1 /*
2 * Copyright (c) 2020, 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/archiveUtils.hpp"
26 #include "cds/archiveBuilder.hpp"
27 #include "cds/cdsConfig.hpp"
28 #include "cds/cppVtables.hpp"
29 #include "cds/metaspaceShared.hpp"
30 #include "logging/log.hpp"
31 #include "oops/flatArrayKlass.hpp"
32 #include "oops/inlineKlass.hpp"
33 #include "oops/instanceClassLoaderKlass.hpp"
34 #include "oops/instanceKlass.inline.hpp"
35 #include "oops/instanceMirrorKlass.hpp"
36 #include "oops/instanceRefKlass.hpp"
37 #include "oops/instanceStackChunkKlass.hpp"
38 #include "oops/methodCounters.hpp"
39 #include "oops/methodData.hpp"
40 #include "oops/trainingData.hpp"
41 #include "oops/objArrayKlass.hpp"
42 #include "oops/refArrayKlass.hpp"
43 #include "oops/typeArrayKlass.hpp"
44 #include "runtime/arguments.hpp"
45 #include "utilities/globalDefinitions.hpp"
46
47 // Objects of the Metadata types (such as Klass and ConstantPool) have C++ vtables.
48 // (In GCC this is the field <Type>::_vptr, i.e., first word in the object.)
49 //
50 // Addresses of the vtables and the methods may be different across JVM runs,
51 // if libjvm.so is dynamically loaded at a different base address.
52 //
53 // To ensure that the Metadata objects in the CDS archive always have the correct vtable:
54 //
55 // + at dump time: we redirect the _vptr to point to our own vtables inside
56 // the CDS image
57 // + at run time: we clone the actual contents of the vtables from libjvm.so
58 // into our own tables.
59
60 // Currently, the archive contains ONLY the following types of objects that have C++ vtables.
61 // NOTE: this table must be in-sync with sun.jvm.hotspot.memory.FileMapInfo::populateMetadataTypeArray().
62 #define CPP_VTABLE_TYPES_DO(f) \
63 f(ConstantPool) \
64 f(InstanceKlass) \
65 f(InstanceClassLoaderKlass) \
66 f(InstanceMirrorKlass) \
67 f(InstanceRefKlass) \
68 f(InstanceStackChunkKlass) \
69 f(Method) \
70 f(MethodData) \
71 f(MethodCounters) \
72 f(ObjArrayKlass) \
73 f(TypeArrayKlass) \
74 f(FlatArrayKlass) \
75 f(InlineKlass) \
76 f(RefArrayKlass) \
77 f(KlassTrainingData) \
78 f(MethodTrainingData) \
79 f(CompileTrainingData)
80
81 class CppVtableInfo {
82 intptr_t _vtable_size;
83 intptr_t _cloned_vtable[1]; // Pseudo flexible array member.
84 static size_t cloned_vtable_offset() { return offset_of(CppVtableInfo, _cloned_vtable); }
85 public:
86 int vtable_size() { return int(uintx(_vtable_size)); }
87 void set_vtable_size(int n) { _vtable_size = intptr_t(n); }
88 // Using _cloned_vtable[i] for i > 0 causes undefined behavior. We use address calculation instead.
89 intptr_t* cloned_vtable() { return (intptr_t*)((char*)this + cloned_vtable_offset()); }
90 void zero() { memset(cloned_vtable(), 0, sizeof(intptr_t) * vtable_size()); }
91 // Returns the address of the next CppVtableInfo that can be placed immediately after this CppVtableInfo
92 static size_t byte_size(int vtable_size) {
93 return cloned_vtable_offset() + (sizeof(intptr_t) * vtable_size);
94 }
95 };
96
97 static inline intptr_t* vtable_of(const Metadata* m) {
98 return *((intptr_t**)m);
99 }
100
101 template <class T> class CppVtableCloner {
102 static int get_vtable_length(const char* name);
103
104 public:
105 // Allocate a clone of the vtable of T from the shared metaspace;
106 // Initialize the contents of this clone.
107 static CppVtableInfo* allocate_and_initialize(const char* name);
108
109 // Copy the contents of the vtable of T into info->_cloned_vtable;
110 static void initialize(const char* name, CppVtableInfo* info);
111
112 static void init_orig_cpp_vtptr(int kind);
113 };
114
115 template <class T>
116 CppVtableInfo* CppVtableCloner<T>::allocate_and_initialize(const char* name) {
117 int n = get_vtable_length(name);
118 CppVtableInfo* info =
119 (CppVtableInfo*)ArchiveBuilder::current()->rw_region()->allocate(CppVtableInfo::byte_size(n));
120 info->set_vtable_size(n);
121 initialize(name, info);
122 return info;
123 }
124
125 template <class T>
126 void CppVtableCloner<T>::initialize(const char* name, CppVtableInfo* info) {
127 T tmp; // Allocate temporary dummy metadata object to get to the original vtable.
128 int n = info->vtable_size();
129 intptr_t* srcvtable = vtable_of(&tmp);
130 intptr_t* dstvtable = info->cloned_vtable();
131
132 // We already checked (and, if necessary, adjusted n) when the vtables were allocated, so we are
133 // safe to do memcpy.
134 log_debug(aot, vtables)("Copying %3d vtable entries for %s", n, name);
135 memcpy(dstvtable, srcvtable, sizeof(intptr_t) * n);
136 }
137
138 // To determine the size of the vtable for each type, we use the following
139 // trick by declaring 2 subclasses:
140 //
141 // class CppVtableTesterA: public InstanceKlass {virtual int last_virtual_method() {return 1;} };
142 // class CppVtableTesterB: public InstanceKlass {virtual void* last_virtual_method() {return nullptr}; };
143 //
144 // CppVtableTesterA and CppVtableTesterB's vtables have the following properties:
145 // - Their size (N+1) is exactly one more than the size of InstanceKlass's vtable (N)
146 // - The first N entries have are exactly the same as in InstanceKlass's vtable.
147 // - Their last entry is different.
148 //
149 // So to determine the value of N, we just walk CppVtableTesterA and CppVtableTesterB's tables
150 // and find the first entry that's different.
151 //
152 // This works on all C++ compilers supported by Oracle, but you may need to tweak it for more
153 // esoteric compilers.
154
155 template <class T> class CppVtableTesterB: public T {
156 public:
157 virtual int last_virtual_method() {return 1;}
158 };
159
160 template <class T> class CppVtableTesterA : public T {
161 public:
162 virtual void* last_virtual_method() {
163 // Make this different than CppVtableTesterB::last_virtual_method so the C++
164 // compiler/linker won't alias the two functions.
165 return nullptr;
166 }
167 };
168
169 template <class T>
170 int CppVtableCloner<T>::get_vtable_length(const char* name) {
171 CppVtableTesterA<T> a;
172 CppVtableTesterB<T> b;
173
174 intptr_t* avtable = vtable_of(&a);
175 intptr_t* bvtable = vtable_of(&b);
176
177 // Start at slot 1, because slot 0 may be RTTI (on Solaris/Sparc)
178 int vtable_len = 1;
179 for (; ; vtable_len++) {
180 if (avtable[vtable_len] != bvtable[vtable_len]) {
181 break;
182 }
183 }
184 log_debug(aot, vtables)("Found %3d vtable entries for %s", vtable_len, name);
185
186 return vtable_len;
187 }
188
189 #define ALLOCATE_AND_INITIALIZE_VTABLE(c) \
190 _index[c##_Kind] = CppVtableCloner<c>::allocate_and_initialize(#c); \
191 ArchivePtrMarker::mark_pointer(&_index[c##_Kind]);
192
193 #define INITIALIZE_VTABLE(c) \
194 CppVtableCloner<c>::initialize(#c, _index[c##_Kind]);
195
196 #define INIT_ORIG_CPP_VTPTRS(c) \
197 CppVtableCloner<c>::init_orig_cpp_vtptr(c##_Kind);
198
199 #define DECLARE_CLONED_VTABLE_KIND(c) c ## _Kind,
200
201 enum ClonedVtableKind {
202 // E.g., ConstantPool_Kind == 0, InstanceKlass_Kind == 1, etc.
203 CPP_VTABLE_TYPES_DO(DECLARE_CLONED_VTABLE_KIND)
204 _num_cloned_vtable_kinds
205 };
206
207 // _orig_cpp_vtptrs and _archived_cpp_vtptrs are used for type checking in
208 // CppVtables::get_archived_vtable().
209 //
210 // _orig_cpp_vtptrs is a map of all the original vtptrs. E.g., for
211 // ConstantPool *cp = new (...) ConstantPool(...) ; // a dynamically allocated constant pool
212 // the following holds true:
213 // _orig_cpp_vtptrs[ConstantPool_Kind] == ((intptr_t**)cp)[0]
214 //
215 // _archived_cpp_vtptrs is a map of all the vptprs used by classes in a preimage. E.g., for
216 // InstanceKlass* k = a class loaded from the preimage;
217 // ConstantPool* cp = k->constants();
218 // the following holds true:
219 // _archived_cpp_vtptrs[ConstantPool_Kind] == ((intptr_t**)cp)[0]
220 static bool _orig_cpp_vtptrs_inited = false;
221 static intptr_t* _orig_cpp_vtptrs[_num_cloned_vtable_kinds];
222 static intptr_t* _archived_cpp_vtptrs[_num_cloned_vtable_kinds];
223
224 template <class T>
225 void CppVtableCloner<T>::init_orig_cpp_vtptr(int kind) {
226 assert(kind < _num_cloned_vtable_kinds, "sanity");
227 T tmp; // Allocate temporary dummy metadata object to get to the original vtable.
228 intptr_t* srcvtable = vtable_of(&tmp);
229 _orig_cpp_vtptrs[kind] = srcvtable;
230 }
231
232 // This is the index of all the cloned vtables. E.g., for
233 // ConstantPool* cp = ....; // an archived constant pool
234 // InstanceKlass* ik = ....;// an archived class
235 // the following holds true:
236 // _index[ConstantPool_Kind]->cloned_vtable() == ((intptr_t**)cp)[0]
237 // _index[InstanceKlass_Kind]->cloned_vtable() == ((intptr_t**)ik)[0]
238 static CppVtableInfo* _index[_num_cloned_vtable_kinds];
239
240 // This marks the location in the archive where _index[0] is stored. This location
241 // will be stored as FileMapHeader::_cloned_vtables_offset into the archive header.
242 // Serviceability Agent uses this information to determine the vtables of
243 // archived Metadata objects.
244 char* CppVtables::_vtables_serialized_base = nullptr;
245
246 void CppVtables::dumptime_init(ArchiveBuilder* builder) {
247 assert(CDSConfig::is_dumping_static_archive(), "cpp tables are only dumped into static archive");
248
249 if (CDSConfig::is_dumping_final_static_archive()) {
250 // When dumping final archive, _index[kind] at this point is in the preimage.
251 // Remember these vtable pointers in _archived_cpp_vtptrs, as _index[kind] will now be rewritten
252 // to point to the runtime vtable data.
253 for (int i = 0; i < _num_cloned_vtable_kinds; i++) {
254 assert(_index[i] != nullptr, "must have been restored by CppVtables::serialize()");
255 _archived_cpp_vtptrs[i] = _index[i]->cloned_vtable();
256 }
257 } else {
258 memset(_archived_cpp_vtptrs, 0, sizeof(_archived_cpp_vtptrs));
259 }
260
261 CPP_VTABLE_TYPES_DO(ALLOCATE_AND_INITIALIZE_VTABLE);
262
263 size_t cpp_tables_size = builder->rw_region()->top() - builder->rw_region()->base();
264 builder->alloc_stats()->record_cpp_vtables((int)cpp_tables_size);
265 }
266
267 void CppVtables::serialize(SerializeClosure* soc) {
268 if (!soc->reading()) {
269 _vtables_serialized_base = (char*)ArchiveBuilder::current()->buffer_top();
270 }
271 for (int i = 0; i < _num_cloned_vtable_kinds; i++) {
272 soc->do_ptr(&_index[i]);
273 }
274 if (soc->reading()) {
275 CPP_VTABLE_TYPES_DO(INITIALIZE_VTABLE);
276 }
277 }
278
279 intptr_t* CppVtables::get_archived_vtable(MetaspaceObj::Type msotype, address obj) {
280 if (!_orig_cpp_vtptrs_inited) {
281 CPP_VTABLE_TYPES_DO(INIT_ORIG_CPP_VTPTRS);
282 _orig_cpp_vtptrs_inited = true;
283 }
284
285 assert(CDSConfig::is_dumping_archive(), "sanity");
286 int kind = -1;
287 switch (msotype) {
288 case MetaspaceObj::SymbolType:
289 case MetaspaceObj::TypeArrayU1Type:
290 case MetaspaceObj::TypeArrayU2Type:
291 case MetaspaceObj::TypeArrayU4Type:
292 case MetaspaceObj::TypeArrayU8Type:
293 case MetaspaceObj::TypeArrayOtherType:
294 case MetaspaceObj::ConstMethodType:
295 case MetaspaceObj::ConstantPoolCacheType:
296 case MetaspaceObj::AnnotationsType:
297 case MetaspaceObj::RecordComponentType:
298 case MetaspaceObj::AdapterHandlerEntryType:
299 case MetaspaceObj::AdapterFingerPrintType:
300 // These have no vtables.
301 break;
302 default:
303 for (kind = 0; kind < _num_cloned_vtable_kinds; kind ++) {
304 if (vtable_of((Metadata*)obj) == _orig_cpp_vtptrs[kind] ||
305 vtable_of((Metadata*)obj) == _archived_cpp_vtptrs[kind]) {
306 break;
307 }
308 }
309 if (kind >= _num_cloned_vtable_kinds) {
310 fatal("Cannot find C++ vtable for " INTPTR_FORMAT " -- you probably added"
311 " a new subtype of Klass or MetaData without updating CPP_VTABLE_TYPES_DO or the cases in this 'switch' statement",
312 p2i(obj));
313 }
314 }
315
316 if (kind >= 0) {
317 assert(kind < _num_cloned_vtable_kinds, "must be");
318 return _index[kind]->cloned_vtable();
319 } else {
320 return nullptr;
321 }
322 }
323
324 void CppVtables::zero_archived_vtables() {
325 assert(CDSConfig::is_dumping_static_archive(), "cpp tables are only dumped into static archive");
326 for (int kind = 0; kind < _num_cloned_vtable_kinds; kind ++) {
327 _index[kind]->zero();
328 }
329 }
330
331 bool CppVtables::is_valid_shared_method(const Method* m) {
332 assert(MetaspaceShared::is_in_shared_metaspace(m), "must be");
333 return vtable_of(m) == _index[Method_Kind]->cloned_vtable() ||
334 vtable_of(m) == _archived_cpp_vtptrs[Method_Kind];
335 }