1 /*
   2  * Copyright (c) 1999, 2018, 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 "ci/ciField.hpp"
  27 #include "ci/ciInstanceKlass.hpp"
  28 #include "ci/ciUtilities.hpp"
  29 #include "classfile/systemDictionary.hpp"
  30 #include "gc/shared/collectedHeap.inline.hpp"
  31 #include "interpreter/linkResolver.hpp"
  32 #include "memory/universe.hpp"
  33 #include "oops/oop.inline.hpp"
  34 #include "runtime/fieldDescriptor.hpp"

  35 
  36 // ciField
  37 //
  38 // This class represents the result of a field lookup in the VM.
  39 // The lookup may not succeed, in which case the information in
  40 // the ciField will be incomplete.
  41 
  42 // The ciObjectFactory cannot create circular data structures in one query.
  43 // To avoid vicious circularities, we initialize ciField::_type to NULL
  44 // for reference types and derive it lazily from the ciField::_signature.
  45 // Primitive types are eagerly initialized, and basic layout queries
  46 // can succeed without initialization, using only the BasicType of the field.
  47 
  48 // Notes on bootstrapping and shared CI objects:  A field is shared if and
  49 // only if it is (a) non-static and (b) declared by a shared instance klass.
  50 // This allows non-static field lists to be cached on shared types.
  51 // Because the _type field is lazily initialized, however, there is a
  52 // special restriction that a shared field cannot cache an unshared type.
  53 // This puts a small performance penalty on shared fields with unshared
  54 // types, such as StackTraceElement[] Throwable.stackTrace.
  55 // (Throwable is shared because ClassCastException is shared, but
  56 // StackTraceElement is not presently shared.)
  57 
  58 // It is not a vicious circularity for a ciField to recursively create
  59 // the ciSymbols necessary to represent its name and signature.
  60 // Therefore, these items are created eagerly, and the name and signature
  61 // of a shared field are themselves shared symbols.  This somewhat
  62 // pollutes the set of shared CI objects:  It grows from 50 to 93 items,
  63 // with all of the additional 43 being uninteresting shared ciSymbols.
  64 // This adds at most one step to the binary search, an amount which
  65 // decreases for complex compilation tasks.
  66 
  67 // ------------------------------------------------------------------
  68 // ciField::ciField
  69 ciField::ciField(ciInstanceKlass* klass, int index) :
  70     _known_to_link_with_put(NULL), _known_to_link_with_get(NULL) {
  71   ASSERT_IN_VM;
  72   CompilerThread *thread = CompilerThread::current();
  73 
  74   assert(ciObjectFactory::is_initialized(), "not a shared field");
  75 
  76   assert(klass->get_instanceKlass()->is_linked(), "must be linked before using its constant-pool");
  77 
  78   constantPoolHandle cpool(thread, klass->get_instanceKlass()->constants());
  79 
  80   // Get the field's name, signature, and type.
  81   Symbol* name  = cpool->name_ref_at(index);
  82   _name = ciEnv::current(thread)->get_symbol(name);
  83 
  84   int nt_index = cpool->name_and_type_ref_index_at(index);
  85   int sig_index = cpool->signature_ref_index_at(nt_index);
  86   Symbol* signature = cpool->symbol_at(sig_index);
  87   _signature = ciEnv::current(thread)->get_symbol(signature);
  88 
  89   BasicType field_type = FieldType::basic_type(signature);
  90 
  91   // If the field is a pointer type, get the klass of the
  92   // field.
  93   if (field_type == T_OBJECT || field_type == T_ARRAY) {
  94     bool ignore;
  95     // This is not really a class reference; the index always refers to the
  96     // field's type signature, as a symbol.  Linkage checks do not apply.
  97     _type = ciEnv::current(thread)->get_klass_by_index(cpool, sig_index, ignore, klass);
  98   } else {
  99     _type = ciType::make(field_type);
 100   }
 101 
 102   _name = (ciSymbol*)ciEnv::current(thread)->get_symbol(name);
 103 
 104   // Get the field's declared holder.
 105   //
 106   // Note: we actually create a ciInstanceKlass for this klass,
 107   // even though we may not need to.
 108   int holder_index = cpool->klass_ref_index_at(index);
 109   bool holder_is_accessible;
 110 
 111   ciKlass* generic_declared_holder = ciEnv::current(thread)->get_klass_by_index(cpool, holder_index,
 112                                                                                 holder_is_accessible,
 113                                                                                 klass);
 114 
 115   if (generic_declared_holder->is_array_klass()) {
 116     // If the declared holder of the field is an array class, assume that
 117     // the canonical holder of that field is java.lang.Object. Arrays
 118     // do not have fields; java.lang.Object is the only supertype of an
 119     // array type that can declare fields and is therefore the canonical
 120     // holder of the array type.
 121     //
 122     // Furthermore, the compilers assume that java.lang.Object does not
 123     // have any fields. Therefore, the field is not looked up. Instead,
 124     // the method returns partial information that will trigger special
 125     // handling in ciField::will_link and will result in a
 126     // java.lang.NoSuchFieldError exception being thrown by the compiled
 127     // code (the expected behavior in this case).
 128     _holder = ciEnv::current(thread)->Object_klass();
 129     _offset = -1;
 130     _is_constant = false;
 131     return;
 132   }
 133 
 134   ciInstanceKlass* declared_holder = generic_declared_holder->as_instance_klass();
 135 
 136   // The declared holder of this field may not have been loaded.
 137   // Bail out with partial field information.
 138   if (!holder_is_accessible) {
 139     // _type has already been set.
 140     // The default values for _flags and _constant_value will suffice.
 141     // We need values for _holder, _offset,  and _is_constant,
 142     _holder = declared_holder;
 143     _offset = -1;
 144     _is_constant = false;
 145     return;
 146   }
 147 
 148   InstanceKlass* loaded_decl_holder = declared_holder->get_instanceKlass();
 149 
 150   // Perform the field lookup.
 151   fieldDescriptor field_desc;
 152   Klass* canonical_holder =
 153     loaded_decl_holder->find_field(name, signature, &field_desc);
 154   if (canonical_holder == NULL) {
 155     // Field lookup failed.  Will be detected by will_link.
 156     _holder = declared_holder;
 157     _offset = -1;
 158     _is_constant = false;
 159     return;
 160   }
 161 
 162   // Access check based on declared_holder. canonical_holder should not be used
 163   // to check access because it can erroneously succeed. If this check fails,
 164   // propagate the declared holder to will_link() which in turn will bail out
 165   // compilation for this field access.
 166   if (!Reflection::verify_field_access(klass->get_Klass(), declared_holder->get_Klass(), canonical_holder, field_desc.access_flags(), true)) {
 167     _holder = declared_holder;
 168     _offset = -1;
 169     _is_constant = false;
 170     return;
 171   }
 172 
 173   assert(canonical_holder == field_desc.field_holder(), "just checking");
 174   initialize_from(&field_desc);
 175 }
 176 
 177 ciField::ciField(fieldDescriptor *fd) :
 178     _known_to_link_with_put(NULL), _known_to_link_with_get(NULL) {
 179   ASSERT_IN_VM;
 180 
 181   // Get the field's name, signature, and type.
 182   ciEnv* env = CURRENT_ENV;
 183   _name = env->get_symbol(fd->name());
 184   _signature = env->get_symbol(fd->signature());
 185 
 186   BasicType field_type = fd->field_type();
 187 
 188   // If the field is a pointer type, get the klass of the
 189   // field.
 190   if (field_type == T_OBJECT || field_type == T_ARRAY) {
 191     _type = NULL;  // must call compute_type on first access
 192   } else {
 193     _type = ciType::make(field_type);
 194   }
 195 
 196   initialize_from(fd);
 197 
 198   // Either (a) it is marked shared, or else (b) we are done bootstrapping.
 199   assert(is_shared() || ciObjectFactory::is_initialized(),
 200          "bootstrap classes must not create & cache unshared fields");
 201 }
 202 
 203 static bool trust_final_non_static_fields(ciInstanceKlass* holder) {
 204   if (holder == NULL)
 205     return false;
 206   if (holder->name() == ciSymbol::java_lang_System())
 207     // Never trust strangely unstable finals:  System.out, etc.
 208     return false;
 209   // Even if general trusting is disabled, trust system-built closures in these packages.
 210   if (holder->is_in_package("java/lang/invoke") || holder->is_in_package("sun/invoke"))
 211     return true;
 212   // Trust VM anonymous classes. They are private API (sun.misc.Unsafe) and can't be serialized,
 213   // so there is no hacking of finals going on with them.
 214   if (holder->is_anonymous())
 215     return true;
 216   // Trust final fields in all boxed classes
 217   if (holder->is_box_klass())
 218     return true;
 219   // Trust final fields in String
 220   if (holder->name() == ciSymbol::java_lang_String())
 221     return true;
 222   // Trust Atomic*FieldUpdaters: they are very important for performance, and make up one
 223   // more reason not to use Unsafe, if their final fields are trusted. See more in JDK-8140483.
 224   if (holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicIntegerFieldUpdater_Impl() ||
 225       holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicLongFieldUpdater_CASUpdater() ||
 226       holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicLongFieldUpdater_LockedUpdater() ||
 227       holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicReferenceFieldUpdater_Impl()) {
 228     return true;
 229   }
 230   return TrustFinalNonStaticFields;
 231 }
 232 
 233 void ciField::initialize_from(fieldDescriptor* fd) {
 234   // Get the flags, offset, and canonical holder of the field.
 235   _flags = ciFlags(fd->access_flags());
 236   _offset = fd->offset();
 237   Klass* field_holder = fd->field_holder();
 238   assert(field_holder != NULL, "null field_holder");
 239   _holder = CURRENT_ENV->get_instance_klass(field_holder);
 240 
 241   // Check to see if the field is constant.
 242   Klass* k = _holder->get_Klass();
 243   bool is_stable_field = FoldStableValues && is_stable();
 244   if ((is_final() && !has_initialized_final_update()) || is_stable_field) {
 245     if (is_static()) {
 246       // This field just may be constant.  The only case where it will
 247       // not be constant is when the field is a *special* static & final field
 248       // whose value may change.  The three examples are java.lang.System.in,
 249       // java.lang.System.out, and java.lang.System.err.
 250       assert(SystemDictionary::System_klass() != NULL, "Check once per vm");
 251       if (k == SystemDictionary::System_klass()) {
 252         // Check offsets for case 2: System.in, System.out, or System.err
 253         if( _offset == java_lang_System::in_offset_in_bytes()  ||
 254             _offset == java_lang_System::out_offset_in_bytes() ||
 255             _offset == java_lang_System::err_offset_in_bytes() ) {
 256           _is_constant = false;
 257           return;
 258         }
 259       }
 260       _is_constant = true;
 261     } else {
 262       // An instance field can be constant if it's a final static field or if
 263       // it's a final non-static field of a trusted class (classes in
 264       // java.lang.invoke and sun.invoke packages and subpackages).
 265       _is_constant = is_stable_field || trust_final_non_static_fields(_holder);
 266     }
 267   } else {
 268     // For CallSite objects treat the target field as a compile time constant.
 269     assert(SystemDictionary::CallSite_klass() != NULL, "should be already initialized");
 270     if (k == SystemDictionary::CallSite_klass() &&
 271         _offset == java_lang_invoke_CallSite::target_offset_in_bytes()) {
 272       assert(!has_initialized_final_update(), "CallSite is not supposed to have writes to final fields outside initializers");
 273       _is_constant = true;
 274     } else {
 275       // Non-final & non-stable fields are not constants.
 276       _is_constant = false;
 277     }
 278   }
 279 }
 280 
 281 // ------------------------------------------------------------------
 282 // ciField::constant_value
 283 // Get the constant value of a this static field.
 284 ciConstant ciField::constant_value() {
 285   assert(is_static() && is_constant(), "illegal call to constant_value()");
 286   if (!_holder->is_initialized()) {
 287     return ciConstant(); // Not initialized yet
 288   }
 289   if (_constant_value.basic_type() == T_ILLEGAL) {
 290     // Static fields are placed in mirror objects.
 291     VM_ENTRY_MARK;
 292     ciInstance* mirror = CURRENT_ENV->get_instance(_holder->get_Klass()->java_mirror());
 293     _constant_value = mirror->field_value_impl(type()->basic_type(), offset());
 294   }
 295   if (FoldStableValues && is_stable() && _constant_value.is_null_or_zero()) {
 296     return ciConstant();
 297   }
 298   return _constant_value;
 299 }
 300 
 301 // ------------------------------------------------------------------
 302 // ciField::constant_value_of
 303 // Get the constant value of non-static final field in the given object.
 304 ciConstant ciField::constant_value_of(ciObject* object) {
 305   assert(!is_static() && is_constant(), "only if field is non-static constant");
 306   assert(object->is_instance(), "must be instance");
 307   ciConstant field_value = object->as_instance()->field_value(this);
 308   if (FoldStableValues && is_stable() && field_value.is_null_or_zero()) {
 309     return ciConstant();
 310   }
 311   return field_value;
 312 }
 313 
 314 // ------------------------------------------------------------------
 315 // ciField::compute_type
 316 //
 317 // Lazily compute the type, if it is an instance klass.
 318 ciType* ciField::compute_type() {
 319   GUARDED_VM_ENTRY(return compute_type_impl();)
 320 }
 321 
 322 ciType* ciField::compute_type_impl() {
 323   ciKlass* type = CURRENT_ENV->get_klass_by_name_impl(_holder, constantPoolHandle(), _signature, false);
 324   if (!type->is_primitive_type() && is_shared()) {
 325     // We must not cache a pointer to an unshared type, in a shared field.
 326     bool type_is_also_shared = false;
 327     if (type->is_type_array_klass()) {
 328       type_is_also_shared = true;  // int[] etc. are explicitly bootstrapped
 329     } else if (type->is_instance_klass()) {
 330       type_is_also_shared = type->as_instance_klass()->is_shared();
 331     } else {
 332       // Currently there is no 'shared' query for array types.
 333       type_is_also_shared = !ciObjectFactory::is_initialized();
 334     }
 335     if (!type_is_also_shared)
 336       return type;              // Bummer.
 337   }
 338   _type = type;
 339   return type;
 340 }
 341 
 342 
 343 // ------------------------------------------------------------------
 344 // ciField::will_link
 345 //
 346 // Can a specific access to this field be made without causing
 347 // link errors?
 348 bool ciField::will_link(ciMethod* accessing_method,
 349                         Bytecodes::Code bc) {
 350   VM_ENTRY_MARK;
 351   assert(bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic ||
 352          bc == Bytecodes::_getfield  || bc == Bytecodes::_putfield,
 353          "unexpected bytecode");
 354 
 355   if (_offset == -1) {
 356     // at creation we couldn't link to our holder so we need to
 357     // maintain that stance, otherwise there's no safe way to use this
 358     // ciField.
 359     return false;
 360   }
 361 
 362   // Check for static/nonstatic mismatch
 363   bool is_static = (bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic);
 364   if (is_static != this->is_static()) {
 365     return false;
 366   }
 367 
 368   // Get and put can have different accessibility rules
 369   bool is_put    = (bc == Bytecodes::_putfield  || bc == Bytecodes::_putstatic);
 370   if (is_put) {
 371     if (_known_to_link_with_put == accessing_method) {
 372       return true;
 373     }
 374   } else {
 375     if (_known_to_link_with_get == accessing_method->holder()) {
 376       return true;
 377     }
 378   }
 379 
 380   LinkInfo link_info(_holder->get_instanceKlass(),
 381                      _name->get_symbol(), _signature->get_symbol(),
 382                      accessing_method->get_Method());
 383   fieldDescriptor result;
 384   LinkResolver::resolve_field(result, link_info, bc, false, KILL_COMPILE_ON_FATAL_(false));
 385 
 386   // update the hit-cache, unless there is a problem with memory scoping:
 387   if (accessing_method->holder()->is_shared() || !is_shared()) {
 388     if (is_put) {
 389       _known_to_link_with_put = accessing_method;
 390     } else {
 391       _known_to_link_with_get = accessing_method->holder();
 392     }
 393   }
 394 
 395   return true;
 396 }
 397 
 398 // ------------------------------------------------------------------
 399 // ciField::print
 400 void ciField::print() {
 401   tty->print("<ciField name=");
 402   _holder->print_name();
 403   tty->print(".");
 404   _name->print_symbol();
 405   tty->print(" signature=");
 406   _signature->print_symbol();
 407   tty->print(" offset=%d type=", _offset);
 408   if (_type != NULL)
 409     _type->print_name();
 410   else
 411     tty->print("(reference)");
 412   tty->print(" flags=%04x", flags().as_int());
 413   tty->print(" is_constant=%s", bool_to_str(_is_constant));
 414   if (_is_constant && is_static()) {
 415     tty->print(" constant_value=");
 416     _constant_value.print();
 417   }
 418   tty->print(">");
 419 }
 420 
 421 // ------------------------------------------------------------------
 422 // ciField::print_name_on
 423 //
 424 // Print the name of this field
 425 void ciField::print_name_on(outputStream* st) {
 426   name()->print_symbol_on(st);
 427 }
--- EOF ---