1 /*
   2  * Copyright (c) 2003, 2020, 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 "aot/aotLoader.hpp"
  27 #include "classfile/classLoaderDataGraph.hpp"
  28 #include "classfile/classFileStream.hpp"
  29 #include "classfile/javaClasses.inline.hpp"
  30 #include "classfile/metadataOnStackMark.hpp"
  31 #include "classfile/symbolTable.hpp"
  32 #include "classfile/systemDictionary.hpp"
  33 #include "classfile/verifier.hpp"
  34 #include "code/codeCache.hpp"
  35 #include "compiler/compileBroker.hpp"
  36 #include "interpreter/oopMapCache.hpp"
  37 #include "interpreter/rewriter.hpp"
  38 #include "jfr/jfrEvents.hpp"
  39 #include "logging/logStream.hpp"
  40 #include "memory/metadataFactory.hpp"
  41 #include "memory/metaspaceShared.hpp"
  42 #include "memory/resourceArea.hpp"
  43 #include "memory/universe.hpp"
  44 #include "oops/annotations.hpp"
  45 #include "oops/constantPool.hpp"
  46 #include "oops/fieldStreams.inline.hpp"
  47 #include "oops/klassVtable.hpp"
  48 #include "oops/oop.inline.hpp"
  49 #include "oops/recordComponent.hpp"
  50 #include "prims/jvmtiImpl.hpp"
  51 #include "prims/jvmtiRedefineClasses.hpp"
  52 #include "prims/jvmtiThreadState.inline.hpp"
  53 #include "prims/resolvedMethodTable.hpp"
  54 #include "prims/methodComparator.hpp"
  55 #include "runtime/atomic.hpp"
  56 #include "runtime/deoptimization.hpp"
  57 #include "runtime/handles.inline.hpp"
  58 #include "runtime/jniHandles.inline.hpp"
  59 #include "runtime/relocator.hpp"
  60 #include "runtime/safepointVerifiers.hpp"
  61 #include "utilities/bitMap.inline.hpp"
  62 #include "utilities/events.hpp"
  63 
  64 Array<Method*>* VM_RedefineClasses::_old_methods = NULL;
  65 Array<Method*>* VM_RedefineClasses::_new_methods = NULL;
  66 Method**  VM_RedefineClasses::_matching_old_methods = NULL;
  67 Method**  VM_RedefineClasses::_matching_new_methods = NULL;
  68 Method**  VM_RedefineClasses::_deleted_methods      = NULL;
  69 Method**  VM_RedefineClasses::_added_methods        = NULL;
  70 int       VM_RedefineClasses::_matching_methods_length = 0;
  71 int       VM_RedefineClasses::_deleted_methods_length  = 0;
  72 int       VM_RedefineClasses::_added_methods_length    = 0;
  73 bool      VM_RedefineClasses::_has_redefined_Object = false;
  74 bool      VM_RedefineClasses::_has_null_class_loader = false;
  75 u8        VM_RedefineClasses::_id_counter = 0;
  76 
  77 VM_RedefineClasses::VM_RedefineClasses(jint class_count,
  78                                        const jvmtiClassDefinition *class_defs,
  79                                        JvmtiClassLoadKind class_load_kind) {
  80   _class_count = class_count;
  81   _class_defs = class_defs;
  82   _class_load_kind = class_load_kind;
  83   _any_class_has_resolved_methods = false;
  84   _res = JVMTI_ERROR_NONE;
  85   _the_class = NULL;
  86   _has_redefined_Object = false;
  87   _has_null_class_loader = false;
  88   _id = next_id();
  89 }
  90 
  91 static inline InstanceKlass* get_ik(jclass def) {
  92   oop mirror = JNIHandles::resolve_non_null(def);
  93   return InstanceKlass::cast(java_lang_Class::as_Klass(mirror));
  94 }
  95 
  96 // If any of the classes are being redefined, wait
  97 // Parallel constant pool merging leads to indeterminate constant pools.
  98 void VM_RedefineClasses::lock_classes() {
  99   MonitorLocker ml(RedefineClasses_lock);
 100   bool has_redefined;
 101   do {
 102     has_redefined = false;
 103     // Go through classes each time until none are being redefined.
 104     for (int i = 0; i < _class_count; i++) {
 105       if (get_ik(_class_defs[i].klass)->is_being_redefined()) {
 106         ml.wait();
 107         has_redefined = true;
 108         break;  // for loop
 109       }
 110     }
 111   } while (has_redefined);
 112   for (int i = 0; i < _class_count; i++) {
 113     get_ik(_class_defs[i].klass)->set_is_being_redefined(true);
 114   }
 115   ml.notify_all();
 116 }
 117 
 118 void VM_RedefineClasses::unlock_classes() {
 119   MonitorLocker ml(RedefineClasses_lock);
 120   for (int i = 0; i < _class_count; i++) {
 121     assert(get_ik(_class_defs[i].klass)->is_being_redefined(),
 122            "should be being redefined to get here");
 123     get_ik(_class_defs[i].klass)->set_is_being_redefined(false);
 124   }
 125   ml.notify_all();
 126 }
 127 
 128 bool VM_RedefineClasses::doit_prologue() {
 129   if (_class_count == 0) {
 130     _res = JVMTI_ERROR_NONE;
 131     return false;
 132   }
 133   if (_class_defs == NULL) {
 134     _res = JVMTI_ERROR_NULL_POINTER;
 135     return false;
 136   }
 137 
 138   for (int i = 0; i < _class_count; i++) {
 139     if (_class_defs[i].klass == NULL) {
 140       _res = JVMTI_ERROR_INVALID_CLASS;
 141       return false;
 142     }
 143     if (_class_defs[i].class_byte_count == 0) {
 144       _res = JVMTI_ERROR_INVALID_CLASS_FORMAT;
 145       return false;
 146     }
 147     if (_class_defs[i].class_bytes == NULL) {
 148       _res = JVMTI_ERROR_NULL_POINTER;
 149       return false;
 150     }
 151 
 152     oop mirror = JNIHandles::resolve_non_null(_class_defs[i].klass);
 153     // classes for primitives and arrays and vm unsafe anonymous classes cannot be redefined
 154     // check here so following code can assume these classes are InstanceKlass
 155     if (!is_modifiable_class(mirror)) {
 156       _res = JVMTI_ERROR_UNMODIFIABLE_CLASS;
 157       return false;
 158     }
 159   }
 160 
 161   // Start timer after all the sanity checks; not quite accurate, but
 162   // better than adding a bunch of stop() calls.
 163   if (log_is_enabled(Info, redefine, class, timer)) {
 164     _timer_vm_op_prologue.start();
 165   }
 166 
 167   lock_classes();
 168   // We first load new class versions in the prologue, because somewhere down the
 169   // call chain it is required that the current thread is a Java thread.
 170   _res = load_new_class_versions(Thread::current());
 171   if (_res != JVMTI_ERROR_NONE) {
 172     // free any successfully created classes, since none are redefined
 173     for (int i = 0; i < _class_count; i++) {
 174       if (_scratch_classes[i] != NULL) {
 175         ClassLoaderData* cld = _scratch_classes[i]->class_loader_data();
 176         // Free the memory for this class at class unloading time.  Not before
 177         // because CMS might think this is still live.
 178         InstanceKlass* ik = get_ik(_class_defs[i].klass);
 179         if (ik->get_cached_class_file() == _scratch_classes[i]->get_cached_class_file()) {
 180           // Don't double-free cached_class_file copied from the original class if error.
 181           _scratch_classes[i]->set_cached_class_file(NULL);
 182         }
 183         cld->add_to_deallocate_list(InstanceKlass::cast(_scratch_classes[i]));
 184       }
 185     }
 186     // Free os::malloc allocated memory in load_new_class_version.
 187     os::free(_scratch_classes);
 188     _timer_vm_op_prologue.stop();
 189     unlock_classes();
 190     return false;
 191   }
 192 
 193   _timer_vm_op_prologue.stop();
 194   return true;
 195 }
 196 
 197 void VM_RedefineClasses::doit() {
 198   Thread *thread = Thread::current();
 199 
 200 #if INCLUDE_CDS
 201   if (UseSharedSpaces) {
 202     // Sharing is enabled so we remap the shared readonly space to
 203     // shared readwrite, private just in case we need to redefine
 204     // a shared class. We do the remap during the doit() phase of
 205     // the safepoint to be safer.
 206     if (!MetaspaceShared::remap_shared_readonly_as_readwrite()) {
 207       log_info(redefine, class, load)("failed to remap shared readonly space to readwrite, private");
 208       _res = JVMTI_ERROR_INTERNAL;
 209       return;
 210     }
 211   }
 212 #endif
 213 
 214   // Mark methods seen on stack and everywhere else so old methods are not
 215   // cleaned up if they're on the stack.
 216   MetadataOnStackMark md_on_stack(/*walk_all_metadata*/true, /*redefinition_walk*/true);
 217   HandleMark hm(thread);   // make sure any handles created are deleted
 218                            // before the stack walk again.
 219 
 220   for (int i = 0; i < _class_count; i++) {
 221     redefine_single_class(_class_defs[i].klass, _scratch_classes[i], thread);
 222   }
 223 
 224   // Flush all compiled code that depends on the classes redefined.
 225   flush_dependent_code();
 226 
 227   // Adjust constantpool caches and vtables for all classes
 228   // that reference methods of the evolved classes.
 229   // Have to do this after all classes are redefined and all methods that
 230   // are redefined are marked as old.
 231   AdjustAndCleanMetadata adjust_and_clean_metadata(thread);
 232   ClassLoaderDataGraph::classes_do(&adjust_and_clean_metadata);
 233 
 234   // JSR-292 support
 235   if (_any_class_has_resolved_methods) {
 236     bool trace_name_printed = false;
 237     ResolvedMethodTable::adjust_method_entries(&trace_name_printed);
 238   }
 239 
 240   // Increment flag indicating that some invariants are no longer true.
 241   // See jvmtiExport.hpp for detailed explanation.
 242   JvmtiExport::increment_redefinition_count();
 243 
 244   // check_class() is optionally called for product bits, but is
 245   // always called for non-product bits.
 246 #ifdef PRODUCT
 247   if (log_is_enabled(Trace, redefine, class, obsolete, metadata)) {
 248 #endif
 249     log_trace(redefine, class, obsolete, metadata)("calling check_class");
 250     CheckClass check_class(thread);
 251     ClassLoaderDataGraph::classes_do(&check_class);
 252 #ifdef PRODUCT
 253   }
 254 #endif
 255 
 256   // Clean up any metadata now unreferenced while MetadataOnStackMark is set.
 257   ClassLoaderDataGraph::clean_deallocate_lists(false);
 258 }
 259 
 260 void VM_RedefineClasses::doit_epilogue() {
 261   unlock_classes();
 262 
 263   // Free os::malloc allocated memory.
 264   os::free(_scratch_classes);
 265 
 266   // Reset the_class to null for error printing.
 267   _the_class = NULL;
 268 
 269   if (log_is_enabled(Info, redefine, class, timer)) {
 270     // Used to have separate timers for "doit" and "all", but the timer
 271     // overhead skewed the measurements.
 272     julong doit_time = _timer_rsc_phase1.milliseconds() +
 273                        _timer_rsc_phase2.milliseconds();
 274     julong all_time = _timer_vm_op_prologue.milliseconds() + doit_time;
 275 
 276     log_info(redefine, class, timer)
 277       ("vm_op: all=" JULONG_FORMAT "  prologue=" JULONG_FORMAT "  doit=" JULONG_FORMAT,
 278        all_time, (julong)_timer_vm_op_prologue.milliseconds(), doit_time);
 279     log_info(redefine, class, timer)
 280       ("redefine_single_class: phase1=" JULONG_FORMAT "  phase2=" JULONG_FORMAT,
 281        (julong)_timer_rsc_phase1.milliseconds(), (julong)_timer_rsc_phase2.milliseconds());
 282   }
 283 }
 284 
 285 bool VM_RedefineClasses::is_modifiable_class(oop klass_mirror) {
 286   // classes for primitives cannot be redefined
 287   if (java_lang_Class::is_primitive(klass_mirror)) {
 288     return false;
 289   }
 290   Klass* k = java_lang_Class::as_Klass(klass_mirror);
 291   // classes for arrays cannot be redefined
 292   if (k == NULL || !k->is_instance_klass()) {
 293     return false;
 294   }
 295 
 296   // Cannot redefine or retransform an unsafe anonymous class.
 297   if (InstanceKlass::cast(k)->is_unsafe_anonymous()) {
 298     return false;
 299   }
 300   return true;
 301 }
 302 
 303 // Append the current entry at scratch_i in scratch_cp to *merge_cp_p
 304 // where the end of *merge_cp_p is specified by *merge_cp_length_p. For
 305 // direct CP entries, there is just the current entry to append. For
 306 // indirect and double-indirect CP entries, there are zero or more
 307 // referenced CP entries along with the current entry to append.
 308 // Indirect and double-indirect CP entries are handled by recursive
 309 // calls to append_entry() as needed. The referenced CP entries are
 310 // always appended to *merge_cp_p before the referee CP entry. These
 311 // referenced CP entries may already exist in *merge_cp_p in which case
 312 // there is nothing extra to append and only the current entry is
 313 // appended.
 314 void VM_RedefineClasses::append_entry(const constantPoolHandle& scratch_cp,
 315        int scratch_i, constantPoolHandle *merge_cp_p, int *merge_cp_length_p,
 316        TRAPS) {
 317 
 318   // append is different depending on entry tag type
 319   switch (scratch_cp->tag_at(scratch_i).value()) {
 320 
 321     // The old verifier is implemented outside the VM. It loads classes,
 322     // but does not resolve constant pool entries directly so we never
 323     // see Class entries here with the old verifier. Similarly the old
 324     // verifier does not like Class entries in the input constant pool.
 325     // The split-verifier is implemented in the VM so it can optionally
 326     // and directly resolve constant pool entries to load classes. The
 327     // split-verifier can accept either Class entries or UnresolvedClass
 328     // entries in the input constant pool. We revert the appended copy
 329     // back to UnresolvedClass so that either verifier will be happy
 330     // with the constant pool entry.
 331     //
 332     // this is an indirect CP entry so it needs special handling
 333     case JVM_CONSTANT_Class:
 334     case JVM_CONSTANT_UnresolvedClass:
 335     {
 336       int name_i = scratch_cp->klass_name_index_at(scratch_i);
 337       int new_name_i = find_or_append_indirect_entry(scratch_cp, name_i, merge_cp_p,
 338                                                      merge_cp_length_p, THREAD);
 339 
 340       if (new_name_i != name_i) {
 341         log_trace(redefine, class, constantpool)
 342           ("Class entry@%d name_index change: %d to %d",
 343            *merge_cp_length_p, name_i, new_name_i);
 344       }
 345 
 346       (*merge_cp_p)->temp_unresolved_klass_at_put(*merge_cp_length_p, new_name_i);
 347       if (scratch_i != *merge_cp_length_p) {
 348         // The new entry in *merge_cp_p is at a different index than
 349         // the new entry in scratch_cp so we need to map the index values.
 350         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 351       }
 352       (*merge_cp_length_p)++;
 353     } break;
 354 
 355     // these are direct CP entries so they can be directly appended,
 356     // but double and long take two constant pool entries
 357     case JVM_CONSTANT_Double:  // fall through
 358     case JVM_CONSTANT_Long:
 359     {
 360       ConstantPool::copy_entry_to(scratch_cp, scratch_i, *merge_cp_p, *merge_cp_length_p,
 361         THREAD);
 362 
 363       if (scratch_i != *merge_cp_length_p) {
 364         // The new entry in *merge_cp_p is at a different index than
 365         // the new entry in scratch_cp so we need to map the index values.
 366         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 367       }
 368       (*merge_cp_length_p) += 2;
 369     } break;
 370 
 371     // these are direct CP entries so they can be directly appended
 372     case JVM_CONSTANT_Float:   // fall through
 373     case JVM_CONSTANT_Integer: // fall through
 374     case JVM_CONSTANT_Utf8:    // fall through
 375 
 376     // This was an indirect CP entry, but it has been changed into
 377     // Symbol*s so this entry can be directly appended.
 378     case JVM_CONSTANT_String:      // fall through
 379     {
 380       ConstantPool::copy_entry_to(scratch_cp, scratch_i, *merge_cp_p, *merge_cp_length_p,
 381         THREAD);
 382 
 383       if (scratch_i != *merge_cp_length_p) {
 384         // The new entry in *merge_cp_p is at a different index than
 385         // the new entry in scratch_cp so we need to map the index values.
 386         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 387       }
 388       (*merge_cp_length_p)++;
 389     } break;
 390 
 391     // this is an indirect CP entry so it needs special handling
 392     case JVM_CONSTANT_NameAndType:
 393     {
 394       int name_ref_i = scratch_cp->name_ref_index_at(scratch_i);
 395       int new_name_ref_i = find_or_append_indirect_entry(scratch_cp, name_ref_i, merge_cp_p,
 396                                                          merge_cp_length_p, THREAD);
 397 
 398       int signature_ref_i = scratch_cp->signature_ref_index_at(scratch_i);
 399       int new_signature_ref_i = find_or_append_indirect_entry(scratch_cp, signature_ref_i,
 400                                                               merge_cp_p, merge_cp_length_p,
 401                                                               THREAD);
 402 
 403       // If the referenced entries already exist in *merge_cp_p, then
 404       // both new_name_ref_i and new_signature_ref_i will both be 0.
 405       // In that case, all we are appending is the current entry.
 406       if (new_name_ref_i != name_ref_i) {
 407         log_trace(redefine, class, constantpool)
 408           ("NameAndType entry@%d name_ref_index change: %d to %d",
 409            *merge_cp_length_p, name_ref_i, new_name_ref_i);
 410       }
 411       if (new_signature_ref_i != signature_ref_i) {
 412         log_trace(redefine, class, constantpool)
 413           ("NameAndType entry@%d signature_ref_index change: %d to %d",
 414            *merge_cp_length_p, signature_ref_i, new_signature_ref_i);
 415       }
 416 
 417       (*merge_cp_p)->name_and_type_at_put(*merge_cp_length_p,
 418         new_name_ref_i, new_signature_ref_i);
 419       if (scratch_i != *merge_cp_length_p) {
 420         // The new entry in *merge_cp_p is at a different index than
 421         // the new entry in scratch_cp so we need to map the index values.
 422         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 423       }
 424       (*merge_cp_length_p)++;
 425     } break;
 426 
 427     // this is a double-indirect CP entry so it needs special handling
 428     case JVM_CONSTANT_Fieldref:           // fall through
 429     case JVM_CONSTANT_InterfaceMethodref: // fall through
 430     case JVM_CONSTANT_Methodref:
 431     {
 432       int klass_ref_i = scratch_cp->uncached_klass_ref_index_at(scratch_i);
 433       int new_klass_ref_i = find_or_append_indirect_entry(scratch_cp, klass_ref_i,
 434                                                           merge_cp_p, merge_cp_length_p, THREAD);
 435 
 436       int name_and_type_ref_i = scratch_cp->uncached_name_and_type_ref_index_at(scratch_i);
 437       int new_name_and_type_ref_i = find_or_append_indirect_entry(scratch_cp, name_and_type_ref_i,
 438                                                           merge_cp_p, merge_cp_length_p, THREAD);
 439 
 440       const char *entry_name = NULL;
 441       switch (scratch_cp->tag_at(scratch_i).value()) {
 442       case JVM_CONSTANT_Fieldref:
 443         entry_name = "Fieldref";
 444         (*merge_cp_p)->field_at_put(*merge_cp_length_p, new_klass_ref_i,
 445           new_name_and_type_ref_i);
 446         break;
 447       case JVM_CONSTANT_InterfaceMethodref:
 448         entry_name = "IFMethodref";
 449         (*merge_cp_p)->interface_method_at_put(*merge_cp_length_p,
 450           new_klass_ref_i, new_name_and_type_ref_i);
 451         break;
 452       case JVM_CONSTANT_Methodref:
 453         entry_name = "Methodref";
 454         (*merge_cp_p)->method_at_put(*merge_cp_length_p, new_klass_ref_i,
 455           new_name_and_type_ref_i);
 456         break;
 457       default:
 458         guarantee(false, "bad switch");
 459         break;
 460       }
 461 
 462       if (klass_ref_i != new_klass_ref_i) {
 463         log_trace(redefine, class, constantpool)
 464           ("%s entry@%d class_index changed: %d to %d", entry_name, *merge_cp_length_p, klass_ref_i, new_klass_ref_i);
 465       }
 466       if (name_and_type_ref_i != new_name_and_type_ref_i) {
 467         log_trace(redefine, class, constantpool)
 468           ("%s entry@%d name_and_type_index changed: %d to %d",
 469            entry_name, *merge_cp_length_p, name_and_type_ref_i, new_name_and_type_ref_i);
 470       }
 471 
 472       if (scratch_i != *merge_cp_length_p) {
 473         // The new entry in *merge_cp_p is at a different index than
 474         // the new entry in scratch_cp so we need to map the index values.
 475         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 476       }
 477       (*merge_cp_length_p)++;
 478     } break;
 479 
 480     // this is an indirect CP entry so it needs special handling
 481     case JVM_CONSTANT_MethodType:
 482     {
 483       int ref_i = scratch_cp->method_type_index_at(scratch_i);
 484       int new_ref_i = find_or_append_indirect_entry(scratch_cp, ref_i, merge_cp_p,
 485                                                     merge_cp_length_p, THREAD);
 486       if (new_ref_i != ref_i) {
 487         log_trace(redefine, class, constantpool)
 488           ("MethodType entry@%d ref_index change: %d to %d", *merge_cp_length_p, ref_i, new_ref_i);
 489       }
 490       (*merge_cp_p)->method_type_index_at_put(*merge_cp_length_p, new_ref_i);
 491       if (scratch_i != *merge_cp_length_p) {
 492         // The new entry in *merge_cp_p is at a different index than
 493         // the new entry in scratch_cp so we need to map the index values.
 494         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 495       }
 496       (*merge_cp_length_p)++;
 497     } break;
 498 
 499     // this is an indirect CP entry so it needs special handling
 500     case JVM_CONSTANT_MethodHandle:
 501     {
 502       int ref_kind = scratch_cp->method_handle_ref_kind_at(scratch_i);
 503       int ref_i = scratch_cp->method_handle_index_at(scratch_i);
 504       int new_ref_i = find_or_append_indirect_entry(scratch_cp, ref_i, merge_cp_p,
 505                                                     merge_cp_length_p, THREAD);
 506       if (new_ref_i != ref_i) {
 507         log_trace(redefine, class, constantpool)
 508           ("MethodHandle entry@%d ref_index change: %d to %d", *merge_cp_length_p, ref_i, new_ref_i);
 509       }
 510       (*merge_cp_p)->method_handle_index_at_put(*merge_cp_length_p, ref_kind, new_ref_i);
 511       if (scratch_i != *merge_cp_length_p) {
 512         // The new entry in *merge_cp_p is at a different index than
 513         // the new entry in scratch_cp so we need to map the index values.
 514         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 515       }
 516       (*merge_cp_length_p)++;
 517     } break;
 518 
 519     // this is an indirect CP entry so it needs special handling
 520     case JVM_CONSTANT_Dynamic:  // fall through
 521     case JVM_CONSTANT_InvokeDynamic:
 522     {
 523       // Index of the bootstrap specifier in the operands array
 524       int old_bs_i = scratch_cp->bootstrap_methods_attribute_index(scratch_i);
 525       int new_bs_i = find_or_append_operand(scratch_cp, old_bs_i, merge_cp_p,
 526                                             merge_cp_length_p, THREAD);
 527       // The bootstrap method NameAndType_info index
 528       int old_ref_i = scratch_cp->bootstrap_name_and_type_ref_index_at(scratch_i);
 529       int new_ref_i = find_or_append_indirect_entry(scratch_cp, old_ref_i, merge_cp_p,
 530                                                     merge_cp_length_p, THREAD);
 531       if (new_bs_i != old_bs_i) {
 532         log_trace(redefine, class, constantpool)
 533           ("Dynamic entry@%d bootstrap_method_attr_index change: %d to %d",
 534            *merge_cp_length_p, old_bs_i, new_bs_i);
 535       }
 536       if (new_ref_i != old_ref_i) {
 537         log_trace(redefine, class, constantpool)
 538           ("Dynamic entry@%d name_and_type_index change: %d to %d", *merge_cp_length_p, old_ref_i, new_ref_i);
 539       }
 540 
 541       if (scratch_cp->tag_at(scratch_i).is_dynamic_constant())
 542         (*merge_cp_p)->dynamic_constant_at_put(*merge_cp_length_p, new_bs_i, new_ref_i);
 543       else
 544         (*merge_cp_p)->invoke_dynamic_at_put(*merge_cp_length_p, new_bs_i, new_ref_i);
 545       if (scratch_i != *merge_cp_length_p) {
 546         // The new entry in *merge_cp_p is at a different index than
 547         // the new entry in scratch_cp so we need to map the index values.
 548         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 549       }
 550       (*merge_cp_length_p)++;
 551     } break;
 552 
 553     // At this stage, Class or UnresolvedClass could be in scratch_cp, but not
 554     // ClassIndex
 555     case JVM_CONSTANT_ClassIndex: // fall through
 556 
 557     // Invalid is used as the tag for the second constant pool entry
 558     // occupied by JVM_CONSTANT_Double or JVM_CONSTANT_Long. It should
 559     // not be seen by itself.
 560     case JVM_CONSTANT_Invalid: // fall through
 561 
 562     // At this stage, String could be here, but not StringIndex
 563     case JVM_CONSTANT_StringIndex: // fall through
 564 
 565     // At this stage JVM_CONSTANT_UnresolvedClassInError should not be
 566     // here
 567     case JVM_CONSTANT_UnresolvedClassInError: // fall through
 568 
 569     default:
 570     {
 571       // leave a breadcrumb
 572       jbyte bad_value = scratch_cp->tag_at(scratch_i).value();
 573       ShouldNotReachHere();
 574     } break;
 575   } // end switch tag value
 576 } // end append_entry()
 577 
 578 
 579 int VM_RedefineClasses::find_or_append_indirect_entry(const constantPoolHandle& scratch_cp,
 580       int ref_i, constantPoolHandle *merge_cp_p, int *merge_cp_length_p, TRAPS) {
 581 
 582   int new_ref_i = ref_i;
 583   bool match = (ref_i < *merge_cp_length_p) &&
 584                scratch_cp->compare_entry_to(ref_i, *merge_cp_p, ref_i, THREAD);
 585 
 586   if (!match) {
 587     // forward reference in *merge_cp_p or not a direct match
 588     int found_i = scratch_cp->find_matching_entry(ref_i, *merge_cp_p, THREAD);
 589     if (found_i != 0) {
 590       guarantee(found_i != ref_i, "compare_entry_to() and find_matching_entry() do not agree");
 591       // Found a matching entry somewhere else in *merge_cp_p so just need a mapping entry.
 592       new_ref_i = found_i;
 593       map_index(scratch_cp, ref_i, found_i);
 594     } else {
 595       // no match found so we have to append this entry to *merge_cp_p
 596       append_entry(scratch_cp, ref_i, merge_cp_p, merge_cp_length_p, THREAD);
 597       // The above call to append_entry() can only append one entry
 598       // so the post call query of *merge_cp_length_p is only for
 599       // the sake of consistency.
 600       new_ref_i = *merge_cp_length_p - 1;
 601     }
 602   }
 603 
 604   return new_ref_i;
 605 } // end find_or_append_indirect_entry()
 606 
 607 
 608 // Append a bootstrap specifier into the merge_cp operands that is semantically equal
 609 // to the scratch_cp operands bootstrap specifier passed by the old_bs_i index.
 610 // Recursively append new merge_cp entries referenced by the new bootstrap specifier.
 611 void VM_RedefineClasses::append_operand(const constantPoolHandle& scratch_cp, int old_bs_i,
 612        constantPoolHandle *merge_cp_p, int *merge_cp_length_p, TRAPS) {
 613 
 614   int old_ref_i = scratch_cp->operand_bootstrap_method_ref_index_at(old_bs_i);
 615   int new_ref_i = find_or_append_indirect_entry(scratch_cp, old_ref_i, merge_cp_p,
 616                                                 merge_cp_length_p, THREAD);
 617   if (new_ref_i != old_ref_i) {
 618     log_trace(redefine, class, constantpool)
 619       ("operands entry@%d bootstrap method ref_index change: %d to %d", _operands_cur_length, old_ref_i, new_ref_i);
 620   }
 621 
 622   Array<u2>* merge_ops = (*merge_cp_p)->operands();
 623   int new_bs_i = _operands_cur_length;
 624   // We have _operands_cur_length == 0 when the merge_cp operands is empty yet.
 625   // However, the operand_offset_at(0) was set in the extend_operands() call.
 626   int new_base = (new_bs_i == 0) ? (*merge_cp_p)->operand_offset_at(0)
 627                                  : (*merge_cp_p)->operand_next_offset_at(new_bs_i - 1);
 628   int argc     = scratch_cp->operand_argument_count_at(old_bs_i);
 629 
 630   ConstantPool::operand_offset_at_put(merge_ops, _operands_cur_length, new_base);
 631   merge_ops->at_put(new_base++, new_ref_i);
 632   merge_ops->at_put(new_base++, argc);
 633 
 634   for (int i = 0; i < argc; i++) {
 635     int old_arg_ref_i = scratch_cp->operand_argument_index_at(old_bs_i, i);
 636     int new_arg_ref_i = find_or_append_indirect_entry(scratch_cp, old_arg_ref_i, merge_cp_p,
 637                                                       merge_cp_length_p, THREAD);
 638     merge_ops->at_put(new_base++, new_arg_ref_i);
 639     if (new_arg_ref_i != old_arg_ref_i) {
 640       log_trace(redefine, class, constantpool)
 641         ("operands entry@%d bootstrap method argument ref_index change: %d to %d",
 642          _operands_cur_length, old_arg_ref_i, new_arg_ref_i);
 643     }
 644   }
 645   if (old_bs_i != _operands_cur_length) {
 646     // The bootstrap specifier in *merge_cp_p is at a different index than
 647     // that in scratch_cp so we need to map the index values.
 648     map_operand_index(old_bs_i, new_bs_i);
 649   }
 650   _operands_cur_length++;
 651 } // end append_operand()
 652 
 653 
 654 int VM_RedefineClasses::find_or_append_operand(const constantPoolHandle& scratch_cp,
 655       int old_bs_i, constantPoolHandle *merge_cp_p, int *merge_cp_length_p, TRAPS) {
 656 
 657   int new_bs_i = old_bs_i; // bootstrap specifier index
 658   bool match = (old_bs_i < _operands_cur_length) &&
 659                scratch_cp->compare_operand_to(old_bs_i, *merge_cp_p, old_bs_i, THREAD);
 660 
 661   if (!match) {
 662     // forward reference in *merge_cp_p or not a direct match
 663     int found_i = scratch_cp->find_matching_operand(old_bs_i, *merge_cp_p,
 664                                                     _operands_cur_length, THREAD);
 665     if (found_i != -1) {
 666       guarantee(found_i != old_bs_i, "compare_operand_to() and find_matching_operand() disagree");
 667       // found a matching operand somewhere else in *merge_cp_p so just need a mapping
 668       new_bs_i = found_i;
 669       map_operand_index(old_bs_i, found_i);
 670     } else {
 671       // no match found so we have to append this bootstrap specifier to *merge_cp_p
 672       append_operand(scratch_cp, old_bs_i, merge_cp_p, merge_cp_length_p, THREAD);
 673       new_bs_i = _operands_cur_length - 1;
 674     }
 675   }
 676   return new_bs_i;
 677 } // end find_or_append_operand()
 678 
 679 
 680 void VM_RedefineClasses::finalize_operands_merge(const constantPoolHandle& merge_cp, TRAPS) {
 681   if (merge_cp->operands() == NULL) {
 682     return;
 683   }
 684   // Shrink the merge_cp operands
 685   merge_cp->shrink_operands(_operands_cur_length, CHECK);
 686 
 687   if (log_is_enabled(Trace, redefine, class, constantpool)) {
 688     // don't want to loop unless we are tracing
 689     int count = 0;
 690     for (int i = 1; i < _operands_index_map_p->length(); i++) {
 691       int value = _operands_index_map_p->at(i);
 692       if (value != -1) {
 693         log_trace(redefine, class, constantpool)("operands_index_map[%d]: old=%d new=%d", count, i, value);
 694         count++;
 695       }
 696     }
 697   }
 698   // Clean-up
 699   _operands_index_map_p = NULL;
 700   _operands_cur_length = 0;
 701   _operands_index_map_count = 0;
 702 } // end finalize_operands_merge()
 703 
 704 // Symbol* comparator for qsort
 705 // The caller must have an active ResourceMark.
 706 static int symcmp(const void* a, const void* b) {
 707   char* astr = (*(Symbol**)a)->as_C_string();
 708   char* bstr = (*(Symbol**)b)->as_C_string();
 709   return strcmp(astr, bstr);
 710 }
 711 
 712 static jvmtiError check_nest_attributes(InstanceKlass* the_class,
 713                                         InstanceKlass* scratch_class) {
 714   // Check whether the class NestHost attribute has been changed.
 715   Thread* thread = Thread::current();
 716   ResourceMark rm(thread);
 717   u2 the_nest_host_idx = the_class->nest_host_index();
 718   u2 scr_nest_host_idx = scratch_class->nest_host_index();
 719 
 720   if (the_nest_host_idx != 0 && scr_nest_host_idx != 0) {
 721     Symbol* the_sym = the_class->constants()->klass_name_at(the_nest_host_idx);
 722     Symbol* scr_sym = scratch_class->constants()->klass_name_at(scr_nest_host_idx);
 723     if (the_sym != scr_sym) {
 724       log_trace(redefine, class, nestmates)
 725         ("redefined class %s attribute change error: NestHost class: %s replaced with: %s",
 726          the_class->external_name(), the_sym->as_C_string(), scr_sym->as_C_string());
 727       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
 728     }
 729   } else if ((the_nest_host_idx == 0) ^ (scr_nest_host_idx == 0)) {
 730     const char* action_str = (the_nest_host_idx != 0) ? "removed" : "added";
 731     log_trace(redefine, class, nestmates)
 732       ("redefined class %s attribute change error: NestHost attribute %s",
 733        the_class->external_name(), action_str);
 734     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
 735   }
 736 
 737   // Check whether the class NestMembers attribute has been changed.
 738   Array<u2>* the_nest_members = the_class->nest_members();
 739   Array<u2>* scr_nest_members = scratch_class->nest_members();
 740   bool the_members_exists = the_nest_members != Universe::the_empty_short_array();
 741   bool scr_members_exists = scr_nest_members != Universe::the_empty_short_array();
 742 
 743   int members_len = the_nest_members->length();
 744   if (the_members_exists && scr_members_exists) {
 745     if (members_len != scr_nest_members->length()) {
 746       log_trace(redefine, class, nestmates)
 747         ("redefined class %s attribute change error: NestMember len=%d changed to len=%d",
 748          the_class->external_name(), members_len, scr_nest_members->length());
 749       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
 750     }
 751 
 752     // The order of entries in the NestMembers array is not specified so we
 753     // have to explicitly check for the same contents. We do this by copying
 754     // the referenced symbols into their own arrays, sorting them and then
 755     // comparing each element pair.
 756 
 757     Symbol** the_syms = NEW_RESOURCE_ARRAY_RETURN_NULL(Symbol*, members_len);
 758     Symbol** scr_syms = NEW_RESOURCE_ARRAY_RETURN_NULL(Symbol*, members_len);
 759 
 760     if (the_syms == NULL || scr_syms == NULL) {
 761       return JVMTI_ERROR_OUT_OF_MEMORY;
 762     }
 763 
 764     for (int i = 0; i < members_len; i++) {
 765       int the_cp_index = the_nest_members->at(i);
 766       int scr_cp_index = scr_nest_members->at(i);
 767       the_syms[i] = the_class->constants()->klass_name_at(the_cp_index);
 768       scr_syms[i] = scratch_class->constants()->klass_name_at(scr_cp_index);
 769     }
 770 
 771     qsort(the_syms, members_len, sizeof(Symbol*), symcmp);
 772     qsort(scr_syms, members_len, sizeof(Symbol*), symcmp);
 773 
 774     for (int i = 0; i < members_len; i++) {
 775       if (the_syms[i] != scr_syms[i]) {
 776         log_trace(redefine, class, nestmates)
 777           ("redefined class %s attribute change error: NestMembers[%d]: %s changed to %s",
 778            the_class->external_name(), i, the_syms[i]->as_C_string(), scr_syms[i]->as_C_string());
 779         return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
 780       }
 781     }
 782   } else if (the_members_exists ^ scr_members_exists) {
 783     const char* action_str = (the_members_exists) ? "removed" : "added";
 784     log_trace(redefine, class, nestmates)
 785       ("redefined class %s attribute change error: NestMembers attribute %s",
 786        the_class->external_name(), action_str);
 787     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
 788   }
 789 
 790   return JVMTI_ERROR_NONE;
 791 }
 792 
 793 // Return an error status if the class Record attribute was changed.
 794 static jvmtiError check_record_attribute(InstanceKlass* the_class, InstanceKlass* scratch_class) {
 795   // Get lists of record components.
 796   Array<RecordComponent*>* the_record = the_class->record_components();
 797   Array<RecordComponent*>* scr_record = scratch_class->record_components();
 798   bool the_record_exists = the_record != NULL;
 799   bool scr_record_exists = scr_record != NULL;
 800 
 801   if (the_record_exists && scr_record_exists) {
 802     int the_num_components = the_record->length();
 803     int scr_num_components = scr_record->length();
 804     if (the_num_components != scr_num_components) {
 805       log_trace(redefine, class, record)
 806         ("redefined class %s attribute change error: Record num_components=%d changed to num_components=%d",
 807          the_class->external_name(), the_num_components, scr_num_components);
 808       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
 809     }
 810 
 811     // Compare each field in each record component.
 812     ConstantPool* the_cp =  the_class->constants();
 813     ConstantPool* scr_cp =  scratch_class->constants();
 814     for (int x = 0; x < the_num_components; x++) {
 815       RecordComponent* the_component = the_record->at(x);
 816       RecordComponent* scr_component = scr_record->at(x);
 817       const Symbol* const the_name = the_cp->symbol_at(the_component->name_index());
 818       const Symbol* const scr_name = scr_cp->symbol_at(scr_component->name_index());
 819       const Symbol* const the_descr = the_cp->symbol_at(the_component->descriptor_index());
 820       const Symbol* const scr_descr = scr_cp->symbol_at(scr_component->descriptor_index());
 821       if (the_name != scr_name || the_descr != scr_descr) {
 822         log_trace(redefine, class, record)
 823           ("redefined class %s attribute change error: Record name_index, descriptor_index, and/or attributes_count changed",
 824            the_class->external_name());
 825         return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
 826       }
 827 
 828       int the_gen_sig = the_component->generic_signature_index();
 829       int scr_gen_sig = scr_component->generic_signature_index();
 830       const Symbol* const the_gen_sig_sym = (the_gen_sig == 0 ? NULL :
 831         the_cp->symbol_at(the_component->generic_signature_index()));
 832       const Symbol* const scr_gen_sig_sym = (scr_gen_sig == 0 ? NULL :
 833         scr_cp->symbol_at(scr_component->generic_signature_index()));
 834       if (the_gen_sig_sym != scr_gen_sig_sym) {
 835         log_trace(redefine, class, record)
 836           ("redefined class %s attribute change error: Record generic_signature attribute changed",
 837            the_class->external_name());
 838         return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
 839       }
 840 
 841       // It's okay if a record component's annotations were changed.
 842     }
 843 
 844   } else if (the_record_exists ^ scr_record_exists) {
 845     const char* action_str = (the_record_exists) ? "removed" : "added";
 846     log_trace(redefine, class, record)
 847       ("redefined class %s attribute change error: Record attribute %s",
 848        the_class->external_name(), action_str);
 849     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
 850   }
 851 
 852   return JVMTI_ERROR_NONE;
 853 }
 854 
 855 
 856 static bool can_add_or_delete(Method* m) {
 857       // Compatibility mode
 858   return (AllowRedefinitionToAddDeleteMethods &&
 859           (m->is_private() && (m->is_static() || m->is_final())));
 860 }
 861 
 862 jvmtiError VM_RedefineClasses::compare_and_normalize_class_versions(
 863              InstanceKlass* the_class,
 864              InstanceKlass* scratch_class) {
 865   int i;
 866 
 867   // Check superclasses, or rather their names, since superclasses themselves can be
 868   // requested to replace.
 869   // Check for NULL superclass first since this might be java.lang.Object
 870   if (the_class->super() != scratch_class->super() &&
 871       (the_class->super() == NULL || scratch_class->super() == NULL ||
 872        the_class->super()->name() !=
 873        scratch_class->super()->name())) {
 874     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_HIERARCHY_CHANGED;
 875   }
 876 
 877   // Check if the number, names and order of directly implemented interfaces are the same.
 878   // I think in principle we should just check if the sets of names of directly implemented
 879   // interfaces are the same, i.e. the order of declaration (which, however, if changed in the
 880   // .java file, also changes in .class file) should not matter. However, comparing sets is
 881   // technically a bit more difficult, and, more importantly, I am not sure at present that the
 882   // order of interfaces does not matter on the implementation level, i.e. that the VM does not
 883   // rely on it somewhere.
 884   Array<InstanceKlass*>* k_interfaces = the_class->local_interfaces();
 885   Array<InstanceKlass*>* k_new_interfaces = scratch_class->local_interfaces();
 886   int n_intfs = k_interfaces->length();
 887   if (n_intfs != k_new_interfaces->length()) {
 888     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_HIERARCHY_CHANGED;
 889   }
 890   for (i = 0; i < n_intfs; i++) {
 891     if (k_interfaces->at(i)->name() !=
 892         k_new_interfaces->at(i)->name()) {
 893       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_HIERARCHY_CHANGED;
 894     }
 895   }
 896 
 897   // Check whether class is in the error init state.
 898   if (the_class->is_in_error_state()) {
 899     // TBD #5057930: special error code is needed in 1.6
 900     return JVMTI_ERROR_INVALID_CLASS;
 901   }
 902 
 903   // Check whether the nest-related attributes have been changed.
 904   jvmtiError err = check_nest_attributes(the_class, scratch_class);
 905   if (err != JVMTI_ERROR_NONE) {
 906     return err;
 907   }
 908 
 909   // Check whether the Record attribute has been changed.
 910   err = check_record_attribute(the_class, scratch_class);
 911   if (err != JVMTI_ERROR_NONE) {
 912     return err;
 913   }
 914 
 915   // Check whether class modifiers are the same.
 916   jushort old_flags = (jushort) the_class->access_flags().get_flags();
 917   jushort new_flags = (jushort) scratch_class->access_flags().get_flags();
 918   if (old_flags != new_flags) {
 919     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_MODIFIERS_CHANGED;
 920   }
 921 
 922   // Check if the number, names, types and order of fields declared in these classes
 923   // are the same.
 924   JavaFieldStream old_fs(the_class);
 925   JavaFieldStream new_fs(scratch_class);
 926   for (; !old_fs.done() && !new_fs.done(); old_fs.next(), new_fs.next()) {
 927     // access
 928     old_flags = old_fs.access_flags().as_short();
 929     new_flags = new_fs.access_flags().as_short();
 930     if ((old_flags ^ new_flags) & JVM_RECOGNIZED_FIELD_MODIFIERS) {
 931       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_SCHEMA_CHANGED;
 932     }
 933     // offset
 934     if (old_fs.offset() != new_fs.offset()) {
 935       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_SCHEMA_CHANGED;
 936     }
 937     // name and signature
 938     Symbol* name_sym1 = the_class->constants()->symbol_at(old_fs.name_index());
 939     Symbol* sig_sym1 = the_class->constants()->symbol_at(old_fs.signature_index());
 940     Symbol* name_sym2 = scratch_class->constants()->symbol_at(new_fs.name_index());
 941     Symbol* sig_sym2 = scratch_class->constants()->symbol_at(new_fs.signature_index());
 942     if (name_sym1 != name_sym2 || sig_sym1 != sig_sym2) {
 943       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_SCHEMA_CHANGED;
 944     }
 945   }
 946 
 947   // If both streams aren't done then we have a differing number of
 948   // fields.
 949   if (!old_fs.done() || !new_fs.done()) {
 950     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_SCHEMA_CHANGED;
 951   }
 952 
 953   // Do a parallel walk through the old and new methods. Detect
 954   // cases where they match (exist in both), have been added in
 955   // the new methods, or have been deleted (exist only in the
 956   // old methods).  The class file parser places methods in order
 957   // by method name, but does not order overloaded methods by
 958   // signature.  In order to determine what fate befell the methods,
 959   // this code places the overloaded new methods that have matching
 960   // old methods in the same order as the old methods and places
 961   // new overloaded methods at the end of overloaded methods of
 962   // that name. The code for this order normalization is adapted
 963   // from the algorithm used in InstanceKlass::find_method().
 964   // Since we are swapping out of order entries as we find them,
 965   // we only have to search forward through the overloaded methods.
 966   // Methods which are added and have the same name as an existing
 967   // method (but different signature) will be put at the end of
 968   // the methods with that name, and the name mismatch code will
 969   // handle them.
 970   Array<Method*>* k_old_methods(the_class->methods());
 971   Array<Method*>* k_new_methods(scratch_class->methods());
 972   int n_old_methods = k_old_methods->length();
 973   int n_new_methods = k_new_methods->length();
 974   Thread* thread = Thread::current();
 975 
 976   int ni = 0;
 977   int oi = 0;
 978   while (true) {
 979     Method* k_old_method;
 980     Method* k_new_method;
 981     enum { matched, added, deleted, undetermined } method_was = undetermined;
 982 
 983     if (oi >= n_old_methods) {
 984       if (ni >= n_new_methods) {
 985         break; // we've looked at everything, done
 986       }
 987       // New method at the end
 988       k_new_method = k_new_methods->at(ni);
 989       method_was = added;
 990     } else if (ni >= n_new_methods) {
 991       // Old method, at the end, is deleted
 992       k_old_method = k_old_methods->at(oi);
 993       method_was = deleted;
 994     } else {
 995       // There are more methods in both the old and new lists
 996       k_old_method = k_old_methods->at(oi);
 997       k_new_method = k_new_methods->at(ni);
 998       if (k_old_method->name() != k_new_method->name()) {
 999         // Methods are sorted by method name, so a mismatch means added
1000         // or deleted
1001         if (k_old_method->name()->fast_compare(k_new_method->name()) > 0) {
1002           method_was = added;
1003         } else {
1004           method_was = deleted;
1005         }
1006       } else if (k_old_method->signature() == k_new_method->signature()) {
1007         // Both the name and signature match
1008         method_was = matched;
1009       } else {
1010         // The name matches, but the signature doesn't, which means we have to
1011         // search forward through the new overloaded methods.
1012         int nj;  // outside the loop for post-loop check
1013         for (nj = ni + 1; nj < n_new_methods; nj++) {
1014           Method* m = k_new_methods->at(nj);
1015           if (k_old_method->name() != m->name()) {
1016             // reached another method name so no more overloaded methods
1017             method_was = deleted;
1018             break;
1019           }
1020           if (k_old_method->signature() == m->signature()) {
1021             // found a match so swap the methods
1022             k_new_methods->at_put(ni, m);
1023             k_new_methods->at_put(nj, k_new_method);
1024             k_new_method = m;
1025             method_was = matched;
1026             break;
1027           }
1028         }
1029 
1030         if (nj >= n_new_methods) {
1031           // reached the end without a match; so method was deleted
1032           method_was = deleted;
1033         }
1034       }
1035     }
1036 
1037     switch (method_was) {
1038     case matched:
1039       // methods match, be sure modifiers do too
1040       old_flags = (jushort) k_old_method->access_flags().get_flags();
1041       new_flags = (jushort) k_new_method->access_flags().get_flags();
1042       if ((old_flags ^ new_flags) & ~(JVM_ACC_NATIVE)) {
1043         return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_METHOD_MODIFIERS_CHANGED;
1044       }
1045       {
1046         u2 new_num = k_new_method->method_idnum();
1047         u2 old_num = k_old_method->method_idnum();
1048         if (new_num != old_num) {
1049           Method* idnum_owner = scratch_class->method_with_idnum(old_num);
1050           if (idnum_owner != NULL) {
1051             // There is already a method assigned this idnum -- switch them
1052             // Take current and original idnum from the new_method
1053             idnum_owner->set_method_idnum(new_num);
1054             idnum_owner->set_orig_method_idnum(k_new_method->orig_method_idnum());
1055           }
1056           // Take current and original idnum from the old_method
1057           k_new_method->set_method_idnum(old_num);
1058           k_new_method->set_orig_method_idnum(k_old_method->orig_method_idnum());
1059           if (thread->has_pending_exception()) {
1060             return JVMTI_ERROR_OUT_OF_MEMORY;
1061           }
1062         }
1063       }
1064       log_trace(redefine, class, normalize)
1065         ("Method matched: new: %s [%d] == old: %s [%d]",
1066          k_new_method->name_and_sig_as_C_string(), ni, k_old_method->name_and_sig_as_C_string(), oi);
1067       // advance to next pair of methods
1068       ++oi;
1069       ++ni;
1070       break;
1071     case added:
1072       // method added, see if it is OK
1073       if (!can_add_or_delete(k_new_method)) {
1074         return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_METHOD_ADDED;
1075       }
1076       {
1077         u2 num = the_class->next_method_idnum();
1078         if (num == ConstMethod::UNSET_IDNUM) {
1079           // cannot add any more methods
1080           return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_METHOD_ADDED;
1081         }
1082         u2 new_num = k_new_method->method_idnum();
1083         Method* idnum_owner = scratch_class->method_with_idnum(num);
1084         if (idnum_owner != NULL) {
1085           // There is already a method assigned this idnum -- switch them
1086           // Take current and original idnum from the new_method
1087           idnum_owner->set_method_idnum(new_num);
1088           idnum_owner->set_orig_method_idnum(k_new_method->orig_method_idnum());
1089         }
1090         k_new_method->set_method_idnum(num);
1091         k_new_method->set_orig_method_idnum(num);
1092         if (thread->has_pending_exception()) {
1093           return JVMTI_ERROR_OUT_OF_MEMORY;
1094         }
1095       }
1096       log_trace(redefine, class, normalize)
1097         ("Method added: new: %s [%d]", k_new_method->name_and_sig_as_C_string(), ni);
1098       ++ni; // advance to next new method
1099       break;
1100     case deleted:
1101       // method deleted, see if it is OK
1102       if (!can_add_or_delete(k_old_method)) {
1103         return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_METHOD_DELETED;
1104       }
1105       log_trace(redefine, class, normalize)
1106         ("Method deleted: old: %s [%d]", k_old_method->name_and_sig_as_C_string(), oi);
1107       ++oi; // advance to next old method
1108       break;
1109     default:
1110       ShouldNotReachHere();
1111     }
1112   }
1113 
1114   return JVMTI_ERROR_NONE;
1115 }
1116 
1117 
1118 // Find new constant pool index value for old constant pool index value
1119 // by seaching the index map. Returns zero (0) if there is no mapped
1120 // value for the old constant pool index.
1121 int VM_RedefineClasses::find_new_index(int old_index) {
1122   if (_index_map_count == 0) {
1123     // map is empty so nothing can be found
1124     return 0;
1125   }
1126 
1127   if (old_index < 1 || old_index >= _index_map_p->length()) {
1128     // The old_index is out of range so it is not mapped. This should
1129     // not happen in regular constant pool merging use, but it can
1130     // happen if a corrupt annotation is processed.
1131     return 0;
1132   }
1133 
1134   int value = _index_map_p->at(old_index);
1135   if (value == -1) {
1136     // the old_index is not mapped
1137     return 0;
1138   }
1139 
1140   return value;
1141 } // end find_new_index()
1142 
1143 
1144 // Find new bootstrap specifier index value for old bootstrap specifier index
1145 // value by seaching the index map. Returns unused index (-1) if there is
1146 // no mapped value for the old bootstrap specifier index.
1147 int VM_RedefineClasses::find_new_operand_index(int old_index) {
1148   if (_operands_index_map_count == 0) {
1149     // map is empty so nothing can be found
1150     return -1;
1151   }
1152 
1153   if (old_index == -1 || old_index >= _operands_index_map_p->length()) {
1154     // The old_index is out of range so it is not mapped.
1155     // This should not happen in regular constant pool merging use.
1156     return -1;
1157   }
1158 
1159   int value = _operands_index_map_p->at(old_index);
1160   if (value == -1) {
1161     // the old_index is not mapped
1162     return -1;
1163   }
1164 
1165   return value;
1166 } // end find_new_operand_index()
1167 
1168 
1169 // Returns true if the current mismatch is due to a resolved/unresolved
1170 // class pair. Otherwise, returns false.
1171 bool VM_RedefineClasses::is_unresolved_class_mismatch(const constantPoolHandle& cp1,
1172        int index1, const constantPoolHandle& cp2, int index2) {
1173 
1174   jbyte t1 = cp1->tag_at(index1).value();
1175   if (t1 != JVM_CONSTANT_Class && t1 != JVM_CONSTANT_UnresolvedClass) {
1176     return false;  // wrong entry type; not our special case
1177   }
1178 
1179   jbyte t2 = cp2->tag_at(index2).value();
1180   if (t2 != JVM_CONSTANT_Class && t2 != JVM_CONSTANT_UnresolvedClass) {
1181     return false;  // wrong entry type; not our special case
1182   }
1183 
1184   if (t1 == t2) {
1185     return false;  // not a mismatch; not our special case
1186   }
1187 
1188   char *s1 = cp1->klass_name_at(index1)->as_C_string();
1189   char *s2 = cp2->klass_name_at(index2)->as_C_string();
1190   if (strcmp(s1, s2) != 0) {
1191     return false;  // strings don't match; not our special case
1192   }
1193 
1194   return true;  // made it through the gauntlet; this is our special case
1195 } // end is_unresolved_class_mismatch()
1196 
1197 
1198 jvmtiError VM_RedefineClasses::load_new_class_versions(TRAPS) {
1199 
1200   // For consistency allocate memory using os::malloc wrapper.
1201   _scratch_classes = (InstanceKlass**)
1202     os::malloc(sizeof(InstanceKlass*) * _class_count, mtClass);
1203   if (_scratch_classes == NULL) {
1204     return JVMTI_ERROR_OUT_OF_MEMORY;
1205   }
1206   // Zero initialize the _scratch_classes array.
1207   for (int i = 0; i < _class_count; i++) {
1208     _scratch_classes[i] = NULL;
1209   }
1210 
1211   ResourceMark rm(THREAD);
1212 
1213   JvmtiThreadState *state = JvmtiThreadState::state_for(JavaThread::current());
1214   // state can only be NULL if the current thread is exiting which
1215   // should not happen since we're trying to do a RedefineClasses
1216   guarantee(state != NULL, "exiting thread calling load_new_class_versions");
1217   for (int i = 0; i < _class_count; i++) {
1218     // Create HandleMark so that any handles created while loading new class
1219     // versions are deleted. Constant pools are deallocated while merging
1220     // constant pools
1221     HandleMark hm(THREAD);
1222     InstanceKlass* the_class = get_ik(_class_defs[i].klass);
1223     Symbol*  the_class_sym = the_class->name();
1224 
1225     log_debug(redefine, class, load)
1226       ("loading name=%s kind=%d (avail_mem=" UINT64_FORMAT "K)",
1227        the_class->external_name(), _class_load_kind, os::available_memory() >> 10);
1228 
1229     ClassFileStream st((u1*)_class_defs[i].class_bytes,
1230                        _class_defs[i].class_byte_count,
1231                        "__VM_RedefineClasses__",
1232                        ClassFileStream::verify);
1233 
1234     // Parse the stream.
1235     Handle the_class_loader(THREAD, the_class->class_loader());
1236     Handle protection_domain(THREAD, the_class->protection_domain());
1237     // Set redefined class handle in JvmtiThreadState class.
1238     // This redefined class is sent to agent event handler for class file
1239     // load hook event.
1240     state->set_class_being_redefined(the_class, _class_load_kind);
1241 
1242     InstanceKlass* scratch_class = SystemDictionary::parse_stream(
1243                                                       the_class_sym,
1244                                                       the_class_loader,
1245                                                       protection_domain,
1246                                                       &st,
1247                                                       THREAD);
1248     // Clear class_being_redefined just to be sure.
1249     state->clear_class_being_redefined();
1250 
1251     // TODO: if this is retransform, and nothing changed we can skip it
1252 
1253     // Need to clean up allocated InstanceKlass if there's an error so assign
1254     // the result here. Caller deallocates all the scratch classes in case of
1255     // an error.
1256     _scratch_classes[i] = scratch_class;
1257 
1258     if (HAS_PENDING_EXCEPTION) {
1259       Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1260       log_info(redefine, class, load, exceptions)("parse_stream exception: '%s'", ex_name->as_C_string());
1261       CLEAR_PENDING_EXCEPTION;
1262 
1263       if (ex_name == vmSymbols::java_lang_UnsupportedClassVersionError()) {
1264         return JVMTI_ERROR_UNSUPPORTED_VERSION;
1265       } else if (ex_name == vmSymbols::java_lang_ClassFormatError()) {
1266         return JVMTI_ERROR_INVALID_CLASS_FORMAT;
1267       } else if (ex_name == vmSymbols::java_lang_ClassCircularityError()) {
1268         return JVMTI_ERROR_CIRCULAR_CLASS_DEFINITION;
1269       } else if (ex_name == vmSymbols::java_lang_NoClassDefFoundError()) {
1270         // The message will be "XXX (wrong name: YYY)"
1271         return JVMTI_ERROR_NAMES_DONT_MATCH;
1272       } else if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1273         return JVMTI_ERROR_OUT_OF_MEMORY;
1274       } else {  // Just in case more exceptions can be thrown..
1275         return JVMTI_ERROR_FAILS_VERIFICATION;
1276       }
1277     }
1278 
1279     // Ensure class is linked before redefine
1280     if (!the_class->is_linked()) {
1281       the_class->link_class(THREAD);
1282       if (HAS_PENDING_EXCEPTION) {
1283         Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1284         log_info(redefine, class, load, exceptions)("link_class exception: '%s'", ex_name->as_C_string());
1285         CLEAR_PENDING_EXCEPTION;
1286         if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1287           return JVMTI_ERROR_OUT_OF_MEMORY;
1288         } else {
1289           return JVMTI_ERROR_INTERNAL;
1290         }
1291       }
1292     }
1293 
1294     // Do the validity checks in compare_and_normalize_class_versions()
1295     // before verifying the byte codes. By doing these checks first, we
1296     // limit the number of functions that require redirection from
1297     // the_class to scratch_class. In particular, we don't have to
1298     // modify JNI GetSuperclass() and thus won't change its performance.
1299     jvmtiError res = compare_and_normalize_class_versions(the_class,
1300                        scratch_class);
1301     if (res != JVMTI_ERROR_NONE) {
1302       return res;
1303     }
1304 
1305     // verify what the caller passed us
1306     {
1307       // The bug 6214132 caused the verification to fail.
1308       // Information about the_class and scratch_class is temporarily
1309       // recorded into jvmtiThreadState. This data is used to redirect
1310       // the_class to scratch_class in the JVM_* functions called by the
1311       // verifier. Please, refer to jvmtiThreadState.hpp for the detailed
1312       // description.
1313       RedefineVerifyMark rvm(the_class, scratch_class, state);
1314       Verifier::verify(scratch_class, true, THREAD);
1315     }
1316 
1317     if (HAS_PENDING_EXCEPTION) {
1318       Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1319       log_info(redefine, class, load, exceptions)("verify_byte_codes exception: '%s'", ex_name->as_C_string());
1320       CLEAR_PENDING_EXCEPTION;
1321       if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1322         return JVMTI_ERROR_OUT_OF_MEMORY;
1323       } else {
1324         // tell the caller the bytecodes are bad
1325         return JVMTI_ERROR_FAILS_VERIFICATION;
1326       }
1327     }
1328 
1329     res = merge_cp_and_rewrite(the_class, scratch_class, THREAD);
1330     if (HAS_PENDING_EXCEPTION) {
1331       Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1332       log_info(redefine, class, load, exceptions)("merge_cp_and_rewrite exception: '%s'", ex_name->as_C_string());
1333       CLEAR_PENDING_EXCEPTION;
1334       if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1335         return JVMTI_ERROR_OUT_OF_MEMORY;
1336       } else {
1337         return JVMTI_ERROR_INTERNAL;
1338       }
1339     }
1340 
1341     if (VerifyMergedCPBytecodes) {
1342       // verify what we have done during constant pool merging
1343       {
1344         RedefineVerifyMark rvm(the_class, scratch_class, state);
1345         Verifier::verify(scratch_class, true, THREAD);
1346       }
1347 
1348       if (HAS_PENDING_EXCEPTION) {
1349         Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1350         log_info(redefine, class, load, exceptions)
1351           ("verify_byte_codes post merge-CP exception: '%s'", ex_name->as_C_string());
1352         CLEAR_PENDING_EXCEPTION;
1353         if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1354           return JVMTI_ERROR_OUT_OF_MEMORY;
1355         } else {
1356           // tell the caller that constant pool merging screwed up
1357           return JVMTI_ERROR_INTERNAL;
1358         }
1359       }
1360     }
1361 
1362     Rewriter::rewrite(scratch_class, THREAD);
1363     if (!HAS_PENDING_EXCEPTION) {
1364       scratch_class->link_methods(THREAD);
1365     }
1366     if (HAS_PENDING_EXCEPTION) {
1367       Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1368       log_info(redefine, class, load, exceptions)
1369         ("Rewriter::rewrite or link_methods exception: '%s'", ex_name->as_C_string());
1370       CLEAR_PENDING_EXCEPTION;
1371       if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1372         return JVMTI_ERROR_OUT_OF_MEMORY;
1373       } else {
1374         return JVMTI_ERROR_INTERNAL;
1375       }
1376     }
1377 
1378     log_debug(redefine, class, load)
1379       ("loaded name=%s (avail_mem=" UINT64_FORMAT "K)", the_class->external_name(), os::available_memory() >> 10);
1380   }
1381 
1382   return JVMTI_ERROR_NONE;
1383 }
1384 
1385 
1386 // Map old_index to new_index as needed. scratch_cp is only needed
1387 // for log calls.
1388 void VM_RedefineClasses::map_index(const constantPoolHandle& scratch_cp,
1389        int old_index, int new_index) {
1390   if (find_new_index(old_index) != 0) {
1391     // old_index is already mapped
1392     return;
1393   }
1394 
1395   if (old_index == new_index) {
1396     // no mapping is needed
1397     return;
1398   }
1399 
1400   _index_map_p->at_put(old_index, new_index);
1401   _index_map_count++;
1402 
1403   log_trace(redefine, class, constantpool)
1404     ("mapped tag %d at index %d to %d", scratch_cp->tag_at(old_index).value(), old_index, new_index);
1405 } // end map_index()
1406 
1407 
1408 // Map old_index to new_index as needed.
1409 void VM_RedefineClasses::map_operand_index(int old_index, int new_index) {
1410   if (find_new_operand_index(old_index) != -1) {
1411     // old_index is already mapped
1412     return;
1413   }
1414 
1415   if (old_index == new_index) {
1416     // no mapping is needed
1417     return;
1418   }
1419 
1420   _operands_index_map_p->at_put(old_index, new_index);
1421   _operands_index_map_count++;
1422 
1423   log_trace(redefine, class, constantpool)("mapped bootstrap specifier at index %d to %d", old_index, new_index);
1424 } // end map_index()
1425 
1426 
1427 // Merge old_cp and scratch_cp and return the results of the merge via
1428 // merge_cp_p. The number of entries in *merge_cp_p is returned via
1429 // merge_cp_length_p. The entries in old_cp occupy the same locations
1430 // in *merge_cp_p. Also creates a map of indices from entries in
1431 // scratch_cp to the corresponding entry in *merge_cp_p. Index map
1432 // entries are only created for entries in scratch_cp that occupy a
1433 // different location in *merged_cp_p.
1434 bool VM_RedefineClasses::merge_constant_pools(const constantPoolHandle& old_cp,
1435        const constantPoolHandle& scratch_cp, constantPoolHandle *merge_cp_p,
1436        int *merge_cp_length_p, TRAPS) {
1437 
1438   if (merge_cp_p == NULL) {
1439     assert(false, "caller must provide scratch constantPool");
1440     return false; // robustness
1441   }
1442   if (merge_cp_length_p == NULL) {
1443     assert(false, "caller must provide scratch CP length");
1444     return false; // robustness
1445   }
1446   // Worst case we need old_cp->length() + scratch_cp()->length(),
1447   // but the caller might be smart so make sure we have at least
1448   // the minimum.
1449   if ((*merge_cp_p)->length() < old_cp->length()) {
1450     assert(false, "merge area too small");
1451     return false; // robustness
1452   }
1453 
1454   log_info(redefine, class, constantpool)("old_cp_len=%d, scratch_cp_len=%d", old_cp->length(), scratch_cp->length());
1455 
1456   {
1457     // Pass 0:
1458     // The old_cp is copied to *merge_cp_p; this means that any code
1459     // using old_cp does not have to change. This work looks like a
1460     // perfect fit for ConstantPool*::copy_cp_to(), but we need to
1461     // handle one special case:
1462     // - revert JVM_CONSTANT_Class to JVM_CONSTANT_UnresolvedClass
1463     // This will make verification happy.
1464 
1465     int old_i;  // index into old_cp
1466 
1467     // index zero (0) is not used in constantPools
1468     for (old_i = 1; old_i < old_cp->length(); old_i++) {
1469       // leave debugging crumb
1470       jbyte old_tag = old_cp->tag_at(old_i).value();
1471       switch (old_tag) {
1472       case JVM_CONSTANT_Class:
1473       case JVM_CONSTANT_UnresolvedClass:
1474         // revert the copy to JVM_CONSTANT_UnresolvedClass
1475         // May be resolving while calling this so do the same for
1476         // JVM_CONSTANT_UnresolvedClass (klass_name_at() deals with transition)
1477         (*merge_cp_p)->temp_unresolved_klass_at_put(old_i,
1478           old_cp->klass_name_index_at(old_i));
1479         break;
1480 
1481       case JVM_CONSTANT_Double:
1482       case JVM_CONSTANT_Long:
1483         // just copy the entry to *merge_cp_p, but double and long take
1484         // two constant pool entries
1485         ConstantPool::copy_entry_to(old_cp, old_i, *merge_cp_p, old_i, CHECK_false);
1486         old_i++;
1487         break;
1488 
1489       default:
1490         // just copy the entry to *merge_cp_p
1491         ConstantPool::copy_entry_to(old_cp, old_i, *merge_cp_p, old_i, CHECK_false);
1492         break;
1493       }
1494     } // end for each old_cp entry
1495 
1496     ConstantPool::copy_operands(old_cp, *merge_cp_p, CHECK_false);
1497     (*merge_cp_p)->extend_operands(scratch_cp, CHECK_false);
1498 
1499     // We don't need to sanity check that *merge_cp_length_p is within
1500     // *merge_cp_p bounds since we have the minimum on-entry check above.
1501     (*merge_cp_length_p) = old_i;
1502   }
1503 
1504   // merge_cp_len should be the same as old_cp->length() at this point
1505   // so this trace message is really a "warm-and-breathing" message.
1506   log_debug(redefine, class, constantpool)("after pass 0: merge_cp_len=%d", *merge_cp_length_p);
1507 
1508   int scratch_i;  // index into scratch_cp
1509   {
1510     // Pass 1a:
1511     // Compare scratch_cp entries to the old_cp entries that we have
1512     // already copied to *merge_cp_p. In this pass, we are eliminating
1513     // exact duplicates (matching entry at same index) so we only
1514     // compare entries in the common indice range.
1515     int increment = 1;
1516     int pass1a_length = MIN2(old_cp->length(), scratch_cp->length());
1517     for (scratch_i = 1; scratch_i < pass1a_length; scratch_i += increment) {
1518       switch (scratch_cp->tag_at(scratch_i).value()) {
1519       case JVM_CONSTANT_Double:
1520       case JVM_CONSTANT_Long:
1521         // double and long take two constant pool entries
1522         increment = 2;
1523         break;
1524 
1525       default:
1526         increment = 1;
1527         break;
1528       }
1529 
1530       bool match = scratch_cp->compare_entry_to(scratch_i, *merge_cp_p,
1531         scratch_i, CHECK_false);
1532       if (match) {
1533         // found a match at the same index so nothing more to do
1534         continue;
1535       } else if (is_unresolved_class_mismatch(scratch_cp, scratch_i,
1536                                               *merge_cp_p, scratch_i)) {
1537         // The mismatch in compare_entry_to() above is because of a
1538         // resolved versus unresolved class entry at the same index
1539         // with the same string value. Since Pass 0 reverted any
1540         // class entries to unresolved class entries in *merge_cp_p,
1541         // we go with the unresolved class entry.
1542         continue;
1543       }
1544 
1545       int found_i = scratch_cp->find_matching_entry(scratch_i, *merge_cp_p,
1546         CHECK_false);
1547       if (found_i != 0) {
1548         guarantee(found_i != scratch_i,
1549           "compare_entry_to() and find_matching_entry() do not agree");
1550 
1551         // Found a matching entry somewhere else in *merge_cp_p so
1552         // just need a mapping entry.
1553         map_index(scratch_cp, scratch_i, found_i);
1554         continue;
1555       }
1556 
1557       // The find_matching_entry() call above could fail to find a match
1558       // due to a resolved versus unresolved class or string entry situation
1559       // like we solved above with the is_unresolved_*_mismatch() calls.
1560       // However, we would have to call is_unresolved_*_mismatch() over
1561       // all of *merge_cp_p (potentially) and that doesn't seem to be
1562       // worth the time.
1563 
1564       // No match found so we have to append this entry and any unique
1565       // referenced entries to *merge_cp_p.
1566       append_entry(scratch_cp, scratch_i, merge_cp_p, merge_cp_length_p,
1567         CHECK_false);
1568     }
1569   }
1570 
1571   log_debug(redefine, class, constantpool)
1572     ("after pass 1a: merge_cp_len=%d, scratch_i=%d, index_map_len=%d",
1573      *merge_cp_length_p, scratch_i, _index_map_count);
1574 
1575   if (scratch_i < scratch_cp->length()) {
1576     // Pass 1b:
1577     // old_cp is smaller than scratch_cp so there are entries in
1578     // scratch_cp that we have not yet processed. We take care of
1579     // those now.
1580     int increment = 1;
1581     for (; scratch_i < scratch_cp->length(); scratch_i += increment) {
1582       switch (scratch_cp->tag_at(scratch_i).value()) {
1583       case JVM_CONSTANT_Double:
1584       case JVM_CONSTANT_Long:
1585         // double and long take two constant pool entries
1586         increment = 2;
1587         break;
1588 
1589       default:
1590         increment = 1;
1591         break;
1592       }
1593 
1594       int found_i =
1595         scratch_cp->find_matching_entry(scratch_i, *merge_cp_p, CHECK_false);
1596       if (found_i != 0) {
1597         // Found a matching entry somewhere else in *merge_cp_p so
1598         // just need a mapping entry.
1599         map_index(scratch_cp, scratch_i, found_i);
1600         continue;
1601       }
1602 
1603       // No match found so we have to append this entry and any unique
1604       // referenced entries to *merge_cp_p.
1605       append_entry(scratch_cp, scratch_i, merge_cp_p, merge_cp_length_p,
1606         CHECK_false);
1607     }
1608 
1609     log_debug(redefine, class, constantpool)
1610       ("after pass 1b: merge_cp_len=%d, scratch_i=%d, index_map_len=%d",
1611        *merge_cp_length_p, scratch_i, _index_map_count);
1612   }
1613   finalize_operands_merge(*merge_cp_p, THREAD);
1614 
1615   return true;
1616 } // end merge_constant_pools()
1617 
1618 
1619 // Scoped object to clean up the constant pool(s) created for merging
1620 class MergeCPCleaner {
1621   ClassLoaderData*   _loader_data;
1622   ConstantPool*      _cp;
1623   ConstantPool*      _scratch_cp;
1624  public:
1625   MergeCPCleaner(ClassLoaderData* loader_data, ConstantPool* merge_cp) :
1626                  _loader_data(loader_data), _cp(merge_cp), _scratch_cp(NULL) {}
1627   ~MergeCPCleaner() {
1628     _loader_data->add_to_deallocate_list(_cp);
1629     if (_scratch_cp != NULL) {
1630       _loader_data->add_to_deallocate_list(_scratch_cp);
1631     }
1632   }
1633   void add_scratch_cp(ConstantPool* scratch_cp) { _scratch_cp = scratch_cp; }
1634 };
1635 
1636 // Merge constant pools between the_class and scratch_class and
1637 // potentially rewrite bytecodes in scratch_class to use the merged
1638 // constant pool.
1639 jvmtiError VM_RedefineClasses::merge_cp_and_rewrite(
1640              InstanceKlass* the_class, InstanceKlass* scratch_class,
1641              TRAPS) {
1642   // worst case merged constant pool length is old and new combined
1643   int merge_cp_length = the_class->constants()->length()
1644         + scratch_class->constants()->length();
1645 
1646   // Constant pools are not easily reused so we allocate a new one
1647   // each time.
1648   // merge_cp is created unsafe for concurrent GC processing.  It
1649   // should be marked safe before discarding it. Even though
1650   // garbage,  if it crosses a card boundary, it may be scanned
1651   // in order to find the start of the first complete object on the card.
1652   ClassLoaderData* loader_data = the_class->class_loader_data();
1653   ConstantPool* merge_cp_oop =
1654     ConstantPool::allocate(loader_data,
1655                            merge_cp_length,
1656                            CHECK_(JVMTI_ERROR_OUT_OF_MEMORY));
1657   MergeCPCleaner cp_cleaner(loader_data, merge_cp_oop);
1658 
1659   HandleMark hm(THREAD);  // make sure handles are cleared before
1660                           // MergeCPCleaner clears out merge_cp_oop
1661   constantPoolHandle merge_cp(THREAD, merge_cp_oop);
1662 
1663   // Get constants() from the old class because it could have been rewritten
1664   // while we were at a safepoint allocating a new constant pool.
1665   constantPoolHandle old_cp(THREAD, the_class->constants());
1666   constantPoolHandle scratch_cp(THREAD, scratch_class->constants());
1667 
1668   // If the length changed, the class was redefined out from under us. Return
1669   // an error.
1670   if (merge_cp_length != the_class->constants()->length()
1671          + scratch_class->constants()->length()) {
1672     return JVMTI_ERROR_INTERNAL;
1673   }
1674 
1675   // Update the version number of the constant pools (may keep scratch_cp)
1676   merge_cp->increment_and_save_version(old_cp->version());
1677   scratch_cp->increment_and_save_version(old_cp->version());
1678 
1679   ResourceMark rm(THREAD);
1680   _index_map_count = 0;
1681   _index_map_p = new intArray(scratch_cp->length(), scratch_cp->length(), -1);
1682 
1683   _operands_cur_length = ConstantPool::operand_array_length(old_cp->operands());
1684   _operands_index_map_count = 0;
1685   int operands_index_map_len = ConstantPool::operand_array_length(scratch_cp->operands());
1686   _operands_index_map_p = new intArray(operands_index_map_len, operands_index_map_len, -1);
1687 
1688   // reference to the cp holder is needed for copy_operands()
1689   merge_cp->set_pool_holder(scratch_class);
1690   bool result = merge_constant_pools(old_cp, scratch_cp, &merge_cp,
1691                   &merge_cp_length, THREAD);
1692   merge_cp->set_pool_holder(NULL);
1693 
1694   if (!result) {
1695     // The merge can fail due to memory allocation failure or due
1696     // to robustness checks.
1697     return JVMTI_ERROR_INTERNAL;
1698   }
1699 
1700   if (old_cp->has_dynamic_constant()) {
1701     merge_cp->set_has_dynamic_constant();
1702     scratch_cp->set_has_dynamic_constant();
1703   }
1704 
1705   log_info(redefine, class, constantpool)("merge_cp_len=%d, index_map_len=%d", merge_cp_length, _index_map_count);
1706 
1707   if (_index_map_count == 0) {
1708     // there is nothing to map between the new and merged constant pools
1709 
1710     if (old_cp->length() == scratch_cp->length()) {
1711       // The old and new constant pools are the same length and the
1712       // index map is empty. This means that the three constant pools
1713       // are equivalent (but not the same). Unfortunately, the new
1714       // constant pool has not gone through link resolution nor have
1715       // the new class bytecodes gone through constant pool cache
1716       // rewriting so we can't use the old constant pool with the new
1717       // class.
1718 
1719       // toss the merged constant pool at return
1720     } else if (old_cp->length() < scratch_cp->length()) {
1721       // The old constant pool has fewer entries than the new constant
1722       // pool and the index map is empty. This means the new constant
1723       // pool is a superset of the old constant pool. However, the old
1724       // class bytecodes have already gone through constant pool cache
1725       // rewriting so we can't use the new constant pool with the old
1726       // class.
1727 
1728       // toss the merged constant pool at return
1729     } else {
1730       // The old constant pool has more entries than the new constant
1731       // pool and the index map is empty. This means that both the old
1732       // and merged constant pools are supersets of the new constant
1733       // pool.
1734 
1735       // Replace the new constant pool with a shrunken copy of the
1736       // merged constant pool
1737       set_new_constant_pool(loader_data, scratch_class, merge_cp, merge_cp_length,
1738                             CHECK_(JVMTI_ERROR_OUT_OF_MEMORY));
1739       // The new constant pool replaces scratch_cp so have cleaner clean it up.
1740       // It can't be cleaned up while there are handles to it.
1741       cp_cleaner.add_scratch_cp(scratch_cp());
1742     }
1743   } else {
1744     if (log_is_enabled(Trace, redefine, class, constantpool)) {
1745       // don't want to loop unless we are tracing
1746       int count = 0;
1747       for (int i = 1; i < _index_map_p->length(); i++) {
1748         int value = _index_map_p->at(i);
1749 
1750         if (value != -1) {
1751           log_trace(redefine, class, constantpool)("index_map[%d]: old=%d new=%d", count, i, value);
1752           count++;
1753         }
1754       }
1755     }
1756 
1757     // We have entries mapped between the new and merged constant pools
1758     // so we have to rewrite some constant pool references.
1759     if (!rewrite_cp_refs(scratch_class, THREAD)) {
1760       return JVMTI_ERROR_INTERNAL;
1761     }
1762 
1763     // Replace the new constant pool with a shrunken copy of the
1764     // merged constant pool so now the rewritten bytecodes have
1765     // valid references; the previous new constant pool will get
1766     // GCed.
1767     set_new_constant_pool(loader_data, scratch_class, merge_cp, merge_cp_length,
1768                           CHECK_(JVMTI_ERROR_OUT_OF_MEMORY));
1769     // The new constant pool replaces scratch_cp so have cleaner clean it up.
1770     // It can't be cleaned up while there are handles to it.
1771     cp_cleaner.add_scratch_cp(scratch_cp());
1772   }
1773 
1774   return JVMTI_ERROR_NONE;
1775 } // end merge_cp_and_rewrite()
1776 
1777 
1778 // Rewrite constant pool references in klass scratch_class.
1779 bool VM_RedefineClasses::rewrite_cp_refs(InstanceKlass* scratch_class,
1780        TRAPS) {
1781 
1782   // rewrite constant pool references in the nest attributes:
1783   if (!rewrite_cp_refs_in_nest_attributes(scratch_class)) {
1784     // propagate failure back to caller
1785     return false;
1786   }
1787 
1788   // rewrite constant pool references in the Record attribute:
1789   if (!rewrite_cp_refs_in_record_attribute(scratch_class, THREAD)) {
1790     // propagate failure back to caller
1791     return false;
1792   }
1793 
1794   // rewrite constant pool references in the methods:
1795   if (!rewrite_cp_refs_in_methods(scratch_class, THREAD)) {
1796     // propagate failure back to caller
1797     return false;
1798   }
1799 
1800   // rewrite constant pool references in the class_annotations:
1801   if (!rewrite_cp_refs_in_class_annotations(scratch_class, THREAD)) {
1802     // propagate failure back to caller
1803     return false;
1804   }
1805 
1806   // rewrite constant pool references in the fields_annotations:
1807   if (!rewrite_cp_refs_in_fields_annotations(scratch_class, THREAD)) {
1808     // propagate failure back to caller
1809     return false;
1810   }
1811 
1812   // rewrite constant pool references in the methods_annotations:
1813   if (!rewrite_cp_refs_in_methods_annotations(scratch_class, THREAD)) {
1814     // propagate failure back to caller
1815     return false;
1816   }
1817 
1818   // rewrite constant pool references in the methods_parameter_annotations:
1819   if (!rewrite_cp_refs_in_methods_parameter_annotations(scratch_class,
1820          THREAD)) {
1821     // propagate failure back to caller
1822     return false;
1823   }
1824 
1825   // rewrite constant pool references in the methods_default_annotations:
1826   if (!rewrite_cp_refs_in_methods_default_annotations(scratch_class,
1827          THREAD)) {
1828     // propagate failure back to caller
1829     return false;
1830   }
1831 
1832   // rewrite constant pool references in the class_type_annotations:
1833   if (!rewrite_cp_refs_in_class_type_annotations(scratch_class, THREAD)) {
1834     // propagate failure back to caller
1835     return false;
1836   }
1837 
1838   // rewrite constant pool references in the fields_type_annotations:
1839   if (!rewrite_cp_refs_in_fields_type_annotations(scratch_class, THREAD)) {
1840     // propagate failure back to caller
1841     return false;
1842   }
1843 
1844   // rewrite constant pool references in the methods_type_annotations:
1845   if (!rewrite_cp_refs_in_methods_type_annotations(scratch_class, THREAD)) {
1846     // propagate failure back to caller
1847     return false;
1848   }
1849 
1850   // There can be type annotations in the Code part of a method_info attribute.
1851   // These annotations are not accessible, even by reflection.
1852   // Currently they are not even parsed by the ClassFileParser.
1853   // If runtime access is added they will also need to be rewritten.
1854 
1855   // rewrite source file name index:
1856   u2 source_file_name_idx = scratch_class->source_file_name_index();
1857   if (source_file_name_idx != 0) {
1858     u2 new_source_file_name_idx = find_new_index(source_file_name_idx);
1859     if (new_source_file_name_idx != 0) {
1860       scratch_class->set_source_file_name_index(new_source_file_name_idx);
1861     }
1862   }
1863 
1864   // rewrite class generic signature index:
1865   u2 generic_signature_index = scratch_class->generic_signature_index();
1866   if (generic_signature_index != 0) {
1867     u2 new_generic_signature_index = find_new_index(generic_signature_index);
1868     if (new_generic_signature_index != 0) {
1869       scratch_class->set_generic_signature_index(new_generic_signature_index);
1870     }
1871   }
1872 
1873   return true;
1874 } // end rewrite_cp_refs()
1875 
1876 // Rewrite constant pool references in the NestHost and NestMembers attributes.
1877 bool VM_RedefineClasses::rewrite_cp_refs_in_nest_attributes(
1878        InstanceKlass* scratch_class) {
1879 
1880   u2 cp_index = scratch_class->nest_host_index();
1881   if (cp_index != 0) {
1882     scratch_class->set_nest_host_index(find_new_index(cp_index));
1883   }
1884   Array<u2>* nest_members = scratch_class->nest_members();
1885   for (int i = 0; i < nest_members->length(); i++) {
1886     u2 cp_index = nest_members->at(i);
1887     nest_members->at_put(i, find_new_index(cp_index));
1888   }
1889   return true;
1890 }
1891 
1892 // Rewrite constant pool references in the Record attribute.
1893 bool VM_RedefineClasses::rewrite_cp_refs_in_record_attribute(
1894        InstanceKlass* scratch_class, TRAPS) {
1895   Array<RecordComponent*>* components = scratch_class->record_components();
1896   if (components != NULL) {
1897     for (int i = 0; i < components->length(); i++) {
1898       RecordComponent* component = components->at(i);
1899       u2 cp_index = component->name_index();
1900       component->set_name_index(find_new_index(cp_index));
1901       cp_index = component->descriptor_index();
1902       component->set_descriptor_index(find_new_index(cp_index));
1903       cp_index = component->generic_signature_index();
1904       if (cp_index != 0) {
1905         component->set_generic_signature_index(find_new_index(cp_index));
1906       }
1907 
1908       AnnotationArray* annotations = component->annotations();
1909       if (annotations != NULL && annotations->length() != 0) {
1910         int byte_i = 0;  // byte index into annotations
1911         if (!rewrite_cp_refs_in_annotations_typeArray(annotations, byte_i, THREAD)) {
1912           log_debug(redefine, class, annotation)("bad record_component_annotations at %d", i);
1913           // propagate failure back to caller
1914           return false;
1915         }
1916       }
1917 
1918       AnnotationArray* type_annotations = component->type_annotations();
1919       if (type_annotations != NULL && type_annotations->length() != 0) {
1920         int byte_i = 0;  // byte index into annotations
1921         if (!rewrite_cp_refs_in_annotations_typeArray(type_annotations, byte_i, THREAD)) {
1922           log_debug(redefine, class, annotation)("bad record_component_type_annotations at %d", i);
1923           // propagate failure back to caller
1924           return false;
1925         }
1926       }
1927     }
1928   }
1929   return true;
1930 }
1931 
1932 // Rewrite constant pool references in the methods.
1933 bool VM_RedefineClasses::rewrite_cp_refs_in_methods(
1934        InstanceKlass* scratch_class, TRAPS) {
1935 
1936   Array<Method*>* methods = scratch_class->methods();
1937 
1938   if (methods == NULL || methods->length() == 0) {
1939     // no methods so nothing to do
1940     return true;
1941   }
1942 
1943   // rewrite constant pool references in the methods:
1944   for (int i = methods->length() - 1; i >= 0; i--) {
1945     methodHandle method(THREAD, methods->at(i));
1946     methodHandle new_method;
1947     rewrite_cp_refs_in_method(method, &new_method, THREAD);
1948     if (!new_method.is_null()) {
1949       // the method has been replaced so save the new method version
1950       // even in the case of an exception.  original method is on the
1951       // deallocation list.
1952       methods->at_put(i, new_method());
1953     }
1954     if (HAS_PENDING_EXCEPTION) {
1955       Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1956       log_info(redefine, class, load, exceptions)("rewrite_cp_refs_in_method exception: '%s'", ex_name->as_C_string());
1957       // Need to clear pending exception here as the super caller sets
1958       // the JVMTI_ERROR_INTERNAL if the returned value is false.
1959       CLEAR_PENDING_EXCEPTION;
1960       return false;
1961     }
1962   }
1963 
1964   return true;
1965 }
1966 
1967 
1968 // Rewrite constant pool references in the specific method. This code
1969 // was adapted from Rewriter::rewrite_method().
1970 void VM_RedefineClasses::rewrite_cp_refs_in_method(methodHandle method,
1971        methodHandle *new_method_p, TRAPS) {
1972 
1973   *new_method_p = methodHandle();  // default is no new method
1974 
1975   // We cache a pointer to the bytecodes here in code_base. If GC
1976   // moves the Method*, then the bytecodes will also move which
1977   // will likely cause a crash. We create a NoSafepointVerifier
1978   // object to detect whether we pass a possible safepoint in this
1979   // code block.
1980   NoSafepointVerifier nsv;
1981 
1982   // Bytecodes and their length
1983   address code_base = method->code_base();
1984   int code_length = method->code_size();
1985 
1986   int bc_length;
1987   for (int bci = 0; bci < code_length; bci += bc_length) {
1988     address bcp = code_base + bci;
1989     Bytecodes::Code c = (Bytecodes::Code)(*bcp);
1990 
1991     bc_length = Bytecodes::length_for(c);
1992     if (bc_length == 0) {
1993       // More complicated bytecodes report a length of zero so
1994       // we have to try again a slightly different way.
1995       bc_length = Bytecodes::length_at(method(), bcp);
1996     }
1997 
1998     assert(bc_length != 0, "impossible bytecode length");
1999 
2000     switch (c) {
2001       case Bytecodes::_ldc:
2002       {
2003         int cp_index = *(bcp + 1);
2004         int new_index = find_new_index(cp_index);
2005 
2006         if (StressLdcRewrite && new_index == 0) {
2007           // If we are stressing ldc -> ldc_w rewriting, then we
2008           // always need a new_index value.
2009           new_index = cp_index;
2010         }
2011         if (new_index != 0) {
2012           // the original index is mapped so we have more work to do
2013           if (!StressLdcRewrite && new_index <= max_jubyte) {
2014             // The new value can still use ldc instead of ldc_w
2015             // unless we are trying to stress ldc -> ldc_w rewriting
2016             log_trace(redefine, class, constantpool)
2017               ("%s@" INTPTR_FORMAT " old=%d, new=%d", Bytecodes::name(c), p2i(bcp), cp_index, new_index);
2018             *(bcp + 1) = new_index;
2019           } else {
2020             log_trace(redefine, class, constantpool)
2021               ("%s->ldc_w@" INTPTR_FORMAT " old=%d, new=%d", Bytecodes::name(c), p2i(bcp), cp_index, new_index);
2022             // the new value needs ldc_w instead of ldc
2023             u_char inst_buffer[4]; // max instruction size is 4 bytes
2024             bcp = (address)inst_buffer;
2025             // construct new instruction sequence
2026             *bcp = Bytecodes::_ldc_w;
2027             bcp++;
2028             // Rewriter::rewrite_method() does not rewrite ldc -> ldc_w.
2029             // See comment below for difference between put_Java_u2()
2030             // and put_native_u2().
2031             Bytes::put_Java_u2(bcp, new_index);
2032 
2033             Relocator rc(method, NULL /* no RelocatorListener needed */);
2034             methodHandle m;
2035             {
2036               PauseNoSafepointVerifier pnsv(&nsv);
2037 
2038               // ldc is 2 bytes and ldc_w is 3 bytes
2039               m = rc.insert_space_at(bci, 3, inst_buffer, CHECK);
2040             }
2041 
2042             // return the new method so that the caller can update
2043             // the containing class
2044             *new_method_p = method = m;
2045             // switch our bytecode processing loop from the old method
2046             // to the new method
2047             code_base = method->code_base();
2048             code_length = method->code_size();
2049             bcp = code_base + bci;
2050             c = (Bytecodes::Code)(*bcp);
2051             bc_length = Bytecodes::length_for(c);
2052             assert(bc_length != 0, "sanity check");
2053           } // end we need ldc_w instead of ldc
2054         } // end if there is a mapped index
2055       } break;
2056 
2057       // these bytecodes have a two-byte constant pool index
2058       case Bytecodes::_anewarray      : // fall through
2059       case Bytecodes::_checkcast      : // fall through
2060       case Bytecodes::_getfield       : // fall through
2061       case Bytecodes::_getstatic      : // fall through
2062       case Bytecodes::_instanceof     : // fall through
2063       case Bytecodes::_invokedynamic  : // fall through
2064       case Bytecodes::_invokeinterface: // fall through
2065       case Bytecodes::_invokespecial  : // fall through
2066       case Bytecodes::_invokestatic   : // fall through
2067       case Bytecodes::_invokevirtual  : // fall through
2068       case Bytecodes::_ldc_w          : // fall through
2069       case Bytecodes::_ldc2_w         : // fall through
2070       case Bytecodes::_multianewarray : // fall through
2071       case Bytecodes::_new            : // fall through
2072       case Bytecodes::_putfield       : // fall through
2073       case Bytecodes::_putstatic      :
2074       {
2075         address p = bcp + 1;
2076         int cp_index = Bytes::get_Java_u2(p);
2077         int new_index = find_new_index(cp_index);
2078         if (new_index != 0) {
2079           // the original index is mapped so update w/ new value
2080           log_trace(redefine, class, constantpool)
2081             ("%s@" INTPTR_FORMAT " old=%d, new=%d", Bytecodes::name(c),p2i(bcp), cp_index, new_index);
2082           // Rewriter::rewrite_method() uses put_native_u2() in this
2083           // situation because it is reusing the constant pool index
2084           // location for a native index into the ConstantPoolCache.
2085           // Since we are updating the constant pool index prior to
2086           // verification and ConstantPoolCache initialization, we
2087           // need to keep the new index in Java byte order.
2088           Bytes::put_Java_u2(p, new_index);
2089         }
2090       } break;
2091       default:
2092         break;
2093     }
2094   } // end for each bytecode
2095 
2096   // We also need to rewrite the parameter name indexes, if there is
2097   // method parameter data present
2098   if(method->has_method_parameters()) {
2099     const int len = method->method_parameters_length();
2100     MethodParametersElement* elem = method->method_parameters_start();
2101 
2102     for (int i = 0; i < len; i++) {
2103       const u2 cp_index = elem[i].name_cp_index;
2104       const u2 new_cp_index = find_new_index(cp_index);
2105       if (new_cp_index != 0) {
2106         elem[i].name_cp_index = new_cp_index;
2107       }
2108     }
2109   }
2110 } // end rewrite_cp_refs_in_method()
2111 
2112 
2113 // Rewrite constant pool references in the class_annotations field.
2114 bool VM_RedefineClasses::rewrite_cp_refs_in_class_annotations(
2115        InstanceKlass* scratch_class, TRAPS) {
2116 
2117   AnnotationArray* class_annotations = scratch_class->class_annotations();
2118   if (class_annotations == NULL || class_annotations->length() == 0) {
2119     // no class_annotations so nothing to do
2120     return true;
2121   }
2122 
2123   log_debug(redefine, class, annotation)("class_annotations length=%d", class_annotations->length());
2124 
2125   int byte_i = 0;  // byte index into class_annotations
2126   return rewrite_cp_refs_in_annotations_typeArray(class_annotations, byte_i,
2127            THREAD);
2128 }
2129 
2130 
2131 // Rewrite constant pool references in an annotations typeArray. This
2132 // "structure" is adapted from the RuntimeVisibleAnnotations_attribute
2133 // that is described in section 4.8.15 of the 2nd-edition of the VM spec:
2134 //
2135 // annotations_typeArray {
2136 //   u2 num_annotations;
2137 //   annotation annotations[num_annotations];
2138 // }
2139 //
2140 bool VM_RedefineClasses::rewrite_cp_refs_in_annotations_typeArray(
2141        AnnotationArray* annotations_typeArray, int &byte_i_ref, TRAPS) {
2142 
2143   if ((byte_i_ref + 2) > annotations_typeArray->length()) {
2144     // not enough room for num_annotations field
2145     log_debug(redefine, class, annotation)("length() is too small for num_annotations field");
2146     return false;
2147   }
2148 
2149   u2 num_annotations = Bytes::get_Java_u2((address)
2150                          annotations_typeArray->adr_at(byte_i_ref));
2151   byte_i_ref += 2;
2152 
2153   log_debug(redefine, class, annotation)("num_annotations=%d", num_annotations);
2154 
2155   int calc_num_annotations = 0;
2156   for (; calc_num_annotations < num_annotations; calc_num_annotations++) {
2157     if (!rewrite_cp_refs_in_annotation_struct(annotations_typeArray,
2158            byte_i_ref, THREAD)) {
2159       log_debug(redefine, class, annotation)("bad annotation_struct at %d", calc_num_annotations);
2160       // propagate failure back to caller
2161       return false;
2162     }
2163   }
2164   assert(num_annotations == calc_num_annotations, "sanity check");
2165 
2166   return true;
2167 } // end rewrite_cp_refs_in_annotations_typeArray()
2168 
2169 
2170 // Rewrite constant pool references in the annotation struct portion of
2171 // an annotations_typeArray. This "structure" is from section 4.8.15 of
2172 // the 2nd-edition of the VM spec:
2173 //
2174 // struct annotation {
2175 //   u2 type_index;
2176 //   u2 num_element_value_pairs;
2177 //   {
2178 //     u2 element_name_index;
2179 //     element_value value;
2180 //   } element_value_pairs[num_element_value_pairs];
2181 // }
2182 //
2183 bool VM_RedefineClasses::rewrite_cp_refs_in_annotation_struct(
2184        AnnotationArray* annotations_typeArray, int &byte_i_ref, TRAPS) {
2185   if ((byte_i_ref + 2 + 2) > annotations_typeArray->length()) {
2186     // not enough room for smallest annotation_struct
2187     log_debug(redefine, class, annotation)("length() is too small for annotation_struct");
2188     return false;
2189   }
2190 
2191   u2 type_index = rewrite_cp_ref_in_annotation_data(annotations_typeArray,
2192                     byte_i_ref, "type_index", THREAD);
2193 
2194   u2 num_element_value_pairs = Bytes::get_Java_u2((address)
2195                                  annotations_typeArray->adr_at(byte_i_ref));
2196   byte_i_ref += 2;
2197 
2198   log_debug(redefine, class, annotation)
2199     ("type_index=%d  num_element_value_pairs=%d", type_index, num_element_value_pairs);
2200 
2201   int calc_num_element_value_pairs = 0;
2202   for (; calc_num_element_value_pairs < num_element_value_pairs;
2203        calc_num_element_value_pairs++) {
2204     if ((byte_i_ref + 2) > annotations_typeArray->length()) {
2205       // not enough room for another element_name_index, let alone
2206       // the rest of another component
2207       log_debug(redefine, class, annotation)("length() is too small for element_name_index");
2208       return false;
2209     }
2210 
2211     u2 element_name_index = rewrite_cp_ref_in_annotation_data(
2212                               annotations_typeArray, byte_i_ref,
2213                               "element_name_index", THREAD);
2214 
2215     log_debug(redefine, class, annotation)("element_name_index=%d", element_name_index);
2216 
2217     if (!rewrite_cp_refs_in_element_value(annotations_typeArray,
2218            byte_i_ref, THREAD)) {
2219       log_debug(redefine, class, annotation)("bad element_value at %d", calc_num_element_value_pairs);
2220       // propagate failure back to caller
2221       return false;
2222     }
2223   } // end for each component
2224   assert(num_element_value_pairs == calc_num_element_value_pairs,
2225     "sanity check");
2226 
2227   return true;
2228 } // end rewrite_cp_refs_in_annotation_struct()
2229 
2230 
2231 // Rewrite a constant pool reference at the current position in
2232 // annotations_typeArray if needed. Returns the original constant
2233 // pool reference if a rewrite was not needed or the new constant
2234 // pool reference if a rewrite was needed.
2235 u2 VM_RedefineClasses::rewrite_cp_ref_in_annotation_data(
2236      AnnotationArray* annotations_typeArray, int &byte_i_ref,
2237      const char * trace_mesg, TRAPS) {
2238 
2239   address cp_index_addr = (address)
2240     annotations_typeArray->adr_at(byte_i_ref);
2241   u2 old_cp_index = Bytes::get_Java_u2(cp_index_addr);
2242   u2 new_cp_index = find_new_index(old_cp_index);
2243   if (new_cp_index != 0) {
2244     log_debug(redefine, class, annotation)("mapped old %s=%d", trace_mesg, old_cp_index);
2245     Bytes::put_Java_u2(cp_index_addr, new_cp_index);
2246     old_cp_index = new_cp_index;
2247   }
2248   byte_i_ref += 2;
2249   return old_cp_index;
2250 }
2251 
2252 
2253 // Rewrite constant pool references in the element_value portion of an
2254 // annotations_typeArray. This "structure" is from section 4.8.15.1 of
2255 // the 2nd-edition of the VM spec:
2256 //
2257 // struct element_value {
2258 //   u1 tag;
2259 //   union {
2260 //     u2 const_value_index;
2261 //     {
2262 //       u2 type_name_index;
2263 //       u2 const_name_index;
2264 //     } enum_const_value;
2265 //     u2 class_info_index;
2266 //     annotation annotation_value;
2267 //     struct {
2268 //       u2 num_values;
2269 //       element_value values[num_values];
2270 //     } array_value;
2271 //   } value;
2272 // }
2273 //
2274 bool VM_RedefineClasses::rewrite_cp_refs_in_element_value(
2275        AnnotationArray* annotations_typeArray, int &byte_i_ref, TRAPS) {
2276 
2277   if ((byte_i_ref + 1) > annotations_typeArray->length()) {
2278     // not enough room for a tag let alone the rest of an element_value
2279     log_debug(redefine, class, annotation)("length() is too small for a tag");
2280     return false;
2281   }
2282 
2283   u1 tag = annotations_typeArray->at(byte_i_ref);
2284   byte_i_ref++;
2285   log_debug(redefine, class, annotation)("tag='%c'", tag);
2286 
2287   switch (tag) {
2288     // These BaseType tag values are from Table 4.2 in VM spec:
2289     case JVM_SIGNATURE_BYTE:
2290     case JVM_SIGNATURE_CHAR:
2291     case JVM_SIGNATURE_DOUBLE:
2292     case JVM_SIGNATURE_FLOAT:
2293     case JVM_SIGNATURE_INT:
2294     case JVM_SIGNATURE_LONG:
2295     case JVM_SIGNATURE_SHORT:
2296     case JVM_SIGNATURE_BOOLEAN:
2297 
2298     // The remaining tag values are from Table 4.8 in the 2nd-edition of
2299     // the VM spec:
2300     case 's':
2301     {
2302       // For the above tag values (including the BaseType values),
2303       // value.const_value_index is right union field.
2304 
2305       if ((byte_i_ref + 2) > annotations_typeArray->length()) {
2306         // not enough room for a const_value_index
2307         log_debug(redefine, class, annotation)("length() is too small for a const_value_index");
2308         return false;
2309       }
2310 
2311       u2 const_value_index = rewrite_cp_ref_in_annotation_data(
2312                                annotations_typeArray, byte_i_ref,
2313                                "const_value_index", THREAD);
2314 
2315       log_debug(redefine, class, annotation)("const_value_index=%d", const_value_index);
2316     } break;
2317 
2318     case 'e':
2319     {
2320       // for the above tag value, value.enum_const_value is right union field
2321 
2322       if ((byte_i_ref + 4) > annotations_typeArray->length()) {
2323         // not enough room for a enum_const_value
2324         log_debug(redefine, class, annotation)("length() is too small for a enum_const_value");
2325         return false;
2326       }
2327 
2328       u2 type_name_index = rewrite_cp_ref_in_annotation_data(
2329                              annotations_typeArray, byte_i_ref,
2330                              "type_name_index", THREAD);
2331 
2332       u2 const_name_index = rewrite_cp_ref_in_annotation_data(
2333                               annotations_typeArray, byte_i_ref,
2334                               "const_name_index", THREAD);
2335 
2336       log_debug(redefine, class, annotation)
2337         ("type_name_index=%d  const_name_index=%d", type_name_index, const_name_index);
2338     } break;
2339 
2340     case 'c':
2341     {
2342       // for the above tag value, value.class_info_index is right union field
2343 
2344       if ((byte_i_ref + 2) > annotations_typeArray->length()) {
2345         // not enough room for a class_info_index
2346         log_debug(redefine, class, annotation)("length() is too small for a class_info_index");
2347         return false;
2348       }
2349 
2350       u2 class_info_index = rewrite_cp_ref_in_annotation_data(
2351                               annotations_typeArray, byte_i_ref,
2352                               "class_info_index", THREAD);
2353 
2354       log_debug(redefine, class, annotation)("class_info_index=%d", class_info_index);
2355     } break;
2356 
2357     case '@':
2358       // For the above tag value, value.attr_value is the right union
2359       // field. This is a nested annotation.
2360       if (!rewrite_cp_refs_in_annotation_struct(annotations_typeArray,
2361              byte_i_ref, THREAD)) {
2362         // propagate failure back to caller
2363         return false;
2364       }
2365       break;
2366 
2367     case JVM_SIGNATURE_ARRAY:
2368     {
2369       if ((byte_i_ref + 2) > annotations_typeArray->length()) {
2370         // not enough room for a num_values field
2371         log_debug(redefine, class, annotation)("length() is too small for a num_values field");
2372         return false;
2373       }
2374 
2375       // For the above tag value, value.array_value is the right union
2376       // field. This is an array of nested element_value.
2377       u2 num_values = Bytes::get_Java_u2((address)
2378                         annotations_typeArray->adr_at(byte_i_ref));
2379       byte_i_ref += 2;
2380       log_debug(redefine, class, annotation)("num_values=%d", num_values);
2381 
2382       int calc_num_values = 0;
2383       for (; calc_num_values < num_values; calc_num_values++) {
2384         if (!rewrite_cp_refs_in_element_value(
2385                annotations_typeArray, byte_i_ref, THREAD)) {
2386           log_debug(redefine, class, annotation)("bad nested element_value at %d", calc_num_values);
2387           // propagate failure back to caller
2388           return false;
2389         }
2390       }
2391       assert(num_values == calc_num_values, "sanity check");
2392     } break;
2393 
2394     default:
2395       log_debug(redefine, class, annotation)("bad tag=0x%x", tag);
2396       return false;
2397   } // end decode tag field
2398 
2399   return true;
2400 } // end rewrite_cp_refs_in_element_value()
2401 
2402 
2403 // Rewrite constant pool references in a fields_annotations field.
2404 bool VM_RedefineClasses::rewrite_cp_refs_in_fields_annotations(
2405        InstanceKlass* scratch_class, TRAPS) {
2406 
2407   Array<AnnotationArray*>* fields_annotations = scratch_class->fields_annotations();
2408 
2409   if (fields_annotations == NULL || fields_annotations->length() == 0) {
2410     // no fields_annotations so nothing to do
2411     return true;
2412   }
2413 
2414   log_debug(redefine, class, annotation)("fields_annotations length=%d", fields_annotations->length());
2415 
2416   for (int i = 0; i < fields_annotations->length(); i++) {
2417     AnnotationArray* field_annotations = fields_annotations->at(i);
2418     if (field_annotations == NULL || field_annotations->length() == 0) {
2419       // this field does not have any annotations so skip it
2420       continue;
2421     }
2422 
2423     int byte_i = 0;  // byte index into field_annotations
2424     if (!rewrite_cp_refs_in_annotations_typeArray(field_annotations, byte_i,
2425            THREAD)) {
2426       log_debug(redefine, class, annotation)("bad field_annotations at %d", i);
2427       // propagate failure back to caller
2428       return false;
2429     }
2430   }
2431 
2432   return true;
2433 } // end rewrite_cp_refs_in_fields_annotations()
2434 
2435 
2436 // Rewrite constant pool references in a methods_annotations field.
2437 bool VM_RedefineClasses::rewrite_cp_refs_in_methods_annotations(
2438        InstanceKlass* scratch_class, TRAPS) {
2439 
2440   for (int i = 0; i < scratch_class->methods()->length(); i++) {
2441     Method* m = scratch_class->methods()->at(i);
2442     AnnotationArray* method_annotations = m->constMethod()->method_annotations();
2443 
2444     if (method_annotations == NULL || method_annotations->length() == 0) {
2445       // this method does not have any annotations so skip it
2446       continue;
2447     }
2448 
2449     int byte_i = 0;  // byte index into method_annotations
2450     if (!rewrite_cp_refs_in_annotations_typeArray(method_annotations, byte_i,
2451            THREAD)) {
2452       log_debug(redefine, class, annotation)("bad method_annotations at %d", i);
2453       // propagate failure back to caller
2454       return false;
2455     }
2456   }
2457 
2458   return true;
2459 } // end rewrite_cp_refs_in_methods_annotations()
2460 
2461 
2462 // Rewrite constant pool references in a methods_parameter_annotations
2463 // field. This "structure" is adapted from the
2464 // RuntimeVisibleParameterAnnotations_attribute described in section
2465 // 4.8.17 of the 2nd-edition of the VM spec:
2466 //
2467 // methods_parameter_annotations_typeArray {
2468 //   u1 num_parameters;
2469 //   {
2470 //     u2 num_annotations;
2471 //     annotation annotations[num_annotations];
2472 //   } parameter_annotations[num_parameters];
2473 // }
2474 //
2475 bool VM_RedefineClasses::rewrite_cp_refs_in_methods_parameter_annotations(
2476        InstanceKlass* scratch_class, TRAPS) {
2477 
2478   for (int i = 0; i < scratch_class->methods()->length(); i++) {
2479     Method* m = scratch_class->methods()->at(i);
2480     AnnotationArray* method_parameter_annotations = m->constMethod()->parameter_annotations();
2481     if (method_parameter_annotations == NULL
2482         || method_parameter_annotations->length() == 0) {
2483       // this method does not have any parameter annotations so skip it
2484       continue;
2485     }
2486 
2487     if (method_parameter_annotations->length() < 1) {
2488       // not enough room for a num_parameters field
2489       log_debug(redefine, class, annotation)("length() is too small for a num_parameters field at %d", i);
2490       return false;
2491     }
2492 
2493     int byte_i = 0;  // byte index into method_parameter_annotations
2494 
2495     u1 num_parameters = method_parameter_annotations->at(byte_i);
2496     byte_i++;
2497 
2498     log_debug(redefine, class, annotation)("num_parameters=%d", num_parameters);
2499 
2500     int calc_num_parameters = 0;
2501     for (; calc_num_parameters < num_parameters; calc_num_parameters++) {
2502       if (!rewrite_cp_refs_in_annotations_typeArray(
2503              method_parameter_annotations, byte_i, THREAD)) {
2504         log_debug(redefine, class, annotation)("bad method_parameter_annotations at %d", calc_num_parameters);
2505         // propagate failure back to caller
2506         return false;
2507       }
2508     }
2509     assert(num_parameters == calc_num_parameters, "sanity check");
2510   }
2511 
2512   return true;
2513 } // end rewrite_cp_refs_in_methods_parameter_annotations()
2514 
2515 
2516 // Rewrite constant pool references in a methods_default_annotations
2517 // field. This "structure" is adapted from the AnnotationDefault_attribute
2518 // that is described in section 4.8.19 of the 2nd-edition of the VM spec:
2519 //
2520 // methods_default_annotations_typeArray {
2521 //   element_value default_value;
2522 // }
2523 //
2524 bool VM_RedefineClasses::rewrite_cp_refs_in_methods_default_annotations(
2525        InstanceKlass* scratch_class, TRAPS) {
2526 
2527   for (int i = 0; i < scratch_class->methods()->length(); i++) {
2528     Method* m = scratch_class->methods()->at(i);
2529     AnnotationArray* method_default_annotations = m->constMethod()->default_annotations();
2530     if (method_default_annotations == NULL
2531         || method_default_annotations->length() == 0) {
2532       // this method does not have any default annotations so skip it
2533       continue;
2534     }
2535 
2536     int byte_i = 0;  // byte index into method_default_annotations
2537 
2538     if (!rewrite_cp_refs_in_element_value(
2539            method_default_annotations, byte_i, THREAD)) {
2540       log_debug(redefine, class, annotation)("bad default element_value at %d", i);
2541       // propagate failure back to caller
2542       return false;
2543     }
2544   }
2545 
2546   return true;
2547 } // end rewrite_cp_refs_in_methods_default_annotations()
2548 
2549 
2550 // Rewrite constant pool references in a class_type_annotations field.
2551 bool VM_RedefineClasses::rewrite_cp_refs_in_class_type_annotations(
2552        InstanceKlass* scratch_class, TRAPS) {
2553 
2554   AnnotationArray* class_type_annotations = scratch_class->class_type_annotations();
2555   if (class_type_annotations == NULL || class_type_annotations->length() == 0) {
2556     // no class_type_annotations so nothing to do
2557     return true;
2558   }
2559 
2560   log_debug(redefine, class, annotation)("class_type_annotations length=%d", class_type_annotations->length());
2561 
2562   int byte_i = 0;  // byte index into class_type_annotations
2563   return rewrite_cp_refs_in_type_annotations_typeArray(class_type_annotations,
2564       byte_i, "ClassFile", THREAD);
2565 } // end rewrite_cp_refs_in_class_type_annotations()
2566 
2567 
2568 // Rewrite constant pool references in a fields_type_annotations field.
2569 bool VM_RedefineClasses::rewrite_cp_refs_in_fields_type_annotations(
2570        InstanceKlass* scratch_class, TRAPS) {
2571 
2572   Array<AnnotationArray*>* fields_type_annotations = scratch_class->fields_type_annotations();
2573   if (fields_type_annotations == NULL || fields_type_annotations->length() == 0) {
2574     // no fields_type_annotations so nothing to do
2575     return true;
2576   }
2577 
2578   log_debug(redefine, class, annotation)("fields_type_annotations length=%d", fields_type_annotations->length());
2579 
2580   for (int i = 0; i < fields_type_annotations->length(); i++) {
2581     AnnotationArray* field_type_annotations = fields_type_annotations->at(i);
2582     if (field_type_annotations == NULL || field_type_annotations->length() == 0) {
2583       // this field does not have any annotations so skip it
2584       continue;
2585     }
2586 
2587     int byte_i = 0;  // byte index into field_type_annotations
2588     if (!rewrite_cp_refs_in_type_annotations_typeArray(field_type_annotations,
2589            byte_i, "field_info", THREAD)) {
2590       log_debug(redefine, class, annotation)("bad field_type_annotations at %d", i);
2591       // propagate failure back to caller
2592       return false;
2593     }
2594   }
2595 
2596   return true;
2597 } // end rewrite_cp_refs_in_fields_type_annotations()
2598 
2599 
2600 // Rewrite constant pool references in a methods_type_annotations field.
2601 bool VM_RedefineClasses::rewrite_cp_refs_in_methods_type_annotations(
2602        InstanceKlass* scratch_class, TRAPS) {
2603 
2604   for (int i = 0; i < scratch_class->methods()->length(); i++) {
2605     Method* m = scratch_class->methods()->at(i);
2606     AnnotationArray* method_type_annotations = m->constMethod()->type_annotations();
2607 
2608     if (method_type_annotations == NULL || method_type_annotations->length() == 0) {
2609       // this method does not have any annotations so skip it
2610       continue;
2611     }
2612 
2613     log_debug(redefine, class, annotation)("methods type_annotations length=%d", method_type_annotations->length());
2614 
2615     int byte_i = 0;  // byte index into method_type_annotations
2616     if (!rewrite_cp_refs_in_type_annotations_typeArray(method_type_annotations,
2617            byte_i, "method_info", THREAD)) {
2618       log_debug(redefine, class, annotation)("bad method_type_annotations at %d", i);
2619       // propagate failure back to caller
2620       return false;
2621     }
2622   }
2623 
2624   return true;
2625 } // end rewrite_cp_refs_in_methods_type_annotations()
2626 
2627 
2628 // Rewrite constant pool references in a type_annotations
2629 // field. This "structure" is adapted from the
2630 // RuntimeVisibleTypeAnnotations_attribute described in
2631 // section 4.7.20 of the Java SE 8 Edition of the VM spec:
2632 //
2633 // type_annotations_typeArray {
2634 //   u2              num_annotations;
2635 //   type_annotation annotations[num_annotations];
2636 // }
2637 //
2638 bool VM_RedefineClasses::rewrite_cp_refs_in_type_annotations_typeArray(
2639        AnnotationArray* type_annotations_typeArray, int &byte_i_ref,
2640        const char * location_mesg, TRAPS) {
2641 
2642   if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
2643     // not enough room for num_annotations field
2644     log_debug(redefine, class, annotation)("length() is too small for num_annotations field");
2645     return false;
2646   }
2647 
2648   u2 num_annotations = Bytes::get_Java_u2((address)
2649                          type_annotations_typeArray->adr_at(byte_i_ref));
2650   byte_i_ref += 2;
2651 
2652   log_debug(redefine, class, annotation)("num_type_annotations=%d", num_annotations);
2653 
2654   int calc_num_annotations = 0;
2655   for (; calc_num_annotations < num_annotations; calc_num_annotations++) {
2656     if (!rewrite_cp_refs_in_type_annotation_struct(type_annotations_typeArray,
2657            byte_i_ref, location_mesg, THREAD)) {
2658       log_debug(redefine, class, annotation)("bad type_annotation_struct at %d", calc_num_annotations);
2659       // propagate failure back to caller
2660       return false;
2661     }
2662   }
2663   assert(num_annotations == calc_num_annotations, "sanity check");
2664 
2665   if (byte_i_ref != type_annotations_typeArray->length()) {
2666     log_debug(redefine, class, annotation)
2667       ("read wrong amount of bytes at end of processing type_annotations_typeArray (%d of %d bytes were read)",
2668        byte_i_ref, type_annotations_typeArray->length());
2669     return false;
2670   }
2671 
2672   return true;
2673 } // end rewrite_cp_refs_in_type_annotations_typeArray()
2674 
2675 
2676 // Rewrite constant pool references in a type_annotation
2677 // field. This "structure" is adapted from the
2678 // RuntimeVisibleTypeAnnotations_attribute described in
2679 // section 4.7.20 of the Java SE 8 Edition of the VM spec:
2680 //
2681 // type_annotation {
2682 //   u1 target_type;
2683 //   union {
2684 //     type_parameter_target;
2685 //     supertype_target;
2686 //     type_parameter_bound_target;
2687 //     empty_target;
2688 //     method_formal_parameter_target;
2689 //     throws_target;
2690 //     localvar_target;
2691 //     catch_target;
2692 //     offset_target;
2693 //     type_argument_target;
2694 //   } target_info;
2695 //   type_path target_path;
2696 //   annotation anno;
2697 // }
2698 //
2699 bool VM_RedefineClasses::rewrite_cp_refs_in_type_annotation_struct(
2700        AnnotationArray* type_annotations_typeArray, int &byte_i_ref,
2701        const char * location_mesg, TRAPS) {
2702 
2703   if (!skip_type_annotation_target(type_annotations_typeArray,
2704          byte_i_ref, location_mesg, THREAD)) {
2705     return false;
2706   }
2707 
2708   if (!skip_type_annotation_type_path(type_annotations_typeArray,
2709          byte_i_ref, THREAD)) {
2710     return false;
2711   }
2712 
2713   if (!rewrite_cp_refs_in_annotation_struct(type_annotations_typeArray,
2714          byte_i_ref, THREAD)) {
2715     return false;
2716   }
2717 
2718   return true;
2719 } // end rewrite_cp_refs_in_type_annotation_struct()
2720 
2721 
2722 // Read, verify and skip over the target_type and target_info part
2723 // so that rewriting can continue in the later parts of the struct.
2724 //
2725 // u1 target_type;
2726 // union {
2727 //   type_parameter_target;
2728 //   supertype_target;
2729 //   type_parameter_bound_target;
2730 //   empty_target;
2731 //   method_formal_parameter_target;
2732 //   throws_target;
2733 //   localvar_target;
2734 //   catch_target;
2735 //   offset_target;
2736 //   type_argument_target;
2737 // } target_info;
2738 //
2739 bool VM_RedefineClasses::skip_type_annotation_target(
2740        AnnotationArray* type_annotations_typeArray, int &byte_i_ref,
2741        const char * location_mesg, TRAPS) {
2742 
2743   if ((byte_i_ref + 1) > type_annotations_typeArray->length()) {
2744     // not enough room for a target_type let alone the rest of a type_annotation
2745     log_debug(redefine, class, annotation)("length() is too small for a target_type");
2746     return false;
2747   }
2748 
2749   u1 target_type = type_annotations_typeArray->at(byte_i_ref);
2750   byte_i_ref += 1;
2751   log_debug(redefine, class, annotation)("target_type=0x%.2x", target_type);
2752   log_debug(redefine, class, annotation)("location=%s", location_mesg);
2753 
2754   // Skip over target_info
2755   switch (target_type) {
2756     case 0x00:
2757     // kind: type parameter declaration of generic class or interface
2758     // location: ClassFile
2759     case 0x01:
2760     // kind: type parameter declaration of generic method or constructor
2761     // location: method_info
2762 
2763     {
2764       // struct:
2765       // type_parameter_target {
2766       //   u1 type_parameter_index;
2767       // }
2768       //
2769       if ((byte_i_ref + 1) > type_annotations_typeArray->length()) {
2770         log_debug(redefine, class, annotation)("length() is too small for a type_parameter_target");
2771         return false;
2772       }
2773 
2774       u1 type_parameter_index = type_annotations_typeArray->at(byte_i_ref);
2775       byte_i_ref += 1;
2776 
2777       log_debug(redefine, class, annotation)("type_parameter_target: type_parameter_index=%d", type_parameter_index);
2778     } break;
2779 
2780     case 0x10:
2781     // kind: type in extends clause of class or interface declaration
2782     //       (including the direct superclass of an unsafe anonymous class declaration),
2783     //       or in implements clause of interface declaration
2784     // location: ClassFile
2785 
2786     {
2787       // struct:
2788       // supertype_target {
2789       //   u2 supertype_index;
2790       // }
2791       //
2792       if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
2793         log_debug(redefine, class, annotation)("length() is too small for a supertype_target");
2794         return false;
2795       }
2796 
2797       u2 supertype_index = Bytes::get_Java_u2((address)
2798                              type_annotations_typeArray->adr_at(byte_i_ref));
2799       byte_i_ref += 2;
2800 
2801       log_debug(redefine, class, annotation)("supertype_target: supertype_index=%d", supertype_index);
2802     } break;
2803 
2804     case 0x11:
2805     // kind: type in bound of type parameter declaration of generic class or interface
2806     // location: ClassFile
2807     case 0x12:
2808     // kind: type in bound of type parameter declaration of generic method or constructor
2809     // location: method_info
2810 
2811     {
2812       // struct:
2813       // type_parameter_bound_target {
2814       //   u1 type_parameter_index;
2815       //   u1 bound_index;
2816       // }
2817       //
2818       if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
2819         log_debug(redefine, class, annotation)("length() is too small for a type_parameter_bound_target");
2820         return false;
2821       }
2822 
2823       u1 type_parameter_index = type_annotations_typeArray->at(byte_i_ref);
2824       byte_i_ref += 1;
2825       u1 bound_index = type_annotations_typeArray->at(byte_i_ref);
2826       byte_i_ref += 1;
2827 
2828       log_debug(redefine, class, annotation)
2829         ("type_parameter_bound_target: type_parameter_index=%d, bound_index=%d", type_parameter_index, bound_index);
2830     } break;
2831 
2832     case 0x13:
2833     // kind: type in field declaration
2834     // location: field_info
2835     case 0x14:
2836     // kind: return type of method, or type of newly constructed object
2837     // location: method_info
2838     case 0x15:
2839     // kind: receiver type of method or constructor
2840     // location: method_info
2841 
2842     {
2843       // struct:
2844       // empty_target {
2845       // }
2846       //
2847       log_debug(redefine, class, annotation)("empty_target");
2848     } break;
2849 
2850     case 0x16:
2851     // kind: type in formal parameter declaration of method, constructor, or lambda expression
2852     // location: method_info
2853 
2854     {
2855       // struct:
2856       // formal_parameter_target {
2857       //   u1 formal_parameter_index;
2858       // }
2859       //
2860       if ((byte_i_ref + 1) > type_annotations_typeArray->length()) {
2861         log_debug(redefine, class, annotation)("length() is too small for a formal_parameter_target");
2862         return false;
2863       }
2864 
2865       u1 formal_parameter_index = type_annotations_typeArray->at(byte_i_ref);
2866       byte_i_ref += 1;
2867 
2868       log_debug(redefine, class, annotation)
2869         ("formal_parameter_target: formal_parameter_index=%d", formal_parameter_index);
2870     } break;
2871 
2872     case 0x17:
2873     // kind: type in throws clause of method or constructor
2874     // location: method_info
2875 
2876     {
2877       // struct:
2878       // throws_target {
2879       //   u2 throws_type_index
2880       // }
2881       //
2882       if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
2883         log_debug(redefine, class, annotation)("length() is too small for a throws_target");
2884         return false;
2885       }
2886 
2887       u2 throws_type_index = Bytes::get_Java_u2((address)
2888                                type_annotations_typeArray->adr_at(byte_i_ref));
2889       byte_i_ref += 2;
2890 
2891       log_debug(redefine, class, annotation)("throws_target: throws_type_index=%d", throws_type_index);
2892     } break;
2893 
2894     case 0x40:
2895     // kind: type in local variable declaration
2896     // location: Code
2897     case 0x41:
2898     // kind: type in resource variable declaration
2899     // location: Code
2900 
2901     {
2902       // struct:
2903       // localvar_target {
2904       //   u2 table_length;
2905       //   struct {
2906       //     u2 start_pc;
2907       //     u2 length;
2908       //     u2 index;
2909       //   } table[table_length];
2910       // }
2911       //
2912       if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
2913         // not enough room for a table_length let alone the rest of a localvar_target
2914         log_debug(redefine, class, annotation)("length() is too small for a localvar_target table_length");
2915         return false;
2916       }
2917 
2918       u2 table_length = Bytes::get_Java_u2((address)
2919                           type_annotations_typeArray->adr_at(byte_i_ref));
2920       byte_i_ref += 2;
2921 
2922       log_debug(redefine, class, annotation)("localvar_target: table_length=%d", table_length);
2923 
2924       int table_struct_size = 2 + 2 + 2; // 3 u2 variables per table entry
2925       int table_size = table_length * table_struct_size;
2926 
2927       if ((byte_i_ref + table_size) > type_annotations_typeArray->length()) {
2928         // not enough room for a table
2929         log_debug(redefine, class, annotation)("length() is too small for a table array of length %d", table_length);
2930         return false;
2931       }
2932 
2933       // Skip over table
2934       byte_i_ref += table_size;
2935     } break;
2936 
2937     case 0x42:
2938     // kind: type in exception parameter declaration
2939     // location: Code
2940 
2941     {
2942       // struct:
2943       // catch_target {
2944       //   u2 exception_table_index;
2945       // }
2946       //
2947       if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
2948         log_debug(redefine, class, annotation)("length() is too small for a catch_target");
2949         return false;
2950       }
2951 
2952       u2 exception_table_index = Bytes::get_Java_u2((address)
2953                                    type_annotations_typeArray->adr_at(byte_i_ref));
2954       byte_i_ref += 2;
2955 
2956       log_debug(redefine, class, annotation)("catch_target: exception_table_index=%d", exception_table_index);
2957     } break;
2958 
2959     case 0x43:
2960     // kind: type in instanceof expression
2961     // location: Code
2962     case 0x44:
2963     // kind: type in new expression
2964     // location: Code
2965     case 0x45:
2966     // kind: type in method reference expression using ::new
2967     // location: Code
2968     case 0x46:
2969     // kind: type in method reference expression using ::Identifier
2970     // location: Code
2971 
2972     {
2973       // struct:
2974       // offset_target {
2975       //   u2 offset;
2976       // }
2977       //
2978       if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
2979         log_debug(redefine, class, annotation)("length() is too small for a offset_target");
2980         return false;
2981       }
2982 
2983       u2 offset = Bytes::get_Java_u2((address)
2984                     type_annotations_typeArray->adr_at(byte_i_ref));
2985       byte_i_ref += 2;
2986 
2987       log_debug(redefine, class, annotation)("offset_target: offset=%d", offset);
2988     } break;
2989 
2990     case 0x47:
2991     // kind: type in cast expression
2992     // location: Code
2993     case 0x48:
2994     // kind: type argument for generic constructor in new expression or
2995     //       explicit constructor invocation statement
2996     // location: Code
2997     case 0x49:
2998     // kind: type argument for generic method in method invocation expression
2999     // location: Code
3000     case 0x4A:
3001     // kind: type argument for generic constructor in method reference expression using ::new
3002     // location: Code
3003     case 0x4B:
3004     // kind: type argument for generic method in method reference expression using ::Identifier
3005     // location: Code
3006 
3007     {
3008       // struct:
3009       // type_argument_target {
3010       //   u2 offset;
3011       //   u1 type_argument_index;
3012       // }
3013       //
3014       if ((byte_i_ref + 3) > type_annotations_typeArray->length()) {
3015         log_debug(redefine, class, annotation)("length() is too small for a type_argument_target");
3016         return false;
3017       }
3018 
3019       u2 offset = Bytes::get_Java_u2((address)
3020                     type_annotations_typeArray->adr_at(byte_i_ref));
3021       byte_i_ref += 2;
3022       u1 type_argument_index = type_annotations_typeArray->at(byte_i_ref);
3023       byte_i_ref += 1;
3024 
3025       log_debug(redefine, class, annotation)
3026         ("type_argument_target: offset=%d, type_argument_index=%d", offset, type_argument_index);
3027     } break;
3028 
3029     default:
3030       log_debug(redefine, class, annotation)("unknown target_type");
3031 #ifdef ASSERT
3032       ShouldNotReachHere();
3033 #endif
3034       return false;
3035   }
3036 
3037   return true;
3038 } // end skip_type_annotation_target()
3039 
3040 
3041 // Read, verify and skip over the type_path part so that rewriting
3042 // can continue in the later parts of the struct.
3043 //
3044 // type_path {
3045 //   u1 path_length;
3046 //   {
3047 //     u1 type_path_kind;
3048 //     u1 type_argument_index;
3049 //   } path[path_length];
3050 // }
3051 //
3052 bool VM_RedefineClasses::skip_type_annotation_type_path(
3053        AnnotationArray* type_annotations_typeArray, int &byte_i_ref, TRAPS) {
3054 
3055   if ((byte_i_ref + 1) > type_annotations_typeArray->length()) {
3056     // not enough room for a path_length let alone the rest of the type_path
3057     log_debug(redefine, class, annotation)("length() is too small for a type_path");
3058     return false;
3059   }
3060 
3061   u1 path_length = type_annotations_typeArray->at(byte_i_ref);
3062   byte_i_ref += 1;
3063 
3064   log_debug(redefine, class, annotation)("type_path: path_length=%d", path_length);
3065 
3066   int calc_path_length = 0;
3067   for (; calc_path_length < path_length; calc_path_length++) {
3068     if ((byte_i_ref + 1 + 1) > type_annotations_typeArray->length()) {
3069       // not enough room for a path
3070       log_debug(redefine, class, annotation)
3071         ("length() is too small for path entry %d of %d", calc_path_length, path_length);
3072       return false;
3073     }
3074 
3075     u1 type_path_kind = type_annotations_typeArray->at(byte_i_ref);
3076     byte_i_ref += 1;
3077     u1 type_argument_index = type_annotations_typeArray->at(byte_i_ref);
3078     byte_i_ref += 1;
3079 
3080     log_debug(redefine, class, annotation)
3081       ("type_path: path[%d]: type_path_kind=%d, type_argument_index=%d",
3082        calc_path_length, type_path_kind, type_argument_index);
3083 
3084     if (type_path_kind > 3 || (type_path_kind != 3 && type_argument_index != 0)) {
3085       // not enough room for a path
3086       log_debug(redefine, class, annotation)("inconsistent type_path values");
3087       return false;
3088     }
3089   }
3090   assert(path_length == calc_path_length, "sanity check");
3091 
3092   return true;
3093 } // end skip_type_annotation_type_path()
3094 
3095 
3096 // Rewrite constant pool references in the method's stackmap table.
3097 // These "structures" are adapted from the StackMapTable_attribute that
3098 // is described in section 4.8.4 of the 6.0 version of the VM spec
3099 // (dated 2005.10.26):
3100 // file:///net/quincunx.sfbay/export/gbracha/ClassFile-Java6.pdf
3101 //
3102 // stack_map {
3103 //   u2 number_of_entries;
3104 //   stack_map_frame entries[number_of_entries];
3105 // }
3106 //
3107 void VM_RedefineClasses::rewrite_cp_refs_in_stack_map_table(
3108        const methodHandle& method, TRAPS) {
3109 
3110   if (!method->has_stackmap_table()) {
3111     return;
3112   }
3113 
3114   AnnotationArray* stackmap_data = method->stackmap_data();
3115   address stackmap_p = (address)stackmap_data->adr_at(0);
3116   address stackmap_end = stackmap_p + stackmap_data->length();
3117 
3118   assert(stackmap_p + 2 <= stackmap_end, "no room for number_of_entries");
3119   u2 number_of_entries = Bytes::get_Java_u2(stackmap_p);
3120   stackmap_p += 2;
3121 
3122   log_debug(redefine, class, stackmap)("number_of_entries=%u", number_of_entries);
3123 
3124   // walk through each stack_map_frame
3125   u2 calc_number_of_entries = 0;
3126   for (; calc_number_of_entries < number_of_entries; calc_number_of_entries++) {
3127     // The stack_map_frame structure is a u1 frame_type followed by
3128     // 0 or more bytes of data:
3129     //
3130     // union stack_map_frame {
3131     //   same_frame;
3132     //   same_locals_1_stack_item_frame;
3133     //   same_locals_1_stack_item_frame_extended;
3134     //   chop_frame;
3135     //   same_frame_extended;
3136     //   append_frame;
3137     //   full_frame;
3138     // }
3139 
3140     assert(stackmap_p + 1 <= stackmap_end, "no room for frame_type");
3141     u1 frame_type = *stackmap_p;
3142     stackmap_p++;
3143 
3144     // same_frame {
3145     //   u1 frame_type = SAME; /* 0-63 */
3146     // }
3147     if (frame_type <= 63) {
3148       // nothing more to do for same_frame
3149     }
3150 
3151     // same_locals_1_stack_item_frame {
3152     //   u1 frame_type = SAME_LOCALS_1_STACK_ITEM; /* 64-127 */
3153     //   verification_type_info stack[1];
3154     // }
3155     else if (frame_type >= 64 && frame_type <= 127) {
3156       rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
3157         calc_number_of_entries, frame_type, THREAD);
3158     }
3159 
3160     // reserved for future use
3161     else if (frame_type >= 128 && frame_type <= 246) {
3162       // nothing more to do for reserved frame_types
3163     }
3164 
3165     // same_locals_1_stack_item_frame_extended {
3166     //   u1 frame_type = SAME_LOCALS_1_STACK_ITEM_EXTENDED; /* 247 */
3167     //   u2 offset_delta;
3168     //   verification_type_info stack[1];
3169     // }
3170     else if (frame_type == 247) {
3171       stackmap_p += 2;
3172       rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
3173         calc_number_of_entries, frame_type, THREAD);
3174     }
3175 
3176     // chop_frame {
3177     //   u1 frame_type = CHOP; /* 248-250 */
3178     //   u2 offset_delta;
3179     // }
3180     else if (frame_type >= 248 && frame_type <= 250) {
3181       stackmap_p += 2;
3182     }
3183 
3184     // same_frame_extended {
3185     //   u1 frame_type = SAME_FRAME_EXTENDED; /* 251*/
3186     //   u2 offset_delta;
3187     // }
3188     else if (frame_type == 251) {
3189       stackmap_p += 2;
3190     }
3191 
3192     // append_frame {
3193     //   u1 frame_type = APPEND; /* 252-254 */
3194     //   u2 offset_delta;
3195     //   verification_type_info locals[frame_type - 251];
3196     // }
3197     else if (frame_type >= 252 && frame_type <= 254) {
3198       assert(stackmap_p + 2 <= stackmap_end,
3199         "no room for offset_delta");
3200       stackmap_p += 2;
3201       u1 len = frame_type - 251;
3202       for (u1 i = 0; i < len; i++) {
3203         rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
3204           calc_number_of_entries, frame_type, THREAD);
3205       }
3206     }
3207 
3208     // full_frame {
3209     //   u1 frame_type = FULL_FRAME; /* 255 */
3210     //   u2 offset_delta;
3211     //   u2 number_of_locals;
3212     //   verification_type_info locals[number_of_locals];
3213     //   u2 number_of_stack_items;
3214     //   verification_type_info stack[number_of_stack_items];
3215     // }
3216     else if (frame_type == 255) {
3217       assert(stackmap_p + 2 + 2 <= stackmap_end,
3218         "no room for smallest full_frame");
3219       stackmap_p += 2;
3220 
3221       u2 number_of_locals = Bytes::get_Java_u2(stackmap_p);
3222       stackmap_p += 2;
3223 
3224       for (u2 locals_i = 0; locals_i < number_of_locals; locals_i++) {
3225         rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
3226           calc_number_of_entries, frame_type, THREAD);
3227       }
3228 
3229       // Use the largest size for the number_of_stack_items, but only get
3230       // the right number of bytes.
3231       u2 number_of_stack_items = Bytes::get_Java_u2(stackmap_p);
3232       stackmap_p += 2;
3233 
3234       for (u2 stack_i = 0; stack_i < number_of_stack_items; stack_i++) {
3235         rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
3236           calc_number_of_entries, frame_type, THREAD);
3237       }
3238     }
3239   } // end while there is a stack_map_frame
3240   assert(number_of_entries == calc_number_of_entries, "sanity check");
3241 } // end rewrite_cp_refs_in_stack_map_table()
3242 
3243 
3244 // Rewrite constant pool references in the verification type info
3245 // portion of the method's stackmap table. These "structures" are
3246 // adapted from the StackMapTable_attribute that is described in
3247 // section 4.8.4 of the 6.0 version of the VM spec (dated 2005.10.26):
3248 // file:///net/quincunx.sfbay/export/gbracha/ClassFile-Java6.pdf
3249 //
3250 // The verification_type_info structure is a u1 tag followed by 0 or
3251 // more bytes of data:
3252 //
3253 // union verification_type_info {
3254 //   Top_variable_info;
3255 //   Integer_variable_info;
3256 //   Float_variable_info;
3257 //   Long_variable_info;
3258 //   Double_variable_info;
3259 //   Null_variable_info;
3260 //   UninitializedThis_variable_info;
3261 //   Object_variable_info;
3262 //   Uninitialized_variable_info;
3263 // }
3264 //
3265 void VM_RedefineClasses::rewrite_cp_refs_in_verification_type_info(
3266        address& stackmap_p_ref, address stackmap_end, u2 frame_i,
3267        u1 frame_type, TRAPS) {
3268 
3269   assert(stackmap_p_ref + 1 <= stackmap_end, "no room for tag");
3270   u1 tag = *stackmap_p_ref;
3271   stackmap_p_ref++;
3272 
3273   switch (tag) {
3274   // Top_variable_info {
3275   //   u1 tag = ITEM_Top; /* 0 */
3276   // }
3277   // verificationType.hpp has zero as ITEM_Bogus instead of ITEM_Top
3278   case 0:  // fall through
3279 
3280   // Integer_variable_info {
3281   //   u1 tag = ITEM_Integer; /* 1 */
3282   // }
3283   case ITEM_Integer:  // fall through
3284 
3285   // Float_variable_info {
3286   //   u1 tag = ITEM_Float; /* 2 */
3287   // }
3288   case ITEM_Float:  // fall through
3289 
3290   // Double_variable_info {
3291   //   u1 tag = ITEM_Double; /* 3 */
3292   // }
3293   case ITEM_Double:  // fall through
3294 
3295   // Long_variable_info {
3296   //   u1 tag = ITEM_Long; /* 4 */
3297   // }
3298   case ITEM_Long:  // fall through
3299 
3300   // Null_variable_info {
3301   //   u1 tag = ITEM_Null; /* 5 */
3302   // }
3303   case ITEM_Null:  // fall through
3304 
3305   // UninitializedThis_variable_info {
3306   //   u1 tag = ITEM_UninitializedThis; /* 6 */
3307   // }
3308   case ITEM_UninitializedThis:
3309     // nothing more to do for the above tag types
3310     break;
3311 
3312   // Object_variable_info {
3313   //   u1 tag = ITEM_Object; /* 7 */
3314   //   u2 cpool_index;
3315   // }
3316   case ITEM_Object:
3317   {
3318     assert(stackmap_p_ref + 2 <= stackmap_end, "no room for cpool_index");
3319     u2 cpool_index = Bytes::get_Java_u2(stackmap_p_ref);
3320     u2 new_cp_index = find_new_index(cpool_index);
3321     if (new_cp_index != 0) {
3322       log_debug(redefine, class, stackmap)("mapped old cpool_index=%d", cpool_index);
3323       Bytes::put_Java_u2(stackmap_p_ref, new_cp_index);
3324       cpool_index = new_cp_index;
3325     }
3326     stackmap_p_ref += 2;
3327 
3328     log_debug(redefine, class, stackmap)
3329       ("frame_i=%u, frame_type=%u, cpool_index=%d", frame_i, frame_type, cpool_index);
3330   } break;
3331 
3332   // Uninitialized_variable_info {
3333   //   u1 tag = ITEM_Uninitialized; /* 8 */
3334   //   u2 offset;
3335   // }
3336   case ITEM_Uninitialized:
3337     assert(stackmap_p_ref + 2 <= stackmap_end, "no room for offset");
3338     stackmap_p_ref += 2;
3339     break;
3340 
3341   default:
3342     log_debug(redefine, class, stackmap)("frame_i=%u, frame_type=%u, bad tag=0x%x", frame_i, frame_type, tag);
3343     ShouldNotReachHere();
3344     break;
3345   } // end switch (tag)
3346 } // end rewrite_cp_refs_in_verification_type_info()
3347 
3348 
3349 // Change the constant pool associated with klass scratch_class to
3350 // scratch_cp. If shrink is true, then scratch_cp_length elements
3351 // are copied from scratch_cp to a smaller constant pool and the
3352 // smaller constant pool is associated with scratch_class.
3353 void VM_RedefineClasses::set_new_constant_pool(
3354        ClassLoaderData* loader_data,
3355        InstanceKlass* scratch_class, constantPoolHandle scratch_cp,
3356        int scratch_cp_length, TRAPS) {
3357   assert(scratch_cp->length() >= scratch_cp_length, "sanity check");
3358 
3359   // scratch_cp is a merged constant pool and has enough space for a
3360   // worst case merge situation. We want to associate the minimum
3361   // sized constant pool with the klass to save space.
3362   ConstantPool* cp = ConstantPool::allocate(loader_data, scratch_cp_length, CHECK);
3363   constantPoolHandle smaller_cp(THREAD, cp);
3364 
3365   // preserve version() value in the smaller copy
3366   int version = scratch_cp->version();
3367   assert(version != 0, "sanity check");
3368   smaller_cp->set_version(version);
3369 
3370   // attach klass to new constant pool
3371   // reference to the cp holder is needed for copy_operands()
3372   smaller_cp->set_pool_holder(scratch_class);
3373 
3374   if (scratch_cp->has_dynamic_constant()) {
3375     smaller_cp->set_has_dynamic_constant();
3376   }
3377 
3378   scratch_cp->copy_cp_to(1, scratch_cp_length - 1, smaller_cp, 1, THREAD);
3379   if (HAS_PENDING_EXCEPTION) {
3380     // Exception is handled in the caller
3381     loader_data->add_to_deallocate_list(smaller_cp());
3382     return;
3383   }
3384   scratch_cp = smaller_cp;
3385 
3386   // attach new constant pool to klass
3387   scratch_class->set_constants(scratch_cp());
3388   scratch_cp->initialize_unresolved_klasses(loader_data, CHECK);
3389 
3390   int i;  // for portability
3391 
3392   // update each field in klass to use new constant pool indices as needed
3393   for (JavaFieldStream fs(scratch_class); !fs.done(); fs.next()) {
3394     jshort cur_index = fs.name_index();
3395     jshort new_index = find_new_index(cur_index);
3396     if (new_index != 0) {
3397       log_trace(redefine, class, constantpool)("field-name_index change: %d to %d", cur_index, new_index);
3398       fs.set_name_index(new_index);
3399     }
3400     cur_index = fs.signature_index();
3401     new_index = find_new_index(cur_index);
3402     if (new_index != 0) {
3403       log_trace(redefine, class, constantpool)("field-signature_index change: %d to %d", cur_index, new_index);
3404       fs.set_signature_index(new_index);
3405     }
3406     cur_index = fs.initval_index();
3407     new_index = find_new_index(cur_index);
3408     if (new_index != 0) {
3409       log_trace(redefine, class, constantpool)("field-initval_index change: %d to %d", cur_index, new_index);
3410       fs.set_initval_index(new_index);
3411     }
3412     cur_index = fs.generic_signature_index();
3413     new_index = find_new_index(cur_index);
3414     if (new_index != 0) {
3415       log_trace(redefine, class, constantpool)("field-generic_signature change: %d to %d", cur_index, new_index);
3416       fs.set_generic_signature_index(new_index);
3417     }
3418   } // end for each field
3419 
3420   // Update constant pool indices in the inner classes info to use
3421   // new constant indices as needed. The inner classes info is a
3422   // quadruple:
3423   // (inner_class_info, outer_class_info, inner_name, inner_access_flags)
3424   InnerClassesIterator iter(scratch_class);
3425   for (; !iter.done(); iter.next()) {
3426     int cur_index = iter.inner_class_info_index();
3427     if (cur_index == 0) {
3428       continue;  // JVM spec. allows null inner class refs so skip it
3429     }
3430     int new_index = find_new_index(cur_index);
3431     if (new_index != 0) {
3432       log_trace(redefine, class, constantpool)("inner_class_info change: %d to %d", cur_index, new_index);
3433       iter.set_inner_class_info_index(new_index);
3434     }
3435     cur_index = iter.outer_class_info_index();
3436     new_index = find_new_index(cur_index);
3437     if (new_index != 0) {
3438       log_trace(redefine, class, constantpool)("outer_class_info change: %d to %d", cur_index, new_index);
3439       iter.set_outer_class_info_index(new_index);
3440     }
3441     cur_index = iter.inner_name_index();
3442     new_index = find_new_index(cur_index);
3443     if (new_index != 0) {
3444       log_trace(redefine, class, constantpool)("inner_name change: %d to %d", cur_index, new_index);
3445       iter.set_inner_name_index(new_index);
3446     }
3447   } // end for each inner class
3448 
3449   // Attach each method in klass to the new constant pool and update
3450   // to use new constant pool indices as needed:
3451   Array<Method*>* methods = scratch_class->methods();
3452   for (i = methods->length() - 1; i >= 0; i--) {
3453     methodHandle method(THREAD, methods->at(i));
3454     method->set_constants(scratch_cp());
3455 
3456     int new_index = find_new_index(method->name_index());
3457     if (new_index != 0) {
3458       log_trace(redefine, class, constantpool)
3459         ("method-name_index change: %d to %d", method->name_index(), new_index);
3460       method->set_name_index(new_index);
3461     }
3462     new_index = find_new_index(method->signature_index());
3463     if (new_index != 0) {
3464       log_trace(redefine, class, constantpool)
3465         ("method-signature_index change: %d to %d", method->signature_index(), new_index);
3466       method->set_signature_index(new_index);
3467     }
3468     new_index = find_new_index(method->generic_signature_index());
3469     if (new_index != 0) {
3470       log_trace(redefine, class, constantpool)
3471         ("method-generic_signature_index change: %d to %d", method->generic_signature_index(), new_index);
3472       method->set_generic_signature_index(new_index);
3473     }
3474 
3475     // Update constant pool indices in the method's checked exception
3476     // table to use new constant indices as needed.
3477     int cext_length = method->checked_exceptions_length();
3478     if (cext_length > 0) {
3479       CheckedExceptionElement * cext_table =
3480         method->checked_exceptions_start();
3481       for (int j = 0; j < cext_length; j++) {
3482         int cur_index = cext_table[j].class_cp_index;
3483         int new_index = find_new_index(cur_index);
3484         if (new_index != 0) {
3485           log_trace(redefine, class, constantpool)("cext-class_cp_index change: %d to %d", cur_index, new_index);
3486           cext_table[j].class_cp_index = (u2)new_index;
3487         }
3488       } // end for each checked exception table entry
3489     } // end if there are checked exception table entries
3490 
3491     // Update each catch type index in the method's exception table
3492     // to use new constant pool indices as needed. The exception table
3493     // holds quadruple entries of the form:
3494     //   (beg_bci, end_bci, handler_bci, klass_index)
3495 
3496     ExceptionTable ex_table(method());
3497     int ext_length = ex_table.length();
3498 
3499     for (int j = 0; j < ext_length; j ++) {
3500       int cur_index = ex_table.catch_type_index(j);
3501       int new_index = find_new_index(cur_index);
3502       if (new_index != 0) {
3503         log_trace(redefine, class, constantpool)("ext-klass_index change: %d to %d", cur_index, new_index);
3504         ex_table.set_catch_type_index(j, new_index);
3505       }
3506     } // end for each exception table entry
3507 
3508     // Update constant pool indices in the method's local variable
3509     // table to use new constant indices as needed. The local variable
3510     // table hold sextuple entries of the form:
3511     // (start_pc, length, name_index, descriptor_index, signature_index, slot)
3512     int lvt_length = method->localvariable_table_length();
3513     if (lvt_length > 0) {
3514       LocalVariableTableElement * lv_table =
3515         method->localvariable_table_start();
3516       for (int j = 0; j < lvt_length; j++) {
3517         int cur_index = lv_table[j].name_cp_index;
3518         int new_index = find_new_index(cur_index);
3519         if (new_index != 0) {
3520           log_trace(redefine, class, constantpool)("lvt-name_cp_index change: %d to %d", cur_index, new_index);
3521           lv_table[j].name_cp_index = (u2)new_index;
3522         }
3523         cur_index = lv_table[j].descriptor_cp_index;
3524         new_index = find_new_index(cur_index);
3525         if (new_index != 0) {
3526           log_trace(redefine, class, constantpool)("lvt-descriptor_cp_index change: %d to %d", cur_index, new_index);
3527           lv_table[j].descriptor_cp_index = (u2)new_index;
3528         }
3529         cur_index = lv_table[j].signature_cp_index;
3530         new_index = find_new_index(cur_index);
3531         if (new_index != 0) {
3532           log_trace(redefine, class, constantpool)("lvt-signature_cp_index change: %d to %d", cur_index, new_index);
3533           lv_table[j].signature_cp_index = (u2)new_index;
3534         }
3535       } // end for each local variable table entry
3536     } // end if there are local variable table entries
3537 
3538     rewrite_cp_refs_in_stack_map_table(method, THREAD);
3539   } // end for each method
3540 } // end set_new_constant_pool()
3541 
3542 
3543 // Unevolving classes may point to methods of the_class directly
3544 // from their constant pool caches, itables, and/or vtables. We
3545 // use the ClassLoaderDataGraph::classes_do() facility and this helper
3546 // to fix up these pointers.  MethodData also points to old methods and
3547 // must be cleaned.
3548 
3549 // Adjust cpools and vtables closure
3550 void VM_RedefineClasses::AdjustAndCleanMetadata::do_klass(Klass* k) {
3551 
3552   // This is a very busy routine. We don't want too much tracing
3553   // printed out.
3554   bool trace_name_printed = false;
3555 
3556   // If the class being redefined is java.lang.Object, we need to fix all
3557   // array class vtables also
3558   if (k->is_array_klass() && _has_redefined_Object) {
3559     k->vtable().adjust_method_entries(&trace_name_printed);
3560 
3561   } else if (k->is_instance_klass()) {
3562     HandleMark hm(_thread);
3563     InstanceKlass *ik = InstanceKlass::cast(k);
3564 
3565     // Clean MethodData of this class's methods so they don't refer to
3566     // old methods that are no longer running.
3567     Array<Method*>* methods = ik->methods();
3568     int num_methods = methods->length();
3569     for (int index = 0; index < num_methods; ++index) {
3570       if (methods->at(index)->method_data() != NULL) {
3571         methods->at(index)->method_data()->clean_weak_method_links();
3572       }
3573     }
3574 
3575     // HotSpot specific optimization! HotSpot does not currently
3576     // support delegation from the bootstrap class loader to a
3577     // user-defined class loader. This means that if the bootstrap
3578     // class loader is the initiating class loader, then it will also
3579     // be the defining class loader. This also means that classes
3580     // loaded by the bootstrap class loader cannot refer to classes
3581     // loaded by a user-defined class loader. Note: a user-defined
3582     // class loader can delegate to the bootstrap class loader.
3583     //
3584     // If the current class being redefined has a user-defined class
3585     // loader as its defining class loader, then we can skip all
3586     // classes loaded by the bootstrap class loader.
3587     if (!_has_null_class_loader && ik->class_loader() == NULL) {
3588       return;
3589     }
3590 
3591     // Adjust all vtables, default methods and itables, to clean out old methods.
3592     ResourceMark rm(_thread);
3593     if (ik->vtable_length() > 0) {
3594       ik->vtable().adjust_method_entries(&trace_name_printed);
3595       ik->adjust_default_methods(&trace_name_printed);
3596     }
3597 
3598     if (ik->itable_length() > 0) {
3599       ik->itable().adjust_method_entries(&trace_name_printed);
3600     }
3601 
3602     // The constant pools in other classes (other_cp) can refer to
3603     // old methods.  We have to update method information in
3604     // other_cp's cache. If other_cp has a previous version, then we
3605     // have to repeat the process for each previous version. The
3606     // constant pool cache holds the Method*s for non-virtual
3607     // methods and for virtual, final methods.
3608     //
3609     // Special case: if the current class being redefined, then new_cp
3610     // has already been attached to the_class and old_cp has already
3611     // been added as a previous version. The new_cp doesn't have any
3612     // cached references to old methods so it doesn't need to be
3613     // updated. We can simply start with the previous version(s) in
3614     // that case.
3615     ConstantPoolCache* cp_cache;
3616 
3617     if (!ik->is_being_redefined()) {
3618       // this klass' constant pool cache may need adjustment
3619       ConstantPool* other_cp = ik->constants();
3620       cp_cache = other_cp->cache();
3621       if (cp_cache != NULL) {
3622         cp_cache->adjust_method_entries(&trace_name_printed);
3623       }
3624     }
3625 
3626     // the previous versions' constant pool caches may need adjustment
3627     for (InstanceKlass* pv_node = ik->previous_versions();
3628          pv_node != NULL;
3629          pv_node = pv_node->previous_versions()) {
3630       cp_cache = pv_node->constants()->cache();
3631       if (cp_cache != NULL) {
3632         cp_cache->adjust_method_entries(&trace_name_printed);
3633       }
3634     }
3635   }
3636 }
3637 
3638 void VM_RedefineClasses::update_jmethod_ids(Thread* thread) {
3639   for (int j = 0; j < _matching_methods_length; ++j) {
3640     Method* old_method = _matching_old_methods[j];
3641     jmethodID jmid = old_method->find_jmethod_id_or_null();
3642     if (jmid != NULL) {
3643       // There is a jmethodID, change it to point to the new method
3644       methodHandle new_method_h(thread, _matching_new_methods[j]);
3645       Method::change_method_associated_with_jmethod_id(jmid, new_method_h());
3646       assert(Method::resolve_jmethod_id(jmid) == _matching_new_methods[j],
3647              "should be replaced");
3648     }
3649   }
3650 }
3651 
3652 int VM_RedefineClasses::check_methods_and_mark_as_obsolete() {
3653   int emcp_method_count = 0;
3654   int obsolete_count = 0;
3655   int old_index = 0;
3656   for (int j = 0; j < _matching_methods_length; ++j, ++old_index) {
3657     Method* old_method = _matching_old_methods[j];
3658     Method* new_method = _matching_new_methods[j];
3659     Method* old_array_method;
3660 
3661     // Maintain an old_index into the _old_methods array by skipping
3662     // deleted methods
3663     while ((old_array_method = _old_methods->at(old_index)) != old_method) {
3664       ++old_index;
3665     }
3666 
3667     if (MethodComparator::methods_EMCP(old_method, new_method)) {
3668       // The EMCP definition from JSR-163 requires the bytecodes to be
3669       // the same with the exception of constant pool indices which may
3670       // differ. However, the constants referred to by those indices
3671       // must be the same.
3672       //
3673       // We use methods_EMCP() for comparison since constant pool
3674       // merging can remove duplicate constant pool entries that were
3675       // present in the old method and removed from the rewritten new
3676       // method. A faster binary comparison function would consider the
3677       // old and new methods to be different when they are actually
3678       // EMCP.
3679       //
3680       // The old and new methods are EMCP and you would think that we
3681       // could get rid of one of them here and now and save some space.
3682       // However, the concept of EMCP only considers the bytecodes and
3683       // the constant pool entries in the comparison. Other things,
3684       // e.g., the line number table (LNT) or the local variable table
3685       // (LVT) don't count in the comparison. So the new (and EMCP)
3686       // method can have a new LNT that we need so we can't just
3687       // overwrite the new method with the old method.
3688       //
3689       // When this routine is called, we have already attached the new
3690       // methods to the_class so the old methods are effectively
3691       // overwritten. However, if an old method is still executing,
3692       // then the old method cannot be collected until sometime after
3693       // the old method call has returned. So the overwriting of old
3694       // methods by new methods will save us space except for those
3695       // (hopefully few) old methods that are still executing.
3696       //
3697       // A method refers to a ConstMethod* and this presents another
3698       // possible avenue to space savings. The ConstMethod* in the
3699       // new method contains possibly new attributes (LNT, LVT, etc).
3700       // At first glance, it seems possible to save space by replacing
3701       // the ConstMethod* in the old method with the ConstMethod*
3702       // from the new method. The old and new methods would share the
3703       // same ConstMethod* and we would save the space occupied by
3704       // the old ConstMethod*. However, the ConstMethod* contains
3705       // a back reference to the containing method. Sharing the
3706       // ConstMethod* between two methods could lead to confusion in
3707       // the code that uses the back reference. This would lead to
3708       // brittle code that could be broken in non-obvious ways now or
3709       // in the future.
3710       //
3711       // Another possibility is to copy the ConstMethod* from the new
3712       // method to the old method and then overwrite the new method with
3713       // the old method. Since the ConstMethod* contains the bytecodes
3714       // for the method embedded in the oop, this option would change
3715       // the bytecodes out from under any threads executing the old
3716       // method and make the thread's bcp invalid. Since EMCP requires
3717       // that the bytecodes be the same modulo constant pool indices, it
3718       // is straight forward to compute the correct new bcp in the new
3719       // ConstMethod* from the old bcp in the old ConstMethod*. The
3720       // time consuming part would be searching all the frames in all
3721       // of the threads to find all of the calls to the old method.
3722       //
3723       // It looks like we will have to live with the limited savings
3724       // that we get from effectively overwriting the old methods
3725       // when the new methods are attached to the_class.
3726 
3727       // Count number of methods that are EMCP.  The method will be marked
3728       // old but not obsolete if it is EMCP.
3729       emcp_method_count++;
3730 
3731       // An EMCP method is _not_ obsolete. An obsolete method has a
3732       // different jmethodID than the current method. An EMCP method
3733       // has the same jmethodID as the current method. Having the
3734       // same jmethodID for all EMCP versions of a method allows for
3735       // a consistent view of the EMCP methods regardless of which
3736       // EMCP method you happen to have in hand. For example, a
3737       // breakpoint set in one EMCP method will work for all EMCP
3738       // versions of the method including the current one.
3739     } else {
3740       // mark obsolete methods as such
3741       old_method->set_is_obsolete();
3742       obsolete_count++;
3743 
3744       // obsolete methods need a unique idnum so they become new entries in
3745       // the jmethodID cache in InstanceKlass
3746       assert(old_method->method_idnum() == new_method->method_idnum(), "must match");
3747       u2 num = InstanceKlass::cast(_the_class)->next_method_idnum();
3748       if (num != ConstMethod::UNSET_IDNUM) {
3749         old_method->set_method_idnum(num);
3750       }
3751 
3752       // With tracing we try not to "yack" too much. The position of
3753       // this trace assumes there are fewer obsolete methods than
3754       // EMCP methods.
3755       if (log_is_enabled(Trace, redefine, class, obsolete, mark)) {
3756         ResourceMark rm;
3757         log_trace(redefine, class, obsolete, mark)
3758           ("mark %s(%s) as obsolete", old_method->name()->as_C_string(), old_method->signature()->as_C_string());
3759       }
3760     }
3761     old_method->set_is_old();
3762   }
3763   for (int i = 0; i < _deleted_methods_length; ++i) {
3764     Method* old_method = _deleted_methods[i];
3765 
3766     assert(!old_method->has_vtable_index(),
3767            "cannot delete methods with vtable entries");;
3768 
3769     // Mark all deleted methods as old, obsolete and deleted
3770     old_method->set_is_deleted();
3771     old_method->set_is_old();
3772     old_method->set_is_obsolete();
3773     ++obsolete_count;
3774     // With tracing we try not to "yack" too much. The position of
3775     // this trace assumes there are fewer obsolete methods than
3776     // EMCP methods.
3777     if (log_is_enabled(Trace, redefine, class, obsolete, mark)) {
3778       ResourceMark rm;
3779       log_trace(redefine, class, obsolete, mark)
3780         ("mark deleted %s(%s) as obsolete", old_method->name()->as_C_string(), old_method->signature()->as_C_string());
3781     }
3782   }
3783   assert((emcp_method_count + obsolete_count) == _old_methods->length(),
3784     "sanity check");
3785   log_trace(redefine, class, obsolete, mark)("EMCP_cnt=%d, obsolete_cnt=%d", emcp_method_count, obsolete_count);
3786   return emcp_method_count;
3787 }
3788 
3789 // This internal class transfers the native function registration from old methods
3790 // to new methods.  It is designed to handle both the simple case of unchanged
3791 // native methods and the complex cases of native method prefixes being added and/or
3792 // removed.
3793 // It expects only to be used during the VM_RedefineClasses op (a safepoint).
3794 //
3795 // This class is used after the new methods have been installed in "the_class".
3796 //
3797 // So, for example, the following must be handled.  Where 'm' is a method and
3798 // a number followed by an underscore is a prefix.
3799 //
3800 //                                      Old Name    New Name
3801 // Simple transfer to new method        m       ->  m
3802 // Add prefix                           m       ->  1_m
3803 // Remove prefix                        1_m     ->  m
3804 // Simultaneous add of prefixes         m       ->  3_2_1_m
3805 // Simultaneous removal of prefixes     3_2_1_m ->  m
3806 // Simultaneous add and remove          1_m     ->  2_m
3807 // Same, caused by prefix removal only  3_2_1_m ->  3_2_m
3808 //
3809 class TransferNativeFunctionRegistration {
3810  private:
3811   InstanceKlass* the_class;
3812   int prefix_count;
3813   char** prefixes;
3814 
3815   // Recursively search the binary tree of possibly prefixed method names.
3816   // Iteration could be used if all agents were well behaved. Full tree walk is
3817   // more resilent to agents not cleaning up intermediate methods.
3818   // Branch at each depth in the binary tree is:
3819   //    (1) without the prefix.
3820   //    (2) with the prefix.
3821   // where 'prefix' is the prefix at that 'depth' (first prefix, second prefix,...)
3822   Method* search_prefix_name_space(int depth, char* name_str, size_t name_len,
3823                                      Symbol* signature) {
3824     TempNewSymbol name_symbol = SymbolTable::probe(name_str, (int)name_len);
3825     if (name_symbol != NULL) {
3826       Method* method = the_class->lookup_method(name_symbol, signature);
3827       if (method != NULL) {
3828         // Even if prefixed, intermediate methods must exist.
3829         if (method->is_native()) {
3830           // Wahoo, we found a (possibly prefixed) version of the method, return it.
3831           return method;
3832         }
3833         if (depth < prefix_count) {
3834           // Try applying further prefixes (other than this one).
3835           method = search_prefix_name_space(depth+1, name_str, name_len, signature);
3836           if (method != NULL) {
3837             return method; // found
3838           }
3839 
3840           // Try adding this prefix to the method name and see if it matches
3841           // another method name.
3842           char* prefix = prefixes[depth];
3843           size_t prefix_len = strlen(prefix);
3844           size_t trial_len = name_len + prefix_len;
3845           char* trial_name_str = NEW_RESOURCE_ARRAY(char, trial_len + 1);
3846           strcpy(trial_name_str, prefix);
3847           strcat(trial_name_str, name_str);
3848           method = search_prefix_name_space(depth+1, trial_name_str, trial_len,
3849                                             signature);
3850           if (method != NULL) {
3851             // If found along this branch, it was prefixed, mark as such
3852             method->set_is_prefixed_native();
3853             return method; // found
3854           }
3855         }
3856       }
3857     }
3858     return NULL;  // This whole branch bore nothing
3859   }
3860 
3861   // Return the method name with old prefixes stripped away.
3862   char* method_name_without_prefixes(Method* method) {
3863     Symbol* name = method->name();
3864     char* name_str = name->as_utf8();
3865 
3866     // Old prefixing may be defunct, strip prefixes, if any.
3867     for (int i = prefix_count-1; i >= 0; i--) {
3868       char* prefix = prefixes[i];
3869       size_t prefix_len = strlen(prefix);
3870       if (strncmp(prefix, name_str, prefix_len) == 0) {
3871         name_str += prefix_len;
3872       }
3873     }
3874     return name_str;
3875   }
3876 
3877   // Strip any prefixes off the old native method, then try to find a
3878   // (possibly prefixed) new native that matches it.
3879   Method* strip_and_search_for_new_native(Method* method) {
3880     ResourceMark rm;
3881     char* name_str = method_name_without_prefixes(method);
3882     return search_prefix_name_space(0, name_str, strlen(name_str),
3883                                     method->signature());
3884   }
3885 
3886  public:
3887 
3888   // Construct a native method transfer processor for this class.
3889   TransferNativeFunctionRegistration(InstanceKlass* _the_class) {
3890     assert(SafepointSynchronize::is_at_safepoint(), "sanity check");
3891 
3892     the_class = _the_class;
3893     prefixes = JvmtiExport::get_all_native_method_prefixes(&prefix_count);
3894   }
3895 
3896   // Attempt to transfer any of the old or deleted methods that are native
3897   void transfer_registrations(Method** old_methods, int methods_length) {
3898     for (int j = 0; j < methods_length; j++) {
3899       Method* old_method = old_methods[j];
3900 
3901       if (old_method->is_native() && old_method->has_native_function()) {
3902         Method* new_method = strip_and_search_for_new_native(old_method);
3903         if (new_method != NULL) {
3904           // Actually set the native function in the new method.
3905           // Redefine does not send events (except CFLH), certainly not this
3906           // behind the scenes re-registration.
3907           new_method->set_native_function(old_method->native_function(),
3908                               !Method::native_bind_event_is_interesting);
3909         }
3910       }
3911     }
3912   }
3913 };
3914 
3915 // Don't lose the association between a native method and its JNI function.
3916 void VM_RedefineClasses::transfer_old_native_function_registrations(InstanceKlass* the_class) {
3917   TransferNativeFunctionRegistration transfer(the_class);
3918   transfer.transfer_registrations(_deleted_methods, _deleted_methods_length);
3919   transfer.transfer_registrations(_matching_old_methods, _matching_methods_length);
3920 }
3921 
3922 // Deoptimize all compiled code that depends on this class.
3923 //
3924 // If the can_redefine_classes capability is obtained in the onload
3925 // phase then the compiler has recorded all dependencies from startup.
3926 // In that case we need only deoptimize and throw away all compiled code
3927 // that depends on the class.
3928 //
3929 // If can_redefine_classes is obtained sometime after the onload
3930 // phase then the dependency information may be incomplete. In that case
3931 // the first call to RedefineClasses causes all compiled code to be
3932 // thrown away. As can_redefine_classes has been obtained then
3933 // all future compilations will record dependencies so second and
3934 // subsequent calls to RedefineClasses need only throw away code
3935 // that depends on the class.
3936 //
3937 
3938 // First step is to walk the code cache for each class redefined and mark
3939 // dependent methods.  Wait until all classes are processed to deoptimize everything.
3940 void VM_RedefineClasses::mark_dependent_code(InstanceKlass* ik) {
3941   assert_locked_or_safepoint(Compile_lock);
3942 
3943   // All dependencies have been recorded from startup or this is a second or
3944   // subsequent use of RedefineClasses
3945   if (JvmtiExport::all_dependencies_are_recorded()) {
3946     CodeCache::mark_for_evol_deoptimization(ik);
3947   }
3948 }
3949 
3950 void VM_RedefineClasses::flush_dependent_code() {
3951   assert(SafepointSynchronize::is_at_safepoint(), "sanity check");
3952 
3953   bool deopt_needed;
3954 
3955   // This is the first redefinition, mark all the nmethods for deoptimization
3956   if (!JvmtiExport::all_dependencies_are_recorded()) {
3957     log_debug(redefine, class, nmethod)("Marked all nmethods for deopt");
3958     CodeCache::mark_all_nmethods_for_evol_deoptimization();
3959     deopt_needed = true;
3960   } else {
3961     int deopt = CodeCache::mark_dependents_for_evol_deoptimization();
3962     log_debug(redefine, class, nmethod)("Marked %d dependent nmethods for deopt", deopt);
3963     deopt_needed = (deopt != 0);
3964   }
3965 
3966   if (deopt_needed) {
3967     CodeCache::flush_evol_dependents();
3968   }
3969 
3970   // From now on we know that the dependency information is complete
3971   JvmtiExport::set_all_dependencies_are_recorded(true);
3972 }
3973 
3974 void VM_RedefineClasses::compute_added_deleted_matching_methods() {
3975   Method* old_method;
3976   Method* new_method;
3977 
3978   _matching_old_methods = NEW_RESOURCE_ARRAY(Method*, _old_methods->length());
3979   _matching_new_methods = NEW_RESOURCE_ARRAY(Method*, _old_methods->length());
3980   _added_methods        = NEW_RESOURCE_ARRAY(Method*, _new_methods->length());
3981   _deleted_methods      = NEW_RESOURCE_ARRAY(Method*, _old_methods->length());
3982 
3983   _matching_methods_length = 0;
3984   _deleted_methods_length  = 0;
3985   _added_methods_length    = 0;
3986 
3987   int nj = 0;
3988   int oj = 0;
3989   while (true) {
3990     if (oj >= _old_methods->length()) {
3991       if (nj >= _new_methods->length()) {
3992         break; // we've looked at everything, done
3993       }
3994       // New method at the end
3995       new_method = _new_methods->at(nj);
3996       _added_methods[_added_methods_length++] = new_method;
3997       ++nj;
3998     } else if (nj >= _new_methods->length()) {
3999       // Old method, at the end, is deleted
4000       old_method = _old_methods->at(oj);
4001       _deleted_methods[_deleted_methods_length++] = old_method;
4002       ++oj;
4003     } else {
4004       old_method = _old_methods->at(oj);
4005       new_method = _new_methods->at(nj);
4006       if (old_method->name() == new_method->name()) {
4007         if (old_method->signature() == new_method->signature()) {
4008           _matching_old_methods[_matching_methods_length  ] = old_method;
4009           _matching_new_methods[_matching_methods_length++] = new_method;
4010           ++nj;
4011           ++oj;
4012         } else {
4013           // added overloaded have already been moved to the end,
4014           // so this is a deleted overloaded method
4015           _deleted_methods[_deleted_methods_length++] = old_method;
4016           ++oj;
4017         }
4018       } else { // names don't match
4019         if (old_method->name()->fast_compare(new_method->name()) > 0) {
4020           // new method
4021           _added_methods[_added_methods_length++] = new_method;
4022           ++nj;
4023         } else {
4024           // deleted method
4025           _deleted_methods[_deleted_methods_length++] = old_method;
4026           ++oj;
4027         }
4028       }
4029     }
4030   }
4031   assert(_matching_methods_length + _deleted_methods_length == _old_methods->length(), "sanity");
4032   assert(_matching_methods_length + _added_methods_length == _new_methods->length(), "sanity");
4033 }
4034 
4035 
4036 void VM_RedefineClasses::swap_annotations(InstanceKlass* the_class,
4037                                           InstanceKlass* scratch_class) {
4038   // Swap annotation fields values
4039   Annotations* old_annotations = the_class->annotations();
4040   the_class->set_annotations(scratch_class->annotations());
4041   scratch_class->set_annotations(old_annotations);
4042 }
4043 
4044 
4045 // Install the redefinition of a class:
4046 //    - house keeping (flushing breakpoints and caches, deoptimizing
4047 //      dependent compiled code)
4048 //    - replacing parts in the_class with parts from scratch_class
4049 //    - adding a weak reference to track the obsolete but interesting
4050 //      parts of the_class
4051 //    - adjusting constant pool caches and vtables in other classes
4052 //      that refer to methods in the_class. These adjustments use the
4053 //      ClassLoaderDataGraph::classes_do() facility which only allows
4054 //      a helper method to be specified. The interesting parameters
4055 //      that we would like to pass to the helper method are saved in
4056 //      static global fields in the VM operation.
4057 void VM_RedefineClasses::redefine_single_class(jclass the_jclass,
4058        InstanceKlass* scratch_class, TRAPS) {
4059 
4060   HandleMark hm(THREAD);   // make sure handles from this call are freed
4061 
4062   if (log_is_enabled(Info, redefine, class, timer)) {
4063     _timer_rsc_phase1.start();
4064   }
4065 
4066   InstanceKlass* the_class = get_ik(the_jclass);
4067 
4068   // Set some flags to control and optimize adjusting method entries
4069   _has_redefined_Object |= the_class == SystemDictionary::Object_klass();
4070   _has_null_class_loader |= the_class->class_loader() == NULL;
4071 
4072   // Remove all breakpoints in methods of this class
4073   JvmtiBreakpoints& jvmti_breakpoints = JvmtiCurrentBreakpoints::get_jvmti_breakpoints();
4074   jvmti_breakpoints.clearall_in_class_at_safepoint(the_class);
4075 
4076   // Mark all compiled code that depends on this class
4077   mark_dependent_code(the_class);
4078 
4079   _old_methods = the_class->methods();
4080   _new_methods = scratch_class->methods();
4081   _the_class = the_class;
4082   compute_added_deleted_matching_methods();
4083   update_jmethod_ids(THREAD);
4084 
4085   _any_class_has_resolved_methods = the_class->has_resolved_methods() || _any_class_has_resolved_methods;
4086 
4087   // Attach new constant pool to the original klass. The original
4088   // klass still refers to the old constant pool (for now).
4089   scratch_class->constants()->set_pool_holder(the_class);
4090 
4091 #if 0
4092   // In theory, with constant pool merging in place we should be able
4093   // to save space by using the new, merged constant pool in place of
4094   // the old constant pool(s). By "pool(s)" I mean the constant pool in
4095   // the klass version we are replacing now and any constant pool(s) in
4096   // previous versions of klass. Nice theory, doesn't work in practice.
4097   // When this code is enabled, even simple programs throw NullPointer
4098   // exceptions. I'm guessing that this is caused by some constant pool
4099   // cache difference between the new, merged constant pool and the
4100   // constant pool that was just being used by the klass. I'm keeping
4101   // this code around to archive the idea, but the code has to remain
4102   // disabled for now.
4103 
4104   // Attach each old method to the new constant pool. This can be
4105   // done here since we are past the bytecode verification and
4106   // constant pool optimization phases.
4107   for (int i = _old_methods->length() - 1; i >= 0; i--) {
4108     Method* method = _old_methods->at(i);
4109     method->set_constants(scratch_class->constants());
4110   }
4111 
4112   // NOTE: this doesn't work because you can redefine the same class in two
4113   // threads, each getting their own constant pool data appended to the
4114   // original constant pool.  In order for the new methods to work when they
4115   // become old methods, they need to keep their updated copy of the constant pool.
4116 
4117   {
4118     // walk all previous versions of the klass
4119     InstanceKlass *ik = the_class;
4120     PreviousVersionWalker pvw(ik);
4121     do {
4122       ik = pvw.next_previous_version();
4123       if (ik != NULL) {
4124 
4125         // attach previous version of klass to the new constant pool
4126         ik->set_constants(scratch_class->constants());
4127 
4128         // Attach each method in the previous version of klass to the
4129         // new constant pool
4130         Array<Method*>* prev_methods = ik->methods();
4131         for (int i = prev_methods->length() - 1; i >= 0; i--) {
4132           Method* method = prev_methods->at(i);
4133           method->set_constants(scratch_class->constants());
4134         }
4135       }
4136     } while (ik != NULL);
4137   }
4138 #endif
4139 
4140   // Replace methods and constantpool
4141   the_class->set_methods(_new_methods);
4142   scratch_class->set_methods(_old_methods);     // To prevent potential GCing of the old methods,
4143                                           // and to be able to undo operation easily.
4144 
4145   Array<int>* old_ordering = the_class->method_ordering();
4146   the_class->set_method_ordering(scratch_class->method_ordering());
4147   scratch_class->set_method_ordering(old_ordering);
4148 
4149   ConstantPool* old_constants = the_class->constants();
4150   the_class->set_constants(scratch_class->constants());
4151   scratch_class->set_constants(old_constants);  // See the previous comment.
4152 #if 0
4153   // We are swapping the guts of "the new class" with the guts of "the
4154   // class". Since the old constant pool has just been attached to "the
4155   // new class", it seems logical to set the pool holder in the old
4156   // constant pool also. However, doing this will change the observable
4157   // class hierarchy for any old methods that are still executing. A
4158   // method can query the identity of its "holder" and this query uses
4159   // the method's constant pool link to find the holder. The change in
4160   // holding class from "the class" to "the new class" can confuse
4161   // things.
4162   //
4163   // Setting the old constant pool's holder will also cause
4164   // verification done during vtable initialization below to fail.
4165   // During vtable initialization, the vtable's class is verified to be
4166   // a subtype of the method's holder. The vtable's class is "the
4167   // class" and the method's holder is gotten from the constant pool
4168   // link in the method itself. For "the class"'s directly implemented
4169   // methods, the method holder is "the class" itself (as gotten from
4170   // the new constant pool). The check works fine in this case. The
4171   // check also works fine for methods inherited from super classes.
4172   //
4173   // Miranda methods are a little more complicated. A miranda method is
4174   // provided by an interface when the class implementing the interface
4175   // does not provide its own method.  These interfaces are implemented
4176   // internally as an InstanceKlass. These special instanceKlasses
4177   // share the constant pool of the class that "implements" the
4178   // interface. By sharing the constant pool, the method holder of a
4179   // miranda method is the class that "implements" the interface. In a
4180   // non-redefine situation, the subtype check works fine. However, if
4181   // the old constant pool's pool holder is modified, then the check
4182   // fails because there is no class hierarchy relationship between the
4183   // vtable's class and "the new class".
4184 
4185   old_constants->set_pool_holder(scratch_class());
4186 #endif
4187 
4188   // track number of methods that are EMCP for add_previous_version() call below
4189   int emcp_method_count = check_methods_and_mark_as_obsolete();
4190   transfer_old_native_function_registrations(the_class);
4191 
4192   // The class file bytes from before any retransformable agents mucked
4193   // with them was cached on the scratch class, move to the_class.
4194   // Note: we still want to do this if nothing needed caching since it
4195   // should get cleared in the_class too.
4196   if (the_class->get_cached_class_file() == 0) {
4197     // the_class doesn't have a cache yet so copy it
4198     the_class->set_cached_class_file(scratch_class->get_cached_class_file());
4199   }
4200   else if (scratch_class->get_cached_class_file() !=
4201            the_class->get_cached_class_file()) {
4202     // The same class can be present twice in the scratch classes list or there
4203     // are multiple concurrent RetransformClasses calls on different threads.
4204     // In such cases we have to deallocate scratch_class cached_class_file.
4205     os::free(scratch_class->get_cached_class_file());
4206   }
4207 
4208   // NULL out in scratch class to not delete twice.  The class to be redefined
4209   // always owns these bytes.
4210   scratch_class->set_cached_class_file(NULL);
4211 
4212   // Replace inner_classes
4213   Array<u2>* old_inner_classes = the_class->inner_classes();
4214   the_class->set_inner_classes(scratch_class->inner_classes());
4215   scratch_class->set_inner_classes(old_inner_classes);
4216 
4217   // Initialize the vtable and interface table after
4218   // methods have been rewritten
4219   // no exception should happen here since we explicitly
4220   // do not check loader constraints.
4221   // compare_and_normalize_class_versions has already checked:
4222   //  - classloaders unchanged, signatures unchanged
4223   //  - all instanceKlasses for redefined classes reused & contents updated
4224   the_class->vtable().initialize_vtable(false, THREAD);
4225   the_class->itable().initialize_itable(false, THREAD);
4226   assert(!HAS_PENDING_EXCEPTION || (THREAD->pending_exception()->is_a(SystemDictionary::ThreadDeath_klass())), "redefine exception");
4227 
4228   // Leave arrays of jmethodIDs and itable index cache unchanged
4229 
4230   // Copy the "source file name" attribute from new class version
4231   the_class->set_source_file_name_index(
4232     scratch_class->source_file_name_index());
4233 
4234   // Copy the "source debug extension" attribute from new class version
4235   the_class->set_source_debug_extension(
4236     scratch_class->source_debug_extension(),
4237     scratch_class->source_debug_extension() == NULL ? 0 :
4238     (int)strlen(scratch_class->source_debug_extension()));
4239 
4240   // Use of javac -g could be different in the old and the new
4241   if (scratch_class->access_flags().has_localvariable_table() !=
4242       the_class->access_flags().has_localvariable_table()) {
4243 
4244     AccessFlags flags = the_class->access_flags();
4245     if (scratch_class->access_flags().has_localvariable_table()) {
4246       flags.set_has_localvariable_table();
4247     } else {
4248       flags.clear_has_localvariable_table();
4249     }
4250     the_class->set_access_flags(flags);
4251   }
4252 
4253   swap_annotations(the_class, scratch_class);
4254 
4255   // Replace minor version number of class file
4256   u2 old_minor_version = the_class->minor_version();
4257   the_class->set_minor_version(scratch_class->minor_version());
4258   scratch_class->set_minor_version(old_minor_version);
4259 
4260   // Replace major version number of class file
4261   u2 old_major_version = the_class->major_version();
4262   the_class->set_major_version(scratch_class->major_version());
4263   scratch_class->set_major_version(old_major_version);
4264 
4265   // Replace CP indexes for class and name+type of enclosing method
4266   u2 old_class_idx  = the_class->enclosing_method_class_index();
4267   u2 old_method_idx = the_class->enclosing_method_method_index();
4268   the_class->set_enclosing_method_indices(
4269     scratch_class->enclosing_method_class_index(),
4270     scratch_class->enclosing_method_method_index());
4271   scratch_class->set_enclosing_method_indices(old_class_idx, old_method_idx);
4272 
4273   // Replace fingerprint data
4274   the_class->set_has_passed_fingerprint_check(scratch_class->has_passed_fingerprint_check());
4275   the_class->store_fingerprint(scratch_class->get_stored_fingerprint());
4276 
4277   the_class->set_has_been_redefined();
4278 
4279   if (!the_class->should_be_initialized()) {
4280     // Class was already initialized, so AOT has only seen the original version.
4281     // We need to let AOT look at it again.
4282     AOTLoader::load_for_klass(the_class, THREAD);
4283   }
4284 
4285   // keep track of previous versions of this class
4286   the_class->add_previous_version(scratch_class, emcp_method_count);
4287 
4288   _timer_rsc_phase1.stop();
4289   if (log_is_enabled(Info, redefine, class, timer)) {
4290     _timer_rsc_phase2.start();
4291   }
4292 
4293   if (the_class->oop_map_cache() != NULL) {
4294     // Flush references to any obsolete methods from the oop map cache
4295     // so that obsolete methods are not pinned.
4296     the_class->oop_map_cache()->flush_obsolete_entries();
4297   }
4298 
4299   increment_class_counter((InstanceKlass *)the_class, THREAD);
4300 
4301   if (EventClassRedefinition::is_enabled()) {
4302     EventClassRedefinition event;
4303     event.set_classModificationCount(java_lang_Class::classRedefinedCount(the_class->java_mirror()));
4304     event.set_redefinedClass(the_class);
4305     event.set_redefinitionId(_id);
4306     event.commit();
4307   }
4308 
4309   {
4310     ResourceMark rm(THREAD);
4311     // increment the classRedefinedCount field in the_class and in any
4312     // direct and indirect subclasses of the_class
4313     log_info(redefine, class, load)
4314       ("redefined name=%s, count=%d (avail_mem=" UINT64_FORMAT "K)",
4315        the_class->external_name(), java_lang_Class::classRedefinedCount(the_class->java_mirror()), os::available_memory() >> 10);
4316     Events::log_redefinition(THREAD, "redefined class name=%s, count=%d",
4317                              the_class->external_name(),
4318                              java_lang_Class::classRedefinedCount(the_class->java_mirror()));
4319 
4320   }
4321   _timer_rsc_phase2.stop();
4322 
4323 } // end redefine_single_class()
4324 
4325 
4326 // Increment the classRedefinedCount field in the specific InstanceKlass
4327 // and in all direct and indirect subclasses.
4328 void VM_RedefineClasses::increment_class_counter(InstanceKlass *ik, TRAPS) {
4329   oop class_mirror = ik->java_mirror();
4330   Klass* class_oop = java_lang_Class::as_Klass(class_mirror);
4331   int new_count = java_lang_Class::classRedefinedCount(class_mirror) + 1;
4332   java_lang_Class::set_classRedefinedCount(class_mirror, new_count);
4333 
4334   if (class_oop != _the_class) {
4335     // _the_class count is printed at end of redefine_single_class()
4336     log_debug(redefine, class, subclass)("updated count in subclass=%s to %d", ik->external_name(), new_count);
4337   }
4338 
4339   for (Klass *subk = ik->subklass(); subk != NULL;
4340        subk = subk->next_sibling()) {
4341     if (subk->is_instance_klass()) {
4342       // Only update instanceKlasses
4343       InstanceKlass *subik = InstanceKlass::cast(subk);
4344       // recursively do subclasses of the current subclass
4345       increment_class_counter(subik, THREAD);
4346     }
4347   }
4348 }
4349 
4350 void VM_RedefineClasses::CheckClass::do_klass(Klass* k) {
4351   bool no_old_methods = true;  // be optimistic
4352 
4353   // Both array and instance classes have vtables.
4354   // a vtable should never contain old or obsolete methods
4355   ResourceMark rm(_thread);
4356   if (k->vtable_length() > 0 &&
4357       !k->vtable().check_no_old_or_obsolete_entries()) {
4358     if (log_is_enabled(Trace, redefine, class, obsolete, metadata)) {
4359       log_trace(redefine, class, obsolete, metadata)
4360         ("klassVtable::check_no_old_or_obsolete_entries failure -- OLD or OBSOLETE method found -- class: %s",
4361          k->signature_name());
4362       k->vtable().dump_vtable();
4363     }
4364     no_old_methods = false;
4365   }
4366 
4367   if (k->is_instance_klass()) {
4368     HandleMark hm(_thread);
4369     InstanceKlass *ik = InstanceKlass::cast(k);
4370 
4371     // an itable should never contain old or obsolete methods
4372     if (ik->itable_length() > 0 &&
4373         !ik->itable().check_no_old_or_obsolete_entries()) {
4374       if (log_is_enabled(Trace, redefine, class, obsolete, metadata)) {
4375         log_trace(redefine, class, obsolete, metadata)
4376           ("klassItable::check_no_old_or_obsolete_entries failure -- OLD or OBSOLETE method found -- class: %s",
4377            ik->signature_name());
4378         ik->itable().dump_itable();
4379       }
4380       no_old_methods = false;
4381     }
4382 
4383     // the constant pool cache should never contain non-deleted old or obsolete methods
4384     if (ik->constants() != NULL &&
4385         ik->constants()->cache() != NULL &&
4386         !ik->constants()->cache()->check_no_old_or_obsolete_entries()) {
4387       if (log_is_enabled(Trace, redefine, class, obsolete, metadata)) {
4388         log_trace(redefine, class, obsolete, metadata)
4389           ("cp-cache::check_no_old_or_obsolete_entries failure -- OLD or OBSOLETE method found -- class: %s",
4390            ik->signature_name());
4391         ik->constants()->cache()->dump_cache();
4392       }
4393       no_old_methods = false;
4394     }
4395   }
4396 
4397   // print and fail guarantee if old methods are found.
4398   if (!no_old_methods) {
4399     if (log_is_enabled(Trace, redefine, class, obsolete, metadata)) {
4400       dump_methods();
4401     } else {
4402       log_trace(redefine, class)("Use the '-Xlog:redefine+class*:' option "
4403         "to see more info about the following guarantee() failure.");
4404     }
4405     guarantee(false, "OLD and/or OBSOLETE method(s) found");
4406   }
4407 }
4408 
4409 u8 VM_RedefineClasses::next_id() {
4410   while (true) {
4411     u8 id = _id_counter;
4412     u8 next_id = id + 1;
4413     u8 result = Atomic::cmpxchg(&_id_counter, id, next_id);
4414     if (result == id) {
4415       return next_id;
4416     }
4417   }
4418 }
4419 
4420 void VM_RedefineClasses::dump_methods() {
4421   int j;
4422   log_trace(redefine, class, dump)("_old_methods --");
4423   for (j = 0; j < _old_methods->length(); ++j) {
4424     LogStreamHandle(Trace, redefine, class, dump) log_stream;
4425     Method* m = _old_methods->at(j);
4426     log_stream.print("%4d  (%5d)  ", j, m->vtable_index());
4427     m->access_flags().print_on(&log_stream);
4428     log_stream.print(" --  ");
4429     m->print_name(&log_stream);
4430     log_stream.cr();
4431   }
4432   log_trace(redefine, class, dump)("_new_methods --");
4433   for (j = 0; j < _new_methods->length(); ++j) {
4434     LogStreamHandle(Trace, redefine, class, dump) log_stream;
4435     Method* m = _new_methods->at(j);
4436     log_stream.print("%4d  (%5d)  ", j, m->vtable_index());
4437     m->access_flags().print_on(&log_stream);
4438     log_stream.print(" --  ");
4439     m->print_name(&log_stream);
4440     log_stream.cr();
4441   }
4442   log_trace(redefine, class, dump)("_matching_methods --");
4443   for (j = 0; j < _matching_methods_length; ++j) {
4444     LogStreamHandle(Trace, redefine, class, dump) log_stream;
4445     Method* m = _matching_old_methods[j];
4446     log_stream.print("%4d  (%5d)  ", j, m->vtable_index());
4447     m->access_flags().print_on(&log_stream);
4448     log_stream.print(" --  ");
4449     m->print_name();
4450     log_stream.cr();
4451 
4452     m = _matching_new_methods[j];
4453     log_stream.print("      (%5d)  ", m->vtable_index());
4454     m->access_flags().print_on(&log_stream);
4455     log_stream.cr();
4456   }
4457   log_trace(redefine, class, dump)("_deleted_methods --");
4458   for (j = 0; j < _deleted_methods_length; ++j) {
4459     LogStreamHandle(Trace, redefine, class, dump) log_stream;
4460     Method* m = _deleted_methods[j];
4461     log_stream.print("%4d  (%5d)  ", j, m->vtable_index());
4462     m->access_flags().print_on(&log_stream);
4463     log_stream.print(" --  ");
4464     m->print_name(&log_stream);
4465     log_stream.cr();
4466   }
4467   log_trace(redefine, class, dump)("_added_methods --");
4468   for (j = 0; j < _added_methods_length; ++j) {
4469     LogStreamHandle(Trace, redefine, class, dump) log_stream;
4470     Method* m = _added_methods[j];
4471     log_stream.print("%4d  (%5d)  ", j, m->vtable_index());
4472     m->access_flags().print_on(&log_stream);
4473     log_stream.print(" --  ");
4474     m->print_name(&log_stream);
4475     log_stream.cr();
4476   }
4477 }
4478 
4479 void VM_RedefineClasses::print_on_error(outputStream* st) const {
4480   VM_Operation::print_on_error(st);
4481   if (_the_class != NULL) {
4482     ResourceMark rm;
4483     st->print_cr(", redefining class %s", _the_class->external_name());
4484   }
4485 }