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]; // Pseudo flexible array member.
76 static size_t cloned_vtable_offset() { return offset_of(CppVtableInfo, _cloned_vtable); }
77 public:
78 int vtable_size() { return int(uintx(_vtable_size)); }
79 void set_vtable_size(int n) { _vtable_size = intptr_t(n); }
80 // Using _cloned_vtable[i] for i > 0 causes undefined behavior. We use address calculation instead.
81 intptr_t* cloned_vtable() { return (intptr_t*)((char*)this + cloned_vtable_offset()); }
82 void zero() { memset(cloned_vtable(), 0, sizeof(intptr_t) * vtable_size()); }
83 // Returns the address of the next CppVtableInfo that can be placed immediately after this CppVtableInfo
84 static size_t byte_size(int vtable_size) {
85 return cloned_vtable_offset() + (sizeof(intptr_t) * vtable_size);
86 }
87 };
88
89 static inline intptr_t* vtable_of(const Metadata* m) {
90 return *((intptr_t**)m);
91 }
92
93 template <class T> class CppVtableCloner {
94 static int get_vtable_length(const char* name);
95
96 public:
97 // Allocate a clone of the vtable of T from the shared metaspace;
98 // Initialize the contents of this clone.
99 static CppVtableInfo* allocate_and_initialize(const char* name);
100
101 // Copy the contents of the vtable of T into info->_cloned_vtable;
102 static void initialize(const char* name, CppVtableInfo* info);
103
104 static void init_orig_cpp_vtptr(int kind);
105 };
106
107 template <class T>
108 CppVtableInfo* CppVtableCloner<T>::allocate_and_initialize(const char* name) {
109 int n = get_vtable_length(name);
110 CppVtableInfo* info =
111 (CppVtableInfo*)ArchiveBuilder::current()->rw_region()->allocate(CppVtableInfo::byte_size(n));
112 info->set_vtable_size(n);
113 initialize(name, info);
114 return info;
115 }
116
117 template <class T>
118 void CppVtableCloner<T>::initialize(const char* name, CppVtableInfo* info) {
119 T tmp; // Allocate temporary dummy metadata object to get to the original vtable.
120 int n = info->vtable_size();
121 intptr_t* srcvtable = vtable_of(&tmp);
122 intptr_t* dstvtable = info->cloned_vtable();
123
124 // We already checked (and, if necessary, adjusted n) when the vtables were allocated, so we are
125 // safe to do memcpy.
126 log_debug(cds, vtables)("Copying %3d vtable entries for %s", n, name);
127 memcpy(dstvtable, srcvtable, sizeof(intptr_t) * n);
128 }
129
130 // To determine the size of the vtable for each type, we use the following
131 // trick by declaring 2 subclasses:
132 //
133 // class CppVtableTesterA: public InstanceKlass {virtual int last_virtual_method() {return 1;} };
134 // class CppVtableTesterB: public InstanceKlass {virtual void* last_virtual_method() {return nullptr}; };
135 //
136 // CppVtableTesterA and CppVtableTesterB's vtables have the following properties:
137 // - Their size (N+1) is exactly one more than the size of InstanceKlass's vtable (N)
138 // - The first N entries have are exactly the same as in InstanceKlass's vtable.
139 // - Their last entry is different.
140 //
141 // So to determine the value of N, we just walk CppVtableTesterA and CppVtableTesterB's tables
142 // and find the first entry that's different.
143 //
144 // This works on all C++ compilers supported by Oracle, but you may need to tweak it for more
145 // esoteric compilers.
146
147 template <class T> class CppVtableTesterB: public T {
148 public:
149 virtual int last_virtual_method() {return 1;}
150 };
151
152 template <class T> class CppVtableTesterA : public T {
153 public:
154 virtual void* last_virtual_method() {
155 // Make this different than CppVtableTesterB::last_virtual_method so the C++
156 // compiler/linker won't alias the two functions.
157 return nullptr;
158 }
159 };
160
161 template <class T>
162 int CppVtableCloner<T>::get_vtable_length(const char* name) {
163 CppVtableTesterA<T> a;
164 CppVtableTesterB<T> b;
165
166 intptr_t* avtable = vtable_of(&a);
167 intptr_t* bvtable = vtable_of(&b);
168
169 // Start at slot 1, because slot 0 may be RTTI (on Solaris/Sparc)
170 int vtable_len = 1;
171 for (; ; vtable_len++) {
172 if (avtable[vtable_len] != bvtable[vtable_len]) {
173 break;
174 }
175 }
176 log_debug(cds, vtables)("Found %3d vtable entries for %s", vtable_len, name);
177
178 return vtable_len;
179 }
180
181 #define ALLOCATE_AND_INITIALIZE_VTABLE(c) \
182 _index[c##_Kind] = CppVtableCloner<c>::allocate_and_initialize(#c); \
183 ArchivePtrMarker::mark_pointer(&_index[c##_Kind]);
184
185 #define INITIALIZE_VTABLE(c) \
186 CppVtableCloner<c>::initialize(#c, _index[c##_Kind]);
187
188 #define INIT_ORIG_CPP_VTPTRS(c) \
189 CppVtableCloner<c>::init_orig_cpp_vtptr(c##_Kind);
190
191 #define DECLARE_CLONED_VTABLE_KIND(c) c ## _Kind,
192
193 enum ClonedVtableKind {
194 // E.g., ConstantPool_Kind == 0, InstanceKlass_Kind == 1, etc.
195 CPP_VTABLE_TYPES_DO(DECLARE_CLONED_VTABLE_KIND)
196 _num_cloned_vtable_kinds
197 };
198
199 // This is a map of all the original vtptrs. E.g., for
200 // ConstantPool *cp = new (...) ConstantPool(...) ; // a dynamically allocated constant pool
201 // the following holds true:
202 // _orig_cpp_vtptrs[ConstantPool_Kind] == ((intptr_t**)cp)[0]
203 static intptr_t* _orig_cpp_vtptrs[_num_cloned_vtable_kinds];
204 static bool _orig_cpp_vtptrs_inited = false;
205
206 template <class T>
207 void CppVtableCloner<T>::init_orig_cpp_vtptr(int kind) {
208 assert(kind < _num_cloned_vtable_kinds, "sanity");
209 T tmp; // Allocate temporary dummy metadata object to get to the original vtable.
210 intptr_t* srcvtable = vtable_of(&tmp);
211 _orig_cpp_vtptrs[kind] = srcvtable;
212 }
213
214 // This is the index of all the cloned vtables. E.g., for
215 // ConstantPool* cp = ....; // an archived constant pool
216 // InstanceKlass* ik = ....;// an archived class
217 // the following holds true:
218 // _index[ConstantPool_Kind]->cloned_vtable() == ((intptr_t**)cp)[0]
219 // _index[InstanceKlass_Kind]->cloned_vtable() == ((intptr_t**)ik)[0]
220 static CppVtableInfo* _index[_num_cloned_vtable_kinds];
221
222 // Vtables are all fixed offsets from ArchiveBuilder::current()->mapped_base()
223 // E.g. ConstantPool is at offset 0x58. We can archive these offsets in the
224 // RO region and use them to alculate their location at runtime without storing
225 // the pointers in the RW region
226 char* CppVtables::_vtables_serialized_base = nullptr;
227
228 void CppVtables::dumptime_init(ArchiveBuilder* builder) {
229 assert(CDSConfig::is_dumping_static_archive(), "cpp tables are only dumped into static archive");
230
231 CPP_VTABLE_TYPES_DO(ALLOCATE_AND_INITIALIZE_VTABLE);
232
233 size_t cpp_tables_size = builder->rw_region()->top() - builder->rw_region()->base();
234 builder->alloc_stats()->record_cpp_vtables((int)cpp_tables_size);
235 }
236
237 void CppVtables::serialize(SerializeClosure* soc) {
238 if (!soc->reading()) {
239 _vtables_serialized_base = (char*)ArchiveBuilder::current()->buffer_top();
240 }
241 for (int i = 0; i < _num_cloned_vtable_kinds; i++) {
242 soc->do_ptr(&_index[i]);
243 }
244 if (soc->reading()) {
245 CPP_VTABLE_TYPES_DO(INITIALIZE_VTABLE);
246 }
247 }
248
249 intptr_t* CppVtables::get_archived_vtable(MetaspaceObj::Type msotype, address obj) {
250 if (!_orig_cpp_vtptrs_inited) {
251 CPP_VTABLE_TYPES_DO(INIT_ORIG_CPP_VTPTRS);
252 _orig_cpp_vtptrs_inited = true;
253 }
254
255 assert(CDSConfig::is_dumping_archive(), "sanity");
256 int kind = -1;
257 switch (msotype) {
258 case MetaspaceObj::SymbolType:
259 case MetaspaceObj::TypeArrayU1Type:
260 case MetaspaceObj::TypeArrayU2Type:
261 case MetaspaceObj::TypeArrayU4Type:
262 case MetaspaceObj::TypeArrayU8Type:
263 case MetaspaceObj::TypeArrayOtherType:
264 case MetaspaceObj::ConstMethodType:
265 case MetaspaceObj::ConstantPoolCacheType:
266 case MetaspaceObj::AnnotationsType:
267 case MetaspaceObj::MethodCountersType:
268 case MetaspaceObj::SharedClassPathEntryType:
269 case MetaspaceObj::RecordComponentType:
270 // These have no vtables.
271 break;
272 case MetaspaceObj::MethodDataType:
273 // We don't archive MethodData <-- should have been removed in removed_unsharable_info
274 ShouldNotReachHere();
275 break;
276 default:
277 for (kind = 0; kind < _num_cloned_vtable_kinds; kind ++) {
278 if (vtable_of((Metadata*)obj) == _orig_cpp_vtptrs[kind]) {
279 break;
280 }
281 }
282 if (kind >= _num_cloned_vtable_kinds) {
283 fatal("Cannot find C++ vtable for " INTPTR_FORMAT " -- you probably added"
284 " a new subtype of Klass or MetaData without updating CPP_VTABLE_TYPES_DO or the cases in this 'switch' statement",
285 p2i(obj));
286 }
287 }
288
289 if (kind >= 0) {
290 assert(kind < _num_cloned_vtable_kinds, "must be");
291 return _index[kind]->cloned_vtable();
292 } else {
293 return nullptr;
294 }
295 }
296
297 void CppVtables::zero_archived_vtables() {
298 assert(CDSConfig::is_dumping_static_archive(), "cpp tables are only dumped into static archive");
299 for (int kind = 0; kind < _num_cloned_vtable_kinds; kind ++) {
300 _index[kind]->zero();
301 }
302 }
303
304 bool CppVtables::is_valid_shared_method(const Method* m) {
305 assert(MetaspaceShared::is_in_shared_metaspace(m), "must be");
306 return vtable_of(m) == _index[Method_Kind]->cloned_vtable();
307 }