1 /*
   2  * Copyright (c) 2003, 2013, 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 
  47 Array<Method*>* VM_RedefineClasses::_old_methods = NULL;
  48 Array<Method*>* VM_RedefineClasses::_new_methods = NULL;
  49 Method**  VM_RedefineClasses::_matching_old_methods = NULL;
  50 Method**  VM_RedefineClasses::_matching_new_methods = NULL;
  51 Method**  VM_RedefineClasses::_deleted_methods      = NULL;
  52 Method**  VM_RedefineClasses::_added_methods        = NULL;
  53 int         VM_RedefineClasses::_matching_methods_length = 0;
  54 int         VM_RedefineClasses::_deleted_methods_length  = 0;
  55 int         VM_RedefineClasses::_added_methods_length    = 0;
  56 Klass*      VM_RedefineClasses::_the_class_oop = NULL;
  57 
  58 
  59 VM_RedefineClasses::VM_RedefineClasses(jint class_count,
  60                                        const jvmtiClassDefinition *class_defs,
  61                                        JvmtiClassLoadKind class_load_kind) {
  62   _class_count = class_count;
  63   _class_defs = class_defs;
  64   _class_load_kind = class_load_kind;
  65   _res = JVMTI_ERROR_NONE;
  66 }
  67 
  68 bool VM_RedefineClasses::doit_prologue() {
  69   if (_class_count == 0) {
  70     _res = JVMTI_ERROR_NONE;
  71     return false;
  72   }
  73   if (_class_defs == NULL) {
  74     _res = JVMTI_ERROR_NULL_POINTER;
  75     return false;
  76   }
  77   for (int i = 0; i < _class_count; i++) {
  78     if (_class_defs[i].klass == NULL) {
  79       _res = JVMTI_ERROR_INVALID_CLASS;
  80       return false;
  81     }
  82     if (_class_defs[i].class_byte_count == 0) {
  83       _res = JVMTI_ERROR_INVALID_CLASS_FORMAT;
  84       return false;
  85     }
  86     if (_class_defs[i].class_bytes == NULL) {
  87       _res = JVMTI_ERROR_NULL_POINTER;
  88       return false;
  89     }
  90   }
  91 
  92   // Start timer after all the sanity checks; not quite accurate, but
  93   // better than adding a bunch of stop() calls.
  94   RC_TIMER_START(_timer_vm_op_prologue);
  95 
  96   // We first load new class versions in the prologue, because somewhere down the
  97   // call chain it is required that the current thread is a Java thread.
  98   _res = load_new_class_versions(Thread::current());
  99   if (_res != JVMTI_ERROR_NONE) {
 100     // free any successfully created classes, since none are redefined
 101     for (int i = 0; i < _class_count; i++) {
 102       if (_scratch_classes[i] != NULL) {
 103         ClassLoaderData* cld = _scratch_classes[i]->class_loader_data();
 104         // Free the memory for this class at class unloading time.  Not before
 105         // because CMS might think this is still live.
 106         cld->add_to_deallocate_list((InstanceKlass*)_scratch_classes[i]);
 107       }
 108     }
 109     // Free os::malloc allocated memory in load_new_class_version.
 110     os::free(_scratch_classes);
 111     RC_TIMER_STOP(_timer_vm_op_prologue);
 112     return false;
 113   }
 114 
 115   RC_TIMER_STOP(_timer_vm_op_prologue);
 116   return true;
 117 }
 118 
 119 void VM_RedefineClasses::doit() {
 120   Thread *thread = Thread::current();
 121 
 122   if (UseSharedSpaces) {
 123     // Sharing is enabled so we remap the shared readonly space to
 124     // shared readwrite, private just in case we need to redefine
 125     // a shared class. We do the remap during the doit() phase of
 126     // the safepoint to be safer.
 127     if (!MetaspaceShared::remap_shared_readonly_as_readwrite()) {
 128       RC_TRACE_WITH_THREAD(0x00000001, thread,
 129         ("failed to remap shared readonly space to readwrite, private"));
 130       _res = JVMTI_ERROR_INTERNAL;
 131       return;
 132     }
 133   }
 134 
 135   // Mark methods seen on stack and everywhere else so old methods are not
 136   // cleaned up if they're on the stack.
 137   MetadataOnStackMark md_on_stack;
 138   HandleMark hm(thread);   // make sure any handles created are deleted
 139                            // before the stack walk again.
 140 
 141   for (int i = 0; i < _class_count; i++) {
 142     redefine_single_class(_class_defs[i].klass, _scratch_classes[i], thread);
 143     ClassLoaderData* cld = _scratch_classes[i]->class_loader_data();
 144     // Free the memory for this class at class unloading time.  Not before
 145     // because CMS might think this is still live.
 146     cld->add_to_deallocate_list((InstanceKlass*)_scratch_classes[i]);
 147     _scratch_classes[i] = NULL;
 148   }
 149 
 150   // Disable any dependent concurrent compilations
 151   SystemDictionary::notice_modification();
 152 
 153   // Set flag indicating that some invariants are no longer true.
 154   // See jvmtiExport.hpp for detailed explanation.
 155   JvmtiExport::set_has_redefined_a_class();
 156 
 157 // check_class() is optionally called for product bits, but is
 158 // always called for non-product bits.
 159 #ifdef PRODUCT
 160   if (RC_TRACE_ENABLED(0x00004000)) {
 161 #endif
 162     RC_TRACE_WITH_THREAD(0x00004000, thread, ("calling check_class"));
 163     CheckClass check_class(thread);
 164     ClassLoaderDataGraph::classes_do(&check_class);
 165 #ifdef PRODUCT
 166   }
 167 #endif
 168 }
 169 
 170 void VM_RedefineClasses::doit_epilogue() {
 171   // Free os::malloc allocated memory.
 172   os::free(_scratch_classes);
 173 
 174   if (RC_TRACE_ENABLED(0x00000004)) {
 175     // Used to have separate timers for "doit" and "all", but the timer
 176     // overhead skewed the measurements.
 177     jlong doit_time = _timer_rsc_phase1.milliseconds() +
 178                       _timer_rsc_phase2.milliseconds();
 179     jlong all_time = _timer_vm_op_prologue.milliseconds() + doit_time;
 180 
 181     RC_TRACE(0x00000004, ("vm_op: all=" UINT64_FORMAT
 182       "  prologue=" UINT64_FORMAT "  doit=" UINT64_FORMAT, all_time,
 183       _timer_vm_op_prologue.milliseconds(), doit_time));
 184     RC_TRACE(0x00000004,
 185       ("redefine_single_class: phase1=" UINT64_FORMAT "  phase2=" UINT64_FORMAT,
 186        _timer_rsc_phase1.milliseconds(), _timer_rsc_phase2.milliseconds()));
 187   }
 188 }
 189 
 190 bool VM_RedefineClasses::is_modifiable_class(oop klass_mirror) {
 191   // classes for primitives cannot be redefined
 192   if (java_lang_Class::is_primitive(klass_mirror)) {
 193     return false;
 194   }
 195   Klass* the_class_oop = java_lang_Class::as_Klass(klass_mirror);
 196   // classes for arrays cannot be redefined
 197   if (the_class_oop == NULL || !the_class_oop->oop_is_instance()) {
 198     return false;
 199   }
 200   return true;
 201 }
 202 
 203 // Append the current entry at scratch_i in scratch_cp to *merge_cp_p
 204 // where the end of *merge_cp_p is specified by *merge_cp_length_p. For
 205 // direct CP entries, there is just the current entry to append. For
 206 // indirect and double-indirect CP entries, there are zero or more
 207 // referenced CP entries along with the current entry to append.
 208 // Indirect and double-indirect CP entries are handled by recursive
 209 // calls to append_entry() as needed. The referenced CP entries are
 210 // always appended to *merge_cp_p before the referee CP entry. These
 211 // referenced CP entries may already exist in *merge_cp_p in which case
 212 // there is nothing extra to append and only the current entry is
 213 // appended.
 214 void VM_RedefineClasses::append_entry(constantPoolHandle scratch_cp,
 215        int scratch_i, constantPoolHandle *merge_cp_p, int *merge_cp_length_p,
 216        TRAPS) {
 217 
 218   // append is different depending on entry tag type
 219   switch (scratch_cp->tag_at(scratch_i).value()) {
 220 
 221     // The old verifier is implemented outside the VM. It loads classes,
 222     // but does not resolve constant pool entries directly so we never
 223     // see Class entries here with the old verifier. Similarly the old
 224     // verifier does not like Class entries in the input constant pool.
 225     // The split-verifier is implemented in the VM so it can optionally
 226     // and directly resolve constant pool entries to load classes. The
 227     // split-verifier can accept either Class entries or UnresolvedClass
 228     // entries in the input constant pool. We revert the appended copy
 229     // back to UnresolvedClass so that either verifier will be happy
 230     // with the constant pool entry.
 231     case JVM_CONSTANT_Class:
 232     {
 233       // revert the copy to JVM_CONSTANT_UnresolvedClass
 234       (*merge_cp_p)->unresolved_klass_at_put(*merge_cp_length_p,
 235         scratch_cp->klass_name_at(scratch_i));
 236 
 237       if (scratch_i != *merge_cp_length_p) {
 238         // The new entry in *merge_cp_p is at a different index than
 239         // the new entry in scratch_cp so we need to map the index values.
 240         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 241       }
 242       (*merge_cp_length_p)++;
 243     } break;
 244 
 245     // these are direct CP entries so they can be directly appended,
 246     // but double and long take two constant pool entries
 247     case JVM_CONSTANT_Double:  // fall through
 248     case JVM_CONSTANT_Long:
 249     {
 250       ConstantPool::copy_entry_to(scratch_cp, scratch_i, *merge_cp_p, *merge_cp_length_p,
 251         THREAD);
 252 
 253       if (scratch_i != *merge_cp_length_p) {
 254         // The new entry in *merge_cp_p is at a different index than
 255         // the new entry in scratch_cp so we need to map the index values.
 256         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 257       }
 258       (*merge_cp_length_p) += 2;
 259     } break;
 260 
 261     // these are direct CP entries so they can be directly appended
 262     case JVM_CONSTANT_Float:   // fall through
 263     case JVM_CONSTANT_Integer: // fall through
 264     case JVM_CONSTANT_Utf8:    // fall through
 265 
 266     // This was an indirect CP entry, but it has been changed into
 267     // Symbol*s so this entry can be directly appended.
 268     case JVM_CONSTANT_String:      // fall through
 269 
 270     // These were indirect CP entries, but they have been changed into
 271     // Symbol*s so these entries can be directly appended.
 272     case JVM_CONSTANT_UnresolvedClass:  // fall through
 273     {
 274       ConstantPool::copy_entry_to(scratch_cp, scratch_i, *merge_cp_p, *merge_cp_length_p,
 275         THREAD);
 276 
 277       if (scratch_i != *merge_cp_length_p) {
 278         // The new entry in *merge_cp_p is at a different index than
 279         // the new entry in scratch_cp so we need to map the index values.
 280         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 281       }
 282       (*merge_cp_length_p)++;
 283     } break;
 284 
 285     // this is an indirect CP entry so it needs special handling
 286     case JVM_CONSTANT_NameAndType:
 287     {
 288       int name_ref_i = scratch_cp->name_ref_index_at(scratch_i);
 289       int new_name_ref_i = find_or_append_indirect_entry(scratch_cp, name_ref_i, merge_cp_p,
 290                                                          merge_cp_length_p, THREAD);
 291 
 292       int signature_ref_i = scratch_cp->signature_ref_index_at(scratch_i);
 293       int new_signature_ref_i = find_or_append_indirect_entry(scratch_cp, signature_ref_i,
 294                                                               merge_cp_p, merge_cp_length_p,
 295                                                               THREAD);
 296 
 297       // If the referenced entries already exist in *merge_cp_p, then
 298       // both new_name_ref_i and new_signature_ref_i will both be 0.
 299       // In that case, all we are appending is the current entry.
 300       if (new_name_ref_i != name_ref_i) {
 301         RC_TRACE(0x00080000,
 302           ("NameAndType entry@%d name_ref_index change: %d to %d",
 303           *merge_cp_length_p, name_ref_i, new_name_ref_i));
 304       }
 305       if (new_signature_ref_i != signature_ref_i) {
 306         RC_TRACE(0x00080000,
 307           ("NameAndType entry@%d signature_ref_index change: %d to %d",
 308           *merge_cp_length_p, signature_ref_i, new_signature_ref_i));
 309       }
 310 
 311       (*merge_cp_p)->name_and_type_at_put(*merge_cp_length_p,
 312         new_name_ref_i, new_signature_ref_i);
 313       if (scratch_i != *merge_cp_length_p) {
 314         // The new entry in *merge_cp_p is at a different index than
 315         // the new entry in scratch_cp so we need to map the index values.
 316         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 317       }
 318       (*merge_cp_length_p)++;
 319     } break;
 320 
 321     // this is a double-indirect CP entry so it needs special handling
 322     case JVM_CONSTANT_Fieldref:           // fall through
 323     case JVM_CONSTANT_InterfaceMethodref: // fall through
 324     case JVM_CONSTANT_Methodref:
 325     {
 326       int klass_ref_i = scratch_cp->uncached_klass_ref_index_at(scratch_i);
 327       int new_klass_ref_i = find_or_append_indirect_entry(scratch_cp, klass_ref_i,
 328                                                           merge_cp_p, merge_cp_length_p, THREAD);
 329 
 330       int name_and_type_ref_i = scratch_cp->uncached_name_and_type_ref_index_at(scratch_i);
 331       int new_name_and_type_ref_i = find_or_append_indirect_entry(scratch_cp, name_and_type_ref_i,
 332                                                           merge_cp_p, merge_cp_length_p, THREAD);
 333 
 334       const char *entry_name;
 335       switch (scratch_cp->tag_at(scratch_i).value()) {
 336       case JVM_CONSTANT_Fieldref:
 337         entry_name = "Fieldref";
 338         (*merge_cp_p)->field_at_put(*merge_cp_length_p, new_klass_ref_i,
 339           new_name_and_type_ref_i);
 340         break;
 341       case JVM_CONSTANT_InterfaceMethodref:
 342         entry_name = "IFMethodref";
 343         (*merge_cp_p)->interface_method_at_put(*merge_cp_length_p,
 344           new_klass_ref_i, new_name_and_type_ref_i);
 345         break;
 346       case JVM_CONSTANT_Methodref:
 347         entry_name = "Methodref";
 348         (*merge_cp_p)->method_at_put(*merge_cp_length_p, new_klass_ref_i,
 349           new_name_and_type_ref_i);
 350         break;
 351       default:
 352         guarantee(false, "bad switch");
 353         break;
 354       }
 355 
 356       if (klass_ref_i != new_klass_ref_i) {
 357         RC_TRACE(0x00080000, ("%s entry@%d class_index changed: %d to %d",
 358           entry_name, *merge_cp_length_p, klass_ref_i, new_klass_ref_i));
 359       }
 360       if (name_and_type_ref_i != new_name_and_type_ref_i) {
 361         RC_TRACE(0x00080000,
 362           ("%s entry@%d name_and_type_index changed: %d to %d",
 363           entry_name, *merge_cp_length_p, name_and_type_ref_i,
 364           new_name_and_type_ref_i));
 365       }
 366 
 367       if (scratch_i != *merge_cp_length_p) {
 368         // The new entry in *merge_cp_p is at a different index than
 369         // the new entry in scratch_cp so we need to map the index values.
 370         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 371       }
 372       (*merge_cp_length_p)++;
 373     } break;
 374 
 375     // this is an indirect CP entry so it needs special handling
 376     case JVM_CONSTANT_MethodType:
 377     {
 378       int ref_i = scratch_cp->method_type_index_at(scratch_i);
 379       int new_ref_i = find_or_append_indirect_entry(scratch_cp, ref_i, merge_cp_p,
 380                                                     merge_cp_length_p, THREAD);
 381       if (new_ref_i != ref_i) {
 382         RC_TRACE(0x00080000,
 383                  ("MethodType entry@%d ref_index change: %d to %d",
 384                   *merge_cp_length_p, ref_i, new_ref_i));
 385       }
 386       (*merge_cp_p)->method_type_index_at_put(*merge_cp_length_p, new_ref_i);
 387       if (scratch_i != *merge_cp_length_p) {
 388         // The new entry in *merge_cp_p is at a different index than
 389         // the new entry in scratch_cp so we need to map the index values.
 390         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 391       }
 392       (*merge_cp_length_p)++;
 393     } break;
 394 
 395     // this is an indirect CP entry so it needs special handling
 396     case JVM_CONSTANT_MethodHandle:
 397     {
 398       int ref_kind = scratch_cp->method_handle_ref_kind_at(scratch_i);
 399       int ref_i = scratch_cp->method_handle_index_at(scratch_i);
 400       int new_ref_i = find_or_append_indirect_entry(scratch_cp, ref_i, merge_cp_p,
 401                                                     merge_cp_length_p, THREAD);
 402       if (new_ref_i != ref_i) {
 403         RC_TRACE(0x00080000,
 404                  ("MethodHandle entry@%d ref_index change: %d to %d",
 405                   *merge_cp_length_p, ref_i, new_ref_i));
 406       }
 407       (*merge_cp_p)->method_handle_index_at_put(*merge_cp_length_p, ref_kind, new_ref_i);
 408       if (scratch_i != *merge_cp_length_p) {
 409         // The new entry in *merge_cp_p is at a different index than
 410         // the new entry in scratch_cp so we need to map the index values.
 411         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 412       }
 413       (*merge_cp_length_p)++;
 414     } break;
 415 
 416     // this is an indirect CP entry so it needs special handling
 417     case JVM_CONSTANT_InvokeDynamic:
 418     {
 419       // Index of the bootstrap specifier in the operands array
 420       int old_bs_i = scratch_cp->invoke_dynamic_bootstrap_specifier_index(scratch_i);
 421       int new_bs_i = find_or_append_operand(scratch_cp, old_bs_i, merge_cp_p,
 422                                             merge_cp_length_p, THREAD);
 423       // The bootstrap method NameAndType_info index
 424       int old_ref_i = scratch_cp->invoke_dynamic_name_and_type_ref_index_at(scratch_i);
 425       int new_ref_i = find_or_append_indirect_entry(scratch_cp, old_ref_i, merge_cp_p,
 426                                                     merge_cp_length_p, THREAD);
 427       if (new_bs_i != old_bs_i) {
 428         RC_TRACE(0x00080000,
 429                  ("InvokeDynamic entry@%d bootstrap_method_attr_index change: %d to %d",
 430                   *merge_cp_length_p, old_bs_i, new_bs_i));
 431       }
 432       if (new_ref_i != old_ref_i) {
 433         RC_TRACE(0x00080000,
 434                  ("InvokeDynamic entry@%d name_and_type_index change: %d to %d",
 435                   *merge_cp_length_p, old_ref_i, new_ref_i));
 436       }
 437 
 438       (*merge_cp_p)->invoke_dynamic_at_put(*merge_cp_length_p, new_bs_i, new_ref_i);
 439       if (scratch_i != *merge_cp_length_p) {
 440         // The new entry in *merge_cp_p is at a different index than
 441         // the new entry in scratch_cp so we need to map the index values.
 442         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 443       }
 444       (*merge_cp_length_p)++;
 445     } break;
 446 
 447     // At this stage, Class or UnresolvedClass could be here, but not
 448     // ClassIndex
 449     case JVM_CONSTANT_ClassIndex: // fall through
 450 
 451     // Invalid is used as the tag for the second constant pool entry
 452     // occupied by JVM_CONSTANT_Double or JVM_CONSTANT_Long. It should
 453     // not be seen by itself.
 454     case JVM_CONSTANT_Invalid: // fall through
 455 
 456     // At this stage, String could be here, but not StringIndex
 457     case JVM_CONSTANT_StringIndex: // fall through
 458 
 459     // At this stage JVM_CONSTANT_UnresolvedClassInError should not be
 460     // here
 461     case JVM_CONSTANT_UnresolvedClassInError: // fall through
 462 
 463     default:
 464     {
 465       // leave a breadcrumb
 466       jbyte bad_value = scratch_cp->tag_at(scratch_i).value();
 467       ShouldNotReachHere();
 468     } break;
 469   } // end switch tag value
 470 } // end append_entry()
 471 
 472 
 473 int VM_RedefineClasses::find_or_append_indirect_entry(constantPoolHandle scratch_cp,
 474       int ref_i, constantPoolHandle *merge_cp_p, int *merge_cp_length_p, TRAPS) {
 475 
 476   int new_ref_i = ref_i;
 477   bool match = (ref_i < *merge_cp_length_p) &&
 478                scratch_cp->compare_entry_to(ref_i, *merge_cp_p, ref_i, THREAD);
 479 
 480   if (!match) {
 481     // forward reference in *merge_cp_p or not a direct match
 482     int found_i = scratch_cp->find_matching_entry(ref_i, *merge_cp_p, THREAD);
 483     if (found_i != 0) {
 484       guarantee(found_i != ref_i, "compare_entry_to() and find_matching_entry() do not agree");
 485       // Found a matching entry somewhere else in *merge_cp_p so just need a mapping entry.
 486       new_ref_i = found_i;
 487       map_index(scratch_cp, ref_i, found_i);
 488     } else {
 489       // no match found so we have to append this entry to *merge_cp_p
 490       append_entry(scratch_cp, ref_i, merge_cp_p, merge_cp_length_p, THREAD);
 491       // The above call to append_entry() can only append one entry
 492       // so the post call query of *merge_cp_length_p is only for
 493       // the sake of consistency.
 494       new_ref_i = *merge_cp_length_p - 1;
 495     }
 496   }
 497 
 498   return new_ref_i;
 499 } // end find_or_append_indirect_entry()
 500 
 501 
 502 // Append a bootstrap specifier into the merge_cp operands that is semantically equal
 503 // to the scratch_cp operands bootstrap specifier passed by the old_bs_i index.
 504 // Recursively append new merge_cp entries referenced by the new bootstrap specifier.
 505 void VM_RedefineClasses::append_operand(constantPoolHandle scratch_cp, int old_bs_i,
 506        constantPoolHandle *merge_cp_p, int *merge_cp_length_p, TRAPS) {
 507 
 508   int old_ref_i = scratch_cp->operand_bootstrap_method_ref_index_at(old_bs_i);
 509   int new_ref_i = find_or_append_indirect_entry(scratch_cp, old_ref_i, merge_cp_p,
 510                                                 merge_cp_length_p, THREAD);
 511   if (new_ref_i != old_ref_i) {
 512     RC_TRACE(0x00080000,
 513              ("operands entry@%d bootstrap method ref_index change: %d to %d",
 514               _operands_cur_length, old_ref_i, new_ref_i));
 515   }
 516 
 517   Array<u2>* merge_ops = (*merge_cp_p)->operands();
 518   int new_bs_i = _operands_cur_length;
 519   // We have _operands_cur_length == 0 when the merge_cp operands is empty yet.
 520   // However, the operand_offset_at(0) was set in the extend_operands() call.
 521   int new_base = (new_bs_i == 0) ? (*merge_cp_p)->operand_offset_at(0)
 522                                  : (*merge_cp_p)->operand_next_offset_at(new_bs_i - 1);
 523   int argc     = scratch_cp->operand_argument_count_at(old_bs_i);
 524 
 525   ConstantPool::operand_offset_at_put(merge_ops, _operands_cur_length, new_base);
 526   merge_ops->at_put(new_base++, new_ref_i);
 527   merge_ops->at_put(new_base++, argc);
 528 
 529   for (int i = 0; i < argc; i++) {
 530     int old_arg_ref_i = scratch_cp->operand_argument_index_at(old_bs_i, i);
 531     int new_arg_ref_i = find_or_append_indirect_entry(scratch_cp, old_arg_ref_i, merge_cp_p,
 532                                                       merge_cp_length_p, THREAD);
 533     merge_ops->at_put(new_base++, new_arg_ref_i);
 534     if (new_arg_ref_i != old_arg_ref_i) {
 535       RC_TRACE(0x00080000,
 536                ("operands entry@%d bootstrap method argument ref_index change: %d to %d",
 537                 _operands_cur_length, old_arg_ref_i, new_arg_ref_i));
 538     }
 539   }
 540   if (old_bs_i != _operands_cur_length) {
 541     // The bootstrap specifier in *merge_cp_p is at a different index than
 542     // that in scratch_cp so we need to map the index values.
 543     map_operand_index(old_bs_i, new_bs_i);
 544   }
 545   _operands_cur_length++;
 546 } // end append_operand()
 547 
 548 
 549 int VM_RedefineClasses::find_or_append_operand(constantPoolHandle scratch_cp,
 550       int old_bs_i, constantPoolHandle *merge_cp_p, int *merge_cp_length_p, TRAPS) {
 551 
 552   int new_bs_i = old_bs_i; // bootstrap specifier index
 553   bool match = (old_bs_i < _operands_cur_length) &&
 554                scratch_cp->compare_operand_to(old_bs_i, *merge_cp_p, old_bs_i, THREAD);
 555 
 556   if (!match) {
 557     // forward reference in *merge_cp_p or not a direct match
 558     int found_i = scratch_cp->find_matching_operand(old_bs_i, *merge_cp_p,
 559                                                     _operands_cur_length, THREAD);
 560     if (found_i != -1) {
 561       guarantee(found_i != old_bs_i, "compare_operand_to() and find_matching_operand() disagree");
 562       // found a matching operand somewhere else in *merge_cp_p so just need a mapping
 563       new_bs_i = found_i;
 564       map_operand_index(old_bs_i, found_i);
 565     } else {
 566       // no match found so we have to append this bootstrap specifier to *merge_cp_p
 567       append_operand(scratch_cp, old_bs_i, merge_cp_p, merge_cp_length_p, THREAD);
 568       new_bs_i = _operands_cur_length - 1;
 569     }
 570   }
 571   return new_bs_i;
 572 } // end find_or_append_operand()
 573 
 574 
 575 void VM_RedefineClasses::finalize_operands_merge(constantPoolHandle merge_cp, TRAPS) {
 576   if (merge_cp->operands() == NULL) {
 577     return;
 578   }
 579   // Shrink the merge_cp operands
 580   merge_cp->shrink_operands(_operands_cur_length, CHECK);
 581 
 582   if (RC_TRACE_ENABLED(0x00040000)) {
 583     // don't want to loop unless we are tracing
 584     int count = 0;
 585     for (int i = 1; i < _operands_index_map_p->length(); i++) {
 586       int value = _operands_index_map_p->at(i);
 587       if (value != -1) {
 588         RC_TRACE_WITH_THREAD(0x00040000, THREAD,
 589           ("operands_index_map[%d]: old=%d new=%d", count, i, value));
 590         count++;
 591       }
 592     }
 593   }
 594   // Clean-up
 595   _operands_index_map_p = NULL;
 596   _operands_cur_length = 0;
 597   _operands_index_map_count = 0;
 598 } // end finalize_operands_merge()
 599 
 600 
 601 jvmtiError VM_RedefineClasses::compare_and_normalize_class_versions(
 602              instanceKlassHandle the_class,
 603              instanceKlassHandle scratch_class) {
 604   int i;
 605 
 606   // Check superclasses, or rather their names, since superclasses themselves can be
 607   // requested to replace.
 608   // Check for NULL superclass first since this might be java.lang.Object
 609   if (the_class->super() != scratch_class->super() &&
 610       (the_class->super() == NULL || scratch_class->super() == NULL ||
 611        the_class->super()->name() !=
 612        scratch_class->super()->name())) {
 613     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_HIERARCHY_CHANGED;
 614   }
 615 
 616   // Check if the number, names and order of directly implemented interfaces are the same.
 617   // I think in principle we should just check if the sets of names of directly implemented
 618   // interfaces are the same, i.e. the order of declaration (which, however, if changed in the
 619   // .java file, also changes in .class file) should not matter. However, comparing sets is
 620   // technically a bit more difficult, and, more importantly, I am not sure at present that the
 621   // order of interfaces does not matter on the implementation level, i.e. that the VM does not
 622   // rely on it somewhere.
 623   Array<Klass*>* k_interfaces = the_class->local_interfaces();
 624   Array<Klass*>* k_new_interfaces = scratch_class->local_interfaces();
 625   int n_intfs = k_interfaces->length();
 626   if (n_intfs != k_new_interfaces->length()) {
 627     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_HIERARCHY_CHANGED;
 628   }
 629   for (i = 0; i < n_intfs; i++) {
 630     if (k_interfaces->at(i)->name() !=
 631         k_new_interfaces->at(i)->name()) {
 632       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_HIERARCHY_CHANGED;
 633     }
 634   }
 635 
 636   // Check whether class is in the error init state.
 637   if (the_class->is_in_error_state()) {
 638     // TBD #5057930: special error code is needed in 1.6
 639     return JVMTI_ERROR_INVALID_CLASS;
 640   }
 641 
 642   // Check whether class modifiers are the same.
 643   jushort old_flags = (jushort) the_class->access_flags().get_flags();
 644   jushort new_flags = (jushort) scratch_class->access_flags().get_flags();
 645   if (old_flags != new_flags) {
 646     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_MODIFIERS_CHANGED;
 647   }
 648 
 649   // Check if the number, names, types and order of fields declared in these classes
 650   // are the same.
 651   JavaFieldStream old_fs(the_class);
 652   JavaFieldStream new_fs(scratch_class);
 653   for (; !old_fs.done() && !new_fs.done(); old_fs.next(), new_fs.next()) {
 654     // access
 655     old_flags = old_fs.access_flags().as_short();
 656     new_flags = new_fs.access_flags().as_short();
 657     if ((old_flags ^ new_flags) & JVM_RECOGNIZED_FIELD_MODIFIERS) {
 658       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_SCHEMA_CHANGED;
 659     }
 660     // offset
 661     if (old_fs.offset() != new_fs.offset()) {
 662       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_SCHEMA_CHANGED;
 663     }
 664     // name and signature
 665     Symbol* name_sym1 = the_class->constants()->symbol_at(old_fs.name_index());
 666     Symbol* sig_sym1 = the_class->constants()->symbol_at(old_fs.signature_index());
 667     Symbol* name_sym2 = scratch_class->constants()->symbol_at(new_fs.name_index());
 668     Symbol* sig_sym2 = scratch_class->constants()->symbol_at(new_fs.signature_index());
 669     if (name_sym1 != name_sym2 || sig_sym1 != sig_sym2) {
 670       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_SCHEMA_CHANGED;
 671     }
 672   }
 673 
 674   // If both streams aren't done then we have a differing number of
 675   // fields.
 676   if (!old_fs.done() || !new_fs.done()) {
 677     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_SCHEMA_CHANGED;
 678   }
 679 
 680   // Do a parallel walk through the old and new methods. Detect
 681   // cases where they match (exist in both), have been added in
 682   // the new methods, or have been deleted (exist only in the
 683   // old methods).  The class file parser places methods in order
 684   // by method name, but does not order overloaded methods by
 685   // signature.  In order to determine what fate befell the methods,
 686   // this code places the overloaded new methods that have matching
 687   // old methods in the same order as the old methods and places
 688   // new overloaded methods at the end of overloaded methods of
 689   // that name. The code for this order normalization is adapted
 690   // from the algorithm used in InstanceKlass::find_method().
 691   // Since we are swapping out of order entries as we find them,
 692   // we only have to search forward through the overloaded methods.
 693   // Methods which are added and have the same name as an existing
 694   // method (but different signature) will be put at the end of
 695   // the methods with that name, and the name mismatch code will
 696   // handle them.
 697   Array<Method*>* k_old_methods(the_class->methods());
 698   Array<Method*>* k_new_methods(scratch_class->methods());
 699   int n_old_methods = k_old_methods->length();
 700   int n_new_methods = k_new_methods->length();
 701   Thread* thread = Thread::current();
 702 
 703   int ni = 0;
 704   int oi = 0;
 705   while (true) {
 706     Method* k_old_method;
 707     Method* k_new_method;
 708     enum { matched, added, deleted, undetermined } method_was = undetermined;
 709 
 710     if (oi >= n_old_methods) {
 711       if (ni >= n_new_methods) {
 712         break; // we've looked at everything, done
 713       }
 714       // New method at the end
 715       k_new_method = k_new_methods->at(ni);
 716       method_was = added;
 717     } else if (ni >= n_new_methods) {
 718       // Old method, at the end, is deleted
 719       k_old_method = k_old_methods->at(oi);
 720       method_was = deleted;
 721     } else {
 722       // There are more methods in both the old and new lists
 723       k_old_method = k_old_methods->at(oi);
 724       k_new_method = k_new_methods->at(ni);
 725       if (k_old_method->name() != k_new_method->name()) {
 726         // Methods are sorted by method name, so a mismatch means added
 727         // or deleted
 728         if (k_old_method->name()->fast_compare(k_new_method->name()) > 0) {
 729           method_was = added;
 730         } else {
 731           method_was = deleted;
 732         }
 733       } else if (k_old_method->signature() == k_new_method->signature()) {
 734         // Both the name and signature match
 735         method_was = matched;
 736       } else {
 737         // The name matches, but the signature doesn't, which means we have to
 738         // search forward through the new overloaded methods.
 739         int nj;  // outside the loop for post-loop check
 740         for (nj = ni + 1; nj < n_new_methods; nj++) {
 741           Method* m = k_new_methods->at(nj);
 742           if (k_old_method->name() != m->name()) {
 743             // reached another method name so no more overloaded methods
 744             method_was = deleted;
 745             break;
 746           }
 747           if (k_old_method->signature() == m->signature()) {
 748             // found a match so swap the methods
 749             k_new_methods->at_put(ni, m);
 750             k_new_methods->at_put(nj, k_new_method);
 751             k_new_method = m;
 752             method_was = matched;
 753             break;
 754           }
 755         }
 756 
 757         if (nj >= n_new_methods) {
 758           // reached the end without a match; so method was deleted
 759           method_was = deleted;
 760         }
 761       }
 762     }
 763 
 764     switch (method_was) {
 765     case matched:
 766       // methods match, be sure modifiers do too
 767       old_flags = (jushort) k_old_method->access_flags().get_flags();
 768       new_flags = (jushort) k_new_method->access_flags().get_flags();
 769       if ((old_flags ^ new_flags) & ~(JVM_ACC_NATIVE)) {
 770         return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_METHOD_MODIFIERS_CHANGED;
 771       }
 772       {
 773         u2 new_num = k_new_method->method_idnum();
 774         u2 old_num = k_old_method->method_idnum();
 775         if (new_num != old_num) {
 776           Method* idnum_owner = scratch_class->method_with_idnum(old_num);
 777           if (idnum_owner != NULL) {
 778             // There is already a method assigned this idnum -- switch them
 779             idnum_owner->set_method_idnum(new_num);
 780           }
 781           k_new_method->set_method_idnum(old_num);
 782           if (thread->has_pending_exception()) {
 783             return JVMTI_ERROR_OUT_OF_MEMORY;
 784           }
 785         }
 786       }
 787       RC_TRACE(0x00008000, ("Method matched: new: %s [%d] == old: %s [%d]",
 788                             k_new_method->name_and_sig_as_C_string(), ni,
 789                             k_old_method->name_and_sig_as_C_string(), oi));
 790       // advance to next pair of methods
 791       ++oi;
 792       ++ni;
 793       break;
 794     case added:
 795       // method added, see if it is OK
 796       new_flags = (jushort) k_new_method->access_flags().get_flags();
 797       if ((new_flags & JVM_ACC_PRIVATE) == 0
 798            // hack: private should be treated as final, but alas
 799           || (new_flags & (JVM_ACC_FINAL|JVM_ACC_STATIC)) == 0
 800          ) {
 801         // new methods must be private
 802         return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_METHOD_ADDED;
 803       }
 804       {
 805         u2 num = the_class->next_method_idnum();
 806         if (num == ConstMethod::UNSET_IDNUM) {
 807           // cannot add any more methods
 808           return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_METHOD_ADDED;
 809         }
 810         u2 new_num = k_new_method->method_idnum();
 811         Method* idnum_owner = scratch_class->method_with_idnum(num);
 812         if (idnum_owner != NULL) {
 813           // There is already a method assigned this idnum -- switch them
 814           idnum_owner->set_method_idnum(new_num);
 815         }
 816         k_new_method->set_method_idnum(num);
 817         if (thread->has_pending_exception()) {
 818           return JVMTI_ERROR_OUT_OF_MEMORY;
 819         }
 820       }
 821       RC_TRACE(0x00008000, ("Method added: new: %s [%d]",
 822                             k_new_method->name_and_sig_as_C_string(), ni));
 823       ++ni; // advance to next new method
 824       break;
 825     case deleted:
 826       // method deleted, see if it is OK
 827       old_flags = (jushort) k_old_method->access_flags().get_flags();
 828       if ((old_flags & JVM_ACC_PRIVATE) == 0
 829            // hack: private should be treated as final, but alas
 830           || (old_flags & (JVM_ACC_FINAL|JVM_ACC_STATIC)) == 0
 831          ) {
 832         // deleted methods must be private
 833         return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_METHOD_DELETED;
 834       }
 835       RC_TRACE(0x00008000, ("Method deleted: old: %s [%d]",
 836                             k_old_method->name_and_sig_as_C_string(), oi));
 837       ++oi; // advance to next old method
 838       break;
 839     default:
 840       ShouldNotReachHere();
 841     }
 842   }
 843 
 844   return JVMTI_ERROR_NONE;
 845 }
 846 
 847 
 848 // Find new constant pool index value for old constant pool index value
 849 // by seaching the index map. Returns zero (0) if there is no mapped
 850 // value for the old constant pool index.
 851 int VM_RedefineClasses::find_new_index(int old_index) {
 852   if (_index_map_count == 0) {
 853     // map is empty so nothing can be found
 854     return 0;
 855   }
 856 
 857   if (old_index < 1 || old_index >= _index_map_p->length()) {
 858     // The old_index is out of range so it is not mapped. This should
 859     // not happen in regular constant pool merging use, but it can
 860     // happen if a corrupt annotation is processed.
 861     return 0;
 862   }
 863 
 864   int value = _index_map_p->at(old_index);
 865   if (value == -1) {
 866     // the old_index is not mapped
 867     return 0;
 868   }
 869 
 870   return value;
 871 } // end find_new_index()
 872 
 873 
 874 // Find new bootstrap specifier index value for old bootstrap specifier index
 875 // value by seaching the index map. Returns unused index (-1) if there is
 876 // no mapped value for the old bootstrap specifier index.
 877 int VM_RedefineClasses::find_new_operand_index(int old_index) {
 878   if (_operands_index_map_count == 0) {
 879     // map is empty so nothing can be found
 880     return -1;
 881   }
 882 
 883   if (old_index == -1 || old_index >= _operands_index_map_p->length()) {
 884     // The old_index is out of range so it is not mapped.
 885     // This should not happen in regular constant pool merging use.
 886     return -1;
 887   }
 888 
 889   int value = _operands_index_map_p->at(old_index);
 890   if (value == -1) {
 891     // the old_index is not mapped
 892     return -1;
 893   }
 894 
 895   return value;
 896 } // end find_new_operand_index()
 897 
 898 
 899 // Returns true if the current mismatch is due to a resolved/unresolved
 900 // class pair. Otherwise, returns false.
 901 bool VM_RedefineClasses::is_unresolved_class_mismatch(constantPoolHandle cp1,
 902        int index1, constantPoolHandle cp2, int index2) {
 903 
 904   jbyte t1 = cp1->tag_at(index1).value();
 905   if (t1 != JVM_CONSTANT_Class && t1 != JVM_CONSTANT_UnresolvedClass) {
 906     return false;  // wrong entry type; not our special case
 907   }
 908 
 909   jbyte t2 = cp2->tag_at(index2).value();
 910   if (t2 != JVM_CONSTANT_Class && t2 != JVM_CONSTANT_UnresolvedClass) {
 911     return false;  // wrong entry type; not our special case
 912   }
 913 
 914   if (t1 == t2) {
 915     return false;  // not a mismatch; not our special case
 916   }
 917 
 918   char *s1 = cp1->klass_name_at(index1)->as_C_string();
 919   char *s2 = cp2->klass_name_at(index2)->as_C_string();
 920   if (strcmp(s1, s2) != 0) {
 921     return false;  // strings don't match; not our special case
 922   }
 923 
 924   return true;  // made it through the gauntlet; this is our special case
 925 } // end is_unresolved_class_mismatch()
 926 
 927 
 928 jvmtiError VM_RedefineClasses::load_new_class_versions(TRAPS) {
 929 
 930   // For consistency allocate memory using os::malloc wrapper.
 931   _scratch_classes = (Klass**)
 932     os::malloc(sizeof(Klass*) * _class_count, mtClass);
 933   if (_scratch_classes == NULL) {
 934     return JVMTI_ERROR_OUT_OF_MEMORY;
 935   }
 936   // Zero initialize the _scratch_classes array.
 937   for (int i = 0; i < _class_count; i++) {
 938     _scratch_classes[i] = NULL;
 939   }
 940 
 941   ResourceMark rm(THREAD);
 942 
 943   JvmtiThreadState *state = JvmtiThreadState::state_for(JavaThread::current());
 944   // state can only be NULL if the current thread is exiting which
 945   // should not happen since we're trying to do a RedefineClasses
 946   guarantee(state != NULL, "exiting thread calling load_new_class_versions");
 947   for (int i = 0; i < _class_count; i++) {
 948     // Create HandleMark so that any handles created while loading new class
 949     // versions are deleted. Constant pools are deallocated while merging
 950     // constant pools
 951     HandleMark hm(THREAD);
 952 
 953     oop mirror = JNIHandles::resolve_non_null(_class_defs[i].klass);
 954     // classes for primitives cannot be redefined
 955     if (!is_modifiable_class(mirror)) {
 956       return JVMTI_ERROR_UNMODIFIABLE_CLASS;
 957     }
 958     Klass* the_class_oop = java_lang_Class::as_Klass(mirror);
 959     instanceKlassHandle the_class = instanceKlassHandle(THREAD, the_class_oop);
 960     Symbol*  the_class_sym = the_class->name();
 961 
 962     // RC_TRACE_WITH_THREAD macro has an embedded ResourceMark
 963     RC_TRACE_WITH_THREAD(0x00000001, THREAD,
 964       ("loading name=%s kind=%d (avail_mem=" UINT64_FORMAT "K)",
 965       the_class->external_name(), _class_load_kind,
 966       os::available_memory() >> 10));
 967 
 968     ClassFileStream st((u1*) _class_defs[i].class_bytes,
 969       _class_defs[i].class_byte_count, (char *)"__VM_RedefineClasses__");
 970 
 971     // Parse the stream.
 972     Handle the_class_loader(THREAD, the_class->class_loader());
 973     Handle protection_domain(THREAD, the_class->protection_domain());
 974     // Set redefined class handle in JvmtiThreadState class.
 975     // This redefined class is sent to agent event handler for class file
 976     // load hook event.
 977     state->set_class_being_redefined(&the_class, _class_load_kind);
 978 
 979     Klass* k = SystemDictionary::parse_stream(the_class_sym,
 980                                                 the_class_loader,
 981                                                 protection_domain,
 982                                                 &st,
 983                                                 THREAD);
 984     // Clear class_being_redefined just to be sure.
 985     state->clear_class_being_redefined();
 986 
 987     // TODO: if this is retransform, and nothing changed we can skip it
 988 
 989     instanceKlassHandle scratch_class (THREAD, k);
 990 
 991     // Need to clean up allocated InstanceKlass if there's an error so assign
 992     // the result here. Caller deallocates all the scratch classes in case of
 993     // an error.
 994     _scratch_classes[i] = k;
 995 
 996     if (HAS_PENDING_EXCEPTION) {
 997       Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
 998       // RC_TRACE_WITH_THREAD macro has an embedded ResourceMark
 999       RC_TRACE_WITH_THREAD(0x00000002, THREAD, ("parse_stream exception: '%s'",
1000         ex_name->as_C_string()));
1001       CLEAR_PENDING_EXCEPTION;
1002 
1003       if (ex_name == vmSymbols::java_lang_UnsupportedClassVersionError()) {
1004         return JVMTI_ERROR_UNSUPPORTED_VERSION;
1005       } else if (ex_name == vmSymbols::java_lang_ClassFormatError()) {
1006         return JVMTI_ERROR_INVALID_CLASS_FORMAT;
1007       } else if (ex_name == vmSymbols::java_lang_ClassCircularityError()) {
1008         return JVMTI_ERROR_CIRCULAR_CLASS_DEFINITION;
1009       } else if (ex_name == vmSymbols::java_lang_NoClassDefFoundError()) {
1010         // The message will be "XXX (wrong name: YYY)"
1011         return JVMTI_ERROR_NAMES_DONT_MATCH;
1012       } else if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1013         return JVMTI_ERROR_OUT_OF_MEMORY;
1014       } else {  // Just in case more exceptions can be thrown..
1015         return JVMTI_ERROR_FAILS_VERIFICATION;
1016       }
1017     }
1018 
1019     // Ensure class is linked before redefine
1020     if (!the_class->is_linked()) {
1021       the_class->link_class(THREAD);
1022       if (HAS_PENDING_EXCEPTION) {
1023         Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1024         // RC_TRACE_WITH_THREAD macro has an embedded ResourceMark
1025         RC_TRACE_WITH_THREAD(0x00000002, THREAD, ("link_class exception: '%s'",
1026           ex_name->as_C_string()));
1027         CLEAR_PENDING_EXCEPTION;
1028         if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1029           return JVMTI_ERROR_OUT_OF_MEMORY;
1030         } else {
1031           return JVMTI_ERROR_INTERNAL;
1032         }
1033       }
1034     }
1035 
1036     // Do the validity checks in compare_and_normalize_class_versions()
1037     // before verifying the byte codes. By doing these checks first, we
1038     // limit the number of functions that require redirection from
1039     // the_class to scratch_class. In particular, we don't have to
1040     // modify JNI GetSuperclass() and thus won't change its performance.
1041     jvmtiError res = compare_and_normalize_class_versions(the_class,
1042                        scratch_class);
1043     if (res != JVMTI_ERROR_NONE) {
1044       return res;
1045     }
1046 
1047     // verify what the caller passed us
1048     {
1049       // The bug 6214132 caused the verification to fail.
1050       // Information about the_class and scratch_class is temporarily
1051       // recorded into jvmtiThreadState. This data is used to redirect
1052       // the_class to scratch_class in the JVM_* functions called by the
1053       // verifier. Please, refer to jvmtiThreadState.hpp for the detailed
1054       // description.
1055       RedefineVerifyMark rvm(&the_class, &scratch_class, state);
1056       Verifier::verify(
1057         scratch_class, Verifier::ThrowException, true, THREAD);
1058     }
1059 
1060     if (HAS_PENDING_EXCEPTION) {
1061       Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1062       // RC_TRACE_WITH_THREAD macro has an embedded ResourceMark
1063       RC_TRACE_WITH_THREAD(0x00000002, THREAD,
1064         ("verify_byte_codes exception: '%s'", ex_name->as_C_string()));
1065       CLEAR_PENDING_EXCEPTION;
1066       if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1067         return JVMTI_ERROR_OUT_OF_MEMORY;
1068       } else {
1069         // tell the caller the bytecodes are bad
1070         return JVMTI_ERROR_FAILS_VERIFICATION;
1071       }
1072     }
1073 
1074     res = merge_cp_and_rewrite(the_class, scratch_class, THREAD);
1075     if (res != JVMTI_ERROR_NONE) {
1076       return res;
1077     }
1078 
1079     if (VerifyMergedCPBytecodes) {
1080       // verify what we have done during constant pool merging
1081       {
1082         RedefineVerifyMark rvm(&the_class, &scratch_class, state);
1083         Verifier::verify(scratch_class, Verifier::ThrowException, true, THREAD);
1084       }
1085 
1086       if (HAS_PENDING_EXCEPTION) {
1087         Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1088         // RC_TRACE_WITH_THREAD macro has an embedded ResourceMark
1089         RC_TRACE_WITH_THREAD(0x00000002, THREAD,
1090           ("verify_byte_codes post merge-CP exception: '%s'",
1091           ex_name->as_C_string()));
1092         CLEAR_PENDING_EXCEPTION;
1093         if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1094           return JVMTI_ERROR_OUT_OF_MEMORY;
1095         } else {
1096           // tell the caller that constant pool merging screwed up
1097           return JVMTI_ERROR_INTERNAL;
1098         }
1099       }
1100     }
1101 
1102     Rewriter::rewrite(scratch_class, THREAD);
1103     if (!HAS_PENDING_EXCEPTION) {
1104       scratch_class->link_methods(THREAD);
1105     }
1106     if (HAS_PENDING_EXCEPTION) {
1107       Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1108       CLEAR_PENDING_EXCEPTION;
1109       if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1110         return JVMTI_ERROR_OUT_OF_MEMORY;
1111       } else {
1112         return JVMTI_ERROR_INTERNAL;
1113       }
1114     }
1115 
1116     // RC_TRACE_WITH_THREAD macro has an embedded ResourceMark
1117     RC_TRACE_WITH_THREAD(0x00000001, THREAD,
1118       ("loaded name=%s (avail_mem=" UINT64_FORMAT "K)",
1119       the_class->external_name(), os::available_memory() >> 10));
1120   }
1121 
1122   return JVMTI_ERROR_NONE;
1123 }
1124 
1125 
1126 // Map old_index to new_index as needed. scratch_cp is only needed
1127 // for RC_TRACE() calls.
1128 void VM_RedefineClasses::map_index(constantPoolHandle scratch_cp,
1129        int old_index, int new_index) {
1130   if (find_new_index(old_index) != 0) {
1131     // old_index is already mapped
1132     return;
1133   }
1134 
1135   if (old_index == new_index) {
1136     // no mapping is needed
1137     return;
1138   }
1139 
1140   _index_map_p->at_put(old_index, new_index);
1141   _index_map_count++;
1142 
1143   RC_TRACE(0x00040000, ("mapped tag %d at index %d to %d",
1144     scratch_cp->tag_at(old_index).value(), old_index, new_index));
1145 } // end map_index()
1146 
1147 
1148 // Map old_index to new_index as needed.
1149 void VM_RedefineClasses::map_operand_index(int old_index, int new_index) {
1150   if (find_new_operand_index(old_index) != -1) {
1151     // old_index is already mapped
1152     return;
1153   }
1154 
1155   if (old_index == new_index) {
1156     // no mapping is needed
1157     return;
1158   }
1159 
1160   _operands_index_map_p->at_put(old_index, new_index);
1161   _operands_index_map_count++;
1162 
1163   RC_TRACE(0x00040000, ("mapped bootstrap specifier at index %d to %d", old_index, new_index));
1164 } // end map_index()
1165 
1166 
1167 // Merge old_cp and scratch_cp and return the results of the merge via
1168 // merge_cp_p. The number of entries in *merge_cp_p is returned via
1169 // merge_cp_length_p. The entries in old_cp occupy the same locations
1170 // in *merge_cp_p. Also creates a map of indices from entries in
1171 // scratch_cp to the corresponding entry in *merge_cp_p. Index map
1172 // entries are only created for entries in scratch_cp that occupy a
1173 // different location in *merged_cp_p.
1174 bool VM_RedefineClasses::merge_constant_pools(constantPoolHandle old_cp,
1175        constantPoolHandle scratch_cp, constantPoolHandle *merge_cp_p,
1176        int *merge_cp_length_p, TRAPS) {
1177 
1178   if (merge_cp_p == NULL) {
1179     assert(false, "caller must provide scratch constantPool");
1180     return false; // robustness
1181   }
1182   if (merge_cp_length_p == NULL) {
1183     assert(false, "caller must provide scratch CP length");
1184     return false; // robustness
1185   }
1186   // Worst case we need old_cp->length() + scratch_cp()->length(),
1187   // but the caller might be smart so make sure we have at least
1188   // the minimum.
1189   if ((*merge_cp_p)->length() < old_cp->length()) {
1190     assert(false, "merge area too small");
1191     return false; // robustness
1192   }
1193 
1194   RC_TRACE_WITH_THREAD(0x00010000, THREAD,
1195     ("old_cp_len=%d, scratch_cp_len=%d", old_cp->length(),
1196     scratch_cp->length()));
1197 
1198   {
1199     // Pass 0:
1200     // The old_cp is copied to *merge_cp_p; this means that any code
1201     // using old_cp does not have to change. This work looks like a
1202     // perfect fit for ConstantPool*::copy_cp_to(), but we need to
1203     // handle one special case:
1204     // - revert JVM_CONSTANT_Class to JVM_CONSTANT_UnresolvedClass
1205     // This will make verification happy.
1206 
1207     int old_i;  // index into old_cp
1208 
1209     // index zero (0) is not used in constantPools
1210     for (old_i = 1; old_i < old_cp->length(); old_i++) {
1211       // leave debugging crumb
1212       jbyte old_tag = old_cp->tag_at(old_i).value();
1213       switch (old_tag) {
1214       case JVM_CONSTANT_Class:
1215       case JVM_CONSTANT_UnresolvedClass:
1216         // revert the copy to JVM_CONSTANT_UnresolvedClass
1217         // May be resolving while calling this so do the same for
1218         // JVM_CONSTANT_UnresolvedClass (klass_name_at() deals with transition)
1219         (*merge_cp_p)->unresolved_klass_at_put(old_i,
1220           old_cp->klass_name_at(old_i));
1221         break;
1222 
1223       case JVM_CONSTANT_Double:
1224       case JVM_CONSTANT_Long:
1225         // just copy the entry to *merge_cp_p, but double and long take
1226         // two constant pool entries
1227         ConstantPool::copy_entry_to(old_cp, old_i, *merge_cp_p, old_i, CHECK_0);
1228         old_i++;
1229         break;
1230 
1231       default:
1232         // just copy the entry to *merge_cp_p
1233         ConstantPool::copy_entry_to(old_cp, old_i, *merge_cp_p, old_i, CHECK_0);
1234         break;
1235       }
1236     } // end for each old_cp entry
1237 
1238     ConstantPool::copy_operands(old_cp, *merge_cp_p, CHECK_0);
1239     (*merge_cp_p)->extend_operands(scratch_cp, CHECK_0);
1240 
1241     // We don't need to sanity check that *merge_cp_length_p is within
1242     // *merge_cp_p bounds since we have the minimum on-entry check above.
1243     (*merge_cp_length_p) = old_i;
1244   }
1245 
1246   // merge_cp_len should be the same as old_cp->length() at this point
1247   // so this trace message is really a "warm-and-breathing" message.
1248   RC_TRACE_WITH_THREAD(0x00020000, THREAD,
1249     ("after pass 0: merge_cp_len=%d", *merge_cp_length_p));
1250 
1251   int scratch_i;  // index into scratch_cp
1252   {
1253     // Pass 1a:
1254     // Compare scratch_cp entries to the old_cp entries that we have
1255     // already copied to *merge_cp_p. In this pass, we are eliminating
1256     // exact duplicates (matching entry at same index) so we only
1257     // compare entries in the common indice range.
1258     int increment = 1;
1259     int pass1a_length = MIN2(old_cp->length(), scratch_cp->length());
1260     for (scratch_i = 1; scratch_i < pass1a_length; scratch_i += increment) {
1261       switch (scratch_cp->tag_at(scratch_i).value()) {
1262       case JVM_CONSTANT_Double:
1263       case JVM_CONSTANT_Long:
1264         // double and long take two constant pool entries
1265         increment = 2;
1266         break;
1267 
1268       default:
1269         increment = 1;
1270         break;
1271       }
1272 
1273       bool match = scratch_cp->compare_entry_to(scratch_i, *merge_cp_p,
1274         scratch_i, CHECK_0);
1275       if (match) {
1276         // found a match at the same index so nothing more to do
1277         continue;
1278       } else if (is_unresolved_class_mismatch(scratch_cp, scratch_i,
1279                                               *merge_cp_p, scratch_i)) {
1280         // The mismatch in compare_entry_to() above is because of a
1281         // resolved versus unresolved class entry at the same index
1282         // with the same string value. Since Pass 0 reverted any
1283         // class entries to unresolved class entries in *merge_cp_p,
1284         // we go with the unresolved class entry.
1285         continue;
1286       }
1287 
1288       int found_i = scratch_cp->find_matching_entry(scratch_i, *merge_cp_p,
1289         CHECK_0);
1290       if (found_i != 0) {
1291         guarantee(found_i != scratch_i,
1292           "compare_entry_to() and find_matching_entry() do not agree");
1293 
1294         // Found a matching entry somewhere else in *merge_cp_p so
1295         // just need a mapping entry.
1296         map_index(scratch_cp, scratch_i, found_i);
1297         continue;
1298       }
1299 
1300       // The find_matching_entry() call above could fail to find a match
1301       // due to a resolved versus unresolved class or string entry situation
1302       // like we solved above with the is_unresolved_*_mismatch() calls.
1303       // However, we would have to call is_unresolved_*_mismatch() over
1304       // all of *merge_cp_p (potentially) and that doesn't seem to be
1305       // worth the time.
1306 
1307       // No match found so we have to append this entry and any unique
1308       // referenced entries to *merge_cp_p.
1309       append_entry(scratch_cp, scratch_i, merge_cp_p, merge_cp_length_p,
1310         CHECK_0);
1311     }
1312   }
1313 
1314   RC_TRACE_WITH_THREAD(0x00020000, THREAD,
1315     ("after pass 1a: merge_cp_len=%d, scratch_i=%d, index_map_len=%d",
1316     *merge_cp_length_p, scratch_i, _index_map_count));
1317 
1318   if (scratch_i < scratch_cp->length()) {
1319     // Pass 1b:
1320     // old_cp is smaller than scratch_cp so there are entries in
1321     // scratch_cp that we have not yet processed. We take care of
1322     // those now.
1323     int increment = 1;
1324     for (; scratch_i < scratch_cp->length(); scratch_i += increment) {
1325       switch (scratch_cp->tag_at(scratch_i).value()) {
1326       case JVM_CONSTANT_Double:
1327       case JVM_CONSTANT_Long:
1328         // double and long take two constant pool entries
1329         increment = 2;
1330         break;
1331 
1332       default:
1333         increment = 1;
1334         break;
1335       }
1336 
1337       int found_i =
1338         scratch_cp->find_matching_entry(scratch_i, *merge_cp_p, CHECK_0);
1339       if (found_i != 0) {
1340         // Found a matching entry somewhere else in *merge_cp_p so
1341         // just need a mapping entry.
1342         map_index(scratch_cp, scratch_i, found_i);
1343         continue;
1344       }
1345 
1346       // No match found so we have to append this entry and any unique
1347       // referenced entries to *merge_cp_p.
1348       append_entry(scratch_cp, scratch_i, merge_cp_p, merge_cp_length_p,
1349         CHECK_0);
1350     }
1351 
1352     RC_TRACE_WITH_THREAD(0x00020000, THREAD,
1353       ("after pass 1b: merge_cp_len=%d, scratch_i=%d, index_map_len=%d",
1354       *merge_cp_length_p, scratch_i, _index_map_count));
1355   }
1356   finalize_operands_merge(*merge_cp_p, THREAD);
1357 
1358   return true;
1359 } // end merge_constant_pools()
1360 
1361 
1362 // Scoped object to clean up the constant pool(s) created for merging
1363 class MergeCPCleaner {
1364   ClassLoaderData*   _loader_data;
1365   ConstantPool*      _cp;
1366   ConstantPool*      _scratch_cp;
1367  public:
1368   MergeCPCleaner(ClassLoaderData* loader_data, ConstantPool* merge_cp) :
1369                  _loader_data(loader_data), _cp(merge_cp), _scratch_cp(NULL) {}
1370   ~MergeCPCleaner() {
1371     _loader_data->add_to_deallocate_list(_cp);
1372     if (_scratch_cp != NULL) {
1373       _loader_data->add_to_deallocate_list(_scratch_cp);
1374     }
1375   }
1376   void add_scratch_cp(ConstantPool* scratch_cp) { _scratch_cp = scratch_cp; }
1377 };
1378 
1379 // Merge constant pools between the_class and scratch_class and
1380 // potentially rewrite bytecodes in scratch_class to use the merged
1381 // constant pool.
1382 jvmtiError VM_RedefineClasses::merge_cp_and_rewrite(
1383              instanceKlassHandle the_class, instanceKlassHandle scratch_class,
1384              TRAPS) {
1385   // worst case merged constant pool length is old and new combined
1386   int merge_cp_length = the_class->constants()->length()
1387         + scratch_class->constants()->length();
1388 
1389   // Constant pools are not easily reused so we allocate a new one
1390   // each time.
1391   // merge_cp is created unsafe for concurrent GC processing.  It
1392   // should be marked safe before discarding it. Even though
1393   // garbage,  if it crosses a card boundary, it may be scanned
1394   // in order to find the start of the first complete object on the card.
1395   ClassLoaderData* loader_data = the_class->class_loader_data();
1396   ConstantPool* merge_cp_oop =
1397     ConstantPool::allocate(loader_data,
1398                                   merge_cp_length,
1399                                   THREAD);
1400   MergeCPCleaner cp_cleaner(loader_data, merge_cp_oop);
1401 
1402   HandleMark hm(THREAD);  // make sure handles are cleared before
1403                           // MergeCPCleaner clears out merge_cp_oop
1404   constantPoolHandle merge_cp(THREAD, merge_cp_oop);
1405 
1406   // Get constants() from the old class because it could have been rewritten
1407   // while we were at a safepoint allocating a new constant pool.
1408   constantPoolHandle old_cp(THREAD, the_class->constants());
1409   constantPoolHandle scratch_cp(THREAD, scratch_class->constants());
1410 
1411   // If the length changed, the class was redefined out from under us. Return
1412   // an error.
1413   if (merge_cp_length != the_class->constants()->length()
1414          + scratch_class->constants()->length()) {
1415     return JVMTI_ERROR_INTERNAL;
1416   }
1417 
1418   // Update the version number of the constant pool
1419   merge_cp->increment_and_save_version(old_cp->version());
1420 
1421   ResourceMark rm(THREAD);
1422   _index_map_count = 0;
1423   _index_map_p = new intArray(scratch_cp->length(), -1);
1424 
1425   _operands_cur_length = ConstantPool::operand_array_length(old_cp->operands());
1426   _operands_index_map_count = 0;
1427   _operands_index_map_p = new intArray(
1428     ConstantPool::operand_array_length(scratch_cp->operands()), -1);
1429 
1430   // reference to the cp holder is needed for copy_operands()
1431   merge_cp->set_pool_holder(scratch_class());
1432   bool result = merge_constant_pools(old_cp, scratch_cp, &merge_cp,
1433                   &merge_cp_length, THREAD);
1434   merge_cp->set_pool_holder(NULL);
1435 
1436   if (!result) {
1437     // The merge can fail due to memory allocation failure or due
1438     // to robustness checks.
1439     return JVMTI_ERROR_INTERNAL;
1440   }
1441 
1442   RC_TRACE_WITH_THREAD(0x00010000, THREAD,
1443     ("merge_cp_len=%d, index_map_len=%d", merge_cp_length, _index_map_count));
1444 
1445   if (_index_map_count == 0) {
1446     // there is nothing to map between the new and merged constant pools
1447 
1448     if (old_cp->length() == scratch_cp->length()) {
1449       // The old and new constant pools are the same length and the
1450       // index map is empty. This means that the three constant pools
1451       // are equivalent (but not the same). Unfortunately, the new
1452       // constant pool has not gone through link resolution nor have
1453       // the new class bytecodes gone through constant pool cache
1454       // rewriting so we can't use the old constant pool with the new
1455       // class.
1456 
1457       // toss the merged constant pool at return
1458     } else if (old_cp->length() < scratch_cp->length()) {
1459       // The old constant pool has fewer entries than the new constant
1460       // pool and the index map is empty. This means the new constant
1461       // pool is a superset of the old constant pool. However, the old
1462       // class bytecodes have already gone through constant pool cache
1463       // rewriting so we can't use the new constant pool with the old
1464       // class.
1465 
1466       // toss the merged constant pool at return
1467     } else {
1468       // The old constant pool has more entries than the new constant
1469       // pool and the index map is empty. This means that both the old
1470       // and merged constant pools are supersets of the new constant
1471       // pool.
1472 
1473       // Replace the new constant pool with a shrunken copy of the
1474       // merged constant pool
1475       set_new_constant_pool(loader_data, scratch_class, merge_cp, merge_cp_length, THREAD);
1476       // The new constant pool replaces scratch_cp so have cleaner clean it up.
1477       // It can't be cleaned up while there are handles to it.
1478       cp_cleaner.add_scratch_cp(scratch_cp());
1479     }
1480   } else {
1481     if (RC_TRACE_ENABLED(0x00040000)) {
1482       // don't want to loop unless we are tracing
1483       int count = 0;
1484       for (int i = 1; i < _index_map_p->length(); i++) {
1485         int value = _index_map_p->at(i);
1486 
1487         if (value != -1) {
1488           RC_TRACE_WITH_THREAD(0x00040000, THREAD,
1489             ("index_map[%d]: old=%d new=%d", count, i, value));
1490           count++;
1491         }
1492       }
1493     }
1494 
1495     // We have entries mapped between the new and merged constant pools
1496     // so we have to rewrite some constant pool references.
1497     if (!rewrite_cp_refs(scratch_class, THREAD)) {
1498       return JVMTI_ERROR_INTERNAL;
1499     }
1500 
1501     // Replace the new constant pool with a shrunken copy of the
1502     // merged constant pool so now the rewritten bytecodes have
1503     // valid references; the previous new constant pool will get
1504     // GCed.
1505     set_new_constant_pool(loader_data, scratch_class, merge_cp, merge_cp_length, THREAD);
1506     // The new constant pool replaces scratch_cp so have cleaner clean it up.
1507     // It can't be cleaned up while there are handles to it.
1508     cp_cleaner.add_scratch_cp(scratch_cp());
1509   }
1510 
1511   return JVMTI_ERROR_NONE;
1512 } // end merge_cp_and_rewrite()
1513 
1514 
1515 // Rewrite constant pool references in klass scratch_class.
1516 bool VM_RedefineClasses::rewrite_cp_refs(instanceKlassHandle scratch_class,
1517        TRAPS) {
1518 
1519   // rewrite constant pool references in the methods:
1520   if (!rewrite_cp_refs_in_methods(scratch_class, THREAD)) {
1521     // propagate failure back to caller
1522     return false;
1523   }
1524 
1525   // rewrite constant pool references in the class_annotations:
1526   if (!rewrite_cp_refs_in_class_annotations(scratch_class, THREAD)) {
1527     // propagate failure back to caller
1528     return false;
1529   }
1530 
1531   // rewrite constant pool references in the fields_annotations:
1532   if (!rewrite_cp_refs_in_fields_annotations(scratch_class, THREAD)) {
1533     // propagate failure back to caller
1534     return false;
1535   }
1536 
1537   // rewrite constant pool references in the methods_annotations:
1538   if (!rewrite_cp_refs_in_methods_annotations(scratch_class, THREAD)) {
1539     // propagate failure back to caller
1540     return false;
1541   }
1542 
1543   // rewrite constant pool references in the methods_parameter_annotations:
1544   if (!rewrite_cp_refs_in_methods_parameter_annotations(scratch_class,
1545          THREAD)) {
1546     // propagate failure back to caller
1547     return false;
1548   }
1549 
1550   // rewrite constant pool references in the methods_default_annotations:
1551   if (!rewrite_cp_refs_in_methods_default_annotations(scratch_class,
1552          THREAD)) {
1553     // propagate failure back to caller
1554     return false;
1555   }
1556 
1557   // rewrite source file name index:
1558   u2 source_file_name_idx = scratch_class->source_file_name_index();
1559   if (source_file_name_idx != 0) {
1560     u2 new_source_file_name_idx = find_new_index(source_file_name_idx);
1561     if (new_source_file_name_idx != 0) {
1562       scratch_class->set_source_file_name_index(new_source_file_name_idx);
1563     }
1564   }
1565 
1566   // rewrite class generic signature index:
1567   u2 generic_signature_index = scratch_class->generic_signature_index();
1568   if (generic_signature_index != 0) {
1569     u2 new_generic_signature_index = find_new_index(generic_signature_index);
1570     if (new_generic_signature_index != 0) {
1571       scratch_class->set_generic_signature_index(new_generic_signature_index);
1572     }
1573   }
1574 
1575   return true;
1576 } // end rewrite_cp_refs()
1577 
1578 // Rewrite constant pool references in the methods.
1579 bool VM_RedefineClasses::rewrite_cp_refs_in_methods(
1580        instanceKlassHandle scratch_class, TRAPS) {
1581 
1582   Array<Method*>* methods = scratch_class->methods();
1583 
1584   if (methods == NULL || methods->length() == 0) {
1585     // no methods so nothing to do
1586     return true;
1587   }
1588 
1589   // rewrite constant pool references in the methods:
1590   for (int i = methods->length() - 1; i >= 0; i--) {
1591     methodHandle method(THREAD, methods->at(i));
1592     methodHandle new_method;
1593     rewrite_cp_refs_in_method(method, &new_method, CHECK_false);
1594     if (!new_method.is_null()) {
1595       // the method has been replaced so save the new method version


1596       methods->at_put(i, new_method());
1597     }



1598   }

1599 
1600   return true;
1601 }
1602 
1603 
1604 // Rewrite constant pool references in the specific method. This code
1605 // was adapted from Rewriter::rewrite_method().
1606 void VM_RedefineClasses::rewrite_cp_refs_in_method(methodHandle method,
1607        methodHandle *new_method_p, TRAPS) {
1608 
1609   *new_method_p = methodHandle();  // default is no new method
1610 
1611   // We cache a pointer to the bytecodes here in code_base. If GC
1612   // moves the Method*, then the bytecodes will also move which
1613   // will likely cause a crash. We create a No_Safepoint_Verifier
1614   // object to detect whether we pass a possible safepoint in this
1615   // code block.
1616   No_Safepoint_Verifier nsv;
1617 
1618   // Bytecodes and their length
1619   address code_base = method->code_base();
1620   int code_length = method->code_size();
1621 
1622   int bc_length;
1623   for (int bci = 0; bci < code_length; bci += bc_length) {
1624     address bcp = code_base + bci;
1625     Bytecodes::Code c = (Bytecodes::Code)(*bcp);
1626 
1627     bc_length = Bytecodes::length_for(c);
1628     if (bc_length == 0) {
1629       // More complicated bytecodes report a length of zero so
1630       // we have to try again a slightly different way.
1631       bc_length = Bytecodes::length_at(method(), bcp);
1632     }
1633 
1634     assert(bc_length != 0, "impossible bytecode length");
1635 
1636     switch (c) {
1637       case Bytecodes::_ldc:
1638       {
1639         int cp_index = *(bcp + 1);
1640         int new_index = find_new_index(cp_index);
1641 
1642         if (StressLdcRewrite && new_index == 0) {
1643           // If we are stressing ldc -> ldc_w rewriting, then we
1644           // always need a new_index value.
1645           new_index = cp_index;
1646         }
1647         if (new_index != 0) {
1648           // the original index is mapped so we have more work to do
1649           if (!StressLdcRewrite && new_index <= max_jubyte) {
1650             // The new value can still use ldc instead of ldc_w
1651             // unless we are trying to stress ldc -> ldc_w rewriting
1652             RC_TRACE_WITH_THREAD(0x00080000, THREAD,
1653               ("%s@" INTPTR_FORMAT " old=%d, new=%d", Bytecodes::name(c),
1654               bcp, cp_index, new_index));
1655             *(bcp + 1) = new_index;
1656           } else {
1657             RC_TRACE_WITH_THREAD(0x00080000, THREAD,
1658               ("%s->ldc_w@" INTPTR_FORMAT " old=%d, new=%d",
1659               Bytecodes::name(c), bcp, cp_index, new_index));
1660             // the new value needs ldc_w instead of ldc
1661             u_char inst_buffer[4]; // max instruction size is 4 bytes
1662             bcp = (address)inst_buffer;
1663             // construct new instruction sequence
1664             *bcp = Bytecodes::_ldc_w;
1665             bcp++;
1666             // Rewriter::rewrite_method() does not rewrite ldc -> ldc_w.
1667             // See comment below for difference between put_Java_u2()
1668             // and put_native_u2().
1669             Bytes::put_Java_u2(bcp, new_index);
1670 
1671             Relocator rc(method, NULL /* no RelocatorListener needed */);
1672             methodHandle m;
1673             {
1674               Pause_No_Safepoint_Verifier pnsv(&nsv);
1675 
1676               // ldc is 2 bytes and ldc_w is 3 bytes
1677               m = rc.insert_space_at(bci, 3, inst_buffer, THREAD);
1678               if (m.is_null() || HAS_PENDING_EXCEPTION) {
1679                 guarantee(false, "insert_space_at() failed");
1680               }
1681             }
1682 
1683             // return the new method so that the caller can update
1684             // the containing class
1685             *new_method_p = method = m;
1686             // switch our bytecode processing loop from the old method
1687             // to the new method
1688             code_base = method->code_base();
1689             code_length = method->code_size();
1690             bcp = code_base + bci;
1691             c = (Bytecodes::Code)(*bcp);
1692             bc_length = Bytecodes::length_for(c);
1693             assert(bc_length != 0, "sanity check");
1694           } // end we need ldc_w instead of ldc
1695         } // end if there is a mapped index
1696       } break;
1697 
1698       // these bytecodes have a two-byte constant pool index
1699       case Bytecodes::_anewarray      : // fall through
1700       case Bytecodes::_checkcast      : // fall through
1701       case Bytecodes::_getfield       : // fall through
1702       case Bytecodes::_getstatic      : // fall through
1703       case Bytecodes::_instanceof     : // fall through
1704       case Bytecodes::_invokedynamic  : // fall through
1705       case Bytecodes::_invokeinterface: // fall through
1706       case Bytecodes::_invokespecial  : // fall through
1707       case Bytecodes::_invokestatic   : // fall through
1708       case Bytecodes::_invokevirtual  : // fall through
1709       case Bytecodes::_ldc_w          : // fall through
1710       case Bytecodes::_ldc2_w         : // fall through
1711       case Bytecodes::_multianewarray : // fall through
1712       case Bytecodes::_new            : // fall through
1713       case Bytecodes::_putfield       : // fall through
1714       case Bytecodes::_putstatic      :
1715       {
1716         address p = bcp + 1;
1717         int cp_index = Bytes::get_Java_u2(p);
1718         int new_index = find_new_index(cp_index);
1719         if (new_index != 0) {
1720           // the original index is mapped so update w/ new value
1721           RC_TRACE_WITH_THREAD(0x00080000, THREAD,
1722             ("%s@" INTPTR_FORMAT " old=%d, new=%d", Bytecodes::name(c),
1723             bcp, cp_index, new_index));
1724           // Rewriter::rewrite_method() uses put_native_u2() in this
1725           // situation because it is reusing the constant pool index
1726           // location for a native index into the ConstantPoolCache.
1727           // Since we are updating the constant pool index prior to
1728           // verification and ConstantPoolCache initialization, we
1729           // need to keep the new index in Java byte order.
1730           Bytes::put_Java_u2(p, new_index);
1731         }
1732       } break;
1733     }
1734   } // end for each bytecode
1735 
1736   // We also need to rewrite the parameter name indexes, if there is
1737   // method parameter data present
1738   if(method->has_method_parameters()) {
1739     const int len = method->method_parameters_length();
1740     MethodParametersElement* elem = method->method_parameters_start();
1741 
1742     for (int i = 0; i < len; i++) {
1743       const u2 cp_index = elem[i].name_cp_index;
1744       const u2 new_cp_index = find_new_index(cp_index);
1745       if (new_cp_index != 0) {
1746         elem[i].name_cp_index = new_cp_index;
1747       }
1748     }
1749   }
1750 } // end rewrite_cp_refs_in_method()
1751 
1752 
1753 // Rewrite constant pool references in the class_annotations field.
1754 bool VM_RedefineClasses::rewrite_cp_refs_in_class_annotations(
1755        instanceKlassHandle scratch_class, TRAPS) {
1756 
1757   AnnotationArray* class_annotations = scratch_class->class_annotations();
1758   if (class_annotations == NULL || class_annotations->length() == 0) {
1759     // no class_annotations so nothing to do
1760     return true;
1761   }
1762 
1763   RC_TRACE_WITH_THREAD(0x02000000, THREAD,
1764     ("class_annotations length=%d", class_annotations->length()));
1765 
1766   int byte_i = 0;  // byte index into class_annotations
1767   return rewrite_cp_refs_in_annotations_typeArray(class_annotations, byte_i,
1768            THREAD);
1769 }
1770 
1771 
1772 // Rewrite constant pool references in an annotations typeArray. This
1773 // "structure" is adapted from the RuntimeVisibleAnnotations_attribute
1774 // that is described in section 4.8.15 of the 2nd-edition of the VM spec:
1775 //
1776 // annotations_typeArray {
1777 //   u2 num_annotations;
1778 //   annotation annotations[num_annotations];
1779 // }
1780 //
1781 bool VM_RedefineClasses::rewrite_cp_refs_in_annotations_typeArray(
1782        AnnotationArray* annotations_typeArray, int &byte_i_ref, TRAPS) {
1783 
1784   if ((byte_i_ref + 2) > annotations_typeArray->length()) {
1785     // not enough room for num_annotations field
1786     RC_TRACE_WITH_THREAD(0x02000000, THREAD,
1787       ("length() is too small for num_annotations field"));
1788     return false;
1789   }
1790 
1791   u2 num_annotations = Bytes::get_Java_u2((address)
1792                          annotations_typeArray->adr_at(byte_i_ref));
1793   byte_i_ref += 2;
1794 
1795   RC_TRACE_WITH_THREAD(0x02000000, THREAD,
1796     ("num_annotations=%d", num_annotations));
1797 
1798   int calc_num_annotations = 0;
1799   for (; calc_num_annotations < num_annotations; calc_num_annotations++) {
1800     if (!rewrite_cp_refs_in_annotation_struct(annotations_typeArray,
1801            byte_i_ref, THREAD)) {
1802       RC_TRACE_WITH_THREAD(0x02000000, THREAD,
1803         ("bad annotation_struct at %d", calc_num_annotations));
1804       // propagate failure back to caller
1805       return false;
1806     }
1807   }
1808   assert(num_annotations == calc_num_annotations, "sanity check");
1809 
1810   return true;
1811 } // end rewrite_cp_refs_in_annotations_typeArray()
1812 
1813 
1814 // Rewrite constant pool references in the annotation struct portion of
1815 // an annotations_typeArray. This "structure" is from section 4.8.15 of
1816 // the 2nd-edition of the VM spec:
1817 //
1818 // struct annotation {
1819 //   u2 type_index;
1820 //   u2 num_element_value_pairs;
1821 //   {
1822 //     u2 element_name_index;
1823 //     element_value value;
1824 //   } element_value_pairs[num_element_value_pairs];
1825 // }
1826 //
1827 bool VM_RedefineClasses::rewrite_cp_refs_in_annotation_struct(
1828        AnnotationArray* annotations_typeArray, int &byte_i_ref, TRAPS) {
1829   if ((byte_i_ref + 2 + 2) > annotations_typeArray->length()) {
1830     // not enough room for smallest annotation_struct
1831     RC_TRACE_WITH_THREAD(0x02000000, THREAD,
1832       ("length() is too small for annotation_struct"));
1833     return false;
1834   }
1835 
1836   u2 type_index = rewrite_cp_ref_in_annotation_data(annotations_typeArray,
1837                     byte_i_ref, "mapped old type_index=%d", THREAD);
1838 
1839   u2 num_element_value_pairs = Bytes::get_Java_u2((address)
1840                                  annotations_typeArray->adr_at(byte_i_ref));
1841   byte_i_ref += 2;
1842 
1843   RC_TRACE_WITH_THREAD(0x02000000, THREAD,
1844     ("type_index=%d  num_element_value_pairs=%d", type_index,
1845     num_element_value_pairs));
1846 
1847   int calc_num_element_value_pairs = 0;
1848   for (; calc_num_element_value_pairs < num_element_value_pairs;
1849        calc_num_element_value_pairs++) {
1850     if ((byte_i_ref + 2) > annotations_typeArray->length()) {
1851       // not enough room for another element_name_index, let alone
1852       // the rest of another component
1853       RC_TRACE_WITH_THREAD(0x02000000, THREAD,
1854         ("length() is too small for element_name_index"));
1855       return false;
1856     }
1857 
1858     u2 element_name_index = rewrite_cp_ref_in_annotation_data(
1859                               annotations_typeArray, byte_i_ref,
1860                               "mapped old element_name_index=%d", THREAD);
1861 
1862     RC_TRACE_WITH_THREAD(0x02000000, THREAD,
1863       ("element_name_index=%d", element_name_index));
1864 
1865     if (!rewrite_cp_refs_in_element_value(annotations_typeArray,
1866            byte_i_ref, THREAD)) {
1867       RC_TRACE_WITH_THREAD(0x02000000, THREAD,
1868         ("bad element_value at %d", calc_num_element_value_pairs));
1869       // propagate failure back to caller
1870       return false;
1871     }
1872   } // end for each component
1873   assert(num_element_value_pairs == calc_num_element_value_pairs,
1874     "sanity check");
1875 
1876   return true;
1877 } // end rewrite_cp_refs_in_annotation_struct()
1878 
1879 
1880 // Rewrite a constant pool reference at the current position in
1881 // annotations_typeArray if needed. Returns the original constant
1882 // pool reference if a rewrite was not needed or the new constant
1883 // pool reference if a rewrite was needed.
1884 u2 VM_RedefineClasses::rewrite_cp_ref_in_annotation_data(
1885      AnnotationArray* annotations_typeArray, int &byte_i_ref,
1886      const char * trace_mesg, TRAPS) {
1887 
1888   address cp_index_addr = (address)
1889     annotations_typeArray->adr_at(byte_i_ref);
1890   u2 old_cp_index = Bytes::get_Java_u2(cp_index_addr);
1891   u2 new_cp_index = find_new_index(old_cp_index);
1892   if (new_cp_index != 0) {
1893     RC_TRACE_WITH_THREAD(0x02000000, THREAD, (trace_mesg, old_cp_index));
1894     Bytes::put_Java_u2(cp_index_addr, new_cp_index);
1895     old_cp_index = new_cp_index;
1896   }
1897   byte_i_ref += 2;
1898   return old_cp_index;
1899 }
1900 
1901 
1902 // Rewrite constant pool references in the element_value portion of an
1903 // annotations_typeArray. This "structure" is from section 4.8.15.1 of
1904 // the 2nd-edition of the VM spec:
1905 //
1906 // struct element_value {
1907 //   u1 tag;
1908 //   union {
1909 //     u2 const_value_index;
1910 //     {
1911 //       u2 type_name_index;
1912 //       u2 const_name_index;
1913 //     } enum_const_value;
1914 //     u2 class_info_index;
1915 //     annotation annotation_value;
1916 //     struct {
1917 //       u2 num_values;
1918 //       element_value values[num_values];
1919 //     } array_value;
1920 //   } value;
1921 // }
1922 //
1923 bool VM_RedefineClasses::rewrite_cp_refs_in_element_value(
1924        AnnotationArray* annotations_typeArray, int &byte_i_ref, TRAPS) {
1925 
1926   if ((byte_i_ref + 1) > annotations_typeArray->length()) {
1927     // not enough room for a tag let alone the rest of an element_value
1928     RC_TRACE_WITH_THREAD(0x02000000, THREAD,
1929       ("length() is too small for a tag"));
1930     return false;
1931   }
1932 
1933   u1 tag = annotations_typeArray->at(byte_i_ref);
1934   byte_i_ref++;
1935   RC_TRACE_WITH_THREAD(0x02000000, THREAD, ("tag='%c'", tag));
1936 
1937   switch (tag) {
1938     // These BaseType tag values are from Table 4.2 in VM spec:
1939     case 'B':  // byte
1940     case 'C':  // char
1941     case 'D':  // double
1942     case 'F':  // float
1943     case 'I':  // int
1944     case 'J':  // long
1945     case 'S':  // short
1946     case 'Z':  // boolean
1947 
1948     // The remaining tag values are from Table 4.8 in the 2nd-edition of
1949     // the VM spec:
1950     case 's':
1951     {
1952       // For the above tag values (including the BaseType values),
1953       // value.const_value_index is right union field.
1954 
1955       if ((byte_i_ref + 2) > annotations_typeArray->length()) {
1956         // not enough room for a const_value_index
1957         RC_TRACE_WITH_THREAD(0x02000000, THREAD,
1958           ("length() is too small for a const_value_index"));
1959         return false;
1960       }
1961 
1962       u2 const_value_index = rewrite_cp_ref_in_annotation_data(
1963                                annotations_typeArray, byte_i_ref,
1964                                "mapped old const_value_index=%d", THREAD);
1965 
1966       RC_TRACE_WITH_THREAD(0x02000000, THREAD,
1967         ("const_value_index=%d", const_value_index));
1968     } break;
1969 
1970     case 'e':
1971     {
1972       // for the above tag value, value.enum_const_value is right union field
1973 
1974       if ((byte_i_ref + 4) > annotations_typeArray->length()) {
1975         // not enough room for a enum_const_value
1976         RC_TRACE_WITH_THREAD(0x02000000, THREAD,
1977           ("length() is too small for a enum_const_value"));
1978         return false;
1979       }
1980 
1981       u2 type_name_index = rewrite_cp_ref_in_annotation_data(
1982                              annotations_typeArray, byte_i_ref,
1983                              "mapped old type_name_index=%d", THREAD);
1984 
1985       u2 const_name_index = rewrite_cp_ref_in_annotation_data(
1986                               annotations_typeArray, byte_i_ref,
1987                               "mapped old const_name_index=%d", THREAD);
1988 
1989       RC_TRACE_WITH_THREAD(0x02000000, THREAD,
1990         ("type_name_index=%d  const_name_index=%d", type_name_index,
1991         const_name_index));
1992     } break;
1993 
1994     case 'c':
1995     {
1996       // for the above tag value, value.class_info_index is right union field
1997 
1998       if ((byte_i_ref + 2) > annotations_typeArray->length()) {
1999         // not enough room for a class_info_index
2000         RC_TRACE_WITH_THREAD(0x02000000, THREAD,
2001           ("length() is too small for a class_info_index"));
2002         return false;
2003       }
2004 
2005       u2 class_info_index = rewrite_cp_ref_in_annotation_data(
2006                               annotations_typeArray, byte_i_ref,
2007                               "mapped old class_info_index=%d", THREAD);
2008 
2009       RC_TRACE_WITH_THREAD(0x02000000, THREAD,
2010         ("class_info_index=%d", class_info_index));
2011     } break;
2012 
2013     case '@':
2014       // For the above tag value, value.attr_value is the right union
2015       // field. This is a nested annotation.
2016       if (!rewrite_cp_refs_in_annotation_struct(annotations_typeArray,
2017              byte_i_ref, THREAD)) {
2018         // propagate failure back to caller
2019         return false;
2020       }
2021       break;
2022 
2023     case '[':
2024     {
2025       if ((byte_i_ref + 2) > annotations_typeArray->length()) {
2026         // not enough room for a num_values field
2027         RC_TRACE_WITH_THREAD(0x02000000, THREAD,
2028           ("length() is too small for a num_values field"));
2029         return false;
2030       }
2031 
2032       // For the above tag value, value.array_value is the right union
2033       // field. This is an array of nested element_value.
2034       u2 num_values = Bytes::get_Java_u2((address)
2035                         annotations_typeArray->adr_at(byte_i_ref));
2036       byte_i_ref += 2;
2037       RC_TRACE_WITH_THREAD(0x02000000, THREAD, ("num_values=%d", num_values));
2038 
2039       int calc_num_values = 0;
2040       for (; calc_num_values < num_values; calc_num_values++) {
2041         if (!rewrite_cp_refs_in_element_value(
2042                annotations_typeArray, byte_i_ref, THREAD)) {
2043           RC_TRACE_WITH_THREAD(0x02000000, THREAD,
2044             ("bad nested element_value at %d", calc_num_values));
2045           // propagate failure back to caller
2046           return false;
2047         }
2048       }
2049       assert(num_values == calc_num_values, "sanity check");
2050     } break;
2051 
2052     default:
2053       RC_TRACE_WITH_THREAD(0x02000000, THREAD, ("bad tag=0x%x", tag));
2054       return false;
2055   } // end decode tag field
2056 
2057   return true;
2058 } // end rewrite_cp_refs_in_element_value()
2059 
2060 
2061 // Rewrite constant pool references in a fields_annotations field.
2062 bool VM_RedefineClasses::rewrite_cp_refs_in_fields_annotations(
2063        instanceKlassHandle scratch_class, TRAPS) {
2064 
2065   Array<AnnotationArray*>* fields_annotations = scratch_class->fields_annotations();
2066 
2067   if (fields_annotations == NULL || fields_annotations->length() == 0) {
2068     // no fields_annotations so nothing to do
2069     return true;
2070   }
2071 
2072   RC_TRACE_WITH_THREAD(0x02000000, THREAD,
2073     ("fields_annotations length=%d", fields_annotations->length()));
2074 
2075   for (int i = 0; i < fields_annotations->length(); i++) {
2076     AnnotationArray* field_annotations = fields_annotations->at(i);
2077     if (field_annotations == NULL || field_annotations->length() == 0) {
2078       // this field does not have any annotations so skip it
2079       continue;
2080     }
2081 
2082     int byte_i = 0;  // byte index into field_annotations
2083     if (!rewrite_cp_refs_in_annotations_typeArray(field_annotations, byte_i,
2084            THREAD)) {
2085       RC_TRACE_WITH_THREAD(0x02000000, THREAD,
2086         ("bad field_annotations at %d", i));
2087       // propagate failure back to caller
2088       return false;
2089     }
2090   }
2091 
2092   return true;
2093 } // end rewrite_cp_refs_in_fields_annotations()
2094 
2095 
2096 // Rewrite constant pool references in a methods_annotations field.
2097 bool VM_RedefineClasses::rewrite_cp_refs_in_methods_annotations(
2098        instanceKlassHandle scratch_class, TRAPS) {
2099 
2100   for (int i = 0; i < scratch_class->methods()->length(); i++) {
2101     Method* m = scratch_class->methods()->at(i);
2102     AnnotationArray* method_annotations = m->constMethod()->method_annotations();
2103 
2104     if (method_annotations == NULL || method_annotations->length() == 0) {
2105       // this method does not have any annotations so skip it
2106       continue;
2107     }
2108 
2109     int byte_i = 0;  // byte index into method_annotations
2110     if (!rewrite_cp_refs_in_annotations_typeArray(method_annotations, byte_i,
2111            THREAD)) {
2112       RC_TRACE_WITH_THREAD(0x02000000, THREAD,
2113         ("bad method_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_methods_annotations()
2121 
2122 
2123 // Rewrite constant pool references in a methods_parameter_annotations
2124 // field. This "structure" is adapted from the
2125 // RuntimeVisibleParameterAnnotations_attribute described in section
2126 // 4.8.17 of the 2nd-edition of the VM spec:
2127 //
2128 // methods_parameter_annotations_typeArray {
2129 //   u1 num_parameters;
2130 //   {
2131 //     u2 num_annotations;
2132 //     annotation annotations[num_annotations];
2133 //   } parameter_annotations[num_parameters];
2134 // }
2135 //
2136 bool VM_RedefineClasses::rewrite_cp_refs_in_methods_parameter_annotations(
2137        instanceKlassHandle scratch_class, TRAPS) {
2138 
2139   for (int i = 0; i < scratch_class->methods()->length(); i++) {
2140     Method* m = scratch_class->methods()->at(i);
2141     AnnotationArray* method_parameter_annotations = m->constMethod()->parameter_annotations();
2142     if (method_parameter_annotations == NULL
2143         || method_parameter_annotations->length() == 0) {
2144       // this method does not have any parameter annotations so skip it
2145       continue;
2146     }
2147 
2148     if (method_parameter_annotations->length() < 1) {
2149       // not enough room for a num_parameters field
2150       RC_TRACE_WITH_THREAD(0x02000000, THREAD,
2151         ("length() is too small for a num_parameters field at %d", i));
2152       return false;
2153     }
2154 
2155     int byte_i = 0;  // byte index into method_parameter_annotations
2156 
2157     u1 num_parameters = method_parameter_annotations->at(byte_i);
2158     byte_i++;
2159 
2160     RC_TRACE_WITH_THREAD(0x02000000, THREAD,
2161       ("num_parameters=%d", num_parameters));
2162 
2163     int calc_num_parameters = 0;
2164     for (; calc_num_parameters < num_parameters; calc_num_parameters++) {
2165       if (!rewrite_cp_refs_in_annotations_typeArray(
2166              method_parameter_annotations, byte_i, THREAD)) {
2167         RC_TRACE_WITH_THREAD(0x02000000, THREAD,
2168           ("bad method_parameter_annotations at %d", calc_num_parameters));
2169         // propagate failure back to caller
2170         return false;
2171       }
2172     }
2173     assert(num_parameters == calc_num_parameters, "sanity check");
2174   }
2175 
2176   return true;
2177 } // end rewrite_cp_refs_in_methods_parameter_annotations()
2178 
2179 
2180 // Rewrite constant pool references in a methods_default_annotations
2181 // field. This "structure" is adapted from the AnnotationDefault_attribute
2182 // that is described in section 4.8.19 of the 2nd-edition of the VM spec:
2183 //
2184 // methods_default_annotations_typeArray {
2185 //   element_value default_value;
2186 // }
2187 //
2188 bool VM_RedefineClasses::rewrite_cp_refs_in_methods_default_annotations(
2189        instanceKlassHandle scratch_class, TRAPS) {
2190 
2191   for (int i = 0; i < scratch_class->methods()->length(); i++) {
2192     Method* m = scratch_class->methods()->at(i);
2193     AnnotationArray* method_default_annotations = m->constMethod()->default_annotations();
2194     if (method_default_annotations == NULL
2195         || method_default_annotations->length() == 0) {
2196       // this method does not have any default annotations so skip it
2197       continue;
2198     }
2199 
2200     int byte_i = 0;  // byte index into method_default_annotations
2201 
2202     if (!rewrite_cp_refs_in_element_value(
2203            method_default_annotations, byte_i, THREAD)) {
2204       RC_TRACE_WITH_THREAD(0x02000000, THREAD,
2205         ("bad default element_value at %d", i));
2206       // propagate failure back to caller
2207       return false;
2208     }
2209   }
2210 
2211   return true;
2212 } // end rewrite_cp_refs_in_methods_default_annotations()
2213 
2214 
2215 // Rewrite constant pool references in the method's stackmap table.
2216 // These "structures" are adapted from the StackMapTable_attribute that
2217 // is described in section 4.8.4 of the 6.0 version of the VM spec
2218 // (dated 2005.10.26):
2219 // file:///net/quincunx.sfbay/export/gbracha/ClassFile-Java6.pdf
2220 //
2221 // stack_map {
2222 //   u2 number_of_entries;
2223 //   stack_map_frame entries[number_of_entries];
2224 // }
2225 //
2226 void VM_RedefineClasses::rewrite_cp_refs_in_stack_map_table(
2227        methodHandle method, TRAPS) {
2228 
2229   if (!method->has_stackmap_table()) {
2230     return;
2231   }
2232 
2233   AnnotationArray* stackmap_data = method->stackmap_data();
2234   address stackmap_p = (address)stackmap_data->adr_at(0);
2235   address stackmap_end = stackmap_p + stackmap_data->length();
2236 
2237   assert(stackmap_p + 2 <= stackmap_end, "no room for number_of_entries");
2238   u2 number_of_entries = Bytes::get_Java_u2(stackmap_p);
2239   stackmap_p += 2;
2240 
2241   RC_TRACE_WITH_THREAD(0x04000000, THREAD,
2242     ("number_of_entries=%u", number_of_entries));
2243 
2244   // walk through each stack_map_frame
2245   u2 calc_number_of_entries = 0;
2246   for (; calc_number_of_entries < number_of_entries; calc_number_of_entries++) {
2247     // The stack_map_frame structure is a u1 frame_type followed by
2248     // 0 or more bytes of data:
2249     //
2250     // union stack_map_frame {
2251     //   same_frame;
2252     //   same_locals_1_stack_item_frame;
2253     //   same_locals_1_stack_item_frame_extended;
2254     //   chop_frame;
2255     //   same_frame_extended;
2256     //   append_frame;
2257     //   full_frame;
2258     // }
2259 
2260     assert(stackmap_p + 1 <= stackmap_end, "no room for frame_type");
2261     // The Linux compiler does not like frame_type to be u1 or u2. It
2262     // issues the following warning for the first if-statement below:
2263     //
2264     // "warning: comparison is always true due to limited range of data type"
2265     //
2266     u4 frame_type = *stackmap_p;
2267     stackmap_p++;
2268 
2269     // same_frame {
2270     //   u1 frame_type = SAME; /* 0-63 */
2271     // }
2272     if (frame_type >= 0 && frame_type <= 63) {
2273       // nothing more to do for same_frame
2274     }
2275 
2276     // same_locals_1_stack_item_frame {
2277     //   u1 frame_type = SAME_LOCALS_1_STACK_ITEM; /* 64-127 */
2278     //   verification_type_info stack[1];
2279     // }
2280     else if (frame_type >= 64 && frame_type <= 127) {
2281       rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
2282         calc_number_of_entries, frame_type, THREAD);
2283     }
2284 
2285     // reserved for future use
2286     else if (frame_type >= 128 && frame_type <= 246) {
2287       // nothing more to do for reserved frame_types
2288     }
2289 
2290     // same_locals_1_stack_item_frame_extended {
2291     //   u1 frame_type = SAME_LOCALS_1_STACK_ITEM_EXTENDED; /* 247 */
2292     //   u2 offset_delta;
2293     //   verification_type_info stack[1];
2294     // }
2295     else if (frame_type == 247) {
2296       stackmap_p += 2;
2297       rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
2298         calc_number_of_entries, frame_type, THREAD);
2299     }
2300 
2301     // chop_frame {
2302     //   u1 frame_type = CHOP; /* 248-250 */
2303     //   u2 offset_delta;
2304     // }
2305     else if (frame_type >= 248 && frame_type <= 250) {
2306       stackmap_p += 2;
2307     }
2308 
2309     // same_frame_extended {
2310     //   u1 frame_type = SAME_FRAME_EXTENDED; /* 251*/
2311     //   u2 offset_delta;
2312     // }
2313     else if (frame_type == 251) {
2314       stackmap_p += 2;
2315     }
2316 
2317     // append_frame {
2318     //   u1 frame_type = APPEND; /* 252-254 */
2319     //   u2 offset_delta;
2320     //   verification_type_info locals[frame_type - 251];
2321     // }
2322     else if (frame_type >= 252 && frame_type <= 254) {
2323       assert(stackmap_p + 2 <= stackmap_end,
2324         "no room for offset_delta");
2325       stackmap_p += 2;
2326       u1 len = frame_type - 251;
2327       for (u1 i = 0; i < len; i++) {
2328         rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
2329           calc_number_of_entries, frame_type, THREAD);
2330       }
2331     }
2332 
2333     // full_frame {
2334     //   u1 frame_type = FULL_FRAME; /* 255 */
2335     //   u2 offset_delta;
2336     //   u2 number_of_locals;
2337     //   verification_type_info locals[number_of_locals];
2338     //   u2 number_of_stack_items;
2339     //   verification_type_info stack[number_of_stack_items];
2340     // }
2341     else if (frame_type == 255) {
2342       assert(stackmap_p + 2 + 2 <= stackmap_end,
2343         "no room for smallest full_frame");
2344       stackmap_p += 2;
2345 
2346       u2 number_of_locals = Bytes::get_Java_u2(stackmap_p);
2347       stackmap_p += 2;
2348 
2349       for (u2 locals_i = 0; locals_i < number_of_locals; locals_i++) {
2350         rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
2351           calc_number_of_entries, frame_type, THREAD);
2352       }
2353 
2354       // Use the largest size for the number_of_stack_items, but only get
2355       // the right number of bytes.
2356       u2 number_of_stack_items = Bytes::get_Java_u2(stackmap_p);
2357       stackmap_p += 2;
2358 
2359       for (u2 stack_i = 0; stack_i < number_of_stack_items; stack_i++) {
2360         rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
2361           calc_number_of_entries, frame_type, THREAD);
2362       }
2363     }
2364   } // end while there is a stack_map_frame
2365   assert(number_of_entries == calc_number_of_entries, "sanity check");
2366 } // end rewrite_cp_refs_in_stack_map_table()
2367 
2368 
2369 // Rewrite constant pool references in the verification type info
2370 // portion of the method's stackmap table. These "structures" are
2371 // adapted from the StackMapTable_attribute that is described in
2372 // section 4.8.4 of the 6.0 version of the VM spec (dated 2005.10.26):
2373 // file:///net/quincunx.sfbay/export/gbracha/ClassFile-Java6.pdf
2374 //
2375 // The verification_type_info structure is a u1 tag followed by 0 or
2376 // more bytes of data:
2377 //
2378 // union verification_type_info {
2379 //   Top_variable_info;
2380 //   Integer_variable_info;
2381 //   Float_variable_info;
2382 //   Long_variable_info;
2383 //   Double_variable_info;
2384 //   Null_variable_info;
2385 //   UninitializedThis_variable_info;
2386 //   Object_variable_info;
2387 //   Uninitialized_variable_info;
2388 // }
2389 //
2390 void VM_RedefineClasses::rewrite_cp_refs_in_verification_type_info(
2391        address& stackmap_p_ref, address stackmap_end, u2 frame_i,
2392        u1 frame_type, TRAPS) {
2393 
2394   assert(stackmap_p_ref + 1 <= stackmap_end, "no room for tag");
2395   u1 tag = *stackmap_p_ref;
2396   stackmap_p_ref++;
2397 
2398   switch (tag) {
2399   // Top_variable_info {
2400   //   u1 tag = ITEM_Top; /* 0 */
2401   // }
2402   // verificationType.hpp has zero as ITEM_Bogus instead of ITEM_Top
2403   case 0:  // fall through
2404 
2405   // Integer_variable_info {
2406   //   u1 tag = ITEM_Integer; /* 1 */
2407   // }
2408   case ITEM_Integer:  // fall through
2409 
2410   // Float_variable_info {
2411   //   u1 tag = ITEM_Float; /* 2 */
2412   // }
2413   case ITEM_Float:  // fall through
2414 
2415   // Double_variable_info {
2416   //   u1 tag = ITEM_Double; /* 3 */
2417   // }
2418   case ITEM_Double:  // fall through
2419 
2420   // Long_variable_info {
2421   //   u1 tag = ITEM_Long; /* 4 */
2422   // }
2423   case ITEM_Long:  // fall through
2424 
2425   // Null_variable_info {
2426   //   u1 tag = ITEM_Null; /* 5 */
2427   // }
2428   case ITEM_Null:  // fall through
2429 
2430   // UninitializedThis_variable_info {
2431   //   u1 tag = ITEM_UninitializedThis; /* 6 */
2432   // }
2433   case ITEM_UninitializedThis:
2434     // nothing more to do for the above tag types
2435     break;
2436 
2437   // Object_variable_info {
2438   //   u1 tag = ITEM_Object; /* 7 */
2439   //   u2 cpool_index;
2440   // }
2441   case ITEM_Object:
2442   {
2443     assert(stackmap_p_ref + 2 <= stackmap_end, "no room for cpool_index");
2444     u2 cpool_index = Bytes::get_Java_u2(stackmap_p_ref);
2445     u2 new_cp_index = find_new_index(cpool_index);
2446     if (new_cp_index != 0) {
2447       RC_TRACE_WITH_THREAD(0x04000000, THREAD,
2448         ("mapped old cpool_index=%d", cpool_index));
2449       Bytes::put_Java_u2(stackmap_p_ref, new_cp_index);
2450       cpool_index = new_cp_index;
2451     }
2452     stackmap_p_ref += 2;
2453 
2454     RC_TRACE_WITH_THREAD(0x04000000, THREAD,
2455       ("frame_i=%u, frame_type=%u, cpool_index=%d", frame_i,
2456       frame_type, cpool_index));
2457   } break;
2458 
2459   // Uninitialized_variable_info {
2460   //   u1 tag = ITEM_Uninitialized; /* 8 */
2461   //   u2 offset;
2462   // }
2463   case ITEM_Uninitialized:
2464     assert(stackmap_p_ref + 2 <= stackmap_end, "no room for offset");
2465     stackmap_p_ref += 2;
2466     break;
2467 
2468   default:
2469     RC_TRACE_WITH_THREAD(0x04000000, THREAD,
2470       ("frame_i=%u, frame_type=%u, bad tag=0x%x", frame_i, frame_type, tag));
2471     ShouldNotReachHere();
2472     break;
2473   } // end switch (tag)
2474 } // end rewrite_cp_refs_in_verification_type_info()
2475 
2476 
2477 // Change the constant pool associated with klass scratch_class to
2478 // scratch_cp. If shrink is true, then scratch_cp_length elements
2479 // are copied from scratch_cp to a smaller constant pool and the
2480 // smaller constant pool is associated with scratch_class.
2481 void VM_RedefineClasses::set_new_constant_pool(
2482        ClassLoaderData* loader_data,
2483        instanceKlassHandle scratch_class, constantPoolHandle scratch_cp,
2484        int scratch_cp_length, TRAPS) {
2485   assert(scratch_cp->length() >= scratch_cp_length, "sanity check");
2486 
2487   // scratch_cp is a merged constant pool and has enough space for a
2488   // worst case merge situation. We want to associate the minimum
2489   // sized constant pool with the klass to save space.
2490   constantPoolHandle smaller_cp(THREAD,
2491           ConstantPool::allocate(loader_data, scratch_cp_length, THREAD));
2492 
2493   // preserve version() value in the smaller copy
2494   int version = scratch_cp->version();
2495   assert(version != 0, "sanity check");
2496   smaller_cp->set_version(version);
2497 
2498   // attach klass to new constant pool
2499   // reference to the cp holder is needed for copy_operands()
2500   smaller_cp->set_pool_holder(scratch_class());
2501 
2502   scratch_cp->copy_cp_to(1, scratch_cp_length - 1, smaller_cp, 1, THREAD);
2503   scratch_cp = smaller_cp;
2504 
2505   // attach new constant pool to klass
2506   scratch_class->set_constants(scratch_cp());
2507 
2508   int i;  // for portability
2509 
2510   // update each field in klass to use new constant pool indices as needed
2511   for (JavaFieldStream fs(scratch_class); !fs.done(); fs.next()) {
2512     jshort cur_index = fs.name_index();
2513     jshort new_index = find_new_index(cur_index);
2514     if (new_index != 0) {
2515       RC_TRACE_WITH_THREAD(0x00080000, THREAD,
2516         ("field-name_index change: %d to %d", cur_index, new_index));
2517       fs.set_name_index(new_index);
2518     }
2519     cur_index = fs.signature_index();
2520     new_index = find_new_index(cur_index);
2521     if (new_index != 0) {
2522       RC_TRACE_WITH_THREAD(0x00080000, THREAD,
2523         ("field-signature_index change: %d to %d", cur_index, new_index));
2524       fs.set_signature_index(new_index);
2525     }
2526     cur_index = fs.initval_index();
2527     new_index = find_new_index(cur_index);
2528     if (new_index != 0) {
2529       RC_TRACE_WITH_THREAD(0x00080000, THREAD,
2530         ("field-initval_index change: %d to %d", cur_index, new_index));
2531       fs.set_initval_index(new_index);
2532     }
2533     cur_index = fs.generic_signature_index();
2534     new_index = find_new_index(cur_index);
2535     if (new_index != 0) {
2536       RC_TRACE_WITH_THREAD(0x00080000, THREAD,
2537         ("field-generic_signature change: %d to %d", cur_index, new_index));
2538       fs.set_generic_signature_index(new_index);
2539     }
2540   } // end for each field
2541 
2542   // Update constant pool indices in the inner classes info to use
2543   // new constant indices as needed. The inner classes info is a
2544   // quadruple:
2545   // (inner_class_info, outer_class_info, inner_name, inner_access_flags)
2546   InnerClassesIterator iter(scratch_class);
2547   for (; !iter.done(); iter.next()) {
2548     int cur_index = iter.inner_class_info_index();
2549     if (cur_index == 0) {
2550       continue;  // JVM spec. allows null inner class refs so skip it
2551     }
2552     int new_index = find_new_index(cur_index);
2553     if (new_index != 0) {
2554       RC_TRACE_WITH_THREAD(0x00080000, THREAD,
2555         ("inner_class_info change: %d to %d", cur_index, new_index));
2556       iter.set_inner_class_info_index(new_index);
2557     }
2558     cur_index = iter.outer_class_info_index();
2559     new_index = find_new_index(cur_index);
2560     if (new_index != 0) {
2561       RC_TRACE_WITH_THREAD(0x00080000, THREAD,
2562         ("outer_class_info change: %d to %d", cur_index, new_index));
2563       iter.set_outer_class_info_index(new_index);
2564     }
2565     cur_index = iter.inner_name_index();
2566     new_index = find_new_index(cur_index);
2567     if (new_index != 0) {
2568       RC_TRACE_WITH_THREAD(0x00080000, THREAD,
2569         ("inner_name change: %d to %d", cur_index, new_index));
2570       iter.set_inner_name_index(new_index);
2571     }
2572   } // end for each inner class
2573 
2574   // Attach each method in klass to the new constant pool and update
2575   // to use new constant pool indices as needed:
2576   Array<Method*>* methods = scratch_class->methods();
2577   for (i = methods->length() - 1; i >= 0; i--) {
2578     methodHandle method(THREAD, methods->at(i));
2579     method->set_constants(scratch_cp());
2580 
2581     int new_index = find_new_index(method->name_index());
2582     if (new_index != 0) {
2583       RC_TRACE_WITH_THREAD(0x00080000, THREAD,
2584         ("method-name_index change: %d to %d", method->name_index(),
2585         new_index));
2586       method->set_name_index(new_index);
2587     }
2588     new_index = find_new_index(method->signature_index());
2589     if (new_index != 0) {
2590       RC_TRACE_WITH_THREAD(0x00080000, THREAD,
2591         ("method-signature_index change: %d to %d",
2592         method->signature_index(), new_index));
2593       method->set_signature_index(new_index);
2594     }
2595     new_index = find_new_index(method->generic_signature_index());
2596     if (new_index != 0) {
2597       RC_TRACE_WITH_THREAD(0x00080000, THREAD,
2598         ("method-generic_signature_index change: %d to %d",
2599         method->generic_signature_index(), new_index));
2600       method->set_generic_signature_index(new_index);
2601     }
2602 
2603     // Update constant pool indices in the method's checked exception
2604     // table to use new constant indices as needed.
2605     int cext_length = method->checked_exceptions_length();
2606     if (cext_length > 0) {
2607       CheckedExceptionElement * cext_table =
2608         method->checked_exceptions_start();
2609       for (int j = 0; j < cext_length; j++) {
2610         int cur_index = cext_table[j].class_cp_index;
2611         int new_index = find_new_index(cur_index);
2612         if (new_index != 0) {
2613           RC_TRACE_WITH_THREAD(0x00080000, THREAD,
2614             ("cext-class_cp_index change: %d to %d", cur_index, new_index));
2615           cext_table[j].class_cp_index = (u2)new_index;
2616         }
2617       } // end for each checked exception table entry
2618     } // end if there are checked exception table entries
2619 
2620     // Update each catch type index in the method's exception table
2621     // to use new constant pool indices as needed. The exception table
2622     // holds quadruple entries of the form:
2623     //   (beg_bci, end_bci, handler_bci, klass_index)
2624 
2625     ExceptionTable ex_table(method());
2626     int ext_length = ex_table.length();
2627 
2628     for (int j = 0; j < ext_length; j ++) {
2629       int cur_index = ex_table.catch_type_index(j);
2630       int new_index = find_new_index(cur_index);
2631       if (new_index != 0) {
2632         RC_TRACE_WITH_THREAD(0x00080000, THREAD,
2633           ("ext-klass_index change: %d to %d", cur_index, new_index));
2634         ex_table.set_catch_type_index(j, new_index);
2635       }
2636     } // end for each exception table entry
2637 
2638     // Update constant pool indices in the method's local variable
2639     // table to use new constant indices as needed. The local variable
2640     // table hold sextuple entries of the form:
2641     // (start_pc, length, name_index, descriptor_index, signature_index, slot)
2642     int lvt_length = method->localvariable_table_length();
2643     if (lvt_length > 0) {
2644       LocalVariableTableElement * lv_table =
2645         method->localvariable_table_start();
2646       for (int j = 0; j < lvt_length; j++) {
2647         int cur_index = lv_table[j].name_cp_index;
2648         int new_index = find_new_index(cur_index);
2649         if (new_index != 0) {
2650           RC_TRACE_WITH_THREAD(0x00080000, THREAD,
2651             ("lvt-name_cp_index change: %d to %d", cur_index, new_index));
2652           lv_table[j].name_cp_index = (u2)new_index;
2653         }
2654         cur_index = lv_table[j].descriptor_cp_index;
2655         new_index = find_new_index(cur_index);
2656         if (new_index != 0) {
2657           RC_TRACE_WITH_THREAD(0x00080000, THREAD,
2658             ("lvt-descriptor_cp_index change: %d to %d", cur_index,
2659             new_index));
2660           lv_table[j].descriptor_cp_index = (u2)new_index;
2661         }
2662         cur_index = lv_table[j].signature_cp_index;
2663         new_index = find_new_index(cur_index);
2664         if (new_index != 0) {
2665           RC_TRACE_WITH_THREAD(0x00080000, THREAD,
2666             ("lvt-signature_cp_index change: %d to %d", cur_index, new_index));
2667           lv_table[j].signature_cp_index = (u2)new_index;
2668         }
2669       } // end for each local variable table entry
2670     } // end if there are local variable table entries
2671 
2672     rewrite_cp_refs_in_stack_map_table(method, THREAD);
2673   } // end for each method
2674 } // end set_new_constant_pool()
2675 
2676 
2677 // Unevolving classes may point to methods of the_class directly
2678 // from their constant pool caches, itables, and/or vtables. We
2679 // use the ClassLoaderDataGraph::classes_do() facility and this helper
2680 // to fix up these pointers.
2681 
2682 // Adjust cpools and vtables closure
2683 void VM_RedefineClasses::AdjustCpoolCacheAndVtable::do_klass(Klass* k) {
2684 
2685   // This is a very busy routine. We don't want too much tracing
2686   // printed out.
2687   bool trace_name_printed = false;
2688 
2689   // Very noisy: only enable this call if you are trying to determine
2690   // that a specific class gets found by this routine.
2691   // RC_TRACE macro has an embedded ResourceMark
2692   // RC_TRACE_WITH_THREAD(0x00100000, THREAD,
2693   //   ("adjust check: name=%s", k->external_name()));
2694   // trace_name_printed = true;
2695 
2696   // If the class being redefined is java.lang.Object, we need to fix all
2697   // array class vtables also
2698   if (k->oop_is_array() && _the_class_oop == SystemDictionary::Object_klass()) {
2699     k->vtable()->adjust_method_entries(_matching_old_methods,
2700                                        _matching_new_methods,
2701                                        _matching_methods_length,
2702                                        &trace_name_printed);
2703   } else if (k->oop_is_instance()) {
2704     HandleMark hm(_thread);
2705     InstanceKlass *ik = InstanceKlass::cast(k);
2706 
2707     // HotSpot specific optimization! HotSpot does not currently
2708     // support delegation from the bootstrap class loader to a
2709     // user-defined class loader. This means that if the bootstrap
2710     // class loader is the initiating class loader, then it will also
2711     // be the defining class loader. This also means that classes
2712     // loaded by the bootstrap class loader cannot refer to classes
2713     // loaded by a user-defined class loader. Note: a user-defined
2714     // class loader can delegate to the bootstrap class loader.
2715     //
2716     // If the current class being redefined has a user-defined class
2717     // loader as its defining class loader, then we can skip all
2718     // classes loaded by the bootstrap class loader.
2719     bool is_user_defined =
2720            InstanceKlass::cast(_the_class_oop)->class_loader() != NULL;
2721     if (is_user_defined && ik->class_loader() == NULL) {
2722       return;
2723     }
2724 
2725     // Fix the vtable embedded in the_class and subclasses of the_class,
2726     // if one exists. We discard scratch_class and we don't keep an
2727     // InstanceKlass around to hold obsolete methods so we don't have
2728     // any other InstanceKlass embedded vtables to update. The vtable
2729     // holds the Method*s for virtual (but not final) methods.
2730     if (ik->vtable_length() > 0 && ik->is_subtype_of(_the_class_oop)) {
2731       // ik->vtable() creates a wrapper object; rm cleans it up
2732       ResourceMark rm(_thread);
2733       ik->vtable()->adjust_method_entries(_matching_old_methods,
2734                                           _matching_new_methods,
2735                                           _matching_methods_length,
2736                                           &trace_name_printed);
2737     }
2738 
2739     // If the current class has an itable and we are either redefining an
2740     // interface or if the current class is a subclass of the_class, then
2741     // we potentially have to fix the itable. If we are redefining an
2742     // interface, then we have to call adjust_method_entries() for
2743     // every InstanceKlass that has an itable since there isn't a
2744     // subclass relationship between an interface and an InstanceKlass.
2745     if (ik->itable_length() > 0 && (_the_class_oop->is_interface()
2746         || ik->is_subclass_of(_the_class_oop))) {
2747       // ik->itable() creates a wrapper object; rm cleans it up
2748       ResourceMark rm(_thread);
2749       ik->itable()->adjust_method_entries(_matching_old_methods,
2750                                           _matching_new_methods,
2751                                           _matching_methods_length,
2752                                           &trace_name_printed);
2753     }
2754 
2755     // The constant pools in other classes (other_cp) can refer to
2756     // methods in the_class. We have to update method information in
2757     // other_cp's cache. If other_cp has a previous version, then we
2758     // have to repeat the process for each previous version. The
2759     // constant pool cache holds the Method*s for non-virtual
2760     // methods and for virtual, final methods.
2761     //
2762     // Special case: if the current class is the_class, then new_cp
2763     // has already been attached to the_class and old_cp has already
2764     // been added as a previous version. The new_cp doesn't have any
2765     // cached references to old methods so it doesn't need to be
2766     // updated. We can simply start with the previous version(s) in
2767     // that case.
2768     constantPoolHandle other_cp;
2769     ConstantPoolCache* cp_cache;
2770 
2771     if (ik != _the_class_oop) {
2772       // this klass' constant pool cache may need adjustment
2773       other_cp = constantPoolHandle(ik->constants());
2774       cp_cache = other_cp->cache();
2775       if (cp_cache != NULL) {
2776         cp_cache->adjust_method_entries(_matching_old_methods,
2777                                         _matching_new_methods,
2778                                         _matching_methods_length,
2779                                         &trace_name_printed);
2780       }
2781     }
2782     {
2783       ResourceMark rm(_thread);
2784       // PreviousVersionInfo objects returned via PreviousVersionWalker
2785       // contain a GrowableArray of handles. We have to clean up the
2786       // GrowableArray _after_ the PreviousVersionWalker destructor
2787       // has destroyed the handles.
2788       {
2789         // the previous versions' constant pool caches may need adjustment
2790         PreviousVersionWalker pvw(ik);
2791         for (PreviousVersionInfo * pv_info = pvw.next_previous_version();
2792              pv_info != NULL; pv_info = pvw.next_previous_version()) {
2793           other_cp = pv_info->prev_constant_pool_handle();
2794           cp_cache = other_cp->cache();
2795           if (cp_cache != NULL) {
2796             cp_cache->adjust_method_entries(_matching_old_methods,
2797                                             _matching_new_methods,
2798                                             _matching_methods_length,
2799                                             &trace_name_printed);
2800           }
2801         }
2802       } // pvw is cleaned up
2803     } // rm is cleaned up
2804   }
2805 }
2806 
2807 void VM_RedefineClasses::update_jmethod_ids() {
2808   for (int j = 0; j < _matching_methods_length; ++j) {
2809     Method* old_method = _matching_old_methods[j];
2810     jmethodID jmid = old_method->find_jmethod_id_or_null();
2811     if (jmid != NULL) {
2812       // There is a jmethodID, change it to point to the new method
2813       methodHandle new_method_h(_matching_new_methods[j]);
2814       Method::change_method_associated_with_jmethod_id(jmid, new_method_h());
2815       assert(Method::resolve_jmethod_id(jmid) == _matching_new_methods[j],
2816              "should be replaced");
2817     }
2818   }
2819 }
2820 
2821 void VM_RedefineClasses::check_methods_and_mark_as_obsolete(
2822        BitMap *emcp_methods, int * emcp_method_count_p) {
2823   *emcp_method_count_p = 0;
2824   int obsolete_count = 0;
2825   int old_index = 0;
2826   for (int j = 0; j < _matching_methods_length; ++j, ++old_index) {
2827     Method* old_method = _matching_old_methods[j];
2828     Method* new_method = _matching_new_methods[j];
2829     Method* old_array_method;
2830 
2831     // Maintain an old_index into the _old_methods array by skipping
2832     // deleted methods
2833     while ((old_array_method = _old_methods->at(old_index)) != old_method) {
2834       ++old_index;
2835     }
2836 
2837     if (MethodComparator::methods_EMCP(old_method, new_method)) {
2838       // The EMCP definition from JSR-163 requires the bytecodes to be
2839       // the same with the exception of constant pool indices which may
2840       // differ. However, the constants referred to by those indices
2841       // must be the same.
2842       //
2843       // We use methods_EMCP() for comparison since constant pool
2844       // merging can remove duplicate constant pool entries that were
2845       // present in the old method and removed from the rewritten new
2846       // method. A faster binary comparison function would consider the
2847       // old and new methods to be different when they are actually
2848       // EMCP.
2849       //
2850       // The old and new methods are EMCP and you would think that we
2851       // could get rid of one of them here and now and save some space.
2852       // However, the concept of EMCP only considers the bytecodes and
2853       // the constant pool entries in the comparison. Other things,
2854       // e.g., the line number table (LNT) or the local variable table
2855       // (LVT) don't count in the comparison. So the new (and EMCP)
2856       // method can have a new LNT that we need so we can't just
2857       // overwrite the new method with the old method.
2858       //
2859       // When this routine is called, we have already attached the new
2860       // methods to the_class so the old methods are effectively
2861       // overwritten. However, if an old method is still executing,
2862       // then the old method cannot be collected until sometime after
2863       // the old method call has returned. So the overwriting of old
2864       // methods by new methods will save us space except for those
2865       // (hopefully few) old methods that are still executing.
2866       //
2867       // A method refers to a ConstMethod* and this presents another
2868       // possible avenue to space savings. The ConstMethod* in the
2869       // new method contains possibly new attributes (LNT, LVT, etc).
2870       // At first glance, it seems possible to save space by replacing
2871       // the ConstMethod* in the old method with the ConstMethod*
2872       // from the new method. The old and new methods would share the
2873       // same ConstMethod* and we would save the space occupied by
2874       // the old ConstMethod*. However, the ConstMethod* contains
2875       // a back reference to the containing method. Sharing the
2876       // ConstMethod* between two methods could lead to confusion in
2877       // the code that uses the back reference. This would lead to
2878       // brittle code that could be broken in non-obvious ways now or
2879       // in the future.
2880       //
2881       // Another possibility is to copy the ConstMethod* from the new
2882       // method to the old method and then overwrite the new method with
2883       // the old method. Since the ConstMethod* contains the bytecodes
2884       // for the method embedded in the oop, this option would change
2885       // the bytecodes out from under any threads executing the old
2886       // method and make the thread's bcp invalid. Since EMCP requires
2887       // that the bytecodes be the same modulo constant pool indices, it
2888       // is straight forward to compute the correct new bcp in the new
2889       // ConstMethod* from the old bcp in the old ConstMethod*. The
2890       // time consuming part would be searching all the frames in all
2891       // of the threads to find all of the calls to the old method.
2892       //
2893       // It looks like we will have to live with the limited savings
2894       // that we get from effectively overwriting the old methods
2895       // when the new methods are attached to the_class.
2896 
2897       // track which methods are EMCP for add_previous_version() call
2898       emcp_methods->set_bit(old_index);
2899       (*emcp_method_count_p)++;
2900 
2901       // An EMCP method is _not_ obsolete. An obsolete method has a
2902       // different jmethodID than the current method. An EMCP method
2903       // has the same jmethodID as the current method. Having the
2904       // same jmethodID for all EMCP versions of a method allows for
2905       // a consistent view of the EMCP methods regardless of which
2906       // EMCP method you happen to have in hand. For example, a
2907       // breakpoint set in one EMCP method will work for all EMCP
2908       // versions of the method including the current one.
2909     } else {
2910       // mark obsolete methods as such
2911       old_method->set_is_obsolete();
2912       obsolete_count++;
2913 
2914       // obsolete methods need a unique idnum
2915       u2 num = InstanceKlass::cast(_the_class_oop)->next_method_idnum();
2916       if (num != ConstMethod::UNSET_IDNUM) {
2917 //      u2 old_num = old_method->method_idnum();
2918         old_method->set_method_idnum(num);
2919 // TO DO: attach obsolete annotations to obsolete method's new idnum
2920       }
2921       // With tracing we try not to "yack" too much. The position of
2922       // this trace assumes there are fewer obsolete methods than
2923       // EMCP methods.
2924       RC_TRACE(0x00000100, ("mark %s(%s) as obsolete",
2925         old_method->name()->as_C_string(),
2926         old_method->signature()->as_C_string()));
2927     }
2928     old_method->set_is_old();
2929   }
2930   for (int i = 0; i < _deleted_methods_length; ++i) {
2931     Method* old_method = _deleted_methods[i];
2932 
2933     assert(old_method->vtable_index() < 0,
2934            "cannot delete methods with vtable entries");;
2935 
2936     // Mark all deleted methods as old and obsolete
2937     old_method->set_is_old();
2938     old_method->set_is_obsolete();
2939     ++obsolete_count;
2940     // With tracing we try not to "yack" too much. The position of
2941     // this trace assumes there are fewer obsolete methods than
2942     // EMCP methods.
2943     RC_TRACE(0x00000100, ("mark deleted %s(%s) as obsolete",
2944                           old_method->name()->as_C_string(),
2945                           old_method->signature()->as_C_string()));
2946   }
2947   assert((*emcp_method_count_p + obsolete_count) == _old_methods->length(),
2948     "sanity check");
2949   RC_TRACE(0x00000100, ("EMCP_cnt=%d, obsolete_cnt=%d", *emcp_method_count_p,
2950     obsolete_count));
2951 }
2952 
2953 // This internal class transfers the native function registration from old methods
2954 // to new methods.  It is designed to handle both the simple case of unchanged
2955 // native methods and the complex cases of native method prefixes being added and/or
2956 // removed.
2957 // It expects only to be used during the VM_RedefineClasses op (a safepoint).
2958 //
2959 // This class is used after the new methods have been installed in "the_class".
2960 //
2961 // So, for example, the following must be handled.  Where 'm' is a method and
2962 // a number followed by an underscore is a prefix.
2963 //
2964 //                                      Old Name    New Name
2965 // Simple transfer to new method        m       ->  m
2966 // Add prefix                           m       ->  1_m
2967 // Remove prefix                        1_m     ->  m
2968 // Simultaneous add of prefixes         m       ->  3_2_1_m
2969 // Simultaneous removal of prefixes     3_2_1_m ->  m
2970 // Simultaneous add and remove          1_m     ->  2_m
2971 // Same, caused by prefix removal only  3_2_1_m ->  3_2_m
2972 //
2973 class TransferNativeFunctionRegistration {
2974  private:
2975   instanceKlassHandle the_class;
2976   int prefix_count;
2977   char** prefixes;
2978 
2979   // Recursively search the binary tree of possibly prefixed method names.
2980   // Iteration could be used if all agents were well behaved. Full tree walk is
2981   // more resilent to agents not cleaning up intermediate methods.
2982   // Branch at each depth in the binary tree is:
2983   //    (1) without the prefix.
2984   //    (2) with the prefix.
2985   // where 'prefix' is the prefix at that 'depth' (first prefix, second prefix,...)
2986   Method* search_prefix_name_space(int depth, char* name_str, size_t name_len,
2987                                      Symbol* signature) {
2988     TempNewSymbol name_symbol = SymbolTable::probe(name_str, (int)name_len);
2989     if (name_symbol != NULL) {
2990       Method* method = the_class()->lookup_method(name_symbol, signature);
2991       if (method != NULL) {
2992         // Even if prefixed, intermediate methods must exist.
2993         if (method->is_native()) {
2994           // Wahoo, we found a (possibly prefixed) version of the method, return it.
2995           return method;
2996         }
2997         if (depth < prefix_count) {
2998           // Try applying further prefixes (other than this one).
2999           method = search_prefix_name_space(depth+1, name_str, name_len, signature);
3000           if (method != NULL) {
3001             return method; // found
3002           }
3003 
3004           // Try adding this prefix to the method name and see if it matches
3005           // another method name.
3006           char* prefix = prefixes[depth];
3007           size_t prefix_len = strlen(prefix);
3008           size_t trial_len = name_len + prefix_len;
3009           char* trial_name_str = NEW_RESOURCE_ARRAY(char, trial_len + 1);
3010           strcpy(trial_name_str, prefix);
3011           strcat(trial_name_str, name_str);
3012           method = search_prefix_name_space(depth+1, trial_name_str, trial_len,
3013                                             signature);
3014           if (method != NULL) {
3015             // If found along this branch, it was prefixed, mark as such
3016             method->set_is_prefixed_native();
3017             return method; // found
3018           }
3019         }
3020       }
3021     }
3022     return NULL;  // This whole branch bore nothing
3023   }
3024 
3025   // Return the method name with old prefixes stripped away.
3026   char* method_name_without_prefixes(Method* method) {
3027     Symbol* name = method->name();
3028     char* name_str = name->as_utf8();
3029 
3030     // Old prefixing may be defunct, strip prefixes, if any.
3031     for (int i = prefix_count-1; i >= 0; i--) {
3032       char* prefix = prefixes[i];
3033       size_t prefix_len = strlen(prefix);
3034       if (strncmp(prefix, name_str, prefix_len) == 0) {
3035         name_str += prefix_len;
3036       }
3037     }
3038     return name_str;
3039   }
3040 
3041   // Strip any prefixes off the old native method, then try to find a
3042   // (possibly prefixed) new native that matches it.
3043   Method* strip_and_search_for_new_native(Method* method) {
3044     ResourceMark rm;
3045     char* name_str = method_name_without_prefixes(method);
3046     return search_prefix_name_space(0, name_str, strlen(name_str),
3047                                     method->signature());
3048   }
3049 
3050  public:
3051 
3052   // Construct a native method transfer processor for this class.
3053   TransferNativeFunctionRegistration(instanceKlassHandle _the_class) {
3054     assert(SafepointSynchronize::is_at_safepoint(), "sanity check");
3055 
3056     the_class = _the_class;
3057     prefixes = JvmtiExport::get_all_native_method_prefixes(&prefix_count);
3058   }
3059 
3060   // Attempt to transfer any of the old or deleted methods that are native
3061   void transfer_registrations(Method** old_methods, int methods_length) {
3062     for (int j = 0; j < methods_length; j++) {
3063       Method* old_method = old_methods[j];
3064 
3065       if (old_method->is_native() && old_method->has_native_function()) {
3066         Method* new_method = strip_and_search_for_new_native(old_method);
3067         if (new_method != NULL) {
3068           // Actually set the native function in the new method.
3069           // Redefine does not send events (except CFLH), certainly not this
3070           // behind the scenes re-registration.
3071           new_method->set_native_function(old_method->native_function(),
3072                               !Method::native_bind_event_is_interesting);
3073         }
3074       }
3075     }
3076   }
3077 };
3078 
3079 // Don't lose the association between a native method and its JNI function.
3080 void VM_RedefineClasses::transfer_old_native_function_registrations(instanceKlassHandle the_class) {
3081   TransferNativeFunctionRegistration transfer(the_class);
3082   transfer.transfer_registrations(_deleted_methods, _deleted_methods_length);
3083   transfer.transfer_registrations(_matching_old_methods, _matching_methods_length);
3084 }
3085 
3086 // Deoptimize all compiled code that depends on this class.
3087 //
3088 // If the can_redefine_classes capability is obtained in the onload
3089 // phase then the compiler has recorded all dependencies from startup.
3090 // In that case we need only deoptimize and throw away all compiled code
3091 // that depends on the class.
3092 //
3093 // If can_redefine_classes is obtained sometime after the onload
3094 // phase then the dependency information may be incomplete. In that case
3095 // the first call to RedefineClasses causes all compiled code to be
3096 // thrown away. As can_redefine_classes has been obtained then
3097 // all future compilations will record dependencies so second and
3098 // subsequent calls to RedefineClasses need only throw away code
3099 // that depends on the class.
3100 //
3101 void VM_RedefineClasses::flush_dependent_code(instanceKlassHandle k_h, TRAPS) {
3102   assert_locked_or_safepoint(Compile_lock);
3103 
3104   // All dependencies have been recorded from startup or this is a second or
3105   // subsequent use of RedefineClasses
3106   if (JvmtiExport::all_dependencies_are_recorded()) {
3107     Universe::flush_evol_dependents_on(k_h);
3108   } else {
3109     CodeCache::mark_all_nmethods_for_deoptimization();
3110 
3111     ResourceMark rm(THREAD);
3112     DeoptimizationMarker dm;
3113 
3114     // Deoptimize all activations depending on marked nmethods
3115     Deoptimization::deoptimize_dependents();
3116 
3117     // Make the dependent methods not entrant (in VM_Deoptimize they are made zombies)
3118     CodeCache::make_marked_nmethods_not_entrant();
3119 
3120     // From now on we know that the dependency information is complete
3121     JvmtiExport::set_all_dependencies_are_recorded(true);
3122   }
3123 }
3124 
3125 void VM_RedefineClasses::compute_added_deleted_matching_methods() {
3126   Method* old_method;
3127   Method* new_method;
3128 
3129   _matching_old_methods = NEW_RESOURCE_ARRAY(Method*, _old_methods->length());
3130   _matching_new_methods = NEW_RESOURCE_ARRAY(Method*, _old_methods->length());
3131   _added_methods        = NEW_RESOURCE_ARRAY(Method*, _new_methods->length());
3132   _deleted_methods      = NEW_RESOURCE_ARRAY(Method*, _old_methods->length());
3133 
3134   _matching_methods_length = 0;
3135   _deleted_methods_length  = 0;
3136   _added_methods_length    = 0;
3137 
3138   int nj = 0;
3139   int oj = 0;
3140   while (true) {
3141     if (oj >= _old_methods->length()) {
3142       if (nj >= _new_methods->length()) {
3143         break; // we've looked at everything, done
3144       }
3145       // New method at the end
3146       new_method = _new_methods->at(nj);
3147       _added_methods[_added_methods_length++] = new_method;
3148       ++nj;
3149     } else if (nj >= _new_methods->length()) {
3150       // Old method, at the end, is deleted
3151       old_method = _old_methods->at(oj);
3152       _deleted_methods[_deleted_methods_length++] = old_method;
3153       ++oj;
3154     } else {
3155       old_method = _old_methods->at(oj);
3156       new_method = _new_methods->at(nj);
3157       if (old_method->name() == new_method->name()) {
3158         if (old_method->signature() == new_method->signature()) {
3159           _matching_old_methods[_matching_methods_length  ] = old_method;
3160           _matching_new_methods[_matching_methods_length++] = new_method;
3161           ++nj;
3162           ++oj;
3163         } else {
3164           // added overloaded have already been moved to the end,
3165           // so this is a deleted overloaded method
3166           _deleted_methods[_deleted_methods_length++] = old_method;
3167           ++oj;
3168         }
3169       } else { // names don't match
3170         if (old_method->name()->fast_compare(new_method->name()) > 0) {
3171           // new method
3172           _added_methods[_added_methods_length++] = new_method;
3173           ++nj;
3174         } else {
3175           // deleted method
3176           _deleted_methods[_deleted_methods_length++] = old_method;
3177           ++oj;
3178         }
3179       }
3180     }
3181   }
3182   assert(_matching_methods_length + _deleted_methods_length == _old_methods->length(), "sanity");
3183   assert(_matching_methods_length + _added_methods_length == _new_methods->length(), "sanity");
3184 }
3185 
3186 
3187 void VM_RedefineClasses::swap_annotations(instanceKlassHandle the_class,
3188                                           instanceKlassHandle scratch_class) {
3189   // Since there is currently no rewriting of type annotations indexes
3190   // into the CP, we null out type annotations on scratch_class before
3191   // we swap annotations with the_class rather than facing the
3192   // possibility of shipping annotations with broken indexes to
3193   // Java-land.
3194   ClassLoaderData* loader_data = scratch_class->class_loader_data();
3195   AnnotationArray* new_class_type_annotations = scratch_class->class_type_annotations();
3196   if (new_class_type_annotations != NULL) {
3197     MetadataFactory::free_array<u1>(loader_data, new_class_type_annotations);
3198     scratch_class->annotations()->set_class_type_annotations(NULL);
3199   }
3200   Array<AnnotationArray*>* new_field_type_annotations = scratch_class->fields_type_annotations();
3201   if (new_field_type_annotations != NULL) {
3202     Annotations::free_contents(loader_data, new_field_type_annotations);
3203     scratch_class->annotations()->set_fields_type_annotations(NULL);
3204   }
3205 
3206   // Swap annotation fields values
3207   Annotations* old_annotations = the_class->annotations();
3208   the_class->set_annotations(scratch_class->annotations());
3209   scratch_class->set_annotations(old_annotations);
3210 }
3211 
3212 
3213 // Install the redefinition of a class:
3214 //    - house keeping (flushing breakpoints and caches, deoptimizing
3215 //      dependent compiled code)
3216 //    - replacing parts in the_class with parts from scratch_class
3217 //    - adding a weak reference to track the obsolete but interesting
3218 //      parts of the_class
3219 //    - adjusting constant pool caches and vtables in other classes
3220 //      that refer to methods in the_class. These adjustments use the
3221 //      ClassLoaderDataGraph::classes_do() facility which only allows
3222 //      a helper method to be specified. The interesting parameters
3223 //      that we would like to pass to the helper method are saved in
3224 //      static global fields in the VM operation.
3225 void VM_RedefineClasses::redefine_single_class(jclass the_jclass,
3226        Klass* scratch_class_oop, TRAPS) {
3227 
3228   HandleMark hm(THREAD);   // make sure handles from this call are freed
3229   RC_TIMER_START(_timer_rsc_phase1);
3230 
3231   instanceKlassHandle scratch_class(scratch_class_oop);
3232 
3233   oop the_class_mirror = JNIHandles::resolve_non_null(the_jclass);
3234   Klass* the_class_oop = java_lang_Class::as_Klass(the_class_mirror);
3235   instanceKlassHandle the_class = instanceKlassHandle(THREAD, the_class_oop);
3236 
3237   // Remove all breakpoints in methods of this class
3238   JvmtiBreakpoints& jvmti_breakpoints = JvmtiCurrentBreakpoints::get_jvmti_breakpoints();
3239   jvmti_breakpoints.clearall_in_class_at_safepoint(the_class_oop);
3240 
3241   // Deoptimize all compiled code that depends on this class
3242   flush_dependent_code(the_class, THREAD);
3243 
3244   _old_methods = the_class->methods();
3245   _new_methods = scratch_class->methods();
3246   _the_class_oop = the_class_oop;
3247   compute_added_deleted_matching_methods();
3248   update_jmethod_ids();
3249 
3250   // Attach new constant pool to the original klass. The original
3251   // klass still refers to the old constant pool (for now).
3252   scratch_class->constants()->set_pool_holder(the_class());
3253 
3254 #if 0
3255   // In theory, with constant pool merging in place we should be able
3256   // to save space by using the new, merged constant pool in place of
3257   // the old constant pool(s). By "pool(s)" I mean the constant pool in
3258   // the klass version we are replacing now and any constant pool(s) in
3259   // previous versions of klass. Nice theory, doesn't work in practice.
3260   // When this code is enabled, even simple programs throw NullPointer
3261   // exceptions. I'm guessing that this is caused by some constant pool
3262   // cache difference between the new, merged constant pool and the
3263   // constant pool that was just being used by the klass. I'm keeping
3264   // this code around to archive the idea, but the code has to remain
3265   // disabled for now.
3266 
3267   // Attach each old method to the new constant pool. This can be
3268   // done here since we are past the bytecode verification and
3269   // constant pool optimization phases.
3270   for (int i = _old_methods->length() - 1; i >= 0; i--) {
3271     Method* method = _old_methods->at(i);
3272     method->set_constants(scratch_class->constants());
3273   }
3274 
3275   {
3276     // walk all previous versions of the klass
3277     InstanceKlass *ik = (InstanceKlass *)the_class();
3278     PreviousVersionWalker pvw(ik);
3279     instanceKlassHandle ikh;
3280     do {
3281       ikh = pvw.next_previous_version();
3282       if (!ikh.is_null()) {
3283         ik = ikh();
3284 
3285         // attach previous version of klass to the new constant pool
3286         ik->set_constants(scratch_class->constants());
3287 
3288         // Attach each method in the previous version of klass to the
3289         // new constant pool
3290         Array<Method*>* prev_methods = ik->methods();
3291         for (int i = prev_methods->length() - 1; i >= 0; i--) {
3292           Method* method = prev_methods->at(i);
3293           method->set_constants(scratch_class->constants());
3294         }
3295       }
3296     } while (!ikh.is_null());
3297   }
3298 #endif
3299 
3300   // Replace methods and constantpool
3301   the_class->set_methods(_new_methods);
3302   scratch_class->set_methods(_old_methods);     // To prevent potential GCing of the old methods,
3303                                           // and to be able to undo operation easily.
3304 
3305   ConstantPool* old_constants = the_class->constants();
3306   the_class->set_constants(scratch_class->constants());
3307   scratch_class->set_constants(old_constants);  // See the previous comment.
3308 #if 0
3309   // We are swapping the guts of "the new class" with the guts of "the
3310   // class". Since the old constant pool has just been attached to "the
3311   // new class", it seems logical to set the pool holder in the old
3312   // constant pool also. However, doing this will change the observable
3313   // class hierarchy for any old methods that are still executing. A
3314   // method can query the identity of its "holder" and this query uses
3315   // the method's constant pool link to find the holder. The change in
3316   // holding class from "the class" to "the new class" can confuse
3317   // things.
3318   //
3319   // Setting the old constant pool's holder will also cause
3320   // verification done during vtable initialization below to fail.
3321   // During vtable initialization, the vtable's class is verified to be
3322   // a subtype of the method's holder. The vtable's class is "the
3323   // class" and the method's holder is gotten from the constant pool
3324   // link in the method itself. For "the class"'s directly implemented
3325   // methods, the method holder is "the class" itself (as gotten from
3326   // the new constant pool). The check works fine in this case. The
3327   // check also works fine for methods inherited from super classes.
3328   //
3329   // Miranda methods are a little more complicated. A miranda method is
3330   // provided by an interface when the class implementing the interface
3331   // does not provide its own method.  These interfaces are implemented
3332   // internally as an InstanceKlass. These special instanceKlasses
3333   // share the constant pool of the class that "implements" the
3334   // interface. By sharing the constant pool, the method holder of a
3335   // miranda method is the class that "implements" the interface. In a
3336   // non-redefine situation, the subtype check works fine. However, if
3337   // the old constant pool's pool holder is modified, then the check
3338   // fails because there is no class hierarchy relationship between the
3339   // vtable's class and "the new class".
3340 
3341   old_constants->set_pool_holder(scratch_class());
3342 #endif
3343 
3344   // track which methods are EMCP for add_previous_version() call below
3345   BitMap emcp_methods(_old_methods->length());
3346   int emcp_method_count = 0;
3347   emcp_methods.clear();  // clears 0..(length() - 1)
3348   check_methods_and_mark_as_obsolete(&emcp_methods, &emcp_method_count);
3349   transfer_old_native_function_registrations(the_class);
3350 
3351   // The class file bytes from before any retransformable agents mucked
3352   // with them was cached on the scratch class, move to the_class.
3353   // Note: we still want to do this if nothing needed caching since it
3354   // should get cleared in the_class too.
3355   if (the_class->get_cached_class_file_bytes() == 0) {
3356     // the_class doesn't have a cache yet so copy it
3357     the_class->set_cached_class_file(scratch_class->get_cached_class_file());
3358   }
3359 #ifndef PRODUCT
3360   else {
3361     assert(the_class->get_cached_class_file_bytes() ==
3362       scratch_class->get_cached_class_file_bytes(), "cache ptrs must match");
3363     assert(the_class->get_cached_class_file_len() ==
3364       scratch_class->get_cached_class_file_len(), "cache lens must match");
3365   }
3366 #endif
3367 
3368   // NULL out in scratch class to not delete twice.  The class to be redefined
3369   // always owns these bytes.
3370   scratch_class->set_cached_class_file(NULL);
3371 
3372   // Replace inner_classes
3373   Array<u2>* old_inner_classes = the_class->inner_classes();
3374   the_class->set_inner_classes(scratch_class->inner_classes());
3375   scratch_class->set_inner_classes(old_inner_classes);
3376 
3377   // Initialize the vtable and interface table after
3378   // methods have been rewritten
3379   {
3380     ResourceMark rm(THREAD);
3381     // no exception should happen here since we explicitly
3382     // do not check loader constraints.
3383     // compare_and_normalize_class_versions has already checked:
3384     //  - classloaders unchanged, signatures unchanged
3385     //  - all instanceKlasses for redefined classes reused & contents updated
3386     the_class->vtable()->initialize_vtable(false, THREAD);
3387     the_class->itable()->initialize_itable(false, THREAD);
3388     assert(!HAS_PENDING_EXCEPTION || (THREAD->pending_exception()->is_a(SystemDictionary::ThreadDeath_klass())), "redefine exception");
3389   }
3390 
3391   // Leave arrays of jmethodIDs and itable index cache unchanged
3392 
3393   // Copy the "source file name" attribute from new class version
3394   the_class->set_source_file_name_index(
3395     scratch_class->source_file_name_index());
3396 
3397   // Copy the "source debug extension" attribute from new class version
3398   the_class->set_source_debug_extension(
3399     scratch_class->source_debug_extension(),
3400     scratch_class->source_debug_extension() == NULL ? 0 :
3401     (int)strlen(scratch_class->source_debug_extension()));
3402 
3403   // Use of javac -g could be different in the old and the new
3404   if (scratch_class->access_flags().has_localvariable_table() !=
3405       the_class->access_flags().has_localvariable_table()) {
3406 
3407     AccessFlags flags = the_class->access_flags();
3408     if (scratch_class->access_flags().has_localvariable_table()) {
3409       flags.set_has_localvariable_table();
3410     } else {
3411       flags.clear_has_localvariable_table();
3412     }
3413     the_class->set_access_flags(flags);
3414   }
3415 
3416   swap_annotations(the_class, scratch_class);
3417 
3418   // Replace minor version number of class file
3419   u2 old_minor_version = the_class->minor_version();
3420   the_class->set_minor_version(scratch_class->minor_version());
3421   scratch_class->set_minor_version(old_minor_version);
3422 
3423   // Replace major version number of class file
3424   u2 old_major_version = the_class->major_version();
3425   the_class->set_major_version(scratch_class->major_version());
3426   scratch_class->set_major_version(old_major_version);
3427 
3428   // Replace CP indexes for class and name+type of enclosing method
3429   u2 old_class_idx  = the_class->enclosing_method_class_index();
3430   u2 old_method_idx = the_class->enclosing_method_method_index();
3431   the_class->set_enclosing_method_indices(
3432     scratch_class->enclosing_method_class_index(),
3433     scratch_class->enclosing_method_method_index());
3434   scratch_class->set_enclosing_method_indices(old_class_idx, old_method_idx);
3435 
3436   // keep track of previous versions of this class
3437   the_class->add_previous_version(scratch_class, &emcp_methods,
3438     emcp_method_count);
3439 
3440   RC_TIMER_STOP(_timer_rsc_phase1);
3441   RC_TIMER_START(_timer_rsc_phase2);
3442 
3443   // Adjust constantpool caches and vtables for all classes
3444   // that reference methods of the evolved class.
3445   AdjustCpoolCacheAndVtable adjust_cpool_cache_and_vtable(THREAD);
3446   ClassLoaderDataGraph::classes_do(&adjust_cpool_cache_and_vtable);
3447 
3448   // JSR-292 support
3449   MemberNameTable* mnt = the_class->member_names();
3450   if (mnt != NULL) {
3451     bool trace_name_printed = false;
3452     mnt->adjust_method_entries(_matching_old_methods,
3453                                _matching_new_methods,
3454                                _matching_methods_length,
3455                                &trace_name_printed);
3456   }
3457 
3458   // Fix Resolution Error table also to remove old constant pools
3459   SystemDictionary::delete_resolution_error(old_constants);
3460 
3461   if (the_class->oop_map_cache() != NULL) {
3462     // Flush references to any obsolete methods from the oop map cache
3463     // so that obsolete methods are not pinned.
3464     the_class->oop_map_cache()->flush_obsolete_entries();
3465   }
3466 
3467   // increment the classRedefinedCount field in the_class and in any
3468   // direct and indirect subclasses of the_class
3469   increment_class_counter((InstanceKlass *)the_class(), THREAD);
3470 
3471   // RC_TRACE macro has an embedded ResourceMark
3472   RC_TRACE_WITH_THREAD(0x00000001, THREAD,
3473     ("redefined name=%s, count=%d (avail_mem=" UINT64_FORMAT "K)",
3474     the_class->external_name(),
3475     java_lang_Class::classRedefinedCount(the_class_mirror),
3476     os::available_memory() >> 10));
3477 
3478   RC_TIMER_STOP(_timer_rsc_phase2);
3479 } // end redefine_single_class()
3480 
3481 
3482 // Increment the classRedefinedCount field in the specific InstanceKlass
3483 // and in all direct and indirect subclasses.
3484 void VM_RedefineClasses::increment_class_counter(InstanceKlass *ik, TRAPS) {
3485   oop class_mirror = ik->java_mirror();
3486   Klass* class_oop = java_lang_Class::as_Klass(class_mirror);
3487   int new_count = java_lang_Class::classRedefinedCount(class_mirror) + 1;
3488   java_lang_Class::set_classRedefinedCount(class_mirror, new_count);
3489 
3490   if (class_oop != _the_class_oop) {
3491     // _the_class_oop count is printed at end of redefine_single_class()
3492     RC_TRACE_WITH_THREAD(0x00000008, THREAD,
3493       ("updated count in subclass=%s to %d", ik->external_name(), new_count));
3494   }
3495 
3496   for (Klass *subk = ik->subklass(); subk != NULL;
3497        subk = subk->next_sibling()) {
3498     if (subk->oop_is_instance()) {
3499       // Only update instanceKlasses
3500       InstanceKlass *subik = (InstanceKlass*)subk;
3501       // recursively do subclasses of the current subclass
3502       increment_class_counter(subik, THREAD);
3503     }
3504   }
3505 }
3506 
3507 void VM_RedefineClasses::CheckClass::do_klass(Klass* k) {
3508   bool no_old_methods = true;  // be optimistic
3509 
3510   // Both array and instance classes have vtables.
3511   // a vtable should never contain old or obsolete methods
3512   ResourceMark rm(_thread);
3513   if (k->vtable_length() > 0 &&
3514       !k->vtable()->check_no_old_or_obsolete_entries()) {
3515     if (RC_TRACE_ENABLED(0x00004000)) {
3516       RC_TRACE_WITH_THREAD(0x00004000, _thread,
3517         ("klassVtable::check_no_old_or_obsolete_entries failure"
3518          " -- OLD or OBSOLETE method found -- class: %s",
3519          k->signature_name()));
3520       k->vtable()->dump_vtable();
3521     }
3522     no_old_methods = false;
3523   }
3524 
3525   if (k->oop_is_instance()) {
3526     HandleMark hm(_thread);
3527     InstanceKlass *ik = InstanceKlass::cast(k);
3528 
3529     // an itable should never contain old or obsolete methods
3530     if (ik->itable_length() > 0 &&
3531         !ik->itable()->check_no_old_or_obsolete_entries()) {
3532       if (RC_TRACE_ENABLED(0x00004000)) {
3533         RC_TRACE_WITH_THREAD(0x00004000, _thread,
3534           ("klassItable::check_no_old_or_obsolete_entries failure"
3535            " -- OLD or OBSOLETE method found -- class: %s",
3536            ik->signature_name()));
3537         ik->itable()->dump_itable();
3538       }
3539       no_old_methods = false;
3540     }
3541 
3542     // the constant pool cache should never contain old or obsolete methods
3543     if (ik->constants() != NULL &&
3544         ik->constants()->cache() != NULL &&
3545         !ik->constants()->cache()->check_no_old_or_obsolete_entries()) {
3546       if (RC_TRACE_ENABLED(0x00004000)) {
3547         RC_TRACE_WITH_THREAD(0x00004000, _thread,
3548           ("cp-cache::check_no_old_or_obsolete_entries failure"
3549            " -- OLD or OBSOLETE method found -- class: %s",
3550            ik->signature_name()));
3551         ik->constants()->cache()->dump_cache();
3552       }
3553       no_old_methods = false;
3554     }
3555   }
3556 
3557   // print and fail guarantee if old methods are found.
3558   if (!no_old_methods) {
3559     if (RC_TRACE_ENABLED(0x00004000)) {
3560       dump_methods();
3561     } else {
3562       tty->print_cr("INFO: use the '-XX:TraceRedefineClasses=16384' option "
3563         "to see more info about the following guarantee() failure.");
3564     }
3565     guarantee(false, "OLD and/or OBSOLETE method(s) found");
3566   }
3567 }
3568 
3569 
3570 void VM_RedefineClasses::dump_methods() {
3571   int j;
3572   RC_TRACE(0x00004000, ("_old_methods --"));
3573   for (j = 0; j < _old_methods->length(); ++j) {
3574     Method* m = _old_methods->at(j);
3575     RC_TRACE_NO_CR(0x00004000, ("%4d  (%5d)  ", j, m->vtable_index()));
3576     m->access_flags().print_on(tty);
3577     tty->print(" --  ");
3578     m->print_name(tty);
3579     tty->cr();
3580   }
3581   RC_TRACE(0x00004000, ("_new_methods --"));
3582   for (j = 0; j < _new_methods->length(); ++j) {
3583     Method* m = _new_methods->at(j);
3584     RC_TRACE_NO_CR(0x00004000, ("%4d  (%5d)  ", j, m->vtable_index()));
3585     m->access_flags().print_on(tty);
3586     tty->print(" --  ");
3587     m->print_name(tty);
3588     tty->cr();
3589   }
3590   RC_TRACE(0x00004000, ("_matching_(old/new)_methods --"));
3591   for (j = 0; j < _matching_methods_length; ++j) {
3592     Method* m = _matching_old_methods[j];
3593     RC_TRACE_NO_CR(0x00004000, ("%4d  (%5d)  ", j, m->vtable_index()));
3594     m->access_flags().print_on(tty);
3595     tty->print(" --  ");
3596     m->print_name(tty);
3597     tty->cr();
3598     m = _matching_new_methods[j];
3599     RC_TRACE_NO_CR(0x00004000, ("      (%5d)  ", m->vtable_index()));
3600     m->access_flags().print_on(tty);
3601     tty->cr();
3602   }
3603   RC_TRACE(0x00004000, ("_deleted_methods --"));
3604   for (j = 0; j < _deleted_methods_length; ++j) {
3605     Method* m = _deleted_methods[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, ("_added_methods --"));
3613   for (j = 0; j < _added_methods_length; ++j) {
3614     Method* m = _added_methods[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 }
--- EOF ---