1 /* 2 * Copyright (c) 1999, 2020, 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 "oops/oop.inline.hpp" 33 #include "runtime/fieldDescriptor.inline.hpp" 34 #include "runtime/handles.inline.hpp" 35 36 // ciField 37 // 38 // This class represents the result of a field lookup in the VM. 39 // The lookup may not succeed, in which case the information in 40 // the ciField will be incomplete. 41 42 // The ciObjectFactory cannot create circular data structures in one query. 43 // To avoid vicious circularities, we initialize ciField::_type to NULL 44 // for reference types and derive it lazily from the ciField::_signature. 45 // Primitive types are eagerly initialized, and basic layout queries 46 // can succeed without initialization, using only the BasicType of the field. 47 48 // Notes on bootstrapping and shared CI objects: A field is shared if and 49 // only if it is (a) non-static and (b) declared by a shared instance klass. 50 // This allows non-static field lists to be cached on shared types. 51 // Because the _type field is lazily initialized, however, there is a 52 // special restriction that a shared field cannot cache an unshared type. 53 // This puts a small performance penalty on shared fields with unshared 54 // types, such as StackTraceElement[] Throwable.stackTrace. 55 // (Throwable is shared because ClassCastException is shared, but 56 // StackTraceElement is not presently shared.) 57 58 // It is not a vicious circularity for a ciField to recursively create 59 // the ciSymbols necessary to represent its name and signature. 60 // Therefore, these items are created eagerly, and the name and signature 61 // of a shared field are themselves shared symbols. This somewhat 62 // pollutes the set of shared CI objects: It grows from 50 to 93 items, 63 // with all of the additional 43 being uninteresting shared ciSymbols. 64 // This adds at most one step to the binary search, an amount which 65 // decreases for complex compilation tasks. 66 67 // ------------------------------------------------------------------ 68 // ciField::ciField 69 ciField::ciField(ciInstanceKlass* klass, int index) : 70 _known_to_link_with_put(NULL), _known_to_link_with_get(NULL) { 71 ASSERT_IN_VM; 72 CompilerThread *THREAD = CompilerThread::current(); 73 74 assert(ciObjectFactory::is_initialized(), "not a shared field"); 75 76 assert(klass->get_instanceKlass()->is_linked(), "must be linked before using its constant-pool"); 77 78 constantPoolHandle cpool(THREAD, klass->get_instanceKlass()->constants()); 79 80 // Get the field's name, signature, and type. 81 Symbol* name = cpool->name_ref_at(index); 82 _name = ciEnv::current(THREAD)->get_symbol(name); 83 84 int nt_index = cpool->name_and_type_ref_index_at(index); 85 int sig_index = cpool->signature_ref_index_at(nt_index); 86 Symbol* signature = cpool->symbol_at(sig_index); 87 _signature = ciEnv::current(THREAD)->get_symbol(signature); 88 89 BasicType field_type = Signature::basic_type(signature); 90 91 // If the field is a pointer type, get the klass of the 92 // field. 93 if (is_reference_type(field_type)) { 94 bool ignore; 95 // This is not really a class reference; the index always refers to the 96 // field's type signature, as a symbol. Linkage checks do not apply. 97 _type = ciEnv::current(THREAD)->get_klass_by_index(cpool, sig_index, ignore, klass); 98 } else { 99 _type = ciType::make(field_type); 100 } 101 102 _name = (ciSymbol*)ciEnv::current(THREAD)->get_symbol(name); 103 104 // Get the field's declared holder. 105 // 106 // Note: we actually create a ciInstanceKlass for this klass, 107 // even though we may not need to. 108 int holder_index = cpool->klass_ref_index_at(index); 109 bool holder_is_accessible; 110 111 ciKlass* generic_declared_holder = ciEnv::current(THREAD)->get_klass_by_index(cpool, holder_index, 112 holder_is_accessible, 113 klass); 114 115 if (generic_declared_holder->is_array_klass()) { 116 // If the declared holder of the field is an array class, assume that 117 // the canonical holder of that field is java.lang.Object. Arrays 118 // do not have fields; java.lang.Object is the only supertype of an 119 // array type that can declare fields and is therefore the canonical 120 // holder of the array type. 121 // 122 // Furthermore, the compilers assume that java.lang.Object does not 123 // have any fields. Therefore, the field is not looked up. Instead, 124 // the method returns partial information that will trigger special 125 // handling in ciField::will_link and will result in a 126 // java.lang.NoSuchFieldError exception being thrown by the compiled 127 // code (the expected behavior in this case). 128 _holder = ciEnv::current(THREAD)->Object_klass(); 129 _offset = -1; 130 _is_constant = false; 131 return; 132 } 133 134 ciInstanceKlass* declared_holder = generic_declared_holder->as_instance_klass(); 135 136 // The declared holder of this field may not have been loaded. 137 // Bail out with partial field information. 138 if (!holder_is_accessible) { 139 // _type has already been set. 140 // The default values for _flags and _constant_value will suffice. 141 // We need values for _holder, _offset, and _is_constant, 142 _holder = declared_holder; 143 _offset = -1; 144 _is_constant = false; 145 return; 146 } 147 148 InstanceKlass* loaded_decl_holder = declared_holder->get_instanceKlass(); 149 150 // Perform the field lookup. 151 fieldDescriptor field_desc; 152 Klass* canonical_holder = 153 loaded_decl_holder->find_field(name, signature, &field_desc); 154 if (canonical_holder == NULL) { 155 // Field lookup failed. Will be detected by will_link. 156 _holder = declared_holder; 157 _offset = -1; 158 _is_constant = false; 159 return; 160 } 161 162 // Access check based on declared_holder. canonical_holder should not be used 163 // to check access because it can erroneously succeed. If this check fails, 164 // propagate the declared holder to will_link() which in turn will bail out 165 // compilation for this field access. 166 bool can_access = Reflection::verify_member_access(klass->get_Klass(), 167 declared_holder->get_Klass(), 168 canonical_holder, 169 field_desc.access_flags(), 170 true, false, THREAD); 171 if (!can_access) { 172 _holder = declared_holder; 173 _offset = -1; 174 _is_constant = false; 175 // It's possible the access check failed due to a nestmate access check 176 // encountering an exception. We can't propagate the exception from here 177 // so we have to clear it. If the access check happens again in a different 178 // context then the exception will be thrown there. 179 if (HAS_PENDING_EXCEPTION) { 180 CLEAR_PENDING_EXCEPTION; 181 } 182 return; 183 } 184 185 assert(canonical_holder == field_desc.field_holder(), "just checking"); 186 initialize_from(&field_desc); 187 } 188 189 ciField::ciField(fieldDescriptor *fd) : 190 _known_to_link_with_put(NULL), _known_to_link_with_get(NULL) { 191 ASSERT_IN_VM; 192 193 // Get the field's name, signature, and type. 194 ciEnv* env = CURRENT_ENV; 195 _name = env->get_symbol(fd->name()); 196 _signature = env->get_symbol(fd->signature()); 197 198 BasicType field_type = fd->field_type(); 199 200 // If the field is a pointer type, get the klass of the 201 // field. 202 if (is_reference_type(field_type)) { 203 _type = NULL; // must call compute_type on first access 204 } else { 205 _type = ciType::make(field_type); 206 } 207 208 initialize_from(fd); 209 210 // Either (a) it is marked shared, or else (b) we are done bootstrapping. 211 assert(is_shared() || ciObjectFactory::is_initialized(), 212 "bootstrap classes must not create & cache unshared fields"); 213 } 214 215 static bool trust_final_non_static_fields(ciInstanceKlass* holder) { 216 if (holder == NULL) 217 return false; 218 if (holder->name() == ciSymbol::java_lang_System()) 219 // Never trust strangely unstable finals: System.out, etc. 220 return false; 221 // Even if general trusting is disabled, trust system-built closures in these packages. 222 if (holder->is_in_package("java/lang/invoke") || holder->is_in_package("sun/invoke") || 223 holder->is_in_package("jdk/internal/foreign") || holder->is_in_package("jdk/incubator/foreign") || 224 holder->is_in_package("java/lang")) 225 return true; 226 // Trust VM hidden and unsafe anonymous classes. They are created via Lookup.defineClass or 227 // the private API (jdk.internal.misc.Unsafe) and can't be serialized, so there is no hacking 228 // of finals going on with them. 229 if (holder->is_hidden() || holder->is_unsafe_anonymous()) 230 return true; 231 // Trust final fields in all boxed classes 232 if (holder->is_box_klass()) 233 return true; 234 // Trust final fields in String 235 if (holder->name() == ciSymbol::java_lang_String()) 236 return true; 237 // Trust Atomic*FieldUpdaters: they are very important for performance, and make up one 238 // more reason not to use Unsafe, if their final fields are trusted. See more in JDK-8140483. 239 if (holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicIntegerFieldUpdater_Impl() || 240 holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicLongFieldUpdater_CASUpdater() || 241 holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicLongFieldUpdater_LockedUpdater() || 242 holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicReferenceFieldUpdater_Impl()) { 243 return true; 244 } 245 return TrustFinalNonStaticFields; 246 } 247 248 void ciField::initialize_from(fieldDescriptor* fd) { 249 // Get the flags, offset, and canonical holder of the field. 250 _flags = ciFlags(fd->access_flags()); 251 _offset = fd->offset(); 252 Klass* field_holder = fd->field_holder(); 253 assert(field_holder != NULL, "null field_holder"); 254 _holder = CURRENT_ENV->get_instance_klass(field_holder); 255 256 // Check to see if the field is constant. 257 Klass* k = _holder->get_Klass(); 258 bool is_stable_field = FoldStableValues && is_stable(); 259 if ((is_final() && !has_initialized_final_update()) || is_stable_field) { 260 if (is_static()) { 261 // This field just may be constant. The only case where it will 262 // not be constant is when the field is a *special* static & final field 263 // whose value may change. The three examples are java.lang.System.in, 264 // java.lang.System.out, and java.lang.System.err. 265 assert(SystemDictionary::System_klass() != NULL, "Check once per vm"); 266 if (k == SystemDictionary::System_klass()) { 267 // Check offsets for case 2: System.in, System.out, or System.err 268 if( _offset == java_lang_System::in_offset_in_bytes() || 269 _offset == java_lang_System::out_offset_in_bytes() || 270 _offset == java_lang_System::err_offset_in_bytes() ) { 271 _is_constant = false; 272 return; 273 } 274 } 275 _is_constant = true; 276 } else { 277 // An instance field can be constant if it's a final static field or if 278 // it's a final non-static field of a trusted class (classes in 279 // java.lang.invoke and sun.invoke packages and subpackages). 280 _is_constant = is_stable_field || trust_final_non_static_fields(_holder); 281 } 282 } else { 283 // For CallSite objects treat the target field as a compile time constant. 284 assert(SystemDictionary::CallSite_klass() != NULL, "should be already initialized"); 285 if (k == SystemDictionary::CallSite_klass() && 286 _offset == java_lang_invoke_CallSite::target_offset_in_bytes()) { 287 assert(!has_initialized_final_update(), "CallSite is not supposed to have writes to final fields outside initializers"); 288 _is_constant = true; 289 } else { 290 // Non-final & non-stable fields are not constants. 291 _is_constant = false; 292 } 293 } 294 } 295 296 // ------------------------------------------------------------------ 297 // ciField::constant_value 298 // Get the constant value of a this static field. 299 ciConstant ciField::constant_value() { 300 assert(is_static() && is_constant(), "illegal call to constant_value()"); 301 if (!_holder->is_initialized()) { 302 return ciConstant(); // Not initialized yet 303 } 304 if (_constant_value.basic_type() == T_ILLEGAL) { 305 // Static fields are placed in mirror objects. 306 VM_ENTRY_MARK; 307 ciInstance* mirror = CURRENT_ENV->get_instance(_holder->get_Klass()->java_mirror()); 308 _constant_value = mirror->field_value_impl(type()->basic_type(), offset()); 309 } 310 if (FoldStableValues && is_stable() && _constant_value.is_null_or_zero()) { 311 return ciConstant(); 312 } 313 return _constant_value; 314 } 315 316 // ------------------------------------------------------------------ 317 // ciField::constant_value_of 318 // Get the constant value of non-static final field in the given object. 319 ciConstant ciField::constant_value_of(ciObject* object) { 320 assert(!is_static() && is_constant(), "only if field is non-static constant"); 321 assert(object->is_instance(), "must be instance"); 322 ciConstant field_value = object->as_instance()->field_value(this); 323 if (FoldStableValues && is_stable() && field_value.is_null_or_zero()) { 324 return ciConstant(); 325 } 326 return field_value; 327 } 328 329 // ------------------------------------------------------------------ 330 // ciField::compute_type 331 // 332 // Lazily compute the type, if it is an instance klass. 333 ciType* ciField::compute_type() { 334 GUARDED_VM_ENTRY(return compute_type_impl();) 335 } 336 337 ciType* ciField::compute_type_impl() { 338 ciKlass* type = CURRENT_ENV->get_klass_by_name_impl(_holder, constantPoolHandle(), _signature, false); 339 if (!type->is_primitive_type() && is_shared()) { 340 // We must not cache a pointer to an unshared type, in a shared field. 341 bool type_is_also_shared = false; 342 if (type->is_type_array_klass()) { 343 type_is_also_shared = true; // int[] etc. are explicitly bootstrapped 344 } else if (type->is_instance_klass()) { 345 type_is_also_shared = type->as_instance_klass()->is_shared(); 346 } else { 347 // Currently there is no 'shared' query for array types. 348 type_is_also_shared = !ciObjectFactory::is_initialized(); 349 } 350 if (!type_is_also_shared) 351 return type; // Bummer. 352 } 353 _type = type; 354 return type; 355 } 356 357 358 // ------------------------------------------------------------------ 359 // ciField::will_link 360 // 361 // Can a specific access to this field be made without causing 362 // link errors? 363 bool ciField::will_link(ciMethod* accessing_method, 364 Bytecodes::Code bc) { 365 VM_ENTRY_MARK; 366 assert(bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic || 367 bc == Bytecodes::_getfield || bc == Bytecodes::_putfield, 368 "unexpected bytecode"); 369 370 if (_offset == -1) { 371 // at creation we couldn't link to our holder so we need to 372 // maintain that stance, otherwise there's no safe way to use this 373 // ciField. 374 return false; 375 } 376 377 // Check for static/nonstatic mismatch 378 bool is_static = (bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic); 379 if (is_static != this->is_static()) { 380 return false; 381 } 382 383 // Get and put can have different accessibility rules 384 bool is_put = (bc == Bytecodes::_putfield || bc == Bytecodes::_putstatic); 385 if (is_put) { 386 if (_known_to_link_with_put == accessing_method) { 387 return true; 388 } 389 } else { 390 if (_known_to_link_with_get == accessing_method->holder()) { 391 return true; 392 } 393 } 394 395 LinkInfo link_info(_holder->get_instanceKlass(), 396 _name->get_symbol(), _signature->get_symbol(), 397 methodHandle(THREAD, accessing_method->get_Method())); 398 fieldDescriptor result; 399 LinkResolver::resolve_field(result, link_info, bc, false, KILL_COMPILE_ON_FATAL_(false)); 400 401 // update the hit-cache, unless there is a problem with memory scoping: 402 if (accessing_method->holder()->is_shared() || !is_shared()) { 403 if (is_put) { 404 _known_to_link_with_put = accessing_method; 405 } else { 406 _known_to_link_with_get = accessing_method->holder(); 407 } 408 } 409 410 return true; 411 } 412 413 // ------------------------------------------------------------------ 414 // ciField::print 415 void ciField::print() { 416 tty->print("<ciField name="); 417 _holder->print_name(); 418 tty->print("."); 419 _name->print_symbol(); 420 tty->print(" signature="); 421 _signature->print_symbol(); 422 tty->print(" offset=%d type=", _offset); 423 if (_type != NULL) 424 _type->print_name(); 425 else 426 tty->print("(reference)"); 427 tty->print(" flags=%04x", flags().as_int()); 428 tty->print(" is_constant=%s", bool_to_str(_is_constant)); 429 if (_is_constant && is_static()) { 430 tty->print(" constant_value="); 431 _constant_value.print(); 432 } 433 tty->print(">"); 434 } 435 436 // ------------------------------------------------------------------ 437 // ciField::print_name_on 438 // 439 // Print the name of this field 440 void ciField::print_name_on(outputStream* st) { 441 name()->print_symbol_on(st); 442 }