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 (HAS_PENDING_EXCEPTION) {
1076       Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1077       CLEAR_PENDING_EXCEPTION;
1078       if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1079         return JVMTI_ERROR_OUT_OF_MEMORY;
1080       } else {
1081         return JVMTI_ERROR_INTERNAL;
1082       }
1083     }
1084 
1085     if (VerifyMergedCPBytecodes) {
1086       // verify what we have done during constant pool merging
1087       {
1088         RedefineVerifyMark rvm(&the_class, &scratch_class, state);
1089         Verifier::verify(scratch_class, Verifier::ThrowException, true, THREAD);
1090       }
1091 
1092       if (HAS_PENDING_EXCEPTION) {
1093         Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1094         // RC_TRACE_WITH_THREAD macro has an embedded ResourceMark
1095         RC_TRACE_WITH_THREAD(0x00000002, THREAD,
1096           ("verify_byte_codes post merge-CP exception: '%s'",
1097           ex_name->as_C_string()));
1098         CLEAR_PENDING_EXCEPTION;
1099         if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1100           return JVMTI_ERROR_OUT_OF_MEMORY;
1101         } else {
1102           // tell the caller that constant pool merging screwed up
1103           return JVMTI_ERROR_INTERNAL;
1104         }
1105       }
1106     }
1107 
1108     Rewriter::rewrite(scratch_class, THREAD);
1109     if (!HAS_PENDING_EXCEPTION) {
1110       scratch_class->link_methods(THREAD);
1111     }
1112     if (HAS_PENDING_EXCEPTION) {
1113       Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1114       CLEAR_PENDING_EXCEPTION;
1115       if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1116         return JVMTI_ERROR_OUT_OF_MEMORY;
1117       } else {
1118         return JVMTI_ERROR_INTERNAL;
1119       }
1120     }
1121 
1122     // RC_TRACE_WITH_THREAD macro has an embedded ResourceMark
1123     RC_TRACE_WITH_THREAD(0x00000001, THREAD,
1124       ("loaded name=%s (avail_mem=" UINT64_FORMAT "K)",
1125       the_class->external_name(), os::available_memory() >> 10));
1126   }
1127 
1128   return JVMTI_ERROR_NONE;
1129 }
1130 
1131 
1132 // Map old_index to new_index as needed. scratch_cp is only needed
1133 // for RC_TRACE() calls.
1134 void VM_RedefineClasses::map_index(constantPoolHandle scratch_cp,
1135        int old_index, int new_index) {
1136   if (find_new_index(old_index) != 0) {
1137     // old_index is already mapped
1138     return;
1139   }
1140 
1141   if (old_index == new_index) {
1142     // no mapping is needed
1143     return;
1144   }
1145 
1146   _index_map_p->at_put(old_index, new_index);
1147   _index_map_count++;
1148 
1149   RC_TRACE(0x00040000, ("mapped tag %d at index %d to %d",
1150     scratch_cp->tag_at(old_index).value(), old_index, new_index));
1151 } // end map_index()
1152 
1153 
1154 // Map old_index to new_index as needed.
1155 void VM_RedefineClasses::map_operand_index(int old_index, int new_index) {
1156   if (find_new_operand_index(old_index) != -1) {
1157     // old_index is already mapped
1158     return;
1159   }
1160 
1161   if (old_index == new_index) {
1162     // no mapping is needed
1163     return;
1164   }
1165 
1166   _operands_index_map_p->at_put(old_index, new_index);
1167   _operands_index_map_count++;
1168 
1169   RC_TRACE(0x00040000, ("mapped bootstrap specifier at index %d to %d", old_index, new_index));
1170 } // end map_index()
1171 
1172 
1173 // Merge old_cp and scratch_cp and return the results of the merge via
1174 // merge_cp_p. The number of entries in *merge_cp_p is returned via
1175 // merge_cp_length_p. The entries in old_cp occupy the same locations
1176 // in *merge_cp_p. Also creates a map of indices from entries in
1177 // scratch_cp to the corresponding entry in *merge_cp_p. Index map
1178 // entries are only created for entries in scratch_cp that occupy a
1179 // different location in *merged_cp_p.
1180 bool VM_RedefineClasses::merge_constant_pools(constantPoolHandle old_cp,
1181        constantPoolHandle scratch_cp, constantPoolHandle *merge_cp_p,
1182        int *merge_cp_length_p, TRAPS) {
1183 
1184   if (merge_cp_p == NULL) {
1185     assert(false, "caller must provide scratch constantPool");
1186     return false; // robustness
1187   }
1188   if (merge_cp_length_p == NULL) {
1189     assert(false, "caller must provide scratch CP length");
1190     return false; // robustness
1191   }
1192   // Worst case we need old_cp->length() + scratch_cp()->length(),
1193   // but the caller might be smart so make sure we have at least
1194   // the minimum.
1195   if ((*merge_cp_p)->length() < old_cp->length()) {
1196     assert(false, "merge area too small");
1197     return false; // robustness
1198   }
1199 
1200   RC_TRACE_WITH_THREAD(0x00010000, THREAD,
1201     ("old_cp_len=%d, scratch_cp_len=%d", old_cp->length(),
1202     scratch_cp->length()));
1203 
1204   {
1205     // Pass 0:
1206     // The old_cp is copied to *merge_cp_p; this means that any code
1207     // using old_cp does not have to change. This work looks like a
1208     // perfect fit for ConstantPool*::copy_cp_to(), but we need to
1209     // handle one special case:
1210     // - revert JVM_CONSTANT_Class to JVM_CONSTANT_UnresolvedClass
1211     // This will make verification happy.
1212 
1213     int old_i;  // index into old_cp
1214 
1215     // index zero (0) is not used in constantPools
1216     for (old_i = 1; old_i < old_cp->length(); old_i++) {
1217       // leave debugging crumb
1218       jbyte old_tag = old_cp->tag_at(old_i).value();
1219       switch (old_tag) {
1220       case JVM_CONSTANT_Class:
1221       case JVM_CONSTANT_UnresolvedClass:
1222         // revert the copy to JVM_CONSTANT_UnresolvedClass
1223         // May be resolving while calling this so do the same for
1224         // JVM_CONSTANT_UnresolvedClass (klass_name_at() deals with transition)
1225         (*merge_cp_p)->unresolved_klass_at_put(old_i,
1226           old_cp->klass_name_at(old_i));
1227         break;
1228 
1229       case JVM_CONSTANT_Double:
1230       case JVM_CONSTANT_Long:
1231         // just copy the entry to *merge_cp_p, but double and long take
1232         // two constant pool entries
1233         ConstantPool::copy_entry_to(old_cp, old_i, *merge_cp_p, old_i, CHECK_0);
1234         old_i++;
1235         break;
1236 
1237       default:
1238         // just copy the entry to *merge_cp_p
1239         ConstantPool::copy_entry_to(old_cp, old_i, *merge_cp_p, old_i, CHECK_0);
1240         break;
1241       }
1242     } // end for each old_cp entry
1243 
1244     ConstantPool::copy_operands(old_cp, *merge_cp_p, CHECK_0);
1245     (*merge_cp_p)->extend_operands(scratch_cp, CHECK_0);
1246 
1247     // We don't need to sanity check that *merge_cp_length_p is within
1248     // *merge_cp_p bounds since we have the minimum on-entry check above.
1249     (*merge_cp_length_p) = old_i;
1250   }
1251 
1252   // merge_cp_len should be the same as old_cp->length() at this point
1253   // so this trace message is really a "warm-and-breathing" message.
1254   RC_TRACE_WITH_THREAD(0x00020000, THREAD,
1255     ("after pass 0: merge_cp_len=%d", *merge_cp_length_p));
1256 
1257   int scratch_i;  // index into scratch_cp
1258   {
1259     // Pass 1a:
1260     // Compare scratch_cp entries to the old_cp entries that we have
1261     // already copied to *merge_cp_p. In this pass, we are eliminating
1262     // exact duplicates (matching entry at same index) so we only
1263     // compare entries in the common indice range.
1264     int increment = 1;
1265     int pass1a_length = MIN2(old_cp->length(), scratch_cp->length());
1266     for (scratch_i = 1; scratch_i < pass1a_length; scratch_i += increment) {
1267       switch (scratch_cp->tag_at(scratch_i).value()) {
1268       case JVM_CONSTANT_Double:
1269       case JVM_CONSTANT_Long:
1270         // double and long take two constant pool entries
1271         increment = 2;
1272         break;
1273 
1274       default:
1275         increment = 1;
1276         break;
1277       }
1278 
1279       bool match = scratch_cp->compare_entry_to(scratch_i, *merge_cp_p,
1280         scratch_i, CHECK_0);
1281       if (match) {
1282         // found a match at the same index so nothing more to do
1283         continue;
1284       } else if (is_unresolved_class_mismatch(scratch_cp, scratch_i,
1285                                               *merge_cp_p, scratch_i)) {
1286         // The mismatch in compare_entry_to() above is because of a
1287         // resolved versus unresolved class entry at the same index
1288         // with the same string value. Since Pass 0 reverted any
1289         // class entries to unresolved class entries in *merge_cp_p,
1290         // we go with the unresolved class entry.
1291         continue;
1292       }
1293 
1294       int found_i = scratch_cp->find_matching_entry(scratch_i, *merge_cp_p,
1295         CHECK_0);
1296       if (found_i != 0) {
1297         guarantee(found_i != scratch_i,
1298           "compare_entry_to() and find_matching_entry() do not agree");
1299 
1300         // Found a matching entry somewhere else in *merge_cp_p so
1301         // just need a mapping entry.
1302         map_index(scratch_cp, scratch_i, found_i);
1303         continue;
1304       }
1305 
1306       // The find_matching_entry() call above could fail to find a match
1307       // due to a resolved versus unresolved class or string entry situation
1308       // like we solved above with the is_unresolved_*_mismatch() calls.
1309       // However, we would have to call is_unresolved_*_mismatch() over
1310       // all of *merge_cp_p (potentially) and that doesn't seem to be
1311       // worth the time.
1312 
1313       // No match found so we have to append this entry and any unique
1314       // referenced entries to *merge_cp_p.
1315       append_entry(scratch_cp, scratch_i, merge_cp_p, merge_cp_length_p,
1316         CHECK_0);
1317     }
1318   }
1319 
1320   RC_TRACE_WITH_THREAD(0x00020000, THREAD,
1321     ("after pass 1a: merge_cp_len=%d, scratch_i=%d, index_map_len=%d",
1322     *merge_cp_length_p, scratch_i, _index_map_count));
1323 
1324   if (scratch_i < scratch_cp->length()) {
1325     // Pass 1b:
1326     // old_cp is smaller than scratch_cp so there are entries in
1327     // scratch_cp that we have not yet processed. We take care of
1328     // those now.
1329     int increment = 1;
1330     for (; scratch_i < scratch_cp->length(); scratch_i += increment) {
1331       switch (scratch_cp->tag_at(scratch_i).value()) {
1332       case JVM_CONSTANT_Double:
1333       case JVM_CONSTANT_Long:
1334         // double and long take two constant pool entries
1335         increment = 2;
1336         break;
1337 
1338       default:
1339         increment = 1;
1340         break;
1341       }
1342 
1343       int found_i =
1344         scratch_cp->find_matching_entry(scratch_i, *merge_cp_p, CHECK_0);
1345       if (found_i != 0) {
1346         // Found a matching entry somewhere else in *merge_cp_p so
1347         // just need a mapping entry.
1348         map_index(scratch_cp, scratch_i, found_i);
1349         continue;
1350       }
1351 
1352       // No match found so we have to append this entry and any unique
1353       // referenced entries to *merge_cp_p.
1354       append_entry(scratch_cp, scratch_i, merge_cp_p, merge_cp_length_p,
1355         CHECK_0);
1356     }
1357 
1358     RC_TRACE_WITH_THREAD(0x00020000, THREAD,
1359       ("after pass 1b: merge_cp_len=%d, scratch_i=%d, index_map_len=%d",
1360       *merge_cp_length_p, scratch_i, _index_map_count));
1361   }
1362   finalize_operands_merge(*merge_cp_p, THREAD);
1363 
1364   return true;
1365 } // end merge_constant_pools()
1366 
1367 
1368 // Scoped object to clean up the constant pool(s) created for merging
1369 class MergeCPCleaner {
1370   ClassLoaderData*   _loader_data;
1371   ConstantPool*      _cp;
1372   ConstantPool*      _scratch_cp;
1373  public:
1374   MergeCPCleaner(ClassLoaderData* loader_data, ConstantPool* merge_cp) :
1375                  _loader_data(loader_data), _cp(merge_cp), _scratch_cp(NULL) {}
1376   ~MergeCPCleaner() {
1377     _loader_data->add_to_deallocate_list(_cp);
1378     if (_scratch_cp != NULL) {
1379       _loader_data->add_to_deallocate_list(_scratch_cp);
1380     }
1381   }
1382   void add_scratch_cp(ConstantPool* scratch_cp) { _scratch_cp = scratch_cp; }
1383 };
1384 
1385 // Merge constant pools between the_class and scratch_class and
1386 // potentially rewrite bytecodes in scratch_class to use the merged
1387 // constant pool.
1388 jvmtiError VM_RedefineClasses::merge_cp_and_rewrite(
1389              instanceKlassHandle the_class, instanceKlassHandle scratch_class,
1390              TRAPS) {
1391   // worst case merged constant pool length is old and new combined
1392   int merge_cp_length = the_class->constants()->length()
1393         + scratch_class->constants()->length();
1394 
1395   // Constant pools are not easily reused so we allocate a new one
1396   // each time.
1397   // merge_cp is created unsafe for concurrent GC processing.  It
1398   // should be marked safe before discarding it. Even though
1399   // garbage,  if it crosses a card boundary, it may be scanned
1400   // in order to find the start of the first complete object on the card.
1401   ClassLoaderData* loader_data = the_class->class_loader_data();
1402   ConstantPool* merge_cp_oop =
1403     ConstantPool::allocate(loader_data,
1404                                   merge_cp_length,
1405                                   THREAD);
1406   MergeCPCleaner cp_cleaner(loader_data, merge_cp_oop);
1407 
1408   HandleMark hm(THREAD);  // make sure handles are cleared before
1409                           // MergeCPCleaner clears out merge_cp_oop
1410   constantPoolHandle merge_cp(THREAD, merge_cp_oop);
1411 
1412   // Get constants() from the old class because it could have been rewritten
1413   // while we were at a safepoint allocating a new constant pool.
1414   constantPoolHandle old_cp(THREAD, the_class->constants());
1415   constantPoolHandle scratch_cp(THREAD, scratch_class->constants());
1416 
1417   // If the length changed, the class was redefined out from under us. Return
1418   // an error.
1419   if (merge_cp_length != the_class->constants()->length()
1420          + scratch_class->constants()->length()) {
1421     return JVMTI_ERROR_INTERNAL;
1422   }
1423 
1424   // Update the version number of the constant pool
1425   merge_cp->increment_and_save_version(old_cp->version());
1426 
1427   ResourceMark rm(THREAD);
1428   _index_map_count = 0;
1429   _index_map_p = new intArray(scratch_cp->length(), -1);
1430 
1431   _operands_cur_length = ConstantPool::operand_array_length(old_cp->operands());
1432   _operands_index_map_count = 0;
1433   _operands_index_map_p = new intArray(
1434     ConstantPool::operand_array_length(scratch_cp->operands()), -1);
1435 
1436   // reference to the cp holder is needed for copy_operands()
1437   merge_cp->set_pool_holder(scratch_class());
1438   bool result = merge_constant_pools(old_cp, scratch_cp, &merge_cp,
1439                   &merge_cp_length, THREAD);
1440   merge_cp->set_pool_holder(NULL);
1441 
1442   if (!result) {
1443     // The merge can fail due to memory allocation failure or due
1444     // to robustness checks.
1445     return JVMTI_ERROR_INTERNAL;
1446   }
1447 
1448   RC_TRACE_WITH_THREAD(0x00010000, THREAD,
1449     ("merge_cp_len=%d, index_map_len=%d", merge_cp_length, _index_map_count));
1450 
1451   if (_index_map_count == 0) {
1452     // there is nothing to map between the new and merged constant pools
1453 
1454     if (old_cp->length() == scratch_cp->length()) {
1455       // The old and new constant pools are the same length and the
1456       // index map is empty. This means that the three constant pools
1457       // are equivalent (but not the same). Unfortunately, the new
1458       // constant pool has not gone through link resolution nor have
1459       // the new class bytecodes gone through constant pool cache
1460       // rewriting so we can't use the old constant pool with the new
1461       // class.
1462 
1463       // toss the merged constant pool at return
1464     } else if (old_cp->length() < scratch_cp->length()) {
1465       // The old constant pool has fewer entries than the new constant
1466       // pool and the index map is empty. This means the new constant
1467       // pool is a superset of the old constant pool. However, the old
1468       // class bytecodes have already gone through constant pool cache
1469       // rewriting so we can't use the new constant pool with the old
1470       // class.
1471 
1472       // toss the merged constant pool at return
1473     } else {
1474       // The old constant pool has more entries than the new constant
1475       // pool and the index map is empty. This means that both the old
1476       // and merged constant pools are supersets of the new constant
1477       // pool.
1478 
1479       // Replace the new constant pool with a shrunken copy of the
1480       // merged constant pool
1481       set_new_constant_pool(loader_data, scratch_class, merge_cp, merge_cp_length, THREAD);
1482       // The new constant pool replaces scratch_cp so have cleaner clean it up.
1483       // It can't be cleaned up while there are handles to it.
1484       cp_cleaner.add_scratch_cp(scratch_cp());
1485     }
1486   } else {
1487     if (RC_TRACE_ENABLED(0x00040000)) {
1488       // don't want to loop unless we are tracing
1489       int count = 0;
1490       for (int i = 1; i < _index_map_p->length(); i++) {
1491         int value = _index_map_p->at(i);
1492 
1493         if (value != -1) {
1494           RC_TRACE_WITH_THREAD(0x00040000, THREAD,
1495             ("index_map[%d]: old=%d new=%d", count, i, value));
1496           count++;
1497         }
1498       }
1499     }
1500 
1501     // We have entries mapped between the new and merged constant pools
1502     // so we have to rewrite some constant pool references.
1503     if (!rewrite_cp_refs(scratch_class, THREAD)) {
1504       return JVMTI_ERROR_INTERNAL;
1505     }
1506 
1507     // Replace the new constant pool with a shrunken copy of the
1508     // merged constant pool so now the rewritten bytecodes have
1509     // valid references; the previous new constant pool will get
1510     // GCed.
1511     set_new_constant_pool(loader_data, scratch_class, merge_cp, merge_cp_length, THREAD);
1512     // The new constant pool replaces scratch_cp so have cleaner clean it up.
1513     // It can't be cleaned up while there are handles to it.
1514     cp_cleaner.add_scratch_cp(scratch_cp());
1515   }
1516 
1517   return JVMTI_ERROR_NONE;
1518 } // end merge_cp_and_rewrite()
1519 
1520 
1521 // Rewrite constant pool references in klass scratch_class.
1522 bool VM_RedefineClasses::rewrite_cp_refs(instanceKlassHandle scratch_class,
1523        TRAPS) {
1524 
1525   // rewrite constant pool references in the methods:
1526   if (!rewrite_cp_refs_in_methods(scratch_class, THREAD)) {
1527     // propagate failure back to caller
1528     return false;
1529   }
1530 
1531   // rewrite constant pool references in the class_annotations:
1532   if (!rewrite_cp_refs_in_class_annotations(scratch_class, THREAD)) {
1533     // propagate failure back to caller
1534     return false;
1535   }
1536 
1537   // rewrite constant pool references in the fields_annotations:
1538   if (!rewrite_cp_refs_in_fields_annotations(scratch_class, THREAD)) {
1539     // propagate failure back to caller
1540     return false;
1541   }
1542 
1543   // rewrite constant pool references in the methods_annotations:
1544   if (!rewrite_cp_refs_in_methods_annotations(scratch_class, THREAD)) {
1545     // propagate failure back to caller
1546     return false;
1547   }
1548 
1549   // rewrite constant pool references in the methods_parameter_annotations:
1550   if (!rewrite_cp_refs_in_methods_parameter_annotations(scratch_class,
1551          THREAD)) {
1552     // propagate failure back to caller
1553     return false;
1554   }
1555 
1556   // rewrite constant pool references in the methods_default_annotations:
1557   if (!rewrite_cp_refs_in_methods_default_annotations(scratch_class,
1558          THREAD)) {
1559     // propagate failure back to caller
1560     return false;
1561   }
1562 
1563   // rewrite source file name index:
1564   u2 source_file_name_idx = scratch_class->source_file_name_index();
1565   if (source_file_name_idx != 0) {
1566     u2 new_source_file_name_idx = find_new_index(source_file_name_idx);
1567     if (new_source_file_name_idx != 0) {
1568       scratch_class->set_source_file_name_index(new_source_file_name_idx);
1569     }
1570   }
1571 
1572   // rewrite class generic signature index:
1573   u2 generic_signature_index = scratch_class->generic_signature_index();
1574   if (generic_signature_index != 0) {
1575     u2 new_generic_signature_index = find_new_index(generic_signature_index);
1576     if (new_generic_signature_index != 0) {
1577       scratch_class->set_generic_signature_index(new_generic_signature_index);
1578     }
1579   }
1580 
1581   return true;
1582 } // end rewrite_cp_refs()
1583 
1584 // Rewrite constant pool references in the methods.
1585 bool VM_RedefineClasses::rewrite_cp_refs_in_methods(
1586        instanceKlassHandle scratch_class, TRAPS) {
1587 
1588   Array<Method*>* methods = scratch_class->methods();
1589 
1590   if (methods == NULL || methods->length() == 0) {
1591     // no methods so nothing to do
1592     return true;
1593   }
1594 
1595   // rewrite constant pool references in the methods:
1596   for (int i = methods->length() - 1; i >= 0; i--) {
1597     methodHandle method(THREAD, methods->at(i));
1598     methodHandle new_method;
1599     rewrite_cp_refs_in_method(method, &new_method, CHECK_false);
1600     if (!new_method.is_null()) {
1601       // the method has been replaced so save the new method version
1602       methods->at_put(i, new_method());
1603     }
1604   }
1605 
1606   return true;
1607 }
1608 
1609 
1610 // Rewrite constant pool references in the specific method. This code
1611 // was adapted from Rewriter::rewrite_method().
1612 void VM_RedefineClasses::rewrite_cp_refs_in_method(methodHandle method,
1613        methodHandle *new_method_p, TRAPS) {
1614 
1615   *new_method_p = methodHandle();  // default is no new method
1616 
1617   // We cache a pointer to the bytecodes here in code_base. If GC
1618   // moves the Method*, then the bytecodes will also move which
1619   // will likely cause a crash. We create a No_Safepoint_Verifier
1620   // object to detect whether we pass a possible safepoint in this
1621   // code block.
1622   No_Safepoint_Verifier nsv;
1623 
1624   // Bytecodes and their length
1625   address code_base = method->code_base();
1626   int code_length = method->code_size();
1627 
1628   int bc_length;
1629   for (int bci = 0; bci < code_length; bci += bc_length) {
1630     address bcp = code_base + bci;
1631     Bytecodes::Code c = (Bytecodes::Code)(*bcp);
1632 
1633     bc_length = Bytecodes::length_for(c);
1634     if (bc_length == 0) {
1635       // More complicated bytecodes report a length of zero so
1636       // we have to try again a slightly different way.
1637       bc_length = Bytecodes::length_at(method(), bcp);
1638     }
1639 
1640     assert(bc_length != 0, "impossible bytecode length");
1641 
1642     switch (c) {
1643       case Bytecodes::_ldc:
1644       {
1645         int cp_index = *(bcp + 1);
1646         int new_index = find_new_index(cp_index);
1647 
1648         if (StressLdcRewrite && new_index == 0) {
1649           // If we are stressing ldc -> ldc_w rewriting, then we
1650           // always need a new_index value.
1651           new_index = cp_index;
1652         }
1653         if (new_index != 0) {
1654           // the original index is mapped so we have more work to do
1655           if (!StressLdcRewrite && new_index <= max_jubyte) {
1656             // The new value can still use ldc instead of ldc_w
1657             // unless we are trying to stress ldc -> ldc_w rewriting
1658             RC_TRACE_WITH_THREAD(0x00080000, THREAD,
1659               ("%s@" INTPTR_FORMAT " old=%d, new=%d", Bytecodes::name(c),
1660               bcp, cp_index, new_index));
1661             *(bcp + 1) = new_index;
1662           } else {
1663             RC_TRACE_WITH_THREAD(0x00080000, THREAD,
1664               ("%s->ldc_w@" INTPTR_FORMAT " old=%d, new=%d",
1665               Bytecodes::name(c), bcp, cp_index, new_index));
1666             // the new value needs ldc_w instead of ldc
1667             u_char inst_buffer[4]; // max instruction size is 4 bytes
1668             bcp = (address)inst_buffer;
1669             // construct new instruction sequence
1670             *bcp = Bytecodes::_ldc_w;
1671             bcp++;
1672             // Rewriter::rewrite_method() does not rewrite ldc -> ldc_w.
1673             // See comment below for difference between put_Java_u2()
1674             // and put_native_u2().
1675             Bytes::put_Java_u2(bcp, new_index);
1676 
1677             Relocator rc(method, NULL /* no RelocatorListener needed */);
1678             methodHandle m;
1679             {
1680               Pause_No_Safepoint_Verifier pnsv(&nsv);
1681 
1682               // ldc is 2 bytes and ldc_w is 3 bytes
1683               m = rc.insert_space_at(bci, 3, inst_buffer, THREAD);
1684               if (m.is_null() || HAS_PENDING_EXCEPTION) {
1685                 guarantee(false, "insert_space_at() failed");
1686               }
1687             }
1688 
1689             // return the new method so that the caller can update
1690             // the containing class
1691             *new_method_p = method = m;
1692             // switch our bytecode processing loop from the old method
1693             // to the new method
1694             code_base = method->code_base();
1695             code_length = method->code_size();
1696             bcp = code_base + bci;
1697             c = (Bytecodes::Code)(*bcp);
1698             bc_length = Bytecodes::length_for(c);
1699             assert(bc_length != 0, "sanity check");
1700           } // end we need ldc_w instead of ldc
1701         } // end if there is a mapped index
1702       } break;
1703 
1704       // these bytecodes have a two-byte constant pool index
1705       case Bytecodes::_anewarray      : // fall through
1706       case Bytecodes::_checkcast      : // fall through
1707       case Bytecodes::_getfield       : // fall through
1708       case Bytecodes::_getstatic      : // fall through
1709       case Bytecodes::_instanceof     : // fall through
1710       case Bytecodes::_invokedynamic  : // fall through
1711       case Bytecodes::_invokeinterface: // fall through
1712       case Bytecodes::_invokespecial  : // fall through
1713       case Bytecodes::_invokestatic   : // fall through
1714       case Bytecodes::_invokevirtual  : // fall through
1715       case Bytecodes::_ldc_w          : // fall through
1716       case Bytecodes::_ldc2_w         : // fall through
1717       case Bytecodes::_multianewarray : // fall through
1718       case Bytecodes::_new            : // fall through
1719       case Bytecodes::_putfield       : // fall through
1720       case Bytecodes::_putstatic      :
1721       {
1722         address p = bcp + 1;
1723         int cp_index = Bytes::get_Java_u2(p);
1724         int new_index = find_new_index(cp_index);
1725         if (new_index != 0) {
1726           // the original index is mapped so update w/ new value
1727           RC_TRACE_WITH_THREAD(0x00080000, THREAD,
1728             ("%s@" INTPTR_FORMAT " old=%d, new=%d", Bytecodes::name(c),
1729             bcp, cp_index, new_index));
1730           // Rewriter::rewrite_method() uses put_native_u2() in this
1731           // situation because it is reusing the constant pool index
1732           // location for a native index into the ConstantPoolCache.
1733           // Since we are updating the constant pool index prior to
1734           // verification and ConstantPoolCache initialization, we
1735           // need to keep the new index in Java byte order.
1736           Bytes::put_Java_u2(p, new_index);
1737         }
1738       } break;
1739     }
1740   } // end for each bytecode
1741 
1742   // We also need to rewrite the parameter name indexes, if there is
1743   // method parameter data present
1744   if(method->has_method_parameters()) {
1745     const int len = method->method_parameters_length();
1746     MethodParametersElement* elem = method->method_parameters_start();
1747 
1748     for (int i = 0; i < len; i++) {
1749       const u2 cp_index = elem[i].name_cp_index;
1750       const u2 new_cp_index = find_new_index(cp_index);
1751       if (new_cp_index != 0) {
1752         elem[i].name_cp_index = new_cp_index;
1753       }
1754     }
1755   }
1756 } // end rewrite_cp_refs_in_method()
1757 
1758 
1759 // Rewrite constant pool references in the class_annotations field.
1760 bool VM_RedefineClasses::rewrite_cp_refs_in_class_annotations(
1761        instanceKlassHandle scratch_class, TRAPS) {
1762 
1763   AnnotationArray* class_annotations = scratch_class->class_annotations();
1764   if (class_annotations == NULL || class_annotations->length() == 0) {
1765     // no class_annotations so nothing to do
1766     return true;
1767   }
1768 
1769   RC_TRACE_WITH_THREAD(0x02000000, THREAD,
1770     ("class_annotations length=%d", class_annotations->length()));
1771 
1772   int byte_i = 0;  // byte index into class_annotations
1773   return rewrite_cp_refs_in_annotations_typeArray(class_annotations, byte_i,
1774            THREAD);
1775 }
1776 
1777 
1778 // Rewrite constant pool references in an annotations typeArray. This
1779 // "structure" is adapted from the RuntimeVisibleAnnotations_attribute
1780 // that is described in section 4.8.15 of the 2nd-edition of the VM spec:
1781 //
1782 // annotations_typeArray {
1783 //   u2 num_annotations;
1784 //   annotation annotations[num_annotations];
1785 // }
1786 //
1787 bool VM_RedefineClasses::rewrite_cp_refs_in_annotations_typeArray(
1788        AnnotationArray* annotations_typeArray, int &byte_i_ref, TRAPS) {
1789 
1790   if ((byte_i_ref + 2) > annotations_typeArray->length()) {
1791     // not enough room for num_annotations field
1792     RC_TRACE_WITH_THREAD(0x02000000, THREAD,
1793       ("length() is too small for num_annotations field"));
1794     return false;
1795   }
1796 
1797   u2 num_annotations = Bytes::get_Java_u2((address)
1798                          annotations_typeArray->adr_at(byte_i_ref));
1799   byte_i_ref += 2;
1800 
1801   RC_TRACE_WITH_THREAD(0x02000000, THREAD,
1802     ("num_annotations=%d", num_annotations));
1803 
1804   int calc_num_annotations = 0;
1805   for (; calc_num_annotations < num_annotations; calc_num_annotations++) {
1806     if (!rewrite_cp_refs_in_annotation_struct(annotations_typeArray,
1807            byte_i_ref, THREAD)) {
1808       RC_TRACE_WITH_THREAD(0x02000000, THREAD,
1809         ("bad annotation_struct at %d", calc_num_annotations));
1810       // propagate failure back to caller
1811       return false;
1812     }
1813   }
1814   assert(num_annotations == calc_num_annotations, "sanity check");
1815 
1816   return true;
1817 } // end rewrite_cp_refs_in_annotations_typeArray()
1818 
1819 
1820 // Rewrite constant pool references in the annotation struct portion of
1821 // an annotations_typeArray. This "structure" is from section 4.8.15 of
1822 // the 2nd-edition of the VM spec:
1823 //
1824 // struct annotation {
1825 //   u2 type_index;
1826 //   u2 num_element_value_pairs;
1827 //   {
1828 //     u2 element_name_index;
1829 //     element_value value;
1830 //   } element_value_pairs[num_element_value_pairs];
1831 // }
1832 //
1833 bool VM_RedefineClasses::rewrite_cp_refs_in_annotation_struct(
1834        AnnotationArray* annotations_typeArray, int &byte_i_ref, TRAPS) {
1835   if ((byte_i_ref + 2 + 2) > annotations_typeArray->length()) {
1836     // not enough room for smallest annotation_struct
1837     RC_TRACE_WITH_THREAD(0x02000000, THREAD,
1838       ("length() is too small for annotation_struct"));
1839     return false;
1840   }
1841 
1842   u2 type_index = rewrite_cp_ref_in_annotation_data(annotations_typeArray,
1843                     byte_i_ref, "mapped old type_index=%d", THREAD);
1844 
1845   u2 num_element_value_pairs = Bytes::get_Java_u2((address)
1846                                  annotations_typeArray->adr_at(byte_i_ref));
1847   byte_i_ref += 2;
1848 
1849   RC_TRACE_WITH_THREAD(0x02000000, THREAD,
1850     ("type_index=%d  num_element_value_pairs=%d", type_index,
1851     num_element_value_pairs));
1852 
1853   int calc_num_element_value_pairs = 0;
1854   for (; calc_num_element_value_pairs < num_element_value_pairs;
1855        calc_num_element_value_pairs++) {
1856     if ((byte_i_ref + 2) > annotations_typeArray->length()) {
1857       // not enough room for another element_name_index, let alone
1858       // the rest of another component
1859       RC_TRACE_WITH_THREAD(0x02000000, THREAD,
1860         ("length() is too small for element_name_index"));
1861       return false;
1862     }
1863 
1864     u2 element_name_index = rewrite_cp_ref_in_annotation_data(
1865                               annotations_typeArray, byte_i_ref,
1866                               "mapped old element_name_index=%d", THREAD);
1867 
1868     RC_TRACE_WITH_THREAD(0x02000000, THREAD,
1869       ("element_name_index=%d", element_name_index));
1870 
1871     if (!rewrite_cp_refs_in_element_value(annotations_typeArray,
1872            byte_i_ref, THREAD)) {
1873       RC_TRACE_WITH_THREAD(0x02000000, THREAD,
1874         ("bad element_value at %d", calc_num_element_value_pairs));
1875       // propagate failure back to caller
1876       return false;
1877     }
1878   } // end for each component
1879   assert(num_element_value_pairs == calc_num_element_value_pairs,
1880     "sanity check");
1881 
1882   return true;
1883 } // end rewrite_cp_refs_in_annotation_struct()
1884 
1885 
1886 // Rewrite a constant pool reference at the current position in
1887 // annotations_typeArray if needed. Returns the original constant
1888 // pool reference if a rewrite was not needed or the new constant
1889 // pool reference if a rewrite was needed.
1890 u2 VM_RedefineClasses::rewrite_cp_ref_in_annotation_data(
1891      AnnotationArray* annotations_typeArray, int &byte_i_ref,
1892      const char * trace_mesg, TRAPS) {
1893 
1894   address cp_index_addr = (address)
1895     annotations_typeArray->adr_at(byte_i_ref);
1896   u2 old_cp_index = Bytes::get_Java_u2(cp_index_addr);
1897   u2 new_cp_index = find_new_index(old_cp_index);
1898   if (new_cp_index != 0) {
1899     RC_TRACE_WITH_THREAD(0x02000000, THREAD, (trace_mesg, old_cp_index));
1900     Bytes::put_Java_u2(cp_index_addr, new_cp_index);
1901     old_cp_index = new_cp_index;
1902   }
1903   byte_i_ref += 2;
1904   return old_cp_index;
1905 }
1906 
1907 
1908 // Rewrite constant pool references in the element_value portion of an
1909 // annotations_typeArray. This "structure" is from section 4.8.15.1 of
1910 // the 2nd-edition of the VM spec:
1911 //
1912 // struct element_value {
1913 //   u1 tag;
1914 //   union {
1915 //     u2 const_value_index;
1916 //     {
1917 //       u2 type_name_index;
1918 //       u2 const_name_index;
1919 //     } enum_const_value;
1920 //     u2 class_info_index;
1921 //     annotation annotation_value;
1922 //     struct {
1923 //       u2 num_values;
1924 //       element_value values[num_values];
1925 //     } array_value;
1926 //   } value;
1927 // }
1928 //
1929 bool VM_RedefineClasses::rewrite_cp_refs_in_element_value(
1930        AnnotationArray* annotations_typeArray, int &byte_i_ref, TRAPS) {
1931 
1932   if ((byte_i_ref + 1) > annotations_typeArray->length()) {
1933     // not enough room for a tag let alone the rest of an element_value
1934     RC_TRACE_WITH_THREAD(0x02000000, THREAD,
1935       ("length() is too small for a tag"));
1936     return false;
1937   }
1938 
1939   u1 tag = annotations_typeArray->at(byte_i_ref);
1940   byte_i_ref++;
1941   RC_TRACE_WITH_THREAD(0x02000000, THREAD, ("tag='%c'", tag));
1942 
1943   switch (tag) {
1944     // These BaseType tag values are from Table 4.2 in VM spec:
1945     case 'B':  // byte
1946     case 'C':  // char
1947     case 'D':  // double
1948     case 'F':  // float
1949     case 'I':  // int
1950     case 'J':  // long
1951     case 'S':  // short
1952     case 'Z':  // boolean
1953 
1954     // The remaining tag values are from Table 4.8 in the 2nd-edition of
1955     // the VM spec:
1956     case 's':
1957     {
1958       // For the above tag values (including the BaseType values),
1959       // value.const_value_index is right union field.
1960 
1961       if ((byte_i_ref + 2) > annotations_typeArray->length()) {
1962         // not enough room for a const_value_index
1963         RC_TRACE_WITH_THREAD(0x02000000, THREAD,
1964           ("length() is too small for a const_value_index"));
1965         return false;
1966       }
1967 
1968       u2 const_value_index = rewrite_cp_ref_in_annotation_data(
1969                                annotations_typeArray, byte_i_ref,
1970                                "mapped old const_value_index=%d", THREAD);
1971 
1972       RC_TRACE_WITH_THREAD(0x02000000, THREAD,
1973         ("const_value_index=%d", const_value_index));
1974     } break;
1975 
1976     case 'e':
1977     {
1978       // for the above tag value, value.enum_const_value is right union field
1979 
1980       if ((byte_i_ref + 4) > annotations_typeArray->length()) {
1981         // not enough room for a enum_const_value
1982         RC_TRACE_WITH_THREAD(0x02000000, THREAD,
1983           ("length() is too small for a enum_const_value"));
1984         return false;
1985       }
1986 
1987       u2 type_name_index = rewrite_cp_ref_in_annotation_data(
1988                              annotations_typeArray, byte_i_ref,
1989                              "mapped old type_name_index=%d", THREAD);
1990 
1991       u2 const_name_index = rewrite_cp_ref_in_annotation_data(
1992                               annotations_typeArray, byte_i_ref,
1993                               "mapped old const_name_index=%d", THREAD);
1994 
1995       RC_TRACE_WITH_THREAD(0x02000000, THREAD,
1996         ("type_name_index=%d  const_name_index=%d", type_name_index,
1997         const_name_index));
1998     } break;
1999 
2000     case 'c':
2001     {
2002       // for the above tag value, value.class_info_index is right union field
2003 
2004       if ((byte_i_ref + 2) > annotations_typeArray->length()) {
2005         // not enough room for a class_info_index
2006         RC_TRACE_WITH_THREAD(0x02000000, THREAD,
2007           ("length() is too small for a class_info_index"));
2008         return false;
2009       }
2010 
2011       u2 class_info_index = rewrite_cp_ref_in_annotation_data(
2012                               annotations_typeArray, byte_i_ref,
2013                               "mapped old class_info_index=%d", THREAD);
2014 
2015       RC_TRACE_WITH_THREAD(0x02000000, THREAD,
2016         ("class_info_index=%d", class_info_index));
2017     } break;
2018 
2019     case '@':
2020       // For the above tag value, value.attr_value is the right union
2021       // field. This is a nested annotation.
2022       if (!rewrite_cp_refs_in_annotation_struct(annotations_typeArray,
2023              byte_i_ref, THREAD)) {
2024         // propagate failure back to caller
2025         return false;
2026       }
2027       break;
2028 
2029     case '[':
2030     {
2031       if ((byte_i_ref + 2) > annotations_typeArray->length()) {
2032         // not enough room for a num_values field
2033         RC_TRACE_WITH_THREAD(0x02000000, THREAD,
2034           ("length() is too small for a num_values field"));
2035         return false;
2036       }
2037 
2038       // For the above tag value, value.array_value is the right union
2039       // field. This is an array of nested element_value.
2040       u2 num_values = Bytes::get_Java_u2((address)
2041                         annotations_typeArray->adr_at(byte_i_ref));
2042       byte_i_ref += 2;
2043       RC_TRACE_WITH_THREAD(0x02000000, THREAD, ("num_values=%d", num_values));
2044 
2045       int calc_num_values = 0;
2046       for (; calc_num_values < num_values; calc_num_values++) {
2047         if (!rewrite_cp_refs_in_element_value(
2048                annotations_typeArray, byte_i_ref, THREAD)) {
2049           RC_TRACE_WITH_THREAD(0x02000000, THREAD,
2050             ("bad nested element_value at %d", calc_num_values));
2051           // propagate failure back to caller
2052           return false;
2053         }
2054       }
2055       assert(num_values == calc_num_values, "sanity check");
2056     } break;
2057 
2058     default:
2059       RC_TRACE_WITH_THREAD(0x02000000, THREAD, ("bad tag=0x%x", tag));
2060       return false;
2061   } // end decode tag field
2062 
2063   return true;
2064 } // end rewrite_cp_refs_in_element_value()
2065 
2066 
2067 // Rewrite constant pool references in a fields_annotations field.
2068 bool VM_RedefineClasses::rewrite_cp_refs_in_fields_annotations(
2069        instanceKlassHandle scratch_class, TRAPS) {
2070 
2071   Array<AnnotationArray*>* fields_annotations = scratch_class->fields_annotations();
2072 
2073   if (fields_annotations == NULL || fields_annotations->length() == 0) {
2074     // no fields_annotations so nothing to do
2075     return true;
2076   }
2077 
2078   RC_TRACE_WITH_THREAD(0x02000000, THREAD,
2079     ("fields_annotations length=%d", fields_annotations->length()));
2080 
2081   for (int i = 0; i < fields_annotations->length(); i++) {
2082     AnnotationArray* field_annotations = fields_annotations->at(i);
2083     if (field_annotations == NULL || field_annotations->length() == 0) {
2084       // this field does not have any annotations so skip it
2085       continue;
2086     }
2087 
2088     int byte_i = 0;  // byte index into field_annotations
2089     if (!rewrite_cp_refs_in_annotations_typeArray(field_annotations, byte_i,
2090            THREAD)) {
2091       RC_TRACE_WITH_THREAD(0x02000000, THREAD,
2092         ("bad field_annotations at %d", i));
2093       // propagate failure back to caller
2094       return false;
2095     }
2096   }
2097 
2098   return true;
2099 } // end rewrite_cp_refs_in_fields_annotations()
2100 
2101 
2102 // Rewrite constant pool references in a methods_annotations field.
2103 bool VM_RedefineClasses::rewrite_cp_refs_in_methods_annotations(
2104        instanceKlassHandle scratch_class, TRAPS) {
2105 
2106   for (int i = 0; i < scratch_class->methods()->length(); i++) {
2107     Method* m = scratch_class->methods()->at(i);
2108     AnnotationArray* method_annotations = m->constMethod()->method_annotations();
2109 
2110     if (method_annotations == NULL || method_annotations->length() == 0) {
2111       // this method does not have any annotations so skip it
2112       continue;
2113     }
2114 
2115     int byte_i = 0;  // byte index into method_annotations
2116     if (!rewrite_cp_refs_in_annotations_typeArray(method_annotations, byte_i,
2117            THREAD)) {
2118       RC_TRACE_WITH_THREAD(0x02000000, THREAD,
2119         ("bad method_annotations at %d", i));
2120       // propagate failure back to caller
2121       return false;
2122     }
2123   }
2124 
2125   return true;
2126 } // end rewrite_cp_refs_in_methods_annotations()
2127 
2128 
2129 // Rewrite constant pool references in a methods_parameter_annotations
2130 // field. This "structure" is adapted from the
2131 // RuntimeVisibleParameterAnnotations_attribute described in section
2132 // 4.8.17 of the 2nd-edition of the VM spec:
2133 //
2134 // methods_parameter_annotations_typeArray {
2135 //   u1 num_parameters;
2136 //   {
2137 //     u2 num_annotations;
2138 //     annotation annotations[num_annotations];
2139 //   } parameter_annotations[num_parameters];
2140 // }
2141 //
2142 bool VM_RedefineClasses::rewrite_cp_refs_in_methods_parameter_annotations(
2143        instanceKlassHandle scratch_class, TRAPS) {
2144 
2145   for (int i = 0; i < scratch_class->methods()->length(); i++) {
2146     Method* m = scratch_class->methods()->at(i);
2147     AnnotationArray* method_parameter_annotations = m->constMethod()->parameter_annotations();
2148     if (method_parameter_annotations == NULL
2149         || method_parameter_annotations->length() == 0) {
2150       // this method does not have any parameter annotations so skip it
2151       continue;
2152     }
2153 
2154     if (method_parameter_annotations->length() < 1) {
2155       // not enough room for a num_parameters field
2156       RC_TRACE_WITH_THREAD(0x02000000, THREAD,
2157         ("length() is too small for a num_parameters field at %d", i));
2158       return false;
2159     }
2160 
2161     int byte_i = 0;  // byte index into method_parameter_annotations
2162 
2163     u1 num_parameters = method_parameter_annotations->at(byte_i);
2164     byte_i++;
2165 
2166     RC_TRACE_WITH_THREAD(0x02000000, THREAD,
2167       ("num_parameters=%d", num_parameters));
2168 
2169     int calc_num_parameters = 0;
2170     for (; calc_num_parameters < num_parameters; calc_num_parameters++) {
2171       if (!rewrite_cp_refs_in_annotations_typeArray(
2172              method_parameter_annotations, byte_i, THREAD)) {
2173         RC_TRACE_WITH_THREAD(0x02000000, THREAD,
2174           ("bad method_parameter_annotations at %d", calc_num_parameters));
2175         // propagate failure back to caller
2176         return false;
2177       }
2178     }
2179     assert(num_parameters == calc_num_parameters, "sanity check");
2180   }
2181 
2182   return true;
2183 } // end rewrite_cp_refs_in_methods_parameter_annotations()
2184 
2185 
2186 // Rewrite constant pool references in a methods_default_annotations
2187 // field. This "structure" is adapted from the AnnotationDefault_attribute
2188 // that is described in section 4.8.19 of the 2nd-edition of the VM spec:
2189 //
2190 // methods_default_annotations_typeArray {
2191 //   element_value default_value;
2192 // }
2193 //
2194 bool VM_RedefineClasses::rewrite_cp_refs_in_methods_default_annotations(
2195        instanceKlassHandle scratch_class, TRAPS) {
2196 
2197   for (int i = 0; i < scratch_class->methods()->length(); i++) {
2198     Method* m = scratch_class->methods()->at(i);
2199     AnnotationArray* method_default_annotations = m->constMethod()->default_annotations();
2200     if (method_default_annotations == NULL
2201         || method_default_annotations->length() == 0) {
2202       // this method does not have any default annotations so skip it
2203       continue;
2204     }
2205 
2206     int byte_i = 0;  // byte index into method_default_annotations
2207 
2208     if (!rewrite_cp_refs_in_element_value(
2209            method_default_annotations, byte_i, THREAD)) {
2210       RC_TRACE_WITH_THREAD(0x02000000, THREAD,
2211         ("bad default element_value at %d", i));
2212       // propagate failure back to caller
2213       return false;
2214     }
2215   }
2216 
2217   return true;
2218 } // end rewrite_cp_refs_in_methods_default_annotations()
2219 
2220 
2221 // Rewrite constant pool references in the method's stackmap table.
2222 // These "structures" are adapted from the StackMapTable_attribute that
2223 // is described in section 4.8.4 of the 6.0 version of the VM spec
2224 // (dated 2005.10.26):
2225 // file:///net/quincunx.sfbay/export/gbracha/ClassFile-Java6.pdf
2226 //
2227 // stack_map {
2228 //   u2 number_of_entries;
2229 //   stack_map_frame entries[number_of_entries];
2230 // }
2231 //
2232 void VM_RedefineClasses::rewrite_cp_refs_in_stack_map_table(
2233        methodHandle method, TRAPS) {
2234 
2235   if (!method->has_stackmap_table()) {
2236     return;
2237   }
2238 
2239   AnnotationArray* stackmap_data = method->stackmap_data();
2240   address stackmap_p = (address)stackmap_data->adr_at(0);
2241   address stackmap_end = stackmap_p + stackmap_data->length();
2242 
2243   assert(stackmap_p + 2 <= stackmap_end, "no room for number_of_entries");
2244   u2 number_of_entries = Bytes::get_Java_u2(stackmap_p);
2245   stackmap_p += 2;
2246 
2247   RC_TRACE_WITH_THREAD(0x04000000, THREAD,
2248     ("number_of_entries=%u", number_of_entries));
2249 
2250   // walk through each stack_map_frame
2251   u2 calc_number_of_entries = 0;
2252   for (; calc_number_of_entries < number_of_entries; calc_number_of_entries++) {
2253     // The stack_map_frame structure is a u1 frame_type followed by
2254     // 0 or more bytes of data:
2255     //
2256     // union stack_map_frame {
2257     //   same_frame;
2258     //   same_locals_1_stack_item_frame;
2259     //   same_locals_1_stack_item_frame_extended;
2260     //   chop_frame;
2261     //   same_frame_extended;
2262     //   append_frame;
2263     //   full_frame;
2264     // }
2265 
2266     assert(stackmap_p + 1 <= stackmap_end, "no room for frame_type");
2267     // The Linux compiler does not like frame_type to be u1 or u2. It
2268     // issues the following warning for the first if-statement below:
2269     //
2270     // "warning: comparison is always true due to limited range of data type"
2271     //
2272     u4 frame_type = *stackmap_p;
2273     stackmap_p++;
2274 
2275     // same_frame {
2276     //   u1 frame_type = SAME; /* 0-63 */
2277     // }
2278     if (frame_type >= 0 && frame_type <= 63) {
2279       // nothing more to do for same_frame
2280     }
2281 
2282     // same_locals_1_stack_item_frame {
2283     //   u1 frame_type = SAME_LOCALS_1_STACK_ITEM; /* 64-127 */
2284     //   verification_type_info stack[1];
2285     // }
2286     else if (frame_type >= 64 && frame_type <= 127) {
2287       rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
2288         calc_number_of_entries, frame_type, THREAD);
2289     }
2290 
2291     // reserved for future use
2292     else if (frame_type >= 128 && frame_type <= 246) {
2293       // nothing more to do for reserved frame_types
2294     }
2295 
2296     // same_locals_1_stack_item_frame_extended {
2297     //   u1 frame_type = SAME_LOCALS_1_STACK_ITEM_EXTENDED; /* 247 */
2298     //   u2 offset_delta;
2299     //   verification_type_info stack[1];
2300     // }
2301     else if (frame_type == 247) {
2302       stackmap_p += 2;
2303       rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
2304         calc_number_of_entries, frame_type, THREAD);
2305     }
2306 
2307     // chop_frame {
2308     //   u1 frame_type = CHOP; /* 248-250 */
2309     //   u2 offset_delta;
2310     // }
2311     else if (frame_type >= 248 && frame_type <= 250) {
2312       stackmap_p += 2;
2313     }
2314 
2315     // same_frame_extended {
2316     //   u1 frame_type = SAME_FRAME_EXTENDED; /* 251*/
2317     //   u2 offset_delta;
2318     // }
2319     else if (frame_type == 251) {
2320       stackmap_p += 2;
2321     }
2322 
2323     // append_frame {
2324     //   u1 frame_type = APPEND; /* 252-254 */
2325     //   u2 offset_delta;
2326     //   verification_type_info locals[frame_type - 251];
2327     // }
2328     else if (frame_type >= 252 && frame_type <= 254) {
2329       assert(stackmap_p + 2 <= stackmap_end,
2330         "no room for offset_delta");
2331       stackmap_p += 2;
2332       u1 len = frame_type - 251;
2333       for (u1 i = 0; i < len; i++) {
2334         rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
2335           calc_number_of_entries, frame_type, THREAD);
2336       }
2337     }
2338 
2339     // full_frame {
2340     //   u1 frame_type = FULL_FRAME; /* 255 */
2341     //   u2 offset_delta;
2342     //   u2 number_of_locals;
2343     //   verification_type_info locals[number_of_locals];
2344     //   u2 number_of_stack_items;
2345     //   verification_type_info stack[number_of_stack_items];
2346     // }
2347     else if (frame_type == 255) {
2348       assert(stackmap_p + 2 + 2 <= stackmap_end,
2349         "no room for smallest full_frame");
2350       stackmap_p += 2;
2351 
2352       u2 number_of_locals = Bytes::get_Java_u2(stackmap_p);
2353       stackmap_p += 2;
2354 
2355       for (u2 locals_i = 0; locals_i < number_of_locals; locals_i++) {
2356         rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
2357           calc_number_of_entries, frame_type, THREAD);
2358       }
2359 
2360       // Use the largest size for the number_of_stack_items, but only get
2361       // the right number of bytes.
2362       u2 number_of_stack_items = Bytes::get_Java_u2(stackmap_p);
2363       stackmap_p += 2;
2364 
2365       for (u2 stack_i = 0; stack_i < number_of_stack_items; stack_i++) {
2366         rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
2367           calc_number_of_entries, frame_type, THREAD);
2368       }
2369     }
2370   } // end while there is a stack_map_frame
2371   assert(number_of_entries == calc_number_of_entries, "sanity check");
2372 } // end rewrite_cp_refs_in_stack_map_table()
2373 
2374 
2375 // Rewrite constant pool references in the verification type info
2376 // portion of the method's stackmap table. These "structures" are
2377 // adapted from the StackMapTable_attribute that is described in
2378 // section 4.8.4 of the 6.0 version of the VM spec (dated 2005.10.26):
2379 // file:///net/quincunx.sfbay/export/gbracha/ClassFile-Java6.pdf
2380 //
2381 // The verification_type_info structure is a u1 tag followed by 0 or
2382 // more bytes of data:
2383 //
2384 // union verification_type_info {
2385 //   Top_variable_info;
2386 //   Integer_variable_info;
2387 //   Float_variable_info;
2388 //   Long_variable_info;
2389 //   Double_variable_info;
2390 //   Null_variable_info;
2391 //   UninitializedThis_variable_info;
2392 //   Object_variable_info;
2393 //   Uninitialized_variable_info;
2394 // }
2395 //
2396 void VM_RedefineClasses::rewrite_cp_refs_in_verification_type_info(
2397        address& stackmap_p_ref, address stackmap_end, u2 frame_i,
2398        u1 frame_type, TRAPS) {
2399 
2400   assert(stackmap_p_ref + 1 <= stackmap_end, "no room for tag");
2401   u1 tag = *stackmap_p_ref;
2402   stackmap_p_ref++;
2403 
2404   switch (tag) {
2405   // Top_variable_info {
2406   //   u1 tag = ITEM_Top; /* 0 */
2407   // }
2408   // verificationType.hpp has zero as ITEM_Bogus instead of ITEM_Top
2409   case 0:  // fall through
2410 
2411   // Integer_variable_info {
2412   //   u1 tag = ITEM_Integer; /* 1 */
2413   // }
2414   case ITEM_Integer:  // fall through
2415 
2416   // Float_variable_info {
2417   //   u1 tag = ITEM_Float; /* 2 */
2418   // }
2419   case ITEM_Float:  // fall through
2420 
2421   // Double_variable_info {
2422   //   u1 tag = ITEM_Double; /* 3 */
2423   // }
2424   case ITEM_Double:  // fall through
2425 
2426   // Long_variable_info {
2427   //   u1 tag = ITEM_Long; /* 4 */
2428   // }
2429   case ITEM_Long:  // fall through
2430 
2431   // Null_variable_info {
2432   //   u1 tag = ITEM_Null; /* 5 */
2433   // }
2434   case ITEM_Null:  // fall through
2435 
2436   // UninitializedThis_variable_info {
2437   //   u1 tag = ITEM_UninitializedThis; /* 6 */
2438   // }
2439   case ITEM_UninitializedThis:
2440     // nothing more to do for the above tag types
2441     break;
2442 
2443   // Object_variable_info {
2444   //   u1 tag = ITEM_Object; /* 7 */
2445   //   u2 cpool_index;
2446   // }
2447   case ITEM_Object:
2448   {
2449     assert(stackmap_p_ref + 2 <= stackmap_end, "no room for cpool_index");
2450     u2 cpool_index = Bytes::get_Java_u2(stackmap_p_ref);
2451     u2 new_cp_index = find_new_index(cpool_index);
2452     if (new_cp_index != 0) {
2453       RC_TRACE_WITH_THREAD(0x04000000, THREAD,
2454         ("mapped old cpool_index=%d", cpool_index));
2455       Bytes::put_Java_u2(stackmap_p_ref, new_cp_index);
2456       cpool_index = new_cp_index;
2457     }
2458     stackmap_p_ref += 2;
2459 
2460     RC_TRACE_WITH_THREAD(0x04000000, THREAD,
2461       ("frame_i=%u, frame_type=%u, cpool_index=%d", frame_i,
2462       frame_type, cpool_index));
2463   } break;
2464 
2465   // Uninitialized_variable_info {
2466   //   u1 tag = ITEM_Uninitialized; /* 8 */
2467   //   u2 offset;
2468   // }
2469   case ITEM_Uninitialized:
2470     assert(stackmap_p_ref + 2 <= stackmap_end, "no room for offset");
2471     stackmap_p_ref += 2;
2472     break;
2473 
2474   default:
2475     RC_TRACE_WITH_THREAD(0x04000000, THREAD,
2476       ("frame_i=%u, frame_type=%u, bad tag=0x%x", frame_i, frame_type, tag));
2477     ShouldNotReachHere();
2478     break;
2479   } // end switch (tag)
2480 } // end rewrite_cp_refs_in_verification_type_info()
2481 
2482 
2483 // Change the constant pool associated with klass scratch_class to
2484 // scratch_cp. If shrink is true, then scratch_cp_length elements
2485 // are copied from scratch_cp to a smaller constant pool and the
2486 // smaller constant pool is associated with scratch_class.
2487 void VM_RedefineClasses::set_new_constant_pool(
2488        ClassLoaderData* loader_data,
2489        instanceKlassHandle scratch_class, constantPoolHandle scratch_cp,
2490        int scratch_cp_length, TRAPS) {
2491   assert(scratch_cp->length() >= scratch_cp_length, "sanity check");
2492 
2493   // scratch_cp is a merged constant pool and has enough space for a
2494   // worst case merge situation. We want to associate the minimum
2495   // sized constant pool with the klass to save space.
2496   constantPoolHandle smaller_cp(THREAD,
2497           ConstantPool::allocate(loader_data, scratch_cp_length, THREAD));
2498 
2499   // preserve version() value in the smaller copy
2500   int version = scratch_cp->version();
2501   assert(version != 0, "sanity check");
2502   smaller_cp->set_version(version);
2503 
2504   // attach klass to new constant pool
2505   // reference to the cp holder is needed for copy_operands()
2506   smaller_cp->set_pool_holder(scratch_class());
2507 
2508   scratch_cp->copy_cp_to(1, scratch_cp_length - 1, smaller_cp, 1, THREAD);
2509   scratch_cp = smaller_cp;
2510 
2511   // attach new constant pool to klass
2512   scratch_class->set_constants(scratch_cp());
2513 
2514   int i;  // for portability
2515 
2516   // update each field in klass to use new constant pool indices as needed
2517   for (JavaFieldStream fs(scratch_class); !fs.done(); fs.next()) {
2518     jshort cur_index = fs.name_index();
2519     jshort new_index = find_new_index(cur_index);
2520     if (new_index != 0) {
2521       RC_TRACE_WITH_THREAD(0x00080000, THREAD,
2522         ("field-name_index change: %d to %d", cur_index, new_index));
2523       fs.set_name_index(new_index);
2524     }
2525     cur_index = fs.signature_index();
2526     new_index = find_new_index(cur_index);
2527     if (new_index != 0) {
2528       RC_TRACE_WITH_THREAD(0x00080000, THREAD,
2529         ("field-signature_index change: %d to %d", cur_index, new_index));
2530       fs.set_signature_index(new_index);
2531     }
2532     cur_index = fs.initval_index();
2533     new_index = find_new_index(cur_index);
2534     if (new_index != 0) {
2535       RC_TRACE_WITH_THREAD(0x00080000, THREAD,
2536         ("field-initval_index change: %d to %d", cur_index, new_index));
2537       fs.set_initval_index(new_index);
2538     }
2539     cur_index = fs.generic_signature_index();
2540     new_index = find_new_index(cur_index);
2541     if (new_index != 0) {
2542       RC_TRACE_WITH_THREAD(0x00080000, THREAD,
2543         ("field-generic_signature change: %d to %d", cur_index, new_index));
2544       fs.set_generic_signature_index(new_index);
2545     }
2546   } // end for each field
2547 
2548   // Update constant pool indices in the inner classes info to use
2549   // new constant indices as needed. The inner classes info is a
2550   // quadruple:
2551   // (inner_class_info, outer_class_info, inner_name, inner_access_flags)
2552   InnerClassesIterator iter(scratch_class);
2553   for (; !iter.done(); iter.next()) {
2554     int cur_index = iter.inner_class_info_index();
2555     if (cur_index == 0) {
2556       continue;  // JVM spec. allows null inner class refs so skip it
2557     }
2558     int new_index = find_new_index(cur_index);
2559     if (new_index != 0) {
2560       RC_TRACE_WITH_THREAD(0x00080000, THREAD,
2561         ("inner_class_info change: %d to %d", cur_index, new_index));
2562       iter.set_inner_class_info_index(new_index);
2563     }
2564     cur_index = iter.outer_class_info_index();
2565     new_index = find_new_index(cur_index);
2566     if (new_index != 0) {
2567       RC_TRACE_WITH_THREAD(0x00080000, THREAD,
2568         ("outer_class_info change: %d to %d", cur_index, new_index));
2569       iter.set_outer_class_info_index(new_index);
2570     }
2571     cur_index = iter.inner_name_index();
2572     new_index = find_new_index(cur_index);
2573     if (new_index != 0) {
2574       RC_TRACE_WITH_THREAD(0x00080000, THREAD,
2575         ("inner_name change: %d to %d", cur_index, new_index));
2576       iter.set_inner_name_index(new_index);
2577     }
2578   } // end for each inner class
2579 
2580   // Attach each method in klass to the new constant pool and update
2581   // to use new constant pool indices as needed:
2582   Array<Method*>* methods = scratch_class->methods();
2583   for (i = methods->length() - 1; i >= 0; i--) {
2584     methodHandle method(THREAD, methods->at(i));
2585     method->set_constants(scratch_cp());
2586 
2587     int new_index = find_new_index(method->name_index());
2588     if (new_index != 0) {
2589       RC_TRACE_WITH_THREAD(0x00080000, THREAD,
2590         ("method-name_index change: %d to %d", method->name_index(),
2591         new_index));
2592       method->set_name_index(new_index);
2593     }
2594     new_index = find_new_index(method->signature_index());
2595     if (new_index != 0) {
2596       RC_TRACE_WITH_THREAD(0x00080000, THREAD,
2597         ("method-signature_index change: %d to %d",
2598         method->signature_index(), new_index));
2599       method->set_signature_index(new_index);
2600     }
2601     new_index = find_new_index(method->generic_signature_index());
2602     if (new_index != 0) {
2603       RC_TRACE_WITH_THREAD(0x00080000, THREAD,
2604         ("method-generic_signature_index change: %d to %d",
2605         method->generic_signature_index(), new_index));
2606       method->set_generic_signature_index(new_index);
2607     }
2608 
2609     // Update constant pool indices in the method's checked exception
2610     // table to use new constant indices as needed.
2611     int cext_length = method->checked_exceptions_length();
2612     if (cext_length > 0) {
2613       CheckedExceptionElement * cext_table =
2614         method->checked_exceptions_start();
2615       for (int j = 0; j < cext_length; j++) {
2616         int cur_index = cext_table[j].class_cp_index;
2617         int new_index = find_new_index(cur_index);
2618         if (new_index != 0) {
2619           RC_TRACE_WITH_THREAD(0x00080000, THREAD,
2620             ("cext-class_cp_index change: %d to %d", cur_index, new_index));
2621           cext_table[j].class_cp_index = (u2)new_index;
2622         }
2623       } // end for each checked exception table entry
2624     } // end if there are checked exception table entries
2625 
2626     // Update each catch type index in the method's exception table
2627     // to use new constant pool indices as needed. The exception table
2628     // holds quadruple entries of the form:
2629     //   (beg_bci, end_bci, handler_bci, klass_index)
2630 
2631     ExceptionTable ex_table(method());
2632     int ext_length = ex_table.length();
2633 
2634     for (int j = 0; j < ext_length; j ++) {
2635       int cur_index = ex_table.catch_type_index(j);
2636       int new_index = find_new_index(cur_index);
2637       if (new_index != 0) {
2638         RC_TRACE_WITH_THREAD(0x00080000, THREAD,
2639           ("ext-klass_index change: %d to %d", cur_index, new_index));
2640         ex_table.set_catch_type_index(j, new_index);
2641       }
2642     } // end for each exception table entry
2643 
2644     // Update constant pool indices in the method's local variable
2645     // table to use new constant indices as needed. The local variable
2646     // table hold sextuple entries of the form:
2647     // (start_pc, length, name_index, descriptor_index, signature_index, slot)
2648     int lvt_length = method->localvariable_table_length();
2649     if (lvt_length > 0) {
2650       LocalVariableTableElement * lv_table =
2651         method->localvariable_table_start();
2652       for (int j = 0; j < lvt_length; j++) {
2653         int cur_index = lv_table[j].name_cp_index;
2654         int new_index = find_new_index(cur_index);
2655         if (new_index != 0) {
2656           RC_TRACE_WITH_THREAD(0x00080000, THREAD,
2657             ("lvt-name_cp_index change: %d to %d", cur_index, new_index));
2658           lv_table[j].name_cp_index = (u2)new_index;
2659         }
2660         cur_index = lv_table[j].descriptor_cp_index;
2661         new_index = find_new_index(cur_index);
2662         if (new_index != 0) {
2663           RC_TRACE_WITH_THREAD(0x00080000, THREAD,
2664             ("lvt-descriptor_cp_index change: %d to %d", cur_index,
2665             new_index));
2666           lv_table[j].descriptor_cp_index = (u2)new_index;
2667         }
2668         cur_index = lv_table[j].signature_cp_index;
2669         new_index = find_new_index(cur_index);
2670         if (new_index != 0) {
2671           RC_TRACE_WITH_THREAD(0x00080000, THREAD,
2672             ("lvt-signature_cp_index change: %d to %d", cur_index, new_index));
2673           lv_table[j].signature_cp_index = (u2)new_index;
2674         }
2675       } // end for each local variable table entry
2676     } // end if there are local variable table entries
2677 
2678     rewrite_cp_refs_in_stack_map_table(method, THREAD);
2679   } // end for each method
2680 } // end set_new_constant_pool()
2681 
2682 
2683 // Unevolving classes may point to methods of the_class directly
2684 // from their constant pool caches, itables, and/or vtables. We
2685 // use the ClassLoaderDataGraph::classes_do() facility and this helper
2686 // to fix up these pointers.
2687 
2688 // Adjust cpools and vtables closure
2689 void VM_RedefineClasses::AdjustCpoolCacheAndVtable::do_klass(Klass* k) {
2690 
2691   // This is a very busy routine. We don't want too much tracing
2692   // printed out.
2693   bool trace_name_printed = false;
2694 
2695   // Very noisy: only enable this call if you are trying to determine
2696   // that a specific class gets found by this routine.
2697   // RC_TRACE macro has an embedded ResourceMark
2698   // RC_TRACE_WITH_THREAD(0x00100000, THREAD,
2699   //   ("adjust check: name=%s", k->external_name()));
2700   // trace_name_printed = true;
2701 
2702   // If the class being redefined is java.lang.Object, we need to fix all
2703   // array class vtables also
2704   if (k->oop_is_array() && _the_class_oop == SystemDictionary::Object_klass()) {
2705     k->vtable()->adjust_method_entries(_matching_old_methods,
2706                                        _matching_new_methods,
2707                                        _matching_methods_length,
2708                                        &trace_name_printed);
2709   } else if (k->oop_is_instance()) {
2710     HandleMark hm(_thread);
2711     InstanceKlass *ik = InstanceKlass::cast(k);
2712 
2713     // HotSpot specific optimization! HotSpot does not currently
2714     // support delegation from the bootstrap class loader to a
2715     // user-defined class loader. This means that if the bootstrap
2716     // class loader is the initiating class loader, then it will also
2717     // be the defining class loader. This also means that classes
2718     // loaded by the bootstrap class loader cannot refer to classes
2719     // loaded by a user-defined class loader. Note: a user-defined
2720     // class loader can delegate to the bootstrap class loader.
2721     //
2722     // If the current class being redefined has a user-defined class
2723     // loader as its defining class loader, then we can skip all
2724     // classes loaded by the bootstrap class loader.
2725     bool is_user_defined =
2726            InstanceKlass::cast(_the_class_oop)->class_loader() != NULL;
2727     if (is_user_defined && ik->class_loader() == NULL) {
2728       return;
2729     }
2730 
2731     // Fix the vtable embedded in the_class and subclasses of the_class,
2732     // if one exists. We discard scratch_class and we don't keep an
2733     // InstanceKlass around to hold obsolete methods so we don't have
2734     // any other InstanceKlass embedded vtables to update. The vtable
2735     // holds the Method*s for virtual (but not final) methods.
2736     if (ik->vtable_length() > 0 && ik->is_subtype_of(_the_class_oop)) {
2737       // ik->vtable() creates a wrapper object; rm cleans it up
2738       ResourceMark rm(_thread);
2739       ik->vtable()->adjust_method_entries(_matching_old_methods,
2740                                           _matching_new_methods,
2741                                           _matching_methods_length,
2742                                           &trace_name_printed);
2743     }
2744 
2745     // If the current class has an itable and we are either redefining an
2746     // interface or if the current class is a subclass of the_class, then
2747     // we potentially have to fix the itable. If we are redefining an
2748     // interface, then we have to call adjust_method_entries() for
2749     // every InstanceKlass that has an itable since there isn't a
2750     // subclass relationship between an interface and an InstanceKlass.
2751     if (ik->itable_length() > 0 && (_the_class_oop->is_interface()
2752         || ik->is_subclass_of(_the_class_oop))) {
2753       // ik->itable() creates a wrapper object; rm cleans it up
2754       ResourceMark rm(_thread);
2755       ik->itable()->adjust_method_entries(_matching_old_methods,
2756                                           _matching_new_methods,
2757                                           _matching_methods_length,
2758                                           &trace_name_printed);
2759     }
2760 
2761     // The constant pools in other classes (other_cp) can refer to
2762     // methods in the_class. We have to update method information in
2763     // other_cp's cache. If other_cp has a previous version, then we
2764     // have to repeat the process for each previous version. The
2765     // constant pool cache holds the Method*s for non-virtual
2766     // methods and for virtual, final methods.
2767     //
2768     // Special case: if the current class is the_class, then new_cp
2769     // has already been attached to the_class and old_cp has already
2770     // been added as a previous version. The new_cp doesn't have any
2771     // cached references to old methods so it doesn't need to be
2772     // updated. We can simply start with the previous version(s) in
2773     // that case.
2774     constantPoolHandle other_cp;
2775     ConstantPoolCache* cp_cache;
2776 
2777     if (ik != _the_class_oop) {
2778       // this klass' constant pool cache may need adjustment
2779       other_cp = constantPoolHandle(ik->constants());
2780       cp_cache = other_cp->cache();
2781       if (cp_cache != NULL) {
2782         cp_cache->adjust_method_entries(_matching_old_methods,
2783                                         _matching_new_methods,
2784                                         _matching_methods_length,
2785                                         &trace_name_printed);
2786       }
2787     }
2788     {
2789       ResourceMark rm(_thread);
2790       // PreviousVersionInfo objects returned via PreviousVersionWalker
2791       // contain a GrowableArray of handles. We have to clean up the
2792       // GrowableArray _after_ the PreviousVersionWalker destructor
2793       // has destroyed the handles.
2794       {
2795         // the previous versions' constant pool caches may need adjustment
2796         PreviousVersionWalker pvw(ik);
2797         for (PreviousVersionInfo * pv_info = pvw.next_previous_version();
2798              pv_info != NULL; pv_info = pvw.next_previous_version()) {
2799           other_cp = pv_info->prev_constant_pool_handle();
2800           cp_cache = other_cp->cache();
2801           if (cp_cache != NULL) {
2802             cp_cache->adjust_method_entries(_matching_old_methods,
2803                                             _matching_new_methods,
2804                                             _matching_methods_length,
2805                                             &trace_name_printed);
2806           }
2807         }
2808       } // pvw is cleaned up
2809     } // rm is cleaned up
2810   }
2811 }
2812 
2813 void VM_RedefineClasses::update_jmethod_ids() {
2814   for (int j = 0; j < _matching_methods_length; ++j) {
2815     Method* old_method = _matching_old_methods[j];
2816     jmethodID jmid = old_method->find_jmethod_id_or_null();
2817     if (jmid != NULL) {
2818       // There is a jmethodID, change it to point to the new method
2819       methodHandle new_method_h(_matching_new_methods[j]);
2820       Method::change_method_associated_with_jmethod_id(jmid, new_method_h());
2821       assert(Method::resolve_jmethod_id(jmid) == _matching_new_methods[j],
2822              "should be replaced");
2823     }
2824   }
2825 }
2826 
2827 void VM_RedefineClasses::check_methods_and_mark_as_obsolete(
2828        BitMap *emcp_methods, int * emcp_method_count_p) {
2829   *emcp_method_count_p = 0;
2830   int obsolete_count = 0;
2831   int old_index = 0;
2832   for (int j = 0; j < _matching_methods_length; ++j, ++old_index) {
2833     Method* old_method = _matching_old_methods[j];
2834     Method* new_method = _matching_new_methods[j];
2835     Method* old_array_method;
2836 
2837     // Maintain an old_index into the _old_methods array by skipping
2838     // deleted methods
2839     while ((old_array_method = _old_methods->at(old_index)) != old_method) {
2840       ++old_index;
2841     }
2842 
2843     if (MethodComparator::methods_EMCP(old_method, new_method)) {
2844       // The EMCP definition from JSR-163 requires the bytecodes to be
2845       // the same with the exception of constant pool indices which may
2846       // differ. However, the constants referred to by those indices
2847       // must be the same.
2848       //
2849       // We use methods_EMCP() for comparison since constant pool
2850       // merging can remove duplicate constant pool entries that were
2851       // present in the old method and removed from the rewritten new
2852       // method. A faster binary comparison function would consider the
2853       // old and new methods to be different when they are actually
2854       // EMCP.
2855       //
2856       // The old and new methods are EMCP and you would think that we
2857       // could get rid of one of them here and now and save some space.
2858       // However, the concept of EMCP only considers the bytecodes and
2859       // the constant pool entries in the comparison. Other things,
2860       // e.g., the line number table (LNT) or the local variable table
2861       // (LVT) don't count in the comparison. So the new (and EMCP)
2862       // method can have a new LNT that we need so we can't just
2863       // overwrite the new method with the old method.
2864       //
2865       // When this routine is called, we have already attached the new
2866       // methods to the_class so the old methods are effectively
2867       // overwritten. However, if an old method is still executing,
2868       // then the old method cannot be collected until sometime after
2869       // the old method call has returned. So the overwriting of old
2870       // methods by new methods will save us space except for those
2871       // (hopefully few) old methods that are still executing.
2872       //
2873       // A method refers to a ConstMethod* and this presents another
2874       // possible avenue to space savings. The ConstMethod* in the
2875       // new method contains possibly new attributes (LNT, LVT, etc).
2876       // At first glance, it seems possible to save space by replacing
2877       // the ConstMethod* in the old method with the ConstMethod*
2878       // from the new method. The old and new methods would share the
2879       // same ConstMethod* and we would save the space occupied by
2880       // the old ConstMethod*. However, the ConstMethod* contains
2881       // a back reference to the containing method. Sharing the
2882       // ConstMethod* between two methods could lead to confusion in
2883       // the code that uses the back reference. This would lead to
2884       // brittle code that could be broken in non-obvious ways now or
2885       // in the future.
2886       //
2887       // Another possibility is to copy the ConstMethod* from the new
2888       // method to the old method and then overwrite the new method with
2889       // the old method. Since the ConstMethod* contains the bytecodes
2890       // for the method embedded in the oop, this option would change
2891       // the bytecodes out from under any threads executing the old
2892       // method and make the thread's bcp invalid. Since EMCP requires
2893       // that the bytecodes be the same modulo constant pool indices, it
2894       // is straight forward to compute the correct new bcp in the new
2895       // ConstMethod* from the old bcp in the old ConstMethod*. The
2896       // time consuming part would be searching all the frames in all
2897       // of the threads to find all of the calls to the old method.
2898       //
2899       // It looks like we will have to live with the limited savings
2900       // that we get from effectively overwriting the old methods
2901       // when the new methods are attached to the_class.
2902 
2903       // track which methods are EMCP for add_previous_version() call
2904       emcp_methods->set_bit(old_index);
2905       (*emcp_method_count_p)++;
2906 
2907       // An EMCP method is _not_ obsolete. An obsolete method has a
2908       // different jmethodID than the current method. An EMCP method
2909       // has the same jmethodID as the current method. Having the
2910       // same jmethodID for all EMCP versions of a method allows for
2911       // a consistent view of the EMCP methods regardless of which
2912       // EMCP method you happen to have in hand. For example, a
2913       // breakpoint set in one EMCP method will work for all EMCP
2914       // versions of the method including the current one.
2915     } else {
2916       // mark obsolete methods as such
2917       old_method->set_is_obsolete();
2918       obsolete_count++;
2919 
2920       // obsolete methods need a unique idnum
2921       u2 num = InstanceKlass::cast(_the_class_oop)->next_method_idnum();
2922       if (num != ConstMethod::UNSET_IDNUM) {
2923 //      u2 old_num = old_method->method_idnum();
2924         old_method->set_method_idnum(num);
2925 // TO DO: attach obsolete annotations to obsolete method's new idnum
2926       }
2927       // With tracing we try not to "yack" too much. The position of
2928       // this trace assumes there are fewer obsolete methods than
2929       // EMCP methods.
2930       RC_TRACE(0x00000100, ("mark %s(%s) as obsolete",
2931         old_method->name()->as_C_string(),
2932         old_method->signature()->as_C_string()));
2933     }
2934     old_method->set_is_old();
2935   }
2936   for (int i = 0; i < _deleted_methods_length; ++i) {
2937     Method* old_method = _deleted_methods[i];
2938 
2939     assert(old_method->vtable_index() < 0,
2940            "cannot delete methods with vtable entries");;
2941 
2942     // Mark all deleted methods as old and obsolete
2943     old_method->set_is_old();
2944     old_method->set_is_obsolete();
2945     ++obsolete_count;
2946     // With tracing we try not to "yack" too much. The position of
2947     // this trace assumes there are fewer obsolete methods than
2948     // EMCP methods.
2949     RC_TRACE(0x00000100, ("mark deleted %s(%s) as obsolete",
2950                           old_method->name()->as_C_string(),
2951                           old_method->signature()->as_C_string()));
2952   }
2953   assert((*emcp_method_count_p + obsolete_count) == _old_methods->length(),
2954     "sanity check");
2955   RC_TRACE(0x00000100, ("EMCP_cnt=%d, obsolete_cnt=%d", *emcp_method_count_p,
2956     obsolete_count));
2957 }
2958 
2959 // This internal class transfers the native function registration from old methods
2960 // to new methods.  It is designed to handle both the simple case of unchanged
2961 // native methods and the complex cases of native method prefixes being added and/or
2962 // removed.
2963 // It expects only to be used during the VM_RedefineClasses op (a safepoint).
2964 //
2965 // This class is used after the new methods have been installed in "the_class".
2966 //
2967 // So, for example, the following must be handled.  Where 'm' is a method and
2968 // a number followed by an underscore is a prefix.
2969 //
2970 //                                      Old Name    New Name
2971 // Simple transfer to new method        m       ->  m
2972 // Add prefix                           m       ->  1_m
2973 // Remove prefix                        1_m     ->  m
2974 // Simultaneous add of prefixes         m       ->  3_2_1_m
2975 // Simultaneous removal of prefixes     3_2_1_m ->  m
2976 // Simultaneous add and remove          1_m     ->  2_m
2977 // Same, caused by prefix removal only  3_2_1_m ->  3_2_m
2978 //
2979 class TransferNativeFunctionRegistration {
2980  private:
2981   instanceKlassHandle the_class;
2982   int prefix_count;
2983   char** prefixes;
2984 
2985   // Recursively search the binary tree of possibly prefixed method names.
2986   // Iteration could be used if all agents were well behaved. Full tree walk is
2987   // more resilent to agents not cleaning up intermediate methods.
2988   // Branch at each depth in the binary tree is:
2989   //    (1) without the prefix.
2990   //    (2) with the prefix.
2991   // where 'prefix' is the prefix at that 'depth' (first prefix, second prefix,...)
2992   Method* search_prefix_name_space(int depth, char* name_str, size_t name_len,
2993                                      Symbol* signature) {
2994     TempNewSymbol name_symbol = SymbolTable::probe(name_str, (int)name_len);
2995     if (name_symbol != NULL) {
2996       Method* method = the_class()->lookup_method(name_symbol, signature);
2997       if (method != NULL) {
2998         // Even if prefixed, intermediate methods must exist.
2999         if (method->is_native()) {
3000           // Wahoo, we found a (possibly prefixed) version of the method, return it.
3001           return method;
3002         }
3003         if (depth < prefix_count) {
3004           // Try applying further prefixes (other than this one).
3005           method = search_prefix_name_space(depth+1, name_str, name_len, signature);
3006           if (method != NULL) {
3007             return method; // found
3008           }
3009 
3010           // Try adding this prefix to the method name and see if it matches
3011           // another method name.
3012           char* prefix = prefixes[depth];
3013           size_t prefix_len = strlen(prefix);
3014           size_t trial_len = name_len + prefix_len;
3015           char* trial_name_str = NEW_RESOURCE_ARRAY(char, trial_len + 1);
3016           strcpy(trial_name_str, prefix);
3017           strcat(trial_name_str, name_str);
3018           method = search_prefix_name_space(depth+1, trial_name_str, trial_len,
3019                                             signature);
3020           if (method != NULL) {
3021             // If found along this branch, it was prefixed, mark as such
3022             method->set_is_prefixed_native();
3023             return method; // found
3024           }
3025         }
3026       }
3027     }
3028     return NULL;  // This whole branch bore nothing
3029   }
3030 
3031   // Return the method name with old prefixes stripped away.
3032   char* method_name_without_prefixes(Method* method) {
3033     Symbol* name = method->name();
3034     char* name_str = name->as_utf8();
3035 
3036     // Old prefixing may be defunct, strip prefixes, if any.
3037     for (int i = prefix_count-1; i >= 0; i--) {
3038       char* prefix = prefixes[i];
3039       size_t prefix_len = strlen(prefix);
3040       if (strncmp(prefix, name_str, prefix_len) == 0) {
3041         name_str += prefix_len;
3042       }
3043     }
3044     return name_str;
3045   }
3046 
3047   // Strip any prefixes off the old native method, then try to find a
3048   // (possibly prefixed) new native that matches it.
3049   Method* strip_and_search_for_new_native(Method* method) {
3050     ResourceMark rm;
3051     char* name_str = method_name_without_prefixes(method);
3052     return search_prefix_name_space(0, name_str, strlen(name_str),
3053                                     method->signature());
3054   }
3055 
3056  public:
3057 
3058   // Construct a native method transfer processor for this class.
3059   TransferNativeFunctionRegistration(instanceKlassHandle _the_class) {
3060     assert(SafepointSynchronize::is_at_safepoint(), "sanity check");
3061 
3062     the_class = _the_class;
3063     prefixes = JvmtiExport::get_all_native_method_prefixes(&prefix_count);
3064   }
3065 
3066   // Attempt to transfer any of the old or deleted methods that are native
3067   void transfer_registrations(Method** old_methods, int methods_length) {
3068     for (int j = 0; j < methods_length; j++) {
3069       Method* old_method = old_methods[j];
3070 
3071       if (old_method->is_native() && old_method->has_native_function()) {
3072         Method* new_method = strip_and_search_for_new_native(old_method);
3073         if (new_method != NULL) {
3074           // Actually set the native function in the new method.
3075           // Redefine does not send events (except CFLH), certainly not this
3076           // behind the scenes re-registration.
3077           new_method->set_native_function(old_method->native_function(),
3078                               !Method::native_bind_event_is_interesting);
3079         }
3080       }
3081     }
3082   }
3083 };
3084 
3085 // Don't lose the association between a native method and its JNI function.
3086 void VM_RedefineClasses::transfer_old_native_function_registrations(instanceKlassHandle the_class) {
3087   TransferNativeFunctionRegistration transfer(the_class);
3088   transfer.transfer_registrations(_deleted_methods, _deleted_methods_length);
3089   transfer.transfer_registrations(_matching_old_methods, _matching_methods_length);
3090 }
3091 
3092 // Deoptimize all compiled code that depends on this class.
3093 //
3094 // If the can_redefine_classes capability is obtained in the onload
3095 // phase then the compiler has recorded all dependencies from startup.
3096 // In that case we need only deoptimize and throw away all compiled code
3097 // that depends on the class.
3098 //
3099 // If can_redefine_classes is obtained sometime after the onload
3100 // phase then the dependency information may be incomplete. In that case
3101 // the first call to RedefineClasses causes all compiled code to be
3102 // thrown away. As can_redefine_classes has been obtained then
3103 // all future compilations will record dependencies so second and
3104 // subsequent calls to RedefineClasses need only throw away code
3105 // that depends on the class.
3106 //
3107 void VM_RedefineClasses::flush_dependent_code(instanceKlassHandle k_h, TRAPS) {
3108   assert_locked_or_safepoint(Compile_lock);
3109 
3110   // All dependencies have been recorded from startup or this is a second or
3111   // subsequent use of RedefineClasses
3112   if (JvmtiExport::all_dependencies_are_recorded()) {
3113     Universe::flush_evol_dependents_on(k_h);
3114   } else {
3115     CodeCache::mark_all_nmethods_for_deoptimization();
3116 
3117     ResourceMark rm(THREAD);
3118     DeoptimizationMarker dm;
3119 
3120     // Deoptimize all activations depending on marked nmethods
3121     Deoptimization::deoptimize_dependents();
3122 
3123     // Make the dependent methods not entrant (in VM_Deoptimize they are made zombies)
3124     CodeCache::make_marked_nmethods_not_entrant();
3125 
3126     // From now on we know that the dependency information is complete
3127     JvmtiExport::set_all_dependencies_are_recorded(true);
3128   }
3129 }
3130 
3131 void VM_RedefineClasses::compute_added_deleted_matching_methods() {
3132   Method* old_method;
3133   Method* new_method;
3134 
3135   _matching_old_methods = NEW_RESOURCE_ARRAY(Method*, _old_methods->length());
3136   _matching_new_methods = NEW_RESOURCE_ARRAY(Method*, _old_methods->length());
3137   _added_methods        = NEW_RESOURCE_ARRAY(Method*, _new_methods->length());
3138   _deleted_methods      = NEW_RESOURCE_ARRAY(Method*, _old_methods->length());
3139 
3140   _matching_methods_length = 0;
3141   _deleted_methods_length  = 0;
3142   _added_methods_length    = 0;
3143 
3144   int nj = 0;
3145   int oj = 0;
3146   while (true) {
3147     if (oj >= _old_methods->length()) {
3148       if (nj >= _new_methods->length()) {
3149         break; // we've looked at everything, done
3150       }
3151       // New method at the end
3152       new_method = _new_methods->at(nj);
3153       _added_methods[_added_methods_length++] = new_method;
3154       ++nj;
3155     } else if (nj >= _new_methods->length()) {
3156       // Old method, at the end, is deleted
3157       old_method = _old_methods->at(oj);
3158       _deleted_methods[_deleted_methods_length++] = old_method;
3159       ++oj;
3160     } else {
3161       old_method = _old_methods->at(oj);
3162       new_method = _new_methods->at(nj);
3163       if (old_method->name() == new_method->name()) {
3164         if (old_method->signature() == new_method->signature()) {
3165           _matching_old_methods[_matching_methods_length  ] = old_method;
3166           _matching_new_methods[_matching_methods_length++] = new_method;
3167           ++nj;
3168           ++oj;
3169         } else {
3170           // added overloaded have already been moved to the end,
3171           // so this is a deleted overloaded method
3172           _deleted_methods[_deleted_methods_length++] = old_method;
3173           ++oj;
3174         }
3175       } else { // names don't match
3176         if (old_method->name()->fast_compare(new_method->name()) > 0) {
3177           // new method
3178           _added_methods[_added_methods_length++] = new_method;
3179           ++nj;
3180         } else {
3181           // deleted method
3182           _deleted_methods[_deleted_methods_length++] = old_method;
3183           ++oj;
3184         }
3185       }
3186     }
3187   }
3188   assert(_matching_methods_length + _deleted_methods_length == _old_methods->length(), "sanity");
3189   assert(_matching_methods_length + _added_methods_length == _new_methods->length(), "sanity");
3190 }
3191 
3192 
3193 void VM_RedefineClasses::swap_annotations(instanceKlassHandle the_class,
3194                                           instanceKlassHandle scratch_class) {
3195   // Since there is currently no rewriting of type annotations indexes
3196   // into the CP, we null out type annotations on scratch_class before
3197   // we swap annotations with the_class rather than facing the
3198   // possibility of shipping annotations with broken indexes to
3199   // Java-land.
3200   ClassLoaderData* loader_data = scratch_class->class_loader_data();
3201   AnnotationArray* new_class_type_annotations = scratch_class->class_type_annotations();
3202   if (new_class_type_annotations != NULL) {
3203     MetadataFactory::free_array<u1>(loader_data, new_class_type_annotations);
3204     scratch_class->annotations()->set_class_type_annotations(NULL);
3205   }
3206   Array<AnnotationArray*>* new_field_type_annotations = scratch_class->fields_type_annotations();
3207   if (new_field_type_annotations != NULL) {
3208     Annotations::free_contents(loader_data, new_field_type_annotations);
3209     scratch_class->annotations()->set_fields_type_annotations(NULL);
3210   }
3211 
3212   // Swap annotation fields values
3213   Annotations* old_annotations = the_class->annotations();
3214   the_class->set_annotations(scratch_class->annotations());
3215   scratch_class->set_annotations(old_annotations);
3216 }
3217 
3218 
3219 // Install the redefinition of a class:
3220 //    - house keeping (flushing breakpoints and caches, deoptimizing
3221 //      dependent compiled code)
3222 //    - replacing parts in the_class with parts from scratch_class
3223 //    - adding a weak reference to track the obsolete but interesting
3224 //      parts of the_class
3225 //    - adjusting constant pool caches and vtables in other classes
3226 //      that refer to methods in the_class. These adjustments use the
3227 //      ClassLoaderDataGraph::classes_do() facility which only allows
3228 //      a helper method to be specified. The interesting parameters
3229 //      that we would like to pass to the helper method are saved in
3230 //      static global fields in the VM operation.
3231 void VM_RedefineClasses::redefine_single_class(jclass the_jclass,
3232        Klass* scratch_class_oop, TRAPS) {
3233 
3234   HandleMark hm(THREAD);   // make sure handles from this call are freed
3235   RC_TIMER_START(_timer_rsc_phase1);
3236 
3237   instanceKlassHandle scratch_class(scratch_class_oop);
3238 
3239   oop the_class_mirror = JNIHandles::resolve_non_null(the_jclass);
3240   Klass* the_class_oop = java_lang_Class::as_Klass(the_class_mirror);
3241   instanceKlassHandle the_class = instanceKlassHandle(THREAD, the_class_oop);
3242 
3243   // Remove all breakpoints in methods of this class
3244   JvmtiBreakpoints& jvmti_breakpoints = JvmtiCurrentBreakpoints::get_jvmti_breakpoints();
3245   jvmti_breakpoints.clearall_in_class_at_safepoint(the_class_oop);
3246 
3247   // Deoptimize all compiled code that depends on this class
3248   flush_dependent_code(the_class, THREAD);
3249 
3250   _old_methods = the_class->methods();
3251   _new_methods = scratch_class->methods();
3252   _the_class_oop = the_class_oop;
3253   compute_added_deleted_matching_methods();
3254   update_jmethod_ids();
3255 
3256   // Attach new constant pool to the original klass. The original
3257   // klass still refers to the old constant pool (for now).
3258   scratch_class->constants()->set_pool_holder(the_class());
3259 
3260 #if 0
3261   // In theory, with constant pool merging in place we should be able
3262   // to save space by using the new, merged constant pool in place of
3263   // the old constant pool(s). By "pool(s)" I mean the constant pool in
3264   // the klass version we are replacing now and any constant pool(s) in
3265   // previous versions of klass. Nice theory, doesn't work in practice.
3266   // When this code is enabled, even simple programs throw NullPointer
3267   // exceptions. I'm guessing that this is caused by some constant pool
3268   // cache difference between the new, merged constant pool and the
3269   // constant pool that was just being used by the klass. I'm keeping
3270   // this code around to archive the idea, but the code has to remain
3271   // disabled for now.
3272 
3273   // Attach each old method to the new constant pool. This can be
3274   // done here since we are past the bytecode verification and
3275   // constant pool optimization phases.
3276   for (int i = _old_methods->length() - 1; i >= 0; i--) {
3277     Method* method = _old_methods->at(i);
3278     method->set_constants(scratch_class->constants());
3279   }
3280 
3281   {
3282     // walk all previous versions of the klass
3283     InstanceKlass *ik = (InstanceKlass *)the_class();
3284     PreviousVersionWalker pvw(ik);
3285     instanceKlassHandle ikh;
3286     do {
3287       ikh = pvw.next_previous_version();
3288       if (!ikh.is_null()) {
3289         ik = ikh();
3290 
3291         // attach previous version of klass to the new constant pool
3292         ik->set_constants(scratch_class->constants());
3293 
3294         // Attach each method in the previous version of klass to the
3295         // new constant pool
3296         Array<Method*>* prev_methods = ik->methods();
3297         for (int i = prev_methods->length() - 1; i >= 0; i--) {
3298           Method* method = prev_methods->at(i);
3299           method->set_constants(scratch_class->constants());
3300         }
3301       }
3302     } while (!ikh.is_null());
3303   }
3304 #endif
3305 
3306   // Replace methods and constantpool
3307   the_class->set_methods(_new_methods);
3308   scratch_class->set_methods(_old_methods);     // To prevent potential GCing of the old methods,
3309                                           // and to be able to undo operation easily.
3310 
3311   ConstantPool* old_constants = the_class->constants();
3312   the_class->set_constants(scratch_class->constants());
3313   scratch_class->set_constants(old_constants);  // See the previous comment.
3314 #if 0
3315   // We are swapping the guts of "the new class" with the guts of "the
3316   // class". Since the old constant pool has just been attached to "the
3317   // new class", it seems logical to set the pool holder in the old
3318   // constant pool also. However, doing this will change the observable
3319   // class hierarchy for any old methods that are still executing. A
3320   // method can query the identity of its "holder" and this query uses
3321   // the method's constant pool link to find the holder. The change in
3322   // holding class from "the class" to "the new class" can confuse
3323   // things.
3324   //
3325   // Setting the old constant pool's holder will also cause
3326   // verification done during vtable initialization below to fail.
3327   // During vtable initialization, the vtable's class is verified to be
3328   // a subtype of the method's holder. The vtable's class is "the
3329   // class" and the method's holder is gotten from the constant pool
3330   // link in the method itself. For "the class"'s directly implemented
3331   // methods, the method holder is "the class" itself (as gotten from
3332   // the new constant pool). The check works fine in this case. The
3333   // check also works fine for methods inherited from super classes.
3334   //
3335   // Miranda methods are a little more complicated. A miranda method is
3336   // provided by an interface when the class implementing the interface
3337   // does not provide its own method.  These interfaces are implemented
3338   // internally as an InstanceKlass. These special instanceKlasses
3339   // share the constant pool of the class that "implements" the
3340   // interface. By sharing the constant pool, the method holder of a
3341   // miranda method is the class that "implements" the interface. In a
3342   // non-redefine situation, the subtype check works fine. However, if
3343   // the old constant pool's pool holder is modified, then the check
3344   // fails because there is no class hierarchy relationship between the
3345   // vtable's class and "the new class".
3346 
3347   old_constants->set_pool_holder(scratch_class());
3348 #endif
3349 
3350   // track which methods are EMCP for add_previous_version() call below
3351   BitMap emcp_methods(_old_methods->length());
3352   int emcp_method_count = 0;
3353   emcp_methods.clear();  // clears 0..(length() - 1)
3354   check_methods_and_mark_as_obsolete(&emcp_methods, &emcp_method_count);
3355   transfer_old_native_function_registrations(the_class);
3356 
3357   // The class file bytes from before any retransformable agents mucked
3358   // with them was cached on the scratch class, move to the_class.
3359   // Note: we still want to do this if nothing needed caching since it
3360   // should get cleared in the_class too.
3361   if (the_class->get_cached_class_file_bytes() == 0) {
3362     // the_class doesn't have a cache yet so copy it
3363     the_class->set_cached_class_file(scratch_class->get_cached_class_file());
3364   }
3365 #ifndef PRODUCT
3366   else {
3367     assert(the_class->get_cached_class_file_bytes() ==
3368       scratch_class->get_cached_class_file_bytes(), "cache ptrs must match");
3369     assert(the_class->get_cached_class_file_len() ==
3370       scratch_class->get_cached_class_file_len(), "cache lens must match");
3371   }
3372 #endif
3373 
3374   // NULL out in scratch class to not delete twice.  The class to be redefined
3375   // always owns these bytes.
3376   scratch_class->set_cached_class_file(NULL);
3377 
3378   // Replace inner_classes
3379   Array<u2>* old_inner_classes = the_class->inner_classes();
3380   the_class->set_inner_classes(scratch_class->inner_classes());
3381   scratch_class->set_inner_classes(old_inner_classes);
3382 
3383   // Initialize the vtable and interface table after
3384   // methods have been rewritten
3385   {
3386     ResourceMark rm(THREAD);
3387     // no exception should happen here since we explicitly
3388     // do not check loader constraints.
3389     // compare_and_normalize_class_versions has already checked:
3390     //  - classloaders unchanged, signatures unchanged
3391     //  - all instanceKlasses for redefined classes reused & contents updated
3392     the_class->vtable()->initialize_vtable(false, THREAD);
3393     the_class->itable()->initialize_itable(false, THREAD);
3394     assert(!HAS_PENDING_EXCEPTION || (THREAD->pending_exception()->is_a(SystemDictionary::ThreadDeath_klass())), "redefine exception");
3395   }
3396 
3397   // Leave arrays of jmethodIDs and itable index cache unchanged
3398 
3399   // Copy the "source file name" attribute from new class version
3400   the_class->set_source_file_name_index(
3401     scratch_class->source_file_name_index());
3402 
3403   // Copy the "source debug extension" attribute from new class version
3404   the_class->set_source_debug_extension(
3405     scratch_class->source_debug_extension(),
3406     scratch_class->source_debug_extension() == NULL ? 0 :
3407     (int)strlen(scratch_class->source_debug_extension()));
3408 
3409   // Use of javac -g could be different in the old and the new
3410   if (scratch_class->access_flags().has_localvariable_table() !=
3411       the_class->access_flags().has_localvariable_table()) {
3412 
3413     AccessFlags flags = the_class->access_flags();
3414     if (scratch_class->access_flags().has_localvariable_table()) {
3415       flags.set_has_localvariable_table();
3416     } else {
3417       flags.clear_has_localvariable_table();
3418     }
3419     the_class->set_access_flags(flags);
3420   }
3421 
3422   swap_annotations(the_class, scratch_class);
3423 
3424   // Replace minor version number of class file
3425   u2 old_minor_version = the_class->minor_version();
3426   the_class->set_minor_version(scratch_class->minor_version());
3427   scratch_class->set_minor_version(old_minor_version);
3428 
3429   // Replace major version number of class file
3430   u2 old_major_version = the_class->major_version();
3431   the_class->set_major_version(scratch_class->major_version());
3432   scratch_class->set_major_version(old_major_version);
3433 
3434   // Replace CP indexes for class and name+type of enclosing method
3435   u2 old_class_idx  = the_class->enclosing_method_class_index();
3436   u2 old_method_idx = the_class->enclosing_method_method_index();
3437   the_class->set_enclosing_method_indices(
3438     scratch_class->enclosing_method_class_index(),
3439     scratch_class->enclosing_method_method_index());
3440   scratch_class->set_enclosing_method_indices(old_class_idx, old_method_idx);
3441 
3442   // keep track of previous versions of this class
3443   the_class->add_previous_version(scratch_class, &emcp_methods,
3444     emcp_method_count);
3445 
3446   RC_TIMER_STOP(_timer_rsc_phase1);
3447   RC_TIMER_START(_timer_rsc_phase2);
3448 
3449   // Adjust constantpool caches and vtables for all classes
3450   // that reference methods of the evolved class.
3451   AdjustCpoolCacheAndVtable adjust_cpool_cache_and_vtable(THREAD);
3452   ClassLoaderDataGraph::classes_do(&adjust_cpool_cache_and_vtable);
3453 
3454   // JSR-292 support
3455   MemberNameTable* mnt = the_class->member_names();
3456   if (mnt != NULL) {
3457     bool trace_name_printed = false;
3458     mnt->adjust_method_entries(_matching_old_methods,
3459                                _matching_new_methods,
3460                                _matching_methods_length,
3461                                &trace_name_printed);
3462   }
3463 
3464   // Fix Resolution Error table also to remove old constant pools
3465   SystemDictionary::delete_resolution_error(old_constants);
3466 
3467   if (the_class->oop_map_cache() != NULL) {
3468     // Flush references to any obsolete methods from the oop map cache
3469     // so that obsolete methods are not pinned.
3470     the_class->oop_map_cache()->flush_obsolete_entries();
3471   }
3472 
3473   // increment the classRedefinedCount field in the_class and in any
3474   // direct and indirect subclasses of the_class
3475   increment_class_counter((InstanceKlass *)the_class(), THREAD);
3476 
3477   // RC_TRACE macro has an embedded ResourceMark
3478   RC_TRACE_WITH_THREAD(0x00000001, THREAD,
3479     ("redefined name=%s, count=%d (avail_mem=" UINT64_FORMAT "K)",
3480     the_class->external_name(),
3481     java_lang_Class::classRedefinedCount(the_class_mirror),
3482     os::available_memory() >> 10));
3483 
3484   RC_TIMER_STOP(_timer_rsc_phase2);
3485 } // end redefine_single_class()
3486 
3487 
3488 // Increment the classRedefinedCount field in the specific InstanceKlass
3489 // and in all direct and indirect subclasses.
3490 void VM_RedefineClasses::increment_class_counter(InstanceKlass *ik, TRAPS) {
3491   oop class_mirror = ik->java_mirror();
3492   Klass* class_oop = java_lang_Class::as_Klass(class_mirror);
3493   int new_count = java_lang_Class::classRedefinedCount(class_mirror) + 1;
3494   java_lang_Class::set_classRedefinedCount(class_mirror, new_count);
3495 
3496   if (class_oop != _the_class_oop) {
3497     // _the_class_oop count is printed at end of redefine_single_class()
3498     RC_TRACE_WITH_THREAD(0x00000008, THREAD,
3499       ("updated count in subclass=%s to %d", ik->external_name(), new_count));
3500   }
3501 
3502   for (Klass *subk = ik->subklass(); subk != NULL;
3503        subk = subk->next_sibling()) {
3504     if (subk->oop_is_instance()) {
3505       // Only update instanceKlasses
3506       InstanceKlass *subik = (InstanceKlass*)subk;
3507       // recursively do subclasses of the current subclass
3508       increment_class_counter(subik, THREAD);
3509     }
3510   }
3511 }
3512 
3513 void VM_RedefineClasses::CheckClass::do_klass(Klass* k) {
3514   bool no_old_methods = true;  // be optimistic
3515 
3516   // Both array and instance classes have vtables.
3517   // a vtable should never contain old or obsolete methods
3518   ResourceMark rm(_thread);
3519   if (k->vtable_length() > 0 &&
3520       !k->vtable()->check_no_old_or_obsolete_entries()) {
3521     if (RC_TRACE_ENABLED(0x00004000)) {
3522       RC_TRACE_WITH_THREAD(0x00004000, _thread,
3523         ("klassVtable::check_no_old_or_obsolete_entries failure"
3524          " -- OLD or OBSOLETE method found -- class: %s",
3525          k->signature_name()));
3526       k->vtable()->dump_vtable();
3527     }
3528     no_old_methods = false;
3529   }
3530 
3531   if (k->oop_is_instance()) {
3532     HandleMark hm(_thread);
3533     InstanceKlass *ik = InstanceKlass::cast(k);
3534 
3535     // an itable should never contain old or obsolete methods
3536     if (ik->itable_length() > 0 &&
3537         !ik->itable()->check_no_old_or_obsolete_entries()) {
3538       if (RC_TRACE_ENABLED(0x00004000)) {
3539         RC_TRACE_WITH_THREAD(0x00004000, _thread,
3540           ("klassItable::check_no_old_or_obsolete_entries failure"
3541            " -- OLD or OBSOLETE method found -- class: %s",
3542            ik->signature_name()));
3543         ik->itable()->dump_itable();
3544       }
3545       no_old_methods = false;
3546     }
3547 
3548     // the constant pool cache should never contain old or obsolete methods
3549     if (ik->constants() != NULL &&
3550         ik->constants()->cache() != NULL &&
3551         !ik->constants()->cache()->check_no_old_or_obsolete_entries()) {
3552       if (RC_TRACE_ENABLED(0x00004000)) {
3553         RC_TRACE_WITH_THREAD(0x00004000, _thread,
3554           ("cp-cache::check_no_old_or_obsolete_entries failure"
3555            " -- OLD or OBSOLETE method found -- class: %s",
3556            ik->signature_name()));
3557         ik->constants()->cache()->dump_cache();
3558       }
3559       no_old_methods = false;
3560     }
3561   }
3562 
3563   // print and fail guarantee if old methods are found.
3564   if (!no_old_methods) {
3565     if (RC_TRACE_ENABLED(0x00004000)) {
3566       dump_methods();
3567     } else {
3568       tty->print_cr("INFO: use the '-XX:TraceRedefineClasses=16384' option "
3569         "to see more info about the following guarantee() failure.");
3570     }
3571     guarantee(false, "OLD and/or OBSOLETE method(s) found");
3572   }
3573 }
3574 
3575 
3576 void VM_RedefineClasses::dump_methods() {
3577   int j;
3578   RC_TRACE(0x00004000, ("_old_methods --"));
3579   for (j = 0; j < _old_methods->length(); ++j) {
3580     Method* m = _old_methods->at(j);
3581     RC_TRACE_NO_CR(0x00004000, ("%4d  (%5d)  ", j, m->vtable_index()));
3582     m->access_flags().print_on(tty);
3583     tty->print(" --  ");
3584     m->print_name(tty);
3585     tty->cr();
3586   }
3587   RC_TRACE(0x00004000, ("_new_methods --"));
3588   for (j = 0; j < _new_methods->length(); ++j) {
3589     Method* m = _new_methods->at(j);
3590     RC_TRACE_NO_CR(0x00004000, ("%4d  (%5d)  ", j, m->vtable_index()));
3591     m->access_flags().print_on(tty);
3592     tty->print(" --  ");
3593     m->print_name(tty);
3594     tty->cr();
3595   }
3596   RC_TRACE(0x00004000, ("_matching_(old/new)_methods --"));
3597   for (j = 0; j < _matching_methods_length; ++j) {
3598     Method* m = _matching_old_methods[j];
3599     RC_TRACE_NO_CR(0x00004000, ("%4d  (%5d)  ", j, m->vtable_index()));
3600     m->access_flags().print_on(tty);
3601     tty->print(" --  ");
3602     m->print_name(tty);
3603     tty->cr();
3604     m = _matching_new_methods[j];
3605     RC_TRACE_NO_CR(0x00004000, ("      (%5d)  ", m->vtable_index()));
3606     m->access_flags().print_on(tty);
3607     tty->cr();
3608   }
3609   RC_TRACE(0x00004000, ("_deleted_methods --"));
3610   for (j = 0; j < _deleted_methods_length; ++j) {
3611     Method* m = _deleted_methods[j];
3612     RC_TRACE_NO_CR(0x00004000, ("%4d  (%5d)  ", j, m->vtable_index()));
3613     m->access_flags().print_on(tty);
3614     tty->print(" --  ");
3615     m->print_name(tty);
3616     tty->cr();
3617   }
3618   RC_TRACE(0x00004000, ("_added_methods --"));
3619   for (j = 0; j < _added_methods_length; ++j) {
3620     Method* m = _added_methods[j];
3621     RC_TRACE_NO_CR(0x00004000, ("%4d  (%5d)  ", j, m->vtable_index()));
3622     m->access_flags().print_on(tty);
3623     tty->print(" --  ");
3624     m->print_name(tty);
3625     tty->cr();
3626   }
3627 }
--- EOF ---