1 /*
   2  * Copyright (c) 2003, 2017, 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/classFileStream.hpp"
  28 #include "classfile/metadataOnStackMark.hpp"
  29 #include "classfile/systemDictionary.hpp"
  30 #include "classfile/verifier.hpp"
  31 #include "code/codeCache.hpp"
  32 #include "compiler/compileBroker.hpp"
  33 #include "gc/shared/gcLocker.hpp"
  34 #include "interpreter/oopMapCache.hpp"
  35 #include "interpreter/rewriter.hpp"
  36 #include "logging/logStream.hpp"
  37 #include "memory/metadataFactory.hpp"
  38 #include "memory/metaspaceShared.hpp"
  39 #include "memory/resourceArea.hpp"
  40 #include "memory/universe.inline.hpp"
  41 #include "oops/fieldStreams.hpp"
  42 #include "oops/klassVtable.hpp"
  43 #include "oops/oop.inline.hpp"
  44 #include "prims/jvmtiImpl.hpp"
  45 #include "prims/jvmtiRedefineClasses.hpp"
  46 #include "prims/resolvedMethodTable.hpp"
  47 #include "prims/methodComparator.hpp"
  48 #include "runtime/deoptimization.hpp"
  49 #include "runtime/relocator.hpp"
  50 #include "utilities/bitMap.inline.hpp"
  51 #include "utilities/events.hpp"
  52 
  53 Array<Method*>* VM_RedefineClasses::_old_methods = NULL;
  54 Array<Method*>* VM_RedefineClasses::_new_methods = NULL;
  55 Method**  VM_RedefineClasses::_matching_old_methods = NULL;
  56 Method**  VM_RedefineClasses::_matching_new_methods = NULL;
  57 Method**  VM_RedefineClasses::_deleted_methods      = NULL;
  58 Method**  VM_RedefineClasses::_added_methods        = NULL;
  59 int         VM_RedefineClasses::_matching_methods_length = 0;
  60 int         VM_RedefineClasses::_deleted_methods_length  = 0;
  61 int         VM_RedefineClasses::_added_methods_length    = 0;
  62 Klass*      VM_RedefineClasses::_the_class = NULL;
  63 
  64 
  65 VM_RedefineClasses::VM_RedefineClasses(jint class_count,
  66                                        const jvmtiClassDefinition *class_defs,
  67                                        JvmtiClassLoadKind class_load_kind) {
  68   _class_count = class_count;
  69   _class_defs = class_defs;
  70   _class_load_kind = class_load_kind;
  71   _any_class_has_resolved_methods = false;
  72   _res = JVMTI_ERROR_NONE;
  73 }
  74 
  75 static inline InstanceKlass* get_ik(jclass def) {
  76   oop mirror = JNIHandles::resolve_non_null(def);
  77   return InstanceKlass::cast(java_lang_Class::as_Klass(mirror));
  78 }
  79 
  80 // If any of the classes are being redefined, wait
  81 // Parallel constant pool merging leads to indeterminate constant pools.
  82 void VM_RedefineClasses::lock_classes() {
  83   MutexLocker ml(RedefineClasses_lock);
  84   bool has_redefined;
  85   do {
  86     has_redefined = false;
  87     // Go through classes each time until none are being redefined.
  88     for (int i = 0; i < _class_count; i++) {
  89       if (get_ik(_class_defs[i].klass)->is_being_redefined()) {
  90         RedefineClasses_lock->wait();
  91         has_redefined = true;
  92         break;  // for loop
  93       }
  94     }
  95   } while (has_redefined);
  96   for (int i = 0; i < _class_count; i++) {
  97     get_ik(_class_defs[i].klass)->set_is_being_redefined(true);
  98   }
  99   RedefineClasses_lock->notify_all();
 100 }
 101 
 102 void VM_RedefineClasses::unlock_classes() {
 103   MutexLocker ml(RedefineClasses_lock);
 104   for (int i = 0; i < _class_count; i++) {
 105     assert(get_ik(_class_defs[i].klass)->is_being_redefined(),
 106            "should be being redefined to get here");
 107     get_ik(_class_defs[i].klass)->set_is_being_redefined(false);
 108   }
 109   RedefineClasses_lock->notify_all();
 110 }
 111 
 112 bool VM_RedefineClasses::doit_prologue() {
 113   if (_class_count == 0) {
 114     _res = JVMTI_ERROR_NONE;
 115     return false;
 116   }
 117   if (_class_defs == NULL) {
 118     _res = JVMTI_ERROR_NULL_POINTER;
 119     return false;
 120   }
 121   for (int i = 0; i < _class_count; i++) {
 122     if (_class_defs[i].klass == NULL) {
 123       _res = JVMTI_ERROR_INVALID_CLASS;
 124       return false;
 125     }
 126     if (_class_defs[i].class_byte_count == 0) {
 127       _res = JVMTI_ERROR_INVALID_CLASS_FORMAT;
 128       return false;
 129     }
 130     if (_class_defs[i].class_bytes == NULL) {
 131       _res = JVMTI_ERROR_NULL_POINTER;
 132       return false;
 133     }
 134 
 135     oop mirror = JNIHandles::resolve_non_null(_class_defs[i].klass);
 136     // classes for primitives and arrays and vm anonymous classes cannot be redefined
 137     // check here so following code can assume these classes are InstanceKlass
 138     if (!is_modifiable_class(mirror)) {
 139       _res = JVMTI_ERROR_UNMODIFIABLE_CLASS;
 140       return false;
 141     }
 142   }
 143 
 144   // Start timer after all the sanity checks; not quite accurate, but
 145   // better than adding a bunch of stop() calls.
 146   if (log_is_enabled(Info, redefine, class, timer)) {
 147     _timer_vm_op_prologue.start();
 148   }
 149 
 150   lock_classes();
 151   // We first load new class versions in the prologue, because somewhere down the
 152   // call chain it is required that the current thread is a Java thread.
 153   _res = load_new_class_versions(Thread::current());
 154   if (_res != JVMTI_ERROR_NONE) {
 155     // free any successfully created classes, since none are redefined
 156     for (int i = 0; i < _class_count; i++) {
 157       if (_scratch_classes[i] != NULL) {
 158         ClassLoaderData* cld = _scratch_classes[i]->class_loader_data();
 159         // Free the memory for this class at class unloading time.  Not before
 160         // because CMS might think this is still live.
 161         cld->add_to_deallocate_list(InstanceKlass::cast(_scratch_classes[i]));
 162       }
 163     }
 164     // Free os::malloc allocated memory in load_new_class_version.
 165     os::free(_scratch_classes);
 166     _timer_vm_op_prologue.stop();
 167     unlock_classes();
 168     return false;
 169   }
 170 
 171   _timer_vm_op_prologue.stop();
 172   return true;
 173 }
 174 
 175 void VM_RedefineClasses::doit() {
 176   Thread *thread = Thread::current();
 177 
 178   if (UseSharedSpaces) {
 179     // Sharing is enabled so we remap the shared readonly space to
 180     // shared readwrite, private just in case we need to redefine
 181     // a shared class. We do the remap during the doit() phase of
 182     // the safepoint to be safer.
 183     if (!MetaspaceShared::remap_shared_readonly_as_readwrite()) {
 184       log_info(redefine, class, load)("failed to remap shared readonly space to readwrite, private");
 185       _res = JVMTI_ERROR_INTERNAL;
 186       return;
 187     }
 188   }
 189 
 190   // Mark methods seen on stack and everywhere else so old methods are not
 191   // cleaned up if they're on the stack.
 192   MetadataOnStackMark md_on_stack(true);
 193   HandleMark hm(thread);   // make sure any handles created are deleted
 194                            // before the stack walk again.
 195 
 196   for (int i = 0; i < _class_count; i++) {
 197     redefine_single_class(_class_defs[i].klass, _scratch_classes[i], thread);
 198   }
 199 
 200   // Clean out MethodData pointing to old Method*
 201   // Have to do this after all classes are redefined and all methods that
 202   // are redefined are marked as old.
 203   MethodDataCleaner clean_weak_method_links;
 204   ClassLoaderDataGraph::classes_do(&clean_weak_method_links);
 205 
 206   // JSR-292 support
 207   if (_any_class_has_resolved_methods) {
 208     bool trace_name_printed = false;
 209     ResolvedMethodTable::adjust_method_entries(&trace_name_printed);
 210   }
 211 
 212   // Disable any dependent concurrent compilations
 213   SystemDictionary::notice_modification();
 214 
 215   // Set flag indicating that some invariants are no longer true.
 216   // See jvmtiExport.hpp for detailed explanation.
 217   JvmtiExport::set_has_redefined_a_class();
 218 
 219   // check_class() is optionally called for product bits, but is
 220   // always called for non-product bits.
 221 #ifdef PRODUCT
 222   if (log_is_enabled(Trace, redefine, class, obsolete, metadata)) {
 223 #endif
 224     log_trace(redefine, class, obsolete, metadata)("calling check_class");
 225     CheckClass check_class(thread);
 226     ClassLoaderDataGraph::classes_do(&check_class);
 227 #ifdef PRODUCT
 228   }
 229 #endif
 230 }
 231 
 232 void VM_RedefineClasses::doit_epilogue() {
 233   unlock_classes();
 234 
 235   // Free os::malloc allocated memory.
 236   os::free(_scratch_classes);
 237 
 238   // Reset the_class to null for error printing.
 239   _the_class = NULL;
 240 
 241   if (log_is_enabled(Info, redefine, class, timer)) {
 242     // Used to have separate timers for "doit" and "all", but the timer
 243     // overhead skewed the measurements.
 244     jlong doit_time = _timer_rsc_phase1.milliseconds() +
 245                       _timer_rsc_phase2.milliseconds();
 246     jlong all_time = _timer_vm_op_prologue.milliseconds() + doit_time;
 247 
 248     log_info(redefine, class, timer)
 249       ("vm_op: all=" UINT64_FORMAT "  prologue=" UINT64_FORMAT "  doit=" UINT64_FORMAT,
 250        all_time, _timer_vm_op_prologue.milliseconds(), doit_time);
 251     log_info(redefine, class, timer)
 252       ("redefine_single_class: phase1=" UINT64_FORMAT "  phase2=" UINT64_FORMAT,
 253        _timer_rsc_phase1.milliseconds(), _timer_rsc_phase2.milliseconds());
 254   }
 255 }
 256 
 257 bool VM_RedefineClasses::is_modifiable_class(oop klass_mirror) {
 258   // classes for primitives cannot be redefined
 259   if (java_lang_Class::is_primitive(klass_mirror)) {
 260     return false;
 261   }
 262   Klass* k = java_lang_Class::as_Klass(klass_mirror);
 263   // classes for arrays cannot be redefined
 264   if (k == NULL || !k->is_instance_klass()) {
 265     return false;
 266   }
 267 
 268   // Cannot redefine or retransform an anonymous class.
 269   if (InstanceKlass::cast(k)->is_anonymous()) {
 270     return false;
 271   }
 272   return true;
 273 }
 274 
 275 // Append the current entry at scratch_i in scratch_cp to *merge_cp_p
 276 // where the end of *merge_cp_p is specified by *merge_cp_length_p. For
 277 // direct CP entries, there is just the current entry to append. For
 278 // indirect and double-indirect CP entries, there are zero or more
 279 // referenced CP entries along with the current entry to append.
 280 // Indirect and double-indirect CP entries are handled by recursive
 281 // calls to append_entry() as needed. The referenced CP entries are
 282 // always appended to *merge_cp_p before the referee CP entry. These
 283 // referenced CP entries may already exist in *merge_cp_p in which case
 284 // there is nothing extra to append and only the current entry is
 285 // appended.
 286 void VM_RedefineClasses::append_entry(const constantPoolHandle& scratch_cp,
 287        int scratch_i, constantPoolHandle *merge_cp_p, int *merge_cp_length_p,
 288        TRAPS) {
 289 
 290   // append is different depending on entry tag type
 291   switch (scratch_cp->tag_at(scratch_i).value()) {
 292 
 293     // The old verifier is implemented outside the VM. It loads classes,
 294     // but does not resolve constant pool entries directly so we never
 295     // see Class entries here with the old verifier. Similarly the old
 296     // verifier does not like Class entries in the input constant pool.
 297     // The split-verifier is implemented in the VM so it can optionally
 298     // and directly resolve constant pool entries to load classes. The
 299     // split-verifier can accept either Class entries or UnresolvedClass
 300     // entries in the input constant pool. We revert the appended copy
 301     // back to UnresolvedClass so that either verifier will be happy
 302     // with the constant pool entry.
 303     //
 304     // this is an indirect CP entry so it needs special handling
 305     case JVM_CONSTANT_Class:
 306     case JVM_CONSTANT_UnresolvedClass:
 307     {
 308       int name_i = scratch_cp->klass_name_index_at(scratch_i);
 309       int new_name_i = find_or_append_indirect_entry(scratch_cp, name_i, merge_cp_p,
 310                                                      merge_cp_length_p, THREAD);
 311 
 312       if (new_name_i != name_i) {
 313         log_trace(redefine, class, constantpool)
 314           ("Class entry@%d name_index change: %d to %d",
 315            *merge_cp_length_p, name_i, new_name_i);
 316       }
 317 
 318       (*merge_cp_p)->temp_unresolved_klass_at_put(*merge_cp_length_p, new_name_i);
 319       if (scratch_i != *merge_cp_length_p) {
 320         // The new entry in *merge_cp_p is at a different index than
 321         // the new entry in scratch_cp so we need to map the index values.
 322         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 323       }
 324       (*merge_cp_length_p)++;
 325     } break;
 326 
 327     // these are direct CP entries so they can be directly appended,
 328     // but double and long take two constant pool entries
 329     case JVM_CONSTANT_Double:  // fall through
 330     case JVM_CONSTANT_Long:
 331     {
 332       ConstantPool::copy_entry_to(scratch_cp, scratch_i, *merge_cp_p, *merge_cp_length_p,
 333         THREAD);
 334 
 335       if (scratch_i != *merge_cp_length_p) {
 336         // The new entry in *merge_cp_p is at a different index than
 337         // the new entry in scratch_cp so we need to map the index values.
 338         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 339       }
 340       (*merge_cp_length_p) += 2;
 341     } break;
 342 
 343     // these are direct CP entries so they can be directly appended
 344     case JVM_CONSTANT_Float:   // fall through
 345     case JVM_CONSTANT_Integer: // fall through
 346     case JVM_CONSTANT_Utf8:    // fall through
 347 
 348     // This was an indirect CP entry, but it has been changed into
 349     // Symbol*s so this entry can be directly appended.
 350     case JVM_CONSTANT_String:      // fall through
 351     {
 352       ConstantPool::copy_entry_to(scratch_cp, scratch_i, *merge_cp_p, *merge_cp_length_p,
 353         THREAD);
 354 
 355       if (scratch_i != *merge_cp_length_p) {
 356         // The new entry in *merge_cp_p is at a different index than
 357         // the new entry in scratch_cp so we need to map the index values.
 358         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 359       }
 360       (*merge_cp_length_p)++;
 361     } break;
 362 
 363     // this is an indirect CP entry so it needs special handling
 364     case JVM_CONSTANT_NameAndType:
 365     {
 366       int name_ref_i = scratch_cp->name_ref_index_at(scratch_i);
 367       int new_name_ref_i = find_or_append_indirect_entry(scratch_cp, name_ref_i, merge_cp_p,
 368                                                          merge_cp_length_p, THREAD);
 369 
 370       int signature_ref_i = scratch_cp->signature_ref_index_at(scratch_i);
 371       int new_signature_ref_i = find_or_append_indirect_entry(scratch_cp, signature_ref_i,
 372                                                               merge_cp_p, merge_cp_length_p,
 373                                                               THREAD);
 374 
 375       // If the referenced entries already exist in *merge_cp_p, then
 376       // both new_name_ref_i and new_signature_ref_i will both be 0.
 377       // In that case, all we are appending is the current entry.
 378       if (new_name_ref_i != name_ref_i) {
 379         log_trace(redefine, class, constantpool)
 380           ("NameAndType entry@%d name_ref_index change: %d to %d",
 381            *merge_cp_length_p, name_ref_i, new_name_ref_i);
 382       }
 383       if (new_signature_ref_i != signature_ref_i) {
 384         log_trace(redefine, class, constantpool)
 385           ("NameAndType entry@%d signature_ref_index change: %d to %d",
 386            *merge_cp_length_p, signature_ref_i, new_signature_ref_i);
 387       }
 388 
 389       (*merge_cp_p)->name_and_type_at_put(*merge_cp_length_p,
 390         new_name_ref_i, new_signature_ref_i);
 391       if (scratch_i != *merge_cp_length_p) {
 392         // The new entry in *merge_cp_p is at a different index than
 393         // the new entry in scratch_cp so we need to map the index values.
 394         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 395       }
 396       (*merge_cp_length_p)++;
 397     } break;
 398 
 399     // this is a double-indirect CP entry so it needs special handling
 400     case JVM_CONSTANT_Fieldref:           // fall through
 401     case JVM_CONSTANT_InterfaceMethodref: // fall through
 402     case JVM_CONSTANT_Methodref:
 403     {
 404       int klass_ref_i = scratch_cp->uncached_klass_ref_index_at(scratch_i);
 405       int new_klass_ref_i = find_or_append_indirect_entry(scratch_cp, klass_ref_i,
 406                                                           merge_cp_p, merge_cp_length_p, THREAD);
 407 
 408       int name_and_type_ref_i = scratch_cp->uncached_name_and_type_ref_index_at(scratch_i);
 409       int new_name_and_type_ref_i = find_or_append_indirect_entry(scratch_cp, name_and_type_ref_i,
 410                                                           merge_cp_p, merge_cp_length_p, THREAD);
 411 
 412       const char *entry_name = NULL;
 413       switch (scratch_cp->tag_at(scratch_i).value()) {
 414       case JVM_CONSTANT_Fieldref:
 415         entry_name = "Fieldref";
 416         (*merge_cp_p)->field_at_put(*merge_cp_length_p, new_klass_ref_i,
 417           new_name_and_type_ref_i);
 418         break;
 419       case JVM_CONSTANT_InterfaceMethodref:
 420         entry_name = "IFMethodref";
 421         (*merge_cp_p)->interface_method_at_put(*merge_cp_length_p,
 422           new_klass_ref_i, new_name_and_type_ref_i);
 423         break;
 424       case JVM_CONSTANT_Methodref:
 425         entry_name = "Methodref";
 426         (*merge_cp_p)->method_at_put(*merge_cp_length_p, new_klass_ref_i,
 427           new_name_and_type_ref_i);
 428         break;
 429       default:
 430         guarantee(false, "bad switch");
 431         break;
 432       }
 433 
 434       if (klass_ref_i != new_klass_ref_i) {
 435         log_trace(redefine, class, constantpool)
 436           ("%s entry@%d class_index changed: %d to %d", entry_name, *merge_cp_length_p, klass_ref_i, new_klass_ref_i);
 437       }
 438       if (name_and_type_ref_i != new_name_and_type_ref_i) {
 439         log_trace(redefine, class, constantpool)
 440           ("%s entry@%d name_and_type_index changed: %d to %d",
 441            entry_name, *merge_cp_length_p, name_and_type_ref_i, new_name_and_type_ref_i);
 442       }
 443 
 444       if (scratch_i != *merge_cp_length_p) {
 445         // The new entry in *merge_cp_p is at a different index than
 446         // the new entry in scratch_cp so we need to map the index values.
 447         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 448       }
 449       (*merge_cp_length_p)++;
 450     } break;
 451 
 452     // this is an indirect CP entry so it needs special handling
 453     case JVM_CONSTANT_MethodType:
 454     {
 455       int ref_i = scratch_cp->method_type_index_at(scratch_i);
 456       int new_ref_i = find_or_append_indirect_entry(scratch_cp, ref_i, merge_cp_p,
 457                                                     merge_cp_length_p, THREAD);
 458       if (new_ref_i != ref_i) {
 459         log_trace(redefine, class, constantpool)
 460           ("MethodType entry@%d ref_index change: %d to %d", *merge_cp_length_p, ref_i, new_ref_i);
 461       }
 462       (*merge_cp_p)->method_type_index_at_put(*merge_cp_length_p, new_ref_i);
 463       if (scratch_i != *merge_cp_length_p) {
 464         // The new entry in *merge_cp_p is at a different index than
 465         // the new entry in scratch_cp so we need to map the index values.
 466         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 467       }
 468       (*merge_cp_length_p)++;
 469     } break;
 470 
 471     // this is an indirect CP entry so it needs special handling
 472     case JVM_CONSTANT_MethodHandle:
 473     {
 474       int ref_kind = scratch_cp->method_handle_ref_kind_at(scratch_i);
 475       int ref_i = scratch_cp->method_handle_index_at(scratch_i);
 476       int new_ref_i = find_or_append_indirect_entry(scratch_cp, ref_i, merge_cp_p,
 477                                                     merge_cp_length_p, THREAD);
 478       if (new_ref_i != ref_i) {
 479         log_trace(redefine, class, constantpool)
 480           ("MethodHandle entry@%d ref_index change: %d to %d", *merge_cp_length_p, ref_i, new_ref_i);
 481       }
 482       (*merge_cp_p)->method_handle_index_at_put(*merge_cp_length_p, ref_kind, new_ref_i);
 483       if (scratch_i != *merge_cp_length_p) {
 484         // The new entry in *merge_cp_p is at a different index than
 485         // the new entry in scratch_cp so we need to map the index values.
 486         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 487       }
 488       (*merge_cp_length_p)++;
 489     } break;
 490 
 491     // this is an indirect CP entry so it needs special handling
 492     case JVM_CONSTANT_InvokeDynamic:
 493     {
 494       // Index of the bootstrap specifier in the operands array
 495       int old_bs_i = scratch_cp->invoke_dynamic_bootstrap_specifier_index(scratch_i);
 496       int new_bs_i = find_or_append_operand(scratch_cp, old_bs_i, merge_cp_p,
 497                                             merge_cp_length_p, THREAD);
 498       // The bootstrap method NameAndType_info index
 499       int old_ref_i = scratch_cp->invoke_dynamic_name_and_type_ref_index_at(scratch_i);
 500       int new_ref_i = find_or_append_indirect_entry(scratch_cp, old_ref_i, merge_cp_p,
 501                                                     merge_cp_length_p, THREAD);
 502       if (new_bs_i != old_bs_i) {
 503         log_trace(redefine, class, constantpool)
 504           ("InvokeDynamic entry@%d bootstrap_method_attr_index change: %d to %d",
 505            *merge_cp_length_p, old_bs_i, new_bs_i);
 506       }
 507       if (new_ref_i != old_ref_i) {
 508         log_trace(redefine, class, constantpool)
 509           ("InvokeDynamic entry@%d name_and_type_index change: %d to %d", *merge_cp_length_p, old_ref_i, new_ref_i);
 510       }
 511 
 512       (*merge_cp_p)->invoke_dynamic_at_put(*merge_cp_length_p, new_bs_i, new_ref_i);
 513       if (scratch_i != *merge_cp_length_p) {
 514         // The new entry in *merge_cp_p is at a different index than
 515         // the new entry in scratch_cp so we need to map the index values.
 516         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 517       }
 518       (*merge_cp_length_p)++;
 519     } break;
 520 
 521     // At this stage, Class or UnresolvedClass could be in scratch_cp, but not
 522     // ClassIndex
 523     case JVM_CONSTANT_ClassIndex: // fall through
 524 
 525     // Invalid is used as the tag for the second constant pool entry
 526     // occupied by JVM_CONSTANT_Double or JVM_CONSTANT_Long. It should
 527     // not be seen by itself.
 528     case JVM_CONSTANT_Invalid: // fall through
 529 
 530     // At this stage, String could be here, but not StringIndex
 531     case JVM_CONSTANT_StringIndex: // fall through
 532 
 533     // At this stage JVM_CONSTANT_UnresolvedClassInError should not be
 534     // here
 535     case JVM_CONSTANT_UnresolvedClassInError: // fall through
 536 
 537     default:
 538     {
 539       // leave a breadcrumb
 540       jbyte bad_value = scratch_cp->tag_at(scratch_i).value();
 541       ShouldNotReachHere();
 542     } break;
 543   } // end switch tag value
 544 } // end append_entry()
 545 
 546 
 547 int VM_RedefineClasses::find_or_append_indirect_entry(const constantPoolHandle& scratch_cp,
 548       int ref_i, constantPoolHandle *merge_cp_p, int *merge_cp_length_p, TRAPS) {
 549 
 550   int new_ref_i = ref_i;
 551   bool match = (ref_i < *merge_cp_length_p) &&
 552                scratch_cp->compare_entry_to(ref_i, *merge_cp_p, ref_i, THREAD);
 553 
 554   if (!match) {
 555     // forward reference in *merge_cp_p or not a direct match
 556     int found_i = scratch_cp->find_matching_entry(ref_i, *merge_cp_p, THREAD);
 557     if (found_i != 0) {
 558       guarantee(found_i != ref_i, "compare_entry_to() and find_matching_entry() do not agree");
 559       // Found a matching entry somewhere else in *merge_cp_p so just need a mapping entry.
 560       new_ref_i = found_i;
 561       map_index(scratch_cp, ref_i, found_i);
 562     } else {
 563       // no match found so we have to append this entry to *merge_cp_p
 564       append_entry(scratch_cp, ref_i, merge_cp_p, merge_cp_length_p, THREAD);
 565       // The above call to append_entry() can only append one entry
 566       // so the post call query of *merge_cp_length_p is only for
 567       // the sake of consistency.
 568       new_ref_i = *merge_cp_length_p - 1;
 569     }
 570   }
 571 
 572   return new_ref_i;
 573 } // end find_or_append_indirect_entry()
 574 
 575 
 576 // Append a bootstrap specifier into the merge_cp operands that is semantically equal
 577 // to the scratch_cp operands bootstrap specifier passed by the old_bs_i index.
 578 // Recursively append new merge_cp entries referenced by the new bootstrap specifier.
 579 void VM_RedefineClasses::append_operand(const constantPoolHandle& scratch_cp, int old_bs_i,
 580        constantPoolHandle *merge_cp_p, int *merge_cp_length_p, TRAPS) {
 581 
 582   int old_ref_i = scratch_cp->operand_bootstrap_method_ref_index_at(old_bs_i);
 583   int new_ref_i = find_or_append_indirect_entry(scratch_cp, old_ref_i, merge_cp_p,
 584                                                 merge_cp_length_p, THREAD);
 585   if (new_ref_i != old_ref_i) {
 586     log_trace(redefine, class, constantpool)
 587       ("operands entry@%d bootstrap method ref_index change: %d to %d", _operands_cur_length, old_ref_i, new_ref_i);
 588   }
 589 
 590   Array<u2>* merge_ops = (*merge_cp_p)->operands();
 591   int new_bs_i = _operands_cur_length;
 592   // We have _operands_cur_length == 0 when the merge_cp operands is empty yet.
 593   // However, the operand_offset_at(0) was set in the extend_operands() call.
 594   int new_base = (new_bs_i == 0) ? (*merge_cp_p)->operand_offset_at(0)
 595                                  : (*merge_cp_p)->operand_next_offset_at(new_bs_i - 1);
 596   int argc     = scratch_cp->operand_argument_count_at(old_bs_i);
 597 
 598   ConstantPool::operand_offset_at_put(merge_ops, _operands_cur_length, new_base);
 599   merge_ops->at_put(new_base++, new_ref_i);
 600   merge_ops->at_put(new_base++, argc);
 601 
 602   for (int i = 0; i < argc; i++) {
 603     int old_arg_ref_i = scratch_cp->operand_argument_index_at(old_bs_i, i);
 604     int new_arg_ref_i = find_or_append_indirect_entry(scratch_cp, old_arg_ref_i, merge_cp_p,
 605                                                       merge_cp_length_p, THREAD);
 606     merge_ops->at_put(new_base++, new_arg_ref_i);
 607     if (new_arg_ref_i != old_arg_ref_i) {
 608       log_trace(redefine, class, constantpool)
 609         ("operands entry@%d bootstrap method argument ref_index change: %d to %d",
 610          _operands_cur_length, old_arg_ref_i, new_arg_ref_i);
 611     }
 612   }
 613   if (old_bs_i != _operands_cur_length) {
 614     // The bootstrap specifier in *merge_cp_p is at a different index than
 615     // that in scratch_cp so we need to map the index values.
 616     map_operand_index(old_bs_i, new_bs_i);
 617   }
 618   _operands_cur_length++;
 619 } // end append_operand()
 620 
 621 
 622 int VM_RedefineClasses::find_or_append_operand(const constantPoolHandle& scratch_cp,
 623       int old_bs_i, constantPoolHandle *merge_cp_p, int *merge_cp_length_p, TRAPS) {
 624 
 625   int new_bs_i = old_bs_i; // bootstrap specifier index
 626   bool match = (old_bs_i < _operands_cur_length) &&
 627                scratch_cp->compare_operand_to(old_bs_i, *merge_cp_p, old_bs_i, THREAD);
 628 
 629   if (!match) {
 630     // forward reference in *merge_cp_p or not a direct match
 631     int found_i = scratch_cp->find_matching_operand(old_bs_i, *merge_cp_p,
 632                                                     _operands_cur_length, THREAD);
 633     if (found_i != -1) {
 634       guarantee(found_i != old_bs_i, "compare_operand_to() and find_matching_operand() disagree");
 635       // found a matching operand somewhere else in *merge_cp_p so just need a mapping
 636       new_bs_i = found_i;
 637       map_operand_index(old_bs_i, found_i);
 638     } else {
 639       // no match found so we have to append this bootstrap specifier to *merge_cp_p
 640       append_operand(scratch_cp, old_bs_i, merge_cp_p, merge_cp_length_p, THREAD);
 641       new_bs_i = _operands_cur_length - 1;
 642     }
 643   }
 644   return new_bs_i;
 645 } // end find_or_append_operand()
 646 
 647 
 648 void VM_RedefineClasses::finalize_operands_merge(const constantPoolHandle& merge_cp, TRAPS) {
 649   if (merge_cp->operands() == NULL) {
 650     return;
 651   }
 652   // Shrink the merge_cp operands
 653   merge_cp->shrink_operands(_operands_cur_length, CHECK);
 654 
 655   if (log_is_enabled(Trace, redefine, class, constantpool)) {
 656     // don't want to loop unless we are tracing
 657     int count = 0;
 658     for (int i = 1; i < _operands_index_map_p->length(); i++) {
 659       int value = _operands_index_map_p->at(i);
 660       if (value != -1) {
 661         log_trace(redefine, class, constantpool)("operands_index_map[%d]: old=%d new=%d", count, i, value);
 662         count++;
 663       }
 664     }
 665   }
 666   // Clean-up
 667   _operands_index_map_p = NULL;
 668   _operands_cur_length = 0;
 669   _operands_index_map_count = 0;
 670 } // end finalize_operands_merge()
 671 
 672 
 673 jvmtiError VM_RedefineClasses::compare_and_normalize_class_versions(
 674              InstanceKlass* the_class,
 675              InstanceKlass* scratch_class) {
 676   int i;
 677 
 678   // Check superclasses, or rather their names, since superclasses themselves can be
 679   // requested to replace.
 680   // Check for NULL superclass first since this might be java.lang.Object
 681   if (the_class->super() != scratch_class->super() &&
 682       (the_class->super() == NULL || scratch_class->super() == NULL ||
 683        the_class->super()->name() !=
 684        scratch_class->super()->name())) {
 685     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_HIERARCHY_CHANGED;
 686   }
 687 
 688   // Check if the number, names and order of directly implemented interfaces are the same.
 689   // I think in principle we should just check if the sets of names of directly implemented
 690   // interfaces are the same, i.e. the order of declaration (which, however, if changed in the
 691   // .java file, also changes in .class file) should not matter. However, comparing sets is
 692   // technically a bit more difficult, and, more importantly, I am not sure at present that the
 693   // order of interfaces does not matter on the implementation level, i.e. that the VM does not
 694   // rely on it somewhere.
 695   Array<Klass*>* k_interfaces = the_class->local_interfaces();
 696   Array<Klass*>* k_new_interfaces = scratch_class->local_interfaces();
 697   int n_intfs = k_interfaces->length();
 698   if (n_intfs != k_new_interfaces->length()) {
 699     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_HIERARCHY_CHANGED;
 700   }
 701   for (i = 0; i < n_intfs; i++) {
 702     if (k_interfaces->at(i)->name() !=
 703         k_new_interfaces->at(i)->name()) {
 704       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_HIERARCHY_CHANGED;
 705     }
 706   }
 707 
 708   // Check whether class is in the error init state.
 709   if (the_class->is_in_error_state()) {
 710     // TBD #5057930: special error code is needed in 1.6
 711     return JVMTI_ERROR_INVALID_CLASS;
 712   }
 713 
 714   // Check whether class modifiers are the same.
 715   jushort old_flags = (jushort) the_class->access_flags().get_flags();
 716   jushort new_flags = (jushort) scratch_class->access_flags().get_flags();
 717   if (old_flags != new_flags) {
 718     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_MODIFIERS_CHANGED;
 719   }
 720 
 721   // Check if the number, names, types and order of fields declared in these classes
 722   // are the same.
 723   JavaFieldStream old_fs(the_class);
 724   JavaFieldStream new_fs(scratch_class);
 725   for (; !old_fs.done() && !new_fs.done(); old_fs.next(), new_fs.next()) {
 726     // access
 727     old_flags = old_fs.access_flags().as_short();
 728     new_flags = new_fs.access_flags().as_short();
 729     if ((old_flags ^ new_flags) & JVM_RECOGNIZED_FIELD_MODIFIERS) {
 730       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_SCHEMA_CHANGED;
 731     }
 732     // offset
 733     if (old_fs.offset() != new_fs.offset()) {
 734       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_SCHEMA_CHANGED;
 735     }
 736     // name and signature
 737     Symbol* name_sym1 = the_class->constants()->symbol_at(old_fs.name_index());
 738     Symbol* sig_sym1 = the_class->constants()->symbol_at(old_fs.signature_index());
 739     Symbol* name_sym2 = scratch_class->constants()->symbol_at(new_fs.name_index());
 740     Symbol* sig_sym2 = scratch_class->constants()->symbol_at(new_fs.signature_index());
 741     if (name_sym1 != name_sym2 || sig_sym1 != sig_sym2) {
 742       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_SCHEMA_CHANGED;
 743     }
 744   }
 745 
 746   // If both streams aren't done then we have a differing number of
 747   // fields.
 748   if (!old_fs.done() || !new_fs.done()) {
 749     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_SCHEMA_CHANGED;
 750   }
 751 
 752   // Do a parallel walk through the old and new methods. Detect
 753   // cases where they match (exist in both), have been added in
 754   // the new methods, or have been deleted (exist only in the
 755   // old methods).  The class file parser places methods in order
 756   // by method name, but does not order overloaded methods by
 757   // signature.  In order to determine what fate befell the methods,
 758   // this code places the overloaded new methods that have matching
 759   // old methods in the same order as the old methods and places
 760   // new overloaded methods at the end of overloaded methods of
 761   // that name. The code for this order normalization is adapted
 762   // from the algorithm used in InstanceKlass::find_method().
 763   // Since we are swapping out of order entries as we find them,
 764   // we only have to search forward through the overloaded methods.
 765   // Methods which are added and have the same name as an existing
 766   // method (but different signature) will be put at the end of
 767   // the methods with that name, and the name mismatch code will
 768   // handle them.
 769   Array<Method*>* k_old_methods(the_class->methods());
 770   Array<Method*>* k_new_methods(scratch_class->methods());
 771   int n_old_methods = k_old_methods->length();
 772   int n_new_methods = k_new_methods->length();
 773   Thread* thread = Thread::current();
 774 
 775   int ni = 0;
 776   int oi = 0;
 777   while (true) {
 778     Method* k_old_method;
 779     Method* k_new_method;
 780     enum { matched, added, deleted, undetermined } method_was = undetermined;
 781 
 782     if (oi >= n_old_methods) {
 783       if (ni >= n_new_methods) {
 784         break; // we've looked at everything, done
 785       }
 786       // New method at the end
 787       k_new_method = k_new_methods->at(ni);
 788       method_was = added;
 789     } else if (ni >= n_new_methods) {
 790       // Old method, at the end, is deleted
 791       k_old_method = k_old_methods->at(oi);
 792       method_was = deleted;
 793     } else {
 794       // There are more methods in both the old and new lists
 795       k_old_method = k_old_methods->at(oi);
 796       k_new_method = k_new_methods->at(ni);
 797       if (k_old_method->name() != k_new_method->name()) {
 798         // Methods are sorted by method name, so a mismatch means added
 799         // or deleted
 800         if (k_old_method->name()->fast_compare(k_new_method->name()) > 0) {
 801           method_was = added;
 802         } else {
 803           method_was = deleted;
 804         }
 805       } else if (k_old_method->signature() == k_new_method->signature()) {
 806         // Both the name and signature match
 807         method_was = matched;
 808       } else {
 809         // The name matches, but the signature doesn't, which means we have to
 810         // search forward through the new overloaded methods.
 811         int nj;  // outside the loop for post-loop check
 812         for (nj = ni + 1; nj < n_new_methods; nj++) {
 813           Method* m = k_new_methods->at(nj);
 814           if (k_old_method->name() != m->name()) {
 815             // reached another method name so no more overloaded methods
 816             method_was = deleted;
 817             break;
 818           }
 819           if (k_old_method->signature() == m->signature()) {
 820             // found a match so swap the methods
 821             k_new_methods->at_put(ni, m);
 822             k_new_methods->at_put(nj, k_new_method);
 823             k_new_method = m;
 824             method_was = matched;
 825             break;
 826           }
 827         }
 828 
 829         if (nj >= n_new_methods) {
 830           // reached the end without a match; so method was deleted
 831           method_was = deleted;
 832         }
 833       }
 834     }
 835 
 836     switch (method_was) {
 837     case matched:
 838       // methods match, be sure modifiers do too
 839       old_flags = (jushort) k_old_method->access_flags().get_flags();
 840       new_flags = (jushort) k_new_method->access_flags().get_flags();
 841       if ((old_flags ^ new_flags) & ~(JVM_ACC_NATIVE)) {
 842         return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_METHOD_MODIFIERS_CHANGED;
 843       }
 844       {
 845         u2 new_num = k_new_method->method_idnum();
 846         u2 old_num = k_old_method->method_idnum();
 847         if (new_num != old_num) {
 848           Method* idnum_owner = scratch_class->method_with_idnum(old_num);
 849           if (idnum_owner != NULL) {
 850             // There is already a method assigned this idnum -- switch them
 851             // Take current and original idnum from the new_method
 852             idnum_owner->set_method_idnum(new_num);
 853             idnum_owner->set_orig_method_idnum(k_new_method->orig_method_idnum());
 854           }
 855           // Take current and original idnum from the old_method
 856           k_new_method->set_method_idnum(old_num);
 857           k_new_method->set_orig_method_idnum(k_old_method->orig_method_idnum());
 858           if (thread->has_pending_exception()) {
 859             return JVMTI_ERROR_OUT_OF_MEMORY;
 860           }
 861         }
 862       }
 863       log_trace(redefine, class, normalize)
 864         ("Method matched: new: %s [%d] == old: %s [%d]",
 865          k_new_method->name_and_sig_as_C_string(), ni, k_old_method->name_and_sig_as_C_string(), oi);
 866       // advance to next pair of methods
 867       ++oi;
 868       ++ni;
 869       break;
 870     case added:
 871       // method added, see if it is OK
 872       new_flags = (jushort) k_new_method->access_flags().get_flags();
 873       if ((new_flags & JVM_ACC_PRIVATE) == 0
 874            // hack: private should be treated as final, but alas
 875           || (new_flags & (JVM_ACC_FINAL|JVM_ACC_STATIC)) == 0
 876          ) {
 877         // new methods must be private
 878         return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_METHOD_ADDED;
 879       }
 880       {
 881         u2 num = the_class->next_method_idnum();
 882         if (num == ConstMethod::UNSET_IDNUM) {
 883           // cannot add any more methods
 884           return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_METHOD_ADDED;
 885         }
 886         u2 new_num = k_new_method->method_idnum();
 887         Method* idnum_owner = scratch_class->method_with_idnum(num);
 888         if (idnum_owner != NULL) {
 889           // There is already a method assigned this idnum -- switch them
 890           // Take current and original idnum from the new_method
 891           idnum_owner->set_method_idnum(new_num);
 892           idnum_owner->set_orig_method_idnum(k_new_method->orig_method_idnum());
 893         }
 894         k_new_method->set_method_idnum(num);
 895         k_new_method->set_orig_method_idnum(num);
 896         if (thread->has_pending_exception()) {
 897           return JVMTI_ERROR_OUT_OF_MEMORY;
 898         }
 899       }
 900       log_trace(redefine, class, normalize)
 901         ("Method added: new: %s [%d]", k_new_method->name_and_sig_as_C_string(), ni);
 902       ++ni; // advance to next new method
 903       break;
 904     case deleted:
 905       // method deleted, see if it is OK
 906       old_flags = (jushort) k_old_method->access_flags().get_flags();
 907       if ((old_flags & JVM_ACC_PRIVATE) == 0
 908            // hack: private should be treated as final, but alas
 909           || (old_flags & (JVM_ACC_FINAL|JVM_ACC_STATIC)) == 0
 910          ) {
 911         // deleted methods must be private
 912         return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_METHOD_DELETED;
 913       }
 914       log_trace(redefine, class, normalize)
 915         ("Method deleted: old: %s [%d]", k_old_method->name_and_sig_as_C_string(), oi);
 916       ++oi; // advance to next old method
 917       break;
 918     default:
 919       ShouldNotReachHere();
 920     }
 921   }
 922 
 923   return JVMTI_ERROR_NONE;
 924 }
 925 
 926 
 927 // Find new constant pool index value for old constant pool index value
 928 // by seaching the index map. Returns zero (0) if there is no mapped
 929 // value for the old constant pool index.
 930 int VM_RedefineClasses::find_new_index(int old_index) {
 931   if (_index_map_count == 0) {
 932     // map is empty so nothing can be found
 933     return 0;
 934   }
 935 
 936   if (old_index < 1 || old_index >= _index_map_p->length()) {
 937     // The old_index is out of range so it is not mapped. This should
 938     // not happen in regular constant pool merging use, but it can
 939     // happen if a corrupt annotation is processed.
 940     return 0;
 941   }
 942 
 943   int value = _index_map_p->at(old_index);
 944   if (value == -1) {
 945     // the old_index is not mapped
 946     return 0;
 947   }
 948 
 949   return value;
 950 } // end find_new_index()
 951 
 952 
 953 // Find new bootstrap specifier index value for old bootstrap specifier index
 954 // value by seaching the index map. Returns unused index (-1) if there is
 955 // no mapped value for the old bootstrap specifier index.
 956 int VM_RedefineClasses::find_new_operand_index(int old_index) {
 957   if (_operands_index_map_count == 0) {
 958     // map is empty so nothing can be found
 959     return -1;
 960   }
 961 
 962   if (old_index == -1 || old_index >= _operands_index_map_p->length()) {
 963     // The old_index is out of range so it is not mapped.
 964     // This should not happen in regular constant pool merging use.
 965     return -1;
 966   }
 967 
 968   int value = _operands_index_map_p->at(old_index);
 969   if (value == -1) {
 970     // the old_index is not mapped
 971     return -1;
 972   }
 973 
 974   return value;
 975 } // end find_new_operand_index()
 976 
 977 
 978 // Returns true if the current mismatch is due to a resolved/unresolved
 979 // class pair. Otherwise, returns false.
 980 bool VM_RedefineClasses::is_unresolved_class_mismatch(const constantPoolHandle& cp1,
 981        int index1, const constantPoolHandle& cp2, int index2) {
 982 
 983   jbyte t1 = cp1->tag_at(index1).value();
 984   if (t1 != JVM_CONSTANT_Class && t1 != JVM_CONSTANT_UnresolvedClass) {
 985     return false;  // wrong entry type; not our special case
 986   }
 987 
 988   jbyte t2 = cp2->tag_at(index2).value();
 989   if (t2 != JVM_CONSTANT_Class && t2 != JVM_CONSTANT_UnresolvedClass) {
 990     return false;  // wrong entry type; not our special case
 991   }
 992 
 993   if (t1 == t2) {
 994     return false;  // not a mismatch; not our special case
 995   }
 996 
 997   char *s1 = cp1->klass_name_at(index1)->as_C_string();
 998   char *s2 = cp2->klass_name_at(index2)->as_C_string();
 999   if (strcmp(s1, s2) != 0) {
1000     return false;  // strings don't match; not our special case
1001   }
1002 
1003   return true;  // made it through the gauntlet; this is our special case
1004 } // end is_unresolved_class_mismatch()
1005 
1006 
1007 jvmtiError VM_RedefineClasses::load_new_class_versions(TRAPS) {
1008 
1009   // For consistency allocate memory using os::malloc wrapper.
1010   _scratch_classes = (InstanceKlass**)
1011     os::malloc(sizeof(InstanceKlass*) * _class_count, mtClass);
1012   if (_scratch_classes == NULL) {
1013     return JVMTI_ERROR_OUT_OF_MEMORY;
1014   }
1015   // Zero initialize the _scratch_classes array.
1016   for (int i = 0; i < _class_count; i++) {
1017     _scratch_classes[i] = NULL;
1018   }
1019 
1020   ResourceMark rm(THREAD);
1021 
1022   JvmtiThreadState *state = JvmtiThreadState::state_for(JavaThread::current());
1023   // state can only be NULL if the current thread is exiting which
1024   // should not happen since we're trying to do a RedefineClasses
1025   guarantee(state != NULL, "exiting thread calling load_new_class_versions");
1026   for (int i = 0; i < _class_count; i++) {
1027     // Create HandleMark so that any handles created while loading new class
1028     // versions are deleted. Constant pools are deallocated while merging
1029     // constant pools
1030     HandleMark hm(THREAD);
1031     InstanceKlass* the_class = get_ik(_class_defs[i].klass);
1032     Symbol*  the_class_sym = the_class->name();
1033 
1034     log_debug(redefine, class, load)
1035       ("loading name=%s kind=%d (avail_mem=" UINT64_FORMAT "K)",
1036        the_class->external_name(), _class_load_kind, os::available_memory() >> 10);
1037 
1038     ClassFileStream st((u1*)_class_defs[i].class_bytes,
1039                        _class_defs[i].class_byte_count,
1040                        "__VM_RedefineClasses__",
1041                        ClassFileStream::verify);
1042 
1043     // Parse the stream.
1044     Handle the_class_loader(THREAD, the_class->class_loader());
1045     Handle protection_domain(THREAD, the_class->protection_domain());
1046     // Set redefined class handle in JvmtiThreadState class.
1047     // This redefined class is sent to agent event handler for class file
1048     // load hook event.
1049     state->set_class_being_redefined(the_class, _class_load_kind);
1050 
1051     InstanceKlass* scratch_class = SystemDictionary::parse_stream(
1052                                                       the_class_sym,
1053                                                       the_class_loader,
1054                                                       protection_domain,
1055                                                       &st,
1056                                                       THREAD);
1057     // Clear class_being_redefined just to be sure.
1058     state->clear_class_being_redefined();
1059 
1060     // TODO: if this is retransform, and nothing changed we can skip it
1061 
1062     // Need to clean up allocated InstanceKlass if there's an error so assign
1063     // the result here. Caller deallocates all the scratch classes in case of
1064     // an error.
1065     _scratch_classes[i] = scratch_class;
1066 
1067     if (HAS_PENDING_EXCEPTION) {
1068       Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1069       log_info(redefine, class, load, exceptions)("parse_stream exception: '%s'", ex_name->as_C_string());
1070       CLEAR_PENDING_EXCEPTION;
1071 
1072       if (ex_name == vmSymbols::java_lang_UnsupportedClassVersionError()) {
1073         return JVMTI_ERROR_UNSUPPORTED_VERSION;
1074       } else if (ex_name == vmSymbols::java_lang_ClassFormatError()) {
1075         return JVMTI_ERROR_INVALID_CLASS_FORMAT;
1076       } else if (ex_name == vmSymbols::java_lang_ClassCircularityError()) {
1077         return JVMTI_ERROR_CIRCULAR_CLASS_DEFINITION;
1078       } else if (ex_name == vmSymbols::java_lang_NoClassDefFoundError()) {
1079         // The message will be "XXX (wrong name: YYY)"
1080         return JVMTI_ERROR_NAMES_DONT_MATCH;
1081       } else if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1082         return JVMTI_ERROR_OUT_OF_MEMORY;
1083       } else {  // Just in case more exceptions can be thrown..
1084         return JVMTI_ERROR_FAILS_VERIFICATION;
1085       }
1086     }
1087 
1088     // Ensure class is linked before redefine
1089     if (!the_class->is_linked()) {
1090       the_class->link_class(THREAD);
1091       if (HAS_PENDING_EXCEPTION) {
1092         Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1093         log_info(redefine, class, load, exceptions)("link_class exception: '%s'", ex_name->as_C_string());
1094         CLEAR_PENDING_EXCEPTION;
1095         if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1096           return JVMTI_ERROR_OUT_OF_MEMORY;
1097         } else {
1098           return JVMTI_ERROR_INTERNAL;
1099         }
1100       }
1101     }
1102 
1103     // Do the validity checks in compare_and_normalize_class_versions()
1104     // before verifying the byte codes. By doing these checks first, we
1105     // limit the number of functions that require redirection from
1106     // the_class to scratch_class. In particular, we don't have to
1107     // modify JNI GetSuperclass() and thus won't change its performance.
1108     jvmtiError res = compare_and_normalize_class_versions(the_class,
1109                        scratch_class);
1110     if (res != JVMTI_ERROR_NONE) {
1111       return res;
1112     }
1113 
1114     // verify what the caller passed us
1115     {
1116       // The bug 6214132 caused the verification to fail.
1117       // Information about the_class and scratch_class is temporarily
1118       // recorded into jvmtiThreadState. This data is used to redirect
1119       // the_class to scratch_class in the JVM_* functions called by the
1120       // verifier. Please, refer to jvmtiThreadState.hpp for the detailed
1121       // description.
1122       RedefineVerifyMark rvm(the_class, scratch_class, state);
1123       Verifier::verify(
1124         scratch_class, Verifier::ThrowException, true, THREAD);
1125     }
1126 
1127     if (HAS_PENDING_EXCEPTION) {
1128       Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1129       log_info(redefine, class, load, exceptions)("verify_byte_codes exception: '%s'", ex_name->as_C_string());
1130       CLEAR_PENDING_EXCEPTION;
1131       if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1132         return JVMTI_ERROR_OUT_OF_MEMORY;
1133       } else {
1134         // tell the caller the bytecodes are bad
1135         return JVMTI_ERROR_FAILS_VERIFICATION;
1136       }
1137     }
1138 
1139     res = merge_cp_and_rewrite(the_class, scratch_class, THREAD);
1140     if (HAS_PENDING_EXCEPTION) {
1141       Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1142       log_info(redefine, class, load, exceptions)("merge_cp_and_rewrite exception: '%s'", ex_name->as_C_string());
1143       CLEAR_PENDING_EXCEPTION;
1144       if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1145         return JVMTI_ERROR_OUT_OF_MEMORY;
1146       } else {
1147         return JVMTI_ERROR_INTERNAL;
1148       }
1149     }
1150 
1151     if (VerifyMergedCPBytecodes) {
1152       // verify what we have done during constant pool merging
1153       {
1154         RedefineVerifyMark rvm(the_class, scratch_class, state);
1155         Verifier::verify(scratch_class, Verifier::ThrowException, true, THREAD);
1156       }
1157 
1158       if (HAS_PENDING_EXCEPTION) {
1159         Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1160         log_info(redefine, class, load, exceptions)
1161           ("verify_byte_codes post merge-CP exception: '%s'", ex_name->as_C_string());
1162         CLEAR_PENDING_EXCEPTION;
1163         if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1164           return JVMTI_ERROR_OUT_OF_MEMORY;
1165         } else {
1166           // tell the caller that constant pool merging screwed up
1167           return JVMTI_ERROR_INTERNAL;
1168         }
1169       }
1170     }
1171 
1172     Rewriter::rewrite(scratch_class, THREAD);
1173     if (!HAS_PENDING_EXCEPTION) {
1174       scratch_class->link_methods(THREAD);
1175     }
1176     if (HAS_PENDING_EXCEPTION) {
1177       Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1178       log_info(redefine, class, load, exceptions)
1179         ("Rewriter::rewrite or link_methods exception: '%s'", ex_name->as_C_string());
1180       CLEAR_PENDING_EXCEPTION;
1181       if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1182         return JVMTI_ERROR_OUT_OF_MEMORY;
1183       } else {
1184         return JVMTI_ERROR_INTERNAL;
1185       }
1186     }
1187 
1188     log_debug(redefine, class, load)
1189       ("loaded name=%s (avail_mem=" UINT64_FORMAT "K)", the_class->external_name(), os::available_memory() >> 10);
1190   }
1191 
1192   return JVMTI_ERROR_NONE;
1193 }
1194 
1195 
1196 // Map old_index to new_index as needed. scratch_cp is only needed
1197 // for log calls.
1198 void VM_RedefineClasses::map_index(const constantPoolHandle& scratch_cp,
1199        int old_index, int new_index) {
1200   if (find_new_index(old_index) != 0) {
1201     // old_index is already mapped
1202     return;
1203   }
1204 
1205   if (old_index == new_index) {
1206     // no mapping is needed
1207     return;
1208   }
1209 
1210   _index_map_p->at_put(old_index, new_index);
1211   _index_map_count++;
1212 
1213   log_trace(redefine, class, constantpool)
1214     ("mapped tag %d at index %d to %d", scratch_cp->tag_at(old_index).value(), old_index, new_index);
1215 } // end map_index()
1216 
1217 
1218 // Map old_index to new_index as needed.
1219 void VM_RedefineClasses::map_operand_index(int old_index, int new_index) {
1220   if (find_new_operand_index(old_index) != -1) {
1221     // old_index is already mapped
1222     return;
1223   }
1224 
1225   if (old_index == new_index) {
1226     // no mapping is needed
1227     return;
1228   }
1229 
1230   _operands_index_map_p->at_put(old_index, new_index);
1231   _operands_index_map_count++;
1232 
1233   log_trace(redefine, class, constantpool)("mapped bootstrap specifier at index %d to %d", old_index, new_index);
1234 } // end map_index()
1235 
1236 
1237 // Merge old_cp and scratch_cp and return the results of the merge via
1238 // merge_cp_p. The number of entries in *merge_cp_p is returned via
1239 // merge_cp_length_p. The entries in old_cp occupy the same locations
1240 // in *merge_cp_p. Also creates a map of indices from entries in
1241 // scratch_cp to the corresponding entry in *merge_cp_p. Index map
1242 // entries are only created for entries in scratch_cp that occupy a
1243 // different location in *merged_cp_p.
1244 bool VM_RedefineClasses::merge_constant_pools(const constantPoolHandle& old_cp,
1245        const constantPoolHandle& scratch_cp, constantPoolHandle *merge_cp_p,
1246        int *merge_cp_length_p, TRAPS) {
1247 
1248   if (merge_cp_p == NULL) {
1249     assert(false, "caller must provide scratch constantPool");
1250     return false; // robustness
1251   }
1252   if (merge_cp_length_p == NULL) {
1253     assert(false, "caller must provide scratch CP length");
1254     return false; // robustness
1255   }
1256   // Worst case we need old_cp->length() + scratch_cp()->length(),
1257   // but the caller might be smart so make sure we have at least
1258   // the minimum.
1259   if ((*merge_cp_p)->length() < old_cp->length()) {
1260     assert(false, "merge area too small");
1261     return false; // robustness
1262   }
1263 
1264   log_info(redefine, class, constantpool)("old_cp_len=%d, scratch_cp_len=%d", old_cp->length(), scratch_cp->length());
1265 
1266   {
1267     // Pass 0:
1268     // The old_cp is copied to *merge_cp_p; this means that any code
1269     // using old_cp does not have to change. This work looks like a
1270     // perfect fit for ConstantPool*::copy_cp_to(), but we need to
1271     // handle one special case:
1272     // - revert JVM_CONSTANT_Class to JVM_CONSTANT_UnresolvedClass
1273     // This will make verification happy.
1274 
1275     int old_i;  // index into old_cp
1276 
1277     // index zero (0) is not used in constantPools
1278     for (old_i = 1; old_i < old_cp->length(); old_i++) {
1279       // leave debugging crumb
1280       jbyte old_tag = old_cp->tag_at(old_i).value();
1281       switch (old_tag) {
1282       case JVM_CONSTANT_Class:
1283       case JVM_CONSTANT_UnresolvedClass:
1284         // revert the copy to JVM_CONSTANT_UnresolvedClass
1285         // May be resolving while calling this so do the same for
1286         // JVM_CONSTANT_UnresolvedClass (klass_name_at() deals with transition)
1287         (*merge_cp_p)->temp_unresolved_klass_at_put(old_i,
1288           old_cp->klass_name_index_at(old_i));
1289         break;
1290 
1291       case JVM_CONSTANT_Double:
1292       case JVM_CONSTANT_Long:
1293         // just copy the entry to *merge_cp_p, but double and long take
1294         // two constant pool entries
1295         ConstantPool::copy_entry_to(old_cp, old_i, *merge_cp_p, old_i, CHECK_0);
1296         old_i++;
1297         break;
1298 
1299       default:
1300         // just copy the entry to *merge_cp_p
1301         ConstantPool::copy_entry_to(old_cp, old_i, *merge_cp_p, old_i, CHECK_0);
1302         break;
1303       }
1304     } // end for each old_cp entry
1305 
1306     ConstantPool::copy_operands(old_cp, *merge_cp_p, CHECK_0);
1307     (*merge_cp_p)->extend_operands(scratch_cp, CHECK_0);
1308 
1309     // We don't need to sanity check that *merge_cp_length_p is within
1310     // *merge_cp_p bounds since we have the minimum on-entry check above.
1311     (*merge_cp_length_p) = old_i;
1312   }
1313 
1314   // merge_cp_len should be the same as old_cp->length() at this point
1315   // so this trace message is really a "warm-and-breathing" message.
1316   log_debug(redefine, class, constantpool)("after pass 0: merge_cp_len=%d", *merge_cp_length_p);
1317 
1318   int scratch_i;  // index into scratch_cp
1319   {
1320     // Pass 1a:
1321     // Compare scratch_cp entries to the old_cp entries that we have
1322     // already copied to *merge_cp_p. In this pass, we are eliminating
1323     // exact duplicates (matching entry at same index) so we only
1324     // compare entries in the common indice range.
1325     int increment = 1;
1326     int pass1a_length = MIN2(old_cp->length(), scratch_cp->length());
1327     for (scratch_i = 1; scratch_i < pass1a_length; scratch_i += increment) {
1328       switch (scratch_cp->tag_at(scratch_i).value()) {
1329       case JVM_CONSTANT_Double:
1330       case JVM_CONSTANT_Long:
1331         // double and long take two constant pool entries
1332         increment = 2;
1333         break;
1334 
1335       default:
1336         increment = 1;
1337         break;
1338       }
1339 
1340       bool match = scratch_cp->compare_entry_to(scratch_i, *merge_cp_p,
1341         scratch_i, CHECK_0);
1342       if (match) {
1343         // found a match at the same index so nothing more to do
1344         continue;
1345       } else if (is_unresolved_class_mismatch(scratch_cp, scratch_i,
1346                                               *merge_cp_p, scratch_i)) {
1347         // The mismatch in compare_entry_to() above is because of a
1348         // resolved versus unresolved class entry at the same index
1349         // with the same string value. Since Pass 0 reverted any
1350         // class entries to unresolved class entries in *merge_cp_p,
1351         // we go with the unresolved class entry.
1352         continue;
1353       }
1354 
1355       int found_i = scratch_cp->find_matching_entry(scratch_i, *merge_cp_p,
1356         CHECK_0);
1357       if (found_i != 0) {
1358         guarantee(found_i != scratch_i,
1359           "compare_entry_to() and find_matching_entry() do not agree");
1360 
1361         // Found a matching entry somewhere else in *merge_cp_p so
1362         // just need a mapping entry.
1363         map_index(scratch_cp, scratch_i, found_i);
1364         continue;
1365       }
1366 
1367       // The find_matching_entry() call above could fail to find a match
1368       // due to a resolved versus unresolved class or string entry situation
1369       // like we solved above with the is_unresolved_*_mismatch() calls.
1370       // However, we would have to call is_unresolved_*_mismatch() over
1371       // all of *merge_cp_p (potentially) and that doesn't seem to be
1372       // worth the time.
1373 
1374       // No match found so we have to append this entry and any unique
1375       // referenced entries to *merge_cp_p.
1376       append_entry(scratch_cp, scratch_i, merge_cp_p, merge_cp_length_p,
1377         CHECK_0);
1378     }
1379   }
1380 
1381   log_debug(redefine, class, constantpool)
1382     ("after pass 1a: merge_cp_len=%d, scratch_i=%d, index_map_len=%d",
1383      *merge_cp_length_p, scratch_i, _index_map_count);
1384 
1385   if (scratch_i < scratch_cp->length()) {
1386     // Pass 1b:
1387     // old_cp is smaller than scratch_cp so there are entries in
1388     // scratch_cp that we have not yet processed. We take care of
1389     // those now.
1390     int increment = 1;
1391     for (; scratch_i < scratch_cp->length(); scratch_i += increment) {
1392       switch (scratch_cp->tag_at(scratch_i).value()) {
1393       case JVM_CONSTANT_Double:
1394       case JVM_CONSTANT_Long:
1395         // double and long take two constant pool entries
1396         increment = 2;
1397         break;
1398 
1399       default:
1400         increment = 1;
1401         break;
1402       }
1403 
1404       int found_i =
1405         scratch_cp->find_matching_entry(scratch_i, *merge_cp_p, CHECK_0);
1406       if (found_i != 0) {
1407         // Found a matching entry somewhere else in *merge_cp_p so
1408         // just need a mapping entry.
1409         map_index(scratch_cp, scratch_i, found_i);
1410         continue;
1411       }
1412 
1413       // No match found so we have to append this entry and any unique
1414       // referenced entries to *merge_cp_p.
1415       append_entry(scratch_cp, scratch_i, merge_cp_p, merge_cp_length_p,
1416         CHECK_0);
1417     }
1418 
1419     log_debug(redefine, class, constantpool)
1420       ("after pass 1b: merge_cp_len=%d, scratch_i=%d, index_map_len=%d",
1421        *merge_cp_length_p, scratch_i, _index_map_count);
1422   }
1423   finalize_operands_merge(*merge_cp_p, THREAD);
1424 
1425   return true;
1426 } // end merge_constant_pools()
1427 
1428 
1429 // Scoped object to clean up the constant pool(s) created for merging
1430 class MergeCPCleaner {
1431   ClassLoaderData*   _loader_data;
1432   ConstantPool*      _cp;
1433   ConstantPool*      _scratch_cp;
1434  public:
1435   MergeCPCleaner(ClassLoaderData* loader_data, ConstantPool* merge_cp) :
1436                  _loader_data(loader_data), _cp(merge_cp), _scratch_cp(NULL) {}
1437   ~MergeCPCleaner() {
1438     _loader_data->add_to_deallocate_list(_cp);
1439     if (_scratch_cp != NULL) {
1440       _loader_data->add_to_deallocate_list(_scratch_cp);
1441     }
1442   }
1443   void add_scratch_cp(ConstantPool* scratch_cp) { _scratch_cp = scratch_cp; }
1444 };
1445 
1446 // Merge constant pools between the_class and scratch_class and
1447 // potentially rewrite bytecodes in scratch_class to use the merged
1448 // constant pool.
1449 jvmtiError VM_RedefineClasses::merge_cp_and_rewrite(
1450              InstanceKlass* the_class, InstanceKlass* scratch_class,
1451              TRAPS) {
1452   // worst case merged constant pool length is old and new combined
1453   int merge_cp_length = the_class->constants()->length()
1454         + scratch_class->constants()->length();
1455 
1456   // Constant pools are not easily reused so we allocate a new one
1457   // each time.
1458   // merge_cp is created unsafe for concurrent GC processing.  It
1459   // should be marked safe before discarding it. Even though
1460   // garbage,  if it crosses a card boundary, it may be scanned
1461   // in order to find the start of the first complete object on the card.
1462   ClassLoaderData* loader_data = the_class->class_loader_data();
1463   ConstantPool* merge_cp_oop =
1464     ConstantPool::allocate(loader_data,
1465                            merge_cp_length,
1466                            CHECK_(JVMTI_ERROR_OUT_OF_MEMORY));
1467   MergeCPCleaner cp_cleaner(loader_data, merge_cp_oop);
1468 
1469   HandleMark hm(THREAD);  // make sure handles are cleared before
1470                           // MergeCPCleaner clears out merge_cp_oop
1471   constantPoolHandle merge_cp(THREAD, merge_cp_oop);
1472 
1473   // Get constants() from the old class because it could have been rewritten
1474   // while we were at a safepoint allocating a new constant pool.
1475   constantPoolHandle old_cp(THREAD, the_class->constants());
1476   constantPoolHandle scratch_cp(THREAD, scratch_class->constants());
1477 
1478   // If the length changed, the class was redefined out from under us. Return
1479   // an error.
1480   if (merge_cp_length != the_class->constants()->length()
1481          + scratch_class->constants()->length()) {
1482     return JVMTI_ERROR_INTERNAL;
1483   }
1484 
1485   // Update the version number of the constant pools (may keep scratch_cp)
1486   merge_cp->increment_and_save_version(old_cp->version());
1487   scratch_cp->increment_and_save_version(old_cp->version());
1488 
1489   ResourceMark rm(THREAD);
1490   _index_map_count = 0;
1491   _index_map_p = new intArray(scratch_cp->length(), scratch_cp->length(), -1);
1492 
1493   _operands_cur_length = ConstantPool::operand_array_length(old_cp->operands());
1494   _operands_index_map_count = 0;
1495   int operands_index_map_len = ConstantPool::operand_array_length(scratch_cp->operands());
1496   _operands_index_map_p = new intArray(operands_index_map_len, operands_index_map_len, -1);
1497 
1498   // reference to the cp holder is needed for copy_operands()
1499   merge_cp->set_pool_holder(scratch_class);
1500   bool result = merge_constant_pools(old_cp, scratch_cp, &merge_cp,
1501                   &merge_cp_length, THREAD);
1502   merge_cp->set_pool_holder(NULL);
1503 
1504   if (!result) {
1505     // The merge can fail due to memory allocation failure or due
1506     // to robustness checks.
1507     return JVMTI_ERROR_INTERNAL;
1508   }
1509 
1510   log_info(redefine, class, constantpool)("merge_cp_len=%d, index_map_len=%d", merge_cp_length, _index_map_count);
1511 
1512   if (_index_map_count == 0) {
1513     // there is nothing to map between the new and merged constant pools
1514 
1515     if (old_cp->length() == scratch_cp->length()) {
1516       // The old and new constant pools are the same length and the
1517       // index map is empty. This means that the three constant pools
1518       // are equivalent (but not the same). Unfortunately, the new
1519       // constant pool has not gone through link resolution nor have
1520       // the new class bytecodes gone through constant pool cache
1521       // rewriting so we can't use the old constant pool with the new
1522       // class.
1523 
1524       // toss the merged constant pool at return
1525     } else if (old_cp->length() < scratch_cp->length()) {
1526       // The old constant pool has fewer entries than the new constant
1527       // pool and the index map is empty. This means the new constant
1528       // pool is a superset of the old constant pool. However, the old
1529       // class bytecodes have already gone through constant pool cache
1530       // rewriting so we can't use the new constant pool with the old
1531       // class.
1532 
1533       // toss the merged constant pool at return
1534     } else {
1535       // The old constant pool has more entries than the new constant
1536       // pool and the index map is empty. This means that both the old
1537       // and merged constant pools are supersets of the new constant
1538       // pool.
1539 
1540       // Replace the new constant pool with a shrunken copy of the
1541       // merged constant pool
1542       set_new_constant_pool(loader_data, scratch_class, merge_cp, merge_cp_length,
1543                             CHECK_(JVMTI_ERROR_OUT_OF_MEMORY));
1544       // The new constant pool replaces scratch_cp so have cleaner clean it up.
1545       // It can't be cleaned up while there are handles to it.
1546       cp_cleaner.add_scratch_cp(scratch_cp());
1547     }
1548   } else {
1549     if (log_is_enabled(Trace, redefine, class, constantpool)) {
1550       // don't want to loop unless we are tracing
1551       int count = 0;
1552       for (int i = 1; i < _index_map_p->length(); i++) {
1553         int value = _index_map_p->at(i);
1554 
1555         if (value != -1) {
1556           log_trace(redefine, class, constantpool)("index_map[%d]: old=%d new=%d", count, i, value);
1557           count++;
1558         }
1559       }
1560     }
1561 
1562     // We have entries mapped between the new and merged constant pools
1563     // so we have to rewrite some constant pool references.
1564     if (!rewrite_cp_refs(scratch_class, THREAD)) {
1565       return JVMTI_ERROR_INTERNAL;
1566     }
1567 
1568     // Replace the new constant pool with a shrunken copy of the
1569     // merged constant pool so now the rewritten bytecodes have
1570     // valid references; the previous new constant pool will get
1571     // GCed.
1572     set_new_constant_pool(loader_data, scratch_class, merge_cp, merge_cp_length,
1573                           CHECK_(JVMTI_ERROR_OUT_OF_MEMORY));
1574     // The new constant pool replaces scratch_cp so have cleaner clean it up.
1575     // It can't be cleaned up while there are handles to it.
1576     cp_cleaner.add_scratch_cp(scratch_cp());
1577   }
1578 
1579   return JVMTI_ERROR_NONE;
1580 } // end merge_cp_and_rewrite()
1581 
1582 
1583 // Rewrite constant pool references in klass scratch_class.
1584 bool VM_RedefineClasses::rewrite_cp_refs(InstanceKlass* scratch_class,
1585        TRAPS) {
1586 
1587   // rewrite constant pool references in the methods:
1588   if (!rewrite_cp_refs_in_methods(scratch_class, THREAD)) {
1589     // propagate failure back to caller
1590     return false;
1591   }
1592 
1593   // rewrite constant pool references in the class_annotations:
1594   if (!rewrite_cp_refs_in_class_annotations(scratch_class, THREAD)) {
1595     // propagate failure back to caller
1596     return false;
1597   }
1598 
1599   // rewrite constant pool references in the fields_annotations:
1600   if (!rewrite_cp_refs_in_fields_annotations(scratch_class, THREAD)) {
1601     // propagate failure back to caller
1602     return false;
1603   }
1604 
1605   // rewrite constant pool references in the methods_annotations:
1606   if (!rewrite_cp_refs_in_methods_annotations(scratch_class, THREAD)) {
1607     // propagate failure back to caller
1608     return false;
1609   }
1610 
1611   // rewrite constant pool references in the methods_parameter_annotations:
1612   if (!rewrite_cp_refs_in_methods_parameter_annotations(scratch_class,
1613          THREAD)) {
1614     // propagate failure back to caller
1615     return false;
1616   }
1617 
1618   // rewrite constant pool references in the methods_default_annotations:
1619   if (!rewrite_cp_refs_in_methods_default_annotations(scratch_class,
1620          THREAD)) {
1621     // propagate failure back to caller
1622     return false;
1623   }
1624 
1625   // rewrite constant pool references in the class_type_annotations:
1626   if (!rewrite_cp_refs_in_class_type_annotations(scratch_class, THREAD)) {
1627     // propagate failure back to caller
1628     return false;
1629   }
1630 
1631   // rewrite constant pool references in the fields_type_annotations:
1632   if (!rewrite_cp_refs_in_fields_type_annotations(scratch_class, THREAD)) {
1633     // propagate failure back to caller
1634     return false;
1635   }
1636 
1637   // rewrite constant pool references in the methods_type_annotations:
1638   if (!rewrite_cp_refs_in_methods_type_annotations(scratch_class, THREAD)) {
1639     // propagate failure back to caller
1640     return false;
1641   }
1642 
1643   // There can be type annotations in the Code part of a method_info attribute.
1644   // These annotations are not accessible, even by reflection.
1645   // Currently they are not even parsed by the ClassFileParser.
1646   // If runtime access is added they will also need to be rewritten.
1647 
1648   // rewrite source file name index:
1649   u2 source_file_name_idx = scratch_class->source_file_name_index();
1650   if (source_file_name_idx != 0) {
1651     u2 new_source_file_name_idx = find_new_index(source_file_name_idx);
1652     if (new_source_file_name_idx != 0) {
1653       scratch_class->set_source_file_name_index(new_source_file_name_idx);
1654     }
1655   }
1656 
1657   // rewrite class generic signature index:
1658   u2 generic_signature_index = scratch_class->generic_signature_index();
1659   if (generic_signature_index != 0) {
1660     u2 new_generic_signature_index = find_new_index(generic_signature_index);
1661     if (new_generic_signature_index != 0) {
1662       scratch_class->set_generic_signature_index(new_generic_signature_index);
1663     }
1664   }
1665 
1666   return true;
1667 } // end rewrite_cp_refs()
1668 
1669 // Rewrite constant pool references in the methods.
1670 bool VM_RedefineClasses::rewrite_cp_refs_in_methods(
1671        InstanceKlass* scratch_class, TRAPS) {
1672 
1673   Array<Method*>* methods = scratch_class->methods();
1674 
1675   if (methods == NULL || methods->length() == 0) {
1676     // no methods so nothing to do
1677     return true;
1678   }
1679 
1680   // rewrite constant pool references in the methods:
1681   for (int i = methods->length() - 1; i >= 0; i--) {
1682     methodHandle method(THREAD, methods->at(i));
1683     methodHandle new_method;
1684     rewrite_cp_refs_in_method(method, &new_method, THREAD);
1685     if (!new_method.is_null()) {
1686       // the method has been replaced so save the new method version
1687       // even in the case of an exception.  original method is on the
1688       // deallocation list.
1689       methods->at_put(i, new_method());
1690     }
1691     if (HAS_PENDING_EXCEPTION) {
1692       Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1693       log_info(redefine, class, load, exceptions)("rewrite_cp_refs_in_method exception: '%s'", ex_name->as_C_string());
1694       // Need to clear pending exception here as the super caller sets
1695       // the JVMTI_ERROR_INTERNAL if the returned value is false.
1696       CLEAR_PENDING_EXCEPTION;
1697       return false;
1698     }
1699   }
1700 
1701   return true;
1702 }
1703 
1704 
1705 // Rewrite constant pool references in the specific method. This code
1706 // was adapted from Rewriter::rewrite_method().
1707 void VM_RedefineClasses::rewrite_cp_refs_in_method(methodHandle method,
1708        methodHandle *new_method_p, TRAPS) {
1709 
1710   *new_method_p = methodHandle();  // default is no new method
1711 
1712   // We cache a pointer to the bytecodes here in code_base. If GC
1713   // moves the Method*, then the bytecodes will also move which
1714   // will likely cause a crash. We create a NoSafepointVerifier
1715   // object to detect whether we pass a possible safepoint in this
1716   // code block.
1717   NoSafepointVerifier nsv;
1718 
1719   // Bytecodes and their length
1720   address code_base = method->code_base();
1721   int code_length = method->code_size();
1722 
1723   int bc_length;
1724   for (int bci = 0; bci < code_length; bci += bc_length) {
1725     address bcp = code_base + bci;
1726     Bytecodes::Code c = (Bytecodes::Code)(*bcp);
1727 
1728     bc_length = Bytecodes::length_for(c);
1729     if (bc_length == 0) {
1730       // More complicated bytecodes report a length of zero so
1731       // we have to try again a slightly different way.
1732       bc_length = Bytecodes::length_at(method(), bcp);
1733     }
1734 
1735     assert(bc_length != 0, "impossible bytecode length");
1736 
1737     switch (c) {
1738       case Bytecodes::_ldc:
1739       {
1740         int cp_index = *(bcp + 1);
1741         int new_index = find_new_index(cp_index);
1742 
1743         if (StressLdcRewrite && new_index == 0) {
1744           // If we are stressing ldc -> ldc_w rewriting, then we
1745           // always need a new_index value.
1746           new_index = cp_index;
1747         }
1748         if (new_index != 0) {
1749           // the original index is mapped so we have more work to do
1750           if (!StressLdcRewrite && new_index <= max_jubyte) {
1751             // The new value can still use ldc instead of ldc_w
1752             // unless we are trying to stress ldc -> ldc_w rewriting
1753             log_trace(redefine, class, constantpool)
1754               ("%s@" INTPTR_FORMAT " old=%d, new=%d", Bytecodes::name(c), p2i(bcp), cp_index, new_index);
1755             *(bcp + 1) = new_index;
1756           } else {
1757             log_trace(redefine, class, constantpool)
1758               ("%s->ldc_w@" INTPTR_FORMAT " old=%d, new=%d", Bytecodes::name(c), p2i(bcp), cp_index, new_index);
1759             // the new value needs ldc_w instead of ldc
1760             u_char inst_buffer[4]; // max instruction size is 4 bytes
1761             bcp = (address)inst_buffer;
1762             // construct new instruction sequence
1763             *bcp = Bytecodes::_ldc_w;
1764             bcp++;
1765             // Rewriter::rewrite_method() does not rewrite ldc -> ldc_w.
1766             // See comment below for difference between put_Java_u2()
1767             // and put_native_u2().
1768             Bytes::put_Java_u2(bcp, new_index);
1769 
1770             Relocator rc(method, NULL /* no RelocatorListener needed */);
1771             methodHandle m;
1772             {
1773               PauseNoSafepointVerifier pnsv(&nsv);
1774 
1775               // ldc is 2 bytes and ldc_w is 3 bytes
1776               m = rc.insert_space_at(bci, 3, inst_buffer, CHECK);
1777             }
1778 
1779             // return the new method so that the caller can update
1780             // the containing class
1781             *new_method_p = method = m;
1782             // switch our bytecode processing loop from the old method
1783             // to the new method
1784             code_base = method->code_base();
1785             code_length = method->code_size();
1786             bcp = code_base + bci;
1787             c = (Bytecodes::Code)(*bcp);
1788             bc_length = Bytecodes::length_for(c);
1789             assert(bc_length != 0, "sanity check");
1790           } // end we need ldc_w instead of ldc
1791         } // end if there is a mapped index
1792       } break;
1793 
1794       // these bytecodes have a two-byte constant pool index
1795       case Bytecodes::_anewarray      : // fall through
1796       case Bytecodes::_checkcast      : // fall through
1797       case Bytecodes::_getfield       : // fall through
1798       case Bytecodes::_getstatic      : // fall through
1799       case Bytecodes::_instanceof     : // fall through
1800       case Bytecodes::_invokedynamic  : // fall through
1801       case Bytecodes::_invokeinterface: // fall through
1802       case Bytecodes::_invokespecial  : // fall through
1803       case Bytecodes::_invokestatic   : // fall through
1804       case Bytecodes::_invokevirtual  : // fall through
1805       case Bytecodes::_ldc_w          : // fall through
1806       case Bytecodes::_ldc2_w         : // fall through
1807       case Bytecodes::_multianewarray : // fall through
1808       case Bytecodes::_new            : // fall through
1809       case Bytecodes::_putfield       : // fall through
1810       case Bytecodes::_putstatic      :
1811       {
1812         address p = bcp + 1;
1813         int cp_index = Bytes::get_Java_u2(p);
1814         int new_index = find_new_index(cp_index);
1815         if (new_index != 0) {
1816           // the original index is mapped so update w/ new value
1817           log_trace(redefine, class, constantpool)
1818             ("%s@" INTPTR_FORMAT " old=%d, new=%d", Bytecodes::name(c),p2i(bcp), cp_index, new_index);
1819           // Rewriter::rewrite_method() uses put_native_u2() in this
1820           // situation because it is reusing the constant pool index
1821           // location for a native index into the ConstantPoolCache.
1822           // Since we are updating the constant pool index prior to
1823           // verification and ConstantPoolCache initialization, we
1824           // need to keep the new index in Java byte order.
1825           Bytes::put_Java_u2(p, new_index);
1826         }
1827       } break;
1828     }
1829   } // end for each bytecode
1830 
1831   // We also need to rewrite the parameter name indexes, if there is
1832   // method parameter data present
1833   if(method->has_method_parameters()) {
1834     const int len = method->method_parameters_length();
1835     MethodParametersElement* elem = method->method_parameters_start();
1836 
1837     for (int i = 0; i < len; i++) {
1838       const u2 cp_index = elem[i].name_cp_index;
1839       const u2 new_cp_index = find_new_index(cp_index);
1840       if (new_cp_index != 0) {
1841         elem[i].name_cp_index = new_cp_index;
1842       }
1843     }
1844   }
1845 } // end rewrite_cp_refs_in_method()
1846 
1847 
1848 // Rewrite constant pool references in the class_annotations field.
1849 bool VM_RedefineClasses::rewrite_cp_refs_in_class_annotations(
1850        InstanceKlass* scratch_class, TRAPS) {
1851 
1852   AnnotationArray* class_annotations = scratch_class->class_annotations();
1853   if (class_annotations == NULL || class_annotations->length() == 0) {
1854     // no class_annotations so nothing to do
1855     return true;
1856   }
1857 
1858   log_debug(redefine, class, annotation)("class_annotations length=%d", class_annotations->length());
1859 
1860   int byte_i = 0;  // byte index into class_annotations
1861   return rewrite_cp_refs_in_annotations_typeArray(class_annotations, byte_i,
1862            THREAD);
1863 }
1864 
1865 
1866 // Rewrite constant pool references in an annotations typeArray. This
1867 // "structure" is adapted from the RuntimeVisibleAnnotations_attribute
1868 // that is described in section 4.8.15 of the 2nd-edition of the VM spec:
1869 //
1870 // annotations_typeArray {
1871 //   u2 num_annotations;
1872 //   annotation annotations[num_annotations];
1873 // }
1874 //
1875 bool VM_RedefineClasses::rewrite_cp_refs_in_annotations_typeArray(
1876        AnnotationArray* annotations_typeArray, int &byte_i_ref, TRAPS) {
1877 
1878   if ((byte_i_ref + 2) > annotations_typeArray->length()) {
1879     // not enough room for num_annotations field
1880     log_debug(redefine, class, annotation)("length() is too small for num_annotations field");
1881     return false;
1882   }
1883 
1884   u2 num_annotations = Bytes::get_Java_u2((address)
1885                          annotations_typeArray->adr_at(byte_i_ref));
1886   byte_i_ref += 2;
1887 
1888   log_debug(redefine, class, annotation)("num_annotations=%d", num_annotations);
1889 
1890   int calc_num_annotations = 0;
1891   for (; calc_num_annotations < num_annotations; calc_num_annotations++) {
1892     if (!rewrite_cp_refs_in_annotation_struct(annotations_typeArray,
1893            byte_i_ref, THREAD)) {
1894       log_debug(redefine, class, annotation)("bad annotation_struct at %d", calc_num_annotations);
1895       // propagate failure back to caller
1896       return false;
1897     }
1898   }
1899   assert(num_annotations == calc_num_annotations, "sanity check");
1900 
1901   return true;
1902 } // end rewrite_cp_refs_in_annotations_typeArray()
1903 
1904 
1905 // Rewrite constant pool references in the annotation struct portion of
1906 // an annotations_typeArray. This "structure" is from section 4.8.15 of
1907 // the 2nd-edition of the VM spec:
1908 //
1909 // struct annotation {
1910 //   u2 type_index;
1911 //   u2 num_element_value_pairs;
1912 //   {
1913 //     u2 element_name_index;
1914 //     element_value value;
1915 //   } element_value_pairs[num_element_value_pairs];
1916 // }
1917 //
1918 bool VM_RedefineClasses::rewrite_cp_refs_in_annotation_struct(
1919        AnnotationArray* annotations_typeArray, int &byte_i_ref, TRAPS) {
1920   if ((byte_i_ref + 2 + 2) > annotations_typeArray->length()) {
1921     // not enough room for smallest annotation_struct
1922     log_debug(redefine, class, annotation)("length() is too small for annotation_struct");
1923     return false;
1924   }
1925 
1926   u2 type_index = rewrite_cp_ref_in_annotation_data(annotations_typeArray,
1927                     byte_i_ref, "type_index", THREAD);
1928 
1929   u2 num_element_value_pairs = Bytes::get_Java_u2((address)
1930                                  annotations_typeArray->adr_at(byte_i_ref));
1931   byte_i_ref += 2;
1932 
1933   log_debug(redefine, class, annotation)
1934     ("type_index=%d  num_element_value_pairs=%d", type_index, num_element_value_pairs);
1935 
1936   int calc_num_element_value_pairs = 0;
1937   for (; calc_num_element_value_pairs < num_element_value_pairs;
1938        calc_num_element_value_pairs++) {
1939     if ((byte_i_ref + 2) > annotations_typeArray->length()) {
1940       // not enough room for another element_name_index, let alone
1941       // the rest of another component
1942       log_debug(redefine, class, annotation)("length() is too small for element_name_index");
1943       return false;
1944     }
1945 
1946     u2 element_name_index = rewrite_cp_ref_in_annotation_data(
1947                               annotations_typeArray, byte_i_ref,
1948                               "element_name_index", THREAD);
1949 
1950     log_debug(redefine, class, annotation)("element_name_index=%d", element_name_index);
1951 
1952     if (!rewrite_cp_refs_in_element_value(annotations_typeArray,
1953            byte_i_ref, THREAD)) {
1954       log_debug(redefine, class, annotation)("bad element_value at %d", calc_num_element_value_pairs);
1955       // propagate failure back to caller
1956       return false;
1957     }
1958   } // end for each component
1959   assert(num_element_value_pairs == calc_num_element_value_pairs,
1960     "sanity check");
1961 
1962   return true;
1963 } // end rewrite_cp_refs_in_annotation_struct()
1964 
1965 
1966 // Rewrite a constant pool reference at the current position in
1967 // annotations_typeArray if needed. Returns the original constant
1968 // pool reference if a rewrite was not needed or the new constant
1969 // pool reference if a rewrite was needed.
1970 u2 VM_RedefineClasses::rewrite_cp_ref_in_annotation_data(
1971      AnnotationArray* annotations_typeArray, int &byte_i_ref,
1972      const char * trace_mesg, TRAPS) {
1973 
1974   address cp_index_addr = (address)
1975     annotations_typeArray->adr_at(byte_i_ref);
1976   u2 old_cp_index = Bytes::get_Java_u2(cp_index_addr);
1977   u2 new_cp_index = find_new_index(old_cp_index);
1978   if (new_cp_index != 0) {
1979     log_debug(redefine, class, annotation)("mapped old %s=%d", trace_mesg, old_cp_index);
1980     Bytes::put_Java_u2(cp_index_addr, new_cp_index);
1981     old_cp_index = new_cp_index;
1982   }
1983   byte_i_ref += 2;
1984   return old_cp_index;
1985 }
1986 
1987 
1988 // Rewrite constant pool references in the element_value portion of an
1989 // annotations_typeArray. This "structure" is from section 4.8.15.1 of
1990 // the 2nd-edition of the VM spec:
1991 //
1992 // struct element_value {
1993 //   u1 tag;
1994 //   union {
1995 //     u2 const_value_index;
1996 //     {
1997 //       u2 type_name_index;
1998 //       u2 const_name_index;
1999 //     } enum_const_value;
2000 //     u2 class_info_index;
2001 //     annotation annotation_value;
2002 //     struct {
2003 //       u2 num_values;
2004 //       element_value values[num_values];
2005 //     } array_value;
2006 //   } value;
2007 // }
2008 //
2009 bool VM_RedefineClasses::rewrite_cp_refs_in_element_value(
2010        AnnotationArray* annotations_typeArray, int &byte_i_ref, TRAPS) {
2011 
2012   if ((byte_i_ref + 1) > annotations_typeArray->length()) {
2013     // not enough room for a tag let alone the rest of an element_value
2014     log_debug(redefine, class, annotation)("length() is too small for a tag");
2015     return false;
2016   }
2017 
2018   u1 tag = annotations_typeArray->at(byte_i_ref);
2019   byte_i_ref++;
2020   log_debug(redefine, class, annotation)("tag='%c'", tag);
2021 
2022   switch (tag) {
2023     // These BaseType tag values are from Table 4.2 in VM spec:
2024     case 'B':  // byte
2025     case 'C':  // char
2026     case 'D':  // double
2027     case 'F':  // float
2028     case 'I':  // int
2029     case 'J':  // long
2030     case 'S':  // short
2031     case 'Z':  // boolean
2032 
2033     // The remaining tag values are from Table 4.8 in the 2nd-edition of
2034     // the VM spec:
2035     case 's':
2036     {
2037       // For the above tag values (including the BaseType values),
2038       // value.const_value_index is right union field.
2039 
2040       if ((byte_i_ref + 2) > annotations_typeArray->length()) {
2041         // not enough room for a const_value_index
2042         log_debug(redefine, class, annotation)("length() is too small for a const_value_index");
2043         return false;
2044       }
2045 
2046       u2 const_value_index = rewrite_cp_ref_in_annotation_data(
2047                                annotations_typeArray, byte_i_ref,
2048                                "const_value_index", THREAD);
2049 
2050       log_debug(redefine, class, annotation)("const_value_index=%d", const_value_index);
2051     } break;
2052 
2053     case 'e':
2054     {
2055       // for the above tag value, value.enum_const_value is right union field
2056 
2057       if ((byte_i_ref + 4) > annotations_typeArray->length()) {
2058         // not enough room for a enum_const_value
2059         log_debug(redefine, class, annotation)("length() is too small for a enum_const_value");
2060         return false;
2061       }
2062 
2063       u2 type_name_index = rewrite_cp_ref_in_annotation_data(
2064                              annotations_typeArray, byte_i_ref,
2065                              "type_name_index", THREAD);
2066 
2067       u2 const_name_index = rewrite_cp_ref_in_annotation_data(
2068                               annotations_typeArray, byte_i_ref,
2069                               "const_name_index", THREAD);
2070 
2071       log_debug(redefine, class, annotation)
2072         ("type_name_index=%d  const_name_index=%d", type_name_index, const_name_index);
2073     } break;
2074 
2075     case 'c':
2076     {
2077       // for the above tag value, value.class_info_index is right union field
2078 
2079       if ((byte_i_ref + 2) > annotations_typeArray->length()) {
2080         // not enough room for a class_info_index
2081         log_debug(redefine, class, annotation)("length() is too small for a class_info_index");
2082         return false;
2083       }
2084 
2085       u2 class_info_index = rewrite_cp_ref_in_annotation_data(
2086                               annotations_typeArray, byte_i_ref,
2087                               "class_info_index", THREAD);
2088 
2089       log_debug(redefine, class, annotation)("class_info_index=%d", class_info_index);
2090     } break;
2091 
2092     case '@':
2093       // For the above tag value, value.attr_value is the right union
2094       // field. This is a nested annotation.
2095       if (!rewrite_cp_refs_in_annotation_struct(annotations_typeArray,
2096              byte_i_ref, THREAD)) {
2097         // propagate failure back to caller
2098         return false;
2099       }
2100       break;
2101 
2102     case '[':
2103     {
2104       if ((byte_i_ref + 2) > annotations_typeArray->length()) {
2105         // not enough room for a num_values field
2106         log_debug(redefine, class, annotation)("length() is too small for a num_values field");
2107         return false;
2108       }
2109 
2110       // For the above tag value, value.array_value is the right union
2111       // field. This is an array of nested element_value.
2112       u2 num_values = Bytes::get_Java_u2((address)
2113                         annotations_typeArray->adr_at(byte_i_ref));
2114       byte_i_ref += 2;
2115       log_debug(redefine, class, annotation)("num_values=%d", num_values);
2116 
2117       int calc_num_values = 0;
2118       for (; calc_num_values < num_values; calc_num_values++) {
2119         if (!rewrite_cp_refs_in_element_value(
2120                annotations_typeArray, byte_i_ref, THREAD)) {
2121           log_debug(redefine, class, annotation)("bad nested element_value at %d", calc_num_values);
2122           // propagate failure back to caller
2123           return false;
2124         }
2125       }
2126       assert(num_values == calc_num_values, "sanity check");
2127     } break;
2128 
2129     default:
2130       log_debug(redefine, class, annotation)("bad tag=0x%x", tag);
2131       return false;
2132   } // end decode tag field
2133 
2134   return true;
2135 } // end rewrite_cp_refs_in_element_value()
2136 
2137 
2138 // Rewrite constant pool references in a fields_annotations field.
2139 bool VM_RedefineClasses::rewrite_cp_refs_in_fields_annotations(
2140        InstanceKlass* scratch_class, TRAPS) {
2141 
2142   Array<AnnotationArray*>* fields_annotations = scratch_class->fields_annotations();
2143 
2144   if (fields_annotations == NULL || fields_annotations->length() == 0) {
2145     // no fields_annotations so nothing to do
2146     return true;
2147   }
2148 
2149   log_debug(redefine, class, annotation)("fields_annotations length=%d", fields_annotations->length());
2150 
2151   for (int i = 0; i < fields_annotations->length(); i++) {
2152     AnnotationArray* field_annotations = fields_annotations->at(i);
2153     if (field_annotations == NULL || field_annotations->length() == 0) {
2154       // this field does not have any annotations so skip it
2155       continue;
2156     }
2157 
2158     int byte_i = 0;  // byte index into field_annotations
2159     if (!rewrite_cp_refs_in_annotations_typeArray(field_annotations, byte_i,
2160            THREAD)) {
2161       log_debug(redefine, class, annotation)("bad field_annotations at %d", i);
2162       // propagate failure back to caller
2163       return false;
2164     }
2165   }
2166 
2167   return true;
2168 } // end rewrite_cp_refs_in_fields_annotations()
2169 
2170 
2171 // Rewrite constant pool references in a methods_annotations field.
2172 bool VM_RedefineClasses::rewrite_cp_refs_in_methods_annotations(
2173        InstanceKlass* scratch_class, TRAPS) {
2174 
2175   for (int i = 0; i < scratch_class->methods()->length(); i++) {
2176     Method* m = scratch_class->methods()->at(i);
2177     AnnotationArray* method_annotations = m->constMethod()->method_annotations();
2178 
2179     if (method_annotations == NULL || method_annotations->length() == 0) {
2180       // this method does not have any annotations so skip it
2181       continue;
2182     }
2183 
2184     int byte_i = 0;  // byte index into method_annotations
2185     if (!rewrite_cp_refs_in_annotations_typeArray(method_annotations, byte_i,
2186            THREAD)) {
2187       log_debug(redefine, class, annotation)("bad method_annotations at %d", i);
2188       // propagate failure back to caller
2189       return false;
2190     }
2191   }
2192 
2193   return true;
2194 } // end rewrite_cp_refs_in_methods_annotations()
2195 
2196 
2197 // Rewrite constant pool references in a methods_parameter_annotations
2198 // field. This "structure" is adapted from the
2199 // RuntimeVisibleParameterAnnotations_attribute described in section
2200 // 4.8.17 of the 2nd-edition of the VM spec:
2201 //
2202 // methods_parameter_annotations_typeArray {
2203 //   u1 num_parameters;
2204 //   {
2205 //     u2 num_annotations;
2206 //     annotation annotations[num_annotations];
2207 //   } parameter_annotations[num_parameters];
2208 // }
2209 //
2210 bool VM_RedefineClasses::rewrite_cp_refs_in_methods_parameter_annotations(
2211        InstanceKlass* scratch_class, TRAPS) {
2212 
2213   for (int i = 0; i < scratch_class->methods()->length(); i++) {
2214     Method* m = scratch_class->methods()->at(i);
2215     AnnotationArray* method_parameter_annotations = m->constMethod()->parameter_annotations();
2216     if (method_parameter_annotations == NULL
2217         || method_parameter_annotations->length() == 0) {
2218       // this method does not have any parameter annotations so skip it
2219       continue;
2220     }
2221 
2222     if (method_parameter_annotations->length() < 1) {
2223       // not enough room for a num_parameters field
2224       log_debug(redefine, class, annotation)("length() is too small for a num_parameters field at %d", i);
2225       return false;
2226     }
2227 
2228     int byte_i = 0;  // byte index into method_parameter_annotations
2229 
2230     u1 num_parameters = method_parameter_annotations->at(byte_i);
2231     byte_i++;
2232 
2233     log_debug(redefine, class, annotation)("num_parameters=%d", num_parameters);
2234 
2235     int calc_num_parameters = 0;
2236     for (; calc_num_parameters < num_parameters; calc_num_parameters++) {
2237       if (!rewrite_cp_refs_in_annotations_typeArray(
2238              method_parameter_annotations, byte_i, THREAD)) {
2239         log_debug(redefine, class, annotation)("bad method_parameter_annotations at %d", calc_num_parameters);
2240         // propagate failure back to caller
2241         return false;
2242       }
2243     }
2244     assert(num_parameters == calc_num_parameters, "sanity check");
2245   }
2246 
2247   return true;
2248 } // end rewrite_cp_refs_in_methods_parameter_annotations()
2249 
2250 
2251 // Rewrite constant pool references in a methods_default_annotations
2252 // field. This "structure" is adapted from the AnnotationDefault_attribute
2253 // that is described in section 4.8.19 of the 2nd-edition of the VM spec:
2254 //
2255 // methods_default_annotations_typeArray {
2256 //   element_value default_value;
2257 // }
2258 //
2259 bool VM_RedefineClasses::rewrite_cp_refs_in_methods_default_annotations(
2260        InstanceKlass* scratch_class, TRAPS) {
2261 
2262   for (int i = 0; i < scratch_class->methods()->length(); i++) {
2263     Method* m = scratch_class->methods()->at(i);
2264     AnnotationArray* method_default_annotations = m->constMethod()->default_annotations();
2265     if (method_default_annotations == NULL
2266         || method_default_annotations->length() == 0) {
2267       // this method does not have any default annotations so skip it
2268       continue;
2269     }
2270 
2271     int byte_i = 0;  // byte index into method_default_annotations
2272 
2273     if (!rewrite_cp_refs_in_element_value(
2274            method_default_annotations, byte_i, THREAD)) {
2275       log_debug(redefine, class, annotation)("bad default element_value at %d", i);
2276       // propagate failure back to caller
2277       return false;
2278     }
2279   }
2280 
2281   return true;
2282 } // end rewrite_cp_refs_in_methods_default_annotations()
2283 
2284 
2285 // Rewrite constant pool references in a class_type_annotations field.
2286 bool VM_RedefineClasses::rewrite_cp_refs_in_class_type_annotations(
2287        InstanceKlass* scratch_class, TRAPS) {
2288 
2289   AnnotationArray* class_type_annotations = scratch_class->class_type_annotations();
2290   if (class_type_annotations == NULL || class_type_annotations->length() == 0) {
2291     // no class_type_annotations so nothing to do
2292     return true;
2293   }
2294 
2295   log_debug(redefine, class, annotation)("class_type_annotations length=%d", class_type_annotations->length());
2296 
2297   int byte_i = 0;  // byte index into class_type_annotations
2298   return rewrite_cp_refs_in_type_annotations_typeArray(class_type_annotations,
2299       byte_i, "ClassFile", THREAD);
2300 } // end rewrite_cp_refs_in_class_type_annotations()
2301 
2302 
2303 // Rewrite constant pool references in a fields_type_annotations field.
2304 bool VM_RedefineClasses::rewrite_cp_refs_in_fields_type_annotations(
2305        InstanceKlass* scratch_class, TRAPS) {
2306 
2307   Array<AnnotationArray*>* fields_type_annotations = scratch_class->fields_type_annotations();
2308   if (fields_type_annotations == NULL || fields_type_annotations->length() == 0) {
2309     // no fields_type_annotations so nothing to do
2310     return true;
2311   }
2312 
2313   log_debug(redefine, class, annotation)("fields_type_annotations length=%d", fields_type_annotations->length());
2314 
2315   for (int i = 0; i < fields_type_annotations->length(); i++) {
2316     AnnotationArray* field_type_annotations = fields_type_annotations->at(i);
2317     if (field_type_annotations == NULL || field_type_annotations->length() == 0) {
2318       // this field does not have any annotations so skip it
2319       continue;
2320     }
2321 
2322     int byte_i = 0;  // byte index into field_type_annotations
2323     if (!rewrite_cp_refs_in_type_annotations_typeArray(field_type_annotations,
2324            byte_i, "field_info", THREAD)) {
2325       log_debug(redefine, class, annotation)("bad field_type_annotations at %d", i);
2326       // propagate failure back to caller
2327       return false;
2328     }
2329   }
2330 
2331   return true;
2332 } // end rewrite_cp_refs_in_fields_type_annotations()
2333 
2334 
2335 // Rewrite constant pool references in a methods_type_annotations field.
2336 bool VM_RedefineClasses::rewrite_cp_refs_in_methods_type_annotations(
2337        InstanceKlass* scratch_class, TRAPS) {
2338 
2339   for (int i = 0; i < scratch_class->methods()->length(); i++) {
2340     Method* m = scratch_class->methods()->at(i);
2341     AnnotationArray* method_type_annotations = m->constMethod()->type_annotations();
2342 
2343     if (method_type_annotations == NULL || method_type_annotations->length() == 0) {
2344       // this method does not have any annotations so skip it
2345       continue;
2346     }
2347 
2348     log_debug(redefine, class, annotation)("methods type_annotations length=%d", method_type_annotations->length());
2349 
2350     int byte_i = 0;  // byte index into method_type_annotations
2351     if (!rewrite_cp_refs_in_type_annotations_typeArray(method_type_annotations,
2352            byte_i, "method_info", THREAD)) {
2353       log_debug(redefine, class, annotation)("bad method_type_annotations at %d", i);
2354       // propagate failure back to caller
2355       return false;
2356     }
2357   }
2358 
2359   return true;
2360 } // end rewrite_cp_refs_in_methods_type_annotations()
2361 
2362 
2363 // Rewrite constant pool references in a type_annotations
2364 // field. This "structure" is adapted from the
2365 // RuntimeVisibleTypeAnnotations_attribute described in
2366 // section 4.7.20 of the Java SE 8 Edition of the VM spec:
2367 //
2368 // type_annotations_typeArray {
2369 //   u2              num_annotations;
2370 //   type_annotation annotations[num_annotations];
2371 // }
2372 //
2373 bool VM_RedefineClasses::rewrite_cp_refs_in_type_annotations_typeArray(
2374        AnnotationArray* type_annotations_typeArray, int &byte_i_ref,
2375        const char * location_mesg, TRAPS) {
2376 
2377   if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
2378     // not enough room for num_annotations field
2379     log_debug(redefine, class, annotation)("length() is too small for num_annotations field");
2380     return false;
2381   }
2382 
2383   u2 num_annotations = Bytes::get_Java_u2((address)
2384                          type_annotations_typeArray->adr_at(byte_i_ref));
2385   byte_i_ref += 2;
2386 
2387   log_debug(redefine, class, annotation)("num_type_annotations=%d", num_annotations);
2388 
2389   int calc_num_annotations = 0;
2390   for (; calc_num_annotations < num_annotations; calc_num_annotations++) {
2391     if (!rewrite_cp_refs_in_type_annotation_struct(type_annotations_typeArray,
2392            byte_i_ref, location_mesg, THREAD)) {
2393       log_debug(redefine, class, annotation)("bad type_annotation_struct at %d", calc_num_annotations);
2394       // propagate failure back to caller
2395       return false;
2396     }
2397   }
2398   assert(num_annotations == calc_num_annotations, "sanity check");
2399 
2400   if (byte_i_ref != type_annotations_typeArray->length()) {
2401     log_debug(redefine, class, annotation)
2402       ("read wrong amount of bytes at end of processing type_annotations_typeArray (%d of %d bytes were read)",
2403        byte_i_ref, type_annotations_typeArray->length());
2404     return false;
2405   }
2406 
2407   return true;
2408 } // end rewrite_cp_refs_in_type_annotations_typeArray()
2409 
2410 
2411 // Rewrite constant pool references in a type_annotation
2412 // field. This "structure" is adapted from the
2413 // RuntimeVisibleTypeAnnotations_attribute described in
2414 // section 4.7.20 of the Java SE 8 Edition of the VM spec:
2415 //
2416 // type_annotation {
2417 //   u1 target_type;
2418 //   union {
2419 //     type_parameter_target;
2420 //     supertype_target;
2421 //     type_parameter_bound_target;
2422 //     empty_target;
2423 //     method_formal_parameter_target;
2424 //     throws_target;
2425 //     localvar_target;
2426 //     catch_target;
2427 //     offset_target;
2428 //     type_argument_target;
2429 //   } target_info;
2430 //   type_path target_path;
2431 //   annotation anno;
2432 // }
2433 //
2434 bool VM_RedefineClasses::rewrite_cp_refs_in_type_annotation_struct(
2435        AnnotationArray* type_annotations_typeArray, int &byte_i_ref,
2436        const char * location_mesg, TRAPS) {
2437 
2438   if (!skip_type_annotation_target(type_annotations_typeArray,
2439          byte_i_ref, location_mesg, THREAD)) {
2440     return false;
2441   }
2442 
2443   if (!skip_type_annotation_type_path(type_annotations_typeArray,
2444          byte_i_ref, THREAD)) {
2445     return false;
2446   }
2447 
2448   if (!rewrite_cp_refs_in_annotation_struct(type_annotations_typeArray,
2449          byte_i_ref, THREAD)) {
2450     return false;
2451   }
2452 
2453   return true;
2454 } // end rewrite_cp_refs_in_type_annotation_struct()
2455 
2456 
2457 // Read, verify and skip over the target_type and target_info part
2458 // so that rewriting can continue in the later parts of the struct.
2459 //
2460 // u1 target_type;
2461 // union {
2462 //   type_parameter_target;
2463 //   supertype_target;
2464 //   type_parameter_bound_target;
2465 //   empty_target;
2466 //   method_formal_parameter_target;
2467 //   throws_target;
2468 //   localvar_target;
2469 //   catch_target;
2470 //   offset_target;
2471 //   type_argument_target;
2472 // } target_info;
2473 //
2474 bool VM_RedefineClasses::skip_type_annotation_target(
2475        AnnotationArray* type_annotations_typeArray, int &byte_i_ref,
2476        const char * location_mesg, TRAPS) {
2477 
2478   if ((byte_i_ref + 1) > type_annotations_typeArray->length()) {
2479     // not enough room for a target_type let alone the rest of a type_annotation
2480     log_debug(redefine, class, annotation)("length() is too small for a target_type");
2481     return false;
2482   }
2483 
2484   u1 target_type = type_annotations_typeArray->at(byte_i_ref);
2485   byte_i_ref += 1;
2486   log_debug(redefine, class, annotation)("target_type=0x%.2x", target_type);
2487   log_debug(redefine, class, annotation)("location=%s", location_mesg);
2488 
2489   // Skip over target_info
2490   switch (target_type) {
2491     case 0x00:
2492     // kind: type parameter declaration of generic class or interface
2493     // location: ClassFile
2494     case 0x01:
2495     // kind: type parameter declaration of generic method or constructor
2496     // location: method_info
2497 
2498     {
2499       // struct:
2500       // type_parameter_target {
2501       //   u1 type_parameter_index;
2502       // }
2503       //
2504       if ((byte_i_ref + 1) > type_annotations_typeArray->length()) {
2505         log_debug(redefine, class, annotation)("length() is too small for a type_parameter_target");
2506         return false;
2507       }
2508 
2509       u1 type_parameter_index = type_annotations_typeArray->at(byte_i_ref);
2510       byte_i_ref += 1;
2511 
2512       log_debug(redefine, class, annotation)("type_parameter_target: type_parameter_index=%d", type_parameter_index);
2513     } break;
2514 
2515     case 0x10:
2516     // kind: type in extends clause of class or interface declaration
2517     //       (including the direct superclass of an anonymous class declaration),
2518     //       or in implements clause of interface declaration
2519     // location: ClassFile
2520 
2521     {
2522       // struct:
2523       // supertype_target {
2524       //   u2 supertype_index;
2525       // }
2526       //
2527       if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
2528         log_debug(redefine, class, annotation)("length() is too small for a supertype_target");
2529         return false;
2530       }
2531 
2532       u2 supertype_index = Bytes::get_Java_u2((address)
2533                              type_annotations_typeArray->adr_at(byte_i_ref));
2534       byte_i_ref += 2;
2535 
2536       log_debug(redefine, class, annotation)("supertype_target: supertype_index=%d", supertype_index);
2537     } break;
2538 
2539     case 0x11:
2540     // kind: type in bound of type parameter declaration of generic class or interface
2541     // location: ClassFile
2542     case 0x12:
2543     // kind: type in bound of type parameter declaration of generic method or constructor
2544     // location: method_info
2545 
2546     {
2547       // struct:
2548       // type_parameter_bound_target {
2549       //   u1 type_parameter_index;
2550       //   u1 bound_index;
2551       // }
2552       //
2553       if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
2554         log_debug(redefine, class, annotation)("length() is too small for a type_parameter_bound_target");
2555         return false;
2556       }
2557 
2558       u1 type_parameter_index = type_annotations_typeArray->at(byte_i_ref);
2559       byte_i_ref += 1;
2560       u1 bound_index = type_annotations_typeArray->at(byte_i_ref);
2561       byte_i_ref += 1;
2562 
2563       log_debug(redefine, class, annotation)
2564         ("type_parameter_bound_target: type_parameter_index=%d, bound_index=%d", type_parameter_index, bound_index);
2565     } break;
2566 
2567     case 0x13:
2568     // kind: type in field declaration
2569     // location: field_info
2570     case 0x14:
2571     // kind: return type of method, or type of newly constructed object
2572     // location: method_info
2573     case 0x15:
2574     // kind: receiver type of method or constructor
2575     // location: method_info
2576 
2577     {
2578       // struct:
2579       // empty_target {
2580       // }
2581       //
2582       log_debug(redefine, class, annotation)("empty_target");
2583     } break;
2584 
2585     case 0x16:
2586     // kind: type in formal parameter declaration of method, constructor, or lambda expression
2587     // location: method_info
2588 
2589     {
2590       // struct:
2591       // formal_parameter_target {
2592       //   u1 formal_parameter_index;
2593       // }
2594       //
2595       if ((byte_i_ref + 1) > type_annotations_typeArray->length()) {
2596         log_debug(redefine, class, annotation)("length() is too small for a formal_parameter_target");
2597         return false;
2598       }
2599 
2600       u1 formal_parameter_index = type_annotations_typeArray->at(byte_i_ref);
2601       byte_i_ref += 1;
2602 
2603       log_debug(redefine, class, annotation)
2604         ("formal_parameter_target: formal_parameter_index=%d", formal_parameter_index);
2605     } break;
2606 
2607     case 0x17:
2608     // kind: type in throws clause of method or constructor
2609     // location: method_info
2610 
2611     {
2612       // struct:
2613       // throws_target {
2614       //   u2 throws_type_index
2615       // }
2616       //
2617       if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
2618         log_debug(redefine, class, annotation)("length() is too small for a throws_target");
2619         return false;
2620       }
2621 
2622       u2 throws_type_index = Bytes::get_Java_u2((address)
2623                                type_annotations_typeArray->adr_at(byte_i_ref));
2624       byte_i_ref += 2;
2625 
2626       log_debug(redefine, class, annotation)("throws_target: throws_type_index=%d", throws_type_index);
2627     } break;
2628 
2629     case 0x40:
2630     // kind: type in local variable declaration
2631     // location: Code
2632     case 0x41:
2633     // kind: type in resource variable declaration
2634     // location: Code
2635 
2636     {
2637       // struct:
2638       // localvar_target {
2639       //   u2 table_length;
2640       //   struct {
2641       //     u2 start_pc;
2642       //     u2 length;
2643       //     u2 index;
2644       //   } table[table_length];
2645       // }
2646       //
2647       if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
2648         // not enough room for a table_length let alone the rest of a localvar_target
2649         log_debug(redefine, class, annotation)("length() is too small for a localvar_target table_length");
2650         return false;
2651       }
2652 
2653       u2 table_length = Bytes::get_Java_u2((address)
2654                           type_annotations_typeArray->adr_at(byte_i_ref));
2655       byte_i_ref += 2;
2656 
2657       log_debug(redefine, class, annotation)("localvar_target: table_length=%d", table_length);
2658 
2659       int table_struct_size = 2 + 2 + 2; // 3 u2 variables per table entry
2660       int table_size = table_length * table_struct_size;
2661 
2662       if ((byte_i_ref + table_size) > type_annotations_typeArray->length()) {
2663         // not enough room for a table
2664         log_debug(redefine, class, annotation)("length() is too small for a table array of length %d", table_length);
2665         return false;
2666       }
2667 
2668       // Skip over table
2669       byte_i_ref += table_size;
2670     } break;
2671 
2672     case 0x42:
2673     // kind: type in exception parameter declaration
2674     // location: Code
2675 
2676     {
2677       // struct:
2678       // catch_target {
2679       //   u2 exception_table_index;
2680       // }
2681       //
2682       if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
2683         log_debug(redefine, class, annotation)("length() is too small for a catch_target");
2684         return false;
2685       }
2686 
2687       u2 exception_table_index = Bytes::get_Java_u2((address)
2688                                    type_annotations_typeArray->adr_at(byte_i_ref));
2689       byte_i_ref += 2;
2690 
2691       log_debug(redefine, class, annotation)("catch_target: exception_table_index=%d", exception_table_index);
2692     } break;
2693 
2694     case 0x43:
2695     // kind: type in instanceof expression
2696     // location: Code
2697     case 0x44:
2698     // kind: type in new expression
2699     // location: Code
2700     case 0x45:
2701     // kind: type in method reference expression using ::new
2702     // location: Code
2703     case 0x46:
2704     // kind: type in method reference expression using ::Identifier
2705     // location: Code
2706 
2707     {
2708       // struct:
2709       // offset_target {
2710       //   u2 offset;
2711       // }
2712       //
2713       if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
2714         log_debug(redefine, class, annotation)("length() is too small for a offset_target");
2715         return false;
2716       }
2717 
2718       u2 offset = Bytes::get_Java_u2((address)
2719                     type_annotations_typeArray->adr_at(byte_i_ref));
2720       byte_i_ref += 2;
2721 
2722       log_debug(redefine, class, annotation)("offset_target: offset=%d", offset);
2723     } break;
2724 
2725     case 0x47:
2726     // kind: type in cast expression
2727     // location: Code
2728     case 0x48:
2729     // kind: type argument for generic constructor in new expression or
2730     //       explicit constructor invocation statement
2731     // location: Code
2732     case 0x49:
2733     // kind: type argument for generic method in method invocation expression
2734     // location: Code
2735     case 0x4A:
2736     // kind: type argument for generic constructor in method reference expression using ::new
2737     // location: Code
2738     case 0x4B:
2739     // kind: type argument for generic method in method reference expression using ::Identifier
2740     // location: Code
2741 
2742     {
2743       // struct:
2744       // type_argument_target {
2745       //   u2 offset;
2746       //   u1 type_argument_index;
2747       // }
2748       //
2749       if ((byte_i_ref + 3) > type_annotations_typeArray->length()) {
2750         log_debug(redefine, class, annotation)("length() is too small for a type_argument_target");
2751         return false;
2752       }
2753 
2754       u2 offset = Bytes::get_Java_u2((address)
2755                     type_annotations_typeArray->adr_at(byte_i_ref));
2756       byte_i_ref += 2;
2757       u1 type_argument_index = type_annotations_typeArray->at(byte_i_ref);
2758       byte_i_ref += 1;
2759 
2760       log_debug(redefine, class, annotation)
2761         ("type_argument_target: offset=%d, type_argument_index=%d", offset, type_argument_index);
2762     } break;
2763 
2764     default:
2765       log_debug(redefine, class, annotation)("unknown target_type");
2766 #ifdef ASSERT
2767       ShouldNotReachHere();
2768 #endif
2769       return false;
2770   }
2771 
2772   return true;
2773 } // end skip_type_annotation_target()
2774 
2775 
2776 // Read, verify and skip over the type_path part so that rewriting
2777 // can continue in the later parts of the struct.
2778 //
2779 // type_path {
2780 //   u1 path_length;
2781 //   {
2782 //     u1 type_path_kind;
2783 //     u1 type_argument_index;
2784 //   } path[path_length];
2785 // }
2786 //
2787 bool VM_RedefineClasses::skip_type_annotation_type_path(
2788        AnnotationArray* type_annotations_typeArray, int &byte_i_ref, TRAPS) {
2789 
2790   if ((byte_i_ref + 1) > type_annotations_typeArray->length()) {
2791     // not enough room for a path_length let alone the rest of the type_path
2792     log_debug(redefine, class, annotation)("length() is too small for a type_path");
2793     return false;
2794   }
2795 
2796   u1 path_length = type_annotations_typeArray->at(byte_i_ref);
2797   byte_i_ref += 1;
2798 
2799   log_debug(redefine, class, annotation)("type_path: path_length=%d", path_length);
2800 
2801   int calc_path_length = 0;
2802   for (; calc_path_length < path_length; calc_path_length++) {
2803     if ((byte_i_ref + 1 + 1) > type_annotations_typeArray->length()) {
2804       // not enough room for a path
2805       log_debug(redefine, class, annotation)
2806         ("length() is too small for path entry %d of %d", calc_path_length, path_length);
2807       return false;
2808     }
2809 
2810     u1 type_path_kind = type_annotations_typeArray->at(byte_i_ref);
2811     byte_i_ref += 1;
2812     u1 type_argument_index = type_annotations_typeArray->at(byte_i_ref);
2813     byte_i_ref += 1;
2814 
2815     log_debug(redefine, class, annotation)
2816       ("type_path: path[%d]: type_path_kind=%d, type_argument_index=%d",
2817        calc_path_length, type_path_kind, type_argument_index);
2818 
2819     if (type_path_kind > 3 || (type_path_kind != 3 && type_argument_index != 0)) {
2820       // not enough room for a path
2821       log_debug(redefine, class, annotation)("inconsistent type_path values");
2822       return false;
2823     }
2824   }
2825   assert(path_length == calc_path_length, "sanity check");
2826 
2827   return true;
2828 } // end skip_type_annotation_type_path()
2829 
2830 
2831 // Rewrite constant pool references in the method's stackmap table.
2832 // These "structures" are adapted from the StackMapTable_attribute that
2833 // is described in section 4.8.4 of the 6.0 version of the VM spec
2834 // (dated 2005.10.26):
2835 // file:///net/quincunx.sfbay/export/gbracha/ClassFile-Java6.pdf
2836 //
2837 // stack_map {
2838 //   u2 number_of_entries;
2839 //   stack_map_frame entries[number_of_entries];
2840 // }
2841 //
2842 void VM_RedefineClasses::rewrite_cp_refs_in_stack_map_table(
2843        const methodHandle& method, TRAPS) {
2844 
2845   if (!method->has_stackmap_table()) {
2846     return;
2847   }
2848 
2849   AnnotationArray* stackmap_data = method->stackmap_data();
2850   address stackmap_p = (address)stackmap_data->adr_at(0);
2851   address stackmap_end = stackmap_p + stackmap_data->length();
2852 
2853   assert(stackmap_p + 2 <= stackmap_end, "no room for number_of_entries");
2854   u2 number_of_entries = Bytes::get_Java_u2(stackmap_p);
2855   stackmap_p += 2;
2856 
2857   log_debug(redefine, class, stackmap)("number_of_entries=%u", number_of_entries);
2858 
2859   // walk through each stack_map_frame
2860   u2 calc_number_of_entries = 0;
2861   for (; calc_number_of_entries < number_of_entries; calc_number_of_entries++) {
2862     // The stack_map_frame structure is a u1 frame_type followed by
2863     // 0 or more bytes of data:
2864     //
2865     // union stack_map_frame {
2866     //   same_frame;
2867     //   same_locals_1_stack_item_frame;
2868     //   same_locals_1_stack_item_frame_extended;
2869     //   chop_frame;
2870     //   same_frame_extended;
2871     //   append_frame;
2872     //   full_frame;
2873     // }
2874 
2875     assert(stackmap_p + 1 <= stackmap_end, "no room for frame_type");
2876     u1 frame_type = *stackmap_p;
2877     stackmap_p++;
2878 
2879     // same_frame {
2880     //   u1 frame_type = SAME; /* 0-63 */
2881     // }
2882     if (frame_type <= 63) {
2883       // nothing more to do for same_frame
2884     }
2885 
2886     // same_locals_1_stack_item_frame {
2887     //   u1 frame_type = SAME_LOCALS_1_STACK_ITEM; /* 64-127 */
2888     //   verification_type_info stack[1];
2889     // }
2890     else if (frame_type >= 64 && frame_type <= 127) {
2891       rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
2892         calc_number_of_entries, frame_type, THREAD);
2893     }
2894 
2895     // reserved for future use
2896     else if (frame_type >= 128 && frame_type <= 246) {
2897       // nothing more to do for reserved frame_types
2898     }
2899 
2900     // same_locals_1_stack_item_frame_extended {
2901     //   u1 frame_type = SAME_LOCALS_1_STACK_ITEM_EXTENDED; /* 247 */
2902     //   u2 offset_delta;
2903     //   verification_type_info stack[1];
2904     // }
2905     else if (frame_type == 247) {
2906       stackmap_p += 2;
2907       rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
2908         calc_number_of_entries, frame_type, THREAD);
2909     }
2910 
2911     // chop_frame {
2912     //   u1 frame_type = CHOP; /* 248-250 */
2913     //   u2 offset_delta;
2914     // }
2915     else if (frame_type >= 248 && frame_type <= 250) {
2916       stackmap_p += 2;
2917     }
2918 
2919     // same_frame_extended {
2920     //   u1 frame_type = SAME_FRAME_EXTENDED; /* 251*/
2921     //   u2 offset_delta;
2922     // }
2923     else if (frame_type == 251) {
2924       stackmap_p += 2;
2925     }
2926 
2927     // append_frame {
2928     //   u1 frame_type = APPEND; /* 252-254 */
2929     //   u2 offset_delta;
2930     //   verification_type_info locals[frame_type - 251];
2931     // }
2932     else if (frame_type >= 252 && frame_type <= 254) {
2933       assert(stackmap_p + 2 <= stackmap_end,
2934         "no room for offset_delta");
2935       stackmap_p += 2;
2936       u1 len = frame_type - 251;
2937       for (u1 i = 0; i < len; i++) {
2938         rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
2939           calc_number_of_entries, frame_type, THREAD);
2940       }
2941     }
2942 
2943     // full_frame {
2944     //   u1 frame_type = FULL_FRAME; /* 255 */
2945     //   u2 offset_delta;
2946     //   u2 number_of_locals;
2947     //   verification_type_info locals[number_of_locals];
2948     //   u2 number_of_stack_items;
2949     //   verification_type_info stack[number_of_stack_items];
2950     // }
2951     else if (frame_type == 255) {
2952       assert(stackmap_p + 2 + 2 <= stackmap_end,
2953         "no room for smallest full_frame");
2954       stackmap_p += 2;
2955 
2956       u2 number_of_locals = Bytes::get_Java_u2(stackmap_p);
2957       stackmap_p += 2;
2958 
2959       for (u2 locals_i = 0; locals_i < number_of_locals; locals_i++) {
2960         rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
2961           calc_number_of_entries, frame_type, THREAD);
2962       }
2963 
2964       // Use the largest size for the number_of_stack_items, but only get
2965       // the right number of bytes.
2966       u2 number_of_stack_items = Bytes::get_Java_u2(stackmap_p);
2967       stackmap_p += 2;
2968 
2969       for (u2 stack_i = 0; stack_i < number_of_stack_items; stack_i++) {
2970         rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
2971           calc_number_of_entries, frame_type, THREAD);
2972       }
2973     }
2974   } // end while there is a stack_map_frame
2975   assert(number_of_entries == calc_number_of_entries, "sanity check");
2976 } // end rewrite_cp_refs_in_stack_map_table()
2977 
2978 
2979 // Rewrite constant pool references in the verification type info
2980 // portion of the method's stackmap table. These "structures" are
2981 // adapted from the StackMapTable_attribute that is described in
2982 // section 4.8.4 of the 6.0 version of the VM spec (dated 2005.10.26):
2983 // file:///net/quincunx.sfbay/export/gbracha/ClassFile-Java6.pdf
2984 //
2985 // The verification_type_info structure is a u1 tag followed by 0 or
2986 // more bytes of data:
2987 //
2988 // union verification_type_info {
2989 //   Top_variable_info;
2990 //   Integer_variable_info;
2991 //   Float_variable_info;
2992 //   Long_variable_info;
2993 //   Double_variable_info;
2994 //   Null_variable_info;
2995 //   UninitializedThis_variable_info;
2996 //   Object_variable_info;
2997 //   Uninitialized_variable_info;
2998 // }
2999 //
3000 void VM_RedefineClasses::rewrite_cp_refs_in_verification_type_info(
3001        address& stackmap_p_ref, address stackmap_end, u2 frame_i,
3002        u1 frame_type, TRAPS) {
3003 
3004   assert(stackmap_p_ref + 1 <= stackmap_end, "no room for tag");
3005   u1 tag = *stackmap_p_ref;
3006   stackmap_p_ref++;
3007 
3008   switch (tag) {
3009   // Top_variable_info {
3010   //   u1 tag = ITEM_Top; /* 0 */
3011   // }
3012   // verificationType.hpp has zero as ITEM_Bogus instead of ITEM_Top
3013   case 0:  // fall through
3014 
3015   // Integer_variable_info {
3016   //   u1 tag = ITEM_Integer; /* 1 */
3017   // }
3018   case ITEM_Integer:  // fall through
3019 
3020   // Float_variable_info {
3021   //   u1 tag = ITEM_Float; /* 2 */
3022   // }
3023   case ITEM_Float:  // fall through
3024 
3025   // Double_variable_info {
3026   //   u1 tag = ITEM_Double; /* 3 */
3027   // }
3028   case ITEM_Double:  // fall through
3029 
3030   // Long_variable_info {
3031   //   u1 tag = ITEM_Long; /* 4 */
3032   // }
3033   case ITEM_Long:  // fall through
3034 
3035   // Null_variable_info {
3036   //   u1 tag = ITEM_Null; /* 5 */
3037   // }
3038   case ITEM_Null:  // fall through
3039 
3040   // UninitializedThis_variable_info {
3041   //   u1 tag = ITEM_UninitializedThis; /* 6 */
3042   // }
3043   case ITEM_UninitializedThis:
3044     // nothing more to do for the above tag types
3045     break;
3046 
3047   // Object_variable_info {
3048   //   u1 tag = ITEM_Object; /* 7 */
3049   //   u2 cpool_index;
3050   // }
3051   case ITEM_Object:
3052   {
3053     assert(stackmap_p_ref + 2 <= stackmap_end, "no room for cpool_index");
3054     u2 cpool_index = Bytes::get_Java_u2(stackmap_p_ref);
3055     u2 new_cp_index = find_new_index(cpool_index);
3056     if (new_cp_index != 0) {
3057       log_debug(redefine, class, stackmap)("mapped old cpool_index=%d", cpool_index);
3058       Bytes::put_Java_u2(stackmap_p_ref, new_cp_index);
3059       cpool_index = new_cp_index;
3060     }
3061     stackmap_p_ref += 2;
3062 
3063     log_debug(redefine, class, stackmap)
3064       ("frame_i=%u, frame_type=%u, cpool_index=%d", frame_i, frame_type, cpool_index);
3065   } break;
3066 
3067   // Uninitialized_variable_info {
3068   //   u1 tag = ITEM_Uninitialized; /* 8 */
3069   //   u2 offset;
3070   // }
3071   case ITEM_Uninitialized:
3072     assert(stackmap_p_ref + 2 <= stackmap_end, "no room for offset");
3073     stackmap_p_ref += 2;
3074     break;
3075 
3076   default:
3077     log_debug(redefine, class, stackmap)("frame_i=%u, frame_type=%u, bad tag=0x%x", frame_i, frame_type, tag);
3078     ShouldNotReachHere();
3079     break;
3080   } // end switch (tag)
3081 } // end rewrite_cp_refs_in_verification_type_info()
3082 
3083 
3084 // Change the constant pool associated with klass scratch_class to
3085 // scratch_cp. If shrink is true, then scratch_cp_length elements
3086 // are copied from scratch_cp to a smaller constant pool and the
3087 // smaller constant pool is associated with scratch_class.
3088 void VM_RedefineClasses::set_new_constant_pool(
3089        ClassLoaderData* loader_data,
3090        InstanceKlass* scratch_class, constantPoolHandle scratch_cp,
3091        int scratch_cp_length, TRAPS) {
3092   assert(scratch_cp->length() >= scratch_cp_length, "sanity check");
3093 
3094   // scratch_cp is a merged constant pool and has enough space for a
3095   // worst case merge situation. We want to associate the minimum
3096   // sized constant pool with the klass to save space.
3097   ConstantPool* cp = ConstantPool::allocate(loader_data, scratch_cp_length, CHECK);
3098   constantPoolHandle smaller_cp(THREAD, cp);
3099 
3100   // preserve version() value in the smaller copy
3101   int version = scratch_cp->version();
3102   assert(version != 0, "sanity check");
3103   smaller_cp->set_version(version);
3104 
3105   // attach klass to new constant pool
3106   // reference to the cp holder is needed for copy_operands()
3107   smaller_cp->set_pool_holder(scratch_class);
3108 
3109   scratch_cp->copy_cp_to(1, scratch_cp_length - 1, smaller_cp, 1, THREAD);
3110   if (HAS_PENDING_EXCEPTION) {
3111     // Exception is handled in the caller
3112     loader_data->add_to_deallocate_list(smaller_cp());
3113     return;
3114   }
3115   scratch_cp = smaller_cp;
3116 
3117   // attach new constant pool to klass
3118   scratch_class->set_constants(scratch_cp());
3119   scratch_cp->initialize_unresolved_klasses(loader_data, CHECK);
3120 
3121   int i;  // for portability
3122 
3123   // update each field in klass to use new constant pool indices as needed
3124   for (JavaFieldStream fs(scratch_class); !fs.done(); fs.next()) {
3125     jshort cur_index = fs.name_index();
3126     jshort new_index = find_new_index(cur_index);
3127     if (new_index != 0) {
3128       log_trace(redefine, class, constantpool)("field-name_index change: %d to %d", cur_index, new_index);
3129       fs.set_name_index(new_index);
3130     }
3131     cur_index = fs.signature_index();
3132     new_index = find_new_index(cur_index);
3133     if (new_index != 0) {
3134       log_trace(redefine, class, constantpool)("field-signature_index change: %d to %d", cur_index, new_index);
3135       fs.set_signature_index(new_index);
3136     }
3137     cur_index = fs.initval_index();
3138     new_index = find_new_index(cur_index);
3139     if (new_index != 0) {
3140       log_trace(redefine, class, constantpool)("field-initval_index change: %d to %d", cur_index, new_index);
3141       fs.set_initval_index(new_index);
3142     }
3143     cur_index = fs.generic_signature_index();
3144     new_index = find_new_index(cur_index);
3145     if (new_index != 0) {
3146       log_trace(redefine, class, constantpool)("field-generic_signature change: %d to %d", cur_index, new_index);
3147       fs.set_generic_signature_index(new_index);
3148     }
3149   } // end for each field
3150 
3151   // Update constant pool indices in the inner classes info to use
3152   // new constant indices as needed. The inner classes info is a
3153   // quadruple:
3154   // (inner_class_info, outer_class_info, inner_name, inner_access_flags)
3155   InnerClassesIterator iter(scratch_class);
3156   for (; !iter.done(); iter.next()) {
3157     int cur_index = iter.inner_class_info_index();
3158     if (cur_index == 0) {
3159       continue;  // JVM spec. allows null inner class refs so skip it
3160     }
3161     int new_index = find_new_index(cur_index);
3162     if (new_index != 0) {
3163       log_trace(redefine, class, constantpool)("inner_class_info change: %d to %d", cur_index, new_index);
3164       iter.set_inner_class_info_index(new_index);
3165     }
3166     cur_index = iter.outer_class_info_index();
3167     new_index = find_new_index(cur_index);
3168     if (new_index != 0) {
3169       log_trace(redefine, class, constantpool)("outer_class_info change: %d to %d", cur_index, new_index);
3170       iter.set_outer_class_info_index(new_index);
3171     }
3172     cur_index = iter.inner_name_index();
3173     new_index = find_new_index(cur_index);
3174     if (new_index != 0) {
3175       log_trace(redefine, class, constantpool)("inner_name change: %d to %d", cur_index, new_index);
3176       iter.set_inner_name_index(new_index);
3177     }
3178   } // end for each inner class
3179 
3180   // Attach each method in klass to the new constant pool and update
3181   // to use new constant pool indices as needed:
3182   Array<Method*>* methods = scratch_class->methods();
3183   for (i = methods->length() - 1; i >= 0; i--) {
3184     methodHandle method(THREAD, methods->at(i));
3185     method->set_constants(scratch_cp());
3186 
3187     int new_index = find_new_index(method->name_index());
3188     if (new_index != 0) {
3189       log_trace(redefine, class, constantpool)
3190         ("method-name_index change: %d to %d", method->name_index(), new_index);
3191       method->set_name_index(new_index);
3192     }
3193     new_index = find_new_index(method->signature_index());
3194     if (new_index != 0) {
3195       log_trace(redefine, class, constantpool)
3196         ("method-signature_index change: %d to %d", method->signature_index(), new_index);
3197       method->set_signature_index(new_index);
3198     }
3199     new_index = find_new_index(method->generic_signature_index());
3200     if (new_index != 0) {
3201       log_trace(redefine, class, constantpool)
3202         ("method-generic_signature_index change: %d to %d", method->generic_signature_index(), new_index);
3203       method->set_generic_signature_index(new_index);
3204     }
3205 
3206     // Update constant pool indices in the method's checked exception
3207     // table to use new constant indices as needed.
3208     int cext_length = method->checked_exceptions_length();
3209     if (cext_length > 0) {
3210       CheckedExceptionElement * cext_table =
3211         method->checked_exceptions_start();
3212       for (int j = 0; j < cext_length; j++) {
3213         int cur_index = cext_table[j].class_cp_index;
3214         int new_index = find_new_index(cur_index);
3215         if (new_index != 0) {
3216           log_trace(redefine, class, constantpool)("cext-class_cp_index change: %d to %d", cur_index, new_index);
3217           cext_table[j].class_cp_index = (u2)new_index;
3218         }
3219       } // end for each checked exception table entry
3220     } // end if there are checked exception table entries
3221 
3222     // Update each catch type index in the method's exception table
3223     // to use new constant pool indices as needed. The exception table
3224     // holds quadruple entries of the form:
3225     //   (beg_bci, end_bci, handler_bci, klass_index)
3226 
3227     ExceptionTable ex_table(method());
3228     int ext_length = ex_table.length();
3229 
3230     for (int j = 0; j < ext_length; j ++) {
3231       int cur_index = ex_table.catch_type_index(j);
3232       int new_index = find_new_index(cur_index);
3233       if (new_index != 0) {
3234         log_trace(redefine, class, constantpool)("ext-klass_index change: %d to %d", cur_index, new_index);
3235         ex_table.set_catch_type_index(j, new_index);
3236       }
3237     } // end for each exception table entry
3238 
3239     // Update constant pool indices in the method's local variable
3240     // table to use new constant indices as needed. The local variable
3241     // table hold sextuple entries of the form:
3242     // (start_pc, length, name_index, descriptor_index, signature_index, slot)
3243     int lvt_length = method->localvariable_table_length();
3244     if (lvt_length > 0) {
3245       LocalVariableTableElement * lv_table =
3246         method->localvariable_table_start();
3247       for (int j = 0; j < lvt_length; j++) {
3248         int cur_index = lv_table[j].name_cp_index;
3249         int new_index = find_new_index(cur_index);
3250         if (new_index != 0) {
3251           log_trace(redefine, class, constantpool)("lvt-name_cp_index change: %d to %d", cur_index, new_index);
3252           lv_table[j].name_cp_index = (u2)new_index;
3253         }
3254         cur_index = lv_table[j].descriptor_cp_index;
3255         new_index = find_new_index(cur_index);
3256         if (new_index != 0) {
3257           log_trace(redefine, class, constantpool)("lvt-descriptor_cp_index change: %d to %d", cur_index, new_index);
3258           lv_table[j].descriptor_cp_index = (u2)new_index;
3259         }
3260         cur_index = lv_table[j].signature_cp_index;
3261         new_index = find_new_index(cur_index);
3262         if (new_index != 0) {
3263           log_trace(redefine, class, constantpool)("lvt-signature_cp_index change: %d to %d", cur_index, new_index);
3264           lv_table[j].signature_cp_index = (u2)new_index;
3265         }
3266       } // end for each local variable table entry
3267     } // end if there are local variable table entries
3268 
3269     rewrite_cp_refs_in_stack_map_table(method, THREAD);
3270   } // end for each method
3271 } // end set_new_constant_pool()
3272 
3273 
3274 // Unevolving classes may point to methods of the_class directly
3275 // from their constant pool caches, itables, and/or vtables. We
3276 // use the ClassLoaderDataGraph::classes_do() facility and this helper
3277 // to fix up these pointers.
3278 
3279 // Adjust cpools and vtables closure
3280 void VM_RedefineClasses::AdjustCpoolCacheAndVtable::do_klass(Klass* k) {
3281 
3282   // This is a very busy routine. We don't want too much tracing
3283   // printed out.
3284   bool trace_name_printed = false;
3285   InstanceKlass *the_class = InstanceKlass::cast(_the_class);
3286 
3287   // If the class being redefined is java.lang.Object, we need to fix all
3288   // array class vtables also
3289   if (k->is_array_klass() && _the_class == SystemDictionary::Object_klass()) {
3290     k->vtable().adjust_method_entries(the_class, &trace_name_printed);
3291 
3292   } else if (k->is_instance_klass()) {
3293     HandleMark hm(_thread);
3294     InstanceKlass *ik = InstanceKlass::cast(k);
3295 
3296     // HotSpot specific optimization! HotSpot does not currently
3297     // support delegation from the bootstrap class loader to a
3298     // user-defined class loader. This means that if the bootstrap
3299     // class loader is the initiating class loader, then it will also
3300     // be the defining class loader. This also means that classes
3301     // loaded by the bootstrap class loader cannot refer to classes
3302     // loaded by a user-defined class loader. Note: a user-defined
3303     // class loader can delegate to the bootstrap class loader.
3304     //
3305     // If the current class being redefined has a user-defined class
3306     // loader as its defining class loader, then we can skip all
3307     // classes loaded by the bootstrap class loader.
3308     bool is_user_defined = (_the_class->class_loader() != NULL);
3309     if (is_user_defined && ik->class_loader() == NULL) {
3310       return;
3311     }
3312 
3313     // Fix the vtable embedded in the_class and subclasses of the_class,
3314     // if one exists. We discard scratch_class and we don't keep an
3315     // InstanceKlass around to hold obsolete methods so we don't have
3316     // any other InstanceKlass embedded vtables to update. The vtable
3317     // holds the Method*s for virtual (but not final) methods.
3318     // Default methods, or concrete methods in interfaces are stored
3319     // in the vtable, so if an interface changes we need to check
3320     // adjust_method_entries() for every InstanceKlass, which will also
3321     // adjust the default method vtable indices.
3322     // We also need to adjust any default method entries that are
3323     // not yet in the vtable, because the vtable setup is in progress.
3324     // This must be done after we adjust the default_methods and
3325     // default_vtable_indices for methods already in the vtable.
3326     // If redefining Unsafe, walk all the vtables looking for entries.
3327     if (ik->vtable_length() > 0 && (_the_class->is_interface()
3328         || _the_class == SystemDictionary::internal_Unsafe_klass()
3329         || ik->is_subtype_of(_the_class))) {
3330       // ik->vtable() creates a wrapper object; rm cleans it up
3331       ResourceMark rm(_thread);
3332 
3333       ik->vtable().adjust_method_entries(the_class, &trace_name_printed);
3334       ik->adjust_default_methods(the_class, &trace_name_printed);
3335     }
3336 
3337     // If the current class has an itable and we are either redefining an
3338     // interface or if the current class is a subclass of the_class, then
3339     // we potentially have to fix the itable. If we are redefining an
3340     // interface, then we have to call adjust_method_entries() for
3341     // every InstanceKlass that has an itable since there isn't a
3342     // subclass relationship between an interface and an InstanceKlass.
3343     // If redefining Unsafe, walk all the itables looking for entries.
3344     if (ik->itable_length() > 0 && (_the_class->is_interface()
3345         || _the_class == SystemDictionary::internal_Unsafe_klass()
3346         || ik->is_subclass_of(_the_class))) {
3347       ResourceMark rm(_thread);
3348       ik->itable().adjust_method_entries(the_class, &trace_name_printed);
3349     }
3350 
3351     // The constant pools in other classes (other_cp) can refer to
3352     // methods in the_class. We have to update method information in
3353     // other_cp's cache. If other_cp has a previous version, then we
3354     // have to repeat the process for each previous version. The
3355     // constant pool cache holds the Method*s for non-virtual
3356     // methods and for virtual, final methods.
3357     //
3358     // Special case: if the current class is the_class, then new_cp
3359     // has already been attached to the_class and old_cp has already
3360     // been added as a previous version. The new_cp doesn't have any
3361     // cached references to old methods so it doesn't need to be
3362     // updated. We can simply start with the previous version(s) in
3363     // that case.
3364     constantPoolHandle other_cp;
3365     ConstantPoolCache* cp_cache;
3366 
3367     if (ik != _the_class) {
3368       // this klass' constant pool cache may need adjustment
3369       other_cp = constantPoolHandle(ik->constants());
3370       cp_cache = other_cp->cache();
3371       if (cp_cache != NULL) {
3372         cp_cache->adjust_method_entries(the_class, &trace_name_printed);
3373       }
3374     }
3375 
3376     // the previous versions' constant pool caches may need adjustment
3377     for (InstanceKlass* pv_node = ik->previous_versions();
3378          pv_node != NULL;
3379          pv_node = pv_node->previous_versions()) {
3380       cp_cache = pv_node->constants()->cache();
3381       if (cp_cache != NULL) {
3382         cp_cache->adjust_method_entries(pv_node, &trace_name_printed);
3383       }
3384     }
3385   }
3386 }
3387 
3388 // Clean method data for this class
3389 void VM_RedefineClasses::MethodDataCleaner::do_klass(Klass* k) {
3390   if (k->is_instance_klass()) {
3391     InstanceKlass *ik = InstanceKlass::cast(k);
3392     // Clean MethodData of this class's methods so they don't refer to
3393     // old methods that are no longer running.
3394     Array<Method*>* methods = ik->methods();
3395     int num_methods = methods->length();
3396     for (int index = 0; index < num_methods; ++index) {
3397       if (methods->at(index)->method_data() != NULL) {
3398         methods->at(index)->method_data()->clean_weak_method_links();
3399       }
3400     }
3401   }
3402 }
3403 
3404 void VM_RedefineClasses::update_jmethod_ids() {
3405   for (int j = 0; j < _matching_methods_length; ++j) {
3406     Method* old_method = _matching_old_methods[j];
3407     jmethodID jmid = old_method->find_jmethod_id_or_null();
3408     if (jmid != NULL) {
3409       // There is a jmethodID, change it to point to the new method
3410       methodHandle new_method_h(_matching_new_methods[j]);
3411       Method::change_method_associated_with_jmethod_id(jmid, new_method_h());
3412       assert(Method::resolve_jmethod_id(jmid) == _matching_new_methods[j],
3413              "should be replaced");
3414     }
3415   }
3416 }
3417 
3418 int VM_RedefineClasses::check_methods_and_mark_as_obsolete() {
3419   int emcp_method_count = 0;
3420   int obsolete_count = 0;
3421   int old_index = 0;
3422   for (int j = 0; j < _matching_methods_length; ++j, ++old_index) {
3423     Method* old_method = _matching_old_methods[j];
3424     Method* new_method = _matching_new_methods[j];
3425     Method* old_array_method;
3426 
3427     // Maintain an old_index into the _old_methods array by skipping
3428     // deleted methods
3429     while ((old_array_method = _old_methods->at(old_index)) != old_method) {
3430       ++old_index;
3431     }
3432 
3433     if (MethodComparator::methods_EMCP(old_method, new_method)) {
3434       // The EMCP definition from JSR-163 requires the bytecodes to be
3435       // the same with the exception of constant pool indices which may
3436       // differ. However, the constants referred to by those indices
3437       // must be the same.
3438       //
3439       // We use methods_EMCP() for comparison since constant pool
3440       // merging can remove duplicate constant pool entries that were
3441       // present in the old method and removed from the rewritten new
3442       // method. A faster binary comparison function would consider the
3443       // old and new methods to be different when they are actually
3444       // EMCP.
3445       //
3446       // The old and new methods are EMCP and you would think that we
3447       // could get rid of one of them here and now and save some space.
3448       // However, the concept of EMCP only considers the bytecodes and
3449       // the constant pool entries in the comparison. Other things,
3450       // e.g., the line number table (LNT) or the local variable table
3451       // (LVT) don't count in the comparison. So the new (and EMCP)
3452       // method can have a new LNT that we need so we can't just
3453       // overwrite the new method with the old method.
3454       //
3455       // When this routine is called, we have already attached the new
3456       // methods to the_class so the old methods are effectively
3457       // overwritten. However, if an old method is still executing,
3458       // then the old method cannot be collected until sometime after
3459       // the old method call has returned. So the overwriting of old
3460       // methods by new methods will save us space except for those
3461       // (hopefully few) old methods that are still executing.
3462       //
3463       // A method refers to a ConstMethod* and this presents another
3464       // possible avenue to space savings. The ConstMethod* in the
3465       // new method contains possibly new attributes (LNT, LVT, etc).
3466       // At first glance, it seems possible to save space by replacing
3467       // the ConstMethod* in the old method with the ConstMethod*
3468       // from the new method. The old and new methods would share the
3469       // same ConstMethod* and we would save the space occupied by
3470       // the old ConstMethod*. However, the ConstMethod* contains
3471       // a back reference to the containing method. Sharing the
3472       // ConstMethod* between two methods could lead to confusion in
3473       // the code that uses the back reference. This would lead to
3474       // brittle code that could be broken in non-obvious ways now or
3475       // in the future.
3476       //
3477       // Another possibility is to copy the ConstMethod* from the new
3478       // method to the old method and then overwrite the new method with
3479       // the old method. Since the ConstMethod* contains the bytecodes
3480       // for the method embedded in the oop, this option would change
3481       // the bytecodes out from under any threads executing the old
3482       // method and make the thread's bcp invalid. Since EMCP requires
3483       // that the bytecodes be the same modulo constant pool indices, it
3484       // is straight forward to compute the correct new bcp in the new
3485       // ConstMethod* from the old bcp in the old ConstMethod*. The
3486       // time consuming part would be searching all the frames in all
3487       // of the threads to find all of the calls to the old method.
3488       //
3489       // It looks like we will have to live with the limited savings
3490       // that we get from effectively overwriting the old methods
3491       // when the new methods are attached to the_class.
3492 
3493       // Count number of methods that are EMCP.  The method will be marked
3494       // old but not obsolete if it is EMCP.
3495       emcp_method_count++;
3496 
3497       // An EMCP method is _not_ obsolete. An obsolete method has a
3498       // different jmethodID than the current method. An EMCP method
3499       // has the same jmethodID as the current method. Having the
3500       // same jmethodID for all EMCP versions of a method allows for
3501       // a consistent view of the EMCP methods regardless of which
3502       // EMCP method you happen to have in hand. For example, a
3503       // breakpoint set in one EMCP method will work for all EMCP
3504       // versions of the method including the current one.
3505     } else {
3506       // mark obsolete methods as such
3507       old_method->set_is_obsolete();
3508       obsolete_count++;
3509 
3510       // obsolete methods need a unique idnum so they become new entries in
3511       // the jmethodID cache in InstanceKlass
3512       assert(old_method->method_idnum() == new_method->method_idnum(), "must match");
3513       u2 num = InstanceKlass::cast(_the_class)->next_method_idnum();
3514       if (num != ConstMethod::UNSET_IDNUM) {
3515         old_method->set_method_idnum(num);
3516       }
3517 
3518       // With tracing we try not to "yack" too much. The position of
3519       // this trace assumes there are fewer obsolete methods than
3520       // EMCP methods.
3521       if (log_is_enabled(Trace, redefine, class, obsolete, mark)) {
3522         ResourceMark rm;
3523         log_trace(redefine, class, obsolete, mark)
3524           ("mark %s(%s) as obsolete", old_method->name()->as_C_string(), old_method->signature()->as_C_string());
3525       }
3526     }
3527     old_method->set_is_old();
3528   }
3529   for (int i = 0; i < _deleted_methods_length; ++i) {
3530     Method* old_method = _deleted_methods[i];
3531 
3532     assert(!old_method->has_vtable_index(),
3533            "cannot delete methods with vtable entries");;
3534 
3535     // Mark all deleted methods as old, obsolete and deleted
3536     old_method->set_is_deleted();
3537     old_method->set_is_old();
3538     old_method->set_is_obsolete();
3539     ++obsolete_count;
3540     // With tracing we try not to "yack" too much. The position of
3541     // this trace assumes there are fewer obsolete methods than
3542     // EMCP methods.
3543     if (log_is_enabled(Trace, redefine, class, obsolete, mark)) {
3544       ResourceMark rm;
3545       log_trace(redefine, class, obsolete, mark)
3546         ("mark deleted %s(%s) as obsolete", old_method->name()->as_C_string(), old_method->signature()->as_C_string());
3547     }
3548   }
3549   assert((emcp_method_count + obsolete_count) == _old_methods->length(),
3550     "sanity check");
3551   log_trace(redefine, class, obsolete, mark)("EMCP_cnt=%d, obsolete_cnt=%d", emcp_method_count, obsolete_count);
3552   return emcp_method_count;
3553 }
3554 
3555 // This internal class transfers the native function registration from old methods
3556 // to new methods.  It is designed to handle both the simple case of unchanged
3557 // native methods and the complex cases of native method prefixes being added and/or
3558 // removed.
3559 // It expects only to be used during the VM_RedefineClasses op (a safepoint).
3560 //
3561 // This class is used after the new methods have been installed in "the_class".
3562 //
3563 // So, for example, the following must be handled.  Where 'm' is a method and
3564 // a number followed by an underscore is a prefix.
3565 //
3566 //                                      Old Name    New Name
3567 // Simple transfer to new method        m       ->  m
3568 // Add prefix                           m       ->  1_m
3569 // Remove prefix                        1_m     ->  m
3570 // Simultaneous add of prefixes         m       ->  3_2_1_m
3571 // Simultaneous removal of prefixes     3_2_1_m ->  m
3572 // Simultaneous add and remove          1_m     ->  2_m
3573 // Same, caused by prefix removal only  3_2_1_m ->  3_2_m
3574 //
3575 class TransferNativeFunctionRegistration {
3576  private:
3577   InstanceKlass* the_class;
3578   int prefix_count;
3579   char** prefixes;
3580 
3581   // Recursively search the binary tree of possibly prefixed method names.
3582   // Iteration could be used if all agents were well behaved. Full tree walk is
3583   // more resilent to agents not cleaning up intermediate methods.
3584   // Branch at each depth in the binary tree is:
3585   //    (1) without the prefix.
3586   //    (2) with the prefix.
3587   // where 'prefix' is the prefix at that 'depth' (first prefix, second prefix,...)
3588   Method* search_prefix_name_space(int depth, char* name_str, size_t name_len,
3589                                      Symbol* signature) {
3590     TempNewSymbol name_symbol = SymbolTable::probe(name_str, (int)name_len);
3591     if (name_symbol != NULL) {
3592       Method* method = the_class->lookup_method(name_symbol, signature);
3593       if (method != NULL) {
3594         // Even if prefixed, intermediate methods must exist.
3595         if (method->is_native()) {
3596           // Wahoo, we found a (possibly prefixed) version of the method, return it.
3597           return method;
3598         }
3599         if (depth < prefix_count) {
3600           // Try applying further prefixes (other than this one).
3601           method = search_prefix_name_space(depth+1, name_str, name_len, signature);
3602           if (method != NULL) {
3603             return method; // found
3604           }
3605 
3606           // Try adding this prefix to the method name and see if it matches
3607           // another method name.
3608           char* prefix = prefixes[depth];
3609           size_t prefix_len = strlen(prefix);
3610           size_t trial_len = name_len + prefix_len;
3611           char* trial_name_str = NEW_RESOURCE_ARRAY(char, trial_len + 1);
3612           strcpy(trial_name_str, prefix);
3613           strcat(trial_name_str, name_str);
3614           method = search_prefix_name_space(depth+1, trial_name_str, trial_len,
3615                                             signature);
3616           if (method != NULL) {
3617             // If found along this branch, it was prefixed, mark as such
3618             method->set_is_prefixed_native();
3619             return method; // found
3620           }
3621         }
3622       }
3623     }
3624     return NULL;  // This whole branch bore nothing
3625   }
3626 
3627   // Return the method name with old prefixes stripped away.
3628   char* method_name_without_prefixes(Method* method) {
3629     Symbol* name = method->name();
3630     char* name_str = name->as_utf8();
3631 
3632     // Old prefixing may be defunct, strip prefixes, if any.
3633     for (int i = prefix_count-1; i >= 0; i--) {
3634       char* prefix = prefixes[i];
3635       size_t prefix_len = strlen(prefix);
3636       if (strncmp(prefix, name_str, prefix_len) == 0) {
3637         name_str += prefix_len;
3638       }
3639     }
3640     return name_str;
3641   }
3642 
3643   // Strip any prefixes off the old native method, then try to find a
3644   // (possibly prefixed) new native that matches it.
3645   Method* strip_and_search_for_new_native(Method* method) {
3646     ResourceMark rm;
3647     char* name_str = method_name_without_prefixes(method);
3648     return search_prefix_name_space(0, name_str, strlen(name_str),
3649                                     method->signature());
3650   }
3651 
3652  public:
3653 
3654   // Construct a native method transfer processor for this class.
3655   TransferNativeFunctionRegistration(InstanceKlass* _the_class) {
3656     assert(SafepointSynchronize::is_at_safepoint(), "sanity check");
3657 
3658     the_class = _the_class;
3659     prefixes = JvmtiExport::get_all_native_method_prefixes(&prefix_count);
3660   }
3661 
3662   // Attempt to transfer any of the old or deleted methods that are native
3663   void transfer_registrations(Method** old_methods, int methods_length) {
3664     for (int j = 0; j < methods_length; j++) {
3665       Method* old_method = old_methods[j];
3666 
3667       if (old_method->is_native() && old_method->has_native_function()) {
3668         Method* new_method = strip_and_search_for_new_native(old_method);
3669         if (new_method != NULL) {
3670           // Actually set the native function in the new method.
3671           // Redefine does not send events (except CFLH), certainly not this
3672           // behind the scenes re-registration.
3673           new_method->set_native_function(old_method->native_function(),
3674                               !Method::native_bind_event_is_interesting);
3675         }
3676       }
3677     }
3678   }
3679 };
3680 
3681 // Don't lose the association between a native method and its JNI function.
3682 void VM_RedefineClasses::transfer_old_native_function_registrations(InstanceKlass* the_class) {
3683   TransferNativeFunctionRegistration transfer(the_class);
3684   transfer.transfer_registrations(_deleted_methods, _deleted_methods_length);
3685   transfer.transfer_registrations(_matching_old_methods, _matching_methods_length);
3686 }
3687 
3688 // Deoptimize all compiled code that depends on this class.
3689 //
3690 // If the can_redefine_classes capability is obtained in the onload
3691 // phase then the compiler has recorded all dependencies from startup.
3692 // In that case we need only deoptimize and throw away all compiled code
3693 // that depends on the class.
3694 //
3695 // If can_redefine_classes is obtained sometime after the onload
3696 // phase then the dependency information may be incomplete. In that case
3697 // the first call to RedefineClasses causes all compiled code to be
3698 // thrown away. As can_redefine_classes has been obtained then
3699 // all future compilations will record dependencies so second and
3700 // subsequent calls to RedefineClasses need only throw away code
3701 // that depends on the class.
3702 //
3703 void VM_RedefineClasses::flush_dependent_code(InstanceKlass* ik, TRAPS) {
3704   assert_locked_or_safepoint(Compile_lock);
3705 
3706   // All dependencies have been recorded from startup or this is a second or
3707   // subsequent use of RedefineClasses
3708   if (JvmtiExport::all_dependencies_are_recorded()) {
3709     CodeCache::flush_evol_dependents_on(ik);
3710   } else {
3711     CodeCache::mark_all_nmethods_for_deoptimization();
3712 
3713     ResourceMark rm(THREAD);
3714     DeoptimizationMarker dm;
3715 
3716     // Deoptimize all activations depending on marked nmethods
3717     Deoptimization::deoptimize_dependents();
3718 
3719     // Make the dependent methods not entrant
3720     CodeCache::make_marked_nmethods_not_entrant();
3721 
3722     // From now on we know that the dependency information is complete
3723     JvmtiExport::set_all_dependencies_are_recorded(true);
3724   }
3725 }
3726 
3727 void VM_RedefineClasses::compute_added_deleted_matching_methods() {
3728   Method* old_method;
3729   Method* new_method;
3730 
3731   _matching_old_methods = NEW_RESOURCE_ARRAY(Method*, _old_methods->length());
3732   _matching_new_methods = NEW_RESOURCE_ARRAY(Method*, _old_methods->length());
3733   _added_methods        = NEW_RESOURCE_ARRAY(Method*, _new_methods->length());
3734   _deleted_methods      = NEW_RESOURCE_ARRAY(Method*, _old_methods->length());
3735 
3736   _matching_methods_length = 0;
3737   _deleted_methods_length  = 0;
3738   _added_methods_length    = 0;
3739 
3740   int nj = 0;
3741   int oj = 0;
3742   while (true) {
3743     if (oj >= _old_methods->length()) {
3744       if (nj >= _new_methods->length()) {
3745         break; // we've looked at everything, done
3746       }
3747       // New method at the end
3748       new_method = _new_methods->at(nj);
3749       _added_methods[_added_methods_length++] = new_method;
3750       ++nj;
3751     } else if (nj >= _new_methods->length()) {
3752       // Old method, at the end, is deleted
3753       old_method = _old_methods->at(oj);
3754       _deleted_methods[_deleted_methods_length++] = old_method;
3755       ++oj;
3756     } else {
3757       old_method = _old_methods->at(oj);
3758       new_method = _new_methods->at(nj);
3759       if (old_method->name() == new_method->name()) {
3760         if (old_method->signature() == new_method->signature()) {
3761           _matching_old_methods[_matching_methods_length  ] = old_method;
3762           _matching_new_methods[_matching_methods_length++] = new_method;
3763           ++nj;
3764           ++oj;
3765         } else {
3766           // added overloaded have already been moved to the end,
3767           // so this is a deleted overloaded method
3768           _deleted_methods[_deleted_methods_length++] = old_method;
3769           ++oj;
3770         }
3771       } else { // names don't match
3772         if (old_method->name()->fast_compare(new_method->name()) > 0) {
3773           // new method
3774           _added_methods[_added_methods_length++] = new_method;
3775           ++nj;
3776         } else {
3777           // deleted method
3778           _deleted_methods[_deleted_methods_length++] = old_method;
3779           ++oj;
3780         }
3781       }
3782     }
3783   }
3784   assert(_matching_methods_length + _deleted_methods_length == _old_methods->length(), "sanity");
3785   assert(_matching_methods_length + _added_methods_length == _new_methods->length(), "sanity");
3786 }
3787 
3788 
3789 void VM_RedefineClasses::swap_annotations(InstanceKlass* the_class,
3790                                           InstanceKlass* scratch_class) {
3791   // Swap annotation fields values
3792   Annotations* old_annotations = the_class->annotations();
3793   the_class->set_annotations(scratch_class->annotations());
3794   scratch_class->set_annotations(old_annotations);
3795 }
3796 
3797 
3798 // Install the redefinition of a class:
3799 //    - house keeping (flushing breakpoints and caches, deoptimizing
3800 //      dependent compiled code)
3801 //    - replacing parts in the_class with parts from scratch_class
3802 //    - adding a weak reference to track the obsolete but interesting
3803 //      parts of the_class
3804 //    - adjusting constant pool caches and vtables in other classes
3805 //      that refer to methods in the_class. These adjustments use the
3806 //      ClassLoaderDataGraph::classes_do() facility which only allows
3807 //      a helper method to be specified. The interesting parameters
3808 //      that we would like to pass to the helper method are saved in
3809 //      static global fields in the VM operation.
3810 void VM_RedefineClasses::redefine_single_class(jclass the_jclass,
3811        InstanceKlass* scratch_class, TRAPS) {
3812 
3813   HandleMark hm(THREAD);   // make sure handles from this call are freed
3814 
3815   if (log_is_enabled(Info, redefine, class, timer)) {
3816     _timer_rsc_phase1.start();
3817   }
3818 
3819   InstanceKlass* the_class = get_ik(the_jclass);
3820 
3821   // Remove all breakpoints in methods of this class
3822   JvmtiBreakpoints& jvmti_breakpoints = JvmtiCurrentBreakpoints::get_jvmti_breakpoints();
3823   jvmti_breakpoints.clearall_in_class_at_safepoint(the_class);
3824 
3825   // Deoptimize all compiled code that depends on this class
3826   flush_dependent_code(the_class, THREAD);
3827 
3828   _old_methods = the_class->methods();
3829   _new_methods = scratch_class->methods();
3830   _the_class = the_class;
3831   compute_added_deleted_matching_methods();
3832   update_jmethod_ids();
3833 
3834   _any_class_has_resolved_methods = the_class->has_resolved_methods() || _any_class_has_resolved_methods;
3835 
3836   // Attach new constant pool to the original klass. The original
3837   // klass still refers to the old constant pool (for now).
3838   scratch_class->constants()->set_pool_holder(the_class);
3839 
3840 #if 0
3841   // In theory, with constant pool merging in place we should be able
3842   // to save space by using the new, merged constant pool in place of
3843   // the old constant pool(s). By "pool(s)" I mean the constant pool in
3844   // the klass version we are replacing now and any constant pool(s) in
3845   // previous versions of klass. Nice theory, doesn't work in practice.
3846   // When this code is enabled, even simple programs throw NullPointer
3847   // exceptions. I'm guessing that this is caused by some constant pool
3848   // cache difference between the new, merged constant pool and the
3849   // constant pool that was just being used by the klass. I'm keeping
3850   // this code around to archive the idea, but the code has to remain
3851   // disabled for now.
3852 
3853   // Attach each old method to the new constant pool. This can be
3854   // done here since we are past the bytecode verification and
3855   // constant pool optimization phases.
3856   for (int i = _old_methods->length() - 1; i >= 0; i--) {
3857     Method* method = _old_methods->at(i);
3858     method->set_constants(scratch_class->constants());
3859   }
3860 
3861   // NOTE: this doesn't work because you can redefine the same class in two
3862   // threads, each getting their own constant pool data appended to the
3863   // original constant pool.  In order for the new methods to work when they
3864   // become old methods, they need to keep their updated copy of the constant pool.
3865 
3866   {
3867     // walk all previous versions of the klass
3868     InstanceKlass *ik = the_class;
3869     PreviousVersionWalker pvw(ik);
3870     do {
3871       ik = pvw.next_previous_version();
3872       if (ik != NULL) {
3873 
3874         // attach previous version of klass to the new constant pool
3875         ik->set_constants(scratch_class->constants());
3876 
3877         // Attach each method in the previous version of klass to the
3878         // new constant pool
3879         Array<Method*>* prev_methods = ik->methods();
3880         for (int i = prev_methods->length() - 1; i >= 0; i--) {
3881           Method* method = prev_methods->at(i);
3882           method->set_constants(scratch_class->constants());
3883         }
3884       }
3885     } while (ik != NULL);
3886   }
3887 #endif
3888 
3889   // Replace methods and constantpool
3890   the_class->set_methods(_new_methods);
3891   scratch_class->set_methods(_old_methods);     // To prevent potential GCing of the old methods,
3892                                           // and to be able to undo operation easily.
3893 
3894   Array<int>* old_ordering = the_class->method_ordering();
3895   the_class->set_method_ordering(scratch_class->method_ordering());
3896   scratch_class->set_method_ordering(old_ordering);
3897 
3898   ConstantPool* old_constants = the_class->constants();
3899   the_class->set_constants(scratch_class->constants());
3900   scratch_class->set_constants(old_constants);  // See the previous comment.
3901 #if 0
3902   // We are swapping the guts of "the new class" with the guts of "the
3903   // class". Since the old constant pool has just been attached to "the
3904   // new class", it seems logical to set the pool holder in the old
3905   // constant pool also. However, doing this will change the observable
3906   // class hierarchy for any old methods that are still executing. A
3907   // method can query the identity of its "holder" and this query uses
3908   // the method's constant pool link to find the holder. The change in
3909   // holding class from "the class" to "the new class" can confuse
3910   // things.
3911   //
3912   // Setting the old constant pool's holder will also cause
3913   // verification done during vtable initialization below to fail.
3914   // During vtable initialization, the vtable's class is verified to be
3915   // a subtype of the method's holder. The vtable's class is "the
3916   // class" and the method's holder is gotten from the constant pool
3917   // link in the method itself. For "the class"'s directly implemented
3918   // methods, the method holder is "the class" itself (as gotten from
3919   // the new constant pool). The check works fine in this case. The
3920   // check also works fine for methods inherited from super classes.
3921   //
3922   // Miranda methods are a little more complicated. A miranda method is
3923   // provided by an interface when the class implementing the interface
3924   // does not provide its own method.  These interfaces are implemented
3925   // internally as an InstanceKlass. These special instanceKlasses
3926   // share the constant pool of the class that "implements" the
3927   // interface. By sharing the constant pool, the method holder of a
3928   // miranda method is the class that "implements" the interface. In a
3929   // non-redefine situation, the subtype check works fine. However, if
3930   // the old constant pool's pool holder is modified, then the check
3931   // fails because there is no class hierarchy relationship between the
3932   // vtable's class and "the new class".
3933 
3934   old_constants->set_pool_holder(scratch_class());
3935 #endif
3936 
3937   // track number of methods that are EMCP for add_previous_version() call below
3938   int emcp_method_count = check_methods_and_mark_as_obsolete();
3939   transfer_old_native_function_registrations(the_class);
3940 
3941   // The class file bytes from before any retransformable agents mucked
3942   // with them was cached on the scratch class, move to the_class.
3943   // Note: we still want to do this if nothing needed caching since it
3944   // should get cleared in the_class too.
3945   if (the_class->get_cached_class_file_bytes() == 0) {
3946     // the_class doesn't have a cache yet so copy it
3947     the_class->set_cached_class_file(scratch_class->get_cached_class_file());
3948   }
3949   else if (scratch_class->get_cached_class_file_bytes() !=
3950            the_class->get_cached_class_file_bytes()) {
3951     // The same class can be present twice in the scratch classes list or there
3952     // are multiple concurrent RetransformClasses calls on different threads.
3953     // In such cases we have to deallocate scratch_class cached_class_file.
3954     os::free(scratch_class->get_cached_class_file());
3955   }
3956 
3957   // NULL out in scratch class to not delete twice.  The class to be redefined
3958   // always owns these bytes.
3959   scratch_class->set_cached_class_file(NULL);
3960 
3961   // Replace inner_classes
3962   Array<u2>* old_inner_classes = the_class->inner_classes();
3963   the_class->set_inner_classes(scratch_class->inner_classes());
3964   scratch_class->set_inner_classes(old_inner_classes);
3965 
3966   // Initialize the vtable and interface table after
3967   // methods have been rewritten
3968   {
3969     ResourceMark rm(THREAD);
3970     // no exception should happen here since we explicitly
3971     // do not check loader constraints.
3972     // compare_and_normalize_class_versions has already checked:
3973     //  - classloaders unchanged, signatures unchanged
3974     //  - all instanceKlasses for redefined classes reused & contents updated
3975     the_class->vtable().initialize_vtable(false, THREAD);
3976     the_class->itable().initialize_itable(false, THREAD);
3977     assert(!HAS_PENDING_EXCEPTION || (THREAD->pending_exception()->is_a(SystemDictionary::ThreadDeath_klass())), "redefine exception");
3978   }
3979 
3980   // Leave arrays of jmethodIDs and itable index cache unchanged
3981 
3982   // Copy the "source file name" attribute from new class version
3983   the_class->set_source_file_name_index(
3984     scratch_class->source_file_name_index());
3985 
3986   // Copy the "source debug extension" attribute from new class version
3987   the_class->set_source_debug_extension(
3988     scratch_class->source_debug_extension(),
3989     scratch_class->source_debug_extension() == NULL ? 0 :
3990     (int)strlen(scratch_class->source_debug_extension()));
3991 
3992   // Use of javac -g could be different in the old and the new
3993   if (scratch_class->access_flags().has_localvariable_table() !=
3994       the_class->access_flags().has_localvariable_table()) {
3995 
3996     AccessFlags flags = the_class->access_flags();
3997     if (scratch_class->access_flags().has_localvariable_table()) {
3998       flags.set_has_localvariable_table();
3999     } else {
4000       flags.clear_has_localvariable_table();
4001     }
4002     the_class->set_access_flags(flags);
4003   }
4004 
4005   swap_annotations(the_class, scratch_class);
4006 
4007   // Replace minor version number of class file
4008   u2 old_minor_version = the_class->minor_version();
4009   the_class->set_minor_version(scratch_class->minor_version());
4010   scratch_class->set_minor_version(old_minor_version);
4011 
4012   // Replace major version number of class file
4013   u2 old_major_version = the_class->major_version();
4014   the_class->set_major_version(scratch_class->major_version());
4015   scratch_class->set_major_version(old_major_version);
4016 
4017   // Replace CP indexes for class and name+type of enclosing method
4018   u2 old_class_idx  = the_class->enclosing_method_class_index();
4019   u2 old_method_idx = the_class->enclosing_method_method_index();
4020   the_class->set_enclosing_method_indices(
4021     scratch_class->enclosing_method_class_index(),
4022     scratch_class->enclosing_method_method_index());
4023   scratch_class->set_enclosing_method_indices(old_class_idx, old_method_idx);
4024 
4025   // Replace fingerprint data
4026   the_class->set_has_passed_fingerprint_check(scratch_class->has_passed_fingerprint_check());
4027   the_class->store_fingerprint(scratch_class->get_stored_fingerprint());
4028 
4029   the_class->set_has_been_redefined();
4030 
4031   if (!the_class->should_be_initialized()) {
4032     // Class was already initialized, so AOT has only seen the original version.
4033     // We need to let AOT look at it again.
4034     AOTLoader::load_for_klass(the_class, THREAD);
4035   }
4036 
4037   // keep track of previous versions of this class
4038   the_class->add_previous_version(scratch_class, emcp_method_count);
4039 
4040   _timer_rsc_phase1.stop();
4041   if (log_is_enabled(Info, redefine, class, timer)) {
4042     _timer_rsc_phase2.start();
4043   }
4044 
4045   // Adjust constantpool caches and vtables for all classes
4046   // that reference methods of the evolved class.
4047   AdjustCpoolCacheAndVtable adjust_cpool_cache_and_vtable(THREAD);
4048   ClassLoaderDataGraph::classes_do(&adjust_cpool_cache_and_vtable);
4049 
4050   if (the_class->oop_map_cache() != NULL) {
4051     // Flush references to any obsolete methods from the oop map cache
4052     // so that obsolete methods are not pinned.
4053     the_class->oop_map_cache()->flush_obsolete_entries();
4054   }
4055 
4056   increment_class_counter((InstanceKlass *)the_class, THREAD);
4057   {
4058     ResourceMark rm(THREAD);
4059     // increment the classRedefinedCount field in the_class and in any
4060     // direct and indirect subclasses of the_class
4061     log_info(redefine, class, load)
4062       ("redefined name=%s, count=%d (avail_mem=" UINT64_FORMAT "K)",
4063        the_class->external_name(), java_lang_Class::classRedefinedCount(the_class->java_mirror()), os::available_memory() >> 10);
4064     Events::log_redefinition(THREAD, "redefined class name=%s, count=%d",
4065                              the_class->external_name(),
4066                              java_lang_Class::classRedefinedCount(the_class->java_mirror()));
4067 
4068   }
4069   _timer_rsc_phase2.stop();
4070 } // end redefine_single_class()
4071 
4072 
4073 // Increment the classRedefinedCount field in the specific InstanceKlass
4074 // and in all direct and indirect subclasses.
4075 void VM_RedefineClasses::increment_class_counter(InstanceKlass *ik, TRAPS) {
4076   oop class_mirror = ik->java_mirror();
4077   Klass* class_oop = java_lang_Class::as_Klass(class_mirror);
4078   int new_count = java_lang_Class::classRedefinedCount(class_mirror) + 1;
4079   java_lang_Class::set_classRedefinedCount(class_mirror, new_count);
4080 
4081   if (class_oop != _the_class) {
4082     // _the_class count is printed at end of redefine_single_class()
4083     log_debug(redefine, class, subclass)("updated count in subclass=%s to %d", ik->external_name(), new_count);
4084   }
4085 
4086   for (Klass *subk = ik->subklass(); subk != NULL;
4087        subk = subk->next_sibling()) {
4088     if (subk->is_instance_klass()) {
4089       // Only update instanceKlasses
4090       InstanceKlass *subik = InstanceKlass::cast(subk);
4091       // recursively do subclasses of the current subclass
4092       increment_class_counter(subik, THREAD);
4093     }
4094   }
4095 }
4096 
4097 void VM_RedefineClasses::CheckClass::do_klass(Klass* k) {
4098   bool no_old_methods = true;  // be optimistic
4099 
4100   // Both array and instance classes have vtables.
4101   // a vtable should never contain old or obsolete methods
4102   ResourceMark rm(_thread);
4103   if (k->vtable_length() > 0 &&
4104       !k->vtable().check_no_old_or_obsolete_entries()) {
4105     if (log_is_enabled(Trace, redefine, class, obsolete, metadata)) {
4106       log_trace(redefine, class, obsolete, metadata)
4107         ("klassVtable::check_no_old_or_obsolete_entries failure -- OLD or OBSOLETE method found -- class: %s",
4108          k->signature_name());
4109       k->vtable().dump_vtable();
4110     }
4111     no_old_methods = false;
4112   }
4113 
4114   if (k->is_instance_klass()) {
4115     HandleMark hm(_thread);
4116     InstanceKlass *ik = InstanceKlass::cast(k);
4117 
4118     // an itable should never contain old or obsolete methods
4119     if (ik->itable_length() > 0 &&
4120         !ik->itable().check_no_old_or_obsolete_entries()) {
4121       if (log_is_enabled(Trace, redefine, class, obsolete, metadata)) {
4122         log_trace(redefine, class, obsolete, metadata)
4123           ("klassItable::check_no_old_or_obsolete_entries failure -- OLD or OBSOLETE method found -- class: %s",
4124            ik->signature_name());
4125         ik->itable().dump_itable();
4126       }
4127       no_old_methods = false;
4128     }
4129 
4130     // the constant pool cache should never contain non-deleted old or obsolete methods
4131     if (ik->constants() != NULL &&
4132         ik->constants()->cache() != NULL &&
4133         !ik->constants()->cache()->check_no_old_or_obsolete_entries()) {
4134       if (log_is_enabled(Trace, redefine, class, obsolete, metadata)) {
4135         log_trace(redefine, class, obsolete, metadata)
4136           ("cp-cache::check_no_old_or_obsolete_entries failure -- OLD or OBSOLETE method found -- class: %s",
4137            ik->signature_name());
4138         ik->constants()->cache()->dump_cache();
4139       }
4140       no_old_methods = false;
4141     }
4142   }
4143 
4144   // print and fail guarantee if old methods are found.
4145   if (!no_old_methods) {
4146     if (log_is_enabled(Trace, redefine, class, obsolete, metadata)) {
4147       dump_methods();
4148     } else {
4149       log_trace(redefine, class)("Use the '-Xlog:redefine+class*:' option "
4150         "to see more info about the following guarantee() failure.");
4151     }
4152     guarantee(false, "OLD and/or OBSOLETE method(s) found");
4153   }
4154 }
4155 
4156 
4157 void VM_RedefineClasses::dump_methods() {
4158   int j;
4159   log_trace(redefine, class, dump)("_old_methods --");
4160   for (j = 0; j < _old_methods->length(); ++j) {
4161     LogStreamHandle(Trace, redefine, class, dump) log_stream;
4162     Method* m = _old_methods->at(j);
4163     log_stream.print("%4d  (%5d)  ", j, m->vtable_index());
4164     m->access_flags().print_on(&log_stream);
4165     log_stream.print(" --  ");
4166     m->print_name(&log_stream);
4167     log_stream.cr();
4168   }
4169   log_trace(redefine, class, dump)("_new_methods --");
4170   for (j = 0; j < _new_methods->length(); ++j) {
4171     LogStreamHandle(Trace, redefine, class, dump) log_stream;
4172     Method* m = _new_methods->at(j);
4173     log_stream.print("%4d  (%5d)  ", j, m->vtable_index());
4174     m->access_flags().print_on(&log_stream);
4175     log_stream.print(" --  ");
4176     m->print_name(&log_stream);
4177     log_stream.cr();
4178   }
4179   log_trace(redefine, class, dump)("_matching_methods --");
4180   for (j = 0; j < _matching_methods_length; ++j) {
4181     LogStreamHandle(Trace, redefine, class, dump) log_stream;
4182     Method* m = _matching_old_methods[j];
4183     log_stream.print("%4d  (%5d)  ", j, m->vtable_index());
4184     m->access_flags().print_on(&log_stream);
4185     log_stream.print(" --  ");
4186     m->print_name();
4187     log_stream.cr();
4188 
4189     m = _matching_new_methods[j];
4190     log_stream.print("      (%5d)  ", m->vtable_index());
4191     m->access_flags().print_on(&log_stream);
4192     log_stream.cr();
4193   }
4194   log_trace(redefine, class, dump)("_deleted_methods --");
4195   for (j = 0; j < _deleted_methods_length; ++j) {
4196     LogStreamHandle(Trace, redefine, class, dump) log_stream;
4197     Method* m = _deleted_methods[j];
4198     log_stream.print("%4d  (%5d)  ", j, m->vtable_index());
4199     m->access_flags().print_on(&log_stream);
4200     log_stream.print(" --  ");
4201     m->print_name(&log_stream);
4202     log_stream.cr();
4203   }
4204   log_trace(redefine, class, dump)("_added_methods --");
4205   for (j = 0; j < _added_methods_length; ++j) {
4206     LogStreamHandle(Trace, redefine, class, dump) log_stream;
4207     Method* m = _added_methods[j];
4208     log_stream.print("%4d  (%5d)  ", j, m->vtable_index());
4209     m->access_flags().print_on(&log_stream);
4210     log_stream.print(" --  ");
4211     m->print_name(&log_stream);
4212     log_stream.cr();
4213   }
4214 }
4215 
4216 void VM_RedefineClasses::print_on_error(outputStream* st) const {
4217   VM_Operation::print_on_error(st);
4218   if (_the_class != NULL) {
4219     ResourceMark rm;
4220     st->print_cr(", redefining class %s", _the_class->external_name());
4221   }
4222 }