1 /* 2 * Copyright (c) 1999, 2015, 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.hpp" 29 #include "classfile/systemDictionary.hpp" 30 #include "gc/shared/collectedHeap.inline.hpp" 31 #include "interpreter/linkResolver.hpp" 32 #include "memory/universe.inline.hpp" 33 #include "oops/oop.inline.hpp" 34 #include "runtime/fieldDescriptor.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 = FieldType::basic_type(signature); 90 91 // If the field is a pointer type, get the klass of the 92 // field. 93 if (field_type == T_OBJECT || field_type == T_ARRAY || field_type == T_VALUETYPE) { 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 if (!Reflection::verify_field_access(klass->get_Klass(), declared_holder->get_Klass(), canonical_holder, field_desc.access_flags(), true)) { 167 _holder = declared_holder; 168 _offset = -1; 169 _is_constant = false; 170 return; 171 } 172 173 assert(canonical_holder == field_desc.field_holder(), "just checking"); 174 initialize_from(&field_desc); 175 } 176 177 ciField::ciField(fieldDescriptor *fd) : 178 _known_to_link_with_put(NULL), _known_to_link_with_get(NULL) { 179 ASSERT_IN_VM; 180 181 // Get the field's name, signature, and type. 182 ciEnv* env = CURRENT_ENV; 183 _name = env->get_symbol(fd->name()); 184 _signature = env->get_symbol(fd->signature()); 185 186 BasicType field_type = fd->field_type(); 187 188 // If the field is a pointer type, get the klass of the 189 // field. 190 if (field_type == T_OBJECT || field_type == T_ARRAY || field_type == T_VALUETYPE) { 191 _type = NULL; // must call compute_type on first access 192 } else { 193 _type = ciType::make(field_type); 194 } 195 196 initialize_from(fd); 197 198 // Either (a) it is marked shared, or else (b) we are done bootstrapping. 199 assert(is_shared() || ciObjectFactory::is_initialized(), 200 "bootstrap classes must not create & cache unshared fields"); 201 } 202 203 // Special copy constructor used to flatten value type fields by 204 // copying the fields of the value type to a new holder klass. 205 ciField::ciField(ciField* field, ciInstanceKlass* holder, int offset, bool is_final) { 206 assert(field->holder()->is_valuetype(), "should only be used for value type field flattening"); 207 // Set the is_final flag 208 jint final = is_final ? JVM_ACC_FINAL : ~JVM_ACC_FINAL; 209 AccessFlags flags(field->flags().as_int() & final); 210 _flags = ciFlags(flags); 211 _holder = holder; 212 _offset = offset; 213 // Copy remaining fields 214 _name = field->_name; 215 _signature = field->_signature; 216 _type = field->_type; 217 _is_constant = field->_is_constant; 218 _known_to_link_with_put = field->_known_to_link_with_put; 219 _known_to_link_with_get = field->_known_to_link_with_get; 220 _constant_value = field->_constant_value; 221 } 222 223 static bool trust_final_non_static_fields(ciInstanceKlass* holder) { 224 if (holder == NULL) 225 return false; 226 if (holder->name() == ciSymbol::java_lang_System()) 227 // Never trust strangely unstable finals: System.out, etc. 228 return false; 229 // Even if general trusting is disabled, trust system-built closures in these packages. 230 if (holder->is_in_package("java/lang/invoke") || holder->is_in_package("sun/invoke")) 231 return true; 232 // Trust VM anonymous classes. They are private API (sun.misc.Unsafe) and can't be serialized, 233 // so there is no hacking of finals going on with them. 234 if (holder->is_anonymous()) 235 return true; 236 // Trust final fields in all boxed classes 237 if (holder->is_box_klass()) 238 return true; 239 // Trust final fields in String 240 if (holder->name() == ciSymbol::java_lang_String()) 241 return true; 242 // Trust Atomic*FieldUpdaters: they are very important for performance, and make up one 243 // more reason not to use Unsafe, if their final fields are trusted. See more in JDK-8140483. 244 if (holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicIntegerFieldUpdater_Impl() || 245 holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicLongFieldUpdater_CASUpdater() || 246 holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicLongFieldUpdater_LockedUpdater() || 247 holder->name() == ciSymbol::java_util_concurrent_atomic_AtomicReferenceFieldUpdater_Impl()) { 248 return true; 249 } 250 return TrustFinalNonStaticFields; 251 } 252 253 void ciField::initialize_from(fieldDescriptor* fd) { 254 // Get the flags, offset, and canonical holder of the field. 255 _flags = ciFlags(fd->access_flags()); 256 _offset = fd->offset(); 257 _holder = CURRENT_ENV->get_instance_klass(fd->field_holder()); 258 259 // Check to see if the field is constant. 260 Klass* k = _holder->get_Klass(); 261 bool is_stable_field = FoldStableValues && is_stable(); 262 if ((is_final() && !has_initialized_final_update()) || is_stable_field) { 263 if (is_static()) { 264 // This field just may be constant. The only case where it will 265 // not be constant is when the field is a *special* static & final field 266 // whose value may change. The three examples are java.lang.System.in, 267 // java.lang.System.out, and java.lang.System.err. 268 assert(SystemDictionary::System_klass() != NULL, "Check once per vm"); 269 if (k == SystemDictionary::System_klass()) { 270 // Check offsets for case 2: System.in, System.out, or System.err 271 if( _offset == java_lang_System::in_offset_in_bytes() || 272 _offset == java_lang_System::out_offset_in_bytes() || 273 _offset == java_lang_System::err_offset_in_bytes() ) { 274 _is_constant = false; 275 return; 276 } 277 } 278 _is_constant = true; 279 } else { 280 // An instance field can be constant if it's a final static field or if 281 // it's a final non-static field of a trusted class (classes in 282 // java.lang.invoke and sun.invoke packages and subpackages). 283 _is_constant = is_stable_field || trust_final_non_static_fields(_holder); 284 } 285 } else { 286 // For CallSite objects treat the target field as a compile time constant. 287 assert(SystemDictionary::CallSite_klass() != NULL, "should be already initialized"); 288 if (k == SystemDictionary::CallSite_klass() && 289 _offset == java_lang_invoke_CallSite::target_offset_in_bytes()) { 290 assert(!has_initialized_final_update(), "CallSite is not supposed to have writes to final fields outside initializers"); 291 _is_constant = true; 292 } else { 293 // Non-final & non-stable fields are not constants. 294 _is_constant = false; 295 } 296 } 297 } 298 299 // ------------------------------------------------------------------ 300 // ciField::constant_value 301 // Get the constant value of a this static field. 302 ciConstant ciField::constant_value() { 303 assert(is_static() && is_constant(), "illegal call to constant_value()"); 304 if (!_holder->is_initialized()) { 305 return ciConstant(); // Not initialized yet 306 } 307 if (_constant_value.basic_type() == T_ILLEGAL) { 308 // Static fields are placed in mirror objects. 309 VM_ENTRY_MARK; 310 ciInstance* mirror = CURRENT_ENV->get_instance(_holder->get_Klass()->java_mirror()); 311 _constant_value = mirror->field_value_impl(type()->basic_type(), offset()); 312 } 313 if (FoldStableValues && is_stable() && _constant_value.is_null_or_zero()) { 314 return ciConstant(); 315 } 316 return _constant_value; 317 } 318 319 // ------------------------------------------------------------------ 320 // ciField::constant_value_of 321 // Get the constant value of non-static final field in the given object. 322 ciConstant ciField::constant_value_of(ciObject* object) { 323 assert(!is_static() && is_constant(), "only if field is non-static constant"); 324 assert(object->is_instance(), "must be instance"); 325 ciConstant field_value = object->as_instance()->field_value(this); 326 if (FoldStableValues && is_stable() && field_value.is_null_or_zero()) { 327 return ciConstant(); 328 } 329 return field_value; 330 } 331 332 // ------------------------------------------------------------------ 333 // ciField::compute_type 334 // 335 // Lazily compute the type, if it is an instance klass. 336 ciType* ciField::compute_type() { 337 GUARDED_VM_ENTRY(return compute_type_impl();) 338 } 339 340 ciType* ciField::compute_type_impl() { 341 ciKlass* type = CURRENT_ENV->get_klass_by_name_impl(_holder, constantPoolHandle(), _signature, false); 342 if (!type->is_primitive_type() && is_shared()) { 343 // We must not cache a pointer to an unshared type, in a shared field. 344 bool type_is_also_shared = false; 345 if (type->is_type_array_klass()) { 346 type_is_also_shared = true; // int[] etc. are explicitly bootstrapped 347 } else if (type->is_instance_klass()) { 348 type_is_also_shared = type->as_instance_klass()->is_shared(); 349 } else { 350 // Currently there is no 'shared' query for array types. 351 type_is_also_shared = !ciObjectFactory::is_initialized(); 352 } 353 if (!type_is_also_shared) 354 return type; // Bummer. 355 } 356 _type = type; 357 return type; 358 } 359 360 361 // ------------------------------------------------------------------ 362 // ciField::will_link 363 // 364 // Can a specific access to this field be made without causing 365 // link errors? 366 bool ciField::will_link(ciMethod* accessing_method, 367 Bytecodes::Code bc) { 368 VM_ENTRY_MARK; 369 assert(bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic || 370 bc == Bytecodes::_getfield || bc == Bytecodes::_putfield || 371 bc == Bytecodes::_vgetfield || bc == Bytecodes::_vwithfield, 372 "unexpected bytecode"); 373 374 if (_offset == -1) { 375 // at creation we couldn't link to our holder so we need to 376 // maintain that stance, otherwise there's no safe way to use this 377 // ciField. 378 return false; 379 } 380 381 // Check for static/nonstatic mismatch 382 bool is_static = (bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic); 383 if (is_static != this->is_static()) { 384 return false; 385 } 386 387 // Get and put can have different accessibility rules 388 bool is_put = (bc == Bytecodes::_putfield || bc == Bytecodes::_putstatic); 389 if (is_put) { 390 if (_known_to_link_with_put == accessing_method) { 391 return true; 392 } 393 } else { 394 if (_known_to_link_with_get == accessing_method->holder()) { 395 return true; 396 } 397 } 398 399 LinkInfo link_info(_holder->get_instanceKlass(), 400 _name->get_symbol(), _signature->get_symbol(), 401 accessing_method->get_Method()); 402 fieldDescriptor result; 403 LinkResolver::resolve_field(result, link_info, bc, false, KILL_COMPILE_ON_FATAL_(false)); 404 405 // update the hit-cache, unless there is a problem with memory scoping: 406 if (accessing_method->holder()->is_shared() || !is_shared()) { 407 if (is_put) { 408 _known_to_link_with_put = accessing_method; 409 } else { 410 _known_to_link_with_get = accessing_method->holder(); 411 } 412 } 413 414 return true; 415 } 416 417 // ------------------------------------------------------------------ 418 // ciField::print 419 void ciField::print() { 420 tty->print("<ciField name="); 421 _holder->print_name(); 422 tty->print("."); 423 _name->print_symbol(); 424 tty->print(" signature="); 425 _signature->print_symbol(); 426 tty->print(" offset=%d type=", _offset); 427 if (_type != NULL) 428 _type->print_name(); 429 else 430 tty->print("(reference)"); 431 tty->print(" flags=%04x", flags().as_int()); 432 tty->print(" is_constant=%s", bool_to_str(_is_constant)); 433 if (_is_constant && is_static()) { 434 tty->print(" constant_value="); 435 _constant_value.print(); 436 } 437 tty->print(">"); 438 } 439 440 // ------------------------------------------------------------------ 441 // ciField::print_name_on 442 // 443 // Print the name of this field 444 void ciField::print_name_on(outputStream* st) { 445 name()->print_symbol_on(st); 446 }