1 /*
2 * Copyright (c) 2020, 2023, 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 "precompiled.hpp"
26 #include "cds/archiveUtils.hpp"
27 #include "cds/archiveBuilder.hpp"
28 #include "cds/cdsConfig.hpp"
29 #include "cds/cppVtables.hpp"
30 #include "cds/metaspaceShared.hpp"
31 #include "logging/log.hpp"
32 #include "oops/instanceClassLoaderKlass.hpp"
33 #include "oops/instanceMirrorKlass.hpp"
34 #include "oops/instanceRefKlass.hpp"
35 #include "oops/instanceStackChunkKlass.hpp"
36 #include "oops/methodData.hpp"
37 #include "oops/objArrayKlass.hpp"
38 #include "oops/typeArrayKlass.hpp"
39 #include "runtime/arguments.hpp"
40 #include "utilities/globalDefinitions.hpp"
41
42 // Objects of the Metadata types (such as Klass and ConstantPool) have C++ vtables.
43 // (In GCC this is the field <Type>::_vptr, i.e., first word in the object.)
44 //
45 // Addresses of the vtables and the methods may be different across JVM runs,
46 // if libjvm.so is dynamically loaded at a different base address.
47 //
48 // To ensure that the Metadata objects in the CDS archive always have the correct vtable:
49 //
50 // + at dump time: we redirect the _vptr to point to our own vtables inside
51 // the CDS image
52 // + at run time: we clone the actual contents of the vtables from libjvm.so
53 // into our own tables.
54
55 // Currently, the archive contains ONLY the following types of objects that have C++ vtables.
56 #define CPP_VTABLE_TYPES_DO(f) \
57 f(ConstantPool) \
58 f(InstanceKlass) \
59 f(InstanceClassLoaderKlass) \
60 f(InstanceMirrorKlass) \
61 f(InstanceRefKlass) \
62 f(InstanceStackChunkKlass) \
63 f(Method) \
64 f(ObjArrayKlass) \
65 f(TypeArrayKlass)
66
67 class CppVtableInfo {
68 intptr_t _vtable_size;
69 intptr_t _cloned_vtable[1];
70 public:
71 static int num_slots(int vtable_size) {
72 return 1 + vtable_size; // Need to add the space occupied by _vtable_size;
73 }
74 int vtable_size() { return int(uintx(_vtable_size)); }
75 void set_vtable_size(int n) { _vtable_size = intptr_t(n); }
76 intptr_t* cloned_vtable() { return &_cloned_vtable[0]; }
77 void zero() { memset(_cloned_vtable, 0, sizeof(intptr_t) * vtable_size()); }
78 // Returns the address of the next CppVtableInfo that can be placed immediately after this CppVtableInfo
79 static size_t byte_size(int vtable_size) {
80 CppVtableInfo i;
81 return pointer_delta(&i._cloned_vtable[vtable_size], &i, sizeof(u1));
82 }
83 };
84
85 static inline intptr_t* vtable_of(const Metadata* m) {
86 return *((intptr_t**)m);
87 }
88
89 template <class T> class CppVtableCloner {
90 static int get_vtable_length(const char* name);
91
92 public:
93 // Allocate a clone of the vtable of T from the shared metaspace;
94 // Initialize the contents of this clone.
95 static CppVtableInfo* allocate_and_initialize(const char* name);
96
97 // Copy the contents of the vtable of T into info->_cloned_vtable;
98 static void initialize(const char* name, CppVtableInfo* info);
99
100 static void init_orig_cpp_vtptr(int kind);
101 };
102
103 template <class T>
104 CppVtableInfo* CppVtableCloner<T>::allocate_and_initialize(const char* name) {
105 int n = get_vtable_length(name);
106 CppVtableInfo* info =
107 (CppVtableInfo*)ArchiveBuilder::current()->rw_region()->allocate(CppVtableInfo::byte_size(n));
108 info->set_vtable_size(n);
109 initialize(name, info);
110 return info;
111 }
112
113 template <class T>
114 void CppVtableCloner<T>::initialize(const char* name, CppVtableInfo* info) {
115 T tmp; // Allocate temporary dummy metadata object to get to the original vtable.
116 int n = info->vtable_size();
117 intptr_t* srcvtable = vtable_of(&tmp);
118 intptr_t* dstvtable = info->cloned_vtable();
119
120 // We already checked (and, if necessary, adjusted n) when the vtables were allocated, so we are
121 // safe to do memcpy.
122 log_debug(cds, vtables)("Copying %3d vtable entries for %s", n, name);
123 memcpy(dstvtable, srcvtable, sizeof(intptr_t) * n);
124 }
125
126 // To determine the size of the vtable for each type, we use the following
127 // trick by declaring 2 subclasses:
128 //
129 // class CppVtableTesterA: public InstanceKlass {virtual int last_virtual_method() {return 1;} };
130 // class CppVtableTesterB: public InstanceKlass {virtual void* last_virtual_method() {return nullptr}; };
131 //
132 // CppVtableTesterA and CppVtableTesterB's vtables have the following properties:
133 // - Their size (N+1) is exactly one more than the size of InstanceKlass's vtable (N)
134 // - The first N entries have are exactly the same as in InstanceKlass's vtable.
135 // - Their last entry is different.
136 //
137 // So to determine the value of N, we just walk CppVtableTesterA and CppVtableTesterB's tables
138 // and find the first entry that's different.
139 //
140 // This works on all C++ compilers supported by Oracle, but you may need to tweak it for more
141 // esoteric compilers.
142
143 template <class T> class CppVtableTesterB: public T {
144 public:
145 virtual int last_virtual_method() {return 1;}
146 };
147
148 template <class T> class CppVtableTesterA : public T {
149 public:
150 virtual void* last_virtual_method() {
151 // Make this different than CppVtableTesterB::last_virtual_method so the C++
152 // compiler/linker won't alias the two functions.
153 return nullptr;
154 }
155 };
156
157 template <class T>
158 int CppVtableCloner<T>::get_vtable_length(const char* name) {
159 CppVtableTesterA<T> a;
160 CppVtableTesterB<T> b;
161
162 intptr_t* avtable = vtable_of(&a);
163 intptr_t* bvtable = vtable_of(&b);
164
165 // Start at slot 1, because slot 0 may be RTTI (on Solaris/Sparc)
166 int vtable_len = 1;
167 for (; ; vtable_len++) {
168 if (avtable[vtable_len] != bvtable[vtable_len]) {
169 break;
170 }
171 }
172 log_debug(cds, vtables)("Found %3d vtable entries for %s", vtable_len, name);
173
174 return vtable_len;
175 }
176
177 #define ALLOCATE_AND_INITIALIZE_VTABLE(c) \
178 _index[c##_Kind] = CppVtableCloner<c>::allocate_and_initialize(#c); \
179 ArchivePtrMarker::mark_pointer(&_index[c##_Kind]);
180
181 #define INITIALIZE_VTABLE(c) \
182 CppVtableCloner<c>::initialize(#c, _index[c##_Kind]);
183
184 #define INIT_ORIG_CPP_VTPTRS(c) \
185 CppVtableCloner<c>::init_orig_cpp_vtptr(c##_Kind);
186
187 #define DECLARE_CLONED_VTABLE_KIND(c) c ## _Kind,
188
189 enum ClonedVtableKind {
190 // E.g., ConstantPool_Kind == 0, InstanceKlass_Kind == 1, etc.
191 CPP_VTABLE_TYPES_DO(DECLARE_CLONED_VTABLE_KIND)
192 _num_cloned_vtable_kinds
193 };
194
195 // This is a map of all the original vtptrs. E.g., for
196 // ConstantPool *cp = new (...) ConstantPool(...) ; // a dynamically allocated constant pool
197 // the following holds true:
198 // _orig_cpp_vtptrs[ConstantPool_Kind] == ((intptr_t**)cp)[0]
199 static intptr_t* _orig_cpp_vtptrs[_num_cloned_vtable_kinds];
200 static bool _orig_cpp_vtptrs_inited = false;
201
202 template <class T>
203 void CppVtableCloner<T>::init_orig_cpp_vtptr(int kind) {
204 assert(kind < _num_cloned_vtable_kinds, "sanity");
205 T tmp; // Allocate temporary dummy metadata object to get to the original vtable.
206 intptr_t* srcvtable = vtable_of(&tmp);
207 _orig_cpp_vtptrs[kind] = srcvtable;
208 }
209
210 // This is the index of all the cloned vtables. E.g., for
211 // ConstantPool* cp = ....; // an archived constant pool
212 // InstanceKlass* ik = ....;// an archived class
213 // the following holds true:
214 // _index[ConstantPool_Kind]->cloned_vtable() == ((intptr_t**)cp)[0]
215 // _index[InstanceKlass_Kind]->cloned_vtable() == ((intptr_t**)ik)[0]
216 CppVtableInfo** CppVtables::_index = nullptr;
217
218 char* CppVtables::dumptime_init(ArchiveBuilder* builder) {
219 assert(CDSConfig::is_dumping_static_archive(), "cpp tables are only dumped into static archive");
220 size_t vtptrs_bytes = _num_cloned_vtable_kinds * sizeof(CppVtableInfo*);
221 _index = (CppVtableInfo**)builder->rw_region()->allocate(vtptrs_bytes);
222
223 CPP_VTABLE_TYPES_DO(ALLOCATE_AND_INITIALIZE_VTABLE);
224
225 size_t cpp_tables_size = builder->rw_region()->top() - builder->rw_region()->base();
226 builder->alloc_stats()->record_cpp_vtables((int)cpp_tables_size);
227
228 return (char*)_index;
229 }
230
231 void CppVtables::serialize(SerializeClosure* soc) {
232 soc->do_ptr(&_index);
233 if (soc->reading()) {
234 CPP_VTABLE_TYPES_DO(INITIALIZE_VTABLE);
235 }
236 }
237
238 intptr_t* CppVtables::get_archived_vtable(MetaspaceObj::Type msotype, address obj) {
239 if (!_orig_cpp_vtptrs_inited) {
240 CPP_VTABLE_TYPES_DO(INIT_ORIG_CPP_VTPTRS);
241 _orig_cpp_vtptrs_inited = true;
242 }
243
244 assert(CDSConfig::is_dumping_archive(), "sanity");
245 int kind = -1;
246 switch (msotype) {
247 case MetaspaceObj::SymbolType:
248 case MetaspaceObj::TypeArrayU1Type:
249 case MetaspaceObj::TypeArrayU2Type:
250 case MetaspaceObj::TypeArrayU4Type:
251 case MetaspaceObj::TypeArrayU8Type:
252 case MetaspaceObj::TypeArrayOtherType:
253 case MetaspaceObj::ConstMethodType:
254 case MetaspaceObj::ConstantPoolCacheType:
255 case MetaspaceObj::AnnotationsType:
256 case MetaspaceObj::MethodCountersType:
257 case MetaspaceObj::SharedClassPathEntryType:
258 case MetaspaceObj::RecordComponentType:
259 // These have no vtables.
260 break;
261 case MetaspaceObj::MethodDataType:
262 // We don't archive MethodData <-- should have been removed in removed_unsharable_info
263 ShouldNotReachHere();
264 break;
265 default:
266 for (kind = 0; kind < _num_cloned_vtable_kinds; kind ++) {
267 if (vtable_of((Metadata*)obj) == _orig_cpp_vtptrs[kind]) {
268 break;
269 }
270 }
271 if (kind >= _num_cloned_vtable_kinds) {
272 fatal("Cannot find C++ vtable for " INTPTR_FORMAT " -- you probably added"
273 " a new subtype of Klass or MetaData without updating CPP_VTABLE_TYPES_DO or the cases in this 'switch' statement",
274 p2i(obj));
275 }
276 }
277
278 if (kind >= 0) {
279 assert(kind < _num_cloned_vtable_kinds, "must be");
280 return _index[kind]->cloned_vtable();
281 } else {
282 return nullptr;
283 }
284 }
285
286 void CppVtables::zero_archived_vtables() {
287 assert(CDSConfig::is_dumping_static_archive(), "cpp tables are only dumped into static archive");
288 for (int kind = 0; kind < _num_cloned_vtable_kinds; kind ++) {
289 _index[kind]->zero();
290 }
291 }
292
293 bool CppVtables::is_valid_shared_method(const Method* m) {
294 assert(MetaspaceShared::is_in_shared_metaspace(m), "must be");
295 return vtable_of(m) == _index[Method_Kind]->cloned_vtable();
296 }