1 /*
   2  * Copyright (c) 1997, 2019, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "jvm.h"
  27 #include "classfile/classLoaderDataGraph.hpp"
  28 #include "classfile/javaClasses.hpp"
  29 #include "classfile/systemDictionary.hpp"
  30 #include "classfile/vmSymbols.hpp"
  31 #include "interpreter/linkResolver.hpp"
  32 #include "logging/log.hpp"
  33 #include "logging/logStream.hpp"
  34 #include "memory/metaspaceShared.hpp"
  35 #include "memory/resourceArea.hpp"
  36 #include "memory/universe.hpp"
  37 #include "oops/instanceKlass.hpp"
  38 #include "oops/klassVtable.hpp"
  39 #include "oops/method.hpp"
  40 #include "oops/objArrayOop.hpp"
  41 #include "oops/oop.inline.hpp"
  42 #include "runtime/arguments.hpp"
  43 #include "runtime/flags/flagSetting.hpp"
  44 #include "runtime/handles.inline.hpp"
  45 #include "runtime/safepointVerifiers.hpp"
  46 #include "utilities/copy.hpp"
  47 
  48 inline InstanceKlass* klassVtable::ik() const {
  49   return InstanceKlass::cast(_klass);
  50 }
  51 
  52 bool klassVtable::is_preinitialized_vtable() {
  53   return _klass->is_shared() && !MetaspaceShared::remapped_readwrite();
  54 }
  55 
  56 
  57 // this function computes the vtable size (including the size needed for miranda
  58 // methods) and the number of miranda methods in this class.
  59 // Note on Miranda methods: Let's say there is a class C that implements
  60 // interface I, and none of C's superclasses implements I.
  61 // Let's say there is an abstract method m in I that neither C
  62 // nor any of its super classes implement (i.e there is no method of any access,
  63 // with the same name and signature as m), then m is a Miranda method which is
  64 // entered as a public abstract method in C's vtable.  From then on it should
  65 // treated as any other public method in C for method over-ride purposes.
  66 void klassVtable::compute_vtable_size_and_num_mirandas(
  67     int* vtable_length_ret, int* num_new_mirandas,
  68     GrowableArray<Method*>* all_mirandas, const Klass* super,
  69     Array<Method*>* methods, AccessFlags class_flags, bool is_class_sealed, u2 major_version,
  70     Handle classloader, Symbol* classname, Array<InstanceKlass*>* local_interfaces,
  71     TRAPS) {
  72   NoSafepointVerifier nsv;
  73 
  74   // set up default result values
  75   int vtable_length = 0;
  76 
  77   // start off with super's vtable length
  78   vtable_length = super == NULL ? 0 : super->vtable_length();
  79 
  80   // go thru each method in the methods table to see if it needs a new entry
  81   int len = methods->length();
  82   for (int i = 0; i < len; i++) {
  83     assert(methods->at(i)->is_method(), "must be a Method*");
  84     methodHandle mh(THREAD, methods->at(i));
  85 
  86     if (needs_new_vtable_entry(mh, super, classloader, classname, class_flags, is_class_sealed, major_version, THREAD)) {
  87       assert(!methods->at(i)->is_private(), "private methods should not need a vtable entry");
  88       vtable_length += vtableEntry::size(); // we need a new entry
  89     }
  90   }
  91 
  92   GrowableArray<Method*> new_mirandas(20);
  93   // compute the number of mirandas methods that must be added to the end
  94   get_mirandas(&new_mirandas, all_mirandas, super, methods, NULL, local_interfaces,
  95                class_flags.is_interface());
  96   *num_new_mirandas = new_mirandas.length();
  97 
  98   // Interfaces do not need interface methods in their vtables
  99   // This includes miranda methods and during later processing, default methods
 100   if (!class_flags.is_interface()) {
 101      vtable_length += *num_new_mirandas * vtableEntry::size();
 102   }
 103 
 104   if (Universe::is_bootstrapping() && vtable_length == 0) {
 105     // array classes don't have their superclass set correctly during
 106     // bootstrapping
 107     vtable_length = Universe::base_vtable_size();
 108   }
 109 
 110   if (super == NULL && vtable_length != Universe::base_vtable_size()) {
 111     if (Universe::is_bootstrapping()) {
 112       // Someone is attempting to override java.lang.Object incorrectly on the
 113       // bootclasspath.  The JVM cannot recover from this error including throwing
 114       // an exception
 115       vm_exit_during_initialization("Incompatible definition of java.lang.Object");
 116     } else {
 117       // Someone is attempting to redefine java.lang.Object incorrectly.  The
 118       // only way this should happen is from
 119       // SystemDictionary::resolve_from_stream(), which will detect this later
 120       // and throw a security exception.  So don't assert here to let
 121       // the exception occur.
 122       vtable_length = Universe::base_vtable_size();
 123     }
 124   }
 125   assert(vtable_length % vtableEntry::size() == 0, "bad vtable length");
 126   assert(vtable_length >= Universe::base_vtable_size(), "vtable too small");
 127 
 128   *vtable_length_ret = vtable_length;
 129 }
 130 
 131 int klassVtable::index_of(Method* m, int len) const {
 132   assert(m->has_vtable_index(), "do not ask this of non-vtable methods");
 133   return m->vtable_index();
 134 }
 135 
 136 // Copy super class's vtable to the first part (prefix) of this class's vtable,
 137 // and return the number of entries copied.  Expects that 'super' is the Java
 138 // super class (arrays can have "array" super classes that must be skipped).
 139 int klassVtable::initialize_from_super(Klass* super) {
 140   if (super == NULL) {
 141     return 0;
 142   } else if (is_preinitialized_vtable()) {
 143     // A shared class' vtable is preinitialized at dump time. No need to copy
 144     // methods from super class for shared class, as that was already done
 145     // during archiving time. However, if Jvmti has redefined a class,
 146     // copy super class's vtable in case the super class has changed.
 147     return super->vtable().length();
 148   } else {
 149     // copy methods from superKlass
 150     klassVtable superVtable = super->vtable();
 151     assert(superVtable.length() <= _length, "vtable too short");
 152 #ifdef ASSERT
 153     superVtable.verify(tty, true);
 154 #endif
 155     superVtable.copy_vtable_to(table());
 156     if (log_develop_is_enabled(Trace, vtables)) {
 157       ResourceMark rm;
 158       log_develop_trace(vtables)("copy vtable from %s to %s size %d",
 159                                  super->internal_name(), klass()->internal_name(),
 160                                  _length);
 161     }
 162     return superVtable.length();
 163   }
 164 }
 165 
 166 //
 167 // Revised lookup semantics   introduced 1.3 (Kestrel beta)
 168 void klassVtable::initialize_vtable(bool checkconstraints, TRAPS) {
 169 
 170   // Note:  Arrays can have intermediate array supers.  Use java_super to skip them.
 171   InstanceKlass* super = _klass->java_super();
 172   int nofNewEntries = 0;
 173 
 174   bool is_shared = _klass->is_shared();
 175 
 176   if (!_klass->is_array_klass()) {
 177     ResourceMark rm(THREAD);
 178     log_develop_debug(vtables)("Initializing: %s", _klass->name()->as_C_string());
 179   }
 180 
 181 #ifdef ASSERT
 182   oop* end_of_obj = (oop*)_klass + _klass->size();
 183   oop* end_of_vtable = (oop*)&table()[_length];
 184   assert(end_of_vtable <= end_of_obj, "vtable extends beyond end");
 185 #endif
 186 
 187   if (Universe::is_bootstrapping()) {
 188     assert(!is_shared, "sanity");
 189     // just clear everything
 190     for (int i = 0; i < _length; i++) table()[i].clear();
 191     return;
 192   }
 193 
 194   int super_vtable_len = initialize_from_super(super);
 195   if (_klass->is_array_klass()) {
 196     assert(super_vtable_len == _length, "arrays shouldn't introduce new methods");
 197   } else {
 198     assert(_klass->is_instance_klass(), "must be InstanceKlass");
 199 
 200     Array<Method*>* methods = ik()->methods();
 201     int len = methods->length();
 202     int initialized = super_vtable_len;
 203 
 204     // Check each of this class's methods against super;
 205     // if override, replace in copy of super vtable, otherwise append to end
 206     for (int i = 0; i < len; i++) {
 207       // update_inherited_vtable can stop for gc - ensure using handles
 208       HandleMark hm(THREAD);
 209       assert(methods->at(i)->is_method(), "must be a Method*");
 210       methodHandle mh(THREAD, methods->at(i));
 211 
 212       bool needs_new_entry = update_inherited_vtable(ik(), mh, super_vtable_len, -1, checkconstraints, CHECK);
 213 
 214       if (needs_new_entry) {
 215         put_method_at(mh(), initialized);
 216         mh()->set_vtable_index(initialized); // set primary vtable index
 217         initialized++;
 218       }
 219     }
 220 
 221     // update vtable with default_methods
 222     Array<Method*>* default_methods = ik()->default_methods();
 223     if (default_methods != NULL) {
 224       len = default_methods->length();
 225       if (len > 0) {
 226         Array<int>* def_vtable_indices = NULL;
 227         if ((def_vtable_indices = ik()->default_vtable_indices()) == NULL) {
 228           assert(!is_shared, "shared class def_vtable_indices does not exist");
 229           def_vtable_indices = ik()->create_new_default_vtable_indices(len, CHECK);
 230         } else {
 231           assert(def_vtable_indices->length() == len, "reinit vtable len?");
 232         }
 233         for (int i = 0; i < len; i++) {
 234           HandleMark hm(THREAD);
 235           assert(default_methods->at(i)->is_method(), "must be a Method*");
 236           methodHandle mh(THREAD, default_methods->at(i));
 237           assert(!mh->is_private(), "private interface method in the default method list");
 238           bool needs_new_entry = update_inherited_vtable(ik(), mh, super_vtable_len, i, checkconstraints, CHECK);
 239 
 240           // needs new entry
 241           if (needs_new_entry) {
 242             put_method_at(mh(), initialized);
 243             if (is_preinitialized_vtable()) {
 244               // At runtime initialize_vtable is rerun for a shared class
 245               // (loaded by the non-boot loader) as part of link_class_impl().
 246               // The dumptime vtable index should be the same as the runtime index.
 247               assert(def_vtable_indices->at(i) == initialized,
 248                      "dump time vtable index is different from runtime index");
 249             } else {
 250               def_vtable_indices->at_put(i, initialized); //set vtable index
 251             }
 252             initialized++;
 253           }
 254         }
 255       }
 256     }
 257 
 258     // add miranda methods; it will also return the updated initialized
 259     // Interfaces do not need interface methods in their vtables
 260     // This includes miranda methods and during later processing, default methods
 261     if (!ik()->is_interface()) {
 262       initialized = fill_in_mirandas(initialized, THREAD);
 263     }
 264 
 265     // In class hierarchies where the accessibility is not increasing (i.e., going from private ->
 266     // package_private -> public/protected), the vtable might actually be smaller than our initial
 267     // calculation, for classfile versions for which we do not do transitive override
 268     // calculations.
 269     if (ik()->major_version() >= VTABLE_TRANSITIVE_OVERRIDE_VERSION) {
 270       assert(initialized == _length, "vtable initialization failed");
 271     } else {
 272       assert(initialized <= _length, "vtable initialization failed");
 273       for(;initialized < _length; initialized++) {
 274         table()[initialized].clear();
 275       }
 276     }
 277     NOT_PRODUCT(verify(tty, true));
 278   }
 279 }
 280 
 281 // Called for cases where a method does not override its superclass' vtable entry
 282 // For bytecodes not produced by javac together it is possible that a method does not override
 283 // the superclass's method, but might indirectly override a super-super class's vtable entry
 284 // If none found, return a null superk, else return the superk of the method this does override
 285 // For public and protected methods: if they override a superclass, they will
 286 // also be overridden themselves appropriately.
 287 // Private methods do not override, and are not overridden and are not in the vtable.
 288 // Package Private methods are trickier:
 289 // e.g. P1.A, pub m
 290 // P2.B extends A, package private m
 291 // P1.C extends B, public m
 292 // P1.C.m needs to override P1.A.m and can not override P2.B.m
 293 // Therefore: all package private methods need their own vtable entries for
 294 // them to be the root of an inheritance overriding decision
 295 // Package private methods may also override other vtable entries
 296 InstanceKlass* klassVtable::find_transitive_override(InstanceKlass* initialsuper, const methodHandle& target_method,
 297                             int vtable_index, Handle target_loader, Symbol* target_classname, Thread * THREAD) {
 298   InstanceKlass* superk = initialsuper;
 299   while (superk != NULL && superk->super() != NULL) {
 300     InstanceKlass* supersuperklass = InstanceKlass::cast(superk->super());
 301     klassVtable ssVtable = supersuperklass->vtable();
 302     if (vtable_index < ssVtable.length()) {
 303       Method* super_method = ssVtable.method_at(vtable_index);
 304 #ifndef PRODUCT
 305       Symbol* name= target_method()->name();
 306       Symbol* signature = target_method()->signature();
 307       assert(super_method->name() == name && super_method->signature() == signature, "vtable entry name/sig mismatch");
 308 #endif
 309       if (supersuperklass->is_override(super_method, target_loader, target_classname, THREAD)) {
 310         if (log_develop_is_enabled(Trace, vtables)) {
 311           ResourceMark rm(THREAD);
 312           LogTarget(Trace, vtables) lt;
 313           LogStream ls(lt);
 314           char* sig = target_method()->name_and_sig_as_C_string();
 315           ls.print("transitive overriding superclass %s with %s index %d, original flags: ",
 316                        supersuperklass->internal_name(),
 317                        sig, vtable_index);
 318           super_method->print_linkage_flags(&ls);
 319           ls.print("overriders flags: ");
 320           target_method->print_linkage_flags(&ls);
 321           ls.cr();
 322         }
 323 
 324         break; // return found superk
 325       }
 326     } else  {
 327       // super class has no vtable entry here, stop transitive search
 328       superk = (InstanceKlass*)NULL;
 329       break;
 330     }
 331     // if no override found yet, continue to search up
 332     superk = superk->super() == NULL ? NULL : InstanceKlass::cast(superk->super());
 333   }
 334 
 335   return superk;
 336 }
 337 
 338 static void log_vtables(int i, bool overrides, const methodHandle& target_method,
 339                         Klass* target_klass, Method* super_method,
 340                         Thread* thread) {
 341 #ifndef PRODUCT
 342   if (log_develop_is_enabled(Trace, vtables)) {
 343     ResourceMark rm(thread);
 344     LogTarget(Trace, vtables) lt;
 345     LogStream ls(lt);
 346     char* sig = target_method()->name_and_sig_as_C_string();
 347     if (overrides) {
 348       ls.print("overriding with %s index %d, original flags: ",
 349                    sig, i);
 350     } else {
 351       ls.print("NOT overriding with %s index %d, original flags: ",
 352                    sig, i);
 353     }
 354     super_method->print_linkage_flags(&ls);
 355     ls.print("overriders flags: ");
 356     target_method->print_linkage_flags(&ls);
 357     ls.cr();
 358   }
 359 #endif
 360 }
 361 
 362 // Update child's copy of super vtable for overrides
 363 // OR return true if a new vtable entry is required.
 364 // Only called for InstanceKlass's, i.e. not for arrays
 365 // If that changed, could not use _klass as handle for klass
 366 bool klassVtable::update_inherited_vtable(InstanceKlass* klass, const methodHandle& target_method,
 367                                           int super_vtable_len, int default_index,
 368                                           bool checkconstraints, TRAPS) {
 369   ResourceMark rm(THREAD);
 370   bool allocate_new = true;
 371   assert(klass->is_instance_klass(), "must be InstanceKlass");
 372 
 373   Array<int>* def_vtable_indices = NULL;
 374   bool is_default = false;
 375 
 376   // default methods are non-private concrete methods in superinterfaces which are added
 377   // to the vtable with their real method_holder.
 378   // Since vtable and itable indices share the same storage, don't touch
 379   // the default method's real vtable/itable index.
 380   // default_vtable_indices stores the vtable value relative to this inheritor
 381   if (default_index >= 0 ) {
 382     is_default = true;
 383     def_vtable_indices = klass->default_vtable_indices();
 384     assert(!target_method()->is_private(), "private interface method flagged as default");
 385     assert(def_vtable_indices != NULL, "def vtable alloc?");
 386     assert(default_index <= def_vtable_indices->length(), "def vtable len?");
 387   } else {
 388     assert(klass == target_method()->method_holder(), "caller resp.");
 389     // Initialize the method's vtable index to "nonvirtual".
 390     // If we allocate a vtable entry, we will update it to a non-negative number.
 391     target_method()->set_vtable_index(Method::nonvirtual_vtable_index);
 392   }
 393 
 394   // Private, static and <init> methods are never in
 395   if (target_method()->is_private() || target_method()->is_static() ||
 396       (target_method()->name()->fast_compare(vmSymbols::object_initializer_name()) == 0)) {
 397     return false;
 398   }
 399 
 400   if (target_method->is_final_method(klass->access_flags(), klass->is_sealed())) {
 401     // a final method never needs a new entry; final methods can be statically
 402     // resolved and they have to be present in the vtable only if they override
 403     // a super's method, in which case they re-use its entry
 404     allocate_new = false;
 405   } else if (klass->is_interface()) {
 406     allocate_new = false;  // see note below in needs_new_vtable_entry
 407     // An interface never allocates new vtable slots, only inherits old ones.
 408     // This method will either be assigned its own itable index later,
 409     // or be assigned an inherited vtable index in the loop below.
 410     // default methods inherited by classes store their vtable indices
 411     // in the inheritor's default_vtable_indices.
 412     // default methods inherited by interfaces may already have a
 413     // valid itable index, if so, don't change it.
 414     // Overpass methods in an interface will be assigned an itable index later
 415     // by an inheriting class.
 416     if ((!is_default || !target_method()->has_itable_index())) {
 417       target_method()->set_vtable_index(Method::pending_itable_index);
 418     }
 419   }
 420 
 421   // we need a new entry if there is no superclass
 422   Klass* super = klass->super();
 423   if (super == NULL) {
 424     return allocate_new;
 425   }
 426 
 427   // search through the vtable and update overridden entries
 428   // Since check_signature_loaders acquires SystemDictionary_lock
 429   // which can block for gc, once we are in this loop, use handles
 430   // For classfiles built with >= jdk7, we now look for transitive overrides
 431 
 432   Symbol* name = target_method()->name();
 433   Symbol* signature = target_method()->signature();
 434 
 435   Klass* target_klass = target_method()->method_holder();
 436   if (target_klass == NULL) {
 437     target_klass = _klass;
 438   }
 439 
 440   Handle target_loader(THREAD, target_klass->class_loader());
 441 
 442   Symbol* target_classname = target_klass->name();
 443   for(int i = 0; i < super_vtable_len; i++) {
 444     Method* super_method;
 445     if (is_preinitialized_vtable()) {
 446       // If this is a shared class, the vtable is already in the final state (fully
 447       // initialized). Need to look at the super's vtable.
 448       klassVtable superVtable = super->vtable();
 449       super_method = superVtable.method_at(i);
 450     } else {
 451       super_method = method_at(i);
 452     }
 453     // Check if method name matches.  Ignore match if klass is an interface and the
 454     // matching method is a non-public java.lang.Object method.  (See JVMS 5.4.3.4)
 455     // This is safe because the method at this slot should never get invoked.
 456     // (TBD: put in a method to throw NoSuchMethodError if this slot is ever used.)
 457     if (super_method->name() == name && super_method->signature() == signature &&
 458         (!_klass->is_interface() ||
 459          !SystemDictionary::is_nonpublic_Object_method(super_method))) {
 460 
 461       // get super_klass for method_holder for the found method
 462       InstanceKlass* super_klass =  super_method->method_holder();
 463 
 464       // Whether the method is being overridden
 465       bool overrides = false;
 466 
 467       // private methods are also never overridden
 468       if (!super_method->is_private() &&
 469           (is_default
 470           || ((super_klass->is_override(super_method, target_loader, target_classname, THREAD))
 471           || ((klass->major_version() >= VTABLE_TRANSITIVE_OVERRIDE_VERSION)
 472           && ((super_klass = find_transitive_override(super_klass,
 473                              target_method, i, target_loader,
 474                              target_classname, THREAD))
 475                              != (InstanceKlass*)NULL)))))
 476         {
 477         // Package private methods always need a new entry to root their own
 478         // overriding. They may also override other methods.
 479         if (!target_method()->is_package_private()) {
 480           allocate_new = false;
 481         }
 482 
 483         // Do not check loader constraints for overpass methods because overpass
 484         // methods are created by the jvm to throw exceptions.
 485         if (checkconstraints && !target_method()->is_overpass()) {
 486           // Override vtable entry if passes loader constraint check
 487           // if loader constraint checking requested
 488           // No need to visit his super, since he and his super
 489           // have already made any needed loader constraints.
 490           // Since loader constraints are transitive, it is enough
 491           // to link to the first super, and we get all the others.
 492           Handle super_loader(THREAD, super_klass->class_loader());
 493 
 494           if (!oopDesc::equals(target_loader(), super_loader())) {
 495             ResourceMark rm(THREAD);
 496             Symbol* failed_type_symbol =
 497               SystemDictionary::check_signature_loaders(signature, target_loader,
 498                                                         super_loader, true,
 499                                                         CHECK_(false));
 500             if (failed_type_symbol != NULL) {
 501               stringStream ss;
 502               ss.print("loader constraint violation for class %s: when selecting "
 503                        "overriding method '", klass->external_name());
 504               target_method()->print_external_name(&ss),
 505               ss.print("' the class loader %s of the "
 506                        "selected method's type %s, and the class loader %s for its super "
 507                        "type %s have different Class objects for the type %s used in the signature (%s; %s)",
 508                        target_klass->class_loader_data()->loader_name_and_id(),
 509                        target_klass->external_name(),
 510                        super_klass->class_loader_data()->loader_name_and_id(),
 511                        super_klass->external_name(),
 512                        failed_type_symbol->as_klass_external_name(),
 513                        target_klass->class_in_module_of_loader(false, true),
 514                        super_klass->class_in_module_of_loader(false, true));
 515               THROW_MSG_(vmSymbols::java_lang_LinkageError(), ss.as_string(), false);
 516             }
 517           }
 518         }
 519 
 520         put_method_at(target_method(), i);
 521         overrides = true;
 522         if (!is_default) {
 523           target_method()->set_vtable_index(i);
 524         } else {
 525           if (def_vtable_indices != NULL) {
 526             if (is_preinitialized_vtable()) {
 527               // At runtime initialize_vtable is rerun as part of link_class_impl()
 528               // for a shared class loaded by the non-boot loader.
 529               // The dumptime vtable index should be the same as the runtime index.
 530               assert(def_vtable_indices->at(default_index) == i,
 531                      "dump time vtable index is different from runtime index");
 532             } else {
 533               def_vtable_indices->at_put(default_index, i);
 534             }
 535           }
 536           assert(super_method->is_default_method() || super_method->is_overpass()
 537                  || super_method->is_abstract(), "default override error");
 538         }
 539       } else {
 540         overrides = false;
 541       }
 542       log_vtables(i, overrides, target_method, target_klass, super_method, THREAD);
 543     }
 544   }
 545   return allocate_new;
 546 }
 547 
 548 void klassVtable::put_method_at(Method* m, int index) {
 549   assert(!m->is_private(), "private methods should not be in vtable");
 550   if (is_preinitialized_vtable()) {
 551     // At runtime initialize_vtable is rerun as part of link_class_impl()
 552     // for shared class loaded by the non-boot loader to obtain the loader
 553     // constraints based on the runtime classloaders' context. The dumptime
 554     // method at the vtable index should be the same as the runtime method.
 555     assert(table()[index].method() == m,
 556            "archived method is different from the runtime method");
 557   } else {
 558     if (log_develop_is_enabled(Trace, vtables)) {
 559       ResourceMark rm;
 560       LogTarget(Trace, vtables) lt;
 561       LogStream ls(lt);
 562       const char* sig = (m != NULL) ? m->name_and_sig_as_C_string() : "<NULL>";
 563       ls.print("adding %s at index %d, flags: ", sig, index);
 564       if (m != NULL) {
 565         m->print_linkage_flags(&ls);
 566       }
 567       ls.cr();
 568     }
 569     table()[index].set(m);
 570   }
 571 }
 572 
 573 // Find out if a method "m" with superclass "super", loader "classloader" and
 574 // name "classname" needs a new vtable entry.  Let P be a class package defined
 575 // by "classloader" and "classname".
 576 // NOTE: The logic used here is very similar to the one used for computing
 577 // the vtables indices for a method. We cannot directly use that function because,
 578 // we allocate the InstanceKlass at load time, and that requires that the
 579 // superclass has been loaded.
 580 // However, the vtable entries are filled in at link time, and therefore
 581 // the superclass' vtable may not yet have been filled in.
 582 bool klassVtable::needs_new_vtable_entry(const methodHandle& target_method,
 583                                          const Klass* super,
 584                                          Handle classloader,
 585                                          Symbol* classname,
 586                                          AccessFlags class_flags,
 587                                          bool is_sealed,
 588                                          u2 major_version,
 589                                          TRAPS) {
 590   if (class_flags.is_interface()) {
 591     // Interfaces do not use vtables, except for java.lang.Object methods,
 592     // so there is no point to assigning
 593     // a vtable index to any of their local methods.  If we refrain from doing this,
 594     // we can use Method::_vtable_index to hold the itable index
 595     return false;
 596   }
 597 
 598   if (target_method->is_final_method(class_flags, is_sealed) ||
 599       // a final method never needs a new entry; final methods can be statically
 600       // resolved and they have to be present in the vtable only if they override
 601       // a super's method, in which case they re-use its entry
 602       (target_method()->is_private()) ||
 603       // private methods don't need to be in vtable
 604       (target_method()->is_static()) ||
 605       // static methods don't need to be in vtable
 606       (target_method()->name()->fast_compare(vmSymbols::object_initializer_name()) == 0)
 607       // <init> is never called dynamically-bound
 608       ) {
 609     return false;
 610   }
 611 
 612   // Concrete interface methods do not need new entries, they override
 613   // abstract method entries using default inheritance rules
 614   if (target_method()->method_holder() != NULL &&
 615       target_method()->method_holder()->is_interface()  &&
 616       !target_method()->is_abstract()) {
 617     assert(target_method()->is_default_method(),
 618            "unexpected interface method type");
 619     return false;
 620   }
 621 
 622   // we need a new entry if there is no superclass
 623   if (super == NULL) {
 624     return true;
 625   }
 626 
 627   // Package private methods always need a new entry to root their own
 628   // overriding. This allows transitive overriding to work.
 629   if (target_method()->is_package_private()) {
 630     return true;
 631   }
 632 
 633   // search through the super class hierarchy to see if we need
 634   // a new entry
 635   ResourceMark rm;
 636   Symbol* name = target_method()->name();
 637   Symbol* signature = target_method()->signature();
 638   const Klass* k = super;
 639   Method* super_method = NULL;
 640   InstanceKlass *holder = NULL;
 641   Method* recheck_method =  NULL;
 642   while (k != NULL) {
 643     // lookup through the hierarchy for a method with matching name and sign.
 644     super_method = InstanceKlass::cast(k)->lookup_method(name, signature);
 645     if (super_method == NULL) {
 646       break; // we still have to search for a matching miranda method
 647     }
 648     // get the class holding the matching method
 649     // make sure you use that class for is_override
 650     InstanceKlass* superk = super_method->method_holder();
 651     // we want only instance method matches
 652     // ignore private methods found via lookup_method since they do not participate in overriding,
 653     // and since we do override around them: e.g. a.m pub/b.m private/c.m pub,
 654     // ignore private, c.m pub does override a.m pub
 655     // For classes that were not javac'd together, we also do transitive overriding around
 656     // methods that have less accessibility
 657     if ((!super_method->is_static()) &&
 658        (!super_method->is_private())) {
 659       if (superk->is_override(super_method, classloader, classname, THREAD)) {
 660         return false;
 661       // else keep looking for transitive overrides
 662       }
 663     }
 664 
 665     // Start with lookup result and continue to search up, for versions supporting transitive override
 666     if (major_version >= VTABLE_TRANSITIVE_OVERRIDE_VERSION) {
 667       k = superk->super(); // haven't found an override match yet; continue to look
 668     } else {
 669       break;
 670     }
 671   }
 672 
 673   // if the target method is public or protected it may have a matching
 674   // miranda method in the super, whose entry it should re-use.
 675   // Actually, to handle cases that javac would not generate, we need
 676   // this check for all access permissions.
 677   const InstanceKlass *sk = InstanceKlass::cast(super);
 678   if (sk->has_miranda_methods()) {
 679     if (sk->lookup_method_in_all_interfaces(name, signature, Klass::find_defaults) != NULL) {
 680       return false;  // found a matching miranda; we do not need a new entry
 681     }
 682   }
 683   return true; // found no match; we need a new entry
 684 }
 685 
 686 // Support for miranda methods
 687 
 688 // get the vtable index of a miranda method with matching "name" and "signature"
 689 int klassVtable::index_of_miranda(Symbol* name, Symbol* signature) {
 690   // search from the bottom, might be faster
 691   for (int i = (length() - 1); i >= 0; i--) {
 692     Method* m = table()[i].method();
 693     if (is_miranda_entry_at(i) &&
 694         m->name() == name && m->signature() == signature) {
 695       return i;
 696     }
 697   }
 698   return Method::invalid_vtable_index;
 699 }
 700 
 701 // check if an entry at an index is miranda
 702 // requires that method m at entry be declared ("held") by an interface.
 703 bool klassVtable::is_miranda_entry_at(int i) {
 704   Method* m = method_at(i);
 705   Klass* method_holder = m->method_holder();
 706   InstanceKlass *mhk = InstanceKlass::cast(method_holder);
 707 
 708   // miranda methods are public abstract instance interface methods in a class's vtable
 709   if (mhk->is_interface()) {
 710     assert(m->is_public(), "should be public");
 711     assert(ik()->implements_interface(method_holder) , "this class should implement the interface");
 712     if (is_miranda(m, ik()->methods(), ik()->default_methods(), ik()->super(), klass()->is_interface())) {
 713       return true;
 714     }
 715   }
 716   return false;
 717 }
 718 
 719 // Check if a method is a miranda method, given a class's methods array,
 720 // its default_method table and its super class.
 721 // "Miranda" means an abstract non-private method that would not be
 722 // overridden for the local class.
 723 // A "miranda" method should only include non-private interface
 724 // instance methods, i.e. not private methods, not static methods,
 725 // not default methods (concrete interface methods), not overpass methods.
 726 // If a given class already has a local (including overpass) method, a
 727 // default method, or any of its superclasses has the same which would have
 728 // overridden an abstract method, then this is not a miranda method.
 729 //
 730 // Miranda methods are checked multiple times.
 731 // Pass 1: during class load/class file parsing: before vtable size calculation:
 732 // include superinterface abstract and default methods (non-private instance).
 733 // We include potential default methods to give them space in the vtable.
 734 // During the first run, the current instanceKlass has not yet been
 735 // created, the superclasses and superinterfaces do have instanceKlasses
 736 // but may not have vtables, the default_methods list is empty, no overpasses.
 737 // Default method generation uses the all_mirandas array as the starter set for
 738 // maximally-specific default method calculation.  So, for both classes and
 739 // interfaces, it is necessary that the first pass will find all non-private
 740 // interface instance methods, whether or not they are concrete.
 741 //
 742 // Pass 2: recalculated during vtable initialization: only include abstract methods.
 743 // The goal of pass 2 is to walk through the superinterfaces to see if any of
 744 // the superinterface methods (which were all abstract pre-default methods)
 745 // need to be added to the vtable.
 746 // With the addition of default methods, we have three new challenges:
 747 // overpasses, static interface methods and private interface methods.
 748 // Static and private interface methods do not get added to the vtable and
 749 // are not seen by the method resolution process, so we skip those.
 750 // Overpass methods are already in the vtable, so vtable lookup will
 751 // find them and we don't need to add a miranda method to the end of
 752 // the vtable. So we look for overpass methods and if they are found we
 753 // return false. Note that we inherit our superclasses vtable, so
 754 // the superclass' search also needs to use find_overpass so that if
 755 // one is found we return false.
 756 // False means - we don't need a miranda method added to the vtable.
 757 //
 758 // During the second run, default_methods is set up, so concrete methods from
 759 // superinterfaces with matching names/signatures to default_methods are already
 760 // in the default_methods list and do not need to be appended to the vtable
 761 // as mirandas. Abstract methods may already have been handled via
 762 // overpasses - either local or superclass overpasses, which may be
 763 // in the vtable already.
 764 //
 765 // Pass 3: They are also checked by link resolution and selection,
 766 // for invocation on a method (not interface method) reference that
 767 // resolves to a method with an interface as its method_holder.
 768 // Used as part of walking from the bottom of the vtable to find
 769 // the vtable index for the miranda method.
 770 //
 771 // Part of the Miranda Rights in the US mean that if you do not have
 772 // an attorney one will be appointed for you.
 773 bool klassVtable::is_miranda(Method* m, Array<Method*>* class_methods,
 774                              Array<Method*>* default_methods, const Klass* super,
 775                              bool is_interface) {
 776   if (m->is_static() || m->is_private() || m->is_overpass()) {
 777     return false;
 778   }
 779   Symbol* name = m->name();
 780   Symbol* signature = m->signature();
 781 
 782   // First look in local methods to see if already covered
 783   if (InstanceKlass::find_local_method(class_methods, name, signature,
 784               Klass::find_overpass, Klass::skip_static, Klass::skip_private) != NULL)
 785   {
 786     return false;
 787   }
 788 
 789   // Check local default methods
 790   if ((default_methods != NULL) &&
 791     (InstanceKlass::find_method(default_methods, name, signature) != NULL))
 792    {
 793      return false;
 794    }
 795 
 796   // Iterate on all superclasses, which should be InstanceKlasses.
 797   // Note that we explicitly look for overpasses at each level.
 798   // Overpasses may or may not exist for supers for pass 1,
 799   // they should have been created for pass 2 and later.
 800 
 801   for (const Klass* cursuper = super; cursuper != NULL; cursuper = cursuper->super())
 802   {
 803      Method* found_mth = InstanceKlass::cast(cursuper)->find_local_method(name, signature,
 804        Klass::find_overpass, Klass::skip_static, Klass::skip_private);
 805      // Ignore non-public methods in java.lang.Object if klass is an interface.
 806      if (found_mth != NULL && (!is_interface ||
 807          !SystemDictionary::is_nonpublic_Object_method(found_mth))) {
 808        return false;
 809      }
 810   }
 811 
 812   return true;
 813 }
 814 
 815 // Scans current_interface_methods for miranda methods that do not
 816 // already appear in new_mirandas, or default methods,  and are also not defined-and-non-private
 817 // in super (superclass).  These mirandas are added to all_mirandas if it is
 818 // not null; in addition, those that are not duplicates of miranda methods
 819 // inherited by super from its interfaces are added to new_mirandas.
 820 // Thus, new_mirandas will be the set of mirandas that this class introduces,
 821 // all_mirandas will be the set of all mirandas applicable to this class
 822 // including all defined in superclasses.
 823 void klassVtable::add_new_mirandas_to_lists(
 824     GrowableArray<Method*>* new_mirandas, GrowableArray<Method*>* all_mirandas,
 825     Array<Method*>* current_interface_methods, Array<Method*>* class_methods,
 826     Array<Method*>* default_methods, const Klass* super, bool is_interface) {
 827 
 828   // iterate thru the current interface's method to see if it a miranda
 829   int num_methods = current_interface_methods->length();
 830   for (int i = 0; i < num_methods; i++) {
 831     Method* im = current_interface_methods->at(i);
 832     bool is_duplicate = false;
 833     int num_of_current_mirandas = new_mirandas->length();
 834     // check for duplicate mirandas in different interfaces we implement
 835     for (int j = 0; j < num_of_current_mirandas; j++) {
 836       Method* miranda = new_mirandas->at(j);
 837       if ((im->name() == miranda->name()) &&
 838           (im->signature() == miranda->signature())) {
 839         is_duplicate = true;
 840         break;
 841       }
 842     }
 843 
 844     if (!is_duplicate) { // we don't want duplicate miranda entries in the vtable
 845       if (is_miranda(im, class_methods, default_methods, super, is_interface)) { // is it a miranda at all?
 846         const InstanceKlass *sk = InstanceKlass::cast(super);
 847         // check if it is a duplicate of a super's miranda
 848         if (sk->lookup_method_in_all_interfaces(im->name(), im->signature(), Klass::find_defaults) == NULL) {
 849           new_mirandas->append(im);
 850         }
 851         if (all_mirandas != NULL) {
 852           all_mirandas->append(im);
 853         }
 854       }
 855     }
 856   }
 857 }
 858 
 859 void klassVtable::get_mirandas(GrowableArray<Method*>* new_mirandas,
 860                                GrowableArray<Method*>* all_mirandas,
 861                                const Klass* super,
 862                                Array<Method*>* class_methods,
 863                                Array<Method*>* default_methods,
 864                                Array<InstanceKlass*>* local_interfaces,
 865                                bool is_interface) {
 866   assert((new_mirandas->length() == 0) , "current mirandas must be 0");
 867 
 868   // iterate thru the local interfaces looking for a miranda
 869   int num_local_ifs = local_interfaces->length();
 870   for (int i = 0; i < num_local_ifs; i++) {
 871     InstanceKlass *ik = InstanceKlass::cast(local_interfaces->at(i));
 872     add_new_mirandas_to_lists(new_mirandas, all_mirandas,
 873                               ik->methods(), class_methods,
 874                               default_methods, super, is_interface);
 875     // iterate thru each local's super interfaces
 876     Array<InstanceKlass*>* super_ifs = ik->transitive_interfaces();
 877     int num_super_ifs = super_ifs->length();
 878     for (int j = 0; j < num_super_ifs; j++) {
 879       InstanceKlass *sik = super_ifs->at(j);
 880       add_new_mirandas_to_lists(new_mirandas, all_mirandas,
 881                                 sik->methods(), class_methods,
 882                                 default_methods, super, is_interface);
 883     }
 884   }
 885 }
 886 
 887 // Discover miranda methods ("miranda" = "interface abstract, no binding"),
 888 // and append them into the vtable starting at index initialized,
 889 // return the new value of initialized.
 890 // Miranda methods use vtable entries, but do not get assigned a vtable_index
 891 // The vtable_index is discovered by searching from the end of the vtable
 892 int klassVtable::fill_in_mirandas(int initialized, TRAPS) {
 893   ResourceMark rm(THREAD);
 894   GrowableArray<Method*> mirandas(20);
 895   get_mirandas(&mirandas, NULL, ik()->super(), ik()->methods(),
 896                ik()->default_methods(), ik()->local_interfaces(),
 897                klass()->is_interface());
 898   for (int i = 0; i < mirandas.length(); i++) {
 899     if (log_develop_is_enabled(Trace, vtables)) {
 900       Method* meth = mirandas.at(i);
 901       LogTarget(Trace, vtables) lt;
 902       LogStream ls(lt);
 903       if (meth != NULL) {
 904         char* sig = meth->name_and_sig_as_C_string();
 905         ls.print("fill in mirandas with %s index %d, flags: ",
 906                      sig, initialized);
 907         meth->print_linkage_flags(&ls);
 908         ls.cr();
 909       }
 910     }
 911     put_method_at(mirandas.at(i), initialized);
 912     ++initialized;
 913   }
 914   return initialized;
 915 }
 916 
 917 // Copy this class's vtable to the vtable beginning at start.
 918 // Used to copy superclass vtable to prefix of subclass's vtable.
 919 void klassVtable::copy_vtable_to(vtableEntry* start) {
 920   Copy::disjoint_words((HeapWord*)table(), (HeapWord*)start, _length * vtableEntry::size());
 921 }
 922 
 923 #if INCLUDE_JVMTI
 924 bool klassVtable::adjust_default_method(int vtable_index, Method* old_method, Method* new_method) {
 925   // If old_method is default, find this vtable index in default_vtable_indices
 926   // and replace that method in the _default_methods list
 927   bool updated = false;
 928 
 929   Array<Method*>* default_methods = ik()->default_methods();
 930   if (default_methods != NULL) {
 931     int len = default_methods->length();
 932     for (int idx = 0; idx < len; idx++) {
 933       if (vtable_index == ik()->default_vtable_indices()->at(idx)) {
 934         if (default_methods->at(idx) == old_method) {
 935           default_methods->at_put(idx, new_method);
 936           updated = true;
 937         }
 938         break;
 939       }
 940     }
 941   }
 942   return updated;
 943 }
 944 
 945 // search the vtable for uses of either obsolete or EMCP methods
 946 void klassVtable::adjust_method_entries(bool * trace_name_printed) {
 947   int prn_enabled = 0;
 948   for (int index = 0; index < length(); index++) {
 949     Method* old_method = unchecked_method_at(index);
 950     if (old_method == NULL || !old_method->is_old()) {
 951       continue; // skip uninteresting entries
 952     }
 953     assert(!old_method->is_deleted(), "vtable methods may not be deleted");
 954 
 955     Method* new_method = old_method->get_new_method();
 956     put_method_at(new_method, index);
 957 
 958     // For default methods, need to update the _default_methods array
 959     // which can only have one method entry for a given signature
 960     bool updated_default = false;
 961     if (old_method->is_default_method()) {
 962       updated_default = adjust_default_method(index, old_method, new_method);
 963     }
 964 
 965     if (log_is_enabled(Info, redefine, class, update)) {
 966       ResourceMark rm;
 967       if (!(*trace_name_printed)) {
 968         log_info(redefine, class, update)
 969           ("adjust: klassname=%s for methods from name=%s",
 970            _klass->external_name(), old_method->method_holder()->external_name());
 971         *trace_name_printed = true;
 972       }
 973       log_debug(redefine, class, update, vtables)
 974         ("vtable method update: %s(%s), updated default = %s",
 975          new_method->name()->as_C_string(), new_method->signature()->as_C_string(), updated_default ? "true" : "false");
 976     }
 977   }
 978 }
 979 
 980 // a vtable should never contain old or obsolete methods
 981 bool klassVtable::check_no_old_or_obsolete_entries() {
 982   for (int i = 0; i < length(); i++) {
 983     Method* m = unchecked_method_at(i);
 984     if (m != NULL &&
 985         (NOT_PRODUCT(!m->is_valid() ||) m->is_old() || m->is_obsolete())) {
 986       return false;
 987     }
 988   }
 989   return true;
 990 }
 991 
 992 void klassVtable::dump_vtable() {
 993   tty->print_cr("vtable dump --");
 994   for (int i = 0; i < length(); i++) {
 995     Method* m = unchecked_method_at(i);
 996     if (m != NULL) {
 997       tty->print("      (%5d)  ", i);
 998       m->access_flags().print_on(tty);
 999       if (m->is_default_method()) {
1000         tty->print("default ");
1001       }
1002       if (m->is_overpass()) {
1003         tty->print("overpass");
1004       }
1005       tty->print(" --  ");
1006       m->print_name(tty);
1007       tty->cr();
1008     }
1009   }
1010 }
1011 #endif // INCLUDE_JVMTI
1012 
1013 // CDS/RedefineClasses support - clear vtables so they can be reinitialized
1014 void klassVtable::clear_vtable() {
1015   for (int i = 0; i < _length; i++) table()[i].clear();
1016 }
1017 
1018 bool klassVtable::is_initialized() {
1019   return _length == 0 || table()[0].method() != NULL;
1020 }
1021 
1022 //-----------------------------------------------------------------------------------------
1023 // Itable code
1024 
1025 // Initialize a itableMethodEntry
1026 void itableMethodEntry::initialize(Method* m) {
1027   if (m == NULL) return;
1028 
1029 #ifdef ASSERT
1030   if (MetaspaceShared::is_in_shared_metaspace((void*)&_method) &&
1031      !MetaspaceShared::remapped_readwrite()) {
1032     // At runtime initialize_itable is rerun as part of link_class_impl()
1033     // for a shared class loaded by the non-boot loader.
1034     // The dumptime itable method entry should be the same as the runtime entry.
1035     assert(_method == m, "sanity");
1036   }
1037 #endif
1038   _method = m;
1039 }
1040 
1041 klassItable::klassItable(InstanceKlass* klass) {
1042   _klass = klass;
1043 
1044   if (klass->itable_length() > 0) {
1045     itableOffsetEntry* offset_entry = (itableOffsetEntry*)klass->start_of_itable();
1046     if (offset_entry  != NULL && offset_entry->interface_klass() != NULL) { // Check that itable is initialized
1047       // First offset entry points to the first method_entry
1048       intptr_t* method_entry  = (intptr_t *)(((address)klass) + offset_entry->offset());
1049       intptr_t* end         = klass->end_of_itable();
1050 
1051       _table_offset      = (intptr_t*)offset_entry - (intptr_t*)klass;
1052       _size_offset_table = (method_entry - ((intptr_t*)offset_entry)) / itableOffsetEntry::size();
1053       _size_method_table = (end - method_entry)                  / itableMethodEntry::size();
1054       assert(_table_offset >= 0 && _size_offset_table >= 0 && _size_method_table >= 0, "wrong computation");
1055       return;
1056     }
1057   }
1058 
1059   // The length of the itable was either zero, or it has not yet been initialized.
1060   _table_offset      = 0;
1061   _size_offset_table = 0;
1062   _size_method_table = 0;
1063 }
1064 
1065 static int initialize_count = 0;
1066 
1067 // Initialization
1068 void klassItable::initialize_itable(bool checkconstraints, TRAPS) {
1069   if (_klass->is_interface()) {
1070     // This needs to go after vtable indices are assigned but
1071     // before implementors need to know the number of itable indices.
1072     assign_itable_indices_for_interface(InstanceKlass::cast(_klass), THREAD);
1073   }
1074 
1075   // Cannot be setup doing bootstrapping, interfaces don't have
1076   // itables, and klass with only ones entry have empty itables
1077   if (Universe::is_bootstrapping() ||
1078       _klass->is_interface() ||
1079       _klass->itable_length() == itableOffsetEntry::size()) return;
1080 
1081   // There's alway an extra itable entry so we can null-terminate it.
1082   guarantee(size_offset_table() >= 1, "too small");
1083   int num_interfaces = size_offset_table() - 1;
1084   if (num_interfaces > 0) {
1085     ResourceMark rm(THREAD);
1086     log_develop_debug(itables)("%3d: Initializing itables for %s", ++initialize_count,
1087                        _klass->name()->as_C_string());
1088 
1089 
1090     // Iterate through all interfaces
1091     int i;
1092     for(i = 0; i < num_interfaces; i++) {
1093       itableOffsetEntry* ioe = offset_entry(i);
1094       HandleMark hm(THREAD);
1095       Klass* interf = ioe->interface_klass();
1096       assert(interf != NULL && ioe->offset() != 0, "bad offset entry in itable");
1097       initialize_itable_for_interface(ioe->offset(), InstanceKlass::cast(interf), checkconstraints, CHECK);
1098     }
1099 
1100   }
1101   // Check that the last entry is empty
1102   itableOffsetEntry* ioe = offset_entry(size_offset_table() - 1);
1103   guarantee(ioe->interface_klass() == NULL && ioe->offset() == 0, "terminator entry missing");
1104 }
1105 
1106 
1107 inline bool interface_method_needs_itable_index(Method* m) {
1108   if (m->is_static())           return false;   // e.g., Stream.empty
1109   if (m->is_initializer())      return false;   // <init> or <clinit>
1110   if (m->is_private())          return false;   // uses direct call
1111   // If an interface redeclares a method from java.lang.Object,
1112   // it should already have a vtable index, don't touch it.
1113   // e.g., CharSequence.toString (from initialize_vtable)
1114   // if (m->has_vtable_index())  return false; // NO!
1115   return true;
1116 }
1117 
1118 int klassItable::assign_itable_indices_for_interface(InstanceKlass* klass, TRAPS) {
1119   // an interface does not have an itable, but its methods need to be numbered
1120   ResourceMark rm(THREAD);
1121   log_develop_debug(itables)("%3d: Initializing itable indices for interface %s",
1122                              ++initialize_count, klass->name()->as_C_string());
1123   Array<Method*>* methods = klass->methods();
1124   int nof_methods = methods->length();
1125   int ime_num = 0;
1126   for (int i = 0; i < nof_methods; i++) {
1127     Method* m = methods->at(i);
1128     if (interface_method_needs_itable_index(m)) {
1129       assert(!m->is_final_method(), "no final interface methods");
1130       // If m is already assigned a vtable index, do not disturb it.
1131       if (log_develop_is_enabled(Trace, itables)) {
1132         LogTarget(Trace, itables) lt;
1133         LogStream ls(lt);
1134         assert(m != NULL, "methods can never be null");
1135         const char* sig = m->name_and_sig_as_C_string();
1136         if (m->has_vtable_index()) {
1137           ls.print("vtable index %d for method: %s, flags: ", m->vtable_index(), sig);
1138         } else {
1139           ls.print("itable index %d for method: %s, flags: ", ime_num, sig);
1140         }
1141         m->print_linkage_flags(&ls);
1142         ls.cr();
1143       }
1144       if (!m->has_vtable_index()) {
1145         // A shared method could have an initialized itable_index that
1146         // is < 0.
1147         assert(m->vtable_index() == Method::pending_itable_index ||
1148                m->is_shared(),
1149                "set by initialize_vtable");
1150         m->set_itable_index(ime_num);
1151         // Progress to next itable entry
1152         ime_num++;
1153       }
1154     }
1155   }
1156   assert(ime_num == method_count_for_interface(klass), "proper sizing");
1157   return ime_num;
1158 }
1159 
1160 int klassItable::method_count_for_interface(InstanceKlass* interf) {
1161   assert(interf->is_interface(), "must be");
1162   Array<Method*>* methods = interf->methods();
1163   int nof_methods = methods->length();
1164   int length = 0;
1165   while (nof_methods > 0) {
1166     Method* m = methods->at(nof_methods-1);
1167     if (m->has_itable_index()) {
1168       length = m->itable_index() + 1;
1169       break;
1170     }
1171     nof_methods -= 1;
1172   }
1173 #ifdef ASSERT
1174   int nof_methods_copy = nof_methods;
1175   while (nof_methods_copy > 0) {
1176     Method* mm = methods->at(--nof_methods_copy);
1177     assert(!mm->has_itable_index() || mm->itable_index() < length, "");
1178   }
1179 #endif //ASSERT
1180   // return the rightmost itable index, plus one; or 0 if no methods have
1181   // itable indices
1182   return length;
1183 }
1184 
1185 
1186 void klassItable::initialize_itable_for_interface(int method_table_offset, InstanceKlass* interf, bool checkconstraints, TRAPS) {
1187   assert(interf->is_interface(), "must be");
1188   Array<Method*>* methods = interf->methods();
1189   int nof_methods = methods->length();
1190   HandleMark hm;
1191   Handle interface_loader (THREAD, interf->class_loader());
1192 
1193   int ime_count = method_count_for_interface(interf);
1194   for (int i = 0; i < nof_methods; i++) {
1195     Method* m = methods->at(i);
1196     methodHandle target;
1197     if (m->has_itable_index()) {
1198       // This search must match the runtime resolution, i.e. selection search for invokeinterface
1199       // to correctly enforce loader constraints for interface method inheritance.
1200       // Private methods are skipped as a private class method can never be the implementation
1201       // of an interface method.
1202       // Invokespecial does not perform selection based on the receiver, so it does not use
1203       // the cached itable.
1204       target = LinkResolver::lookup_instance_method_in_klasses(_klass, m->name(), m->signature(),
1205                                                                Klass::skip_private, CHECK);
1206     }
1207     if (target == NULL || !target->is_public() || target->is_abstract() || target->is_overpass()) {
1208       assert(target == NULL || !target->is_overpass() || target->is_public(),
1209              "Non-public overpass method!");
1210       // Entry does not resolve. Leave it empty for AbstractMethodError or other error.
1211       if (!(target == NULL) && !target->is_public()) {
1212         // Stuff an IllegalAccessError throwing method in there instead.
1213         itableOffsetEntry::method_entry(_klass, method_table_offset)[m->itable_index()].
1214             initialize(Universe::throw_illegal_access_error());
1215       }
1216     } else {
1217       // Entry did resolve, check loader constraints before initializing
1218       // if checkconstraints requested
1219       if (checkconstraints) {
1220         Handle method_holder_loader (THREAD, target->method_holder()->class_loader());
1221         if (!oopDesc::equals(method_holder_loader(), interface_loader())) {
1222           ResourceMark rm(THREAD);
1223           Symbol* failed_type_symbol =
1224             SystemDictionary::check_signature_loaders(m->signature(),
1225                                                       method_holder_loader,
1226                                                       interface_loader,
1227                                                       true, CHECK);
1228           if (failed_type_symbol != NULL) {
1229             stringStream ss;
1230             ss.print("loader constraint violation in interface itable"
1231                      " initialization for class %s: when selecting method '",
1232                      _klass->external_name());
1233             m->print_external_name(&ss),
1234             ss.print("' the class loader %s for super interface %s, and the class"
1235                      " loader %s of the selected method's %s, %s have"
1236                      " different Class objects for the type %s used in the signature (%s; %s)",
1237                      interf->class_loader_data()->loader_name_and_id(),
1238                      interf->external_name(),
1239                      target()->method_holder()->class_loader_data()->loader_name_and_id(),
1240                      target()->method_holder()->external_kind(),
1241                      target()->method_holder()->external_name(),
1242                      failed_type_symbol->as_klass_external_name(),
1243                      interf->class_in_module_of_loader(false, true),
1244                      target()->method_holder()->class_in_module_of_loader(false, true));
1245             THROW_MSG(vmSymbols::java_lang_LinkageError(), ss.as_string());
1246           }
1247         }
1248       }
1249 
1250       // ime may have moved during GC so recalculate address
1251       int ime_num = m->itable_index();
1252       assert(ime_num < ime_count, "oob");
1253       itableOffsetEntry::method_entry(_klass, method_table_offset)[ime_num].initialize(target());
1254       if (log_develop_is_enabled(Trace, itables)) {
1255         ResourceMark rm(THREAD);
1256         if (target() != NULL) {
1257           LogTarget(Trace, itables) lt;
1258           LogStream ls(lt);
1259           char* sig = target()->name_and_sig_as_C_string();
1260           ls.print("interface: %s, ime_num: %d, target: %s, method_holder: %s ",
1261                        interf->internal_name(), ime_num, sig,
1262                        target()->method_holder()->internal_name());
1263           ls.print("target_method flags: ");
1264           target()->print_linkage_flags(&ls);
1265           ls.cr();
1266         }
1267       }
1268     }
1269   }
1270 }
1271 
1272 #if INCLUDE_JVMTI
1273 // search the itable for uses of either obsolete or EMCP methods
1274 void klassItable::adjust_method_entries(bool * trace_name_printed) {
1275 
1276   itableMethodEntry* ime = method_entry(0);
1277   for (int i = 0; i < _size_method_table; i++, ime++) {
1278     Method* old_method = ime->method();
1279     if (old_method == NULL || !old_method->is_old()) {
1280       continue; // skip uninteresting entries
1281     }
1282     assert(!old_method->is_deleted(), "itable methods may not be deleted");
1283     Method* new_method = old_method->get_new_method();
1284     ime->initialize(new_method);
1285 
1286     if (log_is_enabled(Info, redefine, class, update)) {
1287       ResourceMark rm;
1288       if (!(*trace_name_printed)) {
1289         log_info(redefine, class, update)("adjust: name=%s", old_method->method_holder()->external_name());
1290         *trace_name_printed = true;
1291       }
1292       log_trace(redefine, class, update, itables)
1293         ("itable method update: %s(%s)", new_method->name()->as_C_string(), new_method->signature()->as_C_string());
1294     }
1295   }
1296 }
1297 
1298 // an itable should never contain old or obsolete methods
1299 bool klassItable::check_no_old_or_obsolete_entries() {
1300   itableMethodEntry* ime = method_entry(0);
1301   for (int i = 0; i < _size_method_table; i++) {
1302     Method* m = ime->method();
1303     if (m != NULL &&
1304         (NOT_PRODUCT(!m->is_valid() ||) m->is_old() || m->is_obsolete())) {
1305       return false;
1306     }
1307     ime++;
1308   }
1309   return true;
1310 }
1311 
1312 void klassItable::dump_itable() {
1313   itableMethodEntry* ime = method_entry(0);
1314   tty->print_cr("itable dump --");
1315   for (int i = 0; i < _size_method_table; i++) {
1316     Method* m = ime->method();
1317     if (m != NULL) {
1318       tty->print("      (%5d)  ", i);
1319       m->access_flags().print_on(tty);
1320       if (m->is_default_method()) {
1321         tty->print("default ");
1322       }
1323       tty->print(" --  ");
1324       m->print_name(tty);
1325       tty->cr();
1326     }
1327     ime++;
1328   }
1329 }
1330 #endif // INCLUDE_JVMTI
1331 
1332 // Setup
1333 class InterfaceVisiterClosure : public StackObj {
1334  public:
1335   virtual void doit(InstanceKlass* intf, int method_count) = 0;
1336 };
1337 
1338 // Visit all interfaces with at least one itable method
1339 void visit_all_interfaces(Array<InstanceKlass*>* transitive_intf, InterfaceVisiterClosure *blk) {
1340   // Handle array argument
1341   for(int i = 0; i < transitive_intf->length(); i++) {
1342     InstanceKlass* intf = transitive_intf->at(i);
1343     assert(intf->is_interface(), "sanity check");
1344 
1345     // Find no. of itable methods
1346     int method_count = 0;
1347     // method_count = klassItable::method_count_for_interface(intf);
1348     Array<Method*>* methods = intf->methods();
1349     if (methods->length() > 0) {
1350       for (int i = methods->length(); --i >= 0; ) {
1351         if (interface_method_needs_itable_index(methods->at(i))) {
1352           method_count++;
1353         }
1354       }
1355     }
1356 
1357     // Visit all interfaces which either have any methods or can participate in receiver type check.
1358     // We do not bother to count methods in transitive interfaces, although that would allow us to skip
1359     // this step in the rare case of a zero-method interface extending another zero-method interface.
1360     if (method_count > 0 || intf->transitive_interfaces()->length() > 0) {
1361       blk->doit(intf, method_count);
1362     }
1363   }
1364 }
1365 
1366 class CountInterfacesClosure : public InterfaceVisiterClosure {
1367  private:
1368   int _nof_methods;
1369   int _nof_interfaces;
1370  public:
1371    CountInterfacesClosure() { _nof_methods = 0; _nof_interfaces = 0; }
1372 
1373    int nof_methods() const    { return _nof_methods; }
1374    int nof_interfaces() const { return _nof_interfaces; }
1375 
1376    void doit(InstanceKlass* intf, int method_count) { _nof_methods += method_count; _nof_interfaces++; }
1377 };
1378 
1379 class SetupItableClosure : public InterfaceVisiterClosure  {
1380  private:
1381   itableOffsetEntry* _offset_entry;
1382   itableMethodEntry* _method_entry;
1383   address            _klass_begin;
1384  public:
1385   SetupItableClosure(address klass_begin, itableOffsetEntry* offset_entry, itableMethodEntry* method_entry) {
1386     _klass_begin  = klass_begin;
1387     _offset_entry = offset_entry;
1388     _method_entry = method_entry;
1389   }
1390 
1391   itableMethodEntry* method_entry() const { return _method_entry; }
1392 
1393   void doit(InstanceKlass* intf, int method_count) {
1394     int offset = ((address)_method_entry) - _klass_begin;
1395     _offset_entry->initialize(intf, offset);
1396     _offset_entry++;
1397     _method_entry += method_count;
1398   }
1399 };
1400 
1401 int klassItable::compute_itable_size(Array<InstanceKlass*>* transitive_interfaces) {
1402   // Count no of interfaces and total number of interface methods
1403   CountInterfacesClosure cic;
1404   visit_all_interfaces(transitive_interfaces, &cic);
1405 
1406   // There's alway an extra itable entry so we can null-terminate it.
1407   int itable_size = calc_itable_size(cic.nof_interfaces() + 1, cic.nof_methods());
1408 
1409   // Statistics
1410   update_stats(itable_size * wordSize);
1411 
1412   return itable_size;
1413 }
1414 
1415 
1416 // Fill out offset table and interface klasses into the itable space
1417 void klassItable::setup_itable_offset_table(InstanceKlass* klass) {
1418   if (klass->itable_length() == 0) return;
1419   assert(!klass->is_interface(), "Should have zero length itable");
1420 
1421   // Count no of interfaces and total number of interface methods
1422   CountInterfacesClosure cic;
1423   visit_all_interfaces(klass->transitive_interfaces(), &cic);
1424   int nof_methods    = cic.nof_methods();
1425   int nof_interfaces = cic.nof_interfaces();
1426 
1427   // Add one extra entry so we can null-terminate the table
1428   nof_interfaces++;
1429 
1430   assert(compute_itable_size(klass->transitive_interfaces()) ==
1431          calc_itable_size(nof_interfaces, nof_methods),
1432          "mismatch calculation of itable size");
1433 
1434   // Fill-out offset table
1435   itableOffsetEntry* ioe = (itableOffsetEntry*)klass->start_of_itable();
1436   itableMethodEntry* ime = (itableMethodEntry*)(ioe + nof_interfaces);
1437   intptr_t* end               = klass->end_of_itable();
1438   assert((oop*)(ime + nof_methods) <= (oop*)klass->start_of_nonstatic_oop_maps(), "wrong offset calculation (1)");
1439   assert((oop*)(end) == (oop*)(ime + nof_methods),                      "wrong offset calculation (2)");
1440 
1441   // Visit all interfaces and initialize itable offset table
1442   SetupItableClosure sic((address)klass, ioe, ime);
1443   visit_all_interfaces(klass->transitive_interfaces(), &sic);
1444 
1445 #ifdef ASSERT
1446   ime  = sic.method_entry();
1447   oop* v = (oop*) klass->end_of_itable();
1448   assert( (oop*)(ime) == v, "wrong offset calculation (2)");
1449 #endif
1450 }
1451 
1452 
1453 // inverse to itable_index
1454 Method* klassItable::method_for_itable_index(InstanceKlass* intf, int itable_index) {
1455   assert(intf->is_interface(), "sanity check");
1456   assert(intf->verify_itable_index(itable_index), "");
1457   Array<Method*>* methods = InstanceKlass::cast(intf)->methods();
1458 
1459   if (itable_index < 0 || itable_index >= method_count_for_interface(intf))
1460     return NULL;                // help caller defend against bad indices
1461 
1462   int index = itable_index;
1463   Method* m = methods->at(index);
1464   int index2 = -1;
1465   while (!m->has_itable_index() ||
1466          (index2 = m->itable_index()) != itable_index) {
1467     assert(index2 < itable_index, "monotonic");
1468     if (++index == methods->length())
1469       return NULL;
1470     m = methods->at(index);
1471   }
1472   assert(m->itable_index() == itable_index, "correct inverse");
1473 
1474   return m;
1475 }
1476 
1477 void klassVtable::verify(outputStream* st, bool forced) {
1478   // make sure table is initialized
1479   if (!Universe::is_fully_initialized()) return;
1480 #ifndef PRODUCT
1481   // avoid redundant verifies
1482   if (!forced && _verify_count == Universe::verify_count()) return;
1483   _verify_count = Universe::verify_count();
1484 #endif
1485   oop* end_of_obj = (oop*)_klass + _klass->size();
1486   oop* end_of_vtable = (oop *)&table()[_length];
1487   if (end_of_vtable > end_of_obj) {
1488     ResourceMark rm;
1489     fatal("klass %s: klass object too short (vtable extends beyond end)",
1490           _klass->internal_name());
1491   }
1492 
1493   for (int i = 0; i < _length; i++) table()[i].verify(this, st);
1494   // verify consistency with superKlass vtable
1495   Klass* super = _klass->super();
1496   if (super != NULL) {
1497     InstanceKlass* sk = InstanceKlass::cast(super);
1498     klassVtable vt = sk->vtable();
1499     for (int i = 0; i < vt.length(); i++) {
1500       verify_against(st, &vt, i);
1501     }
1502   }
1503 }
1504 
1505 void klassVtable::verify_against(outputStream* st, klassVtable* vt, int index) {
1506   vtableEntry* vte = &vt->table()[index];
1507   if (vte->method()->name()      != table()[index].method()->name() ||
1508       vte->method()->signature() != table()[index].method()->signature()) {
1509     fatal("mismatched name/signature of vtable entries");
1510   }
1511 }
1512 
1513 #ifndef PRODUCT
1514 void klassVtable::print() {
1515   ResourceMark rm;
1516   tty->print("klassVtable for klass %s (length %d):\n", _klass->internal_name(), length());
1517   for (int i = 0; i < length(); i++) {
1518     table()[i].print();
1519     tty->cr();
1520   }
1521 }
1522 #endif
1523 
1524 void vtableEntry::verify(klassVtable* vt, outputStream* st) {
1525   NOT_PRODUCT(FlagSetting fs(IgnoreLockingAssertions, true));
1526   Klass* vtklass = vt->klass();
1527   if (vtklass->is_instance_klass() &&
1528      (InstanceKlass::cast(vtklass)->major_version() >= klassVtable::VTABLE_TRANSITIVE_OVERRIDE_VERSION)) {
1529     assert(method() != NULL, "must have set method");
1530   }
1531   if (method() != NULL) {
1532     method()->verify();
1533     // we sub_type, because it could be a miranda method
1534     if (!vtklass->is_subtype_of(method()->method_holder())) {
1535 #ifndef PRODUCT
1536       print();
1537 #endif
1538       fatal("vtableEntry " PTR_FORMAT ": method is from subclass", p2i(this));
1539     }
1540  }
1541 }
1542 
1543 #ifndef PRODUCT
1544 
1545 void vtableEntry::print() {
1546   ResourceMark rm;
1547   tty->print("vtableEntry %s: ", method()->name()->as_C_string());
1548   if (Verbose) {
1549     tty->print("m " PTR_FORMAT " ", p2i(method()));
1550   }
1551 }
1552 
1553 class VtableStats : AllStatic {
1554  public:
1555   static int no_klasses;                // # classes with vtables
1556   static int no_array_klasses;          // # array classes
1557   static int no_instance_klasses;       // # instanceKlasses
1558   static int sum_of_vtable_len;         // total # of vtable entries
1559   static int sum_of_array_vtable_len;   // total # of vtable entries in array klasses only
1560   static int fixed;                     // total fixed overhead in bytes
1561   static int filler;                    // overhead caused by filler bytes
1562   static int entries;                   // total bytes consumed by vtable entries
1563   static int array_entries;             // total bytes consumed by array vtable entries
1564 
1565   static void do_class(Klass* k) {
1566     Klass* kl = k;
1567     klassVtable vt = kl->vtable();
1568     no_klasses++;
1569     if (kl->is_instance_klass()) {
1570       no_instance_klasses++;
1571       kl->array_klasses_do(do_class);
1572     }
1573     if (kl->is_array_klass()) {
1574       no_array_klasses++;
1575       sum_of_array_vtable_len += vt.length();
1576     }
1577     sum_of_vtable_len += vt.length();
1578   }
1579 
1580   static void compute() {
1581     LockedClassesDo locked_do_class(&do_class);
1582     ClassLoaderDataGraph::classes_do(&locked_do_class);
1583     fixed  = no_klasses * oopSize;      // vtable length
1584     // filler size is a conservative approximation
1585     filler = oopSize * (no_klasses - no_instance_klasses) * (sizeof(InstanceKlass) - sizeof(ArrayKlass) - 1);
1586     entries = sizeof(vtableEntry) * sum_of_vtable_len;
1587     array_entries = sizeof(vtableEntry) * sum_of_array_vtable_len;
1588   }
1589 };
1590 
1591 int VtableStats::no_klasses = 0;
1592 int VtableStats::no_array_klasses = 0;
1593 int VtableStats::no_instance_klasses = 0;
1594 int VtableStats::sum_of_vtable_len = 0;
1595 int VtableStats::sum_of_array_vtable_len = 0;
1596 int VtableStats::fixed = 0;
1597 int VtableStats::filler = 0;
1598 int VtableStats::entries = 0;
1599 int VtableStats::array_entries = 0;
1600 
1601 void klassVtable::print_statistics() {
1602   ResourceMark rm;
1603   HandleMark hm;
1604   VtableStats::compute();
1605   tty->print_cr("vtable statistics:");
1606   tty->print_cr("%6d classes (%d instance, %d array)", VtableStats::no_klasses, VtableStats::no_instance_klasses, VtableStats::no_array_klasses);
1607   int total = VtableStats::fixed + VtableStats::filler + VtableStats::entries;
1608   tty->print_cr("%6d bytes fixed overhead (refs + vtable object header)", VtableStats::fixed);
1609   tty->print_cr("%6d bytes filler overhead", VtableStats::filler);
1610   tty->print_cr("%6d bytes for vtable entries (%d for arrays)", VtableStats::entries, VtableStats::array_entries);
1611   tty->print_cr("%6d bytes total", total);
1612 }
1613 
1614 int  klassItable::_total_classes;   // Total no. of classes with itables
1615 long klassItable::_total_size;      // Total no. of bytes used for itables
1616 
1617 void klassItable::print_statistics() {
1618  tty->print_cr("itable statistics:");
1619  tty->print_cr("%6d classes with itables", _total_classes);
1620  tty->print_cr("%6lu K uses for itables (average by class: %ld bytes)", _total_size / K, _total_size / _total_classes);
1621 }
1622 
1623 #endif // PRODUCT