1 /*
2 * Copyright (c) 2024, 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
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23 */
24
25 #include "cds/aotClassInitializer.hpp"
26 #include "cds/aotClassLinker.hpp"
27 #include "cds/aotLinkedClassBulkLoader.hpp"
28 #include "cds/aotLinkedClassTable.hpp"
29 #include "cds/cdsConfig.hpp"
30 #include "cds/heapShared.hpp"
31 #include "classfile/classLoaderData.hpp"
32 #include "classfile/systemDictionary.hpp"
33 #include "classfile/systemDictionaryShared.hpp"
34 #include "classfile/vmClasses.hpp"
35 #include "gc/shared/gcVMOperations.hpp"
36 #include "memory/resourceArea.hpp"
37 #include "oops/instanceKlass.hpp"
38 #include "oops/klass.inline.hpp"
39 #include "runtime/handles.inline.hpp"
40 #include "runtime/java.hpp"
41
42 bool AOTLinkedClassBulkLoader::_boot2_completed = false;
43 bool AOTLinkedClassBulkLoader::_platform_completed = false;
44 bool AOTLinkedClassBulkLoader::_app_completed = false;
45 bool AOTLinkedClassBulkLoader::_all_completed = false;
46
47 void AOTLinkedClassBulkLoader::serialize(SerializeClosure* soc, bool is_static_archive) {
48 AOTLinkedClassTable::get(is_static_archive)->serialize(soc);
49 }
50
51 void AOTLinkedClassBulkLoader::load_javabase_classes(JavaThread* current) {
52 assert(CDSConfig::is_using_aot_linked_classes(), "sanity");
53 load_classes_in_loader(current, AOTLinkedClassCategory::BOOT1, nullptr); // only java.base classes
54 }
55
56 void AOTLinkedClassBulkLoader::load_non_javabase_classes(JavaThread* current) {
57 assert(CDSConfig::is_using_aot_linked_classes(), "sanity");
58
59 // is_using_aot_linked_classes() requires is_using_full_module_graph(). As a result,
60 // the platform/system class loader should already have been initialized as part
61 // of the FMG support.
62 assert(CDSConfig::is_using_full_module_graph(), "must be");
63 assert(SystemDictionary::java_platform_loader() != nullptr, "must be");
64 assert(SystemDictionary::java_system_loader() != nullptr, "must be");
65
66 load_classes_in_loader(current, AOTLinkedClassCategory::BOOT2, nullptr); // all boot classes outside of java.base
67 _boot2_completed = true;
68
69 load_classes_in_loader(current, AOTLinkedClassCategory::PLATFORM, SystemDictionary::java_platform_loader());
70 _platform_completed = true;
71
72 load_classes_in_loader(current, AOTLinkedClassCategory::APP, SystemDictionary::java_system_loader());
73 _app_completed = true;
74 _all_completed = true;
75 }
76
77 void AOTLinkedClassBulkLoader::load_classes_in_loader(JavaThread* current, AOTLinkedClassCategory class_category, oop class_loader_oop) {
78 load_classes_in_loader_impl(class_category, class_loader_oop, current);
79 if (current->has_pending_exception()) {
80 // We cannot continue, as we might have loaded some of the aot-linked classes, which
81 // may have dangling C++ pointers to other aot-linked classes that we have failed to load.
82 exit_on_exception(current);
83 }
84 }
85
86 void AOTLinkedClassBulkLoader::exit_on_exception(JavaThread* current) {
87 assert(current->has_pending_exception(), "precondition");
88 ResourceMark rm(current);
89 if (current->pending_exception()->is_a(vmClasses::OutOfMemoryError_klass())) {
90 log_error(cds)("Out of memory. Please run with a larger Java heap, current MaxHeapSize = "
91 "%zuM", MaxHeapSize/M);
92 } else {
93 log_error(cds)("%s: %s", current->pending_exception()->klass()->external_name(),
94 java_lang_String::as_utf8_string(java_lang_Throwable::message(current->pending_exception())));
95 }
96 vm_exit_during_initialization("Unexpected exception when loading aot-linked classes.");
97 }
98
99 void AOTLinkedClassBulkLoader::load_classes_in_loader_impl(AOTLinkedClassCategory class_category, oop class_loader_oop, TRAPS) {
100 Handle h_loader(THREAD, class_loader_oop);
101 load_table(AOTLinkedClassTable::for_static_archive(), class_category, h_loader, CHECK);
102 load_table(AOTLinkedClassTable::for_dynamic_archive(), class_category, h_loader, CHECK);
103
104 // Initialize the InstanceKlasses of all archived heap objects that are reachable from the
105 // archived java class mirrors.
106 //
107 // Only the classes in the static archive can have archived mirrors.
108 AOTLinkedClassTable* static_table = AOTLinkedClassTable::for_static_archive();
109 switch (class_category) {
110 case AOTLinkedClassCategory::BOOT1:
111 // Delayed until finish_loading_javabase_classes(), as the VM is not ready to
112 // execute some of the <clinit> methods.
113 break;
114 case AOTLinkedClassCategory::BOOT2:
115 init_required_classes_for_loader(h_loader, static_table->boot2(), CHECK);
116 break;
117 case AOTLinkedClassCategory::PLATFORM:
118 init_required_classes_for_loader(h_loader, static_table->platform(), CHECK);
119 break;
120 case AOTLinkedClassCategory::APP:
121 init_required_classes_for_loader(h_loader, static_table->app(), CHECK);
122 break;
123 case AOTLinkedClassCategory::UNREGISTERED:
124 ShouldNotReachHere();
125 break;
126 }
127
128 if (Universe::is_fully_initialized() && VerifyDuringStartup) {
129 // Make sure we're still in a clean state.
130 VM_Verify verify_op;
131 VMThread::execute(&verify_op);
132 }
133 }
134
135 void AOTLinkedClassBulkLoader::load_table(AOTLinkedClassTable* table, AOTLinkedClassCategory class_category, Handle loader, TRAPS) {
136 if (class_category != AOTLinkedClassCategory::BOOT1) {
137 assert(Universe::is_module_initialized(), "sanity");
138 }
139
140 const char* category_name = AOTClassLinker::class_category_name(class_category);
141 switch (class_category) {
142 case AOTLinkedClassCategory::BOOT1:
143 load_classes_impl(class_category, table->boot(), category_name, loader, CHECK);
144 break;
145
146 case AOTLinkedClassCategory::BOOT2:
147 load_classes_impl(class_category, table->boot2(), category_name, loader, CHECK);
148 break;
149
150 case AOTLinkedClassCategory::PLATFORM:
151 {
152 initiate_loading(THREAD, category_name, loader, table->boot());
153 initiate_loading(THREAD, category_name, loader, table->boot2());
154 load_classes_impl(class_category, table->platform(), category_name, loader, CHECK);
155 }
156 break;
157 case AOTLinkedClassCategory::APP:
158 {
159 initiate_loading(THREAD, category_name, loader, table->boot());
160 initiate_loading(THREAD, category_name, loader, table->boot2());
161 initiate_loading(THREAD, category_name, loader, table->platform());
162 load_classes_impl(class_category, table->app(), category_name, loader, CHECK);
163 }
164 break;
165 case AOTLinkedClassCategory::UNREGISTERED:
166 default:
167 ShouldNotReachHere(); // Currently aot-linked classes are not supported for this category.
168 break;
169 }
170 }
171
172 void AOTLinkedClassBulkLoader::load_classes_impl(AOTLinkedClassCategory class_category, Array<InstanceKlass*>* classes,
173 const char* category_name, Handle loader, TRAPS) {
174 if (classes == nullptr) {
175 return;
176 }
177
178 ClassLoaderData* loader_data = ClassLoaderData::class_loader_data(loader());
179
180 for (int i = 0; i < classes->length(); i++) {
181 InstanceKlass* ik = classes->at(i);
182 if (log_is_enabled(Info, cds, aot, load)) {
183 ResourceMark rm(THREAD);
184 log_info(cds, aot, load)("%-5s %s%s%s", category_name, ik->external_name(),
185 ik->is_loaded() ? " (already loaded)" : "",
186 ik->is_hidden() ? " (hidden)" : "");
187 }
188
189 if (!ik->is_loaded()) {
190 if (ik->is_hidden()) {
191 load_hidden_class(loader_data, ik, CHECK);
192 } else {
193 InstanceKlass* actual;
194 if (loader_data == ClassLoaderData::the_null_class_loader_data()) {
195 actual = SystemDictionary::load_instance_class(ik->name(), loader, CHECK);
196 } else {
197 actual = SystemDictionaryShared::find_or_load_shared_class(ik->name(), loader, CHECK);
198 }
199
200 if (actual != ik) {
201 ResourceMark rm(THREAD);
202 log_error(cds)("Unable to resolve %s class from CDS archive: %s", category_name, ik->external_name());
203 log_error(cds)("Expected: " INTPTR_FORMAT ", actual: " INTPTR_FORMAT, p2i(ik), p2i(actual));
204 log_error(cds)("JVMTI class retransformation is not supported when archive was generated with -XX:+AOTClassLinking.");
205 MetaspaceShared::unrecoverable_loading_error();
206 }
207 assert(actual->is_loaded(), "must be");
208 }
209 }
210 }
211 }
212
213 // Initiate loading of the <classes> in the <initiating_loader>. The <classes> should have already been loaded
214 // by a parent loader of the <initiating_loader>. This is necessary for handling pre-resolved CP entries.
215 //
216 // For example, we initiate the loading of java/lang/String in the AppClassLoader. This will allow
217 // any App classes to have a pre-resolved ConstantPool entry that references java/lang/String.
218 //
219 // TODO: we can limit the number of initiated classes to only those that are actually referenced by
220 // AOT-linked classes loaded by <initiating_loader>.
221 void AOTLinkedClassBulkLoader::initiate_loading(JavaThread* current, const char* category_name,
222 Handle initiating_loader, Array<InstanceKlass*>* classes) {
223 if (classes == nullptr) {
224 return;
225 }
226
227 assert(initiating_loader() == SystemDictionary::java_platform_loader() ||
228 initiating_loader() == SystemDictionary::java_system_loader(), "must be");
229 ClassLoaderData* loader_data = ClassLoaderData::class_loader_data(initiating_loader());
230 MonitorLocker mu1(SystemDictionary_lock);
231
232 for (int i = 0; i < classes->length(); i++) {
233 InstanceKlass* ik = classes->at(i);
234 assert(ik->is_loaded(), "must have already been loaded by a parent loader");
235 assert(ik->class_loader() != initiating_loader(), "must be a parent loader");
236 assert(ik->class_loader() == nullptr ||
237 ik->class_loader() == SystemDictionary::java_platform_loader(), "must be");
238 if (ik->is_public() && !ik->is_hidden()) {
239 if (log_is_enabled(Info, cds, aot, load)) {
240 ResourceMark rm(current);
241 const char* defining_loader = (ik->class_loader() == nullptr ? "boot" : "plat");
242 log_info(cds, aot, load)("%s %s (initiated, defined by %s)", category_name, ik->external_name(),
243 defining_loader);
244 }
245 SystemDictionary::add_to_initiating_loader(current, ik, loader_data);
246 }
247 }
248 }
249
250 // Currently, we archive only three types of hidden classes:
251 // - LambdaForms
252 // - lambda proxy classes
253 // - StringConcat classes
254 // See HeapShared::is_archivable_hidden_klass().
255 //
256 // LambdaForm classes (with names like java/lang/invoke/LambdaForm$MH+0x800000015) logically
257 // belong to the boot loader, but they are usually stored in their own special ClassLoaderData to
258 // facilitate class unloading, as a LambdaForm may refer to a class loaded by a custom loader
259 // that may be unloaded.
260 //
261 // We only support AOT-resolution of indys in the boot/platform/app loader, so there's no need
262 // to support class unloading. For simplicity, we put all archived LambdaForm classes in the
263 // "main" ClassLoaderData of the boot loader.
264 //
265 // (Even if we were to support other loaders, we would still feel free to ignore any requirement
266 // of class unloading, for any class asset in the AOT cache. Anything that makes it into the AOT
267 // cache has a lifetime dispensation from unloading. After all, the AOT cache never grows, and
268 // we can assume that the user is content with its size, and doesn't need its footprint to shrink.)
269 //
270 // Lambda proxy classes are normally stored in the same ClassLoaderData as their nest hosts, and
271 // StringConcat are normally stored in the main ClassLoaderData of the boot class loader. We
272 // do the same for the archived copies of such classes.
273 void AOTLinkedClassBulkLoader::load_hidden_class(ClassLoaderData* loader_data, InstanceKlass* ik, TRAPS) {
274 assert(HeapShared::is_lambda_form_klass(ik) ||
275 HeapShared::is_lambda_proxy_klass(ik) ||
276 HeapShared::is_string_concat_klass(ik), "sanity");
277 DEBUG_ONLY({
278 assert(ik->java_super()->is_loaded(), "must be");
279 for (int i = 0; i < ik->local_interfaces()->length(); i++) {
280 assert(ik->local_interfaces()->at(i)->is_loaded(), "must be");
281 }
282 });
283
284 Handle pd;
285 PackageEntry* pkg_entry = nullptr;
286
287 // Since a hidden class does not have a name, it cannot be reloaded
288 // normally via the system dictionary. Instead, we have to finish the
289 // loading job here.
290
291 if (HeapShared::is_lambda_proxy_klass(ik)) {
292 InstanceKlass* nest_host = ik->nest_host_not_null();
293 assert(nest_host->is_loaded(), "must be");
294 pd = Handle(THREAD, nest_host->protection_domain());
295 pkg_entry = nest_host->package();
296 }
297
298 ik->restore_unshareable_info(loader_data, pd, pkg_entry, CHECK);
299 SystemDictionary::load_shared_class_misc(ik, loader_data);
300 ik->add_to_hierarchy(THREAD);
301 assert(ik->is_loaded(), "Must be in at least loaded state");
302
303 DEBUG_ONLY({
304 // Make sure we don't make this hidden class available by name, even if we don't
305 // use any special ClassLoaderData.
306 Handle loader(THREAD, loader_data->class_loader());
307 ResourceMark rm(THREAD);
308 assert(SystemDictionary::resolve_or_null(ik->name(), loader, THREAD) == nullptr,
309 "hidden classes cannot be accessible by name: %s", ik->external_name());
310 if (HAS_PENDING_EXCEPTION) {
311 CLEAR_PENDING_EXCEPTION;
312 }
313 });
314 }
315
316 void AOTLinkedClassBulkLoader::finish_loading_javabase_classes(TRAPS) {
317 init_required_classes_for_loader(Handle(), AOTLinkedClassTable::for_static_archive()->boot(), CHECK);
318 }
319
320 // Some AOT-linked classes for <class_loader> must be initialized early. This includes
321 // - classes that were AOT-initialized by AOTClassInitializer
322 // - the classes of all objects that are reachable from the archived mirrors of
323 // the AOT-linked classes for <class_loader>.
324 void AOTLinkedClassBulkLoader::init_required_classes_for_loader(Handle class_loader, Array<InstanceKlass*>* classes, TRAPS) {
325 if (classes != nullptr) {
326 for (int i = 0; i < classes->length(); i++) {
327 InstanceKlass* ik = classes->at(i);
328 if (ik->class_loader_data() == nullptr) {
329 // This class is not yet loaded. We will initialize it in a later phase.
330 // For example, we have loaded only AOTLinkedClassCategory::BOOT1 classes
331 // but k is part of AOTLinkedClassCategory::BOOT2.
332 continue;
333 }
334 if (ik->has_aot_initialized_mirror()) {
335 ik->initialize_with_aot_initialized_mirror(CHECK);
336 } else {
337 // Some cached heap objects may hold references to methods in aot-linked
338 // classes (via MemberName). We need to make sure all classes are
339 // linked to allow such MemberNames to be invoked.
340 ik->link_class(CHECK);
341 }
342 }
343 }
344
345 HeapShared::init_classes_for_special_subgraph(class_loader, CHECK);
346 }
347
348 bool AOTLinkedClassBulkLoader::is_pending_aot_linked_class(Klass* k) {
349 if (!CDSConfig::is_using_aot_linked_classes()) {
350 return false;
351 }
352
353 if (_all_completed) { // no more pending aot-linked classes
354 return false;
355 }
356
357 if (k->is_objArray_klass()) {
358 k = ObjArrayKlass::cast(k)->bottom_klass();
359 }
360 if (!k->is_instance_klass()) {
361 // type array klasses (and their higher dimensions),
362 // must have been loaded before a GC can ever happen.
363 return false;
364 }
365
366 // There's a small window during VM start-up where a not-yet loaded aot-linked
367 // class k may be discovered by the GC during VM initialization. This can happen
368 // when the heap contains an aot-cached instance of k, but k is not ready to be
369 // loaded yet. (TODO: JDK-8342429 eliminates this possibility)
370 //
371 // The following checks try to limit this window as much as possible for each of
372 // the four AOTLinkedClassCategory of classes that can be aot-linked.
373
374 InstanceKlass* ik = InstanceKlass::cast(k);
375 if (ik->is_shared_boot_class()) {
376 if (ik->module() != nullptr && ik->in_javabase_module()) {
377 // AOTLinkedClassCategory::BOOT1 -- all aot-linked classes in
378 // java.base must have been loaded before a GC can ever happen.
379 return false;
380 } else {
381 // AOTLinkedClassCategory::BOOT2 classes cannot be loaded until
382 // module system is ready.
383 return !_boot2_completed;
384 }
385 } else if (ik->is_shared_platform_class()) {
386 // AOTLinkedClassCategory::PLATFORM classes cannot be loaded until
387 // the platform class loader is initialized.
388 return !_platform_completed;
389 } else if (ik->is_shared_app_class()) {
390 // AOTLinkedClassCategory::APP cannot be loaded until the app class loader
391 // is initialized.
392 return !_app_completed;
393 } else {
394 return false;
395 }
396 }