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 "runtime/fieldDescriptor.inline.hpp" 40 41 #if INCLUDE_CDS_JAVA_HEAP 42 43 // CDSHeapVerifier is used to check for problems where an archived object references a 44 // static field that may be get a different value at runtime. 45 // 46 // *Please see comments in aotClassInitializer.cpp for how to avoid such problems*, 47 // 48 // In the following example, 49 // Foo.get.test() 50 // correctly returns true when CDS disabled, but incorrectly returns false when CDS is enabled, 51 // because the archived archivedFoo.bar value is different than Bar.bar. 52 // 53 // class Foo { 54 // static final Foo archivedFoo; // this field is archived by CDS 55 // Bar bar; 56 // static { 57 // CDS.initializeFromArchive(Foo.class); 58 // if (archivedFoo == null) { 59 // archivedFoo = new Foo(); 60 // archivedFoo.bar = Bar.bar; 61 // } 62 // } 63 // static Foo get() { return archivedFoo; } 64 // boolean test() { 65 // return bar == Bar.bar; 66 // } 67 // } 68 // 69 // class Bar { 70 // // this field is initialized in both CDS dump time and runtime. 71 // static final Bar bar = new Bar(); 72 // } 73 // 74 // The check itself is simple: 75 // [1] CDSHeapVerifier::do_klass() collects all static fields 76 // [2] CDSHeapVerifier::do_entry() checks all the archived objects. None of them 77 // should be in [1] 78 // 79 // However, it's legal for *some* static fields to be referenced. The reasons are explained 80 // in the table of ADD_EXCL below. 81 // 82 // [A] In most of the cases, the module bootstrap code will update the static field 83 // to point to part of the archived module graph. E.g., 84 // - java/lang/System::bootLayer 85 // - jdk/internal/loader/ClassLoaders::BOOT_LOADER 86 // [B] A final static String that's explicitly initialized inside <clinit>, but 87 // its value is deterministic and is always the same string literal. 88 // [C] A non-final static string that is assigned a string literal during class 89 // initialization; this string is never changed during -Xshare:dump. 90 // [D] Simple caches whose value doesn't matter. 91 // [E] Other cases (see comments in-line below). 92 93 CDSHeapVerifier::CDSHeapVerifier() : _archived_objs(0), _problems(0) 94 { 95 # define ADD_EXCL(...) { static const char* e[] = {__VA_ARGS__, nullptr}; add_exclusion(e); } 96 97 // Unfortunately this needs to be manually maintained. If 98 // test/hotspot/jtreg/runtime/cds/appcds/cacheObject/ArchivedEnumTest.java fails, 99 // you might need to fix the core library code, or fix the ADD_EXCL entries below. 100 // 101 // class field type 102 ADD_EXCL("java/lang/ClassLoader$Holder", "scl"); // A 103 ADD_EXCL("java/lang/Module", "ALL_UNNAMED_MODULE", // A 104 "ALL_UNNAMED_MODULE_SET", // A 105 "EVERYONE_MODULE", // A 106 "EVERYONE_SET"); // A 107 108 // This is the same as java/util/ImmutableCollections::EMPTY_SET, which is archived 109 ADD_EXCL("java/lang/reflect/AccessFlag$Location", "EMPTY_SET"); // E 110 111 ADD_EXCL("java/lang/System", "bootLayer"); // A 112 113 ADD_EXCL("java/util/Collections", "EMPTY_LIST"); // E 114 115 // A dummy object used by HashSet. The value doesn't matter and it's never 116 // tested for equality. 117 ADD_EXCL("java/util/HashSet", "PRESENT"); // E 118 ADD_EXCL("jdk/internal/loader/BuiltinClassLoader", "packageToModule"); // A 119 ADD_EXCL("jdk/internal/loader/ClassLoaders", "BOOT_LOADER", // A 120 "APP_LOADER", // A 121 "PLATFORM_LOADER"); // A 122 ADD_EXCL("jdk/internal/module/Builder", "cachedVersion"); // D 123 ADD_EXCL("jdk/internal/module/ModuleLoaderMap$Mapper", "APP_CLASSLOADER", // A 124 "APP_LOADER_INDEX", // A 125 "PLATFORM_CLASSLOADER", // A 126 "PLATFORM_LOADER_INDEX"); // A 127 ADD_EXCL("jdk/internal/module/ServicesCatalog", "CLV"); // A 128 129 // This just points to an empty Map 130 ADD_EXCL("jdk/internal/reflect/Reflection", "methodFilterMap"); // E 131 132 // Integer for 0 and 1 are in java/lang/Integer$IntegerCache and are archived 133 ADD_EXCL("sun/invoke/util/ValueConversions", "ONE_INT", // E 134 "ZERO_INT"); // E 135 136 if (CDSConfig::is_dumping_method_handles()) { 137 ADD_EXCL("java/lang/invoke/InvokerBytecodeGenerator", "MEMBERNAME_FACTORY", // D 138 "CD_Object_array", // E same as <...>ConstantUtils.CD_Object_array::CD_Object 139 "INVOKER_SUPER_DESC"); // E same as java.lang.constant.ConstantDescs::CD_Object 140 141 ADD_EXCL("java/lang/runtime/ObjectMethods", "CLASS_IS_INSTANCE", // D 142 "FALSE", // D 143 "TRUE", // D 144 "ZERO"); // D 145 } 146 147 if (CDSConfig::is_dumping_packages()) { 148 ADD_EXCL("java/lang/Package$VersionInfo", "NULL_VERSION_INFO"); // D 149 } 150 151 if (CDSConfig::is_dumping_dynamic_proxies()) { 152 ADD_EXCL("java/lang/reflect/ProxyGenerator", "CD_Object_array"); // D 153 } 154 155 // These are used by BuiltinClassLoader::negativeLookupCache, etc but seem to be 156 // OK. TODO - we should completely disable the caching unless ArchiveLoaderLookupCache 157 // is enabled 158 ADD_EXCL("java/lang/Boolean", "TRUE", // E 159 "FALSE"); // E 160 161 # undef ADD_EXCL 162 163 ClassLoaderDataGraph::classes_do(this); 164 } 165 166 CDSHeapVerifier::~CDSHeapVerifier() { 167 if (_problems > 0) { 168 log_error(aot, heap)("Scanned %d objects. Found %d case(s) where " 169 "an object points to a static field that " 170 "may hold a different value at runtime.", _archived_objs, _problems); 171 log_error(aot, heap)("Please see cdsHeapVerifier.cpp and aotClassInitializer.cpp for details"); 172 MetaspaceShared::unrecoverable_writing_error(); 173 } 174 } 175 176 class CDSHeapVerifier::CheckStaticFields : public FieldClosure { 177 CDSHeapVerifier* _verifier; 178 InstanceKlass* _ik; // The class whose static fields are being checked. 179 const char** _exclusions; 180 public: 181 CheckStaticFields(CDSHeapVerifier* verifier, InstanceKlass* ik) 182 : _verifier(verifier), _ik(ik) { 183 _exclusions = _verifier->find_exclusion(_ik); 184 } 185 186 void do_field(fieldDescriptor* fd) { 187 if (fd->field_type() != T_OBJECT) { 188 return; 189 } 190 191 if (fd->signature()->equals("Ljdk/internal/access/JavaLangAccess;")) { 192 // A few classes have static fields that point to SharedSecrets.getJavaLangAccess(). 193 // This object carries no state and we can create a new one in the production run. 194 return; 195 } 196 oop static_obj_field = _ik->java_mirror()->obj_field(fd->offset()); 197 if (static_obj_field != nullptr) { 198 Klass* field_type = static_obj_field->klass(); 199 if (_exclusions != nullptr) { 200 for (const char** p = _exclusions; *p != nullptr; p++) { 201 if (fd->name()->equals(*p)) { 202 return; 203 } 204 } 205 } 206 207 if (fd->is_final() && java_lang_String::is_instance(static_obj_field) && fd->has_initial_value()) { 208 // This field looks like like this in the Java source: 209 // static final SOME_STRING = "a string literal"; 210 // This string literal has been stored in the shared string table, so it's OK 211 // for the archived objects to refer to it. 212 return; 213 } 214 if (fd->is_final() && java_lang_Class::is_instance(static_obj_field)) { 215 // This field points to an archived mirror. 216 return; 217 } 218 219 if (field_type->is_instance_klass()) { 220 InstanceKlass* field_ik = InstanceKlass::cast(field_type); 221 if (field_ik->is_enum_subclass()) { 222 if (field_ik->has_archived_enum_objs() || ArchiveUtils::has_aot_initialized_mirror(field_ik)) { 223 // This field is an Enum. If any instance of this Enum has been archived, we will archive 224 // all static fields of this Enum as well. 225 return; 226 } 227 } 228 229 if (field_ik->is_hidden() && ArchiveUtils::has_aot_initialized_mirror(field_ik)) { 230 // We have a static field in a core-library class that points to a method reference, which 231 // are safe to archive. 232 guarantee(_ik->module()->name() == vmSymbols::java_base(), "sanity"); 233 return; 234 } 235 236 if (field_ik == vmClasses::MethodType_klass()) { 237 // The identity of MethodTypes are preserved between assembly phase and production runs 238 // (by MethodType::AOTHolder::archivedMethodTypes). No need to check. 239 return; 240 } 241 242 if (field_ik == vmClasses::internal_Unsafe_klass() && ArchiveUtils::has_aot_initialized_mirror(field_ik)) { 243 // There's only a single instance of jdk/internal/misc/Unsafe, so all references will 244 // be pointing to this singleton, which has been archived. 245 return; 246 } 247 } 248 249 // This field *may* be initialized to a different value at runtime. Remember it 250 // and check later if it appears in the archived object graph. 251 _verifier->add_static_obj_field(_ik, static_obj_field, fd->name()); 252 } 253 } 254 }; 255 256 // Remember all the static object fields of every class that are currently 257 // loaded. Later, we will check if any archived objects reference one of 258 // these fields. 259 void CDSHeapVerifier::do_klass(Klass* k) { 260 if (k->is_instance_klass()) { 261 InstanceKlass* ik = InstanceKlass::cast(k); 262 263 if (HeapShared::is_subgraph_root_class(ik)) { 264 // ik is inside one of the ArchivableStaticFieldInfo tables 265 // in heapShared.cpp. We assume such classes are programmed to 266 // update their static fields correctly at runtime. 267 return; 268 } 269 270 if (ArchiveUtils::has_aot_initialized_mirror(ik)) { 271 // ik's <clinit> won't be executed at runtime, the static fields in 272 // ik will carry their values to runtime. 273 return; 274 } 275 276 CheckStaticFields csf(this, ik); 277 ik->do_local_static_fields(&csf); 278 } 279 } 280 281 void CDSHeapVerifier::add_static_obj_field(InstanceKlass* ik, oop field, Symbol* name) { 282 StaticFieldInfo info = {ik, name}; 283 _table.put(field, info); 284 } 285 286 // This function is called once for every archived heap object. Warn if this object is referenced by 287 // a static field of a class that's not aot-initialized. 288 inline bool CDSHeapVerifier::do_entry(oop& orig_obj, HeapShared::CachedOopInfo& value) { 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::archived_object_cache()->get(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::archived_object_cache()->get(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