1 /*
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  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/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:
 68   static int num_slots(int vtable_size) {
 69     return 1 + vtable_size; // Need to add the space occupied by _vtable_size;
 70   }
 71   int vtable_size()           { return int(uintx(_vtable_size)); }
 72   void set_vtable_size(int n) { _vtable_size = intptr_t(n); }
 73   intptr_t* cloned_vtable()   { return &_cloned_vtable[0]; }
 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
 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 
 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>
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>
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:
142   virtual int last_virtual_method() {return 1;}
143 };
144 
145 template <class T> class CppVtableTesterA : public T {
146 public:
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>
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>
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 
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 
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 
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 
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 
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 }