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 "code/aotCodeCache.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/reflection.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 _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 // Get the field's declared holder. 107 // 108 // Note: we actually create a ciInstanceKlass for this klass, 109 // even though we may not need to. 110 int holder_index = cpool->klass_ref_index_at(index, bc); 111 bool holder_is_accessible; 112 113 ciKlass* generic_declared_holder = ciEnv::current(THREAD)->get_klass_by_index(cpool, holder_index, 114 holder_is_accessible, 115 klass); 116 117 if (generic_declared_holder->is_array_klass()) { 118 // If the declared holder of the field is an array class, assume that 119 // the canonical holder of that field is java.lang.Object. Arrays 120 // do not have fields; java.lang.Object is the only supertype of an 121 // array type that can declare fields and is therefore the canonical 122 // holder of the array type. 123 // 124 // Furthermore, the compilers assume that java.lang.Object does not 125 // have any fields. Therefore, the field is not looked up. Instead, 126 // the method returns partial information that will trigger special 127 // handling in ciField::will_link and will result in a 128 // java.lang.NoSuchFieldError exception being thrown by the compiled 129 // code (the expected behavior in this case). 130 _holder = ciEnv::current(THREAD)->Object_klass(); 131 _offset = -1; 132 _is_constant = false; 133 return; 134 } 135 136 ciInstanceKlass* declared_holder = generic_declared_holder->as_instance_klass(); 137 138 // The declared holder of this field may not have been loaded. 139 // Bail out with partial field information. 140 if (!holder_is_accessible) { 141 // _type has already been set. 142 // The default values for _flags and _constant_value will suffice. 143 // We need values for _holder, _offset, and _is_constant, 144 _holder = declared_holder; 145 _offset = -1; 146 _is_constant = false; 147 return; 148 } 149 150 InstanceKlass* loaded_decl_holder = declared_holder->get_instanceKlass(); 151 152 // Perform the field lookup. 153 fieldDescriptor field_desc; 154 Klass* canonical_holder = 155 loaded_decl_holder->find_field(name, signature, &field_desc); 156 if (canonical_holder == nullptr) { 157 // Field lookup failed. Will be detected by will_link. 158 _holder = declared_holder; 159 _offset = -1; 160 _is_constant = false; 161 return; 162 } 163 164 // Access check based on declared_holder. canonical_holder should not be used 165 // to check access because it can erroneously succeed. If this check fails, 166 // propagate the declared holder to will_link() which in turn will bail out 167 // compilation for this field access. 168 bool can_access = Reflection::verify_member_access(klass->get_Klass(), 169 declared_holder->get_Klass(), 170 canonical_holder, 171 field_desc.access_flags(), 172 true, false, THREAD); 173 if (!can_access) { 174 _holder = declared_holder; 175 _offset = -1; 176 _is_constant = false; 177 // It's possible the access check failed due to a nestmate access check 178 // encountering an exception. We can't propagate the exception from here 179 // so we have to clear it. If the access check happens again in a different 180 // context then the exception will be thrown there. 181 if (HAS_PENDING_EXCEPTION) { 182 CLEAR_PENDING_EXCEPTION; 183 } 184 return; 185 } 186 187 assert(canonical_holder == field_desc.field_holder(), "just checking"); 188 initialize_from(&field_desc); 189 } 190 191 ciField::ciField(fieldDescriptor *fd) : 192 _known_to_link_with_put(nullptr), _known_to_link_with_get(nullptr) { 193 ASSERT_IN_VM; 194 195 // Get the field's name, signature, and type. 196 ciEnv* env = CURRENT_ENV; 197 _name = env->get_symbol(fd->name()); 198 _signature = env->get_symbol(fd->signature()); 199 200 BasicType field_type = fd->field_type(); 201 202 // If the field is a pointer type, get the klass of the 203 // field. 204 if (is_reference_type(field_type)) { 205 _type = nullptr; // must call compute_type on first access 206 } else { 207 _type = ciType::make(field_type); 208 } 209 210 initialize_from(fd); 211 212 // Either (a) it is marked shared, or else (b) we are done bootstrapping. 213 assert(is_shared() || ciObjectFactory::is_initialized(), 214 "bootstrap classes must not create & cache unshared fields"); 215 } 216 217 static bool trust_final_nonstatic_fields(ciInstanceKlass* holder) { 218 if (holder == nullptr) 219 return false; 220 if (holder->trust_final_fields()) { 221 // Explicit opt-in from system classes 222 return true; 223 } 224 // Even if general trusting is disabled, trust system-built closures in these packages. 225 if (holder->is_in_package("java/lang/invoke") || holder->is_in_package("sun/invoke") || 226 holder->is_in_package("java/lang/reflect") || holder->is_in_package("jdk/internal/reflect") || 227 holder->is_in_package("jdk/internal/foreign/layout") || holder->is_in_package("jdk/internal/foreign") || 228 holder->is_in_package("jdk/internal/vm/vector") || holder->is_in_package("jdk/incubator/vector") || 229 holder->is_in_package("java/lang")) 230 return true; 231 // Trust hidden classes. They are created via Lookup.defineHiddenClass and 232 // can't be serialized, so there is no hacking of finals going on with them. 233 if (holder->is_hidden()) 234 return true; 235 // Trust final fields in records 236 if (holder->is_record()) 237 return true; 238 return TrustFinalNonStaticFields; 239 } 240 241 void ciField::initialize_from(fieldDescriptor* fd) { 242 // Get the flags, offset, and canonical holder of the field. 243 _flags = ciFlags(fd->access_flags(), fd->field_flags().is_stable(), fd->field_status().is_initialized_final_update()); 244 _offset = fd->offset(); 245 Klass* field_holder = fd->field_holder(); 246 assert(field_holder != nullptr, "null field_holder"); 247 _holder = CURRENT_ENV->get_instance_klass(field_holder); 248 249 // Check to see if the field is constant. 250 Klass* k = _holder->get_Klass(); 251 bool is_stable_field = FoldStableValues && is_stable(); 252 if ((is_final() && !has_initialized_final_update()) || is_stable_field) { 253 if (is_static()) { 254 // This field just may be constant. The only case where it will 255 // not be constant is when the field is a *special* static & final field 256 // whose value may change. The three examples are java.lang.System.in, 257 // java.lang.System.out, and java.lang.System.err. 258 _is_constant = !fd->is_mutable_static_final(); 259 } else { 260 // An instance field can be constant if it's a final static field or if 261 // it's a final non-static field of a trusted class (classes in 262 // java.lang.invoke and sun.invoke packages and subpackages). 263 _is_constant = is_stable_field || trust_final_nonstatic_fields(_holder); 264 } 265 } else { 266 // For CallSite objects treat the target field as a compile time constant. 267 assert(vmClasses::CallSite_klass() != nullptr, "should be already initialized"); 268 if (k == vmClasses::CallSite_klass() && 269 _offset == java_lang_invoke_CallSite::target_offset()) { 270 assert(!has_initialized_final_update(), "CallSite is not supposed to have writes to final fields outside initializers"); 271 _is_constant = true; 272 } else { 273 // Non-final & non-stable fields are not constants. 274 _is_constant = false; 275 } 276 } 277 } 278 279 // ------------------------------------------------------------------ 280 // ciField::constant_value 281 // Get the constant value of a this static field. 282 ciConstant ciField::constant_value() { 283 assert(is_static() && is_constant(), "illegal call to constant_value()"); 284 if (!_holder->is_initialized()) { 285 return ciConstant(); // Not initialized yet 286 } 287 if (_constant_value.basic_type() == T_ILLEGAL) { 288 // Static fields are placed in mirror objects. 289 ciInstance* mirror = _holder->java_mirror(); 290 _constant_value = mirror->field_value_impl(type()->basic_type(), offset_in_bytes()); 291 } 292 if (FoldStableValues && is_stable() && _constant_value.is_null_or_zero()) { 293 return ciConstant(); 294 } 295 if (!AOTCodeCache::allow_const_field(_constant_value)) { 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 if (!AOTCodeCache::allow_const_field(field_value)) { 312 return ciConstant(); 313 } 314 return field_value; 315 } 316 317 // ------------------------------------------------------------------ 318 // ciField::compute_type 319 // 320 // Lazily compute the type, if it is an instance klass. 321 ciType* ciField::compute_type() { 322 GUARDED_VM_ENTRY(return compute_type_impl();) 323 } 324 325 ciType* ciField::compute_type_impl() { 326 ciKlass* type = CURRENT_ENV->get_klass_by_name_impl(_holder, constantPoolHandle(), _signature, false); 327 if (!type->is_primitive_type() && is_shared()) { 328 // We must not cache a pointer to an unshared type, in a shared field. 329 bool type_is_also_shared = false; 330 if (type->is_type_array_klass()) { 331 type_is_also_shared = true; // int[] etc. are explicitly bootstrapped 332 } else if (type->is_instance_klass()) { 333 type_is_also_shared = type->as_instance_klass()->is_shared(); 334 } else { 335 // Currently there is no 'shared' query for array types. 336 type_is_also_shared = !ciObjectFactory::is_initialized(); 337 } 338 if (!type_is_also_shared) 339 return type; // Bummer. 340 } 341 _type = type; 342 return type; 343 } 344 345 346 // ------------------------------------------------------------------ 347 // ciField::will_link 348 // 349 // Can a specific access to this field be made without causing 350 // link errors? 351 bool ciField::will_link(ciMethod* accessing_method, 352 Bytecodes::Code bc) { 353 VM_ENTRY_MARK; 354 assert(bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic || 355 bc == Bytecodes::_getfield || bc == Bytecodes::_putfield, 356 "unexpected bytecode"); 357 358 if (_offset == -1) { 359 // at creation we couldn't link to our holder so we need to 360 // maintain that stance, otherwise there's no safe way to use this 361 // ciField. 362 return false; 363 } 364 365 // Check for static/nonstatic mismatch 366 bool is_static = (bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic); 367 if (is_static != this->is_static()) { 368 return false; 369 } 370 371 // Get and put can have different accessibility rules 372 bool is_put = (bc == Bytecodes::_putfield || bc == Bytecodes::_putstatic); 373 if (is_put) { 374 if (_known_to_link_with_put == accessing_method) { 375 return true; 376 } 377 } else { 378 if (_known_to_link_with_get == accessing_method->holder()) { 379 return true; 380 } 381 } 382 383 LinkInfo link_info(_holder->get_instanceKlass(), 384 _name->get_symbol(), _signature->get_symbol(), 385 methodHandle(THREAD, accessing_method->get_Method())); 386 fieldDescriptor result; 387 LinkResolver::resolve_field(result, link_info, bc, ClassInitMode::dont_init, CHECK_AND_CLEAR_(false)); 388 389 // update the hit-cache, unless there is a problem with memory scoping: 390 if (accessing_method->holder()->is_shared() || !is_shared()) { 391 if (is_put) { 392 _known_to_link_with_put = accessing_method; 393 } else { 394 _known_to_link_with_get = accessing_method->holder(); 395 } 396 } 397 398 return true; 399 } 400 401 bool ciField::is_call_site_target() { 402 ciInstanceKlass* callsite_klass = CURRENT_ENV->CallSite_klass(); 403 if (callsite_klass == nullptr) 404 return false; 405 return (holder()->is_subclass_of(callsite_klass) && (name() == ciSymbols::target_name())); 406 } 407 408 bool ciField::is_autobox_cache() { 409 ciSymbol* klass_name = holder()->name(); 410 return (name() == ciSymbols::cache_field_name() && 411 holder()->uses_default_loader() && 412 (klass_name == ciSymbols::java_lang_Character_CharacterCache() || 413 klass_name == ciSymbols::java_lang_Byte_ByteCache() || 414 klass_name == ciSymbols::java_lang_Short_ShortCache() || 415 klass_name == ciSymbols::java_lang_Integer_IntegerCache() || 416 klass_name == ciSymbols::java_lang_Long_LongCache())); 417 } 418 419 // ------------------------------------------------------------------ 420 // ciField::print 421 void ciField::print() { 422 tty->print("<ciField name="); 423 _holder->print_name(); 424 tty->print("."); 425 _name->print_symbol(); 426 tty->print(" signature="); 427 _signature->print_symbol(); 428 tty->print(" offset=%d type=", _offset); 429 if (_type != nullptr) 430 _type->print_name(); 431 else 432 tty->print("(reference)"); 433 tty->print(" flags=%04x", flags().as_int()); 434 tty->print(" is_constant=%s", bool_to_str(_is_constant)); 435 if (_is_constant && is_static()) { 436 tty->print(" constant_value="); 437 _constant_value.print(); 438 } 439 tty->print(">"); 440 } 441 442 // ------------------------------------------------------------------ 443 // ciField::print_name_on 444 // 445 // Print the name of this field 446 void ciField::print_name_on(outputStream* st) { 447 name()->print_symbol_on(st); 448 } --- EOF ---