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/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/methodCounters.hpp"
 37 #include "oops/methodData.hpp"
 38 #include "oops/trainingData.hpp"
 39 #include "oops/objArrayKlass.hpp"
 40 #include "oops/typeArrayKlass.hpp"
 41 #include "runtime/arguments.hpp"
 42 #include "utilities/globalDefinitions.hpp"
 43 
 44 // Objects of the Metadata types (such as Klass and ConstantPool) have C++ vtables.
 45 // (In GCC this is the field <Type>::_vptr, i.e., first word in the object.)
 46 //
 47 // Addresses of the vtables and the methods may be different across JVM runs,
 48 // if libjvm.so is dynamically loaded at a different base address.
 49 //
 50 // To ensure that the Metadata objects in the CDS archive always have the correct vtable:
 51 //
 52 // + at dump time:  we redirect the _vptr to point to our own vtables inside
 53 //                  the CDS image
 54 // + at run time:   we clone the actual contents of the vtables from libjvm.so
 55 //                  into our own tables.
 56 
 57 // Currently, the archive contains ONLY the following types of objects that have C++ vtables.
 58 #define CPP_VTABLE_TYPES_DO(f) \
 59   f(ConstantPool) \
 60   f(InstanceKlass) \
 61   f(InstanceClassLoaderKlass) \
 62   f(InstanceMirrorKlass) \
 63   f(InstanceRefKlass) \
 64   f(InstanceStackChunkKlass) \
 65   f(Method) \
 66   f(MethodData)                \
 67   f(MethodCounters)            \
 68   f(ObjArrayKlass) \
 69   f(TypeArrayKlass)            \
 70   f(KlassTrainingData)         \
 71   f(MethodTrainingData)        \
 72   f(CompileTrainingData)
 73 
 74 class CppVtableInfo {
 75   intptr_t _vtable_size;
 76   intptr_t _cloned_vtable[1]; // Pseudo flexible array member.
 77   static size_t cloned_vtable_offset() { return offset_of(CppVtableInfo, _cloned_vtable); }
 78 public:
 79   int vtable_size()           { return int(uintx(_vtable_size)); }
 80   void set_vtable_size(int n) { _vtable_size = intptr_t(n); }
 81   // Using _cloned_vtable[i] for i > 0 causes undefined behavior. We use address calculation instead.
 82   intptr_t* cloned_vtable()   { return (intptr_t*)((char*)this + cloned_vtable_offset()); }
 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     return cloned_vtable_offset() + (sizeof(intptr_t) * vtable_size);
 87   }
 88 };
 89 
 90 static inline intptr_t* vtable_of(const Metadata* m) {
 91   return *((intptr_t**)m);
 92 }
 93 
 94 template <class T> class CppVtableCloner {
 95   static int get_vtable_length(const char* name);
 96 
 97 public:
 98   // Allocate a clone of the vtable of T from the shared metaspace;
 99   // Initialize the contents of this clone.
100   static CppVtableInfo* allocate_and_initialize(const char* name);
101 
102   // Copy the contents of the vtable of T into info->_cloned_vtable;
103   static void initialize(const char* name, CppVtableInfo* info);
104 
105   static void init_orig_cpp_vtptr(int kind);
106 };
107 
108 template <class T>
109 CppVtableInfo* CppVtableCloner<T>::allocate_and_initialize(const char* name) {
110   int n = get_vtable_length(name);
111   CppVtableInfo* info =
112       (CppVtableInfo*)ArchiveBuilder::current()->rw_region()->allocate(CppVtableInfo::byte_size(n));
113   info->set_vtable_size(n);
114   initialize(name, info);
115   return info;
116 }
117 
118 template <class T>
119 void CppVtableCloner<T>::initialize(const char* name, CppVtableInfo* info) {
120   T tmp; // Allocate temporary dummy metadata object to get to the original vtable.
121   int n = info->vtable_size();
122   intptr_t* srcvtable = vtable_of(&tmp);
123   intptr_t* dstvtable = info->cloned_vtable();
124 
125   // We already checked (and, if necessary, adjusted n) when the vtables were allocated, so we are
126   // safe to do memcpy.
127   log_debug(cds, vtables)("Copying %3d vtable entries for %s", n, name);
128   memcpy(dstvtable, srcvtable, sizeof(intptr_t) * n);
129 }
130 
131 // To determine the size of the vtable for each type, we use the following
132 // trick by declaring 2 subclasses:
133 //
134 //   class CppVtableTesterA: public InstanceKlass {virtual int   last_virtual_method() {return 1;}    };
135 //   class CppVtableTesterB: public InstanceKlass {virtual void* last_virtual_method() {return nullptr}; };
136 //
137 // CppVtableTesterA and CppVtableTesterB's vtables have the following properties:
138 // - Their size (N+1) is exactly one more than the size of InstanceKlass's vtable (N)
139 // - The first N entries have are exactly the same as in InstanceKlass's vtable.
140 // - Their last entry is different.
141 //
142 // So to determine the value of N, we just walk CppVtableTesterA and CppVtableTesterB's tables
143 // and find the first entry that's different.
144 //
145 // This works on all C++ compilers supported by Oracle, but you may need to tweak it for more
146 // esoteric compilers.
147 
148 template <class T> class CppVtableTesterB: public T {
149 public:
150   virtual int last_virtual_method() {return 1;}
151 };
152 
153 template <class T> class CppVtableTesterA : public T {
154 public:
155   virtual void* last_virtual_method() {
156     // Make this different than CppVtableTesterB::last_virtual_method so the C++
157     // compiler/linker won't alias the two functions.
158     return nullptr;
159   }
160 };
161 
162 template <class T>
163 int CppVtableCloner<T>::get_vtable_length(const char* name) {
164   CppVtableTesterA<T> a;
165   CppVtableTesterB<T> b;
166 
167   intptr_t* avtable = vtable_of(&a);
168   intptr_t* bvtable = vtable_of(&b);
169 
170   // Start at slot 1, because slot 0 may be RTTI (on Solaris/Sparc)
171   int vtable_len = 1;
172   for (; ; vtable_len++) {
173     if (avtable[vtable_len] != bvtable[vtable_len]) {
174       break;
175     }
176   }
177   log_debug(cds, vtables)("Found   %3d vtable entries for %s", vtable_len, name);
178 
179   return vtable_len;
180 }
181 
182 #define ALLOCATE_AND_INITIALIZE_VTABLE(c) \
183   _index[c##_Kind] = CppVtableCloner<c>::allocate_and_initialize(#c); \
184   ArchivePtrMarker::mark_pointer(&_index[c##_Kind]);
185 
186 #define INITIALIZE_VTABLE(c) \
187   CppVtableCloner<c>::initialize(#c, _index[c##_Kind]);
188 
189 #define INIT_ORIG_CPP_VTPTRS(c) \
190   CppVtableCloner<c>::init_orig_cpp_vtptr(c##_Kind);
191 
192 #define DECLARE_CLONED_VTABLE_KIND(c) c ## _Kind,
193 
194 enum ClonedVtableKind {
195   // E.g., ConstantPool_Kind == 0, InstanceKlass_Kind == 1, etc.
196   CPP_VTABLE_TYPES_DO(DECLARE_CLONED_VTABLE_KIND)
197   _num_cloned_vtable_kinds
198 };
199 
200 // This is a map of all the original vtptrs. E.g., for
201 //     ConstantPool *cp = new (...) ConstantPool(...) ; // a dynamically allocated constant pool
202 // the following holds true:
203 //     _orig_cpp_vtptrs[ConstantPool_Kind] ==  ((intptr_t**)cp)[0]
204 static intptr_t* _orig_cpp_vtptrs[_num_cloned_vtable_kinds];  // vtptrs set by the C++ compiler
205 static intptr_t* _archived_cpp_vtptrs[_num_cloned_vtable_kinds];  // vtptrs used in the static archive
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 static CppVtableInfo* _index[_num_cloned_vtable_kinds];
223 
224 // Vtables are all fixed offsets from ArchiveBuilder::current()->mapped_base()
225 // E.g. ConstantPool is at offset 0x58. We can archive these offsets in the
226 // RO region and use them to alculate their location at runtime without storing
227 // the pointers in the RW region
228 char* CppVtables::_vtables_serialized_base = nullptr;
229 
230 void CppVtables::dumptime_init(ArchiveBuilder* builder) {
231   assert(CDSConfig::is_dumping_static_archive(), "cpp tables are only dumped into static archive");
232 
233   CPP_VTABLE_TYPES_DO(ALLOCATE_AND_INITIALIZE_VTABLE);
234 
235   if (!CDSConfig::is_dumping_final_static_archive()) {
236     for (int kind = 0; kind < _num_cloned_vtable_kinds; kind++) {
237       _archived_cpp_vtptrs[kind] = _index[kind]->cloned_vtable();
238     }
239   }
240 
241   size_t cpp_tables_size = builder->rw_region()->top() - builder->rw_region()->base();
242   builder->alloc_stats()->record_cpp_vtables((int)cpp_tables_size);
243 }
244 
245 void CppVtables::serialize(SerializeClosure* soc) {
246   if (!soc->reading()) {
247     _vtables_serialized_base = (char*)ArchiveBuilder::current()->buffer_top();
248   }
249   for (int i = 0; i < _num_cloned_vtable_kinds; i++) {
250     soc->do_ptr(&_index[i]);
251   }
252   if (soc->reading()) {
253     CPP_VTABLE_TYPES_DO(INITIALIZE_VTABLE);
254   }
255 
256   if (soc->writing() && CDSConfig::is_dumping_final_static_archive()) {
257     memset(_archived_cpp_vtptrs, 0, sizeof(_archived_cpp_vtptrs));
258   }
259 
260   for (int kind = 0; kind < _num_cloned_vtable_kinds; kind++) {
261     soc->do_ptr(&_archived_cpp_vtptrs[kind]);
262   }
263 }
264 
265 intptr_t* CppVtables::get_archived_vtable(MetaspaceObj::Type msotype, address obj) {
266   if (!_orig_cpp_vtptrs_inited) {
267     CPP_VTABLE_TYPES_DO(INIT_ORIG_CPP_VTPTRS);
268     _orig_cpp_vtptrs_inited = true;
269   }
270 
271   assert(CDSConfig::is_dumping_archive(), "sanity");
272   int kind = -1;
273   switch (msotype) {
274   case MetaspaceObj::SymbolType:
275   case MetaspaceObj::TypeArrayU1Type:
276   case MetaspaceObj::TypeArrayU2Type:
277   case MetaspaceObj::TypeArrayU4Type:
278   case MetaspaceObj::TypeArrayU8Type:
279   case MetaspaceObj::TypeArrayOtherType:
280   case MetaspaceObj::ConstMethodType:
281   case MetaspaceObj::ConstantPoolCacheType:
282   case MetaspaceObj::AnnotationsType:
283   case MetaspaceObj::SharedClassPathEntryType:
284   case MetaspaceObj::RecordComponentType:
285     // These have no vtables.
286     break;
287   default:
288     for (kind = 0; kind < _num_cloned_vtable_kinds; kind ++) {
289       if (vtable_of((Metadata*)obj) == _orig_cpp_vtptrs[kind] ||
290           vtable_of((Metadata*)obj) == _archived_cpp_vtptrs[kind]) {
291         break;
292       }
293     }
294     if (kind >= _num_cloned_vtable_kinds) {
295       fatal("Cannot find C++ vtable for " INTPTR_FORMAT " -- you probably added"
296             " a new subtype of Klass or MetaData without updating CPP_VTABLE_TYPES_DO or the cases in this 'switch' statement",
297             p2i(obj));
298     }
299   }
300 
301   if (kind >= 0) {
302     assert(kind < _num_cloned_vtable_kinds, "must be");
303     return _index[kind]->cloned_vtable();
304   } else {
305     return nullptr;
306   }
307 }
308 
309 void CppVtables::zero_archived_vtables() {
310   assert(CDSConfig::is_dumping_static_archive(), "cpp tables are only dumped into static archive");
311   for (int kind = 0; kind < _num_cloned_vtable_kinds; kind ++) {
312     _index[kind]->zero();
313   }
314 }
315 
316 bool CppVtables::is_valid_shared_method(const Method* m) {
317   assert(MetaspaceShared::is_in_shared_metaspace(m), "must be");
318   return vtable_of(m) == _index[Method_Kind]->cloned_vtable();
319 }