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.
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.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "ci/ciField.hpp"
27 #include "ci/ciInstanceKlass.hpp"
28 #include "ci/ciUtilities.inline.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 #include "runtime/handles.inline.hpp"
36
37 // ciField
38 //
39 // This class represents the result of a field lookup in the VM.
40 // The lookup may not succeed, in which case the information in
41 // the ciField will be incomplete.
42
43 // The ciObjectFactory cannot create circular data structures in one query.
44 // To avoid vicious circularities, we initialize ciField::_type to NULL
45 // for reference types and derive it lazily from the ciField::_signature.
46 // Primitive types are eagerly initialized, and basic layout queries
47 // can succeed without initialization, using only the BasicType of the field.
48
49 // Notes on bootstrapping and shared CI objects: A field is shared if and
50 // only if it is (a) non-static and (b) declared by a shared instance klass.
51 // This allows non-static field lists to be cached on shared types.
52 // Because the _type field is lazily initialized, however, there is a
53 // special restriction that a shared field cannot cache an unshared type.
54 // This puts a small performance penalty on shared fields with unshared
55 // types, such as StackTraceElement[] Throwable.stackTrace.
56 // (Throwable is shared because ClassCastException is shared, but
57 // StackTraceElement is not presently shared.)
58
59 // It is not a vicious circularity for a ciField to recursively create
60 // the ciSymbols necessary to represent its name and signature.
61 // Therefore, these items are created eagerly, and the name and signature
62 // of a shared field are themselves shared symbols. This somewhat
63 // pollutes the set of shared CI objects: It grows from 50 to 93 items,
64 // with all of the additional 43 being uninteresting shared ciSymbols.
65 // This adds at most one step to the binary search, an amount which
66 // decreases for complex compilation tasks.
67
68 // ------------------------------------------------------------------
69 // ciField::ciField
70 ciField::ciField(ciInstanceKlass* klass, int index) :
71 _known_to_link_with_put(NULL), _known_to_link_with_get(NULL) {
72 ASSERT_IN_VM;
73 CompilerThread *THREAD = CompilerThread::current();
74
75 assert(ciObjectFactory::is_initialized(), "not a shared field");
76
77 assert(klass->get_instanceKlass()->is_linked(), "must be linked before using its constant-pool");
78
79 constantPoolHandle cpool(THREAD, klass->get_instanceKlass()->constants());
80
81 // Get the field's name, signature, and type.
82 Symbol* name = cpool->name_ref_at(index);
83 _name = ciEnv::current(THREAD)->get_symbol(name);
84
85 int nt_index = cpool->name_and_type_ref_index_at(index);
86 int sig_index = cpool->signature_ref_index_at(nt_index);
87 Symbol* signature = cpool->symbol_at(sig_index);
88 _signature = ciEnv::current(THREAD)->get_symbol(signature);
89
90 BasicType field_type = FieldType::basic_type(signature);
91
92 // If the field is a pointer type, get the klass of the
93 // field.
94 if (field_type == T_OBJECT || field_type == T_ARRAY) {
95 bool ignore;
96 // This is not really a class reference; the index always refers to the
97 // field's type signature, as a symbol. Linkage checks do not apply.
98 _type = ciEnv::current(THREAD)->get_klass_by_index(cpool, sig_index, ignore, klass);
99 } else {
100 _type = ciType::make(field_type);
101 }
102
103 _name = (ciSymbol*)ciEnv::current(THREAD)->get_symbol(name);
104
105 // Get the field's declared holder.
106 //
107 // Note: we actually create a ciInstanceKlass for this klass,
108 // even though we may not need to.
109 int holder_index = cpool->klass_ref_index_at(index);
110 bool holder_is_accessible;
111
112 ciKlass* generic_declared_holder = ciEnv::current(THREAD)->get_klass_by_index(cpool, holder_index,
113 holder_is_accessible,
114 klass);
115
116 if (generic_declared_holder->is_array_klass()) {
117 // If the declared holder of the field is an array class, assume that
118 // the canonical holder of that field is java.lang.Object. Arrays
119 // do not have fields; java.lang.Object is the only supertype of an
120 // array type that can declare fields and is therefore the canonical
121 // holder of the array type.
122 //
123 // Furthermore, the compilers assume that java.lang.Object does not
124 // have any fields. Therefore, the field is not looked up. Instead,
125 // the method returns partial information that will trigger special
126 // handling in ciField::will_link and will result in a
127 // java.lang.NoSuchFieldError exception being thrown by the compiled
128 // code (the expected behavior in this case).
129 _holder = ciEnv::current(THREAD)->Object_klass();
130 _offset = -1;
131 _is_constant = false;
132 return;
133 }
134
135 ciInstanceKlass* declared_holder = generic_declared_holder->as_instance_klass();
136
137 // The declared holder of this field may not have been loaded.
138 // Bail out with partial field information.
139 if (!holder_is_accessible) {
140 // _type has already been set.
141 // The default values for _flags and _constant_value will suffice.
142 // We need values for _holder, _offset, and _is_constant,
143 _holder = declared_holder;
144 _offset = -1;
145 _is_constant = false;
146 return;
147 }
148
149 InstanceKlass* loaded_decl_holder = declared_holder->get_instanceKlass();
150
151 // Perform the field lookup.
152 fieldDescriptor field_desc;
153 Klass* canonical_holder =
154 loaded_decl_holder->find_field(name, signature, &field_desc);
155 if (canonical_holder == NULL) {
156 // Field lookup failed. Will be detected by will_link.
157 _holder = declared_holder;
158 _offset = -1;
159 _is_constant = false;
160 return;
161 }
162
163 // Access check based on declared_holder. canonical_holder should not be used
164 // to check access because it can erroneously succeed. If this check fails,
165 // propagate the declared holder to will_link() which in turn will bail out
166 // compilation for this field access.
167 bool can_access = Reflection::verify_member_access(klass->get_Klass(),
168 declared_holder->get_Klass(),
169 canonical_holder,
170 field_desc.access_flags(),
171 true, false, THREAD);
172 if (!can_access) {
173 _holder = declared_holder;
174 _offset = -1;
175 _is_constant = false;
176 // It's possible the access check failed due to a nestmate access check
177 // encountering an exception. We can't propagate the exception from here
178 // so we have to clear it. If the access check happens again in a different
179 // context then the exception will be thrown there.
180 if (HAS_PENDING_EXCEPTION) {
181 CLEAR_PENDING_EXCEPTION;
182 }
183 return;
184 }
185
186 assert(canonical_holder == field_desc.field_holder(), "just checking");
187 initialize_from(&field_desc);
188 }
189
190 ciField::ciField(fieldDescriptor *fd) :
191 _known_to_link_with_put(NULL), _known_to_link_with_get(NULL) {
192 ASSERT_IN_VM;
193
194 // Get the field's name, signature, and type.
195 ciEnv* env = CURRENT_ENV;
196 _name = env->get_symbol(fd->name());
197 _signature = env->get_symbol(fd->signature());
198
199 BasicType field_type = fd->field_type();
200
201 // If the field is a pointer type, get the klass of the
202 // field.
203 if (field_type == T_OBJECT || field_type == T_ARRAY) {
204 _type = NULL; // must call compute_type on first access
205 } else {
206 _type = ciType::make(field_type);
207 }
208
209 initialize_from(fd);
210
211 // Either (a) it is marked shared, or else (b) we are done bootstrapping.
212 assert(is_shared() || ciObjectFactory::is_initialized(),
213 "bootstrap classes must not create & cache unshared fields");
214 }
215
216 static bool trust_final_non_static_fields(ciInstanceKlass* holder) {
217 if (holder == NULL)
218 return false;
219 if (holder->name() == ciSymbol::java_lang_System())
220 // Never trust strangely unstable finals: System.out, etc.
221 return false;
222 // Even if general trusting is disabled, trust system-built closures in these packages.
223 if (holder->is_in_package("java/lang/invoke") || holder->is_in_package("sun/invoke"))
224 return true;
225 // Trust VM anonymous classes. They are private API (sun.misc.Unsafe) and can't be serialized,
226 // so there is no hacking of finals going on with them.
227 if (holder->is_anonymous())
228 return true;
229 // Trust final fields in all boxed classes
230 if (holder->is_box_klass())
231 return true;
232 // Trust final fields in String
233 if (holder->name() == ciSymbol::java_lang_String())
234 return true;
235 // Trust Atomic*FieldUpdaters: they are very important for performance, and make up one
236 // more reason not to use Unsafe, if their final fields are trusted. See more in JDK-8140483.
237 if (holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicIntegerFieldUpdater_Impl() ||
238 holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicLongFieldUpdater_CASUpdater() ||
239 holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicLongFieldUpdater_LockedUpdater() ||
240 holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicReferenceFieldUpdater_Impl()) {
241 return true;
242 }
243 return TrustFinalNonStaticFields;
244 }
245
246 void ciField::initialize_from(fieldDescriptor* fd) {
247 // Get the flags, offset, and canonical holder of the field.
248 _flags = ciFlags(fd->access_flags());
249 _offset = fd->offset();
250 Klass* field_holder = fd->field_holder();
251 assert(field_holder != NULL, "null field_holder");
252 _holder = CURRENT_ENV->get_instance_klass(field_holder);
253
254 // Check to see if the field is constant.
255 Klass* k = _holder->get_Klass();
256 bool is_stable_field = FoldStableValues && is_stable();
257 if ((is_final() && !has_initialized_final_update()) || is_stable_field) {
258 if (is_static()) {
259 // This field just may be constant. The only case where it will
260 // not be constant is when the field is a *special* static & final field
261 // whose value may change. The three examples are java.lang.System.in,
262 // java.lang.System.out, and java.lang.System.err.
263 assert(SystemDictionary::System_klass() != NULL, "Check once per vm");
264 if (k == SystemDictionary::System_klass()) {
265 // Check offsets for case 2: System.in, System.out, or System.err
266 if( _offset == java_lang_System::in_offset_in_bytes() ||
267 _offset == java_lang_System::out_offset_in_bytes() ||
268 _offset == java_lang_System::err_offset_in_bytes() ) {
269 _is_constant = false;
270 return;
271 }
272 }
273 _is_constant = true;
274 } else {
275 // An instance field can be constant if it's a final static field or if
276 // it's a final non-static field of a trusted class (classes in
277 // java.lang.invoke and sun.invoke packages and subpackages).
278 _is_constant = is_stable_field || trust_final_non_static_fields(_holder);
279 }
280 } else {
281 // For CallSite objects treat the target field as a compile time constant.
282 assert(SystemDictionary::CallSite_klass() != NULL, "should be already initialized");
283 if (k == SystemDictionary::CallSite_klass() &&
284 _offset == java_lang_invoke_CallSite::target_offset_in_bytes()) {
285 assert(!has_initialized_final_update(), "CallSite is not supposed to have writes to final fields outside initializers");
286 _is_constant = true;
287 } else {
288 // Non-final & non-stable fields are not constants.
289 _is_constant = false;
290 }
291 }
292 }
293
294 // ------------------------------------------------------------------
295 // ciField::constant_value
296 // Get the constant value of a this static field.
297 ciConstant ciField::constant_value() {
298 assert(is_static() && is_constant(), "illegal call to constant_value()");
299 if (!_holder->is_initialized()) {
300 return ciConstant(); // Not initialized yet
301 }
302 if (_constant_value.basic_type() == T_ILLEGAL) {
303 // Static fields are placed in mirror objects.
304 VM_ENTRY_MARK;
305 ciInstance* mirror = CURRENT_ENV->get_instance(_holder->get_Klass()->java_mirror());
306 _constant_value = mirror->field_value_impl(type()->basic_type(), offset());
307 }
308 if (FoldStableValues && is_stable() && _constant_value.is_null_or_zero()) {
309 return ciConstant();
310 }
311 return _constant_value;
312 }
313
314 // ------------------------------------------------------------------
315 // ciField::constant_value_of
316 // Get the constant value of non-static final field in the given object.
317 ciConstant ciField::constant_value_of(ciObject* object) {
318 assert(!is_static() && is_constant(), "only if field is non-static constant");
319 assert(object->is_instance(), "must be instance");
320 ciConstant field_value = object->as_instance()->field_value(this);
321 if (FoldStableValues && is_stable() && field_value.is_null_or_zero()) {
322 return ciConstant();
323 }
324 return field_value;
325 }
326
327 // ------------------------------------------------------------------
328 // ciField::compute_type
329 //
330 // Lazily compute the type, if it is an instance klass.
331 ciType* ciField::compute_type() {
332 GUARDED_VM_ENTRY(return compute_type_impl();)
333 }
334
335 ciType* ciField::compute_type_impl() {
336 ciKlass* type = CURRENT_ENV->get_klass_by_name_impl(_holder, constantPoolHandle(), _signature, false);
337 if (!type->is_primitive_type() && is_shared()) {
338 // We must not cache a pointer to an unshared type, in a shared field.
339 bool type_is_also_shared = false;
340 if (type->is_type_array_klass()) {
341 type_is_also_shared = true; // int[] etc. are explicitly bootstrapped
342 } else if (type->is_instance_klass()) {
343 type_is_also_shared = type->as_instance_klass()->is_shared();
344 } else {
345 // Currently there is no 'shared' query for array types.
346 type_is_also_shared = !ciObjectFactory::is_initialized();
347 }
348 if (!type_is_also_shared)
349 return type; // Bummer.
350 }
351 _type = type;
352 return type;
353 }
354
355
356 // ------------------------------------------------------------------
357 // ciField::will_link
358 //
359 // Can a specific access to this field be made without causing
360 // link errors?
361 bool ciField::will_link(ciMethod* accessing_method,
362 Bytecodes::Code bc) {
363 VM_ENTRY_MARK;
364 assert(bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic ||
365 bc == Bytecodes::_getfield || bc == Bytecodes::_putfield,
366 "unexpected bytecode");
367
368 if (_offset == -1) {
369 // at creation we couldn't link to our holder so we need to
370 // maintain that stance, otherwise there's no safe way to use this
371 // ciField.
372 return false;
373 }
374
375 // Check for static/nonstatic mismatch
376 bool is_static = (bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic);
377 if (is_static != this->is_static()) {
378 return false;
379 }
380
381 // Get and put can have different accessibility rules
382 bool is_put = (bc == Bytecodes::_putfield || bc == Bytecodes::_putstatic);
383 if (is_put) {
384 if (_known_to_link_with_put == accessing_method) {
385 return true;
386 }
387 } else {
388 if (_known_to_link_with_get == accessing_method->holder()) {
389 return true;
390 }
391 }
392
393 LinkInfo link_info(_holder->get_instanceKlass(),
394 _name->get_symbol(), _signature->get_symbol(),
395 accessing_method->get_Method());
396 fieldDescriptor result;
397 LinkResolver::resolve_field(result, link_info, bc, false, KILL_COMPILE_ON_FATAL_(false));
398
399 // update the hit-cache, unless there is a problem with memory scoping:
400 if (accessing_method->holder()->is_shared() || !is_shared()) {
401 if (is_put) {
402 _known_to_link_with_put = accessing_method;
403 } else {
404 _known_to_link_with_get = accessing_method->holder();
405 }
406 }
407
408 return true;
409 }
410
411 // ------------------------------------------------------------------
412 // ciField::print
413 void ciField::print() {
414 tty->print("<ciField name=");
415 _holder->print_name();
416 tty->print(".");
417 _name->print_symbol();
418 tty->print(" signature=");
419 _signature->print_symbol();
420 tty->print(" offset=%d type=", _offset);
421 if (_type != NULL)
422 _type->print_name();
423 else
424 tty->print("(reference)");
425 tty->print(" flags=%04x", flags().as_int());
426 tty->print(" is_constant=%s", bool_to_str(_is_constant));
427 if (_is_constant && is_static()) {
428 tty->print(" constant_value=");
429 _constant_value.print();
430 }
431 tty->print(">");
432 }
433
434 // ------------------------------------------------------------------
435 // ciField::print_name_on
436 //
437 // Print the name of this field
438 void ciField::print_name_on(outputStream* st) {
439 name()->print_symbol_on(st);
440 }