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