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.
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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.
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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 ADD_EXCL("jdk/internal/loader/BuiltinClassLoader", "packageToModule"); // A
120 ADD_EXCL("jdk/internal/loader/ClassLoaders", "BOOT_LOADER", // A
121 "APP_LOADER", // A
122 "PLATFORM_LOADER"); // A
123 ADD_EXCL("jdk/internal/module/Builder", "cachedVersion"); // D
124 ADD_EXCL("jdk/internal/module/ModuleLoaderMap$Mapper", "APP_CLASSLOADER", // A
125 "APP_LOADER_INDEX", // A
126 "PLATFORM_CLASSLOADER", // A
127 "PLATFORM_LOADER_INDEX"); // A
128 ADD_EXCL("jdk/internal/module/ServicesCatalog", "CLV"); // A
129
130 // This just points to an empty Map
131 ADD_EXCL("jdk/internal/reflect/Reflection", "methodFilterMap"); // E
132
133 // Integer for 0 and 1 are in java/lang/Integer$IntegerCache and are archived
134 ADD_EXCL("sun/invoke/util/ValueConversions", "ONE_INT", // E
135 "ZERO_INT"); // E
136
137 if (CDSConfig::is_dumping_method_handles()) {
138 ADD_EXCL("java/lang/invoke/InvokerBytecodeGenerator", "MEMBERNAME_FACTORY", // D
139 "CD_Object_array", // E same as <...>ConstantUtils.CD_Object_array::CD_Object
140 "INVOKER_SUPER_DESC"); // E same as java.lang.constant.ConstantDescs::CD_Object
141
142 ADD_EXCL("java/lang/runtime/ObjectMethods", "CLASS_IS_INSTANCE", // D
143 "FALSE", // D
144 "TRUE", // D
145 "ZERO"); // D
146 }
147
148 if (CDSConfig::is_dumping_packages()) {
149 ADD_EXCL("java/lang/Package$VersionInfo", "NULL_VERSION_INFO"); // D
150 }
151
152 if (CDSConfig::is_dumping_dynamic_proxies()) {
153 ADD_EXCL("java/lang/reflect/ProxyGenerator", "CD_Object_array"); // D
154 }
155
156 // These are used by BuiltinClassLoader::negativeLookupCache, etc but seem to be
157 // OK. TODO - we should completely disable the caching unless ArchiveLoaderLookupCache
158 // is enabled
159 ADD_EXCL("java/lang/Boolean", "TRUE", // E
160 "FALSE"); // E
161
162 # undef ADD_EXCL
163
164 ClassLoaderDataGraph::classes_do(this);
165 }
166
167 CDSHeapVerifier::~CDSHeapVerifier() {
168 if (_problems > 0) {
169 log_error(aot, heap)("Scanned %d objects. Found %d case(s) where "
170 "an object points to a static field that "
171 "may hold a different value at runtime.", _archived_objs, _problems);
172 log_error(aot, heap)("Please see cdsHeapVerifier.cpp and aotClassInitializer.cpp for details");
173 MetaspaceShared::unrecoverable_writing_error();
174 }
175 }
176
177 class CDSHeapVerifier::CheckStaticFields : public FieldClosure {
178 CDSHeapVerifier* _verifier;
179 InstanceKlass* _ik; // The class whose static fields are being checked.
180 const char** _exclusions;
181 public:
182 CheckStaticFields(CDSHeapVerifier* verifier, InstanceKlass* ik)
183 : _verifier(verifier), _ik(ik) {
184 _exclusions = _verifier->find_exclusion(_ik);
185 }
186
187 void do_field(fieldDescriptor* fd) {
188 if (fd->field_type() != T_OBJECT) {
189 return;
190 }
191
192 if (fd->signature()->equals("Ljdk/internal/access/JavaLangAccess;")) {
193 // A few classes have static fields that point to SharedSecrets.getJavaLangAccess().
194 // This object carries no state and we can create a new one in the production run.
195 return;
196 }
197 oop static_obj_field = _ik->java_mirror()->obj_field(fd->offset());
198 if (static_obj_field != nullptr) {
199 Klass* field_type = static_obj_field->klass();
200 if (_exclusions != nullptr) {
201 for (const char** p = _exclusions; *p != nullptr; p++) {
202 if (fd->name()->equals(*p)) {
203 return;
204 }
205 }
206 }
207
208 if (fd->is_final() && java_lang_String::is_instance(static_obj_field) && fd->has_initial_value()) {
209 // This field looks like like this in the Java source:
210 // static final SOME_STRING = "a string literal";
211 // This string literal has been stored in the shared string table, so it's OK
212 // for the archived objects to refer to it.
213 return;
214 }
215 if (fd->is_final() && java_lang_Class::is_instance(static_obj_field)) {
216 // This field points to an archived mirror.
217 return;
218 }
219
220 if (field_type->is_instance_klass()) {
221 InstanceKlass* field_ik = InstanceKlass::cast(field_type);
222 if (field_ik->is_enum_subclass()) {
223 if (field_ik->has_archived_enum_objs() || ArchiveUtils::has_aot_initialized_mirror(field_ik)) {
224 // This field is an Enum. If any instance of this Enum has been archived, we will archive
225 // all static fields of this Enum as well.
226 return;
227 }
228 }
229
230 if (field_ik->is_hidden() && ArchiveUtils::has_aot_initialized_mirror(field_ik)) {
231 // We have a static field in a core-library class that points to a method reference, which
232 // are safe to archive.
233 guarantee(_ik->module()->name() == vmSymbols::java_base(), "sanity");
234 return;
235 }
236
237 if (field_ik == vmClasses::MethodType_klass()) {
238 // The identity of MethodTypes are preserved between assembly phase and production runs
239 // (by MethodType::AOTHolder::archivedMethodTypes). No need to check.
240 return;
241 }
242
243 if (field_ik == vmClasses::internal_Unsafe_klass() && ArchiveUtils::has_aot_initialized_mirror(field_ik)) {
244 // There's only a single instance of jdk/internal/misc/Unsafe, so all references will
245 // be pointing to this singleton, which has been archived.
246 return;
247 }
248 }
249
250 // This field *may* be initialized to a different value at runtime. Remember it
251 // and check later if it appears in the archived object graph.
252 _verifier->add_static_obj_field(_ik, static_obj_field, fd->name());
253 }
254 }
255 };
256
257 // Remember all the static object fields of every class that are currently
258 // loaded. Later, we will check if any archived objects reference one of
259 // these fields.
260 void CDSHeapVerifier::do_klass(Klass* k) {
261 if (k->is_instance_klass()) {
262 InstanceKlass* ik = InstanceKlass::cast(k);
263
264 if (HeapShared::is_subgraph_root_class(ik)) {
265 // ik is inside one of the ArchivableStaticFieldInfo tables
266 // in heapShared.cpp. We assume such classes are programmed to
267 // update their static fields correctly at runtime.
268 return;
269 }
270
271 if (ArchiveUtils::has_aot_initialized_mirror(ik)) {
272 // ik's <clinit> won't be executed at runtime, the static fields in
273 // ik will carry their values to runtime.
274 return;
275 }
276
277 CheckStaticFields csf(this, ik);
278 ik->do_local_static_fields(&csf);
279 }
280 }
281
282 void CDSHeapVerifier::add_static_obj_field(InstanceKlass* ik, oop field, Symbol* name) {
283 StaticFieldInfo info = {ik, name};
284 _table.put(field, info);
285 }
286
287 // This function is called once for every archived heap object. Warn if this object is referenced by
288 // a static field of a class that's not aot-initialized.
289 inline bool CDSHeapVerifier::do_entry(OopHandle& orig_obj_handle, HeapShared::CachedOopInfo& value) {
290 oop orig_obj = orig_obj_handle.resolve();
291 _archived_objs++;
292
293 if (java_lang_String::is_instance(orig_obj) && HeapShared::is_dumped_interned_string(orig_obj)) {
294 // It's quite often for static fields to have interned strings. These are most likely not
295 // problematic (and are hard to filter). So we will ignore them.
296 return true; /* keep on iterating */
297 }
298
299 StaticFieldInfo* info = _table.get(orig_obj);
300 if (info != nullptr) {
301 ResourceMark rm;
302 char* class_name = info->_holder->name()->as_C_string();
303 char* field_name = info->_name->as_C_string();
304 LogStream ls(Log(aot, heap)::warning());
305 ls.print_cr("Archive heap points to a static field that may hold a different value at runtime:");
306 ls.print_cr("Field: %s::%s", class_name, field_name);
307 ls.print("Value: ");
308 orig_obj->print_on(&ls);
309 ls.print_cr("--- trace begin ---");
310 trace_to_root(&ls, orig_obj, nullptr, &value);
311 ls.print_cr("--- trace end ---");
312 ls.cr();
313 _problems ++;
314 }
315
316 return true; /* keep on iterating */
317 }
318
319 class CDSHeapVerifier::TraceFields : public FieldClosure {
320 oop _orig_obj;
321 oop _orig_field;
322 outputStream* _st;
323
324 public:
325 TraceFields(oop orig_obj, oop orig_field, outputStream* st)
326 : _orig_obj(orig_obj), _orig_field(orig_field), _st(st) {}
327
328 void do_field(fieldDescriptor* fd) {
329 if (fd->field_type() == T_OBJECT || fd->field_type() == T_ARRAY) {
330 oop obj_field = _orig_obj->obj_field(fd->offset());
331 if (obj_field == _orig_field) {
332 _st->print("::%s (offset = %d)", fd->name()->as_C_string(), fd->offset());
333 }
334 }
335 }
336 };
337
338 // Call this function (from gdb, etc) if you want to know why an object is archived.
339 void CDSHeapVerifier::trace_to_root(outputStream* st, oop orig_obj) {
340 HeapShared::CachedOopInfo* info = HeapShared::get_cached_oop_info(orig_obj);
341 if (info != nullptr) {
342 trace_to_root(st, orig_obj, nullptr, info);
343 } else {
344 st->print_cr("Not an archived object??");
345 }
346 }
347
348 const char* static_field_name(oop mirror, oop field) {
349 Klass* k = java_lang_Class::as_Klass(mirror);
350 if (k->is_instance_klass()) {
351 for (JavaFieldStream fs(InstanceKlass::cast(k)); !fs.done(); fs.next()) {
352 if (fs.access_flags().is_static()) {
353 fieldDescriptor& fd = fs.field_descriptor();
354 switch (fd.field_type()) {
355 case T_OBJECT:
356 case T_ARRAY:
357 if (mirror->obj_field(fd.offset()) == field) {
358 return fs.name()->as_C_string();
359 }
360 break;
361 default:
362 break;
363 }
364 }
365 }
366 }
367
368 return "<unknown>";
369 }
370
371 int CDSHeapVerifier::trace_to_root(outputStream* st, oop orig_obj, oop orig_field, HeapShared::CachedOopInfo* info) {
372 int level = 0;
373 if (info->orig_referrer() != nullptr) {
374 HeapShared::CachedOopInfo* ref = HeapShared::get_cached_oop_info(info->orig_referrer());
375 assert(ref != nullptr, "sanity");
376 level = trace_to_root(st, info->orig_referrer(), orig_obj, ref) + 1;
377 } else if (java_lang_String::is_instance(orig_obj)) {
378 st->print_cr("[%2d] (shared string table)", level++);
379 }
380 Klass* k = orig_obj->klass();
381 ResourceMark rm;
382 st->print("[%2d] ", level);
383 orig_obj->print_address_on(st);
384 st->print(" %s", k->internal_name());
385 if (java_lang_Class::is_instance(orig_obj)) {
386 st->print(" (%s::%s)", java_lang_Class::as_Klass(orig_obj)->external_name(), static_field_name(orig_obj, orig_field));
387 }
388 if (orig_field != nullptr) {
389 if (k->is_instance_klass()) {
390 TraceFields clo(orig_obj, orig_field, st);
391 InstanceKlass::cast(k)->do_nonstatic_fields(&clo);
392 } else {
393 assert(orig_obj->is_objArray(), "must be");
394 objArrayOop array = (objArrayOop)orig_obj;
395 for (int i = 0; i < array->length(); i++) {
396 if (array->obj_at(i) == orig_field) {
397 st->print(" @[%d]", i);
398 break;
399 }
400 }
401 }
402 }
403 st->cr();
404
405 return level;
406 }
407
408 void CDSHeapVerifier::verify() {
409 CDSHeapVerifier verf;
410 HeapShared::archived_object_cache()->iterate(&verf);
411 }
412
413 #endif // INCLUDE_CDS_JAVA_HEAP