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/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 } --- EOF ---