1 /*
   2  * Copyright (c) 1997, 2016, 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/systemDictionary.hpp"
  27 #include "classfile/vmSymbols.hpp"
  28 #include "gc/shared/gcLocker.hpp"
  29 #include "logging/log.hpp"
  30 #include "memory/metaspaceShared.hpp"
  31 #include "memory/resourceArea.hpp"
  32 #include "memory/universe.inline.hpp"
  33 #include "oops/instanceKlass.hpp"
  34 #include "oops/klassVtable.hpp"
  35 #include "oops/method.hpp"
  36 #include "oops/objArrayOop.hpp"
  37 #include "oops/oop.inline.hpp"
  38 #include "runtime/arguments.hpp"
  39 #include "runtime/handles.inline.hpp"
  40 #include "utilities/copy.hpp"
  41 
  42 inline InstanceKlass* klassVtable::ik() const {
  43   return InstanceKlass::cast(_klass());
  44 }
  45 
  46 bool klassVtable::is_preinitialized_vtable() {
  47   return _klass->is_shared() && !MetaspaceShared::remapped_readwrite();
  48 }
  49 
  50 
  51 // this function computes the vtable size (including the size needed for miranda
  52 // methods) and the number of miranda methods in this class.
  53 // Note on Miranda methods: Let's say there is a class C that implements
  54 // interface I, and none of C's superclasses implements I.
  55 // Let's say there is an abstract method m in I that neither C
  56 // nor any of its super classes implement (i.e there is no method of any access,
  57 // with the same name and signature as m), then m is a Miranda method which is
  58 // entered as a public abstract method in C's vtable.  From then on it should
  59 // treated as any other public method in C for method over-ride purposes.
  60 void klassVtable::compute_vtable_size_and_num_mirandas(
  61     int* vtable_length_ret, int* num_new_mirandas,
  62     GrowableArray<Method*>* all_mirandas, const Klass* super,
  63     Array<Method*>* methods, AccessFlags class_flags, u2 major_version,
  64     Handle classloader, Symbol* classname, Array<Klass*>* local_interfaces,
  65     TRAPS) {
  66   NoSafepointVerifier nsv;
  67 
  68   // set up default result values
  69   int vtable_length = 0;
  70 
  71   // start off with super's vtable length
  72   vtable_length = super == NULL ? 0 : super->vtable_length();
  73 
  74   // go thru each method in the methods table to see if it needs a new entry
  75   int len = methods->length();
  76   for (int i = 0; i < len; i++) {
  77     assert(methods->at(i)->is_method(), "must be a Method*");
  78     methodHandle mh(THREAD, methods->at(i));
  79 
  80     if (needs_new_vtable_entry(mh, super, classloader, classname, class_flags, major_version, THREAD)) {
  81       vtable_length += vtableEntry::size(); // we need a new entry
  82     }
  83   }
  84 
  85   GrowableArray<Method*> new_mirandas(20);
  86   // compute the number of mirandas methods that must be added to the end
  87   get_mirandas(&new_mirandas, all_mirandas, super, methods, NULL, local_interfaces);
  88   *num_new_mirandas = new_mirandas.length();
  89 
  90   // Interfaces do not need interface methods in their vtables
  91   // This includes miranda methods and during later processing, default methods
  92   if (!class_flags.is_interface()) {
  93     vtable_length += *num_new_mirandas * vtableEntry::size();
  94   }
  95 
  96   if (Universe::is_bootstrapping() && vtable_length == 0) {
  97     // array classes don't have their superclass set correctly during
  98     // bootstrapping
  99     vtable_length = Universe::base_vtable_size();
 100   }
 101 
 102   if (super == NULL && vtable_length != Universe::base_vtable_size()) {
 103     if (Universe::is_bootstrapping()) {
 104       // Someone is attempting to override java.lang.Object incorrectly on the
 105       // bootclasspath.  The JVM cannot recover from this error including throwing
 106       // an exception
 107       vm_exit_during_initialization("Incompatible definition of java.lang.Object");
 108     } else {
 109       // Someone is attempting to redefine java.lang.Object incorrectly.  The
 110       // only way this should happen is from
 111       // SystemDictionary::resolve_from_stream(), which will detect this later
 112       // and throw a security exception.  So don't assert here to let
 113       // the exception occur.
 114       vtable_length = Universe::base_vtable_size();
 115     }
 116   }
 117   assert(vtable_length % vtableEntry::size() == 0, "bad vtable length");
 118   assert(vtable_length >= Universe::base_vtable_size(), "vtable too small");
 119 
 120   *vtable_length_ret = vtable_length;
 121 }
 122 
 123 int klassVtable::index_of(Method* m, int len) const {
 124   assert(m->has_vtable_index(), "do not ask this of non-vtable methods");
 125   return m->vtable_index();
 126 }
 127 
 128 // Copy super class's vtable to the first part (prefix) of this class's vtable,
 129 // and return the number of entries copied.  Expects that 'super' is the Java
 130 // super class (arrays can have "array" super classes that must be skipped).
 131 int klassVtable::initialize_from_super(KlassHandle super) {
 132   if (super.is_null()) {
 133     return 0;
 134   } else if (is_preinitialized_vtable()) {
 135     // A shared class' vtable is preinitialized at dump time. No need to copy
 136     // methods from super class for shared class, as that was already done
 137     // during archiving time. However, if Jvmti has redefined a class,
 138     // copy super class's vtable in case the super class has changed.
 139     return super->vtable()->length();
 140   } else {
 141     // copy methods from superKlass
 142     klassVtable* superVtable = super->vtable();
 143     assert(superVtable->length() <= _length, "vtable too short");
 144 #ifdef ASSERT
 145     superVtable->verify(tty, true);
 146 #endif
 147     superVtable->copy_vtable_to(table());
 148     if (log_develop_is_enabled(Trace, vtables)) {
 149       ResourceMark rm;
 150       log_develop_trace(vtables)("copy vtable from %s to %s size %d",
 151                                  super->internal_name(), klass()->internal_name(),
 152                                  _length);
 153     }
 154     return superVtable->length();
 155   }
 156 }
 157 
 158 //
 159 // Revised lookup semantics   introduced 1.3 (Kestrel beta)
 160 void klassVtable::initialize_vtable(bool checkconstraints, TRAPS) {
 161 
 162   // Note:  Arrays can have intermediate array supers.  Use java_super to skip them.
 163   KlassHandle super (THREAD, klass()->java_super());
 164   int nofNewEntries = 0;
 165 
 166   bool is_shared = _klass->is_shared();
 167 
 168   if (!klass()->is_array_klass()) {
 169     ResourceMark rm(THREAD);
 170     log_develop_debug(vtables)("Initializing: %s", _klass->name()->as_C_string());
 171   }
 172 
 173 #ifdef ASSERT
 174   oop* end_of_obj = (oop*)_klass() + _klass()->size();
 175   oop* end_of_vtable = (oop*)&table()[_length];
 176   assert(end_of_vtable <= end_of_obj, "vtable extends beyond end");
 177 #endif
 178 
 179   if (Universe::is_bootstrapping()) {
 180     assert(!is_shared, "sanity");
 181     // just clear everything
 182     for (int i = 0; i < _length; i++) table()[i].clear();
 183     return;
 184   }
 185 
 186   int super_vtable_len = initialize_from_super(super);
 187   if (klass()->is_array_klass()) {
 188     assert(super_vtable_len == _length, "arrays shouldn't introduce new methods");
 189   } else {
 190     assert(_klass->is_instance_klass(), "must be InstanceKlass");
 191 
 192     Array<Method*>* methods = ik()->methods();
 193     int len = methods->length();
 194     int initialized = super_vtable_len;
 195 
 196     // Check each of this class's methods against super;
 197     // if override, replace in copy of super vtable, otherwise append to end
 198     for (int i = 0; i < len; i++) {
 199       // update_inherited_vtable can stop for gc - ensure using handles
 200       HandleMark hm(THREAD);
 201       assert(methods->at(i)->is_method(), "must be a Method*");
 202       methodHandle mh(THREAD, methods->at(i));
 203 
 204       bool needs_new_entry = update_inherited_vtable(ik(), mh, super_vtable_len, -1, checkconstraints, CHECK);
 205 
 206       if (needs_new_entry) {
 207         put_method_at(mh(), initialized);
 208         mh()->set_vtable_index(initialized); // set primary vtable index
 209         initialized++;
 210       }
 211     }
 212 
 213     // update vtable with default_methods
 214     Array<Method*>* default_methods = ik()->default_methods();
 215     if (default_methods != NULL) {
 216       len = default_methods->length();
 217       if (len > 0) {
 218         Array<int>* def_vtable_indices = NULL;
 219         if ((def_vtable_indices = ik()->default_vtable_indices()) == NULL) {
 220           assert(!is_shared, "shared class def_vtable_indices does not exist");
 221           def_vtable_indices = ik()->create_new_default_vtable_indices(len, CHECK);
 222         } else {
 223           assert(def_vtable_indices->length() == len, "reinit vtable len?");
 224         }
 225         for (int i = 0; i < len; i++) {
 226           HandleMark hm(THREAD);
 227           assert(default_methods->at(i)->is_method(), "must be a Method*");
 228           methodHandle mh(THREAD, default_methods->at(i));
 229           assert(!mh->is_private(), "private interface method in the default method list");
 230           bool needs_new_entry = update_inherited_vtable(ik(), mh, super_vtable_len, i, checkconstraints, CHECK);
 231 
 232           // needs new entry
 233           if (needs_new_entry) {
 234             put_method_at(mh(), initialized);
 235             if (is_preinitialized_vtable()) {
 236               // At runtime initialize_vtable is rerun for a shared class
 237               // (loaded by the non-boot loader) as part of link_class_impl().
 238               // The dumptime vtable index should be the same as the runtime index.
 239               assert(def_vtable_indices->at(i) == initialized,
 240                      "dump time vtable index is different from runtime index");
 241             } else {
 242               def_vtable_indices->at_put(i, initialized); //set vtable index
 243             }
 244             initialized++;
 245           }
 246         }
 247       }
 248     }
 249 
 250     // add miranda methods; it will also return the updated initialized
 251     // Interfaces do not need interface methods in their vtables
 252     // This includes miranda methods and during later processing, default methods
 253     if (!ik()->is_interface()) {
 254       initialized = fill_in_mirandas(initialized);
 255     }
 256 
 257     // In class hierarchies where the accessibility is not increasing (i.e., going from private ->
 258     // package_private -> public/protected), the vtable might actually be smaller than our initial
 259     // calculation, for classfile versions for which we do not do transitive override
 260     // calculations.
 261     if (ik()->major_version() >= VTABLE_TRANSITIVE_OVERRIDE_VERSION) {
 262       assert(initialized == _length, "vtable initialization failed");
 263     } else {
 264       assert(initialized <= _length, "vtable initialization failed");
 265       for(;initialized < _length; initialized++) {
 266         table()[initialized].clear();
 267       }
 268     }
 269     NOT_PRODUCT(verify(tty, true));
 270   }
 271 }
 272 
 273 // Called for cases where a method does not override its superclass' vtable entry
 274 // For bytecodes not produced by javac together it is possible that a method does not override
 275 // the superclass's method, but might indirectly override a super-super class's vtable entry
 276 // If none found, return a null superk, else return the superk of the method this does override
 277 // For public and protected methods: if they override a superclass, they will
 278 // also be overridden themselves appropriately.
 279 // Private methods do not override and are not overridden.
 280 // Package Private methods are trickier:
 281 // e.g. P1.A, pub m
 282 // P2.B extends A, package private m
 283 // P1.C extends B, public m
 284 // P1.C.m needs to override P1.A.m and can not override P2.B.m
 285 // Therefore: all package private methods need their own vtable entries for
 286 // them to be the root of an inheritance overriding decision
 287 // Package private methods may also override other vtable entries
 288 InstanceKlass* klassVtable::find_transitive_override(InstanceKlass* initialsuper, methodHandle target_method,
 289                             int vtable_index, Handle target_loader, Symbol* target_classname, Thread * THREAD) {
 290   InstanceKlass* superk = initialsuper;
 291   while (superk != NULL && superk->super() != NULL) {
 292     InstanceKlass* supersuperklass = InstanceKlass::cast(superk->super());
 293     klassVtable* ssVtable = supersuperklass->vtable();
 294     if (vtable_index < ssVtable->length()) {
 295       Method* super_method = ssVtable->method_at(vtable_index);
 296 #ifndef PRODUCT
 297       Symbol* name= target_method()->name();
 298       Symbol* signature = target_method()->signature();
 299       assert(super_method->name() == name && super_method->signature() == signature, "vtable entry name/sig mismatch");
 300 #endif
 301       if (supersuperklass->is_override(super_method, target_loader, target_classname, THREAD)) {
 302         if (log_develop_is_enabled(Trace, vtables)) {
 303           ResourceMark rm(THREAD);
 304           outputStream* logst = Log(vtables)::trace_stream();
 305           char* sig = target_method()->name_and_sig_as_C_string();
 306           logst->print("transitive overriding superclass %s with %s index %d, original flags: ",
 307                        supersuperklass->internal_name(),
 308                        sig, vtable_index);
 309           super_method->print_linkage_flags(logst);
 310           logst->print("overriders flags: ");
 311           target_method->print_linkage_flags(logst);
 312           logst->cr();
 313         }
 314 
 315         break; // return found superk
 316       }
 317     } else  {
 318       // super class has no vtable entry here, stop transitive search
 319       superk = (InstanceKlass*)NULL;
 320       break;
 321     }
 322     // if no override found yet, continue to search up
 323     superk = superk->super() == NULL ? NULL : InstanceKlass::cast(superk->super());
 324   }
 325 
 326   return superk;
 327 }
 328 
 329 static void log_vtables(int i, bool overrides, methodHandle target_method,
 330                         KlassHandle target_klass, Method* super_method,
 331                         Thread* thread) {
 332 #ifndef PRODUCT
 333   if (log_develop_is_enabled(Trace, vtables)) {
 334     ResourceMark rm(thread);
 335     outputStream* logst = Log(vtables)::trace_stream();
 336     char* sig = target_method()->name_and_sig_as_C_string();
 337     if (overrides) {
 338       logst->print("overriding with %s index %d, original flags: ",
 339                    sig, i);
 340     } else {
 341       logst->print("NOT overriding with %s index %d, original flags: ",
 342                    sig, i);
 343     }
 344     super_method->print_linkage_flags(logst);
 345     logst->print("overriders flags: ");
 346     target_method->print_linkage_flags(logst);
 347     logst->cr();
 348   }
 349 #endif
 350 }
 351 
 352 // Update child's copy of super vtable for overrides
 353 // OR return true if a new vtable entry is required.
 354 // Only called for InstanceKlass's, i.e. not for arrays
 355 // If that changed, could not use _klass as handle for klass
 356 bool klassVtable::update_inherited_vtable(InstanceKlass* klass, methodHandle target_method,
 357                                           int super_vtable_len, int default_index,
 358                                           bool checkconstraints, TRAPS) {
 359   ResourceMark rm;
 360   bool allocate_new = true;
 361   assert(klass->is_instance_klass(), "must be InstanceKlass");
 362 
 363   Array<int>* def_vtable_indices = NULL;
 364   bool is_default = false;
 365 
 366   // default methods are non-private concrete methods in superinterfaces which are added
 367   // to the vtable with their real method_holder.
 368   // Since vtable and itable indices share the same storage, don't touch
 369   // the default method's real vtable/itable index.
 370   // default_vtable_indices stores the vtable value relative to this inheritor
 371   if (default_index >= 0 ) {
 372     is_default = true;
 373     def_vtable_indices = klass->default_vtable_indices();
 374     assert(!target_method()->is_private(), "private interface method flagged as default");
 375     assert(def_vtable_indices != NULL, "def vtable alloc?");
 376     assert(default_index <= def_vtable_indices->length(), "def vtable len?");
 377   } else {
 378     assert(klass == target_method()->method_holder(), "caller resp.");
 379     // Initialize the method's vtable index to "nonvirtual".
 380     // If we allocate a vtable entry, we will update it to a non-negative number.
 381     target_method()->set_vtable_index(Method::nonvirtual_vtable_index);
 382   }
 383 
 384   // Static and <init> methods are never in
 385   if (target_method()->is_static() || target_method()->name() ==  vmSymbols::object_initializer_name()) {
 386     return false;
 387   }
 388 
 389   if (target_method->is_final_method(klass->access_flags())) {
 390     // a final method never needs a new entry; final methods can be statically
 391     // resolved and they have to be present in the vtable only if they override
 392     // a super's method, in which case they re-use its entry
 393     allocate_new = false;
 394   } else if (klass->is_interface()) {
 395     allocate_new = false;  // see note below in needs_new_vtable_entry
 396     // An interface never allocates new vtable slots, only inherits old ones.
 397     // This method will either be assigned its own itable index later,
 398     // or be assigned an inherited vtable index in the loop below.
 399     // default methods inherited by classes store their vtable indices
 400     // in the inheritor's default_vtable_indices.
 401     // default methods inherited by interfaces may already have a
 402     // valid itable index, if so, don't change it.
 403     // Overpass methods in an interface will be assigned an itable index later
 404     // by an inheriting class.
 405     // Private interface methods have no itable index and are always invoked nonvirtually,
 406     // so they retain their nonvirtual_vtable_index value, and therefore can_be_statically_bound()
 407     // will return true.
 408     if ((!is_default || !target_method()->has_itable_index()) && !target_method()->is_private()) {
 409       target_method()->set_vtable_index(Method::pending_itable_index);
 410     }
 411   }
 412 
 413   // we need a new entry if there is no superclass
 414   Klass* super = klass->super();
 415   if (super == NULL) {
 416     return allocate_new;
 417   }
 418 
 419   // private methods in classes always have a new entry in the vtable
 420   // specification interpretation since classic has
 421   // private methods not overriding
 422   // JDK8 adds private methods in interfaces which require invokespecial
 423   if (target_method()->is_private()) {
 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   KlassHandle target_klass(THREAD, 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
 454     if (super_method->name() == name && super_method->signature() == signature) {
 455 
 456       // get super_klass for method_holder for the found method
 457       InstanceKlass* super_klass =  super_method->method_holder();
 458 
 459       // Whether the method is being overridden
 460       bool overrides = false;
 461 
 462       // private methods are also never overridden
 463       if (!super_method->is_private() &&
 464           (is_default
 465           || ((super_klass->is_override(super_method, target_loader, target_classname, THREAD))
 466           || ((klass->major_version() >= VTABLE_TRANSITIVE_OVERRIDE_VERSION)
 467           && ((super_klass = find_transitive_override(super_klass,
 468                              target_method, i, target_loader,
 469                              target_classname, THREAD))
 470                              != (InstanceKlass*)NULL)))))
 471         {
 472         // Package private methods always need a new entry to root their own
 473         // overriding. They may also override other methods.
 474         if (!target_method()->is_package_private()) {
 475           allocate_new = false;
 476         }
 477 
 478         if (checkconstraints) {
 479         // Override vtable entry if passes loader constraint check
 480         // if loader constraint checking requested
 481         // No need to visit his super, since he and his super
 482         // have already made any needed loader constraints.
 483         // Since loader constraints are transitive, it is enough
 484         // to link to the first super, and we get all the others.
 485           Handle super_loader(THREAD, super_klass->class_loader());
 486 
 487           if (target_loader() != super_loader()) {
 488             ResourceMark rm(THREAD);
 489             Symbol* failed_type_symbol =
 490               SystemDictionary::check_signature_loaders(signature, target_loader,
 491                                                         super_loader, true,
 492                                                         CHECK_(false));
 493             if (failed_type_symbol != NULL) {
 494               const char* msg = "loader constraint violation: when resolving "
 495                 "overridden method \"%s\" the class loader (instance"
 496                 " of %s) of the current class, %s, and its superclass loader "
 497                 "(instance of %s), have different Class objects for the type "
 498                 "%s used in the signature";
 499               char* sig = target_method()->name_and_sig_as_C_string();
 500               const char* loader1 = SystemDictionary::loader_name(target_loader());
 501               char* current = target_klass->name()->as_C_string();
 502               const char* loader2 = SystemDictionary::loader_name(super_loader());
 503               char* failed_type_name = failed_type_symbol->as_C_string();
 504               size_t buflen = strlen(msg) + strlen(sig) + strlen(loader1) +
 505                 strlen(current) + strlen(loader2) + strlen(failed_type_name);
 506               char* buf = NEW_RESOURCE_ARRAY_IN_THREAD(THREAD, char, buflen);
 507               jio_snprintf(buf, buflen, msg, sig, loader1, current, loader2,
 508                            failed_type_name);
 509               THROW_MSG_(vmSymbols::java_lang_LinkageError(), buf, false);
 510             }
 511           }
 512         }
 513 
 514         put_method_at(target_method(), i);
 515         overrides = true;
 516         if (!is_default) {
 517           target_method()->set_vtable_index(i);
 518         } else {
 519           if (def_vtable_indices != NULL) {
 520             if (is_preinitialized_vtable()) {
 521               // At runtime initialize_vtable is rerun as part of link_class_impl()
 522               // for a shared class loaded by the non-boot loader.
 523               // The dumptime vtable index should be the same as the runtime index.
 524               assert(def_vtable_indices->at(default_index) == i,
 525                      "dump time vtable index is different from runtime index");
 526             } else {
 527               def_vtable_indices->at_put(default_index, i);
 528             }
 529           }
 530           assert(super_method->is_default_method() || super_method->is_overpass()
 531                  || super_method->is_abstract(), "default override error");
 532         }
 533       } else {
 534         overrides = false;
 535       }
 536       log_vtables(i, overrides, target_method, target_klass, super_method, THREAD);
 537     }
 538   }
 539   return allocate_new;
 540 }
 541 
 542 void klassVtable::put_method_at(Method* m, int index) {
 543   if (is_preinitialized_vtable()) {
 544     // At runtime initialize_vtable is rerun as part of link_class_impl()
 545     // for shared class loaded by the non-boot loader to obtain the loader
 546     // constraints based on the runtime classloaders' context. The dumptime
 547     // method at the vtable index should be the same as the runtime method.
 548     assert(table()[index].method() == m,
 549            "archived method is different from the runtime method");
 550   } else {
 551     if (log_develop_is_enabled(Trace, vtables)) {
 552       ResourceMark rm;
 553       outputStream* logst = Log(vtables)::trace_stream();
 554       const char* sig = (m != NULL) ? m->name_and_sig_as_C_string() : "<NULL>";
 555       logst->print("adding %s at index %d, flags: ", sig, index);
 556       if (m != NULL) {
 557         m->print_linkage_flags(logst);
 558       }
 559       logst->cr();
 560     }
 561     table()[index].set(m);
 562   }
 563 }
 564 
 565 // Find out if a method "m" with superclass "super", loader "classloader" and
 566 // name "classname" needs a new vtable entry.  Let P be a class package defined
 567 // by "classloader" and "classname".
 568 // NOTE: The logic used here is very similar to the one used for computing
 569 // the vtables indices for a method. We cannot directly use that function because,
 570 // we allocate the InstanceKlass at load time, and that requires that the
 571 // superclass has been loaded.
 572 // However, the vtable entries are filled in at link time, and therefore
 573 // the superclass' vtable may not yet have been filled in.
 574 bool klassVtable::needs_new_vtable_entry(methodHandle target_method,
 575                                          const Klass* super,
 576                                          Handle classloader,
 577                                          Symbol* classname,
 578                                          AccessFlags class_flags,
 579                                          u2 major_version,
 580                                          TRAPS) {
 581   if (class_flags.is_interface()) {
 582     // Interfaces do not use vtables, except for java.lang.Object methods,
 583     // so there is no point to assigning
 584     // a vtable index to any of their local methods.  If we refrain from doing this,
 585     // we can use Method::_vtable_index to hold the itable index
 586     return false;
 587   }
 588 
 589   if (target_method->is_final_method(class_flags) ||
 590       // a final method never needs a new entry; final methods can be statically
 591       // resolved and they have to be present in the vtable only if they override
 592       // a super's method, in which case they re-use its entry
 593       (target_method()->is_static()) ||
 594       // static methods don't need to be in vtable
 595       (target_method()->name() ==  vmSymbols::object_initializer_name())
 596       // <init> is never called dynamically-bound
 597       ) {
 598     return false;
 599   }
 600 
 601   // Concrete interface methods do not need new entries, they override
 602   // abstract method entries using default inheritance rules
 603   if (target_method()->method_holder() != NULL &&
 604       target_method()->method_holder()->is_interface()  &&
 605       !target_method()->is_abstract()) {
 606     assert(target_method()->is_default_method() || target_method()->is_private(),
 607            "unexpected interface method type");
 608     return false;
 609   }
 610 
 611   // we need a new entry if there is no superclass
 612   if (super == NULL) {
 613     return true;
 614   }
 615 
 616   // private methods in classes always have a new entry in the vtable.
 617   // Specification interpretation since classic has private methods not overriding.
 618   if (target_method()->is_private()) {
 619     return true;
 620   }
 621 
 622   // Package private methods always need a new entry to root their own
 623   // overriding. This allows transitive overriding to work.
 624   if (target_method()->is_package_private()) {
 625     return true;
 626   }
 627 
 628   // search through the super class hierarchy to see if we need
 629   // a new entry
 630   ResourceMark rm;
 631   Symbol* name = target_method()->name();
 632   Symbol* signature = target_method()->signature();
 633   const Klass* k = super;
 634   Method* super_method = NULL;
 635   InstanceKlass *holder = NULL;
 636   Method* recheck_method =  NULL;
 637   while (k != NULL) {
 638     // lookup through the hierarchy for a method with matching name and sign.
 639     super_method = InstanceKlass::cast(k)->lookup_method(name, signature);
 640     if (super_method == NULL) {
 641       break; // we still have to search for a matching miranda method
 642     }
 643     // get the class holding the matching method
 644     // make sure you use that class for is_override
 645     InstanceKlass* superk = super_method->method_holder();
 646     // we want only instance method matches
 647     // pretend private methods are not in the super vtable
 648     // since we do override around them: e.g. a.m pub/b.m private/c.m pub,
 649     // ignore private, c.m pub does override a.m pub
 650     // For classes that were not javac'd together, we also do transitive overriding around
 651     // methods that have less accessibility
 652     if ((!super_method->is_static()) &&
 653        (!super_method->is_private())) {
 654       if (superk->is_override(super_method, classloader, classname, THREAD)) {
 655         return false;
 656       // else keep looking for transitive overrides
 657       }
 658     }
 659 
 660     // Start with lookup result and continue to search up, for versions supporting transitive override
 661     if (major_version >= VTABLE_TRANSITIVE_OVERRIDE_VERSION) {
 662       k = superk->super(); // haven't found an override match yet; continue to look
 663     } else {
 664       break;
 665     }
 666   }
 667 
 668   // if the target method is public or protected it may have a matching
 669   // miranda method in the super, whose entry it should re-use.
 670   // Actually, to handle cases that javac would not generate, we need
 671   // this check for all access permissions.
 672   const InstanceKlass *sk = InstanceKlass::cast(super);
 673   if (sk->has_miranda_methods()) {
 674     if (sk->lookup_method_in_all_interfaces(name, signature, Klass::find_defaults) != NULL) {
 675       return false;  // found a matching miranda; we do not need a new entry
 676     }
 677   }
 678   return true; // found no match; we need a new entry
 679 }
 680 
 681 // Support for miranda methods
 682 
 683 // get the vtable index of a miranda method with matching "name" and "signature"
 684 int klassVtable::index_of_miranda(Symbol* name, Symbol* signature) {
 685   // search from the bottom, might be faster
 686   for (int i = (length() - 1); i >= 0; i--) {
 687     Method* m = table()[i].method();
 688     if (is_miranda_entry_at(i) &&
 689         m->name() == name && m->signature() == signature) {
 690       return i;
 691     }
 692   }
 693   return Method::invalid_vtable_index;
 694 }
 695 
 696 // check if an entry at an index is miranda
 697 // requires that method m at entry be declared ("held") by an interface.
 698 bool klassVtable::is_miranda_entry_at(int i) {
 699   Method* m = method_at(i);
 700   Klass* method_holder = m->method_holder();
 701   InstanceKlass *mhk = InstanceKlass::cast(method_holder);
 702 
 703   // miranda methods are public abstract instance interface methods in a class's vtable
 704   if (mhk->is_interface()) {
 705     assert(m->is_public(), "should be public");
 706     assert(ik()->implements_interface(method_holder) , "this class should implement the interface");
 707     if (is_miranda(m, ik()->methods(), ik()->default_methods(), ik()->super())) {
 708       return true;
 709     }
 710   }
 711   return false;
 712 }
 713 
 714 // Check if a method is a miranda method, given a class's methods array,
 715 // its default_method table and its super class.
 716 // "Miranda" means an abstract non-private method that would not be
 717 // overridden for the local class.
 718 // A "miranda" method should only include non-private interface
 719 // instance methods, i.e. not private methods, not static methods,
 720 // not default methods (concrete interface methods), not overpass methods.
 721 // If a given class already has a local (including overpass) method, a
 722 // default method, or any of its superclasses has the same which would have
 723 // overridden an abstract method, then this is not a miranda method.
 724 //
 725 // Miranda methods are checked multiple times.
 726 // Pass 1: during class load/class file parsing: before vtable size calculation:
 727 // include superinterface abstract and default methods (non-private instance).
 728 // We include potential default methods to give them space in the vtable.
 729 // During the first run, the current instanceKlass has not yet been
 730 // created, the superclasses and superinterfaces do have instanceKlasses
 731 // but may not have vtables, the default_methods list is empty, no overpasses.
 732 // This is seen by default method creation.
 733 //
 734 // Pass 2: recalculated during vtable initialization: only include abstract methods.
 735 // The goal of pass 2 is to walk through the superinterfaces to see if any of
 736 // the superinterface methods (which were all abstract pre-default methods)
 737 // need to be added to the vtable.
 738 // With the addition of default methods, we have three new challenges:
 739 // overpasses, static interface methods and private interface methods.
 740 // Static and private interface methods do not get added to the vtable and
 741 // are not seen by the method resolution process, so we skip those.
 742 // Overpass methods are already in the vtable, so vtable lookup will
 743 // find them and we don't need to add a miranda method to the end of
 744 // the vtable. So we look for overpass methods and if they are found we
 745 // return false. Note that we inherit our superclasses vtable, so
 746 // the superclass' search also needs to use find_overpass so that if
 747 // one is found we return false.
 748 // False means - we don't need a miranda method added to the vtable.
 749 //
 750 // During the second run, default_methods is set up, so concrete methods from
 751 // superinterfaces with matching names/signatures to default_methods are already
 752 // in the default_methods list and do not need to be appended to the vtable
 753 // as mirandas. Abstract methods may already have been handled via
 754 // overpasses - either local or superclass overpasses, which may be
 755 // in the vtable already.
 756 //
 757 // Pass 3: They are also checked by link resolution and selection,
 758 // for invocation on a method (not interface method) reference that
 759 // resolves to a method with an interface as its method_holder.
 760 // Used as part of walking from the bottom of the vtable to find
 761 // the vtable index for the miranda method.
 762 //
 763 // Part of the Miranda Rights in the US mean that if you do not have
 764 // an attorney one will be appointed for you.
 765 bool klassVtable::is_miranda(Method* m, Array<Method*>* class_methods,
 766                              Array<Method*>* default_methods, const Klass* super) {
 767   if (m->is_static() || m->is_private() || m->is_overpass()) {
 768     return false;
 769   }
 770   Symbol* name = m->name();
 771   Symbol* signature = m->signature();
 772 
 773   // First look in local methods to see if already covered
 774   if (InstanceKlass::find_local_method(class_methods, name, signature,
 775               Klass::find_overpass, Klass::skip_static, Klass::skip_private) != NULL)
 776   {
 777     return false;
 778   }
 779 
 780   // Check local default methods
 781   if ((default_methods != NULL) &&
 782     (InstanceKlass::find_method(default_methods, name, signature) != NULL))
 783    {
 784      return false;
 785    }
 786 
 787   // Iterate on all superclasses, which should be InstanceKlasses.
 788   // Note that we explicitly look for overpasses at each level.
 789   // Overpasses may or may not exist for supers for pass 1,
 790   // they should have been created for pass 2 and later.
 791 
 792   for (const Klass* cursuper = super; cursuper != NULL; cursuper = cursuper->super())
 793   {
 794      if (InstanceKlass::cast(cursuper)->find_local_method(name, signature,
 795            Klass::find_overpass, Klass::skip_static, Klass::skip_private) != NULL) {
 796        return false;
 797      }
 798   }
 799 
 800   return true;
 801 }
 802 
 803 // Scans current_interface_methods for miranda methods that do not
 804 // already appear in new_mirandas, or default methods,  and are also not defined-and-non-private
 805 // in super (superclass).  These mirandas are added to all_mirandas if it is
 806 // not null; in addition, those that are not duplicates of miranda methods
 807 // inherited by super from its interfaces are added to new_mirandas.
 808 // Thus, new_mirandas will be the set of mirandas that this class introduces,
 809 // all_mirandas will be the set of all mirandas applicable to this class
 810 // including all defined in superclasses.
 811 void klassVtable::add_new_mirandas_to_lists(
 812     GrowableArray<Method*>* new_mirandas, GrowableArray<Method*>* all_mirandas,
 813     Array<Method*>* current_interface_methods, Array<Method*>* class_methods,
 814     Array<Method*>* default_methods, const Klass* super) {
 815 
 816   // iterate thru the current interface's method to see if it a miranda
 817   int num_methods = current_interface_methods->length();
 818   for (int i = 0; i < num_methods; i++) {
 819     Method* im = current_interface_methods->at(i);
 820     bool is_duplicate = false;
 821     int num_of_current_mirandas = new_mirandas->length();
 822     // check for duplicate mirandas in different interfaces we implement
 823     for (int j = 0; j < num_of_current_mirandas; j++) {
 824       Method* miranda = new_mirandas->at(j);
 825       if ((im->name() == miranda->name()) &&
 826           (im->signature() == miranda->signature())) {
 827         is_duplicate = true;
 828         break;
 829       }
 830     }
 831 
 832     if (!is_duplicate) { // we don't want duplicate miranda entries in the vtable
 833       if (is_miranda(im, class_methods, default_methods, super)) { // is it a miranda at all?
 834         const InstanceKlass *sk = InstanceKlass::cast(super);
 835         // check if it is a duplicate of a super's miranda
 836         if (sk->lookup_method_in_all_interfaces(im->name(), im->signature(), Klass::find_defaults) == NULL) {
 837           new_mirandas->append(im);
 838         }
 839         if (all_mirandas != NULL) {
 840           all_mirandas->append(im);
 841         }
 842       }
 843     }
 844   }
 845 }
 846 
 847 void klassVtable::get_mirandas(GrowableArray<Method*>* new_mirandas,
 848                                GrowableArray<Method*>* all_mirandas,
 849                                const Klass* super,
 850                                Array<Method*>* class_methods,
 851                                Array<Method*>* default_methods,
 852                                Array<Klass*>* local_interfaces) {
 853   assert((new_mirandas->length() == 0) , "current mirandas must be 0");
 854 
 855   // iterate thru the local interfaces looking for a miranda
 856   int num_local_ifs = local_interfaces->length();
 857   for (int i = 0; i < num_local_ifs; i++) {
 858     InstanceKlass *ik = InstanceKlass::cast(local_interfaces->at(i));
 859     add_new_mirandas_to_lists(new_mirandas, all_mirandas,
 860                               ik->methods(), class_methods,
 861                               default_methods, super);
 862     // iterate thru each local's super interfaces
 863     Array<Klass*>* super_ifs = ik->transitive_interfaces();
 864     int num_super_ifs = super_ifs->length();
 865     for (int j = 0; j < num_super_ifs; j++) {
 866       InstanceKlass *sik = InstanceKlass::cast(super_ifs->at(j));
 867       add_new_mirandas_to_lists(new_mirandas, all_mirandas,
 868                                 sik->methods(), class_methods,
 869                                 default_methods, super);
 870     }
 871   }
 872 }
 873 
 874 // Discover miranda methods ("miranda" = "interface abstract, no binding"),
 875 // and append them into the vtable starting at index initialized,
 876 // return the new value of initialized.
 877 // Miranda methods use vtable entries, but do not get assigned a vtable_index
 878 // The vtable_index is discovered by searching from the end of the vtable
 879 int klassVtable::fill_in_mirandas(int initialized) {
 880   GrowableArray<Method*> mirandas(20);
 881   get_mirandas(&mirandas, NULL, ik()->super(), ik()->methods(),
 882                ik()->default_methods(), ik()->local_interfaces());
 883   for (int i = 0; i < mirandas.length(); i++) {
 884     if (log_develop_is_enabled(Trace, vtables)) {
 885       Method* meth = mirandas.at(i);
 886       ResourceMark rm(Thread::current());
 887       outputStream* logst = Log(vtables)::trace_stream();
 888       if (meth != NULL) {
 889         char* sig = meth->name_and_sig_as_C_string();
 890         logst->print("fill in mirandas with %s index %d, flags: ",
 891                      sig, initialized);
 892         meth->print_linkage_flags(logst);
 893         logst->cr();
 894       }
 895     }
 896     put_method_at(mirandas.at(i), initialized);
 897     ++initialized;
 898   }
 899   return initialized;
 900 }
 901 
 902 // Copy this class's vtable to the vtable beginning at start.
 903 // Used to copy superclass vtable to prefix of subclass's vtable.
 904 void klassVtable::copy_vtable_to(vtableEntry* start) {
 905   Copy::disjoint_words((HeapWord*)table(), (HeapWord*)start, _length * vtableEntry::size());
 906 }
 907 
 908 #if INCLUDE_JVMTI
 909 bool klassVtable::adjust_default_method(int vtable_index, Method* old_method, Method* new_method) {
 910   // If old_method is default, find this vtable index in default_vtable_indices
 911   // and replace that method in the _default_methods list
 912   bool updated = false;
 913 
 914   Array<Method*>* default_methods = ik()->default_methods();
 915   if (default_methods != NULL) {
 916     int len = default_methods->length();
 917     for (int idx = 0; idx < len; idx++) {
 918       if (vtable_index == ik()->default_vtable_indices()->at(idx)) {
 919         if (default_methods->at(idx) == old_method) {
 920           default_methods->at_put(idx, new_method);
 921           updated = true;
 922         }
 923         break;
 924       }
 925     }
 926   }
 927   return updated;
 928 }
 929 
 930 // search the vtable for uses of either obsolete or EMCP methods
 931 void klassVtable::adjust_method_entries(InstanceKlass* holder, bool * trace_name_printed) {
 932   int prn_enabled = 0;
 933   for (int index = 0; index < length(); index++) {
 934     Method* old_method = unchecked_method_at(index);
 935     if (old_method == NULL || old_method->method_holder() != holder || !old_method->is_old()) {
 936       continue; // skip uninteresting entries
 937     }
 938     assert(!old_method->is_deleted(), "vtable methods may not be deleted");
 939 
 940     Method* new_method = holder->method_with_idnum(old_method->orig_method_idnum());
 941 
 942     assert(new_method != NULL, "method_with_idnum() should not be NULL");
 943     assert(old_method != new_method, "sanity check");
 944 
 945     put_method_at(new_method, index);
 946     // For default methods, need to update the _default_methods array
 947     // which can only have one method entry for a given signature
 948     bool updated_default = false;
 949     if (old_method->is_default_method()) {
 950       updated_default = adjust_default_method(index, old_method, new_method);
 951     }
 952 
 953     if (log_is_enabled(Info, redefine, class, update)) {
 954       ResourceMark rm;
 955       if (!(*trace_name_printed)) {
 956         log_info(redefine, class, update)
 957           ("adjust: klassname=%s for methods from name=%s",
 958            klass()->external_name(), old_method->method_holder()->external_name());
 959         *trace_name_printed = true;
 960       }
 961       log_debug(redefine, class, update, vtables)
 962         ("vtable method update: %s(%s), updated default = %s",
 963          new_method->name()->as_C_string(), new_method->signature()->as_C_string(), updated_default ? "true" : "false");
 964     }
 965   }
 966 }
 967 
 968 // a vtable should never contain old or obsolete methods
 969 bool klassVtable::check_no_old_or_obsolete_entries() {
 970   for (int i = 0; i < length(); i++) {
 971     Method* m = unchecked_method_at(i);
 972     if (m != NULL &&
 973         (NOT_PRODUCT(!m->is_valid() ||) m->is_old() || m->is_obsolete())) {
 974       return false;
 975     }
 976   }
 977   return true;
 978 }
 979 
 980 void klassVtable::dump_vtable() {
 981   tty->print_cr("vtable dump --");
 982   for (int i = 0; i < length(); i++) {
 983     Method* m = unchecked_method_at(i);
 984     if (m != NULL) {
 985       tty->print("      (%5d)  ", i);
 986       m->access_flags().print_on(tty);
 987       if (m->is_default_method()) {
 988         tty->print("default ");
 989       }
 990       if (m->is_overpass()) {
 991         tty->print("overpass");
 992       }
 993       tty->print(" --  ");
 994       m->print_name(tty);
 995       tty->cr();
 996     }
 997   }
 998 }
 999 #endif // INCLUDE_JVMTI
1000 
1001 // CDS/RedefineClasses support - clear vtables so they can be reinitialized
1002 void klassVtable::clear_vtable() {
1003   for (int i = 0; i < _length; i++) table()[i].clear();
1004 }
1005 
1006 bool klassVtable::is_initialized() {
1007   return _length == 0 || table()[0].method() != NULL;
1008 }
1009 
1010 //-----------------------------------------------------------------------------------------
1011 // Itable code
1012 
1013 // Initialize a itableMethodEntry
1014 void itableMethodEntry::initialize(Method* m) {
1015   if (m == NULL) return;
1016 
1017   if (MetaspaceShared::is_in_shared_space((void*)&_method) &&
1018      !MetaspaceShared::remapped_readwrite()) {
1019     // At runtime initialize_itable is rerun as part of link_class_impl()
1020     // for a shared class loaded by the non-boot loader.
1021     // The dumptime itable method entry should be the same as the runtime entry.
1022     assert(_method == m, "sanity");
1023   } else {
1024     _method = m;
1025   }
1026 }
1027 
1028 klassItable::klassItable(instanceKlassHandle klass) {
1029   _klass = klass;
1030 
1031   if (klass->itable_length() > 0) {
1032     itableOffsetEntry* offset_entry = (itableOffsetEntry*)klass->start_of_itable();
1033     if (offset_entry  != NULL && offset_entry->interface_klass() != NULL) { // Check that itable is initialized
1034       // First offset entry points to the first method_entry
1035       intptr_t* method_entry  = (intptr_t *)(((address)klass()) + offset_entry->offset());
1036       intptr_t* end         = klass->end_of_itable();
1037 
1038       _table_offset      = (intptr_t*)offset_entry - (intptr_t*)klass();
1039       _size_offset_table = (method_entry - ((intptr_t*)offset_entry)) / itableOffsetEntry::size();
1040       _size_method_table = (end - method_entry)                  / itableMethodEntry::size();
1041       assert(_table_offset >= 0 && _size_offset_table >= 0 && _size_method_table >= 0, "wrong computation");
1042       return;
1043     }
1044   }
1045 
1046   // The length of the itable was either zero, or it has not yet been initialized.
1047   _table_offset      = 0;
1048   _size_offset_table = 0;
1049   _size_method_table = 0;
1050 }
1051 
1052 static int initialize_count = 0;
1053 
1054 // Initialization
1055 void klassItable::initialize_itable(bool checkconstraints, TRAPS) {
1056   if (_klass->is_interface()) {
1057     // This needs to go after vtable indices are assigned but
1058     // before implementors need to know the number of itable indices.
1059     assign_itable_indices_for_interface(_klass());
1060   }
1061 
1062   // Cannot be setup doing bootstrapping, interfaces don't have
1063   // itables, and klass with only ones entry have empty itables
1064   if (Universe::is_bootstrapping() ||
1065       _klass->is_interface() ||
1066       _klass->itable_length() == itableOffsetEntry::size()) return;
1067 
1068   // There's alway an extra itable entry so we can null-terminate it.
1069   guarantee(size_offset_table() >= 1, "too small");
1070   int num_interfaces = size_offset_table() - 1;
1071   if (num_interfaces > 0) {
1072     log_develop_debug(itables)("%3d: Initializing itables for %s", ++initialize_count,
1073                        _klass->name()->as_C_string());
1074 
1075 
1076     // Iterate through all interfaces
1077     int i;
1078     for(i = 0; i < num_interfaces; i++) {
1079       itableOffsetEntry* ioe = offset_entry(i);
1080       HandleMark hm(THREAD);
1081       KlassHandle interf_h (THREAD, ioe->interface_klass());
1082       assert(interf_h() != NULL && ioe->offset() != 0, "bad offset entry in itable");
1083       initialize_itable_for_interface(ioe->offset(), interf_h, checkconstraints, CHECK);
1084     }
1085 
1086   }
1087   // Check that the last entry is empty
1088   itableOffsetEntry* ioe = offset_entry(size_offset_table() - 1);
1089   guarantee(ioe->interface_klass() == NULL && ioe->offset() == 0, "terminator entry missing");
1090 }
1091 
1092 
1093 inline bool interface_method_needs_itable_index(Method* m) {
1094   if (m->is_static())           return false;   // e.g., Stream.empty
1095   if (m->is_initializer())      return false;   // <init> or <clinit>
1096   if (m->is_private())          return false;   // requires invokeSpecial
1097   // If an interface redeclares a method from java.lang.Object,
1098   // it should already have a vtable index, don't touch it.
1099   // e.g., CharSequence.toString (from initialize_vtable)
1100   // if (m->has_vtable_index())  return false; // NO!
1101   return true;
1102 }
1103 
1104 int klassItable::assign_itable_indices_for_interface(Klass* klass) {
1105   // an interface does not have an itable, but its methods need to be numbered
1106   log_develop_debug(itables)("%3d: Initializing itable indices for interface %s",
1107                              ++initialize_count, klass->name()->as_C_string());
1108   Array<Method*>* methods = InstanceKlass::cast(klass)->methods();
1109   int nof_methods = methods->length();
1110   int ime_num = 0;
1111   for (int i = 0; i < nof_methods; i++) {
1112     Method* m = methods->at(i);
1113     if (interface_method_needs_itable_index(m)) {
1114       assert(!m->is_final_method(), "no final interface methods");
1115       // If m is already assigned a vtable index, do not disturb it.
1116       if (log_develop_is_enabled(Trace, itables)) {
1117         ResourceMark rm;
1118         outputStream* logst = Log(itables)::trace_stream();
1119         assert(m != NULL, "methods can never be null");
1120         const char* sig = m->name_and_sig_as_C_string();
1121         if (m->has_vtable_index()) {
1122           logst->print("vtable index %d for method: %s, flags: ", m->vtable_index(), sig);
1123         } else {
1124           logst->print("itable index %d for method: %s, flags: ", ime_num, sig);
1125         }
1126         m->print_linkage_flags(logst);
1127         logst->cr();
1128       }
1129       if (!m->has_vtable_index()) {
1130         // A shared method could have an initialized itable_index that
1131         // is < 0.
1132         assert(m->vtable_index() == Method::pending_itable_index ||
1133                m->is_shared(),
1134                "set by initialize_vtable");
1135         m->set_itable_index(ime_num);
1136         // Progress to next itable entry
1137         ime_num++;
1138       }
1139     }
1140   }
1141   assert(ime_num == method_count_for_interface(klass), "proper sizing");
1142   return ime_num;
1143 }
1144 
1145 int klassItable::method_count_for_interface(Klass* interf) {
1146   assert(interf->is_instance_klass(), "must be");
1147   assert(interf->is_interface(), "must be");
1148   Array<Method*>* methods = InstanceKlass::cast(interf)->methods();
1149   int nof_methods = methods->length();
1150   int length = 0;
1151   while (nof_methods > 0) {
1152     Method* m = methods->at(nof_methods-1);
1153     if (m->has_itable_index()) {
1154       length = m->itable_index() + 1;
1155       break;
1156     }
1157     nof_methods -= 1;
1158   }
1159 #ifdef ASSERT
1160   int nof_methods_copy = nof_methods;
1161   while (nof_methods_copy > 0) {
1162     Method* mm = methods->at(--nof_methods_copy);
1163     assert(!mm->has_itable_index() || mm->itable_index() < length, "");
1164   }
1165 #endif //ASSERT
1166   // return the rightmost itable index, plus one; or 0 if no methods have
1167   // itable indices
1168   return length;
1169 }
1170 
1171 
1172 void klassItable::initialize_itable_for_interface(int method_table_offset, KlassHandle interf_h, bool checkconstraints, TRAPS) {
1173   Array<Method*>* methods = InstanceKlass::cast(interf_h())->methods();
1174   int nof_methods = methods->length();
1175   HandleMark hm;
1176   assert(nof_methods > 0, "at least one method must exist for interface to be in vtable");
1177   Handle interface_loader (THREAD, InstanceKlass::cast(interf_h())->class_loader());
1178 
1179   int ime_count = method_count_for_interface(interf_h());
1180   for (int i = 0; i < nof_methods; i++) {
1181     Method* m = methods->at(i);
1182     methodHandle target;
1183     if (m->has_itable_index()) {
1184       // This search must match the runtime resolution, i.e. selection search for invokeinterface
1185       // to correctly enforce loader constraints for interface method inheritance
1186       target = LinkResolver::lookup_instance_method_in_klasses(_klass, m->name(), m->signature(), CHECK);
1187     }
1188     if (target == NULL || !target->is_public() || target->is_abstract()) {
1189       // Entry does not resolve. Leave it empty for AbstractMethodError.
1190         if (!(target == NULL) && !target->is_public()) {
1191           // Stuff an IllegalAccessError throwing method in there instead.
1192           itableOffsetEntry::method_entry(_klass(), method_table_offset)[m->itable_index()].
1193               initialize(Universe::throw_illegal_access_error());
1194         }
1195     } else {
1196       // Entry did resolve, check loader constraints before initializing
1197       // if checkconstraints requested
1198       if (checkconstraints) {
1199         Handle method_holder_loader (THREAD, target->method_holder()->class_loader());
1200         if (method_holder_loader() != interface_loader()) {
1201           ResourceMark rm(THREAD);
1202           Symbol* failed_type_symbol =
1203             SystemDictionary::check_signature_loaders(m->signature(),
1204                                                       method_holder_loader,
1205                                                       interface_loader,
1206                                                       true, CHECK);
1207           if (failed_type_symbol != NULL) {
1208             const char* msg = "loader constraint violation in interface "
1209               "itable initialization: when resolving method \"%s\" the class"
1210               " loader (instance of %s) of the current class, %s, "
1211               "and the class loader (instance of %s) for interface "
1212               "%s have different Class objects for the type %s "
1213               "used in the signature";
1214             char* sig = target()->name_and_sig_as_C_string();
1215             const char* loader1 = SystemDictionary::loader_name(method_holder_loader());
1216             char* current = _klass->name()->as_C_string();
1217             const char* loader2 = SystemDictionary::loader_name(interface_loader());
1218             char* iface = InstanceKlass::cast(interf_h())->name()->as_C_string();
1219             char* failed_type_name = failed_type_symbol->as_C_string();
1220             size_t buflen = strlen(msg) + strlen(sig) + strlen(loader1) +
1221               strlen(current) + strlen(loader2) + strlen(iface) +
1222               strlen(failed_type_name);
1223             char* buf = NEW_RESOURCE_ARRAY_IN_THREAD(THREAD, char, buflen);
1224             jio_snprintf(buf, buflen, msg, sig, loader1, current, loader2,
1225                          iface, failed_type_name);
1226             THROW_MSG(vmSymbols::java_lang_LinkageError(), buf);
1227           }
1228         }
1229       }
1230 
1231       // ime may have moved during GC so recalculate address
1232       int ime_num = m->itable_index();
1233       assert(ime_num < ime_count, "oob");
1234       itableOffsetEntry::method_entry(_klass(), method_table_offset)[ime_num].initialize(target());
1235       if (log_develop_is_enabled(Trace, itables)) {
1236         ResourceMark rm(THREAD);
1237         if (target() != NULL) {
1238           outputStream* logst = Log(itables)::trace_stream();
1239           char* sig = target()->name_and_sig_as_C_string();
1240           logst->print("interface: %s, ime_num: %d, target: %s, method_holder: %s ",
1241                        interf_h()->internal_name(), ime_num, sig,
1242                        target()->method_holder()->internal_name());
1243           logst->print("target_method flags: ");
1244           target()->print_linkage_flags(logst);
1245           logst->cr();
1246         }
1247       }
1248     }
1249   }
1250 }
1251 
1252 // Update entry for specific Method*
1253 void klassItable::initialize_with_method(Method* m) {
1254   itableMethodEntry* ime = method_entry(0);
1255   for(int i = 0; i < _size_method_table; i++) {
1256     if (ime->method() == m) {
1257       ime->initialize(m);
1258     }
1259     ime++;
1260   }
1261 }
1262 
1263 #if INCLUDE_JVMTI
1264 // search the itable for uses of either obsolete or EMCP methods
1265 void klassItable::adjust_method_entries(InstanceKlass* holder, bool * trace_name_printed) {
1266 
1267   itableMethodEntry* ime = method_entry(0);
1268   for (int i = 0; i < _size_method_table; i++, ime++) {
1269     Method* old_method = ime->method();
1270     if (old_method == NULL || old_method->method_holder() != holder || !old_method->is_old()) {
1271       continue; // skip uninteresting entries
1272     }
1273     assert(!old_method->is_deleted(), "itable methods may not be deleted");
1274 
1275     Method* new_method = holder->method_with_idnum(old_method->orig_method_idnum());
1276 
1277     assert(new_method != NULL, "method_with_idnum() should not be NULL");
1278     assert(old_method != new_method, "sanity check");
1279 
1280     ime->initialize(new_method);
1281 
1282     if (log_is_enabled(Info, redefine, class, update)) {
1283       ResourceMark rm;
1284       if (!(*trace_name_printed)) {
1285         log_info(redefine, class, update)("adjust: name=%s", old_method->method_holder()->external_name());
1286         *trace_name_printed = true;
1287       }
1288       log_trace(redefine, class, update, itables)
1289         ("itable method update: %s(%s)", new_method->name()->as_C_string(), new_method->signature()->as_C_string());
1290     }
1291   }
1292 }
1293 
1294 // an itable should never contain old or obsolete methods
1295 bool klassItable::check_no_old_or_obsolete_entries() {
1296   itableMethodEntry* ime = method_entry(0);
1297   for (int i = 0; i < _size_method_table; i++) {
1298     Method* m = ime->method();
1299     if (m != NULL &&
1300         (NOT_PRODUCT(!m->is_valid() ||) m->is_old() || m->is_obsolete())) {
1301       return false;
1302     }
1303     ime++;
1304   }
1305   return true;
1306 }
1307 
1308 void klassItable::dump_itable() {
1309   itableMethodEntry* ime = method_entry(0);
1310   tty->print_cr("itable dump --");
1311   for (int i = 0; i < _size_method_table; i++) {
1312     Method* m = ime->method();
1313     if (m != NULL) {
1314       tty->print("      (%5d)  ", i);
1315       m->access_flags().print_on(tty);
1316       if (m->is_default_method()) {
1317         tty->print("default ");
1318       }
1319       tty->print(" --  ");
1320       m->print_name(tty);
1321       tty->cr();
1322     }
1323     ime++;
1324   }
1325 }
1326 #endif // INCLUDE_JVMTI
1327 
1328 // Setup
1329 class InterfaceVisiterClosure : public StackObj {
1330  public:
1331   virtual void doit(Klass* intf, int method_count) = 0;
1332 };
1333 
1334 // Visit all interfaces with at least one itable method
1335 void visit_all_interfaces(Array<Klass*>* transitive_intf, InterfaceVisiterClosure *blk) {
1336   // Handle array argument
1337   for(int i = 0; i < transitive_intf->length(); i++) {
1338     Klass* intf = transitive_intf->at(i);
1339     assert(intf->is_interface(), "sanity check");
1340 
1341     // Find no. of itable methods
1342     int method_count = 0;
1343     // method_count = klassItable::method_count_for_interface(intf);
1344     Array<Method*>* methods = InstanceKlass::cast(intf)->methods();
1345     if (methods->length() > 0) {
1346       for (int i = methods->length(); --i >= 0; ) {
1347         if (interface_method_needs_itable_index(methods->at(i))) {
1348           method_count++;
1349         }
1350       }
1351     }
1352 
1353     // Only count interfaces with at least one method
1354     if (method_count > 0) {
1355       blk->doit(intf, method_count);
1356     }
1357   }
1358 }
1359 
1360 class CountInterfacesClosure : public InterfaceVisiterClosure {
1361  private:
1362   int _nof_methods;
1363   int _nof_interfaces;
1364  public:
1365    CountInterfacesClosure() { _nof_methods = 0; _nof_interfaces = 0; }
1366 
1367    int nof_methods() const    { return _nof_methods; }
1368    int nof_interfaces() const { return _nof_interfaces; }
1369 
1370    void doit(Klass* intf, int method_count) { _nof_methods += method_count; _nof_interfaces++; }
1371 };
1372 
1373 class SetupItableClosure : public InterfaceVisiterClosure  {
1374  private:
1375   itableOffsetEntry* _offset_entry;
1376   itableMethodEntry* _method_entry;
1377   address            _klass_begin;
1378  public:
1379   SetupItableClosure(address klass_begin, itableOffsetEntry* offset_entry, itableMethodEntry* method_entry) {
1380     _klass_begin  = klass_begin;
1381     _offset_entry = offset_entry;
1382     _method_entry = method_entry;
1383   }
1384 
1385   itableMethodEntry* method_entry() const { return _method_entry; }
1386 
1387   void doit(Klass* intf, int method_count) {
1388     int offset = ((address)_method_entry) - _klass_begin;
1389     _offset_entry->initialize(intf, offset);
1390     _offset_entry++;
1391     _method_entry += method_count;
1392   }
1393 };
1394 
1395 int klassItable::compute_itable_size(Array<Klass*>* transitive_interfaces) {
1396   // Count no of interfaces and total number of interface methods
1397   CountInterfacesClosure cic;
1398   visit_all_interfaces(transitive_interfaces, &cic);
1399 
1400   // There's alway an extra itable entry so we can null-terminate it.
1401   int itable_size = calc_itable_size(cic.nof_interfaces() + 1, cic.nof_methods());
1402 
1403   // Statistics
1404   update_stats(itable_size * wordSize);
1405 
1406   return itable_size;
1407 }
1408 
1409 
1410 // Fill out offset table and interface klasses into the itable space
1411 void klassItable::setup_itable_offset_table(instanceKlassHandle klass) {
1412   if (klass->itable_length() == 0) return;
1413   assert(!klass->is_interface(), "Should have zero length itable");
1414 
1415   // Count no of interfaces and total number of interface methods
1416   CountInterfacesClosure cic;
1417   visit_all_interfaces(klass->transitive_interfaces(), &cic);
1418   int nof_methods    = cic.nof_methods();
1419   int nof_interfaces = cic.nof_interfaces();
1420 
1421   // Add one extra entry so we can null-terminate the table
1422   nof_interfaces++;
1423 
1424   assert(compute_itable_size(klass->transitive_interfaces()) ==
1425          calc_itable_size(nof_interfaces, nof_methods),
1426          "mismatch calculation of itable size");
1427 
1428   // Fill-out offset table
1429   itableOffsetEntry* ioe = (itableOffsetEntry*)klass->start_of_itable();
1430   itableMethodEntry* ime = (itableMethodEntry*)(ioe + nof_interfaces);
1431   intptr_t* end               = klass->end_of_itable();
1432   assert((oop*)(ime + nof_methods) <= (oop*)klass->start_of_nonstatic_oop_maps(), "wrong offset calculation (1)");
1433   assert((oop*)(end) == (oop*)(ime + nof_methods),                      "wrong offset calculation (2)");
1434 
1435   // Visit all interfaces and initialize itable offset table
1436   SetupItableClosure sic((address)klass(), ioe, ime);
1437   visit_all_interfaces(klass->transitive_interfaces(), &sic);
1438 
1439 #ifdef ASSERT
1440   ime  = sic.method_entry();
1441   oop* v = (oop*) klass->end_of_itable();
1442   assert( (oop*)(ime) == v, "wrong offset calculation (2)");
1443 #endif
1444 }
1445 
1446 
1447 // inverse to itable_index
1448 Method* klassItable::method_for_itable_index(Klass* intf, int itable_index) {
1449   assert(InstanceKlass::cast(intf)->is_interface(), "sanity check");
1450   assert(intf->verify_itable_index(itable_index), "");
1451   Array<Method*>* methods = InstanceKlass::cast(intf)->methods();
1452 
1453   if (itable_index < 0 || itable_index >= method_count_for_interface(intf))
1454     return NULL;                // help caller defend against bad indices
1455 
1456   int index = itable_index;
1457   Method* m = methods->at(index);
1458   int index2 = -1;
1459   while (!m->has_itable_index() ||
1460          (index2 = m->itable_index()) != itable_index) {
1461     assert(index2 < itable_index, "monotonic");
1462     if (++index == methods->length())
1463       return NULL;
1464     m = methods->at(index);
1465   }
1466   assert(m->itable_index() == itable_index, "correct inverse");
1467 
1468   return m;
1469 }
1470 
1471 void klassVtable::verify(outputStream* st, bool forced) {
1472   // make sure table is initialized
1473   if (!Universe::is_fully_initialized()) return;
1474 #ifndef PRODUCT
1475   // avoid redundant verifies
1476   if (!forced && _verify_count == Universe::verify_count()) return;
1477   _verify_count = Universe::verify_count();
1478 #endif
1479   oop* end_of_obj = (oop*)_klass() + _klass()->size();
1480   oop* end_of_vtable = (oop *)&table()[_length];
1481   if (end_of_vtable > end_of_obj) {
1482     fatal("klass %s: klass object too short (vtable extends beyond end)",
1483           _klass->internal_name());
1484   }
1485 
1486   for (int i = 0; i < _length; i++) table()[i].verify(this, st);
1487   // verify consistency with superKlass vtable
1488   Klass* super = _klass->super();
1489   if (super != NULL) {
1490     InstanceKlass* sk = InstanceKlass::cast(super);
1491     klassVtable* vt = sk->vtable();
1492     for (int i = 0; i < vt->length(); i++) {
1493       verify_against(st, vt, i);
1494     }
1495   }
1496 }
1497 
1498 void klassVtable::verify_against(outputStream* st, klassVtable* vt, int index) {
1499   vtableEntry* vte = &vt->table()[index];
1500   if (vte->method()->name()      != table()[index].method()->name() ||
1501       vte->method()->signature() != table()[index].method()->signature()) {
1502     fatal("mismatched name/signature of vtable entries");
1503   }
1504 }
1505 
1506 #ifndef PRODUCT
1507 void klassVtable::print() {
1508   ResourceMark rm;
1509   tty->print("klassVtable for klass %s (length %d):\n", _klass->internal_name(), length());
1510   for (int i = 0; i < length(); i++) {
1511     table()[i].print();
1512     tty->cr();
1513   }
1514 }
1515 #endif
1516 
1517 void vtableEntry::verify(klassVtable* vt, outputStream* st) {
1518   NOT_PRODUCT(FlagSetting fs(IgnoreLockingAssertions, true));
1519   KlassHandle vtklass_h = vt->klass();
1520   Klass* vtklass = vtklass_h();
1521   if (vtklass->is_instance_klass() &&
1522      (InstanceKlass::cast(vtklass)->major_version() >= klassVtable::VTABLE_TRANSITIVE_OVERRIDE_VERSION)) {
1523     assert(method() != NULL, "must have set method");
1524   }
1525   if (method() != NULL) {
1526     method()->verify();
1527     // we sub_type, because it could be a miranda method
1528     if (!vtklass_h->is_subtype_of(method()->method_holder())) {
1529 #ifndef PRODUCT
1530       print();
1531 #endif
1532       fatal("vtableEntry " PTR_FORMAT ": method is from subclass", p2i(this));
1533     }
1534  }
1535 }
1536 
1537 #ifndef PRODUCT
1538 
1539 void vtableEntry::print() {
1540   ResourceMark rm;
1541   tty->print("vtableEntry %s: ", method()->name()->as_C_string());
1542   if (Verbose) {
1543     tty->print("m " PTR_FORMAT " ", p2i(method()));
1544   }
1545 }
1546 
1547 class VtableStats : AllStatic {
1548  public:
1549   static int no_klasses;                // # classes with vtables
1550   static int no_array_klasses;          // # array classes
1551   static int no_instance_klasses;       // # instanceKlasses
1552   static int sum_of_vtable_len;         // total # of vtable entries
1553   static int sum_of_array_vtable_len;   // total # of vtable entries in array klasses only
1554   static int fixed;                     // total fixed overhead in bytes
1555   static int filler;                    // overhead caused by filler bytes
1556   static int entries;                   // total bytes consumed by vtable entries
1557   static int array_entries;             // total bytes consumed by array vtable entries
1558 
1559   static void do_class(Klass* k) {
1560     Klass* kl = k;
1561     klassVtable* vt = kl->vtable();
1562     if (vt == NULL) return;
1563     no_klasses++;
1564     if (kl->is_instance_klass()) {
1565       no_instance_klasses++;
1566       kl->array_klasses_do(do_class);
1567     }
1568     if (kl->is_array_klass()) {
1569       no_array_klasses++;
1570       sum_of_array_vtable_len += vt->length();
1571     }
1572     sum_of_vtable_len += vt->length();
1573   }
1574 
1575   static void compute() {
1576     SystemDictionary::classes_do(do_class);
1577     fixed  = no_klasses * oopSize;      // vtable length
1578     // filler size is a conservative approximation
1579     filler = oopSize * (no_klasses - no_instance_klasses) * (sizeof(InstanceKlass) - sizeof(ArrayKlass) - 1);
1580     entries = sizeof(vtableEntry) * sum_of_vtable_len;
1581     array_entries = sizeof(vtableEntry) * sum_of_array_vtable_len;
1582   }
1583 };
1584 
1585 int VtableStats::no_klasses = 0;
1586 int VtableStats::no_array_klasses = 0;
1587 int VtableStats::no_instance_klasses = 0;
1588 int VtableStats::sum_of_vtable_len = 0;
1589 int VtableStats::sum_of_array_vtable_len = 0;
1590 int VtableStats::fixed = 0;
1591 int VtableStats::filler = 0;
1592 int VtableStats::entries = 0;
1593 int VtableStats::array_entries = 0;
1594 
1595 void klassVtable::print_statistics() {
1596   ResourceMark rm;
1597   HandleMark hm;
1598   VtableStats::compute();
1599   tty->print_cr("vtable statistics:");
1600   tty->print_cr("%6d classes (%d instance, %d array)", VtableStats::no_klasses, VtableStats::no_instance_klasses, VtableStats::no_array_klasses);
1601   int total = VtableStats::fixed + VtableStats::filler + VtableStats::entries;
1602   tty->print_cr("%6d bytes fixed overhead (refs + vtable object header)", VtableStats::fixed);
1603   tty->print_cr("%6d bytes filler overhead", VtableStats::filler);
1604   tty->print_cr("%6d bytes for vtable entries (%d for arrays)", VtableStats::entries, VtableStats::array_entries);
1605   tty->print_cr("%6d bytes total", total);
1606 }
1607 
1608 int  klassItable::_total_classes;   // Total no. of classes with itables
1609 long klassItable::_total_size;      // Total no. of bytes used for itables
1610 
1611 void klassItable::print_statistics() {
1612  tty->print_cr("itable statistics:");
1613  tty->print_cr("%6d classes with itables", _total_classes);
1614  tty->print_cr("%6lu K uses for itables (average by class: %ld bytes)", _total_size / K, _total_size / _total_classes);
1615 }
1616 
1617 #endif // PRODUCT