1 /*
   2  * Copyright (c) 2003, 2014, 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 "classfile/metadataOnStackMark.hpp"
  27 #include "classfile/systemDictionary.hpp"
  28 #include "classfile/verifier.hpp"
  29 #include "code/codeCache.hpp"
  30 #include "compiler/compileBroker.hpp"
  31 #include "interpreter/oopMapCache.hpp"
  32 #include "interpreter/rewriter.hpp"
  33 #include "memory/gcLocker.hpp"
  34 #include "memory/metadataFactory.hpp"
  35 #include "memory/metaspaceShared.hpp"
  36 #include "memory/universe.inline.hpp"
  37 #include "oops/fieldStreams.hpp"
  38 #include "oops/klassVtable.hpp"
  39 #include "prims/jvmtiImpl.hpp"
  40 #include "prims/jvmtiRedefineClasses.hpp"
  41 #include "prims/methodComparator.hpp"
  42 #include "runtime/deoptimization.hpp"
  43 #include "runtime/relocator.hpp"
  44 #include "utilities/bitMap.inline.hpp"
  45 
  46 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
  47 
  48 Array<Method*>* VM_RedefineClasses::_old_methods = NULL;
  49 Array<Method*>* VM_RedefineClasses::_new_methods = NULL;
  50 Method**  VM_RedefineClasses::_matching_old_methods = NULL;
  51 Method**  VM_RedefineClasses::_matching_new_methods = NULL;
  52 Method**  VM_RedefineClasses::_deleted_methods      = NULL;
  53 Method**  VM_RedefineClasses::_added_methods        = NULL;
  54 int         VM_RedefineClasses::_matching_methods_length = 0;
  55 int         VM_RedefineClasses::_deleted_methods_length  = 0;
  56 int         VM_RedefineClasses::_added_methods_length    = 0;
  57 Klass*      VM_RedefineClasses::_the_class_oop = NULL;
  58 
  59 
  60 VM_RedefineClasses::VM_RedefineClasses(jint class_count,
  61                                        const jvmtiClassDefinition *class_defs,
  62                                        JvmtiClassLoadKind class_load_kind) {
  63   _class_count = class_count;
  64   _class_defs = class_defs;
  65   _class_load_kind = class_load_kind;
  66   _res = JVMTI_ERROR_NONE;
  67 }
  68 
  69 bool VM_RedefineClasses::doit_prologue() {
  70   if (_class_count == 0) {
  71     _res = JVMTI_ERROR_NONE;
  72     return false;
  73   }
  74   if (_class_defs == NULL) {
  75     _res = JVMTI_ERROR_NULL_POINTER;
  76     return false;
  77   }
  78   for (int i = 0; i < _class_count; i++) {
  79     if (_class_defs[i].klass == NULL) {
  80       _res = JVMTI_ERROR_INVALID_CLASS;
  81       return false;
  82     }
  83     if (_class_defs[i].class_byte_count == 0) {
  84       _res = JVMTI_ERROR_INVALID_CLASS_FORMAT;
  85       return false;
  86     }
  87     if (_class_defs[i].class_bytes == NULL) {
  88       _res = JVMTI_ERROR_NULL_POINTER;
  89       return false;
  90     }
  91   }
  92 
  93   // Start timer after all the sanity checks; not quite accurate, but
  94   // better than adding a bunch of stop() calls.
  95   RC_TIMER_START(_timer_vm_op_prologue);
  96 
  97   // We first load new class versions in the prologue, because somewhere down the
  98   // call chain it is required that the current thread is a Java thread.
  99   _res = load_new_class_versions(Thread::current());
 100   if (_res != JVMTI_ERROR_NONE) {
 101     // free any successfully created classes, since none are redefined
 102     for (int i = 0; i < _class_count; i++) {
 103       if (_scratch_classes[i] != NULL) {
 104         ClassLoaderData* cld = _scratch_classes[i]->class_loader_data();
 105         // Free the memory for this class at class unloading time.  Not before
 106         // because CMS might think this is still live.
 107         cld->add_to_deallocate_list((InstanceKlass*)_scratch_classes[i]);
 108       }
 109     }
 110     // Free os::malloc allocated memory in load_new_class_version.
 111     os::free(_scratch_classes);
 112     RC_TIMER_STOP(_timer_vm_op_prologue);
 113     return false;
 114   }
 115 
 116   RC_TIMER_STOP(_timer_vm_op_prologue);
 117   return true;
 118 }
 119 
 120 void VM_RedefineClasses::doit() {
 121   Thread *thread = Thread::current();
 122 
 123   if (UseSharedSpaces) {
 124     // Sharing is enabled so we remap the shared readonly space to
 125     // shared readwrite, private just in case we need to redefine
 126     // a shared class. We do the remap during the doit() phase of
 127     // the safepoint to be safer.
 128     if (!MetaspaceShared::remap_shared_readonly_as_readwrite()) {
 129       RC_TRACE_WITH_THREAD(0x00000001, thread,
 130         ("failed to remap shared readonly space to readwrite, private"));
 131       _res = JVMTI_ERROR_INTERNAL;
 132       return;
 133     }
 134   }
 135 
 136   // Mark methods seen on stack and everywhere else so old methods are not
 137   // cleaned up if they're on the stack.
 138   MetadataOnStackMark md_on_stack(true);
 139   HandleMark hm(thread);   // make sure any handles created are deleted
 140                            // before the stack walk again.
 141 
 142   for (int i = 0; i < _class_count; i++) {
 143     redefine_single_class(_class_defs[i].klass, _scratch_classes[i], thread);
 144     ClassLoaderData* cld = _scratch_classes[i]->class_loader_data();
 145     // Free the memory for this class at class unloading time.  Not before
 146     // because CMS might think this is still live.
 147     cld->add_to_deallocate_list((InstanceKlass*)_scratch_classes[i]);
 148     _scratch_classes[i] = NULL;
 149   }
 150 
 151   // Disable any dependent concurrent compilations
 152   SystemDictionary::notice_modification();
 153 
 154   // Set flag indicating that some invariants are no longer true.
 155   // See jvmtiExport.hpp for detailed explanation.
 156   JvmtiExport::set_has_redefined_a_class();
 157 
 158 // check_class() is optionally called for product bits, but is
 159 // always called for non-product bits.
 160 #ifdef PRODUCT
 161   if (RC_TRACE_ENABLED(0x00004000)) {
 162 #endif
 163     RC_TRACE_WITH_THREAD(0x00004000, thread, ("calling check_class"));
 164     CheckClass check_class(thread);
 165     ClassLoaderDataGraph::classes_do(&check_class);
 166 #ifdef PRODUCT
 167   }
 168 #endif
 169 }
 170 
 171 void VM_RedefineClasses::doit_epilogue() {
 172   // Free os::malloc allocated memory.
 173   os::free(_scratch_classes);
 174 
 175   if (RC_TRACE_ENABLED(0x00000004)) {
 176     // Used to have separate timers for "doit" and "all", but the timer
 177     // overhead skewed the measurements.
 178     jlong doit_time = _timer_rsc_phase1.milliseconds() +
 179                       _timer_rsc_phase2.milliseconds();
 180     jlong all_time = _timer_vm_op_prologue.milliseconds() + doit_time;
 181 
 182     RC_TRACE(0x00000004, ("vm_op: all=" UINT64_FORMAT
 183       "  prologue=" UINT64_FORMAT "  doit=" UINT64_FORMAT, all_time,
 184       _timer_vm_op_prologue.milliseconds(), doit_time));
 185     RC_TRACE(0x00000004,
 186       ("redefine_single_class: phase1=" UINT64_FORMAT "  phase2=" UINT64_FORMAT,
 187        _timer_rsc_phase1.milliseconds(), _timer_rsc_phase2.milliseconds()));
 188   }
 189 }
 190 
 191 bool VM_RedefineClasses::is_modifiable_class(oop klass_mirror) {
 192   // classes for primitives cannot be redefined
 193   if (java_lang_Class::is_primitive(klass_mirror)) {
 194     return false;
 195   }
 196   Klass* the_class_oop = java_lang_Class::as_Klass(klass_mirror);
 197   // classes for arrays cannot be redefined
 198   if (the_class_oop == NULL || !the_class_oop->oop_is_instance()) {
 199     return false;
 200   }
 201   return true;
 202 }
 203 
 204 // Append the current entry at scratch_i in scratch_cp to *merge_cp_p
 205 // where the end of *merge_cp_p is specified by *merge_cp_length_p. For
 206 // direct CP entries, there is just the current entry to append. For
 207 // indirect and double-indirect CP entries, there are zero or more
 208 // referenced CP entries along with the current entry to append.
 209 // Indirect and double-indirect CP entries are handled by recursive
 210 // calls to append_entry() as needed. The referenced CP entries are
 211 // always appended to *merge_cp_p before the referee CP entry. These
 212 // referenced CP entries may already exist in *merge_cp_p in which case
 213 // there is nothing extra to append and only the current entry is
 214 // appended.
 215 void VM_RedefineClasses::append_entry(constantPoolHandle scratch_cp,
 216        int scratch_i, constantPoolHandle *merge_cp_p, int *merge_cp_length_p,
 217        TRAPS) {
 218 
 219   // append is different depending on entry tag type
 220   switch (scratch_cp->tag_at(scratch_i).value()) {
 221 
 222     // The old verifier is implemented outside the VM. It loads classes,
 223     // but does not resolve constant pool entries directly so we never
 224     // see Class entries here with the old verifier. Similarly the old
 225     // verifier does not like Class entries in the input constant pool.
 226     // The split-verifier is implemented in the VM so it can optionally
 227     // and directly resolve constant pool entries to load classes. The
 228     // split-verifier can accept either Class entries or UnresolvedClass
 229     // entries in the input constant pool. We revert the appended copy
 230     // back to UnresolvedClass so that either verifier will be happy
 231     // with the constant pool entry.
 232     case JVM_CONSTANT_Class:
 233     {
 234       // revert the copy to JVM_CONSTANT_UnresolvedClass
 235       (*merge_cp_p)->unresolved_klass_at_put(*merge_cp_length_p,
 236         scratch_cp->klass_name_at(scratch_i));
 237 
 238       if (scratch_i != *merge_cp_length_p) {
 239         // The new entry in *merge_cp_p is at a different index than
 240         // the new entry in scratch_cp so we need to map the index values.
 241         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 242       }
 243       (*merge_cp_length_p)++;
 244     } break;
 245 
 246     // these are direct CP entries so they can be directly appended,
 247     // but double and long take two constant pool entries
 248     case JVM_CONSTANT_Double:  // fall through
 249     case JVM_CONSTANT_Long:
 250     {
 251       ConstantPool::copy_entry_to(scratch_cp, scratch_i, *merge_cp_p, *merge_cp_length_p,
 252         THREAD);
 253 
 254       if (scratch_i != *merge_cp_length_p) {
 255         // The new entry in *merge_cp_p is at a different index than
 256         // the new entry in scratch_cp so we need to map the index values.
 257         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 258       }
 259       (*merge_cp_length_p) += 2;
 260     } break;
 261 
 262     // these are direct CP entries so they can be directly appended
 263     case JVM_CONSTANT_Float:   // fall through
 264     case JVM_CONSTANT_Integer: // fall through
 265     case JVM_CONSTANT_Utf8:    // fall through
 266 
 267     // This was an indirect CP entry, but it has been changed into
 268     // Symbol*s so this entry can be directly appended.
 269     case JVM_CONSTANT_String:      // fall through
 270 
 271     // These were indirect CP entries, but they have been changed into
 272     // Symbol*s so these entries can be directly appended.
 273     case JVM_CONSTANT_UnresolvedClass:  // fall through
 274     {
 275       ConstantPool::copy_entry_to(scratch_cp, scratch_i, *merge_cp_p, *merge_cp_length_p,
 276         THREAD);
 277 
 278       if (scratch_i != *merge_cp_length_p) {
 279         // The new entry in *merge_cp_p is at a different index than
 280         // the new entry in scratch_cp so we need to map the index values.
 281         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 282       }
 283       (*merge_cp_length_p)++;
 284     } break;
 285 
 286     // this is an indirect CP entry so it needs special handling
 287     case JVM_CONSTANT_NameAndType:
 288     {
 289       int name_ref_i = scratch_cp->name_ref_index_at(scratch_i);
 290       int new_name_ref_i = find_or_append_indirect_entry(scratch_cp, name_ref_i, merge_cp_p,
 291                                                          merge_cp_length_p, THREAD);
 292 
 293       int signature_ref_i = scratch_cp->signature_ref_index_at(scratch_i);
 294       int new_signature_ref_i = find_or_append_indirect_entry(scratch_cp, signature_ref_i,
 295                                                               merge_cp_p, merge_cp_length_p,
 296                                                               THREAD);
 297 
 298       // If the referenced entries already exist in *merge_cp_p, then
 299       // both new_name_ref_i and new_signature_ref_i will both be 0.
 300       // In that case, all we are appending is the current entry.
 301       if (new_name_ref_i != name_ref_i) {
 302         RC_TRACE(0x00080000,
 303           ("NameAndType entry@%d name_ref_index change: %d to %d",
 304           *merge_cp_length_p, name_ref_i, new_name_ref_i));
 305       }
 306       if (new_signature_ref_i != signature_ref_i) {
 307         RC_TRACE(0x00080000,
 308           ("NameAndType entry@%d signature_ref_index change: %d to %d",
 309           *merge_cp_length_p, signature_ref_i, new_signature_ref_i));
 310       }
 311 
 312       (*merge_cp_p)->name_and_type_at_put(*merge_cp_length_p,
 313         new_name_ref_i, new_signature_ref_i);
 314       if (scratch_i != *merge_cp_length_p) {
 315         // The new entry in *merge_cp_p is at a different index than
 316         // the new entry in scratch_cp so we need to map the index values.
 317         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 318       }
 319       (*merge_cp_length_p)++;
 320     } break;
 321 
 322     // this is a double-indirect CP entry so it needs special handling
 323     case JVM_CONSTANT_Fieldref:           // fall through
 324     case JVM_CONSTANT_InterfaceMethodref: // fall through
 325     case JVM_CONSTANT_Methodref:
 326     {
 327       int klass_ref_i = scratch_cp->uncached_klass_ref_index_at(scratch_i);
 328       int new_klass_ref_i = find_or_append_indirect_entry(scratch_cp, klass_ref_i,
 329                                                           merge_cp_p, merge_cp_length_p, THREAD);
 330 
 331       int name_and_type_ref_i = scratch_cp->uncached_name_and_type_ref_index_at(scratch_i);
 332       int new_name_and_type_ref_i = find_or_append_indirect_entry(scratch_cp, name_and_type_ref_i,
 333                                                           merge_cp_p, merge_cp_length_p, THREAD);
 334 
 335       const char *entry_name;
 336       switch (scratch_cp->tag_at(scratch_i).value()) {
 337       case JVM_CONSTANT_Fieldref:
 338         entry_name = "Fieldref";
 339         (*merge_cp_p)->field_at_put(*merge_cp_length_p, new_klass_ref_i,
 340           new_name_and_type_ref_i);
 341         break;
 342       case JVM_CONSTANT_InterfaceMethodref:
 343         entry_name = "IFMethodref";
 344         (*merge_cp_p)->interface_method_at_put(*merge_cp_length_p,
 345           new_klass_ref_i, new_name_and_type_ref_i);
 346         break;
 347       case JVM_CONSTANT_Methodref:
 348         entry_name = "Methodref";
 349         (*merge_cp_p)->method_at_put(*merge_cp_length_p, new_klass_ref_i,
 350           new_name_and_type_ref_i);
 351         break;
 352       default:
 353         guarantee(false, "bad switch");
 354         break;
 355       }
 356 
 357       if (klass_ref_i != new_klass_ref_i) {
 358         RC_TRACE(0x00080000, ("%s entry@%d class_index changed: %d to %d",
 359           entry_name, *merge_cp_length_p, klass_ref_i, new_klass_ref_i));
 360       }
 361       if (name_and_type_ref_i != new_name_and_type_ref_i) {
 362         RC_TRACE(0x00080000,
 363           ("%s entry@%d name_and_type_index changed: %d to %d",
 364           entry_name, *merge_cp_length_p, name_and_type_ref_i,
 365           new_name_and_type_ref_i));
 366       }
 367 
 368       if (scratch_i != *merge_cp_length_p) {
 369         // The new entry in *merge_cp_p is at a different index than
 370         // the new entry in scratch_cp so we need to map the index values.
 371         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 372       }
 373       (*merge_cp_length_p)++;
 374     } break;
 375 
 376     // this is an indirect CP entry so it needs special handling
 377     case JVM_CONSTANT_MethodType:
 378     {
 379       int ref_i = scratch_cp->method_type_index_at(scratch_i);
 380       int new_ref_i = find_or_append_indirect_entry(scratch_cp, ref_i, merge_cp_p,
 381                                                     merge_cp_length_p, THREAD);
 382       if (new_ref_i != ref_i) {
 383         RC_TRACE(0x00080000,
 384                  ("MethodType entry@%d ref_index change: %d to %d",
 385                   *merge_cp_length_p, ref_i, new_ref_i));
 386       }
 387       (*merge_cp_p)->method_type_index_at_put(*merge_cp_length_p, new_ref_i);
 388       if (scratch_i != *merge_cp_length_p) {
 389         // The new entry in *merge_cp_p is at a different index than
 390         // the new entry in scratch_cp so we need to map the index values.
 391         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 392       }
 393       (*merge_cp_length_p)++;
 394     } break;
 395 
 396     // this is an indirect CP entry so it needs special handling
 397     case JVM_CONSTANT_MethodHandle:
 398     {
 399       int ref_kind = scratch_cp->method_handle_ref_kind_at(scratch_i);
 400       int ref_i = scratch_cp->method_handle_index_at(scratch_i);
 401       int new_ref_i = find_or_append_indirect_entry(scratch_cp, ref_i, merge_cp_p,
 402                                                     merge_cp_length_p, THREAD);
 403       if (new_ref_i != ref_i) {
 404         RC_TRACE(0x00080000,
 405                  ("MethodHandle entry@%d ref_index change: %d to %d",
 406                   *merge_cp_length_p, ref_i, new_ref_i));
 407       }
 408       (*merge_cp_p)->method_handle_index_at_put(*merge_cp_length_p, ref_kind, new_ref_i);
 409       if (scratch_i != *merge_cp_length_p) {
 410         // The new entry in *merge_cp_p is at a different index than
 411         // the new entry in scratch_cp so we need to map the index values.
 412         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 413       }
 414       (*merge_cp_length_p)++;
 415     } break;
 416 
 417     // this is an indirect CP entry so it needs special handling
 418     case JVM_CONSTANT_InvokeDynamic:
 419     {
 420       // Index of the bootstrap specifier in the operands array
 421       int old_bs_i = scratch_cp->invoke_dynamic_bootstrap_specifier_index(scratch_i);
 422       int new_bs_i = find_or_append_operand(scratch_cp, old_bs_i, merge_cp_p,
 423                                             merge_cp_length_p, THREAD);
 424       // The bootstrap method NameAndType_info index
 425       int old_ref_i = scratch_cp->invoke_dynamic_name_and_type_ref_index_at(scratch_i);
 426       int new_ref_i = find_or_append_indirect_entry(scratch_cp, old_ref_i, merge_cp_p,
 427                                                     merge_cp_length_p, THREAD);
 428       if (new_bs_i != old_bs_i) {
 429         RC_TRACE(0x00080000,
 430                  ("InvokeDynamic entry@%d bootstrap_method_attr_index change: %d to %d",
 431                   *merge_cp_length_p, old_bs_i, new_bs_i));
 432       }
 433       if (new_ref_i != old_ref_i) {
 434         RC_TRACE(0x00080000,
 435                  ("InvokeDynamic entry@%d name_and_type_index change: %d to %d",
 436                   *merge_cp_length_p, old_ref_i, new_ref_i));
 437       }
 438 
 439       (*merge_cp_p)->invoke_dynamic_at_put(*merge_cp_length_p, new_bs_i, new_ref_i);
 440       if (scratch_i != *merge_cp_length_p) {
 441         // The new entry in *merge_cp_p is at a different index than
 442         // the new entry in scratch_cp so we need to map the index values.
 443         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 444       }
 445       (*merge_cp_length_p)++;
 446     } break;
 447 
 448     // At this stage, Class or UnresolvedClass could be here, but not
 449     // ClassIndex
 450     case JVM_CONSTANT_ClassIndex: // fall through
 451 
 452     // Invalid is used as the tag for the second constant pool entry
 453     // occupied by JVM_CONSTANT_Double or JVM_CONSTANT_Long. It should
 454     // not be seen by itself.
 455     case JVM_CONSTANT_Invalid: // fall through
 456 
 457     // At this stage, String could be here, but not StringIndex
 458     case JVM_CONSTANT_StringIndex: // fall through
 459 
 460     // At this stage JVM_CONSTANT_UnresolvedClassInError should not be
 461     // here
 462     case JVM_CONSTANT_UnresolvedClassInError: // fall through
 463 
 464     default:
 465     {
 466       // leave a breadcrumb
 467       jbyte bad_value = scratch_cp->tag_at(scratch_i).value();
 468       ShouldNotReachHere();
 469     } break;
 470   } // end switch tag value
 471 } // end append_entry()
 472 
 473 
 474 int VM_RedefineClasses::find_or_append_indirect_entry(constantPoolHandle scratch_cp,
 475       int ref_i, constantPoolHandle *merge_cp_p, int *merge_cp_length_p, TRAPS) {
 476 
 477   int new_ref_i = ref_i;
 478   bool match = (ref_i < *merge_cp_length_p) &&
 479                scratch_cp->compare_entry_to(ref_i, *merge_cp_p, ref_i, THREAD);
 480 
 481   if (!match) {
 482     // forward reference in *merge_cp_p or not a direct match
 483     int found_i = scratch_cp->find_matching_entry(ref_i, *merge_cp_p, THREAD);
 484     if (found_i != 0) {
 485       guarantee(found_i != ref_i, "compare_entry_to() and find_matching_entry() do not agree");
 486       // Found a matching entry somewhere else in *merge_cp_p so just need a mapping entry.
 487       new_ref_i = found_i;
 488       map_index(scratch_cp, ref_i, found_i);
 489     } else {
 490       // no match found so we have to append this entry to *merge_cp_p
 491       append_entry(scratch_cp, ref_i, merge_cp_p, merge_cp_length_p, THREAD);
 492       // The above call to append_entry() can only append one entry
 493       // so the post call query of *merge_cp_length_p is only for
 494       // the sake of consistency.
 495       new_ref_i = *merge_cp_length_p - 1;
 496     }
 497   }
 498 
 499   return new_ref_i;
 500 } // end find_or_append_indirect_entry()
 501 
 502 
 503 // Append a bootstrap specifier into the merge_cp operands that is semantically equal
 504 // to the scratch_cp operands bootstrap specifier passed by the old_bs_i index.
 505 // Recursively append new merge_cp entries referenced by the new bootstrap specifier.
 506 void VM_RedefineClasses::append_operand(constantPoolHandle scratch_cp, int old_bs_i,
 507        constantPoolHandle *merge_cp_p, int *merge_cp_length_p, TRAPS) {
 508 
 509   int old_ref_i = scratch_cp->operand_bootstrap_method_ref_index_at(old_bs_i);
 510   int new_ref_i = find_or_append_indirect_entry(scratch_cp, old_ref_i, merge_cp_p,
 511                                                 merge_cp_length_p, THREAD);
 512   if (new_ref_i != old_ref_i) {
 513     RC_TRACE(0x00080000,
 514              ("operands entry@%d bootstrap method ref_index change: %d to %d",
 515               _operands_cur_length, old_ref_i, new_ref_i));
 516   }
 517 
 518   Array<u2>* merge_ops = (*merge_cp_p)->operands();
 519   int new_bs_i = _operands_cur_length;
 520   // We have _operands_cur_length == 0 when the merge_cp operands is empty yet.
 521   // However, the operand_offset_at(0) was set in the extend_operands() call.
 522   int new_base = (new_bs_i == 0) ? (*merge_cp_p)->operand_offset_at(0)
 523                                  : (*merge_cp_p)->operand_next_offset_at(new_bs_i - 1);
 524   int argc     = scratch_cp->operand_argument_count_at(old_bs_i);
 525 
 526   ConstantPool::operand_offset_at_put(merge_ops, _operands_cur_length, new_base);
 527   merge_ops->at_put(new_base++, new_ref_i);
 528   merge_ops->at_put(new_base++, argc);
 529 
 530   for (int i = 0; i < argc; i++) {
 531     int old_arg_ref_i = scratch_cp->operand_argument_index_at(old_bs_i, i);
 532     int new_arg_ref_i = find_or_append_indirect_entry(scratch_cp, old_arg_ref_i, merge_cp_p,
 533                                                       merge_cp_length_p, THREAD);
 534     merge_ops->at_put(new_base++, new_arg_ref_i);
 535     if (new_arg_ref_i != old_arg_ref_i) {
 536       RC_TRACE(0x00080000,
 537                ("operands entry@%d bootstrap method argument ref_index change: %d to %d",
 538                 _operands_cur_length, old_arg_ref_i, new_arg_ref_i));
 539     }
 540   }
 541   if (old_bs_i != _operands_cur_length) {
 542     // The bootstrap specifier in *merge_cp_p is at a different index than
 543     // that in scratch_cp so we need to map the index values.
 544     map_operand_index(old_bs_i, new_bs_i);
 545   }
 546   _operands_cur_length++;
 547 } // end append_operand()
 548 
 549 
 550 int VM_RedefineClasses::find_or_append_operand(constantPoolHandle scratch_cp,
 551       int old_bs_i, constantPoolHandle *merge_cp_p, int *merge_cp_length_p, TRAPS) {
 552 
 553   int new_bs_i = old_bs_i; // bootstrap specifier index
 554   bool match = (old_bs_i < _operands_cur_length) &&
 555                scratch_cp->compare_operand_to(old_bs_i, *merge_cp_p, old_bs_i, THREAD);
 556 
 557   if (!match) {
 558     // forward reference in *merge_cp_p or not a direct match
 559     int found_i = scratch_cp->find_matching_operand(old_bs_i, *merge_cp_p,
 560                                                     _operands_cur_length, THREAD);
 561     if (found_i != -1) {
 562       guarantee(found_i != old_bs_i, "compare_operand_to() and find_matching_operand() disagree");
 563       // found a matching operand somewhere else in *merge_cp_p so just need a mapping
 564       new_bs_i = found_i;
 565       map_operand_index(old_bs_i, found_i);
 566     } else {
 567       // no match found so we have to append this bootstrap specifier to *merge_cp_p
 568       append_operand(scratch_cp, old_bs_i, merge_cp_p, merge_cp_length_p, THREAD);
 569       new_bs_i = _operands_cur_length - 1;
 570     }
 571   }
 572   return new_bs_i;
 573 } // end find_or_append_operand()
 574 
 575 
 576 void VM_RedefineClasses::finalize_operands_merge(constantPoolHandle merge_cp, TRAPS) {
 577   if (merge_cp->operands() == NULL) {
 578     return;
 579   }
 580   // Shrink the merge_cp operands
 581   merge_cp->shrink_operands(_operands_cur_length, CHECK);
 582 
 583   if (RC_TRACE_ENABLED(0x00040000)) {
 584     // don't want to loop unless we are tracing
 585     int count = 0;
 586     for (int i = 1; i < _operands_index_map_p->length(); i++) {
 587       int value = _operands_index_map_p->at(i);
 588       if (value != -1) {
 589         RC_TRACE_WITH_THREAD(0x00040000, THREAD,
 590           ("operands_index_map[%d]: old=%d new=%d", count, i, value));
 591         count++;
 592       }
 593     }
 594   }
 595   // Clean-up
 596   _operands_index_map_p = NULL;
 597   _operands_cur_length = 0;
 598   _operands_index_map_count = 0;
 599 } // end finalize_operands_merge()
 600 
 601 
 602 jvmtiError VM_RedefineClasses::compare_and_normalize_class_versions(
 603              instanceKlassHandle the_class,
 604              instanceKlassHandle scratch_class) {
 605   int i;
 606 
 607   // Check superclasses, or rather their names, since superclasses themselves can be
 608   // requested to replace.
 609   // Check for NULL superclass first since this might be java.lang.Object
 610   if (the_class->super() != scratch_class->super() &&
 611       (the_class->super() == NULL || scratch_class->super() == NULL ||
 612        the_class->super()->name() !=
 613        scratch_class->super()->name())) {
 614     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_HIERARCHY_CHANGED;
 615   }
 616 
 617   // Check if the number, names and order of directly implemented interfaces are the same.
 618   // I think in principle we should just check if the sets of names of directly implemented
 619   // interfaces are the same, i.e. the order of declaration (which, however, if changed in the
 620   // .java file, also changes in .class file) should not matter. However, comparing sets is
 621   // technically a bit more difficult, and, more importantly, I am not sure at present that the
 622   // order of interfaces does not matter on the implementation level, i.e. that the VM does not
 623   // rely on it somewhere.
 624   Array<Klass*>* k_interfaces = the_class->local_interfaces();
 625   Array<Klass*>* k_new_interfaces = scratch_class->local_interfaces();
 626   int n_intfs = k_interfaces->length();
 627   if (n_intfs != k_new_interfaces->length()) {
 628     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_HIERARCHY_CHANGED;
 629   }
 630   for (i = 0; i < n_intfs; i++) {
 631     if (k_interfaces->at(i)->name() !=
 632         k_new_interfaces->at(i)->name()) {
 633       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_HIERARCHY_CHANGED;
 634     }
 635   }
 636 
 637   // Check whether class is in the error init state.
 638   if (the_class->is_in_error_state()) {
 639     // TBD #5057930: special error code is needed in 1.6
 640     return JVMTI_ERROR_INVALID_CLASS;
 641   }
 642 
 643   // Check whether class modifiers are the same.
 644   jushort old_flags = (jushort) the_class->access_flags().get_flags();
 645   jushort new_flags = (jushort) scratch_class->access_flags().get_flags();
 646   if (old_flags != new_flags) {
 647     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_MODIFIERS_CHANGED;
 648   }
 649 
 650   // Check if the number, names, types and order of fields declared in these classes
 651   // are the same.
 652   JavaFieldStream old_fs(the_class);
 653   JavaFieldStream new_fs(scratch_class);
 654   for (; !old_fs.done() && !new_fs.done(); old_fs.next(), new_fs.next()) {
 655     // access
 656     old_flags = old_fs.access_flags().as_short();
 657     new_flags = new_fs.access_flags().as_short();
 658     if ((old_flags ^ new_flags) & JVM_RECOGNIZED_FIELD_MODIFIERS) {
 659       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_SCHEMA_CHANGED;
 660     }
 661     // offset
 662     if (old_fs.offset() != new_fs.offset()) {
 663       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_SCHEMA_CHANGED;
 664     }
 665     // name and signature
 666     Symbol* name_sym1 = the_class->constants()->symbol_at(old_fs.name_index());
 667     Symbol* sig_sym1 = the_class->constants()->symbol_at(old_fs.signature_index());
 668     Symbol* name_sym2 = scratch_class->constants()->symbol_at(new_fs.name_index());
 669     Symbol* sig_sym2 = scratch_class->constants()->symbol_at(new_fs.signature_index());
 670     if (name_sym1 != name_sym2 || sig_sym1 != sig_sym2) {
 671       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_SCHEMA_CHANGED;
 672     }
 673   }
 674 
 675   // If both streams aren't done then we have a differing number of
 676   // fields.
 677   if (!old_fs.done() || !new_fs.done()) {
 678     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_SCHEMA_CHANGED;
 679   }
 680 
 681   // Do a parallel walk through the old and new methods. Detect
 682   // cases where they match (exist in both), have been added in
 683   // the new methods, or have been deleted (exist only in the
 684   // old methods).  The class file parser places methods in order
 685   // by method name, but does not order overloaded methods by
 686   // signature.  In order to determine what fate befell the methods,
 687   // this code places the overloaded new methods that have matching
 688   // old methods in the same order as the old methods and places
 689   // new overloaded methods at the end of overloaded methods of
 690   // that name. The code for this order normalization is adapted
 691   // from the algorithm used in InstanceKlass::find_method().
 692   // Since we are swapping out of order entries as we find them,
 693   // we only have to search forward through the overloaded methods.
 694   // Methods which are added and have the same name as an existing
 695   // method (but different signature) will be put at the end of
 696   // the methods with that name, and the name mismatch code will
 697   // handle them.
 698   Array<Method*>* k_old_methods(the_class->methods());
 699   Array<Method*>* k_new_methods(scratch_class->methods());
 700   int n_old_methods = k_old_methods->length();
 701   int n_new_methods = k_new_methods->length();
 702   Thread* thread = Thread::current();
 703 
 704   int ni = 0;
 705   int oi = 0;
 706   while (true) {
 707     Method* k_old_method;
 708     Method* k_new_method;
 709     enum { matched, added, deleted, undetermined } method_was = undetermined;
 710 
 711     if (oi >= n_old_methods) {
 712       if (ni >= n_new_methods) {
 713         break; // we've looked at everything, done
 714       }
 715       // New method at the end
 716       k_new_method = k_new_methods->at(ni);
 717       method_was = added;
 718     } else if (ni >= n_new_methods) {
 719       // Old method, at the end, is deleted
 720       k_old_method = k_old_methods->at(oi);
 721       method_was = deleted;
 722     } else {
 723       // There are more methods in both the old and new lists
 724       k_old_method = k_old_methods->at(oi);
 725       k_new_method = k_new_methods->at(ni);
 726       if (k_old_method->name() != k_new_method->name()) {
 727         // Methods are sorted by method name, so a mismatch means added
 728         // or deleted
 729         if (k_old_method->name()->fast_compare(k_new_method->name()) > 0) {
 730           method_was = added;
 731         } else {
 732           method_was = deleted;
 733         }
 734       } else if (k_old_method->signature() == k_new_method->signature()) {
 735         // Both the name and signature match
 736         method_was = matched;
 737       } else {
 738         // The name matches, but the signature doesn't, which means we have to
 739         // search forward through the new overloaded methods.
 740         int nj;  // outside the loop for post-loop check
 741         for (nj = ni + 1; nj < n_new_methods; nj++) {
 742           Method* m = k_new_methods->at(nj);
 743           if (k_old_method->name() != m->name()) {
 744             // reached another method name so no more overloaded methods
 745             method_was = deleted;
 746             break;
 747           }
 748           if (k_old_method->signature() == m->signature()) {
 749             // found a match so swap the methods
 750             k_new_methods->at_put(ni, m);
 751             k_new_methods->at_put(nj, k_new_method);
 752             k_new_method = m;
 753             method_was = matched;
 754             break;
 755           }
 756         }
 757 
 758         if (nj >= n_new_methods) {
 759           // reached the end without a match; so method was deleted
 760           method_was = deleted;
 761         }
 762       }
 763     }
 764 
 765     switch (method_was) {
 766     case matched:
 767       // methods match, be sure modifiers do too
 768       old_flags = (jushort) k_old_method->access_flags().get_flags();
 769       new_flags = (jushort) k_new_method->access_flags().get_flags();
 770       if ((old_flags ^ new_flags) & ~(JVM_ACC_NATIVE)) {
 771         return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_METHOD_MODIFIERS_CHANGED;
 772       }
 773       {
 774         u2 new_num = k_new_method->method_idnum();
 775         u2 old_num = k_old_method->method_idnum();
 776         if (new_num != old_num) {
 777           Method* idnum_owner = scratch_class->method_with_idnum(old_num);
 778           if (idnum_owner != NULL) {
 779             // There is already a method assigned this idnum -- switch them
 780             idnum_owner->set_method_idnum(new_num);
 781           }
 782           k_new_method->set_method_idnum(old_num);
 783           if (thread->has_pending_exception()) {
 784             return JVMTI_ERROR_OUT_OF_MEMORY;
 785           }
 786         }
 787       }
 788       RC_TRACE(0x00008000, ("Method matched: new: %s [%d] == old: %s [%d]",
 789                             k_new_method->name_and_sig_as_C_string(), ni,
 790                             k_old_method->name_and_sig_as_C_string(), oi));
 791       // advance to next pair of methods
 792       ++oi;
 793       ++ni;
 794       break;
 795     case added:
 796       // method added, see if it is OK
 797       new_flags = (jushort) k_new_method->access_flags().get_flags();
 798       if ((new_flags & JVM_ACC_PRIVATE) == 0
 799            // hack: private should be treated as final, but alas
 800           || (new_flags & (JVM_ACC_FINAL|JVM_ACC_STATIC)) == 0
 801          ) {
 802         // new methods must be private
 803         return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_METHOD_ADDED;
 804       }
 805       {
 806         u2 num = the_class->next_method_idnum();
 807         if (num == ConstMethod::UNSET_IDNUM) {
 808           // cannot add any more methods
 809           return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_METHOD_ADDED;
 810         }
 811         u2 new_num = k_new_method->method_idnum();
 812         Method* idnum_owner = scratch_class->method_with_idnum(num);
 813         if (idnum_owner != NULL) {
 814           // There is already a method assigned this idnum -- switch them
 815           idnum_owner->set_method_idnum(new_num);
 816         }
 817         k_new_method->set_method_idnum(num);
 818         if (thread->has_pending_exception()) {
 819           return JVMTI_ERROR_OUT_OF_MEMORY;
 820         }
 821       }
 822       RC_TRACE(0x00008000, ("Method added: new: %s [%d]",
 823                             k_new_method->name_and_sig_as_C_string(), ni));
 824       ++ni; // advance to next new method
 825       break;
 826     case deleted:
 827       // method deleted, see if it is OK
 828       old_flags = (jushort) k_old_method->access_flags().get_flags();
 829       if ((old_flags & JVM_ACC_PRIVATE) == 0
 830            // hack: private should be treated as final, but alas
 831           || (old_flags & (JVM_ACC_FINAL|JVM_ACC_STATIC)) == 0
 832          ) {
 833         // deleted methods must be private
 834         return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_METHOD_DELETED;
 835       }
 836       RC_TRACE(0x00008000, ("Method deleted: old: %s [%d]",
 837                             k_old_method->name_and_sig_as_C_string(), oi));
 838       ++oi; // advance to next old method
 839       break;
 840     default:
 841       ShouldNotReachHere();
 842     }
 843   }
 844 
 845   return JVMTI_ERROR_NONE;
 846 }
 847 
 848 
 849 // Find new constant pool index value for old constant pool index value
 850 // by seaching the index map. Returns zero (0) if there is no mapped
 851 // value for the old constant pool index.
 852 int VM_RedefineClasses::find_new_index(int old_index) {
 853   if (_index_map_count == 0) {
 854     // map is empty so nothing can be found
 855     return 0;
 856   }
 857 
 858   if (old_index < 1 || old_index >= _index_map_p->length()) {
 859     // The old_index is out of range so it is not mapped. This should
 860     // not happen in regular constant pool merging use, but it can
 861     // happen if a corrupt annotation is processed.
 862     return 0;
 863   }
 864 
 865   int value = _index_map_p->at(old_index);
 866   if (value == -1) {
 867     // the old_index is not mapped
 868     return 0;
 869   }
 870 
 871   return value;
 872 } // end find_new_index()
 873 
 874 
 875 // Find new bootstrap specifier index value for old bootstrap specifier index
 876 // value by seaching the index map. Returns unused index (-1) if there is
 877 // no mapped value for the old bootstrap specifier index.
 878 int VM_RedefineClasses::find_new_operand_index(int old_index) {
 879   if (_operands_index_map_count == 0) {
 880     // map is empty so nothing can be found
 881     return -1;
 882   }
 883 
 884   if (old_index == -1 || old_index >= _operands_index_map_p->length()) {
 885     // The old_index is out of range so it is not mapped.
 886     // This should not happen in regular constant pool merging use.
 887     return -1;
 888   }
 889 
 890   int value = _operands_index_map_p->at(old_index);
 891   if (value == -1) {
 892     // the old_index is not mapped
 893     return -1;
 894   }
 895 
 896   return value;
 897 } // end find_new_operand_index()
 898 
 899 
 900 // Returns true if the current mismatch is due to a resolved/unresolved
 901 // class pair. Otherwise, returns false.
 902 bool VM_RedefineClasses::is_unresolved_class_mismatch(constantPoolHandle cp1,
 903        int index1, constantPoolHandle cp2, int index2) {
 904 
 905   jbyte t1 = cp1->tag_at(index1).value();
 906   if (t1 != JVM_CONSTANT_Class && t1 != JVM_CONSTANT_UnresolvedClass) {
 907     return false;  // wrong entry type; not our special case
 908   }
 909 
 910   jbyte t2 = cp2->tag_at(index2).value();
 911   if (t2 != JVM_CONSTANT_Class && t2 != JVM_CONSTANT_UnresolvedClass) {
 912     return false;  // wrong entry type; not our special case
 913   }
 914 
 915   if (t1 == t2) {
 916     return false;  // not a mismatch; not our special case
 917   }
 918 
 919   char *s1 = cp1->klass_name_at(index1)->as_C_string();
 920   char *s2 = cp2->klass_name_at(index2)->as_C_string();
 921   if (strcmp(s1, s2) != 0) {
 922     return false;  // strings don't match; not our special case
 923   }
 924 
 925   return true;  // made it through the gauntlet; this is our special case
 926 } // end is_unresolved_class_mismatch()
 927 
 928 
 929 jvmtiError VM_RedefineClasses::load_new_class_versions(TRAPS) {
 930 
 931   // For consistency allocate memory using os::malloc wrapper.
 932   _scratch_classes = (Klass**)
 933     os::malloc(sizeof(Klass*) * _class_count, mtClass);
 934   if (_scratch_classes == NULL) {
 935     return JVMTI_ERROR_OUT_OF_MEMORY;
 936   }
 937   // Zero initialize the _scratch_classes array.
 938   for (int i = 0; i < _class_count; i++) {
 939     _scratch_classes[i] = NULL;
 940   }
 941 
 942   ResourceMark rm(THREAD);
 943 
 944   JvmtiThreadState *state = JvmtiThreadState::state_for(JavaThread::current());
 945   // state can only be NULL if the current thread is exiting which
 946   // should not happen since we're trying to do a RedefineClasses
 947   guarantee(state != NULL, "exiting thread calling load_new_class_versions");
 948   for (int i = 0; i < _class_count; i++) {
 949     // Create HandleMark so that any handles created while loading new class
 950     // versions are deleted. Constant pools are deallocated while merging
 951     // constant pools
 952     HandleMark hm(THREAD);
 953 
 954     oop mirror = JNIHandles::resolve_non_null(_class_defs[i].klass);
 955     // classes for primitives cannot be redefined
 956     if (!is_modifiable_class(mirror)) {
 957       return JVMTI_ERROR_UNMODIFIABLE_CLASS;
 958     }
 959     Klass* the_class_oop = java_lang_Class::as_Klass(mirror);
 960     instanceKlassHandle the_class = instanceKlassHandle(THREAD, the_class_oop);
 961     Symbol*  the_class_sym = the_class->name();
 962 
 963     // RC_TRACE_WITH_THREAD macro has an embedded ResourceMark
 964     RC_TRACE_WITH_THREAD(0x00000001, THREAD,
 965       ("loading name=%s kind=%d (avail_mem=" UINT64_FORMAT "K)",
 966       the_class->external_name(), _class_load_kind,
 967       os::available_memory() >> 10));
 968 
 969     ClassFileStream st((u1*) _class_defs[i].class_bytes,
 970       _class_defs[i].class_byte_count, (char *)"__VM_RedefineClasses__");
 971 
 972     // Parse the stream.
 973     Handle the_class_loader(THREAD, the_class->class_loader());
 974     Handle protection_domain(THREAD, the_class->protection_domain());
 975     // Set redefined class handle in JvmtiThreadState class.
 976     // This redefined class is sent to agent event handler for class file
 977     // load hook event.
 978     state->set_class_being_redefined(&the_class, _class_load_kind);
 979 
 980     Klass* k = SystemDictionary::parse_stream(the_class_sym,
 981                                                 the_class_loader,
 982                                                 protection_domain,
 983                                                 &st,
 984                                                 THREAD);
 985     // Clear class_being_redefined just to be sure.
 986     state->clear_class_being_redefined();
 987 
 988     // TODO: if this is retransform, and nothing changed we can skip it
 989 
 990     instanceKlassHandle scratch_class (THREAD, k);
 991 
 992     // Need to clean up allocated InstanceKlass if there's an error so assign
 993     // the result here. Caller deallocates all the scratch classes in case of
 994     // an error.
 995     _scratch_classes[i] = k;
 996 
 997     if (HAS_PENDING_EXCEPTION) {
 998       Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
 999       // RC_TRACE_WITH_THREAD macro has an embedded ResourceMark
1000       RC_TRACE_WITH_THREAD(0x00000002, THREAD, ("parse_stream exception: '%s'",
1001         ex_name->as_C_string()));
1002       CLEAR_PENDING_EXCEPTION;
1003 
1004       if (ex_name == vmSymbols::java_lang_UnsupportedClassVersionError()) {
1005         return JVMTI_ERROR_UNSUPPORTED_VERSION;
1006       } else if (ex_name == vmSymbols::java_lang_ClassFormatError()) {
1007         return JVMTI_ERROR_INVALID_CLASS_FORMAT;
1008       } else if (ex_name == vmSymbols::java_lang_ClassCircularityError()) {
1009         return JVMTI_ERROR_CIRCULAR_CLASS_DEFINITION;
1010       } else if (ex_name == vmSymbols::java_lang_NoClassDefFoundError()) {
1011         // The message will be "XXX (wrong name: YYY)"
1012         return JVMTI_ERROR_NAMES_DONT_MATCH;
1013       } else if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1014         return JVMTI_ERROR_OUT_OF_MEMORY;
1015       } else {  // Just in case more exceptions can be thrown..
1016         return JVMTI_ERROR_FAILS_VERIFICATION;
1017       }
1018     }
1019 
1020     // Ensure class is linked before redefine
1021     if (!the_class->is_linked()) {
1022       the_class->link_class(THREAD);
1023       if (HAS_PENDING_EXCEPTION) {
1024         Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1025         // RC_TRACE_WITH_THREAD macro has an embedded ResourceMark
1026         RC_TRACE_WITH_THREAD(0x00000002, THREAD, ("link_class exception: '%s'",
1027           ex_name->as_C_string()));
1028         CLEAR_PENDING_EXCEPTION;
1029         if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1030           return JVMTI_ERROR_OUT_OF_MEMORY;
1031         } else {
1032           return JVMTI_ERROR_INTERNAL;
1033         }
1034       }
1035     }
1036 
1037     // Do the validity checks in compare_and_normalize_class_versions()
1038     // before verifying the byte codes. By doing these checks first, we
1039     // limit the number of functions that require redirection from
1040     // the_class to scratch_class. In particular, we don't have to
1041     // modify JNI GetSuperclass() and thus won't change its performance.
1042     jvmtiError res = compare_and_normalize_class_versions(the_class,
1043                        scratch_class);
1044     if (res != JVMTI_ERROR_NONE) {
1045       return res;
1046     }
1047 
1048     // verify what the caller passed us
1049     {
1050       // The bug 6214132 caused the verification to fail.
1051       // Information about the_class and scratch_class is temporarily
1052       // recorded into jvmtiThreadState. This data is used to redirect
1053       // the_class to scratch_class in the JVM_* functions called by the
1054       // verifier. Please, refer to jvmtiThreadState.hpp for the detailed
1055       // description.
1056       RedefineVerifyMark rvm(&the_class, &scratch_class, state);
1057       Verifier::verify(
1058         scratch_class, Verifier::ThrowException, true, THREAD);
1059     }
1060 
1061     if (HAS_PENDING_EXCEPTION) {
1062       Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1063       // RC_TRACE_WITH_THREAD macro has an embedded ResourceMark
1064       RC_TRACE_WITH_THREAD(0x00000002, THREAD,
1065         ("verify_byte_codes exception: '%s'", ex_name->as_C_string()));
1066       CLEAR_PENDING_EXCEPTION;
1067       if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1068         return JVMTI_ERROR_OUT_OF_MEMORY;
1069       } else {
1070         // tell the caller the bytecodes are bad
1071         return JVMTI_ERROR_FAILS_VERIFICATION;
1072       }
1073     }
1074 
1075     res = merge_cp_and_rewrite(the_class, scratch_class, THREAD);
1076     if (HAS_PENDING_EXCEPTION) {
1077       Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1078       // RC_TRACE_WITH_THREAD macro has an embedded ResourceMark
1079       RC_TRACE_WITH_THREAD(0x00000002, THREAD,
1080         ("merge_cp_and_rewrite exception: '%s'", ex_name->as_C_string()));
1081       CLEAR_PENDING_EXCEPTION;
1082       if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1083         return JVMTI_ERROR_OUT_OF_MEMORY;
1084       } else {
1085         return JVMTI_ERROR_INTERNAL;
1086       }
1087     }
1088 
1089     if (VerifyMergedCPBytecodes) {
1090       // verify what we have done during constant pool merging
1091       {
1092         RedefineVerifyMark rvm(&the_class, &scratch_class, state);
1093         Verifier::verify(scratch_class, Verifier::ThrowException, true, THREAD);
1094       }
1095 
1096       if (HAS_PENDING_EXCEPTION) {
1097         Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1098         // RC_TRACE_WITH_THREAD macro has an embedded ResourceMark
1099         RC_TRACE_WITH_THREAD(0x00000002, THREAD,
1100           ("verify_byte_codes post merge-CP exception: '%s'",
1101           ex_name->as_C_string()));
1102         CLEAR_PENDING_EXCEPTION;
1103         if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1104           return JVMTI_ERROR_OUT_OF_MEMORY;
1105         } else {
1106           // tell the caller that constant pool merging screwed up
1107           return JVMTI_ERROR_INTERNAL;
1108         }
1109       }
1110     }
1111 
1112     Rewriter::rewrite(scratch_class, THREAD);
1113     if (!HAS_PENDING_EXCEPTION) {
1114       scratch_class->link_methods(THREAD);
1115     }
1116     if (HAS_PENDING_EXCEPTION) {
1117       Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1118       // RC_TRACE_WITH_THREAD macro has an embedded ResourceMark
1119       RC_TRACE_WITH_THREAD(0x00000002, THREAD,
1120         ("Rewriter::rewrite or link_methods exception: '%s'", ex_name->as_C_string()));
1121       CLEAR_PENDING_EXCEPTION;
1122       if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1123         return JVMTI_ERROR_OUT_OF_MEMORY;
1124       } else {
1125         return JVMTI_ERROR_INTERNAL;
1126       }
1127     }
1128 
1129     // RC_TRACE_WITH_THREAD macro has an embedded ResourceMark
1130     RC_TRACE_WITH_THREAD(0x00000001, THREAD,
1131       ("loaded name=%s (avail_mem=" UINT64_FORMAT "K)",
1132       the_class->external_name(), os::available_memory() >> 10));
1133   }
1134 
1135   return JVMTI_ERROR_NONE;
1136 }
1137 
1138 
1139 // Map old_index to new_index as needed. scratch_cp is only needed
1140 // for RC_TRACE() calls.
1141 void VM_RedefineClasses::map_index(constantPoolHandle scratch_cp,
1142        int old_index, int new_index) {
1143   if (find_new_index(old_index) != 0) {
1144     // old_index is already mapped
1145     return;
1146   }
1147 
1148   if (old_index == new_index) {
1149     // no mapping is needed
1150     return;
1151   }
1152 
1153   _index_map_p->at_put(old_index, new_index);
1154   _index_map_count++;
1155 
1156   RC_TRACE(0x00040000, ("mapped tag %d at index %d to %d",
1157     scratch_cp->tag_at(old_index).value(), old_index, new_index));
1158 } // end map_index()
1159 
1160 
1161 // Map old_index to new_index as needed.
1162 void VM_RedefineClasses::map_operand_index(int old_index, int new_index) {
1163   if (find_new_operand_index(old_index) != -1) {
1164     // old_index is already mapped
1165     return;
1166   }
1167 
1168   if (old_index == new_index) {
1169     // no mapping is needed
1170     return;
1171   }
1172 
1173   _operands_index_map_p->at_put(old_index, new_index);
1174   _operands_index_map_count++;
1175 
1176   RC_TRACE(0x00040000, ("mapped bootstrap specifier at index %d to %d", old_index, new_index));
1177 } // end map_index()
1178 
1179 
1180 // Merge old_cp and scratch_cp and return the results of the merge via
1181 // merge_cp_p. The number of entries in *merge_cp_p is returned via
1182 // merge_cp_length_p. The entries in old_cp occupy the same locations
1183 // in *merge_cp_p. Also creates a map of indices from entries in
1184 // scratch_cp to the corresponding entry in *merge_cp_p. Index map
1185 // entries are only created for entries in scratch_cp that occupy a
1186 // different location in *merged_cp_p.
1187 bool VM_RedefineClasses::merge_constant_pools(constantPoolHandle old_cp,
1188        constantPoolHandle scratch_cp, constantPoolHandle *merge_cp_p,
1189        int *merge_cp_length_p, TRAPS) {
1190 
1191   if (merge_cp_p == NULL) {
1192     assert(false, "caller must provide scratch constantPool");
1193     return false; // robustness
1194   }
1195   if (merge_cp_length_p == NULL) {
1196     assert(false, "caller must provide scratch CP length");
1197     return false; // robustness
1198   }
1199   // Worst case we need old_cp->length() + scratch_cp()->length(),
1200   // but the caller might be smart so make sure we have at least
1201   // the minimum.
1202   if ((*merge_cp_p)->length() < old_cp->length()) {
1203     assert(false, "merge area too small");
1204     return false; // robustness
1205   }
1206 
1207   RC_TRACE_WITH_THREAD(0x00010000, THREAD,
1208     ("old_cp_len=%d, scratch_cp_len=%d", old_cp->length(),
1209     scratch_cp->length()));
1210 
1211   {
1212     // Pass 0:
1213     // The old_cp is copied to *merge_cp_p; this means that any code
1214     // using old_cp does not have to change. This work looks like a
1215     // perfect fit for ConstantPool*::copy_cp_to(), but we need to
1216     // handle one special case:
1217     // - revert JVM_CONSTANT_Class to JVM_CONSTANT_UnresolvedClass
1218     // This will make verification happy.
1219 
1220     int old_i;  // index into old_cp
1221 
1222     // index zero (0) is not used in constantPools
1223     for (old_i = 1; old_i < old_cp->length(); old_i++) {
1224       // leave debugging crumb
1225       jbyte old_tag = old_cp->tag_at(old_i).value();
1226       switch (old_tag) {
1227       case JVM_CONSTANT_Class:
1228       case JVM_CONSTANT_UnresolvedClass:
1229         // revert the copy to JVM_CONSTANT_UnresolvedClass
1230         // May be resolving while calling this so do the same for
1231         // JVM_CONSTANT_UnresolvedClass (klass_name_at() deals with transition)
1232         (*merge_cp_p)->unresolved_klass_at_put(old_i,
1233           old_cp->klass_name_at(old_i));
1234         break;
1235 
1236       case JVM_CONSTANT_Double:
1237       case JVM_CONSTANT_Long:
1238         // just copy the entry to *merge_cp_p, but double and long take
1239         // two constant pool entries
1240         ConstantPool::copy_entry_to(old_cp, old_i, *merge_cp_p, old_i, CHECK_0);
1241         old_i++;
1242         break;
1243 
1244       default:
1245         // just copy the entry to *merge_cp_p
1246         ConstantPool::copy_entry_to(old_cp, old_i, *merge_cp_p, old_i, CHECK_0);
1247         break;
1248       }
1249     } // end for each old_cp entry
1250 
1251     ConstantPool::copy_operands(old_cp, *merge_cp_p, CHECK_0);
1252     (*merge_cp_p)->extend_operands(scratch_cp, CHECK_0);
1253 
1254     // We don't need to sanity check that *merge_cp_length_p is within
1255     // *merge_cp_p bounds since we have the minimum on-entry check above.
1256     (*merge_cp_length_p) = old_i;
1257   }
1258 
1259   // merge_cp_len should be the same as old_cp->length() at this point
1260   // so this trace message is really a "warm-and-breathing" message.
1261   RC_TRACE_WITH_THREAD(0x00020000, THREAD,
1262     ("after pass 0: merge_cp_len=%d", *merge_cp_length_p));
1263 
1264   int scratch_i;  // index into scratch_cp
1265   {
1266     // Pass 1a:
1267     // Compare scratch_cp entries to the old_cp entries that we have
1268     // already copied to *merge_cp_p. In this pass, we are eliminating
1269     // exact duplicates (matching entry at same index) so we only
1270     // compare entries in the common indice range.
1271     int increment = 1;
1272     int pass1a_length = MIN2(old_cp->length(), scratch_cp->length());
1273     for (scratch_i = 1; scratch_i < pass1a_length; scratch_i += increment) {
1274       switch (scratch_cp->tag_at(scratch_i).value()) {
1275       case JVM_CONSTANT_Double:
1276       case JVM_CONSTANT_Long:
1277         // double and long take two constant pool entries
1278         increment = 2;
1279         break;
1280 
1281       default:
1282         increment = 1;
1283         break;
1284       }
1285 
1286       bool match = scratch_cp->compare_entry_to(scratch_i, *merge_cp_p,
1287         scratch_i, CHECK_0);
1288       if (match) {
1289         // found a match at the same index so nothing more to do
1290         continue;
1291       } else if (is_unresolved_class_mismatch(scratch_cp, scratch_i,
1292                                               *merge_cp_p, scratch_i)) {
1293         // The mismatch in compare_entry_to() above is because of a
1294         // resolved versus unresolved class entry at the same index
1295         // with the same string value. Since Pass 0 reverted any
1296         // class entries to unresolved class entries in *merge_cp_p,
1297         // we go with the unresolved class entry.
1298         continue;
1299       }
1300 
1301       int found_i = scratch_cp->find_matching_entry(scratch_i, *merge_cp_p,
1302         CHECK_0);
1303       if (found_i != 0) {
1304         guarantee(found_i != scratch_i,
1305           "compare_entry_to() and find_matching_entry() do not agree");
1306 
1307         // Found a matching entry somewhere else in *merge_cp_p so
1308         // just need a mapping entry.
1309         map_index(scratch_cp, scratch_i, found_i);
1310         continue;
1311       }
1312 
1313       // The find_matching_entry() call above could fail to find a match
1314       // due to a resolved versus unresolved class or string entry situation
1315       // like we solved above with the is_unresolved_*_mismatch() calls.
1316       // However, we would have to call is_unresolved_*_mismatch() over
1317       // all of *merge_cp_p (potentially) and that doesn't seem to be
1318       // worth the time.
1319 
1320       // No match found so we have to append this entry and any unique
1321       // referenced entries to *merge_cp_p.
1322       append_entry(scratch_cp, scratch_i, merge_cp_p, merge_cp_length_p,
1323         CHECK_0);
1324     }
1325   }
1326 
1327   RC_TRACE_WITH_THREAD(0x00020000, THREAD,
1328     ("after pass 1a: merge_cp_len=%d, scratch_i=%d, index_map_len=%d",
1329     *merge_cp_length_p, scratch_i, _index_map_count));
1330 
1331   if (scratch_i < scratch_cp->length()) {
1332     // Pass 1b:
1333     // old_cp is smaller than scratch_cp so there are entries in
1334     // scratch_cp that we have not yet processed. We take care of
1335     // those now.
1336     int increment = 1;
1337     for (; scratch_i < scratch_cp->length(); scratch_i += increment) {
1338       switch (scratch_cp->tag_at(scratch_i).value()) {
1339       case JVM_CONSTANT_Double:
1340       case JVM_CONSTANT_Long:
1341         // double and long take two constant pool entries
1342         increment = 2;
1343         break;
1344 
1345       default:
1346         increment = 1;
1347         break;
1348       }
1349 
1350       int found_i =
1351         scratch_cp->find_matching_entry(scratch_i, *merge_cp_p, CHECK_0);
1352       if (found_i != 0) {
1353         // Found a matching entry somewhere else in *merge_cp_p so
1354         // just need a mapping entry.
1355         map_index(scratch_cp, scratch_i, found_i);
1356         continue;
1357       }
1358 
1359       // No match found so we have to append this entry and any unique
1360       // referenced entries to *merge_cp_p.
1361       append_entry(scratch_cp, scratch_i, merge_cp_p, merge_cp_length_p,
1362         CHECK_0);
1363     }
1364 
1365     RC_TRACE_WITH_THREAD(0x00020000, THREAD,
1366       ("after pass 1b: merge_cp_len=%d, scratch_i=%d, index_map_len=%d",
1367       *merge_cp_length_p, scratch_i, _index_map_count));
1368   }
1369   finalize_operands_merge(*merge_cp_p, THREAD);
1370 
1371   return true;
1372 } // end merge_constant_pools()
1373 
1374 
1375 // Scoped object to clean up the constant pool(s) created for merging
1376 class MergeCPCleaner {
1377   ClassLoaderData*   _loader_data;
1378   ConstantPool*      _cp;
1379   ConstantPool*      _scratch_cp;
1380  public:
1381   MergeCPCleaner(ClassLoaderData* loader_data, ConstantPool* merge_cp) :
1382                  _loader_data(loader_data), _cp(merge_cp), _scratch_cp(NULL) {}
1383   ~MergeCPCleaner() {
1384     _loader_data->add_to_deallocate_list(_cp);
1385     if (_scratch_cp != NULL) {
1386       _loader_data->add_to_deallocate_list(_scratch_cp);
1387     }
1388   }
1389   void add_scratch_cp(ConstantPool* scratch_cp) { _scratch_cp = scratch_cp; }
1390 };
1391 
1392 // Merge constant pools between the_class and scratch_class and
1393 // potentially rewrite bytecodes in scratch_class to use the merged
1394 // constant pool.
1395 jvmtiError VM_RedefineClasses::merge_cp_and_rewrite(
1396              instanceKlassHandle the_class, instanceKlassHandle scratch_class,
1397              TRAPS) {
1398   // worst case merged constant pool length is old and new combined
1399   int merge_cp_length = the_class->constants()->length()
1400         + scratch_class->constants()->length();
1401 
1402   // Constant pools are not easily reused so we allocate a new one
1403   // each time.
1404   // merge_cp is created unsafe for concurrent GC processing.  It
1405   // should be marked safe before discarding it. Even though
1406   // garbage,  if it crosses a card boundary, it may be scanned
1407   // in order to find the start of the first complete object on the card.
1408   ClassLoaderData* loader_data = the_class->class_loader_data();
1409   ConstantPool* merge_cp_oop =
1410     ConstantPool::allocate(loader_data,
1411                            merge_cp_length,
1412                            CHECK_(JVMTI_ERROR_OUT_OF_MEMORY));
1413   MergeCPCleaner cp_cleaner(loader_data, merge_cp_oop);
1414 
1415   HandleMark hm(THREAD);  // make sure handles are cleared before
1416                           // MergeCPCleaner clears out merge_cp_oop
1417   constantPoolHandle merge_cp(THREAD, merge_cp_oop);
1418 
1419   // Get constants() from the old class because it could have been rewritten
1420   // while we were at a safepoint allocating a new constant pool.
1421   constantPoolHandle old_cp(THREAD, the_class->constants());
1422   constantPoolHandle scratch_cp(THREAD, scratch_class->constants());
1423 
1424   // If the length changed, the class was redefined out from under us. Return
1425   // an error.
1426   if (merge_cp_length != the_class->constants()->length()
1427          + scratch_class->constants()->length()) {
1428     return JVMTI_ERROR_INTERNAL;
1429   }
1430 
1431   // Update the version number of the constant pool
1432   merge_cp->increment_and_save_version(old_cp->version());
1433 
1434   ResourceMark rm(THREAD);
1435   _index_map_count = 0;
1436   _index_map_p = new intArray(scratch_cp->length(), -1);
1437 
1438   _operands_cur_length = ConstantPool::operand_array_length(old_cp->operands());
1439   _operands_index_map_count = 0;
1440   _operands_index_map_p = new intArray(
1441     ConstantPool::operand_array_length(scratch_cp->operands()), -1);
1442 
1443   // reference to the cp holder is needed for copy_operands()
1444   merge_cp->set_pool_holder(scratch_class());
1445   bool result = merge_constant_pools(old_cp, scratch_cp, &merge_cp,
1446                   &merge_cp_length, THREAD);
1447   merge_cp->set_pool_holder(NULL);
1448 
1449   if (!result) {
1450     // The merge can fail due to memory allocation failure or due
1451     // to robustness checks.
1452     return JVMTI_ERROR_INTERNAL;
1453   }
1454 
1455   RC_TRACE_WITH_THREAD(0x00010000, THREAD,
1456     ("merge_cp_len=%d, index_map_len=%d", merge_cp_length, _index_map_count));
1457 
1458   if (_index_map_count == 0) {
1459     // there is nothing to map between the new and merged constant pools
1460 
1461     if (old_cp->length() == scratch_cp->length()) {
1462       // The old and new constant pools are the same length and the
1463       // index map is empty. This means that the three constant pools
1464       // are equivalent (but not the same). Unfortunately, the new
1465       // constant pool has not gone through link resolution nor have
1466       // the new class bytecodes gone through constant pool cache
1467       // rewriting so we can't use the old constant pool with the new
1468       // class.
1469 
1470       // toss the merged constant pool at return
1471     } else if (old_cp->length() < scratch_cp->length()) {
1472       // The old constant pool has fewer entries than the new constant
1473       // pool and the index map is empty. This means the new constant
1474       // pool is a superset of the old constant pool. However, the old
1475       // class bytecodes have already gone through constant pool cache
1476       // rewriting so we can't use the new constant pool with the old
1477       // class.
1478 
1479       // toss the merged constant pool at return
1480     } else {
1481       // The old constant pool has more entries than the new constant
1482       // pool and the index map is empty. This means that both the old
1483       // and merged constant pools are supersets of the new constant
1484       // pool.
1485 
1486       // Replace the new constant pool with a shrunken copy of the
1487       // merged constant pool
1488       set_new_constant_pool(loader_data, scratch_class, merge_cp, merge_cp_length,
1489                             CHECK_(JVMTI_ERROR_OUT_OF_MEMORY));
1490       // The new constant pool replaces scratch_cp so have cleaner clean it up.
1491       // It can't be cleaned up while there are handles to it.
1492       cp_cleaner.add_scratch_cp(scratch_cp());
1493     }
1494   } else {
1495     if (RC_TRACE_ENABLED(0x00040000)) {
1496       // don't want to loop unless we are tracing
1497       int count = 0;
1498       for (int i = 1; i < _index_map_p->length(); i++) {
1499         int value = _index_map_p->at(i);
1500 
1501         if (value != -1) {
1502           RC_TRACE_WITH_THREAD(0x00040000, THREAD,
1503             ("index_map[%d]: old=%d new=%d", count, i, value));
1504           count++;
1505         }
1506       }
1507     }
1508 
1509     // We have entries mapped between the new and merged constant pools
1510     // so we have to rewrite some constant pool references.
1511     if (!rewrite_cp_refs(scratch_class, THREAD)) {
1512       return JVMTI_ERROR_INTERNAL;
1513     }
1514 
1515     // Replace the new constant pool with a shrunken copy of the
1516     // merged constant pool so now the rewritten bytecodes have
1517     // valid references; the previous new constant pool will get
1518     // GCed.
1519     set_new_constant_pool(loader_data, scratch_class, merge_cp, merge_cp_length,
1520                           CHECK_(JVMTI_ERROR_OUT_OF_MEMORY));
1521     // The new constant pool replaces scratch_cp so have cleaner clean it up.
1522     // It can't be cleaned up while there are handles to it.
1523     cp_cleaner.add_scratch_cp(scratch_cp());
1524   }
1525 
1526   return JVMTI_ERROR_NONE;
1527 } // end merge_cp_and_rewrite()
1528 
1529 
1530 // Rewrite constant pool references in klass scratch_class.
1531 bool VM_RedefineClasses::rewrite_cp_refs(instanceKlassHandle scratch_class,
1532        TRAPS) {
1533 
1534   // rewrite constant pool references in the methods:
1535   if (!rewrite_cp_refs_in_methods(scratch_class, THREAD)) {
1536     // propagate failure back to caller
1537     return false;
1538   }
1539 
1540   // rewrite constant pool references in the class_annotations:
1541   if (!rewrite_cp_refs_in_class_annotations(scratch_class, THREAD)) {
1542     // propagate failure back to caller
1543     return false;
1544   }
1545 
1546   // rewrite constant pool references in the fields_annotations:
1547   if (!rewrite_cp_refs_in_fields_annotations(scratch_class, THREAD)) {
1548     // propagate failure back to caller
1549     return false;
1550   }
1551 
1552   // rewrite constant pool references in the methods_annotations:
1553   if (!rewrite_cp_refs_in_methods_annotations(scratch_class, THREAD)) {
1554     // propagate failure back to caller
1555     return false;
1556   }
1557 
1558   // rewrite constant pool references in the methods_parameter_annotations:
1559   if (!rewrite_cp_refs_in_methods_parameter_annotations(scratch_class,
1560          THREAD)) {
1561     // propagate failure back to caller
1562     return false;
1563   }
1564 
1565   // rewrite constant pool references in the methods_default_annotations:
1566   if (!rewrite_cp_refs_in_methods_default_annotations(scratch_class,
1567          THREAD)) {
1568     // propagate failure back to caller
1569     return false;
1570   }
1571 
1572   // rewrite source file name index:
1573   u2 source_file_name_idx = scratch_class->source_file_name_index();
1574   if (source_file_name_idx != 0) {
1575     u2 new_source_file_name_idx = find_new_index(source_file_name_idx);
1576     if (new_source_file_name_idx != 0) {
1577       scratch_class->set_source_file_name_index(new_source_file_name_idx);
1578     }
1579   }
1580 
1581   // rewrite class generic signature index:
1582   u2 generic_signature_index = scratch_class->generic_signature_index();
1583   if (generic_signature_index != 0) {
1584     u2 new_generic_signature_index = find_new_index(generic_signature_index);
1585     if (new_generic_signature_index != 0) {
1586       scratch_class->set_generic_signature_index(new_generic_signature_index);
1587     }
1588   }
1589 
1590   return true;
1591 } // end rewrite_cp_refs()
1592 
1593 // Rewrite constant pool references in the methods.
1594 bool VM_RedefineClasses::rewrite_cp_refs_in_methods(
1595        instanceKlassHandle scratch_class, TRAPS) {
1596 
1597   Array<Method*>* methods = scratch_class->methods();
1598 
1599   if (methods == NULL || methods->length() == 0) {
1600     // no methods so nothing to do
1601     return true;
1602   }
1603 
1604   // rewrite constant pool references in the methods:
1605   for (int i = methods->length() - 1; i >= 0; i--) {
1606     methodHandle method(THREAD, methods->at(i));
1607     methodHandle new_method;
1608     rewrite_cp_refs_in_method(method, &new_method, THREAD);
1609     if (!new_method.is_null()) {
1610       // the method has been replaced so save the new method version
1611       // even in the case of an exception.  original method is on the
1612       // deallocation list.
1613       methods->at_put(i, new_method());
1614     }
1615     if (HAS_PENDING_EXCEPTION) {
1616       Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1617       // RC_TRACE_WITH_THREAD macro has an embedded ResourceMark
1618       RC_TRACE_WITH_THREAD(0x00000002, THREAD,
1619         ("rewrite_cp_refs_in_method exception: '%s'", ex_name->as_C_string()));
1620       // Need to clear pending exception here as the super caller sets
1621       // the JVMTI_ERROR_INTERNAL if the returned value is false.
1622       CLEAR_PENDING_EXCEPTION;
1623       return false;
1624     }
1625   }
1626 
1627   return true;
1628 }
1629 
1630 
1631 // Rewrite constant pool references in the specific method. This code
1632 // was adapted from Rewriter::rewrite_method().
1633 void VM_RedefineClasses::rewrite_cp_refs_in_method(methodHandle method,
1634        methodHandle *new_method_p, TRAPS) {
1635 
1636   *new_method_p = methodHandle();  // default is no new method
1637 
1638   // We cache a pointer to the bytecodes here in code_base. If GC
1639   // moves the Method*, then the bytecodes will also move which
1640   // will likely cause a crash. We create a No_Safepoint_Verifier
1641   // object to detect whether we pass a possible safepoint in this
1642   // code block.
1643   No_Safepoint_Verifier nsv;
1644 
1645   // Bytecodes and their length
1646   address code_base = method->code_base();
1647   int code_length = method->code_size();
1648 
1649   int bc_length;
1650   for (int bci = 0; bci < code_length; bci += bc_length) {
1651     address bcp = code_base + bci;
1652     Bytecodes::Code c = (Bytecodes::Code)(*bcp);
1653 
1654     bc_length = Bytecodes::length_for(c);
1655     if (bc_length == 0) {
1656       // More complicated bytecodes report a length of zero so
1657       // we have to try again a slightly different way.
1658       bc_length = Bytecodes::length_at(method(), bcp);
1659     }
1660 
1661     assert(bc_length != 0, "impossible bytecode length");
1662 
1663     switch (c) {
1664       case Bytecodes::_ldc:
1665       {
1666         int cp_index = *(bcp + 1);
1667         int new_index = find_new_index(cp_index);
1668 
1669         if (StressLdcRewrite && new_index == 0) {
1670           // If we are stressing ldc -> ldc_w rewriting, then we
1671           // always need a new_index value.
1672           new_index = cp_index;
1673         }
1674         if (new_index != 0) {
1675           // the original index is mapped so we have more work to do
1676           if (!StressLdcRewrite && new_index <= max_jubyte) {
1677             // The new value can still use ldc instead of ldc_w
1678             // unless we are trying to stress ldc -> ldc_w rewriting
1679             RC_TRACE_WITH_THREAD(0x00080000, THREAD,
1680               ("%s@" INTPTR_FORMAT " old=%d, new=%d", Bytecodes::name(c),
1681               bcp, cp_index, new_index));
1682             *(bcp + 1) = new_index;
1683           } else {
1684             RC_TRACE_WITH_THREAD(0x00080000, THREAD,
1685               ("%s->ldc_w@" INTPTR_FORMAT " old=%d, new=%d",
1686               Bytecodes::name(c), bcp, cp_index, new_index));
1687             // the new value needs ldc_w instead of ldc
1688             u_char inst_buffer[4]; // max instruction size is 4 bytes
1689             bcp = (address)inst_buffer;
1690             // construct new instruction sequence
1691             *bcp = Bytecodes::_ldc_w;
1692             bcp++;
1693             // Rewriter::rewrite_method() does not rewrite ldc -> ldc_w.
1694             // See comment below for difference between put_Java_u2()
1695             // and put_native_u2().
1696             Bytes::put_Java_u2(bcp, new_index);
1697 
1698             Relocator rc(method, NULL /* no RelocatorListener needed */);
1699             methodHandle m;
1700             {
1701               Pause_No_Safepoint_Verifier pnsv(&nsv);
1702 
1703               // ldc is 2 bytes and ldc_w is 3 bytes
1704               m = rc.insert_space_at(bci, 3, inst_buffer, CHECK);
1705             }
1706 
1707             // return the new method so that the caller can update
1708             // the containing class
1709             *new_method_p = method = m;
1710             // switch our bytecode processing loop from the old method
1711             // to the new method
1712             code_base = method->code_base();
1713             code_length = method->code_size();
1714             bcp = code_base + bci;
1715             c = (Bytecodes::Code)(*bcp);
1716             bc_length = Bytecodes::length_for(c);
1717             assert(bc_length != 0, "sanity check");
1718           } // end we need ldc_w instead of ldc
1719         } // end if there is a mapped index
1720       } break;
1721 
1722       // these bytecodes have a two-byte constant pool index
1723       case Bytecodes::_anewarray      : // fall through
1724       case Bytecodes::_checkcast      : // fall through
1725       case Bytecodes::_getfield       : // fall through
1726       case Bytecodes::_getstatic      : // fall through
1727       case Bytecodes::_instanceof     : // fall through
1728       case Bytecodes::_invokedynamic  : // fall through
1729       case Bytecodes::_invokeinterface: // fall through
1730       case Bytecodes::_invokespecial  : // fall through
1731       case Bytecodes::_invokestatic   : // fall through
1732       case Bytecodes::_invokevirtual  : // fall through
1733       case Bytecodes::_ldc_w          : // fall through
1734       case Bytecodes::_ldc2_w         : // fall through
1735       case Bytecodes::_multianewarray : // fall through
1736       case Bytecodes::_new            : // fall through
1737       case Bytecodes::_putfield       : // fall through
1738       case Bytecodes::_putstatic      :
1739       {
1740         address p = bcp + 1;
1741         int cp_index = Bytes::get_Java_u2(p);
1742         int new_index = find_new_index(cp_index);
1743         if (new_index != 0) {
1744           // the original index is mapped so update w/ new value
1745           RC_TRACE_WITH_THREAD(0x00080000, THREAD,
1746             ("%s@" INTPTR_FORMAT " old=%d, new=%d", Bytecodes::name(c),
1747             bcp, cp_index, new_index));
1748           // Rewriter::rewrite_method() uses put_native_u2() in this
1749           // situation because it is reusing the constant pool index
1750           // location for a native index into the ConstantPoolCache.
1751           // Since we are updating the constant pool index prior to
1752           // verification and ConstantPoolCache initialization, we
1753           // need to keep the new index in Java byte order.
1754           Bytes::put_Java_u2(p, new_index);
1755         }
1756       } break;
1757     }
1758   } // end for each bytecode
1759 
1760   // We also need to rewrite the parameter name indexes, if there is
1761   // method parameter data present
1762   if(method->has_method_parameters()) {
1763     const int len = method->method_parameters_length();
1764     MethodParametersElement* elem = method->method_parameters_start();
1765 
1766     for (int i = 0; i < len; i++) {
1767       const u2 cp_index = elem[i].name_cp_index;
1768       const u2 new_cp_index = find_new_index(cp_index);
1769       if (new_cp_index != 0) {
1770         elem[i].name_cp_index = new_cp_index;
1771       }
1772     }
1773   }
1774 } // end rewrite_cp_refs_in_method()
1775 
1776 
1777 // Rewrite constant pool references in the class_annotations field.
1778 bool VM_RedefineClasses::rewrite_cp_refs_in_class_annotations(
1779        instanceKlassHandle scratch_class, TRAPS) {
1780 
1781   AnnotationArray* class_annotations = scratch_class->class_annotations();
1782   if (class_annotations == NULL || class_annotations->length() == 0) {
1783     // no class_annotations so nothing to do
1784     return true;
1785   }
1786 
1787   RC_TRACE_WITH_THREAD(0x02000000, THREAD,
1788     ("class_annotations length=%d", class_annotations->length()));
1789 
1790   int byte_i = 0;  // byte index into class_annotations
1791   return rewrite_cp_refs_in_annotations_typeArray(class_annotations, byte_i,
1792            THREAD);
1793 }
1794 
1795 
1796 // Rewrite constant pool references in an annotations typeArray. This
1797 // "structure" is adapted from the RuntimeVisibleAnnotations_attribute
1798 // that is described in section 4.8.15 of the 2nd-edition of the VM spec:
1799 //
1800 // annotations_typeArray {
1801 //   u2 num_annotations;
1802 //   annotation annotations[num_annotations];
1803 // }
1804 //
1805 bool VM_RedefineClasses::rewrite_cp_refs_in_annotations_typeArray(
1806        AnnotationArray* annotations_typeArray, int &byte_i_ref, TRAPS) {
1807 
1808   if ((byte_i_ref + 2) > annotations_typeArray->length()) {
1809     // not enough room for num_annotations field
1810     RC_TRACE_WITH_THREAD(0x02000000, THREAD,
1811       ("length() is too small for num_annotations field"));
1812     return false;
1813   }
1814 
1815   u2 num_annotations = Bytes::get_Java_u2((address)
1816                          annotations_typeArray->adr_at(byte_i_ref));
1817   byte_i_ref += 2;
1818 
1819   RC_TRACE_WITH_THREAD(0x02000000, THREAD,
1820     ("num_annotations=%d", num_annotations));
1821 
1822   int calc_num_annotations = 0;
1823   for (; calc_num_annotations < num_annotations; calc_num_annotations++) {
1824     if (!rewrite_cp_refs_in_annotation_struct(annotations_typeArray,
1825            byte_i_ref, THREAD)) {
1826       RC_TRACE_WITH_THREAD(0x02000000, THREAD,
1827         ("bad annotation_struct at %d", calc_num_annotations));
1828       // propagate failure back to caller
1829       return false;
1830     }
1831   }
1832   assert(num_annotations == calc_num_annotations, "sanity check");
1833 
1834   return true;
1835 } // end rewrite_cp_refs_in_annotations_typeArray()
1836 
1837 
1838 // Rewrite constant pool references in the annotation struct portion of
1839 // an annotations_typeArray. This "structure" is from section 4.8.15 of
1840 // the 2nd-edition of the VM spec:
1841 //
1842 // struct annotation {
1843 //   u2 type_index;
1844 //   u2 num_element_value_pairs;
1845 //   {
1846 //     u2 element_name_index;
1847 //     element_value value;
1848 //   } element_value_pairs[num_element_value_pairs];
1849 // }
1850 //
1851 bool VM_RedefineClasses::rewrite_cp_refs_in_annotation_struct(
1852        AnnotationArray* annotations_typeArray, int &byte_i_ref, TRAPS) {
1853   if ((byte_i_ref + 2 + 2) > annotations_typeArray->length()) {
1854     // not enough room for smallest annotation_struct
1855     RC_TRACE_WITH_THREAD(0x02000000, THREAD,
1856       ("length() is too small for annotation_struct"));
1857     return false;
1858   }
1859 
1860   u2 type_index = rewrite_cp_ref_in_annotation_data(annotations_typeArray,
1861                     byte_i_ref, "mapped old type_index=%d", THREAD);
1862 
1863   u2 num_element_value_pairs = Bytes::get_Java_u2((address)
1864                                  annotations_typeArray->adr_at(byte_i_ref));
1865   byte_i_ref += 2;
1866 
1867   RC_TRACE_WITH_THREAD(0x02000000, THREAD,
1868     ("type_index=%d  num_element_value_pairs=%d", type_index,
1869     num_element_value_pairs));
1870 
1871   int calc_num_element_value_pairs = 0;
1872   for (; calc_num_element_value_pairs < num_element_value_pairs;
1873        calc_num_element_value_pairs++) {
1874     if ((byte_i_ref + 2) > annotations_typeArray->length()) {
1875       // not enough room for another element_name_index, let alone
1876       // the rest of another component
1877       RC_TRACE_WITH_THREAD(0x02000000, THREAD,
1878         ("length() is too small for element_name_index"));
1879       return false;
1880     }
1881 
1882     u2 element_name_index = rewrite_cp_ref_in_annotation_data(
1883                               annotations_typeArray, byte_i_ref,
1884                               "mapped old element_name_index=%d", THREAD);
1885 
1886     RC_TRACE_WITH_THREAD(0x02000000, THREAD,
1887       ("element_name_index=%d", element_name_index));
1888 
1889     if (!rewrite_cp_refs_in_element_value(annotations_typeArray,
1890            byte_i_ref, THREAD)) {
1891       RC_TRACE_WITH_THREAD(0x02000000, THREAD,
1892         ("bad element_value at %d", calc_num_element_value_pairs));
1893       // propagate failure back to caller
1894       return false;
1895     }
1896   } // end for each component
1897   assert(num_element_value_pairs == calc_num_element_value_pairs,
1898     "sanity check");
1899 
1900   return true;
1901 } // end rewrite_cp_refs_in_annotation_struct()
1902 
1903 
1904 // Rewrite a constant pool reference at the current position in
1905 // annotations_typeArray if needed. Returns the original constant
1906 // pool reference if a rewrite was not needed or the new constant
1907 // pool reference if a rewrite was needed.
1908 PRAGMA_DIAG_PUSH
1909 PRAGMA_FORMAT_NONLITERAL_IGNORED
1910 u2 VM_RedefineClasses::rewrite_cp_ref_in_annotation_data(
1911      AnnotationArray* annotations_typeArray, int &byte_i_ref,
1912      const char * trace_mesg, TRAPS) {
1913 
1914   address cp_index_addr = (address)
1915     annotations_typeArray->adr_at(byte_i_ref);
1916   u2 old_cp_index = Bytes::get_Java_u2(cp_index_addr);
1917   u2 new_cp_index = find_new_index(old_cp_index);
1918   if (new_cp_index != 0) {
1919     RC_TRACE_WITH_THREAD(0x02000000, THREAD, (trace_mesg, old_cp_index));
1920     Bytes::put_Java_u2(cp_index_addr, new_cp_index);
1921     old_cp_index = new_cp_index;
1922   }
1923   byte_i_ref += 2;
1924   return old_cp_index;
1925 }
1926 PRAGMA_DIAG_POP
1927 
1928 
1929 // Rewrite constant pool references in the element_value portion of an
1930 // annotations_typeArray. This "structure" is from section 4.8.15.1 of
1931 // the 2nd-edition of the VM spec:
1932 //
1933 // struct element_value {
1934 //   u1 tag;
1935 //   union {
1936 //     u2 const_value_index;
1937 //     {
1938 //       u2 type_name_index;
1939 //       u2 const_name_index;
1940 //     } enum_const_value;
1941 //     u2 class_info_index;
1942 //     annotation annotation_value;
1943 //     struct {
1944 //       u2 num_values;
1945 //       element_value values[num_values];
1946 //     } array_value;
1947 //   } value;
1948 // }
1949 //
1950 bool VM_RedefineClasses::rewrite_cp_refs_in_element_value(
1951        AnnotationArray* annotations_typeArray, int &byte_i_ref, TRAPS) {
1952 
1953   if ((byte_i_ref + 1) > annotations_typeArray->length()) {
1954     // not enough room for a tag let alone the rest of an element_value
1955     RC_TRACE_WITH_THREAD(0x02000000, THREAD,
1956       ("length() is too small for a tag"));
1957     return false;
1958   }
1959 
1960   u1 tag = annotations_typeArray->at(byte_i_ref);
1961   byte_i_ref++;
1962   RC_TRACE_WITH_THREAD(0x02000000, THREAD, ("tag='%c'", tag));
1963 
1964   switch (tag) {
1965     // These BaseType tag values are from Table 4.2 in VM spec:
1966     case 'B':  // byte
1967     case 'C':  // char
1968     case 'D':  // double
1969     case 'F':  // float
1970     case 'I':  // int
1971     case 'J':  // long
1972     case 'S':  // short
1973     case 'Z':  // boolean
1974 
1975     // The remaining tag values are from Table 4.8 in the 2nd-edition of
1976     // the VM spec:
1977     case 's':
1978     {
1979       // For the above tag values (including the BaseType values),
1980       // value.const_value_index is right union field.
1981 
1982       if ((byte_i_ref + 2) > annotations_typeArray->length()) {
1983         // not enough room for a const_value_index
1984         RC_TRACE_WITH_THREAD(0x02000000, THREAD,
1985           ("length() is too small for a const_value_index"));
1986         return false;
1987       }
1988 
1989       u2 const_value_index = rewrite_cp_ref_in_annotation_data(
1990                                annotations_typeArray, byte_i_ref,
1991                                "mapped old const_value_index=%d", THREAD);
1992 
1993       RC_TRACE_WITH_THREAD(0x02000000, THREAD,
1994         ("const_value_index=%d", const_value_index));
1995     } break;
1996 
1997     case 'e':
1998     {
1999       // for the above tag value, value.enum_const_value is right union field
2000 
2001       if ((byte_i_ref + 4) > annotations_typeArray->length()) {
2002         // not enough room for a enum_const_value
2003         RC_TRACE_WITH_THREAD(0x02000000, THREAD,
2004           ("length() is too small for a enum_const_value"));
2005         return false;
2006       }
2007 
2008       u2 type_name_index = rewrite_cp_ref_in_annotation_data(
2009                              annotations_typeArray, byte_i_ref,
2010                              "mapped old type_name_index=%d", THREAD);
2011 
2012       u2 const_name_index = rewrite_cp_ref_in_annotation_data(
2013                               annotations_typeArray, byte_i_ref,
2014                               "mapped old const_name_index=%d", THREAD);
2015 
2016       RC_TRACE_WITH_THREAD(0x02000000, THREAD,
2017         ("type_name_index=%d  const_name_index=%d", type_name_index,
2018         const_name_index));
2019     } break;
2020 
2021     case 'c':
2022     {
2023       // for the above tag value, value.class_info_index is right union field
2024 
2025       if ((byte_i_ref + 2) > annotations_typeArray->length()) {
2026         // not enough room for a class_info_index
2027         RC_TRACE_WITH_THREAD(0x02000000, THREAD,
2028           ("length() is too small for a class_info_index"));
2029         return false;
2030       }
2031 
2032       u2 class_info_index = rewrite_cp_ref_in_annotation_data(
2033                               annotations_typeArray, byte_i_ref,
2034                               "mapped old class_info_index=%d", THREAD);
2035 
2036       RC_TRACE_WITH_THREAD(0x02000000, THREAD,
2037         ("class_info_index=%d", class_info_index));
2038     } break;
2039 
2040     case '@':
2041       // For the above tag value, value.attr_value is the right union
2042       // field. This is a nested annotation.
2043       if (!rewrite_cp_refs_in_annotation_struct(annotations_typeArray,
2044              byte_i_ref, THREAD)) {
2045         // propagate failure back to caller
2046         return false;
2047       }
2048       break;
2049 
2050     case '[':
2051     {
2052       if ((byte_i_ref + 2) > annotations_typeArray->length()) {
2053         // not enough room for a num_values field
2054         RC_TRACE_WITH_THREAD(0x02000000, THREAD,
2055           ("length() is too small for a num_values field"));
2056         return false;
2057       }
2058 
2059       // For the above tag value, value.array_value is the right union
2060       // field. This is an array of nested element_value.
2061       u2 num_values = Bytes::get_Java_u2((address)
2062                         annotations_typeArray->adr_at(byte_i_ref));
2063       byte_i_ref += 2;
2064       RC_TRACE_WITH_THREAD(0x02000000, THREAD, ("num_values=%d", num_values));
2065 
2066       int calc_num_values = 0;
2067       for (; calc_num_values < num_values; calc_num_values++) {
2068         if (!rewrite_cp_refs_in_element_value(
2069                annotations_typeArray, byte_i_ref, THREAD)) {
2070           RC_TRACE_WITH_THREAD(0x02000000, THREAD,
2071             ("bad nested element_value at %d", calc_num_values));
2072           // propagate failure back to caller
2073           return false;
2074         }
2075       }
2076       assert(num_values == calc_num_values, "sanity check");
2077     } break;
2078 
2079     default:
2080       RC_TRACE_WITH_THREAD(0x02000000, THREAD, ("bad tag=0x%x", tag));
2081       return false;
2082   } // end decode tag field
2083 
2084   return true;
2085 } // end rewrite_cp_refs_in_element_value()
2086 
2087 
2088 // Rewrite constant pool references in a fields_annotations field.
2089 bool VM_RedefineClasses::rewrite_cp_refs_in_fields_annotations(
2090        instanceKlassHandle scratch_class, TRAPS) {
2091 
2092   Array<AnnotationArray*>* fields_annotations = scratch_class->fields_annotations();
2093 
2094   if (fields_annotations == NULL || fields_annotations->length() == 0) {
2095     // no fields_annotations so nothing to do
2096     return true;
2097   }
2098 
2099   RC_TRACE_WITH_THREAD(0x02000000, THREAD,
2100     ("fields_annotations length=%d", fields_annotations->length()));
2101 
2102   for (int i = 0; i < fields_annotations->length(); i++) {
2103     AnnotationArray* field_annotations = fields_annotations->at(i);
2104     if (field_annotations == NULL || field_annotations->length() == 0) {
2105       // this field does not have any annotations so skip it
2106       continue;
2107     }
2108 
2109     int byte_i = 0;  // byte index into field_annotations
2110     if (!rewrite_cp_refs_in_annotations_typeArray(field_annotations, byte_i,
2111            THREAD)) {
2112       RC_TRACE_WITH_THREAD(0x02000000, THREAD,
2113         ("bad field_annotations at %d", i));
2114       // propagate failure back to caller
2115       return false;
2116     }
2117   }
2118 
2119   return true;
2120 } // end rewrite_cp_refs_in_fields_annotations()
2121 
2122 
2123 // Rewrite constant pool references in a methods_annotations field.
2124 bool VM_RedefineClasses::rewrite_cp_refs_in_methods_annotations(
2125        instanceKlassHandle scratch_class, TRAPS) {
2126 
2127   for (int i = 0; i < scratch_class->methods()->length(); i++) {
2128     Method* m = scratch_class->methods()->at(i);
2129     AnnotationArray* method_annotations = m->constMethod()->method_annotations();
2130 
2131     if (method_annotations == NULL || method_annotations->length() == 0) {
2132       // this method does not have any annotations so skip it
2133       continue;
2134     }
2135 
2136     int byte_i = 0;  // byte index into method_annotations
2137     if (!rewrite_cp_refs_in_annotations_typeArray(method_annotations, byte_i,
2138            THREAD)) {
2139       RC_TRACE_WITH_THREAD(0x02000000, THREAD,
2140         ("bad method_annotations at %d", i));
2141       // propagate failure back to caller
2142       return false;
2143     }
2144   }
2145 
2146   return true;
2147 } // end rewrite_cp_refs_in_methods_annotations()
2148 
2149 
2150 // Rewrite constant pool references in a methods_parameter_annotations
2151 // field. This "structure" is adapted from the
2152 // RuntimeVisibleParameterAnnotations_attribute described in section
2153 // 4.8.17 of the 2nd-edition of the VM spec:
2154 //
2155 // methods_parameter_annotations_typeArray {
2156 //   u1 num_parameters;
2157 //   {
2158 //     u2 num_annotations;
2159 //     annotation annotations[num_annotations];
2160 //   } parameter_annotations[num_parameters];
2161 // }
2162 //
2163 bool VM_RedefineClasses::rewrite_cp_refs_in_methods_parameter_annotations(
2164        instanceKlassHandle scratch_class, TRAPS) {
2165 
2166   for (int i = 0; i < scratch_class->methods()->length(); i++) {
2167     Method* m = scratch_class->methods()->at(i);
2168     AnnotationArray* method_parameter_annotations = m->constMethod()->parameter_annotations();
2169     if (method_parameter_annotations == NULL
2170         || method_parameter_annotations->length() == 0) {
2171       // this method does not have any parameter annotations so skip it
2172       continue;
2173     }
2174 
2175     if (method_parameter_annotations->length() < 1) {
2176       // not enough room for a num_parameters field
2177       RC_TRACE_WITH_THREAD(0x02000000, THREAD,
2178         ("length() is too small for a num_parameters field at %d", i));
2179       return false;
2180     }
2181 
2182     int byte_i = 0;  // byte index into method_parameter_annotations
2183 
2184     u1 num_parameters = method_parameter_annotations->at(byte_i);
2185     byte_i++;
2186 
2187     RC_TRACE_WITH_THREAD(0x02000000, THREAD,
2188       ("num_parameters=%d", num_parameters));
2189 
2190     int calc_num_parameters = 0;
2191     for (; calc_num_parameters < num_parameters; calc_num_parameters++) {
2192       if (!rewrite_cp_refs_in_annotations_typeArray(
2193              method_parameter_annotations, byte_i, THREAD)) {
2194         RC_TRACE_WITH_THREAD(0x02000000, THREAD,
2195           ("bad method_parameter_annotations at %d", calc_num_parameters));
2196         // propagate failure back to caller
2197         return false;
2198       }
2199     }
2200     assert(num_parameters == calc_num_parameters, "sanity check");
2201   }
2202 
2203   return true;
2204 } // end rewrite_cp_refs_in_methods_parameter_annotations()
2205 
2206 
2207 // Rewrite constant pool references in a methods_default_annotations
2208 // field. This "structure" is adapted from the AnnotationDefault_attribute
2209 // that is described in section 4.8.19 of the 2nd-edition of the VM spec:
2210 //
2211 // methods_default_annotations_typeArray {
2212 //   element_value default_value;
2213 // }
2214 //
2215 bool VM_RedefineClasses::rewrite_cp_refs_in_methods_default_annotations(
2216        instanceKlassHandle scratch_class, TRAPS) {
2217 
2218   for (int i = 0; i < scratch_class->methods()->length(); i++) {
2219     Method* m = scratch_class->methods()->at(i);
2220     AnnotationArray* method_default_annotations = m->constMethod()->default_annotations();
2221     if (method_default_annotations == NULL
2222         || method_default_annotations->length() == 0) {
2223       // this method does not have any default annotations so skip it
2224       continue;
2225     }
2226 
2227     int byte_i = 0;  // byte index into method_default_annotations
2228 
2229     if (!rewrite_cp_refs_in_element_value(
2230            method_default_annotations, byte_i, THREAD)) {
2231       RC_TRACE_WITH_THREAD(0x02000000, THREAD,
2232         ("bad default element_value at %d", i));
2233       // propagate failure back to caller
2234       return false;
2235     }
2236   }
2237 
2238   return true;
2239 } // end rewrite_cp_refs_in_methods_default_annotations()
2240 
2241 
2242 // Rewrite constant pool references in the method's stackmap table.
2243 // These "structures" are adapted from the StackMapTable_attribute that
2244 // is described in section 4.8.4 of the 6.0 version of the VM spec
2245 // (dated 2005.10.26):
2246 // file:///net/quincunx.sfbay/export/gbracha/ClassFile-Java6.pdf
2247 //
2248 // stack_map {
2249 //   u2 number_of_entries;
2250 //   stack_map_frame entries[number_of_entries];
2251 // }
2252 //
2253 void VM_RedefineClasses::rewrite_cp_refs_in_stack_map_table(
2254        methodHandle method, TRAPS) {
2255 
2256   if (!method->has_stackmap_table()) {
2257     return;
2258   }
2259 
2260   AnnotationArray* stackmap_data = method->stackmap_data();
2261   address stackmap_p = (address)stackmap_data->adr_at(0);
2262   address stackmap_end = stackmap_p + stackmap_data->length();
2263 
2264   assert(stackmap_p + 2 <= stackmap_end, "no room for number_of_entries");
2265   u2 number_of_entries = Bytes::get_Java_u2(stackmap_p);
2266   stackmap_p += 2;
2267 
2268   RC_TRACE_WITH_THREAD(0x04000000, THREAD,
2269     ("number_of_entries=%u", number_of_entries));
2270 
2271   // walk through each stack_map_frame
2272   u2 calc_number_of_entries = 0;
2273   for (; calc_number_of_entries < number_of_entries; calc_number_of_entries++) {
2274     // The stack_map_frame structure is a u1 frame_type followed by
2275     // 0 or more bytes of data:
2276     //
2277     // union stack_map_frame {
2278     //   same_frame;
2279     //   same_locals_1_stack_item_frame;
2280     //   same_locals_1_stack_item_frame_extended;
2281     //   chop_frame;
2282     //   same_frame_extended;
2283     //   append_frame;
2284     //   full_frame;
2285     // }
2286 
2287     assert(stackmap_p + 1 <= stackmap_end, "no room for frame_type");
2288     // The Linux compiler does not like frame_type to be u1 or u2. It
2289     // issues the following warning for the first if-statement below:
2290     //
2291     // "warning: comparison is always true due to limited range of data type"
2292     //
2293     u4 frame_type = *stackmap_p;
2294     stackmap_p++;
2295 
2296     // same_frame {
2297     //   u1 frame_type = SAME; /* 0-63 */
2298     // }
2299     if (frame_type >= 0 && frame_type <= 63) {
2300       // nothing more to do for same_frame
2301     }
2302 
2303     // same_locals_1_stack_item_frame {
2304     //   u1 frame_type = SAME_LOCALS_1_STACK_ITEM; /* 64-127 */
2305     //   verification_type_info stack[1];
2306     // }
2307     else if (frame_type >= 64 && frame_type <= 127) {
2308       rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
2309         calc_number_of_entries, frame_type, THREAD);
2310     }
2311 
2312     // reserved for future use
2313     else if (frame_type >= 128 && frame_type <= 246) {
2314       // nothing more to do for reserved frame_types
2315     }
2316 
2317     // same_locals_1_stack_item_frame_extended {
2318     //   u1 frame_type = SAME_LOCALS_1_STACK_ITEM_EXTENDED; /* 247 */
2319     //   u2 offset_delta;
2320     //   verification_type_info stack[1];
2321     // }
2322     else if (frame_type == 247) {
2323       stackmap_p += 2;
2324       rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
2325         calc_number_of_entries, frame_type, THREAD);
2326     }
2327 
2328     // chop_frame {
2329     //   u1 frame_type = CHOP; /* 248-250 */
2330     //   u2 offset_delta;
2331     // }
2332     else if (frame_type >= 248 && frame_type <= 250) {
2333       stackmap_p += 2;
2334     }
2335 
2336     // same_frame_extended {
2337     //   u1 frame_type = SAME_FRAME_EXTENDED; /* 251*/
2338     //   u2 offset_delta;
2339     // }
2340     else if (frame_type == 251) {
2341       stackmap_p += 2;
2342     }
2343 
2344     // append_frame {
2345     //   u1 frame_type = APPEND; /* 252-254 */
2346     //   u2 offset_delta;
2347     //   verification_type_info locals[frame_type - 251];
2348     // }
2349     else if (frame_type >= 252 && frame_type <= 254) {
2350       assert(stackmap_p + 2 <= stackmap_end,
2351         "no room for offset_delta");
2352       stackmap_p += 2;
2353       u1 len = frame_type - 251;
2354       for (u1 i = 0; i < len; i++) {
2355         rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
2356           calc_number_of_entries, frame_type, THREAD);
2357       }
2358     }
2359 
2360     // full_frame {
2361     //   u1 frame_type = FULL_FRAME; /* 255 */
2362     //   u2 offset_delta;
2363     //   u2 number_of_locals;
2364     //   verification_type_info locals[number_of_locals];
2365     //   u2 number_of_stack_items;
2366     //   verification_type_info stack[number_of_stack_items];
2367     // }
2368     else if (frame_type == 255) {
2369       assert(stackmap_p + 2 + 2 <= stackmap_end,
2370         "no room for smallest full_frame");
2371       stackmap_p += 2;
2372 
2373       u2 number_of_locals = Bytes::get_Java_u2(stackmap_p);
2374       stackmap_p += 2;
2375 
2376       for (u2 locals_i = 0; locals_i < number_of_locals; locals_i++) {
2377         rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
2378           calc_number_of_entries, frame_type, THREAD);
2379       }
2380 
2381       // Use the largest size for the number_of_stack_items, but only get
2382       // the right number of bytes.
2383       u2 number_of_stack_items = Bytes::get_Java_u2(stackmap_p);
2384       stackmap_p += 2;
2385 
2386       for (u2 stack_i = 0; stack_i < number_of_stack_items; stack_i++) {
2387         rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
2388           calc_number_of_entries, frame_type, THREAD);
2389       }
2390     }
2391   } // end while there is a stack_map_frame
2392   assert(number_of_entries == calc_number_of_entries, "sanity check");
2393 } // end rewrite_cp_refs_in_stack_map_table()
2394 
2395 
2396 // Rewrite constant pool references in the verification type info
2397 // portion of the method's stackmap table. These "structures" are
2398 // adapted from the StackMapTable_attribute that is described in
2399 // section 4.8.4 of the 6.0 version of the VM spec (dated 2005.10.26):
2400 // file:///net/quincunx.sfbay/export/gbracha/ClassFile-Java6.pdf
2401 //
2402 // The verification_type_info structure is a u1 tag followed by 0 or
2403 // more bytes of data:
2404 //
2405 // union verification_type_info {
2406 //   Top_variable_info;
2407 //   Integer_variable_info;
2408 //   Float_variable_info;
2409 //   Long_variable_info;
2410 //   Double_variable_info;
2411 //   Null_variable_info;
2412 //   UninitializedThis_variable_info;
2413 //   Object_variable_info;
2414 //   Uninitialized_variable_info;
2415 // }
2416 //
2417 void VM_RedefineClasses::rewrite_cp_refs_in_verification_type_info(
2418        address& stackmap_p_ref, address stackmap_end, u2 frame_i,
2419        u1 frame_type, TRAPS) {
2420 
2421   assert(stackmap_p_ref + 1 <= stackmap_end, "no room for tag");
2422   u1 tag = *stackmap_p_ref;
2423   stackmap_p_ref++;
2424 
2425   switch (tag) {
2426   // Top_variable_info {
2427   //   u1 tag = ITEM_Top; /* 0 */
2428   // }
2429   // verificationType.hpp has zero as ITEM_Bogus instead of ITEM_Top
2430   case 0:  // fall through
2431 
2432   // Integer_variable_info {
2433   //   u1 tag = ITEM_Integer; /* 1 */
2434   // }
2435   case ITEM_Integer:  // fall through
2436 
2437   // Float_variable_info {
2438   //   u1 tag = ITEM_Float; /* 2 */
2439   // }
2440   case ITEM_Float:  // fall through
2441 
2442   // Double_variable_info {
2443   //   u1 tag = ITEM_Double; /* 3 */
2444   // }
2445   case ITEM_Double:  // fall through
2446 
2447   // Long_variable_info {
2448   //   u1 tag = ITEM_Long; /* 4 */
2449   // }
2450   case ITEM_Long:  // fall through
2451 
2452   // Null_variable_info {
2453   //   u1 tag = ITEM_Null; /* 5 */
2454   // }
2455   case ITEM_Null:  // fall through
2456 
2457   // UninitializedThis_variable_info {
2458   //   u1 tag = ITEM_UninitializedThis; /* 6 */
2459   // }
2460   case ITEM_UninitializedThis:
2461     // nothing more to do for the above tag types
2462     break;
2463 
2464   // Object_variable_info {
2465   //   u1 tag = ITEM_Object; /* 7 */
2466   //   u2 cpool_index;
2467   // }
2468   case ITEM_Object:
2469   {
2470     assert(stackmap_p_ref + 2 <= stackmap_end, "no room for cpool_index");
2471     u2 cpool_index = Bytes::get_Java_u2(stackmap_p_ref);
2472     u2 new_cp_index = find_new_index(cpool_index);
2473     if (new_cp_index != 0) {
2474       RC_TRACE_WITH_THREAD(0x04000000, THREAD,
2475         ("mapped old cpool_index=%d", cpool_index));
2476       Bytes::put_Java_u2(stackmap_p_ref, new_cp_index);
2477       cpool_index = new_cp_index;
2478     }
2479     stackmap_p_ref += 2;
2480 
2481     RC_TRACE_WITH_THREAD(0x04000000, THREAD,
2482       ("frame_i=%u, frame_type=%u, cpool_index=%d", frame_i,
2483       frame_type, cpool_index));
2484   } break;
2485 
2486   // Uninitialized_variable_info {
2487   //   u1 tag = ITEM_Uninitialized; /* 8 */
2488   //   u2 offset;
2489   // }
2490   case ITEM_Uninitialized:
2491     assert(stackmap_p_ref + 2 <= stackmap_end, "no room for offset");
2492     stackmap_p_ref += 2;
2493     break;
2494 
2495   default:
2496     RC_TRACE_WITH_THREAD(0x04000000, THREAD,
2497       ("frame_i=%u, frame_type=%u, bad tag=0x%x", frame_i, frame_type, tag));
2498     ShouldNotReachHere();
2499     break;
2500   } // end switch (tag)
2501 } // end rewrite_cp_refs_in_verification_type_info()
2502 
2503 
2504 // Change the constant pool associated with klass scratch_class to
2505 // scratch_cp. If shrink is true, then scratch_cp_length elements
2506 // are copied from scratch_cp to a smaller constant pool and the
2507 // smaller constant pool is associated with scratch_class.
2508 void VM_RedefineClasses::set_new_constant_pool(
2509        ClassLoaderData* loader_data,
2510        instanceKlassHandle scratch_class, constantPoolHandle scratch_cp,
2511        int scratch_cp_length, TRAPS) {
2512   assert(scratch_cp->length() >= scratch_cp_length, "sanity check");
2513 
2514   // scratch_cp is a merged constant pool and has enough space for a
2515   // worst case merge situation. We want to associate the minimum
2516   // sized constant pool with the klass to save space.
2517   ConstantPool* cp = ConstantPool::allocate(loader_data, scratch_cp_length, CHECK);
2518   constantPoolHandle smaller_cp(THREAD, cp);
2519 
2520   // preserve version() value in the smaller copy
2521   int version = scratch_cp->version();
2522   assert(version != 0, "sanity check");
2523   smaller_cp->set_version(version);
2524 
2525   // attach klass to new constant pool
2526   // reference to the cp holder is needed for copy_operands()
2527   smaller_cp->set_pool_holder(scratch_class());
2528 
2529   scratch_cp->copy_cp_to(1, scratch_cp_length - 1, smaller_cp, 1, THREAD);
2530   if (HAS_PENDING_EXCEPTION) {
2531     // Exception is handled in the caller
2532     loader_data->add_to_deallocate_list(smaller_cp());
2533     return;
2534   }
2535   scratch_cp = smaller_cp;
2536 
2537   // attach new constant pool to klass
2538   scratch_class->set_constants(scratch_cp());
2539 
2540   int i;  // for portability
2541 
2542   // update each field in klass to use new constant pool indices as needed
2543   for (JavaFieldStream fs(scratch_class); !fs.done(); fs.next()) {
2544     jshort cur_index = fs.name_index();
2545     jshort new_index = find_new_index(cur_index);
2546     if (new_index != 0) {
2547       RC_TRACE_WITH_THREAD(0x00080000, THREAD,
2548         ("field-name_index change: %d to %d", cur_index, new_index));
2549       fs.set_name_index(new_index);
2550     }
2551     cur_index = fs.signature_index();
2552     new_index = find_new_index(cur_index);
2553     if (new_index != 0) {
2554       RC_TRACE_WITH_THREAD(0x00080000, THREAD,
2555         ("field-signature_index change: %d to %d", cur_index, new_index));
2556       fs.set_signature_index(new_index);
2557     }
2558     cur_index = fs.initval_index();
2559     new_index = find_new_index(cur_index);
2560     if (new_index != 0) {
2561       RC_TRACE_WITH_THREAD(0x00080000, THREAD,
2562         ("field-initval_index change: %d to %d", cur_index, new_index));
2563       fs.set_initval_index(new_index);
2564     }
2565     cur_index = fs.generic_signature_index();
2566     new_index = find_new_index(cur_index);
2567     if (new_index != 0) {
2568       RC_TRACE_WITH_THREAD(0x00080000, THREAD,
2569         ("field-generic_signature change: %d to %d", cur_index, new_index));
2570       fs.set_generic_signature_index(new_index);
2571     }
2572   } // end for each field
2573 
2574   // Update constant pool indices in the inner classes info to use
2575   // new constant indices as needed. The inner classes info is a
2576   // quadruple:
2577   // (inner_class_info, outer_class_info, inner_name, inner_access_flags)
2578   InnerClassesIterator iter(scratch_class);
2579   for (; !iter.done(); iter.next()) {
2580     int cur_index = iter.inner_class_info_index();
2581     if (cur_index == 0) {
2582       continue;  // JVM spec. allows null inner class refs so skip it
2583     }
2584     int new_index = find_new_index(cur_index);
2585     if (new_index != 0) {
2586       RC_TRACE_WITH_THREAD(0x00080000, THREAD,
2587         ("inner_class_info change: %d to %d", cur_index, new_index));
2588       iter.set_inner_class_info_index(new_index);
2589     }
2590     cur_index = iter.outer_class_info_index();
2591     new_index = find_new_index(cur_index);
2592     if (new_index != 0) {
2593       RC_TRACE_WITH_THREAD(0x00080000, THREAD,
2594         ("outer_class_info change: %d to %d", cur_index, new_index));
2595       iter.set_outer_class_info_index(new_index);
2596     }
2597     cur_index = iter.inner_name_index();
2598     new_index = find_new_index(cur_index);
2599     if (new_index != 0) {
2600       RC_TRACE_WITH_THREAD(0x00080000, THREAD,
2601         ("inner_name change: %d to %d", cur_index, new_index));
2602       iter.set_inner_name_index(new_index);
2603     }
2604   } // end for each inner class
2605 
2606   // Attach each method in klass to the new constant pool and update
2607   // to use new constant pool indices as needed:
2608   Array<Method*>* methods = scratch_class->methods();
2609   for (i = methods->length() - 1; i >= 0; i--) {
2610     methodHandle method(THREAD, methods->at(i));
2611     method->set_constants(scratch_cp());
2612 
2613     int new_index = find_new_index(method->name_index());
2614     if (new_index != 0) {
2615       RC_TRACE_WITH_THREAD(0x00080000, THREAD,
2616         ("method-name_index change: %d to %d", method->name_index(),
2617         new_index));
2618       method->set_name_index(new_index);
2619     }
2620     new_index = find_new_index(method->signature_index());
2621     if (new_index != 0) {
2622       RC_TRACE_WITH_THREAD(0x00080000, THREAD,
2623         ("method-signature_index change: %d to %d",
2624         method->signature_index(), new_index));
2625       method->set_signature_index(new_index);
2626     }
2627     new_index = find_new_index(method->generic_signature_index());
2628     if (new_index != 0) {
2629       RC_TRACE_WITH_THREAD(0x00080000, THREAD,
2630         ("method-generic_signature_index change: %d to %d",
2631         method->generic_signature_index(), new_index));
2632       method->set_generic_signature_index(new_index);
2633     }
2634 
2635     // Update constant pool indices in the method's checked exception
2636     // table to use new constant indices as needed.
2637     int cext_length = method->checked_exceptions_length();
2638     if (cext_length > 0) {
2639       CheckedExceptionElement * cext_table =
2640         method->checked_exceptions_start();
2641       for (int j = 0; j < cext_length; j++) {
2642         int cur_index = cext_table[j].class_cp_index;
2643         int new_index = find_new_index(cur_index);
2644         if (new_index != 0) {
2645           RC_TRACE_WITH_THREAD(0x00080000, THREAD,
2646             ("cext-class_cp_index change: %d to %d", cur_index, new_index));
2647           cext_table[j].class_cp_index = (u2)new_index;
2648         }
2649       } // end for each checked exception table entry
2650     } // end if there are checked exception table entries
2651 
2652     // Update each catch type index in the method's exception table
2653     // to use new constant pool indices as needed. The exception table
2654     // holds quadruple entries of the form:
2655     //   (beg_bci, end_bci, handler_bci, klass_index)
2656 
2657     ExceptionTable ex_table(method());
2658     int ext_length = ex_table.length();
2659 
2660     for (int j = 0; j < ext_length; j ++) {
2661       int cur_index = ex_table.catch_type_index(j);
2662       int new_index = find_new_index(cur_index);
2663       if (new_index != 0) {
2664         RC_TRACE_WITH_THREAD(0x00080000, THREAD,
2665           ("ext-klass_index change: %d to %d", cur_index, new_index));
2666         ex_table.set_catch_type_index(j, new_index);
2667       }
2668     } // end for each exception table entry
2669 
2670     // Update constant pool indices in the method's local variable
2671     // table to use new constant indices as needed. The local variable
2672     // table hold sextuple entries of the form:
2673     // (start_pc, length, name_index, descriptor_index, signature_index, slot)
2674     int lvt_length = method->localvariable_table_length();
2675     if (lvt_length > 0) {
2676       LocalVariableTableElement * lv_table =
2677         method->localvariable_table_start();
2678       for (int j = 0; j < lvt_length; j++) {
2679         int cur_index = lv_table[j].name_cp_index;
2680         int new_index = find_new_index(cur_index);
2681         if (new_index != 0) {
2682           RC_TRACE_WITH_THREAD(0x00080000, THREAD,
2683             ("lvt-name_cp_index change: %d to %d", cur_index, new_index));
2684           lv_table[j].name_cp_index = (u2)new_index;
2685         }
2686         cur_index = lv_table[j].descriptor_cp_index;
2687         new_index = find_new_index(cur_index);
2688         if (new_index != 0) {
2689           RC_TRACE_WITH_THREAD(0x00080000, THREAD,
2690             ("lvt-descriptor_cp_index change: %d to %d", cur_index,
2691             new_index));
2692           lv_table[j].descriptor_cp_index = (u2)new_index;
2693         }
2694         cur_index = lv_table[j].signature_cp_index;
2695         new_index = find_new_index(cur_index);
2696         if (new_index != 0) {
2697           RC_TRACE_WITH_THREAD(0x00080000, THREAD,
2698             ("lvt-signature_cp_index change: %d to %d", cur_index, new_index));
2699           lv_table[j].signature_cp_index = (u2)new_index;
2700         }
2701       } // end for each local variable table entry
2702     } // end if there are local variable table entries
2703 
2704     rewrite_cp_refs_in_stack_map_table(method, THREAD);
2705   } // end for each method
2706 } // end set_new_constant_pool()
2707 
2708 
2709 // Unevolving classes may point to methods of the_class directly
2710 // from their constant pool caches, itables, and/or vtables. We
2711 // use the ClassLoaderDataGraph::classes_do() facility and this helper
2712 // to fix up these pointers.
2713 
2714 // Adjust cpools and vtables closure
2715 void VM_RedefineClasses::AdjustCpoolCacheAndVtable::do_klass(Klass* k) {
2716 
2717   // This is a very busy routine. We don't want too much tracing
2718   // printed out.
2719   bool trace_name_printed = false;
2720 
2721   // Very noisy: only enable this call if you are trying to determine
2722   // that a specific class gets found by this routine.
2723   // RC_TRACE macro has an embedded ResourceMark
2724   // RC_TRACE_WITH_THREAD(0x00100000, THREAD,
2725   //   ("adjust check: name=%s", k->external_name()));
2726   // trace_name_printed = true;
2727 
2728   // If the class being redefined is java.lang.Object, we need to fix all
2729   // array class vtables also
2730   if (k->oop_is_array() && _the_class_oop == SystemDictionary::Object_klass()) {
2731     k->vtable()->adjust_method_entries(_matching_old_methods,
2732                                        _matching_new_methods,
2733                                        _matching_methods_length,
2734                                        &trace_name_printed);
2735   } else if (k->oop_is_instance()) {
2736     HandleMark hm(_thread);
2737     InstanceKlass *ik = InstanceKlass::cast(k);
2738 
2739     // HotSpot specific optimization! HotSpot does not currently
2740     // support delegation from the bootstrap class loader to a
2741     // user-defined class loader. This means that if the bootstrap
2742     // class loader is the initiating class loader, then it will also
2743     // be the defining class loader. This also means that classes
2744     // loaded by the bootstrap class loader cannot refer to classes
2745     // loaded by a user-defined class loader. Note: a user-defined
2746     // class loader can delegate to the bootstrap class loader.
2747     //
2748     // If the current class being redefined has a user-defined class
2749     // loader as its defining class loader, then we can skip all
2750     // classes loaded by the bootstrap class loader.
2751     bool is_user_defined =
2752            InstanceKlass::cast(_the_class_oop)->class_loader() != NULL;
2753     if (is_user_defined && ik->class_loader() == NULL) {
2754       return;
2755     }
2756 
2757     // Fix the vtable embedded in the_class and subclasses of the_class,
2758     // if one exists. We discard scratch_class and we don't keep an
2759     // InstanceKlass around to hold obsolete methods so we don't have
2760     // any other InstanceKlass embedded vtables to update. The vtable
2761     // holds the Method*s for virtual (but not final) methods.
2762     // Default methods, or concrete methods in interfaces are stored
2763     // in the vtable, so if an interface changes we need to check
2764     // adjust_method_entries() for every InstanceKlass, which will also
2765     // adjust the default method vtable indices.
2766     // We also need to adjust any default method entries that are
2767     // not yet in the vtable, because the vtable setup is in progress.
2768     // This must be done after we adjust the default_methods and
2769     // default_vtable_indices for methods already in the vtable.
2770     if (ik->vtable_length() > 0 && (_the_class_oop->is_interface()
2771         || ik->is_subtype_of(_the_class_oop))) {
2772       // ik->vtable() creates a wrapper object; rm cleans it up
2773       ResourceMark rm(_thread);
2774       ik->vtable()->adjust_method_entries(_matching_old_methods,
2775                                           _matching_new_methods,
2776                                           _matching_methods_length,
2777                                           &trace_name_printed);
2778       ik->adjust_default_methods(_matching_old_methods,
2779                                  _matching_new_methods,
2780                                  _matching_methods_length,
2781                                  &trace_name_printed);
2782     }
2783 
2784     // If the current class has an itable and we are either redefining an
2785     // interface or if the current class is a subclass of the_class, then
2786     // we potentially have to fix the itable. If we are redefining an
2787     // interface, then we have to call adjust_method_entries() for
2788     // every InstanceKlass that has an itable since there isn't a
2789     // subclass relationship between an interface and an InstanceKlass.
2790     if (ik->itable_length() > 0 && (_the_class_oop->is_interface()
2791         || ik->is_subclass_of(_the_class_oop))) {
2792       // ik->itable() creates a wrapper object; rm cleans it up
2793       ResourceMark rm(_thread);
2794       ik->itable()->adjust_method_entries(_matching_old_methods,
2795                                           _matching_new_methods,
2796                                           _matching_methods_length,
2797                                           &trace_name_printed);
2798     }
2799 
2800     // The constant pools in other classes (other_cp) can refer to
2801     // methods in the_class. We have to update method information in
2802     // other_cp's cache. If other_cp has a previous version, then we
2803     // have to repeat the process for each previous version. The
2804     // constant pool cache holds the Method*s for non-virtual
2805     // methods and for virtual, final methods.
2806     //
2807     // Special case: if the current class is the_class, then new_cp
2808     // has already been attached to the_class and old_cp has already
2809     // been added as a previous version. The new_cp doesn't have any
2810     // cached references to old methods so it doesn't need to be
2811     // updated. We can simply start with the previous version(s) in
2812     // that case.
2813     constantPoolHandle other_cp;
2814     ConstantPoolCache* cp_cache;
2815 
2816     if (ik != _the_class_oop) {
2817       // this klass' constant pool cache may need adjustment
2818       other_cp = constantPoolHandle(ik->constants());
2819       cp_cache = other_cp->cache();
2820       if (cp_cache != NULL) {
2821         cp_cache->adjust_method_entries(_matching_old_methods,
2822                                         _matching_new_methods,
2823                                         _matching_methods_length,
2824                                         &trace_name_printed);
2825       }
2826     }
2827 
2828     // the previous versions' constant pool caches may need adjustment
2829     for (InstanceKlass* pv_node = ik->previous_versions();
2830          pv_node != NULL;
2831          pv_node = pv_node->previous_versions()) {
2832       cp_cache = pv_node->constants()->cache();
2833       if (cp_cache != NULL) {
2834         cp_cache->adjust_method_entries(_matching_old_methods,
2835                                         _matching_new_methods,
2836                                         _matching_methods_length,
2837                                         &trace_name_printed);
2838       }
2839     }
2840   }
2841 }
2842 
2843 void VM_RedefineClasses::update_jmethod_ids() {
2844   for (int j = 0; j < _matching_methods_length; ++j) {
2845     Method* old_method = _matching_old_methods[j];
2846     jmethodID jmid = old_method->find_jmethod_id_or_null();
2847     if (jmid != NULL) {
2848       // There is a jmethodID, change it to point to the new method
2849       methodHandle new_method_h(_matching_new_methods[j]);
2850       Method::change_method_associated_with_jmethod_id(jmid, new_method_h());
2851       assert(Method::resolve_jmethod_id(jmid) == _matching_new_methods[j],
2852              "should be replaced");
2853     }
2854   }
2855 }
2856 
2857 int VM_RedefineClasses::check_methods_and_mark_as_obsolete() {
2858   int emcp_method_count = 0;
2859   int obsolete_count = 0;
2860   int old_index = 0;
2861   for (int j = 0; j < _matching_methods_length; ++j, ++old_index) {
2862     Method* old_method = _matching_old_methods[j];
2863     Method* new_method = _matching_new_methods[j];
2864     Method* old_array_method;
2865 
2866     // Maintain an old_index into the _old_methods array by skipping
2867     // deleted methods
2868     while ((old_array_method = _old_methods->at(old_index)) != old_method) {
2869       ++old_index;
2870     }
2871 
2872     if (MethodComparator::methods_EMCP(old_method, new_method)) {
2873       // The EMCP definition from JSR-163 requires the bytecodes to be
2874       // the same with the exception of constant pool indices which may
2875       // differ. However, the constants referred to by those indices
2876       // must be the same.
2877       //
2878       // We use methods_EMCP() for comparison since constant pool
2879       // merging can remove duplicate constant pool entries that were
2880       // present in the old method and removed from the rewritten new
2881       // method. A faster binary comparison function would consider the
2882       // old and new methods to be different when they are actually
2883       // EMCP.
2884       //
2885       // The old and new methods are EMCP and you would think that we
2886       // could get rid of one of them here and now and save some space.
2887       // However, the concept of EMCP only considers the bytecodes and
2888       // the constant pool entries in the comparison. Other things,
2889       // e.g., the line number table (LNT) or the local variable table
2890       // (LVT) don't count in the comparison. So the new (and EMCP)
2891       // method can have a new LNT that we need so we can't just
2892       // overwrite the new method with the old method.
2893       //
2894       // When this routine is called, we have already attached the new
2895       // methods to the_class so the old methods are effectively
2896       // overwritten. However, if an old method is still executing,
2897       // then the old method cannot be collected until sometime after
2898       // the old method call has returned. So the overwriting of old
2899       // methods by new methods will save us space except for those
2900       // (hopefully few) old methods that are still executing.
2901       //
2902       // A method refers to a ConstMethod* and this presents another
2903       // possible avenue to space savings. The ConstMethod* in the
2904       // new method contains possibly new attributes (LNT, LVT, etc).
2905       // At first glance, it seems possible to save space by replacing
2906       // the ConstMethod* in the old method with the ConstMethod*
2907       // from the new method. The old and new methods would share the
2908       // same ConstMethod* and we would save the space occupied by
2909       // the old ConstMethod*. However, the ConstMethod* contains
2910       // a back reference to the containing method. Sharing the
2911       // ConstMethod* between two methods could lead to confusion in
2912       // the code that uses the back reference. This would lead to
2913       // brittle code that could be broken in non-obvious ways now or
2914       // in the future.
2915       //
2916       // Another possibility is to copy the ConstMethod* from the new
2917       // method to the old method and then overwrite the new method with
2918       // the old method. Since the ConstMethod* contains the bytecodes
2919       // for the method embedded in the oop, this option would change
2920       // the bytecodes out from under any threads executing the old
2921       // method and make the thread's bcp invalid. Since EMCP requires
2922       // that the bytecodes be the same modulo constant pool indices, it
2923       // is straight forward to compute the correct new bcp in the new
2924       // ConstMethod* from the old bcp in the old ConstMethod*. The
2925       // time consuming part would be searching all the frames in all
2926       // of the threads to find all of the calls to the old method.
2927       //
2928       // It looks like we will have to live with the limited savings
2929       // that we get from effectively overwriting the old methods
2930       // when the new methods are attached to the_class.
2931 
2932       // Count number of methods that are EMCP.  The method will be marked
2933       // old but not obsolete if it is EMCP.
2934       emcp_method_count++;
2935 
2936       // An EMCP method is _not_ obsolete. An obsolete method has a
2937       // different jmethodID than the current method. An EMCP method
2938       // has the same jmethodID as the current method. Having the
2939       // same jmethodID for all EMCP versions of a method allows for
2940       // a consistent view of the EMCP methods regardless of which
2941       // EMCP method you happen to have in hand. For example, a
2942       // breakpoint set in one EMCP method will work for all EMCP
2943       // versions of the method including the current one.
2944     } else {
2945       // mark obsolete methods as such
2946       old_method->set_is_obsolete();
2947       obsolete_count++;
2948 
2949       // obsolete methods need a unique idnum so they become new entries in
2950       // the jmethodID cache in InstanceKlass
2951       u2 num = InstanceKlass::cast(_the_class_oop)->next_method_idnum();
2952       if (num != ConstMethod::UNSET_IDNUM) {
2953         old_method->set_method_idnum(num);
2954       }
2955 
2956       // With tracing we try not to "yack" too much. The position of
2957       // this trace assumes there are fewer obsolete methods than
2958       // EMCP methods.
2959       RC_TRACE(0x00000100, ("mark %s(%s) as obsolete",
2960         old_method->name()->as_C_string(),
2961         old_method->signature()->as_C_string()));
2962     }
2963     old_method->set_is_old();
2964   }
2965   for (int i = 0; i < _deleted_methods_length; ++i) {
2966     Method* old_method = _deleted_methods[i];
2967 
2968     assert(!old_method->has_vtable_index(),
2969            "cannot delete methods with vtable entries");;
2970 
2971     // Mark all deleted methods as old, obsolete and deleted
2972     old_method->set_is_deleted();
2973     old_method->set_is_old();
2974     old_method->set_is_obsolete();
2975     ++obsolete_count;
2976     // With tracing we try not to "yack" too much. The position of
2977     // this trace assumes there are fewer obsolete methods than
2978     // EMCP methods.
2979     RC_TRACE(0x00000100, ("mark deleted %s(%s) as obsolete",
2980                           old_method->name()->as_C_string(),
2981                           old_method->signature()->as_C_string()));
2982   }
2983   assert((emcp_method_count + obsolete_count) == _old_methods->length(),
2984     "sanity check");
2985   RC_TRACE(0x00000100, ("EMCP_cnt=%d, obsolete_cnt=%d", emcp_method_count,
2986     obsolete_count));
2987   return emcp_method_count;
2988 }
2989 
2990 // This internal class transfers the native function registration from old methods
2991 // to new methods.  It is designed to handle both the simple case of unchanged
2992 // native methods and the complex cases of native method prefixes being added and/or
2993 // removed.
2994 // It expects only to be used during the VM_RedefineClasses op (a safepoint).
2995 //
2996 // This class is used after the new methods have been installed in "the_class".
2997 //
2998 // So, for example, the following must be handled.  Where 'm' is a method and
2999 // a number followed by an underscore is a prefix.
3000 //
3001 //                                      Old Name    New Name
3002 // Simple transfer to new method        m       ->  m
3003 // Add prefix                           m       ->  1_m
3004 // Remove prefix                        1_m     ->  m
3005 // Simultaneous add of prefixes         m       ->  3_2_1_m
3006 // Simultaneous removal of prefixes     3_2_1_m ->  m
3007 // Simultaneous add and remove          1_m     ->  2_m
3008 // Same, caused by prefix removal only  3_2_1_m ->  3_2_m
3009 //
3010 class TransferNativeFunctionRegistration {
3011  private:
3012   instanceKlassHandle the_class;
3013   int prefix_count;
3014   char** prefixes;
3015 
3016   // Recursively search the binary tree of possibly prefixed method names.
3017   // Iteration could be used if all agents were well behaved. Full tree walk is
3018   // more resilent to agents not cleaning up intermediate methods.
3019   // Branch at each depth in the binary tree is:
3020   //    (1) without the prefix.
3021   //    (2) with the prefix.
3022   // where 'prefix' is the prefix at that 'depth' (first prefix, second prefix,...)
3023   Method* search_prefix_name_space(int depth, char* name_str, size_t name_len,
3024                                      Symbol* signature) {
3025     TempNewSymbol name_symbol = SymbolTable::probe(name_str, (int)name_len);
3026     if (name_symbol != NULL) {
3027       Method* method = the_class()->lookup_method(name_symbol, signature);
3028       if (method != NULL) {
3029         // Even if prefixed, intermediate methods must exist.
3030         if (method->is_native()) {
3031           // Wahoo, we found a (possibly prefixed) version of the method, return it.
3032           return method;
3033         }
3034         if (depth < prefix_count) {
3035           // Try applying further prefixes (other than this one).
3036           method = search_prefix_name_space(depth+1, name_str, name_len, signature);
3037           if (method != NULL) {
3038             return method; // found
3039           }
3040 
3041           // Try adding this prefix to the method name and see if it matches
3042           // another method name.
3043           char* prefix = prefixes[depth];
3044           size_t prefix_len = strlen(prefix);
3045           size_t trial_len = name_len + prefix_len;
3046           char* trial_name_str = NEW_RESOURCE_ARRAY(char, trial_len + 1);
3047           strcpy(trial_name_str, prefix);
3048           strcat(trial_name_str, name_str);
3049           method = search_prefix_name_space(depth+1, trial_name_str, trial_len,
3050                                             signature);
3051           if (method != NULL) {
3052             // If found along this branch, it was prefixed, mark as such
3053             method->set_is_prefixed_native();
3054             return method; // found
3055           }
3056         }
3057       }
3058     }
3059     return NULL;  // This whole branch bore nothing
3060   }
3061 
3062   // Return the method name with old prefixes stripped away.
3063   char* method_name_without_prefixes(Method* method) {
3064     Symbol* name = method->name();
3065     char* name_str = name->as_utf8();
3066 
3067     // Old prefixing may be defunct, strip prefixes, if any.
3068     for (int i = prefix_count-1; i >= 0; i--) {
3069       char* prefix = prefixes[i];
3070       size_t prefix_len = strlen(prefix);
3071       if (strncmp(prefix, name_str, prefix_len) == 0) {
3072         name_str += prefix_len;
3073       }
3074     }
3075     return name_str;
3076   }
3077 
3078   // Strip any prefixes off the old native method, then try to find a
3079   // (possibly prefixed) new native that matches it.
3080   Method* strip_and_search_for_new_native(Method* method) {
3081     ResourceMark rm;
3082     char* name_str = method_name_without_prefixes(method);
3083     return search_prefix_name_space(0, name_str, strlen(name_str),
3084                                     method->signature());
3085   }
3086 
3087  public:
3088 
3089   // Construct a native method transfer processor for this class.
3090   TransferNativeFunctionRegistration(instanceKlassHandle _the_class) {
3091     assert(SafepointSynchronize::is_at_safepoint(), "sanity check");
3092 
3093     the_class = _the_class;
3094     prefixes = JvmtiExport::get_all_native_method_prefixes(&prefix_count);
3095   }
3096 
3097   // Attempt to transfer any of the old or deleted methods that are native
3098   void transfer_registrations(Method** old_methods, int methods_length) {
3099     for (int j = 0; j < methods_length; j++) {
3100       Method* old_method = old_methods[j];
3101 
3102       if (old_method->is_native() && old_method->has_native_function()) {
3103         Method* new_method = strip_and_search_for_new_native(old_method);
3104         if (new_method != NULL) {
3105           // Actually set the native function in the new method.
3106           // Redefine does not send events (except CFLH), certainly not this
3107           // behind the scenes re-registration.
3108           new_method->set_native_function(old_method->native_function(),
3109                               !Method::native_bind_event_is_interesting);
3110         }
3111       }
3112     }
3113   }
3114 };
3115 
3116 // Don't lose the association between a native method and its JNI function.
3117 void VM_RedefineClasses::transfer_old_native_function_registrations(instanceKlassHandle the_class) {
3118   TransferNativeFunctionRegistration transfer(the_class);
3119   transfer.transfer_registrations(_deleted_methods, _deleted_methods_length);
3120   transfer.transfer_registrations(_matching_old_methods, _matching_methods_length);
3121 }
3122 
3123 // Deoptimize all compiled code that depends on this class.
3124 //
3125 // If the can_redefine_classes capability is obtained in the onload
3126 // phase then the compiler has recorded all dependencies from startup.
3127 // In that case we need only deoptimize and throw away all compiled code
3128 // that depends on the class.
3129 //
3130 // If can_redefine_classes is obtained sometime after the onload
3131 // phase then the dependency information may be incomplete. In that case
3132 // the first call to RedefineClasses causes all compiled code to be
3133 // thrown away. As can_redefine_classes has been obtained then
3134 // all future compilations will record dependencies so second and
3135 // subsequent calls to RedefineClasses need only throw away code
3136 // that depends on the class.
3137 //
3138 void VM_RedefineClasses::flush_dependent_code(instanceKlassHandle k_h, TRAPS) {
3139   assert_locked_or_safepoint(Compile_lock);
3140 
3141   // All dependencies have been recorded from startup or this is a second or
3142   // subsequent use of RedefineClasses
3143   if (JvmtiExport::all_dependencies_are_recorded()) {
3144     Universe::flush_evol_dependents_on(k_h);
3145   } else {
3146     CodeCache::mark_all_nmethods_for_deoptimization();
3147 
3148     ResourceMark rm(THREAD);
3149     DeoptimizationMarker dm;
3150 
3151     // Deoptimize all activations depending on marked nmethods
3152     Deoptimization::deoptimize_dependents();
3153 
3154     // Make the dependent methods not entrant (in VM_Deoptimize they are made zombies)
3155     CodeCache::make_marked_nmethods_not_entrant();
3156 
3157     // From now on we know that the dependency information is complete
3158     JvmtiExport::set_all_dependencies_are_recorded(true);
3159   }
3160 }
3161 
3162 void VM_RedefineClasses::compute_added_deleted_matching_methods() {
3163   Method* old_method;
3164   Method* new_method;
3165 
3166   _matching_old_methods = NEW_RESOURCE_ARRAY(Method*, _old_methods->length());
3167   _matching_new_methods = NEW_RESOURCE_ARRAY(Method*, _old_methods->length());
3168   _added_methods        = NEW_RESOURCE_ARRAY(Method*, _new_methods->length());
3169   _deleted_methods      = NEW_RESOURCE_ARRAY(Method*, _old_methods->length());
3170 
3171   _matching_methods_length = 0;
3172   _deleted_methods_length  = 0;
3173   _added_methods_length    = 0;
3174 
3175   int nj = 0;
3176   int oj = 0;
3177   while (true) {
3178     if (oj >= _old_methods->length()) {
3179       if (nj >= _new_methods->length()) {
3180         break; // we've looked at everything, done
3181       }
3182       // New method at the end
3183       new_method = _new_methods->at(nj);
3184       _added_methods[_added_methods_length++] = new_method;
3185       ++nj;
3186     } else if (nj >= _new_methods->length()) {
3187       // Old method, at the end, is deleted
3188       old_method = _old_methods->at(oj);
3189       _deleted_methods[_deleted_methods_length++] = old_method;
3190       ++oj;
3191     } else {
3192       old_method = _old_methods->at(oj);
3193       new_method = _new_methods->at(nj);
3194       if (old_method->name() == new_method->name()) {
3195         if (old_method->signature() == new_method->signature()) {
3196           _matching_old_methods[_matching_methods_length  ] = old_method;
3197           _matching_new_methods[_matching_methods_length++] = new_method;
3198           ++nj;
3199           ++oj;
3200         } else {
3201           // added overloaded have already been moved to the end,
3202           // so this is a deleted overloaded method
3203           _deleted_methods[_deleted_methods_length++] = old_method;
3204           ++oj;
3205         }
3206       } else { // names don't match
3207         if (old_method->name()->fast_compare(new_method->name()) > 0) {
3208           // new method
3209           _added_methods[_added_methods_length++] = new_method;
3210           ++nj;
3211         } else {
3212           // deleted method
3213           _deleted_methods[_deleted_methods_length++] = old_method;
3214           ++oj;
3215         }
3216       }
3217     }
3218   }
3219   assert(_matching_methods_length + _deleted_methods_length == _old_methods->length(), "sanity");
3220   assert(_matching_methods_length + _added_methods_length == _new_methods->length(), "sanity");
3221 }
3222 
3223 
3224 void VM_RedefineClasses::swap_annotations(instanceKlassHandle the_class,
3225                                           instanceKlassHandle scratch_class) {
3226   // Since there is currently no rewriting of type annotations indexes
3227   // into the CP, we null out type annotations on scratch_class before
3228   // we swap annotations with the_class rather than facing the
3229   // possibility of shipping annotations with broken indexes to
3230   // Java-land.
3231   ClassLoaderData* loader_data = scratch_class->class_loader_data();
3232   AnnotationArray* new_class_type_annotations = scratch_class->class_type_annotations();
3233   if (new_class_type_annotations != NULL) {
3234     MetadataFactory::free_array<u1>(loader_data, new_class_type_annotations);
3235     scratch_class->annotations()->set_class_type_annotations(NULL);
3236   }
3237   Array<AnnotationArray*>* new_field_type_annotations = scratch_class->fields_type_annotations();
3238   if (new_field_type_annotations != NULL) {
3239     Annotations::free_contents(loader_data, new_field_type_annotations);
3240     scratch_class->annotations()->set_fields_type_annotations(NULL);
3241   }
3242 
3243   // Swap annotation fields values
3244   Annotations* old_annotations = the_class->annotations();
3245   the_class->set_annotations(scratch_class->annotations());
3246   scratch_class->set_annotations(old_annotations);
3247 }
3248 
3249 
3250 // Install the redefinition of a class:
3251 //    - house keeping (flushing breakpoints and caches, deoptimizing
3252 //      dependent compiled code)
3253 //    - replacing parts in the_class with parts from scratch_class
3254 //    - adding a weak reference to track the obsolete but interesting
3255 //      parts of the_class
3256 //    - adjusting constant pool caches and vtables in other classes
3257 //      that refer to methods in the_class. These adjustments use the
3258 //      ClassLoaderDataGraph::classes_do() facility which only allows
3259 //      a helper method to be specified. The interesting parameters
3260 //      that we would like to pass to the helper method are saved in
3261 //      static global fields in the VM operation.
3262 void VM_RedefineClasses::redefine_single_class(jclass the_jclass,
3263        Klass* scratch_class_oop, TRAPS) {
3264 
3265   HandleMark hm(THREAD);   // make sure handles from this call are freed
3266   RC_TIMER_START(_timer_rsc_phase1);
3267 
3268   instanceKlassHandle scratch_class(scratch_class_oop);
3269 
3270   oop the_class_mirror = JNIHandles::resolve_non_null(the_jclass);
3271   Klass* the_class_oop = java_lang_Class::as_Klass(the_class_mirror);
3272   instanceKlassHandle the_class = instanceKlassHandle(THREAD, the_class_oop);
3273 
3274   // Remove all breakpoints in methods of this class
3275   JvmtiBreakpoints& jvmti_breakpoints = JvmtiCurrentBreakpoints::get_jvmti_breakpoints();
3276   jvmti_breakpoints.clearall_in_class_at_safepoint(the_class_oop);
3277 
3278   // Deoptimize all compiled code that depends on this class
3279   flush_dependent_code(the_class, THREAD);
3280 
3281   _old_methods = the_class->methods();
3282   _new_methods = scratch_class->methods();
3283   _the_class_oop = the_class_oop;
3284   compute_added_deleted_matching_methods();
3285   update_jmethod_ids();
3286 
3287   // Attach new constant pool to the original klass. The original
3288   // klass still refers to the old constant pool (for now).
3289   scratch_class->constants()->set_pool_holder(the_class());
3290 
3291 #if 0
3292   // In theory, with constant pool merging in place we should be able
3293   // to save space by using the new, merged constant pool in place of
3294   // the old constant pool(s). By "pool(s)" I mean the constant pool in
3295   // the klass version we are replacing now and any constant pool(s) in
3296   // previous versions of klass. Nice theory, doesn't work in practice.
3297   // When this code is enabled, even simple programs throw NullPointer
3298   // exceptions. I'm guessing that this is caused by some constant pool
3299   // cache difference between the new, merged constant pool and the
3300   // constant pool that was just being used by the klass. I'm keeping
3301   // this code around to archive the idea, but the code has to remain
3302   // disabled for now.
3303 
3304   // Attach each old method to the new constant pool. This can be
3305   // done here since we are past the bytecode verification and
3306   // constant pool optimization phases.
3307   for (int i = _old_methods->length() - 1; i >= 0; i--) {
3308     Method* method = _old_methods->at(i);
3309     method->set_constants(scratch_class->constants());
3310   }
3311 
3312   {
3313     // walk all previous versions of the klass
3314     InstanceKlass *ik = (InstanceKlass *)the_class();
3315     PreviousVersionWalker pvw(ik);
3316     instanceKlassHandle ikh;
3317     do {
3318       ikh = pvw.next_previous_version();
3319       if (!ikh.is_null()) {
3320         ik = ikh();
3321 
3322         // attach previous version of klass to the new constant pool
3323         ik->set_constants(scratch_class->constants());
3324 
3325         // Attach each method in the previous version of klass to the
3326         // new constant pool
3327         Array<Method*>* prev_methods = ik->methods();
3328         for (int i = prev_methods->length() - 1; i >= 0; i--) {
3329           Method* method = prev_methods->at(i);
3330           method->set_constants(scratch_class->constants());
3331         }
3332       }
3333     } while (!ikh.is_null());
3334   }
3335 #endif
3336 
3337   // Replace methods and constantpool
3338   the_class->set_methods(_new_methods);
3339   scratch_class->set_methods(_old_methods);     // To prevent potential GCing of the old methods,
3340                                           // and to be able to undo operation easily.
3341 
3342   ConstantPool* old_constants = the_class->constants();
3343   the_class->set_constants(scratch_class->constants());
3344   scratch_class->set_constants(old_constants);  // See the previous comment.
3345 #if 0
3346   // We are swapping the guts of "the new class" with the guts of "the
3347   // class". Since the old constant pool has just been attached to "the
3348   // new class", it seems logical to set the pool holder in the old
3349   // constant pool also. However, doing this will change the observable
3350   // class hierarchy for any old methods that are still executing. A
3351   // method can query the identity of its "holder" and this query uses
3352   // the method's constant pool link to find the holder. The change in
3353   // holding class from "the class" to "the new class" can confuse
3354   // things.
3355   //
3356   // Setting the old constant pool's holder will also cause
3357   // verification done during vtable initialization below to fail.
3358   // During vtable initialization, the vtable's class is verified to be
3359   // a subtype of the method's holder. The vtable's class is "the
3360   // class" and the method's holder is gotten from the constant pool
3361   // link in the method itself. For "the class"'s directly implemented
3362   // methods, the method holder is "the class" itself (as gotten from
3363   // the new constant pool). The check works fine in this case. The
3364   // check also works fine for methods inherited from super classes.
3365   //
3366   // Miranda methods are a little more complicated. A miranda method is
3367   // provided by an interface when the class implementing the interface
3368   // does not provide its own method.  These interfaces are implemented
3369   // internally as an InstanceKlass. These special instanceKlasses
3370   // share the constant pool of the class that "implements" the
3371   // interface. By sharing the constant pool, the method holder of a
3372   // miranda method is the class that "implements" the interface. In a
3373   // non-redefine situation, the subtype check works fine. However, if
3374   // the old constant pool's pool holder is modified, then the check
3375   // fails because there is no class hierarchy relationship between the
3376   // vtable's class and "the new class".
3377 
3378   old_constants->set_pool_holder(scratch_class());
3379 #endif
3380 
3381   // track number of methods that are EMCP for add_previous_version() call below
3382   int emcp_method_count = check_methods_and_mark_as_obsolete();
3383   transfer_old_native_function_registrations(the_class);
3384 
3385   // The class file bytes from before any retransformable agents mucked
3386   // with them was cached on the scratch class, move to the_class.
3387   // Note: we still want to do this if nothing needed caching since it
3388   // should get cleared in the_class too.
3389   if (the_class->get_cached_class_file_bytes() == 0) {
3390     // the_class doesn't have a cache yet so copy it
3391     the_class->set_cached_class_file(scratch_class->get_cached_class_file());
3392   }
3393 #ifndef PRODUCT
3394   else {
3395     assert(the_class->get_cached_class_file_bytes() ==
3396       scratch_class->get_cached_class_file_bytes(), "cache ptrs must match");
3397     assert(the_class->get_cached_class_file_len() ==
3398       scratch_class->get_cached_class_file_len(), "cache lens must match");
3399   }
3400 #endif
3401 
3402   // NULL out in scratch class to not delete twice.  The class to be redefined
3403   // always owns these bytes.
3404   scratch_class->set_cached_class_file(NULL);
3405 
3406   // Replace inner_classes
3407   Array<u2>* old_inner_classes = the_class->inner_classes();
3408   the_class->set_inner_classes(scratch_class->inner_classes());
3409   scratch_class->set_inner_classes(old_inner_classes);
3410 
3411   // Initialize the vtable and interface table after
3412   // methods have been rewritten
3413   {
3414     ResourceMark rm(THREAD);
3415     // no exception should happen here since we explicitly
3416     // do not check loader constraints.
3417     // compare_and_normalize_class_versions has already checked:
3418     //  - classloaders unchanged, signatures unchanged
3419     //  - all instanceKlasses for redefined classes reused & contents updated
3420     the_class->vtable()->initialize_vtable(false, THREAD);
3421     the_class->itable()->initialize_itable(false, THREAD);
3422     assert(!HAS_PENDING_EXCEPTION || (THREAD->pending_exception()->is_a(SystemDictionary::ThreadDeath_klass())), "redefine exception");
3423   }
3424 
3425   // Leave arrays of jmethodIDs and itable index cache unchanged
3426 
3427   // Copy the "source file name" attribute from new class version
3428   the_class->set_source_file_name_index(
3429     scratch_class->source_file_name_index());
3430 
3431   // Copy the "source debug extension" attribute from new class version
3432   the_class->set_source_debug_extension(
3433     scratch_class->source_debug_extension(),
3434     scratch_class->source_debug_extension() == NULL ? 0 :
3435     (int)strlen(scratch_class->source_debug_extension()));
3436 
3437   // Use of javac -g could be different in the old and the new
3438   if (scratch_class->access_flags().has_localvariable_table() !=
3439       the_class->access_flags().has_localvariable_table()) {
3440 
3441     AccessFlags flags = the_class->access_flags();
3442     if (scratch_class->access_flags().has_localvariable_table()) {
3443       flags.set_has_localvariable_table();
3444     } else {
3445       flags.clear_has_localvariable_table();
3446     }
3447     the_class->set_access_flags(flags);
3448   }
3449 
3450   swap_annotations(the_class, scratch_class);
3451 
3452   // Replace minor version number of class file
3453   u2 old_minor_version = the_class->minor_version();
3454   the_class->set_minor_version(scratch_class->minor_version());
3455   scratch_class->set_minor_version(old_minor_version);
3456 
3457   // Replace major version number of class file
3458   u2 old_major_version = the_class->major_version();
3459   the_class->set_major_version(scratch_class->major_version());
3460   scratch_class->set_major_version(old_major_version);
3461 
3462   // Replace CP indexes for class and name+type of enclosing method
3463   u2 old_class_idx  = the_class->enclosing_method_class_index();
3464   u2 old_method_idx = the_class->enclosing_method_method_index();
3465   the_class->set_enclosing_method_indices(
3466     scratch_class->enclosing_method_class_index(),
3467     scratch_class->enclosing_method_method_index());
3468   scratch_class->set_enclosing_method_indices(old_class_idx, old_method_idx);
3469 
3470   the_class->set_has_been_redefined();
3471 
3472   // keep track of previous versions of this class
3473   the_class->add_previous_version(scratch_class, emcp_method_count);
3474 
3475   RC_TIMER_STOP(_timer_rsc_phase1);
3476   RC_TIMER_START(_timer_rsc_phase2);
3477 
3478   // Adjust constantpool caches and vtables for all classes
3479   // that reference methods of the evolved class.
3480   AdjustCpoolCacheAndVtable adjust_cpool_cache_and_vtable(THREAD);
3481   ClassLoaderDataGraph::classes_do(&adjust_cpool_cache_and_vtable);
3482 
3483   // JSR-292 support
3484   {
3485     bool trace_name_printed = false;
3486     the_class->adjust_member_name_table(_matching_old_methods, _matching_new_methods, _matching_methods_length, &trace_name_printed);
3487   }
3488 
3489   // Fix Resolution Error table also to remove old constant pools
3490   SystemDictionary::delete_resolution_error(old_constants);
3491 
3492   if (the_class->oop_map_cache() != NULL) {
3493     // Flush references to any obsolete methods from the oop map cache
3494     // so that obsolete methods are not pinned.
3495     the_class->oop_map_cache()->flush_obsolete_entries();
3496   }
3497 
3498   // increment the classRedefinedCount field in the_class and in any
3499   // direct and indirect subclasses of the_class
3500   increment_class_counter((InstanceKlass *)the_class(), THREAD);
3501 
3502   // RC_TRACE macro has an embedded ResourceMark
3503   RC_TRACE_WITH_THREAD(0x00000001, THREAD,
3504     ("redefined name=%s, count=%d (avail_mem=" UINT64_FORMAT "K)",
3505     the_class->external_name(),
3506     java_lang_Class::classRedefinedCount(the_class_mirror),
3507     os::available_memory() >> 10));
3508 
3509   RC_TIMER_STOP(_timer_rsc_phase2);
3510 } // end redefine_single_class()
3511 
3512 
3513 // Increment the classRedefinedCount field in the specific InstanceKlass
3514 // and in all direct and indirect subclasses.
3515 void VM_RedefineClasses::increment_class_counter(InstanceKlass *ik, TRAPS) {
3516   oop class_mirror = ik->java_mirror();
3517   Klass* class_oop = java_lang_Class::as_Klass(class_mirror);
3518   int new_count = java_lang_Class::classRedefinedCount(class_mirror) + 1;
3519   java_lang_Class::set_classRedefinedCount(class_mirror, new_count);
3520 
3521   if (class_oop != _the_class_oop) {
3522     // _the_class_oop count is printed at end of redefine_single_class()
3523     RC_TRACE_WITH_THREAD(0x00000008, THREAD,
3524       ("updated count in subclass=%s to %d", ik->external_name(), new_count));
3525   }
3526 
3527   for (Klass *subk = ik->subklass(); subk != NULL;
3528        subk = subk->next_sibling()) {
3529     if (subk->oop_is_instance()) {
3530       // Only update instanceKlasses
3531       InstanceKlass *subik = (InstanceKlass*)subk;
3532       // recursively do subclasses of the current subclass
3533       increment_class_counter(subik, THREAD);
3534     }
3535   }
3536 }
3537 
3538 void VM_RedefineClasses::CheckClass::do_klass(Klass* k) {
3539   bool no_old_methods = true;  // be optimistic
3540 
3541   // Both array and instance classes have vtables.
3542   // a vtable should never contain old or obsolete methods
3543   ResourceMark rm(_thread);
3544   if (k->vtable_length() > 0 &&
3545       !k->vtable()->check_no_old_or_obsolete_entries()) {
3546     if (RC_TRACE_ENABLED(0x00004000)) {
3547       RC_TRACE_WITH_THREAD(0x00004000, _thread,
3548         ("klassVtable::check_no_old_or_obsolete_entries failure"
3549          " -- OLD or OBSOLETE method found -- class: %s",
3550          k->signature_name()));
3551       k->vtable()->dump_vtable();
3552     }
3553     no_old_methods = false;
3554   }
3555 
3556   if (k->oop_is_instance()) {
3557     HandleMark hm(_thread);
3558     InstanceKlass *ik = InstanceKlass::cast(k);
3559 
3560     // an itable should never contain old or obsolete methods
3561     if (ik->itable_length() > 0 &&
3562         !ik->itable()->check_no_old_or_obsolete_entries()) {
3563       if (RC_TRACE_ENABLED(0x00004000)) {
3564         RC_TRACE_WITH_THREAD(0x00004000, _thread,
3565           ("klassItable::check_no_old_or_obsolete_entries failure"
3566            " -- OLD or OBSOLETE method found -- class: %s",
3567            ik->signature_name()));
3568         ik->itable()->dump_itable();
3569       }
3570       no_old_methods = false;
3571     }
3572 
3573     // the constant pool cache should never contain non-deleted old or obsolete methods
3574     if (ik->constants() != NULL &&
3575         ik->constants()->cache() != NULL &&
3576         !ik->constants()->cache()->check_no_old_or_obsolete_entries()) {
3577       if (RC_TRACE_ENABLED(0x00004000)) {
3578         RC_TRACE_WITH_THREAD(0x00004000, _thread,
3579           ("cp-cache::check_no_old_or_obsolete_entries failure"
3580            " -- OLD or OBSOLETE method found -- class: %s",
3581            ik->signature_name()));
3582         ik->constants()->cache()->dump_cache();
3583       }
3584       no_old_methods = false;
3585     }
3586   }
3587 
3588   // print and fail guarantee if old methods are found.
3589   if (!no_old_methods) {
3590     if (RC_TRACE_ENABLED(0x00004000)) {
3591       dump_methods();
3592     } else {
3593       tty->print_cr("INFO: use the '-XX:TraceRedefineClasses=16384' option "
3594         "to see more info about the following guarantee() failure.");
3595     }
3596     guarantee(false, "OLD and/or OBSOLETE method(s) found");
3597   }
3598 }
3599 
3600 
3601 void VM_RedefineClasses::dump_methods() {
3602   int j;
3603   RC_TRACE(0x00004000, ("_old_methods --"));
3604   for (j = 0; j < _old_methods->length(); ++j) {
3605     Method* m = _old_methods->at(j);
3606     RC_TRACE_NO_CR(0x00004000, ("%4d  (%5d)  ", j, m->vtable_index()));
3607     m->access_flags().print_on(tty);
3608     tty->print(" --  ");
3609     m->print_name(tty);
3610     tty->cr();
3611   }
3612   RC_TRACE(0x00004000, ("_new_methods --"));
3613   for (j = 0; j < _new_methods->length(); ++j) {
3614     Method* m = _new_methods->at(j);
3615     RC_TRACE_NO_CR(0x00004000, ("%4d  (%5d)  ", j, m->vtable_index()));
3616     m->access_flags().print_on(tty);
3617     tty->print(" --  ");
3618     m->print_name(tty);
3619     tty->cr();
3620   }
3621   RC_TRACE(0x00004000, ("_matching_(old/new)_methods --"));
3622   for (j = 0; j < _matching_methods_length; ++j) {
3623     Method* m = _matching_old_methods[j];
3624     RC_TRACE_NO_CR(0x00004000, ("%4d  (%5d)  ", j, m->vtable_index()));
3625     m->access_flags().print_on(tty);
3626     tty->print(" --  ");
3627     m->print_name(tty);
3628     tty->cr();
3629     m = _matching_new_methods[j];
3630     RC_TRACE_NO_CR(0x00004000, ("      (%5d)  ", m->vtable_index()));
3631     m->access_flags().print_on(tty);
3632     tty->cr();
3633   }
3634   RC_TRACE(0x00004000, ("_deleted_methods --"));
3635   for (j = 0; j < _deleted_methods_length; ++j) {
3636     Method* m = _deleted_methods[j];
3637     RC_TRACE_NO_CR(0x00004000, ("%4d  (%5d)  ", j, m->vtable_index()));
3638     m->access_flags().print_on(tty);
3639     tty->print(" --  ");
3640     m->print_name(tty);
3641     tty->cr();
3642   }
3643   RC_TRACE(0x00004000, ("_added_methods --"));
3644   for (j = 0; j < _added_methods_length; ++j) {
3645     Method* m = _added_methods[j];
3646     RC_TRACE_NO_CR(0x00004000, ("%4d  (%5d)  ", j, m->vtable_index()));
3647     m->access_flags().print_on(tty);
3648     tty->print(" --  ");
3649     m->print_name(tty);
3650     tty->cr();
3651   }
3652 }