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. 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/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 }