1 /*
   2  * Copyright (c) 2003, 2019, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "aot/aotLoader.hpp"
  27 #include "classfile/classLoaderDataGraph.hpp"
  28 #include "classfile/classFileStream.hpp"
  29 #include "classfile/javaClasses.inline.hpp"
  30 #include "classfile/metadataOnStackMark.hpp"
  31 #include "classfile/symbolTable.hpp"
  32 #include "classfile/systemDictionary.hpp"
  33 #include "classfile/verifier.hpp"
  34 #include "code/codeCache.hpp"
  35 #include "compiler/compileBroker.hpp"
  36 #include "interpreter/oopMapCache.hpp"
  37 #include "interpreter/rewriter.hpp"
  38 #include "logging/logStream.hpp"
  39 #include "memory/metadataFactory.hpp"
  40 #include "memory/metaspaceShared.hpp"
  41 #include "memory/resourceArea.hpp"
  42 #include "memory/universe.hpp"
  43 #include "oops/constantPool.hpp"
  44 #include "oops/fieldStreams.hpp"
  45 #include "oops/klassVtable.hpp"
  46 #include "oops/oop.inline.hpp"
  47 #include "prims/jvmtiImpl.hpp"
  48 #include "prims/jvmtiRedefineClasses.hpp"
  49 #include "prims/jvmtiThreadState.inline.hpp"
  50 #include "prims/resolvedMethodTable.hpp"
  51 #include "prims/methodComparator.hpp"
  52 #include "runtime/deoptimization.hpp"
  53 #include "runtime/handles.inline.hpp"
  54 #include "runtime/jniHandles.inline.hpp"
  55 #include "runtime/relocator.hpp"
  56 #include "runtime/safepointVerifiers.hpp"
  57 #include "utilities/bitMap.inline.hpp"
  58 #include "utilities/events.hpp"
  59 
  60 Array<Method*>* VM_RedefineClasses::_old_methods = NULL;
  61 Array<Method*>* VM_RedefineClasses::_new_methods = NULL;
  62 Method**  VM_RedefineClasses::_matching_old_methods = NULL;
  63 Method**  VM_RedefineClasses::_matching_new_methods = NULL;
  64 Method**  VM_RedefineClasses::_deleted_methods      = NULL;
  65 Method**  VM_RedefineClasses::_added_methods        = NULL;
  66 int       VM_RedefineClasses::_matching_methods_length = 0;
  67 int       VM_RedefineClasses::_deleted_methods_length  = 0;
  68 int       VM_RedefineClasses::_added_methods_length    = 0;
  69 bool      VM_RedefineClasses::_has_redefined_Object = false;
  70 bool      VM_RedefineClasses::_has_null_class_loader = false;
  71 
  72 
  73 VM_RedefineClasses::VM_RedefineClasses(jint class_count,
  74                                        const jvmtiClassDefinition *class_defs,
  75                                        JvmtiClassLoadKind class_load_kind) {
  76   _class_count = class_count;
  77   _class_defs = class_defs;
  78   _class_load_kind = class_load_kind;
  79   _any_class_has_resolved_methods = false;
  80   _res = JVMTI_ERROR_NONE;
  81   _the_class = NULL;
  82   _has_redefined_Object = false;
  83   _has_null_class_loader = false;
  84 }
  85 
  86 static inline InstanceKlass* get_ik(jclass def) {
  87   oop mirror = JNIHandles::resolve_non_null(def);
  88   return InstanceKlass::cast(java_lang_Class::as_Klass(mirror));
  89 }
  90 
  91 // If any of the classes are being redefined, wait
  92 // Parallel constant pool merging leads to indeterminate constant pools.
  93 void VM_RedefineClasses::lock_classes() {
  94   MonitorLocker ml(RedefineClasses_lock);
  95   bool has_redefined;
  96   do {
  97     has_redefined = false;
  98     // Go through classes each time until none are being redefined.
  99     for (int i = 0; i < _class_count; i++) {
 100       if (get_ik(_class_defs[i].klass)->is_being_redefined()) {
 101         ml.wait();
 102         has_redefined = true;
 103         break;  // for loop
 104       }
 105     }
 106   } while (has_redefined);
 107   for (int i = 0; i < _class_count; i++) {
 108     get_ik(_class_defs[i].klass)->set_is_being_redefined(true);
 109   }
 110   ml.notify_all();
 111 }
 112 
 113 void VM_RedefineClasses::unlock_classes() {
 114   MonitorLocker ml(RedefineClasses_lock);
 115   for (int i = 0; i < _class_count; i++) {
 116     assert(get_ik(_class_defs[i].klass)->is_being_redefined(),
 117            "should be being redefined to get here");
 118     get_ik(_class_defs[i].klass)->set_is_being_redefined(false);
 119   }
 120   ml.notify_all();
 121 }
 122 
 123 bool VM_RedefineClasses::doit_prologue() {
 124   if (_class_count == 0) {
 125     _res = JVMTI_ERROR_NONE;
 126     return false;
 127   }
 128   if (_class_defs == NULL) {
 129     _res = JVMTI_ERROR_NULL_POINTER;
 130     return false;
 131   }
 132 
 133   for (int i = 0; i < _class_count; i++) {
 134     if (_class_defs[i].klass == NULL) {
 135       _res = JVMTI_ERROR_INVALID_CLASS;
 136       return false;
 137     }
 138     if (_class_defs[i].class_byte_count == 0) {
 139       _res = JVMTI_ERROR_INVALID_CLASS_FORMAT;
 140       return false;
 141     }
 142     if (_class_defs[i].class_bytes == NULL) {
 143       _res = JVMTI_ERROR_NULL_POINTER;
 144       return false;
 145     }
 146 
 147     oop mirror = JNIHandles::resolve_non_null(_class_defs[i].klass);
 148     // classes for primitives and arrays and vm unsafe anonymous classes cannot be redefined
 149     // check here so following code can assume these classes are InstanceKlass
 150     if (!is_modifiable_class(mirror)) {
 151       _res = JVMTI_ERROR_UNMODIFIABLE_CLASS;
 152       return false;
 153     }
 154   }
 155 
 156   // Start timer after all the sanity checks; not quite accurate, but
 157   // better than adding a bunch of stop() calls.
 158   if (log_is_enabled(Info, redefine, class, timer)) {
 159     _timer_vm_op_prologue.start();
 160   }
 161 
 162   lock_classes();
 163   // We first load new class versions in the prologue, because somewhere down the
 164   // call chain it is required that the current thread is a Java thread.
 165   _res = load_new_class_versions(Thread::current());
 166   if (_res != JVMTI_ERROR_NONE) {
 167     // free any successfully created classes, since none are redefined
 168     for (int i = 0; i < _class_count; i++) {
 169       if (_scratch_classes[i] != NULL) {
 170         ClassLoaderData* cld = _scratch_classes[i]->class_loader_data();
 171         // Free the memory for this class at class unloading time.  Not before
 172         // because CMS might think this is still live.
 173         InstanceKlass* ik = get_ik(_class_defs[i].klass);
 174         if (ik->get_cached_class_file() == _scratch_classes[i]->get_cached_class_file()) {
 175           // Don't double-free cached_class_file copied from the original class if error.
 176           _scratch_classes[i]->set_cached_class_file(NULL);
 177         }
 178         cld->add_to_deallocate_list(InstanceKlass::cast(_scratch_classes[i]));
 179       }
 180     }
 181     // Free os::malloc allocated memory in load_new_class_version.
 182     os::free(_scratch_classes);
 183     _timer_vm_op_prologue.stop();
 184     unlock_classes();
 185     return false;
 186   }
 187 
 188   _timer_vm_op_prologue.stop();
 189   return true;
 190 }
 191 
 192 void VM_RedefineClasses::doit() {
 193   Thread *thread = Thread::current();
 194 
 195 #if INCLUDE_CDS
 196   if (UseSharedSpaces) {
 197     // Sharing is enabled so we remap the shared readonly space to
 198     // shared readwrite, private just in case we need to redefine
 199     // a shared class. We do the remap during the doit() phase of
 200     // the safepoint to be safer.
 201     if (!MetaspaceShared::remap_shared_readonly_as_readwrite()) {
 202       log_info(redefine, class, load)("failed to remap shared readonly space to readwrite, private");
 203       _res = JVMTI_ERROR_INTERNAL;
 204       return;
 205     }
 206   }
 207 #endif
 208 
 209   // Mark methods seen on stack and everywhere else so old methods are not
 210   // cleaned up if they're on the stack.
 211   MetadataOnStackMark md_on_stack(/*walk_all_metadata*/true, /*redefinition_walk*/true);
 212   HandleMark hm(thread);   // make sure any handles created are deleted
 213                            // before the stack walk again.
 214 
 215   for (int i = 0; i < _class_count; i++) {
 216     redefine_single_class(_class_defs[i].klass, _scratch_classes[i], thread);
 217   }
 218 
 219   // Flush all compiled code that depends on the classes redefined.
 220   flush_dependent_code();
 221 
 222   // Adjust constantpool caches and vtables for all classes
 223   // that reference methods of the evolved classes.
 224   // Have to do this after all classes are redefined and all methods that
 225   // are redefined are marked as old.
 226   AdjustAndCleanMetadata adjust_and_clean_metadata(thread);
 227   ClassLoaderDataGraph::classes_do(&adjust_and_clean_metadata);
 228 
 229   // JSR-292 support
 230   if (_any_class_has_resolved_methods) {
 231     bool trace_name_printed = false;
 232     ResolvedMethodTable::adjust_method_entries(&trace_name_printed);
 233   }
 234 
 235   // Set flag indicating that some invariants are no longer true.
 236   // See jvmtiExport.hpp for detailed explanation.
 237   JvmtiExport::set_has_redefined_a_class();
 238 
 239   // check_class() is optionally called for product bits, but is
 240   // always called for non-product bits.
 241 #ifdef PRODUCT
 242   if (log_is_enabled(Trace, redefine, class, obsolete, metadata)) {
 243 #endif
 244     log_trace(redefine, class, obsolete, metadata)("calling check_class");
 245     CheckClass check_class(thread);
 246     ClassLoaderDataGraph::classes_do(&check_class);
 247 #ifdef PRODUCT
 248   }
 249 #endif
 250 
 251   // Clean up any metadata now unreferenced while MetadataOnStackMark is set.
 252   ClassLoaderDataGraph::clean_deallocate_lists(false);
 253 }
 254 
 255 void VM_RedefineClasses::doit_epilogue() {
 256   unlock_classes();
 257 
 258   // Free os::malloc allocated memory.
 259   os::free(_scratch_classes);
 260 
 261   // Reset the_class to null for error printing.
 262   _the_class = NULL;
 263 
 264   if (log_is_enabled(Info, redefine, class, timer)) {
 265     // Used to have separate timers for "doit" and "all", but the timer
 266     // overhead skewed the measurements.
 267     julong doit_time = _timer_rsc_phase1.milliseconds() +
 268                        _timer_rsc_phase2.milliseconds();
 269     julong all_time = _timer_vm_op_prologue.milliseconds() + doit_time;
 270 
 271     log_info(redefine, class, timer)
 272       ("vm_op: all=" JULONG_FORMAT "  prologue=" JULONG_FORMAT "  doit=" JULONG_FORMAT,
 273        all_time, (julong)_timer_vm_op_prologue.milliseconds(), doit_time);
 274     log_info(redefine, class, timer)
 275       ("redefine_single_class: phase1=" JULONG_FORMAT "  phase2=" JULONG_FORMAT,
 276        (julong)_timer_rsc_phase1.milliseconds(), (julong)_timer_rsc_phase2.milliseconds());
 277   }
 278 }
 279 
 280 bool VM_RedefineClasses::is_modifiable_class(oop klass_mirror) {
 281   // classes for primitives cannot be redefined
 282   if (java_lang_Class::is_primitive(klass_mirror)) {
 283     return false;
 284   }
 285   Klass* k = java_lang_Class::as_Klass(klass_mirror);
 286   // classes for arrays cannot be redefined
 287   if (k == NULL || !k->is_instance_klass()) {
 288     return false;
 289   }
 290 
 291   // Cannot redefine or retransform an unsafe anonymous class.
 292   if (InstanceKlass::cast(k)->is_unsafe_anonymous()) {
 293     return false;
 294   }
 295   return true;
 296 }
 297 
 298 // Append the current entry at scratch_i in scratch_cp to *merge_cp_p
 299 // where the end of *merge_cp_p is specified by *merge_cp_length_p. For
 300 // direct CP entries, there is just the current entry to append. For
 301 // indirect and double-indirect CP entries, there are zero or more
 302 // referenced CP entries along with the current entry to append.
 303 // Indirect and double-indirect CP entries are handled by recursive
 304 // calls to append_entry() as needed. The referenced CP entries are
 305 // always appended to *merge_cp_p before the referee CP entry. These
 306 // referenced CP entries may already exist in *merge_cp_p in which case
 307 // there is nothing extra to append and only the current entry is
 308 // appended.
 309 void VM_RedefineClasses::append_entry(const constantPoolHandle& scratch_cp,
 310        int scratch_i, constantPoolHandle *merge_cp_p, int *merge_cp_length_p,
 311        TRAPS) {
 312 
 313   // append is different depending on entry tag type
 314   switch (scratch_cp->tag_at(scratch_i).value()) {
 315 
 316     // The old verifier is implemented outside the VM. It loads classes,
 317     // but does not resolve constant pool entries directly so we never
 318     // see Class entries here with the old verifier. Similarly the old
 319     // verifier does not like Class entries in the input constant pool.
 320     // The split-verifier is implemented in the VM so it can optionally
 321     // and directly resolve constant pool entries to load classes. The
 322     // split-verifier can accept either Class entries or UnresolvedClass
 323     // entries in the input constant pool. We revert the appended copy
 324     // back to UnresolvedClass so that either verifier will be happy
 325     // with the constant pool entry.
 326     //
 327     // this is an indirect CP entry so it needs special handling
 328     case JVM_CONSTANT_Class:
 329     case JVM_CONSTANT_UnresolvedClass:
 330     {
 331       int name_i = scratch_cp->klass_name_index_at(scratch_i);
 332       int new_name_i = find_or_append_indirect_entry(scratch_cp, name_i, merge_cp_p,
 333                                                      merge_cp_length_p, THREAD);
 334 
 335       if (new_name_i != name_i) {
 336         log_trace(redefine, class, constantpool)
 337           ("Class entry@%d name_index change: %d to %d",
 338            *merge_cp_length_p, name_i, new_name_i);
 339       }
 340 
 341       (*merge_cp_p)->temp_unresolved_klass_at_put(*merge_cp_length_p, new_name_i);
 342       if (scratch_i != *merge_cp_length_p) {
 343         // The new entry in *merge_cp_p is at a different index than
 344         // the new entry in scratch_cp so we need to map the index values.
 345         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 346       }
 347       (*merge_cp_length_p)++;
 348     } break;
 349 
 350     // these are direct CP entries so they can be directly appended,
 351     // but double and long take two constant pool entries
 352     case JVM_CONSTANT_Double:  // fall through
 353     case JVM_CONSTANT_Long:
 354     {
 355       ConstantPool::copy_entry_to(scratch_cp, scratch_i, *merge_cp_p, *merge_cp_length_p,
 356         THREAD);
 357 
 358       if (scratch_i != *merge_cp_length_p) {
 359         // The new entry in *merge_cp_p is at a different index than
 360         // the new entry in scratch_cp so we need to map the index values.
 361         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 362       }
 363       (*merge_cp_length_p) += 2;
 364     } break;
 365 
 366     // these are direct CP entries so they can be directly appended
 367     case JVM_CONSTANT_Float:   // fall through
 368     case JVM_CONSTANT_Integer: // fall through
 369     case JVM_CONSTANT_Utf8:    // fall through
 370 
 371     // This was an indirect CP entry, but it has been changed into
 372     // Symbol*s so this entry can be directly appended.
 373     case JVM_CONSTANT_String:      // fall through
 374     {
 375       ConstantPool::copy_entry_to(scratch_cp, scratch_i, *merge_cp_p, *merge_cp_length_p,
 376         THREAD);
 377 
 378       if (scratch_i != *merge_cp_length_p) {
 379         // The new entry in *merge_cp_p is at a different index than
 380         // the new entry in scratch_cp so we need to map the index values.
 381         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 382       }
 383       (*merge_cp_length_p)++;
 384     } break;
 385 
 386     // this is an indirect CP entry so it needs special handling
 387     case JVM_CONSTANT_NameAndType:
 388     {
 389       int name_ref_i = scratch_cp->name_ref_index_at(scratch_i);
 390       int new_name_ref_i = find_or_append_indirect_entry(scratch_cp, name_ref_i, merge_cp_p,
 391                                                          merge_cp_length_p, THREAD);
 392 
 393       int signature_ref_i = scratch_cp->signature_ref_index_at(scratch_i);
 394       int new_signature_ref_i = find_or_append_indirect_entry(scratch_cp, signature_ref_i,
 395                                                               merge_cp_p, merge_cp_length_p,
 396                                                               THREAD);
 397 
 398       // If the referenced entries already exist in *merge_cp_p, then
 399       // both new_name_ref_i and new_signature_ref_i will both be 0.
 400       // In that case, all we are appending is the current entry.
 401       if (new_name_ref_i != name_ref_i) {
 402         log_trace(redefine, class, constantpool)
 403           ("NameAndType entry@%d name_ref_index change: %d to %d",
 404            *merge_cp_length_p, name_ref_i, new_name_ref_i);
 405       }
 406       if (new_signature_ref_i != signature_ref_i) {
 407         log_trace(redefine, class, constantpool)
 408           ("NameAndType entry@%d signature_ref_index change: %d to %d",
 409            *merge_cp_length_p, signature_ref_i, new_signature_ref_i);
 410       }
 411 
 412       (*merge_cp_p)->name_and_type_at_put(*merge_cp_length_p,
 413         new_name_ref_i, new_signature_ref_i);
 414       if (scratch_i != *merge_cp_length_p) {
 415         // The new entry in *merge_cp_p is at a different index than
 416         // the new entry in scratch_cp so we need to map the index values.
 417         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 418       }
 419       (*merge_cp_length_p)++;
 420     } break;
 421 
 422     // this is a double-indirect CP entry so it needs special handling
 423     case JVM_CONSTANT_Fieldref:           // fall through
 424     case JVM_CONSTANT_InterfaceMethodref: // fall through
 425     case JVM_CONSTANT_Methodref:
 426     {
 427       int klass_ref_i = scratch_cp->uncached_klass_ref_index_at(scratch_i);
 428       int new_klass_ref_i = find_or_append_indirect_entry(scratch_cp, klass_ref_i,
 429                                                           merge_cp_p, merge_cp_length_p, THREAD);
 430 
 431       int name_and_type_ref_i = scratch_cp->uncached_name_and_type_ref_index_at(scratch_i);
 432       int new_name_and_type_ref_i = find_or_append_indirect_entry(scratch_cp, name_and_type_ref_i,
 433                                                           merge_cp_p, merge_cp_length_p, THREAD);
 434 
 435       const char *entry_name = NULL;
 436       switch (scratch_cp->tag_at(scratch_i).value()) {
 437       case JVM_CONSTANT_Fieldref:
 438         entry_name = "Fieldref";
 439         (*merge_cp_p)->field_at_put(*merge_cp_length_p, new_klass_ref_i,
 440           new_name_and_type_ref_i);
 441         break;
 442       case JVM_CONSTANT_InterfaceMethodref:
 443         entry_name = "IFMethodref";
 444         (*merge_cp_p)->interface_method_at_put(*merge_cp_length_p,
 445           new_klass_ref_i, new_name_and_type_ref_i);
 446         break;
 447       case JVM_CONSTANT_Methodref:
 448         entry_name = "Methodref";
 449         (*merge_cp_p)->method_at_put(*merge_cp_length_p, new_klass_ref_i,
 450           new_name_and_type_ref_i);
 451         break;
 452       default:
 453         guarantee(false, "bad switch");
 454         break;
 455       }
 456 
 457       if (klass_ref_i != new_klass_ref_i) {
 458         log_trace(redefine, class, constantpool)
 459           ("%s entry@%d class_index changed: %d to %d", entry_name, *merge_cp_length_p, klass_ref_i, new_klass_ref_i);
 460       }
 461       if (name_and_type_ref_i != new_name_and_type_ref_i) {
 462         log_trace(redefine, class, constantpool)
 463           ("%s entry@%d name_and_type_index changed: %d to %d",
 464            entry_name, *merge_cp_length_p, name_and_type_ref_i, new_name_and_type_ref_i);
 465       }
 466 
 467       if (scratch_i != *merge_cp_length_p) {
 468         // The new entry in *merge_cp_p is at a different index than
 469         // the new entry in scratch_cp so we need to map the index values.
 470         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 471       }
 472       (*merge_cp_length_p)++;
 473     } break;
 474 
 475     // this is an indirect CP entry so it needs special handling
 476     case JVM_CONSTANT_MethodType:
 477     {
 478       int ref_i = scratch_cp->method_type_index_at(scratch_i);
 479       int new_ref_i = find_or_append_indirect_entry(scratch_cp, ref_i, merge_cp_p,
 480                                                     merge_cp_length_p, THREAD);
 481       if (new_ref_i != ref_i) {
 482         log_trace(redefine, class, constantpool)
 483           ("MethodType entry@%d ref_index change: %d to %d", *merge_cp_length_p, ref_i, new_ref_i);
 484       }
 485       (*merge_cp_p)->method_type_index_at_put(*merge_cp_length_p, new_ref_i);
 486       if (scratch_i != *merge_cp_length_p) {
 487         // The new entry in *merge_cp_p is at a different index than
 488         // the new entry in scratch_cp so we need to map the index values.
 489         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 490       }
 491       (*merge_cp_length_p)++;
 492     } break;
 493 
 494     // this is an indirect CP entry so it needs special handling
 495     case JVM_CONSTANT_MethodHandle:
 496     {
 497       int ref_kind = scratch_cp->method_handle_ref_kind_at(scratch_i);
 498       int ref_i = scratch_cp->method_handle_index_at(scratch_i);
 499       int new_ref_i = find_or_append_indirect_entry(scratch_cp, ref_i, merge_cp_p,
 500                                                     merge_cp_length_p, THREAD);
 501       if (new_ref_i != ref_i) {
 502         log_trace(redefine, class, constantpool)
 503           ("MethodHandle entry@%d ref_index change: %d to %d", *merge_cp_length_p, ref_i, new_ref_i);
 504       }
 505       (*merge_cp_p)->method_handle_index_at_put(*merge_cp_length_p, ref_kind, new_ref_i);
 506       if (scratch_i != *merge_cp_length_p) {
 507         // The new entry in *merge_cp_p is at a different index than
 508         // the new entry in scratch_cp so we need to map the index values.
 509         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 510       }
 511       (*merge_cp_length_p)++;
 512     } break;
 513 
 514     // this is an indirect CP entry so it needs special handling
 515     case JVM_CONSTANT_Dynamic:  // fall through
 516     case JVM_CONSTANT_InvokeDynamic:
 517     {
 518       // Index of the bootstrap specifier in the operands array
 519       int old_bs_i = scratch_cp->bootstrap_methods_attribute_index(scratch_i);
 520       int new_bs_i = find_or_append_operand(scratch_cp, old_bs_i, merge_cp_p,
 521                                             merge_cp_length_p, THREAD);
 522       // The bootstrap method NameAndType_info index
 523       int old_ref_i = scratch_cp->bootstrap_name_and_type_ref_index_at(scratch_i);
 524       int new_ref_i = find_or_append_indirect_entry(scratch_cp, old_ref_i, merge_cp_p,
 525                                                     merge_cp_length_p, THREAD);
 526       if (new_bs_i != old_bs_i) {
 527         log_trace(redefine, class, constantpool)
 528           ("Dynamic entry@%d bootstrap_method_attr_index change: %d to %d",
 529            *merge_cp_length_p, old_bs_i, new_bs_i);
 530       }
 531       if (new_ref_i != old_ref_i) {
 532         log_trace(redefine, class, constantpool)
 533           ("Dynamic entry@%d name_and_type_index change: %d to %d", *merge_cp_length_p, old_ref_i, new_ref_i);
 534       }
 535 
 536       if (scratch_cp->tag_at(scratch_i).is_dynamic_constant())
 537         (*merge_cp_p)->dynamic_constant_at_put(*merge_cp_length_p, new_bs_i, new_ref_i);
 538       else
 539         (*merge_cp_p)->invoke_dynamic_at_put(*merge_cp_length_p, new_bs_i, new_ref_i);
 540       if (scratch_i != *merge_cp_length_p) {
 541         // The new entry in *merge_cp_p is at a different index than
 542         // the new entry in scratch_cp so we need to map the index values.
 543         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 544       }
 545       (*merge_cp_length_p)++;
 546     } break;
 547 
 548     // At this stage, Class or UnresolvedClass could be in scratch_cp, but not
 549     // ClassIndex
 550     case JVM_CONSTANT_ClassIndex: // fall through
 551 
 552     // Invalid is used as the tag for the second constant pool entry
 553     // occupied by JVM_CONSTANT_Double or JVM_CONSTANT_Long. It should
 554     // not be seen by itself.
 555     case JVM_CONSTANT_Invalid: // fall through
 556 
 557     // At this stage, String could be here, but not StringIndex
 558     case JVM_CONSTANT_StringIndex: // fall through
 559 
 560     // At this stage JVM_CONSTANT_UnresolvedClassInError should not be
 561     // here
 562     case JVM_CONSTANT_UnresolvedClassInError: // fall through
 563 
 564     default:
 565     {
 566       // leave a breadcrumb
 567       jbyte bad_value = scratch_cp->tag_at(scratch_i).value();
 568       ShouldNotReachHere();
 569     } break;
 570   } // end switch tag value
 571 } // end append_entry()
 572 
 573 
 574 int VM_RedefineClasses::find_or_append_indirect_entry(const constantPoolHandle& scratch_cp,
 575       int ref_i, constantPoolHandle *merge_cp_p, int *merge_cp_length_p, TRAPS) {
 576 
 577   int new_ref_i = ref_i;
 578   bool match = (ref_i < *merge_cp_length_p) &&
 579                scratch_cp->compare_entry_to(ref_i, *merge_cp_p, ref_i, THREAD);
 580 
 581   if (!match) {
 582     // forward reference in *merge_cp_p or not a direct match
 583     int found_i = scratch_cp->find_matching_entry(ref_i, *merge_cp_p, THREAD);
 584     if (found_i != 0) {
 585       guarantee(found_i != ref_i, "compare_entry_to() and find_matching_entry() do not agree");
 586       // Found a matching entry somewhere else in *merge_cp_p so just need a mapping entry.
 587       new_ref_i = found_i;
 588       map_index(scratch_cp, ref_i, found_i);
 589     } else {
 590       // no match found so we have to append this entry to *merge_cp_p
 591       append_entry(scratch_cp, ref_i, merge_cp_p, merge_cp_length_p, THREAD);
 592       // The above call to append_entry() can only append one entry
 593       // so the post call query of *merge_cp_length_p is only for
 594       // the sake of consistency.
 595       new_ref_i = *merge_cp_length_p - 1;
 596     }
 597   }
 598 
 599   return new_ref_i;
 600 } // end find_or_append_indirect_entry()
 601 
 602 
 603 // Append a bootstrap specifier into the merge_cp operands that is semantically equal
 604 // to the scratch_cp operands bootstrap specifier passed by the old_bs_i index.
 605 // Recursively append new merge_cp entries referenced by the new bootstrap specifier.
 606 void VM_RedefineClasses::append_operand(const constantPoolHandle& scratch_cp, int old_bs_i,
 607        constantPoolHandle *merge_cp_p, int *merge_cp_length_p, TRAPS) {
 608 
 609   int old_ref_i = scratch_cp->operand_bootstrap_method_ref_index_at(old_bs_i);
 610   int new_ref_i = find_or_append_indirect_entry(scratch_cp, old_ref_i, merge_cp_p,
 611                                                 merge_cp_length_p, THREAD);
 612   if (new_ref_i != old_ref_i) {
 613     log_trace(redefine, class, constantpool)
 614       ("operands entry@%d bootstrap method ref_index change: %d to %d", _operands_cur_length, old_ref_i, new_ref_i);
 615   }
 616 
 617   Array<u2>* merge_ops = (*merge_cp_p)->operands();
 618   int new_bs_i = _operands_cur_length;
 619   // We have _operands_cur_length == 0 when the merge_cp operands is empty yet.
 620   // However, the operand_offset_at(0) was set in the extend_operands() call.
 621   int new_base = (new_bs_i == 0) ? (*merge_cp_p)->operand_offset_at(0)
 622                                  : (*merge_cp_p)->operand_next_offset_at(new_bs_i - 1);
 623   int argc     = scratch_cp->operand_argument_count_at(old_bs_i);
 624 
 625   ConstantPool::operand_offset_at_put(merge_ops, _operands_cur_length, new_base);
 626   merge_ops->at_put(new_base++, new_ref_i);
 627   merge_ops->at_put(new_base++, argc);
 628 
 629   for (int i = 0; i < argc; i++) {
 630     int old_arg_ref_i = scratch_cp->operand_argument_index_at(old_bs_i, i);
 631     int new_arg_ref_i = find_or_append_indirect_entry(scratch_cp, old_arg_ref_i, merge_cp_p,
 632                                                       merge_cp_length_p, THREAD);
 633     merge_ops->at_put(new_base++, new_arg_ref_i);
 634     if (new_arg_ref_i != old_arg_ref_i) {
 635       log_trace(redefine, class, constantpool)
 636         ("operands entry@%d bootstrap method argument ref_index change: %d to %d",
 637          _operands_cur_length, old_arg_ref_i, new_arg_ref_i);
 638     }
 639   }
 640   if (old_bs_i != _operands_cur_length) {
 641     // The bootstrap specifier in *merge_cp_p is at a different index than
 642     // that in scratch_cp so we need to map the index values.
 643     map_operand_index(old_bs_i, new_bs_i);
 644   }
 645   _operands_cur_length++;
 646 } // end append_operand()
 647 
 648 
 649 int VM_RedefineClasses::find_or_append_operand(const constantPoolHandle& scratch_cp,
 650       int old_bs_i, constantPoolHandle *merge_cp_p, int *merge_cp_length_p, TRAPS) {
 651 
 652   int new_bs_i = old_bs_i; // bootstrap specifier index
 653   bool match = (old_bs_i < _operands_cur_length) &&
 654                scratch_cp->compare_operand_to(old_bs_i, *merge_cp_p, old_bs_i, THREAD);
 655 
 656   if (!match) {
 657     // forward reference in *merge_cp_p or not a direct match
 658     int found_i = scratch_cp->find_matching_operand(old_bs_i, *merge_cp_p,
 659                                                     _operands_cur_length, THREAD);
 660     if (found_i != -1) {
 661       guarantee(found_i != old_bs_i, "compare_operand_to() and find_matching_operand() disagree");
 662       // found a matching operand somewhere else in *merge_cp_p so just need a mapping
 663       new_bs_i = found_i;
 664       map_operand_index(old_bs_i, found_i);
 665     } else {
 666       // no match found so we have to append this bootstrap specifier to *merge_cp_p
 667       append_operand(scratch_cp, old_bs_i, merge_cp_p, merge_cp_length_p, THREAD);
 668       new_bs_i = _operands_cur_length - 1;
 669     }
 670   }
 671   return new_bs_i;
 672 } // end find_or_append_operand()
 673 
 674 
 675 void VM_RedefineClasses::finalize_operands_merge(const constantPoolHandle& merge_cp, TRAPS) {
 676   if (merge_cp->operands() == NULL) {
 677     return;
 678   }
 679   // Shrink the merge_cp operands
 680   merge_cp->shrink_operands(_operands_cur_length, CHECK);
 681 
 682   if (log_is_enabled(Trace, redefine, class, constantpool)) {
 683     // don't want to loop unless we are tracing
 684     int count = 0;
 685     for (int i = 1; i < _operands_index_map_p->length(); i++) {
 686       int value = _operands_index_map_p->at(i);
 687       if (value != -1) {
 688         log_trace(redefine, class, constantpool)("operands_index_map[%d]: old=%d new=%d", count, i, value);
 689         count++;
 690       }
 691     }
 692   }
 693   // Clean-up
 694   _operands_index_map_p = NULL;
 695   _operands_cur_length = 0;
 696   _operands_index_map_count = 0;
 697 } // end finalize_operands_merge()
 698 
 699 // Symbol* comparator for qsort
 700 // The caller must have an active ResourceMark.
 701 static int symcmp(const void* a, const void* b) {
 702   char* astr = (*(Symbol**)a)->as_C_string();
 703   char* bstr = (*(Symbol**)b)->as_C_string();
 704   return strcmp(astr, bstr);
 705 }
 706 
 707 static jvmtiError check_nest_attributes(InstanceKlass* the_class,
 708                                         InstanceKlass* scratch_class) {
 709   // Check whether the class NestHost attribute has been changed.
 710   Thread* thread = Thread::current();
 711   ResourceMark rm(thread);
 712   u2 the_nest_host_idx = the_class->nest_host_index();
 713   u2 scr_nest_host_idx = scratch_class->nest_host_index();
 714 
 715   if (the_nest_host_idx != 0 && scr_nest_host_idx != 0) {
 716     Symbol* the_sym = the_class->constants()->klass_name_at(the_nest_host_idx);
 717     Symbol* scr_sym = scratch_class->constants()->klass_name_at(scr_nest_host_idx);
 718     if (the_sym != scr_sym) {
 719       log_trace(redefine, class, nestmates)
 720         ("redefined class %s attribute change error: NestHost class: %s replaced with: %s",
 721          the_class->external_name(), the_sym->as_C_string(), scr_sym->as_C_string());
 722       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
 723     }
 724   } else if ((the_nest_host_idx == 0) ^ (scr_nest_host_idx == 0)) {
 725     const char* action_str = (the_nest_host_idx != 0) ? "removed" : "added";
 726     log_trace(redefine, class, nestmates)
 727       ("redefined class %s attribute change error: NestHost attribute %s",
 728        the_class->external_name(), action_str);
 729     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
 730   }
 731 
 732   // Check whether the class NestMembers attribute has been changed.
 733   Array<u2>* the_nest_members = the_class->nest_members();
 734   Array<u2>* scr_nest_members = scratch_class->nest_members();
 735   bool the_members_exists = the_nest_members != Universe::the_empty_short_array();
 736   bool scr_members_exists = scr_nest_members != Universe::the_empty_short_array();
 737 
 738   int members_len = the_nest_members->length();
 739   if (the_members_exists && scr_members_exists) {
 740     if (members_len != scr_nest_members->length()) {
 741       log_trace(redefine, class, nestmates)
 742         ("redefined class %s attribute change error: NestMember len=%d changed to len=%d",
 743          the_class->external_name(), members_len, scr_nest_members->length());
 744       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
 745     }
 746 
 747     // The order of entries in the NestMembers array is not specified so we
 748     // have to explicitly check for the same contents. We do this by copying
 749     // the referenced symbols into their own arrays, sorting them and then
 750     // comparing each element pair.
 751 
 752     Symbol** the_syms = NEW_RESOURCE_ARRAY_RETURN_NULL(Symbol*, members_len);
 753     Symbol** scr_syms = NEW_RESOURCE_ARRAY_RETURN_NULL(Symbol*, members_len);
 754 
 755     if (the_syms == NULL || scr_syms == NULL) {
 756       return JVMTI_ERROR_OUT_OF_MEMORY;
 757     }
 758 
 759     for (int i = 0; i < members_len; i++) {
 760       int the_cp_index = the_nest_members->at(i);
 761       int scr_cp_index = scr_nest_members->at(i);
 762       the_syms[i] = the_class->constants()->klass_name_at(the_cp_index);
 763       scr_syms[i] = scratch_class->constants()->klass_name_at(scr_cp_index);
 764     }
 765 
 766     qsort(the_syms, members_len, sizeof(Symbol*), symcmp);
 767     qsort(scr_syms, members_len, sizeof(Symbol*), symcmp);
 768 
 769     for (int i = 0; i < members_len; i++) {
 770       if (the_syms[i] != scr_syms[i]) {
 771         log_trace(redefine, class, nestmates)
 772           ("redefined class %s attribute change error: NestMembers[%d]: %s changed to %s",
 773            the_class->external_name(), i, the_syms[i]->as_C_string(), scr_syms[i]->as_C_string());
 774         return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
 775       }
 776     }
 777   } else if (the_members_exists ^ scr_members_exists) {
 778     const char* action_str = (the_members_exists) ? "removed" : "added";
 779     log_trace(redefine, class, nestmates)
 780       ("redefined class %s attribute change error: NestMembers attribute %s",
 781        the_class->external_name(), action_str);
 782     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
 783   }
 784 
 785   return JVMTI_ERROR_NONE;
 786 }
 787 
 788 static bool can_add_or_delete(Method* m) {
 789       // Compatibility mode
 790   return (AllowRedefinitionToAddDeleteMethods &&
 791           (m->is_private() && (m->is_static() || m->is_final())));
 792 }
 793 
 794 jvmtiError VM_RedefineClasses::compare_and_normalize_class_versions(
 795              InstanceKlass* the_class,
 796              InstanceKlass* scratch_class) {
 797   int i;
 798 
 799   // Check superclasses, or rather their names, since superclasses themselves can be
 800   // requested to replace.
 801   // Check for NULL superclass first since this might be java.lang.Object
 802   if (the_class->super() != scratch_class->super() &&
 803       (the_class->super() == NULL || scratch_class->super() == NULL ||
 804        the_class->super()->name() !=
 805        scratch_class->super()->name())) {
 806     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_HIERARCHY_CHANGED;
 807   }
 808 
 809   // Check if the number, names and order of directly implemented interfaces are the same.
 810   // I think in principle we should just check if the sets of names of directly implemented
 811   // interfaces are the same, i.e. the order of declaration (which, however, if changed in the
 812   // .java file, also changes in .class file) should not matter. However, comparing sets is
 813   // technically a bit more difficult, and, more importantly, I am not sure at present that the
 814   // order of interfaces does not matter on the implementation level, i.e. that the VM does not
 815   // rely on it somewhere.
 816   Array<InstanceKlass*>* k_interfaces = the_class->local_interfaces();
 817   Array<InstanceKlass*>* k_new_interfaces = scratch_class->local_interfaces();
 818   int n_intfs = k_interfaces->length();
 819   if (n_intfs != k_new_interfaces->length()) {
 820     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_HIERARCHY_CHANGED;
 821   }
 822   for (i = 0; i < n_intfs; i++) {
 823     if (k_interfaces->at(i)->name() !=
 824         k_new_interfaces->at(i)->name()) {
 825       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_HIERARCHY_CHANGED;
 826     }
 827   }
 828 
 829   // Check whether class is in the error init state.
 830   if (the_class->is_in_error_state()) {
 831     // TBD #5057930: special error code is needed in 1.6
 832     return JVMTI_ERROR_INVALID_CLASS;
 833   }
 834 
 835   // Check whether the nest-related attributes have been changed.
 836   jvmtiError err = check_nest_attributes(the_class, scratch_class);
 837   if (err != JVMTI_ERROR_NONE) {
 838     return err;
 839   }
 840 
 841   // Check whether class modifiers are the same.
 842   jushort old_flags = (jushort) the_class->access_flags().get_flags();
 843   jushort new_flags = (jushort) scratch_class->access_flags().get_flags();
 844   if (old_flags != new_flags) {
 845     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_MODIFIERS_CHANGED;
 846   }
 847 
 848   // Check if the number, names, types and order of fields declared in these classes
 849   // are the same.
 850   JavaFieldStream old_fs(the_class);
 851   JavaFieldStream new_fs(scratch_class);
 852   for (; !old_fs.done() && !new_fs.done(); old_fs.next(), new_fs.next()) {
 853     // access
 854     old_flags = old_fs.access_flags().as_short();
 855     new_flags = new_fs.access_flags().as_short();
 856     if ((old_flags ^ new_flags) & JVM_RECOGNIZED_FIELD_MODIFIERS) {
 857       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_SCHEMA_CHANGED;
 858     }
 859     // offset
 860     if (old_fs.offset() != new_fs.offset()) {
 861       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_SCHEMA_CHANGED;
 862     }
 863     // name and signature
 864     Symbol* name_sym1 = the_class->constants()->symbol_at(old_fs.name_index());
 865     Symbol* sig_sym1 = the_class->constants()->symbol_at(old_fs.signature_index());
 866     Symbol* name_sym2 = scratch_class->constants()->symbol_at(new_fs.name_index());
 867     Symbol* sig_sym2 = scratch_class->constants()->symbol_at(new_fs.signature_index());
 868     if (name_sym1 != name_sym2 || sig_sym1 != sig_sym2) {
 869       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_SCHEMA_CHANGED;
 870     }
 871   }
 872 
 873   // If both streams aren't done then we have a differing number of
 874   // fields.
 875   if (!old_fs.done() || !new_fs.done()) {
 876     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_SCHEMA_CHANGED;
 877   }
 878 
 879   // Do a parallel walk through the old and new methods. Detect
 880   // cases where they match (exist in both), have been added in
 881   // the new methods, or have been deleted (exist only in the
 882   // old methods).  The class file parser places methods in order
 883   // by method name, but does not order overloaded methods by
 884   // signature.  In order to determine what fate befell the methods,
 885   // this code places the overloaded new methods that have matching
 886   // old methods in the same order as the old methods and places
 887   // new overloaded methods at the end of overloaded methods of
 888   // that name. The code for this order normalization is adapted
 889   // from the algorithm used in InstanceKlass::find_method().
 890   // Since we are swapping out of order entries as we find them,
 891   // we only have to search forward through the overloaded methods.
 892   // Methods which are added and have the same name as an existing
 893   // method (but different signature) will be put at the end of
 894   // the methods with that name, and the name mismatch code will
 895   // handle them.
 896   Array<Method*>* k_old_methods(the_class->methods());
 897   Array<Method*>* k_new_methods(scratch_class->methods());
 898   int n_old_methods = k_old_methods->length();
 899   int n_new_methods = k_new_methods->length();
 900   Thread* thread = Thread::current();
 901 
 902   int ni = 0;
 903   int oi = 0;
 904   while (true) {
 905     Method* k_old_method;
 906     Method* k_new_method;
 907     enum { matched, added, deleted, undetermined } method_was = undetermined;
 908 
 909     if (oi >= n_old_methods) {
 910       if (ni >= n_new_methods) {
 911         break; // we've looked at everything, done
 912       }
 913       // New method at the end
 914       k_new_method = k_new_methods->at(ni);
 915       method_was = added;
 916     } else if (ni >= n_new_methods) {
 917       // Old method, at the end, is deleted
 918       k_old_method = k_old_methods->at(oi);
 919       method_was = deleted;
 920     } else {
 921       // There are more methods in both the old and new lists
 922       k_old_method = k_old_methods->at(oi);
 923       k_new_method = k_new_methods->at(ni);
 924       if (k_old_method->name() != k_new_method->name()) {
 925         // Methods are sorted by method name, so a mismatch means added
 926         // or deleted
 927         if (k_old_method->name()->fast_compare(k_new_method->name()) > 0) {
 928           method_was = added;
 929         } else {
 930           method_was = deleted;
 931         }
 932       } else if (k_old_method->signature() == k_new_method->signature()) {
 933         // Both the name and signature match
 934         method_was = matched;
 935       } else {
 936         // The name matches, but the signature doesn't, which means we have to
 937         // search forward through the new overloaded methods.
 938         int nj;  // outside the loop for post-loop check
 939         for (nj = ni + 1; nj < n_new_methods; nj++) {
 940           Method* m = k_new_methods->at(nj);
 941           if (k_old_method->name() != m->name()) {
 942             // reached another method name so no more overloaded methods
 943             method_was = deleted;
 944             break;
 945           }
 946           if (k_old_method->signature() == m->signature()) {
 947             // found a match so swap the methods
 948             k_new_methods->at_put(ni, m);
 949             k_new_methods->at_put(nj, k_new_method);
 950             k_new_method = m;
 951             method_was = matched;
 952             break;
 953           }
 954         }
 955 
 956         if (nj >= n_new_methods) {
 957           // reached the end without a match; so method was deleted
 958           method_was = deleted;
 959         }
 960       }
 961     }
 962 
 963     switch (method_was) {
 964     case matched:
 965       // methods match, be sure modifiers do too
 966       old_flags = (jushort) k_old_method->access_flags().get_flags();
 967       new_flags = (jushort) k_new_method->access_flags().get_flags();
 968       if ((old_flags ^ new_flags) & ~(JVM_ACC_NATIVE)) {
 969         return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_METHOD_MODIFIERS_CHANGED;
 970       }
 971       {
 972         u2 new_num = k_new_method->method_idnum();
 973         u2 old_num = k_old_method->method_idnum();
 974         if (new_num != old_num) {
 975           Method* idnum_owner = scratch_class->method_with_idnum(old_num);
 976           if (idnum_owner != NULL) {
 977             // There is already a method assigned this idnum -- switch them
 978             // Take current and original idnum from the new_method
 979             idnum_owner->set_method_idnum(new_num);
 980             idnum_owner->set_orig_method_idnum(k_new_method->orig_method_idnum());
 981           }
 982           // Take current and original idnum from the old_method
 983           k_new_method->set_method_idnum(old_num);
 984           k_new_method->set_orig_method_idnum(k_old_method->orig_method_idnum());
 985           if (thread->has_pending_exception()) {
 986             return JVMTI_ERROR_OUT_OF_MEMORY;
 987           }
 988         }
 989       }
 990       log_trace(redefine, class, normalize)
 991         ("Method matched: new: %s [%d] == old: %s [%d]",
 992          k_new_method->name_and_sig_as_C_string(), ni, k_old_method->name_and_sig_as_C_string(), oi);
 993       // advance to next pair of methods
 994       ++oi;
 995       ++ni;
 996       break;
 997     case added:
 998       // method added, see if it is OK
 999       if (!can_add_or_delete(k_new_method)) {
1000         return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_METHOD_ADDED;
1001       }
1002       {
1003         u2 num = the_class->next_method_idnum();
1004         if (num == ConstMethod::UNSET_IDNUM) {
1005           // cannot add any more methods
1006           return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_METHOD_ADDED;
1007         }
1008         u2 new_num = k_new_method->method_idnum();
1009         Method* idnum_owner = scratch_class->method_with_idnum(num);
1010         if (idnum_owner != NULL) {
1011           // There is already a method assigned this idnum -- switch them
1012           // Take current and original idnum from the new_method
1013           idnum_owner->set_method_idnum(new_num);
1014           idnum_owner->set_orig_method_idnum(k_new_method->orig_method_idnum());
1015         }
1016         k_new_method->set_method_idnum(num);
1017         k_new_method->set_orig_method_idnum(num);
1018         if (thread->has_pending_exception()) {
1019           return JVMTI_ERROR_OUT_OF_MEMORY;
1020         }
1021       }
1022       log_trace(redefine, class, normalize)
1023         ("Method added: new: %s [%d]", k_new_method->name_and_sig_as_C_string(), ni);
1024       ++ni; // advance to next new method
1025       break;
1026     case deleted:
1027       // method deleted, see if it is OK
1028       if (!can_add_or_delete(k_old_method)) {
1029         return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_METHOD_DELETED;
1030       }
1031       log_trace(redefine, class, normalize)
1032         ("Method deleted: old: %s [%d]", k_old_method->name_and_sig_as_C_string(), oi);
1033       ++oi; // advance to next old method
1034       break;
1035     default:
1036       ShouldNotReachHere();
1037     }
1038   }
1039 
1040   return JVMTI_ERROR_NONE;
1041 }
1042 
1043 
1044 // Find new constant pool index value for old constant pool index value
1045 // by seaching the index map. Returns zero (0) if there is no mapped
1046 // value for the old constant pool index.
1047 int VM_RedefineClasses::find_new_index(int old_index) {
1048   if (_index_map_count == 0) {
1049     // map is empty so nothing can be found
1050     return 0;
1051   }
1052 
1053   if (old_index < 1 || old_index >= _index_map_p->length()) {
1054     // The old_index is out of range so it is not mapped. This should
1055     // not happen in regular constant pool merging use, but it can
1056     // happen if a corrupt annotation is processed.
1057     return 0;
1058   }
1059 
1060   int value = _index_map_p->at(old_index);
1061   if (value == -1) {
1062     // the old_index is not mapped
1063     return 0;
1064   }
1065 
1066   return value;
1067 } // end find_new_index()
1068 
1069 
1070 // Find new bootstrap specifier index value for old bootstrap specifier index
1071 // value by seaching the index map. Returns unused index (-1) if there is
1072 // no mapped value for the old bootstrap specifier index.
1073 int VM_RedefineClasses::find_new_operand_index(int old_index) {
1074   if (_operands_index_map_count == 0) {
1075     // map is empty so nothing can be found
1076     return -1;
1077   }
1078 
1079   if (old_index == -1 || old_index >= _operands_index_map_p->length()) {
1080     // The old_index is out of range so it is not mapped.
1081     // This should not happen in regular constant pool merging use.
1082     return -1;
1083   }
1084 
1085   int value = _operands_index_map_p->at(old_index);
1086   if (value == -1) {
1087     // the old_index is not mapped
1088     return -1;
1089   }
1090 
1091   return value;
1092 } // end find_new_operand_index()
1093 
1094 
1095 // Returns true if the current mismatch is due to a resolved/unresolved
1096 // class pair. Otherwise, returns false.
1097 bool VM_RedefineClasses::is_unresolved_class_mismatch(const constantPoolHandle& cp1,
1098        int index1, const constantPoolHandle& cp2, int index2) {
1099 
1100   jbyte t1 = cp1->tag_at(index1).value();
1101   if (t1 != JVM_CONSTANT_Class && t1 != JVM_CONSTANT_UnresolvedClass) {
1102     return false;  // wrong entry type; not our special case
1103   }
1104 
1105   jbyte t2 = cp2->tag_at(index2).value();
1106   if (t2 != JVM_CONSTANT_Class && t2 != JVM_CONSTANT_UnresolvedClass) {
1107     return false;  // wrong entry type; not our special case
1108   }
1109 
1110   if (t1 == t2) {
1111     return false;  // not a mismatch; not our special case
1112   }
1113 
1114   char *s1 = cp1->klass_name_at(index1)->as_C_string();
1115   char *s2 = cp2->klass_name_at(index2)->as_C_string();
1116   if (strcmp(s1, s2) != 0) {
1117     return false;  // strings don't match; not our special case
1118   }
1119 
1120   return true;  // made it through the gauntlet; this is our special case
1121 } // end is_unresolved_class_mismatch()
1122 
1123 
1124 jvmtiError VM_RedefineClasses::load_new_class_versions(TRAPS) {
1125 
1126   // For consistency allocate memory using os::malloc wrapper.
1127   _scratch_classes = (InstanceKlass**)
1128     os::malloc(sizeof(InstanceKlass*) * _class_count, mtClass);
1129   if (_scratch_classes == NULL) {
1130     return JVMTI_ERROR_OUT_OF_MEMORY;
1131   }
1132   // Zero initialize the _scratch_classes array.
1133   for (int i = 0; i < _class_count; i++) {
1134     _scratch_classes[i] = NULL;
1135   }
1136 
1137   ResourceMark rm(THREAD);
1138 
1139   JvmtiThreadState *state = JvmtiThreadState::state_for(JavaThread::current());
1140   // state can only be NULL if the current thread is exiting which
1141   // should not happen since we're trying to do a RedefineClasses
1142   guarantee(state != NULL, "exiting thread calling load_new_class_versions");
1143   for (int i = 0; i < _class_count; i++) {
1144     // Create HandleMark so that any handles created while loading new class
1145     // versions are deleted. Constant pools are deallocated while merging
1146     // constant pools
1147     HandleMark hm(THREAD);
1148     InstanceKlass* the_class = get_ik(_class_defs[i].klass);
1149     Symbol*  the_class_sym = the_class->name();
1150 
1151     log_debug(redefine, class, load)
1152       ("loading name=%s kind=%d (avail_mem=" UINT64_FORMAT "K)",
1153        the_class->external_name(), _class_load_kind, os::available_memory() >> 10);
1154 
1155     ClassFileStream st((u1*)_class_defs[i].class_bytes,
1156                        _class_defs[i].class_byte_count,
1157                        "__VM_RedefineClasses__",
1158                        ClassFileStream::verify);
1159 
1160     // Parse the stream.
1161     Handle the_class_loader(THREAD, the_class->class_loader());
1162     Handle protection_domain(THREAD, the_class->protection_domain());
1163     // Set redefined class handle in JvmtiThreadState class.
1164     // This redefined class is sent to agent event handler for class file
1165     // load hook event.
1166     state->set_class_being_redefined(the_class, _class_load_kind);
1167 
1168     InstanceKlass* scratch_class = SystemDictionary::parse_stream(
1169                                                       the_class_sym,
1170                                                       the_class_loader,
1171                                                       protection_domain,
1172                                                       &st,
1173                                                       THREAD);
1174     // Clear class_being_redefined just to be sure.
1175     state->clear_class_being_redefined();
1176 
1177     // TODO: if this is retransform, and nothing changed we can skip it
1178 
1179     // Need to clean up allocated InstanceKlass if there's an error so assign
1180     // the result here. Caller deallocates all the scratch classes in case of
1181     // an error.
1182     _scratch_classes[i] = scratch_class;
1183 
1184     if (HAS_PENDING_EXCEPTION) {
1185       Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1186       log_info(redefine, class, load, exceptions)("parse_stream exception: '%s'", ex_name->as_C_string());
1187       CLEAR_PENDING_EXCEPTION;
1188 
1189       if (ex_name == vmSymbols::java_lang_UnsupportedClassVersionError()) {
1190         return JVMTI_ERROR_UNSUPPORTED_VERSION;
1191       } else if (ex_name == vmSymbols::java_lang_ClassFormatError()) {
1192         return JVMTI_ERROR_INVALID_CLASS_FORMAT;
1193       } else if (ex_name == vmSymbols::java_lang_ClassCircularityError()) {
1194         return JVMTI_ERROR_CIRCULAR_CLASS_DEFINITION;
1195       } else if (ex_name == vmSymbols::java_lang_NoClassDefFoundError()) {
1196         // The message will be "XXX (wrong name: YYY)"
1197         return JVMTI_ERROR_NAMES_DONT_MATCH;
1198       } else if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1199         return JVMTI_ERROR_OUT_OF_MEMORY;
1200       } else {  // Just in case more exceptions can be thrown..
1201         return JVMTI_ERROR_FAILS_VERIFICATION;
1202       }
1203     }
1204 
1205     // Ensure class is linked before redefine
1206     if (!the_class->is_linked()) {
1207       the_class->link_class(THREAD);
1208       if (HAS_PENDING_EXCEPTION) {
1209         Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1210         log_info(redefine, class, load, exceptions)("link_class exception: '%s'", ex_name->as_C_string());
1211         CLEAR_PENDING_EXCEPTION;
1212         if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1213           return JVMTI_ERROR_OUT_OF_MEMORY;
1214         } else {
1215           return JVMTI_ERROR_INTERNAL;
1216         }
1217       }
1218     }
1219 
1220     // Do the validity checks in compare_and_normalize_class_versions()
1221     // before verifying the byte codes. By doing these checks first, we
1222     // limit the number of functions that require redirection from
1223     // the_class to scratch_class. In particular, we don't have to
1224     // modify JNI GetSuperclass() and thus won't change its performance.
1225     jvmtiError res = compare_and_normalize_class_versions(the_class,
1226                        scratch_class);
1227     if (res != JVMTI_ERROR_NONE) {
1228       return res;
1229     }
1230 
1231     // verify what the caller passed us
1232     {
1233       // The bug 6214132 caused the verification to fail.
1234       // Information about the_class and scratch_class is temporarily
1235       // recorded into jvmtiThreadState. This data is used to redirect
1236       // the_class to scratch_class in the JVM_* functions called by the
1237       // verifier. Please, refer to jvmtiThreadState.hpp for the detailed
1238       // description.
1239       RedefineVerifyMark rvm(the_class, scratch_class, state);
1240       Verifier::verify(scratch_class, true, THREAD);
1241     }
1242 
1243     if (HAS_PENDING_EXCEPTION) {
1244       Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1245       log_info(redefine, class, load, exceptions)("verify_byte_codes exception: '%s'", ex_name->as_C_string());
1246       CLEAR_PENDING_EXCEPTION;
1247       if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1248         return JVMTI_ERROR_OUT_OF_MEMORY;
1249       } else {
1250         // tell the caller the bytecodes are bad
1251         return JVMTI_ERROR_FAILS_VERIFICATION;
1252       }
1253     }
1254 
1255     res = merge_cp_and_rewrite(the_class, scratch_class, THREAD);
1256     if (HAS_PENDING_EXCEPTION) {
1257       Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1258       log_info(redefine, class, load, exceptions)("merge_cp_and_rewrite exception: '%s'", ex_name->as_C_string());
1259       CLEAR_PENDING_EXCEPTION;
1260       if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1261         return JVMTI_ERROR_OUT_OF_MEMORY;
1262       } else {
1263         return JVMTI_ERROR_INTERNAL;
1264       }
1265     }
1266 
1267     if (VerifyMergedCPBytecodes) {
1268       // verify what we have done during constant pool merging
1269       {
1270         RedefineVerifyMark rvm(the_class, scratch_class, state);
1271         Verifier::verify(scratch_class, true, THREAD);
1272       }
1273 
1274       if (HAS_PENDING_EXCEPTION) {
1275         Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1276         log_info(redefine, class, load, exceptions)
1277           ("verify_byte_codes post merge-CP exception: '%s'", ex_name->as_C_string());
1278         CLEAR_PENDING_EXCEPTION;
1279         if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1280           return JVMTI_ERROR_OUT_OF_MEMORY;
1281         } else {
1282           // tell the caller that constant pool merging screwed up
1283           return JVMTI_ERROR_INTERNAL;
1284         }
1285       }
1286     }
1287 
1288     Rewriter::rewrite(scratch_class, THREAD);
1289     if (!HAS_PENDING_EXCEPTION) {
1290       scratch_class->link_methods(THREAD);
1291     }
1292     if (HAS_PENDING_EXCEPTION) {
1293       Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1294       log_info(redefine, class, load, exceptions)
1295         ("Rewriter::rewrite or link_methods exception: '%s'", ex_name->as_C_string());
1296       CLEAR_PENDING_EXCEPTION;
1297       if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1298         return JVMTI_ERROR_OUT_OF_MEMORY;
1299       } else {
1300         return JVMTI_ERROR_INTERNAL;
1301       }
1302     }
1303 
1304     log_debug(redefine, class, load)
1305       ("loaded name=%s (avail_mem=" UINT64_FORMAT "K)", the_class->external_name(), os::available_memory() >> 10);
1306   }
1307 
1308   return JVMTI_ERROR_NONE;
1309 }
1310 
1311 
1312 // Map old_index to new_index as needed. scratch_cp is only needed
1313 // for log calls.
1314 void VM_RedefineClasses::map_index(const constantPoolHandle& scratch_cp,
1315        int old_index, int new_index) {
1316   if (find_new_index(old_index) != 0) {
1317     // old_index is already mapped
1318     return;
1319   }
1320 
1321   if (old_index == new_index) {
1322     // no mapping is needed
1323     return;
1324   }
1325 
1326   _index_map_p->at_put(old_index, new_index);
1327   _index_map_count++;
1328 
1329   log_trace(redefine, class, constantpool)
1330     ("mapped tag %d at index %d to %d", scratch_cp->tag_at(old_index).value(), old_index, new_index);
1331 } // end map_index()
1332 
1333 
1334 // Map old_index to new_index as needed.
1335 void VM_RedefineClasses::map_operand_index(int old_index, int new_index) {
1336   if (find_new_operand_index(old_index) != -1) {
1337     // old_index is already mapped
1338     return;
1339   }
1340 
1341   if (old_index == new_index) {
1342     // no mapping is needed
1343     return;
1344   }
1345 
1346   _operands_index_map_p->at_put(old_index, new_index);
1347   _operands_index_map_count++;
1348 
1349   log_trace(redefine, class, constantpool)("mapped bootstrap specifier at index %d to %d", old_index, new_index);
1350 } // end map_index()
1351 
1352 
1353 // Merge old_cp and scratch_cp and return the results of the merge via
1354 // merge_cp_p. The number of entries in *merge_cp_p is returned via
1355 // merge_cp_length_p. The entries in old_cp occupy the same locations
1356 // in *merge_cp_p. Also creates a map of indices from entries in
1357 // scratch_cp to the corresponding entry in *merge_cp_p. Index map
1358 // entries are only created for entries in scratch_cp that occupy a
1359 // different location in *merged_cp_p.
1360 bool VM_RedefineClasses::merge_constant_pools(const constantPoolHandle& old_cp,
1361        const constantPoolHandle& scratch_cp, constantPoolHandle *merge_cp_p,
1362        int *merge_cp_length_p, TRAPS) {
1363 
1364   if (merge_cp_p == NULL) {
1365     assert(false, "caller must provide scratch constantPool");
1366     return false; // robustness
1367   }
1368   if (merge_cp_length_p == NULL) {
1369     assert(false, "caller must provide scratch CP length");
1370     return false; // robustness
1371   }
1372   // Worst case we need old_cp->length() + scratch_cp()->length(),
1373   // but the caller might be smart so make sure we have at least
1374   // the minimum.
1375   if ((*merge_cp_p)->length() < old_cp->length()) {
1376     assert(false, "merge area too small");
1377     return false; // robustness
1378   }
1379 
1380   log_info(redefine, class, constantpool)("old_cp_len=%d, scratch_cp_len=%d", old_cp->length(), scratch_cp->length());
1381 
1382   {
1383     // Pass 0:
1384     // The old_cp is copied to *merge_cp_p; this means that any code
1385     // using old_cp does not have to change. This work looks like a
1386     // perfect fit for ConstantPool*::copy_cp_to(), but we need to
1387     // handle one special case:
1388     // - revert JVM_CONSTANT_Class to JVM_CONSTANT_UnresolvedClass
1389     // This will make verification happy.
1390 
1391     int old_i;  // index into old_cp
1392 
1393     // index zero (0) is not used in constantPools
1394     for (old_i = 1; old_i < old_cp->length(); old_i++) {
1395       // leave debugging crumb
1396       jbyte old_tag = old_cp->tag_at(old_i).value();
1397       switch (old_tag) {
1398       case JVM_CONSTANT_Class:
1399       case JVM_CONSTANT_UnresolvedClass:
1400         // revert the copy to JVM_CONSTANT_UnresolvedClass
1401         // May be resolving while calling this so do the same for
1402         // JVM_CONSTANT_UnresolvedClass (klass_name_at() deals with transition)
1403         (*merge_cp_p)->temp_unresolved_klass_at_put(old_i,
1404           old_cp->klass_name_index_at(old_i));
1405         break;
1406 
1407       case JVM_CONSTANT_Double:
1408       case JVM_CONSTANT_Long:
1409         // just copy the entry to *merge_cp_p, but double and long take
1410         // two constant pool entries
1411         ConstantPool::copy_entry_to(old_cp, old_i, *merge_cp_p, old_i, CHECK_0);
1412         old_i++;
1413         break;
1414 
1415       default:
1416         // just copy the entry to *merge_cp_p
1417         ConstantPool::copy_entry_to(old_cp, old_i, *merge_cp_p, old_i, CHECK_0);
1418         break;
1419       }
1420     } // end for each old_cp entry
1421 
1422     ConstantPool::copy_operands(old_cp, *merge_cp_p, CHECK_0);
1423     (*merge_cp_p)->extend_operands(scratch_cp, CHECK_0);
1424 
1425     // We don't need to sanity check that *merge_cp_length_p is within
1426     // *merge_cp_p bounds since we have the minimum on-entry check above.
1427     (*merge_cp_length_p) = old_i;
1428   }
1429 
1430   // merge_cp_len should be the same as old_cp->length() at this point
1431   // so this trace message is really a "warm-and-breathing" message.
1432   log_debug(redefine, class, constantpool)("after pass 0: merge_cp_len=%d", *merge_cp_length_p);
1433 
1434   int scratch_i;  // index into scratch_cp
1435   {
1436     // Pass 1a:
1437     // Compare scratch_cp entries to the old_cp entries that we have
1438     // already copied to *merge_cp_p. In this pass, we are eliminating
1439     // exact duplicates (matching entry at same index) so we only
1440     // compare entries in the common indice range.
1441     int increment = 1;
1442     int pass1a_length = MIN2(old_cp->length(), scratch_cp->length());
1443     for (scratch_i = 1; scratch_i < pass1a_length; scratch_i += increment) {
1444       switch (scratch_cp->tag_at(scratch_i).value()) {
1445       case JVM_CONSTANT_Double:
1446       case JVM_CONSTANT_Long:
1447         // double and long take two constant pool entries
1448         increment = 2;
1449         break;
1450 
1451       default:
1452         increment = 1;
1453         break;
1454       }
1455 
1456       bool match = scratch_cp->compare_entry_to(scratch_i, *merge_cp_p,
1457         scratch_i, CHECK_0);
1458       if (match) {
1459         // found a match at the same index so nothing more to do
1460         continue;
1461       } else if (is_unresolved_class_mismatch(scratch_cp, scratch_i,
1462                                               *merge_cp_p, scratch_i)) {
1463         // The mismatch in compare_entry_to() above is because of a
1464         // resolved versus unresolved class entry at the same index
1465         // with the same string value. Since Pass 0 reverted any
1466         // class entries to unresolved class entries in *merge_cp_p,
1467         // we go with the unresolved class entry.
1468         continue;
1469       }
1470 
1471       int found_i = scratch_cp->find_matching_entry(scratch_i, *merge_cp_p,
1472         CHECK_0);
1473       if (found_i != 0) {
1474         guarantee(found_i != scratch_i,
1475           "compare_entry_to() and find_matching_entry() do not agree");
1476 
1477         // Found a matching entry somewhere else in *merge_cp_p so
1478         // just need a mapping entry.
1479         map_index(scratch_cp, scratch_i, found_i);
1480         continue;
1481       }
1482 
1483       // The find_matching_entry() call above could fail to find a match
1484       // due to a resolved versus unresolved class or string entry situation
1485       // like we solved above with the is_unresolved_*_mismatch() calls.
1486       // However, we would have to call is_unresolved_*_mismatch() over
1487       // all of *merge_cp_p (potentially) and that doesn't seem to be
1488       // worth the time.
1489 
1490       // No match found so we have to append this entry and any unique
1491       // referenced entries to *merge_cp_p.
1492       append_entry(scratch_cp, scratch_i, merge_cp_p, merge_cp_length_p,
1493         CHECK_0);
1494     }
1495   }
1496 
1497   log_debug(redefine, class, constantpool)
1498     ("after pass 1a: merge_cp_len=%d, scratch_i=%d, index_map_len=%d",
1499      *merge_cp_length_p, scratch_i, _index_map_count);
1500 
1501   if (scratch_i < scratch_cp->length()) {
1502     // Pass 1b:
1503     // old_cp is smaller than scratch_cp so there are entries in
1504     // scratch_cp that we have not yet processed. We take care of
1505     // those now.
1506     int increment = 1;
1507     for (; scratch_i < scratch_cp->length(); scratch_i += increment) {
1508       switch (scratch_cp->tag_at(scratch_i).value()) {
1509       case JVM_CONSTANT_Double:
1510       case JVM_CONSTANT_Long:
1511         // double and long take two constant pool entries
1512         increment = 2;
1513         break;
1514 
1515       default:
1516         increment = 1;
1517         break;
1518       }
1519 
1520       int found_i =
1521         scratch_cp->find_matching_entry(scratch_i, *merge_cp_p, CHECK_0);
1522       if (found_i != 0) {
1523         // Found a matching entry somewhere else in *merge_cp_p so
1524         // just need a mapping entry.
1525         map_index(scratch_cp, scratch_i, found_i);
1526         continue;
1527       }
1528 
1529       // No match found so we have to append this entry and any unique
1530       // referenced entries to *merge_cp_p.
1531       append_entry(scratch_cp, scratch_i, merge_cp_p, merge_cp_length_p,
1532         CHECK_0);
1533     }
1534 
1535     log_debug(redefine, class, constantpool)
1536       ("after pass 1b: merge_cp_len=%d, scratch_i=%d, index_map_len=%d",
1537        *merge_cp_length_p, scratch_i, _index_map_count);
1538   }
1539   finalize_operands_merge(*merge_cp_p, THREAD);
1540 
1541   return true;
1542 } // end merge_constant_pools()
1543 
1544 
1545 // Scoped object to clean up the constant pool(s) created for merging
1546 class MergeCPCleaner {
1547   ClassLoaderData*   _loader_data;
1548   ConstantPool*      _cp;
1549   ConstantPool*      _scratch_cp;
1550  public:
1551   MergeCPCleaner(ClassLoaderData* loader_data, ConstantPool* merge_cp) :
1552                  _loader_data(loader_data), _cp(merge_cp), _scratch_cp(NULL) {}
1553   ~MergeCPCleaner() {
1554     _loader_data->add_to_deallocate_list(_cp);
1555     if (_scratch_cp != NULL) {
1556       _loader_data->add_to_deallocate_list(_scratch_cp);
1557     }
1558   }
1559   void add_scratch_cp(ConstantPool* scratch_cp) { _scratch_cp = scratch_cp; }
1560 };
1561 
1562 // Merge constant pools between the_class and scratch_class and
1563 // potentially rewrite bytecodes in scratch_class to use the merged
1564 // constant pool.
1565 jvmtiError VM_RedefineClasses::merge_cp_and_rewrite(
1566              InstanceKlass* the_class, InstanceKlass* scratch_class,
1567              TRAPS) {
1568   // worst case merged constant pool length is old and new combined
1569   int merge_cp_length = the_class->constants()->length()
1570         + scratch_class->constants()->length();
1571 
1572   // Constant pools are not easily reused so we allocate a new one
1573   // each time.
1574   // merge_cp is created unsafe for concurrent GC processing.  It
1575   // should be marked safe before discarding it. Even though
1576   // garbage,  if it crosses a card boundary, it may be scanned
1577   // in order to find the start of the first complete object on the card.
1578   ClassLoaderData* loader_data = the_class->class_loader_data();
1579   ConstantPool* merge_cp_oop =
1580     ConstantPool::allocate(loader_data,
1581                            merge_cp_length,
1582                            CHECK_(JVMTI_ERROR_OUT_OF_MEMORY));
1583   MergeCPCleaner cp_cleaner(loader_data, merge_cp_oop);
1584 
1585   HandleMark hm(THREAD);  // make sure handles are cleared before
1586                           // MergeCPCleaner clears out merge_cp_oop
1587   constantPoolHandle merge_cp(THREAD, merge_cp_oop);
1588 
1589   // Get constants() from the old class because it could have been rewritten
1590   // while we were at a safepoint allocating a new constant pool.
1591   constantPoolHandle old_cp(THREAD, the_class->constants());
1592   constantPoolHandle scratch_cp(THREAD, scratch_class->constants());
1593 
1594   // If the length changed, the class was redefined out from under us. Return
1595   // an error.
1596   if (merge_cp_length != the_class->constants()->length()
1597          + scratch_class->constants()->length()) {
1598     return JVMTI_ERROR_INTERNAL;
1599   }
1600 
1601   // Update the version number of the constant pools (may keep scratch_cp)
1602   merge_cp->increment_and_save_version(old_cp->version());
1603   scratch_cp->increment_and_save_version(old_cp->version());
1604 
1605   ResourceMark rm(THREAD);
1606   _index_map_count = 0;
1607   _index_map_p = new intArray(scratch_cp->length(), scratch_cp->length(), -1);
1608 
1609   _operands_cur_length = ConstantPool::operand_array_length(old_cp->operands());
1610   _operands_index_map_count = 0;
1611   int operands_index_map_len = ConstantPool::operand_array_length(scratch_cp->operands());
1612   _operands_index_map_p = new intArray(operands_index_map_len, operands_index_map_len, -1);
1613 
1614   // reference to the cp holder is needed for copy_operands()
1615   merge_cp->set_pool_holder(scratch_class);
1616   bool result = merge_constant_pools(old_cp, scratch_cp, &merge_cp,
1617                   &merge_cp_length, THREAD);
1618   merge_cp->set_pool_holder(NULL);
1619 
1620   if (!result) {
1621     // The merge can fail due to memory allocation failure or due
1622     // to robustness checks.
1623     return JVMTI_ERROR_INTERNAL;
1624   }
1625 
1626   log_info(redefine, class, constantpool)("merge_cp_len=%d, index_map_len=%d", merge_cp_length, _index_map_count);
1627 
1628   if (_index_map_count == 0) {
1629     // there is nothing to map between the new and merged constant pools
1630 
1631     if (old_cp->length() == scratch_cp->length()) {
1632       // The old and new constant pools are the same length and the
1633       // index map is empty. This means that the three constant pools
1634       // are equivalent (but not the same). Unfortunately, the new
1635       // constant pool has not gone through link resolution nor have
1636       // the new class bytecodes gone through constant pool cache
1637       // rewriting so we can't use the old constant pool with the new
1638       // class.
1639 
1640       // toss the merged constant pool at return
1641     } else if (old_cp->length() < scratch_cp->length()) {
1642       // The old constant pool has fewer entries than the new constant
1643       // pool and the index map is empty. This means the new constant
1644       // pool is a superset of the old constant pool. However, the old
1645       // class bytecodes have already gone through constant pool cache
1646       // rewriting so we can't use the new constant pool with the old
1647       // class.
1648 
1649       // toss the merged constant pool at return
1650     } else {
1651       // The old constant pool has more entries than the new constant
1652       // pool and the index map is empty. This means that both the old
1653       // and merged constant pools are supersets of the new constant
1654       // pool.
1655 
1656       // Replace the new constant pool with a shrunken copy of the
1657       // merged constant pool
1658       set_new_constant_pool(loader_data, scratch_class, merge_cp, merge_cp_length,
1659                             CHECK_(JVMTI_ERROR_OUT_OF_MEMORY));
1660       // The new constant pool replaces scratch_cp so have cleaner clean it up.
1661       // It can't be cleaned up while there are handles to it.
1662       cp_cleaner.add_scratch_cp(scratch_cp());
1663     }
1664   } else {
1665     if (log_is_enabled(Trace, redefine, class, constantpool)) {
1666       // don't want to loop unless we are tracing
1667       int count = 0;
1668       for (int i = 1; i < _index_map_p->length(); i++) {
1669         int value = _index_map_p->at(i);
1670 
1671         if (value != -1) {
1672           log_trace(redefine, class, constantpool)("index_map[%d]: old=%d new=%d", count, i, value);
1673           count++;
1674         }
1675       }
1676     }
1677 
1678     // We have entries mapped between the new and merged constant pools
1679     // so we have to rewrite some constant pool references.
1680     if (!rewrite_cp_refs(scratch_class, THREAD)) {
1681       return JVMTI_ERROR_INTERNAL;
1682     }
1683 
1684     // Replace the new constant pool with a shrunken copy of the
1685     // merged constant pool so now the rewritten bytecodes have
1686     // valid references; the previous new constant pool will get
1687     // GCed.
1688     set_new_constant_pool(loader_data, scratch_class, merge_cp, merge_cp_length,
1689                           CHECK_(JVMTI_ERROR_OUT_OF_MEMORY));
1690     // The new constant pool replaces scratch_cp so have cleaner clean it up.
1691     // It can't be cleaned up while there are handles to it.
1692     cp_cleaner.add_scratch_cp(scratch_cp());
1693   }
1694 
1695   return JVMTI_ERROR_NONE;
1696 } // end merge_cp_and_rewrite()
1697 
1698 
1699 // Rewrite constant pool references in klass scratch_class.
1700 bool VM_RedefineClasses::rewrite_cp_refs(InstanceKlass* scratch_class,
1701        TRAPS) {
1702 
1703   // rewrite constant pool references in the nest attributes:
1704   if (!rewrite_cp_refs_in_nest_attributes(scratch_class)) {
1705     // propagate failure back to caller
1706     return false;
1707   }
1708 
1709   // rewrite constant pool references in the methods:
1710   if (!rewrite_cp_refs_in_methods(scratch_class, THREAD)) {
1711     // propagate failure back to caller
1712     return false;
1713   }
1714 
1715   // rewrite constant pool references in the class_annotations:
1716   if (!rewrite_cp_refs_in_class_annotations(scratch_class, THREAD)) {
1717     // propagate failure back to caller
1718     return false;
1719   }
1720 
1721   // rewrite constant pool references in the fields_annotations:
1722   if (!rewrite_cp_refs_in_fields_annotations(scratch_class, THREAD)) {
1723     // propagate failure back to caller
1724     return false;
1725   }
1726 
1727   // rewrite constant pool references in the methods_annotations:
1728   if (!rewrite_cp_refs_in_methods_annotations(scratch_class, THREAD)) {
1729     // propagate failure back to caller
1730     return false;
1731   }
1732 
1733   // rewrite constant pool references in the methods_parameter_annotations:
1734   if (!rewrite_cp_refs_in_methods_parameter_annotations(scratch_class,
1735          THREAD)) {
1736     // propagate failure back to caller
1737     return false;
1738   }
1739 
1740   // rewrite constant pool references in the methods_default_annotations:
1741   if (!rewrite_cp_refs_in_methods_default_annotations(scratch_class,
1742          THREAD)) {
1743     // propagate failure back to caller
1744     return false;
1745   }
1746 
1747   // rewrite constant pool references in the class_type_annotations:
1748   if (!rewrite_cp_refs_in_class_type_annotations(scratch_class, THREAD)) {
1749     // propagate failure back to caller
1750     return false;
1751   }
1752 
1753   // rewrite constant pool references in the fields_type_annotations:
1754   if (!rewrite_cp_refs_in_fields_type_annotations(scratch_class, THREAD)) {
1755     // propagate failure back to caller
1756     return false;
1757   }
1758 
1759   // rewrite constant pool references in the methods_type_annotations:
1760   if (!rewrite_cp_refs_in_methods_type_annotations(scratch_class, THREAD)) {
1761     // propagate failure back to caller
1762     return false;
1763   }
1764 
1765   // There can be type annotations in the Code part of a method_info attribute.
1766   // These annotations are not accessible, even by reflection.
1767   // Currently they are not even parsed by the ClassFileParser.
1768   // If runtime access is added they will also need to be rewritten.
1769 
1770   // rewrite source file name index:
1771   u2 source_file_name_idx = scratch_class->source_file_name_index();
1772   if (source_file_name_idx != 0) {
1773     u2 new_source_file_name_idx = find_new_index(source_file_name_idx);
1774     if (new_source_file_name_idx != 0) {
1775       scratch_class->set_source_file_name_index(new_source_file_name_idx);
1776     }
1777   }
1778 
1779   // rewrite class generic signature index:
1780   u2 generic_signature_index = scratch_class->generic_signature_index();
1781   if (generic_signature_index != 0) {
1782     u2 new_generic_signature_index = find_new_index(generic_signature_index);
1783     if (new_generic_signature_index != 0) {
1784       scratch_class->set_generic_signature_index(new_generic_signature_index);
1785     }
1786   }
1787 
1788   return true;
1789 } // end rewrite_cp_refs()
1790 
1791 // Rewrite constant pool references in the NestHost and NestMembers attributes.
1792 bool VM_RedefineClasses::rewrite_cp_refs_in_nest_attributes(
1793        InstanceKlass* scratch_class) {
1794 
1795   u2 cp_index = scratch_class->nest_host_index();
1796   if (cp_index != 0) {
1797     scratch_class->set_nest_host_index(find_new_index(cp_index));
1798   }
1799   Array<u2>* nest_members = scratch_class->nest_members();
1800   for (int i = 0; i < nest_members->length(); i++) {
1801     u2 cp_index = nest_members->at(i);
1802     nest_members->at_put(i, find_new_index(cp_index));
1803   }
1804   return true;
1805 }
1806 
1807 // Rewrite constant pool references in the methods.
1808 bool VM_RedefineClasses::rewrite_cp_refs_in_methods(
1809        InstanceKlass* scratch_class, TRAPS) {
1810 
1811   Array<Method*>* methods = scratch_class->methods();
1812 
1813   if (methods == NULL || methods->length() == 0) {
1814     // no methods so nothing to do
1815     return true;
1816   }
1817 
1818   // rewrite constant pool references in the methods:
1819   for (int i = methods->length() - 1; i >= 0; i--) {
1820     methodHandle method(THREAD, methods->at(i));
1821     methodHandle new_method;
1822     rewrite_cp_refs_in_method(method, &new_method, THREAD);
1823     if (!new_method.is_null()) {
1824       // the method has been replaced so save the new method version
1825       // even in the case of an exception.  original method is on the
1826       // deallocation list.
1827       methods->at_put(i, new_method());
1828     }
1829     if (HAS_PENDING_EXCEPTION) {
1830       Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1831       log_info(redefine, class, load, exceptions)("rewrite_cp_refs_in_method exception: '%s'", ex_name->as_C_string());
1832       // Need to clear pending exception here as the super caller sets
1833       // the JVMTI_ERROR_INTERNAL if the returned value is false.
1834       CLEAR_PENDING_EXCEPTION;
1835       return false;
1836     }
1837   }
1838 
1839   return true;
1840 }
1841 
1842 
1843 // Rewrite constant pool references in the specific method. This code
1844 // was adapted from Rewriter::rewrite_method().
1845 void VM_RedefineClasses::rewrite_cp_refs_in_method(methodHandle method,
1846        methodHandle *new_method_p, TRAPS) {
1847 
1848   *new_method_p = methodHandle();  // default is no new method
1849 
1850   // We cache a pointer to the bytecodes here in code_base. If GC
1851   // moves the Method*, then the bytecodes will also move which
1852   // will likely cause a crash. We create a NoSafepointVerifier
1853   // object to detect whether we pass a possible safepoint in this
1854   // code block.
1855   NoSafepointVerifier nsv;
1856 
1857   // Bytecodes and their length
1858   address code_base = method->code_base();
1859   int code_length = method->code_size();
1860 
1861   int bc_length;
1862   for (int bci = 0; bci < code_length; bci += bc_length) {
1863     address bcp = code_base + bci;
1864     Bytecodes::Code c = (Bytecodes::Code)(*bcp);
1865 
1866     bc_length = Bytecodes::length_for(c);
1867     if (bc_length == 0) {
1868       // More complicated bytecodes report a length of zero so
1869       // we have to try again a slightly different way.
1870       bc_length = Bytecodes::length_at(method(), bcp);
1871     }
1872 
1873     assert(bc_length != 0, "impossible bytecode length");
1874 
1875     switch (c) {
1876       case Bytecodes::_ldc:
1877       {
1878         int cp_index = *(bcp + 1);
1879         int new_index = find_new_index(cp_index);
1880 
1881         if (StressLdcRewrite && new_index == 0) {
1882           // If we are stressing ldc -> ldc_w rewriting, then we
1883           // always need a new_index value.
1884           new_index = cp_index;
1885         }
1886         if (new_index != 0) {
1887           // the original index is mapped so we have more work to do
1888           if (!StressLdcRewrite && new_index <= max_jubyte) {
1889             // The new value can still use ldc instead of ldc_w
1890             // unless we are trying to stress ldc -> ldc_w rewriting
1891             log_trace(redefine, class, constantpool)
1892               ("%s@" INTPTR_FORMAT " old=%d, new=%d", Bytecodes::name(c), p2i(bcp), cp_index, new_index);
1893             *(bcp + 1) = new_index;
1894           } else {
1895             log_trace(redefine, class, constantpool)
1896               ("%s->ldc_w@" INTPTR_FORMAT " old=%d, new=%d", Bytecodes::name(c), p2i(bcp), cp_index, new_index);
1897             // the new value needs ldc_w instead of ldc
1898             u_char inst_buffer[4]; // max instruction size is 4 bytes
1899             bcp = (address)inst_buffer;
1900             // construct new instruction sequence
1901             *bcp = Bytecodes::_ldc_w;
1902             bcp++;
1903             // Rewriter::rewrite_method() does not rewrite ldc -> ldc_w.
1904             // See comment below for difference between put_Java_u2()
1905             // and put_native_u2().
1906             Bytes::put_Java_u2(bcp, new_index);
1907 
1908             Relocator rc(method, NULL /* no RelocatorListener needed */);
1909             methodHandle m;
1910             {
1911               PauseNoSafepointVerifier pnsv(&nsv);
1912 
1913               // ldc is 2 bytes and ldc_w is 3 bytes
1914               m = rc.insert_space_at(bci, 3, inst_buffer, CHECK);
1915             }
1916 
1917             // return the new method so that the caller can update
1918             // the containing class
1919             *new_method_p = method = m;
1920             // switch our bytecode processing loop from the old method
1921             // to the new method
1922             code_base = method->code_base();
1923             code_length = method->code_size();
1924             bcp = code_base + bci;
1925             c = (Bytecodes::Code)(*bcp);
1926             bc_length = Bytecodes::length_for(c);
1927             assert(bc_length != 0, "sanity check");
1928           } // end we need ldc_w instead of ldc
1929         } // end if there is a mapped index
1930       } break;
1931 
1932       // these bytecodes have a two-byte constant pool index
1933       case Bytecodes::_anewarray      : // fall through
1934       case Bytecodes::_checkcast      : // fall through
1935       case Bytecodes::_getfield       : // fall through
1936       case Bytecodes::_getstatic      : // fall through
1937       case Bytecodes::_instanceof     : // fall through
1938       case Bytecodes::_invokedynamic  : // fall through
1939       case Bytecodes::_invokeinterface: // fall through
1940       case Bytecodes::_invokespecial  : // fall through
1941       case Bytecodes::_invokestatic   : // fall through
1942       case Bytecodes::_invokevirtual  : // fall through
1943       case Bytecodes::_ldc_w          : // fall through
1944       case Bytecodes::_ldc2_w         : // fall through
1945       case Bytecodes::_multianewarray : // fall through
1946       case Bytecodes::_new            : // fall through
1947       case Bytecodes::_putfield       : // fall through
1948       case Bytecodes::_putstatic      :
1949       {
1950         address p = bcp + 1;
1951         int cp_index = Bytes::get_Java_u2(p);
1952         int new_index = find_new_index(cp_index);
1953         if (new_index != 0) {
1954           // the original index is mapped so update w/ new value
1955           log_trace(redefine, class, constantpool)
1956             ("%s@" INTPTR_FORMAT " old=%d, new=%d", Bytecodes::name(c),p2i(bcp), cp_index, new_index);
1957           // Rewriter::rewrite_method() uses put_native_u2() in this
1958           // situation because it is reusing the constant pool index
1959           // location for a native index into the ConstantPoolCache.
1960           // Since we are updating the constant pool index prior to
1961           // verification and ConstantPoolCache initialization, we
1962           // need to keep the new index in Java byte order.
1963           Bytes::put_Java_u2(p, new_index);
1964         }
1965       } break;
1966       default:
1967         break;
1968     }
1969   } // end for each bytecode
1970 
1971   // We also need to rewrite the parameter name indexes, if there is
1972   // method parameter data present
1973   if(method->has_method_parameters()) {
1974     const int len = method->method_parameters_length();
1975     MethodParametersElement* elem = method->method_parameters_start();
1976 
1977     for (int i = 0; i < len; i++) {
1978       const u2 cp_index = elem[i].name_cp_index;
1979       const u2 new_cp_index = find_new_index(cp_index);
1980       if (new_cp_index != 0) {
1981         elem[i].name_cp_index = new_cp_index;
1982       }
1983     }
1984   }
1985 } // end rewrite_cp_refs_in_method()
1986 
1987 
1988 // Rewrite constant pool references in the class_annotations field.
1989 bool VM_RedefineClasses::rewrite_cp_refs_in_class_annotations(
1990        InstanceKlass* scratch_class, TRAPS) {
1991 
1992   AnnotationArray* class_annotations = scratch_class->class_annotations();
1993   if (class_annotations == NULL || class_annotations->length() == 0) {
1994     // no class_annotations so nothing to do
1995     return true;
1996   }
1997 
1998   log_debug(redefine, class, annotation)("class_annotations length=%d", class_annotations->length());
1999 
2000   int byte_i = 0;  // byte index into class_annotations
2001   return rewrite_cp_refs_in_annotations_typeArray(class_annotations, byte_i,
2002            THREAD);
2003 }
2004 
2005 
2006 // Rewrite constant pool references in an annotations typeArray. This
2007 // "structure" is adapted from the RuntimeVisibleAnnotations_attribute
2008 // that is described in section 4.8.15 of the 2nd-edition of the VM spec:
2009 //
2010 // annotations_typeArray {
2011 //   u2 num_annotations;
2012 //   annotation annotations[num_annotations];
2013 // }
2014 //
2015 bool VM_RedefineClasses::rewrite_cp_refs_in_annotations_typeArray(
2016        AnnotationArray* annotations_typeArray, int &byte_i_ref, TRAPS) {
2017 
2018   if ((byte_i_ref + 2) > annotations_typeArray->length()) {
2019     // not enough room for num_annotations field
2020     log_debug(redefine, class, annotation)("length() is too small for num_annotations field");
2021     return false;
2022   }
2023 
2024   u2 num_annotations = Bytes::get_Java_u2((address)
2025                          annotations_typeArray->adr_at(byte_i_ref));
2026   byte_i_ref += 2;
2027 
2028   log_debug(redefine, class, annotation)("num_annotations=%d", num_annotations);
2029 
2030   int calc_num_annotations = 0;
2031   for (; calc_num_annotations < num_annotations; calc_num_annotations++) {
2032     if (!rewrite_cp_refs_in_annotation_struct(annotations_typeArray,
2033            byte_i_ref, THREAD)) {
2034       log_debug(redefine, class, annotation)("bad annotation_struct at %d", calc_num_annotations);
2035       // propagate failure back to caller
2036       return false;
2037     }
2038   }
2039   assert(num_annotations == calc_num_annotations, "sanity check");
2040 
2041   return true;
2042 } // end rewrite_cp_refs_in_annotations_typeArray()
2043 
2044 
2045 // Rewrite constant pool references in the annotation struct portion of
2046 // an annotations_typeArray. This "structure" is from section 4.8.15 of
2047 // the 2nd-edition of the VM spec:
2048 //
2049 // struct annotation {
2050 //   u2 type_index;
2051 //   u2 num_element_value_pairs;
2052 //   {
2053 //     u2 element_name_index;
2054 //     element_value value;
2055 //   } element_value_pairs[num_element_value_pairs];
2056 // }
2057 //
2058 bool VM_RedefineClasses::rewrite_cp_refs_in_annotation_struct(
2059        AnnotationArray* annotations_typeArray, int &byte_i_ref, TRAPS) {
2060   if ((byte_i_ref + 2 + 2) > annotations_typeArray->length()) {
2061     // not enough room for smallest annotation_struct
2062     log_debug(redefine, class, annotation)("length() is too small for annotation_struct");
2063     return false;
2064   }
2065 
2066   u2 type_index = rewrite_cp_ref_in_annotation_data(annotations_typeArray,
2067                     byte_i_ref, "type_index", THREAD);
2068 
2069   u2 num_element_value_pairs = Bytes::get_Java_u2((address)
2070                                  annotations_typeArray->adr_at(byte_i_ref));
2071   byte_i_ref += 2;
2072 
2073   log_debug(redefine, class, annotation)
2074     ("type_index=%d  num_element_value_pairs=%d", type_index, num_element_value_pairs);
2075 
2076   int calc_num_element_value_pairs = 0;
2077   for (; calc_num_element_value_pairs < num_element_value_pairs;
2078        calc_num_element_value_pairs++) {
2079     if ((byte_i_ref + 2) > annotations_typeArray->length()) {
2080       // not enough room for another element_name_index, let alone
2081       // the rest of another component
2082       log_debug(redefine, class, annotation)("length() is too small for element_name_index");
2083       return false;
2084     }
2085 
2086     u2 element_name_index = rewrite_cp_ref_in_annotation_data(
2087                               annotations_typeArray, byte_i_ref,
2088                               "element_name_index", THREAD);
2089 
2090     log_debug(redefine, class, annotation)("element_name_index=%d", element_name_index);
2091 
2092     if (!rewrite_cp_refs_in_element_value(annotations_typeArray,
2093            byte_i_ref, THREAD)) {
2094       log_debug(redefine, class, annotation)("bad element_value at %d", calc_num_element_value_pairs);
2095       // propagate failure back to caller
2096       return false;
2097     }
2098   } // end for each component
2099   assert(num_element_value_pairs == calc_num_element_value_pairs,
2100     "sanity check");
2101 
2102   return true;
2103 } // end rewrite_cp_refs_in_annotation_struct()
2104 
2105 
2106 // Rewrite a constant pool reference at the current position in
2107 // annotations_typeArray if needed. Returns the original constant
2108 // pool reference if a rewrite was not needed or the new constant
2109 // pool reference if a rewrite was needed.
2110 u2 VM_RedefineClasses::rewrite_cp_ref_in_annotation_data(
2111      AnnotationArray* annotations_typeArray, int &byte_i_ref,
2112      const char * trace_mesg, TRAPS) {
2113 
2114   address cp_index_addr = (address)
2115     annotations_typeArray->adr_at(byte_i_ref);
2116   u2 old_cp_index = Bytes::get_Java_u2(cp_index_addr);
2117   u2 new_cp_index = find_new_index(old_cp_index);
2118   if (new_cp_index != 0) {
2119     log_debug(redefine, class, annotation)("mapped old %s=%d", trace_mesg, old_cp_index);
2120     Bytes::put_Java_u2(cp_index_addr, new_cp_index);
2121     old_cp_index = new_cp_index;
2122   }
2123   byte_i_ref += 2;
2124   return old_cp_index;
2125 }
2126 
2127 
2128 // Rewrite constant pool references in the element_value portion of an
2129 // annotations_typeArray. This "structure" is from section 4.8.15.1 of
2130 // the 2nd-edition of the VM spec:
2131 //
2132 // struct element_value {
2133 //   u1 tag;
2134 //   union {
2135 //     u2 const_value_index;
2136 //     {
2137 //       u2 type_name_index;
2138 //       u2 const_name_index;
2139 //     } enum_const_value;
2140 //     u2 class_info_index;
2141 //     annotation annotation_value;
2142 //     struct {
2143 //       u2 num_values;
2144 //       element_value values[num_values];
2145 //     } array_value;
2146 //   } value;
2147 // }
2148 //
2149 bool VM_RedefineClasses::rewrite_cp_refs_in_element_value(
2150        AnnotationArray* annotations_typeArray, int &byte_i_ref, TRAPS) {
2151 
2152   if ((byte_i_ref + 1) > annotations_typeArray->length()) {
2153     // not enough room for a tag let alone the rest of an element_value
2154     log_debug(redefine, class, annotation)("length() is too small for a tag");
2155     return false;
2156   }
2157 
2158   u1 tag = annotations_typeArray->at(byte_i_ref);
2159   byte_i_ref++;
2160   log_debug(redefine, class, annotation)("tag='%c'", tag);
2161 
2162   switch (tag) {
2163     // These BaseType tag values are from Table 4.2 in VM spec:
2164     case 'B':  // byte
2165     case 'C':  // char
2166     case 'D':  // double
2167     case 'F':  // float
2168     case 'I':  // int
2169     case 'J':  // long
2170     case 'S':  // short
2171     case 'Z':  // boolean
2172 
2173     // The remaining tag values are from Table 4.8 in the 2nd-edition of
2174     // the VM spec:
2175     case 's':
2176     {
2177       // For the above tag values (including the BaseType values),
2178       // value.const_value_index is right union field.
2179 
2180       if ((byte_i_ref + 2) > annotations_typeArray->length()) {
2181         // not enough room for a const_value_index
2182         log_debug(redefine, class, annotation)("length() is too small for a const_value_index");
2183         return false;
2184       }
2185 
2186       u2 const_value_index = rewrite_cp_ref_in_annotation_data(
2187                                annotations_typeArray, byte_i_ref,
2188                                "const_value_index", THREAD);
2189 
2190       log_debug(redefine, class, annotation)("const_value_index=%d", const_value_index);
2191     } break;
2192 
2193     case 'e':
2194     {
2195       // for the above tag value, value.enum_const_value is right union field
2196 
2197       if ((byte_i_ref + 4) > annotations_typeArray->length()) {
2198         // not enough room for a enum_const_value
2199         log_debug(redefine, class, annotation)("length() is too small for a enum_const_value");
2200         return false;
2201       }
2202 
2203       u2 type_name_index = rewrite_cp_ref_in_annotation_data(
2204                              annotations_typeArray, byte_i_ref,
2205                              "type_name_index", THREAD);
2206 
2207       u2 const_name_index = rewrite_cp_ref_in_annotation_data(
2208                               annotations_typeArray, byte_i_ref,
2209                               "const_name_index", THREAD);
2210 
2211       log_debug(redefine, class, annotation)
2212         ("type_name_index=%d  const_name_index=%d", type_name_index, const_name_index);
2213     } break;
2214 
2215     case 'c':
2216     {
2217       // for the above tag value, value.class_info_index is right union field
2218 
2219       if ((byte_i_ref + 2) > annotations_typeArray->length()) {
2220         // not enough room for a class_info_index
2221         log_debug(redefine, class, annotation)("length() is too small for a class_info_index");
2222         return false;
2223       }
2224 
2225       u2 class_info_index = rewrite_cp_ref_in_annotation_data(
2226                               annotations_typeArray, byte_i_ref,
2227                               "class_info_index", THREAD);
2228 
2229       log_debug(redefine, class, annotation)("class_info_index=%d", class_info_index);
2230     } break;
2231 
2232     case '@':
2233       // For the above tag value, value.attr_value is the right union
2234       // field. This is a nested annotation.
2235       if (!rewrite_cp_refs_in_annotation_struct(annotations_typeArray,
2236              byte_i_ref, THREAD)) {
2237         // propagate failure back to caller
2238         return false;
2239       }
2240       break;
2241 
2242     case '[':
2243     {
2244       if ((byte_i_ref + 2) > annotations_typeArray->length()) {
2245         // not enough room for a num_values field
2246         log_debug(redefine, class, annotation)("length() is too small for a num_values field");
2247         return false;
2248       }
2249 
2250       // For the above tag value, value.array_value is the right union
2251       // field. This is an array of nested element_value.
2252       u2 num_values = Bytes::get_Java_u2((address)
2253                         annotations_typeArray->adr_at(byte_i_ref));
2254       byte_i_ref += 2;
2255       log_debug(redefine, class, annotation)("num_values=%d", num_values);
2256 
2257       int calc_num_values = 0;
2258       for (; calc_num_values < num_values; calc_num_values++) {
2259         if (!rewrite_cp_refs_in_element_value(
2260                annotations_typeArray, byte_i_ref, THREAD)) {
2261           log_debug(redefine, class, annotation)("bad nested element_value at %d", calc_num_values);
2262           // propagate failure back to caller
2263           return false;
2264         }
2265       }
2266       assert(num_values == calc_num_values, "sanity check");
2267     } break;
2268 
2269     default:
2270       log_debug(redefine, class, annotation)("bad tag=0x%x", tag);
2271       return false;
2272   } // end decode tag field
2273 
2274   return true;
2275 } // end rewrite_cp_refs_in_element_value()
2276 
2277 
2278 // Rewrite constant pool references in a fields_annotations field.
2279 bool VM_RedefineClasses::rewrite_cp_refs_in_fields_annotations(
2280        InstanceKlass* scratch_class, TRAPS) {
2281 
2282   Array<AnnotationArray*>* fields_annotations = scratch_class->fields_annotations();
2283 
2284   if (fields_annotations == NULL || fields_annotations->length() == 0) {
2285     // no fields_annotations so nothing to do
2286     return true;
2287   }
2288 
2289   log_debug(redefine, class, annotation)("fields_annotations length=%d", fields_annotations->length());
2290 
2291   for (int i = 0; i < fields_annotations->length(); i++) {
2292     AnnotationArray* field_annotations = fields_annotations->at(i);
2293     if (field_annotations == NULL || field_annotations->length() == 0) {
2294       // this field does not have any annotations so skip it
2295       continue;
2296     }
2297 
2298     int byte_i = 0;  // byte index into field_annotations
2299     if (!rewrite_cp_refs_in_annotations_typeArray(field_annotations, byte_i,
2300            THREAD)) {
2301       log_debug(redefine, class, annotation)("bad field_annotations at %d", i);
2302       // propagate failure back to caller
2303       return false;
2304     }
2305   }
2306 
2307   return true;
2308 } // end rewrite_cp_refs_in_fields_annotations()
2309 
2310 
2311 // Rewrite constant pool references in a methods_annotations field.
2312 bool VM_RedefineClasses::rewrite_cp_refs_in_methods_annotations(
2313        InstanceKlass* scratch_class, TRAPS) {
2314 
2315   for (int i = 0; i < scratch_class->methods()->length(); i++) {
2316     Method* m = scratch_class->methods()->at(i);
2317     AnnotationArray* method_annotations = m->constMethod()->method_annotations();
2318 
2319     if (method_annotations == NULL || method_annotations->length() == 0) {
2320       // this method does not have any annotations so skip it
2321       continue;
2322     }
2323 
2324     int byte_i = 0;  // byte index into method_annotations
2325     if (!rewrite_cp_refs_in_annotations_typeArray(method_annotations, byte_i,
2326            THREAD)) {
2327       log_debug(redefine, class, annotation)("bad method_annotations at %d", i);
2328       // propagate failure back to caller
2329       return false;
2330     }
2331   }
2332 
2333   return true;
2334 } // end rewrite_cp_refs_in_methods_annotations()
2335 
2336 
2337 // Rewrite constant pool references in a methods_parameter_annotations
2338 // field. This "structure" is adapted from the
2339 // RuntimeVisibleParameterAnnotations_attribute described in section
2340 // 4.8.17 of the 2nd-edition of the VM spec:
2341 //
2342 // methods_parameter_annotations_typeArray {
2343 //   u1 num_parameters;
2344 //   {
2345 //     u2 num_annotations;
2346 //     annotation annotations[num_annotations];
2347 //   } parameter_annotations[num_parameters];
2348 // }
2349 //
2350 bool VM_RedefineClasses::rewrite_cp_refs_in_methods_parameter_annotations(
2351        InstanceKlass* scratch_class, TRAPS) {
2352 
2353   for (int i = 0; i < scratch_class->methods()->length(); i++) {
2354     Method* m = scratch_class->methods()->at(i);
2355     AnnotationArray* method_parameter_annotations = m->constMethod()->parameter_annotations();
2356     if (method_parameter_annotations == NULL
2357         || method_parameter_annotations->length() == 0) {
2358       // this method does not have any parameter annotations so skip it
2359       continue;
2360     }
2361 
2362     if (method_parameter_annotations->length() < 1) {
2363       // not enough room for a num_parameters field
2364       log_debug(redefine, class, annotation)("length() is too small for a num_parameters field at %d", i);
2365       return false;
2366     }
2367 
2368     int byte_i = 0;  // byte index into method_parameter_annotations
2369 
2370     u1 num_parameters = method_parameter_annotations->at(byte_i);
2371     byte_i++;
2372 
2373     log_debug(redefine, class, annotation)("num_parameters=%d", num_parameters);
2374 
2375     int calc_num_parameters = 0;
2376     for (; calc_num_parameters < num_parameters; calc_num_parameters++) {
2377       if (!rewrite_cp_refs_in_annotations_typeArray(
2378              method_parameter_annotations, byte_i, THREAD)) {
2379         log_debug(redefine, class, annotation)("bad method_parameter_annotations at %d", calc_num_parameters);
2380         // propagate failure back to caller
2381         return false;
2382       }
2383     }
2384     assert(num_parameters == calc_num_parameters, "sanity check");
2385   }
2386 
2387   return true;
2388 } // end rewrite_cp_refs_in_methods_parameter_annotations()
2389 
2390 
2391 // Rewrite constant pool references in a methods_default_annotations
2392 // field. This "structure" is adapted from the AnnotationDefault_attribute
2393 // that is described in section 4.8.19 of the 2nd-edition of the VM spec:
2394 //
2395 // methods_default_annotations_typeArray {
2396 //   element_value default_value;
2397 // }
2398 //
2399 bool VM_RedefineClasses::rewrite_cp_refs_in_methods_default_annotations(
2400        InstanceKlass* scratch_class, TRAPS) {
2401 
2402   for (int i = 0; i < scratch_class->methods()->length(); i++) {
2403     Method* m = scratch_class->methods()->at(i);
2404     AnnotationArray* method_default_annotations = m->constMethod()->default_annotations();
2405     if (method_default_annotations == NULL
2406         || method_default_annotations->length() == 0) {
2407       // this method does not have any default annotations so skip it
2408       continue;
2409     }
2410 
2411     int byte_i = 0;  // byte index into method_default_annotations
2412 
2413     if (!rewrite_cp_refs_in_element_value(
2414            method_default_annotations, byte_i, THREAD)) {
2415       log_debug(redefine, class, annotation)("bad default element_value at %d", i);
2416       // propagate failure back to caller
2417       return false;
2418     }
2419   }
2420 
2421   return true;
2422 } // end rewrite_cp_refs_in_methods_default_annotations()
2423 
2424 
2425 // Rewrite constant pool references in a class_type_annotations field.
2426 bool VM_RedefineClasses::rewrite_cp_refs_in_class_type_annotations(
2427        InstanceKlass* scratch_class, TRAPS) {
2428 
2429   AnnotationArray* class_type_annotations = scratch_class->class_type_annotations();
2430   if (class_type_annotations == NULL || class_type_annotations->length() == 0) {
2431     // no class_type_annotations so nothing to do
2432     return true;
2433   }
2434 
2435   log_debug(redefine, class, annotation)("class_type_annotations length=%d", class_type_annotations->length());
2436 
2437   int byte_i = 0;  // byte index into class_type_annotations
2438   return rewrite_cp_refs_in_type_annotations_typeArray(class_type_annotations,
2439       byte_i, "ClassFile", THREAD);
2440 } // end rewrite_cp_refs_in_class_type_annotations()
2441 
2442 
2443 // Rewrite constant pool references in a fields_type_annotations field.
2444 bool VM_RedefineClasses::rewrite_cp_refs_in_fields_type_annotations(
2445        InstanceKlass* scratch_class, TRAPS) {
2446 
2447   Array<AnnotationArray*>* fields_type_annotations = scratch_class->fields_type_annotations();
2448   if (fields_type_annotations == NULL || fields_type_annotations->length() == 0) {
2449     // no fields_type_annotations so nothing to do
2450     return true;
2451   }
2452 
2453   log_debug(redefine, class, annotation)("fields_type_annotations length=%d", fields_type_annotations->length());
2454 
2455   for (int i = 0; i < fields_type_annotations->length(); i++) {
2456     AnnotationArray* field_type_annotations = fields_type_annotations->at(i);
2457     if (field_type_annotations == NULL || field_type_annotations->length() == 0) {
2458       // this field does not have any annotations so skip it
2459       continue;
2460     }
2461 
2462     int byte_i = 0;  // byte index into field_type_annotations
2463     if (!rewrite_cp_refs_in_type_annotations_typeArray(field_type_annotations,
2464            byte_i, "field_info", THREAD)) {
2465       log_debug(redefine, class, annotation)("bad field_type_annotations at %d", i);
2466       // propagate failure back to caller
2467       return false;
2468     }
2469   }
2470 
2471   return true;
2472 } // end rewrite_cp_refs_in_fields_type_annotations()
2473 
2474 
2475 // Rewrite constant pool references in a methods_type_annotations field.
2476 bool VM_RedefineClasses::rewrite_cp_refs_in_methods_type_annotations(
2477        InstanceKlass* scratch_class, TRAPS) {
2478 
2479   for (int i = 0; i < scratch_class->methods()->length(); i++) {
2480     Method* m = scratch_class->methods()->at(i);
2481     AnnotationArray* method_type_annotations = m->constMethod()->type_annotations();
2482 
2483     if (method_type_annotations == NULL || method_type_annotations->length() == 0) {
2484       // this method does not have any annotations so skip it
2485       continue;
2486     }
2487 
2488     log_debug(redefine, class, annotation)("methods type_annotations length=%d", method_type_annotations->length());
2489 
2490     int byte_i = 0;  // byte index into method_type_annotations
2491     if (!rewrite_cp_refs_in_type_annotations_typeArray(method_type_annotations,
2492            byte_i, "method_info", THREAD)) {
2493       log_debug(redefine, class, annotation)("bad method_type_annotations at %d", i);
2494       // propagate failure back to caller
2495       return false;
2496     }
2497   }
2498 
2499   return true;
2500 } // end rewrite_cp_refs_in_methods_type_annotations()
2501 
2502 
2503 // Rewrite constant pool references in a type_annotations
2504 // field. This "structure" is adapted from the
2505 // RuntimeVisibleTypeAnnotations_attribute described in
2506 // section 4.7.20 of the Java SE 8 Edition of the VM spec:
2507 //
2508 // type_annotations_typeArray {
2509 //   u2              num_annotations;
2510 //   type_annotation annotations[num_annotations];
2511 // }
2512 //
2513 bool VM_RedefineClasses::rewrite_cp_refs_in_type_annotations_typeArray(
2514        AnnotationArray* type_annotations_typeArray, int &byte_i_ref,
2515        const char * location_mesg, TRAPS) {
2516 
2517   if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
2518     // not enough room for num_annotations field
2519     log_debug(redefine, class, annotation)("length() is too small for num_annotations field");
2520     return false;
2521   }
2522 
2523   u2 num_annotations = Bytes::get_Java_u2((address)
2524                          type_annotations_typeArray->adr_at(byte_i_ref));
2525   byte_i_ref += 2;
2526 
2527   log_debug(redefine, class, annotation)("num_type_annotations=%d", num_annotations);
2528 
2529   int calc_num_annotations = 0;
2530   for (; calc_num_annotations < num_annotations; calc_num_annotations++) {
2531     if (!rewrite_cp_refs_in_type_annotation_struct(type_annotations_typeArray,
2532            byte_i_ref, location_mesg, THREAD)) {
2533       log_debug(redefine, class, annotation)("bad type_annotation_struct at %d", calc_num_annotations);
2534       // propagate failure back to caller
2535       return false;
2536     }
2537   }
2538   assert(num_annotations == calc_num_annotations, "sanity check");
2539 
2540   if (byte_i_ref != type_annotations_typeArray->length()) {
2541     log_debug(redefine, class, annotation)
2542       ("read wrong amount of bytes at end of processing type_annotations_typeArray (%d of %d bytes were read)",
2543        byte_i_ref, type_annotations_typeArray->length());
2544     return false;
2545   }
2546 
2547   return true;
2548 } // end rewrite_cp_refs_in_type_annotations_typeArray()
2549 
2550 
2551 // Rewrite constant pool references in a type_annotation
2552 // field. This "structure" is adapted from the
2553 // RuntimeVisibleTypeAnnotations_attribute described in
2554 // section 4.7.20 of the Java SE 8 Edition of the VM spec:
2555 //
2556 // type_annotation {
2557 //   u1 target_type;
2558 //   union {
2559 //     type_parameter_target;
2560 //     supertype_target;
2561 //     type_parameter_bound_target;
2562 //     empty_target;
2563 //     method_formal_parameter_target;
2564 //     throws_target;
2565 //     localvar_target;
2566 //     catch_target;
2567 //     offset_target;
2568 //     type_argument_target;
2569 //   } target_info;
2570 //   type_path target_path;
2571 //   annotation anno;
2572 // }
2573 //
2574 bool VM_RedefineClasses::rewrite_cp_refs_in_type_annotation_struct(
2575        AnnotationArray* type_annotations_typeArray, int &byte_i_ref,
2576        const char * location_mesg, TRAPS) {
2577 
2578   if (!skip_type_annotation_target(type_annotations_typeArray,
2579          byte_i_ref, location_mesg, THREAD)) {
2580     return false;
2581   }
2582 
2583   if (!skip_type_annotation_type_path(type_annotations_typeArray,
2584          byte_i_ref, THREAD)) {
2585     return false;
2586   }
2587 
2588   if (!rewrite_cp_refs_in_annotation_struct(type_annotations_typeArray,
2589          byte_i_ref, THREAD)) {
2590     return false;
2591   }
2592 
2593   return true;
2594 } // end rewrite_cp_refs_in_type_annotation_struct()
2595 
2596 
2597 // Read, verify and skip over the target_type and target_info part
2598 // so that rewriting can continue in the later parts of the struct.
2599 //
2600 // u1 target_type;
2601 // union {
2602 //   type_parameter_target;
2603 //   supertype_target;
2604 //   type_parameter_bound_target;
2605 //   empty_target;
2606 //   method_formal_parameter_target;
2607 //   throws_target;
2608 //   localvar_target;
2609 //   catch_target;
2610 //   offset_target;
2611 //   type_argument_target;
2612 // } target_info;
2613 //
2614 bool VM_RedefineClasses::skip_type_annotation_target(
2615        AnnotationArray* type_annotations_typeArray, int &byte_i_ref,
2616        const char * location_mesg, TRAPS) {
2617 
2618   if ((byte_i_ref + 1) > type_annotations_typeArray->length()) {
2619     // not enough room for a target_type let alone the rest of a type_annotation
2620     log_debug(redefine, class, annotation)("length() is too small for a target_type");
2621     return false;
2622   }
2623 
2624   u1 target_type = type_annotations_typeArray->at(byte_i_ref);
2625   byte_i_ref += 1;
2626   log_debug(redefine, class, annotation)("target_type=0x%.2x", target_type);
2627   log_debug(redefine, class, annotation)("location=%s", location_mesg);
2628 
2629   // Skip over target_info
2630   switch (target_type) {
2631     case 0x00:
2632     // kind: type parameter declaration of generic class or interface
2633     // location: ClassFile
2634     case 0x01:
2635     // kind: type parameter declaration of generic method or constructor
2636     // location: method_info
2637 
2638     {
2639       // struct:
2640       // type_parameter_target {
2641       //   u1 type_parameter_index;
2642       // }
2643       //
2644       if ((byte_i_ref + 1) > type_annotations_typeArray->length()) {
2645         log_debug(redefine, class, annotation)("length() is too small for a type_parameter_target");
2646         return false;
2647       }
2648 
2649       u1 type_parameter_index = type_annotations_typeArray->at(byte_i_ref);
2650       byte_i_ref += 1;
2651 
2652       log_debug(redefine, class, annotation)("type_parameter_target: type_parameter_index=%d", type_parameter_index);
2653     } break;
2654 
2655     case 0x10:
2656     // kind: type in extends clause of class or interface declaration
2657     //       (including the direct superclass of an unsafe anonymous class declaration),
2658     //       or in implements clause of interface declaration
2659     // location: ClassFile
2660 
2661     {
2662       // struct:
2663       // supertype_target {
2664       //   u2 supertype_index;
2665       // }
2666       //
2667       if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
2668         log_debug(redefine, class, annotation)("length() is too small for a supertype_target");
2669         return false;
2670       }
2671 
2672       u2 supertype_index = Bytes::get_Java_u2((address)
2673                              type_annotations_typeArray->adr_at(byte_i_ref));
2674       byte_i_ref += 2;
2675 
2676       log_debug(redefine, class, annotation)("supertype_target: supertype_index=%d", supertype_index);
2677     } break;
2678 
2679     case 0x11:
2680     // kind: type in bound of type parameter declaration of generic class or interface
2681     // location: ClassFile
2682     case 0x12:
2683     // kind: type in bound of type parameter declaration of generic method or constructor
2684     // location: method_info
2685 
2686     {
2687       // struct:
2688       // type_parameter_bound_target {
2689       //   u1 type_parameter_index;
2690       //   u1 bound_index;
2691       // }
2692       //
2693       if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
2694         log_debug(redefine, class, annotation)("length() is too small for a type_parameter_bound_target");
2695         return false;
2696       }
2697 
2698       u1 type_parameter_index = type_annotations_typeArray->at(byte_i_ref);
2699       byte_i_ref += 1;
2700       u1 bound_index = type_annotations_typeArray->at(byte_i_ref);
2701       byte_i_ref += 1;
2702 
2703       log_debug(redefine, class, annotation)
2704         ("type_parameter_bound_target: type_parameter_index=%d, bound_index=%d", type_parameter_index, bound_index);
2705     } break;
2706 
2707     case 0x13:
2708     // kind: type in field declaration
2709     // location: field_info
2710     case 0x14:
2711     // kind: return type of method, or type of newly constructed object
2712     // location: method_info
2713     case 0x15:
2714     // kind: receiver type of method or constructor
2715     // location: method_info
2716 
2717     {
2718       // struct:
2719       // empty_target {
2720       // }
2721       //
2722       log_debug(redefine, class, annotation)("empty_target");
2723     } break;
2724 
2725     case 0x16:
2726     // kind: type in formal parameter declaration of method, constructor, or lambda expression
2727     // location: method_info
2728 
2729     {
2730       // struct:
2731       // formal_parameter_target {
2732       //   u1 formal_parameter_index;
2733       // }
2734       //
2735       if ((byte_i_ref + 1) > type_annotations_typeArray->length()) {
2736         log_debug(redefine, class, annotation)("length() is too small for a formal_parameter_target");
2737         return false;
2738       }
2739 
2740       u1 formal_parameter_index = type_annotations_typeArray->at(byte_i_ref);
2741       byte_i_ref += 1;
2742 
2743       log_debug(redefine, class, annotation)
2744         ("formal_parameter_target: formal_parameter_index=%d", formal_parameter_index);
2745     } break;
2746 
2747     case 0x17:
2748     // kind: type in throws clause of method or constructor
2749     // location: method_info
2750 
2751     {
2752       // struct:
2753       // throws_target {
2754       //   u2 throws_type_index
2755       // }
2756       //
2757       if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
2758         log_debug(redefine, class, annotation)("length() is too small for a throws_target");
2759         return false;
2760       }
2761 
2762       u2 throws_type_index = Bytes::get_Java_u2((address)
2763                                type_annotations_typeArray->adr_at(byte_i_ref));
2764       byte_i_ref += 2;
2765 
2766       log_debug(redefine, class, annotation)("throws_target: throws_type_index=%d", throws_type_index);
2767     } break;
2768 
2769     case 0x40:
2770     // kind: type in local variable declaration
2771     // location: Code
2772     case 0x41:
2773     // kind: type in resource variable declaration
2774     // location: Code
2775 
2776     {
2777       // struct:
2778       // localvar_target {
2779       //   u2 table_length;
2780       //   struct {
2781       //     u2 start_pc;
2782       //     u2 length;
2783       //     u2 index;
2784       //   } table[table_length];
2785       // }
2786       //
2787       if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
2788         // not enough room for a table_length let alone the rest of a localvar_target
2789         log_debug(redefine, class, annotation)("length() is too small for a localvar_target table_length");
2790         return false;
2791       }
2792 
2793       u2 table_length = Bytes::get_Java_u2((address)
2794                           type_annotations_typeArray->adr_at(byte_i_ref));
2795       byte_i_ref += 2;
2796 
2797       log_debug(redefine, class, annotation)("localvar_target: table_length=%d", table_length);
2798 
2799       int table_struct_size = 2 + 2 + 2; // 3 u2 variables per table entry
2800       int table_size = table_length * table_struct_size;
2801 
2802       if ((byte_i_ref + table_size) > type_annotations_typeArray->length()) {
2803         // not enough room for a table
2804         log_debug(redefine, class, annotation)("length() is too small for a table array of length %d", table_length);
2805         return false;
2806       }
2807 
2808       // Skip over table
2809       byte_i_ref += table_size;
2810     } break;
2811 
2812     case 0x42:
2813     // kind: type in exception parameter declaration
2814     // location: Code
2815 
2816     {
2817       // struct:
2818       // catch_target {
2819       //   u2 exception_table_index;
2820       // }
2821       //
2822       if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
2823         log_debug(redefine, class, annotation)("length() is too small for a catch_target");
2824         return false;
2825       }
2826 
2827       u2 exception_table_index = Bytes::get_Java_u2((address)
2828                                    type_annotations_typeArray->adr_at(byte_i_ref));
2829       byte_i_ref += 2;
2830 
2831       log_debug(redefine, class, annotation)("catch_target: exception_table_index=%d", exception_table_index);
2832     } break;
2833 
2834     case 0x43:
2835     // kind: type in instanceof expression
2836     // location: Code
2837     case 0x44:
2838     // kind: type in new expression
2839     // location: Code
2840     case 0x45:
2841     // kind: type in method reference expression using ::new
2842     // location: Code
2843     case 0x46:
2844     // kind: type in method reference expression using ::Identifier
2845     // location: Code
2846 
2847     {
2848       // struct:
2849       // offset_target {
2850       //   u2 offset;
2851       // }
2852       //
2853       if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
2854         log_debug(redefine, class, annotation)("length() is too small for a offset_target");
2855         return false;
2856       }
2857 
2858       u2 offset = Bytes::get_Java_u2((address)
2859                     type_annotations_typeArray->adr_at(byte_i_ref));
2860       byte_i_ref += 2;
2861 
2862       log_debug(redefine, class, annotation)("offset_target: offset=%d", offset);
2863     } break;
2864 
2865     case 0x47:
2866     // kind: type in cast expression
2867     // location: Code
2868     case 0x48:
2869     // kind: type argument for generic constructor in new expression or
2870     //       explicit constructor invocation statement
2871     // location: Code
2872     case 0x49:
2873     // kind: type argument for generic method in method invocation expression
2874     // location: Code
2875     case 0x4A:
2876     // kind: type argument for generic constructor in method reference expression using ::new
2877     // location: Code
2878     case 0x4B:
2879     // kind: type argument for generic method in method reference expression using ::Identifier
2880     // location: Code
2881 
2882     {
2883       // struct:
2884       // type_argument_target {
2885       //   u2 offset;
2886       //   u1 type_argument_index;
2887       // }
2888       //
2889       if ((byte_i_ref + 3) > type_annotations_typeArray->length()) {
2890         log_debug(redefine, class, annotation)("length() is too small for a type_argument_target");
2891         return false;
2892       }
2893 
2894       u2 offset = Bytes::get_Java_u2((address)
2895                     type_annotations_typeArray->adr_at(byte_i_ref));
2896       byte_i_ref += 2;
2897       u1 type_argument_index = type_annotations_typeArray->at(byte_i_ref);
2898       byte_i_ref += 1;
2899 
2900       log_debug(redefine, class, annotation)
2901         ("type_argument_target: offset=%d, type_argument_index=%d", offset, type_argument_index);
2902     } break;
2903 
2904     default:
2905       log_debug(redefine, class, annotation)("unknown target_type");
2906 #ifdef ASSERT
2907       ShouldNotReachHere();
2908 #endif
2909       return false;
2910   }
2911 
2912   return true;
2913 } // end skip_type_annotation_target()
2914 
2915 
2916 // Read, verify and skip over the type_path part so that rewriting
2917 // can continue in the later parts of the struct.
2918 //
2919 // type_path {
2920 //   u1 path_length;
2921 //   {
2922 //     u1 type_path_kind;
2923 //     u1 type_argument_index;
2924 //   } path[path_length];
2925 // }
2926 //
2927 bool VM_RedefineClasses::skip_type_annotation_type_path(
2928        AnnotationArray* type_annotations_typeArray, int &byte_i_ref, TRAPS) {
2929 
2930   if ((byte_i_ref + 1) > type_annotations_typeArray->length()) {
2931     // not enough room for a path_length let alone the rest of the type_path
2932     log_debug(redefine, class, annotation)("length() is too small for a type_path");
2933     return false;
2934   }
2935 
2936   u1 path_length = type_annotations_typeArray->at(byte_i_ref);
2937   byte_i_ref += 1;
2938 
2939   log_debug(redefine, class, annotation)("type_path: path_length=%d", path_length);
2940 
2941   int calc_path_length = 0;
2942   for (; calc_path_length < path_length; calc_path_length++) {
2943     if ((byte_i_ref + 1 + 1) > type_annotations_typeArray->length()) {
2944       // not enough room for a path
2945       log_debug(redefine, class, annotation)
2946         ("length() is too small for path entry %d of %d", calc_path_length, path_length);
2947       return false;
2948     }
2949 
2950     u1 type_path_kind = type_annotations_typeArray->at(byte_i_ref);
2951     byte_i_ref += 1;
2952     u1 type_argument_index = type_annotations_typeArray->at(byte_i_ref);
2953     byte_i_ref += 1;
2954 
2955     log_debug(redefine, class, annotation)
2956       ("type_path: path[%d]: type_path_kind=%d, type_argument_index=%d",
2957        calc_path_length, type_path_kind, type_argument_index);
2958 
2959     if (type_path_kind > 3 || (type_path_kind != 3 && type_argument_index != 0)) {
2960       // not enough room for a path
2961       log_debug(redefine, class, annotation)("inconsistent type_path values");
2962       return false;
2963     }
2964   }
2965   assert(path_length == calc_path_length, "sanity check");
2966 
2967   return true;
2968 } // end skip_type_annotation_type_path()
2969 
2970 
2971 // Rewrite constant pool references in the method's stackmap table.
2972 // These "structures" are adapted from the StackMapTable_attribute that
2973 // is described in section 4.8.4 of the 6.0 version of the VM spec
2974 // (dated 2005.10.26):
2975 // file:///net/quincunx.sfbay/export/gbracha/ClassFile-Java6.pdf
2976 //
2977 // stack_map {
2978 //   u2 number_of_entries;
2979 //   stack_map_frame entries[number_of_entries];
2980 // }
2981 //
2982 void VM_RedefineClasses::rewrite_cp_refs_in_stack_map_table(
2983        const methodHandle& method, TRAPS) {
2984 
2985   if (!method->has_stackmap_table()) {
2986     return;
2987   }
2988 
2989   AnnotationArray* stackmap_data = method->stackmap_data();
2990   address stackmap_p = (address)stackmap_data->adr_at(0);
2991   address stackmap_end = stackmap_p + stackmap_data->length();
2992 
2993   assert(stackmap_p + 2 <= stackmap_end, "no room for number_of_entries");
2994   u2 number_of_entries = Bytes::get_Java_u2(stackmap_p);
2995   stackmap_p += 2;
2996 
2997   log_debug(redefine, class, stackmap)("number_of_entries=%u", number_of_entries);
2998 
2999   // walk through each stack_map_frame
3000   u2 calc_number_of_entries = 0;
3001   for (; calc_number_of_entries < number_of_entries; calc_number_of_entries++) {
3002     // The stack_map_frame structure is a u1 frame_type followed by
3003     // 0 or more bytes of data:
3004     //
3005     // union stack_map_frame {
3006     //   same_frame;
3007     //   same_locals_1_stack_item_frame;
3008     //   same_locals_1_stack_item_frame_extended;
3009     //   chop_frame;
3010     //   same_frame_extended;
3011     //   append_frame;
3012     //   full_frame;
3013     // }
3014 
3015     assert(stackmap_p + 1 <= stackmap_end, "no room for frame_type");
3016     u1 frame_type = *stackmap_p;
3017     stackmap_p++;
3018 
3019     // same_frame {
3020     //   u1 frame_type = SAME; /* 0-63 */
3021     // }
3022     if (frame_type <= 63) {
3023       // nothing more to do for same_frame
3024     }
3025 
3026     // same_locals_1_stack_item_frame {
3027     //   u1 frame_type = SAME_LOCALS_1_STACK_ITEM; /* 64-127 */
3028     //   verification_type_info stack[1];
3029     // }
3030     else if (frame_type >= 64 && frame_type <= 127) {
3031       rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
3032         calc_number_of_entries, frame_type, THREAD);
3033     }
3034 
3035     // reserved for future use
3036     else if (frame_type >= 128 && frame_type <= 246) {
3037       // nothing more to do for reserved frame_types
3038     }
3039 
3040     // same_locals_1_stack_item_frame_extended {
3041     //   u1 frame_type = SAME_LOCALS_1_STACK_ITEM_EXTENDED; /* 247 */
3042     //   u2 offset_delta;
3043     //   verification_type_info stack[1];
3044     // }
3045     else if (frame_type == 247) {
3046       stackmap_p += 2;
3047       rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
3048         calc_number_of_entries, frame_type, THREAD);
3049     }
3050 
3051     // chop_frame {
3052     //   u1 frame_type = CHOP; /* 248-250 */
3053     //   u2 offset_delta;
3054     // }
3055     else if (frame_type >= 248 && frame_type <= 250) {
3056       stackmap_p += 2;
3057     }
3058 
3059     // same_frame_extended {
3060     //   u1 frame_type = SAME_FRAME_EXTENDED; /* 251*/
3061     //   u2 offset_delta;
3062     // }
3063     else if (frame_type == 251) {
3064       stackmap_p += 2;
3065     }
3066 
3067     // append_frame {
3068     //   u1 frame_type = APPEND; /* 252-254 */
3069     //   u2 offset_delta;
3070     //   verification_type_info locals[frame_type - 251];
3071     // }
3072     else if (frame_type >= 252 && frame_type <= 254) {
3073       assert(stackmap_p + 2 <= stackmap_end,
3074         "no room for offset_delta");
3075       stackmap_p += 2;
3076       u1 len = frame_type - 251;
3077       for (u1 i = 0; i < len; i++) {
3078         rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
3079           calc_number_of_entries, frame_type, THREAD);
3080       }
3081     }
3082 
3083     // full_frame {
3084     //   u1 frame_type = FULL_FRAME; /* 255 */
3085     //   u2 offset_delta;
3086     //   u2 number_of_locals;
3087     //   verification_type_info locals[number_of_locals];
3088     //   u2 number_of_stack_items;
3089     //   verification_type_info stack[number_of_stack_items];
3090     // }
3091     else if (frame_type == 255) {
3092       assert(stackmap_p + 2 + 2 <= stackmap_end,
3093         "no room for smallest full_frame");
3094       stackmap_p += 2;
3095 
3096       u2 number_of_locals = Bytes::get_Java_u2(stackmap_p);
3097       stackmap_p += 2;
3098 
3099       for (u2 locals_i = 0; locals_i < number_of_locals; locals_i++) {
3100         rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
3101           calc_number_of_entries, frame_type, THREAD);
3102       }
3103 
3104       // Use the largest size for the number_of_stack_items, but only get
3105       // the right number of bytes.
3106       u2 number_of_stack_items = Bytes::get_Java_u2(stackmap_p);
3107       stackmap_p += 2;
3108 
3109       for (u2 stack_i = 0; stack_i < number_of_stack_items; stack_i++) {
3110         rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
3111           calc_number_of_entries, frame_type, THREAD);
3112       }
3113     }
3114   } // end while there is a stack_map_frame
3115   assert(number_of_entries == calc_number_of_entries, "sanity check");
3116 } // end rewrite_cp_refs_in_stack_map_table()
3117 
3118 
3119 // Rewrite constant pool references in the verification type info
3120 // portion of the method's stackmap table. These "structures" are
3121 // adapted from the StackMapTable_attribute that is described in
3122 // section 4.8.4 of the 6.0 version of the VM spec (dated 2005.10.26):
3123 // file:///net/quincunx.sfbay/export/gbracha/ClassFile-Java6.pdf
3124 //
3125 // The verification_type_info structure is a u1 tag followed by 0 or
3126 // more bytes of data:
3127 //
3128 // union verification_type_info {
3129 //   Top_variable_info;
3130 //   Integer_variable_info;
3131 //   Float_variable_info;
3132 //   Long_variable_info;
3133 //   Double_variable_info;
3134 //   Null_variable_info;
3135 //   UninitializedThis_variable_info;
3136 //   Object_variable_info;
3137 //   Uninitialized_variable_info;
3138 // }
3139 //
3140 void VM_RedefineClasses::rewrite_cp_refs_in_verification_type_info(
3141        address& stackmap_p_ref, address stackmap_end, u2 frame_i,
3142        u1 frame_type, TRAPS) {
3143 
3144   assert(stackmap_p_ref + 1 <= stackmap_end, "no room for tag");
3145   u1 tag = *stackmap_p_ref;
3146   stackmap_p_ref++;
3147 
3148   switch (tag) {
3149   // Top_variable_info {
3150   //   u1 tag = ITEM_Top; /* 0 */
3151   // }
3152   // verificationType.hpp has zero as ITEM_Bogus instead of ITEM_Top
3153   case 0:  // fall through
3154 
3155   // Integer_variable_info {
3156   //   u1 tag = ITEM_Integer; /* 1 */
3157   // }
3158   case ITEM_Integer:  // fall through
3159 
3160   // Float_variable_info {
3161   //   u1 tag = ITEM_Float; /* 2 */
3162   // }
3163   case ITEM_Float:  // fall through
3164 
3165   // Double_variable_info {
3166   //   u1 tag = ITEM_Double; /* 3 */
3167   // }
3168   case ITEM_Double:  // fall through
3169 
3170   // Long_variable_info {
3171   //   u1 tag = ITEM_Long; /* 4 */
3172   // }
3173   case ITEM_Long:  // fall through
3174 
3175   // Null_variable_info {
3176   //   u1 tag = ITEM_Null; /* 5 */
3177   // }
3178   case ITEM_Null:  // fall through
3179 
3180   // UninitializedThis_variable_info {
3181   //   u1 tag = ITEM_UninitializedThis; /* 6 */
3182   // }
3183   case ITEM_UninitializedThis:
3184     // nothing more to do for the above tag types
3185     break;
3186 
3187   // Object_variable_info {
3188   //   u1 tag = ITEM_Object; /* 7 */
3189   //   u2 cpool_index;
3190   // }
3191   case ITEM_Object:
3192   {
3193     assert(stackmap_p_ref + 2 <= stackmap_end, "no room for cpool_index");
3194     u2 cpool_index = Bytes::get_Java_u2(stackmap_p_ref);
3195     u2 new_cp_index = find_new_index(cpool_index);
3196     if (new_cp_index != 0) {
3197       log_debug(redefine, class, stackmap)("mapped old cpool_index=%d", cpool_index);
3198       Bytes::put_Java_u2(stackmap_p_ref, new_cp_index);
3199       cpool_index = new_cp_index;
3200     }
3201     stackmap_p_ref += 2;
3202 
3203     log_debug(redefine, class, stackmap)
3204       ("frame_i=%u, frame_type=%u, cpool_index=%d", frame_i, frame_type, cpool_index);
3205   } break;
3206 
3207   // Uninitialized_variable_info {
3208   //   u1 tag = ITEM_Uninitialized; /* 8 */
3209   //   u2 offset;
3210   // }
3211   case ITEM_Uninitialized:
3212     assert(stackmap_p_ref + 2 <= stackmap_end, "no room for offset");
3213     stackmap_p_ref += 2;
3214     break;
3215 
3216   default:
3217     log_debug(redefine, class, stackmap)("frame_i=%u, frame_type=%u, bad tag=0x%x", frame_i, frame_type, tag);
3218     ShouldNotReachHere();
3219     break;
3220   } // end switch (tag)
3221 } // end rewrite_cp_refs_in_verification_type_info()
3222 
3223 
3224 // Change the constant pool associated with klass scratch_class to
3225 // scratch_cp. If shrink is true, then scratch_cp_length elements
3226 // are copied from scratch_cp to a smaller constant pool and the
3227 // smaller constant pool is associated with scratch_class.
3228 void VM_RedefineClasses::set_new_constant_pool(
3229        ClassLoaderData* loader_data,
3230        InstanceKlass* scratch_class, constantPoolHandle scratch_cp,
3231        int scratch_cp_length, TRAPS) {
3232   assert(scratch_cp->length() >= scratch_cp_length, "sanity check");
3233 
3234   // scratch_cp is a merged constant pool and has enough space for a
3235   // worst case merge situation. We want to associate the minimum
3236   // sized constant pool with the klass to save space.
3237   ConstantPool* cp = ConstantPool::allocate(loader_data, scratch_cp_length, CHECK);
3238   constantPoolHandle smaller_cp(THREAD, cp);
3239 
3240   // preserve version() value in the smaller copy
3241   int version = scratch_cp->version();
3242   assert(version != 0, "sanity check");
3243   smaller_cp->set_version(version);
3244 
3245   // attach klass to new constant pool
3246   // reference to the cp holder is needed for copy_operands()
3247   smaller_cp->set_pool_holder(scratch_class);
3248 
3249   scratch_cp->copy_cp_to(1, scratch_cp_length - 1, smaller_cp, 1, THREAD);
3250   if (HAS_PENDING_EXCEPTION) {
3251     // Exception is handled in the caller
3252     loader_data->add_to_deallocate_list(smaller_cp());
3253     return;
3254   }
3255   scratch_cp = smaller_cp;
3256 
3257   // attach new constant pool to klass
3258   scratch_class->set_constants(scratch_cp());
3259   scratch_cp->initialize_unresolved_klasses(loader_data, CHECK);
3260 
3261   int i;  // for portability
3262 
3263   // update each field in klass to use new constant pool indices as needed
3264   for (JavaFieldStream fs(scratch_class); !fs.done(); fs.next()) {
3265     jshort cur_index = fs.name_index();
3266     jshort new_index = find_new_index(cur_index);
3267     if (new_index != 0) {
3268       log_trace(redefine, class, constantpool)("field-name_index change: %d to %d", cur_index, new_index);
3269       fs.set_name_index(new_index);
3270     }
3271     cur_index = fs.signature_index();
3272     new_index = find_new_index(cur_index);
3273     if (new_index != 0) {
3274       log_trace(redefine, class, constantpool)("field-signature_index change: %d to %d", cur_index, new_index);
3275       fs.set_signature_index(new_index);
3276     }
3277     cur_index = fs.initval_index();
3278     new_index = find_new_index(cur_index);
3279     if (new_index != 0) {
3280       log_trace(redefine, class, constantpool)("field-initval_index change: %d to %d", cur_index, new_index);
3281       fs.set_initval_index(new_index);
3282     }
3283     cur_index = fs.generic_signature_index();
3284     new_index = find_new_index(cur_index);
3285     if (new_index != 0) {
3286       log_trace(redefine, class, constantpool)("field-generic_signature change: %d to %d", cur_index, new_index);
3287       fs.set_generic_signature_index(new_index);
3288     }
3289   } // end for each field
3290 
3291   // Update constant pool indices in the inner classes info to use
3292   // new constant indices as needed. The inner classes info is a
3293   // quadruple:
3294   // (inner_class_info, outer_class_info, inner_name, inner_access_flags)
3295   InnerClassesIterator iter(scratch_class);
3296   for (; !iter.done(); iter.next()) {
3297     int cur_index = iter.inner_class_info_index();
3298     if (cur_index == 0) {
3299       continue;  // JVM spec. allows null inner class refs so skip it
3300     }
3301     int new_index = find_new_index(cur_index);
3302     if (new_index != 0) {
3303       log_trace(redefine, class, constantpool)("inner_class_info change: %d to %d", cur_index, new_index);
3304       iter.set_inner_class_info_index(new_index);
3305     }
3306     cur_index = iter.outer_class_info_index();
3307     new_index = find_new_index(cur_index);
3308     if (new_index != 0) {
3309       log_trace(redefine, class, constantpool)("outer_class_info change: %d to %d", cur_index, new_index);
3310       iter.set_outer_class_info_index(new_index);
3311     }
3312     cur_index = iter.inner_name_index();
3313     new_index = find_new_index(cur_index);
3314     if (new_index != 0) {
3315       log_trace(redefine, class, constantpool)("inner_name change: %d to %d", cur_index, new_index);
3316       iter.set_inner_name_index(new_index);
3317     }
3318   } // end for each inner class
3319 
3320   // Attach each method in klass to the new constant pool and update
3321   // to use new constant pool indices as needed:
3322   Array<Method*>* methods = scratch_class->methods();
3323   for (i = methods->length() - 1; i >= 0; i--) {
3324     methodHandle method(THREAD, methods->at(i));
3325     method->set_constants(scratch_cp());
3326 
3327     int new_index = find_new_index(method->name_index());
3328     if (new_index != 0) {
3329       log_trace(redefine, class, constantpool)
3330         ("method-name_index change: %d to %d", method->name_index(), new_index);
3331       method->set_name_index(new_index);
3332     }
3333     new_index = find_new_index(method->signature_index());
3334     if (new_index != 0) {
3335       log_trace(redefine, class, constantpool)
3336         ("method-signature_index change: %d to %d", method->signature_index(), new_index);
3337       method->set_signature_index(new_index);
3338     }
3339     new_index = find_new_index(method->generic_signature_index());
3340     if (new_index != 0) {
3341       log_trace(redefine, class, constantpool)
3342         ("method-generic_signature_index change: %d to %d", method->generic_signature_index(), new_index);
3343       method->set_generic_signature_index(new_index);
3344     }
3345 
3346     // Update constant pool indices in the method's checked exception
3347     // table to use new constant indices as needed.
3348     int cext_length = method->checked_exceptions_length();
3349     if (cext_length > 0) {
3350       CheckedExceptionElement * cext_table =
3351         method->checked_exceptions_start();
3352       for (int j = 0; j < cext_length; j++) {
3353         int cur_index = cext_table[j].class_cp_index;
3354         int new_index = find_new_index(cur_index);
3355         if (new_index != 0) {
3356           log_trace(redefine, class, constantpool)("cext-class_cp_index change: %d to %d", cur_index, new_index);
3357           cext_table[j].class_cp_index = (u2)new_index;
3358         }
3359       } // end for each checked exception table entry
3360     } // end if there are checked exception table entries
3361 
3362     // Update each catch type index in the method's exception table
3363     // to use new constant pool indices as needed. The exception table
3364     // holds quadruple entries of the form:
3365     //   (beg_bci, end_bci, handler_bci, klass_index)
3366 
3367     ExceptionTable ex_table(method());
3368     int ext_length = ex_table.length();
3369 
3370     for (int j = 0; j < ext_length; j ++) {
3371       int cur_index = ex_table.catch_type_index(j);
3372       int new_index = find_new_index(cur_index);
3373       if (new_index != 0) {
3374         log_trace(redefine, class, constantpool)("ext-klass_index change: %d to %d", cur_index, new_index);
3375         ex_table.set_catch_type_index(j, new_index);
3376       }
3377     } // end for each exception table entry
3378 
3379     // Update constant pool indices in the method's local variable
3380     // table to use new constant indices as needed. The local variable
3381     // table hold sextuple entries of the form:
3382     // (start_pc, length, name_index, descriptor_index, signature_index, slot)
3383     int lvt_length = method->localvariable_table_length();
3384     if (lvt_length > 0) {
3385       LocalVariableTableElement * lv_table =
3386         method->localvariable_table_start();
3387       for (int j = 0; j < lvt_length; j++) {
3388         int cur_index = lv_table[j].name_cp_index;
3389         int new_index = find_new_index(cur_index);
3390         if (new_index != 0) {
3391           log_trace(redefine, class, constantpool)("lvt-name_cp_index change: %d to %d", cur_index, new_index);
3392           lv_table[j].name_cp_index = (u2)new_index;
3393         }
3394         cur_index = lv_table[j].descriptor_cp_index;
3395         new_index = find_new_index(cur_index);
3396         if (new_index != 0) {
3397           log_trace(redefine, class, constantpool)("lvt-descriptor_cp_index change: %d to %d", cur_index, new_index);
3398           lv_table[j].descriptor_cp_index = (u2)new_index;
3399         }
3400         cur_index = lv_table[j].signature_cp_index;
3401         new_index = find_new_index(cur_index);
3402         if (new_index != 0) {
3403           log_trace(redefine, class, constantpool)("lvt-signature_cp_index change: %d to %d", cur_index, new_index);
3404           lv_table[j].signature_cp_index = (u2)new_index;
3405         }
3406       } // end for each local variable table entry
3407     } // end if there are local variable table entries
3408 
3409     rewrite_cp_refs_in_stack_map_table(method, THREAD);
3410   } // end for each method
3411 } // end set_new_constant_pool()
3412 
3413 
3414 // Unevolving classes may point to methods of the_class directly
3415 // from their constant pool caches, itables, and/or vtables. We
3416 // use the ClassLoaderDataGraph::classes_do() facility and this helper
3417 // to fix up these pointers.  MethodData also points to old methods and
3418 // must be cleaned.
3419 
3420 // Adjust cpools and vtables closure
3421 void VM_RedefineClasses::AdjustAndCleanMetadata::do_klass(Klass* k) {
3422 
3423   // This is a very busy routine. We don't want too much tracing
3424   // printed out.
3425   bool trace_name_printed = false;
3426 
3427   // If the class being redefined is java.lang.Object, we need to fix all
3428   // array class vtables also
3429   if (k->is_array_klass() && _has_redefined_Object) {
3430     k->vtable().adjust_method_entries(&trace_name_printed);
3431 
3432   } else if (k->is_instance_klass()) {
3433     HandleMark hm(_thread);
3434     InstanceKlass *ik = InstanceKlass::cast(k);
3435 
3436     // Clean MethodData of this class's methods so they don't refer to
3437     // old methods that are no longer running.
3438     Array<Method*>* methods = ik->methods();
3439     int num_methods = methods->length();
3440     for (int index = 0; index < num_methods; ++index) {
3441       if (methods->at(index)->method_data() != NULL) {
3442         methods->at(index)->method_data()->clean_weak_method_links();
3443       }
3444     }
3445 
3446     // HotSpot specific optimization! HotSpot does not currently
3447     // support delegation from the bootstrap class loader to a
3448     // user-defined class loader. This means that if the bootstrap
3449     // class loader is the initiating class loader, then it will also
3450     // be the defining class loader. This also means that classes
3451     // loaded by the bootstrap class loader cannot refer to classes
3452     // loaded by a user-defined class loader. Note: a user-defined
3453     // class loader can delegate to the bootstrap class loader.
3454     //
3455     // If the current class being redefined has a user-defined class
3456     // loader as its defining class loader, then we can skip all
3457     // classes loaded by the bootstrap class loader.
3458     if (!_has_null_class_loader && ik->class_loader() == NULL) {
3459       return;
3460     }
3461 
3462     // Adjust all vtables, default methods and itables, to clean out old methods.
3463     ResourceMark rm(_thread);
3464     if (ik->vtable_length() > 0) {
3465       ik->vtable().adjust_method_entries(&trace_name_printed);
3466       ik->adjust_default_methods(&trace_name_printed);
3467     }
3468 
3469     if (ik->itable_length() > 0) {
3470       ik->itable().adjust_method_entries(&trace_name_printed);
3471     }
3472 
3473     // The constant pools in other classes (other_cp) can refer to
3474     // old methods.  We have to update method information in
3475     // other_cp's cache. If other_cp has a previous version, then we
3476     // have to repeat the process for each previous version. The
3477     // constant pool cache holds the Method*s for non-virtual
3478     // methods and for virtual, final methods.
3479     //
3480     // Special case: if the current class being redefined, then new_cp
3481     // has already been attached to the_class and old_cp has already
3482     // been added as a previous version. The new_cp doesn't have any
3483     // cached references to old methods so it doesn't need to be
3484     // updated. We can simply start with the previous version(s) in
3485     // that case.
3486     constantPoolHandle other_cp;
3487     ConstantPoolCache* cp_cache;
3488 
3489     if (!ik->is_being_redefined()) {
3490       // this klass' constant pool cache may need adjustment
3491       other_cp = constantPoolHandle(ik->constants());
3492       cp_cache = other_cp->cache();
3493       if (cp_cache != NULL) {
3494         cp_cache->adjust_method_entries(&trace_name_printed);
3495       }
3496     }
3497 
3498     // the previous versions' constant pool caches may need adjustment
3499     for (InstanceKlass* pv_node = ik->previous_versions();
3500          pv_node != NULL;
3501          pv_node = pv_node->previous_versions()) {
3502       cp_cache = pv_node->constants()->cache();
3503       if (cp_cache != NULL) {
3504         cp_cache->adjust_method_entries(&trace_name_printed);
3505       }
3506     }
3507   }
3508 }
3509 
3510 void VM_RedefineClasses::update_jmethod_ids() {
3511   for (int j = 0; j < _matching_methods_length; ++j) {
3512     Method* old_method = _matching_old_methods[j];
3513     jmethodID jmid = old_method->find_jmethod_id_or_null();
3514     if (jmid != NULL) {
3515       // There is a jmethodID, change it to point to the new method
3516       methodHandle new_method_h(_matching_new_methods[j]);
3517       Method::change_method_associated_with_jmethod_id(jmid, new_method_h());
3518       assert(Method::resolve_jmethod_id(jmid) == _matching_new_methods[j],
3519              "should be replaced");
3520     }
3521   }
3522   // Update deleted jmethodID
3523   for (int j = 0; j < _deleted_methods_length; ++j) {
3524     Method* old_method = _deleted_methods[j];
3525     jmethodID jmid = old_method->find_jmethod_id_or_null();
3526     if (jmid != NULL) {
3527       // Change the jmethodID to point to NSME.
3528       Method::change_method_associated_with_jmethod_id(jmid, Universe::throw_no_such_method_error());
3529     }
3530   }
3531 }
3532 
3533 int VM_RedefineClasses::check_methods_and_mark_as_obsolete() {
3534   int emcp_method_count = 0;
3535   int obsolete_count = 0;
3536   int old_index = 0;
3537   for (int j = 0; j < _matching_methods_length; ++j, ++old_index) {
3538     Method* old_method = _matching_old_methods[j];
3539     Method* new_method = _matching_new_methods[j];
3540     Method* old_array_method;
3541 
3542     // Maintain an old_index into the _old_methods array by skipping
3543     // deleted methods
3544     while ((old_array_method = _old_methods->at(old_index)) != old_method) {
3545       ++old_index;
3546     }
3547 
3548     if (MethodComparator::methods_EMCP(old_method, new_method)) {
3549       // The EMCP definition from JSR-163 requires the bytecodes to be
3550       // the same with the exception of constant pool indices which may
3551       // differ. However, the constants referred to by those indices
3552       // must be the same.
3553       //
3554       // We use methods_EMCP() for comparison since constant pool
3555       // merging can remove duplicate constant pool entries that were
3556       // present in the old method and removed from the rewritten new
3557       // method. A faster binary comparison function would consider the
3558       // old and new methods to be different when they are actually
3559       // EMCP.
3560       //
3561       // The old and new methods are EMCP and you would think that we
3562       // could get rid of one of them here and now and save some space.
3563       // However, the concept of EMCP only considers the bytecodes and
3564       // the constant pool entries in the comparison. Other things,
3565       // e.g., the line number table (LNT) or the local variable table
3566       // (LVT) don't count in the comparison. So the new (and EMCP)
3567       // method can have a new LNT that we need so we can't just
3568       // overwrite the new method with the old method.
3569       //
3570       // When this routine is called, we have already attached the new
3571       // methods to the_class so the old methods are effectively
3572       // overwritten. However, if an old method is still executing,
3573       // then the old method cannot be collected until sometime after
3574       // the old method call has returned. So the overwriting of old
3575       // methods by new methods will save us space except for those
3576       // (hopefully few) old methods that are still executing.
3577       //
3578       // A method refers to a ConstMethod* and this presents another
3579       // possible avenue to space savings. The ConstMethod* in the
3580       // new method contains possibly new attributes (LNT, LVT, etc).
3581       // At first glance, it seems possible to save space by replacing
3582       // the ConstMethod* in the old method with the ConstMethod*
3583       // from the new method. The old and new methods would share the
3584       // same ConstMethod* and we would save the space occupied by
3585       // the old ConstMethod*. However, the ConstMethod* contains
3586       // a back reference to the containing method. Sharing the
3587       // ConstMethod* between two methods could lead to confusion in
3588       // the code that uses the back reference. This would lead to
3589       // brittle code that could be broken in non-obvious ways now or
3590       // in the future.
3591       //
3592       // Another possibility is to copy the ConstMethod* from the new
3593       // method to the old method and then overwrite the new method with
3594       // the old method. Since the ConstMethod* contains the bytecodes
3595       // for the method embedded in the oop, this option would change
3596       // the bytecodes out from under any threads executing the old
3597       // method and make the thread's bcp invalid. Since EMCP requires
3598       // that the bytecodes be the same modulo constant pool indices, it
3599       // is straight forward to compute the correct new bcp in the new
3600       // ConstMethod* from the old bcp in the old ConstMethod*. The
3601       // time consuming part would be searching all the frames in all
3602       // of the threads to find all of the calls to the old method.
3603       //
3604       // It looks like we will have to live with the limited savings
3605       // that we get from effectively overwriting the old methods
3606       // when the new methods are attached to the_class.
3607 
3608       // Count number of methods that are EMCP.  The method will be marked
3609       // old but not obsolete if it is EMCP.
3610       emcp_method_count++;
3611 
3612       // An EMCP method is _not_ obsolete. An obsolete method has a
3613       // different jmethodID than the current method. An EMCP method
3614       // has the same jmethodID as the current method. Having the
3615       // same jmethodID for all EMCP versions of a method allows for
3616       // a consistent view of the EMCP methods regardless of which
3617       // EMCP method you happen to have in hand. For example, a
3618       // breakpoint set in one EMCP method will work for all EMCP
3619       // versions of the method including the current one.
3620     } else {
3621       // mark obsolete methods as such
3622       old_method->set_is_obsolete();
3623       obsolete_count++;
3624 
3625       // obsolete methods need a unique idnum so they become new entries in
3626       // the jmethodID cache in InstanceKlass
3627       assert(old_method->method_idnum() == new_method->method_idnum(), "must match");
3628       u2 num = InstanceKlass::cast(_the_class)->next_method_idnum();
3629       if (num != ConstMethod::UNSET_IDNUM) {
3630         old_method->set_method_idnum(num);
3631       }
3632 
3633       // With tracing we try not to "yack" too much. The position of
3634       // this trace assumes there are fewer obsolete methods than
3635       // EMCP methods.
3636       if (log_is_enabled(Trace, redefine, class, obsolete, mark)) {
3637         ResourceMark rm;
3638         log_trace(redefine, class, obsolete, mark)
3639           ("mark %s(%s) as obsolete", old_method->name()->as_C_string(), old_method->signature()->as_C_string());
3640       }
3641     }
3642     old_method->set_is_old();
3643   }
3644   for (int i = 0; i < _deleted_methods_length; ++i) {
3645     Method* old_method = _deleted_methods[i];
3646 
3647     assert(!old_method->has_vtable_index(),
3648            "cannot delete methods with vtable entries");;
3649 
3650     // Mark all deleted methods as old, obsolete and deleted
3651     old_method->set_is_deleted();
3652     old_method->set_is_old();
3653     old_method->set_is_obsolete();
3654     ++obsolete_count;
3655     // With tracing we try not to "yack" too much. The position of
3656     // this trace assumes there are fewer obsolete methods than
3657     // EMCP methods.
3658     if (log_is_enabled(Trace, redefine, class, obsolete, mark)) {
3659       ResourceMark rm;
3660       log_trace(redefine, class, obsolete, mark)
3661         ("mark deleted %s(%s) as obsolete", old_method->name()->as_C_string(), old_method->signature()->as_C_string());
3662     }
3663   }
3664   assert((emcp_method_count + obsolete_count) == _old_methods->length(),
3665     "sanity check");
3666   log_trace(redefine, class, obsolete, mark)("EMCP_cnt=%d, obsolete_cnt=%d", emcp_method_count, obsolete_count);
3667   return emcp_method_count;
3668 }
3669 
3670 // This internal class transfers the native function registration from old methods
3671 // to new methods.  It is designed to handle both the simple case of unchanged
3672 // native methods and the complex cases of native method prefixes being added and/or
3673 // removed.
3674 // It expects only to be used during the VM_RedefineClasses op (a safepoint).
3675 //
3676 // This class is used after the new methods have been installed in "the_class".
3677 //
3678 // So, for example, the following must be handled.  Where 'm' is a method and
3679 // a number followed by an underscore is a prefix.
3680 //
3681 //                                      Old Name    New Name
3682 // Simple transfer to new method        m       ->  m
3683 // Add prefix                           m       ->  1_m
3684 // Remove prefix                        1_m     ->  m
3685 // Simultaneous add of prefixes         m       ->  3_2_1_m
3686 // Simultaneous removal of prefixes     3_2_1_m ->  m
3687 // Simultaneous add and remove          1_m     ->  2_m
3688 // Same, caused by prefix removal only  3_2_1_m ->  3_2_m
3689 //
3690 class TransferNativeFunctionRegistration {
3691  private:
3692   InstanceKlass* the_class;
3693   int prefix_count;
3694   char** prefixes;
3695 
3696   // Recursively search the binary tree of possibly prefixed method names.
3697   // Iteration could be used if all agents were well behaved. Full tree walk is
3698   // more resilent to agents not cleaning up intermediate methods.
3699   // Branch at each depth in the binary tree is:
3700   //    (1) without the prefix.
3701   //    (2) with the prefix.
3702   // where 'prefix' is the prefix at that 'depth' (first prefix, second prefix,...)
3703   Method* search_prefix_name_space(int depth, char* name_str, size_t name_len,
3704                                      Symbol* signature) {
3705     TempNewSymbol name_symbol = SymbolTable::probe(name_str, (int)name_len);
3706     if (name_symbol != NULL) {
3707       Method* method = the_class->lookup_method(name_symbol, signature);
3708       if (method != NULL) {
3709         // Even if prefixed, intermediate methods must exist.
3710         if (method->is_native()) {
3711           // Wahoo, we found a (possibly prefixed) version of the method, return it.
3712           return method;
3713         }
3714         if (depth < prefix_count) {
3715           // Try applying further prefixes (other than this one).
3716           method = search_prefix_name_space(depth+1, name_str, name_len, signature);
3717           if (method != NULL) {
3718             return method; // found
3719           }
3720 
3721           // Try adding this prefix to the method name and see if it matches
3722           // another method name.
3723           char* prefix = prefixes[depth];
3724           size_t prefix_len = strlen(prefix);
3725           size_t trial_len = name_len + prefix_len;
3726           char* trial_name_str = NEW_RESOURCE_ARRAY(char, trial_len + 1);
3727           strcpy(trial_name_str, prefix);
3728           strcat(trial_name_str, name_str);
3729           method = search_prefix_name_space(depth+1, trial_name_str, trial_len,
3730                                             signature);
3731           if (method != NULL) {
3732             // If found along this branch, it was prefixed, mark as such
3733             method->set_is_prefixed_native();
3734             return method; // found
3735           }
3736         }
3737       }
3738     }
3739     return NULL;  // This whole branch bore nothing
3740   }
3741 
3742   // Return the method name with old prefixes stripped away.
3743   char* method_name_without_prefixes(Method* method) {
3744     Symbol* name = method->name();
3745     char* name_str = name->as_utf8();
3746 
3747     // Old prefixing may be defunct, strip prefixes, if any.
3748     for (int i = prefix_count-1; i >= 0; i--) {
3749       char* prefix = prefixes[i];
3750       size_t prefix_len = strlen(prefix);
3751       if (strncmp(prefix, name_str, prefix_len) == 0) {
3752         name_str += prefix_len;
3753       }
3754     }
3755     return name_str;
3756   }
3757 
3758   // Strip any prefixes off the old native method, then try to find a
3759   // (possibly prefixed) new native that matches it.
3760   Method* strip_and_search_for_new_native(Method* method) {
3761     ResourceMark rm;
3762     char* name_str = method_name_without_prefixes(method);
3763     return search_prefix_name_space(0, name_str, strlen(name_str),
3764                                     method->signature());
3765   }
3766 
3767  public:
3768 
3769   // Construct a native method transfer processor for this class.
3770   TransferNativeFunctionRegistration(InstanceKlass* _the_class) {
3771     assert(SafepointSynchronize::is_at_safepoint(), "sanity check");
3772 
3773     the_class = _the_class;
3774     prefixes = JvmtiExport::get_all_native_method_prefixes(&prefix_count);
3775   }
3776 
3777   // Attempt to transfer any of the old or deleted methods that are native
3778   void transfer_registrations(Method** old_methods, int methods_length) {
3779     for (int j = 0; j < methods_length; j++) {
3780       Method* old_method = old_methods[j];
3781 
3782       if (old_method->is_native() && old_method->has_native_function()) {
3783         Method* new_method = strip_and_search_for_new_native(old_method);
3784         if (new_method != NULL) {
3785           // Actually set the native function in the new method.
3786           // Redefine does not send events (except CFLH), certainly not this
3787           // behind the scenes re-registration.
3788           new_method->set_native_function(old_method->native_function(),
3789                               !Method::native_bind_event_is_interesting);
3790         }
3791       }
3792     }
3793   }
3794 };
3795 
3796 // Don't lose the association between a native method and its JNI function.
3797 void VM_RedefineClasses::transfer_old_native_function_registrations(InstanceKlass* the_class) {
3798   TransferNativeFunctionRegistration transfer(the_class);
3799   transfer.transfer_registrations(_deleted_methods, _deleted_methods_length);
3800   transfer.transfer_registrations(_matching_old_methods, _matching_methods_length);
3801 }
3802 
3803 // Deoptimize all compiled code that depends on this class.
3804 //
3805 // If the can_redefine_classes capability is obtained in the onload
3806 // phase then the compiler has recorded all dependencies from startup.
3807 // In that case we need only deoptimize and throw away all compiled code
3808 // that depends on the class.
3809 //
3810 // If can_redefine_classes is obtained sometime after the onload
3811 // phase then the dependency information may be incomplete. In that case
3812 // the first call to RedefineClasses causes all compiled code to be
3813 // thrown away. As can_redefine_classes has been obtained then
3814 // all future compilations will record dependencies so second and
3815 // subsequent calls to RedefineClasses need only throw away code
3816 // that depends on the class.
3817 //
3818 
3819 // First step is to walk the code cache for each class redefined and mark
3820 // dependent methods.  Wait until all classes are processed to deoptimize everything.
3821 void VM_RedefineClasses::mark_dependent_code(InstanceKlass* ik) {
3822   assert_locked_or_safepoint(Compile_lock);
3823 
3824   // All dependencies have been recorded from startup or this is a second or
3825   // subsequent use of RedefineClasses
3826   if (JvmtiExport::all_dependencies_are_recorded()) {
3827     CodeCache::mark_for_evol_deoptimization(ik);
3828   }
3829 }
3830 
3831 void VM_RedefineClasses::flush_dependent_code() {
3832   assert(SafepointSynchronize::is_at_safepoint(), "sanity check");
3833 
3834   bool deopt_needed;
3835 
3836   // This is the first redefinition, mark all the nmethods for deoptimization
3837   if (!JvmtiExport::all_dependencies_are_recorded()) {
3838     log_debug(redefine, class, nmethod)("Marked all nmethods for deopt");
3839     CodeCache::mark_all_nmethods_for_evol_deoptimization();
3840     deopt_needed = true;
3841   } else {
3842     int deopt = CodeCache::mark_dependents_for_evol_deoptimization();
3843     log_debug(redefine, class, nmethod)("Marked %d dependent nmethods for deopt", deopt);
3844     deopt_needed = (deopt != 0);
3845   }
3846 
3847   if (deopt_needed) {
3848     CodeCache::flush_evol_dependents();
3849   }
3850 
3851   // From now on we know that the dependency information is complete
3852   JvmtiExport::set_all_dependencies_are_recorded(true);
3853 }
3854 
3855 void VM_RedefineClasses::compute_added_deleted_matching_methods() {
3856   Method* old_method;
3857   Method* new_method;
3858 
3859   _matching_old_methods = NEW_RESOURCE_ARRAY(Method*, _old_methods->length());
3860   _matching_new_methods = NEW_RESOURCE_ARRAY(Method*, _old_methods->length());
3861   _added_methods        = NEW_RESOURCE_ARRAY(Method*, _new_methods->length());
3862   _deleted_methods      = NEW_RESOURCE_ARRAY(Method*, _old_methods->length());
3863 
3864   _matching_methods_length = 0;
3865   _deleted_methods_length  = 0;
3866   _added_methods_length    = 0;
3867 
3868   int nj = 0;
3869   int oj = 0;
3870   while (true) {
3871     if (oj >= _old_methods->length()) {
3872       if (nj >= _new_methods->length()) {
3873         break; // we've looked at everything, done
3874       }
3875       // New method at the end
3876       new_method = _new_methods->at(nj);
3877       _added_methods[_added_methods_length++] = new_method;
3878       ++nj;
3879     } else if (nj >= _new_methods->length()) {
3880       // Old method, at the end, is deleted
3881       old_method = _old_methods->at(oj);
3882       _deleted_methods[_deleted_methods_length++] = old_method;
3883       ++oj;
3884     } else {
3885       old_method = _old_methods->at(oj);
3886       new_method = _new_methods->at(nj);
3887       if (old_method->name() == new_method->name()) {
3888         if (old_method->signature() == new_method->signature()) {
3889           _matching_old_methods[_matching_methods_length  ] = old_method;
3890           _matching_new_methods[_matching_methods_length++] = new_method;
3891           ++nj;
3892           ++oj;
3893         } else {
3894           // added overloaded have already been moved to the end,
3895           // so this is a deleted overloaded method
3896           _deleted_methods[_deleted_methods_length++] = old_method;
3897           ++oj;
3898         }
3899       } else { // names don't match
3900         if (old_method->name()->fast_compare(new_method->name()) > 0) {
3901           // new method
3902           _added_methods[_added_methods_length++] = new_method;
3903           ++nj;
3904         } else {
3905           // deleted method
3906           _deleted_methods[_deleted_methods_length++] = old_method;
3907           ++oj;
3908         }
3909       }
3910     }
3911   }
3912   assert(_matching_methods_length + _deleted_methods_length == _old_methods->length(), "sanity");
3913   assert(_matching_methods_length + _added_methods_length == _new_methods->length(), "sanity");
3914 }
3915 
3916 
3917 void VM_RedefineClasses::swap_annotations(InstanceKlass* the_class,
3918                                           InstanceKlass* scratch_class) {
3919   // Swap annotation fields values
3920   Annotations* old_annotations = the_class->annotations();
3921   the_class->set_annotations(scratch_class->annotations());
3922   scratch_class->set_annotations(old_annotations);
3923 }
3924 
3925 
3926 // Install the redefinition of a class:
3927 //    - house keeping (flushing breakpoints and caches, deoptimizing
3928 //      dependent compiled code)
3929 //    - replacing parts in the_class with parts from scratch_class
3930 //    - adding a weak reference to track the obsolete but interesting
3931 //      parts of the_class
3932 //    - adjusting constant pool caches and vtables in other classes
3933 //      that refer to methods in the_class. These adjustments use the
3934 //      ClassLoaderDataGraph::classes_do() facility which only allows
3935 //      a helper method to be specified. The interesting parameters
3936 //      that we would like to pass to the helper method are saved in
3937 //      static global fields in the VM operation.
3938 void VM_RedefineClasses::redefine_single_class(jclass the_jclass,
3939        InstanceKlass* scratch_class, TRAPS) {
3940 
3941   HandleMark hm(THREAD);   // make sure handles from this call are freed
3942 
3943   if (log_is_enabled(Info, redefine, class, timer)) {
3944     _timer_rsc_phase1.start();
3945   }
3946 
3947   InstanceKlass* the_class = get_ik(the_jclass);
3948 
3949   // Set some flags to control and optimize adjusting method entries
3950   _has_redefined_Object |= the_class == SystemDictionary::Object_klass();
3951   _has_null_class_loader |= the_class->class_loader() == NULL;
3952 
3953   // Remove all breakpoints in methods of this class
3954   JvmtiBreakpoints& jvmti_breakpoints = JvmtiCurrentBreakpoints::get_jvmti_breakpoints();
3955   jvmti_breakpoints.clearall_in_class_at_safepoint(the_class);
3956 
3957   // Mark all compiled code that depends on this class
3958   mark_dependent_code(the_class);
3959 
3960   _old_methods = the_class->methods();
3961   _new_methods = scratch_class->methods();
3962   _the_class = the_class;
3963   compute_added_deleted_matching_methods();
3964   update_jmethod_ids();
3965 
3966   _any_class_has_resolved_methods = the_class->has_resolved_methods() || _any_class_has_resolved_methods;
3967 
3968   // Attach new constant pool to the original klass. The original
3969   // klass still refers to the old constant pool (for now).
3970   scratch_class->constants()->set_pool_holder(the_class);
3971 
3972 #if 0
3973   // In theory, with constant pool merging in place we should be able
3974   // to save space by using the new, merged constant pool in place of
3975   // the old constant pool(s). By "pool(s)" I mean the constant pool in
3976   // the klass version we are replacing now and any constant pool(s) in
3977   // previous versions of klass. Nice theory, doesn't work in practice.
3978   // When this code is enabled, even simple programs throw NullPointer
3979   // exceptions. I'm guessing that this is caused by some constant pool
3980   // cache difference between the new, merged constant pool and the
3981   // constant pool that was just being used by the klass. I'm keeping
3982   // this code around to archive the idea, but the code has to remain
3983   // disabled for now.
3984 
3985   // Attach each old method to the new constant pool. This can be
3986   // done here since we are past the bytecode verification and
3987   // constant pool optimization phases.
3988   for (int i = _old_methods->length() - 1; i >= 0; i--) {
3989     Method* method = _old_methods->at(i);
3990     method->set_constants(scratch_class->constants());
3991   }
3992 
3993   // NOTE: this doesn't work because you can redefine the same class in two
3994   // threads, each getting their own constant pool data appended to the
3995   // original constant pool.  In order for the new methods to work when they
3996   // become old methods, they need to keep their updated copy of the constant pool.
3997 
3998   {
3999     // walk all previous versions of the klass
4000     InstanceKlass *ik = the_class;
4001     PreviousVersionWalker pvw(ik);
4002     do {
4003       ik = pvw.next_previous_version();
4004       if (ik != NULL) {
4005 
4006         // attach previous version of klass to the new constant pool
4007         ik->set_constants(scratch_class->constants());
4008 
4009         // Attach each method in the previous version of klass to the
4010         // new constant pool
4011         Array<Method*>* prev_methods = ik->methods();
4012         for (int i = prev_methods->length() - 1; i >= 0; i--) {
4013           Method* method = prev_methods->at(i);
4014           method->set_constants(scratch_class->constants());
4015         }
4016       }
4017     } while (ik != NULL);
4018   }
4019 #endif
4020 
4021   // Replace methods and constantpool
4022   the_class->set_methods(_new_methods);
4023   scratch_class->set_methods(_old_methods);     // To prevent potential GCing of the old methods,
4024                                           // and to be able to undo operation easily.
4025 
4026   Array<int>* old_ordering = the_class->method_ordering();
4027   the_class->set_method_ordering(scratch_class->method_ordering());
4028   scratch_class->set_method_ordering(old_ordering);
4029 
4030   ConstantPool* old_constants = the_class->constants();
4031   the_class->set_constants(scratch_class->constants());
4032   scratch_class->set_constants(old_constants);  // See the previous comment.
4033 #if 0
4034   // We are swapping the guts of "the new class" with the guts of "the
4035   // class". Since the old constant pool has just been attached to "the
4036   // new class", it seems logical to set the pool holder in the old
4037   // constant pool also. However, doing this will change the observable
4038   // class hierarchy for any old methods that are still executing. A
4039   // method can query the identity of its "holder" and this query uses
4040   // the method's constant pool link to find the holder. The change in
4041   // holding class from "the class" to "the new class" can confuse
4042   // things.
4043   //
4044   // Setting the old constant pool's holder will also cause
4045   // verification done during vtable initialization below to fail.
4046   // During vtable initialization, the vtable's class is verified to be
4047   // a subtype of the method's holder. The vtable's class is "the
4048   // class" and the method's holder is gotten from the constant pool
4049   // link in the method itself. For "the class"'s directly implemented
4050   // methods, the method holder is "the class" itself (as gotten from
4051   // the new constant pool). The check works fine in this case. The
4052   // check also works fine for methods inherited from super classes.
4053   //
4054   // Miranda methods are a little more complicated. A miranda method is
4055   // provided by an interface when the class implementing the interface
4056   // does not provide its own method.  These interfaces are implemented
4057   // internally as an InstanceKlass. These special instanceKlasses
4058   // share the constant pool of the class that "implements" the
4059   // interface. By sharing the constant pool, the method holder of a
4060   // miranda method is the class that "implements" the interface. In a
4061   // non-redefine situation, the subtype check works fine. However, if
4062   // the old constant pool's pool holder is modified, then the check
4063   // fails because there is no class hierarchy relationship between the
4064   // vtable's class and "the new class".
4065 
4066   old_constants->set_pool_holder(scratch_class());
4067 #endif
4068 
4069   // track number of methods that are EMCP for add_previous_version() call below
4070   int emcp_method_count = check_methods_and_mark_as_obsolete();
4071   transfer_old_native_function_registrations(the_class);
4072 
4073   // The class file bytes from before any retransformable agents mucked
4074   // with them was cached on the scratch class, move to the_class.
4075   // Note: we still want to do this if nothing needed caching since it
4076   // should get cleared in the_class too.
4077   if (the_class->get_cached_class_file() == 0) {
4078     // the_class doesn't have a cache yet so copy it
4079     the_class->set_cached_class_file(scratch_class->get_cached_class_file());
4080   }
4081   else if (scratch_class->get_cached_class_file() !=
4082            the_class->get_cached_class_file()) {
4083     // The same class can be present twice in the scratch classes list or there
4084     // are multiple concurrent RetransformClasses calls on different threads.
4085     // In such cases we have to deallocate scratch_class cached_class_file.
4086     os::free(scratch_class->get_cached_class_file());
4087   }
4088 
4089   // NULL out in scratch class to not delete twice.  The class to be redefined
4090   // always owns these bytes.
4091   scratch_class->set_cached_class_file(NULL);
4092 
4093   // Replace inner_classes
4094   Array<u2>* old_inner_classes = the_class->inner_classes();
4095   the_class->set_inner_classes(scratch_class->inner_classes());
4096   scratch_class->set_inner_classes(old_inner_classes);
4097 
4098   // Initialize the vtable and interface table after
4099   // methods have been rewritten
4100   // no exception should happen here since we explicitly
4101   // do not check loader constraints.
4102   // compare_and_normalize_class_versions has already checked:
4103   //  - classloaders unchanged, signatures unchanged
4104   //  - all instanceKlasses for redefined classes reused & contents updated
4105   the_class->vtable().initialize_vtable(false, THREAD);
4106   the_class->itable().initialize_itable(false, THREAD);
4107   assert(!HAS_PENDING_EXCEPTION || (THREAD->pending_exception()->is_a(SystemDictionary::ThreadDeath_klass())), "redefine exception");
4108 
4109   // Leave arrays of jmethodIDs and itable index cache unchanged
4110 
4111   // Copy the "source file name" attribute from new class version
4112   the_class->set_source_file_name_index(
4113     scratch_class->source_file_name_index());
4114 
4115   // Copy the "source debug extension" attribute from new class version
4116   the_class->set_source_debug_extension(
4117     scratch_class->source_debug_extension(),
4118     scratch_class->source_debug_extension() == NULL ? 0 :
4119     (int)strlen(scratch_class->source_debug_extension()));
4120 
4121   // Use of javac -g could be different in the old and the new
4122   if (scratch_class->access_flags().has_localvariable_table() !=
4123       the_class->access_flags().has_localvariable_table()) {
4124 
4125     AccessFlags flags = the_class->access_flags();
4126     if (scratch_class->access_flags().has_localvariable_table()) {
4127       flags.set_has_localvariable_table();
4128     } else {
4129       flags.clear_has_localvariable_table();
4130     }
4131     the_class->set_access_flags(flags);
4132   }
4133 
4134   swap_annotations(the_class, scratch_class);
4135 
4136   // Replace minor version number of class file
4137   u2 old_minor_version = the_class->minor_version();
4138   the_class->set_minor_version(scratch_class->minor_version());
4139   scratch_class->set_minor_version(old_minor_version);
4140 
4141   // Replace major version number of class file
4142   u2 old_major_version = the_class->major_version();
4143   the_class->set_major_version(scratch_class->major_version());
4144   scratch_class->set_major_version(old_major_version);
4145 
4146   // Replace CP indexes for class and name+type of enclosing method
4147   u2 old_class_idx  = the_class->enclosing_method_class_index();
4148   u2 old_method_idx = the_class->enclosing_method_method_index();
4149   the_class->set_enclosing_method_indices(
4150     scratch_class->enclosing_method_class_index(),
4151     scratch_class->enclosing_method_method_index());
4152   scratch_class->set_enclosing_method_indices(old_class_idx, old_method_idx);
4153 
4154   // Replace fingerprint data
4155   the_class->set_has_passed_fingerprint_check(scratch_class->has_passed_fingerprint_check());
4156   the_class->store_fingerprint(scratch_class->get_stored_fingerprint());
4157 
4158   the_class->set_has_been_redefined();
4159 
4160   if (!the_class->should_be_initialized()) {
4161     // Class was already initialized, so AOT has only seen the original version.
4162     // We need to let AOT look at it again.
4163     AOTLoader::load_for_klass(the_class, THREAD);
4164   }
4165 
4166   // keep track of previous versions of this class
4167   the_class->add_previous_version(scratch_class, emcp_method_count);
4168 
4169   _timer_rsc_phase1.stop();
4170   if (log_is_enabled(Info, redefine, class, timer)) {
4171     _timer_rsc_phase2.start();
4172   }
4173 
4174   if (the_class->oop_map_cache() != NULL) {
4175     // Flush references to any obsolete methods from the oop map cache
4176     // so that obsolete methods are not pinned.
4177     the_class->oop_map_cache()->flush_obsolete_entries();
4178   }
4179 
4180   increment_class_counter((InstanceKlass *)the_class, THREAD);
4181   {
4182     ResourceMark rm(THREAD);
4183     // increment the classRedefinedCount field in the_class and in any
4184     // direct and indirect subclasses of the_class
4185     log_info(redefine, class, load)
4186       ("redefined name=%s, count=%d (avail_mem=" UINT64_FORMAT "K)",
4187        the_class->external_name(), java_lang_Class::classRedefinedCount(the_class->java_mirror()), os::available_memory() >> 10);
4188     Events::log_redefinition(THREAD, "redefined class name=%s, count=%d",
4189                              the_class->external_name(),
4190                              java_lang_Class::classRedefinedCount(the_class->java_mirror()));
4191 
4192   }
4193   _timer_rsc_phase2.stop();
4194 } // end redefine_single_class()
4195 
4196 
4197 // Increment the classRedefinedCount field in the specific InstanceKlass
4198 // and in all direct and indirect subclasses.
4199 void VM_RedefineClasses::increment_class_counter(InstanceKlass *ik, TRAPS) {
4200   oop class_mirror = ik->java_mirror();
4201   Klass* class_oop = java_lang_Class::as_Klass(class_mirror);
4202   int new_count = java_lang_Class::classRedefinedCount(class_mirror) + 1;
4203   java_lang_Class::set_classRedefinedCount(class_mirror, new_count);
4204 
4205   if (class_oop != _the_class) {
4206     // _the_class count is printed at end of redefine_single_class()
4207     log_debug(redefine, class, subclass)("updated count in subclass=%s to %d", ik->external_name(), new_count);
4208   }
4209 
4210   for (Klass *subk = ik->subklass(); subk != NULL;
4211        subk = subk->next_sibling()) {
4212     if (subk->is_instance_klass()) {
4213       // Only update instanceKlasses
4214       InstanceKlass *subik = InstanceKlass::cast(subk);
4215       // recursively do subclasses of the current subclass
4216       increment_class_counter(subik, THREAD);
4217     }
4218   }
4219 }
4220 
4221 void VM_RedefineClasses::CheckClass::do_klass(Klass* k) {
4222   bool no_old_methods = true;  // be optimistic
4223 
4224   // Both array and instance classes have vtables.
4225   // a vtable should never contain old or obsolete methods
4226   ResourceMark rm(_thread);
4227   if (k->vtable_length() > 0 &&
4228       !k->vtable().check_no_old_or_obsolete_entries()) {
4229     if (log_is_enabled(Trace, redefine, class, obsolete, metadata)) {
4230       log_trace(redefine, class, obsolete, metadata)
4231         ("klassVtable::check_no_old_or_obsolete_entries failure -- OLD or OBSOLETE method found -- class: %s",
4232          k->signature_name());
4233       k->vtable().dump_vtable();
4234     }
4235     no_old_methods = false;
4236   }
4237 
4238   if (k->is_instance_klass()) {
4239     HandleMark hm(_thread);
4240     InstanceKlass *ik = InstanceKlass::cast(k);
4241 
4242     // an itable should never contain old or obsolete methods
4243     if (ik->itable_length() > 0 &&
4244         !ik->itable().check_no_old_or_obsolete_entries()) {
4245       if (log_is_enabled(Trace, redefine, class, obsolete, metadata)) {
4246         log_trace(redefine, class, obsolete, metadata)
4247           ("klassItable::check_no_old_or_obsolete_entries failure -- OLD or OBSOLETE method found -- class: %s",
4248            ik->signature_name());
4249         ik->itable().dump_itable();
4250       }
4251       no_old_methods = false;
4252     }
4253 
4254     // the constant pool cache should never contain non-deleted old or obsolete methods
4255     if (ik->constants() != NULL &&
4256         ik->constants()->cache() != NULL &&
4257         !ik->constants()->cache()->check_no_old_or_obsolete_entries()) {
4258       if (log_is_enabled(Trace, redefine, class, obsolete, metadata)) {
4259         log_trace(redefine, class, obsolete, metadata)
4260           ("cp-cache::check_no_old_or_obsolete_entries failure -- OLD or OBSOLETE method found -- class: %s",
4261            ik->signature_name());
4262         ik->constants()->cache()->dump_cache();
4263       }
4264       no_old_methods = false;
4265     }
4266   }
4267 
4268   // print and fail guarantee if old methods are found.
4269   if (!no_old_methods) {
4270     if (log_is_enabled(Trace, redefine, class, obsolete, metadata)) {
4271       dump_methods();
4272     } else {
4273       log_trace(redefine, class)("Use the '-Xlog:redefine+class*:' option "
4274         "to see more info about the following guarantee() failure.");
4275     }
4276     guarantee(false, "OLD and/or OBSOLETE method(s) found");
4277   }
4278 }
4279 
4280 
4281 void VM_RedefineClasses::dump_methods() {
4282   int j;
4283   log_trace(redefine, class, dump)("_old_methods --");
4284   for (j = 0; j < _old_methods->length(); ++j) {
4285     LogStreamHandle(Trace, redefine, class, dump) log_stream;
4286     Method* m = _old_methods->at(j);
4287     log_stream.print("%4d  (%5d)  ", j, m->vtable_index());
4288     m->access_flags().print_on(&log_stream);
4289     log_stream.print(" --  ");
4290     m->print_name(&log_stream);
4291     log_stream.cr();
4292   }
4293   log_trace(redefine, class, dump)("_new_methods --");
4294   for (j = 0; j < _new_methods->length(); ++j) {
4295     LogStreamHandle(Trace, redefine, class, dump) log_stream;
4296     Method* m = _new_methods->at(j);
4297     log_stream.print("%4d  (%5d)  ", j, m->vtable_index());
4298     m->access_flags().print_on(&log_stream);
4299     log_stream.print(" --  ");
4300     m->print_name(&log_stream);
4301     log_stream.cr();
4302   }
4303   log_trace(redefine, class, dump)("_matching_methods --");
4304   for (j = 0; j < _matching_methods_length; ++j) {
4305     LogStreamHandle(Trace, redefine, class, dump) log_stream;
4306     Method* m = _matching_old_methods[j];
4307     log_stream.print("%4d  (%5d)  ", j, m->vtable_index());
4308     m->access_flags().print_on(&log_stream);
4309     log_stream.print(" --  ");
4310     m->print_name();
4311     log_stream.cr();
4312 
4313     m = _matching_new_methods[j];
4314     log_stream.print("      (%5d)  ", m->vtable_index());
4315     m->access_flags().print_on(&log_stream);
4316     log_stream.cr();
4317   }
4318   log_trace(redefine, class, dump)("_deleted_methods --");
4319   for (j = 0; j < _deleted_methods_length; ++j) {
4320     LogStreamHandle(Trace, redefine, class, dump) log_stream;
4321     Method* m = _deleted_methods[j];
4322     log_stream.print("%4d  (%5d)  ", j, m->vtable_index());
4323     m->access_flags().print_on(&log_stream);
4324     log_stream.print(" --  ");
4325     m->print_name(&log_stream);
4326     log_stream.cr();
4327   }
4328   log_trace(redefine, class, dump)("_added_methods --");
4329   for (j = 0; j < _added_methods_length; ++j) {
4330     LogStreamHandle(Trace, redefine, class, dump) log_stream;
4331     Method* m = _added_methods[j];
4332     log_stream.print("%4d  (%5d)  ", j, m->vtable_index());
4333     m->access_flags().print_on(&log_stream);
4334     log_stream.print(" --  ");
4335     m->print_name(&log_stream);
4336     log_stream.cr();
4337   }
4338 }
4339 
4340 void VM_RedefineClasses::print_on_error(outputStream* st) const {
4341   VM_Operation::print_on_error(st);
4342   if (_the_class != NULL) {
4343     ResourceMark rm;
4344     st->print_cr(", redefining class %s", _the_class->external_name());
4345   }
4346 }