1 /*
2 * Copyright (c) 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/archiveBuilder.hpp"
27 #include "cds/cdsConfig.hpp"
28 #include "cds/classPreinitializer.hpp"
29 #include "dumpTimeClassInfo.inline.hpp"
30 #include "cds/heapShared.hpp"
31 #include "classfile/systemDictionaryShared.hpp"
32 #include "memory/resourceArea.hpp"
33 #include "oops/fieldStreams.inline.hpp"
34 #include "oops/instanceKlass.inline.hpp"
35 #include "runtime/mutexLocker.hpp"
36
37 // Warning -- this is fragile!!!
38 //
39 // This is a hard-coded list of classes that are safe to preinitialize at dump time. It needs
40 // to be updated if the Java source code changes.
41 bool ClassPreinitializer::is_forced_preinit_class(InstanceKlass* ik) {
42 if (!CDSConfig::is_dumping_invokedynamic()) {
43 return false;
44 }
45
46 static const char* forced_preinit_classes[] = {
47 "java/util/HexFormat",
48 "jdk/internal/util/ClassFileDumper",
49 "java/lang/reflect/ClassFileFormatVersion",
50 "java/lang/Character$CharacterCache",
51 "java/lang/invoke/Invokers",
52 "java/lang/invoke/Invokers$Holder",
53 "java/lang/invoke/MethodHandle",
54 "java/lang/invoke/MethodHandleStatics",
55 "java/lang/invoke/DelegatingMethodHandle",
56 "java/lang/invoke/DelegatingMethodHandle$Holder",
57 "java/lang/invoke/LambdaForm",
58 "java/lang/invoke/LambdaForm$NamedFunction",
59 "java/lang/invoke/ClassSpecializer",
60 "java/lang/invoke/DirectMethodHandle",
61 "java/lang/invoke/DirectMethodHandle$Holder",
62 "java/lang/invoke/BoundMethodHandle$Specializer",
63 "java/lang/invoke/MethodHandles$Lookup",
64
65 //TODO: these use java.lang.ClassValue$Entry which is a subtype of WeakReference
66 //"java/lang/reflect/Proxy$ProxyBuilder",
67 //"java/lang/reflect/Proxy",
68
69 // TODO -- need to clear internTable, etc
70 //"java/lang/invoke/MethodType",
71
72 // TODO -- these need to link to native code
73 //"java/lang/invoke/BoundMethodHandle",
74 //"java/lang/invoke/BoundMethodHandle$Holder",
75 //"java/lang/invoke/MemberName",
76 //"java/lang/invoke/MethodHandleNatives",
77 };
78
79 for (const char* class_name : forced_preinit_classes) {
80 if (ik->name()->equals(class_name)) {
81 if (log_is_enabled(Info, cds, init)) {
82 ResourceMark rm;
83 log_info(cds, init)("Force initialization %s", ik->external_name());
84 }
85 return true;
86 }
87 }
88
89 return false;
90 }
91
92 // check_can_be_preinited() is quite costly, so we cache the results inside
93 // DumpTimeClassInfo::_can_be_preinited. See also ClassPreinitializer::reset_preinit_check().
94 bool ClassPreinitializer::check_can_be_preinited(InstanceKlass* ik) {
95 ResourceMark rm;
96
97 if (!SystemDictionaryShared::is_builtin(ik)) {
98 log_info(cds, init)("cannot initialize %s (not built-in loader)", ik->external_name());
99 return false;
100 }
101
102 InstanceKlass* super = ik->java_super();
103 if (super != nullptr && !can_be_preinited_locked(super)) {
104 log_info(cds, init)("cannot initialize %s (super %s not initable)", ik->external_name(), super->external_name());
105 return false;
106 }
107
108 Array<InstanceKlass*>* interfaces = ik->local_interfaces();
109 for (int i = 0; i < interfaces->length(); i++) {
110 if (!can_be_preinited_locked(interfaces->at(i))) {
111 log_info(cds, init)("cannot initialize %s (interface %s not initable)",
112 ik->external_name(), interfaces->at(i)->external_name());
113 return false;
114 }
115 }
116
117 if (HeapShared::is_lambda_form_klass(ik) || is_forced_preinit_class(ik)) {
118 // We allow only these to have <clinit> or non-default static fields
119 } else {
120 if (ik->class_initializer() != nullptr) {
121 log_info(cds, init)("cannot initialize %s (has <clinit>)", ik->external_name());
122 return false;
123 }
124 if (ik->is_initialized() && !has_non_default_static_fields(ik)) {
125 return false;
126 }
127 }
128
129 return true;
130 }
131
132 bool ClassPreinitializer::has_non_default_static_fields(InstanceKlass* ik) {
133 oop mirror = ik->java_mirror();
134
135 for (JavaFieldStream fs(ik); !fs.done(); fs.next()) {
136 if (fs.access_flags().is_static()) {
137 fieldDescriptor& fd = fs.field_descriptor();
138 int offset = fd.offset();
139 bool is_default = true;
140 bool has_initval = fd.has_initial_value();
141 switch (fd.field_type()) {
142 case T_OBJECT:
143 case T_ARRAY:
144 is_default = mirror->obj_field(offset) == nullptr;
145 break;
146 case T_BOOLEAN:
147 is_default = mirror->bool_field(offset) == (has_initval ? fd.int_initial_value() : 0);
148 break;
149 case T_BYTE:
150 is_default = mirror->byte_field(offset) == (has_initval ? fd.int_initial_value() : 0);
151 break;
152 case T_SHORT:
153 is_default = mirror->short_field(offset) == (has_initval ? fd.int_initial_value() : 0);
154 break;
155 case T_CHAR:
156 is_default = mirror->char_field(offset) == (has_initval ? fd.int_initial_value() : 0);
157 break;
158 case T_INT:
159 is_default = mirror->int_field(offset) == (has_initval ? fd.int_initial_value() : 0);
160 break;
161 case T_LONG:
162 is_default = mirror->long_field(offset) == (has_initval ? fd.long_initial_value() : 0);
163 break;
164 case T_FLOAT:
165 is_default = mirror->float_field(offset) == (has_initval ? fd.float_initial_value() : 0);
166 break;
167 case T_DOUBLE:
168 is_default = mirror->double_field(offset) == (has_initval ? fd.double_initial_value() : 0);
169 break;
170 default:
171 ShouldNotReachHere();
172 }
173
174 if (!is_default) {
175 log_info(cds, init)("cannot initialize %s (static field %s has non-default value)",
176 ik->external_name(), fd.name()->as_C_string());
177 return false;
178 }
179 }
180 }
181
182 return true;
183 }
184
185 bool ClassPreinitializer::can_be_preinited(InstanceKlass* ik) {
186 MutexLocker ml(DumpTimeTable_lock, Mutex::_no_safepoint_check_flag);
187 return can_be_preinited_locked(ik);
188 }
189
190 bool ClassPreinitializer::can_be_preinited_locked(InstanceKlass* ik) {
191 if (!CDSConfig::is_initing_classes_at_dump_time()) {
192 return false;
193 }
194
195 assert_lock_strong(DumpTimeTable_lock);
196 DumpTimeClassInfo* info = SystemDictionaryShared::get_info_locked(ik);
197 if (!info->has_done_preinit_check()) {
198 info->set_can_be_preinited(ClassPreinitializer::check_can_be_preinited(ik));
199 }
200 return info->can_be_preinited();
201 }
202
203 // Initialize a class at dump time, if possible.
204 void ClassPreinitializer::maybe_preinit_class(InstanceKlass* ik, TRAPS) {
205 if (!ik->is_initialized() && ClassPreinitializer::can_be_preinited(ik)) {
206 if (log_is_enabled(Info, cds, init)) {
207 ResourceMark rm;
208 log_info(cds, init)("preinitializing %s", ik->external_name());
209 }
210 ik->initialize(CHECK);
211 }
212 }
213
214 // ClassPreinitializer::can_be_preinited(ik) is called in two different phases:
215 //
216 // [1] Before the VM_PopulateDumpSharedSpace safepoint:
217 // when MetaspaceShared::link_shared_classes calls ClassPreinitializer::maybe_preinit_class(ik)
218 // [2] Inside the VM_PopulateDumpSharedSpace safepoint
219 // when HeapShared::archive_java_mirrors() calls ClassPreinitializer::can_archive_preinitialized_mirror(ik)
220 //
221 // Between the two phases, some Java code may have been executed to contaminate the
222 // some initialized mirrors. So we call reset_preinit_check() at the beginning of the
223 // [2] so that we will re-run has_non_default_static_fields() on all the classes.
224 // As a result, phase [2] may archive fewer mirrors that were initialized in phase [1].
225 void ClassPreinitializer::reset_preinit_check() {
226 auto iterator = [&] (InstanceKlass* k, DumpTimeClassInfo& info) {
227 if (info.can_be_preinited()) {
228 info.reset_preinit_check();
229 }
230 };
231 SystemDictionaryShared::dumptime_table()->iterate_all_live_classes(iterator);
232 }
233
234 bool ClassPreinitializer::can_archive_preinitialized_mirror(InstanceKlass* ik) {
235 assert(!ArchiveBuilder::current()->is_in_buffer_space(ik), "must be source klass");
236 if (!CDSConfig::is_initing_classes_at_dump_time()) {
237 return false;
238 }
239
240 if (ik->is_hidden()) {
241 return HeapShared::is_archivable_hidden_klass(ik);
242 } else {
243 return ClassPreinitializer::can_be_preinited_locked(ik);
244 }
245 }