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
 21  * questions.
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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     _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   // Get the field's declared holder.
109   //
110   // Note: we actually create a ciInstanceKlass for this klass,
111   // even though we may not need to.
112   int holder_index = cpool->klass_ref_index_at(index);
113   bool holder_is_accessible;
114 
115   ciKlass* generic_declared_holder = ciEnv::current(THREAD)->get_klass_by_index(cpool, holder_index,
116                                                                                 holder_is_accessible,
117                                                                                 klass);
118 
119   if (generic_declared_holder->is_array_klass()) {
120     // If the declared holder of the field is an array class, assume that
121     // the canonical holder of that field is java.lang.Object. Arrays
122     // do not have fields; java.lang.Object is the only supertype of an
123     // array type that can declare fields and is therefore the canonical
124     // holder of the array type.
125     //
126     // Furthermore, the compilers assume that java.lang.Object does not
127     // have any fields. Therefore, the field is not looked up. Instead,
128     // the method returns partial information that will trigger special
129     // handling in ciField::will_link and will result in a
130     // java.lang.NoSuchFieldError exception being thrown by the compiled
131     // code (the expected behavior in this case).
132     _holder = ciEnv::current(THREAD)->Object_klass();
133     _offset = -1;
134     _is_constant = false;
135     return;
136   }
137 
138   ciInstanceKlass* declared_holder = generic_declared_holder->as_instance_klass();
139 
140   // The declared holder of this field may not have been loaded.
141   // Bail out with partial field information.
142   if (!holder_is_accessible) {
143     // _type has already been set.
144     // The default values for _flags and _constant_value will suffice.
145     // We need values for _holder, _offset,  and _is_constant,
146     _holder = declared_holder;
147     _offset = -1;
148     _is_constant = false;
149     return;
150   }
151 
152   InstanceKlass* loaded_decl_holder = declared_holder->get_instanceKlass();
153 
154   // Perform the field lookup.
155   fieldDescriptor field_desc;
156   Klass* canonical_holder =
157     loaded_decl_holder->find_field(name, signature, &field_desc);
158   if (canonical_holder == NULL) {
159     // Field lookup failed.  Will be detected by will_link.
160     _holder = declared_holder;
161     _offset = -1;
162     _is_constant = false;
163     return;
164   }
165 
166   // Access check based on declared_holder. canonical_holder should not be used
167   // to check access because it can erroneously succeed. If this check fails,
168   // propagate the declared holder to will_link() which in turn will bail out
169   // compilation for this field access.
170   bool can_access = Reflection::verify_member_access(klass->get_Klass(),
171                                                      declared_holder->get_Klass(),
172                                                      canonical_holder,
173                                                      field_desc.access_flags(),
174                                                      true, false, THREAD);
175   if (!can_access) {
176     _holder = declared_holder;
177     _offset = -1;
178     _is_constant = false;
179     // It's possible the access check failed due to a nestmate access check
180     // encountering an exception. We can't propagate the exception from here
181     // so we have to clear it. If the access check happens again in a different
182     // context then the exception will be thrown there.
183     if (HAS_PENDING_EXCEPTION) {
184       CLEAR_PENDING_EXCEPTION;
185     }
186     return;
187   }
188 
189   assert(canonical_holder == field_desc.field_holder(), "just checking");
190   initialize_from(&field_desc);
191 }
192 
193 ciField::ciField(fieldDescriptor *fd) :
194     _known_to_link_with_put(NULL), _known_to_link_with_get(NULL) {
195   ASSERT_IN_VM;
196 
197   // Get the field's name, signature, and type.
198   ciEnv* env = CURRENT_ENV;
199   _name = env->get_symbol(fd->name());
200   _signature = env->get_symbol(fd->signature());
201 
202   BasicType field_type = fd->field_type();
203 
204   // If the field is a pointer type, get the klass of the
205   // field.
206   if (is_reference_type(field_type)) {
207     _type = NULL;  // must call compute_type on first access
208   } else {
209     _type = ciType::make(field_type);
210   }
211 
212   initialize_from(fd);
213 
214   // Either (a) it is marked shared, or else (b) we are done bootstrapping.
215   assert(is_shared() || ciObjectFactory::is_initialized(),
216          "bootstrap classes must not create & cache unshared fields");
217 }
218 
219 static bool trust_final_non_static_fields(ciInstanceKlass* holder) {
220   if (holder == NULL)
221     return false;
222   if (holder->name() == ciSymbols::java_lang_System())
223     // Never trust strangely unstable finals:  System.out, etc.
224     return false;
225   // Even if general trusting is disabled, trust system-built closures in these packages.
226   if (holder->is_in_package("java/lang/invoke") || holder->is_in_package("sun/invoke") ||
227       holder->is_in_package("jdk/internal/foreign") || holder->is_in_package("jdk/incubator/foreign") ||
228       holder->is_in_package("jdk/internal/vm/vector") || holder->is_in_package("jdk/incubator/vector") ||
229       holder->is_in_package("java/lang"))
230     return true;
231   // Trust hidden classes. They are created via Lookup.defineHiddenClass and
232   // can't be serialized, so there is no hacking of finals going on with them.
233   if (holder->is_hidden())
234     return true;
235   // Trust final fields in all boxed classes
236   if (holder->is_box_klass())
237     return true;
238   // Trust final fields in records
239   if (holder->is_record())
240     return true;
241   // Trust final fields in String
242   if (holder->name() == ciSymbols::java_lang_String())
243     return true;
244   // Trust Atomic*FieldUpdaters: they are very important for performance, and make up one
245   // more reason not to use Unsafe, if their final fields are trusted. See more in JDK-8140483.
246   if (holder->name() == ciSymbols::java_util_concurrent_atomic_AtomicIntegerFieldUpdater_Impl() ||
247       holder->name() == ciSymbols::java_util_concurrent_atomic_AtomicLongFieldUpdater_CASUpdater() ||
248       holder->name() == ciSymbols::java_util_concurrent_atomic_AtomicLongFieldUpdater_LockedUpdater() ||
249       holder->name() == ciSymbols::java_util_concurrent_atomic_AtomicReferenceFieldUpdater_Impl()) {
250     return true;
251   }
252   return TrustFinalNonStaticFields;
253 }
254 
255 void ciField::initialize_from(fieldDescriptor* fd) {
256   // Get the flags, offset, and canonical holder of the field.
257   _flags = ciFlags(fd->access_flags());
258   _offset = fd->offset();
259   Klass* field_holder = fd->field_holder();
260   assert(field_holder != NULL, "null field_holder");
261   _holder = CURRENT_ENV->get_instance_klass(field_holder);
262 
263   // Check to see if the field is constant.
264   Klass* k = _holder->get_Klass();
265   bool is_stable_field = FoldStableValues && is_stable();
266   if ((is_final() && !has_initialized_final_update()) || is_stable_field) {
267     if (is_static()) {
268       // This field just may be constant.  The only case where it will
269       // not be constant is when the field is a *special* static & final field
270       // whose value may change.  The three examples are java.lang.System.in,
271       // java.lang.System.out, and java.lang.System.err.
272       assert(vmClasses::System_klass() != NULL, "Check once per vm");
273       if (k == vmClasses::System_klass()) {
274         // Check offsets for case 2: System.in, System.out, or System.err
275         if (_offset == java_lang_System::in_offset()  ||
276             _offset == java_lang_System::out_offset() ||
277             _offset == java_lang_System::err_offset()) {
278           _is_constant = false;
279           return;
280         }
281       }
282       _is_constant = true;
283     } else {
284       // An instance field can be constant if it's a final static field or if
285       // it's a final non-static field of a trusted class (classes in
286       // java.lang.invoke and sun.invoke packages and subpackages).
287       _is_constant = is_stable_field || trust_final_non_static_fields(_holder);
288     }
289   } else {
290     // For CallSite objects treat the target field as a compile time constant.
291     assert(vmClasses::CallSite_klass() != NULL, "should be already initialized");
292     if (k == vmClasses::CallSite_klass() &&
293         _offset == java_lang_invoke_CallSite::target_offset()) {
294       assert(!has_initialized_final_update(), "CallSite is not supposed to have writes to final fields outside initializers");
295       _is_constant = true;
296     } else {
297       // Non-final & non-stable fields are not constants.
298       _is_constant = false;
299     }
300   }
301 }
302 
303 // ------------------------------------------------------------------
304 // ciField::constant_value
305 // Get the constant value of a this static field.
306 ciConstant ciField::constant_value() {
307   assert(is_static() && is_constant(), "illegal call to constant_value()");
308   if (!_holder->is_initialized()) {
309     return ciConstant(); // Not initialized yet
310   }
311   if (_constant_value.basic_type() == T_ILLEGAL) {
312     // Static fields are placed in mirror objects.
313     VM_ENTRY_MARK;
314     ciInstance* mirror = CURRENT_ENV->get_instance(_holder->get_Klass()->java_mirror());
315     _constant_value = mirror->field_value_impl(type()->basic_type(), offset());
316   }
317   if (FoldStableValues && is_stable() && _constant_value.is_null_or_zero()) {
318     return ciConstant();
319   }
320   return _constant_value;
321 }
322 
323 // ------------------------------------------------------------------
324 // ciField::constant_value_of
325 // Get the constant value of non-static final field in the given object.
326 ciConstant ciField::constant_value_of(ciObject* object) {
327   assert(!is_static() && is_constant(), "only if field is non-static constant");
328   assert(object->is_instance(), "must be instance");
329   ciConstant field_value = object->as_instance()->field_value(this);
330   if (FoldStableValues && is_stable() && field_value.is_null_or_zero()) {
331     return ciConstant();
332   }
333   return field_value;
334 }
335 
336 // ------------------------------------------------------------------
337 // ciField::compute_type
338 //
339 // Lazily compute the type, if it is an instance klass.
340 ciType* ciField::compute_type() {
341   GUARDED_VM_ENTRY(return compute_type_impl();)
342 }
343 
344 ciType* ciField::compute_type_impl() {
345   ciKlass* type = CURRENT_ENV->get_klass_by_name_impl(_holder, constantPoolHandle(), _signature, false);
346   if (!type->is_primitive_type() && is_shared()) {
347     // We must not cache a pointer to an unshared type, in a shared field.
348     bool type_is_also_shared = false;
349     if (type->is_type_array_klass()) {
350       type_is_also_shared = true;  // int[] etc. are explicitly bootstrapped
351     } else if (type->is_instance_klass()) {
352       type_is_also_shared = type->as_instance_klass()->is_shared();
353     } else {
354       // Currently there is no 'shared' query for array types.
355       type_is_also_shared = !ciObjectFactory::is_initialized();
356     }
357     if (!type_is_also_shared)
358       return type;              // Bummer.
359   }
360   _type = type;
361   return type;
362 }
363 
364 
365 // ------------------------------------------------------------------
366 // ciField::will_link
367 //
368 // Can a specific access to this field be made without causing
369 // link errors?
370 bool ciField::will_link(ciMethod* accessing_method,
371                         Bytecodes::Code bc) {
372   VM_ENTRY_MARK;
373   assert(bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic ||
374          bc == Bytecodes::_getfield  || bc == Bytecodes::_putfield,
375          "unexpected bytecode");
376 
377   if (_offset == -1) {
378     // at creation we couldn't link to our holder so we need to
379     // maintain that stance, otherwise there's no safe way to use this
380     // ciField.
381     return false;
382   }
383 
384   // Check for static/nonstatic mismatch
385   bool is_static = (bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic);
386   if (is_static != this->is_static()) {
387     return false;
388   }
389 
390   // Get and put can have different accessibility rules
391   bool is_put    = (bc == Bytecodes::_putfield  || bc == Bytecodes::_putstatic);
392   if (is_put) {
393     if (_known_to_link_with_put == accessing_method) {
394       return true;
395     }
396   } else {
397     if (_known_to_link_with_get == accessing_method->holder()) {
398       return true;
399     }
400   }
401 
402   LinkInfo link_info(_holder->get_instanceKlass(),
403                      _name->get_symbol(), _signature->get_symbol(),
404                      methodHandle(THREAD, accessing_method->get_Method()));
405   fieldDescriptor result;
406   LinkResolver::resolve_field(result, link_info, bc, false, CHECK_AND_CLEAR_(false));
407 
408   // update the hit-cache, unless there is a problem with memory scoping:
409   if (accessing_method->holder()->is_shared() || !is_shared()) {
410     if (is_put) {
411       _known_to_link_with_put = accessing_method;
412     } else {
413       _known_to_link_with_get = accessing_method->holder();
414     }
415   }
416 
417   return true;
418 }
419 
420 bool ciField::is_call_site_target() {
421   ciInstanceKlass* callsite_klass = CURRENT_ENV->CallSite_klass();
422   if (callsite_klass == NULL)
423     return false;
424   return (holder()->is_subclass_of(callsite_klass) && (name() == ciSymbols::target_name()));
425 }
426 
427 bool ciField::is_autobox_cache() {
428   ciSymbol* klass_name = holder()->name();
429   return (name() == ciSymbols::cache_field_name() &&
430           holder()->uses_default_loader() &&
431           (klass_name == ciSymbols::java_lang_Character_CharacterCache() ||
432             klass_name == ciSymbols::java_lang_Byte_ByteCache() ||
433             klass_name == ciSymbols::java_lang_Short_ShortCache() ||
434             klass_name == ciSymbols::java_lang_Integer_IntegerCache() ||
435             klass_name == ciSymbols::java_lang_Long_LongCache()));
436 }
437 
438 // ------------------------------------------------------------------
439 // ciField::print
440 void ciField::print() {
441   tty->print("<ciField name=");
442   _holder->print_name();
443   tty->print(".");
444   _name->print_symbol();
445   tty->print(" signature=");
446   _signature->print_symbol();
447   tty->print(" offset=%d type=", _offset);
448   if (_type != NULL)
449     _type->print_name();
450   else
451     tty->print("(reference)");
452   tty->print(" flags=%04x", flags().as_int());
453   tty->print(" is_constant=%s", bool_to_str(_is_constant));
454   if (_is_constant && is_static()) {
455     tty->print(" constant_value=");
456     _constant_value.print();
457   }
458   tty->print(">");
459 }
460 
461 // ------------------------------------------------------------------
462 // ciField::print_name_on
463 //
464 // Print the name of this field
465 void ciField::print_name_on(outputStream* st) {
466   name()->print_symbol_on(st);
467 }