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   // Disable any dependent concurrent compilations
 236   SystemDictionary::notice_modification();
 237 
 238   // Set flag indicating that some invariants are no longer true.
 239   // See jvmtiExport.hpp for detailed explanation.
 240   JvmtiExport::set_has_redefined_a_class();
 241 
 242   // check_class() is optionally called for product bits, but is
 243   // always called for non-product bits.
 244 #ifdef PRODUCT
 245   if (log_is_enabled(Trace, redefine, class, obsolete, metadata)) {
 246 #endif
 247     log_trace(redefine, class, obsolete, metadata)("calling check_class");
 248     CheckClass check_class(thread);
 249     ClassLoaderDataGraph::classes_do(&check_class);
 250 #ifdef PRODUCT
 251   }
 252 #endif
 253 
 254   // Clean up any metadata now unreferenced while MetadataOnStackMark is set.
 255   ClassLoaderDataGraph::clean_deallocate_lists(false);
 256 }
 257 
 258 void VM_RedefineClasses::doit_epilogue() {
 259   unlock_classes();
 260 
 261   // Free os::malloc allocated memory.
 262   os::free(_scratch_classes);
 263 
 264   // Reset the_class to null for error printing.
 265   _the_class = NULL;
 266 
 267   if (log_is_enabled(Info, redefine, class, timer)) {
 268     // Used to have separate timers for "doit" and "all", but the timer
 269     // overhead skewed the measurements.
 270     julong doit_time = _timer_rsc_phase1.milliseconds() +
 271                        _timer_rsc_phase2.milliseconds();
 272     julong all_time = _timer_vm_op_prologue.milliseconds() + doit_time;
 273 
 274     log_info(redefine, class, timer)
 275       ("vm_op: all=" JULONG_FORMAT "  prologue=" JULONG_FORMAT "  doit=" JULONG_FORMAT,
 276        all_time, (julong)_timer_vm_op_prologue.milliseconds(), doit_time);
 277     log_info(redefine, class, timer)
 278       ("redefine_single_class: phase1=" JULONG_FORMAT "  phase2=" JULONG_FORMAT,
 279        (julong)_timer_rsc_phase1.milliseconds(), (julong)_timer_rsc_phase2.milliseconds());
 280   }
 281 }
 282 
 283 bool VM_RedefineClasses::is_modifiable_class(oop klass_mirror) {
 284   // classes for primitives cannot be redefined
 285   if (java_lang_Class::is_primitive(klass_mirror)) {
 286     return false;
 287   }
 288   Klass* k = java_lang_Class::as_Klass(klass_mirror);
 289   // classes for arrays cannot be redefined
 290   if (k == NULL || !k->is_instance_klass()) {
 291     return false;
 292   }
 293 
 294   // Cannot redefine or retransform an unsafe anonymous class.
 295   if (InstanceKlass::cast(k)->is_unsafe_anonymous()) {
 296     return false;
 297   }
 298   return true;
 299 }
 300 
 301 // Append the current entry at scratch_i in scratch_cp to *merge_cp_p
 302 // where the end of *merge_cp_p is specified by *merge_cp_length_p. For
 303 // direct CP entries, there is just the current entry to append. For
 304 // indirect and double-indirect CP entries, there are zero or more
 305 // referenced CP entries along with the current entry to append.
 306 // Indirect and double-indirect CP entries are handled by recursive
 307 // calls to append_entry() as needed. The referenced CP entries are
 308 // always appended to *merge_cp_p before the referee CP entry. These
 309 // referenced CP entries may already exist in *merge_cp_p in which case
 310 // there is nothing extra to append and only the current entry is
 311 // appended.
 312 void VM_RedefineClasses::append_entry(const constantPoolHandle& scratch_cp,
 313        int scratch_i, constantPoolHandle *merge_cp_p, int *merge_cp_length_p,
 314        TRAPS) {
 315 
 316   // append is different depending on entry tag type
 317   switch (scratch_cp->tag_at(scratch_i).value()) {
 318 
 319     // The old verifier is implemented outside the VM. It loads classes,
 320     // but does not resolve constant pool entries directly so we never
 321     // see Class entries here with the old verifier. Similarly the old
 322     // verifier does not like Class entries in the input constant pool.
 323     // The split-verifier is implemented in the VM so it can optionally
 324     // and directly resolve constant pool entries to load classes. The
 325     // split-verifier can accept either Class entries or UnresolvedClass
 326     // entries in the input constant pool. We revert the appended copy
 327     // back to UnresolvedClass so that either verifier will be happy
 328     // with the constant pool entry.
 329     //
 330     // this is an indirect CP entry so it needs special handling
 331     case JVM_CONSTANT_Class:
 332     case JVM_CONSTANT_UnresolvedClass:
 333     {
 334       int name_i = scratch_cp->klass_name_index_at(scratch_i);
 335       int new_name_i = find_or_append_indirect_entry(scratch_cp, name_i, merge_cp_p,
 336                                                      merge_cp_length_p, THREAD);
 337 
 338       if (new_name_i != name_i) {
 339         log_trace(redefine, class, constantpool)
 340           ("Class entry@%d name_index change: %d to %d",
 341            *merge_cp_length_p, name_i, new_name_i);
 342       }
 343 
 344       (*merge_cp_p)->temp_unresolved_klass_at_put(*merge_cp_length_p, new_name_i);
 345       if (scratch_i != *merge_cp_length_p) {
 346         // The new entry in *merge_cp_p is at a different index than
 347         // the new entry in scratch_cp so we need to map the index values.
 348         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 349       }
 350       (*merge_cp_length_p)++;
 351     } break;
 352 
 353     // these are direct CP entries so they can be directly appended,
 354     // but double and long take two constant pool entries
 355     case JVM_CONSTANT_Double:  // fall through
 356     case JVM_CONSTANT_Long:
 357     {
 358       ConstantPool::copy_entry_to(scratch_cp, scratch_i, *merge_cp_p, *merge_cp_length_p,
 359         THREAD);
 360 
 361       if (scratch_i != *merge_cp_length_p) {
 362         // The new entry in *merge_cp_p is at a different index than
 363         // the new entry in scratch_cp so we need to map the index values.
 364         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 365       }
 366       (*merge_cp_length_p) += 2;
 367     } break;
 368 
 369     // these are direct CP entries so they can be directly appended
 370     case JVM_CONSTANT_Float:   // fall through
 371     case JVM_CONSTANT_Integer: // fall through
 372     case JVM_CONSTANT_Utf8:    // fall through
 373 
 374     // This was an indirect CP entry, but it has been changed into
 375     // Symbol*s so this entry can be directly appended.
 376     case JVM_CONSTANT_String:      // fall through
 377     {
 378       ConstantPool::copy_entry_to(scratch_cp, scratch_i, *merge_cp_p, *merge_cp_length_p,
 379         THREAD);
 380 
 381       if (scratch_i != *merge_cp_length_p) {
 382         // The new entry in *merge_cp_p is at a different index than
 383         // the new entry in scratch_cp so we need to map the index values.
 384         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 385       }
 386       (*merge_cp_length_p)++;
 387     } break;
 388 
 389     // this is an indirect CP entry so it needs special handling
 390     case JVM_CONSTANT_NameAndType:
 391     {
 392       int name_ref_i = scratch_cp->name_ref_index_at(scratch_i);
 393       int new_name_ref_i = find_or_append_indirect_entry(scratch_cp, name_ref_i, merge_cp_p,
 394                                                          merge_cp_length_p, THREAD);
 395 
 396       int signature_ref_i = scratch_cp->signature_ref_index_at(scratch_i);
 397       int new_signature_ref_i = find_or_append_indirect_entry(scratch_cp, signature_ref_i,
 398                                                               merge_cp_p, merge_cp_length_p,
 399                                                               THREAD);
 400 
 401       // If the referenced entries already exist in *merge_cp_p, then
 402       // both new_name_ref_i and new_signature_ref_i will both be 0.
 403       // In that case, all we are appending is the current entry.
 404       if (new_name_ref_i != name_ref_i) {
 405         log_trace(redefine, class, constantpool)
 406           ("NameAndType entry@%d name_ref_index change: %d to %d",
 407            *merge_cp_length_p, name_ref_i, new_name_ref_i);
 408       }
 409       if (new_signature_ref_i != signature_ref_i) {
 410         log_trace(redefine, class, constantpool)
 411           ("NameAndType entry@%d signature_ref_index change: %d to %d",
 412            *merge_cp_length_p, signature_ref_i, new_signature_ref_i);
 413       }
 414 
 415       (*merge_cp_p)->name_and_type_at_put(*merge_cp_length_p,
 416         new_name_ref_i, new_signature_ref_i);
 417       if (scratch_i != *merge_cp_length_p) {
 418         // The new entry in *merge_cp_p is at a different index than
 419         // the new entry in scratch_cp so we need to map the index values.
 420         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 421       }
 422       (*merge_cp_length_p)++;
 423     } break;
 424 
 425     // this is a double-indirect CP entry so it needs special handling
 426     case JVM_CONSTANT_Fieldref:           // fall through
 427     case JVM_CONSTANT_InterfaceMethodref: // fall through
 428     case JVM_CONSTANT_Methodref:
 429     {
 430       int klass_ref_i = scratch_cp->uncached_klass_ref_index_at(scratch_i);
 431       int new_klass_ref_i = find_or_append_indirect_entry(scratch_cp, klass_ref_i,
 432                                                           merge_cp_p, merge_cp_length_p, THREAD);
 433 
 434       int name_and_type_ref_i = scratch_cp->uncached_name_and_type_ref_index_at(scratch_i);
 435       int new_name_and_type_ref_i = find_or_append_indirect_entry(scratch_cp, name_and_type_ref_i,
 436                                                           merge_cp_p, merge_cp_length_p, THREAD);
 437 
 438       const char *entry_name = NULL;
 439       switch (scratch_cp->tag_at(scratch_i).value()) {
 440       case JVM_CONSTANT_Fieldref:
 441         entry_name = "Fieldref";
 442         (*merge_cp_p)->field_at_put(*merge_cp_length_p, new_klass_ref_i,
 443           new_name_and_type_ref_i);
 444         break;
 445       case JVM_CONSTANT_InterfaceMethodref:
 446         entry_name = "IFMethodref";
 447         (*merge_cp_p)->interface_method_at_put(*merge_cp_length_p,
 448           new_klass_ref_i, new_name_and_type_ref_i);
 449         break;
 450       case JVM_CONSTANT_Methodref:
 451         entry_name = "Methodref";
 452         (*merge_cp_p)->method_at_put(*merge_cp_length_p, new_klass_ref_i,
 453           new_name_and_type_ref_i);
 454         break;
 455       default:
 456         guarantee(false, "bad switch");
 457         break;
 458       }
 459 
 460       if (klass_ref_i != new_klass_ref_i) {
 461         log_trace(redefine, class, constantpool)
 462           ("%s entry@%d class_index changed: %d to %d", entry_name, *merge_cp_length_p, klass_ref_i, new_klass_ref_i);
 463       }
 464       if (name_and_type_ref_i != new_name_and_type_ref_i) {
 465         log_trace(redefine, class, constantpool)
 466           ("%s entry@%d name_and_type_index changed: %d to %d",
 467            entry_name, *merge_cp_length_p, name_and_type_ref_i, new_name_and_type_ref_i);
 468       }
 469 
 470       if (scratch_i != *merge_cp_length_p) {
 471         // The new entry in *merge_cp_p is at a different index than
 472         // the new entry in scratch_cp so we need to map the index values.
 473         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 474       }
 475       (*merge_cp_length_p)++;
 476     } break;
 477 
 478     // this is an indirect CP entry so it needs special handling
 479     case JVM_CONSTANT_MethodType:
 480     {
 481       int ref_i = scratch_cp->method_type_index_at(scratch_i);
 482       int new_ref_i = find_or_append_indirect_entry(scratch_cp, ref_i, merge_cp_p,
 483                                                     merge_cp_length_p, THREAD);
 484       if (new_ref_i != ref_i) {
 485         log_trace(redefine, class, constantpool)
 486           ("MethodType entry@%d ref_index change: %d to %d", *merge_cp_length_p, ref_i, new_ref_i);
 487       }
 488       (*merge_cp_p)->method_type_index_at_put(*merge_cp_length_p, new_ref_i);
 489       if (scratch_i != *merge_cp_length_p) {
 490         // The new entry in *merge_cp_p is at a different index than
 491         // the new entry in scratch_cp so we need to map the index values.
 492         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 493       }
 494       (*merge_cp_length_p)++;
 495     } break;
 496 
 497     // this is an indirect CP entry so it needs special handling
 498     case JVM_CONSTANT_MethodHandle:
 499     {
 500       int ref_kind = scratch_cp->method_handle_ref_kind_at(scratch_i);
 501       int ref_i = scratch_cp->method_handle_index_at(scratch_i);
 502       int new_ref_i = find_or_append_indirect_entry(scratch_cp, ref_i, merge_cp_p,
 503                                                     merge_cp_length_p, THREAD);
 504       if (new_ref_i != ref_i) {
 505         log_trace(redefine, class, constantpool)
 506           ("MethodHandle entry@%d ref_index change: %d to %d", *merge_cp_length_p, ref_i, new_ref_i);
 507       }
 508       (*merge_cp_p)->method_handle_index_at_put(*merge_cp_length_p, ref_kind, new_ref_i);
 509       if (scratch_i != *merge_cp_length_p) {
 510         // The new entry in *merge_cp_p is at a different index than
 511         // the new entry in scratch_cp so we need to map the index values.
 512         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 513       }
 514       (*merge_cp_length_p)++;
 515     } break;
 516 
 517     // this is an indirect CP entry so it needs special handling
 518     case JVM_CONSTANT_Dynamic:  // fall through
 519     case JVM_CONSTANT_InvokeDynamic:
 520     {
 521       // Index of the bootstrap specifier in the operands array
 522       int old_bs_i = scratch_cp->bootstrap_methods_attribute_index(scratch_i);
 523       int new_bs_i = find_or_append_operand(scratch_cp, old_bs_i, merge_cp_p,
 524                                             merge_cp_length_p, THREAD);
 525       // The bootstrap method NameAndType_info index
 526       int old_ref_i = scratch_cp->bootstrap_name_and_type_ref_index_at(scratch_i);
 527       int new_ref_i = find_or_append_indirect_entry(scratch_cp, old_ref_i, merge_cp_p,
 528                                                     merge_cp_length_p, THREAD);
 529       if (new_bs_i != old_bs_i) {
 530         log_trace(redefine, class, constantpool)
 531           ("Dynamic entry@%d bootstrap_method_attr_index change: %d to %d",
 532            *merge_cp_length_p, old_bs_i, new_bs_i);
 533       }
 534       if (new_ref_i != old_ref_i) {
 535         log_trace(redefine, class, constantpool)
 536           ("Dynamic entry@%d name_and_type_index change: %d to %d", *merge_cp_length_p, old_ref_i, new_ref_i);
 537       }
 538 
 539       if (scratch_cp->tag_at(scratch_i).is_dynamic_constant())
 540         (*merge_cp_p)->dynamic_constant_at_put(*merge_cp_length_p, new_bs_i, new_ref_i);
 541       else
 542         (*merge_cp_p)->invoke_dynamic_at_put(*merge_cp_length_p, new_bs_i, new_ref_i);
 543       if (scratch_i != *merge_cp_length_p) {
 544         // The new entry in *merge_cp_p is at a different index than
 545         // the new entry in scratch_cp so we need to map the index values.
 546         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 547       }
 548       (*merge_cp_length_p)++;
 549     } break;
 550 
 551     // At this stage, Class or UnresolvedClass could be in scratch_cp, but not
 552     // ClassIndex
 553     case JVM_CONSTANT_ClassIndex: // fall through
 554 
 555     // Invalid is used as the tag for the second constant pool entry
 556     // occupied by JVM_CONSTANT_Double or JVM_CONSTANT_Long. It should
 557     // not be seen by itself.
 558     case JVM_CONSTANT_Invalid: // fall through
 559 
 560     // At this stage, String could be here, but not StringIndex
 561     case JVM_CONSTANT_StringIndex: // fall through
 562 
 563     // At this stage JVM_CONSTANT_UnresolvedClassInError should not be
 564     // here
 565     case JVM_CONSTANT_UnresolvedClassInError: // fall through
 566 
 567     default:
 568     {
 569       // leave a breadcrumb
 570       jbyte bad_value = scratch_cp->tag_at(scratch_i).value();
 571       ShouldNotReachHere();
 572     } break;
 573   } // end switch tag value
 574 } // end append_entry()
 575 
 576 
 577 int VM_RedefineClasses::find_or_append_indirect_entry(const constantPoolHandle& scratch_cp,
 578       int ref_i, constantPoolHandle *merge_cp_p, int *merge_cp_length_p, TRAPS) {
 579 
 580   int new_ref_i = ref_i;
 581   bool match = (ref_i < *merge_cp_length_p) &&
 582                scratch_cp->compare_entry_to(ref_i, *merge_cp_p, ref_i, THREAD);
 583 
 584   if (!match) {
 585     // forward reference in *merge_cp_p or not a direct match
 586     int found_i = scratch_cp->find_matching_entry(ref_i, *merge_cp_p, THREAD);
 587     if (found_i != 0) {
 588       guarantee(found_i != ref_i, "compare_entry_to() and find_matching_entry() do not agree");
 589       // Found a matching entry somewhere else in *merge_cp_p so just need a mapping entry.
 590       new_ref_i = found_i;
 591       map_index(scratch_cp, ref_i, found_i);
 592     } else {
 593       // no match found so we have to append this entry to *merge_cp_p
 594       append_entry(scratch_cp, ref_i, merge_cp_p, merge_cp_length_p, THREAD);
 595       // The above call to append_entry() can only append one entry
 596       // so the post call query of *merge_cp_length_p is only for
 597       // the sake of consistency.
 598       new_ref_i = *merge_cp_length_p - 1;
 599     }
 600   }
 601 
 602   return new_ref_i;
 603 } // end find_or_append_indirect_entry()
 604 
 605 
 606 // Append a bootstrap specifier into the merge_cp operands that is semantically equal
 607 // to the scratch_cp operands bootstrap specifier passed by the old_bs_i index.
 608 // Recursively append new merge_cp entries referenced by the new bootstrap specifier.
 609 void VM_RedefineClasses::append_operand(const constantPoolHandle& scratch_cp, int old_bs_i,
 610        constantPoolHandle *merge_cp_p, int *merge_cp_length_p, TRAPS) {
 611 
 612   int old_ref_i = scratch_cp->operand_bootstrap_method_ref_index_at(old_bs_i);
 613   int new_ref_i = find_or_append_indirect_entry(scratch_cp, old_ref_i, merge_cp_p,
 614                                                 merge_cp_length_p, THREAD);
 615   if (new_ref_i != old_ref_i) {
 616     log_trace(redefine, class, constantpool)
 617       ("operands entry@%d bootstrap method ref_index change: %d to %d", _operands_cur_length, old_ref_i, new_ref_i);
 618   }
 619 
 620   Array<u2>* merge_ops = (*merge_cp_p)->operands();
 621   int new_bs_i = _operands_cur_length;
 622   // We have _operands_cur_length == 0 when the merge_cp operands is empty yet.
 623   // However, the operand_offset_at(0) was set in the extend_operands() call.
 624   int new_base = (new_bs_i == 0) ? (*merge_cp_p)->operand_offset_at(0)
 625                                  : (*merge_cp_p)->operand_next_offset_at(new_bs_i - 1);
 626   int argc     = scratch_cp->operand_argument_count_at(old_bs_i);
 627 
 628   ConstantPool::operand_offset_at_put(merge_ops, _operands_cur_length, new_base);
 629   merge_ops->at_put(new_base++, new_ref_i);
 630   merge_ops->at_put(new_base++, argc);
 631 
 632   for (int i = 0; i < argc; i++) {
 633     int old_arg_ref_i = scratch_cp->operand_argument_index_at(old_bs_i, i);
 634     int new_arg_ref_i = find_or_append_indirect_entry(scratch_cp, old_arg_ref_i, merge_cp_p,
 635                                                       merge_cp_length_p, THREAD);
 636     merge_ops->at_put(new_base++, new_arg_ref_i);
 637     if (new_arg_ref_i != old_arg_ref_i) {
 638       log_trace(redefine, class, constantpool)
 639         ("operands entry@%d bootstrap method argument ref_index change: %d to %d",
 640          _operands_cur_length, old_arg_ref_i, new_arg_ref_i);
 641     }
 642   }
 643   if (old_bs_i != _operands_cur_length) {
 644     // The bootstrap specifier in *merge_cp_p is at a different index than
 645     // that in scratch_cp so we need to map the index values.
 646     map_operand_index(old_bs_i, new_bs_i);
 647   }
 648   _operands_cur_length++;
 649 } // end append_operand()
 650 
 651 
 652 int VM_RedefineClasses::find_or_append_operand(const constantPoolHandle& scratch_cp,
 653       int old_bs_i, constantPoolHandle *merge_cp_p, int *merge_cp_length_p, TRAPS) {
 654 
 655   int new_bs_i = old_bs_i; // bootstrap specifier index
 656   bool match = (old_bs_i < _operands_cur_length) &&
 657                scratch_cp->compare_operand_to(old_bs_i, *merge_cp_p, old_bs_i, THREAD);
 658 
 659   if (!match) {
 660     // forward reference in *merge_cp_p or not a direct match
 661     int found_i = scratch_cp->find_matching_operand(old_bs_i, *merge_cp_p,
 662                                                     _operands_cur_length, THREAD);
 663     if (found_i != -1) {
 664       guarantee(found_i != old_bs_i, "compare_operand_to() and find_matching_operand() disagree");
 665       // found a matching operand somewhere else in *merge_cp_p so just need a mapping
 666       new_bs_i = found_i;
 667       map_operand_index(old_bs_i, found_i);
 668     } else {
 669       // no match found so we have to append this bootstrap specifier to *merge_cp_p
 670       append_operand(scratch_cp, old_bs_i, merge_cp_p, merge_cp_length_p, THREAD);
 671       new_bs_i = _operands_cur_length - 1;
 672     }
 673   }
 674   return new_bs_i;
 675 } // end find_or_append_operand()
 676 
 677 
 678 void VM_RedefineClasses::finalize_operands_merge(const constantPoolHandle& merge_cp, TRAPS) {
 679   if (merge_cp->operands() == NULL) {
 680     return;
 681   }
 682   // Shrink the merge_cp operands
 683   merge_cp->shrink_operands(_operands_cur_length, CHECK);
 684 
 685   if (log_is_enabled(Trace, redefine, class, constantpool)) {
 686     // don't want to loop unless we are tracing
 687     int count = 0;
 688     for (int i = 1; i < _operands_index_map_p->length(); i++) {
 689       int value = _operands_index_map_p->at(i);
 690       if (value != -1) {
 691         log_trace(redefine, class, constantpool)("operands_index_map[%d]: old=%d new=%d", count, i, value);
 692         count++;
 693       }
 694     }
 695   }
 696   // Clean-up
 697   _operands_index_map_p = NULL;
 698   _operands_cur_length = 0;
 699   _operands_index_map_count = 0;
 700 } // end finalize_operands_merge()
 701 
 702 // Symbol* comparator for qsort
 703 // The caller must have an active ResourceMark.
 704 static int symcmp(const void* a, const void* b) {
 705   char* astr = (*(Symbol**)a)->as_C_string();
 706   char* bstr = (*(Symbol**)b)->as_C_string();
 707   return strcmp(astr, bstr);
 708 }
 709 
 710 static jvmtiError check_nest_attributes(InstanceKlass* the_class,
 711                                         InstanceKlass* scratch_class) {
 712   // Check whether the class NestHost attribute has been changed.
 713   Thread* thread = Thread::current();
 714   ResourceMark rm(thread);
 715   u2 the_nest_host_idx = the_class->nest_host_index();
 716   u2 scr_nest_host_idx = scratch_class->nest_host_index();
 717 
 718   if (the_nest_host_idx != 0 && scr_nest_host_idx != 0) {
 719     Symbol* the_sym = the_class->constants()->klass_name_at(the_nest_host_idx);
 720     Symbol* scr_sym = scratch_class->constants()->klass_name_at(scr_nest_host_idx);
 721     if (the_sym != scr_sym) {
 722       log_trace(redefine, class, nestmates)
 723         ("redefined class %s attribute change error: NestHost class: %s replaced with: %s",
 724          the_class->external_name(), the_sym->as_C_string(), scr_sym->as_C_string());
 725       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
 726     }
 727   } else if ((the_nest_host_idx == 0) ^ (scr_nest_host_idx == 0)) {
 728     const char* action_str = (the_nest_host_idx != 0) ? "removed" : "added";
 729     log_trace(redefine, class, nestmates)
 730       ("redefined class %s attribute change error: NestHost attribute %s",
 731        the_class->external_name(), action_str);
 732     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
 733   }
 734 
 735   // Check whether the class NestMembers attribute has been changed.
 736   Array<u2>* the_nest_members = the_class->nest_members();
 737   Array<u2>* scr_nest_members = scratch_class->nest_members();
 738   bool the_members_exists = the_nest_members != Universe::the_empty_short_array();
 739   bool scr_members_exists = scr_nest_members != Universe::the_empty_short_array();
 740 
 741   int members_len = the_nest_members->length();
 742   if (the_members_exists && scr_members_exists) {
 743     if (members_len != scr_nest_members->length()) {
 744       log_trace(redefine, class, nestmates)
 745         ("redefined class %s attribute change error: NestMember len=%d changed to len=%d",
 746          the_class->external_name(), members_len, scr_nest_members->length());
 747       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
 748     }
 749 
 750     // The order of entries in the NestMembers array is not specified so we
 751     // have to explicitly check for the same contents. We do this by copying
 752     // the referenced symbols into their own arrays, sorting them and then
 753     // comparing each element pair.
 754 
 755     Symbol** the_syms = NEW_RESOURCE_ARRAY_RETURN_NULL(Symbol*, members_len);
 756     Symbol** scr_syms = NEW_RESOURCE_ARRAY_RETURN_NULL(Symbol*, members_len);
 757 
 758     if (the_syms == NULL || scr_syms == NULL) {
 759       return JVMTI_ERROR_OUT_OF_MEMORY;
 760     }
 761 
 762     for (int i = 0; i < members_len; i++) {
 763       int the_cp_index = the_nest_members->at(i);
 764       int scr_cp_index = scr_nest_members->at(i);
 765       the_syms[i] = the_class->constants()->klass_name_at(the_cp_index);
 766       scr_syms[i] = scratch_class->constants()->klass_name_at(scr_cp_index);
 767     }
 768 
 769     qsort(the_syms, members_len, sizeof(Symbol*), symcmp);
 770     qsort(scr_syms, members_len, sizeof(Symbol*), symcmp);
 771 
 772     for (int i = 0; i < members_len; i++) {
 773       if (the_syms[i] != scr_syms[i]) {
 774         log_trace(redefine, class, nestmates)
 775           ("redefined class %s attribute change error: NestMembers[%d]: %s changed to %s",
 776            the_class->external_name(), i, the_syms[i]->as_C_string(), scr_syms[i]->as_C_string());
 777         return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
 778       }
 779     }
 780   } else if (the_members_exists ^ scr_members_exists) {
 781     const char* action_str = (the_members_exists) ? "removed" : "added";
 782     log_trace(redefine, class, nestmates)
 783       ("redefined class %s attribute change error: NestMembers attribute %s",
 784        the_class->external_name(), action_str);
 785     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_ATTRIBUTE_CHANGED;
 786   }
 787 
 788   return JVMTI_ERROR_NONE;
 789 }
 790 
 791 static bool can_add_or_delete(Method* m) {
 792       // Compatibility mode
 793   return (AllowRedefinitionToAddDeleteMethods &&
 794           (m->is_private() && (m->is_static() || m->is_final())));
 795 }
 796 
 797 jvmtiError VM_RedefineClasses::compare_and_normalize_class_versions(
 798              InstanceKlass* the_class,
 799              InstanceKlass* scratch_class) {
 800   int i;
 801 
 802   // Check superclasses, or rather their names, since superclasses themselves can be
 803   // requested to replace.
 804   // Check for NULL superclass first since this might be java.lang.Object
 805   if (the_class->super() != scratch_class->super() &&
 806       (the_class->super() == NULL || scratch_class->super() == NULL ||
 807        the_class->super()->name() !=
 808        scratch_class->super()->name())) {
 809     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_HIERARCHY_CHANGED;
 810   }
 811 
 812   // Check if the number, names and order of directly implemented interfaces are the same.
 813   // I think in principle we should just check if the sets of names of directly implemented
 814   // interfaces are the same, i.e. the order of declaration (which, however, if changed in the
 815   // .java file, also changes in .class file) should not matter. However, comparing sets is
 816   // technically a bit more difficult, and, more importantly, I am not sure at present that the
 817   // order of interfaces does not matter on the implementation level, i.e. that the VM does not
 818   // rely on it somewhere.
 819   Array<InstanceKlass*>* k_interfaces = the_class->local_interfaces();
 820   Array<InstanceKlass*>* k_new_interfaces = scratch_class->local_interfaces();
 821   int n_intfs = k_interfaces->length();
 822   if (n_intfs != k_new_interfaces->length()) {
 823     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_HIERARCHY_CHANGED;
 824   }
 825   for (i = 0; i < n_intfs; i++) {
 826     if (k_interfaces->at(i)->name() !=
 827         k_new_interfaces->at(i)->name()) {
 828       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_HIERARCHY_CHANGED;
 829     }
 830   }
 831 
 832   // Check whether class is in the error init state.
 833   if (the_class->is_in_error_state()) {
 834     // TBD #5057930: special error code is needed in 1.6
 835     return JVMTI_ERROR_INVALID_CLASS;
 836   }
 837 
 838   // Check whether the nest-related attributes have been changed.
 839   jvmtiError err = check_nest_attributes(the_class, scratch_class);
 840   if (err != JVMTI_ERROR_NONE) {
 841     return err;
 842   }
 843 
 844   // Check whether class modifiers are the same.
 845   jushort old_flags = (jushort) the_class->access_flags().get_flags();
 846   jushort new_flags = (jushort) scratch_class->access_flags().get_flags();
 847   if (old_flags != new_flags) {
 848     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_MODIFIERS_CHANGED;
 849   }
 850 
 851   // Check if the number, names, types and order of fields declared in these classes
 852   // are the same.
 853   JavaFieldStream old_fs(the_class);
 854   JavaFieldStream new_fs(scratch_class);
 855   for (; !old_fs.done() && !new_fs.done(); old_fs.next(), new_fs.next()) {
 856     // access
 857     old_flags = old_fs.access_flags().as_short();
 858     new_flags = new_fs.access_flags().as_short();
 859     if ((old_flags ^ new_flags) & JVM_RECOGNIZED_FIELD_MODIFIERS) {
 860       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_SCHEMA_CHANGED;
 861     }
 862     // offset
 863     if (old_fs.offset() != new_fs.offset()) {
 864       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_SCHEMA_CHANGED;
 865     }
 866     // name and signature
 867     Symbol* name_sym1 = the_class->constants()->symbol_at(old_fs.name_index());
 868     Symbol* sig_sym1 = the_class->constants()->symbol_at(old_fs.signature_index());
 869     Symbol* name_sym2 = scratch_class->constants()->symbol_at(new_fs.name_index());
 870     Symbol* sig_sym2 = scratch_class->constants()->symbol_at(new_fs.signature_index());
 871     if (name_sym1 != name_sym2 || sig_sym1 != sig_sym2) {
 872       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_SCHEMA_CHANGED;
 873     }
 874   }
 875 
 876   // If both streams aren't done then we have a differing number of
 877   // fields.
 878   if (!old_fs.done() || !new_fs.done()) {
 879     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_SCHEMA_CHANGED;
 880   }
 881 
 882   // Do a parallel walk through the old and new methods. Detect
 883   // cases where they match (exist in both), have been added in
 884   // the new methods, or have been deleted (exist only in the
 885   // old methods).  The class file parser places methods in order
 886   // by method name, but does not order overloaded methods by
 887   // signature.  In order to determine what fate befell the methods,
 888   // this code places the overloaded new methods that have matching
 889   // old methods in the same order as the old methods and places
 890   // new overloaded methods at the end of overloaded methods of
 891   // that name. The code for this order normalization is adapted
 892   // from the algorithm used in InstanceKlass::find_method().
 893   // Since we are swapping out of order entries as we find them,
 894   // we only have to search forward through the overloaded methods.
 895   // Methods which are added and have the same name as an existing
 896   // method (but different signature) will be put at the end of
 897   // the methods with that name, and the name mismatch code will
 898   // handle them.
 899   Array<Method*>* k_old_methods(the_class->methods());
 900   Array<Method*>* k_new_methods(scratch_class->methods());
 901   int n_old_methods = k_old_methods->length();
 902   int n_new_methods = k_new_methods->length();
 903   Thread* thread = Thread::current();
 904 
 905   int ni = 0;
 906   int oi = 0;
 907   while (true) {
 908     Method* k_old_method;
 909     Method* k_new_method;
 910     enum { matched, added, deleted, undetermined } method_was = undetermined;
 911 
 912     if (oi >= n_old_methods) {
 913       if (ni >= n_new_methods) {
 914         break; // we've looked at everything, done
 915       }
 916       // New method at the end
 917       k_new_method = k_new_methods->at(ni);
 918       method_was = added;
 919     } else if (ni >= n_new_methods) {
 920       // Old method, at the end, is deleted
 921       k_old_method = k_old_methods->at(oi);
 922       method_was = deleted;
 923     } else {
 924       // There are more methods in both the old and new lists
 925       k_old_method = k_old_methods->at(oi);
 926       k_new_method = k_new_methods->at(ni);
 927       if (k_old_method->name() != k_new_method->name()) {
 928         // Methods are sorted by method name, so a mismatch means added
 929         // or deleted
 930         if (k_old_method->name()->fast_compare(k_new_method->name()) > 0) {
 931           method_was = added;
 932         } else {
 933           method_was = deleted;
 934         }
 935       } else if (k_old_method->signature() == k_new_method->signature()) {
 936         // Both the name and signature match
 937         method_was = matched;
 938       } else {
 939         // The name matches, but the signature doesn't, which means we have to
 940         // search forward through the new overloaded methods.
 941         int nj;  // outside the loop for post-loop check
 942         for (nj = ni + 1; nj < n_new_methods; nj++) {
 943           Method* m = k_new_methods->at(nj);
 944           if (k_old_method->name() != m->name()) {
 945             // reached another method name so no more overloaded methods
 946             method_was = deleted;
 947             break;
 948           }
 949           if (k_old_method->signature() == m->signature()) {
 950             // found a match so swap the methods
 951             k_new_methods->at_put(ni, m);
 952             k_new_methods->at_put(nj, k_new_method);
 953             k_new_method = m;
 954             method_was = matched;
 955             break;
 956           }
 957         }
 958 
 959         if (nj >= n_new_methods) {
 960           // reached the end without a match; so method was deleted
 961           method_was = deleted;
 962         }
 963       }
 964     }
 965 
 966     switch (method_was) {
 967     case matched:
 968       // methods match, be sure modifiers do too
 969       old_flags = (jushort) k_old_method->access_flags().get_flags();
 970       new_flags = (jushort) k_new_method->access_flags().get_flags();
 971       if ((old_flags ^ new_flags) & ~(JVM_ACC_NATIVE)) {
 972         return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_METHOD_MODIFIERS_CHANGED;
 973       }
 974       {
 975         u2 new_num = k_new_method->method_idnum();
 976         u2 old_num = k_old_method->method_idnum();
 977         if (new_num != old_num) {
 978           Method* idnum_owner = scratch_class->method_with_idnum(old_num);
 979           if (idnum_owner != NULL) {
 980             // There is already a method assigned this idnum -- switch them
 981             // Take current and original idnum from the new_method
 982             idnum_owner->set_method_idnum(new_num);
 983             idnum_owner->set_orig_method_idnum(k_new_method->orig_method_idnum());
 984           }
 985           // Take current and original idnum from the old_method
 986           k_new_method->set_method_idnum(old_num);
 987           k_new_method->set_orig_method_idnum(k_old_method->orig_method_idnum());
 988           if (thread->has_pending_exception()) {
 989             return JVMTI_ERROR_OUT_OF_MEMORY;
 990           }
 991         }
 992       }
 993       log_trace(redefine, class, normalize)
 994         ("Method matched: new: %s [%d] == old: %s [%d]",
 995          k_new_method->name_and_sig_as_C_string(), ni, k_old_method->name_and_sig_as_C_string(), oi);
 996       // advance to next pair of methods
 997       ++oi;
 998       ++ni;
 999       break;
1000     case added:
1001       // method added, see if it is OK
1002       if (!can_add_or_delete(k_new_method)) {
1003         return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_METHOD_ADDED;
1004       }
1005       {
1006         u2 num = the_class->next_method_idnum();
1007         if (num == ConstMethod::UNSET_IDNUM) {
1008           // cannot add any more methods
1009           return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_METHOD_ADDED;
1010         }
1011         u2 new_num = k_new_method->method_idnum();
1012         Method* idnum_owner = scratch_class->method_with_idnum(num);
1013         if (idnum_owner != NULL) {
1014           // There is already a method assigned this idnum -- switch them
1015           // Take current and original idnum from the new_method
1016           idnum_owner->set_method_idnum(new_num);
1017           idnum_owner->set_orig_method_idnum(k_new_method->orig_method_idnum());
1018         }
1019         k_new_method->set_method_idnum(num);
1020         k_new_method->set_orig_method_idnum(num);
1021         if (thread->has_pending_exception()) {
1022           return JVMTI_ERROR_OUT_OF_MEMORY;
1023         }
1024       }
1025       log_trace(redefine, class, normalize)
1026         ("Method added: new: %s [%d]", k_new_method->name_and_sig_as_C_string(), ni);
1027       ++ni; // advance to next new method
1028       break;
1029     case deleted:
1030       // method deleted, see if it is OK
1031       if (!can_add_or_delete(k_old_method)) {
1032         return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_METHOD_DELETED;
1033       }
1034       log_trace(redefine, class, normalize)
1035         ("Method deleted: old: %s [%d]", k_old_method->name_and_sig_as_C_string(), oi);
1036       ++oi; // advance to next old method
1037       break;
1038     default:
1039       ShouldNotReachHere();
1040     }
1041   }
1042 
1043   return JVMTI_ERROR_NONE;
1044 }
1045 
1046 
1047 // Find new constant pool index value for old constant pool index value
1048 // by seaching the index map. Returns zero (0) if there is no mapped
1049 // value for the old constant pool index.
1050 int VM_RedefineClasses::find_new_index(int old_index) {
1051   if (_index_map_count == 0) {
1052     // map is empty so nothing can be found
1053     return 0;
1054   }
1055 
1056   if (old_index < 1 || old_index >= _index_map_p->length()) {
1057     // The old_index is out of range so it is not mapped. This should
1058     // not happen in regular constant pool merging use, but it can
1059     // happen if a corrupt annotation is processed.
1060     return 0;
1061   }
1062 
1063   int value = _index_map_p->at(old_index);
1064   if (value == -1) {
1065     // the old_index is not mapped
1066     return 0;
1067   }
1068 
1069   return value;
1070 } // end find_new_index()
1071 
1072 
1073 // Find new bootstrap specifier index value for old bootstrap specifier index
1074 // value by seaching the index map. Returns unused index (-1) if there is
1075 // no mapped value for the old bootstrap specifier index.
1076 int VM_RedefineClasses::find_new_operand_index(int old_index) {
1077   if (_operands_index_map_count == 0) {
1078     // map is empty so nothing can be found
1079     return -1;
1080   }
1081 
1082   if (old_index == -1 || old_index >= _operands_index_map_p->length()) {
1083     // The old_index is out of range so it is not mapped.
1084     // This should not happen in regular constant pool merging use.
1085     return -1;
1086   }
1087 
1088   int value = _operands_index_map_p->at(old_index);
1089   if (value == -1) {
1090     // the old_index is not mapped
1091     return -1;
1092   }
1093 
1094   return value;
1095 } // end find_new_operand_index()
1096 
1097 
1098 // Returns true if the current mismatch is due to a resolved/unresolved
1099 // class pair. Otherwise, returns false.
1100 bool VM_RedefineClasses::is_unresolved_class_mismatch(const constantPoolHandle& cp1,
1101        int index1, const constantPoolHandle& cp2, int index2) {
1102 
1103   jbyte t1 = cp1->tag_at(index1).value();
1104   if (t1 != JVM_CONSTANT_Class && t1 != JVM_CONSTANT_UnresolvedClass) {
1105     return false;  // wrong entry type; not our special case
1106   }
1107 
1108   jbyte t2 = cp2->tag_at(index2).value();
1109   if (t2 != JVM_CONSTANT_Class && t2 != JVM_CONSTANT_UnresolvedClass) {
1110     return false;  // wrong entry type; not our special case
1111   }
1112 
1113   if (t1 == t2) {
1114     return false;  // not a mismatch; not our special case
1115   }
1116 
1117   char *s1 = cp1->klass_name_at(index1)->as_C_string();
1118   char *s2 = cp2->klass_name_at(index2)->as_C_string();
1119   if (strcmp(s1, s2) != 0) {
1120     return false;  // strings don't match; not our special case
1121   }
1122 
1123   return true;  // made it through the gauntlet; this is our special case
1124 } // end is_unresolved_class_mismatch()
1125 
1126 
1127 jvmtiError VM_RedefineClasses::load_new_class_versions(TRAPS) {
1128 
1129   // For consistency allocate memory using os::malloc wrapper.
1130   _scratch_classes = (InstanceKlass**)
1131     os::malloc(sizeof(InstanceKlass*) * _class_count, mtClass);
1132   if (_scratch_classes == NULL) {
1133     return JVMTI_ERROR_OUT_OF_MEMORY;
1134   }
1135   // Zero initialize the _scratch_classes array.
1136   for (int i = 0; i < _class_count; i++) {
1137     _scratch_classes[i] = NULL;
1138   }
1139 
1140   ResourceMark rm(THREAD);
1141 
1142   JvmtiThreadState *state = JvmtiThreadState::state_for(JavaThread::current());
1143   // state can only be NULL if the current thread is exiting which
1144   // should not happen since we're trying to do a RedefineClasses
1145   guarantee(state != NULL, "exiting thread calling load_new_class_versions");
1146   for (int i = 0; i < _class_count; i++) {
1147     // Create HandleMark so that any handles created while loading new class
1148     // versions are deleted. Constant pools are deallocated while merging
1149     // constant pools
1150     HandleMark hm(THREAD);
1151     InstanceKlass* the_class = get_ik(_class_defs[i].klass);
1152     Symbol*  the_class_sym = the_class->name();
1153 
1154     log_debug(redefine, class, load)
1155       ("loading name=%s kind=%d (avail_mem=" UINT64_FORMAT "K)",
1156        the_class->external_name(), _class_load_kind, os::available_memory() >> 10);
1157 
1158     ClassFileStream st((u1*)_class_defs[i].class_bytes,
1159                        _class_defs[i].class_byte_count,
1160                        "__VM_RedefineClasses__",
1161                        ClassFileStream::verify);
1162 
1163     // Parse the stream.
1164     Handle the_class_loader(THREAD, the_class->class_loader());
1165     Handle protection_domain(THREAD, the_class->protection_domain());
1166     // Set redefined class handle in JvmtiThreadState class.
1167     // This redefined class is sent to agent event handler for class file
1168     // load hook event.
1169     state->set_class_being_redefined(the_class, _class_load_kind);
1170 
1171     InstanceKlass* scratch_class = SystemDictionary::parse_stream(
1172                                                       the_class_sym,
1173                                                       the_class_loader,
1174                                                       protection_domain,
1175                                                       &st,
1176                                                       THREAD);
1177     // Clear class_being_redefined just to be sure.
1178     state->clear_class_being_redefined();
1179 
1180     // TODO: if this is retransform, and nothing changed we can skip it
1181 
1182     // Need to clean up allocated InstanceKlass if there's an error so assign
1183     // the result here. Caller deallocates all the scratch classes in case of
1184     // an error.
1185     _scratch_classes[i] = scratch_class;
1186 
1187     if (HAS_PENDING_EXCEPTION) {
1188       Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1189       log_info(redefine, class, load, exceptions)("parse_stream exception: '%s'", ex_name->as_C_string());
1190       CLEAR_PENDING_EXCEPTION;
1191 
1192       if (ex_name == vmSymbols::java_lang_UnsupportedClassVersionError()) {
1193         return JVMTI_ERROR_UNSUPPORTED_VERSION;
1194       } else if (ex_name == vmSymbols::java_lang_ClassFormatError()) {
1195         return JVMTI_ERROR_INVALID_CLASS_FORMAT;
1196       } else if (ex_name == vmSymbols::java_lang_ClassCircularityError()) {
1197         return JVMTI_ERROR_CIRCULAR_CLASS_DEFINITION;
1198       } else if (ex_name == vmSymbols::java_lang_NoClassDefFoundError()) {
1199         // The message will be "XXX (wrong name: YYY)"
1200         return JVMTI_ERROR_NAMES_DONT_MATCH;
1201       } else if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1202         return JVMTI_ERROR_OUT_OF_MEMORY;
1203       } else {  // Just in case more exceptions can be thrown..
1204         return JVMTI_ERROR_FAILS_VERIFICATION;
1205       }
1206     }
1207 
1208     // Ensure class is linked before redefine
1209     if (!the_class->is_linked()) {
1210       the_class->link_class(THREAD);
1211       if (HAS_PENDING_EXCEPTION) {
1212         Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1213         log_info(redefine, class, load, exceptions)("link_class exception: '%s'", ex_name->as_C_string());
1214         CLEAR_PENDING_EXCEPTION;
1215         if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1216           return JVMTI_ERROR_OUT_OF_MEMORY;
1217         } else {
1218           return JVMTI_ERROR_INTERNAL;
1219         }
1220       }
1221     }
1222 
1223     // Do the validity checks in compare_and_normalize_class_versions()
1224     // before verifying the byte codes. By doing these checks first, we
1225     // limit the number of functions that require redirection from
1226     // the_class to scratch_class. In particular, we don't have to
1227     // modify JNI GetSuperclass() and thus won't change its performance.
1228     jvmtiError res = compare_and_normalize_class_versions(the_class,
1229                        scratch_class);
1230     if (res != JVMTI_ERROR_NONE) {
1231       return res;
1232     }
1233 
1234     // verify what the caller passed us
1235     {
1236       // The bug 6214132 caused the verification to fail.
1237       // Information about the_class and scratch_class is temporarily
1238       // recorded into jvmtiThreadState. This data is used to redirect
1239       // the_class to scratch_class in the JVM_* functions called by the
1240       // verifier. Please, refer to jvmtiThreadState.hpp for the detailed
1241       // description.
1242       RedefineVerifyMark rvm(the_class, scratch_class, state);
1243       Verifier::verify(scratch_class, true, THREAD);
1244     }
1245 
1246     if (HAS_PENDING_EXCEPTION) {
1247       Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1248       log_info(redefine, class, load, exceptions)("verify_byte_codes exception: '%s'", ex_name->as_C_string());
1249       CLEAR_PENDING_EXCEPTION;
1250       if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1251         return JVMTI_ERROR_OUT_OF_MEMORY;
1252       } else {
1253         // tell the caller the bytecodes are bad
1254         return JVMTI_ERROR_FAILS_VERIFICATION;
1255       }
1256     }
1257 
1258     res = merge_cp_and_rewrite(the_class, scratch_class, THREAD);
1259     if (HAS_PENDING_EXCEPTION) {
1260       Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1261       log_info(redefine, class, load, exceptions)("merge_cp_and_rewrite exception: '%s'", ex_name->as_C_string());
1262       CLEAR_PENDING_EXCEPTION;
1263       if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1264         return JVMTI_ERROR_OUT_OF_MEMORY;
1265       } else {
1266         return JVMTI_ERROR_INTERNAL;
1267       }
1268     }
1269 
1270     if (VerifyMergedCPBytecodes) {
1271       // verify what we have done during constant pool merging
1272       {
1273         RedefineVerifyMark rvm(the_class, scratch_class, state);
1274         Verifier::verify(scratch_class, true, THREAD);
1275       }
1276 
1277       if (HAS_PENDING_EXCEPTION) {
1278         Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1279         log_info(redefine, class, load, exceptions)
1280           ("verify_byte_codes post merge-CP exception: '%s'", ex_name->as_C_string());
1281         CLEAR_PENDING_EXCEPTION;
1282         if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1283           return JVMTI_ERROR_OUT_OF_MEMORY;
1284         } else {
1285           // tell the caller that constant pool merging screwed up
1286           return JVMTI_ERROR_INTERNAL;
1287         }
1288       }
1289     }
1290 
1291     Rewriter::rewrite(scratch_class, THREAD);
1292     if (!HAS_PENDING_EXCEPTION) {
1293       scratch_class->link_methods(THREAD);
1294     }
1295     if (HAS_PENDING_EXCEPTION) {
1296       Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1297       log_info(redefine, class, load, exceptions)
1298         ("Rewriter::rewrite or link_methods exception: '%s'", ex_name->as_C_string());
1299       CLEAR_PENDING_EXCEPTION;
1300       if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1301         return JVMTI_ERROR_OUT_OF_MEMORY;
1302       } else {
1303         return JVMTI_ERROR_INTERNAL;
1304       }
1305     }
1306 
1307     log_debug(redefine, class, load)
1308       ("loaded name=%s (avail_mem=" UINT64_FORMAT "K)", the_class->external_name(), os::available_memory() >> 10);
1309   }
1310 
1311   return JVMTI_ERROR_NONE;
1312 }
1313 
1314 
1315 // Map old_index to new_index as needed. scratch_cp is only needed
1316 // for log calls.
1317 void VM_RedefineClasses::map_index(const constantPoolHandle& scratch_cp,
1318        int old_index, int new_index) {
1319   if (find_new_index(old_index) != 0) {
1320     // old_index is already mapped
1321     return;
1322   }
1323 
1324   if (old_index == new_index) {
1325     // no mapping is needed
1326     return;
1327   }
1328 
1329   _index_map_p->at_put(old_index, new_index);
1330   _index_map_count++;
1331 
1332   log_trace(redefine, class, constantpool)
1333     ("mapped tag %d at index %d to %d", scratch_cp->tag_at(old_index).value(), old_index, new_index);
1334 } // end map_index()
1335 
1336 
1337 // Map old_index to new_index as needed.
1338 void VM_RedefineClasses::map_operand_index(int old_index, int new_index) {
1339   if (find_new_operand_index(old_index) != -1) {
1340     // old_index is already mapped
1341     return;
1342   }
1343 
1344   if (old_index == new_index) {
1345     // no mapping is needed
1346     return;
1347   }
1348 
1349   _operands_index_map_p->at_put(old_index, new_index);
1350   _operands_index_map_count++;
1351 
1352   log_trace(redefine, class, constantpool)("mapped bootstrap specifier at index %d to %d", old_index, new_index);
1353 } // end map_index()
1354 
1355 
1356 // Merge old_cp and scratch_cp and return the results of the merge via
1357 // merge_cp_p. The number of entries in *merge_cp_p is returned via
1358 // merge_cp_length_p. The entries in old_cp occupy the same locations
1359 // in *merge_cp_p. Also creates a map of indices from entries in
1360 // scratch_cp to the corresponding entry in *merge_cp_p. Index map
1361 // entries are only created for entries in scratch_cp that occupy a
1362 // different location in *merged_cp_p.
1363 bool VM_RedefineClasses::merge_constant_pools(const constantPoolHandle& old_cp,
1364        const constantPoolHandle& scratch_cp, constantPoolHandle *merge_cp_p,
1365        int *merge_cp_length_p, TRAPS) {
1366 
1367   if (merge_cp_p == NULL) {
1368     assert(false, "caller must provide scratch constantPool");
1369     return false; // robustness
1370   }
1371   if (merge_cp_length_p == NULL) {
1372     assert(false, "caller must provide scratch CP length");
1373     return false; // robustness
1374   }
1375   // Worst case we need old_cp->length() + scratch_cp()->length(),
1376   // but the caller might be smart so make sure we have at least
1377   // the minimum.
1378   if ((*merge_cp_p)->length() < old_cp->length()) {
1379     assert(false, "merge area too small");
1380     return false; // robustness
1381   }
1382 
1383   log_info(redefine, class, constantpool)("old_cp_len=%d, scratch_cp_len=%d", old_cp->length(), scratch_cp->length());
1384 
1385   {
1386     // Pass 0:
1387     // The old_cp is copied to *merge_cp_p; this means that any code
1388     // using old_cp does not have to change. This work looks like a
1389     // perfect fit for ConstantPool*::copy_cp_to(), but we need to
1390     // handle one special case:
1391     // - revert JVM_CONSTANT_Class to JVM_CONSTANT_UnresolvedClass
1392     // This will make verification happy.
1393 
1394     int old_i;  // index into old_cp
1395 
1396     // index zero (0) is not used in constantPools
1397     for (old_i = 1; old_i < old_cp->length(); old_i++) {
1398       // leave debugging crumb
1399       jbyte old_tag = old_cp->tag_at(old_i).value();
1400       switch (old_tag) {
1401       case JVM_CONSTANT_Class:
1402       case JVM_CONSTANT_UnresolvedClass:
1403         // revert the copy to JVM_CONSTANT_UnresolvedClass
1404         // May be resolving while calling this so do the same for
1405         // JVM_CONSTANT_UnresolvedClass (klass_name_at() deals with transition)
1406         (*merge_cp_p)->temp_unresolved_klass_at_put(old_i,
1407           old_cp->klass_name_index_at(old_i));
1408         break;
1409 
1410       case JVM_CONSTANT_Double:
1411       case JVM_CONSTANT_Long:
1412         // just copy the entry to *merge_cp_p, but double and long take
1413         // two constant pool entries
1414         ConstantPool::copy_entry_to(old_cp, old_i, *merge_cp_p, old_i, CHECK_0);
1415         old_i++;
1416         break;
1417 
1418       default:
1419         // just copy the entry to *merge_cp_p
1420         ConstantPool::copy_entry_to(old_cp, old_i, *merge_cp_p, old_i, CHECK_0);
1421         break;
1422       }
1423     } // end for each old_cp entry
1424 
1425     ConstantPool::copy_operands(old_cp, *merge_cp_p, CHECK_0);
1426     (*merge_cp_p)->extend_operands(scratch_cp, CHECK_0);
1427 
1428     // We don't need to sanity check that *merge_cp_length_p is within
1429     // *merge_cp_p bounds since we have the minimum on-entry check above.
1430     (*merge_cp_length_p) = old_i;
1431   }
1432 
1433   // merge_cp_len should be the same as old_cp->length() at this point
1434   // so this trace message is really a "warm-and-breathing" message.
1435   log_debug(redefine, class, constantpool)("after pass 0: merge_cp_len=%d", *merge_cp_length_p);
1436 
1437   int scratch_i;  // index into scratch_cp
1438   {
1439     // Pass 1a:
1440     // Compare scratch_cp entries to the old_cp entries that we have
1441     // already copied to *merge_cp_p. In this pass, we are eliminating
1442     // exact duplicates (matching entry at same index) so we only
1443     // compare entries in the common indice range.
1444     int increment = 1;
1445     int pass1a_length = MIN2(old_cp->length(), scratch_cp->length());
1446     for (scratch_i = 1; scratch_i < pass1a_length; scratch_i += increment) {
1447       switch (scratch_cp->tag_at(scratch_i).value()) {
1448       case JVM_CONSTANT_Double:
1449       case JVM_CONSTANT_Long:
1450         // double and long take two constant pool entries
1451         increment = 2;
1452         break;
1453 
1454       default:
1455         increment = 1;
1456         break;
1457       }
1458 
1459       bool match = scratch_cp->compare_entry_to(scratch_i, *merge_cp_p,
1460         scratch_i, CHECK_0);
1461       if (match) {
1462         // found a match at the same index so nothing more to do
1463         continue;
1464       } else if (is_unresolved_class_mismatch(scratch_cp, scratch_i,
1465                                               *merge_cp_p, scratch_i)) {
1466         // The mismatch in compare_entry_to() above is because of a
1467         // resolved versus unresolved class entry at the same index
1468         // with the same string value. Since Pass 0 reverted any
1469         // class entries to unresolved class entries in *merge_cp_p,
1470         // we go with the unresolved class entry.
1471         continue;
1472       }
1473 
1474       int found_i = scratch_cp->find_matching_entry(scratch_i, *merge_cp_p,
1475         CHECK_0);
1476       if (found_i != 0) {
1477         guarantee(found_i != scratch_i,
1478           "compare_entry_to() and find_matching_entry() do not agree");
1479 
1480         // Found a matching entry somewhere else in *merge_cp_p so
1481         // just need a mapping entry.
1482         map_index(scratch_cp, scratch_i, found_i);
1483         continue;
1484       }
1485 
1486       // The find_matching_entry() call above could fail to find a match
1487       // due to a resolved versus unresolved class or string entry situation
1488       // like we solved above with the is_unresolved_*_mismatch() calls.
1489       // However, we would have to call is_unresolved_*_mismatch() over
1490       // all of *merge_cp_p (potentially) and that doesn't seem to be
1491       // worth the time.
1492 
1493       // No match found so we have to append this entry and any unique
1494       // referenced entries to *merge_cp_p.
1495       append_entry(scratch_cp, scratch_i, merge_cp_p, merge_cp_length_p,
1496         CHECK_0);
1497     }
1498   }
1499 
1500   log_debug(redefine, class, constantpool)
1501     ("after pass 1a: merge_cp_len=%d, scratch_i=%d, index_map_len=%d",
1502      *merge_cp_length_p, scratch_i, _index_map_count);
1503 
1504   if (scratch_i < scratch_cp->length()) {
1505     // Pass 1b:
1506     // old_cp is smaller than scratch_cp so there are entries in
1507     // scratch_cp that we have not yet processed. We take care of
1508     // those now.
1509     int increment = 1;
1510     for (; scratch_i < scratch_cp->length(); scratch_i += increment) {
1511       switch (scratch_cp->tag_at(scratch_i).value()) {
1512       case JVM_CONSTANT_Double:
1513       case JVM_CONSTANT_Long:
1514         // double and long take two constant pool entries
1515         increment = 2;
1516         break;
1517 
1518       default:
1519         increment = 1;
1520         break;
1521       }
1522 
1523       int found_i =
1524         scratch_cp->find_matching_entry(scratch_i, *merge_cp_p, CHECK_0);
1525       if (found_i != 0) {
1526         // Found a matching entry somewhere else in *merge_cp_p so
1527         // just need a mapping entry.
1528         map_index(scratch_cp, scratch_i, found_i);
1529         continue;
1530       }
1531 
1532       // No match found so we have to append this entry and any unique
1533       // referenced entries to *merge_cp_p.
1534       append_entry(scratch_cp, scratch_i, merge_cp_p, merge_cp_length_p,
1535         CHECK_0);
1536     }
1537 
1538     log_debug(redefine, class, constantpool)
1539       ("after pass 1b: merge_cp_len=%d, scratch_i=%d, index_map_len=%d",
1540        *merge_cp_length_p, scratch_i, _index_map_count);
1541   }
1542   finalize_operands_merge(*merge_cp_p, THREAD);
1543 
1544   return true;
1545 } // end merge_constant_pools()
1546 
1547 
1548 // Scoped object to clean up the constant pool(s) created for merging
1549 class MergeCPCleaner {
1550   ClassLoaderData*   _loader_data;
1551   ConstantPool*      _cp;
1552   ConstantPool*      _scratch_cp;
1553  public:
1554   MergeCPCleaner(ClassLoaderData* loader_data, ConstantPool* merge_cp) :
1555                  _loader_data(loader_data), _cp(merge_cp), _scratch_cp(NULL) {}
1556   ~MergeCPCleaner() {
1557     _loader_data->add_to_deallocate_list(_cp);
1558     if (_scratch_cp != NULL) {
1559       _loader_data->add_to_deallocate_list(_scratch_cp);
1560     }
1561   }
1562   void add_scratch_cp(ConstantPool* scratch_cp) { _scratch_cp = scratch_cp; }
1563 };
1564 
1565 // Merge constant pools between the_class and scratch_class and
1566 // potentially rewrite bytecodes in scratch_class to use the merged
1567 // constant pool.
1568 jvmtiError VM_RedefineClasses::merge_cp_and_rewrite(
1569              InstanceKlass* the_class, InstanceKlass* scratch_class,
1570              TRAPS) {
1571   // worst case merged constant pool length is old and new combined
1572   int merge_cp_length = the_class->constants()->length()
1573         + scratch_class->constants()->length();
1574 
1575   // Constant pools are not easily reused so we allocate a new one
1576   // each time.
1577   // merge_cp is created unsafe for concurrent GC processing.  It
1578   // should be marked safe before discarding it. Even though
1579   // garbage,  if it crosses a card boundary, it may be scanned
1580   // in order to find the start of the first complete object on the card.
1581   ClassLoaderData* loader_data = the_class->class_loader_data();
1582   ConstantPool* merge_cp_oop =
1583     ConstantPool::allocate(loader_data,
1584                            merge_cp_length,
1585                            CHECK_(JVMTI_ERROR_OUT_OF_MEMORY));
1586   MergeCPCleaner cp_cleaner(loader_data, merge_cp_oop);
1587 
1588   HandleMark hm(THREAD);  // make sure handles are cleared before
1589                           // MergeCPCleaner clears out merge_cp_oop
1590   constantPoolHandle merge_cp(THREAD, merge_cp_oop);
1591 
1592   // Get constants() from the old class because it could have been rewritten
1593   // while we were at a safepoint allocating a new constant pool.
1594   constantPoolHandle old_cp(THREAD, the_class->constants());
1595   constantPoolHandle scratch_cp(THREAD, scratch_class->constants());
1596 
1597   // If the length changed, the class was redefined out from under us. Return
1598   // an error.
1599   if (merge_cp_length != the_class->constants()->length()
1600          + scratch_class->constants()->length()) {
1601     return JVMTI_ERROR_INTERNAL;
1602   }
1603 
1604   // Update the version number of the constant pools (may keep scratch_cp)
1605   merge_cp->increment_and_save_version(old_cp->version());
1606   scratch_cp->increment_and_save_version(old_cp->version());
1607 
1608   ResourceMark rm(THREAD);
1609   _index_map_count = 0;
1610   _index_map_p = new intArray(scratch_cp->length(), scratch_cp->length(), -1);
1611 
1612   _operands_cur_length = ConstantPool::operand_array_length(old_cp->operands());
1613   _operands_index_map_count = 0;
1614   int operands_index_map_len = ConstantPool::operand_array_length(scratch_cp->operands());
1615   _operands_index_map_p = new intArray(operands_index_map_len, operands_index_map_len, -1);
1616 
1617   // reference to the cp holder is needed for copy_operands()
1618   merge_cp->set_pool_holder(scratch_class);
1619   bool result = merge_constant_pools(old_cp, scratch_cp, &merge_cp,
1620                   &merge_cp_length, THREAD);
1621   merge_cp->set_pool_holder(NULL);
1622 
1623   if (!result) {
1624     // The merge can fail due to memory allocation failure or due
1625     // to robustness checks.
1626     return JVMTI_ERROR_INTERNAL;
1627   }
1628 
1629   log_info(redefine, class, constantpool)("merge_cp_len=%d, index_map_len=%d", merge_cp_length, _index_map_count);
1630 
1631   if (_index_map_count == 0) {
1632     // there is nothing to map between the new and merged constant pools
1633 
1634     if (old_cp->length() == scratch_cp->length()) {
1635       // The old and new constant pools are the same length and the
1636       // index map is empty. This means that the three constant pools
1637       // are equivalent (but not the same). Unfortunately, the new
1638       // constant pool has not gone through link resolution nor have
1639       // the new class bytecodes gone through constant pool cache
1640       // rewriting so we can't use the old constant pool with the new
1641       // class.
1642 
1643       // toss the merged constant pool at return
1644     } else if (old_cp->length() < scratch_cp->length()) {
1645       // The old constant pool has fewer entries than the new constant
1646       // pool and the index map is empty. This means the new constant
1647       // pool is a superset of the old constant pool. However, the old
1648       // class bytecodes have already gone through constant pool cache
1649       // rewriting so we can't use the new constant pool with the old
1650       // class.
1651 
1652       // toss the merged constant pool at return
1653     } else {
1654       // The old constant pool has more entries than the new constant
1655       // pool and the index map is empty. This means that both the old
1656       // and merged constant pools are supersets of the new constant
1657       // pool.
1658 
1659       // Replace the new constant pool with a shrunken copy of the
1660       // merged constant pool
1661       set_new_constant_pool(loader_data, scratch_class, merge_cp, merge_cp_length,
1662                             CHECK_(JVMTI_ERROR_OUT_OF_MEMORY));
1663       // The new constant pool replaces scratch_cp so have cleaner clean it up.
1664       // It can't be cleaned up while there are handles to it.
1665       cp_cleaner.add_scratch_cp(scratch_cp());
1666     }
1667   } else {
1668     if (log_is_enabled(Trace, redefine, class, constantpool)) {
1669       // don't want to loop unless we are tracing
1670       int count = 0;
1671       for (int i = 1; i < _index_map_p->length(); i++) {
1672         int value = _index_map_p->at(i);
1673 
1674         if (value != -1) {
1675           log_trace(redefine, class, constantpool)("index_map[%d]: old=%d new=%d", count, i, value);
1676           count++;
1677         }
1678       }
1679     }
1680 
1681     // We have entries mapped between the new and merged constant pools
1682     // so we have to rewrite some constant pool references.
1683     if (!rewrite_cp_refs(scratch_class, THREAD)) {
1684       return JVMTI_ERROR_INTERNAL;
1685     }
1686 
1687     // Replace the new constant pool with a shrunken copy of the
1688     // merged constant pool so now the rewritten bytecodes have
1689     // valid references; the previous new constant pool will get
1690     // GCed.
1691     set_new_constant_pool(loader_data, scratch_class, merge_cp, merge_cp_length,
1692                           CHECK_(JVMTI_ERROR_OUT_OF_MEMORY));
1693     // The new constant pool replaces scratch_cp so have cleaner clean it up.
1694     // It can't be cleaned up while there are handles to it.
1695     cp_cleaner.add_scratch_cp(scratch_cp());
1696   }
1697 
1698   return JVMTI_ERROR_NONE;
1699 } // end merge_cp_and_rewrite()
1700 
1701 
1702 // Rewrite constant pool references in klass scratch_class.
1703 bool VM_RedefineClasses::rewrite_cp_refs(InstanceKlass* scratch_class,
1704        TRAPS) {
1705 
1706   // rewrite constant pool references in the nest attributes:
1707   if (!rewrite_cp_refs_in_nest_attributes(scratch_class)) {
1708     // propagate failure back to caller
1709     return false;
1710   }
1711 
1712   // rewrite constant pool references in the methods:
1713   if (!rewrite_cp_refs_in_methods(scratch_class, THREAD)) {
1714     // propagate failure back to caller
1715     return false;
1716   }
1717 
1718   // rewrite constant pool references in the class_annotations:
1719   if (!rewrite_cp_refs_in_class_annotations(scratch_class, THREAD)) {
1720     // propagate failure back to caller
1721     return false;
1722   }
1723 
1724   // rewrite constant pool references in the fields_annotations:
1725   if (!rewrite_cp_refs_in_fields_annotations(scratch_class, THREAD)) {
1726     // propagate failure back to caller
1727     return false;
1728   }
1729 
1730   // rewrite constant pool references in the methods_annotations:
1731   if (!rewrite_cp_refs_in_methods_annotations(scratch_class, THREAD)) {
1732     // propagate failure back to caller
1733     return false;
1734   }
1735 
1736   // rewrite constant pool references in the methods_parameter_annotations:
1737   if (!rewrite_cp_refs_in_methods_parameter_annotations(scratch_class,
1738          THREAD)) {
1739     // propagate failure back to caller
1740     return false;
1741   }
1742 
1743   // rewrite constant pool references in the methods_default_annotations:
1744   if (!rewrite_cp_refs_in_methods_default_annotations(scratch_class,
1745          THREAD)) {
1746     // propagate failure back to caller
1747     return false;
1748   }
1749 
1750   // rewrite constant pool references in the class_type_annotations:
1751   if (!rewrite_cp_refs_in_class_type_annotations(scratch_class, THREAD)) {
1752     // propagate failure back to caller
1753     return false;
1754   }
1755 
1756   // rewrite constant pool references in the fields_type_annotations:
1757   if (!rewrite_cp_refs_in_fields_type_annotations(scratch_class, THREAD)) {
1758     // propagate failure back to caller
1759     return false;
1760   }
1761 
1762   // rewrite constant pool references in the methods_type_annotations:
1763   if (!rewrite_cp_refs_in_methods_type_annotations(scratch_class, THREAD)) {
1764     // propagate failure back to caller
1765     return false;
1766   }
1767 
1768   // There can be type annotations in the Code part of a method_info attribute.
1769   // These annotations are not accessible, even by reflection.
1770   // Currently they are not even parsed by the ClassFileParser.
1771   // If runtime access is added they will also need to be rewritten.
1772 
1773   // rewrite source file name index:
1774   u2 source_file_name_idx = scratch_class->source_file_name_index();
1775   if (source_file_name_idx != 0) {
1776     u2 new_source_file_name_idx = find_new_index(source_file_name_idx);
1777     if (new_source_file_name_idx != 0) {
1778       scratch_class->set_source_file_name_index(new_source_file_name_idx);
1779     }
1780   }
1781 
1782   // rewrite class generic signature index:
1783   u2 generic_signature_index = scratch_class->generic_signature_index();
1784   if (generic_signature_index != 0) {
1785     u2 new_generic_signature_index = find_new_index(generic_signature_index);
1786     if (new_generic_signature_index != 0) {
1787       scratch_class->set_generic_signature_index(new_generic_signature_index);
1788     }
1789   }
1790 
1791   return true;
1792 } // end rewrite_cp_refs()
1793 
1794 // Rewrite constant pool references in the NestHost and NestMembers attributes.
1795 bool VM_RedefineClasses::rewrite_cp_refs_in_nest_attributes(
1796        InstanceKlass* scratch_class) {
1797 
1798   u2 cp_index = scratch_class->nest_host_index();
1799   if (cp_index != 0) {
1800     scratch_class->set_nest_host_index(find_new_index(cp_index));
1801   }
1802   Array<u2>* nest_members = scratch_class->nest_members();
1803   for (int i = 0; i < nest_members->length(); i++) {
1804     u2 cp_index = nest_members->at(i);
1805     nest_members->at_put(i, find_new_index(cp_index));
1806   }
1807   return true;
1808 }
1809 
1810 // Rewrite constant pool references in the methods.
1811 bool VM_RedefineClasses::rewrite_cp_refs_in_methods(
1812        InstanceKlass* scratch_class, TRAPS) {
1813 
1814   Array<Method*>* methods = scratch_class->methods();
1815 
1816   if (methods == NULL || methods->length() == 0) {
1817     // no methods so nothing to do
1818     return true;
1819   }
1820 
1821   // rewrite constant pool references in the methods:
1822   for (int i = methods->length() - 1; i >= 0; i--) {
1823     methodHandle method(THREAD, methods->at(i));
1824     methodHandle new_method;
1825     rewrite_cp_refs_in_method(method, &new_method, THREAD);
1826     if (!new_method.is_null()) {
1827       // the method has been replaced so save the new method version
1828       // even in the case of an exception.  original method is on the
1829       // deallocation list.
1830       methods->at_put(i, new_method());
1831     }
1832     if (HAS_PENDING_EXCEPTION) {
1833       Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1834       log_info(redefine, class, load, exceptions)("rewrite_cp_refs_in_method exception: '%s'", ex_name->as_C_string());
1835       // Need to clear pending exception here as the super caller sets
1836       // the JVMTI_ERROR_INTERNAL if the returned value is false.
1837       CLEAR_PENDING_EXCEPTION;
1838       return false;
1839     }
1840   }
1841 
1842   return true;
1843 }
1844 
1845 
1846 // Rewrite constant pool references in the specific method. This code
1847 // was adapted from Rewriter::rewrite_method().
1848 void VM_RedefineClasses::rewrite_cp_refs_in_method(methodHandle method,
1849        methodHandle *new_method_p, TRAPS) {
1850 
1851   *new_method_p = methodHandle();  // default is no new method
1852 
1853   // We cache a pointer to the bytecodes here in code_base. If GC
1854   // moves the Method*, then the bytecodes will also move which
1855   // will likely cause a crash. We create a NoSafepointVerifier
1856   // object to detect whether we pass a possible safepoint in this
1857   // code block.
1858   NoSafepointVerifier nsv;
1859 
1860   // Bytecodes and their length
1861   address code_base = method->code_base();
1862   int code_length = method->code_size();
1863 
1864   int bc_length;
1865   for (int bci = 0; bci < code_length; bci += bc_length) {
1866     address bcp = code_base + bci;
1867     Bytecodes::Code c = (Bytecodes::Code)(*bcp);
1868 
1869     bc_length = Bytecodes::length_for(c);
1870     if (bc_length == 0) {
1871       // More complicated bytecodes report a length of zero so
1872       // we have to try again a slightly different way.
1873       bc_length = Bytecodes::length_at(method(), bcp);
1874     }
1875 
1876     assert(bc_length != 0, "impossible bytecode length");
1877 
1878     switch (c) {
1879       case Bytecodes::_ldc:
1880       {
1881         int cp_index = *(bcp + 1);
1882         int new_index = find_new_index(cp_index);
1883 
1884         if (StressLdcRewrite && new_index == 0) {
1885           // If we are stressing ldc -> ldc_w rewriting, then we
1886           // always need a new_index value.
1887           new_index = cp_index;
1888         }
1889         if (new_index != 0) {
1890           // the original index is mapped so we have more work to do
1891           if (!StressLdcRewrite && new_index <= max_jubyte) {
1892             // The new value can still use ldc instead of ldc_w
1893             // unless we are trying to stress ldc -> ldc_w rewriting
1894             log_trace(redefine, class, constantpool)
1895               ("%s@" INTPTR_FORMAT " old=%d, new=%d", Bytecodes::name(c), p2i(bcp), cp_index, new_index);
1896             *(bcp + 1) = new_index;
1897           } else {
1898             log_trace(redefine, class, constantpool)
1899               ("%s->ldc_w@" INTPTR_FORMAT " old=%d, new=%d", Bytecodes::name(c), p2i(bcp), cp_index, new_index);
1900             // the new value needs ldc_w instead of ldc
1901             u_char inst_buffer[4]; // max instruction size is 4 bytes
1902             bcp = (address)inst_buffer;
1903             // construct new instruction sequence
1904             *bcp = Bytecodes::_ldc_w;
1905             bcp++;
1906             // Rewriter::rewrite_method() does not rewrite ldc -> ldc_w.
1907             // See comment below for difference between put_Java_u2()
1908             // and put_native_u2().
1909             Bytes::put_Java_u2(bcp, new_index);
1910 
1911             Relocator rc(method, NULL /* no RelocatorListener needed */);
1912             methodHandle m;
1913             {
1914               PauseNoSafepointVerifier pnsv(&nsv);
1915 
1916               // ldc is 2 bytes and ldc_w is 3 bytes
1917               m = rc.insert_space_at(bci, 3, inst_buffer, CHECK);
1918             }
1919 
1920             // return the new method so that the caller can update
1921             // the containing class
1922             *new_method_p = method = m;
1923             // switch our bytecode processing loop from the old method
1924             // to the new method
1925             code_base = method->code_base();
1926             code_length = method->code_size();
1927             bcp = code_base + bci;
1928             c = (Bytecodes::Code)(*bcp);
1929             bc_length = Bytecodes::length_for(c);
1930             assert(bc_length != 0, "sanity check");
1931           } // end we need ldc_w instead of ldc
1932         } // end if there is a mapped index
1933       } break;
1934 
1935       // these bytecodes have a two-byte constant pool index
1936       case Bytecodes::_anewarray      : // fall through
1937       case Bytecodes::_checkcast      : // fall through
1938       case Bytecodes::_getfield       : // fall through
1939       case Bytecodes::_getstatic      : // fall through
1940       case Bytecodes::_instanceof     : // fall through
1941       case Bytecodes::_invokedynamic  : // fall through
1942       case Bytecodes::_invokeinterface: // fall through
1943       case Bytecodes::_invokespecial  : // fall through
1944       case Bytecodes::_invokestatic   : // fall through
1945       case Bytecodes::_invokevirtual  : // fall through
1946       case Bytecodes::_ldc_w          : // fall through
1947       case Bytecodes::_ldc2_w         : // fall through
1948       case Bytecodes::_multianewarray : // fall through
1949       case Bytecodes::_new            : // fall through
1950       case Bytecodes::_putfield       : // fall through
1951       case Bytecodes::_putstatic      :
1952       {
1953         address p = bcp + 1;
1954         int cp_index = Bytes::get_Java_u2(p);
1955         int new_index = find_new_index(cp_index);
1956         if (new_index != 0) {
1957           // the original index is mapped so update w/ new value
1958           log_trace(redefine, class, constantpool)
1959             ("%s@" INTPTR_FORMAT " old=%d, new=%d", Bytecodes::name(c),p2i(bcp), cp_index, new_index);
1960           // Rewriter::rewrite_method() uses put_native_u2() in this
1961           // situation because it is reusing the constant pool index
1962           // location for a native index into the ConstantPoolCache.
1963           // Since we are updating the constant pool index prior to
1964           // verification and ConstantPoolCache initialization, we
1965           // need to keep the new index in Java byte order.
1966           Bytes::put_Java_u2(p, new_index);
1967         }
1968       } break;
1969       default:
1970         break;
1971     }
1972   } // end for each bytecode
1973 
1974   // We also need to rewrite the parameter name indexes, if there is
1975   // method parameter data present
1976   if(method->has_method_parameters()) {
1977     const int len = method->method_parameters_length();
1978     MethodParametersElement* elem = method->method_parameters_start();
1979 
1980     for (int i = 0; i < len; i++) {
1981       const u2 cp_index = elem[i].name_cp_index;
1982       const u2 new_cp_index = find_new_index(cp_index);
1983       if (new_cp_index != 0) {
1984         elem[i].name_cp_index = new_cp_index;
1985       }
1986     }
1987   }
1988 } // end rewrite_cp_refs_in_method()
1989 
1990 
1991 // Rewrite constant pool references in the class_annotations field.
1992 bool VM_RedefineClasses::rewrite_cp_refs_in_class_annotations(
1993        InstanceKlass* scratch_class, TRAPS) {
1994 
1995   AnnotationArray* class_annotations = scratch_class->class_annotations();
1996   if (class_annotations == NULL || class_annotations->length() == 0) {
1997     // no class_annotations so nothing to do
1998     return true;
1999   }
2000 
2001   log_debug(redefine, class, annotation)("class_annotations length=%d", class_annotations->length());
2002 
2003   int byte_i = 0;  // byte index into class_annotations
2004   return rewrite_cp_refs_in_annotations_typeArray(class_annotations, byte_i,
2005            THREAD);
2006 }
2007 
2008 
2009 // Rewrite constant pool references in an annotations typeArray. This
2010 // "structure" is adapted from the RuntimeVisibleAnnotations_attribute
2011 // that is described in section 4.8.15 of the 2nd-edition of the VM spec:
2012 //
2013 // annotations_typeArray {
2014 //   u2 num_annotations;
2015 //   annotation annotations[num_annotations];
2016 // }
2017 //
2018 bool VM_RedefineClasses::rewrite_cp_refs_in_annotations_typeArray(
2019        AnnotationArray* annotations_typeArray, int &byte_i_ref, TRAPS) {
2020 
2021   if ((byte_i_ref + 2) > annotations_typeArray->length()) {
2022     // not enough room for num_annotations field
2023     log_debug(redefine, class, annotation)("length() is too small for num_annotations field");
2024     return false;
2025   }
2026 
2027   u2 num_annotations = Bytes::get_Java_u2((address)
2028                          annotations_typeArray->adr_at(byte_i_ref));
2029   byte_i_ref += 2;
2030 
2031   log_debug(redefine, class, annotation)("num_annotations=%d", num_annotations);
2032 
2033   int calc_num_annotations = 0;
2034   for (; calc_num_annotations < num_annotations; calc_num_annotations++) {
2035     if (!rewrite_cp_refs_in_annotation_struct(annotations_typeArray,
2036            byte_i_ref, THREAD)) {
2037       log_debug(redefine, class, annotation)("bad annotation_struct at %d", calc_num_annotations);
2038       // propagate failure back to caller
2039       return false;
2040     }
2041   }
2042   assert(num_annotations == calc_num_annotations, "sanity check");
2043 
2044   return true;
2045 } // end rewrite_cp_refs_in_annotations_typeArray()
2046 
2047 
2048 // Rewrite constant pool references in the annotation struct portion of
2049 // an annotations_typeArray. This "structure" is from section 4.8.15 of
2050 // the 2nd-edition of the VM spec:
2051 //
2052 // struct annotation {
2053 //   u2 type_index;
2054 //   u2 num_element_value_pairs;
2055 //   {
2056 //     u2 element_name_index;
2057 //     element_value value;
2058 //   } element_value_pairs[num_element_value_pairs];
2059 // }
2060 //
2061 bool VM_RedefineClasses::rewrite_cp_refs_in_annotation_struct(
2062        AnnotationArray* annotations_typeArray, int &byte_i_ref, TRAPS) {
2063   if ((byte_i_ref + 2 + 2) > annotations_typeArray->length()) {
2064     // not enough room for smallest annotation_struct
2065     log_debug(redefine, class, annotation)("length() is too small for annotation_struct");
2066     return false;
2067   }
2068 
2069   u2 type_index = rewrite_cp_ref_in_annotation_data(annotations_typeArray,
2070                     byte_i_ref, "type_index", THREAD);
2071 
2072   u2 num_element_value_pairs = Bytes::get_Java_u2((address)
2073                                  annotations_typeArray->adr_at(byte_i_ref));
2074   byte_i_ref += 2;
2075 
2076   log_debug(redefine, class, annotation)
2077     ("type_index=%d  num_element_value_pairs=%d", type_index, num_element_value_pairs);
2078 
2079   int calc_num_element_value_pairs = 0;
2080   for (; calc_num_element_value_pairs < num_element_value_pairs;
2081        calc_num_element_value_pairs++) {
2082     if ((byte_i_ref + 2) > annotations_typeArray->length()) {
2083       // not enough room for another element_name_index, let alone
2084       // the rest of another component
2085       log_debug(redefine, class, annotation)("length() is too small for element_name_index");
2086       return false;
2087     }
2088 
2089     u2 element_name_index = rewrite_cp_ref_in_annotation_data(
2090                               annotations_typeArray, byte_i_ref,
2091                               "element_name_index", THREAD);
2092 
2093     log_debug(redefine, class, annotation)("element_name_index=%d", element_name_index);
2094 
2095     if (!rewrite_cp_refs_in_element_value(annotations_typeArray,
2096            byte_i_ref, THREAD)) {
2097       log_debug(redefine, class, annotation)("bad element_value at %d", calc_num_element_value_pairs);
2098       // propagate failure back to caller
2099       return false;
2100     }
2101   } // end for each component
2102   assert(num_element_value_pairs == calc_num_element_value_pairs,
2103     "sanity check");
2104 
2105   return true;
2106 } // end rewrite_cp_refs_in_annotation_struct()
2107 
2108 
2109 // Rewrite a constant pool reference at the current position in
2110 // annotations_typeArray if needed. Returns the original constant
2111 // pool reference if a rewrite was not needed or the new constant
2112 // pool reference if a rewrite was needed.
2113 u2 VM_RedefineClasses::rewrite_cp_ref_in_annotation_data(
2114      AnnotationArray* annotations_typeArray, int &byte_i_ref,
2115      const char * trace_mesg, TRAPS) {
2116 
2117   address cp_index_addr = (address)
2118     annotations_typeArray->adr_at(byte_i_ref);
2119   u2 old_cp_index = Bytes::get_Java_u2(cp_index_addr);
2120   u2 new_cp_index = find_new_index(old_cp_index);
2121   if (new_cp_index != 0) {
2122     log_debug(redefine, class, annotation)("mapped old %s=%d", trace_mesg, old_cp_index);
2123     Bytes::put_Java_u2(cp_index_addr, new_cp_index);
2124     old_cp_index = new_cp_index;
2125   }
2126   byte_i_ref += 2;
2127   return old_cp_index;
2128 }
2129 
2130 
2131 // Rewrite constant pool references in the element_value portion of an
2132 // annotations_typeArray. This "structure" is from section 4.8.15.1 of
2133 // the 2nd-edition of the VM spec:
2134 //
2135 // struct element_value {
2136 //   u1 tag;
2137 //   union {
2138 //     u2 const_value_index;
2139 //     {
2140 //       u2 type_name_index;
2141 //       u2 const_name_index;
2142 //     } enum_const_value;
2143 //     u2 class_info_index;
2144 //     annotation annotation_value;
2145 //     struct {
2146 //       u2 num_values;
2147 //       element_value values[num_values];
2148 //     } array_value;
2149 //   } value;
2150 // }
2151 //
2152 bool VM_RedefineClasses::rewrite_cp_refs_in_element_value(
2153        AnnotationArray* annotations_typeArray, int &byte_i_ref, TRAPS) {
2154 
2155   if ((byte_i_ref + 1) > annotations_typeArray->length()) {
2156     // not enough room for a tag let alone the rest of an element_value
2157     log_debug(redefine, class, annotation)("length() is too small for a tag");
2158     return false;
2159   }
2160 
2161   u1 tag = annotations_typeArray->at(byte_i_ref);
2162   byte_i_ref++;
2163   log_debug(redefine, class, annotation)("tag='%c'", tag);
2164 
2165   switch (tag) {
2166     // These BaseType tag values are from Table 4.2 in VM spec:
2167     case 'B':  // byte
2168     case 'C':  // char
2169     case 'D':  // double
2170     case 'F':  // float
2171     case 'I':  // int
2172     case 'J':  // long
2173     case 'S':  // short
2174     case 'Z':  // boolean
2175 
2176     // The remaining tag values are from Table 4.8 in the 2nd-edition of
2177     // the VM spec:
2178     case 's':
2179     {
2180       // For the above tag values (including the BaseType values),
2181       // value.const_value_index is right union field.
2182 
2183       if ((byte_i_ref + 2) > annotations_typeArray->length()) {
2184         // not enough room for a const_value_index
2185         log_debug(redefine, class, annotation)("length() is too small for a const_value_index");
2186         return false;
2187       }
2188 
2189       u2 const_value_index = rewrite_cp_ref_in_annotation_data(
2190                                annotations_typeArray, byte_i_ref,
2191                                "const_value_index", THREAD);
2192 
2193       log_debug(redefine, class, annotation)("const_value_index=%d", const_value_index);
2194     } break;
2195 
2196     case 'e':
2197     {
2198       // for the above tag value, value.enum_const_value is right union field
2199 
2200       if ((byte_i_ref + 4) > annotations_typeArray->length()) {
2201         // not enough room for a enum_const_value
2202         log_debug(redefine, class, annotation)("length() is too small for a enum_const_value");
2203         return false;
2204       }
2205 
2206       u2 type_name_index = rewrite_cp_ref_in_annotation_data(
2207                              annotations_typeArray, byte_i_ref,
2208                              "type_name_index", THREAD);
2209 
2210       u2 const_name_index = rewrite_cp_ref_in_annotation_data(
2211                               annotations_typeArray, byte_i_ref,
2212                               "const_name_index", THREAD);
2213 
2214       log_debug(redefine, class, annotation)
2215         ("type_name_index=%d  const_name_index=%d", type_name_index, const_name_index);
2216     } break;
2217 
2218     case 'c':
2219     {
2220       // for the above tag value, value.class_info_index is right union field
2221 
2222       if ((byte_i_ref + 2) > annotations_typeArray->length()) {
2223         // not enough room for a class_info_index
2224         log_debug(redefine, class, annotation)("length() is too small for a class_info_index");
2225         return false;
2226       }
2227 
2228       u2 class_info_index = rewrite_cp_ref_in_annotation_data(
2229                               annotations_typeArray, byte_i_ref,
2230                               "class_info_index", THREAD);
2231 
2232       log_debug(redefine, class, annotation)("class_info_index=%d", class_info_index);
2233     } break;
2234 
2235     case '@':
2236       // For the above tag value, value.attr_value is the right union
2237       // field. This is a nested annotation.
2238       if (!rewrite_cp_refs_in_annotation_struct(annotations_typeArray,
2239              byte_i_ref, THREAD)) {
2240         // propagate failure back to caller
2241         return false;
2242       }
2243       break;
2244 
2245     case '[':
2246     {
2247       if ((byte_i_ref + 2) > annotations_typeArray->length()) {
2248         // not enough room for a num_values field
2249         log_debug(redefine, class, annotation)("length() is too small for a num_values field");
2250         return false;
2251       }
2252 
2253       // For the above tag value, value.array_value is the right union
2254       // field. This is an array of nested element_value.
2255       u2 num_values = Bytes::get_Java_u2((address)
2256                         annotations_typeArray->adr_at(byte_i_ref));
2257       byte_i_ref += 2;
2258       log_debug(redefine, class, annotation)("num_values=%d", num_values);
2259 
2260       int calc_num_values = 0;
2261       for (; calc_num_values < num_values; calc_num_values++) {
2262         if (!rewrite_cp_refs_in_element_value(
2263                annotations_typeArray, byte_i_ref, THREAD)) {
2264           log_debug(redefine, class, annotation)("bad nested element_value at %d", calc_num_values);
2265           // propagate failure back to caller
2266           return false;
2267         }
2268       }
2269       assert(num_values == calc_num_values, "sanity check");
2270     } break;
2271 
2272     default:
2273       log_debug(redefine, class, annotation)("bad tag=0x%x", tag);
2274       return false;
2275   } // end decode tag field
2276 
2277   return true;
2278 } // end rewrite_cp_refs_in_element_value()
2279 
2280 
2281 // Rewrite constant pool references in a fields_annotations field.
2282 bool VM_RedefineClasses::rewrite_cp_refs_in_fields_annotations(
2283        InstanceKlass* scratch_class, TRAPS) {
2284 
2285   Array<AnnotationArray*>* fields_annotations = scratch_class->fields_annotations();
2286 
2287   if (fields_annotations == NULL || fields_annotations->length() == 0) {
2288     // no fields_annotations so nothing to do
2289     return true;
2290   }
2291 
2292   log_debug(redefine, class, annotation)("fields_annotations length=%d", fields_annotations->length());
2293 
2294   for (int i = 0; i < fields_annotations->length(); i++) {
2295     AnnotationArray* field_annotations = fields_annotations->at(i);
2296     if (field_annotations == NULL || field_annotations->length() == 0) {
2297       // this field does not have any annotations so skip it
2298       continue;
2299     }
2300 
2301     int byte_i = 0;  // byte index into field_annotations
2302     if (!rewrite_cp_refs_in_annotations_typeArray(field_annotations, byte_i,
2303            THREAD)) {
2304       log_debug(redefine, class, annotation)("bad field_annotations at %d", i);
2305       // propagate failure back to caller
2306       return false;
2307     }
2308   }
2309 
2310   return true;
2311 } // end rewrite_cp_refs_in_fields_annotations()
2312 
2313 
2314 // Rewrite constant pool references in a methods_annotations field.
2315 bool VM_RedefineClasses::rewrite_cp_refs_in_methods_annotations(
2316        InstanceKlass* scratch_class, TRAPS) {
2317 
2318   for (int i = 0; i < scratch_class->methods()->length(); i++) {
2319     Method* m = scratch_class->methods()->at(i);
2320     AnnotationArray* method_annotations = m->constMethod()->method_annotations();
2321 
2322     if (method_annotations == NULL || method_annotations->length() == 0) {
2323       // this method does not have any annotations so skip it
2324       continue;
2325     }
2326 
2327     int byte_i = 0;  // byte index into method_annotations
2328     if (!rewrite_cp_refs_in_annotations_typeArray(method_annotations, byte_i,
2329            THREAD)) {
2330       log_debug(redefine, class, annotation)("bad method_annotations at %d", i);
2331       // propagate failure back to caller
2332       return false;
2333     }
2334   }
2335 
2336   return true;
2337 } // end rewrite_cp_refs_in_methods_annotations()
2338 
2339 
2340 // Rewrite constant pool references in a methods_parameter_annotations
2341 // field. This "structure" is adapted from the
2342 // RuntimeVisibleParameterAnnotations_attribute described in section
2343 // 4.8.17 of the 2nd-edition of the VM spec:
2344 //
2345 // methods_parameter_annotations_typeArray {
2346 //   u1 num_parameters;
2347 //   {
2348 //     u2 num_annotations;
2349 //     annotation annotations[num_annotations];
2350 //   } parameter_annotations[num_parameters];
2351 // }
2352 //
2353 bool VM_RedefineClasses::rewrite_cp_refs_in_methods_parameter_annotations(
2354        InstanceKlass* scratch_class, TRAPS) {
2355 
2356   for (int i = 0; i < scratch_class->methods()->length(); i++) {
2357     Method* m = scratch_class->methods()->at(i);
2358     AnnotationArray* method_parameter_annotations = m->constMethod()->parameter_annotations();
2359     if (method_parameter_annotations == NULL
2360         || method_parameter_annotations->length() == 0) {
2361       // this method does not have any parameter annotations so skip it
2362       continue;
2363     }
2364 
2365     if (method_parameter_annotations->length() < 1) {
2366       // not enough room for a num_parameters field
2367       log_debug(redefine, class, annotation)("length() is too small for a num_parameters field at %d", i);
2368       return false;
2369     }
2370 
2371     int byte_i = 0;  // byte index into method_parameter_annotations
2372 
2373     u1 num_parameters = method_parameter_annotations->at(byte_i);
2374     byte_i++;
2375 
2376     log_debug(redefine, class, annotation)("num_parameters=%d", num_parameters);
2377 
2378     int calc_num_parameters = 0;
2379     for (; calc_num_parameters < num_parameters; calc_num_parameters++) {
2380       if (!rewrite_cp_refs_in_annotations_typeArray(
2381              method_parameter_annotations, byte_i, THREAD)) {
2382         log_debug(redefine, class, annotation)("bad method_parameter_annotations at %d", calc_num_parameters);
2383         // propagate failure back to caller
2384         return false;
2385       }
2386     }
2387     assert(num_parameters == calc_num_parameters, "sanity check");
2388   }
2389 
2390   return true;
2391 } // end rewrite_cp_refs_in_methods_parameter_annotations()
2392 
2393 
2394 // Rewrite constant pool references in a methods_default_annotations
2395 // field. This "structure" is adapted from the AnnotationDefault_attribute
2396 // that is described in section 4.8.19 of the 2nd-edition of the VM spec:
2397 //
2398 // methods_default_annotations_typeArray {
2399 //   element_value default_value;
2400 // }
2401 //
2402 bool VM_RedefineClasses::rewrite_cp_refs_in_methods_default_annotations(
2403        InstanceKlass* scratch_class, TRAPS) {
2404 
2405   for (int i = 0; i < scratch_class->methods()->length(); i++) {
2406     Method* m = scratch_class->methods()->at(i);
2407     AnnotationArray* method_default_annotations = m->constMethod()->default_annotations();
2408     if (method_default_annotations == NULL
2409         || method_default_annotations->length() == 0) {
2410       // this method does not have any default annotations so skip it
2411       continue;
2412     }
2413 
2414     int byte_i = 0;  // byte index into method_default_annotations
2415 
2416     if (!rewrite_cp_refs_in_element_value(
2417            method_default_annotations, byte_i, THREAD)) {
2418       log_debug(redefine, class, annotation)("bad default element_value at %d", i);
2419       // propagate failure back to caller
2420       return false;
2421     }
2422   }
2423 
2424   return true;
2425 } // end rewrite_cp_refs_in_methods_default_annotations()
2426 
2427 
2428 // Rewrite constant pool references in a class_type_annotations field.
2429 bool VM_RedefineClasses::rewrite_cp_refs_in_class_type_annotations(
2430        InstanceKlass* scratch_class, TRAPS) {
2431 
2432   AnnotationArray* class_type_annotations = scratch_class->class_type_annotations();
2433   if (class_type_annotations == NULL || class_type_annotations->length() == 0) {
2434     // no class_type_annotations so nothing to do
2435     return true;
2436   }
2437 
2438   log_debug(redefine, class, annotation)("class_type_annotations length=%d", class_type_annotations->length());
2439 
2440   int byte_i = 0;  // byte index into class_type_annotations
2441   return rewrite_cp_refs_in_type_annotations_typeArray(class_type_annotations,
2442       byte_i, "ClassFile", THREAD);
2443 } // end rewrite_cp_refs_in_class_type_annotations()
2444 
2445 
2446 // Rewrite constant pool references in a fields_type_annotations field.
2447 bool VM_RedefineClasses::rewrite_cp_refs_in_fields_type_annotations(
2448        InstanceKlass* scratch_class, TRAPS) {
2449 
2450   Array<AnnotationArray*>* fields_type_annotations = scratch_class->fields_type_annotations();
2451   if (fields_type_annotations == NULL || fields_type_annotations->length() == 0) {
2452     // no fields_type_annotations so nothing to do
2453     return true;
2454   }
2455 
2456   log_debug(redefine, class, annotation)("fields_type_annotations length=%d", fields_type_annotations->length());
2457 
2458   for (int i = 0; i < fields_type_annotations->length(); i++) {
2459     AnnotationArray* field_type_annotations = fields_type_annotations->at(i);
2460     if (field_type_annotations == NULL || field_type_annotations->length() == 0) {
2461       // this field does not have any annotations so skip it
2462       continue;
2463     }
2464 
2465     int byte_i = 0;  // byte index into field_type_annotations
2466     if (!rewrite_cp_refs_in_type_annotations_typeArray(field_type_annotations,
2467            byte_i, "field_info", THREAD)) {
2468       log_debug(redefine, class, annotation)("bad field_type_annotations at %d", i);
2469       // propagate failure back to caller
2470       return false;
2471     }
2472   }
2473 
2474   return true;
2475 } // end rewrite_cp_refs_in_fields_type_annotations()
2476 
2477 
2478 // Rewrite constant pool references in a methods_type_annotations field.
2479 bool VM_RedefineClasses::rewrite_cp_refs_in_methods_type_annotations(
2480        InstanceKlass* scratch_class, TRAPS) {
2481 
2482   for (int i = 0; i < scratch_class->methods()->length(); i++) {
2483     Method* m = scratch_class->methods()->at(i);
2484     AnnotationArray* method_type_annotations = m->constMethod()->type_annotations();
2485 
2486     if (method_type_annotations == NULL || method_type_annotations->length() == 0) {
2487       // this method does not have any annotations so skip it
2488       continue;
2489     }
2490 
2491     log_debug(redefine, class, annotation)("methods type_annotations length=%d", method_type_annotations->length());
2492 
2493     int byte_i = 0;  // byte index into method_type_annotations
2494     if (!rewrite_cp_refs_in_type_annotations_typeArray(method_type_annotations,
2495            byte_i, "method_info", THREAD)) {
2496       log_debug(redefine, class, annotation)("bad method_type_annotations at %d", i);
2497       // propagate failure back to caller
2498       return false;
2499     }
2500   }
2501 
2502   return true;
2503 } // end rewrite_cp_refs_in_methods_type_annotations()
2504 
2505 
2506 // Rewrite constant pool references in a type_annotations
2507 // field. This "structure" is adapted from the
2508 // RuntimeVisibleTypeAnnotations_attribute described in
2509 // section 4.7.20 of the Java SE 8 Edition of the VM spec:
2510 //
2511 // type_annotations_typeArray {
2512 //   u2              num_annotations;
2513 //   type_annotation annotations[num_annotations];
2514 // }
2515 //
2516 bool VM_RedefineClasses::rewrite_cp_refs_in_type_annotations_typeArray(
2517        AnnotationArray* type_annotations_typeArray, int &byte_i_ref,
2518        const char * location_mesg, TRAPS) {
2519 
2520   if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
2521     // not enough room for num_annotations field
2522     log_debug(redefine, class, annotation)("length() is too small for num_annotations field");
2523     return false;
2524   }
2525 
2526   u2 num_annotations = Bytes::get_Java_u2((address)
2527                          type_annotations_typeArray->adr_at(byte_i_ref));
2528   byte_i_ref += 2;
2529 
2530   log_debug(redefine, class, annotation)("num_type_annotations=%d", num_annotations);
2531 
2532   int calc_num_annotations = 0;
2533   for (; calc_num_annotations < num_annotations; calc_num_annotations++) {
2534     if (!rewrite_cp_refs_in_type_annotation_struct(type_annotations_typeArray,
2535            byte_i_ref, location_mesg, THREAD)) {
2536       log_debug(redefine, class, annotation)("bad type_annotation_struct at %d", calc_num_annotations);
2537       // propagate failure back to caller
2538       return false;
2539     }
2540   }
2541   assert(num_annotations == calc_num_annotations, "sanity check");
2542 
2543   if (byte_i_ref != type_annotations_typeArray->length()) {
2544     log_debug(redefine, class, annotation)
2545       ("read wrong amount of bytes at end of processing type_annotations_typeArray (%d of %d bytes were read)",
2546        byte_i_ref, type_annotations_typeArray->length());
2547     return false;
2548   }
2549 
2550   return true;
2551 } // end rewrite_cp_refs_in_type_annotations_typeArray()
2552 
2553 
2554 // Rewrite constant pool references in a type_annotation
2555 // field. This "structure" is adapted from the
2556 // RuntimeVisibleTypeAnnotations_attribute described in
2557 // section 4.7.20 of the Java SE 8 Edition of the VM spec:
2558 //
2559 // type_annotation {
2560 //   u1 target_type;
2561 //   union {
2562 //     type_parameter_target;
2563 //     supertype_target;
2564 //     type_parameter_bound_target;
2565 //     empty_target;
2566 //     method_formal_parameter_target;
2567 //     throws_target;
2568 //     localvar_target;
2569 //     catch_target;
2570 //     offset_target;
2571 //     type_argument_target;
2572 //   } target_info;
2573 //   type_path target_path;
2574 //   annotation anno;
2575 // }
2576 //
2577 bool VM_RedefineClasses::rewrite_cp_refs_in_type_annotation_struct(
2578        AnnotationArray* type_annotations_typeArray, int &byte_i_ref,
2579        const char * location_mesg, TRAPS) {
2580 
2581   if (!skip_type_annotation_target(type_annotations_typeArray,
2582          byte_i_ref, location_mesg, THREAD)) {
2583     return false;
2584   }
2585 
2586   if (!skip_type_annotation_type_path(type_annotations_typeArray,
2587          byte_i_ref, THREAD)) {
2588     return false;
2589   }
2590 
2591   if (!rewrite_cp_refs_in_annotation_struct(type_annotations_typeArray,
2592          byte_i_ref, THREAD)) {
2593     return false;
2594   }
2595 
2596   return true;
2597 } // end rewrite_cp_refs_in_type_annotation_struct()
2598 
2599 
2600 // Read, verify and skip over the target_type and target_info part
2601 // so that rewriting can continue in the later parts of the struct.
2602 //
2603 // u1 target_type;
2604 // union {
2605 //   type_parameter_target;
2606 //   supertype_target;
2607 //   type_parameter_bound_target;
2608 //   empty_target;
2609 //   method_formal_parameter_target;
2610 //   throws_target;
2611 //   localvar_target;
2612 //   catch_target;
2613 //   offset_target;
2614 //   type_argument_target;
2615 // } target_info;
2616 //
2617 bool VM_RedefineClasses::skip_type_annotation_target(
2618        AnnotationArray* type_annotations_typeArray, int &byte_i_ref,
2619        const char * location_mesg, TRAPS) {
2620 
2621   if ((byte_i_ref + 1) > type_annotations_typeArray->length()) {
2622     // not enough room for a target_type let alone the rest of a type_annotation
2623     log_debug(redefine, class, annotation)("length() is too small for a target_type");
2624     return false;
2625   }
2626 
2627   u1 target_type = type_annotations_typeArray->at(byte_i_ref);
2628   byte_i_ref += 1;
2629   log_debug(redefine, class, annotation)("target_type=0x%.2x", target_type);
2630   log_debug(redefine, class, annotation)("location=%s", location_mesg);
2631 
2632   // Skip over target_info
2633   switch (target_type) {
2634     case 0x00:
2635     // kind: type parameter declaration of generic class or interface
2636     // location: ClassFile
2637     case 0x01:
2638     // kind: type parameter declaration of generic method or constructor
2639     // location: method_info
2640 
2641     {
2642       // struct:
2643       // type_parameter_target {
2644       //   u1 type_parameter_index;
2645       // }
2646       //
2647       if ((byte_i_ref + 1) > type_annotations_typeArray->length()) {
2648         log_debug(redefine, class, annotation)("length() is too small for a type_parameter_target");
2649         return false;
2650       }
2651 
2652       u1 type_parameter_index = type_annotations_typeArray->at(byte_i_ref);
2653       byte_i_ref += 1;
2654 
2655       log_debug(redefine, class, annotation)("type_parameter_target: type_parameter_index=%d", type_parameter_index);
2656     } break;
2657 
2658     case 0x10:
2659     // kind: type in extends clause of class or interface declaration
2660     //       (including the direct superclass of an unsafe anonymous class declaration),
2661     //       or in implements clause of interface declaration
2662     // location: ClassFile
2663 
2664     {
2665       // struct:
2666       // supertype_target {
2667       //   u2 supertype_index;
2668       // }
2669       //
2670       if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
2671         log_debug(redefine, class, annotation)("length() is too small for a supertype_target");
2672         return false;
2673       }
2674 
2675       u2 supertype_index = Bytes::get_Java_u2((address)
2676                              type_annotations_typeArray->adr_at(byte_i_ref));
2677       byte_i_ref += 2;
2678 
2679       log_debug(redefine, class, annotation)("supertype_target: supertype_index=%d", supertype_index);
2680     } break;
2681 
2682     case 0x11:
2683     // kind: type in bound of type parameter declaration of generic class or interface
2684     // location: ClassFile
2685     case 0x12:
2686     // kind: type in bound of type parameter declaration of generic method or constructor
2687     // location: method_info
2688 
2689     {
2690       // struct:
2691       // type_parameter_bound_target {
2692       //   u1 type_parameter_index;
2693       //   u1 bound_index;
2694       // }
2695       //
2696       if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
2697         log_debug(redefine, class, annotation)("length() is too small for a type_parameter_bound_target");
2698         return false;
2699       }
2700 
2701       u1 type_parameter_index = type_annotations_typeArray->at(byte_i_ref);
2702       byte_i_ref += 1;
2703       u1 bound_index = type_annotations_typeArray->at(byte_i_ref);
2704       byte_i_ref += 1;
2705 
2706       log_debug(redefine, class, annotation)
2707         ("type_parameter_bound_target: type_parameter_index=%d, bound_index=%d", type_parameter_index, bound_index);
2708     } break;
2709 
2710     case 0x13:
2711     // kind: type in field declaration
2712     // location: field_info
2713     case 0x14:
2714     // kind: return type of method, or type of newly constructed object
2715     // location: method_info
2716     case 0x15:
2717     // kind: receiver type of method or constructor
2718     // location: method_info
2719 
2720     {
2721       // struct:
2722       // empty_target {
2723       // }
2724       //
2725       log_debug(redefine, class, annotation)("empty_target");
2726     } break;
2727 
2728     case 0x16:
2729     // kind: type in formal parameter declaration of method, constructor, or lambda expression
2730     // location: method_info
2731 
2732     {
2733       // struct:
2734       // formal_parameter_target {
2735       //   u1 formal_parameter_index;
2736       // }
2737       //
2738       if ((byte_i_ref + 1) > type_annotations_typeArray->length()) {
2739         log_debug(redefine, class, annotation)("length() is too small for a formal_parameter_target");
2740         return false;
2741       }
2742 
2743       u1 formal_parameter_index = type_annotations_typeArray->at(byte_i_ref);
2744       byte_i_ref += 1;
2745 
2746       log_debug(redefine, class, annotation)
2747         ("formal_parameter_target: formal_parameter_index=%d", formal_parameter_index);
2748     } break;
2749 
2750     case 0x17:
2751     // kind: type in throws clause of method or constructor
2752     // location: method_info
2753 
2754     {
2755       // struct:
2756       // throws_target {
2757       //   u2 throws_type_index
2758       // }
2759       //
2760       if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
2761         log_debug(redefine, class, annotation)("length() is too small for a throws_target");
2762         return false;
2763       }
2764 
2765       u2 throws_type_index = Bytes::get_Java_u2((address)
2766                                type_annotations_typeArray->adr_at(byte_i_ref));
2767       byte_i_ref += 2;
2768 
2769       log_debug(redefine, class, annotation)("throws_target: throws_type_index=%d", throws_type_index);
2770     } break;
2771 
2772     case 0x40:
2773     // kind: type in local variable declaration
2774     // location: Code
2775     case 0x41:
2776     // kind: type in resource variable declaration
2777     // location: Code
2778 
2779     {
2780       // struct:
2781       // localvar_target {
2782       //   u2 table_length;
2783       //   struct {
2784       //     u2 start_pc;
2785       //     u2 length;
2786       //     u2 index;
2787       //   } table[table_length];
2788       // }
2789       //
2790       if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
2791         // not enough room for a table_length let alone the rest of a localvar_target
2792         log_debug(redefine, class, annotation)("length() is too small for a localvar_target table_length");
2793         return false;
2794       }
2795 
2796       u2 table_length = Bytes::get_Java_u2((address)
2797                           type_annotations_typeArray->adr_at(byte_i_ref));
2798       byte_i_ref += 2;
2799 
2800       log_debug(redefine, class, annotation)("localvar_target: table_length=%d", table_length);
2801 
2802       int table_struct_size = 2 + 2 + 2; // 3 u2 variables per table entry
2803       int table_size = table_length * table_struct_size;
2804 
2805       if ((byte_i_ref + table_size) > type_annotations_typeArray->length()) {
2806         // not enough room for a table
2807         log_debug(redefine, class, annotation)("length() is too small for a table array of length %d", table_length);
2808         return false;
2809       }
2810 
2811       // Skip over table
2812       byte_i_ref += table_size;
2813     } break;
2814 
2815     case 0x42:
2816     // kind: type in exception parameter declaration
2817     // location: Code
2818 
2819     {
2820       // struct:
2821       // catch_target {
2822       //   u2 exception_table_index;
2823       // }
2824       //
2825       if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
2826         log_debug(redefine, class, annotation)("length() is too small for a catch_target");
2827         return false;
2828       }
2829 
2830       u2 exception_table_index = Bytes::get_Java_u2((address)
2831                                    type_annotations_typeArray->adr_at(byte_i_ref));
2832       byte_i_ref += 2;
2833 
2834       log_debug(redefine, class, annotation)("catch_target: exception_table_index=%d", exception_table_index);
2835     } break;
2836 
2837     case 0x43:
2838     // kind: type in instanceof expression
2839     // location: Code
2840     case 0x44:
2841     // kind: type in new expression
2842     // location: Code
2843     case 0x45:
2844     // kind: type in method reference expression using ::new
2845     // location: Code
2846     case 0x46:
2847     // kind: type in method reference expression using ::Identifier
2848     // location: Code
2849 
2850     {
2851       // struct:
2852       // offset_target {
2853       //   u2 offset;
2854       // }
2855       //
2856       if ((byte_i_ref + 2) > type_annotations_typeArray->length()) {
2857         log_debug(redefine, class, annotation)("length() is too small for a offset_target");
2858         return false;
2859       }
2860 
2861       u2 offset = Bytes::get_Java_u2((address)
2862                     type_annotations_typeArray->adr_at(byte_i_ref));
2863       byte_i_ref += 2;
2864 
2865       log_debug(redefine, class, annotation)("offset_target: offset=%d", offset);
2866     } break;
2867 
2868     case 0x47:
2869     // kind: type in cast expression
2870     // location: Code
2871     case 0x48:
2872     // kind: type argument for generic constructor in new expression or
2873     //       explicit constructor invocation statement
2874     // location: Code
2875     case 0x49:
2876     // kind: type argument for generic method in method invocation expression
2877     // location: Code
2878     case 0x4A:
2879     // kind: type argument for generic constructor in method reference expression using ::new
2880     // location: Code
2881     case 0x4B:
2882     // kind: type argument for generic method in method reference expression using ::Identifier
2883     // location: Code
2884 
2885     {
2886       // struct:
2887       // type_argument_target {
2888       //   u2 offset;
2889       //   u1 type_argument_index;
2890       // }
2891       //
2892       if ((byte_i_ref + 3) > type_annotations_typeArray->length()) {
2893         log_debug(redefine, class, annotation)("length() is too small for a type_argument_target");
2894         return false;
2895       }
2896 
2897       u2 offset = Bytes::get_Java_u2((address)
2898                     type_annotations_typeArray->adr_at(byte_i_ref));
2899       byte_i_ref += 2;
2900       u1 type_argument_index = type_annotations_typeArray->at(byte_i_ref);
2901       byte_i_ref += 1;
2902 
2903       log_debug(redefine, class, annotation)
2904         ("type_argument_target: offset=%d, type_argument_index=%d", offset, type_argument_index);
2905     } break;
2906 
2907     default:
2908       log_debug(redefine, class, annotation)("unknown target_type");
2909 #ifdef ASSERT
2910       ShouldNotReachHere();
2911 #endif
2912       return false;
2913   }
2914 
2915   return true;
2916 } // end skip_type_annotation_target()
2917 
2918 
2919 // Read, verify and skip over the type_path part so that rewriting
2920 // can continue in the later parts of the struct.
2921 //
2922 // type_path {
2923 //   u1 path_length;
2924 //   {
2925 //     u1 type_path_kind;
2926 //     u1 type_argument_index;
2927 //   } path[path_length];
2928 // }
2929 //
2930 bool VM_RedefineClasses::skip_type_annotation_type_path(
2931        AnnotationArray* type_annotations_typeArray, int &byte_i_ref, TRAPS) {
2932 
2933   if ((byte_i_ref + 1) > type_annotations_typeArray->length()) {
2934     // not enough room for a path_length let alone the rest of the type_path
2935     log_debug(redefine, class, annotation)("length() is too small for a type_path");
2936     return false;
2937   }
2938 
2939   u1 path_length = type_annotations_typeArray->at(byte_i_ref);
2940   byte_i_ref += 1;
2941 
2942   log_debug(redefine, class, annotation)("type_path: path_length=%d", path_length);
2943 
2944   int calc_path_length = 0;
2945   for (; calc_path_length < path_length; calc_path_length++) {
2946     if ((byte_i_ref + 1 + 1) > type_annotations_typeArray->length()) {
2947       // not enough room for a path
2948       log_debug(redefine, class, annotation)
2949         ("length() is too small for path entry %d of %d", calc_path_length, path_length);
2950       return false;
2951     }
2952 
2953     u1 type_path_kind = type_annotations_typeArray->at(byte_i_ref);
2954     byte_i_ref += 1;
2955     u1 type_argument_index = type_annotations_typeArray->at(byte_i_ref);
2956     byte_i_ref += 1;
2957 
2958     log_debug(redefine, class, annotation)
2959       ("type_path: path[%d]: type_path_kind=%d, type_argument_index=%d",
2960        calc_path_length, type_path_kind, type_argument_index);
2961 
2962     if (type_path_kind > 3 || (type_path_kind != 3 && type_argument_index != 0)) {
2963       // not enough room for a path
2964       log_debug(redefine, class, annotation)("inconsistent type_path values");
2965       return false;
2966     }
2967   }
2968   assert(path_length == calc_path_length, "sanity check");
2969 
2970   return true;
2971 } // end skip_type_annotation_type_path()
2972 
2973 
2974 // Rewrite constant pool references in the method's stackmap table.
2975 // These "structures" are adapted from the StackMapTable_attribute that
2976 // is described in section 4.8.4 of the 6.0 version of the VM spec
2977 // (dated 2005.10.26):
2978 // file:///net/quincunx.sfbay/export/gbracha/ClassFile-Java6.pdf
2979 //
2980 // stack_map {
2981 //   u2 number_of_entries;
2982 //   stack_map_frame entries[number_of_entries];
2983 // }
2984 //
2985 void VM_RedefineClasses::rewrite_cp_refs_in_stack_map_table(
2986        const methodHandle& method, TRAPS) {
2987 
2988   if (!method->has_stackmap_table()) {
2989     return;
2990   }
2991 
2992   AnnotationArray* stackmap_data = method->stackmap_data();
2993   address stackmap_p = (address)stackmap_data->adr_at(0);
2994   address stackmap_end = stackmap_p + stackmap_data->length();
2995 
2996   assert(stackmap_p + 2 <= stackmap_end, "no room for number_of_entries");
2997   u2 number_of_entries = Bytes::get_Java_u2(stackmap_p);
2998   stackmap_p += 2;
2999 
3000   log_debug(redefine, class, stackmap)("number_of_entries=%u", number_of_entries);
3001 
3002   // walk through each stack_map_frame
3003   u2 calc_number_of_entries = 0;
3004   for (; calc_number_of_entries < number_of_entries; calc_number_of_entries++) {
3005     // The stack_map_frame structure is a u1 frame_type followed by
3006     // 0 or more bytes of data:
3007     //
3008     // union stack_map_frame {
3009     //   same_frame;
3010     //   same_locals_1_stack_item_frame;
3011     //   same_locals_1_stack_item_frame_extended;
3012     //   chop_frame;
3013     //   same_frame_extended;
3014     //   append_frame;
3015     //   full_frame;
3016     // }
3017 
3018     assert(stackmap_p + 1 <= stackmap_end, "no room for frame_type");
3019     u1 frame_type = *stackmap_p;
3020     stackmap_p++;
3021 
3022     // same_frame {
3023     //   u1 frame_type = SAME; /* 0-63 */
3024     // }
3025     if (frame_type <= 63) {
3026       // nothing more to do for same_frame
3027     }
3028 
3029     // same_locals_1_stack_item_frame {
3030     //   u1 frame_type = SAME_LOCALS_1_STACK_ITEM; /* 64-127 */
3031     //   verification_type_info stack[1];
3032     // }
3033     else if (frame_type >= 64 && frame_type <= 127) {
3034       rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
3035         calc_number_of_entries, frame_type, THREAD);
3036     }
3037 
3038     // reserved for future use
3039     else if (frame_type >= 128 && frame_type <= 246) {
3040       // nothing more to do for reserved frame_types
3041     }
3042 
3043     // same_locals_1_stack_item_frame_extended {
3044     //   u1 frame_type = SAME_LOCALS_1_STACK_ITEM_EXTENDED; /* 247 */
3045     //   u2 offset_delta;
3046     //   verification_type_info stack[1];
3047     // }
3048     else if (frame_type == 247) {
3049       stackmap_p += 2;
3050       rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
3051         calc_number_of_entries, frame_type, THREAD);
3052     }
3053 
3054     // chop_frame {
3055     //   u1 frame_type = CHOP; /* 248-250 */
3056     //   u2 offset_delta;
3057     // }
3058     else if (frame_type >= 248 && frame_type <= 250) {
3059       stackmap_p += 2;
3060     }
3061 
3062     // same_frame_extended {
3063     //   u1 frame_type = SAME_FRAME_EXTENDED; /* 251*/
3064     //   u2 offset_delta;
3065     // }
3066     else if (frame_type == 251) {
3067       stackmap_p += 2;
3068     }
3069 
3070     // append_frame {
3071     //   u1 frame_type = APPEND; /* 252-254 */
3072     //   u2 offset_delta;
3073     //   verification_type_info locals[frame_type - 251];
3074     // }
3075     else if (frame_type >= 252 && frame_type <= 254) {
3076       assert(stackmap_p + 2 <= stackmap_end,
3077         "no room for offset_delta");
3078       stackmap_p += 2;
3079       u1 len = frame_type - 251;
3080       for (u1 i = 0; i < len; i++) {
3081         rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
3082           calc_number_of_entries, frame_type, THREAD);
3083       }
3084     }
3085 
3086     // full_frame {
3087     //   u1 frame_type = FULL_FRAME; /* 255 */
3088     //   u2 offset_delta;
3089     //   u2 number_of_locals;
3090     //   verification_type_info locals[number_of_locals];
3091     //   u2 number_of_stack_items;
3092     //   verification_type_info stack[number_of_stack_items];
3093     // }
3094     else if (frame_type == 255) {
3095       assert(stackmap_p + 2 + 2 <= stackmap_end,
3096         "no room for smallest full_frame");
3097       stackmap_p += 2;
3098 
3099       u2 number_of_locals = Bytes::get_Java_u2(stackmap_p);
3100       stackmap_p += 2;
3101 
3102       for (u2 locals_i = 0; locals_i < number_of_locals; locals_i++) {
3103         rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
3104           calc_number_of_entries, frame_type, THREAD);
3105       }
3106 
3107       // Use the largest size for the number_of_stack_items, but only get
3108       // the right number of bytes.
3109       u2 number_of_stack_items = Bytes::get_Java_u2(stackmap_p);
3110       stackmap_p += 2;
3111 
3112       for (u2 stack_i = 0; stack_i < number_of_stack_items; stack_i++) {
3113         rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
3114           calc_number_of_entries, frame_type, THREAD);
3115       }
3116     }
3117   } // end while there is a stack_map_frame
3118   assert(number_of_entries == calc_number_of_entries, "sanity check");
3119 } // end rewrite_cp_refs_in_stack_map_table()
3120 
3121 
3122 // Rewrite constant pool references in the verification type info
3123 // portion of the method's stackmap table. These "structures" are
3124 // adapted from the StackMapTable_attribute that is described in
3125 // section 4.8.4 of the 6.0 version of the VM spec (dated 2005.10.26):
3126 // file:///net/quincunx.sfbay/export/gbracha/ClassFile-Java6.pdf
3127 //
3128 // The verification_type_info structure is a u1 tag followed by 0 or
3129 // more bytes of data:
3130 //
3131 // union verification_type_info {
3132 //   Top_variable_info;
3133 //   Integer_variable_info;
3134 //   Float_variable_info;
3135 //   Long_variable_info;
3136 //   Double_variable_info;
3137 //   Null_variable_info;
3138 //   UninitializedThis_variable_info;
3139 //   Object_variable_info;
3140 //   Uninitialized_variable_info;
3141 // }
3142 //
3143 void VM_RedefineClasses::rewrite_cp_refs_in_verification_type_info(
3144        address& stackmap_p_ref, address stackmap_end, u2 frame_i,
3145        u1 frame_type, TRAPS) {
3146 
3147   assert(stackmap_p_ref + 1 <= stackmap_end, "no room for tag");
3148   u1 tag = *stackmap_p_ref;
3149   stackmap_p_ref++;
3150 
3151   switch (tag) {
3152   // Top_variable_info {
3153   //   u1 tag = ITEM_Top; /* 0 */
3154   // }
3155   // verificationType.hpp has zero as ITEM_Bogus instead of ITEM_Top
3156   case 0:  // fall through
3157 
3158   // Integer_variable_info {
3159   //   u1 tag = ITEM_Integer; /* 1 */
3160   // }
3161   case ITEM_Integer:  // fall through
3162 
3163   // Float_variable_info {
3164   //   u1 tag = ITEM_Float; /* 2 */
3165   // }
3166   case ITEM_Float:  // fall through
3167 
3168   // Double_variable_info {
3169   //   u1 tag = ITEM_Double; /* 3 */
3170   // }
3171   case ITEM_Double:  // fall through
3172 
3173   // Long_variable_info {
3174   //   u1 tag = ITEM_Long; /* 4 */
3175   // }
3176   case ITEM_Long:  // fall through
3177 
3178   // Null_variable_info {
3179   //   u1 tag = ITEM_Null; /* 5 */
3180   // }
3181   case ITEM_Null:  // fall through
3182 
3183   // UninitializedThis_variable_info {
3184   //   u1 tag = ITEM_UninitializedThis; /* 6 */
3185   // }
3186   case ITEM_UninitializedThis:
3187     // nothing more to do for the above tag types
3188     break;
3189 
3190   // Object_variable_info {
3191   //   u1 tag = ITEM_Object; /* 7 */
3192   //   u2 cpool_index;
3193   // }
3194   case ITEM_Object:
3195   {
3196     assert(stackmap_p_ref + 2 <= stackmap_end, "no room for cpool_index");
3197     u2 cpool_index = Bytes::get_Java_u2(stackmap_p_ref);
3198     u2 new_cp_index = find_new_index(cpool_index);
3199     if (new_cp_index != 0) {
3200       log_debug(redefine, class, stackmap)("mapped old cpool_index=%d", cpool_index);
3201       Bytes::put_Java_u2(stackmap_p_ref, new_cp_index);
3202       cpool_index = new_cp_index;
3203     }
3204     stackmap_p_ref += 2;
3205 
3206     log_debug(redefine, class, stackmap)
3207       ("frame_i=%u, frame_type=%u, cpool_index=%d", frame_i, frame_type, cpool_index);
3208   } break;
3209 
3210   // Uninitialized_variable_info {
3211   //   u1 tag = ITEM_Uninitialized; /* 8 */
3212   //   u2 offset;
3213   // }
3214   case ITEM_Uninitialized:
3215     assert(stackmap_p_ref + 2 <= stackmap_end, "no room for offset");
3216     stackmap_p_ref += 2;
3217     break;
3218 
3219   default:
3220     log_debug(redefine, class, stackmap)("frame_i=%u, frame_type=%u, bad tag=0x%x", frame_i, frame_type, tag);
3221     ShouldNotReachHere();
3222     break;
3223   } // end switch (tag)
3224 } // end rewrite_cp_refs_in_verification_type_info()
3225 
3226 
3227 // Change the constant pool associated with klass scratch_class to
3228 // scratch_cp. If shrink is true, then scratch_cp_length elements
3229 // are copied from scratch_cp to a smaller constant pool and the
3230 // smaller constant pool is associated with scratch_class.
3231 void VM_RedefineClasses::set_new_constant_pool(
3232        ClassLoaderData* loader_data,
3233        InstanceKlass* scratch_class, constantPoolHandle scratch_cp,
3234        int scratch_cp_length, TRAPS) {
3235   assert(scratch_cp->length() >= scratch_cp_length, "sanity check");
3236 
3237   // scratch_cp is a merged constant pool and has enough space for a
3238   // worst case merge situation. We want to associate the minimum
3239   // sized constant pool with the klass to save space.
3240   ConstantPool* cp = ConstantPool::allocate(loader_data, scratch_cp_length, CHECK);
3241   constantPoolHandle smaller_cp(THREAD, cp);
3242 
3243   // preserve version() value in the smaller copy
3244   int version = scratch_cp->version();
3245   assert(version != 0, "sanity check");
3246   smaller_cp->set_version(version);
3247 
3248   // attach klass to new constant pool
3249   // reference to the cp holder is needed for copy_operands()
3250   smaller_cp->set_pool_holder(scratch_class);
3251 
3252   scratch_cp->copy_cp_to(1, scratch_cp_length - 1, smaller_cp, 1, THREAD);
3253   if (HAS_PENDING_EXCEPTION) {
3254     // Exception is handled in the caller
3255     loader_data->add_to_deallocate_list(smaller_cp());
3256     return;
3257   }
3258   scratch_cp = smaller_cp;
3259 
3260   // attach new constant pool to klass
3261   scratch_class->set_constants(scratch_cp());
3262   scratch_cp->initialize_unresolved_klasses(loader_data, CHECK);
3263 
3264   int i;  // for portability
3265 
3266   // update each field in klass to use new constant pool indices as needed
3267   for (JavaFieldStream fs(scratch_class); !fs.done(); fs.next()) {
3268     jshort cur_index = fs.name_index();
3269     jshort new_index = find_new_index(cur_index);
3270     if (new_index != 0) {
3271       log_trace(redefine, class, constantpool)("field-name_index change: %d to %d", cur_index, new_index);
3272       fs.set_name_index(new_index);
3273     }
3274     cur_index = fs.signature_index();
3275     new_index = find_new_index(cur_index);
3276     if (new_index != 0) {
3277       log_trace(redefine, class, constantpool)("field-signature_index change: %d to %d", cur_index, new_index);
3278       fs.set_signature_index(new_index);
3279     }
3280     cur_index = fs.initval_index();
3281     new_index = find_new_index(cur_index);
3282     if (new_index != 0) {
3283       log_trace(redefine, class, constantpool)("field-initval_index change: %d to %d", cur_index, new_index);
3284       fs.set_initval_index(new_index);
3285     }
3286     cur_index = fs.generic_signature_index();
3287     new_index = find_new_index(cur_index);
3288     if (new_index != 0) {
3289       log_trace(redefine, class, constantpool)("field-generic_signature change: %d to %d", cur_index, new_index);
3290       fs.set_generic_signature_index(new_index);
3291     }
3292   } // end for each field
3293 
3294   // Update constant pool indices in the inner classes info to use
3295   // new constant indices as needed. The inner classes info is a
3296   // quadruple:
3297   // (inner_class_info, outer_class_info, inner_name, inner_access_flags)
3298   InnerClassesIterator iter(scratch_class);
3299   for (; !iter.done(); iter.next()) {
3300     int cur_index = iter.inner_class_info_index();
3301     if (cur_index == 0) {
3302       continue;  // JVM spec. allows null inner class refs so skip it
3303     }
3304     int new_index = find_new_index(cur_index);
3305     if (new_index != 0) {
3306       log_trace(redefine, class, constantpool)("inner_class_info change: %d to %d", cur_index, new_index);
3307       iter.set_inner_class_info_index(new_index);
3308     }
3309     cur_index = iter.outer_class_info_index();
3310     new_index = find_new_index(cur_index);
3311     if (new_index != 0) {
3312       log_trace(redefine, class, constantpool)("outer_class_info change: %d to %d", cur_index, new_index);
3313       iter.set_outer_class_info_index(new_index);
3314     }
3315     cur_index = iter.inner_name_index();
3316     new_index = find_new_index(cur_index);
3317     if (new_index != 0) {
3318       log_trace(redefine, class, constantpool)("inner_name change: %d to %d", cur_index, new_index);
3319       iter.set_inner_name_index(new_index);
3320     }
3321   } // end for each inner class
3322 
3323   // Attach each method in klass to the new constant pool and update
3324   // to use new constant pool indices as needed:
3325   Array<Method*>* methods = scratch_class->methods();
3326   for (i = methods->length() - 1; i >= 0; i--) {
3327     methodHandle method(THREAD, methods->at(i));
3328     method->set_constants(scratch_cp());
3329 
3330     int new_index = find_new_index(method->name_index());
3331     if (new_index != 0) {
3332       log_trace(redefine, class, constantpool)
3333         ("method-name_index change: %d to %d", method->name_index(), new_index);
3334       method->set_name_index(new_index);
3335     }
3336     new_index = find_new_index(method->signature_index());
3337     if (new_index != 0) {
3338       log_trace(redefine, class, constantpool)
3339         ("method-signature_index change: %d to %d", method->signature_index(), new_index);
3340       method->set_signature_index(new_index);
3341     }
3342     new_index = find_new_index(method->generic_signature_index());
3343     if (new_index != 0) {
3344       log_trace(redefine, class, constantpool)
3345         ("method-generic_signature_index change: %d to %d", method->generic_signature_index(), new_index);
3346       method->set_generic_signature_index(new_index);
3347     }
3348 
3349     // Update constant pool indices in the method's checked exception
3350     // table to use new constant indices as needed.
3351     int cext_length = method->checked_exceptions_length();
3352     if (cext_length > 0) {
3353       CheckedExceptionElement * cext_table =
3354         method->checked_exceptions_start();
3355       for (int j = 0; j < cext_length; j++) {
3356         int cur_index = cext_table[j].class_cp_index;
3357         int new_index = find_new_index(cur_index);
3358         if (new_index != 0) {
3359           log_trace(redefine, class, constantpool)("cext-class_cp_index change: %d to %d", cur_index, new_index);
3360           cext_table[j].class_cp_index = (u2)new_index;
3361         }
3362       } // end for each checked exception table entry
3363     } // end if there are checked exception table entries
3364 
3365     // Update each catch type index in the method's exception table
3366     // to use new constant pool indices as needed. The exception table
3367     // holds quadruple entries of the form:
3368     //   (beg_bci, end_bci, handler_bci, klass_index)
3369 
3370     ExceptionTable ex_table(method());
3371     int ext_length = ex_table.length();
3372 
3373     for (int j = 0; j < ext_length; j ++) {
3374       int cur_index = ex_table.catch_type_index(j);
3375       int new_index = find_new_index(cur_index);
3376       if (new_index != 0) {
3377         log_trace(redefine, class, constantpool)("ext-klass_index change: %d to %d", cur_index, new_index);
3378         ex_table.set_catch_type_index(j, new_index);
3379       }
3380     } // end for each exception table entry
3381 
3382     // Update constant pool indices in the method's local variable
3383     // table to use new constant indices as needed. The local variable
3384     // table hold sextuple entries of the form:
3385     // (start_pc, length, name_index, descriptor_index, signature_index, slot)
3386     int lvt_length = method->localvariable_table_length();
3387     if (lvt_length > 0) {
3388       LocalVariableTableElement * lv_table =
3389         method->localvariable_table_start();
3390       for (int j = 0; j < lvt_length; j++) {
3391         int cur_index = lv_table[j].name_cp_index;
3392         int new_index = find_new_index(cur_index);
3393         if (new_index != 0) {
3394           log_trace(redefine, class, constantpool)("lvt-name_cp_index change: %d to %d", cur_index, new_index);
3395           lv_table[j].name_cp_index = (u2)new_index;
3396         }
3397         cur_index = lv_table[j].descriptor_cp_index;
3398         new_index = find_new_index(cur_index);
3399         if (new_index != 0) {
3400           log_trace(redefine, class, constantpool)("lvt-descriptor_cp_index change: %d to %d", cur_index, new_index);
3401           lv_table[j].descriptor_cp_index = (u2)new_index;
3402         }
3403         cur_index = lv_table[j].signature_cp_index;
3404         new_index = find_new_index(cur_index);
3405         if (new_index != 0) {
3406           log_trace(redefine, class, constantpool)("lvt-signature_cp_index change: %d to %d", cur_index, new_index);
3407           lv_table[j].signature_cp_index = (u2)new_index;
3408         }
3409       } // end for each local variable table entry
3410     } // end if there are local variable table entries
3411 
3412     rewrite_cp_refs_in_stack_map_table(method, THREAD);
3413   } // end for each method
3414 } // end set_new_constant_pool()
3415 
3416 
3417 // Unevolving classes may point to methods of the_class directly
3418 // from their constant pool caches, itables, and/or vtables. We
3419 // use the ClassLoaderDataGraph::classes_do() facility and this helper
3420 // to fix up these pointers.  MethodData also points to old methods and
3421 // must be cleaned.
3422 
3423 // Adjust cpools and vtables closure
3424 void VM_RedefineClasses::AdjustAndCleanMetadata::do_klass(Klass* k) {
3425 
3426   // This is a very busy routine. We don't want too much tracing
3427   // printed out.
3428   bool trace_name_printed = false;
3429 
3430   // If the class being redefined is java.lang.Object, we need to fix all
3431   // array class vtables also
3432   if (k->is_array_klass() && _has_redefined_Object) {
3433     k->vtable().adjust_method_entries(&trace_name_printed);
3434 
3435   } else if (k->is_instance_klass()) {
3436     HandleMark hm(_thread);
3437     InstanceKlass *ik = InstanceKlass::cast(k);
3438 
3439     // Clean MethodData of this class's methods so they don't refer to
3440     // old methods that are no longer running.
3441     Array<Method*>* methods = ik->methods();
3442     int num_methods = methods->length();
3443     for (int index = 0; index < num_methods; ++index) {
3444       if (methods->at(index)->method_data() != NULL) {
3445         methods->at(index)->method_data()->clean_weak_method_links();
3446       }
3447     }
3448 
3449     // HotSpot specific optimization! HotSpot does not currently
3450     // support delegation from the bootstrap class loader to a
3451     // user-defined class loader. This means that if the bootstrap
3452     // class loader is the initiating class loader, then it will also
3453     // be the defining class loader. This also means that classes
3454     // loaded by the bootstrap class loader cannot refer to classes
3455     // loaded by a user-defined class loader. Note: a user-defined
3456     // class loader can delegate to the bootstrap class loader.
3457     //
3458     // If the current class being redefined has a user-defined class
3459     // loader as its defining class loader, then we can skip all
3460     // classes loaded by the bootstrap class loader.
3461     if (!_has_null_class_loader && ik->class_loader() == NULL) {
3462       return;
3463     }
3464 
3465     // Adjust all vtables, default methods and itables, to clean out old methods.
3466     ResourceMark rm(_thread);
3467     if (ik->vtable_length() > 0) {
3468       ik->vtable().adjust_method_entries(&trace_name_printed);
3469       ik->adjust_default_methods(&trace_name_printed);
3470     }
3471 
3472     if (ik->itable_length() > 0) {
3473       ik->itable().adjust_method_entries(&trace_name_printed);
3474     }
3475 
3476     // The constant pools in other classes (other_cp) can refer to
3477     // old methods.  We have to update method information in
3478     // other_cp's cache. If other_cp has a previous version, then we
3479     // have to repeat the process for each previous version. The
3480     // constant pool cache holds the Method*s for non-virtual
3481     // methods and for virtual, final methods.
3482     //
3483     // Special case: if the current class being redefined, then new_cp
3484     // has already been attached to the_class and old_cp has already
3485     // been added as a previous version. The new_cp doesn't have any
3486     // cached references to old methods so it doesn't need to be
3487     // updated. We can simply start with the previous version(s) in
3488     // that case.
3489     constantPoolHandle other_cp;
3490     ConstantPoolCache* cp_cache;
3491 
3492     if (!ik->is_being_redefined()) {
3493       // this klass' constant pool cache may need adjustment
3494       other_cp = constantPoolHandle(ik->constants());
3495       cp_cache = other_cp->cache();
3496       if (cp_cache != NULL) {
3497         cp_cache->adjust_method_entries(&trace_name_printed);
3498       }
3499     }
3500 
3501     // the previous versions' constant pool caches may need adjustment
3502     for (InstanceKlass* pv_node = ik->previous_versions();
3503          pv_node != NULL;
3504          pv_node = pv_node->previous_versions()) {
3505       cp_cache = pv_node->constants()->cache();
3506       if (cp_cache != NULL) {
3507         cp_cache->adjust_method_entries(&trace_name_printed);
3508       }
3509     }
3510   }
3511 }
3512 
3513 void VM_RedefineClasses::update_jmethod_ids() {
3514   for (int j = 0; j < _matching_methods_length; ++j) {
3515     Method* old_method = _matching_old_methods[j];
3516     jmethodID jmid = old_method->find_jmethod_id_or_null();
3517     if (jmid != NULL) {
3518       // There is a jmethodID, change it to point to the new method
3519       methodHandle new_method_h(_matching_new_methods[j]);
3520       Method::change_method_associated_with_jmethod_id(jmid, new_method_h());
3521       assert(Method::resolve_jmethod_id(jmid) == _matching_new_methods[j],
3522              "should be replaced");
3523     }
3524   }
3525   // Update deleted jmethodID
3526   for (int j = 0; j < _deleted_methods_length; ++j) {
3527     Method* old_method = _deleted_methods[j];
3528     jmethodID jmid = old_method->find_jmethod_id_or_null();
3529     if (jmid != NULL) {
3530       // Change the jmethodID to point to NSME.
3531       Method::change_method_associated_with_jmethod_id(jmid, Universe::throw_no_such_method_error());
3532     }
3533   }
3534 }
3535 
3536 int VM_RedefineClasses::check_methods_and_mark_as_obsolete() {
3537   int emcp_method_count = 0;
3538   int obsolete_count = 0;
3539   int old_index = 0;
3540   for (int j = 0; j < _matching_methods_length; ++j, ++old_index) {
3541     Method* old_method = _matching_old_methods[j];
3542     Method* new_method = _matching_new_methods[j];
3543     Method* old_array_method;
3544 
3545     // Maintain an old_index into the _old_methods array by skipping
3546     // deleted methods
3547     while ((old_array_method = _old_methods->at(old_index)) != old_method) {
3548       ++old_index;
3549     }
3550 
3551     if (MethodComparator::methods_EMCP(old_method, new_method)) {
3552       // The EMCP definition from JSR-163 requires the bytecodes to be
3553       // the same with the exception of constant pool indices which may
3554       // differ. However, the constants referred to by those indices
3555       // must be the same.
3556       //
3557       // We use methods_EMCP() for comparison since constant pool
3558       // merging can remove duplicate constant pool entries that were
3559       // present in the old method and removed from the rewritten new
3560       // method. A faster binary comparison function would consider the
3561       // old and new methods to be different when they are actually
3562       // EMCP.
3563       //
3564       // The old and new methods are EMCP and you would think that we
3565       // could get rid of one of them here and now and save some space.
3566       // However, the concept of EMCP only considers the bytecodes and
3567       // the constant pool entries in the comparison. Other things,
3568       // e.g., the line number table (LNT) or the local variable table
3569       // (LVT) don't count in the comparison. So the new (and EMCP)
3570       // method can have a new LNT that we need so we can't just
3571       // overwrite the new method with the old method.
3572       //
3573       // When this routine is called, we have already attached the new
3574       // methods to the_class so the old methods are effectively
3575       // overwritten. However, if an old method is still executing,
3576       // then the old method cannot be collected until sometime after
3577       // the old method call has returned. So the overwriting of old
3578       // methods by new methods will save us space except for those
3579       // (hopefully few) old methods that are still executing.
3580       //
3581       // A method refers to a ConstMethod* and this presents another
3582       // possible avenue to space savings. The ConstMethod* in the
3583       // new method contains possibly new attributes (LNT, LVT, etc).
3584       // At first glance, it seems possible to save space by replacing
3585       // the ConstMethod* in the old method with the ConstMethod*
3586       // from the new method. The old and new methods would share the
3587       // same ConstMethod* and we would save the space occupied by
3588       // the old ConstMethod*. However, the ConstMethod* contains
3589       // a back reference to the containing method. Sharing the
3590       // ConstMethod* between two methods could lead to confusion in
3591       // the code that uses the back reference. This would lead to
3592       // brittle code that could be broken in non-obvious ways now or
3593       // in the future.
3594       //
3595       // Another possibility is to copy the ConstMethod* from the new
3596       // method to the old method and then overwrite the new method with
3597       // the old method. Since the ConstMethod* contains the bytecodes
3598       // for the method embedded in the oop, this option would change
3599       // the bytecodes out from under any threads executing the old
3600       // method and make the thread's bcp invalid. Since EMCP requires
3601       // that the bytecodes be the same modulo constant pool indices, it
3602       // is straight forward to compute the correct new bcp in the new
3603       // ConstMethod* from the old bcp in the old ConstMethod*. The
3604       // time consuming part would be searching all the frames in all
3605       // of the threads to find all of the calls to the old method.
3606       //
3607       // It looks like we will have to live with the limited savings
3608       // that we get from effectively overwriting the old methods
3609       // when the new methods are attached to the_class.
3610 
3611       // Count number of methods that are EMCP.  The method will be marked
3612       // old but not obsolete if it is EMCP.
3613       emcp_method_count++;
3614 
3615       // An EMCP method is _not_ obsolete. An obsolete method has a
3616       // different jmethodID than the current method. An EMCP method
3617       // has the same jmethodID as the current method. Having the
3618       // same jmethodID for all EMCP versions of a method allows for
3619       // a consistent view of the EMCP methods regardless of which
3620       // EMCP method you happen to have in hand. For example, a
3621       // breakpoint set in one EMCP method will work for all EMCP
3622       // versions of the method including the current one.
3623     } else {
3624       // mark obsolete methods as such
3625       old_method->set_is_obsolete();
3626       obsolete_count++;
3627 
3628       // obsolete methods need a unique idnum so they become new entries in
3629       // the jmethodID cache in InstanceKlass
3630       assert(old_method->method_idnum() == new_method->method_idnum(), "must match");
3631       u2 num = InstanceKlass::cast(_the_class)->next_method_idnum();
3632       if (num != ConstMethod::UNSET_IDNUM) {
3633         old_method->set_method_idnum(num);
3634       }
3635 
3636       // With tracing we try not to "yack" too much. The position of
3637       // this trace assumes there are fewer obsolete methods than
3638       // EMCP methods.
3639       if (log_is_enabled(Trace, redefine, class, obsolete, mark)) {
3640         ResourceMark rm;
3641         log_trace(redefine, class, obsolete, mark)
3642           ("mark %s(%s) as obsolete", old_method->name()->as_C_string(), old_method->signature()->as_C_string());
3643       }
3644     }
3645     old_method->set_is_old();
3646   }
3647   for (int i = 0; i < _deleted_methods_length; ++i) {
3648     Method* old_method = _deleted_methods[i];
3649 
3650     assert(!old_method->has_vtable_index(),
3651            "cannot delete methods with vtable entries");;
3652 
3653     // Mark all deleted methods as old, obsolete and deleted
3654     old_method->set_is_deleted();
3655     old_method->set_is_old();
3656     old_method->set_is_obsolete();
3657     ++obsolete_count;
3658     // With tracing we try not to "yack" too much. The position of
3659     // this trace assumes there are fewer obsolete methods than
3660     // EMCP methods.
3661     if (log_is_enabled(Trace, redefine, class, obsolete, mark)) {
3662       ResourceMark rm;
3663       log_trace(redefine, class, obsolete, mark)
3664         ("mark deleted %s(%s) as obsolete", old_method->name()->as_C_string(), old_method->signature()->as_C_string());
3665     }
3666   }
3667   assert((emcp_method_count + obsolete_count) == _old_methods->length(),
3668     "sanity check");
3669   log_trace(redefine, class, obsolete, mark)("EMCP_cnt=%d, obsolete_cnt=%d", emcp_method_count, obsolete_count);
3670   return emcp_method_count;
3671 }
3672 
3673 // This internal class transfers the native function registration from old methods
3674 // to new methods.  It is designed to handle both the simple case of unchanged
3675 // native methods and the complex cases of native method prefixes being added and/or
3676 // removed.
3677 // It expects only to be used during the VM_RedefineClasses op (a safepoint).
3678 //
3679 // This class is used after the new methods have been installed in "the_class".
3680 //
3681 // So, for example, the following must be handled.  Where 'm' is a method and
3682 // a number followed by an underscore is a prefix.
3683 //
3684 //                                      Old Name    New Name
3685 // Simple transfer to new method        m       ->  m
3686 // Add prefix                           m       ->  1_m
3687 // Remove prefix                        1_m     ->  m
3688 // Simultaneous add of prefixes         m       ->  3_2_1_m
3689 // Simultaneous removal of prefixes     3_2_1_m ->  m
3690 // Simultaneous add and remove          1_m     ->  2_m
3691 // Same, caused by prefix removal only  3_2_1_m ->  3_2_m
3692 //
3693 class TransferNativeFunctionRegistration {
3694  private:
3695   InstanceKlass* the_class;
3696   int prefix_count;
3697   char** prefixes;
3698 
3699   // Recursively search the binary tree of possibly prefixed method names.
3700   // Iteration could be used if all agents were well behaved. Full tree walk is
3701   // more resilent to agents not cleaning up intermediate methods.
3702   // Branch at each depth in the binary tree is:
3703   //    (1) without the prefix.
3704   //    (2) with the prefix.
3705   // where 'prefix' is the prefix at that 'depth' (first prefix, second prefix,...)
3706   Method* search_prefix_name_space(int depth, char* name_str, size_t name_len,
3707                                      Symbol* signature) {
3708     TempNewSymbol name_symbol = SymbolTable::probe(name_str, (int)name_len);
3709     if (name_symbol != NULL) {
3710       Method* method = the_class->lookup_method(name_symbol, signature);
3711       if (method != NULL) {
3712         // Even if prefixed, intermediate methods must exist.
3713         if (method->is_native()) {
3714           // Wahoo, we found a (possibly prefixed) version of the method, return it.
3715           return method;
3716         }
3717         if (depth < prefix_count) {
3718           // Try applying further prefixes (other than this one).
3719           method = search_prefix_name_space(depth+1, name_str, name_len, signature);
3720           if (method != NULL) {
3721             return method; // found
3722           }
3723 
3724           // Try adding this prefix to the method name and see if it matches
3725           // another method name.
3726           char* prefix = prefixes[depth];
3727           size_t prefix_len = strlen(prefix);
3728           size_t trial_len = name_len + prefix_len;
3729           char* trial_name_str = NEW_RESOURCE_ARRAY(char, trial_len + 1);
3730           strcpy(trial_name_str, prefix);
3731           strcat(trial_name_str, name_str);
3732           method = search_prefix_name_space(depth+1, trial_name_str, trial_len,
3733                                             signature);
3734           if (method != NULL) {
3735             // If found along this branch, it was prefixed, mark as such
3736             method->set_is_prefixed_native();
3737             return method; // found
3738           }
3739         }
3740       }
3741     }
3742     return NULL;  // This whole branch bore nothing
3743   }
3744 
3745   // Return the method name with old prefixes stripped away.
3746   char* method_name_without_prefixes(Method* method) {
3747     Symbol* name = method->name();
3748     char* name_str = name->as_utf8();
3749 
3750     // Old prefixing may be defunct, strip prefixes, if any.
3751     for (int i = prefix_count-1; i >= 0; i--) {
3752       char* prefix = prefixes[i];
3753       size_t prefix_len = strlen(prefix);
3754       if (strncmp(prefix, name_str, prefix_len) == 0) {
3755         name_str += prefix_len;
3756       }
3757     }
3758     return name_str;
3759   }
3760 
3761   // Strip any prefixes off the old native method, then try to find a
3762   // (possibly prefixed) new native that matches it.
3763   Method* strip_and_search_for_new_native(Method* method) {
3764     ResourceMark rm;
3765     char* name_str = method_name_without_prefixes(method);
3766     return search_prefix_name_space(0, name_str, strlen(name_str),
3767                                     method->signature());
3768   }
3769 
3770  public:
3771 
3772   // Construct a native method transfer processor for this class.
3773   TransferNativeFunctionRegistration(InstanceKlass* _the_class) {
3774     assert(SafepointSynchronize::is_at_safepoint(), "sanity check");
3775 
3776     the_class = _the_class;
3777     prefixes = JvmtiExport::get_all_native_method_prefixes(&prefix_count);
3778   }
3779 
3780   // Attempt to transfer any of the old or deleted methods that are native
3781   void transfer_registrations(Method** old_methods, int methods_length) {
3782     for (int j = 0; j < methods_length; j++) {
3783       Method* old_method = old_methods[j];
3784 
3785       if (old_method->is_native() && old_method->has_native_function()) {
3786         Method* new_method = strip_and_search_for_new_native(old_method);
3787         if (new_method != NULL) {
3788           // Actually set the native function in the new method.
3789           // Redefine does not send events (except CFLH), certainly not this
3790           // behind the scenes re-registration.
3791           new_method->set_native_function(old_method->native_function(),
3792                               !Method::native_bind_event_is_interesting);
3793         }
3794       }
3795     }
3796   }
3797 };
3798 
3799 // Don't lose the association between a native method and its JNI function.
3800 void VM_RedefineClasses::transfer_old_native_function_registrations(InstanceKlass* the_class) {
3801   TransferNativeFunctionRegistration transfer(the_class);
3802   transfer.transfer_registrations(_deleted_methods, _deleted_methods_length);
3803   transfer.transfer_registrations(_matching_old_methods, _matching_methods_length);
3804 }
3805 
3806 // Deoptimize all compiled code that depends on this class.
3807 //
3808 // If the can_redefine_classes capability is obtained in the onload
3809 // phase then the compiler has recorded all dependencies from startup.
3810 // In that case we need only deoptimize and throw away all compiled code
3811 // that depends on the class.
3812 //
3813 // If can_redefine_classes is obtained sometime after the onload
3814 // phase then the dependency information may be incomplete. In that case
3815 // the first call to RedefineClasses causes all compiled code to be
3816 // thrown away. As can_redefine_classes has been obtained then
3817 // all future compilations will record dependencies so second and
3818 // subsequent calls to RedefineClasses need only throw away code
3819 // that depends on the class.
3820 //
3821 
3822 // First step is to walk the code cache for each class redefined and mark
3823 // dependent methods.  Wait until all classes are processed to deoptimize everything.
3824 void VM_RedefineClasses::mark_dependent_code(InstanceKlass* ik) {
3825   assert_locked_or_safepoint(Compile_lock);
3826 
3827   // All dependencies have been recorded from startup or this is a second or
3828   // subsequent use of RedefineClasses
3829   if (JvmtiExport::all_dependencies_are_recorded()) {
3830     CodeCache::mark_for_evol_deoptimization(ik);
3831   }
3832 }
3833 
3834 void VM_RedefineClasses::flush_dependent_code() {
3835   assert(SafepointSynchronize::is_at_safepoint(), "sanity check");
3836 
3837   bool deopt_needed;
3838 
3839   // This is the first redefinition, mark all the nmethods for deoptimization
3840   if (!JvmtiExport::all_dependencies_are_recorded()) {
3841     log_debug(redefine, class, nmethod)("Marked all nmethods for deopt");
3842     CodeCache::mark_all_nmethods_for_evol_deoptimization();
3843     deopt_needed = true;
3844   } else {
3845     int deopt = CodeCache::mark_dependents_for_evol_deoptimization();
3846     log_debug(redefine, class, nmethod)("Marked %d dependent nmethods for deopt", deopt);
3847     deopt_needed = (deopt != 0);
3848   }
3849 
3850   if (deopt_needed) {
3851     CodeCache::flush_evol_dependents();
3852   }
3853 
3854   // From now on we know that the dependency information is complete
3855   JvmtiExport::set_all_dependencies_are_recorded(true);
3856 }
3857 
3858 void VM_RedefineClasses::compute_added_deleted_matching_methods() {
3859   Method* old_method;
3860   Method* new_method;
3861 
3862   _matching_old_methods = NEW_RESOURCE_ARRAY(Method*, _old_methods->length());
3863   _matching_new_methods = NEW_RESOURCE_ARRAY(Method*, _old_methods->length());
3864   _added_methods        = NEW_RESOURCE_ARRAY(Method*, _new_methods->length());
3865   _deleted_methods      = NEW_RESOURCE_ARRAY(Method*, _old_methods->length());
3866 
3867   _matching_methods_length = 0;
3868   _deleted_methods_length  = 0;
3869   _added_methods_length    = 0;
3870 
3871   int nj = 0;
3872   int oj = 0;
3873   while (true) {
3874     if (oj >= _old_methods->length()) {
3875       if (nj >= _new_methods->length()) {
3876         break; // we've looked at everything, done
3877       }
3878       // New method at the end
3879       new_method = _new_methods->at(nj);
3880       _added_methods[_added_methods_length++] = new_method;
3881       ++nj;
3882     } else if (nj >= _new_methods->length()) {
3883       // Old method, at the end, is deleted
3884       old_method = _old_methods->at(oj);
3885       _deleted_methods[_deleted_methods_length++] = old_method;
3886       ++oj;
3887     } else {
3888       old_method = _old_methods->at(oj);
3889       new_method = _new_methods->at(nj);
3890       if (old_method->name() == new_method->name()) {
3891         if (old_method->signature() == new_method->signature()) {
3892           _matching_old_methods[_matching_methods_length  ] = old_method;
3893           _matching_new_methods[_matching_methods_length++] = new_method;
3894           ++nj;
3895           ++oj;
3896         } else {
3897           // added overloaded have already been moved to the end,
3898           // so this is a deleted overloaded method
3899           _deleted_methods[_deleted_methods_length++] = old_method;
3900           ++oj;
3901         }
3902       } else { // names don't match
3903         if (old_method->name()->fast_compare(new_method->name()) > 0) {
3904           // new method
3905           _added_methods[_added_methods_length++] = new_method;
3906           ++nj;
3907         } else {
3908           // deleted method
3909           _deleted_methods[_deleted_methods_length++] = old_method;
3910           ++oj;
3911         }
3912       }
3913     }
3914   }
3915   assert(_matching_methods_length + _deleted_methods_length == _old_methods->length(), "sanity");
3916   assert(_matching_methods_length + _added_methods_length == _new_methods->length(), "sanity");
3917 }
3918 
3919 
3920 void VM_RedefineClasses::swap_annotations(InstanceKlass* the_class,
3921                                           InstanceKlass* scratch_class) {
3922   // Swap annotation fields values
3923   Annotations* old_annotations = the_class->annotations();
3924   the_class->set_annotations(scratch_class->annotations());
3925   scratch_class->set_annotations(old_annotations);
3926 }
3927 
3928 
3929 // Install the redefinition of a class:
3930 //    - house keeping (flushing breakpoints and caches, deoptimizing
3931 //      dependent compiled code)
3932 //    - replacing parts in the_class with parts from scratch_class
3933 //    - adding a weak reference to track the obsolete but interesting
3934 //      parts of the_class
3935 //    - adjusting constant pool caches and vtables in other classes
3936 //      that refer to methods in the_class. These adjustments use the
3937 //      ClassLoaderDataGraph::classes_do() facility which only allows
3938 //      a helper method to be specified. The interesting parameters
3939 //      that we would like to pass to the helper method are saved in
3940 //      static global fields in the VM operation.
3941 void VM_RedefineClasses::redefine_single_class(jclass the_jclass,
3942        InstanceKlass* scratch_class, TRAPS) {
3943 
3944   HandleMark hm(THREAD);   // make sure handles from this call are freed
3945 
3946   if (log_is_enabled(Info, redefine, class, timer)) {
3947     _timer_rsc_phase1.start();
3948   }
3949 
3950   InstanceKlass* the_class = get_ik(the_jclass);
3951 
3952   // Set some flags to control and optimize adjusting method entries
3953   _has_redefined_Object |= the_class == SystemDictionary::Object_klass();
3954   _has_null_class_loader |= the_class->class_loader() == NULL;
3955 
3956   // Remove all breakpoints in methods of this class
3957   JvmtiBreakpoints& jvmti_breakpoints = JvmtiCurrentBreakpoints::get_jvmti_breakpoints();
3958   jvmti_breakpoints.clearall_in_class_at_safepoint(the_class);
3959 
3960   // Mark all compiled code that depends on this class
3961   mark_dependent_code(the_class);
3962 
3963   _old_methods = the_class->methods();
3964   _new_methods = scratch_class->methods();
3965   _the_class = the_class;
3966   compute_added_deleted_matching_methods();
3967   update_jmethod_ids();
3968 
3969   _any_class_has_resolved_methods = the_class->has_resolved_methods() || _any_class_has_resolved_methods;
3970 
3971   // Attach new constant pool to the original klass. The original
3972   // klass still refers to the old constant pool (for now).
3973   scratch_class->constants()->set_pool_holder(the_class);
3974 
3975 #if 0
3976   // In theory, with constant pool merging in place we should be able
3977   // to save space by using the new, merged constant pool in place of
3978   // the old constant pool(s). By "pool(s)" I mean the constant pool in
3979   // the klass version we are replacing now and any constant pool(s) in
3980   // previous versions of klass. Nice theory, doesn't work in practice.
3981   // When this code is enabled, even simple programs throw NullPointer
3982   // exceptions. I'm guessing that this is caused by some constant pool
3983   // cache difference between the new, merged constant pool and the
3984   // constant pool that was just being used by the klass. I'm keeping
3985   // this code around to archive the idea, but the code has to remain
3986   // disabled for now.
3987 
3988   // Attach each old method to the new constant pool. This can be
3989   // done here since we are past the bytecode verification and
3990   // constant pool optimization phases.
3991   for (int i = _old_methods->length() - 1; i >= 0; i--) {
3992     Method* method = _old_methods->at(i);
3993     method->set_constants(scratch_class->constants());
3994   }
3995 
3996   // NOTE: this doesn't work because you can redefine the same class in two
3997   // threads, each getting their own constant pool data appended to the
3998   // original constant pool.  In order for the new methods to work when they
3999   // become old methods, they need to keep their updated copy of the constant pool.
4000 
4001   {
4002     // walk all previous versions of the klass
4003     InstanceKlass *ik = the_class;
4004     PreviousVersionWalker pvw(ik);
4005     do {
4006       ik = pvw.next_previous_version();
4007       if (ik != NULL) {
4008 
4009         // attach previous version of klass to the new constant pool
4010         ik->set_constants(scratch_class->constants());
4011 
4012         // Attach each method in the previous version of klass to the
4013         // new constant pool
4014         Array<Method*>* prev_methods = ik->methods();
4015         for (int i = prev_methods->length() - 1; i >= 0; i--) {
4016           Method* method = prev_methods->at(i);
4017           method->set_constants(scratch_class->constants());
4018         }
4019       }
4020     } while (ik != NULL);
4021   }
4022 #endif
4023 
4024   // Replace methods and constantpool
4025   the_class->set_methods(_new_methods);
4026   scratch_class->set_methods(_old_methods);     // To prevent potential GCing of the old methods,
4027                                           // and to be able to undo operation easily.
4028 
4029   Array<int>* old_ordering = the_class->method_ordering();
4030   the_class->set_method_ordering(scratch_class->method_ordering());
4031   scratch_class->set_method_ordering(old_ordering);
4032 
4033   ConstantPool* old_constants = the_class->constants();
4034   the_class->set_constants(scratch_class->constants());
4035   scratch_class->set_constants(old_constants);  // See the previous comment.
4036 #if 0
4037   // We are swapping the guts of "the new class" with the guts of "the
4038   // class". Since the old constant pool has just been attached to "the
4039   // new class", it seems logical to set the pool holder in the old
4040   // constant pool also. However, doing this will change the observable
4041   // class hierarchy for any old methods that are still executing. A
4042   // method can query the identity of its "holder" and this query uses
4043   // the method's constant pool link to find the holder. The change in
4044   // holding class from "the class" to "the new class" can confuse
4045   // things.
4046   //
4047   // Setting the old constant pool's holder will also cause
4048   // verification done during vtable initialization below to fail.
4049   // During vtable initialization, the vtable's class is verified to be
4050   // a subtype of the method's holder. The vtable's class is "the
4051   // class" and the method's holder is gotten from the constant pool
4052   // link in the method itself. For "the class"'s directly implemented
4053   // methods, the method holder is "the class" itself (as gotten from
4054   // the new constant pool). The check works fine in this case. The
4055   // check also works fine for methods inherited from super classes.
4056   //
4057   // Miranda methods are a little more complicated. A miranda method is
4058   // provided by an interface when the class implementing the interface
4059   // does not provide its own method.  These interfaces are implemented
4060   // internally as an InstanceKlass. These special instanceKlasses
4061   // share the constant pool of the class that "implements" the
4062   // interface. By sharing the constant pool, the method holder of a
4063   // miranda method is the class that "implements" the interface. In a
4064   // non-redefine situation, the subtype check works fine. However, if
4065   // the old constant pool's pool holder is modified, then the check
4066   // fails because there is no class hierarchy relationship between the
4067   // vtable's class and "the new class".
4068 
4069   old_constants->set_pool_holder(scratch_class());
4070 #endif
4071 
4072   // track number of methods that are EMCP for add_previous_version() call below
4073   int emcp_method_count = check_methods_and_mark_as_obsolete();
4074   transfer_old_native_function_registrations(the_class);
4075 
4076   // The class file bytes from before any retransformable agents mucked
4077   // with them was cached on the scratch class, move to the_class.
4078   // Note: we still want to do this if nothing needed caching since it
4079   // should get cleared in the_class too.
4080   if (the_class->get_cached_class_file() == 0) {
4081     // the_class doesn't have a cache yet so copy it
4082     the_class->set_cached_class_file(scratch_class->get_cached_class_file());
4083   }
4084   else if (scratch_class->get_cached_class_file() !=
4085            the_class->get_cached_class_file()) {
4086     // The same class can be present twice in the scratch classes list or there
4087     // are multiple concurrent RetransformClasses calls on different threads.
4088     // In such cases we have to deallocate scratch_class cached_class_file.
4089     os::free(scratch_class->get_cached_class_file());
4090   }
4091 
4092   // NULL out in scratch class to not delete twice.  The class to be redefined
4093   // always owns these bytes.
4094   scratch_class->set_cached_class_file(NULL);
4095 
4096   // Replace inner_classes
4097   Array<u2>* old_inner_classes = the_class->inner_classes();
4098   the_class->set_inner_classes(scratch_class->inner_classes());
4099   scratch_class->set_inner_classes(old_inner_classes);
4100 
4101   // Initialize the vtable and interface table after
4102   // methods have been rewritten
4103   // no exception should happen here since we explicitly
4104   // do not check loader constraints.
4105   // compare_and_normalize_class_versions has already checked:
4106   //  - classloaders unchanged, signatures unchanged
4107   //  - all instanceKlasses for redefined classes reused & contents updated
4108   the_class->vtable().initialize_vtable(false, THREAD);
4109   the_class->itable().initialize_itable(false, THREAD);
4110   assert(!HAS_PENDING_EXCEPTION || (THREAD->pending_exception()->is_a(SystemDictionary::ThreadDeath_klass())), "redefine exception");
4111 
4112   // Leave arrays of jmethodIDs and itable index cache unchanged
4113 
4114   // Copy the "source file name" attribute from new class version
4115   the_class->set_source_file_name_index(
4116     scratch_class->source_file_name_index());
4117 
4118   // Copy the "source debug extension" attribute from new class version
4119   the_class->set_source_debug_extension(
4120     scratch_class->source_debug_extension(),
4121     scratch_class->source_debug_extension() == NULL ? 0 :
4122     (int)strlen(scratch_class->source_debug_extension()));
4123 
4124   // Use of javac -g could be different in the old and the new
4125   if (scratch_class->access_flags().has_localvariable_table() !=
4126       the_class->access_flags().has_localvariable_table()) {
4127 
4128     AccessFlags flags = the_class->access_flags();
4129     if (scratch_class->access_flags().has_localvariable_table()) {
4130       flags.set_has_localvariable_table();
4131     } else {
4132       flags.clear_has_localvariable_table();
4133     }
4134     the_class->set_access_flags(flags);
4135   }
4136 
4137   swap_annotations(the_class, scratch_class);
4138 
4139   // Replace minor version number of class file
4140   u2 old_minor_version = the_class->minor_version();
4141   the_class->set_minor_version(scratch_class->minor_version());
4142   scratch_class->set_minor_version(old_minor_version);
4143 
4144   // Replace major version number of class file
4145   u2 old_major_version = the_class->major_version();
4146   the_class->set_major_version(scratch_class->major_version());
4147   scratch_class->set_major_version(old_major_version);
4148 
4149   // Replace CP indexes for class and name+type of enclosing method
4150   u2 old_class_idx  = the_class->enclosing_method_class_index();
4151   u2 old_method_idx = the_class->enclosing_method_method_index();
4152   the_class->set_enclosing_method_indices(
4153     scratch_class->enclosing_method_class_index(),
4154     scratch_class->enclosing_method_method_index());
4155   scratch_class->set_enclosing_method_indices(old_class_idx, old_method_idx);
4156 
4157   // Replace fingerprint data
4158   the_class->set_has_passed_fingerprint_check(scratch_class->has_passed_fingerprint_check());
4159   the_class->store_fingerprint(scratch_class->get_stored_fingerprint());
4160 
4161   the_class->set_has_been_redefined();
4162 
4163   if (!the_class->should_be_initialized()) {
4164     // Class was already initialized, so AOT has only seen the original version.
4165     // We need to let AOT look at it again.
4166     AOTLoader::load_for_klass(the_class, THREAD);
4167   }
4168 
4169   // keep track of previous versions of this class
4170   the_class->add_previous_version(scratch_class, emcp_method_count);
4171 
4172   _timer_rsc_phase1.stop();
4173   if (log_is_enabled(Info, redefine, class, timer)) {
4174     _timer_rsc_phase2.start();
4175   }
4176 
4177   if (the_class->oop_map_cache() != NULL) {
4178     // Flush references to any obsolete methods from the oop map cache
4179     // so that obsolete methods are not pinned.
4180     the_class->oop_map_cache()->flush_obsolete_entries();
4181   }
4182 
4183   increment_class_counter((InstanceKlass *)the_class, THREAD);
4184   {
4185     ResourceMark rm(THREAD);
4186     // increment the classRedefinedCount field in the_class and in any
4187     // direct and indirect subclasses of the_class
4188     log_info(redefine, class, load)
4189       ("redefined name=%s, count=%d (avail_mem=" UINT64_FORMAT "K)",
4190        the_class->external_name(), java_lang_Class::classRedefinedCount(the_class->java_mirror()), os::available_memory() >> 10);
4191     Events::log_redefinition(THREAD, "redefined class name=%s, count=%d",
4192                              the_class->external_name(),
4193                              java_lang_Class::classRedefinedCount(the_class->java_mirror()));
4194 
4195   }
4196   _timer_rsc_phase2.stop();
4197 } // end redefine_single_class()
4198 
4199 
4200 // Increment the classRedefinedCount field in the specific InstanceKlass
4201 // and in all direct and indirect subclasses.
4202 void VM_RedefineClasses::increment_class_counter(InstanceKlass *ik, TRAPS) {
4203   oop class_mirror = ik->java_mirror();
4204   Klass* class_oop = java_lang_Class::as_Klass(class_mirror);
4205   int new_count = java_lang_Class::classRedefinedCount(class_mirror) + 1;
4206   java_lang_Class::set_classRedefinedCount(class_mirror, new_count);
4207 
4208   if (class_oop != _the_class) {
4209     // _the_class count is printed at end of redefine_single_class()
4210     log_debug(redefine, class, subclass)("updated count in subclass=%s to %d", ik->external_name(), new_count);
4211   }
4212 
4213   for (Klass *subk = ik->subklass(); subk != NULL;
4214        subk = subk->next_sibling()) {
4215     if (subk->is_instance_klass()) {
4216       // Only update instanceKlasses
4217       InstanceKlass *subik = InstanceKlass::cast(subk);
4218       // recursively do subclasses of the current subclass
4219       increment_class_counter(subik, THREAD);
4220     }
4221   }
4222 }
4223 
4224 void VM_RedefineClasses::CheckClass::do_klass(Klass* k) {
4225   bool no_old_methods = true;  // be optimistic
4226 
4227   // Both array and instance classes have vtables.
4228   // a vtable should never contain old or obsolete methods
4229   ResourceMark rm(_thread);
4230   if (k->vtable_length() > 0 &&
4231       !k->vtable().check_no_old_or_obsolete_entries()) {
4232     if (log_is_enabled(Trace, redefine, class, obsolete, metadata)) {
4233       log_trace(redefine, class, obsolete, metadata)
4234         ("klassVtable::check_no_old_or_obsolete_entries failure -- OLD or OBSOLETE method found -- class: %s",
4235          k->signature_name());
4236       k->vtable().dump_vtable();
4237     }
4238     no_old_methods = false;
4239   }
4240 
4241   if (k->is_instance_klass()) {
4242     HandleMark hm(_thread);
4243     InstanceKlass *ik = InstanceKlass::cast(k);
4244 
4245     // an itable should never contain old or obsolete methods
4246     if (ik->itable_length() > 0 &&
4247         !ik->itable().check_no_old_or_obsolete_entries()) {
4248       if (log_is_enabled(Trace, redefine, class, obsolete, metadata)) {
4249         log_trace(redefine, class, obsolete, metadata)
4250           ("klassItable::check_no_old_or_obsolete_entries failure -- OLD or OBSOLETE method found -- class: %s",
4251            ik->signature_name());
4252         ik->itable().dump_itable();
4253       }
4254       no_old_methods = false;
4255     }
4256 
4257     // the constant pool cache should never contain non-deleted old or obsolete methods
4258     if (ik->constants() != NULL &&
4259         ik->constants()->cache() != NULL &&
4260         !ik->constants()->cache()->check_no_old_or_obsolete_entries()) {
4261       if (log_is_enabled(Trace, redefine, class, obsolete, metadata)) {
4262         log_trace(redefine, class, obsolete, metadata)
4263           ("cp-cache::check_no_old_or_obsolete_entries failure -- OLD or OBSOLETE method found -- class: %s",
4264            ik->signature_name());
4265         ik->constants()->cache()->dump_cache();
4266       }
4267       no_old_methods = false;
4268     }
4269   }
4270 
4271   // print and fail guarantee if old methods are found.
4272   if (!no_old_methods) {
4273     if (log_is_enabled(Trace, redefine, class, obsolete, metadata)) {
4274       dump_methods();
4275     } else {
4276       log_trace(redefine, class)("Use the '-Xlog:redefine+class*:' option "
4277         "to see more info about the following guarantee() failure.");
4278     }
4279     guarantee(false, "OLD and/or OBSOLETE method(s) found");
4280   }
4281 }
4282 
4283 
4284 void VM_RedefineClasses::dump_methods() {
4285   int j;
4286   log_trace(redefine, class, dump)("_old_methods --");
4287   for (j = 0; j < _old_methods->length(); ++j) {
4288     LogStreamHandle(Trace, redefine, class, dump) log_stream;
4289     Method* m = _old_methods->at(j);
4290     log_stream.print("%4d  (%5d)  ", j, m->vtable_index());
4291     m->access_flags().print_on(&log_stream);
4292     log_stream.print(" --  ");
4293     m->print_name(&log_stream);
4294     log_stream.cr();
4295   }
4296   log_trace(redefine, class, dump)("_new_methods --");
4297   for (j = 0; j < _new_methods->length(); ++j) {
4298     LogStreamHandle(Trace, redefine, class, dump) log_stream;
4299     Method* m = _new_methods->at(j);
4300     log_stream.print("%4d  (%5d)  ", j, m->vtable_index());
4301     m->access_flags().print_on(&log_stream);
4302     log_stream.print(" --  ");
4303     m->print_name(&log_stream);
4304     log_stream.cr();
4305   }
4306   log_trace(redefine, class, dump)("_matching_methods --");
4307   for (j = 0; j < _matching_methods_length; ++j) {
4308     LogStreamHandle(Trace, redefine, class, dump) log_stream;
4309     Method* m = _matching_old_methods[j];
4310     log_stream.print("%4d  (%5d)  ", j, m->vtable_index());
4311     m->access_flags().print_on(&log_stream);
4312     log_stream.print(" --  ");
4313     m->print_name();
4314     log_stream.cr();
4315 
4316     m = _matching_new_methods[j];
4317     log_stream.print("      (%5d)  ", m->vtable_index());
4318     m->access_flags().print_on(&log_stream);
4319     log_stream.cr();
4320   }
4321   log_trace(redefine, class, dump)("_deleted_methods --");
4322   for (j = 0; j < _deleted_methods_length; ++j) {
4323     LogStreamHandle(Trace, redefine, class, dump) log_stream;
4324     Method* m = _deleted_methods[j];
4325     log_stream.print("%4d  (%5d)  ", j, m->vtable_index());
4326     m->access_flags().print_on(&log_stream);
4327     log_stream.print(" --  ");
4328     m->print_name(&log_stream);
4329     log_stream.cr();
4330   }
4331   log_trace(redefine, class, dump)("_added_methods --");
4332   for (j = 0; j < _added_methods_length; ++j) {
4333     LogStreamHandle(Trace, redefine, class, dump) log_stream;
4334     Method* m = _added_methods[j];
4335     log_stream.print("%4d  (%5d)  ", j, m->vtable_index());
4336     m->access_flags().print_on(&log_stream);
4337     log_stream.print(" --  ");
4338     m->print_name(&log_stream);
4339     log_stream.cr();
4340   }
4341 }
4342 
4343 void VM_RedefineClasses::print_on_error(outputStream* st) const {
4344   VM_Operation::print_on_error(st);
4345   if (_the_class != NULL) {
4346     ResourceMark rm;
4347     st->print_cr(", redefining class %s", _the_class->external_name());
4348   }
4349 }