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_nonstatic_fields(ciInstanceKlass* holder) { 217 if (holder == nullptr) 218 return false; 219 if (holder->trust_final_fields()) { 220 // Explicit opt-in from system classes 221 return true; 222 } 223 // Even if general trusting is disabled, trust system-built closures in these packages. 224 if (holder->is_in_package("java/lang/invoke") || holder->is_in_package("sun/invoke") || 225 holder->is_in_package("java/lang/reflect") || holder->is_in_package("jdk/internal/reflect") || 226 holder->is_in_package("jdk/internal/foreign/layout") || holder->is_in_package("jdk/internal/foreign") || 227 holder->is_in_package("jdk/internal/vm/vector") || holder->is_in_package("jdk/incubator/vector") || 228 holder->is_in_package("java/lang")) 229 return true; 230 // Trust hidden classes. They are created via Lookup.defineHiddenClass and 231 // can't be serialized, so there is no hacking of finals going on with them. 232 if (holder->is_hidden()) 233 return true; 234 // Trust final fields in records 235 if (holder->is_record()) 236 return true; 237 return TrustFinalNonStaticFields; 238 } 239 240 void ciField::initialize_from(fieldDescriptor* fd) { 241 // Get the flags, offset, and canonical holder of the field. 242 _flags = ciFlags(fd->access_flags(), fd->field_flags().is_stable(), fd->field_status().is_initialized_final_update()); 243 _offset = fd->offset(); 244 Klass* field_holder = fd->field_holder(); 245 assert(field_holder != nullptr, "null field_holder"); 246 _holder = CURRENT_ENV->get_instance_klass(field_holder); 247 248 // Check to see if the field is constant. 249 Klass* k = _holder->get_Klass(); 250 bool is_stable_field = FoldStableValues && is_stable(); 251 if ((is_final() && !has_initialized_final_update()) || is_stable_field) { 252 if (is_static()) { 253 // This field just may be constant. The only case where it will 254 // not be constant is when the field is a *special* static & final field 255 // whose value may change. The three examples are java.lang.System.in, 256 // java.lang.System.out, and java.lang.System.err. 257 _is_constant = !fd->is_mutable_static_final(); 258 } else { 259 // An instance field can be constant if it's a final static field or if 260 // it's a final non-static field of a trusted class (classes in 261 // java.lang.invoke and sun.invoke packages and subpackages). 262 _is_constant = is_stable_field || trust_final_nonstatic_fields(_holder); 263 } 264 } else { 265 // For CallSite objects treat the target field as a compile time constant. 266 assert(vmClasses::CallSite_klass() != nullptr, "should be already initialized"); 267 if (k == vmClasses::CallSite_klass() && 268 _offset == java_lang_invoke_CallSite::target_offset()) { 269 assert(!has_initialized_final_update(), "CallSite is not supposed to have writes to final fields outside initializers"); 270 _is_constant = true; 271 } else { 272 // Non-final & non-stable fields are not constants. 273 _is_constant = false; 274 } 275 } 276 } 277 278 // ------------------------------------------------------------------ 279 // ciField::constant_value 280 // Get the constant value of a this static field. 281 ciConstant ciField::constant_value() { 282 assert(is_static() && is_constant(), "illegal call to constant_value()"); 283 if (!_holder->is_initialized()) { 284 return ciConstant(); // Not initialized yet 285 } 286 if (_constant_value.basic_type() == T_ILLEGAL) { 287 // Static fields are placed in mirror objects. 288 ciInstance* mirror = _holder->java_mirror(); 289 _constant_value = mirror->field_value_impl(type()->basic_type(), offset_in_bytes()); 290 } 291 if (FoldStableValues && is_stable() && _constant_value.is_null_or_zero()) { 292 return ciConstant(); 293 } 294 return _constant_value; 295 } 296 297 // ------------------------------------------------------------------ 298 // ciField::constant_value_of 299 // Get the constant value of non-static final field in the given object. 300 ciConstant ciField::constant_value_of(ciObject* object) { 301 assert(!is_static() && is_constant(), "only if field is non-static constant"); 302 assert(object->is_instance(), "must be instance"); 303 ciConstant field_value = object->as_instance()->field_value(this); 304 if (FoldStableValues && is_stable() && field_value.is_null_or_zero()) { 305 return ciConstant(); 306 } 307 return field_value; 308 } 309 310 // ------------------------------------------------------------------ 311 // ciField::compute_type 312 // 313 // Lazily compute the type, if it is an instance klass. 314 ciType* ciField::compute_type() { 315 GUARDED_VM_ENTRY(return compute_type_impl();) 316 } 317 318 ciType* ciField::compute_type_impl() { 319 ciKlass* type = CURRENT_ENV->get_klass_by_name_impl(_holder, constantPoolHandle(), _signature, false); 320 if (!type->is_primitive_type() && is_shared()) { 321 // We must not cache a pointer to an unshared type, in a shared field. 322 bool type_is_also_shared = false; 323 if (type->is_type_array_klass()) { 324 type_is_also_shared = true; // int[] etc. are explicitly bootstrapped 325 } else if (type->is_instance_klass()) { 326 type_is_also_shared = type->as_instance_klass()->is_shared(); 327 } else { 328 // Currently there is no 'shared' query for array types. 329 type_is_also_shared = !ciObjectFactory::is_initialized(); 330 } 331 if (!type_is_also_shared) 332 return type; // Bummer. 333 } 334 _type = type; 335 return type; 336 } 337 338 339 // ------------------------------------------------------------------ 340 // ciField::will_link 341 // 342 // Can a specific access to this field be made without causing 343 // link errors? 344 bool ciField::will_link(ciMethod* accessing_method, 345 Bytecodes::Code bc) { 346 VM_ENTRY_MARK; 347 assert(bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic || 348 bc == Bytecodes::_getfield || bc == Bytecodes::_putfield, 349 "unexpected bytecode"); 350 351 if (_offset == -1) { 352 // at creation we couldn't link to our holder so we need to 353 // maintain that stance, otherwise there's no safe way to use this 354 // ciField. 355 return false; 356 } 357 358 // Check for static/nonstatic mismatch 359 bool is_static = (bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic); 360 if (is_static != this->is_static()) { 361 return false; 362 } 363 364 // Get and put can have different accessibility rules 365 bool is_put = (bc == Bytecodes::_putfield || bc == Bytecodes::_putstatic); 366 if (is_put) { 367 if (_known_to_link_with_put == accessing_method) { 368 return true; 369 } 370 } else { 371 if (_known_to_link_with_get == accessing_method->holder()) { 372 return true; 373 } 374 } 375 376 LinkInfo link_info(_holder->get_instanceKlass(), 377 _name->get_symbol(), _signature->get_symbol(), 378 methodHandle(THREAD, accessing_method->get_Method())); 379 fieldDescriptor result; 380 LinkResolver::resolve_field(result, link_info, bc, ClassInitMode::dont_init, CHECK_AND_CLEAR_(false)); 381 382 // update the hit-cache, unless there is a problem with memory scoping: 383 if (accessing_method->holder()->is_shared() || !is_shared()) { 384 if (is_put) { 385 _known_to_link_with_put = accessing_method; 386 } else { 387 _known_to_link_with_get = accessing_method->holder(); 388 } 389 } 390 391 return true; 392 } 393 394 bool ciField::is_call_site_target() { 395 ciInstanceKlass* callsite_klass = CURRENT_ENV->CallSite_klass(); 396 if (callsite_klass == nullptr) 397 return false; 398 return (holder()->is_subclass_of(callsite_klass) && (name() == ciSymbols::target_name())); 399 } 400 401 bool ciField::is_autobox_cache() { 402 ciSymbol* klass_name = holder()->name(); 403 return (name() == ciSymbols::cache_field_name() && 404 holder()->uses_default_loader() && 405 (klass_name == ciSymbols::java_lang_Character_CharacterCache() || 406 klass_name == ciSymbols::java_lang_Byte_ByteCache() || 407 klass_name == ciSymbols::java_lang_Short_ShortCache() || 408 klass_name == ciSymbols::java_lang_Integer_IntegerCache() || 409 klass_name == ciSymbols::java_lang_Long_LongCache())); 410 } 411 412 // ------------------------------------------------------------------ 413 // ciField::print 414 void ciField::print() { 415 tty->print("<ciField name="); 416 _holder->print_name(); 417 tty->print("."); 418 _name->print_symbol(); 419 tty->print(" signature="); 420 _signature->print_symbol(); 421 tty->print(" offset=%d type=", _offset); 422 if (_type != nullptr) 423 _type->print_name(); 424 else 425 tty->print("(reference)"); 426 tty->print(" flags=%04x", flags().as_int()); 427 tty->print(" is_constant=%s", bool_to_str(_is_constant)); 428 if (_is_constant && is_static()) { 429 tty->print(" constant_value="); 430 _constant_value.print(); 431 } 432 tty->print(">"); 433 } 434 435 // ------------------------------------------------------------------ 436 // ciField::print_name_on 437 // 438 // Print the name of this field 439 void ciField::print_name_on(outputStream* st) { 440 name()->print_symbol_on(st); 441 } --- EOF ---