extension" attribute from new class version
4422   the_class->set_source_debug_extension(
4423     scratch_class->source_debug_extension(),
4424     scratch_class->source_debug_extension() == nullptr ? 0 :
4425     (int)strlen(scratch_class->source_debug_extension()));
4426 
4427   // Use of javac -g could be different in the old and the new
4428   if (scratch_class->has_localvariable_table() !=
4429       the_class->has_localvariable_table()) {
4430     the_class->set_has_localvariable_table(scratch_class->has_localvariable_table());
4431   }
4432 
4433   swap_annotations(the_class, scratch_class);
4434 
4435   // Replace minor version number of class file
4436   u2 old_minor_version = the_class->constants()->minor_version();
4437   the_class->constants()->set_minor_version(scratch_class->constants()->minor_version());
4438   scratch_class->constants()->set_minor_version(old_minor_version);
4439 
4440   // Replace major version number of class file
4441   u2 old_major_version = the_class->constants()->major_version();
4442   the_class->constants()->set_major_version(scratch_class->constants()->major_version());
4443   scratch_class->constants()->set_major_version(old_major_version);
4444 
4445   // Replace CP indexes for class and name+type of enclosing method
4446   u2 old_class_idx  = the_class->enclosing_method_class_index();
4447   u2 old_method_idx = the_class->enclosing_method_method_index();
4448   the_class->set_enclosing_method_indices(
4449     scratch_class->enclosing_method_class_index(),
4450     scratch_class->enclosing_method_method_index());
4451   scratch_class->set_enclosing_method_indices(old_class_idx, old_method_idx);
4452 
4453   if (!the_class->has_been_redefined()) {
4454     the_class->set_has_been_redefined();
4455   }
4456 
4457   // Scratch class is unloaded but still needs cleaning, and skipping for CDS.
4458   scratch_class->set_is_scratch_class();
4459 
4460   // keep track of previous versions of this class
4461   the_class->add_previous_version(scratch_class, emcp_method_count);
4462 
4463   _timer_rsc_phase1.stop();
4464   if (log_is_enabled(Info, redefine, class, timer)) {
4465     _timer_rsc_phase2.start();
4466   }
4467 
4468   if (the_class->oop_map_cache() != nullptr) {
4469     // Flush references to any obsolete methods from the oop map cache
4470     // so that obsolete methods are not pinned.
4471     the_class->oop_map_cache()->flush_obsolete_entries();
4472   }
4473 
4474   increment_class_counter(the_class);
4475 
4476   if (EventClassRedefinition::is_enabled()) {
4477     EventClassRedefinition event;
4478     event.set_classModificationCount(java_lang_Class::classRedefinedCount(the_class->java_mirror()));
4479     event.set_redefinedClass(the_class);
4480     event.set_redefinitionId(_id);
4481     event.commit();
4482   }
4483 
4484   {
4485     ResourceMark rm(current);
4486     // increment the classRedefinedCount field in the_class and in any
4487     // direct and indirect subclasses of the_class
4488     log_info(redefine, class, load)
4489       ("redefined name=%s, count=%d (avail_mem=" UINT64_FORMAT "K)",
4490        the_class->external_name(), java_lang_Class::classRedefinedCount(the_class->java_mirror()), os::available_memory() >> 10);
4491     Events::log_redefinition(current, "redefined class name=%s, count=%d",
4492                              the_class->external_name(),
4493                              java_lang_Class::classRedefinedCount(the_class->java_mirror()));
4494 
4495   }
4496   _timer_rsc_phase2.stop();
4497 
4498 } // end redefine_single_class()
4499 
4500 
4501 // Increment the classRedefinedCount field in the specific InstanceKlass
4502 // and in all direct and indirect subclasses.
4503 void VM_RedefineClasses::increment_class_counter(InstanceKlass* ik) {
4504   for (ClassHierarchyIterator iter(ik); !iter.done(); iter.next()) {
4505     // Only update instanceKlasses
4506     Klass* sub = iter.klass();
4507     if (sub->is_instance_klass()) {
4508       oop class_mirror = InstanceKlass::cast(sub)->java_mirror();
4509       Klass* class_oop = java_lang_Class::as_Klass(class_mirror);
4510       int new_count = java_lang_Class::classRedefinedCount(class_mirror) + 1;
4511       java_lang_Class::set_classRedefinedCount(class_mirror, new_count);
4512 
4513       if (class_oop != _the_class) {
4514         // _the_class count is printed at end of redefine_single_class()
4515         log_debug(redefine, class, subclass)("updated count in subclass=%s to %d", ik->external_name(), new_count);
4516       }
4517     }
4518   }
4519 }
4520 
4521 void VM_RedefineClasses::CheckClass::do_klass(Klass* k) {
4522   bool no_old_methods = true;  // be optimistic
4523 
4524   // Both array and instance classes have vtables.
4525   // a vtable should never contain old or obsolete methods
4526   ResourceMark rm(_thread);
4527   if (k->vtable_length() > 0 &&
4528       !k->vtable().check_no_old_or_obsolete_entries()) {
4529     if (log_is_enabled(Trace, redefine, class, obsolete, metadata)) {
4530       log_trace(redefine, class, obsolete, metadata)
4531         ("klassVtable::check_no_old_or_obsolete_entries failure -- OLD or OBSOLETE method found -- class: %s",
4532          k->signature_name());
4533       k->vtable().dump_vtable();
4534     }
4535     no_old_methods = false;
4536   }
4537 
4538   if (k->is_instance_klass()) {
4539     HandleMark hm(_thread);
4540     InstanceKlass *ik = InstanceKlass::cast(k);
4541 
4542     // an itable should never contain old or obsolete methods
4543     if (ik->itable_length() > 0 &&
4544         !ik->itable().check_no_old_or_obsolete_entries()) {
4545       if (log_is_enabled(Trace, redefine, class, obsolete, metadata)) {
4546         log_trace(redefine, class, obsolete, metadata)
4547           ("klassItable::check_no_old_or_obsolete_entries failure -- OLD or OBSOLETE method found -- class: %s",
4548            ik->signature_name());
4549         ik->itable().dump_itable();
4550       }
4551       no_old_methods = false;
4552     }
4553 
4554     // the constant pool cache should never contain non-deleted old or obsolete methods
4555     if (ik->constants() != nullptr &&
4556         ik->constants()->cache() != nullptr &&
4557         !ik->constants()->cache()->check_no_old_or_obsolete_entries()) {
4558       if (log_is_enabled(Trace, redefine, class, obsolete, metadata)) {
4559         log_trace(redefine, class, obsolete, metadata)
4560           ("cp-cache::check_no_old_or_obsolete_entries failure -- OLD or OBSOLETE method found -- class: %s",
4561            ik->signature_name());
4562         ik->constants()->cache()->dump_cache();
4563       }
4564       no_old_methods = false;
4565     }
4566   }
4567 
4568   // print and fail guarantee if old methods are found.
4569   if (!no_old_methods) {
4570     if (log_is_enabled(Trace, redefine, class, obsolete, metadata)) {
4571       dump_methods();
4572     } else {
4573       log_trace(redefine, class)("Use the '-Xlog:redefine+class*:' option "
4574         "to see more info about the following guarantee() failure.");
4575     }
4576     guarantee(false, "OLD and/or OBSOLETE method(s) found");
4577   }
4578 }
4579 
4580 u8 VM_RedefineClasses::next_id() {
4581   while (true) {
4582     u8 id = _id_counter;
4583     u8 next_id = id + 1;
4584     u8 result = Atomic::cmpxchg(&_id_counter, id, next_id);
4585     if (result == id) {
4586       return next_id;
4587     }
4588   }
4589 }
4590 
4591 void VM_RedefineClasses::dump_methods() {
4592   int j;
4593   log_trace(redefine, class, dump)("_old_methods --");
4594   for (j = 0; j < _old_methods->length(); ++j) {
4595     LogStreamHandle(Trace, redefine, class, dump) log_stream;
4596     Method* m = _old_methods->at(j);
4597     log_stream.print("%4d  (%5d)  ", j, m->vtable_index());
4598     m->access_flags().print_on(&log_stream);
4599     log_stream.print(" --  ");
4600     m->print_name(&log_stream);
4601     log_stream.cr();
4602   }
4603   log_trace(redefine, class, dump)("_new_methods --");
4604   for (j = 0; j < _new_methods->length(); ++j) {
4605     LogStreamHandle(Trace, redefine, class, dump) log_stream;
4606     Method* m = _new_methods->at(j);
4607     log_stream.print("%4d  (%5d)  ", j, m->vtable_index());
4608     m->access_flags().print_on(&log_stream);
4609     log_stream.print(" --  ");
4610     m->print_name(&log_stream);
4611     log_stream.cr();
4612   }
4613   log_trace(redefine, class, dump)("_matching_methods --");
4614   for (j = 0; j < _matching_methods_length; ++j) {
4615     LogStreamHandle(Trace, redefine, class, dump) log_stream;
4616     Method* m = _matching_old_methods[j];
4617     log_stream.print("%4d  (%5d)  ", j, m->vtable_index());
4618     m->access_flags().print_on(&log_stream);
4619     log_stream.print(" --  ");
4620     m->print_name();
4621     log_stream.cr();
4622 
4623     m = _matching_new_methods[j];
4624     log_stream.print("      (%5d)  ", m->vtable_index());
4625     m->access_flags().print_on(&log_stream);
4626     log_stream.cr();
4627   }
4628   log_trace(redefine, class, dump)("_deleted_methods --");
4629   for (j = 0; j < _deleted_methods_length; ++j) {
4630     LogStreamHandle(Trace, redefine, class, dump) log_stream;
4631     Method* m = _deleted_methods[j];
4632     log_stream.print("%4d  (%5d)  ", j, m->vtable_index());
4633     m->access_flags().print_on(&log_stream);
4634     log_stream.print(" --  ");
4635     m->print_name(&log_stream);
4636     log_stream.cr();
4637   }
4638   log_trace(redefine, class, dump)("_added_methods --");
4639   for (j = 0; j < _added_methods_length; ++j) {
4640     LogStreamHandle(Trace, redefine, class, dump) log_stream;
4641     Method* m = _added_methods[j];
4642     log_stream.print("%4d  (%5d)  ", j, m->vtable_index());
4643     m->access_flags().print_on(&log_stream);
4644     log_stream.print(" --  ");
4645     m->print_name(&log_stream);
4646     log_stream.cr();
4647   }
4648 }
4649 
4650 void VM_RedefineClasses::print_on_error(outputStream* st) const {
4651   VM_Operation::print_on_error(st);
4652   if (_the_class != nullptr) {
4653     ResourceMark rm;
4654     st->print_cr(", redefining class %s", _the_class->external_name());
4655   }
4656 }