1 /*
2 * Copyright (c) 1999, 2023, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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5 * This code is free software; you can redistribute it and/or modify it
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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23 */
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, 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 // 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, bc);
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 == nullptr) {
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(nullptr), _known_to_link_with_get(nullptr) {
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 = nullptr; // 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 flat 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_flat(), "field must not be flat");
242 _is_flat = false;
243 _is_null_free = field->_is_null_free;
244 _original_holder = (field->_original_holder != nullptr) ? field->_original_holder : field->_holder;
245 }
246
247 static bool trust_final_non_static_fields(ciInstanceKlass* holder) {
248 if (holder == nullptr)
249 return false;
250 if (holder->name() == ciSymbols::java_lang_System())
251 // Never trust strangely unstable finals: System.out, etc.
252 return false;
253 // Even if general trusting is disabled, trust system-built closures in these packages.
254 if (holder->is_in_package("java/lang/invoke") || holder->is_in_package("sun/invoke") ||
255 holder->is_in_package("java/lang/reflect") || holder->is_in_package("jdk/internal/reflect") ||
256 holder->is_in_package("jdk/internal/foreign/layout") || holder->is_in_package("jdk/internal/foreign") ||
257 holder->is_in_package("jdk/internal/vm/vector") || holder->is_in_package("jdk/incubator/vector") ||
258 holder->is_in_package("java/lang"))
259 return true;
260 // Trust hidden classes. They are created via Lookup.defineHiddenClass and
261 // can't be serialized, so there is no hacking of finals going on with them.
262 if (holder->is_hidden())
263 return true;
264 // Trust final fields in inline type buffers
265 if (holder->is_inlinetype())
266 return true;
267 // Trust final fields in all boxed classes
268 if (holder->is_box_klass())
269 return true;
270 // Trust final fields in records
271 if (holder->is_record())
272 return true;
273 // Trust final fields in String
274 if (holder->name() == ciSymbols::java_lang_String())
275 return true;
276 // Trust Atomic*FieldUpdaters: they are very important for performance, and make up one
277 // more reason not to use Unsafe, if their final fields are trusted. See more in JDK-8140483.
278 if (holder->name() == ciSymbols::java_util_concurrent_atomic_AtomicIntegerFieldUpdater_Impl() ||
279 holder->name() == ciSymbols::java_util_concurrent_atomic_AtomicLongFieldUpdater_CASUpdater() ||
280 holder->name() == ciSymbols::java_util_concurrent_atomic_AtomicLongFieldUpdater_LockedUpdater() ||
281 holder->name() == ciSymbols::java_util_concurrent_atomic_AtomicReferenceFieldUpdater_Impl()) {
282 return true;
283 }
284 return TrustFinalNonStaticFields;
285 }
286
287 void ciField::initialize_from(fieldDescriptor* fd) {
288 // Get the flags, offset, and canonical holder of the field.
289 _flags = ciFlags(fd->access_flags(), fd->field_flags().is_stable(), fd->field_status().is_initialized_final_update());
290 _offset = fd->offset();
291 Klass* field_holder = fd->field_holder();
292 assert(field_holder != nullptr, "null field_holder");
293 _holder = CURRENT_ENV->get_instance_klass(field_holder);
294 _is_flat = fd->is_flat();
295 _is_null_free = fd->is_null_free_inline_type();
296 _original_holder = nullptr;
297
298 // Check to see if the field is constant.
299 Klass* k = _holder->get_Klass();
300 bool is_stable_field = FoldStableValues && is_stable();
301 if ((is_final() && !has_initialized_final_update()) || is_stable_field) {
302 if (is_static()) {
303 // This field just may be constant. The only case where it will
304 // not be constant is when the field is a *special* static & final field
305 // whose value may change. The three examples are java.lang.System.in,
306 // java.lang.System.out, and java.lang.System.err.
307 assert(vmClasses::System_klass() != nullptr, "Check once per vm");
308 if (k == vmClasses::System_klass()) {
309 // Check offsets for case 2: System.in, System.out, or System.err
310 if (_offset == java_lang_System::in_offset() ||
311 _offset == java_lang_System::out_offset() ||
312 _offset == java_lang_System::err_offset()) {
313 _is_constant = false;
314 return;
315 }
316 }
317 _is_constant = true;
318 } else {
319 // An instance field can be constant if it's a final static field or if
320 // it's a final non-static field of a trusted class (classes in
321 // java.lang.invoke and sun.invoke packages and subpackages).
322 _is_constant = is_stable_field || trust_final_non_static_fields(_holder);
323 }
324 } else {
325 // For CallSite objects treat the target field as a compile time constant.
326 assert(vmClasses::CallSite_klass() != nullptr, "should be already initialized");
327 if (k == vmClasses::CallSite_klass() &&
328 _offset == java_lang_invoke_CallSite::target_offset()) {
329 assert(!has_initialized_final_update(), "CallSite is not supposed to have writes to final fields outside initializers");
330 _is_constant = true;
331 } else {
332 // Non-final & non-stable fields are not constants.
333 _is_constant = false;
334 }
335 }
336 }
337
338 // ------------------------------------------------------------------
339 // ciField::constant_value
340 // Get the constant value of a this static field.
341 ciConstant ciField::constant_value() {
342 assert(is_static() && is_constant(), "illegal call to constant_value()");
343 if (!_holder->is_initialized()) {
344 return ciConstant(); // Not initialized yet
345 }
346 if (_constant_value.basic_type() == T_ILLEGAL) {
347 // Static fields are placed in mirror objects.
348 ciInstance* mirror = _holder->java_mirror();
349 _constant_value = mirror->field_value_impl(type()->basic_type(), offset_in_bytes());
350 }
351 if (FoldStableValues && is_stable() && _constant_value.is_null_or_zero()) {
352 return ciConstant();
353 }
354 return _constant_value;
355 }
356
357 // ------------------------------------------------------------------
358 // ciField::constant_value_of
359 // Get the constant value of non-static final field in the given object.
360 ciConstant ciField::constant_value_of(ciObject* object) {
361 assert(!is_static() && is_constant(), "only if field is non-static constant");
362 assert(object->is_instance(), "must be instance");
363 ciConstant field_value = object->as_instance()->field_value(this);
364 if (FoldStableValues && is_stable() && field_value.is_null_or_zero()) {
365 return ciConstant();
366 }
367 return field_value;
368 }
369
370 // ------------------------------------------------------------------
371 // ciField::compute_type
372 //
373 // Lazily compute the type, if it is an instance klass.
374 ciType* ciField::compute_type() {
375 GUARDED_VM_ENTRY(return compute_type_impl();)
376 }
377
378 ciType* ciField::compute_type_impl() {
379 // Use original holder for fields that came in through flattening
380 ciKlass* accessing_klass = (_original_holder != nullptr) ? _original_holder : _holder;
381 ciKlass* type = CURRENT_ENV->get_klass_by_name_impl(accessing_klass, constantPoolHandle(), _signature, false);
382 if (!type->is_primitive_type() && is_shared()) {
383 // We must not cache a pointer to an unshared type, in a shared field.
384 bool type_is_also_shared = false;
385 if (type->is_type_array_klass()) {
386 type_is_also_shared = true; // int[] etc. are explicitly bootstrapped
387 } else if (type->is_instance_klass()) {
388 type_is_also_shared = type->as_instance_klass()->is_shared();
389 } else {
390 // Currently there is no 'shared' query for array types.
391 type_is_also_shared = !ciObjectFactory::is_initialized();
392 }
393 if (!type_is_also_shared)
394 return type; // Bummer.
395 }
396 _type = type;
397 return type;
398 }
399
400
401 // ------------------------------------------------------------------
402 // ciField::will_link
403 //
404 // Can a specific access to this field be made without causing
405 // link errors?
406 bool ciField::will_link(ciMethod* accessing_method,
407 Bytecodes::Code bc) {
408 VM_ENTRY_MARK;
409 assert(bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic ||
410 bc == Bytecodes::_getfield || bc == Bytecodes::_putfield ||
411 bc == Bytecodes::_withfield, "unexpected bytecode");
412
413 if (_offset == -1) {
414 // at creation we couldn't link to our holder so we need to
415 // maintain that stance, otherwise there's no safe way to use this
416 // ciField.
417 return false;
418 }
419
420 // Check for static/nonstatic mismatch
421 bool is_static = (bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic);
422 if (is_static != this->is_static()) {
423 return false;
424 }
425
426 // Get and put can have different accessibility rules
427 bool is_put = (bc == Bytecodes::_putfield || bc == Bytecodes::_putstatic);
428 if (is_put) {
429 if (_known_to_link_with_put == accessing_method) {
430 return true;
431 }
432 } else {
433 if (_known_to_link_with_get == accessing_method->holder()) {
434 return true;
435 }
436 }
437
438 LinkInfo link_info(_holder->get_instanceKlass(),
439 _name->get_symbol(), _signature->get_symbol(),
440 methodHandle(THREAD, accessing_method->get_Method()));
441 fieldDescriptor result;
442 LinkResolver::resolve_field(result, link_info, bc, false, CHECK_AND_CLEAR_(false));
443
444 // update the hit-cache, unless there is a problem with memory scoping:
445 if (accessing_method->holder()->is_shared() || !is_shared()) {
446 if (is_put) {
447 _known_to_link_with_put = accessing_method;
448 } else {
449 _known_to_link_with_get = accessing_method->holder();
450 }
451 }
452
453 return true;
454 }
455
456 bool ciField::is_call_site_target() {
457 ciInstanceKlass* callsite_klass = CURRENT_ENV->CallSite_klass();
458 if (callsite_klass == nullptr)
459 return false;
460 return (holder()->is_subclass_of(callsite_klass) && (name() == ciSymbols::target_name()));
461 }
462
463 bool ciField::is_autobox_cache() {
464 ciSymbol* klass_name = holder()->name();
465 return (name() == ciSymbols::cache_field_name() &&
466 holder()->uses_default_loader() &&
467 (klass_name == ciSymbols::java_lang_Character_CharacterCache() ||
468 klass_name == ciSymbols::java_lang_Byte_ByteCache() ||
469 klass_name == ciSymbols::java_lang_Short_ShortCache() ||
470 klass_name == ciSymbols::java_lang_Integer_IntegerCache() ||
471 klass_name == ciSymbols::java_lang_Long_LongCache()));
472 }
473
474 // ------------------------------------------------------------------
475 // ciField::print
476 void ciField::print() {
477 tty->print("<ciField name=");
478 _holder->print_name();
479 tty->print(".");
480 _name->print_symbol();
481 tty->print(" signature=");
482 _signature->print_symbol();
483 tty->print(" offset=%d type=", _offset);
484 if (_type != nullptr)
485 _type->print_name();
486 else
487 tty->print("(reference)");
488 tty->print(" flags=%04x", flags().as_int());
489 tty->print(" is_constant=%s", bool_to_str(_is_constant));
490 if (_is_constant && is_static()) {
491 tty->print(" constant_value=");
492 _constant_value.print();
493 }
494 tty->print(" is_flat=%s", bool_to_str(_is_flat));
495 tty->print(" is_null_free=%s", bool_to_str(_is_null_free));
496 tty->print(">");
497 }
498
499 // ------------------------------------------------------------------
500 // ciField::print_name_on
501 //
502 // Print the name of this field
503 void ciField::print_name_on(outputStream* st) {
504 name()->print_symbol_on(st);
505 }