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.
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  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "ci/ciField.hpp"
  27 #include "ci/ciInstanceKlass.hpp"
  28 #include "ci/ciUtilities.inline.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.inline.hpp"
  35 #include "runtime/handles.inline.hpp"
  36 
  37 // ciField
  38 //
  39 // This class represents the result of a field lookup in the VM.
  40 // The lookup may not succeed, in which case the information in
  41 // the ciField will be incomplete.
  42 
  43 // The ciObjectFactory cannot create circular data structures in one query.
  44 // To avoid vicious circularities, we initialize ciField::_type to NULL
  45 // for reference types and derive it lazily from the ciField::_signature.
  46 // Primitive types are eagerly initialized, and basic layout queries
  47 // can succeed without initialization, using only the BasicType of the field.
  48 
  49 // Notes on bootstrapping and shared CI objects:  A field is shared if and
  50 // only if it is (a) non-static and (b) declared by a shared instance klass.
  51 // This allows non-static field lists to be cached on shared types.
  52 // Because the _type field is lazily initialized, however, there is a
  53 // special restriction that a shared field cannot cache an unshared type.
  54 // This puts a small performance penalty on shared fields with unshared
  55 // types, such as StackTraceElement[] Throwable.stackTrace.
  56 // (Throwable is shared because ClassCastException is shared, but
  57 // StackTraceElement is not presently shared.)
  58 
  59 // It is not a vicious circularity for a ciField to recursively create
  60 // the ciSymbols necessary to represent its name and signature.
  61 // Therefore, these items are created eagerly, and the name and signature
  62 // of a shared field are themselves shared symbols.  This somewhat
  63 // pollutes the set of shared CI objects:  It grows from 50 to 93 items,
  64 // with all of the additional 43 being uninteresting shared ciSymbols.
  65 // This adds at most one step to the binary search, an amount which
  66 // decreases for complex compilation tasks.
  67 
  68 // ------------------------------------------------------------------
  69 // ciField::ciField
  70 ciField::ciField(ciInstanceKlass* klass, int index) :
  71     _known_to_link_with_put(NULL), _known_to_link_with_get(NULL) {
  72   ASSERT_IN_VM;
  73   CompilerThread *THREAD = CompilerThread::current();
  74 
  75   assert(ciObjectFactory::is_initialized(), "not a shared field");
  76 
  77   assert(klass->get_instanceKlass()->is_linked(), "must be linked before using its constant-pool");
  78 
  79   constantPoolHandle cpool(THREAD, klass->get_instanceKlass()->constants());
  80 
  81   // Get the field's name, signature, and type.
  82   Symbol* name  = cpool->name_ref_at(index);
  83   _name = ciEnv::current(THREAD)->get_symbol(name);
  84 
  85   int nt_index = cpool->name_and_type_ref_index_at(index);
  86   int sig_index = cpool->signature_ref_index_at(nt_index);
  87   Symbol* signature = cpool->symbol_at(sig_index);
  88   _signature = ciEnv::current(THREAD)->get_symbol(signature);
  89 
  90   BasicType field_type = FieldType::basic_type(signature);
  91 
  92   // If the field is a pointer type, get the klass of the
  93   // field.
  94   if (field_type == T_OBJECT || field_type == T_ARRAY) {
  95     bool ignore;
  96     // This is not really a class reference; the index always refers to the
  97     // field's type signature, as a symbol.  Linkage checks do not apply.
  98     _type = ciEnv::current(THREAD)->get_klass_by_index(cpool, sig_index, ignore, klass);
  99   } else {
 100     _type = ciType::make(field_type);
 101   }
 102 
 103   _name = (ciSymbol*)ciEnv::current(THREAD)->get_symbol(name);
 104 
 105   // Get the field's declared holder.
 106   //
 107   // Note: we actually create a ciInstanceKlass for this klass,
 108   // even though we may not need to.
 109   int holder_index = cpool->klass_ref_index_at(index);
 110   bool holder_is_accessible;
 111 
 112   ciKlass* generic_declared_holder = ciEnv::current(THREAD)->get_klass_by_index(cpool, holder_index,
 113                                                                                 holder_is_accessible,
 114                                                                                 klass);
 115 
 116   if (generic_declared_holder->is_array_klass()) {
 117     // If the declared holder of the field is an array class, assume that
 118     // the canonical holder of that field is java.lang.Object. Arrays
 119     // do not have fields; java.lang.Object is the only supertype of an
 120     // array type that can declare fields and is therefore the canonical
 121     // holder of the array type.
 122     //
 123     // Furthermore, the compilers assume that java.lang.Object does not
 124     // have any fields. Therefore, the field is not looked up. Instead,
 125     // the method returns partial information that will trigger special
 126     // handling in ciField::will_link and will result in a
 127     // java.lang.NoSuchFieldError exception being thrown by the compiled
 128     // code (the expected behavior in this case).
 129     _holder = ciEnv::current(THREAD)->Object_klass();
 130     _offset = -1;
 131     _is_constant = false;
 132     return;
 133   }
 134 
 135   ciInstanceKlass* declared_holder = generic_declared_holder->as_instance_klass();
 136 
 137   // The declared holder of this field may not have been loaded.
 138   // Bail out with partial field information.
 139   if (!holder_is_accessible) {
 140     // _type has already been set.
 141     // The default values for _flags and _constant_value will suffice.
 142     // We need values for _holder, _offset,  and _is_constant,
 143     _holder = declared_holder;
 144     _offset = -1;
 145     _is_constant = false;
 146     return;
 147   }
 148 
 149   InstanceKlass* loaded_decl_holder = declared_holder->get_instanceKlass();
 150 
 151   // Perform the field lookup.
 152   fieldDescriptor field_desc;
 153   Klass* canonical_holder =
 154     loaded_decl_holder->find_field(name, signature, &field_desc);
 155   if (canonical_holder == NULL) {
 156     // Field lookup failed.  Will be detected by will_link.
 157     _holder = declared_holder;
 158     _offset = -1;
 159     _is_constant = false;
 160     return;
 161   }
 162 
 163   // Access check based on declared_holder. canonical_holder should not be used
 164   // to check access because it can erroneously succeed. If this check fails,
 165   // propagate the declared holder to will_link() which in turn will bail out
 166   // compilation for this field access.
 167   bool can_access = Reflection::verify_member_access(klass->get_Klass(),
 168                                                      declared_holder->get_Klass(),
 169                                                      canonical_holder,
 170                                                      field_desc.access_flags(),
 171                                                      true, false, THREAD);
 172   if (!can_access) {
 173     _holder = declared_holder;
 174     _offset = -1;
 175     _is_constant = false;
 176     // It's possible the access check failed due to a nestmate access check
 177     // encountering an exception. We can't propagate the exception from here
 178     // so we have to clear it. If the access check happens again in a different
 179     // context then the exception will be thrown there.
 180     if (HAS_PENDING_EXCEPTION) {
 181       CLEAR_PENDING_EXCEPTION;
 182     }
 183     return;
 184   }
 185 
 186   assert(canonical_holder == field_desc.field_holder(), "just checking");
 187   initialize_from(&field_desc);
 188 }
 189 
 190 ciField::ciField(fieldDescriptor *fd) :
 191     _known_to_link_with_put(NULL), _known_to_link_with_get(NULL) {
 192   ASSERT_IN_VM;
 193 
 194   // Get the field's name, signature, and type.
 195   ciEnv* env = CURRENT_ENV;
 196   _name = env->get_symbol(fd->name());
 197   _signature = env->get_symbol(fd->signature());
 198 
 199   BasicType field_type = fd->field_type();
 200 
 201   // If the field is a pointer type, get the klass of the
 202   // field.
 203   if (field_type == T_OBJECT || field_type == T_ARRAY) {
 204     _type = NULL;  // must call compute_type on first access
 205   } else {
 206     _type = ciType::make(field_type);
 207   }
 208 
 209   initialize_from(fd);
 210 
 211   // Either (a) it is marked shared, or else (b) we are done bootstrapping.
 212   assert(is_shared() || ciObjectFactory::is_initialized(),
 213          "bootstrap classes must not create & cache unshared fields");
 214 }
 215 
 216 static bool trust_final_non_static_fields(ciInstanceKlass* holder) {
 217   if (holder == NULL)
 218     return false;
 219   if (holder->name() == ciSymbol::java_lang_System())
 220     // Never trust strangely unstable finals:  System.out, etc.
 221     return false;
 222   // Even if general trusting is disabled, trust system-built closures in these packages.
 223   if (holder->is_in_package("java/lang/invoke") || holder->is_in_package("sun/invoke"))
 224     return true;
 225   // Trust VM nonfindable and unsafe anonymous classes. They are created via Lookup.defineClass or
 226   // the private API (jdk.internal.misc.Unsafe) and can't be serialized, so there is no hacking
 227   // of finals going on with them.
 228   if (holder->is_nonfindable() || holder->is_unsafe_anonymous())
 229     return true;
 230   // Trust final fields in all boxed classes
 231   if (holder->is_box_klass())
 232     return true;
 233   // Trust final fields in String
 234   if (holder->name() == ciSymbol::java_lang_String())
 235     return true;
 236   // Trust Atomic*FieldUpdaters: they are very important for performance, and make up one
 237   // more reason not to use Unsafe, if their final fields are trusted. See more in JDK-8140483.
 238   if (holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicIntegerFieldUpdater_Impl() ||
 239       holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicLongFieldUpdater_CASUpdater() ||
 240       holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicLongFieldUpdater_LockedUpdater() ||
 241       holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicReferenceFieldUpdater_Impl()) {
 242     return true;
 243   }
 244   return TrustFinalNonStaticFields;
 245 }
 246 
 247 void ciField::initialize_from(fieldDescriptor* fd) {
 248   // Get the flags, offset, and canonical holder of the field.
 249   _flags = ciFlags(fd->access_flags());
 250   _offset = fd->offset();
 251   Klass* field_holder = fd->field_holder();
 252   assert(field_holder != NULL, "null field_holder");
 253   _holder = CURRENT_ENV->get_instance_klass(field_holder);
 254 
 255   // Check to see if the field is constant.
 256   Klass* k = _holder->get_Klass();
 257   bool is_stable_field = FoldStableValues && is_stable();
 258   if ((is_final() && !has_initialized_final_update()) || is_stable_field) {
 259     if (is_static()) {
 260       // This field just may be constant.  The only case where it will
 261       // not be constant is when the field is a *special* static & final field
 262       // whose value may change.  The three examples are java.lang.System.in,
 263       // java.lang.System.out, and java.lang.System.err.
 264       assert(SystemDictionary::System_klass() != NULL, "Check once per vm");
 265       if (k == SystemDictionary::System_klass()) {
 266         // Check offsets for case 2: System.in, System.out, or System.err
 267         if( _offset == java_lang_System::in_offset_in_bytes()  ||
 268             _offset == java_lang_System::out_offset_in_bytes() ||
 269             _offset == java_lang_System::err_offset_in_bytes() ) {
 270           _is_constant = false;
 271           return;
 272         }
 273       }
 274       _is_constant = true;
 275     } else {
 276       // An instance field can be constant if it's a final static field or if
 277       // it's a final non-static field of a trusted class (classes in
 278       // java.lang.invoke and sun.invoke packages and subpackages).
 279       _is_constant = is_stable_field || trust_final_non_static_fields(_holder);
 280     }
 281   } else {
 282     // For CallSite objects treat the target field as a compile time constant.
 283     assert(SystemDictionary::CallSite_klass() != NULL, "should be already initialized");
 284     if (k == SystemDictionary::CallSite_klass() &&
 285         _offset == java_lang_invoke_CallSite::target_offset_in_bytes()) {
 286       assert(!has_initialized_final_update(), "CallSite is not supposed to have writes to final fields outside initializers");
 287       _is_constant = true;
 288     } else {
 289       // Non-final & non-stable fields are not constants.
 290       _is_constant = false;
 291     }
 292   }
 293 }
 294 
 295 // ------------------------------------------------------------------
 296 // ciField::constant_value
 297 // Get the constant value of a this static field.
 298 ciConstant ciField::constant_value() {
 299   assert(is_static() && is_constant(), "illegal call to constant_value()");
 300   if (!_holder->is_initialized()) {
 301     return ciConstant(); // Not initialized yet
 302   }
 303   if (_constant_value.basic_type() == T_ILLEGAL) {
 304     // Static fields are placed in mirror objects.
 305     VM_ENTRY_MARK;
 306     ciInstance* mirror = CURRENT_ENV->get_instance(_holder->get_Klass()->java_mirror());
 307     _constant_value = mirror->field_value_impl(type()->basic_type(), offset());
 308   }
 309   if (FoldStableValues && is_stable() && _constant_value.is_null_or_zero()) {
 310     return ciConstant();
 311   }
 312   return _constant_value;
 313 }
 314 
 315 // ------------------------------------------------------------------
 316 // ciField::constant_value_of
 317 // Get the constant value of non-static final field in the given object.
 318 ciConstant ciField::constant_value_of(ciObject* object) {
 319   assert(!is_static() && is_constant(), "only if field is non-static constant");
 320   assert(object->is_instance(), "must be instance");
 321   ciConstant field_value = object->as_instance()->field_value(this);
 322   if (FoldStableValues && is_stable() && field_value.is_null_or_zero()) {
 323     return ciConstant();
 324   }
 325   return field_value;
 326 }
 327 
 328 // ------------------------------------------------------------------
 329 // ciField::compute_type
 330 //
 331 // Lazily compute the type, if it is an instance klass.
 332 ciType* ciField::compute_type() {
 333   GUARDED_VM_ENTRY(return compute_type_impl();)
 334 }
 335 
 336 ciType* ciField::compute_type_impl() {
 337   ciKlass* type = CURRENT_ENV->get_klass_by_name_impl(_holder, constantPoolHandle(), _signature, false);
 338   if (!type->is_primitive_type() && is_shared()) {
 339     // We must not cache a pointer to an unshared type, in a shared field.
 340     bool type_is_also_shared = false;
 341     if (type->is_type_array_klass()) {
 342       type_is_also_shared = true;  // int[] etc. are explicitly bootstrapped
 343     } else if (type->is_instance_klass()) {
 344       type_is_also_shared = type->as_instance_klass()->is_shared();
 345     } else {
 346       // Currently there is no 'shared' query for array types.
 347       type_is_also_shared = !ciObjectFactory::is_initialized();
 348     }
 349     if (!type_is_also_shared)
 350       return type;              // Bummer.
 351   }
 352   _type = type;
 353   return type;
 354 }
 355 
 356 
 357 // ------------------------------------------------------------------
 358 // ciField::will_link
 359 //
 360 // Can a specific access to this field be made without causing
 361 // link errors?
 362 bool ciField::will_link(ciMethod* accessing_method,
 363                         Bytecodes::Code bc) {
 364   VM_ENTRY_MARK;
 365   assert(bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic ||
 366          bc == Bytecodes::_getfield  || bc == Bytecodes::_putfield,
 367          "unexpected bytecode");
 368 
 369   if (_offset == -1) {
 370     // at creation we couldn't link to our holder so we need to
 371     // maintain that stance, otherwise there's no safe way to use this
 372     // ciField.
 373     return false;
 374   }
 375 
 376   // Check for static/nonstatic mismatch
 377   bool is_static = (bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic);
 378   if (is_static != this->is_static()) {
 379     return false;
 380   }
 381 
 382   // Get and put can have different accessibility rules
 383   bool is_put    = (bc == Bytecodes::_putfield  || bc == Bytecodes::_putstatic);
 384   if (is_put) {
 385     if (_known_to_link_with_put == accessing_method) {
 386       return true;
 387     }
 388   } else {
 389     if (_known_to_link_with_get == accessing_method->holder()) {
 390       return true;
 391     }
 392   }
 393 
 394   LinkInfo link_info(_holder->get_instanceKlass(),
 395                      _name->get_symbol(), _signature->get_symbol(),
 396                      accessing_method->get_Method());
 397   fieldDescriptor result;
 398   LinkResolver::resolve_field(result, link_info, bc, false, KILL_COMPILE_ON_FATAL_(false));
 399 
 400   // update the hit-cache, unless there is a problem with memory scoping:
 401   if (accessing_method->holder()->is_shared() || !is_shared()) {
 402     if (is_put) {
 403       _known_to_link_with_put = accessing_method;
 404     } else {
 405       _known_to_link_with_get = accessing_method->holder();
 406     }
 407   }
 408 
 409   return true;
 410 }
 411 
 412 // ------------------------------------------------------------------
 413 // ciField::print
 414 void ciField::print() {
 415   tty->print("<ciField name=");
 416   _holder->print_name();
 417   tty->print(".");
 418   _name->print_symbol();
 419   tty->print(" signature=");
 420   _signature->print_symbol();
 421   tty->print(" offset=%d type=", _offset);
 422   if (_type != NULL)
 423     _type->print_name();
 424   else
 425     tty->print("(reference)");
 426   tty->print(" flags=%04x", flags().as_int());
 427   tty->print(" is_constant=%s", bool_to_str(_is_constant));
 428   if (_is_constant && is_static()) {
 429     tty->print(" constant_value=");
 430     _constant_value.print();
 431   }
 432   tty->print(">");
 433 }
 434 
 435 // ------------------------------------------------------------------
 436 // ciField::print_name_on
 437 //
 438 // Print the name of this field
 439 void ciField::print_name_on(outputStream* st) {
 440   name()->print_symbol_on(st);
 441 }