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