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.
22 *
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/flatArrayKlass.hpp"
33 #include "oops/inlineKlass.hpp"
34 #include "oops/instanceClassLoaderKlass.hpp"
35 #include "oops/instanceKlass.inline.hpp"
36 #include "oops/instanceMirrorKlass.hpp"
37 #include "oops/instanceRefKlass.hpp"
38 #include "oops/instanceStackChunkKlass.hpp"
39 #include "oops/methodData.hpp"
40 #include "oops/objArrayKlass.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 // Currently, the archive contains ONLY the following types of objects that have C++ vtables.
59 // NOTE: this table must be in-sync with sun.jvm.hotspot.memory.FileMapInfo::populateMetadataTypeArray().
60 #define CPP_VTABLE_TYPES_DO(f) \
61 f(ConstantPool) \
62 f(InstanceKlass) \
63 f(InstanceClassLoaderKlass) \
64 f(InstanceMirrorKlass) \
65 f(InstanceRefKlass) \
66 f(InstanceStackChunkKlass) \
67 f(Method) \
68 f(ObjArrayKlass) \
69 f(TypeArrayKlass) \
70 f(FlatArrayKlass) \
71 f(InlineKlass)
72
73 class CppVtableInfo {
74 intptr_t _vtable_size;
75 intptr_t _cloned_vtable[1];
76 public:
77 static int num_slots(int vtable_size) {
78 return 1 + vtable_size; // Need to add the space occupied by _vtable_size;
79 }
80 int vtable_size() { return int(uintx(_vtable_size)); }
81 void set_vtable_size(int n) { _vtable_size = intptr_t(n); }
82 intptr_t* cloned_vtable() { return &_cloned_vtable[0]; }
83 void zero() { memset(_cloned_vtable, 0, sizeof(intptr_t) * vtable_size()); }
84 // Returns the address of the next CppVtableInfo that can be placed immediately after this CppVtableInfo
85 static size_t byte_size(int vtable_size) {
86 CppVtableInfo i;
87 return pointer_delta(&i._cloned_vtable[vtable_size], &i, sizeof(u1));
88 }
89 };
90
91 static inline intptr_t* vtable_of(const Metadata* m) {
92 return *((intptr_t**)m);
93 }
94
95 template <class T> class CppVtableCloner {
96 static int get_vtable_length(const char* name);
97
98 public:
99 // Allocate a clone of the vtable of T from the shared metaspace;
100 // Initialize the contents of this clone.
101 static CppVtableInfo* allocate_and_initialize(const char* name);
102
103 // Copy the contents of the vtable of T into info->_cloned_vtable;
104 static void initialize(const char* name, CppVtableInfo* info);
105
106 static void init_orig_cpp_vtptr(int kind);
107 };
108
109 template <class T>
110 CppVtableInfo* CppVtableCloner<T>::allocate_and_initialize(const char* name) {
111 int n = get_vtable_length(name);
112 CppVtableInfo* info =
113 (CppVtableInfo*)ArchiveBuilder::current()->rw_region()->allocate(CppVtableInfo::byte_size(n));
114 info->set_vtable_size(n);
115 initialize(name, info);
116 return info;
117 }
118
119 template <class T>
120 void CppVtableCloner<T>::initialize(const char* name, CppVtableInfo* info) {
121 T tmp; // Allocate temporary dummy metadata object to get to the original vtable.
122 int n = info->vtable_size();
123 intptr_t* srcvtable = vtable_of(&tmp);
124 intptr_t* dstvtable = info->cloned_vtable();
125
126 // We already checked (and, if necessary, adjusted n) when the vtables were allocated, so we are
127 // safe to do memcpy.
128 log_debug(cds, vtables)("Copying %3d vtable entries for %s", n, name);
129 memcpy(dstvtable, srcvtable, sizeof(intptr_t) * n);
130 }
131
132 // To determine the size of the vtable for each type, we use the following
133 // trick by declaring 2 subclasses:
134 //
135 // class CppVtableTesterA: public InstanceKlass {virtual int last_virtual_method() {return 1;} };
136 // class CppVtableTesterB: public InstanceKlass {virtual void* last_virtual_method() {return nullptr}; };
137 //
138 // CppVtableTesterA and CppVtableTesterB's vtables have the following properties:
139 // - Their size (N+1) is exactly one more than the size of InstanceKlass's vtable (N)
140 // - The first N entries have are exactly the same as in InstanceKlass's vtable.
141 // - Their last entry is different.
142 //
143 // So to determine the value of N, we just walk CppVtableTesterA and CppVtableTesterB's tables
144 // and find the first entry that's different.
145 //
146 // This works on all C++ compilers supported by Oracle, but you may need to tweak it for more
147 // esoteric compilers.
148
149 template <class T> class CppVtableTesterB: public T {
150 public:
151 virtual int last_virtual_method() {return 1;}
152 };
153
154 template <class T> class CppVtableTesterA : public T {
155 public:
156 virtual void* last_virtual_method() {
157 // Make this different than CppVtableTesterB::last_virtual_method so the C++
158 // compiler/linker won't alias the two functions.
159 return nullptr;
160 }
161 };
162
163 template <class T>
164 int CppVtableCloner<T>::get_vtable_length(const char* name) {
165 CppVtableTesterA<T> a;
166 CppVtableTesterB<T> b;
167
168 intptr_t* avtable = vtable_of(&a);
169 intptr_t* bvtable = vtable_of(&b);
170
171 // Start at slot 1, because slot 0 may be RTTI (on Solaris/Sparc)
172 int vtable_len = 1;
173 for (; ; vtable_len++) {
174 if (avtable[vtable_len] != bvtable[vtable_len]) {
175 break;
176 }
177 }
178 log_debug(cds, vtables)("Found %3d vtable entries for %s", vtable_len, name);
179
180 return vtable_len;
181 }
182
183 #define ALLOCATE_AND_INITIALIZE_VTABLE(c) \
184 _index[c##_Kind] = CppVtableCloner<c>::allocate_and_initialize(#c); \
185 ArchivePtrMarker::mark_pointer(&_index[c##_Kind]);
186
187 #define INITIALIZE_VTABLE(c) \
188 CppVtableCloner<c>::initialize(#c, _index[c##_Kind]);
189
190 #define INIT_ORIG_CPP_VTPTRS(c) \
191 CppVtableCloner<c>::init_orig_cpp_vtptr(c##_Kind);
192
193 #define DECLARE_CLONED_VTABLE_KIND(c) c ## _Kind,
194
195 enum ClonedVtableKind {
196 // E.g., ConstantPool_Kind == 0, InstanceKlass_Kind == 1, etc.
197 CPP_VTABLE_TYPES_DO(DECLARE_CLONED_VTABLE_KIND)
198 _num_cloned_vtable_kinds
199 };
200
201 // This 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 static intptr_t* _orig_cpp_vtptrs[_num_cloned_vtable_kinds];
206 static bool _orig_cpp_vtptrs_inited = false;
207
208 template <class T>
209 void CppVtableCloner<T>::init_orig_cpp_vtptr(int kind) {
210 assert(kind < _num_cloned_vtable_kinds, "sanity");
211 T tmp; // Allocate temporary dummy metadata object to get to the original vtable.
212 intptr_t* srcvtable = vtable_of(&tmp);
213 _orig_cpp_vtptrs[kind] = srcvtable;
214 }
215
216 // This is the index of all the cloned vtables. E.g., for
217 // ConstantPool* cp = ....; // an archived constant pool
218 // InstanceKlass* ik = ....;// an archived class
219 // the following holds true:
220 // _index[ConstantPool_Kind]->cloned_vtable() == ((intptr_t**)cp)[0]
221 // _index[InstanceKlass_Kind]->cloned_vtable() == ((intptr_t**)ik)[0]
222 CppVtableInfo** CppVtables::_index = nullptr;
223
224 char* CppVtables::dumptime_init(ArchiveBuilder* builder) {
225 assert(CDSConfig::is_dumping_static_archive(), "cpp tables are only dumped into static archive");
226 size_t vtptrs_bytes = _num_cloned_vtable_kinds * sizeof(CppVtableInfo*);
227 _index = (CppVtableInfo**)builder->rw_region()->allocate(vtptrs_bytes);
228
229 CPP_VTABLE_TYPES_DO(ALLOCATE_AND_INITIALIZE_VTABLE);
230
231 size_t cpp_tables_size = builder->rw_region()->top() - builder->rw_region()->base();
232 builder->alloc_stats()->record_cpp_vtables((int)cpp_tables_size);
233
234 return (char*)_index;
235 }
236
237 void CppVtables::serialize(SerializeClosure* soc) {
238 soc->do_ptr(&_index);
239 if (soc->reading()) {
240 CPP_VTABLE_TYPES_DO(INITIALIZE_VTABLE);
241 }
242 }
243
244 intptr_t* CppVtables::get_archived_vtable(MetaspaceObj::Type msotype, address obj) {
245 if (!_orig_cpp_vtptrs_inited) {
246 CPP_VTABLE_TYPES_DO(INIT_ORIG_CPP_VTPTRS);
247 _orig_cpp_vtptrs_inited = true;
248 }
249
250 assert(CDSConfig::is_dumping_archive(), "sanity");
251 int kind = -1;
252 switch (msotype) {
253 case MetaspaceObj::SymbolType:
254 case MetaspaceObj::TypeArrayU1Type:
255 case MetaspaceObj::TypeArrayU2Type:
256 case MetaspaceObj::TypeArrayU4Type:
257 case MetaspaceObj::TypeArrayU8Type:
258 case MetaspaceObj::TypeArrayOtherType:
259 case MetaspaceObj::ConstMethodType:
260 case MetaspaceObj::ConstantPoolCacheType:
261 case MetaspaceObj::AnnotationsType:
262 case MetaspaceObj::MethodCountersType:
263 case MetaspaceObj::SharedClassPathEntryType:
264 case MetaspaceObj::RecordComponentType:
265 // These have no vtables.
266 break;
267 case MetaspaceObj::MethodDataType:
268 // We don't archive MethodData <-- should have been removed in removed_unsharable_info
269 ShouldNotReachHere();
270 break;
271 default:
272 for (kind = 0; kind < _num_cloned_vtable_kinds; kind ++) {
273 if (vtable_of((Metadata*)obj) == _orig_cpp_vtptrs[kind]) {
274 break;
275 }
276 }
277 if (kind >= _num_cloned_vtable_kinds) {
278 fatal("Cannot find C++ vtable for " INTPTR_FORMAT " -- you probably added"
279 " a new subtype of Klass or MetaData without updating CPP_VTABLE_TYPES_DO or the cases in this 'switch' statement",
280 p2i(obj));
281 }
282 }
283
284 if (kind >= 0) {
285 assert(kind < _num_cloned_vtable_kinds, "must be");
286 return _index[kind]->cloned_vtable();
287 } else {
288 return nullptr;
289 }
290 }
291
292 void CppVtables::zero_archived_vtables() {
293 assert(CDSConfig::is_dumping_static_archive(), "cpp tables are only dumped into static archive");
294 for (int kind = 0; kind < _num_cloned_vtable_kinds; kind ++) {
295 _index[kind]->zero();
296 }
297 }
298
299 bool CppVtables::is_valid_shared_method(const Method* m) {
300 assert(MetaspaceShared::is_in_shared_metaspace(m), "must be");
301 return vtable_of(m) == _index[Method_Kind]->cloned_vtable();
302 }