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]; 70 public: 71 static int num_slots(int vtable_size) { 72 return 1 + vtable_size; // Need to add the space occupied by _vtable_size; 73 } 74 int vtable_size() { return int(uintx(_vtable_size)); } 75 void set_vtable_size(int n) { _vtable_size = intptr_t(n); } 76 intptr_t* cloned_vtable() { return &_cloned_vtable[0]; } 77 void zero() { memset(_cloned_vtable, 0, sizeof(intptr_t) * vtable_size()); } 78 // Returns the address of the next CppVtableInfo that can be placed immediately after this CppVtableInfo 79 static size_t byte_size(int vtable_size) { 80 CppVtableInfo i; 81 return pointer_delta(&i._cloned_vtable[vtable_size], &i, sizeof(u1)); 82 } 83 }; 84 85 static inline intptr_t* vtable_of(const Metadata* m) { 86 return *((intptr_t**)m); 87 } 88 89 template <class T> class CppVtableCloner { 90 static int get_vtable_length(const char* name); 91 92 public: 93 // Allocate a clone of the vtable of T from the shared metaspace; 94 // Initialize the contents of this clone. 95 static CppVtableInfo* allocate_and_initialize(const char* name); 96 97 // Copy the contents of the vtable of T into info->_cloned_vtable; 98 static void initialize(const char* name, CppVtableInfo* info); 99 100 static void init_orig_cpp_vtptr(int kind); 101 }; 102 103 template <class T> 104 CppVtableInfo* CppVtableCloner<T>::allocate_and_initialize(const char* name) { 105 int n = get_vtable_length(name); 106 CppVtableInfo* info = 107 (CppVtableInfo*)ArchiveBuilder::current()->rw_region()->allocate(CppVtableInfo::byte_size(n)); 108 info->set_vtable_size(n); 109 initialize(name, info); 110 return info; 111 } 112 113 template <class T> 114 void CppVtableCloner<T>::initialize(const char* name, CppVtableInfo* info) { 115 T tmp; // Allocate temporary dummy metadata object to get to the original vtable. 116 int n = info->vtable_size(); 117 intptr_t* srcvtable = vtable_of(&tmp); 118 intptr_t* dstvtable = info->cloned_vtable(); 119 120 // We already checked (and, if necessary, adjusted n) when the vtables were allocated, so we are 121 // safe to do memcpy. 122 log_debug(cds, vtables)("Copying %3d vtable entries for %s", n, name); 123 memcpy(dstvtable, srcvtable, sizeof(intptr_t) * n); 124 } 125 126 // To determine the size of the vtable for each type, we use the following 127 // trick by declaring 2 subclasses: 128 // 129 // class CppVtableTesterA: public InstanceKlass {virtual int last_virtual_method() {return 1;} }; 130 // class CppVtableTesterB: public InstanceKlass {virtual void* last_virtual_method() {return nullptr}; }; 131 // 132 // CppVtableTesterA and CppVtableTesterB's vtables have the following properties: 133 // - Their size (N+1) is exactly one more than the size of InstanceKlass's vtable (N) 134 // - The first N entries have are exactly the same as in InstanceKlass's vtable. 135 // - Their last entry is different. 136 // 137 // So to determine the value of N, we just walk CppVtableTesterA and CppVtableTesterB's tables 138 // and find the first entry that's different. 139 // 140 // This works on all C++ compilers supported by Oracle, but you may need to tweak it for more 141 // esoteric compilers. 142 143 template <class T> class CppVtableTesterB: public T { 144 public: 145 virtual int last_virtual_method() {return 1;} 146 }; 147 148 template <class T> class CppVtableTesterA : public T { 149 public: 150 virtual void* last_virtual_method() { 151 // Make this different than CppVtableTesterB::last_virtual_method so the C++ 152 // compiler/linker won't alias the two functions. 153 return nullptr; 154 } 155 }; 156 157 template <class T> 158 int CppVtableCloner<T>::get_vtable_length(const char* name) { 159 CppVtableTesterA<T> a; 160 CppVtableTesterB<T> b; 161 162 intptr_t* avtable = vtable_of(&a); 163 intptr_t* bvtable = vtable_of(&b); 164 165 // Start at slot 1, because slot 0 may be RTTI (on Solaris/Sparc) 166 int vtable_len = 1; 167 for (; ; vtable_len++) { 168 if (avtable[vtable_len] != bvtable[vtable_len]) { 169 break; 170 } 171 } 172 log_debug(cds, vtables)("Found %3d vtable entries for %s", vtable_len, name); 173 174 return vtable_len; 175 } 176 177 #define ALLOCATE_AND_INITIALIZE_VTABLE(c) \ 178 _index[c##_Kind] = CppVtableCloner<c>::allocate_and_initialize(#c); \ 179 ArchivePtrMarker::mark_pointer(&_index[c##_Kind]); 180 181 #define INITIALIZE_VTABLE(c) \ 182 CppVtableCloner<c>::initialize(#c, _index[c##_Kind]); 183 184 #define INIT_ORIG_CPP_VTPTRS(c) \ 185 CppVtableCloner<c>::init_orig_cpp_vtptr(c##_Kind); 186 187 #define DECLARE_CLONED_VTABLE_KIND(c) c ## _Kind, 188 189 enum ClonedVtableKind { 190 // E.g., ConstantPool_Kind == 0, InstanceKlass_Kind == 1, etc. 191 CPP_VTABLE_TYPES_DO(DECLARE_CLONED_VTABLE_KIND) 192 _num_cloned_vtable_kinds 193 }; 194 195 // This is a map of all the original vtptrs. E.g., for 196 // ConstantPool *cp = new (...) ConstantPool(...) ; // a dynamically allocated constant pool 197 // the following holds true: 198 // _orig_cpp_vtptrs[ConstantPool_Kind] == ((intptr_t**)cp)[0] 199 static intptr_t* _orig_cpp_vtptrs[_num_cloned_vtable_kinds]; 200 static bool _orig_cpp_vtptrs_inited = false; 201 202 template <class T> 203 void CppVtableCloner<T>::init_orig_cpp_vtptr(int kind) { 204 assert(kind < _num_cloned_vtable_kinds, "sanity"); 205 T tmp; // Allocate temporary dummy metadata object to get to the original vtable. 206 intptr_t* srcvtable = vtable_of(&tmp); 207 _orig_cpp_vtptrs[kind] = srcvtable; 208 } 209 210 // This is the index of all the cloned vtables. E.g., for 211 // ConstantPool* cp = ....; // an archived constant pool 212 // InstanceKlass* ik = ....;// an archived class 213 // the following holds true: 214 // _index[ConstantPool_Kind]->cloned_vtable() == ((intptr_t**)cp)[0] 215 // _index[InstanceKlass_Kind]->cloned_vtable() == ((intptr_t**)ik)[0] 216 CppVtableInfo** CppVtables::_index = nullptr; 217 218 char* CppVtables::dumptime_init(ArchiveBuilder* builder) { 219 assert(CDSConfig::is_dumping_static_archive(), "cpp tables are only dumped into static archive"); 220 size_t vtptrs_bytes = _num_cloned_vtable_kinds * sizeof(CppVtableInfo*); 221 _index = (CppVtableInfo**)builder->rw_region()->allocate(vtptrs_bytes); 222 223 CPP_VTABLE_TYPES_DO(ALLOCATE_AND_INITIALIZE_VTABLE); 224 225 size_t cpp_tables_size = builder->rw_region()->top() - builder->rw_region()->base(); 226 builder->alloc_stats()->record_cpp_vtables((int)cpp_tables_size); 227 228 return (char*)_index; 229 } 230 231 void CppVtables::serialize(SerializeClosure* soc) { 232 soc->do_ptr(&_index); 233 if (soc->reading()) { 234 CPP_VTABLE_TYPES_DO(INITIALIZE_VTABLE); 235 } 236 } 237 238 intptr_t* CppVtables::get_archived_vtable(MetaspaceObj::Type msotype, address obj) { 239 if (!_orig_cpp_vtptrs_inited) { 240 CPP_VTABLE_TYPES_DO(INIT_ORIG_CPP_VTPTRS); 241 _orig_cpp_vtptrs_inited = true; 242 } 243 244 assert(CDSConfig::is_dumping_archive(), "sanity"); 245 int kind = -1; 246 switch (msotype) { 247 case MetaspaceObj::SymbolType: 248 case MetaspaceObj::TypeArrayU1Type: 249 case MetaspaceObj::TypeArrayU2Type: 250 case MetaspaceObj::TypeArrayU4Type: 251 case MetaspaceObj::TypeArrayU8Type: 252 case MetaspaceObj::TypeArrayOtherType: 253 case MetaspaceObj::ConstMethodType: 254 case MetaspaceObj::ConstantPoolCacheType: 255 case MetaspaceObj::AnnotationsType: 256 case MetaspaceObj::MethodCountersType: 257 case MetaspaceObj::SharedClassPathEntryType: 258 case MetaspaceObj::RecordComponentType: 259 // These have no vtables. 260 break; 261 case MetaspaceObj::MethodDataType: 262 // We don't archive MethodData <-- should have been removed in removed_unsharable_info 263 ShouldNotReachHere(); 264 break; 265 default: 266 for (kind = 0; kind < _num_cloned_vtable_kinds; kind ++) { 267 if (vtable_of((Metadata*)obj) == _orig_cpp_vtptrs[kind]) { 268 break; 269 } 270 } 271 if (kind >= _num_cloned_vtable_kinds) { 272 fatal("Cannot find C++ vtable for " INTPTR_FORMAT " -- you probably added" 273 " a new subtype of Klass or MetaData without updating CPP_VTABLE_TYPES_DO or the cases in this 'switch' statement", 274 p2i(obj)); 275 } 276 } 277 278 if (kind >= 0) { 279 assert(kind < _num_cloned_vtable_kinds, "must be"); 280 return _index[kind]->cloned_vtable(); 281 } else { 282 return nullptr; 283 } 284 } 285 286 void CppVtables::zero_archived_vtables() { 287 assert(CDSConfig::is_dumping_static_archive(), "cpp tables are only dumped into static archive"); 288 for (int kind = 0; kind < _num_cloned_vtable_kinds; kind ++) { 289 _index[kind]->zero(); 290 } 291 } 292 293 bool CppVtables::is_valid_shared_method(const Method* m) { 294 assert(MetaspaceShared::is_in_shared_metaspace(m), "must be"); 295 return vtable_of(m) == _index[Method_Kind]->cloned_vtable(); 296 }