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 "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