1 /* 2 * Copyright (c) 1999, 2025, 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 "ci/ciField.hpp" 26 #include "ci/ciInstanceKlass.hpp" 27 #include "ci/ciSymbols.hpp" 28 #include "ci/ciUtilities.inline.hpp" 29 #include "classfile/javaClasses.hpp" 30 #include "classfile/vmClasses.hpp" 31 #include "gc/shared/collectedHeap.inline.hpp" 32 #include "interpreter/linkResolver.hpp" 33 #include "oops/klass.inline.hpp" 34 #include "oops/oop.inline.hpp" 35 #include "runtime/fieldDescriptor.inline.hpp" 36 #include "runtime/handles.inline.hpp" 37 #include "runtime/reflection.hpp" 38 39 // ciField 40 // 41 // This class represents the result of a field lookup in the VM. 42 // The lookup may not succeed, in which case the information in 43 // the ciField will be incomplete. 44 45 // The ciObjectFactory cannot create circular data structures in one query. 46 // To avoid vicious circularities, we initialize ciField::_type to null 47 // for reference types and derive it lazily from the ciField::_signature. 48 // Primitive types are eagerly initialized, and basic layout queries 49 // can succeed without initialization, using only the BasicType of the field. 50 51 // Notes on bootstrapping and shared CI objects: A field is shared if and 52 // only if it is (a) non-static and (b) declared by a shared instance klass. 53 // This allows non-static field lists to be cached on shared types. 54 // Because the _type field is lazily initialized, however, there is a 55 // special restriction that a shared field cannot cache an unshared type. 56 // This puts a small performance penalty on shared fields with unshared 57 // types, such as StackTraceElement[] Throwable.stackTrace. 58 // (Throwable is shared because ClassCastException is shared, but 59 // StackTraceElement is not presently shared.) 60 61 // It is not a vicious circularity for a ciField to recursively create 62 // the ciSymbols necessary to represent its name and signature. 63 // Therefore, these items are created eagerly, and the name and signature 64 // of a shared field are themselves shared symbols. This somewhat 65 // pollutes the set of shared CI objects: It grows from 50 to 93 items, 66 // with all of the additional 43 being uninteresting shared ciSymbols. 67 // This adds at most one step to the binary search, an amount which 68 // decreases for complex compilation tasks. 69 70 // ------------------------------------------------------------------ 71 // ciField::ciField 72 ciField::ciField(ciInstanceKlass* klass, int index, Bytecodes::Code bc) : 73 _known_to_link_with_put(nullptr), _known_to_link_with_get(nullptr) { 74 ASSERT_IN_VM; 75 CompilerThread *THREAD = CompilerThread::current(); 76 77 assert(ciObjectFactory::is_initialized(), "not a shared field"); 78 79 assert(klass->get_instanceKlass()->is_linked(), "must be linked before using its constant-pool"); 80 81 constantPoolHandle cpool(THREAD, klass->get_instanceKlass()->constants()); 82 83 // Get the field's name, signature, and type. 84 Symbol* name = cpool->name_ref_at(index, bc); 85 _name = ciEnv::current(THREAD)->get_symbol(name); 86 87 int nt_index = cpool->name_and_type_ref_index_at(index, bc); 88 int sig_index = cpool->signature_ref_index_at(nt_index); 89 Symbol* signature = cpool->symbol_at(sig_index); 90 _signature = ciEnv::current(THREAD)->get_symbol(signature); 91 92 BasicType field_type = Signature::basic_type(signature); 93 94 // If the field is a pointer type, get the klass of the 95 // field. 96 if (is_reference_type(field_type)) { 97 bool ignore; 98 // This is not really a class reference; the index always refers to the 99 // field's type signature, as a symbol. Linkage checks do not apply. 100 _type = ciEnv::current(THREAD)->get_klass_by_index(cpool, sig_index, ignore, klass); 101 } else { 102 _type = ciType::make(field_type); 103 } 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, bc); 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 == nullptr) { 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(nullptr), _known_to_link_with_get(nullptr) { 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 (is_reference_type(field_type)) { 204 _type = nullptr; // 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 == nullptr) 218 return false; 219 // Even if general trusting is disabled, trust system-built closures in these packages. 220 if (holder->is_in_package("java/lang/invoke") || holder->is_in_package("sun/invoke") || 221 holder->is_in_package("java/lang/reflect") || holder->is_in_package("jdk/internal/reflect") || 222 holder->is_in_package("jdk/internal/foreign/layout") || holder->is_in_package("jdk/internal/foreign") || 223 holder->is_in_package("jdk/internal/vm/vector") || holder->is_in_package("jdk/incubator/vector") || 224 holder->is_in_package("java/lang")) 225 return true; 226 // Trust hidden classes. They are created via Lookup.defineHiddenClass and 227 // can't be serialized, so there is no hacking of finals going on with them. 228 if (holder->is_hidden()) 229 return true; 230 // Trust final fields in records 231 if (holder->is_record()) 232 return true; 233 // Trust Atomic*FieldUpdaters: they are very important for performance, and make up one 234 // more reason not to use Unsafe, if their final fields are trusted. See more in JDK-8140483. 235 if (holder->name() == ciSymbols::java_util_concurrent_atomic_AtomicIntegerFieldUpdater_Impl() || 236 holder->name() == ciSymbols::java_util_concurrent_atomic_AtomicLongFieldUpdater_CASUpdater() || 237 holder->name() == ciSymbols::java_util_concurrent_atomic_AtomicLongFieldUpdater_LockedUpdater() || 238 holder->name() == ciSymbols::java_util_concurrent_atomic_AtomicReferenceFieldUpdater_Impl()) { 239 return true; 240 } 241 return TrustFinalNonStaticFields; 242 } 243 244 void ciField::initialize_from(fieldDescriptor* fd) { 245 // Get the flags, offset, and canonical holder of the field. 246 _flags = ciFlags(fd->access_flags(), fd->field_flags().is_stable(), fd->field_status().is_initialized_final_update()); 247 _offset = fd->offset(); 248 Klass* field_holder = fd->field_holder(); 249 assert(field_holder != nullptr, "null field_holder"); 250 _holder = CURRENT_ENV->get_instance_klass(field_holder); 251 252 // Check to see if the field is constant. 253 Klass* k = _holder->get_Klass(); 254 bool is_stable_field = FoldStableValues && is_stable(); 255 if ((is_final() && !has_initialized_final_update()) || is_stable_field) { 256 if (is_static()) { 257 // This field just may be constant. The only case where it will 258 // not be constant is when the field is a *special* static & final field 259 // whose value may change. The three examples are java.lang.System.in, 260 // java.lang.System.out, and java.lang.System.err. 261 _is_constant = !fd->is_mutable_static_final(); 262 } else { 263 // An instance field can be constant if it's a final static field or if 264 // it's a final non-static field of a trusted class (classes in 265 // java.lang.invoke and sun.invoke packages and subpackages). 266 _is_constant = is_stable_field || trust_final_non_static_fields(_holder); 267 } 268 } else { 269 // For CallSite objects treat the target field as a compile time constant. 270 assert(vmClasses::CallSite_klass() != nullptr, "should be already initialized"); 271 if (k == vmClasses::CallSite_klass() && 272 _offset == java_lang_invoke_CallSite::target_offset()) { 273 assert(!has_initialized_final_update(), "CallSite is not supposed to have writes to final fields outside initializers"); 274 _is_constant = true; 275 } else { 276 // Non-final & non-stable fields are not constants. 277 _is_constant = false; 278 } 279 } 280 } 281 282 // ------------------------------------------------------------------ 283 // ciField::constant_value 284 // Get the constant value of a this static field. 285 ciConstant ciField::constant_value() { 286 assert(is_static() && is_constant(), "illegal call to constant_value()"); 287 if (!_holder->is_initialized()) { 288 return ciConstant(); // Not initialized yet 289 } 290 if (_constant_value.basic_type() == T_ILLEGAL) { 291 // Static fields are placed in mirror objects. 292 ciInstance* mirror = _holder->java_mirror(); 293 _constant_value = mirror->field_value_impl(type()->basic_type(), offset_in_bytes()); 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 methodHandle(THREAD, accessing_method->get_Method())); 383 fieldDescriptor result; 384 LinkResolver::resolve_field(result, link_info, bc, ClassInitMode::dont_init, CHECK_AND_CLEAR_(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 bool ciField::is_call_site_target() { 399 ciInstanceKlass* callsite_klass = CURRENT_ENV->CallSite_klass(); 400 if (callsite_klass == nullptr) 401 return false; 402 return (holder()->is_subclass_of(callsite_klass) && (name() == ciSymbols::target_name())); 403 } 404 405 bool ciField::is_autobox_cache() { 406 ciSymbol* klass_name = holder()->name(); 407 return (name() == ciSymbols::cache_field_name() && 408 holder()->uses_default_loader() && 409 (klass_name == ciSymbols::java_lang_Character_CharacterCache() || 410 klass_name == ciSymbols::java_lang_Byte_ByteCache() || 411 klass_name == ciSymbols::java_lang_Short_ShortCache() || 412 klass_name == ciSymbols::java_lang_Integer_IntegerCache() || 413 klass_name == ciSymbols::java_lang_Long_LongCache())); 414 } 415 416 // ------------------------------------------------------------------ 417 // ciField::print 418 void ciField::print() { 419 tty->print("<ciField name="); 420 _holder->print_name(); 421 tty->print("."); 422 _name->print_symbol(); 423 tty->print(" signature="); 424 _signature->print_symbol(); 425 tty->print(" offset=%d type=", _offset); 426 if (_type != nullptr) 427 _type->print_name(); 428 else 429 tty->print("(reference)"); 430 tty->print(" flags=%04x", flags().as_int()); 431 tty->print(" is_constant=%s", bool_to_str(_is_constant)); 432 if (_is_constant && is_static()) { 433 tty->print(" constant_value="); 434 _constant_value.print(); 435 } 436 tty->print(">"); 437 } 438 439 // ------------------------------------------------------------------ 440 // ciField::print_name_on 441 // 442 // Print the name of this field 443 void ciField::print_name_on(outputStream* st) { 444 name()->print_symbol_on(st); 445 } --- EOF ---