1 /*
2 * Copyright (c) 1999, 2018, 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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7 * published by the Free Software Foundation.
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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).
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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/ciUtilities.hpp"
29 #include "classfile/systemDictionary.hpp"
30 #include "gc/shared/collectedHeap.inline.hpp"
31 #include "interpreter/linkResolver.hpp"
32 #include "memory/universe.hpp"
33 #include "oops/oop.inline.hpp"
34 #include "runtime/fieldDescriptor.hpp"
35
36 // ciField
37 //
38 // This class represents the result of a field lookup in the VM.
39 // The lookup may not succeed, in which case the information in
40 // the ciField will be incomplete.
41
42 // The ciObjectFactory cannot create circular data structures in one query.
43 // To avoid vicious circularities, we initialize ciField::_type to NULL
44 // for reference types and derive it lazily from the ciField::_signature.
45 // Primitive types are eagerly initialized, and basic layout queries
46 // can succeed without initialization, using only the BasicType of the field.
47
48 // Notes on bootstrapping and shared CI objects: A field is shared if and
49 // only if it is (a) non-static and (b) declared by a shared instance klass.
50 // This allows non-static field lists to be cached on shared types.
51 // Because the _type field is lazily initialized, however, there is a
52 // special restriction that a shared field cannot cache an unshared type.
53 // This puts a small performance penalty on shared fields with unshared
54 // types, such as StackTraceElement[] Throwable.stackTrace.
55 // (Throwable is shared because ClassCastException is shared, but
56 // StackTraceElement is not presently shared.)
57
58 // It is not a vicious circularity for a ciField to recursively create
59 // the ciSymbols necessary to represent its name and signature.
60 // Therefore, these items are created eagerly, and the name and signature
61 // of a shared field are themselves shared symbols. This somewhat
62 // pollutes the set of shared CI objects: It grows from 50 to 93 items,
63 // with all of the additional 43 being uninteresting shared ciSymbols.
64 // This adds at most one step to the binary search, an amount which
65 // decreases for complex compilation tasks.
66
67 // ------------------------------------------------------------------
68 // ciField::ciField
69 ciField::ciField(ciInstanceKlass* klass, int index) :
70 _known_to_link_with_put(NULL), _known_to_link_with_get(NULL) {
71 ASSERT_IN_VM;
72 CompilerThread *thread = CompilerThread::current();
73
74 assert(ciObjectFactory::is_initialized(), "not a shared field");
75
76 assert(klass->get_instanceKlass()->is_linked(), "must be linked before using its constant-pool");
77
78 constantPoolHandle cpool(thread, klass->get_instanceKlass()->constants());
79
80 // Get the field's name, signature, and type.
81 Symbol* name = cpool->name_ref_at(index);
82 _name = ciEnv::current(thread)->get_symbol(name);
83
84 int nt_index = cpool->name_and_type_ref_index_at(index);
85 int sig_index = cpool->signature_ref_index_at(nt_index);
86 Symbol* signature = cpool->symbol_at(sig_index);
87 _signature = ciEnv::current(thread)->get_symbol(signature);
88
89 BasicType field_type = FieldType::basic_type(signature);
90
91 // If the field is a pointer type, get the klass of the
92 // field.
93 if (field_type == T_OBJECT || field_type == T_ARRAY) {
94 bool ignore;
95 // This is not really a class reference; the index always refers to the
96 // field's type signature, as a symbol. Linkage checks do not apply.
97 _type = ciEnv::current(thread)->get_klass_by_index(cpool, sig_index, ignore, klass);
98 } else {
99 _type = ciType::make(field_type);
100 }
101
102 _name = (ciSymbol*)ciEnv::current(thread)->get_symbol(name);
103
104 // Get the field's declared holder.
105 //
106 // Note: we actually create a ciInstanceKlass for this klass,
107 // even though we may not need to.
108 int holder_index = cpool->klass_ref_index_at(index);
109 bool holder_is_accessible;
110
111 ciKlass* generic_declared_holder = ciEnv::current(thread)->get_klass_by_index(cpool, holder_index,
112 holder_is_accessible,
113 klass);
114
115 if (generic_declared_holder->is_array_klass()) {
116 // If the declared holder of the field is an array class, assume that
117 // the canonical holder of that field is java.lang.Object. Arrays
118 // do not have fields; java.lang.Object is the only supertype of an
119 // array type that can declare fields and is therefore the canonical
120 // holder of the array type.
121 //
122 // Furthermore, the compilers assume that java.lang.Object does not
123 // have any fields. Therefore, the field is not looked up. Instead,
124 // the method returns partial information that will trigger special
125 // handling in ciField::will_link and will result in a
126 // java.lang.NoSuchFieldError exception being thrown by the compiled
127 // code (the expected behavior in this case).
128 _holder = ciEnv::current(thread)->Object_klass();
129 _offset = -1;
130 _is_constant = false;
131 return;
132 }
133
134 ciInstanceKlass* declared_holder = generic_declared_holder->as_instance_klass();
135
136 // The declared holder of this field may not have been loaded.
137 // Bail out with partial field information.
138 if (!holder_is_accessible) {
139 // _type has already been set.
140 // The default values for _flags and _constant_value will suffice.
141 // We need values for _holder, _offset, and _is_constant,
142 _holder = declared_holder;
143 _offset = -1;
144 _is_constant = false;
145 return;
146 }
147
148 InstanceKlass* loaded_decl_holder = declared_holder->get_instanceKlass();
149
150 // Perform the field lookup.
151 fieldDescriptor field_desc;
152 Klass* canonical_holder =
153 loaded_decl_holder->find_field(name, signature, &field_desc);
154 if (canonical_holder == NULL) {
155 // Field lookup failed. Will be detected by will_link.
156 _holder = declared_holder;
157 _offset = -1;
158 _is_constant = false;
159 return;
160 }
161
162 // Access check based on declared_holder. canonical_holder should not be used
163 // to check access because it can erroneously succeed. If this check fails,
164 // propagate the declared holder to will_link() which in turn will bail out
165 // compilation for this field access.
166 if (!Reflection::verify_field_access(klass->get_Klass(), declared_holder->get_Klass(), canonical_holder, field_desc.access_flags(), true)) {
167 _holder = declared_holder;
168 _offset = -1;
169 _is_constant = false;
170 return;
171 }
172
173 assert(canonical_holder == field_desc.field_holder(), "just checking");
174 initialize_from(&field_desc);
175 }
176
177 ciField::ciField(fieldDescriptor *fd) :
178 _known_to_link_with_put(NULL), _known_to_link_with_get(NULL) {
179 ASSERT_IN_VM;
180
181 // Get the field's name, signature, and type.
182 ciEnv* env = CURRENT_ENV;
183 _name = env->get_symbol(fd->name());
184 _signature = env->get_symbol(fd->signature());
185
186 BasicType field_type = fd->field_type();
187
188 // If the field is a pointer type, get the klass of the
189 // field.
190 if (field_type == T_OBJECT || field_type == T_ARRAY) {
191 _type = NULL; // must call compute_type on first access
192 } else {
193 _type = ciType::make(field_type);
194 }
195
196 initialize_from(fd);
197
198 // Either (a) it is marked shared, or else (b) we are done bootstrapping.
199 assert(is_shared() || ciObjectFactory::is_initialized(),
200 "bootstrap classes must not create & cache unshared fields");
201 }
202
203 static bool trust_final_non_static_fields(ciInstanceKlass* holder) {
204 if (holder == NULL)
205 return false;
206 if (holder->name() == ciSymbol::java_lang_System())
207 // Never trust strangely unstable finals: System.out, etc.
208 return false;
209 // Even if general trusting is disabled, trust system-built closures in these packages.
210 if (holder->is_in_package("java/lang/invoke") || holder->is_in_package("sun/invoke"))
211 return true;
212 // Trust VM anonymous classes. They are private API (sun.misc.Unsafe) and can't be serialized,
213 // so there is no hacking of finals going on with them.
214 if (holder->is_anonymous())
215 return true;
216 // Trust final fields in all boxed classes
217 if (holder->is_box_klass())
218 return true;
219 // Trust final fields in String
220 if (holder->name() == ciSymbol::java_lang_String())
221 return true;
222 // Trust Atomic*FieldUpdaters: they are very important for performance, and make up one
223 // more reason not to use Unsafe, if their final fields are trusted. See more in JDK-8140483.
224 if (holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicIntegerFieldUpdater_Impl() ||
225 holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicLongFieldUpdater_CASUpdater() ||
226 holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicLongFieldUpdater_LockedUpdater() ||
227 holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicReferenceFieldUpdater_Impl()) {
228 return true;
229 }
230 return TrustFinalNonStaticFields;
231 }
232
233 void ciField::initialize_from(fieldDescriptor* fd) {
234 // Get the flags, offset, and canonical holder of the field.
235 _flags = ciFlags(fd->access_flags());
236 _offset = fd->offset();
237 Klass* field_holder = fd->field_holder();
238 assert(field_holder != NULL, "null field_holder");
239 _holder = CURRENT_ENV->get_instance_klass(field_holder);
240
241 // Check to see if the field is constant.
242 Klass* k = _holder->get_Klass();
243 bool is_stable_field = FoldStableValues && is_stable();
244 if ((is_final() && !has_initialized_final_update()) || is_stable_field) {
245 if (is_static()) {
246 // This field just may be constant. The only case where it will
247 // not be constant is when the field is a *special* static & final field
248 // whose value may change. The three examples are java.lang.System.in,
249 // java.lang.System.out, and java.lang.System.err.
250 assert(SystemDictionary::System_klass() != NULL, "Check once per vm");
251 if (k == SystemDictionary::System_klass()) {
252 // Check offsets for case 2: System.in, System.out, or System.err
253 if( _offset == java_lang_System::in_offset_in_bytes() ||
254 _offset == java_lang_System::out_offset_in_bytes() ||
255 _offset == java_lang_System::err_offset_in_bytes() ) {
256 _is_constant = false;
257 return;
258 }
259 }
260 _is_constant = true;
261 } else {
262 // An instance field can be constant if it's a final static field or if
263 // it's a final non-static field of a trusted class (classes in
264 // java.lang.invoke and sun.invoke packages and subpackages).
265 _is_constant = is_stable_field || trust_final_non_static_fields(_holder);
266 }
267 } else {
268 // For CallSite objects treat the target field as a compile time constant.
269 assert(SystemDictionary::CallSite_klass() != NULL, "should be already initialized");
270 if (k == SystemDictionary::CallSite_klass() &&
271 _offset == java_lang_invoke_CallSite::target_offset_in_bytes()) {
272 assert(!has_initialized_final_update(), "CallSite is not supposed to have writes to final fields outside initializers");
273 _is_constant = true;
274 } else {
275 // Non-final & non-stable fields are not constants.
276 _is_constant = false;
277 }
278 }
279 }
280
281 // ------------------------------------------------------------------
282 // ciField::constant_value
283 // Get the constant value of a this static field.
284 ciConstant ciField::constant_value() {
285 assert(is_static() && is_constant(), "illegal call to constant_value()");
286 if (!_holder->is_initialized()) {
287 return ciConstant(); // Not initialized yet
288 }
289 if (_constant_value.basic_type() == T_ILLEGAL) {
290 // Static fields are placed in mirror objects.
291 VM_ENTRY_MARK;
292 ciInstance* mirror = CURRENT_ENV->get_instance(_holder->get_Klass()->java_mirror());
293 _constant_value = mirror->field_value_impl(type()->basic_type(), offset());
294 }
295 if (FoldStableValues && is_stable() && _constant_value.is_null_or_zero()) {
296 return ciConstant();
297 }
298 return _constant_value;
299 }
300
301 // ------------------------------------------------------------------
302 // ciField::constant_value_of
303 // Get the constant value of non-static final field in the given object.
304 ciConstant ciField::constant_value_of(ciObject* object) {
305 assert(!is_static() && is_constant(), "only if field is non-static constant");
306 assert(object->is_instance(), "must be instance");
307 ciConstant field_value = object->as_instance()->field_value(this);
308 if (FoldStableValues && is_stable() && field_value.is_null_or_zero()) {
309 return ciConstant();
310 }
311 return field_value;
312 }
313
314 // ------------------------------------------------------------------
315 // ciField::compute_type
316 //
317 // Lazily compute the type, if it is an instance klass.
318 ciType* ciField::compute_type() {
319 GUARDED_VM_ENTRY(return compute_type_impl();)
320 }
321
322 ciType* ciField::compute_type_impl() {
323 ciKlass* type = CURRENT_ENV->get_klass_by_name_impl(_holder, constantPoolHandle(), _signature, false);
324 if (!type->is_primitive_type() && is_shared()) {
325 // We must not cache a pointer to an unshared type, in a shared field.
326 bool type_is_also_shared = false;
327 if (type->is_type_array_klass()) {
328 type_is_also_shared = true; // int[] etc. are explicitly bootstrapped
329 } else if (type->is_instance_klass()) {
330 type_is_also_shared = type->as_instance_klass()->is_shared();
331 } else {
332 // Currently there is no 'shared' query for array types.
333 type_is_also_shared = !ciObjectFactory::is_initialized();
334 }
335 if (!type_is_also_shared)
336 return type; // Bummer.
337 }
338 _type = type;
339 return type;
340 }
341
342
343 // ------------------------------------------------------------------
344 // ciField::will_link
345 //
346 // Can a specific access to this field be made without causing
347 // link errors?
348 bool ciField::will_link(ciMethod* accessing_method,
349 Bytecodes::Code bc) {
350 VM_ENTRY_MARK;
351 assert(bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic ||
352 bc == Bytecodes::_getfield || bc == Bytecodes::_putfield,
353 "unexpected bytecode");
354
355 if (_offset == -1) {
356 // at creation we couldn't link to our holder so we need to
357 // maintain that stance, otherwise there's no safe way to use this
358 // ciField.
359 return false;
360 }
361
362 // Check for static/nonstatic mismatch
363 bool is_static = (bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic);
364 if (is_static != this->is_static()) {
365 return false;
366 }
367
368 // Get and put can have different accessibility rules
369 bool is_put = (bc == Bytecodes::_putfield || bc == Bytecodes::_putstatic);
370 if (is_put) {
371 if (_known_to_link_with_put == accessing_method) {
372 return true;
373 }
374 } else {
375 if (_known_to_link_with_get == accessing_method->holder()) {
376 return true;
377 }
378 }
379
380 LinkInfo link_info(_holder->get_instanceKlass(),
381 _name->get_symbol(), _signature->get_symbol(),
382 accessing_method->get_Method());
383 fieldDescriptor result;
384 LinkResolver::resolve_field(result, link_info, bc, false, KILL_COMPILE_ON_FATAL_(false));
385
386 // update the hit-cache, unless there is a problem with memory scoping:
387 if (accessing_method->holder()->is_shared() || !is_shared()) {
388 if (is_put) {
389 _known_to_link_with_put = accessing_method;
390 } else {
391 _known_to_link_with_get = accessing_method->holder();
392 }
393 }
394
395 return true;
396 }
397
398 // ------------------------------------------------------------------
399 // ciField::print
400 void ciField::print() {
401 tty->print("<ciField name=");
402 _holder->print_name();
403 tty->print(".");
404 _name->print_symbol();
405 tty->print(" signature=");
406 _signature->print_symbol();
407 tty->print(" offset=%d type=", _offset);
408 if (_type != NULL)
409 _type->print_name();
410 else
411 tty->print("(reference)");
412 tty->print(" flags=%04x", flags().as_int());
413 tty->print(" is_constant=%s", bool_to_str(_is_constant));
414 if (_is_constant && is_static()) {
415 tty->print(" constant_value=");
416 _constant_value.print();
417 }
418 tty->print(">");
419 }
420
421 // ------------------------------------------------------------------
422 // ciField::print_name_on
423 //
424 // Print the name of this field
425 void ciField::print_name_on(outputStream* st) {
426 name()->print_symbol_on(st);
427 }