1 /*
2 * Copyright (c) 2020, 2021, 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/cppVtables.hpp"
29 #include "cds/metaspaceShared.hpp"
30 #include "logging/log.hpp"
31 #include "oops/instanceClassLoaderKlass.hpp"
32 #include "oops/instanceMirrorKlass.hpp"
33 #include "oops/instanceRefKlass.hpp"
34 #include "oops/methodData.hpp"
35 #include "oops/objArrayKlass.hpp"
36 #include "oops/typeArrayKlass.hpp"
37 #include "runtime/arguments.hpp"
38 #include "utilities/globalDefinitions.hpp"
39
40 // Objects of the Metadata types (such as Klass and ConstantPool) have C++ vtables.
41 // (In GCC this is the field <Type>::_vptr, i.e., first word in the object.)
42 //
43 // Addresses of the vtables and the methods may be different across JVM runs,
44 // if libjvm.so is dynamically loaded at a different base address.
45 //
46 // To ensure that the Metadata objects in the CDS archive always have the correct vtable:
47 //
48 // + at dump time: we redirect the _vptr to point to our own vtables inside
49 // the CDS image
50 // + at run time: we clone the actual contents of the vtables from libjvm.so
51 // into our own tables.
52
53 // Currently, the archive contains ONLY the following types of objects that have C++ vtables.
54 #define CPP_VTABLE_TYPES_DO(f) \
55 f(ConstantPool) \
56 f(InstanceKlass) \
57 f(InstanceClassLoaderKlass) \
58 f(InstanceMirrorKlass) \
59 f(InstanceRefKlass) \
60 f(Method) \
61 f(ObjArrayKlass) \
62 f(TypeArrayKlass)
63
64 class CppVtableInfo {
65 intptr_t _vtable_size;
66 intptr_t _cloned_vtable[1];
67 public:
num_slots(int vtable_size)68 static int num_slots(int vtable_size) {
69 return 1 + vtable_size; // Need to add the space occupied by _vtable_size;
70 }
vtable_size()71 int vtable_size() { return int(uintx(_vtable_size)); }
set_vtable_size(int n)72 void set_vtable_size(int n) { _vtable_size = intptr_t(n); }
cloned_vtable()73 intptr_t* cloned_vtable() { return &_cloned_vtable[0]; }
zero()74 void zero() { memset(_cloned_vtable, 0, sizeof(intptr_t) * vtable_size()); }
75 // Returns the address of the next CppVtableInfo that can be placed immediately after this CppVtableInfo
byte_size(int vtable_size)76 static size_t byte_size(int vtable_size) {
77 CppVtableInfo i;
78 return pointer_delta(&i._cloned_vtable[vtable_size], &i, sizeof(u1));
79 }
80 };
81
vtable_of(const Metadata * m)82 static inline intptr_t* vtable_of(const Metadata* m) {
83 return *((intptr_t**)m);
84 }
85
86 template <class T> class CppVtableCloner {
87 static int get_vtable_length(const char* name);
88
89 public:
90 // Allocate a clone of the vtable of T from the shared metaspace;
91 // Initialize the contents of this clone.
92 static CppVtableInfo* allocate_and_initialize(const char* name);
93
94 // Copy the contents of the vtable of T into info->_cloned_vtable;
95 static void initialize(const char* name, CppVtableInfo* info);
96
97 static void init_orig_cpp_vtptr(int kind);
98 };
99
100 template <class T>
allocate_and_initialize(const char * name)101 CppVtableInfo* CppVtableCloner<T>::allocate_and_initialize(const char* name) {
102 int n = get_vtable_length(name);
103 CppVtableInfo* info =
104 (CppVtableInfo*)ArchiveBuilder::current()->rw_region()->allocate(CppVtableInfo::byte_size(n));
105 info->set_vtable_size(n);
106 initialize(name, info);
107 return info;
108 }
109
110 template <class T>
initialize(const char * name,CppVtableInfo * info)111 void CppVtableCloner<T>::initialize(const char* name, CppVtableInfo* info) {
112 T tmp; // Allocate temporary dummy metadata object to get to the original vtable.
113 int n = info->vtable_size();
114 intptr_t* srcvtable = vtable_of(&tmp);
115 intptr_t* dstvtable = info->cloned_vtable();
116
117 // We already checked (and, if necessary, adjusted n) when the vtables were allocated, so we are
118 // safe to do memcpy.
119 log_debug(cds, vtables)("Copying %3d vtable entries for %s", n, name);
120 memcpy(dstvtable, srcvtable, sizeof(intptr_t) * n);
121 }
122
123 // To determine the size of the vtable for each type, we use the following
124 // trick by declaring 2 subclasses:
125 //
126 // class CppVtableTesterA: public InstanceKlass {virtual int last_virtual_method() {return 1;} };
127 // class CppVtableTesterB: public InstanceKlass {virtual void* last_virtual_method() {return NULL}; };
128 //
129 // CppVtableTesterA and CppVtableTesterB's vtables have the following properties:
130 // - Their size (N+1) is exactly one more than the size of InstanceKlass's vtable (N)
131 // - The first N entries have are exactly the same as in InstanceKlass's vtable.
132 // - Their last entry is different.
133 //
134 // So to determine the value of N, we just walk CppVtableTesterA and CppVtableTesterB's tables
135 // and find the first entry that's different.
136 //
137 // This works on all C++ compilers supported by Oracle, but you may need to tweak it for more
138 // esoteric compilers.
139
140 template <class T> class CppVtableTesterB: public T {
141 public:
last_virtual_method()142 virtual int last_virtual_method() {return 1;}
143 };
144
145 template <class T> class CppVtableTesterA : public T {
146 public:
last_virtual_method()147 virtual void* last_virtual_method() {
148 // Make this different than CppVtableTesterB::last_virtual_method so the C++
149 // compiler/linker won't alias the two functions.
150 return NULL;
151 }
152 };
153
154 template <class T>
get_vtable_length(const char * name)155 int CppVtableCloner<T>::get_vtable_length(const char* name) {
156 CppVtableTesterA<T> a;
157 CppVtableTesterB<T> b;
158
159 intptr_t* avtable = vtable_of(&a);
160 intptr_t* bvtable = vtable_of(&b);
161
162 // Start at slot 1, because slot 0 may be RTTI (on Solaris/Sparc)
163 int vtable_len = 1;
164 for (; ; vtable_len++) {
165 if (avtable[vtable_len] != bvtable[vtable_len]) {
166 break;
167 }
168 }
169 log_debug(cds, vtables)("Found %3d vtable entries for %s", vtable_len, name);
170
171 return vtable_len;
172 }
173
174 #define ALLOCATE_AND_INITIALIZE_VTABLE(c) \
175 _index[c##_Kind] = CppVtableCloner<c>::allocate_and_initialize(#c); \
176 ArchivePtrMarker::mark_pointer(&_index[c##_Kind]);
177
178 #define INITIALIZE_VTABLE(c) \
179 CppVtableCloner<c>::initialize(#c, _index[c##_Kind]);
180
181 #define INIT_ORIG_CPP_VTPTRS(c) \
182 CppVtableCloner<c>::init_orig_cpp_vtptr(c##_Kind);
183
184 #define DECLARE_CLONED_VTABLE_KIND(c) c ## _Kind,
185
186 enum ClonedVtableKind {
187 // E.g., ConstantPool_Kind == 0, InstanceKlass_Kind == 1, etc.
188 CPP_VTABLE_TYPES_DO(DECLARE_CLONED_VTABLE_KIND)
189 _num_cloned_vtable_kinds
190 };
191
192 // This is a map of all the original vtptrs. E.g., for
193 // ConstantPool *cp = new (...) ConstantPool(...) ; // a dynamically allocated constant pool
194 // the following holds true:
195 // _orig_cpp_vtptrs[ConstantPool_Kind] == ((intptr_t**)cp)[0]
196 static intptr_t* _orig_cpp_vtptrs[_num_cloned_vtable_kinds];
197 static bool _orig_cpp_vtptrs_inited = false;
198
199 template <class T>
init_orig_cpp_vtptr(int kind)200 void CppVtableCloner<T>::init_orig_cpp_vtptr(int kind) {
201 assert(kind < _num_cloned_vtable_kinds, "sanity");
202 T tmp; // Allocate temporary dummy metadata object to get to the original vtable.
203 intptr_t* srcvtable = vtable_of(&tmp);
204 _orig_cpp_vtptrs[kind] = srcvtable;
205 }
206
207 // This is the index of all the cloned vtables. E.g., for
208 // ConstantPool* cp = ....; // an archived constant pool
209 // InstanceKlass* ik = ....;// an archived class
210 // the following holds true:
211 // _index[ConstantPool_Kind]->cloned_vtable() == ((intptr_t**)cp)[0]
212 // _index[InstanceKlass_Kind]->cloned_vtable() == ((intptr_t**)ik)[0]
213 CppVtableInfo** CppVtables::_index = NULL;
214
dumptime_init(ArchiveBuilder * builder)215 char* CppVtables::dumptime_init(ArchiveBuilder* builder) {
216 assert(DumpSharedSpaces, "must");
217 size_t vtptrs_bytes = _num_cloned_vtable_kinds * sizeof(CppVtableInfo*);
218 _index = (CppVtableInfo**)builder->rw_region()->allocate(vtptrs_bytes);
219
220 CPP_VTABLE_TYPES_DO(ALLOCATE_AND_INITIALIZE_VTABLE);
221
222 size_t cpp_tables_size = builder->rw_region()->top() - builder->rw_region()->base();
223 builder->alloc_stats()->record_cpp_vtables((int)cpp_tables_size);
224
225 return (char*)_index;
226 }
227
serialize(SerializeClosure * soc)228 void CppVtables::serialize(SerializeClosure* soc) {
229 soc->do_ptr((void**)&_index);
230 if (soc->reading()) {
231 CPP_VTABLE_TYPES_DO(INITIALIZE_VTABLE);
232 }
233 }
234
get_archived_vtable(MetaspaceObj::Type msotype,address obj)235 intptr_t* CppVtables::get_archived_vtable(MetaspaceObj::Type msotype, address obj) {
236 if (!_orig_cpp_vtptrs_inited) {
237 CPP_VTABLE_TYPES_DO(INIT_ORIG_CPP_VTPTRS);
238 _orig_cpp_vtptrs_inited = true;
239 }
240
241 Arguments::assert_is_dumping_archive();
242 int kind = -1;
243 switch (msotype) {
244 case MetaspaceObj::SymbolType:
245 case MetaspaceObj::TypeArrayU1Type:
246 case MetaspaceObj::TypeArrayU2Type:
247 case MetaspaceObj::TypeArrayU4Type:
248 case MetaspaceObj::TypeArrayU8Type:
249 case MetaspaceObj::TypeArrayOtherType:
250 case MetaspaceObj::ConstMethodType:
251 case MetaspaceObj::ConstantPoolCacheType:
252 case MetaspaceObj::AnnotationsType:
253 case MetaspaceObj::MethodCountersType:
254 case MetaspaceObj::RecordComponentType:
255 // These have no vtables.
256 break;
257 case MetaspaceObj::MethodDataType:
258 // We don't archive MethodData <-- should have been removed in removed_unsharable_info
259 ShouldNotReachHere();
260 break;
261 default:
262 for (kind = 0; kind < _num_cloned_vtable_kinds; kind ++) {
263 if (vtable_of((Metadata*)obj) == _orig_cpp_vtptrs[kind]) {
264 break;
265 }
266 }
267 if (kind >= _num_cloned_vtable_kinds) {
268 fatal("Cannot find C++ vtable for " INTPTR_FORMAT " -- you probably added"
269 " a new subtype of Klass or MetaData without updating CPP_VTABLE_TYPES_DO",
270 p2i(obj));
271 }
272 }
273
274 if (kind >= 0) {
275 assert(kind < _num_cloned_vtable_kinds, "must be");
276 return _index[kind]->cloned_vtable();
277 } else {
278 return NULL;
279 }
280 }
281
zero_archived_vtables()282 void CppVtables::zero_archived_vtables() {
283 assert(DumpSharedSpaces, "dump-time only");
284 for (int kind = 0; kind < _num_cloned_vtable_kinds; kind ++) {
285 _index[kind]->zero();
286 }
287 }
288
is_valid_shared_method(const Method * m)289 bool CppVtables::is_valid_shared_method(const Method* m) {
290 assert(MetaspaceShared::is_in_shared_metaspace(m), "must be");
291 return vtable_of(m) == _index[Method_Kind]->cloned_vtable();
292 }
293