1 /*
  2  * Copyright (c) 1999, 2021, 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
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 24 
 25 #include "precompiled.hpp"
 26 #include "ci/ciField.hpp"
 27 #include "ci/ciInstanceKlass.hpp"
 28 #include "ci/ciSymbols.hpp"
 29 #include "ci/ciUtilities.inline.hpp"
 30 #include "classfile/javaClasses.hpp"
 31 #include "classfile/vmClasses.hpp"
 32 #include "gc/shared/collectedHeap.inline.hpp"
 33 #include "interpreter/linkResolver.hpp"
 34 #include "oops/klass.inline.hpp"
 35 #include "oops/oop.inline.hpp"
 36 #include "runtime/fieldDescriptor.inline.hpp"
 37 #include "runtime/handles.inline.hpp"
 38 #include "runtime/reflectionUtils.hpp"
 39 
 40 // ciField
 41 //
 42 // This class represents the result of a field lookup in the VM.
 43 // The lookup may not succeed, in which case the information in
 44 // the ciField will be incomplete.
 45 
 46 // The ciObjectFactory cannot create circular data structures in one query.
 47 // To avoid vicious circularities, we initialize ciField::_type to NULL
 48 // for reference types and derive it lazily from the ciField::_signature.
 49 // Primitive types are eagerly initialized, and basic layout queries
 50 // can succeed without initialization, using only the BasicType of the field.
 51 
 52 // Notes on bootstrapping and shared CI objects:  A field is shared if and
 53 // only if it is (a) non-static and (b) declared by a shared instance klass.
 54 // This allows non-static field lists to be cached on shared types.
 55 // Because the _type field is lazily initialized, however, there is a
 56 // special restriction that a shared field cannot cache an unshared type.
 57 // This puts a small performance penalty on shared fields with unshared
 58 // types, such as StackTraceElement[] Throwable.stackTrace.
 59 // (Throwable is shared because ClassCastException is shared, but
 60 // StackTraceElement is not presently shared.)
 61 
 62 // It is not a vicious circularity for a ciField to recursively create
 63 // the ciSymbols necessary to represent its name and signature.
 64 // Therefore, these items are created eagerly, and the name and signature
 65 // of a shared field are themselves shared symbols.  This somewhat
 66 // pollutes the set of shared CI objects:  It grows from 50 to 93 items,
 67 // with all of the additional 43 being uninteresting shared ciSymbols.
 68 // This adds at most one step to the binary search, an amount which
 69 // decreases for complex compilation tasks.
 70 
 71 // ------------------------------------------------------------------
 72 // ciField::ciField
 73 ciField::ciField(ciInstanceKlass* klass, int index) :
 74   _is_flattened(false), _known_to_link_with_put(NULL), _known_to_link_with_get(NULL) {
 75   ASSERT_IN_VM;
 76   CompilerThread *THREAD = CompilerThread::current();
 77 
 78   assert(ciObjectFactory::is_initialized(), "not a shared field");
 79 
 80   assert(klass->get_instanceKlass()->is_linked(), "must be linked before using its constant-pool");
 81 
 82   constantPoolHandle cpool(THREAD, klass->get_instanceKlass()->constants());
 83 
 84   // Get the field's name, signature, and type.
 85   Symbol* name  = cpool->name_ref_at(index);
 86   _name = ciEnv::current(THREAD)->get_symbol(name);
 87 
 88   int nt_index = cpool->name_and_type_ref_index_at(index);
 89   int sig_index = cpool->signature_ref_index_at(nt_index);
 90   Symbol* signature = cpool->symbol_at(sig_index);
 91   _signature = ciEnv::current(THREAD)->get_symbol(signature);
 92 
 93   BasicType field_type = Signature::basic_type(signature);
 94 
 95   // If the field is a pointer type, get the klass of the
 96   // field.
 97   if (is_reference_type(field_type)) {
 98     bool ignore;
 99     // This is not really a class reference; the index always refers to the
100     // field's type signature, as a symbol.  Linkage checks do not apply.
101     _type = ciEnv::current(THREAD)->get_klass_by_index(cpool, sig_index, ignore, klass);
102   } else {
103     _type = ciType::make(field_type);
104   }
105 
106   _name = (ciSymbol*)ciEnv::current(THREAD)->get_symbol(name);
107 
108   // this is needed if the field class is not yet loaded.
109   _is_null_free = _signature->is_Q_signature();
110 
111   // Get the field's declared holder.
112   //
113   // Note: we actually create a ciInstanceKlass for this klass,
114   // even though we may not need to.
115   int holder_index = cpool->klass_ref_index_at(index);
116   bool holder_is_accessible;
117 
118   ciKlass* generic_declared_holder = ciEnv::current(THREAD)->get_klass_by_index(cpool, holder_index,
119                                                                                 holder_is_accessible,
120                                                                                 klass);
121 
122   if (generic_declared_holder->is_array_klass()) {
123     // If the declared holder of the field is an array class, assume that
124     // the canonical holder of that field is java.lang.Object. Arrays
125     // do not have fields; java.lang.Object is the only supertype of an
126     // array type that can declare fields and is therefore the canonical
127     // holder of the array type.
128     //
129     // Furthermore, the compilers assume that java.lang.Object does not
130     // have any fields. Therefore, the field is not looked up. Instead,
131     // the method returns partial information that will trigger special
132     // handling in ciField::will_link and will result in a
133     // java.lang.NoSuchFieldError exception being thrown by the compiled
134     // code (the expected behavior in this case).
135     _holder = ciEnv::current(THREAD)->Object_klass();
136     _offset = -1;
137     _is_constant = false;
138     return;
139   }
140 
141   ciInstanceKlass* declared_holder = generic_declared_holder->as_instance_klass();
142 
143   // The declared holder of this field may not have been loaded.
144   // Bail out with partial field information.
145   if (!holder_is_accessible) {
146     // _type has already been set.
147     // The default values for _flags and _constant_value will suffice.
148     // We need values for _holder, _offset,  and _is_constant,
149     _holder = declared_holder;
150     _offset = -1;
151     _is_constant = false;
152     return;
153   }
154 
155   InstanceKlass* loaded_decl_holder = declared_holder->get_instanceKlass();
156 
157   // Perform the field lookup.
158   fieldDescriptor field_desc;
159   Klass* canonical_holder =
160     loaded_decl_holder->find_field(name, signature, &field_desc);
161   if (canonical_holder == NULL) {
162     // Field lookup failed.  Will be detected by will_link.
163     _holder = declared_holder;
164     _offset = -1;
165     _is_constant = false;
166     return;
167   }
168 
169   // Access check based on declared_holder. canonical_holder should not be used
170   // to check access because it can erroneously succeed. If this check fails,
171   // propagate the declared holder to will_link() which in turn will bail out
172   // compilation for this field access.
173   bool can_access = Reflection::verify_member_access(klass->get_Klass(),
174                                                      declared_holder->get_Klass(),
175                                                      canonical_holder,
176                                                      field_desc.access_flags(),
177                                                      true, false, THREAD);
178   if (!can_access) {
179     _holder = declared_holder;
180     _offset = -1;
181     _is_constant = false;
182     // It's possible the access check failed due to a nestmate access check
183     // encountering an exception. We can't propagate the exception from here
184     // so we have to clear it. If the access check happens again in a different
185     // context then the exception will be thrown there.
186     if (HAS_PENDING_EXCEPTION) {
187       CLEAR_PENDING_EXCEPTION;
188     }
189     return;
190   }
191 
192   assert(canonical_holder == field_desc.field_holder(), "just checking");
193   initialize_from(&field_desc);
194 }
195 
196 ciField::ciField(fieldDescriptor *fd) :
197     _known_to_link_with_put(NULL), _known_to_link_with_get(NULL) {
198   ASSERT_IN_VM;
199 
200   // Get the field's name, signature, and type.
201   ciEnv* env = CURRENT_ENV;
202   _name = env->get_symbol(fd->name());
203   _signature = env->get_symbol(fd->signature());
204 
205   BasicType field_type = fd->field_type();
206 
207   // If the field is a pointer type, get the klass of the
208   // field.
209   if (is_reference_type(field_type)) {
210     _type = NULL;  // must call compute_type on first access
211   } else {
212     _type = ciType::make(field_type);
213   }
214 
215   initialize_from(fd);
216 
217   // Either (a) it is marked shared, or else (b) we are done bootstrapping.
218   assert(is_shared() || ciObjectFactory::is_initialized(),
219          "bootstrap classes must not create & cache unshared fields");
220 }
221 
222 // Special copy constructor used to flatten inline type fields by
223 // copying the fields of the inline type to a new holder klass.
224 ciField::ciField(ciField* field, ciInstanceKlass* holder, int offset, bool is_final) {
225   assert(field->holder()->is_inlinetype(), "should only be used for inline type field flattening");
226   // Set the is_final flag
227   jint final = is_final ? JVM_ACC_FINAL : ~JVM_ACC_FINAL;
228   AccessFlags flags(field->flags().as_int() & final);
229   _flags = ciFlags(flags);
230   _holder = holder;
231   _offset = offset;
232   // Copy remaining fields
233   _name = field->_name;
234   _signature = field->_signature;
235   _type = field->_type;
236   // Trust final flattened fields
237   _is_constant = is_final;
238   _known_to_link_with_put = field->_known_to_link_with_put;
239   _known_to_link_with_get = field->_known_to_link_with_get;
240   _constant_value = field->_constant_value;
241   assert(!field->is_flattened(), "field must not be flattened");
242   _is_flattened = false;
243   _is_null_free = field->is_null_free();
244 }
245 
246 static bool trust_final_non_static_fields(ciInstanceKlass* holder) {
247   if (holder == NULL)
248     return false;
249   if (holder->name() == ciSymbols::java_lang_System())
250     // Never trust strangely unstable finals:  System.out, etc.
251     return false;
252   // Even if general trusting is disabled, trust system-built closures in these packages.
253   if (holder->is_in_package("java/lang/invoke") || holder->is_in_package("sun/invoke") ||
254       holder->is_in_package("jdk/internal/foreign") || holder->is_in_package("jdk/incubator/foreign") ||
255       holder->is_in_package("jdk/internal/vm/vector") || holder->is_in_package("jdk/incubator/vector") ||
256       holder->is_in_package("java/lang"))
257     return true;
258   // Trust hidden classes. They are created via Lookup.defineHiddenClass and
259   // can't be serialized, so there is no hacking of finals going on with them.
260   if (holder->is_hidden())
261     return true;
262   // Trust final fields in inline type buffers
263   if (holder->is_inlinetype())
264     return true;
265   // Trust final fields in all boxed classes
266   if (holder->is_box_klass())
267     return true;
268   // Trust final fields in records
269   if (holder->is_record())
270     return true;
271   // Trust final fields in String
272   if (holder->name() == ciSymbols::java_lang_String())
273     return true;
274   // Trust Atomic*FieldUpdaters: they are very important for performance, and make up one
275   // more reason not to use Unsafe, if their final fields are trusted. See more in JDK-8140483.
276   if (holder->name() == ciSymbols::java_util_concurrent_atomic_AtomicIntegerFieldUpdater_Impl() ||
277       holder->name() == ciSymbols::java_util_concurrent_atomic_AtomicLongFieldUpdater_CASUpdater() ||
278       holder->name() == ciSymbols::java_util_concurrent_atomic_AtomicLongFieldUpdater_LockedUpdater() ||
279       holder->name() == ciSymbols::java_util_concurrent_atomic_AtomicReferenceFieldUpdater_Impl()) {
280     return true;
281   }
282   return TrustFinalNonStaticFields;
283 }
284 
285 void ciField::initialize_from(fieldDescriptor* fd) {
286   // Get the flags, offset, and canonical holder of the field.
287   _flags = ciFlags(fd->access_flags());
288   _offset = fd->offset();
289   Klass* field_holder = fd->field_holder();
290   assert(field_holder != NULL, "null field_holder");
291   _holder = CURRENT_ENV->get_instance_klass(field_holder);
292   _is_flattened = fd->is_inlined();
293   _is_null_free = fd->signature()->is_Q_signature();
294 
295   // Check to see if the field is constant.
296   Klass* k = _holder->get_Klass();
297   bool is_stable_field = FoldStableValues && is_stable();
298   if ((is_final() && !has_initialized_final_update()) || is_stable_field) {
299     if (is_static()) {
300       // This field just may be constant.  The only case where it will
301       // not be constant is when the field is a *special* static & final field
302       // whose value may change.  The three examples are java.lang.System.in,
303       // java.lang.System.out, and java.lang.System.err.
304       assert(vmClasses::System_klass() != NULL, "Check once per vm");
305       if (k == vmClasses::System_klass()) {
306         // Check offsets for case 2: System.in, System.out, or System.err
307         if (_offset == java_lang_System::in_offset()  ||
308             _offset == java_lang_System::out_offset() ||
309             _offset == java_lang_System::err_offset()) {
310           _is_constant = false;
311           return;
312         }
313       }
314       _is_constant = true;
315     } else {
316       // An instance field can be constant if it's a final static field or if
317       // it's a final non-static field of a trusted class (classes in
318       // java.lang.invoke and sun.invoke packages and subpackages).
319       _is_constant = is_stable_field || trust_final_non_static_fields(_holder);
320     }
321   } else {
322     // For CallSite objects treat the target field as a compile time constant.
323     assert(vmClasses::CallSite_klass() != NULL, "should be already initialized");
324     if (k == vmClasses::CallSite_klass() &&
325         _offset == java_lang_invoke_CallSite::target_offset()) {
326       assert(!has_initialized_final_update(), "CallSite is not supposed to have writes to final fields outside initializers");
327       _is_constant = true;
328     } else {
329       // Non-final & non-stable fields are not constants.
330       _is_constant = false;
331     }
332   }
333 }
334 
335 // ------------------------------------------------------------------
336 // ciField::constant_value
337 // Get the constant value of a this static field.
338 ciConstant ciField::constant_value() {
339   assert(is_static() && is_constant(), "illegal call to constant_value()");
340   if (!_holder->is_initialized()) {
341     return ciConstant(); // Not initialized yet
342   }
343   if (_constant_value.basic_type() == T_ILLEGAL) {
344     // Static fields are placed in mirror objects.
345     VM_ENTRY_MARK;
346     ciInstance* mirror = CURRENT_ENV->get_instance(_holder->get_Klass()->java_mirror());
347     _constant_value = mirror->field_value_impl(type()->basic_type(), offset());
348   }
349   if (FoldStableValues && is_stable() && _constant_value.is_null_or_zero()) {
350     return ciConstant();
351   }
352   return _constant_value;
353 }
354 
355 // ------------------------------------------------------------------
356 // ciField::constant_value_of
357 // Get the constant value of non-static final field in the given object.
358 ciConstant ciField::constant_value_of(ciObject* object) {
359   assert(!is_static() && is_constant(), "only if field is non-static constant");
360   assert(object->is_instance(), "must be instance");
361   ciConstant field_value = object->as_instance()->field_value(this);
362   if (FoldStableValues && is_stable() && field_value.is_null_or_zero()) {
363     return ciConstant();
364   }
365   return field_value;
366 }
367 
368 // ------------------------------------------------------------------
369 // ciField::compute_type
370 //
371 // Lazily compute the type, if it is an instance klass.
372 ciType* ciField::compute_type() {
373   GUARDED_VM_ENTRY(return compute_type_impl();)
374 }
375 
376 ciType* ciField::compute_type_impl() {
377   ciKlass* type = CURRENT_ENV->get_klass_by_name_impl(_holder, constantPoolHandle(), _signature, false);
378   if (!type->is_primitive_type() && is_shared()) {
379     // We must not cache a pointer to an unshared type, in a shared field.
380     bool type_is_also_shared = false;
381     if (type->is_type_array_klass()) {
382       type_is_also_shared = true;  // int[] etc. are explicitly bootstrapped
383     } else if (type->is_instance_klass()) {
384       type_is_also_shared = type->as_instance_klass()->is_shared();
385     } else {
386       // Currently there is no 'shared' query for array types.
387       type_is_also_shared = !ciObjectFactory::is_initialized();
388     }
389     if (!type_is_also_shared)
390       return type;              // Bummer.
391   }
392   _type = type;
393   return type;
394 }
395 
396 
397 // ------------------------------------------------------------------
398 // ciField::will_link
399 //
400 // Can a specific access to this field be made without causing
401 // link errors?
402 bool ciField::will_link(ciMethod* accessing_method,
403                         Bytecodes::Code bc) {
404   VM_ENTRY_MARK;
405   assert(bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic ||
406          bc == Bytecodes::_getfield  || bc == Bytecodes::_putfield  ||
407          bc == Bytecodes::_withfield, "unexpected bytecode");
408 
409   if (_offset == -1) {
410     // at creation we couldn't link to our holder so we need to
411     // maintain that stance, otherwise there's no safe way to use this
412     // ciField.
413     return false;
414   }
415 
416   // Check for static/nonstatic mismatch
417   bool is_static = (bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic);
418   if (is_static != this->is_static()) {
419     return false;
420   }
421 
422   // Get and put can have different accessibility rules
423   bool is_put    = (bc == Bytecodes::_putfield  || bc == Bytecodes::_putstatic);
424   if (is_put) {
425     if (_known_to_link_with_put == accessing_method) {
426       return true;
427     }
428   } else {
429     if (_known_to_link_with_get == accessing_method->holder()) {
430       return true;
431     }
432   }
433 
434   LinkInfo link_info(_holder->get_instanceKlass(),
435                      _name->get_symbol(), _signature->get_symbol(),
436                      methodHandle(THREAD, accessing_method->get_Method()));
437   fieldDescriptor result;
438   LinkResolver::resolve_field(result, link_info, bc, false, CHECK_AND_CLEAR_(false));
439 
440   // update the hit-cache, unless there is a problem with memory scoping:
441   if (accessing_method->holder()->is_shared() || !is_shared()) {
442     if (is_put) {
443       _known_to_link_with_put = accessing_method;
444     } else {
445       _known_to_link_with_get = accessing_method->holder();
446     }
447   }
448 
449   return true;
450 }
451 
452 bool ciField::is_call_site_target() {
453   ciInstanceKlass* callsite_klass = CURRENT_ENV->CallSite_klass();
454   if (callsite_klass == NULL)
455     return false;
456   return (holder()->is_subclass_of(callsite_klass) && (name() == ciSymbols::target_name()));
457 }
458 
459 bool ciField::is_autobox_cache() {
460   ciSymbol* klass_name = holder()->name();
461   return (name() == ciSymbols::cache_field_name() &&
462           holder()->uses_default_loader() &&
463           (klass_name == ciSymbols::java_lang_Character_CharacterCache() ||
464             klass_name == ciSymbols::java_lang_Byte_ByteCache() ||
465             klass_name == ciSymbols::java_lang_Short_ShortCache() ||
466             klass_name == ciSymbols::java_lang_Integer_IntegerCache() ||
467             klass_name == ciSymbols::java_lang_Long_LongCache()));
468 }
469 
470 // ------------------------------------------------------------------
471 // ciField::print
472 void ciField::print() {
473   tty->print("<ciField name=");
474   _holder->print_name();
475   tty->print(".");
476   _name->print_symbol();
477   tty->print(" signature=");
478   _signature->print_symbol();
479   tty->print(" offset=%d type=", _offset);
480   if (_type != NULL)
481     _type->print_name();
482   else
483     tty->print("(reference)");
484   tty->print(" flags=%04x", flags().as_int());
485   tty->print(" is_constant=%s", bool_to_str(_is_constant));
486   if (_is_constant && is_static()) {
487     tty->print(" constant_value=");
488     _constant_value.print();
489   }
490   tty->print(" is_flattened=%s", bool_to_str(_is_flattened));
491   tty->print(" is_null_free=%s", bool_to_str(_is_null_free));
492   tty->print(">");
493 }
494 
495 // ------------------------------------------------------------------
496 // ciField::print_name_on
497 //
498 // Print the name of this field
499 void ciField::print_name_on(outputStream* st) {
500   name()->print_symbol_on(st);
501 }