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