1 /*
  2  * Copyright (c) 1999, 2024, 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.
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  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  *
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 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/reflection.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, Bytecodes::Code bc) :
 74   _original_holder(nullptr), _is_flat(false), _known_to_link_with_put(nullptr), _known_to_link_with_get(nullptr) {
 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, bc);
 86   _name = ciEnv::current(THREAD)->get_symbol(name);
 87 
 88   int nt_index = cpool->name_and_type_ref_index_at(index, bc);
 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   _is_null_free = false;
109 
110   // Get the field's declared holder.
111   //
112   // Note: we actually create a ciInstanceKlass for this klass,
113   // even though we may not need to.
114   int holder_index = cpool->klass_ref_index_at(index, bc);
115   bool holder_is_accessible;
116 
117   ciKlass* generic_declared_holder = ciEnv::current(THREAD)->get_klass_by_index(cpool, holder_index,
118                                                                                 holder_is_accessible,
119                                                                                 klass);
120 
121   if (generic_declared_holder->is_array_klass()) {
122     // If the declared holder of the field is an array class, assume that
123     // the canonical holder of that field is java.lang.Object. Arrays
124     // do not have fields; java.lang.Object is the only supertype of an
125     // array type that can declare fields and is therefore the canonical
126     // holder of the array type.
127     //
128     // Furthermore, the compilers assume that java.lang.Object does not
129     // have any fields. Therefore, the field is not looked up. Instead,
130     // the method returns partial information that will trigger special
131     // handling in ciField::will_link and will result in a
132     // java.lang.NoSuchFieldError exception being thrown by the compiled
133     // code (the expected behavior in this case).
134     _holder = ciEnv::current(THREAD)->Object_klass();
135     _offset = -1;
136     _is_constant = false;
137     return;
138   }
139 
140   ciInstanceKlass* declared_holder = generic_declared_holder->as_instance_klass();
141 
142   // The declared holder of this field may not have been loaded.
143   // Bail out with partial field information.
144   if (!holder_is_accessible) {
145     // _type has already been set.
146     // The default values for _flags and _constant_value will suffice.
147     // We need values for _holder, _offset,  and _is_constant,
148     _holder = declared_holder;
149     _offset = -1;
150     _is_constant = false;
151     return;
152   }
153 
154   InstanceKlass* loaded_decl_holder = declared_holder->get_instanceKlass();
155 
156   // Perform the field lookup.
157   fieldDescriptor field_desc;
158   Klass* canonical_holder =
159     loaded_decl_holder->find_field(name, signature, &field_desc);
160   if (canonical_holder == nullptr) {
161     // Field lookup failed.  Will be detected by will_link.
162     _holder = declared_holder;
163     _offset = -1;
164     _is_constant = false;
165     return;
166   }
167 
168   // Access check based on declared_holder. canonical_holder should not be used
169   // to check access because it can erroneously succeed. If this check fails,
170   // propagate the declared holder to will_link() which in turn will bail out
171   // compilation for this field access.
172   bool can_access = Reflection::verify_member_access(klass->get_Klass(),
173                                                      declared_holder->get_Klass(),
174                                                      canonical_holder,
175                                                      field_desc.access_flags(),
176                                                      true, false, THREAD);
177   if (!can_access) {
178     _holder = declared_holder;
179     _offset = -1;
180     _is_constant = false;
181     // It's possible the access check failed due to a nestmate access check
182     // encountering an exception. We can't propagate the exception from here
183     // so we have to clear it. If the access check happens again in a different
184     // context then the exception will be thrown there.
185     if (HAS_PENDING_EXCEPTION) {
186       CLEAR_PENDING_EXCEPTION;
187     }
188     return;
189   }
190 
191   assert(canonical_holder == field_desc.field_holder(), "just checking");
192   initialize_from(&field_desc);
193 }
194 
195 ciField::ciField(fieldDescriptor *fd) :
196     _known_to_link_with_put(nullptr), _known_to_link_with_get(nullptr) {
197   ASSERT_IN_VM;
198 
199   // Get the field's name, signature, and type.
200   ciEnv* env = CURRENT_ENV;
201   _name = env->get_symbol(fd->name());
202   _signature = env->get_symbol(fd->signature());
203 
204   BasicType field_type = fd->field_type();
205 
206   // If the field is a pointer type, get the klass of the
207   // field.
208   if (is_reference_type(field_type)) {
209     _type = nullptr;  // must call compute_type on first access
210   } else {
211     _type = ciType::make(field_type);
212   }
213 
214   initialize_from(fd);
215 
216   // Either (a) it is marked shared, or else (b) we are done bootstrapping.
217   assert(is_shared() || ciObjectFactory::is_initialized(),
218          "bootstrap classes must not create & cache unshared fields");
219 }
220 
221 // Special copy constructor used to flatten inline type fields by
222 // copying the fields of the inline type to a new holder klass.
223 ciField::ciField(ciField* field, ciInstanceKlass* holder, int offset, bool is_final) {
224   assert(field->holder()->is_inlinetype(), "should only be used for inline type field flattening");
225   // Set the is_final flag
226   jint final = is_final ? JVM_ACC_FINAL : ~JVM_ACC_FINAL;
227   AccessFlags flags(field->flags().as_int() & final);
228   _flags = ciFlags(flags);
229   _holder = holder;
230   _offset = offset;
231   // Copy remaining fields
232   _name = field->_name;
233   _signature = field->_signature;
234   _type = field->_type;
235   // Trust final flat fields
236   _is_constant = is_final;
237   _known_to_link_with_put = field->_known_to_link_with_put;
238   _known_to_link_with_get = field->_known_to_link_with_get;
239   _constant_value = field->_constant_value;
240   assert(!field->is_flat(), "field must not be flat");
241   _is_flat = false;
242   _is_null_free = field->_is_null_free;
243   _original_holder = (field->_original_holder != nullptr) ? field->_original_holder : field->_holder;
244 }
245 
246 static bool trust_final_non_static_fields(ciInstanceKlass* holder) {
247   if (holder == nullptr)
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("java/lang/reflect") || holder->is_in_package("jdk/internal/reflect") ||
255       holder->is_in_package("jdk/internal/foreign/layout") || holder->is_in_package("jdk/internal/foreign") ||
256       holder->is_in_package("jdk/internal/vm/vector") || holder->is_in_package("jdk/incubator/vector") ||
257       holder->is_in_package("java/lang"))
258     return true;
259   // Trust hidden classes. They are created via Lookup.defineHiddenClass and
260   // can't be serialized, so there is no hacking of finals going on with them.
261   if (holder->is_hidden())
262     return true;
263   // Trust final fields in inline type buffers
264   if (holder->is_inlinetype())
265     return true;
266   // Trust final fields in all boxed classes
267   if (holder->is_box_klass())
268     return true;
269   // Trust final fields in records
270   if (holder->is_record())
271     return true;
272   // Trust final fields in String
273   if (holder->name() == ciSymbols::java_lang_String())
274     return true;
275   // Trust Atomic*FieldUpdaters: they are very important for performance, and make up one
276   // more reason not to use Unsafe, if their final fields are trusted. See more in JDK-8140483.
277   if (holder->name() == ciSymbols::java_util_concurrent_atomic_AtomicIntegerFieldUpdater_Impl() ||
278       holder->name() == ciSymbols::java_util_concurrent_atomic_AtomicLongFieldUpdater_CASUpdater() ||
279       holder->name() == ciSymbols::java_util_concurrent_atomic_AtomicLongFieldUpdater_LockedUpdater() ||
280       holder->name() == ciSymbols::java_util_concurrent_atomic_AtomicReferenceFieldUpdater_Impl()) {
281     return true;
282   }
283   return TrustFinalNonStaticFields;
284 }
285 
286 void ciField::initialize_from(fieldDescriptor* fd) {
287   // Get the flags, offset, and canonical holder of the field.
288   _flags = ciFlags(fd->access_flags(), fd->field_flags().is_stable(), fd->field_status().is_initialized_final_update());
289   _offset = fd->offset();
290   Klass* field_holder = fd->field_holder();
291   assert(field_holder != nullptr, "null field_holder");
292   _holder = CURRENT_ENV->get_instance_klass(field_holder);
293   _is_flat = fd->is_flat();
294   _is_null_free = fd->is_null_free_inline_type();
295   _original_holder = nullptr;
296 
297   // Check to see if the field is constant.
298   Klass* k = _holder->get_Klass();
299   bool is_stable_field = FoldStableValues && is_stable();
300   if ((is_final() && !has_initialized_final_update()) || is_stable_field) {
301     if (is_static()) {
302       // This field just may be constant.  The only case where it will
303       // not be constant is when the field is a *special* static & final field
304       // whose value may change.  The three examples are java.lang.System.in,
305       // java.lang.System.out, and java.lang.System.err.
306       assert(vmClasses::System_klass() != nullptr, "Check once per vm");
307       if (k == vmClasses::System_klass()) {
308         // Check offsets for case 2: System.in, System.out, or System.err
309         if (_offset == java_lang_System::in_offset()  ||
310             _offset == java_lang_System::out_offset() ||
311             _offset == java_lang_System::err_offset()) {
312           _is_constant = false;
313           return;
314         }
315       }
316       _is_constant = true;
317     } else {
318       // An instance field can be constant if it's a final static field or if
319       // it's a final non-static field of a trusted class (classes in
320       // java.lang.invoke and sun.invoke packages and subpackages).
321       _is_constant = is_stable_field || trust_final_non_static_fields(_holder);
322     }
323   } else {
324     // For CallSite objects treat the target field as a compile time constant.
325     assert(vmClasses::CallSite_klass() != nullptr, "should be already initialized");
326     if (k == vmClasses::CallSite_klass() &&
327         _offset == java_lang_invoke_CallSite::target_offset()) {
328       assert(!has_initialized_final_update(), "CallSite is not supposed to have writes to final fields outside initializers");
329       _is_constant = true;
330     } else {
331       // Non-final & non-stable fields are not constants.
332       _is_constant = false;
333     }
334   }
335 }
336 
337 // ------------------------------------------------------------------
338 // ciField::constant_value
339 // Get the constant value of a this static field.
340 ciConstant ciField::constant_value() {
341   assert(is_static() && is_constant(), "illegal call to constant_value()");
342   if (!_holder->is_initialized()) {
343     return ciConstant(); // Not initialized yet
344   }
345   if (_constant_value.basic_type() == T_ILLEGAL) {
346     // Static fields are placed in mirror objects.
347     ciInstance* mirror = _holder->java_mirror();
348     _constant_value = mirror->field_value_impl(type()->basic_type(), offset_in_bytes());
349   }
350   if (FoldStableValues && is_stable() && _constant_value.is_null_or_zero()) {
351     return ciConstant();
352   }
353   return _constant_value;
354 }
355 
356 // ------------------------------------------------------------------
357 // ciField::constant_value_of
358 // Get the constant value of non-static final field in the given object.
359 ciConstant ciField::constant_value_of(ciObject* object) {
360   assert(!is_static() && is_constant(), "only if field is non-static constant");
361   assert(object->is_instance(), "must be instance");
362   ciConstant field_value = object->as_instance()->field_value(this);
363   if (FoldStableValues && is_stable() && field_value.is_null_or_zero()) {
364     return ciConstant();
365   }
366   return field_value;
367 }
368 
369 // ------------------------------------------------------------------
370 // ciField::compute_type
371 //
372 // Lazily compute the type, if it is an instance klass.
373 ciType* ciField::compute_type() {
374   GUARDED_VM_ENTRY(return compute_type_impl();)
375 }
376 
377 ciType* ciField::compute_type_impl() {
378   // Use original holder for fields that came in through flattening
379   ciKlass* accessing_klass = (_original_holder != nullptr) ? _original_holder : _holder;
380   ciKlass* type = CURRENT_ENV->get_klass_by_name_impl(accessing_klass, constantPoolHandle(), _signature, false);
381   if (!type->is_primitive_type() && is_shared()) {
382     // We must not cache a pointer to an unshared type, in a shared field.
383     bool type_is_also_shared = false;
384     if (type->is_type_array_klass()) {
385       type_is_also_shared = true;  // int[] etc. are explicitly bootstrapped
386     } else if (type->is_instance_klass()) {
387       type_is_also_shared = type->as_instance_klass()->is_shared();
388     } else {
389       // Currently there is no 'shared' query for array types.
390       type_is_also_shared = !ciObjectFactory::is_initialized();
391     }
392     if (!type_is_also_shared)
393       return type;              // Bummer.
394   }
395   _type = type;
396   return type;
397 }
398 
399 
400 // ------------------------------------------------------------------
401 // ciField::will_link
402 //
403 // Can a specific access to this field be made without causing
404 // link errors?
405 bool ciField::will_link(ciMethod* accessing_method,
406                         Bytecodes::Code bc) {
407   VM_ENTRY_MARK;
408   assert(bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic ||
409          bc == Bytecodes::_getfield  || bc == Bytecodes::_putfield,
410          "unexpected bytecode");
411 
412   if (_offset == -1) {
413     // at creation we couldn't link to our holder so we need to
414     // maintain that stance, otherwise there's no safe way to use this
415     // ciField.
416     return false;
417   }
418 
419   // Check for static/nonstatic mismatch
420   bool is_static = (bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic);
421   if (is_static != this->is_static()) {
422     return false;
423   }
424 
425   // Get and put can have different accessibility rules
426   bool is_put    = (bc == Bytecodes::_putfield  || bc == Bytecodes::_putstatic);
427   if (is_put) {
428     if (_known_to_link_with_put == accessing_method) {
429       return true;
430     }
431   } else {
432     if (_known_to_link_with_get == accessing_method->holder()) {
433       return true;
434     }
435   }
436 
437   LinkInfo link_info(_holder->get_instanceKlass(),
438                      _name->get_symbol(), _signature->get_symbol(),
439                      methodHandle(THREAD, accessing_method->get_Method()));
440   fieldDescriptor result;
441   LinkResolver::resolve_field(result, link_info, bc, false, CHECK_AND_CLEAR_(false));
442 
443   // update the hit-cache, unless there is a problem with memory scoping:
444   if (accessing_method->holder()->is_shared() || !is_shared()) {
445     if (is_put) {
446       _known_to_link_with_put = accessing_method;
447     } else {
448       _known_to_link_with_get = accessing_method->holder();
449     }
450   }
451 
452   return true;
453 }
454 
455 bool ciField::is_call_site_target() {
456   ciInstanceKlass* callsite_klass = CURRENT_ENV->CallSite_klass();
457   if (callsite_klass == nullptr)
458     return false;
459   return (holder()->is_subclass_of(callsite_klass) && (name() == ciSymbols::target_name()));
460 }
461 
462 bool ciField::is_autobox_cache() {
463   ciSymbol* klass_name = holder()->name();
464   return (name() == ciSymbols::cache_field_name() &&
465           holder()->uses_default_loader() &&
466           (klass_name == ciSymbols::java_lang_Character_CharacterCache() ||
467             klass_name == ciSymbols::java_lang_Byte_ByteCache() ||
468             klass_name == ciSymbols::java_lang_Short_ShortCache() ||
469             klass_name == ciSymbols::java_lang_Integer_IntegerCache() ||
470             klass_name == ciSymbols::java_lang_Long_LongCache()));
471 }
472 
473 // ------------------------------------------------------------------
474 // ciField::print
475 void ciField::print() {
476   tty->print("<ciField name=");
477   _holder->print_name();
478   tty->print(".");
479   _name->print_symbol();
480   tty->print(" signature=");
481   _signature->print_symbol();
482   tty->print(" offset=%d type=", _offset);
483   if (_type != nullptr)
484     _type->print_name();
485   else
486     tty->print("(reference)");
487   tty->print(" flags=%04x", flags().as_int());
488   tty->print(" is_constant=%s", bool_to_str(_is_constant));
489   if (_is_constant && is_static()) {
490     tty->print(" constant_value=");
491     _constant_value.print();
492   }
493   tty->print(" is_flat=%s", bool_to_str(_is_flat));
494   tty->print(" is_null_free=%s", bool_to_str(_is_null_free));
495   tty->print(">");
496 }
497 
498 // ------------------------------------------------------------------
499 // ciField::print_name_on
500 //
501 // Print the name of this field
502 void ciField::print_name_on(outputStream* st) {
503   name()->print_symbol_on(st);
504 }