1 /*
   2  * Copyright (c) 2003, 2013, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "classfile/metadataOnStackMark.hpp"
  27 #include "classfile/systemDictionary.hpp"
  28 #include "classfile/verifier.hpp"
  29 #include "code/codeCache.hpp"
  30 #include "compiler/compileBroker.hpp"
  31 #include "interpreter/oopMapCache.hpp"
  32 #include "interpreter/rewriter.hpp"
  33 #include "memory/gcLocker.hpp"
  34 #include "memory/metadataFactory.hpp"
  35 #include "memory/metaspaceShared.hpp"
  36 #include "memory/universe.inline.hpp"
  37 #include "oops/fieldStreams.hpp"
  38 #include "oops/klassVtable.hpp"
  39 #include "prims/jvmtiImpl.hpp"
  40 #include "prims/jvmtiRedefineClasses.hpp"
  41 #include "prims/methodComparator.hpp"
  42 #include "runtime/deoptimization.hpp"
  43 #include "runtime/relocator.hpp"
  44 #include "utilities/bitMap.inline.hpp"
  45 
  46 
  47 Array<Method*>* VM_RedefineClasses::_old_methods = NULL;
  48 Array<Method*>* VM_RedefineClasses::_new_methods = NULL;
  49 Method**  VM_RedefineClasses::_matching_old_methods = NULL;
  50 Method**  VM_RedefineClasses::_matching_new_methods = NULL;
  51 Method**  VM_RedefineClasses::_deleted_methods      = NULL;
  52 Method**  VM_RedefineClasses::_added_methods        = NULL;
  53 int         VM_RedefineClasses::_matching_methods_length = 0;
  54 int         VM_RedefineClasses::_deleted_methods_length  = 0;
  55 int         VM_RedefineClasses::_added_methods_length    = 0;
  56 Klass*      VM_RedefineClasses::_the_class_oop = NULL;
  57 
  58 
  59 VM_RedefineClasses::VM_RedefineClasses(jint class_count,
  60                                        const jvmtiClassDefinition *class_defs,
  61                                        JvmtiClassLoadKind class_load_kind) {
  62   _class_count = class_count;
  63   _class_defs = class_defs;
  64   _class_load_kind = class_load_kind;
  65   _res = JVMTI_ERROR_NONE;
  66 }
  67 
  68 bool VM_RedefineClasses::doit_prologue() {
  69   if (_class_count == 0) {
  70     _res = JVMTI_ERROR_NONE;
  71     return false;
  72   }
  73   if (_class_defs == NULL) {
  74     _res = JVMTI_ERROR_NULL_POINTER;
  75     return false;
  76   }
  77   for (int i = 0; i < _class_count; i++) {
  78     if (_class_defs[i].klass == NULL) {
  79       _res = JVMTI_ERROR_INVALID_CLASS;
  80       return false;
  81     }
  82     if (_class_defs[i].class_byte_count == 0) {
  83       _res = JVMTI_ERROR_INVALID_CLASS_FORMAT;
  84       return false;
  85     }
  86     if (_class_defs[i].class_bytes == NULL) {
  87       _res = JVMTI_ERROR_NULL_POINTER;
  88       return false;
  89     }
  90   }
  91 
  92   // Start timer after all the sanity checks; not quite accurate, but
  93   // better than adding a bunch of stop() calls.
  94   RC_TIMER_START(_timer_vm_op_prologue);
  95 
  96   // We first load new class versions in the prologue, because somewhere down the
  97   // call chain it is required that the current thread is a Java thread.
  98   _res = load_new_class_versions(Thread::current());
  99   if (_res != JVMTI_ERROR_NONE) {
 100     // free any successfully created classes, since none are redefined
 101     for (int i = 0; i < _class_count; i++) {
 102       if (_scratch_classes[i] != NULL) {
 103         ClassLoaderData* cld = _scratch_classes[i]->class_loader_data();
 104         // Free the memory for this class at class unloading time.  Not before
 105         // because CMS might think this is still live.
 106         cld->add_to_deallocate_list((InstanceKlass*)_scratch_classes[i]);
 107       }
 108     }
 109     // Free os::malloc allocated memory in load_new_class_version.
 110     os::free(_scratch_classes);
 111     RC_TIMER_STOP(_timer_vm_op_prologue);
 112     return false;
 113   }
 114 
 115   RC_TIMER_STOP(_timer_vm_op_prologue);
 116   return true;
 117 }
 118 
 119 void VM_RedefineClasses::doit() {
 120   Thread *thread = Thread::current();
 121 
 122   if (UseSharedSpaces) {
 123     // Sharing is enabled so we remap the shared readonly space to
 124     // shared readwrite, private just in case we need to redefine
 125     // a shared class. We do the remap during the doit() phase of
 126     // the safepoint to be safer.
 127     if (!MetaspaceShared::remap_shared_readonly_as_readwrite()) {
 128       RC_TRACE_WITH_THREAD(0x00000001, thread,
 129         ("failed to remap shared readonly space to readwrite, private"));
 130       _res = JVMTI_ERROR_INTERNAL;
 131       return;
 132     }
 133   }
 134 
 135   // Mark methods seen on stack and everywhere else so old methods are not
 136   // cleaned up if they're on the stack.
 137   MetadataOnStackMark md_on_stack;
 138   HandleMark hm(thread);   // make sure any handles created are deleted
 139                            // before the stack walk again.
 140 
 141   for (int i = 0; i < _class_count; i++) {
 142     redefine_single_class(_class_defs[i].klass, _scratch_classes[i], thread);
 143     ClassLoaderData* cld = _scratch_classes[i]->class_loader_data();
 144     // Free the memory for this class at class unloading time.  Not before
 145     // because CMS might think this is still live.
 146     cld->add_to_deallocate_list((InstanceKlass*)_scratch_classes[i]);
 147     _scratch_classes[i] = NULL;
 148   }
 149 
 150   // Disable any dependent concurrent compilations
 151   SystemDictionary::notice_modification();
 152 
 153   // Set flag indicating that some invariants are no longer true.
 154   // See jvmtiExport.hpp for detailed explanation.
 155   JvmtiExport::set_has_redefined_a_class();
 156 
 157 // check_class() is optionally called for product bits, but is
 158 // always called for non-product bits.
 159 #ifdef PRODUCT
 160   if (RC_TRACE_ENABLED(0x00004000)) {
 161 #endif
 162     RC_TRACE_WITH_THREAD(0x00004000, thread, ("calling check_class"));
 163     CheckClass check_class(thread);
 164     ClassLoaderDataGraph::classes_do(&check_class);
 165 #ifdef PRODUCT
 166   }
 167 #endif
 168 }
 169 
 170 void VM_RedefineClasses::doit_epilogue() {
 171   // Free os::malloc allocated memory.
 172   os::free(_scratch_classes);
 173 
 174   if (RC_TRACE_ENABLED(0x00000004)) {
 175     // Used to have separate timers for "doit" and "all", but the timer
 176     // overhead skewed the measurements.
 177     jlong doit_time = _timer_rsc_phase1.milliseconds() +
 178                       _timer_rsc_phase2.milliseconds();
 179     jlong all_time = _timer_vm_op_prologue.milliseconds() + doit_time;
 180 
 181     RC_TRACE(0x00000004, ("vm_op: all=" UINT64_FORMAT
 182       "  prologue=" UINT64_FORMAT "  doit=" UINT64_FORMAT, all_time,
 183       _timer_vm_op_prologue.milliseconds(), doit_time));
 184     RC_TRACE(0x00000004,
 185       ("redefine_single_class: phase1=" UINT64_FORMAT "  phase2=" UINT64_FORMAT,
 186        _timer_rsc_phase1.milliseconds(), _timer_rsc_phase2.milliseconds()));
 187   }
 188 }
 189 
 190 bool VM_RedefineClasses::is_modifiable_class(oop klass_mirror) {
 191   // classes for primitives cannot be redefined
 192   if (java_lang_Class::is_primitive(klass_mirror)) {
 193     return false;
 194   }
 195   Klass* the_class_oop = java_lang_Class::as_Klass(klass_mirror);
 196   // classes for arrays cannot be redefined
 197   if (the_class_oop == NULL || !the_class_oop->oop_is_instance()) {
 198     return false;
 199   }
 200   return true;
 201 }
 202 
 203 // Append the current entry at scratch_i in scratch_cp to *merge_cp_p
 204 // where the end of *merge_cp_p is specified by *merge_cp_length_p. For
 205 // direct CP entries, there is just the current entry to append. For
 206 // indirect and double-indirect CP entries, there are zero or more
 207 // referenced CP entries along with the current entry to append.
 208 // Indirect and double-indirect CP entries are handled by recursive
 209 // calls to append_entry() as needed. The referenced CP entries are
 210 // always appended to *merge_cp_p before the referee CP entry. These
 211 // referenced CP entries may already exist in *merge_cp_p in which case
 212 // there is nothing extra to append and only the current entry is
 213 // appended.
 214 void VM_RedefineClasses::append_entry(constantPoolHandle scratch_cp,
 215        int scratch_i, constantPoolHandle *merge_cp_p, int *merge_cp_length_p,
 216        TRAPS) {
 217 
 218   // append is different depending on entry tag type
 219   switch (scratch_cp->tag_at(scratch_i).value()) {
 220 
 221     // The old verifier is implemented outside the VM. It loads classes,
 222     // but does not resolve constant pool entries directly so we never
 223     // see Class entries here with the old verifier. Similarly the old
 224     // verifier does not like Class entries in the input constant pool.
 225     // The split-verifier is implemented in the VM so it can optionally
 226     // and directly resolve constant pool entries to load classes. The
 227     // split-verifier can accept either Class entries or UnresolvedClass
 228     // entries in the input constant pool. We revert the appended copy
 229     // back to UnresolvedClass so that either verifier will be happy
 230     // with the constant pool entry.
 231     case JVM_CONSTANT_Class:
 232     {
 233       // revert the copy to JVM_CONSTANT_UnresolvedClass
 234       (*merge_cp_p)->unresolved_klass_at_put(*merge_cp_length_p,
 235         scratch_cp->klass_name_at(scratch_i));
 236 
 237       if (scratch_i != *merge_cp_length_p) {
 238         // The new entry in *merge_cp_p is at a different index than
 239         // the new entry in scratch_cp so we need to map the index values.
 240         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 241       }
 242       (*merge_cp_length_p)++;
 243     } break;
 244 
 245     // these are direct CP entries so they can be directly appended,
 246     // but double and long take two constant pool entries
 247     case JVM_CONSTANT_Double:  // fall through
 248     case JVM_CONSTANT_Long:
 249     {
 250       ConstantPool::copy_entry_to(scratch_cp, scratch_i, *merge_cp_p, *merge_cp_length_p,
 251         THREAD);
 252 
 253       if (scratch_i != *merge_cp_length_p) {
 254         // The new entry in *merge_cp_p is at a different index than
 255         // the new entry in scratch_cp so we need to map the index values.
 256         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 257       }
 258       (*merge_cp_length_p) += 2;
 259     } break;
 260 
 261     // these are direct CP entries so they can be directly appended
 262     case JVM_CONSTANT_Float:   // fall through
 263     case JVM_CONSTANT_Integer: // fall through
 264     case JVM_CONSTANT_Utf8:    // fall through
 265 
 266     // This was an indirect CP entry, but it has been changed into
 267     // Symbol*s so this entry can be directly appended.
 268     case JVM_CONSTANT_String:      // fall through
 269 
 270     // These were indirect CP entries, but they have been changed into
 271     // Symbol*s so these entries can be directly appended.
 272     case JVM_CONSTANT_UnresolvedClass:  // fall through
 273     {
 274       ConstantPool::copy_entry_to(scratch_cp, scratch_i, *merge_cp_p, *merge_cp_length_p,
 275         THREAD);
 276 
 277       if (scratch_i != *merge_cp_length_p) {
 278         // The new entry in *merge_cp_p is at a different index than
 279         // the new entry in scratch_cp so we need to map the index values.
 280         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 281       }
 282       (*merge_cp_length_p)++;
 283     } break;
 284 
 285     // this is an indirect CP entry so it needs special handling
 286     case JVM_CONSTANT_NameAndType:
 287     {
 288       int name_ref_i = scratch_cp->name_ref_index_at(scratch_i);
 289       int new_name_ref_i = find_or_append_indirect_entry(scratch_cp, name_ref_i, merge_cp_p,
 290                                                          merge_cp_length_p, THREAD);
 291 
 292       int signature_ref_i = scratch_cp->signature_ref_index_at(scratch_i);
 293       int new_signature_ref_i = find_or_append_indirect_entry(scratch_cp, signature_ref_i,
 294                                                               merge_cp_p, merge_cp_length_p,
 295                                                               THREAD);
 296 
 297       // If the referenced entries already exist in *merge_cp_p, then
 298       // both new_name_ref_i and new_signature_ref_i will both be 0.
 299       // In that case, all we are appending is the current entry.
 300       if (new_name_ref_i != name_ref_i) {
 301         RC_TRACE(0x00080000,
 302           ("NameAndType entry@%d name_ref_index change: %d to %d",
 303           *merge_cp_length_p, name_ref_i, new_name_ref_i));
 304       }
 305       if (new_signature_ref_i != signature_ref_i) {
 306         RC_TRACE(0x00080000,
 307           ("NameAndType entry@%d signature_ref_index change: %d to %d",
 308           *merge_cp_length_p, signature_ref_i, new_signature_ref_i));
 309       }
 310 
 311       (*merge_cp_p)->name_and_type_at_put(*merge_cp_length_p,
 312         new_name_ref_i, new_signature_ref_i);
 313       if (scratch_i != *merge_cp_length_p) {
 314         // The new entry in *merge_cp_p is at a different index than
 315         // the new entry in scratch_cp so we need to map the index values.
 316         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 317       }
 318       (*merge_cp_length_p)++;
 319     } break;
 320 
 321     // this is a double-indirect CP entry so it needs special handling
 322     case JVM_CONSTANT_Fieldref:           // fall through
 323     case JVM_CONSTANT_InterfaceMethodref: // fall through
 324     case JVM_CONSTANT_Methodref:
 325     {
 326       int klass_ref_i = scratch_cp->uncached_klass_ref_index_at(scratch_i);
 327       int new_klass_ref_i = find_or_append_indirect_entry(scratch_cp, klass_ref_i,
 328                                                           merge_cp_p, merge_cp_length_p, THREAD);
 329 
 330       int name_and_type_ref_i = scratch_cp->uncached_name_and_type_ref_index_at(scratch_i);
 331       int new_name_and_type_ref_i = find_or_append_indirect_entry(scratch_cp, name_and_type_ref_i,
 332                                                           merge_cp_p, merge_cp_length_p, THREAD);
 333 
 334       const char *entry_name;
 335       switch (scratch_cp->tag_at(scratch_i).value()) {
 336       case JVM_CONSTANT_Fieldref:
 337         entry_name = "Fieldref";
 338         (*merge_cp_p)->field_at_put(*merge_cp_length_p, new_klass_ref_i,
 339           new_name_and_type_ref_i);
 340         break;
 341       case JVM_CONSTANT_InterfaceMethodref:
 342         entry_name = "IFMethodref";
 343         (*merge_cp_p)->interface_method_at_put(*merge_cp_length_p,
 344           new_klass_ref_i, new_name_and_type_ref_i);
 345         break;
 346       case JVM_CONSTANT_Methodref:
 347         entry_name = "Methodref";
 348         (*merge_cp_p)->method_at_put(*merge_cp_length_p, new_klass_ref_i,
 349           new_name_and_type_ref_i);
 350         break;
 351       default:
 352         guarantee(false, "bad switch");
 353         break;
 354       }
 355 
 356       if (klass_ref_i != new_klass_ref_i) {
 357         RC_TRACE(0x00080000, ("%s entry@%d class_index changed: %d to %d",
 358           entry_name, *merge_cp_length_p, klass_ref_i, new_klass_ref_i));
 359       }
 360       if (name_and_type_ref_i != new_name_and_type_ref_i) {
 361         RC_TRACE(0x00080000,
 362           ("%s entry@%d name_and_type_index changed: %d to %d",
 363           entry_name, *merge_cp_length_p, name_and_type_ref_i,
 364           new_name_and_type_ref_i));
 365       }
 366 
 367       if (scratch_i != *merge_cp_length_p) {
 368         // The new entry in *merge_cp_p is at a different index than
 369         // the new entry in scratch_cp so we need to map the index values.
 370         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 371       }
 372       (*merge_cp_length_p)++;
 373     } break;
 374 
 375     // this is an indirect CP entry so it needs special handling
 376     case JVM_CONSTANT_MethodType:
 377     {
 378       int ref_i = scratch_cp->method_type_index_at(scratch_i);
 379       int new_ref_i = find_or_append_indirect_entry(scratch_cp, ref_i, merge_cp_p,
 380                                                     merge_cp_length_p, THREAD);
 381       if (new_ref_i != ref_i) {
 382         RC_TRACE(0x00080000,
 383                  ("MethodType entry@%d ref_index change: %d to %d",
 384                   *merge_cp_length_p, ref_i, new_ref_i));
 385       }
 386       (*merge_cp_p)->method_type_index_at_put(*merge_cp_length_p, new_ref_i);
 387       if (scratch_i != *merge_cp_length_p) {
 388         // The new entry in *merge_cp_p is at a different index than
 389         // the new entry in scratch_cp so we need to map the index values.
 390         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 391       }
 392       (*merge_cp_length_p)++;
 393     } break;
 394 
 395     // this is an indirect CP entry so it needs special handling
 396     case JVM_CONSTANT_MethodHandle:
 397     {
 398       int ref_kind = scratch_cp->method_handle_ref_kind_at(scratch_i);
 399       int ref_i = scratch_cp->method_handle_index_at(scratch_i);
 400       int new_ref_i = find_or_append_indirect_entry(scratch_cp, ref_i, merge_cp_p,
 401                                                     merge_cp_length_p, THREAD);
 402       if (new_ref_i != ref_i) {
 403         RC_TRACE(0x00080000,
 404                  ("MethodHandle entry@%d ref_index change: %d to %d",
 405                   *merge_cp_length_p, ref_i, new_ref_i));
 406       }
 407       (*merge_cp_p)->method_handle_index_at_put(*merge_cp_length_p, ref_kind, new_ref_i);
 408       if (scratch_i != *merge_cp_length_p) {
 409         // The new entry in *merge_cp_p is at a different index than
 410         // the new entry in scratch_cp so we need to map the index values.
 411         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 412       }
 413       (*merge_cp_length_p)++;
 414     } break;
 415 
 416     // this is an indirect CP entry so it needs special handling
 417     case JVM_CONSTANT_InvokeDynamic:
 418     {
 419       // Index of the bootstrap specifier in the operands array
 420       int old_bs_i = scratch_cp->invoke_dynamic_bootstrap_specifier_index(scratch_i);
 421       int new_bs_i = find_or_append_operand(scratch_cp, old_bs_i, merge_cp_p,
 422                                             merge_cp_length_p, THREAD);
 423       // The bootstrap method NameAndType_info index
 424       int old_ref_i = scratch_cp->invoke_dynamic_name_and_type_ref_index_at(scratch_i);
 425       int new_ref_i = find_or_append_indirect_entry(scratch_cp, old_ref_i, merge_cp_p,
 426                                                     merge_cp_length_p, THREAD);
 427       if (new_bs_i != old_bs_i) {
 428         RC_TRACE(0x00080000,
 429                  ("InvokeDynamic entry@%d bootstrap_method_attr_index change: %d to %d",
 430                   *merge_cp_length_p, old_bs_i, new_bs_i));
 431       }
 432       if (new_ref_i != old_ref_i) {
 433         RC_TRACE(0x00080000,
 434                  ("InvokeDynamic entry@%d name_and_type_index change: %d to %d",
 435                   *merge_cp_length_p, old_ref_i, new_ref_i));
 436       }
 437 
 438       (*merge_cp_p)->invoke_dynamic_at_put(*merge_cp_length_p, new_bs_i, new_ref_i);
 439       if (scratch_i != *merge_cp_length_p) {
 440         // The new entry in *merge_cp_p is at a different index than
 441         // the new entry in scratch_cp so we need to map the index values.
 442         map_index(scratch_cp, scratch_i, *merge_cp_length_p);
 443       }
 444       (*merge_cp_length_p)++;
 445     } break;
 446 
 447     // At this stage, Class or UnresolvedClass could be here, but not
 448     // ClassIndex
 449     case JVM_CONSTANT_ClassIndex: // fall through
 450 
 451     // Invalid is used as the tag for the second constant pool entry
 452     // occupied by JVM_CONSTANT_Double or JVM_CONSTANT_Long. It should
 453     // not be seen by itself.
 454     case JVM_CONSTANT_Invalid: // fall through
 455 
 456     // At this stage, String could be here, but not StringIndex
 457     case JVM_CONSTANT_StringIndex: // fall through
 458 
 459     // At this stage JVM_CONSTANT_UnresolvedClassInError should not be
 460     // here
 461     case JVM_CONSTANT_UnresolvedClassInError: // fall through
 462 
 463     default:
 464     {
 465       // leave a breadcrumb
 466       jbyte bad_value = scratch_cp->tag_at(scratch_i).value();
 467       ShouldNotReachHere();
 468     } break;
 469   } // end switch tag value
 470 } // end append_entry()
 471 
 472 
 473 int VM_RedefineClasses::find_or_append_indirect_entry(constantPoolHandle scratch_cp,
 474       int ref_i, constantPoolHandle *merge_cp_p, int *merge_cp_length_p, TRAPS) {
 475 
 476   int new_ref_i = ref_i;
 477   bool match = (ref_i < *merge_cp_length_p) &&
 478                scratch_cp->compare_entry_to(ref_i, *merge_cp_p, ref_i, THREAD);
 479 
 480   if (!match) {
 481     // forward reference in *merge_cp_p or not a direct match
 482     int found_i = scratch_cp->find_matching_entry(ref_i, *merge_cp_p, THREAD);
 483     if (found_i != 0) {
 484       guarantee(found_i != ref_i, "compare_entry_to() and find_matching_entry() do not agree");
 485       // Found a matching entry somewhere else in *merge_cp_p so just need a mapping entry.
 486       new_ref_i = found_i;
 487       map_index(scratch_cp, ref_i, found_i);
 488     } else {
 489       // no match found so we have to append this entry to *merge_cp_p
 490       append_entry(scratch_cp, ref_i, merge_cp_p, merge_cp_length_p, THREAD);
 491       // The above call to append_entry() can only append one entry
 492       // so the post call query of *merge_cp_length_p is only for
 493       // the sake of consistency.
 494       new_ref_i = *merge_cp_length_p - 1;
 495     }
 496   }
 497 
 498   return new_ref_i;
 499 } // end find_or_append_indirect_entry()
 500 
 501 
 502 // Append a bootstrap specifier into the merge_cp operands that is semantically equal
 503 // to the scratch_cp operands bootstrap specifier passed by the old_bs_i index.
 504 // Recursively append new merge_cp entries referenced by the new bootstrap specifier.
 505 void VM_RedefineClasses::append_operand(constantPoolHandle scratch_cp, int old_bs_i,
 506        constantPoolHandle *merge_cp_p, int *merge_cp_length_p, TRAPS) {
 507 
 508   int old_ref_i = scratch_cp->operand_bootstrap_method_ref_index_at(old_bs_i);
 509   int new_ref_i = find_or_append_indirect_entry(scratch_cp, old_ref_i, merge_cp_p,
 510                                                 merge_cp_length_p, THREAD);
 511   if (new_ref_i != old_ref_i) {
 512     RC_TRACE(0x00080000,
 513              ("operands entry@%d bootstrap method ref_index change: %d to %d",
 514               _operands_cur_length, old_ref_i, new_ref_i));
 515   }
 516 
 517   Array<u2>* merge_ops = (*merge_cp_p)->operands();
 518   int new_bs_i = _operands_cur_length;
 519   // We have _operands_cur_length == 0 when the merge_cp operands is empty yet.
 520   // However, the operand_offset_at(0) was set in the extend_operands() call.
 521   int new_base = (new_bs_i == 0) ? (*merge_cp_p)->operand_offset_at(0)
 522                                  : (*merge_cp_p)->operand_next_offset_at(new_bs_i - 1);
 523   int argc     = scratch_cp->operand_argument_count_at(old_bs_i);
 524 
 525   ConstantPool::operand_offset_at_put(merge_ops, _operands_cur_length, new_base);
 526   merge_ops->at_put(new_base++, new_ref_i);
 527   merge_ops->at_put(new_base++, argc);
 528 
 529   for (int i = 0; i < argc; i++) {
 530     int old_arg_ref_i = scratch_cp->operand_argument_index_at(old_bs_i, i);
 531     int new_arg_ref_i = find_or_append_indirect_entry(scratch_cp, old_arg_ref_i, merge_cp_p,
 532                                                       merge_cp_length_p, THREAD);
 533     merge_ops->at_put(new_base++, new_arg_ref_i);
 534     if (new_arg_ref_i != old_arg_ref_i) {
 535       RC_TRACE(0x00080000,
 536                ("operands entry@%d bootstrap method argument ref_index change: %d to %d",
 537                 _operands_cur_length, old_arg_ref_i, new_arg_ref_i));
 538     }
 539   }
 540   if (old_bs_i != _operands_cur_length) {
 541     // The bootstrap specifier in *merge_cp_p is at a different index than
 542     // that in scratch_cp so we need to map the index values.
 543     map_operand_index(old_bs_i, new_bs_i);
 544   }
 545   _operands_cur_length++;
 546 } // end append_operand()
 547 
 548 
 549 int VM_RedefineClasses::find_or_append_operand(constantPoolHandle scratch_cp,
 550       int old_bs_i, constantPoolHandle *merge_cp_p, int *merge_cp_length_p, TRAPS) {
 551 
 552   int new_bs_i = old_bs_i; // bootstrap specifier index
 553   bool match = (old_bs_i < _operands_cur_length) &&
 554                scratch_cp->compare_operand_to(old_bs_i, *merge_cp_p, old_bs_i, THREAD);
 555 
 556   if (!match) {
 557     // forward reference in *merge_cp_p or not a direct match
 558     int found_i = scratch_cp->find_matching_operand(old_bs_i, *merge_cp_p,
 559                                                     _operands_cur_length, THREAD);
 560     if (found_i != -1) {
 561       guarantee(found_i != old_bs_i, "compare_operand_to() and find_matching_operand() disagree");
 562       // found a matching operand somewhere else in *merge_cp_p so just need a mapping
 563       new_bs_i = found_i;
 564       map_operand_index(old_bs_i, found_i);
 565     } else {
 566       // no match found so we have to append this bootstrap specifier to *merge_cp_p
 567       append_operand(scratch_cp, old_bs_i, merge_cp_p, merge_cp_length_p, THREAD);
 568       new_bs_i = _operands_cur_length - 1;
 569     }
 570   }
 571   return new_bs_i;
 572 } // end find_or_append_operand()
 573 
 574 
 575 void VM_RedefineClasses::finalize_operands_merge(constantPoolHandle merge_cp, TRAPS) {
 576   if (merge_cp->operands() == NULL) {
 577     return;
 578   }
 579   // Shrink the merge_cp operands
 580   merge_cp->shrink_operands(_operands_cur_length, CHECK);
 581 
 582   if (RC_TRACE_ENABLED(0x00040000)) {
 583     // don't want to loop unless we are tracing
 584     int count = 0;
 585     for (int i = 1; i < _operands_index_map_p->length(); i++) {
 586       int value = _operands_index_map_p->at(i);
 587       if (value != -1) {
 588         RC_TRACE_WITH_THREAD(0x00040000, THREAD,
 589           ("operands_index_map[%d]: old=%d new=%d", count, i, value));
 590         count++;
 591       }
 592     }
 593   }
 594   // Clean-up
 595   _operands_index_map_p = NULL;
 596   _operands_cur_length = 0;
 597   _operands_index_map_count = 0;
 598 } // end finalize_operands_merge()
 599 
 600 
 601 jvmtiError VM_RedefineClasses::compare_and_normalize_class_versions(
 602              instanceKlassHandle the_class,
 603              instanceKlassHandle scratch_class) {
 604   int i;
 605 
 606   // Check superclasses, or rather their names, since superclasses themselves can be
 607   // requested to replace.
 608   // Check for NULL superclass first since this might be java.lang.Object
 609   if (the_class->super() != scratch_class->super() &&
 610       (the_class->super() == NULL || scratch_class->super() == NULL ||
 611        the_class->super()->name() !=
 612        scratch_class->super()->name())) {
 613     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_HIERARCHY_CHANGED;
 614   }
 615 
 616   // Check if the number, names and order of directly implemented interfaces are the same.
 617   // I think in principle we should just check if the sets of names of directly implemented
 618   // interfaces are the same, i.e. the order of declaration (which, however, if changed in the
 619   // .java file, also changes in .class file) should not matter. However, comparing sets is
 620   // technically a bit more difficult, and, more importantly, I am not sure at present that the
 621   // order of interfaces does not matter on the implementation level, i.e. that the VM does not
 622   // rely on it somewhere.
 623   Array<Klass*>* k_interfaces = the_class->local_interfaces();
 624   Array<Klass*>* k_new_interfaces = scratch_class->local_interfaces();
 625   int n_intfs = k_interfaces->length();
 626   if (n_intfs != k_new_interfaces->length()) {
 627     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_HIERARCHY_CHANGED;
 628   }
 629   for (i = 0; i < n_intfs; i++) {
 630     if (k_interfaces->at(i)->name() !=
 631         k_new_interfaces->at(i)->name()) {
 632       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_HIERARCHY_CHANGED;
 633     }
 634   }
 635 
 636   // Check whether class is in the error init state.
 637   if (the_class->is_in_error_state()) {
 638     // TBD #5057930: special error code is needed in 1.6
 639     return JVMTI_ERROR_INVALID_CLASS;
 640   }
 641 
 642   // Check whether class modifiers are the same.
 643   jushort old_flags = (jushort) the_class->access_flags().get_flags();
 644   jushort new_flags = (jushort) scratch_class->access_flags().get_flags();
 645   if (old_flags != new_flags) {
 646     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_CLASS_MODIFIERS_CHANGED;
 647   }
 648 
 649   // Check if the number, names, types and order of fields declared in these classes
 650   // are the same.
 651   JavaFieldStream old_fs(the_class);
 652   JavaFieldStream new_fs(scratch_class);
 653   for (; !old_fs.done() && !new_fs.done(); old_fs.next(), new_fs.next()) {
 654     // access
 655     old_flags = old_fs.access_flags().as_short();
 656     new_flags = new_fs.access_flags().as_short();
 657     if ((old_flags ^ new_flags) & JVM_RECOGNIZED_FIELD_MODIFIERS) {
 658       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_SCHEMA_CHANGED;
 659     }
 660     // offset
 661     if (old_fs.offset() != new_fs.offset()) {
 662       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_SCHEMA_CHANGED;
 663     }
 664     // name and signature
 665     Symbol* name_sym1 = the_class->constants()->symbol_at(old_fs.name_index());
 666     Symbol* sig_sym1 = the_class->constants()->symbol_at(old_fs.signature_index());
 667     Symbol* name_sym2 = scratch_class->constants()->symbol_at(new_fs.name_index());
 668     Symbol* sig_sym2 = scratch_class->constants()->symbol_at(new_fs.signature_index());
 669     if (name_sym1 != name_sym2 || sig_sym1 != sig_sym2) {
 670       return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_SCHEMA_CHANGED;
 671     }
 672   }
 673 
 674   // If both streams aren't done then we have a differing number of
 675   // fields.
 676   if (!old_fs.done() || !new_fs.done()) {
 677     return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_SCHEMA_CHANGED;
 678   }
 679 
 680   // Do a parallel walk through the old and new methods. Detect
 681   // cases where they match (exist in both), have been added in
 682   // the new methods, or have been deleted (exist only in the
 683   // old methods).  The class file parser places methods in order
 684   // by method name, but does not order overloaded methods by
 685   // signature.  In order to determine what fate befell the methods,
 686   // this code places the overloaded new methods that have matching
 687   // old methods in the same order as the old methods and places
 688   // new overloaded methods at the end of overloaded methods of
 689   // that name. The code for this order normalization is adapted
 690   // from the algorithm used in InstanceKlass::find_method().
 691   // Since we are swapping out of order entries as we find them,
 692   // we only have to search forward through the overloaded methods.
 693   // Methods which are added and have the same name as an existing
 694   // method (but different signature) will be put at the end of
 695   // the methods with that name, and the name mismatch code will
 696   // handle them.
 697   Array<Method*>* k_old_methods(the_class->methods());
 698   Array<Method*>* k_new_methods(scratch_class->methods());
 699   int n_old_methods = k_old_methods->length();
 700   int n_new_methods = k_new_methods->length();
 701   Thread* thread = Thread::current();
 702 
 703   int ni = 0;
 704   int oi = 0;
 705   while (true) {
 706     Method* k_old_method;
 707     Method* k_new_method;
 708     enum { matched, added, deleted, undetermined } method_was = undetermined;
 709 
 710     if (oi >= n_old_methods) {
 711       if (ni >= n_new_methods) {
 712         break; // we've looked at everything, done
 713       }
 714       // New method at the end
 715       k_new_method = k_new_methods->at(ni);
 716       method_was = added;
 717     } else if (ni >= n_new_methods) {
 718       // Old method, at the end, is deleted
 719       k_old_method = k_old_methods->at(oi);
 720       method_was = deleted;
 721     } else {
 722       // There are more methods in both the old and new lists
 723       k_old_method = k_old_methods->at(oi);
 724       k_new_method = k_new_methods->at(ni);
 725       if (k_old_method->name() != k_new_method->name()) {
 726         // Methods are sorted by method name, so a mismatch means added
 727         // or deleted
 728         if (k_old_method->name()->fast_compare(k_new_method->name()) > 0) {
 729           method_was = added;
 730         } else {
 731           method_was = deleted;
 732         }
 733       } else if (k_old_method->signature() == k_new_method->signature()) {
 734         // Both the name and signature match
 735         method_was = matched;
 736       } else {
 737         // The name matches, but the signature doesn't, which means we have to
 738         // search forward through the new overloaded methods.
 739         int nj;  // outside the loop for post-loop check
 740         for (nj = ni + 1; nj < n_new_methods; nj++) {
 741           Method* m = k_new_methods->at(nj);
 742           if (k_old_method->name() != m->name()) {
 743             // reached another method name so no more overloaded methods
 744             method_was = deleted;
 745             break;
 746           }
 747           if (k_old_method->signature() == m->signature()) {
 748             // found a match so swap the methods
 749             k_new_methods->at_put(ni, m);
 750             k_new_methods->at_put(nj, k_new_method);
 751             k_new_method = m;
 752             method_was = matched;
 753             break;
 754           }
 755         }
 756 
 757         if (nj >= n_new_methods) {
 758           // reached the end without a match; so method was deleted
 759           method_was = deleted;
 760         }
 761       }
 762     }
 763 
 764     switch (method_was) {
 765     case matched:
 766       // methods match, be sure modifiers do too
 767       old_flags = (jushort) k_old_method->access_flags().get_flags();
 768       new_flags = (jushort) k_new_method->access_flags().get_flags();
 769       if ((old_flags ^ new_flags) & ~(JVM_ACC_NATIVE)) {
 770         return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_METHOD_MODIFIERS_CHANGED;
 771       }
 772       {
 773         u2 new_num = k_new_method->method_idnum();
 774         u2 old_num = k_old_method->method_idnum();
 775         if (new_num != old_num) {
 776           Method* idnum_owner = scratch_class->method_with_idnum(old_num);
 777           if (idnum_owner != NULL) {
 778             // There is already a method assigned this idnum -- switch them
 779             idnum_owner->set_method_idnum(new_num);
 780           }
 781           k_new_method->set_method_idnum(old_num);
 782           if (thread->has_pending_exception()) {
 783             return JVMTI_ERROR_OUT_OF_MEMORY;
 784           }
 785         }
 786       }
 787       RC_TRACE(0x00008000, ("Method matched: new: %s [%d] == old: %s [%d]",
 788                             k_new_method->name_and_sig_as_C_string(), ni,
 789                             k_old_method->name_and_sig_as_C_string(), oi));
 790       // advance to next pair of methods
 791       ++oi;
 792       ++ni;
 793       break;
 794     case added:
 795       // method added, see if it is OK
 796       new_flags = (jushort) k_new_method->access_flags().get_flags();
 797       if ((new_flags & JVM_ACC_PRIVATE) == 0
 798            // hack: private should be treated as final, but alas
 799           || (new_flags & (JVM_ACC_FINAL|JVM_ACC_STATIC)) == 0
 800          ) {
 801         // new methods must be private
 802         return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_METHOD_ADDED;
 803       }
 804       {
 805         u2 num = the_class->next_method_idnum();
 806         if (num == ConstMethod::UNSET_IDNUM) {
 807           // cannot add any more methods
 808           return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_METHOD_ADDED;
 809         }
 810         u2 new_num = k_new_method->method_idnum();
 811         Method* idnum_owner = scratch_class->method_with_idnum(num);
 812         if (idnum_owner != NULL) {
 813           // There is already a method assigned this idnum -- switch them
 814           idnum_owner->set_method_idnum(new_num);
 815         }
 816         k_new_method->set_method_idnum(num);
 817         if (thread->has_pending_exception()) {
 818           return JVMTI_ERROR_OUT_OF_MEMORY;
 819         }
 820       }
 821       RC_TRACE(0x00008000, ("Method added: new: %s [%d]",
 822                             k_new_method->name_and_sig_as_C_string(), ni));
 823       ++ni; // advance to next new method
 824       break;
 825     case deleted:
 826       // method deleted, see if it is OK
 827       old_flags = (jushort) k_old_method->access_flags().get_flags();
 828       if ((old_flags & JVM_ACC_PRIVATE) == 0
 829            // hack: private should be treated as final, but alas
 830           || (old_flags & (JVM_ACC_FINAL|JVM_ACC_STATIC)) == 0
 831          ) {
 832         // deleted methods must be private
 833         return JVMTI_ERROR_UNSUPPORTED_REDEFINITION_METHOD_DELETED;
 834       }
 835       RC_TRACE(0x00008000, ("Method deleted: old: %s [%d]",
 836                             k_old_method->name_and_sig_as_C_string(), oi));
 837       ++oi; // advance to next old method
 838       break;
 839     default:
 840       ShouldNotReachHere();
 841     }
 842   }
 843 
 844   return JVMTI_ERROR_NONE;
 845 }
 846 
 847 
 848 // Find new constant pool index value for old constant pool index value
 849 // by seaching the index map. Returns zero (0) if there is no mapped
 850 // value for the old constant pool index.
 851 int VM_RedefineClasses::find_new_index(int old_index) {
 852   if (_index_map_count == 0) {
 853     // map is empty so nothing can be found
 854     return 0;
 855   }
 856 
 857   if (old_index < 1 || old_index >= _index_map_p->length()) {
 858     // The old_index is out of range so it is not mapped. This should
 859     // not happen in regular constant pool merging use, but it can
 860     // happen if a corrupt annotation is processed.
 861     return 0;
 862   }
 863 
 864   int value = _index_map_p->at(old_index);
 865   if (value == -1) {
 866     // the old_index is not mapped
 867     return 0;
 868   }
 869 
 870   return value;
 871 } // end find_new_index()
 872 
 873 
 874 // Find new bootstrap specifier index value for old bootstrap specifier index
 875 // value by seaching the index map. Returns unused index (-1) if there is
 876 // no mapped value for the old bootstrap specifier index.
 877 int VM_RedefineClasses::find_new_operand_index(int old_index) {
 878   if (_operands_index_map_count == 0) {
 879     // map is empty so nothing can be found
 880     return -1;
 881   }
 882 
 883   if (old_index == -1 || old_index >= _operands_index_map_p->length()) {
 884     // The old_index is out of range so it is not mapped.
 885     // This should not happen in regular constant pool merging use.
 886     return -1;
 887   }
 888 
 889   int value = _operands_index_map_p->at(old_index);
 890   if (value == -1) {
 891     // the old_index is not mapped
 892     return -1;
 893   }
 894 
 895   return value;
 896 } // end find_new_operand_index()
 897 
 898 
 899 // Returns true if the current mismatch is due to a resolved/unresolved
 900 // class pair. Otherwise, returns false.
 901 bool VM_RedefineClasses::is_unresolved_class_mismatch(constantPoolHandle cp1,
 902        int index1, constantPoolHandle cp2, int index2) {
 903 
 904   jbyte t1 = cp1->tag_at(index1).value();
 905   if (t1 != JVM_CONSTANT_Class && t1 != JVM_CONSTANT_UnresolvedClass) {
 906     return false;  // wrong entry type; not our special case
 907   }
 908 
 909   jbyte t2 = cp2->tag_at(index2).value();
 910   if (t2 != JVM_CONSTANT_Class && t2 != JVM_CONSTANT_UnresolvedClass) {
 911     return false;  // wrong entry type; not our special case
 912   }
 913 
 914   if (t1 == t2) {
 915     return false;  // not a mismatch; not our special case
 916   }
 917 
 918   char *s1 = cp1->klass_name_at(index1)->as_C_string();
 919   char *s2 = cp2->klass_name_at(index2)->as_C_string();
 920   if (strcmp(s1, s2) != 0) {
 921     return false;  // strings don't match; not our special case
 922   }
 923 
 924   return true;  // made it through the gauntlet; this is our special case
 925 } // end is_unresolved_class_mismatch()
 926 
 927 
 928 jvmtiError VM_RedefineClasses::load_new_class_versions(TRAPS) {
 929 
 930   // For consistency allocate memory using os::malloc wrapper.
 931   _scratch_classes = (Klass**)
 932     os::malloc(sizeof(Klass*) * _class_count, mtClass);
 933   if (_scratch_classes == NULL) {
 934     return JVMTI_ERROR_OUT_OF_MEMORY;
 935   }
 936   // Zero initialize the _scratch_classes array.
 937   for (int i = 0; i < _class_count; i++) {
 938     _scratch_classes[i] = NULL;
 939   }
 940 
 941   ResourceMark rm(THREAD);
 942 
 943   JvmtiThreadState *state = JvmtiThreadState::state_for(JavaThread::current());
 944   // state can only be NULL if the current thread is exiting which
 945   // should not happen since we're trying to do a RedefineClasses
 946   guarantee(state != NULL, "exiting thread calling load_new_class_versions");
 947   for (int i = 0; i < _class_count; i++) {
 948     // Create HandleMark so that any handles created while loading new class
 949     // versions are deleted. Constant pools are deallocated while merging
 950     // constant pools
 951     HandleMark hm(THREAD);
 952 
 953     oop mirror = JNIHandles::resolve_non_null(_class_defs[i].klass);
 954     // classes for primitives cannot be redefined
 955     if (!is_modifiable_class(mirror)) {
 956       return JVMTI_ERROR_UNMODIFIABLE_CLASS;
 957     }
 958     Klass* the_class_oop = java_lang_Class::as_Klass(mirror);
 959     instanceKlassHandle the_class = instanceKlassHandle(THREAD, the_class_oop);
 960     Symbol*  the_class_sym = the_class->name();
 961 
 962     // RC_TRACE_WITH_THREAD macro has an embedded ResourceMark
 963     RC_TRACE_WITH_THREAD(0x00000001, THREAD,
 964       ("loading name=%s kind=%d (avail_mem=" UINT64_FORMAT "K)",
 965       the_class->external_name(), _class_load_kind,
 966       os::available_memory() >> 10));
 967 
 968     ClassFileStream st((u1*) _class_defs[i].class_bytes,
 969       _class_defs[i].class_byte_count, (char *)"__VM_RedefineClasses__");
 970 
 971     // Parse the stream.
 972     Handle the_class_loader(THREAD, the_class->class_loader());
 973     Handle protection_domain(THREAD, the_class->protection_domain());
 974     // Set redefined class handle in JvmtiThreadState class.
 975     // This redefined class is sent to agent event handler for class file
 976     // load hook event.
 977     state->set_class_being_redefined(&the_class, _class_load_kind);
 978 
 979     Klass* k = SystemDictionary::parse_stream(the_class_sym,
 980                                                 the_class_loader,
 981                                                 protection_domain,
 982                                                 &st,
 983                                                 THREAD);
 984     // Clear class_being_redefined just to be sure.
 985     state->clear_class_being_redefined();
 986 
 987     // TODO: if this is retransform, and nothing changed we can skip it
 988 
 989     instanceKlassHandle scratch_class (THREAD, k);
 990 
 991     // Need to clean up allocated InstanceKlass if there's an error so assign
 992     // the result here. Caller deallocates all the scratch classes in case of
 993     // an error.
 994     _scratch_classes[i] = k;
 995 
 996     if (HAS_PENDING_EXCEPTION) {
 997       Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
 998       // RC_TRACE_WITH_THREAD macro has an embedded ResourceMark
 999       RC_TRACE_WITH_THREAD(0x00000002, THREAD, ("parse_stream exception: '%s'",
1000         ex_name->as_C_string()));
1001       CLEAR_PENDING_EXCEPTION;
1002 
1003       if (ex_name == vmSymbols::java_lang_UnsupportedClassVersionError()) {
1004         return JVMTI_ERROR_UNSUPPORTED_VERSION;
1005       } else if (ex_name == vmSymbols::java_lang_ClassFormatError()) {
1006         return JVMTI_ERROR_INVALID_CLASS_FORMAT;
1007       } else if (ex_name == vmSymbols::java_lang_ClassCircularityError()) {
1008         return JVMTI_ERROR_CIRCULAR_CLASS_DEFINITION;
1009       } else if (ex_name == vmSymbols::java_lang_NoClassDefFoundError()) {
1010         // The message will be "XXX (wrong name: YYY)"
1011         return JVMTI_ERROR_NAMES_DONT_MATCH;
1012       } else if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1013         return JVMTI_ERROR_OUT_OF_MEMORY;
1014       } else {  // Just in case more exceptions can be thrown..
1015         return JVMTI_ERROR_FAILS_VERIFICATION;
1016       }
1017     }
1018 
1019     // Ensure class is linked before redefine
1020     if (!the_class->is_linked()) {
1021       the_class->link_class(THREAD);
1022       if (HAS_PENDING_EXCEPTION) {
1023         Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1024         // RC_TRACE_WITH_THREAD macro has an embedded ResourceMark
1025         RC_TRACE_WITH_THREAD(0x00000002, THREAD, ("link_class exception: '%s'",
1026           ex_name->as_C_string()));
1027         CLEAR_PENDING_EXCEPTION;
1028         if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1029           return JVMTI_ERROR_OUT_OF_MEMORY;
1030         } else {
1031           return JVMTI_ERROR_INTERNAL;
1032         }
1033       }
1034     }
1035 
1036     // Do the validity checks in compare_and_normalize_class_versions()
1037     // before verifying the byte codes. By doing these checks first, we
1038     // limit the number of functions that require redirection from
1039     // the_class to scratch_class. In particular, we don't have to
1040     // modify JNI GetSuperclass() and thus won't change its performance.
1041     jvmtiError res = compare_and_normalize_class_versions(the_class,
1042                        scratch_class);
1043     if (res != JVMTI_ERROR_NONE) {
1044       return res;
1045     }
1046 
1047     // verify what the caller passed us
1048     {
1049       // The bug 6214132 caused the verification to fail.
1050       // Information about the_class and scratch_class is temporarily
1051       // recorded into jvmtiThreadState. This data is used to redirect
1052       // the_class to scratch_class in the JVM_* functions called by the
1053       // verifier. Please, refer to jvmtiThreadState.hpp for the detailed
1054       // description.
1055       RedefineVerifyMark rvm(&the_class, &scratch_class, state);
1056       Verifier::verify(
1057         scratch_class, Verifier::ThrowException, true, THREAD);
1058     }
1059 
1060     if (HAS_PENDING_EXCEPTION) {
1061       Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1062       // RC_TRACE_WITH_THREAD macro has an embedded ResourceMark
1063       RC_TRACE_WITH_THREAD(0x00000002, THREAD,
1064         ("verify_byte_codes exception: '%s'", ex_name->as_C_string()));
1065       CLEAR_PENDING_EXCEPTION;
1066       if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1067         return JVMTI_ERROR_OUT_OF_MEMORY;
1068       } else {
1069         // tell the caller the bytecodes are bad
1070         return JVMTI_ERROR_FAILS_VERIFICATION;
1071       }
1072     }
1073 
1074     res = merge_cp_and_rewrite(the_class, scratch_class, THREAD);
1075     if (res != JVMTI_ERROR_NONE) {
1076       return res;
1077     }
1078 
1079     if (VerifyMergedCPBytecodes) {
1080       // verify what we have done during constant pool merging
1081       {
1082         RedefineVerifyMark rvm(&the_class, &scratch_class, state);
1083         Verifier::verify(scratch_class, Verifier::ThrowException, true, THREAD);
1084       }
1085 
1086       if (HAS_PENDING_EXCEPTION) {
1087         Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1088         // RC_TRACE_WITH_THREAD macro has an embedded ResourceMark
1089         RC_TRACE_WITH_THREAD(0x00000002, THREAD,
1090           ("verify_byte_codes post merge-CP exception: '%s'",
1091           ex_name->as_C_string()));
1092         CLEAR_PENDING_EXCEPTION;
1093         if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1094           return JVMTI_ERROR_OUT_OF_MEMORY;
1095         } else {
1096           // tell the caller that constant pool merging screwed up
1097           return JVMTI_ERROR_INTERNAL;
1098         }
1099       }
1100     }
1101 
1102     Rewriter::rewrite(scratch_class, THREAD);
1103     if (!HAS_PENDING_EXCEPTION) {
1104       scratch_class->link_methods(THREAD);
1105     }
1106     if (HAS_PENDING_EXCEPTION) {
1107       Symbol* ex_name = PENDING_EXCEPTION->klass()->name();
1108       CLEAR_PENDING_EXCEPTION;
1109       if (ex_name == vmSymbols::java_lang_OutOfMemoryError()) {
1110         return JVMTI_ERROR_OUT_OF_MEMORY;
1111       } else {
1112         return JVMTI_ERROR_INTERNAL;
1113       }
1114     }
1115 
1116     // RC_TRACE_WITH_THREAD macro has an embedded ResourceMark
1117     RC_TRACE_WITH_THREAD(0x00000001, THREAD,
1118       ("loaded name=%s (avail_mem=" UINT64_FORMAT "K)",
1119       the_class->external_name(), os::available_memory() >> 10));
1120   }
1121 
1122   return JVMTI_ERROR_NONE;
1123 }
1124 
1125 
1126 // Map old_index to new_index as needed. scratch_cp is only needed
1127 // for RC_TRACE() calls.
1128 void VM_RedefineClasses::map_index(constantPoolHandle scratch_cp,
1129        int old_index, int new_index) {
1130   if (find_new_index(old_index) != 0) {
1131     // old_index is already mapped
1132     return;
1133   }
1134 
1135   if (old_index == new_index) {
1136     // no mapping is needed
1137     return;
1138   }
1139 
1140   _index_map_p->at_put(old_index, new_index);
1141   _index_map_count++;
1142 
1143   RC_TRACE(0x00040000, ("mapped tag %d at index %d to %d",
1144     scratch_cp->tag_at(old_index).value(), old_index, new_index));
1145 } // end map_index()
1146 
1147 
1148 // Map old_index to new_index as needed.
1149 void VM_RedefineClasses::map_operand_index(int old_index, int new_index) {
1150   if (find_new_operand_index(old_index) != -1) {
1151     // old_index is already mapped
1152     return;
1153   }
1154 
1155   if (old_index == new_index) {
1156     // no mapping is needed
1157     return;
1158   }
1159 
1160   _operands_index_map_p->at_put(old_index, new_index);
1161   _operands_index_map_count++;
1162 
1163   RC_TRACE(0x00040000, ("mapped bootstrap specifier at index %d to %d", old_index, new_index));
1164 } // end map_index()
1165 
1166 
1167 // Merge old_cp and scratch_cp and return the results of the merge via
1168 // merge_cp_p. The number of entries in *merge_cp_p is returned via
1169 // merge_cp_length_p. The entries in old_cp occupy the same locations
1170 // in *merge_cp_p. Also creates a map of indices from entries in
1171 // scratch_cp to the corresponding entry in *merge_cp_p. Index map
1172 // entries are only created for entries in scratch_cp that occupy a
1173 // different location in *merged_cp_p.
1174 bool VM_RedefineClasses::merge_constant_pools(constantPoolHandle old_cp,
1175        constantPoolHandle scratch_cp, constantPoolHandle *merge_cp_p,
1176        int *merge_cp_length_p, TRAPS) {
1177 
1178   if (merge_cp_p == NULL) {
1179     assert(false, "caller must provide scratch constantPool");
1180     return false; // robustness
1181   }
1182   if (merge_cp_length_p == NULL) {
1183     assert(false, "caller must provide scratch CP length");
1184     return false; // robustness
1185   }
1186   // Worst case we need old_cp->length() + scratch_cp()->length(),
1187   // but the caller might be smart so make sure we have at least
1188   // the minimum.
1189   if ((*merge_cp_p)->length() < old_cp->length()) {
1190     assert(false, "merge area too small");
1191     return false; // robustness
1192   }
1193 
1194   RC_TRACE_WITH_THREAD(0x00010000, THREAD,
1195     ("old_cp_len=%d, scratch_cp_len=%d", old_cp->length(),
1196     scratch_cp->length()));
1197 
1198   {
1199     // Pass 0:
1200     // The old_cp is copied to *merge_cp_p; this means that any code
1201     // using old_cp does not have to change. This work looks like a
1202     // perfect fit for ConstantPool*::copy_cp_to(), but we need to
1203     // handle one special case:
1204     // - revert JVM_CONSTANT_Class to JVM_CONSTANT_UnresolvedClass
1205     // This will make verification happy.
1206 
1207     int old_i;  // index into old_cp
1208 
1209     // index zero (0) is not used in constantPools
1210     for (old_i = 1; old_i < old_cp->length(); old_i++) {
1211       // leave debugging crumb
1212       jbyte old_tag = old_cp->tag_at(old_i).value();
1213       switch (old_tag) {
1214       case JVM_CONSTANT_Class:
1215       case JVM_CONSTANT_UnresolvedClass:
1216         // revert the copy to JVM_CONSTANT_UnresolvedClass
1217         // May be resolving while calling this so do the same for
1218         // JVM_CONSTANT_UnresolvedClass (klass_name_at() deals with transition)
1219         (*merge_cp_p)->unresolved_klass_at_put(old_i,
1220           old_cp->klass_name_at(old_i));
1221         break;
1222 
1223       case JVM_CONSTANT_Double:
1224       case JVM_CONSTANT_Long:
1225         // just copy the entry to *merge_cp_p, but double and long take
1226         // two constant pool entries
1227         ConstantPool::copy_entry_to(old_cp, old_i, *merge_cp_p, old_i, CHECK_0);
1228         old_i++;
1229         break;
1230 
1231       default:
1232         // just copy the entry to *merge_cp_p
1233         ConstantPool::copy_entry_to(old_cp, old_i, *merge_cp_p, old_i, CHECK_0);
1234         break;
1235       }
1236     } // end for each old_cp entry
1237 
1238     ConstantPool::copy_operands(old_cp, *merge_cp_p, CHECK_0);
1239     (*merge_cp_p)->extend_operands(scratch_cp, CHECK_0);
1240 
1241     // We don't need to sanity check that *merge_cp_length_p is within
1242     // *merge_cp_p bounds since we have the minimum on-entry check above.
1243     (*merge_cp_length_p) = old_i;
1244   }
1245 
1246   // merge_cp_len should be the same as old_cp->length() at this point
1247   // so this trace message is really a "warm-and-breathing" message.
1248   RC_TRACE_WITH_THREAD(0x00020000, THREAD,
1249     ("after pass 0: merge_cp_len=%d", *merge_cp_length_p));
1250 
1251   int scratch_i;  // index into scratch_cp
1252   {
1253     // Pass 1a:
1254     // Compare scratch_cp entries to the old_cp entries that we have
1255     // already copied to *merge_cp_p. In this pass, we are eliminating
1256     // exact duplicates (matching entry at same index) so we only
1257     // compare entries in the common indice range.
1258     int increment = 1;
1259     int pass1a_length = MIN2(old_cp->length(), scratch_cp->length());
1260     for (scratch_i = 1; scratch_i < pass1a_length; scratch_i += increment) {
1261       switch (scratch_cp->tag_at(scratch_i).value()) {
1262       case JVM_CONSTANT_Double:
1263       case JVM_CONSTANT_Long:
1264         // double and long take two constant pool entries
1265         increment = 2;
1266         break;
1267 
1268       default:
1269         increment = 1;
1270         break;
1271       }
1272 
1273       bool match = scratch_cp->compare_entry_to(scratch_i, *merge_cp_p,
1274         scratch_i, CHECK_0);
1275       if (match) {
1276         // found a match at the same index so nothing more to do
1277         continue;
1278       } else if (is_unresolved_class_mismatch(scratch_cp, scratch_i,
1279                                               *merge_cp_p, scratch_i)) {
1280         // The mismatch in compare_entry_to() above is because of a
1281         // resolved versus unresolved class entry at the same index
1282         // with the same string value. Since Pass 0 reverted any
1283         // class entries to unresolved class entries in *merge_cp_p,
1284         // we go with the unresolved class entry.
1285         continue;
1286       }
1287 
1288       int found_i = scratch_cp->find_matching_entry(scratch_i, *merge_cp_p,
1289         CHECK_0);
1290       if (found_i != 0) {
1291         guarantee(found_i != scratch_i,
1292           "compare_entry_to() and find_matching_entry() do not agree");
1293 
1294         // Found a matching entry somewhere else in *merge_cp_p so
1295         // just need a mapping entry.
1296         map_index(scratch_cp, scratch_i, found_i);
1297         continue;
1298       }
1299 
1300       // The find_matching_entry() call above could fail to find a match
1301       // due to a resolved versus unresolved class or string entry situation
1302       // like we solved above with the is_unresolved_*_mismatch() calls.
1303       // However, we would have to call is_unresolved_*_mismatch() over
1304       // all of *merge_cp_p (potentially) and that doesn't seem to be
1305       // worth the time.
1306 
1307       // No match found so we have to append this entry and any unique
1308       // referenced entries to *merge_cp_p.
1309       append_entry(scratch_cp, scratch_i, merge_cp_p, merge_cp_length_p,
1310         CHECK_0);
1311     }
1312   }
1313 
1314   RC_TRACE_WITH_THREAD(0x00020000, THREAD,
1315     ("after pass 1a: merge_cp_len=%d, scratch_i=%d, index_map_len=%d",
1316     *merge_cp_length_p, scratch_i, _index_map_count));
1317 
1318   if (scratch_i < scratch_cp->length()) {
1319     // Pass 1b:
1320     // old_cp is smaller than scratch_cp so there are entries in
1321     // scratch_cp that we have not yet processed. We take care of
1322     // those now.
1323     int increment = 1;
1324     for (; scratch_i < scratch_cp->length(); scratch_i += increment) {
1325       switch (scratch_cp->tag_at(scratch_i).value()) {
1326       case JVM_CONSTANT_Double:
1327       case JVM_CONSTANT_Long:
1328         // double and long take two constant pool entries
1329         increment = 2;
1330         break;
1331 
1332       default:
1333         increment = 1;
1334         break;
1335       }
1336 
1337       int found_i =
1338         scratch_cp->find_matching_entry(scratch_i, *merge_cp_p, CHECK_0);
1339       if (found_i != 0) {
1340         // Found a matching entry somewhere else in *merge_cp_p so
1341         // just need a mapping entry.
1342         map_index(scratch_cp, scratch_i, found_i);
1343         continue;
1344       }
1345 
1346       // No match found so we have to append this entry and any unique
1347       // referenced entries to *merge_cp_p.
1348       append_entry(scratch_cp, scratch_i, merge_cp_p, merge_cp_length_p,
1349         CHECK_0);
1350     }
1351 
1352     RC_TRACE_WITH_THREAD(0x00020000, THREAD,
1353       ("after pass 1b: merge_cp_len=%d, scratch_i=%d, index_map_len=%d",
1354       *merge_cp_length_p, scratch_i, _index_map_count));
1355   }
1356   finalize_operands_merge(*merge_cp_p, THREAD);
1357 
1358   return true;
1359 } // end merge_constant_pools()
1360 
1361 
1362 // Scoped object to clean up the constant pool(s) created for merging
1363 class MergeCPCleaner {
1364   ClassLoaderData*   _loader_data;
1365   ConstantPool*      _cp;
1366   ConstantPool*      _scratch_cp;
1367  public:
1368   MergeCPCleaner(ClassLoaderData* loader_data, ConstantPool* merge_cp) :
1369                  _loader_data(loader_data), _cp(merge_cp), _scratch_cp(NULL) {}
1370   ~MergeCPCleaner() {
1371     _loader_data->add_to_deallocate_list(_cp);
1372     if (_scratch_cp != NULL) {
1373       _loader_data->add_to_deallocate_list(_scratch_cp);
1374     }
1375   }
1376   void add_scratch_cp(ConstantPool* scratch_cp) { _scratch_cp = scratch_cp; }
1377 };
1378 
1379 // Merge constant pools between the_class and scratch_class and
1380 // potentially rewrite bytecodes in scratch_class to use the merged
1381 // constant pool.
1382 jvmtiError VM_RedefineClasses::merge_cp_and_rewrite(
1383              instanceKlassHandle the_class, instanceKlassHandle scratch_class,
1384              TRAPS) {
1385   // worst case merged constant pool length is old and new combined
1386   int merge_cp_length = the_class->constants()->length()
1387         + scratch_class->constants()->length();
1388 
1389   // Constant pools are not easily reused so we allocate a new one
1390   // each time.
1391   // merge_cp is created unsafe for concurrent GC processing.  It
1392   // should be marked safe before discarding it. Even though
1393   // garbage,  if it crosses a card boundary, it may be scanned
1394   // in order to find the start of the first complete object on the card.
1395   ClassLoaderData* loader_data = the_class->class_loader_data();
1396   ConstantPool* merge_cp_oop =
1397     ConstantPool::allocate(loader_data,
1398                                   merge_cp_length,
1399                                   THREAD);
1400   MergeCPCleaner cp_cleaner(loader_data, merge_cp_oop);
1401 
1402   HandleMark hm(THREAD);  // make sure handles are cleared before
1403                           // MergeCPCleaner clears out merge_cp_oop
1404   constantPoolHandle merge_cp(THREAD, merge_cp_oop);
1405 
1406   // Get constants() from the old class because it could have been rewritten
1407   // while we were at a safepoint allocating a new constant pool.
1408   constantPoolHandle old_cp(THREAD, the_class->constants());
1409   constantPoolHandle scratch_cp(THREAD, scratch_class->constants());
1410 
1411   // If the length changed, the class was redefined out from under us. Return
1412   // an error.
1413   if (merge_cp_length != the_class->constants()->length()
1414          + scratch_class->constants()->length()) {
1415     return JVMTI_ERROR_INTERNAL;
1416   }
1417 
1418   // Update the version number of the constant pool
1419   merge_cp->increment_and_save_version(old_cp->version());
1420 
1421   ResourceMark rm(THREAD);
1422   _index_map_count = 0;
1423   _index_map_p = new intArray(scratch_cp->length(), -1);
1424 
1425   _operands_cur_length = ConstantPool::operand_array_length(old_cp->operands());
1426   _operands_index_map_count = 0;
1427   _operands_index_map_p = new intArray(
1428     ConstantPool::operand_array_length(scratch_cp->operands()), -1);
1429 
1430   // reference to the cp holder is needed for copy_operands()
1431   merge_cp->set_pool_holder(scratch_class());
1432   bool result = merge_constant_pools(old_cp, scratch_cp, &merge_cp,
1433                   &merge_cp_length, THREAD);
1434   merge_cp->set_pool_holder(NULL);
1435 
1436   if (!result) {
1437     // The merge can fail due to memory allocation failure or due
1438     // to robustness checks.
1439     return JVMTI_ERROR_INTERNAL;
1440   }
1441 
1442   RC_TRACE_WITH_THREAD(0x00010000, THREAD,
1443     ("merge_cp_len=%d, index_map_len=%d", merge_cp_length, _index_map_count));
1444 
1445   if (_index_map_count == 0) {
1446     // there is nothing to map between the new and merged constant pools
1447 
1448     if (old_cp->length() == scratch_cp->length()) {
1449       // The old and new constant pools are the same length and the
1450       // index map is empty. This means that the three constant pools
1451       // are equivalent (but not the same). Unfortunately, the new
1452       // constant pool has not gone through link resolution nor have
1453       // the new class bytecodes gone through constant pool cache
1454       // rewriting so we can't use the old constant pool with the new
1455       // class.
1456 
1457       // toss the merged constant pool at return
1458     } else if (old_cp->length() < scratch_cp->length()) {
1459       // The old constant pool has fewer entries than the new constant
1460       // pool and the index map is empty. This means the new constant
1461       // pool is a superset of the old constant pool. However, the old
1462       // class bytecodes have already gone through constant pool cache
1463       // rewriting so we can't use the new constant pool with the old
1464       // class.
1465 
1466       // toss the merged constant pool at return
1467     } else {
1468       // The old constant pool has more entries than the new constant
1469       // pool and the index map is empty. This means that both the old
1470       // and merged constant pools are supersets of the new constant
1471       // pool.
1472 
1473       // Replace the new constant pool with a shrunken copy of the
1474       // merged constant pool
1475       set_new_constant_pool(loader_data, scratch_class, merge_cp, merge_cp_length, THREAD);
1476       // The new constant pool replaces scratch_cp so have cleaner clean it up.
1477       // It can't be cleaned up while there are handles to it.
1478       cp_cleaner.add_scratch_cp(scratch_cp());
1479     }
1480   } else {
1481     if (RC_TRACE_ENABLED(0x00040000)) {
1482       // don't want to loop unless we are tracing
1483       int count = 0;
1484       for (int i = 1; i < _index_map_p->length(); i++) {
1485         int value = _index_map_p->at(i);
1486 
1487         if (value != -1) {
1488           RC_TRACE_WITH_THREAD(0x00040000, THREAD,
1489             ("index_map[%d]: old=%d new=%d", count, i, value));
1490           count++;
1491         }
1492       }
1493     }
1494 
1495     // We have entries mapped between the new and merged constant pools
1496     // so we have to rewrite some constant pool references.
1497     if (!rewrite_cp_refs(scratch_class, THREAD)) {
1498       return JVMTI_ERROR_INTERNAL;
1499     }
1500 
1501     // Replace the new constant pool with a shrunken copy of the
1502     // merged constant pool so now the rewritten bytecodes have
1503     // valid references; the previous new constant pool will get
1504     // GCed.
1505     set_new_constant_pool(loader_data, scratch_class, merge_cp, merge_cp_length, THREAD);
1506     // The new constant pool replaces scratch_cp so have cleaner clean it up.
1507     // It can't be cleaned up while there are handles to it.
1508     cp_cleaner.add_scratch_cp(scratch_cp());
1509   }
1510 
1511   return JVMTI_ERROR_NONE;
1512 } // end merge_cp_and_rewrite()
1513 
1514 
1515 // Rewrite constant pool references in klass scratch_class.
1516 bool VM_RedefineClasses::rewrite_cp_refs(instanceKlassHandle scratch_class,
1517        TRAPS) {
1518 
1519   // rewrite constant pool references in the methods:
1520   if (!rewrite_cp_refs_in_methods(scratch_class, THREAD)) {
1521     // propagate failure back to caller
1522     return false;
1523   }
1524 
1525   // rewrite constant pool references in the class_annotations:
1526   if (!rewrite_cp_refs_in_class_annotations(scratch_class, THREAD)) {
1527     // propagate failure back to caller
1528     return false;
1529   }
1530 
1531   // rewrite constant pool references in the fields_annotations:
1532   if (!rewrite_cp_refs_in_fields_annotations(scratch_class, THREAD)) {
1533     // propagate failure back to caller
1534     return false;
1535   }
1536 
1537   // rewrite constant pool references in the methods_annotations:
1538   if (!rewrite_cp_refs_in_methods_annotations(scratch_class, THREAD)) {
1539     // propagate failure back to caller
1540     return false;
1541   }
1542 
1543   // rewrite constant pool references in the methods_parameter_annotations:
1544   if (!rewrite_cp_refs_in_methods_parameter_annotations(scratch_class,
1545          THREAD)) {
1546     // propagate failure back to caller
1547     return false;
1548   }
1549 
1550   // rewrite constant pool references in the methods_default_annotations:
1551   if (!rewrite_cp_refs_in_methods_default_annotations(scratch_class,
1552          THREAD)) {
1553     // propagate failure back to caller
1554     return false;
1555   }
1556 
1557   // rewrite source file name index:
1558   u2 source_file_name_idx = scratch_class->source_file_name_index();
1559   if (source_file_name_idx != 0) {
1560     u2 new_source_file_name_idx = find_new_index(source_file_name_idx);
1561     if (new_source_file_name_idx != 0) {
1562       scratch_class->set_source_file_name_index(new_source_file_name_idx);
1563     }
1564   }
1565 
1566   // rewrite class generic signature index:
1567   u2 generic_signature_index = scratch_class->generic_signature_index();
1568   if (generic_signature_index != 0) {
1569     u2 new_generic_signature_index = find_new_index(generic_signature_index);
1570     if (new_generic_signature_index != 0) {
1571       scratch_class->set_generic_signature_index(new_generic_signature_index);
1572     }
1573   }
1574 
1575   return true;
1576 } // end rewrite_cp_refs()
1577 
1578 // Rewrite constant pool references in the methods.
1579 bool VM_RedefineClasses::rewrite_cp_refs_in_methods(
1580        instanceKlassHandle scratch_class, TRAPS) {
1581 
1582   Array<Method*>* methods = scratch_class->methods();
1583 
1584   if (methods == NULL || methods->length() == 0) {
1585     // no methods so nothing to do
1586     return true;
1587   }
1588 
1589   // rewrite constant pool references in the methods:
1590   for (int i = methods->length() - 1; i >= 0; i--) {
1591     methodHandle method(THREAD, methods->at(i));
1592     methodHandle new_method;
1593     rewrite_cp_refs_in_method(method, &new_method, THREAD);
1594     if (!new_method.is_null()) {
1595       // the method has been replaced so save the new method version
1596       // even in the case of an exception.  original method is on the
1597       // deallocation list.
1598       methods->at_put(i, new_method());
1599     }
1600     if (HAS_PENDING_EXCEPTION) {
1601       CLEAR_PENDING_EXCEPTION;
1602       return false;
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, CHECK);


1684             }

1685 
1686             // return the new method so that the caller can update
1687             // the containing class
1688             *new_method_p = method = m;
1689             // switch our bytecode processing loop from the old method
1690             // to the new method
1691             code_base = method->code_base();
1692             code_length = method->code_size();
1693             bcp = code_base + bci;
1694             c = (Bytecodes::Code)(*bcp);
1695             bc_length = Bytecodes::length_for(c);
1696             assert(bc_length != 0, "sanity check");
1697           } // end we need ldc_w instead of ldc
1698         } // end if there is a mapped index
1699       } break;
1700 
1701       // these bytecodes have a two-byte constant pool index
1702       case Bytecodes::_anewarray      : // fall through
1703       case Bytecodes::_checkcast      : // fall through
1704       case Bytecodes::_getfield       : // fall through
1705       case Bytecodes::_getstatic      : // fall through
1706       case Bytecodes::_instanceof     : // fall through
1707       case Bytecodes::_invokedynamic  : // fall through
1708       case Bytecodes::_invokeinterface: // fall through
1709       case Bytecodes::_invokespecial  : // fall through
1710       case Bytecodes::_invokestatic   : // fall through
1711       case Bytecodes::_invokevirtual  : // fall through
1712       case Bytecodes::_ldc_w          : // fall through
1713       case Bytecodes::_ldc2_w         : // fall through
1714       case Bytecodes::_multianewarray : // fall through
1715       case Bytecodes::_new            : // fall through
1716       case Bytecodes::_putfield       : // fall through
1717       case Bytecodes::_putstatic      :
1718       {
1719         address p = bcp + 1;
1720         int cp_index = Bytes::get_Java_u2(p);
1721         int new_index = find_new_index(cp_index);
1722         if (new_index != 0) {
1723           // the original index is mapped so update w/ new value
1724           RC_TRACE_WITH_THREAD(0x00080000, THREAD,
1725             ("%s@" INTPTR_FORMAT " old=%d, new=%d", Bytecodes::name(c),
1726             bcp, cp_index, new_index));
1727           // Rewriter::rewrite_method() uses put_native_u2() in this
1728           // situation because it is reusing the constant pool index
1729           // location for a native index into the ConstantPoolCache.
1730           // Since we are updating the constant pool index prior to
1731           // verification and ConstantPoolCache initialization, we
1732           // need to keep the new index in Java byte order.
1733           Bytes::put_Java_u2(p, new_index);
1734         }
1735       } break;
1736     }
1737   } // end for each bytecode
1738 
1739   // We also need to rewrite the parameter name indexes, if there is
1740   // method parameter data present
1741   if(method->has_method_parameters()) {
1742     const int len = method->method_parameters_length();
1743     MethodParametersElement* elem = method->method_parameters_start();
1744 
1745     for (int i = 0; i < len; i++) {
1746       const u2 cp_index = elem[i].name_cp_index;
1747       const u2 new_cp_index = find_new_index(cp_index);
1748       if (new_cp_index != 0) {
1749         elem[i].name_cp_index = new_cp_index;
1750       }
1751     }
1752   }
1753 } // end rewrite_cp_refs_in_method()
1754 
1755 
1756 // Rewrite constant pool references in the class_annotations field.
1757 bool VM_RedefineClasses::rewrite_cp_refs_in_class_annotations(
1758        instanceKlassHandle scratch_class, TRAPS) {
1759 
1760   AnnotationArray* class_annotations = scratch_class->class_annotations();
1761   if (class_annotations == NULL || class_annotations->length() == 0) {
1762     // no class_annotations so nothing to do
1763     return true;
1764   }
1765 
1766   RC_TRACE_WITH_THREAD(0x02000000, THREAD,
1767     ("class_annotations length=%d", class_annotations->length()));
1768 
1769   int byte_i = 0;  // byte index into class_annotations
1770   return rewrite_cp_refs_in_annotations_typeArray(class_annotations, byte_i,
1771            THREAD);
1772 }
1773 
1774 
1775 // Rewrite constant pool references in an annotations typeArray. This
1776 // "structure" is adapted from the RuntimeVisibleAnnotations_attribute
1777 // that is described in section 4.8.15 of the 2nd-edition of the VM spec:
1778 //
1779 // annotations_typeArray {
1780 //   u2 num_annotations;
1781 //   annotation annotations[num_annotations];
1782 // }
1783 //
1784 bool VM_RedefineClasses::rewrite_cp_refs_in_annotations_typeArray(
1785        AnnotationArray* annotations_typeArray, int &byte_i_ref, TRAPS) {
1786 
1787   if ((byte_i_ref + 2) > annotations_typeArray->length()) {
1788     // not enough room for num_annotations field
1789     RC_TRACE_WITH_THREAD(0x02000000, THREAD,
1790       ("length() is too small for num_annotations field"));
1791     return false;
1792   }
1793 
1794   u2 num_annotations = Bytes::get_Java_u2((address)
1795                          annotations_typeArray->adr_at(byte_i_ref));
1796   byte_i_ref += 2;
1797 
1798   RC_TRACE_WITH_THREAD(0x02000000, THREAD,
1799     ("num_annotations=%d", num_annotations));
1800 
1801   int calc_num_annotations = 0;
1802   for (; calc_num_annotations < num_annotations; calc_num_annotations++) {
1803     if (!rewrite_cp_refs_in_annotation_struct(annotations_typeArray,
1804            byte_i_ref, THREAD)) {
1805       RC_TRACE_WITH_THREAD(0x02000000, THREAD,
1806         ("bad annotation_struct at %d", calc_num_annotations));
1807       // propagate failure back to caller
1808       return false;
1809     }
1810   }
1811   assert(num_annotations == calc_num_annotations, "sanity check");
1812 
1813   return true;
1814 } // end rewrite_cp_refs_in_annotations_typeArray()
1815 
1816 
1817 // Rewrite constant pool references in the annotation struct portion of
1818 // an annotations_typeArray. This "structure" is from section 4.8.15 of
1819 // the 2nd-edition of the VM spec:
1820 //
1821 // struct annotation {
1822 //   u2 type_index;
1823 //   u2 num_element_value_pairs;
1824 //   {
1825 //     u2 element_name_index;
1826 //     element_value value;
1827 //   } element_value_pairs[num_element_value_pairs];
1828 // }
1829 //
1830 bool VM_RedefineClasses::rewrite_cp_refs_in_annotation_struct(
1831        AnnotationArray* annotations_typeArray, int &byte_i_ref, TRAPS) {
1832   if ((byte_i_ref + 2 + 2) > annotations_typeArray->length()) {
1833     // not enough room for smallest annotation_struct
1834     RC_TRACE_WITH_THREAD(0x02000000, THREAD,
1835       ("length() is too small for annotation_struct"));
1836     return false;
1837   }
1838 
1839   u2 type_index = rewrite_cp_ref_in_annotation_data(annotations_typeArray,
1840                     byte_i_ref, "mapped old type_index=%d", THREAD);
1841 
1842   u2 num_element_value_pairs = Bytes::get_Java_u2((address)
1843                                  annotations_typeArray->adr_at(byte_i_ref));
1844   byte_i_ref += 2;
1845 
1846   RC_TRACE_WITH_THREAD(0x02000000, THREAD,
1847     ("type_index=%d  num_element_value_pairs=%d", type_index,
1848     num_element_value_pairs));
1849 
1850   int calc_num_element_value_pairs = 0;
1851   for (; calc_num_element_value_pairs < num_element_value_pairs;
1852        calc_num_element_value_pairs++) {
1853     if ((byte_i_ref + 2) > annotations_typeArray->length()) {
1854       // not enough room for another element_name_index, let alone
1855       // the rest of another component
1856       RC_TRACE_WITH_THREAD(0x02000000, THREAD,
1857         ("length() is too small for element_name_index"));
1858       return false;
1859     }
1860 
1861     u2 element_name_index = rewrite_cp_ref_in_annotation_data(
1862                               annotations_typeArray, byte_i_ref,
1863                               "mapped old element_name_index=%d", THREAD);
1864 
1865     RC_TRACE_WITH_THREAD(0x02000000, THREAD,
1866       ("element_name_index=%d", element_name_index));
1867 
1868     if (!rewrite_cp_refs_in_element_value(annotations_typeArray,
1869            byte_i_ref, THREAD)) {
1870       RC_TRACE_WITH_THREAD(0x02000000, THREAD,
1871         ("bad element_value at %d", calc_num_element_value_pairs));
1872       // propagate failure back to caller
1873       return false;
1874     }
1875   } // end for each component
1876   assert(num_element_value_pairs == calc_num_element_value_pairs,
1877     "sanity check");
1878 
1879   return true;
1880 } // end rewrite_cp_refs_in_annotation_struct()
1881 
1882 
1883 // Rewrite a constant pool reference at the current position in
1884 // annotations_typeArray if needed. Returns the original constant
1885 // pool reference if a rewrite was not needed or the new constant
1886 // pool reference if a rewrite was needed.
1887 u2 VM_RedefineClasses::rewrite_cp_ref_in_annotation_data(
1888      AnnotationArray* annotations_typeArray, int &byte_i_ref,
1889      const char * trace_mesg, TRAPS) {
1890 
1891   address cp_index_addr = (address)
1892     annotations_typeArray->adr_at(byte_i_ref);
1893   u2 old_cp_index = Bytes::get_Java_u2(cp_index_addr);
1894   u2 new_cp_index = find_new_index(old_cp_index);
1895   if (new_cp_index != 0) {
1896     RC_TRACE_WITH_THREAD(0x02000000, THREAD, (trace_mesg, old_cp_index));
1897     Bytes::put_Java_u2(cp_index_addr, new_cp_index);
1898     old_cp_index = new_cp_index;
1899   }
1900   byte_i_ref += 2;
1901   return old_cp_index;
1902 }
1903 
1904 
1905 // Rewrite constant pool references in the element_value portion of an
1906 // annotations_typeArray. This "structure" is from section 4.8.15.1 of
1907 // the 2nd-edition of the VM spec:
1908 //
1909 // struct element_value {
1910 //   u1 tag;
1911 //   union {
1912 //     u2 const_value_index;
1913 //     {
1914 //       u2 type_name_index;
1915 //       u2 const_name_index;
1916 //     } enum_const_value;
1917 //     u2 class_info_index;
1918 //     annotation annotation_value;
1919 //     struct {
1920 //       u2 num_values;
1921 //       element_value values[num_values];
1922 //     } array_value;
1923 //   } value;
1924 // }
1925 //
1926 bool VM_RedefineClasses::rewrite_cp_refs_in_element_value(
1927        AnnotationArray* annotations_typeArray, int &byte_i_ref, TRAPS) {
1928 
1929   if ((byte_i_ref + 1) > annotations_typeArray->length()) {
1930     // not enough room for a tag let alone the rest of an element_value
1931     RC_TRACE_WITH_THREAD(0x02000000, THREAD,
1932       ("length() is too small for a tag"));
1933     return false;
1934   }
1935 
1936   u1 tag = annotations_typeArray->at(byte_i_ref);
1937   byte_i_ref++;
1938   RC_TRACE_WITH_THREAD(0x02000000, THREAD, ("tag='%c'", tag));
1939 
1940   switch (tag) {
1941     // These BaseType tag values are from Table 4.2 in VM spec:
1942     case 'B':  // byte
1943     case 'C':  // char
1944     case 'D':  // double
1945     case 'F':  // float
1946     case 'I':  // int
1947     case 'J':  // long
1948     case 'S':  // short
1949     case 'Z':  // boolean
1950 
1951     // The remaining tag values are from Table 4.8 in the 2nd-edition of
1952     // the VM spec:
1953     case 's':
1954     {
1955       // For the above tag values (including the BaseType values),
1956       // value.const_value_index is right union field.
1957 
1958       if ((byte_i_ref + 2) > annotations_typeArray->length()) {
1959         // not enough room for a const_value_index
1960         RC_TRACE_WITH_THREAD(0x02000000, THREAD,
1961           ("length() is too small for a const_value_index"));
1962         return false;
1963       }
1964 
1965       u2 const_value_index = rewrite_cp_ref_in_annotation_data(
1966                                annotations_typeArray, byte_i_ref,
1967                                "mapped old const_value_index=%d", THREAD);
1968 
1969       RC_TRACE_WITH_THREAD(0x02000000, THREAD,
1970         ("const_value_index=%d", const_value_index));
1971     } break;
1972 
1973     case 'e':
1974     {
1975       // for the above tag value, value.enum_const_value is right union field
1976 
1977       if ((byte_i_ref + 4) > annotations_typeArray->length()) {
1978         // not enough room for a enum_const_value
1979         RC_TRACE_WITH_THREAD(0x02000000, THREAD,
1980           ("length() is too small for a enum_const_value"));
1981         return false;
1982       }
1983 
1984       u2 type_name_index = rewrite_cp_ref_in_annotation_data(
1985                              annotations_typeArray, byte_i_ref,
1986                              "mapped old type_name_index=%d", THREAD);
1987 
1988       u2 const_name_index = rewrite_cp_ref_in_annotation_data(
1989                               annotations_typeArray, byte_i_ref,
1990                               "mapped old const_name_index=%d", THREAD);
1991 
1992       RC_TRACE_WITH_THREAD(0x02000000, THREAD,
1993         ("type_name_index=%d  const_name_index=%d", type_name_index,
1994         const_name_index));
1995     } break;
1996 
1997     case 'c':
1998     {
1999       // for the above tag value, value.class_info_index is right union field
2000 
2001       if ((byte_i_ref + 2) > annotations_typeArray->length()) {
2002         // not enough room for a class_info_index
2003         RC_TRACE_WITH_THREAD(0x02000000, THREAD,
2004           ("length() is too small for a class_info_index"));
2005         return false;
2006       }
2007 
2008       u2 class_info_index = rewrite_cp_ref_in_annotation_data(
2009                               annotations_typeArray, byte_i_ref,
2010                               "mapped old class_info_index=%d", THREAD);
2011 
2012       RC_TRACE_WITH_THREAD(0x02000000, THREAD,
2013         ("class_info_index=%d", class_info_index));
2014     } break;
2015 
2016     case '@':
2017       // For the above tag value, value.attr_value is the right union
2018       // field. This is a nested annotation.
2019       if (!rewrite_cp_refs_in_annotation_struct(annotations_typeArray,
2020              byte_i_ref, THREAD)) {
2021         // propagate failure back to caller
2022         return false;
2023       }
2024       break;
2025 
2026     case '[':
2027     {
2028       if ((byte_i_ref + 2) > annotations_typeArray->length()) {
2029         // not enough room for a num_values field
2030         RC_TRACE_WITH_THREAD(0x02000000, THREAD,
2031           ("length() is too small for a num_values field"));
2032         return false;
2033       }
2034 
2035       // For the above tag value, value.array_value is the right union
2036       // field. This is an array of nested element_value.
2037       u2 num_values = Bytes::get_Java_u2((address)
2038                         annotations_typeArray->adr_at(byte_i_ref));
2039       byte_i_ref += 2;
2040       RC_TRACE_WITH_THREAD(0x02000000, THREAD, ("num_values=%d", num_values));
2041 
2042       int calc_num_values = 0;
2043       for (; calc_num_values < num_values; calc_num_values++) {
2044         if (!rewrite_cp_refs_in_element_value(
2045                annotations_typeArray, byte_i_ref, THREAD)) {
2046           RC_TRACE_WITH_THREAD(0x02000000, THREAD,
2047             ("bad nested element_value at %d", calc_num_values));
2048           // propagate failure back to caller
2049           return false;
2050         }
2051       }
2052       assert(num_values == calc_num_values, "sanity check");
2053     } break;
2054 
2055     default:
2056       RC_TRACE_WITH_THREAD(0x02000000, THREAD, ("bad tag=0x%x", tag));
2057       return false;
2058   } // end decode tag field
2059 
2060   return true;
2061 } // end rewrite_cp_refs_in_element_value()
2062 
2063 
2064 // Rewrite constant pool references in a fields_annotations field.
2065 bool VM_RedefineClasses::rewrite_cp_refs_in_fields_annotations(
2066        instanceKlassHandle scratch_class, TRAPS) {
2067 
2068   Array<AnnotationArray*>* fields_annotations = scratch_class->fields_annotations();
2069 
2070   if (fields_annotations == NULL || fields_annotations->length() == 0) {
2071     // no fields_annotations so nothing to do
2072     return true;
2073   }
2074 
2075   RC_TRACE_WITH_THREAD(0x02000000, THREAD,
2076     ("fields_annotations length=%d", fields_annotations->length()));
2077 
2078   for (int i = 0; i < fields_annotations->length(); i++) {
2079     AnnotationArray* field_annotations = fields_annotations->at(i);
2080     if (field_annotations == NULL || field_annotations->length() == 0) {
2081       // this field does not have any annotations so skip it
2082       continue;
2083     }
2084 
2085     int byte_i = 0;  // byte index into field_annotations
2086     if (!rewrite_cp_refs_in_annotations_typeArray(field_annotations, byte_i,
2087            THREAD)) {
2088       RC_TRACE_WITH_THREAD(0x02000000, THREAD,
2089         ("bad field_annotations at %d", i));
2090       // propagate failure back to caller
2091       return false;
2092     }
2093   }
2094 
2095   return true;
2096 } // end rewrite_cp_refs_in_fields_annotations()
2097 
2098 
2099 // Rewrite constant pool references in a methods_annotations field.
2100 bool VM_RedefineClasses::rewrite_cp_refs_in_methods_annotations(
2101        instanceKlassHandle scratch_class, TRAPS) {
2102 
2103   for (int i = 0; i < scratch_class->methods()->length(); i++) {
2104     Method* m = scratch_class->methods()->at(i);
2105     AnnotationArray* method_annotations = m->constMethod()->method_annotations();
2106 
2107     if (method_annotations == NULL || method_annotations->length() == 0) {
2108       // this method does not have any annotations so skip it
2109       continue;
2110     }
2111 
2112     int byte_i = 0;  // byte index into method_annotations
2113     if (!rewrite_cp_refs_in_annotations_typeArray(method_annotations, byte_i,
2114            THREAD)) {
2115       RC_TRACE_WITH_THREAD(0x02000000, THREAD,
2116         ("bad method_annotations at %d", i));
2117       // propagate failure back to caller
2118       return false;
2119     }
2120   }
2121 
2122   return true;
2123 } // end rewrite_cp_refs_in_methods_annotations()
2124 
2125 
2126 // Rewrite constant pool references in a methods_parameter_annotations
2127 // field. This "structure" is adapted from the
2128 // RuntimeVisibleParameterAnnotations_attribute described in section
2129 // 4.8.17 of the 2nd-edition of the VM spec:
2130 //
2131 // methods_parameter_annotations_typeArray {
2132 //   u1 num_parameters;
2133 //   {
2134 //     u2 num_annotations;
2135 //     annotation annotations[num_annotations];
2136 //   } parameter_annotations[num_parameters];
2137 // }
2138 //
2139 bool VM_RedefineClasses::rewrite_cp_refs_in_methods_parameter_annotations(
2140        instanceKlassHandle scratch_class, TRAPS) {
2141 
2142   for (int i = 0; i < scratch_class->methods()->length(); i++) {
2143     Method* m = scratch_class->methods()->at(i);
2144     AnnotationArray* method_parameter_annotations = m->constMethod()->parameter_annotations();
2145     if (method_parameter_annotations == NULL
2146         || method_parameter_annotations->length() == 0) {
2147       // this method does not have any parameter annotations so skip it
2148       continue;
2149     }
2150 
2151     if (method_parameter_annotations->length() < 1) {
2152       // not enough room for a num_parameters field
2153       RC_TRACE_WITH_THREAD(0x02000000, THREAD,
2154         ("length() is too small for a num_parameters field at %d", i));
2155       return false;
2156     }
2157 
2158     int byte_i = 0;  // byte index into method_parameter_annotations
2159 
2160     u1 num_parameters = method_parameter_annotations->at(byte_i);
2161     byte_i++;
2162 
2163     RC_TRACE_WITH_THREAD(0x02000000, THREAD,
2164       ("num_parameters=%d", num_parameters));
2165 
2166     int calc_num_parameters = 0;
2167     for (; calc_num_parameters < num_parameters; calc_num_parameters++) {
2168       if (!rewrite_cp_refs_in_annotations_typeArray(
2169              method_parameter_annotations, byte_i, THREAD)) {
2170         RC_TRACE_WITH_THREAD(0x02000000, THREAD,
2171           ("bad method_parameter_annotations at %d", calc_num_parameters));
2172         // propagate failure back to caller
2173         return false;
2174       }
2175     }
2176     assert(num_parameters == calc_num_parameters, "sanity check");
2177   }
2178 
2179   return true;
2180 } // end rewrite_cp_refs_in_methods_parameter_annotations()
2181 
2182 
2183 // Rewrite constant pool references in a methods_default_annotations
2184 // field. This "structure" is adapted from the AnnotationDefault_attribute
2185 // that is described in section 4.8.19 of the 2nd-edition of the VM spec:
2186 //
2187 // methods_default_annotations_typeArray {
2188 //   element_value default_value;
2189 // }
2190 //
2191 bool VM_RedefineClasses::rewrite_cp_refs_in_methods_default_annotations(
2192        instanceKlassHandle scratch_class, TRAPS) {
2193 
2194   for (int i = 0; i < scratch_class->methods()->length(); i++) {
2195     Method* m = scratch_class->methods()->at(i);
2196     AnnotationArray* method_default_annotations = m->constMethod()->default_annotations();
2197     if (method_default_annotations == NULL
2198         || method_default_annotations->length() == 0) {
2199       // this method does not have any default annotations so skip it
2200       continue;
2201     }
2202 
2203     int byte_i = 0;  // byte index into method_default_annotations
2204 
2205     if (!rewrite_cp_refs_in_element_value(
2206            method_default_annotations, byte_i, THREAD)) {
2207       RC_TRACE_WITH_THREAD(0x02000000, THREAD,
2208         ("bad default element_value at %d", i));
2209       // propagate failure back to caller
2210       return false;
2211     }
2212   }
2213 
2214   return true;
2215 } // end rewrite_cp_refs_in_methods_default_annotations()
2216 
2217 
2218 // Rewrite constant pool references in the method's stackmap table.
2219 // These "structures" are adapted from the StackMapTable_attribute that
2220 // is described in section 4.8.4 of the 6.0 version of the VM spec
2221 // (dated 2005.10.26):
2222 // file:///net/quincunx.sfbay/export/gbracha/ClassFile-Java6.pdf
2223 //
2224 // stack_map {
2225 //   u2 number_of_entries;
2226 //   stack_map_frame entries[number_of_entries];
2227 // }
2228 //
2229 void VM_RedefineClasses::rewrite_cp_refs_in_stack_map_table(
2230        methodHandle method, TRAPS) {
2231 
2232   if (!method->has_stackmap_table()) {
2233     return;
2234   }
2235 
2236   AnnotationArray* stackmap_data = method->stackmap_data();
2237   address stackmap_p = (address)stackmap_data->adr_at(0);
2238   address stackmap_end = stackmap_p + stackmap_data->length();
2239 
2240   assert(stackmap_p + 2 <= stackmap_end, "no room for number_of_entries");
2241   u2 number_of_entries = Bytes::get_Java_u2(stackmap_p);
2242   stackmap_p += 2;
2243 
2244   RC_TRACE_WITH_THREAD(0x04000000, THREAD,
2245     ("number_of_entries=%u", number_of_entries));
2246 
2247   // walk through each stack_map_frame
2248   u2 calc_number_of_entries = 0;
2249   for (; calc_number_of_entries < number_of_entries; calc_number_of_entries++) {
2250     // The stack_map_frame structure is a u1 frame_type followed by
2251     // 0 or more bytes of data:
2252     //
2253     // union stack_map_frame {
2254     //   same_frame;
2255     //   same_locals_1_stack_item_frame;
2256     //   same_locals_1_stack_item_frame_extended;
2257     //   chop_frame;
2258     //   same_frame_extended;
2259     //   append_frame;
2260     //   full_frame;
2261     // }
2262 
2263     assert(stackmap_p + 1 <= stackmap_end, "no room for frame_type");
2264     // The Linux compiler does not like frame_type to be u1 or u2. It
2265     // issues the following warning for the first if-statement below:
2266     //
2267     // "warning: comparison is always true due to limited range of data type"
2268     //
2269     u4 frame_type = *stackmap_p;
2270     stackmap_p++;
2271 
2272     // same_frame {
2273     //   u1 frame_type = SAME; /* 0-63 */
2274     // }
2275     if (frame_type >= 0 && frame_type <= 63) {
2276       // nothing more to do for same_frame
2277     }
2278 
2279     // same_locals_1_stack_item_frame {
2280     //   u1 frame_type = SAME_LOCALS_1_STACK_ITEM; /* 64-127 */
2281     //   verification_type_info stack[1];
2282     // }
2283     else if (frame_type >= 64 && frame_type <= 127) {
2284       rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
2285         calc_number_of_entries, frame_type, THREAD);
2286     }
2287 
2288     // reserved for future use
2289     else if (frame_type >= 128 && frame_type <= 246) {
2290       // nothing more to do for reserved frame_types
2291     }
2292 
2293     // same_locals_1_stack_item_frame_extended {
2294     //   u1 frame_type = SAME_LOCALS_1_STACK_ITEM_EXTENDED; /* 247 */
2295     //   u2 offset_delta;
2296     //   verification_type_info stack[1];
2297     // }
2298     else if (frame_type == 247) {
2299       stackmap_p += 2;
2300       rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
2301         calc_number_of_entries, frame_type, THREAD);
2302     }
2303 
2304     // chop_frame {
2305     //   u1 frame_type = CHOP; /* 248-250 */
2306     //   u2 offset_delta;
2307     // }
2308     else if (frame_type >= 248 && frame_type <= 250) {
2309       stackmap_p += 2;
2310     }
2311 
2312     // same_frame_extended {
2313     //   u1 frame_type = SAME_FRAME_EXTENDED; /* 251*/
2314     //   u2 offset_delta;
2315     // }
2316     else if (frame_type == 251) {
2317       stackmap_p += 2;
2318     }
2319 
2320     // append_frame {
2321     //   u1 frame_type = APPEND; /* 252-254 */
2322     //   u2 offset_delta;
2323     //   verification_type_info locals[frame_type - 251];
2324     // }
2325     else if (frame_type >= 252 && frame_type <= 254) {
2326       assert(stackmap_p + 2 <= stackmap_end,
2327         "no room for offset_delta");
2328       stackmap_p += 2;
2329       u1 len = frame_type - 251;
2330       for (u1 i = 0; i < len; i++) {
2331         rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
2332           calc_number_of_entries, frame_type, THREAD);
2333       }
2334     }
2335 
2336     // full_frame {
2337     //   u1 frame_type = FULL_FRAME; /* 255 */
2338     //   u2 offset_delta;
2339     //   u2 number_of_locals;
2340     //   verification_type_info locals[number_of_locals];
2341     //   u2 number_of_stack_items;
2342     //   verification_type_info stack[number_of_stack_items];
2343     // }
2344     else if (frame_type == 255) {
2345       assert(stackmap_p + 2 + 2 <= stackmap_end,
2346         "no room for smallest full_frame");
2347       stackmap_p += 2;
2348 
2349       u2 number_of_locals = Bytes::get_Java_u2(stackmap_p);
2350       stackmap_p += 2;
2351 
2352       for (u2 locals_i = 0; locals_i < number_of_locals; locals_i++) {
2353         rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
2354           calc_number_of_entries, frame_type, THREAD);
2355       }
2356 
2357       // Use the largest size for the number_of_stack_items, but only get
2358       // the right number of bytes.
2359       u2 number_of_stack_items = Bytes::get_Java_u2(stackmap_p);
2360       stackmap_p += 2;
2361 
2362       for (u2 stack_i = 0; stack_i < number_of_stack_items; stack_i++) {
2363         rewrite_cp_refs_in_verification_type_info(stackmap_p, stackmap_end,
2364           calc_number_of_entries, frame_type, THREAD);
2365       }
2366     }
2367   } // end while there is a stack_map_frame
2368   assert(number_of_entries == calc_number_of_entries, "sanity check");
2369 } // end rewrite_cp_refs_in_stack_map_table()
2370 
2371 
2372 // Rewrite constant pool references in the verification type info
2373 // portion of the method's stackmap table. These "structures" are
2374 // adapted from the StackMapTable_attribute that is described in
2375 // section 4.8.4 of the 6.0 version of the VM spec (dated 2005.10.26):
2376 // file:///net/quincunx.sfbay/export/gbracha/ClassFile-Java6.pdf
2377 //
2378 // The verification_type_info structure is a u1 tag followed by 0 or
2379 // more bytes of data:
2380 //
2381 // union verification_type_info {
2382 //   Top_variable_info;
2383 //   Integer_variable_info;
2384 //   Float_variable_info;
2385 //   Long_variable_info;
2386 //   Double_variable_info;
2387 //   Null_variable_info;
2388 //   UninitializedThis_variable_info;
2389 //   Object_variable_info;
2390 //   Uninitialized_variable_info;
2391 // }
2392 //
2393 void VM_RedefineClasses::rewrite_cp_refs_in_verification_type_info(
2394        address& stackmap_p_ref, address stackmap_end, u2 frame_i,
2395        u1 frame_type, TRAPS) {
2396 
2397   assert(stackmap_p_ref + 1 <= stackmap_end, "no room for tag");
2398   u1 tag = *stackmap_p_ref;
2399   stackmap_p_ref++;
2400 
2401   switch (tag) {
2402   // Top_variable_info {
2403   //   u1 tag = ITEM_Top; /* 0 */
2404   // }
2405   // verificationType.hpp has zero as ITEM_Bogus instead of ITEM_Top
2406   case 0:  // fall through
2407 
2408   // Integer_variable_info {
2409   //   u1 tag = ITEM_Integer; /* 1 */
2410   // }
2411   case ITEM_Integer:  // fall through
2412 
2413   // Float_variable_info {
2414   //   u1 tag = ITEM_Float; /* 2 */
2415   // }
2416   case ITEM_Float:  // fall through
2417 
2418   // Double_variable_info {
2419   //   u1 tag = ITEM_Double; /* 3 */
2420   // }
2421   case ITEM_Double:  // fall through
2422 
2423   // Long_variable_info {
2424   //   u1 tag = ITEM_Long; /* 4 */
2425   // }
2426   case ITEM_Long:  // fall through
2427 
2428   // Null_variable_info {
2429   //   u1 tag = ITEM_Null; /* 5 */
2430   // }
2431   case ITEM_Null:  // fall through
2432 
2433   // UninitializedThis_variable_info {
2434   //   u1 tag = ITEM_UninitializedThis; /* 6 */
2435   // }
2436   case ITEM_UninitializedThis:
2437     // nothing more to do for the above tag types
2438     break;
2439 
2440   // Object_variable_info {
2441   //   u1 tag = ITEM_Object; /* 7 */
2442   //   u2 cpool_index;
2443   // }
2444   case ITEM_Object:
2445   {
2446     assert(stackmap_p_ref + 2 <= stackmap_end, "no room for cpool_index");
2447     u2 cpool_index = Bytes::get_Java_u2(stackmap_p_ref);
2448     u2 new_cp_index = find_new_index(cpool_index);
2449     if (new_cp_index != 0) {
2450       RC_TRACE_WITH_THREAD(0x04000000, THREAD,
2451         ("mapped old cpool_index=%d", cpool_index));
2452       Bytes::put_Java_u2(stackmap_p_ref, new_cp_index);
2453       cpool_index = new_cp_index;
2454     }
2455     stackmap_p_ref += 2;
2456 
2457     RC_TRACE_WITH_THREAD(0x04000000, THREAD,
2458       ("frame_i=%u, frame_type=%u, cpool_index=%d", frame_i,
2459       frame_type, cpool_index));
2460   } break;
2461 
2462   // Uninitialized_variable_info {
2463   //   u1 tag = ITEM_Uninitialized; /* 8 */
2464   //   u2 offset;
2465   // }
2466   case ITEM_Uninitialized:
2467     assert(stackmap_p_ref + 2 <= stackmap_end, "no room for offset");
2468     stackmap_p_ref += 2;
2469     break;
2470 
2471   default:
2472     RC_TRACE_WITH_THREAD(0x04000000, THREAD,
2473       ("frame_i=%u, frame_type=%u, bad tag=0x%x", frame_i, frame_type, tag));
2474     ShouldNotReachHere();
2475     break;
2476   } // end switch (tag)
2477 } // end rewrite_cp_refs_in_verification_type_info()
2478 
2479 
2480 // Change the constant pool associated with klass scratch_class to
2481 // scratch_cp. If shrink is true, then scratch_cp_length elements
2482 // are copied from scratch_cp to a smaller constant pool and the
2483 // smaller constant pool is associated with scratch_class.
2484 void VM_RedefineClasses::set_new_constant_pool(
2485        ClassLoaderData* loader_data,
2486        instanceKlassHandle scratch_class, constantPoolHandle scratch_cp,
2487        int scratch_cp_length, TRAPS) {
2488   assert(scratch_cp->length() >= scratch_cp_length, "sanity check");
2489 
2490   // scratch_cp is a merged constant pool and has enough space for a
2491   // worst case merge situation. We want to associate the minimum
2492   // sized constant pool with the klass to save space.
2493   constantPoolHandle smaller_cp(THREAD,
2494           ConstantPool::allocate(loader_data, scratch_cp_length, THREAD));
2495 
2496   // preserve version() value in the smaller copy
2497   int version = scratch_cp->version();
2498   assert(version != 0, "sanity check");
2499   smaller_cp->set_version(version);
2500 
2501   // attach klass to new constant pool
2502   // reference to the cp holder is needed for copy_operands()
2503   smaller_cp->set_pool_holder(scratch_class());
2504 
2505   scratch_cp->copy_cp_to(1, scratch_cp_length - 1, smaller_cp, 1, THREAD);
2506   scratch_cp = smaller_cp;
2507 
2508   // attach new constant pool to klass
2509   scratch_class->set_constants(scratch_cp());
2510 
2511   int i;  // for portability
2512 
2513   // update each field in klass to use new constant pool indices as needed
2514   for (JavaFieldStream fs(scratch_class); !fs.done(); fs.next()) {
2515     jshort cur_index = fs.name_index();
2516     jshort new_index = find_new_index(cur_index);
2517     if (new_index != 0) {
2518       RC_TRACE_WITH_THREAD(0x00080000, THREAD,
2519         ("field-name_index change: %d to %d", cur_index, new_index));
2520       fs.set_name_index(new_index);
2521     }
2522     cur_index = fs.signature_index();
2523     new_index = find_new_index(cur_index);
2524     if (new_index != 0) {
2525       RC_TRACE_WITH_THREAD(0x00080000, THREAD,
2526         ("field-signature_index change: %d to %d", cur_index, new_index));
2527       fs.set_signature_index(new_index);
2528     }
2529     cur_index = fs.initval_index();
2530     new_index = find_new_index(cur_index);
2531     if (new_index != 0) {
2532       RC_TRACE_WITH_THREAD(0x00080000, THREAD,
2533         ("field-initval_index change: %d to %d", cur_index, new_index));
2534       fs.set_initval_index(new_index);
2535     }
2536     cur_index = fs.generic_signature_index();
2537     new_index = find_new_index(cur_index);
2538     if (new_index != 0) {
2539       RC_TRACE_WITH_THREAD(0x00080000, THREAD,
2540         ("field-generic_signature change: %d to %d", cur_index, new_index));
2541       fs.set_generic_signature_index(new_index);
2542     }
2543   } // end for each field
2544 
2545   // Update constant pool indices in the inner classes info to use
2546   // new constant indices as needed. The inner classes info is a
2547   // quadruple:
2548   // (inner_class_info, outer_class_info, inner_name, inner_access_flags)
2549   InnerClassesIterator iter(scratch_class);
2550   for (; !iter.done(); iter.next()) {
2551     int cur_index = iter.inner_class_info_index();
2552     if (cur_index == 0) {
2553       continue;  // JVM spec. allows null inner class refs so skip it
2554     }
2555     int new_index = find_new_index(cur_index);
2556     if (new_index != 0) {
2557       RC_TRACE_WITH_THREAD(0x00080000, THREAD,
2558         ("inner_class_info change: %d to %d", cur_index, new_index));
2559       iter.set_inner_class_info_index(new_index);
2560     }
2561     cur_index = iter.outer_class_info_index();
2562     new_index = find_new_index(cur_index);
2563     if (new_index != 0) {
2564       RC_TRACE_WITH_THREAD(0x00080000, THREAD,
2565         ("outer_class_info change: %d to %d", cur_index, new_index));
2566       iter.set_outer_class_info_index(new_index);
2567     }
2568     cur_index = iter.inner_name_index();
2569     new_index = find_new_index(cur_index);
2570     if (new_index != 0) {
2571       RC_TRACE_WITH_THREAD(0x00080000, THREAD,
2572         ("inner_name change: %d to %d", cur_index, new_index));
2573       iter.set_inner_name_index(new_index);
2574     }
2575   } // end for each inner class
2576 
2577   // Attach each method in klass to the new constant pool and update
2578   // to use new constant pool indices as needed:
2579   Array<Method*>* methods = scratch_class->methods();
2580   for (i = methods->length() - 1; i >= 0; i--) {
2581     methodHandle method(THREAD, methods->at(i));
2582     method->set_constants(scratch_cp());
2583 
2584     int new_index = find_new_index(method->name_index());
2585     if (new_index != 0) {
2586       RC_TRACE_WITH_THREAD(0x00080000, THREAD,
2587         ("method-name_index change: %d to %d", method->name_index(),
2588         new_index));
2589       method->set_name_index(new_index);
2590     }
2591     new_index = find_new_index(method->signature_index());
2592     if (new_index != 0) {
2593       RC_TRACE_WITH_THREAD(0x00080000, THREAD,
2594         ("method-signature_index change: %d to %d",
2595         method->signature_index(), new_index));
2596       method->set_signature_index(new_index);
2597     }
2598     new_index = find_new_index(method->generic_signature_index());
2599     if (new_index != 0) {
2600       RC_TRACE_WITH_THREAD(0x00080000, THREAD,
2601         ("method-generic_signature_index change: %d to %d",
2602         method->generic_signature_index(), new_index));
2603       method->set_generic_signature_index(new_index);
2604     }
2605 
2606     // Update constant pool indices in the method's checked exception
2607     // table to use new constant indices as needed.
2608     int cext_length = method->checked_exceptions_length();
2609     if (cext_length > 0) {
2610       CheckedExceptionElement * cext_table =
2611         method->checked_exceptions_start();
2612       for (int j = 0; j < cext_length; j++) {
2613         int cur_index = cext_table[j].class_cp_index;
2614         int new_index = find_new_index(cur_index);
2615         if (new_index != 0) {
2616           RC_TRACE_WITH_THREAD(0x00080000, THREAD,
2617             ("cext-class_cp_index change: %d to %d", cur_index, new_index));
2618           cext_table[j].class_cp_index = (u2)new_index;
2619         }
2620       } // end for each checked exception table entry
2621     } // end if there are checked exception table entries
2622 
2623     // Update each catch type index in the method's exception table
2624     // to use new constant pool indices as needed. The exception table
2625     // holds quadruple entries of the form:
2626     //   (beg_bci, end_bci, handler_bci, klass_index)
2627 
2628     ExceptionTable ex_table(method());
2629     int ext_length = ex_table.length();
2630 
2631     for (int j = 0; j < ext_length; j ++) {
2632       int cur_index = ex_table.catch_type_index(j);
2633       int new_index = find_new_index(cur_index);
2634       if (new_index != 0) {
2635         RC_TRACE_WITH_THREAD(0x00080000, THREAD,
2636           ("ext-klass_index change: %d to %d", cur_index, new_index));
2637         ex_table.set_catch_type_index(j, new_index);
2638       }
2639     } // end for each exception table entry
2640 
2641     // Update constant pool indices in the method's local variable
2642     // table to use new constant indices as needed. The local variable
2643     // table hold sextuple entries of the form:
2644     // (start_pc, length, name_index, descriptor_index, signature_index, slot)
2645     int lvt_length = method->localvariable_table_length();
2646     if (lvt_length > 0) {
2647       LocalVariableTableElement * lv_table =
2648         method->localvariable_table_start();
2649       for (int j = 0; j < lvt_length; j++) {
2650         int cur_index = lv_table[j].name_cp_index;
2651         int new_index = find_new_index(cur_index);
2652         if (new_index != 0) {
2653           RC_TRACE_WITH_THREAD(0x00080000, THREAD,
2654             ("lvt-name_cp_index change: %d to %d", cur_index, new_index));
2655           lv_table[j].name_cp_index = (u2)new_index;
2656         }
2657         cur_index = lv_table[j].descriptor_cp_index;
2658         new_index = find_new_index(cur_index);
2659         if (new_index != 0) {
2660           RC_TRACE_WITH_THREAD(0x00080000, THREAD,
2661             ("lvt-descriptor_cp_index change: %d to %d", cur_index,
2662             new_index));
2663           lv_table[j].descriptor_cp_index = (u2)new_index;
2664         }
2665         cur_index = lv_table[j].signature_cp_index;
2666         new_index = find_new_index(cur_index);
2667         if (new_index != 0) {
2668           RC_TRACE_WITH_THREAD(0x00080000, THREAD,
2669             ("lvt-signature_cp_index change: %d to %d", cur_index, new_index));
2670           lv_table[j].signature_cp_index = (u2)new_index;
2671         }
2672       } // end for each local variable table entry
2673     } // end if there are local variable table entries
2674 
2675     rewrite_cp_refs_in_stack_map_table(method, THREAD);
2676   } // end for each method
2677 } // end set_new_constant_pool()
2678 
2679 
2680 // Unevolving classes may point to methods of the_class directly
2681 // from their constant pool caches, itables, and/or vtables. We
2682 // use the ClassLoaderDataGraph::classes_do() facility and this helper
2683 // to fix up these pointers.
2684 
2685 // Adjust cpools and vtables closure
2686 void VM_RedefineClasses::AdjustCpoolCacheAndVtable::do_klass(Klass* k) {
2687 
2688   // This is a very busy routine. We don't want too much tracing
2689   // printed out.
2690   bool trace_name_printed = false;
2691 
2692   // Very noisy: only enable this call if you are trying to determine
2693   // that a specific class gets found by this routine.
2694   // RC_TRACE macro has an embedded ResourceMark
2695   // RC_TRACE_WITH_THREAD(0x00100000, THREAD,
2696   //   ("adjust check: name=%s", k->external_name()));
2697   // trace_name_printed = true;
2698 
2699   // If the class being redefined is java.lang.Object, we need to fix all
2700   // array class vtables also
2701   if (k->oop_is_array() && _the_class_oop == SystemDictionary::Object_klass()) {
2702     k->vtable()->adjust_method_entries(_matching_old_methods,
2703                                        _matching_new_methods,
2704                                        _matching_methods_length,
2705                                        &trace_name_printed);
2706   } else if (k->oop_is_instance()) {
2707     HandleMark hm(_thread);
2708     InstanceKlass *ik = InstanceKlass::cast(k);
2709 
2710     // HotSpot specific optimization! HotSpot does not currently
2711     // support delegation from the bootstrap class loader to a
2712     // user-defined class loader. This means that if the bootstrap
2713     // class loader is the initiating class loader, then it will also
2714     // be the defining class loader. This also means that classes
2715     // loaded by the bootstrap class loader cannot refer to classes
2716     // loaded by a user-defined class loader. Note: a user-defined
2717     // class loader can delegate to the bootstrap class loader.
2718     //
2719     // If the current class being redefined has a user-defined class
2720     // loader as its defining class loader, then we can skip all
2721     // classes loaded by the bootstrap class loader.
2722     bool is_user_defined =
2723            InstanceKlass::cast(_the_class_oop)->class_loader() != NULL;
2724     if (is_user_defined && ik->class_loader() == NULL) {
2725       return;
2726     }
2727 
2728     // Fix the vtable embedded in the_class and subclasses of the_class,
2729     // if one exists. We discard scratch_class and we don't keep an
2730     // InstanceKlass around to hold obsolete methods so we don't have
2731     // any other InstanceKlass embedded vtables to update. The vtable
2732     // holds the Method*s for virtual (but not final) methods.
2733     if (ik->vtable_length() > 0 && ik->is_subtype_of(_the_class_oop)) {
2734       // ik->vtable() creates a wrapper object; rm cleans it up
2735       ResourceMark rm(_thread);
2736       ik->vtable()->adjust_method_entries(_matching_old_methods,
2737                                           _matching_new_methods,
2738                                           _matching_methods_length,
2739                                           &trace_name_printed);
2740     }
2741 
2742     // If the current class has an itable and we are either redefining an
2743     // interface or if the current class is a subclass of the_class, then
2744     // we potentially have to fix the itable. If we are redefining an
2745     // interface, then we have to call adjust_method_entries() for
2746     // every InstanceKlass that has an itable since there isn't a
2747     // subclass relationship between an interface and an InstanceKlass.
2748     if (ik->itable_length() > 0 && (_the_class_oop->is_interface()
2749         || ik->is_subclass_of(_the_class_oop))) {
2750       // ik->itable() creates a wrapper object; rm cleans it up
2751       ResourceMark rm(_thread);
2752       ik->itable()->adjust_method_entries(_matching_old_methods,
2753                                           _matching_new_methods,
2754                                           _matching_methods_length,
2755                                           &trace_name_printed);
2756     }
2757 
2758     // The constant pools in other classes (other_cp) can refer to
2759     // methods in the_class. We have to update method information in
2760     // other_cp's cache. If other_cp has a previous version, then we
2761     // have to repeat the process for each previous version. The
2762     // constant pool cache holds the Method*s for non-virtual
2763     // methods and for virtual, final methods.
2764     //
2765     // Special case: if the current class is the_class, then new_cp
2766     // has already been attached to the_class and old_cp has already
2767     // been added as a previous version. The new_cp doesn't have any
2768     // cached references to old methods so it doesn't need to be
2769     // updated. We can simply start with the previous version(s) in
2770     // that case.
2771     constantPoolHandle other_cp;
2772     ConstantPoolCache* cp_cache;
2773 
2774     if (ik != _the_class_oop) {
2775       // this klass' constant pool cache may need adjustment
2776       other_cp = constantPoolHandle(ik->constants());
2777       cp_cache = other_cp->cache();
2778       if (cp_cache != NULL) {
2779         cp_cache->adjust_method_entries(_matching_old_methods,
2780                                         _matching_new_methods,
2781                                         _matching_methods_length,
2782                                         &trace_name_printed);
2783       }
2784     }
2785     {
2786       ResourceMark rm(_thread);
2787       // PreviousVersionInfo objects returned via PreviousVersionWalker
2788       // contain a GrowableArray of handles. We have to clean up the
2789       // GrowableArray _after_ the PreviousVersionWalker destructor
2790       // has destroyed the handles.
2791       {
2792         // the previous versions' constant pool caches may need adjustment
2793         PreviousVersionWalker pvw(ik);
2794         for (PreviousVersionInfo * pv_info = pvw.next_previous_version();
2795              pv_info != NULL; pv_info = pvw.next_previous_version()) {
2796           other_cp = pv_info->prev_constant_pool_handle();
2797           cp_cache = other_cp->cache();
2798           if (cp_cache != NULL) {
2799             cp_cache->adjust_method_entries(_matching_old_methods,
2800                                             _matching_new_methods,
2801                                             _matching_methods_length,
2802                                             &trace_name_printed);
2803           }
2804         }
2805       } // pvw is cleaned up
2806     } // rm is cleaned up
2807   }
2808 }
2809 
2810 void VM_RedefineClasses::update_jmethod_ids() {
2811   for (int j = 0; j < _matching_methods_length; ++j) {
2812     Method* old_method = _matching_old_methods[j];
2813     jmethodID jmid = old_method->find_jmethod_id_or_null();
2814     if (jmid != NULL) {
2815       // There is a jmethodID, change it to point to the new method
2816       methodHandle new_method_h(_matching_new_methods[j]);
2817       Method::change_method_associated_with_jmethod_id(jmid, new_method_h());
2818       assert(Method::resolve_jmethod_id(jmid) == _matching_new_methods[j],
2819              "should be replaced");
2820     }
2821   }
2822 }
2823 
2824 void VM_RedefineClasses::check_methods_and_mark_as_obsolete(
2825        BitMap *emcp_methods, int * emcp_method_count_p) {
2826   *emcp_method_count_p = 0;
2827   int obsolete_count = 0;
2828   int old_index = 0;
2829   for (int j = 0; j < _matching_methods_length; ++j, ++old_index) {
2830     Method* old_method = _matching_old_methods[j];
2831     Method* new_method = _matching_new_methods[j];
2832     Method* old_array_method;
2833 
2834     // Maintain an old_index into the _old_methods array by skipping
2835     // deleted methods
2836     while ((old_array_method = _old_methods->at(old_index)) != old_method) {
2837       ++old_index;
2838     }
2839 
2840     if (MethodComparator::methods_EMCP(old_method, new_method)) {
2841       // The EMCP definition from JSR-163 requires the bytecodes to be
2842       // the same with the exception of constant pool indices which may
2843       // differ. However, the constants referred to by those indices
2844       // must be the same.
2845       //
2846       // We use methods_EMCP() for comparison since constant pool
2847       // merging can remove duplicate constant pool entries that were
2848       // present in the old method and removed from the rewritten new
2849       // method. A faster binary comparison function would consider the
2850       // old and new methods to be different when they are actually
2851       // EMCP.
2852       //
2853       // The old and new methods are EMCP and you would think that we
2854       // could get rid of one of them here and now and save some space.
2855       // However, the concept of EMCP only considers the bytecodes and
2856       // the constant pool entries in the comparison. Other things,
2857       // e.g., the line number table (LNT) or the local variable table
2858       // (LVT) don't count in the comparison. So the new (and EMCP)
2859       // method can have a new LNT that we need so we can't just
2860       // overwrite the new method with the old method.
2861       //
2862       // When this routine is called, we have already attached the new
2863       // methods to the_class so the old methods are effectively
2864       // overwritten. However, if an old method is still executing,
2865       // then the old method cannot be collected until sometime after
2866       // the old method call has returned. So the overwriting of old
2867       // methods by new methods will save us space except for those
2868       // (hopefully few) old methods that are still executing.
2869       //
2870       // A method refers to a ConstMethod* and this presents another
2871       // possible avenue to space savings. The ConstMethod* in the
2872       // new method contains possibly new attributes (LNT, LVT, etc).
2873       // At first glance, it seems possible to save space by replacing
2874       // the ConstMethod* in the old method with the ConstMethod*
2875       // from the new method. The old and new methods would share the
2876       // same ConstMethod* and we would save the space occupied by
2877       // the old ConstMethod*. However, the ConstMethod* contains
2878       // a back reference to the containing method. Sharing the
2879       // ConstMethod* between two methods could lead to confusion in
2880       // the code that uses the back reference. This would lead to
2881       // brittle code that could be broken in non-obvious ways now or
2882       // in the future.
2883       //
2884       // Another possibility is to copy the ConstMethod* from the new
2885       // method to the old method and then overwrite the new method with
2886       // the old method. Since the ConstMethod* contains the bytecodes
2887       // for the method embedded in the oop, this option would change
2888       // the bytecodes out from under any threads executing the old
2889       // method and make the thread's bcp invalid. Since EMCP requires
2890       // that the bytecodes be the same modulo constant pool indices, it
2891       // is straight forward to compute the correct new bcp in the new
2892       // ConstMethod* from the old bcp in the old ConstMethod*. The
2893       // time consuming part would be searching all the frames in all
2894       // of the threads to find all of the calls to the old method.
2895       //
2896       // It looks like we will have to live with the limited savings
2897       // that we get from effectively overwriting the old methods
2898       // when the new methods are attached to the_class.
2899 
2900       // track which methods are EMCP for add_previous_version() call
2901       emcp_methods->set_bit(old_index);
2902       (*emcp_method_count_p)++;
2903 
2904       // An EMCP method is _not_ obsolete. An obsolete method has a
2905       // different jmethodID than the current method. An EMCP method
2906       // has the same jmethodID as the current method. Having the
2907       // same jmethodID for all EMCP versions of a method allows for
2908       // a consistent view of the EMCP methods regardless of which
2909       // EMCP method you happen to have in hand. For example, a
2910       // breakpoint set in one EMCP method will work for all EMCP
2911       // versions of the method including the current one.
2912     } else {
2913       // mark obsolete methods as such
2914       old_method->set_is_obsolete();
2915       obsolete_count++;
2916 
2917       // obsolete methods need a unique idnum
2918       u2 num = InstanceKlass::cast(_the_class_oop)->next_method_idnum();
2919       if (num != ConstMethod::UNSET_IDNUM) {
2920 //      u2 old_num = old_method->method_idnum();
2921         old_method->set_method_idnum(num);
2922 // TO DO: attach obsolete annotations to obsolete method's new idnum
2923       }
2924       // With tracing we try not to "yack" too much. The position of
2925       // this trace assumes there are fewer obsolete methods than
2926       // EMCP methods.
2927       RC_TRACE(0x00000100, ("mark %s(%s) as obsolete",
2928         old_method->name()->as_C_string(),
2929         old_method->signature()->as_C_string()));
2930     }
2931     old_method->set_is_old();
2932   }
2933   for (int i = 0; i < _deleted_methods_length; ++i) {
2934     Method* old_method = _deleted_methods[i];
2935 
2936     assert(old_method->vtable_index() < 0,
2937            "cannot delete methods with vtable entries");;
2938 
2939     // Mark all deleted methods as old and obsolete
2940     old_method->set_is_old();
2941     old_method->set_is_obsolete();
2942     ++obsolete_count;
2943     // With tracing we try not to "yack" too much. The position of
2944     // this trace assumes there are fewer obsolete methods than
2945     // EMCP methods.
2946     RC_TRACE(0x00000100, ("mark deleted %s(%s) as obsolete",
2947                           old_method->name()->as_C_string(),
2948                           old_method->signature()->as_C_string()));
2949   }
2950   assert((*emcp_method_count_p + obsolete_count) == _old_methods->length(),
2951     "sanity check");
2952   RC_TRACE(0x00000100, ("EMCP_cnt=%d, obsolete_cnt=%d", *emcp_method_count_p,
2953     obsolete_count));
2954 }
2955 
2956 // This internal class transfers the native function registration from old methods
2957 // to new methods.  It is designed to handle both the simple case of unchanged
2958 // native methods and the complex cases of native method prefixes being added and/or
2959 // removed.
2960 // It expects only to be used during the VM_RedefineClasses op (a safepoint).
2961 //
2962 // This class is used after the new methods have been installed in "the_class".
2963 //
2964 // So, for example, the following must be handled.  Where 'm' is a method and
2965 // a number followed by an underscore is a prefix.
2966 //
2967 //                                      Old Name    New Name
2968 // Simple transfer to new method        m       ->  m
2969 // Add prefix                           m       ->  1_m
2970 // Remove prefix                        1_m     ->  m
2971 // Simultaneous add of prefixes         m       ->  3_2_1_m
2972 // Simultaneous removal of prefixes     3_2_1_m ->  m
2973 // Simultaneous add and remove          1_m     ->  2_m
2974 // Same, caused by prefix removal only  3_2_1_m ->  3_2_m
2975 //
2976 class TransferNativeFunctionRegistration {
2977  private:
2978   instanceKlassHandle the_class;
2979   int prefix_count;
2980   char** prefixes;
2981 
2982   // Recursively search the binary tree of possibly prefixed method names.
2983   // Iteration could be used if all agents were well behaved. Full tree walk is
2984   // more resilent to agents not cleaning up intermediate methods.
2985   // Branch at each depth in the binary tree is:
2986   //    (1) without the prefix.
2987   //    (2) with the prefix.
2988   // where 'prefix' is the prefix at that 'depth' (first prefix, second prefix,...)
2989   Method* search_prefix_name_space(int depth, char* name_str, size_t name_len,
2990                                      Symbol* signature) {
2991     TempNewSymbol name_symbol = SymbolTable::probe(name_str, (int)name_len);
2992     if (name_symbol != NULL) {
2993       Method* method = the_class()->lookup_method(name_symbol, signature);
2994       if (method != NULL) {
2995         // Even if prefixed, intermediate methods must exist.
2996         if (method->is_native()) {
2997           // Wahoo, we found a (possibly prefixed) version of the method, return it.
2998           return method;
2999         }
3000         if (depth < prefix_count) {
3001           // Try applying further prefixes (other than this one).
3002           method = search_prefix_name_space(depth+1, name_str, name_len, signature);
3003           if (method != NULL) {
3004             return method; // found
3005           }
3006 
3007           // Try adding this prefix to the method name and see if it matches
3008           // another method name.
3009           char* prefix = prefixes[depth];
3010           size_t prefix_len = strlen(prefix);
3011           size_t trial_len = name_len + prefix_len;
3012           char* trial_name_str = NEW_RESOURCE_ARRAY(char, trial_len + 1);
3013           strcpy(trial_name_str, prefix);
3014           strcat(trial_name_str, name_str);
3015           method = search_prefix_name_space(depth+1, trial_name_str, trial_len,
3016                                             signature);
3017           if (method != NULL) {
3018             // If found along this branch, it was prefixed, mark as such
3019             method->set_is_prefixed_native();
3020             return method; // found
3021           }
3022         }
3023       }
3024     }
3025     return NULL;  // This whole branch bore nothing
3026   }
3027 
3028   // Return the method name with old prefixes stripped away.
3029   char* method_name_without_prefixes(Method* method) {
3030     Symbol* name = method->name();
3031     char* name_str = name->as_utf8();
3032 
3033     // Old prefixing may be defunct, strip prefixes, if any.
3034     for (int i = prefix_count-1; i >= 0; i--) {
3035       char* prefix = prefixes[i];
3036       size_t prefix_len = strlen(prefix);
3037       if (strncmp(prefix, name_str, prefix_len) == 0) {
3038         name_str += prefix_len;
3039       }
3040     }
3041     return name_str;
3042   }
3043 
3044   // Strip any prefixes off the old native method, then try to find a
3045   // (possibly prefixed) new native that matches it.
3046   Method* strip_and_search_for_new_native(Method* method) {
3047     ResourceMark rm;
3048     char* name_str = method_name_without_prefixes(method);
3049     return search_prefix_name_space(0, name_str, strlen(name_str),
3050                                     method->signature());
3051   }
3052 
3053  public:
3054 
3055   // Construct a native method transfer processor for this class.
3056   TransferNativeFunctionRegistration(instanceKlassHandle _the_class) {
3057     assert(SafepointSynchronize::is_at_safepoint(), "sanity check");
3058 
3059     the_class = _the_class;
3060     prefixes = JvmtiExport::get_all_native_method_prefixes(&prefix_count);
3061   }
3062 
3063   // Attempt to transfer any of the old or deleted methods that are native
3064   void transfer_registrations(Method** old_methods, int methods_length) {
3065     for (int j = 0; j < methods_length; j++) {
3066       Method* old_method = old_methods[j];
3067 
3068       if (old_method->is_native() && old_method->has_native_function()) {
3069         Method* new_method = strip_and_search_for_new_native(old_method);
3070         if (new_method != NULL) {
3071           // Actually set the native function in the new method.
3072           // Redefine does not send events (except CFLH), certainly not this
3073           // behind the scenes re-registration.
3074           new_method->set_native_function(old_method->native_function(),
3075                               !Method::native_bind_event_is_interesting);
3076         }
3077       }
3078     }
3079   }
3080 };
3081 
3082 // Don't lose the association between a native method and its JNI function.
3083 void VM_RedefineClasses::transfer_old_native_function_registrations(instanceKlassHandle the_class) {
3084   TransferNativeFunctionRegistration transfer(the_class);
3085   transfer.transfer_registrations(_deleted_methods, _deleted_methods_length);
3086   transfer.transfer_registrations(_matching_old_methods, _matching_methods_length);
3087 }
3088 
3089 // Deoptimize all compiled code that depends on this class.
3090 //
3091 // If the can_redefine_classes capability is obtained in the onload
3092 // phase then the compiler has recorded all dependencies from startup.
3093 // In that case we need only deoptimize and throw away all compiled code
3094 // that depends on the class.
3095 //
3096 // If can_redefine_classes is obtained sometime after the onload
3097 // phase then the dependency information may be incomplete. In that case
3098 // the first call to RedefineClasses causes all compiled code to be
3099 // thrown away. As can_redefine_classes has been obtained then
3100 // all future compilations will record dependencies so second and
3101 // subsequent calls to RedefineClasses need only throw away code
3102 // that depends on the class.
3103 //
3104 void VM_RedefineClasses::flush_dependent_code(instanceKlassHandle k_h, TRAPS) {
3105   assert_locked_or_safepoint(Compile_lock);
3106 
3107   // All dependencies have been recorded from startup or this is a second or
3108   // subsequent use of RedefineClasses
3109   if (JvmtiExport::all_dependencies_are_recorded()) {
3110     Universe::flush_evol_dependents_on(k_h);
3111   } else {
3112     CodeCache::mark_all_nmethods_for_deoptimization();
3113 
3114     ResourceMark rm(THREAD);
3115     DeoptimizationMarker dm;
3116 
3117     // Deoptimize all activations depending on marked nmethods
3118     Deoptimization::deoptimize_dependents();
3119 
3120     // Make the dependent methods not entrant (in VM_Deoptimize they are made zombies)
3121     CodeCache::make_marked_nmethods_not_entrant();
3122 
3123     // From now on we know that the dependency information is complete
3124     JvmtiExport::set_all_dependencies_are_recorded(true);
3125   }
3126 }
3127 
3128 void VM_RedefineClasses::compute_added_deleted_matching_methods() {
3129   Method* old_method;
3130   Method* new_method;
3131 
3132   _matching_old_methods = NEW_RESOURCE_ARRAY(Method*, _old_methods->length());
3133   _matching_new_methods = NEW_RESOURCE_ARRAY(Method*, _old_methods->length());
3134   _added_methods        = NEW_RESOURCE_ARRAY(Method*, _new_methods->length());
3135   _deleted_methods      = NEW_RESOURCE_ARRAY(Method*, _old_methods->length());
3136 
3137   _matching_methods_length = 0;
3138   _deleted_methods_length  = 0;
3139   _added_methods_length    = 0;
3140 
3141   int nj = 0;
3142   int oj = 0;
3143   while (true) {
3144     if (oj >= _old_methods->length()) {
3145       if (nj >= _new_methods->length()) {
3146         break; // we've looked at everything, done
3147       }
3148       // New method at the end
3149       new_method = _new_methods->at(nj);
3150       _added_methods[_added_methods_length++] = new_method;
3151       ++nj;
3152     } else if (nj >= _new_methods->length()) {
3153       // Old method, at the end, is deleted
3154       old_method = _old_methods->at(oj);
3155       _deleted_methods[_deleted_methods_length++] = old_method;
3156       ++oj;
3157     } else {
3158       old_method = _old_methods->at(oj);
3159       new_method = _new_methods->at(nj);
3160       if (old_method->name() == new_method->name()) {
3161         if (old_method->signature() == new_method->signature()) {
3162           _matching_old_methods[_matching_methods_length  ] = old_method;
3163           _matching_new_methods[_matching_methods_length++] = new_method;
3164           ++nj;
3165           ++oj;
3166         } else {
3167           // added overloaded have already been moved to the end,
3168           // so this is a deleted overloaded method
3169           _deleted_methods[_deleted_methods_length++] = old_method;
3170           ++oj;
3171         }
3172       } else { // names don't match
3173         if (old_method->name()->fast_compare(new_method->name()) > 0) {
3174           // new method
3175           _added_methods[_added_methods_length++] = new_method;
3176           ++nj;
3177         } else {
3178           // deleted method
3179           _deleted_methods[_deleted_methods_length++] = old_method;
3180           ++oj;
3181         }
3182       }
3183     }
3184   }
3185   assert(_matching_methods_length + _deleted_methods_length == _old_methods->length(), "sanity");
3186   assert(_matching_methods_length + _added_methods_length == _new_methods->length(), "sanity");
3187 }
3188 
3189 
3190 void VM_RedefineClasses::swap_annotations(instanceKlassHandle the_class,
3191                                           instanceKlassHandle scratch_class) {
3192   // Since there is currently no rewriting of type annotations indexes
3193   // into the CP, we null out type annotations on scratch_class before
3194   // we swap annotations with the_class rather than facing the
3195   // possibility of shipping annotations with broken indexes to
3196   // Java-land.
3197   ClassLoaderData* loader_data = scratch_class->class_loader_data();
3198   AnnotationArray* new_class_type_annotations = scratch_class->class_type_annotations();
3199   if (new_class_type_annotations != NULL) {
3200     MetadataFactory::free_array<u1>(loader_data, new_class_type_annotations);
3201     scratch_class->annotations()->set_class_type_annotations(NULL);
3202   }
3203   Array<AnnotationArray*>* new_field_type_annotations = scratch_class->fields_type_annotations();
3204   if (new_field_type_annotations != NULL) {
3205     Annotations::free_contents(loader_data, new_field_type_annotations);
3206     scratch_class->annotations()->set_fields_type_annotations(NULL);
3207   }
3208 
3209   // Swap annotation fields values
3210   Annotations* old_annotations = the_class->annotations();
3211   the_class->set_annotations(scratch_class->annotations());
3212   scratch_class->set_annotations(old_annotations);
3213 }
3214 
3215 
3216 // Install the redefinition of a class:
3217 //    - house keeping (flushing breakpoints and caches, deoptimizing
3218 //      dependent compiled code)
3219 //    - replacing parts in the_class with parts from scratch_class
3220 //    - adding a weak reference to track the obsolete but interesting
3221 //      parts of the_class
3222 //    - adjusting constant pool caches and vtables in other classes
3223 //      that refer to methods in the_class. These adjustments use the
3224 //      ClassLoaderDataGraph::classes_do() facility which only allows
3225 //      a helper method to be specified. The interesting parameters
3226 //      that we would like to pass to the helper method are saved in
3227 //      static global fields in the VM operation.
3228 void VM_RedefineClasses::redefine_single_class(jclass the_jclass,
3229        Klass* scratch_class_oop, TRAPS) {
3230 
3231   HandleMark hm(THREAD);   // make sure handles from this call are freed
3232   RC_TIMER_START(_timer_rsc_phase1);
3233 
3234   instanceKlassHandle scratch_class(scratch_class_oop);
3235 
3236   oop the_class_mirror = JNIHandles::resolve_non_null(the_jclass);
3237   Klass* the_class_oop = java_lang_Class::as_Klass(the_class_mirror);
3238   instanceKlassHandle the_class = instanceKlassHandle(THREAD, the_class_oop);
3239 
3240   // Remove all breakpoints in methods of this class
3241   JvmtiBreakpoints& jvmti_breakpoints = JvmtiCurrentBreakpoints::get_jvmti_breakpoints();
3242   jvmti_breakpoints.clearall_in_class_at_safepoint(the_class_oop);
3243 
3244   // Deoptimize all compiled code that depends on this class
3245   flush_dependent_code(the_class, THREAD);
3246 
3247   _old_methods = the_class->methods();
3248   _new_methods = scratch_class->methods();
3249   _the_class_oop = the_class_oop;
3250   compute_added_deleted_matching_methods();
3251   update_jmethod_ids();
3252 
3253   // Attach new constant pool to the original klass. The original
3254   // klass still refers to the old constant pool (for now).
3255   scratch_class->constants()->set_pool_holder(the_class());
3256 
3257 #if 0
3258   // In theory, with constant pool merging in place we should be able
3259   // to save space by using the new, merged constant pool in place of
3260   // the old constant pool(s). By "pool(s)" I mean the constant pool in
3261   // the klass version we are replacing now and any constant pool(s) in
3262   // previous versions of klass. Nice theory, doesn't work in practice.
3263   // When this code is enabled, even simple programs throw NullPointer
3264   // exceptions. I'm guessing that this is caused by some constant pool
3265   // cache difference between the new, merged constant pool and the
3266   // constant pool that was just being used by the klass. I'm keeping
3267   // this code around to archive the idea, but the code has to remain
3268   // disabled for now.
3269 
3270   // Attach each old method to the new constant pool. This can be
3271   // done here since we are past the bytecode verification and
3272   // constant pool optimization phases.
3273   for (int i = _old_methods->length() - 1; i >= 0; i--) {
3274     Method* method = _old_methods->at(i);
3275     method->set_constants(scratch_class->constants());
3276   }
3277 
3278   {
3279     // walk all previous versions of the klass
3280     InstanceKlass *ik = (InstanceKlass *)the_class();
3281     PreviousVersionWalker pvw(ik);
3282     instanceKlassHandle ikh;
3283     do {
3284       ikh = pvw.next_previous_version();
3285       if (!ikh.is_null()) {
3286         ik = ikh();
3287 
3288         // attach previous version of klass to the new constant pool
3289         ik->set_constants(scratch_class->constants());
3290 
3291         // Attach each method in the previous version of klass to the
3292         // new constant pool
3293         Array<Method*>* prev_methods = ik->methods();
3294         for (int i = prev_methods->length() - 1; i >= 0; i--) {
3295           Method* method = prev_methods->at(i);
3296           method->set_constants(scratch_class->constants());
3297         }
3298       }
3299     } while (!ikh.is_null());
3300   }
3301 #endif
3302 
3303   // Replace methods and constantpool
3304   the_class->set_methods(_new_methods);
3305   scratch_class->set_methods(_old_methods);     // To prevent potential GCing of the old methods,
3306                                           // and to be able to undo operation easily.
3307 
3308   ConstantPool* old_constants = the_class->constants();
3309   the_class->set_constants(scratch_class->constants());
3310   scratch_class->set_constants(old_constants);  // See the previous comment.
3311 #if 0
3312   // We are swapping the guts of "the new class" with the guts of "the
3313   // class". Since the old constant pool has just been attached to "the
3314   // new class", it seems logical to set the pool holder in the old
3315   // constant pool also. However, doing this will change the observable
3316   // class hierarchy for any old methods that are still executing. A
3317   // method can query the identity of its "holder" and this query uses
3318   // the method's constant pool link to find the holder. The change in
3319   // holding class from "the class" to "the new class" can confuse
3320   // things.
3321   //
3322   // Setting the old constant pool's holder will also cause
3323   // verification done during vtable initialization below to fail.
3324   // During vtable initialization, the vtable's class is verified to be
3325   // a subtype of the method's holder. The vtable's class is "the
3326   // class" and the method's holder is gotten from the constant pool
3327   // link in the method itself. For "the class"'s directly implemented
3328   // methods, the method holder is "the class" itself (as gotten from
3329   // the new constant pool). The check works fine in this case. The
3330   // check also works fine for methods inherited from super classes.
3331   //
3332   // Miranda methods are a little more complicated. A miranda method is
3333   // provided by an interface when the class implementing the interface
3334   // does not provide its own method.  These interfaces are implemented
3335   // internally as an InstanceKlass. These special instanceKlasses
3336   // share the constant pool of the class that "implements" the
3337   // interface. By sharing the constant pool, the method holder of a
3338   // miranda method is the class that "implements" the interface. In a
3339   // non-redefine situation, the subtype check works fine. However, if
3340   // the old constant pool's pool holder is modified, then the check
3341   // fails because there is no class hierarchy relationship between the
3342   // vtable's class and "the new class".
3343 
3344   old_constants->set_pool_holder(scratch_class());
3345 #endif
3346 
3347   // track which methods are EMCP for add_previous_version() call below
3348   BitMap emcp_methods(_old_methods->length());
3349   int emcp_method_count = 0;
3350   emcp_methods.clear();  // clears 0..(length() - 1)
3351   check_methods_and_mark_as_obsolete(&emcp_methods, &emcp_method_count);
3352   transfer_old_native_function_registrations(the_class);
3353 
3354   // The class file bytes from before any retransformable agents mucked
3355   // with them was cached on the scratch class, move to the_class.
3356   // Note: we still want to do this if nothing needed caching since it
3357   // should get cleared in the_class too.
3358   if (the_class->get_cached_class_file_bytes() == 0) {
3359     // the_class doesn't have a cache yet so copy it
3360     the_class->set_cached_class_file(scratch_class->get_cached_class_file());
3361   }
3362 #ifndef PRODUCT
3363   else {
3364     assert(the_class->get_cached_class_file_bytes() ==
3365       scratch_class->get_cached_class_file_bytes(), "cache ptrs must match");
3366     assert(the_class->get_cached_class_file_len() ==
3367       scratch_class->get_cached_class_file_len(), "cache lens must match");
3368   }
3369 #endif
3370 
3371   // NULL out in scratch class to not delete twice.  The class to be redefined
3372   // always owns these bytes.
3373   scratch_class->set_cached_class_file(NULL);
3374 
3375   // Replace inner_classes
3376   Array<u2>* old_inner_classes = the_class->inner_classes();
3377   the_class->set_inner_classes(scratch_class->inner_classes());
3378   scratch_class->set_inner_classes(old_inner_classes);
3379 
3380   // Initialize the vtable and interface table after
3381   // methods have been rewritten
3382   {
3383     ResourceMark rm(THREAD);
3384     // no exception should happen here since we explicitly
3385     // do not check loader constraints.
3386     // compare_and_normalize_class_versions has already checked:
3387     //  - classloaders unchanged, signatures unchanged
3388     //  - all instanceKlasses for redefined classes reused & contents updated
3389     the_class->vtable()->initialize_vtable(false, THREAD);
3390     the_class->itable()->initialize_itable(false, THREAD);
3391     assert(!HAS_PENDING_EXCEPTION || (THREAD->pending_exception()->is_a(SystemDictionary::ThreadDeath_klass())), "redefine exception");
3392   }
3393 
3394   // Leave arrays of jmethodIDs and itable index cache unchanged
3395 
3396   // Copy the "source file name" attribute from new class version
3397   the_class->set_source_file_name_index(
3398     scratch_class->source_file_name_index());
3399 
3400   // Copy the "source debug extension" attribute from new class version
3401   the_class->set_source_debug_extension(
3402     scratch_class->source_debug_extension(),
3403     scratch_class->source_debug_extension() == NULL ? 0 :
3404     (int)strlen(scratch_class->source_debug_extension()));
3405 
3406   // Use of javac -g could be different in the old and the new
3407   if (scratch_class->access_flags().has_localvariable_table() !=
3408       the_class->access_flags().has_localvariable_table()) {
3409 
3410     AccessFlags flags = the_class->access_flags();
3411     if (scratch_class->access_flags().has_localvariable_table()) {
3412       flags.set_has_localvariable_table();
3413     } else {
3414       flags.clear_has_localvariable_table();
3415     }
3416     the_class->set_access_flags(flags);
3417   }
3418 
3419   swap_annotations(the_class, scratch_class);
3420 
3421   // Replace minor version number of class file
3422   u2 old_minor_version = the_class->minor_version();
3423   the_class->set_minor_version(scratch_class->minor_version());
3424   scratch_class->set_minor_version(old_minor_version);
3425 
3426   // Replace major version number of class file
3427   u2 old_major_version = the_class->major_version();
3428   the_class->set_major_version(scratch_class->major_version());
3429   scratch_class->set_major_version(old_major_version);
3430 
3431   // Replace CP indexes for class and name+type of enclosing method
3432   u2 old_class_idx  = the_class->enclosing_method_class_index();
3433   u2 old_method_idx = the_class->enclosing_method_method_index();
3434   the_class->set_enclosing_method_indices(
3435     scratch_class->enclosing_method_class_index(),
3436     scratch_class->enclosing_method_method_index());
3437   scratch_class->set_enclosing_method_indices(old_class_idx, old_method_idx);
3438 
3439   // keep track of previous versions of this class
3440   the_class->add_previous_version(scratch_class, &emcp_methods,
3441     emcp_method_count);
3442 
3443   RC_TIMER_STOP(_timer_rsc_phase1);
3444   RC_TIMER_START(_timer_rsc_phase2);
3445 
3446   // Adjust constantpool caches and vtables for all classes
3447   // that reference methods of the evolved class.
3448   AdjustCpoolCacheAndVtable adjust_cpool_cache_and_vtable(THREAD);
3449   ClassLoaderDataGraph::classes_do(&adjust_cpool_cache_and_vtable);
3450 
3451   // JSR-292 support
3452   MemberNameTable* mnt = the_class->member_names();
3453   if (mnt != NULL) {
3454     bool trace_name_printed = false;
3455     mnt->adjust_method_entries(_matching_old_methods,
3456                                _matching_new_methods,
3457                                _matching_methods_length,
3458                                &trace_name_printed);
3459   }
3460 
3461   // Fix Resolution Error table also to remove old constant pools
3462   SystemDictionary::delete_resolution_error(old_constants);
3463 
3464   if (the_class->oop_map_cache() != NULL) {
3465     // Flush references to any obsolete methods from the oop map cache
3466     // so that obsolete methods are not pinned.
3467     the_class->oop_map_cache()->flush_obsolete_entries();
3468   }
3469 
3470   // increment the classRedefinedCount field in the_class and in any
3471   // direct and indirect subclasses of the_class
3472   increment_class_counter((InstanceKlass *)the_class(), THREAD);
3473 
3474   // RC_TRACE macro has an embedded ResourceMark
3475   RC_TRACE_WITH_THREAD(0x00000001, THREAD,
3476     ("redefined name=%s, count=%d (avail_mem=" UINT64_FORMAT "K)",
3477     the_class->external_name(),
3478     java_lang_Class::classRedefinedCount(the_class_mirror),
3479     os::available_memory() >> 10));
3480 
3481   RC_TIMER_STOP(_timer_rsc_phase2);
3482 } // end redefine_single_class()
3483 
3484 
3485 // Increment the classRedefinedCount field in the specific InstanceKlass
3486 // and in all direct and indirect subclasses.
3487 void VM_RedefineClasses::increment_class_counter(InstanceKlass *ik, TRAPS) {
3488   oop class_mirror = ik->java_mirror();
3489   Klass* class_oop = java_lang_Class::as_Klass(class_mirror);
3490   int new_count = java_lang_Class::classRedefinedCount(class_mirror) + 1;
3491   java_lang_Class::set_classRedefinedCount(class_mirror, new_count);
3492 
3493   if (class_oop != _the_class_oop) {
3494     // _the_class_oop count is printed at end of redefine_single_class()
3495     RC_TRACE_WITH_THREAD(0x00000008, THREAD,
3496       ("updated count in subclass=%s to %d", ik->external_name(), new_count));
3497   }
3498 
3499   for (Klass *subk = ik->subklass(); subk != NULL;
3500        subk = subk->next_sibling()) {
3501     if (subk->oop_is_instance()) {
3502       // Only update instanceKlasses
3503       InstanceKlass *subik = (InstanceKlass*)subk;
3504       // recursively do subclasses of the current subclass
3505       increment_class_counter(subik, THREAD);
3506     }
3507   }
3508 }
3509 
3510 void VM_RedefineClasses::CheckClass::do_klass(Klass* k) {
3511   bool no_old_methods = true;  // be optimistic
3512 
3513   // Both array and instance classes have vtables.
3514   // a vtable should never contain old or obsolete methods
3515   ResourceMark rm(_thread);
3516   if (k->vtable_length() > 0 &&
3517       !k->vtable()->check_no_old_or_obsolete_entries()) {
3518     if (RC_TRACE_ENABLED(0x00004000)) {
3519       RC_TRACE_WITH_THREAD(0x00004000, _thread,
3520         ("klassVtable::check_no_old_or_obsolete_entries failure"
3521          " -- OLD or OBSOLETE method found -- class: %s",
3522          k->signature_name()));
3523       k->vtable()->dump_vtable();
3524     }
3525     no_old_methods = false;
3526   }
3527 
3528   if (k->oop_is_instance()) {
3529     HandleMark hm(_thread);
3530     InstanceKlass *ik = InstanceKlass::cast(k);
3531 
3532     // an itable should never contain old or obsolete methods
3533     if (ik->itable_length() > 0 &&
3534         !ik->itable()->check_no_old_or_obsolete_entries()) {
3535       if (RC_TRACE_ENABLED(0x00004000)) {
3536         RC_TRACE_WITH_THREAD(0x00004000, _thread,
3537           ("klassItable::check_no_old_or_obsolete_entries failure"
3538            " -- OLD or OBSOLETE method found -- class: %s",
3539            ik->signature_name()));
3540         ik->itable()->dump_itable();
3541       }
3542       no_old_methods = false;
3543     }
3544 
3545     // the constant pool cache should never contain old or obsolete methods
3546     if (ik->constants() != NULL &&
3547         ik->constants()->cache() != NULL &&
3548         !ik->constants()->cache()->check_no_old_or_obsolete_entries()) {
3549       if (RC_TRACE_ENABLED(0x00004000)) {
3550         RC_TRACE_WITH_THREAD(0x00004000, _thread,
3551           ("cp-cache::check_no_old_or_obsolete_entries failure"
3552            " -- OLD or OBSOLETE method found -- class: %s",
3553            ik->signature_name()));
3554         ik->constants()->cache()->dump_cache();
3555       }
3556       no_old_methods = false;
3557     }
3558   }
3559 
3560   // print and fail guarantee if old methods are found.
3561   if (!no_old_methods) {
3562     if (RC_TRACE_ENABLED(0x00004000)) {
3563       dump_methods();
3564     } else {
3565       tty->print_cr("INFO: use the '-XX:TraceRedefineClasses=16384' option "
3566         "to see more info about the following guarantee() failure.");
3567     }
3568     guarantee(false, "OLD and/or OBSOLETE method(s) found");
3569   }
3570 }
3571 
3572 
3573 void VM_RedefineClasses::dump_methods() {
3574   int j;
3575   RC_TRACE(0x00004000, ("_old_methods --"));
3576   for (j = 0; j < _old_methods->length(); ++j) {
3577     Method* m = _old_methods->at(j);
3578     RC_TRACE_NO_CR(0x00004000, ("%4d  (%5d)  ", j, m->vtable_index()));
3579     m->access_flags().print_on(tty);
3580     tty->print(" --  ");
3581     m->print_name(tty);
3582     tty->cr();
3583   }
3584   RC_TRACE(0x00004000, ("_new_methods --"));
3585   for (j = 0; j < _new_methods->length(); ++j) {
3586     Method* m = _new_methods->at(j);
3587     RC_TRACE_NO_CR(0x00004000, ("%4d  (%5d)  ", j, m->vtable_index()));
3588     m->access_flags().print_on(tty);
3589     tty->print(" --  ");
3590     m->print_name(tty);
3591     tty->cr();
3592   }
3593   RC_TRACE(0x00004000, ("_matching_(old/new)_methods --"));
3594   for (j = 0; j < _matching_methods_length; ++j) {
3595     Method* m = _matching_old_methods[j];
3596     RC_TRACE_NO_CR(0x00004000, ("%4d  (%5d)  ", j, m->vtable_index()));
3597     m->access_flags().print_on(tty);
3598     tty->print(" --  ");
3599     m->print_name(tty);
3600     tty->cr();
3601     m = _matching_new_methods[j];
3602     RC_TRACE_NO_CR(0x00004000, ("      (%5d)  ", m->vtable_index()));
3603     m->access_flags().print_on(tty);
3604     tty->cr();
3605   }
3606   RC_TRACE(0x00004000, ("_deleted_methods --"));
3607   for (j = 0; j < _deleted_methods_length; ++j) {
3608     Method* m = _deleted_methods[j];
3609     RC_TRACE_NO_CR(0x00004000, ("%4d  (%5d)  ", j, m->vtable_index()));
3610     m->access_flags().print_on(tty);
3611     tty->print(" --  ");
3612     m->print_name(tty);
3613     tty->cr();
3614   }
3615   RC_TRACE(0x00004000, ("_added_methods --"));
3616   for (j = 0; j < _added_methods_length; ++j) {
3617     Method* m = _added_methods[j];
3618     RC_TRACE_NO_CR(0x00004000, ("%4d  (%5d)  ", j, m->vtable_index()));
3619     m->access_flags().print_on(tty);
3620     tty->print(" --  ");
3621     m->print_name(tty);
3622     tty->cr();
3623   }
3624 }
--- EOF ---