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/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 }
--- EOF ---