1 /*
   2  * Copyright (c) 2003, 2024, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "cds/metaspaceShared.hpp"
  27 #include "classfile/classFileStream.hpp"
  28 #include "classfile/classLoaderDataGraph.hpp"
  29 #include "classfile/classLoadInfo.hpp"
  30 #include "classfile/javaClasses.inline.hpp"
  31 #include "classfile/metadataOnStackMark.hpp"
  32 #include "classfile/symbolTable.hpp"
  33 #include "classfile/klassFactory.hpp"
  34 #include "classfile/verifier.hpp"
  35 #include "classfile/vmClasses.hpp"
  36 #include "classfile/vmSymbols.hpp"
  37 #include "code/codeCache.hpp"
  38 #include "compiler/compileBroker.hpp"
  39 #include "interpreter/oopMapCache.hpp"
  40 #include "interpreter/rewriter.hpp"
  41 #include "jfr/jfrEvents.hpp"
  42 #include "logging/logStream.hpp"
  43 #include "memory/metadataFactory.hpp"
  44 #include "memory/resourceArea.hpp"
  45 #include "memory/universe.hpp"
  46 #include "oops/annotations.hpp"
  47 #include "oops/constantPool.hpp"
  48 #include "oops/fieldStreams.inline.hpp"
  49 #include "oops/klass.inline.hpp"
  50 #include "oops/klassVtable.hpp"
  51 #include "oops/method.hpp"
  52 #include "oops/oop.inline.hpp"
  53 #include "oops/recordComponent.hpp"
  54 #include "prims/jvmtiImpl.hpp"
  55 #include "prims/jvmtiRedefineClasses.hpp"
  56 #include "prims/jvmtiThreadState.inline.hpp"
  57 #include "prims/resolvedMethodTable.hpp"
  58 #include "prims/methodComparator.hpp"
  59 #include "runtime/atomic.hpp"
  60 #include "runtime/deoptimization.hpp"
  61 #include "runtime/handles.inline.hpp"
  62 #include "runtime/jniHandles.inline.hpp"
  63 #include "runtime/relocator.hpp"
  64 #include "runtime/safepointVerifiers.hpp"
  65 #include "utilities/bitMap.inline.hpp"
  66 #include "utilities/checkedCast.hpp"
  67 #include "utilities/events.hpp"
  68 #include "utilities/macros.hpp"
  69 
  70 Array<Method*>* VM_RedefineClasses::_old_methods = nullptr;
  71 Array<Method*>* VM_RedefineClasses::_new_methods = nullptr;
  72 Method**  VM_RedefineClasses::_matching_old_methods = nullptr;
  73 Method**  VM_RedefineClasses::_matching_new_methods = nullptr;
  74 Method**  VM_RedefineClasses::_deleted_methods      = nullptr;
  75 Method**  VM_RedefineClasses::_added_methods        = nullptr;
  76 int       VM_RedefineClasses::_matching_methods_length = 0;
  77 int       VM_RedefineClasses::_deleted_methods_length  = 0;
  78 int       VM_RedefineClasses::_added_methods_length    = 0;
  79 
  80 // This flag is global as the constructor does not reset it:
  81 bool      VM_RedefineClasses::_has_redefined_Object = false;
  82 u8        VM_RedefineClasses::_id_counter = 0;
  83 
  84 VM_RedefineClasses::VM_RedefineClasses(jint class_count,
  85                                        const jvmtiClassDefinition *class_defs,
  86                                        JvmtiClassLoadKind class_load_kind) {
  87   _class_count = class_count;
  88   _class_defs = class_defs;
  89   _class_load_kind = class_load_kind;
  90   _any_class_has_resolved_methods = false;
  91   _res = JVMTI_ERROR_NONE;
  92   _the_class = nullptr;
  93   _id = next_id();
  94 }
  95 
  96 static inline InstanceKlass* get_ik(jclass def) {
  97   oop mirror = JNIHandles::resolve_non_null(def);
  98   return InstanceKlass::cast(java_lang_Class::as_Klass(mirror));
  99 }
 100 
 101 // If any of the classes are being redefined, wait
 102 // Parallel constant pool merging leads to indeterminate constant pools.
 103 void VM_RedefineClasses::lock_classes() {
 104   JvmtiThreadState *state = JvmtiThreadState::state_for(JavaThread::current());
 105   GrowableArray<Klass*>* redef_classes = state->get_classes_being_redefined();
 106 
 107   MonitorLocker ml(RedefineClasses_lock);
 108 
 109   if (redef_classes == nullptr) {
 110     redef_classes = new (mtClass) GrowableArray<Klass*>(1, mtClass);
 111     state->set_classes_being_redefined(redef_classes);
 112   }
 113 
 114   bool has_redefined;
 115   do {
 116     has_redefined = false;
 117     // Go through classes each time until none are being redefined. Skip
 118     // the ones that are being redefined by this thread currently. Class file
 119     // load hook event may trigger new class redefine when we are redefining
 120     // a class (after lock_classes()).
 121     for (int i = 0; i < _class_count; i++) {
 122       InstanceKlass* ik = get_ik(_class_defs[i].klass);
 123       // Check if we are currently redefining the class in this thread already.
 124       if (redef_classes->contains(ik)) {
 125         assert(ik->is_being_redefined(), "sanity");
 126       } else {
 127         if (ik->is_being_redefined()) {
 128           ml.wait();
 129           has_redefined = true;
 130           break;  // for loop
 131         }
 132       }
 133     }
 134   } while (has_redefined);
 135 
 136   for (int i = 0; i < _class_count; i++) {
 137     InstanceKlass* ik = get_ik(_class_defs[i].klass);
 138     redef_classes->push(ik); // Add to the _classes_being_redefined list
 139     ik->set_is_being_redefined(true);
 140   }
 141   ml.notify_all();
 142 }
 143 
 144 void VM_RedefineClasses::unlock_classes() {
 145   JvmtiThreadState *state = JvmtiThreadState::state_for(JavaThread::current());
 146   GrowableArray<Klass*>* redef_classes = state->get_classes_being_redefined();
 147   assert(redef_classes != nullptr, "_classes_being_redefined is not allocated");
 148 
 149   MonitorLocker ml(RedefineClasses_lock);
 150 
 151   for (int i = _class_count - 1; i >= 0; i--) {
 152     InstanceKlass* def_ik = get_ik(_class_defs[i].klass);
 153     if (redef_classes->length() > 0) {
 154       // Remove the class from _classes_being_redefined list
 155       Klass* k = redef_classes->pop();
 156       assert(def_ik == k, "unlocking wrong class");
 157     }
 158     assert(def_ik->is_being_redefined(),
 159            "should be being redefined to get here");
 160 
 161     // Unlock after we finish all redefines for this class within
 162     // the thread. Same class can be pushed to the list multiple
 163     // times (not more than once by each recursive redefinition).
 164     if (!redef_classes->contains(def_ik)) {
 165       def_ik->set_is_being_redefined(false);
 166     }
 167   }
 168   ml.notify_all();
 169 }
 170 
 171 bool VM_RedefineClasses::doit_prologue() {
 172   if (_class_count == 0) {
 173     _res = JVMTI_ERROR_NONE;
 174     return false;
 175   }
 176   if (_class_defs == nullptr) {
 177     _res = JVMTI_ERROR_NULL_POINTER;
 178     return false;
 179   }
 180 
 181   for (int i = 0; i < _class_count; i++) {
 182     if (_class_defs[i].klass == nullptr) {
 183       _res = JVMTI_ERROR_INVALID_CLASS;
 184       return false;
 185     }
 186     if (_class_defs[i].class_byte_count == 0) {
 187       _res = JVMTI_ERROR_INVALID_CLASS_FORMAT;
 188       return false;
 189     }
 190     if (_class_defs[i].class_bytes == nullptr) {
 191       _res = JVMTI_ERROR_NULL_POINTER;
 192       return false;
 193     }
 194 
 195     oop mirror = JNIHandles::resolve_non_null(_class_defs[i].klass);
 196     // classes for primitives, arrays, and hidden classes
 197     // cannot be redefined.
 198     if (!is_modifiable_class(mirror)) {
 199       _res = JVMTI_ERROR_UNMODIFIABLE_CLASS;
 200       return false;
 201     }
 202   }
 203 
 204   // Start timer after all the sanity checks; not quite accurate, but
 205   // better than adding a bunch of stop() calls.
 206   if (log_is_enabled(Info, redefine, class, timer)) {
 207     _timer_vm_op_prologue.start();
 208   }
 209 
 210   lock_classes();
 211   // We first load new class versions in the prologue, because somewhere down the
 212   // call chain it is required that the current thread is a Java thread.
 213   _res = load_new_class_versions();
 214   if (_res != JVMTI_ERROR_NONE) {
 215     // free any successfully created classes, since none are redefined
 216     for (int i = 0; i < _class_count; i++) {
 217       if (_scratch_classes[i] != nullptr) {
 218         ClassLoaderData* cld = _scratch_classes[i]->class_loader_data();
 219         // Free the memory for this class at class unloading time.  Not before
 220         // because CMS might think this is still live.
 221         InstanceKlass* ik = get_ik(_class_defs[i].klass);
 222         if (ik->get_cached_class_file() == _scratch_classes[i]->get_cached_class_file()) {
 223           // Don't double-free cached_class_file copied from the original class if error.
 224           _scratch_classes[i]->set_cached_class_file(nullptr);
 225         }
 226         cld->add_to_deallocate_list(InstanceKlass::cast(_scratch_classes[i]));
 227       }
 228     }
 229     // Free os::malloc allocated memory in load_new_class_version.
 230     os::free(_scratch_classes);
 231     _timer_vm_op_prologue.stop();
 232     unlock_classes();
 233     return false;
 234   }
 235 
 236   _timer_vm_op_prologue.stop();
 237   return true;
 238 }
 239 
 240 void VM_RedefineClasses::doit() {
 241   Thread* current = Thread::current();
 242 
 243   if (log_is_enabled(Info, redefine, class, timer)) {
 244     _timer_vm_op_doit.start();
 245   }
 246 
 247 #if INCLUDE_CDS
 248   if (UseSharedSpaces) {
 249     // Sharing is enabled so we remap the shared readonly space to
 250     // shared readwrite, private just in case we need to redefine
 251     // a shared class. We do the remap during the doit() phase of
 252     // the safepoint to be safer.
 253     if (!MetaspaceShared::remap_shared_readonly_as_readwrite()) {
 254       log_info(redefine, class, load)("failed to remap shared readonly space to readwrite, private");
 255       _res = JVMTI_ERROR_INTERNAL;
 256       _timer_vm_op_doit.stop();
 257       return;
 258     }
 259   }
 260 #endif
 261 
 262   // Mark methods seen on stack and everywhere else so old methods are not
 263   // cleaned up if they're on the stack.
 264   MetadataOnStackMark md_on_stack(/*walk_all_metadata*/true, /*redefinition_walk*/true);
 265   HandleMark hm(current);   // make sure any handles created are deleted
 266                             // before the stack walk again.
 267 
 268   for (int i = 0; i < _class_count; i++) {
 269     redefine_single_class(current, _class_defs[i].klass, _scratch_classes[i]);
 270   }
 271 
 272   // Flush all compiled code that depends on the classes redefined.
 273   flush_dependent_code();
 274 
 275   // Adjust constantpool caches and vtables for all classes
 276   // that reference methods of the evolved classes.
 277   // Have to do this after all classes are redefined and all methods that
 278   // are redefined are marked as old.
 279   AdjustAndCleanMetadata adjust_and_clean_metadata(current);
 280   ClassLoaderDataGraph::classes_do(&adjust_and_clean_metadata);
 281 
 282   // JSR-292 support
 283   if (_any_class_has_resolved_methods) {
 284     bool trace_name_printed = false;
 285     ResolvedMethodTable::adjust_method_entries(&trace_name_printed);
 286   }
 287 
 288   // Increment flag indicating that some invariants are no longer true.
 289   // See jvmtiExport.hpp for detailed explanation.
 290   JvmtiExport::increment_redefinition_count();
 291 
 292   // check_class() is optionally called for product bits, but is
 293   // always called for non-product bits.
 294 #ifdef PRODUCT
 295   if (log_is_enabled(Trace, redefine, class, obsolete, metadata)) {
 296 #endif
 297     log_trace(redefine, class, obsolete, metadata)("calling check_class");
 298     CheckClass check_class(current);
 299     ClassLoaderDataGraph::classes_do(&check_class);
 300 #ifdef PRODUCT
 301   }
 302 #endif
 303 
 304   // Clean up any metadata now unreferenced while MetadataOnStackMark is set.
 305   ClassLoaderDataGraph::clean_deallocate_lists(false);
 306 
 307   _timer_vm_op_doit.stop();
 308 }
 309 
 310 void VM_RedefineClasses::doit_epilogue() {
 311   unlock_classes();
 312 
 313   // Free os::malloc allocated memory.
 314   os::free(_scratch_classes);
 315 
 316   // Reset the_class to null for error printing.
 317   _the_class = nullptr;
 318 
 319   if (log_is_enabled(Info, redefine, class, timer)) {
 320     // Used to have separate timers for "doit" and "all", but the timer
 321     // overhead skewed the measurements.
 322     julong doit_time = _timer_vm_op_doit.milliseconds();
 323     julong all_time = _timer_vm_op_prologue.milliseconds() + doit_time;
 324 
 325     log_info(redefine, class, timer)
 326       ("vm_op: all=" JULONG_FORMAT "  prologue=" JULONG_FORMAT "  doit=" JULONG_FORMAT,
 327        all_time, (julong)_timer_vm_op_prologue.milliseconds(), doit_time);
 328     log_info(redefine, class, timer)
 329       ("redefine_single_class: phase1=" JULONG_FORMAT "  phase2=" JULONG_FORMAT,
 330        (julong)_timer_rsc_phase1.milliseconds(), (julong)_timer_rsc_phase2.milliseconds());
 331   }
 332 }
 333 
 334 bool VM_RedefineClasses::is_modifiable_class(oop klass_mirror) {
 335   // classes for primitives cannot be redefined
 336   if (java_lang_Class::is_primitive(klass_mirror)) {
 337     return false;
 338   }
 339   Klass* k = java_lang_Class::as_Klass(klass_mirror);
 340   // classes for arrays cannot be redefined
 341   if (k == nullptr || !k->is_instance_klass()) {
 342     return false;
 343   }
 344 
 345   // Cannot redefine or retransform a hidden class.
 346   if (InstanceKlass::cast(k)->is_hidden()) {
 347     return false;
 348   }
 349   if (InstanceKlass::cast(k) == vmClasses::Continuation_klass()) {
 350     // Don't redefine Continuation class. See 8302779.
 351     return false;
 352   }
 353   return true;
 354 }
 355 
 356 // Append the current entry at scratch_i in scratch_cp to *merge_cp_p
 357 // where the end of *merge_cp_p is specified by *merge_cp_length_p. For
 358 // direct CP entries, there is just the current entry to append. For
 359 // indirect and double-indirect CP entries, there are zero or more
 360 // referenced CP entries along with the current entry to append.
 361 // Indirect and double-indirect CP entries are handled by recursive
 362 // calls to append_entry() as needed. The referenced CP entries are
 363 // always appended to *merge_cp_p before the referee CP entry. These
 364 // referenced CP entries may already exist in *merge_cp_p in which case
 365 // there is nothing extra to append and only the current entry is
 366 // appended.
 367 void VM_RedefineClasses::append_entry(const constantPoolHandle& scratch_cp,
 368        int scratch_i, constantPoolHandle *merge_cp_p, int *merge_cp_length_p) {
 369 
 370   // append is different depending on entry tag type
 371   switch (scratch_cp->tag_at(scratch_i).value()) {
 372 
 373     // The old verifier is implemented outside the VM. It loads classes,
 374     // but does not resolve constant pool entries directly so we never
 375     // see Class entries here with the old verifier. Similarly the old
 376     // verifier does not like Class entries in the input constant pool.
 377     // The split-verifier is implemented in the VM so it can optionally
 378     // and directly resolve constant pool entries to load classes. The
 379     // split-verifier can accept either Class entries or UnresolvedClass
 380     // entries in the input constant pool. We revert the appended copy
 381     // back to UnresolvedClass so that either verifier will be happy
 382     // with the constant pool entry.
 383     //
 384     // this is an indirect CP entry so it needs special handling
 385     case JVM_CONSTANT_Class:
 386     case JVM_CONSTANT_UnresolvedClass:
 387     {
 388       int name_i = scratch_cp->klass_name_index_at(scratch_i);
 389       int new_name_i = find_or_append_indirect_entry(scratch_cp, name_i, merge_cp_p,
 390                                                      merge_cp_length_p);
 391 
 392       if (new_name_i != name_i) {
 393         log_trace(redefine, class, constantpool)
 394           ("Class entry@%d name_index change: %d to %d",
 395            *merge_cp_length_p, name_i, new_name_i);
 396       }
 397 
 398       (*merge_cp_p)->temp_unresolved_klass_at_put(*merge_cp_length_p, new_name_i);
 399       if (scratch_i != *merge_cp_length_p) {
 400         // The new entry in *merge_cp_p is at a different index than
 401         // the new entry in scratch_cp so we need to map the index values.
 402         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 403       }
 404       (*merge_cp_length_p)++;
 405     } break;
 406 
 407     // these are direct CP entries so they can be directly appended,
 408     // but double and long take two constant pool entries
 409     case JVM_CONSTANT_Double:  // fall through
 410     case JVM_CONSTANT_Long:
 411     {
 412       ConstantPool::copy_entry_to(scratch_cp, scratch_i, *merge_cp_p, *merge_cp_length_p);
 413 
 414       if (scratch_i != *merge_cp_length_p) {
 415         // The new entry in *merge_cp_p is at a different index than
 416         // the new entry in scratch_cp so we need to map the index values.
 417         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 418       }
 419       (*merge_cp_length_p) += 2;
 420     } break;
 421 
 422     // these are direct CP entries so they can be directly appended
 423     case JVM_CONSTANT_Float:   // fall through
 424     case JVM_CONSTANT_Integer: // fall through
 425     case JVM_CONSTANT_Utf8:    // fall through
 426 
 427     // This was an indirect CP entry, but it has been changed into
 428     // Symbol*s so this entry can be directly appended.
 429     case JVM_CONSTANT_String:      // fall through
 430     {
 431       ConstantPool::copy_entry_to(scratch_cp, scratch_i, *merge_cp_p, *merge_cp_length_p);
 432 
 433       if (scratch_i != *merge_cp_length_p) {
 434         // The new entry in *merge_cp_p is at a different index than
 435         // the new entry in scratch_cp so we need to map the index values.
 436         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 437       }
 438       (*merge_cp_length_p)++;
 439     } break;
 440 
 441     // this is an indirect CP entry so it needs special handling
 442     case JVM_CONSTANT_NameAndType:
 443     {
 444       int name_ref_i = scratch_cp->name_ref_index_at(scratch_i);
 445       int new_name_ref_i = find_or_append_indirect_entry(scratch_cp, name_ref_i, merge_cp_p,
 446                                                          merge_cp_length_p);
 447 
 448       int signature_ref_i = scratch_cp->signature_ref_index_at(scratch_i);
 449       int new_signature_ref_i = find_or_append_indirect_entry(scratch_cp, signature_ref_i,
 450                                                               merge_cp_p, merge_cp_length_p);
 451 
 452       // If the referenced entries already exist in *merge_cp_p, then
 453       // both new_name_ref_i and new_signature_ref_i will both be 0.
 454       // In that case, all we are appending is the current entry.
 455       if (new_name_ref_i != name_ref_i) {
 456         log_trace(redefine, class, constantpool)
 457           ("NameAndType entry@%d name_ref_index change: %d to %d",
 458            *merge_cp_length_p, name_ref_i, new_name_ref_i);
 459       }
 460       if (new_signature_ref_i != signature_ref_i) {
 461         log_trace(redefine, class, constantpool)
 462           ("NameAndType entry@%d signature_ref_index change: %d to %d",
 463            *merge_cp_length_p, signature_ref_i, new_signature_ref_i);
 464       }
 465 
 466       (*merge_cp_p)->name_and_type_at_put(*merge_cp_length_p,
 467         new_name_ref_i, new_signature_ref_i);
 468       if (scratch_i != *merge_cp_length_p) {
 469         // The new entry in *merge_cp_p is at a different index than
 470         // the new entry in scratch_cp so we need to map the index values.
 471         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 472       }
 473       (*merge_cp_length_p)++;
 474     } break;
 475 
 476     // this is a double-indirect CP entry so it needs special handling
 477     case JVM_CONSTANT_Fieldref:           // fall through
 478     case JVM_CONSTANT_InterfaceMethodref: // fall through
 479     case JVM_CONSTANT_Methodref:
 480     {
 481       int klass_ref_i = scratch_cp->uncached_klass_ref_index_at(scratch_i);
 482       int new_klass_ref_i = find_or_append_indirect_entry(scratch_cp, klass_ref_i,
 483                                                           merge_cp_p, merge_cp_length_p);
 484 
 485       int name_and_type_ref_i = scratch_cp->uncached_name_and_type_ref_index_at(scratch_i);
 486       int new_name_and_type_ref_i = find_or_append_indirect_entry(scratch_cp, name_and_type_ref_i,
 487                                                           merge_cp_p, merge_cp_length_p);
 488 
 489       const char *entry_name = nullptr;
 490       switch (scratch_cp->tag_at(scratch_i).value()) {
 491       case JVM_CONSTANT_Fieldref:
 492         entry_name = "Fieldref";
 493         (*merge_cp_p)->field_at_put(*merge_cp_length_p, new_klass_ref_i,
 494           new_name_and_type_ref_i);
 495         break;
 496       case JVM_CONSTANT_InterfaceMethodref:
 497         entry_name = "IFMethodref";
 498         (*merge_cp_p)->interface_method_at_put(*merge_cp_length_p,
 499           new_klass_ref_i, new_name_and_type_ref_i);
 500         break;
 501       case JVM_CONSTANT_Methodref:
 502         entry_name = "Methodref";
 503         (*merge_cp_p)->method_at_put(*merge_cp_length_p, new_klass_ref_i,
 504           new_name_and_type_ref_i);
 505         break;
 506       default:
 507         guarantee(false, "bad switch");
 508         break;
 509       }
 510 
 511       if (klass_ref_i != new_klass_ref_i) {
 512         log_trace(redefine, class, constantpool)
 513           ("%s entry@%d class_index changed: %d to %d", entry_name, *merge_cp_length_p, klass_ref_i, new_klass_ref_i);
 514       }
 515       if (name_and_type_ref_i != new_name_and_type_ref_i) {
 516         log_trace(redefine, class, constantpool)
 517           ("%s entry@%d name_and_type_index changed: %d to %d",
 518            entry_name, *merge_cp_length_p, name_and_type_ref_i, new_name_and_type_ref_i);
 519       }
 520 
 521       if (scratch_i != *merge_cp_length_p) {
 522         // The new entry in *merge_cp_p is at a different index than
 523         // the new entry in scratch_cp so we need to map the index values.
 524         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 525       }
 526       (*merge_cp_length_p)++;
 527     } break;
 528 
 529     // this is an indirect CP entry so it needs special handling
 530     case JVM_CONSTANT_MethodType:
 531     {
 532       int ref_i = scratch_cp->method_type_index_at(scratch_i);
 533       int new_ref_i = find_or_append_indirect_entry(scratch_cp, ref_i, merge_cp_p,
 534                                                     merge_cp_length_p);
 535       if (new_ref_i != ref_i) {
 536         log_trace(redefine, class, constantpool)
 537           ("MethodType entry@%d ref_index change: %d to %d", *merge_cp_length_p, ref_i, new_ref_i);
 538       }
 539       (*merge_cp_p)->method_type_index_at_put(*merge_cp_length_p, new_ref_i);
 540       if (scratch_i != *merge_cp_length_p) {
 541         // The new entry in *merge_cp_p is at a different index than
 542         // the new entry in scratch_cp so we need to map the index values.
 543         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 544       }
 545       (*merge_cp_length_p)++;
 546     } break;
 547 
 548     // this is an indirect CP entry so it needs special handling
 549     case JVM_CONSTANT_MethodHandle:
 550     {
 551       int ref_kind = scratch_cp->method_handle_ref_kind_at(scratch_i);
 552       int ref_i = scratch_cp->method_handle_index_at(scratch_i);
 553       int new_ref_i = find_or_append_indirect_entry(scratch_cp, ref_i, merge_cp_p,
 554                                                     merge_cp_length_p);
 555       if (new_ref_i != ref_i) {
 556         log_trace(redefine, class, constantpool)
 557           ("MethodHandle entry@%d ref_index change: %d to %d", *merge_cp_length_p, ref_i, new_ref_i);
 558       }
 559       (*merge_cp_p)->method_handle_index_at_put(*merge_cp_length_p, ref_kind, new_ref_i);
 560       if (scratch_i != *merge_cp_length_p) {
 561         // The new entry in *merge_cp_p is at a different index than
 562         // the new entry in scratch_cp so we need to map the index values.
 563         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 564       }
 565       (*merge_cp_length_p)++;
 566     } break;
 567 
 568     // this is an indirect CP entry so it needs special handling
 569     case JVM_CONSTANT_Dynamic:  // fall through
 570     case JVM_CONSTANT_InvokeDynamic:
 571     {
 572       // Index of the bootstrap specifier in the operands array
 573       int old_bs_i = scratch_cp->bootstrap_methods_attribute_index(scratch_i);
 574       int new_bs_i = find_or_append_operand(scratch_cp, old_bs_i, merge_cp_p,
 575                                             merge_cp_length_p);
 576       // The bootstrap method NameAndType_info index
 577       int old_ref_i = scratch_cp->bootstrap_name_and_type_ref_index_at(scratch_i);
 578       int new_ref_i = find_or_append_indirect_entry(scratch_cp, old_ref_i, merge_cp_p,
 579                                                     merge_cp_length_p);
 580       if (new_bs_i != old_bs_i) {
 581         log_trace(redefine, class, constantpool)
 582           ("Dynamic entry@%d bootstrap_method_attr_index change: %d to %d",
 583            *merge_cp_length_p, old_bs_i, new_bs_i);
 584       }
 585       if (new_ref_i != old_ref_i) {
 586         log_trace(redefine, class, constantpool)
 587           ("Dynamic entry@%d name_and_type_index change: %d to %d", *merge_cp_length_p, old_ref_i, new_ref_i);
 588       }
 589 
 590       if (scratch_cp->tag_at(scratch_i).is_dynamic_constant())
 591         (*merge_cp_p)->dynamic_constant_at_put(*merge_cp_length_p, new_bs_i, new_ref_i);
 592       else
 593         (*merge_cp_p)->invoke_dynamic_at_put(*merge_cp_length_p, new_bs_i, new_ref_i);
 594       if (scratch_i != *merge_cp_length_p) {
 595         // The new entry in *merge_cp_p is at a different index than
 596         // the new entry in scratch_cp so we need to map the index values.
 597         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 598       }
 599       (*merge_cp_length_p)++;
 600     } break;
 601 
 602     // At this stage, Class or UnresolvedClass could be in scratch_cp, but not
 603     // ClassIndex
 604     case JVM_CONSTANT_ClassIndex: // fall through
 605 
 606     // Invalid is used as the tag for the second constant pool entry
 607     // occupied by JVM_CONSTANT_Double or JVM_CONSTANT_Long. It should
 608     // not be seen by itself.
 609     case JVM_CONSTANT_Invalid: // fall through
 610 
 611     // At this stage, String could be here, but not StringIndex
 612     case JVM_CONSTANT_StringIndex: // fall through
 613 
 614     // At this stage JVM_CONSTANT_UnresolvedClassInError should not be
 615     // here
 616     case JVM_CONSTANT_UnresolvedClassInError: // fall through
 617 
 618     default:
 619     {
 620       // leave a breadcrumb
 621       jbyte bad_value = scratch_cp->tag_at(scratch_i).value();
 622       ShouldNotReachHere();
 623     } break;
 624   } // end switch tag value
 625 } // end append_entry()
 626 
 627 
 628 u2 VM_RedefineClasses::find_or_append_indirect_entry(const constantPoolHandle& scratch_cp,
 629       int ref_i, constantPoolHandle *merge_cp_p, int *merge_cp_length_p) {
 630 
 631   int new_ref_i = ref_i;
 632   bool match = (ref_i < *merge_cp_length_p) &&
 633                scratch_cp->compare_entry_to(ref_i, *merge_cp_p, ref_i);
 634 
 635   if (!match) {
 636     // forward reference in *merge_cp_p or not a direct match
 637     int found_i = scratch_cp->find_matching_entry(ref_i, *merge_cp_p);
 638     if (found_i != 0) {
 639       guarantee(found_i != ref_i, "compare_entry_to() and find_matching_entry() do not agree");
 640       // Found a matching entry somewhere else in *merge_cp_p so just need a mapping entry.
 641       new_ref_i = found_i;
 642       map_index(scratch_cp, ref_i, found_i);
 643     } else {
 644       // no match found so we have to append this entry to *merge_cp_p
 645       append_entry(scratch_cp, ref_i, merge_cp_p, merge_cp_length_p);
 646       // The above call to append_entry() can only append one entry
 647       // so the post call query of *merge_cp_length_p is only for
 648       // the sake of consistency.
 649       new_ref_i = *merge_cp_length_p - 1;
 650     }
 651   }
 652 
 653   // constant pool indices are u2, unless the merged constant pool overflows which
 654   // we don't check for.
 655   return checked_cast<u2>(new_ref_i);
 656 } // end find_or_append_indirect_entry()
 657 
 658 
 659 // Append a bootstrap specifier into the merge_cp operands that is semantically equal
 660 // to the scratch_cp operands bootstrap specifier passed by the old_bs_i index.
 661 // Recursively append new merge_cp entries referenced by the new bootstrap specifier.
 662 void VM_RedefineClasses::append_operand(const constantPoolHandle& scratch_cp, int old_bs_i,
 663        constantPoolHandle *merge_cp_p, int *merge_cp_length_p) {
 664 
 665   u2 old_ref_i = scratch_cp->operand_bootstrap_method_ref_index_at(old_bs_i);
 666   u2 new_ref_i = find_or_append_indirect_entry(scratch_cp, old_ref_i, merge_cp_p,
 667                                                merge_cp_length_p);
 668   if (new_ref_i != old_ref_i) {
 669     log_trace(redefine, class, constantpool)
 670       ("operands entry@%d bootstrap method ref_index change: %d to %d", _operands_cur_length, old_ref_i, new_ref_i);
 671   }
 672 
 673   Array<u2>* merge_ops = (*merge_cp_p)->operands();
 674   int new_bs_i = _operands_cur_length;
 675   // We have _operands_cur_length == 0 when the merge_cp operands is empty yet.
 676   // However, the operand_offset_at(0) was set in the extend_operands() call.
 677   int new_base = (new_bs_i == 0) ? (*merge_cp_p)->operand_offset_at(0)
 678                                  : (*merge_cp_p)->operand_next_offset_at(new_bs_i - 1);
 679   u2 argc      = scratch_cp->operand_argument_count_at(old_bs_i);
 680 
 681   ConstantPool::operand_offset_at_put(merge_ops, _operands_cur_length, new_base);
 682   merge_ops->at_put(new_base++, new_ref_i);
 683   merge_ops->at_put(new_base++, argc);
 684 
 685   for (int i = 0; i < argc; i++) {
 686     u2 old_arg_ref_i = scratch_cp->operand_argument_index_at(old_bs_i, i);
 687     u2 new_arg_ref_i = find_or_append_indirect_entry(scratch_cp, old_arg_ref_i, merge_cp_p,
 688                                                      merge_cp_length_p);
 689     merge_ops->at_put(new_base++, new_arg_ref_i);
 690     if (new_arg_ref_i != old_arg_ref_i) {
 691       log_trace(redefine, class, constantpool)
 692         ("operands entry@%d bootstrap method argument ref_index change: %d to %d",
 693          _operands_cur_length, old_arg_ref_i, new_arg_ref_i);
 694     }
 695   }
 696   if (old_bs_i != _operands_cur_length) {
 697     // The bootstrap specifier in *merge_cp_p is at a different index than
 698     // that in scratch_cp so we need to map the index values.
 699     map_operand_index(old_bs_i, new_bs_i);
 700   }
 701   _operands_cur_length++;
 702 } // end append_operand()
 703 
 704 
 705 int VM_RedefineClasses::find_or_append_operand(const constantPoolHandle& scratch_cp,
 706       int old_bs_i, constantPoolHandle *merge_cp_p, int *merge_cp_length_p) {
 707 
 708   int new_bs_i = old_bs_i; // bootstrap specifier index
 709   bool match = (old_bs_i < _operands_cur_length) &&
 710                scratch_cp->compare_operand_to(old_bs_i, *merge_cp_p, old_bs_i);
 711 
 712   if (!match) {
 713     // forward reference in *merge_cp_p or not a direct match
 714     int found_i = scratch_cp->find_matching_operand(old_bs_i, *merge_cp_p,
 715                                                     _operands_cur_length);
 716     if (found_i != -1) {
 717       guarantee(found_i != old_bs_i, "compare_operand_to() and find_matching_operand() disagree");
 718       // found a matching operand somewhere else in *merge_cp_p so just need a mapping
 719       new_bs_i = found_i;
 720       map_operand_index(old_bs_i, found_i);
 721     } else {
 722       // no match found so we have to append this bootstrap specifier to *merge_cp_p
 723       append_operand(scratch_cp, old_bs_i, merge_cp_p, merge_cp_length_p);
 724       new_bs_i = _operands_cur_length - 1;
 725     }
 726   }
 727   return new_bs_i;
 728 } // end find_or_append_operand()
 729 
 730 
 731 void VM_RedefineClasses::finalize_operands_merge(const constantPoolHandle& merge_cp, TRAPS) {
 732   if (merge_cp->operands() == nullptr) {
 733     return;
 734   }
 735   // Shrink the merge_cp operands
 736   merge_cp->shrink_operands(_operands_cur_length, CHECK);
 737 
 738   if (log_is_enabled(Trace, redefine, class, constantpool)) {
 739     // don't want to loop unless we are tracing
 740     int count = 0;
 741     for (int i = 1; i < _operands_index_map_p->length(); i++) {
 742       int value = _operands_index_map_p->at(i);
 743       if (value != -1) {
 744         log_trace(redefine, class, constantpool)("operands_index_map[%d]: old=%d new=%d", count, i, value);
 745         count++;
 746       }
 747     }
 748   }
 749   // Clean-up
 750   _operands_index_map_p = nullptr;
 751   _operands_cur_length = 0;
 752   _operands_index_map_count = 0;
 753 } // end finalize_operands_merge()
 754 
 755 // Symbol* comparator for qsort
 756 // The caller must have an active ResourceMark.
 757 static int symcmp(const void* a, const void* b) {
 758   char* astr = (*(Symbol**)a)->as_C_string();
 759   char* bstr = (*(Symbol**)b)->as_C_string();
 760   return strcmp(astr, bstr);
 761 }
 762 
 763 // The caller must have an active ResourceMark.
 764 static jvmtiError check_attribute_arrays(const char* attr_name,
 765            InstanceKlass* the_class, InstanceKlass* scratch_class,
 766            Array<u2>* the_array, Array<u2>* scr_array) {
 767   bool the_array_exists = the_array != Universe::the_empty_short_array();
 768   bool scr_array_exists = scr_array != Universe::the_empty_short_array();
 769 
 770   int array_len = the_array->length();
 771   if (the_array_exists && scr_array_exists) {
 772     if (array_len != scr_array->length()) {
 773       log_trace(redefine, class)
 774         ("redefined class %s attribute change error: %s len=%d changed to len=%d",
 775          the_class->external_name(), attr_name, array_len, scr_array->length());
 776       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
 777     }
 778 
 779     // The order of entries in the attribute array is not specified so we
 780     // have to explicitly check for the same contents. We do this by copying
 781     // the referenced symbols into their own arrays, sorting them and then
 782     // comparing each element pair.
 783 
 784     Symbol** the_syms = NEW_RESOURCE_ARRAY_RETURN_NULL(Symbol*, array_len);
 785     Symbol** scr_syms = NEW_RESOURCE_ARRAY_RETURN_NULL(Symbol*, array_len);
 786 
 787     if (the_syms == nullptr || scr_syms == nullptr) {
 788       return JVMTI_ERROR_OUT_OF_MEMORY;
 789     }
 790 
 791     for (int i = 0; i < array_len; i++) {
 792       int the_cp_index = the_array->at(i);
 793       int scr_cp_index = scr_array->at(i);
 794       the_syms[i] = the_class->constants()->klass_name_at(the_cp_index);
 795       scr_syms[i] = scratch_class->constants()->klass_name_at(scr_cp_index);
 796     }
 797 
 798     qsort(the_syms, array_len, sizeof(Symbol*), symcmp);
 799     qsort(scr_syms, array_len, sizeof(Symbol*), symcmp);
 800 
 801     for (int i = 0; i < array_len; i++) {
 802       if (the_syms[i] != scr_syms[i]) {
 803         log_info(redefine, class)
 804           ("redefined class %s attribute change error: %s[%d]: %s changed to %s",
 805            the_class->external_name(), attr_name, i,
 806            the_syms[i]->as_C_string(), scr_syms[i]->as_C_string());
 807         return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
 808       }
 809     }
 810   } else if (the_array_exists ^ scr_array_exists) {
 811     const char* action_str = (the_array_exists) ? "removed" : "added";
 812     log_info(redefine, class)
 813       ("redefined class %s attribute change error: %s attribute %s",
 814        the_class->external_name(), attr_name, action_str);
 815     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
 816   }
 817   return JVMTI_ERROR_NONE;
 818 }
 819 
 820 static jvmtiError check_nest_attributes(InstanceKlass* the_class,
 821                                         InstanceKlass* scratch_class) {
 822   // Check whether the class NestHost attribute has been changed.
 823   Thread* thread = Thread::current();
 824   ResourceMark rm(thread);
 825   u2 the_nest_host_idx = the_class->nest_host_index();
 826   u2 scr_nest_host_idx = scratch_class->nest_host_index();
 827 
 828   if (the_nest_host_idx != 0 && scr_nest_host_idx != 0) {
 829     Symbol* the_sym = the_class->constants()->klass_name_at(the_nest_host_idx);
 830     Symbol* scr_sym = scratch_class->constants()->klass_name_at(scr_nest_host_idx);
 831     if (the_sym != scr_sym) {
 832       log_info(redefine, class, nestmates)
 833         ("redefined class %s attribute change error: NestHost class: %s replaced with: %s",
 834          the_class->external_name(), the_sym->as_C_string(), scr_sym->as_C_string());
 835       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
 836     }
 837   } else if ((the_nest_host_idx == 0) ^ (scr_nest_host_idx == 0)) {
 838     const char* action_str = (the_nest_host_idx != 0) ? "removed" : "added";
 839     log_info(redefine, class, nestmates)
 840       ("redefined class %s attribute change error: NestHost attribute %s",
 841        the_class->external_name(), action_str);
 842     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
 843   }
 844 
 845   // Check whether the class NestMembers attribute has been changed.
 846   return check_attribute_arrays("NestMembers",
 847                                 the_class, scratch_class,
 848                                 the_class->nest_members(),
 849                                 scratch_class->nest_members());
 850 }
 851 
 852 // Return an error status if the class Record attribute was changed.
 853 static jvmtiError check_record_attribute(InstanceKlass* the_class, InstanceKlass* scratch_class) {
 854   // Get lists of record components.
 855   Array<RecordComponent*>* the_record = the_class->record_components();
 856   Array<RecordComponent*>* scr_record = scratch_class->record_components();
 857   bool the_record_exists = the_record != nullptr;
 858   bool scr_record_exists = scr_record != nullptr;
 859 
 860   if (the_record_exists && scr_record_exists) {
 861     int the_num_components = the_record->length();
 862     int scr_num_components = scr_record->length();
 863     if (the_num_components != scr_num_components) {
 864       log_info(redefine, class, record)
 865         ("redefined class %s attribute change error: Record num_components=%d changed to num_components=%d",
 866          the_class->external_name(), the_num_components, scr_num_components);
 867       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
 868     }
 869 
 870     // Compare each field in each record component.
 871     ConstantPool* the_cp =  the_class->constants();
 872     ConstantPool* scr_cp =  scratch_class->constants();
 873     for (int x = 0; x < the_num_components; x++) {
 874       RecordComponent* the_component = the_record->at(x);
 875       RecordComponent* scr_component = scr_record->at(x);
 876       const Symbol* const the_name = the_cp->symbol_at(the_component->name_index());
 877       const Symbol* const scr_name = scr_cp->symbol_at(scr_component->name_index());
 878       const Symbol* const the_descr = the_cp->symbol_at(the_component->descriptor_index());
 879       const Symbol* const scr_descr = scr_cp->symbol_at(scr_component->descriptor_index());
 880       if (the_name != scr_name || the_descr != scr_descr) {
 881         log_info(redefine, class, record)
 882           ("redefined class %s attribute change error: Record name_index, descriptor_index, and/or attributes_count changed",
 883            the_class->external_name());
 884         return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
 885       }
 886 
 887       int the_gen_sig = the_component->generic_signature_index();
 888       int scr_gen_sig = scr_component->generic_signature_index();
 889       const Symbol* const the_gen_sig_sym = (the_gen_sig == 0 ? nullptr :
 890         the_cp->symbol_at(the_component->generic_signature_index()));
 891       const Symbol* const scr_gen_sig_sym = (scr_gen_sig == 0 ? nullptr :
 892         scr_cp->symbol_at(scr_component->generic_signature_index()));
 893       if (the_gen_sig_sym != scr_gen_sig_sym) {
 894         log_info(redefine, class, record)
 895           ("redefined class %s attribute change error: Record generic_signature attribute changed",
 896            the_class->external_name());
 897         return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
 898       }
 899 
 900       // It's okay if a record component's annotations were changed.
 901     }
 902 
 903   } else if (the_record_exists ^ scr_record_exists) {
 904     const char* action_str = (the_record_exists) ? "removed" : "added";
 905     log_info(redefine, class, record)
 906       ("redefined class %s attribute change error: Record attribute %s",
 907        the_class->external_name(), action_str);
 908     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
 909   }
 910 
 911   return JVMTI_ERROR_NONE;
 912 }
 913 
 914 
 915 static jvmtiError check_permitted_subclasses_attribute(InstanceKlass* the_class,
 916                                                        InstanceKlass* scratch_class) {
 917   Thread* thread = Thread::current();
 918   ResourceMark rm(thread);
 919 
 920   // Check whether the class PermittedSubclasses attribute has been changed.
 921   return check_attribute_arrays("PermittedSubclasses",
 922                                 the_class, scratch_class,
 923                                 the_class->permitted_subclasses(),
 924                                 scratch_class->permitted_subclasses());
 925 }
 926 












 927 static bool can_add_or_delete(Method* m) {
 928       // Compatibility mode
 929   return (AllowRedefinitionToAddDeleteMethods &&
 930           (m->is_private() && (m->is_static() || m->is_final())));
 931 }
 932 
 933 jvmtiError VM_RedefineClasses::compare_and_normalize_class_versions(
 934              InstanceKlass* the_class,
 935              InstanceKlass* scratch_class) {
 936   int i;
 937 
 938   // Check superclasses, or rather their names, since superclasses themselves can be
 939   // requested to replace.
 940   // Check for null superclass first since this might be java.lang.Object
 941   if (the_class->super() != scratch_class->super() &&
 942       (the_class->super() == nullptr || scratch_class->super() == nullptr ||
 943        the_class->super()->name() !=
 944        scratch_class->super()->name())) {
 945     log_info(redefine, class, normalize)
 946       ("redefined class %s superclass change error: superclass changed from %s to %s.",
 947        the_class->external_name(),
 948        the_class->super() == nullptr ? "null" : the_class->super()->external_name(),
 949        scratch_class->super() == nullptr ? "null" : scratch_class->super()->external_name());
 950     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_HIERARCHY_CHANGED;
 951   }
 952 
 953   // Check if the number, names and order of directly implemented interfaces are the same.
 954   // I think in principle we should just check if the sets of names of directly implemented
 955   // interfaces are the same, i.e. the order of declaration (which, however, if changed in the
 956   // .java file, also changes in .class file) should not matter. However, comparing sets is
 957   // technically a bit more difficult, and, more importantly, I am not sure at present that the
 958   // order of interfaces does not matter on the implementation level, i.e. that the VM does not
 959   // rely on it somewhere.
 960   Array<InstanceKlass*>* k_interfaces = the_class->local_interfaces();
 961   Array<InstanceKlass*>* k_new_interfaces = scratch_class->local_interfaces();
 962   int n_intfs = k_interfaces->length();
 963   if (n_intfs != k_new_interfaces->length()) {
 964     log_info(redefine, class, normalize)
 965       ("redefined class %s interfaces change error: number of implemented interfaces changed from %d to %d.",
 966        the_class->external_name(), n_intfs, k_new_interfaces->length());
 967     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_HIERARCHY_CHANGED;
 968   }
 969   for (i = 0; i < n_intfs; i++) {
 970     if (k_interfaces->at(i)->name() !=
 971         k_new_interfaces->at(i)->name()) {
 972       log_info(redefine, class, normalize)
 973           ("redefined class %s interfaces change error: interface changed from %s to %s.",
 974            the_class->external_name(),
 975            k_interfaces->at(i)->external_name(), k_new_interfaces->at(i)->external_name());
 976       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_HIERARCHY_CHANGED;
 977     }
 978   }
 979 
 980   // Check whether class is in the error init state.
 981   if (the_class->is_in_error_state()) {
 982     log_info(redefine, class, normalize)
 983       ("redefined class %s is in error init state.", the_class->external_name());
 984     // TBD #5057930: special error code is needed in 1.6
 985     return JVMTI_ERROR_INVALID_CLASS;
 986   }
 987 
 988   // Check whether the nest-related attributes have been changed.
 989   jvmtiError err = check_nest_attributes(the_class, scratch_class);
 990   if (err != JVMTI_ERROR_NONE) {
 991     return err;
 992   }
 993 
 994   // Check whether the Record attribute has been changed.
 995   err = check_record_attribute(the_class, scratch_class);
 996   if (err != JVMTI_ERROR_NONE) {
 997     return err;
 998   }
 999 
1000   // Check whether the PermittedSubclasses attribute has been changed.
1001   err = check_permitted_subclasses_attribute(the_class, scratch_class);
1002   if (err != JVMTI_ERROR_NONE) {
1003     return err;
1004   }
1005 






1006   // Check whether class modifiers are the same.
1007   jushort old_flags = (jushort) the_class->access_flags().get_flags();
1008   jushort new_flags = (jushort) scratch_class->access_flags().get_flags();
1009   if (old_flags != new_flags) {
1010     log_info(redefine, class, normalize)
1011         ("redefined class %s modifiers change error: modifiers changed from %d to %d.",
1012          the_class->external_name(), old_flags, new_flags);
1013     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_MODIFIERS_CHANGED;
1014   }
1015 
1016   // Check if the number, names, types and order of fields declared in these classes
1017   // are the same.
1018   JavaFieldStream old_fs(the_class);
1019   JavaFieldStream new_fs(scratch_class);
1020   for (; !old_fs.done() && !new_fs.done(); old_fs.next(), new_fs.next()) {
1021     // name and signature
1022     Symbol* name_sym1 = the_class->constants()->symbol_at(old_fs.name_index());
1023     Symbol* sig_sym1 = the_class->constants()->symbol_at(old_fs.signature_index());
1024     Symbol* name_sym2 = scratch_class->constants()->symbol_at(new_fs.name_index());
1025     Symbol* sig_sym2 = scratch_class->constants()->symbol_at(new_fs.signature_index());
1026     if (name_sym1 != name_sym2 || sig_sym1 != sig_sym2) {
1027       log_info(redefine, class, normalize)
1028           ("redefined class %s fields change error: field %s %s changed to %s %s.",
1029            the_class->external_name(),
1030            sig_sym1->as_C_string(), name_sym1->as_C_string(),
1031            sig_sym2->as_C_string(), name_sym2->as_C_string());
1032       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_SCHEMA_CHANGED;
1033     }
1034     // offset
1035     if (old_fs.offset() != new_fs.offset()) {
1036       log_info(redefine, class, normalize)
1037           ("redefined class %s field %s change error: offset changed from %d to %d.",
1038            the_class->external_name(), name_sym2->as_C_string(), old_fs.offset(), new_fs.offset());
1039       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_SCHEMA_CHANGED;
1040     }
1041     // access
1042     old_flags = old_fs.access_flags().as_short();
1043     new_flags = new_fs.access_flags().as_short();
1044     if ((old_flags ^ new_flags) & JVM_RECOGNIZED_FIELD_MODIFIERS) {
1045       log_info(redefine, class, normalize)
1046           ("redefined class %s field %s change error: modifiers changed from %d to %d.",
1047            the_class->external_name(), name_sym2->as_C_string(), old_flags, new_flags);
1048       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_SCHEMA_CHANGED;
1049     }
1050   }
1051 
1052   // If both streams aren't done then we have a differing number of
1053   // fields.
1054   if (!old_fs.done() || !new_fs.done()) {
1055     const char* action = old_fs.done() ? "added" : "deleted";
1056     log_info(redefine, class, normalize)
1057         ("redefined class %s fields change error: some fields were %s.",
1058          the_class->external_name(), action);
1059     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_SCHEMA_CHANGED;
1060   }
1061 
1062   // Do a parallel walk through the old and new methods. Detect
1063   // cases where they match (exist in both), have been added in
1064   // the new methods, or have been deleted (exist only in the
1065   // old methods).  The class file parser places methods in order
1066   // by method name, but does not order overloaded methods by
1067   // signature.  In order to determine what fate befell the methods,
1068   // this code places the overloaded new methods that have matching
1069   // old methods in the same order as the old methods and places
1070   // new overloaded methods at the end of overloaded methods of
1071   // that name. The code for this order normalization is adapted
1072   // from the algorithm used in InstanceKlass::find_method().
1073   // Since we are swapping out of order entries as we find them,
1074   // we only have to search forward through the overloaded methods.
1075   // Methods which are added and have the same name as an existing
1076   // method (but different signature) will be put at the end of
1077   // the methods with that name, and the name mismatch code will
1078   // handle them.
1079   Array<Method*>* k_old_methods(the_class->methods());
1080   Array<Method*>* k_new_methods(scratch_class->methods());
1081   int n_old_methods = k_old_methods->length();
1082   int n_new_methods = k_new_methods->length();
1083   Thread* thread = Thread::current();
1084 
1085   int ni = 0;
1086   int oi = 0;
1087   while (true) {
1088     Method* k_old_method;
1089     Method* k_new_method;
1090     enum { matched, added, deleted, undetermined } method_was = undetermined;
1091 
1092     if (oi >= n_old_methods) {
1093       if (ni >= n_new_methods) {
1094         break; // we've looked at everything, done
1095       }
1096       // New method at the end
1097       k_new_method = k_new_methods->at(ni);
1098       method_was = added;
1099     } else if (ni >= n_new_methods) {
1100       // Old method, at the end, is deleted
1101       k_old_method = k_old_methods->at(oi);
1102       method_was = deleted;
1103     } else {
1104       // There are more methods in both the old and new lists
1105       k_old_method = k_old_methods->at(oi);
1106       k_new_method = k_new_methods->at(ni);
1107       if (k_old_method->name() != k_new_method->name()) {
1108         // Methods are sorted by method name, so a mismatch means added
1109         // or deleted
1110         if (k_old_method->name()->fast_compare(k_new_method->name()) > 0) {
1111           method_was = added;
1112         } else {
1113           method_was = deleted;
1114         }
1115       } else if (k_old_method->signature() == k_new_method->signature()) {
1116         // Both the name and signature match
1117         method_was = matched;
1118       } else {
1119         // The name matches, but the signature doesn't, which means we have to
1120         // search forward through the new overloaded methods.
1121         int nj;  // outside the loop for post-loop check
1122         for (nj = ni + 1; nj < n_new_methods; nj++) {
1123           Method* m = k_new_methods->at(nj);
1124           if (k_old_method->name() != m->name()) {
1125             // reached another method name so no more overloaded methods
1126             method_was = deleted;
1127             break;
1128           }
1129           if (k_old_method->signature() == m->signature()) {
1130             // found a match so swap the methods
1131             k_new_methods->at_put(ni, m);
1132             k_new_methods->at_put(nj, k_new_method);
1133             k_new_method = m;
1134             method_was = matched;
1135             break;
1136           }
1137         }
1138 
1139         if (nj >= n_new_methods) {
1140           // reached the end without a match; so method was deleted
1141           method_was = deleted;
1142         }
1143       }
1144     }
1145 
1146     switch (method_was) {
1147     case matched:
1148       // methods match, be sure modifiers do too
1149       old_flags = (jushort) k_old_method->access_flags().get_flags();
1150       new_flags = (jushort) k_new_method->access_flags().get_flags();
1151       if ((old_flags ^ new_flags) & ~(JVM_ACC_NATIVE)) {
1152         log_info(redefine, class, normalize)
1153           ("redefined class %s  method %s modifiers error: modifiers changed from %d to %d",
1154            the_class->external_name(), k_old_method->name_and_sig_as_C_string(), old_flags, new_flags);
1155         return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_METHOD_MODIFIERS_CHANGED;
1156       }
1157       {
1158         u2 new_num = k_new_method->method_idnum();
1159         u2 old_num = k_old_method->method_idnum();
1160         if (new_num != old_num) {
1161           Method* idnum_owner = scratch_class->method_with_idnum(old_num);
1162           if (idnum_owner != nullptr) {
1163             // There is already a method assigned this idnum -- switch them
1164             // Take current and original idnum from the new_method
1165             idnum_owner->set_method_idnum(new_num);
1166             idnum_owner->set_orig_method_idnum(k_new_method->orig_method_idnum());
1167           }
1168           // Take current and original idnum from the old_method
1169           k_new_method->set_method_idnum(old_num);
1170           k_new_method->set_orig_method_idnum(k_old_method->orig_method_idnum());
1171           if (thread->has_pending_exception()) {
1172             return JVMTI_ERROR_OUT_OF_MEMORY;
1173           }
1174         }
1175       }
1176       JFR_ONLY(k_new_method->copy_trace_flags(*k_old_method->trace_flags_addr());)
1177       log_trace(redefine, class, normalize)
1178         ("Method matched: new: %s [%d] == old: %s [%d]",
1179          k_new_method->name_and_sig_as_C_string(), ni, k_old_method->name_and_sig_as_C_string(), oi);
1180       // advance to next pair of methods
1181       ++oi;
1182       ++ni;
1183       break;
1184     case added:
1185       // method added, see if it is OK
1186       if (!can_add_or_delete(k_new_method)) {
1187         log_info(redefine, class, normalize)
1188           ("redefined class %s methods error: added method: %s [%d]",
1189            the_class->external_name(), k_new_method->name_and_sig_as_C_string(), ni);
1190         return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_METHOD_ADDED;
1191       }
1192       {
1193         u2 num = the_class->next_method_idnum();
1194         if (num == ConstMethod::UNSET_IDNUM) {
1195           // cannot add any more methods
1196           log_info(redefine, class, normalize)
1197             ("redefined class %s methods error: can't create ID for new method %s [%d]",
1198              the_class->external_name(), k_new_method->name_and_sig_as_C_string(), ni);
1199           return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_METHOD_ADDED;
1200         }
1201         u2 new_num = k_new_method->method_idnum();
1202         Method* idnum_owner = scratch_class->method_with_idnum(num);
1203         if (idnum_owner != nullptr) {
1204           // There is already a method assigned this idnum -- switch them
1205           // Take current and original idnum from the new_method
1206           idnum_owner->set_method_idnum(new_num);
1207           idnum_owner->set_orig_method_idnum(k_new_method->orig_method_idnum());
1208         }
1209         k_new_method->set_method_idnum(num);
1210         k_new_method->set_orig_method_idnum(num);
1211         if (thread->has_pending_exception()) {
1212           return JVMTI_ERROR_OUT_OF_MEMORY;
1213         }
1214       }
1215       log_trace(redefine, class, normalize)
1216         ("Method added: new: %s [%d]", k_new_method->name_and_sig_as_C_string(), ni);
1217       ++ni; // advance to next new method
1218       break;
1219     case deleted:
1220       // method deleted, see if it is OK
1221       if (!can_add_or_delete(k_old_method)) {
1222         log_info(redefine, class, normalize)
1223           ("redefined class %s methods error: deleted method %s [%d]",
1224            the_class->external_name(), k_old_method->name_and_sig_as_C_string(), oi);
1225         return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_METHOD_DELETED;
1226       }
1227       log_trace(redefine, class, normalize)
1228         ("Method deleted: old: %s [%d]", k_old_method->name_and_sig_as_C_string(), oi);
1229       ++oi; // advance to next old method
1230       break;
1231     default:
1232       ShouldNotReachHere();
1233     }
1234   }
1235 
1236   return JVMTI_ERROR_NONE;
1237 }
1238 
1239 
1240 // Find new constant pool index value for old constant pool index value
1241 // by searching the index map. Returns zero (0) if there is no mapped
1242 // value for the old constant pool index.
1243 u2 VM_RedefineClasses::find_new_index(int old_index) {
1244   if (_index_map_count == 0) {
1245     // map is empty so nothing can be found
1246     return 0;
1247   }
1248 
1249   if (old_index < 1 || old_index >= _index_map_p->length()) {
1250     // The old_index is out of range so it is not mapped. This should
1251     // not happen in regular constant pool merging use, but it can
1252     // happen if a corrupt annotation is processed.
1253     return 0;
1254   }
1255 
1256   int value = _index_map_p->at(old_index);
1257   if (value == -1) {
1258     // the old_index is not mapped
1259     return 0;
1260   }
1261 
1262   // constant pool indices are u2, unless the merged constant pool overflows which
1263   // we don't check for.
1264   return checked_cast<u2>(value);
1265 } // end find_new_index()
1266 
1267 
1268 // Find new bootstrap specifier index value for old bootstrap specifier index
1269 // value by searching the index map. Returns unused index (-1) if there is
1270 // no mapped value for the old bootstrap specifier index.
1271 int VM_RedefineClasses::find_new_operand_index(int old_index) {
1272   if (_operands_index_map_count == 0) {
1273     // map is empty so nothing can be found
1274     return -1;
1275   }
1276 
1277   if (old_index == -1 || old_index >= _operands_index_map_p->length()) {
1278     // The old_index is out of range so it is not mapped.
1279     // This should not happen in regular constant pool merging use.
1280     return -1;
1281   }
1282 
1283   int value = _operands_index_map_p->at(old_index);
1284   if (value == -1) {
1285     // the old_index is not mapped
1286     return -1;
1287   }
1288 
1289   return value;
1290 } // end find_new_operand_index()
1291 
1292 
1293 // The bug 6214132 caused the verification to fail.
1294 // 1. What's done in RedefineClasses() before verification:
1295 //  a) A reference to the class being redefined (_the_class) and a
1296 //     reference to new version of the class (_scratch_class) are
1297 //     saved here for use during the bytecode verification phase of
1298 //     RedefineClasses.
1299 //  b) The _java_mirror field from _the_class is copied to the
1300 //     _java_mirror field in _scratch_class. This means that a jclass
1301 //     returned for _the_class or _scratch_class will refer to the
1302 //     same Java mirror. The verifier will see the "one true mirror"
1303 //     for the class being verified.
1304 // 2. See comments in JvmtiThreadState for what is done during verification.
1305 
1306 class RedefineVerifyMark : public StackObj {
1307  private:
1308   JvmtiThreadState* _state;
1309   Klass*            _scratch_class;
1310   OopHandle         _scratch_mirror;
1311 
1312  public:
1313 
1314   RedefineVerifyMark(Klass* the_class, Klass* scratch_class,
1315                      JvmtiThreadState* state) : _state(state), _scratch_class(scratch_class)
1316   {
1317     _state->set_class_versions_map(the_class, scratch_class);
1318     _scratch_mirror = the_class->java_mirror_handle();  // this is a copy that is swapped
1319     _scratch_class->swap_java_mirror_handle(_scratch_mirror);
1320   }
1321 
1322   ~RedefineVerifyMark() {
1323     // Restore the scratch class's mirror, so when scratch_class is removed
1324     // the correct mirror pointing to it can be cleared.
1325     _scratch_class->swap_java_mirror_handle(_scratch_mirror);
1326     _state->clear_class_versions_map();
1327   }
1328 };
1329 
1330 
1331 jvmtiError VM_RedefineClasses::load_new_class_versions() {
1332 
1333   // For consistency allocate memory using os::malloc wrapper.
1334   _scratch_classes = (InstanceKlass**)
1335     os::malloc(sizeof(InstanceKlass*) * _class_count, mtClass);
1336   if (_scratch_classes == nullptr) {
1337     return JVMTI_ERROR_OUT_OF_MEMORY;
1338   }
1339   // Zero initialize the _scratch_classes array.
1340   for (int i = 0; i < _class_count; i++) {
1341     _scratch_classes[i] = nullptr;
1342   }
1343 
1344   JavaThread* current = JavaThread::current();
1345   ResourceMark rm(current);
1346 
1347   JvmtiThreadState *state = JvmtiThreadState::state_for(current);
1348   // state can only be null if the current thread is exiting which
1349   // should not happen since we're trying to do a RedefineClasses
1350   guarantee(state != nullptr, "exiting thread calling load_new_class_versions");
1351   for (int i = 0; i < _class_count; i++) {
1352     // Create HandleMark so that any handles created while loading new class
1353     // versions are deleted. Constant pools are deallocated while merging
1354     // constant pools
1355     HandleMark hm(current);
1356     InstanceKlass* the_class = get_ik(_class_defs[i].klass);
1357 
1358     log_debug(redefine, class, load)
1359       ("loading name=%s kind=%d (avail_mem=" UINT64_FORMAT "K)",
1360        the_class->external_name(), _class_load_kind, os::available_memory() >> 10);
1361 
1362     ClassFileStream st((u1*)_class_defs[i].class_bytes,
1363                        _class_defs[i].class_byte_count,
1364                        "__VM_RedefineClasses__",
1365                        ClassFileStream::verify);
1366 
1367     // Set redefined class handle in JvmtiThreadState class.
1368     // This redefined class is sent to agent event handler for class file
1369     // load hook event.
1370     state->set_class_being_redefined(the_class, _class_load_kind);
1371 
1372     JavaThread* THREAD = current; // For exception macros.
1373     ExceptionMark em(THREAD);
1374     Handle protection_domain(THREAD, the_class->protection_domain());
1375     ClassLoadInfo cl_info(protection_domain);
1376     // Parse and create a class from the bytes, but this class isn't added
1377     // to the dictionary, so do not call resolve_from_stream.
1378     InstanceKlass* scratch_class = KlassFactory::create_from_stream(&st,
1379                                                       the_class->name(),
1380                                                       the_class->class_loader_data(),
1381                                                       cl_info,
1382                                                       THREAD);
1383 
1384     // Clear class_being_redefined just to be sure.
1385     state->clear_class_being_redefined();
1386 
1387     // TODO: if this is retransform, and nothing changed we can skip it
1388 
1389     // Need to clean up allocated InstanceKlass if there's an error so assign
1390     // the result here. Caller deallocates all the scratch classes in case of
1391     // an error.
1392     _scratch_classes[i] = scratch_class;
1393 
1394     if (HAS_PENDING_EXCEPTION) {
1395       Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1396       log_info(redefine, class, load, exceptions)("create_from_stream exception: '%s'", ex_name->as_C_string());
1397       CLEAR_PENDING_EXCEPTION;
1398 
1399       if (ex_name == vmSymbols::java_lang_UnsupportedClassVersionError()) {
1400         return JVMTI_ERROR_UNSUPPORTED_VERSION;
1401       } else if (ex_name == vmSymbols::java_lang_ClassFormatError()) {
1402         return JVMTI_ERROR_INVALID_CLASS_FORMAT;
1403       } else if (ex_name == vmSymbols::java_lang_ClassCircularityError()) {
1404         return JVMTI_ERROR_CIRCULAR_CLASS_DEFINITION;
1405       } else if (ex_name == vmSymbols::java_lang_NoClassDefFoundError()) {
1406         // The message will be "XXX (wrong name: YYY)"
1407         return JVMTI_ERROR_NAMES_DONT_MATCH;
1408       } else if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1409         return JVMTI_ERROR_OUT_OF_MEMORY;
1410       } else {  // Just in case more exceptions can be thrown..
1411         return JVMTI_ERROR_FAILS_VERIFICATION;
1412       }
1413     }
1414 
1415     // Ensure class is linked before redefine
1416     if (!the_class->is_linked()) {
1417       the_class->link_class(THREAD);
1418       if (HAS_PENDING_EXCEPTION) {
1419         Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1420         oop message = java_lang_Throwable::message(PENDING_EXCEPTION);
1421         if (message != nullptr) {
1422           char* ex_msg = java_lang_String::as_utf8_string(message);
1423           log_info(redefine, class, load, exceptions)("link_class exception: '%s %s'",
1424                    ex_name->as_C_string(), ex_msg);
1425         } else {
1426           log_info(redefine, class, load, exceptions)("link_class exception: '%s'",
1427                    ex_name->as_C_string());
1428         }
1429         CLEAR_PENDING_EXCEPTION;
1430         if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1431           return JVMTI_ERROR_OUT_OF_MEMORY;
1432         } else if (ex_name == vmSymbols::java_lang_NoClassDefFoundError()) {
1433           return JVMTI_ERROR_INVALID_CLASS;
1434         } else {
1435           return JVMTI_ERROR_INTERNAL;
1436         }
1437       }
1438     }
1439 
1440     // Do the validity checks in compare_and_normalize_class_versions()
1441     // before verifying the byte codes. By doing these checks first, we
1442     // limit the number of functions that require redirection from
1443     // the_class to scratch_class. In particular, we don't have to
1444     // modify JNI GetSuperclass() and thus won't change its performance.
1445     jvmtiError res = compare_and_normalize_class_versions(the_class,
1446                        scratch_class);
1447     if (res != JVMTI_ERROR_NONE) {
1448       return res;
1449     }
1450 
1451     // verify what the caller passed us
1452     {
1453       // The bug 6214132 caused the verification to fail.
1454       // Information about the_class and scratch_class is temporarily
1455       // recorded into jvmtiThreadState. This data is used to redirect
1456       // the_class to scratch_class in the JVM_* functions called by the
1457       // verifier. Please, refer to jvmtiThreadState.hpp for the detailed
1458       // description.
1459       RedefineVerifyMark rvm(the_class, scratch_class, state);
1460       Verifier::verify(scratch_class, true, THREAD);
1461     }
1462 
1463     if (HAS_PENDING_EXCEPTION) {
1464       Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1465       log_info(redefine, class, load, exceptions)("verify_byte_codes exception: '%s'", ex_name->as_C_string());
1466       CLEAR_PENDING_EXCEPTION;
1467       if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1468         return JVMTI_ERROR_OUT_OF_MEMORY;
1469       } else {
1470         // tell the caller the bytecodes are bad
1471         return JVMTI_ERROR_FAILS_VERIFICATION;
1472       }
1473     }
1474 
1475     res = merge_cp_and_rewrite(the_class, scratch_class, THREAD);
1476     if (HAS_PENDING_EXCEPTION) {
1477       Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1478       log_info(redefine, class, load, exceptions)("merge_cp_and_rewrite exception: '%s'", ex_name->as_C_string());
1479       CLEAR_PENDING_EXCEPTION;
1480       if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1481         return JVMTI_ERROR_OUT_OF_MEMORY;
1482       } else {
1483         return JVMTI_ERROR_INTERNAL;
1484       }
1485     }
1486 
1487 #ifdef ASSERT
1488     {
1489       // verify what we have done during constant pool merging
1490       {
1491         RedefineVerifyMark rvm(the_class, scratch_class, state);
1492         Verifier::verify(scratch_class, true, THREAD);
1493       }
1494 
1495       if (HAS_PENDING_EXCEPTION) {
1496         Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1497         log_info(redefine, class, load, exceptions)
1498           ("verify_byte_codes post merge-CP exception: '%s'", ex_name->as_C_string());
1499         CLEAR_PENDING_EXCEPTION;
1500         if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1501           return JVMTI_ERROR_OUT_OF_MEMORY;
1502         } else {
1503           // tell the caller that constant pool merging screwed up
1504           return JVMTI_ERROR_INTERNAL;
1505         }
1506       }
1507     }
1508 #endif // ASSERT
1509 
1510     Rewriter::rewrite(scratch_class, THREAD);
1511     if (!HAS_PENDING_EXCEPTION) {
1512       scratch_class->link_methods(THREAD);
1513     }
1514     if (HAS_PENDING_EXCEPTION) {
1515       Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1516       log_info(redefine, class, load, exceptions)
1517         ("Rewriter::rewrite or link_methods exception: '%s'", ex_name->as_C_string());
1518       CLEAR_PENDING_EXCEPTION;
1519       if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1520         return JVMTI_ERROR_OUT_OF_MEMORY;
1521       } else {
1522         return JVMTI_ERROR_INTERNAL;
1523       }
1524     }
1525 
1526     log_debug(redefine, class, load)
1527       ("loaded name=%s (avail_mem=" UINT64_FORMAT "K)", the_class->external_name(), os::available_memory() >> 10);
1528   }
1529 
1530   return JVMTI_ERROR_NONE;
1531 }
1532 
1533 
1534 // Map old_index to new_index as needed. scratch_cp is only needed
1535 // for log calls.
1536 void VM_RedefineClasses::map_index(const constantPoolHandle& scratch_cp,
1537        int old_index, int new_index) {
1538   if (find_new_index(old_index) != 0) {
1539     // old_index is already mapped
1540     return;
1541   }
1542 
1543   if (old_index == new_index) {
1544     // no mapping is needed
1545     return;
1546   }
1547 
1548   _index_map_p->at_put(old_index, new_index);
1549   _index_map_count++;
1550 
1551   log_trace(redefine, class, constantpool)
1552     ("mapped tag %d at index %d to %d", scratch_cp->tag_at(old_index).value(), old_index, new_index);
1553 } // end map_index()
1554 
1555 
1556 // Map old_index to new_index as needed.
1557 void VM_RedefineClasses::map_operand_index(int old_index, int new_index) {
1558   if (find_new_operand_index(old_index) != -1) {
1559     // old_index is already mapped
1560     return;
1561   }
1562 
1563   if (old_index == new_index) {
1564     // no mapping is needed
1565     return;
1566   }
1567 
1568   _operands_index_map_p->at_put(old_index, new_index);
1569   _operands_index_map_count++;
1570 
1571   log_trace(redefine, class, constantpool)("mapped bootstrap specifier at index %d to %d", old_index, new_index);
1572 } // end map_index()
1573 
1574 
1575 // Merge old_cp and scratch_cp and return the results of the merge via
1576 // merge_cp_p. The number of entries in *merge_cp_p is returned via
1577 // merge_cp_length_p. The entries in old_cp occupy the same locations
1578 // in *merge_cp_p. Also creates a map of indices from entries in
1579 // scratch_cp to the corresponding entry in *merge_cp_p. Index map
1580 // entries are only created for entries in scratch_cp that occupy a
1581 // different location in *merged_cp_p.
1582 bool VM_RedefineClasses::merge_constant_pools(const constantPoolHandle& old_cp,
1583        const constantPoolHandle& scratch_cp, constantPoolHandle *merge_cp_p,
1584        int *merge_cp_length_p, TRAPS) {
1585 
1586   if (merge_cp_p == nullptr) {
1587     assert(false, "caller must provide scratch constantPool");
1588     return false; // robustness
1589   }
1590   if (merge_cp_length_p == nullptr) {
1591     assert(false, "caller must provide scratch CP length");
1592     return false; // robustness
1593   }
1594   // Worst case we need old_cp->length() + scratch_cp()->length(),
1595   // but the caller might be smart so make sure we have at least
1596   // the minimum.
1597   if ((*merge_cp_p)->length() < old_cp->length()) {
1598     assert(false, "merge area too small");
1599     return false; // robustness
1600   }
1601 
1602   log_info(redefine, class, constantpool)("old_cp_len=%d, scratch_cp_len=%d", old_cp->length(), scratch_cp->length());
1603 
1604   {
1605     // Pass 0:
1606     // The old_cp is copied to *merge_cp_p; this means that any code
1607     // using old_cp does not have to change. This work looks like a
1608     // perfect fit for ConstantPool*::copy_cp_to(), but we need to
1609     // handle one special case:
1610     // - revert JVM_CONSTANT_Class to JVM_CONSTANT_UnresolvedClass
1611     // This will make verification happy.
1612 
1613     int old_i;  // index into old_cp
1614 
1615     // index zero (0) is not used in constantPools
1616     for (old_i = 1; old_i < old_cp->length(); old_i++) {
1617       // leave debugging crumb
1618       jbyte old_tag = old_cp->tag_at(old_i).value();
1619       switch (old_tag) {
1620       case JVM_CONSTANT_Class:
1621       case JVM_CONSTANT_UnresolvedClass:
1622         // revert the copy to JVM_CONSTANT_UnresolvedClass
1623         // May be resolving while calling this so do the same for
1624         // JVM_CONSTANT_UnresolvedClass (klass_name_at() deals with transition)
1625         (*merge_cp_p)->temp_unresolved_klass_at_put(old_i,
1626           old_cp->klass_name_index_at(old_i));
1627         break;
1628 
1629       case JVM_CONSTANT_Double:
1630       case JVM_CONSTANT_Long:
1631         // just copy the entry to *merge_cp_p, but double and long take
1632         // two constant pool entries
1633         ConstantPool::copy_entry_to(old_cp, old_i, *merge_cp_p, old_i);
1634         old_i++;
1635         break;
1636 
1637       default:
1638         // just copy the entry to *merge_cp_p
1639         ConstantPool::copy_entry_to(old_cp, old_i, *merge_cp_p, old_i);
1640         break;
1641       }
1642     } // end for each old_cp entry
1643 
1644     ConstantPool::copy_operands(old_cp, *merge_cp_p, CHECK_false);
1645     (*merge_cp_p)->extend_operands(scratch_cp, CHECK_false);
1646 
1647     // We don't need to sanity check that *merge_cp_length_p is within
1648     // *merge_cp_p bounds since we have the minimum on-entry check above.
1649     (*merge_cp_length_p) = old_i;
1650   }
1651 
1652   // merge_cp_len should be the same as old_cp->length() at this point
1653   // so this trace message is really a "warm-and-breathing" message.
1654   log_debug(redefine, class, constantpool)("after pass 0: merge_cp_len=%d", *merge_cp_length_p);
1655 
1656   int scratch_i;  // index into scratch_cp
1657   {
1658     // Pass 1a:
1659     // Compare scratch_cp entries to the old_cp entries that we have
1660     // already copied to *merge_cp_p. In this pass, we are eliminating
1661     // exact duplicates (matching entry at same index) so we only
1662     // compare entries in the common indice range.
1663     int increment = 1;
1664     int pass1a_length = MIN2(old_cp->length(), scratch_cp->length());
1665     for (scratch_i = 1; scratch_i < pass1a_length; scratch_i += increment) {
1666       switch (scratch_cp->tag_at(scratch_i).value()) {
1667       case JVM_CONSTANT_Double:
1668       case JVM_CONSTANT_Long:
1669         // double and long take two constant pool entries
1670         increment = 2;
1671         break;
1672 
1673       default:
1674         increment = 1;
1675         break;
1676       }
1677 
1678       bool match = scratch_cp->compare_entry_to(scratch_i, *merge_cp_p, scratch_i);
1679       if (match) {
1680         // found a match at the same index so nothing more to do
1681         continue;
1682       }
1683 
1684       int found_i = scratch_cp->find_matching_entry(scratch_i, *merge_cp_p);
1685       if (found_i != 0) {
1686         guarantee(found_i != scratch_i,
1687           "compare_entry_to() and find_matching_entry() do not agree");
1688 
1689         // Found a matching entry somewhere else in *merge_cp_p so
1690         // just need a mapping entry.
1691         map_index(scratch_cp, scratch_i, found_i);
1692         continue;
1693       }
1694 
1695       // No match found so we have to append this entry and any unique
1696       // referenced entries to *merge_cp_p.
1697       append_entry(scratch_cp, scratch_i, merge_cp_p, merge_cp_length_p);
1698     }
1699   }
1700 
1701   log_debug(redefine, class, constantpool)
1702     ("after pass 1a: merge_cp_len=%d, scratch_i=%d, index_map_len=%d",
1703      *merge_cp_length_p, scratch_i, _index_map_count);
1704 
1705   if (scratch_i < scratch_cp->length()) {
1706     // Pass 1b:
1707     // old_cp is smaller than scratch_cp so there are entries in
1708     // scratch_cp that we have not yet processed. We take care of
1709     // those now.
1710     int increment = 1;
1711     for (; scratch_i < scratch_cp->length(); scratch_i += increment) {
1712       switch (scratch_cp->tag_at(scratch_i).value()) {
1713       case JVM_CONSTANT_Double:
1714       case JVM_CONSTANT_Long:
1715         // double and long take two constant pool entries
1716         increment = 2;
1717         break;
1718 
1719       default:
1720         increment = 1;
1721         break;
1722       }
1723 
1724       int found_i =
1725         scratch_cp->find_matching_entry(scratch_i, *merge_cp_p);
1726       if (found_i != 0) {
1727         // Found a matching entry somewhere else in *merge_cp_p so
1728         // just need a mapping entry.
1729         map_index(scratch_cp, scratch_i, found_i);
1730         continue;
1731       }
1732 
1733       // No match found so we have to append this entry and any unique
1734       // referenced entries to *merge_cp_p.
1735       append_entry(scratch_cp, scratch_i, merge_cp_p, merge_cp_length_p);
1736     }
1737 
1738     log_debug(redefine, class, constantpool)
1739       ("after pass 1b: merge_cp_len=%d, scratch_i=%d, index_map_len=%d",
1740        *merge_cp_length_p, scratch_i, _index_map_count);
1741   }
1742   finalize_operands_merge(*merge_cp_p, CHECK_false);
1743 
1744   return true;
1745 } // end merge_constant_pools()
1746 
1747 
1748 // Scoped object to clean up the constant pool(s) created for merging
1749 class MergeCPCleaner {
1750   ClassLoaderData*   _loader_data;
1751   ConstantPool*      _cp;
1752   ConstantPool*      _scratch_cp;
1753  public:
1754   MergeCPCleaner(ClassLoaderData* loader_data, ConstantPool* merge_cp) :
1755                  _loader_data(loader_data), _cp(merge_cp), _scratch_cp(nullptr) {}
1756   ~MergeCPCleaner() {
1757     _loader_data->add_to_deallocate_list(_cp);
1758     if (_scratch_cp != nullptr) {
1759       _loader_data->add_to_deallocate_list(_scratch_cp);
1760     }
1761   }
1762   void add_scratch_cp(ConstantPool* scratch_cp) { _scratch_cp = scratch_cp; }
1763 };
1764 
1765 // Merge constant pools between the_class and scratch_class and
1766 // potentially rewrite bytecodes in scratch_class to use the merged
1767 // constant pool.
1768 jvmtiError VM_RedefineClasses::merge_cp_and_rewrite(
1769              InstanceKlass* the_class, InstanceKlass* scratch_class,
1770              TRAPS) {
1771   // worst case merged constant pool length is old and new combined
1772   int merge_cp_length = the_class->constants()->length()
1773         + scratch_class->constants()->length();
1774 
1775   // Constant pools are not easily reused so we allocate a new one
1776   // each time.
1777   // merge_cp is created unsafe for concurrent GC processing.  It
1778   // should be marked safe before discarding it. Even though
1779   // garbage,  if it crosses a card boundary, it may be scanned
1780   // in order to find the start of the first complete object on the card.
1781   ClassLoaderData* loader_data = the_class->class_loader_data();
1782   ConstantPool* merge_cp_oop =
1783     ConstantPool::allocate(loader_data,
1784                            merge_cp_length,
1785                            CHECK_(JVMTI_ERROR_OUT_OF_MEMORY));
1786   MergeCPCleaner cp_cleaner(loader_data, merge_cp_oop);
1787 
1788   HandleMark hm(THREAD);  // make sure handles are cleared before
1789                           // MergeCPCleaner clears out merge_cp_oop
1790   constantPoolHandle merge_cp(THREAD, merge_cp_oop);
1791 
1792   // Get constants() from the old class because it could have been rewritten
1793   // while we were at a safepoint allocating a new constant pool.
1794   constantPoolHandle old_cp(THREAD, the_class->constants());
1795   constantPoolHandle scratch_cp(THREAD, scratch_class->constants());
1796 
1797   // If the length changed, the class was redefined out from under us. Return
1798   // an error.
1799   if (merge_cp_length != the_class->constants()->length()
1800          + scratch_class->constants()->length()) {
1801     return JVMTI_ERROR_INTERNAL;
1802   }
1803 
1804   // Update the version number of the constant pools (may keep scratch_cp)
1805   merge_cp->increment_and_save_version(old_cp->version());
1806   scratch_cp->increment_and_save_version(old_cp->version());
1807 
1808   ResourceMark rm(THREAD);
1809   _index_map_count = 0;
1810   _index_map_p = new intArray(scratch_cp->length(), scratch_cp->length(), -1);
1811 
1812   _operands_cur_length = ConstantPool::operand_array_length(old_cp->operands());
1813   _operands_index_map_count = 0;
1814   int operands_index_map_len = ConstantPool::operand_array_length(scratch_cp->operands());
1815   _operands_index_map_p = new intArray(operands_index_map_len, operands_index_map_len, -1);
1816 
1817   // reference to the cp holder is needed for copy_operands()
1818   merge_cp->set_pool_holder(scratch_class);
1819   bool result = merge_constant_pools(old_cp, scratch_cp, &merge_cp,
1820                   &merge_cp_length, THREAD);
1821   merge_cp->set_pool_holder(nullptr);
1822 
1823   if (!result) {
1824     // The merge can fail due to memory allocation failure or due
1825     // to robustness checks.
1826     return JVMTI_ERROR_INTERNAL;
1827   }
1828 
1829   // ensure merged constant pool size does not overflow u2
1830   if (merge_cp_length > 0xFFFF) {
1831     log_warning(redefine, class, constantpool)("Merged constant pool overflow: %d entries", merge_cp_length);
1832     return JVMTI_ERROR_INTERNAL;
1833   }
1834 
1835   // Set dynamic constants attribute from the original CP.
1836   if (old_cp->has_dynamic_constant()) {
1837     scratch_cp->set_has_dynamic_constant();
1838   }
1839 
1840   log_info(redefine, class, constantpool)("merge_cp_len=%d, index_map_len=%d", merge_cp_length, _index_map_count);
1841 
1842   if (_index_map_count == 0) {
1843     // there is nothing to map between the new and merged constant pools
1844 
1845     // Copy attributes from scratch_cp to merge_cp
1846     merge_cp->copy_fields(scratch_cp());
1847 
1848     if (old_cp->length() == scratch_cp->length()) {
1849       // The old and new constant pools are the same length and the
1850       // index map is empty. This means that the three constant pools
1851       // are equivalent (but not the same). Unfortunately, the new
1852       // constant pool has not gone through link resolution nor have
1853       // the new class bytecodes gone through constant pool cache
1854       // rewriting so we can't use the old constant pool with the new
1855       // class.
1856 
1857       // toss the merged constant pool at return
1858     } else if (old_cp->length() < scratch_cp->length()) {
1859       // The old constant pool has fewer entries than the new constant
1860       // pool and the index map is empty. This means the new constant
1861       // pool is a superset of the old constant pool. However, the old
1862       // class bytecodes have already gone through constant pool cache
1863       // rewriting so we can't use the new constant pool with the old
1864       // class.
1865 
1866       // toss the merged constant pool at return
1867     } else {
1868       // The old constant pool has more entries than the new constant
1869       // pool and the index map is empty. This means that both the old
1870       // and merged constant pools are supersets of the new constant
1871       // pool.
1872 
1873       // Replace the new constant pool with a shrunken copy of the
1874       // merged constant pool
1875       set_new_constant_pool(loader_data, scratch_class, merge_cp, merge_cp_length,
1876                             CHECK_(JVMTI_ERROR_OUT_OF_MEMORY));
1877       // The new constant pool replaces scratch_cp so have cleaner clean it up.
1878       // It can't be cleaned up while there are handles to it.
1879       cp_cleaner.add_scratch_cp(scratch_cp());
1880     }
1881   } else {
1882     if (log_is_enabled(Trace, redefine, class, constantpool)) {
1883       // don't want to loop unless we are tracing
1884       int count = 0;
1885       for (int i = 1; i < _index_map_p->length(); i++) {
1886         int value = _index_map_p->at(i);
1887 
1888         if (value != -1) {
1889           log_trace(redefine, class, constantpool)("index_map[%d]: old=%d new=%d", count, i, value);
1890           count++;
1891         }
1892       }
1893     }
1894 
1895     // We have entries mapped between the new and merged constant pools
1896     // so we have to rewrite some constant pool references.
1897     if (!rewrite_cp_refs(scratch_class)) {
1898       return JVMTI_ERROR_INTERNAL;
1899     }
1900 
1901     // Copy attributes from scratch_cp to merge_cp (should be done after rewrite_cp_refs())
1902     merge_cp->copy_fields(scratch_cp());
1903 
1904     // Replace the new constant pool with a shrunken copy of the
1905     // merged constant pool so now the rewritten bytecodes have
1906     // valid references; the previous new constant pool will get
1907     // GCed.
1908     set_new_constant_pool(loader_data, scratch_class, merge_cp, merge_cp_length,
1909                           CHECK_(JVMTI_ERROR_OUT_OF_MEMORY));
1910     // The new constant pool replaces scratch_cp so have cleaner clean it up.
1911     // It can't be cleaned up while there are handles to it.
1912     cp_cleaner.add_scratch_cp(scratch_cp());
1913   }
1914 
1915   return JVMTI_ERROR_NONE;
1916 } // end merge_cp_and_rewrite()
1917 
1918 
1919 // Rewrite constant pool references in klass scratch_class.
1920 bool VM_RedefineClasses::rewrite_cp_refs(InstanceKlass* scratch_class) {
1921 
1922   // rewrite constant pool references in the nest attributes:
1923   if (!rewrite_cp_refs_in_nest_attributes(scratch_class)) {
1924     // propagate failure back to caller
1925     return false;
1926   }
1927 
1928   // rewrite constant pool references in the Record attribute:
1929   if (!rewrite_cp_refs_in_record_attribute(scratch_class)) {
1930     // propagate failure back to caller
1931     return false;
1932   }
1933 
1934   // rewrite constant pool references in the PermittedSubclasses attribute:
1935   if (!rewrite_cp_refs_in_permitted_subclasses_attribute(scratch_class)) {
1936     // propagate failure back to caller
1937     return false;
1938   }
1939 






1940   // rewrite constant pool references in the methods:
1941   if (!rewrite_cp_refs_in_methods(scratch_class)) {
1942     // propagate failure back to caller
1943     return false;
1944   }
1945 
1946   // rewrite constant pool references in the class_annotations:
1947   if (!rewrite_cp_refs_in_class_annotations(scratch_class)) {
1948     // propagate failure back to caller
1949     return false;
1950   }
1951 
1952   // rewrite constant pool references in the fields_annotations:
1953   if (!rewrite_cp_refs_in_fields_annotations(scratch_class)) {
1954     // propagate failure back to caller
1955     return false;
1956   }
1957 
1958   // rewrite constant pool references in the methods_annotations:
1959   if (!rewrite_cp_refs_in_methods_annotations(scratch_class)) {
1960     // propagate failure back to caller
1961     return false;
1962   }
1963 
1964   // rewrite constant pool references in the methods_parameter_annotations:
1965   if (!rewrite_cp_refs_in_methods_parameter_annotations(scratch_class)) {
1966     // propagate failure back to caller
1967     return false;
1968   }
1969 
1970   // rewrite constant pool references in the methods_default_annotations:
1971   if (!rewrite_cp_refs_in_methods_default_annotations(scratch_class)) {
1972     // propagate failure back to caller
1973     return false;
1974   }
1975 
1976   // rewrite constant pool references in the class_type_annotations:
1977   if (!rewrite_cp_refs_in_class_type_annotations(scratch_class)) {
1978     // propagate failure back to caller
1979     return false;
1980   }
1981 
1982   // rewrite constant pool references in the fields_type_annotations:
1983   if (!rewrite_cp_refs_in_fields_type_annotations(scratch_class)) {
1984     // propagate failure back to caller
1985     return false;
1986   }
1987 
1988   // rewrite constant pool references in the methods_type_annotations:
1989   if (!rewrite_cp_refs_in_methods_type_annotations(scratch_class)) {
1990     // propagate failure back to caller
1991     return false;
1992   }
1993 
1994   // There can be type annotations in the Code part of a method_info attribute.
1995   // These annotations are not accessible, even by reflection.
1996   // Currently they are not even parsed by the ClassFileParser.
1997   // If runtime access is added they will also need to be rewritten.
1998 
1999   // rewrite source file name index:
2000   u2 source_file_name_idx = scratch_class->source_file_name_index();
2001   if (source_file_name_idx != 0) {
2002     u2 new_source_file_name_idx = find_new_index(source_file_name_idx);
2003     if (new_source_file_name_idx != 0) {
2004       scratch_class->set_source_file_name_index(new_source_file_name_idx);
2005     }
2006   }
2007 
2008   // rewrite class generic signature index:
2009   u2 generic_signature_index = scratch_class->generic_signature_index();
2010   if (generic_signature_index != 0) {
2011     u2 new_generic_signature_index = find_new_index(generic_signature_index);
2012     if (new_generic_signature_index != 0) {
2013       scratch_class->set_generic_signature_index(new_generic_signature_index);
2014     }
2015   }
2016 
2017   return true;
2018 } // end rewrite_cp_refs()
2019 
2020 // Rewrite constant pool references in the NestHost and NestMembers attributes.
2021 bool VM_RedefineClasses::rewrite_cp_refs_in_nest_attributes(
2022        InstanceKlass* scratch_class) {
2023 
2024   u2 cp_index = scratch_class->nest_host_index();
2025   if (cp_index != 0) {
2026     scratch_class->set_nest_host_index(find_new_index(cp_index));
2027   }
2028   Array<u2>* nest_members = scratch_class->nest_members();
2029   for (int i = 0; i < nest_members->length(); i++) {
2030     u2 cp_index = nest_members->at(i);
2031     nest_members->at_put(i, find_new_index(cp_index));
2032   }
2033   return true;
2034 }
2035 
2036 // Rewrite constant pool references in the Record attribute.
2037 bool VM_RedefineClasses::rewrite_cp_refs_in_record_attribute(InstanceKlass* scratch_class) {
2038   Array<RecordComponent*>* components = scratch_class->record_components();
2039   if (components != nullptr) {
2040     for (int i = 0; i < components->length(); i++) {
2041       RecordComponent* component = components->at(i);
2042       u2 cp_index = component->name_index();
2043       component->set_name_index(find_new_index(cp_index));
2044       cp_index = component->descriptor_index();
2045       component->set_descriptor_index(find_new_index(cp_index));
2046       cp_index = component->generic_signature_index();
2047       if (cp_index != 0) {
2048         component->set_generic_signature_index(find_new_index(cp_index));
2049       }
2050 
2051       AnnotationArray* annotations = component->annotations();
2052       if (annotations != nullptr && annotations->length() != 0) {
2053         int byte_i = 0;  // byte index into annotations
2054         if (!rewrite_cp_refs_in_annotations_typeArray(annotations, byte_i)) {
2055           log_debug(redefine, class, annotation)("bad record_component_annotations at %d", i);
2056           // propagate failure back to caller
2057           return false;
2058         }
2059       }
2060 
2061       AnnotationArray* type_annotations = component->type_annotations();
2062       if (type_annotations != nullptr && type_annotations->length() != 0) {
2063         int byte_i = 0;  // byte index into annotations
2064         if (!rewrite_cp_refs_in_annotations_typeArray(type_annotations, byte_i)) {
2065           log_debug(redefine, class, annotation)("bad record_component_type_annotations at %d", i);
2066           // propagate failure back to caller
2067           return false;
2068         }
2069       }
2070     }
2071   }
2072   return true;
2073 }
2074 
2075 // Rewrite constant pool references in the PermittedSubclasses attribute.
2076 bool VM_RedefineClasses::rewrite_cp_refs_in_permitted_subclasses_attribute(
2077        InstanceKlass* scratch_class) {
2078 
2079   Array<u2>* permitted_subclasses = scratch_class->permitted_subclasses();
2080   assert(permitted_subclasses != nullptr, "unexpected null permitted_subclasses");
2081   for (int i = 0; i < permitted_subclasses->length(); i++) {
2082     u2 cp_index = permitted_subclasses->at(i);
2083     permitted_subclasses->at_put(i, find_new_index(cp_index));
2084   }
2085   return true;
2086 }
2087 













2088 // Rewrite constant pool references in the methods.
2089 bool VM_RedefineClasses::rewrite_cp_refs_in_methods(InstanceKlass* scratch_class) {
2090 
2091   Array<Method*>* methods = scratch_class->methods();
2092 
2093   if (methods == nullptr || methods->length() == 0) {
2094     // no methods so nothing to do
2095     return true;
2096   }
2097 
2098   JavaThread* THREAD = JavaThread::current(); // For exception macros.
2099   ExceptionMark em(THREAD);
2100 
2101   // rewrite constant pool references in the methods:
2102   for (int i = methods->length() - 1; i >= 0; i--) {
2103     methodHandle method(THREAD, methods->at(i));
2104     methodHandle new_method;
2105     rewrite_cp_refs_in_method(method, &new_method, THREAD);
2106     if (!new_method.is_null()) {
2107       // the method has been replaced so save the new method version
2108       // even in the case of an exception.  original method is on the
2109       // deallocation list.
2110       methods->at_put(i, new_method());
2111     }
2112     if (HAS_PENDING_EXCEPTION) {
2113       Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
2114       log_info(redefine, class, load, exceptions)("rewrite_cp_refs_in_method exception: '%s'", ex_name->as_C_string());
2115       // Need to clear pending exception here as the super caller sets
2116       // the JVMTI_ERROR_INTERNAL if the returned value is false.
2117       CLEAR_PENDING_EXCEPTION;
2118       return false;
2119     }
2120   }
2121 
2122   return true;
2123 }
2124 
2125 
2126 // Rewrite constant pool references in the specific method. This code
2127 // was adapted from Rewriter::rewrite_method().
2128 void VM_RedefineClasses::rewrite_cp_refs_in_method(methodHandle method,
2129        methodHandle *new_method_p, TRAPS) {
2130 
2131   *new_method_p = methodHandle();  // default is no new method
2132 
2133   // We cache a pointer to the bytecodes here in code_base. If GC
2134   // moves the Method*, then the bytecodes will also move which
2135   // will likely cause a crash. We create a NoSafepointVerifier
2136   // object to detect whether we pass a possible safepoint in this
2137   // code block.
2138   NoSafepointVerifier nsv;
2139 
2140   // Bytecodes and their length
2141   address code_base = method->code_base();
2142   int code_length = method->code_size();
2143 
2144   int bc_length;
2145   for (int bci = 0; bci < code_length; bci += bc_length) {
2146     address bcp = code_base + bci;
2147     Bytecodes::Code c = (Bytecodes::Code)(*bcp);
2148 
2149     bc_length = Bytecodes::length_for(c);
2150     if (bc_length == 0) {
2151       // More complicated bytecodes report a length of zero so
2152       // we have to try again a slightly different way.
2153       bc_length = Bytecodes::length_at(method(), bcp);
2154     }
2155 
2156     assert(bc_length != 0, "impossible bytecode length");
2157 
2158     switch (c) {
2159       case Bytecodes::_ldc:
2160       {
2161         u1 cp_index = *(bcp + 1);
2162         u2 new_index = find_new_index(cp_index);
2163 
2164         if (StressLdcRewrite && new_index == 0) {
2165           // If we are stressing ldc -> ldc_w rewriting, then we
2166           // always need a new_index value.
2167           new_index = cp_index;
2168         }
2169         if (new_index != 0) {
2170           // the original index is mapped so we have more work to do
2171           if (!StressLdcRewrite && new_index <= max_jubyte) {
2172             // The new value can still use ldc instead of ldc_w
2173             // unless we are trying to stress ldc -> ldc_w rewriting
2174             log_trace(redefine, class, constantpool)
2175               ("%s@" INTPTR_FORMAT " old=%d, new=%d", Bytecodes::name(c), p2i(bcp), cp_index, new_index);
2176             // We checked that new_index fits in a u1 so this cast is safe
2177             *(bcp + 1) = (u1)new_index;
2178           } else {
2179             log_trace(redefine, class, constantpool)
2180               ("%s->ldc_w@" INTPTR_FORMAT " old=%d, new=%d", Bytecodes::name(c), p2i(bcp), cp_index, new_index);
2181             // the new value needs ldc_w instead of ldc
2182             u_char inst_buffer[4]; // max instruction size is 4 bytes
2183             bcp = (address)inst_buffer;
2184             // construct new instruction sequence
2185             *bcp = Bytecodes::_ldc_w;
2186             bcp++;
2187             // Rewriter::rewrite_method() does not rewrite ldc -> ldc_w.
2188             // See comment below for difference between put_Java_u2()
2189             // and put_native_u2().
2190             Bytes::put_Java_u2(bcp, new_index);
2191 
2192             Relocator rc(method, nullptr /* no RelocatorListener needed */);
2193             methodHandle m;
2194             {
2195               PauseNoSafepointVerifier pnsv(&nsv);
2196 
2197               // ldc is 2 bytes and ldc_w is 3 bytes
2198               m = rc.insert_space_at(bci, 3, inst_buffer, CHECK);
2199             }
2200 
2201             // return the new method so that the caller can update
2202             // the containing class
2203             *new_method_p = method = m;
2204             // switch our bytecode processing loop from the old method
2205             // to the new method
2206             code_base = method->code_base();
2207             code_length = method->code_size();
2208             bcp = code_base + bci;
2209             c = (Bytecodes::Code)(*bcp);
2210             bc_length = Bytecodes::length_for(c);
2211             assert(bc_length != 0, "sanity check");
2212           } // end we need ldc_w instead of ldc
2213         } // end if there is a mapped index
2214       } break;
2215 
2216       // these bytecodes have a two-byte constant pool index
2217       case Bytecodes::_anewarray      : // fall through
2218       case Bytecodes::_checkcast      : // fall through
2219       case Bytecodes::_getfield       : // fall through
2220       case Bytecodes::_getstatic      : // fall through
2221       case Bytecodes::_instanceof     : // fall through
2222       case Bytecodes::_invokedynamic  : // fall through
2223       case Bytecodes::_invokeinterface: // fall through
2224       case Bytecodes::_invokespecial  : // fall through
2225       case Bytecodes::_invokestatic   : // fall through
2226       case Bytecodes::_invokevirtual  : // fall through
2227       case Bytecodes::_ldc_w          : // fall through
2228       case Bytecodes::_ldc2_w         : // fall through
2229       case Bytecodes::_multianewarray : // fall through
2230       case Bytecodes::_new            : // fall through
2231       case Bytecodes::_putfield       : // fall through
2232       case Bytecodes::_putstatic      :
2233       {
2234         address p = bcp + 1;
2235         int cp_index = Bytes::get_Java_u2(p);
2236         u2 new_index = find_new_index(cp_index);
2237         if (new_index != 0) {
2238           // the original index is mapped so update w/ new value
2239           log_trace(redefine, class, constantpool)
2240             ("%s@" INTPTR_FORMAT " old=%d, new=%d", Bytecodes::name(c),p2i(bcp), cp_index, new_index);
2241           // Rewriter::rewrite_method() uses put_native_u2() in this
2242           // situation because it is reusing the constant pool index
2243           // location for a native index into the ConstantPoolCache.
2244           // Since we are updating the constant pool index prior to
2245           // verification and ConstantPoolCache initialization, we
2246           // need to keep the new index in Java byte order.
2247           Bytes::put_Java_u2(p, new_index);
2248         }
2249       } break;
2250       default:
2251         break;
2252     }
2253   } // end for each bytecode
2254 } // end rewrite_cp_refs_in_method()
2255 
2256 
2257 // Rewrite constant pool references in the class_annotations field.
2258 bool VM_RedefineClasses::rewrite_cp_refs_in_class_annotations(InstanceKlass* scratch_class) {
2259 
2260   AnnotationArray* class_annotations = scratch_class->class_annotations();
2261   if (class_annotations == nullptr || class_annotations->length() == 0) {
2262     // no class_annotations so nothing to do
2263     return true;
2264   }
2265 
2266   log_debug(redefine, class, annotation)("class_annotations length=%d", class_annotations->length());
2267 
2268   int byte_i = 0;  // byte index into class_annotations
2269   return rewrite_cp_refs_in_annotations_typeArray(class_annotations, byte_i);
2270 }
2271 
2272 
2273 // Rewrite constant pool references in an annotations typeArray. This
2274 // "structure" is adapted from the RuntimeVisibleAnnotations_attribute
2275 // that is described in section 4.8.15 of the 2nd-edition of the VM spec:
2276 //
2277 // annotations_typeArray {
2278 //   u2 num_annotations;
2279 //   annotation annotations[num_annotations];
2280 // }
2281 //
2282 bool VM_RedefineClasses::rewrite_cp_refs_in_annotations_typeArray(
2283        AnnotationArray* annotations_typeArray, int &byte_i_ref) {
2284 
2285   if ((byte_i_ref + 2) > annotations_typeArray->length()) {
2286     // not enough room for num_annotations field
2287     log_debug(redefine, class, annotation)("length() is too small for num_annotations field");
2288     return false;
2289   }
2290 
2291   u2 num_annotations = Bytes::get_Java_u2((address)
2292                          annotations_typeArray->adr_at(byte_i_ref));
2293   byte_i_ref += 2;
2294 
2295   log_debug(redefine, class, annotation)("num_annotations=%d", num_annotations);
2296 
2297   int calc_num_annotations = 0;
2298   for (; calc_num_annotations < num_annotations; calc_num_annotations++) {
2299     if (!rewrite_cp_refs_in_annotation_struct(annotations_typeArray, byte_i_ref)) {
2300       log_debug(redefine, class, annotation)("bad annotation_struct at %d", calc_num_annotations);
2301       // propagate failure back to caller
2302       return false;
2303     }
2304   }
2305   assert(num_annotations == calc_num_annotations, "sanity check");
2306 
2307   return true;
2308 } // end rewrite_cp_refs_in_annotations_typeArray()
2309 
2310 
2311 // Rewrite constant pool references in the annotation struct portion of
2312 // an annotations_typeArray. This "structure" is from section 4.8.15 of
2313 // the 2nd-edition of the VM spec:
2314 //
2315 // struct annotation {
2316 //   u2 type_index;
2317 //   u2 num_element_value_pairs;
2318 //   {
2319 //     u2 element_name_index;
2320 //     element_value value;
2321 //   } element_value_pairs[num_element_value_pairs];
2322 // }
2323 //
2324 bool VM_RedefineClasses::rewrite_cp_refs_in_annotation_struct(
2325        AnnotationArray* annotations_typeArray, int &byte_i_ref) {
2326   if ((byte_i_ref + 2 + 2) > annotations_typeArray->length()) {
2327     // not enough room for smallest annotation_struct
2328     log_debug(redefine, class, annotation)("length() is too small for annotation_struct");
2329     return false;
2330   }
2331 
2332   u2 type_index = rewrite_cp_ref_in_annotation_data(annotations_typeArray,
2333                     byte_i_ref, "type_index");
2334 
2335   u2 num_element_value_pairs = Bytes::get_Java_u2((address)
2336                                  annotations_typeArray->adr_at(byte_i_ref));
2337   byte_i_ref += 2;
2338 
2339   log_debug(redefine, class, annotation)
2340     ("type_index=%d  num_element_value_pairs=%d", type_index, num_element_value_pairs);
2341 
2342   int calc_num_element_value_pairs = 0;
2343   for (; calc_num_element_value_pairs < num_element_value_pairs;
2344        calc_num_element_value_pairs++) {
2345     if ((byte_i_ref + 2) > annotations_typeArray->length()) {
2346       // not enough room for another element_name_index, let alone
2347       // the rest of another component
2348       log_debug(redefine, class, annotation)("length() is too small for element_name_index");
2349       return false;
2350     }
2351 
2352     u2 element_name_index = rewrite_cp_ref_in_annotation_data(
2353                               annotations_typeArray, byte_i_ref,
2354                               "element_name_index");
2355 
2356     log_debug(redefine, class, annotation)("element_name_index=%d", element_name_index);
2357 
2358     if (!rewrite_cp_refs_in_element_value(annotations_typeArray, byte_i_ref)) {
2359       log_debug(redefine, class, annotation)("bad element_value at %d", calc_num_element_value_pairs);
2360       // propagate failure back to caller
2361       return false;
2362     }
2363   } // end for each component
2364   assert(num_element_value_pairs == calc_num_element_value_pairs,
2365     "sanity check");
2366 
2367   return true;
2368 } // end rewrite_cp_refs_in_annotation_struct()
2369 
2370 
2371 // Rewrite a constant pool reference at the current position in
2372 // annotations_typeArray if needed. Returns the original constant
2373 // pool reference if a rewrite was not needed or the new constant
2374 // pool reference if a rewrite was needed.
2375 u2 VM_RedefineClasses::rewrite_cp_ref_in_annotation_data(
2376      AnnotationArray* annotations_typeArray, int &byte_i_ref,
2377      const char * trace_mesg) {
2378 
2379   address cp_index_addr = (address)
2380     annotations_typeArray->adr_at(byte_i_ref);
2381   u2 old_cp_index = Bytes::get_Java_u2(cp_index_addr);
2382   u2 new_cp_index = find_new_index(old_cp_index);
2383   if (new_cp_index != 0) {
2384     log_debug(redefine, class, annotation)("mapped old %s=%d", trace_mesg, old_cp_index);
2385     Bytes::put_Java_u2(cp_index_addr, new_cp_index);
2386     old_cp_index = new_cp_index;
2387   }
2388   byte_i_ref += 2;
2389   return old_cp_index;
2390 }
2391 
2392 
2393 // Rewrite constant pool references in the element_value portion of an
2394 // annotations_typeArray. This "structure" is from section 4.8.15.1 of
2395 // the 2nd-edition of the VM spec:
2396 //
2397 // struct element_value {
2398 //   u1 tag;
2399 //   union {
2400 //     u2 const_value_index;
2401 //     {
2402 //       u2 type_name_index;
2403 //       u2 const_name_index;
2404 //     } enum_const_value;
2405 //     u2 class_info_index;
2406 //     annotation annotation_value;
2407 //     struct {
2408 //       u2 num_values;
2409 //       element_value values[num_values];
2410 //     } array_value;
2411 //   } value;
2412 // }
2413 //
2414 bool VM_RedefineClasses::rewrite_cp_refs_in_element_value(
2415        AnnotationArray* annotations_typeArray, int &byte_i_ref) {
2416 
2417   if ((byte_i_ref + 1) > annotations_typeArray->length()) {
2418     // not enough room for a tag let alone the rest of an element_value
2419     log_debug(redefine, class, annotation)("length() is too small for a tag");
2420     return false;
2421   }
2422 
2423   u1 tag = annotations_typeArray->at(byte_i_ref);
2424   byte_i_ref++;
2425   log_debug(redefine, class, annotation)("tag='%c'", tag);
2426 
2427   switch (tag) {
2428     // These BaseType tag values are from Table 4.2 in VM spec:
2429     case JVM_SIGNATURE_BYTE:
2430     case JVM_SIGNATURE_CHAR:
2431     case JVM_SIGNATURE_DOUBLE:
2432     case JVM_SIGNATURE_FLOAT:
2433     case JVM_SIGNATURE_INT:
2434     case JVM_SIGNATURE_LONG:
2435     case JVM_SIGNATURE_SHORT:
2436     case JVM_SIGNATURE_BOOLEAN:
2437 
2438     // The remaining tag values are from Table 4.8 in the 2nd-edition of
2439     // the VM spec:
2440     case 's':
2441     {
2442       // For the above tag values (including the BaseType values),
2443       // value.const_value_index is right union field.
2444 
2445       if ((byte_i_ref + 2) > annotations_typeArray->length()) {
2446         // not enough room for a const_value_index
2447         log_debug(redefine, class, annotation)("length() is too small for a const_value_index");
2448         return false;
2449       }
2450 
2451       u2 const_value_index = rewrite_cp_ref_in_annotation_data(
2452                                annotations_typeArray, byte_i_ref,
2453                                "const_value_index");
2454 
2455       log_debug(redefine, class, annotation)("const_value_index=%d", const_value_index);
2456     } break;
2457 
2458     case 'e':
2459     {
2460       // for the above tag value, value.enum_const_value is right union field
2461 
2462       if ((byte_i_ref + 4) > annotations_typeArray->length()) {
2463         // not enough room for a enum_const_value
2464         log_debug(redefine, class, annotation)("length() is too small for a enum_const_value");
2465         return false;
2466       }
2467 
2468       u2 type_name_index = rewrite_cp_ref_in_annotation_data(
2469                              annotations_typeArray, byte_i_ref,
2470                              "type_name_index");
2471 
2472       u2 const_name_index = rewrite_cp_ref_in_annotation_data(
2473                               annotations_typeArray, byte_i_ref,
2474                               "const_name_index");
2475 
2476       log_debug(redefine, class, annotation)
2477         ("type_name_index=%d  const_name_index=%d", type_name_index, const_name_index);
2478     } break;
2479 
2480     case 'c':
2481     {
2482       // for the above tag value, value.class_info_index is right union field
2483 
2484       if ((byte_i_ref + 2) > annotations_typeArray->length()) {
2485         // not enough room for a class_info_index
2486         log_debug(redefine, class, annotation)("length() is too small for a class_info_index");
2487         return false;
2488       }
2489 
2490       u2 class_info_index = rewrite_cp_ref_in_annotation_data(
2491                               annotations_typeArray, byte_i_ref,
2492                               "class_info_index");
2493 
2494       log_debug(redefine, class, annotation)("class_info_index=%d", class_info_index);
2495     } break;
2496 
2497     case '@':
2498       // For the above tag value, value.attr_value is the right union
2499       // field. This is a nested annotation.
2500       if (!rewrite_cp_refs_in_annotation_struct(annotations_typeArray, byte_i_ref)) {
2501         // propagate failure back to caller
2502         return false;
2503       }
2504       break;
2505 
2506     case JVM_SIGNATURE_ARRAY:
2507     {
2508       if ((byte_i_ref + 2) > annotations_typeArray->length()) {
2509         // not enough room for a num_values field
2510         log_debug(redefine, class, annotation)("length() is too small for a num_values field");
2511         return false;
2512       }
2513 
2514       // For the above tag value, value.array_value is the right union
2515       // field. This is an array of nested element_value.
2516       u2 num_values = Bytes::get_Java_u2((address)
2517                         annotations_typeArray->adr_at(byte_i_ref));
2518       byte_i_ref += 2;
2519       log_debug(redefine, class, annotation)("num_values=%d", num_values);
2520 
2521       int calc_num_values = 0;
2522       for (; calc_num_values < num_values; calc_num_values++) {
2523         if (!rewrite_cp_refs_in_element_value(annotations_typeArray, byte_i_ref)) {
2524           log_debug(redefine, class, annotation)("bad nested element_value at %d", calc_num_values);
2525           // propagate failure back to caller
2526           return false;
2527         }
2528       }
2529       assert(num_values == calc_num_values, "sanity check");
2530     } break;
2531 
2532     default:
2533       log_debug(redefine, class, annotation)("bad tag=0x%x", tag);
2534       return false;
2535   } // end decode tag field
2536 
2537   return true;
2538 } // end rewrite_cp_refs_in_element_value()
2539 
2540 
2541 // Rewrite constant pool references in a fields_annotations field.
2542 bool VM_RedefineClasses::rewrite_cp_refs_in_fields_annotations(
2543        InstanceKlass* scratch_class) {
2544 
2545   Array<AnnotationArray*>* fields_annotations = scratch_class->fields_annotations();
2546 
2547   if (fields_annotations == nullptr || fields_annotations->length() == 0) {
2548     // no fields_annotations so nothing to do
2549     return true;
2550   }
2551 
2552   log_debug(redefine, class, annotation)("fields_annotations length=%d", fields_annotations->length());
2553 
2554   for (int i = 0; i < fields_annotations->length(); i++) {
2555     AnnotationArray* field_annotations = fields_annotations->at(i);
2556     if (field_annotations == nullptr || field_annotations->length() == 0) {
2557       // this field does not have any annotations so skip it
2558       continue;
2559     }
2560 
2561     int byte_i = 0;  // byte index into field_annotations
2562     if (!rewrite_cp_refs_in_annotations_typeArray(field_annotations, byte_i)) {
2563       log_debug(redefine, class, annotation)("bad field_annotations at %d", i);
2564       // propagate failure back to caller
2565       return false;
2566     }
2567   }
2568 
2569   return true;
2570 } // end rewrite_cp_refs_in_fields_annotations()
2571 
2572 
2573 // Rewrite constant pool references in a methods_annotations field.
2574 bool VM_RedefineClasses::rewrite_cp_refs_in_methods_annotations(
2575        InstanceKlass* scratch_class) {
2576 
2577   for (int i = 0; i < scratch_class->methods()->length(); i++) {
2578     Method* m = scratch_class->methods()->at(i);
2579     AnnotationArray* method_annotations = m->constMethod()->method_annotations();
2580 
2581     if (method_annotations == nullptr || method_annotations->length() == 0) {
2582       // this method does not have any annotations so skip it
2583       continue;
2584     }
2585 
2586     int byte_i = 0;  // byte index into method_annotations
2587     if (!rewrite_cp_refs_in_annotations_typeArray(method_annotations, byte_i)) {
2588       log_debug(redefine, class, annotation)("bad method_annotations at %d", i);
2589       // propagate failure back to caller
2590       return false;
2591     }
2592   }
2593 
2594   return true;
2595 } // end rewrite_cp_refs_in_methods_annotations()
2596 
2597 
2598 // Rewrite constant pool references in a methods_parameter_annotations
2599 // field. This "structure" is adapted from the
2600 // RuntimeVisibleParameterAnnotations_attribute described in section
2601 // 4.8.17 of the 2nd-edition of the VM spec:
2602 //
2603 // methods_parameter_annotations_typeArray {
2604 //   u1 num_parameters;
2605 //   {
2606 //     u2 num_annotations;
2607 //     annotation annotations[num_annotations];
2608 //   } parameter_annotations[num_parameters];
2609 // }
2610 //
2611 bool VM_RedefineClasses::rewrite_cp_refs_in_methods_parameter_annotations(
2612        InstanceKlass* scratch_class) {
2613 
2614   for (int i = 0; i < scratch_class->methods()->length(); i++) {
2615     Method* m = scratch_class->methods()->at(i);
2616     AnnotationArray* method_parameter_annotations = m->constMethod()->parameter_annotations();
2617     if (method_parameter_annotations == nullptr
2618         || method_parameter_annotations->length() == 0) {
2619       // this method does not have any parameter annotations so skip it
2620       continue;
2621     }
2622 
2623     if (method_parameter_annotations->length() < 1) {
2624       // not enough room for a num_parameters field
2625       log_debug(redefine, class, annotation)("length() is too small for a num_parameters field at %d", i);
2626       return false;
2627     }
2628 
2629     int byte_i = 0;  // byte index into method_parameter_annotations
2630 
2631     u1 num_parameters = method_parameter_annotations->at(byte_i);
2632     byte_i++;
2633 
2634     log_debug(redefine, class, annotation)("num_parameters=%d", num_parameters);
2635 
2636     int calc_num_parameters = 0;
2637     for (; calc_num_parameters < num_parameters; calc_num_parameters++) {
2638       if (!rewrite_cp_refs_in_annotations_typeArray(method_parameter_annotations, byte_i)) {
2639         log_debug(redefine, class, annotation)("bad method_parameter_annotations at %d", calc_num_parameters);
2640         // propagate failure back to caller
2641         return false;
2642       }
2643     }
2644     assert(num_parameters == calc_num_parameters, "sanity check");
2645   }
2646 
2647   return true;
2648 } // end rewrite_cp_refs_in_methods_parameter_annotations()
2649 
2650 
2651 // Rewrite constant pool references in a methods_default_annotations
2652 // field. This "structure" is adapted from the AnnotationDefault_attribute
2653 // that is described in section 4.8.19 of the 2nd-edition of the VM spec:
2654 //
2655 // methods_default_annotations_typeArray {
2656 //   element_value default_value;
2657 // }
2658 //
2659 bool VM_RedefineClasses::rewrite_cp_refs_in_methods_default_annotations(
2660        InstanceKlass* scratch_class) {
2661 
2662   for (int i = 0; i < scratch_class->methods()->length(); i++) {
2663     Method* m = scratch_class->methods()->at(i);
2664     AnnotationArray* method_default_annotations = m->constMethod()->default_annotations();
2665     if (method_default_annotations == nullptr
2666         || method_default_annotations->length() == 0) {
2667       // this method does not have any default annotations so skip it
2668       continue;
2669     }
2670 
2671     int byte_i = 0;  // byte index into method_default_annotations
2672 
2673     if (!rewrite_cp_refs_in_element_value(
2674            method_default_annotations, byte_i)) {
2675       log_debug(redefine, class, annotation)("bad default element_value at %d", i);
2676       // propagate failure back to caller
2677       return false;
2678     }
2679   }
2680 
2681   return true;
2682 } // end rewrite_cp_refs_in_methods_default_annotations()
2683 
2684 
2685 // Rewrite constant pool references in a class_type_annotations field.
2686 bool VM_RedefineClasses::rewrite_cp_refs_in_class_type_annotations(
2687        InstanceKlass* scratch_class) {
2688 
2689   AnnotationArray* class_type_annotations = scratch_class->class_type_annotations();
2690   if (class_type_annotations == nullptr || class_type_annotations->length() == 0) {
2691     // no class_type_annotations so nothing to do
2692     return true;
2693   }
2694 
2695   log_debug(redefine, class, annotation)("class_type_annotations length=%d", class_type_annotations->length());
2696 
2697   int byte_i = 0;  // byte index into class_type_annotations
2698   return rewrite_cp_refs_in_type_annotations_typeArray(class_type_annotations,
2699       byte_i, "ClassFile");
2700 } // end rewrite_cp_refs_in_class_type_annotations()
2701 
2702 
2703 // Rewrite constant pool references in a fields_type_annotations field.
2704 bool VM_RedefineClasses::rewrite_cp_refs_in_fields_type_annotations(InstanceKlass* scratch_class) {
2705 
2706   Array<AnnotationArray*>* fields_type_annotations = scratch_class->fields_type_annotations();
2707   if (fields_type_annotations == nullptr || fields_type_annotations->length() == 0) {
2708     // no fields_type_annotations so nothing to do
2709     return true;
2710   }
2711 
2712   log_debug(redefine, class, annotation)("fields_type_annotations length=%d", fields_type_annotations->length());
2713 
2714   for (int i = 0; i < fields_type_annotations->length(); i++) {
2715     AnnotationArray* field_type_annotations = fields_type_annotations->at(i);
2716     if (field_type_annotations == nullptr || field_type_annotations->length() == 0) {
2717       // this field does not have any annotations so skip it
2718       continue;
2719     }
2720 
2721     int byte_i = 0;  // byte index into field_type_annotations
2722     if (!rewrite_cp_refs_in_type_annotations_typeArray(field_type_annotations,
2723            byte_i, "field_info")) {
2724       log_debug(redefine, class, annotation)("bad field_type_annotations at %d", i);
2725       // propagate failure back to caller
2726       return false;
2727     }
2728   }
2729 
2730   return true;
2731 } // end rewrite_cp_refs_in_fields_type_annotations()
2732 
2733 
2734 // Rewrite constant pool references in a methods_type_annotations field.
2735 bool VM_RedefineClasses::rewrite_cp_refs_in_methods_type_annotations(
2736        InstanceKlass* scratch_class) {
2737 
2738   for (int i = 0; i < scratch_class->methods()->length(); i++) {
2739     Method* m = scratch_class->methods()->at(i);
2740     AnnotationArray* method_type_annotations = m->constMethod()->type_annotations();
2741 
2742     if (method_type_annotations == nullptr || method_type_annotations->length() == 0) {
2743       // this method does not have any annotations so skip it
2744       continue;
2745     }
2746 
2747     log_debug(redefine, class, annotation)("methods type_annotations length=%d", method_type_annotations->length());
2748 
2749     int byte_i = 0;  // byte index into method_type_annotations
2750     if (!rewrite_cp_refs_in_type_annotations_typeArray(method_type_annotations,
2751            byte_i, "method_info")) {
2752       log_debug(redefine, class, annotation)("bad method_type_annotations at %d", i);
2753       // propagate failure back to caller
2754       return false;
2755     }
2756   }
2757 
2758   return true;
2759 } // end rewrite_cp_refs_in_methods_type_annotations()
2760 
2761 
2762 // Rewrite constant pool references in a type_annotations
2763 // field. This "structure" is adapted from the
2764 // RuntimeVisibleTypeAnnotations_attribute described in
2765 // section 4.7.20 of the Java SE 8 Edition of the VM spec:
2766 //
2767 // type_annotations_typeArray {
2768 //   u2              num_annotations;
2769 //   type_annotation annotations[num_annotations];
2770 // }
2771 //
2772 bool VM_RedefineClasses::rewrite_cp_refs_in_type_annotations_typeArray(
2773        AnnotationArray* type_annotations_typeArray, int &byte_i_ref,
2774        const char * location_mesg) {
2775 
2776   if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
2777     // not enough room for num_annotations field
2778     log_debug(redefine, class, annotation)("length() is too small for num_annotations field");
2779     return false;
2780   }
2781 
2782   u2 num_annotations = Bytes::get_Java_u2((address)
2783                          type_annotations_typeArray->adr_at(byte_i_ref));
2784   byte_i_ref += 2;
2785 
2786   log_debug(redefine, class, annotation)("num_type_annotations=%d", num_annotations);
2787 
2788   int calc_num_annotations = 0;
2789   for (; calc_num_annotations < num_annotations; calc_num_annotations++) {
2790     if (!rewrite_cp_refs_in_type_annotation_struct(type_annotations_typeArray,
2791            byte_i_ref, location_mesg)) {
2792       log_debug(redefine, class, annotation)("bad type_annotation_struct at %d", calc_num_annotations);
2793       // propagate failure back to caller
2794       return false;
2795     }
2796   }
2797   assert(num_annotations == calc_num_annotations, "sanity check");
2798 
2799   if (byte_i_ref != type_annotations_typeArray->length()) {
2800     log_debug(redefine, class, annotation)
2801       ("read wrong amount of bytes at end of processing type_annotations_typeArray (%d of %d bytes were read)",
2802        byte_i_ref, type_annotations_typeArray->length());
2803     return false;
2804   }
2805 
2806   return true;
2807 } // end rewrite_cp_refs_in_type_annotations_typeArray()
2808 
2809 
2810 // Rewrite constant pool references in a type_annotation
2811 // field. This "structure" is adapted from the
2812 // RuntimeVisibleTypeAnnotations_attribute described in
2813 // section 4.7.20 of the Java SE 8 Edition of the VM spec:
2814 //
2815 // type_annotation {
2816 //   u1 target_type;
2817 //   union {
2818 //     type_parameter_target;
2819 //     supertype_target;
2820 //     type_parameter_bound_target;
2821 //     empty_target;
2822 //     method_formal_parameter_target;
2823 //     throws_target;
2824 //     localvar_target;
2825 //     catch_target;
2826 //     offset_target;
2827 //     type_argument_target;
2828 //   } target_info;
2829 //   type_path target_path;
2830 //   annotation anno;
2831 // }
2832 //
2833 bool VM_RedefineClasses::rewrite_cp_refs_in_type_annotation_struct(
2834        AnnotationArray* type_annotations_typeArray, int &byte_i_ref,
2835        const char * location_mesg) {
2836 
2837   if (!skip_type_annotation_target(type_annotations_typeArray,
2838          byte_i_ref, location_mesg)) {
2839     return false;
2840   }
2841 
2842   if (!skip_type_annotation_type_path(type_annotations_typeArray, byte_i_ref)) {
2843     return false;
2844   }
2845 
2846   if (!rewrite_cp_refs_in_annotation_struct(type_annotations_typeArray, byte_i_ref)) {
2847     return false;
2848   }
2849 
2850   return true;
2851 } // end rewrite_cp_refs_in_type_annotation_struct()
2852 
2853 
2854 // Read, verify and skip over the target_type and target_info part
2855 // so that rewriting can continue in the later parts of the struct.
2856 //
2857 // u1 target_type;
2858 // union {
2859 //   type_parameter_target;
2860 //   supertype_target;
2861 //   type_parameter_bound_target;
2862 //   empty_target;
2863 //   method_formal_parameter_target;
2864 //   throws_target;
2865 //   localvar_target;
2866 //   catch_target;
2867 //   offset_target;
2868 //   type_argument_target;
2869 // } target_info;
2870 //
2871 bool VM_RedefineClasses::skip_type_annotation_target(
2872        AnnotationArray* type_annotations_typeArray, int &byte_i_ref,
2873        const char * location_mesg) {
2874 
2875   if ((byte_i_ref + 1) > type_annotations_typeArray->length()) {
2876     // not enough room for a target_type let alone the rest of a type_annotation
2877     log_debug(redefine, class, annotation)("length() is too small for a target_type");
2878     return false;
2879   }
2880 
2881   u1 target_type = type_annotations_typeArray->at(byte_i_ref);
2882   byte_i_ref += 1;
2883   log_debug(redefine, class, annotation)("target_type=0x%.2x", target_type);
2884   log_debug(redefine, class, annotation)("location=%s", location_mesg);
2885 
2886   // Skip over target_info
2887   switch (target_type) {
2888     case 0x00:
2889     // kind: type parameter declaration of generic class or interface
2890     // location: ClassFile
2891     case 0x01:
2892     // kind: type parameter declaration of generic method or constructor
2893     // location: method_info
2894 
2895     {
2896       // struct:
2897       // type_parameter_target {
2898       //   u1 type_parameter_index;
2899       // }
2900       //
2901       if ((byte_i_ref + 1) > type_annotations_typeArray->length()) {
2902         log_debug(redefine, class, annotation)("length() is too small for a type_parameter_target");
2903         return false;
2904       }
2905 
2906       u1 type_parameter_index = type_annotations_typeArray->at(byte_i_ref);
2907       byte_i_ref += 1;
2908 
2909       log_debug(redefine, class, annotation)("type_parameter_target: type_parameter_index=%d", type_parameter_index);
2910     } break;
2911 
2912     case 0x10:
2913     // kind: type in extends clause of class or interface declaration
2914     //       or in implements clause of interface declaration
2915     // location: ClassFile
2916 
2917     {
2918       // struct:
2919       // supertype_target {
2920       //   u2 supertype_index;
2921       // }
2922       //
2923       if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
2924         log_debug(redefine, class, annotation)("length() is too small for a supertype_target");
2925         return false;
2926       }
2927 
2928       u2 supertype_index = Bytes::get_Java_u2((address)
2929                              type_annotations_typeArray->adr_at(byte_i_ref));
2930       byte_i_ref += 2;
2931 
2932       log_debug(redefine, class, annotation)("supertype_target: supertype_index=%d", supertype_index);
2933     } break;
2934 
2935     case 0x11:
2936     // kind: type in bound of type parameter declaration of generic class or interface
2937     // location: ClassFile
2938     case 0x12:
2939     // kind: type in bound of type parameter declaration of generic method or constructor
2940     // location: method_info
2941 
2942     {
2943       // struct:
2944       // type_parameter_bound_target {
2945       //   u1 type_parameter_index;
2946       //   u1 bound_index;
2947       // }
2948       //
2949       if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
2950         log_debug(redefine, class, annotation)("length() is too small for a type_parameter_bound_target");
2951         return false;
2952       }
2953 
2954       u1 type_parameter_index = type_annotations_typeArray->at(byte_i_ref);
2955       byte_i_ref += 1;
2956       u1 bound_index = type_annotations_typeArray->at(byte_i_ref);
2957       byte_i_ref += 1;
2958 
2959       log_debug(redefine, class, annotation)
2960         ("type_parameter_bound_target: type_parameter_index=%d, bound_index=%d", type_parameter_index, bound_index);
2961     } break;
2962 
2963     case 0x13:
2964     // kind: type in field declaration
2965     // location: field_info
2966     case 0x14:
2967     // kind: return type of method, or type of newly constructed object
2968     // location: method_info
2969     case 0x15:
2970     // kind: receiver type of method or constructor
2971     // location: method_info
2972 
2973     {
2974       // struct:
2975       // empty_target {
2976       // }
2977       //
2978       log_debug(redefine, class, annotation)("empty_target");
2979     } break;
2980 
2981     case 0x16:
2982     // kind: type in formal parameter declaration of method, constructor, or lambda expression
2983     // location: method_info
2984 
2985     {
2986       // struct:
2987       // formal_parameter_target {
2988       //   u1 formal_parameter_index;
2989       // }
2990       //
2991       if ((byte_i_ref + 1) > type_annotations_typeArray->length()) {
2992         log_debug(redefine, class, annotation)("length() is too small for a formal_parameter_target");
2993         return false;
2994       }
2995 
2996       u1 formal_parameter_index = type_annotations_typeArray->at(byte_i_ref);
2997       byte_i_ref += 1;
2998 
2999       log_debug(redefine, class, annotation)
3000         ("formal_parameter_target: formal_parameter_index=%d", formal_parameter_index);
3001     } break;
3002 
3003     case 0x17:
3004     // kind: type in throws clause of method or constructor
3005     // location: method_info
3006 
3007     {
3008       // struct:
3009       // throws_target {
3010       //   u2 throws_type_index
3011       // }
3012       //
3013       if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
3014         log_debug(redefine, class, annotation)("length() is too small for a throws_target");
3015         return false;
3016       }
3017 
3018       u2 throws_type_index = Bytes::get_Java_u2((address)
3019                                type_annotations_typeArray->adr_at(byte_i_ref));
3020       byte_i_ref += 2;
3021 
3022       log_debug(redefine, class, annotation)("throws_target: throws_type_index=%d", throws_type_index);
3023     } break;
3024 
3025     case 0x40:
3026     // kind: type in local variable declaration
3027     // location: Code
3028     case 0x41:
3029     // kind: type in resource variable declaration
3030     // location: Code
3031 
3032     {
3033       // struct:
3034       // localvar_target {
3035       //   u2 table_length;
3036       //   struct {
3037       //     u2 start_pc;
3038       //     u2 length;
3039       //     u2 index;
3040       //   } table[table_length];
3041       // }
3042       //
3043       if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
3044         // not enough room for a table_length let alone the rest of a localvar_target
3045         log_debug(redefine, class, annotation)("length() is too small for a localvar_target table_length");
3046         return false;
3047       }
3048 
3049       u2 table_length = Bytes::get_Java_u2((address)
3050                           type_annotations_typeArray->adr_at(byte_i_ref));
3051       byte_i_ref += 2;
3052 
3053       log_debug(redefine, class, annotation)("localvar_target: table_length=%d", table_length);
3054 
3055       int table_struct_size = 2 + 2 + 2; // 3 u2 variables per table entry
3056       int table_size = table_length * table_struct_size;
3057 
3058       if ((byte_i_ref + table_size) > type_annotations_typeArray->length()) {
3059         // not enough room for a table
3060         log_debug(redefine, class, annotation)("length() is too small for a table array of length %d", table_length);
3061         return false;
3062       }
3063 
3064       // Skip over table
3065       byte_i_ref += table_size;
3066     } break;
3067 
3068     case 0x42:
3069     // kind: type in exception parameter declaration
3070     // location: Code
3071 
3072     {
3073       // struct:
3074       // catch_target {
3075       //   u2 exception_table_index;
3076       // }
3077       //
3078       if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
3079         log_debug(redefine, class, annotation)("length() is too small for a catch_target");
3080         return false;
3081       }
3082 
3083       u2 exception_table_index = Bytes::get_Java_u2((address)
3084                                    type_annotations_typeArray->adr_at(byte_i_ref));
3085       byte_i_ref += 2;
3086 
3087       log_debug(redefine, class, annotation)("catch_target: exception_table_index=%d", exception_table_index);
3088     } break;
3089 
3090     case 0x43:
3091     // kind: type in instanceof expression
3092     // location: Code
3093     case 0x44:
3094     // kind: type in new expression
3095     // location: Code
3096     case 0x45:
3097     // kind: type in method reference expression using ::new
3098     // location: Code
3099     case 0x46:
3100     // kind: type in method reference expression using ::Identifier
3101     // location: Code
3102 
3103     {
3104       // struct:
3105       // offset_target {
3106       //   u2 offset;
3107       // }
3108       //
3109       if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
3110         log_debug(redefine, class, annotation)("length() is too small for a offset_target");
3111         return false;
3112       }
3113 
3114       u2 offset = Bytes::get_Java_u2((address)
3115                     type_annotations_typeArray->adr_at(byte_i_ref));
3116       byte_i_ref += 2;
3117 
3118       log_debug(redefine, class, annotation)("offset_target: offset=%d", offset);
3119     } break;
3120 
3121     case 0x47:
3122     // kind: type in cast expression
3123     // location: Code
3124     case 0x48:
3125     // kind: type argument for generic constructor in new expression or
3126     //       explicit constructor invocation statement
3127     // location: Code
3128     case 0x49:
3129     // kind: type argument for generic method in method invocation expression
3130     // location: Code
3131     case 0x4A:
3132     // kind: type argument for generic constructor in method reference expression using ::new
3133     // location: Code
3134     case 0x4B:
3135     // kind: type argument for generic method in method reference expression using ::Identifier
3136     // location: Code
3137 
3138     {
3139       // struct:
3140       // type_argument_target {
3141       //   u2 offset;
3142       //   u1 type_argument_index;
3143       // }
3144       //
3145       if ((byte_i_ref + 3) > type_annotations_typeArray->length()) {
3146         log_debug(redefine, class, annotation)("length() is too small for a type_argument_target");
3147         return false;
3148       }
3149 
3150       u2 offset = Bytes::get_Java_u2((address)
3151                     type_annotations_typeArray->adr_at(byte_i_ref));
3152       byte_i_ref += 2;
3153       u1 type_argument_index = type_annotations_typeArray->at(byte_i_ref);
3154       byte_i_ref += 1;
3155 
3156       log_debug(redefine, class, annotation)
3157         ("type_argument_target: offset=%d, type_argument_index=%d", offset, type_argument_index);
3158     } break;
3159 
3160     default:
3161       log_debug(redefine, class, annotation)("unknown target_type");
3162 #ifdef ASSERT
3163       ShouldNotReachHere();
3164 #endif
3165       return false;
3166   }
3167 
3168   return true;
3169 } // end skip_type_annotation_target()
3170 
3171 
3172 // Read, verify and skip over the type_path part so that rewriting
3173 // can continue in the later parts of the struct.
3174 //
3175 // type_path {
3176 //   u1 path_length;
3177 //   {
3178 //     u1 type_path_kind;
3179 //     u1 type_argument_index;
3180 //   } path[path_length];
3181 // }
3182 //
3183 bool VM_RedefineClasses::skip_type_annotation_type_path(
3184        AnnotationArray* type_annotations_typeArray, int &byte_i_ref) {
3185 
3186   if ((byte_i_ref + 1) > type_annotations_typeArray->length()) {
3187     // not enough room for a path_length let alone the rest of the type_path
3188     log_debug(redefine, class, annotation)("length() is too small for a type_path");
3189     return false;
3190   }
3191 
3192   u1 path_length = type_annotations_typeArray->at(byte_i_ref);
3193   byte_i_ref += 1;
3194 
3195   log_debug(redefine, class, annotation)("type_path: path_length=%d", path_length);
3196 
3197   int calc_path_length = 0;
3198   for (; calc_path_length < path_length; calc_path_length++) {
3199     if ((byte_i_ref + 1 + 1) > type_annotations_typeArray->length()) {
3200       // not enough room for a path
3201       log_debug(redefine, class, annotation)
3202         ("length() is too small for path entry %d of %d", calc_path_length, path_length);
3203       return false;
3204     }
3205 
3206     u1 type_path_kind = type_annotations_typeArray->at(byte_i_ref);
3207     byte_i_ref += 1;
3208     u1 type_argument_index = type_annotations_typeArray->at(byte_i_ref);
3209     byte_i_ref += 1;
3210 
3211     log_debug(redefine, class, annotation)
3212       ("type_path: path[%d]: type_path_kind=%d, type_argument_index=%d",
3213        calc_path_length, type_path_kind, type_argument_index);
3214 
3215     if (type_path_kind > 3 || (type_path_kind != 3 && type_argument_index != 0)) {
3216       // not enough room for a path
3217       log_debug(redefine, class, annotation)("inconsistent type_path values");
3218       return false;
3219     }
3220   }
3221   assert(path_length == calc_path_length, "sanity check");
3222 
3223   return true;
3224 } // end skip_type_annotation_type_path()
3225 
3226 
3227 // Rewrite constant pool references in the method's stackmap table.
3228 // These "structures" are adapted from the StackMapTable_attribute that
3229 // is described in section 4.8.4 of the 6.0 version of the VM spec
3230 // (dated 2005.10.26):
3231 // file:///net/quincunx.sfbay/export/gbracha/ClassFile-Java6.pdf
3232 //
3233 // stack_map {
3234 //   u2 number_of_entries;
3235 //   stack_map_frame entries[number_of_entries];
3236 // }
3237 //
3238 void VM_RedefineClasses::rewrite_cp_refs_in_stack_map_table(
3239        const methodHandle& method) {
3240 
3241   if (!method->has_stackmap_table()) {
3242     return;
3243   }
3244 
3245   AnnotationArray* stackmap_data = method->stackmap_data();
3246   address stackmap_p = (address)stackmap_data->adr_at(0);
3247   address stackmap_end = stackmap_p + stackmap_data->length();
3248 
3249   assert(stackmap_p + 2 <= stackmap_end, "no room for number_of_entries");
3250   u2 number_of_entries = Bytes::get_Java_u2(stackmap_p);
3251   stackmap_p += 2;
3252 
3253   log_debug(redefine, class, stackmap)("number_of_entries=%u", number_of_entries);
3254 
3255   // walk through each stack_map_frame
3256   u2 calc_number_of_entries = 0;
3257   for (; calc_number_of_entries < number_of_entries; calc_number_of_entries++) {
3258     // The stack_map_frame structure is a u1 frame_type followed by
3259     // 0 or more bytes of data:
3260     //
3261     // union stack_map_frame {
3262     //   same_frame;
3263     //   same_locals_1_stack_item_frame;
3264     //   same_locals_1_stack_item_frame_extended;
3265     //   chop_frame;
3266     //   same_frame_extended;
3267     //   append_frame;
3268     //   full_frame;
3269     // }
3270 
3271     assert(stackmap_p + 1 <= stackmap_end, "no room for frame_type");
3272     u1 frame_type = *stackmap_p;
3273     stackmap_p++;
3274 
3275     // same_frame {
3276     //   u1 frame_type = SAME; /* 0-63 */
3277     // }
3278     if (frame_type <= 63) {
3279       // nothing more to do for same_frame
3280     }
3281 
3282     // same_locals_1_stack_item_frame {
3283     //   u1 frame_type = SAME_LOCALS_1_STACK_ITEM; /* 64-127 */
3284     //   verification_type_info stack[1];
3285     // }
3286     else if (frame_type >= 64 && frame_type <= 127) {
3287       rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
3288         calc_number_of_entries, frame_type);
3289     }
3290 
3291     // reserved for future use
3292     else if (frame_type >= 128 && frame_type <= 246) {
3293       // nothing more to do for reserved frame_types
3294     }
3295 
3296     // same_locals_1_stack_item_frame_extended {
3297     //   u1 frame_type = SAME_LOCALS_1_STACK_ITEM_EXTENDED; /* 247 */
3298     //   u2 offset_delta;
3299     //   verification_type_info stack[1];
3300     // }
3301     else if (frame_type == 247) {
3302       stackmap_p += 2;
3303       rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
3304         calc_number_of_entries, frame_type);
3305     }
3306 
3307     // chop_frame {
3308     //   u1 frame_type = CHOP; /* 248-250 */
3309     //   u2 offset_delta;
3310     // }
3311     else if (frame_type >= 248 && frame_type <= 250) {
3312       stackmap_p += 2;
3313     }
3314 
3315     // same_frame_extended {
3316     //   u1 frame_type = SAME_FRAME_EXTENDED; /* 251*/
3317     //   u2 offset_delta;
3318     // }
3319     else if (frame_type == 251) {
3320       stackmap_p += 2;
3321     }
3322 
3323     // append_frame {
3324     //   u1 frame_type = APPEND; /* 252-254 */
3325     //   u2 offset_delta;
3326     //   verification_type_info locals[frame_type - 251];
3327     // }
3328     else if (frame_type >= 252 && frame_type <= 254) {
3329       assert(stackmap_p + 2 <= stackmap_end,
3330         "no room for offset_delta");
3331       stackmap_p += 2;
3332       u1 len = frame_type - 251;
3333       for (u1 i = 0; i < len; i++) {
3334         rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
3335           calc_number_of_entries, frame_type);
3336       }
3337     }
3338 
3339     // full_frame {
3340     //   u1 frame_type = FULL_FRAME; /* 255 */
3341     //   u2 offset_delta;
3342     //   u2 number_of_locals;
3343     //   verification_type_info locals[number_of_locals];
3344     //   u2 number_of_stack_items;
3345     //   verification_type_info stack[number_of_stack_items];
3346     // }
3347     else if (frame_type == 255) {
3348       assert(stackmap_p + 2 + 2 <= stackmap_end,
3349         "no room for smallest full_frame");
3350       stackmap_p += 2;
3351 
3352       u2 number_of_locals = Bytes::get_Java_u2(stackmap_p);
3353       stackmap_p += 2;
3354 
3355       for (u2 locals_i = 0; locals_i < number_of_locals; locals_i++) {
3356         rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
3357           calc_number_of_entries, frame_type);
3358       }
3359 
3360       // Use the largest size for the number_of_stack_items, but only get
3361       // the right number of bytes.
3362       u2 number_of_stack_items = Bytes::get_Java_u2(stackmap_p);
3363       stackmap_p += 2;
3364 
3365       for (u2 stack_i = 0; stack_i < number_of_stack_items; stack_i++) {
3366         rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
3367           calc_number_of_entries, frame_type);
3368       }
3369     }
3370   } // end while there is a stack_map_frame
3371   assert(number_of_entries == calc_number_of_entries, "sanity check");
3372 } // end rewrite_cp_refs_in_stack_map_table()
3373 
3374 
3375 // Rewrite constant pool references in the verification type info
3376 // portion of the method's stackmap table. These "structures" are
3377 // adapted from the StackMapTable_attribute that is described in
3378 // section 4.8.4 of the 6.0 version of the VM spec (dated 2005.10.26):
3379 // file:///net/quincunx.sfbay/export/gbracha/ClassFile-Java6.pdf
3380 //
3381 // The verification_type_info structure is a u1 tag followed by 0 or
3382 // more bytes of data:
3383 //
3384 // union verification_type_info {
3385 //   Top_variable_info;
3386 //   Integer_variable_info;
3387 //   Float_variable_info;
3388 //   Long_variable_info;
3389 //   Double_variable_info;
3390 //   Null_variable_info;
3391 //   UninitializedThis_variable_info;
3392 //   Object_variable_info;
3393 //   Uninitialized_variable_info;
3394 // }
3395 //
3396 void VM_RedefineClasses::rewrite_cp_refs_in_verification_type_info(
3397        address& stackmap_p_ref, address stackmap_end, u2 frame_i,
3398        u1 frame_type) {
3399 
3400   assert(stackmap_p_ref + 1 <= stackmap_end, "no room for tag");
3401   u1 tag = *stackmap_p_ref;
3402   stackmap_p_ref++;
3403 
3404   switch (tag) {
3405   // Top_variable_info {
3406   //   u1 tag = ITEM_Top; /* 0 */
3407   // }
3408   // verificationType.hpp has zero as ITEM_Bogus instead of ITEM_Top
3409   case 0:  // fall through
3410 
3411   // Integer_variable_info {
3412   //   u1 tag = ITEM_Integer; /* 1 */
3413   // }
3414   case ITEM_Integer:  // fall through
3415 
3416   // Float_variable_info {
3417   //   u1 tag = ITEM_Float; /* 2 */
3418   // }
3419   case ITEM_Float:  // fall through
3420 
3421   // Double_variable_info {
3422   //   u1 tag = ITEM_Double; /* 3 */
3423   // }
3424   case ITEM_Double:  // fall through
3425 
3426   // Long_variable_info {
3427   //   u1 tag = ITEM_Long; /* 4 */
3428   // }
3429   case ITEM_Long:  // fall through
3430 
3431   // Null_variable_info {
3432   //   u1 tag = ITEM_Null; /* 5 */
3433   // }
3434   case ITEM_Null:  // fall through
3435 
3436   // UninitializedThis_variable_info {
3437   //   u1 tag = ITEM_UninitializedThis; /* 6 */
3438   // }
3439   case ITEM_UninitializedThis:
3440     // nothing more to do for the above tag types
3441     break;
3442 
3443   // Object_variable_info {
3444   //   u1 tag = ITEM_Object; /* 7 */
3445   //   u2 cpool_index;
3446   // }
3447   case ITEM_Object:
3448   {
3449     assert(stackmap_p_ref + 2 <= stackmap_end, "no room for cpool_index");
3450     u2 cpool_index = Bytes::get_Java_u2(stackmap_p_ref);
3451     u2 new_cp_index = find_new_index(cpool_index);
3452     if (new_cp_index != 0) {
3453       log_debug(redefine, class, stackmap)("mapped old cpool_index=%d", cpool_index);
3454       Bytes::put_Java_u2(stackmap_p_ref, new_cp_index);
3455       cpool_index = new_cp_index;
3456     }
3457     stackmap_p_ref += 2;
3458 
3459     log_debug(redefine, class, stackmap)
3460       ("frame_i=%u, frame_type=%u, cpool_index=%d", frame_i, frame_type, cpool_index);
3461   } break;
3462 
3463   // Uninitialized_variable_info {
3464   //   u1 tag = ITEM_Uninitialized; /* 8 */
3465   //   u2 offset;
3466   // }
3467   case ITEM_Uninitialized:
3468     assert(stackmap_p_ref + 2 <= stackmap_end, "no room for offset");
3469     stackmap_p_ref += 2;
3470     break;
3471 
3472   default:
3473     log_debug(redefine, class, stackmap)("frame_i=%u, frame_type=%u, bad tag=0x%x", frame_i, frame_type, tag);
3474     ShouldNotReachHere();
3475     break;
3476   } // end switch (tag)
3477 } // end rewrite_cp_refs_in_verification_type_info()
3478 
3479 
3480 // Change the constant pool associated with klass scratch_class to scratch_cp.
3481 // scratch_cp_length elements are copied from scratch_cp to a smaller constant pool
3482 // and the smaller constant pool is associated with scratch_class.
3483 void VM_RedefineClasses::set_new_constant_pool(
3484        ClassLoaderData* loader_data,
3485        InstanceKlass* scratch_class, constantPoolHandle scratch_cp,
3486        int scratch_cp_length, TRAPS) {
3487   assert(scratch_cp->length() >= scratch_cp_length, "sanity check");
3488 
3489   // scratch_cp is a merged constant pool and has enough space for a
3490   // worst case merge situation. We want to associate the minimum
3491   // sized constant pool with the klass to save space.
3492   ConstantPool* cp = ConstantPool::allocate(loader_data, scratch_cp_length, CHECK);
3493   constantPoolHandle smaller_cp(THREAD, cp);
3494 
3495   // preserve version() value in the smaller copy
3496   int version = scratch_cp->version();
3497   assert(version != 0, "sanity check");
3498   smaller_cp->set_version(version);
3499 
3500   // attach klass to new constant pool
3501   // reference to the cp holder is needed for copy_operands()
3502   smaller_cp->set_pool_holder(scratch_class);
3503 
3504   smaller_cp->copy_fields(scratch_cp());
3505 
3506   scratch_cp->copy_cp_to(1, scratch_cp_length - 1, smaller_cp, 1, THREAD);
3507   if (HAS_PENDING_EXCEPTION) {
3508     // Exception is handled in the caller
3509     loader_data->add_to_deallocate_list(smaller_cp());
3510     return;
3511   }
3512   scratch_cp = smaller_cp;
3513 
3514   // attach new constant pool to klass
3515   scratch_class->set_constants(scratch_cp());
3516   scratch_cp->initialize_unresolved_klasses(loader_data, CHECK);
3517 
3518   int i;  // for portability
3519 
3520   // update each field in klass to use new constant pool indices as needed
3521   int java_fields;
3522   int injected_fields;
3523   bool update_required = false;
3524   GrowableArray<FieldInfo>* fields = FieldInfoStream::create_FieldInfoArray(scratch_class->fieldinfo_stream(), &java_fields, &injected_fields);
3525   for (int i = 0; i < java_fields; i++) {
3526     FieldInfo* fi = fields->adr_at(i);
3527     jshort cur_index = fi->name_index();
3528     jshort new_index = find_new_index(cur_index);
3529     if (new_index != 0) {
3530       log_trace(redefine, class, constantpool)("field-name_index change: %d to %d", cur_index, new_index);
3531       fi->set_name_index(new_index);
3532       update_required = true;
3533     }
3534     cur_index = fi->signature_index();
3535     new_index = find_new_index(cur_index);
3536     if (new_index != 0) {
3537       log_trace(redefine, class, constantpool)("field-signature_index change: %d to %d", cur_index, new_index);
3538       fi->set_signature_index(new_index);
3539       update_required = true;
3540     }
3541     cur_index = fi->initializer_index();
3542     new_index = find_new_index(cur_index);
3543     if (new_index != 0) {
3544       log_trace(redefine, class, constantpool)("field-initval_index change: %d to %d", cur_index, new_index);
3545       fi->set_initializer_index(new_index);
3546       update_required = true;
3547     }
3548     cur_index = fi->generic_signature_index();
3549     new_index = find_new_index(cur_index);
3550     if (new_index != 0) {
3551       log_trace(redefine, class, constantpool)("field-generic_signature change: %d to %d", cur_index, new_index);
3552       fi->set_generic_signature_index(new_index);
3553       update_required = true;
3554     }
3555   }
3556   if (update_required) {
3557     Array<u1>* old_stream = scratch_class->fieldinfo_stream();
3558     assert(fields->length() == (java_fields + injected_fields), "Must be");
3559     Array<u1>* new_fis = FieldInfoStream::create_FieldInfoStream(fields, java_fields, injected_fields, scratch_class->class_loader_data(), CHECK);
3560     scratch_class->set_fieldinfo_stream(new_fis);
3561     MetadataFactory::free_array<u1>(scratch_class->class_loader_data(), old_stream);
3562   }
3563 
3564   // Update constant pool indices in the inner classes info to use
3565   // new constant indices as needed. The inner classes info is a
3566   // quadruple:
3567   // (inner_class_info, outer_class_info, inner_name, inner_access_flags)
3568   InnerClassesIterator iter(scratch_class);
3569   for (; !iter.done(); iter.next()) {
3570     int cur_index = iter.inner_class_info_index();
3571     if (cur_index == 0) {
3572       continue;  // JVM spec. allows null inner class refs so skip it
3573     }
3574     u2 new_index = find_new_index(cur_index);
3575     if (new_index != 0) {
3576       log_trace(redefine, class, constantpool)("inner_class_info change: %d to %d", cur_index, new_index);
3577       iter.set_inner_class_info_index(new_index);
3578     }
3579     cur_index = iter.outer_class_info_index();
3580     new_index = find_new_index(cur_index);
3581     if (new_index != 0) {
3582       log_trace(redefine, class, constantpool)("outer_class_info change: %d to %d", cur_index, new_index);
3583       iter.set_outer_class_info_index(new_index);
3584     }
3585     cur_index = iter.inner_name_index();
3586     new_index = find_new_index(cur_index);
3587     if (new_index != 0) {
3588       log_trace(redefine, class, constantpool)("inner_name change: %d to %d", cur_index, new_index);
3589       iter.set_inner_name_index(new_index);
3590     }
3591   } // end for each inner class
3592 
3593   // Attach each method in klass to the new constant pool and update
3594   // to use new constant pool indices as needed:
3595   Array<Method*>* methods = scratch_class->methods();
3596   for (i = methods->length() - 1; i >= 0; i--) {
3597     methodHandle method(THREAD, methods->at(i));
3598     method->set_constants(scratch_cp());
3599 
3600     u2 new_index = find_new_index(method->name_index());
3601     if (new_index != 0) {
3602       log_trace(redefine, class, constantpool)
3603         ("method-name_index change: %d to %d", method->name_index(), new_index);
3604       method->set_name_index(new_index);
3605     }
3606     new_index = find_new_index(method->signature_index());
3607     if (new_index != 0) {
3608       log_trace(redefine, class, constantpool)
3609         ("method-signature_index change: %d to %d", method->signature_index(), new_index);
3610       method->set_signature_index(new_index);
3611     }
3612     new_index = find_new_index(method->generic_signature_index());
3613     if (new_index != 0) {
3614       log_trace(redefine, class, constantpool)
3615         ("method-generic_signature_index change: %d to %d", method->generic_signature_index(), new_index);
3616       method->constMethod()->set_generic_signature_index(new_index);
3617     }
3618 
3619     // Update constant pool indices in the method's checked exception
3620     // table to use new constant indices as needed.
3621     int cext_length = method->checked_exceptions_length();
3622     if (cext_length > 0) {
3623       CheckedExceptionElement * cext_table =
3624         method->checked_exceptions_start();
3625       for (int j = 0; j < cext_length; j++) {
3626         int cur_index = cext_table[j].class_cp_index;
3627         int new_index = find_new_index(cur_index);
3628         if (new_index != 0) {
3629           log_trace(redefine, class, constantpool)("cext-class_cp_index change: %d to %d", cur_index, new_index);
3630           cext_table[j].class_cp_index = (u2)new_index;
3631         }
3632       } // end for each checked exception table entry
3633     } // end if there are checked exception table entries
3634 
3635     // Update each catch type index in the method's exception table
3636     // to use new constant pool indices as needed. The exception table
3637     // holds quadruple entries of the form:
3638     //   (beg_bci, end_bci, handler_bci, klass_index)
3639 
3640     ExceptionTable ex_table(method());
3641     int ext_length = ex_table.length();
3642 
3643     for (int j = 0; j < ext_length; j ++) {
3644       int cur_index = ex_table.catch_type_index(j);
3645       u2 new_index = find_new_index(cur_index);
3646       if (new_index != 0) {
3647         log_trace(redefine, class, constantpool)("ext-klass_index change: %d to %d", cur_index, new_index);
3648         ex_table.set_catch_type_index(j, new_index);
3649       }
3650     } // end for each exception table entry
3651 
3652     // Update constant pool indices in the method's local variable
3653     // table to use new constant indices as needed. The local variable
3654     // table hold sextuple entries of the form:
3655     // (start_pc, length, name_index, descriptor_index, signature_index, slot)
3656     int lvt_length = method->localvariable_table_length();
3657     if (lvt_length > 0) {
3658       LocalVariableTableElement * lv_table =
3659         method->localvariable_table_start();
3660       for (int j = 0; j < lvt_length; j++) {
3661         int cur_index = lv_table[j].name_cp_index;
3662         int new_index = find_new_index(cur_index);
3663         if (new_index != 0) {
3664           log_trace(redefine, class, constantpool)("lvt-name_cp_index change: %d to %d", cur_index, new_index);
3665           lv_table[j].name_cp_index = (u2)new_index;
3666         }
3667         cur_index = lv_table[j].descriptor_cp_index;
3668         new_index = find_new_index(cur_index);
3669         if (new_index != 0) {
3670           log_trace(redefine, class, constantpool)("lvt-descriptor_cp_index change: %d to %d", cur_index, new_index);
3671           lv_table[j].descriptor_cp_index = (u2)new_index;
3672         }
3673         cur_index = lv_table[j].signature_cp_index;
3674         new_index = find_new_index(cur_index);
3675         if (new_index != 0) {
3676           log_trace(redefine, class, constantpool)("lvt-signature_cp_index change: %d to %d", cur_index, new_index);
3677           lv_table[j].signature_cp_index = (u2)new_index;
3678         }
3679       } // end for each local variable table entry
3680     } // end if there are local variable table entries
3681 
3682     // Update constant pool indices in the method's method_parameters.
3683     int mp_length = method->method_parameters_length();
3684     if (mp_length > 0) {
3685       MethodParametersElement* elem = method->method_parameters_start();
3686       for (int j = 0; j < mp_length; j++) {
3687         const int cp_index = elem[j].name_cp_index;
3688         const int new_cp_index = find_new_index(cp_index);
3689         if (new_cp_index != 0) {
3690           elem[j].name_cp_index = (u2)new_cp_index;
3691         }
3692       }
3693     }
3694 
3695     rewrite_cp_refs_in_stack_map_table(method);
3696   } // end for each method
3697 } // end set_new_constant_pool()
3698 
3699 
3700 // Unevolving classes may point to methods of the_class directly
3701 // from their constant pool caches, itables, and/or vtables. We
3702 // use the ClassLoaderDataGraph::classes_do() facility and this helper
3703 // to fix up these pointers.  MethodData also points to old methods and
3704 // must be cleaned.
3705 
3706 // Adjust cpools and vtables closure
3707 void VM_RedefineClasses::AdjustAndCleanMetadata::do_klass(Klass* k) {
3708 
3709   // This is a very busy routine. We don't want too much tracing
3710   // printed out.
3711   bool trace_name_printed = false;
3712 
3713   // If the class being redefined is java.lang.Object, we need to fix all
3714   // array class vtables also. The _has_redefined_Object flag is global.
3715   // Once the java.lang.Object has been redefined (by the current or one
3716   // of the previous VM_RedefineClasses operations) we have to always
3717   // adjust method entries for array classes.
3718   if (k->is_array_klass() && _has_redefined_Object) {
3719     k->vtable().adjust_method_entries(&trace_name_printed);
3720 
3721   } else if (k->is_instance_klass()) {
3722     HandleMark hm(_thread);
3723     InstanceKlass *ik = InstanceKlass::cast(k);
3724 
3725     // Clean MethodData of this class's methods so they don't refer to
3726     // old methods that are no longer running.
3727     Array<Method*>* methods = ik->methods();
3728     int num_methods = methods->length();
3729     for (int index = 0; index < num_methods; ++index) {
3730       if (methods->at(index)->method_data() != nullptr) {
3731         methods->at(index)->method_data()->clean_weak_method_links();
3732       }
3733     }
3734 
3735     // Adjust all vtables, default methods and itables, to clean out old methods.
3736     ResourceMark rm(_thread);
3737     if (ik->vtable_length() > 0) {
3738       ik->vtable().adjust_method_entries(&trace_name_printed);
3739       ik->adjust_default_methods(&trace_name_printed);
3740     }
3741 
3742     if (ik->itable_length() > 0) {
3743       ik->itable().adjust_method_entries(&trace_name_printed);
3744     }
3745 
3746     // The constant pools in other classes (other_cp) can refer to
3747     // old methods.  We have to update method information in
3748     // other_cp's cache. If other_cp has a previous version, then we
3749     // have to repeat the process for each previous version. The
3750     // constant pool cache holds the Method*s for non-virtual
3751     // methods and for virtual, final methods.
3752     //
3753     // Special case: if the current class is being redefined by the current
3754     // VM_RedefineClasses operation, then new_cp has already been attached
3755     // to the_class and old_cp has already been added as a previous version.
3756     // The new_cp doesn't have any cached references to old methods so it
3757     // doesn't need to be updated and we could optimize by skipping it.
3758     // However, the current class can be marked as being redefined by another
3759     // VM_RedefineClasses operation which has already executed its doit_prologue
3760     // and needs cpcache method entries adjusted. For simplicity, the cpcache
3761     // update is done unconditionally. It should result in doing nothing for
3762     // classes being redefined by the current VM_RedefineClasses operation.
3763     // Method entries in the previous version(s) are adjusted as well.
3764     ConstantPoolCache* cp_cache;
3765 
3766     // this klass' constant pool cache may need adjustment
3767     ConstantPool* other_cp = ik->constants();
3768     cp_cache = other_cp->cache();
3769     if (cp_cache != nullptr) {
3770       cp_cache->adjust_method_entries(&trace_name_printed);
3771     }
3772 
3773     // the previous versions' constant pool caches may need adjustment
3774     for (InstanceKlass* pv_node = ik->previous_versions();
3775          pv_node != nullptr;
3776          pv_node = pv_node->previous_versions()) {
3777       cp_cache = pv_node->constants()->cache();
3778       if (cp_cache != nullptr) {
3779         cp_cache->adjust_method_entries(&trace_name_printed);
3780       }
3781     }
3782   }
3783 }
3784 
3785 void VM_RedefineClasses::update_jmethod_ids() {
3786   for (int j = 0; j < _matching_methods_length; ++j) {
3787     Method* old_method = _matching_old_methods[j];
3788     jmethodID jmid = old_method->find_jmethod_id_or_null();
3789     if (jmid != nullptr) {
3790       // There is a jmethodID, change it to point to the new method
3791       Method* new_method = _matching_new_methods[j];
3792       Method::change_method_associated_with_jmethod_id(jmid, new_method);
3793       assert(Method::resolve_jmethod_id(jmid) == _matching_new_methods[j],
3794              "should be replaced");
3795     }
3796   }
3797 }
3798 
3799 int VM_RedefineClasses::check_methods_and_mark_as_obsolete() {
3800   int emcp_method_count = 0;
3801   int obsolete_count = 0;
3802   int old_index = 0;
3803   for (int j = 0; j < _matching_methods_length; ++j, ++old_index) {
3804     Method* old_method = _matching_old_methods[j];
3805     Method* new_method = _matching_new_methods[j];
3806     Method* old_array_method;
3807 
3808     // Maintain an old_index into the _old_methods array by skipping
3809     // deleted methods
3810     while ((old_array_method = _old_methods->at(old_index)) != old_method) {
3811       ++old_index;
3812     }
3813 
3814     if (MethodComparator::methods_EMCP(old_method, new_method)) {
3815       // The EMCP definition from JSR-163 requires the bytecodes to be
3816       // the same with the exception of constant pool indices which may
3817       // differ. However, the constants referred to by those indices
3818       // must be the same.
3819       //
3820       // We use methods_EMCP() for comparison since constant pool
3821       // merging can remove duplicate constant pool entries that were
3822       // present in the old method and removed from the rewritten new
3823       // method. A faster binary comparison function would consider the
3824       // old and new methods to be different when they are actually
3825       // EMCP.
3826       //
3827       // The old and new methods are EMCP and you would think that we
3828       // could get rid of one of them here and now and save some space.
3829       // However, the concept of EMCP only considers the bytecodes and
3830       // the constant pool entries in the comparison. Other things,
3831       // e.g., the line number table (LNT) or the local variable table
3832       // (LVT) don't count in the comparison. So the new (and EMCP)
3833       // method can have a new LNT that we need so we can't just
3834       // overwrite the new method with the old method.
3835       //
3836       // When this routine is called, we have already attached the new
3837       // methods to the_class so the old methods are effectively
3838       // overwritten. However, if an old method is still executing,
3839       // then the old method cannot be collected until sometime after
3840       // the old method call has returned. So the overwriting of old
3841       // methods by new methods will save us space except for those
3842       // (hopefully few) old methods that are still executing.
3843       //
3844       // A method refers to a ConstMethod* and this presents another
3845       // possible avenue to space savings. The ConstMethod* in the
3846       // new method contains possibly new attributes (LNT, LVT, etc).
3847       // At first glance, it seems possible to save space by replacing
3848       // the ConstMethod* in the old method with the ConstMethod*
3849       // from the new method. The old and new methods would share the
3850       // same ConstMethod* and we would save the space occupied by
3851       // the old ConstMethod*. However, the ConstMethod* contains
3852       // a back reference to the containing method. Sharing the
3853       // ConstMethod* between two methods could lead to confusion in
3854       // the code that uses the back reference. This would lead to
3855       // brittle code that could be broken in non-obvious ways now or
3856       // in the future.
3857       //
3858       // Another possibility is to copy the ConstMethod* from the new
3859       // method to the old method and then overwrite the new method with
3860       // the old method. Since the ConstMethod* contains the bytecodes
3861       // for the method embedded in the oop, this option would change
3862       // the bytecodes out from under any threads executing the old
3863       // method and make the thread's bcp invalid. Since EMCP requires
3864       // that the bytecodes be the same modulo constant pool indices, it
3865       // is straight forward to compute the correct new bcp in the new
3866       // ConstMethod* from the old bcp in the old ConstMethod*. The
3867       // time consuming part would be searching all the frames in all
3868       // of the threads to find all of the calls to the old method.
3869       //
3870       // It looks like we will have to live with the limited savings
3871       // that we get from effectively overwriting the old methods
3872       // when the new methods are attached to the_class.
3873 
3874       // Count number of methods that are EMCP.  The method will be marked
3875       // old but not obsolete if it is EMCP.
3876       emcp_method_count++;
3877 
3878       // An EMCP method is _not_ obsolete. An obsolete method has a
3879       // different jmethodID than the current method. An EMCP method
3880       // has the same jmethodID as the current method. Having the
3881       // same jmethodID for all EMCP versions of a method allows for
3882       // a consistent view of the EMCP methods regardless of which
3883       // EMCP method you happen to have in hand. For example, a
3884       // breakpoint set in one EMCP method will work for all EMCP
3885       // versions of the method including the current one.
3886     } else {
3887       // mark obsolete methods as such
3888       old_method->set_is_obsolete();
3889       obsolete_count++;
3890 
3891       // obsolete methods need a unique idnum so they become new entries in
3892       // the jmethodID cache in InstanceKlass
3893       assert(old_method->method_idnum() == new_method->method_idnum(), "must match");
3894       u2 num = InstanceKlass::cast(_the_class)->next_method_idnum();
3895       if (num != ConstMethod::UNSET_IDNUM) {
3896         old_method->set_method_idnum(num);
3897       }
3898 
3899       // With tracing we try not to "yack" too much. The position of
3900       // this trace assumes there are fewer obsolete methods than
3901       // EMCP methods.
3902       if (log_is_enabled(Trace, redefine, class, obsolete, mark)) {
3903         ResourceMark rm;
3904         log_trace(redefine, class, obsolete, mark)
3905           ("mark %s(%s) as obsolete", old_method->name()->as_C_string(), old_method->signature()->as_C_string());
3906       }
3907     }
3908     old_method->set_is_old();
3909   }
3910   for (int i = 0; i < _deleted_methods_length; ++i) {
3911     Method* old_method = _deleted_methods[i];
3912 
3913     assert(!old_method->has_vtable_index(),
3914            "cannot delete methods with vtable entries");;
3915 
3916     // Mark all deleted methods as old, obsolete and deleted
3917     old_method->set_is_deleted();
3918     old_method->set_is_old();
3919     old_method->set_is_obsolete();
3920     ++obsolete_count;
3921     // With tracing we try not to "yack" too much. The position of
3922     // this trace assumes there are fewer obsolete methods than
3923     // EMCP methods.
3924     if (log_is_enabled(Trace, redefine, class, obsolete, mark)) {
3925       ResourceMark rm;
3926       log_trace(redefine, class, obsolete, mark)
3927         ("mark deleted %s(%s) as obsolete", old_method->name()->as_C_string(), old_method->signature()->as_C_string());
3928     }
3929   }
3930   assert((emcp_method_count + obsolete_count) == _old_methods->length(),
3931     "sanity check");
3932   log_trace(redefine, class, obsolete, mark)("EMCP_cnt=%d, obsolete_cnt=%d", emcp_method_count, obsolete_count);
3933   return emcp_method_count;
3934 }
3935 
3936 // This internal class transfers the native function registration from old methods
3937 // to new methods.  It is designed to handle both the simple case of unchanged
3938 // native methods and the complex cases of native method prefixes being added and/or
3939 // removed.
3940 // It expects only to be used during the VM_RedefineClasses op (a safepoint).
3941 //
3942 // This class is used after the new methods have been installed in "the_class".
3943 //
3944 // So, for example, the following must be handled.  Where 'm' is a method and
3945 // a number followed by an underscore is a prefix.
3946 //
3947 //                                      Old Name    New Name
3948 // Simple transfer to new method        m       ->  m
3949 // Add prefix                           m       ->  1_m
3950 // Remove prefix                        1_m     ->  m
3951 // Simultaneous add of prefixes         m       ->  3_2_1_m
3952 // Simultaneous removal of prefixes     3_2_1_m ->  m
3953 // Simultaneous add and remove          1_m     ->  2_m
3954 // Same, caused by prefix removal only  3_2_1_m ->  3_2_m
3955 //
3956 class TransferNativeFunctionRegistration {
3957  private:
3958   InstanceKlass* the_class;
3959   int prefix_count;
3960   char** prefixes;
3961 
3962   // Recursively search the binary tree of possibly prefixed method names.
3963   // Iteration could be used if all agents were well behaved. Full tree walk is
3964   // more resilent to agents not cleaning up intermediate methods.
3965   // Branch at each depth in the binary tree is:
3966   //    (1) without the prefix.
3967   //    (2) with the prefix.
3968   // where 'prefix' is the prefix at that 'depth' (first prefix, second prefix,...)
3969   Method* search_prefix_name_space(int depth, char* name_str, size_t name_len,
3970                                      Symbol* signature) {
3971     TempNewSymbol name_symbol = SymbolTable::probe(name_str, (int)name_len);
3972     if (name_symbol != nullptr) {
3973       Method* method = the_class->lookup_method(name_symbol, signature);
3974       if (method != nullptr) {
3975         // Even if prefixed, intermediate methods must exist.
3976         if (method->is_native()) {
3977           // Wahoo, we found a (possibly prefixed) version of the method, return it.
3978           return method;
3979         }
3980         if (depth < prefix_count) {
3981           // Try applying further prefixes (other than this one).
3982           method = search_prefix_name_space(depth+1, name_str, name_len, signature);
3983           if (method != nullptr) {
3984             return method; // found
3985           }
3986 
3987           // Try adding this prefix to the method name and see if it matches
3988           // another method name.
3989           char* prefix = prefixes[depth];
3990           size_t prefix_len = strlen(prefix);
3991           size_t trial_len = name_len + prefix_len;
3992           char* trial_name_str = NEW_RESOURCE_ARRAY(char, trial_len + 1);
3993           strcpy(trial_name_str, prefix);
3994           strcat(trial_name_str, name_str);
3995           method = search_prefix_name_space(depth+1, trial_name_str, trial_len,
3996                                             signature);
3997           if (method != nullptr) {
3998             // If found along this branch, it was prefixed, mark as such
3999             method->set_is_prefixed_native();
4000             return method; // found
4001           }
4002         }
4003       }
4004     }
4005     return nullptr;  // This whole branch bore nothing
4006   }
4007 
4008   // Return the method name with old prefixes stripped away.
4009   char* method_name_without_prefixes(Method* method) {
4010     Symbol* name = method->name();
4011     char* name_str = name->as_utf8();
4012 
4013     // Old prefixing may be defunct, strip prefixes, if any.
4014     for (int i = prefix_count-1; i >= 0; i--) {
4015       char* prefix = prefixes[i];
4016       size_t prefix_len = strlen(prefix);
4017       if (strncmp(prefix, name_str, prefix_len) == 0) {
4018         name_str += prefix_len;
4019       }
4020     }
4021     return name_str;
4022   }
4023 
4024   // Strip any prefixes off the old native method, then try to find a
4025   // (possibly prefixed) new native that matches it.
4026   Method* strip_and_search_for_new_native(Method* method) {
4027     ResourceMark rm;
4028     char* name_str = method_name_without_prefixes(method);
4029     return search_prefix_name_space(0, name_str, strlen(name_str),
4030                                     method->signature());
4031   }
4032 
4033  public:
4034 
4035   // Construct a native method transfer processor for this class.
4036   TransferNativeFunctionRegistration(InstanceKlass* _the_class) {
4037     assert(SafepointSynchronize::is_at_safepoint(), "sanity check");
4038 
4039     the_class = _the_class;
4040     prefixes = JvmtiExport::get_all_native_method_prefixes(&prefix_count);
4041   }
4042 
4043   // Attempt to transfer any of the old or deleted methods that are native
4044   void transfer_registrations(Method** old_methods, int methods_length) {
4045     for (int j = 0; j < methods_length; j++) {
4046       Method* old_method = old_methods[j];
4047 
4048       if (old_method->is_native() && old_method->has_native_function()) {
4049         Method* new_method = strip_and_search_for_new_native(old_method);
4050         if (new_method != nullptr) {
4051           // Actually set the native function in the new method.
4052           // Redefine does not send events (except CFLH), certainly not this
4053           // behind the scenes re-registration.
4054           new_method->set_native_function(old_method->native_function(),
4055                               !Method::native_bind_event_is_interesting);
4056         }
4057       }
4058     }
4059   }
4060 };
4061 
4062 // Don't lose the association between a native method and its JNI function.
4063 void VM_RedefineClasses::transfer_old_native_function_registrations(InstanceKlass* the_class) {
4064   TransferNativeFunctionRegistration transfer(the_class);
4065   transfer.transfer_registrations(_deleted_methods, _deleted_methods_length);
4066   transfer.transfer_registrations(_matching_old_methods, _matching_methods_length);
4067 }
4068 
4069 // Deoptimize all compiled code that depends on the classes redefined.
4070 //
4071 // If the can_redefine_classes capability is obtained in the onload
4072 // phase or 'AlwaysRecordEvolDependencies' is true, then the compiler has
4073 // recorded all dependencies from startup. In that case we need only
4074 // deoptimize and throw away all compiled code that depends on the class.
4075 //
4076 // If can_redefine_classes is obtained sometime after the onload phase
4077 // (and 'AlwaysRecordEvolDependencies' is false) then the dependency
4078 // information may be incomplete. In that case the first call to
4079 // RedefineClasses causes all compiled code to be thrown away. As
4080 // can_redefine_classes has been obtained then all future compilations will
4081 // record dependencies so second and subsequent calls to RedefineClasses
4082 // need only throw away code that depends on the class.
4083 //
4084 
4085 void VM_RedefineClasses::flush_dependent_code() {
4086   assert(SafepointSynchronize::is_at_safepoint(), "sanity check");
4087   assert(JvmtiExport::all_dependencies_are_recorded() || !AlwaysRecordEvolDependencies, "sanity check");
4088 
4089   DeoptimizationScope deopt_scope;
4090 
4091   // This is the first redefinition, mark all the nmethods for deoptimization
4092   if (!JvmtiExport::all_dependencies_are_recorded()) {
4093     CodeCache::mark_all_nmethods_for_evol_deoptimization(&deopt_scope);
4094     log_debug(redefine, class, nmethod)("Marked all nmethods for deopt");
4095   } else {
4096     CodeCache::mark_dependents_for_evol_deoptimization(&deopt_scope);
4097     log_debug(redefine, class, nmethod)("Marked dependent nmethods for deopt");
4098   }
4099 
4100   deopt_scope.deoptimize_marked();
4101 
4102   // From now on we know that the dependency information is complete
4103   JvmtiExport::set_all_dependencies_are_recorded(true);
4104 }
4105 
4106 void VM_RedefineClasses::compute_added_deleted_matching_methods() {
4107   Method* old_method;
4108   Method* new_method;
4109 
4110   _matching_old_methods = NEW_RESOURCE_ARRAY(Method*, _old_methods->length());
4111   _matching_new_methods = NEW_RESOURCE_ARRAY(Method*, _old_methods->length());
4112   _added_methods        = NEW_RESOURCE_ARRAY(Method*, _new_methods->length());
4113   _deleted_methods      = NEW_RESOURCE_ARRAY(Method*, _old_methods->length());
4114 
4115   _matching_methods_length = 0;
4116   _deleted_methods_length  = 0;
4117   _added_methods_length    = 0;
4118 
4119   int nj = 0;
4120   int oj = 0;
4121   while (true) {
4122     if (oj >= _old_methods->length()) {
4123       if (nj >= _new_methods->length()) {
4124         break; // we've looked at everything, done
4125       }
4126       // New method at the end
4127       new_method = _new_methods->at(nj);
4128       _added_methods[_added_methods_length++] = new_method;
4129       ++nj;
4130     } else if (nj >= _new_methods->length()) {
4131       // Old method, at the end, is deleted
4132       old_method = _old_methods->at(oj);
4133       _deleted_methods[_deleted_methods_length++] = old_method;
4134       ++oj;
4135     } else {
4136       old_method = _old_methods->at(oj);
4137       new_method = _new_methods->at(nj);
4138       if (old_method->name() == new_method->name()) {
4139         if (old_method->signature() == new_method->signature()) {
4140           _matching_old_methods[_matching_methods_length  ] = old_method;
4141           _matching_new_methods[_matching_methods_length++] = new_method;
4142           ++nj;
4143           ++oj;
4144         } else {
4145           // added overloaded have already been moved to the end,
4146           // so this is a deleted overloaded method
4147           _deleted_methods[_deleted_methods_length++] = old_method;
4148           ++oj;
4149         }
4150       } else { // names don't match
4151         if (old_method->name()->fast_compare(new_method->name()) > 0) {
4152           // new method
4153           _added_methods[_added_methods_length++] = new_method;
4154           ++nj;
4155         } else {
4156           // deleted method
4157           _deleted_methods[_deleted_methods_length++] = old_method;
4158           ++oj;
4159         }
4160       }
4161     }
4162   }
4163   assert(_matching_methods_length + _deleted_methods_length == _old_methods->length(), "sanity");
4164   assert(_matching_methods_length + _added_methods_length == _new_methods->length(), "sanity");
4165 }
4166 
4167 
4168 void VM_RedefineClasses::swap_annotations(InstanceKlass* the_class,
4169                                           InstanceKlass* scratch_class) {
4170   // Swap annotation fields values
4171   Annotations* old_annotations = the_class->annotations();
4172   the_class->set_annotations(scratch_class->annotations());
4173   scratch_class->set_annotations(old_annotations);
4174 }
4175 
4176 
4177 // Install the redefinition of a class:
4178 //    - house keeping (flushing breakpoints and caches, deoptimizing
4179 //      dependent compiled code)
4180 //    - replacing parts in the_class with parts from scratch_class
4181 //    - adding a weak reference to track the obsolete but interesting
4182 //      parts of the_class
4183 //    - adjusting constant pool caches and vtables in other classes
4184 //      that refer to methods in the_class. These adjustments use the
4185 //      ClassLoaderDataGraph::classes_do() facility which only allows
4186 //      a helper method to be specified. The interesting parameters
4187 //      that we would like to pass to the helper method are saved in
4188 //      static global fields in the VM operation.
4189 void VM_RedefineClasses::redefine_single_class(Thread* current, jclass the_jclass,
4190                                                InstanceKlass* scratch_class) {
4191 
4192   HandleMark hm(current);   // make sure handles from this call are freed
4193 
4194   if (log_is_enabled(Info, redefine, class, timer)) {
4195     _timer_rsc_phase1.start();
4196   }
4197 
4198   InstanceKlass* the_class = get_ik(the_jclass);
4199 
4200   // Set a flag to control and optimize adjusting method entries
4201   _has_redefined_Object |= the_class == vmClasses::Object_klass();
4202 
4203   // Remove all breakpoints in methods of this class
4204   JvmtiBreakpoints& jvmti_breakpoints = JvmtiCurrentBreakpoints::get_jvmti_breakpoints();
4205   jvmti_breakpoints.clearall_in_class_at_safepoint(the_class);
4206 
4207   _old_methods = the_class->methods();
4208   _new_methods = scratch_class->methods();
4209   _the_class = the_class;
4210   compute_added_deleted_matching_methods();
4211   update_jmethod_ids();
4212 
4213   _any_class_has_resolved_methods = the_class->has_resolved_methods() || _any_class_has_resolved_methods;
4214 
4215   // Attach new constant pool to the original klass. The original
4216   // klass still refers to the old constant pool (for now).
4217   scratch_class->constants()->set_pool_holder(the_class);
4218 
4219 #if 0
4220   // In theory, with constant pool merging in place we should be able
4221   // to save space by using the new, merged constant pool in place of
4222   // the old constant pool(s). By "pool(s)" I mean the constant pool in
4223   // the klass version we are replacing now and any constant pool(s) in
4224   // previous versions of klass. Nice theory, doesn't work in practice.
4225   // When this code is enabled, even simple programs throw NullPointer
4226   // exceptions. I'm guessing that this is caused by some constant pool
4227   // cache difference between the new, merged constant pool and the
4228   // constant pool that was just being used by the klass. I'm keeping
4229   // this code around to archive the idea, but the code has to remain
4230   // disabled for now.
4231 
4232   // Attach each old method to the new constant pool. This can be
4233   // done here since we are past the bytecode verification and
4234   // constant pool optimization phases.
4235   for (int i = _old_methods->length() - 1; i >= 0; i--) {
4236     Method* method = _old_methods->at(i);
4237     method->set_constants(scratch_class->constants());
4238   }
4239 
4240   // NOTE: this doesn't work because you can redefine the same class in two
4241   // threads, each getting their own constant pool data appended to the
4242   // original constant pool.  In order for the new methods to work when they
4243   // become old methods, they need to keep their updated copy of the constant pool.
4244 
4245   {
4246     // walk all previous versions of the klass
4247     InstanceKlass *ik = the_class;
4248     PreviousVersionWalker pvw(ik);
4249     do {
4250       ik = pvw.next_previous_version();
4251       if (ik != nullptr) {
4252 
4253         // attach previous version of klass to the new constant pool
4254         ik->set_constants(scratch_class->constants());
4255 
4256         // Attach each method in the previous version of klass to the
4257         // new constant pool
4258         Array<Method*>* prev_methods = ik->methods();
4259         for (int i = prev_methods->length() - 1; i >= 0; i--) {
4260           Method* method = prev_methods->at(i);
4261           method->set_constants(scratch_class->constants());
4262         }
4263       }
4264     } while (ik != nullptr);
4265   }
4266 #endif
4267 
4268   // Replace methods and constantpool
4269   the_class->set_methods(_new_methods);
4270   scratch_class->set_methods(_old_methods);     // To prevent potential GCing of the old methods,
4271                                           // and to be able to undo operation easily.
4272 
4273   Array<int>* old_ordering = the_class->method_ordering();
4274   the_class->set_method_ordering(scratch_class->method_ordering());
4275   scratch_class->set_method_ordering(old_ordering);
4276 
4277   ConstantPool* old_constants = the_class->constants();
4278   the_class->set_constants(scratch_class->constants());
4279   scratch_class->set_constants(old_constants);  // See the previous comment.
4280 #if 0
4281   // We are swapping the guts of "the new class" with the guts of "the
4282   // class". Since the old constant pool has just been attached to "the
4283   // new class", it seems logical to set the pool holder in the old
4284   // constant pool also. However, doing this will change the observable
4285   // class hierarchy for any old methods that are still executing. A
4286   // method can query the identity of its "holder" and this query uses
4287   // the method's constant pool link to find the holder. The change in
4288   // holding class from "the class" to "the new class" can confuse
4289   // things.
4290   //
4291   // Setting the old constant pool's holder will also cause
4292   // verification done during vtable initialization below to fail.
4293   // During vtable initialization, the vtable's class is verified to be
4294   // a subtype of the method's holder. The vtable's class is "the
4295   // class" and the method's holder is gotten from the constant pool
4296   // link in the method itself. For "the class"'s directly implemented
4297   // methods, the method holder is "the class" itself (as gotten from
4298   // the new constant pool). The check works fine in this case. The
4299   // check also works fine for methods inherited from super classes.
4300   //
4301   // Miranda methods are a little more complicated. A miranda method is
4302   // provided by an interface when the class implementing the interface
4303   // does not provide its own method.  These interfaces are implemented
4304   // internally as an InstanceKlass. These special instanceKlasses
4305   // share the constant pool of the class that "implements" the
4306   // interface. By sharing the constant pool, the method holder of a
4307   // miranda method is the class that "implements" the interface. In a
4308   // non-redefine situation, the subtype check works fine. However, if
4309   // the old constant pool's pool holder is modified, then the check
4310   // fails because there is no class hierarchy relationship between the
4311   // vtable's class and "the new class".
4312 
4313   old_constants->set_pool_holder(scratch_class());
4314 #endif
4315 
4316   // track number of methods that are EMCP for add_previous_version() call below
4317   int emcp_method_count = check_methods_and_mark_as_obsolete();
4318   transfer_old_native_function_registrations(the_class);
4319 
4320   if (scratch_class->get_cached_class_file() != the_class->get_cached_class_file()) {
4321     // 1. the_class doesn't have a cache yet, scratch_class does have a cache.
4322     // 2. The same class can be present twice in the scratch classes list or there
4323     // are multiple concurrent RetransformClasses calls on different threads.
4324     // the_class and scratch_class have the same cached bytes, but different buffers.
4325     // In such cases we need to deallocate one of the buffers.
4326     // 3. RedefineClasses and the_class has cached bytes from a previous transformation.
4327     // In the case we need to use class bytes from scratch_class.
4328     if (the_class->get_cached_class_file() != nullptr) {
4329       os::free(the_class->get_cached_class_file());
4330     }
4331     the_class->set_cached_class_file(scratch_class->get_cached_class_file());
4332   }
4333 
4334   // null out in scratch class to not delete twice.  The class to be redefined
4335   // always owns these bytes.
4336   scratch_class->set_cached_class_file(nullptr);
4337 
4338   // Replace inner_classes
4339   Array<u2>* old_inner_classes = the_class->inner_classes();
4340   the_class->set_inner_classes(scratch_class->inner_classes());
4341   scratch_class->set_inner_classes(old_inner_classes);
4342 
4343   // Initialize the vtable and interface table after
4344   // methods have been rewritten
4345   // no exception should happen here since we explicitly
4346   // do not check loader constraints.
4347   // compare_and_normalize_class_versions has already checked:
4348   //  - classloaders unchanged, signatures unchanged
4349   //  - all instanceKlasses for redefined classes reused & contents updated
4350   the_class->vtable().initialize_vtable();
4351   the_class->itable().initialize_itable();
4352 
4353   // Leave arrays of jmethodIDs and itable index cache unchanged
4354 
4355   // Copy the "source debug extension" attribute from new class version
4356   the_class->set_source_debug_extension(
4357     scratch_class->source_debug_extension(),
4358     scratch_class->source_debug_extension() == nullptr ? 0 :
4359     (int)strlen(scratch_class->source_debug_extension()));
4360 
4361   // Use of javac -g could be different in the old and the new
4362   if (scratch_class->has_localvariable_table() !=
4363       the_class->has_localvariable_table()) {
4364     the_class->set_has_localvariable_table(scratch_class->has_localvariable_table());
4365   }
4366 
4367   swap_annotations(the_class, scratch_class);
4368 
4369   // Replace minor version number of class file
4370   u2 old_minor_version = the_class->constants()->minor_version();
4371   the_class->constants()->set_minor_version(scratch_class->constants()->minor_version());
4372   scratch_class->constants()->set_minor_version(old_minor_version);
4373 
4374   // Replace major version number of class file
4375   u2 old_major_version = the_class->constants()->major_version();
4376   the_class->constants()->set_major_version(scratch_class->constants()->major_version());
4377   scratch_class->constants()->set_major_version(old_major_version);
4378 
4379   // Replace CP indexes for class and name+type of enclosing method
4380   u2 old_class_idx  = the_class->enclosing_method_class_index();
4381   u2 old_method_idx = the_class->enclosing_method_method_index();
4382   the_class->set_enclosing_method_indices(
4383     scratch_class->enclosing_method_class_index(),
4384     scratch_class->enclosing_method_method_index());
4385   scratch_class->set_enclosing_method_indices(old_class_idx, old_method_idx);
4386 
4387   if (!the_class->has_been_redefined()) {
4388     the_class->set_has_been_redefined();
4389   }
4390 
4391   // Scratch class is unloaded but still needs cleaning, and skipping for CDS.
4392   scratch_class->set_is_scratch_class();
4393 
4394   // keep track of previous versions of this class
4395   the_class->add_previous_version(scratch_class, emcp_method_count);
4396 
4397   _timer_rsc_phase1.stop();
4398   if (log_is_enabled(Info, redefine, class, timer)) {
4399     _timer_rsc_phase2.start();
4400   }
4401 
4402   if (the_class->oop_map_cache() != nullptr) {
4403     // Flush references to any obsolete methods from the oop map cache
4404     // so that obsolete methods are not pinned.
4405     the_class->oop_map_cache()->flush_obsolete_entries();
4406   }
4407 
4408   increment_class_counter(the_class);
4409 
4410   if (EventClassRedefinition::is_enabled()) {
4411     EventClassRedefinition event;
4412     event.set_classModificationCount(java_lang_Class::classRedefinedCount(the_class->java_mirror()));
4413     event.set_redefinedClass(the_class);
4414     event.set_redefinitionId(_id);
4415     event.commit();
4416   }
4417 
4418   {
4419     ResourceMark rm(current);
4420     // increment the classRedefinedCount field in the_class and in any
4421     // direct and indirect subclasses of the_class
4422     log_info(redefine, class, load)
4423       ("redefined name=%s, count=%d (avail_mem=" UINT64_FORMAT "K)",
4424        the_class->external_name(), java_lang_Class::classRedefinedCount(the_class->java_mirror()), os::available_memory() >> 10);
4425     Events::log_redefinition(current, "redefined class name=%s, count=%d",
4426                              the_class->external_name(),
4427                              java_lang_Class::classRedefinedCount(the_class->java_mirror()));
4428 
4429   }
4430   _timer_rsc_phase2.stop();
4431 
4432 } // end redefine_single_class()
4433 
4434 
4435 // Increment the classRedefinedCount field in the specific InstanceKlass
4436 // and in all direct and indirect subclasses.
4437 void VM_RedefineClasses::increment_class_counter(InstanceKlass* ik) {
4438   for (ClassHierarchyIterator iter(ik); !iter.done(); iter.next()) {
4439     // Only update instanceKlasses
4440     Klass* sub = iter.klass();
4441     if (sub->is_instance_klass()) {
4442       oop class_mirror = InstanceKlass::cast(sub)->java_mirror();
4443       Klass* class_oop = java_lang_Class::as_Klass(class_mirror);
4444       int new_count = java_lang_Class::classRedefinedCount(class_mirror) + 1;
4445       java_lang_Class::set_classRedefinedCount(class_mirror, new_count);
4446 
4447       if (class_oop != _the_class) {
4448         // _the_class count is printed at end of redefine_single_class()
4449         log_debug(redefine, class, subclass)("updated count in subclass=%s to %d", ik->external_name(), new_count);
4450       }
4451     }
4452   }
4453 }
4454 
4455 void VM_RedefineClasses::CheckClass::do_klass(Klass* k) {
4456   bool no_old_methods = true;  // be optimistic
4457 
4458   // Both array and instance classes have vtables.
4459   // a vtable should never contain old or obsolete methods
4460   ResourceMark rm(_thread);
4461   if (k->vtable_length() > 0 &&
4462       !k->vtable().check_no_old_or_obsolete_entries()) {
4463     if (log_is_enabled(Trace, redefine, class, obsolete, metadata)) {
4464       log_trace(redefine, class, obsolete, metadata)
4465         ("klassVtable::check_no_old_or_obsolete_entries failure -- OLD or OBSOLETE method found -- class: %s",
4466          k->signature_name());
4467       k->vtable().dump_vtable();
4468     }
4469     no_old_methods = false;
4470   }
4471 
4472   if (k->is_instance_klass()) {
4473     HandleMark hm(_thread);
4474     InstanceKlass *ik = InstanceKlass::cast(k);
4475 
4476     // an itable should never contain old or obsolete methods
4477     if (ik->itable_length() > 0 &&
4478         !ik->itable().check_no_old_or_obsolete_entries()) {
4479       if (log_is_enabled(Trace, redefine, class, obsolete, metadata)) {
4480         log_trace(redefine, class, obsolete, metadata)
4481           ("klassItable::check_no_old_or_obsolete_entries failure -- OLD or OBSOLETE method found -- class: %s",
4482            ik->signature_name());
4483         ik->itable().dump_itable();
4484       }
4485       no_old_methods = false;
4486     }
4487 
4488     // the constant pool cache should never contain non-deleted old or obsolete methods
4489     if (ik->constants() != nullptr &&
4490         ik->constants()->cache() != nullptr &&
4491         !ik->constants()->cache()->check_no_old_or_obsolete_entries()) {
4492       if (log_is_enabled(Trace, redefine, class, obsolete, metadata)) {
4493         log_trace(redefine, class, obsolete, metadata)
4494           ("cp-cache::check_no_old_or_obsolete_entries failure -- OLD or OBSOLETE method found -- class: %s",
4495            ik->signature_name());
4496         ik->constants()->cache()->dump_cache();
4497       }
4498       no_old_methods = false;
4499     }
4500   }
4501 
4502   // print and fail guarantee if old methods are found.
4503   if (!no_old_methods) {
4504     if (log_is_enabled(Trace, redefine, class, obsolete, metadata)) {
4505       dump_methods();
4506     } else {
4507       log_trace(redefine, class)("Use the '-Xlog:redefine+class*:' option "
4508         "to see more info about the following guarantee() failure.");
4509     }
4510     guarantee(false, "OLD and/or OBSOLETE method(s) found");
4511   }
4512 }
4513 
4514 u8 VM_RedefineClasses::next_id() {
4515   while (true) {
4516     u8 id = _id_counter;
4517     u8 next_id = id + 1;
4518     u8 result = Atomic::cmpxchg(&_id_counter, id, next_id);
4519     if (result == id) {
4520       return next_id;
4521     }
4522   }
4523 }
4524 
4525 void VM_RedefineClasses::dump_methods() {
4526   int j;
4527   log_trace(redefine, class, dump)("_old_methods --");
4528   for (j = 0; j < _old_methods->length(); ++j) {
4529     LogStreamHandle(Trace, redefine, class, dump) log_stream;
4530     Method* m = _old_methods->at(j);
4531     log_stream.print("%4d  (%5d)  ", j, m->vtable_index());
4532     m->access_flags().print_on(&log_stream);
4533     log_stream.print(" --  ");
4534     m->print_name(&log_stream);
4535     log_stream.cr();
4536   }
4537   log_trace(redefine, class, dump)("_new_methods --");
4538   for (j = 0; j < _new_methods->length(); ++j) {
4539     LogStreamHandle(Trace, redefine, class, dump) log_stream;
4540     Method* m = _new_methods->at(j);
4541     log_stream.print("%4d  (%5d)  ", j, m->vtable_index());
4542     m->access_flags().print_on(&log_stream);
4543     log_stream.print(" --  ");
4544     m->print_name(&log_stream);
4545     log_stream.cr();
4546   }
4547   log_trace(redefine, class, dump)("_matching_methods --");
4548   for (j = 0; j < _matching_methods_length; ++j) {
4549     LogStreamHandle(Trace, redefine, class, dump) log_stream;
4550     Method* m = _matching_old_methods[j];
4551     log_stream.print("%4d  (%5d)  ", j, m->vtable_index());
4552     m->access_flags().print_on(&log_stream);
4553     log_stream.print(" --  ");
4554     m->print_name();
4555     log_stream.cr();
4556 
4557     m = _matching_new_methods[j];
4558     log_stream.print("      (%5d)  ", m->vtable_index());
4559     m->access_flags().print_on(&log_stream);
4560     log_stream.cr();
4561   }
4562   log_trace(redefine, class, dump)("_deleted_methods --");
4563   for (j = 0; j < _deleted_methods_length; ++j) {
4564     LogStreamHandle(Trace, redefine, class, dump) log_stream;
4565     Method* m = _deleted_methods[j];
4566     log_stream.print("%4d  (%5d)  ", j, m->vtable_index());
4567     m->access_flags().print_on(&log_stream);
4568     log_stream.print(" --  ");
4569     m->print_name(&log_stream);
4570     log_stream.cr();
4571   }
4572   log_trace(redefine, class, dump)("_added_methods --");
4573   for (j = 0; j < _added_methods_length; ++j) {
4574     LogStreamHandle(Trace, redefine, class, dump) log_stream;
4575     Method* m = _added_methods[j];
4576     log_stream.print("%4d  (%5d)  ", j, m->vtable_index());
4577     m->access_flags().print_on(&log_stream);
4578     log_stream.print(" --  ");
4579     m->print_name(&log_stream);
4580     log_stream.cr();
4581   }
4582 }
4583 
4584 void VM_RedefineClasses::print_on_error(outputStream* st) const {
4585   VM_Operation::print_on_error(st);
4586   if (_the_class != nullptr) {
4587     ResourceMark rm;
4588     st->print_cr(", redefining class %s", _the_class->external_name());
4589   }
4590 }
--- EOF ---