1 /*
2 * Copyright (c) 2020, 2026, 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 "cds/aotGrowableArray.hpp"
26 #include "cds/aotMetaspace.hpp"
27 #include "cds/archiveBuilder.hpp"
28 #include "cds/archiveUtils.hpp"
29 #include "cds/cdsConfig.hpp"
30 #include "cds/cppVtables.hpp"
31 #include "logging/log.hpp"
32 #include "memory/resourceArea.hpp"
33 #include "oops/flatArrayKlass.hpp"
34 #include "oops/inlineKlass.hpp"
35 #include "oops/instanceClassLoaderKlass.hpp"
36 #include "oops/instanceKlass.inline.hpp"
37 #include "oops/instanceMirrorKlass.hpp"
38 #include "oops/instanceRefKlass.hpp"
39 #include "oops/instanceStackChunkKlass.hpp"
40 #include "oops/methodCounters.hpp"
41 #include "oops/methodData.hpp"
42 #include "oops/objArrayKlass.hpp"
43 #include "oops/refArrayKlass.hpp"
44 #include "oops/trainingData.hpp"
45 #include "oops/typeArrayKlass.hpp"
46 #include "runtime/arguments.hpp"
47 #include "utilities/globalDefinitions.hpp"
48
49 // Objects of the Metadata types (such as Klass and ConstantPool) have C++ vtables.
50 // (In GCC this is the field <Type>::_vptr, i.e., first word in the object.)
51 //
52 // Addresses of the vtables and the methods may be different across JVM runs,
53 // if libjvm.so is dynamically loaded at a different base address.
54 //
55 // To ensure that the Metadata objects in the CDS archive always have the correct vtable:
56 //
57 // + at dump time: we redirect the _vptr to point to our own vtables inside
58 // the CDS image
59 // + at run time: we clone the actual contents of the vtables from libjvm.so
60 // into our own tables.
61
62
63 #ifndef PRODUCT
64
65 // AOTGrowableArray has a vtable only when in non-product builds (due to
66 // the virtual printing functions in AnyObj).
67
68 using GrowableArray_ModuleEntry_ptr = AOTGrowableArray<ModuleEntry*>;
69
70 #define DEBUG_CPP_VTABLE_TYPES_DO(f) \
71 f(GrowableArray_ModuleEntry_ptr) \
72
73 #endif
74
75 // Currently, the archive contains ONLY the following types of objects that have C++ vtables.
76 // NOTE: this table must be in-sync with sun.jvm.hotspot.memory.FileMapInfo::populateMetadataTypeArray().
77 #define CPP_VTABLE_TYPES_DO(f) \
78 f(ConstantPool) \
79 f(InstanceKlass) \
80 f(InstanceClassLoaderKlass) \
81 f(InstanceMirrorKlass) \
82 f(InstanceRefKlass) \
83 f(InstanceStackChunkKlass) \
84 f(Method) \
85 f(MethodData) \
86 f(MethodCounters) \
87 f(TypeArrayKlass) \
88 f(ObjArrayKlass) \
89 f(RefArrayKlass) \
90 f(FlatArrayKlass) \
91 f(InlineKlass) \
92 f(KlassTrainingData) \
93 f(MethodTrainingData) \
94 f(CompileTrainingData) \
95 NOT_PRODUCT(DEBUG_CPP_VTABLE_TYPES_DO(f))
96
97 class CppVtableInfo {
98 intptr_t _vtable_size;
99 intptr_t _cloned_vtable[1]; // Pseudo flexible array member.
100 static size_t cloned_vtable_offset() { return offset_of(CppVtableInfo, _cloned_vtable); }
101 public:
102 int vtable_size() { return int(uintx(_vtable_size)); }
103 void set_vtable_size(int n) { _vtable_size = intptr_t(n); }
104 // Using _cloned_vtable[i] for i > 0 causes undefined behavior. We use address calculation instead.
105 intptr_t* cloned_vtable() { return (intptr_t*)((char*)this + cloned_vtable_offset()); }
106 void zero() { memset(cloned_vtable(), 0, sizeof(intptr_t) * vtable_size()); }
107 // Returns the address of the next CppVtableInfo that can be placed immediately after this CppVtableInfo
108 static size_t byte_size(int vtable_size) {
109 return cloned_vtable_offset() + (sizeof(intptr_t) * vtable_size);
110 }
111 };
112
113 static inline intptr_t* vtable_of(const void* m) {
114 return *((intptr_t**)m);
115 }
116
117 template <class T> class CppVtableCloner {
118 static int get_vtable_length(const char* name);
119
120 public:
121 // Allocate a clone of the vtable of T from the shared metaspace;
122 // Initialize the contents of this clone.
123 static CppVtableInfo* allocate_and_initialize(const char* name);
124
125 // Copy the contents of the vtable of T into info->_cloned_vtable;
126 static void initialize(const char* name, CppVtableInfo* info);
127
128 static void init_orig_cpp_vtptr(int kind);
129 };
130
131 template <class T>
132 CppVtableInfo* CppVtableCloner<T>::allocate_and_initialize(const char* name) {
133 int n = get_vtable_length(name);
134 CppVtableInfo* info =
135 (CppVtableInfo*)ArchiveBuilder::current()->rw_region()->allocate(CppVtableInfo::byte_size(n));
136 info->set_vtable_size(n);
137 initialize(name, info);
138 return info;
139 }
140
141 template <class T>
142 void CppVtableCloner<T>::initialize(const char* name, CppVtableInfo* info) {
143 ResourceMark rm;
144 T tmp; // Allocate temporary dummy metadata object to get to the original vtable.
145 int n = info->vtable_size();
146 intptr_t* srcvtable = vtable_of(&tmp);
147 intptr_t* dstvtable = info->cloned_vtable();
148
149 // We already checked (and, if necessary, adjusted n) when the vtables were allocated, so we are
150 // safe to do memcpy.
151 log_debug(aot, vtables)("Copying %3d vtable entries for %s", n, name);
152 memcpy(dstvtable, srcvtable, sizeof(intptr_t) * n);
153 }
154
155 // To determine the size of the vtable for each type, we use the following
156 // trick by declaring 2 subclasses:
157 //
158 // class CppVtableTesterA: public InstanceKlass {virtual int last_virtual_method() {return 1;} };
159 // class CppVtableTesterB: public InstanceKlass {virtual void* last_virtual_method() {return nullptr}; };
160 //
161 // CppVtableTesterA and CppVtableTesterB's vtables have the following properties:
162 // - Their size (N+1) is exactly one more than the size of InstanceKlass's vtable (N)
163 // - The first N entries have are exactly the same as in InstanceKlass's vtable.
164 // - Their last entry is different.
165 //
166 // So to determine the value of N, we just walk CppVtableTesterA and CppVtableTesterB's tables
167 // and find the first entry that's different.
168 //
169 // This works on all C++ compilers supported by Oracle, but you may need to tweak it for more
170 // esoteric compilers.
171
172 template <class T> class CppVtableTesterB: public T {
173 public:
174 virtual int last_virtual_method() {return 1;}
175 };
176
177 template <class T> class CppVtableTesterA : public T {
178 public:
179 virtual void* last_virtual_method() {
180 // Make this different than CppVtableTesterB::last_virtual_method so the C++
181 // compiler/linker won't alias the two functions.
182 return nullptr;
183 }
184 };
185
186 template <class T>
187 int CppVtableCloner<T>::get_vtable_length(const char* name) {
188 CppVtableTesterA<T> a;
189 CppVtableTesterB<T> b;
190
191 intptr_t* avtable = vtable_of(&a);
192 intptr_t* bvtable = vtable_of(&b);
193
194 // Start at slot 1, because slot 0 may be RTTI (on Solaris/Sparc)
195 int vtable_len = 1;
196 for (; ; vtable_len++) {
197 if (avtable[vtable_len] != bvtable[vtable_len]) {
198 break;
199 }
200 }
201 log_debug(aot, vtables)("Found %3d vtable entries for %s", vtable_len, name);
202
203 return vtable_len;
204 }
205
206 #define ALLOCATE_AND_INITIALIZE_VTABLE(c) \
207 _index[c##_Kind] = CppVtableCloner<c>::allocate_and_initialize(#c); \
208 ArchivePtrMarker::mark_pointer(&_index[c##_Kind]);
209
210 #define INITIALIZE_VTABLE(c) \
211 CppVtableCloner<c>::initialize(#c, _index[c##_Kind]);
212
213 #define INIT_ORIG_CPP_VTPTRS(c) \
214 CppVtableCloner<c>::init_orig_cpp_vtptr(c##_Kind);
215
216 #define DECLARE_CLONED_VTABLE_KIND(c) c ## _Kind,
217
218 enum ClonedVtableKind {
219 // E.g., ConstantPool_Kind == 0, InstanceKlass_Kind == 1, etc.
220 CPP_VTABLE_TYPES_DO(DECLARE_CLONED_VTABLE_KIND)
221 _num_cloned_vtable_kinds
222 };
223
224 // _orig_cpp_vtptrs and _archived_cpp_vtptrs are used for type checking in
225 // CppVtables::get_archived_vtable().
226 //
227 // _orig_cpp_vtptrs is a map of all the original vtptrs. E.g., for
228 // ConstantPool *cp = new (...) ConstantPool(...) ; // a dynamically allocated constant pool
229 // the following holds true:
230 // _orig_cpp_vtptrs[ConstantPool_Kind] == ((intptr_t**)cp)[0]
231 //
232 // _archived_cpp_vtptrs is a map of all the vptprs used by classes in a preimage. E.g., for
233 // InstanceKlass* k = a class loaded from the preimage;
234 // ConstantPool* cp = k->constants();
235 // the following holds true:
236 // _archived_cpp_vtptrs[ConstantPool_Kind] == ((intptr_t**)cp)[0]
237 static bool _orig_cpp_vtptrs_inited = false;
238 static intptr_t* _orig_cpp_vtptrs[_num_cloned_vtable_kinds];
239 static intptr_t* _archived_cpp_vtptrs[_num_cloned_vtable_kinds];
240
241 template <class T>
242 void CppVtableCloner<T>::init_orig_cpp_vtptr(int kind) {
243 assert(kind < _num_cloned_vtable_kinds, "sanity");
244 T tmp; // Allocate temporary dummy metadata object to get to the original vtable.
245 intptr_t* srcvtable = vtable_of(&tmp);
246 _orig_cpp_vtptrs[kind] = srcvtable;
247 }
248
249 // This is the index of all the cloned vtables. E.g., for
250 // ConstantPool* cp = ....; // an archived constant pool
251 // InstanceKlass* ik = ....;// an archived class
252 // the following holds true:
253 // _index[ConstantPool_Kind]->cloned_vtable() == ((intptr_t**)cp)[0]
254 // _index[InstanceKlass_Kind]->cloned_vtable() == ((intptr_t**)ik)[0]
255 static CppVtableInfo* _index[_num_cloned_vtable_kinds];
256
257 // This marks the location in the archive where _index[0] is stored. This location
258 // will be stored as FileMapHeader::_cloned_vtables_offset into the archive header.
259 // Serviceability Agent uses this information to determine the vtables of
260 // archived Metadata objects.
261 char* CppVtables::_vtables_serialized_base = nullptr;
262
263 void CppVtables::dumptime_init(ArchiveBuilder* builder) {
264 assert(CDSConfig::is_dumping_static_archive(), "cpp tables are only dumped into static archive");
265
266 if (CDSConfig::is_dumping_final_static_archive()) {
267 // When dumping final archive, _index[kind] at this point is in the preimage.
268 // Remember these vtable pointers in _archived_cpp_vtptrs, as _index[kind] will now be rewritten
269 // to point to the runtime vtable data.
270 for (int i = 0; i < _num_cloned_vtable_kinds; i++) {
271 assert(_index[i] != nullptr, "must have been restored by CppVtables::serialize()");
272 _archived_cpp_vtptrs[i] = _index[i]->cloned_vtable();
273 }
274 } else {
275 memset(_archived_cpp_vtptrs, 0, sizeof(_archived_cpp_vtptrs));
276 }
277
278 CPP_VTABLE_TYPES_DO(ALLOCATE_AND_INITIALIZE_VTABLE);
279
280 size_t cpp_tables_size = builder->rw_region()->top() - builder->rw_region()->base();
281 builder->alloc_stats()->record_cpp_vtables((int)cpp_tables_size);
282 }
283
284 void CppVtables::serialize(SerializeClosure* soc) {
285 if (!soc->reading()) {
286 _vtables_serialized_base = (char*)ArchiveBuilder::current()->buffer_top();
287 }
288 for (int i = 0; i < _num_cloned_vtable_kinds; i++) {
289 soc->do_ptr(&_index[i]);
290 }
291 if (soc->reading()) {
292 CPP_VTABLE_TYPES_DO(INITIALIZE_VTABLE);
293 }
294 }
295
296 intptr_t* CppVtables::get_archived_vtable(MetaspaceClosureType type, address obj) {
297 if (!_orig_cpp_vtptrs_inited) {
298 CPP_VTABLE_TYPES_DO(INIT_ORIG_CPP_VTPTRS);
299 _orig_cpp_vtptrs_inited = true;
300 }
301
302 assert(CDSConfig::is_dumping_archive(), "sanity");
303 int kind = -1;
304 switch (type) {
305 case MetaspaceClosureType::SymbolType:
306 case MetaspaceClosureType::TypeArrayU1Type:
307 case MetaspaceClosureType::TypeArrayU2Type:
308 case MetaspaceClosureType::TypeArrayU4Type:
309 case MetaspaceClosureType::TypeArrayU8Type:
310 case MetaspaceClosureType::TypeArrayOtherType:
311 case MetaspaceClosureType::CArrayType:
312 case MetaspaceClosureType::ConstMethodType:
313 case MetaspaceClosureType::ConstantPoolCacheType:
314 case MetaspaceClosureType::AnnotationsType:
315 case MetaspaceClosureType::ModuleEntryType:
316 case MetaspaceClosureType::PackageEntryType:
317 case MetaspaceClosureType::RecordComponentType:
318 case MetaspaceClosureType::AdapterHandlerEntryType:
319 case MetaspaceClosureType::AdapterFingerPrintType:
320 PRODUCT_ONLY(case MetaspaceClosureType::GrowableArrayType:)
321 // These have no vtables.
322 break;
323 default:
324 for (kind = 0; kind < _num_cloned_vtable_kinds; kind ++) {
325 if (vtable_of((Metadata*)obj) == _orig_cpp_vtptrs[kind] ||
326 vtable_of((Metadata*)obj) == _archived_cpp_vtptrs[kind]) {
327 break;
328 }
329 }
330 if (kind >= _num_cloned_vtable_kinds) {
331 fatal("Cannot find C++ vtable for " INTPTR_FORMAT " -- you probably added"
332 " a new subtype of Klass or MetaData without updating CPP_VTABLE_TYPES_DO or the cases in this 'switch' statement",
333 p2i(obj));
334 }
335 }
336
337 if (kind >= 0) {
338 assert(kind < _num_cloned_vtable_kinds, "must be");
339 return _index[kind]->cloned_vtable();
340 } else {
341 return nullptr;
342 }
343 }
344
345 void CppVtables::zero_archived_vtables() {
346 assert(CDSConfig::is_dumping_static_archive(), "cpp tables are only dumped into static archive");
347 for (int kind = 0; kind < _num_cloned_vtable_kinds; kind ++) {
348 _index[kind]->zero();
349 }
350 }
351
352 bool CppVtables::is_valid_shared_method(const Method* m) {
353 assert(AOTMetaspace::in_aot_cache(m), "must be");
354 return vtable_of(m) == _index[Method_Kind]->cloned_vtable() ||
355 vtable_of(m) == _archived_cpp_vtptrs[Method_Kind];
356 }