1 /* 2 * Copyright (c) 2022, 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 "cds/aotClassInitializer.hpp" 26 #include "cds/archiveBuilder.hpp" 27 #include "cds/cdsHeapVerifier.hpp" 28 #include "classfile/classLoaderDataGraph.hpp" 29 #include "classfile/javaClasses.inline.hpp" 30 #include "classfile/moduleEntry.hpp" 31 #include "classfile/systemDictionaryShared.hpp" 32 #include "classfile/vmSymbols.hpp" 33 #include "logging/log.hpp" 34 #include "logging/logStream.hpp" 35 #include "memory/resourceArea.hpp" 36 #include "oops/fieldStreams.inline.hpp" 37 #include "oops/klass.inline.hpp" 38 #include "oops/oop.inline.hpp" 39 #include "oops/oopHandle.inline.hpp" 40 #include "runtime/fieldDescriptor.inline.hpp" 41 42 #if INCLUDE_CDS_JAVA_HEAP 43 44 // CDSHeapVerifier is used to check for problems where an archived object references a 45 // static field that may be get a different value at runtime. 46 // 47 // *Please see comments in aotClassInitializer.cpp for how to avoid such problems*, 48 // 49 // In the following example, 50 // Foo.get.test() 51 // correctly returns true when CDS disabled, but incorrectly returns false when CDS is enabled, 52 // because the archived archivedFoo.bar value is different than Bar.bar. 53 // 54 // class Foo { 55 // static final Foo archivedFoo; // this field is archived by CDS 56 // Bar bar; 57 // static { 58 // CDS.initializeFromArchive(Foo.class); 59 // if (archivedFoo == null) { 60 // archivedFoo = new Foo(); 61 // archivedFoo.bar = Bar.bar; 62 // } 63 // } 64 // static Foo get() { return archivedFoo; } 65 // boolean test() { 66 // return bar == Bar.bar; 67 // } 68 // } 69 // 70 // class Bar { 71 // // this field is initialized in both CDS dump time and runtime. 72 // static final Bar bar = new Bar(); 73 // } 74 // 75 // The check itself is simple: 76 // [1] CDSHeapVerifier::do_klass() collects all static fields 77 // [2] CDSHeapVerifier::do_entry() checks all the archived objects. None of them 78 // should be in [1] 79 // 80 // However, it's legal for *some* static fields to be referenced. The reasons are explained 81 // in the table of ADD_EXCL below. 82 // 83 // [A] In most of the cases, the module bootstrap code will update the static field 84 // to point to part of the archived module graph. E.g., 85 // - java/lang/System::bootLayer 86 // - jdk/internal/loader/ClassLoaders::BOOT_LOADER 87 // [B] A final static String that's explicitly initialized inside <clinit>, but 88 // its value is deterministic and is always the same string literal. 89 // [C] A non-final static string that is assigned a string literal during class 90 // initialization; this string is never changed during -Xshare:dump. 91 // [D] Simple caches whose value doesn't matter. 92 // [E] Other cases (see comments in-line below). 93 94 CDSHeapVerifier::CDSHeapVerifier() : _archived_objs(0), _problems(0) 95 { 96 # define ADD_EXCL(...) { static const char* e[] = {__VA_ARGS__, nullptr}; add_exclusion(e); } 97 98 // Unfortunately this needs to be manually maintained. If 99 // test/hotspot/jtreg/runtime/cds/appcds/cacheObject/ArchivedEnumTest.java fails, 100 // you might need to fix the core library code, or fix the ADD_EXCL entries below. 101 // 102 // class field type 103 ADD_EXCL("java/lang/ClassLoader$Holder", "scl"); // A 104 ADD_EXCL("java/lang/Module", "ALL_UNNAMED_MODULE", // A 105 "ALL_UNNAMED_MODULE_SET", // A 106 "EVERYONE_MODULE", // A 107 "EVERYONE_SET"); // A 108 109 // This is the same as java/util/ImmutableCollections::EMPTY_SET, which is archived 110 ADD_EXCL("java/lang/reflect/AccessFlag$Location", "EMPTY_SET"); // E 111 112 ADD_EXCL("java/lang/System", "bootLayer"); // A 113 114 ADD_EXCL("java/util/Collections", "EMPTY_LIST"); // E 115 116 // A dummy object used by HashSet. The value doesn't matter and it's never 117 // tested for equality. 118 ADD_EXCL("java/util/HashSet", "PRESENT"); // E 119 120 ADD_EXCL("jdk/internal/loader/BootLoader", "UNNAMED_MODULE"); // A 121 ADD_EXCL("jdk/internal/loader/BuiltinClassLoader", "packageToModule"); // A 122 ADD_EXCL("jdk/internal/loader/ClassLoaders", "BOOT_LOADER", // A 123 "APP_LOADER", // A 124 "PLATFORM_LOADER"); // A 125 ADD_EXCL("jdk/internal/module/Builder", "cachedVersion"); // D 126 ADD_EXCL("jdk/internal/module/ModuleLoaderMap$Mapper", "APP_CLASSLOADER", // A 127 "APP_LOADER_INDEX", // A 128 "PLATFORM_CLASSLOADER", // A 129 "PLATFORM_LOADER_INDEX"); // A 130 ADD_EXCL("jdk/internal/module/ServicesCatalog", "CLV"); // A 131 132 // This just points to an empty Map 133 ADD_EXCL("jdk/internal/reflect/Reflection", "methodFilterMap"); // E 134 135 // Integer for 0 and 1 are in java/lang/Integer$IntegerCache and are archived 136 ADD_EXCL("sun/invoke/util/ValueConversions", "ONE_INT", // E 137 "ZERO_INT"); // E 138 139 if (CDSConfig::is_dumping_method_handles()) { 140 ADD_EXCL("java/lang/invoke/InvokerBytecodeGenerator", "MEMBERNAME_FACTORY", // D 141 "CD_Object_array", // E same as <...>ConstantUtils.CD_Object_array::CD_Object 142 "INVOKER_SUPER_DESC"); // E same as java.lang.constant.ConstantDescs::CD_Object 143 144 ADD_EXCL("java/lang/runtime/ObjectMethods", "CLASS_IS_INSTANCE", // D 145 "FALSE", // D 146 "TRUE", // D 147 "ZERO"); // D 148 } 149 150 if (CDSConfig::is_dumping_aot_linked_classes()) { 151 ADD_EXCL("java/lang/Package$VersionInfo", "NULL_VERSION_INFO"); // D 152 } 153 154 # undef ADD_EXCL 155 156 ClassLoaderDataGraph::classes_do(this); 157 } 158 159 CDSHeapVerifier::~CDSHeapVerifier() { 160 if (_problems > 0) { 161 log_error(aot, heap)("Scanned %d objects. Found %d case(s) where " 162 "an object points to a static field that " 163 "may hold a different value at runtime.", _archived_objs, _problems); 164 log_error(aot, heap)("Please see cdsHeapVerifier.cpp and aotClassInitializer.cpp for details"); 165 AOTMetaspace::unrecoverable_writing_error(); 166 } 167 } 168 169 class CDSHeapVerifier::CheckStaticFields : public FieldClosure { 170 CDSHeapVerifier* _verifier; 171 InstanceKlass* _ik; // The class whose static fields are being checked. 172 const char** _exclusions; 173 public: 174 CheckStaticFields(CDSHeapVerifier* verifier, InstanceKlass* ik) 175 : _verifier(verifier), _ik(ik) { 176 _exclusions = _verifier->find_exclusion(_ik); 177 } 178 179 void do_field(fieldDescriptor* fd) { 180 if (fd->field_type() != T_OBJECT) { 181 return; 182 } 183 184 if (fd->signature()->equals("Ljdk/internal/access/JavaLangAccess;")) { 185 // A few classes have static fields that point to SharedSecrets.getJavaLangAccess(). 186 // This object carries no state and we can create a new one in the production run. 187 return; 188 } 189 oop static_obj_field = _ik->java_mirror()->obj_field(fd->offset()); 190 if (static_obj_field != nullptr) { 191 Klass* field_type = static_obj_field->klass(); 192 if (_exclusions != nullptr) { 193 for (const char** p = _exclusions; *p != nullptr; p++) { 194 if (fd->name()->equals(*p)) { 195 return; 196 } 197 } 198 } 199 200 if (fd->is_final() && java_lang_String::is_instance(static_obj_field) && fd->has_initial_value()) { 201 // This field looks like like this in the Java source: 202 // static final SOME_STRING = "a string literal"; 203 // This string literal has been stored in the shared string table, so it's OK 204 // for the archived objects to refer to it. 205 return; 206 } 207 if (fd->is_final() && java_lang_Class::is_instance(static_obj_field)) { 208 // This field points to an archived mirror. 209 return; 210 } 211 212 if (field_type->is_instance_klass()) { 213 InstanceKlass* field_ik = InstanceKlass::cast(field_type); 214 if (field_ik->is_enum_subclass()) { 215 if (field_ik->has_archived_enum_objs() || ArchiveUtils::has_aot_initialized_mirror(field_ik)) { 216 // This field is an Enum. If any instance of this Enum has been archived, we will archive 217 // all static fields of this Enum as well. 218 return; 219 } 220 } 221 222 if (field_ik->is_hidden() && ArchiveUtils::has_aot_initialized_mirror(field_ik)) { 223 // We have a static field in a core-library class that points to a method reference, which 224 // are safe to archive. 225 guarantee(_ik->module()->name() == vmSymbols::java_base(), "sanity"); 226 return; 227 } 228 229 if (field_ik == vmClasses::MethodType_klass()) { 230 // The identity of MethodTypes are preserved between assembly phase and production runs 231 // (by MethodType::AOTHolder::archivedMethodTypes). No need to check. 232 return; 233 } 234 235 if (ArchiveUtils::has_aot_initialized_mirror(field_ik)) { 236 if (field_ik == vmClasses::internal_Unsafe_klass()) { 237 // There's only a single instance of jdk/internal/misc/Unsafe, so all references will 238 // be pointing to this singleton, which has been archived. 239 return; 240 } 241 if (field_ik == vmClasses::Boolean_klass()) { 242 // TODO: check if is TRUE or FALSE 243 return; 244 } 245 } 246 } 247 248 // This field *may* be initialized to a different value at runtime. Remember it 249 // and check later if it appears in the archived object graph. 250 _verifier->add_static_obj_field(_ik, static_obj_field, fd->name()); 251 } 252 } 253 }; 254 255 // Remember all the static object fields of every class that are currently 256 // loaded. Later, we will check if any archived objects reference one of 257 // these fields. 258 void CDSHeapVerifier::do_klass(Klass* k) { 259 if (k->is_instance_klass()) { 260 InstanceKlass* ik = InstanceKlass::cast(k); 261 262 if (HeapShared::is_subgraph_root_class(ik)) { 263 // ik is inside one of the ArchivableStaticFieldInfo tables 264 // in heapShared.cpp. We assume such classes are programmed to 265 // update their static fields correctly at runtime. 266 return; 267 } 268 269 if (ArchiveUtils::has_aot_initialized_mirror(ik)) { 270 // ik's <clinit> won't be executed at runtime, the static fields in 271 // ik will carry their values to runtime. 272 return; 273 } 274 275 CheckStaticFields csf(this, ik); 276 ik->do_local_static_fields(&csf); 277 } 278 } 279 280 void CDSHeapVerifier::add_static_obj_field(InstanceKlass* ik, oop field, Symbol* name) { 281 StaticFieldInfo info = {ik, name}; 282 _table.put(field, info); 283 } 284 285 // This function is called once for every archived heap object. Warn if this object is referenced by 286 // a static field of a class that's not aot-initialized. 287 inline bool CDSHeapVerifier::do_entry(OopHandle& orig_obj_handle, HeapShared::CachedOopInfo& value) { 288 oop orig_obj = orig_obj_handle.resolve(); 289 _archived_objs++; 290 291 if (java_lang_String::is_instance(orig_obj) && HeapShared::is_dumped_interned_string(orig_obj)) { 292 // It's quite often for static fields to have interned strings. These are most likely not 293 // problematic (and are hard to filter). So we will ignore them. 294 return true; /* keep on iterating */ 295 } 296 297 StaticFieldInfo* info = _table.get(orig_obj); 298 if (info != nullptr) { 299 ResourceMark rm; 300 char* class_name = info->_holder->name()->as_C_string(); 301 char* field_name = info->_name->as_C_string(); 302 LogStream ls(Log(aot, heap)::warning()); 303 ls.print_cr("Archive heap points to a static field that may hold a different value at runtime:"); 304 ls.print_cr("Field: %s::%s", class_name, field_name); 305 ls.print("Value: "); 306 orig_obj->print_on(&ls); 307 ls.print_cr("--- trace begin ---"); 308 trace_to_root(&ls, orig_obj, nullptr, &value); 309 ls.print_cr("--- trace end ---"); 310 ls.cr(); 311 _problems ++; 312 } 313 314 return true; /* keep on iterating */ 315 } 316 317 class CDSHeapVerifier::TraceFields : public FieldClosure { 318 oop _orig_obj; 319 oop _orig_field; 320 outputStream* _st; 321 322 public: 323 TraceFields(oop orig_obj, oop orig_field, outputStream* st) 324 : _orig_obj(orig_obj), _orig_field(orig_field), _st(st) {} 325 326 void do_field(fieldDescriptor* fd) { 327 if (fd->field_type() == T_OBJECT || fd->field_type() == T_ARRAY) { 328 oop obj_field = _orig_obj->obj_field(fd->offset()); 329 if (obj_field == _orig_field) { 330 _st->print("::%s (offset = %d)", fd->name()->as_C_string(), fd->offset()); 331 } 332 } 333 } 334 }; 335 336 // Call this function (from gdb, etc) if you want to know why an object is archived. 337 void CDSHeapVerifier::trace_to_root(outputStream* st, oop orig_obj) { 338 HeapShared::CachedOopInfo* info = HeapShared::get_cached_oop_info(orig_obj); 339 if (info != nullptr) { 340 trace_to_root(st, orig_obj, nullptr, info); 341 } else { 342 st->print_cr("Not an archived object??"); 343 } 344 } 345 346 const char* static_field_name(oop mirror, oop field) { 347 Klass* k = java_lang_Class::as_Klass(mirror); 348 if (k->is_instance_klass()) { 349 for (JavaFieldStream fs(InstanceKlass::cast(k)); !fs.done(); fs.next()) { 350 if (fs.access_flags().is_static()) { 351 fieldDescriptor& fd = fs.field_descriptor(); 352 switch (fd.field_type()) { 353 case T_OBJECT: 354 case T_ARRAY: 355 if (mirror->obj_field(fd.offset()) == field) { 356 return fs.name()->as_C_string(); 357 } 358 break; 359 default: 360 break; 361 } 362 } 363 } 364 } 365 366 return "<unknown>"; 367 } 368 369 int CDSHeapVerifier::trace_to_root(outputStream* st, oop orig_obj, oop orig_field, HeapShared::CachedOopInfo* info) { 370 int level = 0; 371 if (info->orig_referrer() != nullptr) { 372 HeapShared::CachedOopInfo* ref = HeapShared::get_cached_oop_info(info->orig_referrer()); 373 assert(ref != nullptr, "sanity"); 374 level = trace_to_root(st, info->orig_referrer(), orig_obj, ref) + 1; 375 } else if (java_lang_String::is_instance(orig_obj)) { 376 st->print_cr("[%2d] (shared string table)", level++); 377 } 378 Klass* k = orig_obj->klass(); 379 ResourceMark rm; 380 st->print("[%2d] ", level); 381 orig_obj->print_address_on(st); 382 st->print(" %s", k->internal_name()); 383 if (java_lang_Class::is_instance(orig_obj)) { 384 st->print(" (%s::%s)", java_lang_Class::as_Klass(orig_obj)->external_name(), static_field_name(orig_obj, orig_field)); 385 } 386 if (orig_field != nullptr) { 387 if (k->is_instance_klass()) { 388 TraceFields clo(orig_obj, orig_field, st); 389 InstanceKlass::cast(k)->do_nonstatic_fields(&clo); 390 } else { 391 assert(orig_obj->is_objArray(), "must be"); 392 objArrayOop array = (objArrayOop)orig_obj; 393 for (int i = 0; i < array->length(); i++) { 394 if (array->obj_at(i) == orig_field) { 395 st->print(" @[%d]", i); 396 break; 397 } 398 } 399 } 400 } 401 st->cr(); 402 403 return level; 404 } 405 406 void CDSHeapVerifier::verify() { 407 CDSHeapVerifier verf; 408 HeapShared::archived_object_cache()->iterate(&verf); 409 } 410 411 #endif // INCLUDE_CDS_JAVA_HEAP