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