1 /*
2 * Copyright (c) 2022, 2024, 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 "cds/aotClassInitializer.hpp"
27 #include "cds/archiveBuilder.hpp"
28 #include "cds/cdsHeapVerifier.hpp"
29 #include "classfile/classLoaderDataGraph.hpp"
30 #include "classfile/javaClasses.inline.hpp"
31 #include "classfile/moduleEntry.hpp"
32 #include "classfile/systemDictionaryShared.hpp"
33 #include "classfile/vmSymbols.hpp"
34 #include "logging/log.hpp"
35 #include "logging/logStream.hpp"
36 #include "memory/resourceArea.hpp"
37 #include "oops/fieldStreams.inline.hpp"
38 #include "oops/klass.inline.hpp"
39 #include "oops/oop.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. In the following example,
46 // Foo.get.test()
47 // correctly returns true when CDS disabled, but incorrectly returns false when CDS is enabled,
48 // because the archived archivedFoo.bar value is different than Bar.bar.
49 //
50 // class Foo {
51 // static final Foo archivedFoo; // this field is archived by CDS
52 // Bar bar;
53 // static {
54 // CDS.initializeFromArchive(Foo.class);
55 // if (archivedFoo == null) {
56 // archivedFoo = new Foo();
57 // archivedFoo.bar = Bar.bar;
58 // }
59 // }
60 // static Foo get() { return archivedFoo; }
61 // boolean test() {
62 // return bar == Bar.bar;
63 // }
64 // }
65 //
66 // class Bar {
67 // // this field is initialized in both CDS dump time and runtime.
68 // static final Bar bar = new Bar();
69 // }
70 //
71 // The check itself is simple:
72 // [1] CDSHeapVerifier::do_klass() collects all static fields
73 // [2] CDSHeapVerifier::do_entry() checks all the archived objects. None of them
74 // should be in [1]
75 //
76 // However, it's legal for *some* static fields to be referenced. The reasons are explained
77 // in the table of ADD_EXCL below.
78 //
79 // [A] In most of the cases, the module bootstrap code will update the static field
80 // to point to part of the archived module graph. E.g.,
81 // - java/lang/System::bootLayer
82 // - jdk/internal/loader/ClassLoaders::BOOT_LOADER
83 // [B] A final static String that's explicitly initialized inside <clinit>, but
84 // its value is deterministic and is always the same string literal.
85 // [C] A non-final static string that is assigned a string literal during class
86 // initialization; this string is never changed during -Xshare:dump.
87 // [D] Simple caches whose value doesn't matter.
88 // [E] Other cases (see comments in-line below).
89
90 CDSHeapVerifier::CDSHeapVerifier() : _archived_objs(0), _problems(0)
91 {
92 # define ADD_EXCL(...) { static const char* e[] = {__VA_ARGS__, nullptr}; add_exclusion(e); }
93
94 // Unfortunately this needs to be manually maintained. If
95 // test/hotspot/jtreg/runtime/cds/appcds/cacheObject/ArchivedEnumTest.java fails,
96 // you might need to fix the core library code, or fix the ADD_EXCL entries below.
97 //
98 // class field type
99 ADD_EXCL("java/lang/ClassLoader", "scl"); // A
100 ADD_EXCL("java/lang/Module", "ALL_UNNAMED_MODULE", // A
101 "ALL_UNNAMED_MODULE_SET", // A
102 "EVERYONE_MODULE", // A
103 "EVERYONE_SET"); // A
104
105 // This is the same as java/util/ImmutableCollections::EMPTY_SET, which is archived
106 ADD_EXCL("java/lang/reflect/AccessFlag$Location", "EMPTY_SET"); // E
107
108 ADD_EXCL("java/lang/System", "bootLayer"); // A
109
110 // A dummy object used by HashSet. The value doesn't matter and it's never
111 // tested for equality.
112 ADD_EXCL("java/util/HashSet", "PRESENT"); // E
113 ADD_EXCL("jdk/internal/loader/BuiltinClassLoader", "packageToModule"); // A
114 ADD_EXCL("jdk/internal/loader/ClassLoaders", "BOOT_LOADER", // A
115 "APP_LOADER", // A
116 "PLATFORM_LOADER"); // A
117 ADD_EXCL("jdk/internal/module/Builder", "cachedVersion"); // D
118 ADD_EXCL("jdk/internal/module/ModuleLoaderMap$Mapper", "APP_CLASSLOADER", // A
119 "APP_LOADER_INDEX", // A
120 "PLATFORM_CLASSLOADER", // A
121 "PLATFORM_LOADER_INDEX"); // A
122 ADD_EXCL("jdk/internal/module/ServicesCatalog", "CLV"); // A
123
124 // This just points to an empty Map
125 ADD_EXCL("jdk/internal/reflect/Reflection", "methodFilterMap"); // E
126
127 // Integer for 0 and 1 are in java/lang/Integer$IntegerCache and are archived
128 ADD_EXCL("sun/invoke/util/ValueConversions", "ONE_INT", // E
129 "ZERO_INT"); // E
130
131 if (CDSConfig::is_dumping_invokedynamic()) {
132 ADD_EXCL("java/lang/invoke/InvokerBytecodeGenerator", "MEMBERNAME_FACTORY", // D
133 "CD_Object_array", // E same as <...>ConstantUtils.CD_Object_array::CD_Object
134 "INVOKER_SUPER_DESC"); // E same as java.lang.constant.ConstantDescs::CD_Object
135 }
136
137 # undef ADD_EXCL
138
139 ClassLoaderDataGraph::classes_do(this);
140 }
141
142 CDSHeapVerifier::~CDSHeapVerifier() {
143 if (_problems > 0) {
144 log_error(cds, heap)("Scanned %d objects. Found %d case(s) where "
145 "an object points to a static field that "
146 "may hold a different value at runtime.", _archived_objs, _problems);
147 MetaspaceShared::unrecoverable_writing_error();
148 }
149 }
150
151 class CDSHeapVerifier::CheckStaticFields : public FieldClosure {
152 CDSHeapVerifier* _verifier;
153 InstanceKlass* _ik; // The class whose static fields are being checked.
154 const char** _exclusions;
155 public:
156 CheckStaticFields(CDSHeapVerifier* verifier, InstanceKlass* ik)
157 : _verifier(verifier), _ik(ik) {
158 _exclusions = _verifier->find_exclusion(_ik);
159 }
160
161 void do_field(fieldDescriptor* fd) {
162 if (fd->field_type() != T_OBJECT) {
163 return;
164 }
165
166 if (fd->signature()->equals("Ljdk/internal/access/JavaLangAccess;")) {
167 // A few classes have static fields that point to SharedSecrets.getJavaLangAccess().
168 // This object carries no state and we can create a new one in the production run.
169 return;
170 }
171 oop static_obj_field = _ik->java_mirror()->obj_field(fd->offset());
172 if (static_obj_field != nullptr) {
173 Klass* field_type = static_obj_field->klass();
174 if (_exclusions != nullptr) {
175 for (const char** p = _exclusions; *p != nullptr; p++) {
176 if (fd->name()->equals(*p)) {
177 return;
178 }
179 }
180 }
181
182 if (fd->is_final() && java_lang_String::is_instance(static_obj_field) && fd->has_initial_value()) {
183 // This field looks like like this in the Java source:
184 // static final SOME_STRING = "a string literal";
185 // This string literal has been stored in the shared string table, so it's OK
186 // for the archived objects to refer to it.
187 return;
188 }
189 if (fd->is_final() && java_lang_Class::is_instance(static_obj_field)) {
190 // This field points to an archived mirror.
191 return;
192 }
193
194 if (field_type->is_instance_klass()) {
195 InstanceKlass* field_ik = InstanceKlass::cast(field_type);
196 if (field_ik->is_enum_subclass()) {
197 if (field_ik->has_archived_enum_objs() || ArchiveUtils::has_aot_initialized_mirror(field_ik)) {
198 // This field is an Enum. If any instance of this Enum has been archived, we will archive
199 // all static fields of this Enum as well.
200 return;
201 }
202 }
203
204 if (field_ik->is_hidden() && ArchiveUtils::has_aot_initialized_mirror(field_ik)) {
205 // We have a static field in a core-library class that points to a method reference, which
206 // are safe to archive.
207 guarantee(_ik->module()->name() == vmSymbols::java_base(), "sanity");
208 return;
209 }
210
211 if (field_ik == vmClasses::MethodType_klass()) {
212 // The identity of MethodTypes are preserved between assembly phase and production runs
213 // (by MethodType::AOTHolder::archivedMethodTypes). No need to check.
214 return;
215 }
216
217 if (field_ik == vmClasses::internal_Unsafe_klass() && ArchiveUtils::has_aot_initialized_mirror(field_ik)) {
218 // There's only a single instance of jdk/internal/misc/Unsafe, so all references will
219 // be pointing to this singleton, which has been archived.
220 return;
221 }
222 }
223
224 // This field *may* be initialized to a different value at runtime. Remember it
225 // and check later if it appears in the archived object graph.
226 _verifier->add_static_obj_field(_ik, static_obj_field, fd->name());
227 }
228 }
229 };
230
231 // Remember all the static object fields of every class that are currently
232 // loaded. Later, we will check if any archived objects reference one of
233 // these fields.
234 void CDSHeapVerifier::do_klass(Klass* k) {
235 if (k->is_instance_klass()) {
236 InstanceKlass* ik = InstanceKlass::cast(k);
237
238 if (HeapShared::is_subgraph_root_class(ik)) {
239 // ik is inside one of the ArchivableStaticFieldInfo tables
240 // in heapShared.cpp. We assume such classes are programmed to
241 // update their static fields correctly at runtime.
242 return;
243 }
244
245 if (ArchiveUtils::has_aot_initialized_mirror(ik)) {
246 // ik's <clinit> won't be executed at runtime, the static fields in
247 // ik will carry their values to runtime.
248 return;
249 }
250
251 CheckStaticFields csf(this, ik);
252 ik->do_local_static_fields(&csf);
253 }
254 }
255
256 void CDSHeapVerifier::add_static_obj_field(InstanceKlass* ik, oop field, Symbol* name) {
257 StaticFieldInfo info = {ik, name};
258 _table.put(field, info);
259 }
260
261 inline bool CDSHeapVerifier::do_entry(oop& orig_obj, HeapShared::CachedOopInfo& value) {
262 _archived_objs++;
263
264 StaticFieldInfo* info = _table.get(orig_obj);
265 if (info != nullptr) {
266 if (value.orig_referrer() == nullptr && java_lang_String::is_instance(orig_obj)) {
267 // This string object is not referenced by any of the archived object graphs. It's archived
268 // only because it's in the interned string table. So we are not in a condition that
269 // should be flagged by CDSHeapVerifier.
270 return true; /* keep on iterating */
271 }
272 if (info->_holder->is_hidden()) {
273 return true;
274 }
275 ResourceMark rm;
276 char* class_name = info->_holder->name()->as_C_string();
277 char* field_name = info->_name->as_C_string();
278 LogStream ls(Log(cds, heap)::warning());
279 ls.print_cr("Archive heap points to a static field that may hold a different value at runtime:");
280 ls.print_cr("Field: %s::%s", class_name, field_name);
281 ls.print("Value: ");
282 orig_obj->print_on(&ls);
283 ls.print_cr("--- trace begin ---");
284 trace_to_root(&ls, orig_obj, nullptr, &value);
285 ls.print_cr("--- trace end ---");
286 ls.cr();
287 _problems ++;
288 }
289
290 return true; /* keep on iterating */
291 }
292
293 class CDSHeapVerifier::TraceFields : public FieldClosure {
294 oop _orig_obj;
295 oop _orig_field;
296 outputStream* _st;
297
298 public:
299 TraceFields(oop orig_obj, oop orig_field, outputStream* st)
300 : _orig_obj(orig_obj), _orig_field(orig_field), _st(st) {}
301
302 void do_field(fieldDescriptor* fd) {
303 if (fd->field_type() == T_OBJECT || fd->field_type() == T_ARRAY) {
304 oop obj_field = _orig_obj->obj_field(fd->offset());
305 if (obj_field == _orig_field) {
306 _st->print("::%s (offset = %d)", fd->name()->as_C_string(), fd->offset());
307 }
308 }
309 }
310 };
311
312 // Call this function (from gdb, etc) if you want to know why an object is archived.
313 void CDSHeapVerifier::trace_to_root(outputStream* st, oop orig_obj) {
314 HeapShared::CachedOopInfo* info = HeapShared::archived_object_cache()->get(orig_obj);
315 if (info != nullptr) {
316 trace_to_root(st, orig_obj, nullptr, info);
317 } else {
318 st->print_cr("Not an archived object??");
319 }
320 }
321
322 const char* static_field_name(oop mirror, oop field) {
323 Klass* k = java_lang_Class::as_Klass(mirror);
324 if (k->is_instance_klass()) {
325 for (JavaFieldStream fs(InstanceKlass::cast(k)); !fs.done(); fs.next()) {
326 if (fs.access_flags().is_static()) {
327 fieldDescriptor& fd = fs.field_descriptor();
328 switch (fd.field_type()) {
329 case T_OBJECT:
330 case T_ARRAY:
331 if (mirror->obj_field(fd.offset()) == field) {
332 return fs.name()->as_C_string();
333 }
334 break;
335 default:
336 break;
337 }
338 }
339 }
340 }
341
342 return "<unknown>";
343 }
344
345 int CDSHeapVerifier::trace_to_root(outputStream* st, oop orig_obj, oop orig_field, HeapShared::CachedOopInfo* info) {
346 int level = 0;
347 if (info->orig_referrer() != nullptr) {
348 HeapShared::CachedOopInfo* ref = HeapShared::archived_object_cache()->get(info->orig_referrer());
349 assert(ref != nullptr, "sanity");
350 level = trace_to_root(st, info->orig_referrer(), orig_obj, ref) + 1;
351 } else if (java_lang_String::is_instance(orig_obj)) {
352 st->print_cr("[%2d] (shared string table)", level++);
353 }
354 Klass* k = orig_obj->klass();
355 ResourceMark rm;
356 st->print("[%2d] ", level);
357 orig_obj->print_address_on(st);
358 st->print(" %s", k->internal_name());
359 if (java_lang_Class::is_instance(orig_obj)) {
360 st->print(" (%s::%s)", java_lang_Class::as_Klass(orig_obj)->external_name(), static_field_name(orig_obj, orig_field));
361 }
362 if (orig_field != nullptr) {
363 if (k->is_instance_klass()) {
364 TraceFields clo(orig_obj, orig_field, st);
365 InstanceKlass::cast(k)->do_nonstatic_fields(&clo);
366 } else {
367 assert(orig_obj->is_objArray(), "must be");
368 objArrayOop array = (objArrayOop)orig_obj;
369 for (int i = 0; i < array->length(); i++) {
370 if (array->obj_at(i) == orig_field) {
371 st->print(" @[%d]", i);
372 break;
373 }
374 }
375 }
376 }
377 st->cr();
378
379 return level;
380 }
381
382 void CDSHeapVerifier::verify() {
383 CDSHeapVerifier verf;
384 HeapShared::archived_object_cache()->iterate(&verf);
385 }
386
387 #endif // INCLUDE_CDS_JAVA_HEAP