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